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Biomedical subjects

H Dobson

Publications and source records attributed to H Dobson.

157 records · Page 9Linked to original sources
PubMedDate not supplied

The relationship between milk yield and cystic ovarian disease in cattle.

Studies were conducted to understand the relationship, if any, between the amount and pattern of milk yield and the occurrence of cystic ovarian disease (COD) in dairy cattle. More than 70 cows with cysts were compared with herd mates of similar lactation number. Total milk yield in lactations when cysts occurred and in the preceding lactations were not different from the corresponding lactations in control cows. Patterns of monthly milk yield did not differ between the two groups of cows. However, weekly analysis in early lactation revealed differences. Both groups of cows achieved peak yields at a similar time (5.4 +/- 1.2 vs 5.7 +/- 1.9 weeks post partum in normal vs cows with COD). However, owing to an early decline in yield of cows with COD, their duration of peak yield was significantly shorter (P less than 0.05) than in the control cows (3.2 +/- 2.2 vs 5.6 +/- 2.4 weeks). Both the attainment and the decline of peak yield occurred 5.6 (range = 2-15) weeks before the cysts were diagnosed. It is concluded that COD is not particularly a disease of higher yielding cows and that COD has no discernible effect on the milk yield or its pattern. It is speculated, however, that some cows in early lactation, while trying to meet the requirements of sustained peak milk production, are more susceptible to minor environmental changes (such as new social interactions, or changes in diet). These events may lead to a drop in milk production and disruption of events controlling normal ovulation, resulting in the formation of ovarian cysts.

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PubMedDate not supplied

The effect of different types of transportation on plasma cortisol and testosterone concentrations in male goats.

Plasma cortisol and testosterone concentrations were measured in three male goats before and after transportation for 15 min in a quiet trolley, a noisy trolley or a motorized van. Cortisol concentrations remained within the basal range (1-5 ng/ml) during the control periods and during the trip in the quiet trolley. However, maximum values of cortisol (13-24 ng/ml) were achieved by 15 min after transport in the noisy trolley; concentrations of greater than 27 ng/ml were recorded immediately after motorized van transport. Plasma testosterone values ranged between 0.5 and 4.0 ng/ml and were unaffected by any mode of transport tested. It is concluded that adrenal cortex activity in male goats is stimulated more by noise than motion.

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PubMedDate not supplied

Development of an endocrine challenge test to investigate subfertility in ewes.

Simultaneous or sequential injection of 250 ng gonadotrophin releasing hormone (GnRH) and 25 micrograms oestradiol benzoate, with luteinizing hormone (LH) measurements at 0, +20 min (after GnRH) and +16 h (after oestradiol), enabled investigation of the positive feedback effects on the hypothalamus and pituitary. Control ewes had pretreatment LH values of 3.1 +/- 1.2 ng/ml with an increment of 3.2 +/- 2.3 ng/ml 20 min after GnRH. Subfertile ewes, in spite of elevated pretreatment LH concentrations (15.8 +/- 9.5 ng/ml) in eight out of 10 ewes, had increments of 1.4-84 ng/ml after GnRH. Control ewes had LH increments of 3-75 ng/ml 16 h after oestradiol. Subfertile ewes with pretreatment LH concentrations less than 15 ng/ml also responded to oestradiol whereas those with initial LH concentrations 16-40 ng/ml had no further LH increment. Subsequent administration of 1000 iu pregnant mares' serum gonadotrophin (PMSG), with measurement of LH and oestradiol at 0, +24, +30, +48, +54, and +72 h, allowed assessment of ovarian response and hypothalamus-pituitary function. Five control ewes were sampled up to 30 h post-PMSG and only 1 had oestradiol concentrations greater than 10 pg/ml. Sampling up to 72 h in another five control ewes resulted in oestradiol concentrations greater than 10 pg/ml. Increments in LH concentration greater than 3 ng/ml were recorded in control and subfertile ewes with oestradiol concentrations greater than 10 pg/ml. The use of these endocrine challenge tests enabled positive diagnosis of abnormality on 8 out of 10 occasions.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
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Plasma concentrations of cortisol, testosterone, glucose and blood gases in male goats during anaesthesia with pentobarbitone sodium.

Fasting for 24 h had no statistically significant effect on cortisol, glucose or testosterone concentrations. A dose of pentobarbitone sodium which induced light anaesthesia resulted in an immediate decrease in cortisol values from 5.0-11.1 ng/ml to 2.2-3.6 ng/ml until waking-this latter event was accompanied by an excessive release of cortisol (up to 16.6 ng/ml). In two out of three goats testosterone concentrations decreased from 4.0-9.0 ng/ml to less than 0.5 ng/ml after pentobarbitone; low values were maintained for 4.5-6 hours. Glucose concentrations were unaffected. Precise doses of pentobarbitone (20 mg/kg or 30 mg/kg) resulted in similar cortisol profiles as above but with higher concentrations achieved upon waking from the higher dose of pentobarbitone. On two out of nine occasions increased PCO2 values were recorded concurrently with increased cortisol concentrations during the period of anaesthesia, suggesting that a sufficiently strong stressful stimulus can break through the pentobarbitone blockade.

Anesthesia↗
PubMedDate not supplied

Pentobarbitone inhibits the stress response to transport in male goats.

Pentobarbitone (20 mg/kg i.v.) blocked plasma cortisol release when administered either before a 20 min journey or during a 2 h journey. This confirms that pentobarbitone can block stimulated, as well as resting, cortisol secretion. In general, blood glucose concentrations were not increased above 90 mg/100 ml until at least 30 min after the start of transport; however, this increase was also blocked by pentobarbitone administered 30 min into the 2 h journey. Significant increases in respiratory and heart rates occurred within 15 min of the start of transport; pentobarbitone caused an immediate decrease in these parameters. In conclusion, pentobarbitone was shown to reverse many metabolic changes induced by transport.

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PubMedDate not supplied

Mechanical properties of the ovine cervix during pregnancy, labour and immediately after parturition.

The stretch modulus (stress/strain) of strips of ovine cervical tissue in vitro was measured at different stages of gestation. A decrease in stretch modulus implies softening of the tissue. There was a gradual but progressive reduction in the stretch modulus with advancing pregnancy between 30 and 140 days gestation with a marked increase between 140 days gestation and the onset of labour (P less than 0.005). After the first trimester, the uterine end of the cervix was usually more distensible than the vaginal end. No further reduction in the stretch modulus of the cervix occurred between labour and delivery of the fetus. The results of this study suggest that while there is some softening of the ovine cervix during pregnancy, most of the softening takes place immediately prior to the onset of labour and delivery of the fetus.

Animals↗
PubMedDate not supplied

Effects of xylazine on the stress response to transport in male goats.

A 20-min van journey increased plasma cortisol concentrations to 15-25 ng/ml in male goats, blood glucose concentrations were not affected, but respiratory rates and heart rates were increased, the latter by 40 beats per min. A 2-h van journey increased plasma cortisol to greater than 25 ng/ml and blood glucose to greater than 5 mmol/l. Respiratory rates were increased to greater than 40 breaths per min and heart rates by greater than 100 beats per min. Xylazine alone (0.01 mg/kg) suppressed resting plasma cortisol concentrations, increased blood glucose concentrations to 4.5 +/- 0.8 mmol/l and suppressed respiratory rates by 5-10 breaths per min and heart rates by 20 beats per min. Cortisol concentrations were suppressed by xylazine treatment if given before a 20-min van journey, and for approximately 60 min if given 20 min after the start of a 2-h journey. When combined with transport, xylazine caused an additive effect on glucose concentrations, but suppressed respiratory and heart rates. However, for the latter criteria the timing of suppression was different depending on the time of onset and duration of the stressor. Injection of 50 micrograms ovine corticotrophin releasing factor (CRF) caused an immediate elevation of cortisol concentrations (but not glucose) which lasted for at least 6 h compared with the return to baseline within 60 min after either length of journey. Xylazine pretreatment did not alter the cortisol response to CRF, suggesting that xylazine must act centrally above pituitary level when blocking the cortisol response to transport. It is proposed that under resting conditions the hypothalamus is under alpha 2-adrenergic suppression. Stimulation of cortisol secretion in response to a stressor can be inhibited by an alpha 2-adrenergic agonist.

Animals↗
PubMedDate not supplied

Ultrasound and progesterone monitoring of ovarian follicular cysts in cows treated with GnRH.

Five cows, diagnosed as having follicular cysts (by palpation per rectum, ultrasonography and progesterone determination), were treated with 0.5 mg gonadotrophin releasing hormone (GnRH) 10 days after initial diagnosis. The ovaries were scanned weekly from the day of treatment (day 0) until day 35. Mean (+/- SEM) plasma progesterone concentration on the day of diagnosis (day -10) and day 0 were 0.2 +/- 0.13 ng ml-1 and 0.72 +/- 0.27 ng ml-1, respectively. Elevated progesterone (5.58 +/- 0.67 ng ml-1) was found in all cows by day 7 after treatment. Changes noted during weekly ultrasonography included clouding of the uniformly nonechogenic (dark) antrum of cysts, luteinization of the cyst wall, reduction in cyst size (cyst resolution) and/or development of 1-4 corpora lutea in the ovary bearing the cyst or in the contralateral ovary. Oestrus was observed in all cows 18.8 +/- 1.74 days after treatment. It is concluded that ultrasonography and progesterone determination are useful tools for veterinarians in the monitoring of responses of follicular cysts to treatment.

Animals↗
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Plasma glucose and cortisol responses to exogenous insulin in fasted donkeys.

Susceptibility to equine hyperlipaemia is increased by poor food intake. To assess the contribution of changes in insulin sensitivity, plasma glucose and cortisol responses to an intravenous insulin challenge (0.4 IU kg-1 bodyweight) were compared with those observed after saline administration in six donkeys fasted either overnight or for three days. Three days of fasting decreased both the rate of insulin-induced hypoglycemia and the maximal hypoglycemic response. A transitory increase in plasma cortisol which peaked within one to four hours of insulin administration was observed in three of the six overnight-fasted donkeys and in all of the three-day fasted donkeys; inter-animal variation appeared to exist in the responsiveness of the hypothalamic-pituitary-adrenocortical (HPA) axis to stimulation by insulin-induced hypoglycemia. Fasting is likely to present a risk of equine hyperlipaemia, at least on part, by the reduction in tissue sensitivity to the glucoregulatory action of insulin.

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Gastrointestinal studies in the green iguana: technique and reference values.

Five healthy green iguana (Iguana iguana) were used to determine appropriate technique and normal transit times for gastrointestinal contrast studies and to describe normal radiographic anatomy. The animals were maintained at 27-29 degrees C. There was rapid transit through a U shaped stomach, with a median gastric emptying time of 8 h, and median small intestinal transit and small intestine emptying times of 4 h and 16 h respectively. Median large colon transit and emptying times were 15 h and 66 h. Maintaining the iguana at a reduced ambient temperature increased all of these times. The vaso-vagal response or mechanical methods were adequate for restraint. A 25 ml/kg dose of a 25% w/v suspension of barium administered by stomach tube gave the best results. Lateral and ventrodorsal projections of the abdomen should be made immediately following the administration of the barium and at 1-hour intervals for the first 6 h and at 12-hour intervals thereafter until barium can be identified in the distal descending small colon.

Animals↗
PubMedDate not supplied

The psychological effects of breast screening in terms of patients' perceived health anxieties.

This study aimed to assess and compare the impact of letter of invitation, initial breast screening mammography, and subsequent recall procedures on the level of anxiety over breast problems. The survey of females undergoing routine breast screening procedures in a primary care setting is part of the first wave of a national breast screening programme in the UK. Women aged 50-64 registered with six general practices (n = 2618) were invited by letter to attend for screening. Their self-perceived impact of receipt of invitation letter, attendance at initial screening, and recall, in terms of anxiety and concern about breast problems, was measured by a self-report questionnaire and the physical, emotional and social dysfunction subscales of the Psychological Consequences of Screening Mammography Questionnaire (PCQ). Overall, subjects' anxiety levels diminished between the receipt of their invitation letter and the completion of their screening examination. Subjects did not, however, respond to the letter of invitation and screening procedure in a homogeneous manner. In a sample of 1253, the letter of invitation reduced anxiety about breast problems in 39.7%, increased anxiety in 24.6%, and had no appreciable effect in 35.7%. In the 1280 who attended for breast screening, the examination procedure reduced anxiety about breast problems in 55.9%, increased anxiety in 12.8%, and had no appreciable effect in 31.3%. In a smaller sample (n = 33) who completed questionnaires at recall, there were significant increases in PCQ-measured anxiety. Throughout the study, the PCQ was sensitive to change in anxiety over breast problems. We conclude that screening procedures can either increase or reduce anxiety about breast problems, or have no appreciable effect. Subjects' perception of the impact of receiving the letter of invitation and undergoing the screening examination procedure is related to previous levels of concern over breast problems. Conclusions about the psychological effect of breast screening cannot be drawn without consideration of the time and place of the baseline assessment. Participants in breast screening programmes therefore cannot be considered a homogeneous entity. Caution should be exercised when assessing the impact of screening procedures on entire populations as this approach might mask an important diversity of response.

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