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Biomedical subjects

A Walter

Publications and source records attributed to A Walter.

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

Coupled transport of protons and anions through lipid bilayer membranes containing a long-chain secondary amine.

Transport of protons and halide ions through planar lipid bilayers made from egg lecithin and a long-chain secondary amine (n-lauryl [trialkylmethyl] amine) in n-decane was studied. Net proton fluxes were measured with a pH electrode, and halide fluxes were measured with 82Br- and 36Cl-. In membranes containing the secondary amine, a large net proton flux was produced either by a Br- gradient with symmetrical pH or by a pH gradient with symmetrical Br-, but not by a pH gradient in Br--free solutions. This H+ flux was electrically silent (nonconductive), and the H+ permeability coefficient was greater than 10(-3) cm sec-1 in 0.1 M NaBr. In Br--free solutions, H+ selectivity was observed electrically by measuring conductances and zero-current potentials generated by H+ activity gradients. The permeability coefficient for this ionic (conductive) H+ flux was about 10(-5) cm sec-1, several orders of magnitude smaller than the H+ permeability of the electroneutral pathway. Large electroneutral Br- exchange fluxes occurred under symmetrical conditions, and the permeability coefficient for Br- exchange was about 10(-3) cm sec-1 at pH 5. The one-way Br- flux was inhibited by substituting SO4= for Br- on the "trans" side of the membrane. These results support a "titratable carrier" model in which the secondary amine exists in three forms (C, CH+ and CHBr). Protons can cross the membrane either as CHBr (nonconductive) or as CH+ (conductive), whereas Br- crosses the membrane primarily as CHBr (nonconductive). In addition to these three types of transport, there is also a pH-dependent conductive flux of Br- which has a permeability coefficient of about 10(-7) cm sec-1 at pH 5. Experiments with lipid monolayers suggest that the pH dependence of this conductive flux is caused by a change in surface potential of about +100 mV between pH 9.5 and 5.0.

Amines↗
PubMed1979

Molecular characterization of the genomes of actinophages SH3, SH10, SH11, and SH12 infecting Streptomyces hygroscopicus.

Some physico-chemical properties of the DNAs released from the actinophages SH3, SH10, SH11, and SH12 are described. The four phage DNAs have a linear double-stranded secondary structure and are unique with respect to their high G.C contents which, from melting studies and buoyant density experiments, were found to be in the range of 68-73 mol-%. The DNA molecular weights were determined by sedimentation velocity experiments and by electron microscopic length measurements, the mean values of the two corresponding data sets being 34.0 x 10(6) (SH3), 26.7 x 10(6) (SH10), 26.1 x 10(6) (SH11), and 28.7 x 10(6) (SH12) with a mean relative error of +/- 5%. From different observations it was concluded that SH10 DNA, and possibly also SH11 and SH12 DNA, have cohesive ends and can undergo intramolecular or intermolecular association to form ring-like monomers or linear and ring-like multimers. Cleavage of the DNAs of SH3, SH10, SH11, and SH12 by EcoRI restriction endonuclease delivered two, one, zero, and two cleavage sites, respectively, and by BamHI restriction endonuclease eight, zero, zero, and zero cleavage sites, respectively.

Bacteriophages↗
PubMed1978

[About "a new syndrome" associated with a familial translocation 13/14 (author's transl)].

The report describes the case of a 7,9-year-old boy who seems to have clinically the same syndrome described by Ruvalcaba et al. in 1971 and uncertified till now. The propositus in characterized by severe mental retardation, peculiar facies, osseous dysplasia (including clinodactilism), urogenital and skin abnormalities, congenital heart disease (missing to the mentioned author's cases). In contrast with the normal karyotype of Ruvalcaba et al. cases, the boy shows a familial 13/14 Robertsonian translocation, karyotype 45,XY,-13,-14, t (13q14q). The boy's father, not entirely clinically investigated, shows apparently only clinodactilism, but cytogenetically the same chromosomal aberration. The mother is clinically and cytogenetically normal. The boy's grandmother (father's side) has had clinically clinodactilism and heart disease; her karyotype is unknown. The syndrome of the propositus presented in our study is identical clinically, but differs cytogenetically to the one described in "a new familial syndrome with osseous dysplasia and mental deficiency" by R. H. A. Ruvalcaba et al. It is not out of the question that the father's and boy's translocation should be balanced, irrespective of the morphological abnormalities and fortuitous associated with them the more so as to the same karyotype, the boy's and father's phenotype have few common features.

Abnormalities, Multiple↗
PubMed1977

Interactions of Hg(II) ions with DNA as revealed by CD measurements.

The circular dichroism spectra of Hg(II) complexes with native calf thymus DNA, chemically methylated Streptomyces chrysomallus DNA and with Ag(I)-DNA complexes were measured in the region of 220 - 340 nm. As a main result a conversion of the conservative CD spectrum of DNA to a distinct nonconservative type of CD spectrum for the complexes occurs with increasing Hg(II) concentration. The CD spectra of the Hg(II) complexes as well as some additional arguments strongly support the idea, that DNA in the complex undergoes a structural transition to a more condensed state with 4 -like character.

Animals↗
PubMed1976

[Spinocerebellar ataxia with monilethrix, typical facial features, and dental anomalies].

The authors present a form of heredodegenerative spinocerebellar ataxia with concomitant involvement of ectodermal structures, different from other variants. The disease was characterized by spinocerebellar ataxia (the complete form); curly, thin, short and dense hair, mikroskopically monilethrix; a characteristic face (hypertelorism, flattened and wide base of the nose, prominent nostrils, large mouth, thick lips); and abnormal teeth which were reduced in number and had gaps inbetween. The psycho intellectual development and the voice of the patient were normal. The first neurological symptomes were observed at the age of 3 years and progressively developed until now at the age of 6 years. Data necessary to establish the mode of hereditary transmission were not available.

Adolescent↗