Analysis of Flow Phenomena in Gastric Contents Induced by Human Gastric Peristalsis Using CFD

This paper uses computational fluid dynamics to simulate and analyze intragastric fluid motions induced by human peristalsis. We created a two-dimensional computational domain of the distal stomach where peristalsis occurs. The motion of the gastric walls induced by an antral contraction wave (ACW) on the wall of the computational domain was well simulated using a function defined in this study. Retropulsive flow caused by ACW was observed near the occluded region, reaching its highest velocity of approximately 12 mm/s in the narrowest region. The viscosity of the model gastric contents applied in this study hardly affected the highest velocity, but greatly affected the velocity profile in the computational domain. The shear rate due to gastric fluid motion was calculated using the numerical output data. The shear rate reached relatively high values of approximately 20 s⁻¹ in the most occluded region. The shear rate profile was almost independent of the fluid viscosity. We also simulated mass transfer of a gastric digestive enzyme (pepsin) in model gastric content when peristalsis occurs on the gastric walls. The visualized simulation results suggest that gastric peristalsis is capable of efficiently mixing pepsin secreted from the gastric walls with an intragastric fluid.     

Analysis of water in Autonomous Biological Systems (ABS) samples.

Several soluble components, peptidase and amino acids, and carbon isotopic ratio in the water retrieved from flight experiments of Autonomous Biological Systems (ABS) as well as ground control samples are analyzed to interpret the condition, dynamics, material balance of the ABS ecosystems. Organic carbons in flight samples were found to be more abundant compared with the control ones, which suggested the uniform ecosystems in low gravity might easily dissolve more soluble components. The Mir-1997 flight sample showed higher C/N ratio probably because of the dissolution of carbon-rich plant materials.     

Purification and characterization of cathepsin L from the white muscle of chum salmon, Oncorhynchus keta

1. Cathepsin L of the white muscle of chum salmon (Oncorhynchus keta) in spawning migration was purified to homogeneity by a series of chromatography on DEAE-Sephadex (1st), SP-Sephadex, CM-Sephadex, DEAE-Sephadex (2nd) and Sephadex G-100. 2. The molecular weight of salmon muscle cathepsin L was estimated to be 30,000 and its isoelectric point was 5.2. 3. Cathepsin L had a pH optimum of 5.6, required a thiol-reducing reagent for activation, and was inhibited by cysteine protease inhibitors. 4. The Km and kcat values for Z-Phe-Arg-MCA were determined to be 1.68 microM and 15.8 s-1, respectively. This enzyme hydrolyzed proteins such as insulin B chain, hemoglobin, serum albumin and azocasein easily. 5. The bond specificity to oxidized insulin B chain inferred that the enzyme had a preference for hydrophobic amino acid in P2 and P3 residues.     

Immune response to Toxoplasma gondii--analysis of suppressor T cells in a patient with symptomatic acute toxoplasmosis

Unresponsiveness of antigen-dependent (Toxoplasma-specific and purified protein derivative of tuberculin [PPD]-specific) T-cell proliferative responses of peripheral blood leukocytes (PBL) was observed in a patient with symptomatic acute toxoplasmosis. The immunosuppression of T-cell responses was mediated by Leu 1+, Leu 2a+, and Leu 3a- suppressor T cells that were induced by Toxoplasma gondii antigen and suppressed both Toxoplasma-specific and PPD-specific PBL T-cell responses from a patient with chronic toxoplasmosis when PBL of these patients were mixed and cocultured in vitro. Participation of class II molecules of HLA in Toxoplasma-specific proliferative T-cell responses and activation of suppressor T cells was examined by using monoclonal antibodies specific for HLA-DR and HLA-DQ molecules. Anti-HLA-DQ monoclonal antibody released the suppressive activity, while anti-HLA-DR monoclonal antibody inhibited Toxoplasma-specific T-cell responses. Thus, the suppressive effect of PBL from a patient with acute toxoplasmosis on antigen-dependent PBL T-cell responses from a patient with chronic toxoplasmosis was mediated by HLA-DQ molecules. By contrast, Toxoplasma-specific T-cell responses were activated by HLA-DR molecules (presumably present on antigen-presenting cells).     

Secretion of Mucor rennin, a fungal aspartic protease of Mucor pusillus, by recombinant yeast cells

Summary The aspartic protease gene of a zygomycete fungus Mucor pusillus was expressed in Saccharomyces cerevisiae under the control of the yeast GAL7 promoter. A putative preproenzyme with an NH₂-terminal extension of 66 amino acids directed by the gene was processed in yeast cells and the mature enzyme, whose NH₂-terminus was identical to that of the Mucor enzyme, was efficiently secreted into the medium at a concentration exceeding 150 mg/l. The enzyme secreted from the recombinant yeast was more glycosylated than the native Mucor enzyme but its enzymatic properties were almost identical with those of the native enzyme, which has been used as a milk coagulant in cheese manufacture.     

Somatic hybrids between Brassica oleracea and B. campestris: selection by the use of iodoacetamide inactivation and regeneration ability

Summary An efficient procedure for obtaining somatic hybrids between B. oleracea and B. campestris has been developed. Hypocotyl protoplasts of B. oleracea were fused with mesophyll protoplasts from three different varieties of B. campestris by the polyethylene glycoldimethylsulfoxide method. The selection of somatic hybrids utilized the inactivation of B. oleracea protoplasts by iodoacetamide (IOA) and the low regeneration ability of B. campestris. The efficiency of recovery of somatic hybrids depended upon the IOA concentration, and when 15 mM IOA was used, 90% of the regenerated plants were found to be hybrid. The somatic hybrids were examined for i) leaf morphology, ii) leucine aminopeptidase (LAP) isozyme and iii) chromosome number. All the hybrids had intermediate leaf morphology and possessed LAP isozymes of both parental species. The chromosome analysis revealed a considerable variation in chromosome number of somatic hybrids, showing the occurrence of multiple fusion and chromosome loss during the culture. Some of the hybrids flowered and set seeds.