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131.
Morphology and morphodynamics of the stenotele nematocyst of Hydra attenuata Pall. (Hydrozoa,Cnidaria) 总被引:1,自引:0,他引:1
This light- and electron-microscopic study has investigated the structure, the morphodynamics of discharge, and the impact of the stenotele cyst of Hydra attenuata (Hydrozoa, Cnidaria) on the prey's integument. The triggered capsule, which is ejected from the cell, discharges its tubular content (shaft, stylets and tubule) by a process of evagination. In doing so the three joined stylets punch a hole into the cuticle of the prey through which the long evaginating tubule penetrates into the interior of the target. The behaviour of the tubule is described in detail and the functional significances of the various parts of the capsule are discussed. 相似文献
132.
Summary In a previous article (Demos et al. 1981), we reported a significant and specific reduction of the activity index (AI) of the diphenoloxidases (DPox) in patients and heterozygotes with progressive Duchenne muscular dystrophy (DMD), which is transmitted genetically by female subjects by a sex-linked recessive mechanism (SLR). This same anomaly was detected in patients suffering from other types of dystrophy: Becker, limbgirdle, fascio-scapulo-humeral, and in heterozygotes, of either sex in diseases transmitted by an obviously recessive autosomic mechanism. These anomalies were detected using blood spots collected on absorbent paper and stored at 4°C for differnt periods. They were of the same type as had previously been detected using blood platelets (Demos 1973). 相似文献
133.
A colorimetric method is described which can be used for the routine determination of primary and secondary N-hydroxylamino compounds in drug metabolism studies using microsomal preparations. The assay is carried out on the supernatant obtained after protein precipitation of the incubation mixture. The method is based on the reduction of ferric ion by the hydroxylamino moiety with the resulting ferrous ion being quantitated by coupling with 2,4,6-tripyridyl-s-triazine to form a purple color with a maximum absorbance at 595 nm. The method is specific to primary and secondary hydroxylamino compounds and calibration curves can be obtained in the range of concentrations of 1 to 20 μg/ml. Hydroxamic acid, amido, amino, phenolic, nitro, nitroso, oxime, nitrone, aldehyde, and ketone compounds do not produce any color reaction when analyzed by the same method. The method is simple, rapid, and many samples can be analyzed in a short period of time. 相似文献
134.
(1) Incubation of the beef heart mitochondrial ATPase, F1 with Mg-ATP was required for the binding of the natural inhibitor, IF1, to F1 to form the inactive F1-IF1 complex. When F1 was incubated in the presence of [14C]ATP and MgCl2, about 2 mol 14C-labeled adenine nucleotides were found to bind per mol of F1; the bound 14C-labeled nucleotides consisted of [14C]ADP arising from [14C]ATP hydrolysis and [14C]ATP. The 14C-labeled nucleotide binding was not prevented by IF1. These data are in agreement with the idea that the formation of the F1-IF1 complex requires an appropriate conformation of F1. (2) The 14C-labeled adenine nucleotides bound to F1 following preincubation of F1 with Mg-[14C]ATP could be exchanged with added [3H]ADP or [3H]ATP. No exchange occurred between added [3H]ADP or [3H]ATP and the 14C-labeled adenine nucleotides bound to the F1-IF1 complex. These data suggest that the conformation of F1 in the isolated F1-IF1 complex is further modified in such a way that the bound 14C-labeled nucleotides are no longer available for exchange. (3) 32Pi was able to bind to isolated F1 with a stoichiometry of about 1 mol of Pi per mol of F1 (Penefsky, H.S. (1977) J. Biol. Chem. 252, 2891–2899). There was no binding of 32Pi to the F1-IF1 complex. Thus, not only the nucleotides sites, but also the Pi site, are masked from interaction with external ligands in the isolated F1-IF1 complex. 相似文献
135.
136.
Summary Following the observation of a close sequence homology between the N-terminal moiety of the -chain of fibrinogen with large parts of-casein, the occurrence of a keratin domain in the middle section of the Achain is suggested. 相似文献
137.
The Quaternary Structure of Chicken Acetylcholinesterase and Butyrylcholinesterase; Effect of Collagenase and Trypsin 总被引:8,自引:4,他引:4
Acetylcholinesterase (EC 3.1.1.7.; AChE) and butyrylcholinesterase (EC 3.1.1.8.; BuChE) from chicken muscle exist as sets of structurally homologous forms with very similar properties. The collagenase sensitivity and aggregation properties of the 'heavy' forms of both enzymes indicate that they possess a collagen-like tail, and their stepwise dissociation by trypsin confirms that they correspond to triple (A12) and double (A8) collagen-tailed tetramers. In addition to this dissociating effect, trypsin digests an important fraction of the catalytic units of AChE, in a progressive manner, removing as much as 30% of the enzyme's mass, without inactivation of the tetramers and of the tailed molecules. The trypsin-modified AChE forms closely resemble the corresponding mammalian AChE forms in their hydrodynamic properties. It is not known whether the trypsin-digestible peptides, which do not appear to be involved in the ionic or hydrophobic interactions of the enzymes, are a fragment of the catalytic subunit or whether they constitute distinct polypeptides. 相似文献
138.
Glial fibrillary acidic (GFA) protein has been synthesized in an RNA-dependent cell-free system derived from rabbit reticulocytes. The cell-free synthesized product appears to have the same size as GFA protein isolated from bovine spinal cord, thus showing that GFA protein does not undergo detectable proteolytic processing. 相似文献
139.
Elementary chemical composition in carbon, hydrogen and nitrogenof the Pontellid Copepod Pontella mediterranea was studied on148 males and 146 females from automnal populations of the gulfof Marseilles, which are the last annual generations. Data arecompared to those obtained from spring and summer. The increasein animal weight from the last generations is greater in femalesthan males. The dry weight ratio of females against males is1.6 while it is only 1.4 in the previous generations. At theend of the natural biological cycle, C:N ratio shows a lightbut significant difference between males and females. The valuesof C:N ratio remain close to 3.4, which means that the observedincrease of animal weight on the last generations mainly proceedsfrom an increase in protein compounds. 相似文献
140.
[14C]-assimilation rates were measured on cultures of two unicellulargreen algae (Chlamydomonas sp. and Oocystis sp.) as a functionof light intensities (saturation curves), under steady lightand also under rapidly alternating high and low light intensities.Assimilation rates vary according to the frequency of the intermittentlight regime and it falls under two categories: (1) at 0.1 and0.2 Hz, the assimilation rate is equal to the average of therates observed at high and low light intensities under steadylight, and (2) under 1.0, 1.6 and 10 Hz the assimilation rateis equal to the rate observed under a mean steady irradiance.Moreover, the range of assimilation rates at a given frequencydepends on the difference between the high and the low intensities.Batch cultures of Oocystis sp. have been grown under intermittentlight of 0.1, 1.0 and 10.0 Hz (same mean intensity). Growthrate under intermittent light of 0.1 Hz is 40% lowerthan the control under steady light. Photosynthetic potential(PBmax)and efficiency () change with the growth stages of thecultures. At the end of the logarithmic growth phase, both photosyntheticparameters are maximum at 1.0 Hz and minimum at 0.1 Hz. Averagecell concentrations of chlorophyll a increase as the frequencyof the light regime decreases. During the log phase, concentrationof carotenoids relative to chlorophyll a increases at 1.0 Hz,decreases at 0.1 Hz, and remains constant at 10.0 Hz. Underclear sky conditions, wave-induced light fluctuations in thephotic layer may therefore enhance primary production, especially(1) in the lower part of the photic layer, where low frequencylight changes might cause cell chlorophyll a to increase, and(2) at a depth of 14 m, where the main frequencies (ofthe order of 1.0 Hz), might cause a significant increase ofboth the photosynthetic potential (PBmax)and efficiency ().
1Contribution au programme du GIROQ (Groupe interuniversitairede recherches océanographiques du Québec)
2Adresse actuelle: Centre de recherches en nutrition, UniversitéLaval, Québec, Qué. G1K 7P4, Canada 相似文献