Charles Eil

Mutation in the Gene Encoding the Stimulatory G Protein of Adenylate Cyclase in Albright's Hereditary Osteodystrophy

Albrights hereditary osteodystrophy is an autosomal dominant disorder characterized by a short stature, brachydactyly, subcutaneous ossifications, and reduced expression or function of the alpha subunit of the stimulatory G protein (Gs alpha) of adenylate cyclase, which is necessary for the action of parathyroid and other hormones that use cyclic AMP as an intracellular second messenger. We identified a unique Gs alpha protein in erythrocytes from two related patients with Albrights hereditary osteodystrophy and reduced Gs alpha bioactivity. The Gs alpha variant was recognized by a carboxyl terminal-specific Gs alpha antiserum but not by polyclonal antiserums specific for the amino terminus of Gs alpha. To investigate the molecular basis for this structurally abnormal Gs alpha protein, we studied the Gs alpha gene by restriction-endonuclease analysis. DNA from the two patients had an abnormal restriction-fragment pattern when digested with Ncol, which was consistent with loss of an Ncol restriction site in exon 1 of one Gs alpha allele. Amplification of a 260-base-pair region that includes exon 1 of the Gs alpha gene and direct sequencing of the amplified DNA revealed an A-to-G transition at position +1 in one Gs alpha allele from each of the two patients. This mutation converts the initiator ATG (methionine) codon to GTG (valine), blocking initiation of translation at the normal site. Translation of the abnormal Gs alpha messenger RNA would result in the synthesis of a truncated Gs alpha molecule lacking the amino terminus. We conclude that in at least some patients with Albrights hereditary osteodystrophy, the disease is caused by a single-base substitution in the Gs alpha gene and is thus due to an inherited mutation in a human G protein.

A Cellular Defect in Hereditary Vitamin-D-Dependent Rickets Type II: Defective Nuclear Uptake of 1,25-Dihydroxyvitamin D in Cultured Skin Fibroblasts

VITAMIN-D-dependent (or pseudo-vitamin-D-deficient) rickets is characterized by clinical and biochemical features of vitamin-D-deficient rickets and by remission of these features during treatment ...

The binding properties of pyrethroids to human skin fibroblast androgen receptors and to sex hormone binding globulin

The pyrethroids are a class of natural and synthetic pesticides which were associated with an epidemic of gynecomastia in Haitian men in 1981. In the present study we tested several pyrethroids for their ability to interact with androgen binding sites in dispersed, intact human genital skin fibroblasts and in human plasma to sex hormone binding globulin (SHBG). All the pyrethroids tested inhibited fibroblast binding of [3H]methyltrienolone (R1881) at 22 degrees C with the following rank order of potency:pyrethrins greater than bioallethrin greater than fenvalerate greater than fenothrin greater than fluvalinate greater than permethrin greater than resmethrin. 50% displacement of [3H]R1881 binding to fibroblast androgen receptors was achieved by 1.5-44 x 10(-5) M concentrations of the competitors, respectively. Previous studies with cimetidine, a known inhibitor of androgen receptor binding, showed 50% competition at a concentration of 1.4 x 10(-4) M in this system. Scatchard analysis of binding experiments performed with increasing concentrations of [3H]R1881 in the presence of the pyrethroids indicated that the binding inhibition was competitive. On the other hand, of the pyrethroids examined only the pyrethrins (50% inhibition) and bioallethrin (43% inhibition) were able to displace [3H]testosterone from SHBG when tested at a concentration of 10(-4) M. These data indicate that a novel class of non-steroidal compounds, the pyrethroids, can interact competitively with human androgen receptors and SHBG. These findings provide a mechanism by which chronic exposure of humans or animals to pesticides containing these compounds may result in disturbances in endocrine effects relating to androgen action.

A dispersed-whole cell method for the determination of androgen receptors in human skin fibroblasts

A method is described for the determination of binding capacity (Ro) and dissociation constant (Kd) of androgen receptors in dispersed, whole, cultured human skin fibroblasts. The cells obtained from punch biopsies or operative specimens of skin, are grown to confluence in monolayers, harvested, washed, and dispersed in medium. Binding is assessed by incubating the cells with [3H]dihydrotestosterone (DHT) at 22 degrees C for one hour followed by washing, centrifugation and counting. Non-specific binding is determined by adding radioinert methyltrienolone (R1881). Scatchard plots are constructed using 6 concentration points; binding is expressed as sites/cell. The method is precise (Ro = 12,105 +/- 4305 (S.D.) sites/cell; Kd = 1.0 +/- 0.7 (S.D.) x 10(-9)M, n = 14 for one prepuce cell line) and independent of cell passage number. Binding is linear with respect to cell number and shows those characteristics commonly attributed to androgen receptors: high affinity, low binding capacity, saturable nuclear binding, androgen specificity, and an 8S peak in fibroblast cytosol using sucrose density gradients. Cell lines shown by other published methods to lack androgen receptors had no detectable DHT binding with this method. This assay technique has the advantages of simplicity, rapidity, and precision.

Hyperphosphatemia in multiple myeloma due to a phosphate‐binding immunoglobulin

Hyperphosphatemia (HP) is usually seen in patients with hypoparathyroidism, renal failure, and tumor lysis. The authors described a patient with HP due to a phosphate‐binding immunoglobulin (Ig). An 86‐year‐old woman had serum phosphate levels as high as 4.75 mmol/l, (normal, 0.77 to 1.45 mmol/l). Serum ionized calcium, blood urea nitrogen (BUN), creatinine, and N‐terminal parathyroid hormone (PTH) levels were normal, but serum 1,25‐dihydroxyvitamin D level was subnormal at less than 12 pmol/l (normal, 36 to 146 pmol/l). Serum total protein was elevated at 105 g/l (normal, 60 to 80 g/l), and additional studies confirmed a diagnosis of immunoglobulin G (IgG) multiple myeloma. Results of in vitro studies using anti‐human IgG antibodies showed that the IgG of the patient bound inorganic phosphate. Several isolated case reports have documented spurious HP due to interference of the paraprotein in the routine serum phosphate assay. In only one patient, however, has actual binding of phosphate to a myeloma protein been documented. The studies of the authors document phosphate binding by an IgG paraprotein and suggest that in this setting HP may be of physiologic significance as evidenced by depressed serum levels of 1,25‐dihydroxyvitamin D.

Hypercalcemia and Disseminated Cytomegalovirus Infection in the Acquired Immunodeficiency Syndrome

Two patients with the acquired immunodeficiency syndrome and disseminated cytomegalovirus infection developed hypercalcemia associated with suppressed parathyroid gland activity. Neither patient had evidence of a malignant, endocrinologic, granulomatous, or drug-related cause for hypercalcemia. Increased osteoblastic bone resorption induced by cytomegalovirus infection may have been the cause for the hypercalcemia. Physicians should be alert for the occurrence of endocrinologic and metabolic problems in immunosuppressed patients.

The Molecular Basis for Resistance to 1,25-Dihydroxyvitamin D: Studies in Cells Cultured from Patients with Hereditary Hypocalcemic 1,25(OH)2D3-Resistant Rickets

Vitamin D-dependent rickets, type II, is a rare, hereditary syndrome characterized by early onset rickets, hypocalcemia, secondary hyperparathyroidism, normal vitamin D intake, and normal or elevated circulating levels of 1,25-dihydroxyvitamin D (1,25(OH)2D). It is thought to result from target tissue resistance to the action of 1,25(OH)2D in a manner analogous to the resistance to androgens and glucocorticoids seen in patients with decreased hormone action in the face of elevated blood levels of those hormones.1,2 We will refer to this form of rickets as hereditary, hypocalcemic 1,25(OH)2D3-resistant rickets (HHDR).

ANDROGEN RECEPTOR CHARACTERISTICS IN SKIN FIBROBLASTS FROM MEN WITH PUBERTAL MACROMASTIA

Endocrine studies in men with pubertal macromastia (PM) have failed to reveal a hormonal abnormality to account for the disorder. As a result, it has been hypothesized that this form of gynecomastia may be a manifestation of a target organ abnormality.

Caution on bone scans in eosinophilic granuloma.

Excerpt To the editor: Multifocal eosinophilic granuloma (Hand-Schuller-Christian disease) often produces lytic lesions of the skeletal system. Scintiscanning with bone-seeking agents is thought to...