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Biomedical subjects

M Wiederholt

Publications and source records attributed to M Wiederholt.

At least 163 records · Page 9Linked to original sources
PubMed1971

Potassium and sodium transport across single distal tubules of Amphiuma.

The transport properties of potassium (K) and sodium (Na) were studied in single distal tubules of Amphiuma using free-flow micropuncture techniques and stationary microperfusion methods. The transepithelial movement of labeled potassium was measured utilizing a three-compartment system in series in which the time course of tracer disappearance from the lumen was followed. Under control conditions, in blood- and doubly-perfused kidneys, extensive active net reabsorption of sodium and potassium obtains along single distal tubules. Tubular potassium reabsorption is abolished by ouabain at a concentration of 5 x 10(-6)M. Significant net secretion of K can be induced by exposing Amphiuma to a high K environment (100 mM KCl) or by adding acetazoleamide (1 x 10(-4)M) to the perfusion fluid. Transepithelial movement of potassium involves mixing with only a small fraction of total distal tubular cell potassium. This transport pool of potassium increases significantly with the transition from tubular net reabsorption to net secretion. Indirect evidence is presented which indicates that increased active K uptake across the peritubular cell boundary may be of prime importance during states of net K secretion.

Acetazolamide↗
PubMedDate not supplied

Regulation of trabecular meshwork contractility.

Ample evidence supports the theory that trabecular meshwork possesses smooth-muscle-like properties. Trabecular meshwork cells express a large number of transporters, channels and receptors, many of which are known to regulate smooth-muscle contractility. It has been shown that trabecular meshwork can be induced to contract and relax in response to pharmacological agents. In the model of the bovine eye, confirmed in some cases by experiments on primates, agents that contract trabecular meshwork reduce outflow. On the cellular level, this is coupled with depolarization and a rise in intracellular calcium. Relaxation of trabecular meshwork, on the other hand, appears to be coupled to a stimulation of the maxi-K channel, inducing hyperpolarization and a closure of L-type calcium channels. No significant differences between cells from a human and a bovine source emerged, either in classical measurements of membrane voltage, in measurements of intracellular calcium or patch-clamp experiments. Thus, pharmacological agents that relax trabecular meshwork seem promising candidates for further research - the ultimate goal being an improvement of glaucoma therapy in humans.

Adrenergic Agonists↗
PubMedDate not supplied

Influence of cyclosporin A, dexamethasone, and benzalkonium chloride (BAK) on corneal epithelial wound healing in the rabbit and guinea pig eye.

Corneal erosions were produced by iodine vapor application in rabbit and guinea pig eyes. The corneal erosion of each eye was photographed four times daily after fluorescein staining and the erosion area measured planimetrically. Thirty-six percent of the corneal epithelium was destroyed in rabbits and 67% in guinea pigs. In guinea pigs, wound healing was delayed significantly by Spersadex, Totocortin, and benzalkonium chloride (BAK) 0.01% in the experimental eye. Spersadex also caused a significant delay in wound healing in the nontreated contralateral eye. Cyclosporin A 2% and Oculotect had no influence on epithelial wound healing. An 8-day pretreatment of guinea pig eyes with cyclosporin A or Spersadex had no further influence on the epithelial wound-healing rate.

Animals↗