Organic-solvent water pollution and low birth weight in Michigan.

This pilot study explored the association between a measure of water pollution caused by benzene or chlorinated solvents and the incidence of low birth weights for white residents of Michigan counties. A positive relationship between water pollution by these contaminants and the per cent of low-weight births (less than 2,500 grams, or about 5.5 pounds) resulted despite controls for the incidence of teenaged childbearing, infrequent prenatal care, and mean household income from wages or salaries. Water pollution showed an association with the incidence of low birth weight that was as strong as that between low birth weight and low prenatal care. While correlation cannot prove causation, the finding suggests that impure water may impair fetal growth in Michigan.     

Interaction of rat mammary gland thioesterase II with fatty acid synthetase is dependent on the presence of acyl chains on the synthetase

The interaction between rat mammary gland thioesterase II and fatty acid synthetase has been studied by a variety of physicochemical techniques. Pyrene-labeled thioesterase II does not exhibit increased fluorescence anisotropy when mixed with fatty acid synthetase, suggesting that the enzymes do not readily form a complex. Nevertheless, the functional interaction between the enzymes can be easily demonstrated by observing the hydrolysis, by unmodified thioesterase II, of acyl chains from their thioester linkage to the 4-phosphopantetheine of the fatty acid synthetase. This hydrolytic reaction is not inhibited even in the presence of a large excess of fatty acid synthetase with vacant 4'-phosphopantetheine thiols, indicating that interaction occurs only between thioesterase and fatty acid synthetase species which carry acyl chains on the 4'-phosphopantetheine thiols. A novel model system was devised which allowed us to explore the nature of the physical interaction between the two enzymes under conditions where the synthetase was actively engaged in acyl chain assembly. Fatty acid synthetase was treated with phenylmethanesulfonyl fluoride to inhibit its resident thioesterase activity, immobilized via a specific antibody to a column of Sepharose 4B, and exposed to the substrates required for acyl-enzyme assembly. When thioesterase II was introduced to the column, it passed through unretarded even though it efficiently catalyzed hydrolysis of the immobilized S-acyl synthetase en route. These results indicate that the two enzymes associate when an acyl chain is present on the synthetase and that they dissociate rapidly following completion of the catalytic process. Thus, the mammary system differs from that of the avian uropygial gland in which the two enzymes associate to form a stable complex even in the absence of substrates.     

Prenatal diagnosis of Duchenne muscular dystrophy: prospective linkage analysis and retrospective dystrophin cDNA analysis.

The accuracy of DNA-based prenatal diagnosis of Duchenne muscular dystrophy (DMD) was determined by study of 174 families. Only 60% of families had a living affected male, and 63% had history of a single affected male. Prenatal diagnosis was declined by 47% of mothers whose DNA studies predicted a carrier risk below 2%, and none have had affected sons. Fetal risk was estimated prospectively by linkage analysis using intragenic and flanking RFLPs and retrospectively using dystrophin cDNA analysis for families whose linkage estimates lacked precision. Diagnostic accuracy was determined by comparing predictions with 40 male pregnancy outcomes. On the basis of linkage analysis, we anticipated 3.2 DMD males and observed 3.0. Retrospective cDNA analysis identified deletions in 2 of these 3 males. The combined use of linkage and cDNA deletion analysis provided a highly accurate method for prenatal diagnosis of DMD.     

Book reviews

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Book reviews

     

Disproportionate allocation of mineral nutrients and carbon between vegetative and reproductive structures in Banksia hookeriana

We compared above-ground allocation patterns in mature shrubs of Banksia hookeriana from three 13-year-old populations, growing on nutrient-impoverished sands to determine whether C (dry mass) could be a substitute for mineral nutrients (N, P, K, Ca, Mg and NA). The percentage of reproductive structures to total above-ground growth (reproductive effort; RE) was integrated over nine successive reproductive cycles. Only 0.5% of above-ground dry mass was allocated to seeds compared with 31% to total RE. Allocations of N (24%) and P (48%) to seeds, and N (44%) and P (65%) to RE were much higher. Allocations of K, Ca, Mg and Na to seeds (<1–3%), and RE (21–35%) were closer to that of dry mass. Relative allocation (RA) is defined as the proportion of a nutrient element allocated to a structure relative to its dry mass. RA of P to seeds was 91 and N was 44, but for K, Ca, Mg and Na ranged from only 6 for K to<1 for Na. Thus P, and to a lesser extent N, provide a much more sensitive measure of the relative cost of reproduction than C in this nutrient-limited system.     

Population fragmentation may reduce fertility to zero in Banksia goodii — a demonstration of the Allee effect

All individuals of all known populations of Banksia goodii were assessed for seed production. Small populations produced no or only a few seeds per unit canopy area. Effects of population size on seed production per unit area and seed production per plant were present over the whole range of population sizes, indicating that even in large populations seed production may still not be at its maximum. Resource differences could not explain this disproportionate decrease in seed production with decline in population size, because there were no differences in soil properties and understorey or overstorey cover between the small and large populations. Although plants in small and large populations were similar in size, seed production per plant was much lower in small populations. This was not because plants in small populations produced fewer cones but because the fraction of these cones that was fertile was much lower. Five of the nine smallest populations (<200 m²) produced no fertile cones over the last 10 years. The number of seeds per fertile cone did not depend on population size. The results are discussed in relation to pollination biology.     

Age-related nonrandom chromosomal abnormalities in human low-grade astrocytomas

We report a cytogenetic investigation of 55 low-grade astrocytomas in 52 patients, 15 children and 37 adults. In addition to numerical aberrations such as trisomy 7 and gonosomal losses, we found structural and/or numerical aberrations of chromosome 1 in eight astrocytomas. There was a striking difference between the rearranged chromosomes in pediatric and adult patients. Whereas the pediatric tumors revealed monosomies 1p with accompanying trisomy 1q, the astrocytomas in adults showed partial or complete monosomies 1q.     

Morphology and molecular phylogeny of the marine diatom genus Nagumoea (Bacillariophyceae) from Japan

The canal-bearing diatom genus Nagumoea, described based on only morphological evidence, was tentatively assigned to the order Bacillariales, although its phylogenetic position remained unclear. Because three isolates of Nagumoea (SK002, SK024 and SK053) were successfully established from Japanese coasts, we performed their morphological observations and molecular phylogenetic analyses to discuss the phylogeny and taxonomic position of this genus. Strains SK002 and SK024 were identified as Nagumoea africana, whereas SK053 conformed with Nagumoea serrata. There was high interspecific divergence between N. africana and N. serrata in the rbcL sequences (8.03–8.17%), indicating their distinctness. Furthermore, intraspecific variations were detected within N. africana (2.35%) in the rbcL, implying its cryptic diversity. The maximum likelihood and Bayesian phylogenetic trees inferred from the plastid rbcL, psbC and nuclear 18S rDNA genes recovered Nagumoea as monophyletic with strong statistical support and embedded within an unresolved, poorly supported lineage containing Achnanthes, Craspedostauros, Staurotropis and Undatella in the canal-bearing order Bacillariales (= the family Bacillariaceae). Although the constrained tree based on the monophyly of Nagumoea and the other canal-bearing clade (Surirellales and Rhopalodiales) was statistically rejected by the topology tests, the phylogenetic position of Nagumoea with other Bacillarialean members remains equivocal. The possession of two plastids positioned fore and aft, observed in the present study, and lack of keel, typical of the Bacillariales, indicate the possibility of Nagumoea being part of the ingroup of the Bacillariales or its closely related outgroup.