Environmental determinants on the assemblage structure of Drosophilidae flies in a temperate-subtropical region

The species composition and the relative abundance of species in an insect community can vary in time and space for many reasons, including climatic variables and habitat preferences. Drosophilids were collected each quarter from April 2011 to April 2012 (five collections in all) in a natural area of the Pampa biome, considering three environments: open field, forest edge and the interior of forest patches. Kruskal-Wallis and chi-square tests were used to examine the effects of temporal and spatial components on the drosophilid assemblage. Four diversity measures: S obs , S rar , H' and E var were used to evaluate the community structure. A total of 7164 drosophilids belonging to 51 species were collected. The interaction of species in each environment varied among sampling periods. The abundance of both Neotropical and exotic species was affected by temporal and spatial components. The species of the D. repleta group were predominantly more abundant in the open field, but they migrated to the forest patches during periods of thermal stress. Generally, diversity was greatest in the interior of forest patches. Nevertheless, temporal components appear to be the predominant environmental determinant of the characteristics of the drosophilid community of the Pampas. Furthermore, the forest patches appear to act as a center of recolonization, reinforcing their importance in the maintenance of biodiversity in the Pampas; this function will be even more important in the future, when the temperatures will, most likely, be higher.

Implications of the admixture process in skin color molecular assessment

The understanding of the complex genotype-phenotype architecture of human pigmentation has clear implications for the evolutionary history of humans, as well as for medical and forensic practices. Although dozens of genes have previously been associated with human skin color, knowledge about this trait remains incomplete. In particular, studies focusing on populations outside the European-North American axis are rare, and, until now, admixed populations have seldom been considered. The present study was designed to help fill this gap. Our objective was to evaluate possible associations of 18 single nucleotide polymorphisms (SNPs), located within nine genes, and one pseudogene with the Melanin Index (MI) in two admixed Brazilian populations (Gaucho, N = 352; Baiano, N = 148) with different histories of geographic and ethnic colonization. Of the total sample, four markers were found to be significantly associated with skin color, but only two (SLC24A5 rs1426654, and SLC45A2 rs16891982) were consistently associated with MI in both samples (Gaucho and Baiano). Therefore, only these 2 SNPs should be preliminarily considered to have forensic significance because they consistently showed the association independently of the admixture level of the populations studied. We do not discard that the other two markers (HERC2 rs1129038 and TYR rs1126809) might be also relevant to admixed samples, but additional studies are necessary to confirm the real importance of these markers for skin pigmentation. Finally, our study shows associations of some SNPs with MI in a modern Brazilian admixed sample, with possible applications in forensic genetics. Some classical genetic markers in Euro-North American populations are not associated with MI in our sample. Our results point out the relevance of considering population differences in selecting an appropriate set of SNPs as phenotype predictors in forensic practice.

HLA-G +3142 polymorphism as a susceptibility marker in two rheumatoid arthritis populations in Brazil

In this study, we sought to investigate the genetic influence of two HLA-G 3'-untranslated region (3'-UTR) polymorphisms - 14 bp (rs66554220) and +3142C>G (rs1063320) and their compounding haplotypes in susceptibility to rheumatoid arthritis (RA) in a two-region Brazilian study comprising of 539 patients and 489 controls. All subjects were polymerase chain reaction (PCR) genotyped for the referred polymorphisms and logistic regression models controlling for sex, city and age were performed. Homozygozity for the +3142G allele was associated with an increased risk of RA [odds ratio (OR) = 1.45, 95% confidence interval (CI) = 1.075-1.959, P(Bonf)  = 0.030], whereas no association was observed for the 14 bp polymorphism. Haplotype comparisons between patients and controls showed a decreased frequency of the delC haplotype in patients (OR = 0.70, 95% CI = 0.521-0.946, P(Bonf)  = 0.040), which remained significant in the rheumatoid factor (RF)-positive group (OR = 0.66, 95% CI = 0.482-0.900, P(Bonf)  = 0.018), but not in the RF-negative group. These results corroborate the hypothesis of an involvement of HLA-G in the susceptibility of RA. The +3142G allele is associated with haplotype lineages that share high identity and are regarded as low producers. The presence of the G allele in homozygosis could be responsible for a low HLA-G expression profile that could favor the triggering of RA.

Effect of nortriptyline on brain responses to painful esophageal acid infusion in patients with non-erosive reflux disease

BACKGROUND

Non-erosive reflux disease (NERD) patients generally present with heartburn as the main symptom. Antidepressants might help to relieve heartburn by acting on the esophagus-brain axis. We aimed to assess the effect of nortriptyline on behavioral and brain responses to painful esophageal acid infusion in NERD patients evaluated with functional magnetic resonance imaging (fMRI).

METHODS

In a randomized double-blind crossover design, 20 NERD patients off proton pump inhibitors (36.1 ± 9.3 years, 75% women) were assigned to 21 days of nortriptyline and placebo, in counterbalanced order, with a 21 days washout period in between both treatment periods. Changes in acid-induced brain response on fMRI and heartburn perception were assessed and at the end of each treatment.

KEY RESULTS

Nortriptyline significantly reduced the acid-induced brain response in prefrontal cortex (median [IQR]: -1.9 [-4.5 to -0.1] vs -0.3 [-2.5 to 2.3]; p = 0.050), caudate (-3.0 [-5.1 to -0.01] vs 0.48 [-1.9 to 3.1]; p = 0.029), insula (-2.4 [-4.8 to -0.6] vs -0.2 [-1.5 to 1.5]; p = 0.029), cingulate (-4.2 [-8.8 to -0.1] vs -0.6 [-1.8 to 3.0]; p = 0.017), and hippocampus (-2.7 [-6.0 to 0.5] vs -0.04 [-2.3 to 1.9]; p = 0.006) in comparison with placebo. However, there was no significant difference between nortriptyline and placebo in clinical outcomes and side effects.

CONCLUSIONS & INFERENCES

Nortriptyline decreased the brain response to esophageal acid infusion more markedly than placebo, but without clinical significance.

N-acetyl transferase 2 and cytochrome P450 2E1 genes and isoniazid-induced hepatotoxicity in Brazilian patients

SETTING

Isoniazid (INH) is related to the development of hepatotoxicity in some patients.

OBJECTIVE

To investigate the role of N-acetyl transferase 2 (NAT2) and cytochrome P450 2E1 (CYP2E1) in the hepatotoxicity of patients treated with INH in an Amazonian Brazilian population.

DESIGN

Patients undergoing anti-tuberculosis treatment were investigated. Hepatotoxicity was defined as an increase of more than three times the upper limit of normal in serum alanine aminotransferase levels after treatment. NAT2 genotypes were identified by sequencing, whereas CYP2E1 alleles were detected using polymerase chain reaction based methods.

RESULTS

Of the 270 individuals included in the study, 18 (6.7%) developed drug-related hepatotoxicity. A high association was found between slow acetylators and hepatotoxicity, particularly with regard to allele *5. The adjusted risk of developing hepatotoxicity was significant in individuals carrying two slow acetylation alleles (P = 0.036, OR 3.05, 95%CI 1.07-8.64). In all of the CYP2E1 markers examined, wild homozygous genotypes were more prevalent in subjects with hepatotoxicity than in controls; however, the difference was not statistically significant. Joint evaluation of the genes revealed a high risk of developing hepatotoxicity in slow acetylators with CYP2E1 wild alleles (adjusted OR 4.26; 95%CI 1.47-12.37, P = 0.008).

CONCLUSIONS

Large-scale screening for NAT2 and CYP2E1 genotypes can prove useful in predicting the risk of adverse effects.

Is there an association between hiatal hernia and ineffective esophageal motility in patients with gastroesophageal reflux disease?

INTRODUCTION

The pathophysiology of gastroesophageal reflux disease is multifactorial, where esophageal motility is one of the factors implicated in its genesis. However, there is still no consensus on the existence of an association between esophageal dysmotility and hiatal hernia in patients with gastroesophageal reflux disease. The objective of this study was to establish the prevalence of esophageal dysmotility in patients with hiatal hernia and to determine if herniation is a factor related to esophageal dysmotility in patients with gastroesophageal reflux disease.

METHODS

The study included 356 patients with a clinical diagnosis of gastroesophageal reflux disease submitted to upper digestive endoscopy and esophageal functional diagnostics. Hiatal hernia was defined endoscopically by a distance equal to or greater than 2 cm between the diaphragmatic constriction and the squamocolumnar junction and esophageal dysmotility when the esophageal manometry identified the amplitude of the peristaltic waves in the distal esophagus as <30 mmHg and/or less than 80% of effective contractions. For univariate statistical analysis, the patients were divided into two groups: with and without hiatal hernia. Poisson regression models were used to estimate crude and adjusted prevalence ratios (PR) of esophageal dysmotility according to hiatal hernia.

RESULTS

Gastroesophageal reflux disease patients with hiatal hernia had a prevalence of esophageal dysmotility equal to 14.8% and those without hiatal hernia, a prevalence of 7.7% (p = 0.041). Patients with hiatal hernia also showed a higher frequency of erosive esophagitis (47.5% versus 24.2%, p < 0.001), lower low esophageal sphincter pressure (10.4 versus 13.10; p < 0.001), and higher frequency of individuals with abnormal pH-metry values (p < 0.001). The crude PR for esophageal dysmotility, according to the presence of hiatal hernia, was 1.92 (confidence interval (CI), 1.04-3.53; p = 0.037), but this association did not persist when controlled for age, esophagitis, altered pH-metry, and altered low esophageal sphincter (adjusted PR, 1.69; CI, 0.68-4.15; p = 0.257).

CONCLUSION

Despite the prevalence of esophageal dysmotility in the hiatal hernia group being higher than that in the group without hiatal hernia, the association between these variables in individuals with gastroesophageal reflux disease disappeared when controlling for age, esophagitis, altered pH-metry, and altered low esophageal sphincter, leading us to believe that in these patients, hiatal hernia is not an independent risk factor for dysmotility.

Heartburn during sleep: a clinical marker of gastro-oesophageal reflux disease in morbidly obese patients

Gastro-oesophageal reflux disease (GORD) and morbid obesity are entities with increasing prevalence. New clinical strategies are cornerstones for their management. The aim of this study was to assess the prevalence of heartburn during sleep (HDS) and whether this symptom predicts the presence of objective GORD parameters and increased heartburn perception in morbidly obese patients. Ninety-one consecutive morbidly obese patients underwent clinical evaluation, upper gastrointestinal endoscopy and oesophageal pH monitoring. HDS was characterized when patients replied positively to the question, 'Does heartburn wake you from sleep?'. A General Score for Heartburn (GSH) ranging between 0 and 5 was assessed with the question 'How bad is your heartburn?'. HDS was reported by 33 patients (36%). More patients with HDS had abnormal acid contact time or reflux oesophagitis than patients without HDS (94%vs 57%, P < 0.001). HDS had a positive predictive value of 94% (0.95 CI 82-98), sensitivity of 48% (0.95 CI 37-60%) and specificity of 93% (0.95 CI 77-98%) for detection of GORD. A higher proportion of patients with HDS perceived heartburn preceded by acid reflux in diurnal (39%vs 9%; P < 0.001) periods during pH-metry. HDS patients showed higher GSH (2.4 +/- 0.5 vs 1.7 +/- 0.4; P < 0.0001) compared with patients who denied HDS but reported diurnal heartburn. HDS occurs in a significant minority of patients with morbid obesity and has high positive predictive value for GORD. Symptomatic reflux during the sleep seems to be a marker of increased heartburn perception in this population.

Nutcracker oesophagus: association with chest pain and dysphagia controlling for gastro-oesophageal reflux

BACKGROUND

The association between nutcracker oesophagus, gastro-oesophageal reflux and their symptoms is controversial.

AIM

To evaluate the association of nutcracker oesophagus with chest pain and dysphagia controlling for gastro-oesophageal reflux.

METHODS

From a database of 935 consecutive patients investigated with oesophageal manometry and pH-metry, we selected all patients with nutcracker oesophagus including diffuse and segmental patterns. Patients with normal oesophageal peristalsis served as controls. Symptoms assessment, manometry testing and 24h oesophageal pH monitoring off acid-suppressive medications were performed following a standardized protocol. The associations between nutcracker oesophagus and symptoms were assessed by logistic regression analysis.

RESULTS

Nutcracker oesophagus was found in 60 patients (6.4%), of which 30 had diffuse nutcracker oesophagus and 30 had segmental nutcracker oesophagus. The control group was composed by 656 patients with normal oesophageal peristalsis. Diffuse nutcracker oesophagus was associated with chest pain (odds ratio 4.3; 95% CI 1.9-9.9; P<0.0001) and dysphagia (odds ratio 5.3; 95% CI 2.3-12.2; P<0.0001), whereas segmental nutcracker oesophagus was associated with chest pain (odds ratio 2.8; 95% CI 1.1-6.9; P=0.026), controlling for total oesophageal acid exposure, age, sex and lower oesophageal sphincter (LOS) pressure.

CONCLUSION

This study suggests that both diffuse and segmental nutcracker oesophagus should be regarded as meaningful abnormalities and not mere manometric curiosities.

DNA sequence analysis and the phylogeographical history of the rodent Deltamys kempi (Sigmodontinae, Cricetidae) on the Atlantic Coastal Plain of south of Brazil

The rodent Deltamys kempiThomas, 1917 is found on the Coastal Plain - a recently formed geographic region located on Brazil's south-east coast. Considering that Deltamys is the only South American sigmodontine with a sex chromosome system of type X(1)X(1)X(2)X(2)/X(1)X(2)Y, this investigation was focused on the phylogeographic history of this taxon by using gene sequence analysis, trying to clarify when Deltamys differentiated, what was its centre of diversification, and what were the probable routes it used to reach its present distribution. We analysed sequences of the mitochondrial cytochrome b gene and nuclear recombination activating gene 2, performed cranial measurements and searched for centric fusions in individuals collected in distinct localities. The results, clearly demonstrate that D. kempi, on the Coastal Plain, divided into two groups, one occupying a small portion to the north of this region and the other spreading widely to the south. In this process, the phenomena of marine transgression and regressions which moulded its habitat, together with the occurrence of successive chromosomal rearrangements, were certainly the fundamental factors in shaping D. kempi diversification.

Genetic diversity and relatedness within and between species of the genus Oligoryzomys (Rodentia; Sigmodontinae)

A RAPD analysis on six species of the rodent genus Oligoryzomys trapped in a wide area (ranging from 01 degrees N to 32 degrees S) of Brazilian territory was performed in order to determine the levels of genetic variability within and between its populations and species. One-hundred and ninety-three animals were collected in 13 different sites (corresponding to 17 samples) located at Pampas, Atlantic Rain Forest, Cerrado, and Amazon domains. Oligoryzomys sp., O. nigripes (8 populations), O. flavescens (4 populations), O. moojeni, O. stramineus, and O. fornesi were the taxa analyzed. Of the 20 primers tested, 4 generated a total of 75 polymorphic products simultaneously amplified in 151 specimens. Various diversity estimators analyzed showed considerable differences between species and populations, indicating a great genetic variation occurring in the Oligoryzomys taxa investigated. A cluster analysis was made using Nei's standard genetic distances, however, it did not correlate the genetic heterogeneity of the species and populations with the geographical areas.

Application of an African Ancestry Index as a Genomic Control Approach in a Brazilian Population

Ten ancestry informative markers were investigated in 101 coronary artery disease patients and 102 healthy controls from a Southern Brazilian population, in order to determine if stratification occurs in this population. The degree of African admixture detected in this population was estimated to be as high as 6%, but no differences between cases and controls were observed. Using an African Ancestry Index (AAI) that estimates admixture at the individual level it was possible to remove from the samples those individuals with evidence of African admixture. Therefore we have shown that it is possible to control for population stratification by choosing individuals, without the loss of statistical power that occurs with the use of other methods of genomic control.

Estrogen-metabolizing gene polymorphisms and lipid levels in women with different hormonal status

Endogenous and exogenous sex steroid hormones have multiple effects on lipid and lipoprotein metabolism. It is also known that estrogen has antiatherogenic actions, therefore we considered examining whether there was any association between polymorphisms in estrogen-metabolizing genes and lipid levels in women. We investigated the association between variants in genes related to estrogen biosynthesis (CYP19-TTTA(n)) and estrogen catabolism (CYP1A1*2A, CYP1A1*2C, CYP1A2-Asn516Asn, CYP3A4*1B, and COMT-Val158Met) with serum lipid levels in a cross-sectional study with 472 Brazilian women of European descent. They were divided into three subgroups according to their hormonal status: premenopausal women (n=187), postmenopausal women exposed to hormonal replacement therapy (HRT) (n=118), and postmenopausal women unexposed to HRT (n=167). The postmenopausal women receiving HRT who were carriers of the CYP3A4*1B variant showed lower low-density lipoprotein cholesterol levels than wild-type homozygotes. Premenopausal women homozygous for the CYP1A1*2C allele had higher high-density lipoprotein cholesterol levels than heterozygotes. While the CYP1A1*2C variant probably has a higher catalytic activity, the functional implications of the CYP3A4 polymorphism are still uncertain. These data are the first attempt to associate estrogen metabolism genes to lipid levels in women.

Interaction between SREBP-1a and APOB polymorphisms influences total and low-density lipoprotein cholesterol levels in patients with coronary artery disease

In this study, we examined the insertion/deletion (Ins/Del) and XbaI polymorphisms of the apolipoprotein B (APOB) gene and the -36delG polymorphism in the sterol regulatory element binding protein-1a (SREBP-1a) gene in 298 patients with non-diabetic angiographically assessed coronary artery disease (CAD), and 188 healthy controls, from a Brazilian population of European descent. Del/X+ haplotype carriers had higher levels of total cholesterol (TC) and low-density lipoprotein cholesterol (LDL-C) in patients (TC, p = 0.05; LDL-C, p = 0.049) and controls (TC, p = 0.004; LDL-C, p = 0.013). No association was detected between the SREBP-1a-36delG polymorphism and lipid levels, but a significant interaction effect between APOB and SREBP-1a polymorphisms was observed in the patient sample on TC (p = 0.005) and on LDL-C (p = 0.019) levels. Carriers of the APOB Del/X+ haplotype and SREBP-1a G-G- genotype showed the highest levels of these lipid parameters. This effect of interaction was not observed in the control sample. Despite the associations with lipids, these polymorphisms were not associated with CAD risk or severity in this sample.

Alu insertions versus blood group plus protein genetic variability in four Amerindian populations

BACKGROUND

Do the population relationships obtained using DNA or blood group plus protein markers remain the same or do they reveal different patterns, indicating that the factors which influence genetic variation at these two levels of analysis are diverse? Can these markers shed light on the biological classification of the Aché, a Paraguayan tribe which only recently established more permanent contacts with non-Indians?

SUBJECTS AND METHODS

To consider these questions we typed 193 individuals from four Amerindian tribes in relation to 12 Alu polymorphisms (five of them never studied in these populations), while 22 blood group plus protein systems were studied among the Aché. These data were then integrated with those previously available (blood groups plus proteins) for the three other populations. DNA extraction and amplification, as well as the other laboratory procedures, were performed using standard methods currently in use in our laboratory. The genetic relationships were obtained using the D(A) distance, and the trees were constructed by the neighbour-joining method, both developed by M. Nei and collaborators. Reliability of the trees was tested by bootstrap replications. Other population variability values were also determined using Nei's methods.

RESULTS

Alu polymorphism was observed in all populations and for most of the loci; in the seven systems from which we could compare our results with those of other Amerindian groups agreement was satisfactory. Unusual findings on the blood group plus protein systems of the Aché were a very low (5%) HP*1 frequency and the presence of the C(W) phenotype in the Rh blood group. The intertribal patterns of relationship and other aspects of their variation were remarkably congruent in the two sets (Alu; blood group plus protein) of systems.

CONCLUSIONS

The answer to the first question posed above is affirmative. However, the problem of whether the Aché derived from a Gê group that preceded the Guarani colonization of Paraguay, or are just a differentiated Guarani group, could not be answered with the genetic information available; the second hypothesis seems more likely at present, but the point to be emphasized is the striking genetic distinctiveness of the Aché as compared to other Amerindians.

Genetic, geographic, and linguistic variation among South American Indians: possible sex influence

To better understand the relationship between genetic variability, geographical distance, and linguistic affiliation in South Amerinds, and to elucidate whether the migration rate is the same for both sexes, spatial autocorrelation, Mantel's test, and F(ST) analyses were performed in four sets of populations and alleles (group 1: 48 populations, 12 alleles; group 2: 16 (all belonging to the Tupi linguistic group) and 12; group 3: 21 and 17; and group 4: 28 and 4 haplotypes). Groups 1-3 included blood group and protein (i.e., serum protein, red cell enzymes, and immunoglobulin systems), while group 4 was concerned with mitochondrial DNA (mtDNA) only. The latter set was also subjected to a molecular analysis of variance (AMOVA) evaluation. The frequencies of statistically significant correlograms were lower than those obtained in other populations when the blood groups and protein systems were considered, but 3 of the 4 mtDNA haplogroups gave suggestions of population structure. The variability in this organelle is also significantly correlated with language when geography is held constant. Migration per generation is generally low, but higher estimates were obtained for females. The AMOVA results suggest that populations whose members speak the same language are genetically homogeneous and may be viewed as the ultimate evolutionary unit at this level of analysis.

New genetic data on Amerindians from the Paraguayan Chaco

New data on 17 blood group and protein genetic systems obtained among the Ayoreo and Lengua Indians of Paraguay are presented. They include the first report on the red cell band-3 protein investigated among South American Indians. This information was integrated with previous results available for these two and four other groups. Five of the six populations reside in the Chaco area, while the sixth was included as an outgroup living elsewhere in Paraguay. Four of the five Chaco tribes exhibit good genetic homogeneity, but the Ayoreo are somewhat different. The results confirm the Chaco as a distinct biological (as well as cultural and economic) region, which should be considered in evaluations of genetic variability among South American Indians.

Genetic relationships between Amerindian populations of Argentina

A total of 495 individuals from five different Argentinian tribes was examined for variation in 23 blood group and protein genetic systems, and the results were integrated with previous data on some of these systems. These tribes generally present RH * R1, PGM1 * 1, and ACP * A frequencies lower and RH * R2, ESD * 1, and GLO * 1 prevalences higher than those observed in other South American Indian groups. Earlier studies with mitochondrial DNA showed that haplogroup A was present in low frequencies in these tribes, but haplogroup B showed a high prevalence among the Mataco. Average heterozygosities are very similar in the five tribes, while estimates of non-Indian ancestry are generally low. Both the blood group and protein, as well as the mtDNA data sets, divide the five tribes into two groups, and the relationships obtained with the blood group and protein systems are exactly those expected on the basis of geography and language. However, the topology obtained with the mtDNA results was different, possibly due to sampling effects or diverse patterns of exchange between the groups related to sex.

Association of apolipoprotein E polymorphism with plasma lipids and Alzheimer's disease in a Southern Brazilian population

Apolipoprotein E (protein: apo E; gene: APOE) plays an important role in the multifactorial etiology of both Alzheimer's disease (AD) and lipid level concentrations. The polymerase chain reaction (PCR) was used to investigate the APOE gene polymorphism in 446 unrelated Caucasians, among them 23 AD patients, and 100 Afro-Brazilians living in Porto Alegre, Brazil. The frequencies of the APOE*2, APOE*3 and APOE*4 alleles were 0.075, 0.810 and 0.115 in Caucasians and 0.075, 0.700 and 0.225 in Afro-Brazilians, respectively (chi2 = 8.72, P = 0.013). A highly significant association was observed between the APOE*4 allele and AD in this population-based sample. The APOE*4 frequency in AD patients (39%) was about four times higher than in the general Caucasian population (11.5%). The influence of each of the three common APOE alleles on lipid traits was evaluated by the use of the average excess statistic. The E*2 allele is associated with lower levels of triglycerides and of total and non-HDL cholesterol in both men and women. Conversely, the E*4 allele is associated with higher levels of these traits in women only. The effect of APOE alleles was of greater magnitude in women.

New protein genetic studies in six Amazonian Indian populations

A total of 732 individuals affiliated with six Amazonian Indian populations were variously studied in relation to 26 protein genetic systems. Eleven of them were found to be monomorphic in these groups, in accordance with previous investigations. Similarities and dissimilarities (the latter involving the Rh, Duffy, haptoglobin and transferrin systems) were observed in relation to earlier investigations in four of these populations (Galibi, Palikour, Mundurucu and Tenharim). A dimeric, cathodal variant of albumin was found among two Galibi subjects, and the fairly common occurrence of CP* ACAY among some South American Indian populations was confirmed. The results in the six populations were compared with those from 29 others. When relationships are searched for among tribes of the same linguistic group, the factor that seems to be most influential is geographical localization, an exception being the pattern observed among the Cayapo subgroups. The latter shows genetic differences of the same level of magnitude as those observed among Ge-speaking tribes.

Diversity in protein, nuclear DNA, and mtDNA in South Amerinds--agreement or discrepancy?

Two sets of markers and populations were considered in this study: (a) the variability at 17 protein loci and in the sequences of the first hypervariable segment of the mitochondrial DNA (mtDNA) were compared in 10 South American Indian tribes, in a total 3016 and 241 individuals, respectively; and (b) a triple comparison was made, in relation to 17 protein, mtDNA and six hypervariable tandem repeat loci in four Brazilian Indian tribes, involving 1567, 56 and 194 persons, respectively. Both the intrapopulational diversities and the population relationships obtained in these groups with these different sets of markers showed no significant correlation. High levels of heterogeneity were observed both at the protein and hypervariable individual loci, as well between mtDNA sites. The different positions observed for the Yanomama (but not for the other nine tribes) in the trees which summarized the protein and mtDNA data suggest some degree of asymmetric interchange related to sex between them and neighbouring tribes.

The Brazilian Xavante Indians revisited: new protein genetic studies

A total of 94 individuals from the Xavante village of Rio das Mortes were variously studied in relation to 28 protein genetic systems. No variation was observed for 15 of them, in accordance with previous studies. Of the remaining 13, four (Rh, Duffy, acid phosphatase, and GC) showed significant departures from the averages obtained in 32 other South American Indian populations. If studies performed in the 1960s are considered, there is indication that no significant changes in this village's gene pool has occurred in the last 30 years. Comparison with two other Xavante populations included nine systems with variation, and for three of them (MNSs, Rh, and Duffy) significant differences were found. Genetically the Rio das Mortes are closer to the São Marcos than to the Simões Lopes Xavantes. A dendrogram considering 25 genetic systems and 33 South American Indian populations was constructed. There the Xavante were grouped together, in two neighboring clusters, with three other tribes who speak Ge languages, But these clusters also present populations who speak other languages, and the reproducibility of the tree is low. South American Indians, at least with this set of markers, do not seem to be clearly classified into defined subgroups.

D1S80 locus variability in South American Indians

We have studied the hypervariable D1S80 locus in 185 individuals from five South American Indian tribes, integrating these results with previous investigations. Three alleles (*18, *24 and *30) were common to all tribes, but their frequencies varied between northern and southern populations. Brazilian tribes have a high frequency of *30 (average 35%) while in Argentinian and Chilean Indian populations this allele is present, on average, in 7% of the chromosomes only. Allele *24, the most common in other ethnic groups, was observed in 10% and 25% of northern and southern Amerindians respectively. Genetic distance and dendrogram analyses placed the Argentinian and Chilean tribes closer to Brazilian Caucasians, suggesting non-Indian admixture among them.

Gradients of HLA diversity in South American Indians

Information concerning the HLA-A and -B loci was considered in relation to 3796 Amerindians living in 39 places in South America, data related to HLA-C being based on a smaller subset of 2989 persons distributed among 33 localities. Synthetic gene frequency maps were then constructed using principal-components analysis. Clearly significant longitudinal (principal component 1) and latitudinal (principal components 1, 2, and 3) clines were observed, most probably indicating ancient migration routes.

The Wai Wai Indians of South America: history and genetics

Demographic medical and genetic information was obtained in a population of Carib-speaking Wai Wai Indians living in northern Brazil. At present mortality is low and fertility moderate, with a low variance in offspring number in completed families. Mobility is high, but about two-thirds of the unions are endogamic. Malaria is the main health problem. Phenotype and allele frequencies were obtained for 27 protein genetic systems. Comparison with six other Carib groups indicates closet affinities with another Amazonian tribe, the Arara. Quantification of the intra- and interpopulation genetic diversity in these seven populations indicate that the variation within groups is only slightly lower than the variation between groups. The level of Carib interpopulation diversity, on the other hand, does not differ significantly from that found in 11 Tupi-speaking populations. In accordance with their history of intermarriage with groups which speak slightly different languages, and consider themselves as distinct, the Wai Wai are clearly more diversified at the intrapopulation level than at least three of the six Carib populations with which they were compared.

Evolutionary relationships between black South American and African populations

Data related to ten protein genetic loci expressed in blood obtained from four South American black populations were compared with data from seven African countries. Estimates of admixture among South American blacks were revised, and several indexes of gene diversity and genetic distances between the 11 populations were calculated. The admixture values and genetic relationships observed among the South American black communities conform well with those expected on historical grounds, and they show only moderate reductions in genetic diversity.

Further blood genetic studies on Amazonian diversity--data from four Indian groups

Information related to 31 protein genetic systems was obtained for 307 individuals affiliated with the Cinta Larga, Karitiana, Surui and Kararaô Indians of northern Brazil. In terms of genetic distances the Cinta Larga showed more similarities with the Karitiana (both are Tupi-speaking tribes), while at a more distant level the Surui clustered with the Kararaô. The latter, a Cayapo subgroup, showed a completely different genetic constitution from the other subgroups of this same tribe. Both the Kararaô and Karitiana are small, remnant populations, and their gene pools have presumably been severely affected by random and founder effects. These results were incorporated with those of 25 other Amazonian Indian tribes, and analysis by two multivariate techniques confirmed a previously observed geographical dichotomy, suggesting either that the Amazon river constitutes a barrier to north-south gene flow or that latitudinally different past migrations entered the region from the west.

Genetic similarity and mate selection in Uruguay

It has been suggested that average genetic similarity, as assessed by blood genetic markers, could influence mate choice in humans. In the present study, average genetic similarity was assessed in 183 couples submitting to paternity determinations in relation to six blood group systems and three HLA loci. Couples in which the putative father was excluded were compared with those in which such exclusion did not occur, and real couples were compared to random pairs. The differences were all statistically nonsignificant. Possible reasons for the different results found in the previous sample and in the present study are considered.

Gm haplotype distribution in Amerindians: relationship with geography and language

A review is made of the Gm haplotype distribution in 60 groups of Eskimos, North, Central and South American Indians, totaling 22,808 individuals. Differences were observed in the shapes of the distribution of Gm*ag and the other markers. Nearly identical values for FST and average heterozygosities were obtained in the North+Central/South comparisons. North-South and Southwest/Northeast clinal differences were observed in the Americas using correspondence factorial analysis. The two haplotypes mainly responsible for these differences are Gm*axg and Gm*abOst. When the populations are classified by language groups, besides the recognized differences between Eskimos and Athabaskan (Na-Dene) speakers compared with Amerinds, others are found. For instance, Uto-Aztecan speakers of the United States and Mexico differ in Gm frequencies from the Nuclear Chibchan, Macro-Arawak, and Carib speakers of Central and South America. The notion of a homogeneous Amerind genetic pool does not conform with these and other results.

Blood genetic systems in four Amazonian tribes

Data on 31 genetic systems were obtained for 421 individuals belonging to the Arara, Araweté, Mundurucu, and Jamamadi tribes of northern Brazil. The Jamamadi depart farthest, and the Mundurucu least, from South American Indian averages. These data are analyzed together with those of 24 other Amazonian groups. Genetic distances and corresponding dendrograms indicate a cluster of 14 related tribes living north of the Amazon river. These genetic results show only a modest correlation with linguistic and geographic relationships among these groups.

Genetic and nongenetic determinants of blood pressure in a southern Brazilian sample

A probabilistic sample representative of the adult population of Rio Grande do Sul, Brazil, was studied to estimate the genetic and nongenetic determinants of blood pressure. Four thousand five hundred and sixty-five individuals, 20 to 74 years old, from 2050 households, were examined. The genetic determination of the SBP (systolic blood pressure) and DBP (diastolic blood pressure) was evaluated in 557 families extracted from this sample. The analysis was performed first with no adjustments for other influencing factors, and then adjusting for the effects of the two significant covariates, age and Quetelet's index, identified through a multiple stepwise regression analysis with nine independent variables. Higher heritability estimates were obtained for DBP (raw data: 0.40; residuals: 0.45) than for SBP (raw data: 0.22; residuals: 0.26). The significant correlation coefficients varied from 0.13 (for father-offspring raw data, total sample), to 0.36 (for siblings, adjusted data, untreated sample). Slight differences were observed between the total and pharmacologically untreated samples in relation to correlation and heritability estimates.

Reconstructing history: the Amazonian Mura Indians

We studied demographic characteristics of two Mura Indian villages. Two-hundred six inhabitants of these villages and another population were tested in relation to 30 blood and 4 saliva genetic systems. These groups exhibit high mobility and exogamy rates and high fertility but relatively low mortality and variance in number of children per woman. Hb J Oxford and albumin Maku were observed, and they show high prevalences of GPT*1 and RH*R1 but low of HP*1 compared to other South American Indians. Four electrophoretic saliva systems are reported here for the first time in a predominantly Amerindian group. The amount of polymorphism was more limited than that found in Caucasian, black, and Oriental populations. The Mura are still predominantly Indian (82%) but have African (11%) and Caucasoid (7%) admixture. Using these values, the putative ancestral Mura gene frequencies were assessed. Problems related to quantitative estimations of admixture and the factors that influence the process are discussed.

Genetic variation within two linguistic Amerindian groups: relationship to geography and population size

Nine Carib and eight Tupi groups were studied for a minimum of eight common polymorphic systems and compared in terms of genetic distances using the methods of Nei and Edwards. Two levels of genetic information were distinguished, one with a maximum of 20 loci and another with a maximum of 12 loci considered. The dendrograms produced consistent, reproducible results, independent of the method used, when a minimum of ten polymorphic systems were included in the analysis. Irrespective of the number of systems or the method used, the Tupi showed two to three times higher average interpopulation genetic distances than the Carib groups, which may be due to their lower average population sizes, allowing for the action of genetic drift and/or founder effects, as these two sets of populations do not differ significantly in geographic range, years of contact with non-Indians, or degree of acculturation.

Genetic variation within the Tupi linguistic group: new data on three Amazonian tribes

A total of 505 individuals belonging to four populations of three Brazilian Indian tribes were variously studied in relation to 34 genetic systems, and the results were compared with South American Indian averages and five other Tupi populations. Rare variants (CdE of the Rh system, PGM211-1, Cp A-CAY1, serum cholinesterase2 C5+ and some Gm combinations) were observed with varying prevalences, and the three tribes showed different degrees of departure (28%-40% of differences of 10% or more in gene frequencies) from South American Indian averages. People from two communities who speak the same language and are labelled as belonging to the same tribe (Asurini) showed a large degree of genetic differentiation. Another of the tribes studied (Urubu-Kaapor) link through genetic distance analyses with two other tribes from the north of the continent, forming a distinct microevolutionary unit. These features emphasize the peculiarities of the genetic variation in populations with a hunter-gatherer, rudimentary agriculture type of economy.

Genetic variation within a linguistic group: Apalai-Wayana and other Carib tribes

A total of 136 individuals were studied in relation to 31 genetic systems, and the results were compared with South American Indian averages and previous surveys on the Wayana of French Guiana and Surinam. The information was afterwards integrated with data from other Carib groups, and two types of genetic distances (Nei's and Edwards') were calculated a) between five groups, considering ten systems; and b) between nine groups, using five systems. The two measures of genetic distances correlated well (Spearman's correlation coefficient around 0.70), and there was good agreement between the geographical and genetic distances. All analyses indicated a peripheral position for the Apalai-Wayana and their distinctiveness from the Wayana of French Guiana and Surinam, suggesting that intertribal fusions may play an important role in the genetic differentiation of these populations.