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1.
2.
Ultrastructural changes of the midgut epithelial cells in feeding and moulting nymphs of the tick Haemaphysalis longicornis 总被引:1,自引:0,他引:1
The midgut epithelial cells in nymphs fed on laboratory rabbits were examined during feeding and after detachment. The midgut epithelium at the unfed stage consisted of digestive cells of lower activity, containing such nutritive substances as protein, lipid and glycogen. As feeding proceeded, the cells became active in intracellular digestion. At the middle of the feeding stage, the spent digestive cells derived from the active digestive cells began to be replaced by the new digestive cells of lower activity. After detachment, the pinocytotic activity of the above cells increased greatly, and the digestive activity increased to some extent. As a result, many large endosomes were formed by fusion of numerous pinosomes. Thereafter, endosomes decreased in size as digestion proceeded and there was an increase of haematin granules. On day 7 after detachment, the new digestive cells of lower activity, belonging to the 'nutritional reserve' type, appeared adjacent to the spent digestive cells which had almost exhausted all endosomes, and these new cells had completely replaced the spent cells by day 3 after moulting. 相似文献
3.
S Kim S Morimoto E Koh Y Miyashita T Ogihara 《Biochemical and biophysical research communications》1989,164(3):1003-1008
The effects of a potassium (K+) channel opener BRL34915 and a specific K+ ionophore valinomycin on vasoconstriction induced by endothelin (ET) were compared with those of calcium (Ca2+) channel blockers, nicardipine and verapamil, using helical strips from rat thoracic aorta. ET induced potent and persistent contraction in control solution and similar but smaller contraction in Ca2+-free solution. BRL34915 and valinomycin inhibited the ET-induced contraction dose-dependently in control solution, but not in Ca2+-free solution. The ET-induced contraction was also inhibited by nicardipine and verapamil, though less strongly. On the other hand, high K+ (35 mM)-induced vasoconstriction was strongly inhibited by nicardipine and verapamil, but not by BRL34915 or valinomycin. These results support the idea that the extracellular Ca2+-dependent component of the ET-induced contraction may be mediated by Ca2+ influx by a route other than voltage-dependent Ca2+-channels. 相似文献
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5.
Phylogenetic distribution in the genus Mus of t-complex-specific DNA and protein markers: inferences on the origin of t-haplotypes 总被引:8,自引:0,他引:8
Delarbre C; Kashi Y; Boursot P; Beckmann JS; Kourilsky P; Bonhomme F; Gachelin G 《Molecular biology and evolution》1988,5(2):120-133
We have examined the phylogenetic distribution of two t-specific markers
among representatives of various taxa belonging to the genus Mus. The
centromeric TCP-1a marker (a testicular protein variant specific for all
t-haplotypes so far studied) has also been apparently detected in several
non-t representatives of the Mus IVA, Mus IVB, and probably M. cervicolor
species. By contrast, a t-specific restriction- fragment-length
polymorphism allele (RFLP) of the telomeric alpha- globin pseudogene DNA
marker alpha-psi-4 was found only in animals belonging to the M.
musculus-complex species either bearing genuine t- haplotypes or, like the
M. m. bactrianus specimen studied here, likely to do so. This t-specific
alpha-psi-4 RFLP allele was found to be as divergent from the RFLP alleles
of the latter, non-t, taxonomical groups as it is from Mus 4A, Mus 4B, or
M. spretus ones. These results suggest the presence of t-haplotypes and of
t-specific markers in populations other than those belonging to the M. m.
domesticus and M. m. musculus subspecies, implying a possible origin for
t-haplotypes prior to the radiation of the most recent offshoot of the Mus
genus (i.e., the spretus/domesticus divergence), some 1-3 Myr ago.
相似文献
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Protein synthesis during germination at 24?C and vernalizationat 4?C in winter wheat embryos were investigated with a cell-freesystem. During germination, the capacity for protein synthesisincreased in the early stage between 12 and 36 hr of imbibitionthen declined to a final low level between 48 and 72 hr. Thistransition was due to quantitative changes of the activitiesof ribosomal and supernatant fractions in the early stage andmainly to those of the supernatant fraction in the later stage.During vernalization, the capacity for protein synthesis continuedto decline over 15 to 60 days at 4?C. This transition was dueto the change in activity of the supernatant fraction; the activityof the ribosomal fraction was nearly constant. Electrophoretic analysis of in vitro products indicated thatthe high molecular weight proteins present in 12-hr embryoshad disappeared in 48-hr germinated wheat embryos and that theproducts in 24- and 36-hr embryos were types intermediate betweenthose of 12- and 48-hr embryos. The products in each vernalizedembryo resembled those in 24- and 36-hr germinated embryos.Therefore, it was concluded that the mRNA species for translationchanged during germination and vernalization in winter wheatembryos. (Received January 20, 1977; ) 相似文献
9.
Koh Iba Ken-Ichiro Takamiya Yoshihiro Toh Hikaru Satoh Mitsuo Nishimura 《Genesis (New York, N.Y. : 2000)》1991,12(5):342-348
The ability to form functionally active chloroplasts is determined at a certain early stage of leaf development in three non-allelic temperature-sensitive virescent mutants of rice. Temperature-shift analysis, together with anatomical observations, indicates that the intrinsic developmental signals of the virescent genes are expressed at the stage immediately following the formation of basic leaf structure, but just before the onset of leaf elongation. These signals control the expression of chloroplast-encoded genes but do not affect the subsequent morphological development of the leaf or the photo-regulation of the expression of nuclear genes encoding chloroplast proteins. 相似文献
10.
Duk-Su Koh Peter Jonas Michael E. Bräu Werner Vogel 《The Journal of membrane biology》1992,130(2):149-162
A novel potassium-selective channel which is active at membrane potentials between -100 mV and +40 mV has been identified in peripheral myelinated axons of Xenopus laevis using the patch-clamp technique. At negative potentials with 105 mM-K on both sides of the membrane, the channel at 1 kHz resolution showed a series of brief openings and closings interrupted by longer closings, resulting in a flickery bursting activity. Measurements with resolution up to 10 kHz revealed a single-channel conductance of 49 pS with 105 mM-K and 17 pS with 2.5 mM-K on the outer side of the membrane. The channel was selective for K ions over Na ions (PNa/PK = 0.033). The probability of being within a burst in outside-out patches varied from patch to patch (> 0.2, but often > 0.9), and was independent of membrane potential. Open-time histograms were satisfactorily described with a single exponential (tau o = 0.09 msec), closed times with the sum of three exponentials (tau c = 0.13, 5.9, and 36.6 msec). Sensitivity to external tetraethylammonium was comparatively low (IC50 = 19.0 mM). External Cs ions reduced the apparent unitary conductance for inward currents at Em = -90 mV (IC50 = 1.1 mM). Ba and, more potently, Zn ions lowered not only the apparent single-channel conductance but also open probability. The local anesthetic bupivacaine with high potency reduced probability of being within a burst (IC50 = 165 nM). The flickering K channel is clearly different from the other five types of K channels identified so far in the same preparation. We suggest that this channel may form the molecular basis of the resting potential in vertebrate myelinated axons. 相似文献