Effect of high-protein feed supplements on concentrations of growth hormone (GH), insulin-like growth factor-I (IGF-I) and IGF-binding protein-3 in plasma and on the amounts of GH and messenger RNA for GH in the pituitary glands of adult rams.

Three groups of mature rams were maintained on diets of hay, hay + 2% lupin or hay + 2% cowpea for 11 weeks. Serial blood samples were taken at 15-min intervals for 12 h for the determination of GH and IGF-I content by radioimmunoassay and for IGF-binding protein-3 (IGFBP-3) levels by Western blotting. The rams were killed after 77 days of supplementary feeding and their pituitary glands analysed for content of GH and GH mRNA. Mean plasma GH and baseline GH levels were significantly (P < 0.01) decreased in the rams fed lupin and cowpea compared with controls fed hay and GH pulse amplitude was significantly (P < 0.001) decreased in the group fed the cowpea diet. The frequency of GH pulses was not significantly altered by either treatment. Plasma concentrations of IGF-I were elevated in rams fed lupin (P < 0.001) or cowpea (P < 0.05). IGFBP-3 levels were not significantly (P > 0.05) altered by either treatment. There were no significant differences in pituitary content of GH mRNA but pituitary content of GH was increased in rams fed lupin (P < 0.05) and cowpea (P = 0.07). In conclusion, a high-protein diet decreases plasma GH levels and increases IGF-I without changing plasma IGFBP-3 levels in rams. Thus ongoing synthesis of GH, as indicated by the mRNA levels, may cause a build up of GH stores in the pituitary gland.

Treatment of young rams with an agonist of GnRH delays reproductive development.

The objective of this study was to determine if the continuous treatment of young rams with an agonist of gonadotropin-releasing hormone (GnRH) in the period immediately prior to puberty would delay the onset of adult sexual behavior and retard testicular development. In the first experiment the GnRH agonist was shown to be effective in suppressing the plasma concentrations of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) in adult wethers (neonatally castrated rams) when administered by either a biocompatible slow release implant (implant) or a mini osmotic pump (minipump) that released the agonist for 4 weeks. The minipumps were more effective than the implants in suppressing the secretion of LH and FSH. In a second experiment, administration of the GnRH agonist by implant or minipump to prepubertal rams for 16 weeks immediately prior to puberty inhibited the development of sexual behavior, reduced the plasma concentrations of testosterone, retarded testicular and epididymal development, and inhibited growth rates. The effects on sexual behavior were clearly reversible but testicular and epididymal weights were still reduced in treated rams 8 weeks after the end of treatment. These results indicate that the reproductive function of rams is sensitive to gonadotropins and testicular hormones immediately prior to puberty. The agonist of GnRH was successfully delivered to the rams in a biocompatible implant which may offer a practical means of manipulating reproductive function in young rams.

An outbreak of gonadal hypoplasia in a sheep flock: clinical, pathological and endocrinological features, and aetiological studies.

In 1984, 31 per cent of 437 ram lambs reared on one property were found to have either bilateral or unilateral testicular hypoplasia. Similar numbers of ram lambs were reared in the next three years and 13, 2 and 0.5 per cent were affected. Severely abnormal testicles typically produced no spermatozoa and presented a 'Sertoli cell only' picture. Sixty-six of 200 ewe lambs born in 1984 were not marked by a harnessed teaser before mating; 12 of these were examined further and eight were found to have bilateral ovarian hypoplasia. The ovaries were very small and contained no oocytes or follicles. Plasma gonadotrophin levels were higher than normal in bilaterally affected rams and ewes but plasma testosterone and inhibin concentrations in rams with bilateral hypoplasia were not significantly different from those in normal rams. A genetic cause of the gonadal hypoplasia was considered unlikely in view of the pattern of occurrence and an examination of the flock pedigrees. No environmental cause was found. Two environmental sources of toxins were considered worthy of further investigation; onion grass (Romulea species) with its leaf spot fungus Helminthosporium biseptatum and the water supply which could have contained high concentrations of arsenic or other toxins during the period when the mothers of the affected lambs were in early pregnancy.

Changes in luteinizing hormone bioactivity associated with gonadotrophin pulses in the cycling mare.

Equine plasma luteinizing hormone (LH) possesses both biological (in vitro bioassay, B) and immunological (radioimmunoassay, I) activities and the ratio of B:I varies with stage of the oestrous cycle. To estimate the contribution made by pituitary secretion and peripheral metabolism to changes in the B:I ratio, pituitary venous effluent and circulating plasma from 5 dioestrous and 2 oestrous mares were analyzed using both an in vitro bioassay and a radioimmunoassay. During dioestrus, LH was released in a pulsatile fashion with a frequency of 1.4 pulses/24 h and a pulse duration of 20-40 min (centrally) or 2-4 h (peripherally). Between pulses, further secretion of LH from the pituitary was undetectable. During spontaneous pulses, the B:I ratio increased as much as 2- to 3-fold and remained elevated for at least 1 h. A low dose of 10 ng/kg bodyweight (bwt) of the GnRH agonist Buserelin provoked similar changes, unless the exogenous stimulus was close to an endogenous LH discharge. A high dose (50 micrograms) of Buserelin reduced the B:I ratio significantly, in spite of a massive LH release. Samples taken from mares during oestrus showed constantly elevated B:I ratios, a consequence of much greater LH pulse frequency.

Low and conventional dose cyclopenthiazide on glucose and lipid metabolism in mild hypertension.

In a double-blind, placebo controlled, randomised parallel study we investigated the antihypertensive activity and metabolic adverse effects of three doses of cyclopenthiazide in 53 patients with mild hypertension. After a 4 week placebo washout period, patients with diastolic blood pressures between 90-110 mm Hg were randomly assigned to receive 50 micrograms, 125 micrograms and 500 micrograms of cyclopenthiazide or matching placebo, over an 8 week active treatment period. Blood pressure was recorded at 2 weekly intervals during the trial. Venous samples were taken for evaluation of drug effect on indices of carbohydrate and lipid metabolism just prior to, and on completion of, the active treatment period. Systolic and diastolic blood pressure decreased significantly (P less than 0.05) with the 125 micrograms and 500 micrograms doses of cyclopenthiazide. No change was apparent in any index of glucose and lipid metabolism over time. Low and conventional doses of cyclopenthiazide lower blood pressure without alteration to the metabolic profile in the short term.

Determination of morphine in human plasma by radioimmunoassay utilising a preliminary liquid-solid extraction.

Numerous assays are available for the pharmacokinetic study of morphine. Two of these methods are compared with a new assay procedure, which involves a solid-phase extraction to clean up human plasma before radioimmunoassay allowing the determination of morphine levels to a sensitivity of 1 mugl(-1). Data are presented to show the importance of correct method choice if clinical studies are to be used in pharmacokinetic interpretations.

The effect of midazolam (Hypnovel) administration on antipyrine pharmacokinetics in humans.

1. Twelve healthy volunteers were given a standard regimen of oral midazolam (Hypnovel) (15 mg nightly) for 10 consecutive nights. 2. Antipyrine pharmacokinetics were studied immediately before midazolam administration was started, after the dosage schedule had been completed and one week after dosing had been discontinued. 3. No statistically significant changes were seen in the disposition of antipyrine as assessed by the plasma half-lives, areas under the curve and plasma clearances. Therefore, although previous studies have demonstrated that high doses of midazolam induced the drug-metabolising enzymes in laboratory animals, such effects are unlikely to occur in humans being treated with therapeutic doses.

A clinical trial using a regimen which includes a norgestomet implant and norgestomet plus oestradiol valerate injection as a treatment for anoestrus in dairy cows.

In seasonally calving dairy herds in the Macalister Irrigation Area of Gippsland, Victoria, cows that had not been observed in oestrus by the start of the mating season and which had inactive ovaries based on rectal palpation and progesterone assay were treated with a hormonal treatment (n = 49). Mature cows had calved at least 40 days previously and 2-year-olds had been calved at least 60 days. The treatment consisted of a norgestomet implant and a norgestomet and oestradiol injection on day 1; prostaglandin analogue Prosolvin) on day 8; withdrawal of implant on day 10 and an injection of PMSG; and fixed time artificial insemination 54 to 56 h after implant withdrawal. This treatment was called the Syncro-mate regimen. Control cows (n = 46) were injected with water on days 1, 8 and 10 and artificially inseminated or served by a bull when seen on heat. Forty seven percent of the treated cows became pregnant within 14 days from the start of treatment compared with 20% of control cows (P less than 0.01). There was an effect of age group on the response to treatment. A greater proportion of 2-year-old cows than mature cows became pregnant within 14 days of treatment (79% of 19 v. 27% of 20; Chi square interaction, treatment by age, 6.4, P less than 0.05). In the younger cows there was also a gain of 22 days in the treatment to conception interval over the control cows (P less than 0.001). It was concluded that the Syncro-mate regimen can be an effective treatment for post partum anoestrus in dairy cows under certain conditions.

Pharmacokinetics of single and multiple doses of flusoxolol (Ro 31-1411) in healthy subjects.

Flusoxolol (Ro 31-1411) is the pharmacologically active optical isomer of Ro 31-1118, a potent cardioselective beta-adrenoceptor antagonist with partial agonist activity. It was given to 6 healthy volunteers in a single dose, 40 mg, and then in multiple doses, 40 mg daily for 8 days. Plasma concentration data were best described by a linear two-compartment pharmacokinetic model with first order absorption, and the results confirmed linear kinetics. Pharmacokinetic data for flusoxolol were comparable to those for the racemate Ro 31-1118.

Human pharmacokinetic and pharmacodynamic studies on Ro31-1118, a new beta-adrenoceptor antagonist.

The pharmacokinetic and pharmacodynamic effects of Ro31-1118 were examined in groups of healthy volunteers. In three subjects given 10 mg of [14C]-Ro31-1118 orally, peak levels of radioactivity (84 +/- 5 ng/ml) were 16 times those of the parent drug (approximately 5 ng/ml). Very little parent drug was recovered in the urine, although recovery of total radioactivity was nearly 80% in the urine by day 5. In five subjects studied after both oral and intravenous administration of 20 mg Ro31-1118 the average bioavailability was 57% (range 41-73%). Following intravenous infusion the apparent volume of distribution for the five subjects averaged 590 1 (range 510-700 1). The elimination half-life averaged 18 h (range 17-26 h). In eight subjects who received 40, 80, 160 and 320 mg of Ro31-1118 orally there was a linear relationship between dose and plasma concentration (r = 0.999) and between dose and AUC (r = 0.996). Ro31-1118 had no effect on resting heart rate whereas atenolol reduced resting heart rate up to 6 h after all doses. The maximum reduction of an exercise tachycardia after Ro31-1118 (320 mg) was 23.13 +/- 0.7% and compared with atenolol (100 mg) was 28.2 +/- 1.25%. At 24 h the percentage reduction after Ro31-1118 was 21.5 +/- 1.7%, while after atenolol the percentage inhibition had decreased to 11.1 +/- 1.6%. In three subjects Ro31-1118 (160 mg) orally had no effect on resting heart rate, forearm blood flow and systolic blood pressure, while atenolol (50 mg) reduced all three parameters.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of bromazepam (Lexotan) administration on antipyrine pharmacokinetics in humans.

Six healthy volunteers were given a standard regimen of bromazepam (Lexotan) (6 mg t.d.s.) for five days. Compliance with the study protocol was demonstrated by measuring drug concentrations at steady state. Steady-state levels of 3-hydroxybromazepam were also determined. These were found to be much lower than the concentrations of bromazepam. Since the metabolite is known to be less active than the parent drug, it is likely that the metabolic will contribute little to the pharmacological effects of the drug in humans. Antipyrine pharmacokinetics were studied immediately before bromazepam administration was started, after the dosing schedule had been completed and one week after dosing had been discontinued. There were no significant changes in the disposition of antipyrine on any occasion. Therefore, although previous studies have demonstrated enzyme induction in laboratory animals given high doses of bromazepam, similar effects are unlikely to occur in humans being treated with therapeutic doses of the compound.

An assessment of faecal blood loss from Ro 21-5521, a novel non-steroidal anti-inflammatory agent, in normal volunteers.

Faecal blood loss arising from Ro 21-5521, a novel non-steroidal anti-inflammatory agent with a long plasma half-life of about 41 hours, was evaluated in a double-blind crossover study against matched placebo in 12 volunteers. After a 1-week run-in period to determine baseline values, subjects were allocated at random to receive either 250 mg Ro 21-5521 per day or placebo for 2 weeks before being crossed over to the alternative treatment for 2 weeks. They were then followed-up for a further 2 weeks. Blood loss was calculated from 51Chromium tagged red blood cells in stools collected for a 96-hour period during each week of the study. Plasma levels of Ro 21-5521 were also measured twice weekly throughout the study. The results showed that with a drug of this long half-life, faecal blood loss may continue for at least 4 weeks after cessation of trial therapy of 2 weeks. It is recommended that in the evaluation of faecal blood loss resulting from drugs with a long half-life, a parallel group study, each group receiving only one drug (or one drug crossed against placebo), is the study design of choice.

Gastro-intestinal blood loss with high dose tilcotil (Ro 12-0068) and aspirin: an open crossover clinical trial and pharmacokinetic assessment in normal volunteers.

An open crossover study was carried out in 8 normal volunteer subjects to compare faecal blood loss resulting from tilcotil (Ro12-0068), a new anti-inflammatory agent, and from enteric-coated aspirin. After a 1-week run-in period, subjects were allocated at random to receive treatment for 2 weeks with either 40 mg tilcotil as a single dose per day or aspirin, 900 mg 4-times daily, reduced if necessary to a maximum tolerated dose. Subjects were then crossed over to the alternative treatment for a further 2 weeks. The results showed that tilcotil produced less blood loss, assessed by a radioactive labelling method, and was better tolerated than aspirin. Plasma concentrations of tilcotil showed that the drug's half-life was approximately 50 hours, compatible with once daily dosage, and steady state concentrations on multiple dosing were reached after 10 to 12 days.

A comparison between gastrointestinal blood loss caused by tilcotil (Ro 12-0068) and aspirin in normal volunteers.

An open crossover study was carried out in 6 normal volunteers to measure faecal blood loss caused by tilcotil (Ro 12-0068), a new anti-inflammatory drug, compared with that caused by enteric-coated aspirin. Subjects were allocated at random to receive either single doses of 20 mg tilcotil daily or 900 mg aspirin 4-times daily, reducing to a maximum tolerated dose, over a period of 2 weeks before being crossed over to the alternative medication for a further 2 weeks. Faecal specimens passed during 4 consecutive days in a run-in-period of 1 week, in each treatment period, and in the 2 weeks after the finish of drug therapy were analyzed for blood using a radioactive labelling method. The results showed that faecal blood loss was lower and it did not produce any haematological or biochemical abnormalities or any increase in urinary N-acetyl-beta-glucosaminidase activity indicative of renal damage. It is suggested that the method described provides a simple and reliable means of comparing faecal blood loss with different anti-inflammatory drugs.