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Biomedical subjects

R A Roth

Publications and source records attributed to R A Roth.

At least 253 records · Page 14Linked to original sources
PubMed1987

Arachidonic acid metabolites and the mechanisms of monocrotaline pneumotoxicity.

MCT produces pulmonary vascular injury and pulmonary hypertension in rats by unknown mechanisms and provides a useful animal model with which to study chronic pulmonary hypertension. Several arachidonic acid metabolites including TxA2 and LT are present in increased concentration in lungs of rats made chronically pulmonary hypertensive with MCT or MCTP. The lack of protection afforded by cotreatment with drugs that inhibit the biosynthesis or antagonize the actions of TxA2 indicates that TxA2 does not play a major role in the pathogenesis of cardiopulmonary injury in this model. Results with DEC suggest the possibility of involvement of LT in the response to MCT and MCTP; additional work is needed to clarify the exact role of LT in this model. The roles of other biologically active lipid mediators such as platelet activating factor and HETEs are currently unknown. Increased understanding of the role of various mediators will come partly from the identification and careful use in vivo of improved drugs that have specific effects as synthesis inhibitors or receptor antagonists.

Animals↗
PubMed1987

In vivo association of [125I]-insulin with a cytosolic insulin-degrading enzyme: detection by covalent cross-linking and immunoprecipitation with a monoclonal antibody.

A cytosolic insulin-degrading enzyme (Mr = 110,000) was found to be cross-linked to [125I]-insulin in intact human hepatoma cells, HepG2, incubated with the hormone and treated with the bifunctional cross-linker, disuccinimidyl suberate. The labeling of this protein was greatly increased by concurrent treatment of the cells with N-ethylmaleimide, to the extent that the amount of [125I]-insulin cross-linked to the enzyme in these cells was approximately 20 to 50% that cross-linked to the insulin receptor. The labeling of the insulin-degrading enzyme required the prior interaction of [125I]-insulin with its receptor as well as a temperature- and energy-dependent processing of the hormone. The present work therefore supports a role for this protease in the cellular processing of insulin.

Antibodies, Monoclonal↗
PubMed1987

A membrane-anchored cytoplasmic domain of the human insulin receptor mediates a constitutively elevated insulin-independent uptake of 2-deoxyglucose.

Insulin stimulates the autophosphorylation of the beta-subunit of the insulin receptor (IR) on tyrosine residues. Mutations which compromise IR autophosphorylation in vivo result in a decrease of the insulin-activated uptake of 2-deoxyglucose. These results are consistent with previous results which implicate IR autophosphorylation in the generation of the insulin response by cells. To further explore the specificity of the IR tyrosine phosphokinase (TPK) domain in IR function, we have altered the human IR (hIR) cDNA to encode truncated insulin-independent TPKs, which are expressed in chinese hamster ovary (CHO) cells as either membrane-anchored or cytosolic proteins. Both mutant hIRs exhibit TPK activity in vitro, although the cytosolic form is approximately 20 times more active. The carbohydrate moiety of the membrane-anchored form is of the high mannose type, consistent with an intracellular localization for this mutant hIR. The two mutant hIRs mediate very different physiological responses in transfected cells: the membrane-anchored, but not the cytosolic, hIR TPK mediates a constitutively elevated (135% the maximum insulin-stimulated response in CHO cells) insulin-independent uptake of 2-deoxyglucose. These results thus suggest that the hIR TPK is in fact specific for this aspect of IR function and, when membrane-associated, can mediate the insulin-independent uptake of 2-deoxyglucose. Neither of these mutant hIRs appears to transform CHO cells.

Animals↗
PubMed1987

Phosphorylation of purified insulin receptor by cAMP kinase.

Highly purified insulin receptor was shown to be a substrate for cAMP kinase. Approximately 1 phosphate was incorporated per molecule of receptor, and the cAMP kinase's affinity for the receptor was at least as high as its affinity for histone. The sites phosphorylated by cAMP kinase seemed distinct from those phosphorylated by the protein kinase C. Phosphorylation by cAMP kinase had no effect on the ability of several monoclonal antibodies to recognize the receptor or on the insulin-binding activity of the receptor. However, cAMP phosphorylation partially inhibited the tyrosine kinase activity of the receptor (approximately 25%). These results suggest that catecholamine-induced resistance to insulin may be partly due to a direct phosphorylation of the receptor by cAMP kinase and a subsequent inhibition of the ability of the receptor kinase to be activated by insulin.

Humans↗
PubMed1987

6-keto prostaglandin F1 alpha and thromboxane B2 in isolated, buffer-perfused lungs from monocrotaline pyrrole-treated rats.

Monocrotaline pyrrole (MCTP) causes pulmonary endothelial cell injury and pulmonary hypertension in rats. Damage to endothelial cells in culture has been associated with altered prostacyclin (PGI2) production; therefore, it was of interest to determine if MCTP affected pulmonary PGI2 production. Release of the stable metabolites of PGI2 and thromboxane A2, 6-keto prostaglandin F1 alpha (6-keto PGF1 alpha) and thromboxane B2 (TxB2), respectively, was examined in isolated, buffer-perfused lungs from MCTP-treated rats at times when elevated pulmonary arterial pressure is first observed (day 7) and when the pulmonary hypertensive state has existed for some time (day 14), 6-keto PGF1 alpha release was not affected by MCTP treatment 7 or 14 days after a single intravenous injection of MCTP. TxB2 release was also unaffected at day 7, however 14 days after treatment TxB2 release was greater in lungs from MCTP-treated rats compared to controls. The concentration of both 6-keto PGF1 alpha and TxB2 increased when arachidonic acid was infused into lungs from control or treated rats. These data indicate that MCTP treatment increases the release of TxB2 from isolated lungs at a time when pulmonary hypertension is well-established, but not during early development of pulmonary hypertension.

6-Ketoprostaglandin F1 alpha↗
PubMed1987

The human insulin receptor cDNA: a new tool to study the function of this receptor.

The human insulin receptor (hIR) is an integral transmembrane glycoprotein comprised of two alpha and two beta subunits. An immediate consequence of insulin binding to the extracellular alpha subunit is the autophosphorylation of tyrosine residues on the intracellular domain of the beta subunit. The placental hIR cDNA has been cloned and sequenced, providing the primary structural features of the protein. In order to investigate the functions of the beta subunit and particularly the role of autophosphorylation and tyrosine phosphokinase (TPK) activity (a feature shared by other receptors and oncogene proteins) in transmembrane signalling, we designed an expression system of the hIR cDNA in eucaryotic cells. Superexpressing CHO cell lines that contain about 10(6) functional hIR/cell have been developed. In these cells half maximum stimulation of glucose uptake occurs at 5 X 10(-10)M insulin, whereas normal CHO cells require 5 X 10(-12)M insulin. In this expression system we have carried out site-directed mutagenesis experiments in which domains of the molecule have been deleted or particular amino acids have been replaced by others. The replacement of either or both the tyrosine residues 1162 and 1163 compromise an autophosphorylated site that is important for kinase function and the insulin response. Expression of an isolated membrane-bound form of the beta-subunit produces a 6 fold increase in glucose uptake. This insulin-independent effect disappears if the twin tyrosines are mutated or if the beta subunit is expressed in the cytoplasm. These studies also show that the C terminal 112 amino acid portion of the beta subunit is important for the stability of this protein.

Amino Acid Sequence↗
PubMed1987

[Rigid uretero-renoscopy: critical study of a series of 116 consecutive patients].

We have reviewed the first 116 cases of uretero-renoscopy using rigid ureteroscopes. Procedures were done for either diagnostic or therapeutic purposes (27 and 2 respectively), and for stone manipulation (87). The overall success rate for stone removal was 73%. The success rate for removal of stones the proximal two-thirds and distal third of the ureter were 38% and 83% respectively. Stones larger than 10 mm. Were successfully removed in 64% of cases. In 13 cases (11%), ureterolithotomy was necessary to successfully remove the stone. Diagnostic ureteroscopies for pathology of the ureter were 100% successful. The factors which affected success and failure rates, e.g. stone size, stone composition, ureteral abnormality and operator experience are delineated.

Adult↗
PubMed1986

A solid-phase competitive radioimmunoassay for the insulin receptor.

A radioimmunoassay for the insulin receptor has been developed. In this assay, unlabeled receptor competes with 125I-labeled receptor for binding to monoclonal anti-receptor antibodies immobilized on microtiter wells coated with affinity-purified anti-mouse immunoglobulin G. This assay was highly reproducible and could detect 7 ng (14 fmol) of insulin receptor. By utilizing monoclonal antibodies to various antigenic regions of the receptor, different parts of the receptor molecule could be examined. By utilizing antibodies to the cytoplasmic domain of the receptor, an assay was developed which was not influenced by the presence of insulin and could equally detect the insulin receptor from different species (rat and human) and different tissues (placenta and brain). By utilizing antibodies to an autophosphorylation site of the receptor, the assay was shown capable of detecting the extent of phosphorylation of the receptor. Finally, this assay was utilized to monitor the decrease in insulin receptors in lysates of insulin-treated human lymphocytes. This radioimmunoassay should be useful for monitoring both the number and status of the insulin receptor under a variety of physiological conditions.

Animals↗
PubMed1986

Effect of a mixed function oxidase inducer and inhibitor on monocrotaline pyrrole pneumotoxicity.

Monocrotaline (MCT) produces vascular injury to the lung, pulmonary hypertension, and right ventricular hypertrophy when injected into rats. It is well established that the pneumotoxicity of MCT depends on its hepatic bioactivation to monocrotaline pyrrole (MCTP) and perhaps other toxic metabolites. To test whether MCTP requires further bioactivation, we synthesized this metabolite chemically, confirmed its structure using fast-atom bombardment-mass spectrometry and nuclear magnetic resonance, and injected it into rats previously treated with an inducer or inhibitor of MFOs. Pretreatment with either phenobarbital or SKF-525A did not alter the pneumotoxic effects of an intravenous injection of MCTP. Rats given the same intravenous dose of either MCT, MCT N-oxide, or MCTP responded with toxicity only to MCTP. MCTP added to rat serum in vitro resulted in a color change (Amax = 477 nm) that developed over several seconds, an observation consistent with degradation of MCTP in serum. To explore the possibility that aqueous degradation products might contribute to its toxicity, the same intravenous dose of MCTP was administered to rats in N,N-dimethylformamide (DMF), serum, or saline. Only MCTP administered in in DMF resulted in toxicity. These results support the contention that MCT requires metabolism to MCTP to produce pneumotoxicity and that exposure to aqueous media renders MCTP incapable of causing lung injury.

Animals↗
PubMed1986

Purification and characterization of the receptor for insulin-like growth factor I.

The receptor for insulin-like growth factor I (IGF-I) was purified from the rat liver cell line BRL-3A by a combination monoclonal anti-receptor antibody column and a wheat germ agglutinin column. Analyses of these receptor preparations on reduced sodium dodecyl sulfate-polyacrylamide gels yielded protein bands of Mr 136K (alpha subunit) and Mr 85K and 94K (beta subunit). These receptor preparations bound 5 times more IGF-I than insulin, and the binding of both labeled ligands was more potently inhibited by unlabeled IGF-I than by insulin. These results indicate that these receptor preparations contained predominantly the IGF-I receptor. This highly purified receptor preparation was found to possess an intrinsic kinase activity; autophosphorylation of the receptor beta subunit was stimulated by low concentrations of IGF-I (half-maximal stimulation at 0.4 nM IGF-I). Twentyfold higher concentrations of insulin were required to give comparable levels of stimulation. A monoclonal antibody that inhibits the insulin receptor kinase was found to inhibit the IGF-I receptor kinase with the same potency with which it inhibits the insulin receptor. In contrast, monoclonal antibodies to other parts of the insulin receptor only poorly recognized the IGF-I receptor. A comparison of V8 protease digests of the insulin and IGF-I receptors again revealed some similarities and also some differences in the structures of these two receptors. Thus, the IGF-I receptor is structurally, antigenically, and functionally similar to but not identical with the insulin receptor.

Animals↗
PubMed1986

Identification of a monoclonal antibody which can distinguish between two distinct species of the type I receptor for insulin-like growth factor.

A monoclonal antibody was identified which equally inhibits 125I-labeled insulin and insulin-like growth factor I (IGF-I) binding to their respective receptors in human IM-9 lymphoid cells and solubilized placenta receptor preparations. In contrast, this monoclonal antibody inhibits insulin but not IGF-I binding to human hepatoma (HepG2) cells, fibroblasts and muscle cells. These results indicate that there are two distinct species of the type I insulin-like growth factor receptor (which we have named type IA and type IB) and suggest that this monoclonal antibody may be useful in determining whether different biological effects are mediated through these two receptors.

Antibodies, Monoclonal↗
PubMed1986

Replacement of insulin receptor tyrosine residues 1162 and 1163 compromises insulin-stimulated kinase activity and uptake of 2-deoxyglucose.

Insulin stimulates the autophosphorylation of tyrosine residues of the beta subunit of the insulin receptor (IR); this modified insulin-independent kinase has increased activity toward exogenous substrates in vitro. We show here that replacement of one or both of the twin tyrosines (residues 1162 and 1163) with phenylalanine results in a dramatic reduction in or loss of insulin-activated autophosphorylation and kinase activity in vitro. In vivo, these mutations not only result in a substantial decrease in insulin-stimulated IR autophosphorylation but also in a parallel decrease in the insulin-activated uptake of 2-deoxyglucose. Furthermore, a truncated IR protein (lacking the last 112 amino acids) has an unstable beta subunit; this mutant has no kinase activity in vitro or in vivo and does not mediate insulin-stimulated uptake of 2-deoxyglucose. IR autophosphorylation is thus implicated in the regulation of IR activities, with tyrosines 1162 and 1163 as major sites of this regulation.

Amino Acid Sequence↗
PubMed1986

Characterization of the insulin and insulin-like growth factor receptors and responsitivity of a fibroblast/adipocyte cell line before and after differentiation.

TA1 cells, like 3T3-L1 cells, undergo a differentiation process in vitro from a fibroblast to an adipocyte phenotype. The TA1 pre-adipocytes were found to have low numbers of insulin receptors but high numbers of receptors for insulin-like growth factors (IGF) I and II. Also, the pre-adipocytes were more responsive to IGF than insulin as measured by either stimulation of glucose or amino acid uptake. After differentiation, the adipocytes had higher numbers of insulin receptors and a better responsitivity to insulin than to IGF-I. These results indicate that insulin-like growth factors are the primary regulators of the pre-adipocytes whereas insulin regulates the adipocytes.

Adipose Tissue↗
PubMed1986

Mapping surface structures of the human insulin receptor with monoclonal antibodies: localization of main immunogenic regions to the receptor kinase domain.

A panel of 37 monoclonal antibodies to the human insulin receptor has been used to characterize the receptor's major antigenic regions and their relationship to receptor functions. Three antibodies recognized extracellular surface structures, including the insulin binding site and a region not associated with insulin binding. The remaining 34 monoclonal antibodies were directed against the cytoplasmic domain of the receptor beta subunit. Competitive binding studies demonstrated that four antigenic regions (beta 1, beta 2, beta 3, and beta 4) are found on this domain. Sixteen of the antibodies were found to be directed against beta 1, nine against beta 2, seven against beta 3, and two against beta 4. Antibodies to all four regions inhibited the receptor-associated protein kinase activity to some extent, although antibodies directed against the beta 2 region completely inhibited the kinase activity of the receptor both in the autophosphorylation reaction and in the phosphorylation of an exogenous substrate, histone. Antibodies to the beta 2 region also did not recognize autophosphorylated receptor. In addition, antibodies to this same region recognized the receptor for insulin-like growth factor I (IGF-I) as well as the insulin receptor. In contrast, antibodies to other cytoplasmic regions did not recognize the IGF-I receptor as well as the insulin receptor. These results indicate that the major immunogenic regions of the insulin receptor are located on the cytoplasmic domain of the receptor beta subunit and are associated with the tyrosine-specific kinase activity of the receptor. In addition, these results suggest that a portion of the insulin receptor is highly homologous to that of the IGF-I receptor.

Adenosine Triphosphate↗
PubMed1986

Purification and characterization of the human brain insulin receptor.

The insulin receptor from human brain cortex was purified by a combination monoclonal antibody affinity column and a wheat germ agglutinin column. This purified receptor preparation exhibited major protein bands of apparent Mr = 135,000 and 95,000, molecular weights comparable to those for the alpha and beta subunits of the purified human placental and rat liver receptors. A minor protein band of apparent Mr = 120,000 was also observed in the brain receptor preparation. Crosslinking of 125I-insulin to all three receptor preparations was found to preferentially label a protein of apparent Mr = 135,000. In contrast, cross-linking of 125I-labeled insulin-like growth factor I to the brain preparation preferentially labeled the protein of apparent Mr = 120,000. The purified brain insulin receptor was found to be identical with the placental insulin receptor in the amount of neuraminidase-sensitive sialic acid and reaction with three monoclonal antibodies to the beta subunit of the placental receptor. In contrast, a monoclonal antibody to the insulin binding site recognized the placental receptor approximately 300 times better than the brain receptor. These results indicate that the brain insulin receptor differs from the receptor in other tissues and suggests that this difference is not simply due to the amount of sialic acid on the receptor.

Amino Acid Sequence↗
PubMed1986

Technical grade but not recrystallized alpha-naphthylthiourea potentiates superoxide release by rat neutrophils stimulated in vitro by phorbol myristate acetate.

alpha-Naphthylthiourea (ANTU) causes pulmonary edema and pleural effusion in rats. It has been suggested that ANTU pneumotoxicity may be mediated by blood neutrophils (PMNs) via the release of reactive oxygen species. Accordingly, we tested the effect of technical grade ANTU (tANTU) on the ability of rat peritoneal PMNs to release superoxide (O2-). tANTU did not itself stimulate O2- production by PMNs, but it increased the O2- released in response to PMN stimulation by phorbol myristate acetate (PMA). This effect was dependent upon the amount of tANTU added. In PMNs activated in vitro by a submaximal PMA stimulus, addition of 20 micrograms/ml tANTU doubled superoxide release. When tANTU was recrystallized from ethanol, the purified ANTU was not effective in potentiating the effect of PMA on PMNs. This suggests that an impurity in technical grade ANTU is capable of increasing O2- release by stimulated PMNs. tANTU and recrystallized ANTU caused similar pneumotoxicity in rats in vivo, suggesting that the unidentified impurity does not markedly influence the biologic effects of ANTU.

Animals↗