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Biomedical subjects

R Schmidt

Publications and source records attributed to R Schmidt.

At least 757 records · Page 42Linked to original sources
PubMed1978

On the mechanism of substrate binding to the purine-transport system of Saccharomyces cerevisiae.

The yeast Saccharomyces cerevisiae takes up adenine, guanine, hypoxanthine, and cytosine via a common energy-dependent transport system. The apparent affinity of the transport system to these and other purines and pyrimidines is correlated with their capability to be protonated to the positively charged form. Further organic molecules are competitive inhibitors when they are cationic, e.g. guanidine and octylguanidine in contrast to urea, or hexadecyltrimethylammonium in contrast to dodecylsulfate and Triton X-100. The influence of the pH on the kinetic constants of hypoxanthine transport points to a stoichiometry of one proton being associated to the transport system together with one substrate molecule. The pKa values of two ionizable groups that are involved in substrate binding are revealed; one of which (pKa = 1.8) may be attributed to the substrate, the other (pKa = 5.1) to an amino acid residue in the recognition site of the transport system. Studies with group-specific inhibitors indicate that this amino acid residue contains a carboxyl group. The results are in accordance with the assumption that a carboxyl group of the transport system, a proton and a substrate molecule arrange to an uncharged ternary complex.

Biological Transport, Active↗
PubMed1978

Infantile spasms in Down syndrome: a report of 5 cases and review of the literature.

Five patients with Down syndrome (DS) and infantile spasms were examined in a four-year interval. Previous reports of this association have been infrequent except during experimental treatment with 5-hydroxytryptophan, a precursor of serotonin. Malformations of the brain in DS are associated with an increased incidence of epilepsy, and both gross and cytoarchitectural anomalies have been described. The severity and distribution of these central nervous system anomalies presumably predispose to the infantile spasms. The contribution of altered serotonin metabolism is uncertain.

5-Hydroxytryptophan↗
PubMed1978

Inflammatory, tumor initiating and promoting activities of polycyclic aromatic hydrocarbons and diterpene esters in mouse skin as compared with their prostaglandin releasing potency in vitro.

Release of prostaglandin E2 (PGE2) in cultured peritoneal macrophages of NMRI mice by skin irritant tumor initiators and promoters was investigated. Initiators of the polycyclic aromatic hydrocarbon type, e.g., DMBA, caused slight irritation on the mouse ear but even relatively high doses did not stimulate PGE2-release to any measurable extent within 4 h after administration in vitro. Apparently there is no correlation between irritation and initiating activity in mouse skin and PGE2-release in macrophages. On the other hand, promoters of the diterpene ester type, e.g., TPA, were strong irritants on the mouse ear. Even low doses of these compounds stimulated PGE2-release from macrophages dramatically within 1 h after administration in vitro. Moreover, a good correlation was established between irritant and promoting activity in mouse skin and PGE2-release in macrophages of a series of tigliane, ingenane and daphnane type diterpene derivatives. These results suggest that also in mouse skin PGE2-release may occur following exposure of the target cells to promoters of the diterpene ester type resembling one of the most early molecular events of promotion. This event could initiate both skin irritation and cell proliferation.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1978

[Thoracic myelography with water-soluble contrast medium (metrizamide) (author's transl)].

The use of water-soluble contrast media for the thoracic myelography has become possible with the introduction of Metrizamide (Amipaque). A modification of the technique used with oily contrast media results in excellent demonstration of detail of intraspinal structures and of pathological changes. The medium is well tolerated and does not cause irritation of the spinal cord; the results must be regarded as excellent.

Headache↗
PubMed1978

Epiphysial dysplasia: a constant finding in the XXXXY syndrome.

Two patients with the XXXXY syndrome are presented. Both boys are mentally retarded with short stature, muscular hypotonia, and hypogonadism. A constant feature of this syndrome is a varying degree of epiphysial dysplasia probably secondary to hypotonia and growth deceleration.

Bone and Bones↗
PubMed1978

[The influence of moderate intrauterine nutrition on later physical and mental development in twins (author's transl)].

Follow-up examinations on 45 dizygotic and monozygotic twins were performed in order to establish differences in physical and mental development with regard to differences in birth-weight. The "critical" weight difference of at least 650 g could be established where mental abilities, height and head circumference scored lower in the lower birth weight group. Our findings stress the positive home environment as being responsible for the lack of differences between the two groups in the development during early childhood, of psychosocial behaviour and school performance.

Adolescent↗
PubMed1978

[Gas chromatographic determination of di- and trisaccharides (author's transl)].

Three new methods are reported for the gas chromatographic analysis of di- and trisaccharides. Method I: Sugars are converted into their methoximes by reaction with methoxylamine hydrochloride in pyridine, followed by esterification with acetic anhydride. The separation is performed on OV 225 at 260 degrees C. Method II: Disaccharides are reduced to the alditols with sodium borohydride in aqueous solution, followed by acetylation with acetic anhydride in pyridine. In this method, only one peak is observed for each sugar. The derivatives are separated on OV 225 at 260 degrees C. Method III: Sugars are converted into their methoximes by reaction with methoxylamine hydrochloride in pyridine, followed by trifluoroacetylation with N-methyl-bis (trifluoroacetamide). The trisaccharide derivatives still show sufficient volatility. The separation is performed on OV 101 at 130 degrees C for disaccharides, and at 160 degrees C for trisaccharides. The retention times for biologically occurring di- and trisaccharides such as maltose, maltotriose, lactose, and sucrose are reported. The reliability criteria for method I are reported for the analysis of lactose, maltose and sucrose.

Chromatography, Gas↗
PubMed1978

The neutron therapy facility (DT, 14 MeV) at the radiotherapy department of the university hospital Hamburg-Eppendorf.

The neutron therapy facility at the Radiotherapy Department of the University Hospital Hamburg-Eppendorf is described. This unit has been developed for clinical purposes according to the initiative and conception of the radiotherapist by AEG/Fed. Rep. of Germany and RDI/USA since 1969. The installation was completed at the beginning of 1974. Special treatment head and bed systems allow isocentric treatment and arc or multiple port therapy. For routine work operation conditions of 8 to 12 mA total beam current and 500 kV accelerating voltage are used. The neutron output at 12 mA is about 3.5 x 10(12) n/s giving a phantom dose rate of more than 20 rad/min for a field size of 17.8 x 17.8 cm2 at 80 cm source-skin distance. Technical installations for improvement of dose rate and half-life of the target are planned. Results of physical measurements about neutron energy distributions, contributions from neutrons and gamma-rays to the total absorbed dose, build-up effect, axial and lateral dose distributions as well as isodose profiles for different field sizes in a homogeneous phantom are presented. Bewteen February 1976 and November 1977 up to 180 patients have been treated.

Mathematics↗
PubMed1978

[Characterization of heavy metal secretory granules in the islet tissue of adult white rats by means of the light and electron microscopy, including the high voltage electron miscroscopy and the electron microanalysis (author's transl)].

The metal secretory granules of Langerhans' islets of white rats were examined after histochemical detection by sulfide silver staining method as well as by conventional electron microscopy and high voltage electron microscopy. Zinc and calcium were determined with electron probe x-ray-microanalysis. The metals are located at the inside of cytoplasmatic vacuoles, a result, we discuss in connection with the release of pancreatic hormones.

Animals↗
PubMed1977

Split hand and food deformity and the syndrome of ectrodactyly, ectodermal dysplasia, and clefting (EEC). A report of five patients.

Five new casses of ectrodactyly are described. Two patients have the syndrome of ectrodactyly, extodermal dysplasia, and clefting (EEC). In one patient with the EEC syndrome, the disorder seems to represent a new mutation. One woman with isolated ectrodactyly has a daughter with the EEC syndrome. The variation in the clinical expression of this disorder among affected members of the same family makes it difficult to determine whether there may be several mutant alleles responsible for ectrodactyly and its related manifestations.

Abnormalities, Multiple↗