Ontogeny of pituitary regulation of growth in the developing rat: comparison of effects of hypophysectomy and hormone replacement on somatic and organ growth, serum insulin-like growth factor-I (IGF-I) and IGF-II levels, and IGF-binding protein levels in the neonatal and juvenile rat.

We investigated pituitary regulation of growth during two critical stages of development in the rat, using hypophysectomy (Hx) with replacement of GH and/or T4. In the neonatal period (Hx on day 6), body weight and tail length were inhibited by 60% and 50%, respectively, while these parameters were inhibited by 80% and 85% by Hx in the juvenile period (Hx on day 45). Administration of T4 alone significantly increased skeletal growth (tail length) in neonatal Hx rats, while T4 alone proved ineffective in promoting somatic growth in juvenile Hx rats. GH effects were greater on body weight than on tail length at both stages of development. Replacement of both GH and T4 restored somatic growth to normal values during both time periods. The brain was the sole organ whose growth appeared to be independent of the pituitary. Hx reduced serum insulin-like growth factor-I (IGF-I) and -II in both age groups, and GH alone restored IGF-I and -II levels to the control range. The major IGF-binding proteins (IGFBPs) were analyzed by Western ligand blots. The effect of Hx on the predominant IGFBP was greater in the juvenile rat. T4 replacement in the neonate and GH replacement in the juvenile rat restored IGFBPs to control levels. We conclude that somatic growth in the rat is less pituitary dependent in the neonatal period. There are also important age-specific differences in organ response to GH and T4. Serum IGFs and their binding proteins are pituitary dependent even in infancy, and GH is their primary regulator. The neonatal Hx rat is an important model for the study of the dynamic development of the pituitary-dependent growth.     

Low achieved diastolic pressure in tightly controlled mid-older hypertensive subjects is associated with favorable arterial properties

Low diastolic blood pressure (DBP) is commonly seen in well-controlled hypertensive subjects. We evaluated arterial properties in 53 hypertensive subjects with low on-treatment DBP (<70 mm Hg; LODP), 54 subjects with normal BP and spontaneously low DBP (SLDP), and 52 treated hypertensive subjects with DBP ≥70 mm Hg (HNDP). The two measures of large artery rigidity, pulse wave velocity and augmentation index, were similar in LODP and SLDP groups. In contrast, the HNDP group had higher PWV and the lowest large and small artery compliance in comparison with all other groups. Low on-treatment DBP is associated with favorable arterial properties in mid-older hypertensive patients.     

The role of neuroimaging in the evaluation process of children with isolated sixth nerve palsy

Purpose

The purpose of this study was to assess the role of neuroimaging in identifying the etiology of pediatric isolated sixth nerve palsy (SNP).

Methods

A retrospective cohort study was conducted of all patients younger than 18 years of age with an isolated SNP seen at our medical center between 2003 and 2011.

Results

Sixteen children (nine girls; mean age, 4.5 years) with isolated SNP were identified during an 8-year period. Only cases with normal optic disk appearance and otherwise normal neurological examination were included into this study. Thus, 12 other children with SNP were excluded: ten children with papilledema, one child who developed a SNP following a resection of a brain tumor, and one with hydrocephalus and a shunt malfunction. All cases of isolated SNP were unilateral (ten left eyes). The most common cause for the SNP in these children was a tumor that was found in five patients. Other etiologies encountered in decreasing frequencies were: benign recurrent SNP (in four children), postviral or vaccination (in three children), and one case each of post trauma, Chiari malformation, congenital, and undetermined. Children who were found to have a tumor (9.9?±?5.5 years) were significantly older (P?=?0.019) than children who did not have a tumor (2.1?±?1.8 years).

Conclusions

Isolated SNP can be the presentation of a brain tumor in children, and therefore, early neuroimaging of the brain is recommended, especially in older children.     

Introduction of rat growth hormone gene into mouse fibroblasts via a retroviral DNA vector: expression and regulation.

We have introduced the rat growth hormone gene into mouse fibroblasts via a retroviral DNA vector. The ability of the viral DNA to induce foci in the recipient cells was used as a dominant selection marker. Several copies of rat growth hormone DNA were integrated in the mouse cells. The transformed mouse cells expressed rat growth hormone-specific mRNA and secreted mature rat growth hormone. In rat cells, the expression of this gene is regulated by glucocorticoids. We demonstrate that hormone-dependent regulation transfers with the clone and thus appears to be an intrinsic property of the gene or its RNA products.