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Biomedical subjects

P Sentein

Publications and source records attributed to P Sentein.

At least 19 recordsLinked to original sources
PubMed1997

Progressive disassembly of the mitotic spindle into two halves at anaphase and assembly of an astral neo-spindle during cleavage mitosis in the newt embryo.

In the second cleavage mitosis of newt embryos at anaphase, disassembly of mitotic spindle fibres, mediated by the 'plus' ends of their microtubules, results in equatorial division into two half-spindles. Yolk-filled cytoplasm invades the area free of fibres and is itself penetrated by antiparallel fibres from asters, which have become nucleated at opposite poles. These fibres immediately supplant the mitotic spindle; they participate in the lengthening of the interpolar distance and in the positioning of the newly formed daughter nuclei. The mechanisms of these successive phenomena must be considered in order to understand the complexities of the cell cycle in early mitosis.

Anaphase↗
PubMed1986

Enhanced polyploidy by glutaraldehyde in cultured HL60 leukemic cells.

Glutaraldehyde 10(-4) M weakened cell proliferation of HL60 cultured cells and enhanced the appearance of giant polyploid cells, up to 32.5% after 6 days. The size and structure of these cells, the quantitative changes in their DNA content with respect to diploid ones demonstrate their polyploid nature, which may be corrected by the occurrence of pluripolar mitoses. However the slowing down of cell proliferation is not enough to orient the cells towards differentiation. Maturation of polyploid cells may be stimulated by retinoic acid and dexamethasone as for diploid ones. Several possible mechanisms of polyploidy are discussed. Except the possibility that the cells may directly fuse, the mechanisms which are considered, may involve a preprophase inhibition, a mitotic arrest at metaphase or a reduction of asters which may result in a defect in cytokinesis, the latter followed by secondary fusion of nuclei.

Aldehydes↗
PubMed1982

[Effect of methylmercury chloride on mitosis in human lymphocytes in culture: ultrastructural study].

The ultrastructural study of proliferating human lymphocytes poisoned by methylmercury chloride, shows that this product disorganizes and alters the different constituents of the mitotic figure. The chromosomes, partially decondensed, are covered with protuberances and connected by various chromatin bridges. Tubular structures are changed. In disorganized cellular centers, the badly bounded centrioles are often thickened. Membraneous systems are altered.

Cells, Cultured↗
PubMed1981

Nuclear and mitotic abnormalities produced by cycloheximide in the newt egg during cleavage and their relationship to the cell cycle.

In cleaving newt eggs short-lasting treatments with millimolar quantities of cycloheximide (1/2, 1/3, 1/6 cycle) produce, after 6 h recovery, nuclear and mitotic abnormalities which are less drastic, but similar to those produced by treatments lasting 6 h. Special disturbances of the spindle and asters are different from those produced by spindle inhibitors (reduction in size of the asters and of the number of poles by nucleus, usual suppression of the spindle, failure of cytokinesis, separation of asters from nuclei). But the structure of nuclei is different according to the time when the treatment started (telophasic when it begun at anaphase or telophase, prophasic when begun at prophase). The difference in percentage of these two types of nuceli is highly significant and independent of the time passed after the beginning of the treatment. Each nucleus has to complete the whole cycle before the effect can be stopped.

Animals↗
PubMed1981

[Effects of propham and chlorpropham on the embryonic development of various vertebrates].

The effect of propham and chlorpropham on Amphibians embryonic development changes with doses as well as species. The action of C.I.P.C. is always determinative. The egg poisoned in albumen involves important chick embryo malformations, but the development is stopped by the yolky vesicle poisoning. The intraperitoneal injection of C.I.P.C., strongly disturbs fetus physiology in Mouse.

Animals↗
PubMed1981

[Comparative hepatic toxicity of perhexiline maleate and griseofulvin in mice].

Hepatic toxicity was observed in mice which had received Griseofulvin or Perhexilin Maleate over a period of several months. Treatment of griseofulvin alone gave rise to hepatitis with the presence of Mallory bodies (MB) whereas the same length of treatment with Perhexilin Maleate was associated with steatonecrosis with an absence of MB. When treatment was followed by a one month rest period hepatic lesions disappeared with no trace of sequelae. Cross-treatment studies showed that one week of Perhexiline Maleate was sufficient to induce MB in mice pretreated with Griseofulvin. Similarly, Griseofulvin administered to mice pretreated with Perhexilin Maleate gave rise to MB formation after one week as opposed to the usual two months incubation time (DENK et al.). The histological nature and mode of formation of these MB was identical to that encountered in acute alcoholic hepatitis. On addition, combined drug therapy employing Perhexilin Maleate suggests a particular hepatic toxicity in man in cases where the liver has become predisposed due to other therapeutic.

Animals↗
PubMed1981

Transformation, remodeling and dissociation of achromatic fibres by butyric acid in mitoses of cleaving eggs. Effects of associated antitubulin substances.

A mM solution of butyric acid transforms the achromatic apparatus of segmentation mitoses: asters are reduced or suppressed, cytokinesis is inhibited before mitosis, spindle fibers are broken and fan out progressively in the equatoria; region becoming radially oriented instead of axially. The results are either: 1) hollow fibrillar systems, 2) radiating spindle systems, apparently pluripolar, 3) dissociated fibrillar systems, depending on the phase of the mitotic cycle in which the butyric acid acted. Colchicine 2.5 X 10-3 M and vincaleukoblastine 2 X 10-4 M cause the depolarized nuclei and mitoses to migrate towards the animal cortex and the furrows, if they are administered before the abnormal systems produced by butyric acid are fully formed. Once formed, these systems are usually unchanged by administration of these drugs. Thus their formation appears to depend on microtubule assembly, since colchicine and VLB can prevent it.

Animals↗
PubMed1980

Characterization of actin microfilaments at the apical pole of thyroid cells.

In thyroid cells (rat or hog), actin has been detected by immunofluorescence with an antiactin antibody and, in electron microscopy by decoration "in situ" with heavy meromyosin. The antibody as the heavy meromyosin method have shown that actin microfilaments are especially localized at the apical pole of the cells, in a region where thin filaments are usually observed by conventional methods of electron microscopy. These microfilaments are attached to the apical membrane at the ends of the microvilli and form dense bundles at their cores. They are polarized towards the interior of the cell. Decorated filaments are also organized in a clear network, parallel to the apical membrane; they are associated with microvillar bundles, but also with small apical vesicles and lateral membranes, in tight or gap junctions.

Actins↗
PubMed1980

[Effects of propham and chloropropham on mitosis in cultured human lymphocytes. Ultrastructural study].

Propham and Chloropropham disturb the several mitotic figure components of proliferating human lymphocytes. The tubular structures, affected in preference by the C.I.P.C., become abnormal, disorganized or disappear. The chromosomal changes (protuberances,absence of condensation and chromosomal bridges) are principally given by I.P.C. I.P.C. and C.I.P.C. lead to the disappearance of the endoplasmic reticulum. These effects are correlated with the action of the two pesticides on DNA and protein synthesis.

Carbamates↗
PubMed1980

Action of short-term cycloheximide administration associated with colchicine on nuclear and chromosome structure in cleaving Newt eggs. Reappearance of chromomeres?

Association of short-term cycloheximide (CHM) administration (1/3, 1/2 or 1 cycle) with long-term treatment by colchicine (Co) confirms the results obtained by CHM alone under similar conditions, namely the striking relationship between the starting-time of treatment and the type of nuclei obtained (centred telophasic or non-centred prophasic). This relationship is highly significant. Various nuclear structures were observed: they correspond to a special evolution of the abnormal nuclei during telophase, telo-prophase and prophase which is very different from that in untreated ones. A difference in evolution of the central and peripheral parts of the same nucleus explains their centred structure. On the contrary, this difference disappears at prophase. The association CHM-Co favours the unveiling of beads which are interpreted as prophasic chromomeres. These beads are of different size, spacing and form according to the moment of the prophasic evolution attained. Electron microscopy study confirms the strong dispersion of chromatin by CHM and the beaded appearance of chromosomes by CHM and Co. Simultaneously, many dense bodies are accumulated in the centrospheres, as after quinoline and glutaraldehyde administration. The mechanisms of production of centred nuclei and of the beaded appearance of chromosomes are discussed.

Animals↗
PubMed1979

The fine structure of meningiomas: an attempted classification.

We examined 23 meningiomas by electron microscopy. In each case it was possible to distinguish certain cells with epithelial features (desmosomes, microfliaments, interdigitating extensions) and others with fibroblastic features (collagen fibers). Others cells of transitional form were also seen. The proportion of these cellular types is variable, making it possible to classify meningiomas into seven types of progressing gradually from a purely epithelial type to a purely fibroblastic one.-We found no important ultrastructural abnormalities in the cells. These case reports confirm the uniqueness of meningiomas, which are composed of variously shaped cells but have their origin from a single cellular type. This has double potentiality for fibroblastic and epithelial differentiation.

Cell Differentiation↗
PubMed1979

[Coating of centrospheres by reticulum cisternae and formation of spindle residues in segmentation mitosis under the action of an antitubulin substance: nocodazole].

When cleaving eggs are treated by nocodazole the reticulum cisternae coat the centrospheres instead of the chromosomes, as normally occurs at the late anaphase. At the same time the spindle is reduced to a common mass or spindle remnant, constituted of unorientated and fragmented microtubules which embed the kinetochores, i. e. the star configuration of the chromosomes. This action is quite similar to that of chloralhydrate but is different from that of colchicine.

Anaphase↗
PubMed1979

Inhibition of spindle assembly by colchicine and of cell cycle by cycloheximide. Comparison and combination of their cytological action on cleavage mitoses.

In cleavage mitoses colchicine (2 x 10(-3) M) does not interrupt the cycle of chromatin and its action is exerted on all the mitotic phases. Cycloheximide (10(-3) M) prevent normal condensation of the chromosomes and breakdown of the nuclear envelope; it brings on various nuclear abnormalities, particularly irregularities in chromosome condensation. At 10(-4) M, cycloheximide allows some mitoses, often abnormal ones, but anaphase is inhibited. The action of colchicine, more efficient upon the spindle, obscures the action of cycloheximide when both substances are associated. In return, cycloheximide imposes its action upon chromosome condensation, so that the structure of the nuclei treated by both substances is determined by cycloheximide.

Animals↗
PubMed1979

[Mitotic index modifications in a series of gliomas related to degree of malignancy].

We have measured on semi-thin sections, the mitotic index in 5 benign gliomas and 5 malignant gliomas among a whole of about 80,000 cells in each group, divided into fields of 750 cells on an average. We have differentiated between normal mitoses and abnormal mitoses on one hand, between viable and adequate mitoses and non-viable mitoses on the other. If we take into account the total number of mitoses, the mitotic index is not greatly different between the 2 groups of tumors (about 5 per thousand), although slightly superior in the benign gliomas. If we take into account the viable or adequate mitoses only, the mitotic index is greatly superior among the benign gliomas. These results are discussed according to other data related with the kinetics of proliferation of gliomas and according to the possibility of cellular fusions as a process of a minor spreading of malignant gliomas.

Cell Fusion↗
PubMed1979

[Thyroid incorporation of radioactive iodine in neotenic tritons (Triturus helveticus Raz.). In vivo studies by high resolution radioautography. Comparison of iodine incorporation in adults and larvae].

In vivo kinetics of radioiodine incorporation have been established for 70 newts, collected from Triturus helveticus Raz. populations where spontaneous neoteny occurs. Fifty of these newts which appeared to present four degrees of neoteny (more or less metamorphosed), have been studied. Main results obtained were: 1) The intensity of the iodine incorporation varies according to the degree of neoteny. The higher is this one, the lower is the intensity. 2) In general, iodine uptake rates are more or less similar to these of adults, but more often the evolution of the 125I uptake approaches a plateau-curve. From thyroid radioautographies on some animals (17 neotenic and 2 adult newts) for which in vivo iodine kinetics have been examined and on 9 normal larvae in premetamorphosis or in metamorphosis, we have noticed in those neotenic thyroids, a very small number of silver grains on apical vesicles and colloidal lumina when the degree of neoteny is the highest. This number of marked apical vesicles and colloid is more important in the neotenics which have lost some larval characters. Silver grains on colloid droplets indicating thyroid hormone excretion are inexistent in the most larval neotenics, more numerous in most metamorphosed neotenics. But they always are less numerous than in metamorphosing larvae. For a few animals, the fixation curve is very high, probably because of a stimulation of thyroid function, induced by the test and not because of a goitrous tendancy, as radioautographic observation of their thyroid shows. Thyroid function and its relation with the origin of this total and accidental neoteny are discussed.

Aging↗
PubMed1979

[Round cells of human sperm].

Many round cells are found whose number may become conspicuous. These cells may originate as well from germinal as from somatic lines. Electron microscopy is the only way to distinguish the two kinds of origin. In some specimens germinal cells predominate (spermattids, plurinuclear cells), in others there are many phagocytic cells which may ingest a great number of spermatozoa and this phenomeon may stimulate an azoospermy by failure of spermatogenesis. The study of human sperm (or testicular biopsies) by electron microscopy is needed to obtain the necessary information in order to orient diagnosis, prognosis and therapy.

Cell Nucleus↗