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C R Carvalho

Publications and source records attributed to C R Carvalho.

At least 55 records · Page 3Linked to original sources
PubMed1997

Tissue-specific regulation of IRS-1 in unilaterally nephrectomized rats.

Insulin stimulates the tyrosine kinase activity of its receptor, resulting in the phosphorylation of its cytosolic substrate, insulin receptor substrate 1 (IRS-1). IRS-1 is also a substrate for different peptides and growth factors, and a transgenic mouse "knockout" for this protein does not have normal growth. However, the role of IRS-1 in kidney hypertrophy and/or hyperplasia was not investigated. In the present study we investigated IRS-1 protein and tyrosine phosphorylation levels in the remnant kidney after unilateral nephrectomy (UNX) in 6-week-old male Wistar rats. After insulin stimulation the levels of insulin receptor and IRS-1 tyrosine phosphorylation were reduced to 79 +/- 5% (P < 0.005) and 58 +/- 6% (P < 0.0001), respectively, of the control (C) levels, in the remnant kidney. It is possible that a circulating factor and/or a local (paracrine) factor playing a role in kidney growth can influence the early steps of insulin action in parallel. To investigate the hypothesis of a circulating factor, we studied the early steps of insulin action in liver and muscle of unilateral nephrectomized rats. There was no change in pp185 tyrosine phosphorylation levels in liver (C 100 +/- 12% vs UNX 89 +/- 9%, NS) and muscle (C 100 +/- 22% vs UNX 91 +/- 17%, NS), and also there was no change in IRS-1 phosphorylation levels in both tissues. These data demonstrate that after unilateral nephrectomy there is a decrease in insulin-induced insulin receptor and IRS-1 tyrosine phosphorylation levels in kidney but not in liver and muscle. It will be of interest to investigate which factors, probably paracrine ones, regulate these early steps of insulin action in the contralateral kidney of unilaterally nephrectomized rats.

Animals↗
PubMed1997

Effect of captopril, losartan, and bradykinin on early steps of insulin action.

Insulin initiates its metabolic and growth-promoting effects by binding to the alpha subunit of its receptor, thereby activating the kinase in the beta subunit. This event leads to tyrosyl phosphorylation of its cytosolic substrate, insulin receptor substrate 1 (IRS-1), which in turn associates with and activates phosphatidylinositol (PI) 3-kinase. The clinical use of ACE inhibitors has been associated with increased insulin sensitivity. However, the exact molecular mechanism is unknown. In the present study, we examined the phosphorylation status of the insulin receptor and IRS-1, as well as the association between IRS-1 and PI 3-kinase in the liver and muscle of 20-month-old rats treated acutely with captopril, using immunoprecipitation with antipeptide antibodies to the insulin receptor and IRS-1, and immunoblotting with antiphosphotyrosine and anti-PI 3-kinase antibodies. Insulin stimulation increased receptor autophosphorylation to 462 +/- 253% (P < 0.05) in the liver and 697 +/- 78% (P < 0.001) in the muscle of ACE inhibitor-treated rats. There were also increases to 250 +/- 17% (P < 0.001) and 280 +/- 50% (P < 0.05) in the insulin-stimulated IRS-1 phosphorylation levels in the liver and muscle, respectively, of animals treated with captopril. The insulin-stimulated IRS-1 association with PI 3-kinase rose to 305 +/- 20% (P < 0.001) in liver and 267 +/- 48% (P < 0.05) in muscle. Losartan, an ANG receptor blocker, had no significant effect on insulin-stimulated IRS-1 phosphorylation in both tissues. The acute administration of bradykinin increased insulin-stimulated tyrosine phosphorylation of the insulin receptor and IRS-1 in the liver and muscle. These data demonstrate that ACE inhibitors modulate the early steps of insulin signaling, and that this effect may be simulated by the administration of bradykinin.

Aging↗
PubMed1996

Insulin induces tyrosine phosphorylation of JAK2 in insulin-sensitive tissues of the intact rat.

The Janus kinase family of protein tyrosine kinases constitutes a novel type of signal transduction pathway activated in response to a wide variety of polypeptide ligands and has four known members: JAK1, JAK2, JAK3, and Tyk2. In this study, we examined the ability of insulin to stimulate JAK2 tyrosine phosphorylation in insulin-sensitive tissues of the intact rat using immunoprecipitation and immunoblotting. The results demonstrate that after an infusion of insulin, JAK2 is rapidly tyrosine phosphorylated (and the kinase is activated) in the liver, adipose tissue, skeletal muscle, heart, and isolated adipocytes. The presence of phosphorylated JAK2 was detectable after an infusion of insulin that increased serum insulin to physiological postprandial levels (40-70 microunits/ml). Co-immunoprecipitation with anti-insulin receptor antibody, anti-JAK2 antibody, and anti-IRS-1 antibody showed that JAK2 interacts with the insulin receptor and IRS-1 to form stable complexes following stimulation by insulin. In two animal models of insulin resistance the regulation of JAK2 tyrosine phosphorylation after insulin infusion paralleled the phosphorylation of the insulin receptor and of IRS-1. In conclusion, our data indicate that after physiological stimulation by insulin in the intact animal, JAK2 associates with the insulin receptor and is tyrosine phosphorylated in insulin-sensitive tissues in a time- and dose-dependent fashion.

Adipose Tissue↗
PubMed1996

Indirect effects are independent of the way of tolerance induction.

Oral tolerance is a T-cell mediated phenomenon defined by a refractoriness to parenteral immunization with a protein that was first contacted by oral route. However, the authors have shown that the injection of a tolerated protein is not neutral for the immune system. In mice made tolerant to KLH by gavage, co-immunization with KLH and DNP-Ova blocks anti-DNP antibody formation. Anti-DNP antibody formation resulting from immunization with DNP-Ova can also be blocked by co-immunization with a dietary protein (zein) or a self component (fibrinogen). The inhibitory effects resulting from immunization with a tolerated protein, designated indirect effects, do not affect the induction of oral tolerance to another protein. These results support the hypothesis that active mechanism are involved in the maintenance of tolerance.

Administration, Oral↗
PubMed1996

Effect of aging on insulin receptor, insulin receptor substrate-1, and phosphatidylinositol 3-kinase in liver and muscle of rats.

Insulin stimulates the tyrosine kinase activity of its receptor, resulting in the phosphorylation of its cytosolic substrate, insulin receptor substrate-1 (IRS-1), which, in turn, associates with phosphatidylinositol 3-kinase (PI 3-kinase), thereby activating the latter. Aging is associated with insulin resistance, but the exact molecular mechanism is unknown. In the present study, we examined the levels and phosphorylation status of the insulin receptor and IRS-1 as well as the association between IRS-1 and PI 3-kinase in the liver and muscle of 2-, 5-, 12-, and 20-month-old rats. There were no changes in the insulin receptor concentration in the liver and muscle of rats 2-. 5-, 12-, and 20-month rats. There were no changes in the insulin receptor concentration in the liver and muscle of rats 2-20 months old, as determined by immunoblotting using antibody to the COOH-terminus of the receptor. However, insulin stimulation of receptor autophosphorylation, as determined by immunoblotting with antiphosphotyrosine antibody was reduced by 25% (P < 0.05) in the liver and muscle of rats at 20 months. Interestingly, IRS-1 protein levels decrease at an early stage (5 months) by 58 +/- 9%, (P < 0.01) and remained at low levels thereafter in muscle, but not in liver. In samples previously immunoprecipitated with anti-IRS-1 antibody and blotted with antiphosphotyrosine antibody, there were 60 +/- 9% (P < 0.001) and 92 +/- 4% (P < 0.001) decreases in the insulin-stimulated IRS-1 association with PI 3-kinase was decreased by 70 +/- 2% in the liver and muscle, respectively, of 20-month rats. The insulin-stimulated IRS-1 association with PI 3-kinase was decreased by 70 +/- 2% in the liver (P < 0.001) and by 98 +/- 3% (P < 0.001) in the muscle of 20-month-old rats, with no change in the PI 3-kinase protein levels. The phosphotyrosine-associated PI 3-kinase activity after insulin stimulation was dramatically reduced in liver and muscle of 20-month-old rats compared to that in 2-month-old rats. Finally, by immunoprecipitation, the detection of insulin-stimulated IRS-2 phosphorylation followed the same pattern as that for IRS-1 in both liver of 2- and 20-month-old rats. These data suggest that changes in the early steps of insulin signal transduction may have an important role in the insulin resistance observed in old animals.

Aging↗
PubMed1996

Chronic amiodarone ingestion induces pulmonary toxicity in rats.

Patients who receive amiodarone may develop interstitial pulmonary disease. The objective of the present study was to develop an experimental model of interstitial pulmonary disease in rats based on the chronic oral administration of amiodarone diluted in water ad libitum. A total of 97 three-month old male Wistar rats weighing 133-167 g (control and intoxicated) were studied after daily administration of amiodarone (about 50 mg/kg) for 3 weeks and 3, 6, and 13 months. We carried out conventional histopathologic evaluation, morphometric studies of the alveolar wall, transmission electron microscopy, measurement of pulmonary volumes and forced expiratory flows, and computed respiratory system resistance and elastance during spontaneous breath cycles. Chronic ingestion of amiodarone by rats produced pulmonary disease that started as a phospholipidosis, as early as 3 weeks after the use of the drug. After 6, and mainly after 13 months, a focal inflammatory reaction with reactive alveolar epithelium was observed. Signals of a concomitant repair process were also present, but fibrosis was visible only by electron microscopy. The physiologic dysfunction could be identified after 13 months; expiratory flow (ml/sec) limitation and an increased respiratory system elastance (cmH2O/ml) were the main functional changes, respectively 10.8 (forced expiratory mean flow between 0-25% of forced vital capacity) and 5.36 in treated animals vs 13.3 and 3.65 in controls, reported as mean +/- SD for 6 animals in each group. A body of evidence suggests that amiodarone may cause changes in lung phospholipid metabolism that may be responsible for a part of the functional derangement observed in this study.

Amiodarone↗
PubMed1996

Effect of fasting on insulin signaling in the aorta of intact rats.

Insulin stimulates the tyrosine kinase activity of its receptor, resulting in the phosphorylation of its cytosolic substrate, insulin receptor substrate 1 (IRS-1). Previous studies have demonstrated a tissue-specific regulation of IRS-1. In the present study we investigated the levels and phosphorylation state of IRS-1 after insulin stimulation in the rat aorta in vivo, and the modulation of this protein after 72 h of fasting, using immunoprecipitation and immunoblotting with anti-insulin receptor, anti-IRS-1 and antiphosphotyrosine antibodies. We show that IRS-1 is present in rat aorta, and is tyrosine phosphorylated after insulin stimulation. After insulin stimulation, rats fasted for 72 h showed an increase in insulin receptor (100 +/- 45%, P < 0.05) and IRS-1 phosphorylation (68 +/- 24%, P < 0.05) in aorta, compared to fed rats. There was no change in insulin receptor of IRS-1 protein levels in fasted rats. In summary, the present study demonstrated that proteins involved in the early steps of insulin signal transduction are present in the rat aorta and can be modulated by fasting. It will be of interest to study the regulation of these proteins in the aorta of animal models of hypertension and/or atherosclerosis.

Animals↗
PubMed1995

Angiotensin II induces tyrosine phosphorylation of insulin receptor substrate 1 and its association with phosphatidylinositol 3-kinase in rat heart.

We have investigated whether angiotensin II (AII) is able to induce insulin receptor substrate 1 (IRS-1) phosphorylation and its association with phosphatidylinositol 3-kinase (PI 3-kinase) in the rat heart in vivo. The phosphorylation state of IRS-1 following infusion of insulin or AII via the vena cava was assessed after immunoprecipitation with an anti-peptide antibody to IRS-1 followed by immunoblotting with an anti-phosphotyrosine antibody and an anti-PI 3-kinase antibody. Densitometry indicated a 5.6 +/- 1.3-fold increase in IRS-1 phosphorylation after stimulation with AII and a 12.8 +/- 3.1-fold increase after insulin. The effect was maximal at an AII concentration of 10(-8) M and occurred 1 min after infusion. There was also a 6.1 +/- 1.2-fold increase in IRS-1-associated PI 3-kinase in response to AII. In the isolated perfused heart the result was similar, showing a direct effect of AII on this pathway. When the animals were pretreated for 1 h with DuP 753, a non-peptide AII-receptor 1 (AT1 receptor) antagonist, there was a marked reduction in the AII-induced tyrosine phosphorylation of IRS-1, suggesting that phosphorylation is initially mediated by the AT1 receptor. We conclude that AII stimulates tyrosine phosphorylation of IRS-1 and its association with PI 3-kinase. This pathway thus represents an additional signalling mechanism stimulated by AII in the rat heart in vivo.

Angiotensin II↗
PubMed1995

Effect of glucagon on insulin receptor substrate-1 (IRS-1) phosphorylation and association with phosphatidylinositol 3-kinase (PI 3-kinase).

In the present study we have examined the levels and phosphorylation state of the insulin receptor and insulin receptor substrate 1 (IRS-1) as well as the association between IRS-1 and phosphatidylinositol 3-kinase (PI 3-kinase) in the liver and muscle of rats treated with glucagon. There was a decrease in the insulin-stimulated receptor and IRS-1 phosphorylation levels which was paralleled by a reduced association between IRS-1 and PI 3-kinase in vivo in the liver and muscle of glucagon-treated rats. These observations suggest that glucagon, probably acting through cAMP, may impair insulin signaling in the three early steps in insulin action after binding.

Animals↗
PubMed1994

Indirect effects of oral tolerance in mice.

Anti-DNP antibody formation resulting from intraperitoneal (i.p.) immunization with DNP-KLH may be blocked by simultaneous (i.p.) injection of DNP-Ova or native Ova in mice orally tolerant to Ova, but not in normal mice. In Ova-tolerant mice the inhibition of anti-DNP antibody formation also occurred when DNP-Ova and DNP-KLH were given by separate routes of immunization: subcutaneous (s.c.) and i.p. A second exposure to Ova by gastric intubation (gavage) or intravenous administration simultaneously with i.p. immunization with DNP-KLH failed to inhibit anti-DNP antibody formation. There was inhibition of responses to DNP-KLH i.p. by DNP-Ova given 24 h before, but not 24 h after, and in the Ova-tolerant mice, addition of DNP-Ova only to the primary immunization with DNP-KLH inhibited secondary and tertiary responses to DNP-KLH in the absence of further exposures to DNP-Ova. These results suggest that the indirect effects of parenteral exposure of tolerant mice to the tolerated immunogen may inhibit unrelated immune responses. This inhibition is not due to 'innocent bystanding' suppression, i.e., to inhibitory cytokines provided locally by specific suppressor lymphocytes; it may derive from more durable perturbations of immune system.

Administration, Oral↗
PubMed1993

Nuclear/cytoplasmic ratio correlates strongly with survival in non-disseminated neuroendocrine carcinoma of the lung.

In order to verify whether quantitative morphological indices of neuroendocrine carcinoma of the lung may help to predict survival, 47 biopsies (from 37 males and 10 females; 16-82 years of age) were studied by light microscopy. Areal fractions of nuclei, cytoplasm, stroma, and blood vessels were determined using a standard point counting method. The counts were made in six non-coincident microscopic fields in each case, and the areal fractions of nuclei, of the entire tumour cell, stroma, blood vessels and the nuclear/cytoplasmic ratio were computed. In a multivariate linear regression analysis, survival in months after biopsy was considered the dependent variable of age and of all morphometric parameters listed above. The significance level was set at 5%. For all patients (disregarding staging) survival was negatively correlated (P < 0.001, multiple r = 0.5435) with age and nuclear/cytoplasmic ratio. When only patients with disease confined to the thorax (stages I, II and III) were taken into account, the accuracy of the function predicting survival increased considerably (P = 0.004, multiple r = 0.7957). The use of simple stereological methods, therefore, proved to be of value in predicting survival in patients with neuroendocrine carcinomas of the lung.

Adolescent↗
PubMed1993

Systemic immunization of mature mice by the oral route.

1. Mice of several strains which are susceptible to the induction of oral tolerance by a single gavage with 20 mg of ovalbumin (Ova) when young adults (7-8 weeks old) become less susceptible or refractory to tolerance induction when mature (20-40 weeks old). The antibody-forming capacity of these mature animals remains invariant compared to young adults (8-10 weeks old). 2. Mature mice of several strains display significant serum antibody responses to 3 gavages (days 0, 7 and 28) with Ova; as assessed by ELISA titers, these responses are similar in magnitude to those elicited by standard ip immunization with small doses of Ova. 3. In mature H-III mice, gavages on days 0, 7 and 28 induced significant antibody formation. On the contrary, the ingestion of the same amounts of Ova on days 0, 7 and 28 induced oral tolerance. Concomitant gavage with saline on the days of Ova ingestion failed to inhibit tolerance induction. 4. In H-III mice displaying circulating antibodies induced by repeated gavage with Ova, additional ip injections of Ova failed to increase the antibody titers.

Administration, Oral↗
PubMed1993

Hydroxyurea before oral antigen blocks the induction of oral tolerance.

1. Treatment with hydroxyurea (HU, 1 mg/g ip, 2 doses applied 7 h apart) eliminates the majority of cells undergoing mitosis (cycling cells) without affecting non-cycling cells. Oral tolerance, induced by a single gavage with 20 mg of ovalbumin, results in a drastic inhibition of anti-Ova antibody responses in young adult mice. Oral tolerance is actively maintained by the presence of specific suppressor T cells which may adoptively transfer the tolerance to naive syngeneic recipients. Under the clonal selection hypothesis, the induction of oral tolerance should be blocked by HU treatment applied soon after oral exposure to the antigen by the elimination of specific clones of lymphocytes activated by tolerogenic presentation of the antigen. 2. However, treatment with HU initiated 3, 6 or 24 h after oral exposure to ovalbumin had no effect on the induction of oral tolerance in B6D2F1 mice. However, treatment with HU 24 h before antigen exposure, totally blocked the induction of tolerance. Treatment with HU 72 h before ovalbumin had no effect. 3. In animals treated with HU 24 h before, the adoptive transfer of normal thymus, bone marrow or spleen cells partially restored the susceptibility to the induction of oral tolerance. 4. The results suggest that cycling cells, which may be totally regenerated within 72 h after treatment with HU, and are present in normal thymus, bone marrow and spleen, are crucially important for the induction of oral tolerance.

Administration, Oral↗
PubMed1990

Flow and volume dependence of respiratory system mechanics during constant flow ventilation in normal subjects and in adult respiratory distress syndrome.

Seven control subjects and seven patients with adult respiratory distress syndrome (ARDS) were artificially ventilated and flow, volume, and tracheal pressure were monitored. Respiratory system resistance (Rrs,max) was partitioned into its homogeneous (Rrs,min) and uneven (Rrs,u) components. Respiratory system elastance (Ers) was also measured. In both groups Ers did not vary with different inspiratory flows and volumes, but was significantly higher in ARDS. With increasing volume (isoflow maneuvers), Rrs,max and Rrs,u increased but Rrs,min remained unaltered in ARDS. In control patients, however, resistances did not vary but Rrs,max and Rrs,u were smaller and Rrs,min equaled their corresponding values in ARDS. Hence, stress relaxation seems to be increased in ARDS. During isovolume maneuvers Rrs,max and Rrs,u decreased with increasing flows (both groups), although they were significantly higher in ARDS. Rrs,min was not modified by different flows and was similar in both groups. Thus, pendelluft is also increased in ARDS. In conclusion, the mechanical profile of ARDS is characterized by increased Ers and Rrs,max, the latter being secondary to augmented mechanical unevenness within the system.

Adolescent↗
PubMed1990

Specific responses to two unrelated antigens in mice made orally tolerant to one of them.

BDF1 and B10 mice, either normal or exclusively fed egg white diluted in water, were immunized with ovalbumin (OVA), sheep erythrocytes (SRBC) or OVA + SRBC. BDF1, but not B10, mice became tolerant to OVA and presented a 100% increase in the total number of immunoglobulin-secreting cells in the spleen. Immunization with OVA + SRBC markedly increased the response to OVA, except in tolerant BDF1 mice, and had no effect on the anti-SRBC PFC response, except in normal (non-tolerant) BDF1 mice.

Animals↗
PubMed1989

Concurrent Churg-Strauss syndrome and temporal arteritis in a young patient with pulmonary nodules.

Very few cases of pulmonary vasculitis that cannot be classified into a single category of vasculitis have been described. We report the first case of a vasculitic process in which pulmonary involvement with asthma, eosinophilic interstitial infiltrates, and small nodules were seen in association with jaw claudication and temporal arteritis with giant cells found on biopsy. Other signs of systemic involvement were also present such as peripheral neuropathy, hematuria with erythrocytic casts and proteinuria, pericardial effusion, and a dilated cardiomyopathy. The histopathologic picture was complex and unique. The early age of onset, the multisystemic involvement, and the prompt response to cyclophosphamide pointed to a diagnosis of "polyangiitis overlap syndrome," with some aspects of Churg-Strauss syndrome and also temporal arteritis. Physicians should be aware of these polymorphous and life-threatening pulmonary vasculitic syndromes, which require aggressive immunosuppressor therapy.

Adult↗