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Biomedical subjects

M J Edwards

Publications and source records attributed to M J Edwards.

At least 217 records · Page 12Linked to original sources
PubMed1984

Prevalence of congenital abnormalities in pigs.

The prevalence of congenital defects in piglets in a large intensive piggery was determined by autopsy examination of piglets dying in the first week of life and from records kept by the farm staff. A total of 1908 piglets was examined at autopsy and 14,535 were born over the period of the survey. The prevalence of defects on this farm was estimated to be 2.9% of all piglets born, and at least one piglet with a congenital defect was found in 17.4% of litters. Of the piglets dying in the first week 9.5% had a defect and of these 8% had multiple anomalies. The mean litter size at birth for litters with a malformed piglet was 10.9 compared with 9.9 for litters without a malformed piglet. The total preweaning loss in litters containing a malformed pig was higher (29.8%) than that in litters without malformations (17.4%). The antepartum and parturient deaths in litters with a malformed piglet were 35% higher than normal litters. Parturient and anteparturient deaths amounted to 7.5% of piglets born and the total preweaning mortality was 19.9%. Sixty-six per cent of these mortalities occurred within the first week of life. The litter size at birth increased with parity as did the prevalence of litters containing malformed piglets. Neonatal loss was about 2 pigs per litter for all parities. Litter size at birth in litters containing a malformed pig was consistently higher by one pig per litter from all parities, but parturient (7.1%) and anteparturient (1.4%) deaths were also higher in these litters than in litters without malformations (5.1% and 1.2% respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1983

Comparison of the effects of radiation and hyperthermia on prenatal retardation of brain growth of guinea-pigs.

On day 21 of pregnancy guinea-pigs were exposed to hyperthermia or gamma radiation. The effects on prenatal growth and especially brain growth of offspring were compared. Doses of 0.04-0.99 Gy of radiation produced a dose-dependent and irreversible reduction of brain weight in the offspring, but had little effect on body weight. Treatment with hyperthermia resulting in maternal temperatures of 41.8-43.9 degrees C after exposure in a heated incubator for an hour also produced a dose-related micrencephaly in the offspring. Comparison of the two agents showed that a dose increment of 0.525 Gy of radiation produced a deficit in brain weight equivalent to an elevation of 1 degree C in maternal temperature. Using this guinea-pig brain weight assay system a threshold was detected of between 0.05 and 0.10 Gy for retardation of brain growth.

Abnormalities, Radiation-Induced↗
PubMed1983

Effects of the DNA strand-cleaving antitumor agent, streptonigrin, on ataxia telangiectasia cells.

Cells from patients with ataxia telangiectasia (A-T) were shown to be more sensitive to streptonigrin than were cells from normal individuals. A linear dose-dependent cell survival was observed for both normal and A-T cells exposed to streptonigrin (up to 1.5 ng/ml) for 3-hr, with the A-T cells being about twice as sensitive as were the normal cells (Do approximately 0.25 ng compared with Do approximately 0.5 ng). The extreme toxicity of streptonigrin is also seen in the response of DNA synthesis which is inhibited sharply in both A-T and normal cells using doses of up to 125 ng/ml, although the effect was less pronounced in A-T cells. A greater amount of time was needed for recovery of DNA synthesis in normal cells compared with that of A-T cells. Finally, chromosomes from both A-T lymphocytes and fibroblasts show about a doubling of breakage rate following exposure to streptonigrin. The increased sensitivity of A-T cells to streptonigrin appears to be fairly comparable to the sensitivity to ionizing radiation, bleomycin, or neocarzinostatin and provides further evidence that perhaps A-T cells are deficient in some form of DNA strand repair.

Ataxia Telangiectasia↗
PubMed1982

Replicative DNA synthesis in permeable fibroblasts from normal individuals and ataxia-telangiectasia patients.

Replicative DNA synthesis in normal human fibroblasts was inhibited by 50% when they were X-irradiated (8 Gy) and made permeable 30 min later, whereas only a slight inhibition (20%) was observed in similarly treated ataxia-telangiectasia cells. Treatment of irradiated normal cells with caffeine (2 mM) before permeabilization reversed the inhibitory effects of X-rays, buf caffeine had no effect on DNA synthesis in permeable ataxia-telangiectasia cells. Diadenosine tetraphosphate (0.1 mM) did not affect DNA synthesis in permeable normal fibroblasts.

Ataxia Telangiectasia↗
PubMed1982

Malignancy, DNA damage and chromosomal aberrations in ataxia telangiectasia.

Ataxia telangiectasia (AT) is a recessively inherited disorder with features that include a greatly increased susceptibility to malignant disease, an immunological defect and increased sensitivity to ionizing radiation and bleomycin. Recently, we and others have shown that AT cells do not show the same decrease in DNA synthesis as normal cells following gamma-irradiation. They may also have a defect in DNA repair following gamma-irradiation. Some of our patients show the presence of one or more cytogenetically abnormal clones involving chromosome 14 in their circulating lymphocytes; these are actively proliferating, in the absence of any clinically diagnosed malignancy, and can exist for several years. A variety of subclones also appear at different times, pointing to an instability in the major clone. Lymphocytic leukaemia arising in such clones in AT patients has been described by others. The defective response of AT cells to some types of damage to DNA may increase the probability of translocations of chromosomal segments to other sites, resulting in the observed chromosomal rearrangements. Furthermore, in vivo, cells with such rearrangements may develop into clones before a malignant change is seen, rather than being a secondary feature of lesser importance.

Ataxia Telangiectasia↗
PubMed1981

Accelerated respiratory response to moderate exercise in late pregnancy.

We studied the rates of change of expired ventilation (VE, BTPS), O2 consumption (VO2, STPD) and CO2 production (VCO2, STPD) at the start and stop of 6 min of 50-W bicycle exercise, comparing 20 healthy young women at 38 weeks of pregnancy (G) and 3 months postpartum (NG). VO2, VCO2 and VE were significantly greater at rest for G than for NG. The absolute increases of VO2 and VCO2 from steady-state rest (SSR) to steady-state exercise (SSE) were the same for G and NG. The absolute increase of VE from SSR to SSE was significantly greater for G than NG. VCO2 and VE increased more rapidly in G than NG, but only during the first 90 sec of exercise. Recovery rates after exercise were equal for G and NG. We believe that lower extremity muscles of G contract on more distended veins at the onset of exercise, forcing increased volumes of venous blood through the lungs, increasing VO2 and VCO2. VE follows VCO2 closely.

Adult↗
PubMed1981

The detection of arthritis in pigs in an abattoir and its public health significance.

The results of a study of the prevalence in each joint of arthritis in pigs as detected by meat inspectors is presented. A prevalence of arthritis in 1.07% of carcases was obtained, of which 0.28% were condemned totally and 0.79% condemned partially. With partial condemnations there was a bias to the left side in the hindquarters, and a significant bias to the hindquarter as compared with the forequarter. A consequence was that undetected arthritis lesions, especially in the forequarter and probably containing viable Erysipelothrix rhusiopathiae, are finding their way to the consumer.

Abattoirs↗
PubMed1980

Unusual levels of (ADP-ribose)n and DNA synthesis in ataxia telangiectasia cells following gamma-ray irradiation.

Poly (ADP-ribose) polymerase is a eukaryotic chromosomal enzyme which utilizes the ADP-ribose moiety of NAD to synthesize the nucleic acid homopolymer (ADP-ribose)n (ref. 1). The precise function of (ADP-ribose)n has not been fully established although it does covalently modify chromosomal proteins by ADP-ribosylation. Here we demonstrate that gamma-ray irradiation of lymphoblastoid cells from normal subjects results in depressed DNA synthesis and increased (ADP-ribose)n synthesis. Irradiation of lymphoblastoid cells from patients with the autosomal recessive disease ataxia telangiectasia (AT), however, failed to depress DNA synthesis and did not elevate (ADP-ribose)n levels. We have confirmed that (ADP-ribose)n is synthesized in response to DNA damage and we propose that this polymer may function in the recovery from DNA damage by suppressing DNA synthesis.

Ataxia Telangiectasia↗
PubMed1980

An enzyme activity in normal and ataxia telangiectasia cell lines which is involved in the repair of gamma-irradiation-induced DNA damage.

An enzyme that enhances the activity of DNA polymerase I (EC 2.7.7.7) for gamma-irradiated calf thymus DNA was demonstrated in cellular extracts of normal human fibroblasts and lymphoid-cell lines. This enzyme was found to be deficient in all cellular extracts of fibroblasts and lymphoid-cell lines examined from patients with the autosomal recessive disease ataxia telangiectasia. The activity in cellular extracts from normal fibroblasts was removed when heated to 100 degrees C for 2 min or when the assay was performed at 4 degrees C. No significant deficiency in primer-activating enzyme activity was observed in cell-free extracts of lymphoid lines from patients with xeroderma pigmentosum, Huntington's chorea or neurofibromatosis, or from an ataxia telangiectasia heterozygote.

Ataxia Telangiectasia↗
PubMed1977

Proliferative haemorrhagic enteropathy in pigs.

An outbreak of proliferative haemorrhagic enteropathy (PHE) occurred in two epidodes and affected 372 adult pigs in the breeding units of a minimal disease piggery; 186 pigs died. In the initial episode breeding sows and boars of all ages were affected, suggesting infection of a fully susceptible population. Animals involved in the first episode of the disease did not show clinical symptoms at a later date and further clinical cases occurred only in animals introduced into the breeding population. Antibiotic feed medication was an effective method of prophylaxis. Bacteria resembling Campylobacter sputorum subspecies mucosalis were isolated from the intestinal mucosa of affected animals.

Animals↗