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 296,593 document(s) hit in 31,850,051 MEDLINE articles (0.02 seconds)

A theoretical model of the process of respiratory gas exchange between capillary and tissue is described, with special reference to the importance of variations in blood properties. The volume of tissue supplied with oxygen from a single vessel, as a function of the blood flowrate (u), hematocrit (h), and 2,3 diphosphoglycerate concentration (DPG), is calculated from a solution to the set of equations governing species distributions in the blood and tissue. The results, which are presented in the form of crossplots of the three blood parameters (u, h, and DPG) at a constant oxygen supply rate, show the possible significance of in vivo variations in the oxygen affinity of hemoglobin as a compensatory mechanism. Of further physiological interest is the sharp increase in venous erythrocyte pH in response to decreases in hematocrit, once the hematocrit is below a certain level. These results, and those relating DPG to hematocrit at constant O2 supply, are consistent with experimental observations of elevated DPG and pH levels in anemic individualts, and the dependence of erythrocyte DPG concentration upon pH.
Acta Med Scand Suppl 1975
PMID:The blood oxygen transport system. A numerical simulation of capillary-tissue respiratory gas exchange. 23 26

The underlying cause leading to the reversible functional changes in the microcirculation of insulin-dependent diabetic subjects early during the disease prior to any clinical signs of retinopathy and nephropathy (functional microangiopathy) is discussed. It is suggested that the initial microvascular dilation observed in diabetics is due to an autoregulatory response to relative tissue hypoxia providing an increased tissue perfusion in order to improve tissue oxygen delivery. Supporting evidence for this suggestion is derived from the findings that diabetics simultaneously may show increased tissue oxygen consumption and decreased ability of the circulating blood to release oxygen to the tissues. The latter defect is likely to be caused by two interrelated factors: 1. an increased proportion of haemoglobin A1c with high oxygen affinity, and 2. difficulties of maintaining a sufficiently high concentration of plasma inorganic phosphate in order to provide an optimal 2,3-diphosphoglycerate (2,3-DPG) content in the erythrocytes. The basal oxygen demand of diabetics may fluctuate even within a few hours dependent upon the state of metabolic control and is increased at times of poor regulation. Hence, diabetics may suffer from innumerable cellular hypoxic injuries, which during the first years of the disease are counteracted in the microcirculation by an autoregulatory response. These microvascular reactions associated with increased plasma permeation may over the years be of major importance for the development of the degenerative microangiopathy in diabetes.
Acta Med Scand Suppl 1975
PMID:The problem of tissue oxygenation in diabetes mellitus. I. Its relation to the early functional changes in the microcirculation of diabetic subjects. 23 27

In order to study the determining factors for oxygen transport the oxyhaemoglobin dissociation curve (ODC), red cell 2,3-diphosphoglycerate (2,3-DPG), and plasma inorganic phosphate were estimated in insulin-requiring juvenile and adult diabetics in various conditions of metabolic control. 2,3-DPG has been shown to vary much more in diabetics than in normals, depending upon the state of metabolic control. These fluctuations of 2,3-DPG are mediated by variations in plasma inorganic phosphate as indicated by a close correlation. While 2,3-DPG was markedly decreased in diabetic ketoacidosis, it tended to be increased in ambulatory, non-acidotic patients. Since in the non-acidotic patients the oxygen-carrying capacity, i.e. the haemoglobin concentration was simultaneously elevated, these findings suggest the presence of relative tissue hypoxia in diabetes. Both in non-acidotic and in ketoacidotic patients there was a strong correlation between the amount of 2,3-DPG and the P50 at actual pH as an experssion of the oxygen affinity of haemoglobin. In order to guarantee an optimal erythrocyte oxygen release in diabetics the content of red cell 2,3-DPG and plasma inorganic phosphate should be higher than normal.
Acta Med Scand Suppl 1975
PMID:The problem of tissue oxygenation in diabetes mellitus. 23 28

Normal mice exposed to 10% oxygen concentration developed a slight but statistically significant decrease in blood pH and a slight statistically insignificant decrease in red cell 2,3-DPG. Mice that were infected intraperitoneally with Staphylococcus aureus or Klebsiella pneumoniae and exposed to 20% oxygen developed acidosis, hemoconcentration, and decreased red cell 2,3-DPG levels. When mice with acute bacterial peritonitis were exposed to 10% oxygen concentration they likewise developed significant acidosis and hemoconcentration, but their reduction in red cell 2,3-DPG was not as great as that in the similarly infected mice exposed to 20% oxygen concentration.
J Med 1975
PMID:The effects of Staphylococcus aureus and Klebsiella pneumoniae peritonitis in mice exposed to normal and hypoxic conditions on red cell oxygen transport function. 23 91

Studied were the changes in the total acidity and the amount of the water-soluble fatty acids in bovine and swine fats following the irradiation with gamma-rays. The treatment was effected by means of a 60Co source at 12--15 degrees C. The samples were kept at temperatures ranging from 2 to 4 degrees C, and from --18 to --20 degrees C in the course of 45 and 90 days, resp., being irradiated in the presence and absence of oxygen at rates of from 0.1 up to 2.0 Mrad. Results showed that gamma-treated at the rate of up to 2.00 Mrad produces no effect on the changes observed with the total acidity and the changes taking place during storage. The changes of the water-soluble fatty acids in the presence of oxygen, the type of fat, the temperature value, and the period of storage. The higher the irradiation rates used the greater the changes and shorter the time they need to take place. The presence of oxygen also proved of substantial importance for the changes in the amount of the watersoluble fatty acids. Bovine fats proved more sensitive to the changes referred to than swine fats.
Vet Med Nauki 1975
PMID:[Influence of gamma-rays on the general acidity and the water-soluble fatty acids of swine and cattle fats]. 24 14

The oxygen consumption (Vo2) of three castrated male red deer was measured while they walked on a treadmill at 7 degree and 14 degree slopes and on the level at speeds varying from 44.3 to 172.9 m.min(-1). The energy cost of horizontal locomotion in excess of standing was 2.6 J kg(-1).m(-1). The cost of maintenance of posture when walking was the same as that of standing. The energy cost of walking up gradients was 21.5 J kg(-1).vertical m(-1). These results are discussed in relation to values reported for other species.
Q J Exp Physiol Cogn Med Sci 1977 Oct
PMID:The energy cost of locomotion on the level and on gradients for the red deer (Cervus elaphus). 24 23

Measurements of total body oxygen consumption, visceral and hepatic blood flow, oxygen consumption, exchanges of amino acids, lactate, pyruvate and glucose were made on sheep fed 3--6 h or 21 h before the experiment and exposed for 3 h to a neutral environment (15 degrees C) or a cold environment (0.5 to 4 degrees C with clipped coat and wind speed 2 m.s-1). Recent feeding significantly increasedd the total oxygen consumption and the oxygen consumption of the viscera and liver. No general release of amino acids from the viscera or uptake by the liver after feeding was detected although the arterial plasma concentration of essential amino acids did increase significantly after feeding. The plasma concentration of most non-essential amino acids also increased except that of glycine, which decreased significantly. Cold exposure increased the total oxygen consumption and reduced the respiratory quotient significantly. Release of amino acids from the viscera was stimulated by cold exposure. There was a variable increase in the hepatic uptake of lactate and alanine when the sheep were fasted and cold-exposed. The liver's glucose output doubled and the blood (arterial) glucose concentration significantly increased in the cold.
Q J Exp Physiol Cogn Med Sci 1978 Apr
PMID:Acute cold exposure and the metabolism of glucose and some of its precursors in the liver of the fed and fasted sheep. 24 36

The authors presented their own material of years 1974-1977. During this period 8788 children were born, in it 737 (8,3%) with low birth weight (below 2500 g). Retrolental fibroplasia was diagnosed in 4 children, it was 0,5% of newborns with low birth weight, and 0,04% of the all live-borns. The retrolental fibroplasia was diagnosed in: 1) the child born in 27 week of pregnancy with 1000 g of body weight, 2) in two children born in 32-33 week of pregnancy with 1450 g and 1350 g of body weight, 3) in a child born in 31 week of pregnancy with 1600 g of body weight. The infants were nursed in incubators with about 30% of oxygen during 36 to 46 days. Contemporary hypoglycemia, hypoproteinemia, atelectasia of lungs with respiratory insufficiency were diagnosed. In the discussion the authors underlined the role of immaturity and hypoxia of the premature baby, which play the role in the secondary injury of vessel's walls of retina. The disturbancy of carbohydrate and protein metabolism were certainly secondary pathogenic agent sin retrolental fibroplasia. There exists the necessity of oxygen therapy of premature baby, but to take cre of the infant in the incubator does not mean the necessity of oxygen therapy . Even with controlled oxygen dosage in incubator the retrolental fibroplasia may occur as a result of relative hyperoxydation induced by the constriction of retina vessels. The authors underlined the necessity of repeated ophthalmologic examination of premature babies in about every 2 weeks, what makes very early diagnosis possible.
Probl Med Wieku Rozwoj 1979
PMID:[Risk of damage to the organ of vision in low birth weight infants]. 26 40

We measured the action of dopamine given intravenously at dosage ranging from 2.5 to 320 micrograms/kg per min in closed chest anaesthetized dogs. Dopamine produced a dose-dependent increase in heart rate, cardiac index, mean arterial pressure, total peripheral resistance, pulmonary artery pressure, left ventricular end diastolic pressure, coronary flow and myocardial oxygen consumption. At dopamine dosage of 80-320 micrograms/kg per min, the coronary vascular resistance, the stroke volume index, the efficiency of heart work and the central venous pressure are all decreased. The maximum effect of dopamine on the circulation was seen at a dose between 40 and 80 micrograms/kg per min.
Proc R Soc Med 1977
PMID:Dopamine effects on circulation and myocardial oxygen supply. 26 1

The protective effect of propranolol on ischemic myocardium was studied experimentally and clinically by electron microscope. In an animal experiment, ischemic changes were produced in the posterior papillary muscle of the rabbit following 3, 15, 30 minutes of occlusion of the circumflex coronary artery. Propranolol (0.25 mg/kg) was injected into the left atrial cavity before occlusion of the artery. The posterior papillary muscle was excised and examined by electron microscope. In clinical experience, propranolol (20 microng/kg) was given intravenously to 6 patients who underwent open heart surgery. Transmural left ventricular myocardial biopsy was performed after the anoxic cardic arrest and the material, particularly the subendocardium, was examined by electron microscope. It was shown that propranolol was effective, both in the experiment and in the clinical experience, in preserving ischemic myocardium. The possible mechanisms through which propranolol might act were considered to be (1) indirect effect of altered oxygen supply vs. demand, effect by reducing heart rate and reducing cardiac output due to the drug's function as a beta blocker, (2) direct cellular effect, i.e., reducing myocardial substrate metabolism along with stabilization of cellular structure, and (3) increase collateral circulation to the subendocardium.
Bull Tokyo Med Dent Univ 1977 Mar
PMID:The protective effect of propranolol on ischemic myocardium: an electron microscopic study. 26 77


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