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381.
Johannes H. Altena Godefridus A.M. van den Ouweland Cornelis J. Teunis Sing B. Tjan 《Carbohydrate research》1981,92(1):37-49
In order to establish whether p.m.r. spectroscopy is useful for identifying Amadori- and Heyns-rearrangement products, the p.m.r. spectra at 220 MHz of 16 rearrangement products derived from d-glucose or d-fructose and amino acids have been investigated. At pH 3, the protons of the NCH2 group of N-substituted 1-amino-1-deoxy-d-fructose (Amadori-rearrangement products) resonate at δ 3.25–3.60 in D2O and are shifted upfield by 0.3–0.6 p.p.m. at pH 9. These protons exchange with deuterium. Also, in D2O there is an equilibrium of the acyclic, furanose, and pyranose structures, the last being favoured. At pH ? 7, the equilibrium is completely shifted to the β-pyranose form, which adopts exclusively the 2C5 conformation. At pH 3, the equilibrium favours the β-furanose form. At pH 3, H-1e and H-1a of N-substituted 2-amino-2-deoxy-d-glucoses (Heyns-rearrangement products) resonate at δ 5.55 and 5.04, respectively. At pH 9, the signal for H-2 is shifted upfield by 0.2–0.7 p.p.m. In D2O solution, these compounds exist as an equilibrium of α- and β-pyranose forms in the 4C1 conformation. The α anomer is stabilised by the amino acid group at position 2. At pH 3, the αβ-ratio is 2–4:1, and, at pH 9, 1.0–1.1:1. 相似文献
382.
Ryo Higuchi-Sanabria Joseph K. Charalel Matheus P. Viana Enrique J. Garcia Cierra N. Sing Andrea Koenigsberg Theresa C. Swayne Jason D. Vevea Istvan R. Boldogh Susanne M. Rafelski Liza A. Pon 《Molecular biology of the cell》2016,27(5):776-787
Higher-functioning mitochondria that are more reduced and have less ROS are anchored in the yeast bud tip by the Dsl1-family protein Mmr1p. Here we report a role for mitochondrial fusion in bud-tip anchorage of mitochondria. Fluorescence loss in photobleaching (FLIP) and network analysis experiments revealed that mitochondria in large buds are a continuous reticulum that is physically distinct from mitochondria in mother cells. FLIP studies also showed that mitochondria that enter the bud can fuse with mitochondria that are anchored in the bud tip. In addition, loss of fusion and mitochondrial DNA (mtDNA) by deletion of mitochondrial outer or inner membrane fusion proteins (Fzo1p or Mgm1p) leads to decreased accumulation of mitochondria at the bud tip and inheritance of fitter mitochondria by buds compared with cells with no mtDNA. Conversely, increasing the accumulation and anchorage of mitochondria in the bud tip by overexpression of MMR1 results in inheritance of less-fit mitochondria by buds and decreased replicative lifespan and healthspan. Thus quantity and quality of mitochondrial inheritance are ensured by two opposing processes: bud-tip anchorage by mitochondrial fusion and Mmr1p, which favors bulk inheritance; and quality control mechanisms that promote segregation of fitter mitochondria to the bud. 相似文献
383.
Plant scientists often assess correlation coefficients to develope a selection strategy for better plant type. They generate data on the desired traits on several genotypes grown in a randomized complete block design. Using the data from such experiments, this paper presents the asymptotic standard error of an estimate of phenotypic correlations coefficient and a test of significance. The method is illustrated using data on chickpea crop. 相似文献
384.
Christoph G.O. Baerwald C. C. Mok Mark S. Fife Mohammad Tikly Chak Sing Lau B. Paul Wordsworth Bill Ollier G.S. Panayi J.S. Lanchbury 《Immunogenetics》1999,49(10):894-899
The regulatory region of the corticotropin-releasing hormone (CRH) is highly conserved across species and plays a crucial
role in the response of the organism to stress. Release of CRH initiates a cascade of events leading to the release of cortisol
and the regulation of inflammatory and immune events. In this report we describe polymorphisms in the 5′ regulatory region
of the CRH gene in humans. We studied the distribution of CRH alleles in three different African populations, in white UK Caucasoids, and in a Chinese population. In the African and UK
populations we found three new polymorphisms which cosegregated, resulting in two alleles, A1 and A2. Gene frequencies for A1 and A2 were extremely divergent between the African and the UK populations. The African A1 frequency ranged from 0.27–0.3, while the UK Caucasoid frequency was 0.9. Compound alleles could be assigned by taking into
account the previously described biallelic polymorphism at position 225 in the CRH promoter. The A2B1 compound allele is the commonest in contemporary African human populations (allele frequency range 0.44–0.61) and was the
only allele observed in a population of chimpanzees from Sierra Leone. Wright's FST for the A2B1 allele over the four sampled populations was 0.612, a value exceeded in human populations only by loci which have apparently
been subject to natural selection. Taken together, these findings support A2B1 as the ancestral allele and suggest that the CRH genomic region may have been subject to strong disruptive selection throughout human evolution.
Received: 29 October 1998 / Revised: 24 March 1999 相似文献
385.
386.
Urs Kuhnlein Siu Sing Tsang Opal Lokken Silvian Tong Daniel Twa 《Bioscience reports》1983,3(7):667-674
Human fibroblasts and HeLa cells contain two major DNA-binding activities for superhelical DNA, which can be separated by phosphocellulose chromatography. The DNA-binding activity which elutes first from the column coelutes with and is probably identical to a single-stranded-DNA-binding activity. The second activity has been characterized previously. It binds preferentially to super-helical DNA containing DNA damage, but does not bind to single-stranded DNA. Five cell lines derived from patients with the repairdeficiency syndrome xeroderma pigmentosum (XP) were analyzed for the presence of these binding activities. Four of the cell lines were from the A-complementation group and one was from the D-complementation group of XP. The binding activity with preference for damaged DNA was present in all cell lines. The single-stranded-DNA-binding activity was present in the XP-D cell line but was absent or reduced in all of the four XP-A cell lines tested. 相似文献
387.
This paper presents an analysis of the relationship between variation in the low-density lipoprotein receptor (LDLR) gene
region and interindividual variation in plasma lipid and apolipoprotein levels in a sample representative of the adult population
of Rochester, Minn. (217 females and 187 males aged 26 to 63). This relationship was analyzed by estimating the average excesses
of alleles of the LDLR gene defined using RFLP markers both singly and simultaneously. We also used a cladistic approach to
illustrate the consequences of incorporating evolutionary information into the analysis of genotype-phenotype relationships.
Although results from both approaches supported the inference that common variation in the LDLR gene region associates with
small effects on plasma lipid and apolipoprotein levels, only the cladistic approach provides direction for further work aimed
at identifying the functional DNA sequence variations responsible for the observed associations.
Received: 19 March 1996 / Revised: 30 July 1996 相似文献
388.
389.
Three common alleles, ɛ
2
, ɛ
3
, and ɛ
4
, of the gene coding for apolipoprotein E (apoE) have been identified as predictors of interindividual variation in measures
of lipid and lipoprotein metabolism, and ultimately risk of coronary heart disease (CHD), within many populations. Here we
evaluated the utility of the geographic distribution of these alleles for prediction of interpopulation variation in average
level of serum total cholesterol and other traditional risk factors, and CHD mortality rate. We employed published estimates
of the relative frequencies of the three common apoE alleles, average levels of risk factors such as serum total cholesterol, systolic and diastolic blood pressure, body mass
index, smoking prevalence and CHD mortality rate for nine population-based samples of middle-aged males studied by the international
WHO MONICA Project. There was approximately a 10-fold difference between the highest and lowest CHD mortality rate. Of the
traditional risk factors, variation in the average level of serum total cholesterol was the best predictor (approximately
33%) of the observed interpopulation variation in estimates of CHD mortality rate (Pr=0.10). Variation in the relative frequency of the ɛ
4
allele predicted approximately 50% of interpopulation variation in average serum total cholesterol level (Pr=0.02) and 75% of the variation in CHD mortality rate (Pr=0.002) when information about variation in the other risk factors and the ɛ
2
andɛ
3
alleles is ignored. Furthermore, variation in the relative frequency of the ɛ
4
allele predicted approximately 40% of the variation in CHD mortality rate (Pr=0.02) after considering the contribution of variation in average serum total cholesterol level. Average serum total cholesterol
level was estimated to increase by 0.114 mmol/l (4.405 mg/dl), and CHD mortality rate by 24.5/100 000, for an increase of
0.01 in the relative frequency of the ɛ
4
allele. The predictive utility of the ɛ
2
andɛ
3
alleles was considerably less than that of the ɛ
4
allele. For the sample of populations considered, the geographic distribution of the apoE alleles can be a statistically significant predictor of interpopulation variation in both the average serum total cholesterol
level and CHD mortality rate. In particular, the ɛ
4
allele may confer valuable ecological risk information.
Received: 2 December 1997 / Accepted: 28 May 1998 相似文献
390.
This study illustrates the very complex nature of gene by environmental interactions influencing the blood pressure (BP) distribution in a series of genetically distinctive populations undergoing rapid acculturation. We report the results of two BP and anthropometric surveys on Solomon Islands societies separated by an interval of 14 to 19 years. While differences in acculturation existed at the time of the initial survey, the interval between surveys was marked by rapid acculturation in almost all societies. Seven of the eight societies originally covered were included in the resurvey, and a large but variable proportion of the original sample subjects was recovered in the follow-up. Because the genetic relationships of the societies have been described, we were able to establish the following points concerning the role of genetic differences in determining the distribution of BP among these populations and, more important, the interaction of these genetic differences with changes associated with increasing acculturation: 1) In the initial survey, mean adjusted systolic and diastolic BPs were significantly heterogeneous among societies within and among genetically related clusters of societies (genetic clusters) and sexes. At the same time, rank differences in these means were not associated with rank differences in acculturation status among societies ignoring cluster membership. 2) Importantly, in the follow-up survey increasing acculturation resulted in the disappearance of significant differences in mean systolic and diastolic BP among genetic clusters in males, despite continued significant heterogeneity among societies within genetic clusters. In females, differences among genetic clusters persisted, but the degree of significance was substantially less with increasing acculturation. We interpret these changes as evidence for genotype by environment interaction. 3) There were significant differences in interindividual variances of both systolic and diastolic BPs among genetic clusters in the first survey. Ranks of these variances were not significantly associated with acculturation rank. In the follow-up survey, however, most societies showed striking increases in the variance of both systolic and diastolic BPs with increased acculturation. These increases in variance of both systolic and diastolic BPs may be related to a) shifts in demography and/or anthropometry of some societies; b) increased range and intensity of environmental factors affecting BP and associated with increased acculturation; and/or c) genotype by environmental interactions. 4) The correlation between systolic and diastolic BP decreased over the interval for all societies within and among genetic clusters. This trend was partly the result of larger changes in variances for systolic than diastolic BP in the resurveys.(ABSTRACT TRUNCATED AT 400 WORDS) 相似文献