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At least 667 records · Page 37Linked to original sources
PubMed2002

Genetic variation of symbiotic fungi cultivated by the macrotermitine termite Odontotermes formosanus (Isoptera: Termitidae) in the Ryukyu Archipelago.

Fungus-growing termites have a mutualistic relationship with their cultivated fungi. To improve understanding of genetic aspects of this relationship, we examined molecular markers in the fungus-growing termite Odontotermes formosanus and its fungi Termitomyces spp. from the Ryukyu Archipelago. Based on the polymorphic band patterns obtained from arbitrarily primed polymerase chain reaction methods, we constructed cladograms for related colonies of the termites and fungi. The resulting trees indicated that the termites display little genetic variation among the colonies, while the symbiotic fungi consist of two major genetic types. In addition, molecular phylogenetic trees of the symbiotic fungi based on internal transcribed spacer and 18S rDNA suggested that these two types of fungi are different species. We also demonstrated that the fungi comprising the fruiting bodies and fungus combs are identical, and that fungus combs are probably a monoculture within a single termite colony. Our results indicate that horizontal transmission of symbiotic fungi among termite colonies occurred during the evolutionary history of this symbiosis.

Animals↗
PubMed1989

Somaclonal variation--genetic basis and breeding applications.

Somaclonal variation, the recovery of genetic changes in plants regenerated from tissue culture, offers an opportunity to uncover natural variability and to use this variability for the development of new varieties. This review focuses on the unique variation generated by this technique and the current use of somaclonal variation to develop new plant varieties.

Breeding↗
PubMed1986

Genetic variation of neonatal stress response to reduced temperature brooding in a randombred population of chickens.

Chicks from a randombred population were assessed for genetic variation in 1-day body weight and serum corticosterone under two brooding temperatures (26.7 and 32.2 C). Brooding at 26.7 C resulted in lower 1-day body weights and higher corticosterone levels. Heritability estimates (h2) for 1-day body weight were moderately high in both temperature groups but were low for gain in both temperatures. The h2 for corticosterone level from chicks brooded at 26.7 C was moderate, whereas estimates for those brooded at 32.2 were very low. Statistically significant (but low) negative phenotypic correlations were obtained for corticosterone with body weight and gain in both temperature groups. A significant negative genotypic correlation was observed between corticosterone and body weight for chicks brooded at 26.7 C but not for those brooded at 32.2 C. Corticosterone data from the highest and lowest responding sire families revealed a significant response group by temperature interaction. Chicks from the first of two additional hatches showed significant response group differences in serum corticosterone to the reduced brooding temperature. The neonatal serum corticosterone response to cold stress has a genetic basis; however, because there was a negative genotypic correlation between serum corticosterone and body weight, selection for increased corticosterone levels under reduced temperature brooding would likely result in decreased body size.

Animals↗
PubMed2000

Genetic variation among endosymbionts of widely distributed vestimentiferan tubeworms.

Vestimentiferan tubeworms thriving in sulfidic deep-sea hydrothermal vents and cold seeps are constrained by their nutritional reliance on chemoautotrophic endosymbionts. In a recent phylogenetic study using 16S ribosomal DNA, we found that endosymbionts from vent and seep habitats form two distinct clades with little variation within each clade. In the present study, we used two different approaches to assess the genetic variation among biogeographically distinct vestimentiferan symbionts. DNA sequences were obtained for the noncoding, internal transcribed spacer (ITS) regions of the rRNA operons of symbionts associated with six different genera of vestimentiferan tubeworms. ITS sequences from endosymbionts of host genera collected from different habitats and widely distributed vent sites were surprisingly conserved. Because the ITS region was not sufficient for distinguishing endosymbionts from different habitats or locations, we used a DNA fingerprinting technique, repetitive-extragenic-palindrome PCR (REP-PCR), to reveal differences in the distribution of repetitive sequences in the genomes of the bacterial endosymbionts. Most of the endosymbionts displayed unique REP-PCR patterns. A cladogram generated from these fingerprints reflected relationships that may be influenced by a variety of factors, including host genera, geographic location, and bottom type.

Animals↗
PubMed2006

Genetic variations in ZFP36 and their possible relationship to autoimmune diseases.

The ZFP36 gene codes for TTP, a regulator of TNF alpha. In mice, TTP deficiency results in a systemic autoimmune inflammatory syndrome with severe arthritis. We hypothesized that genetic variations in ZFP36 are associated with autoimmune disease in humans. The primary objective of this study was to identify human ZFP36 genetic variants in autoimmune disease cases and controls, determine their frequencies in a general clinic population, and construct haplotypes. We resequenced ZFP36 in 316 individuals with autoimmune diseases and identified 28 polymorphisms and determined the frequency of all the known ZFP36 polymorphisms in 484 participants of the Environmental Polymorphism Registry, a regional registry being conducted by the NIEHS. Based on the sequence-verified ZFP36 genotypes, 34 haplotypes were constructed. As a secondary objective, we examined autoimmune disease cases and controls for potential ZFP36 genetic associations. One novel polymorphism, ZFP36*8, a C to T transition in the protein coding domain, was significantly associated with rheumatoid arthritis (RA) in African-Americans (RR=1.23, 95% CI: 1.11-1.36). The data presented here suggest a tentative association between ZFP36 and RA. This finding, as well as the ZFP36 polymorphisms and haplotypes identified here, should form the basis for future association studies in autoimmune diseases.

Adult↗
PubMed2001

Genetic variation in angiotensin-converting enzyme does not prevent development of cardiac hypertrophy or upregulation of angiotensin II in response to aortocaval fistula.

BACKGROUND: Experimental and clinical evidence suggests that angiotensin II may be an important mediator of cardiac hypertrophy in response to hemodynamic stress. We investigated the effect of genetic variation in angiotensin-converting enzyme (ACE) on the development of cardiac hypertrophy and left ventricular (LV) dysfunction in response to volume overload. METHODS AND RESULTS: Male heterozygous ACE knockout (1/0) and wild-type (1/1) mice were studied 4 weeks after the creation of an aortocaval fistula (ACF). The LV weight/body weight ratio increased 74% in ACF versus sham-operated control mice but did not differ between genotypes. Echocardiographic circumferential stress versus rate-corrected velocity of circumferential shortening curves demonstrated depressed LV function in ACF versus sham-operated mice but no difference between genotypes. LV ACE activity was higher in 1/1 versus 1/0 mice and in ACF versus sham-operated mice, and it increased significantly more in the 1/1 versus the 1/0 mice after ACF (P<0.001 for effect of genotype, ACF/sham operation, and interaction term). LV angiotensin II was higher in ACF versus sham-operated mice but did not differ between genotypes, despite 3-fold higher LV ACE activity in ACF 1/1 versus ACF 1/0 mice. CONCLUSIONS: ACE underexpression does not prevent cardiac hypertrophy or LV dysfunction in response to volume overload. LV angiotensin II is unaffected by ACE genotype, both at baseline and after volume overload, indicating that the heart can maintain angiotensin II levels across a broad range of genetic ACE variation under both physiological and pathophysiological conditions.

Angiotensin II↗
PubMedDate not supplied

Genetic variation observed at three tetrameric short tandem repeat loci HumTHO1, TPOX, and CSF1PO--in five ethnic population groups of northeastern India.

This paper portrays the genetic variation observed at three tetrameric short tandem repeat (STR) loci HumTHO1, TPOX, and CSF1PO in five ethnic population groups from northeastern India. The study also specifies the suitability of use of these markers for forensic testing. The populations studied included three tribal groups (Kuki, Naga and Hmar), one Mongoloid caste group (Meitei), and a religious caste group (Manipuri Muslims). The loci were highly polymorphic in the populations, and all loci met Hardy-Weinberg expectations. No evidence for association of alleles among the loci was detected. The probability of match for the three loci of the most frequent genotype in the five population groups ranged between 2.6 x 10(-4) and 6.6 x 10(-5). The average heterozygosity among the population groups was approximately 70% with the overall extent of gene differentiation among the five groups being high (Gst = 0.046). Genetic affinity among the populations reveal very close association between the Kuki, Hmar, Naga, and Meitei. The Manipuri Muslims, despite being found in the same region, have had no admixture with these populations and maintain a substantial distance with the other groups. The genetic polymorphism data suggest that the studied systems can be used for human identity testing to estimate the frequency of a multiple locus STR DNA profile in population groups of northeastern India.

DNA Fingerprinting↗
PubMed1992

Lipoproteins and their genetic variation in subjects with and without angiographically verified coronary artery disease.

To examine the concentration of serum lipoproteins and the association of their genetic variation with the occurrence of coronary artery disease (CAD), composite serum lipoprotein profiles including lipoprotein(a) (Lp[a]), apolipoprotein (apo) E phenotypes, and apo B Xba I genotypes were determined in patients with angiographically verified CAD (CAD+ group, n = 111) and in subjects with no angiographic evidence of CAD (CAD- group, n = 46). In addition, we determined the concentrations of serum lipids, lipoproteins, and apolipoproteins in 96 healthy controls. Both CAD- and CAD+ groups had lower concentrations of apos A-I and A-II but higher concentrations of serum total and very low density lipoprotein triglyceride and very low density lipoprotein cholesterol than did healthy controls. The mean concentrations of serum total and low density lipoprotein cholesterol and the median values of Lp(a) were similar in the CAD+ and CAD- groups, both having higher concentrations of low density lipoprotein cholesterol and apo B than the healthy controls. Irrespective of gender, patients with CAD had significantly lower serum high density lipoprotein cholesterol than did those without CAD (1.48 +/- 0.40 versus 1.16 +/- 0.29 mmol/l, p less than 0.001). In women, the mean serum total and very low density lipoprotein triglyceride concentration was also higher in the CAD+ than in the CAD- group. The frequency of the apo E4 allele (epsilon 4) was significantly higher in the CAD+ group (0.293) than in the CAD- group (0.174; p less than 0.001). The frequencies of the two apo B alleles, X1 (Xba I restriction site absent) and X2 (Xba I restriction site present), were similar in the two groups. Stepwise discriminant analysis revealed that in men, serum high density lipoprotein cholesterol had the highest power to discriminate for CAD. In addition, the concentration of plasma apo B levels and the occurrence of apo E phenotypes were independently associated with CAD in men. In women, the only independent factor associated with CAD after adjustment for beta-blocker and diuretics usage was the concentration of serum triglycerides.

Adult↗
PubMed2002

Joint effects of pleiotropic selection and stabilizing selection on the maintenance of quantitative genetic variation at mutation-selection balance.

In quantitative genetics, there are two basic "conflicting" observations: abundant polygenic variation and strong stabilizing selection that should rapidly deplete that variation. This conflict, although having attracted much theoretical attention, still stands open. Two classes of model have been proposed: real stabilizing selection directly on the metric trait under study and apparent stabilizing selection caused solely by the deleterious pleiotropic side effects of mutations on fitness. Here these models are combined and the total stabilizing selection observed is assumed to derive simultaneously through these two different mechanisms. Mutations have effects on a metric trait and on fitness, and both effects vary continuously. The genetic variance (V(G)) and the observed strength of total stabilizing selection (V(s,t)) are analyzed with a rare-alleles model. Both kinds of selection reduce V(G) but their roles in depleting it are not independent: The magnitude of pleiotropic selection depends on real stabilizing selection and such dependence is subject to the shape of the distributions of mutational effects. The genetic variation maintained thus depends on the kurtosis as well as the variance of mutational effects: All else being equal, V(G) increases with increasing leptokurtosis of mutational effects on fitness, while for a given distribution of mutational effects on fitness, V(G) decreases with increasing leptokurtosis of mutational effects on the trait. The V(G) and V(s,t) are determined primarily by real stabilizing selection while pleiotropic effects, which can be large, have only a limited impact. This finding provides some promise that a high heritability can be explained under strong total stabilizing selection for what are regarded as typical values of mutation and selection parameters.

Genetic Variation↗
PubMed1998

Genetic variation in paraoxonase-1 and paraoxonase-2 is associated with variation in plasma lipoproteins in Alberta Hutterites.

In a sample taken from the genetically isolated Alberta Hutterites, we previously found that PON1 variation was associated with variation in plasma lipoprotein traits, including LDL and HDL cholesterol. With the recent cloning of the PON1-related gene PON2, we undertook studies of the association between genetic variation in PON2 and variation in plasma quantitative traits variation in a sample of 745 Alberta Hutterites. We found novel genetic associations between PON2 variation and variation in fasting plasma concentrations of total cholesterol and apolipoprotein AI. We confirmed our previously observed significant associations in this study sample between PON1 genetic variation and variation in plasma apo B-related traits, such as LDL, non-HDL and HDL cholesterol and apo B itself. Furthermore, there was almost complete linkage disequilibrium between PON2 alleles G148 and C311. We found no association between PON2 variation and plasma glucose or insulin. Taken together, our results suggest that common genetic variation on chromosome 7q21.3-22.1 in both PON1 and PON2 that affects the amino acid sequence of the respective gene products is associated with significant variation in intermediate traits in plasma lipoprotein metabolism.

Alberta↗
PubMed2001

Genetic variation in stimulated GH release and in IGF-I of young dairy cattle and their associations with the leucine/valine polymorphism in the GH gene.

Genetic variations in plasma GH concentrations before and following thyrotropin-releasing hormone (TRH) stimulation and in IGF-I concentrations were studied in 11-mo-old Polish Friesian cattle (104 heifers and 110 bulls). A possible association between stimulated GH release, IGF-I, and the polymorphism in the GH gene causing substitution of leucine-Leu to valine-Val at amino acid position 127 of the protein was also investigated. The GH concentrations were determined in serial plasma samples collected every 15 min from 15 min before to 135 min after intravenous administration of 0.15 microg TRH/kg live weight. The analysis was performed on three variables: baseline (mean of samples at -15 and 0 min), peak (sample at 15 min after injection) and rate (peak minus sample at 60 min, divided by 45 min). The IGF-I concentrations were measured in plasma samples taken before the TRH stimulation. Additionally, first lactation records from the 75 cows earlier tested for GH release and IGF-I were used to study a possible association of milk production traits with GH genotypes. The data were analyzed by multivariate mixed linear models. The heritability of IGF-I reached a higher value (0.35) than variables baseline, peak, and rate (0.02, 0.14, and 0.14, respectively). The GH variables were positively genetically correlated with each other (0.22 to 0.93), whereas they had negative genetic correlations with IGF-I (-0.26). The Val/Val genotypes reached the highest peak value compared with other GH genotypes (P > 0.01), whereas the Leu/Leu genotypes had the highest IGF-I concentrations (P < or = 0.05). Moreover, the Leu/Val heterozygotes were superior to others in milk and protein yields, whereas the Leu/Leu homozygotes reached the highest fat yield (P > or = 0.01). We conclude that GH peak, GH rate, and IGF-I are heritable traits in young dairy cattle and are affected by the Leu/Val polymorphism in the GH gene.

Alleles↗
PubMed1998

Extensive genetic variation revealed in adjacent populations of the schistosome intermediate host Biomphalaria pfeifferi from a single river system.

Random amplified polymorphic DNA (RAPD) analysis was used to study genetic variation among schistosome hosts of the species Biomphalaria pfeifferi. The analysed snails came from 15 sites along a 6-km stretch of a Zimbabwean river, providing data on genetic-geographical relationships over, probably, the smallest scale yet studied for any snail intermediate host species. Only 6% of the DNA fragments were common to all snails, and snail populations as geographically close as 100 m were genetically distinct. The most genetically polymorphic snail populations were those collected within and downstream from human water-contact sites.

Animals↗
PubMed1989

Genetic variation in the body weight of ticks of the Rhipicephalus appendiculatus/zambeziensis complex.

Sixteen strains of ticks of the Rhipicephalus appendiculatus/zambeziensis complex were created by cross-breeding for one to three generations. The body-weights of adult male ticks of these consanguineous lines were compared. A significant genetic variation was distinguished between the groups. Three classes whose mean weights varied around, respectively, 2, 3 and 4 mg/adult male tick, were found. This variation in weight may be explained by hybridization between R. appendiculatus Neumann and R. zambeziensis Walker, Norval & Corwin. Hybrid ticks were undersized whereas R. appendiculatus and R. zambeziensis groups had significantly higher weights.

Animals↗
PubMed1978

Genetic variation of some aldehyde-oxidizing enzymes in the mouse.

1. Twenty-six strains of mice were surveyed by starch gel electrophoresis for genetic variation of four liver enzymes; aldehyde dehydrogenase, aldehyde oxidase, xanthine oxidase and formaldehyde dehydrogenase. 2. A variant of aldehyde dehydrogenase was found in strains ICFW, IS/Cam, NZB, NZW, Simpson and Schneider. A variant of aldehyde oxidase was found in CE. A possible variant of xanthine oxidase was found in SF/Cam. 3. The gene determining the electrophoretic variant of aldehyde oxidase is either the same as, or very closely linked to, the Aox gene which determines aldehyde oxidase activity.

Aldehyde Oxidoreductases↗
PubMed1995

Genetic variation in susceptibility to Trypanoplasma borreli infection in common carp (Cyprinus carpio L.).

Gynogenetic reproduction of homozygous females, or crossbreeding two homozygous animals, results in fish lines without genetic variation. Hybrid crosses are expected to express a more stable development than homozygous lines, the latter may have an important value for gaining insight into genetic components of host resistance to parasite infection. We examined the antibody response of carp (Cyprinus carpio L.) to infection with Trypanoplasma borreli. Outbred carp responded with a production of specific antibodies, but highly susceptible isogenic hybrid carp did not. This suggests an apparent relationship between susceptibility and the lack of specific antibody production. This relation was partially confirmed by the passive transfer of immunity with immune plasma. In addition, two isogenic homozygous carp lines were highly susceptible to the trypanoplasm (100% mortality), in contrast with outbred carp, the majority of which survived infection. None of the carp in either homozygous carp line produced an antibody response to parasite-unrelated antigen (DNP-KLH). This suggests that the low antibody response was not entirely due to a poor state of health, but that these carp have a genetically predetermined low antibody response.

Animals↗
PubMed2003

Genetic variations of matrix metalloproteinase-1 and -3 promoter regions and their associations with susceptibility to myocardial infarction in Japanese.

Matrix metalloproteinases (MMPs) are involved in plaque rupture, which is the main pathological cause of myocardial infarction (MI). Recently, several genetic studies have demonstrated that MMP-1 1G/2G polymorphism and MMP-3 5A/6A polymorphism modify each transcriptional activity in allele specific manners. Within this context, we conducted case-control studies to examine whether these genetic polymorphisms are associated with susceptibility to MI. Two groups comprising patients with MI (group-1 164 patients, group-2 302 patients) were compared with control group comprising 335 patients without cardiovascular diseases. The MMP-3 5A allele was more frequent in patients with MI than in the control subjects (P=0.018 MI group-1, P=0.0059 MI group-2), whereas there was no disease association for MMP-1 genotypes. Logistic regression analyses revealed that MMP-3 5A/6A polymorphism was associated with susceptibility to MI [odds ratio(OR) (95% confidential interval) 1.67 (1.02-2.74); P=0.042, MI group-1; 1.61 (1.12-2.23); P=0.0095, MI group-2]. Other important findings were that there was strong linkage disequilibrium between these polymorphisms, which are located closely on chromosome 11q.22, and that the 5A-1G haplotype was a genetic risk factor for MI (OR 1.97 P=0.0082, MI group-1 OR 1.51 P=0.017, MI group-2). Taken together, the present findings suggest that genetic variations in these MMP genes and especially their haplotype may be useful genetic markers for determining susceptibility to MI in Japanese.

Aged↗