Showing papers by "University of Montpellier published in 1987"

Further evidence for a central stimulatory action of catecholamines on adrenocorticotropin release in the rat.

Abstract: Catecholamines may stimulate ACTH secretion during stress. To investigate the nature and site of such an action, plasma ACTH was measured in four groups of unanesthetized adult female rats with an indwelling carotid cannula. Sequential 300-microliter blood samples were taken 60 min, 30 min, and immediately before an intracerebroventricular (icv) infusion of 2.5 microliter adrenaline or noradrenaline and 5, 15, 45, 60, and 120 min after the infusion. The four groups were: 1) intact rats; 2) rats infused 7 days after undergoing a discrete bilateral lesion of the ventral noradrenergic ascending bundle caused by 6-hydroxydopamine, which depleted their hypothalamic adrenaline and noradrenaline levels by 90% and 80%, respectively; 3) rats infused 30 min after pretreatment via the icv route with either prazosin or propranolol; and 4) rats infused 16 and 2 h after two successive intracarotid injections of an anti-rCRH-41 serum. In another group, the effects of icv catecholamine administration were compared with those of an intracerebral (ic) microinfusion close to a single paraventricular nucleus (PVN). Finally, in two additional groups blood was sampled at the above-mentioned times before and after a 2-min ether inhalation by intact rats or prazosin- and/or propranolol-pretreated rats. In the intact rats (group 1), a stress-like stimulatory dose response was noted after both adrenaline and noradrenaline infusions, with a half-maximal effect at concentrations of about 0.6 nmol and a maximal effect at 2.7 nmol or more. At maximally effective doses, adrenaline was significantly more active than noradrenaline. In the rats with ventral noradrenergic ascending bundle lesions (group 2), 2.7 nM adrenaline or noradrenaline stimulated ACTH release as in the controls without lesions. In group 3, prazosin blocked the ACTH responses to both adrenaline and noradrenaline, whereas propranolol only blocked the response to adrenaline. In group 4, i.e. rats pretreated with an anti-rCRH-41 serum, the amplitude of the ACTH surge after icv adrenaline or noradrenaline infusion was halved. A unilateral ic catecholamine microinfusion next to the PVN (half the icv dose given in group 1) led to a rapid ACTH release that peaked at half the response measured in the icv infused rats. Ether stress-induced ACTH release was decreased by 50-60% after icv pretreatment with 1 or 10 micrograms prazosin, 1 or 6.5 micrograms propranolol, or a combined dose comprising 1 microgram of both. The following conclusions were reached.(ABSTRACT TRUNCATED AT 400 WORDS)

Estrogen-induced lysosomal proteases secreted by breast cancer cells: a role in carcinogenesis?

Abstract: In an attempt to understand the mechanism by which estrogens stimulate cell proliferation and mammary carcinogenesis, metastatic human breast cancer cell lines (MCF7, ZR75-1) were found to secrete a 52,000 dalton (52K) protein under estrogen stimulation. Following its purification to homogeneity, the 52K protein was identified as a secreted procathepsin-D-like aspartyl protease bearing mannose-6-phosphate signals. This precursor displays an in vitro autocrine mitogenic activity on estrogen-deprived MCF7 cells and is able to degrade basement membrane and proteoglycans following its autoactivation. The total protease (52K + 48K and 34K) was detected and assayed by monoclonal antibodies and was found to be highly concentrated in proliferative and cystic mastopathies. In breast cancer, its cytosolic concentration appears to be correlated more to tumor invasiveness than to hormone responsiveness. The mRNA of the 52K protease accumulates rapidly following estradiol treatment, as was shown by Northern blot analysis with cloned cDNA. The 52K cathepsin-D-like protease is the first example of a lysosomal protease induced by estrogens in cancer cells. Results obtained using different approaches suggest that two cysteinyl cathepsins are also related to cell transformation and invasiveness. It has been proposed that cathepsin-B is involved in breast cancer and metastatic melanoma, and its regulation by estrogen has been shown in the rat uterus. Cathepsin-L corresponds to the major excreted protein (MEP) whose synthesis and secretion are markedly increased by transformation of NIH 3T3 cells with Ki ras and are regulated by several growth factors. In addition to secreted autocrine growth factors and to other proteases (plasminogen activator, collagenase), lysosomal cathepsins may therefore play an important role in the process of tumor growth and invasion as long as their precursor is secreted abundantly.

DNA-DNA hybridization evidence of the rapid rate of muroid rodent DNA evolution.

Abstract: Single-copy nuclear DNAs (scnDNAs) of eight species of arvicoline and six species of murine rodents were compared using DNA-DNA hybridization. The branching pattern derived from the DNA comparisons is congruent with the fossil evidence and supported by comparative biochemical, chromosomal, and morphological studies. The recently improved fossil record for these lineages provides seven approximate divergence dates, which were used to calibrate the DNA-hybridization data. The average rate of scnDNA divergence was estimated as 2.5%/Myr. This is approximately 10 times the rate in the hominoid primates. These results agree with previous reports of accelerated DNA evolution in muroid rodents and extend the DNA-DNA hybridization data set of Brownell.

The polyphyletic origin of laboratory inbred mice and their rate of evolution

Abstract: The analysis of various genetic components in the standard inbred laboratory strains of mice shows that several taxonomic units of the complex species Mus musculus have contributed to their genetic background. These laboratory lines are often taken as archetypes of the mammalian genome and since their genealogy is known for around 80 years they have been used to estimate mutation rates and various other evolutionary parameters. The knowledge of their origins is important if one is to avoid erroneous interpretations. Do they possess haplotypes that could have existed in natural populations of M. musculus domesticus or are they the fruit of artificial recombinations between divergent genomes? We discuss this in the light of various genetic systems.

Ecology of dling beetles in the french mediterranean region (coleoptera: scarabaeidae)

Abstract: Si no fuera por la actividad de los insectos escarabeidos coprofagos, en las tierras bajo pastoreo el estiercol podria convertirse en el cuello de botella en el proceso de reciclaje de la materia organica. los estudios origen de este trabajo han sido realizados en el languedoc, region meridional francesa situada sobre el litoral del Mediterraneo. la mayor parte de las estaciones de estudio estuvieron localizadas en el sector de “garrigues” (formacion mediterranea de matorral esclerofilo), correspondiente a una situacion karstica de baja altitud (200 a 400 metros), con una vegetacion dominada por la encina verde {Quercus iles l.), en condiciones climaticas mediterraneas tipicas (invierno fresco y humedo, verano calido y seco). los escarabeidos coprofagos estan organizados en comunidades de especies emparentadas, del mismo nivel trofico, que juegan unas en relacion a las otras papeles complementarios en la utilizacion de las deyecciones animales. Hemos estudiado: 1) como la estructura de las comunidades se modifica a traves del ano y a lo largo de dos gradientes de vegetacion; 2) cuales son las estrategias desarrolladas por los insectos para utilizar los excrementos; 3) como la tasa de dispersion de la boniga esta determinada por la distribucion espacial de los insectos y su nivel de actividad. Dispusimos trampas atrayentes de un modelo estandar en diferentes lugares a lo largo de dos gradientes de la misma serie de vegetacion, gradientes que se distinguen e! uno del otro por la naturaleza del suelo, y que en ambos casos comprenden de los pastos mas abiertos al bosque mas cerrado. Resalta en forma muy neta que la estructura de la vegetacion controla estrechamente la riqueza de las comunidades de escarabeidos coprofagos a lo largo de las sucesiones vegetales. Sin embargo, a la inversa de lo que se ha observado en otras regiones, en especial en las tropicales, no se observa la coexistencia de dos grandes grupos faunisticos, uno de lugar abierto y otro de bosque. En nuestra area de estudio la cubierta forestal juega simplemente un papel de filtro en relacion a los insectos: solo las especies mas abundantes en medio abierto pueden penetrar al bosque. En estas circunstancias el numero de individuos de las poblaciones bajo cubierta forestal se mantiene muy bajo. Otro factor determinante de las comunidades de escarabeidos coprofagos, es la textura y la capacidad de los suelos para retener agua. los suelos mejor drenados son en general los mas favorables y las estaciones de trabajo correspondientes incluyen una fauna rica y variada. A otra escala, la temperatura juega un gran papel y podemos ver, incluso sobre cortas distancias, una modificacion en la composicion de las comunidades sin que el funcionamiento general del sistema sea perturbado. lo mas frecuente es que ios cambios se efectuen por reemplazamiento de unas especies por otras en el seno del mismo “guild” de insectos, asi como por modificaciones de las frecuencias relativas de las especies. Desde un punto de vista funcional, dos tipos principales de excrementos existen en la region estudiada. Uno representado por las bonigas de vaca, el otro por las bolitas de oveja. las bonigas, utilizables en la superficie del suelo durante un periodo bastante largo, son empleadas en todas las estaciones por las grandes especies cavadoras {Geotrupes, Copns, Bubas) o de tallas media {Onthophagus) y por varios Aphodius que oviponen en el interior del excremento, en la parte donde la humedad es optima. las larvas de los Aphodius emigran progresivamente hacia la base del excremento y la ninfosis se verifica en el suelo. las bolitas de oveja constituyen por el contrario una fuente de alimento extremadamente transitoria que se seca muy rapido, entre algunas horas y pocos dias segun las circunstancias. En estas condiciones los escarabeidos han desarrollado diversas estrategias para utilizar este tipo de excremento. Asi los Aphodius oviponen directamente bajo el excremento en el contacto con el suelo y las larvas a su emergencia cavan ellas mismas una galeria que aprovisionan con los excrementos. En ciertos casos la hembra puede cavar pequenas galerias ramificadas en las que ovipone y que antes habra aprovisionado con alimento. la mayor parte de los insectos escarabeidos ovipone en la primavera o en el otono es decir durante los periodos templados y humedos del ano. estos pueden permanecer en la superficie del suelo durante varios meses. Sin embargo, la diversidad de los “guild” de escarabeidos coprofagos y su abundancia son tales que las cantidades de excremento que permanecen sin usarse son reducidas, lo que limita la tasa potencial de infeccion del ganado por diversos parasitos.

Physiology of neural pathways affecting CRH secretion.

Abstract: During the early years of modern neuroendocrinology, the discovery that the C N S played a major part in controlling the adrenocorticotropic axis was based on a series of pioneer investigations. They included the demonstration that the regulation of adrenocorticotropic hormonal levels was drastically impaired by the disconnection of the anterior pituitary from the hypothalamus and also by lesions in the mediobasal hypothalamus, as well as the discovery of a corticotropin releasing potency in hypothalamic extracts.' During the decades that followed significant progress was made in understanding the neural control of the hypothalamic-pituitary-adrenal (HPA) axis, with the development of reliable radiocompetition and RIA methods of measuring plasma corticosterone and ACTH levels. A decisive breakthrough was recently achieved with the biochemical characterization of CRH41 by Vale et al.' It opened the way to the immunocytochemical identification of the CRH4 1 -producing neurons in the parvocellular paraventricular nuclei (PVN) and their ensuing morphological e~plorat ion,~ and to the in-vivo measurement of radioimmunoassayable CRH41 in hypophysial portal vessels\"' and in the median eminence cannulated by the push-pull method.*v9 In the meantime, a variety of approaches converged to provide greater insight into the many and varied regulations controlling the HPA axis. They included neuroanatomical identification of the major neurotransmitter systems innervating the hypothalamus, and physiological experiments based on stereotaxic and neuropharmacological manipulations of discrete hypothalamic areas.'&'* Because of the technical difficulties and drawbacks inherent in the in-vivo measurement of C R H secretion, most of the recent data in this line of research are still based on measurements of the peripheral hormones of the HPA axis-i.e. of ACTH and sometimes only of corticosterone. Nevertheless, it seems timely to evaluate present knowledge of the neural components controlling C R H secretion, and this is the aim of the present review.

Skeletal density of silica aerogels

Abstract: The skeletal density of silica aerogels, produced by hypercritical drying of gels, is studied by helium pycnometry. The bulk and the skeletal densities vary as a function of parameters such as TMOS concentration. pH and densifying heat treatment. Skeletal densities were found to be slightly lower than that of vitreous silica. The results are compared to values obtained on xerogels.

Concurrent Certifications by Intervals of Timestamps in Distributed Database Systems

Abstract: This paper introduces, as an optimistic concurrency control method, a new certification method by means of intervals of timestamps, usable in a distributed database system. The main advantage of this method is that it allows a chronological commit order which differs from the serialization one (thus avoiding rejections or delays of transactions which occur in usual certification methods or in classical locking or timestamping ones). The use of the dependency graph permits both classifying this method among existing ones and proving it. The certification protocol is first presented under the hypothesis that transactions' certifications are processed in the same order on all the concerned sites; it is then extended to allow concurrent certifications of transactions.

Elastic properties of silica aerogels

Abstract: We have measured the elastic properties of silica aerogels with densities in the range 0.1 to 0.4 g/cm3. The static Young's modulus E was obtained from three-point flexion experiments, while Brillouin scattering allowed the determination of the elastic constants C11 and C44, at hypersonic frequencies. The comparison of these frequency-dependent determinations shows that the samples exhibit large scale homogeneity down to a few μm. The density dependence of the Young's modulus and elastic constants is shown to obey the same power dependence pα with α = ∼- 3.8. The ratio of the compressibility to the shear modulus is similar to that found in bulk vitreous silica. Percolation models are used for the discussion of these elastic behaviour.

Anti-actin antibodies. An immunological approach to the myosin-actin and the tropomyosin-actin interfaces

Abstract: The topography of the rigor complex between subfragment-1 (S-1) of myosin and actin was investigated by using several specific antibodies directed to well-located sequences in actin. A major contact area for S-1 was characterized in the hydrophilic 18-28 constant sequence, and the variable 1-7 sequence was only found to be in close proximity to the interface. The C-terminal extremity of actin situated around Cys-374 appeared to be included in a region close to the S-1 heavy chain and the N-terminal part of actin. The interaction between tropomyosin and actin was also studied. Neither of the terminal parts of actin were involved in this interaction. Thus, the regions involved in the interactions of S-1 and tropomyosin with actin do not overlap.

8-alkylaminoimidazo[1,2-a]pyrazines and derivatives, their preparation and their application in therapy

Abstract: ##STR1## Novel 8-alkylamino-imidazo(1,2-a)pyrazines of formula (I) show advantages pharmacological activities. They can be used for medical products in human and veterinary therapy in the field of applications of antispasmodics, uterine relaxants, bronchodilators, cardiac analeptics and neurosedatives.

Inheritance of chlorpyrifos resistance in Culex pipiens L. (Diptera: Culicidae) and estimation of the number of genes involved

Abstract: Inheritance of chlorpyrifos resistance in Culex pipiens L. (diptera: culicidae) and estimation of the number of genes involved

Multiple incompatibilities within populations of Culex pipiens L. in southern France.

Abstract: Strains of Culex pipiens derived from natural populations collected in southern France were crossed to determine their ability to give fertile offspring. Uni- and bi-directional incompatibilities occurred between these strains and each of them had its own crossing properties. Compatibility or incompatibility of a cross seemed to be related to the geographic distance separating the parental colonies, but not to their ecological origin (hypogeous or epigeous). Our results showed evidence for the variation in time of crossing properties of a strain.

5'-modified agonist and antagonist (2'-5')(A)n analogues: synthesis and biological activity.

Abstract: Two 5'-modified (2'-5')(A)4 oligomers with an increased resistance to phosphatase degradation were synthesized and evaluated for their ability to develop an antiviral response when introduced into intact cells by microinjection or by chemical conjugation to poly(L-lysine). The enzymatic synthesis of 5'-gamma-phosphorothioate and beta,gamma-difluoromethylene (2'-5')(A)4 from adenosine 5'-O-(3-thiotriphosphate) and adenosine beta,gamma-difluoromethylenetriphosphate by (2'-5')-oligoadenylate synthetase is described. The isolation and characterization of these (2'-5')(A)4 analogues were achieved by high-performance liquid chromatography. The structures of 5'-modified tetramers were corroborated by enzyme digestion. These two 5'-modified tetramers compete as efficiently as natural (2'-5')(A)4 for the binding of a radiolabeled (2'-5')(A)4 probe to ribonuclease (RNase) L. Nevertheless, at the opposite to 5'-gamma-phosphorothioate (2'-5')(A)4, beta,gamma-difluoromethylene (2'-5')(A)4 failed to induce an antiviral response after microinjection in HeLa cells. In addition, it behaves as an antagonist of RNase L as demonstrated by its ability to inhibit the antiviral properties of 5'-gamma-phosphorothioate (2'-5')(A)4 when both are microinjected in HeLa cells. The increased metabolic stability of 5'-gamma-phosphorothioate (2'-5')(A)4 as compared to that of (2'-5')(A)4 was first demonstrated in cell-free extracts and then confirmed in intact cells after introduction in the form of a conjugate to poly(L-lysine). Indeed, 5'-gamma-phosphorothioate (2'-5')(A)4-poly(L-lysine) conjugate induces protein synthesis inhibition and characteristic ribosomal RNA cleavages for longer times than unmodified (2'-5')(A)4-poly(L-lysine) in the same cell system.(ABSTRACT TRUNCATED AT 250 WORDS)

SAXS and BET studies of aging and densification of silica aerogels

Abstract: Aerogels prepared by hypercritical drying of gels obtained by hydrolysis of TMOS/methanol 50% solution in acid and basic conditions were studied combining SAXS and BET methods. Diffraction results do not seem to reveal a fractal character as the POROD's limit I(q) q4 → Cte was obtained in all cases without well characterised portions in log I(q) vs log q graphs. Aging produces a small increase in the density of the matrix. Densification studies indicate that for moderate temperatures 530°–810°C the poresshow a shrinkage due to a diffusion controlled mechanism with an activation energy ΔE ~ 9 Kcal/mole. For higher temperatures expansion due to bloating was observed. The density of the matrix undergoes only a slight increase.

Effects of coculture on the morphology of identified raphe and substantia nigra neurons from the embryonic rat brain

Abstract: The substantia nigra (SN) is one of the earliest targets of the 5-HT neurons of the raphe nuclei (RN) To test the hypothesis that embryonic 5-HT and catechol-amine neurons may influence the differentiation of their target cells or source neurons, we have produced dissociated cell cultures from embryonic day 14 (E14) rat rhombencephalon (containing the serotonergic RN) and mesencephalon (containing the dopaminergic substantia nigra, SN) These cells were grown for 6 days in vitro, either as single cultures (RN or SN) or cocultures (RN + SN) Effects of coculture on the morphological development of neurons immunoreactive (IR) for 5-HT or tyrosine hydroxylase (TH) were studied by measuring a series of morphological parameters related to size of the cell body and dendritic field, as well as to the complexity of neurites within this field, using computer-assisted morphometry Increases in a number of these parameters were found in cocultures compared to single cultures for both types of monoamine neurons, but a greater number of parameters were increased for TH-IR cells, including size of the cell body Although this might suggest that there was a greater effect of coculture on the TH-IR (dopaminergic) cells of the SN than on the 5-HT-IR cells of the RN, we must consider the fact that a significant population of TH-IR cells were present in single RN cultures, which contributed to the total population of TH-IR cells in cocultures Indeed, when morphometric parameters for TH-IR cells in RN and SN single cultures were compared, it was found that TH-IR cells from the RN were generally larger and more complex than those from the SN Therefore, an analysis was made of which parameters were significantly increased for TH-IR cells in cocultures compared to single cultures from both SN and RN This was the case for two parameters: cell body size and absolute field area, indicating that these increases were probably due to the effects of coculture itself rather than to contamination by the larger and more complex TH-IR cells from the RN It is impossible to ascertain, however, whether this effect was on cells from the RN, SN, or both Coculture effects on 5-HT-IR cells were easier to analyze, since no such cells were found in single cultures of SN Three parameters were consistently increased for 5-HT-IR cells in coculture: cumulative length of all segments, segment length density, and absolute field area This indicates that 5-HT-IR cells in coculture had larger dendritic fields that contained a more complex array of neurites than their counterparts in single cultures In sum, coculture seems to promote the growth of both 5-HT and TH-IR neurons, but in different ways and to different degrees These results suggest that some factor or factors related to growth of these monoamine neurons are altered when the rhombencephalon and mesencephalon are cultured together The exact nature of this developmental signal remains to be determined

Fractal properties of gels

Abstract: After defining the basic concepts of fractal geometry, the different methods of resolution analysis used in practice to determine fractal parameters : X-ray scattering, adsorption and electronic energy transfers are briefly presented. The results obtained for silica gels are reviewed and the difficulties of interpretation discussed.

Antigenic probes locate a serum-gelsolin-interaction site on the C-terminal part of actin.

Abstract: The implication of part of the C-terminal of actin (within the 285-375 sequence) in the interaction of serum gelsolin was investigated by the use of specific antibodies. These antibodies were directed against two or three discrete epitopes, one of which was specific for skeletal-muscle actin. Some of these epitopes were found to be near the serum gelsolin-actin interface. Thus it can be assumed that part of the C-terminal of actin is exposed at the barbed end of the actin filament. The interaction between tropomyosin and actin was also studied.