Enhancement of α-lactalbumin-like activity in mammary explants from pregnant rats in the absence of exogenous prolactin

Mammary explants from pregnant rats showed a progressive increase in α-lactalbumin activity during culture with insulin, hydrocortisone and prolactin. Unexpectedly, culture with only insulin and hydrocortisone produced a similar rate of increase of α-lactalbumin-like activity, but this increase commenced about 24 hr later. The delay suggests that the enhanced activity effected by insulin and hydrocortisone is not a reflection of carry-over of endogenous mammotrophic hormones. Insulin plus hydrocortisone did not stimulate casein or fatty acid synthesis by pregnancy tissue, and did not enhance α-lactalbumin-like activity in virgin rat mammary explants. Enhancement of this activity by insulin plus hydrocortisone in pregnant tissue was constant over a wide range of glucocorticoid concentrations, but was inhibited by progesterone. Available evidence indicates that the active factor in extracts from insulin-hydrocortisone-explants is a heat-stable protein which is either α-lactalbumin itself, or another molecule with similar specifier properties.     

Comparison of factor IX methylation on human active and inactive X chromosomes: implications for X inactivation and transcription of tissue-specific genes.

Maintenance of dosage compensation for housekeeping genes on the human X chromosome is mediated through differential methylation of clustered CpG nucleotides associated with these genes. To determine if methylation has a role in maintaining inactivity of X-linked genes which show tissue-specific expression, we examined the locus for blood clotting Factor IX. The analysis encompassed 91% of the HpaII and HhaI sites in the 41-kb region that includes the presumed promoter region, 5 kb of 5'- and 4 kb of 3'-flanking sequences. Although there are sex differences in methylation of the locus in leukocytes, the methylation pattern in liver, where the gene is expressed, is essentially the same for loci on the active and inactive X chromosome. The lack of differences in methylation of active and inactive genes makes it unlikely that methylation within the locus has a role in expression of the Factor IX gene. These findings, along with the absence of clustered CpG dinucleotides within the Factor IX locus, suggest that functional differences in DNA methylation related to X chromosome dosage compensation may be limited to CpG clusters. In any event, dosage compensation seems to be maintained regionally, rather than locus by locus.     

The effectiveness of constructed wetland for treatment of woodwaste leachate

Percolation of rainfall through woodwaste piles leaches natural chemicals from the wood residuals that can have adverse impacts on the environment. A study was conducted on a woodwaste storage site, adjacent to the Lower Fraser River, near Mission, BC, Canada. The objective of this research was to evaluate the effectiveness of constructed wetland for treatment of this woodwaste leachate. The leachate was characterized by high oxygen demand, tannin and lignin, and volatile fatty acids (VFAs), but low pH and nutrients. Diluted leachate passed through six pilot-scale wetland cells, four planted with cattail (Typha latifolia) and two unplanted controls, with a hydraulic retention time of 7 days and an average depth of 40 cm. Nutrient addition and pH adjustments were made to improve contaminant removal. Reductions in contaminants were consistently achieved, with average removals for BOD, COD, VFAs and tannin and lignin of 60, 50, 69 and 42%, respectively. Climatic conditions had an impact on the performance of the constructed wetland. Further operation of the system will help to elucidate the seasonal fluctuations. Aging of the constructed wetland system increased the treatment performance.     

CHARACTER DISCRIMINATORY POWER,CHARACTER-SET CONGRUENCE,AND THE CLASSIFICATION OF INDIVIDUALS FROM HYBRID ZONES: AN EXAMPLE USING STONE CRABS (MENIPPE)

Many investigators categorize individuals from hybrid zones to facilitate comparisons among genotypic classes (e.g., parental, F₁, backcross) for comparative studies in which components of fitness or geographic variation are being analyzed. Frequently, multiple character sets representing genetically independent traits are used to classify these individuals and various methodologies are employed to combine the classifications obtained from the different character sets. We adapted the principles of total evidence and taxonomic congruence (two formalized approaches used by systematists in formulating phylogenetic hypotheses) to address the problem of discriminating hybridizing species and classifying individuals from hybrid zones. As our model, we used two morphological (coloration and morphometric) and two molecular (allozyme and mitochondrial DNA restriction-fragment-length polymorphism) character sets that differentiate two stone crab species (Menippe adina and M. mercenaria). Using principal-components analysis, we determined that combining character sets and eliminating characters or character sets that did not have large eigenvector coefficients for the principal component that best separated the two species yielded the highest level of discrimination between species and allowed us to classify a broad range of morpho-genotypes as hybrids. For the stone crabs, three diagnostic allozyme loci and five diagnostic coloration characters best separated the species. The two character sets were not completely congruent, but they agreed in their classification of 50% of the individuals from the hybrid zone and rarely strongly disagreed in their classifications. Classification discrepancies between the two character sets probably represent variation between traits in interspecific gene flow rather than intraspecific, ecologically mediated variation. Our results support the assertions of previous investigators who espoused the benefits associated with using multiple character sets to classify individuals from hybrid zones and demonstrate that, if character sets are reasonably congruent and numerically balanced, combining diagnostic characters from multiple character sets (a total-evidence approach) can enhance discriminatory power between species and facilitate the assignment of hybrid-zone individuals to genotypic classes. On the contrary, classifying hybrid-zone individuals using character sets separately (a taxonomic-congruence approach) provides the opportunity to compare levels of introgression between species and to assess reasons for discordance among the data sets.