Increased pancreatic islet mass is accompanied by activation of the insulin receptor substrate-2/serine-threonine kinase pathway and augmented cyclin D(2) protein levels in insulin-resistant rats

It is well known that glucocorticoids induce peripheral insulin resistance in rodents and humans. Here, we investigated the structural and ultrastructural modifications, as well as the proteins involved in beta-cell function and proliferation, in islets from insulin-resistant rats. Adult male Wistar rats were made insulin resistant by daily administration of dexamethasone (DEX; 1mg/kg, i.p.) for five consecutive days, whilst control (CTL) rats received saline alone. Structure analyses showed a marked hypertrophy of DEX islets with an increase of 1.7-fold in islet mass and of 1.6-fold in islet density compared with CTL islets (P < 0.05). Ultrastructural evaluation of islets revealed an increased amount of secreting organelles, such as endoplasmic reticulum and Golgi apparatus in DEX islets. Mitotic figures were observed in DEX islets at structural and ultrastructural levels. Beta-cell proliferation, evaluated at the immunohistochemical level using anti-PCNA (proliferating cell nuclear antigen), showed an increase in pancreatic beta-cell proliferation of 6.4-fold in DEX islets compared with CTL islets (P < 0.0001). Increases in insulin receptor substrate-2 (IRS-2), phosphorylated-serine-threonine kinase AKT (p-AKT), cyclin D(2) and a decrease in retinoblastoma protein (pRb) levels were observed in DEX islets compared with CTL islets (P < 0.05). Therefore, during the development of insulin resistance, the endocrine pancreas adapts itself increasing beta-cell mass and proliferation, resulting in an amelioration of the functions. The potential mechanisms that underlie these events involve the activation of the IRS-2/AKT pathway and activation of the cell cycle, mediated by cyclin D(2). These adaptations permit the maintenance of glycaemia at near-physiological ranges.

beta-carotene attenuates the paradoxical effect of tobacco smoke on the mortality of rats after experimental myocardial infarction

The objective of this study was to investigate the effects of exposure to tobacco smoke (ETS) in rats that were or were not supplemented with dietary beta-carotene (BC), on ventricular remodeling and survival after myocardial infarction (MI). Rats (n = 189) were allocated to 4 groups: the control group, n = 45; group BC administered 500 mg/kg diet, n = 49, BC supplemented rats; group ETS, n = 55, rats exposed to tobacco smoke; and group BC+ETS, n = 40. Wistar rats weighing 100 g were administered one of the treatments until they weighed 200 to 250 g (similar to 5 wk). The ETS rats were exposed to cigarette smoke for 30 min 4 times/d, in a chamber connected to a smoking device. After reaching a weight of 200-250 g, rats were subjected to experimental MI (coronary artery occlusion) and mortality rates were determined over the next 105 d. In addition, echocardiographic, isolated heart, morphometrical, and biochemical studies were performed. Mortality data were tested using Kaplan-Meyer curves and other data by 2-way ANOVA. Survival rates were greater in the ETS group (58.2%) than in the control (33.3%) (P = 0.001) and BC+ETS rats (30.0%) (P = 0.007). The groups did not differ in the other comparisons. Left ventricular end-diastolic diameter normalized to body weight was greater and maximal systolic pressures were lower in the ETS groups than in non-ETS groups. Previous exposure to tobacco smoke induced a process of cardiac remodeling after MI. There is a paradoxical protector effect with tobacco smoke exposure, characterized by lower mortality, which is offset by BC supplementation.

Granulocytic sarcoma of the small intestine with CBF beta/MYH11 fusion gene: report of an aleukaemic case and review of the literature

Granulocytic sarcomas (GS) are rare extramedullary tumours composed of immature myeloid cells. Inversion of chromosome 16 [inv(16)] is a cytogenetic marker for M4Eo subtype of acute myeloid leukaemia (AML). The possibility of an association between the development of granulocytic sarcoma of the small intestine (GSSI) and the M4Eo subtype of AML was suggested in nine previous case reports.Here we report an aleukaemic case of GSSI with inv(16) and its molecular equivalent, the CBFbeta/MYH11 fusion gene, detected by reverse transcriptase-polymerase chain reaction (RT-PCR), that after treatment with conventional AML chemotherapy followed by autologous bone marrow transplantation, achieved complete haematological and molecular remission on bone marrow examination. After chemotherapy, a thickened ileum wall positive for CBFbeta/MYH11 on tumour mass samples was still observed on computed tomography (CT) studies, raising the question of residual GS representing a reservoir of malignant cells. This case demonstrates the critical need of multidisciplinary diagnosis and follow-up of this entity combining immunopathologic, cytogenetic and molecular studies, reinforcing the potentiality of risk-adapted therapy strategies, as it is increasingly claimed for patients with overt AML. (C) 2003 Elsevier Ltd. All rights reserved.

Intermittent Therapy with 1,25 Vitamin D and Calcitonin Prevents Cyclosporin-Induced Alveolar Bone Loss in Rats

Bone loss associated with cyclosporin A (CsA) therapy can result in serious morbidity to patients. Intermittent administration of 1,25 Vitamin D and calcitonin reduces osteopenia in a murine model of postmenopausal osteoporosis. The purpose of this study was to evaluate the effects of this therapeutic approach on CsA-induced alveolar bone loss in rats. Forty male Wistar rats were allocated to four experimental groups according to the treatment received during 8 weeks: (1) CsA (10 mg/kg/day, s.c.); (2) 1,25 Vitamin D (2 mu g/kg, p.o.; in weeks 1, 3, 5, and 7) plus calcitonin (2 mu g/kg, i.p.; in weeks 2, 4, 6, and 8); (3) CsA concurrently with intermittent 1,25 Vitamin D and calcitonin administration; and (4) the control treatment group (vehicle). At the end of the 8-week treatment period, serum concentrations of bone-specific alkaline phosphatase, tartrate-resistant acid phosphatase (TRAP-5b), osteocalcin, interleukin (IL)-1 beta, IL-6, and tumor necrosis factor alpha (TNF-alpha) were measured and an analysis of bone volume, bone surface, number of osteoblasts, and osteoclasts was performed. CsA administration resulted in significant alveolar bone resorption, as assessed by a lower bone volume and an increased number of osteoclasts, and increased serum bone-specific alkaline phosphatase, TRAP-5b, IL-1 beta, IL-6, and TNF-alpha concentrations. The intermittent administration of calcitriol and calcitonin prevented the CsA-induced osteopenic changes and the increased serum concentrations of TRAP-5b and inflammatory cytokines. Intermittent calcitriol/calcitonin therapy prevents CsA-induced alveolar bone loss in rats and normalizes the production of associated inflammatory mediators.

Tumor Necrosis Factor alpha and Interleukin-1 beta Modulate Calcium and Nitric Oxide Signaling in Mechanically Stimulated Osteocytes

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Chemoenzymatic Synthesis of alpha-Hydroxy-beta-methyl-gamma-hydroxy Esters: Role of the Keto-Enol Equilibrium To Control the Stereoselective Hydrogenation in a Key Step

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Avaliação eletroforética, cromatográfica e molecular da Hb D Los Angeles no Brasil

A variante de hemoglobina (Hb) D mais comum, Hb D Los Angeles ou D Punjab, é originada de uma transversão GAA->CAA no códon 121 da globina beta; essa mutação resulta na substituição do ácido glutâmico por glutamina na proteína. É a terceira variante de hemoglobina mais freqüente da população brasileira. Como as hemoglobinas D apresentam migração similar à hemoglobina S em pH alcalino, e com a hemoglobina A em pH ácido, são necessários vários testes para o correto diagnóstico. No presente estudo objetivou-se relacionar os diferentes procedimentos laboratoriais de rotina diagnóstica, além da análise molecular, para estabelecer o perfil de Hb D Los Angeles no Brasil. Foram analisados 47 indivíduos da população brasileira com provável Hb D Los Angeles, por vários procedimentos eletroforéticos em diferentes condições de pH, além da cromatografia líquida de alta pressão, e testes moleculares para confirmação da mutação. Foram encontrados quatro tipos de combinações de hemoglobinas: 42 indivíduos portadores de hemoglobina AD Los Angeles, dois indivíduos com doença de Hb S/D Los Angeles, dois indivíduos com Hb D Los Angeles e talassemia beta e um indivíduo com Hb D Los Angeles e Hb Lepore. Os indivíduos heterozigotos para D Los Angeles são assintomáticos, entretanto, em associação com outras variantes e talassemias podem apresentar graus variáveis de manifestações clínicas. Os resultados apresentados enfatizaram a necessidade da associação de várias metodologias para a identificação da Hb D Los Angeles, além de auxiliar na elucidação de combinações raras.

Initial structural analysis of an alpha(4)beta(4) C-type lectin from the venom of Crotalus durissus terrificus

Convulxin, an alphabeta C-type lectin, is a potent platelet activator isolated from the venom of the South American rattlesnake Crotalus durissus terrificus. It is a 26.5 kDa alphabeta heterodimer consisting of two homologous disulfide-linked chains. The crystals belong to space group I4, with unit-cell parameters a = b = 131.61, c = 121.85 Angstrom, and diffraction data were collected to 2.7 Angstrom. The structure was solved by molecular replacement and the asymmetric unit contains two alphabeta heterodimers, each of which forms a disulfide-linked cyclic alpha(4)beta(4) tetramer in the unit cell. These alpha(4)beta(4) tetramers are stacked to form a large solvent channel.

Structural basis for metal ion coordination and the catalytic mechanism of sphingomyelinases D

Sphingomyelinases D (SMases D) from Loxosceles spider venom are the principal toxins responsible for the manifestation of dermonecrosis, intravascular hemolysis, and acute renal failure, which can result in death. These enzymes catalyze the hydrolysis of sphingomyelin, resulting in the formation of ceramide 1-phosphate and choline or the hydrolysis of lysophosphatidyl choline, generating the lipid mediator lysophosphatidic acid. This report represents the first crystal structure of a member of the sphingomyelinase D family from Loxosceles laeta (SMase I), which has been determined at 1.75-angstrom resolution using the quick cryo-soaking technique and phases obtained from a single iodine derivative and data collected from a conventional rotating anode x-ray source. SMase I folds as an (alpha/beta)(8) barrel, the interfacial and catalytic sites encompass hydrophobic loops and a negatively charged surface. Substrate binding and/or the transition state are stabilized by a Mg2+ ion, which is coordinated by Glu(32), Asp(34), Asp(91), and solvent molecules. In the proposed acid base catalytic mechanism, His(12) and His(47) play key roles and are supported by a network of hydrogen bonds between Asp(34), Asp(52), Trp(230), Asp(233), and Asn(252).

Crystallization and preliminary X-ray diffraction analysis of a class II phospholipase D from Loxosceles intermedia venom

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Neutrino decay and neutrinoless double beta decay in a 3-3-1 model

In this work we show that the implementation of spontaneous breaking of the lepton number in the 3-3-1 model with right-handed neutrinos gives rise to fast neutrino decay with Majoron emission and generates a bunch of new contributions to the neutrinoless double beta decay.

Scalar field theory at finite temperature in D=2+1

We discuss the phi(6) theory defined in D=2+1-dimensional space-time and assume that the system is in equilibrium with a thermal bath at temperature beta(-1). We use the 1/N expansion and the method of the composite operator (Cornwall, Jackiw, and Tomboulis) for summing a large set of Feynman graphs. We demonstrate explicitly the Coleman-Mermin-Wagner theorem at finite temperature.

Measurement of beta (t -> Wb)/beta(t -> Wq) at root s=1.96 TeV

We present the measurement of R = B(t -> Wb)/B(t -> Wq) in pp collisions at root s = 1.96 TeV, using 230 pb(-1) of data collected by the DO experiment at the Fermilab Tevatron Collider. We fit simultaneously R and the number (N-tt) of selected top quark pairs (tt), to the number of identified b-quark jets in events with one electron or one muon, three or more jets, and high transverse energy imbalance. To improve sensitivity, kinematical properties of events with no identified b-quark jets are included in the fit. We measure R = 1.03(-0.17)(0.19) (stat + syst), in good agreement with the standard model. We set lower limits of R > 0.61 and vertical bar V-tb vertical bar > 0.78 at 95% confidence level. (c) 2006 Elsevier B.V. All rights reserved.

Scalar field theory at finite temperature in D=2+1

We discuss the phi(6) theory defined in D = 2 + 1-dimensional space-time and assume that the system is in equilibrium with a thermal bath at temperature beta(-1). We use the 1/N expansion and the method of composite operator (CJT) for summing a large set of Feynman graphs. We demonstrate explicitly the Coleman-Mermin-Wagner theorem at finite temperature.