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Biomedical subjects

U Weber

Publications and source records attributed to U Weber.

At least 181 records · Page 10Linked to original sources
PubMed1986

Experimental calcium oxalate retinopathy compared with cystine- and tyrosine-induced retinal damage. An ophthalmoscopical, histological, and electrophysiological study.

Subcutaneously administered calcium chloride and dibutyloxalate solutions produce calcium-oxalate retinopathy in rabbits that is demonstrable opthalmoscopically and histologically, with remarkable impairment of the electroretinogram, whereas orally administered cystine seems to be inefficient. Orally administered tyrosine induces transitory pathological ERG signals in rabbits.

Animals↗
PubMed1986

Experimentally induced cystine keratopathy in rabbits.

L-Cystine was administered orally to albino and nonalbino rabbits in order to study cystine-induced corneal lesions. Contact and noncontact specular microscopy revealed opaque preendothelial structures similar to those found in benign cystinosis in humans. Light microscopy showed cytoplasmatic vacuoles in the basal cell layer of the corneal epithelium. Using scanning electron microscopy, increased desquamation of the corneal epithelial cells and massive deposition of proteinic material on the surface of the corneal endothelium were demonstrated.

Animals↗
PubMed1986

Experimentally induced calcium oxalate keratopathy in rabbits.

In a period of 21 days, six subcutaneous injections of calcium chloride and dibutyloxalate solution produced a flecklike, polymorphous corneal opacity and a slight stromal clouding in chinchilla rabbits, as seen with the slit lamp. In front of the endothelium, opaque structures could be seen with the specular microscope. New Zealand white rabbits showed only a diffuse corneal clouding. Light microscopy revealed a reticular alteration of the cytoplasm in the basal layers of the corneal epithelium primarily in chinchilla bastard rabbits. In central corneal areas an irregular structure of the basal epithelial cells and a papillalike alteration of the stromal-epithelial border was seen. In the endothelium an increased formation of vacuoles was observed in both species. Scanning electron microscopy demonstrated endothelial cell loss.

Animals↗
PubMed1986

[Carotinoid retinopathy. III. Reversibility].

Twenty-five patients (erythropoietic protoporphyria 23, polymorphous light eruption 1, "cosmetics" 1) were re-examined 2-10 months after therapy with beta-carotene and canthaxanthine was discontinued. Dark adaptation and ERG parameters had normalized, whereas crystalline retinopathy and pigment epithelial defects showed no signs of reversibility.

Canthaxanthin↗
PubMed1986

[Experimental tyrosine keratopathy in rabbits].

Tyrosine was given to White New Zealand and Chinchilla bastard rabbits. The corneal epithelium showed pinpoint lesions and a pseudokeratitis dendritica from the fourth day on. In spite of continued tyrosine dosage these lesions disappeared clinically within 6 days. Scanning electron microscopy revealed necrosis of isolated epithelial cells even after the twentieth day of tyrosine dosage. Specular microscopy sporadically revealed glittering pre-endothelial structures. It was found by light microscopy that there was a tendency to focal proliferation of corneal epithelial cells and a vacuolization in the basal epithelial cell layers. Endothelial defects may be responsible for circumscribed edema of the corneal stroma.

Administration, Oral↗
PubMed1985

[Central areolar choroidal dystrophy with retinal crystals].

Central choroidal dystrophy is characterized by lack of large parts of the central choroid. In the dystrophic region outer retinal layers are also involved whereas inner retinal layers may be unaffected. Three patients with central choroidal dystrophy and retinal crystals in the dystrophic region or near its border are described. Predominantly, these crystals are located in the inner or middle retinal layers. The amplitude of the electroretinogram is reduced according to the extent of the defect in the neurosensory epithelium. In the cases described here the inner retinal layers may also be involved in the pathologic process. In two patients with the most marked clinical and electrophysiological disturbances, a multiple lipoprotein-type hyerlipidemia was found.

Aged↗
PubMed1985

[Carotenoid retinopathy. I. Morphologic and functional findings].

Thirty patients who had undergone long-term treatment with carotenoids (max. 14 years and 336 g of carotenoids) were examined. Ophthalmoscopy revealed retinal crystals in 20 patients. The retinal crystals were usually located around the macula, forming a ring, and in one case they were even found in the macula itself. No deterioration of visual acuity or visual field defects were found, but there was a markedly dose-dependent prolongation of the duration of dark adaptation.

Adolescent↗
PubMed1985

[Carotinoid retinopathy. II. Electrophysiologic findings in 23 carotenoid-treated patients].

Twenty-three patients on long-term therapy (up to 14 years) with carotenoids (up to 336 g) were tested electrophysiologically. The EOG revealed a small but not significant delay of the light peak. Arden's ratio, however, was normal. The ERG was depressed as far as photopic activity was concerned. At low dosages of carotenoids the scotopic ERG amplitudes were found to be hypernormal, whereas at higher dosages the increase in amplitude during dark-adaptation was markedly delayed. There was a dose-dependent prolongation of b-wave implicit time and a dose-dependent reduction in oscillatory potentials. The marked effect on the b-wave and on the oscillatory potentials and the site of the retinal crystals permit the assumption that a mechanism of carotenoid action is located in the middle layers of the retina.

Carotenoids↗
PubMed1985

[Central chorioretinal dystrophy with drusen and retinal crystals].

4 patients out of 2 pedigrees present an association of dominant drusen, central chorioretinal dystrophy and retinal crystals. It seems to be transmitted in an autosomal dominant mode. Drusen have also been found in 4 patients (3rd generation) at the age of 40 years. Central chorioretinal dystrophy and retinal crystals have not been found prior to the age of 60 years. Visual acuity and central scotoma depend on the central chorioretinal dystrophy. Electro-oculograms and electroretinograms exhibited relatively little changes. 2 patients showed phenotype II and IV of Fredriksen.

Adult↗
PubMed1985

[Dissolution processes and surface changes. 3. Determination of the surface with the BET process].

Two methods are demonstrated for the determination of the surfaces of solid substances by the BET-method. Using a newly constructed apparatus substances with high specific surfaces can be determined by the two-point-method with a good precision. For the determination of pulverous drugs we used the one-point-method proposed by Haul and Dümbgen [2] improving it in calibration und practicability.

Chemistry, Pharmaceutical↗
PubMed1985

[Dissolution processes and surface alteration. 4. Determination of the "effective" surface].

A method is described for measuring the "effective" surface of a drug by means of dissolution parameters using the Paddle-model or a resorption-model respectively. The obtained values were compared with the specific surface which was determined by BET-technique. The "effective" surfaces obtained by means of the dissolution parameters are smaller than those determined BET-technique.

Diffusion↗
PubMed1984

[Diagnosis and surgery of an insulinoma using a glucose-controlled insulin infusion system].

A 71-year-old woman with insulinoma was studied. Preoperatively, using the glucose controlled insulin infusion system (GCIIS) for glucose clamping at various blood glucose levels, autonomous insulin production was demonstrated and intravenous glucose needs for maintenance of normoglycaemia were evaluated. The results of a somatostatin suppression test, guided by the GCIIS, supported the postulation of a well differentiated beta cell adenoma with reduced storage capacity. These assumptions were later confirmed by histochemical and ultrastructural investigations. Hypoglycaemia during surgery was avoided by means of the GCIIS. Upon clamping of the plasma glucose at 90 mg/dl, 15.5 g dextrose had to be given until resection of the tumour. Immediately thereafter, a sharp rise in plasma glucose to 140 mg/dl together with a need for 4.1 U insulin showed that the insulinoma tissue had been removed completely.

Adenoma, Islet Cell↗
PubMed1984

Functional analysis of the white gene of Drosophila by P-factor-mediated transformation.

A 12-kb DNA segment spanning the white (w) locus of Drosophila has been inserted into a P-transposon vector and used for P-factor-mediated germ-line transformation. Several red-eyed transformants were recovered which complement the white mutant phenotype. Analysis of the eye pigments and the interaction with the zeste mutation indicates that the w gene inserted at several new chromosomal sites is expressed normally. The tissue-specific accumulation of w transcripts, as studied by in situ hybridization to tissue sections, is the same in transformant and wild-type larvae. This indicates that all the genetic information specified by the w locus is contained within this 12-kb segment of DNA. By secondary mobilization it was shown that the w sequences have been inserted as a functional P(w) transposon which is capable of further transposition.

Journal Article↗