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Biomedical subjects

P Walker

Publications and source records attributed to P Walker.

At least 253 records · Page 14Linked to original sources
PubMed1980

Hypothalamic somatostatin and pituitary and serum growth hormone concentrations during postnatal development in rats exposed chronically to propylthiouracil or a low iodine diet.

The developmental profiles of hypothalamic somatostatin and pituitary and serum growth hormone (GH) concentrations were examined in rats exposed chronically to a low iodine diet or propylthiouracil. Hypothalamic somatostatin and pituitary and serum GH concentrations were similar during development in control and low-iodine-diet animals. Propylthiouracil-induced hypothyroidism, however, was associated with reduced hypothalamic somatostatin and pituitary and serum GH concentrations, the latter being undetectable after 6 days. These data indicate that hypothalamic control of GH secretion is unaltered in low-iodine-diet rats who maintain an euthyroid status by preferential triiodothyronine (T3) production. The marked derangements observed in the hypothyroid animals indicate that thyroid hormones are critical for the postnatal maturation of the GH regulatory mechanism.

Animals↗
PubMed1979

Thyroxine increases nerve growth factor concentration in adult mouse brain.

The effects of thyroxine and propylthiouracil on nerve growth factor concentrations in cerebral cortex, cerebellum, and brainstem of adult male mice were assessed by using a sensitive radioimmunoassay for the beta-subunit of mouse nerve growth factor. Thyroxine administration significantly increased the concentration of nerve growth factor in all three brain areas compared to control values, whereas propylthiouracil was without effect. These results suggest that thyroid hormones stimulate nerve growth factor synthesis in the mature central nervous system, and raise the possibility that the influence of thyroid hormones on central nervous system development might be mediated or influenced by nerve growth factor.

Animals↗
PubMed1979

Follow-up of 11 XYY males with impulsive and/or sex-offending behaviour.

Eleven behaviourally abnormal XYY males who had been treated in a structured combined programme of antiandrogen medication and counseling were followed up 1 year after cessation of the programme. Behavioural ratings were made in each of 5 categories: assault against people, destructiveness against things, threatening behaviour, stealing, and self-harming. On examining the follow-up findings, therapeutic success appeared questionable.

Adolescent↗
PubMed1979

Effect of prolonged intermittent thyrotropin-releasing hormone administration to fetal and neonatal rats.

Fetal and neonatal rats received daily subcutaneous injections of 10 microgram thyrotropin-releasing hormone (TRH) until 7 or 14 days postnatally. At 70 days the pups were challenged with 1 microgram TRH intravenously via an indwelling jugular cannula. Basal serum thyroxine, triiodothyronine, and thyroid-stimulating hormone (TSH) concentrations did not differ among the three groups. The mean TSH responses as determined by the mean peak TSH concentration and the total TSH response as determined by planimetry were not significantly different, and there was no significant difference in pituitary TSH content following the TRH challenge among the three groups. This study suggests that the integrity of the hypothalamo--pituitary axis in adult rats cannot be affected by the repeated administration of pharmacologic doses of TRH during the perinatal period.

Animals↗
PubMed1978

Orientation-selective inhibition and binocular rivalry.

It is hypothesized that a negative correlation exists between the readiness with which two visual stimuli display rivalry and the magnitude of the inhibition effects between the corresponding neural channels. With binocular rivalry being more readily observed than monocular rivalry, it is predicted that lateral inhibition between neural channels selectively sensitive to such fundamental parameters as orientation, is primarily confined to those monocularly driven channels deriving their sensory input from the same eye. In confirmation, it is shown that the visual tilt illusion, thought to reflect lateral inhibition between orientation-sensitive channels, is very much reduced under dichoptic viewing conditions. Moreover, it is shown that those subjects displaying the greatest interocular transfer of the illusion least readily experience binocular rivalry.

Eye↗
PubMed1978

The subliminal perception of movement and the course of autokinesis.

The course of autokinesis is shown to be sensitive to the real movement of a surrounding stimulus. With the supraliminal presentation of this stimulus, apparent movement in a direction opposite to that of the real movement is induced. With the subliminal presentation of the same stimulus the real movement serves to inhibit autokinesis by inducing brief periods of stationarity between the phases of upward and downward apparent movement. The results confirm previous findings that the movement of a stimulus may be discriminated without there being any perceptual (phenomenal) adjunct.

Adult↗
PubMed1978

Survival and complications in cervical cancer treated by pelvic and extended field radiation after paraaortic lymphadenectomy.

Over a 3 year period, 49 patients with invasive cancer of the cervix underwent paraaortic lymphadenectomy. Of this group, 18 were stage lb, with cervix 3 cm or smaller, and were treated by radical hysterectomy. All had negative paraaortic nodes. The remaining 31 patients had more advanced disease and underwent radiation therapy in addition to the paraaortic lymphadenectomy. Thirteen patients with positive paraaortic nodes were treated with extended field radiation to the level of the diaphragms with 4,500 rad plus intracavitary radium applications. The remaining 18 patients with negative paraaortic nodes were treated to the fifth lumbar vertebra with 5,000 rad plus radium applications. The age of the patients and stage of the disease were similar for both groups. After 13-36 months of follow-up, the survival rate was 38% for patients with positive nodes compared to 72% for those with negative nodes. About half of both groups suffered complications. More study must be given to alternative treatments of advanced carcinoma of the cervix.

Cobalt Radioisotopes↗
PubMed1977

Thyrotoxicosis detected in a mass-screening program for neonatal hypothyroidism: demonstration of placental transfer of an immunoglobulin with marked lipolytic activity.

A female infant born to a mother with active Graves disease and a strongly positive LATS developed neonatal thyrotoxicosis. The diagnosis was confirmed rapidly by the markedly elevated filter paper spot T4 (5.45 ng/40 microliter) taken on the fifth day of life as part of the Quebec Screening Program for Neonatal Hypothyroidism. Although the infant's serum was negative for LATS, it reacted strongly (as did the maternal serum) in the lipolytic assay for LATS. This case illustrates the ability of screening programs for neonatal hypothyroidism to detect cases of neonatal thyrotoxicosis and supports the hypothesis that this condition is secondary to the placental transfer of a thyroid-stimulating immunoglobulin.

Female↗
PubMed1977

A potential diagnostic method for food allergy: clinical application and immunogenicity evaluation of an elemental diet.

The use of a simple, hypoallergenic elemental diet would appear well suited for diagnosing food allergy. Vivonex was used in 21 patients (5 to 40 years old) suspected of food allergy or those who had failed to respond to the usual management of inhalant allergy. To study immunogenicity, five New Zealand rabbits were immunized with Vivonex, milk, and egg and were evaluated for the production of precipitin and passive cutaneous anaphylactic antibodies, the latter was evaluated in three Hartley guinea pigs. The clinical study was conducted over a 2- to 3-week period with evaluation of symptom and medication scores, physical examination, and hematological and biochemical measurements made before and after the Vivonex trial, which was a minimum of 1 week. No consistent, significant improvement of allergic manifestations were seen while patients received Vivonex. On the other hand, there were no serious side effects noted either clinically or by laboratory measurements, although four patients discontinued the study because of Vivonex palatibility. Vivonex was not immunogenic by either the precipitin reaction or passive cutaneous anaphylactic response. Although Vivonex did not prove helpful in these severe, refractory allergic individuals, we were encouraged by its safety and acceptance in the outpatient setting. Further studies in young allergic children who are more likely to have clear-cut food sensitivity are being planned.

Adolescent↗
PubMed1977

The development of the hypothalamo-pituitary axis in the neonatal rat: pituitary and serum prolactin concentrations.

Using highly specific double-antibody radioimmunoassay techniques, we have measured pituitary and serum prolactin (PRL) concentrations in neonatal rats from birth to 60 d. Pituitary PRL concentration was low at birth in both sexes and peak prepuberal values were attained at 25-28 d. Following this time, pituitary PRL concentrations in females were significantly higher than those observed in males (p less than 0.01). Serum PRL concentrations were low at birth in both sexes and remained low until 15 d, when they rose to peak values just before puberty. There were no significant sex differences with respect to serum PRL concentrations. These data indicate that hypothalamic control of PRL secretion developes during the neonatal period of the rat. The relationship of this developmental process in the neonatal rat as a possible model for the study of the midgestational hypothalamic maturation of the human fetus is discussed.

Age Factors↗