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Biomedical subjects

O Christensen

Publications and source records attributed to O Christensen.

72 records · Page 4Linked to original sources
PubMed1979

Potassium permeability of the mesothelium of the frog mesentery.

The mesothelium of the mesentery is a single cell layer described to offer no or every little hindrance to diffusion of small water soluble solutes. We have measured the potassium permeability of the mesothelium of the frog mesentery both in vivo and in vitro. The permeability measured in vivo--using K+--sensitive microelectrodes is 2.4 X 10(-5) cm s-1. In vitro measurements using conventional tracer flux technique on isolated mesentery yields a K+-permeability of 5.7 X 10(-5) cm s-1. These values are 15--30 times smaller than values previously reported from in vitro experiments on rat and rabbit mesentery. Also, the permeability is 12--15 times lower than the K+-permeability of the capillary wall determined on single capillaries in the frog mesentery. In the frog mesentery the mesothelium thus represents an important diffusion barrier compared to the capillary wall. This may be critical in experiments where filtration and reflexion coefficients of the capillaries are determined from measurements of fluid exchange across the capillary wall in response to application of hypertonic solutions on the surface of the mesentery.

Animals↗
PubMed1979

Hormonal response to volume depletion in non-nephrectomised patients on regular haemodialysis.

The hormonal response to volume depletion by isolated ultrafiltration has been studied in seven non-nephrectomised haemodialysis patients. The mean reduction in blood volume was 14%, and pulmonary artery wedge pressure reduction averaged 77%. No increments in heart rate were observed in any of the patients. Cardiac output decreased while systemic vascular resistance increased. Mean arterial blood pressure remained stable in all but two patients. Significant increments in plasma vasopressin concentration were only found during hypotensive episodes, while in the whole group no significant increase was found. Both plasma renin activity, plasma aldosterone and plasma cortisol increased significantly during isolated ultrafiltration. The moderate increase in systemic vascular resistance indicates that the peripheral sympathetic nervous system - at least partly - was functioning. It was, however, not correlated with changes in any of the measured hormones. Furthermore the adrenal and cardiac response appeared to be absent.

Aldosterone↗
PubMed1978

Relationships between abnormal IgG index, oligoclonal bands, acute phase reactants and some clinical data in multiple sclerosis.

The IgG-index and acute phase reactants were measured and oligoclonal bands were looked for in 30 patients with clinically definite multiple sclerosis (MS) and were compared with the clinical data. IgG-index was found elevated in 77% against 22% in a comparable material of patients with other neurological diseases. Oligoclonal bands were found in 74 and 17%, respectively. No correlation was found between these parameters and age, duration of illness, disability, coefficient of progression or age of onset. A statistical evaluation defines the specificity, sensitivity and validity of the methods used. CRP could no be demonstrated in 28, the rest had normal values. C3A was normal in all cases, but appeared to be elevated a little with increasing age, and to be positively correlated to the albumin-index, indicative of a defective blood-brain barrier. No correlation was found between CRP, C3A and the clinical data.

Acute Disease↗
PubMed1978

The permeability of single capillaries to potassium ions.

This paper reports a description of methods for determining the diffusional permeability to potassium ions of single capillaries in the frog mesentery. By means of micropipettes, injections or infusions were delivered into a single capillary. The subsequent concentration variations in and about the capillary were followed with K(+)-sensitive microelectrodes. A theoretical analysis is provided which give a quantitative frame of reference for evaluating the observed time-concentration curves in terms of capillary permeability. The advantage of single capillary studies is that the surface area through which diffusion occurs is known as is the concentration difference across the capillary membrane. Three different techniques are: (a) the "single injection" method which represents an application of the indicator diffusion technique where a high-K(+) bolus is injected into a single capillary; (b) the "sack" method which determines the rate of K(+) disappearance from within and immediately outside an occluded capillary segment, after a brief increase in intracapillary K(+) concentration; and (c) the "interstitial diffusion" method which records time and spatial distribution of K(+) in the interstitial space after a step-change in intracapillary K(+) concentration. The methods gave an average potassium permeability of the capillary membrane of 67x10(-5) cm s(-1) (SD: 23, n=26) at room temperature. These figures are clearly higher than those previously reported in mammalian capillary studies using whole-organ techniques. In terms of the pappenheimer pore model, this estimate of capillary permeability is consistent with the behavior of a membrane with a thickness of 1.0 mum which possesses equivalent pores with a radius of 110 A, a fractional pore area of 0.3 percent, and a pore density of 8 mum(-2).

Animals↗
PubMed1977

Social remedial measures for multiple sclerosis patients in Denmark.

A total of 57 patients admitted to the Danish Multiple Sclerosis Society's treatment and nursing home in Haslev have been interviewed about their socio-medical situation concerning their course of disease, physical, psychic and economic status, family relationships, and different assistance needs. Sixty per cent lived together, and of the solitary only 9 were unmarried. None were employed fulltime and as a whole they received higher allowances than other disabled persons. All suffered from walking impairment. 17 had no wheelchair, 21 had a wheelchair and limited walking ability, 19 could move around only by wheelchair. None were bedridden. The distribution of housing corresponded to that of other disabled persons but was inferior to that of the population as a whole. 54 per cent had got modifications to housing paid for by the public authorities and 42 per cent had a car for the disabled. 47 per cent alleged that their need for transportation remained uncared for. None of the patients were lonely to a severe degree. Expenses for medicine and transportation varied greatly, showing inequality of grant administration. The results of the investigation are discussed.

Adult↗
PubMed1976

Bumetanide in congestive heart failure.

Bumetanide, a new diuretic exerting its major effect on the ascending limb of the loop of Henle, was evaluated in 20 patients with congestive heart failure. Dosage ranged from 1 mg to 3 mg daily depending on the patient's condition. The results after 3 and 8 days' treatment showed that bumetanide caused a significant diuresis, an increased excretion of sodium, potassium and chloride, and a comparable fall in the serum levels of these electrolytes. Changes in electrolyte levels were directly related to the dose of the drug. The resultant hypochloraemia was accompanied by a slight metabolic alkalosis. A comparative crossover study between placebo, bumetanide and frusemide using equipotent doses was performed in 10 patients. Both drugs had a similar effect upon water excretion and the serum and urinary electrolytes.

Bumetanide↗
PubMedDate not supplied

Mediation of cell volume regulation by Ca2+ influx through stretch-activated channels.

Animal cells initially swell in hypotonic media by osmotic water equilibration, but their volume is subsequently regulated by a net loss of KCl and amino acids with concomitant loss of cell water. Mechanisms for regulating cell volume are important in allowing cells to adapt to variations in external tonicity and metabolic load. In red cells the KCl loss is mediated by electroneutral ion transport mechanisms. In contrast, conductive K+ and Cl- transport pathways are activated during regulatory volume decrease in several cell types including epithelia. The activation seems to be mediated by internal Ca2+, but the detailed mechanism is not known. In a leaky epithelium, the choroid plexus epithelium, we have found a cation-selective, Ca2+-permeable channel which opens with membrane stretch. The epithelium also contains a high density of the large (approximately 200 pS) type of Ca2+- voltage-activated K+ channel. Both channels are normally closed. I propose that in hypotonic media, the stretching of the cell membrane produced by the initial swelling causes influx of Ca2+ through the stretch-activated channels, which activates the neighbouring large K+ channels to produce increased K+ outflux with associated loss of cell water.

Animals↗
PubMedDate not supplied

A mass attack by the biting midge culicoides nubeculosus (Mg.) (Dipteria, Ceratopogonidae) on grazing cattle in Denmark. A new aspect of sewage discharge.

A consequence of sewage discharge into a shallow marsh pool was large-scale hatching of the biting midge Culicoides nubeculosus from the recipient and mass attacks by this blood-sucking insect on grazing cattle. Culicoides nubeculosus is a great nuisance due to the painful bite and in Denmark it is a potential vector of pathogenic agents. In the future, these aspects of sewage discharge must be borne in mind.

Animals↗