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D Hemon

Publications and source records attributed to D Hemon.

34 records · Page 2Linked to original sources
PubMed1983

Comparative influence of hyperthermia and ionizing radiation on cycle and mitosis lengths in EMT6 mouse tumour cells.

With exponentially growing EMT6 mouse tumour cells in vitro, we have compared the effects of a dose of ionizing radiation and different temperature-time combinations on the lengths of the cell cycle and of mitosis using time-lapse cinematography on individual cells. The radiation dose and various temperature-time combinations all produced 50 per cent lethality. The hyperthermia treatments between 42 and 45 degrees C all caused a mitosis delay (MD) which was greater than that induced by ionizing radiation. The MD was greater with increasing temperature. In contrast, hyperthermia also induced a mitosis lengthening (ML) but this was only of the same order of magnitude as radioinduced ML. The results argue in favour of different mechanisms underlying thermoinduced MD and ML.

Animals↗
PubMed1982

Maternal factors associated with small-for-dateness among twins.

The maternal risk factors that correlate with small-for-dateness among twins have been analyzed using a sample of 659 twins pairs and a matched sample of singletons. Non-marital status, job involvement, and the previous delivery of a low-birth weight (less than 2,500g) infant present a negative interaction with twinning, as low gestational age-adjusted birth weight does not correlate significantly with these risk factors among twin gestations, while it does among singleton gestations. On the other hand, the effects of parity, habitual maternal weight, smoking during pregnancy, and twinning are additive on gestational age-adjusted birth weight. Indeed, the decrease in adjusted birth weight associated with these risk factors is of the same magnitude among twins and singletons and is statistically significant in both cases. These findings suggest that exposure of twin pregnancies to these latter risk factors, and particularly to smoking during pregnancy, can lead to the delivery of newborns with extremely low birth weights.

Birth Weight↗
PubMed1981

Comparative effects of 60Co gamma-rays and neon and helium ions on cycle duration and division probability of EMT 6 cells. A time-lapse cinematography study.

Exponentially growing cultures of EMT 6 cells were irradiated in vitro with neon ions, helium ions or 60Co gamma-rays. Time-lapse cinematography allowed the determination, for individual cells, of cycle duration, success of the mitotic division and the age of the cell at the moment of irradiation. Irradiation induced a significant mitotic delay increasing proportionally with the delivered dose. Using mitotic delay as an endpoint, the r.b.e. for neon ions with respect to 60Co gamma-rays was 3.3 +/- 0.2 while for helium ions it was 1.2 +/- 0.1. Mitotic delay was greatest in those cells that had progressed furthest in their cycle at the time of irradiation. No significant mitotic delay was observed in the post-irradiation generation. Division probability was significantly reduced by irradiation both in the irradiated and in the post-irradiated generation. The reduction in division probability obtained with 3 Gy of neon ions was similar to that obtained after irradiation with 6 Gy of helium ions or 60Co gamma-rays.

Cell Cycle↗
PubMed1981

Twinning following oral contraceptive discontinuation.

The characteristics of 673 mothers of twins were compared to those of a matched sample of mothers of singletons. Both groups of mothers were interviewed just after delivery, and births in each group were matched for time and place. Of the characteristics studied, the use of oral contraceptives (OC) displayed a significant negative association with dizygotic twinning, with an estimated relative risk of 0.55 (95% confidence limits: 0.39/0.78). Among other maternal trails significantly associated with dizygotic twinning, ony age, parity and weight were possible confounders as far as the relationship between OC use and dizygotic twinning was concerned. Adjustment for these 3 characteristics left this relationship unaltered. These findings are compatible with the existence of the a direct relationship between OC use and a reduction in dizygotic twinning. Review of the available evidence concerning reproductive capacities following OC discontinuation suggests that the higher incidence of chromosomic abnormalities among spontaneous abortuses of OC users or their lower fertility could explain a reduction of dizygotic twinning rate after OC discontinuation. It is concluded that examination of te time and place variations in OC use and dizygotic twinning would help to clarify the nature of their relationship.

Adult↗
PubMed1981

Analysis of the spatial organization of the cell: a statistical method for revealing the non-random location of an organelle.

A method is proposed for testing the randomness of the location of an organelle within a given area of a cell section. The approach chosen is to analyse the distance between this organelle and a specific point considered as a point of reference. The method consists of converting this distance into the ratio of one given area to another and comparing the statistical distribution of the converted values to the uniform distribution. This method has the advantage of being valid in the absence of any restrictive assumptions concerning the heterogeneity in size and/or shape of the collection of sections sampled. Detailed examples are given to illustrate the practical use of the method, and its possible extensions are discussed.

Cell Nucleolus↗
PubMed1979

[Analysis of the geographical variations of twinning rate in France. An indirect approach to study spontaneous abortions (author's transl)].

The hypothesis of the existence of spatial variations of spontaneous abortion rates has two logical consequences on dizygotic twinning rates: they must be heterogeneously distributed and show a positive correlation with natality. French data available on dizygotic twinning rates from 1950 to 1974 are in agreement with both implications. Although alternative explanations are possible, these findings do reinforce the relevance of dizygotic twinning rate variations as a tool for the assessment of reproduction failures.

Abortion, Spontaneous↗
PubMed1979

Mechanisms of transcription in nucleoli of amphibian oocytes as visualized by high-resolution autoradiography.

In oocytes of Pleurodeles waltlii, the method of Miller and Beatty has been combined with a method of high-resolution autoradiography especially suitable for the study of isolated molecules. In vitro labeling of RNA by tritiated precursors was carried out with increasing incubation times (1, 4, 15, 24, 48, and 72 h). Silver grains were present over ribonucleoprotein fibrils in amounts sufficient for quantitative analysis of nucleolar DNA transcription. Statistical analysis of the data revealed that: (a) The units of any one nucleolus exhibited a large degree of heterogeneity in their number of grains. (b) There was a parallelism between the increasing grain number and the ribonucleoprotein-fibril lengthening as observed along the transcription unit.

Amphibians↗
PubMed1978

Twinning rate and reproduction failures.

Spontaneous abortion of one of the zygotes is shown to explain some of the main epidemiologic features of dizygotic twinning: its decrease at higher maternal ages and its spatial and secular variations. Conversely, the dizygotic twinning rate offers a precious tool for the study of the etiology of reproduction failures.

Abortion, Spontaneous↗
PubMed1977

[Distribution of birth weights and influenza epidemics (author's transl)].

The possible consequences of influenza during pregnancy on the weight of the new born were studied. It was shown that the major 1969-70 winter influenza epidemic in Alsace was followed by a decrease in the mean birth weight registered in Haguenau's maternity hospital. This study confirms previous work on the subject and shows that birth weight can be used as a valuable tool at the epidemiologic scale.

Birth Weight↗
PubMed1976

[Effect of a polyvitamin preparation on the immune response to antibodies. Demonstration of the immunostimulating activity of propylene glycol].

Humoral antibody to sheep erythrocytes was studied by plaque forming cell and hemagglutinin assays in mice receiving a polyvitaminic preparation containing vitamins A, D, E, and C. A statistically significant increase in PFC on days 6, 12 and 18 after immunization, and an increase in hemagglutinin titers was observed in animals treated with this vitamin containing solution. These results are interpreted as an immunostimulating activity of the preparation. Nevertheless, as shown by the results obtained with each component injected separately, a major proportion of the immunostimulating activity seems to be related to propylene glycol, a simple compound contained as an hydrodispersant in the preparation. Further studies of the immunostimulating properties of propylene glycol are now in progress in our laboratory.

Adjuvants, Immunologic↗