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.     

Free radical mechanisms in enzyme reactions

Free radicals are formed in prosthetic groups or amino acid residues of certain enzymes. These free radicals are closely related to the activation process in enzyme catalysis, but their formation does not always result in the formation of substrate free radicals as a product of the enzyme reactions. The role of free radicals in enzyme catalysis is discussed.     

Hydrogen evolution by co-immobilized Chlorella vulgaris and Clostridium butyricum cells

Whole cells of Chlorella vulgaris and Clostridium butyricum were co-immobilized in 2% agar gel. NADP was suitable as an electron carrier. The rate of hydrogen evolution increased with increasing NADP concentration. The optimum conditions for hydrogen evolution were pH 7.0 and 37°C. The immobilized C. vulgaris-NADP-immobilized Cl. butyricum system continuously evolved hydrogen at a rate of 0.29–1.34 μmol/h per mg Chl for 6 days. On the other hand, the system without NADP evolved only a trace amount of hydrogen.     

Carbonic anhydrase inhibitors: Inhibition of the tumor-associated isozymes IX and XII with polyfluorinated aromatic/heterocyclic sulfonamides

The tumor-associated transmembrane carbonic anhydrase (CA, EC 4.2.1.1) isozymes IX (CA IX) and XII (CA XII) are involved in acidification of hypoxic tumors, a process correlated with poor prognosis and clinical outcome of patients harboring such tumors. This process may be reversed by inhibiting these enzymes with potent sulfonamide/sulfamate inhibitors. A series of such aromatic/heterocyclic sulfonamides incorporating 2,3,5,6-tetrafluorobenzoyl-, 2,3,5,6-tetrafluoro- phenylsulfonyl- and pentafluorophenylureido moieties has been investigated for its interaction with the catalytic domain of the human isozymes hCA IX and hCA XII. Some of these compounds showed excellent inhibitory properties against both isozymes IX and XII, with several subnanomolar inhibitors detected for the first time. These sulfonamides may constitute valuable candidates for the development of novel antitumor therapies based on the inhibition of such tumor-associated CA isozymes.     

Cleavage of double helical DNA by Cu2+ ion in the presence of bisintercalator containing penta(ethylene glycol) connector chain

In designing new DNA recognizing and cleaving reagents, we introduce herein a bisacridine derivative (referred to as bisacridine) in which two acridine heterocycles are connected by a penta(ethylene glycol) bridging chain. This compound offers two possible functions: 1, stabilization of DNA bisacridine intercalator complex by metal ion. The penta(ethylene glycol) chain stabilizes metal ions binding to the phosphate site of DNA, where the penta(ethylene glycol) chain constitutes a part of a pseudomacrocyclic ligand for metal binding; and 2, enhancement of metal-assisted hydrolytic cleavage of DNA by means of a metal concentration effect by the pseudomacrocyclic ethereal chain. The binding isotherms of bisacridine with DNA in the presence of metal ions showed that the binding was mainly governed by the cation exchange reaction on the anionic DNA polymer chain, i.e., the exchange between metal ions and the cationic bisacridine. The bisacridine showed an increase DNA binding ability compared to quinacrine, the monoacridine counterpart, and caused an enhancement of DNA cleavage in the presence of Cu2+ ions. Additional experiments which included DNase 1 footprinting in the presence of bisacridine and the DNA cleavage by Cu2+/bisacridine using a 32P end-labelled DNA fragment, suggested that the Cu2(+)-assisted DNA cleavage sites in the presence of bisacridine were in reasonable overlap with the DNA binding sites of bisacridine.     

Inhibition of ovulation in PMSG/hCG-treated immature rats by rotenone, a specific inhibitor of mitochondrial oxidation

Immature Wistar rats were induced to ovulate by treatment with PMSG and hCG. Control animals ovulated 43.5 +/- 0.36 ova/rat. Intraperitoneal injection of rotenone doses of 0.125, 0.25 and 0.50 mg/kg reduced the ovulation rate to 24.0 +/- 3.08, 8.0 +/- 0.88 and 1.5 +/- 0.44 ova/rat, respectively. The rotenone significantly reduced ovarian cytochrome oxidase activity and progesterone production, but not production of oestradiol or testosterone. Thyroxine treatment at a dose of 5 mg/kg s.c. reversed the rotenone inhibition of ovulation. The results suggest that an increase in mitochondrial respiration is an essential feature of the ovulation process in mammals.     

Diurnal Rhythm and Characteristics of Photosynthesis and Respiration in the Leaf and Root of a Phalaenopsis Plant

A hybrid Phalaenopsis plant was grown hydroponically on a nutrientsolution of Hyponex in the greenhouse. Typical daily patternsof CO₂ fixation, production of malic acid and citric acid andpH of the leaf and root were determined. The rate of primaryfixation of CO₂ in the leaf increased markedly in the evening,remained high until well into the afternoon, then decreasedsharply. The pattern of production of organic acids resultedfrom the fact that the rate of uptake of CO₂ gas was highestat night and fell during the day. A high correlation betweenpH value and level of malic acid in the leaves was observed,and an exponential relationship appeared to exist between theseparameters. These rhythmic sequences were not observed in theroot. The results suggest that metabolism in the leaf had characteristicsof CAM (Crassulacean Acid Metabolism), while the root did not. (Received May 6, 1988; Accepted October 25, 1988)     

CD16+ lymphoblastic cell lines of crab-eating monkeys (Macaca fascicularis) shared U-5 antigen and expressed natural killer activity

The CD16+ lymphoblastic cell lines of crab-eating monkeys shared the U-5 antigen recognized by a monoclonal antibody. The CD16+U-5+ cell lines expressed high natural killer activity to K562 cells, whereas the CD16-U-5- control cell line had no significant natural killer activity. A possible involvement of the U-5 antigen in natural killer function was also suggested by reduction of the natural killer activity in peripheral blood mononuclear cells of Japanese monkeys after treatment with U-5 monoclonal antibody and complement.     

Development of a series of monoclonal antibodies recognizing leukocyte differentiation antigens of Japanese monkeys (Macaca fuscata)

Six monoclonal antibodies to Japanese monkey leukocytes were developed. These monoclonal antibodies, designated the U series, cover most kinds of leukocytes (pan T cells, CD8+ cells, CD8+ subset and granulocytes, CD16+ cells, monocytes/macrophages), and should be useful in the immunological analysis of primate models, such as tissue transplants and virus-related diseases, in particular, acquired immune deficiency syndrome (AIDS).