Search PubMed⌕ Search

Biomedical subjects

J J Wright

Publications and source records attributed to J J Wright.

At least 109 records · Page 6Linked to original sources
PubMed1984

A linear theory for global electrocortical activity and its control by the lateral hypothalamus.

A linear model for electrocortical waves and their control by the lateral hypothalamus is proposed. It is argued that such a linear model is not in contradiction to non-linearity of neural elements on the microscopic scale. Telencephalic structures are treated as a mass of linked oscillators generating activity with a number of resonant modes. The lateral hypothalamus is regarded as controlling damping of activity in the telencephalic mass, and therefore exerting a specific parametric control over all signal processing in the cortical networks. An initial test is proposed to assess the constancy of telencephalic natural frequencies, with variation in lateral hypothalamic damping.

Animals↗
PubMed1984

A test for constant natural frequencies in electrocortical activity under lateral hypothalamic control.

An initial test for a theory of lateral hypothalamic regulation of electrocortical activity is undertaken. The theory supposes lateral hypothalamic input directly or indirectly damps telencephalic resonances involving linear wave phenomena, enabling this pathway to act as parametric control of information processing in cortical neural networks. Relative changes in left and right electrocortical power spectra are used to test for the presence of resonant modes with constant natural frequencies in conditions of asymmetrical damping, following unilateral lesion of the lateral hypothalamus. Natural frequency values for the modes clustered about center frequencies in the EEG band are obtained. This method has the advantage of minimising the effects of time-variation and the recorded signal's distortion from the electrocortical local spatial average, but limits consideration to five dominant modes of resonance. The uncertainty of true model order, and errors in curve-fitting impose limitations on the test.

Animals↗
PubMed1984

Inference of a stable dispersion relation for electrocortical activity controlled by the lateral hypothalamus.

A second test is undertaken for a theory of linear wave motion in electrocortical waves, under lateral hypothalamic control via regulation of damping. This test invokes a general property of linear systems, namely that wave motion with characteristic natural frequencies implies fixed phase velocities associated with each wavelength, independent of the changes in hypothalamic input. A means of testing the invariance of this dispersion relation at the point of recording is derived from a simplified biophysical model for waves in a dipole layer. The method avoids some problems implicit in direct spatio-temporal wave analysis. Results confirm that the model under test is internally consistent, and is also consistent with other findings concerning the origin and spatial nature of the EEG.

Animals↗
PubMed1984

Psychoendocrine interaction in anorexia nervosa, and the retreat from puberty: a study of attitudes to adolescent conflict, and luteinizing hormone response to luteinizing hormone releasing factor, in refed anorexia nervosa subjects.

Seventeen young women suffering from anorexia nervosa underwent LHRF infusion, and repertory grid psychometric measures, soon after they had regained ideal body weight. Those who had regained normal LH responsiveness showed repertory grid evidence of increased adolescent conflict compared to those who failed to respond to LHRF. Certain other clinical variables which might account for this finding were excluded, and the hypothesis that amenorrhoea in anorexia nervosa is partly explicable as a psychobiological defence against adolescent conflict is supported.

Adaptation, Psychological↗
PubMed1981

Lateral hypothalamic regulation of electrocortical activity.

The EEG power spectrum of normal and split-brain cats was analysed before and after unilateral hypothalamic lesion at sites which prior to lesion had ICSS or aversive properties on stimulation, and which gave rise to sensorimotor neglect after lesion. A filter-gain function was calculated to describe the lesions' effect upon the ipsilateral EEG spectrum in stable conditions, and was found to be approximated by a specific gamma function. This partially defines the action that the lateral hypothalamus may exert on electrocortical activity.

Animals↗
PubMed1980

A pilot study of the effects of methylphenidate on the vigilance-related EEG in hyperactivity.

Seven hyperactive children underwent a reaction time (RT) test requiring prolonged (15 min) vigilance, once while receiving methylphenidate and once without medication. EEG samples taken immediately before each RT measurement were subjected to power-spectral analysis. Compared to the off-medication condition, methylphenidate reduced the RT whilst paradoxically increasing EEG alpha power relative to higher and lower frequencies in 5 out of the 7 children. On this medication, the RT increased during the course of the task, and the relative EEG alpha power increased compared to other frequencies. Off medication, RTs showed an even greater increase with prolonged vigilance, but the accompanying EEG changes were the reverse of those seen on medication. The altered EEG power spectrum on methylphenidate appears closer to that of a normal EEG, and may be related to the improvement in specific attention produced by this drug in hyperactivity.

Alpha Rhythm↗
PubMed1980

Netilmicin: chemical development and overview of clinical research.

Netilmicin is a new semisynthetic aminoglycoside which was developed by Schering Corporation, USA, for the treatment of serious gram-negative and staphylococcal infections. Nephrotoxicity and ototoxicity in animal studies have indicated that netilmicin is both quantitatively and qualitatively safer than other aminoglycosides. Also, netilmicin has a broader spectrum of activity than either gentamicin or tobramycin. 37 clinical studies were conducted by 29 investigators in 10 countries. 840 courses of treatment in 960 infection sites were analyzed for effectiveness. Of the 724 courses in which a clinical determination could be made, 91% had either complete resolution or improvement. Bacteriologic responses were available for 782 infecting organisms and showed an 82% elimination rate. The pharmacokinetic profile of netilmicin permits twice daily administration in most patients with systemic infections and in all patients with urinary tract infections. The clinical safety of netilmicin was measured in 890 evaluable treatment courses, and only 0.4% auditory reactions, 0.6% vestibular reactions, and 0.9% renal reactions were considered to be probably netilmicin related, when netilmicin was given as recommended.

Adolescent↗
PubMed1978

Behavioural effects of methylphenidate in 6-hydroxydopamine-treated neonatal rats.

Neonatal rats treated at 7 days of age with 6-hydroxydopamine show normal levels of activity during maturation, but less hyperactivity than normals do when additionally treated with methylphenidate hydrochloride between 14 and 22 days of age. Comparison of these results with those of other workers suggests that several experimental variables must be controlled precisely if reproducible results analogous to the disturbed behaviour of children with minimal brain dysfunction (MBD) are to be obtained.

Aging↗
PubMed1978

Pituitary-adrenal response to stimulation of the limbic system and lateral hypothalamus in the rhesus monkey (Macacca mulatta).

Various sites within the limbic system, frontal lobe and lateral hypothalamus of the rhesus monkey brain were electrically stimulated using chronically implanted electrodes. Increases in plasma cortisol was observed after stimulation of the lateral hypothalamic area, basolateral amygdala, pyriform cortex, hippocampus, certain sites in the cingulate gyrus and orbital part of the frontal lobe. Inactive sites included the caudate nucleus, putamen and white matter in the frontal lobe.

Amygdala↗
PubMed1978

Chemical modification of some gentamicins and sisomicin at the 3''-position.

Chemical and photochemical oxidative methods of de-N-methylation of some gentamicins and sisomicins at the 3''-position are described. Selective acetylation of gentamicins and sisomicins at the 1, 3, 2' and 6' and of gentamicin B at the 1, 3, and 6'positions are achieved by treatment of the free bases with carbon dioxide prior to acetylation. De-N-methylation of the above selectively blocked gentamicins and sisomicins followed by re-alkylation at the 3''-position and de-N-protection gives a series of 3''-N-alkyl analogues. The in vitro antibacterial properties of the new derivatives of gentamicins and sisomicins are given.

Acetylation↗