Role of the neonatal period of pituitary-testicular activity in germ cell proliferation and differentiation in the primate testis.

BACKGROUND: The neonatal period of pituitary-testicular activity (NPTA) in human males has been hypothesized to play a role in germ cell proliferation and differentiation and to be defective in cryptorchid testes. The present study was carried out to establish in the marmoset if suppression of the NPTA, by treatment with a GnRH antagonist, results in impaired germ cell proliferation and/or differentiation. METHODS: Comparison of germ cell (GC) numbers and differentiation from gonocytes to pre-spermatogonia and spermatogonia, at birth (in controls) and at the end of the NPTA in marmoset co-twin males treated from birth to age 14 weeks with vehicle or GnRH antagonist. RESULTS: From birth to age 18-24 weeks, testis weight increased approximately 5-fold and GC number approximately 10-fold, including increased numbers of gonocytes and pre-spermatogonia and the first appearance of spermatogonia. Treatment with GnRH antagonist attenuated the increase in testis weight and GC numbers, but the effect was only partial (24-30% reduction), and the relative proportions of gonocytes, pre-spermatogonia and spermatogonia in the GnRH antagonist-treated group were unchanged from control values. CONCLUSIONS: The NPTA plays only a minor, if any, role in GC proliferation and differentiation in the marmoset. The changes in GnRH antagonist-treated co-twins may reflect impaired GC survival due to withdrawal of gonadotrophin support for Sertoli cells. These findings do not support a pivotal role for the NPTA in neonatal GC development in primates.

Effect of glucocorticoid therapy on energy intake in children treated for acute lymphoblastic leukemia.

Despite a widespread belief that glucocorticoid therapy is associated with positive energy balance and excess weight gain there is a dearth of quantitative evidence about its effects and the underlying mechanisms of any effects. The primary aim of the present study was to quantify the effect of dexamethasone and prednisone treatment on energy intake in children treated for childhood acute lymphoblastic leukemia. A secondary aim was to test for differences in excess weight gain between patients treated using the 2 glucocorticoids. We measured energy intake in 26 patients (mean +/- SD age, 6.3 +/- 2.3 yr) during a 5-d period "on" steroids and again in the week before steroid treatment. Changes in body mass index from diagnosis to 1 and 2 yr postdiagnosis were expressed as SD scores. Steroid treatment was associated with a significant increase in energy intake of approximately 20% (mean paired difference, 1.7 MJ/d; SD, 2.8; 95% confidence interval, 0.7-2.8 MJ/d), with no significant difference between the 2 steroids. The mean change in body mass index SD score was +0.38 (SD, 1.10; P < 0.05) to 1 yr and +0.68 (SD, 1.38; P < 0.05) to 2 yr, with no significant difference between the 2 groups of patients. Glucocorticoid treatment in childhood acute lymphoblastic leukemia increases energy intake markedly, and this effect contributes to the excess weight gain and obesity characteristic of patients being treated for acute lymphoblastic leukemia.

Topoisomerase from Ustilago maydis forms a covalent complex with single-stranded DNA through a phosphodiester bond to tyrosine.

Highly purified topoisomerase from Ustilago breaks single-stranded DNA, forming a complex with protein covalently bound to the DNA. Methods used to detect the complexes include a nitrocellulose filter assay, electrophoresis of the DNA-protein complex in agarose gels containing alkali, and isolation of the complex after removal of all but a small oligonucleotide fragment bound to the protein. The linkage of the Ustilago topoisomerase is to the 3' end of the broken strand of DNA. The DNA-protein complex formed is through a phosphodiester bond to tyrosine.

Properties of a purified nuclear topoisomerase from L1210 cells.

A nuclear type I topoisomerase from mouse leukemia L1210 cells has been partially purified and characterized. The sedimentation coefficient of the enzyme by velocity sedimentation is 4.3 S, consistent with a globular protein of 68 kDa. Enzyme activity is stimulated 20-fold in the presence of magnesium over that achieved in KCl alone. The enzyme is completely inhibited in the presence of the berenil congeners HOE 13548 and 15030 while berenil itself caused only partial inhibition at concentrations below 200 micrograms/ml. An acid soluble protein of 30 kDa (by SDS-polyacrylamide gel electrophoresis) co-purified with the topoisomerase but could be separated by precipitation in a low salt buffer. This protein, as well as a protein of similar characteristics, histone H1, stimulated topoisomerase activity over a narrow concentration range. The role of topoisomerase in the DNA strand scission observed in L1210 cells following exposure to intercalating agents remains conjectural as the purified enzyme did not produce nicks in plasmid DNA in the presence of adriamycin.

Topological linkage of circular DNA molecules promoted by Ustilago rec 1 protein and topoisomerase.

We studied the formation of linked circular DNA molecules promoted by the combined action of rec 1 protein and type I topoisomerase of Ustilago maydis. When ATP was added as cofactor to reactions containing rec 1 protein, pairs of homologous circular DNA molecules became linked after addition of topoisomerase. Closed circular duplex molecules could be joined at homologous sites with circular single-stranded molecules or with other circular duplex molecules, provided that homologous single-stranded DNA fragments or RNA polymerase and nucleoside triphosphates were also added. Complexes formed were topologically linked through regions of heteroduplex DNA. When the analog adenylyl-imidodiphosphate was substituted for ATP, nonhomologous pairs of circular DNA molecules became linked.

Purification and properties of a topoisomerase from Ustilago maydis.

The lower eukaryote Ustilago maydis contains a topoisomerase that removes supercoils from negative and positive superhelical DNA. The enzyme may be a multimeric protein or an aggregate of polypeptides with a native molecular weight of 270,000 as estimated by gel filtration. No cofactors are required by the enzyme, but activity is enhanced by Mg2+. Dependence of activity upon enzyme concentration is not linear. Below a threshold level where topoisomerase cannot ordinarily be detected, addition of H1 histone sharply stimulates activity. ATP and a number of structural analogues inhibit the enzyme.

Suprasellar arachnoid cyst diagnosed preoperatively by computerized tomographic scanning.

True arachnoid cysts of the suprasellar region are uncommon and have rarely been diagnosed pre-operatively. An histologically verified suprasellar arachnoid cyst producing hydrocephalus and visual loss in a 19-year-old man was diagnosed by a combination of pneumoencephalography and computerized tomographic (CT) scanning prior to surgery. The incidence, pathogenesis, signs, and treatment of suprasellar arachnoid cysts are discussed.