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Biomedical subjects

R Nielsen

Publications and source records attributed to R Nielsen.

At least 145 records · Page 8Linked to original sources
PubMed1984

Active transepithelial potassium transport in frog skin via specific potassium channels in the apical membrane.

In frog skin bathed in Cl--Ringer's solution the short circuit current (SCC) is equal to the net Na+ flux. In the present study Na+ and K+ transport across frog skin have been investigated in skins bathed in a solution where all Cl- has been substituted by the impermeable anion gluconate. In this solution the net Na+ flux (9.22 +/- 0.72 nmole/cm2/min) was significantly higher than the SCC (7.61 +/- 0.63) nmole/cm2/min). Measurement of the transepithelial K+ influx and K+ efflux showed that the discrepancy between the net Na+ flux and the SCC was caused by an active outwards going transepithelial K+ transport. The K+ but not the Na+ transport could be blocked by adding the K+ channel blocking agent Ba++ to the apical solution. Thus, the K+ transport occurs via a K+ specific pathway in the apical membrane. Ouabain blocked both the Na+ and the K+ transport, whereas the presence of the Na+ channel blocking agent amiloride in the apical solution blocked the Na+ transport and reduced the K+ transport. In the presence of amiloride in the apical solution the SCC and the transepithelial potential difference (PD) reversed so that the outside (the apical side) of the frog skin became positive with respect to the basolateral side. The inverted SCC was carried by an active transepithelial K+ transport, this K+ transport required the presence of Na+ in the basolateral solution. The experiments show that frog skin can insert or activate K+ channels in the apical membrane, indicating that the frog may regulate its K+ content by varying the K+ permeability of the apical membrane.

Amiloride↗
PubMed1982

Effect of ouabain, amiloride, and antidiuretic hormone on the sodium-transport pool in isolated epithelia from frog skin (Rana temporaria).

When tracer Na+ is added to the solution bathing the apical side of isolated epithelia the observed transepithelial tracer influx increases with time until a steady state is reached. The build-up of the tracer flux follows a single exponential course. The halftime for this build-up under control conditions was 0.92 +/- 0.06 min, and in the presence of ouabain 4.51 +/- 0.7 min. It is shown that the calculated Na+-transport pool is located in the cells. The Na+-transport pool under control conditions was 35.6 +/- 3.4 nmol/cm2, which corresponds to an intracellular Na+ concentration of 7.9 mM. Activation of the active Na+ transport by addition of antidiuretic hormone resulted in a highly significant increase in the Na+ transport pool, and inhibition of the transcellular Na+ transport with amiloride resulted in a decrease in the Na+-transport pool. Furthermore, the active Na+ transport increased along an S-shaped curve with increasing intracellular Na+ concentration (Na+-transport pool). The Na+ pump was found to be half saturated at an intracellular Na+ concentration of 12.5 mM.

Amiloride↗
PubMed1982

Enhanced sensitivity to stimulation of sodium transport and cyclic AMP by antidiuretic hormone after Ca2+ depletion of isolated frog skin epithelium.

The role of Ca2+ in the stimulation by antidiuretic hormone (ADH) of active sodium transport across the isolated epithelium of frog skin was investigated. This has been done by bathing the blood side with Ca2+-free solution containing 0.1 mM EGTA. This Ca2+ depletion halved the resistance but had no significant effect on the short-circuit current (SCC). The sensitivity of both cAMP- and SCC-stimulation to ADH was increased 40-fold by Ca2+ depletion. Sensitivity to stimulation by theophylline was only changed a little, while stimulation by exogenous cAMP was completely unaltered. The increase in sensitivity to ADH was dependent on the duration of preincubation in Ca2+-free solution, which indicates that a slowly exchanging Ca2+ pool is involved in the determination of sensitivity to ADH. We suggest this pool is of cellular origin and the increased sensitivity is due to the decrease of a Ca2+ inhibition of the ADH-stimulated adenylate cyclase. But a direct effect of Ca2+ on binding of ADH to the receptor cannot be excluded. Our results are not compatible with the hypothesis that entry of extracellular Ca2+ is an obligatory step in the natriferic action of ADH, although it may be so in the hydroosmotic action of ADH. We also found the maximal response to ADH to be higher after Ca2+ depletion. This is in agreement with the hypothesis of intracellular Ca2+ as a modulator of the sodium permeability of the outward-facing membrane.

Animals↗
PubMed1982

Theophylline-induced stimulation of sodium transport in frog skin by a mechanism different from the antidiuretic hormone activated pathway.

Theophylline (theo) induced a marked increase in the short circuit current (SCC) after maximal stimulation by the antidiuretic hormone, arginine vasotocin (AVT). The stimulation amounted to 20-70% of the AVT-stimulation. Practically no effect was seen on osmotic water flow after maximal AVT-stimulation. A concentration dependence of the SCC stimulation was found from 0.04 to 4 mM theo, 16 mM inhibited the SCC. The response to theo was independent of the time of preincubation with AVT. The theo induced increase of SCC was accounted for by active sodium transport. Theo did induce an increase in the cyclic AMP level after stimulation with a maximal concentration of AVT, but so did a supramaximal dose of AVT. This indicates that the mechanism, by which theo stimulated the SCC additional to maximal AVT stimulation, is different from that by which AVT works. This effect of theo may be unrelated to cAMP or it may be explained by differences in cellular specificity of theo and AVT.

Animals↗
PubMed1980

Primary and secondary displacement of central venous catheters.

The purpose of this study was to investigate the frequency of primary and secondary displacement of central venous catheters. One hundred and two central venous catheters, inserted through a peripheral or a central vein before surgery or in the intensive care unit, were controlled by chest X-ray 5-720 min after insertion. The number of primarily displaced catheters was 27. Of these, the position was corrected in 8. Thereafter, the 83 correctly placed catheters were observed for 4-560 h. The number of X-ray controls was 2-24. The number of secondary displacement was 2, whereas 12 catheters showed minimal secondary displacement. The rate of complication was very low. We conclude that chest X-ray immediately after insertion of central venous catheters is absolutely necessary, but since the number of secondary displacements is very low, daily chest X-ray control is not necessary. We also conclude that the internal jugular vein is the best route for introducing a central venous catheter, since complications are very few and the number of displacements is very low.

Adolescent↗
PubMed1980

Sodium nitroprusside induced cGMP accumulation in isolated frog skin epithelium. Effect on cAMP, hydroosmotic and natriferic response to antidiuretic horomone.

UNLABELLED: The cGMP content of isolated frog skin epithelia has been measured, and the basal level was found to be 14.3 +/- 1.7 fmol/mg dry lweight. 0.1 mM sodium nitroprusside induced a 10-fold increase in the cGNP level within 5 min after which it rose more slowly. The maximum increase in cGMP level was obtained with 1 mM sodium nitroprusside, giving a 20-50-fold increase. 1 mM sodium nitroprusside per se had no effect on osmotic water flow or active sodium transport. On the other hand, the osmotic water flow response to arginine vasotocin was somewhat enhanced in skins which had been pretreated with 1 mM sodium nitroprusside; thus the water flow responses to 1 and 31 ng/ml arginine vasotocin were on the average 31 and 14% higher in skins exposed to sodium nitroprusside than in control skins. Sodium nitroprusside had no effect on the increment in sodium transport rate elicited by arginine vasotocin. Sodium nitroprusside alone increased the cAMP level slightly; the enhanced cAMP level, reached after 30 min incubation with 40 ng/ml arginine vasotocin, was 20% higher in the presence of 1 mM sodium nitroprusside. IN CONCLUSION: cGMP has no effect on osmotic water flow nor on active sodium transport and is not involved in the regulation of sodium transport by antidiuretic hormone. However, cGMP (or sodium nitroprusside) has a moderate effect on the hormone-stimulated osmotic water flow.

Animals↗
PubMed1980

Duplicate exstrophy of the bladder.

Duplicate exstrophy is a very rare variant of the exstrophy complex. Treatment is gratifying, because the patients have normal internal urogenital structures. Two different cases of duplicate exstrophy are presented. One is completely similar to the type, described by Marshall and Muecke, of which now 9 cases have been reported. It is suggested that the other, together with 4 earlier reported cases, belongs to a different type of duplicate exstrophy. The embryological mechanism responsible for this type is probably a coincidence of 1) duplication of cloacal structures and 2) exstrophy of one of the bladders.

Abdominal Muscles↗
PubMed1979

Coupled transepithelial sodium and potassium transport across isolated frog skin: effect of ouabain, amiloride and the polyene antibiotic filipin.

Addition of the polyene antibiotic filipin (50 microM) to the outside bathing solution (OBS) of the isolated frog skin resulted in a highly significant active outward transport of K+ because filipin per se increases the nonspecific Na+ and K+ permeability of the outward facing membrane. The K+ transport was calculated from the chemically determined changes in K+ concentrations in the solution bathing the two sides of the skin. The active transepithelial K+ transport required the presence of Na+ in the OBS, but not in the inside bathing solution (IBS), and it was inhibited by the Na+, K+-ATPase inhibitor ouabain. The addition of Ba++ to the IBS in the presence of filipin in the OBS resulted in an activation of the transepithelial K+ transport and in an inhibition of the active Na+ transport. This is in agreement with the notion that Ba++ decreases the passive K+ permeability of the inward facing membrane. In the presence of amiloride (which blocks the specific Na permeability of the outward facing membrane) and Ba++ there was a good correlation between the active Na+ and K+ transport. It is concluded that the active transepithelial K+ transport is carried out by a coupled electrogenic Na-K pump, and it is suggested that the pump ratio (Na/K) is 1.5.

Amiloride↗
PubMed1979

Haemophilus parahaemolyticus serotypes. Pathogenicity and cross immunity.

Pigs inoculated intranasally with Haemophilus parahaemolyticus, serotype 2, resisted challenge 3 weeks later with serotypes 2, 4 and 5 without showing clinical symptoms. The pigs were sacrificed 2 days after challenge, and post mortem examination showed a chronic pleuropneumonia from which only serotype 2 was re-isolated. Pigs inoculated intranasally with H. parahaemolyticus, serotype 2, showed no clinical symptoms when challenged 3 weeks later with serotype 1. Post mortem examination revealed a chronic pleuropneumonia with areas of necrosis from which H. parahaemolyticus, serotype 2, was re-isolated, but also small areas of a more acute fibrinous pneumonia from which serotype 1 was re-isolated. The control pig inoculated with only serotype 1 showed a severe acute fibrinous pleuropneumonia. The results indicate that a considerable cross immunity exists between the various serotypes of H. parahaemolyticus.

Animals↗
PubMed1979

Haemophilus parahaemolyticus serotypes. Serological response.

Serotypes 1,2,4 and 5 of Haemophilus parahaemolyticus were inoculated into, respectively, 4,4,2 and 5 pigs. Serum samples were tested for circulating antibodies by the modified complement fixation test (CF test). When individual serotypes were used as antigen, titers were found only to the serotype which had been used for inoculation. Using antigen in which the serotypes were pooled, antibodies were demonstrated in sera from all the pigs. The CF titers obtained with the pooled antigen were equivalent to those found with each serotype separately. When the CF test was used for serological examination of field sera there was full agreement between the results obtained with the pooled antigen and those obtained with serotype 2 antigen alone. No cross reactions were found with the pooled antigen in herds that were sero-positive to Haemophilus parasuis, strain 4800. The experiment has shown that there is no serological cross reaction between serotypes 1, 2, 4 and 5 when they are used as antigen in the CF test. Also, the results imply that with a pool of the different serotypes of Haemophilus paralyticus as antigen similar results may be obtained as with the single serotype 2 antigen.

Animals↗
PubMed1978

Effect of the polyene antibiotic filipin and the calcium ionophore A23187 on sodium transport in isolated frog skin (Rana temporaria).

Addition of filipin (50 micrometer) to the inside bathing solution of the frog skin resulted in a transient increase in the active sodium transport [measured as short-circuit current (SCC)]. The filipin-induced increase in the SCC required the presence of calcium. The calcium ionophore A23187 (4 micrometer) also induced a transient increase in the SCC. After the activation of the SCC by A23187, the SCC could not be activated by filipin. This indicates that the polyene antibiotic filipin acts as a calcium ionophore. Higher concentrations (40 micrometer) of A23187 resulted in a shrinking of the cells in the transporting cell layer. A23187 also increased the potassium-42 exchange in the isolated epithelium. It is suggested that calcium ionophores enhanced the intracellular calcium concentration; this increase in the calcium concentration resulted in an increase in the potassium permeability of the inward-facing membrane. The increase in the potassium permeability might explain the observed increase in the SCC.

Action Potentials↗
PubMed1978

Effects of the antidiuretic hormone, arginine vasotocin, theophylline, filipin and A23187 on cyclic AMP in isolated frog skin epithelium (Rana temporaria).

A method for measuring cAMP in frog skin epithelium was developed. The epithelia were isolated after collagenase-treatment. cAMP was extracted by boiling water and the extract was purified on dry Al2O3. The change with time of the cAMP level after addition of arginine vasotocin (AVT) was studied. The hormone caused a rapid increase in cAMP level with a maximum after 3-5 min, whereafter the cAMP level declined. Incubation with AVT made the epithelia refractory to a second dose of AVT, which indicates that the decline in cAMP level was caused by a feedback mechanism and not by inactivation of the hormone. cAMP appeared evenly distributed in all cell-layers of the epithelia both before and after stimulation with AVT. Theophylline caused a rapid increase in the cAMP level, which remained elevated for at least 45 min. Addition of the ionophore A23187 or of filipin had no effect on the cAMP level. However, in the presence of theophylline, A23187 enhanced the cAMP level, whereas filipin had no effect. Therefore the involvement of cAMP in the action of A23187 has to be considered.

Animals↗
PubMed1977

Effect of the polyene antibiotic filipin on the permeability of the inward- and the outward-facing membranes of the isolated from skin (Rana temporaria).

The effect of the polyene antibiotic filipin on the electrical properties and the passive permeability of the cell membranes was investigated. The addition of filipin to the outside bathing solution has the following effects: 1. it results in a drastic reduction in the transepithelial resistance and potential, 2. it causes a 10-20 times increase in the passive transepithelial chloride, sodium and sucrose flux, 3. it results in the formation of an amiloride insensitive sodium pathway in the outward facing membrane, 4. it results in an active outward transport of potassium, 5. it results in a highly significant swelling of all the cells in the epithelium. The addition of filipin to the inside bathing solution has the following effects 1. it results in an activation of the active sodium transport, 2. it causes a slight increase in the passive transepithelial chloride and sodium permeabilities but has no effect on the sucrose permeability, 3. it has no effect on the amiloride inhibition of the short-circuit current, 4. it has no effect on the volume of the cells in the epithelium. It is suggested that the addition of filipin to the outside bathing solution increases the direct sodium flow from cell to cell in neighbour layers. Furthermore these experiments indicate that the outward facing membrane of the isolated frog skin has a high cholesterol content as compared with the cholesterol content of the inward facing membrane.

Amiloride↗
PubMed1977

Pleuropneumonia in swine caused by Haemophilus parahaemolyticus. A study of the epidemiology of the infection.

Haemophilus parahaemolyticus infection was studied in a herd with continuous production, i.e., continuous introduction of stock to replace animals delivered for slaughter. None of 30 seronegative pigs contracted the infection when exposed to contact with two pigs that were seropositive after inoculation with H. Parahaemolyticus three weeks earlier. After aerosol infection had been applied in the building an acute outbreak with a morbidity rate of 100 per cent developed in less than 24 hours. Following recovery the majority of the 16 pigs present became seropositive, and when 30 seronegative pigs were introduced 7 weeks later, antibody response occurred in three of them. The persistence of H. parahaemolyticus in pigs that had been infected during the acute outbreak was confirmed at slaughter, in that the organism was re-isolated from the tonsils of 2 of these pigs. Most serum titres persisted for several months, but some animals showed just a transient antibody response.

Animals↗