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Biomedical subjects

A L Johnson

Publications and source records attributed to A L Johnson.

At least 253 records · Page 14Linked to original sources
PubMed1984

Failure of castration to prevent the prepubescent decline in the circulating concentration of growth hormone in the domestic fowl.

In the domestic fowl, plasma concentrations of growth hormone (GH) have been observed to be elevated in young, rapidly growing chicks and low in older chicks and in adults. In this present study the plasma concentration of GH was high in 35-day-old male chickens and declined to the low adult concentration by 91 days of age. This decrease was observed in male chickens irrespective of whether they remained intact, were castrated at 35 days of age, or were castrated and implanted with testosterone. The plasma concentrations of GH in castrated birds were lower than those in the controls at 49 and 63 days of age. As would be expected, the plasma concentrations of luteinizing hormone (LH) were elevated by castration while testosterone implantation reduced the castration-induced rise in LH concentrations. Castration was followed by very low but detectable plasma concentrations of androgen. These were increased by testosterone implants.

Aging↗
PubMed1984

Factors in the dose-response effect of testosterone in the male ring dove.

The dose-response effect of testosterone propionate on six behavioral patterns was examined in the castrated male ring dove. There was no dose-response effect when all behaviors were compared on the 13th day, the last day of systemic injection. However, a discernible dose-response effect in two behavioral patterns (Bow-coos and Nest-coos) was found on the day when maximal response was manifested. The latency (days) of maximal response differs from one behavioral pattern to the next, but is generally constant for each behavioral pattern at all dose levels.

Animals↗
PubMed1984

Continuation therapy with lithium and amitriptyline in unipolar depressive illness: a randomized, double-blind, controlled trial.

A detailed analysis of the results of a multi-centre clinical trial shows that, while the relapse rate following recovery from an operationally defined depressive illness was smaller among patients subsequently treated with either amitryptiline or lithium than with a placebo, there was no clinically significant difference between the prophylactic efficacy of the 2 antidepressants. An account is given of the relative adverse effects of the treatments, and the implications of the findings are discussed.

Adult↗
PubMed1984

Ovulatory response, and plasma concentrations of luteinizing hormone and progesterone following administration of synthetic mammalian or chicken luteinizing hormone-releasing hormone relative to the first or second ovulation in the sequence of the domestic hen.

Experiments were conducted to investigate hypophyseal and follicular competency at two distinct stages of the hen's egg laying sequence: 1) 14 h prior to the first (C1) ovulation of a sequence (27 h following the previous ovulation); and 2) 14 h prior to the second (C2) ovulation of a sequence (13 h following the previous ovulation). When a single dose of mammalian luteinizing hormone-releasing hormone (mLHRH) or chicken luteinizing hormone-releasing hormone (cLHRH) was injected 14 h prior to a C1 ovulation, premature ovulation was induced in 19 of 20 hens. In contrast, ovulation was premature in only 1 of 20 hens when mLHRH or cLHRH was injected 14 h prior to a C2 ovulation. There was no difference between the two stages of the sequence in the amount of luteinizing hormone (LH) released for up to 60 min following a single i.v. injection of 20 micrograms mLHRH. However, only prior to a C1 ovulation did LH levels further increase to reach preovulatory concentrations. By contrast, progesterone (P4) concentrations were increased within the first 60 min to a lesser extent in hens injected prior to a C2 ovulation compared to a C1 ovulation. In C2-injected birds, P4 fell to levels that were not different from vehicle-injected controls by 45 to 60 min following injection, whereas P4 secretion was maintained in hens injected prior to a C1 ovulation. We suggest that the lack of sustained LH secretion following treatment with either species of LHRH 14 h prior to a C2 ovulation is related to follicular immaturity with respect to ability to produce and secrete P4. At the dosage administered, there was no difference in the ability of mLHRH compared to cLHRH to release LH at either stage of the sequence. Finally, two successive injections of mLHRH at 14 and 13 h prior to a C2 ovulation induced premature ovulation in 6 of 11 hens. It is suggested that LH, and possibly P4, exerts a priming effect on the largest preovulatory follicle to initiate fully potentiated P4 production and secretion.

Animals↗
PubMed1984

Anticonvulsant drugs alter plasma tryptophan concentrations in epileptic patients: implications for antiepileptic action and mental function.

In epileptic patients carbamazepine and diphenylhydantoin have opposite effects on whole and free plasma tryptophan concentrations, the former elevating and the latter depressing them. It is unlikely that these observations relate to the similar anti-epileptic properties of these two drugs but they may relate to their different effects on mental function and mood.

Adolescent↗
PubMed1984

Effects of aminoglutethimide on luteinizing hormone and steroid secretion, and ovulation in the hen, Gallus domesticus.

Two experiments were conducted: 1) to assess the ovulation-blocking ability and steroidogenesis-inhibiting activity of aminoglutethimide in the laying hen; and 2) to determine whether LHRH or progesterone (P4) administration can overcome the ovulation-blocking effect of aminoglutethimide. Aminoglutethimide inhibited ovulation and suppressed the secretion of P4 and testosterone (T) in a dose-related fashion. In the absence of any increase in plasma P4 and T, there was no preovulatory increase in plasma LH. These results indicate that the preovulatory surge of LH is initiated by an increase in steroid. The effectiveness of P4 and LHRH to stimulate LH release and overcome the ovulation-blocking effect of aminoglutethimide was tested in the second experiment. Administration of 500 micrograms P4 (im) to aminoglutethimide-treated hens resulted in a significant and sustained release of LH [peak, 3.08 +/- 0.62 (+/- SEM) ng/ml; 120 min after injection] and induced ovulation in the absence of any increase in plasma T or estrogen. In contrast, injection of 20 micrograms LHRH (iv) failed to overcome the blocking effect of aminoglutethimide and caused an attenuated (peak, 2.17 +/- 0.37 ng/ml; 60 min after injection) and short-lived increase in plasma LH. These results are consistent with the model for a true positive feedback mechanism in which P4 initiates and sustains the preovulatory LH surge of the hen.

Aminoglutethimide↗
PubMed1984

Effects of castration, with and without testosterone replacement, on leg bone integrity in the domestic fowl.

Studies were conducted to assess the effects of castration on leg bone integrity of male White Leghorn chickens. Eighteen 5-week-old males were randomly allocated to 3 groups: group 1--intact controls, group 2--castrated, and group 3--castrated and subsequently treated with testosterone (T)-filled Silastic capsule implants. Body weight and plasma concentrations of luteinizing hormone, androgens, and total calcium were measured in each bird at intervals throughout the experiment. Subsequently, radiographs were performed upon the tibiotarsus-tarsometatarsus region of the left limb of birds from the 3 treatment groups at 7, 35, and 47 weeks of age and assigned a score of 1 to 3 (1 = normal; 3 = greatest pathologic change). Analysis of radiologic scores indicated that at 35 and 47 weeks, castrated birds (group 2) had a mean score significantly greater than that of control birds (group 1). The abnormality was typified by hyperossification with exostoses in the ossified tibial cartilage and lateral calcaneal ridge. In contrast, radiologic scores from individual T-implanted castrated birds (group 3) at 35 and 47 weeks were more variable, but the mean score was not statistically different from that of the control group. We conclude that the depression of circulating concentrations of sex steroids, by castration, in young male chickens results in hypercalcification of the tibiotarsus-tarsometatarsus region of the limb. This effect appears to be mediated directly or indirectly by T or a metabolite of T.

Animals↗
PubMed1983

Yeast mutants affecting the spontaneous mutation frequency on both the mitochondrial and nuclear genomes.

We have previously described two complementation groups of mutants affecting the spontaneous mutation frequency on the mitochondrial genome (Johnston, 1979). In a further search for such mutants the majority isolated fell into one of these groups, 3 into group I and 14 into group II. There are now a total of 12 alleles in the first group and 19 in the second complementation group, suggesting that these are the major classes of mutants affecting spontaneous mutation frequency in the mitochondrion. However, this search also identified a third complementation group, consisting of 2 mutants, which, like the existing groups, is recessive and is coded on the nuclear genome. In contrast to complementation groups I and II, these new mutants have no effect on spontaneous petite mutagenesis and they also increase the spontaneous mutation frequency on the nuclear genome. This nuclear mutation activity may be novel, as it complemented the existing nuclear mutators mut1-mut10. None of the three complementation groups has any detectable phenotype, other than the mutator activity.

Cell Nucleus↗
PubMed1983

Low risk of late post-traumatic seizures following severe head injury: implications for clinical trials of prophylaxis.

A randomised, controlled, double-blind clinical trial designed to determine the effectiveness of phenytoin in preventing epilepsy in patients who had suffered a serious head injury is reported. One hundred and sixty-four patients were randomly assigned to treatment with phenytoin or placebo capsules for one year. Patients who had a fit within one week of injury were excluded. Drug levels were monitored throughout with appropriate dosage adjustment; however only 48% of the phenytoin group had plasma levels greater than 40 mumol/l. There were seven deaths during the study. Only 11 patients (six in the phenytoin group and five in the placebo group) developed post-traumatic epilepsy within one year; a further four patients developed seizures between 1 and 2 years after injury. This low incidence of post-traumatic epilepsy (7% (SE 2%) at one year and 10 (SE 2%) at two years) means that future clinical trials of prophylaxis will have to be much larger (at least six fold).

Adolescent↗
PubMed1983

Progesterone-induced delay of the onset of lay in the prepubertal pullet.

Thirty-six 119-day-old White Leghorn pullets were administered either a 2 cm progesterone (P4) implant or an empty (control) implant. Plasma samples drawn at 7, 14, and 43 days postimplant were assayed for P4 and luteinizing hormone (LH), and the day of first egg production and total egg production to 200 days of age was recorded. Treatment with P4 significantly elevated plasma concentrations of P4 at all sampling intervals and depressed plasma LH at the sampling intervals 14 and 42 days postimplant. In addition, P4 treatment significantly delayed the mean time of the onset of egg production by greater than 16 days and decreased the total number of eggs laid to 200 days of age. It is suggested that P4 can inhibit LH secretion in the prepubertal pullet. However, from the present study, it is not possible to determine whether the decrease in plasma LH in P4-implanted birds is directly or indirectly related to the delayed onset of egg production.

Age Factors↗
PubMed1982

A post-mortem study of the cholinergic and GABA systems in senile dementia.

Choline acetyltransferase (ChAT) activity and gamma-aminobutyric acid (GABA) concentration were measured in 19 cerebral cortical areas and 22 subcortical areas of brains from 26 control and 25 histologically proven cases of Alzheimer's disease. Reduced ChAt activity was observed in all the cortical areas examined in the Alzheimer cases dying before the median age of 79 years. In the Alzheimer cases aged greater than 79 years at death, 7 out of the 9 frontal cortical areas had a normal ChAT activity when compared with controls. Significant reductions in GABA concentrations in the Alzheimer cases were confined to the temporal cortex. Significant reductions in ChAT activity in subcortical areas were confined to 8 of the 22 regions examined. Notably these included the septal nuclei and substantia innominata, the proposed origins of the cholinergic projections to the hippocampus and neocortex, respectively. There were no reductions in GABA concentrations outside the cerebral cortex. Four multi-infarct cases and 6 cases with normal histology were found to have a small reduction in ChAT activity confined to only a few areas. The data are consistent with a predominant loss in Alzheimer's disease of the diffuse cholinergic projection from the brainstem and basal forebrain.

Aged↗
PubMed1982

A placebo-controlled study to determine the efficacy of oral disopyramide phosphate for the prophylaxis of ventricular dysrhythmias after acute myocardial infarction.

1 To evaluate oral disopyramide phosphate in the prophylaxis of dysrhythmias occurring in acute myocardial infarction (MI) patients (presenting within 12 h of symptoms, age 21-70 years), a placebo-controlled, randomized double-blind, in hospital trial was conducted. After prognostic stratification (anterior and non-anterior MI at each of 4 regional hospitals) patients were randomly assigned to receive oral disopyramide phosphate (loading dose 150, 200, or 300 mg followed 6 h later by 100, 150, or 200 mg every 6 h for patients assessed to weigh less than 55, 55-85, or greater than 85 kg, respectively or matching placebo. The primary exclusion criteria were overt heart failure, systolic BP less than 100 mmHg, significant heart block or history of urinary retention. Active drug or placebo was continued for 7 days or until (a) detection of "warning arrhythmias' requiring i.v. lignocaine intervention (greater than 5 for 7 days or until (a) detection of "warning arrhythmias' requiring i.v. lignocaine intervention (greater than 5 premature ventricular contractions (PVCs)/min, R on T PVCs, multifocal PVCs, bigeminal PVCs, ventricular tachycardia or ventricular fibrillation) or (b) onset of exclusion criteria. In addition, plasma drug concentrations were determined and 24 h electrocardiographic tapes were obtained on day 1, and on one of days 4-7 but these results are not presented here. 2 Out of 121 patients entering the trial, 101 had confirmatory ECG and enzyme changes. Of these, 9 of 47 patients receiving disopyramide phosphate required lignocaine compared to 20 of 54 receiving placebo (19% v 37%; P = 0.047). Corresponding numbers for patients discontinuing trial medication for other non-fatal complications of MI were 5 and 3, and for those dying, were 3 (2 infarct extensions and 1 massive infarction), and 0, respectively. Respective numbers discontinuing trial medication for possible drug side effects (viz. urinary retention requiring catheterization) were 6 and 1 (P = 0.031). 3 In circumstances where i.v. therapy is deemed impractical, use of oral disopyramide phosphate given prophylactically in patients with acute MI may reduce the incidence of "warning arrhythmias' by a clinically significant extent.

Adult↗
PubMed1982

Effect of selected light treatments on pineal weight and lipid content in the cockerel (Gallus domesticus).

The effect of early and prolonged exposure of growing cockerels to selected photoperiods and wavelengths of light on pineal gland weight and lipid composition was investigated. The six treatments included 14L:10D white (control), 24L:OD white, OL:24D dark, and 14L:10D narrow-band blue, green or red light. Pineal gland fresh and dry weights were greatest under the white light treatment and least under the dark and red treatments. Examination of histological preparations and biochemical analysis both indicated that the absence of light depleted pineal lipid. When expressed as a percent of dry tissue weight, lipid from the colored light treatments was significantly greater than from the control. We conclude that both the photoperiod and the wavelength of light are capable of influencing pineal gland lipid metabolism in the cockerel.

Animals↗