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At least 1,621 records · Page 90Linked to original sources
PubMed1980

Genetic variation in Cameroon: thermostability variants of hemoglobin and of glucose-6-phosphate dehydrogenase.

The technique of heat denaturation was used in addition to electrophoresis for the detection of thermostability variants of hemoglobin and glucose-6-phosphate dehydrogenase in an attempt to measure the amount of genetic variability present in villages in the United Republic of Cameroon, Equatorial Africa. A minimum of three to a maximum of 13 thermostability variants were estimated for HbA and HbS, and a minimum of two to a maximum of ten thermostability variants were estimated for GdA, GdB, and GdA-. It is suggested that hemoglobin and glucose-6-phosphate dehydrogenase thermostability variants are genetically determined and that the sites of these variants are at the hemoglobin and glucose-6-phosphate dehydrogenase structural loci. The evidence for the existence of these hidden variants and their importance in the neutralist v. selectionist controversy are discussed.

Cameroon↗
PubMed1984

Genetic variation among lentiviruses: homology between visna virus and caprine arthritis-encephalitis virus is confined to the 5' gag-pol region and a small portion of the env gene.

Visna virus of sheep and arthritis-encephalitis virus of goats are serologically related but genetically distinct retroviruses which cause slowly progressive diseases in their natural hosts. To localize homologous regions of the DNAs of these two viruses, we constructed a physical map of caprine arthritis-encephalitis virus DNA and aligned it with the viral RNA. Cloned probes of visna virus DNA were then used to localize regions of homology with the caprine arthritis-encephalitis virus DNA. These studies showed homology in the 5' region of the genome encompassing U5 and the gag and pol genes and also in a small region in the env gene. These findings correlate with biological data suggesting that the regions of the DNA which are homologous may be responsible for virus group characteristics such as the closely related virus core antigens. Regions which did not show homology such as large sections in the env gene may represent unique sequences which control highly strain-specific characteristics such as the neutralization antigen and specific cell tropisms.

Animals↗
PubMed2000

Quantitative genetic variation in CD19 expression correlates with autoimmunity.

Signaling thresholds influence the balance between humoral immunity and autoimmunity. Cell surface CD19 regulates intrinsic and Ag receptor-induced B lymphocyte signaling thresholds, and transgenic mice that overexpress CD19 by 3-fold generate spontaneous autoantibodies in a genetic background not associated with autoimmunity. To quantify the extent that genetically determined differences in expression of a single cell surface molecule can influence autoantibody production, we have assessed autoimmunity in a C57BL/6-transgenic mouse line with subtle 15-29% increases in CD19 cell surface expression (CD19 transgenic). Antinuclear Abs, especially anti-spindle pole Abs, rheumatoid factor, and autoantibodies for ssDNA, dsDNA, and histone were produced in these transgenic mice, but not littermate controls. This demonstrates that small changes in CD19 expression can induce autoantibody production. Remarkably, similar changes in CD19 expression were found on B cells from patients with systemic sclerosis, a multisystem disorder of connective tissue with autoantibody production. CD19 density on blood B cells from systemic sclerosis patients was significantly ( approximately 20%) higher compared with normal individuals, whereas CD20, CD22, and CD40 expression were normal. These results suggest that modest changes in the expression or function of regulatory molecules such as CD19 may shift the balance between tolerance and immunity to autoimmunity. Thereby autoimmune disease may result from a collection of subtle multigenic alterations that could include incremental density changes in cell surface signaling molecules.

Adult↗
PubMedDate not supplied

Intraspecific genetic variation in Paramecium revealed by mitochondrial cytochrome C oxidase I sequences.

Studies of intraspecific genetic diversity of ciliates, such as population genetics and biogeography, are particularly hampered by the lack of suitable DNA markers. For example, sequences of the non-coding ribosomal internal transcribed spacer (ITS) regions are often too conserved for intraspecific analyses. We have therefore identified primers for the mitochondrial cytochrome c oxidase I (COI) gene and applied them for intraspecific investigations in Paramecium caudatum and Paramecium multimicronucleatum. Furthermore, we obtained sequences of the ITS regions from the same strains and carried out comparative sequence analyses of both data sets. The mitochondrial sequences revealed substantially higher variation in both Paramecium species, with intraspecific divergences up to 7% in P. caudatum and 9.5% in P. multimicronucleatum. Moreover, an initial survey of the population structure discovered different mitochondrial haplotypes of P. caudatum in one pond, thereby demonstrating the potential of this genetic marker for population genetic analyses. Our primers successfully amplified the COI gene of other Paramecium. This is the first report of intraspecific variation in free-living protozoans based on mitochondrial sequence data. Our results show that the high variation in mitochondrial DNA makes it a suitable marker for intraspecific and population genetic studies.

Animals↗
PubMed2006

Genetic variation suggests interaction between cold acclimation and metabolic regulation of leaf senescence.

The extent to which leaf senescence is induced by nitrogen deficiency or by sugar accumulation varies between natural accessions of Arabidopsis (Arabidopsis thaliana). Analysis of senescence in plants of the Bay-0 x Shahdara recombinant inbred line (RIL) population revealed a large variation in developmental senescence of the whole leaf rosette, which was in agreement with the extent to which glucose (Glc) induced senescence in the different lines. To determine the regulatory basis of genetic differences in the Glc response, we investigated changes in gene expression using Complete Arabidopsis Transcriptome MicroArray (CATMA) analysis. Genes whose regulation did not depend on the genetic background, as well as genes whose regulation was specific to individual RILs, were identified. In RIL 310, a line that does not show the typical senescence response to Glc, stress response genes, especially those responding to cold stress, were induced by Glc. We therefore tested whether cold acclimation delays senescence by reducing sugar sensitivity. In cold-acclimated plants, leaf senescence was severely delayed and Glc did not induce the typical senescence response. Together, our results suggest that cold acclimation extends rosette longevity by affecting metabolic regulation of senescence, thereby allowing vernalization-dependent plants to survive the winter period. The role of functional chloroplasts and of nitrogen and phosphate availability in this regulation is discussed.

Acclimatization↗
PubMed1988

Genetic variations of human serum beta 2-glycoprotein I demonstrated by isoelectric focusing.

Human serum beta 2-glycoprotein I was analyzed by isoelectric focusing followed by immunoprinting or immunoblotting with monospecific antiserum. Isoelectric focusing revealed a heterogeneous pattern consisting of 4 major and 4-5 minor bands with isoelectric points of the major bands between pH 5.4 and 6.2. Comparative analysis of sera from more than 400 healthy blood donors showed individual variations of band patterns: six different phenotypes were observed. A family study of 44 families with a total of 129 children demonstrated the genetic control of this variation. Presumably, three alleles, called B2G*1, B2G*2, and B2G*3, determine six phenotypes: B2G 1, 2, 3, 1-2, 1-3 and 2-3. The phenotype 3, however, has not been found in this study. An additional phenotype, noted in one serum specimen, was tentatively classified as B2G 2-4. The distribution of phenotypes and alleles in two populations, from Munich and from Tyrol, has been examined and the frequencies are presented. This genetic polymorphism appears not to be associated with inherited quantitative variations of beta 2-glycoprotein I found earlier. The inherited variations can still be recognized after treatment of sera with neuraminidase and with endoglycosidase F, although the banding pattern is altered and shifted towards the cathode. The genetic polymorphism can, therefore, not be ascribed to variations residing in the carbohydrate side chains.

Alleles↗
PubMed1995

Genetic variation in locomotor activity rhythm among populations of Leptopilina heterotoma (Hymenoptera: Eucoilidae), a larval parasitoid of Drosophila species.

The locomotor activity rhythm of Leptopilina heterotoma, a parasitoid insect of Drosophila larvae, was investigated under laboratory conditions. Under LD 12:12, the locomotor activity of females shows a clear rhythm which persists under continuous darkness (circadian rhythm). However, comparative study of five populations indicates that both the rate of activity and the profile of the rhythm vary according to the origin of females. The Mediterranean populations (Tunisia and Antibes) show two peaks of activity, at the beginning and at the end of the photophase, whereas more northern populations (Lyon and the Netherlands) are mostly active during the afternoon. Females originating from the area of Lyon have a very low level of activity. Reciprocal crosses (F1 hybrids and backcrosses) between the French and the Tunisian strains demonstrated the genetic basis of these variations and the biparental inheritance of the trait. This genetic variability is interpreted as a consequence of selective pressures and suggests a local adaptation of natural populations in host foraging behavior. The selective factors which could act on the daily organization of parasitoid behaviors are discussed.

Activity Cycles↗
PubMed2003

Genetic variation of glycoproteins B and H of human herpesvirus 7 in Hong Kong.

Glycoprotein B (gB) and glycoprotein H (gH) of human herpesvirus 7 (HHV-7) are believed to play an important role in virus entry and as targets for host immune response. This study examined the genetic diversity of these glycoproteins among 90 HHV-7 isolates collected from different individuals in Hong Kong. Overall, both the gB and gH genes were found to be highly conserved. Nucleotide polymorphism was detected only at four positions of the gB-encoding region, and all of these were synonymous substitutions. Most (97.8%) Hong Kong isolates were of gB allele group C. Two isolates collected from a Pakistani family showed a novel sequence pattern that did not match known gB allele groups. This sequence pattern was detected consistently from serial samples collected from the same individual, indicating a stable genetic entity. The gH-encoding region exhibited nucleotide polymorphism at six positions. Three of these were nonsynonymous substitutions (codon 271 Lys --> Gln, codon 308 Gly --> Glu, codon 397 Asn --> Tyr). Most (84.4%) Hong Kong isolates were of the gH allele group B, and all others were of the gH allele group C. These data indicate the possibility of using gB or gH alleles as markers for studying world-wide population movements and genetics.

Adolescent↗