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11.
M F Kagnoff L S Arner S L Swain 《Journal of immunology (Baltimore, Md. : 1950)》1983,131(5):2210-2214
Immune responses to bacterial polysaccharides are important to host immunity at mucosal surfaces. We previously showed that BALB/c mice produce substantial T cell-dependent IgA responses to alpha (1,3) glucan determinants on the bacterial capsular polysaccharide dextran B1355. The data in this study demonstrate that the requirement for T cells for the activation of the IgA anti-alpha (1,3) dextran B1355 response can be replaced by T cell-derived nonantigen specific helper factors that appear to act during the late stages of B cell differentiation. Supernatants from the activated T cell lines cr-15 and (DL)C.C3.11.75, which contain interferon and late-acting T cell replacing factor activity, supported terminal differentiation of dextran-stimulated B cells to IgA anti-alpha (1,3) glucan antibody-forming cells and substantially increased IgM anti-alpha (1,3) glucan responses in culture. Although supernatants with interleukin 2 activity did not support optimal antigen-driven plaque-forming cell responses, they synergized with supernatants having interferon and T cell replacing factor activity in the production of IgA and IgM anti-alpha (1,3) glucan responses and IgM anti-SRBC responses. Supernatants from the T cell lines B6.11 and (DL)A.4 contained B cell growth factor activity but did not support activation of IgA anti-alpha (1,3) glucan PFC. These studies suggest that interferon and/or T cell replacing factor play an important role in the antigen-driven differentiation of B cells of the IgA and IgM isotypes to antibody-forming cells. 相似文献
12.
对我国52种微茎类吸虫的18项成虫形态学特征进行主成分分析,结果表明:卵巢位置、子宫延伸位置等7项性状对第一主成分贡献较大,提示描述器官位置的指标是重要的分类依据。52个虫种在前三个主成分上的排序图显示应将其划分成4个亚科。 相似文献
13.
本文就萤叶甲亚科中柱萤叶甲属鞘翅具黑色刻点的种类进行研究,共记述4种,我国已记录3种,其中1种为新种。 相似文献
14.
15.
Estimation of ruminal bacteriophage numbers by pulsed-field gel electrophoresis and laser densitometry. 总被引:11,自引:4,他引:7
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To investigate phage activity in the rumen, a method for quantifying phage has been developed. By differential centrifugation and ultrafiltration, phage particles were separated and concentrated from ruminal fluid. Linear double-stranded DNA from this fraction containing predominantly tailed phage was isolated and separated by size, using pulsed-field gel electrophoresis (PFGE). Laser densitometry of gel photographs allowed the numbers of phages with DNA in each size region to be calculated and, therefore, the total numbers per milliliter of ruminal fluid to be estimated. Phage numbers were estimated to be between 3 x 10(9) and 1.6 x 10(10) particles ml of ruminal fluid-1. The phage population, as gauged by the appearance of DNA on PFGE gels, had two major components. A broad region of DNA between 30 and 200 kb was always present on PFGE gels. It appears this region comprises DNA from a great many different phages and would include most of the temperate phages. In addition, discrete DNA bands ranging in size from 10 to 850 kb were frequently observed. DNA from one such band, of 12 kb in size, was shown to consist primarily of a single DNA type, suggesting that it originated from a specific phage. It is postulated that the discrete bands are due to epidemics or blooms of phage activity from specific, probably lytic, phages. The method that has been developed will greatly enhance future investigations into the interactions between the ruminal phage population, the ruminal bacterial population, and animal nutrition and growth.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
16.
The Ih and lh
i alleles have been shown previously to reduce the level of endogenous gibberellin A1 (GA1) in shoots of pea (Pisum sativum L.), resulting in a dwarf phenotype compared with the wild type, cv. Torsdag (Lh). In addition, plants homozygous for the lh
i allele have reduced seed yield compared with Lh (tall, wild type) and lh (dwarf) plants. In this paper we show that the lh
i mutation is expressed in developing seeds and pods. Comparison of GA levels in young shoots and developing seeds of genotypes lh and lh
i demonstrates that the relative severity of the two mutations varies in different tissues. Homozygous h
i seeds have reduced GA levels, weigh less, and are less likely to develop to maturity when compared with Lh seeds. However, fertilization of lh
i plants with Lh pollen increases seed GA levels, seed weight and seed survival, indicating that an increase in seed GA levels due to the presence of the Lh allele can restore normal seed growth. Pods developing on self-pollinated lh
i plants are shorter than pods on Lh (wild type) plants, although this may be an indirect effect of the increased seed abortion of lh
i plants. Based on these results we suggest that endogenous GAs play an important role in the development of seeds of P. sativum L.Abbreviations GA(n)
gibberellin An
We wish to thank Katherine McPherson, Peter Newman, Leigh Johnson and Peter Bobbi for technical assistance, Professor L. Mander (ANU, Canberra) and Professor B.O. Phinney (UCLA, USA) for labelled GA standards, and the Australian Research Council for financial support. 相似文献
17.
Jonathan C. Fox Judith L. Swain 《In vitro cellular & developmental biology. Animal》1993,29(3):228-230
Summary Fibroblast growth factors (FGFs) are potent inhibitors of myogenic differentiation. The recent observation that the endogenous
expression of acidic and basic FGF by myogenic cells decreases coordinately with differentiation suggests a regulatory role
for these growth factors in myogenesis. Inasmuch as other proteins known to influence myogenesis (e.g., MyoD1 and myogenin)
activate their own expression as well as the expression of other members of their family, we hypothesized that the FGFs might
be capable of similar autoregulation. We examined the effect of exogenously supplied FGF on the abundance of the mRNAs encoding
acidic and basic FGF in Sol 8 myoblasts, and demonstrate that either acidic or basic FGF stimulate, through paracrine mechanisms,
the accumulation of the mRNAs encoding both of these FGFs. Thus FGFs can auto- and transregulate their own expression in a
manner analogous to that observed for the myogenic determination proteins. In addition, similar to that previously observed
for MyoD1, both acidic and basic FGF suppress myogenin expression in myoblasts. These results suggest two mechanisms whereby
endogenously produced FGFs participate in the maintenance of the undifferentiated state of myogenic cells. These data provide
support for paracrine, and suggest potential autocrine, roles for FGFs in the regulation of myogenic differentiation. 相似文献
18.
本文报道在湛江市附近海域海鸟体内获得的两种吸虫,经鉴定为新种,命名为巨口类茎吸虫,新种Microphalloides macrostonrs sp.nov.,珊瑚多黄吸虫,新种Multivitellus coralius sp.nov. 相似文献
19.
Douglas P. Swain 《Evolution; international journal of organic evolution》1992,46(4):987-997
Previous studies have demonstrated selective predation for vertebral traits of larvae in the stickleback Gasterosteus aculeatus. I tested the hypothesis that this selection results from a direct functional advantage to particular vertebral phenotypes by direct measurement of the burst swimming performance of larvae. Within a narrow window of lengths, burst speed did depend on vertebral phenotype. As in the previous predation experiments, performance was related more directly to the ratio of abdominal to caudal vertebrae (VR) than to the total number of vertebrae (VN), and the optimal VR decreased as larval length increased. Changes with length in the vertebral phenotype frequencies of wild larvae provided evidence of selection for VR and for VN in the wild. Larvae with particular VR increased in frequency in the wild at just those lengths when their relative performance was superior in the laboratory. The observed pattern of length-dependent selection for vertebral number provides an explanation for the widespread trends in vertebral number that occur among populations of related fishes. 相似文献
20.
Douglas P. Swain 《Evolution; international journal of organic evolution》1992,46(4):998-1013
Variation in the number of vertebrae is widespread in fishes, and is partly genetic in origin. The adaptive significance of this variation was tested by exposing larvae of the threespine stickleback (Gasterosteus aculeatus) to predation by sunfish (Lepomis gibbosus). Two vertebral characters were considered: the total number (VN) and the ratio of abdominal to caudal vertebrae (VR). Predation was selective for both characters, but selection was more directly related to VR than to VN. The direction of selection depended on larval length: as length increased, optimal VR decreased. Total selection for VR was a combination of direct selection and an indirect effect of selection acting on a correlated trait, the ratio of precaudal to caudal length. Direct and indirect selection were in opposing directions at a given larval length. Variation in vertebral number may be maintained in populations partly because the strength of selection is reduced by opposing directions between direct and indirect selection, and between total selection at different larval lengths. 相似文献