ALBERT

Notes: Mycobacterium avium is a major opportunistic pathogen of AIDS patients in the United States. The understanding of M. avium pathogenesis has been hampered by the inability to create gene knockouts by homologous recombination, an important mechanism for defining and characterizing virulence factors. In this study a functional methyltransferase D (mtfD) gene was deleted by allelic replacement in the M. avium strain 104. Methyltransferase D is involved in the methylation of glycopeptidolipids (GPLs); highly antigenic glycolipids found in copious amounts on the M. avium cell surface. Interestingly, the loss of mtfD resulted in M. avium 104 containing only the non-serotype specific GPL. Results also suggest that the mtfD encodes for a 3-O-methyltransferase. The absence of significant amounts of any serotype-specific GPLs as a consequence of mtfD deletion indicates that the synthesis of the core 3,4-di-O-methyl rhamnose is a prerequisite for synthesis of the serotype-specific GPLs. Macrophages infected with the mtfD mutant show elevated production of tumour necrosis factor-α (TNF-α) and RANTES compared to control infections. In addition, the M. avium 104 mtfD mutant exhibits decreased ability to survive/proliferate in mouse liver and lung compared to wild-type 104, as assessed by bacterial counts. Importantly, the mtfD mutant complemented with a wild-type mtfD gene maintained an infection level similar to wild-type. These experiments demonstrate that the loss of mtfD results in a M. avium 104 strain, which preferentially activates macrophages in vitro and shows attenuated virulence in mice. Together our data support a role for GPLs in M. avium pathogenesis.

Notes: Four different fertilization frequencies, namely twice per week, once per week, twice a month and once a month, were used in ponds to assess their effects on nutrient release, pond productivity and fish biomass. All ponds received the same total fertilizer inputs during the experimental period of 60 days (cow dung 208.3 kg ha−1 week−1, TSP 9.8 kg ha−1 week−1, urea 6.0 kg ha−1 week−1). Studies have revealed that the highest values of fish biomass, specific growth rate (SGR), net primary productivity (NPP), plankton population and nutrients were observed in the ponds that were fertilized twice a month. A strong and significant correlation of fertilization frequency was observed with dissolved oxygen, biochemical oxygen demand (BOD), alkalinity, nutrient release, NPP, plankton density (no. L−1), fish biomass and SGR. The linear relationship between NPP and fish biomass/SGR for all the ponds was strong (r2= 0.88). Sediment chemistry revealed that O-PO4, NO3-N, organic carbon and electrical conductivity (EC) increased significantly (P〈0.05) with a decrease in the frequency of fertilization, while alkalinity and calcium were high in ponds that were fertilized twice a month.

Notes: To study the effect of four different raw and hydrothermically processed leguminous seeds, namely Glycine max (soybean), Vigna radiata (moong), Vigna ungiculata (cowpea) and Cyamopsis tetragonaloba (guar) on growth in the fingerlings of Cirrhinus mrigala (mrigal) and Labeo rohita (rohu), two experiments were conducted. The first experiment was conducted under laboratory conditions (LD 12:12 at 25 °C) and the mrigal fingerlings were fed @2% BW d−1 for 30 days. Before using the seeds as feeds, they were hydrothermically processed (15 lbs at 121 °C for 15 min) for the elimination of antinutrient factors (ANF). The results indicate that 15 minute autoclaving significantly reduces the trypsin inhibitor activity. Phytase-phosphorous and tannins were also analysed from raw and treated beans. Studies on mrigal have revealed that weight gain was significantly low (P 〈 0.05) in the fish fed on raw beans compared with the fingerlings fed on processed bean proteins. Among the various raw diets used, significantly highest growth (P 〈 0.05) was observed in fish fingerlings fed on raw moong, followed by raw soybean, cowpea and guar. On the other hand, when beans were processed, the highest growth was observed in fingerlings fed on processed soybean. Studies have further revealed that hydrothermal processing also affected the values of the feed conversion ratio, gross conversion efficiency, protein efficiency ratio, gross protein retention, gross energy retention and ammonia excretion. Proximate composition of the carcass revealed high accumulation of protein, fat and energy in fingerlings fed on processed soybean in comparison with other diets. Keeping in view the higher weight gain in fish fed on hydrothermically processed bean proteins, only processed bean diets were fed to the fingerlings of mrigal and rohu stocked in fish ponds (experiment 2). A significant (P 〈 0.05) increase in mean fish weight, and specific growth rate was observed in fingerlings fed on hydrothermically processed soybean, followed by moong and cowpea. Weight gain for mrigal fingerlings remained significantly low in comparison to the rohu fingerlings fed on similar diets. An investigation on the effects of feeds on water quality parameters indicate that the trophic status of the ponds where soybean was used as fish feed remained high in comparison to the other treatments. A significant positive correlation of nutrients, NPP and plankton population with fish growth was also observed.

Notes: Summary Malaria remains a public health problem of enormous magnitude, affecting over 500 million people every year. Lack of success in the past in the development of new drug/vaccines has mainly been attributed to poor understanding of the functions of different parasite proteins. Recently, RNA interference (RNAi) has emerged as a simple and incisive technique to study gene functions in a variety of organisms. In this study, we report the results of RNAi by double-stranded RNA of cysteine protease genes (falcipain-1 and -2) in the malaria parasite, Plasmodium falciparum. Using RNAi directed towards falcipain genes, we demonstrate that blocking the expression of these genes results in severe morphological abnormalities in parasites, inhibition of parasite growth in vitro and substantial ­accumulation of haemoglobin in the parasite. The inhibitory effects produced by falcipain double-stranded (ds)RNAs are reminiscent of the effects observed upon administering E-64, a cysteine protease inhibitor. The parasites treated with falcipain's dsRNAs also show marked reduction in the levels of corresponding endogenous falcipain mRNAs. We also demonstrate that dsRNAs of falcipains are ­broken into short interference RNAs ≈ 25 nucleotides in size, a characteristic of RNAi, which in turn activates sequence-specific nuclease activity in the malaria parasites. These results thus provide more evidence for the existence of RNAi in P. falciparum and also suggest possibilities for using RNAi as an effective tool to determine the functions of the genes identified from the P. falciparum genome sequencing project.