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961.
962.
963.
The seminal receptacle or spermatheca of Portunus sanguinolentus consists of two parts--an anterior glandular and a posterior chitinous part. The chitinous part continues as the oviduct, which opens on the sternite of the sixth thoracic segment. Significant morphological and histological differences were observed between the spermatheca, as well as the oviduct, of mated and unmated crabs. In mated crabs the spermatheca is much more bulging, owing to receipt of a copious supply of seminal products, and its cells are hyperactive. Further stages of ovarian development were observed as indicators of sequential changes in the spermatheca. The secretory cells gradually disintegrate by way of holocrine secretion; this results in cellular stratification and the formation of distinct furrows in the chitinous posterior part. 相似文献
964.
965.
H Zitzer H H H?nck D B?chner D Richter H J Kreienkamp 《The Journal of biological chemistry》1999,274(46):32997-33001
By using the yeast two-hybrid system we identified a novel protein from the human brain interacting with the C terminus of somatostatin receptor subtype 2. This protein termed somatostatin receptor interacting protein is characterized by a novel domain structure, consisting of six N-terminal ankyrin repeats followed by SH3 and PDZ domains, several proline-rich regions, and a C-terminal sterile alpha motif. It consists of 2185 amino acid residues encoded by a 9-kilobase pair mRNA; several splice variants have been detected in human and rat cDNA libraries. Sequence comparison suggests that the novel multidomain protein, together with cortactin-binding protein, forms a family of cytoskeletal anchoring proteins. Fractionation of rat brain membranes indicated that somatostatin receptor interacting protein is enriched in the postsynaptic density fraction. The interaction of somatostatin receptor subtype 2 with its interacting protein was verified by overlay assays and coimmunoprecipitation experiments from transfected human embryonic kidney cells. Somatostatin receptor subtype 2 and the interacting protein display a striking overlap of their expression patterns in the rat brain. Interestingly, in the hippocampus the mRNA for somatostatin receptor interacting protein was not confined to the cell bodies but was also observed in the molecular layer, suggesting a dendritic localization of this mRNA. 相似文献
966.
Jürgen Sühnel 《Bulletin of mathematical biology》1998,60(2):197-213
A possible experimental design for combination experiments is to compare the doseresponse curve of a single agent with the
corresponding curve of the same agent using either a fixed amount of a second one or a fixed dose ratio. No interaction is
then often defined by a parallel shift of these curves. We have performed a systematic study for various types of doseresponse
relations both for the dose-additivity (Loewe additivity) and for the independence (Bliss independence) criteria for defining
zero interaction. Parallelism between doseresponse curves of a single agent and those of the same agent in the presence of
a fixed amount of another one is found for the Loewe-additivity criterion for linear doseresponse relations. For nonlinear
relations, one has to differentiate between effect parallelism (parallel shift on the effect scale) and dose parallelism (parallel
shift on the dose scale). In the case of Loewe additivity, zero-interaction dose parallelism is found for power, Weibull,
median-effect and logistic doseresponse relations, given that special parameter relationships are fulfilled. The mechanistic
model of competitive interaction exhibits dose parallelism but not effect parallelism for Loewe additivity. Bliss independence
and Loewe additivity lead to identical results for exponential doseresponse curves. This is the only case for which dose parallelism
was found for Bliss independence. Parallelism between single-agent doseresponse relations and Loewe additivity mixture relations
is found for examples with a fixed doseratio design. However, this is again not a general property of the design adopted but
holds only if special conditions are fulfilled. The comparison of combination doseresponse curves with single-agent relations
has to be performed taking into account both potency and shape parameters. The results of this analysis lead to the conclusion
that parallelism between zero interaction combination and single-agent doseresponse relations is found only for special cases
and cannot be used as a general criterion for defining zero-interaction in combined-action assessment even if the correct
potency shift is taken into account. 相似文献
967.
V T Kondakov A B Okulov M A Filippkin R Z Tandilava I U Artamonov O A Voronenko A N Sazonov 《Vestnik rentgenologii i radiologii》1991,(4):31-35
The paper is concerned with analysis of the results of intraoperative phlebotesticulography, performed in 50 patients with varicocele of degree I-II during Ivanissevich's operation. The effect of surgical intervention was shown to depend upon the quality of ligation of the testicular vein, some parts of which are anastomosed between themselves. The localization of this anastomosis is revealed by means of intraoperative phlebotesticulography, which permits increasing the results of surgical treatment and predicting a course of a postoperative period. 相似文献
968.
Dietary restriction causes chronic elevation of corticosterone and enhances stress response in red-legged kittiwake chicks 总被引:12,自引:0,他引:12
Alexander S. Kitaysky Evgenia V. Kitaiskaia John C. Wingfield John F. Piatt 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2001,171(8):701-709
Release of corticosterone in hungry kittiwake chicks facilitates begging and allows them to restore depleted energy reserves by increasing parental food provisioning. However, in order to avoid detrimental effects of chronic elevation of corticosterone, chicks might suppress adrenocortical activity in response to prolonged food shortages. In this study we examined temporal dynamics of corticosterone release in red-legged kittiwake (Rissa brevirostris) chicks exposed to prolonged restrictions in energy content and/or nutritional quality (low versus high lipid content) of their food. Starting at the age of 15 days, chicks were fed either high- or low-lipid fish at 40%, 65%, and 100% of ad libitum energy intake. Body mass measurements and baseline plasma samples were taken on a weekly basis after beginning of the treatment. After 3 weeks of treatment, chicks were exposed to a standardized acute handling and restraint stress protocol, where in addition to a baseline sample, three plasma samples were taken at intervals up to 50 min. We found that food-restricted chicks had lower body mass, chronically (during 2-3 weeks) elevated baseline and higher acute stress-induced levels of corticosterone compared to chicks fed ad libitum. Low lipid content of food further exacerbated these effects. An increase in baseline levels of corticosterone was observed within a week after energy requirements of food-restricted chicks exceeded their daily energy intake. A tendency for suppression of adrenocortical activity was observed in treatments fed low-lipid diets only at the end of the experiment. We suggest that nest-bound chicks, if food-stressed, might suffer deleterious effects of chronic elevation of corticosterone. 相似文献
969.
Toxicity of Dopamine to Striatal Neurons In Vitro and Potentiation of Cell Death by a Mitochondrial Inhibitor 总被引:8,自引:2,他引:6
B. A. McLaughlin †D. Nelson †‡M. Ereciska † M.-F. Chesselet 《Journal of neurochemistry》1998,70(6):2406-2415
Abstract: Intrastriatal injections of the mitochondrial toxins malonate and 3-nitropropionic acid produce selective cell death similar to that seen in transient ischemia and Huntington's disease. The extent of cell death can be attenuated by pharmacological or surgical blockade of cortical glutamatergic input. It is not known, however, if dopamine contributes to toxicity caused by inhibition of mitochondrial function. Exposure of primary striatal cultures to dopamine resulted in dose-dependent death of neurons. Addition of medium supplement containing free radical scavengers and antioxidants decreased neuronal loss. At high concentrations of the amine, cell death was predominantly apoptotic. Methyl malonate was used to inhibit activity of the mitochondrial respiratory chain. Neither methyl malonate (50 µ M ) nor dopamine (2.5 µ M ) caused significant toxicity when added individually to cultures, whereas simultaneous addition of both compounds killed 60% of neurons. Addition of antioxidants and free radical scavengers to the incubation medium prevented this cell death. Dopamine (up to 250 µ M ) did not alter the ATP/ADP ratio after a 6-h incubation. Methyl malonate, at 500 µ M , reduced the ATP/ADP ratio by ∼30% after 6 h; this decrease was not augmented by coincubation with 25 µ M dopamine. Our results suggest that dopamine causes primarily apoptotic death of striatal neurons in culture without damaging cells by an early adverse action on oxidative phosphorylation. However, when combined with minimal inhibition of mitochondrial function, dopamine neurotoxicity is markedly enhanced. 相似文献
970.