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Biomedical subjects

H T Groeneveld

Publications and source records attributed to H T Groeneveld.

61 records · Page 4Linked to original sources
PubMed1980

A technique for the recovery of nematodes from ruminants by migration from gastro-intestinal ingesta gelled in agar: large-scale application.

A gelled-agar technique for worm recovery was adapted to facilitate the recovery of larval and adult nematodes from the total ingesta of large numbers of sheep. The technique was also used to recover nematodes from 4 calves. In one trial involving 120 sheep, 100% of 2013 4th stage larvae (L4) and 92,1% of 134,205 adult Haemonchus contortus migrated from the agar preparations. Highly significantly more male than female worms failed to migrate. Using 1 x 1/10 aliquot to estimate the numbers of worms that failed to migrate from the agar, the mean error in the total worm count (worms that migrated plus those that failed to migrate) per sheep was 2,2%; with an examination of 2 x 1/10 aliquot the error was 1,7%. We concluded from this that the gelled-agar method may be of value for quantitative worm recovery, for example, in anthelmintic tests. In a second trial, 98,5% of 17,056 L4 and adult nematodes of 5 genera migrated from the ingesta of 4 calves and 96,4% of 62,597 L4 and adult nematodes of 9 species from the ingesta of 15 sheep. In general, L4 migrated slightly more efficiently than adult worms. In sheep and, to a lesser extent, in calves, Haemonchus spp. did not migrate as efficiently as the other genera such as Ostertagia, Trichostrongylus, Nematodirus, Oesophagostomum, Marshallagia and Chabertia.

Abomasum↗
PubMedDate not supplied

Fluctuating odontometric asymmetry in the Lengua Indians of Paraguay.

Fluctuating dental asymmetry was evaluated as an indicator of environmental stress in a group of 202 living Lengua Indians from the Paraguayan Chaco area. Older, less accultured individuals were shown to be significantly more asymmetric than younger individuals who had been increasingly exposed to western foodstuffs and medicine. Lengua Indians demonstrated similar levels of asymmetry to another preliterate group, the Ticuna Indians of Columbia, but were found to be significantly more asymmetric than contemporary caucasoids. Similar patterns of asymmetry in both arcades for males and females were confirmed by analyses of variance and by Spearman's rank-order correlation coefficients. Partitioning variation in the degree of asymmetry by arcade, dimension and tooth revealed significant differences in the effects of tooth and arcade only: asymmetry was greater in the maxilla and greater in the more distal teeth within each morphogenic class.

Ethnicity↗
PubMedDate not supplied

Evidence for a secular trend in the Negro dentition.

Metric changes in the Negro dentition were evaluated in a sample of artificial stone casts of the dental arcades of 106 living South African Negroes (56 males, 50 females) and in 100 Negro crania (50 males, 50 females) drawn from the R. A. Dart Collection. Comparison of the mesiodistal and buccolingual dimensions of these two samples to the published results of a similar study on earlier Negroes revealed a statistically significant trend towards tooth-size enlargement. This positive secular trend was found to be most pronounced in the mesiodistal diameter, with less than half of the teeth considered showing significant buccolingual enlargement. Although the trend was equally pronounced in both sexes and in both arcades, mesiodistal change was found to increase in an antero-posterior direction, while buccolingual change centred around the anterior teeth.

Black People↗
PubMedDate not supplied

Measurement error in human dental mensuration.

The reliability of human odontometric data was evaluated in a sample of 60 teeth. Three observers, using their own instruments and the same definition of the mesiodistal and buccolingual dimensions were asked to repeat their measurements after 2 months. Precision, or repeatability, was analysed by means of Pearsonian correlation coefficients and mean absolute error values. Accuracy, or the absence of bias, was evaluated by means of Bland-Altman procedures and attendant Student t-tests, and also by an ANOVA procedure. The present investigation suggests that odontometric data have a high interobserver error component. Mesiodistal dimensions show greater imprecision and bias than buccolingual measurements. The results of the ANOVA suggest that bias is the result of interobserver error and is not due to the time between repeated measurements.

Analysis of Variance↗
PubMedDate not supplied

Effects of prenatal exposure to tobacco smoke on developmental stability in children.

The effects of maternal and paternal smoking on fetal and neonatal dental development were investigated in a sample of 199 school children. Fluctuating asymmetry was evaluated in the maxillary arcades of four groups of children: those whose mothers had smoked, those whose fathers had smoked, those whose parents both had smoked, and finally, those whose parents had not smoked. When the magnitudes of fluctuating asymmetry in children exposed to parental tobacco smoke from one parent only were compared with the control group, no general univariate differences were found. Children exposed to smoke from both parents, however, showed significantly elevated levels of asymmetry in four out of six comparisons. In contrast, an analysis of variance failed to find significant differences on the basis of sex, parity, smoking status, or their interactions. It is concluded that parental smoking does not result in developmental destabilization of the fetus and neonate.

Adolescent↗