Exploring tear viscosity with quartz crystal microbalance technology.

Tear viscosity is a critical property affecting tear distribution and ocular surface stability. While not widely established as a primary diagnostic marker, deviations from normal viscosity can impact ocular health, potentially contributing to conditions such as dry eye syndrome. Despite their importance, traditional viscometers require sample volumes that are not feasible to use with tear volume. This research introduces a novel Quartz Crystal Microbalance (QCM)-based method for tear viscosity measurement, offering a viscometer prototype that operates with minimal sample volumes. Human tear samples, solutions used in artificial eye drops, and various commercial eye drop brands were evaluated. Results show that the QCM method aligns with established viscosity ranges. The average viscosity of healthy human tears was found to be 1.73 ± 0.61 cP, aligning with the typical range of 1-10 cP. Variability in the viscosities of eye drop can be attributed to differences in their chemical compositions. The QCM method offers benefits such as reduced sample consumption and rapid results, enhancing understanding of tear dynamics for ocular health. Further research with larger sample sizes is needed to establish normative viscosity values in healthy individuals and those with dry eye syndrome, which is crucial for validating the device's clinical efficacy.

Quartz crystal Microbalance with dissipation monitoring for biomedical applications: Open source and low cost prototype with active temperature control.

Advances in sensors have revolutionized the biomedical engineering field, having an extreme affinity for specific analytes also providing an effective, real-time, point-of-care testing for an accurate diagnosis. Quartz Crystal Microbalance (QCM) is a well-established sensor that has been successfully applied in a broad range of applications to monitor and explore various surface interactions, in situ thin-film formations, and layer properties. This technology has gained interest in biomedical applications since novel QCM systems are able to work in liquid media. QCM with dissipation monitoring (QCM-D) is an expanded version of a QCM that measures changes in damping properties of adsorbed layers thus providing information on its viscoelastic nature. In this article, an open source and low cost QCM-D prototype for biomedical applications was developed. In addition, the system was validated using different Polyethylene Glycol (PEG) concentrations due to its importance for many medical applications. The statistics show a bigger dissipation of the system as the fluid becomes more viscous, also having a very acceptable sensibility when temperature is controlled.

AntVideoRecord: Autonomous system to capture the locomotor activity of leafcutter ants.

The leafcutter ants (LCA) are considered plague in a great part of the American continent, causing great damage in production fields. Knowing the locomotion and foraging rhythm in LCA on a continuous basis would imply a significant advance for ecological studies, fundamentally of animal behavior. However, studying the forage rhythm of LCA in the field involves a significant human effort. This also adds a risk of subjective results due to the operator fatigue. In this work a new development named 'AntVideoRecord' is proposed to address this issue. This device is a low-cost autonomous system that records videos of the LCA path in a fixed position. The device can be easily reproduced using the freely accessible source code provided. The evaluation of this novel device was successful because it has exceeded all the basic requirements in the field: record continuously for at least seven days, withstand high and low temperatures, capture acceptable videos during the day and night, and have a simple configuration protocol by mobile devices and laptops. It was possible to confirm the correct operation of the device, being able to record more than 1900 h in the field at different climate conditions and times of the day.

[Oral nutritional supplementation in hematologic patients]. / Suplementación oral nutricional en pacientes hematológicos.

RATIONALE: Hematological patients often present anorexia which along with other secondary effects from the chemotherapy and/or radiotherapy treatments compromise their nutritional status. Oral supplementation can aid to fulfill the energy and protein requirements of these patients. Nevertheless, the use of commercial nutritional supplements normally available, is limited by its poor intake. OBJECTIVE: To evaluate the degree of fulfillment of the prescribed supplements and fulfillment of energy requirements, as well as the development of nutritional status in hematological patients hospitalized for treatment with chemotherapy and/or radiotherapy. METHODS: Prospective, randomized and open study of inpatients at the hematological ward. Patients were randomized sequentially and they were assigned into 3 different nutritional interventions providing: Group 1 (G1), a flavored supplement; Group 2 (G2): a non flavored (neutral) supplement and Group 3 (G3): "kitchen" foods as supplements. Need and amount of nutritional supplements were provided according to the oral intake previously analyzed. Nutritional assessment (at admission and discharge) was based in the Subjective Global Assessment test (SGA), Risk Nutritional Index (RNI) and percentage of lost weight. Both fulfillment of supplement intake and achievement of energetic requirements were analyzed. RESULTS: 125 patients of 51.3 +/- 16.8 years; 45% men and 55% women. DIAGNOSIS: 54% lymphoma, 33% leukemia, 8% myeloma and others 4%. Length of stay (LOS): 7.0 +/- 3.6 d. The nutritional assessment done by SGA showed significant negative changes in G2 and G3 (G1: 30% developed malnutrition and 28% improved their nutritional status, p = NS; G2: 50% developed malnutrition against 7% whom improved their nutritional status, p = 0.002; y G3: 37% developed malnutrition against 21% whom improved their nutritional status, p = 0.02). According to RNI, patients evolved negatively from their nutritional state but no significant differences were found within groups (G1, from 81% of malnutrition to 90%; G2, from 77% to 91%, and G3 from 71% to 85%). Globally, during hospitalization patients lost weight significantly (2.3 +/- 2.2 kg, p < 0.001), but within groups weight loss differences were not significant (G1, 1.16 kg; G2, 1.75 kg, y G3, 1.17 kg). All three groups required intake of supplements (G1, 47%; G2, 30%, and G3, 47%). The percentage of fulfillment of oral intake was similar in both commercial supplemented groups (G1, 47% and G2, 58%) although it was significantly greater in those receiving kitchen supplements (G3, 100%, p < 0.001). The fulfillment of energy requirements at admission and discharge did not showed significant changes (G1, from 53% to 46%; G2, from 67% to 52% and G3 from 49% to 55%). CONCLUSION: Our results suggest that hematological patients admitted to hospital for treatment with chemotherapy and/or radiotherapy loose weight during their hospitalization and present intakes below their energy requirements so they need supplementation. Kitchen supplements are better accepted than commercial ones although that does not result in an increased total energy intake. The group which received commercial flavored supplements was the only one which did not showed negative significant changes in the nutritional status evaluated by SGA.

Suplementación oral nutricional en pacientes hemotológicos / Oral Nutritional supplementation in hematologic patients

Introducción: Los pacientes afectos de neoplasias hematológicas presentan con frecuencia anorexia que sumada a los efectos secundarios del tratamiento con quimioterapia y/o radioterapia comprometen su estado nutricional. La suplementación oral puede ayudar a cumplir los requerimientos energético-proteicos de estos pacientes. No obstante, el uso de los suplementos nutritivos comerciales habitualmente disponibles está limitado por su pobre aceptación. Objetivo: Evaluar el grado de cumplimiento de la prescripción de suplementos y de los requerimientos energéticos así como de la evolución del estado nutricional en pacientes hematológicos hospitalizados para tratamiento con quimioterapia y/o radioterapia. Metodología: Estudio prospectivo, aleatorio y abierto de pacientes ingresados en la planta de hematología. De forma secuencial los pacientes se asignaron a 3 tipos de intervención nutricional: Grupo 1 (G1), suplemento comercial oral con sabores; Grupo 2 (G2), suplemento comercial oral de sabor neutro, y Grupo 3 (G3), suplemento de cocina. Necesidad y cantidad de suplementos nutricionales pautados en función de la ingesta calórica calculada. Valoración nutricional (al ingreso y al alta) mediante Valoración Global Subjetiva (VGS), Índice de Riesgo Nutricional (IRN) y % de pérdida de peso (%PP). Se analizaron tanto el cumplimiento de la ingesta de suplementos como el cumplimiento de los requerimientos energéticos. Resultados: Se analizaron 125 pacientes de 51,3 ± 16,8 años (45% hombres y 55% mujeres). Diagnósticos: 54% linfoma; 33% leucemia; 8% mieloma y 4% otros. Estancia hospitalaria: 7,0 ± 3,6 días. La valoración nutricional mostró cambios significativos negativos en los pacientes de los grupos G2 y G3 con respecto a la VGS (G1: 30% desarrollaron malnutrición y 28% mejoraron su estado nutricional, p = NS; G2: 50% desarrollaron malnutrición frente al 7% que mejoraron su estado de nutrición, p = 0,002; y G3: 37% desarrollaron malnutrición versus el 21% que mejoró su estado de nutrición, p = 0,02). Según el IRN, los pacientes evolucionaron negativamente de su estado de nutrición, sin que las diferencias fueran significativas (G1, del 81% de malnutrición al 90%; G2, del 77% al 91%, y G3 del 71% al 85%). Globalmente, durante la hospitalización los pacientes perdieron peso de manera significativa (2,3 ± 2,2 kg, p < 0,001), sin que fueran significativas las pérdidas de cada grupo (G1, 1,16 kg; G2, 1,75 kg, y G3, 1,17 kg). Todos los grupos presentaron necesidad de suplementos (G1, 47%; G2, 30%, y G3, 47%). El porcentaje de cumplimiento de la ingesta de suplemento fue similar en los grupos con suplementos comerciales (G1, 47% y G2, 58%) siendo significativamente mayor en los que recibieron suplementos de cocina (G3, 100%, p < 0,001). El cumplimiento de los requerimientos energéticos al ingreso y alta del paciente no mostró cambios significativos (G1, del 53% al 46%; G2, del 67% al 52% y G3 del 49% al 55%). Conclusión: Nuestros resultados sugieren que los pacientes hematológicos ingresados en el hospital por tratamiento con quimioterapia y/o radioterapia pierden peso durante su hospitalización y presentan ingestas inferiores a sus requerimientos energéticos por lo que requieren suplementos. Los suplementos de cocina son mejor aceptados que los suplementos comerciales pero ello no comporta que incrementen las ingestas energéticas totales. El grupo que recibió suplementos comerciales con sabores fue el único que no presentó cambios negativos significativos en el estado de nutrición evaluada por la VGS (AU)

Rationale: Hematological patients often present anorexia which along with other secondary effects from the chemotherapy and/or radiotherapy treatments compromise their nutritional status. Oral supplementation can aid to fulfill the energy and protein requirements of these patients. Nevertheless, the use of commercial nutritional supplements normally available, is limited by its poor intake. Objective: To evaluate the degree of fulfillment of the prescribed supplements and fulfillment of energy requirements, as well as the development of nutritional status in hematological patients hospitalized for treatment with chemotherapy and/or radiotherapy. Methods: Prospective, randomized and open study of inpatients at the hematological ward. Patients were randomized sequentially and they were assigned into 3 different nutritional interventions providing: Group 1 (G1), a flavored supplement; Group 2 (G2): a non flavored (neutral) supplement and Group 3 (G3): "kitchen" foods as supplements. Need and amount of nutritional supplements were provided according to the oral intake previously analyzed. Nutritional assessment (at admission and discharge) was based in the Subjective Global Assessment test (SGA), Risk Nutritional Index (RNI) and percentage of lost weight. Both fulfillment of supplement intake and achievement of energetic requirements were analyzed. Results: 125 patients of 51.3 ± 16.8 years; 45% men and 55% women. Diagnosis: 54% lymphoma, 33% leukemia, 8% myeloma and others 4%. Length of stay (LOS): 7.0 ± 3.6 d. The nutritional assessment done by SGA showed significant negative changes in G2 and G3 (G1: 30% developed malnutrition and 28% improved their nutritional status, p = NS; G2: 50% developed malnutrition against 7% whom improved their nutritional status, p = 0.002; y G3: 37% developed malnutrition against 21% whom improved their nutritional status, p = 0.02). According to RNI, patients evolved negatively from their nutritional state but no significant differences were found within groups (G1, from 81% of malnutrition to 90%; G2, from 77% to 91%, and G3 from 71% to 85%). Globally, during hospitalization patients lost weight significantly (2.3 ± 2.2 kg, p < 0.001), but within groups weight loss differences were not significant (G1, 1.16 kg; G2, 1.75 kg, y G3, 1.17 kg). All three groups required intake of supplements (G1, 47%; G2, 30%, and G3, 47%). The percentage of fulfillment of oral intake was similar in both commercial supplemented groups (G1, 47% and G2, 58%) although it was significantly greater in those receiving kitchen supplements (G3, 100%, p < 0.001). The fulfillment of energy requirements at admission and discharge did not showed significant changes (G1, from 53% to 46%; G2, from 67% to 52% and G3 from 49% to 55%). Conclusion: Our results suggest that hematological patients admitted to hospital for treatment with chemotherapy and/or radiotherapy loose weight during their hospitalization and present intakes below their energy requirements so they need supplementation. Kitchen supplements are better accepted than commercial ones although that does not result in an increased total energy intake. The group which received commercial flavored supplements was the only one which did not showed negative significant changes in the nutritional status evaluated by SGA (AU)

Guidelines for colorectal cancer: effects on nutritional intervention.

INTRODUCTION: Although parenteral nutrition is a vital method of delivery essential nutrients in patients with malnutrition associated to gastro-intestinal insufficiency, its inappropriate use can increase the risk of complications and incur unnecessary expenses. OBJECTIVE: Our goal was to evaluate the influence of both, the presence of the Nutritional Support Unit and the implementing clinical practice guidelines on post-operative nutritional status, complications and length of stay among patients undergoing elective colorectal cancer surgery. METHODS: Prospective and observational study: Three period times were included-the year during the guidelines elaboration (A), and the first (B) and the second year (C) after their implementation. All patients submitted to elective colorectal cancer surgery at least 18 years of age were included (A: n=297; B: n=103, and C: n=149). WE ANALYSED: Nutritional status (NS) on admission to hospital and at discharge, use of post-operative parenteral nutrition (PPN), incidence of post-operative complications (PC), number of days of nil by mouth following surgery (NPO), and hospital length of stay (LOS). RESULTS: Although the prevalence of malnutrition on admission was low, an increment was observed during the hospitalisation time. However, only in the first period time, the increment was significantly different (A: from 8.4% to 19.5%, p<0.001; B: from 3.9% to 8.7%, and C: from 4.7% to 6.7%). Globally, the use of PPN decreased (A: 79.1%, B: 47.0%, and C: 12.8%; p<0.001). This behaviour was mainly observed in well-nourished patients (use of PPN in well nourished, A: 79.3%, B: 44.4%, and C: 11.3%; p<0.001). Significant differences were observed in the global incidence of PC (A: 27.9%, B: 28.2%, and C: 8.1%, p<0.001). Furthermore, PC was higher in well-nourished patients with PPN versus without PPN, with significant differences in B and C periods (A: 29.3% vs. 25.0%; B: 38.6% vs. 18.8%, p=0.004; C: 31.3% vs. 4.8%, p=0.003). The NPO was higher in patients without PPN in period A (7 d vs. 5 d, p<0.001) and higher in those with PPN in period C (8 d vs. 6 d, p=0.035). All in all, LOS decreased significantly during the study period time (A: 16 d, B: 13 d, and C: 11 d, p<0.001). CONCLUSION: The presence of Nutritional Support Unit and clinical practice guidelines for colorectal cancer management and treatment, optimised the use of hospital resources, namely unnecessary use of parenteral nutrition, reduction along with decrease in number of complications and length of hospital stay.

Presence of bovine leptin in edible commercial milk and infant formula.

Leptin is a hormone secreted by the adipocytes that contribute to the control of energy balance, and circulating leptin levels reflect the amount of adipose tissue in the body, helping to regulate food intake and energy expenditure. Since it has been shown that human milk contains immunoreactive leptin, which is identical to intact human leptin, we decided to investigate the possible presence of immunoreactive bovine leptin in different kinds of common commercial milk. To determine the presence or absence of immunoreactive leptin in bovine milk for human consumption, 81 samples (66 commercial pasteurized milk and 15 artificial formulae for new-born babies) of the most common Spanish commercial types of milk were studied. All samples were evaluated before and after centrifugation, and leptin levels were measured by RIA. Leptin was detected in all samples and RIA standard curves were not perturbed when centrifuged and non-centrifuged milk replaced the buffer. Mean values of leptin in full-cream, semi-skimmed and skimmed samples, were: 5.7+/-0.3 ng/ml, 4.1+/-0.1 ng/ml, 3.7+/-0.1 ng/ml (significantly different). Leptin values were reduced after centrifugation. A significant correlation was observed between leptin levels and lipid content (p<0.0005, r=0.67) while no correlation was observed with respect to carbohydrate and protein levels. Interestingly, some preparations of infant formulae present very high leptin values reaching up to 18.9 ng/ml. In conclusion, leptin is present in significant and variable concentrations in edible commercial bovine milk, with higher concentrations in infant formula.

Involvement of nitric oxide in the regulation of growth hormone secretion in dogs.

Nitric oxide (NO) is a highly reactive gas that has been suggested to function as a neurotransmitter in the neuroendocrine system. In this work, we have evaluated the role of NO pathways in growth hormone (GH) secretion by assessing the effect of L-arginine infusion, a precursor of NO formation, and L-NAME, a nitric oxide synthase (NOS) inhibitor. The experiments were carried out on 7 adult beagle dogs. A saline infusion was carried out on all the dogs as a control test. L-arginine (infusion i.v. 10 g in 100 ml of saline, from t = 0 to 30 min) and L-nitro-arginine-methyl ester, L-NAME (infusion of 300 microg/kg in 120 ml of saline, from t = -30 to 45 min) were administered alone and together with growth hormone-releasing hormone (GHRH) (i.v. bolus at 0 min, at a dose of 100 microg), the synthetic GH secretagogue GHRP-6 (i.v. bolus at 0 min, at a dose of 90 microg), and the 5-HT1D serotonin receptor agonist sumatriptan, SUM (s.c. injection at the dose of 3 mg). Plasma cGH was determined by RIA. Results were evaluated by one-way analysis of variance, followed by the Newman-Keuls test for multiple comparisons. L-arginine administration resulted in a slight increase in plasma cGH in comparison with saline controls. Combined administration of L-arginine and GHRH enhanced cGH release in comparison with GHRH alone. L-NAME alone did not modify baseline cGH levels, but completely suppressed the GH release induced by GHRH or GHRP-6. It also strongly reduced, but did not abolish the effect of the two peptides (GHRH plus GHRP-6) administered together. Finally, administration of the 5-HT1D agonist SUM induced a significant cGH secretion in all dogs, a response which was not modified when L-NAME was administered in combination with SUM. In conclusion, our data show that inhibition of NO blunts both GHRH or GHRP-6-induced cGH release, and are compatible with the hypothesis that it acts by decreasing hypothalamic somatostatin release.

Effect of acute pharmacological modulation of plasma free fatty acids on GH secretion in acromegalic patients.

OBJECTIVES: In acromegaly GH secretion is markedly increased due in most cases to a GH secreting pituitary adenoma. GH secretion is modulated by variations in the levels of free fatty acids (FFA). Recent studies in different clinical situations, have shown that reduction in FFA with acipimox (A) modifies somatotroph cell responsiveness. The aim of the present study was to evaluate the effect of acute pharmacological reduction of plasma FFA on both basal GH levels and GHRH-mediated GH secretion in acromegalic patients. PATIENTS: Six acromegalic patients (four female, two male) aged 57 +/- 4 years., with active disease due to pituitary adenomas were studied. Four of the patients had been treated previously by surgery and/or radiotherapy. The diagnosis of active acromegaly was established by clinical assessment, increased serum IGF-I and impaired GH suppression after oral glucose. MEASUREMENTS: Four tests were performed: placebo, A (250 mg, orally, - 210 minutes and - 60 minutes), GHRH (100 microg, iv, 0 minutes) and GHRH plus A. The different tests on each subject were performed in random order one week apart, each subject served as their own control. Serum GH was measured by RIA at appropriate intervals. The area under the curve (AUC) was calculated by the trapezoidal METHOD: Statistical analysis was performed by Wilcoxon test. P < 0.05 was considered significant. RESULTS: The administration of A induced a FFA reduction during the entire test both when administered with placebo and with GHRH: AUC (mmol/l x 90 minutes): placebo plus placebo: 88.2 +/- 7.3. Placebo plus A: 23.2 +/- 4.6 (P < 0.05). Placebo plus GHRH: 85.4 +/- 6.9. A plus GHRH: 21.8 +/- 3.8 (P < 0.05). Mean peak GH level (microg/l) after placebo plus placebo was 5.0 +/- 1.8 not significantly different than after placebo plus A with a mean peak of 6.2 +/- 2 (P = ns). Mean peak GHRH-induced GH secretion was 26.0 +/- 15.4 and was not modified by previous A administration with mean peak of 24.4 +/- 11.8 (P = ns). CONCLUSIONS: In acromegalic patients acute pharmacological reduction of FFA with acipimox did not modify basal GH levels or GHRH-induced GH secretion, suggesting that the adenomatous somatotroph cell is unresponsive to physiological signals such as FFA which act at a pituitary level. These data support the hypothesis of an intrinsic neoplastic pituitary defect for the pathogenesis of acromegaly.

Physiology and possible pathology of growth hormone secretagogues.

Growth hormone segretagogues (GHS) are artificial molecules able to stimulate growth hormone (GH) secretion. They were discovered before the hypothalamic growth hormone-releasing hormone (GHRH). These molecules had a structure devoid of opiate activity, and GHRP-6 is the most representative compound. These compounds identified a new physiological system involved in GH regulation, and their action is independent of GHRH or somatostatin. Recently an endogenous ligand for the GHS receptor, ghrelin, was discovered, suggesting that this may be the third factor in the control of GH secretion. This peptide was isolated from the stomach and is characterized by the presence of an acylated group representing a new type of molecular hormonal structure; it is able to stimulate GH secretion in vitro and in vivo in the rat. As observed for the majority of GHS, ghrelin's action is not fully specific for GH release; the acute administration of ghrelin stimulates the release of significant amounts of PRL, ACTH and cortisol. Moreover, the presence of ghrelin in rat and human placenta has been reported, suggesting a possible role of this peptide in the local modulation of GH release and in maternal and fetal pituitary secretion. Ghrelin stimulates gastric acid secretion, is able to induce adiposity by activating a central mechanism for increasing food intake and decreasing fat utilization, and ghrelin mRNA and peptide are expressed in normal and adenomatous human pituitary tissue. Possible therapeutic applications of ghrelin remain to be assessed.

Influence of different serotonin receptor subtypes on growth hormone secretion.

The role of serotonin (5-HT) in the regulation of growth hormone (GH) secretion remains unclear due to the existence of many different receptors that mediate the 5-HT actions, and the lack of suitable specific agonist and antagonist drugs. In the present work we have taken advantage of the recent development of new selective 5-HT drugs in order to clarify the role played by different 5-HT receptor types and subtypes on GH secretion. The experiments were carried out on beagle dogs. GH-releasing hormone (GHRH) increased basal canine GH (cGH) levels from 0.8 +/- 0.2 to 8.8 +/- 1.7 microg/l at 15 min. Administration of 5-HT(1D) receptor agonist sumatriptan (SUM) induced a cGH peak at 30 min of 12.9 +/- 2.7 microg/l. The combined administration of GHRH plus SUM strikingly potentiated cGH release with a peak of 36.9 +/- 6 microg/l at 30 min (p < 0.05). Pretreatment with the muscarinic receptor antagonist atropine completely abolished the cGH response to SUM, while the cholinergic agonist pyridostigmine (PYR) did not modify this response (15.3 +/- 5 microg/l PYR plus SUM vs. SUM alone 12.9 +/- 2. 7 microg/l). On the other hand, administration of drugs with activity at 5-HT(2A/C) receptors showed a stimulatory role for the 5-HT(2C) receptor subtype, since LY-53857 (antagonist 5-HT(2A/C)) and DOI agonist (5-HT(2A/C)) both modified the GH response stimulated by GHRH (AUC 88.5 +/- 30.4 and 400 +/- 64.6 vs. 267.3 +/- 52.6 respectively), while ketanserin (antagonist 5-HT(2A)) did not modify this response. The 5-HT(3) antagonist ICS-205-930 failed to modify either basal or GHRH induced GH responses. In conclusion, our data show that 5-HT(1D) receptors play a stimulatory role on GH secretion in the dog, possibly by acting through a decrease in hypothalamic somatostatin release. Similarly, the 5-HT(2C) receptor subtypes also appear to play a stimulatory role. However, 5-HT(2A) and 5-HT(3) receptors do not appear to be involved in the control of basal and GHRH-induced GH secretion.

Effect of acute pharmacological reduction of plasma free fatty acids on growth hormone (GH) releasing hormone-induced GH secretion in obese adults with and without hypopituitarism.

In obesity, there is a markedly decreased GH secretion. The diagnosis of GH deficiency (GHD) in adults is based on peak GH responses to stimulation tests. In the severely obese, peak GH levels after pharmacological stimulation are often in the range that is observed in hypopituitary patients. To distinguish obese subjects from GHD patients, it will be necessary to demonstrate that reduced GH responsiveness to a given test is reversible in the former, but not in the latter, group. Recent studies have shown that reduction of plasma free fatty acids (FFA) with acipimox in obese patients restores their somatotrope responsiveness. There are no data evaluating GH responsiveness to acipimox plus GHRH in obese adults with hypopituitarism. The aim of the present study was to evaluate the effect of acute pharmacological reduction of plasma FFA on GHRH-mediated GH secretion in obese normal subjects and obese adults with hypopituitarism. Eight obese patients with a body mass index of 34.2+/-1.2; eight obese adults with hypopituitarism, with a body mass index of 35.5+/-1.9; and six control subjects were studied. All the patients showed an impaired response to an insulin-tolerance test (0.15 U/kg, i.v.), with a peak GH secretion of less than 3 microg/L. Two tests were carried out. On one day, they were given GHRH (100 microg, i.v., 0 min), preceded by placebo; and blood samples were taken every 15 min for 60 min. On the second day, they were given GHRH (100 microg, i.v., 0 min), preceded by acipimox (250 mg, orally, at -270 min and -60 min); and blood samples were taken every 15 min for 60 min. The administration of acipimox induced a FFA reduction during the entire test. Normal control subjects had a mean peak (microg/L) of 23.8+/-4.8 after GHRH-induced GH secretion; previous acipimox administration increased GHRH-induced GH secretion, with a mean peak of 54.7+/-14.5. In obese patients, GHRH-induced GH secretion was markedly reduced, with a mean peak (microg/L) of 3.9+/-1; previous administration of acipimox markedly increased GHRH-mediated GH secretion, with a mean peak of 16.0+/-3.2 (P < 0.05). In obese adults with hypopituitarism, GHRH-induced GH secretion was markedly reduced, with a mean peak (microg/L) of 2+/-0.7; previous acipimox administration did not significantly modify GHRH-mediated GH secretion, with a mean peak of 3.3+/-1.1 (P < 0.05). The GH response of obese patients and obese adults with hypopituitarism was similar after GHRH alone. In contrast, the GH response after GHRH plus acipimox, was markedly decreased in obese adults with hypopituitarism (mean peak, 3.3+/-1.1), compared with obese patients (mean peak, 16.0+/-3.2) (P < 0.05) and control subjects (mean peak, 54.7+/-14.5) (P < 0.01). In conclusion, GH secretion, after GHRH-plus-acipimox administration, is reduced in obese adults with hypopituitarism patients, when compared with obese normal patients. Testing with GHRH plus acipimox is safe and is free from side effects and could be used for the diagnosis of GHD in adults.

Acute changes in free-fatty acids (FFA) do not alter serum leptin levels.

Leptin, the product of the ob gene, is a recently discovered hormone secreted by adipocytes. Serum leptin concentrations increase in correlation with the percentage of body fat, but besides that little is known about the physiological actions of leptin in humans. The aim of this study was to assess the influence of changes in circulating free-fatty acids on serum leptin levels. Increases in plasma FFA levels (p < 0.02) were obtained in a group of normal subjects following the administration of intralipid plus heparin (250 ml 10% Intralipid plus 5000 U heparin). FFA reduction was achieved through the administration of acipimox (250 mg, orally, at 0 min and at 210 min), a lipid-lowering drug devoid of side effects, to a group of normal (p < 0.02) and obese subjects (p < 0.05). An increase in circulating FFA levels in normal subjects (n = 6), following administration of a lipid-heparin infusion, failed to modify plasma leptin levels as assessed by the area under the curve (AUC; mean +/- SE 892 +/- 168 for placebo vs 896 +/- 260 following intralipid plus heparin). Similarly, whereas acipimox pretreatment induced a reduction in FFA levels compared to placebo in normal (n = 6) and obese subjects (n = 8), it also failed to modify plasma leptin levels at any time-point studied. The results indicate that short-term reduction or increase in circulating FFA are not associated to changes in plasma leptin levels.

Growth hormone releasing hexapeptide-6 (GHRP-6) test in the diagnosis of GH-deficiency.

Pituitary GH reserve can be assessed by substances that act directly at the somatotroph, such as GHRH, or by a variety of metabolic and neuropharmacological tests acting at the hypothalamic level, such as hypoglycemia, clonidine or L-Dopa. In order to evaluate GHRP-6 as a test of pituitary GH reserve, we studied GH responses of i.v. administered GHRP-6 in a group of short-statured children, as well as in a group of adults diagnosed with growth hormone deficiency (GHD) by conventional GH testing. Although we found that the GH response to GHRP-6 was lower in patients with GHD than in normal children, on an individual basis a considerable degree of overlap was observed between the two groups. In contrast, we found an almost complete blockade of GH response to either GHRP-6 or GHRH plus GHRP-6 in patients with pituitary stalk transection, suggesting that this could be a cost-effective test for the diagnosis of this condition. A similar finding was also obtained in GH response to the combined administration of GHRH plus GHRP-6 in patients with GHD of adult onset; this test may well prove valuable in the diagnosis of this clinical entity.

Acipimox-mediated plasma free fatty acid depression per se stimulates growth hormone (GH) secretion in normal subjects and potentiates the response to other GH-releasing stimuli.

Increases in plasma free fatty acids (FFA) inhibit the GH response to a variety of stimuli; however, the role of FFA depression in GH control is far from understood. In the present work, FFA reduction was obtained by the administration to normal subjects of acipimox, a lipid-lowering drug devoid of side-effects. Each subject tested underwent two paired tests. In one, acipimox was administered orally at a dose of 250 mg at -270 min and at a dose of 250 mg at -60 min; in the matched test, placebo was given at similar intervals. To induce GH release, four stimuli acting through different mechanisms were used: pyridostigmine (120 mg, orally) at -60 min, GHRH (1 microgram/kg, iv) at 0 min, GH-releasing peptide (GHRP-6; His-D-Trp-Ala-Trp-D-Phe-Lys-NH2; 1 microgram/kg, iv) at 0 min, and finally, GHRH plus GHRP-6 at the same doses at 0 min. GH secretion was analyzed as the area under the secretory curve (AUC; mean +/- SE, micrograms per L/120 min). Acipimox pretreatment alone (n = 6) induced a reduction in FFA levels compared with placebo treatment. The FFA reduction led to a sustained GH secretion that increased from 2.4 +/- 1.8 micrograms/L at -120 min to 14.2 +/- 4.0 at 120 min. The GH AUC for placebo was 266 +/- 100, and that for acipimox was 1781 +/- 408 (P < 0.05). In the pyridostigmine-treated group (n = 6), the acipimox-pyridostigmine AUC (2046 +/- 323) was higher (P < 0.05) than the placebo-pyridostigmine AUC (764 +/- 101), but was not different from the AUC of acipimox alone. Previous FFA reduction nearly doubled the GHRH-mediated GH secretion (n = 6; placebo-GHRH AUC, 1817 +/- 365; acipimox-GHRH test, 3228 +/- 876; P < 0.05). A similar enhancement was observed when the stimulus employed was GHRP-6 (n = 6; placebo-GHRP-6 AUC, 2034 +/- 295; acipimox-GHRP-6, 4827 +/- 703; P < 0.05). Furthermore, even the most potent GH stimulus known to date, i.e. GHRH plus GHRP-6, was enhanced by the FFA suppression (placebo-GHRH-GHRP-6 AUC, 2034 +/- 277; acipimox-GHRH-GHRP-6, 5809 +/- 758; P < 0.05). The enhancing effect of lowering FFA levels was additive regardless of the stimulus employed. These results indicate that 1) FFA reduction per se stimulates GH secretion with a delayed time of action; 2) FFA reduction enhanced in an additive manner the GH secretion elicited by such different stimuli as pyridostigmine, GHRH, and GHRP-6; and 3) the observation that FFA reduction enhanced the response to the most potent GH stimulus, GHRH plus GHRP-6, suggests that FFA suppression acts by a separate mechanism. FFA reduction may have value in the clinical setting for assessing GH reserve.

Impaired growth hormone secretion in obese subjects is partially reversed by acipimox-mediated plasma free fatty acid depression.

GH secretion in response to provocative stimuli is blunted in obese patients. On the other hand, increases in plasma free fatty acids (FFA) inhibit the GH response to a variety of stimuli, and FFA levels in plasma are increased with obesity. To ascertain whether FFA might be responsible for the GH secretory alterations of obesity, we studied spontaneous and stimulated GH secretion in 31 obese patients after FFA reduction by acipimox, a lipid-lowering drug devoid of serious side-effects. Each subject underwent two paired tests. In one, acipimox was administered orally at a dose of 250 mg at -270 min and at a dose of 250 mg at -60 min; in the matched test, placebo was given at similar intervals. To induce GH release, three stimuli acting through different mechanisms were used: pyridostigmine (60 mg, orally, at -60 min), GHRH (100 micrograms, iv, at 0 min), and GHRH plus GH-releasing peptide (GHRP-6; His-D-Trp-Ala-Trp-D-Phe-Lys-NH2; both at a dose of 100 micrograms, iv, at 0 min). GH secretion was analyzed as the area under the secretory curve (AUC; mean +/- SE; micrograms per L/60 min). Acipimox pretreatment alone (n = 13) induced a large reduction in FFA levels compared with placebo treatment. The FFA reduction led to a slight GH rise (AUC, 123 +/- 47), not different from that in the placebo group (61 +/- 15). In the pyridostigmine-treated group (n = 6), the acipimox-pyridostigmine AUC (408 +/- 107) was significantly higher (P < 0.05) than that in the placebo-pyridostigmine group (191 +/- 25). Furthermore, the GHRH-mediated (n = 6) AUC of GH secretion in the placebo test (221 +/- 55) was tripled by FFA reduction due to acipimox, with an AUC of (691 +/- 134; P < 0.05). Even the most potent GH stimulus known to date, i.e. GHRH plus GHRP-6, was enhanced by FFA suppression. In fact, the placebo-GHRH-GHRP-6 AUC was 1591 +/- 349, lower (P < 0.05) than that in the acipimox-GHRH-GHRP-6 test (2373 +/- 242). The enhancing effects of FFA lowering on GHRH-mediated and GHRH- plus GHRP-6-mediated GH release were synergistic. These results indicate that in obese subjects, unlike normal weight subjects. FFA reduction per se does not stimulate GH secretion. A reduction in FFA with acipimox, however, increased pyridostigmine-. GHRH-, and even GHRH- plus GHRP-6-mediated GH release, suggesting that FFA reduction operates through a different mechanism from that of these three stimuli. The abnormally high FFA levels may be a contributing factor for the disrupted GH secretory mechanisms in obesity.

Absence of growth hormone (GH) secretion after the administration of either GH-releasing hormone (GHRH), GH-releasing peptide (GHRP-6), or GHRH plus GHRP-6 in children with neonatal pituitary stalk transection.

GH-releasing peptide (GHRP-6; His-D-Trp-Ala-Trp-D-Phe-Lys-NH2) is a synthetic compound that releases GH in a specific and dose-related manner through mechanisms and a point of action that are mostly unknown, but different from those of GHRH. In man, GHRP-6 is more efficacious than GHRH, and a striking synergistic action occurs when both compounds are administered together. To explain such a synergistic effect, it has been postulated, but not proven, that GHRP-6 acts through a double mechanism, with actions exerted at the pituitary and the hypothalamic level. On the other hand, patients with the syndrome of GH deficiency due to perinatal pituitary stalk transection have any hypothalamic factor nonoperandi. The aim of the present study was 3-fold: 1) to further understand how relevant, if at all, the hypothalamic action of GHRP-6 is for GH regulation; 2) to evaluate whether GHRP-6 plus GHRH could be a suitable diagnostic tool in children with pituitary stalk transection; and 3) to compare these results with similar published studies performed in patients with hypothalamo-pituitary disconnection, who developed the disease as adults. Seven patients with GH deficiency and different degrees of panhypopituitarism due to perinatal pituitary stalk transection and 7 age- and sex-matched normal controls were studied. The subjects underwent 3 different tests on separate occasions, being challenged with GHRH (1 microgram/kg, iv), GHRP-6 (1 microgram/kg, iv), or GHRH plus GHRP-6. GH was analyzed as the area under the curve (mean +/- SE; micrograms per L/90 min). In normal subjects, GH secretion was 1029 +/- 202 after GHRH treatment, 1221 +/- 345 after GHRP-6, and 3542 +/- 650 after GHRH plus GHRP-6; the latter value was significantly (P < 0.05) higher than the secretion elicited by GHRH or GHRP-6 alone. In the group of patients with perinatal pituitary stalk transection, the level of GH after GHRH treatment was 116 +/- 22 and was even more reduced (P < 0.05) after GHRP-6 treatment (37 +/- 8). After GHRH plus GHRP-6, GH secretion in those patients was 177 +/- 27, significantly higher (P < 0.05) than the secretion induced by either GHRH or GHRP-6 alone. Individually examined, none of the patients tested with the most potent stimulus known to date (GHRH plus GHRP-6) exhibited GH secretion greater than 5 micrograms/L.(ABSTRACT TRUNCATED AT 400 WORDS)

Plasma growth hormone response to growth hormone-releasing hexapeptide (GH-RP-6) in children with short stature.

Eighteen children with short stature were evaluated for growth hormone (GH) reserve after pharmacological tests and a single iv injection of GH-RP-6. These children were divided into two groups: 10 were diagnosed as having idiopathic GH deficiency by classical stimulation tests (group A) and the remaining 8 (group B) were considered growth-retarded children with normal GH secretion, following conventional stimulation, but reduced endogenous GH secretion. The results were compared with a group of 12 normal children. As a group, patients in group A showed a lower GH response to GH-RP-6, while patients in group B had a similar response as normal controls. However, on an individual basis, a considerable degree of overlapping in responses among the three groups was evident. These data indicate that, on an individual basis, GH-RP-6 testing is not of diagnostic value in children suspected of having idiopathic GH deficiency.

Effect of combined administration of growth hormone (GH)-releasing hormone, GH-releasing peptide-6, and pyridostigmine in normal and obese subjects.

Growth hormone (GH) secretion in response to all provocative stimuli is decreased in patients with obesity. Recently, we found that the combined administration of GH-releasing hormone (GHRH) and the hexapeptide GH-releasing peptide-6 (GHRP-6) induced a large increase in plasma GH levels. To gain further insight into the disrupted mechanism of GH regulation in obesity, we investigated whether the inhibition of somatostatinergic tone with pyridostigmine could further increase the GH response to combined administration of GHRH and GHRP-6. In normal subjects, administration of GHRH plus GHRP-6 induced a marked increase in plasma GH with a peak at 30 minutes (mean +/- SEM, 76.7 +/- 9.7 micrograms/L), which was similar to that obtained after pretreatment with pyridostigmine (74.7 +/- 9.4 micrograms/L). In obese patients, combined administration of GHRH plus GHRP-6 induced a clear increase in GH secretion with a peak at 15 minutes of 42.2 +/- 10.0 micrograms/L, which was also unaffected after pretreatment with pyridostigmine (38.4 +/- 5.8 micrograms/L). The GH response was lower in obese patients than in controls as assessed by the area under the curve after administration of both GHRH plus GHRP-6 (1,846 +/- 396 v 4,773 +/- 653, P < .01) and pyridostigmine plus GHRH plus GHRP-6 (1,989 +/- 372 v 5,098 +/- 679, P < .005). In conclusion, these data suggest that GHRP-6 can behave as a functional somatostatin antagonist, and that somatotrope responsiveness to the combined administration of GHRH plus GHRP-6 is largely independent of somatostatinergic tone.(ABSTRACT TRUNCATED AT 250 WORDS)

Role of the serotonin receptor subtype 5-HT1D on basal and stimulated growth hormone secretion.

At present, four main types of serotonin (5-HT) receptors have been identified in the brain (5-HT1, 5-HT2, 5-HT3, and 5-HT4). In addition, the 5-HT1 have been further subclassified. We have taken advantage of a new selective 5-HT1D receptor agonist 3-[2-(dimethylamino)ethyl]-N-methyl-1H-indole-5-methanesulfonamide succinate, Sumatriptan, to evaluate the role of 5-HT1D receptors on GH secretion. To this end, several tests with or without sumatriptan were undertaken in normal prepubertal children. Furthermore, we assessed the effect of Sumatriptan on basal GH secretion and the GH response to GHRH in obese children. In normal children, Sumatriptan administration (3 mg, sc) resulted in an increase in basal GH levels at 30 min (7.7 +/- 1.5 micrograms/L; P < 0.05) and increased GH responses to GHRH (47.3 +/- 6.4 vs. 29.6 +/- 9.7 micrograms/L; P < 0.05). The Sumatriptan-induced increase in GH responses to GHRH was dependent on the stimulus tested. Pretreatment with Sumatriptan did not modify the GH response to clonidine or pyridostigmine, as assessed by the peak GH response and the area under the curve. In contrast, it increased the GH response to arginine. In the obese subjects, the GH response to GHRH was reduced (7.3 +/- 1.0 vs. 29.6 +/- 9.7 micrograms/L at 30 min) compared to that in control children (P < 0.05). Sumatriptan administration did not alter the basal GH value (peak GH, 1.7 +/- 0.3 micrograms/L at 30 min). However, Sumatriptan administration clearly increased the effect of GHRH, resulting in a GH peak of 14.6 +/- 3.1 micrograms/L at 30 min (P < 0.01). To assess the specificity of Sumatriptan on anterior pituitary hormone secretion, we studied its effect on TSH and PRL responses to TRH as well as LH-releasing hormone-induced LH and FSH secretion. Administration of Sumatriptan did not alter the response of any of these hormones. Our results indicate that 5-HT1D receptors have a stimulatory effect on GH secretion, possibly by inhibiting hypothalamic somatostatin release.