HLA molecular markers in Tuvinians: a population with both Oriental and Caucasoid characteristics.

HLA class I and class II alleles have been studied for the first time in the Turkish-speaking Tuvinian population, which lives in Russia, North of Mongolia and close to the Altai mountains. Comparisons have been done with about 11000 chromosomes from other worldwide populations, and extended haplotypes, genetic distances, neighbor joining dendrograms and correspondence analyses have been calculated. Tuvinians show an admixture of Mongoloid and Caucasoid characters, the latter probably coming from the ancient Kyrgyz background or, less feasibly, more recent Russian Caucasoid admixture. However, Siberian population traits are not found and thus Tuvinians are closer to Central Asian populations. Siberians are more related to Na-Dene and Eskimo American Indians; Amerindians (from nowadays Iberian--America) are not related to any other group, including Pacific Islanders, Siberians or other American Indians. The 'more than one wave' model for the peopling of the Americas is supported.

Plasma epinephrine levels in hypertension and across gender and ethnicity.

Epinephrine (E) infusions raise blood pressure and there is an excess incidence of hypertension among males and blacks. However, reports of E levels by ethnicity, gender, and blood pressure status are inconsistent. Insensitive assays, variability in plasma E levels within individuals, and the small size of most studies have contributed to these conflicting reports. We measured plasma E levels in a large diverse sample of subjects, using a highly sensitive assay. A total of 361 individuals participated in the study: 61% were men and 39% women, 74% were normotensive and 26% hypertensive, 59% were white and 41% were black. Except for difference in blood pressure and body mass index between the normotensives and hypertensives, subjects had similar baseline characteristics and took no antihypertensive medications for at least five days prior to sampling. All blood samples were collected after resting for a least 30 minutes following the insertion of an indwelling i.v. catheter. Catecholamine levels were determined using a radioenzymatic assay (assay sensitivities for E and norepinephrine were 6 pg/ml and 10 pg/ml, respectively). An ethnicity by gender interaction was found (F(1,315) = 5.126, p = .024). Subsequent analysis revealed that white women had significantly lower basal plasma E levels than white men (p <0.001) and black women (p = 0.036). There were no significant differences in E levels between black men and women or between white men and black men. Uncorrected E levels were lower in normotensive than hypertensive subjects (p = .009) but this difference was not significant when corrected for body mass index (BMI). Uncorrected norepinephrine levels were higher in women than men (p = .03) but the difference was no longer significant when corrected for BMI. Plasma E levels were significantly lower among white women than men or black women. In contrast to prior studies, E levels were lower in hypertensives, but this may reflect obesity among hypertensives.

The origin of Cretan populations as determined by characterization of HLA alleles.

The Cretan HLA gene profile has been compared with those of other Mediterranean populations in order to provide additional information regarding the history of their origins. The allele frequencies, genetic distances between populations, relatedness dendrograms and correspondence analyses were calculated. Our results indicate that the Indoeuropean Greeks may be considered as a Mediterranean population of a more recent origin (after 2000 B.C.), while all other studied Mediterraneans (including Cretans) belong to an older substratum which was present in the area since pre-Neolithic times. A significant Turkish gene flow has not been detected in the Greek or Cretan populations, although Greeks and Turks have two high frequency HLA-DRB-DQB haplotypes in common. It is proposed that Imazighen (Caucasoid Berbers living at present in the North African coast and Saharan areas) are the remains of pre-Neolithic Saharan populations which could emigrate northwards between about 8000-6000 B.C., when desert desiccation began. They also could be part of the stock that gave rise to Sumerians, Cretans and Iberians; this is supported by both linguistic and HLA genetic data.

Prevalence of hepatitis C virus infection at three hemodialysis units in the western region of Puerto Rico.

OBJECTIVE: In the United States hepatitis C virus infection (HCV) affects approximately 20 percent of hemodialysis patients but its prevalence in Puerto Rico has not been established. We have sought to determine the prevalence of HCV infection in a homogeneous sample of patients on hemodialysis in the western region of Puerto Rico and to identify its risks factors. METHODS: All patients in the hemodialysis units of Aguadilla, Mayagüez and San Germán, during December 1997 to March 1998, completed a written questionnaire in which they were asked about transfusions, multiple sexual partners, i.v. drugs use, tattooing, occupation, imprisonment, organ transplantation and years on hemodialysis. Serum samples were analysed for HCV antibodies by an enzyme-linked immunoadsorbent assay (ELISA). Sera with positive results for HCV were subjected to a confirmatory test by the polymerase chain reaction (PCR). RESULTS: Thirteen of the 376 (3%) subjects had a positive ELISA (one patient died prior the confirmatory test with PCR). Six out of the twelve patients had a positive PCR. Two had been transfused. Three were illicit i.v. drug users and one had received a renal transplant. The liver biopsies in all patients showed chronic hepatitis and in two there was cirrhosis. CONCLUSIONS: Our prevalence was two percent. As reported elsewhere blood transfusion, organ transplantation and illicit i.v. drug abuse were the major risk factors for HCV infection in our patients. Nosocomial factors were irrelevant in the results.

Detection of HLA-E and -G DNA alleles for population and disease studies.

HLA-E and -G genes show a restricted polymorphism encoding for molecules whose variability is limited at the peptide binding site. Fourteen alleles that give rise to only three productive proteins for HLA-G (*0101, *0103 and *0104) and five alleles with three different proteins for HLA-E (*0101, *0102 and *0103) have been described. Expression of these molecules is low and found in many tissues for HLA-E: HLA-G protein is expressed in extravillous trophoblast cells and thymic epithelium. Molecular studies have shown how HLA-G and HLA-E bind to natural killer (NK) cells immunoglobulin and lectin-type inhibitory receptors. HLA-E may act as a sentinel of the cell; if classical class I and HLA-G are being expressed, HLA-E molecules may reach the cell surface and inhibit the lysis by NK cells. Most findings are consistent with the hypothesis that HLA-E and -G proteins may be tolerogenic molecules at either the T-cell receptor (TcR) (inflammation, graft rejection) or NK level, switching off cells which usually attack foreign (including foetus) or self (autoimmune) antigens. A low HLA-E and -G polymorphism is observed in humans, and their allele frequencies are mostly homogeneous in the populations tested so far. Many studies to detect these alleles are now being performed in isolated populations and also in pregnancy-associated pathologies. In the present paper, standard and detailed techniques to detect HLA-E and -G DNA polymorphism are reported and discussed.