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Biomedical subjects

G Bernier

Publications and source records attributed to G Bernier.

At least 37 records · Page 2Linked to original sources
PubMed1991

Changes in mRNA level rhythmicity in the leaves of Sinapis alba during a lengthening of the photoperiod which induces flowering.

A previous study has shown that mRNAs exhibit complex patterns of diurnal rhythms in their quantity in the leaves of Sinapis alba during an 8 h light/16 h dark short day (SD). In order to determine whether this situation is rapidly modified in plants subjected to an extended light treatment, we have used in vitro translation and two-dimensional polyacrylamide gel electrophoresis, together with a strict gel comparison procedure giving a P = 0.03 certitude level, to analyse the mRNA complement at different times during a 22 h light/2 h dark long day (LD). During this LD, complex changes affected about 10% of the mRNAs. Thirty-four different patterns were observed. Some diurnal rhythms present in SD are not modified by the lengthening of the light period, but most are affected. Moreover, we have shown that some mRNAs presenting a constant quantity under a SD regime show an increase or a decrease during the first hours of the photoperiod lengthening. In Sinapis, this LD also induces flowering. All the changes in mRNA quantity detected thus parallel the photoperiodic induction of flowering in the leaves and are quantitative; no mRNA was shown to appear or to disappear.

Electrophoresis, Gel, Two-Dimensional↗
PubMed1990

Diurnal Rhythmicity in the Pattern of mRNAs in the Leaves of Sinapis alba.

Previous studies have shown that certain specific leaf mRNAs exhibit a diurnal rhythmicity in their quantity in higher plants. To determine whether this situation is restricted to a few mRNAs, or affects a large number, we have used in vitro translation and two-dimensional polyacrylamide gel electrophoresis to analyze the mRNA complement in leaves of Sinapis alba at different times during an 8-hour/16-hour day/night cycle. A method for the visual analysis of two-dimensional polyacrylamide gel electrophoresis was also developed. This method selected, at each sampling time, spots that were significant. It then selected, between two sampling times, intensity changes that were significant at the 0.02 confidence level. During a day/night cycle, complex rhythmic changes affected about 10% of the mRNAs. Nineteen different rhythm patterns were found. These 19 patterns fell into four main classes: mRNAs that increase during the light period and decrease during the dark, mRNAs that increase and then decrease during the light period, mRNAs that decrease during the light period and increase during the dark period, and mRNAs that increase and then decrease during the dark period.

Journal Article↗
PubMed1988

Cytokinin Fluxes during Floral Induction in the Long Day Plant Sinapis alba L.

Sinapis alba is a long-day (LD) plant that can be induced to flower by a single LD. A number of changes normally occurring in the meristem of plants subjected to the LD can be produced in short day by a single application of a cytokinin to the apical bud. However, flower buds are not produced indicating that evocation by the cytokinin is only partial. In this work, the cytokinin content of root exudate, obtained under vacuum, and of leaf exudate, obtained by the EDTA-method, has been analyzed comparatively in vegetative and induced plants, using reversed-phase HPLC coupled to the Amaranthus bioassay. The results show that, as early as 16 hours after the start of the LD, there is an increase of cytokinin activity in both the root and leaf exudates of induced plants. These observations fit nicely with previous results obtained on Sinapis, and they indicate that cytokinins are part of the floral stimulus in this species.

Journal Article↗
PubMed1987

Ecogenetics of Parkinson's disease: prevalence and environmental aspects in rural areas.

We make use of the unique combination of a homogeneous genetic and racial origin in the rural population of Quebec and the facilities of free and universal access to medical care, to study the distribution of the prevalence of Parkinson's disease in the 9 rural hydrographic regions of the Province. Through 3 different methods of ascertainment, confirmed by two control probes, we demonstrate that the prevalence of Parkinson's disease is of uneven distribution within rural areas. We further investigated the characteristics of the regions of high prevalence. These regions which are predominantly agricultural and areas of intensive market gardening were also the areas with the highest use of pesticides.

Geography↗
PubMed1986

The flowering process as an example of plastic development.

The field of flowering has been characterized by simplistic ideas, as exemplified by the attempts to classify plants on the basis of the kinds of environmental factors required for their transition to flower initiation and the claims that the process of flower formation in photoperiodic and cold-requiring plants is independent of correlative influences from various organs, e.g. the roots. Other examples of this simplified picture are the concept of a specific leaf-generated floral hormone and floral inhibitor and the search at the level of the meristem of a specific evocational event which would set in motion the whole sequence of other events and commit the meristem to flower initiation. Finally, there is the belief that because flower morphology is basis to species classification the morphogenesis of flowers is a rather invariable process. All these ideas are essentially erroneous and it is shown that all aspects of the flowering process are much more flexible than is usually believed. Floral induction may be completed by many, if not all, plants in several alternative sets of environmental factors. At least in some plants, the alternative inductive factors are perceived by different organs, indicating that these factors affect most probably entirely different processes. Thus, at induction, plasticity is extremely large and the fate of any shoot meristem appears to be controlled by a complex and flexible array of promoters and inhibitors arising from all plant parts. At meristem evocation, there are a number of events which are fundamentally the same in many plants, but so far no single initial critical event has been found. The various evocational changes appear to form sets of interconnected systems and this complex network seems to embody some plasticity since it has been possible to suppress experimentally some of the most universal evocational events or alter their temporal order without impairing evocation itself. At later stages, it has been observed that all the morphological characters of inflorescences and flowers may be experimentally altered. However, if the occasional and extreme malformations (monstrosities) caused by some growth substances are excluded, morphogenetic processes do not appear flexible to the point that the reproductive structures of one species are transformed into those of a taxonomically unrelated species. Thus, despite the fact that these processes are never absolutely fixed, plasticity at morphogenesis appears less than that at induction.(ABSTRACT TRUNCATED AT 400 WORDS)

Light↗
PubMed1984

Promotion of Flowering in Brassica campestris L. cv Ceres by Sucrose.

Flower initiation of the quantitative long-day plant Brassica campestris cv Ceres was earlier and at a lower final leaf number when sucrose was added to the medium in which plants were grown in sterile culture. The optimal concentration of sucrose was 40 to 80 millimolar. This flower-promoting effect of sucrose was not osmotic, as mannitol, sodium chloride, and polyethylene glycol were not effective at equal osmotic potentials.Seedlings grown heterotrophically after treatment with 4-chloro-5-(dimethylamino)-2-phenyl-3-(2H)-pyridazinone to prevent chlorophyll accumulation were also induced to form flower primordia earlier as the sucrose concentration in the medium was increased up to 80 millimolar. Inclusion of 4 millimolar sodium nitrate in the culture medium of green plants did not reduce the flower-promoting effects of sucrose but delayed initiation in plants grown without added sucrose.Removal of CO(2) during a single main or supplementary light period, or both, greatly reduced flower initiation. It is concluded that sucrose may be an important controlling factor determining floral initiation in Brassica.

Journal Article↗
PubMed1981

Flowering in Xanthium strumarium: INITIATION AND DEVELOPMENT OF FEMALE INFLORESCENCE AND SEX EXPRESSION.

Vegetative plants of Xanthium strumarium L. grown in long days were induced to flower by exposure to one or several 16-hour dark periods. The distribution of male and female inflorescences on the flowering shoot was described, and a scoring system was designed to assess the development of the female inflorescences. The time of movement of the floral stimulus out of the induced leaf and the timing of action of high temperature were shown to be similar for both the apical male and lateral female inflorescences.Strong photoperiodic induction of the plants favored female sex expression, while maleness was enhanced by exogenous gibberellic acid. The problem of the control of sex expression in Xanthium is discussed in relation to the distribution pattern of male and female inflorescences on the flowering shoot and to the state of the meristem at the time of the arrival of the floral stimulus.

Journal Article↗
PubMed1977

Cytokinin as a Possible Component of the Floral Stimulus in Sinapis alba.

Results of previous investigations indicated that one of the early and essential events occurring in the apical meristem of Sinapis alba L. during the transition to flowering is the release to mitosis of the G(2) nuclei; the trigger to mitosis is generated in the leaves and its movement out of the leaves begins around 16 hours after the start of the inductive treatment. The mitotic wave in the meristem culminates 10 hours later.In this paper, it is shown that a single application of a cytokinin (benzyladenine or zeatin) at concentrations ranging from 1 to 20 mug/ml directly to the apical bud of vegetative plants, at a time corresponding to the time of movement of the mitotic trigger in induced plants, produces a mitotic wave which is very similar to that found in induced plants. It is thus proposed that the mitotic component of the floral stimulus in Sinapis is a cytokinin. As the cytokinins are completely unable to induce flowering, it appears that there is a multicomponent floral stimulus in this species.

Journal Article↗
PubMed1977

[Necrotic enteritis in broiler chickens. III. Study of the factors favoring the multiplication of Clostridium perfringens and the experimental transmission of the disease].

Necrotic enteritis was reproduced experimentally in two week old broiler chickens by intravenous injection and also by oral administration of a pure culture of Clostridium perfringens. In the first experiment, gross and microscopic intestinal lesions, typical of necrotic enteritis, were observed in all diseased birds and mortality was obtained only in the group of birds that were injected with 0.4 ml or more of the pure culture of the microorganism. In the second experiment, the highest mortality was noted in the group of birds that received orally, in addition to the Clostridium culture, a solution of sodium bicarbonate, to obtain an alkaline intestinal content and opium to decrease the intestinal peristaltism. The gross and microscopie intestinal lesions of the diseased and killed birds were more severe than those observed in the other groups and were similar to those encountered in field outbreaks of necrotic enteritis.

Animals↗
PubMed1976

Sequence of Reactivation of Ribonucleic Acid Synthesis during Early Germination of the Maize Embryo.

The onset of RNA synthesis in primary roots of germinating Zea mays embryos was studied. Incubation of excised embryos in the radioactive precursor solution was performed after different germination periods.It was observed that there are three successive stages in the reactivation of RNA synthesis. Stage one is characterized by the synthesis in the chromatin of heterodisperse nuclear RNA rich in adenine. Stage two is characterized by the synthesis of heterodisperse nuclear RNA in the chromatin and 2.3 x 10(6) rRNA precursor in the nucleolus. Stage three is characterized by the synthesis of heterodisperse nuclear RNA and rRNA precursor and by the processing of the latter in mature rRNA.

Journal Article↗