Search PubMed⌕ Search

Biomedical subjects

A Spiegel

Publications and source records attributed to A Spiegel.

At least 127 records · Page 7Linked to original sources
PubMed1986

Use of specific antibodies to quantitate the guanine nucleotide-binding protein Go in brain.

We immunized rabbits with purified guanine nucleotide-binding proteins (G proteins) from bovine brain and obtained an antiserum, RV3, that reacts specifically with the alpha subunit (39 kDa) of a G protein of unknown function, termed Go, as well as with the beta subunit (35 kDa) common to all G proteins. RV3 showed no crossreactivity with the alpha subunits of the stimulatory (Gs) or inhibitory (Gi) G proteins associated with adenylate cyclase, nor with that of the rod outer segment G protein, transducin. Immunoblots with crude and affinity-purified antiserum showed that RV3 specifically recognizes the Go alpha subunit and the beta subunit in crude brain membranes. Using RV3, we found approximately equal amounts of Go in brain membranes from frog, chicken, rat, cow, and man. Quantitative immunoblotting gave Go alpha subunit/ beta subunit ratios approximately equal to 1 in cerebral cortex, raising the possibility that free Go alpha subunit (unassociated with beta subunit) may exist in brain. The concentration of Go alpha subunit in cortex is about 5 times that of Gi alpha subunit. The results show that Go is an immunochemically distinct, highly conserved protein distributed throughout the brain, with particularly high concentrations in forebrain.

Animals↗
PubMed1986

Selective resistance to parathyroid hormone in cultured skin fibroblasts from patients with pseudohypoparathyroidism type Ib.

We measured cAMP production in response to agonists in cultured skin fibroblasts from subjects with pseudohypoparathyroidism type Ib (PHP Ib; normal phenotype, resistance to PTH only, normal guanine nucleotide stimulatory coupling protein activity) and skin fibroblasts from normal subjects. There were no significant differences in basal or prostaglandin E1- and forskolin-stimulated cAMP production in PHP Ib vs. normal fibroblasts. Fibroblasts from 7 of 10 subjects with PHP Ib had significantly reduced peak cAMP responses to PTH [3.95 +/- 0.88 vs. 15.9 +/- 4.2 pmol/100 micrograms protein (mean +/- SD); n = 7 for both groups; P less than 0.001]. PTH-stimulated cAMP production was significantly reduced in the 7 subjects with PHP Ib at all concentrations of PTH tested [3-1000 ng/ml human PTH-(1-34)]. In the other 3 subjects with PHP Ib, the cAMP response to PTH was either normal (2 subjects) or above the normal range (1 subject). Thus, skin fibroblasts from many, but not all, subjects with PHP Ib have selective resistance to PTH in terms of cAMP response. Since the defect is hormone specific and persists in culture, we suggest that an intrinsic defect in the PTH receptor may cause PTH resistance in certain subjects with PHP Ib. The cause of PTH resistance in the subjects with a normal cAMP response to PTH is not known, but the data suggest heterogeneity even within the PHP Ib subgroup.

Adolescent↗
PubMed1986

The inhibitory guanine nucleotide regulatory protein modulates agonist-stimulated cAMP production in rat osteosarcoma cells.

We identified the subunits of the stimulatory and inhibitory guanine nucleotide binding proteins (Gs and Gi, respectively) associated with adenylate cyclase in rat osteosarcoma (ROS) cells. Pertussis toxin catalyzed ADP-ribosylation of Gi alpha in ROS cells increased agonist (PTH and isoproterenol)-stimulated, but not basal, cAMP production. The effect of pertussis toxin was dose and time dependent, and slowly reversible (T 1/2 approximately 30 h) during continued culture without toxin. Pertussis toxin treatment of ROS cell lines (17/2.8 and 24/l) with markedly different agonist responsiveness increased agonist-stimulated cAMP production in proportion to the response without toxin treatment. Pertussis toxin treatment further increased cAMP response to PTH in dexamethasone treated cells. We conclude that ROS cells contain functional Gi which modulates agonist-stimulated cAMP formation. Alterations in ROS cAMP responsiveness caused by steroids, and the reduced responsiveness of the 24/1 cell line, however, are unlikely to be due to changes in Gi.

Adenylate Cyclase Toxin↗
PubMed1985

The tryptic and chymotryptic fragments of the beta-subunit of guanine nucleotide binding proteins in brain are identical to those of retinal transducin.

The 35-kDa beta-subunit of transducin purified from rod outer segment membranes is cleaved into 2 major fragments by trypsin, and 7 major fragments by chymotrypsin. Identical fragments are visualized by immunoblotting with transducin-beta specific antisera after proteolysis of rod outer segment membranes, purified brain guanine nucleotide binding proteins, and brain membranes. The results indicate that the beta-subunits of transducin and of brain guanine nucleotide binding proteins are not only similar structurally, but are also similarly oriented in membranes with respect to accessibility to proteolytic enzymes.

Animals↗
PubMed1985

Antibodies against the carboxyl-terminal 5-kDa peptide of the alpha subunit of transducin crossreact with the 40-kDa but not the 39-kDa guanine nucleotide binding protein from brain.

We tested 18 antisera showing reactivity against the alpha subunit of transducin, the guanine nucleotide binding protein from rod outer segment, for crossreactivity against the 40- and 39-kDa guanine nucleotide binding proteins purified from bovine brain. A single antiserum, CW6, showed crossreactivity, and this was predominantly against the 40-kDa protein. Immunoblots of the tryptic fragments of transducin alpha subunit with multiple antisera raised against that subunit showed that only CW6 recognizes a COOH-terminal 5-kDa peptide that includes the site of pertussis toxin ADP-ribosylation. Antibodies against the 5-kDa peptide, affinity-purified from CW6, specifically react with the 40-kDa brain protein on immunoblots. The results show that the 39- and 40-kDa guanine nucleotide binding proteins from brain differ immunochemically and that the COOH-terminal 5-kDa peptide of transducin alpha subunit is homologous to a region in the 40-kDa brain protein. We speculate that this homologous region may be in a domain that confers specificity for receptor interactions of guanine nucleotide binding proteins.

Adenosine Diphosphate Ribose↗
PubMed1985

Antisera against a guanine nucleotide binding protein from retina cross-react with the beta subunit of the adenylyl cyclase-associated guanine nucleotide binding proteins, Ns and Ni.

Antisera were produced in rabbits against a guanine nucleotide binding protein (N protein), transducin, purified from bovine retina. Antiserum AS/1, which recognized all three subunits (alpha, beta, and gamma) of the holoprotein, was tested for cross-reactivity with the subunits of the adenylyl cyclase [adenylate cyclase; ATP pyrophosphate-lyase (cyclizing), EC 4.6.1.1]-associated stimulatory (Ns) and inhibitory (Ni) N proteins purified from human erythrocytes. As/1 showed strong reactivity against the beta subunits of both Ns and Ni but failed to cross-react with either the alpha or gamma subunits of Ns and Ni. Seven additional antisera against transducin reacted with the beta subunits but not with the alpha or gamma subunits of Ns and Ni. A single antiserum against transducin reacted with the alpha subunit of Ni but not of Ns. Immunostaining of the beta subunits of Ns and Ni was proportional to the amount of beta subunit blotted and to the antiserum concentration. Immunostaining of either human erythrocyte or bovine cerebral cortical plasma membrane proteins with AS/1 showed a single band, comigrating with the beta subunit of transducin; this band was absent in bovine erythrocyte membranes. Estimation of the amount of beta subunit by immunoblotting with AS/1 showed that the beta subunit comprises approximately equal to 2% of bovine cerebral cortical plasma membrane protein, approximately equal to 100-fold more than in human erythrocyte membranes. These findings provide immunochemical evidence for similarities in the beta subunits and differences in the alpha and gamma subunits of this family of N proteins. Antisera against transducin react specifically with the beta subunits of Ns and Ni in crude plasma membranes and, thus, can serve as specific probes for the beta subunit.

Adenylyl Cyclases↗
PubMed1985

A factor produced by cultured rat Leydig tumor (Rice 500) cells associated with humoral hypercalcemia stimulates adenosine 3',5'-monophosphate production via the parathyroid hormone receptor in human skin fibroblasts.

The Rice-500 Leydig cell tumor of Fischer rats is associated with humoral hypercalcemia in vivo and produces a factor that stimulates cAMP formation in cultured rat osteosarcoma cells. We found that cultured human skin fibroblasts respond to both human PTH-(1-34) and the factor produced by cultured rat Leydig tumor cells with a dose-dependent rise in cAMP formation. The time courses for stimulation of the two agents were similar, and stimulation by both was blocked by the competitive PTH antagonist [8,18-norleucine,34-tyrosine]bovine PTH-(3-34) amide. These data suggest that PTH-like factors secreted by a murine tumor are capable of interacting with the human PTH receptor.

Adult↗
PubMed1985

Morphologic and functional studies of a rat hypercalcemia-associated testicular tumor maintained in cell culture.

The Rice H500 tumor is a transplantable nonmetastasizing testicular tumor of Fischer rats associated with hypercalcemia and increased urine cyclic adenosine monophosphate (AMP) excretion, features similar to those of the clinical syndrome of humoral hypercalcemia of malignancy. Tumor cells can be maintained in tissue culture; one million cells grown in culture reinoculated in Fischer rats reproduce the syndrome of tumor growth and lethal hypercalcemia. Infusion of concentrated, serum-free cell culture supernatant into parathyroidectomized rats produced an increase in urine cyclic AMP similar to that produced by an infusion of bovine parathyroid hormone. Light and electron microscopic appearance of the H500 tumor in vivo and in vitro is similar to previous descriptions of a hypercalcemia-associated rat testicular tumor believed to be of Leydig cell origin. Ultrastructural characteristics of microvilli, intracellular glandlike lumina, and cell-cell attachments, however, suggest an epithelial origin. Absence of smooth endoplasmic reticulum typical of steroid-secreting Leydig cells suggest these cells are not actively involved in steroid synthesis and secretion. The ultrastructure of this tumor is sufficiently different from that of normal Leydig cells that the cell of origin is unclear. Nonetheless, this tumor provides a useful model of hormonally mediated tumor-associated hypercalcemia.

Animals↗
PubMed1984

Antibodies against a retinal guanine nucleotide-binding protein cross-react with a single plasma membrane protein in non-retinal tissues.

Antisera (AS/1-AS/6) to purified bovine retinal transducin, a guanine nucleotide-binding protein, were produced in 6 rabbits. Immunoblots showed that the antisera varied in their reactivity with the subunits of transducin; AS/1 reacted strongly with all 3 subunits, while the others reacted with only the beta and/or gamma subunits. Only AS/1 specifically immunoprecipitated the alpha subunit radiolabeled with non-covalently bound guanine nucleotides. Immunostaining of plasma membrane proteins from non-retinal tissues with AS-1 revealed a single protein (approx. 35 kDa), most likely representing the beta subunit of the guanine nucleotide-binding proteins (Gs and Gi) associated with adenylate cyclase. Cerebral cortex showed the highest content of this protein. Antisera against transducin provide a highly specific and sensitive probe for quantitation of the beta subunit of Gs and Gi.

Animals↗
PubMed1982

Radiographic findings in recurrent parathyroid carcinoma.

Seven cases of recurrent parathyroid carcinoma were reviewed. Subperiosteal resorption was seen in 6, pulmonary nodules in 4, renal calculi in 5, brown tumors in 5, and pancreatic calcification in 1. Angiography was performed in 5 patients, showing 1 definite and 2 probable cervical recurrences, 1 mediastinal lesion, and 1 case of possible bone metastases. Venous sampling for parathyroid hormone was carried out in 4 patients and suggested residual disease in 2; in addition, there were 1 false and 1 true negative. CT was performed in 4 patients and was useful in delineating metastatic pulmonary nodules, cervical recurrence, and hepatic metastases. The radiographic approach to recurrent parathyroid carcinoma and the use of CT and angiography are discussed.

Adult↗
PubMed1981

Results of reoperation for persistent and recurrent hyperparathyroidism.

Between August 1975 and January 1981, 106 patients thought to have persistent or recurrent hyperparathyroidism underwent a total of 108 parathyroid re-explorations at the National Institutes of Health. These 106 patients had a total of 175 previous operations for hyperparathyroidism (156 cervical and 19 mediastinal). Nephrolithiasis (54% of patients) and bone disease (24% o patients) were the predominant symptoms. Arteriographic examination and selective venous sampling provided highly accurate localizing results in 33% of the patients, and were of some help in 64%. The final diagnoses after reoperation and re-evaluation were: single-gland disease in 58 patients, primary nonfamilial hyperplasia in 19 patients, familial hyperplasia in three patients, multiple endocrine neoplasia (MEN) Type I in ten patients, MEN Type II in two, parathyroid carcinoma in four patients, secondary hyperplasia in three patients, and familial hypocalciuric hypercalcemia (FHH) in two patients. The diagnosis was in doubt in five patients. In the 95 patients with unequivocal hyperparathyroidism, not due to parathyroid carcinoma, surgery eliminated hypercalcemia in 91 (96%). Two patients died after operation, one of disseminated candidiasis, and one patient, with an immunodeficiency, of sepsis. Five patients developed temporary, and one permanent, recurrent nerve damage; 41% of the patients were hypocalcemic, at the time of discharge from the hospital.

Adenoma↗
PubMed1979

Angiographic ablation of parathyroid adenomas.

Six mediastinal parathyroid adenomas were stained by infusing contrast agent through a catheter wedged in the feeding artery. Adenomas in the first three cases were stained unintentionally with small volumes of dilute contrast media and hypercalcemia recurred within 3 to 6 months. In the next three patients, adenomas were deliberately stained with larger doses of concentrated contrast media and these patients have remained normocalcemic from 2 to 18 months following staining. The permanency of parathyroid ablation following deliberate staining with contrast media has not been established.

Adenoma↗
PubMed1979

Differential diagnosis of brown tumor vs. cystic osteitis by arteriography and computed tomography.

An expansile lytic lesion of bone can be either a brown tumor or a cyst when the patient has hyperparathyroidism. If weight-bearing bones are involved, the diagnosis must be made prior to parathyroidectomy in order to avert a possible pathological fracture. In the authors' patient, arteriography and computed tomography both demonstrated that the lesion in question was a brown tumor, which is hypervascular and clearly separable from a fluid-filled cyst; however, CT has the advantage of being a noninvasive procedure.

Adult↗
PubMed1978

Hypercalcemia with suppressed parathyroid hormone in Burkitt's lymphoma.

Two patients with Burkitt's lymphoma presented with severe hypercalcemia, a previously unreported complication of this tumor. Roentgenograms and radionuclide scans showed multiple osteolytic lesions in both patients. Plasma parathyroid hormone (PTH) was undetectable during the hypercalcemia phase. Chemotherapy was followed by rapid tumor lysis, hyperphosphatemia, phosphaturia and hypocalcemia. The hypocalcemic phase persisted for two weeks despite rapid normalization of serum phosphorus and renal function. Measurement of urinary cyclic AMP, an index of PTH action, indicated that parathyroid function had been suppressed by the hypercalcemia and remained suppressed for almost one week despite marked hypocalcemia.

Adult↗
PubMed1978

Bordetella pertussis does not induce beta-adrenergic blockade.

Bordetella pertussis organisms induce histamine sensitivity and diminish the normal hyperglycemic response to epinephrine in experimental animals. These effects have been attributed to beta-adrenergic blockade. However, under conditions in which the decrease in epinephrine-induced hyperglycemia after B. pertussis administration was demonstrable, there was no change in rat reticulocyte beta-adrenergic receptor number or affinity measured by iodohydroxybenzylpindolol binding or in isoproterenol-stimulated adenylate cyclase activity. Therefore, there was no generalized beta-adrenergic blockade induced by B. pertussis. The observed effects can be explained by the hypersecretion of insulin resulting from B. pertussis administration.

Adenylyl Cyclases↗