Growth hormone secretion in chicks during dietary calcium deficiency

The role of calcium in the secretion of growth hormone (GH) has been examined in vivo in immature domestic fowl. Chicks reared on a low calcium (0.16% calcium in the feed) diet showed a reduced growth rate, compared with those on a normal (0.86%) calcium diet and had lower basal levels of plasma GH 1, 5, 10 and 15 d after calcium deprivation, but not after 20, 25, 30 or 35 d of calcium deficiency. No consistent changes in the concentration of immunoreactive somatomedin C were observed during calcium restriction. In both the control and low calcium fed birds the plasma concentrations of GH were elevated by the intravenous administration of human pancreatic GH releasing factor (hpGRF) and by thyrotropin releasing hormone (TRH). The GH responses to these provocative stimuli were not reduced in magnitude by calcium deficiency. It is suggested, therefore, that the effect of calcium deprivation on the secretion of GH is mediated via the reduced release of stimulatory hypophysiotrophic factors from the hypothalamus.

Pharmacological alterations in calcium status also suggest that calcium deprivation inhibits GH secretion. Plasma concentrations of GH were acutely depressed in young chicks following the administration of a calcium chelator (ethylene diaminotetraacetic acid) a calcium channel blocker (verapamil) and after calmodulin inhibition (by chlordiazapine and trifluorpenazine administration). These data therefore demonstrate the importance of calcium in the stimulation of GH secretion in the domestic fowl.     

B‐cell lymphoma with Mott cell differentiation in two young adult dogs

Abstract: Two young adult dogs with gastrointestinal signs were each found to have an intra‐abdominal mass based on physical examination and diagnostic imaging. On exploratory laparotomy, small intestinal masses and mesenteric lymphadenopathy were found in both dogs; a liver mass was also found in dog 1. Cytologic and histologic examination of intestinal and liver masses and mesenteric lymph nodes revealed 2 distinct lymphoid cell populations: lymphoblasts and atypical Mott cells. With Romanowsky stains, the atypical Mott cells contained many discrete, clear to pale blue cytoplasmic inclusions consistent with Russell bodies that were positive by immunohistochemistry for IgM and CD79a in both dogs and for IgG in dog 2. The Mott cells and occasional lymphoblasts stained strongly positive with periodic acid‐Schiff. Using flow cytometric immunophenotyping in dog 1, 60% of peripheral blood mononuclear cells and 85% of cells in an affected lymph node were positive for CD21, CD79a, IgM, and MCH II, indicative of B‐cells. With electron microscopy, disorganized and dilated endoplasmic reticulum was seen in Mott cells in tumors from both dogs. Antigen receptor gene rearrangement analysis of lymph node and intestinal masses indicated a clonal B‐cell population. Based on cell morphology, tissue involvement, and evidence for clonal B‐cell proliferation, we diagnosed neoplasms involving Mott cells. To the authors' knowledge, this is the second report of Mott cell tumors or, more appropriately, B‐cell lymphoma with Mott cell differentiation, in dogs. More complete characterization of this neoplasm requires further investigation of additional cases. This lymphoproliferative disease should be considered as a differential diagnosis for canine gastrointestinal tumors.     

Animal genetic resource trade flows: The utilization of newly imported breeds and the gene flow of imported animals in the United States of America

Animal germplasm exchange has recently received attention as a product of the FAO's State of the World's Animal Genetic Resources effort. Some have advocated a need to explore policies and regulations on the exchange of germplasm (e.g., Hiemstra, S.J., Drucker, A., Tvedt, M., Louwaars, N., Oldenbroek, J., Awgichew, K., Kebede, S., Bhat, P., da Silva Mariante, A. 2006. Exchange, use and conservation of animal genetic resources: policies and regulatory options. Centre for Genetic Resources. Wageningen Univ., the Netherlands, pp. 1­43). However, there has been little comprehensive assessment of either the economic or genetic impact of introduced germplasm into national populations. As a result, much of the discussion of gene flows has been based on assumptions and generalizations. The objective of this paper is to evaluate the genetic impact of germplasm imported into the United States during the last 25 to 50 years. The paper considers both new breeds (Meishan pigs, Tuli cattle, and Boer goats) and new animals within existing breeds (Limousin and Jersey cattle). Of the new breeds recently imported only one had an impact on US animal agriculture. Neither the Tuli nor the Meishan has impacted the US livestock industry. It appears that these breeds were initially viewed as attractive because of single traits, but producers did not find it attractive to adopt the new breeds based on these specific traits. In the end, these breeds did not prove competitive in the US under the current set of market conditions. This result would indicate that importation of new genetic resources due to a single trait of interest is not a viable importation strategy. By contrast, the Boer goat exhibited a number of production characteristics which made it desirable to US producers and thereby allowed the breed to become well established. A second portion of the study evaluated the importation and parentage pattern of Limousin cattle as they became established in the U. S. and the gene flow of imported Jersey cattle since the 1950′s. In both cases, the study relied on pedigree analysis. Over the past fifty years, Jersey cattle have been sporadically imported from various countries, but no imported animal has had an overpowering effect on the population. It appears that by the great-grand progeny level, the genes from imported animals are diminishing rather than increasing in the population. In evaluating the predicted transmitting abilities for imported cattle relative to high and moderately ranked domestically bred cattle, there were significant differences between these groups for milk production. This would be sufficient to explain why the impact of the imported cattle diminished. The results of our analysis at both the breed and individual level underscore the speculative nature of germplasm importation — even within breeds where there is a great deal of information available about production characteristics. From this analysis, we conclude that successful importation of new breeds into the US must be based on a large number of production characteristics; importation for a single characteristic (e.g., high prolificacy) while the breed is deficient in other areas does not lead to the breed's adoption. While not fully explored in this work, it appears that initial interest and acceptance from the private sector is crucial for breed acceptance, as the Boer goat demonstrates. Within an existing breed, importation of individual animals still appears to have a relatively high degree of risk and is dependent upon the importer's ability to pick viable candidates. However, once animals are imported their progeny must effectively compete with the domestic population, or else their genetic contribution will rapidly diminish.     

Population variation of apple scab (Venturia inaequalis) within mixed orchards in the UK

Apple scab, caused by Venturia inaequalis, is one of the most important apple diseases worldwide. To investigate between- and within-orchard fungal variability, 212 isolates were sampled from two mixed orchards, one of 10?years of age and the other of 45?years of age, in the UK and genotyped with AFLP and SSR markers. Populations of isolates from the two orchards did not differ significantly in terms of allele frequencies at the screened AFLP and SSR loci. However, groups of isolates from individual cultivars differed significantly within each orchard and there were also significant differences between groups of isolates from individual trees of the same cultivar in the same orchard. These differences were less pronounced in the younger mixed orchard than in the older one. The existence of tree-to-tree fungal variability indicates a possible role for conidia as a source of primary inoculum. Non-random mating may be one of the factors causing the significant differences among fungal populations from different cultivars. These results suggest that apparently ??susceptible?? cultivars have different background genetic resistance factors, which can be exploited for disease management in mixtures.