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Biomedical subjects

P Aarseth

Publications and source records attributed to P Aarseth.

9 recordsLinked to original sources
PubMed1979

Circulatory homeostasis in rats after bile duct ligation.

The bile duct was ligated in rats, and their tolerance against a small blood loss was evaluated 7 days later. A 10% blood loss precipitated a large and sometimes fatal reduction in arterial blood pressure, while no reduction was seen in shamoperated rats. The plasma and erythrocytes were labelled by isotopes and the animals were rapidly frozen in liquid nitrogen. The splanchnic and pulmonary blood volumes were estimated from the isotope content in blood and tissue. These vascular beds will normally reduce their blood volumes during a blood loss and thus serve as vascular depots. In the bile duct occluded animals, the partition of blood is changed. More blood is to be found in the splanchnic vessels, and the depot function of the lung vessels is partly used for compensation. When these rats were bled, their liver blood volumes were not reduced, and only a small further reduction took place in the lung vessels. It is concluded that rats with bile duct occlusion will suffer considerably from small blood losses. This may be due to a lacking depot function of the splanchnic vessels.

Animals↗
PubMed1979

On the existence of stretchable pores in the exchange vessels of the isolated rabbit lung preparation.

In the present work our aim has been to seek evidence for or against the existence of stretchable pores in the exchange vessels of the lungs. In isolated rabbit lungs ventilated by positive pressure and perfused with homologous blood we performed repeated tests with fluid filtration from the exchange vessels. In these tests the outflow pressure was elevated to specific values for periods of 6 min. The rate of weight gain of the preparation during the last 2 min of each test period was taken as the rate of fluid filtration from the exchange vessels. We found a linear relationship between rate of filtration and outflow pressure in the range from 5 to 20 mm Hg. This indicates that the hydraulic conductivity of the exchange vessels did not change with outflow pressure and thus that no pore stretching occurred within this pressure range. An abrupt increase in filtration rate took place when the outflow pressure was set at 25 or 30 mm Hg. The hydraulic conductivity of the exchange vessels was therefore probably increased at these high pressures. Since in 3 lungs this increase in filtration rate was fully reversible we suggest that a stretching of pores in the exchange vessels of the lungs contributed to the increase in hydraulic conductivity. This stretching of pores occurred only when vascular pressures were at or above the upper level of the physiological pressure range for the lungs.

Animals↗
PubMed1978

Alpha-1-antitrypsin (Pi)-types in recurrent miscarriages.

Chromosome analysis was carried out in a consecutive series of 57 couples with a history of recurrent miscarriage. All 114 subjects from these couples had normal karyotypes by conventional analysis. Pi typing was performed in 30 couples. The constellation of Pi heterozygosity in both partners occurred in two of the couples. The expected frequencies of the observed MS-MS and MS-MZ constellations occurring by chance would be 2.1 per 1,000 and 2.2 per 1,000 couples, respectively.

Abortion, Spontaneous↗
PubMed1978

Rabbit lung plasma and erythrocyte volumes. Lung hematocrit in relation to total body hematocrit.

The total body hematocrit has been reported to be 85--90% of packed cell volume (PCV) in several species. We have found similar values in rabbits. An "extra" plasma volume must exist somewhere in the vascular bed to explain this observation. We have looked for such an extra plasma volume in the pulmonary vasculature. The dynamic hematocrit was estimated in isolated, perfused rabbit lungs from distribution volumes for plasma and erythrocyte tracers. Estimation was also obtained from indicator-dilution curves using bolus-injections of such tracers avoiding their recirculation. It was thus possible to calculate mean transit times for the tracers from their dilution curves directly or applying monoexponential extrapolation from the first part of the downslope of the curves. The dynamic hematocrit of the lung vessels was about 94% of perfusate PCV and there was no difference between the results obtained by the different methods. We concluded that in the rabbit only a very small part of the extra plasma volume is located in the lung vessels. The lung plasma volume is not underestimated by the indicator-dilution technique.

Animals↗
PubMed1977

Hydrostatic pulmonary edema in the cat. Effects on pulmonary blood and water volumes and on lung compliance.

The effect on lung compliance of changes in intra- and extravascular volumes has been studied. Such changes were induced by inflation and deflation of a balloon placed in the left atrium in open-chest cats. Blood constituents were labeled with isotopes, and tissue water content was found from the wet/dry labeled with isotopes, and tissue water content was found from the wet/dry weight ratio. When left atrial pressure (PLA) was elevated to a value not exceeding 32 mmHg (4.256 kPa), there was only a minute increase in tissue water volume, and we observed a reversible reduction in lung compliance related to the rise in lung blood volume. At higher PLA, a rapid rise occurred in extravascular fluid volume, with evidence of alveolar flooding. Earlier experiemtns have shown that, in isolated perfused lung, a situation of slow, steady increase in interstitial fluid can be created. This does not seem to be the case with lungs in situ: once the lymphatic drainage is unable to cope with transvascular fluid flow, an unstable situation is created. This rapidly leads to alveolar flooding and a fall in compliance in addition to that caused by a rise in blood volume. From our fluid and pressure determinations, we calculated a filtration coefficient (Kf) of 0.45 ml/100 g wet lung X cmH2O X h. This is within the range reported for sheep lungs. Observation of dynamic lung compliance cannot be used for detection of interstitial fluid accumulation. It appears, however, that in contrast to isolated lungs, this phase of edema-formation rapidly leads to alveolar flooding.

Animals↗
PubMed1977

Blood volume and extravascular water content in the rat lung during acute alveolar hypoxia.

Values for pulmonary blood volume and extravascular lung water (estimated as wet weight of lung tissue) were arrived at in intact, anesthetized rats by labelling of blood constituents with isotopes and rapidly freezing the whole animals in liquid nitrogen. On ventilating the animals with 10% O2 in N2/N2O, a reduction in lung blood content could be demonstrated. The degree of reduction depended on the type of anesthesia and ventilation used. In some animals the volume reduction was so marked that both arterial, venous and capillary blood compartments have most probably been involved. The water content of the lung tissue was also rapidly and markedly reduced during hypoxia. Increased plasma osmolarity in mixed venous blood could partly be responsible for this tissue water reduction.

Animals↗
PubMed1976

Interstitial fluid and transcapillary fluid balance in the lung.

Alterations in extravascular lung water content when capillary pressure or plasma colloid osmotic pressure is increased have been evaluated in isolated, continuously weighed, plasma-perfused pairs of rabbit lungs. After modest increases in left atrial pressure, most preparations rapidly reached a new stable weight, and thus a new transcapillary fluid balance, but no significant increase in extravascular lung water content could be detected. In preparations where there was still a steady, slow gain in weight and thus still some transvascular filtration of fluid 15 min after the increase in pressure, a moderate but significant increase in extravascular water could be detected. It is concluded that only very small transvascular shifts of fluid occur in the lungs when capillary pressure changes, as long as this change is kept below the level that causes oedema. This limitation of pressure-induced transvascular shifts of fluid in the lung could be explained by the existence, close to the capillaries, of a small interstitial space containing fluid with a high protein concentration. Alterations in the colloid osmotic pressure exerted by this fluid would then contribute markedly towards continuous readjustment of the transcapillary fluid balance in the lung. Experiments by other workers indicate that alveolar pressure can markedly affect the transcapillary fluid balance of the isolated perfused lung.

Animals↗
PubMed1975

Effects of catecholamine-infusions and hypoxia on pulmonary blood volume and extravascular lung water content in cats.

The effects of catecholamine-infusions and of hypoxia on lung blood volume and on extravascular lung water content have been studied in anesthetized cats with opened chests. To this end a biopsy technique, with isotope labelling of blood and with successive removal of the smaller lung lobes, was employed. Mean pulmonary arterial pressure increased by 30-75% upon infusing catecholamines or upon inducing general hypoxia, the latter stimulus being the more powerful one. Pulmonary blood volume did not increase during these procedures, where an active constriction of pulmonary vessels thus apparently took place. The extravascular lung water content was found to be reduced in animals infused with noradrenaline or ventilated by hypoxic air, whereas a small increase was observed in the animals receiving adrenaline. This difference might reflect domination of precapillary vasoconstriction in the former groups, whereas postcapillary vasoconstriction could be more pronounced with adrenaline.

Animals↗