Analysis of early growth of guppy strains,Poecilia reticulata,with different color patterns

Summary The guppy, Poecilia reticulata, is economically the most important species of freshwater ornamental fish cultured in Singapore. About 30 strains with different color patterns and fin shapes are reared in guppy farms practising monoculture in Singapore. To compare the growth rates of domesticated strains with different color patterns, newborn fry of 11 strains were obtained on the same day from a single farm in Singapore and were reared experimentally in the laboratory for about 100 days. Each strain was distributed randomly into 4 tanks with 30 fish/tank. Weekly weighings of 10 fish/tank were made from 17 to 100 days of age. Three strains were homozygous for the autosomal recessive blond gene which gives rise to a pale yellow background pigmentation (bb). These blond strains had significantly smaller body weights than corresponding ones with the same color pattern but with the wild-type grey-brown background coloration due to the dominant allele (BB). The strains with the red tail pattern due to a dominant X-linked gene (Rdt) had more rapid growth than those with other tail color patterns including the blue, black, green snakeskin and variegated. However, no significant differences were detected among the other color pattern strains. Thus among the strains studied, the blond strains were associated with slower growth while those with the red tail color were associated with faster growth.     

An in situ study of the nanomechanical properties of barnacle (Balanus amphitrite) cyprid cement using atomic force microscopy (AFM)

Abstract

Cyprids are the final planktonic stage in the larval dispersal of barnacles and are responsible for surface exploration and attachment to appropriate substrata. The nanomechanical properties of barnacle (Balanus amphitrite) cyprid permanent cement were studied in situ using atomic force microscopy (AFM). Force curves were recorded from the cement disc continually over the course of its curing and these were subsequently analysed using custom software. Results showed a narrowing of the pull-off force distribution with time, as well as a reduction in molecular stretch length over time. In addition, there was a strong correlation between maximum pull-off force and molecular stretch length for the cement, suggesting ‘curing’ of the adhesive; some force curves also contained a ‘fingerprint’ of modular protein unfolding. This study provides the first direct experimental evidence in support of a putative ‘tanning’ mechanism in barnacle cyprid cement.     

Microdetermination of phosphorylated intermediates of sodium-potassium adenosine triphosphatase

We have described a simple, rapid, reliable, and sensitive method for measuring the covalent phosphoenzyme intermediates that form in the reaction of ATP and sodium-potassium sensitive adenosine triphosphatase. Results are reproducible even when microgram amounts of microsomal protein are used. The method involves recovery of ³²P-labeled phosphoenzyme intermediates on a Millipore filter.     

The importance of ornithine as a precursor for proline in mammalian cells.

Ornithine aminotransferase catalyzes the reversible transamination of L-ornithine to delta1-pyrroline-5-carboxylate, the immediate precursor of proline. The direction and flux through this pathway in mammalian cells has not been established. Glutamate has generally been considered to be the most important precursor for proline biosynthesis, but recent studies in xiphoid cartilage indicate that a significant fraction of cellular proline is derived from ornithine. Using newly isolated mutant Chinese hamster ovary cells with defined defects in the proline biosynthetic pathways, we now have established that cells can grow at a maximal rate with ornithine as the sole source of proline. Furthermore, we have measured the rate of proline formation from ornithine (1.6 nmol/h/10(6) cells); Future studies with these mutant Chinese hamster ovary cells may offer insight into the regulatory mechanism which coordinates proline biosynthesis from ornithine and glutamate.     

Proline oxidase, a proapoptotic gene, is induced by troglitazone: evidence for both peroxisome proliferator-activated receptor gamma-dependent and -independent mechanisms

Proline oxidase (POX) is a redox enzyme localized in the mitochondrial inner membrane. We and others have shown that POX is a p53-induced gene that can mediate apoptosis through generation of reactive oxygen species (ROS). The peroxisome proliferator-activated receptor gamma (PPARgamma) ligand troglitazone was found to activate the POX promoter in colon cancer cells. PPARgamma ligands have been reported to induce apoptosis in a variety of cancer cells. In HCT116 cells expressing a wild-type PPARgamma, troglitazone enhanced the binding of PPARgamma to PPAR-responsive element in the POX promoter and increased endogenous POX expression. Blocking of PPARgamma activation either by antagonist GW9662 or deletion of PPAR-responsive element in the POX promoter only partially decreased the POX promoter activation in response to troglitazone, indicating also the involvement of PPARgamma-independent mechanisms. Further, troglitazone also induced p53 protein expression in HCT116 cells, which may be the possible mechanism for PPARgamma-independent POX activation, since POX has been shown to be a downstream mediator in p53-induced apoptosis. In HCT15 cells, with both mutant p53 and mutant PPARgamma, there was no effect of troglitazone on POX activation, whereas in HT29 cells, with a mutant p53 and wild type PPARgamma, increased activation was observed by ligand stimulation, indicating that both PPARgamma-dependent and -independent mechanisms are involved in the troglitazone-induced POX expression. A time- and dose-dependent increase in POX catalytic activity was obtained in HCT116 cells treated with troglitazone with a concomitant increase in the production of intracellular ROS. Our results suggest that the induction of apoptosis by troglitazone may, at least in part, be mediated by targeting POX gene expression for generation of ROS by POX both by PPARgamma-dependent and -independent mechanisms.     

The enigma of the CLIC proteins: Ion channels, redox proteins, enzymes, scaffolding proteins?

Chloride intracellular channel proteins (CLICs) are distinct from most ion channels in that they have both soluble and integral membrane forms. CLICs are highly conserved in chordates, with six vertebrate paralogues. CLIC-like proteins are found in other metazoans. CLICs form channels in artificial bilayers in a process favoured by oxidising conditions and low pH. They are structurally plastic, with CLIC1 adopting two distinct soluble conformations. Phylogenetic and structural data indicate that CLICs are likely to have enzymatic function. The physiological role of CLICs appears to be maintenance of intracellular membranes, which is associated with tubulogenesis but may involve other substructures.     

Improved biogas production from palm oil mill effluent by a scaled-down anaerobic treatment process

This is a scale-down study of a 500-m³ methane recovery test plant for anaerobic treatment of palm oil mill effluent (POME) where biomass washout has become one of the problems because of the continuous mixing of effluent during anaerobic treatment of POME. Therefore, in this study, anaerobic POME treatment using a scaled down 50-l bioreactor which mimicked the 500-m³ bioreactor was carried out to improve biogas production with and without biomass sedimentation. Three sets of experiments were conducted under different conditions in terms of biomass sedimentation applied to the system. The first experiment was operated under semi-continuous mode whereas the second and third experiments were operated based on mix and settle mode. As expected, biomass retention improved the anaerobic process as the POME treatment incorporated with mix and settle system were able to operate at an organic loading rate (OLR) of 3.5 and 6.0 kg COD/m³/day respectively, while the semi-continuous operated anaerobic treatment only achieved OLR of 3.0 kg COD/m³/day. The highest biogas and methane production rates achieved were 2.42 m³/m³ of reactor/day and 0.992 m³/m³ of reactor/day, respectively at OLR 6.0 kg COD/m³/day. The biomass or solids retention in the reactors was represented by the total solids measured in this study.     

Electron microscopic visualization of asymmetric precursor translocation intermediates: SecA functions as a dimer

SecA, the ATPase of Sec translocase, mediates the post-translational translocation of preprotein through the protein-conducting channel SecYEG in the bacterial inner membrane. Here we report the structures of Escherichia coli Sec intermediates during preprotein translocation as visualized by electron microscopy to probe the oligomeric states of SecA during this process. We found that the translocase holoenzyme is symmetrically assembled by SecA and SecYEG on proteoliposomes, whereas the translocation intermediate 31 (I₃₁) becomes asymmetric because of the presence of preprotein. Moreover, SecA is a dimer in these two translocation complexes. This work also shows surface topological changes in the components of translocation intermediates by immunogold labeling. The channel entry for preprotein translocation was found at the center of the I₃₁ structures. Our results indicate that the presence of preprotein introduces asymmetry into translocation intermediates, while SecA remains dimeric during the translocation process.