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Biomedical subjects

M V Kameneva

Publications and source records attributed to M V Kameneva.

At least 19 recordsLinked to original sources
PubMed2006

I.V. infusion of a drag-reducing polymer extracted from aloe vera prolonged survival time in a rat model of acute myocardial ischaemia.

BACKGROUND: I.V. infusion of drag-reducing polymers (DRPs) has been shown to improve survival time in animals subjected to haemorrhagic shock. We hypothesized that DRPs might prolong survival time in rats following acute myocardial ischaemia (AMI). METHODS: Sixteen adult male rats were anaesthetized and mechanically ventilated. An i.v. infusion of either Dextran-40 2.5% (Control, n=8) or Dextran-40 2.5% containing 50 microg ml(-1) of an aloe vera-based DRP (DRP, n=8) was initiated at 3.5 ml h(-1). The left anterior descending coronary artery was ligated. Blood pressure, skin-tissue perfusion, and heart rate were monitored and arterial blood samples were analysed. RESULTS: The mortality at 60 min following coronary ligation was 0% in the DRP group vs 50% in the control group (P=0.025). DRP-treated animals maintained higher mean arterial pressure [60.9 (5.1) vs 47.5 (5.1) mm Hg, P=0.004] and tissue perfusion [4.2 (3.4) vs 1.2 (0.5) TPU, P=0.029]. The DRP group trended towards better acid-base status with base excess [-5.0 (1.7) vs -8.1 (5.1) mmol litre(-1), P=0.083] and pH [7.42 (0.07) vs 7.35 (0.02), P=0.03]. CONCLUSIONS: Administration of nanomolar concentrations of aloe vera-based DRP prolonged survival time in animals with AMI. DRPs may offer a novel method to treat organ/tissue hypoperfusion.

Acute Disease↗
PubMed2001

The role of diastolic pump flow in centrifugal blood pump hemodynamics.

We tried to verify the hypothesis that increases in pump flow during diastole are matched by decreases in left ventricular (LV) output during systole. A calf (80 kg) was implanted with an implantable centrifugal blood pump (EVAHEART, SunMedical Technology Research Corp., Nagano, Japan) with left ventricle to aorta (LV-Ao) bypass, and parameters were recorded at different pump speeds under general anesthesia. Pump inflow and outflow pressure, arterial pressure, systemic and pulmonary blood flow, and electrocardiogram (ECG) were recorded on the computer every 5 ms. All parameters were separated into systolic and diastolic components and analyzed. The pulmonary flow was the same as the systemic flow during the study (p > 0.1). Systemic flow consisted of pump flow and LV output through the aortic valve. The ratio of systolic pump flow to pulmonary flow (51.3%) did not change significantly at variable pump speeds (p > 0.1). The other portions of the systemic flow were shared by the left ventricular output and the pump flow during diastole. When pump flow increased during diastole, there was a corresponding decrease in the LV output (Y = -1.068X + 51.462; R(insert)(2) = 0.9501). These show that pump diastolic flow may regulate expansion of the left ventricle in diastole.

Analysis of Variance↗
PubMed2000

Assessing acute platelet adhesion on opaque metallic and polymeric biomaterials with fiber optic microscopy.

The degree of platelet adhesion and subsequent thrombus formation is an important measure of biocompatibility for cardiovascular biomaterials. Traditional methods of quantifying platelet adhesion often are limited by the need for direct optical access, limited spatial resolution, or the lack of temporal resolution. We have developed a new imaging system that utilizes fiber optics and fluorescence microscopy for the quantification of platelet adhesion. This fiber optic remote microscope is capable of imaging individual fluorescently labeled platelets in whole blood on opaque surfaces. Using this method, platelet adhesion was quantified on a series of metallic [low-temperature isotropic carbon (LTIC); titanium alloy (Ti); diamond-like carbon (DLC); oxidized titanium alloy (TiO); and polycrystalline diamond (PCD)] and polymeric [woven Dacron (WD)] collagen-impregnated Dacron (HEM), expanded polytetrafluoroethylene (ePTFE), and denucleated ePTFE (dePTFE)] biomaterials designed for use in cardiovascular applications. These materials were perfused with heparinized whole human blood in an in vitro parallel plate flow chamber. Platelet adhesion after 5 min of perfusion ranged from 3.7 +/- 1.0 (dePTFE) to 16.8 +/- 1.5 (WD) platelets/1000 micrometer. The temporal information revealed by these studies provides a comparative measure of the acute thrombogenicity of these materials as well as some insight into their long-term hemocompatibilities. Also studied here were the effects of wall shear rate and axial position on platelet adhesion. A predicted increase in platelet adhesion with increased wall shear rate and a trend toward a decrease in platelet adhesion with increased axial distance was observed with the fiber optic microscope. Future applications for this imaging technique may include the long-term evaluation of thrombosis in blood-contacting devices in vitro and, in animal models, in vivo.

Alloys↗
PubMed2000

Continuously maintaining positive flow avoids endocardial suction of a rotary blood pump with left ventricular bypass.

This study showed the usefulness of maintaining positive pump flow to avoid endocardial suction and as an assist bypass. Three calves were implanted with centrifugal pumps. Hemodynamics and pump parameters were measured at varying pump speeds (from 1,100 to 2,300 rpm). In each test pump, speed was adjusted to create 3 hemodynamic states: both positive and negative flow (PNF), positive and zero flow (PZF), and continuously positive flow (CPF). The pump flow volume was determined during systole (Vs) and diastole (Vd). Vs in PNF was 29.6 ml and was not significantly different from Vs in PZF (p > 0.15). Vd in PNF was significantly different from Vd in PZF (p < 0.05). All bypass rates of PNF were over 30% of pulmonary flow. All PZF bypass rates were between the PNF rate and the CPF rate. These data showed that PZF satisfied the minimum requirement of assist flow and was under 100% bypass. Thus, PZF may avoid endocardial suction.

Analysis of Variance↗
PubMed1999

Rotary blood pump flow spontaneously increases during exercise under constant pump speed: results of a chronic study.

Many types of rotary blood pumps and pump control methods have recently been developed with the goal of clinical use. From experiments, we know that pump flow spontaneously increases during exercise without changing pump control parameters. The purpose of this study was to determine the hemodynamics associated with the long-term observation of calves implanted with centrifugal blood pumps (EVAHEART, Sun Medical Technology Research Corporation, Nagano, Japan). Two healthy female Jersey calves were implanted with devices in the left thoracic cavity. A total of 22 treadmill exercise tests were performed after the 50th postoperative day. During exercise, the following parameters were compared with conditions at rest: heart rate, blood pressure, central venous oxygen saturation (SvO2), pump speed, and pump flow. The pump flow in a cardiac cycle was analyzed by separating the systole and diastole. Compared to the base data, statistically significant differences were found in the following interrelated parameters: the heart rate (66.8 +/- 5.2 vs. 106 +/- 9.7 bpm), mean pump flow (4.8 +/- 0.2 vs. 7.0 +/- 0.3 L/min), and volume of pump flow in diastole (26.0 +/- 1.8 vs. 13.5 +/- 2.5 ml). During exercise, the volume of pump flow in systole was 3 times larger than that measured in diastole. Blood pressure, SvO2, and pump speed did not change significantly from rest to exercise. These results suggested that the mean pump flow depends on the systolic pump flow. Therefore, the increase in the mean pump flow during exercise under constant pump speed was caused by an increase in the heart rate.

Animals↗
PubMed1999

Gender difference in rheologic properties of blood and risk of cardiovascular diseases.

According to official statistical data there is a significant difference between pre-menopausal women and age-matched men in morbidity and mortality from cardiac diseases and especially from myocardial infarction. There are several speculations regarding the nature of this phenomenon which have both supporting and refuting evidence. Our hypothesis was that due to regular physiologic bleeding, rheological properties of blood of pre-menopausal women are superior to those of men, and place such women at a lower risk of cardiovascular diseases than men in any age group. We believe that this difference in hemorheological properties is due to the reduced concentration of red blood cells (RBCs) and due to greater population of younger and less population of older RBCs in female blood. We studied mechanical properties of blood from 47 pre-menopausal women and 50 age-matched men. Compared to female blood, male blood had higher viscosity and RBC aggregation and lower RBC deformability. Oxygen Delivery Index, calculated as a ratio of hematocrit to blood viscosity, was found to be significantly lower in male blood. Decreased oxygen delivery along with increased RBC aggregation and decreased RBC deformability may contribute to the higher risk for the development of cardiovascular diseases. Regular blood donation may reduce hematocrit and blood viscosity, improve rheological properties of blood, and increase oxygen delivery in men.

Adult↗
PubMed1998

Assessment of bovine platelet life span with biotinylation and flow cytometry.

Reduced platelet life span is associated with the implantation of a variety of cardiovascular devices and may be used as a gauge of device biocompatibility. In the bovine model, platelet life span has previously been assessed with radioisotope labeling of removed platelets followed by reinjection and periodic gamma counting of blood samples. We report here the use of protein-reactive biotin (sulfo-N-hydroxysuccinimido [NHS]-biotin) as an alternative to radioisotope techniques whereby reinjected biotinylated platelets are subsequently detected in blood samples using phycoerythrin-streptavidin and flow cytometric techniques. Platelet life span was quantified in a normal calf (4.9 days) and in a calf prior to (6.1 days) and following (3.1 days) implantation of a Nimbus Axial Flow Pump ventricular assist device. The assessment of bovine platelet life span with biotinylation and flow cytometry avoids the technical, regulatory, and safety considerations associated with radioisotope usage and appears readily amenable to application in cardiovascular device testing.

Animals↗
PubMed1998

Red blood cell aging and risk of cardiovascular diseases.

We hypothesized that due to monthly bloodloss, the mechanical properties of blood of premenopausal women are superior to men, and place them at less risk for cardiovascular diseases than men in any age group. Rheological properties of blood of premenopausal women and age-matched men were compared. It was found that male blood possesses an increased viscosity, RBC aggregability and RBC rigidity. Additionally, male RBCs were found to have higher mechanical fragility. Since women in reproductive age have almost half as many old RBCs and almost twice as many young RBCs as men, we investigated the effect of in vivo aging of RBCs on their mechanical properties. Old RBCs were shown to have an increased mechanical fragility and aggregability, and decreased deformability as compared to young RBCs. Decreased deformability and increased aggregability of RBCs cause an increase in blood viscosity and are known as risk factors of cardiovascular diseases. Since men possess a higher number of old RBCs with suboptimum mechanical properties than premenopausal women, who due to monthly bloodloss have a higher number of young cells and a lower number of old RBCs than their male counterparts, our results suggest that an elevated hemorheological risk for males is associated with the age distribution of RBCs. This, in addition to significantly higher hematocrit, may be the reason for the increased risk of morbidity and mortality from cardiovascular diseases of men as compared to women of reproductive age.

Adult↗
PubMed1997

Cellular content and permeability of intraluminal thrombus in abdominal aortic aneurysm.

PURPOSE: A pathologic feature commonly associated with abdominal aortic aneurysms is the presence of variably sized and shaped intraluminal thrombus, which may be fundamental to the disease process. However, the precise role of the intraluminal thrombus in the formation, enlargement, and rupture of abdominal aortic aneurysms is unknown. The hypothesis tested in this study was whether there were structural features of aortic thrombi to suggest that it may be involved in the pathogenesis of abdominal aortic aneurysms. We have investigated this hypothesis using a variety of structural and biochemical techniques. METHODS: Tests performed were light, transmission, and scanning electron microscopy; fluid permeability measurements; and Western blots. RESULTS: Intraluminal thrombus found in abdominal aortic aneurysms is structurally complex and is traversed from the luminal to abluminal surface by a continuous network of interconnected canaliculi. Quantitative microscopic analysis of the thrombus shows cellular penetration for at least 1 cm from the luminal surface of the thrombus. Macro-molecular penetration may be unrestricted throughout the entire thickness of the thrombus. Fibrin deposition occurred throughout the thrombus, whereas fibrin degradation occurred principally at the abluminal surface. CONCLUSIONS: These principally structural studies support the hypothesis that the thrombus is a self-sustaining entity that may have significance in the pathophysiologic mechanism of abdominal aortic aneurysms.

Aorta, Abdominal↗
PubMed1996

Reduction of cytochrome-c oxidase copper precedes failing cerebral O2 utilization in fluorocarbon-perfused cats.

We determined the relationship of the low-potential copper (CuA) redox state of cytochrome-c oxidase to the brain tissue PO2 (PtiO2) and global cerebral O2 consumption (CMRO2) in vivo. The redox state of cytochrome-c oxidase copper was monitored in perfluorocarbon-exchanged cats under normoxic and graded hypoxic conditions with use of near-infrared spectroscopy. Continuous spectra ranging from 730 to 960 nm were acquired, and the change in copper redox state was assessed by the absorption changes at 830 nm. PtiO2 was measured with O2-sensitive electrodes implanted into the cortex, and CMRO2 was determined by sampling arterial and superior sagittal sinus perfusate and by measuring blood flow with radiolabeled microspheres. As PtiO2 decreased with hypoxia, the CuA of cytochrome-c oxidase became progressively reduced, whereas the CMRO2 was unchanged during the initial stages of hypoxia. Only with severe hypoxia, did CMRO2 and the amplitude of somatosensory evoked potentials decrease. We conclude that the CuA site of cytochrome-c oxidase is involved in a regulatory adjustment that helps maintain CMRO2 constant.

Animals↗
PubMed1995

A mathematical model for shear-induced hemolysis.

The time-varying history of stress exposure within a rotary blood pump makes it difficult to arrive at a quantifiable design criterion for predicting cell traumatization. Constant stress experiments have revealed that there is a threshold stress level above which damage to blood cells occurs depending upon the time of exposure. The shear stress history experienced by cells within a rotary blood pump, however, is highly unsteady. In order to better predict cell trauma under these realistic conditions, a mathematical damage model based on a concept of "damage accumulation" has been developed. This model is evaluated within the context of red cell trauma. Experimental results support the hypothesis that the rate of damage accumulation increases nonlinearly with the stress level as well as the age of the cell.

Erythrocytes↗
PubMed1994

Capacity for red blood cell aggregation is higher in athletic mammalian species than in sedentary species.

The purpose of this study was to show that two rheological parameters, red blood cell (RBC) sedimentation rate and apparent blood viscosity at low shear rate, characterizing the degree of RBC aggregation, correlate significantly with the maximal mass-specific rate of oxygen consumption or aerobic capacity (VO2max). Comparisons were made within two groups of similarly sized athletic and sedentary species: group 1, pronghorn antelope, dog, goat, and sheep; and group 2, horse and cow. The pronghorn antelope (Antilocapra americana) is one of the most athletic mammals, and we have obtained data on the rheological properties of blood from this species for the first time. The values of apparent viscosity at hematocrit = 40% and shear rate = 0.277 s-1 measured in a rotational viscometer were 59.5, 42.6, and 9.1 cP for antelope, dog, and sheep blood, respectively, and 55.3 and 11.5 cP for horse and cow blood, respectively. The viscosity values for antelope, dog, and sheep blood can be correlated with aerobic capacity: ln viscosity = 4.48-106.3 VO2(-1)max (r2 = 0.998; P < 0.05). The values of RBC sedimentation rate at hematocrit = 40% were 12.8, 7.0, and 0 mm/h for antelope, dog, and sheep blood, respectively, and 45.3 and 0.1 mm/h for horse and cow blood, respectively. Therefore, the data showed that the athletic species exhibit a consistently higher degree of RBC aggregation than do the corresponding nonathletic species.

Animals↗
PubMed1988

[Effect on the systemic hemodynamics of polymers that decrease hydrodynamic resistance].

It has been shown that intravenous injections of drug-reducing polymers (at a dose of 2 x1 0(-6) g/ml) to rabbits produced a decrease in the total peripheral resistance with an increase in the cardiac output and simultaneous diminution of the mean blood pressure. These hemodynamic effects did not depend on vasodilatation as it had previously been shown. The alterations were retained for not less than 72 hours after one polymer injection; the effects were due to the influence of polymers on the flow structure.

Animals↗