Biomedical subjects

A Dostal

Publications and source records attributed to A Dostal.

3 recordsLinked to original sources

PubMed1996

Hexacyanoferrate-based composite ion-sensitive electrodes for voltammetry.

Composite electrodes made of graphite, paraffin and metal hexacyanoferrates exhibit a voltammetric response of the hexacyanoferrate ions, the potential of which depends linearly on the logarithm of concentration of alkali and alkaline-earth metal ions. This behaviour has been observed on account of the fact that the electrochemical reaction is accompanied by an exchange of these ions between the solution and the zeolitic lattice of the hexacyanoferrates for charge compensation. The voltammetric determination of the formal potential of these electrodes in a solution allows the quantitative analysis of the ions which are exchanged between the metal hexacyanoferrates and the aqueous solutions. Iron(III), copper(II), silver(I), nickel(II) and cadmium(II) hexacyanoferrates have been studied for the determination of H(+), Li(+), Na(+), K(+), Rb(+), Cs(+), NH(+)(4), Mg(2+), Ca(2+) and Ba(2+). In some cases, the selectivity constants are as low as 3.10(-4), or even so small that their exact value is inaccessible. Electrodes made of iron (III), copper (II), silver (I), nickel (II) and cadmium (II) hexacyanoferrates are most suitable for the determination of potassium ions. Electrodes with nickel (II) and cadmium (II) hexacyanoferrates are also suitable for the determination of caesium ions. The working range of the electrodes also depends on the conductivity of the solutions and can range from 10(-5) to 1 mol l(-1). Typical standard deviations of the potential measurements are 3 mV.

Journal Article↗

PubMed1986

[Dental enamel prisms of Mesopithecus pentelicus Wagner, 1839, compared with recent cercopithecids (Primates: Cercopithecidae)].

The dental enamel prisms of Cercopithecidae were examined by scanning electron microscopy. The main task of this study was to show the prism morphology representatives of different genera as well as their comparison with the fossil Mesopithecus pentelicus Wagner, 1839. The method used to show the enamel prisms was to etch the tooth surface with hydrochloric acid. In this way the outlines of the prisms were better contrasted for the descriptive morphology of the prisms than in etching with phosphoric acid. Two types were determined, in accord with the systematic division into subfamilies. In the subfamily Cercopithecinae elongated slender prisms were dominating, some with pointed, others with truncated tops. Most characteristic of this type were Macaca and Cercopithecus. An exception was Papio hamadryas which had broader, rounded prisms. In this way it differed largely from P. anubis whose prisms were short and mostly triangular. A very interesting fact was that very different patterns were found in P. anubis and P. hamadryas, although these two species are regarded as only one species by many authors. The second subfamily, the Colobinae, was characterized by broader prisms with a rounded shape, nearly as long as wide. Exceptions of the 'Colobine type' were at first Colobus with prisms little longer than wide and secondly Nasalis, with mostly parallel sides and truncated tops of the prisms. The prism outlines of Mesopithecus showed the greatest similarity to those of Presbytis which represents the characteristic 'Colobine type'. This fact confirmed the actual systematic position of the fossil Mesopithecus within the subfamily Colobinae. In addition to previously known primitive features of Mesopithecus within the subfamily of Colobinae, we present here a further concrete, common feature with asiatic Colobines.

Animals↗

PubMedDate not supplied

Single mutations of the PTEN gene in recurrent ovarian carcinomas.

OBJECTIVE: To establish the role of phosphate and tensin homologue on chromosome 10 (PTEN) mutations in tumorigenesis of the ovary, we determined the mutational spectrum of the PTENgene in surgical specimens of ovarian carcinomas. METHODS: The study group consisted of 86 ovarian cancer specimens (18 fluids, 68 solid specimens), including 30 primary ovarian cancer specimens and 56 of relapsed ovarian cancer from women with a median age of 57.9 years and a range of 27-85 years. Each of the nine exons of the PTEN gene was amplified separately by polymerase chain reaction (PCR). Both strands of the PCR products were sequenced directly by standard cycle sequencing procedures and subsequent computer-aided alignments with the wild-type sequence. RESULTS: In ascitic fluids of two women with recurrence of cancer, we observed mutations: one seven-base-pair insertion at codon 52 (GATGATG) and the other a base-pair substitution resulting in an amino acid change (T131I). We found no mutation in the primary ovarian cancers. CONCLUSIONS: Our data indicate that PTEN mutations have a subordinate role in tumorigenesis of the ovary.

Adult↗