Sirt1 protects from K‐Ras‐driven lung carcinogenesis

The NAD⁺‐dependent deacetylase SIRT1 can be oncogenic or tumor suppressive depending on the tissue. Little is known about the role of SIRT1 in non‐small cell lung carcinoma (NSCLC), one of the deadliest cancers, that is frequently associated with mutated K‐RAS. Therefore, we investigated the effect of SIRT1 on K‐RAS‐driven lung carcinogenesis. We report that SIRT1 protein levels are downregulated by oncogenic K‐RAS in a MEK and PI3K‐dependent manner in mouse embryo fibroblasts (MEFs), and in human lung adenocarcinoma cell lines. Furthermore, Sirt1 overexpression in mice delays the appearance of K‐Ras^G12V‐driven lung adenocarcinomas, reducing the number and size of carcinomas at the time of death and extending survival. Consistently, lower levels of SIRT1 are associated with worse prognosis in human NSCLCs. Mechanistically, analysis of mouse Sirt1‐Tg pneumocytes, isolated shortly after K‐Ras^G12V activation, reveals that Sirt1 overexpression alters pathways involved in tumor development: proliferation, apoptosis, or extracellular matrix organization. Our work demonstrates a tumor suppressive role of SIRT1 in the development of K‐RAS‐driven lung adenocarcinomas in mice and humans, suggesting that the SIRT1–K‐RAS axis could be a therapeutic target for NSCLCs.     

Robertsonian metacentrics of the house mouse lose telomeric sequences but retain some minor satellite DNA in the pericentromeric area

A combination of cytogenetic and molecular biology techniques were used to study the molecular composition and organisation of the pericentromeric regions of house mouse metacentric chromosomes, the products of Robertsonian (Rb) translocations between telocentrics. Regardless of whether mitotic or meiotic preparations were used, in situ hybridisation failed to reveal pericentromeric telomeric sequences on any of the Rb chromosomes, while all metacentrics retained detectable, although reduced (average 50 kb), amounts of minor satellite DNA in the vicinity of their centromeres. These results were supported by slot blot hybridisation which indicated that mice with 2n=22 Rb chromosomes have 65% of telomeric sequences (which are allocated to the distal telomeres of both Rb and telocentric chromosomes and to the proximal telomeres of telocentrics) and 15% the amount of minor satellite, compared with mice with 2n=40 all-telocentric chromosomes. Pulsed field gel electrophoresis and Southern analysis of DNA from Rb mice showed that the size of the telomeric arrays is similar to that of mice with all-telocentric chromosomes and that the minor satellite sequences were hybridising to larger fragments incorporating major satellite DNA. Since the telomeric sequences are closer to the physical end of the chromosome than the minor satellite sequences, the absence of telomeric sequences and the reduced amount of minor satellite sequences at the pericentromeric region of the Rb metacentrics suggest that the breakpoints for the Rb translocation occur very close to the minor satellite-major satellite border. Moreover, it is likely that the minor satellite is required for centromeric function, 50–67 kb being enough DNA to organise one centromere with a functionally active kinetochore.     

Acute and Chronic Experimental Trypanosoma cruzi Infection in the Rat. Response to Systemic Treatment with Recombinant Rat Interferon-Gamma

We examined the effects of recombinant rat inteferon-gamma (IFN-γ) injections on the parasitologic, serologic, immunologic and histopathologic features of acute and chronic experimental Trypanosoma cruzi (T. cruzi) infections in “l” rats. Upon infection at weaning, two rat groups were allocated to receive a 20-day cycle of IFN-γ injections, 20,000 IU/rat each, which started at 1, and 7 days post-infection (pi). Treatment with IFN-γ, initiated at either 1 or 7 days pi, resulted in comparatively lower peak parasitemias (P<0.02) but in similar levels of anti-T. cruzi circulating antibodies and serum IFN-γ activities. The latter appeared significantly increased during acute infection whereas biologically active tumor necrosis factor was virtually undetectable in serum from infected rats regardless of whether they had been given IFN-γ or not. The prevalence of chronic focal myocarditis in IFN-γ-treated infected rats showed no differences with respect to the one recorded in control-infected counterparts. The inverse CD4/CD8 ratio of spleen and lymph node T cells that usually accompanies chronic infection was reversed by IFN-γ. Mononuclear cells carrying class III-A and I-E molecules, that were found to have increased at both compartments, appeared also modified upon IFN-γ treatment with an overincrease of I-A-positive cells, and a normalization of I-E-bearing cells.     

Major Enteropathogenic Bacteria Isolated from Diarrheal Patients in Bolivia: A Hospital-Based Study

A total of 1,234 fecal samples from diarrhea cases were examined for etiological bacterial agents at medical facilities in La Paz and Sucre, Bolivia. Eighty strains of Shigella spp., 39 strains of Salmonella spp., 29 strains of Vibrio cholerae, and 222 strains of enteropathogenic Escherichia coli (139 EPEC, 55 ETEC, 29 EIEC, and 1 EHEC) were isolated. With regard to the serovars of Shigella, S. flexneri 2a, 3a, and 1b were predominant. In the case of Salmonella, S. enteritidis was the most common, followed by S. typhi, S. poona, and S. paratyphi B. Out of 29 cholera strains, 25 belonged to biovar El Tor, serovar Ogawa while the remaining 4 were serovar Inaba. Among 55 strains of ETEC serotypes, 5 showed ST producers but none showed LT producers. Likewise, among 55 strains of enterohemorrhagic serotypes, only one strain (O157:H7) produced verocytotoxin (VT 2). The results of drug sensitivity tests revealed the predominance of Shigella, EPEC, and ETEC strains resistant to aminobenzil-penicillin (ABPC) and trimethoprim. Since diarrheal patients in Bolivia are treated mainly with ABPC or sulfamethoxazole/trimethoprim (SXT) and rarely with gentamicin, kanamycin, or other drugs, it is possible that ABPC- and SXT-resistant strains will increase and persist in the near future.     

Role of thyroid hormones in renal tubule acidification

Renal tubule acidification was studied in thyroparathyroidectomized rats which had the parathyroids reimplanted into cervical muscle tissue, by stopped-flow microperfusion using ion-exchange resin microelectrodes. Hypothyroid rats had decreased rates of proximal and late distal bicarbonate reabsorption. This reduction occurred in the absence of changes in pH gradients, and was due mostly to decreases in acidification half-times, that is, of the rate of bicarbonate exit from the tubule lumen. H⁺ back-flux from the lumen measured during luminal perfusion with solutions at pH 6 (below stationary pH) was decreased in proximal tubule of hypothyroid rats, showing that the acidification defect was not due to an increased H⁺ shunt across the epithelium. These data indicate that in hypothyroid rats the proximal tubule luminal density of Na⁺/H⁺ exchangers or their turnover is decreased in the absence of alterations in the driving force (H⁺ and Na⁺ gradients across the luminal membrane) for H⁺ secretion. The effect observed in distal tubule may be due to action on Na⁺/H⁺ exchangers that are present also on this site, or to an impairment of the action of other H⁺ transporters such as H⁺-ATPases, including the provision of energy for them.This paper is dedicated to Prof. Carlos Chagas Filho, founder of the Institute of Biophysics, on the occasion of its 50th anniversary.     

Use of transfer factor for the treatment of recurrent non-bacterial female cystitis (NBRC): A preliminary report

Results of conventional treatment of female non-bacterial recurrent cystitis (NBRC) are discouraging. Most patients show an unexpected high incidence of vaginal candidiasis, while their cell mediated immunity to Herpes simplex viruses (HSV) and Candida antigens seems impaired, and it is known that the persistence of mucocutaneous chronic candidiasis is mainly due to a selective defect of CMI to Canadida antigens. Twenty nine women suffering of NBRC, and in whom previous treatment with antibiotics and non-steroid anti-inflammatory drugs was unsuccessful, underwent oral transfer factor (TF) therapy. TF specific to Canadida and/or to HSV was administered bi-weekly for the first 2 weeks, and then once a week for the following 6 months. No side effects were observed during treatment. The total observation period of our cohort was 24379 days with 353 episodes of cystitis recorded and a cumulative relapse index (RI) of 43. The observation period during and after treatment was 13920 days with 108 relapses and a cumulative RI of 23 (P < 0.0001). It, thus, seems that specific TF may be capable of controlling NBRC and alleviate the symptoms.     

Comparative measurements of chlorophyll a fluorescence, acid accumulation and gas exchange in exposed and shaded plants of Clusia minor L. and Clusia multiflora H. B. K. in the field

 Changes in chlorophyll a fluorescence during the day and diurnal-changes of net CO₂-exchange and organic acid contents were determined in two species of the genus Clusia during the dry season in Venezuela. The investigations included plants of the C₃/CAM intermediate species Clusia minor and the C₃ species C. multiflora growing at exposed and shaded sites. Both species showed a C₃ pattern of net CO₂-exchange at the exposed site. In the shade under extreme drought stress C. minor showed a weak expression of CAM without CO₂-uptake during the afternoon (phase IV of CAM). C. multiflora growing in the shade exhibited a C₃-pattern of net CO₂-exchange and a small but significant nocturnal accumulation of citrate. Shaded plants of C. minor were able to double their light utilisation for electron transport and to reduce non-photochemical quenching during phase III compared to phase II of CAM. Furthermore, increase of electron transport rate through photosystem II in phase III of CAM is correlated to decarboxylation of malate. At the exposed site C. multiflora was less negatively affected by high PPFD than C. minor. This was shown by a lower reduction of potential electron quantum yield (F_v/F_m) and higher light utilisation of electron transport of C. multiflora compared to C. minor. At the exposed site C. minor did not make use of the CAM option to increase light utilisation of electron transport and to reduce non-photochemical quenching as did the plants growing in the shade. Received: 20 March 1996 / Accepted: 24 June 1996     

Dammarane triterpenes from the resin of Boswellia freerana

The resin of Boswellia freerana afforded in addition to the known 3β,20(S)-dihydroxydammar-24-ene, its 3-acetyl derivative and (20S)-protopanaxadiol, a new triterpene that was characterized as 3β-acetoxy-16(S),20(R)-dihydroxydammar-24-ene on the basis of chemical and physico-chemical evidence.     

Identifying airways responsible for heterogeneous ventilation and mechanical dysfunction in asthma: an image functional modeling approach.

We present an image functional modeling approach, which synthesizes imaging and mechanical data with anatomically explicit computational models. This approach is utilized to identify the relative importance of small and large airways in the simultaneous deterioration of mechanical function and ventilation in asthma. Positron emission tomographic (PET) images provide the spatial distribution and relative extent of ventilation defects in asthmatic subjects postbronchoconstriction. We also measured lung resistance and elastance from 0.15 to 8 Hz. The first step in image functional modeling involves mapping ventilation three-dimensional images to the computational model and identifying the largest sized airways of the model that, if selectively constricted, could precisely match the size and anatomic location of ventilation defects imaged by PET. In data from six asthmatic subjects, these airways had diameters <2.39 mm and mostly <0.44 mm. After isolating and effectively closing airways in the model associated with these ventilation defects, we imposed constriction with various means and standard deviations to the remaining airways to match the measured lung resistance and elastance from the same subject. Our results show that matching both the degree of mechanical impairment and the size and location of the PET ventilation defects requires either constriction of airways <2.4 mm alone, or a simultaneous constriction of small and large airways, but not just large airways alone. Also, whereas larger airway constriction may contribute to mechanical dysfunction during asthma, degradation in ventilation function requires heterogeneous distribution of near closures confined to small airways.