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HLA histocompatibility antigens in a Polynesian population -- Cook islanders of Mauke.

Polynesians living on the island of Mauke in the Cook Island group were typed for HLA-A and -B locus antigens. The Mauke population has restricted HLA polymorphism, with five A-locus antigens and four B-locus antigens accounting for a majority of the HLA phenotypes. Although some differences in antigen frequency were found when Mauke Islanders were compared with Polynesians from Easter Island and Samoa, the Mauke Islanders were closer in their HLA antigenic profile to polynesians than to Melanesians.

Epitopes↗

HLA and non-HLA phenotyping and genotyping in Austral and Gambier Polynesian Archipelagos.

Forty-one individuals from Rurutu Island (Austral Archipelagos) and 41 individuals from the Gambier Archipelagos have been typed for HLA; for blood groups ABO, Rh, MNSs, P, Kell, Kp, Lewis, Lutheran, Kidd; for the electrophoretic systems G6PD, 6-PGD, PGM1, PGM2, AcP, ADA, GPT, Est-D, GLO I, and for the immunoglobulin allotypes Gm and Km. There is a high degree of homogeneity among these Polynesian populations and among other Polynesian populations previously typed. However, small differences exist between the populations of the two archipelagos, possibly due to endogamy or to the smallness of the samples studied. A variant of HLA-Bw22 (called Bw22x) is described.

Blood Group Antigens↗

Eleven human platelet systems studied in the Vietnamese and Ma'ohis Polynesian populations.

The frequencies of human platelet antigens (HPA) are variable among different ethnic groups. Platelet phenotyping and genotyping in different populations are important to the clinical implications of antiplatelet alloimmunization. No report on HPA prevalence has been published concerning the Vietnamese Kinh and Ma'ohis Polynesian populations. Recent anthropological and genetic marker studies suggest that these two groups have a common origin in East Asia, so we have conducted a combined study concerning the frequency of HPA-1 to HPA-11w systems (excluding HPA-8w) and Gov in these two populations. The results demonstrate a similar pattern of prevalence between Ma'ohis and most of the Asian populations. However, it should be noted that the frequency of HPA-2 is closer to northern Caucasian frequencies than to Asian frequencies. The population of Kinh shows an HPA distribution that is closer to the Chinese population than to the northeastern Thais except for HPA-3, closer to the Indonesian population. Given HPA-3 gene frequency distribution fetomaternal incompatibility could occur more frequently with the risk of alloantibody production.

Adult↗

Low-cost, simultaneous, single-sequence genotyping of the HLA-A, HLA-B and HLA-C loci.

New automated DNA sequencing technology has enabled the development of an assay for genotyping the three major HLA class 1 loci from a single sequence of each gene containing exon 3, intron 2 and exon 2. The assay allows 31 subjects (with 3 negative controls) to be genotyped at all three loci simultaneously, using a 96-well plate format. Genotypes were assigned by comparing each sequence to a database of 307 HLA-A, 563 HLA-B and 166 HLA-C alleles. Unequivocal, 4-digit allele assignments were made for 40 of 130 HLA-A genes, 82 of 130 HLA-B genes and 97 of 130 HLA-C genes from 21 European, 20 Tongan and 24 Niuean subjects. Ambiguity in interpretation of the sequence contributed to 66 of the 170 equivocal allele assignments, and 105 equivocal assignments were due to polymorphisms outside exons 2 and 3. All known alternative interpretations of ambiguous genotypes were identified, and seven HLA-B and two HLA-C ambiguities were resolved by reading the out-of-phase exon 2 sequence that followed an indel in intron 2. The genotypes of a subgroup of 27 heterozygous subjects, whose genotypes contained all of the alleles identified in this study, were confirmed with commercial, generic PCR-SSP typing. In European subjects, the repertoire of HLA-B/HLA-C haplotypes was almost identical to previously published data. We identified five new HLA-B/HLA-C haplotypes in the Polynesian subjects, and the remaining haplotypes were of Asian origin. In summary, we are describing a low-cost, sequencing assay for the three major HLA class I loci that provides a level of resolution that is comparable with a commercial PCR-SSP assay.

Alleles↗

Extinction of the acoustic startle response in moths endemic to a bat-free habitat.

Most moths use ears solely to detect the echolocation calls of hunting, insectivorous bats and evoke evasive flight manoeuvres. This singularity of purpose predicts that this sensoribehavioural network will regress if the selective force that originally maintained it is removed. We tested this with noctuid moths from the islands of Tahiti and Moorea, sites where bats have never existed and where an earlier study demonstrated that the ears of endemic species resemble those of adventives although partially reduced in sensitivity. To determine if these moths still express the anti-bat defensive behaviour of acoustic startle response (ASR) we compared the nocturnal flight times of six endemic to six adventive species in the presence and absence of artificial bat echolocation sounds. Whereas all of the adventive species reduced their flight times when exposed to ultrasound, only one of the six endemic species did so. These differences were significant when tested using a phylogenetically based pairwise comparison and when comparing effect sizes. We conclude that the absence of bats in this habitat has caused the neural circuitry that normally controls the ASR behaviour in bat-exposed moths to become decoupled from the functionally vestigial ears of endemic Tahitian moths.

Animals↗

H, A and A1 reactivity in two Polynesian groups.

Polynesian O bloods from Samoans and Tokelau Islanders have the same mean H reactivity as Caucasian, and their A1 bloods the same A1 content. However, Polynesian A1 bloods have significantly greater H reactivity than Caucasian, and the Tokelau Islanders also showed enhanced A and IT. It is suggested that the Polynesian AHI molecular conformation must differ from the Caucasian pattern, providing an arrangement of antigen sites more favourable to some antigen-antibody reactions.

ABO Blood-Group System↗

Investigation of Lewis phenotypes in Polynesians: evidence of a weak secretor phenotype.

The salivary ABH and Lewis antigens of Polynesians were measured using a standardised red cell agglutination microplate assay and compared with the red cell defined Lewis phenotypes. Salivary ABH substances were detected in almost all saliva samples tested, with low levels (partial secretion) of ABH substances in the saliva from Le(a+b-) and Le(a+b+) individuals. Salivary Leb substance was detected in all Le(a-b+) and Le(a+b+) samples and in almost all Le(a+b-) samples. It is evident from the results obtained that Polynesian red cell phenotypes cannot be used to predict the presence or absence of salivary substances. If the presence of a coding secretor gene is presumed responsible for salivary ABH antigens and salivary Leb antigen expression, then the incidence of a coding secretor gene in Polynesians is 98%. These results indicate that the recessive non-secretor gene is absent or rare in a Polynesian derived gene pool. Two variants of secretor individuals are found among Polynesians, secretors with expression of normal amounts of the product of the secretor gene, similar to Caucasians, and partial secretors with weak expression of the secretor gene products.

ABO Blood-Group System↗

Plasma and red-cell glycolipid patterns of Le(a+b+) and Le(a+b-) Polynesians as further evidence of the weak secretor gene Se(w).

Monoclonal antibodies and thin-layer chromatography were used to study the unusual erythrocyte Lewis phenotypes found in healthy Polynesians. A single monoclonal anti-Leb reagent 073 (clone LM129) was found which could detect Leb antigen on the Polynesian erythrocytes of samples that were unreactive with various polyclonal and monoclonal anti-Leb reagents. Glycolipid fractions prepared from the plasma and erythrocytes of selected Polynesian samples of red-cell Le(a-b-), Le(a+b-) and Le(a+b+) phenotypes were found to have Leb glycolipids. The Leb antigen in some individuals is so weakly expressed that it is undetectable by routine erythrocyte phenotyping. Unusually large glycolipids bearing the Leb epitope were also found in some Polynesian samples, although the contribution of these novel glycolipids to phenotyping is unclear. The inability to detect Leb by routine methods and the presence of novel structures can be partially explained in terms of the presence of a weak secretor gene Se(w).

Chromatography, Thin Layer↗

Detection and characterization of Lewis antigens in plasma of Lewis-negative individuals. Evidence of chain extension as a result of reduced fucosyltransferase competition.

Nonacid plasma glycolipids from Lewis-negative individuals of nonsecretor, partial-secretor and secretor phenotypes were prepared and separated by thin-layer chromatography and immunostained with radiolabelled Lewis antibodies. Lewis-positive plasma and intestinal epithelial cell glycolipids from Caucasians representing the four recognized Lewis and secretor combined phenotypes were used as controls. By presenting these purified total glycolipids in a cell-free environment to Lewis antibodies we were able to demonstrate the presence of small amounts of Lewis antigens in Lewis-negative individuals. It is shown that lactotetraosylceramide and extended precursor glycolipids are present in all Le(a-b-) nonsecretors. Le(a) was detected in 1 of the 3 Le(a-b-) nonsecretor plasmas and in the intestinal sample of the same phenotype. Lactotetraosylceramide was absent but H type 1 and Le(b) were both present in all group O Le(a-b-) secretors, and extended H type 1 reactive structures were also found in the partial secretor. These results clearly demonstrate that although the Lewis-negative phenotype exists at the serological level, this phenotype is not an 'all-or-nothing' phenomenon at the chemical level. We also show that in the presence of reduced fucosyltransferase activity, increased elongation of the precursor chain occurs, which allows us to postulate that fucosylation of the precursor prevents or at least markedly reduces chain elongation.

ABO Blood-Group System↗

A second nonsecretor allele of the blood group alpha(1,2)fucosyl-transferase gene (FUT2).

While screening Le(a+b+)Polynesian DNA samples for a candidate Se(w) allele, a point mutation (C571-->T) resulting in a new stop codon (Arg191-->stop) in the alpha(1,2)fucosyltransferase gene (FUT2) was identified. This point mutation resulted in the gaining of a new restriction enzyme cleavage site (DdeI), which allowed restriction enzyme cleavage screening of 40 selected Polynesians and 42 random Caucasians. The nonsecretor phenotype in two of the three nonsecretor Polynesians analyzed was due to homozygosity for the 'new' mutation, whereas the third Polynesian nonsecretor (with Caucasian ancestors) was due to homozygosity of the 'old' (Trp143-->stop) mutation. The nonsecretor phenotype in all Caucasians analyzed was a consequence of homozygosity for the 'old' mutation. Both the new and the old nonsecretor mutations were identified in the heterozygous state in some secretor-positive Polynesians, while only the old mutation was found in the heterozygous state in Caucasians of the same phenotype.

Alleles↗

The immunogenicity of Haemophilus influenzae: meningococcal protein conjugate vaccine in Polynesian and non-Polynesian New Zealand infants.

OBJECTIVE: To examine the comparative immunogenicity of the Haemophilus influenzae type b-meningococcal protein (PRP-OMP) conjugate vaccine in Polynesian and non-Polynesian New Zealand infants. METHODOLOGY: Fifty-six Polynesian and 53 non-Polynesian infants aged 2-7 months recruited from primary health care settings in Auckland received a two-dose primary series of PRP-OMP. A sub-sample of 83 participants received a booster dose of PRP-OMP at 12-16 months of age. Anti-PRP antibody concentrations were measured in pre- and post-vaccination blood samples. RESULTS: Antibody responses consistent with long-term protection (> or = 1.00 microgram/mL) were observed in 72, 85 and 95% of children following the first, second and booster doses. CONCLUSIONS: Despite differences in disease epidemiology, PRP-OMP was highly immunogenic in Polynesian and non-Polynesian infants.

Antibody Formation↗

Asthma phenotypes in Niue Islanders.

OBJECTIVE: The aim of this study was to identify asthma phenotypes in patients of Niue Island ancestry that might be suitable for susceptibility gene mapping studies. METHODOLOGY: Two hundred and sixteen Niue Islanders with physician-diagnosed asthma that was not secondary to other medical conditions were recruited through community organisations. Fifty-one of the subjects with asthma were resident on Niue Island and 165 in New Zealand. Each subject was interviewed and tested for atopy, serum [IgE] (5% quantile, median, 95% quantile) and lung function. RESULTS: There were two groups of subjects defined by an age of onset of asthma less than 12 years of age (childhood-onset, boys:girls 64:65) and greater than 12 years of age (adult-onset, men:women 11:76). A positive response (wheal > 3 mm) to at least one aeroallergen was seen in 181 patients, with 168/181 (92.8%) responding to house dust mite. Twenty-eight subjects with asthma were non-atopic (no detectable wheal) and the atopy status of seven subjects with asthma could not be determined (wheal < 3 mm). In childhood-onset asthma, serum IgE levels were higher (P < 0.0001) in subjects with atopic than in subjects with non-atopic asthma. In adult-onset asthma, serum IgE levels were higher (P < 0.0001) in subjects with atopic asthma than in either subjects with non-atopic asthma or matched non-atopic subjects without asthma. The asthma phenotypes in Niue Island and New Zealand residents were similar. CONCLUSIONS: Both atopic and non-atopic asthma phenotypes exist in Niue Islanders resident in Niue and New Zealand. The potential for mapping asthma susceptibility genes in this isolated population is discussed.

Adolescent↗

Ophthalmic findings among one thousand inhabitants of Rarotonga, Cook Islands.

A survey of 986 Polynesians was conducted in Rarotonga, Cook Islands, for the complications of diabetes. The ophthalmologists in the team made a general assessment of eye health. Trauma was a major cause of blindness. Diabetic retinopathy, trachoma, cataract and macular degeneration were not common findings. The initial criteria of nuclear cataract were pigmentation or opacification with loss of fetal suture detail. This was invalidated by the finding in young adults of enhanced pigmentation may augment the intrinsic filter of near ultraviolet light. Of the 118 people with chorioretinal scars, 25 shared features with cases reported from the Pacific region attributed to filariasis. The majority, however, were typical of toxoplasmosis. Cases of pseudoexfoliation were rare. This is surprising in view of the high prevalence reported among Australian Aborigines at a comparable latitude.

Adult↗

Meningiomas and the Polynesian population.

BACKGROUND: In Auckland Hospital, New Zealand there has been a perception for many years that the incidence of meningiomas was higher in Polynesians. It was also suspected these occurred at a younger age in Polynesians and were more likely to be multiple. The purpose of the present study was to confirm whether the Polynesian population does have a higher incidence of meningioma, review at what age they presented with meningioma and compare the outcome of treatment with Caucasians. METHODS: A retrospective review was performed of 302 patients who had had a cranial meningioma excised in the 10 years between 1991 and 2001 at Auckland hospital. Age, sex, ethnicity, number of tumours, type, size, comorbidities, time to presentation and outcome at discharge and follow-up were recorded. RESULTS: Polynesians had a significantly higher incidence of meningiomas (P < 0.0001). In particular Polynesian women were significantly over represented. (P < 0.05). Polynesians were more likely to have two or more tumours (P < 0.02) and they presented at a significantly younger age (P < 0.0001). The tumours were also larger. (P = 0.0006). Despite this Polynesians did not have a worse outcome at discharge or at follow up (P > 0.1) nor did they have a higher incidence of comorbidites, perhaps reflected by their younger age. CONCLUSIONS: There is a higher incidence of meningiomas in the Polynesian population, particularly young Polynesian women. The tumours are more likely to be multiple and larger in Polynesians. The present study confirms a predisposition to meningioma in New Zealand Polynesians and should lead to further investigation into whether this is genetic (likely chromosome 22) or hormonal possibly mediated by insulin-like growth factor-1.

Adult↗

Observations on Maori-European lung function differences.

One hundred and twenty-one regular soldiers between the ages of 18 and 34 years, who had lived and worked under identical conditions for the two previous years were examined. All subjects with respiratory symptoms of wheeze, dyspnoea, persistent cough or sputum were excluded. Smoking, per se, was not a reason for exclusion. Eighty-three "respiratorily fit" men, comprising 47 Maoris and 36 Europeans, were studied to see whether height, weight or obesity could account for the ethnic differences in lung function. The forced vital capacity in the Maoris was found to be about 9% lower than in the Europeans. The one-second forced expiratory volume of the Maoris was about 8% lower than in the Europeans. No significant difference could be found in the peak expiratory flow rates between the two ethnic groups. The only significant physical difference found between the two ethnic groups was that the Maoris were heavier for their height than the Europeans. Statistical tests showed that neither weight nor an obesity index accounted for the ethnic differences in lung function. Full laboratory investigation of these ethnic differences is recommended.

Adolescent↗