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Biomedical subjects

J Hoover

Publications and source records attributed to J Hoover.

5 recordsLinked to original sources
PubMed1991

Effect of chronobiological alteration of the circadian rhythm of prolactin and somatotropin release in the dairy cow.

The objective of this study was to determine if a skeletal photoperiod administered at the appropriate time of a 24-h day could stimulate prolactin and somatotropin release in dairy cattle. Cows in mo 8 of gestation were exposed to either 12 to 13 h of continuous light or to three skeletal photoperiods consisting of a total of 8 h of light. Cows in the skeletal photoperiod light regimens received 6 h of light from 0500 to 1100 h and a 2-h light pulse at either 1500 to 1700 h, 1800 to 2000 h, or 2100 to 2300 h. Cows exposed to the light regimen pulse at 1800 to 2000 h exhibited a circadian rhythm of prolactin and somatotropin release. The mean prolactin and somatotropin concentrations were also higher in this treatment. It is concluded that a circadian rhythm with a photosensitive phase is present for prolactin and somatotropin release in the lactating dairy cow. The photosensitive phase for both hormones occurs between 13 and 15 h after subjective dawn. The expression of the circadian rhythm of these hormones depends on the photoperiod to which cows are exposed.

Animals↗
PubMed1979

Altered plasma lipid and lipoprotein levels associated with oral contraceptive and oestrogen use. Report from the Medications Working Group of the Lipid Research Clinics Program.

In a study of women attending ten North American Lipid Research Clinics plasma total cholesterol, triglyceride, low density (L.D.L.), very low density (V.L.D.L.), and high density (H.D.L.) lipoprotein levels in those taking oral contraceptives (O.C.) and in those taking oestrogens for menopausal symptoms were compared with those in women not taking gonadal hormones, after adjustment for age, educational attainment, and body-mass index, O.C. and oestrogen users were leaner than non-users. Compared with controls, O.C. users showed increased cholesterol, triglyceride, and L.D.L.-cholesterol and V.L.D.L.-cholesterol levels, but H.D.L.-cholesterol levels were similar. Cholesterol, triglyceride, and H.D.L.-cholesterol and V.L.D.L.-cholesterol levels were positively associated with the quantity of the oestrogen component of the O.C. preparations. Compared with non-users, menopausal oestrogen users had slightly lower cholesterol and triglyceride levels, significant decreases in L.D.L.-cholesterol and V.L.D.L.-cholesterol, and a significant increase in H.D.L.-cholesterol.

Adolescent↗
PubMed1977

Altered plasma-lipids associated with oral contraceptive or oestrogen consumption. The Lipid Research Clinic Program.

Mean plasma cholesterol and triglyceride concentrations were measured in White female users and non-users of oral contraceptives and oestrogens in 10 diverse, demographically defined North American populations. About 50% of the younger women (20-24 years old) were taking oral contraceptives. In these women mean triglyceride concentrations were up to 48% higher and mean cholesterol concentrations were about 5% higher than in non-users. The 95% percentile of the total lipid distribution among non-users was used to define hyperlipidaemia. In young women on oral contraceptives hypercholesterolaemia was up to three times more common and hypertriglyceridaemia was up to five times more common than in non-users. 37% of older women (50-54 years) (presumably intramenopausal and postmenopausal) were hormone users, and in this group there were small, inconsistent alterations in plasma-triglyceride and a modest but consistent reduction in mean cholesterol concentration.

Adolescent↗
PubMedDate not supplied

The prevalence of smokeless tobacco use in native children in northern Saskatchewan, Canada.

We used a self-administered questionnaire to develop a profile of smokeless tobacco use among 1,170 Canadian native children aged 7 to 21 years attending schools situated in remote communities in northern Saskatchewan. Nearly 30% of the sample were current users of smokeless tobacco; more than 50% of users began to use these products before the age of 12 years. More males than females chewed tobacco or dipped snuff. The results revealed a relatively high prevalence of smokeless tobacco users among the present sample of native children and were found to be consistent with data from other studies of similarly aged native populations. The results also showed a prevailing pattern of addiction among the users of smokeless tobacco. It is suggested that educational programs aimed at preventing or reducing the use of tobacco products among native populations be intensified and as well, these programs would benefit from the active participation of trained native personnel.

Adolescent↗