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At least 883 records · Page 49Linked to original sources
PubMed2002

Radiosensitization of hypoxic tumor cells by dodecafluoropentane: a gas-phase perfluorochemical emulsion.

One method to make hypoxic, radioresistant cells more radiation sensitive has been to increase the oxygen carrying capacity of normal blood using liquid perfluorochemical emulsions combined with breathing high pO2 gases. We investigated the ability of dodecafluoropentane (DDFP) to sensitize the moderately radiation-resistant Morris 7777 hepatoma based on our previous inability to modify the radiation response of this tumor. DDFP is used in very small quantities compared with perfluorchemicals reported previously. Rats under isoflurane anesthesia were administered EF5 3 h before irradiation to monitor the pretreatment level of tissue hypoxia. At -40 min, DDFP was administered i.v. at 3.5 ml/kg over 30 min. At -10 min, the rats were either continued with air (for controls) or switched to carbogen. The tumors were then irradiated and processed for evaluation of radiation response. Tumor-cell survival for DDFP treatment with air-breathing animals was not significantly different from controls treated without DDFP. Carbogen alone provided minimal sensitization. DDFP plus carbogen caused dramatic radiosensitization, and the radiation response of cells from these tumors was the same as a completely aerobic radiation response. DDFP plus carbogen appears to completely reverse the hypoxic cell radioresistance in this tumor model.

Animals↗
PubMed2002

The application of infinite element method to endodontic endosseous implant stress analysis.

OBJECTIVE: To study the precise stress distribution of the apical foramen area of endodontic endosseous implant, in order to improve the prosthetics of endodontic endosseous implant. METHODS: After analysis of the two-dimensional endodontic endosseous implants model with finite element method, left and right areas beside the apical foramen were selected as infinite domains to calculate. D-N interactive method was used to connect the finite and infinite domains. RESULTS: Under 45 degrees axial right oblique loading, the stress concentration occurred in both infinite domains of the apical foramen. The infinite domain nearing the load side was tension stress concentration, but the other side was compressive stress concentration. Two stress concentration points were just at the central points, which were intersections between implant and dentin. The stress reduced in all directions from these two stress concentration points, but in the ligament, the result was contrary. CONCLUSIONS: The change of the tooth rotational center is helpful to the tooth stability and carrying capacity after restoration. In the implant area, the diameter of implant at the apical foramen of root shall not be reduced to protect root in clinical work. It is very important to preserve the tissue of periodontal ligament for endodontic endosseous implants.

Dental Implantation, Endosseous↗
PubMed2002

Hemorrheological variables in critical limb ischemia.

BACKGROUND: Impaired hemorrheological properties may worsen the tissue hypoxia distal to an arterial narrowing in patients with peripheral arterial occlusive disease (PAOD). The objective of this study was to investigate the changes in red blood cell rigidity, blood viscosity and plasma viscosity as contributing factors in the development of hypoxia in patients with critical limb ischemia (CLI). METHODS: Forty patients with critical limb ischemia and 40 healthy subjects were included in the study. The subjects included in the study were non-diabetic with blood pressure measurements within the normal range. Compound known to interfere with hemorrheological parameters were not taken by the patients for at least 7 days prior to investigation. Routine blood counts (WBC, RBC, Hb, Hct), plasma fibrinogen levels, plasma total cholesterol levels, red blood cell rigidity, blood and plasma viscosity were determined in both groups. Statistical evaluation of the results of both groups was compared by student's "t"-test. The level of significance was set at p<0.05. RESULTS: Blood viscosity at a shear rate of 6.00 sec(-1) was found to be significantly lower in the CLI group (p<0.001), whereas no significant difference was encountered when blood viscosity was measured at a shear rate of 225 sec(-1). Plasma viscosity and plasma fibrinogen levels were comparable. Plasma total cholesterol levels were found to be significantly higher in the CLI group (p<0.05) and red blood cell rigidity significantly lower (p<0.001). CONCLUSIONS: These findings may provide new insights into the role of blood viscosity in patients with CLI contrary to the previous reports in the literature. Therapies that address red blood cell rigidity more directly may decrease tissue hypoxia distal to arterial narrowing by preventing hemolysis, improving microcirculation, and increasing oxygen carrying capacity and may be more beneficial for these patients.

Arterial Occlusive Diseases↗
PubMed2001

[Effect of huancongdan capsule on lipoprotein, apolipoprotein and serum immunoglobulin in vascular dementia patients].

OBJECTIVE: To probe into the effect of Huancongdan capsule (HCDC) on the vascular dementia (VD) related factors, including lipoprotein, apolipoprotein (apo) and serum immunoglobulin. METHODS: Fifty-two patients of VD were divided into the HCDC group (27 patients, treated with HCDC) and the control group (25 patients, treated with Naofukang). Changes of related parameters were observed. RESULTS: The effects in lowering triglyceride and total cholesterol and elevating high density lipoprotein cholesterol in the HCDC group were superior to those in the control group (P < 0.01 or P < 0.05), but the effect in lowering low density lipoprotein cholesterol was similar in the two groups (P > 0.05). Compared with data before treatment, in the HCDC group after treatment, the levels of serum apoA1 increased, and serum apoB100, IgA, IgG and circulating immune complex decreased significantly (P < 0.05 or P < 0.01), but the change of apoE level was insignificant (P > 0.05). CONCLUSION: Through adjusting lipid metabolism, HCDC could improve blood rheologic characteristics, promote cerebral blood flow, improve the oxygen carrying capacity of blood to prevent and treat VD. One of its mechanisms is increasing apoA1 and decreasing apoB100 levels, preventing and improving atherosclerosis and reducing damage of vascular endothelial cells, the another may be its action in improving immune function.

Aged↗
PubMed2002

Epidemics in predator-prey models: disease in the predators.

The author has recently proposed and investigated models for the study of interacting species subject to an additional factor, a disease spreading among one of them, that somehow affects the other one. The inadequacy of such a model comes from the basic assumption on the interacting species. It is well known that the cycles found in the Lotka-Volterra system exhibit a neutral stability, and this phenomenon is carried over to the proposed model. Here we would like to extend the study to account for population dynamics leading to carrying capacities, i.e. logistic behaviour. This corresponds to the so-called quadratic predator-prey models found in the literature. We are able to show that in some cases the trajectories are bounded, and also analyse the local stability of some equilibria.

Animals↗
PubMed1976

Spacelab and its utilization for biomedical experiments.

The types of investigations possible in the orbital laboratory Spacelab are considered. A summary of services available to the Spacelab user is given, in which the load carrying capacity and the characteristics of the main subsystems (e.g. thermal control, environmental control, electrical power and energy as well as data management) are briefly described. Life science investigations may be undertaken for two reasons: firstly, to ensure safety and efficiency, and, secondly, for their scientific interest relating to effects of weightlessness or cosmic radiation. Safety of the crew and their genetic cells in relation to cosmic radiation is considered vital; essential knowledge is also required about the performance of the vestibular balancing mechanism and the related problem of "stomach awareness". The effect of zero-gravity on the cardiovascular system is studied, and the effect of circulatory changes in the brain, possible psychological stress and effects on exercise tolerance measured. Due to their rapid reproduction, important information may be gained from micro-organisms in respect of mutation rates when exposed to radiation. Plants depend, to some extent, on gravity in germination and growth. Of interest here is the relative importance of gravitational and photonic influences.

Adaptation, Physiological↗
PubMed2003

The structural properties of normal and osteoporotic bone.

Although numerous advances have been made in the diagnosis and treatment of osteoporosis, only a fraction of those patients with osteoporosis who receive orthopaedic care are actually treated or referred for treatment of their osteoporotic condition. A review of the basic anatomic and structural properties of normal and osteoporotic bones and how these properties influence the load-carrying capacity of the skeleton is important. Anatomic and mechanical risk factors for osteoporosis form the basis for an appreciation of the clinical risk of fracture among patients. Because vertebral fractures are the most common fractures seen in patients with osteoporosis, attention is focused on the biomechanics of the vertebrae. This information should assist orthopaedic surgeons in the evaluation of patients who have or who are at risk for developing osteoporosis and prepare them for a variety of interventions, both pharmacologic and surgical, that can improve patient care.

Biomechanical Phenomena↗
PubMedDate not supplied

[The involvement of nitric oxide in formation of hemoglobin oxygen-binding properties].

The analysis of literature and results of our investigations indicate the possible involvement of L-arginine-nitric oxide (NO) system in formation of blood oxygen-carrying capacity. In reaction with hemoglobin NO forms methemoglobin, nitrosyl-hemoglobin (HbFe2+NO) and S-nitrosohemoglobin (SNO-Hb). The NO-hemoglobin derivatives have the various biological functions (NO transport, storage, elimination etc.) and are involved in the genesis of different pathologic conditions. The presence of different NO-hemoglobin derivatives can differently influence on the whole blood hemoglobin-oxygen affinity (HOA): methemoglobin and SNO-Hb increases, and HbFe2+NO decreases it. Their effect on the blood oxygen-binding properties may be important for the gas exchange processes. At the level of lung capillaries such effect may be the additional mechanism promoting a blood oxygenation, and in the systemic microcirculation it may optimize blood desaturation and hence the tissue oxygen delivery. Blood oxygen-binding properties affect the state of L-arginine-NO system, however this system also may determine HOA through the intraerythrocytic regulatory mechanisms, oxygen-dependent nature of NO generation, regulation of vascular tone and effect of peroxynitrite.

Animals↗
PubMed1992

[The critical hemoglobin value in the therapy of chronic anemia].

Adequate oxygen delivery to the tissues can usually be assured until the hemoglobin concentration falls below 7-8 g/dl in patients with chronic anemia provided their compensatory mechanisms are not impaired. Such a reduction of hemoglobin concentration is usually tolerated without symptoms at rest. Under increased physical activity or by an underlying impaired function of the lung or the cardiovascular system, adaptation to anemia may not be sufficient. For this reason the impact of anemia and the resulting hypoxemia must be assessed by determining oxygen needs at various levels of physical activity. The clinical assessment for adequate oxygenation of tissues can be sufficiently estimated by simple parameters as tachycardia, dyspnea etc. Benefits from replenishing O2 carrying capacity by transfusion must be always balanced against transfusion-associated risks. Below a hemoglobin concentration of 7 g/dl oxygen transport is impeded and transfusions are necessary to avoid jeopardizing the patient by additional stressful illnesses such as fever.

2,3-Diphosphoglycerate↗
PubMed1975

Reactive hyperaemia in the hind limbs of the rabbits. III. The effect of hypervolemia and venous congestion.

The effect of increased circulatory fluid volume and local venous congestion on reactive hyperaemia was studied in the hind limbs of rabbits. Compared with controls, hypervolemia reduced maximal flow significantly after all occlusion times. Percentual repayment decreased after 10 second occlusions, increased above control level after 60 second occlusions, and otherwise was similar to controls. Hypervolemia increased recovery time significantly after occlusions longer than 10 seconds. It is possible that decreased oxygen carrying capacity of the blood due to decreased haematocrit after infusion can explain the increased repayment observed during hypervolemia. Furthermore, oedema formation may to some extent prolong the wash-out of metabolites in the postischaemic period. During venous congestion, maximal flow, percentual repayment as well as recovery time were significantly reduced after all occlusion times. Venous congestion may represent an increased resistance against blood arriving from the arterial side after release of the arterial occlusion, thereby reducing the initial part of reactive hyperaemia and perhaps a major part of the hyperaemia after short occlusions. In addition the congested blood may represent an increased amount of oxygen made available for the tissue, and finally venoarterial reflexes may contribute to the reduction of reactive hyperaemia during venous congestion. These results show that factors such as circulatory blood volume and venous pressure and blood volume of the local vascular bed affect reactive hyperaemia significantly.

Animals↗
PubMed2003

Certain haematological responses in Swiss albino mice following exposure to textile dye wastewater.

Adults Swiss mice were administered 5% solution of textile industry wastewater orally for 25 days and haematological parameters like RBC, WBC, Hb, and PCV were studied. Red cell indices like MCV, MCH and MCHC were calculated. Results indicate significant reduction in RBC, Hb and PCV levels. It is inferred that toxic effluents cause metabolic alteration in erythrocytes and reduce their Hb carrying capacity.

Administration, Oral↗
PubMed1992

Phagocytic activation of human neutrophils by the detergent component of fluosol.

Fluosol (Alpha Therapeutic Corporation, Los Angeles, CA) an emulsion of perfluorocarbons with a high oxygen-carrying capacity, was approved as an adjunct to alleviate myocardial ischemia during coronary angioplasty. This drug also significantly enhances myocardial salvage presumably related to an action on the neutrophil. The mechanism by which fluosol and its individual components, including the detergent Pluronic F-68, affected neutrophil function was examined. During the incubation of neutrophils with fluosol, a rapid stimulation of superoxide anion production and degranulation which progressively increased over a 30-minute period was detected. Neutrophils incubated with only Pluronic F-68 produced similar amounts of superoxide anion. Cytochalasin B, an inhibitor of phagocytosis, significantly inhibited this superoxide anion generation. As shown previously, neutrophils incubated with fluosol for 30 minutes and then subsequently stimulated manifested a reduction in lysozyme release as compared with untreated cells. Results of an electron microscopic examination confirmed the cellular uptake of the fluosol within phagocytic vacuoles. Neutrophil viability determined by trypan blue was unaffected after fluosol treatment. These observations show that the fluosol emulsion, primarily through micelles formed by the detergent Pluronic F-68, activates human neutrophils by serving as a phagocytic stimulus, which produces a cell refractory to subsequent stimulation.

Blood Substitutes↗
PubMed1992

Comparison of hematologic parameters in normal and streptozotocin-induced diabetic rats.

Hematologic values are compared for normal and streptozotocin-induced diabetic rats after 6 weeks of induced diabetes. Most hematologic parameters were the same in the two groups except for blood glucose, glycated hemoglobin, and 2,3 diphosphoglycerate, all of which were elevated in the streptozotocin group. However the P50 (the PO2 at which the oxygen-carrying capacity of blood is 50% of maximal) remained normal. We hypothesize that a left shift in the oxyhemoglobin dissociation curve caused by the glycation of a small percentage of the hemoglobin is compensated by elevation in the 2,3-diphosphoglycerate which returns the P50 to normal values. This compensatory mechanism also occurs in some stages of human diabetes.

2,3-Diphosphoglycerate↗
PubMedDate not supplied

Cardiovascular benefits of smoking cessation.

Cigarette smoking causes significant exposure to nicotine, which increases heart rate, blood pressure, and thus myocardial oxygen demand, and to carbon monoxide, which decreases the oxygen-carrying capacity of the blood because of carboxyhemoglobin formation. Cigarette smoking also predisposes the patient to coronary vasoconstriction. Smoking cessation results in the early elimination of nicotine and carbon monoxide from the system and decreases the risks of ischemia based on these mechanisms. Over the long term, smoking cessation results in elimination of the increased risk of myocardial infarction in patients without previous heart disease as early as 2 years after smoking stops. In addition, for patients with known coronary artery disease, smoking cessation results in an increase in HDL level, which may result in a retardation of atherogenesis and reduced cardiovascular morbidity and mortality. It is important for all physicians to reiterate both the short- and long-term risks of cigarette smoking as well as the good news-that smoking cessation results in a substantial, if not complete, reversal of the risk of myocardial infarction and death, particularly for patients with established coronary artery disease. In light of those established facts, efforts to develop more effective methods to help patients quit smoking must be increased so patients can realize these important health benefits.

Carboxyhemoglobin↗
PubMed1992

Effects of the calcium channel blocker flunarizine on the hemodynamics and oxygenation of tumor microvasculature.

Flunarizine is a diphenylpiperazine calcium entry blocker that has been shown previously to increase tumor blood flow and sensitivity to radiotherapy via reduction in the radiobiologically significant hypoxic fraction. Two mechanisms of action have been proposed previously (vasodilation, altered blood viscosity), but no studies have been performed to examine its mechanisms of action in vivo. Such information would be invaluable in determining the role of flunarizine in multimodality approaches to reduce tumor hypoxia. Fisher-344 rats bearing R3230Ac tumors transplanted into dorsal flap window chambers were used to examine microcirculatory changes after administration of flunarizine (1.0 mg/kg, iv). The drug increased the diameters of the microvasculature and red cell velocities specifically in central tumor regions (producing an average increase in vessel flow by a factor of 1.96), which was accompanied by an increase in perivascular pO2 of 12 mm Hg, on the average. The drug did not change the diameters of tumor "feeding" vessels, nor did it change vascular length densities. Thus the improvement in central tumor blood flow and oxygenation could not be attributed to dilation of feeding vessels. The oxygen-carrying capacity of the blood was not altered either since hemoglobin saturation (measured in vitro) and the hematocrits of the microvasculature were unchanged after drug administration. Therefore, by a process of elimination, the most likely explanation for the effect of the drug is modification of blood viscosity. Additional studies are under way in this laboratory to examine whether changes in viscosity occur after flunarizine administration.

Adenocarcinoma↗
PubMed1992

Splanchnic hemodynamics and oxygen supply during acute normovolemic hemodilution alone and with isoflurane-induced hypotension in the anesthetized pig.

Safety of combined hemodilution and isoflurane-induced hypotension was assessed by studying their effects on splanchnic hemodynamics and oxygenation in nine anesthetized (ketamine/flunitrazepam) pigs. Acute normovolemic hemodilution (decrease in hematocrit from 29% to 15%) with 6% hydroxyethyl starch decreased (P < 0.05) O2 delivery despite increases in cardiac output and all splanchnic flows, as measured by electromagnetic flow probes. Superimposed isoflurane (1.45% end-tidal concentrations) caused marked decreases in arterial blood pressure, cardiac output, and splanchnic flows. Oxygen uptake of the liver became O2 supply dependent. A liver surface PO2 histogram (Clark-type electrode) showed 38% of PO2 values between 0 and 5 mm Hg. Hepatic lactate uptake decreased by 75%. These data suggest that depression of cardiovascular function during reduced O2-carrying capacity adversely affects hepatic perfusion, oxygenation, and function. Combined hemodilution and isoflurane-induced hypotension may not be appropriate in patients.

Anesthesia↗
PubMed1992

Distribution of phosphatidylcholine molecular species between mixed micelles and phospholipid-cholesterol vesicles in human gallbladder bile: dependence on acyl chain length and unsaturation.

The partitioning of phosphatidylcholine (PC) molecular species between mixed micelles and vesicles was studied in each of seven human gallbladder biles. Biles were fractionated by Sephacryl S-300 SF gel filtration chromatography, and PC species in the micellar and vesicular fractions were quantitated by high performance liquid chromatography. Micelles were enriched in species containing unsaturated acyl groups (e.g., 16:1-18:2, 18:1-18:2, and 18:1-18:3); vesicles were enriched in more highly saturated species (e.g., 16:0-16:1, 16:0-18:1, and 18:0-18:1). Separate multivariate analyses for each bile demonstrated that the distribution of PC species between vesicles and micelles was related to the degree of sn-1 and sn-2 unsaturation, and sn-1, but not sn-2, chain length. In addition, the tendency to partition into the micellar phase was particularly marked when unsaturation was present at both the sn-1 and sn-2 positions. When this interaction was included in the multivariate analyses, the regression models accounted for virtually all of the variation in PC partitioning (for each of the seven patients r2 = 0.92-0.98, P less than 0.03). These results suggest that the partitioning of PC species between micelles and vesicles is strictly determined by sn-1 chain length and the degree of unsaturation at both the sn-1 and sn-2 positions. In light of recent reports that fatty acyl composition influences the cholesterol content of vesicles and micelles in model biles, these results raise the possibility that diet-induced alterations in the phospholipid species and the relative proportions of biliary lipid particles may influence the cholesterol-carrying capacity of bile.

Bile↗