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Biomedical subjects

J A Milne

Publications and source records attributed to J A Milne.

At least 19 recordsLinked to original sources
PubMed1991

Chronic treatment with long-acting bromocriptine does not affect duration of the breeding season, voluntary food intake, body weight, or wool growth in the Scottish blackface ewe.

The aim of this study was to determine whether suppression of the seasonal increase in prolactin concentrations by chronic treatment with the dopamine agonist bromocriptine would affect onset of anoestrus, voluntary food intake, body weight, and wool growth in a seasonal breed of sheep. Groups of eight Scottish Blackface ewes were injected i.m. each week with either the vehicle (Group A) or 2.0 mg (Group B), 6.0 mg (Group C), or 18.0 mg (Group D) of bromocriptine in a long-acting formulation, commencing on 18 January and terminating on 25 July (midwinter to midsummer in the northern hemisphere). Immediately before the bromocriptine injection, blood samples were taken for progesterone and prolactin determination. Voluntary food intakes were measured daily, and body weights were recorded every fortnight. Estimates of wool growth were made by weighing wool clipped from a measured area of skin once a month. Treatment had no effect on onset of anoestrus, voluntary food intake, body weight, or wool growth. Plasma prolactin concentrations increased significantly in all groups during the treatment period. From January to April, all doses of bromocriptine significantly reduced prolactin concentrations but later in the study (May and June) prolactin was significantly suppressed in Group D only, although even in this group prolactin concentrations increased between March and June. Pituitary prolactin content, measured at the end of the study in July, was also suppressed by bromocriptine. The gradual increase in prolactin concentrations in ewes receiving chronic bromocriptine was further investigated by treating a fifth group of ewes (Group E) with 18.0 mg of long-acting bromocriptine each week, commencing on 20 June.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Effects of melatonin and a dopamine agonist and antagonist on seasonal changes in voluntary intake, reproductive activity and plasma concentrations of prolactin and tri-iodothyronine in red deer hinds.

Three experiments were conducted in the period between July and November with non-lactating red deer hinds to describe the effects of treatment with melatonin during this period on voluntary food intake (VFI), the onset of the breeding season, coat changes and plasma concentrations of prolactin and triiodothyronine (T3), and to examine whether prolactin mediated the observed effects. In experiment 1, eight animals were treated orally each day with either 10 mg melatonin at 16.00 h or 10 mg melatonin at 16.00 h plus 10 mg domperidone (a dopamine antagonist) given twice daily for 120 days from July; eight animals were maintained as controls. In experiment 2, the same numbers of animals per treatment were used to compare treatments in which 10 mg melatonin or 20 mg bromocriptine (a dopamine agonist) were given orally each day at 16.00 h for 119 days from late June and compared with an untreated control group. In experiment 3, six animals were treated daily for 105 days from mid August with 5 mg domperidone given i.m. and compared with six control animals. In experiments 1 and 2, the VFI of control animals reached a peak in late August and thereafter declined. Melatonin-treated animals showed a similar pattern but the peak in VFI was significantly (P less than 0.05) advanced by 2 weeks compared with controls, although the VFIs of both groups were similar in November.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

A comparison of the seasonal hormone changes and patterns of growth, voluntary food intake and reproduction in juvenile and adult red deer (Cervus elaphus) and Père David's deer (Elaphurus davidianus) hinds.

Non-domesticated seasonally breeding ungulates exhibit marked seasonal changes in metabolic rate, voluntary food intake (VFI), pelage growth and moult and hormone secretion. It is not known whether these seasonal rhythms are regulated by the same central processes which control the onset and termination of the breeding season. Here we compare two closely related deer species which have significantly different mating and calving seasons. Seasonal changes in VFI, liveweight, coat growth, plasma prolactin and tri-iodothyronine (T3), and the timing of the breeding season were examined over a 15-month period in six adult post-pubertal red and Père David's deer from January to April the following year. The timing of the seasonal changes in prolactin, T3, VFI and coat growth were all significantly advanced by 56, 23, 60 and 54 days respectively in the Père David's deer. The times of onset and termination of the breeding season of Père David's deer were also significantly advanced by 90 days, but in both species, the breeding season was of similar duration (160 +/- 5 (S.E.M.) days). Changes in liveweight of adult red deer could be explained by changes in VFI rather than efficiency of utilization. This was not the case in Père David's deer and may indicate seasonal changes in the efficiency of energy utilization. In order to establish whether these species differences develop with age, we undertook a second study in which seasonal changes in VFI, growth, plasma prolactin concentrations and the timing of the onset of the breeding season were recorded for ten red deer and six Père David's deer from 6 to 18 months of age. Both species exhibited a similar decline in VFI in the first autumn of life. Subsequently, the Père David's deer exhibited an advance in the timing of the seasonal peak in VFI and prolactin (21 and 66 days respectively); puberty occurred 3 months earlier than in red deer. The earlier breeding season of the Père David's deer was associated with a significant advance in a range of seasonal endocrine and physiological parameters. These species differences may develop with age. Our data indicate that seasonal patterns of metabolism and growth may be closely linked to those mechanisms which also regulate the onset and termination of the breeding season.

Animals↗
PubMed1988

Circadian variation in abomasal digesta flow in grazing ewes during lactation.

1. Lactating grazing ewes, fistulated at the rumen and abomasum were either not supplemented or offered, individually, 600 g/d of either pelleted, molassed sugar-beet pulp ('energy' supplement) or a pelleted 1:1 (w/w) mixture of this feed and formaldehyde-treated soya-bean meal ('protein' supplement). Digesta flows at the abomasum were estimated from the concentrations of the markers CrEDTA and ruthenium phenanthroline complex, during their administration by continuous intra-rumen infusion. Digesta samples were taken at 09.00 hours and at six further times at 4 h intervals. This was repeated 2 d later. 2. No significant difference in flow between days was noted. Daily flows of dry matter (DM) and non-ammonia-nitrogen (NAN) (g/d) in supplemented ewes were significantly higher than in unsupplemented ewes, both in total digesta and its particulate phase. However, there were significant differences between sampling times or significant interactions between sampling time and supplement treatment. The results were therefore examined by Fourier analysis for possible circadian variation in digesta flow. As there was marked between-animal variability in flow-rate, the digesta-flow values for each sampling time were re-expressed as percentages of the flows calculated from daily mean marker concentrations. 3. In unsupplemented animals, marked and significant circadian variation was then identified in the flow of DM, total N and NAN in both whole digesta and the particulate phase. There was also significant circadian variation in the flow of DM, total N and NAN in the digesta of the supplemented ewes. Curves were of the same general shape as those for unsupplemented animals, but some significant differences were found, principally for digesta NAN flow. In both supplemented and unsupplemented animals, peak flows occurred in the period 20.00-01.00 hours. The proportion of DM and NAN flowing in the particulate phase was relatively constant through the day for unsupplemented ewes, but significant circadian variation occurred for supplemented ewes. 4. The possible mechanisms generating the circadian variation in digesta flow, such as grazing behaviour and the rumen digestion of supplements, are discussed. Values are also presented to indicate the extent of the likely errors if digesta flows were estimated from samples which did not represent all stages of the circadian pattern.

Abomasum↗
PubMed1988

Effects of chronic long-acting bromocriptine treatment on liveweight, voluntary food intake, coat growth and breeding season in non-pregnant red deer hinds.

Seventeen red deer hinds were housed in individual pens and from 28 February until 11 November were injected each week with vehicle (group A; n = 6) or 5 (group B; n = 6) or 12.5 mg (group C; n = 5) of a long-acting formulation of bromocriptine. Liveweight and voluntary food intake (VFI) were recorded for each hind, and blood was collected for determination of progesterone, prolactin, tri-iodothyronine (T3) and cortisol concentrations by radioimmunoassay. Treatment with the high dose of bromocriptine was associated with a significant (P less than 0.05) reduction in VFI, with the effect being greatest between March and July. There was no treatment effect on liveweight, but there was a significant (P less than 0.01) interaction between time and treatment due to the faster rate of weight gain in control animals at the beginning of the experiment. Changes in liveweight could be explained by changes in VFI rather than by changes in the efficiency of utilization of intake. Termination of the breeding season was significantly (P less than 0.01) delayed by 54 days in group C hinds. Growth of the summer coat and subsequent winter coats was delayed by 1 and 3 months respectively in group C hinds, and in groups B and C the duration that animals were in summer coat was increased by about 1 month. The seasonal increase in prolactin concentrations was seen in all groups, but levels were significantly (P less than 0.05) lower in group C hinds. Concentrations of T3 and cortisol were not affected by bromocriptine.

Animals↗
PubMed1979

Nitrogen digestion in sheep given poor-quality indigenous hill herbages.

1. In two experiments, the sites of digestion of non-ammonia nitrogen (NAN) and the amounts of urea N recycled to the rumen were measured in mature wether sheep given diets of indigenous hill herbage (Agrostis-Festuca and heather). 2. Duodenal and ileal flow values were obtained using 103Ru-phenanthroline and 51Cr-EDTA markers in animals prepared with simple (T-shaped) cannulas. Amounts of urea N recycled to the rumen were estimated from measurements of the transfer of plasma urea carbon into rumen bicarbonate and the production rate of rumen bicarbonate using 14C-labelled urea and bicarbonate respectively. 3. The flows of NAN at the duodenum and ileum were linearly related to the intake of herbage (P less than 0.001). There was a net gain of non-ammonia N anterior to the duodenum on both diets (at an intake of 460 g organic matter (OM)/d, 3.7 g NAN/d on Agrostis-Festuca and 3.3 g NAN/d on heather). 4. Net digestibility of NAN entering the small intestine was within a normal range on the Agrostis-Festuca (0.58 at 460 g OM intake) diet but low on the heather diet (0.43 at 460 g OM intake). 5. It was calculated that at 460 g OM intake only 0.9 and 1.1 g/d respectively of the duodenal NAN on the Agrostis-Festuca and heather diets could have been derived from urea-N recycled to the rumen. Thus 2.8 g and 2.2 g/d had to be accounted for as non-urea endogenous NAN.

Animal Feed↗
PubMed1979

The respiratory response to pregnancy.

The respiratory response to pregnancy appears to be largely mediated by the action of progesterone and, perhaps to a lesser extent, oestrogens, at least in the first and second trimesters. The mechanical effects of the gravid uterus cause relatively little change in pulmonary mechanics, although finer changes in airways function require further investigation. Dyspnoea during pregnancy is also probably hormone-mediated but the exact temporal relationship between hormone status, functional change and the development of symptoms is not yet clearly defined.

Dyspnea↗
PubMed1978

A comparison of the voluntary intake and digestion of a range of forages at different times of the year by the sheep and the red deer (Cervus elaphus).

1. Comparisons were made between castrated male Scottish Blackface sheep and red deer (Cervus elaphus) of voluntary forage intake (VFI), digestibility and the mean retention time (MRT) of a particulate-phase marker (103Ru-phenanthroline) in the alimentary tract, when a range of forages: dried-grass pellets, chopped dried grass, fresh-frozen Agrostis-Festuca spp. and heather (Calluna vulgaris, L. Hull) were given at different times of the year. 2. On both the dried-grass-pellet and chopped dried-grass diets the red deer and sheep ate similar quantities. Both species had a higher VFI of dried-grass pellets in July than in November. The sheep digested the dried-grass-pellet diet better than the red deer and this was associated with a longer MRT of the particulate-phase marker in the alimentary tract. 3. The VFI of Agrostis-Festuca spp. and heather by the red deer was twice that of the sheep. The VFI of heather by the sheep increased by 32% between January and April, and the VFI of both the Agrostis--Festuca spp. and heather diets by the red deer increased by 65--70%. The sheep digested the Agrostis--Festuca spp. better than the red deer but the red deer digested the heather slightly better than the sheep. MRT of the particulate-phase marker was greater for the sheep than for the red deer on both the diets. The digestibility and MRT of both diets in the red deer did not decrease with the seasonal increase in VFI, suggesting a possible hypertrophy of the alimentary tract.

Animal Feed↗
PubMed1978

Pregnancy in patients with bronchiectasis.

Pulmonary function was monitored at regular intervals throughout pregnancy in three patients with bronchiectasis. They tolerated pregnancy well, and the underlying lung disease did not appear to have any adverse effect on the outcome of the pregnancy.

Adult↗
PubMed1978

Dyspnoea during normal pregnancy.

The incidence, severity and time-course of dyspnoea were assessed in 62 women on eight occasions throughout a normal pregnancy. Fifteen per cent of subjects noticed an increase in dyspnoea in the first trimester compared with the nonpregnant state and in almost half of them dyspnoea was experienced before 19 weeks gestation; 76% complained of this symptom by 31 weeks gestation. After this time, few subjects noticed any increase in their symptoms.

Adolescent↗
PubMed1977

The effect of human pregnancy on the pulmonary transfer factor for carbon monoxide as measured by the single-breath method.

1. The pulmonary transfer factor for carbon monoxide was measured by the single-breath method in 21 pregnant women with no previous history of cardiac or respiratory disease. Measurements were made at monthly intervals throughout pregnancy and once post partum. 2. The transfer factor was higher in the first trimester of pregnancy than in the non-pregnant state. There was a fall in the transfer factor during pregnancy until 26 weeks gestation, after which no further decrease was observed. 3. The changes in transfer factor were not explained by alterations in haemoglobin concentration or alveolar volume. 4. Simultaneous serial estimation of plasma 17beta-oestradiol were performed in all the subjects. There was no obvious direct relation between changes in the concentration of this hormone and transfer factor measurements.

Adult↗
PubMed1977

Large airways function during normal pregnancy.

Specific airways conductance and forced expiratory volume in one second were measured monthly from the first trimester until term in 30 subjects in the course of a normal pregnancy. Measurements were also made in the postpartum period. There was no significant change in these measurements either throughout pregnancy or compared with postpartum values. Our results suggested that the function of the larger pulmonary airways was not altered in pregnancy.

Adolescent↗
PubMed1977

An effect of enzyme and ligand concentration on the state of aggregation of aspartate transcarbamylase of E. coli: I. The binding of CTP and ATP to the enzyme.

Detailed binding studies of the inhibitor, cytidine triphosphate (CTP), to native Escherichia coli aspartate transcarbamylase (EC 2.1.3.2) reveal significant changes in subunit interaction when enzyme concentration is altered. In contrast, similar binding studies of the activator, adenosine triphosphate (ATP), do not reveal such changes, but do indicate more complex subunit interactions than previously reported. Equilibrium dialysis studies of 4 degrees C are consistent with six binding sites for CTP and ATP per enzyme molecule of molecular weight 310 000, at all enzyme concentrations. CTP binding studies reveal a progressive change from apparent positive to negative cooperativity as the enzyme concentration is decreased. ATP binding studies reveal complex subunit interactions involving a mixture of apparent negative and positive cooperativity. Sucrose gradient studies indicate the presence of at least three enzymatically active polymeric forms of the enzyme. The preliminary sedimentation studies indicate possible ligand and enzyme concentration perturbations of a preexisting association equilibrium in the aspartate transcarbamylase system. The binding data are therefore interpreted in terms of an association model.

Adenosine Triphosphate↗