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Biomedical subjects

G Kelemen

Publications and source records attributed to G Kelemen.

At least 19 recordsLinked to original sources
PubMed2000

Identification and characterization of the mre gene region of Streptomyces coelicolor A3(2).

During a search for new differentiation factors in Streptomyces coelicolor A3(2), a locus at 11 o'clock on the S. coelicolor map was identified which harbours several genes that show extensive similarity to cell division and differentiation genes from Escherichia coli and Bacillus subtilis. From the sequence data it was concluded that the region contains the genes mireB, mreC, mreD (murein formation gene cluster E), pbp83 (high-molecular-weight penicillin-binding protein) and sfr (member of the spoVE/ftsW/rodA family). Mre gene products are reported to be responsible for determining cell shape in E. coli and Bacillus. The S. coelicolor mreC gene was inactivated by gene disruption, resulting in mutants which showed significant growth retardation in comparison to the wild type. Inactivation of the mreB gene was incompatible with viability, and thus mreB represents a Streptomyces cell division gene that is essential for survival. Promoter-probe experiments led to the identification of an operon structure, with promoters located upstream of mreB, pbp83 and sfr. Detailed studies of mreB transcription revealed the existence of three promoters; two of them are constitutively transcribed, whereas the third is developmentally regulated.

Amino Acid Sequence↗
PubMed1986

Agents inducing high Mg2+-ATPase activity of isolated coupling factor 1 from spinach chloroplasts.

Conditions are reported under which purified coupling factor 1 (CF1) from spinach chloroplasts exhibits Mg2+-dependent ATPase activity of about 120 mumoles/min/mg protein. It is shown that CF1, partially activated by treatment with heat and dithiothreitol (DTT), can be further activated by octyl glucoside. The Mg2+-dependent ATPase activity increases linearly as a function of the concentration of octyl glucoside from about 20 mumoles/min/mg protein in the absence of detergent to 120 mumoles/min/mg protein in the presence 15 mM octyl glucoside. This concentration is below the critical micellar concentration (CMC) of the detergent, indicating that the monomeric form is responsible for the activation. Without treatment with heat and DTT, the Mg2+-dependent ATPase activity of CF1 is virtually zero, but can be stimulated by octyl glucoside. In this case, however, only concentrations around CMC give a substantial increase in activity (about 50 mumoles/min/mg at 28 mM octyl glucoside). Concentrations higher than CMC inhibit both latent and heat-activated CF1.

Ca(2+) Mg(2+)-ATPase↗
PubMed1986

High-performance liquid chromatography of isopeptides.

High-performance liquid chromatographic (HPLC) methods are described for the structural analysis of clavicepamines, their analogues and branched-chain polypeptides, the analysis in synthetic stages of isopeptides (analysis of half-protected derivatives and purity control of active esters) and the differentiation between alpha- and iso-peptides (such as alpha- and gamma-glutamyl peptides). Pre-column derivatization was used to label the free amino groups for the structural investigation. Dansylated and hydrolysed isopeptides were analysed by HPLC methods based on isocratic separation of alpha-, epsilon- and bis-Dns-lysines using Hypersil, ODS-Hypersil and Partisil PAC columns. For the analysis of peptide active esters, an RP-HPLC method was developed, with methanol-acetonitrile-water mobile phases containing an acidic buffer. Peptides containing alpha-glutamyl residues were analysed for gamma-isomer content in the same system.

Chemical Phenomena↗
PubMed1986

Supercoil induced S1 hypersensitive sites in the rat and human ribosomal RNA genes.

Rat and human ribosomal RNA gene fragments in supercoiled plasmids were examined for S1 nuclease hypersensitivity. In the transcribed portion of genes the number and distribution of S1 sites were found to be species specific. No S1 sites were detected in the promoter regions. In the nontranscribed spacer (NTS), downstream of the 3' end of 28S RNA gene, S1 sites appear to be conserved in rat and human rDNAs. A rat NTS fragment (2987 nucleotides long), containing three S1 sites was sequenced and the S1 sites in this region were localized in polypyrimidine . polypurine simple repeat sequences. Other types of simple sequences, two type 2 Alu repeats and an ID sequence were also found in the sequenced region. The possible role of simple sequences and S1 sites in transcription and in recombination events of rDNA is discussed.

Animals↗
PubMed1979

The cochlear aqueduct: structural considerations.

Perusing 170 series of temporal bone sections, the course of the aqueduct was found to be a spindle shape, based on numerous dilatations in the middle section. Ample space was offered for development of bony excrescences such as exostotic depositions and osteoma-like protrusions of all sizes. These added considerably to the difficulties of a free passage through the aqueduct.

Adolescent↗
PubMed1978

[Earstructures in one case of anencephalie (author's transl)].

According to the majority of cases under observation the following anomalies could be found: extended, separated or manifold developed crura of the stapes, reduction in the circular windings of the cochlea down to 1 1/2 with a normal development of Corti's organum, reduction of the nerve structures of the nervus cochlearis to a munimum and an open facial canal.

Abnormalities, Multiple↗
PubMed1978

Further observations on the vestibulo-dural channel.

A channel between the vestibular aqueduct and the dura, corresponding in texture to the main aqueduct, has been observed in an un-negligible number of cases. All attempts to establish a connection between this phenomenon and a variety of clinical entities, among them Menière's disease, have so far been unsuccessful.

Aged↗
PubMed1978

In vitro effect of transfer factor on the cyclic nucleotide level of human lymphocytes in chronic lymphocytic leukaemia and of mouse lymphocytes.

In the present study transfer factor (TF) failed to produce any change in the cAMP- and cGMP-levels of lymphocytes of patients with chronic lymphoid leukaemia (CLL). This is attributed to the malignant transformation of the lymphocytes or to a changed proportion of different lymphocyte populations in CLL. Human TF leaves the cyclic nucleotide levels of splenic lymphocytes of BALB/c mice unaffected.

Animals↗
PubMed1977

Morquio's disease and the hearing organ.

Histopathologic evidence offered by a case of Morquio's disease and observed in the hearing organ showed widespread collagen damage, possibly initiated by the general hemorrhageous tendency, while the family history bore evidence of a genetic source. The clinical manifestations comprise striking dwarfism, beaking of the lumbar spine, sternal bulging, flaring of the rib cage, falt vertebrae, marked osteoporosis, prominent joints, semi-crouching stance, short nose. Roentgenograms showed retarded ossification.

Cartilage↗