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Biomedical subjects

G R Bentley

Publications and source records attributed to G R Bentley.

9 recordsLinked to original sources
PubMed2000

The 9-bp deletion between the mitochondrial lysine tRNA and COII genes in tribal populations of India.

A 9-base-pair (bp) deletion located between the lysine tRNA (MTTK) and COII (MTCOX*2) genes in the human mitochondrial genome is a valuable marker for tracing population relationships. Previous research has shown that the 9-bp deletion is associated with two major clusters of control region sequences; one occurs in sub-Saharan Africa, while the other is associated with Asian populations and populations of Asian origin. We surveyed 898 individuals from 16 tribal populations in India and found 6 individuals with the 9-bp deletion. Sequences of the first hypervariable segment (HV1) of the mtDNA control region from these 9-bp deletion-bearing mtDNAs were compared to those previously reported from Asian and African populations. Phylogenetic analysis indicates three distinct clusters of tribal Indian 9-bp deletion mtDNA types. One cluster, found in northeast India, includes southeast Asian and Indonesian mtDNA types. The remaining two clusters appear to have unique origins in southern India. These data provide further evidence of past migrations from Asia into the northeast corner of the Indian subcontinent.

Asian People↗
PubMed1999

Salivary estradiol and progesterone levels in conception and nonconception cycles in women: evaluation of a new assay for salivary estradiol.

OBJECTIVE: To determine the usefulness of salivary E2 and progesterone for noninvasive assessment of ovarian function. DESIGN: Prospective study of salivary hormone levels in women planning a pregnancy. SETTING: Department of Obstetrics and Gynecology at Northwestern University Medical School in Chicago, Illinois. PATIENT(S): Fourteen women aged 23-39 years with regular menstrual cycles who were planning a pregnancy. INTERVENTION(S): None. MAIN OUTCOME MEASURE(S): Salivary estradiol and progesterone concentrations. RESULT(S): The sensitivity of the E2 assay is 2.0 pmol/L; the interassay coefficient of variation was 5.2% (mean value 17 pmol/L). Recovery of E2 added to saliva was 106%. The correlation with simultaneous serum samples was 0.71. Menstrual cycle patterns contained a preovulatory depression and a midcycle surge. By comparison with nonconception cycles, the luteal phases of conception cycles had significantly elevated salivary E2 within the first 5 days after ovulation. Salivary progesterone was significantly elevated but not until 10 days after ovulation. CONCLUSION(S): Salivary measurements of E2 and progesterone can be used as noninvasive methods for assessment of ovarian function. Salivary specimens can be collected at home and brought to the laboratory for analysis, obviating the need for frequent phlebotomy. The sensitivity and precision of the salivary E2 assay make it comparable with assays of serum E2 for assessing changes in hormone levels.

Adult↗
PubMed1999

Women's strategies to alleviate nutritional stress in a rural African society.

Many agricultural populations are subject to chronic or seasonal undernutrition, reproductive women and children often being most vulnerable. This paper presents quantitative and qualitative data on food consumption, food distribution practices, food taboos, garden sizes and work effort to show how Lese horticulturalist women living in the Ituri Forest of northeast Democratic Republic of Congo attempt to alleviate nutritional stress. The Lese experience an annual hunger season when approximately one quarter of the population suffer from energy deficiency. Nutritional intake is also compromised by a complex system of food taboos against meat from wild forest animals. Anthropometric data collected over several years suggest that Lese women suffer from nutritional stress more than men during the hunger season. They also have more food taboos particularly during pregnancy and lactation. Their low fertility is compounded by nutritional stress. Despite these inequities, Lese women use several strategies to improve their food intake. Since they are responsible for all household cooking, they manipulate food portions. During the hunger season, they snack frequently, and increase their consumption of palliative foods. Women with more food taboos plant larger gardens to supplement their diet with vegetable foods. Although this results in their consumption of more daily protein, they work harder compared to women with smaller gardens. Women cheat in their adherence to specific food taboos by actively discounting them, or by eating prophylactic plants that supposedly prevent the consequences (usually illness) of eating tabooed foods. In addition, women resort to subterfuge to access desirable resources. Lese women do not reduce work effort during the hunger season, but adapt physiologically by reducing resting metabolic rates during periods of weight loss. These results point to the ability of Lese women to minimize the ecological and cultural constraints on their nutrition. More data, however, are required to assess the long-term effectiveness of these strategies.

Adult↗
PubMed1998

Dietary composition and ovarian function among Lese horticulturalist women of the Ituri Forest, Democratic Republic of Congo.

OBJECTIVE: To assess dietary composition in relation to energetic status and ovarian function. DESIGN: An eight-month prospective study undertaken in 1989. SETTING: Ituri Forest, northeast Democratic Republic of Congo. SUBJECTS: Sixty-four female volunteers of reproductive age (16-45), with a subsample of 30 for nutritional focal follows, 39 for analysis of salivary progesterone levels, and 18 for analysis of salivary oestradiol. INTERVENTIONS: Regular anthropometric measurements of heights, weights, and mid-triceps skinfolds, 204 h of nutritional focal follows when all foods prepared and consumed were recorded and weighed, analysis of dietary composition using African food tables, collection of saliva samples every-other day for radioimmunoassay of salivary oestradiol and progesterone. RESULTS: The primary staple in the Lese diet is manioc, consumed at nearly every meal, but the diet is subject to seasonal fluctuations. Important seasonal crops are groundnuts and rice. Carbohydrates comprise 64% of the diet, protein 14% and fat 22%, but seasonal fluctuations in food items create significant differences in protein content (P = 0.007). Energy intake falls by 25% in the hunger season. Lese energy balance reflects this lack with women losing a mean 7% of total body weight. The mean BMI for Lese women at the beginning of the study was 22.8 but, during the hunger season, the BMI for 20% of women fell to < 18.5, indicative of chronic energy shortage. Mean levels of Lese salivary oestradiol and progesterone are chronically and significantly lower than healthy, Western controls (P = 0.0001 for progesterone; P = 0.03 for follicular values of oestradiol, P = 0.0001 for mid-cycle values, and P = 0.0002 for luteal values). Mean salivary progesterone levels were significantly lower for those Lese women losing weight (P = 0.03), and significantly lower for weight-loss women when comparing levels at the beginning and end of the hunger season (P = 0.03). DISCUSSION: The relatively low-fat, high-fibre diet of the Lese appears healthy, but there are occasional seasonal deficiencies in protein-energy and micronutrient content, especially for pregnant and lactating women. Dietary composition may affect Lese levels of reproductive steroids, partly explaining the chronically low salivary oestradiol profile of this population.

Adolescent↗
PubMed1995

An analysis for menstrual data with time-varying covariates.

This paper concerns the analysis of menstrual data; in particular, methodology to identify variables that contribute to the variability of menstrual cycles both within and between women. The basis for the proposed methodology is a parameterization of the mean length of a menstrual cycle conditional upon the past cycles and covariates. This approach accommodates the length-bias and censoring commonly found in menstrual data. Data from a longitudinal study of menstrual patterns and other variables among Lese women of the Ituri Forest, Zaire, illustrate the methodology. A small simulation illustrates the bias caused by incorrectly deleting the censored cycles.

Adolescent↗
PubMed1992

The ecology of birth seasonality among agriculturalists in central Africa.

The Lese are subsistence farmers living in the Ituri Forest of north-east Zaïre. They exhibit significant birth seasonality, with lowest frequencies of conception when food production is least, nutritional status is low and ovarian function, as measured by salivary steroid hormone levels, is reduced. Efe pygmy foragers, who live in the same geographical area but are less dependent on cultivated foods and have a more flexible life style, do not exhibit frequent fluctuations in nutritional status nor significant birth seasonality. These findings support a model of birth seasonality relating climatic variables to variation in fertility through a causal chain linking rainfall to food production to energy balance to ovarian function to fertility. The model, which emphasises an ecological approach to the study of human reproduction, should have broad applicability since seasonality of food production and energy balance is widespread geographically and across a wide variety of economies and cultures.

Agriculture↗