Stabilization of pressure drop in the feeder arteries of rats as affected by an increase in blood flow

The dependence of the pressure drop (PD) along conducting vessels between the aorta and the distal end of a. saphena on the blood flow in the artery has been studied in rats. The PD was shown to react to rapid blood flow increase from 0.6 to 1.2 ml/min, with a drastic upstroke followed by a gradual decrease to the initial value within 20 s. When the blood flow was returned to the initial level the PD was recovered during 40 s. A rapid flow increase from 0.1 to 1.0 ml/min in 3 s was accompanied by proportional changes in PD. However, a slow blood flow increase from 0.1 to 1.5 ml/min in 600 s did not induce any marked changes in PD in the range of the blood flow from 0.5 to 1.5 ml/min. The observed stabilization of PD may be attributed to the property of conducting arteries to increase their internal diameter in response to blood flow increase.     

Hypoxia enhances unilateral lung injury by increasing blood flow to the injured lung

We hypothesized that in unilateral lung injury, bilateral hypoxic ventilation would induce vasoconstriction in the normal lung, redirect blood flow to the injured lung, and cause enhanced edema formation. Unilateral left lung injury was induced by intrabronchial instillation of 1.5 ml/kg of 0.1 N HCl. After HCl injury, blood flow to the injured left lung decreased progressively from 0.70 +/- 0.04 to 0.37 +/- 0.05 l/min and percent of flow to the injured left lung (QL/QT) decreased from 37.7 +/- 2.2 to 23.6 +/- 2.2% at 240 min. Exposure to hypoxia (12% O2) for three 10-min episodes did not affect QL/QT in normal animals, but after unilateral HCl injury, it caused blood flow to the injured left lung to increase significantly. A concomitant decrease in blood flow occurred to the noninjured right lung, resulting in a significant increase in QL/QT. The enhanced blood flow to the injured lung was associated with a significant increase in the wet-to-dry lung weight ratio in the dependent regions of the injured lung. These findings demonstrate that in unilateral HCl-induced lung injury, transient hypoxia can enhance blood flow to the areas of injury and increase lung edema formation.     

Rheologic changes with streptokinase--experimental studies]

In dogs with artificial stenosis of the femoral artery application of 96 000 IU Awelysin/kg initially and subsequent infusion of 1200 IU/kg/min caused an increase of the blood flow below the stenosis. The improvement in blood flow is attributed to the decrease in fibrinogen and to the increase in fibrinogen degradation products.     

Endothelium-derived relaxing factor participates in the increased blood flow in response to pentagastrin in the rat stomach mucosa

The stimulation of gastric-acid secretion by pentagastrin, a synthetic analogue of the endogenous peptide gastrin, is associated with an increased blood flow to the stomach mucosa, commonly referred to as functional hyperaemia. There are at least two potent vasodilator substances, the local release of which from endothelial cells could contribute to this hyperaemia, endothelium-derived relaxing factor (EDRF) and prostacyclin. EDRF has been identified as nitric oxide, released enzymatically from the guanidino group of L-arginine. In the present studies, the involvement of prostacyclin in the pentagastrin-induced increase in stomach blood flow was eliminated by using the cyclo-oxygenase inhibitor indomethacin. Thus this work was designed to elucidate the participation of EDRF/NO in the pentagastrin-induced hyperaemia and not its relative importance to prostacyclin. The increase in blood flow to the gastric mucosa in response to pentagastrin was measured by laser Doppler flowmetry in situ. Inhibition of EDRF/NO biosynthesis with the L-arginine analogues NG-monomethyl-L-arginine (MeArg) or N omega-nitro-L-arginine (NO2Arg) significantly attenuated (by more than 80%) the increase in mucosal blood flow in response to pentagastrin. However, infusions of the natural substrate L-arginine reversed the inhibitor effect of MeArg on pentagastrin-induced increase in mucosal blood flow. Local intra-arterial injections of the endothelium-independent vasodilator glyceryl trinitrate produced a dose-related increase in blood flow to the rat stomach mucosa that was unaffected by infusion of MeArg. Thus, in the absence of prostacyclin, EDRF/NO participates in the pentagastrin-induced increase in blood flow to the rat stomach mucosa.     

Change in the rheologic properties of blood during the early postreanimation period]

Experiments were conducted on nembutal-anesthetized cats; a study was made of the dynamic viscosity of the blood, and also of an aggregation capacity of the blood formed elements for two hours of the postresuscitative period. There was established an increase in the viscosity both in the zone of a low (1.82 dynes/cm2) and high (10.94 dynes/cm2) sear stress. A definite role in increase of the blood viscosity is played by a rise in the hematocrite index and by enhanced aggregation capacity of the blood formed elements.     

Cerebral hemodynamics response to low intensity physical exercise

The aim of this research was to study the cerebral hemodynamics reaction to step increase of physical exercises intensity during bicycle ergometer test in young healthy male subjects. Hemodynamics parameters were registered with the transcranial Doppler ultrasonography of middle cerebral artery (MCA) prior to the study and during the last seconds of every step of physical exercise. Cerebral hemodynamics response to physical exercise was characterized by a significant increase of peak systolic blood velocity in the MCA up to 0.25 W/kg of the body weight (90 rpm with regard to 0 W/kg) without further increase of blood velocity in the same physical exercise becoming more intensive up to 0.5 W/kg of the body weight. The stabilization mechanism of blood velocity in cerebral arteries in case of physical exercise increase and, hence, the autoregulation mechanism of cerebral circulation means that the increase of regional cerebral vascular resistance depends on the value of arterial pressure. The autoregulation mechanism of cerebral circulation starts working with he exercise intensity of 0.25 W/kg and the value of systolic blood pressure about 140-145 mm Hg.     

Local vasodilatation with metacholine, but not with nitroprusside, increases forearm glucose uptake

Insulin is known to increase blood flow in parallel to glucose uptake in skeletal muscle. However, it is not known if an increase in blood flow by itself is associated with an increase in glucose uptake in the absence of hyperinsulinemia. To investigate further this matter, the effect of increased blood flow on forearm glucose uptake was studied in the fasting state during intra-arterial infusions of two different vasodilators, metacholine and nitroprusside, in 19 hypertensive subjects. Both metacholine (4 microg/min) and nitroprusside (10 microg/min) increased resting forearm blood flow, measured by venous occlusion plethysmography, to a similar degree (180 % and 170 %, respectively, p<0.0001 for both). However, metacholine infusion increased the forearm glucose uptake from 2.0+/-0.9 (S.D.) during rest to 5.5+/-3.0 umol/min/100 ml tissue (p<0.0001), while no significant change in glucose uptake was seen during nitroprusside infusion (2.3+/-1.4 micromol/min/100 ml tissue). In conclusion, vasodilatation induced by metacholine, but not by nitroprusside, increased glucose uptake in the forearm of hypertensive patients. Thus, an increase in forearm blood flow does not necessarily improve glucose uptake in the forearm during the fasting state.     

Cephazolin and cephapirin circulation in the blood of rabbits

Circulation of 2 semi-synthetic cephalosporins, i. e. cephazoline and cephapyrine in the blood of rabbits after their intramuscular administration in single doses of 5 and 20 mg/kg was studied. It was found that the antibiotics were well adsorbed into the blood. Their maximum blood levels were achieved 15--30 minutes after administration. Cephazoline provided a higher blood level persisting for longer periods of time as compared to cephapyrine. The value of the time of the two-fold decrease in the cephazoline blood level was higher. A four-fold increase in the dose of the cephalosporines resulted in an increase in their blood levels but did not induce any significant increase in the time of their circulation.     

Nature of alpha receptors implicated in the hypertensive effect of high doses of isoprenaline in dogs and rats

Isoproterenol injected intravenously in dogs (3 mg/kg-1) and rats (5 mg/kg-1) induced an increase in blood pressure. After alpha 1 blockade (by AR-C 239, 0.1 mg . kg-1 i.v.) or alpha 2 blockade (by yohimbine, 1 mg/kg-1 i.v.) isoproterenol, as adrenaline, again induced an increase in blood pressure. This hypertensive effect was suppressed by an alpha 2 adrenoceptor blocking agent after an alpha 1 adrenoceptor blocking agent, and vice versa. These results are compatible with stimulation by high doses of isoproterenol of both alpha 1 and alpha 2 adrenoceptors to produce increase in blood pressure.     

Antidiabetic effect of an active fraction extracted from dragon's blood (Dracaena Cochinchinensis)

The active fraction extracted from dragon's blood displayed an inhibitory effect on alpha-glucosidase activity with an IC50 of 0.152 microg/mL, which is nearly half of the crude material. Its inhibition on alpha-glucosidase was noncompetitive. In addition, when this fraction was orally administered to mice dosed with Acarbose (20 mg/kg), the active fraction (100, 300, 500 mg/kg) significantly suppressed increase of blood glucose levels after sucrose loading in a dose-dependent manner. These results suggest that this extract from dragon's blood exerts an anti-diabetic effect by suppressing intestinal carbohydrate absorption and thereby reducing the postprandial increase of blood glucose.     

Renal cortical and medullary blood flow responses to L-NAME and ANG II in wild-type, nNOS null mutant, and eNOS null mutant mice

Experiments in wild-type (WT; C57BL/6J) mice, endothelial nitric oxide synthase null mutant [eNOS(-/-)] mice, and neuronal NOS null mutant [nNOS(-/-)] mice were performed to determine which NOS isoform regulates renal cortical and medullary blood flow under basal conditions and during the infusion of ANG II. Inhibition of NOS with N(omega)-nitro-l-arginine methyl ester (l-NAME; 50 mg/kg iv) in Inactin-anesthetized WT and nNOS(-/-) mice increased arterial blood pressure by 28-31 mmHg and significantly decreased blood flow in the renal cortex (18-24%) and the renal medulla (13-18%). In contrast, blood pressure and renal cortical and medullary blood flow were unaltered after l-NAME administration to eNOS(-/-) mice, indicating that NO derived from eNOS regulates baseline vascular resistance in mice. In subsequent experiments, intravenous ANG II (20 ng x kg(-1) x min(-1)) significantly decreased renal cortical blood flow (by 15-25%) in WT, eNOS(-/-), nNOS(-/-), and WT mice treated with l-NAME. The infusion of ANG II, however, led to a significant increase in medullary blood flow (12-15%) in WT and eNOS(-/-) mice. The increase in medullary blood flow following ANG II infusion was not observed in nNOS(-/-) mice, in WT or eNOS(-/-) mice pretreated with l-NAME, or in WT mice administered the nNOS inhibitor 5-(1-imino-3-butenyl)-l-ornithine (1 mg x kg(-1) x h(-1)). These data demonstrate that NO from eNOS regulates baseline blood flow in the mouse renal cortex and medulla, while NO produced by nNOS mediates an increase in medullary blood flow in response to ANG II.     

Cytochrome P450 1A1 (CYP1A1) in blood lymphocytes evidence for catalytic activity and mRNA expression.

Studies initiated to characterise the catalytic activity and expression of CYP1A1 in rat blood lymphocytes revealed significant activity of 7-ethoxyresorufin-O-deethylase (EROD) in rat blood lymphocytes. Pretreatment with 3-methylcholanthrene (MC) and beta-naphthoflavone (NF) resulted in significant induction in the activity of lymphocyte EROD suggesting that like the liver enzyme, EROD activity in lymphocytes is inducible and is mediated by the MC inducible isoenzymes of P450. The increase in the activity of EROD was associated with a significant increase in the apparent Vmax and affinity of the substrate towards EROD. That this increase in the activity of EROD could be primarily due to the increase in the expression of CYP1A1 isoenzymes was demonstrated by RT-PCR and western immunoblotting studies indicating an increase in the expression of CYP1A1 in blood lymphocytes after MC pretreatment. Significant inhibition in the EROD activity of MC induced lymphocyte by anti-CYP1A1/1A2 and alpha-naphthoflavone further provided evidence that the CYP1A1/1A2 isoenzymes are involved in the activity of EROD in blood lymphocytes. The data indicating similarities in the regulation of CYP1A1 in blood lymphocytes with the liver isoenzyme suggests that factors which may affect expression of CYP1A1 in liver may also affect expression in blood lymphocytes and that blood lymphocytes could be used as a surrogates for studying hepatic expression of the xenobiotic metabolising enzymes.     

The role of free amino acids in osmoregulation of cricket blood (Acheta domesticus)

The blood volume increased during normal feeding, and did not decrease during fasting at the end of the stadium. The unexpectedly high blood volume of starved crickets might be an adaptation to increase chances for moulting via stretch receptor stimulation.The amount of blood amino acids was not changed by feeding, but increased with fasting or starvation. Thus amino acid levels in the blood were not directly related to amino acid input from the gut.The blood protein concentration did not change during starvation, but the amino acid concentration was 33% higher in starved crickets that drank water as opposed to those given saline to drink. Thus amino acid levels in the blood were not related directly to blood protein concentration.The blood amino acid concentration was 19–22 mM/l in response to salt intake by feeding crickets or starved crickets drinking saline. The concentration was 32–38 mM/l when the crickets were fasting prior to and after ecdysis or when starved with water to drink during the time when they would normally be feeding. The increase of amino acids during fasting was due to a proportional increase in all amino acids augmented by a 3 × increase in tyrosine. The increase during salt depleting starvation was due to a doubling of the two predominant amino acids proline and glycine. Proline and glycine were not increased in starved crickets drinking saline, thus starvation was not the reason for the increase. This is the first instance where specific amino acids have been implicated in osmoregulation.     

Intraportal glucose infusion and pancreatic islet blood flow in anesthetized rats

The aim of the study was to evaluate whether a selective increase in portal vein blood glucose concentration can affect pancreatic islet blood flow. Anesthetized rats were infused (0.1 ml/min for 3 min) directly into the portal vein with saline, glucose, or 3-O-methylglucose. The infused dose of glucose (1 mg. kg body wt(-1). min(-1)) was chosen so that the systemic blood glucose concentration was unaffected. Intraportal infusion of D-glucose increased insulin release and islet blood flow; the osmotic control substance 3-O-methylglucose had no such effect. A bilateral vagotomy performed 20 min before the infusions potentiated the islet blood flow response and also induced an increase in whole pancreatic blood flow, whereas the insulin response was abolished. Administration of atropine to vagotomized animals did not change the blood flow responses to intraportal glucose infusions. When the vagotomy was combined with a denervation of the hepatic artery, there was no stimulation of islet blood flow or insulin release after intraportal glucose infusion. We conclude that a selective increase in portal vein blood glucose concentration may participate in the islet blood flow increase in response to hyperglycemia. This effect is probably mediated via periarterial nerves and not through the vagus nerve. Furthermore, this blood flow increase can be dissociated from changes in insulin release.     

Control of tissue blood flow at very low temperatures

Maximum levels of sustainable swimming activity rely on aerobic metabolism, and hence are limited by the cardiovascular supply capacity which is impaired at low temperatures. It is unclear to what extent species adapted to a continuous cold environment retain control of regional blood flow. Muscle blood flow (MBF) was therefore measured using the radiolabelled microsphere method in the Antarctic teleost Notothenia coriiceps and compared with data for trout at their preferred (optimal) temperatures of 0°C and 11°C, respectively. In resting fish, blood flow distribution to skeletal muscle was similar (around 8 ml/min/100 g), despite a lower cardiac output in Notothenia (7 vs. 27 ml/min). Following maximal exercise there was a significant increase in specific blood flow to slow, but not fast, muscle in both species. However, the relative hyperaemia was greater in trout (6.6- vs. 9.3-fold, respectively), with a similar relative increase in cardiac output (2.3- vs. 3.4-fold, respectively). The increase in blood flow to slow muscle, and decrease in peripheral resistance, during maximal exercise in trout (and hence regional O₂ delivery by convective transport) appears to be determined centrally. In contrast, reduced active redistribution from the viscera in Notothenia is presumably responsible for the attenuated increase in MBF on exercise. However, regional hyper- and hypoperfusion can occur within a single locomotory muscle, suggesting control of vascular tone is maintained.     

Proceedings: The effects of hypothalamic and reflexogenic hypertension on renal and femoral circulation.

In anaesthetized dogs, electrical stimulation of the median posterior hypothalamus provoked hypertension accompanied by a decrease of renal blood flow and an increase of femoral blood flow. Similar hypothalamic reactions occurred after bilateral cervical vagotomy or after atropine, 2 mg/kg i.v. During reflexogenic hypertension induced by bilateral carotid occlusion in bivagotomized dogs, the renal and femoral blood flows were not significantly modified. The decrease of the renal blood flow and the increase of the femoral blood flow, during hypothalamic stimulation were greatly reduced or reversed after R 28935 equals erythro-1-(1--e12-(1,4-benzodioxan-2-yl)-2-OH-Et]-4-piperidyl)-2-benzimidaxolinone, 80 mug/kg i.v., but not after clonidine, 5 mug/kg i.v.     

Vasoactive intestinal polypeptide (VIP) provokes vaginal lubrication in normal women

The human vagina is known to be heavily innervated by vasoactive intestinal polypeptide (VIP) immunoreactive nerve fibres. In the present study we have examined the effect of VIP (900 pmol x kg-1 x h-1, IV during 30 min) on vaginal lubrication and blood flow in fourteen normal non-pregnant women. Vaginal blood flow was measured by the heat clearance technique and the vaginal lubrication quantified by the weight gain of preweighed filter papers placed on the surface of the vaginal wall for 30 min. Arterial blood pressure, pulse frequency and the concentration of VIP in peripheral blood were monitored. VIP (median concentrations of 200-300 pmol x l-1) induced a significant increase in vaginal blood flow accompanied by a 100% increase in vaginal lubrication (from 27 mg/cm2 to 53 mg/cm2). The VIP infusion lead to a significant increase in pulse frequency and a significant fall in diastolic arterial blood pressure. The findings suggest that VIP may participate in the control of the local physiological changes observed during sexual arousal: genital vasodilation and increase in vaginal lubrication.     

Visceral pain decreases tolerance to blood loss in conscious female but not male rabbits

Pain is a component of traumatic blood loss, yet little is known about how pain alters the response to blood loss in conscious animals. We evaluated the effects of colorectal distension on the cardiorespiratory response to blood loss in six male and six female conscious, chronically instrumented New Zealand White rabbits. The goal of these experiments was to test the hypotheses that 1) colorectal distension would increase tolerance to hemorrhage (i.e., increase the blood loss required to decrease mean arterial pressure 相似文献   

Blood Glutathione as an Index of Radiation-Induced Oxidative Stress in Mice and Humans

The effect of x-rays on GSH and GSSG levels in blood was studied in mice and humans. An HPLC method that we recently developed was applied to accurately determine GSSG levels in blood. The glutathione redox status (GSH/GSSG) decreases after irradiation. This effect is mainly due to an increase in GSSG levels. Mice received single fraction radiotherapy, at total doses of 1.0 to 7.0 Gy. Changes in GSSG in mouse blood can be detected 10 min after irradiation and last for 6 h within a range of 2.0–7.0 Gy. The highest levels of GSSG (20.1 ± 2.9 ), a 4.7-fold increase as compared with controls) in mouse blood are found 2 h after radiation exposure (5 Gy). Breast and lung cancer patients received fractionated radiotherapy at total doses of 50.0 or 60.0 Gy, respectively. GSH/GSSG also decreases in humans in a dose–response fashion. Two reasons may explain the radiation-induced increase in blood GSSG: (a) the reaction of GSH with radiation-induced free radicals resulting in the formation of thyl radicals that react to produce GSSG; and (b) an increase of GSSG release from different organs (e.g., the liver) into the blood. Our results indicate that the glutathione redox ratio in blood can be used as an index of radiation-induced oxidative stress. © 1997 Elsevier Science Inc.     

Effects of Roundup Herbicide and Increase in Water Temperature on the Parameters of Peripheral Blood Cells in Amur Sleeper <Emphasis Type="Italic">Perccottus glenii</Emphasis> Dybowski

The separate and combined effects of chronic 30-day exposure to the herbicide Roundup in a sublethal concentration of 2 μg/L and an increase in water temperature at a rate of 8°C/h on the parameters of red and white blood in juveniles of Amur sleeper Perccottus glenii Dybowski have been studied. The ratio of mature and immature erythrocytes in the peripheral blood do not change under the influence of the studied factors. An increase in temperature after chronic exposure to Roundup leads to a decrease in red blood cell sizes and increase in the share of abnormal cells. Exposure to the herbicide and the rise in water temperature have the opposite effect on the number of amitosis in erythrocytes and the ratio of leucocyte cells; an antagonistic effect is identified under the combined action of the factors. Changes in white blood correspond to a nonspecific stress response; changes in red blood indicate a reduction in compensatory responses to hypoxia.