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51.
Incubation of dejellied spawned oocytes from Bufo arenarum with different lectins results in a decrease of oocyte fertility. Concanavalin A was the most effective lectin; phytohem-agglutinin P and wheat germ lectin were less effective. Agglutinin from soybean was scarcely active. These lectin effects could be ascribed to a hindering of specific sites for some proteases, since the same treatment renders the oocyte vitelline envelope insensitive to spermatolysin (an essential requisite for fertilization) and to trypsin. Also in this case concanavalin A was the most effective lectin. Univalent concanavalin A was also effective in blocking the fertility of dejellied oocytes. These results indicate that the residues of α-D-glucose and α-D-mannose present in the vitelline envelope are involved in gamete interactions in Bufo arenarum. This idea is also supported by the finding that dejellied oocytes (fertilizables) have a number of binding sites for concanavalin A that is three or four orders of magnitude higher than coelomic or fertilized oocytes (both not penetrable by spermatozoa). 相似文献
52.
Isovolumetric and isobaric tracheal smooth muscle (TSM) contraction were studied in vitro in a preparation of the whole rabbit trachea. Eight tracheae from New Zealand White rabbits were excised and mounted at a fixed length in an organ bath. Electrical field stimulation (EFS) was performed in isovolumetric and isobaric conditions at varying transmural pressures (TMP). Supramaximal stimulation with methacholine was done at 0 TMP. Active change in pressure (delta P) with EFS showed a peak at 3.1 +/- 1.06 cmH2O TMP during inflation and at 4.1 +/- 1.18 cmH2O TMP during deflation (mean +/- SE). Active delta P decreased at higher or lower TMP. Active change in volume with EFS showed a peak at 3.2 +/- 1.26 cmH2O TMP during inflation and at 1.8 +/- 0.98 cmH2O TMP during deflation. A decrease in response was also observed at higher and lower TMP. From these data, we concluded that TSM is at optimal length (Lmax) at TMP of 2-3 cmH2O. Maximal TSM shortening with supramaximal stimulation with methacholine was 32% Lmax. This figure is considerably smaller than the 80% shortening found in unloaded strips of TSM. We conclude that rabbit TSM length is close to Lmax at TMP similar to those found at functional residual capacity and that the loads that the muscle has to overcome probably contribute to the limited shortening observed in situ. 相似文献
53.
James A. L.; Pare P. D.; Moreno R. H.; Hogg J. C. 《Journal of applied physiology》1987,63(4):1360-1365
Matched porcine tracheal rings were exposed to theophylline and increasing doses of carbachol in Krebs solution. Histological sections of each ring were traced and each of the following dimensions measured: the external perimeter (Pe) and external area (Ae) defined by the outer border of smooth muscle and inner surface of cartilage, and the internal perimeter (Pi) and internal area (Ai) defined by the luminal surface of the epithelium and the muscle length (L) along its outer border. Absolute wall area (WA = Ae - Ai) and relative wall area (PW = WA/Ae) were calculated. Carbachol-treated tracheal ring dimensions were compared with those of their matched theophylline-treated rings. In tracheal rings with intact cartilage, maximal smooth muscle shortening of 44% was achieved with 10(-2) M carbachol. In tracheal rings in which anterior and posterior segments of cartilage were excised, the trachealis muscle passively shortened by 20% and maximal shortening (10(-3) M carbachol) was 57%. Although Ai decreased with maximal smooth muscle shortening, there were no changes in the length of Pi or in WA. These data show that the cartilage in the porcine trachea exerts both a preload that passively stretches the trachealis muscle and an afterload that limits maximal smooth muscle shortening. 相似文献
54.
Production,by filamentous,nitrogen-fixing cyanobacteria,of a bacteriocin and of other antibiotics that kill related strains 总被引:7,自引:0,他引:7
Colonies of sixty-five filamentous cyanobacteria were screened for the production of temperate phages and/or antibiotics on solid medium. None of them was observed to release phages. However, seven N2-fixing strains were found to produce antibiotics very active against other cyanobacteria. The antibiotic produced by Nostoc sp. 78-11 A-E represents a bacteriocin of low molecular weight. Nostoc sp. ATCC 29132 appears to secrete, together with an antibiotic, a protein that inhibits its action. 相似文献
55.
Josep J. Centelles Rafael Franco Enrique I. Canela Jorge Bozal 《Neurochemical research》1986,11(4):471-479
Suspensions of rat brain microsomes, synaptosomes, and synaptic vesicles were able to convert adenosine to inosine by means of adenosine deaminase. Isosbestic points of this transformation, at 222, 250 and 281 nm, remained unchanged with time-course. This fact suggests that adenosine deaminase (ADA, E.C. 3.5.4.4) is located on the surface of the vesicles whereas purine nucleoside phosphorylase (PNP, E.C. 2.1.2.4) is located inside the vesicles. Kinetic parameters of the particulate 5-nucleotidase (5N, E.C. 3.1.3.5) and adenosine deaminase were analogous to those of the cytosolic enzymes. These results suggest that soluble and particulate enzymes represent different pools of the same molecular species. 相似文献
56.
The activity of guanine deaminase (GAH, E.C. 3.5.4.3) was lower in rat cerebellum soluble and microsomal fractions than in rat brain subfractions. Adenosine deaminase (ADA, E.C. 3.5.4.4) activity was released in higher proportion than guanine deaminase, purine nucleoside phosphorylase (PNP, E.C. 2.1.2.4), 5-nucleotidase (5N, E.C. 3.1.3.5), and lactate (LDH, E.C. 1.1.1.27) and malate (MDH, E.C. 1.1.1.37) dehydrogenase in press-juices of rat brain. Furthermore, nerve ending-derived fractions (synaptosomes and synaptic vesicles) showed an enrichment of adenosine deaminase and also of 5-nucleotidase. The action of deoxycholate over the subfractions did not increase the activity of either enzyme. The contrary occurred with the remaining enzymes studied. Thus, it is possible that one set of enzymes are located on the surface of the particulate vesicles, whereas another set are located inside these vesicles, suggesting a compartmentation of purine catabolic enzymes in different areas of the central nervous system. 相似文献
57.
C Castellano M Moreno L A Raggi E Martinez de Victoria F J Mataix 《Comp. Biochem. Physiol. C, Comp. Pharmacol. Toxicol.》1986,85(2):291-296
A study was made of basal secretion and the effect of the infusion of pilocarpine on the flow and composition of saliva in the parotid and mandibular glands of the anaesthetized lactating goat. In the parotid gland there was a basal flow (1.6 +/- 0.29 microliter/min) which was not present in the mandibular gland. There is a statistically significant dose-effect relationship between pilocarpine and salivary flow in both glands. Salival composition and its variation with respect to the flow of saliva did not conform to either of the two glands to an exclusive monogastric or ruminant model. 相似文献
58.
The rate of photosynthetic nitrate utilization in Anacystis nidulans is strongly influenced by the availability of carbon dioxide. This dependence can be relieved by inhibiting the metabolism of the ammonium derived from nitrate reduction. Nitrate uptake seems to be modulated through a sensitive regulatory system integrating the photosynthetic metabolism of carbon and nitrogen, with CO2 fixation products antagonizing the inhibitory effect of ammonium derivatives. 相似文献
59.
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