Experimental studies of shift-work. II. Stabilized 8-hour shift systems.
Explore the source record for details and available documents.
Adaptation, Physiological↗
Biomedical subjects
M J Blake
Publications and source records attributed to M J Blake.
Relationship between circadian rhythm of body temperature and introversion-extraversion.
Explore the source record for details and available documents.
Body Temperature↗
Effects of exercise training on brain opioid peptides and serum LH in female rats.
In order to investigate the effects of long-term exercise training on brain endorphin systems, and the latter's possible effects on the hypothalamic-pituitary-gonadal axis, female Wistar rats were subjected to daily treadmill running. A sedentary control group was also employed. After 8 weeks of training, and just prior to sacrifice, one-half of each group received a final fatiguing bout of exercise. Thus the final four groups consisted of a trained-fatigued (TF), trained-nonfatigued (TN), control-fatigued (CF), and control-nonfatigued (CN) group. Regional brain levels of beta-endorphin (beta E), methionine enkephalin and leucine enkephalin (LE) were assayed with independent RIAs from the nucleus accumbens, cortex, caudate-putamen, septum, amygdala, anterior and posterior hypothalamus, substantia nigra and ventral tegmentum. Diestrus serum levels of luteinizing hormone (LH), follicle stimulating hormone and prolactin (PRL) were also determined. Fatiguing resulted in a decrease in serum LH levels as well as an increase in beta E content in the nucleus accumbens, and LE content in the ventral tegmentum. Finally, TF animals exhibited less LE in the amygdala than the TN rats. Taken together, these changes in brain endorphins may indicate an acute, fatigue-running modulation of the hypothalamic-pituitary-gonadal axis.
Analysis of Variance↗
Muscarinic acetylcholine receptor subtype mRNA expression and ligand binding in the aged rat forebrain.
Previous studies indicate that a 20-30% decline in muscarinic acetylcholine receptor binding occurs in localized areas of rat brain during aging. In this study, reduced [3H]-quinuclidinyl benzilate binding was observed in striata from 24-25-month-old rats relative to 5-6-month-old animals using homogenate binding assays. To determine if the decline in receptor concentration occurs as a result of decreased receptor synthesis, the expression of the m1, m3, and m4 muscarinic receptor mRNAs as well as [3H]-QNB binding were determined in adjacent sections of young and old male rats using in situ hybridization and in vitro receptor autoradiography respectively. A significant decline in collective muscarinic receptor binding as assessed by [3H]-QNB was observed in the caudate putamen, olfactory tubercle, nucleus accumbens, and several frontal and parietal cortical areas. The only difference observed in muscarinic mRNA expression for any of the three subtypes examined was a decline in m1 hybridization in the olfactory tubercle. The results of this study demonstrate that the regional brain areas displaying age-related decreases in receptor binding do not correlate with those areas showing a decrease in muscarinic receptor expression. Apparently, the decline in muscarinic acetylcholine receptor density with age does not result from a decline in receptor gene expression.
Aging↗
Dynamic but not static cerebral autoregulation is impaired in acute ischaemic stroke.
It remains unclear as to whether dynamic and static cerebral autoregulation (CA) are impaired in acute ischaemic stroke, and whether these changes are related to stroke subtype. This could have important implications with regard to post-stroke prognosis and the management of blood pressure (BP) in the acute post-ictal period. Using transcranial Doppler ultrasonography and non-invasive manipulation of BP, we compared both mechanisms in 61 patients with ischaemic stroke within 96 h of ictus, and 54 age- and sex-matched controls. There was no difference in static and dynamic CA indices between the various stroke subtypes. Combining all stroke subtypes dynamic autoregulation, as measured using thigh cuff release, was significantly impaired in both the affected and non-affected stroke hemispheres compared to controls (mean autoregulation index 4.1 +/- 3.3, 4.8 +/- 3.1 and 6.2 +/- 2.3, respectively, p < 0.05). By comparison static autoregulation, assessed using isometric hand grip and thigh cuff inflation, was not significantly different. In conclusion, dynamic but not static CA appears to be globally impaired in acute ischaemic stroke. This deserves further study and may identify possibilities for therapeutic intervention.
Aged↗