Evolution des cellules gonadotropes préhypophysaires au cours du cycle oestral chez la ratte

Résumé L'évolution des cellules gonadotropes préhypophysaires ß et a été étudiée au cours de cycles de 4 jours chez la ratte.Ces 2 catégories cellulaires subissent au cours du cycle ovarien des variations morphologiques et numériques qui paraissent témoigner d'une activité folliculostimulante pour les cellules ß et d'une activité ovulatoire pour les cellules .Les cellules ß se dégranulent une l^ère fois pendant la nuit du dioestrus II au prooestrus, puis une 2^e fois, lors de la phase préovulatoire, l'après-midi du prooestrus.Les cellules présentent, au cours de l'après-midi du prooestrus, une dégranulation massive, qui peut etre mise en rapport avec la décharge de L. H. qui se produit à ce stade du cycle.La l^ère dégranulation des cellules ß en dioestrus II correspondrait à la vague de croissance folliculaire qui, selon Long et Evans, a lieu à ce stade du cycle et mènerait certains follicules à la rupture. La seconde traduirait une décharge de FSH synergique de l'excrétion de L. H. par les cellules , pendant la phase préovulatoire du cycle ovarien.

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Summary Morphological and numerical variations of the pituitary gonadotrophs ß and were studied during 4 days cycles at different stages of the oestrous cycle in the Rat.The highest degree of degranulation of the ß cells was observed first during the night of dioestrous II to prooestrous and afterwards on the afternon of prooestrous.The degranulation of the cells began in the morning of prooestrous and reached its higher degree at 4 p. m. in prooestrous.The first peak of degranulation of the ß cells was supposed to be related to the wave of follicular growth which occurs on the day of dioestrous II according to Long and Evans. The second phase of degranulation of these cells was considered as a prooestrous diurnal discharge of FSH synergically with the ovulatory discharge of LH by the cells during the critical period of the cycle.

     

INCORPORATION OF TRITIATED THYMIDINE IN THE CELLS OF CAENORHABDITIS BRIGGSAE (NEMATODA) REARED IN AXENIC CULTURE

In the rhabditid nematode Caenorhabditis briggsae the incorporation of thymidine-H³ has been studied by autoradiography after Feulgen staining, with animals maintained under axenic conditions in a medium of only partly defined composition. Labeling has been followed in adults left in the presence of thymidine-H³ for periods of from ½ to 24 hours, as well as in adults reared from larvae in the presence of the tritiated nucleoside. A massive incorporation is found in the nuclei of the gonads and intestine; also a less intense particulate cytoplasmic incorporation is clear in certain cells, especially those of the intestine. In general, all labeling has proved to be sensitive to DNase, but resistant to RNase. The label's stability has been tested by the transfer of adults into a medium containing "cold" thymidine. They remain there for up to 48 hours. A transfer for 24 hours results in a considerable decrease in the intensity of nuclear and cytoplasmic labeling; a stay of 48 hours leads to its complete disappearance from non-dividing (intestinal) as well as dividing (gonadal) nuclei. A phenomenon of DNA turnover is envisaged and discussed as a possible physiological attribute of C. briggsae.     

Bdellovibrios in Callinectus sapidus, the Blue Crab

Bdellovibrios were recovered from the gill tissue of all of 31 crabs sampled and from all samples of epibiota obtained from the ventral shell surface of 15 crabs. The results suggest that the blue crab is a reservoir for bdellovibrios. The association with crabs may be an important factor in the ecology of the bdellovibrios.     

Genes encoding the small subunit of RUBISCO belong to two highly conserved subfamilies in Nicotianeae

Summary The sequences of seven complementary DNAs or genes encoding the small subunit (SSU) of ribulose-1,5-bisphosphate carboxylase oxygenase (RUBISCO) in several Nicotianeae were examined. Two new SSU genes isolated fromNicotiana sylvestris were included. Both sequence comparisons and Southern analyses with specific probes reveal that SSU genes fall into two homogeneous subfamilies that are highly conserved in Nicotianeae and are also present in other Solanaceae. Additional criteria such as number of introns and level of expression fitted to this classification. Homogeneity must have been maintained by gene conversion and/or an unusually high fidelity of DNA replication, whereas traces of slippage-stranded DNA mispairing and/or transposition probably explain local changes. Taken as a whole, these results show that the divergence between the two subfamilies predated the divergence between genera inside the Solanaceae, but that Nicotianeae retained the most simple SSU gene family structure.     

Declines in sociosexual behavior in golden monkeys (Rhinopithecus roxellana): Associated environmental and social variables

Between February 22 and August 10, 1986, 200 h of systematic observation were conducted on a male and female golden monkey (Rhinopithecus roxellana) at Seattle's Woodland Park Zoo and Portland's Washington Park Zoo. The pair was moved to Portland on May 6, and on July 24 the female unexpectedly gave birth to a male infant, the first such birth in the United States. Dramatic behavioral changes occurred immediately after the pair was moved to Portland, the midpoint of the female's pregnancy, including the disappearance of sexual behavior and a sharp decline in time spent in contact. Explanations for these changes are discussed.     

Chiral linear hydroxamates as biomimetic analogues of ferrioxamine and coprogen and their use in probing siderophore-receptor specificity in bacteria and fungi

Summary Linear hydroxamate derivatives, possessing chiral -amino acid moieties, were synthesized and their iron transport activities were studied in bacteria and fungi. No growth-promoting activity could be detected in the Gram-positive hydroxamate-auxotrophAureobacterium flavescens JG9. However, Gram-negative enterobacteria, such asEscherichia coli, Pantoea agglomerans andHafnia alvei were able to utilize iron from these analogues. Uptake of⁵⁵Fe-labeled analogues was inhibited by sodium azide, suggesting an active transport process. The receptors involved during uptake in enterobacteria were identified by using appropriate indicator organisms which are defective in the transport of either ferrioxamines (P. agglomerans FM13), coprogens (H. alvei), or both of these siderophore classes (E. coli fhuE). Our data suggest that the chiral hydroxamates are recognized by the ferrioxamine receptor (FoxA) and the coprogen receptor (FhuE) at a ratio which depends on the optical/ isomer fraction and the nature of side chains. Transport was also observed in the fungusNeurospora crassa, known to take up coprogen rather than ferrioxamines, suggesting that in this fungus the synthetic analogues behave like coprogen.     

Changes in calmodulin level after fertilization and during first cleavage in the egg of the urodelan amphibian Pleurodeles waltlii

We report three significant calmodulin rises related to Pleurodeles waltlii egg fertilization and following developmental events. These elevations are correlated to the major obvious Ca2+-dependent events: Na+-H+ exchange, activation of NAD kinase, triggering of cortical reaction, resumption of meiotic division II, initiation of DNA synthesis and regulation of cell division. Therefore, it is suggested that alterations in calmodulin level in fertilized egg may be part of the Ca2+-dependent regulatory mechanisms which turn on metabolisms, initiate development and govern cell cleavages.     

DNA Changes in Spinal Cords of Rats with Experimental Allergic Encephalomyelitis

DNA levels were measured in the spinal cords of Lewis rats during the development of and recovery from experimental allergic encephalomyelitis (EAE). Spinal cord DNA was first increased 11 days after immunizing the rats with guinea pig myelin and rose to levels four times that of the Freund's adjuvant controls at day 14, then subsided after day 22. Spinal cord DNA was still 150% of control levels 60 days after immunization. These DNA changes were compared with fluctuations in spinal cord acid proteinase in the same animals. Acid proteinase activity in EAE spinal cord increased later than the rise in DNA and attained a level of 170% of control at days 15-17, then subsided. Spinal cord DNA was higher in rats immunized with whole myelin than in those administered equivalent amounts of purified myelin basic protein. Furthermore DNA was higher in spinal cords of rats immunized with a larger dose of myelin (1.0 mg) than with a lower amount (0.5 mg). Various protease inhibitors including pepstatin, nitrophenyl p-guanidino benzoate, polylysine, and dipropionyl rhein, previously shown to protect Lewis rats against EAE, suppressed the increase of DNA in the spinal cord. Measurement of DNA increases in the spinal cord of EAE animals provides a convenient reproducible measurement of the severity of inflammation in the CNS and provides an objective criterion for assessment of the efficacy of various agents screened as possible therapeutic treatment for multiple sclerosis.     

The antagonism of bombesin in the CNS by substance P analogues

The ability of substance P analogues to inhibit the action of bombesin in the CNS was investigated using receptor binding and biological assays. The putative substance P antagonists inhibited binding to central receptors for both substance P and bombesin-like peptides. Spantide, which was the most potent analogue tested, reversed the bombesin induced hypothermia and grooming. Therefore the putative substance P antagonists may also antagonize the actions of bombesin in the CNS