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Biomedical subjects

J W Wood

Publications and source records attributed to J W Wood.

At least 19 recordsLinked to original sources
PubMed1997

The evaluation of delayed-type hypersensitivity responsiveness and nutritional status as predictors of gastro-intestinal and acute respiratory infection: a prospective field study among traditional nomadic Kenyan children.

A 10-month prospective study of children from a nomadic pastoralist community in northwest Kenya was conducted to examine the relationship between nutritional status, cell-mediated immunity (CMI), and morbidity due to gastroenteritis and acute respiratory infection (ARI). In children ages 6 months to 10 years, nutritional status and cellular immunocompetence, determined by delayed-type hypersensitivity (DTH), were related to individual attack rates of diarrhoea and ARI over two 5-month observation periods, one each in the wet and dry season. While no association was found between premorbid nutritional status and gastroenteritis, DTH responsiveness was a significant predictor of diarrhoeal disease, with anergic children experiencing, on average, 20 per cent higher attack rates than immunocompetent children. When examined separately, both nutritional status and DTH responsiveness were significant predictors of individual attack rates of ARI in the wet season. However, when the effects of nutritional and immunological status were simultaneously tested, only DTH responsiveness was significant. Anergic children experienced 34 per cent excess ARI, compared to immunocompetent children. These results indicate that cellular immunocompetence is a sensitive predictor of gastrointestinal and respiratory infection, and that the effect of nutritional status on the occurrence of ARI may be mediated by cellular immune function.

Child↗
PubMed1994

Proportional hazards analysis of diarrhea due to enterotoxigenic Escherichia coli and breast feeding in a cohort of urban Mexican children.

Ninety-eight women-infant pairs were followed for up to 50 weeks in the northern part of Guadalajara, Mexico, from August 1986 to July 1987 as part of a community-based, prospective study of the relation between infant feeding patterns and enterotoxigenic Escherichia coli producing heat-labile toxin (LT-ETEC) diarrheal disease. Strictly formula-fed children had an incidence of diarrhea over three times that of strictly breast-fed infants and twice that of breast-fed and supplementally fed children. Strictly formula-fed infants colonized by LT-ETEC were symptomatic for diarrhea nearly three times as often as strictly breast-fed infants and twice as often as infants receiving a mixed diet. The fitting of parametric hazard models to durations until LT-ETEC colonization revealed that the hazard for the first colonization was time invariant. The hazard of diarrhea increased by 400-500% during the rainy season or among children 3 months of age or older who received avena, a barley drink. The best-fitting hazard models to durations until symptomatic expression of LT-ETEC infection all increased through time. This hazard was inversely impacted by the overall amount of LT-ETEC-specific, immunoglobulin A antibodies the infant received via the mother's breast milk and by the provision of traditional medicinal teas.

Bacterial Toxins↗
PubMed1994

Women's reproductive cancers in evolutionary context.

Reproductive experiences for women in today's affluent Western nations differ from those of women in hunting and gathering societies, who continue the ancestral human pattern. These differences parallel commonly accepted reproductive risk factors for cancers of the breast, endometrium and ovary. Nutritional practices, exercise requirements, and body composition are nonreproductive influences that have been proposed as additional factors affecting the incidence of women's cancers. In each case, these would further increase risk for women in industrialized countries relative to forager women. Lifestyles and reproductive patterns new from an evolutionary perspective may promote women's cancers. Calculations based on a theoretical model suggest that, to age 60, modern Western women have a breast cancer risk as much as 100 times that of preagricultural women.

Biological Evolution↗
PubMed1994

A multistate model of fecundability and sterility.

This paper develops a multistate hazards model for estimating fecundability and sterility from data on waiting times to conception. Important features of the model include separate sterile and nonsterile states, a distinction between preexisting sterility and sterility that begins after initiation of exposure, and log-normally distributed fecundability among nonsterile couples. Application of the model to data on first birth intervals from Taiwan, Sri Lanka, and the Amish shows that heterogeneity in fecundability is statistically significant at most ages, but that preexisting sterility and new sterility are unimportant before age 40. These results suggest that sterility may not be an important determinant of natural fertility until later reproductive ages.

Adolescent↗
PubMed1990

Birth spacing patterns in humans and apes.

Comparative studies of birth interval dynamics in wild primates suffer from several problems of analysis and interpretation: (1) the data are always right-censored, (2) sample sizes are usually small, (3) the distribution of birth intervals is expected to be non-normal, (4) early offspring mortality is a confounding variable, and (5) differences in life history (e.g., presence or absence of menopause) can complicate interpretation of the results. A survival analysis designed to minimize these problems is applied to published data on wild chimpanzees and gorillas from Gombe and Virunga Parks, respectively, and to new data on wild orangutans from Tanjung Puting National Park and on a human population, the Gainj of highland Papua New Guinea. According to this analysis, the estimated median birth interval (when the offspring whose birth opens the interval does not die within the interval) is 43.3 +/- 1.0 months for the Gainj, 45.5 +/- 1.2 months for gorillas, 66.6 +/- 1.3 months for chimpanzees, and 92.6 +/- 2.4 months for orangutans.

Animals↗
PubMed1990

A possible mechanism of action for azelaic acid in the human epidermis.

Azelaic acid, and other saturated dicarboxylic acids (C9-C12), are shown to be competitive inhibitors of tyrosinase (KI azelaic acid = 2.73 X 10(-3) M) and of membrane-associated thioredoxin reductase (KI azelaic acid = 1.25 X 10(-5) M). The monomethyl ester of azelaic acid does not inhibit thioredoxin reductase, but it does inhibit tyrosinase, although double the concentration is necessary compared with azelaic acid (KI azelaic acid monomethyl ester = 5.24 X 10(-3) M). Neither azelaic acid nor its monomethyl ester inhibit tyrosinase when catechol is used as a substrate instead of L-tyrosine. Therefore, the weak inhibitory action of azelaic acid on tyrosinase appears to be due to the competition of a single carboxylate group on this inhibitor for the alpha-carboxylate binding site of the L-tyrosine substrate on the enzyme active site. Based on the inhibitor constant on tyrosinase, at least cytotoxic levels of azelaic acid would be required for the direct inhibition of melanin biosynthesis in melanosomes if this mechanism is responsible for depigmentation in the hyperpigmentation disorders lentigo maligna and melasma. Alternatively only 10(-5) M azelaic acid is required to inhibit thioredoxin reductase. This enzyme is shown to regulate tyrosinase through a feedback mechanism involving electron transfer to intracellular thioredoxin, followed by a specific interaction between reduced thioredoxin and tyrosinase. Furthermore, the thioredoxin reductase/thioredoxin system is shown to be a principal electron donor for the ribonucleotide reductases which regulates DNA synthesis.(ABSTRACT TRUNCATED AT 250 WORDS)

Cells, Cultured↗
PubMed1987

The allelic correlation structure of Gainj- and Kalam-speaking people. II. The genetic distance between population subdivisions.

The patterning of allele frequency variability among 18 local groups of Gainj and Kalam speakers of highland Papua New Guinea is investigated using new genetic distance methods. The genetic distances proposed here are obtained by decomposing Sewall Wright's coefficient FST into a set of coefficients corresponding to all pairs of population subdivisions. Two statistical methods are given to estimate these quantities. One method provides estimates weighted by sample sizes, while the other method does not use sample size weighting. Both methods correct for the within-individual and between-individual-within-groups sums of squares. Genetic distances among the Gainj and Kalam subdivisions are analyzed with respect to demographic, geographic, and linguistic variables. We find that a demographic feature, group size, has the greatest demonstrable association with the patterning of genetic distances. The pattern of geographic distances among groups displays a weak congruence with the pattern of genetic distances, and the association of genetic and linguistic diversity is very low. An effect of differences in group size on genetic distances is not surprising, from basic theoretical considerations, but genetic distances have not often been analyzed with respect to these variables in the past. The lack of correspondence between genetic distances and linguistic and geographic differences is an unusual feature that distinguishes the Gainj and Kalam from most other tribal populations.

Alleles↗
PubMed1987

The relative efficiency of cryogens used for plunge-cooling biological specimens.

Coolants used for freezing biological specimens were tested for cooling performance in the continuous plunge mode. Results from bare thermocouples showed that ethane cooled faster than propane or a propane:pentane mixture, even when warmed to 25 K above its freezing point. Propane coolants were more efficient than Freon 22 and the slowest cooling occurred in boiling liquid nitrogen. Hydrated gelatin specimens showed similar results with ethane cooling about 33% faster than propane. Epoxy resin specimens cooled faster than hydrated gelatin specimens of similar size. Hydrated and resin specimens cooled over increasing distances as plunge velocity increased. A bare thermocouple, however, cooled over a constant distance when plunged above a critical velocity. This phenomenon may reflect vapour formation and its suppression at high plunge velocities. The rate of cooling in hydrated specimens is shown to have an absolute limit and cannot be modelled by bare thermocouples or resin specimens.

Epoxy Resins↗
PubMed1986

Genetic characterization of Gainj- and Kalam-speaking peoples of Papua New Guinea.

The research presented focuses on genetic variation in the Gainj- and Kalam-speaking peoples of highland Papua New Guinea. The primary data are typings at 51 genetic loci observed on 600 individuals who reside in 21 census units, called parishes. These data are augmented by cultural and demographic information that has also been collected. Parish sizes are small, ranging from 20 to about 200 individuals. Direct Western contact with these people has been occurring only for the past three decades. Although Westernization is currently increasing, we find that much of the traditional settlement pattern and mate exchange system is preserved. There are segregating variants at 27 loci. Four rare variants are initially described: NP 4-Kalam, ADA 6-Kalam, PEPA 3-Kalam, and FUM 2-Kalam. We find evidence for a new Gm haplotype, a;-, that is recessive to all other Gm haplotypes. It occurs at a high enough frequency, f(a;-) = 0.119, to be considered a "private polymorphism." Average per locus heterozygosity is estimated to be 0.053. This value is not statistically different from levels observed on two modern urban populations. Thus, there is no evidence for a reduced level of genetic variation in these people, despite small parish sizes and a relatively unacculturated social structure.

Adolescent↗
PubMed1986

Convergence of genetic distances in a migration matrix model.

A recurring problem with the use of migration matrix models of genetic differentiation has to do with their convergence properties. In practice, predictions can be drawn from these models only at equilibrium; but in the case of the standard predictors (most of which are modifications of Wright's FST), it can take an unrealistically large number of generations to approach equilibrium. An alternative set of predictors, the set of all pairwise genetic distances among the populations that define the rows and columns of the migration matrix, is investigated here. These distances are shown analytically to converge much more rapidly than the more commonly used predictors. In an application of the model to migration data on a human population from Papua New Guinea, it takes only about three to four generations for the pairwise distances to converge, in contrast to more than 100 generations for one of the standard predictors. In this case, moreover, the distances predicted by the model at equilibrium are similar to those calculated from the available genetic data.

Alleles↗
PubMed1985

Laser therapy--things to come: multiple spectra and photodynamic therapy.

The clinical application of endoscopic laser therapy has expanded recently to include the resolution of various strictures of the gastrointestinal tract and the fracture of gallstones. These uses and the growing utilization of photodynamic therapy of tumors in conjunction with hematoporphyrin derivative is reviewed. These advances hold enough therapeutic promise to demand careful consideration.

Endoscopy↗