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Biomedical subjects

H G Purchase

Publications and source records attributed to H G Purchase.

At least 73 records · Page 4Linked to original sources
PubMedDate not supplied

Are we ready for a National Salmonella Control Program?

Control of contamination of meat and poultry with Salmonella is difficult because of the complexity of the paths of transmission of the organism, the large number of sources of the organism, and the large number of persons, groups, and agencies involved in the production of animal feed and food and in the regulation of these industries. Furthermore, there is a gap between the basic technology available to destroy or prevent contamination with Salmonella and the technology available that is acceptable, inexpensive, and applicable on a large scale. Support of research for the development of new technology amounts only to about $2.7 million. There are programs for the control of Salmonella in certain feeds and in the production, processing, further processing, and cooking of food. With current technology, an eradication program would likely cost far more to the consumer than could be justified by the benefits the consumer would derive from such eradication. Nevertheless, practical control of salmonella contamination can be achieved through progressive application of new technology developed through research.

Animal Feed↗
PubMedDate not supplied

Phenotypic mixing test to detect and assay avian leukosis viruses.

A phenotypic mixing (PM) test for detecting and assaying avian leukosis viruses (ALV) of the A, B, C, and D subgroups is described. An ALV and Rous sarcoma virus RSV-0) are phenotypically mixed by co-cultivating on C/O (cells susceptible to all subgroups of ALV) cells for a certain period. Then the RSV with the new virus property is assayed on C/E cells (cells resistant to infection with subgroup E leukosis/sarcoma viruses). The test is relatively simple and rapid, and its results are unequivocal. It is as sensitive as the more lengthy complement-fixation test (COFAL). The system is suitable for detecting avian leukosis viruses in samples such as heparinized blood, plasma, and embryo extracts.

Animals↗
PubMedDate not supplied

Practical application of nucleic acid techniques to avian disease problems.

A workshop in which 17 practicing scientists participated was intended to address primarily people who use or could use biotechnology in their work and was confined to five techniques. Endonuclease fingerprinting and mapping involved cleaving nucleic acid with a specific restriction enzyme and separating the nucleic acid fragments by electrophoresis. Field and vaccine isolates of Pasteurella multocida could be distinguished; Salmonella enteritidis could be divided into three groups; chlamydia could be grouped into seven groups; and vaccinia, quail pox, and fowl pox could be clearly distinguished. Preparation of nucleic acid probes involved producing large amounts of labeled oligonucleotides, usually of unknown sequence. Successful probes had been made for infectious bursal disease virus, avian influenza virus, Newcastle disease virus, and infectious bronchitis virus. In Southern, Northern, and dot blotting, either DNA or RNA fragments were placed on or transferred to a solid substrate and probed. The procedure was able to detect infectious bursal disease virus, infectious bronchitis virus, Mycoplasma gallisepticum, and Marek's disease virus. In situ hybridization involved applying a labeled probe to frozen or fixed sections or to intact cells. In Polymerase chain reaction, two primers, some distance apart, were annealed to a denatured target DNA. Repeated cycles of DNA synthesis with a thermostable polymerase, denaturing, and reannealing resulted in great amplification of a rare sequence. After 30 cycles, a rare gene sequence could be amplified more than 10(6) times. It was used successfully to detect minute quantities of influenza virus and infectious bursal disease virus, and the process was used to facilitate DNA sequencing of coccidiosis gene segments.

Animals↗
PubMedDate not supplied

Future applications of biotechnology in poultry.

The major biotechnological advances that can be applied in the poultry industry will include molecular genetics, molecular immunology, and solid-state reactions. The elucidation of the genetic code and the development of techniques to manipulate genes offer new opportunities for changing pathogenic agents and changing chickens to reduce the effect of disease and improve productivity. The monoclonal antibody technique and the discovery that cells of the immune response communicate with one another through peptide factors will permit improved diagnostic techniques and enhanced immune responses to vaccines. Immunologic and biochemical reactions that occur on a solid substrate can be used to simplify and accelerate diagnostic tests and to purify antigens and antibodies. These advances will lead to improvements in diagnosis, disease resistance, and productivity of poultry.

Animals↗
PubMedDate not supplied

Absence of B stem cells in spleens of chickens fed the androgen analog mibolerone.

Bursa-derived stem cells in the spleens of chickens treated with the androgen analog mibolerone or with cyclophosphamide and in the spleens of untreated controls were examined by a transplantation technique. Spleen cells from syngeneic donors 2-20 weeks old were transferred to syngeneic cyclophosphamide-treated recipients, and the immunocompetence of the recipients was tested 5 weeks after the transfer by antigenic stimuli with sheep erythrocytes and Brucella abortus. Spleens of mibolerone-treated chickens failed to reconstitute the immunologic capability of cyclophosphamide-treated recipients in a manner similar to spleen cells from normal donors. Spleens of cyclophosphamide-treated donors did not contain stem cells. Stem cells were detected in the spleens of untreated controls as young as 2 weeks old; activity was highest after the 13th week of age.

Animals↗
PubMedDate not supplied

Immune responses of chickens fed the androgen analog mibolerone.

Mibolerone, an androgen analog (17 beta-hydroxy-7-alpha, 17-dimethylestr-4-en-3-one), induces a slow but progressive involution of the bursa of Fabricius when fed to chickens at microng levels during the first 7 weeks of life. Chickens receiving mibolerone remained immunologically competent, evidenced by: 1) their antibody response to nonreplicating antigens and infectious antigens; 2) the number of antibody-producing cells in their spleens; 3) the stimulation of their peripheral leukocytes with the plant mitogen phytohemagglutinin; and 4) their capacity to resist challenge with Marek's disease virus and Newcastle disease virus after vaccinations with turkey herpes-virus and the B-1 LaSota strain. This, coupled with the fact that it prevents experimental lymphoid leukosis, makes mibolerone a potential agent to be used under field conditions for the control of lymphoid leukosis.

Anabolic Agents↗