Showing papers by "Institut national de la recherche agronomique published in 1977"

Thermosensitive step associated with transfer of the Ti plasmid during conjugation: Possible relation to transformation in crown gall

Abstract: It is reported here that transfer by means of a conjugative process of an oncogenic plasmid from a virulent strain of Agrobacterium tumefaciens to a strain of that organism that had been cured of the plasmid is thermosensitive. Since the thermosensitive step found in the conjugative process appears similar in every respect to a thermosensitive step that is involved in the transformation of a normal cell to a tumor cell in the crown gall disease of plants, it is suggested that the observed results may reflect the existence of a thermosensitive step that is common to these two processes.

Prolactin–progesterone antagonism in self regulation of prolactin receptors in the mammary gland

Abstract: THE role of prolactin during growth of the mammary gland and in lactation is well established (see ref. 1 for review) and the antagonising action of progesterone on lactogenesis (but not on mammary growth) has been recognised2–4. A specific receptor for prolactin has been described5 and purified6 and it seems that the level of this receptor in the target cells is very sensitive to hormonal environments and might be one of the essential parameters which modulates the intensity of prolactin action. Titration of this receptor under controlled hormonal conditions has been mainly performed in the liver and its concentrations found to be sensitive to oestrogens7; this effect may be amplified or even mediated by prolactin itself8. We have shown9 that the number of prolactin receptors in the mammary gland of pregnant or lactating rabbits undergoes a sudden increase at the onset of lactation but that the Ka of the receptor–hormone interaction remains constant. The question arises as to which hormonal environment is required for this amplification; is the inhibitory action of high progesterone levels on lactogenesis associated with a reduction of receptor concentrations? We describe here a study of this possibility and of the positive regulation of prolactin on its own receptors in the rabbit mammary gland. We extend to the mammary gland the stimulating effect of prolactin on the levels of its receptors and demonstrate an antagonising action of progesterone on this process.

Transfer of virulence in vivo and in vitro in Agrobacterium.

Abstract: TRANSFER of virulence from a pathogenic to a non-pathogenic strain of Agrobacterium has been reported to occur in vivo1,2 and is due to the transfer of a plasmid which codes for virulence3,4. In the experimental conditions described, virulence transfer can be detected only after several weeks. The reason for this delay is not clear. The most likely explanations are (1) that infrequent transfer occurs long before it can be detected, detection being dependent on a subsequent increase in the ratio of converted to unconverted recipients or (2) that conditions suitable for virulence transfer occur only after donor and recipient have been in contact for several weeks. The main difficulty in distinguishing between these two alternatives is technical. When pathogenicity testing is used to detect virulence transfer, low frequency transfer is impossible to detect unless thousands of inoculations are made at each assessment. It is known, however, that the virulence plasmid codes for characters other than virulence5–7. One of these is utilisation of octopine and, as Kerr8 has pointed out, this could be used instead of pathogenicity testing to detect plasmid transfer. This communication describes both in vivo and in vitro transfer of virulence using octopine utilisation to detect plasmid transfer.

Evolution of prolactin receptors in rabbit mammary gland during pregnancy and lactation.

Abstract: The numbers and affinity of prolactin receptors in the rabbit mammary gland were determined during pregnancy and early lactation under conditions in which the endogenous lactogenic hormone was depleted by means of the compound CB 154. In untreated rabbits the number of prolactin binding sites per mg protein increased from 25 ± 3 (SE) fmol at Day 14 of gestation to 54.8 ± 5.8 fmol/mg at Day 22, after which binding declined to 14.2 ± 8.5 fmol/mg, then increased in late pregnancy and during lactation to 110.5 ±11.5 fmol/mg at Day 28. In animals treated with CB 154, binding was always higher than in non-treated animals, with a peak during pregnancy of 149 ± 24 fmol/mg at Day 22. After declining in late pregnancy, the number of receptors was highest at Day 6 of lactation (257.4 ± 34.6 fmol/mg). There is an almost linear increase in the weight of the mammary gland from Day 14 of pregnancy until Day 6 of lactation and this increase is unaffected (except at Day 6 of lactation) by CB 154 treatment. It was observed...

Considerations on the specificity of entomopathogenic fungi

Abstract: Various aspects of the specificity are reviewed among entomopathogenic species of Entomophthorales and Hyphomycetes. The duality between parasitic capacities and saprophytic affinities of these microorganisms defined different degrees of specificity according to the species or groups. Recent results on taxonomy of Entomophthorales and on characterization of pathotypes of Hyphomycetes are discussed. Fungus toxicity and immunity reactions of the host influence the parasitic adaptation. The specificity of entomopathogenic fungi is also determined by the ecological relations between the fungus and the microorganisms of the environment and by the spatial-temporal coincidence between the populations of the pathogen and those of the host insect.

A study of insulin binding sites in the chicken tissues.

Abstract: Specific binding of chicken and porcine insulin was demonstrated in isolated chicken hepatocytes, chicken liver plasma membranes and chicken erythrocytes. In the liver, the binding reaction was characterized by a sensitivity and an apparent affinity which were similar to those observed in rat liver and, in contrast, by a decreased number of binding sites. In chicken liver, there were about 5 times fewer binding sites per mg of membrane protein or per unit of cell surface area than in rat liver. In chicken erythrocytes, the number of insulin binding sites per cell was even lower than in chicken hepatocytes. This decreased insulin binding was not accounted for by a faster insulin degradation in chicken tissues. Glucagon binding sites also appeared to be less numerous in chicken than in rat liver, at least at low glucagon concentration; however, the decrease in maximal binding capacity in chicken liver involved insulin and not glucagon binding. That chicken cells are equipped with insulin receptors which are less numerous than in mammalian cells may explain, partly at least, the physiological state of insulin resistance observed in the chicken.

ESTUDO GEOOUÍMICO DOS SOLOS E FORMAÇÕES SUPERFICIAIS DO BRASIL. PARTE 1 Caracterização e repartição dos principais tipos de evolução pedogeoquímica

Abstract: The pedologic classifications used in Brazil are mainly morphogenetic; hence they are not irrecise indicators for the reconstruction of the nature of the processes involved during surface evolution of the mineral fraction of soils. The geochemical type ofsoil evolution in Brazil is characterized by the study of chrystallochemical essentially and physico-chemical aspects related to the clay fraction. Thus an essencially pedogeochemical interpretation is obtained. As a consequence the geographical distribution of the types is presented.

Antagonistic effect of extremely oxygen-sensitive clostridia from the microflora of conventional mice and of Escherichia coli against Shigella flexneri in the digestive tract of gnotobiotic mice.

Abstract: Two extremely oxygen-sensitive strains of Clostridium sp., designated Clostridium E and P, were obtained from digestive microflora of conventional mice and found to constitute a barrier against Shigella flexneri SF-2 when associated in vivo with Escherichia coli K-12. These and other simplified fractions of the conventional microflora were demonstrated to have an effect comparable to that of the total flora. When K-12 and Clostridium E were established in gnotobiotic mice before the introduction of SF-2, the latter was reduced to a level below detection in the digestive tract. Whe SF-2 was established first, the antagonistic effect exerted by Clostridium E and K-12 was variable and, apparently, related to the rate of establishment of Clostridium E. Mutants of SF-2 resistant to the barrier effect of Clostridium E and K-12 appeared at the end of 3 months when SF-2 was established in gnotobiotic mice alone or with K-12, and after only a week when SF-2 was associated only with Clostridium E. These results suggest that the bacterial antagonsim in this model is related to the production in vivo of an antibiotic substance active against SF-2. It appears that the substance may be produced by Clostridium E, stimulated by K-12.

Immunofluorescence study of LH-RH producing cells in the human fetal hypothalamus.

Abstract: The use of antibodies to synthetic LH-RH has enabled the detection by immunofluorescence of hypothalamic LH-RH producing cells in the human fetus. The perikarya of these cells are located in the pericommissural and peroptic regions, in the lamina terminalis and in the premamillary region. Reactive axons occur in the median eminence. The first LH-RH producing cells are seen as early as nine weeks of gestation. The specificity of immunocytological reaction has been controlled.

Apricot Chlorotic Leaf Roll

Abstract: Apricot chlorotic leaf roll is a graft-transmissible disease, apparently a mycoplasm infection, which affects Japanese plum and sometimes peach. It is particularly important in Mediterranean areas. First symptoms are a rolling and a yellowing of the leaves, often localized on some twigs. Later, various disorders, often localized on a part of the tree, are observed: proliferation of branched and slender shoots, growth of buds in autumn and winter. Leaf buds break before flower buds. This growth in winter induces sensitivity to frost. Phloem tissues of affected branches are more or less damaged, taking on a brown discolouration. Some branches are destroyed, while on others, new shoots may develop. The presence of weak shoots with small leaves among normal shoots and irregularly distributed dried twigs on the branches is a characteristic aspect of the disease. Symptom expression and evolution of the disease vary much according to environmental conditions, age and rootstocks.

Tailing of Survival Curves of Bacillus licheniformis Spores Treated with Hydrogen Peroxide

Abstract: An attempt has been made to rule out possible causes of artefacts in establishing survival curves of Bacillus licheniformis spores heated (30–80 °C) in 4.4 mol/l hydrogen peroxide (pH 2.0). A tailing phenomenon apparent as that of a suspension of spores produced by routine subculture was obtained with those grown-up from a single spore selected by micromanipulation. No spore fraction differing in size or density could be separated from the whole population. The tail was not due to decomposition of hydrogen peroxide, protective effect by other spores, release of protective factors, or temperature heterogeneity during treatment. Changing from an open vessel to a closed tube did not influence the tailing. The only apparent artefact was therefore the formation of clumps under the conditions of the treatment. Since the spore catalase was demonstrated to be highly resistant, it was concluded that a spore could be protected against hydrogen peroxide by the catalase of the other spores in the clump. Conditions resembling those arising in spore suspensions could occur under industrial conditions, for example in sterilizing surfaces contaminated with aggregates of Bacillus spores.

Contribution of pharmacokinetic studies to mycotoxicology—Ochratoxin A

Abstract: A pharmacokinetic study of ochratoxin A in rats has demonstrated the binding of the toxin to serum albumin and its presence in all organs investigated. The acidic properties of the mycotoxin explain its absorption from the stomach and the fact that it binds to some macromolecules.

The caseins of buffalo milk

Abstract: The components of whole casein from water buffalo (Bubalis L.) have been re-investigated in the light of recent studies elucidating the primary structure of all the bovine caseins (αs1, αs2, β & κ). Whole casein samples obtained from individual Italian buffaloes all contained 2 αs1- and 2αs2-casein fractions. These 4 components were isolated and identified by their amino acid compositions and terminal amino acid sequences. The 2 αs1-casein fractions seem to have identical peptide chains as do the 2 αs2 fractions, with the individual fractions within each group differing only in their phosphate content. Buffalo β-casein was also isolated and characterized by its amino acid composition and terminal sequences. The isolation of different buffalo κ-casein fractions was reported earlier (Addeo, Chobert & Ribadeau-Dumas, 1977). These fractions were purified and analysed. They were found to have the same amino acid compositions and C-terminal sequences, but to differ in their carbohydrate content. The prominent component, κ1, was treated with chymosin; the caseinomacropeptide and para κ-casein were separated from the digest and analysed. Starchgel electrophoresis at alkaline pH showed no polymorphism of αs1-, β- and κ-caseins in 170 individual buffalo whole casein samples. On 5 occasions the electrophoretic pattern of αs2-casein suggested genetic polymorphism. The behaviour of buffalo αs1−and αs2-caseins in the presence of Ca2+ was also studied.

A new technique of artificial insemination for salmonids using a sperm diluent

Abstract: A French diluent has recently been produced for use on rainbow trout (Salmo gairdneri) in fish farms. It is superior to existing dry methods, since the diluent allows a longer period for fertilisation, and prevents precipitation of vitellus and inhibition of sperm motility. Recommendations are made regarding details of the insemination technique, such as temperature and egg collection. The technique gives a higher fertilisation rate than the dry method, and requires only a minute quantity of sperm. Sire populations in hatcheries can be reduced because a few males can fertilise hundreds of females.

Influence of age, dietary protein and weaning on calf abomasal enzymic secretion.

Abstract: Using fistulated calves, the influence of the age, type of dietary protein and weaning on the secretion of chymosin and pepsin by the abomasum were studied. The abomasum secreted both chymosin and pepsin when the animals were fed milk. Chymosin secretion appeared to be independent of the age of the animals, whereas a slow increase in pepsin secretion was observed as the calves aged. Several preruminant animals were fed either a skim-milk diet or a milt substitute in which proteins were provided by fish, soya or whey concentrates. Each of these 3 milk substitutes led to a decrease in chymosin secretion without modification of pepsin secretion. Chymosin secretion was partly restored when the calves were again given a skim-milk diet. At weaning, chymosin secretion dropped abruptly, but the pepsin level was not affected. These results indicate that milk (most probably its casein fraction) is responsible for the activation of chymosin secretion.

A New Case of Robertsonian Translocation in Cattle

Abstract: A new Robertsonian translocation was found in several animals of the Blonde d'Aquitaine breed. The fused chromosome analyzed by G- and R-banding results from the fusion of chromosomes 21 and 27. C-banding suggests that the fused chromosome is dicentric.

Fractionation of whole casein on hydroxyapatite. Application to a study of buffalo κ-casein

Abstract: When whole caseins from cow and Italian buffalo (Bubalus arnee) were fractionated by chromatography on a column of hydroxyapatite they behaved in a similar manner. kappa-Casein was eluted with 5 mM phosphate buffer, pH 6-8, containing 0-2 M-KCl, 4-5 M-urea and 2 mM-2-mercaptoethanol, but beta- and alphas-caseins were retained and could be eluted successively by a linear gradient from 5 mM to 250 mM-phosphate buffer. Buffalo kappa-casein preparations, obtained from bulk milk or from milks of individual animals by chromatography on hydroxyapatite, produced identical electrophoretic patterns at pH 8-6. By further fractionation of these kappa-caseins on DEAE-cellulose, in each case, at least 7 components were purified; they had different electrophoretic mobilities but were all sensitive towards chymosin. The major fraction migrated like component 1 of bovine kappa-casein B.

Specific distribution of fatty acids in the triglycerides of rainbow trout adipose tissue. Influence of temperature.

Abstract: In the trout, the unsaturated fatty acids are preferentially located in the β-position and the saturated fatty acids in the α-position of triglycerides. This fatty acid distribution is retained even with diets containing lard. The fish are, therefore, able to modify completely the fatty acid distribution of dietary triglycerides. There is no retention of the β-monoglyceride structure during the biosynthetic processes. However, the modification of the dietary fatty acid distribution by the trout seems to be more difficult at 18 C than at 10C.

Industrial and international standardization of microbial pesticides — I. Bacillus thuringiensis

Abstract: Bacillus thuringiensis preparations are standardized by bioassay based on a comparison with a reference standard preparation By this way the standardization of industrial formulations is satisfactory in order to maintain a constant quality within a given product International standardization is quite another problem and cannot be achieved by facing only standardized titration methods, since other factors, particularly the used strains, contribute to different host activity An account is given of the actual situation with historical backgrounds and some suggestions are made to avoid possible pitfall Essentially it would be most useful to demonstrate the biological activity differences of different products This work could be done by the different specialized laboratories with the help of internationally distributed standard preparations of each proposed serotype and using various technics and multiple test insects