Construction and characterization of a yeast artificial chromosome library for Xpter-Xq27.3: a systematic determination of cocloning rate and X-chromosome representation

We describe the construction and characterization of a human X-chromosome-specific yeast artificial chromosome (YAC) library. Starting with 60 micrograms of hybrid cell line genomic DNA, we generated over 150,000 recombinants, over 90% of which range from 150 to 500 kb. From these recombinants, 3300 human-positive YACs (representing coverage of 4.5 X chromosomes) were identified by genomic human DNA hybridization. Mapping of random clones revealed that they are derived from the X chromosome in a regionally unbiased fashion, and screening with single-copy X-chromosome probes has repeatedly produced YACs from the library. By determining the frequency of YAC clones containing both hamster and human repetitive sequences, we estimated that approximately 11% of clones contain discontiguous sequences. Taken together, the low cocloning rate, the unbiased coverage, and a consistent recovery of YACs using specific X-chromosome markers indicate that YAC technology can be used for extensive cloning and mapping purposes. Because a certain amount of genomic rearrangement is present in YAC libraries, chromosome walking must be undertaken with a degree of caution.

Linkage analysis of neurofibromatosis type 1. Study of a homogeneous North Italian population with five DNA markers of chromosome 17

The authors report the results of a genetic analysis performed in 34 neurofibromatosis type 1 (NF1) Italian families using five loci tightly linked to NF1: D17S33, D17S82, D17S83, D17S37, and D17S36. A two-point linkage analysis was performed with the LINKAGE and the CRI-MAP programs. The map of the region was constructed using the MAP90 program. Data from the present study lend further support to evidence that all NF1 mutations are allelic and that the NF1 locus resides in the proximal region of chromosome 17q. Close linkage of NF1 to all the markers was found. Two of them, namely D17S82 and D17S83, showed the highest linkage with a value of 0 recombination frequency and lod scores of 3.77 and 4.02, respectively. The best map found is D17S33-D17S82-NF1-D17S83-D17S37-D17S36+ ++. The authors stress that knowledge of precise order is essential; if D17S82 and D17S83 are proved to flank the NF1 gene, they allow an acceptable presymptomatic diagnosis in informative families.

Cell surface vitamin D-binding protein (GC-globulin) is acquired from plasma

Vitamin D-binding protein (DBP) is an abundant plasma protein. The observation of immunodetectable, cell-associated DBP on peripheral blood mononuclear cells and placental cytotrophoblasts had presented the question of the origin, function, and precise subcellular localization of cell-associated DBP. Using anti-human DBP F(ab')2 with fluorescence-activated cytometric analysis and immunogold electron microscopy, we detected DBP on the plasmalemma of U937 cells, a monoblastic, histiocytic cell line grown in media supplemented with fetal calf serum (FCS). DBP was then removed from FCS by actin affinity chromatography followed by anti-DBP immunoaffinity chromatography. U937 cells in this DBP-free medium exhibited nearly identical growth rates to cells grown in medium containing native FCS. However, in contrast to cells grown with native FCS, those grown for seven to eight generations with DBP-free FCS exhibited less cell-surface DBP as quantified by fluorescence-activated cytometric analysis (73% decrease) and immunoelectron microscopy (88% decrease). DBP mRNA could not be detected in U937 cells, placental tissues, freshly prepared resting and stimulated B and T lymphocytes, or lymphocyte-derived cell lines by Northern analysis. In addition, using the sensitive reverse transcriptase/polymerase chain reaction assay no DBP fragments were detectable in U937 cells. We conclude that U937 cell-associated DBP is exogenously derived from plasma and is located on the plasmalemma. Based upon this conclusion, we postulate that specific binding sites for DBP may exist on the plasma membranes of certain cell types.

Histopathological study of a case of systemic angiofollicular hyperplasia (Castleman's disease)

This report describes the nodal and hepatic lesions observed in a patient with generalized disorders that had been histologically diagnosed as a systemic angiofollicular hyperplasia. The diagnostic morphological findings were observed in the nodes of the axilla and were represented by diffuse marked plasmacytosis, prominence of the germinal centres, preservation of the architecture with a reactive proliferation of blood vessels and fibrous tissue in interfollicular areas.

Oncologic causes of precocious puberty

Tumors are rare, but well-documented causes of precocious puberty in both sexes. The therapeutic and prognostic implications of a diagnosis of cancer require that the presence of a neoplastic process be ruled out in any case of precocious puberty. Granulosa-cell tumor of the ovary and Leydig-cell tumor of the testis are the most frequent gonadal tumors inducing precocious pseudopuberty in the two sexes. Adrenal tumors sustain a variety of endocrine syndromes, the most frequent one being virilization with or without hypercortisolism. Pure feminizing adrenal neoplasms have been described. For reasons not yet well understood, hypothalamochiasmatic glioma (beta-HCG) secreting tumors have almost never been described in association with female precocious puberty. Among these neoplasia, pineal germ-cell tumor inducing sexual maturation must be included. Hypothalamochiasmatic glioma and craniopharyngioma are the two cerebral tumors capable of inducing true precocious puberty. Even if equally distributed between both sexes, these tumors interfere with sexual maturation less frequently in girls than in boys. Hypothalamic hamartoma is considered a benign tumor, since it does represent a space-occupying mass. It more correctly could be called a malformation if its histologic characteristics are recalled. This cerebral lesion is now frequently described in children with true precocious puberty, probably because of improved diagnostic imaging methods.

Effect of verapamil on aldosterone secretion in primary aldosteronism

Intracytoplasmic calcium seems to act as second messenger for aldosterone secretion. Both in vitro and in vivo studies demonstrate that drugs which block calcium entry cause a decreased responsiveness of glomerulosa cells to Angiotensin II and potassium. In order to evaluate the effect of a calcium channel blocking agent (Verapamil) in conditions of abnormal aldosterone secretion, we have studied 11 patients with primary aldosteronism, 5 with idiopathic hyperaldosteronism (IHA) and 6 with aldosterone producing adenoma (APA). In our study plasma aldosterone levels decreased after Verapamil infusion in IHA whereas no significant variations were observed in APA patients. These results suggest that calcium blockade can interfere with a possible regulatory system which plays a greater role in idiopathic aldosteronism.

Effect of verapamil on the aldosterone-stimulating properties of metoclopramide: in vitro and in vivo studies

The role of calcium in the regulation of aldosterone secretion has been recently clarified. Angiotensin II and potassium stimulate aldosterone secretion through a calcium-entry dependent mechanism, while ACTH action is both calcium and cyclic AMP dependent. To establish whether also the so-called aldosterone dopaminergic regulatory system is calcium-dependent we have studied, in vitro and in vivo, the effect of verapamil, a calcium entry blocker agent, on the aldosterone-stimulating properties of the antidopaminergic drug, metoclopramide. In the rat adrenal cells perfusion system, verapamil blocked both angiotensin II and metoclopramide-stimulated aldosterone. This effect on metoclopramide action seems to be present also in vivo in normal subjects: in fact aldosterone response was slightly but significantly reduced after pretreatment with verapamil. In conclusion the results suggest that also the dopaminergic system could regulate aldosterone secretion through calcium-mediated mechanisms.

Effect of metergoline on the aldosterone-stimulating properties of metoclopramide

The mechanism by which metoclopramide stimulates aldosterone secretion is still unclear, since it cannot be explained by known regulatory systems. On the other hand we have recently shown that serotonin is also a potent aldosterone-stimulatory substance in man and its action can be blunted by the antiserotoninergic drug, metergoline. To test if metoclopramide could act through a serotoninergic pathway we have studied the effect of metergoline on the aldosterone response to metoclopramide in 8 normal subjects. The effect of metoclopramide (10 mg i.v.) on plasma aldosterone, PRA, cortisol, prolactin and K was studied before and after acute metergoline administration. Metergoline pretreatment significantly reduced the aldosterone response to metoclopramide, together with a slight reduction of prolactin, whereas no changes were seen on PRA, cortisol and K. In vitro, metoclopramide induced a significant aldosterone output from human adrenal adenoma cells, which was partially reduced by metergoline and not by bromocriptine. Despite a lack of specificity of metergoline these data may suggest the hypothesis of a serotoninergic component in the aldosterone-stimulating properties of metoclopramide.

Cholesterol HDL in phenobarbital-treated male and female Wistar rats

The effect of phenobarbital treatment on HDL cholesterol was studied in male and female Wister rats. An increase of HDL cholesterol was observed in both sexes one day after the administration of the barbiturate. The values of HDL cholesterol returned to those of the control animals l7 days after treatment.