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Biomedical subjects

O Christensen

Publications and source records attributed to O Christensen.

At least 55 records · Page 3Linked to original sources
PubMed1983

Mecillinam, a new prophylactic for travellers' diarrhoea. A prospective double-blind study in tourists travelling to Egypt and the Far East.

The efficacy of mecillinam when given orally in preventing travellers' diarrhoea has been studied. Preliminary investigations in volunteers showed that single daily doses of up to 200 mg for 3 weeks were well tolerated. A randomised double-blind study was carried out in a group of tourists visiting Egypt and the Far East. The subjects took either mecillinam (200 mg daily) or placebo for 25 days. 19/36 tourists (53%) taking placebo and 5/38 tourists (13%) taking mecillinam developed travellers' diarrhoea during the treatment period (p less than 0.001). In the placebo group enterotoxigenic Escherichia coli (LT/ST) were found in 2 cases of diarrhoea and Salmonella in another 2 cases. In the remaining cases of diarrhoea the etiological agent was not found in either of the 2 groups.

Administration, Oral↗
PubMed1982

The combination of pivmecillinam and pivampicillin compared to co-trimoxazole in the treatment of enteric fever.

Typhoid fever is an infectious disease with multisystem involvement and is commonly seen in the tropics. Twelve patients with acute typhoid fever were successfully treated with a fixed dose combination of pivmecillinam and pivampicillin. The treatment results were compared to those obtained from the treatment of ten other patients with co-trimoxazole, which is the routine treatment of our Department. The two forms of treatment appeared to be equally effective, suggesting that the combination mecillinam/ampicillin may represent a valuable alternative to the antityphoidal drugs currently available. Eleven patients were infected with strains resistant in vitro to either ampicillin, chloramphenicol, or both. All clinical isolates were sensitive to co-trimoxazole and to the combination of mecillinam and ampicillin. MIC values for the combination ranged from 0.16 to 2.5 mg/l. No side-effects were recorded.

Adolescent↗
PubMed1982

Fluctuation analysis of short-circuit current in a warm-blooded sodium-retaining epithelium: site current, density, and interaction with triamterene.

Density and conductance of the Na-site in hen coprodeum were studied by employing fluctuation analysis of short-circuit current at sodium concentrations from 26 to 130 mM. Fluctuations of current in the frequency range 2-800 Hz were induced by triamterene, a reversible blocker of conducting epithelial Na-sites. At 130 mM Na the site density was 5.8 +/- 1.0 micrometer-2 and the site conductance was 4 pS. This conductance is equal to that of the frog skin (W. Van Driessche and B. Lindemann, 1979, Nature (London) 282:519-520). Extrapolation of site density to zero sodium renders a total of 38 +/- 28 sites micrometer-2, which is compared with other estimates for the coprodeum. The site-triamterene association and dissociation constants were 9.5 +/- 0.4 rad sec-1 micrometer-1 and 255 +/- 20 rad sec-1 and they were independent of external sodium concentration. An analysis of the affinity constant for triamterene based on the DC-short-circuit current was found to be unrelated to the external sodium concentration and identical to that obtained from fluctuation analysis indicating a noncompetitive interaction between sodium and triamterene. Due to the oxygen demand of the epithelium we have developed an experimental method using short data processing times. A new analytical approach using integration of the power density spectrum proved necessary because of low signal-to-noise ratios.

Animals↗
PubMed1982

Steady states and the effects of ouabain in the Necturus gallbladder epithelium: a model analysis.

A simple numerical model for the Necturus gallbladder epithelium is presented. K+, Na+ and Cl- cross the mucosal and serosal membranes as well as the junctions by means of electrodiffusion; furthermore the mucosal membrane contains a neutral entry mechanism for NaCl and the serosal membrane contains an active pump for K+ and Na+. The values which have been used for the model are taken from the literature. The model can only attain steady states if the resistance of the serosal membrane is lower than 1000 omega cm2. Values reported in the literature for the resistance of this membrane vary from about 3000 to about 100 omega cm2. We shall argue, however, that the higher estimates are in error because they are derived from a model of the tissue in which each membrane and the junction are modeled by a resistor; this procedure is invalid because the resistance of the lateral intercellular space relative to the resistance of the tight junctions is neglected and consequently the resistance of the serosal membrane is overestimated by a factor of about four. Apart from predicting a realistic steady state at normal external concentrations the model can predict quantitatively several experimental results obtained from the living epithelium. We have focused on the experiments which test the permeabilities of the serosal membrane and the properties of the pump: i) Replacement of serosal Cl- by an impermeant ion. ii) Replacement of serosal K+ by Na+. iii) Inhibiting the (Na+, K+)-pump. The best correspondence between model and experiments is obtained when the pump is assumed to be electrogenic (or rheogenic) with a ratio of coupling between Na+ and K+ of 3:2. In this case both model and direct experiments (also presented in this paper) show an initial abrupt depolarization of 6 to 7 mV. The model also shows that it cannot be concluded from i and ii that the Cl- permeability of the serosal membrane is low. The model explains, even with high passive Cl- permeabilities, why the intracellular Cl- concentration is relatively unaffected by paracellular currents, a fact which in other epithelia has been taken as an implication of a low Cl- permeability of the serosal membranes.

Animals↗
PubMed1982

Transport of glucose across the blood-brain barrier: reevaluation of the accelerative exchange diffusion.

In an earlier study of glucose transport across the blood-brain barrier it was concluded that the kinetic transport constants increase as the brain glucose concentration increases, a finding that was attributed to accelerative exchange diffusion (Betz et al. 1975). The conclusion, however, relied upon application of a commonly used simplified treatment of tracer extraction data. In this study it is demonstrated that the simplified treatment is applicable only in the case of zero brain glucose concentration, and a more general model for determination of the kinetic constants is developed. Re-analysis by this model of the data of Betz et al. (1975)--comprising a range of brain glucose concentrations--gave kinetic constants which did not vary significantly over a wide range of brain glucose concentrations. For brain glucose concentrations up to about 12 mmol 1(-1), the kinetic constants obtained for glucose transport across the blood-brain barrier are Km = 6.18 +/- 0.38 mmol 1(-1) Vmax = 1.65 +/- 0.06 mu mol g -1 min -1.

Animals↗
PubMed1982

Augmented release of gastric inhibitory polypeptide into the portal vein in response to intraduodenal glucose and amino acids in anesthetized rats treated with methylprednisolone or alloxan.

Thirty rats were treated with methylprednisolone, 30 rats were treated with alloxan, and 30 control rats were treated with saline alone. The levels of fasting serum insulin and blood glucose and of plasma GIP before and after duodenal instillation of glucose or amino acids were measured using an acute rat preparation that enabled multiple blood samplings from the portal vein. Treatment of the rats with methylprednisolone was followed by increased fasting levels of serum insulin, blood glucose, and plasma GIP and by an augmented GIP release in response to duodenal glucose and amino acids as compared with normal controls. Similarly, treatment with alloxan was followed by decreased fasting levels of serum insulin, by increased fasting levels of blood glucose and plasma GIP, and by an increased GIP release in response to duodenal glucose and amino acids. The augmented GIP release in response to duodenal instillation of glucose and amino acids both in methylprednisolone-treated rats and in alloxan-treated rats may be explained by an increased absorption of these nutrients owing to an increased Na+ K+ ATPase activity in the intestinal mucosa of corticosteroid- and alloxan-treated rats. The elevated fasting GIP levels, on the other hand, are difficult to explain.

Alloxan↗
PubMed1982

Abdominal aortic aneurysms: survival analysis of four hundred thirty-four patients.

Cases of 434 patients who underwent surgery for abdominal aortic aneurysms in five surgical departments in Norway have been studied with respect to survival patterns and survival probabilities. Of these, 200 patients (median age 63 years) had elective surgery, 173 patients (median age 69 years) had ruptured aneurysms, and 61 patients (median age 67 years) had impending rupture (i.e., emergency operations were performed, but no rupture was found). The hospital mortality rates in the groups were 3.5%, 59%, and 24.6%, respectively. The general probabilities of survival of these groups have been compared with those of a demographically similar population (standard population). Patients who had elective surgery had a slightly, but significantly, lower survival probabilities than did the standard population, whereas the patients who underwent emergency surgery and who survived the first postoperative month showed no increased risk of dying as compared with the standard population. For the elective surgery group, age had a significant effect on survival, whereas the period of operation did not. In the group with ruptured aneurysms both the age of the patient and the period of operation had significant effects on survival, whereas no such effects were found for patients with impending rupture. The survival probabilities for patients surviving the operation were generally good, with a high 5-year survival rate. The mortality rate for patients with ruptured aneurysms decreased significantly from period I (surgery performed before 1976) to period II (surgery performed in 1976 or later). The survival probabilities for patients of advanced age were relatively good, even for patients who had emergency surgery.

Adult↗
PubMed1981

Electrical resistance of a capillary endothelium.

The electrical resistance of consecutive segments of capillaries has been determined by a method in which the microvessels were treated as a leaky, infinite cable. A two-dimensional analytical model to describe the potential field in response to intracapillary current injection was formulated. The model allowed determination of the electrical resistance from four sets of data: the capillary radius, the capillary length constant, the length constant in the mesentery perpendicular to the capillary, and the relative potential drop across the capillary wall. Of particular importance were the mesothelial membranes covering the mesenteric capillaries with resistances several times higher than that of the capillary endothelium. 27 frog mesenteric capillaries were characterized. The average resistance of the endothelium was 1.85 omega cm2, which compares well with earlier determinations of the ionic permeability of such capillaries. However, heterogeneity with respect to resistance was observed, that of 10 arterial capillaries being 3.0 omega cm2 as compared with 0.95 omega cm2 for 17 mid- and venous capillaries. The average in situ length constant was 99 micrometers for the arterial capillaries and 57 micrometers for the mid- and venous capillaries. It is likely that the ions that carry the current must move paracellularly, through junctions that are leaky to small solutes.

Animals↗
PubMed1981

A mathematical model of fluid transport in the kidney.

A mathematical model of the rat kidney is developed from glomerular and tubular submodels. It is assumed that all nephrons are identical, that the hydraulic pressure in the tubules obeys Hagen-Poiseuille's law, that the rate of fluid reabsorption depends on the flow rate of tubular fluid, and that the tubules are distensible. The independent variables of the model are selected to comply with experimental measurements in the hydropenic rat. The model is used to evaluate the mechanism of glomerulotubular balance: changing the mean ultrafiltration pressure to the glomerular capillaries has a substantial influence on glomerular filtration rate (GFR). A change in the rate of fluid reabsorption in the proximal tubules has a strong influence on GFR notwithstanding that the change in GFR is smaller than that in the rate of fluid reabsorption. The calculated values for the hydraulic pressure profile in the tubular system and the interstitial pressure during ureteral obstruction are in close agreement with experimental measurements. Increasing the arterial haematocrit above normal causes a substantial decrease in GFR, whilst reducing it below normal has only a small effect on GRF.

Animals↗
PubMed1981

Long-term results after left ventricular aneurysmectomy.

Twenty-six patients (21 men and five women) with a mean age of 54.8 years have been reinvestigated nine to 62 months (mean 29.7) after left ventricular aneurysmectomy. Preoperatively left ventricular angiography disclosed an anterior aneurysm in all cases, which was large in 15 (57%) and small to medium in 11 (42%). At follow-up a large residual aneurysm was found in five (19%), a small to medium one in 13 (50%), and akinesia without aneurysm in eight (31%). The sum of ST elevation (sigma ST) in praecordial leads in the electrocardiogram was reduced from a mean value of 11.2 mm to 7.7 mm. In no patient did ST segments return to normal after operation. Preoperatively, mean sigma ST was identical in patients with large and with small to medium aneurysms. At reinvestigation mean sigma ST was identical in patients with large and with small to medium residual aneurysms as well as in patients with akinesia. Left ventricular end-diastolic pressure before angiography was reduced from a mean value of 21.5 mm to 15.1 mmHg and after angiography from 26.7 mm to 21.1 mmHg. Progression of coronary artery stenoses was a characteristic finding in patients whose left ventricular end-diastolic pressures did not return to normal. These patients had a longer follow-up time than those with no progression of coronary disease, who all showed an improvement in left ventricular end-diastolic pressure. Six patients who had coronary bypass grafting performed had unchanged left ventricular end-diastolic pressures at follow-up. The results indicate that progression of coronary artery disease may be responsible for an eventual further deterioration in left ventricular function after aneurysmectomy. Additional bypass grafting did not result in improved left ventricular function.

Adult↗
PubMed1979

Surgical treatment of chronic hyperplastic sinusitis and maxillary sinus empyema of oral/dental origin.

Twelve patients with maxillary hyperplastic sinusitis or maxillary sinus empyema of oral/dental etiology have been treated according to a modified surgical technique. The treatment was initiated by several oro-nasal irrigations and drainage facilitated by an intact semilunar hiatus. This was followed by a surgical procedure including conservative curettage of inflamed sinus mucosa, adequate closure of the oro/antral communication, with establishment of a postoperative oral antrostomy. This antrostomy, through the canine fossa, was established by a vacuum drain, enabling continuous postoperative irrigation and aspiration. The rationale for this technique is discussed. A total of 12 patients operated according to this technique are described. Complete clinical and radiographic healing in all patients was observed over a postoperative period ranging from 6-12 months.

Adult↗