Biomedical subjects
Publications and source records attributed to G E Bacon.
Neutron diffraction measurements of the orientation of the apatite crystals show a significant preference of their c-axes for the vertical direction. This preference increases from bottom to top of each vertebral body and is substantially greater for the second than for the fifth lumbar vertebrae. This is in line with the predominantly vertical forces which the former withstands.
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The temporal relationship between administration of cortisol and serum 17alpha-hydroxyprogesterone was investigated in five patients aged 9-19 years with congenital adrenal hyperplasia due to 21-hydroxylase deficiency. There was marked variability in the 17alpha-hydroxyprogesterone response (determined hourly for 24 h) of individual patients to administration of cortisol. Mean concentration was less than 0.030 micronmol/l in one patient but 0.519 micronmol/l in another. Levels were higher in all patients while off treatment, and were greatest in those with salt-losing adrenal hyperplasia. Growth hormone secretion was not suppressed by treatment with cortisol. Withdrawal of cortisol for 3 days resulted in a significant decrease in the mean serum FSH/LH ratio and a rise in serum testosterone in all subjects. Episodic release of gonadotrophins persisted in the adolescent patients.
Two half-brothers with short stature secondary to growth hormone deficiency and a family history implicating X-linked transmission were studied extensively for other endocrine abnormalities. The proband had a normal physical examination, except for small stature and small external genitalia. ACTH and TSH release were normal. LH and FSH responses during an i.v. GnRH test were severely blunted. His half-brother also had a normal physical examination, except for severe short stature and very small external genitalia. Deficiencies of ACTH, and TSH as well as GH were documented. An i.v. GnRH test showed no LH or FSH response. These studies support the existence of an X-linked recessive form of hypopituitarism and portend the clinical usefulness of the i.v. GnRH test in evaluating gonadotropin reserve.
Serial plasma samples for corticoid determination were obtained during the neonatal period in 16 infants with RDS (eight of whom died) and 44 healthy babies. The median corticoid level in the eight infants with RDS who was considerably higher than that of patients with RDS who survived, or the normal babies. The median corticoid level in the surviving RDS infants was statistically greater than that of the normal controls, but the actual difference was only 1.9 mug/100 ml. Simultaneous pH, PCO2, PO2, HCO3- and corticoid measurements were obtained serially in five patients with fatal RDS. However, the correlation between plasma corticoids and the acid-base determination was poor in all but one infant. It is concluded that infants are able to respond to severe physical stress in the neonatal period with an appropriate rise in plasma corticoid concentration, but lesser degrees of illness may cause only minimal changes in corticoid levels.
An intravenous metyrapone tartrate test was performed on 26 children to assess growth hormone (GH) reserve and pituitary-adrenal axis. Results were compared to the response evoked by an estrogen-primed arginine-insulin tolerance test (ATT/ITT). Administration of metyrapone intravenously proved to be a reliable means of evaluating pituitary-adrenal function. However, a normal serum GH concentration (greater than or equal to 7 ng/ml) during the test occurred in only nine of 18 children who had an adequate response to the ATT/ITT, and in three of these, the peak GH level occurred at the start of the infusion. Therefore, this procedure does not appear to be a satisfactory test for GH reserve in children. Further, the discrepancy between time of the peak serum concentrations of compound S and GH following intravenous administration of metyrapone does not support the contention that the rise of GH level during stress is secondary to release of adrenocorticotrophic hormone.
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