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.     

Determinants of Slow Walking Speed in Ambulatory Patients Undergoing Maintenance Hemodialysis

Walking ability is significantly lower in hemodialysis patients compared to healthy people. Decreased walking ability characterized by slow walking speed is associated with adverse clinical events, but determinants of decreased walking speed in hemodialysis patients are unknown. The purpose of this study was to identify factors associated with slow walking speed in ambulatory hemodialysis patients. Subjects were 122 outpatients (64 men, 58 women; mean age, 68 years) undergoing hemodialysis. Clinical characteristics including comorbidities, motor function (strength, flexibility, and balance), and maximum walking speed (MWS) were measured and compared across sex-specific tertiles of MWS. Univariate and multivariate logistic regression analyses were performed to examine whether clinical characteristics and motor function could discriminate between the lowest, middle, and highest tertiles of MWS. Significant and common factors that discriminated the lowest and highest tertiles of MWS from other categories were presence of cardiac disease (lowest: odds ratio [OR] = 3.33, 95% confidence interval [CI] = 1.26–8.83, P<0.05; highest: OR = 2.84, 95% CI = 1.18–6.84, P<0.05), leg strength (OR = 0.62, 95% CI = 0.40–0.95, P<0.05; OR = 0.57, 95% CI = 0.39–0.82, P<0.01), and standing balance (OR = 0.76, 95% CI = 0.63–0.92, P<0.01; OR = 0.81, 95% CI = 0.68–0.97, P<0.05). History of fracture (OR = 3.35, 95% CI = 1.08–10.38; P<0.05) was a significant factor only in the lowest tertile. Cardiac disease, history of fracture, decreased leg strength, and poor standing balance were independently associated with slow walking speed in ambulatory hemodialysis patients. These findings provide useful data for planning effective therapeutic regimens to prevent decreases in walking ability in ambulatory hemodialysis patients.     

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.     

Chemical, physicochemical and spectrophotometric properties of crystalline chlorophyll-protein complexes from Lepidium virginicum L

Two kinds of water-soluble chlorophyll-protein complexes were prepared from leaves of Lepidium virginicum L., one (CP661) from the plant cultivated in a green house from seeds collected near Mono Lake, CA, and the other (CP-663) from a plant collected at Narashino, Chiba, Japan, by ammonium sulfate fractionation followed by column chromatography on DEAE-cellulose and Sephacryl S-200. The chlorophyll . proteins were further purified by crystallization. CP661 has absorption peaks at 661, 468, 439, 419, 380, 339 and 272 nm. CP663 had absorption peaks at 663, 469, 438, 419, 379, 338 and 272 nm. Estimated molecular weights were 78 000 for CP661 and 80 000 for CP663 by gel filtration chromatography and 83 000 for CP661 and 107 000 for CP663 by an equilibrium sedimentation method. 1 mol chlorophyll . protein contained 4 mol chlorophyll a and b with ratios of 1.0 in CP661 and 1.6 to 1.9 in CP663, but no carotenoids. These characters are different from those of chlorophyll-protein complexes which are prepared from the thylakoid membranes of chloroplasts with detergents.     

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.     

Precise identification of gene products in hearts after in vivo gene transfection, using Sendai virus-coated proteoliposomes.

Both efficient gene transfer and the exact identification of gene product are required for gene therapy. Gene transfection of green fluorescence protein (GFP) might be useful for the reporter. After in vivo cotransfection of GFP and beta-galactosidase (beta-Gal) genes in Sendai virus-coated proteoliposomes to rat hearts, we compared the sensitivity and specificity of three methods: GFP detection, histochemical staining (HC) of beta-Gal activity, and immunostaining (IS) of the beta-Gal protein. Fluorescence microscopy and double staining of HC and IS revealed that both GFP and IS were equally sensitive and fourfold superior to HC at the peak of gene expression. However, different from skeletal muscle, the GFP of transfected cardiomyocytes showed two demerits: the fluorescence quenching due to the intense staining of beta-Gal activity, and nonspecific autofluorescence from myocardium. Thus, specific IS would be so far the most reliable to identify the gene product in heart.     

Effects of epinephrine and oxytocin on the release of prostaglandin F from the rat uterus in vitro

Isolated uteri from rats with regular 4-day cycles were incubated in Krebs-Ringer bicarbonate buffer and the release of PGF into the medium was measured by radioimmunoassay after extraction of the incubation medium with ethyl acetate at pH 3.0-3.5. PGF was produced from endogenous precursors and accumulated in equal amounts in the medium during two successive 60 min periods on each day of cycle, but the magnitude of the production varied significantly during the cycle, being greatest in estrus. Oxytocin in doses up to 500 mU/ml had no effect on PGF accumulation in the incubation period at any stage of the cycle, while epinephrine (10(-3)) greatly stimulated PGF release from the estrous uterus but had no effect on PGF release from the diestrous uterus. Phentolamine, an alpha-blocking agent, had no effect on the epinephrine-induced release of PGF, while propranolol, a beta-blocking agent, not only prevented in increase in PGF production induced by epinephrine but also reduced the basal release of PGF by the estrous uterus. Since oxytocin contracts and epinephrine relaxes the nonpregnant rat uterus both in vivo and in vitro, it is unlikely that the effects of these two compounds on uterine contractility are mediated by the release of PGF2alpha.     

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.     

Chromosomal mapping of 18S-28S rRNA genes and 10 cDNA clones of human chromosome 1 in the musk shrew (Suncus murinus).

The direct R-banding fluorescence in situ hybridization (FISH) method was used to map 18S-28S ribosomal RNA genes and 10 human cDNA clones on the chromosomes of the musk shrew (Suncus murinus). The chromosomal locations of 18S-28S ribosomal RNA genes were examined in the five laboratory lines and wild animals captured in the Philippines and Vietnam, and the genes were found on chromosomes 5, 6, 9, and 13 with geographic variation. The comparative mapping of 10 cDNA clones of human chromosome 1 demonstrated that human chromosome 1 consisted of at least three segments homologous to Suncus chromosomes (chromosomes 7, 10, and 14). This approach with the direct R-banding FISH method is useful for constructing comparative maps between human and insectivore species and for explicating the process of chromosomal rearrangements during the evolution of mammals.