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We evaluated the possible genetic contribution to hyperinsulinism in a series of patients seen during the past 15 years. Of 26 families, 5 (19%) had more than one child affected (multiplex family). There were no apparent differences between patients in the 5 multiplex and 21 simplex families, clinically, biochemically, or on histologic examination of the pancreatic specimens. The families studied had a total of 63 offspring; the 26 index patients had 37 siblings, 6 of whom were affected. After four patients with hyperinsulinism caused by adenoma were excluded from the study, segregation analysis was carried out to test the data for agreement with results expected if familial and isolated hyperinsulinism represented a single disease with recessive mode of inheritance and a segregation ratio of 0.25. Excellent agreement was found between the observed number of affected siblings (20) and the expected number (19.65), with a segregation ratio of 0.254. The results were consistent with the hypothesis that in most or all cases, hyperinsulinism is inherited as an autosomal recessive disease. There was no evidence of distinct familial and sporadic types.

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Plasma levels of glucose, insulin, growth hormone, and pancreatic polypeptide in response to a standard oral glucose load were studied in the Yanomama and the Marubo, two relatively unacculturated Amerindian tribes of the Brazilian Amazon. The findings in the two tribes differed significantly from each other and in the degree of deviation from control subjects. The average responses in both tribes differed significantly from those of age- and sex-matched Caucasoid control subjects studied in Ann Arbor, Michigan; however, of the two tribes, the Marubo, the more acculturated group, resembled the controls more closely. Plasma concentrations of glucose and the hormones at three time points (fasting, 1 h, 2 h) were compared by means of a multivariate analysis. When the Marubo were compared with the control subjects, the only highly significant difference was in the plasma glucose concentrations (all three points were higher in the Marubo); however, the Yanomama differed significantly from the control subjects with respect to all four plasma indicators (p less than 0.05). Unlike the Marubo, the Yanomama showed no significant rise in plasma glucose at 1 h and no decrease at 2 h. Neither tribe exhibited the bimodality of the 2 h glucose value characteristic of acculturated Amerindians, such as the Pima, but the samples studied were small.

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The Ticuna are an Amerindian tribe of Central Amazonas, a key location in theories of the peopling of eastern South America. The results of typing some 1760 members of the tribe with respect to 37 different genetic systems are reported, as are the results of HLA typings on a subsample of 129 persons. Salient findings include the following. (1) Except for a high frequency of LMs allele and an unusual combination of HLA allele frequencies, there are no notable findings with respect to the commonly studied polymorphic systems. A multivariate treatment of six of the most commonly studied genetic polymorphisms accords the Ticuna an 'average' position among Amerindian tribes. (2) There is much less intervillage heterogenicity than usually encountered in Amerindian tribes; this is attributed to recent high rates of intervillage migration due to religious developments. (3) A thus-far unique polymorphism of ACP1 was identified, the responsible allele having a frequency of 0.111. (4) In proportion to the size of the tribe, there was a relative paucity of 'private' genetic variants, the ACP1 allele being the only one. This discrepancy is attributed to a relatively recent numerical expansion of the tribe; effective population size over the past several thousand years is thought to have been well below what present numbers would suggest. (5) The thesis is again advanced that 'private variants' (alleles not occurring as polymorphisms of wide distribution) are more common in Amerindian than in Caucasian or Japanese populations.

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Blood samples from 509 Macushi (3 villages) and 623 Wapishana (11 villages) of Northern Brasil and Southern Guyana have been analyzed with respect to the phenotype and gene frequencies at the following 12 polymorphic loci: ABO, Kell-Cellano, MNSs, Rh, P, Duffy, Kidd, Diego, Lewis, Group-specific component, and the immunoglobulin allotypes of the Gm and Inv systems. The data suggest that 5-6% of the Wapishana gene pool is derived from non-Indians but only 1-2% of the Macushi. Inter- and intratribal genetic distances between villages are calculated for these data in an effort to understand gene flow between the tribes and to account for the unusual distribution of a newly-discovered genetic polymorphism of erythrocyte esterase A thus far limited to these 2 tribes (Neel et al., 1977). The data are puzzling and consistent with the possibility that both the Carib-speaking Macushi and the Arawak-speaking Wapishana have derived the esterase A allele in question from some third group now extinct or thus far undiscovered. Intertribal genetic distances based on gene frequencies at 6 loci are derived for 20 Amerindian tribes (including these 2); the "central" position of these 2 tribes can in part be explained by the active migration matrix connecting them.

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Blood samples from 509 Macushi and 623 Wapishana Amerindians of of Northern Brazil and Southern Guyana have been analyzed with reference to the occurrence of rare variants and genetic polymorphisms of the following 25 systems: (i) Erythrocyte enzymes: acid phosphatase-1, adenosine deaminase, adenylate kinase-k, carbonic anhydrase-1, carbonic anhydrase-2, esterase A1,2,3, esterase D, galactose-1-phosphate uridyltransferase, isocitrate dehydrogenase, lactate dehydrogenase, malate dehydrogenase, nucleoside phosphorylase, peptidase A, peptidase B, phosphoglucomutase 1, phosphoglucomutase 2, phosphogluconate dehydrogenase, phosphohexoseisomerase, triosephosphate isomerase and (ii) Serum proteins: albumin, ceruloplasmin, haptoglobin, hemoglobin A2 and transferrin. Fifteen different rare variants were detected, involving 11 of these systems. In addition, a previously undescribed variant of ESA 1,2,3 which achieves polymorphic proportions in both these tribes is described. Excluding this variant, the frequency of rare variants is 1.1/1000 in 12510 determinations in the Macushi and 4.7/1000 in 15396 determinations in the Wapishana. The ESA 1,2,3 polymorphism was not observed in 382 Makiritare, 232 Yanomama, 146 Piaroa, 404 Cayapo, 190 Kraho and 112 Moro. Irregularities in the intratribal distribution of this polymorphism in the Macushi and Wapishana render a decision as to the tribe of origin impossible at present. Gene frequencies are also given for previously described polymorphisms of 5 systems: haptoglobin, phosphoglucomutase 1, erythrocyte acid phosphatase, esterase D, and galactose-1-phosphate-uridyl-transferase.

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Four different estimation procedures for models of population structure are compared. The parameters of the models are shown to be equivalent and, in most cases, easily expressed in terms of the parameters WRIGHT calls "F-statistics." We have estimated the parameters of each of these models with data on nine codominant allele pairs in 47 Yanomama villages, and we find that the different estimators for a given parameter all yield more or less equivalent results. F-statistics are often equated to inbreeding coefficients that are definid as the probability of identity by descent from alleles taken to be unique in some founding population. However, we are led to infer from computer simulation and general historical considerations that all estimates from genotype frequencies greatly underestimate the inbreeding coefficient for alleles in the founding population of American Indians in the western hemisphere. We surmise that in the highly subdivided tribal populations which prevailed until the recent advent of civilization, the probability of identity by descent for homologous alleles was roughly 0.5. We consider some consequences of working with the customary, much lower, estimates--0.005 to 0.01--if, on the time scale of human evolution, these represent only a very recent departure from the inbreeding intensity that prevailed before civilization.

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A set of 12 anthropometric measures and six genetic traits, available for 520 Yanomama Indians from 19 villages in nine clusters, were used to allocate individuals to villages. On the basis of anthropometrics alone, 36% of the individuals were allocated to the right village and 60% to the right cluster. On the basis of genetic traits alone, 16% were allocated to the right village and 26% to the right cluster. A combination of all 18 characters yielded 41% allocation to the right village and 63% to the right cluster. Of the 924 possible combinations of six anthropometric measures, only one provided poorer resolution than did the six genetic traits. We explain the better resolution of the anthropometric traits by noting that the anthropometric traits are not totally heritable and that genetic traits are not continuously distributed. Randomization studies indicated that all of the observed correct-allocation fractions are far in excess of random expectation. We infer that the village phenotype distributions overlap only partially, and that they represent real and substantial population differentiation.

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