Studies examining an association between artificial cranial deformation and the presence of wormian bones in the lambdoid suture have been inconclusive. Cranial deformation, however, does not seem to have a direct effect of increasing the sutural complexity of the pars lambdica of the lambdoid suture and also increasing the mean number of lambdoidal wormian bones, given their presence.

The taxonomic status and phylogenetic position of the bonobo or pygmy chimpanzee continues to be debated. In this report we examined the phylogenetic position and taxonomic status of the pygmy chimpanzee by a three-way comparison of the banded chromosomes of humans, Pan troglodytes and Pan paniscus. The evaluation pays particular attention to distinguishing ancestral versus derived chromosomes in order to determine the direction of the chromosomal differences found between these three taxa. l? paniscus and l? trog2odytes are shown to share a number of derived chromosomal changes indicative of a probable extensive period of common evolution after the divergence of the humans. The karyological evidence also demonstrates that the pygmy chimpanzee is most likely a valid species, and that it is also the most chromosomally specialized of the three taxa examined. Therefore, from the chromosomal perspective, the pygmy chimpanzee is not the best model for the last common ancestor of both humans and African apes. The chromosomal data also suggest that all the African apes have evolved more from this last common ancestor than is generally considered. cator of genetic homology (Seuanez, 1982;Pearson and Roderick, 1982).

Human placental microsomes isolated from term placentas derived from nonsmoking women and women smoking 1 to 40 cigarettes a day were analyzed for the metabolism of benzo(a)pyrene measured as various metabolites by HPLC and/or as aryl hydrocarbon hydroxylase (AHH)6 activity. In accordance with other reports, AHH activity was several times higher in smokers than in nonsmokers. Regression analysis on 13 different placental tissues from women smoking from 1 to 40 cigarettes demonstrated a high correlation (r = 0.8 to 0.9) between AHH activity (or the formation of benzo(a)pyrene phenols resolved by HPLC) versus the formation of the procarcinogenic benzo(a)pyrene-7,8-diol. Subsequent studies on placentas derived from 67 women who smoked 10 to 40 cigarettes per day demonstrated a definite dose-response relationship between AHH activity and the number of cigarettes smoked/day. The dose-response curve was sigmoidal in shape; however, when the data were plotted on a semi-log scale the curve assumed a linear shape, reaching saturation of AHH induction beyond 20 to 25 cigarettes/day. While mean AHH activity was dependent upon the number of cigarettes smoked/day, considerable interindividual variability in AHH (ranging more than 1,000-fold in some cases) was observed among individuals with comparable smoking histories, i.e. smoking the same number of cigarettes. Population distribution suggested clustering of the population in the low-AHH-activity region while cord-blood thiocyanate analysis and twin studies suggested that genetic factors contributed to a major portion of the inter-individual variability in AHH activity observed among smokers.

The present study assesses the contribution of genetic and environmental factors to variability in placental aryl hydrocarbon hydroxylase and glutathione transferase activities using twin study methodology. Twin placentas were collected at the time of delivery. The placenta, except for a single layer of maternal decidua, consists of fetal tissue exhibiting fetal genotype. Microsomal and cytosolic fractions were prepared under stringent protocols to prevent enzyme activity loss. There were two monozygotic-monochorionic pairs, five monozygotic-dichorionic pairs, and 21 dizygotic-dichorionic pairs that showed measurable aryl hydrocarbon hydroxylase activity using the direct fluorometric assay. Most of the mothers were smokers. Aryl hydrocarbon hydroxylase activity was measured with two different substrates, benzo(a)pyrene and 7-ethoxyresorufin. Glutathione transferase activity was measured using glutathione and 1-chloro-2,4-dinitrobenzene as substrates for a spectrophotometric assay that follows the conversion of the aromatic substrate. Twin pair similarity was calculated with intraclass correlation coefficients. There is a high correlation between the activities of the two aryl hydrocarbon hydroxylase substrates (r = .814), but no correlation between aryl hydrocarbon hydroxylase and glutathione transferase activity levels. There is little evidence of genetic variability underlying the variation in the enzyme activities because monozygotic-dichorionic twins are no more similar to each other for the three substrate activities than are the dizygotic twins. To delineate the prenatal environmental influences on placental enzyme variability, dichorionic placentation was subdivided further into contiguous and noncontiguous placental position. Lower intraclass correlation coefficients are obtained for the dizygotic twins whose placentas were noncontiguous compared with dizygotic twins with contiguous placentas. The results suggest that most of the variability seen in these placental enzyme systems is due to environmental differences within uteri, rather than genetic variability in the population. This does not negate the possibility that between-pair, or population, variability may have a genetic component, because even dizygotic twins share a large proportion of their genes. This study points out that a significantly variable environment exists within the human uterus.

We measured blood lead levels and inquired about environmental exposure pathways in 443 children aged 6 mo to 6 y in four lower socioeconomic Denver, Colorado, neighborhoods. Two neighborhoods were adjacent to a cadmium refinery. Eight percent of the children had blood lead levels > or = 10 micrograms/dl and 45% were below the detection limit of 4 micrograms/dl. Statistical analyses specific to the problem of below-detection values (i.e., dichotomization of variables, the probability plot method of estimation, and the bootstrap estimate of the standard error) were conducted to detect neighborhood differences. A child who lived in Globeville, the neighborhood surrounding the refinery, had a slightly higher probability of having a blood lead level > or = 5 micrograms/dl. Yet, the results as a whole documented the striking decline in blood lead levels in urban children after the deleading of gasoline.