Search PubMed⌕ Search

Biomedical subjects

R Elsner

Publications and source records attributed to R Elsner.

At least 55 records · Page 3Linked to original sources
PubMed1981

2,3-Biphosphoglycerate, inorganic phosphate, pH and hemoglobin concentration in chronic renal failure of man.

In a group of 69 patients with chronic renal failure, 18 patients after renal transplantation and 8 healthy controls the influence of inorganic phosphate and pH of plasma and of the hemoglobin concentration in whole blood on the 2,3-DPG concentration in red blood cells was investigated. The data were treated by linear regression analysis as well as by multivalent correlation analysis with graph-theoretical methods. Hemoglobin and inorganic phosphate are the factors of renal importance for the 2,3-DPG concentration. The pH affects 2,3-DPG directly (positively) and indirectly via inorganic phosphate (negatively). Therefore, the influence of pH on 2,3-DPG usually observed is abolished in this group of patients. Determinations of inorganic phosphate and hemoglobin seem to be valuable for the diagnosis of the 2,3-DPG-dependent oxygen transport function during chronic renal failure. All the parameters studied were found to be normalized in the group of patients after renal transplantation.

2,3-Diphosphoglycerate↗
PubMed1981

Accumulation of phosphate esters and decline of ATP in red cells incubated in vitro is caused by lack of pyruvate.

Addition of pyruvate to human red cells incubated in vitro at alkaline pH values inhibits the accumulation of phosphate esters otherwise observed as well as the decrease of ATP and the corresponding increase of ADP and AMP. The increase of glycolysis at alkaline pH values is only partly due to a pH effect per se. About one-half of it is caused by a partial release of the inhibition of phosphofructokinase by a lowering of the ATP concentration and particularly by the increase of AMP. Only in the presence of pyruvate there occurs an increase of 2,3-bisphosphoglycerate, such as is observed in vivo, which is balanced by the consumption of pyruvate. At alkaline pH values in the absence of pyruvate there is a low movement from the fructose-1,6-bisphosphate + triosephosphates pool to the components of the pentose phosphate pathway, mostly by way of recombination from glyceraldehyde-phosphate.

Adenosine Triphosphate↗
PubMed1980

[ATP-dependent and ATP-independent changes in deformability of human erythrocytes].

By means of a simple filtration procedure it is shown that the deformability of red blood cells depends indirectly on their relative ATP-concentration. Losses in deformability were observed even with concentrations of ATP, which occur in the course of normal ageing of red blood cells in situ. If erythrocytes are incubated for longer times, their membrane is alterated to such a degree, that the changes cannot be reversed solely by restitution of ATP. The cells remain rigid.

Adenosine Triphosphate↗
PubMed1979

Role of carotid-body chemoreceptors and their reflex interactions in bradycardia and cardiac arrest.

Stimulation of the carotid-body chemo-receptors by asphyxia during an apnoeic episode may contribute to the vagally mediated cardiac arrest and sudden death that sometimes occurs in man. Apnoeic asphyxia may be induced centrally or reflexly by stimulation of upper airways receptors. Conditions associated with apnoeic asphyxia and in which the risk is likely to be greatest include intubation, laryngoscopy and bronchoscopy; accidents involving underwater swimming; inhalation of sympathomimetic amines in aerosols by asthmatic patients; and chronic hypoventilation syndromes. These reflexes may be responsible for some victims of sudden infant death syndrome. Stimulation of the carotid bodies normally produces hyperventilation and bradycardia. When apnoea occurs centrally or reflexly, carotid chemoreceptor excitation resulting from asphyxia now causes a much enhanced bradycardia and even cardiac arrest, but paradoxically does not usually affect respiration. These reflexes and their interactions normally serve protective and purposeful functions, but may under certain circumstances become exaggerated and put the patient's life at risk.

Animals↗
PubMed1979

Newborn northern fur seals (Callorhinus ursinus)--do they suffer from cold?

Several hundred thousand northern fur seals (C. ursinus) are born each summer during July at St. Paul Island in the Bering Sea. The weather in the area is usually cold, wet, and windy during the breeding season. At birth the pups are small (5--6 kg) and insulated only by a partly wettable pelt and a 2- to 4-mm layer of blubber. In air, the pups' lower critical temperature appears to be below the 6 degrees C 50-yr record low July temperature for the islands. During rainy weather much of the insulative value of the pelt is lost, and the pups, which already have a high resting metabolic rate of 3.5 W.kg-1, must increase heat production by shivering and/or nonshivering thermogenesis to maintain deep body temperature. The high level of metabolism (up to 18 W.kg-1) is supported by a very rich milk. The pups will, nevertheless, become hypothermic if their insulation is not improved through peripheral vasoconstriction and shedding of water from the pelt by periodic shudder. Even with these protections the newborn and very young pups are brought close to their limit of tolerance during rainy and windy days. Unfit pups are likely to succumb under such circumstances.

Adipose Tissue↗
PubMed1979

NADPH production in the oxidative pentose phosphate pathway as source of reducing equivalents in glycolysis of human red cells in vitro.

Studies have been carried out on human erythrocytes in vitro to clarify the deficit of pyruvate formation under conditions when 2,3 DPG is degraded. The results lead to the conclusion that there exist a cross connection between the glycolytic and the oxidative pentose phosphate pathway which is mediated by the NADP/NADPH couple. NADPH serves as additional reducing equivalent in the reaction of the LDH. In the absence of glucose the pool of the metabolites of the pentose phosphate pathway is able to supply glucose-6-phosphate for the production of NADPH by recombination. The reaction of NADPH at the LDH is probably of significance under in vivo conditions.

Diphosphoglyceric Acids↗
PubMed1979

The breakdown of adenine nucleotides in glucose-depleted human red cells.

1) The rate of 2,3-bisphosphoglycerate breakdown is independent of pH value. 2) The adenine nucleotide pattern at alkaline pH values with its characteristic lowering of ATP and the accompanying accumulation of fructose-1,6-bisphosphate is caused by a relative excess of the activity of the hexokinase-phosphofructokinase system as compared wity pyruvate kinase. 3) The breakdown of adenine nucleotides proceeds via AMP mainly through phosphatase and not via AMP deaminase. 4) The constancy of the sum of nucleotides as long as glucose is present is postulated to be due to resynthesis via adenosine kinase which competes successfully with adenosine deaminase. 5) A procedure is given to calculate ATPase activity of glucose-depleted red cells. The results indicate that the ATPase activity is less at lower pH values and declines with time. An ATPase with a high Km for ATP is postulated. 6) During glucose depletion ATP production is mostly derived from the breakdown of 2,3-bisphosphoglycerate and the supply from the pentose phosphate pool both of which proceed at a constant rate. The contribution of pentose phosphate from the breakdown of adenine nucleotides amounts to 40% of the lactate formed at pH 6.8 and is about twice the lactate at pH 8.1.

Adenine Nucleotides↗
PubMed1977

PH-dependent changes of 2,3-bisphosphoglycerate in human red cells during transitional and steady states in vitro.

A systematic study of the pH-dependent changes in the range 6.6--7.4 of 2,3-bisphosphoglycerate and the adenine nucleotides was performed in the presence and absence of glucose during transitional and steady states. 1. The results indicatethat 2,3-gisphosphoglycerate phosphatase breaks down 2,3-bisphosphoglycerate nearly independent of pH at a rate of 480 mumol 2,3-bisphosphoglycerate x1 cells-1xh-1.2,3-Bisphosphoglycerate mutase is practically completely inhibited below pH value increases in long-term experiments with lower 2,3-bisphosphoglycerate levels. The formation of pyruvate corresponds to the breakdown of 2,3-bisphosphoglycerate afterconsumption of an unknown reducing substance.

Adenosine Diphosphate↗
PubMed1977

Cardiorespiratory control by carotid chemoreceptors during experimental dives in the seal.

The diving responses of apnea and bradycardia, produced experimentally by immersing the face in water, were successfully elicited in the harbor seal Phoca vitulina anesthetized with urethan. The role of the carotid body chemoreceptors in the production of the diving bradycardia was studied in isolated carotid sinus-body preparations autoperfused with blood from the arterial circulation. When asphyxia was well developed during a dive the chemoreceptor drive was withdrawn by temporarily perfusing the chemoreceptors with blood of high PO2 (greater than 400 mmHg) and normal PCO2 from a disk oxygenator. The heart rate immediately rose to its predive value. Reestablishing hypoxic hypercapnic blood perfusion of the chemoreceptors from the animal's own circulation caused bradycardia with persistence of the apnea. Breathing restarted only on emersion. Substitution of normal arterialized blood from the oxygenator before or at the onset of a dive had no effect on the existing heart rate. It is concluded that the carotid bodies play an important part in maintaining the diving bradycardia during developing asphyxia without affecting respiration.

Animals↗
PubMed1977

Carotid body chemoreceptor reflexes and their interactions in the seal.

In the anesthetized spontaneously breathing harbor seal Phoca vitulina stimulation of the carotid body chemoreceptors by intracarotid injections of sodium cyanide or by hypoxic hypercapnic blood causes an increase in tidal volume, respiratory frequency, and respiratory minute volume. The heart rate invariably decreased. Experimental dives caused apnea and bradycardia. When the carotid bodies are stimulated within 10 s of the commencement of a dive, the chemoreceptor-respiratory response is abolished, but the chemoreceptor-cardioinhibitory response is considerably enhanced. Electrical stimulation of the central cut end of a superior laryngeal nerve also causes apnea and bradycardia; stimulation of the carotid body now fails to produce a respiratory response but the cardioinhibitory effect is enhanced. These results indicate that the carotid bodies cause reflexly hyperventilation and bradycardia, and that these responses are considerably modified by other inputs to the central nervous system.

Animals↗
PubMed1977

Effects of growth, diving history, and high altitude on blood oxygen capacity in harbor seals.

Blood volume and body composition measurements were carried out on diving and nondiving harbor seals, Phoca vitulina. There were small, statistically significant differences in several red blood cell parameters between diving and nondiving seals, but the effect was superimposed on uniformly large blood volumes ranging from 11 to 12% of body weight found in all the animals. It is suggested that the large blood oxygen transport and storage capacity is not so much a direct result of the apneic diving experience, but an expression of phylogenetic control. The development of blood volume during early growth was closely related to the increase in lean body mass. In spite of the inherently large blood volume, this marine mammal when exposed to high altitude for 85 days at an elevation of 3.1 km above sea level appeared to exhibit typical mammalian erythropoietic and ventilatory responses to long-term, mild hypoxia. Thus, it probably cannot be considered to be preacclimatized to high altitude.

Age Factors↗
PubMed1977

pH-dependent changes of 2,3-bisphosphoglycerate.

A systematic study of the pH dependent changes in the range 6.6--7.4 of 2,3 bisphosphoglycerate (2,3-DPG) was performed in the presence and absence of glucose during transitional and steady states. The results indicate that 2,3-DPGase breaks down 2,3-DPG nealy independent of pH at a rate of 480 mu moles 2,3-DPG/1 cells.h. The 2,3-DPG mutase is practically completely inhibited below pH 6.9. The 2,3-DPG level in the presence of glucose reaches a pH dependent steady state after about 18 h. The share of the 2,3-DPG bypass in the steady state decreases from 24% at pH 7.4 to 12% at pH 7.0. The formation of pyruvate corresponds to the beadkdown of 2,3-DPG after consumption of an unknown reducing substance.

Adenosine Triphosphate↗
PubMed1976

Response of the glycolysis of human erythrocytes to the transition from the oxygenated to the deoxygenated state at constant intracellular pH.

The time course of the rate of the glycolysis of human erythrocytes and of some metabolites were determined before and after rapid deoxygenation at constant intracellular pH. For this purpose stripped deoxygenated haemoglobin was used as a rapid oxygen acceptor. Deoxygenation causes an increase of the glycolytic rate by 26%. Glucose 6-phosphate is decreased while the adenine nucleotides and 2,3-bisphosphoglycerate remain constant. Fructose 1,6-bisphosphate and the triose phosphates decrease transiently before rising. The data can be explained by increased binding of phosphocompounds to deoxygenated as compared with oxygenated haemoglobin. Thereby the control enzymes hexokinase and phosphofructokinase are influenced. It is concluded that under physiological conditions changes in the oxygenation state of haemoglobin per se alter the glycolytic rate.

Erythrocytes↗