Development of digestive enzymes in larvae of Mayan cichlid Cichlasoma urophthalmus.

The development of digestive enzymes during the early ontogeny of the Mayan cichlid (Cichlasoma urophthalmus) was studied using biochemical and electrophoretic techniques. From yolk absorption (6 days after hatching: dah), larvae were fed Artemia nauplii until 15 dah, afterward they were fed with commercial microparticulated trout food (45% protein and 16% lipids) from 16 to 60 dah. Several samples were collected including yolk-sac larvae (considered as day 1 after hatching) and specimens up to 60 dah. Most digestive enzymes were present from yolk absorption (5-6 dah), except for the specific acid proteases activity (pepsin-like), which increase rapidly from 8 dah up to 20 dah. Three alkaline proteases isoforms (24.0, 24.8, 84.5 kDa) were detected at 8 dah using SDS-PAGE zymogram, corresponding to trypsin, chymotrypsin and probably leucine aminopeptidase enzymes, and only one isoform was detected (relative electromobility, Rf = 0.54) for acid proteases (pepsin-like) from 3 dah onwards using PAGE zymogram. We concluded that C. urophthamus is a precocious fish with a great capacity to digest all kinds of food items, including artificial diets provided from 13 dah.

Cytokine transcripts in pediatric tuberculosis: a study with bronchoalveolar cells.

Pediatric tuberculosis (TB) differs from adult TB in many features. To date, cytokine expression has not been studied in children with TB. The relative amounts of the various cytokines released at the site of infection may be important determinants of TB disease development and pathology. We determined cytokine transcripts in bronchoalveolar cells (BACs) recovered from 9 children presenting with TB and from 9 children with pulmonary diseases other than TB. An RT-PCR-based method was developed to quantify the mRNAs encoding six cytokines (IFN- gamma, IL-12, TNF- alpha, IL-10, IL-4, TGF- beta 1) known to play key roles in mycobacterial infections. Expression of mRNA encoding TGF- beta, TNF- alpha and IFN- gamma was statistically significantly higher in BACs from children with TB than in BACs from children with other pulmonary diseases; whereas the levels of mRNA transcription for TGF- beta is high, the levels of mRNA transcription for IFN- gamma and TNF- alpha remain low. All children had low levels of mRNA for IL-12(p40). IL-4 was barely detectable in all cases. Children with miliary TB had high levels of IL-10 transcripts and low levels of mRNA encoding TGF- beta. The immunosuppressive cytokines TGF- beta and IL-10, are overproduced in children with non-miliary TB and miliary TB respectively and are probably involved in the progression of the disease. These data suggest that Th1 responses are reduced in children with TB.

Urease activity does not contribute dramatically to persistence of Mycobacterium bovis bacillus Calmette-Guérin.

Multiplication of BCGure-, an isogenic urease-negative mutant of Mycobacterium bovis BCG constructed by allelic exchange (J. M. Reyrat, F. X. Berthet, and B. Gicquel, Proc. Natl. Acad. Sci. USA 92:8768-8772, 1995), was examined in human macrophages and mice. Although ureolytic activity was not essential to BCGure-growth, a slight decrease in the multiplication and persistence of the mutated strain compared with wild-type BCG was observed in lungs of infected mice.

Mycobacterium tuberculosis alters expression of adhesion molecules on monocytic cells.

The host response to Mycobacterium tuberculosis is characterized by interactions between mononuclear cells, with recruitment and fusion of these cells culminating in granuloma formation. In addition, the host response to M. tuberculosis requires CD4+ T-cell reactivity, mediated by antigen-independent as well as antigen-dependent mechanisms. Thus, we hypothesized that cell adhesion molecules such as intercellular adhesion molecule 1 (ICAM-1; CD54) would participate in the response to infection with M. tuberculosis. Exposure of THP-1 cells derived from a monocyte/macrophage cell line to M. tuberculosis (1:1 bacterium/cell ratio) elicited a sustained increase (660% +/- 49% above resting level) in the expression of ICAM-1 that continued for at least 72 h. Neither the expression of vascular cell adhesion molecule 1 (VCAM-1; CD106) nor that of the integrins lymphocyte function-associated antigen 1 (LFA-1; CD11a/CD18) or CR3 (CD11b/CD18) was increased to a similar extent at corresponding time points. The increase in ICAM-1 protein expression was accompanied by an increase in steady-state mRNA (Northern [RNA] analysis). Neutralizing monoclonal antibodies directed against tumor necrosis factor alpha but not interleukin 1 alpha or interleukin 1 beta substantially abrogated the response to M. tuberculosis consistent with a paracrine or autocrine response. Continuous upregulation of the expression of ICAM-1 on mononuclear phagocytes induced by M. tuberculosis may mediate the recruitment of monocytes and enhance the antigen presentation of M. tuberculosis, thus permitting the generation and maintenance of the host response.