Effects of inhibition of nitric oxide synthase on blood-brain barrier transport in focal cerebral ischemia

This study was performed to determine whether nitric oxide (NO) alters the transport of small hydrophilic molecules across the blood-brain barrier in focal cerebral ischemia by administering an NO synthase inhibitor, NG-nitro-L-arginine methyl ester (L-NAME) and by measuring the blood-brain barrier transfer coefficient (Ki) of 14C-alpha-aminoisobutyric acid (14C-AIB) in the rats with middle cerebral artery occluded under isoflurane anesthesia. L-NAME increased the mean arterial blood pressure from 91 +/- 9 to 134 +/- 13 mm Hg. The Ki of the ischemic cortex (ICO) was 26% higher than that of the contralateral cortex (CCO) in the control animals without the L-NAME treatment. However, in the L-NAME-treated animals, Ki was 33% lower in the ICO than in the CCO. The Ki of ICO in the L-NAME group was significantly lower (-54%) than that of the control group. L-NAME did not affect Ki significantly in the nonischemic brain regions. Our data demonstrate that focal ischemia increased Ki of 14C-AIB, but L-NAME significantly decreased the Ki in the focal ischemic area of the brain without causing significant changes in the nonischemic tissue. Our results suggest that NO may participate in increasing transport of small hydrophilic molecules across the blood-brain barrier in focal ischemia.

Clinical heterogeneity of skeletal dysplasia in Roberts syndrome: a review

Roberts syndrome is a rare autosomal recessive disorder with highly variable clinical features. The most notable manifestations include pre- and postnatal growth retardation, craniofacial anomalies and improper development of all four extremities. We reviewed 50 cases whose clinical evaluation has been vigorously pursued. A relationship of deformities exists between humerus versus femur, and radius and ulna versus tibia and fibula. Only six cases had clubfoot. The number of fingers and toes was variable. The sex ratio was 1:1. Most individuals died in early infancy, although the longest follow-up survival was 13 years in one case. Premature centromere separation, centromere splitting and puffing were common chromosomal abnormalities. An annotated bibliography on notable cases is also provided which should serve as an aid for clinicians who wish to further understand the genetic and clinical heterogeneity noted in their cases.

Nitric oxide synthase inhibition alters cerebral blood flow and oxygen balance in focal cerebral ischemia in rats

BACKGROUND AND PURPOSE

This study investigated whether the nitric oxide synthase inhibitor NG-nitro-L-arginine-methyl ester (L-NAME) would alter blood flow and oxygen balance in the ischemic cerebrocortex of isoflurane-anesthetized Long-Evans rats.

METHODS

Fifteen minutes after middle cerebral artery occlusion, L-NAME (1.5 mg/min per kilogram) was infused intravenously to the L-NAME group (n = 14), and normal saline was given to the control group (n = 14) for 45 minutes. In each group, regional cerebral blood flow was determined with [14C]iodoantipyrine, and arterial and venous oxygen saturations were determined by microspectrophotometry.

RESULTS

In both groups regional cerebral blood flow of the ischemic cortex was significantly lower than that of the contralateral cortex ([mean +/- SD] 55 +/- 13 versus 110 +/- 29 mL/min per 100 g in the control group and 35 +/- 13 versus 90 +/- 24 mL/min per 100 g in the L-NAME group). Compared with the blood flow in the ischemic cortex of the control group, L-NAME significantly reduced ischemic blood flow by 36%. Venous oxygen saturation was significantly increased in the ischemic cortex (41 +/- 1% versus 44 +/- 3%) but decreased in the contralateral cortex (65 +/- 3% versus 61 +/- 4%) by L-NAME. Calculated ischemic cortical oxygen consumption in the L-NAME group was 39% lower than that in the corresponding control group, whereas the difference was only 11% in the contralateral sides between groups. In both groups, the ratio of oxygen supply to consumption was lower in the ischemic than in the nonischemic regions. In the ischemic cortex, this ratio was significantly lower in the control group than in the L-NAME group (1.7 +/- 0.1 versus 1.9 +/- 0.1). In contrast, the ratio tended to be decreased by L-NAME in nonischemic regions.

CONCLUSIONS

These observations suggest that despite a decrease in cerebral blood flow, inhibition of nitric oxide synthesis mildly improves the oxygen supply and consumption balance in the ischemic cortex.

Transient decrease of binding of insulin to platelets in acute ischemic heart disease

The specific binding sites of 125I-insulin in platelets from nondiabetic patients with acute myocardial infarction and unstable angina pectoris was significantly decreased (192 +/- 84/cell) during the acute ischemic condition when compared with normal platelets (496 +/- 76/cell; p < 0.001, n = 9). A relatively low mean plasma insulin level (20 microU/mL) with an elevated mean glucose level (130 mg/dL) was noted. The decreased binding of insulin and the relatively low mean plasma insulin level during the acute ischemic condition improved into the normal range during 8 to 12 weeks of recuperation. The decrease of insulin binding sites in the acute phase and their subsequent increase during recovery were directly related to the hormone-induced increase in sensitivity to prostaglandin E1 through the stimulation of adenosine 3',5'-cyclic monophosphate formation in platelets by the prostanoid.

Transport of thyroid hormones to target tissues

Endemic iodine deficiency is associated with maternal hypothyroxinemia and a relatively high incidence of neurological disorders in the offspring. The previous assumption that the placenta is impermeable to maternal thyroid hormone, has resulted in the erroneous suggestion that iodine per se has an essential role in brain development. Furthermore, the observed factorial rise in thyroxine-binding globulin (TBG) in pregnancy has often been misinterpreted as preventing thyroid hormone loss to either the fetal compartment or excretory systems. However, physiochemical analysis of the role of specific binding proteins in hormone delivery, combined with epidemiological evidence and evolutionary considerations has led us to postulate that a) maternal thyroxine (T4) is transported to the fetus, and is of crucial importance in early fetal development, and b) TBG forms part of a control system specifically designed to maintain at an optimal level the T4 environment to which the developing fetus is exposed. Placental transfer of maternal T4 in a variety of mammalian species (including humans) is now well established. Further experimental studies in rats have shown that perturbation of the intrauterine thyroid hormone environment during critical phases of brain development results in a spectrum of biochemical dysgenesis. For example, in fetal brains deriving from hypothyroxinemic (Tx) rat dams, severe disruption of phosphate metabolism is observed and the ontogenesis of two enzyme activities associated with growth control, protein kinase C and ornithine decarboxylase, are compromised. Development of brain function is also impaired, as evidenced by the dysgenesis of certain neurotransmitter metabolic activities (choline acetyltransferase and DOPA decarboxylase).(ABSTRACT TRUNCATED AT 250 WORDS)

Diminished effect of inhibition of nitric oxide synthase on regional cerebral vascular resistance in conscious and in isoflurane anesthetized rats during hemorrhage

Effects of a nitric oxide (NO) synthase inhibitor on regional cerebral vascular resistance (rCVR) and regional cerebral blood flow (rCBF) were studied during a severe hemorrhage in conscious and in isoflurane anesthetized groups of rats. Half of each group was infused with NG-nitro-L-arginine-methyl ester (L-NAME), a NO synthase inhibitor, at a rate of 2 mg.kg-1.min-1 for 30 min. Half of the L-NAME infused and half of the normal saline infused rats were bled to reduce the mean arterial blood pressure (MAP) to 44-49 mmHg. rCBF was measured using [14C]iodoantipyrine. rCVR was calculated as the ratio of MAP to rCBF. In the conscious non-hemorrhagic rats, L-NAME markedly increased rCVR in all the brain regions that we studied. In the conscious rats without L-NAME treatment, hemorrhage decreased rCVR in most of the brain regions. With L-NAME treatment in this group, hemorrhage increased rCVR only in the rostral part of the brain. Isoflurane decreased rCVR in most of the brain regions except the cortical area. L-NAME markedly increased rCVR in all the brain regions that we studied in the isoflurane anesthetized rats. In the isoflurane anesthetized rats, hemorrhage did not reduce rCVR in any of the brain regions. In the isoflurane anesthetized hemorrhagic rats, L-NAME did not significantly affect rCVR in any of the brain regions that we studied. We found that L-NAME increased rCVR to a greater extent in the non-hemorrhagic rats than in the hemorrhagic rats in both the conscious and in the isoflurane anesthetized rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Awareness of diarrheal disease control in rural and urban areas of Bihar

Awareness regarding different aspects of prevention and treatment of diarrheal diseases among parents in rural and urban areas of Patna district were studied. Survey was done in 245 households from 30 villages of Bihta block and about 275 households from 30 different mohallas of Patna town. All aspects were poorly known to the rural community, particularly the illiterates and a large segment of literates of Bihta block. Rural people were significantly less aware than their urban counterparts regarding value of prolonged breast feeding, spoon feeding rather than bottle feeding, using hand pump and tap water for drinking and using latrine for nightsoil disposal in preventing diarrhea. Utility of measles immunization in prevention of diarrhea was unknown to the community. Generally parents thought antidiarrheal drugs a must for treatment. Knowledge regarding ORS and its use in diarrhea and vomiting was very poor and significant difference (p < 0.001) in awareness was observed between educated and illiterates. Majority parents did not know the correct method of preparation and uses of ORS and SSS. Due to high literacy rate and health consciousness, the educated and majority of literate parents of Patna town were better aware, more factual and had rational view regarding causes, method of prevention, fundamentals of use of ORS and home management of diarrhea in children, although certain aspects are yet to be cleared to them.(ABSTRACT TRUNCATED AT 250 WORDS)

Serum lipid concentrations in the Koki community: a preliminary report

Serum cholesterol and triglyceride concentrations were estimated in a self-selected sample of 9% of the adults over the age of 18 years in the urban community of Koki in Port Moresby, in which there is a high prevalence of diabetes. There were 84 males and 58 females in the sample. The mean age was 32.6 years, with the males significantly older than the females. Mean cholesterol and triglyceride levels were 4.7 mmol/l and 1.2 mmol/l respectively, and significant sex differences were observed, with males demonstrating higher levels, even in the younger age group. A high prevalence of obesity was observed in both males (40%) and females (55%). The prevalence of hyperlipidaemia was higher in males than females and was also more frequently observed in obese than non-obese subjects of either sex. A significant number (25%) of young subjects (18-30 years) exhibited serum lipid concentrations in excess of recommended levels. Our results suggest that, in contrast to previous reports, elevated serum cholesterol and triglyceride levels are present in this community, and may represent an increased risk for the development of ischaemic heart disease.

Inhibition of platelet aggregation and the stimulation of prostacyclin synthesis by insulin in humans

An intravenous bolus injection of insulin (35.5 microM) followed by an infusion of insulin (0.53 microM.kg-1.h-1) for 2.5 h (which maintained plasma levels between 0.71 nM to 1.4 nM) in normal fasting volunteers (n = 16), increased [3H]prostaglandin E1 (a probe for prostacyclin) binding to platelets by two- to threefold over the control. Scatchard analyses showed that the increased binding was due to the increase of both high and low affinity receptor numbers with little change in the receptor affinities. Similar results were obtained by using [3H]prostacyclin as the radioligand. The increased binding was associated with more than a twofold decrease of the minimum concentration of prostanoid needed to inhibit aggregation of platelets through the increased formation of adenosine 3',5'-cyclic monophosphate. Furthermore, the infusion increased the mean plasma prostacyclin level from 12.10 +/- 4.5 pM to 23.9 +/- 6.7 pM (n = 16; P < 0.001). These effects of insulin were at least partially direct, since the treatment of endothelial cells with insulin in tissue culture stimulated the production of the autacoid. Bolus injection of insulin (0.71 microM/kg) showed that the above effects of insulin could be demonstrated within 20 min after the injection, attained maximal ranges in approximately 60 min, and disappeared by 2-4 h.

Effects of hemorrhage on regional cerebral blood flow in awake and in isoflurane-anesthetized rats

During hemorrhage, redistribution of cerebral blood flow may occur. We compared the effects of hemorrhage on regional cerebral blood flow in awake rats and in rats anesthetized with 1% or 2% isoflurane. In half of each group, regional cerebral blood flow was measured without hemorrhage. The other half was slowly bled to a mean arterial blood pressure of 40-45 mm Hg before measuring the regional cerebral blood flow. Without hemorrhage, the cortical regional blood flow was greater in the awake animals than that of the caudal part of the brain. In the 2% isoflurane group, however, the regional cerebral blood flow of the caudal part was greater than the cortical regional cerebral blood flow. After hemorrhage, a similar decrease (-45%) of the regional cerebral blood flow was observed in each brain region and the pattern of distribution of it remained unchanged in all experimental groups. However, the absolute value of the cortical flow was higher in the awake animals than in the isoflurane groups. Our experiment demonstrated that hemorrhage decreased the regional cerebral blood flow. However, it did not alter the redistribution of the cerebral blood flow in awake animals nor in the animals anesthetized with isoflurane.

The influence of the maternal thyroid hormone environment during pregnancy on the ontogenesis of brain and placental ornithine decarboxylase activity in the rat

The influence of maternal hypothyroxinaemia on early brain and placental development was examined in a partially thyroidectomized (parathyroid-spared; TX) rat dam model. Ornithine decarboxylase (ODC) specific activity, along with more general indices of cell growth, were determined in prenatal whole brain (at 15, 19 and 22 days of gestation), postnatal brain regions (at 5, 10 and 14 days) and placenta. Maternal hypothyroxinaemia resulted in reductions in fetal body weight, brain weight, brain DNA content and brain total protein content at 15 days of gestation; the latter effect persisting until 19 days of gestation. Further changes in brain cell growth were observed near term, when an increase in the DNA concentration was accompanied by a decrease in the total protein:DNA ratio. Growth of the postnatal brain regions appeared normal, with the exception of an isolated increase in the protein content of the cerebellum at postnatal day 5. Determination of the specific activity of brain ODC revealed a complex pattern of change in the progeny of TX dams, superimposed upon the normal ontogenetic decline. In the fetal brain, activity was initially deficient at 15 days of gestation but was increased at 22 days of gestation relative to controls. The compromise extended into the postnatal period; ODC specific activity being transiently reduced in the brainstem, the subcortex and the cerebral cortex. Placental development was less consistently affected; wet weight, gross indices of cell growth (DNA content, DNA concentration, total protein:DNA ratio) and ODC specific activity were all normal in the TX dam. However, cytosolic and total protein concentrations were reduced at 15 and 19 days of gestation respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of nitric oxide synthase inhibition on regional cerebral blood flow and vascular resistance in conscious and isoflurane-anesthetized rats

Nitric oxide is an important regulator of the regional cerebral vascular tone. We compared the magnitude of nitric oxide-related changes in the vascular tone by studying the regional cerebral blood flow (rCBF) and vascular resistance in conscious and isoflurane-anesthetized rats by using a nitric oxide synthase inhibitor, NG-nitro-L-arginine methyl ester (L-NAME). In the conscious group (n = 12), after cannulation of a femoral artery and two veins under isoflurane anesthesia, rats were allowed to remain awake for 90 min. In the anesthetized group (n = 18), rats were anesthetized with 2% isoflurane and mechanically ventilated. Six rats in each group were treated with L-NAME (2 mg.kg-1 x min-1 for 30 min) or saline. For the remaining rats in the isoflurane-anesthetized group (n = 6), arterial blood pressure was increased by phenylephrine infusion to the same level as that in the L-NAME-treated, isoflurane-anesthetized rats. Regional vascular resistance was determined by the ratio of mean arterial blood pressure and rCBF which was measured by [14C]iodoantipyrine. L-NAME significantly increased mean arterial blood pressure in both the conscious (123 to 158 mm Hg) and anesthetized (82 to 144 mm Hg) rats. Regional vascular resistance increased significantly in all 12 brain regions studied with the average value increasing from 1.19 +/- 0.33 mm Hg.mL-1 x min x 100 g to 2.22 +/- 0.48 (P < 0.0001) in the conscious and from 0.78 +/- 0.27 to 1.61 +/- 0.48 (P < 0.0001) in the isoflurane-anesthetized rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of pentobarbital and isoflurane on regional cerebral oxygen extraction and consumption with middle cerebral artery occlusion in rats

BACKGROUND

When compared with barbiturates, isoflurane may lack protective effects during focal cerebral ischemia. The reason for this difference is not clear. In this study, regional cerebral blood flow (rCBF), arterial and venous O2 saturation, and O2 extraction were compared in the ischemic cortex and in the nonischemic brain regions of rats anesthetized with isoflurane or pentobarbital using a microspectrophotometric technique that directly measures the O2 saturation of blood in the small arteries and veins.

METHODS

Twenty-eight rats were anesthetized with 1.4% isoflurane or 50 mg/kg pentobarbital. One hour after a middle cerebral artery (MCA) occlusion, rCBF was measured in the ischemic cortex and in the nonischemic brain regions using 14C-iodoantipyrine in one-half of each group of animals. Regional arterial and venous O2 saturation were determined using microspectrophotometry in the other one-half of each group.

RESULTS

The rCBF of the ischemic cortex (IC) and the non-ischemic contralateral cortex (CC) of the isoflurane group were significantly higher than those of the pentobarbital group. The venous O2 saturation was significantly less, and the O2 extraction was significantly higher, in the IC than in the nonischemic regions in both groups of animals (pentobarbital group, IC 10.5 +/- 1.1 ml O2.100 ml blood-1, CC 6.3 +/- 0.7; isoflurane group, IC 10.8 +/- 0.6, CC 5.9 +/- 0.2). There was no significant difference between the two groups.

CONCLUSIONS

Because the rCBF was less and the O2 extraction was similar, O2 consumption in the focal ischemic area of the brain during pentobarbital anesthesia must have been less than that during isoflurane anesthesia.

Hypothyroidism in the adult rat causes brain region-specific biochemical dysfunction

The influence of hypothyroidism in the adult rat on brain biochemistry was investigated. Hypothyroidism was induced in 6-month-old male rats by partial thyroidectomy coupled with the administration of 6-n-propyl-2-thiouracil (0.005%, w/v) in the drinking water. Age-matched euthyroid males served as the controls. Hypothyroidism resulted in brain region-specific changes in certain catabolic enzyme activities. Acid phosphatase activity was reduced in the cerebellum (by 34%) and the medulla (by 38%), whereas alkaline phosphatase activity was decreased in the midbrain (by 37%) and the subcortex (by 49%). A differential response was also observed in the case of aryl sulphatase activity: aryl sulphatase A (myelin-degradative activity) was diminished in the cerebellum (by 56%), whereas aryl sulphatase B remained unchanged in all regions. Acetylcholine esterase activity was reduced in the cerebellum (by 45%), the medulla (by 34%) and the subcortex (by 45%), whereas monoamine oxidase activity was affected in only one region, the cerebellum, where it was increased by (61%). The compromise of myelin and neurotransmitter degradative enzyme activities may place severe restrictions on normal brain function. The vulnerability of the adult rat cerebellum to the effects of thyroidectomy is commensurate with the known clinical signs of cerebellar dysfunction in adult hypothyroid man. These findings raise the possibility of an important role for the thyroid hormones in the mature brain.

Middle cerebral artery occlusion increases cerebral capillary permeability

One hour after middle cerebral artery occlusion, the regional blood to brain transfer coefficient of alpha-aminoisobutyric acid was determined in eight barbiturate anaesthetized rats. The transfer coefficient (microliter/min-1/g-1) was significantly higher in the ischaemic cortex (10.6 +/- 2.3) than in the contralateral cortex (6.5 +/- 1.0). Cerebral regional capillary surface area was determined in another group of twelve rats using an alkaline phosphatase stain for the total capillary bed and fluorescein isothiocyanate-dextran to visualize the perfused capillaries. Perfused capillary surface area (cm2/cm3) was lower in the ischaemic cortex (141 +/- 31) than in the contralateral cortex (426 +/- 32). Using these values for the transfer coefficient, surface area and our previously published data of regional cerebral blood flow after middle cerebral artery occlusion, we calculated the extraction fraction of alpha-aminoisobutyric acid, the permeability-surface area product and the permeability of cerebral regional capillary beds. Although, there are numerous reports of permeability-surface area product of brain capillaries, to our knowledge, the permeability has never been determined before. The calculated extraction fraction ratio for alpha-aminoisobutyric acid for ischaemic cortex/contralateral cortex was 3.1. Similar ratios for permeability-surface area product and capillary permeability were 1.6 and 4.4, respectively. Thus, there was a more than four fold increase in capillary permeability to small molecules in the ischaemic cortex one hour after middle cerebral artery occlusion.

Trichophytobezoar as a cause of transverse colon obstruction in a foal

A 5-week-old belgian colt was examined for colic of 12 hours duration after several episodes of diarrhea. Physical examination revealed signs of abdominal pain, mild dehydration and normal auscultable borborygmi in all abdominal quadrants. Distention of the cecum, large colon and small intestinal was evident on abdominal radiographs. The foal was treated medically as the owners declined surgery. The colt was euthanized because of continued deterioration and failure to respond to medical therapy. Post-mortem exam revealed the presence of a trichophytobezoar obstructing the distal part of the transverse colon.

Cervical sympathectomy reduces the heterogeneity of oxygen saturation in small cerebrocortical veins

This study evaluated the hypothesis that the peripheral sympathetic nervous system is one of the factors increasing the heterogeneity of venous O2 saturation in selective brain regions. Regional cerebral blood flow and O2 saturation were determined in the anterior cortex, posterior cortex, and medulla of either sham-operated or bilaterally sympathectomized Long-Evans rats. Cerebral venous O2 saturations, indicating the balance between local O2 supply and consumption, were found to be significantly more heterogeneous in the sham-operated group. In the anterior cortex, the coefficient of variation [100(SD/mean)] for the sham-operated animals was 22.4%. Sympathectomy significantly reduced this heterogeneity in the anterior cortex through a reduction in the number of low O2 saturation veins (coefficient of variation 11.7%). Blood flow and O2 consumption in the anterior cortex were not different between groups. The effects of sympathectomy in the posterior cortex were similar to those in the anterior cortex. However, sympathectomy did not alter any measured variables in the medulla. Thus, bilateral superior cervical ganglionectomy reduced the heterogeneity of cerebrocortical venous O2 saturation by reducing the number of low O2 saturation veins in the rostral part of the brain.

Effect of constant load training on skeletal muscle histochemistry of thoroughbred horses

Skeletal muscle adaptations to training of differing intensities were examined in 10 thoroughbred horses that underwent six weeks of treadmill training followed by six weeks of detraining. The horses were randomly assigned to either a slow group exercised at 40 per cent maximum oxygen uptake (VO2max) or a fast group at 80 per cent VO2max. Resting muscle biopsies were taken before training, after six weeks of training and after six weeks of detraining, from m gluteus medius and m biceps femoris. Muscle was analysed histochemically for fibre type composition (myosin ATPase) and capillary supply (PAS amylase). Cross sectional area and lesser fibre diameter were measured by planimetry and image analysis. No alterations were found in the proportions of different muscle fibre types during training or detraining. Capillary density increased by 54 per cent in m biceps femoris of the fast group during training and decreased to the pretraining level following detraining. Few changes in fibre size occurred as a result of training and detraining. It was not possible to draw conclusions as to the effects of detraining because of the small number of training induced changes. The results suggest that for major adaptations in skeletal muscle, an increasing exercise intensity throughout training may be more significant than the degree of exercise load, when exercise intensity is submaximal.

Effect of cervical sympathectomy and hypoxia on the heterogeneity of O2 saturation of small cerebrocortical veins

This study evaluated the hypothesis that the sympathetic nervous system was one of the factors increasing the heterogeneity of cerebrocortical venous O2 saturation and this heterogeneity would be greater during hypoxia when cervical sympathetic activity was elevated. Thirty-two male Long-Evans rats were either sham operated (n = 16) or received bilateral cervical sympathectomy (n = 16). One-half of the animals (n = 8) in each treatment were challenged by hypoxia (8% O2 in N2). Cerebral blood flow was determined in five brain regions with [14C]iodoantipyrine. Oxygen saturation was measured microspectrophotometrically in small cerebrocortical arteries and veins. The degree of hypoxic hyperemia was not significantly different between sham-operated and sympathectomized rats. Cortical venous O2 saturations, indicating the balance between O2 supply and consumption, were significantly more heterogeneous in the sham-operated group under both normoxic and hypoxic conditions. The coefficient of variation (CV = 100 x SD/mean) for the normoxic sham-operated animals was 24.9% and the average venous O2 saturation was 53.8%. During hypoxia, venous O2 saturation was significantly decreased to 43.1% without a change in CV (24.5%). Sympathectomy significantly reduced this heterogeneity through a reduction in the number of low O2 saturation veins (CV = 13.2%) under normoxic conditions and the effect was similar under hypoxic conditions (CV = 15.3%). In both sham-operated and sympathectomized groups, hypoxia elicited a significantly higher cerebrocortical O2 consumption. Thus, bilateral cervical sympathectomy improved the O2 supply in selective cerebrocortical regions with high O2 extraction. However, the effect of sympathetic innervation on the heterogeneity of cerebrocortical venous O2 saturation was not potentiated by hypoxia.(ABSTRACT TRUNCATED AT 250 WORDS)

Imbalance of regional cerebral blood flow and oxygen consumption: effect of vascular alpha adrenoceptor blockade

This study tested the hypothesis that local cerebral O2 supply and consumption are not precisely balanced and that vascular alpha adrenoceptors affect this equilibrium. Twenty-two male Long-Evans rats were used in this study. Cerebral blood flow was determined in six regions, using 4-iodo [N-methyl-14C]antipyrine. Oxygen saturation was determined microspectrophotometrically in small veins draining three regions of the brain of the rat. Comparisons were made between a control group and a group given N-methyl chlorpromazine, an alpha adrenergic blocker that does not affect central neuronal alpha adrenoceptors. Under control conditions, no regional differences in flow were found. With N-methyl chlorpromazine, cerebral blood flow in the basal ganglia was greater than all other regions, except the frontal cortex. Cerebral O2 consumption was higher in the frontal cortex than the medulla under control conditions and this difference was not statistically significant after N-methyl chlorpromazine. Cerebral venous O2 saturations (a measure of cerebral O2 supply/consumption balance) were found to be significantly heterogeneous under control conditions. The coefficient of variation (CV = 100 x SD/mean) averaged 18%. The average cerebral venous O2 saturation was 59 +/- 11%. Administration of N-methyl chlorpromazine significantly reduced this heterogeneity through a reduction in the number of veins with low O2 saturations (CV = 11%). The average value increased slightly but significantly to 62 +/- 8%. Thus, N-methyl chlorpromazine eliminated many microregions of high O2 extraction. This indicated that vascular alpha adrenoceptors limit cerebral blood flow to some of the brain regions.

Laser-induced stimulation of thromboxane B2 synthesis in human blood platelets: role of superoxide radicals

Exposure of platelet-rich plasma to laser radiation at 3.5 W for 30 seconds reduced the threshold concentrations of adenosine diphosphate and L-epinephrine needed from complete platelet aggregation by 20% to 60% and by 30% to 50%, respectively. The irradiation of platelet-rich plasma with laser also increased the basal level of thromboxane A2 from < 0.5 pmol/10(8) platelets for each second of exposure. In contrast, the exposure of gel-filtered platelets to laser produced no effect on the prostanoid formation. However, the addition of laser-exposed platelet-free plasma to gel-filtered platelets stimulated the synthesis of thromboxane A2 in these cells. The effect of laser was completely blocked by adding superoxide dismutase or catalase to the platelet-rich plasma, indicating that the radiation-induced stimulation of thromboxane A2 production was mediated through the generation of superoxide radicals. Electron microscopic studies indicated that the laser-induced stimulation of thromboxane A2 production in platelet can occur without any noticeable damage in the cellular structure.

Evaluation of the efficacy of different antibiotics in inhibiting colonisation of Vibrio cholerae O1 in the rabbit intestine

The efficacy of ciprofloxacin, norfloxacin and tetracycline in prevention of colonisation of V. cholerae O1 in the rabbit intestine were tested. V. cholerae O1 highly colonised the gut of rabbits which did not receive any antibiotic. All antibiotics tested inhibited the colonisation of V. cholerae O1 within the rabbit intestine. Moreover, ciprofloxacin and norfloxacin were found to be as effective as tetracycline suggesting that these drugs should be subjected to clinical trials for the treatment of cholera in comparison with tetracycline.

Effect of pentobarbital on cerebral regional venous O2 saturation heterogeneity

Observed venous O2 saturation inhomogeneity in the brain implies a microregional imbalance in O2 supply/consumption. We hypothesized that this heterogeneity should be decreased by pentobarbital anesthesia through a reduction in regional metabolic heterogeneity. Male, Long-Evans, approximately 350 g rats were either anesthetized with 50 mg/kg pentobarbital (n = 10) or used as a conscious control group (n = 10, catheters inserted two hours earlier under ether anesthesia). In each rat, regional cerebral blood flow was determined by [14C]iodoantipyrine and regional arterial and venous O2 saturation were determined by microspectrophotometry. In the PB group, the mean blood pressure (107 +/- 7 Torr), heart rate (362 +/- 29/min), average cerebral blood flow (63 +/- 19 ml/min/100 g), and average cerebral O2 consumption (3.7 +/- 1.2 ml O2/min/100 g) were lower than those values in the conscious group (128 +/- 15, 474 +/- 44, 112 +/- 40, and 7 +/- 3), respectively. O2 extraction did not change after pentobarbital anesthesia. However, the dispersion of venous O2 saturation narrowed. The distribution of O2 saturations in 373 cerebral veins of anesthetized rats had a significantly reduced coefficient of variation [C.V. = 100 x (S.D./mean) = 13] as compared to a C.V. of 18 in 320 veins in conscious rats. Thus, pentobarbital anesthesia reduced the microregional venous O2 saturation inhomogeneity in the brain, creating a more uniform balance of oxygen supply and consumption.

Normalization of impaired response of platelets to prostaglandin E1/I2 and synthesis of prostacyclin by insulin in unstable angina pectoris and in acute myocardial infarction

The minimal inhibitory concentration of prostaglandin E1 (used as a probe for prostacyclin [PGI2]) needed to inhibit platelet aggregation (36 +/- 16 nM) in normal volunteers (n = 40) increased (64 +/- 30 nM) in patients (n = 46) with acute coronary artery disease. Bolus injection of insulin in 20 patients, 0.1 U/kg body weight 4 times a day (every 6 hours) for 7 days decreased the minimal inhibitory concentration of prostaglandin E1 from 64 +/- 30 to 26 +/- 12 nM (p less than 0.001). Twenty other patients who received only saline solution had no decrease in minimal inhibitory concentration of the prostanoid. The bolus injection of insulin also increased the plasma level of PGI2 (9 +/- 2 pM) two-fold in these patients (28 +/- 10 pM). Administration of aspirin inhibited the insulin-induced increase of plasma prostanoid level. Patients in the placebo group had no increase in plasma PGI2 level. The bolus injection of insulin administered only once to another group of patients (n = 6) demonstrated that the hormonal effects were maximally increased within an hour of insulin administration, and were directly related to the increased insulin level in plasma. These results indicated the feasibility of using physiologic quantities of insulin for controlling of platelet aggregation through resensitization of platelet response to prostaglandin and increased synthesis of PGI2 in vivo in acute coronary artery disease.