Leishmania mexicana: expression; characterization and activity assessment of E. coli-expressed recombinant CRK3.

OBJECTIVES AND METHODS: Previous studies have shown that CRK3 protein kinase of Leishmania mexicana is a potential drug target. Therefore, the aim of this study was to provide an active protein kinase for chemical inhibitors testing. A system was developed to express and affinity-purify recombinant L. mexicana CRK3 protein from Escherichia coli. RESULTS: Biochemical analysis has confirmed the expression of the pure kinase. The bacterial-expressed kinase was found to be inactive as a monomer. The mutated CRK3-E178 protein kinase was also found to be inactive. CONCLUSION: This study suggests that cyclin binding and phosphorylation status are both important for reconstituting protein kinase activity. Work presented by this paper has confirmed the usefulness of the prokaryotic system for production of pure homogenous recombinant protein kinase of Leishmania parasite, though this system is unable to produce active CRK3 protein kinase  

Larvicidal activity of some plant extracts to larvae of the mosquito Culex quinquefasciatus (Say 1823).

OBJECTIVES AND METHODS: Searching for potent plant larvicides, crude aqueous extract of the latex of Uschar (Calotropis procera) and Labakh (Ficus benghalensis) were tested against the fourth instar larvae of the lymphatic filariasis vector Culex quinquefasciatus (Diptera: Culicidae) using the conventional methods recommended by the WHO. Likewise, the toxicity level of Malathion was tested. The dose/response mortality relationship was statistically determined using double transformation regression analysis. The 24-hour LC50 of the test agents was taken as a measure of its acute toxicity. The 24-hour LC50 of Malathion to the larvae was 2.2693 mg/L. The most potent plant extract was the latex of Uschar which killed 50% of the larval population at a concentration of 0.0062% (V/V). RESULTS: The 24-hour LC50 of Labakh latex was 0.4796% (V/V). A range of concentration extending between 0.0195 and 10% (W/V) of the Labakh fruits (figs) produced more or less the same % of mortality (25%). CONCLUSION: Since the latex of the plants tested are hazardous to man and his animals, it is recommended that these extract must be used in bodies of water not accessible to man or animals such as pit latrines and septic tanks.

Regulation of the acetoin catabolic pathway is controlled by sigma L in Bacillus subtilis.

Bacillus subtilis grown in media containing amino acids or glucose secretes acetate, pyruvate, and large quantities of acetoin into the growth medium. Acetoin can be reused by the bacteria during stationary phase when other carbon sources have been depleted. The acoABCL operon encodes the E1alpha, E1beta, E2, and E3 subunits of the acetoin dehydrogenase complex in B. subtilis. Expression of this operon is induced by acetoin and repressed by glucose in the growth medium. The acoR gene is located downstream from the acoABCL operon and encodes a positive regulator which stimulates the transcription of the operon. The product of acoR has similarities to transcriptional activators of sigma 54-dependent promoters. The four genes of the operon are transcribed from a -12, -24 promoter, and transcription is abolished in acoR and sigL mutants. Deletion analysis showed that DNA sequences more than 85 bp upstream from the transcriptional start site are necessary for full induction of the operon. These upstream activating sequences are probably the targets of AcoR. Analysis of an acoR'-'lacZ strain of B. subtilis showed that the expression of acoR is not induced by acetoin and is repressed by the presence of glucose in the growth medium. Transcription of acoR is also negatively controlled by CcpA, a global regulator of carbon catabolite repression. A specific interaction of CcpA in the upstream region of acoR was demonstrated by DNase I footprinting experiments, suggesting that repression of transcription of acoR is mediated by the binding of CcpA to the promoter region of acoR.

Pulmonary alveolar proteinosis complicating chronic myelogenous leukemia.

Pulmonary alveolar proteinosis (PAP) has been reported in 5 patients with chronic myelogenous leukemia and approximately 20 patients with other hematologic malignancies. These patients have had recurrent infections, frequently by opportunistic organisms. This susceptibility suggests that they have impaired cell-mediated immunity. In the case reported, splenectomy early in the course of illness may have contributed to the susceptibility to infection and PAP. Awareness of the possibility of pulmonary alveolar proteinosis in a patient with progressive dyspnea and unexplained pulmonary infiltrates should prompt early open lung biopsy to establish the diagnosis. Therapeutic pulmonary lavage is currently the treatment of choice.

Malignant myelosclerosis (acute myelofibrosis): report of two cases following cytotoxic chemotherapy.

Malignant myelosclerosis or acute myelofibrosis is a rare acute myeloproliferative disorder characterized by pancytopenia, myeloblastosis and marrow fibrosis. We describe two patients who developed malignant myelosclerosis after receiving cytotoxic chemotherapy, one for Hodgkin's disease, and the other for membranous nephritis. In view of the known leukemogenic effect of cytotoxic drugs, we presume that chemotherapy played a role in the pathogenesis of malignant myelosclerosis in these two patients.