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Biomedical subjects

A R Peters

Publications and source records attributed to A R Peters.

At least 55 records · Page 3Linked to original sources
PubMed1989

Effect of prostaglandin F2 alpha on hormone concentrations in dairy cows after parturition.

This study was designed to evaluate the effects of exogenous prostaglandin F2 alpha (PGF2 alpha) on hormone secretion in cows without a corpus luteum. Blood samples were taken from 10 Friesian dairy cows at frequent intervals from a jugular vein and the caudal vena cava starting between nine and 20 days after parturition. PGF2 alpha (25 mg dinoprost) was injected intramuscularly into five cows after the first eight hours of sampling. Plasma concentrations of 13,14-dihydro 15-keto PGF2 alpha (PGFM) increased rapidly but had returned to baseline by 14 hours after injection. There was no significant effect of the treatment on the time taken by the cows to resume ovarian cycles, and it had no consistent effect on plasma luteinising hormone (LH) patterns; however the amplitude of pulses of LH was temporarily suppressed in two cows and the frequency of pulses of LH was immediately increased in one cow. Treatment with PGF2 alpha had no significant effect on the concentration of oestradiol in blood from the vena cava. It is concluded that any enhancement of the reproductive performance of cows treated with PGF2 alpha after parturition is not due to a direct effect on pituitary-ovarian function.

Animals↗
PubMed1989

Sequence-specific 1H-n.m.r. assignments and peptide backbone conformation in rat epidermal growth factor.

The solution conformation of rat epidermal growth factor (EGF) has been investigated by proton n.m.r. techniques. Two-dimensional proton n.m.r. experiments have allowed sequential resonance assignments to be made for most protons. On the basis of these assignments, two regions of anti-parallel beta-sheet structure have been derived from the n.m.r. data. A beta-sheet segment running from about V19 to V23 (capital letters refer to amino acids in the single-letter notation) is folded onto a beta-sheet segment running from R28 to N32 and joined by a chain reversal from E24 to D27. A second region involves a beta-turn from V34 to Y37, which starts a short beta-sheet up to G39, followed by a chain reversal up to Q43, which leads to folding of the C-terminal beta-sheet segment, i.e. H44-R45, running antiparallel to the short Y37 beta-sheet segment. The N-terminal segment up to G18 exists in a multiple bend conformation and is folded on to the V29-V23/R28-N32 beta-sheet such that Y10, Y13, Y22 and Y29 are proximal to each other. Structural comparison of rat, murine and human EGFs indicates a number of highly conserved structural features common to at least these species of EGF.

Animals↗
PubMed1988

Associations between viral infection and respiratory disease in young beef bulls.

Blood samples were taken from bull calves at two Meat and Livestock Commission performance testing centres, just after weaning at six months of age and at six weekly intervals until the end of the performance test seven months later. Sera were assayed by specific ELISAS for antibodies to bovine herpes virus 1 (BHV1), respiratory syncytial virus, parainfluenza 3 (Pi3) and adenoviruses A and B. Seroconversions between each sampling were related to the occurrence of clinical respiratory disease using chi-squared (chi 2) and relative risk (RR) analyses. In 294 bulls there were 123 cases of respiratory disease. Seroconversion to bovine respiratory syncytial virus (RR = 4.7, chi 2 = 96.3, P less than 0.001) and adenovirus A (RR = 1.8, chi 2 = 8.9, P less than 0.001) and adenovirus B (RR = 1.9, chi 2 = 5.6, P less than 0.05) were significantly associated with clinical respiratory disease. There was evidence that prior exposure to respiratory syncytial virus (RR = 0.4, chi 2 = 9.8, P less than 0.01) Pi3 (RR = 0.4, chi 2 = 12.8, P less than 0.01) and adenovirus A (RR = 0.7, chi 2 = 7.5, P less than 0.01) conferred some protection against respiratory disease after arrival at the centre. It is concluded that vaccination before weaning, at least against bovine respiratory syncytial virus, would be beneficial.

Adenoviridae↗
PubMed1988

Relationship of calf antibody status to disease and performance.

Three tests were used to measure the circulating immunoglobulin in 381 purchased calves as they entered a commercial calf-rearing unit. A correlation of 0.64 was found between the zinc sulphate turbidity (ZST) test and a quantitative latex agglutination test (LAT) measuring IgG1 (P less than 0.001). A qualitative version of the LAT related poorly to the quantitative version. The proportion of plasma samples identified by the quantitative LAT as having an IgG1 concentration of less than 5 g/litre which were incorrectly identified as positives (greater than or equal to 5 g/litre) by the qualitative LAT was 0.65. The proportion of plasma samples identified by the quantitative LAT as having a IgG1 concentration of greater than or equal to 5 g/litre which were incorrectly identified as negative (less than 5 g/litre) was 0.11. There was no statistically significant relationship between plasma IgG1 concentration and initial liveweight, subsequent overall daily liveweight gain or disease incidence (P greater than 0.05). Calves treated for infectious disease, particularly respiratory disease after weaning, had statistically significantly lower liveweight gains than healthy calves (P less than 0.001).

Analysis of Variance↗
PubMed1988

Water balance during saline imbibition in the Mongolian gerbil (Meriones unguiculatus).

1. There were few changes in the water balance of gerbils drinking 0.25 and 0.50 M NaCl solutions for 5 days. 2. Imbibition of 0.75 and 1.0 M saline resulted in some dehydration of the body fluids and considerable depletion of the neural lobe vasopressin store. 3. Although large amounts of NaCl were excreted, the maximum urine osmolality was considerably less than that found following water deprivation. 4. The imbibition of 1.0 M saline caused similar changes in water balance to water deprivation showing that little, if any, water was gained from this solution.

Animals↗
PubMed1988

Endocrine changes from birth to puberty in the heifer.

Twelve autumn-born Hereford x Friesian heifers were studied to characterize changes in the patterns of LH and FSH secretion occurring from birth through the peripubertal period. A once weekly blood sampling regimen, starting 3 days after birth, was combined with periods of frequent sampling (15-min intervals for 24 h) every month from 3 weeks of age. Mean plasma LH concentrations decreased over the period from birth to 15 weeks of age, largely due to a decrease in basal LH concentrations. Thereafter, mean plasma LH concentrations increased to 39 weeks of age, mainly as a consequence of increasing LH episode frequency and LH episode amplitude. Oestrus was detected using an oestradiol-treated steer, and ovulation inferred from progesterone profiles. A 'short luteal phase' oestrous cycle preceded the first observed oestrus, and this was followed in all heifers by a normal length luteal phase. However, no increase in mean LH concentrations, basal LH concentrations, LH episode frequency, LH episode amplitude or change in mean FSH concentration could be directly associated with the onset of puberty. It is therefore concluded that the gonadotrophic stimulus for first ovulation must occur abruptly.

Aging↗
PubMed1988

Gonadotropins--domestic animals.

The application of RIAs for the gonadotropins to the study of domestic animal reproduction has depended on the availability of sensitive and specific reagents, automated systems for increased throughput and an awareness of the assay errors. Illustrations are given on the measurement of seasonal, surge and episodic changes in LH secretion and the advantages gained by such investigation are outlined.

Animals↗
PubMed1987

Future developments in the manipulation of growth in farm animals.

The anabolic steroid and antimicrobial growth promoters may be regarded as the first generation of animal growth promoters or performance enhancers. There is major investment in the development of new techniques to improve the efficiency of farm animal production. These techniques are reviewed under the headings of growth hormone (somatotrophin) and related techniques, immunological techniques, the beta-adrenergic agonists and the direct genetic manipulation of farm animals.

Adrenergic beta-Agonists↗
PubMed1987

Effect of trenbolone acetate on ovarian function in culled dairy cows.

The ovarian cycles of 48 culled dairy cows were monitored by assaying plasma progesterone concentrations. Twenty-four cows received a subcutaneous implant of 300 mg trenbolone acetate (Finaplix; Hoechst) at the beginning of the study. Of the implanted cows, two were pregnant, six continued to cycle although their peak progesterone concentrations were significantly lower than in control cows (5.65 +/- 0.71 compared with 8.19 +/- 0.47 ng/ml; P less than 0.01). Prolonged periods (13 to 92 days) of low progesterone concentrations (less than 1 ng/ml) occurred in 12 of the implanted cows. In six of seven cows in which normal cycles had not resumed by the time of slaughter two to five ovarian follicles of diameter greater than or equal to 10 mm were found post mortem. Persistent luteal function (greater than 35 days) occurred in the absence of pregnancy or gross uterine pathology in five of the implanted cows, two of which had recovered spontaneously by the time they were slaughtered. There was no difference in plasma luteinising hormone concentrations between the implanted and control cows. It is concluded that trenbolone acetate affected the ovarian cycle of the cows in several ways through changes other than the modification of tonic luteinising hormone secretion.

Anabolic Agents↗
PubMed1987

Vaccines for respiratory disease in cattle.

Respiratory disease is one of the most serious disease complexes affecting beef cattle production. For example, it is claimed to cost the UK industry about 70 million pounds per year. It is usually associated with young cattle and can occur in a variety of situations. It is a good example of multifactorial disease in that its aetiology involves both infection by a variety of microorganisms and a number of environmental factors. Several distinct syndromes occur and a number of microorganisms are thought to be important including the bacteria Pasteurella haemolytica type A1, P. multocida, Haemophilus somnus, Corynebacterium pyogenes, Mycoplasma bovis and M. dispar. Of the viruses, bovine herpes virus 1 (BHV1) and respiratory syncytial virus (RSV) are known to be important, the former also causing the specific syndrome, infectious bovine rhinotracheitis (IBR) in addition to its involvement in the pneumonia complex. Other viruses of possible importance include para-influenza 3 (Pi3), adenoviruses, bovine viral diarrhoea (BVD) virus, coronavirus and rhinovirus.

Animals↗
PubMed1987

Opioid modulation of LH secretion during the oestrous cycle of heifers.

Injections of an opioid agonist (bremazocine) and/or an antagonist (quadazocine) were given to heifers during the luteal or follicular phase of the oestrous cycle. Quadazocine was injected (210 mg/injection) three times at 2-h intervals, and bremazocine was injected (0.45 mg/injection) every 15 min for 6 h. Blood samples were taken every 15 min beginning 6 h before treatments started and continued for 18 h. LH secretion patterns were not affected by quadazocine in the luteal-phase heifers, but quadazocine and bremazocine had marked effects during the follicular phase. Quadazocine increased LH secretion by increasing peak height but not peak frequency. Bremazocine decreased LH secretion through both peak height and frequency. This decrease was of greater magnitude than the increase due to quadazocine. When quadazocine and bremazocine were given together, these effects were cancelled and none of the effects carried over into the bleeding period after treatments stopped. No apparent interruption of follicular maturation was detected since all follicular-phase heifers were detected in oestrus at normal intervals. We conclude that heifers in this experiment did not have an opioid-mediated mechanism for progesterone suppression of LH but that an opioid mechanism for modulating LH does exist during the follicular phase.

Animals↗
PubMed1987

Hormone responses to low-dose GnRH treatment in post-partum beef cows.

Acyclic beef cows received 1.0, 2.5 or 5.0 micrograms GnRH/2 h for 48 h as 24 X 2 h repeated i.v. injections or by continuous i.v. infusion. Preovulatory-type LH surges were detected in 9/18 injected and 8/15 infused cows and occurred 30.6 +/- 5.1 h and 3.3 +/- 0.7 h after the start of treatment respectively. Cows receiving the lowest infusion dose did not exhibit gonadotrophin surges. The LH response to individual injections increased with dose but the proportion of injected cows showing preovulatory-type surges at each dose level did not change. A total of 20 cows (10 injected and 10 infused) showed evidence of luteal activity within 7 days of the end of GnRH treatment, although this was transitory in most animals. Cows which exhibited preovulatory-type LH surges in response to treatment had significantly higher plasma oestradiol-17 beta concentrations and lower FSH concentrations before treatment than those which did not. The results suggest that the LH response to GnRH treatment is dependent on follicular status in the immediate pretreatment period.

Animals↗
PubMed1986

Some husbandry factors affecting mortality and morbidity on a calf-rearing unit.

The influence of some husbandry factors on morbidity and mortality was studied in 1996 artificially reared, dairy bred calves over the period from purchase until about six weeks of age. The effects of housing (indoors versus outdoors), penning (individual versus group), breed, time since purchase and season of purchase were examined. The overall mortality rate was approximately 4 per cent and calves were more likely to die if reared in groups outdoors than if reared either singly or in groups indoors. The mortality rate was significantly lower in calves purchased between April and June than at other times of year. Pneumonia was the most common disease symptom (48.3 per cent of calves) with diarrhoea the second most common (14.1 per cent). Neither the type of penning nor housing affected the incidence of pneumonia but diarrhoea was most common in individually penned calves. Case mortality rates for diarrhoeic calves in group pens were higher than for those in single pens and case mortality rates for pneumonia were highest for calves reared in groups outdoors. More than half the cases of pneumonia occurred between one and three weeks after purchase whereas two-thirds of the cases of diarrhoea occurred within the first week after purchase. However, case mortality rates for both conditions appeared to increase with time since purchase.

Animal Husbandry↗
PubMed1986

Regulation of ovarian function in the post partum cow: an endocrine model.

Recent studies of endocrine function during the period after parturition are discussed and used as a basis for the development of a hypothetical model for the control of ovarian function in the cow after calving. It is postulated that the main sequence of endocrine changes is as follows. At first gonadotrophin releasing hormone is secreted infrequently in small quantities. Very early after parturition the secretion of follicle stimulating hormone increases, thus stimulating the development of follicles. There is then a gradual increase in responsiveness to gonadotrophin releasing hormone which results in an increased frequency of release of pulses of luteinising hormone. Follicular growth results in the production of oestradiol and inhibin. Finally there is a gradual restoration of the positive feedback mechanism by which preovulatory gonadotrophin release occurs. In a normal cow the whole process appears to be complete by approximately two weeks after parturition.

Animals↗
PubMed1986

Reaction products from platinum(IV) amine compounds and 5'-GMP are mainly bis(5'-GMP)platinum(II) amine adducts.

The reaction products obtained from mixtures of 5'-GMP and platinum(IV) compounds with formula Pt(IV)Cl4(LL) and Pt(IV)Cl2(OH)2(LL) (LL representing two monodentate or one bidentate amine ligand) have been characterized by proton NMR spectroscopy. The amines used are NH3, H2N-CH2-CH2-NH2 (ethylenediamine, en), H2N-CH2-C(CH3)2-CH2-NH2 (2,2-dimethyl-1,3-diaminopropane, dmdap), and HC(CH3)2-NH2 (isopropylamine, ipa). Conditions varied during the reaction are pH (values of 4, 7, and 10), effect of visible light, and addition of vitamin C as a reducing agent. In all cases, the major product appeared to be the bis(5'-GMP)(LL)Pt(II) compound. The pH effect is limited; i.e., at pH 4 the reactions proceed somewhat faster than at neutral pH, while at pH 10 slower reactions occur. The illumination with visible light also induces only slight differences in the yields of the products. On the other hand, when vitamin C is present, the reactions proceed quite rapidly, resulting in the same main product but in higher yields (up to 80%). The facts that apparently no Pt(IV) adducts with 5'-GMP can be observed under these conditions and that the major products are bis(5'-GMP)(LL)Pt(II) compounds clearly support the hypothesis that the antitumor activity of certain platinum(IV) compounds is based upon in vivo reduction to the corresponding platinum(II) compounds.

Ascorbic Acid↗
PubMed1985

Survey of the prevalence of warble fly larvae in market cattle in Great Britain.

A survey of warble-infested 'fat' cattle in 57 selected livestock markets in Great Britain was carried out during June 1972 and during May each year from 1973 to 1984. The annual total number of cattle inspected varied from 41,587 to 60,481. The level of infestation increased from 22.3 per cent in 1972 to 38.0 per cent in 1976 and then declined slightly to 34.3 per cent in 1978. Following the introduction of legislation and the warble fly eradication campaign in 1978 there was a rapid decrease to 8.6 per cent infestation by 1979 and by 1984 the level was less than 0.02 per cent.

Animals↗