Calcium control of glycogen synthase activities in mouse diaphragms, rat adipocytes and rat hepatocytes

The following article provides evidence that cellular calcium controls the activity of glycogen synthase in all three major glycogen storage tissues; muscle, fat, and liver. Depletion of cellular calcium resulted in a moderate increase of glycogen synthase %I activities in intact mouse diaphragms, in isolated rat adipocytes, and in rat hepatocytes. The increase in %I activity of glycogen synthase was more pronounced when the uridine di-phosphoglucose concentration in the glycogen synthase assay was lowered from 4.4 mM to 0.2 mM. Calcium depletion resulted in an approximately two-fold decrease in the Ka values for glucose-6-phosphate in all three tissues. The activities of glycogen synthase also correlated well with the content of cell-associated calcium in rat hepatocytes. The glucose-6-phosphate independent activities of glycogen synthase in extracts of calcium-replete and calcium-depleted tissue approached the same value following the exposure to crude phosphoprotein phosphatase. The activities of glycogen phosphorylase decreased in calcium-depleted tissues and cells. Insulin stimulated the activity of glycogen synthase in muscle and fat in the absence of added sugar and in the absence of extracellular calcium. It is concluded that glycogen synthase is under the control of calcium in the three main glycogen storage tissues. The actions of calcium are probably mediated through the actions of calcium-sensitive protein kinase(s).     

Nanoplanktonic coccolithophorids (Prymnesiophyceae, Haptophyceae) from the Weddell Sea, Antarctica

The examination of whole mounts prepared for transmission electron microscopy has resulted in the finding of thirteen taxa of nanoplanktonic coccolithophorids from the Weddell Sea, Antarctica. The material was collected as part of the AMERIEZ programme, March 1986. Cold-water adapted nanoplanktonic coccolithophorids have previously been shown to constitute a recurrent plankton element at subarctic and arctic localities. Three of the Weddell Sea species, Wigwamma annulifera, W. arctica , and Papposphaera sagittifera , are conspecific with northern hemisphere material, while two species, Calciarcus alaskensis and Turrisphaera arctica , are possibly identical with previously described arctidsubarctic material. Six taxa new to science have been described from the Weddell Sea, Wigwamma antarctica, W. triradiata, Trigonaspis melvillea, Pappomonas weddellensis, Papposphaera obpyramidalis , and P. simplicissima . The cooccurrence of identical forms at the two poles, and the fact that the species described are allocated to "arctic" genera, indicate a geologically relatively recent exchange of biological material between the poles.     

Dramatic founder effects in Amerindian mitochondrial DNAs

Southwestern American Indian (Amerindian) mitochondrial DNAs (mtDNAs) were analyzed with restriction endonucleases and found to contain Asian restriction fragment length polymorphisms (RFLPs) but at frequencies very different from those found in Asia. One rare Asian HincII RFLP was found in 40% of the Amerindians. Several mtDNAs were discovered which have not yet been observed on other continents and different tribes were found to have distinctive mtDNAs. Since the mtDNA is inherited exclusively through the maternal lineage, these results suggest that Amerindian tribes were founded by small numbers of female lineages and that new mutations have been fixed in these lineages since their separation from Asia.     

The purification of human serum 1 -antitrypsin by affinity chromatography on concanavalin A

α₁-Antitrypsin (α₁-AT) has been isolated from human serum by a two-step procedure which involves chromatography on DEAE-Sephadex followed by affinity chromatography on insolubilized concanavalin A. This protein appeared to be homogeneous when examined by electrophoresis on cellulose acetate and double immunodiffusion; minor contaminants, however, were detected by gel electrophoresis and immunoelectrophoresis. This procedure is readily adaptable to the large-scale purification of α₁-AT and should facilitate further studies on the physicochemical and biological properties of α₁-AT and its genetic variants.     

Two-dimensional protein electrophoretic analysis of postponed aging inDrosophila

Five populations ofDrosophila melanogaster that had been selected for postponed aging were compared with five control populations using two-dimensional protein gel electrophoresis. The goals of the study were to identify specific proteins associated with postponed aging and to survey the population genetics of the response to selection. A total of 321 proteins were resolvable per population; these proteins were scored according to their intensity. The resulting data were analyzed using resampling, combinatoric, and maximum parsimony methods. The analysis indicated that the populations with postponed aging were different from their controls with respect to specific proteins and with respect to the variation between populations. The populations selected for postponed aging were more heterogeneous between populations than were the control populations. Maximum parsimony trees separate the selected populations, as a group, from their controls, thereby exhibiting a homoplastic pattern.     

Drosophila acidic ribosomal protein rpA2: Sequence and characterization

A cDNA encoding the Drosophila melanogaster acidic ribosomal protein rpA2 was cloned and sequenced. rpA2 is homologous to the Artemia salina acidic ribosomal protein eL12′. In situ hybridization to salivary gland polytene chromosomes localizes the rpA2 gene to band 21C. It is a single copy gene, with an mRNA of 0.8 kb. Two-dimensional gel electrophoresis of Drosophila ribosomal proteins followed by immuno-blotting showed that the rpA2 protein has an apparent relative mobility in SDS of 17 kD and an isoelectric point less than pH 5.0. Although the Drosophila gene rp21C may be the same as rpA2, the reported sequences differ. Comparisons of the aligned nucleotide sequences coding for the acidic ribosomal proteins rpA1 and rpA2 of Drosophila with those of other eukaryotes support the view of two separate, though closely related, groups of acidic proteins. Comparison with the Artemia homologues suggests that nucleotide identity may have been conserved by some constraint that acts in addition to the requirement for substantial similarity of amino acid sequences. © 1993 Wiley-Liss, Inc.     

Approaches to breeding for salinity tolerance - a case study on Porteresia coarctata

Cereals are the world's major source of food for human nutrition. Among these, rice (Oryza sativa) is the most prominent and represents the staple diet for more than two-fifths (2.4 billion) of the world's population, making it the most important food crop of the developing world (Anon., 2000a). Rice production in vast stretches of coastal areas is hampered due to high soil salinity. This is because rice is a glycophyte and it does not grow well under saline conditions. In order to increase rice production in these areas there is a need to develop rice varieties suited to saline environments. Research has shown that Porteresia coarctata, a highly salt tolerant wild relative of rice growing in estuarine soils, is an important material for transferring salt tolerant characteristics to rice. It is quite possible that Porteresia may be used as a parent for evolving better and truly salt resistant varieties. The inadequate results and the difficulties associated with conventional breeding techniques necessitate the use of the tools of crop biotechnology in unravelling some of the characteristics of Porteresia that have been highlighted in this report. In view of the limited resources available for increasing salinity tolerance to the breeders to wild rice germplasm, Porteresia is undoubtedly one of the key source species for elevating salinity tolerance in cultivated rice.