Increase in hepatic microsomal lipid peroxidation mediated by α-adrenergic system under cold stress and noradrenaline treatment

A membrane protein recognized by monoclonal antibody SQM1 was identified in human squamous carcinomas, including those originating in the head and neck (SqCHN), lung and cervix. Cell lines derived from SqCHN of previously untreated patients expressed high amounts of this protein. In contrast, many cell lines established from SqCHN of patients previously treated with chemotherapy and/or radiation showed diminished amounts of this SQM1 protein. The expression of SQM1 antigen was determined in several SgCHN cell lines made resistant by exposure to methotrexate (MTX) in vitro. The parent cell lines all exhibited strong binding to SQM1 antibody. The MTX-resistant sublines showed much lower membrane binding of SQM1. The lowest SQM1 reactivity was found in cell lines with high resistance to MTX and with diminished rate of MTX transport. Some highly MTX-resistant cell lines which had high levels of dihydrofolate reductase, but which retained a high rate of MTX transport, also retained high levels of SQM1 binding. Reduced SQM1 protein was also found in SgCHN cells which developed resistance to the alkylating drug cis-platinum (CDDP) and which showed reduced membrane transport of CDDP. Cell growth kinetics and non-specific antigenic shifts were not responsible for the differences in SQM1 binding between the parent cell lines and their drug-resistant sublines. The finding of a novel protein which is reduced in cells resistant to MTX and CDDP could contribute to our understanding of the basic mechanisms of drug resistance. By detecting SQM1 protein in clinical specimens, it may be possible to monitor the development of drug resistance in tumors.Abbreviations SqCHN Squamous Carcinoma of the Head and Neck - MTX Methotrexate - CDDP Cis-Platinum - DHFR Dihydrofolate Reductase     

A comparative description of mitochondrial DNA differentiation in selected avian and other vertebrate genera

Levels of mitochondrial DNA (mtDNA) sequence divergence between species within each of several avian (Anas, Aythya, Dendroica, Melospiza, and Zonotrichia) and nonavian (Lepomis and Hyla) vertebrate genera were compared. An analysis of digestion profiles generated by 13-18 restriction endonucleases indicates little overlap in magnitude of mtDNA divergence for the avian versus nonavian taxa examined. In 55 interspecific comparisons among the avian congeners, the fraction of identical fragment lengths (F) ranged from 0.26 to 0.96 (F = 0.46), and, given certain assumptions, these translate into estimates of nucleotide sequence divergence (p) ranging from 0.007 to 0.088; in 46 comparisons among the fish and amphibian congeners, F values ranged from 0.00 to 0.36 (F = 0.09), yielding estimates of P greater than 0.070. The small mtDNA distances among avian congeners are associated with protein-electrophoretic distances (D values) less than approximately 0.2, while the mtDNA distances among assayed fish and amphibian congeners are associated with D values usually greater than 0.4. Since the conservative pattern of protein differentiation previously reported for many avian versus nonavian taxa now appears to be paralleled by a conservative pattern of mtDNA divergence, it seems increasingly likely that many avian species have shared more recent common ancestors than have their nonavian taxonomic counterparts. However, estimates of avian divergence times derived from mtDNA- and protein-calibrated clocks cannot readily be reconciled with some published dates based on limited fossil remains. If the earlier paleontological interpretations are valid, then protein and mtDNA evolution must be somewhat decelerated in birds. The empirical and conceptual issues raised by these findings are highly analogous to those in the long-standing debate about rates of molecular evolution and times of separation of ancestral hominids from African apes.      

Methods for computing the standard errors of branching points in an evolutionary tree and their application to molecular data from humans and apes

Statistical methods for computing the standard errors of the branching points of an evolutionary tree are developed. These methods are for the unweighted pair-group method-determined (UPGMA) trees reconstructed from molecular data such as amino acid sequences, nucleotide sequences, restriction-sites data, and electrophoretic distances. They were applied to data for the human, chimpanzee, gorilla, orangutan, and gibbon species. Among the four different sets of data used, DNA sequences for an 895-nucleotide segment of mitochondrial DNA (Brown et al. 1982) gave the most reliable tree, whereas electrophoretic data (Bruce and Ayala 1979) gave the least reliable one. The DNA sequence data suggested that the chimpanzee is the closest and that the gorilla is the next closest to the human species. The orangutan and gibbon are more distantly related to man than is the gorilla. This topology of the tree is in agreement with that for the tree obtained from chromosomal studies and DNA-hybridization experiments. However, the difference between the branching point for the human and the chimpanzee species and that for the gorilla species and the human-chimpanzee group is not statistically significant. In addition to this analysis, various factors that affect the accuracy of an estimated tree are discussed.      

Anonymous nuclear DNA markers in the American oyster and their implications for the heterozygote deficiency phenomenon in marine bivalves

A puzzling population-genetic phenomenon widely reported in allozyme surveys of marine bivalves is the occurrence of heterozygote deficits relative to Hardy-Weinberg expectations. Possible explanations for this pattern are categorized with respect to whether the effects should be confined to protein-level assays or are genomically pervasive and expected to be registered in both protein- and DNA-level assays. Anonymous nuclear DNA markers from the American oyster were employed to reexamine the phenomenon. In assays based on the polymerase chain reaction (PCR), two DNA-level processes were encountered that can lead to artifactual genotypic scorings: (a) differential amplification of alleles at a target locus and (b) amplification from multiple paralogous loci. We describe symptoms of these complications and prescribe methods that should generally help to ameliorate them. When artifactual scorings at two anonymous DNA loci in the American oyster were corrected, Hardy-Weinberg deviations registered in preliminary population assays decreased to nonsignificant values. Implications of these findings for the heterozygote-deficit phenomenon in marine bivalves, and for the general development and use of PCR-based assays, are discussed.      

ENDOSPERM DEVELOPMENT IN THE DATE PALM (PHOENIX DACTYLIFERA) (ARECACEAE)

Date seeds were sampled at regular intervals from pollination (March) to mature fruit (September) and processed for light microscopy and SDS-PAGE. Seed fresh weight rose until early June and then declined slightly through September due to a continuous decrease in water content. Cell wall formation started in May in the free nuclear endosperm and proceeded centripetally from the inner integument to the seed center. Wall thickening in each cell started in cell corners and showed a layered appearance with calcofluor white staining. It started in early June in the center of the seed and proceeded centrifugally such that the outer cells showed cell wall thickening in late June. Thickened cell walls were soft and PAS positive at inception, but staining disappeared and hardness increased during wall maturation. Cell elongation in the radial direction accompanied wall thickening. Protein body formation started after cell wall thickening and followed the same centrifugal developmental pattern. Mature protein bodies occurred in even the outermost cells by early July. No further structural changes occurred after this time. The high molecular weight storage proteins appeared in late June, which is when protein bodies had formed in all but the outer endosperm cells; however, these proteins did not appear simultaneously and minor changes in protein bands continued until maturation. α-Galactosidase activity was present in the developing endosperm and peaked at 13 wk after pollination. The data suggest that the thickened wall is deposited as a highly substituted galactomannan, but that most of the galactose side branches are clipped off presumably by α-galactosidase during cell wall polymerization.     

A highly conserved nuclear gene for low-level phylogenetics: elongation factor-1 alpha recovers morphology-based tree for heliothine moths

Molecular systematists need increased access to nuclear genes. Highly conserved, low copy number protein-encoding nuclear genes have attractive features for phylogenetic inference but have heretofore been applied mostly to very ancient divergences. By virtue of their synonymous substitutions, such genes should contain a wealth of information about lower-level taxonomic relationships as well, with the advantage that amino acid conservatism makes both alignment and primer definition straightforward. We tested this postulate for the elongation factor-1 alpha (EF-1 alpha) gene in the noctuid moth subfamily Heliothinae, which has probably diversified since the middle Tertiary. We sequenced 1,240 bp in 18 taxa representing heliothine groupings strongly supported by previous morphological and allozyme studies. The single most parsimonious gene tree and the neighbor-joining tree for all nucleotides show almost complete concordance with the morphological tree. Homoplasy and pairwise divergence levels are low, transition/transversion ratios are high, and phylogenetic information is spread evenly across gene regions. The EF-1 alpha gene and presumably other highly conserved genes hold much promise for phylogenetics of Tertiary age eukaryote groups.      

Mesodern-inducing factors and mesodermal patterning

Identification of the signalling molecules involved in mesoderm formation in amphibian embryos still presents problems. None of the original candidates, such as activin, have been definitively ruled out, and the new factors, such as the nodal-related genes, have come on to the scene. Of the original candidates, activin has been definitively shown to act as a morphogen, whereas bone morphogenetic protein (BMP)-4 has emerged as a ventral inducer and an inhibitor of neural differentiation. The effects of BMP-4 are antagonized by chordin, a molecule related to the product of the Drosophila gene short gastrulation.