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Biomedical subjects

G W Clayton

Publications and source records attributed to G W Clayton.

At least 19 recordsLinked to original sources
PubMed2006

Effects of fall and spring seeding date and other agronomic factors on infestations of root maggots, Delia spp. (Diptera: Anthomyiidae), in canola.

Several agronomic benefits can result from fall seeding of canola (Brassica spp.), but extensive research data are lacking on the potential impact of this practice on infestations of root maggots (Delia spp.) (Diptera: Anthomyiidae), which are major pests of the crop in western Canada. Field experiments making up 13 location by year combinations were conducted in central Alberta, Canada, from 1998 to 2001 to determine the effect of fall versus spring seeding of canola on root maggot damage. Depending on the experiment, interactions with seeding rate, seed treatment, timing of weed removal, and canola species (cultivar) also were investigated. Root maggot damage declined with an increase in seeding rate for plots seeded in May but not in fall or April. Susceptibility to infestation was greater for plants of Brassica rapa L. than Brassica napus L., but seed treatment had no effect on damage by these pests. Combined analysis using data from all experiment by location by year combinations indicated that seeding date had no significant effect on root maggot damage. The extended emergence of Delia spp. adults, which spans the appearance of crop stages vulnerable to oviposition regardless of seeding date, prevented reduced root maggot attack. Covariance analysis demonstrated the importance of increasing seeding rate for reducing root maggot infestations, a practice that can be especially beneficial for May-seeded canola when growing conditions limit the ability of plants to compensate for root maggot damage. Results determined with the small plot studies described here should be validated in larger plots or on a commercial field scale, but both the combined and covariance analyses indicate that seeding canola in fall does not predispose plants to greater damage by larval root maggots than seeding in spring.

Agriculture↗
PubMed2001

Rhizobium population dynamics in the pea rhizosphere of rhizobial inoculant strain applied in different formulations.

The effect of inoculant formulation on the population dynamics of rhizobia in the pea rhizosphere was investigated using a streptomycin-resistant mutant of Rhizobium leguminosarum bv. viceae NITRAGIN128C56G (128C56G strR). The isolate was formulated into liquid, peat powder, and granular peat carriers, and was tested on pea at field sites near Saskatoon, Saskatchewan, and Beaverlodge, Alberta, in 1996 and 1997. The liquid and peat powder formulations were applied to seed while the granular inoculant was applied to soil. In three out of four site years, population dynamics were similar among formulations: an initial decline or lag period lasting 2-5 days followed by an increase to approximately 10(5) colony-forming units (CFU)/seedling by 14-28 days after planting (DAP) and, where sampled, a continuing increase from 10(7) to 10(8) CFU/plant at 63 DAP. In these same site years, nodule number (not determined at Beaverlodge in 1997) and nodule occupancy at 60 days were not significantly different among formulations. In contrast, soil populations of 128C56G strR from the liquid formulation declined to near zero by 28 DAP at Beaverlodge in 1996, when soil moisture was excessive in spring because of high rainfall. Populations increased in this treatment after this time, but remained significantly lower than the populations of the other two formulations throughout the sampling period. Pea seed yields were not significantly different among treatments in either year at Beaverlodge, but were significantly higher with granular inoculant than the noninoculated control in Saskatoon. Within inoculated treatments at Saskatoon, there were no significant differences in grain yield.

Colony Count, Microbial↗
PubMed1990

Inappropriate adrenal androgen secretion with once-a-day corticosteroid therapy for congenital adrenal hyperplasia.

To determine whether cortisone acetate given as a single daily dose would be as effective as the same amount divided into three doses in suppressing adrenal androgen secretion in congenital adrenal hyperplasia, we studied three patients with the salt-losing variety, who were judged to have been adequately treated during the previous year. Each patient was receiving cortisone acetate, 20.6 to 22.6 mg/m2 body surface area per day, divided into three doses, and 9 alpha-fluorohydrocortisone, 0.05 to 0.1 mg/day. Their spontaneous and adrenocorticotropic hormone-stimulated blood concentrations of 17 alpha-hydroxyprogesterone, androstenedione, and testosterone were measured initially and were normal. Cortisone acetate was then given once a day in the same total daily dose. After 3 months, plasma adrenocorticotropic hormone concentration was increased in all three patients, and in two of them the plasma levels of 17 alpha-hydroxyprogesterone and androstenedione were also increased. In the third patient, after 7 months of once-daily therapy, plasma levels of 17 alpha-hydroxyprogesterone and androstenedione were increased. We conclude that a physiologic replacement dosage of cortisone acetate given once daily is not effective in controlling excessive adrenal androgen secretion in congenital adrenal hyperplasia.

17-alpha-Hydroxyprogesterone↗
PubMed1986

Central diabetes insipidus. 22 years' experience.

The etiology of diabetes insipidus (DI) was determined in 73 children evaluated from 1962 through 1983. Intracranial tumors produced DI in 34 children, but 27 of these 34 children developed DI only after excision of the tumor. Diabetes insipidus occurred in ten children with intracranial birth defects, eight with severe central nervous system infections, and six with histiocytosis. Six had other causes. No etiology was detected in nine. Division of the cases into two time periods (1962 through 1972 and 1973 through 1983) revealed a decrease in the frequency of idiopathic DI (26.7% to 8.6%), an increase in the frequency of intracranial birth defects (0% to 17.3%), and an increase in the frequency of severe central nervous system infections (0% to 13.8%). Significant changes in therapy for DI have occurred during these 22 years. Use of desmopressin acetate has facilitated treatment of this complex management problem.

Brain Neoplasms↗
PubMed1986

Patterns of growth from birth to maturity in infants and children with congenital adrenal hyperplasia.

Patterns of growth of 30 children with Congenital Adrenal Hyperplasia of the 21-hydroxylase type were studied from infancy to maturity. These children were compliant as to therapy. Intramuscular (I.M.) Cortisone (40 mg/M2) given every three days resulted in growth failure after the first year of life. A marked increase in height velocity occurred when oral Cortisone (20-25 mg/M2) was given at approximately 3 years. Growth was relatively normal during childhood in both boys and girls but there was a marked increase in mean weight in both sexes. Pubertal growth spurt occurred normally in males but was delayed in females. Weight decreased in both sexes at puberty but not to normal. Better methods of monitoring this condition should result in therapeutic regimes which allow normal growth patterns as well as normal mature height.

Adrenal Hyperplasia, Congenital↗
PubMed1980

Neonatal salt loss in the hypertensive form of congenital adrenal hyperplasia.

The 11 beta-hydroxylase deficiency (11OHD) form of congenital adrenal hyperplasia is diagnosed infrequently during the newborn period. A child presumed to have the 21-hydroxylase deficiency form of congenital adrenal hyperplasia was studied extensively as an infant. The diagnosis was based on ambiguous genitalia, elevated 17-ketosteroids, evidence of urinary 11-ketopregnanetriol, and salt loss. Severe hypertension was detected at 11 years, and 11 beta-hydroxylase deficiency was confirmed with elevated plasma 11-deoxycorticosterone and 11-deoxycortisol, low cortisol, and normalization of blood pressure following glucocorticoid replacement. Impaired aldosterone biosynthesis and salt loss were demonstrated during dexamethasone therapy. Salt loss during infancy does not distinguish between the 11 beta- and 21-hydroxylase deficiency forms of congenital adrenal hyperplasia.

Adrenal Hyperplasia, Congenital↗
PubMed1979

Growth increments with low dose intermittent growth hormone and fluoxymesterone in first year of therapy in hypopituitarism.

The availability of a commercial preparation of human growth hormone (hGH) prompted a study in children with hypopituitarism to determine the efficacy of a lower dose of hGH. Thirteen children, ages 4 years 3 months to 13 years 7 months, were given hGH concomitant with fluoxymesterone in an intermittent regimen. The hGH was given intramuscularly, 1 IU daily for 12 to 36 days in each course. There were four courses per year. The fluoxymesterone was given orally, 1 to 2 mg. The total amount of hGH administered was between 48 and 112 IU per year, as compared with the regimen of 312 IU per year, 2 units three times a week. The growth velocity in all 13 children improved, and the mean growth velocity was 6.4 cm +/- 1.13 SD. The mean bone age increment was 0.57 years +/- 0.14 SEM in one chronological year of therapy. The low dose regimen permits a significant reduction in cost of hGH without causing undue advance in bone age.

Adolescent↗
PubMed1977

Bilateral testicular tumors in congenital adrenal hyperplasia.

A 22-year-old male with bilateral testicular tumors and the 21-hydroxylase variety of congenital adrenal hyperplasia (CAH) was studied. Preoperatively, on his usual glucocorticoid regimen, his urinary pregnanetriol excretion was increased (8.0-23.5 mg/day), serum LH and FSH were normal to increased (14.3-28.7 mIU/ml and 13.2-19.5 mIU/ml, respectively) and testosterone (T) was normal to decreased (176-600 ng/dl). At surgery, testicular vein concentrations of 17-alpha-hydroxyprogesterone (17-OHP) and adnrostenedione (delta) were increased (30.1 mug/dl and 38.3 mug/dl respectively) while T was decreased (1,503 ng/dl); a positive peripheral vein--testicular vein gradient was not seen for these steroids. Following injection of 10 U of crystalline ACTH into the testicular artery; testicular vein concentrations of 17-OHP, delta and T increased to 729 mug/dl, 2,390 mug/dl and 9,660 ng/dl respectively. Microscopic examination of the testes revealed multinodular tumors composed of polygonal or rounded eosinophilic cells, arranged in cords, nests and clusters. The tumors extended from the hilus and compressed the adjacent testicular tissue. Electron microscopic examination of the tumors showed features, common to steroid-secreting tissues, with abundant smooth endoplasmic reticulum in close proximity to mitochondria which was moderate in number. The adjacent testicular tissue was composed of immature tubules with normally developed Leydig cells in the interstitial tissues. From these data and a survey of previous works, it was postulated that these tumors were dependent upon ACTH for growth and steroid secretion. In view of the high serum LH concentration seen in association with incomplete suppression of adrenal steroid secretion in this study and the association of evidence of gonadotropin secretion with testicular tumors in other CAH patients, LH may also have contributed to the growth of these tumors.

17-Ketosteroids↗