Pre-vaccination screening strategies for the use of the CYD-TDV dengue vaccine: A meeting report.

The first licensed dengue vaccine, CYD-TDV (Dengvaxia) is efficacious in seropositive individuals, but increases the risk for severe dengue in seronegative persons about two years after administration of the first dose. For countries considering the introduction of Dengvaxia, WHO recommends a pre-vaccination screening strategy whereby only persons with evidence of a past dengue infection would be vaccinated. Policy-makers need to consider the risk-benefit of vaccination strategies based on such screening tests, the optimal age to introduce the vaccine, communication and implementation strategies. To address these questions, the Global Dengue and Aedes-transmitted diseases Consortium (GDAC) organized a 3-day workshop in January 2019 with country representatives from Asia and Latin America. The meeting discussions highlighted many challenges in introducing Dengvaxia, in terms of screening test characteristics, costs of such tests combined with a 3-dose schedule, logistics, achieving high coverage rates, vaccine confidence and communication; more challenges than for any other vaccine introduction programme. A screening test would require a high specificity to minimize individual risk, and at the same time high sensitivity to maximize individual and population benefit. The underlying seroprevalence dependent positive predictive value is the best indicator for an acceptable safety profile of a pre-vaccination screening strategy. The working groups discussed many possible implementation strategies. Addressing the bottlenecks in school-based vaccine introduction for Dengvaxia will also benefit other vaccines such as HPV and booster doses for tetanus and pertussis. Levels of public trust are highly variable and context specific, and understanding of population perceptions and concerns is essential to tailor interventions, monitor and mitigate risks.

Ankyrin-G isoform imbalance and interneuronopathy link epilepsy and bipolar disorder.

ANK3, encoding the adaptor protein Ankyrin-G (AnkG), has been implicated in bipolar disorder by genome-wide association studies. ANK3 has multiple alternative first exons, and a bipolar disorder-associated ANK3 variant has been shown to reduce the expression of exon 1b. Here we identify mechanisms through which reduced ANK3 exon 1b isoform expression disrupts neuronal excitation-inhibition balance. We find that parvalbumin (PV) interneurons and principal cells differentially express ANK3 first exon subtypes. PV interneurons express only isoforms containing exon 1b, whereas excitatory principal cells express exon 1e alone or both 1e and 1b. In transgenic mice deficient for exon 1b, PV interneurons lack voltage-gated sodium channels at their axonal initial segments and have increased firing thresholds and diminished action potential dynamic range. These mice exhibit an Ank3 gene dosage-dependent phenotype including behavior changes modeling bipolar disorder, epilepsy and sudden death. Thus ANK3's important association with human bipolar susceptibility may arise from imbalance between AnkG function in interneurons and principal cells and resultant excessive circuit sensitivity and output. AnkG isoform imbalance is a novel molecular endophenotype and potential therapeutic target.

Data errors in the National Hip Fracture Database: a local validation study.

AIMS: We present an audit comparing our level I major trauma centre's data for a cohort of patients with hip fractures in the National Hip Fracture Database (NHFD) with locally held data on these patients. PATIENTS AND METHODS: A total of 2036 records for episodes between July 2009 and June 2014 were reviewed. RESULTS: The demographics of nine patients were recorded incorrectly. The rate of incorrect data in operation codes was most significant with overall accuracy of 0.637 (95% CI 0.615 to 0.658). The sensitivity of NHFD coding ranged from 0.250 to 1.000 and the specificity 0.879 to 0.999. The recording of cementation had a sensitivity of 0.932 and specificity of 0.713. The recording of total hip arthroplasty had a sensitivity of 0.739 and specificity of 0.983. The overall accuracy of mortality data was 0.942 (95% CI 0.931 to 0.952), with sensitivity of 0.967 and specificity of 0.419. CONCLUSION: This paper highlights the need for local audit of the integrity of data uploaded to the NHFD. Cite this article: Bone Joint J 2016;98-B:1406-9.

Oxytocin-dependent consolation behavior in rodents.

Consolation behavior toward distressed others is common in humans and great apes, yet our ability to explore the biological mechanisms underlying this behavior is limited by its apparent absence in laboratory animals. Here, we provide empirical evidence that a rodent species, the highly social and monogamous prairie vole (Microtus ochrogaster), greatly increases partner-directed grooming toward familiar conspecifics (but not strangers) that have experienced an unobserved stressor, providing social buffering. Prairie voles also match the fear response, anxiety-related behaviors, and corticosterone increase of the stressed cagemate, suggesting an empathy mechanism. Exposure to the stressed cagemate increases activity in the anterior cingulate cortex, and oxytocin receptor antagonist infused into this region abolishes the partner-directed response, showing conserved neural mechanisms between prairie vole and human.

Intravesical chondroitin sulphate for interstitial cystitis/painful bladder syndrome.

INTRODUCTION: Interstitial cystitis/painful bladder syndrome (IC/PBS) is a chronic inflammatory condition of the bladder. Bladder instillation is one avenue of treatment but evidence for its effectiveness is limited. Chondroitin sulphate solution 2.0% (Urocyst) is a glycosaminoglycan (GAG) replenishment therapy instilled for patients with IC/PBS. We assessed its effectiveness for treating IC/PBS in Northern Ireland. METHODS: Patients with IC/PBS were assessed with the O'Leary-Sant interstitial cystitis index score and global response assessment questionnaire prior to commencing treatment. Assessment with these questionnaires was performed after 6 treatments (10 weeks) and again after 10 treatments (24 weeks). Assessment end points were pain, urgency, symptom score and problem score. RESULTS: Data was collected on 10 patients, 9 female and 1 male. 6 patients had failed RIMSO-50 dimethyl sulphoxide (DMSO) 50% treatment prior. At baseline the mean pain score was 6.6, urgency score 7.00, symptom score 13.5 and problem score 12.5. After 24 weeks the mean pain score fell to 2.0, urgency score to 1.80, symptom score to 6.89 and problem score to 5.67. At 10 weeks the global response to treatment was 100%. Nocturia was the first symptom to improve with urgency and pain following. No side effects were noted during instillation and all patients tolerated the treatments. CONCLUSION: IC/PBS is a difficult disease to treat. It requires a multimodal approach. We found that intravesical chondroitin sulphate reduced pain, urgency and O'Leary-Sant symptom and problem scores in patients with IC/PBS. All patients tolerated the treatment and no side effects were reported.

Surgical treatment of pediatric epileptic encephalopathies.

Pediatric epileptiform encephalopathies are a group of neurologically devastating disorders related to uncontrolled ictal and interictal epileptic activity, with a poor prognosis. Despite the number of pharmacological options for treatment of epilepsy, many of these patients are drug resistant. For these patients with uncontrolled epilepsy, motor and/or neuropsychological deterioration is common. To prevent these secondary consequences, surgery is often considered as either a curative or a palliative option. Magnetic resonance imaging to look for epileptic lesions that may be surgically treated is an essential part of the workup for these patients. Many surgical procedures for the treatment of epileptiform encephalopathies have been reported in the literature. In this paper the evidence for these procedures for the treatment of pediatric epileptiform encephalopathies is reviewed.

Social status alters defeat-induced neural activation in Syrian hamsters.

Although exposure to social stress leads to increased depression-like and anxiety-like behavior, some individuals are more vulnerable than others to these stress-induced changes in behavior. Prior social experience is one factor that can modulate how individuals respond to stressful events. In this study, we investigated whether experience-dependent resistance to the behavioral consequences of social defeat was associated with a specific pattern of neural activation. We paired weight-matched male Syrian hamsters in daily aggressive encounters for 2 weeks, during which they formed a stable dominance relationship. We also included control animals that were exposed to an empty cage each day for 2 weeks. Twenty-four hours after the final pairing or empty cage exposure, half of the subjects were socially defeated in 3, 5-min encounters, whereas the others were not socially defeated. Twenty-four hours after social defeat, animals were tested for conditioned defeat in a 5-min social interaction test with a non-aggressive intruder. We collected brains after social defeat and processed the tissue for c-Fos immunoreactivity. We found that dominants were more likely than subordinates to counter-attack the resident aggressor during social defeat, and they showed less submissive and defensive behavior at conditioned defeat testing compared with subordinates. Also, social status was associated with distinct patterns of defeat-induced neural activation in select brain regions, including the amygdala, prefrontal cortex, hypothalamus, and lateral septum. Our results indicate that social status is an important form of prior experience that predicts both initial coping style and the degree of resistance to social defeat. Further, the differences in defeat-induced neural activation suggest possible brain regions that may control resistance to conditioned defeat in dominant individuals.

Trends in the incidence rates of tonsil and base of tongue cancer in England, 1985-2006.

INTRODUCTION: The aim of this study was to investigate whether incidence rates of tonsil and base of tongue cancer in England are increasing using data from the UK cancer registry. SUBJECTS AND METHODS: Cancer registrations for oral cavity and oropharynx cancer from 1985-2006 in England were obtained from the National Cancer Information Service. Population estimates were obtained from the Office for National Statistics. Age-adjusted incidence rates and age-specific incidence rates were calculated. The sexes were considered separately as incidence rates are known to differ significantly between men and women. Linear regression was performed to establish whether there was a relationship between incidence rates and time. RESULTS: There has been an increase in all oral cavity and oropharyngeal cancer in the study period. Linear regression analysis suggests that approximately 90% of the variance in age-adjusted incidence rates for men and women for tonsil, base of tongue and other oral cavity cancer is explained by the passage of time. For other oropharyngeal cancer, the variance is 62% and 46% in men and women, respectively. The estimated annual percentage change from 1985 to 2006 in age-adjusted incidence rates for tonsil and base of tongue cancer is 5.7% and 6.7% for men, and 4.3% and 6.5% for women, respectively. CONCLUSIONS: This study confirms a wide-spread clinical impression that there has been an increase in age-adjusted incidence rates, between 1985 and 2006, in all oral cavity cancer in England. The age range 40-69 years has seen the biggest increases in age-specific incidence rates for tonsil and base of tongue cancer. This reflects the findings of similar studies in other countries.

Marcadores de riesgo de estenosis carotidea en pacientes geriátricos / Risk markers of carotid stenosis in old patients

INTRODUCCIÓN. Las Enfermedades Cerebro-Vasculares son la tercera causa de muerte en Cuba y la primera causa de pérdida de independencia y habilidad; de ellas el 80% son de tipo Isquémico y se estima que el 40% son provocadas por Estenosis de la Arteria Carótida Extracraneal. OBJETIVOS: descubrir marcadores de riesgo para la estenosis carotidea en los pacientes geriátricos de nuestra área. PACIENTES Y MÉTODOS: realizamos un estudio de serie de casos buscando soplo carotideo asintomático, a través del examen físico y confirmación con Ecodoppler, en pacientes procedentes de instituciones de salud del unicipio Holguín, excluyendo a todos aquellos con antecedentes previos de enfermedad cerebro-vascular isquémica. RESULTADOS. Se estudiaron 55 pacientes mayores de 60 años, 19 tenían soplo a nivel de la carótida predominando el sexo masculino. La enfermedad vascular periférica, el hábito de fumar y la Hipertensión Arterial resultaron los marcadores de riesgo más frecuentes. Confirmamos con el estudio hemodinámico que todos tenían algún grado de estenosis carotidea, el 79% en el rango de 50 al 69%. CONCLUSIÓN. La enfermedad vascular periférica, el hábito de fumar y la Hipertensión Arterial resultaron los marcadores de riesgo más frecuentes (AU)

INTRODUCTION. The cerebrovascular Diseases are the third cause of death in Cuba and the first cause of loss of independence and ability; of them 80% are of ischemic type and esteem that 40% are caused by stenosis of the extracraneal Carotid artery. OBJECTIVES: to discover markers of risk for the carotid stenosis in the aged patients of our area. PATIENTS AND METHODS: we made a study of series of cases looking for asymptomatic carotid blowing, through physical examination and confirmation with Duplex scan, in patients coming from institutions of health of the Holguín municipality, excluding all those with previous antecedents of disease brain-vascular ischemic. RESULTS: 55 greater patients of 60 years studied, 19 had blowing at level of the carotid predominating masculine sex. The peripheral vascular disease, the habit to smoke and the Arterial Hypertension were the more frequent markers of risk. We confirmed with the hemodynamic study that all had some degree of carotid stenosis, 79% in the rank from 50 to 69%. CONCLUSION: the peripheral vascular disease, the habit to smoke and the Arterial Hypertension were the markers from risk more frequent (AU)

High-speed detection of occult tumor cells in peripheral blood.

Although detection of tumor cells in peripheral blood using imitiunocytochemistry and optical scanning is a promising method for screening and monitoring cancer, it poses a major technical challenge due to the extremely low tumor cell concentration in blood. The preferred detection method - digital microscopy - is far too slow for analysis of the large numbers of cells required for statistical validity. We describe here a novel prescan instrument that rapidly identifies a small number of candidates for subsequent examination by digital microscopy to determine if they are genuine tumor cells. The prescan is 500 times faster than digital microscopy and yet has a similar sensitivity. The high prescan speed is accomplished by trading resolution for field of view. The resolution of the prescan is determined by the laser spot size of about 10 microns. While this resolution is much coarser than the submicron resolution of microscopes, it is still sufficient for detecting fluorescent cells because it matches the size of a typical cell. The wide field of view and high scan rate are enabled by a novel application of fiber optics.

First Report of a Leaf Blight of Onion Caused by Xanthomonas spp. in Georgia.

In October of 2001 and 2002, a leaf blight was reported affecting Vidalia onion (Allium cepa) cvs. Pegasus and Sweet Vidalia, respectively, in one field each. Lesions on onion seedlings began as a water-soaked, tip dieback that gradually blighted the entire leaf. Symptoms on onion transplants appeared as elongated, water-soaked lesions that typically collapsed at the point of initial infection. In both cases, disease was very severe on seedlings, and disease incidence was 50% or more in both fields. Warm temperatures combined with overhead irrigation and above average rainfall likely enhanced the severity and spread of disease. Disease was not detected on more mature onions once cool, dry conditions occurred later in the season, and no significant economic loss occurred. Seed was tested from seed lots of the aforementioned cultivars and Xanthomonas spp. were not found. Diseased tissue was macerated in sterile, phosphate-buffered saline, and 10 µl of the resulting suspension was streaked on nutrient agar plates. Yellow-pigmented, gram-negative, rod-shaped bacteria were isolated routinely from diseased tissue. Bacteria were catalase-positive, cellulolytic, oxidase-negative, amylolytic, proteolytic, and utilized glucose in an oxidative manner. Analysis of whole cell, fatty acid methyl esters (FAME) using the Microbial Identification System (MIS, Sherlock version 3.1; MIDI, Inc., Newark, DE) identified four representative strains of the bacterium as a pathovar of Xanthomonas axonopodis (similarity indices 0.75 to 0.83). Known Xanthomonas spp. from onion from Colorado and Texas (1,2) had similar FAME profiles when analyzed by the MIDI system. Onion plants were grown under greenhouse conditions for 2 months and inoculated by injecting the base of a quill with 1.0 ml of bacterial suspensions (1 × 107 CFU ml-1) of the Xanthomonas sp. isolated from Georgia, and negative controls were inoculated with 1 ml of sterile water. Disease symptoms developed on plants inoculated with bacterial suspensions in 4 to 7 days and Xanthomonas sp. was isolated from the lesions produced. Disease symptoms occurred when the same suspension was sprayed on onion foliage. No symptoms occurred on plants inoculated with 1 ml of sterile water. To our knowledge, this is the first report of Xanthomonas spp. affecting Vidalia onions. References: (1) T. Isakeit et al. Plant Dis. 84:201, 2000. (2) H. F. Schwartz and K. Otto. Plant Dis. 84:922, 2000.

Evaluation of a training and diagnostic ultrasound service for general practitioners using narrowband ISDN.

We carried out a four-month pilot study of telemedicine for the delivery of training and diagnostic ultrasound services for general practitioners (GPs). Two health centres and a district general hospital were linked using ISDN (128 kbit/s) and PC-based videoconferencing units. Sixteen videoconferencing sessions were conducted, with 64 patients scanned over the ISDN link for a range of clinical conditions. Nine cases of pathology were demonstrated and confirmed by a consultant radiologist. A total of 229 images were transmitted using the store-and-forward facility, of which 194 (85%) images were of diagnostic quality and 35 (15%) were regarded as non-diagnostic. Allowing for sampling error, we would expect 79-89% of stored images to provide diagnostic information at a 95% confidence level. A total of 115 store-and-forward images (SAFI) were randomly selected and compared with hard-copy images (HCI) for technical quality. There was a significant difference in the quality of images. The results show that SAFI are far superior to HCI, traditionally used by clinicians for making primary diagnosis and that the superior quality of the SAFI improved diagnostic accuracy. This pilot study showed a high degree of confidence in videoconferencing for training GPs to carry out ultrasound clinics, enhancing their ability to make accurate diagnoses, and providing them with immediate access the second and higher opinion.

Does nitric oxide play a role in stimulus-secretion and/or synthesis-secretion coupling of insulin?

By using the perfused rat pancreas model and the nitric oxide synthase inhibitor, nitro-arginine methyl ester (NAME), we examined the hypothesis that first-phase potentiation or second-phase inhibition of insulin release due to the amino acid arginine (or both) are the result of its conversion to nitric oxide (NO). In the presence of 16.7 mM glucose, 20 mM arginine caused a first-phase potentiation of insulin release when compared with glucose controls, while inhibiting the second-phase insulin release. When 20 mM NAME was added in addition to 20 mM arginine and 16.7 mM glucose, the total insulin released during the first secretory phase was not significantly different from that of the glucose plus arginine group, suggesting that inhibition of NO production does not affect arginine-potentiated first-phase insulin release. Similarly, the presence of NAME failed to reverse the arginine inhibition of second-phase insulin release. The presence of NAME resulted in a more pronounced inhibition of insulin secretion. Correspondingly, compared with the glucose-only controls, the presence of 20 mM NAME plus 16.7 mM glucose resulted in a significant decrease in insulin release during the second phase, whereas the presence of NAME did not affect first-phase glucose-stimulated insulin release. Thus we conclude that the conversion of arginine to nitric oxide does not play a significant role in glucose-stimulated first-phase potentiation or second-phase inhibition of insulin release due to arginine.

Predictors of childhood immunization completion in a rural population.

Despite the availability of effective vaccines, immunization rates among two-year old children continue to be low in many areas of the United States including rural West Virginia. The goal of this study was to identify barriers to childhood immunization in rural West Virginia and determine factors that were important in the completion of the childhood immunization schedule. A telephone survey was used to collect data from a randomly selected sample of 316 mothers, of two-year olds, from 18 rural counties of West Virginia. Results indicated that two-thirds or 65% of the children in the study sample had completed their recommended immunizations by two years of age. Immunization barriers identified in this study include: living in health professional shortage areas, lack of health insurance, negative beliefs and attitudes regarding childhood immunizations, problems accessing the immunization clinic, and a perception of inadequate support from the immunization clinic. Results of the structural equation modeling, using LISREL-8, indicated that 20% of the variation in immunization completion (R2 = 0.197) was explained by attitude towards immunization and perceived support received from the immunization clinic. Furthermore, 42% of the variation in attitude towards immunization (R2 = 0.419) was explained by immunization-related beliefs, and 28% of the variation in immunization-related beliefs (the R2 = 0.277) was explained by general problems faced during immunization and perceived clinic support. The study concluded that positive immunization-related beliefs and attitudes, support from the immunization clinic, and ease of the immunization seeking process are important factors in the timely completion of the childhood immunization schedule.

Reductions in criminality subsequent to group, individual, and family therapy in adolescent residential and day treatment settings.

The complete population of adolescents in a residential and day-treatment program over a 4-year period, 532 youths, served in two studies. Along with residential and day-treatment settings, predictive variables of interest were the number of hours spent in group, individual, and family therapy. A total of 227 adolescents qualified for Study 1 which found a reduction of rates of criminal charges from pre- to posttreatment. Study 1 also found that hours in group therapy explained the most variance in the reduction in rates of criminal charges, followed closely by hours in individual therapy. Hours in family therapy was not a significant predictor. A total of 430 adolescents qualified for Study 2, which found that residential treatment was associated with greater reductions in adult correctional commitments than day treatment. Implications stress the need for further research examining the relationships between therapeutic components of residential treatment and behavioral outcomes.

Arachidonic acid directly mediates the rapid effects of 24,25-dihydroxyvitamin D3 via protein kinase C and indirectly through prostaglandin production in resting zone chondrocytes.

Prior studies have shown that 24,25-dihydroxyvitamin D3 [24,25-(OH)2D3] plays a major role in resting zone chondrocyte differentiation and that this vitamin D metabolite regulates both phospholipase A2 and protein kinase C (PKC) specific activities. Arachidonic acid is the product of phospholipase A2 action and has been shown in other systems to affect a variety of cellular functions, including PKC activity. The aim of the present study was to examine the interrelationship between arachidonic acid and 24,25-(OH)2D3 on markers of proliferation, differentiation, and matrix production in resting zone chondrocytes and to characterize the mechanisms by which arachidonic acid regulates PKC, which was shown previously to mediate the rapid effects of 24,25-(OH)2D3 and arachidonic acid on these cells. Confluent, fourth passage resting zone cells from rat costochondral cartilage were used to evaluate these mechanisms. The addition of arachidonic acid to resting zone cultures stimulated [3H]thymidine incorporation and inhibited the activity of alkaline phosphatase and PKC, but had no effect on proteoglycan sulfation. In contrast, 24,25-(OH)2D3 inhibited [3H]thymidine incorporation and stimulated alkaline phosphatase, proteoglycan sulfation, and PKC activity. In cultures treated with both agents, the effects of 24,25-(OH)2D3 were reversed by arachidonic acid. The PKC isoform affected by arachidonic acid was PKCalpha; cytosolic levels were decreased, but membrane levels were unaffected, indicating that translocation did not occur. Arachidonic acid had a direct effect on PKC in isolated plasma membranes and matrix vesicles, indicating a nongenomic mechanism. Plasma membrane PKCalpha was inhibited, and matrix vesicle PKCzeta was stimulated; these effects were blocked by 24,25-(OH)2D3. Studies using cyclooxygenase and lipoxygenase inhibitors indicate that the effects of arachidonic acid are due in part to PG production, but not to leukotriene production. This is supported by the fact that H8-dependent inhibition of protein kinase A, which mediates the effects of PGE2, had no effect on the direct action of arachidonic acid but did mediate the role of arachidonic acid in the cell response to 24,25-(OH)2D3. Diacylglycerol does not appear to be involved, indicating that phospholipase C and/or D do not play a role. Gamma-linolenic acid, an unsaturated precursor of arachidonic acid, elicited a similar response in matrix vesicles but not plasma membranes, whereas palmitic acid, a saturated fatty acid, had no effect. These data suggest that arachidonic acid may act as a negative regulator of 24,25-(OH)2D3 action in resting zone chondrocytes.

Delayed repair of open depressed skull fracture.

INTRODUCTION: Elevation and repair of an open depressed skull fracture is often thought of as an emergency procedure. Common indications for emergent elevation of a depressed skull fracture have been dural tear, seizure, gross contamination or mass effect from bone or a sizable underlying intracerebral hematoma. As treatment of head injury moves towards management of cerebral perfusion pressure (CPP) rather than intracranial pressure (ICP), we sought a way to maximize CPP in the initial treatment of head-injured patients with depressed skull fractures that would eventually require surgery by delaying surgery, when possible, until after the initial period of elevated ICP. METHODS: Over a 12-month period, 7 patients (all male, ages 1-15 years) were admitted to our institution with the diagnosis of open depressed skull fracture without significant mass effect requiring urgent decompression. All had significant head trauma with altered mental status and a Glasgow Coma Score of 3-12. Patients were treated with antibiotic prophylaxis (nafcillin, ceftriaxone, metronidazole), seizure prophylaxis (phenytoin) and underwent CPP management in an intensive care unit setting as indicated by intracranial pressure monitoring or clinical assessment. Length of medical management of CPP ranged from 4 to 12 days. Upon stabilization of CPP, patients were operated for repair of their dural, bone and scalp injuries. RESULTS: All 7 patients treated in the above manner suffered no ill effects from their delayed surgery: there was no meningitis, no late seizures, and no cerebrospinal fluid leak. Complications attributable to delay were not present at follow-up ranging from 12 to 24 months. CONCLUSIONS: We have delayed surgery for repair of open depressed skull fractures in order to maximize medical management of CPP in the setting of acute trauma. Among other considerations, the risk of intraoperative hypotension occurring at a time of acutely raised ICP was avoided by this delay. We conclude that there is a role, in this specifically defined subset of head trauma patients, for delayed surgical repair of open depressed skull fractures.

Arachidonic acid is an autocoid mediator of the differential action of 1,25-(OH)2D3 and 24,25-(OH)2D3 on growth plate chondrocytes.

Prior studies have shown that 24,25-(OH)2D3 and 1,25-(OH)2D3 regulate protein kinase C (PKC) in costochondral chondrocytes in a cell maturation-dependent manner, with 1,25-(OH)2D3 affecting primarily growth zone (GC) cells and 24,25-(OH)2D3 affecting primarily resting zone (RC) cells. In addition, 1,25-(OH)2D3 has been shown to increase phospholipase A2 activity in GC, while 24,25-(OH)2D3 has been shown to decrease phospholipase A2 activity in RC. Stimulation of phospholipase A2 in GC caused an increase in PKC, whereas inhibition of phospholipase A2 activity in RC cultures increased both basal and 24,25-(OH)2D3-induced PKC activity, suggesting that phospholipase A2 may play a central role in mediating the effects of the vitamin D metabolites on PKC. To test this hypothesis, RC and GC cells were cultured in the presence and absence of phospholipase A2 inhibitors (quinacrine and oleyloxyethylphosphorylcholine [OEPC]), phospholipase A2 activators (melittin and mastoparan), or arachidonic acid alone or in the presence of the target cell-specific vitamin D metabolite. PKC specific activity in the cell layer was determined as a function of time. Phospholipase A2 inhibitors decreased both basal and 1,25-(OH)2D3-induced PKC activity in GC. When phospholipase A2 activity was activated by inclusion of melittin or mastoparan in the cultures, basal PKC activity in RC was reduced, while that in GC was increased. Similarly, melittin and mastoparan decreased 24,25-(OH)2D3-induced PKC activity in RC and increased 1,25-(OH)2D3-induced PKC activity in GC. For both cell types, the addition of arachidonic acid to the culture media produced an effect on PKC activity that was similar to that observed when phospholipase A2 activators were added to the cells. These results demonstrate that vitamin D metabolite-induced changes in phospholipase A2 activity are directly related to changes in PKC activity. Similarly, exogenous arachidonic acid affects PKC in a manner consistent with activation of phospholipase A2. These effects are cell maturation- and time-dependent and metabolite-specific.

Differential insulin secretory responses to cationic and branched-chain amino acids.

The long-term effects on the dynamics of glucose-stimulated insulin release by the cationic amino acids arginine and lysine and the branched-chain amino acid leucine were examined. The rat pancreas perfusion model was utilized and particular emphasis was placed on modulation of the glucose-stimulated synthesis-secretion coupling second phase. In the presence of 16.7 mM glucose, 20 mM arginine, lysine, and leucine each potentiated first-phase insulin release by approximately 50%, compared to glucose-only controls. Conversely, in the presence of 16.7 mM glucose, 20 mM arginine resulted in a 50% inhibition of second-phase (min 30-120) insulin release compared to glucose-only controls. Similarly, 20 mM lysine in the presence of 16.7 mM glucose also caused a comparable inhibition of second-phase insulin release. Paradoxically, 20 mM leucine in the presence of glucose had no significant inhibitory effect on second-phase glucose-stimulated insulin release. The data suggest that these amino acids mediate their effects on first- and second-phase insulin release via different mechanisms of action, which may reflect differences and similarities in charge and/or metabolic fates within the beta cell. The data do not support the hypothesis that cationic charge is solely involved in the stimulus-secretion component, since all three amino acids caused comparable potentiation of first-phase insulin release. Conversely, the inhibitory component of the second secretory phase may be mediated via a common charge-related metabolic pathway in the synthesis-secretion coupling mechanism, since only the cationic amino acids inhibit this component, whereas leucine has no such effect.