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Biomedical subjects

E H Larsen

Publications and source records attributed to E H Larsen.

At least 73 records · Page 4Linked to original sources
PubMed1985

Infectious complications after instrumentation of urinary tract.

Urethral catheterization is the single most important predisposing factor in the development of nosocomial urinary tract infection. Infection rates, etiologies, and possible methods of prevention are reviewed. Cystoscopy may be followed by a transient bacteremia. It is recommended that patients with positive urine cultures who undergo diagnostic cystoscopy receive antibiotic prophylaxis, but this is not required in patients with sterile urine. The incidence of urinary tract infection following transurethral surgery in patients who have not been given prophylactic antibiotics ranges from 6 to 60 per cent. The value of antibacterial prophylaxis in TUR, is still somewhat controversial. The incidence of infection and the value of antibacterial prophylaxis in prostatic biopsy appear to be related to the technique (transperineal or transrectal) used for the biopsy. It is too early to assess the infection risks associated with relatively new urologic procedures, such as ureteroscopy and percutaneous nephrostomy. Nevertheless, any procedure that crushes or manipulates a potentially bacteria-harboring stone carries at least a theoretical risk of infection.

Bacterial Infections↗
PubMed1985

Peptic ulcer in the gallbladder. A case report.

Gastric mucosa can be found in the gallbladder as a congenital heterotopia. A case of a perforated peptic ulcer in the gallbladder with concomitant hemorrhage in heterotopic gastric mucosa causing hematemesis and melena is presented.

Child↗
PubMed1984

Chloride transport in toad skin (Bufo viridis). The effect of salt adaptation.

The steady-state Cl- current across the skin of Bufo viridis adapted to tap water was found to be rectified. In skins bathed with NaCl Ringer on both sides, a large outward current, carried by influx of Cl-, was observed at a clamping voltage (V) of less than -50 mV (outside of the skin negative). for V = -50 mV the transepithelial Cl- conductance calculated from isotope flux measurements was 2.5 +/- 0.3 mS cm-2, N = 10. When the skin was clamped at + 50 mV the net flux of Cl- was reversed, but Cl- conductance was only 0.3 +/- 0.1 mScm-2. Flux ratio analysis indicated that the potential-activated Cl- conductance carries Cl- ions by way of passive transport. With NaCl Ringer bathing the outer surface of the skin the spontaneous potential was about -30 mV. At this potential the Cl- conductance of the skin was about half of its maximum value. The time course of Cl- current activation following a fast, stepwise change of V from 50 mV to a potential below O mV showed an initial delay of a few seconds, and proceeded with a halftime (T 1/2) which varied as a bell-shaped function of V. The maximum T 1/2 was about 100 s for V = -10 mV in skins exposed to KCl Ringer on the outside. Following adaptation of the toads to a 250 mM-NaCl solution, the fully activated Cl- conductance of the skin was greatly reduced, and the conductance-voltage curve was shifted to the left along the voltage-axis. With NaCl Ringer on the outside the spontaneous potential was about -20 mV, and Cl- conductance activation was possible only outside the physiological range of potentials. The time constant of Cl- conductance activation from closed to fully activated state was more than doubled following salt adaptation of the toads. The active inward Cl- flux disappeared in skins of toads adapted to a 250 mM-NaCl solution, and apparent leakage conductance was reduced. Application of the phosphodiesterase inhibitor 3-isobutyl-1-methyl-xanthine to skin of fully salt-adapted toads increased the transepithelial Cl- conductance, and the time courses of voltage clamp currents became more like those of water-adapted toads. Apparent leakage conductance was increased.(ABSTRACT TRUNCATED AT 400 WORDS)

Adaptation, Physiological↗
PubMed1983

Membrane potential plays a dual role for chloride transport across toad skin.

The Cl- -current through toad skin epithelium depends on the potential in a way consistent with a potential-controlled Cl- permeability. Computer analysis of the Koefoed-Johnsen Ussing two-membrane model provided with constant membrane permeabilities indicates that the voltage- and time-dependent currents are not caused by a trivial Goldmand-type rectification and ion redistributions following transepithelial potential pertubations. Extended with a dynamic Cl- permeability in the apical membrane according to a Hodgkin-Huxley kinetic scheme, the model predicts voltage clamp data which closely resemble experimental observations. This extension of the classic frog skin model implies that the Cl- permeability is activated by a voltage change caused by the inward Na+ current through the apical membrane.

Animals↗
PubMed1983

Ammonium bicarbonate as a replacement for carbon dioxide in Transgrow bottles for primary isolation of Neisseria gonorrhoeae.

Transgrow bottles with medium containing ammonium bicarbonate and Transgrow bottles gassed with 10% carbon dioxide performed equally well in detecting Neisseria gonorrhoeae in 434 clinical specimens. It appears that incorporation of ammonium bicarbonate into the medium increased the efficiency of the manufacturing process while maintaining the effectiveness of the medium.

Bacteriological Techniques↗
PubMed1982

Chloride channels in toad skin.

A study of the voltage and time dependence of a transepithelial Cl- current in toad skin (Bufo bufo) by the voltage-clamp method leads to the conclusion that potential has a dual role for Cl- transport. One is to control the permeability of an apical membrane Cl-pathway, the other is to drive Cl- ions through this pathway. Experimental analysis of the gating kinetics is rendered difficult owing to a contamination of the gated currents by cellular ion redistribution currents. To obtain insight into the effects of accumulation-depletion currents on voltage clamp currents of epithelial membranes, a mathematical model of the epithelium has been developed for computer analysis. By assuming that the apical membrane Cl- permeability is governed by a single gating variable (Hodgkin-Huxley kinetics), the model predicts fairly well steady-state current-voltage curves, the time course of current activations from a closed state, and the dependence of unidirectional fluxes on potential. Other predictions of the model do not agree with experimental findings, and it is suggested that the gating kinetics are governed by rate coefficients that also depend on the holding potential. Evidence is presented that Cl- transport through open channels does not obey the constant-field equation.

Animals↗
PubMed1977

Current-voltage curve of sodium channels and concentration dependence of sodium permeability in frog skin.

1. The inward facing membranes of in vitro frog skin epithelium were depolarized with solutions of high K concentration. The electrical properties of the epithelium are then expected to be governed by the outward facing, Na-selective membrane.2. In this state, the transepithelial voltage (V) was clamped to zero and step-changes of Na activity in the outer solution ((Na)(o)) were performed with a fast-flow chamber at constant ionic strength, while the short-circuit current was recorded.3. At pre-selected times after a step-change of (Na)(o) the current response (I) to a fast voltage staircase was recorded. This procedure was repeated after blocking the Na channels with amiloride to obtain the current-voltage curve of transmembrane and paracellular shunt pathways. The current-voltage curve of the Na channels was computed by subtracting the shunt current from the total current.4. The instantaneous I(Na)-V curve thus obtained at a given (Na)(o) could easily be fitted with the constant field equation in the range between -50 and zero mV. This fit yielded approximate estimates of P(Na), the Na- permeability of the Na-selective membrane (at this (Na)(o)) and the cellular Na activity, (Na)(c). As residual properties of the serosal membrane were ignored the computed values are expected to underestimate the true ones.5. At constant (Na)(c), the steady-state value of 1/P(Na) increases linearly with (Na)(o). Error analysis and the effect of drugs show that the dependence is not due to the residual properties of the inward facing membranes but reflects the true behaviour of P(Na).6. The steady-state P(Na) at a given (Na)(o) is smaller than the transient P(Na) observed right after a stepwise increase of (Na)(o) to this value. The time constant of P(Na)-relaxation is in the order of seconds.7. In conclusion, Na transport through open Na-selective channels of the outward facing membrane of the stratum granulosum cells can be described as an electrodiffusion process which as such does not saturate with increasing (Na)(o). However, when added to the outer border of the membrane Na causes a decrease of P(Na) within several seconds. It is considered that binding of Na results in closure of Na channels.

Amiloride↗
PubMed1976

Pathways for chloride and sodium transport across toad skin.

The voltage dependecies of Na and Cl fluxes were investigated in the isolated toad skin. With Cl-Ringer's on both sides Cl outflux varied very little with clamping voltage. The same was true for the influx of Cl at depolarizing voltages (psii -psio lessthan0 mV), wheras hyperpolarization led to a marked increase in this flux. A net chloride influx under short circuit conditions indicated active transport of chloride. The outflux of Cl was a saturable function of outside Cl concentration. The outflux of urea was hardly affected by raising outside Cl concentration, and the effect of varying outside nitrate concentration on Cl outflux was likewise small. Both influx and outflux could be inhibited partially bt acetazolamide. The outflux of Na varied with the clamping voltage as would be expected for an ion transported by electrodiffusion, and it was shown that amiloride had no effect on Na outflux, so it was concluded that the Na outflux route is particular. In the absence of Cl in the outside solution a small outflux of Cl persists. Also this flux varied with the clamping voltage according to laws for electrodiffusion. The variation of the ratio of sodium outflux to chloride outflux with clamping voltage indicated free passive diffusion of both these ions under the conditions mentioned. A comparison of the outfluxes of Na and Cl in skins bathed with gluconate Ringer's outside showed that the outflux route of these two ions was cation selective (PNa/PCl=1.88). When the paracellular leak pathway of the skins was opened by exposing the outside to hyperosmolar urea solutions, the ratio of the transport numbers was found to be TNa/TCl=1.71. The roles of the two ions in determining the steady state current-voltage relationships were compared. At hyperpolarizing voltages most or all of the clamping current was carried by an inward Cl flux. By depolarization sodium influx plays an increasing role with increasing depolarization. Under short circuit conditions active chloride transport was found to contribute to the short circuit current.

Acetazolamide↗
PubMedDate not supplied

Beverages as a source of toxic trace element intake.

Beverages of different kinds have been investigated for their content of lead, cadmium, nickel, chromium, arsenic and mercury. About a ten times higher lead concentration was found in wine than in most other beverages. Cocoa was high in cadmium and nickel and some vegetable juices contained high levels of nickel. The daily intake of trace elements from beverages was estimated. Wine was still the most significant source of lead even if the bottles did not have lead capsules. By consumption of half a bottle per day the daily intake of lead would be doubled and it would contribute 12% of Provisional Tolerable Weekly Intake. Cocoa is an important source of cadmium and nickel, and consumption of tea as well as vegetable juices could increase the nickel intake significantly. The data are compared to Danish maximum limits on lead and cadmium.

Beverages↗