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Biomedical subjects

V Brezina

Publications and source records attributed to V Brezina.

6 recordsLinked to original sources
PubMed1992

Peptidergic co-transmission in Aplysia: functional implications for rhythmic behaviors.

Despite their ubiquitous presence in the central and peripheral nervous systems, the behavioral functions of peptide co-transmitters remain to be elucidated. The marine mollusc Aplysia, whose simple nervous system facilitates the study of the neural basis of behavior, was used to investigate the role of peptidergic co-transmission in feeding behavior. Several novel modulatory neuropeptides were purified, and localized to identified cholinergic motorneurons. Physiological and biochemical studies demonstrated that these peptides are released when the motorneurons fire at frequencies that occur during normal behavior, and that the peptides modify the relationship between muscle contraction amplitude and relaxation rate so as to maintain optimal motor output when the intensity and frequency of feeding behavior change.

Amino Acid Sequence↗
PubMed1992

Fusion-induced malignancy? A preliminary study. (a challenge to today's common wisdom).

Five fusions between mouse embryonic cells and syngeneic adult peritoneal macrophages were performed. The resulting hybrids as well as both parental cells (6 cultures of embryonal cells and 6 cultures of adult macrophages) were grown in vitro under the same culture conditions. All populations of explanted macrophages died during the second month in primary culture and five populations of cultured embryonic cells were lost within six months under in vitro conditions as well. One embryonic cell line survived and acquired transformed and/or malignant phenotype: When inoculated into either newborn or adult syngeneic mice, progressive growth of tumors with 100% take (6/6), histologically classified as poorly differentiated fibrosarcoma with areas of metaplastic bone and osteoid, was observed. Two out of five wild hybrid strains died within six months of cell culture. The resulting three hybrid cultures adapted themselves to in vitro conditions and finally permanent lines were established with all features of transformed phenotype in vitro and with the capacity to grow as undifferentiated fibrosarcomas with 100% take (6/6) when inoculated into syngeneic mice either s.c. or i.p. Cytogenetic studies were performed and phenotypic characteristics of these lines were explored as well. Biological assays performed for the presence of oncogenic viruses were negative and none of the malignant cell lines showed positive staining with the monoclonal antibody specific for large T-antigen. It is suggested that cell fusion of two normal partners may switch on the cascade of abnormal processes which may culminate in neoplastic conversion. Cell fusion might play also a significant role in the so called "spontaneous" transformation.

3T3 Cells↗
PubMed1977

Cell cycle in heteronuclear cell line VUP-1. I. Locomotion behaviour analysis.

Time-lapse cinemicrography was used to study the locomotory activity of sperical cells of a heteronuclear cell line VUP-1 originating from a malignant melanoma of chorioidea. Migration of cells was followed during the entire cell cycle and locomotion was analyzed in relation to the population density and to the morphological and functional characteristics of the leading undulating membrane. The variations in cellular motility were related to the morphology of the membranes and their possible functional regulation.

Cell Line↗
PubMed1977

Cell cycle in heteronuclear cell line VUP-1. II. Analysis of mitosis.

Mitosis in spherical cells of heteronuclear cell line VUP-1 was analyzed by means of time-lapse cinemicrography. A comparison with another permanent cell line (hamster) revealed some differences in the duration of individual mitotic stages. Metaphase was the longest stage in VUP-1 line cells (about 3-4 hours). Various irregularities in mitotic cycle kinetics were also found, such as absence of anaphase or separation of chromosomes from the aster in metaphase. Attention was further focussed on cytokinesis.

Animals↗