Genetic diversity in Cucumis sativus L. assessed by variation at 18 allozyme coding loci

Summary The genetic diversity of the U.S. Cucumis sativus L. germplasm collection [757 plant introductions (PI) representing 45 countries] was assessed using 40 enzymes which represented 74 biochemical loci. Polymorphisms were observed at 18 loci (G2dh-1, Gpi-1, Gpi-2, Gr-1, Gr-2, Idh, Mdh-1, Mdh-2, Mdh-3, Mpi-2, Pepla-2, Peppap-2, Per-4, Pgd-1, Pgd-2, Pgm-1, Pgm-3, and Skdh). Two PIs (285606 and 215589) contained alleles [G2dh-1(1) and Per-4(2), respectively] which did not occur in any other PI. Other alleles which occurred in low frequencies (in < 1% of the PIs) included Gpi-1(3), Gpi-2(3), Gr-1(3), Gr-2(1), Idh(1), Mdh-1(2), Mdh-2(1), Peppap-2(1), and Pgd-1(1). Individual loci containing more than one allele in greater than 20% of the PIs included Mpi-2, Pepla-2, Pgd-2, and Pgm-1. Multivariate analyses aided in the reduction of data (principle components), depicted relationships among PIs (cluster), and identified the most discriminating enzyme loci (Pgm-1, Pepla-2, Gr-1, Pgd-2, Mpi-2, and Skdh) (classification and regression tree).Research partially supported by Asgrow, DeRuiter, Nickerson-Zwaan, Nunhems, and Sun Seed Companies; and the Graduate School, University of Wisconsin, Madison     

Early and late effects in the bone marrow of mice following 2 Gy (6 MeV) neutron irradiation

Summary Following 5 Gy gamma irradiation, residual damage in bone marrow persisted up to one year and was ascribed to genetic defects in hemopoietic stem cells (von Wangenheim et al. 1986). To see whether high LET radiation is more efficient in inducing late effects, mice were whole-body irradiated with a single dose of 2 Gy neutrons ( = 6 MeV) and femoral cellularity, CFU-S number, proliferation ability of bone marrow cells (PF) and the compartment ratio (CR), i.e. the splenic 125-iodo-deoxyuridine incorporation per transfused CFU-S were measured up to one year after the radiation insult. Within 12 weeks, femoral cellularity, PF and CR recovered to control or near-control level, whereas CFU-S numbers remained significantly below control. No further recovery was observed. On the contrary, PF and CR deteriorated again after 12 and 26 weeks, respectively. CFU-S per femur tended to decrease as well. Thus it is demonstrated that a single dose of 2 Gy 6 MeV neutrons causes significant injury in function (PF) and structure (CFU-S numbers, CR) of bone marrow which persisted up to one year. While this residual injury can be attributed to genetic defects in hemopoietic stem cells, its increasing expression is probably due to late evolving damage in microenvironmental cells. The RBE of 6 MeV neutrons for the introduction of late effects in the bone marrow is in the range of 3.     

Does interference competition from Daphnia affect populations of Keratella cochlearis in Loch Leven, Scotland?

A very marked inverse relationship between Daphnia hyalina var.lacustris Sars and Keratella cochlearis (Gosse) population densitieswas observed in Loch Leven, Scotland, UK between 1978 and 1982.The natural death rates of the rotifer population were far lowerthan would have been expected in response to interference competitionfrom Daphnia. Keratella birth rates fell, along with chlorophylla concentrations, when Daphnia filtration rates were high. Theresults indicate that, when Daphnia were abundant, direct competitionfor food was the most likely factor suppressing Keratella populationgrowth.     

High degree of homology between primary structure of human lysosomal acid phosphatase and human prostatic acid phosphatase

Alignment of the amino-acid sequences of the human lysosomal acid phosphatase (LAP) and human prostatic acid phosphatase (PAP) yielded an extensive homology between the two mature polypeptide chains. In the overlapping part, which extends over the entire PAP sequence and the N-terminal 90% of the LAP sequence, the identity is 49.1%. The LAP has an additional C-terminal sequence, which is encoded by the last exon of the LAP gene. This sequence contains the transmembrane domain of LAP, which is lacking in the secretory PAP. All six cysteine residues as well as 20 out of 27 (LAP) and 26 (PAP) proline residues present in the overlapping part of the proteins are conserved, suggesting that they are involved in stabilization of the tertiary structure of both proteins. Only two out of 8 N-glycosylation sites in LAP and 3 in PAP are conserved, suggesting that the dense N-glycosylation of LAP is related to its function in lysosomes.     

Carbonic anhydrase activity in acetate grown Methanosarcina barkeri

Cell extracts (27000xg supernatant) of acetate grown Methanosarcina barkeri were found to have carbonic anhydrase activity (0.41 U/mg protein), which was lost upon heating or incubation with proteinase K. The activity was inhibited by Diamox (apparent K _i=0.5 mM), by azide (apparent K _i=1 mM), and by cyanide (apparent K _i=0.02 mM). These and other properties indicate that the archaebacterium contains the enzyme carbonic anhydrase (EC 4.2.1.1). Evidence is presented that the protein is probably located in the cytoplasm. Methanol or H₂/CO₂ grown cells of M. barkeri showed no or only very little carbonic anhydrase activity. After transfer of these cells to acetate medium the activity was induced suggesting a function of this enzyme in acetate fermentation to CO₂ and CH₄. Interestingly, Desulfobacter postgatei and Desulfotomaculum acetoxidans, which oxidize acetate to 2 CO₂ with sulfate as electron acceptor, were also found to exhibit carbonic anhydrase activity (0.2 U/mg protein).     

Structural comparison of the 68 kDa laminin-binding protein and 5'-nucleotidase from chicken muscular sources: evidence against a gross structural similarity of both proteins

The 68 kDa laminin-binding protein purified from chicken skeletal muscle and the ectoenzyme 5'-nucleotidase from chicken gizzard are both able to interact with laminin. They were both shown to possess a nearly identical amino acid composition. The 79 kDa glycosylated form of 5'-nucleotidase can be transformed into an enzymatically active form by treatment with endoglycosidase F (Endo F). Deglycosylated (Endo F-treated) 5'-nucleotidase exhibits an apparent molecular mass of 68 kDa. Using immunological and finger-printing techniques, both proteins were analysed to determine their structural relatedness. The results obtained indicate that both proteins are not identical but may posses a few common peptides of yet unknown sequence and length.     

The heat generated by yeast cultures with a mixed metabolism in the transition between respiration and fermentation

The heat generated by both batch and continuous cultures of the yeast K. fragilis was studied using a modified Bench Scale Calorimeter. Batch cultures were used to measure the heat dissipation rates and the heat yields during fully aerobic and completely anaerobic growth, whereas continuous cultures enabled, in addition, a quantitative study of heat dissipation rates during growth on mixed metabolism. In this case, the extent of fermentation versus respiration could be specified and controlled by varying the degree of oxygen limitation. The heat dissipated per unit biomass formed was highest for fully respirative catabolism and fell continuously to a much lower value typical of anaerobic cultures as the catabolism was shifted increasingly to the fermentative mode. The heat generated per mole of oxygen taken up stayed quite close to the fully aerobic value of 506 kJ mol(-1) even when a sizable fraction of the substrate available to catabolism was fermented. If the fraction of respiration in the metabolism is lowered beyond a certain threshold, the ratio of the heat generation to oxygen consumption starts to increase dramatically and finally tends to infinity for fully anaerobic growth. All experimental results were quantitatively analyzed and explained on the basis of a simple model which formally describes the cultures in terms of two parallel "chemical" reactions. In simple cases such as the one presented here, the model enables calculation of the whole stoichiometry of the culture from a single measured heat yield.     

Cell attachment properties of collagen type VI and arg-gly-asp dependent binding to its α2(VI) and α3(VI) chains

Twelve of sixteen different cell types including fibroblasts and tumor cells were able to attach and spread on substrates of pepsin-solubilized or intact collagen VI, and on its triple helical domain. Attachment and spreading were independent of soluble mediator proteins (fibronectin, laminin) and collagen VI was distinct from collagens I, IV and V in the cells with which it interacted. Many of the same cells bound and spread on substrates prepared from unfolded α2(VI) and α3(VI) chains but not on the α1(VI) chain. The interactions with the chains were inhibited by low concentrations (10–100 μM) of synthetic RGDS and RGDT but not RGES peptides while the binding of cells to pepsin-solubilized collagen VI was more than 20-fold less sensitive to these peptides. The data incidate that cells have the ability to bind to collagen VI in a specific manner suggesting a similar function for collagen VI in situ.     

N-succinimidyl methoxyphenylacetic acid ester, an amine-directed chiral derivatizing reagent suitable for enzymatic scale resolutions

A chiral derivatizing reagent, N-succinimidyl-2-(S)-methoxy-2-phenylacetic acid ester (SMPA), directed toward reaction with primary amine-containing compounds has been synthesized and characterized. This reagent is suitable for HPLC resolution from enzymatic-scale reactions where only microgram quantities of chiral products may be obtainable. SMPA derivatization was shown to be effective in the resolution of the enantiomers of a number of different racemic compounds. SMPA was used to resolve the diastereoisomeric derivatives of a previously unknown enzymatically oxygenated product, allowing determination of the stereochemical course of the enzymatic reaction. SMPA is easily prepared from an inexpensive, commercially available, and enantiomerically pure precursor with the formation of a shelf-stable crystalline product which is utilizable in water-containing solutions. In addition to its usefulness for micro-determinations, SMPA is useful for preparative-scale resolutions of enantiomers since the reagent is cleaved from the diastereoisomeric derivative by acid hydrolysis.