Re-examination ofPyrenomonas andRhodomonas (class cryptophyceae) through ultrastructural survey of red pigmented cryptomonads

Several taxa of cryptomonads, including species of marineChroomonas, Cryptomonas and freshwaterRhodomonas were examined using transmission electron microscopy. They have cellular structures fundamentally in common: a single bilobed chlorplast, a single pyrenoid between the chloroplast lobes, and a nuclemorph embedded within a cleft of the pyrenoidal matrix. These features are in accordance with the taxonomic characteristics of the recently established genusPyrenomonas. The algae also have similar pigmentation to that ofRhodomonas andPyrenomonas which is red or reddish-brown. On the basis of these observations, the genusRhodomonas Karsten (1898) is redescribed in this paper and the genusPyrenomonas Santore is considered to be synonymous withRhodomonas.     

Immobilized mitochondrial electron transport particle for NADH determination

Nonphosphorylating electron transport particles (ETP) prepared from beef heart mitochondrion were immobilized in agar gel. The immobilized ETP showed an oxidase activity to both NADH and succinate. The immobilized ETP was reusable. An electrochemical device for the determination of either NADH or succinate was assembled consisting of the membrane-bound ETP and an oxygen probe. The response to succinate was specifically inhibited by the addition of malonate.     

Mathematical description of stress relaxation of bovine femoral cortical bone

In 1993 we proposed an empirical formula for describing the relaxation modulus of cortical bone based on the results of stress relaxation experiments performed for 1 x 10(5) sec: [E(t) = E0{A exp[ -(t/tau1)beta] + (1 - A) exp(-t/tau2)}, (0 < A, beta <1 and tau1 < tau2) where E0 is the initial value of the relaxation modulus, A is the portion of the first term, tau1 and tau2 are characteristic relaxation times, and beta is a shape factor [Sasaki et al., J. Biomechanics 26 (1993), 1369]. Although the relaxation properties of bone under various external conditions were described well by the above equation, recent experimental results have indicated some limitations in its application. In order to construct an empirical formula for the relaxation modulus of cortical bone that has a high degree of completeness, stress relaxation experiments were performed for 6 x 10(5) seconds. The second term in the equation was determined as an apparently linear portion in a log E(t) vs t plot at t>1 x 10(4) sec. The same plot for experiments performed for 6 x 10(5) seconds revealed that the linear portion corresponding to the second term was in fact a curve with a large radius of curvature. On the basis of this fact, we proposed a second improved empirical equation E(t) = E0{A exp [ -(t/tau1)beta] + (1 - A) exp[-(t/tau2)gamma]}, (0相似文献   

Cell elongation and cell death of helicobacter pylori is modulated by the disruption of cdrA (cell division-related gene A)

The cell division-related gene A (cdrA) of Helicobacter pylori is dispensable in vivo and unique in having a repressive role on cell division and long-term survival. To clarify its role, comparisons of the wildtype HPK5 and isogenic cdrA-disrupted mutant HPKT510 were examined by ultrastructural morphology, PBP profiles, and susceptibility to beta-lactam antibiotics during long-term cultivation. Ultrastructural analyses revealed that the shorter rods of HPKT510 had a slightly wider periplasmic space between the inner and the outer membrane than those of HPK5. Cell division of HPKT510 cells was complete even under high-salt conditions in which HPK5 cells became filamentous due to inhibition of division. The filamentous HPK5 cells constructed an inner membrane without a cell wall at the presumed division site. After 4 days of cultivation (the late stationary phase), most of the HPK5 cells turned into ghosts and aggregates, while some of the HPKT510 cells remained as curved rods, which coincided with the results of cell viability. HPKT510 cells became resistant to ampicillin killing compared to HPK5 cells, although their minimum inhibitory concentrations (MICs) and PBP profiles were not significantly different. These results suggest that the cdrA product represses cell division via inhibiting cell wall synthesis at division site. During infection in both mice and humans, inactivation of cdrA eventually gains biological aspects such as increased viability, long-term survival and tolerance to antibiotics and high-salt condition, which might enhance a persistent infection.     

Myosin X transports Mena/VASP to the tip of filopodia

Myosin X (M10) is a two-headed actin based motor expressed in a variety of cell types, that is thought to play a role in cargo movement in mammalian cells, but its cellular function is unknown. Here we found that M10 binds to Mena/VASP, which facilitates actin polymerization by competing with actin capping proteins. Immunocytochemistry revealed that endogenous M10 co-localized with Mena/VASP at the tip of filopodia. Consistently, both EGFP-M10 and RFP-VASP were found at the tip of filopodia. The result raises a hypothesis that M10 transports Mena/VASP towards the tip of filopodia. Supporting this idea, the amount of VASP at the tip of filopodia was proportional to that of M10. Furthermore, we directly visualized the movement of M10 and VASP in living HeLa cells under fluorescence microscope. EGFP-M10 and RFP-VASP move together from the root to the tip of the filopodia. Interestingly, the amount of M10 at the tip of filopodia was linearly related to the length of filopodia, consistent with the actin filament extending function of VASP. These results show that M10 is a specific motor carrying Mena/VASP from the root to the tip of the filopodia where extension of actin filament takes place.     

Human chromosome 21q22.2-qter carries a gene(s) responsible for downregulation of mlc2a and PEBP in Down syndrome model mice

Congenital heart disease (CHD) is a major clinical manifestation of Down syndrome (DS). We recently showed that chimeric mice containing a human chromosome 21 (Chr 21) exhibited phenotypic traits of DS, including CHD. Our previous study showed that myosin light chain-2a (mlc2a) expression was reduced in the hearts of chimeric mice and DS patients. We found that phosphatidylethanolamine binding protein (PEBP) was also downregulated in Chr 21 chimeras in this study. As mlc2a is involved in heart morphogenesis, and PEBP controls the proliferation and differentiation of different cell types, these genes are candidates for involvement in DS-CHD. The DS-CHD candidate region has been suggested to span between PFKL and D21S3, which is the STS marker near the ETS2 loci. To identify gene(s) or a gene cluster on Chr 21 responsible for the downregulation of mlc2a and PEBP, we fragmented Chr 21 at the EST2 loci, by telomere-directed chromosome truncation in homologous recombination-proficient chicken DT40 cells. The modified Chr 21 was transferred to mouse ES cells by microcell-mediated chromosome transfer (MMCT), via CHO cells. We used ES cell lines retaining the Chr 21 truncated at the ETS2 locus (Chr 21E) to produce chimeric mice and compared overall protein expression patterns in hearts of the chimeras containing the intact and the fragmented Chr 21 by two-dimensional electrophoresis. While mouse mlc2a and PEBP expression was downregulated in the chimeras containing the intact Chr 21, the expression was not affected in the Chr 21E chimeras. Therefore, we suggest that Chr 21 gene(s) distal from the ETS2 locus reduce mouse mlc2a and PEBP expression in DS model mice and DS. Thus, this chromosome engineering technology is a useful tool for identification or mapping of genes that contribute to the DS phenotypes.     

Role of arginine in protein refolding, solubilization, and purification

Recombinant proteins are often expressed in the form of insoluble inclusion bodies in bacteria. To facilitate refolding of recombinant proteins obtained from inclusion bodies, 0.1 to 1 M arginine is customarily included in solvents used for refolding the proteins by dialysis or dilution. In addition, arginine at higher concentrations, e.g., 0.5-2 M, can be used to extract active, folded proteins from insoluble pellets obtained after lysing Escherichia coli cells. Moreover, arginine increases the yield of proteins secreted to the periplasm, enhances elution of antibodies from Protein-A columns, and stabilizes proteins during storage. All these arginine effects are apparently due to suppression of protein aggregation. Little is known, however, about the mechanism. Various effects of solvent additives on proteins have been attributed to their preferential interaction with the protein, effects on surface tension, or effects on amino acid solubility. The suppression of protein aggregation by arginine cannot be readily explained by either surface tension effects or preferential interactions. In this review we show that interactions between the guanidinium group of arginine and tryptophan side chains may be responsible for suppression of protein aggregation by arginine.     

Composition of seed storage proteins changed by glutathione treatment of soybeans

The application of glutathione to immature soybean cotyledons reduced the accumulation of the beta subunit of beta-conglycinin, and increased the accumulation of most glycinins. Both reduced and oxidized forms of glutathione had these effects. The application of an inhibitor of glutathione synthesis, buthionine sulfoximine, increased accumulation of beta subunit. These results suggest that glutathione is important in affecting the composition of seed storage proteins.