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排序方式: 共有332条查询结果,搜索用时 15 毫秒
1.
2.
Feeding and energy budget estimations inDaphnia obtusa 总被引:2,自引:2,他引:0
The reproductive and growth strategies ofDaphnia obtusa are discussed in terms of energy budget.
The results obtained through feeding and life table experiments allow us to understand the role of biotic factors, such as
competition and predation, in the evolution of life history traits. 相似文献
3.
B. Cesca M. C. Manca de Nadra A. M. Strasser de Saad A. Pesce de Ruiz Holgado G. Oliver 《Folia microbiologica》1984,29(4):288-294
The activity of β-D-galactosidase was studied in 13 strains of lactobacilli (groupsStreptobacterium, Thermobacterium andBetabacterium). Using 2-nitrophenyl galactopyranoside as substrate, the enzyme activity varied with the strain. The values found in theThermobacterium group were superior to those in theStreptobacterium group. The optimum pH for the species belonging to theThermobacterium group was uniform, in contrast to the ph for those from theStreptobacterium which varied according to the species. The optimum temperature was quite uniform within each group and higher in theStreptobacterium. Lactose acted as a competitive inhibitor. MgCl2 protected the enzyme from thermal denaturation. The calcium ions inhibited the activity in all cases. The behaviour of the
protectors of the SH groups varied according to the strain. 6-Phospho-β-D-galactosidase activity was also determined, levels lower than β-D-galactosidase were found, except inLactobacillus plantarum ATCC 8014 and 14917. 相似文献
4.
A limited region within hen egg-white lysozyme serves as the focus for a diversity of T cell clones 总被引:11,自引:0,他引:11
F Manca J A Clarke A Miller E E Sercarz N Shastri 《Journal of immunology (Baltimore, Md. : 1950)》1984,133(4):2075-2078
The C57BL/6 (H-2b) mouse is a nonresponder to hen egg-white lysozyme (HEL) injected i.p., owing to a T suppressor cell-inducing determinant at the amino-terminal region. After immunization with a 93-amino acid fragment (a.a. 13-105) of HEL lacking this determinant, all clones from two independently derived C57BL/6 T cell lines were found to be specific for epitopes within a subregion of peptide 74-96. Three specificity patterns for the clones could be defined on the basis of cross-reactivities with only two other species variant lysozymes. Reactivities of all three specificity groups was consistent with the serine to threonine substitution at position 91, although reactivity of one of the groups could be affected by substitutions at position 84. The results confirm at the clonal level that even for distantly related antigens, only limited regions are recognized by T cells. They are consistent with the notion that specific sites on the antigen capable of interaction with Ia molecules lead to dominance of certain regions for T cell reactivity. Moreover, the diversity in specificity among clones suggests that the limiting feature of T cell responsiveness is not a lack of available T cells in the repertoire directed against a single antigenic site. 相似文献
5.
P Preziosi P Manca 《Bollettino della Società italiana di biologia sperimentale》1964,40(24):Suppl:1940-Suppl:1943
6.
A microdeletion of less than 250 kb, including the proximal part of the FMR-1 gene and the fragile-X site, in a male with the clinical phenotype of fragile-X syndrome
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Doris Whrle Dieter Kotzot Mark C. Hirst Antonella Manca Bernhard Korn Angela Schmidt Gotthold Barbi Hans-Dieter Rott Annemarie Poustka Kay E. Davies Peter Steinbach 《American journal of human genetics》1992,51(2):299-306
A gene designated "FMR-1" has been isolated at the fragile-X locus. One exon of this gene is carried on a 5.1-kb EcoRI fragment that exhibits length variation in fragile-X patients because of amplification of or insertion into a CGG-repeat sequence. This repeat probably represents the fragile site. The EcoRI fragment also includes an HTF island that is hypermethylated in fragile-X patients showing absence of FMR-1 mRNA. In this paper, we present further evidence that the FMR-1 gene is involved in the clinical manifestation of the fragile-X syndrome and also in the expression of the cellular phenotype. A deletion including the HTF island and exons of the FMR-1 gene was detected in a fragile X-negative mentally retarded male who presented the clinical phenotype of the fragile-X syndrome. The deletion involves less than 250 kb of genomic DNA, including DXS548 and at least five exons of the FMR-1 gene. These data support the hypothesis that loss of function of the FMR-1 gene leads to the clinical phenotype of the fragile-X syndrome. In the fragile-X syndrome, there are pathogenetic mechanisms other than amplification of the CGG repeat that do have the same phenotypic consequences. 相似文献
7.
“Bacillus thermoantarcticus” sp. nov., from Mount Melbourne,Antarctica: a novel thermophilic species
B. Nicolaus Licia Lama Enrico Esposito Maria Cristina Manca Guido di Prisco Agata Gambacorta 《Polar Biology》1996,16(2):101-104
A novel thermophilic Gram-positive bacillus, “Bacillus thermoantarcticus”, isolated from geothermal soil near the crater of Mount Melbourne, is described. The organism grows at an optimal temperature
of 63°C at pH 6.0, is oxidase-positive, catalase-negative and produces an exopolysaccharide, an exocellular xylanase, an intracellular
alcohol dehydrogenase and exo- and endocellular α-glucosidase(s). The sequence of 16S rDNA is very similar to that of “Bacillus thermoglucosidasius”; however, the guanine-plus-cytosine (G+C) content is 8 mol% higher. The type strain is “Bacillus thermoantarcticus” (DSM 9572).
Received : 3 February 1995/Accepted : 12 May 1995 相似文献
8.
In mixed culture of Lactobacillus hilgardii X1B and Leuconostoc oenos X2L, isolated from Argentinian wines, an amensalistic growth response was observed: Leuconostoc oenos did not grow, and after 24 h of incubation at 30°C no viable cells were detected. In pure and mixed cultures, Lactobacillus hilgardii produced hydrogen peroxide early in the growth cycle, reaching the maximum at 24 h. The values of minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) for the action of hydrogen peroxide on the growth of Leuconostoc oenos were: 4.08g ml-1 and 17.00 g ml-1 respectively. 相似文献
9.
M Manca M Bottoni R Eleopra V Tugnoli M C Cristofori G Serra 《Bollettino della Società italiana di biologia sperimentale》1984,60(5):1019-1022
The Authors studied the checkerboard pattern electroretinogram (PERG) behaviour in normal subjects and in patients suffering from traumatic lesion of optic nerve, demyelinating optic neuritis, axonal optic neuritis, retinal vascular disorders and retinitis pigmentosa in order to verify the PERG origin. According to our data the PERG appears to originate from ganglion cells since the signal diminished or disappeared in axonal lesion of optic nerve, as a result of retrograde ganglion cell degeneration. Furthermore, the demyelinating lesions of optic nerve were not able to modify the PERG wave. In patients suffering from retinal receptor disturbances the flash electroretinogram (FERG), which is probably an expression of receptor activity, was greatly impaired, whereas PERGs were either normal or less impaired than FERGs. These data demonstrate the different origin of PERG and FERG. 相似文献
10.
The envelope glycoprotein of HIV gp120 is a T cell Ag in experimental animals and in humans infected with HIV or deliberately immunized with gp120 in various forms. Inasmuch as T cell responses result from the interaction of Ag processed and presented by APC with the unprimed T cell repertoire, we have investigated the human T cell repertoire specific for gp120 in seronegative, normal individuals. T cell lines and clones specific for HIV gp120 were generated by repeated in vitro stimulation of peripheral blood T lymphocytes with gp120-pulsed APC, followed by IL-2 expansion. We observed that the T cell response to whole gp120 involved single restricted immunodominant epitopes in gp120 that differ between responding individuals. Focusing of the response to limited regions of gp120 when the whole Ag is used for priming suggests that one or more adjacent epitopes are immunodominant and mask responses to "immunorecessive" epitopes. We have been able to generate primary in vitro responses to recessive epitopes by stimulation in vitro with synthetic peptides of gp120. The results indicate that a much broader T repertoire can be detected when individual peptides are used for priming in vitro rather than gp120. This information has important implications for the development of vaccination protocols aimed at eliciting diverse immune responses to "immunorecessive" regions of envelope glycoprotein. 相似文献