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Biomedical subjects

R Elsner

Publications and source records attributed to R Elsner.

At least 37 records · Page 2Linked to original sources
PubMed1990

Red cell aggregation and viscoelasticity of blood from seals, swine and man.

RBC aggregation and viscoelasticity parameters were determined for 40% suspensions of washed cells in autologous plasma from elephant seals (ES), Mirounga angustirostris, ringed seals (RS), Phoca hispida, and swine, (SS), Sus scrofa. Interspecific comparisons including human (HS) blood data revealed unusual rheological properties of seal blood relative to that from pigs or man: 1) RBC aggregation extent, rate and sedimentation were lower for seals (AI = 0, ZSR = .40, ESR = 0 for RS blood) relative to humans; 2) Viscous (n') and elastic (n") components of complex viscosity (OCRD) were lower for both seal species relative to SS blood, but only at shear rates less than or equal to 10 sec-1 (P less than 0.05), while n"/n' ratios for RS blood were lower than HS blood at all shear rates (P less than 0.01); 3) Blood viscosity measurements for RS and SS blood from rotational viscometry (Contraves) were consistent with OCRD data; 4) Seal plasma fibrinogen levels were low compared to pigs or humans (RS fibrinogen = -43% v. HS and -57% v. SS; ES fibrinogen = -58% v. HS and -69% v. SS). Electrophoretic mobility of RS red cells was +25% relative to those of humans. These results demonstrate differences in hemorheological indices among mammalian species and suggest the value of comparative rheologic studies.

Animals↗
PubMed1989

Determination of the apparent functional molecular mass of the hepatocellular sodium-dependent taurocholate transporter by radiation inactivation.

The apparent target size of the sodium-dependent taurocholate transporter in basolateral rat liver plasma membrane vesicles, showing overshooting taurocholate uptake in the presence of sodium was estimated by radiation inactivation. Radiation at -105 to -120 degrees C and 2.5 Mrad/min causes a dose-dependent monoexponential reduction of the overshoot of taurocholate uptake in the presence of sodium. In contrast, taurocholate transport in the absence of sodium and taurocholate permeation at 4 degrees C remained totally unaffected by the radiation dose, indicating that the passive permeability of the membrane towards taurocholate remained unaffected. Radiation inactivation by high-energy electrons provides information about the size of the functional unit of the transporter in situ. The target size determined represents the size of the radiation-sensitive mass which is compact enough for significant energy transfer to occur within all parts of the transport system. The minimal function molecular mass was determined to be 170 kDa for the sodium-dependent taurocholate transporter. To prove the validity of radiation inactivation data four internal standard enzymes were tested under identical conditions.

Animals↗
PubMed1989

Blood viscosity in phocid seals: possible adaptations to diving.

1. Mean corpuscular volume (MCV) and mean corpuscular hemoglobin concentration (MCHC) of phocid seal red blood cells (RBC) are elevated compared to those of most terrestrial mammalian species. The influence of these characteristics on blood flow was revealed by viscosity (VIS) measurements. 2. RBC morphology and VIS of whole blood from 7 harbor seals and 5 northern elephant seals were compared with blood of the domestic pig. Samples were analysed for RBC count, white blood cell (WBC) count, total plasma proteins, hematocrit (HCT), MCV and MCHC. Viscosity measurements were made at shear rates from 11.5 to 230.4 s-1 on a Wells-Brookfield cone-plate viscometer at 37 degrees C. 3. Mean values for HCT (%), MCV (micron 3) and MCHC (%) were, respectively: elephant seal: 57, 176, 44; harbour seal: 53, 105, 38; domestic pig: 28, 54, 34. Pig blood was reconstituted to match seal blood HCTs. VIS determinations showed that seal and pig blood conform to the general mammalian dependence of VIS upon shear rate and HCT. 4. Seal blood VIS was 28% (harbour seal) and 16% (elephant seal) less than pig blood VIS at low shear (P less than 0.05). Seal blood carried more hemoglobin per unit volume than did pig blood reconstituted to the same HCT. Fewer, larger RBC with higher MCHC, and hence elevated oxygen storage, accompanied by reduced VIS and reduced flow resistance near stasis suggests that this feature of phocid seal blood is an adaptation to circulatory redistribution during long dives.

Adaptation, Physiological↗
PubMed1989

Perspectives in diving and asphyxia.

Animals vary in their ability to tolerate asphyxia. Among aquatic species, some are well adapted to asphyxia associated with the apnea of their diving behavior. The related mechanisms and their regulation are not unique to aquatic animals, rather they are extensions of similar reactions noted in terrestrial species. Our understanding of asphyxia has grown in large part from research on aquatic mammals and birds and by comparing the responses of these natural breath-holding specialists with those of other animals. Studies in nature and in the laboratory have both contributed to this knowledge. The divers have been shown to rely ultimately on oxygen conservation and enhanced anaerobic reserves, producing a strategic retreat into a hypometabolic state.

Adaptation, Physiological↗
PubMed1986

The carotid body of the harbour seal (Phoca vitulina richardsi).

The bilateral distribution of carotid body type 1 and 11 cells was investigated in five harbour seals (Phoca vitulina richardsi), by serially sectioning the carotid bifurcation regions. The cells occurred bilaterally in the animals and were also present in one specimen from a sixth animal available for study. The type 1 and 11 cells were located in the space between the internal and external carotid arteries and had a varied relationship to the occipital and condyloid arteries. They lay within a division of connective tissue with irregular but defineable borders and this combination of connective tissue and type 1 and 11 cells constituted the principal mass of the carotid body. The carotid body occurred in a variety of forms: wedge-shaped, crescentic or horse-shoe shaped, or as a discrete oval structure. In some specimens the carotid body had a central 'neurovascular' core of small blood vessels and nerves. The artery to the organ originated from either the external carotid, internal carotid or common carotid arteries. Using an interactive image analysis system in eight specimens, which had been perfusion-fixed at a normal arterial pressure, the mean volume of the carotid body was 1.666 +/- 0.45 (SD) mm3. Caudally and separate from the principal mass of the carotid body periadventitial type 1 and 11 cells were noted in 4 out of 11 specimens in the connective tissues adjacent to the external carotid artery, origin of the occipital, and the rostral part of the common carotid artery and its bifurcation.

Animals↗
PubMed1986

Pressure-volume characteristics of aortas of harbor and Weddell seals.

The mechanical properties of the radially enlarged proximal segment of the aorta of diving marine mammals was studied on 15 excised aortas of harbor seals and five aortas of Weddell seals. This was done by recording static pressure-volume relationships for the whole thoracic aorta, the aortic bulb, and the descending thoracic aorta and passive length-tension measurements of aortic strips. Aortic bulb volume distensibility was found to be much greater than that of the descending thoracic aorta or of an equivalent aortic segment of terrestrial mammals. The consequences were that the total potential energy and volume that may be stored within the aortic bulb is very large, with a capacity for storage of the stroke work of more than two normal heart beats and a volume of more than three times normal stroke volume. The aortic bulb has an average radius and wall thickness twice that of the descending aorta, but at any level of distension the wall stress (g/cm2) is the same throughout. The static mechanical properties of aortic strips from the bulb and descending thoracic aortas were not markedly different, so that the differences in the pressure-volume relationships are explained by differences in geometry of the two sections. The expanded aortic bulb functions through energy and volume storage actions and through uncoupling actions to maintain arterial pressures and stroke volume at near predive levels during a dive.

Animals↗
PubMed1986

Limits to exercise performance: some ideas from comparative studies.

Examples of exercise performance and metabolic scope in non-human mammalian species are considered from the point of view of problems and questions which may provide insights into evolutionary processes influencing adaptations to muscular activity. Consideration of both aerobic and anaerobic performance is required. Some recent approaches, notably that concerned with the concept of symmorphosis, the integration of design for the accommodation of variations in activity, show promise of new ways for comparative investigations of the adjustments to exercise.

Aerobiosis↗
PubMed1985

Coronary blood flow and myocardial segment dimensions during simulated dives in seals.

Three harbor seals Phoca vitulina richardsi and five spotted seals Phoca vitulina largha were used in studies of acute episodes of local myocardial ischemia in open-chest, anesthetized animals and of coronary blood flow and regional function as indicated by left ventricular segment dimensions during experimentally simulated dives of conscious, instrumented animals. We observed that seal myocardium, in which there are few coronary anastomoses, responded to brief local occlusion with prompt local dysfunction and systolic bulging; coronary flow in the nondiving seal oscillated irregularly and declined with spontaneous apnea and related falling heart rate; flow continued to oscillate but was much reduced during dives, frequently ceasing entirely for periods as long as 45 s; ventricular segment dimension shortening was reduced intermittently during dives; and elevated heart rate induced during dives by cardiac pacing or by administration of atropine diminished or eliminated the reductions in coronary blood flow. Responses of seal heart reflect the reduction in cardiac metabolic demand during diving and the seal's myocardial adaptation for enhanced anaerobic glycolysis. The seal heart can maintain mechanical function during dives with minimal coronary perfusion, despite the progressive and ultimately profound hypoxia, hypercapnia, and acidosis. Reduced cardiac metabolism, copious glycolytic reserves, and metabolite washout by intermittent brief bursts of coronary blood flow are apparently sufficient to support continued cardiac function, even though the seal heart has little tolerance for acute localized ischemia.

Animals↗
PubMed1984

Enzymatic adaptations to asphyxia in the harbor seal and dog.

The activities of the glycolytic enzymes were determined in heart, liver, kidney cortex and cerebrum from the harbor seal (Phoca vitulina ) and the adult and newborn dog. Activities were similar in the four dog tissues as well as myocardium and brain tissue from both the newborn dog and seal. Most of the enzyme activities were markedly lower in kidney cortex and liver of the seal and the newborn dog, suggesting that the organs which are rendered ischemic in the diving seal or asphyxiated newborn dog have a lowered demand for glycolytic metabolism. This is perceived as an adaptation to prolong the time tissues can rely on anaerobic metabolism. Expression of the enzyme data in a 'similarity criterion' by dividing activity from an organ likely to be perfused during long diving or asphyxia (e.g., heart), by that from one rendered ischemic (e.g., kidney), yields a quotient which provides a convenient indicator of anaerobic potential. Such a treatment would reflect the contribution of a discrete tissue to the total anaerobic demand of the whole animal. The values thus generated for the glycolytic enzymes are generally higher in the seal and the newborn dog than in the adult dog, and suggest an index for determining the capacity of an animal to withstand repeated and variable asphyxia.

Adaptation, Physiological↗
PubMed1984

How seals avoid myocardial infarction when they should have got it.

The arterial oxygen tension of diving seals decreases to values as low as 1.33 kPa at the end of prolonged dives. In spite of this, cardiac function is unimpaired due to a profound reduction of myocardial oxygen demands: Heart rate is immediately reduced some 90%, left ventricular dP/dt(max) is reduced some 25%, and ventricular wall tension is slightly reduced. This reduction of myocardial workload even allows coronary blood flow to be reduced some 90% and a significant proportion of myocardial energy expenditure to be covered by anaerobic metabolism based on endogenous stores of glycogen. It is suggested that the myocardial ischaemic defence, as worked out by nature herself, in the diving seal has important implications for the treatment of acute myocardial ischaemia in man.

Animals↗
PubMed1983

Comparative functional properties of mitochondria from seal and dog hearts.

The harbor seal (Phoca vitulina) is capable of protracted dives resulting in low arterial PO2 levels. The mammalian heart is an aerobic organ depending primarily on mitochondrial oxidations for energy (ATP). Heart mitochondria were isolated from freshly killed seals and the functional data obtained compared to dog heart mitochondria isolated under similar conditions. The percentage yields of mitochondria based on cytochrome oxidase recovery were essentially the same from dog and seal hearts. However, the actual quantity of mitochondrial protein obtained per gram of seal heart tissue was lower than that isolated from dog heart. Phosphorylating rates of respiration (State 3; Q02) and cytochrome content were significantly lower in seal heart mitochondria compared to dog. The data indicate that seal hearts have fewer mitochondria per gram of tissue, lower active respiratory rates and lower cytochrome contents than dog heart.

Animals↗
PubMed1983

Cardiac output and its distribution through capillaries and A-V shunts in diving seals.

Regional blood flow and cardiac output were determined by distribution of radioactive microspheres injected via catheter into the left ventricle during experimental diving and recovery in juvenile spotted seals (Phoca vitulina largha) and grey seals (Halichoerus grypus). Cardiac output was 9.7 L/min before diving, declined 90% during submersion and increased to 12.1 L/min after 40 s of recovery. Left ventricular myocardial perfusion declined from 179 +/- 24 (21) to 25 +/- 2 (6) ml/min . 100 g at 2 min submersion, and measured 23 +/- 3 (8) after 10 min of submersion. Cerebral cortical flow was reduced from a pre-dive value of 115 +/- 3 (15) to 40 +/- 5 (3) and 49 +/- 6 (3) at 2 and 5 min of diving, respectively, but increased to 253 +/- 14 (4) ml/min . 100 g at 10 min along with elevated PCO2 (84 torr) and lowered pH (7.10) in arterial blood. It remained at that level in recovery. Brain stem perfusion after 10 min submersion was still identical with control, but increased to 275% of control in recovery. Adrenal flow decreased to 34 and 27% of control at 2 and 5 min of diving, respectively. Recovery flow after 10 min of diving was 200% of control. Liver, kidney, fat, skin, and stomach were ischemic throughout the dive. Recovery flow increased slowly in these tissues. Skeletal muscle (M. psoas) was perfused at a low rate. (3 ml/min . 100 g) pre-dive and was ischemic during diving. Recovery muscle perfusion was variable at different sites (from 5 to 105 ml/min . 100 g). Pre-dive pulmonary capillary perfusion was 58 +/- 8 (9) ml/min . 100 g, decreased to 7 +/- 0 (3) ml/min . 100 g min of submersion, and had increased to 50% of pre-dive value after 40 s of recovery from a 10 min dive. Conclusions are: (1) previous information from implanted flow transducers was confirmed, (2) detailed data for discrete tissues elaborate the concept of selective redistribution of cardiac output in diving seals, (3) non-uniform reperfusion contributes to the maintenance of arterial pressure during recovery, and (4) substantial A-V shunting of cardiac output took place in the first 2-5 min of the dive, when total capillary/nutritive flow was low. Late in the dive, however, CO was routed through systemic capillaries mainly in the cerebral circulation and less than 15% through A-V shunts.

Adrenal Glands↗
PubMed1982

Myocardial blood flow and metabolism in the diving seal.

The adaptations of myocardial metabolism to diving asphyxia have been studied in 12 harbor seals (Phoca vitulina). Unanesthetized animals were submerged for periods of 10-16 min. Heart rate decreased from 135 to 12 beats/min. Myocardial blood flow decreased to an average of 10% of predive values and remained constant during the dive. The progressive reduction in arterial O2 content was associated with an increase in myocardial lactate and hydrogen ion production, but no change in glucose or free fatty acid extraction occurred. After restoration of breathing a reactive myocardial hyperemia and an immediate return to myocardial uptake of lactate were observed. Despite increased glycogenolytic activity throughout the dive, coronary flow distribution was fully controlled, and no evidence of ischemic dilatation of the left ventricle or S-T segment elevation in the electrocardiogram was observed. These adaptations to diving asphyxia in the seal myocardium permit a reduction of coronary blood flow comparable to that observed in the infarcted dog myocardium and therefore have relevance for therapeutic approaches to reduction of myocardial ischemic injury in humans.

Animals↗
PubMed1981

Lung inflation: effects on heart rate, respiration, and vagal afferent activity in seals.

In the anesthetized harbor seal, Phoca vitulina, the Hering-Breuer inflation reflex was weak and comparable to that in humans. Single inflations of the lungs from a syringe during the expiratory phase of normal breathing caused temporary inhibition of breathing and an immediate tachycardia dependent on the integrity of the cervical vagosympathetic nerves. A similar cardiac response occurred when the lungs were artificially inflated during an experimental dive and under conditions in which apnea and bradycardia were reflexly induced by a combination of stimulation of the carotid body chemoreceptors and of the trigeminal or laryngeal input. Recordings from single vagal afferent nerve fibers innervating presumptive pulmonary stretch receptors showed a close relationship between the increase in impulse frequency and increase in lung volume or transpulmonary pressure. It appears that in diving the decrease in pulmonary stretch receptor activity during apnea, combined with cessation of central inspiratory neuronal drive, is an important integrative mechanism that helps development of the reflex bradycardia of trigeminal, carotid, chemoreceptor, and baroreceptor origin.

Animals↗