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.

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.

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.

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.

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.

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.

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.

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.

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]

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.

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.

Phentolamine suppresses the increase in arteriolar vasomotion frequency due to systemic hypoxia in hamster skeletal muscle microcirculation

Systemic hypoxia (8%, 11% and 15% oxygen gas mixture inspiration) has been shown to increase the frequency of arteriolar rhythmic diameter changes in hamster skeletal muscle microcirculation. The effects of phentolamine on vasomotion frequency during systemic hypoxia were studied in Syrian hamsters implanted with a plastic chamber in the dorsum skin. Phentolamine (50 microg/100 g body wt.) was injected intravenously before the 20-min exposure to 11% oxygen gas mixture. The microvessels were studied with a fluorescent microscopy technique, using fluorescein isothiocyanate bound to dextran (mol. wt. 150,000) as a tracer. Vessel diameters were measured with a shearing method. Fourier transform and autoregressive modeling were used to assess the time variant features of diameter changes. Under baseline conditions, the arterioles were characterized by rhythmic diameter changes with fundamental frequency related to vessel size. The terminal branchings were dominated by order 3 vessel activity (frequency: 0.08-0.16 Hz) spreading downstream to all daughter arterioles. Systemic hypoxia caused an increase in vasomotion frequency of order 3 arterioles up to 0.3-0.5 Hz (average: 0.40 +/- 0.06 Hz) and a significant decrease in mean diameter (-28 +/- 5%). Phentolamine completely suppressed the rhythmic changes in diameter of order 3 arterioles that dilated significantly (+ 30 +/- 4%). Therefore, the effects of systemic hypoxia on arteriolar vasomotion appear to be triggered by an increase in sympathetic nervous discharge that induces a rise in frequency up to 0.3-0.5 Hz.

Protective effects of leukopenia and tissue plasminogen activator in microvascular ischemia-reperfusion injury

Ischemia shifts the anticoaugulant/procoagulant balance of the endothelium in favor of activation of coagulation. We studied whether cheek pouch microcirculation of leukopenic hamsters was protected by tissue plasminogen activator (tPA) (50 microg/100 g body wt) against ischemia-reperfusion injury. Adherent leukocytes, total perfused capillary length (PCL), permeability increase, and arteriolar and venular red blood cell (RBC) velocity were investigated by fluorescence microscopy. Measurements were made at control, 30 or 60 min of ischemia, and at 30 or 60 min of reperfusion. Hamsters were made leukopenic by treatment with cyclophosphamide (20 mg/100 g body wt ip, 4 days before the experiment), which decreased circulating leukocyte count by 85-90%. Leukopenic hamsters undergoing 30 min of ischemia followed by 30 min of reperfusion showed no significant decrease in PCL or increased permeability. Leukopenic hamsters undergoing 60 min of ischemia followed by 60 min of reperfusion presented a significant decrease in microvascular perfusion where PCL was 28 +/- 7% of baseline, low-flow conditions, and increased permeability. In leukopenic hamsters treated with tPA there was complete protection of capillary perfusion with no significant changes in permeability or arteriolar and venular RBC velocity. In conclusion, thrombus formation may be an additional and independent factor that with leukocyte-mediated mechanisms determines ischemia-reperfusion injury.

Time-variant spectral analysis of LDF signals on the basis of multivariate autoregressive modelling

Time-variant AR-modelling was used to analyse the non-stationary properties of LDF signals during provocation tests. The procedure for the estimation of time-varying AR parameters based on Kalman filtering is presented. The estimates can be used to calculate instantaneous measures, such as peak frequency, spectral band power and coherence. The resulting course of instantaneous peak frequency of a sinusoidal signal with frequency jump was compared to similar parameters derived from short-time FFT and Hilbert transformation. Univariate time-variant spectral analysis was used to investigate LDF measurements in patients with Raynaud's phenomena. The experimental protocol was splitted into phases of different room temperature. The results demonstrate time-dependent variations of spectral components (amplitude and frequency). By means of time-variant coherence analysis of LDF and diameter measurements of vessels in a hamster skin fold the existence of a main rhythm around 0.1 Hz in the LDF signals which is related to vasomotion is shown.

Different flowmotion patterns in healthy controls and patients with Raynaud's phenomenon

Flowmotion was characterized in healthy controls and 61 Raynaud's phenomenon (RP) patients by spectral analysis of laser-Doppler perfusion monitoring (LDPM) tracings. Healthy subjects flowmotion patterns revealed a main frequency of 3 cycles per min (cpm) with another low frequency and heart rate synchronous components. A first group of RP patients presented a low frequency and heart rate frequency component but no significant difference in blood flow. The second group presented the predominating heart rate related frequency with low microvascular perfusion. The third group presented a flowmotion pattern with overlapping of heart rate and low frequency components. Patients with primary and secondary RP show specific changes in flowmotion, probably related to increased sympathetic nervous activity or vessel wall alterations causing disappearance of arteriolar tone and impairment of microvascular perfusion. The group of patients with overlapping frequency components presents an intermediate flowmotion pattern indicating a different grade of alterations in microvasculature.

Red blood cell velocity and volumetric flow assessment by enhanced high-resolution laser Doppler imaging in separate vessels of the hamster cheek pouch microcirculation

An enhanced high-resolution laser Doppler imager (EHR-LDI), configured to fit the demands of a measurement area containing separate microvessels, was evaluated for perfusion measurements in hamster cheek pouch preparations during ischemia, reperfusion, and pharmacologically induced vasodilation and vasoconstriction. Measurements in separate microvessels where the laser beam was smaller than the vessel diameter were referred to as red blood cell (RBC) velocity estimates, as previously validated in vitro, whereas a relative flow index, RFI (mean RBC velocity/tissue area), was introduced as a volumetric flow measure. Microvessel diameter and RBC velocity changes during ischemia, reperfusion, as well as during vasoconstriction and vasodilation correlated to the data obtained from the microscope. Correspondingly, during the described provocations anticipated volumetric flow changes were registered as changes in the RFI. When data on intravessel RBC velocity profiles are presented they reflect a parabolic flow profile usually seen in this size microvessel. The EHR-LDI appears a promising tool for investigation of the microvasculature, as it almost simultaneously provides information on relative changes of both in vivo RBC velocity and volumetric flow (RFI), although the latter estimate needs to be further refined.

Vasomotion and blood flow regulation in hamster skeletal muscle microcirculation: A theoretical and experimental study

A mathematical model of a microvasculature was used to study the effects of myogenic and flow-dependent stimuli on the characteristics of vasomotion and microvascular perfusion regulation. The model includes three branching orders of arterioles derived from in vivo observations and incorporates a mechanism for terminal arteriolar closure during vasomotion. Simulations were performed to evaluate the effect of vasodilation and vasoconstriction on vasomotion pattern, and the changes in arteriolar effective diameter and flow in response to arterial blood pressure variations triggering the regulatory mechanisms. Vasomotion patterns were studied in the hamster cutaneous muscle, visualized by fluorescent microscopy, in control conditions and after injection of acetylcholine (Ach) or NG-monomethyl-L-arginine (L-NMMA). We have found that vasomotion may be caused by different combinations of feedback mechanisms, including a strong rate-dependent myogenic response or a strong flow-dependent mechanism with no rate-dependent response. Decreasing the rate-dependent component of the myogenic mechanism and increasing the time constant of the flow-dependent mechanism causes vessel stabilization and disappearance of vasomotion. In hamster microcirculation, Ach decreased vasomotion frequency and increased vasomotion amplitude and arteriolar effective diameter, whereas L-NMMA caused a slight increase in vasomotion frequency and decrease in effective diameter. Model simulations, under dilatory and constrictory stimuli, confirmed these results. Moreover, the model predicted that mean blood flow is maintained closer to normal despite arterial pressure changes (+/-15% flow changes versus +/-50% pressure variations) when the vessels were in nonoscillatory than when they are in oscillatory state. In conclusion, a large variety of vasomotion patterns affect arteriolar resistance and microvessel perfusion in skeletal muscle. Furthermore, in the presence of vasomotion the network exhibits a poorer aptitude for regulating blood flow during arterial pressure changes (i.e., worse autoregulation) than the nonoscillatory network.

Evaluation of enhanced high-resolution laser Doppler imaging in an in vitro tube model with the aim of assessing blood flow in separate microvessels

An enhanced high-resolution laser Doppler imaging (EHR-LDI) technique intended for visualization of separate microvessels was evaluated by use of in vitro flow models. In EHR-LDI, a laser beam focused to a half-power diameter less than 40 microm successively scans the tissue under study in steps of 25 microm. Spatial blood flow variations within microvascular structures of 1.5 x 1.5 mm are rendered by 64 x 64 measurement sites. Individual microvessel diameters could be estimated and an average difference of 11 microm compared to microscopic measurements was obtained. For the flow algorithm used, the LDI output signal was found to scale linearly with average velocity (0-3.5 mm/s) when a plastic tube of inner diameter 175 microm was perfused with human blood (correlation coefficient 0.99). The LDI output signal was further found insensitive to hematocrit variations in the range 16-44%. Due to the limited laser light penetration in blood, a reduction in the LDI output signal was observed as the inner tube diameters were successively changed from 280 to 1400 microm.

Capillary density and leukocyte adhesion in hamsters with hereditary cardiomyopathy

The aim of this study was to characterize microvascular networks in cheek pouch of cardiomyopathic Syrian hamster (CM) (Bio 14.6), which is an interesting model of idiopathic cardiomyopathy and congestive heart failure. Microcirculation was visualized by fluorescence microscopy. Diameter and length of arterioles, classified according to centrifugal ordering scheme, were measured. A computational method was arranged to determine the density of arterioles and capillaries (total vessel length per unit area, cm-1), fractal dimension of capillaries, and the associated Voronoi tesselation. Furthermore, leukocyte adhesion to venules and arteriolar reactivity to drugs were studied. Increase in the number of terminal arterioles and capillary rarefication characterized CM microvasculature compared with that of age-matched controls (58 +/- 7 versus 25 +/- 5 cm-1, and 128 +/- 15 versus 240 +/- 10 cm-1, respectively). Fractal dimension of capillaries was reduced in CM compared with controls (1. 40 +/- 0.10 versus 1.85 +/- 0.09) and associated with increased avascular spaces, as shown by Voronoi tesselation results. Leukocyte adhesion to venules increased significantly in CM. In CM responsiveness of arterioles to nitric oxide inhibition and propranolol was slighter but more marked to norepinephrine and angiotensin II compared with that of control hamsters. In conclusion, the different geometry, increased leukocyte adhesion, and altered arterial responsiveness may contribute to flow disturbances in the microcirculation of CM hamsters.

Insulin-induced arteriolar dilation after tyrosine kinase and nitric oxide synthase inhibition in hamster cheek pouch microcirculation

We investigated the effects of tyrosine kinase (TK) and nitric oxide synthase (NOS) inhibition on insulin-induced dilation of arterioles. We determined the arteriolar diameter, red blood cell velocity (VRBC) and blood flow changes in hamster cheek pouch microcirculation as affected by insulin in presence of TK and NOS inhibitors, genistein, piceatannol and NG-monomethyl-L-arginine (L-NMMA). Microvessels were visualized by a fluorescent microscopy technique. Arteriolar diameter and VRBC were measured after topical application of insulin and genistein or piceatannol or L-NMMA. Insulin (10 microU/ml) induced diameter and VRBC increase in A3 and A2 arterioles by 30 +/- 5 and 123 +/- 4%, 16 +/- 4 and 102 +/- 3%, as percent of baseline values, respectively. After genistein or piceatannol prior to insulin A3 and A2 arterioles dilated by 10 +/- 4, 5 +/- 2% and 9 +/- 4, 2 +/- 1%, respectively. After L-NMMA prior to insulin A2 and A3, arteriole diameters increased by 12 +/- 3 and 7 +/- 2%, respectively. VRBC increased significantly in all the cases. TK and NOS inhibitors applied together abolished insulin-induced dilation with a reduction in VRBC and blood flow. In conclusion, full insulin-induced dilation of hamster cheek pouch arterioles requires TK signaling pathways. Furthermore, activation of insulin receptors, as well as other TK receptors, appears to be required for vasomotor tone regulation.

Venular oscillatory flow during hemorrhagic shock and NO inhibition in hamster cheek pouch microcirculation

Blood flow oscillations (flowmotion) during hemorrhagic shock (HS) were recorded with laser Doppler perfusion monitoring (LDPM) and red blood cell (RBC) velocimetry in arterioles and venules in hamster cheek pouch microcirculation. Experiments were carried out after baroceptor denervation or inhibition of nitric oxide (NO) synthesis with NG-monomethyl-L-arginine prior to and during HS. Flowmotion was characterized by spectral analysis with fast Fourier transform and autoregressive modeling. Low frequency flowmotion was detected in LDPM and RBC velocity tracings derived from arterioles while high frequency oscillations dominated in venules under baseline conditions. Venular blood flow was significantly higher compared with arteriolar flow during HS, while large amplitude low frequency flowmotion was found in venules but not in arterioles where dominated small amplitude high frequency oscillations coincident with respiratory or heart rates. Baroceptor denervation did not affect venular blood flow and low frequency flowmotion during HS. NO inhibition reduced significantly venular blood flow compared with control and abolished low frequency flowmotion in venules. High frequency oscillations remained in arterioles during HS. In conclusion, LDPM low frequency flowmotion was not originated by variations in the diameter of vessels, but corresponded to RBC velocity changes. A compensatory higher blood flow and concomitant low frequency flowmotion in venules appeared to be related to NO production during HS, independently of neural mechanism.

Correlation between laser Doppler perfusion monitoring and hematocrit in hamster cheek pouch microcirculation

The aim of this study was to investigate the relationships between laser Doppler perfusion monitoring (LDPM) measurements and different systemic hematocrits in microcirculation in terms of changes in oscillatory flow patterns. The hamster cheek pouch microvasculature was visualized by a fluorescent microscopy technique, and LDPM signals were derived from arterioles and venules under control conditions and after isovolemic hemodilution with saline and 6% dextran, MW 70,000 to 26.1 +/- 2.1%. Vasomotion, oscillations of microvascular blood flow (flow motion) and red blood cell (RBC) velocity were analyzed with Fourier transform and autoregressive modeling. LDPM recordings presented a significant increase in perfusion units (PU) during hemodilution-184 +/- 15 versus baseline 137 +/- 11 PU in arterioles and 40.2 +/- 3.5 versus 28.6 +/- 4.3 PU in venules-that was correlated with a significant increment in arteriolar and venular RBC velocity. There was a rise in the frequency [2.9 +/- 0.5 cycles per min (cpm) vs. 1.8 +/- 0.5 cpm] and spectral power of flow motion in arterioles whereas the increase in spectral power was related to a decrease in frequency (12.6 +/- 2.1 vs. 3.6 +/- 0.7 cpm) in venules. Oscillations in arteriolar and venular RBC velocity revealed coincident frequency components with flow motion patterns. The present data suggest that the LDPM measurements are more sensitive to velocity than hematocrit. Furthermore, hemodilution appears to affect differently arteriolar and venular flow motion patterns.

Dynamic coherence analysis of vasomotion and flow motion in skeletal muscle microcirculation

The aim of our study was to determine the cause of fluctuations in microvascular blood flow measured by laser Doppler perfusion monitoring (LDPM) in microvessels of the hamster skin fold preparation. LDPM flow fluctuations (flow motion) were compared to simultaneous records of diameter changes obtained from arterioles and venules. Time-varying coherence analysis was used to quantify the frequency of flow and diameter changes in awake hamsters in control conditions and during sodium nitroprusside-induced vasodilation. Power spectrum analysis of LDPM signals of order 4 and 3 arterioles indicated frequencies of 0.06 +/- 0.01 and 0.08 +/- 0.02 Hz, respectively. Order 3 arterioles exhibited significant temporal coherence between flow motion and vasomotion signals at a frequency of the order of 0.1 Hz. There was lack of coherence when vasomotion was absent in arterioles. Order 4 arterioles had several coherent frequencies in addition to that around 0.1 Hz. In conclusion, time-variant coherence analysis indicated that spontaneous fluctuations in flow are caused by vasomotion of order 3 arterioles with frequency around 0.1 Hz that appears to coordinate local control processes in the microcirculation. Additional frequency components present in LDPM signals are unrelated to vasomotion.

Melatonin prevents ischemia reperfusion injury in hamster cheek pouch microcirculation

OBJECTIVE

We used the hamster cheek pouch microcirculation to investigate the effects of melatonin (ME) on ischemia reperfusion (I-R) injury by in vivo microscopy. ME is a hormone produced by the pineal gland and is the most powerful and effective hydroxyl radical scavenger detected to date in vitro. The second aim was to determine the scavenger effect of ME in cheek pouch microcirculation when topically applying an oxygen-derived free radical generating system.

METHODS

Ischemia was induced by clamping the cheek pouch for 30 min followed by 30 min of reperfusion. We quantified the increase in permeability, the perfused capillary length and leukocyte adhesion by computerized methods. Microcirculation was also exposed to a hypoxanthine-xanthine oxidase (H-X) system.

RESULTS

In control hamsters I-R was associated with increased permeability, increased number of leukocytes sticking to venules, and decreased perfused capillary length. Treatment with ME completely inhibited microvascular edema formation and reduced the number of leukocytes sticking to venules after reperfusion. Moreover, ME prevented the marked decrease in perfused capillary length, preserving microvascular perfusion. ME topically applied reduced significantly the permeability increase due to H-X exposure.

CONCLUSIONS

The beneficial effect of ME may be related to its antioxidant properties. These protect the endothelial barrier integrity as well as preserve microvascular blood perfusion by dysfunctions after I-R.

Theoretical analysis of complex oscillations in multibranched microvascular networks

A mathematical model was used to study the origin of complex self-sustained diameter oscillations in multibranched microvascular networks. The model includes three branching levels (order 3, 2, and 1 arterioles) of a microvascular network derived from in vivo observation in the hamster dorsal cutaneous muscle. The main biomechanical aspects covered by the model are (1) the dependence of the elastic and active wall stress on the inner radius and (2) the static and dynamic myogenic response. Simulations on isolated arterioles indicate that self-sustained periodic diameter oscillations may occur at constant transmural pressure. Conversely, simulations on the entire network reveal different oscillatory patterns, including periodic, quasiperiodic, and chaotic fluctuations. Chaos in the model is revealed by the presence of a broad noise-like component in the frequency spectrum and by the sensitivity dependence of model results on small perturbations. Our results suggest that, owing to the intrinsic nonlinearity of the system, a contracting mechanism, such as the myogenic response, may induce different oscillatory patterns. The change from periodic to chaotic oscillations may be a consequence of a modest variation in a parameter (systemic pressure or arterial resistance) not necessarily related to pathophysiological conditions. Accordingly, our in vivo observations in the skeletal muscle showed that in some instances arteriolar vasomotion is converted from regular to highly irregular patterns in basal conditions. Vasomotion is found to affect mean blood flow compared with the nonoscillatory steady state. Chaotic oscillations tend to maintain a constant ratio of blood flows entering into bifurcation vessels, whereas periodic vasomotion determines a different flow distribution at branches.

Capillary reperfusion after L-arginine, L-NMMA, and L-NNA treatment in cheek pouch microvasculature

The effects of arginine (L-arg), promoter of nitric oxide (NO) production and NO synthesis inhibitors, NG-monomethyl-L-arginine (L-NMMA) and N omega-nitro-L-arginine (L-NNA), on arteriolar responses and capillary perfusion after 30 min ischemia were studied in the cheek pouch preparation under pentobarbital anesthesia and intravenous drug infusion. Capillary density, venular leukocyte sticking, and vessel diameters were investigated by fluorescence microscopy. Damage due to photoactivation of intravascular dyes was investigated by injecting fluorescent dextran 150,000 MW prior to and after ischemia reperfusion. No difference was found indicating that effects were independent from exposure time to photoactivated dyes. Capillary perfusion reduction was always present after reperfusion in untreated, L-NMMA-treated, and L-NNA-treated animals, with increased venular leukocytes adhesion. Arteriolar vasomotion was induced by L-NMMA treatment. Capillary perfusion recovered in L-arg-treated hamsters, where capillary blood flow velocity was lower than in L-NMMA group and the number of adhering leukocytes was lower than in untreated controls, L-NMMA, and L-NNA groups. It is concluded that L-arg determines perfusion with increased blood flow heterogeneity while inhibition of NO preserves capillary perfusion causing appearance of vasomotion in the arterial network.

Effects of the natural flavonoid delphinidin on diabetic microangiopathy

The purpose of the present study was to investigate the effects of the flavonoid delphinidin chloride (CAS 528-53-0, IdB 1056) on diabetic microangiopathy. Hamsters were injected with alloxan and cheek pouch microcirculation was observed by a fluorescent microscopy technique 90 days from alloxan. The increase in permeability, the number of adhering leukocytes to venular vessel wall and vasodilatory responses to acetylcholine (Ach) and sodium nitroprusside (SNP) were measured. In diabetic group microvascular permeability and the number of sticking leukocytes to the venular endothelium were increased. Vasoconstriction by Ach was observed while the vasodilation by SNP was significantly attenuated in diabetic animals. These results are consistent for a decreased relaxation and suggest also an impairment in the smooth muscle cell function in diabetic arterioles. IdB 1056 exhibited an inhibitory effect on increased microvascular permeability and on leukocytes adhering to the venular vessels. Indeed, the treatment with IdB 1056 in diabetic hamsters pretreated or not with indometacin, a cyclooxygenase inhibitor, restored the relaxant responses to Ach and SNP. In conclusion, the effects of IdB 1056 observed in vivo at the microcirculatory level prevent the injury to endothelial cell function associated with diabetes and/or oxidative stress.

Effect of Vaccinium myrtillus anthocyanosides on ischaemia reperfusion injury in hamster cheek pouch microcirculation

The effects of Vaccinium myrtillus anthocyanosides (VMA) on ischaemia reperfusion injury were investigated in the hamster cheek pouch microcirculation. Ischaemia was induced by clamping the cheek pouch for 30 min followed by 30 min of reperfusion. The microvasculature was visualized by a fluorescence technique. VMA [10 mg (100 g body weight)-1] were orally administered for 2 and 4 weeks. The number of adhering leukocytes to venular vessel walls, the perfused capillary length, the increase in permeability, the arteriolar diameter changes were determined. Ischaemia and reperfusion were associated with increased number of leukocytes sticking to venules, decreased number of perfused capillaries, and increased permeability. VMA decreased the number of leukocytes sticking to the venular wall and preserved the capillary perfusion; the increase in permeability was significantly reduced after reperfusion. VMA saved the arteriolar tone and induced the appearance of rhythmic diameter changes of arterioles. These results demonstrate the ability of Vaccinium myrtillus anthocyanosides to reduce microvascular impairments due to ischaemia reperfusion injury, with preservation of endothelium, attenuation of leukocyte adhesion and improvement of capillary perfusion.

Effects of L-NMMA and indomethacin on arteriolar vasomotion in skeletal muscle microcirculation of conscious and anesthetized hamsters

The purpose of this study was to determine the influence of NG-monomethyl-L-arginine (L-NMMA) and indomethacin (INDO), respectively inhibitors of nitric oxide synthase and cyclooxygenase, on spontaneous arteriolar activity (vasomotion) in the skeletal muscle of awake and anesthetized hamsters. Unanesthetized hamsters, implemented with the skin fold chamber window, displayed vasomotion, whose frequency and amplitude were quantified by power spectrum analysis. Intravenous administration of L-NMMA significantly increased vasomotion frequency and did not change the amplitude at the lower dose, but in order 3 arterioles amplitude decreased significantly. With higher doses L-NMMA caused constriction of order 1-2 vessels, frequency decreased and amplitude increased, and the arteriolar vasodilator response to acetylcholine decreased significantly. During anesthesia topically applied L-NMMA significantly decreased diameter and caused the appearance of vasomotion in order 1-2 arterioles. INDO did not affect vasomotion in unanesthetized hamsters and did not initiate vasomotion during anesthesia leading to the conclusion that prostaglandins do not regulate vasomotion. Vasomotion is not directly related to nitric oxide (NO) in conscious animals while NO blockage stimulates vasomotion in smaller arterioles of anesthetized hamsters without vasomotion; however, the simultaneous inhibition of cyclooxygenase and NO had no effect on arteriolar diameter during anesthesia. It is concluded that vasomotion is regulated by a mechanism that modulates smooth muscle cell activity through the endothelium.

Microvascular vasomotion: origin of laser Doppler flux motion

Intravital microscopy and laser Doppler fluxmetry (LDF) were used to assess vasomotion and flux motion in skeletal muscle microcirculation. To clarify the relation between vessel type and LDF signals, arterioles, capillaries, and venules were sequentially studied. We used as an experimental model the hamster skin fold window preparation to record vasomotion and flux motion under control conditions and after injection of an alpha 2-adrenoceptor antagonist, yohimbine, since terminal arterioles appear to be subserved primarily by alpha 2-adrenoceptors. LDF signals were characterized by using an autoregressive modeling power spectrum technique. This analysis indicated that the flux motion fundamental frequency of terminal arterioles coincided with order 2 arteriole vasomotion fundamental frequency. The LDF fundamental frequency of order 3 arterioles was synchronous with the vasomotion frequency in the same-order vessels. The LDF fundamental frequency of order 3 venules corresponded to the frequency component coincident with the respiratory rate. The pattern of LDF oscillations was peculiar for each type of vessels, and the total power was greater in larger arterioles than in venules. Yohimbine reduced frequency and amplitude of vasomotion and flux motion in terminal arterioles, but it was possible to detect LDF oscillatory patterns due to the activity of parent vessels with a low frequency. In conclusion, the flux motion is fundamentally dependent on the type of vessel from which it originates and is directly related to the vasomotion of the arterioles.

Biological zero of laser Doppler fluxmetry: microcirculatory correlates in the hamster cheek pouch during flow and no flow conditions

The microcirculation of the hamster cheek pouch was visualized by the intravenous injection of FITC-dextran 150,000 during normal flow conditions and when flow was interrupted by clamping proximal to the pouch. Laser Doppler fluxmetry (LDF) was used to evaluate flow during control, 30 min of occlusion and after reperfusion. Intravital video recordings of the microcirculation during occlusion show that blood moves between the different arteriolar segments after occlusion and during the whole period of no flow. This motion was oscillatory in nature, had maximum velocity of order of 30 microns sec-1, and was related to progressive decrease of arteriolar diameter. The LDF output was in the range of 60-100 AU during control. This value fell in the range of 5-25 +/- 15% AU during occlusion and was assumed to constitute the biological zero for this system. The variability of the LDF signals was characterized by the autoregressive modeling power spectrum technique. The power spectra during control, occlusion, and reperfusion were similar, suggesting that motion of blood not related to perfusion or blood flow is present in all conditions. These findings suggest that the biological zero arises from signals that are not flow related and that it should be subtracted from the flow signal.

Effect of leukocyte adhesion and microvascular permeability on capillary perfusion during ischemia-reperfusion injury in hamster cheek pouch

The role of leukocyte sticking and permeability changes in the variation of perfused capillaries induced by ischemia reperfusion was studied in the hamster cheek pouch microcirculation. The drugs utilized were the antiperoxidative agents allopurinol, the calcium antagonists verapamil and diltiazem, and phenidone and adenosine, which inhibit leukotriene formation as well as leukocyte adhesion to the endothelium. The microvasculature was visualized by a fluorescence technique. Ischemia was induced by clamping the cheek pouch for 30 minutes followed by 30 minutes of reperfusion. The increase in permeability, the perfused capillary length and the number of adhering leukocytes to venular vessel wall were measured. Ischemia and reperfusion were associated with increased permeability, increased number of leukocytes sticking to the venular wall, and decreased number of functional capillaries. Microvascular injury evidenced by increased permeability was apparent in the first 5 min of ischemia. All the drugs decreased the number of leukocytes sticking to the venular wall; allopurinol, verapamil and adenosine reduced the increase in permeability, whereas phenidone and diltiazem were effective only during ischemia. In addition verapamil and adenosine preserved capillary blood flow during reperfusion. In conclusion, leukocyte sticking is correlated with increased microvascular permeability, but not with decreased perfusion of the capillary bed. These data suggest that leukocytes did not play a prominent role in the reduction of functional capillaries at the end of reperfusion.

Effects of Vaccinium Myrtillus anthocyanosides on arterial vasomotion

The effects of Vaccinium Myrtillus anthocyanosides (Myrtocyan, VMA; CAS 84082-34-8) on arteriolar vasomotion were assessed in cheek pouch microcirculation of anesthetized hamsters and in skeletal muscle microvasculature of unanesthetized hamster skin fold window preparation. Intravenously injected VMA induced vasomotion in cheek pouch arterioles and terminal arterioles with higher frequency in smaller vessels. In the skeletal muscle arteriolar networks VMA increased vasomotion frequency and amplitude in all vessel orders. The results indicate that VMA are effective in promoting and enhancing arteriolar rhythmic diameter changes, that play a role in the redistribution of microvascular blood flow and interstitial fluid formation.

Hypoxia- or hyperoxia-induced changes in arteriolar vasomotion in skeletal muscle microcirculation

Arteriolar vasomotion was characterized in the skin muscle of the unanesthetized hamster skinfold window preparation and related to the specific arterioles that give rise to the different types of activity. The arterioles were classified according to the Strahler method: order 0 was assigned to capillaries and order 4 to the largest arterioles. The arterioles showed vasomotion with a specific range of frequencies that varied according to the vessel order; the highest fundamental frequency (9.1 +/- 3.9 cycles/min) was detected in the smallest order 1 arterioles and the lowest frequency (2.1 +/- 0.9 cycles/min) in order 4 vessels. Hypoxia (8, 11, and 15% O2 gas mixture inspiration) increased the frequency of vasomotion, decreased mean and effective diameters, and reduced capillary blood flow. The effects were more pronounced with an 8 and 11% O2 gas mixture. Hypoxia caused high-frequency vasomotion to shift from order 1 and 2 arterioles to the beginning of order 3 arterioles, which in this condition dominated the daughter vessels and generated the prominent activity (24 +/- 4 cycles/min, 11% O2 gas mixture). Hypertoxia (100% O2) induced differentiated arteriolar responses. The smallest vessels showed prolonged constriction, decreased mean and effective diameters, and reduced frequency of vasomotion. Capillary blood flow was restricted. Order 3 vessels did not constrict or dilate.

Superposition of arteriolar vasomotion waves and regulation of blood flow in skeletal muscle microcirculation

In skin muscle microcirculation of Syrian hamsters, rhythmic diameter changes were studied along the arteriolar network, under normoxic conditions, at rest. A teflon coated-aluminum chamber was implanted in the dorsum skin of animals. The microcirculation was investigated using intravital microscopy technique. Vessel diameters were determined by a computer-assisted method. Power spectrum analysis of vasomotion recordings was carried out with Fast Fourier Transform and Autoregressive modelling. To determine vasomotion waveform spreading, cross-spectral data (amplitude and phase) were computed, using the modified periodogram method (FFT). The arterioles were classified according to Strahler's method. Order 1 vessels (diameter: 7.50 +/- 1.16 microns) showed the highest frequency, 4-15 cycles per min, and percentage amplitude in the range 60-100%. Order 2 and 3 arterioles had intermediate frequencies, and amplitude in the range 50-100%, and 15-50%, respectively. The largest order 4 vessels (diameter: 28.97 +/- 9.55 microns) had the lowest frequency, 0.3-3 cpm, and amplitude in the range 5-20%. In most networks, cross-correlation analysis revealed two groups of frequency components. Low frequency group was propagated from order 4 and 3 vessels downstream. High frequency components were transmitted upstream from order 1 and 2 arterioles. Therefore, a complex superposition of waveforms resulted from the activity of discrete points along the microvasculature. In conclusion, rhythmic diameter changes of arterioles in skeletal muscle microcirculation regulate blood flow distribution in capillary units and control tissue oxygenation.

Functional microangiopathy in alloxan-treated Syrian hamsters

Intraperitoneally injected alloxan determined long term hyperglycemia in a group of Syrian hamsters (35 hyperglycemic hamsters); transitory hyperglycemia, with recovery of normal blood glucose concentration but impairment of glucose tolerance test, was observed in a second group of alloxan-treated animals (70 normoglycemic hamsters). Microvascular permeability by fluorescent microscopy technique, capillary basement membrane thickening and pancreatic islet B, A, and D cell degranulation by computer-assisted microdensitometry were studied in Syrian hamsters at different intervals (30, 40, 60, 90, and 120 days) after intraperitoneal alloxan administration. Hyperglycemic groups showed increased permeability of venous microvasculature to high molecular weight dextran in 50%, 71.4%, and 100% of animals studied at 30, 40, and 60, 90, 120 days from treatment, respectively; indeed, they revealed pancreatic islet B cell degranulation and no capillary basement membrane thickening. Normoglycemic groups presented increased venular leakage in 28.5%, 42.8%, 71.4%, and 100% of animals investigated at 40, 60, 90, and 120 days after treatment, respectively; moreover, they showed moderate pancreatic islet B cell degranulation and no capillary basement membrane thickening. In conclusion, more severe microvascular alterations seemed to be related to more severe impairment of glucose metabolism and to longer duration of diabetes; even in normoglycemic hamsters with pathological glucose tolerance test, enhanced permeability developed.