Role of nutrient bound of prey on the dynamics of predator-mediated competitive-coexistence

The coexistence of competitive species with a shared predator is well established. The effect of 'food-value' on predator-prey dynamics has also received much attention. However, the study of a nutrient bound of prey, specifically on predator-mediated competitive-coexistence has not received much attention. Here we study the effects of the caloric content or a nutrient bound of prey on the dynamics of competitive-coexistence with the shared predator in a specific model. We propose and analyze a mathematical model for exploitative competition of two prey species with a shared predator. The change of dynamic stability due to the variation of a nutrient bound of each prey on predator-mediated dynamics is studied through extensive numerical experiments. Our analytical and numerical results demonstrate that variation in a nutrient bound promotes the switching of dynamics and may be treated as a driving force for the dynamics of competitive-coexistence with the shared predator.     

High level expression of surface glycoprotein of rabies virus in tobacco leaves and its immunoprotective activity in mice

A synthetic gene coding for the surface glycoprotein (G protein) of rabies virus was strategically designed to achieve high-level expression in transgenic plants. The native signal peptide was replaced by that of the pathogenesis related protein, PR-S of Nicotiana tabacum. An endoplasmic reticulum retention signal was included at C-terminus of the G protein. Tobacco plants were genetically engineered by nuclear transformation. Selected transgenic lines expressed the chimeric G protein at 0.38% of the total soluble leaf protein. Mice immunized intraperitoneally with the G protein purified from tobacco leaf microsomal fraction elicited high level of immune response as compared to the inactivated commercial viral vaccine. The plant-derived G protein induced complete protective immunity in mice against intracerebral lethal challenge with live rabies virus. The results establish that plants can provide a safe and effective production system for the expression of immunoprotective rabies virus surface protein.     

Development and assessment of a real-time pcr assay for rapid and sensitive detection of a novel thermotolerant bacterium, Lactobacillus thermotolerans, in chicken feces

A new real-time PCR assay was successfully developed using a TaqMan fluorescence probe for specific detection and enumeration of a novel bacterium, Lactobacillus thermotolerans, in chicken feces. The specific primers and probe were designed based on the L. thermotolerans 16S rRNA gene sequences, and these sequences were compared to those of all available 16S rRNA genes in the GenBank database. The assay, targeting 16S rRNA gene, was evaluated using DNA from a pure culture of L. thermotolerans, DNA from the closely related bacteria Lactobacillus mucosae DSM 13345(T) and Lactobacillus fermentum JCM 1173(T), and DNA from other lactic acid bacteria in quantitative experiments. Serial dilutions of L. thermotolerans DNA were used as external standards for calibration. The minimum detection limit of this technique was 1.84 x 10(3) cells/ml of an L. thermotolerans pure culture. The assay was then applied to chicken feces in two different trials. In the first trial, the cell population was 10(4) cells/g feces on day 4 and 10(5) cells/g feces on days 11 to 18. However, cell populations of 10(6) to 10(7) cells/g feces were detected in the second trial. The total bacterial count, measured by 4',6-diamidino-2-phenylindole (DAPI) staining, was approximately 10(11) cells/g feces. These results suggest that in general, L. thermotolerans is a normal member of the chicken gut microbiota, although it is present at relatively low levels in the feces.     

A diffusion model for drying of a heat sensitive solid under multiple heat input modes

To obtain optimal drying kinetics as well as quality of the dried product in a batch dryer, the energy required may be supplied by combining different modes of heat transfer. In this work, using potato slice as a model heat sensitive drying object, experimental studies were conducted using a batch heat pump dryer designed to permit simultaneous application of conduction and radiation heat. Four heat input schemes were compared: pure convection, radiation-coupled convection, conduction-coupled convection and radiation-conduction-coupled convection. A two-dimensional drying model was developed assuming the drying rate to be controlled by liquid water diffusion. Both drying rates and temperatures within the slab during drying under all these four heat input schemes showed good accord with measurements. Radiation-coupled convection is the recommended heat transfer scheme from the viewpoint of high drying rate and low energy consumption.     

Antigenicity and immunogenicity of a synthetic human immunodeficiency virus type 1 group m consensus envelope glycoprotein

Genetic variation of human immunodeficiency virus (HIV-1) represents a major obstacle for AIDS vaccine development. To decrease the genetic distances between candidate immunogens and field virus strains, we have designed and synthesized an artificial group M consensus env gene (CON6 gene) to be equidistant from contemporary HIV-1 subtypes and recombinants. This novel envelope gene expresses a glycoprotein that binds soluble CD4, utilizes CCR5 but not CXCR4 as a coreceptor, and mediates HIV-1 entry. Key linear, conformational, and glycan-dependent monoclonal antibody epitopes are preserved in CON6, and the glycoprotein is recognized equally well by sera from individuals infected with different HIV-1 subtypes. When used as a DNA vaccine followed by a recombinant vaccinia virus boost in BALB/c mice, CON6 env gp120 and gp140CF elicited gamma interferon-producing T-cell responses that recognized epitopes within overlapping peptide pools from three HIV-1 Env proteins, CON6, MN (subtype B), and Chn19 (subtype C). Sera from guinea pigs immunized with recombinant CON6 Env gp120 and gp140CF glycoproteins weakly neutralized selected HIV-1 primary isolates. Thus, the computer-generated "consensus" env genes are capable of expressing envelope glycoproteins that retain the structural, functional, and immunogenic properties of wild-type HIV-1 envelopes.     

Uptake of sodium in protoplasts of salt-sensitive and salt-tolerant cultivars of rice, Oryza sativa L. determined by the fluorescent dye SBFI

In this study, the uptake of Na+ into the cytosol of rice (Oryza sativa L. cvs Pokkali and BRRI Dhan29) protoplasts was measured using the acetoxy methyl ester of the fluorescent sodium-binding benzofuran isopthalate, SBFI-AM, and fluorescence microscopy. By means of inhibitor analyses the mechanisms for uptake and sequestration of Na+ in the salt-sensitive indica rice cv. BRRI Dhan29 and in the salt-tolerant indica rice cv. Pokkali were detected. Less Na+ was taken up into the cytosol of Pokkali than into BRRI Dhan29. The results indicate that K+-selective channels do not contribute to the Na+ uptake in Pokkali, whereas they are the major pathways for Na+ uptake in BRRI Dhan29 along with non-selective cation channels. However, non-selective cation channels seem to be the main pathways for Na+ uptake in Pokkali. Protoplasts from Pokkali leaves took up Na+ only transiently in the presence of extracellular Na+ at 5-100 mM. Therefore, it is likely that the protoplasts have a mechanism for fast extrusion of Na+ out of the cytoplasm. Experiments with protoplasts pretreated with NH4NO3 and NH4VO3 suggest that the salt-tolerant Pokkali extrudes Na+ mainly into the vacuole. After cultivation of both cultivars in the presence of 10 or 50 mM NaCl for 72 h, the isolated protoplasts from Pokkali took up less Na+ than the control protoplasts. The results suggest that the salt-tolerance in Pokkali depends on reduced uptake through K+-selective channels and a fast extrusion of Na+ into the vacuoles.     

Signaling mediated by the cytosolic domain of peptidylglycine alpha-amidating monooxygenase

The luminal domains of membrane peptidylglycine alpha-amidating monooxygenase (PAM) are essential for peptide alpha-amidation, and the cytosolic domain (CD) is essential for trafficking. Overexpression of membrane PAM in corticotrope tumor cells reorganizes the actin cytoskeleton, shifts endogenous adrenocorticotropic hormone (ACTH) from mature granules localized at the tips of processes to the TGN region, and blocks regulated secretion. PAM-CD interactor proteins include a protein kinase that phosphorylates PAM (P-CIP2) and Kalirin, a Rho family GDP/GTP exchange factor. We engineered a PAM protein unable to interact with either P-CIP2 or Kalirin (PAM-1/K919R), along with PAM proteins able to interact with Kalirin but not with P-CIP2. AtT-20 cells expressing PAM-1/K919R produce fully active membrane enzyme but still exhibit regulated secretion, with ACTH-containing granules localized to process tips. Immunoelectron microscopy demonstrates accumulation of PAM and ACTH in tubular structures at the trans side of the Golgi in AtT-20 cells expressing PAM-1 but not in AtT-20 cells expressing PAM-1/K919R. The ability of PAM to interact with P-CIP2 is critical to its ability to block exit from the Golgi and affect regulated secretion. Consistent with this, mutation of its P-CIP2 phosphorylation site alters the ability of PAM to affect regulated secretion.     

Beneficial effect of nitric oxide synthase inhibitor on hepatotoxicity induced by allyl alcohol

The effect of aminoguanidine (a selective inhibitor of inducible nitric oxide synthase) on allyl alcohol-induced liver injury was assessed by the measurement of serum ALT and AST activities and histopathological examination. When aminoguanidine (50-300 mg/kg, i.p.) was administered to mice 30 min before a toxic dose of allyl alcohol (75 microL/kg, i.p.), significant changes related to liver injury were observed. In the presence of aminoguanidine the level of ALT and AST enzymes were significantly decreased. All symptoms of liver necrosis produced by allyl alcohol toxicity almost completely disappeared when animals were pretreated with aminoguanidine at 300 mg/kg. Depletion of hepatic glutathione as a consequence of allyl alcohol metabolism was minimal in mice pretreated with aminoguanidine at 300 mg/kg. It was found that the inhibition of toxicity was not due to alteration in allyl alcohol metabolism since aminoguanidine did not effect alcohol dehydrogenase activity both in vivo and in vitro.