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Biomedical subjects

C Dumas

Publications and source records attributed to C Dumas.

At least 127 records · Page 7Linked to original sources
PubMed1990

Effect of D ala2 metenkephalinamide on feline jejunal and ileal water and electrolyte transport.

The aim of this investigation was to compare the effect of an opioid, D ala2 metenkephalinamide (DAMA), on net jejunal and ileal water and electrolyte fluxes using the gut perfusion technique in the anesthetized cat. Intestinal transport was measured during intravenous infusion of serial doses of 2, 6, and 18 micrograms.kg-1.h-1 of DAMA in 6 cats. Each cat was its own control during an intravenous infusion of 150 mmol/l NaCl preceding the first dose of peptide and following the last dose of DAMA. Both jejunal and ileal segments were isolated by inflated balloons and were studied at the same time. Fifteen ml of an iso-osmolar test solution with hypo-osmolar ion contents and complementary mannitol were administered in the upstream tube and collected 1 h later in the downstream tube. In the jejunum, water secretion was dose-dependently reversed to an absorption from a control value of +0.5 +/- 0.4 to -0.83 +/- 0.5 ml.h-1.10 cm-1; in the ileum, water absorption was increased from -0.5 +/- 0.3 to -1.5 +/- 0.2 ml.h-1.10 cm-1. The net absorption of all electrolytes, ie sodium, chloride, bicarbonate, potassium and calcium also increased during peptide administration. However, a qualitative difference in the ion transport was observed between the jejunum and the ileum.

Animals↗
PubMed1990

Influence of Temperature Stress on in Vitro Fertilization and Heat Shock Protein Synthesis in Maize (Zea mays L.) Reproductive Tissues.

This study was conducted to investigate the response of maize (Zea mays) male and female mature reproductive tissues to temperature stress. We have tested the fertilization abilities of the stressed spikelets and pollen using in vitro pollination-fertilization to determine their respective tolerance to stress. The synthesis of heat shock proteins (HSPs) was also analyzed in male and female tissues using electrophoresis of (35)S-labeled proteins and fluorography, to establish a relationship between the physiological and molecular responses. Pollen, spikelets, and pollinated spikelets were exposed to selected temperatures (4, 28, 32, 36, or 40 degrees C) and tested using an in vitro fertilization system. The fertilization rate is highly reduced when pollinated spikelets are exposed to temperatures over 36 degrees C. When pollen and spikelets are exposed separately to temperature stress, the female tissues appear resistant to 4 hours of cold stress (4 degrees C) or heat stress (40 degrees C). Under heat shock conditions, the synthesis of a typical set of HSPs is induced in the female tissues. In contrast, the mature pollen is sensitive to heat stress and is responsible for the failure of fertilization at high temperatures. At the molecular level, no heat shock response is detected in the mature pollen.

Journal Article↗
PubMed1989

Cloning of rodent cDNA coding the poly(ADP-ribose) polymerase catalytic domain and analysis of mRNA levels during the cell cycle.

We have isolated a partial 2.0 kb cDNA (pRATC) encoding the entire 489 amino acids of the NAD binding domain located at the C terminus of the rat poly(ADP-ribose) polymerase. pRATC sequences were analysed and compared with the human mRNA. Our analysis reveals a remarkable homology between the rat and human nucleotide and amino acid sequences. Although a few minor amino acid changes were detected, we have found that the total number of possible phosphorylation sites remained constant in the NAD binding domain of both enzymes. We have also found that a 102 amino acid sequence, containing the putative nucleotide binding site Gly-Lys-Gly (position 378), is perfectly conserved between the rat and human sequences. Strong homology was also detected between pRATC and genomic DNA isolated from various vertebrates. In addition, we have analysed the levels of poly(ADP-ribose) polymerase mRNA throughout the cell cycle. Our results show that the levels of mRNA culminate in the G1 phase. We have also found that the increase in enzymatic activity observed in rats following treatment with phenobarbital did not correspond to an increase in the mRNA levels.

Amino Acid Sequence↗
PubMed1988

Isolation of viable wheat male gametophytes of different stages of development and variations in their protein patterns.

Procedures have been designed to isolate viable immature male gametophytes from wheat (Triticum aestivum L.) anthers of different stages of development. Maceration of anthers by a micro-blender allowed for the release of numerous intact vacuolate microspores. Tris-buffered media prevented tricellular pollen grains from bursting during the isolation procedure. Proteins from the undamaged male gametophytes have been analyzed by isoelectric focusing and sodium dodecyl sulfate-polyacryl-amide gel electrophoresis. A set of new proteins was detected at the onset of the second pollen grain mitosis. The results demonstrate the opportunity for studies on haploid gene expression at the translational level.

Journal Article↗
PubMed1987

Male Germ Unit Isolation from Three Tricellular Pollen Species: Brassica oleracea, Zea mays, and Triticum aestivum.

A technical procedure is described to follow the in vitro release of the ;male germ unit' and the sperm cells from three tricellular pollen species (Brassica, Zea, and Triticum). The condition of the sperm cell was controlled using light microscopy. In addition, for the first time, the sperm cells viability has been checked by the fluorochromatic reaction test. These preliminary results indicate that this procedure appears to be a prerequisite for the successful preparation of purified viable sperm cells.

Journal Article↗
PubMed1987

Procedure to Isolate Viable Sperm Cells from Corn (Zea mays L.) Pollen Grains.

Sperm cells were isolated from corn (Zea mays L.) tricellular pollen grains. They were released using a light osmotic chock, and separated from pollen contaminants (especially starch grains) by a Percoll gradient centrifugation. Isolated sperm cells (3 x 10(6) per milliliter) show a high viability score (90%) as demonstrated with the fluorochromatic reaction. They appeared as spherical cells which lack cell wall and plastids, and can be considered as haploid protoplasts.

Journal Article↗
PubMed1987

Proteolytic activity of bacteria isolated from the oral cavities of BALB/c mice toward salivary proteins.

The proteolytic activities of 350 bacterial isolates from different sites (saliva, tongue, teeth, and mucosa) of the oral cavities of BALB/c mice were tested against different proteins found in saliva (immunoglobulins A, M, G, albumin, lysozyme, mucin, lactoferrin, and lactoperoxidase), some of which are considered to possess antibacterial activity. The results indicate that: (1) lysozyme, lactoferrin, and lactoperoxidase are hydrolyzed by from 46 to 70% of the indigenous flora of the oral cavities of BALB/c mice; (2) IgA and IgM appeared less sensitive to the proteolytic activities of these strains than did the other proteins tested; (3) the colonization of the oral cavity does not seem to be correlated with the proteolytic activity; and (4) the presence of specific Ig proteases is relatively scarce within this population.

Animals↗
PubMed1987

Incompatibility in Populus: structural and cytochemical characteristics of the receptive stigmas of Populus alba and P. nigra.

Structural and cytochemical characteristics of stigmas of Populus alba (section Leuce) and P. nigra (section Aigeiros) have been studied to provide an understanding of the cell biology of the interspecific incompatibility reactions between these two species. In addition to specific morphological characteristics, stigma surfaces differ in the presence of an exudate studied by ultrastructural and stigma print techniques. P. nigra shows features of a dry-type stigma covered by a pellicle, whereas P. alba has a copious exudate typical of a wet-type stigma that contains unsaturated lipids.

Histocytochemistry↗
PubMed1987

Rapid assessment of microspore and pollen development stage in wheat and maize using DAPI and membrane permeabilization.

The use of the DNA-specific fluorochrome DAPI has been extended to stage assessment of fresh pollen in wheat and maize. Membrane permeabilization by Triton X-100 incorporated in the staining solution allows access of the fluorochrome to nuclear DNA. At all stages of gametophytic development, the nuclei can be sharply visualized. Starch does not interfere with the fluorochrome so that it is possible to study the second pollen grain mitosis and sperm differentiation. With its rapidity and reliability, this technique represents an efficient tool for routine staging or investigation of the nuclear status of the pollen grains.

Cell Membrane Permeability↗
PubMed1987

[Male-female recognition during sexual reproduction in flowering plants].

In flowering plants, the recognition reactions occur between male and female partners at the stigma level or along the style and in the embryo sac between the gametes. The study of these biological events implies to check the viability of the two partners. Interacting molecules are glycoproteins. A cDNA coding for the stigma protein molecules has recently been cloned. The specific pollen molecules have been also characterized. They are glycoproteins which are localized at the periphery of the grain and rapidly diffuse. These recognitive molecules present some analogies with pollen allergens.

Female↗
PubMed1986

Organization of stigma surface components in Brassica: a cytochemical study.

The nature of secretion products forming the pellicle of the dry-type stigma surface has been investigated in Brassica by an electron-microscopic cytochemical study. In order to determine whether the pellicle is organized like a membrane, we used a series of cytochemical methods to visualize cell membranes. Three groups of techniques presenting different degrees of specificity in terms of cell surface markers have been used: non-specific labelling of cell-surface components, characterization of glycoconjugates and localization of enzymic activities. We demonstrated that the pellicle of Brassica stigmas, although not possessing a trilamellar structure, presents numerous characteristics encountered in biological membranes. In particular, it possesses cytochemically demonstrable enzyme activities, including ATPase and adenylate cyclase, whose role remains to be elucidated in relation to the pollen-stigma interactions.

Adenosine Triphosphatases↗
PubMed1984

FFT method to compute solution X-ray scattering curves.

We present an efficient algorithm to compute X-ray intensities scattered by macromolecules in solution, from atomic positions found in crystal structures. The algorithm applies the Fast Fourier Transform to an electron density map created from the atomic coordinates and corrected for solvent density. We compute scattering curves for both allosteric forms of E. coli aspartate carbamoyltransferase. Calculated intensities are in agreement with the ones measured by Moody et al. which shows that the structures observed in solution in the presence or in the absence of a substrate analogue do correspond to those of two crystal forms analyzed by Lipscomb and collaborators .

Aspartate Carbamoyltransferase↗
PubMed1984

Pollen-pistil interactions in interspecific crosses of Populus (sections Aigeiros and Leuce): pollen adhesion, hydration and callose responses.

Intersectional crosses between species of sections Aigeiros (Populus deltoides, P. X euramericana or P. nigra) and Leuce (P. alba or P. tremuloides) are known to be reciprocally incompatible. The site of pollen tube arrest is on the stigma surface in pollinations between pistils of section Leuce and pollen of section Aigeiros; tubes failed to penetrate the stigma surface. In reciprocal matings, pollen of section Leuce germinated and tubes penetrated the stigma and style, where arrest occurred. Rejection may be accompanied by swelling of the tube tips, and callose plug formation. In the cross between P. deltoides and P. alba a callose response was detected in the cell walls of the transmitting tissue, adjacent to the rejected pollen tubes.

Microscopy, Electron, Scanning↗
PubMed1983

Interactions of serotypes A and B of Candida albicans in mice.

Candida albicans serotypes A and B were mixed in different proportions and administered orally to white mice receiving a protein-free diet. Recoveries of the serotype from the stomach and rectosigmoid showed that the relative proportion of serotype A was consistently higher than in the inoculating suspension. No modification of serotype was observed in mice given only one serotype, and there was no change in proportions of serotypes coincubated in vitro. These observations indicate that host factors must be involved in selective colonization by the serotypes in vivo.

Animals↗
PubMed1983

Iatrogenic lesions of the upper airway in the newborn.

A retrospective study of 140 babies who survived the first week of life and who had endotracheal intubation showed that 65 of them had either or both of the following complications of endotracheal tube therapy: (a) Collapse of one or more lobes with the tube in place or within the first two days following extubation and lasting less than 24 hours. When collapse lasted more than 48 hours, it often required repeated intubation for tracheal cleansing. The right lung, especially its upper lobe, was predominantly affected. (b) Tracheal lesions and nasal necrosis. A statistical comparison with intubated babies of similar age without complications showed the following factors to predispose to lobar collapse: younger gestational age, maximal high oxygen concentration administered, and prolonged duration of intubation. The results of endotracheal tube cultures bore no relation to the complication rate.

Airway Obstruction↗
PubMed1982

[Reese's conjunctival melanosis. Two anatomicoclinical observations with ultrastructural study in one case].

Two cases of Reese's conjunctival melanosis are reported. Inflammatory signs revealed the presence of the lesion in a 58-year-old woman, examination demonstrating diffuse brown conjunctival, tarsal, and bulbar pigmentation in the right eye, raised above the surface at the sclerocorneal junction. Histology after exenteration demonstrated coexisting diffuse atypical melanocytic hyperplasia (precancerous melanosis), an intraepithelial melanoma (cancerous melanosis), and an invasive melanoma which was the object of an ultrastructural study. The second case, a 57-year-old woman, had a 20-year history of stable, diffuse black pigmentation of the bulbar conjunctiva of the right eye. Four months after biopsy, a pedunculated tumor of the internal canthus developed, corresponding to a poorly differentiated epithelioid cell malignant melanoma. These two cases are compared with similar observations reported in the literature.

Adult↗
PubMed1979

A study of 666 strains of Candida albicans: correlation between serotype and susceptibility to 5-fluorocytosine.

The minimal inhibitory concentrations (MICs) of 5-fluorocytosine (5-FC) and the serotypes were determined for 666 strains of Candida albicans isolated from white patients in Canada. Of these strains, 495 (74.3%) were serotype A and 71 (25.7%) were serotype B. Resistance to 5-FC (MIC, greater than or equal to 25 microgram/ml) was observed in 11.3% of the serotype A strains and in 49.7% of the strains of serotype B. Most specimens were from the urogenital and respiratory tracts. The results showed the difference between the distribution of the two serotypes of C. albicans in North America and that in Europe. Serotyping of C. albicans strains by indirect immunofluorescence is a rapid means of predicting the de novo sensitivity of this year to 5-FC. The specificity of this technique for the isolated strains was approximately 79%.

Animals↗