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Biomedical subjects

P Thompson

Publications and source records attributed to P Thompson.

At least 253 records · Page 14Linked to original sources
PubMed1981

Detection and discrimination of moving gratings.

Two techniques are described which have been used to investigate mechanisms underlying the perception of velocity. The first, subthreshold summation establishes detection thresholds of two gratings of different spatial frequencies moving at the same velocity and also the detection thresholds of combinations of these gratings. The second technique employed a detection/discrimination procedure which establishes the discriminability of two different moving gratings at detection threshold. These experiments suggest that at low velocities the detection of 2 and 6 cycle/degree gratings is mediated by independent mechanisms, this independence being diminished at higher velocities. Gratings of 2 cycles/degree moving at different velocities are only discriminably different at detection threshold when widely separated in velocity.

Differential Threshold↗
PubMed1981

Phenytoin and cognitive function: effects on normal volunteers and implications for epilepsy.

Despite the widespread use of phenytoin in the treatment of epilepsy, few studies have examined its effects on cognitive functioning. We report here the results of an investigation into the effects of phenytoin on the performance of non-epileptic volunteers, on a series of specially designed psychological tests. Subjects received placebo or phenytoin 300 mg per day for two weeks in a double-blind crossover design and measures were taken of phenytoin serum levels. The results demonstrate a deleterious effect of phenytoin upon several important aspects of cognition, including memory, concentration, mental and motor speed. The implications of our findings for the treatment of patients with epilepsy are discussed.

Adolescent↗
PubMed1981

Plasma angiotensin II changes with noise exposure at three levels of ambient temperature.

Significant plasma elevations of the powerful vasoconstrictor angiotensin II (AII) were measured in rats following exposure to either 100-dB or 20-dB SPL white noise in three environmental temperatures (5 degrees 21 degrees, and 38 degrees C). Loud noise exposure in the normal temperature condition (21 degrees C) and both temperature extremes with soft noise exposure resulted in plasma AII elevations. The two extreme temperatures combined with loud noise exposure resulted in plasma AII concentrations not different from the levels observed following 20-dB noise at normal temperature. These results indicate that separately administered noise and temperature extremes stimulate the production of AII and thus vasoconstriction. Simultaneous exposure to multiple stressors including noise and temperature extremes may result in severely elevated plasma catecholamines and reduce renal responsiveness to beta-adrenergic stimulation thus reducing plasma AII levels.

Angiotensin II↗
PubMed1981

Behavioural correlates of an experimental hippocampal epileptiform syndrome in rats.

Experiments are reported describing assessment of abnormal behaviour of rats in which a chronic epileptiform syndrome has been induced by the injection of tetanus toxin bilaterally into their hippocampi. The abnormal behaviour included hyper-reactivity to a novel environment, intermittent aggression on handling, and abnormally passive response to a strange rat introduced into their home cage. In animals with unilateral injection of toxin, electrical records from the hippocampi have been obtained. They illustrated bilaterally simultaneous discharges and also some independence between the two hippocampi. The discharges were accompanied by overt signs of complex partial seizures during the first few weeks of the syndrome but later occurred without motor signs. In this later stage the rats were somewhat resistant to the convulsant effects of pentylenetetrazol.

Aggression↗
PubMed1981

[Antiviral agents and corneal epithelium cicatrisation: study in rabbits (author's transl)].

Five clinically-used antiviral drugs (3% adenine arabinoside ointment; 3% acycloguanosine ointment; 0.24% idoxuridine ointment; 1% trifluorothymidine drops) were compared with a control (petrolatum base) to determine their toxic effects on rabbit corneal epithelium after injury by iodine vapors: --Only trifluorothymidine significantly retarded healing of epithelial erosions. --Histopathologic examination after seven-day treatment showed that all five drugs, except vidarabine and to a lesser degree acycloguanosine, caused toxic changes in the regenerating epithelium.

Acyclovir↗
PubMed1980

Renal disease. Its pathology, treatment, and effects on the ear.

Twenty-six hemodialysis and renal transplant patients were studied for the effects of age, duration of kidney failure, amounts and types of treatment, disturbed calcium metabolism, and vascular disease on clinical and pathologic inner ear manifestations. Three subgroups of patients were compared with each other: (1) those having hearing loss of unknown etiology, (2) those having strial deposits, and (3) those having neither. Severity of treatment was not necessarily predictive for severity of inner ear disease. Within each subgroup there was wide variability and almost complete overlap for the factors studied when the three groups were compared. Cochlear strial deposits seem to bear little relationship to disturbed calcium meatbolism or to vascular disease, but their size may be related to the presence of hearing loss.

Adolescent↗
PubMed1980

Adaptation to a "spatial-frequency doubled" stimulus.

The perceived spatial frequency of low-frequency sinusoidal gratings is elevated when the gratings are temporally modulated sufficiently rapidly. Although this phenomenon is usually called "spatial-frequency doubling", the magnitude of this spatial-frequency elevation depends on the spatial and temporal parameters of the grating and may be less than or greater than doubling. Adaptation to such a pattern produces contrast-threshold elevation whose spatial-frequency tuning is centered upon the grating's real rather than perceived spatial frequency. These results suggest that the spatial-frequency elevation occurs later in the visual system than adaptation or that these two processes are independent of one another, at least under the conditions of these experiments.

Adaptation, Ocular↗
PubMed1980

Uremia decreases nuclear 3,5,3'-triiodothyronine receptors in rats.

The maximal binding capacity (MBC) of hepatic T3 nuclear receptors was decreased in uremic rats (132 +/- 37 fmol/mg DNA) compared to sham-operated controls (212 +/- 44 fmol/mg DNA; P < 0.025), while the equilibrium affinity constants (Ka) remained unaltered (1.8 +/- 0.4 and 1.5 +/- 0.3 X 10(9) M-1 in the uremic and control rats, respectively, P = NS). There was also a reduction in the MBC of the kidney T3 receptors, from 73 +/- 14 fmol/mg DNA in the control animals to 32 +/- 7 fmol/mg DNA in the uremic rats (P < 0.10), while the Ka values were identical in both groups (1.9 +/- 0.5 X 10(9) M-1). In addition, there were significant reductions in serum T4 (1.5 +/- 0.7 microgram/dl) and T3 (92 +/- 10 ng/dl) in the uremic rats compared to control rats, whose T4 levels averaged 4.4 +/- 0.1 microgram/dl (P < 0.005) and whose T3 levels averaged 140 +/- 13 ng/dl (P < 0.005). Further, insulin levels averaged 83 +/- 21 microU/ml in uremic rats and 38 +/- 7 microU/ml in control rats (P < 0.025), while glucagon levels averaged 457 +/- 114 pg/ml in the uremic rats and 101 +/- 30 pg/ml in the control animals (P < 0.0125). These data suggest that 1) in addition to starvation and hepatectomy, uremia is another pathological condition associated with the modification of the number of T3 receptors, 2) the reduction in MBC observed may be generalized rather than organ specific for hepatic nuclear receptors, and 3) elevated glucagon levels are associated with reduced MBC in uremia, but it is indeterminate whether hyperglucagonemia is the etiology of the decrease.

Animals↗
PubMed1980

Erythromycin ototoxicity.

Erythromycin is considered one of the safest antibiotics in common use today. In its otolaryngologic use, the authors have found it effective in treating acute suppurative sinusitis and occasionally otitis media, when combined with sulfonamides. There are few complications of erythromycin administration. Probably the least generally acknowledged of these is ototoxicity. There have been three reports of six cases with ototoxic complications from erythromycin, primarily from administration of its intravenous form. The authors present a case study of an 18 year old girl in severe renal failure, who suffered a reversible sensorineural hearing loss from high doses of an oral erythromycin preparation. The clinical manifestations of this case are compared to those previously reported.

Adolescent↗