Evolution of sprouting versus seeding inAspalathus linearis

We have tested the hypothesis that reseeding is a plesiomorphic character state and that sprouting is a derived state inAspalathus linearis, and that the latter is an adaptation to ensure fire-survival in a fireprone environment. Samples of five seeder and four sprouter populations of A.linearis were examined by horizontal starch gel electrophoresis to assess the amount of genetic differentiation within and between sprouting and seeding populations, and to determine the extent of gene flow between the populations. Leaf extracts were surveyed for ten enzymes and gene products revealed genetic variation at 13 (76%) of 17 protein coding loci. Allele frequency differences were found between sprouting and seeding populations and genetic distance values show that the sprouters are grouped separate from the seeders, thus providing support for the morphological data on which the above mentioned hypothesis is based. It is evident that evolution operates at the population level inA. linearis.     

Analysis of the binding of p-chlorophenyl-methoxybenzyl-ketoxime (CPMB-oxime) to mitochondrial cytochrome c reductase.

Cytochrome c reductase is inhibited by p-chlorophenyl-methoxybenzyl-ketoxime (CPMB-oxime). CPMB-oxime induces a red-shift of the reduced spectrum of cytochrome b. The inhibitor blocks the oxidation of ubihydroquinone at the QP center of this enzyme in a non-competitive way. The binding stoichiometry equals one inhibitor molecule per Qp center. The apparent Kd in a red-shift assay was 6.9 +/- 0.6 microM. All binding characteristics analysed in this study were very similar to those of the E-beta-methoxyacrylate inhibitors, although the chemical structure is different from these inhibitors. This result is interpreted as a support for the inhibitory mechanism based on the model of a 'catalytic switch' proposed recently for the E-beta-methoxyacrylate inhibitors (MOA-inhibitors (Brandt and von Jagow, Eur. J. Biochem.     

Mutagenesis of hydroxylamine oxidoreductase in Nitrosomonas europaea by transformation and recombination.

Mutagenesis of Nitrosomonas europaea was achieved by electroporation and recombination. To demonstrate this, an aminoglycoside 3'-phosphotransferase (kan) gene was specifically inserted into each of the three gene copies of hao individually. Southern hybridizations and PCR analysis showed the incorporation of the kan gene at the chosen genetic loci. The isolation of mutant strains was achieved in 7 to 14 days when the strains were grown on solid medium. The induced mutations were stable even in the absence of kanamycin-selective pressure for periods of up to 45 days in culture. The mutant strains did not show an observable phenotype different from that of the wild type when grown under the same conditions.     

Comparative analysis of the cattle and human genomes: detection of ZOO-FISH and gene mapping-based chromosomal homologies

Comparative chromosome painting with individual human chromosome-specific libraries (CSLs) on cattle metaphase chromosomes delineated 46 homologous chromosomal segments between the two species. Continuous arrangement of these segments on individual cattle chromosomes demonstrates a nearly complete coverage of the bovine karyotype and shows physical boundaries of bovine chromosomal segments homologous to individual human chromosomes. Alignment of the available comparative gene mapping data with the homologous segments strongly supports the detected gross homologies between the karyotypes of the two species. In addition to cattle, four human CSLs were hybridized to sheep metaphase chromosomes also, to further verify the known karyotype homology within the Bovidae. Besides its application to karyotype evolution research, the comparative knowledge provides for rapid expansion of the much needed Type I locus-based bovine gene map. Received: 9 September 1995 / Accepted: 4 December 1995     

Evidence for the expression of two distinct MHC class II DRβ like molecules in the sheep

This study used monoclonal antibodies to sheep MHC class II molecules as well as an L cell transfectant (T8.1) which expresses DRA and DRB genes to show that two distinct DRβ chains are expressed in the sheep. Two anti-β chain specific monoclonal antibodies VPM37 and VPM43 react with DR antigen but not DQ antigen by ELISA. These two antibodies do not react with the DRβ chain expressed in the T8.1 cell line. Two-dimensional immunoblotting shows that these antibodies recognize a subgroup of the spots recognized by the DR-specific monoclonal antibody VPM57 which does react with the T8.1 β chain. Amino-terminal sequence analysis of the α chain associated with VPM37β chain shows that this α chain is homologous to the human DRα chain strongly indicating that the β chain is DR-like. VPM37 and VPM43 are shown to be directed against different epitopes on sheep MHC class II molecules so it is highly unlikely that the data can be explained by the presence of posttranslational modifications or the existence of a very common allele. These data provide clear evidence for the expression of two distinct DRP chains in the sheep.     

Hormonal adaptation determines the increase in muscle mass and strength during low-intensity strength training without relaxation

The study was designed to test the hypothesis that, during strength training, a restricted blood supply to the working muscles stimulates the secretion of anabolic hormones and an increase in the muscle mass and strength can be achieved with significantly lower training loads. During eight weeks, three times a week, 18 young, physically active males trained their leg extensor muscles. Nine subjects (group I) worked at 80% of the maximal voluntary contraction (MVC), whereas the rest (group II) performed their exercise without relaxation and at a lower load (50% MVC). The total training load in group II was significantly lower than in group I (77 ± 5 vs. 157 ± 7 kJ, respectively). The eight-week training of both groups significantly increased the mean maximum strength (by 35 and 21% in groups I and II, respectively) and volume (by 17 and 9%, respectively) of the muscles trained (however, the differences between the groups with respect to these changes were nonsignificant). Group I displayed a higher increase in the blood level of creatine phosphokinase than group II, while group II showed a greater increase in the blood concentration of lactate. In contrast to group I, group II displayed a significant increase in the blood concentrations of growth hormone, insulin-like growth factor 1 (IGF-1), and cortisol. Hence, the suggestion that the secretion of metabolic hormones is triggered by a metabolic, rather than mechanical, stimulus from working muscles seems plausible.     

Efficacy of intermittent or continuous administration of GnRH in inducing ovulation in early and late seasonal anoestrus in the Père David's deer hind (Elaphurus davidianus)

Père David's deer hinds were treated with GnRH, administered as intermittent i.v. injections (2.0 micrograms/injection at 2-h intervals) for 4 days, or as a continuous s.c. infusion (1.0 micrograms/h) for 14 days. These treatments were given early (February-March) and late (May-June) in the period of seasonal anoestrus. The administration of repeated injections of GnRH increased mean LH concentrations from pretreatment values of 0.54 +/- 0.09 to 2.10 +/- 0.25 ng/ml over the first 8 h of treatment in early anoestrus, and from 0.62 +/- 0.11 to 2.73 +/- 0.49 ng/ml in late anoestrus. The mean amplitude of GnRH-induced LH episodes was greater (P less than 0.01) in late (4.03 +/- 0.28 ng/ml) than in early (3.12 +/- 0.26 ng/ml) anoestrus, but within each replicate (early or late anoestrus), neither mean LH episode amplitude nor mean plasma LH concentrations differed significantly between the four periods of intensive blood sampling. On the basis of their progesterone profiles, 6/12 hinds had ovulated in response to treatment with injections of GnRH (1/6 in early anoestrus and 5/6 in late anoestrus), and oestrus and a preovulatory LH surge were recorded in all of these animals. Oestrus and a preovulatory LH surge were also recorded in one other animal treated in early anoestrus in which progesterone concentrations remained low. The mean times of onset of oestrus (91.0 +/- 1.00 and 62.4 +/- 0.98 h) and of the preovulatory LH surge (85.8 +/- 3.76 and 59.4 +/- 0.25 h) both occurred significantly earlier (P less than 0.001) in animals treated in late anoestrus. Continuous infusion of GnRH to seasonally anoestrous hinds resulted in an increase in mean plasma LH concentrations, but this response did not differ significantly between early (2.15 +/- 0.28 ng/ml) and late (2.48 +/- 0.26 ng/ml) anoestrus. Ovulation, based on progesterone profiles, occurred in 2/7 hinds in early anoestrus and in 4/6 hinds in late anoestrus. Oestrus was detected in all except one of these hinds. The mean time of onset of oestrus occurred earlier in animals treated in late anoestrus (66.2 +/- 0.32 h and 46.7 +/- 0.67 h, P less than 0.01). The administration of GnRH, given either intermittently or continuously, will induce ovulation in a proportion of seasonally anoestrous Père David's deer. However, more animals ovulate in response to this treatment in late than in early anoestrus (75% compared with 23%).