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M Marcelli

Publications and source records attributed to M Marcelli.

At least 55 records · Page 3Linked to original sources
PubMed1992

Immunoreactive androgen receptor expression in subjects with androgen resistance.

Individuals with androgen resistance encompass a spectrum of phenotypic abnormalities ranging from complete testicular feminization to undervirilized men. Such subjects have been classified according to the hormone-binding characteristics in genital skin fibroblasts and on the basis of the mutation in the androgen receptor (AR) gene. Antibodies to the amino-terminal region of the human AR were used to develop an immunoblot assay for the comparison of androgen binding with the amount of AR expressed in genital skin fibroblasts. In controls and 4 androgen-resistant subjects with DNA-binding domain mutations, levels of immunoreactive AR correlated closely with androgen-binding capacity. In 15 androgen-resistant subjects with qualitatively abnormal AR, immunoreactive AR levels tended to be higher than predicted from the ligand-binding capacity. Discordance between immunoreactivity and androgen binding also occurred in fibroblasts from 3 other subjects. One carries a stop codon in the AR gene and produces a truncated AR that is immunoreactive but does not bind androgen. Two carry single point mutations in the hormone-binding domain and produce immunoreactive AR that is normal in size but does not bind androgen.

Androgens↗
PubMed1992

Amino acid substitutions in the DNA-binding domain of the human androgen receptor are a frequent cause of receptor-binding positive androgen resistance.

In some subjects with genetic and endocrine evidence of androgen resistance, no defect is demonstrable in the binding of androgen to its receptor in cultured genital skin fibroblasts. We have defined the molecular defect in the androgen receptor in four unrelated subjects in this category (termed receptor positive) with the phenotype of compete or incomplete testicular feminization. In these patients we detected amino acid substitutions in either exon 2 or exon 3, which encodes the DNA-binding domain of the androgen receptor. In one patient with incomplete testicular feminization, two separate mutations were present in exon 3. Introduction of these amino acid substitutions into the androgen receptor-coding segment leads to the expression of receptor proteins that bind ligand in a normal fashion but do not activate the transcription of the androgen-responsive mouse mammary tumor virus promoter. Mobility shift assays using androgen receptor fusion proteins produced in E. coli indicate that these mutations impair binding of the receptor to specific DNA sequences. In the subject with incomplete testicular feminization, a Ser-Gly substitution at amino acid residue 595 is able to partially restore DNA-binding activity to a mutant receptor protein that carries an Arg-Pro substitution at position 615. These findings indicate that mutations in amino acid residues crucial to the binding of the androgen receptor to target DNA sequences are a common cause of receptor-binding positive androgen resistance and that variable impairment of DNA binding can lead to distinctive phenotypes.

Adolescent↗
PubMed1992

[Clinical and molecular basis of androgen resistance].

Androgen resistance is responsible for the development of a spectrum of abnormalities of male sexual differentiation, and can be broadly divided in two categories: deficiency of 5-alpha-reductase and defects in the androgen receptor. Recent developments in the field on molecular biology have allowed the cloning and characterization of the genes responsible for both syndromes and have made it possible to detect the subtle molecular defects underlying these diseases. This discussion will review some of the most recent development in this field of research.

Androgen-Binding Protein↗
PubMed1991

Androgen resistance caused by mutations in the androgen receptor gene.

Defects in the human androgen receptor cause a spectrum of defects in male phenotypic sexual development associated with abnormalities in the receptor protein assayed in cultured fibroblasts and in broken cell assays. In some patients these abnormalities are associated with absent ligand binding, in other qualitative or quantitative abnormalities of ligand binding are present, and in some no abnormality of ligand binding is detected. Analysis of the androgen gene structure in such patients has permitted identification of the causative mutation in many families. Although results of these studies often reinforce concepts established by in vitro mutagenesis studies of other steroid receptors, some mutations have provided unusual insight into the structural organization of the androgen receptor molecule.

Androgens↗
PubMed1991

A mutation in the DNA-binding domain of the androgen receptor gene causes complete testicular feminization in a patient with receptor-positive androgen resistance.

Androgen resistance is associated with a wide range of quantitative and qualitative defects in the androgen receptor. However, fibroblast cultures from approximately 10% of patients with the clinical, endocrine, and genetic features characteristic of androgen resistance express normal quantities of apparently normal androgen receptor in cultured genital skin fibroblasts (receptor-positive androgen resistance). We have analyzed the androgen receptor gene of one patient (P321) with receptor-positive, complete testicular feminization and detected a single nucleotide substitution at nucleotide 2006 (G----C) within the second "zinc finger" of the DNA-binding domain that results in the conversion of the arginine residue at position 615 into a proline residue. Introduction of this mutation into the androgen receptor cDNA and transfection of the expression plasmid into eukaryotic cells lead to the synthesis of a receptor protein that displays normal binding kinetics but is inactive in functional assays of receptor activity. We conclude that substitution mutations in the DNA-binding domain of the androgen receptor are one cause of "receptor-positive" androgen resistance.

Androgen-Insensitivity Syndrome↗
PubMed1991

Molecular basis of androgen resistance in a family with a qualitative abnormality of the androgen receptor and responsive to high-dose androgen therapy.

We have examined the nature of the mutant androgen receptor in a family with a severe defect in virilization associated with a qualitative defect in receptor function. The androgen receptor gene in this family contains two structural alterations: a single nucleotide substitution at position 2444 in exon 5 (adenosine----guanosine) that converts tyrosine 761 to a cysteine residue and a shortened glutamine homopolymeric segment in exon 1 that encodes 12 rather than the usual 20-22 glutamines. A family study was performed using polymerase chain reaction amplification of the glutamine-rich segment, and it was shown that the sister of the proband does not carry the mutant allele. The effects of these two mutations on the function of the androgen receptor were studied by introducing the changes, individually and in combination, into cDNAs encoding the normal human androgen receptor and analyzing the receptor protein produced after transfection of the cDNAs into eukaryotic cells. The presence of a cysteine residue at position 761 causes rapid dissociation of dihydrotestosterone from the receptor protein. Marked thermolability of the transfected receptor protein, however, was demonstrable only upon introduction of an androgen receptor cDNA containing both the partial deletion of the glutamine homopolymeric segment and a cysteine residue at position 761. Likewise, the ability of the receptor to stimulate a reporter gene is strikingly diminished only when both alterations are present, suggesting that the shortened glutamine homopolymeric segment amplifies the impairment of receptor function caused by the tyrosine to cysteine substitution.

Base Sequence↗
PubMed1991

Androgen resistance associated with a mutation of the androgen receptor at amino acid 772 (Arg----Cys) results from a combination of decreased messenger ribonucleic acid levels and impairment of receptor function.

Analysis of the nucleotide sequence of the coding segment of the androgen receptor gene in a patient (N105) with the receptor-negative form of complete testicular feminization has revealed a single substitution (CGC----TGC) at nucleotide 2476. This alteration results in the conversion of an arginine at amino acid 772 to a cysteine. Introduction of this mutation into an androgen receptor cDNA and transfection of the mutant cDNA into COS cells result in the production of a receptor protein with an alteration in the apparent Kd of ligand binding (3 nM) compared to that of the normal androgen receptor (0.5 nM). The mutant receptor protein predicted for patient N105 also demonstrates thermal instability of ligand binding that is not associated with quantitative or qualitative changes in the immunoreactive androgen receptor protein. When assayed in cotransfection experiments using a mouse mammary tumor virus-chloramphenicol acetyl transferase reporter system, the N105 receptor protein appears to be about a tenth as active as the control receptor. These functional characteristics do not appear sufficient to account for the phenotype of complete testicular feminization and do not explain the profound deficiency of androgen receptor in cultured skin fibroblasts. Quantitative S1 nuclease protection assays reveal that the level of androgen receptor mRNA in fibroblasts from patient N105 is markedly reduced. These results suggest that the phenotype in patient N105 is due to two effects of the nucleotide substitution at residue 2476: the replacement of a crucial amino acid (772) in the hormone-binding domain that impairs the function of any receptor molecules formed and a decrease in the level of androgen receptor mRNA.

Androgen-Insensitivity Syndrome↗
PubMed1990

Androgen receptor gene expression in human prostate carcinoma cell lines.

Responses to androgen vary widely among prostate cancers and prostatic carcinoma cell lines. We have explored the basis for this heterogeneity by examining the levels of androgen receptor expression in a prostate carcinoma cell line (LNCaP) that expresses the androgen receptor and two prostate carcinoma cell lines that do not contain detectable androgen receptor. We find that while the LNCaP cell line contains high levels of both the androgen receptor protein and mRNA, the receptor-negative cell lines DU-145 and PC-3 do not express androgen receptor protein as detected by immunoblotting or mRNA as detected by Northern analysis or S1 nuclease protection. These results indicate that the absence of androgen receptor expression in the androgen receptor-negative cell lines is caused by diminished androgen receptor mRNA levels. Genomic Southern analysis indicates that the differences in androgen receptor expression in each of these cell lines is not associated with detectable alterations in the structure of the androgen receptor gene.

Cell Line↗
PubMed1990

Expression of the human androgen receptor gene utilizes a common promoter in diverse human tissues and cell lines.

Androgens mediate their effects through an intracellular receptor that is a member of the steroid/thyroid hormone family of receptors. The expression of this protein is tightly regulated in different tissues and among cell types within a single tissue. To define the mechanisms controlling the expression of the androgen receptor, we have isolated and characterized the promoter of the androgen receptor gene in the human prostate cell line LNCaP. The major site of transcription initiation is approximately 1.1 kilobases upstream of the initiator methionine of the androgen receptor protein. The promoter region lacks typical "TATA" and "CAAT" sequence motifs but lies in a GC-rich region and contains a putative Sp1 binding site characteristic of a "housekeeping" promoter and a 44-base segment composed of alternating adenosine and guanosine residues. S1 nuclease protection analyses indicate that the same promoter is employed both in human tissues (prostate, testes), in genital skin fibroblasts, in T47D and MCF-7 breast cancer cells, and in LNCaP prostate cancer cells.

Base Sequence↗
PubMed1990

A single nucleotide substitution introduces a premature termination codon into the androgen receptor gene of a patient with receptor-negative androgen resistance.

Mutations of the androgen receptor that impair the action of 5 alpha-dihydrotestosterone and testosterone result in abnormal male sexual development. The definition of the organization of the androgen receptor gene has permitted us to examine its structure in nine patients with androgen resistance that exhibit absent 5 alpha-dihydrotestosterone binding in cultured fibroblasts (receptor-negative androgen resistance). Using labeled probes specific for each individual coding exon, we find no gross rearrangements, insertions, or deletions of the androgen receptor gene in these patients. To analyze the genetic defect in these receptor-negative patients, we used the polymerase chain reaction to amplify each individual exon of the androgen receptor gene in nine affected patients. In all patients, the size of each amplified exon segment was identical to that in normal individuals. The nucleotide sequence of the entire coding region of the androgen receptor was determined in one of these patients. A single nucleotide substitution was identified that results in a premature termination codon in exon 6 at amino acid 794. S1 nuclease protection assays demonstrated that normal levels of androgen receptor mRNA are present in skin fibroblasts of this patient. Transfection of a mutated androgen receptor cDNA containing a termination codon at position 794 into eukaryotic cells resulted in formation of a normal amount of receptor protein, as indicated by immunoblotting, but the expressed protein does not bind 5 alpha-dihydrotestosterone. These findings suggest that the presence of a premature termination codon at amino acid 794 of the androgen receptor is the cause of androgen resistance in this patient.

Adolescent↗
PubMed1990

Definition of the human androgen receptor gene structure permits the identification of mutations that cause androgen resistance: premature termination of the receptor protein at amino acid residue 588 causes complete androgen resistance.

We have isolated and characterized the gene encoding the human androgen receptor. The coding sequence is divided into eight coding exons and spans a minimum of 54 kilobases. The positions of the exon boundaries are highly conserved when compared to the location of the exon boundaries of the chicken progesterone and human estrogen receptor genes. Definition of the intron/exon boundaries has permitted the synthesis of specific oligonucleotides for use in the amplification of segments of the androgen receptor gene from samples of total genomic DNA. This technique allows the analysis of all segments of the androgen receptor gene except a small region of exon 1 that encodes the glycine homopolymeric segment. Using these methods we have analyzed samples of DNA prepared from a patient with complete androgen resistance and have detected a single nucleotide substitution at nucleotide 1924 in exon 3 of the androgen receptor gene that results in the conversion of a lysine codon into a premature termination codon at amino acid position 588. The introduction of a termination codon into the sequence of the normal androgen receptor cDNA at this position leads to a decrease in the amount of mRNA encoding the human androgen receptor and the synthesis of a truncated receptor protein that is unable to bind ligand and is unable to activate the long terminal repeat of the mouse mammary tumor virus in cotransfection assays.

Amino Acid Sequence↗
PubMed1989

Effects of long-term glibenclamide administration on gastrointestinal and pancreatic hormones in normal fasting rats.

We previously reported that sulfonylurea treatment reduces insulin (IRI), glucagon (IRG) and somatostatin (SRIF) release following metabolic stimuli from the isolated perfused pancreas of normal rats and that a reduction in IRI, IRG and SRIF pancreatic content was also observed. The present work was undertaken to investigate the effects of long-term glibenclamide treatment on the gastrointestinal content of gut hormones in normal rats. Moreover, the effects of sulfonylurea treatment on IRI, IRG, and SRIF pancreatic content were also analyzed and compared to the peripheral hormone plasma levels. Two groups of male Sprague-Dawley rats received glibenclamide (1 mg/kg/day per os; n = 14) or placebo (distilled water; n = 10) for 5 months, respectively. Tissue contents of IRI, IRG and SRIF in acid-ethanol extracts of pancreas and of gastric inhibitory peptide (GIP), vasoactive intestinal polypeptide (VIP), entero-glucagon (gut-GLI) and SRIF in acid-ethanol extracts of intestine were determined. Blood glucose and plasma pancreatic hormone levels were also measured. Glibenclamide treatment lowered the levels of IRI, IRG and SRIF in the pancreatic tissue; in the same way gut-GLI, SRIF and VIP intestinal concentrations were significantly reduced, whereas no significant inhibition was detected in intestinal GIP content. Blood glucose levels and IRI and SRIF plasma concentrations were similar in the two groups. IRG plasma levels were reduced in the sulfonylurea group. These findings might suggest that sulfonylurea suppresses hormone biosynthesis in a non-specific manner.

Administration, Oral↗
PubMed1989

Characterization and expression of a cDNA encoding the human androgen receptor.

We report the isolation of a cDNA that encodes the complete human androgen receptor. The cDNA predicts a protein of 917 amino acids with a molecular weight of 98,918. Introduction of the cDNA into heterologous mammalian cells caused expression of high levels of a protein that binds dihydrotestosterone with the affinity, specificity, and sedimentation properties characteristic of the native human androgen receptor. Comparisons with the amino acid sequence of previously cloned steroid hormone receptors revealed a high degree of sequence conservation with the progesterone, glucocorticoid, and mineralocorticoid receptors in the putative hormone and DNA-binding domain regions.

Amino Acid Sequence↗
PubMed1988

Food fiber choices for diabetic diets.

The use of dietary fiber (DF) in the diet of diabetics, although recommended, is often prevented by a limited tolerance and/or by the high cost and unpalatability of fiber supplements. Knowing that only or mainly the water soluble fraction of DF is effective in modulating postprandial hyperglycemia, the DF content (soluble, insoluble, and total) of a variety of common foodstuffs was determined. Such data were then utilized in the formulation of two complete meals, isocaloric and isoglucidic, characterized by a high-soluble, low-soluble, and total fiber content. The meals were administered to 13 NIDDM patients in good metabolic control. The data confirmed a significant reduction (p less than 0.001) of postprandial hyperglycemia and a moderate less significant reduction of insulinemia after the high fiber meal.

Adult↗
PubMed1988

Soluble and insoluble dietary fibre in diabetic diets.

The possibility of modulating postprandial metabolic responses in diabetics by an increase in the amount of soluble fibre rather than by the use of the high amounts of total dietary fibre (DF), so far strongly advocated, was investigated. Soluble and insoluble DF components of common foodstuffs were analysed and the data utilized to formulate three different meals with similar quantities of available carbohydrate, protein and fat and differing only in the quantity and quality of DF: low fibre (LF), high soluble fibre (HSF) and high insoluble fibre (HIF). Ten NIDDM patients in good metabolic control received each test meal in randomized order at 2-week intervals. The postprandial blood glucose and serum insulin responses to the LF and HIF test meals were similar. The HSF meal produced significantly lower glucose (P less than 0.001) and insulin (P less than 0.05) responses, compared to either LF or HIF meals. Such results may be of relevance in the formulation of diabetic diets in order to prevent an excess of insoluble fibre, so improving patients' compliance. Fruits and vegetables may be used advantageously to increase quantities of soluble fibre, limiting excesses of legumes or guar additives.

Adult↗
PubMed1988

A technical aid in stapled esophagojejunal anastomosis.

A technique that allows a safer use of the pursestring applicator in stapled esophagojejunostomy is described. By means of five stitches, all esophageal layers are incorporated in the stapled line. Thus, missing a segment of esophageal mucosal layer is avoided. No clinical or radiologic leak was observed in 48 patients who underwent total gastrectomy using this technique.

Anastomosis, Roux-en-Y↗
PubMed1988

Abdominotransanal approach in the treatment of the low-lying rectal carcinoma.

Seven patients with non advanced cancer of the lower third of the rectum underwent sphincter-saving resection through a combined abdominoperineal approach. In this procedure not only coloanal anastomosis, but also bowel transection were performed through the anus. All the patients had cancer located between 3.5-5.5 centimeters from the anal verge. The main advantages of the technique are precise lines of bowel transection with desired distal clearance of tumor, and easier and safer mobilization of the distal end of the rectum during the abdominal phase of the procedure. No mortality was observed; morbidity was comparable to low anterior resection. The mean follow-up is 8 months and all patients are free of recurrence and continent.

Adenocarcinoma↗