Tritium forms discrimination in ryegrass under constant tritium exposure: From seed germination to seedling autotrophy.

Uncertainties remain regarding the fate of atmospheric tritium after it has been assimilated in grasslands (ryegrass) in the form of TFWT (Tissue Free Water Tritium) or OBT (Organically Bound Tritium). One such uncertainty relates to the tritium forms discrimination during transfer from TFWT to OBT resulting from photosynthesis (OBTphoto), corresponding to the OBTphoto/TFWT ratio. In this study, the OBT/TFWT ratio is determined by experiments in the laboratory using a ryegrass model and hydroponic cultures, with constant activity of tritium in the form of tritiated water (denoted as HTO) in the "water" compartment (liquid HTO) and "air" compartment (HTO vapour in the air). The OBTphoto/TFWT ratio and the exchangeable OBT fraction are measured for three parts of the plant: the leaf, seed and root. Plant growth is modelled using dehydrated biomass measurements taken over time in the laboratory and integrating physiological functions of the plant during the first ten days after germination. The results suggest that there is no measurable discrimination of tritium in the plant organic matter produced by photosynthesis.

TREM-1 modulation during early stages of dengue virus infection.

Uncontrolled and intricate production of inflammatory factors is the characteristic feature of dengue infection. The triggering receptor expressed in myeloid cells-1 (TREM-1), expressed on the surface of monocytes and neutrophils, is capable of enhancing and regulating the inflammatory response via the production of different mediators in bacterial and viral infections. Here, both the expression of TREM-1 on human monocytes and neutrophils from peripheral blood of dengue infected individuals, as well as the levels of the soluble form of TREM-1 (sTREM-1) in the sera of these patients were compared against healthy controls. A significant reduction of TREM-1 expression was observed in neutrophils during the first days of infection, followed by a gradual recovery throughout the course of infection. Also, sera from DENV-infected patients exhibited significantly higher sTREM-1 levels than healthy individuals. The difference was more pronounced during the first 5 days after the onset of symptoms. These findings highlight the dynamic process of TREM-1 expression during DENV infection. We hypothesized that increment of free sTREM-1 could be a compensatory mechanism aiming to counteract the inflammatory process elicited during DENV infection.

Frequency of Mycobacterium bovis as an etiologic agent in extrapulmonary tuberculosis in HIV-positive and -negative Mexican patients.

Mycobacterium bovis can be an important etiological agent for extrapulmonary (EP) manifestations of tuberculosis, especially in HIV-infected persons. From January 2000 to December 2003, M. bovis as a cause of EP tuberculosis was investigated at the Pneumonology Service, Hospital General de Mexico, Mexico City. Eighty HIV-positive (HIV+) patients and 83 HIV-negative (HIV-) with EP involvement (ganglionar, genitourinary, meningeal, cutaneous, peritoneal, and pericardial) were analyzed using clinical, immunological, bacteriological, histopathological, and molecular biology methods. Mycobacterium species were identified by hsp65-RFLP analysis and species of M. tuberculosis complex isolates by spoligotyping. M. bovis was present in 6 HIV- cases (7.2%; 3 with lymphadenitis and 3 genitourinary) vs 11 in HIV+ cases (13.75%; 7 with lymphadenitis, 3 genitourinary, and 1 meningeal). Favorable response to retroviral and specific M. bovis chemotherapy was observed. Spoligotyping showed a unique profile in each isolate, 16 belonging to BOV1 lineage and 1 to BOV2 lineage. M. bovis is an significant re-emerging cause of EPTB in Mexico. Consumption of unpasteurized dairy products is the most likely source of transmission. Successful treatment depends on the adequate and opportune identification of the agent responsible.

Analysis of antibody response in human dengue patients from the Mexican coast using recombinant antigens.

This study was undertaken to evaluate the feasibility of using recombinant dengue proteins to discriminate between acute dengue infections versus uninfected dengue samples. Dengue virus proteins E, NS1, NS3, and NS4B were cloned as fusion proteins and expressed in Escherichia coli. Recombinant products were tested in 100 serum samples obtained from acute dengue fever cases collected from 3 states of Mexico where dengue is endemic. Sera from 75 healthy individuals living in nonendemic areas for dengue were used as a control group. In sera from the dengue patients group, antibody responses to E protein were demonstrated in 91% of cases and NS1 protein was recognized to various extents (99%) within the first 7 days of infection. The antibody responses to NS3 and NS4B were frequently of low magnitude. Consistent negative antibody responses to all proteins were found in sera from the control group. These data suggest that the glutathione-S-transferase (GST)-dengue fusion proteins may be feasible antigens for a sensitive and specific serological assay.

Peripheral blood CD161+ T cells from asthmatic patients are activated during asthma attack and predominantly produce IFN-gamma.

In humans, T cells expressing the CD161 molecule NKR-P1A constitute around 20% of the circulating CD3(+) cells and are potentially immunoregulatory in several diseases. Their role in asthma is not well known, but they could participate in asthma attacks. To determinate whether activation of CD161(+) T cells and their cytokine production correlate with clinical status of asthma, we analysed blood samples from asthma attack patients (AAP) and stable asthma patients (SAP) in comparison with healthy non-atopic controls (HC). There was a significant higher baseline expression of CD69 on T cells from AAP and the difference was more notorious on CD161(+) T cells; upregulation of CD69 was observed on both CD161(-) and CD161(+) T cells driven by Dermatophagoides pteronyssinus crude extract, whereas polyclonal stimulation with phorbol 12-myristate 13-acetate plus ionomycin predominantly induced IFN-gamma but no IL-4, IL-5 and IL-13 by CD161(+) T cells in all groups; upon polyclonal stimulation, there were more CD161(+) T cells producing IFN-gamma and less CD161(-) T cells producing this cytokine, contrasting with the opposite results observed in SAP and HC groups. Our results indicate that, during asthma attack, CD161(+) T cells are activated and are able to produce predominantly IFN-gamma but no Th2 cytokines. We hypothesize that during an asthma attack, IFN-gamma produced by CD161(+) T cells could help to reestablish the Th1/Th2 equilibrium. These observations may contribute to the understanding of the immune mechanisms involved in asthma attacks.

Prevalence of Escherichia coli and Salmonella spp. in street-vended food of open markets (tianguis) and general hygienic and trading practices in Mexico City.

Street-vendors in Mexico City provide ready-to-eat food to a high proportion of the inhabitants. Nevertheless, their microbiological status, general hygienic and trading practices are not well known. During spring and summer 2000, five tianguis (open markets) were visited and 48 vendors in 48 stalls interviewed. A total of 103 taco dressings were sampled for E. coli and Salmonella spp.: 44 (43%) contained E. coli and 5 (5%) Salmonella (2 S. Enteritidis phage type 8, 1 S. Agona, 2 S. B group). Both E. coli and salmonellas were isolated from three samples. Of Salmonella-positive stalls 80% (4/5) had three or more food-vendors and 80% of vendors were males, compared with 37.3% (16/43) and 46.4% (20/43) in the Salmonella-negative stalls respectively. Food-vendors kept water in buckets (reusing it all day), lacked toilet facilities, and prepared taco dressings the day before which remained at the tianguis without protection for 7.8 h on average. Consumption of street-vended food by local and tourist populations poses a health risk.

Evaluation of the polymerase chain reaction in the diagnosis of miliary tuberculosis in bone marrow smear.

OBJECTIVE: Miliary tuberculosis (MTB) is difficult to diagnose. When prompt diagnosis is necessary, the polymerase chain reaction (PCR) to detect mycobacterial DNA may be valuable. SETTING: Tuberculosis clinic in an academic tertiary-level hospital in Mexico. DESIGN: Bone marrow (BM) aspiration samples from 30 consecutive clinically suspected MTB patients and 58 non-tuberculosis hematologic patients were evaluated by in-house PCR using a fragment of the insertion sequence IS6110; results were compared with those obtained by acid-fast-stained smears, culture in Löwenstein-Jensen medium, histology, and serology. RESULTS: Tuberculosis diagnosis was confirmed in all MTB suspects, 28 by microscopy and culture in pulmonary or extra-pulmonary samples other than BM, and two by clinical and radiologic improvement after antituberculosis treatment. In fresh BM specimens, in-house PCR was positive in 21/30 (70%) suspects, contrasting with only one positive (3.3%) in staining and culture, and four with compatible histologic findings (13.3%). BM samples from the control group showed negative results in bacteriologic and histologic studies, except in nine who had positive PCR results. These nine control cases had malignant processes. CONCLUSION: PCR in aspirates of BM is a useful diagnostic assay in cases of MTB, mainly when bacteriological results are negative.

Tuberculosis is still a major cause of cervical lymphadenopathies in adults from developing countries.

To establish the frequency of infectious aetiology in Mexican adult patients with cervical lymphadenopathies (CLAs), 87 consecutive patients with enlarged cervical lymphatic nodes, HIV negative and without anti-tuberculous treatment, were selected from a tertiary-level speciality concentration hospital. Histopathological studies, investigation of acid-fast bacilli, cultures in Löwenstein Jensen and Mycobacterium growth indicator tube (MGIT) media, and in-house polymerase chain reaction (PCR) with IS6110-based primers for Mycobacterium tuberculosis complex were performed in resected lymphatic nodes. Non-infectious aetiology corresponded to 45 cases (52 %). Tuberculosis was suspected in 42 cases (48%) by histology and confirmed positive results were obtained by staining in 8 (19%), by culture in 23 (55%), and by PCR in 34 (81 %) patients. All were confirmed after therapeutic success. In addition to the epidemiological transition process occurring in Mexico, tuberculosis remains an important cause of CLA. Histopathology with confirmatory studies including PCR can detect tuberculous aetiology.

Influx and accumulation of Cs(+) by the akt1 mutant of Arabidopsis thaliana (L.) Heynh. lacking a dominant K(+) transport system.

An extensive literature reports that Cs(+), an environmental contaminant, enters plant cells through K(+) transport systems. Several recently identified plant K(+) transport systems are permeable to Cs(+). Permeation models indicate that most Cs(+) uptake into plant roots under typical soil ionic conditions will be mediated by voltage-insensitive cation (VIC) channels in the plasma membrane and not by the inward rectifying K(+) (KIR) channels implicated in plant K nutrition. Cation fluxes through KIR channels are blocked by Cs(+). This paper tests directly the hypothesis that the dominant KIR channel in plant roots (AKT1) does not contribute significantly to Cs(+) uptake by comparing Cs(+) uptake into wild-type and the akt1 knockout mutant of Arabidopsis thaliana (L.) Heynh. Wild-type and akt1 plants were grown to comparable size and K(+) content on agar containing 10 mM K(+). Both Cs(+) influx to roots of intact plants and Cs(+) accumulation in roots and shoots were identical in wild-type and akt1 plants. These data indicate that AKT1 is unlikely to contribute significantly to Cs(+) uptake by wild-type Arabidopsis from 'single-salt' solutions. The influx of Cs(+) to roots of intact wild-type and akt1 plants was inhibited by 1 mM Ba(2+), Ca(2+) and La(3+), but not by 10 microM Br-cAMP. This pharmacology resembles that of VIC channels and is consistent with the hypothesis that VIC channels mediate most Cs(+) influx under 'single-salt' conditions.

Underestimation of Mycobacterium tuberculosis infection in HIV-infected subjects using reactivity to tuberculin and anergy panel.

BACKGROUND: This study aimed to evaluate purified protein derivative (PPD) reactivity and its interrelationship with anergy panel and CD4+ lymphocytes in HIV-infected subjects as compared to PPD reactivity in HIV-uninfected individuals in a tuberculosis endemic and high Bacillus Calmette-Guérin (BCG) coverage environment. METHODS: Clients of four Mexico City HIV detection centres were screened for HIV-1 antibodies (ELISA or haemagglutination, Western Blot); reactivity to PPD (Mantoux PPD, 5TU RT-23), Candida (1:1000, 0.1 ml), and tetanus toxoid (10Lf, 0.1 ml); and CD4+ T cells. Active tuberculosis was excluded. Informed consent was obtained. RESULTS: From 5130 clients 1168 subjects were enrolled; of these 801 (68.6%) were HIV positive. Reactivity to PPD among HIV-positive subjects was found in 174 (22%), 261 (32.6%), and 296 (37%), at PPD cutoff levels of > or =10 mm, > or =5 mm, and > or =2 mm as compared to 224 (61%) of 367 HIV-negative individuals' reactors to PPD (> or =10 mm) (P < 0.001). After exclusion of anergic individuals using two cutoff levels for cutaneous allergens (< or =2 mm and < or =5 mm), PPD reactivity between HIV-infected and uninfected individuals continued to be significantly different. Only HIV-infected individuals with CD4+ T cells > or =500 cells/mm3 had similar reactivity to PPD as HIV-uninfected individuals. Variables associated with PPD reactivity were CD4+ T cell counts, BCG scar, HIV infection and age. CONCLUSIONS: PPD reactivity was useful to diagnose tuberculosis infection only among HIV-infected individuals with CD4+ counts > or =500 cells/mm3. Among individuals with lower counts, lowering cutoff levels or using anergy panel did not permit comparable reactivity as that observed among HIV-uninfected individuals.