Microvascular Blood Flow Improvement in Hyperglycemic Obese Adult Patients by Hypocaloric Diet.

The present study was aimed to assess the changes in skin microvascular blood flow (SBF) in newly diagnosed hyperglycemic obese subjects, administered with hypocaloric diet. Adult patients were recruited and divided in three groups: NW group (n=54), NG (n=54) and HG (n=54) groups were constituted by normal weight, normoglycemic and hyperglycemic obese subjects, respectively. SBF was measured by laser Doppler perfusion monitoring technique and oscillations in blood flow were analyzed by spectral methods under baseline conditions, at 3 and 6 months of dietary treatment. Under resting conditions, SBF was lower in HG group than in NG and NW ones. Moreover, all subjects showed blood flow oscillations with several frequency components. In particular, hyperglycemic obese patients revealed lower spectral density in myogenic-related component than normoglycemic obese and normal weight ones. Moreover, post-occlusive reactive hyperemia (PORH) was impaired in hyperglycemic obese compared to normoglycemic and normal weigh subjects. After hypocaloric diet, in hyperglycemic obese patients there was an improvement in SBF accompanied by recovery in myogenic-related oscillations and arteriolar responses during PORH. In conclusion, hyperglycemia markedly affected peripheral microvascular function; hypocaloric diet ameliorated tissue blood flow.

Further evidence of a prolonged hypotensive and a bradycardic effect after mandibular extension in normal volunteers.

We previously reported that in normotensive humans submaximal mouth opening (mandibular extension) obtained by an ad hoc dilator (spring device), associated with partial masticatory movements and prolonged for 10 minutes is followed by a long-lasting reduction of blood pressure (BP) and heart rate (HR). Similar results were obtained by us in anesthetized rats. A recent independent study failed to confirm the results in the normotensive human. We reassessed, in 25 normotensive volunteers, the effects on BP and HR of mandibular extension obtained by the spring device associated with partial masticatory movements compared to a control procedure, consisting in keeping a tongue depressor between the incisor teeth. Both procedures were applied for 10 minutes and systolic BP (SBP), diastolic BP (DBP) and HR were measured every 10 minutes by an automatic recorder, for 30 minutes before and 120 minutes after the procedures in seated subjects watching nature documentary films on laptop screen.Baseline levels (mean of the last 3 measurements before procedure) did not significantly differ between the experimental and control sessions. Two way repeated measures ANOVA on absolute (recorded) values did not reveal a significant main effect of treatment for SBP, DBP and HR, but a significant main effect of time (P<0.001) for BP and HR. In addition, a significant interaction of time and treatment was found for SBP (P<0.001) and DBP (P=0.005), but not for HR. In addition, two way repeated measures ANOVA was done on changes from baseline obtaining a significant main effect of treatment (P<0.001) and time (P<0.001) and a significant interaction of time and treatment for SBP (P<0.001) and DBP (P<0.01). Post-hoc comparisons revealed significantly lower values for SBP and DBP in experimental compared to control values at almost all times and this decrement was by about 5 mmHg. Furthermore, for both absolute values and changes from baseline, the interaction effect was, for BP, of a qualitative type as indicated by an opposite effect in the time-course between control and experimental sessions. This study thus provides confirmatory evidence that submaximal mouth opening for a relatively brief time is followed by prolonged albeit small reductions of BP in normotensive human volunteers.

Lower weight loss expectations and healthier eating attitudes in older overweight and obese women attempting weight loss.

Weight loss outcomes in overweight and obese individuals may be influenced by individual weight loss expectations (WLEs). Research on these phenomena in older women is lacking. This cross-sectional study compared groups of younger and older women on their WLEs and related attitudes (body dissatisfaction and disordered eating). Twenty-six younger (18-38 years) and 33 older (60-78 years) overweight and obese women were recruited from a weight loss clinic, prior to treatment. Disordered eating attitudes and body dissatisfaction were assessed using validated questionnaires and a pictorial figure-choice scale. Participants reported 10 WLEs categorized according to personal, lifestyle and social factors. Overall, women with a higher body mass index had greater WLEs. Older women reported lower WLEs than younger women (-14.5 kg vs. -22.4 kg) in all categories except past weight. Older women perceived that career success would necessitate the greatest level of weight loss (-18.5 kg), whereas younger women derived their greatest WLEs from mass media (-28.5 kg). Both older and younger groups perceived that their families would be supportive of the smallest amount of weight loss (-8.4 and -17.6 kg, respectively). The groups did not differ on body dissatisfaction, but younger women's disordered eating attitudes were significantly higher (p < .001). Older overweight and obese women have lower WLEs than younger women but experience similar levels of body dissatisfaction and healthier eating attitudes. The attitudinal constructs underlying these differences may be useful in clinical practice to tailor age-specific weight loss interventions.

Hypolipidic diet and phytosubstance supplement in hypercholesterolemia.

AIM: This study aimed to evaluate the effects of phyto-supplements on hyperlipidemia. METHODS: For this study 191 patients, affected by hyperlipidemia, attending the Outpatient Clinics of Clinical Medicine Department, were recruited. The patients were divided in two groups. The first group (80) has been treated with hypolipidic diet for six months (group D). The second one (111) has been administered with hypolipidic diet and supplement (red yeast, guggulsterones, flavonoid, sylimarin) (group E). Anthropometric measurements and bioimpedance analysis were evaluated before and after treatment. Moreover, total cholesterol, LDL, HDL, triglycerides (TG) and hepatic transaminases (AST, ALT) were measured before, after 3 and 6 months of treatment. RESULTS: D group showed a significant reduction in BMI (32.6 ± 0.7 vs. 34.3 ± 0.7 kg/m²), waist circumference (104.4 ± 1.6 vs. 108.3 ± 1.5 cm), hip circumference (107.9 ± 1.1 vs. 111.2 ± 1.1 cm), total cholesterol (214.2 ± 3.7 vs. 236.6 ± 2.2 mg/dL, -9.4 ± 68.2%), LDL cholesterol (133 ± 3 vs. 152.9 ± 2.8 mg/dL, -13 ± 7.1%). E group showed a significant reduction in BMI (30.2 ± 0.7 vs. 32.6 ± 0.6 kg/m²), waist circumference (94.5 ± 1.6 vs. 101.3 ± 1.3 cm), hip circumference (106.6 ± 1.1 vs. 110.5 ± 1 cm), total cholesterol (212.4 ± 3.7 vs. 256.9 ± 2.1 mg/dL, -17.3 ± 76.2%), LDL cholesterol (133.4 ± 3.4 vs. 168.4 ± 2.3 mg/dL, -20.8 ± 47.8%). CONCLUSION: Low fat diet, associated to phyto-substance supplement, have been proven useful to decrease serum cholesterol level and to improve nutritional status.

Weight loss expectations and body dissatisfaction in young women attempting to lose weight.

BACKGROUND: Unrealistic weight loss expectations (WLEs) and greater body dissatisfaction may be associated with the poor long-term outcomes of dietary and lifestyle weight loss treatments. We evaluated the association between body size, WLEs and body dissatisfaction in young women attempting to lose weight. METHODS: Forty-four young healthy women [age range 18-35 years, body mass index (BMI) range 23-40 kg/m2] were recruited. Women were classified as obese (BMI ≥ 30.0 kg/m2) and non-obese (BMI <30.0 kg/m2). The Body Dissatisfaction scale of the Eating Disorder Inventory-2 and the Body Image Assessment for Obesity silhouette charts were used to assess body dissatisfaction. WLEs were categorised according to personal (ideal, happiness, satisfaction, weight history), lifestyle (fitness) and social (career, family acceptance, peer acceptance, mass media, social pressure) factors. Individual WLEs were compared with recommended clinical targets (5%, 10% and 20%) for weight loss. RESULTS: Body dissatisfaction was lower in non-obese subjects and was directly associated with BMI (P < 0.05). WLEs were directly associated with BMI and the obese group reported greater expectations. Five non-obese subjects (23%) desired to lose more than 20% of their body weight, whereas the proportion was significantly higher in the obese group (17 subjects; 74%). Subjects derived the greatest WLEs from mass media, whereas they perceived that family and friends were supportive of a lesser degree of weight loss. CONCLUSIONS: We observed a mismatch between clinical and personal expectations, and social pressure and interpersonal relationships appear to have a prominent role with respect to influencing the association.

Association of the body adiposity index (BAI) with metabolic risk factors in young and older overweight and obese women.

PURPOSE: Body adiposity index (BAI) is a novel index for the assessment of percentage fat mass (FM%). We tested the association between BAI and metabolic outcomes in overweight and obese women of different ages. METHODS: 260 young women (24.7 ± 5.3 years, 31.0 ± 5.0 kg/m(2)) and 328 older women (66.9 ± 4.6 years, 34.8 ± 4.7 kg/m(2)) were recruited. BAI was calculated using hip circumference and height. Bioimpedance analysis was used to measure FM%. Metabolic risk was assessed using a composite z score integrating standardised measurements of fasting glucose, total cholesterol, liver enzymes and triglycerides. RESULTS: The association between BAI and FM% was modest in both young (r = 0.56, p < 0.001) and older (r = 0.49, p < 0.001) groups. BAI was directly associated with metabolic risk in young women (r = 0.29, p < 0.001), whereas it showed a weak, inverse association in the older group (r = -0.14, p = 0.01). CONCLUSIONS: BAI validity needs to be re-assessed in older individuals for better definition of its predictive accuracy.

Long-term remodeling of rat pial microcirculation after transient middle cerebral artery occlusion and reperfusion.

OBJECTIVE: The aim of this study was to assess the in vivo structural and functional remodeling of pial arteriolar networks in the ischemic area of rats submitted to transient middle cerebral artery occlusion (MCAO) and different time intervals of reperfusion. METHODS AND RESULTS: Two closed cranial windows were implanted above the left and right parietal cortex to observe pial microcirculation by fluorescence microscopy. The geometric characteristics of pial arteriolar networks, permeability increase, leukocyte adhesion and capillary density were analyzed after 1 h or 1, 7, 14 or 28 days of reperfusion. MCAO and 1-hour reperfusion caused marked microvascular changes in pial networks. The necrotic core was devoid of vessels, while the penumbra area presented a few arterioles, capillaries and venules with severe neuronal damage. Penumbra microvascular permeability and leukocyte adhesion were pronounced. At 7 days of reperfusion, new pial arterioles were organized in anastomotic vessels, overlapping the ischemic core and in penetrating pial arterioles. Vascular remodeling caused different arteriolar rearrangement up to 28 days of reperfusion and animals gradually regained their motor and sensory functions. CONCLUSIONS: Transient MCAO-induced pial-network remodeling is characterized by arteriolar anastomotic arcades. Remodeling mechanisms appear to be accompanied by an increased expression of nitric oxide synthases.

Persistent effects after trigeminal nerve proprioceptive stimulation by mandibular extension on rat blood pressure, heart rate and pial microcirculation.

The trigemino-cardiac reflex is a brainstem reflex known to lead to a decrement in heart rate and blood pressure, whereas few data have been collected about its effects on the cerebral hemodynamic. In this study we assess the in vivo effects of trigeminal nerve peripheral stimulation by mandibular extension on pial microcirculation and systemic arterial blood pressure in rats. Experiments were performed in male Wistar rats subjected to mandibular extension obtained inserting an ad hoc developed retractor between the dental arches. Mean arterial blood pressure and heart rate were recorded and the pial arterioles were visualized by fluorescence microscopy to measure the vessel diameters before (15 minutes) during (5-15 minutes) and after (80 minutes) mandibular extension. While in control rats (sham-operated rats) and in rats subjected to the dissection of the trigeminal peripheral branches mean arterial blood pressure, heart rate and pial microcirculation did not change during the whole observation period (110 minutes), in rats submitted to mandibular extension, mean arterial blood pressure, heart rate and arteriolar diameter significantly decreased during stimulation. Afterward mean arterial blood pressure remained reduced as well as heart rate, while arteriolar diameter significantly increased evidencing a vasodilatation persisting for the whole remaining observation time. Therefore, trigeminal nerve proprioceptive stimulation appears to trigger specific mechanisms regulating systemic arterial blood pressure and pial microcirculation.

Rat Pial Microvascular Responses to Transient Bilateral Common Carotid Artery Occlusion and Reperfusion: Quercetin's Mechanism of Action.

The aim of the present study was to assess quercetin's mechanism of action in rat pial microvessels during transient bilateral common carotid artery occlusion (BCCAO) and reperfusion. Rat pial microcirculation was visualized using fluorescence microscopy through a closed cranial window. Pial arterioles were classified in five orders of branchings. In ischemic rats, 30 min BCCAO and 60 min reperfusion caused arteriolar diameter decrease, microvascular leakage, leukocyte adhesion in venules, and reduction of capillary perfusion. Quercetin highest dose determined dilation in all arteriolar orders, by 40 ± 4% of baseline in order 2 vessels, and prevented microvascular permeability [0.15 ± 0.02 normalized gray levels (NGL)], leukocyte adhesion, and capillary failure. Protein kinase C (PKC) inhibition exerted by chelerythrine prior to quercetin attenuated quercetin-induced effects: order 2 arterioles dilated by 19.0 ± 2.4% baseline, while there was an increase in permeability (0.40 ± 0.05 NGL) and leukocyte adhesion with a marked decrease in capillary perfusion. Tyrosine kinase (TK) inhibition by tyrphostin 47 prior to quercetin lessened smaller pial arterioles responses, dilating by 20.7 ± 2.5% of baseline, while leakage increased (0.39 ± 0.04 NGL) sustained by slight leukocyte adhesion and ameliorated capillary perfusion. Inhibition of endothelium nitric oxide synthase (eNOS) by N(G)-nitro-L-arginine-methyl ester (L-NAME) prior to PKC or TK reduced the quercetin's effects on pial arteriolar diameter and leakage. eNOS inhibition by L-NAME reduced quercetin effects on pial arteriolar diameter and leakage. Finally, combined inhibition of PKC and TK prior to quercetin abolished quercetin-induced effects, decreasing eNOS expression, while blocking ATP-sensitive potassium (K(ATP)) channels by glibenclamide suppressed arteriolar dilation. In conclusion, the protective effects of quercetin could be due to different mechanisms resulting in NO release throughout PKC and TK intracellular signaling pathway activation.

Ageing, adiposity indexes and low muscle mass in a clinical sample of overweight and obese women.

OBJECTIVE: Ageing is associated with a progressive decline in the quantity (mass) and quality (function) of the muscular tissue. To assess the prevalence of low muscle mass (LMM) alone and in combination with high adiposity (LMM-HA) in a clinical representative sample of adult women and to determine how the prevalence of (LMM-HA) changes using different adiposity indexes. METHODS: 763 overweight and obese women (age range: 18-87 years) attending a weight loss clinic. Weight, height, and waist circumference (WC) were measured and BMI calculated. Bioelectrical impedance (BIA) was used to measure fat mass (FM). Skeletal muscle index (SMI) was used for the diagnosis of LMM. Adiposity indexes (BMI, WC, FM%, FM index) were combined with SMI to assess the prevalence of LMM-HA. RESULTS: The prevalence of LMM was 27.4% in women older than 60 years. Established cut-off scores for excess adiposity determined differences in the prevalence of LMM-HA. The lowest was observed using the BMI derived cut-off score (≥30 kg/m(2)), with FM% (≥35%) the most inclusive, classifying more than 90% of sarcopenia cases as LMM-HA. CONCLUSIONS: The prevalence of LMM-HA is different between anthropometric (BMI, WC) and bioimpedance measures (FM% and FMI) of adiposity. The sensitivity of the adiposity indexes for the diagnosis of sarcopenic obesity and its impact on the prediction of cardio-metabolic diseases remain to be tested.

Intentional weight loss in overweight and obese individuals and cognitive function: a systematic review and meta-analysis.

High adiposity in middle age is associated with higher dementia risk. The association between weight loss and cognitive function in older adults is still controversial. A meta-analysis was undertaken to estimate the effectiveness of intentional weight loss on cognitive function in overweight and obese adults. A structured strategy was used to search randomized and non-randomized studies reporting the effect of intentional and significant weight loss on cognitive function in overweight and obese subjects. Information on study design, age, nutritional status, weight-loss strategy, weight lost and cognitive testing was extracted. A random-effect meta-analysis was conducted to obtain summary effect estimates for memory and attention-executive domains. Twelve studies met inclusion criteria. Seven were randomized trials and the remaining five included a control group. A low-order significant effect was found for an improvement in cognitive performance with weight loss in memory (effect size 0.13, 95% CI 0.00-0.26, P=0.04) and attention/executive functioning (effect size 0.14, 95% CI 0.01-0.27, P<0.001). Studies were heterogeneous in study design, sample selection, weight-loss intervention and assessment of cognitive function. Weight loss appears to be associated with low-order improvements in executive/attention functioning and memory in obese but not in overweight individuals.

First-borns have a higher metabolic rate and carry a higher metabolic risk in young women attending a weight loss clinic.

BACKGROUND: Birth order has been associated with variability in early life growth and subsequent obesity risk, but the consequent metabolic risks have not been assessed. OBJECTIVE: To quantify the metabolic risk in young adulthood of being first-born relative to those born second or subsequently. METHODS: Body composition, resting metabolic rate and metabolic risk were assessed in 383 women, aged 18-35 years, from a clinical setting in southern Italy. RESULTS: First-borns had increased body mass index, adiposity and metabolic risk (p<0.05) and increased resting metabolic rate adjusted for fat-free mass (p<0.05) in the Italian women. CONCLUSION: First-born status is associated with significantly elevated metabolic risk in a clinical population of overweight and obese young women attending a weight loss clinic. If these findings are confirmed in other studies, they may suggest that the prevalence of the metabolic syndrome worldwide may increase as a function of the trend to smaller family size.

Assessment of eating behaviour in young women requesting nutritional counselling and their mothers.

OBJECTIVE: The aim of this study was to explore the influence of maternal eating behaviour on a clinical population of young women compared with a non-clinical one. METHODS: A group of 59 young women (age 16-30 yr) attending a weight-loss Clinic and their mothers (n=59; age 37-64 yr) were enrolled. They were compared with a group of female students (n=59; age 18-36 yr) and their mothers (n=59; age 41-67 yr). Body weight and height were measured and body mass index (BMI) calculated. Eating behaviour was assessed by using the Eating Disorders Inventory (EDI), Eating Inventory (EI) and Eating Attitude Test 26 (EAT-26). RESULTS: The EDI-2 scales significantly different between the groups were drive for thinness, bulimia, body dissatisfaction, inadequacy, enteroceptive awareness and insecurity. The EI scales values were all different between the groups and consistently higher in the clinical populations. The differences between groups were even more striking for the EAT-26 scales; the clinical young women had the highest scores. The daughter-mother correlation for each scale in the clinical and non-clinical groups showed that the EDI-2 scales assessing eating behaviour, drive for thinness, bulimia and body dissatisfaction, were significantly related in the non clinical group but not in the clinical group. On the other side, the clinical group showed correlation for the scales assessing psychopathological traits such as perfectionism, interpersonal disrupt, enteroceptive awareness, impulsivity and insecurity. For EI scales the correlation was significant for disinhibition in the non clinical group. A correspondence was observed for dieting in the non clinical group and for food preoccupation in the clinical group. EDI-2, EI and EAT-26 scales assessing eating behaviour were strongly predictive of BMI in both groups. CONCLUSIONS: Maternal eating behaviour influences the young women; in particular mothers-daughters of the clinical group showed some problems, for which they still had to grow up and stand out. Finally, the control population revealed some eating disorders as well.

[Physiology and in vivo measurements of nitric oxide in man]. / Fisiologia e metodi di misura della produzione di ossido nitrico nell'uomo.

Nitric oxide (NO) is a simple molecule, highly conserved across species with important effects on several physiological mechanisms. In the cardiovascular system, NO is tonically released by the endothelial cells in response to shear stress to maintain vascular tone. This effect is due to the relaxation of the vascular smooth muscle cells in the medium layer (tunica media) of the arterial wall. However, NO is also involved in the regulation of synaptic neurotransmission, platelet aggregation, inflammation, appetite, peristalsis, renal metabolism, respiratory function, lipid metabolism and glucose metabolism. Therefore, an abnormal production of NO (over- or under-production) has multi-systemic effects. Metabolic disorders like hypertension, obesity or dyslipidaemia are associated with a reduction of NO production. The mechanisms responsible for a decreased NO synthesis are partially known but oxidative stress, overproduction of endogenous inhibitors of the Nitric Oxide Synthase (NOS) such as asymmetric dimethylarginine (ADMA) and genetic factors may be implicated. The half-life of NO is extremely short in biological samples (t1/2 < or = 0.2 sec) and its in vivo measurement is very difficult. Therefore, indirect methods have been developed to measure the end products of NO metabolism in biological samples. Some of these methods have used stable isotopes to trace the metabolic fate of the precursor of NO (Arginine) and measure the appearance of stable isotopes in the end products [nitrate (NO3), nitrite (NO2), citrulline]. However, the existing methods are expensive, invasive and require complex analytical laboratory techniques.

Validity of some prediction equations to assess resting energy expenditure (REE) in 29 elderly obese subjects (>60 years).

BACKGROUND AND AIMS: Recent estimates in US have shown that more than a third of 65 years old subjects are obese. The objective of this study was to test the accuracy of six prediction equations to estimate resting energy expenditure (REE) in elderly obese subjects (age >60 years). METHODS: Twenty-nine obese Caucasian male (n=8) and female (n=21) subjects (age range: 60-77 years) attended the Outpatient Clinic of the Neuroscience Department of Naples "Federico II" University Medical School (Italy), Section of Aging and Nutrition from January 2005 to January 2006. Weight, height, BMI and body composition (bioimpedance) were measured. REE was measured using a ventilated-hood indirect calorimetry and compared to six prediction equations (Harris-Benedict, Fredrix, Mifflin, Owen, WHO, Livingston). RESULTS: Mean age and body mass index (BMI) were 65.9+/-4.8 years and 36.8+/-5.3 kg/m2, respectively. The measured REE was 1658+/-289 kcal/day. The Harris-Benedict', Owen' and Livingston's equations performed less well than the other equations and they showed a tendency towards underestimation. The equation with the best REE prediction was the Fredrix's one (DeltaREE=-19.4kcal/day) with 66% of REE predictions lying within 10% of measured REE. CONCLUSIONS: These data support the utilization of the Fredrix's equation to calculate REE in obese elderly subjects.

Pial microvascular responses to transient bilateral common carotid artery occlusion: effects of hypertonic glycerol.

OBJECTIVE: The aim of the study was to assess the rat pial microvessel alterations due to transient bilateral common carotid artery occlusion (BCCAO) and to investigate the mechanism of 10% hypertonic glycerol neuroprotection. Our suggestion was that 10% glycerol solution infusion could dilate pial arterioles through nitric oxide release and/or stimulation of ATP-sensitive potassium (K(ATP)) channels. Therefore, we studied the effects of hypertonic glycerol after inhibition of nitric oxide synthase, with N(G)-nitro-L-arginine-methyl ester or N(G)-nitro-L-arginine, or K(ATP) channels with glibenclamide. METHODS: Pial microcirculation of male Wistar rats was visualized by a fluorescent microscopy technique through an open cranial window, using fluorescein isothiocyanate bound to dextran (molecular weight 70 kDa). BCCAO was induced for 30 min and reperfusion lasted 60 min. The arterioles were classified according to the Strahler ordering scheme. Permeability increase was quantified by normalized grey levels (NGL). Leucocytes were stained with rhodamine 6G. Perfused capillary length and capillary red blood cell (RBC) velocity were measured by computer-assisted methods. RESULTS: The arterioles were assigned 5 orders of branchings, from order 1 (diameter 16.0 +/- 2.5 microm) to order 5 (62.0 +/- 5.0 microm). BCCAO caused inhomogenous changes in diameter of arterioles and leakage of fluorescent dextran, that was further enhanced by reperfusion (0.45 +/- 0.05 NGL, p < 0.01). Adhesion of leukocytes to venules was marked and capillary perfusion was reduced by 39.2 +/- 6.0% of baseline as well as capillary RBC velocity. 10% glycerol solution caused an increase in diameter of all arterioles within 25 +/- 2 min of administration (by 20 +/- 5% in order 4, 25 +/- 4% in order 3 and 18 +/- 3% in order 2; p < 0.01). Leakage (0.19 +/- 0.03 NGL, p < 0.01), leukocyte adhesion (2.0 +/- 1.0/100 microm of venular length, p < 0.01) and capillary occlusion (reduction by 13.0 +/- 5.5% of baseline) were prevented compared with controls. Capillary RBC velocity increased compared with controls. N(G)-nitro-L-arginine-methyl ester or N(G)-nitro-L-arginine infused prior to glycerol caused vasoconstriction and reduced the protective effects of hypertonic glycerol on permeability increase. The number of adherent leukocytes and perfused capillary length decreased, while capillary RBC velocity was higher than baseline. Glibenclamide prior to 10% glycerol solution blunted glycerol-induced vasodilatation, but did not affect protection by hypertonic glycerol on blood-brain barrier disruption, leukocyte adhesion and capillary perfusion, preserving high capillary RBC velocity. Papaverine (20 mg/kg body weight) induced an increase in arteriolar diameter, enhancing interstitial edema; adhesion of leukocytes was marked as well as capillary occlusion, while capillary RBC velocity increased. CONCLUSIONS: 10% glycerol solution was able to prevent microvascular alterations due to BCCAO protecting cerebral tissue. The effects appear to be due to hyperosmolality causing stimulation of K(ATP) channels, increase in vessel wall shear stress and release of nitric oxide.

Geometric characteristics of arterial network of rat pial microcirculation.

OBJECTIVE: The aim of the study was to assess the geometric characteristics of rat pial microcirculation and describe the vessel bifurcation patterns by 'connectivity matrix'. METHODS: Male Wistar rats were used to visualize pial microcirculation by a fluorescent microscopy technique through an open cranial window, using fluorescein isothiocyanate bound to dextran (molecular weight 70 kDa). The arteriolar network was mapped by stop-frame images. Diameters and lengths of arterioles were measured with a computer-assisted method. Pial arterioles were classified according to a centripetal ordering scheme (Strahler method modified according to diameter) from the smallest order 1 to the largest order 5 arterioles in the preparation. A distinction between arteriolar segments and elements was used to express the series-parallel features of the pial arteriolar networks. A connectivity matrix was used to describe the connection of blood vessels from one order to another. RESULTS: The arterioles were assigned 5 orders of branching by Strahler's ordering scheme, from order 1 (diameter: 16.0 +/- 2.5 microm) to order 5 (62 +/- 5.0 microm). Order 1 arterioles gave origin to capillaries, assigned order 0. The diameter, length and branching of the 5 arteriolar orders grew as a geometric sequence with the order number in accordance with Horton's law. The segments/elements ratio was the highest in order 4 and 3 arterioles, indicating the greatest asymmetry of ramifications. Finally, the branching vessels in the networks were described in details by the connectivity matrix. Fractal dimensions of arteriolar length and diameter were 1.75 and 1.78, respectively. CONCLUSIONS: The geometric characteristics of rat pial microcirculation indicate that distribution of vessels is fractal. The connectivity matrix allowed us to describe the number of daughter vessels spreading from parent vessels. This ordering scheme may be useful to describe vessel function, according to diameter, length and branching.

Protective effects of insulin during ischemia-reperfusion injury in hamster cheek pouch microcirculation.

OBJECTIVE: The effects of insulin (0.18 nM-0.18 microM) on reduced capillary perfusion, microvascular permeability increase and leukocyte adhesion induced by ischemia-reperfusion injury were investigated in the hamster cheek pouch microcirculation. To gain insight into the insulin's mechanism of action, the effects of its higher concentration (0.18 microM) were investigated after inhibition of tyrosine kinase (TK), nitric oxide synthase (NOS), protein kinase C (PKC), phosphatidylinositol 3-kinase and K+(ATP) channels, alone or in combination. Two concentrations for each inhibitor were used. METHODS: Microcirculation was visualized by fluorescence microscopy. Perfused capillary length, microvascular permeability, leukocyte adhesion to venular walls, vessel diameter and capillary red blood cell velocity were assessed by computer-assisted methods. Measurements were made at baseline (B), after 30 min of ischemia (I), and after 30 min of reperfusion (R). RESULTS: In control animals, perfused capillary length decreased by 63 +/- 5% of baseline at R. Microvascular permeability increased at I and R, while leukocyte adhesion was most pronounced in V1 postcapillary venules at R. Insulin dose-dependently preserved capillary perfusion at R (-28 +/- 6 and -15 +/- 6% of baseline), but was unable to prevent the increase in permeability at I (0.25 +/- 0.05 and 0.29 +/- 0.06 Normalized Grey Levels, NGL) and R (0.49 +/- 0.10 and 0.53 +/- 0.09 NGL), according to the concentrations. Adhesion of leukocytes was observed mostly in V3 venules at R (9 +/- 2 and 10 +/- 2/100 microm venular length, with the lower and higher concentration, respectively). Nitric oxide synthase inhibition by N(G)-nitro-L-arginine-methyl ester prior to insulin did not affect capillary perfusion at R (-18 +/- 3% of baseline with higher concentration), but prevented permeability increase (0.20 +/- 0.04 NGL, according to higher concentration) and reduced leukocyte adhesion in V3 venules at R (1.5 +/- 1.0/100 microm of venular length, with higher concentration). Blockade of K+(ATP) channels by glibenclamide prior to insulin decreased perfused capillary length at R (-58 +/- 6% of baseline with higher concentration), attenuated leakage at R (0.30 +/- 0.04 NGL, according to higher concentration) and caused leukocyte adhesion mainly in V1 venules at R (9.0 +/- 1.5/100 microm of venular length, with higher concentration). Inhibition of either TK, PKC or phosphatidylinositol 3-kinase did not affect microvascular responses to insulin. Simultaneous inhibition of TK and NOS did not increase protection. CONCLUSIONS: Insulin prevents ischemia-reperfusion injury by promoting capillary perfusion through an apparent activation of K+(ATP) channels and increase in nitric oxide release.

Effects of tetraiodothyronine and triiodothyronine on hamster cheek pouch microcirculation.

The aim of the present study was to assess the effects of topically applied triiodothyronine (T(3)) and thyroxine (T(4)) on the arterioles of hamster cheek pouch microcirculation in vivo. Microvessels were visualized using a fluorescent microscopy technique. Topical application of T(3) (3.08, 30.8, 61.5, 307, 615, and 6,150 nM/l) consistently induced dose-dependent dilation of arterioles within 2.0 +/- 0.5 min of administration. The application of T(4) (150, 257, 514, and 5,140 nM/l) caused different dose-dependent effects: dilation at the three lower doses within 16 +/- 2 min and rhythmic diameter changes at the highest dose. Aging of hamsters did not alter the arteriolar responses to T(3) and T(4). T(3)-induced dilation was countered by the inhibition of nitric oxide synthase with N(G)-nitro-L-arginine-methyl ester or N(G)-nitro-L-arginine. Iopanoic acid (IPA), which inhibits types I and II 5'-deiodinase, abolished the dilation elicited by 514 nM T(4) but did not affect T(3)-dependent dilation. 6-Propyl-2-thiouracil (PTU), which inhibits type I 5'-deiodinase only, did not affect the dilation induced by T(4). IPA and PTU did not impair arteriolar dilation induced by acetylcholine or sodium nitroprusside. These results indicate that T(3) induces arteriolar dilation, likely through nitric oxide release. The local conversion of T(4) to T(3) appears to be crucial for the dilation induced by T(4).

Retinal photoreceptors of Syrian hamsters undergo oxidative stress during streptozotocin-induced diabetes.

AIMS/HYPOTHESIS: The aim of this study was to verify whether retinal photoreceptors, like other tissues, are subject to oxidative stress during diabetes. METHODS: Oxidative stress was monitored by the oxidation of preloaded dehydrorhodamine 123 into fluorescent rhodamine 123, during a period of intense illumination of isolated rod retinal receptor cells. These were obtained from 22 Syrian hamsters injected with streptozotocin (50 mg/kg body weight., intraperitoneal route) 90 days before the study began. Eleven hamsters were treated daily with melatonin (0.4 mg/kg body wt., per os), an antioxidant synthesized within photoreceptors. Isolated photoreceptors were bathed on the stage of a Leitz Orthoplan microscope, where the fluorescent lamp also served as the light stimulus (485 nm). Fluorescence irradiance was measured by photometry and stored in a personal computer for further analysis. RESULTS: The light-induced oxidant production greatly decreased and was also delayed in the streptozotocin-injected hamsters compared with the control hamsters matched for age. Similar effects were obtained in control photoreceptors after 40 min incubation with 2-2'-azobis (2-amidinopropane) dihydrochloride, a potent lipoperoxidation inducer. The effect of melatonin was to partially restore the light-induced fluorescence response. CONCLUSION/INTERPRETATION: The depression of the light-induced oxidative response in diabetic photoreceptors could be ascribed to a hyperglycaemia-induced background of oxidative stress whereby the light-oxidizable substrate is actually lowered. Melatonin induces a larger fluorescence response during illumination, probably as a consequence of its antioxidant effect during diabetes, which would provide more oxidizable lipids.