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PubMed2026

Host immunogenetic variation and gut microbiome functionality in a wild vertebrate population.

BACKGROUND: The gut microbiome (GM) -important for host health and survival- is partially shaped by host immunogenetics. However, to date, no study has investigated the influence of host Major Histocompatibility Complex (MHC) genes on gut microbiome functionality in a wild population. Here we use a natural population of the Seychelles warbler (Acrocephalus sechellensis) to assess the effects of MHC genes on GM taxonomy and functionality using shotgun metagenomics. RESULTS: Our results show that taxonomic GM composition was associated with MHC-II diversity and the presence of one specific MHC-I allele (Ase-ua 7). Specifically, MHC-II diversity was associated with decreased Lactococcus lactis and increased Staphylococcus lloydii abundance, while Ase-ua 7 was linked to reduced Enterococcus casselifavus and Gordonia sp OPL2 but increased Escherichia coli and Vulcaniibacterium thermophilum. These taxonomic changes may reflect differences in MHC-mediated microbial recognition. In contrast, functional GM composition was significantly associated with increasing individual MHC-I diversity but not MHC-II diversity. In particular, increasing MHC-I diversity was associated with an increased prevalence of microbial defence genes but a reduced prevalence of microbial metabolism genes. Analysis also revealed that functional GM networks were more fragmented in high compared to low MHC-I diversity hosts. CONCLUSION: These results suggest that MHC variation (particularly at MHC-I) plays an important role in shaping both the taxonomy and function of the GM in wild vertebrates. In the Seychelles warbler, this results in trade-offs whereby there is an increase in microbial defence and a reduction in GM metabolic potential in individuals with higher MHC-I diversity. Thus, this work sheds light on the possible costs and benefits of maintaining a healthy microbiome, which is essential for understanding how the GM and immune system co-evolve. Video Abstract.

Animals↗
PubMed2002

[Impact of prenatal methylmercury exposure on child neurodevelopment in the Faroe Islands].

Recent interest concerning methylmercury that accumulates in the aquatic food chain appears to be directed not to the adverse effects of high-dose exposure in humans, but to the critical concentration at which methylmercury may affect the progeny of the exposed population. In epidemiological studies, however, uncertainties and limitations in estimating exposure make it difficult to quantify dose-response associations and can thereby lead to inaccuracies when deriving such concentrations. In this respect, benchmark dose calculation for quantitative outcomes may shed new light on the epidemiological procedure for estimating the critical concentration. After the epidemic outbreaks of methylmercury poisoning in Japan and Iraq, large-scale follow-up studies were carried out in the Faroe Islands, Seychelles and New Zealand, to clarify the effects of prenatal methylmercury exposure on child neurodevelopment in the latter half of the 1980s. This article presents an overview of the outcomes obtained from the Faroe Islands Prospective Study, as well as a brief interpretation of the benchmark dose calculation. Although the Faroe and Seychelles Islands studies did not seem to differ greatly in the study setting, such as the exposure level and sample size, the former study observed some significant dose-effect relationships between methylmercury concentrations at birth and neurobehavioral end-points, but the latter failed to find any significant associations except in one test. The discrepancy between the two conclusions is also discussed.

Adolescent↗
PubMed2006

Prenatal methylmercury exposure and developmental outcomes: review of the evidence and discussion of future directions.

I conducted a review of the published literature to assess the strength of the evidence for an association between prenatal exposure to methylmercury (MeHg) and subsequent child development. I identified 12 studies on this subject published since 1980. Of these, 3 were longitudinal studies--2 conducted in the Seychelle Islands, and 1 in the Faroe Islands. Nine were cross-sectional studies conducted in different countries where seafood, a source of MeHg, constituted a major part of the diet. The ages of the children studied ranged from 2 weeks to 12 years. The results of the longitudinal studies were contradictory. Researchers in the Faroe Islands identified an association between MeHg exposure and developmental effects, whereas those in the Seychelle Islands identified no such association. This inconsistency was mirrored in the results of the cross-sectional studies where there were some positive and some negative findings. It was concluded that it was not possible from currently available data to determine whether there is an association between prenatal MeHg exposure and adverse developmental effects in children. In advance of future research, consideration should be given to resolving the uncertainties surrounding exposure assessment and outcome measurement, as both elements varied between studies. It was suggested that questions of exposure assessment would benefit from the application of an expert review process. Outcome assessment would benefit from the development of theoretically based measures of specific aspects of cognitive functioning to replace the relatively crude measures of attainment and IQ currently employed in most studies. This would assist in the development of classic longitudinal studies by allowing repeated assessment over the full age range and providing data that are more readily interpretable and comparable between studies.

Adult↗
PubMed1998

Prenatal methylmercury exposure and children: neurologic, developmental, and behavioral research.

Mercury is present in the earth's crust and is methylated by bacteria in aquatic environments to methylmercury (MeHg). It is then concentrated by the food chain so predatory fish and sea mammals have the highest levels. Thus, consuming seafood leads to exposure. MeHg readily crosses the placenta and the blood-brain barrier and is neurotoxic. The developing fetal nervous system is especially sensitive to its effects. Prenatal poisoning with high dose MeHg causes mental retardation and cerebral palsy. Lower level exposures from maternal consumption of a fish diet have not been consistently associated with adverse neurodevelopmental outcomes. However, most studies have considerable uncertainty associated with their results. Two large controlled longitudinal studies of populations consuming seafood are underway that are likely to determine if any adverse effects can be identified. No adverse associations have been found in the Seychelles, where exposure is mainly from fish consumption. In the Faroe Islands where exposure is primarily from consumption of whale meat and not fish, adverse associations have been reported. The Seychelles population consumes large amounts of marine fish containing MeHg concentrations similar to commercial fish in the United States. Current evidence does not support the hypothesis that consumption of such fish during pregnancy places the fetus at increased neurodevelopmental risk.

Child↗
PubMed1985

Follicular development, ovulation, fertilization and fetal development in tenrecs (Tenrec ecaudatus).

Reproduction in female tenrecs was studied on Praslin Island (4 degrees 20'S, 55 degrees 45'E) in the Seychelles from November 1977 to September 1980. Dissection and histological examination of reproductive tracts revealed that each ovary is encapsulated in a bursa. Polyovular follicles were abundant and contained up to 5 oocytes. The occurrence of more implanted fetuses than corpora lutea (CL) indicated successful polyovuly in 25% of pregnancies. No antrum was observed during follicular growth at oestrus, and follicles were relatively small at maturation, reaching a maximum diameter of 570 microns. Ovulation involves a gentle extrusion of the granulosa and ovum into the periovarian space. Spermatozoa were abundant in the female reproductive tract including the periovarian space at oestrus. Spermatozoa penetrated the loosely-packed theca of mature follicles and were present in CL, indicating that intrafollicular fertilization may occur. The relatively small CL formed by eversion, reaching a maximum size after implantation. Fusion of up to four CL occurred in the ovaries of 41% of pregnant females. Polyovulation in the tenrec was confirmed by the occurrence of 10.4 +/- 0.5 (mean +/- s.e.m.) CL and 9.7 +/- 0.5 (mean +/- s.e.m.) implantations. Resorption occurred in 74% of 19 dissectable pregnancies, occurring in both uterine horns in 26% of pregnancies. Coefficients of variation in weights of fetuses in each litter were 10.0-26.8%, with the largest value corresponding to 273% variation in fetus weights. Litter size in the Seychelles tenrecs was smaller than in the same species in Madagascar (17.1 +/- 1.9 implantations) where the tenrec is native.

Animals↗
PubMed1988

The neuroepidemiology of tropical spastic paraparesis.

Recent neuroepidemiological studies of endemic tropical spastic paraparesis (TSP) have confirmed the existence of high-prevalence foci in several tropical islands, including Jamaica and Martinique in the Caribbean, Tumaco off the Pacific coast of Colombia, and the Seychelles in the Indian Ocean. There is a net preponderance of TSP in persons of Black African ancestry, although Caucasian, Hindu, Amerindian, and Orientals have been affected. The epidemiological, clinical, laboratory, and neuropathological features of TSP are reviewed here, as well as the evidence in favor of its retroviral origin.

Adolescent↗
PubMed2000

Neurodevelopmental outcomes of Seychellois children from the pilot cohort at 108 months following prenatal exposure to methylmercury from a maternal fish diet.

The Seychelles Child Development Study has been unable to confirm any relationship between maternal exposure to MeHg during pregnancy and adverse developmental outcomes. In this report, 87 children from a pilot cohort were evaluated at 9 years of age. Each child was given a battery testing specific cognitive, visual motor, and motor skills using standardized psychometric and neuro-psychological tests. The results indicated no adverse association between maternal MeHg exposure and any developmental outcome measure. For three endpoints (Boston Naming Test and two tests of visual motor coordination), enhanced performance in males was associated with increasing prenatal MeHg exposure. A secondary analysis including both prenatal MeHg and postnatal MeHg exposure was done even though we lacked postnatal hair for about 35% of the cohort. The results of the secondary analysis mirrored the outcomes of the primary analysis regarding prenatal exposure but were less robust. The results of this study are consistent with earlier findings from the 66-month evaluations of the SCDS Main cohort. Since MeHg is neurotoxic, this effect is likely due to other factors associated with consumption of fish.

Adult↗
PubMedDate not supplied

The epidemiology of myelopathy associated with human T-lymphotropic virus 1.

A progressive spastic myelopathy is one of the principal manifestations of the human T cell lymphotropic virus type 1. Recent research is reviewed on the geography and epidemiology of this specific form of tropical spastic paraparesis. First recognized in the Caribbean, Colombia and Japan, it is now also confirmed as a major neurological problem in areas of eastern Brazil, western equatorial Africa, Natal and Seychelles, with other scattered foci world-wide. Accurate surveys call for sophisticated techniques including polymerase chain reaction amplification. The only defined modes of spread are by breast feeding, sexual contact and blood cell infusion. The onset of neurological disease is associated with high antibody titres and a high rate of spontaneous T lymphocyte proliferation. Molecular analysis has revealed no nucleotide sequence variation in cases with or without myelopathy. In non-transfusion cases the clinical attack rate is low with a very long latent period, but there are unexplained regional differences and familial cases are an important exception. Current research is focused on possible local, ethnic, or genetic co-factors.

Africa↗
PubMed2004

Patients' sibling history was sensitive for hypertension and specific for diabetes.

OBJECTIVE: We examined the analytic validity of reported family history of hypertension and diabetes among siblings in the Seychelles. STUDY DESIGN AND SETTING: Four hundred four siblings from 73 families with at least two hypertensive persons were identified through a national hypertension register. Two gold standards were used prospectively. Sensitivity was the proportion of respondents who indicated the presence of disease in a sibling, given that the sibling reported to be affected (personal history gold standard) or was clinically affected (clinical status gold standard). Specificity was the proportion of respondents who reported an unaffected sibling, given that the sibling reported to be unaffected or was clinically unaffected. Respondents gave information on the disease status in their siblings in approximately two-thirds of instances. RESULTS: When sibling history could be obtained (n=348 for hypertension, n=404 for diabetes), the sensitivity and the specificity of the sibling history were, respectively, 90 and 55% for hypertension, and 61 and 98% for diabetes, using clinical status and, respectively, 89 and 78% for hypertension, and 53 and 98% for diabetes, using personal history. CONCLUSION: The sibling history, when available, is a useful screening test to detect hypertension, but it is less useful to detect diabetes.

Adult↗
PubMed2006

[Chikungunya on Reunion Island: chronicle of an epidemic foretold].

Chikungunya is a viral disease transmitted by a mosquito of the genus Aedes. It is currently epidemic on Reunion Island, in the Indian Ocean. It is essentially characterized by an influenza syndrome but associated with polyarthralgia and an eruption. The disabling and chronic nature of the arthralgia is the most remarkable clinical aspect of chikungunya infection. Severe and unusual forms have appeared, not previously described in the literature. These forms must be studied to determine whether there is a direct relation between the chikungunya virus and the severity factors. Treatment is solely symptomatic, combining analgesic and/or antiinflammatory agents. There is no vaccine. The epidemic is not limited to Reunion: cases of chikungunya have also been reported in neighboring islands (Maurice, Seychelles, and Madagascar). Travelers planning to visit the region should be counseled.

Adult↗
PubMed2000

Dyslipidemia and abdominal obesity: an assessment in three general populations.

Several studies show a relationship between abdominal obesity and cardiovascular diseases, partially mediated through an altered metabolism of dyslipidemia. The present study was aimed at testing the robustness of this association across three contrasted populations and at assessing the performances of abdominal obesity as a screening tool for dyslipidemia. Data were drawn from three population health surveys recently conducted in two regions of a developed country (Switzerland, mostly of Caucasian origin, n = 2650) and in a less developed country (Seychelles, Indian Ocean, mostly of black descent, n = 806). Dyslipidemia was defined as a ratio of total cholesterol to high-density lipoprotein cholesterol (TC-HDL) greater than 5. Two anthropometric circumference measurements, waist-to-hip ratio (WHR) and waist circumference (WC), were used to define abdominal obesity either as WHR >/= 0.9 in men and WHR >/= 0.8 in women or as WC >/= 94 cm and WC >/= 80 cm, respectively. A consistent direct association between abdominal obesity and dyslipidemia (odds ratios varying from 1.85 to 4.56) was found in the three populations, independently of gender, age, body mass index, blood pressure, and smoking. This consistency across ethnicities and environments strengthens the hypothesis of a common etiopathological mechanism. The sensitivity for detecting dyslipidemia was generally higher for abdominal obesity, based on either WHR or WC, than for criteria based on the other risk factors under study. In addition, the sensitivity was higher in the study populations with a low prevalence of dyslipidemia (Swiss women and Seychellois of both sexes) than in the others. These findings support that WHR and WC may be useful as simple and inexpensive screening tools to select individuals eligible for more sophisticated and costly serum lipid determinations, especially in developing countries.

Abdomen↗
PubMed1994

Six new diterpene isonitriles from the sponge Acanthella cavernosa.

Six new diterpene isonitriles, 10-epi-isokalihinol F [1], 10-epi-isokalihinol H [2], 1-epi-kalihinene [4], 15-isothiocyanato-1-epi-kalihinene [5], 1,10-diepi-kalihinene [6], and kalihipyran [7] were isolated, together with the known compound isokalihinol B [3], from Acanthella cavernosa collected in the Seychelles. The structures of the new diterpenes were elucidated by interpretation of spectral data. The ring system of kalihipyran [7] differs from that of the kalihinols and kalihinenes.

Animals↗
PubMed1997

Diabetic eye disease: a natural history study.

In previous studies on diabetic retinopathy it has not been possible to relate risk factors to reduced vision because of the influence of vision-preserving treatment. Demographic data, cardiovascular risk factors and ocular features from the diabetic population of the Seychelles are described. Diabetic retinopathy in this population had not been modified by laser treatment. The population described consists of entirely type 2, maturity onset diabetics. Using a multivariate logistic regression model, the risk factors were deduced for three outcome variables: (1) reduced vision, defined as 6/36 or worse in both eyes; (2) the presence of diabetic retinopathy; and (3) the presence of maculopathy, preproliferative and proliferative retinopathy, grouped as severe retinopathy. Insulin treatment was associated with all outcome variables, duration from diagnosis of diabetes with retinopathy of all forms, and increasing age with reduced vision and severe retinopathy. Hypertensive diabetic patients were twice as likely to have reduced vision as compared with non-hypertensive diabetic individuals.

Adult↗
PubMed2006

Dynamic fragility of oceanic coral reef ecosystems.

As one of the most diverse and productive ecosystems known, and one of the first ecosystems to exhibit major climate-warming impacts (coral bleaching), coral reefs have drawn much scientific attention to what may prove to be their Achilles heel, the thermal sensitivity of reef-building corals. Here we show that climate change-driven loss of live coral, and ultimately structural complexity, in the Seychelles results in local extinctions, substantial reductions in species richness, reduced taxonomic distinctness, and a loss of species within key functional groups of reef fish. The importance of deteriorating physical structure to these patterns demonstrates the longer-term impacts of bleaching on reefs and raises questions over the potential for recovery. We suggest that isolated reef systems may be more susceptible to climate change, despite escaping many of the stressors impacting continental reefs.

Animals↗
PubMed1994

Comparison of serum lipoprotein(a) distribution and its correlates among black and white populations.

BACKGROUND: Epidemiological data on serum lipoprotein(a) (Lp(a)), a presumably strong risk factor for coronary artery disease in White populations, has mostly been derived, in Black populations, from small samples. This study compares the distribution and the determinants of serum Lp(a) in Blacks and in Whites using large representative samples and the same methods in both populations. METHODS: The distribution and the correlates of serum Lp(a) were investigated in population-based samples of 701 Blacks in the Seychelles and 634 Whites in Switzerland, aged 25-64 years. Serum Lp(a) was quantified using a commercial immunoradiometric assay. RESULTS: The distribution of serum Lp(a) was similarly skewed in both ethnic groups, but median Lp(a) concentration was about twofold higher in Blacks (210 mg/l) compared to Whites (100 mg/l). The proportions of individuals with elevated serum Lp(a) (> 300 mg/l) was about 50% higher in Blacks (37.5%) than in Whites (25.2%). In both ethnic groups, serum Lp(a) was found to correlate with total cholesterol, LDL-cholesterol and apoprotein B but not with HDL-cholesterol, alcohol intake, smoking, and body mass index. The variance in serum Lp(a) concentration explained by any combination of these factors was smaller than 5.3% in the two populations. CONCLUSIONS: The measured factors did not explain the higher levels of serum Lp(a) found in Blacks compared to Whites. These findings are consistent with the hypothesis that genetic factors account for much of the variation of serum Lp(a) in both populations.

Adult↗
PubMed2007

Microalbuminuria, but not cystatin C, is associated with carotid atherosclerosis in middle-aged adults.

BACKGROUND: Cystatin C, a marker of renal function, has been shown to be an independent predictor of cardiovascular disease (CVD) in older adults, but few data are available in middle-aged adults. Moreover, no study has compared cystatin C and microalbuminuria as risk factors for CVD outcomes in middle-aged adults, and it is not known whether cystatin C is related to an early stage of atherosclerosis. METHODS: We evaluated the relationships between serum creatinine, estimated glomerular filtration rate (GFR), serum cystatin C (all divided into tertiles), microalbuminuria and carotid atherosclerosis in a population-based random sample of 523 adults aged 35-64 years from the Seychelles (Indian Ocean). GFR was estimated using the modification of diet in renal disease (MDRD) equation. Intima-media thickness (IMT) was assessed by B-mode ultrasound. RESULTS: The mean age of the study sample was 52 years, and 55% were women. Carotid IMT was higher in participants with microalbuminuria (802 vs 732 microm, P<0.001) and was inversely associated with GFR tertiles (from 728 to 809 microm, P for trend=0.002). IMT was not associated with cystatin C or creatinine (P for trend=0.10 and 0.16, respectively). In multivariate analyses adjusted for cardiovascular risk factors, the association between microalbuminuria and IMT remained (P=0.047), while the association between GFR and IMT disappeared (P for trend=0.33). CONCLUSIONS: Microalbuminuria, but not cystatin C, is associated with carotid atherosclerosis beyond traditional cardiovascular risk factors among middle-aged adults. Cystatin C does not have a stronger relationship with carotid atherosclerosis in middle-aged adults than creatinine.

Adult↗
PubMed2004

Gender difference in the response to an angiotensin-converting enzyme inhibitor and a diuretic in hypertensive patients of African descent.

BACKGROUND: The efficacy of angiotensin-converting enzyme (ACE) inhibitors in decreasing blood pressure in African patients is controversial. OBJECTIVE: We examined the ambulatory blood pressure (ABP) response to a diuretic and an ACE inhibitor in hypertensive patients of East African descent and evaluated the individual characteristics that determined treatment efficacy. DESIGN: A single-blind randomized AB/BA crossover design. SETTING: Hypertensive families of East African descent from the general population in the Seychelles. PARTICIPANTS: Fifty-two (29 men and 23 women) out of 62 eligible hypertensive patients were included.Main outcome measures ABP response to 20 mg lisinopril (LIS) daily and 25 mg hydrochlorothiazide (HCT) daily given for a 4-week period. Results The daytime systolic/diastolic ABP response to HCT was 4.9 [95% confidence interval (CI) 1.2-8.6]/3.6 (1.0-6.2) mmHg for men and 12.9 (9.2-16.6)/6.3 (3.7-8.8) mmHg for women. With LIS the response was 18.8 (15.0-22.5)/14.6 (12.0-17.1) mmHg for men and 12.4 (8.7-16.2)/7.7 (5.1-10.2) mmHg for women. The night-time systolic/diastolic response to HCT was 5.0 (0.6-9.4)/2.7 [(-0.4)-5.7] mmHg for men and 11.5 (7.1-16.0)/5.7 (2.6-8.8) mmHg for women, and to LIS was 18.7 (14.2-22.1)/15.4 (12.4-18.5) mmHg for men and 3.5 [(-1.0)-7.9]/2.3 [(-0.8)-5.4] mmHg for women. Linear regression analyses showed that gender is an independent predictor of the ABP responses to HCT and to LIS. CONCLUSIONS: Hypertensive patients of African descent responded better to LIS than to HCT. Men responded better to LIS than to HCT and women responded similarly to both drugs.

Adult↗
PubMed2006

Comparison of smoking, drinking, and marijuana use between students present or absent on the day of a school-based survey.

The aim of this population-based survey was to compare the prevalence of selected risk behaviors between students present or absent on the day of a school-based survey. The study population was a representative sample of all students of secondary schools in the Seychelles (Indian Ocean). Students absent on the day of the survey were traced and requested to complete the same self-administered questionnaire as did present students. Self-reported consumption of cigarettes, alcohol, and marijuana were measured. Of the sample of 1453 eligible students aged 11 to 17 years, 1321 "present students" completed the survey (90.9% participation), 11 refused to answer all questions, and 121 were not present at school. We could trace 105 of the 121 students not present at school on the survey day ("absent students"), and all of them completed the questionnaire over the next 4 weeks. The prevalence of risk behaviors was significantly higher in absent than present students for current smoking and drinking. Inclusion of data from the absent students resulted in a relative increase in the prevalence of the considered behaviors by 3% to 8% as compared to data based on present students only. In conclusion, the prevalence of risk behaviors was higher in absent than present students. Adjusting for data of absent students increased the prevalence estimates in the base population.

Absenteeism↗