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Biomedical subjects

M Wiederholt

Publications and source records attributed to M Wiederholt.

At least 145 records · Page 8Linked to original sources
PubMed1979

Effect of intraocular irrigating solutions on intracellular membrane potentials and swelling rate of isolated human and rabbit cornea.

Isolated human and rabbit corneas were incubated in glutathione bicarbonate Ringer solution (GBR), balanced salt solution (BSS), or 0.9% NaCl solution. The swelling rate of human corneas was 25.5 micron/hr in GBR and significantly increased to 32.7 in BSS and 66.1 in NaCl. The epithelial intracellular potential of human cornea was constant at about 60 mV up to 5 hr of incubation in GBR and decreased continuously to 40 mV in BSS and NaCl. Endothelial cell potentials were stable for up to 3 hr of incubation in GBR or BSS and decreased from a control value of about 18 mV to 10 mV 2 hr after bathing in NaCl. Qualitatively similar data were obtained in the isolated rabbit cornea. The results demonstrate the advantage of GBR as an intraocular irrigating solution.

Animals↗
PubMed1979

[Clinical and experimental evaluation of hydrophilic contact lenses for continuous-wear (author's transl)].

In a clinical and experimental study we tested a new contact lens for continuous-wear. The modified HEMA-lens ("Permalens", Global Vision Ltd, Southampton/GB; Cooper Laboratories, Düsseldorf) has a water content of 74% at pH 7.4. The oxygen transmissibility is, depending on the thickness of the lens, 38--67% of the oxygen in the air. In a first trial we had to eliminate 6 patients due to wrong fitting (much too steep) or dry eyes. After development of a new guide for selection of lens base curves 10 patients with monocular aphakia (10 eyes) and 12 patients with mild myopia (24 eyes) were fitted with the hydrophilic soft contact lens for permanent wear. From a total of 34 eyes in 11 cases (32%) the lenses were removed due to complications (1 conjunctivitis, 1 keratitis, 1 vascularization) or due to lack of cooperation. In 23 cases (68%) the continuous-war lenses were well tolerated without complications for 5 months. In a comparative study in vitro we tested the effect of the contact lens on the viability (swelling rate, intracellular membrane potential of the epithelium) of the isolated human cornea. A damaging effect of the lens on corneal function was not observed. The hydrophilic soft contact lens can be fitted for continuous-wear.

Adult↗
PubMed1978

Sodium and chloride transport in the isolated human cornea.

22Na and 36Cl fluxes in isolated human cornea preparations were measured under short-circuited conditions. At pH 7.3-PH 7.6 sodium net flux was directed from aqueous humour to tear side, chloride net flux was statistically not different from zero. Alkalinization of the bathing solution to pH 8.6 stimulated unidirectional sodium and chloride fluxes from aqueous humour to tear side resulting in net sodium and chloride fluxes towards the tear side which both were statistically different from zero. Cyclic AMP (10(-3) M) was found to stimulate sodium and chloride unidirectional fluxes from aqueous humour to tear side, thus leading to significant net sodium and chloride fluxes in the same direction. Epinephrine (10(-4) M) increased the unidirectional chloride flux from aqueous humour to tear side more pronounced than in the opposite direction, producing a significant net chloride flux towards the tear side. The results are consistent with the hypothesis that the electrolyte pumps may under certain conditions contribute to the dehydration of the stroma.

Biological Transport, Active↗
PubMed1978

The pH dependency of sodium and chloride transport in the isolated human cornea.

Sodium and chloride net transport in isolated human cornea preparations were found to be pH dependent. Sodium net transport was directed from aqueous humor to tear side at pH 7.6 and 8.6. At pH 7.4, net sodium flux did not differ significantly from zero, and at pH 7.0, net sodium transport was directed toward the aqueous humor side. Chloride net flux at pH 8.6 and 7.6 was also directed from aqueous humor to tear side. Acidification of the bathing solution to pH 7.4 and 7.0 was followed by a decrease in chloride net fluxes to values not significantly different from zero.

Biological Transport↗
PubMed1977

[Catamnestic and endocrinological investigations in women with idiopathic edema (author's transl)].

The clinical picture and the course of idiopathic edema is described after evaluating catamnestic questionnaires on 39 patients. It appears that the syndrome often occurs in other female family members, especially in mothers of propositi and that two thirds of patients have also suffered from symptoms of allergy. In contrast to observations of other groups, diabetes mellitus and slight hypoalbuminemia were found only in a few patients. Secondary hyperaldosteronism was almost exclusively observed in patients who had been taking diuretics during the last few days before the measurements were done. The plasma concentrations of 6 other adrenal steroidal hormones were measured in 33 patients. Only in few of them, mostly patients who had taken diuretics, increased level of 11-deoxycorticosterone, 18-OH-11-deoxycorticosterone and corticosterone were observed. Idiopathic edema does not seem to be a disease entity, but some prediposing factor related to the female reproductive system is likely to exist. Results of systematic psychosomatic studies in our patients will be reported later on.

Adolescent↗
PubMed1975

Effects of graded solute diuresis on renal tubular sodium transport in the rat.

Sodium transport was studied across proximal and distal tubules of rats undergoing progressive intravenous loading with either isomotic saline or urea (200 mosmol)-saline (100 mosmol) solutions. Free-flow as well as recollection micropuncture techniques were used, and tubular fluid (TF) samples were analyzed for inulin-14C and sodium (Na). With administration of progressively larger intravenous saline loads, the delivery of fluid and sodium into the distal tubule rose. Concomitantly, the normally observed decline of tubular sodium concentrations along the distal tubule became attenuated until it was abolished at the highest infusion rates of saline solutions. Absolute reabsorption rates of Na across the distal tubule increased in proportion to tubular flow rate, and no tubular maximum (Tm) was observed. It is suggested that the delivery of increased amounts of sodium to the normally unsaturated later parts of the distal tubule and the elevated tubular sodium concentration after saline loading account for the observed stimulation of distal tubular net sodium transport. The extent of transport stimulation is also subject to control by the amount of urea accumulation along the distal tubule. As the latter declines, sodium reabsorption is proportionately enhanced.

Animals↗