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Biomedical subjects

T Nicholson

Publications and source records attributed to T Nicholson.

At least 19 recordsLinked to original sources
PubMed1992

Inhibition of food intake and reticulo-rumen motility of sheep by the alpha-2 adrenoreceptor agonist clonidine.

The investigation of the effect of intravenous clonidine, an alpha-2 adrenoreceptor agonist, was carried out in sheep with recording of forestomach motility for 3 h and intake of chopped hay for 8 h after drug administration. Motility and food intake were inhibited by clonidine at 2 micrograms.kg-1 and at 5 micrograms.kg-1. The effects of the lower dose were prevented by idazoxan, an alpha-2 antagonist, at 0.1 mg.kg-1 but not by prazosin, an alpha-1 antagonist, at 0.1 mg.kg-1. Minor effects of the antagonists alone were noted. Blood glucose concentration was measured in all the experiments and the possibility discussed that changes in concentration, not absolute values, may have contributed to inhibitory effects. Vagal stimulation in anaesthetised sheep indicated that inhibition of motility was a central neural effect, not an effect on forestomach muscle.

Animals↗
PubMed1991

Alpha-2 adrenoreceptors mediate clonidine-induced hypoinsulinaemia in sheep.

Insulin and glucose concentrations in the blood of sheep were measured before, and up to 7 h after, feeding. The patterns reported by other workers were confirmed, namely: an early insulin concentration peak and decline in glucose concentration and, later, more prolonged changes. Intravenous injection of clonidine (2 micrograms/kg or 5 micrograms/kg) just before offering food caused hypoinsulinaemia and hyperglycaemia, abolishing the normal patterns. Administration of idazoxan (0.1 mg kg-1), an alpha-2 adrenoreceptor antagonist, before a 2 micrograms/kg dose of clonidine, completely blocked the effects of clonidine. By contrast, with prior injection of prazosin (0.1 mg/kg), an alpha-1 adrenoreceptor antagonist, the hypoinsulinaemia in response to clonidine still occurred and the hyperglycaemia appeared to be enhanced. The antagonists injected alone had only slight effects: idazoxan caused a slight hypoglycaemia and prazosin a slight hyperglycaemia. The results indicate that clonidine causes hypoinsulinaemia and hyperglycaemia by action on alpha-2 receptors. Possible mechanisms are discussed.

Adrenergic alpha-Antagonists↗
PubMed1991

The inhibition of the reticular groove reflex in sheep by clonidine.

Intravenous clonidine, an alpha-2 adrenoreceptor agonist, at 2 micrograms.kg-1 and 4 micrograms.kg-1, inhibited the activation by oral copper sulphate of the reticular groove reflex in adult sheep. The plasma concentration of xylose after oral dosing was used as an indicator of groove activation. The inhibition was prevented by prior injection of an alpha-2 antagonist, idazoxan. Indirect evidence of prolongation of intestinal transit time was found with the lower dose of clonidine. Idazoxan injected alone appeared to increase the absorption of xylose.

Animals↗
PubMed1991

The Health Knowledge Inventory-Alpha: a personal health knowledge test for high school seniors.

This study assessed validity and reliability of the Health Knowledge Inventory-Alpha (HKI-Alpha) in a sample of high school seniors. The HKI-Alpha, a general health knowledge test, consists of 110 multiple choice items covering 11 health content areas. All seniors attending one of four high schools completed HKI-Alpha twice, one week apart. A secondary sample of college students also was tested. Descriptive analysis revealed the test discriminated among examinees and avoided ceiling and floor effects. Test-retest reliability was .81 (n = 355). Internal consistency reliability (KR20) was .85 (n = 418). A sample of college students scored significantly higher than the high school students, demonstrating construct validity. Other estimates of content validity, criterion-related validity, and construct validity were high.

Adolescent↗
PubMed1990

Rumination may be stimulated by a recording balloon in the reticulum of the sheep.

Rumination activity was recorded by three different methods in five sheep which had been fasted for 12 hours. When a balloon on plastic tubing was passed into the reticulum via a rumen cannula there was significantly more rumination recorded during the subsequent three hours than when rumination was recorded by registering jaw movements alone. The greater part of this stimulation occurred in the first half hour of recording. There was a significantly greater effect when the tubing to the reticulum balloon was stiffened with wire. Care is needed in comparing rumination times determined by different procedures.

Animals↗
PubMed1988

Inhibition of rumination in sheep by alpha-adrenoreceptor antagonists.

Rumination activity was recorded in sheep during a period of 3 h. The amount of rumination occurring in 30 min following the intravenous injection of an alpha 1 blocking drug (prazosin, 0.1 mg/kg) and an alpha 2 blocking drug (idazoxan, 0.1 mg/kg) was reduced compared with control days when saline was given. The observation that rumination can be stimulated by a rapid, intravenous dose of adrenalin was confirmed. The induction of rumination by adrenalin was prevented by these alpha-adrenoreceptor antagonists given singly or together at the dose rate mentioned. These findings are discussed in the light of knowledge that normal reticulo-ruminal motility and food intake can be inhibited by stimulation of alpha 2-adrenoreceptors.

Adrenergic alpha-Antagonists↗
PubMed1987

Characteristics of the frequent visitor to the industrial medical department and implications for health promotion.

The number of visits to an in-house industrial medical clinic, of absences in three categories, and of late arrivals found in 1,505 employees of an automobile assembly plant were compared with respect to the age, sex, race, department, and shift characteristics of the employees. Less than 16% of the work force was found to account for over 50% of the medical visits. Those 235 frequent visitors were found to have significantly more absences and more tardiness compared with the rest of the plant population. The frequent visitors who completed a health risk appraisal had significantly greater health risks compared with a responding sample of nonfrequent visitors.

Absenteeism↗