Livestock production in central Mali: Reproductive performance and reproductive wastage in ruminants in the agro-pastoral system

Results of a 7-yr field study and a 3-yr slaughterhouse study into reproductive performance and reproductive wastage of ruminants in central Mali are reported. Cattle had delayed age at first puberty (40), long calving intervals (644) and produced few young (3.02) per lifetime. Goats and sheep first conceived at about 11 mo, had shorter parturition intervals (298 and 280 d) but also produced few young (2.64 and 1.92) per lifetime. Conceptions showed a strong seasonality in cattle and mainly occurred during and shortly after the short rainy season. Seasonality was less marked in small ruminants, but most females conceived before the rains. However, maximum litter sizes were associated with late-rain and post-rain conceptions. Early embryonic wastage did not appear to be a major problem but abortions, stillbirths and heavy preweaning mortality were sources of loss of reproductive potential. Additionally at a secondary (government controlled) abattoir, 15.0 % of cows, 31.7 % of goats and 20.0 % of sheep that were slaughtered were found to be pregnant.     

Molecular analysis of HLA-A2.4 functional variant KLO: close structural and evolutionary relatedness to the HLA-A2.2 subtype

The structure of an HLA-A2.4 functional variant (A2.4c) expressed on donor KLO has been examined by comparative peptide mapping with other HLA-A2 antigens of known structure and radiochemical sequencing. All the peptide differences between A2.4c and A2.1 could be accounted for by five amino acid changes at positions 9, 43, 66, 95, and 156. The nature of residues 9, 43, and 95 in A2.4c was determined by sequencing to be identical to those in A2.2Y. The nature of residue 156 in A2.4c was also assigned as identical to that in A2.2Y on the basis of the identity of the corresponding peptide in its chromatographic comparison with A2.2Y. Position 66 was unique to A2.4c. It was determined to be an Asn residue instead of the Lys present in all other HLA-A2 antigens of known structure. This was the only detected amino acid difference between A2.4c and A2.2Y. The results indicate that, from a structural point of view, A2.4c is most closely related to the A2.2 subtype antigens and not to other A2.4 antigens. The data are compatible with the assumption that A2.4c was derived from A2.2Y by a single point mutation event.     

An HLA-A2 population variant with structural polymorphism in the α3 region

The HLA-A2 antigen expressed by donor OZB can be distinguished from the main HLA-A2.1 subtype by isoelectric focusing - it is one charge unit more acidic — and by some alloreactive T-cell clones but not by cytolytic T lymphocyte lines. The structure of variant OZB has been examined by comparative peptide mapping with A2.1 and radiochemical sequence analysis. The two molecules were found to differ in a single tryptic peptide from the 0 region, spanning residues 220–243. The amino acid sequence of this peptide from variant OZB revealed that there was only one amino acid change of Glu instead of Ala at position 236, a hitherto invariant residue in class I HLA antigens. All previously characterized HLA or H-2 natural variants have structural changes restricted to the 1 and/or 2 domains. Thus, variant OZB is unique in that (1) it has one amino acid change in 3 and (2) it has no changes in l and 2. The only detected substitution of this variant may be accounted for by a single base change at the DNA level, suggesting that it might have resulted from a point mutation in the A2.1 gene. The structural features of variant OZB open a novel way to examine the influence of polymorphism in 3 on cytolytic T-cell recognition of naturally occurring class I antigens.Abbreviations CTL cytolytic T lymphocytes - HPLC high performance liquid chromatography - IEF isoelectric focusing - MHC major histocompatibility complex     

The chalcone synthase multigene family of Petunia hybrida (V30): sequence homology,chromosomal localization and evolutionary aspects

Chalcone synthase (CHS) genes in Petunia hybrida comprise a multigene family containing at least 7 complete members in the strain Violet 30 (V30). Based on a high sequence homology in both coding and non-coding sequence, a number of CHS genes can be placed into two subfamilies. By restriction fragment length polymorphism (RFLP) analysis it was shown that both chromosomes II and V carry one of these subfamilies, in addition to the other CHS genes identified so far. Members of a subfamily were found to be closely linked genetically. Analysis of the Petunia species that contributed to the hybrid nature of P. hybrida (P. axillaris, P. parodii, P. inflata and P. violacea) shows that none of the CHS gene clusters is specific for either one of the parents and therefore did not arise as a consequence of the hybridization. The number of CHS genes within a subfamily varies considerably among these Petunia species. From this we infer that the CHS subfamilies arose from very recent gene duplications.     

Variation in host susceptibility among and within populations ofPlantago lanceolata L. infected by the fungusPhomopsis subordinaria (Desm.) Trav.

Summary Susceptibility toPhomopsis stalk disease ofPlantago lanceolata genotypes, sampled in three different populations with a variable degree of infection by the fungusPhomopsis subordinaria, was determined under greenhouse conditions. Susceptibility of the host varied within, but not among populations. No relationship between the intensity of the disease in the field and the mean susceptibility of the host genotypes sampled at those locations could be established. Host susceptibility appeared to be composed of the host genotypes sampled at those locations could be established. Host susceptibility appeared to be composed of different (uncorrelated) plant characteristics. Determining whether host genotypes are highly or slightly susceptible can only be achieved by field trials, where the plants are exposed to the whole set of disease inducing factors. The relevance of host susceptibility to the intensity of disease in the field is discussed in relation to the variation in pathogenicity of the fungus and the variation in environmental factors prevailing inP. lanceolata populations underP. subordinaria pathogen pressure. Grassland Species Research Group Number 123     

Response to grazing after nine years of cattle exlusion in a Flooding Pampa grassland,Argentina

This paper reports on changes induced by the introduction of cattle in a grassland that had remained ungrazed for 9 yr, in comparison with two adjacent grasslands: one that remained enclosed and one that has been continuously subject to grazing. Basal cover was measured on 25 interception lines, each 1 m long, three times during one year. The variables studied were: total cover, cover of grasses and dicots, cover of creeping grasses, floristic composition, and dissimilarity among sites. At the first sampling, 2 yr after cattle re-introduction, the newly grazed site was more similar to the ungrazed than to the grazed site. The newly grazed site had very low cover of dicots; the species of dicots present were different from those found in the continuously grazed area. Creeping grasses had higher cover in the newly grazed site than in the other sites, and continued to increase. At the last sampling, one year later, the newly grazed site had become more similar to the contiuously grazed site. Only after 5 yr of cattle grazing the exotic dicots that were dominant in the continuously grazed site, were recorded in the re-opened site. The absence of propagules of these species or the absence of safe sites may account for this delayed invasion.     

The origin of the luteinizing hormone-releasing hormone (LHRH) neurons in newts (Cynops pyrrhogaster): the effect of olfactory placode ablation

Summary Neurons containing luteinizing hormone-releasing hormone (LHRH) are first detected in newt embryos (Cynops pyrrhogaster) in the olfactory epithelium and ventromedial portion of the olfactory nerve, after which they sequentially appear in the intracerebral course of the terminal nerve at prometamorphosis, and in the septo-preoptic area at postmetamorphosis. In adults, however, LHRH-immunoreactive cells are rarely seen in the nasal region, and their distribution shifts into the brain, suggesting their migration. In order to ascertain the origin and possible migration route of these neurons in newt larvae, the effect of unilateral or bilateral olfactory placodectomy on the LHRH neuronal system has been studied. Removal of the olfactory placode results in the absence of LHRH-immunoreactive cells in the nasal and brain regions of the operated side, whereas the subsequent growth and the LHRH-immunoreactive cellular distribution in the contralateral side are identical to those of normal larvae. Following bilateral placodectomy, no LHRH immunoreactivity is detected on either side of the olfactory-brain axis. These results suggest that LHRH neurons of the newt, Cynops pyrrhogaster, originate in the olfactory placode and then migrate into the brain during embryonic development.     

Glutathione reductase fromSaccharomyces cerevisiae undergoes redox interconversionin situ andin vivo

Redox interconversion of glutathione reductase was studiedin situ withS. cerevisiae. The enzyme was more sensitive to redox inactivation in 24 hour-starved cells than in freshly-grown ones. While 5 μM NADPH or 100 μM NADH caused 50% inactivation in normal cells in 30 min, 0.75 μM NADPH or 50 μM NADH promoted a similar effect in starved cells. GSSG reactivated the enzyme previously inactivated by NADPH, ascertaining that the enzyme was subjected to redox interconversion. Low EDTA concentrations fully protected the enzyme from NADPH inactivation, thus confirming the participation of metals in such a process. Extensive inactivation was obtained in permeabilized cells incubated with glucose-6-phosphate or 6-phosphogluconate, in agreement with the very high specific activities of the corresponding dehydrogenases. Some inactivation was also observed with malate, L-lactate, gluconate or isocitrate in the presence of low NADP⁺ concentrations. The inactivation of yeast glutathione reductase has also been studiedin vivo. The activity decreased to 75% after 2 hours of growth with glucono-δ-lactone as carbon source, while NADPH rose to 144% and NADP⁺ fell to 86% of their initial values. Greater changes were observed in the presence of 1.5 μM rotenone: enzymatic activity descended to 23% of the control value, while the NADH/NAD⁺ and NADPH/NADP⁺ ratios rose to 171% and 262% of their initial values, respectively. Such results indicate that the lowered redox potential of the pyridine nucleotide pool existing when glucono-δ-lactone is oxidized promotesin vivo inactivation of glutathione reductase.     

Effects of phorbol esters on insulin receptor function and insulin action in hepatocytes: evidence for heterogeneity

We investigated the effect of phorbol 12-myristate 13-acetate (PMA), a protein kinase C (PKC) activator on insulin receptors and insulin action in freshly isolated and primary cultures of rat hepatocytes. PMA (1 x 10^–7 M) did not alter insulin receptor numbers or affinity either acutely or chronically but within 60 minute inactivated insulin stimulated tyrosine kinase of the insulin receptor. PKC activation inhibitied insulin (1 x 10^–7M) stimulation of glycogen and lipid synthesis with a decrease or no change in basal glycogenesis and lipogenesis respectively. However, PKC activation did not alter insulin stimulated or basal amino acid transport even though PCK activation inhibited insulin stimulation of the insulin. receptor tyrosine kinase. Thus, within one tissue, PKC activation has differential effect on insulin action depending on which pathway is examined. Furthermore, insulin stimulation of the insulin receptor tyrosine kinase may not be a necessary step for all insulin signaling pathways.