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1.
Sodium azide, a classical inhibitor of cytochrome oxidase, is an effective inhibitor of gastric acid secretion in bullfrog and skate gastric mucosae at low concentrations. While a portion of the oxygen uptake in these tissues is sensitive to azide (KI less than 2 mM), there remains a large fraction (25-60%) with a KI more than 10 times this value, suggesting the presence of a second oxidase. The spectra of cytochromes c and b change with oxygen-nitrogen alternation in the presence of high azide concentrations which essentially eliminate the reactivity of cytochrome oxidase. In both species two additional components are observed in the spectra. The first has a peak at 590 nm, is not the cytochrome oxidase-CO complex, is fully reactive in the presence of azide and accounts for the asymmetry of the oxidase peak. The second is a component at 557 nm which can only be separated from cytochromes c and b by spectral deconvolution, and seems to react in a manner similar to cytochrome c. It is suggested that the 590 compound may be the alternate cytochrome oxidase. 相似文献
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Gerald M. Kidder Douglas J. Barron Joanna B. Olmsted 《Development genes and evolution》1988,197(2):110-114
Summary We have examined the persistence of midbody channels during the second, third, and fourth cleavage cycles of the mouse using immunofluorescence to map the distribution of midbody microtubule bundles in intact embryos. Electron microscopy showed these bundles to be a characteristic feature of midbodies throughout the interphase period. In recently-divided embryos at each cleavage stage the number of midbodies was half the number of blastomeres, and declined towards zero as the next cleavage approached. This indicated to us that the only midbodies present in each stage were those which had arisen in the immediately-preceding division. Of those blastomeres which were in mitosis at the time of fixation, less than 4% were connected via a midbody to another blastomere, demonstrating that persistence of midbodies beyond a single cleavage cycle is a rare event. We conclude that midbody channels in our embryos are likely to connect only pairs of sister blastomeres because midbodies do not persist through multiple cleavage cycles. Midbody channels cannot, therefore, be regarded as providing extensive cell coupling in advance of the onset of gap junctional communication. 相似文献
4.
The molecular evolution of mammalian Y-linked DNA sequences is of special
interest because of their unique mode of inheritance: most Y- linked
sequences are clonally inherited from father to son. Here we investigate
the use of Y-linked sequences for phylogenetic inference. We describe a
comparative analysis of a 515-bp region from the male sex- determining
locus, Sry, in 22 murine rodents (subfamily Murinae, family Muridae),
including representatives from nine species of Mus, and from two additional
murine genera--Mastomys and Hylomyscus. Percent sequence divergence was
< 0.01% for comparisons between populations within a species and was
0.19%-8.16% for comparisons between species. Our phylogenetic analysis of
12 murine taxa resulted in a single most- parsimonius tree that is highly
concordant with phylogenies based on mitochondrial DNA and allozymes. A
total evidence tree based on the combined data from Sry, mitochondrial DNA,
and allozymes supports (1) the monophyly of the subgenus Mus, (2) its
division into a Palearctic group (M. musculus, M. domesticus, M.
spicilegus, M. Macedonicus, and M. spretus) and an Oriental group (M.
cookii++, M. cervicolor, and M. caroli), and (3) sister-group relationships
between M. spicilegus and M. macedonicus and between M. cookii and M.
cervicolor. We argue that Y- chromosome DNA sequences represent a valuable
new source of characters for phylogenetic inference.
相似文献
5.
G.W. Kidder Virginia C. Dewey Linda L. Nolan 《Archives of biochemistry and biophysics》1977,183(1):7-12
Adenine deaminase (adenine aminohydrolase, EC 3.5.4.2) has been found to occur in Crithidia fasciculata with a specific activity higher than that of the same enzymes of bacteria and yeasts. It is remarkable for its stability to heat, exhibiting no appreciable loss of activity after 60 min at 55 °C. It occurs in the soluble portion of cell extracts but can be released into the suspending medium by osmotic and/or cold shock. 相似文献
6.
The acrosomic status of spermatozoa prepared for IVF has been evaluated by means of immunofluorescence test from Fenichel and Hsi using calcium A 23187 ionophore as inductor of acrosome reaction (AR). The spontaneous AR remains slight, even after 6 hour-incubation in Menezo B2 (6,8+2,7%). The response to ionophore, moderate before (11,2+9%), frankly increases after a 6h-capacitation (28,9+8,3%) in a group of 25 IVF couples (tubal indication, normal semen, positive fertilization). Nevertheless, it remains slight or null in 4 cases of unexplained repeated failure of fertilization. The response to ionophore A 23187 allows to explore the kinetics of capacitation of spermatozoa and their ability to perform AR. Its significance in terms of fecondance remains to be precised. 相似文献
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FLORIAN MENZEL MICHAEL STAAB ARTHUR Y. C. CHUNG GERHARD GEBAUER NICO BLÜTHGEN 《Austral ecology》2012,37(5):537-546
Organisms associated with another species may experience both costs and benefits from their partner. One of these costs is competition, which is the more likely if the two species are ecologically similar. Parabioses are associations between two ant species that share a nest and often attend the same food sources. Albeit parabioses are probably mutualistic, parabiotic partners may compete for food. We therefore investigated feeding niches and dietary overlap of two parabiotically associated ants in Borneo using cafeteria experiments and stable isotope analyses. The two species strongly differed in their food choices. While Crematogaster modiglianii mostly foraged at carbohydrate‐rich baits, Camponotus rufifemur preferred urea‐rich sources. Both species also consumed animal protein. The 15N concentration in Ca. rufifemur workers was consistently lower than in Cr. modiglianii. Camponotus rufifemur but not Cr. modiglianii possesses microbial endosymbionts, which can metabolize urea and synthesize essential amino acids. Its lower 15N signature may result from a relatively higher intake of plant‐based or otherwise 15N‐depleted nitrogen. Isotopic signatures of the two partners in the same parabiosis showed strongly parallel variation across nests. As we did not find evidence for spatial autocorrelation, this correlation suggests an overlap of food sources between the two ant species. Based on model simulations, we estimated a diet overlap of 22–66% for nitrogen sources and 45–74% for carbon sources. The overlap may arise from either joint exploitation of the same food sources or trophallactic exchange of food. This suggests an intense trophic interaction and potential for competition between the parabiotic partners. 相似文献