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Biomedical subjects

H Stark

Publications and source records attributed to H Stark.

At least 19 recordsLinked to original sources
PubMed1992

Severe tubular resistance to aldosterone in a child with familial juvenile nephronophthisis.

A 9.5-year-old girl, whose early symptoms were polyuria and growth retardation, is described. During the progression of her disease, hyperkalaemia developed out of proportion to the degree of renal insufficiency. Her fractional excretion of sodium increased from 3.3% to 35%, and her fractional excretion of potassium decreased from 55% to 22%. The plasma aldosterone level and plasma renin activity (PRA) were very high--290 ng/ml and 100 ng/dl per hour, respectively (normal range for this age 2.6-20.8 ng/ml and 1.2-2.7 ng/ml per hour, respectively). In an attempt to reduce these hormone levels, an acute and sustained saline load, captopril and peritoneal dialysis were used. Only the sustained saline load normalized the PRA, and only peritoneal dialysis sufficiently suppressed the plasma aldosterone level. Successful renal transplantation normalized both plasma aldosterone and PRA. This girl presents the unusual occurrence of pseudohypoaldosteronism type I, during the course of familial juvenile nephronophthisis.

Aldosterone↗
PubMed1992

[Documentation of glaucomatous visual field defects in threshold and suprathreshold perimetry].

In contrast to normal subjects, the individual stimulus threshold for differential light sensitivity (DLS) in glaucoma patients fluctuates considerably. The sensitivity and the size of the defect are correlated: with a higher individual stimulus threshold, i.e. when sensitivity deteriorates, the number of defects decreases. Conversely, when the individual stimulus threshold drops, i.e. when sensitivity improves, the number of defects recorded increases. The trend is the same with extensive Grade 3 defects. This correlation between sensitivity and defect size means that the number and depth of individual defects change constantly, due to the fluctuation of the individual stimulus threshold. In follow-up examinations test positions with permanent defects (a defects) can be distinguished from those where defects have been detected several times, but not permanently (b defects) and, respectively, only once in 2 1/2 years (c defects). Defects must therefore be classified not only according to depth, but also according to behaviour at individual test positions. Such a classification can be accomplished by tabulating all newly numbered test positions and the defects identified there. After 5 visual field examinations the defects are then classified as a, b, or c defects. They are then identified by colour symbols and transferred to a test position chart representing a synopsis of 5 visual fields. The chart not only permits exact topographical analysis but also furnishes information on certain structural features of the glaucomatous visual field: stable nuclear areas of a defects surrounded by fluctuating peripheral defects (b defects) or concomitant c defects. After a further 1 1/2-2 years, 5 more follow-ups are summarized, classified and transferred to a follow-up test position chart. Comparison of these two test position charts furnishes information of major prognostic value.

Aged↗
PubMed1991

The histamine H3-receptor: pharmacology, roles and clinical implications studied with agonists.

Among a series of methylated histamine derivatives, (R) alpha, (S) beta,-dimethylhistamine has been identified as a novel potent and selective H3-receptor agonist, even slightly more potent than (R) alpha-methylhistamine and displaying similar properties in vivo. Several studies suggesting that (R) alpha-methylhistamine might find various clinical applications, it was submitted to toxicological studies and initial clinical trials. The drug seems to display a very low animal toxicity, and, in humans, is well absorbed orally and metabolized via ring methylation before urinary excretion.

Animals↗
PubMed1991

Histamine H3-receptor activation inhibits acetylcholine release from the guinea pig myenteric plexus.

The role of histamine H3-receptors in the control of acetylcholine release from peripheral cholinergic neurons was evaluated in the isolated guinea pig ileum, previously loaded with 3H-choline. When tested in the presence of H1- and H2-blockade, histamine (0.1-100 mumol/l) and (R) alpha-methylhistamine (0.01-1 mumol/l) dose-dependently reduced the electrically-evoked choline outflow, with (R) alpha-methylhistamine being a partial agonist. Selective H3-receptor blocking drugs, thioperamide (0.1 mumol/l) and impromidine (0.1 mumol/l) reversed the histamine-induced inhibitory effect. These data suggest that intestinal cholinergic nerves are endowed with histamine H3-receptors whose activation produces an inhibitory effect upon acetylcholine release. The practical implications of these findings are obvious.

Acetylcholine↗
PubMed1991

[Does temporary cementing have an effect on the bond strength of definitively cemented crowns?].

To establish whether or not temporary cementing with zinc oxide-eugenol (ZOE) cement affects the bond strength of the subsequent zinc phosphate cement, 60 standardized metal blocks with cylindrical drill holes were produced. 50 specimens were coated with ZOE cement and subjected to different cleansing techniques (mechanical, with alcohol or organic solvent, soap, Al2O3) in groups of ten. After examination of the cleansed surfaces under the light microscope, amalgam cylinders manufactured according to a standardized procedure were cemented into the cavities using zinc phosphate cement and pressed out. Only the Al2O3 jet-cleaned surfaces were free of ZOE cement residues. With high statistical significance the knock-through test revealed lower bonding strength values for the specimens cleaned either with alcohol or organic solvents.

Aluminum Oxide↗
PubMed1990

Increase in aldose reductase mRNA in dog lens epithelial cells under hypertonic conditions.

Aldose reductase (AR) mRNA levels increase when dog lens epithelial cells are exposed to hypertonic conditions. Hybridization of mRNA to an AR cDNA, using Northern and slot blots, showed that AR mRNA is elevated at least fourfold when primary dog lens epithelial cells are grown in media (300 mosmol kg-1) supplemented with 150 mM NaCl (600 mosmol kg-1 final). A time course showed an increase in AR mRNA of approximately twofold by 24 hr with a maximum increase of between four- and eightfold by 48 hr. AR mRNA remained elevated for the duration of the experiment, 8 days. The addition of Tolrestat, an inhibitor of aldose reductase, had no effect on the increased level of AR mRNA in these hypertonically stressed cells. Cells grown in media supplemented with 250 mM sorbitol also showed a substantial increase in AR mRNA. These data indicate, as in other cell types, the lens, a target tissue of diabetes, responds to hypersomotic stress with an induction of AR expression and suggests that AR may play a role in intracellular osmotic regulation.

Aldehyde Reductase↗
PubMed1990

[Survey of the dental prosthodontic care provided for residents of Würzburg old people's homes].

Three hundred and six residents of Würzburg old people's homes (average age: 81 years) were interviewed and examined with regard to their dentures and need for treatment as well as their oral hygiene. Most of the subjects had removable dentures. Oral symptoms, restricted masticatory ability and difficulties with the dentures were reported by only about one third of the senior citizens, although the caries and periodontopathy morbidity was high and considerable defects were found in the crowns, bridges and dentures. Similarly, the subjects own reports on their oral care regimen was contradicted by the poor oral and denture hygiene observed in fact. Neither was there assistance in oral hygiene from the nursing staff nor systematic professional care. Altogether, there is a great need for dental prosthetic treatment in the subjects of this study.

Aged↗
PubMed1989

Parameters of evaluation and correlation of renal phosphate handling and of parathyroid function in children.

The aim of the study was to establish normal values for parameters of parathyroid (PT) function in childhood and to examine whether a correlation could be found between these parameters and tubular phosphate (P) reabsorption. Values for PTH (carboxyl terminal) and urinary cAMP (UcAMP) throughout childhood were found to be significantly lower than in adults, with mean values of 0.3 ng/ml (30 pmol/l) and 1.96 nmol/dl glomerular filtrate (GF) respectively. A significant correlation was found between UcAMP and tubular P reabsorption (TP), expressed by the equation: TP = 5.5-(0.5 x UcAMP) mg/dl GF (= 1.78-(0.16 x UcAMP) mmol/dl GF, with a scatter of 10.6 mg/dl around the mean (+/- 1 SD). These data appear to permit the evaluation of primary tubular components in patients with defects of renal P handling, as opposed to those related to PT activity.

Absorption↗
PubMed1989

High-resolution image recovery from image-plane arrays, using convex projections.

We consider the problem of reconstructing remotely obtained images from image-plane detector arrays. Although the individual detectors may be larger than the blur spot of the imaging optics, high-resolution reconstructions can be obtained by scanning or rotating the image with respect to the detector. As an alternative to matrix inversion or least-squares estimation [Appl. Opt. 26, 3615 (1987)], the method of convex projections is proposed. We show that readily obtained prior knowledge can be used to obtain good-quality imagery with reduced data. The effect of noise on the reconstruction process is considered.

Algorithms↗