Synthesis and characterization of new siloxane-modified addition polyimides

A new series of polyimides was synthesized by addition polymerization of 4,4′-(bismaleimido)-diphenylmethane, 1,4-piperazine and an amino-terminated polydimethylsiloxane. The synthesis was carried out in m-cresol solution following a two-step procedure. Copolymers containing 15 and 20 wt.-% of the polydimethylsiloxane elastomer were prepared, together with the unmodified base copolymer. Infrared spectroscopy, ¹³C and ¹H NMR, thermal and thermogravimetric analyses were used to characterize the copolymers. The DSC curves of all the samples showed an exotherm in the temperature range 230–280°C, attributable to curing and addition reactions involving the chain-end groups. Different glass transition temperatures (T_g) were observed, depending on the elastomer content. Thermogravimetric analysis indicated that no significant changes occur in the thermal stability of rubber-modified copolymers.     

Expression of insulin-like growth factor II (IGF–II) in human hepatocellular carcinomas: An immunohistochemical study

Recent results obtained using molecular biology techniques have suggested a possible role for insulin-like growth factor II (IGF-II) in the pathogenesis of hepatocellular carcinoma (HCC). To investigate this phenomenon, a monoclonal anti-body was used against IGF-II to study 54 patients with HCC. The presence of HBsAg was also tested both in serum and liver tissue. A positive immunoreaction was found in 9/15 (60%) of the HCC arising in cirrhotic livers of patients who had serum markers for HBV (HBV+ positive patients). These results provide further evidence that HBV might play a role in the expression of IGF-II. In HCC of patients without any markers of HBV infection (HBV- negative patients), IGF–II was detected in 10/39 (25.6%) of the tumors, and in some benign neoplastic lesions. It was found not only in neoplastic cells but also in some dysplastic nodules. The speculation arises that IGF–II expression may play a role in some steps of hepato-carcinogenesis.     

Nitrosative stress in the bronchial mucosa of severe chronic obstructive pulmonary disease

BACKGROUND: Reactive nitrogen species, formed via the reaction of nitric oxide (NO) with superoxide anion and via (myelo)peroxidase-dependent oxidation of NO(2)(-), have potent proinflammatory and oxidizing actions. Reactive nitrogen species formation and nitrosative stress are potentially involved in chronic obstructive pulmonary disease (COPD) pathogenesis. OBJECTIVES: To investigate the expression of markers of nitrosative stress, including nitrotyrosine (NT), inducible NO synthase (iNOS), endothelial NO synthase (eNOS), myeloperoxidase (MPO), and xanthine oxidase (XO) in bronchial biopsies and bronchoalveolar lavage from patients with mild to severe stable COPD compared with control groups (smokers with normal lung function and nonsmokers). METHODS: The expression of NT, iNOS, eNOS, MPO and XO in the bronchial mucosa and bronchoalveolar lavage of patients was measured by using immunohistochemistry, Western blotting, and ELISA and correlated with the inflammatory cell profile. RESULTS: Patients with severe COPD in stable phase had higher numbers of NT(+) and MPO(+) cells in their bronchial submucosa compared with mild/moderate COPD, smokers with normal lung function, and nonsmokers (P < .01). iNOS(+) and eNOS(+) but not XO(+) cells were significantly increased in smokers with COPD or normal lung function compared with nonsmokers (P < .05 and P < .01, respectively). In patients with COPD, the number of MPO(+) cells was significantly correlated with the number of neutrophils (r = +0.61; P < .0025) in the bronchial submucosa. Furthermore, the number of NT(+) and MPO(+) cells was negatively correlated with postbronchodilator FEV(1). CONCLUSION: These data suggest that nitrosative stress, mainly mediated by MPO and neutrophilic inflammation, may contribute to the pathogenesis of severe COPD.     

Clinical,immunological, and molecular analysis in a large cohort of patients with X-linked agammaglobulinemia: an Italian multicenter study

A questionnaire-based retrospective clinical and immunological survey was conducted in 73 males with a definite diagnosis of X-linked agammaglobulinemia based on BTK sequence analysis. Forty-four were sporadic and 29 familial cases. At December 2000, the patients' ages ranged from 2 to 33 years; mean age at diagnosis and mean duration of follow-up were 3.5 and 10 years respectively. After the mid-1980s all but 2 were on intravenous immunoglobulin (IVIG) substitution therapy, with residual IgG >500 mg/dl in 94% of the patients at the time of enrollment. Respiratory infections were the most frequent manifestation both prior to diagnosis and over follow-up. Chronic lung disease (CLD) was present in 24 patients, in 15 already at diagnosis and in 9 more by 2000. The cumulative risk to present at diagnosis with CLD increased from 0.17 to 0.40 and 0.78 when the diagnosis was made at the ages of 5, 10, and 15 years respectively. For the 9 patients who developed CLD during follow-up, the duration of follow-up, rather than age at diagnosis; previous administration of intramuscular immunoglobulin; and residual IgG levels had a significant effect on the development of CLD. Chronic sinusitis was present in 35 patients (48%), in 15 already at diagnosis and in 20 by 2000. Sistemic infections such as sepsis and meningitis/meningoencephalitis decreased over follow-up, probably due to optimal protection provided by high circulating IgG levels reached with IVIG.     

Successful xenografting of cryopreserved primary pancreatic cancers

In order to assess the suitability of cryopreserved neoplastic tissues for xenografting into nude (nu/nu) mice, we compared the take rate in 28 samples of pancreatic ductal carcinoma. Eleven fresh samples were implanted in nu/nu mice, and 17 were frozen in cryopreserving solution and implanted at a later time. All samples were examined for the presence of neoplastic tissue in cryostat sections. A total of 15 tumors grew in the animals; five from the freshly implanted samples and ten from those cryopreserved. Ten xenografted tumors were characterized for alterations in p53, K-ras, and p16 genes, which were found in six, eight, and nine cases, respectively. Our results demonstrate that the take rate for xenografting is comparable between cryopreserved and fresh tissue samples. The procedure allows for the exchange of tumor material between institutions and permits the establishment of centralized facilities for the storage of an array of different primary tumor samples suitable for the production of in vivo models of cancers.     

Cell signalling-mediating insulin increase of mRNA expression for cationic amino acid transporters-1 and -2 and membrane hyperpolarization in human umbilical vein endothelial cells

Insulin induces vasodilatation in human subjects and increases l-arginine transport and NO synthesis in human umbilical vein endothelial cells (HUVEC). Cell signalling events associated with insulin effects on activity and mRNA expression of the human cationic amino acid transporters 1 (hCAT-1) and 2B (hCAT-2B) are unknown. l-Arginine transport and eNOS activity were determined in HUVEC exposed to insulin. mRNA levels for hCAT-1, hCAT-2B and eNOS were quantitated by real time RT-PCR and endothelial NO synthase (eNOS) protein was identified by Western blot analysis. Intracellular Ca²⁺, l-arginine and l-citrulline levels, l-[³H]citrulline formation from l-[³H]arginine, cGMP formation, nitrite level, ATP release and membrane potential were determined. Insulin increased l-arginine transport and the mRNA levels for hCAT-1 and hCAT-2B and eNOS expression and activity. Insulin also induced membrane hyperpolarization and increased intracellular Ca²⁺, l-[³H]citrulline, cGMP and nitrite formation. Insulin-mediated stimulation of the l-arginine/NO pathway is thus associated with increased hCAT-1 and hCAT-2B mRNA, and eNOS expression, via mechanisms involving membrane hyperpolarization, mitogen-activated protein kinases p42 and p44, phosphatidylinositol 3-kinase, NO and protein kinase C. We have characterized a cell signalling pathway by which hyperinsulinaemia could lead to vasodilatation in human subjects, and which could have implications in patients in whom plasma insulin levels are altered, such as in diabetes mellitus.     

Two new mutations and three novel polymorphisms in the<Emphasis Type="Italic"> RB1</Emphasis> gene in Ecuadorian patients

RB1 is the gene responsible for retinoblastoma, the most common malignant intraocular tumor of infancy and early childhood. There are no reports about this gene in Ecuadorian populations, and only a few studies have been published in Latin America about this subject. There is a spectrum of more than 370 mutations described in the RB1 gene mutation database (http://www.d-lohmann.de/Rb/mutations.html), and alterations have been found in 25 of the 27 exons. During the exon-by-exon analysis of 31 tumor and blood samples from Ecuadorian patients, we found two new mutations and three novel polymorphisms. One of the polymorphisms is located in intron 26 where no alterations of the gene have been described previously. The polymorphisms were found in all of the patients tumor samples, but not in normal population, suggesting there might be a relationship between these polymorphisms and the development of retinoblastoma in the Ecuadorian population.The nucleotide sequence data reported are available in the GenBank database under the accession numbers: AY243567, AY260472, AY260473, AY273783     

Evidence that Ca/calmodulin-dependent protein kinase mediates the modulation of the Ca2+-dependent K+ current,I AHP,by acetylcholine,but not by glutamate,in hippocampal neurons

Muscarinic and metabotropic glutamate receptor agonists increase the excitability of hippocampal and other cortical neurons by suppressing the Ca²⁺-activated K⁺current,I _AHP, which underlies the slow afterhyperpolarization (AHP) and spike frequency adaptation. We have examined the mechanism of action of a muscarinic agonist (carbachol) and a metabotropic glutamate receptor agonist (1-Aminocyclopentane-trans-1,3-dicarboxylic acid; t-ACPD) onI _AHP in hippocampal CA1 neurons in slices, by using highly specific protein kinase inhibitors. We found that inhibition of protein kinase A (PKA) with the adenosine 3,5-cyclic monophosphate (cAMP) analogue Rp-adenosine-3,5-cyclic phosphorothioate Rp-cAMPS, did not prevent the muscarinic and glutamatergic suppression ofI _AHP. In contrast, two specific peptide inhibitors of Ca²⁺/calmodulin-dependent protein kinase II (CaM-K II), each partially blocked the effect of carbachol, but not the effect of t-ACPD onI _AHP. We conclude that CaM-K II, but not PKA, is involved in mediating the muscarinic suppression ofI _AHP, although other pathways may also contribute. In contrast, neither CaM-K II nor PKA seems to mediate the metabotropic glutamate receptor action onI _AHP.     

Tuning of innate immunity and polarized responses by decoy receptors

After the identification of the interleukin (IL)-1 type II receptor as the prototype, decoy receptors have been identified for a number of members of the IL-1/IL-18, TNF, IL-10 and IL-13 receptor families. Moreover, the silent receptor D6 is a promiscuous decoy and scavenger receptor of inflammatory chemokines. The IL-1 decoy receptor is regulated by pro- and anti-inflammatory signals and its levels may serve as a readout of the activation of anti-inflammatory pathways, for instance by glucocorticoid hormones. Decoy receptors represent a strategy to tune inflammatory and polarized adaptive responses.     

Diltiazem impairs maturation and functions of human dendritic cells

The aim of this study was to define the effects of diltiazem, a calcium antagonist drug used in cardiology and in clinical transplantation, on the differentiation and maturation of human dendritic cells (DC). Herein, we demonstrate that diltiazem, in association with granulocyte macrophage-colony-stimulating factor (GM-CSF) and interleukin-4 (IL-4), induces monocytes to differentiate into cells with many of the characteristic of DC. However, diltiazem-induced DC express high levels of mannose receptor and Fc gamma RII and, consequently, manifest a higher endocytic activity compared with GM-CSF+IL-4-induced DC. Importantly, diltiazem-induced DCs have an impaired responsiveness to lipopolysaccharide and CD40 ligand because they produce decreased levels of IL-12 and reveal a reduced ability to stimulate alloreactive T-cell responses as well as in inducing interferon-gamma producing Th1 cells. These effects may contribute to a decreased DC-dependent T-cell activation and may help to explain the immunoregulatory function of diltiazem and its effectiveness in preventing transplant rejection.