Human transferrin polymorphism

The application of isoelectric focussing (IEF) has revealed a large amount of heterogeneity in the human transferrin (TF) system and has enhanced its potential value in anthropological and genetic studies. The average heterozygosity has been elevated from 0.05, observed by conventional methods of electrophoresis, to 0.29 detected by IEF. So far approximately 30,000 individuals from 122 population groups have been analyzed for TF subtypes to evaluate the magnitude of genetic variation at the TF locus. Possible environmental and biological factors, which may be operating to maintain the TF polymorphism, are discussed.     

Genetic studies of human apolipoproteins. V. A novel rapid procedure to screen apolipoprotein E polymorphism

A simple and new method has been developed to detect apolipoprotein E polymorphism directly from plasma or serum without prior ultracentrifugation and delipidation. The method combines the use of dialyzed plasma or serum samples with or without neuraminidase treatment followed by monodimensional isoelectric focusing in simple or 3 M urea gels at a constant low power and progressively increasing voltage over a 3-hr period, and finally protein blotting to a nitrocellulose membrane. Apolipoprotein E phenotypes are identified immunologically using a double antibody reaction, the primary antibody being a monospecific, polyclonal goat anti-apolipoprotein E, and the secondary antibody being a rabbit anti-goat IgG conjugated with alkaline phosphatase. The method was employed to screen apolipoprotein E polymorphism in two white populations in the United States. The frequency values are comparable to those reported previously by other investigators using conventional detection methods. The procedure is simple, accurate, suitable for large scale epidemiologic, clinical, and genetic studies.     

田螺科五种螺的核型研究

以早期胚胎细胞为材料,用火焰干燥法制片,对分布于我国湖北省武汉市近郊的常见田螺科(Viviparidae)五种螺的核型进行了分析。结果:两种圆田螺的染色体数和国外报道的同一属的种类的一致。而三种环棱螺的染色体数,则较国外报道的另两种的少得多。在铜锈环棱螺的核型中,其m组的第一对和sm组的第四对染色体上,具有明显的随体,出现频率甚高。     

Genetic studies of low abundance human plasma proteins. II. Population genetics of coagulation factor XIIIB.

Plasma samples from a large number of different ethnic groups, consisting of U.S. whites, U.S. blacks, Eskimos from Kodiak and St. Lawrence Island, Aleuts of the Pribilof Islands, and three Amerindian groups from Canada and Mexico have been analyzed by isoelectric focusing followed by immunoblotting to determine the magnitude of genetic variation at the F XIIIB structural locus. The synthesis of published data and our new data demonstrate remarkable variation in the distribution of the three common alleles at this locus and establishes F XIIIB as an extremely informative marker for population differentiation and evolutionary studies. Genetic distance analysis based on this variation separates Caucasian, black, and Mongoloid populations into three distinct clusters.     

Ethnic variation in vitamin D-binding protein (GC): a review of isoelectric focusing studies in human populations

Summary Since the discovery in 1977 that the GC1 gene could be resolved into two common subcomponents on an isoelectric focusing (IEF) gel, a large number of ethnic groups have been screened to analyze the extent of genetic variation in human populations. Using the IEF technique, approximately 50,000 individuals from 160 different populations have been tested for the GC polymorphism. A marked variation in common GC suballele frequencies in different geographic areas seems to correlate with skin pigmentation and intensity of sun light. Pigmented (black) and keratinized (yellowish) skin type populations have a relatively high frequency of the GC ^*IF allele as compared to white skin populations. By comparison non-pigmented and non-keratinized white skin populations are generally characterized by having the maximum values of the GC ^*IS allele. The anthropologic significance of the GC locus has been enhanced further by detecting additional unique GC variants which provide useful information about evolutionary links between different populations. However, the presence of some electrophoretically identical unique variants in genetically and geographically distinct populations demand further investigation of these allelic variants to shed more light on their origins.     

中国鲤科鱼类染色体组型的研究 Ⅱ.鲴亚科四种鱼的染色体组型

鲴亚科(Xenocyprininae)鱼类多为中小型鱼类,常见于江河湖泊等较宽阔的水域中,我国长江、黑龙江、黄河及珠江诸流域皆有分布,共有10种,隶属4个属(伍献文等,1964)。迄今尚未见有该亚科鱼类染色体组型的研究报道。本文是对其中三属四种鱼的染色体组型的观察结果。这四种鱼是银鲴(Xenocypris argentea)、黄尾鲴(Xenocypris davidi)、细鳞斜颌鲴(Plagiognathops microlepis)和逆鱼(Acanthobrama simoni)。其中黄尾鲴和细鳞斜颌鲴均为新的淡水养殖鱼(沈德长等,1981;陈楚星,1979)。     

植物冷锻炼对于胁强敏感度的影响(英文)

前文由柑桔枝条在不同低温下、不同冷冻时间的电解质外渗测定,提出胁强(stress)、作用时间与胁变(strain)之间关系的数学模型。在这个模型中共有3个参数:屈服点温度(yield point temperature),胁强敏感度(stress sensitivity)和作用时间敏感度(sensitivity to duration),用以描述植物的抗性。抗性强的植物应表现为屈服点温度较低,胁强敏感度或者时间敏感度较低。为验证此数学模型,本工作以经冷锻炼与未经冷锻炼的盆栽柑桔枝条为材料,作不同温度与时间处理的电解质外渗率的测定,研究了冷锻炼对于上述3个参数的影响。发现胁强敏感度和屈服点温度受冷锻炼影响而下降,时间敏感度未表现明显变化。对于田间柑桔、油桐与毛竹的定期测定,在固定冷冻时间下,得到了类似于盆栽柑桔的结果。入冬时,植物抗冻性提高,3种植物都表现出下列两种变化:1.胁强敏感度的明显下降;2.屈服点温度和/或时间敏感度亦下降。开春时的变化则相反。胁强敏感度的变化与后一种变化有各自的规律,且因植物种类而不同。拐点胁强(stress at inflection point)具有与半致死温度(50％killing point temperature)不同的意义,它的变化是上述两种变化的综合结果。本试验结果表明,冷锻炼对于植物胁强敏感度有明显影响,用本数学模型的3个抗性指标描述     

微生物发酵法生产S-腺苷甲硫氨酸的研究进展

S-腺苷甲硫氨酸(S-adenosyl-l-methionine, SAM)广泛存在于生物体内,主要参与生物体内的转甲基过程、转硫过程及转氨丙基过程,具有重要的生理功能,其生产备受重视。目前SAM生产的研究主要集中于微生物发酵法,该方法与化学合成法和酶催化法相比,成本较低且更容易实现工业化生产。随着需求量的迅速增加,通过菌种改良提高SAM产量备受关注。当前SAM生产菌种改良的主要策略包括常规育种和代谢工程。本文综述了提高微生物生产SAM能力的近期研究进展并探讨了SAM生产中的瓶颈问题及解决方法,以期为进一步提高SAM产量提供思路。     

Population genetics of the vitamin D binding protein (GC) subtypes in the Asian-Pacific area: Description of new alleles at the GC locus

Isoelectric focussing (IEF) in thin layer polyacrylamide gels pH range 4-6.5 has been used to analyse the GC phenotypes of 4233 individuals from 28 different population groups in the Asian, Pacific, and Australian area. Because this technique reveals subtypes of the common GC*1 allele, there is almost a two-fold increase in the mean heterozygosity at the GC locus using IEF compared with conventional electrophoresis. The highest frequency (above 50%) of the GC*1S allele was encountered in Indian populations, reflecting genetic affinities with Europeans. By comparison, east and south east Asians are unique offing maximum values of the GC*1F allele (50%). With the exception of a few Pacific populations which show similar frequencies to east Asians, all other groups in the Pacific area, including Australia, have values of GC*1F similar to GC*1S ranging from 27% to 40%. The GC*2 frequency in most populations varies from 20% to 30%. However, some Polynesian groups have values up to 40% and Australian Aborigines less than 10%. Among other alleles, GC*1A1 is found to be widely distributed among Australian Aborigines and Melanesians and occurs sporadically in Polynesians, Micronesians, and in the Lesser Sunda Islands. Four new alleles, GC*1C24, GC*1C35 Aborigine, GC*1A21, and GC*1A22 are described. The gene frequency data at the GC locus has been used to calculate Nei genetic distances between the populations studied.     

Biochemical and genetic characterization of three hamster cell mutants resistant to diphtheria toxin

We describe here three different hamster cell mutants which are resistant to diphtheria toxin and which provide models for investigating some of the functions required by the toxin inactivates elongation factor 2 (EF-2). Cell-free extracts from mutants Dtx(r)-3 was codominant. The evidence suggests that the codominant phenotype is the result of a mutation in a gene coding for EF-2. The recessive phenotype might arise by alteration of an enzyme which modifies the structure of EF-2 so that it becomes a substrate for reaction with the toxin. Another mutant, Dtx(r)-2, contained EF-2 that was sensitive to the toxin and this phenotype was recessive. Pseudomonas aeruginosa exotoxin is known to inactivate EF-2 as does diphtheria toxin and we tested the mutants for cross-resistance to pseudomonas exotoxin. Dtx(r)-1 and Dtx(r)-3 were cross-resistant while Dtx(r)-2 was not. It is known that diphtheria toxin does not penetrate to the cytoplasm of mouse cells and that these cell have a naturally occurring phenotype of diphtheria toxin resistance. We fused each of the mutants with mouse 3T3 cells and measured the resistance. We fused each of the mutants with mouse 3T3 cells and measured the resistance of the hybrid cells to diphtheria toxin. Intraspecies hybrids containing the genome of mutants Dtx(r)-1 and Dtx(r)-3 had some resistance while those formed with Dtx(r)-2 were as sensitive as hybrids derived from fusions between wild-type hamster cells and mouse 3T3 cells.