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21.
Effect of season and photoperiod on the follicle-stimulating hormone receptors in a subtropical bird
Annual changes in and photoperiodic influence oh the weight of gonads, a parameter of gonadal activity, are much smaller in
female birds than in males. Effect of season and photoperiod on the follicle-stimulating hormone receptors in the testis or
ovary was studied using a subtropical weaver finch. The number of follicle-stimulating hormone binding sites per unit testicular
weight showed a peak in the non-breeding phase; while the total number of binding sites per two testes was maximal in the
breeding phase and minimal in the regressive phase. In contrast, seasonal changes in follicle-stimulating hormone binding
sites in the ovary were less marked. Exposure to short-day during the breeding phase induced marked decreases in the numbers
of binding sites per unit testicular weight and per two testes. These numbers markedly increased after transfer to long-day
during the non-breeding phase. However, there was no significant effect of short-day or long-day exposure on follicle-stimulating
hormone binding sites in the ovary. These results suggest that photoperiod is an effective environmental factor in the regulation
of follicle-stimulating hormone receptors in the testis and the effect is manifested by pronounced changes in the testicular
weight during annual breeding cycle. 相似文献
22.
The DNP derivative of sonicate antigens of the H37Ra strain ofMycobacterium tuberculosis (Ra-DNP) is known to induce marked B-cell proliferation. In order to understand whether B-cell proliferation in response
to Ra-DNP was antigen driven or represented a non-specific mitogenic effect of Ra-DNP, the effect of Ra-DNP was compared with
that of lipopolysaccharide a potent B-cell mitogen. Parameters used for comparison were (i) thymidine incorporation, (ii)
viable cell counts, (iii) amount of lg secreted, (iv) isotype profile of Ig released and (v) cell cycling pattern of B-cells
in culture. Overall the effect of Ra-DNP was found to be essentially similar to that of lipopolysaccharide for all parameters
examined. Yet quantitatively, the effect of the former was always relatively poorer. At optimal doses, the effect of Ra-DNP
ranged from 50 to 70% of the lipopolysaccharide effect in different assays. These results suggest that Ra-DNP may have a B-cell
mitogenic effect similar to the effect of lipopolysaccharide, but all B-cells may not respond to Ra-DNP. 相似文献
23.
Dr P. P. Srivastava A. K. Bansal R. M. Shukla N. D. Banerjee N. N. Saxena S. S. Sinha 《Mycopathologia》1994,128(2):81-84
The major cuticular components of Indian tasar silkworm,Antheraea mylitta Drury, were sequentially extracted and estimated to ascertain preferential utilization of these components for growth by the entomopathogenic fungusPenicillium citrinum Thom. Proteins which constituted 61.64% dry weight of cuticule were found to play a key role in the growth ofP. citrinum whereas lipids (7.15%) and chitin (30.02%) were least involved. Also, this study suggests absence of any mycocidal substance in the cuticle ofA. mylitta. 相似文献
24.
Characterization of genes in the cellulose-synthesizing operon (acs operon) of Acetobacter xylinum: implications for cellulose crystallization. 总被引:9,自引:3,他引:6 下载免费PDF全文
The synthesis of an extracellular ribbon of cellulose in the bacterium Acetobacter xylinum takes place from linearly arranged, membrane-localized, cellulose-synthesizing and extrusion complexes that direct the coupled steps of polymerization and crystallization. To identify the different components involved in this process, we isolated an Acetobacter cellulose-synthesizing (acs) operon from this bacterium. Analysis of DNA sequence shows the presence of three genes in the acs operon, in which the first gene (acsAB) codes for a polypeptide with a molecular mass of 168 kDa, which was identified as the cellulose synthase. A single base change in the previously reported DNA sequence of this gene, resulting in a frameshift and synthesis of a larger protein, is described in the present paper, along with the sequences of the other two genes (acsC and acsD). The requirement of the acs operon genes for cellulose production was determined using site-determined TnphoA/Kanr GenBlock insertion mutants. Mutant analysis showed that while the acsAB and acsC genes were essential for cellulose production in vivo, the acsD mutant produced reduced amounts of two cellulose allomorphs (cellulose I and cellulose II), suggesting that the acsD gene is involved in cellulose crystallization. The role of the acs operon genes in determining the linear array of intramembranous particles, which are believed to be sites of cellulose synthesis, was investigated for the different mutants; however, this arrangement was observed only in cells that actively produced cellulose microfibrils, suggesting that it may be influenced by the crystallization of the nascent glucan chains. 相似文献
25.
In a two-choice test, moreS. furcifera females settled more often on exposed plants than on parafilm-masked ones, regardless of the susceptibility of rice varieties. This indicates that rice volatiles play an important role in the insect's short-range orientation to its host. The fact that more insects settled on exposed resistant Rathu Heenati (RHT) than to masked susceptible Taichung Native 1 (TN1) suggests that there must be certain common volatiles released by both varieties. Few females landed on masked plants of either RHT or TN1. This implies that the insect could not recognize at a distance that a plant was resistant or susceptible without olfactory stimuli.S. furcifera excreted less honeydew on masked plants than on exposed ones for both varieties and more on masked TN1 than on exposed RHT. The electronic monitoring of feeding behavior demonstrates that the insect made more frequent probes and had shorter phloem ingestion durations on exposed RHT than on exposed TN1 and on masked RHT than on masked TN1. Moreover, the insect had longer phloem ingestion durations on masked TN1 than on exposed RHT. These results suggest that volatile chemicals given off by resistant RHT plants have a negative effect on feeding. 相似文献
26.
Christena Visser-Tenyenhuis B. N. S. Murthy Joseph Odumeru Praveen K. Saxena 《In vitro cellular & developmental biology. Plant》1994,30(3):140-143
Summary The Ringo Rose cultivar of zonal geranium (Pelargonium x hortorum Bailey) has been shown to be morphogenetically unresponsive. Attempts to improve somatic embryogenesis using various seed
stress treatments before germination proved ineffective. However, bacterial contamination of one of the seed-stress treatments
led to infected explants that had a significant increase in frequency of high-quality somatic embryos. The co-cultivation
of explants with the isolated bacterium (tentatively identified asBacillus sp.) was found to be repeatable, and potentially represents a novel way to improve morphogenesis in geranium and possibly
other species. 相似文献
27.
Growth response ofPhormidium uncinatum, a filamentous cyanobacterium without heterocysts, in the presence of graded concentrations of zinc was studied in pure culture.
Growth at higher zinc concentrations was lower than the control. Tolerance to zinc (50 ppm) was induced in this strain by
gradually transferring it to higher concentrations of Zn. The Zn-tolerant strain in turn developed tolerance to other heavy
metals,e.g. Cd, Pb, along with resistance to infection by LPP-1 cyanophage, as distinct from the normal Zn sensitive strain. 相似文献
28.
Effect of hypoxia by intermittent altitude exposure on semen characteristics and testicular morphology of male rhesus monkeys 总被引:3,自引:0,他引:3
D. K. Saxena 《International journal of biometeorology》1995,38(3):137-140
Semen characteristics and testicular morphology of rhesus monkeys were studied on exposure to a simulated high altitude of 4411 m for 21 days. There was a partially reversible decrease in the semen volume, sperm count and sperm motility, as well as an elevation of pH and fructose concentration. These changes were associated with degeneration of the germinal epithelium and spermatogenic arrest at the end of third week of exposure which had not recovered even 3 weeks after the exposure. 相似文献
29.
Identification of a second cellulose synthase gene (acsAII) in Acetobacter xylinum. 总被引:4,自引:0,他引:4 下载免费PDF全文
A second cellulose synthase gene (acsAII) coding for a 175-kDa polypeptide that is similar in size and sequence to the acsAB gene product has been identified in Acetobacter xylinum AY201. Evidence for the presence of this gene was obtained during analysis of A. xylinum mutants in which the acsAB gene was disrupted (I.M. Saxena, K. Kudlicka, K. Okuda, and R.M. Brown, Jr., J. Bacteriol. 176:5735-5752, 1994). Although these mutants produced no detectable cellulose, they exhibited significant cellulose synthase activity in vitro. The acsAII gene was isolated by using an acsAB gene fragment as a probe. The acsAII gene coded for cellulose synthase activity as determined from sequence analysis and study of mutants in which this gene was disrupted. A mutant in which only the acsAII gene was disrupted showed no significant differences in either the in vivo cellulose production or the in vitro cellulose synthase activity compared with wild-type cells. Mutants in which both the acsAII and acsAB genes were disrupted produced no cellulose in vivo and exhibited negligible cellulose synthase activity in vitro, thus confirming that the cellulose synthase activity observed in the acsAB mutants was coded by the acsAII gene. These results establish the presence of an additional gene for cellulose synthase expressed in cells of A. xylinum, yet this gene is not required for cellulose production when cells are grown under laboratory conditions. 相似文献
30.
S K Saxena 《Anthropologischer Anzeiger; Bericht über die biologisch-anthropologische Literatur》1984,42(4):265-269
The length of the nasolacrimal canal and the diameter of its superior aperture were measured in 200 adult skulls from Uttar Pradesh (India). The mean length of the right and left canals were 2.15 cm and 2.39 cm, respectively. The antero-posterior diameter of the superior aperture is more than that of the transverse diameter in both the sides. The right canal has got a larger transverse diameter. But its antero-posterior diameter is less than that of the left side. The correlations between the various measurements were calculated. A positive correlation between the canal length and the nose length has been observed. 相似文献