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Biomedical subjects

B Menkes

Publications and source records attributed to B Menkes.

At least 19 recordsLinked to original sources
PubMed1975

[Stratification in the central nervous system].

Stratigenesis in the optic tectum of developing chick embryos was investigated between the 4th and the 11th day of incubation. Stratification is achieved by successive emigration of cell contigents from the proliferative layer. In the opinion of the authors the main factor which determines this very regular cell migration would be a gradient of oxygen and of metabolites. The gradient has to appear in the wall of tectum due to its typical vascular network. Experiences with induced hypoxia or with selective damage of the proliferative layer strengthen the hypotesis of an oxygen gradient playing the role of a generally active epigenetic factor in the stratigenesis of the central nervous system.

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PubMedDate not supplied

[Stratification in the central nervous system].

In the authors' opinion the neuroblasts (glioblasts respectively) are moving along an oxigen-gradient, out of the proliferative layers toward the source of O2 (the vascular plexi). Stratigenesis is influenced by "guiding structures" (fibrillar plate in the tectum opticum), by the elongations of ependymal cells and by the similarly oriented vascular-connectives.

Animals↗
PubMedDate not supplied

[Fine-structure and function of the primary proliferative layer of the embryonal central nervous system].

Results obtained by mechanical isolation of neuroblasts from the primary proliferative layer of the central nervous system in chick embryos by the aid of an original method and by electronmicroscopic investigations are consistent with Sauer's concept on neuroepithelial cell proliferation. The bipolar form of the undifferentiated neuroblast is maintained--at the beginning--by external factors of cell contact only. Each end-feet contains two centrioles, one of which represents the basal body of a cilium. During mitosis, the position parallel to the lumen of the spingle axis and the subsequent appearance of two identical daughter cells depend on the behaviour of the centrioles. The later may move in an abnormal direction, and induce thus an obliquely or perpendicularly laying spindle axis. These changes may influence--on the other hand--the mechanism of proliferation.

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PubMedDate not supplied

[Vital fluorochroming showing the effect of cyclophosphamide on the embryo].

Besides the usual methods, vital fluorochroming may globally show the extent of the cytotoxic effect of Cyclophosphamide (CP). By intravital treatment with highly diluted fluorochromes (acridine-orange, etc.) necrobiotic and dead cells, cell debris and phagosomes appear electively fluorescent. Glycosaminoglycans and various mucopolysaccharides show a somewhat weaker fluorescence. Autopods and the mesencephalon were selected for comparative assessment of the effect of other cytotoxic agents. Important results were also obtained by the repeated examination of blood (erythrocytes) and of hemopoetic foci. Cytotoxic effect within the embryo, teratogenesis and chemotherapeutic action are strongly correlated.

Acridine Orange↗
PubMedDate not supplied

[The ultrastructure of embryonic capillaries in the neuroepithelium of the brain vesicles].

The electronmicroscopic control of the capillaries of the brain vesicles in 5--6-day-old chick embryos revealed an intimate contact between capillary walls and neuroblasts, and on the other hand the presence of a functional endoplasmic reticulum in the endothelial cells. These are only very few vacuoles for protein transport in the cytoplasm of endothelial cells.

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PubMedDate not supplied

[Dynamics of the action of cyclophosphamide. Studies in the chick embryo].

The dynamics of the Cyclophosphamide (CPA) effect was investigated in the chick embryo by a vital fluorochroming method worked out previously. In the 4-day-old embryo the morphological changes (at the level of light microscopy) in the limbs and in the mesencephalon induced by 100 microgram CPA appeared after a period of latency of about 10 hours. Successive blood control in the same embryo, treated with 50 microgram CPA, revealed three consecutive modifications of the blood cells: a great number of abnormal mitoses, the appearance of a great number of multinucleated, nonviable cells and the recovery of the lost cells. No difference could be detected between the effect of freshly prepared and stored CPA solutions. The fate of CPA (a bifunctionally alkylating agent) in contact with living tissues is discussed.

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