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Biomedical subjects

R Porter

Publications and source records attributed to R Porter.

At least 199 records · Page 11Linked to original sources
PubMed1975

Relationship of neuronal discharges in the precentral gyrus of monkeys to the performance of arm movements.

Recordings have been made from 162 pyramidal tract neurones which discharged bursts of nerve impulses in characteristic temporal association with performances of a stereotyped motor task by monkeys. Clinical evaluation of the relationship between discharges of the neurones and free movement led to the view that each cell's firing was associated with a characteristic aspect of movement performance and the contraction of a particular group of muscles. Quantitative evaluation of these relationships led to the conclusion that coding of the recruitment of motor units to the movement task could have been conferred by the number of pyramidal tract neurones discharging to those motoneurone targets. A ramp of "recruitment" of pyramidal tract neurones preceded the development of a ramp of force by about 100 msec. This general conclusion was supported by the observations made in a single animal in which orderly discharge of precentral neurones in relation to a sterotyped movement performance was clearly evident.

Animals↗
PubMed1975

Commissural and cortico-cortical "columns" in the somatic sensory cortex of primates.

Anatomical experiments demonstrate that commissural and cortico-cortical fibers arising and terminating in the somatic sensor- cortex of monkeys terminate in layers I through IV in a mosaic of precisely ordered vertical bands. The cells of origin of these fibers, found predominantly in layer III, are also arranged in vertical aggregations.

Animals↗
PubMed1975

Effect of diet on serum accumulation and renal excretion of aryl acids and secretory activity in normal and uremic man.

The influence of diet on aryl acid metabolism was determined in normal and azotemic subjects. Aryl acid content of serum and urine was estimated by fluorometry in relation to hippuric acid as a standard (FI-Hipp). Secretory activity, a reflection of the biological potency of aromatic acids in serum and urine, was determined by bioassay. The urinary excretion of FI-Hipp and secretory activity of five normal persons on an ad lib diet was 0.78 and 2.25 mM/day, respectively; similar values were observed in two subjects with chronic renal insufficiency. Subjects were fed prunes and cranberries, since these foods contain abundant quantities of hippurate precursors. Prunes 1.5 g/kg body weight, caused the urinary excretion of both FI-Hipp and secretory activity to increase about tenfold in normal and azotemic subjects. Prune feeding caused the serum levels of FI-Hipp and secretory activity to increase about threefold. Cranberries increased the renal excretion of FI-Hipp and secretory activity as did the ingestion of a beverage containing benzoate as a preservative. On the basis of these studies it is clear that diet is an important determinant of the load of aryl acids for urinary excretion; in patients with renal insufficiency the ingestion of foods containing precursors may cause serum level of biologically active aryl acids to increase strikingly.

Benzoates↗
PubMed1973

The effect of a preceding stimulus on temporal facilitation at corticomotoneuronal synapses.

1. Intracellular recordings were made of minimal corticomotoneuronal e.p.s.p.s in lumbar motoneurones of anaesthetized monkeys. For intervals of 2 msec and greater between paired cortical shocks, the average time course of facilitation of the second e.p.s.p. with respect to the first could be fitted closely by a negative exponential with a time constant of 10 msec.2. In the same motoneurones, ;triplets' of corticomotoneuronal e.p.s.p.s were generated by delivering three identical stimuli to the motor cortex. Considering the triplet as a conditioning e.p.s.p. followed by a test pair, the facilitation of the third e.p.s.p. with respect to the second was measured for various combinations of test and conditioning intervals. In each case the amplitude of the third e.p.s.p. was also compared with that of the first (conditioning) e.p.s.p.3. The effect of a brief conditioning interval was to reduce considerably the facilitation of the third e.p.s.p. with respect to the second at all test intervals from 2 to 50 msec. Combinations of brief conditioning intervals (e.g. 2 or 5 msec) and long test intervals (e.g. 20 or 50 msec) caused the third e.p.s.p. to be smaller than the second. As the conditioning interval lengthened, facilitation in the test pair increased towards the unconditioned values at all test intervals.4. Facilitation of the third e.p.s.p. with respect to the first could be described approximately as the linear addition of two facilitation components, one due to the conditioning input and one due to the first stimulus of the test pair. Each component followed the same negative exponential time course as found for an isolated pair of e.p.s.p.s and each of the first two inputs contributed to the facilitation of the third e.p.s.p. as if the other of these two inputs had not occurred.

Anesthesia, General↗
PubMed1972

Incidence of ocular complications in patients undergoing renal transplantation.

The eyes of 39 patients who had received allogenic renal transplants were examined for signs of disease. Nine (23%) had early posterior subcapsular cataracts, two (5%) developed acute cytomegalovirus retinitis, and one developed steroid-induced glaucoma. The lesions which were found were all attributable to the immunosuppressive drug therapy. Thirty-five (87%) had detectable complement-fixing antibodies to cytomegalovirus.

Adolescent↗