Biomedical subjects

R A Roth

Publications and source records attributed to R A Roth.

At least 181 records · Page 10Linked to original sources

PubMed1991

Characterization of latent transforming growth factor-beta 2 from monkey kidney cells.

Serum-free medium conditioned by BSC-40 cells was analyzed for the presence of transforming growth factor-beta 2 (TGF beta 2)-related proteins. Western blot analysis was performed using site-specific antipeptide antibodies directed against the pro- and mature regions of the TGF beta 2 precursor. When conditioned medium was analyzed by polyacrylamide gel electrophoresis under reducing conditions, proteins with mol wt of 53 kDa (containing both mature and proregion sequences), 34-38 kDa (containing proregion sequences only), and 12 kDa (containing mature sequences) were detected. Under nonreducing conditions, complexes of 60- to 80-kDa, 160- to 200-kDa, as well as 24-kDa mature dimers were seen. Cleavage of mature TGF beta 2 from its precursor was inhibited by monensin and chloroquin, but not by ammonium chloride or methylamine. Two peaks of bioactivity were detected after fractionation on a TSK column corresponding to mol wt of 130 and 400 kDa. These peaks contained TGF beta 2 and pro-TGF beta 2 proteins. Partial purification of the 130-kDa complex followed by N-glyconase digestion indicated that the pro-TGF beta 2 proteins were glycosylated. These data demonstrate that BSC-40 cells secrete mature TGF beta 2 complexed with proregion-containing proteins and suggest that this association may contribute to the latency phenomena observed with respect to this growth regulator.

Amidohydrolases↗

PubMed1991

Assessment of the in situ tyrosine kinase activity of mutant insulin receptors lacking tyrosine autophosphorylation sites 1162 and 1163.

In the present studies mutant insulin receptors with regulatory tyrosine residues 1162 and 1163 changed to phenylalanines were tested for tyrosine kinase activity. In agreement with prior studies, this mutant receptor was found to exhibit almost no insulin-stimulated exogenous kinase activity when assayed in vitro. In contrast, this mutant receptor was found in situ to have a significant, albeit reduced, ability to mediate the tyrosine phosphorylation of various endogenous proteins, as assessed by Western blotting with antiphosphotyrosine antibodies. In addition, extracts of insulin-treated cells overexpressing this mutant receptor exhibited increased amounts of tyrosine phosphorylated phosphatidylinositol 3-kinase compared to control cells. Finally, this mutant receptor, like the wild-type receptor, was found to mediate an increase in the activity of a membrane-associated phosphatidylinositol 4,5-biphosphate kinase. These results indicate that 1) in vitro assessments of the tyrosine kinase activity of mutant insulin receptors may not accurately reflect their in vivo activities; and 2) the ability of the mutant receptor lacking tyrosine autophosphorylation sites 1162 and 1163 to mediate insulin-stimulated tyrosine phosphorylation of various endogenous substrates may account for the reported ability of this receptor to mediate various biological responses.

Animals↗

PubMed1991

An antibody to neutrophils attenuates alpha-naphthylisothiocyanate-induced liver injury.

alpha-Naphthylisothiocyanate (ANIT) causes cholestasis and injury to bile duct epithelium and hepatic parenchymal cells in rats. The mechanism of toxicity is unknown. Neutrophils (PMNs) infiltrate periportal regions of the liver after ANIT intoxication. Because PMNs play a causal role in other extrahepatic models of tissue injury, we determined whether PMNs might be involved in ANIT-induced liver injury in rats by reducing circulating PMN numbers with a polyclonal antibody (antineutrophil serum). ANIT treatment caused cholestasis and elevations in serum of total bilirubin concentration, total bile acid concentration, aspartate amino-transferase activity, gamma-glutamyltransferase activity and histologic lesions consistent with acute, neutrophilic cholangiohepatitis. Cotreatment of rats with antineutrophil serum reduced circulating PMN numbers, prevented ANIT-induced cholestasis and attenuated other markers of liver injury elevated by ANIT. In addition, antineutrophil serum treatment attenuated the severity of histologic lesions within the liver and reduced the number of PMNs in periportal regions. Numbers of PMNs in liver sections correlated positively with markers of liver injury, histologic evidence of cholangiohepatitis and numbers of circulating PMNs in peripheral blood. The protection afforded by antineutrophil serum appeared to result from a specific reduction of PMNs and not lymphocytes, because administration of an antilymphocyte serum reduced circulating lymphocyte numbers without offering protection. Inasmuch as ANIT stimulates PMNs in vitro to release O2- and since PMN-derived oxygen species may cause tissue injury, we determined whether administration of agents which degrade oxygen radicals afforded protection against the liver injury caused by ANIT.(ABSTRACT TRUNCATED AT 250 WORDS)

1-Naphthylisothiocyanate↗

PubMed1991

Activated neutrophils injure the isolated, perfused rat liver by an oxygen radical-dependent mechanism.

Under certain circumstances, segmented neutrophils (PMNs) injure extrahepatic tissue by releasing toxic oxygen species and degradative enzymes. The authors used an isolated, perfused rat liver preparation to determine whether PMNs might injure the liver. Livers from fasted rats were perfused with Krebs-Ringer bicarbonate buffer (pH 7.4) containing 3% bovine serum albumin (BSA) in a recirculating system. Rat peritoneal PMNs (4 x 10(8] or vehicle (Hank's balanced salt solution [HBSS], pH 7.35) were added, and liver injury was assessed 90 minutes later by release of alanine aminotransferase (ALT) into the perfusion medium and histopathologic analysis of liver sections. Perfusion of livers receiving only HBSS for 90 minutes resulted in a small increase in ALT activity in the perfusion medium but did not significantly alter histologic features of liver sections. Addition of unstimulated PMNs did not increase further the ALT activity and, with the exception of vascular neutrophilia, did not significantly change the histomorphology compared with controls. When PMNs activated with a combination of phorbol myristate acetate (PMA, 31 ng/ml) and lithocholate (100 mumol/l [micromolar]) were added to the perfusion system, however, livers released greater amounts of ALT than those perfused with PMA, lithocholate, and HBSS. Activated PMNs caused a transient reduction in flow of perfusion medium that lasted approximately 5 to 15 minutes. Liver sections had multifocal to coalescing foci of moderate to severe, acute hepatocellular necrosis associated with the areas of intense sinusoidal neutrophilia. In addition a second type of lesion was observed and was characterized by triangular foci of necrosis located adjacent to periportal regions of sinusoids or portal veins containing neutrophilic thrombi. These lesions were void of PMNs and were consistent with infarcts. A combination of superoxide dismutase and catalase added to the perfusion medium (500 U/ml each) prevented the elevation in ALT activity but not the transient reduction in flow. These results indicate that activated PMNs may cause liver injury by an oxygen radical-dependent mechanism. It is unclear whether PMN-derived oxygen radicals, hepatocellular-derived oxygen species resulting from reduced tissue perfusion and reperfusion, or both are involved in the pathogenesis.

Alanine Transaminase↗

PubMed1991

The effects of monocrotaline pyrrole on cultured bovine pulmonary artery endothelial and smooth muscle cells.

Monocrotaline pyrrole (MCTP), a reactive electrophile, induces delayed and progressive pulmonary edema, vascular remodeling, and pulmonary hypertension after a single intravenous administration to rats. The effects of a single exposure of cultured bovine pulmonary artery endothelial cells (BEC) and bovine pulmonary artery smooth muscle cells (BSMC) to MCTP were examined. Monocrotaline pyrrole caused a dose-dependent, delayed, and progressive cell detachment and release of lactate dehydrogenase activity from monolayers of BECs but not BSMCs. Monolayers of BECs also released increased concentrations of 6-keto-prostaglandin F1 degrees, the stable metabolite of prostacyclin, as the post-treatment interval increased. Progressive and marked endothelial cell hypertrophy occurred after exposure to a nominal concentration of 5 or 50 micrograms/ml of MCTP but not after 0.5 micrograms/ml. Morphologic changes in monolayers of BSMCs were minimal, even up to 2 weeks after exposure. Ultrastructurally the hypertrophic, MCTP-treated BECs had enlarged cell profiles with enlarged nuclei. The nucleoli were prominent, occasionally multiple, and had separation of granular and fibrillar components. Cytoplasmic microtubules and perinuclear intermediate filaments were prominent in some cells, as were the golgi apparatus and endoplasmic reticulum. Degenerative changes were not prominent in cells that remained in the monolayer. Monocrotaline pyrrole inhibited proliferation of both cell types at concentrations (0.5 micrograms/ml) that were not cytotoxic. These findings indicate that MCTP induces direct, dose-dependent injury to cells in culture that is delayed and progressive, and the expression of this injury depends, in part, on the cell type.

6-Ketoprostaglandin F1 alpha↗

PubMed1990

Monoclonal antibody alpha IR-3 inhibits the ability of insulin-like growth factor II to stimulate a signal from the type I receptor without inhibiting its binding.

We have previously shown that the protein encoded by a human insulin-like growth factor I (IGF-I) receptor cDNA binds both IGF-I and II with high affinity. In the present studies, we show that a monoclonal antibody to the IGF-I receptor, alpha IR-3, inhibits the binding of IGF-I but not IGF-II to the expressed receptor in intact cells and after solubilization. Surprisingly, this monoclonal antibody inhibits the ability of both IGF-I and II to stimulate thymidine synthesis in cells with the expressed receptor. Moreover, this antibody inhibits the ability of both IGF-I and II to stimulate the kinase activity of the IGF-I receptor in intact cells. These results indicate that alpha IR-3 binds to the IGF-I receptor in such a way that it does not inhibit the binding of IGF-II but does inhibit the subsequent ability of the receptor to be activated to transmit a signal.

Animals↗

PubMed1990

Identification of residues in the insulin molecule important for binding to insulin-degrading enzyme.

Insulin-degrading enzyme (IDE) hydrolyzes insulin at a limited number of sites. Although the positions of these cleavages are known, the residues of insulin important in its binding to IDE have not been defined. To this end, we have studied the binding of a variety of insulin analogues to the protease in a solid-phase binding assay using immunoimmobilized IDE. Since IDE binds insulin with 600-fold greater affinity than it does insulin-like growth factor I (25 nM and approximately 16,000 nM, respectively), the first set of analogues studied were hybrid molecules of insulin and IGF I. IGF I mutants [insB1-17,17-70]IGF I, [Tyr55,Gln56]IGF I, and [Phe23,Phe24,Tyr25]IGF I have been synthesized and share the property of having insulin-like amino acids at positions corresponding to primary sites of cleavage of insulin by IDE. Whereas the first two exhibit affinities for IDE similar to that of wild type IGF I, the [Phe23,Phe24,Tyr25]IGF I analogue has a 32-fold greater affinity for the immobilized enzyme. Replacement of Phe-23 by Ser eliminates this increase. Removal of the eight amino acid D-chain region of IGF I (which has been predicted to interfere with binding to the 23-25 region) results in a 25-fold increase in affinity for IDE, confirming the importance of residues 23-25 in the high-affinity recognition of IDE. A similar role for the corresponding (B24-26) residues of insulin is supported by the use of site-directed mutant and semisynthetic insulin analogues. Insulin mutants [B25-Asp]insulin and [B25-His]insulin display 16- and 20-fold decreases in IDE affinity versus wild-type insulin.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1990

Insulin activates the kinase activity of the Raf-1 proto-oncogene by increasing its serine phosphorylation.

Insulin was found to stimulate the serine/threonine kinase activity of the proto-oncogene product Raf-1. This stimulation was observed in HeLa, NIH 3T3, and Chinese hamster ovary cells, all overexpressing the human insulin receptor. In the HeLa cells, 100 pM insulin gave a significant increase in Raf-1 kinase activity, and 100 nM insulin caused a maximal 2-5-fold increase in activity. The increase in activity was detected after 2 min of insulin treatment and peaked after 5 min. In addition to stimulating Raf-1 kinase activity, insulin caused a shift in the electrophoretic mobility of the Raf-1 protein and an increase in the amount of serine phosphorylation of Raf-1. Moreover, a serine/threonine-specific phosphatase, phosphatase 1, but not two tyrosine-specific phosphatases, was found to deactivate the insulin-activated Raf-1 kinase activity. These findings indicate that insulin activates the serine/threonine kinase activity of the Raf-1 proto-oncogene by increasing its content of phosphoserine.

Amino Acid Sequence↗

PubMed1990

Insulin-mimetic anti-insulin receptor monoclonal antibodies stimulate receptor kinase activity in intact cells.

In the present studies, nine different monoclonal antibodies to the extracellular domain of the insulin receptor were tested in three different cell types for their ability to stimulate the intrinsic tyrosine kinase activity of the receptor. Previous studies had suggested that several of these monoclonal antibodies stimulate biological responses without stimulating the intrinsic tyrosine kinase activity of the receptor (Hawley, D. M., Maddux, B. A., Patel, R. G., Wong, K. Y., Manula, P. W., Firestone, G. L., Brunetti, A., Verspohl, E., and Goldfine, I. D. (1989) J. Biol. Chem. 264, 2438-2444 and Soos, M. A., O'Brien, R. M., Brindle, N. P. J., Stigter, J. M., Okamoto, A. K., Whittaker, J., and Siddle, K. (1989) Proc. Natl. Acad. Sci. U. S. A. 86, 5217-5221). In the present study, a more sensitive assay was utilized, and these same monoclonal antibodies, when added to intact cells, were found to stimulate the phosphotransferase activity of the receptor. This increase in activity was reversed by phosphatase treatment of the receptor. In contrast, monoclonal antibodies which had no insulin-mimetic activities did not stimulate the receptor's kinase activity. In addition, Western blot analyses of lysates with anti-phosphotyrosine antibodies showed that insulin-mimetic, but not non-insulin-mimetic antibodies, stimulated tyrosine phosphorylation of the receptor as well as an endogenous substrate (phosphoprotein Mr = 160,000). Finally, these antibodies were found to stimulate the tyrosine phosphorylation of another endogenous substrate of the insulin receptor kinase, the type I phosphatidylinositol kinase. These studies support the hypothesis that monoclonal antibodies, like insulin, stimulate biological responses via their ability to stimulate the tyrosine kinase activity of the receptor.

1-Phosphatidylinositol 4-Kinase↗

PubMed1990

Human red blood cell insulin-degrading enzyme and rat skeletal muscle insulin protease share antigenic sites and generate identical products from insulin.

The mechanisms of cellular insulin degradation remain uncertain. Considerable evidence now exists that the primary cellular insulin-degrading activity is a metallothiol proteinase. Two similar degrading activities have been purified and characterized. Insulin protease has been purified from rat skeletal muscle and insulin-degrading enzyme from human red blood cells. Whereas the two degrading activities share a number of similar properties, significant differences have also been reported; and it is not at all established that they are the same enzyme. To examine this, we have compared antigenic and catalytic properties of the two enzymatic activities. Monoclonal antibodies against the red blood cell enzyme adsorb the skeletal muscle enzyme; and on Western blots, the antibodies react with an identical 110-kDa protein. Immunoaffinity-purified enzymes from both red blood cells and skeletal muscle degrade [125I]iodo(B26)insulin to the same products as seen with purified insulin protease and with intact liver and kidney. Chelator-treated muscle and red blood cell enzymes can be reactivated with either Mn2+ or Ca2+. Thus, insulin-degrading enzyme and insulin protease have similar properties. These results support the hypothesis that these activities reside in the same enzyme.

Animals↗

PubMed1990

Various proteins modulate the kinase activity of the insulin receptor.

Previous studies of the substrate specificity of the purified insulin receptor tyrosine kinase using synthetic random polymers have demonstrated that the receptor kinase phosphorylates poly (Glu, Tyr) 4:1 but not poly (Glu, Tyr) 1:1. In the present study, insulin treatment of Chinese hamster ovary cells overexpressing the human insulin receptor was found to stimulate the ability of their membrane extracts to phosphorylate poly (Glu, Tyr) 1:1. It was concluded that this activity was due to the receptor itself because: 1) it was precipitated with a monoclonal antibody to the receptor; 2) the addition of various membrane extracts to purified insulin receptor preparations stimulated the ability of these preparations to phosphorylate poly (Glu, Tyr) 1:1; and 3) certain purified proteins, including bovine serum albumin and casein, were also capable of stimulating the purified receptor to phosphorylate poly (Glu, Tyr) 1:1. The effect of albumin was dose-dependent; 0.5 and 10 mg/ml bovine serum albumin stimulated the phosphorylation of poly (Glu, Tyr) 1:1 by 2- and 230-fold, respectively. In contrast, albumin had no effect on the phosphorylation of poly (Glu, Tyr) 4:1. These results indicate that the activity of the insulin receptor kinase on certain substrates can be modulated by the presence of other proteins.

Animals↗

PubMed1990

Phosphatidylinositol kinase or an associated protein is a substrate for the insulin receptor tyrosine kinase.

The tyrosine kinase activity intrinsic to the insulin receptor is thought to be important in eliciting the intracellular responses to insulin; however, it has been difficult to determine the biochemical functions of the proteins which are substrates for this receptor. Treatment of Chinese hamster ovary (CHO) cells overexpressing the human insulin receptor (CHO.T) with insulin results in a 38 +/- 11 (mean +/- S.E., n = 9)-fold increase in a phosphatidylinositol (PtdIns) kinase activity in anti-phosphotyrosine immunoprecipitates of whole cell lysates. One minute of treatment of cells with insulin causes a dramatic increase in the PtdIns kinase activity in the anti-phosphotyrosine immunoprecipitates; the activity peaks within 5 min and remains elevated for at least 60 min after addition of insulin to the cells. This response is only slightly delayed compared with the time course we observe for activation of the insulin receptor tyrosine kinase. The insulin dose-response curves are also very similar for the activation of the insulin receptor tyrosine kinase activity and for the appearance of PtdIns kinase in the anti-phosphotyrosine immunoprecipitates. Stimulation of the endogenous insulin receptor of CHO cells also results in the association of PtdIns kinase activity with phosphotyrosine-containing proteins. However, CHO cells are less sensitive to insulin than CHO.T cells, and the maximal PtdIns kinase activity in antiphosphotyrosine immunoprecipitates from CHO cells is one-sixth that of CHO.T cells. In contrast, immunoprecipitates from CHO.T cells made with anti-insulin receptor antibodies do not contain significant levels of PtdIns kinase activity. This demonstrates that the PtdIns kinase is either a substrate for the insulin receptor tyrosine kinase or is tightly associated with another tyrosine phosphoprotein, which is not the insulin receptor.

1-Phosphatidylinositol 4-Kinase↗

PubMed1990

Differential effects of lithocholate on rat neutrophil activation.

Neutrophils (PMNs) may be exposed to high concentrations of biliary products during cholestasis and other hepatic disorders. We have previously reported that bile and certain bile salts enhance superoxide (O2-) release from neutrophils activated with phorbol myristate acetate (PMA) (Dahm et al.: Toxicol. Appl. Pharmacol. 95, 82, 1988), suggesting that PMN oxidative metabolism might be altered in toxicoses or disease states characterized by elevations in serum bile salts and other biliary products. In the present study, we characterized the priming effect of lithocholate for O2- release and also examined the effects of lithocholate on enzyme release from PMNs. PMNs preincubated with lithocholate at concentrations which did not directly stimulate O2- release (3-100 microM) and activated with PMA released greater amounts of O2- than controls exposed to PMA alone, illustrating a priming effect. O2- release from lithocholate-primed PMNs rose sharply between 5 and 10 min after PMA addition and then ceased between 10 and 30 min. The priming effect of lithocholate toward PMA-activated PMNs was reduced approximately 50% by washing PMNs after lithocholate addition and was not dependent on extracellular Ca2+, although removal of Ca2+ from the incubation buffer enhanced the cytotoxicity of lithocholate toward PMNs. In Ca2(+)-supplemented medium, lithocholate primed PMNs for O2- release when formyl-methionyl-leucyl-phenylalanine (FMLP, 10(-8)-10(-6) M) or calcium ionophore, A23187 (10(-7) or 10(-6)M), was used to activate PMNs. Lithocholate (100 microM) by itself had only marginal effects on release of lysozyme or beta-glucuronidase from PMNs. However, lithocholate (100 microM) inhibited beta-glucuronidase release from FMLP-stimulated PMNs to near-baseline levels. When FMLP was added to PMNs prior to lithocholate, beta-glucuronidase release was not reduced as it was when the order of addition was the reverse. Lithocholate had no effect on PMA-stimulated lysozyme release. These results indicate that lithocholate has different actions on PMN O2- release and enzyme release and suggest that lithocholate might exert its action on the PMN plasma membrane.

Animals↗

PubMed1990

Development of morphologic, hemodynamic, and biochemical changes in lungs of rats given monocrotaline pyrrole.

A single, intravenous administration of a low dose of monocrotaline pyrrole (MCTP), a derivative of the pyrrolizidine alkaloid monocrotaline (MCT), induces progressive pulmonary hypertension and right ventricular hypertrophy (RVH) in rats. The temporal relationship between morphologic alterations, biochemical markers of lung injury, and the development of pulmonary hypertension was determined during the developing pulmonary disease. Three days after a single iv injection of 3.5 mg/kg MCTP, small increases in bronchoalveolar lavage (BAL) fluid lactate dehydrogenase (LDH) activity and accumulation in the lungs of intravenously administered 125I-bovine serum albumin (BSA) were associated with minimal to mild interstitial edema around large airways and blood vessels. By Day 5, BAL fluid LDH activity and 125I-BSA accumulation had increased further, and lung weight/body weight ratio and BAL fluid protein concentration were greater than those of control. Interstitial edema was more pronounced and involved patches of alveolar septal walls. A mild increase in numbers of mononuclear cells, including hypertrophied interstitial cells, was evident in these areas. Walls of pulmonary arteries less than 60 microns in diameter were mildly thickened. By Day 8, scattered clusters of alveolar sacs contained serous exudate, and interstitial mononuclear infiltrates were more pronounced. Mild to moderate thickening of arterial walls was apparent in small and large vessels. By Day 14, pulmonary arterial pressure was elevated and RVH was evident. Arterial walls were thickened and had hypertrophy of medial smooth muscle cells and intercellular edema, which was particularly prominent in areas with perivascular interstitial inflammation. Large patches of lung interstitium and alveolar lumens contained serous or fibrinous exudate. In summary, a single, intravenous administration of MCTP induced a delayed and progressive pulmonary microvascular leak, interstitial inflammation, and alterations in muscular blood vessels which resulted in pulmonary hypertension within 14 days. These morphologic, biochemical, and hemodynamic changes are nearly identical to alterations induced by the parent alkaloid, MCT.

Animals↗

PubMed1990

Action by the lungs on circulating xenobiotic agents, with a case study of physiologically based pharmacokinetic modeling of benzo(a)pyrene disposition.

The lungs contain enzyme systems that metabolize xenobiotic agents, and the structure and position in the circulation render this organ potentially important in the metabolic removal of substances from the blood. Pulmonary enzyme systems that oxidize xenobiotic agents include cytochrome P450- or flavin-containing monooxygenases. In addition, the lungs accumulate certain agents, notably basic amines, without substantially metabolizing them. Benzo(a)pyrene (B(a)P) is one example of a xenobiotic agents that is eliminated from the circulation largely by oxidative metabolism. We have described the metabolic elimination of B(a)P using a physiologically based pharmacokinetic model applied retrospectively to existing data sets of B(a)P metabolism and disposition in rats. The result suggests that the lungs may, under certain conditions, contribute significantly to xenobiotic disposition and that this contribution is greater than that predicted by the activity of dispositional enzyme in this organ. Thus, the lungs may play a significant role in the metabolic elimination of some xenobiotic agents under certain circumstances.

Animals↗

PubMed1990

Multimodality treatment of complex renal calculi.

More than 2,500 patients were treated for urolithiasis from 1984 to 1987. In an effort to define the relative role of extracorporeal shock wave lithotripsy and percutaneous nephrolithotomy with respect to size, location and composition of the calculus 912 of these patients (224 of whom underwent percutaneous nephrolithotomy and 688 of whom underwent extracorporeal shock wave lithotripsy) were reviewed. Size proved to be the only significant factor in the success and complication rates of extracorporeal shock wave lithotripsy but it did not affect the outcome of percutaneous nephrolithotomy. The roles of these 2 modalities were then examined with respect to the treatment of complex renal calculi. We reviewed 376 patients with complex renal calculi, including 40 percutaneous nephrolithotomy patients from the initial 912 patients studied. The initial therapy in 100 of these patients, treated consecutively, was extracorporeal shock wave lithotripsy. The remaining 276 patients were treated by percutaneous nephrolithotomy. The success rate of extracorporeal shock wave lithotripsy monotherapy in the treatment of complex renal calculi was 36%. The success rate of primary percutaneous nephrolithotomy was 83%. We conclude that percutaneous nephrolithotomy should be the primary therapy for patients with complex renal calculi. Extracorporeal shock wave lithotripsy is the preferred treatment for patients with smaller calculi and as an adjunct to percutaneous nephrolithotomy.

Combined Modality Therapy↗

PubMed1990

Effect of carbon tetrachloride on hamster tracheal epithelial cells.

This study was designed to assess effects of carbon tetrachloride (CCl4) in hamster tracheal epithelium. Adult, male, Syrian golden hamsters were treated with 2.5 ml/kg CCl4 ip, and controls received only the vehicle (peanut oil). Animals were sacrificed after 1, 4, 12, and 24 h. Tissue samples from upper and lower tracheal levels were fixed and embedded in glycol methacrylate for light microscopy. Some tracheal rings were also fixed in formaldehyde/glutaraldehyde cacodylate buffer for transmission electron microscopy. For histopathologic evaluation of the tracheal epithelial cells, each tracheal level was cut transversely at 3 microns and stained with toluidine blue. CCl4 produced injury to ciliated and nonciliated cells in all portions of hamster trachea, although the severity of CCl4-induced injury differed in various levels and regions. The number of damaged cells increased markedly after 1 h in the lower trachea, but not until after 4 h in the upper trachea. By 24 h, the number of injured cells had decreased so that no significant difference from control was evident. The ultrastructural alterations in epithelial cells were obvious as early as 1 h after CCl4 administration. Intracellular organelles, including smooth and rough endoplasmic reticulum, mitochondria, and Golgi apparatuses, were damaged by this chemical. Since CCl4-induced cell injury is dependent on metabolism by intracellular NADPH-dependent cytochrome P450 monooxygenases, these results suggest that hamster tracheal epithelial cells have the potential to activate CCl4 metabolically.

Animals↗

PubMed1990

Insulin receptor structure and function in normal and pathological conditions.

The insulin receptor is a large cell surface glycoprotein that concentrates insulin at the site of action and also initiates responses to insulin. The receptor is a disulfide-linked oligomer comprised of two alpha and two beta subunits. Signal transduction through the insulin receptor appears to require the activation of an intrinsic tyrosine-specific protein kinase activity. A variety of disorders, both acquired and genetic, are associated with the development of insulin resistance and are frequently the result of cellular defects in insulin receptor structure, function, and action. The recent cloning of several mutant receptors from patients with genetic forms of extreme insulin resistance has increased our understanding of insulin resistance on the molecular level.

Amino Acid Sequence↗