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1.
Betamethasone 17, 21-dipropionate (BMDP), a potent glucocorticoid, produces adrenal hypertrophy in the rat fetus. The present study was performed to investigate the possible alterations of corticosteroidogenesis due to endogeneous substrates or exogenous pregnenolone in the incubation of homogenates of fetal hypertrophic adrenals caused by BMDP given to pregnant rats at day 19 of pregnancy.The corticosteroidal products and those levels per mg homogenate in an incubate of the hypertrophic adrenal homogenate did not differ from those of a normal adrenal. No accumulations of abnormal precursors or intermediates were found in the incubates of the hypertrophic adrenals. It is concluded from these findings that no qualitative alterations in the pathway of corticosteroidogenesis occurred in the hypertrophic adrenal glands caused by BMDP in the rat fetus. When the calculation was done per adrenal gland, the content of corticosterone in the incubate of the homogenate of the hypertrophic adrenal was remarkably higher than that found in a normal gland. This finding was compatible with the significant increase of the plasma corticosterone concentration in the fetuses with the adrenal hypertrophy caused by BMDP. 相似文献
2.
Four semi-synthetic and fourteen quassinoids were tested for their antifeedant and insecticidal activity against 3rd instar larvae of the diamondback moth (Plutella xylostella). In this quassinoid series, isobrucein-B was the most potent compound in both assays. Chemical conversion of the methoxy and/or methylenedioxy groups in the A and C rings to hydroxy groups among these quassinoids resulted in decreased activity. 相似文献
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N Nakagata K Matsumoto M Anzai A Takahashi Y Takahashi Y Matsuzaki K Miyata 《Jikken dobutsu》1992,41(4):537-540
Spermatozoa of a homozygous transgenic mouse, in which the firefly luciferase gene was expressed under the control of beta-actin promoter, were frozen at -196 degrees C. One fourth of the frozen sperm was later thawed and used for in vitro fertilization. Thirty-six of 65 oocytes (55.4%) developed to the 2-cell stage. All the 2-cell embryos were transferred to the oviducts of pseudopregnant recipients and 23 young (63.9%, 23/36) were born. All of young analyzed carried the transgene and showed the luciferase gene expression. 相似文献
5.
Mycoplasmas exhibit a novel, substrate-dependent gliding motility that is driven by ∼400 “leg” proteins. The legs interact with the substrate and transmit the forces generated by an assembly of ATPase motors. The velocity of the cell increases linearly by nearly 10-fold over a narrow temperature range of 10-40°C. This corresponds to an Arrhenius factor that decreases from ∼45 kBT at 10°C to ∼10 kBT at 40°C. On the other hand, load-velocity curves at different temperatures extrapolate to nearly the same stall force, suggesting a temperature-insensitive force-generation mechanism near stall. In this article, we propose a leg-substrate interaction mechanism that explains the intriguing temperature sensitivity of this motility. The large Arrhenius factor at low temperature comes about from the addition of many smaller energy barriers arising from many substrate-binding sites at the distal end of the leg protein. The Arrhenius dependence attenuates at high temperature due to two factors: 1), the reduced effective multiplicity of energy barriers intrinsic to the multiple-site binding mechanism; and 2), the temperature-sensitive weakly facilitated leg release that curtails the power stroke. The model suggests an explanation for the similar steep, sub-Arrhenius temperature-velocity curves observed in many molecular motors, such as kinesin and myosin, wherein the temperature behavior is dominated not by the catalytic biochemistry, but by the motor-substrate interaction. 相似文献
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To determine a possible relationship between organismal and molecular
evolution, the divergence patterns of gene families were examined by taking
special notice of functional difference, tissue distribution, and
intracellular localization of the members. A phylogenetic analysis of 25
different gene families revealed interesting patterns of divergence of
these families: Most gene duplications giving rise to different functions
antedate the vertebrates-arthropods separation. On the other hand, in a
group of members carrying virtually identical function to one another but
differing in tissue distribution (tissue- specific isoform), most gene
duplications have occurred independently in each of vertebrates and
arthropods after the separation of the two animal groups. In family members
encoding molecules localizing in cell compartments (compartmentalized
isoforms), the gene duplications antedate the animals-fungi separation. In
the cases of the Ca2+ pump and rab subfamilies, the compartmentalized
isoforms were shown to have diverged during the early evolution of
eukaryotes. A phylogenetic analysis of the tissue-specific isoforms from 26
different subfamilies revealed extensive gene duplications and rapid rates
of amino acid substitutions in the early evolution of chordates before the
separation of fishes and tetrapods. On the contrary, the genetic variations
are relatively low in the later period. This pattern of evolution observed
at the molecular level is correlated well with that of tissue evolution
based on fossil evidence and morphological data, and thus evolution at the
two levels may be related.
相似文献
8.
Nucleotide sequences of the human X-linked red and green pigment genes were compared, and the number of silent substitutions per site (KSc) between these genes was analysed in comparison with the corresponding values of primate genes. Taking the retarded mutation rate of X-linked genes into consideration (Miyata et al., 1987), the red and green pigment genes were shown to have undergone gene conversion at around the time of separation of African apes and orangutan. Thus the recent gene conversion and retarded mutation rate in these X-linked genes are probably responsible for the strong sequence similarity between these genes, which is likely to facilitate the occurrence of red-green color blindness in the human population. It was also shown that the red pigment gene evolved about five times more rapidly than the green pigment gene since the latest gene conversion. 相似文献
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