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131.
Synopsis The ability of embryos of the viviparous scorpaenidSebastes melanops to take up nutrients from an exogenous substrate was demonstrated by incubating embryos at various stages of development
(18–30 days after fertilization) in14C-labeled glycine for 24 h. Uptake was highest for embryos at the latest stages (28–30 days) and increased at a linear rate
during the incubation period. Nutrient uptake was not time dependent in embryos at the early stages (18–22 days). Nutrient
utilization byS. melanops embryos was measured by the oxidation of14C-labeled glycine to14CO2. The amount of respired14CO2 by the oldest embryos increased significantly at a linear rate over the 24 h incubation period. There was no evidence of
nutrient utilization by the youngest embryos. The developmental changes we observed in the uptake and utilization of exogenous
glycine are supported by our previous findings that the oldest embryos have fully developed mouths and guts, and require additional
nutrition from intraovarian sources at this stage of development. 相似文献
132.
133.
Csaba Vadsz George Kobor Pter Kabai Istvn Szirki Ilona Vadsz Abel Lajtha 《Hormones and behavior》1988,22(4):528-539
Sex and strain differences in tyrosine hydroxylase activity (TH) of brain dopamine systems have been reported for mice. To investigate if there might be a causal relationship between perinatal androgen secretion and regional mesotelencephalic TH activity, BALB/cJ and C57BL/6ByJ male mice were treated perinatally with cyproterone, a steroidal anti-androgen (or vehicle), and orchiectomized at 1 month of age. Two-way analysis of variance indicated significant treatment and strain effects in the mesencephalon and tuber olfactorium: perinatal cyproterone treatment lowered TH activity, and BALB/cJ had higher regional TH activities than those of C57BL/6ByJ. The most prominent behavioral effects of cyproterone treatment were found in the expression of scratching, which was considerably increased in both strains. Possible implications of these results are discussed. 相似文献
134.
135.
Characterization of sodium transport in Acholeplasma laidlawii B cells and in lipid vesicles containing purified A. laidlawii (Na+-Mg2+)-ATPase by using nuclear magnetic resonance spectroscopy and 22Na tracer techniques. 下载免费PDF全文
S Mahajan R N Lewis R George B D Sykes R N McElhaney 《Journal of bacteriology》1988,170(12):5739-5746
The active transport of sodium ions in live Acholeplasma laidlawii B cells and in lipid vesicles containing the (Na+-Mg2+)-ATPase from the plasma membrane of this microorganism was studied by 23Na nuclear magnetic resonance spectroscopic and 22Na tracer techniques, respectively. In live A. laidlawii B cells, the transport of sodium was an active process in which metabolic energy was harnessed for the extrusion of sodium ions against a concentration gradient. The process was inhibited by low temperatures and by the formation of gel state lipid in the plasma membrane of this organism. In reconstituted proteoliposomes containing the purified (Na+-Mg2+)-ATPase, the hydrolysis of ATP was accompanied by the transport of sodium ions into the lipid vesicles, and the transport process was impaired by reagents known to inhibit ATPase activity. At the normal growth temperature (37 degrees C), this transport process required a maximum of 1 mol of ATP per mol of sodium ion transported. Together, these results provide direct experimental evidence that the (Na+-Mg2+)-ATPase of the Acholeplasma laidlawii B membrane is the cation pump which maintains the low levels of intracellular sodium characteristic of this microorganism. 相似文献
136.
A new marine bacterium that digested a variety of storage and structural polysaccharides, including agar, was isolated. Strain 2-40 is a nonfermentative gram-negative, polarly flagellated rod that sometimes grew as a filamentous helix and secreted a melaninlike pigment. Its characteristics conform to those of no previously described species. 相似文献
137.
Rates of oxidation of Mn(II) were measured by an in situ incubation technique in the water column of Toolik Lake, Alaska. Measured rates were lower than those observed in other aquatic systems but were sufficient to oxidize all Mn(II) in the lake within a 3-month period. Measured rates compared favorably with rates estimated from a previous study of the geochemical cycling of Mn in Toolik Lake. The Mn(II) oxidation was largely microbially mediated, as indicated by inhibition of oxidation rates by sodium azide. Azide had been previously demonstrated to be a suitable microbial poison for studying Mn(II) oxidation in seawater. This study demonstrates that azide is also a suitable poison for freshwaters and that it inhibits microbial but not abiotic oxidation of Mn(II). Manganese(II) oxidation rates were similar during cold, under-ice conditions in early spring and during warmer summer conditions. This observation suggests that Mn(II) concentration, rather than temperature or oxygen concentration, is the most important factor regulating Mn(II) oxidation rates in Toolik Lake. 相似文献
138.
(Z)-4-Amino-2-fluorobut-2-enoic acid (1) is shown to be a mechanism-based inactivator of pig brain gamma-aminobutyric acid aminotransferase. Approximately 750 inactivator molecules are consumed prior to complete enzyme inactivation. Concurrent with enzyme inactivation is the release of 708 +/- 79 fluoride ions; transamination occurs 737 +/- 15 times per inactivation event. Inactivation of [3H]pyridoxal 5'-phosphate ([3H]PLP) reconstituted GABA aminotransferase by 1 followed by denaturation releases [3H]PMP with no radioactivity remaining attached to the protein. A similar experiment carried out with 4-amino-5-fluoropent-2-enoic acid [Silverman, R. B., Invergo, B. J., & Mathew, J. (1986) J. Med. Chem. 29, 1840-1846] as the inactivator produces no [3H]PMP; rather, another radioactive species is released. These results support an inactivation mechanism for 1 that involves normal catalytic isomerization followed by active site nucleophilic attack on the activated Michael acceptor. A general hypothesis for predicting the inactivation mechanism (Michael addition vs enamine addition) of GABA aminotransferase inactivators is proposed. 相似文献
139.
The human genetic material is packed hierarchically within the metaphase chromosome: the DNA moleculet together with histone proteins form 11 nm diameter nucleosomes, which are then ordered into the 30 nm thick chromatin fiber. Little is known about the packing of this fiber within the chromosome. We have developed a tracking algorithm with which we followed its path within a three-dimensional reconstruction of a human chromosome computed from a series of electron micrographie projections. Fiber segments were seen to form loops of 100–350 nm diameter. Our observations indicate that these loops — which themselves show no preferred orientation — are organised into regions of roughly 200 nm axial extent. 相似文献
140.
George M. Diggs 《Brittonia》1986,38(4):344-351
Comarostaphylis spinulosa subsp.glandulifera is described from the mountains of Oaxaca and Puebla, Mexico. Four new combinations inComarostaphylis are also made:C. arbutoides subsp.costaricensis, C. discolor subsp.rupestris, C. polifolia subsp.minor, andC. spinulosa.Arctostaphylos glabrata, A. rupestris, andA. spinulosa are lectotypified and the status ofC. polifolia is discussed. 相似文献