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Biomedical subjects

H M Chapman

Publications and source records attributed to H M Chapman.

At least 19 recordsLinked to original sources
PubMed1991

Assisted fertilization of mouse oocytes and preliminary results for human oocytes using zona drilling.

The zona-drilling procedure was investigated in mouse oocytes prior to a study on human oocytes. The procedure involved the injection of 5-nl volumes of acidic Hepes-buffered medium at pH 2.5 using a microinjection instrument. Zona-drilled mouse oocytes had significantly higher rates of fertilization (60/99; 61%) than zona-intact oocytes (6/103; 6%) at an insemination concentration of 1 x 10(4) sperm/ml (P less than 0.001). The procedure did not induce parthenogenetic activation of oocytes and more than 97% of zygotes developed to the blastocyst stage. A similar rate of live progeny was observed when zona-drilled (38.0%) and control embryos (38.5%) were transferred to pseudopregnant recipients. Chromosome analyses were performed on zona-intact, zona-free, and zona-drilled oocytes inseminated with varying concentrations of sperm and analysed at the first cleavage division. Zona-free oocytes had high rates of polyploidy (greater than or equal to 40%) with varying insemination numbers but the zona-drilled oocytes did not reveal significant increases in the rate of polyploidy or aneuploidy when compared to controls. In the human studies, zona-drilled oocytes achieved higher rates of fertilization than zona-intact oocytes, with sperm numbers as low as 1 x 10(4)/ml (6/8; 75%). Polyspermic fertilization was observed in 1/2 and 2/6 of fertilized oocytes inseminated with 1 x 10(5) and 1 x 10(4) sperm/ml, respectively. With the low sperm concentration 2/4 of those which were normally fertilized developed to healthy blastocysts. These studies suggest that the zona-drilling technique as described can be performed without apparent harm to oocytes and generate normal embryos.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

The effects of Arctotheca calendula (capeweed) on digestive function of sheep.

The effects of Arctotheca calendula (capeweed) on digestive function in the rumen, caecum and colon of sheep were studied. Three groups of 2-year-old Merino wethers were compared: 13 grazing capeweed-free pasture for 23 days; 8 fed 700 g of lucerne hay daily for 18 days, and 13 fed 6 kg of freshly cut capeweed (dry matter 11.3%) daily for 7 days. Capeweed did not cause diarrhoea and based on measurements of products of fermentation in the rumen, the plants were as nutritious as pasture containing grasses and clovers. The main disadvantage of capeweed in this single feeding trial was that sheep eating it lost body weight due to their inability, or lack of incentive, to consume enough dry matter.

Animal Feed↗
PubMed1991

A survey of farmers' attitudes to services provided by consulting veterinarians to the Western Australian sheep industry.

A postal survey was conducted of 80 sheep farmers in the Kojonup and Esperance districts of Western Australia to establish what they wanted from a veterinary service. Twenty five of the farmers surveyed used a sheep consultant, 25 did not, and 30 were interested in employing one. Farmers were asked questions about themselves and their attitudes to private veterinarians who provide specialist services to sheep farmers. Data reported here showed that farmers wanted a veterinarian who lived in the district, was well trained in sheep management and production, was enthusiastic and had good communication skills. The service provided should be whole-farm and available to members of the consultant's group only. Regular newsletters and field days were necessary, but the provision of contract services, such as mulesing, lamb-marking, drenching, pregnancy testing and sheep classing, and 'fire-brigade' services for sick animals, were not rated as important. Most farmers were unwilling or unable to give a dollar value for the likely benefits of a consultancy service. Non-financial benefits included keeping farmers up to date with new technical developments and information. The survey also showed that a veterinarian specialising in services to sheep farmers could be confident of employment.

Agriculture↗
PubMed1987

Neurological disease and lipofuscinosis in horses and sheep grazing Trachyandra divaricata (branched onion weed) in south Western Australia.

A severe paretic syndrome accompanied by intense neuronal lipofuscinosis is described in sheep and horses exposed to Trachyandra divaricata. This is a newly recognised toxic hazard for grazing livestock in the coastal region of the south west of Western Australia. Animals appear to become affected over a period of weeks when summer conditions induce a scarcity of alternative feed. The disease is discussed in relation to its recent documentation in South Africa where the plant is indigenous.

Animals↗
PubMed1984

The epidemiology of squamous cell carcinoma of the perineal region of sheep: abattoir and flock studies.

The roles of age, tail length and the Mules operation in the epidemiology of squamous cell carcinoma in ewes were studied. The prevalence of the disease in adult sheep slaughtered at 2 abattoirs was 0.08%. No cases occurred in lambs. Of all adult sheep condemnations before slaughter, 38.5% were due to squamous cell carcinoma. Of these sheep, 73.3% had a single lesion of the vulva (62.9%), tail (6.6%), or anus (3.8%), while 26.7% had lesions at more than one site. The number of lesions was significantly greater (p less than 0.01) in sheep with a radical Mules operation than in those with a modified Mules operation or not mulesed. Tails were significantly shorter (p less than 0.01) in affected than unaffected sheep. Small keratinised outgrowths on the skin of the tail and perineum were considered on histological grounds to be precursors of squamous cell carcinomas. On one affected farm 4% of ewes were culled in one year for gross lesions of squamous cell carcinomas. A further 3.5% of sheep with gross lesions and 25.3% with precursor lesions remained in the flock, undetected by the farmer. Gross lesions were not observed in ewes under 3 years of age, whereas precursors occurred in all age groups, including one-year-old ewes. The prevalence of lesions increased with age, from 0.43% in 5-year-old ewes to 5.14% in 6-year-old and 41% in 7-year-old ewes. Discriminant analysis indicated that age of ewe, tail length and the width of the healed Mules operation were important determinants of squamous cell carcinoma.(ABSTRACT TRUNCATED AT 250 WORDS)

Abattoirs↗
PubMed1977

Chromosome morphology during meiosis of normal and Robertsonian translocation-carrying rams (Ovis aries).

A detailed description is given of the meiotic chromosomes of the normal ram (54,XY) and of the chromosomes at diakinesis-metaphase I in rams heterozygous for the t1, t2 and t3 and homozygous for the t1 and t3 Robertsonian translocation chromosomes. Analyses were made on diakinesis-metaphase I chromosomes in 309 cells from normal rams and 2402 cells from the Robertsonian translocation carriers. Hypomodal cell counts were due to missing chromosomal elements and hypermodal counts were due either to separation of the chromosomes of the sex bivalent or to separation of the components of an autosomal bivalent. Trivalent formation was characteristic for the heterozygous Robertsonian translocation carriers while the homozygous carriers had an additional large bivalent. An association between the sex bivalent and a small autosomal bivalent at diakinesis-metaphase I is reported.

Animals↗
PubMed1975

The frequency of aneuploidy in the secondary spermatocytes of normal and Robertsonian translocation-carrying rams.

A detailed analysis was made of the chromosomes in 1008 M II figures from three different types of heterozygous Robertsonian translocation-carrying rams (53,xy,t1; 53,xy,t3) and 225 M II figures from homozygous Robertsonian translocation-carrying rams (52,xy,t1t1; 52,xy,t3t3) and rams of normal karotype (54,xy). No hypermodal cells were recorded in either the normal or the homozygous rams, but from 4-5% to 9-2% of M II cells from the heterozygous rams were hypermodal. The heterozygous rams also produced a significantly higher level of hypomodal cells suggesting that, in addition to non-disjunction, lagging at anaphase I may have occurred. There were also distinct differences in M II aneuploid spermatocyte frequency between heterozygous versus normal and homozygous rams. Fewer balanced translocation X-carrying M II cells were recorded than expected in three of the four 53,xy,t2 rams. This coincides with mating data which suggest that 26,x,t2 gametes may occur less frequently than expected. Since ewes of normal karotype mated to 53,xy,t rams conceive to first service at a rate equal to or better than normal mating groups, and because no blastocysts with unbalanced karotypes associated with the t1 translocation have been recorded, it is suggested that only euploid spermatozoa are involved in fertilization. In the sheep, aneuploid spermatocytes probably degenerate before sperm maturation.

Aneuploidy↗