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981.
A group of antigens of 24-kD Mr from rat testes were characterised biochemically. These antigens were part of a larger molecule of approximately 200 kD. On treatment with disulfide bond reducing agent, the 200-kD molecule was reduced to subunits. Immunoreactivity was confined to a doublet of approximately 24 kD and a single band of approximately 50 kD Mr after the reduction. Glycoprotein in nature, this antigen shared immunoreactive epitopes with a 40-kD antigen on human spermatozoa. Antiserum raised in rabbits against the 24-kD antigen from rat testes reacted with antigens on the acrosome of human spermatozoa. Agglutination of sperm could be induced by the antiserum. The carbohydrate residue could be removed by mannosidase digestion. Chemical deglycosylation studies showed a slight decrease in molecular weight. Immunoreactivity was however not completely lost after chemical deglycosylation. Isoelectric focusing of the antigen identified nine isoelectric species. Two relatively minor species showed immunoreactivity. Acrosome-reacted spermatozoa showed loss of antigens from acrosome. 相似文献
982.
《Journal of lipid research》2023,64(5):100367
For the past 20 years, the majority of cell culture studies reported that increasing cholesterol level increases amyloid-β (Aβ) production. Conversely, other studies and genetic evidences support that cellular cholesterol loss leads to Aβ generation. As a highly controversial issue in Alzheimer’s disease pathogenesis, the apparent contradiction prompted us to again explore the role of cellular cholesterol in Aβ production. Here, we adopted new neuronal and astrocytic cell models induced by 3β-hydroxysterol-Δ24 reductase (DHCR24), which obviously differ from the widely used cell models with overexpressing amyloid precursor protein (APP) in the majority of previous studies. In neuronal and astrocytic cell model, we found that deficiency of cellular cholesterol by DHCR24 knockdown obviously increased intracellular and extracellular Aβ generation. Importantly, in cell models with overexpressing APP, we found that APP overexpression could disrupt cellular cholesterol homeostasis and affect function of cells, coupled with the increase of APP β-cleavage product, 99-residue transmembrane C-terminal domain. Therefore, we suppose the results derived from the APP knockin models will need to be re-evaluated. One rational explanation for the discrepancy between our outcomes and the previous studies could be attributed to the two different cell models. Mechanistically, we showed that cellular cholesterol loss obviously altered APP intracellular localization by affecting cholesterol-related trafficking protein of APP. Therefore, our outcomes strongly support cellular cholesterol loss by DHCR24 knockdown leads to Aβ production. 相似文献
983.
984.
The triterpenes of the five Lithocarpus species examined comprised members of the friedo- and unrearranged oleanane groups, viz. friedelin, friedelan-3β-ol, taraxerol and β-amyrin. Glutinol was also present, except in L. harlandi where friedelan-2α,3β-diol was found. In addition, three new cycloartane triterpenes, lithocarpolone (21,24-epoxy-24-hydroxymethyl-cycloartan-3-one), lithocarpdiol (21,24-epoxy-24-hydroxymethyl-cycloartan-3β-ol). and 24-methylenecycloartan-3β,21-diol were found in L. polystachya, and their structures determined. 相似文献
985.
M. F. Feldlaufer E. W. Herbert J. A. Svoboda M. J. Thompson 《Archives of insect biochemistry and physiology》1986,3(5):415-421
In an effort to determine the sterol precursor(s) of the 28-carbon ecdysteroid, makisterone A, honey bee pupae (13 days post-oviposition) were injected with radiolabeled sterols and subsequently examined for labeled ecdysteroids. High performance liquid chromatography of the pupal extracts revealed that [3H]campesterol was converted to a compound that behaved chromatographically identical to authentic makisterone A, and [14C]cholesterol was incorporated into a compound chromatographically like 20-hydroxyecdysone. No incorporation of either 24-[3H]methylenecholesterol or [14C]sitosterol into an ecdysteroid was observed. The neutral sterols of uninjected honey bee pupae contained 49.8% 24-methylenecholesterol on a relative percent basis and, with three other C28 and C29 sterols, accounted for over 99% of the total sterols present. 相似文献
986.
987.
988.
Robert E. Norton Michael Heuzenroeder Paul A. Manning 《FEMS immunology and medical microbiology》1996,16(3-4):267-271
Abstract Rheumatic fever continues to be a significant problem in Australian Aboriginal communities and developing countries worldwide. Early diagnosis could facilitate the institution of penicillin prophylaxis resulting in the prevention of recurrences of rheumatic fever. An overlapping biotinylated peptide bank of 82 peptides, based on the known sequence of Streptococcus pyogenes M24 protein, was used in a standard enzyme immunoassay. A total of 82 sera were tested from both aboriginal and non-aboriginal subjects with clinically proven rheumatic fever, rheumatic heart disease and matched controls. Two peptides with significant sequence homology at the C-terminal end were found to be discriminatory between aboriginal cases and controls. It is proposed that these peptides could be the basis of a serological test for rheumatic fever. 相似文献
989.
990.
Taeshin Parka Jung-Ha Leea Hyun-Kyu Kima Hyang-Sook Hoea Suk-Tae Kwona 《FEMS microbiology letters》1999,180(2):133-139
The gene encoding Thermus caldophilus GK24 (Tca) alkaline phosphatase was cloned into Escherichia coli. The primary structure of Tca alkaline phosphatase was deduced from its nucleotide sequence. The Tca alkaline phosphatase precursor, including the signal peptide sequence, was comprised of 501 amino acid residues. Its molecular mass was determined to be 54? omitted?760 Da. On the alignment of the amino acid sequence, Tca alkaline phosphatase showed sequence homology with the microbial alkaline phosphatases, 20% identity with E. coli alkaline phosphatase and 22% Bacillus subtilis (Bsu) alkaline phosphatases. High sequence identity was observed in the regions containing the Ser-102 residue of the active site, the zinc and magnesium binding sites of E. coli alkaline phosphatase. Comparison of Tca alkaline phosphatase and E. coli alkaline phosphatase structures suggests that the reduced activity of the Tca alkaline phosphatase, in the presence of zinc, is directly involved in some of the different metal binding sites. Heat-stable Tca alkaline phosphatase activity was detected in E. coli YK537, harboring pJRAP. 相似文献