首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 31 毫秒
1.
G. ERHARDT 《Animal genetics》1989,20(3):197-204
Summary. Milk samples from 189 Merinoland Sheep, 145 Black Faced Mutton Sheep, 89 East Friesian Milk Sheep, 36 Rhön, 36 Pleven, 23 Tsigaja, 25 Black Razka and 86 Hungarian Merino x Pleven (F1) sheep were analysed by polyacrylamide gel electrophoresis under acid conditions and isoelectric focusing in ultrathin layer polyacrylamide gels with carrier ampholytes. Six different β-lactoglobulin (β-Lg) phenotypes (A, AB, B, AC, BC and C) were observed by both methods. The occurrence of three codominant alleles (β-LgA, β-LgB, β-Lgc) at an autosomal locus (β-Lg) was supported by family and population data on genetic equilibrium. Differences in gene frequencies between the breeds were observed.  相似文献   

2.
Fifteen tagged female sea bass Dicentrarchus labrax were sampled weekly from September to April and plasma vitellogenin (VTG), testosterone (T), 17β-estradiol (E2), and two potential maturation inducing steroids (MISs): 17,20β-dihydroxy-4-pregnen-3-one (17,20βP) and 17,20β,21-trihydroxy-4-pregnen-3-one (20βS) assayed. An oocyte sample was obtained via intraovarian cannulation at each sampling time from every female and the stage of development of the most advanced clutch of oocytes determined and related to VTG and hormone plasma levels for each female. The mean number of ovulations per female was 1·75+0·25 when those females that did not present ovulations were excluded and up to 4 ovulations detected in some females. The highest plasma levels of T ( c. 6 ng ml-1) were observed during postvitellogenesis and the beginning of maturation while maximum plasma levels of E2 (>5 ng ml-1) were obtained during late vitellogenesis. VTG plasma levels increased throughout vitellogenesis peaking ( c. 2·5 mg ml-1) at postvittelogenesis. For the first time significant changes of plasma progestogens were detected in European sea bass during the sexual cycle. The highest plasma level of 17,20βP ( c. 1·1 ng ml-1) was observed during postvitellogenesis while the highest level of 20βS ( c. 1·4 ng ml-1) coincided with final maturation. These results suggest that 17,20βP and 20βS play a role in the early and final maturation, respectively, in the European sea bass.  相似文献   

3.
Abstract: In human astrocyte cultures established from second-trimester fetal brain tissue, ∼5–10% of total astrocyte population in unstimulated cultures were GD3+/glial fibrillary acidic protein (GFAP)+. The GD3+ cells were always GFAP+ and grew as flat, highly spread cells but changed to process-bearing cells after interleukin-1β (IL-1β) stimulation. It is interesting that IL-1β, a known mitogen for rat astrocytes, suppressed human fetal astrocyte proliferation as determined by [3H]thymidine incorporation, bromodeoxyuridine (BrdU) labeling, and cell counting. The GD3+ population, however, consistently increased in absolute number after IL-1β stimulation, in a dose- and time-dependent manner. The IL-1β-mediated increase in number of GD3+ astrocytes was independent of initial cell density or serum concentration. By flow cytometry, IL-1β enhanced both the mean fluorescence intensity and the percentage of GD3+ cells. To investigate whether the increase in GD3+ astrocyte cell number was due to proliferation of preexisting GD3+ astrocytes or due to conversion of GD3 to GD3+ cells, we performed BrdU/GD3 double immunocytochemistry. BrdU/GD3 double-positive cells were extremely rare in both control and IL-1β-stimulated cultures. Moreover, an increase in number of GD3+ astrocytes was still observed in control and IL-1β-stimulated cultures where GD3+ cells had been initially eliminated by cell sorting. These results indicate that GD3+ astrocytes in human fetal culture may represent a postmitotic, differentiated, distinct phenotype.  相似文献   

4.
A method for genotyping K-casein ( A, B, E ), β-casein ( A 1, A 2, A 3, A5, B ) and β-lactoglobulin ( A, B ) simultaneously by the use of allele discrimination by primer length combined with automated detection of fragments with a sequencing instrument is described. Seven different mutations within the milk protein genes were analysed in order to distinguish between the alleles examined. The samples were amplified in two separate multiplex polymerase chain reactions (PCRs), which were then pooled and separated according to size in a single lane on the gel. By using stringent PCR conditions, we have been able to achieve allele-specific amplifications and minimize amplification of mismatched primer for all seven mutations.  相似文献   

5.
The permeability of the coho salmon, Oncorhynchus kisutch (Walbaum), gut to orally administered LHRH and LHRHa (des-Gly10 [D-Ala6] LHRH ethylamide) was examined over a 360 min time-course. Both forms of LHRH were detected in the blood plasma of treated fish within 30 min of delivery. Retained biological activity of the absorbed LHRH was also assessed. Oral delivery of LHRH or LHRHa to 17β-oestradiol-primed coho resulted in a significant ( P < 0.01) release of gonadotropin (GtH) when compared to saline intubated, 17β-oestradiol-primed animals. The dose response of 17β-oestradiol-primed coho salmon to orally delivered LHRHa revealed that maximal GtH release occurred at doses between 2.0 and 20 μg LHRHa per g body weight.  相似文献   

6.
Abstract: The amyloid protein (βA4) is found in the CNS of patients with Alzheimer's disease; however, the pathogenic role of this protein is not known. In the present study, a peptide fragment of βA4βA4 25–35; Gly-Ser-Asn-Lys-Gly-Ala-Ile-Ile-Gly-Leu-Met-NH2), which contains the conserved C-terminal sequence of substance P (X-Gly-Leu-Met-NH2), and the neuropeptide substance P (SP) were examined for their ability to modulate nicotine-evoked secretion from cultured bovine adrenal chromaffin cells. Secretion of the released endogenous catecholamines was monitored by electrochemical detection after separation by HPLC. Secretion induced by 10−5 M nicotine was inhibited by SP and βA4 25–35. The IC50 of SP and βA4 25–35 was 3 × 10−6 and 3 × 10−5 M , respectively. SP and βA4 25–35 both protected against nicotinic receptor desensitization. However, βA4 25–35 was ∼ 10-fold less effective than SP in its protective effect. The present work shows that βA4 25–35 can mimic the modulatory actions of SP on the nicotinic response of cultured bovine chromaffin cells, i.e., inhibition of the nicotinic response and protection against nicotinic desensitization. These modulatory actions may be associated with changes in nicotinic receptor levels reported to occur in Alzheimer's disease.  相似文献   

7.
R.A. MUSMANNO, T. DI MAGGIO and G. CORATZA.1999.Two different killer phenotypes were detected among K+ (killer) yeasts isolated from spontaneous wine fermentations using a plate bioassay. The two phenotypes differed in their degree of killer activity, and were designated as SK+(strong killer) and WK+(weak killer). Strains showing either phenotype were assayed for expression of killer activity under different growth conditions. Growth in must negatively affected expression of the killer activity of both phenotypes. The supernatant fluids from must cultures showed a lower killing effect than those from yeast phosphate dextrose broth (YPDB) cultures. The ability of the two K+ phenotypes to prevail on K-sensitive yeasts was studied in mixed-culture fermentation experiments. Under these conditions, only strains showing SK+ phenotype were able to prevail on the K-sensitive yeasts. These results suggest that the K+ phenotype could play a relevant role in spontaneous fermentations provided that the strain exhibits an SK+ phenotype, and that the latter phenotype should be preferred when selected K + strains are to be used as fermentation starters.  相似文献   

8.
Galacto-oligosaccharide-producing β-galactosidase from Sirobasidium magnum CBS6803 was purified to homogeneity with a yield of 60% by DEAE–toyopearl, butyl–toyopearl, p -aminobenzyl 1-thio-β- d -galactopyranoside–agarose and concanavalin A–agarose columns, from a solubilized cell wall preparation. The isoelectric point (pI) of purified β-galactosidase was 3·8, and the relative molecular mass was 67 000 as estimated by SDS gel electrophoresis, and 135 000 as estimated by gel filtration. Optimal β-galactosidase activity was observed at a temperature and pH of 65°C and pH 4·5–5·5, respectively. The K m values for o -nitrophenyl-β- d -galactopyranoside and lactose were 14·3 and 5·5 mmol l−1, respectively, and the V max values for these substrates were 33·4 and 94·5 μmol min−1 mg of protein−1, respectively. In addition this enzyme possessed a high level of transgalactosylation activity, and 72 mg ml−1 galacto-oligosaccharide was produced from 200 mg ml−1 lactose.  相似文献   

9.
Abstract β-xylosidase (EC 3.2.1.37) has been purified from Aspergillus nidulans mycelium grown on oat-spelt xylan as sole carbon source. Its pH optimum for activity was found to be 5.0 and the optimum temperature was 50 °C. Its molecular mass was estimated by gel filtration to be 180000. Using p-nitrophenyl-β-d-xylopyranoside as substrate, the K m and V max values have been found to be 1.1 mM and 25.6 μmol min−1(mg protein)−1, respectively. Enzyme activity was inhibited by Hg2+, Ag2+, and Cu2+ at a concentration of 1 × 10−3 M. The synthesis of β-xylosidase in A. nidulans is strongly induced by arabinose and xylose and is subject to carbon catabolite repression mediated by the cre A gene product.  相似文献   

10.
Abstract: Three isoforms of catalytic α subunits and two isoforms of β subunits of Na+,K+-ATPase were detected in rat sciatic nerves by western blotting. Unlike the enzyme in brain, sciatic nerve Na+,K+-ATPase was highly resistant to ouabain. The ouabain-resistant α1 isoform was demonstrated to be the predominant form in rat intact sciatic nerve by quantitative densitometric analysis and is mainly responsible for sciatic nerve Na+,K+-ATPase activity. After sciatic nerve injury, the α3 and β1 isoforms completely disappeared from the distal segment owing to Wallerian degeneration. In contrast, α2 and β2 isoform expression and Na+,K+-ATPase activity sensitive to pyrithiamine (a specific inhibitor of the α2 isoform) were markedly increased in Schwann cells in the distal segment of the injured sciatic nerve. These latter levels returned to baseline with nerve regeneration. Our results suggest that α3 and β1 isoforms are exclusive for the axon and α2 and β2 isoforms are exclusive for the Schwann cell, although axonal contact regulates α2 and β2 isoform expressions. Because the β2 isoform of Na+,K+-ATPase is known as an adhesion molecule on glia (AMOG), increased expression of AMOG/β2 on Schwann cells in the segment distal to sciatic nerve injury suggests that AMOG/β2 may act as an adhesion molecule in peripheral nerve regeneration.  相似文献   

11.
Abstract: The characteristics of β-alanine transport at the blood-brain barrier were studied by using primary cultured bovine brain capillary endothelial cells. Kinetic analysis of the β-[3H]alanine transport indicated that the transporter for β-alanine functions with Kt of 25.3 ± 2.5 µ M and J max of 6.90 ± 0.48 nmol/30 min/mg of protein in the brain capillary endothelial cells. β-[3H]Alanine uptake is mediated by an active transporter, because metabolic inhibitors (2,4-dinitrophenol and NaN3) and low temperature reduced the uptake significantly. Furthermore, the uptake of β-[3H]alanine required Na+ and Cl in the external medium. Stoichiometric analysis of the transport demonstrated that two sodium ions and one chloride ion are associated with one β-alanine molecule. The Na+ and Cl-dependent uptake of β-[3H]alanine was stimulated by a valinomycin-induced inside-negative K+-diffusion potential. β-Amino acids (β-alanine, taurine, and hypotaurine) inhibited strongly the uptake of β-[3H]alanine, whereas α- and γ-amino acids had little or no inhibitory effect. In ATP-depleted cells, the uptake of β-[3H]alanine was stimulated by preloading of β-alanine or taurine but not l -leucine. These results show that β-alanine is taken up by brain capillary endothelial cells, via the secondary active transport mechanism that is common to β-amino acids.  相似文献   

12.
A study of the β-galactosidase produced by the psychrotrophic bacterium Buttiauxella agrestis has been carried out. This micro-organism was isolated from raw milk and the enzyme isolated using standard methods. Molecular mass was estimated to be 515 kDa. The isoelectric point was close to 4·45. Optimum pH was 7·25. Maximal activity was observed at 50°C and activation energy was estimated to be 39·1 kJ mol-1. Lactose enhanced thermal stability. Using α-nitrophenyl-β-D-galactopyranoside as the substrate, the K m was 11 μmol 1-1 and V max was 85 U mg-1 protein. β-Mercaptoethanol and ethanol were inhibitors; glycerol acted as a complex effector. The enzyme required divalent cations for activity while it was inhibited by EDTA. When the enzyme was immobilized in diethyl aminoethylcellulose the optimum pH of activity was 8. K m was 47 μmol 1-1 and V max was 96 U mg-1 protein.  相似文献   

13.
β-Galactosidase (β-Galase, EC 3.2.1.23) activity has been detected in a culture medium of cell suspension cultures of carrot ( Daucus carota L. cv. Kintoki). The extracellular β-Galase (β-Galase-II) was purified to electrophoretic homogeneity from the concentrated medium using ammonium sulfate precipitation, chromatography on CM-Sephadex C-50. DEAE-Sepharose CL-6B and Sephacryl S-200HR, and preparative PAGE. The molecular mass of the purified enzyme was estimated to be 65 kDa by Sephacryl S-200HR gel-permeation, and 60 kDa by SDS-PAGE after treatment with SDS and 2-mercaptoethanol. The pI was 6.5. The Km and Vmax values for p -nitrophenyl (PNP)-β-D-galactopyranoside were 0.17 m M and 31.9 μmol (mg protein)-1, h-1, respectively. The optimal activity in McIlvaine's buffer occurred at pH 4.0–4.4. The enzyme activity was inhibited by Co24, Cu2+, Hg2-, p -chloromercuribenzoate (PCMB) and D-galactono-1,4-lactone. The enzyme acted on citrus galactan and larchwood arabinogalactan in an exo-fashion, and was slightly involved in the hydrolysis of an acidic pectic polymer containing arabinosyl and galactosyl residues and in the breakdown of cell walls isolated from carrot cell cultures.  相似文献   

14.
Y. ODA AND K. TONOMURA. 1996. β-Mannanase and β-mannosidase were purified from the culture fluid of the yeast Trichosporon cutaneum JCM 2947 (= T. beigelii CBS 5790). The molecular weights of the two enzymes were estimated to be 49 900 and 114000 by SDS-PAGE and 4500 and 193 000 by gel filtration, respectively. β-Mannanase contained 43% molecular weight as carbohydrate. The K m and V max values of β-mannanase for konjac glucomannan were 2.7 (mg ml-1) and 10.6 (U mg protein-1), and those of β-mannosidase for p -nitrophenyl β-D-mannopyranoside were 0.25 (mmol l-1) and 91.7 (U mg protein-1). Maximal activities were observed between pH 4.0 and 6.5 at 50°C for β-mannanase and around 6.5 at 40°C for β-mannosidase.  相似文献   

15.
Abstract: Defective protein kinase C (PKC) has been implicated in impaired Na+,K+-ATPase activity in the sciatic nerve of streptozotocin-induced diabetic rats. In the present study, α, βI, βII, γ, δ, and ε isoform-specific antibodies were used in parallel to the measurement of compound PKC activity for the characterization of PKC distribution and isoform expression in sciatic nerves of normal and diabetic rats. To distinguish isoform expression between the axonal and glial compartments, PKC isoforms were evaluated in nerves subjected to Wallerian degeneration and in a pure primary Schwann cell culture. α, βI, βII, δ, and ε but no γ isoforms were detected in sciatic nerve. Similar immunoreactivity was observed in degenerated nerves 3–4 days after transection except for diminished βI and ε species; in Schwann cell cultures, only α, βII, δ, and ε were detected. In normal nerves, two-thirds of PKC compound activity was found in the cytosol and 50% of total enzyme activity translocated to the Na+,K+-ATPase-enriched membrane fraction with phorbol myristate acetate. Similar redistribution patterns were observed for the immunoreactivity of all isoforms with the exception of δ, which did not translocate to the membrane with phorbol myristate acetate. No abnormality in compound PKC activity, in the immunoreactive intensity, or in the distribution of PKC isoforms could be detected in rat sciatic nerve after 6–12 weeks of diabetes. Thus, defective activation rather than decreased intrinsic PKC activity may occur in diabetic neuropathy.  相似文献   

16.
Differences in starch metabolism during seed development and germination of two soybean [ Glycine max (L.) Merrill] genotypes with normal seed β-amylase activity ['Williams' ( Sp 1b and 'Altona' ( Sp 1b)] and two soybean genotypes with undetectable seed β-amylase activity ['Chestnut' ( Sp 1au) and 'Altona' ( Sp 1)] were investigated. Starch and soluble sugar profiles were essentially the same during seed development and germination. Total amylase activity of Williams and Altona ( Sp 1b) peaked just prior to seed maturity and then dropped off slowly; whereas, the total amylase activity of Chestnut and Altona ( sp 1) was very low throughout seed development and germination. The differences in amylase activity between Altona ( Sp 1 b) and Altona ( sp 1) was also seen in leaves. α-Amylase activity was similar in the four genotypes when β-amylase was inhibited with Hg2+ but was higher in the two genotypes with normal β-amylase activity when β-amylase was inhibited with heat plus Ca2+. Low levels of starch phosphorylase activity were detected throughout seed development and germination, and the activity was similar in three of the genotypes and higher in Altona ( sp 1).
The protein, oil and oligosaccharide contents of mature seeds of the four genotypes were similar. Altona ( sp 1 b) and ( sp 1), which appear to be near isogenic lines, were not different in any morphological character or yield.
Altona ( Sp 1 b) showed greater hydrolysis of soybean seed starch than Altona ( sp 1), but the evidence indicates that the mutation resulting in greatly reduced or missing β-amylase activity has no effect on starch metabolism of developing and germinating soybean seeds.  相似文献   

17.
An investigation of β-galactosidase activity of Escherichia coli strain H10407, under different physiological and environmental conditions, e.g. induced and uninduced osmotic stress, light, etc., was undertaken. In this study E. coli was employed as a model for faecal coliforms in waste water. β-Galactosidase activity was induced by isopropyl-β-D-thiogalactoside (IPTG). Enzyme activity (U cell-1)/cell for sewage bacteria and for induced E. coli was similar, i.e. log U cell-1= -8.5 whereas uninduced E. coli yielded log U cell-1= -12.1. Initial enzyme activity was not dependent on phase of growth of the cell (exponential vs stationary phase) or whether marine or fresh water at the time of initial dilution. However, osmotic change resulted in a decrease in culturable cells, even though enzyme activity remained constant. A significant decrease in the number of culturable bacteria, followed by a decrease in β-galactosidase activity, was observed after exposure of cells to visible light radiation. It is concluded that β-galactosidase enzyme is retained in viable but non-culturable E. coli. Furthermore, β-galactosidase appears to offer a useful and rapid (25 min) measure of the viability of faecal coliforms, and therefore, of the water quality of bathing and shellfishing areas.  相似文献   

18.
Abstract A mitogenic substance on murine lymphocytes was detected in the culture supernate of Streptococcus pyogenes type 12 strain. This substance had a molecular weight of 28 000 and p I 9.2, and was designated as S. pyogenes mitogen (SPM). The proliferative response of C3H/HeN spleen cells began at 1 ng ml−1 and reached a maximal response at 100 ng ml−1 of SPM for 4 days culture. Anti-Thy 1.2 mAb and complement-treated spleen cells abrogated the proliferative response to any dose of SPM. Although the anti-major histocompatibility complex class I mAbs had no blocking effect on proliferation by SPM, this proliferation was substantially inhibited by the addition of either anti-I-A or anti-I-E mAb, and complete inhibition was produced by the addition of both mAbs. Fixed antigen-presenting cells still induced T cell proliferation by SPM. A significant expansion of T cells bearing Vβ13 T-cell receptor was observed up to 73% among the Thy1.2+ cells in cultures stimulated with SPM, indicating expansion in a Vβ-specific manner. Immunoblotting of IEF-separated proteins showed that anti-streptococcal pyrogenic exotoxin (SPE) C reacted with a protein of p I 6.9 and anti-SPEB did not show any reactivity. SPEA was reported to expand Vβ8.1 and 8.2 bearing murine T cells, and SPM did not. SPM also exhibited potent mitogenic activity on human T cells and Vβ21+ T cells were selectively expanded. These results lead to the conclusion that SPM was neither SPEA, B nor C, but a new protein belonging to a group of streptococcal superantigens with activity on not only human but also murine lymphocytes.  相似文献   

19.
Abstract: There are two α-subunit isoforms (α1 and α2) and two β-subunit isoforms (β1 and β2) of Na+,K+-ATPase in astrocytes, but the functional heterodimer composition is not known. Ouabain (0.5–1.0 m M ) increased the levels of α1 and β1 mRNAs, whereas it decreased those of α2 and β2 mRNAs in cultured rat astrocytes. The increases in α1 and β1 mRNAs were observed at 6–48 h after addition of the inhibitor. Immunochemical analyses showed that ouabain increased α1 and β1, but not α2 and β2, proteins, and that the isoforms in control and ouabain-treated cultures were of glial origin. Low extracellular K+ and monensin (20 µ M ) mimicked the effect of ouabain on α1 mRNA. The ouabain-induced increase in α1 mRNA was blocked by the protein synthesis inhibitor cycloheximide (10 µ M ), the intracellular Ca2+ chelator 1,2-bis(2-aminophenoxy)ethane- N,N,N',N' -tetraacetic acid tetraacetoxymethyl ester (30 µ M ), and the calcineurin inhibitor FK506 (1 n M ). These findings indicate that chronic inhibition of Na+,K+-ATPase up-regulates the α1 and β1, but not α2 and β2, isoforms in astrocytes, suggesting a functional coupling of α1β1 complex. They also suggest that intracellular Na+, Ca2+, and calcineurin may be involved in ouabain-induced up-regulation of the enzyme in astrocytes.  相似文献   

20.
R. GUPTA, R.K. SAXENA, P. CHATURVEDI AND J.S. VIRDI. 1995. Streptomyces viridificans was found to be a good chitinase producer among nine species of Streptomyces screened. Minimum levels of constitutive enzyme were observed with both simple and complex carbon substrate. Arabinose doubled the enzyme production amongst the various pentoses and hexoses used with chitin. However, with glucose end-product inhibition and catabolite repression were observed. The enzyme tolerated a wide range of temperature (30–55°C) and pH (3–7˙5). Among various divalent cations Mn2+ and Hg2+ completely inhibited the purified enzyme while β-mercaptoethanol stimulated its activity. Crude and purified enzyme had potential for cell wall lysis of many fungal pathogens tested.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号