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.     

Biological activity and receptor binding characteristics to various human tumors of acetylated somatostatin analogs.

Several somatostatin analogs with recently synthesized acetylated N terminus were assayed in vivo for their effects on sodium pentobarbital-stimulated growth hormone (GH) levels in fed male rats and gastrin-releasing peptide (14-27)-stimulated gastrin levels in fasted male rats. The binding characteristics of these analogs to somatostatin receptors were also examined in various human tumors and normal tissues. The analog RC-101-I, injected at a dose of 0.1 micrograms/100 g body wt, significantly suppressed GH release (P less than 0.01) for at least 2 hr. Analog RC-160-II caused the longest inhibition of GH release, greater than that induced by nonacetylated parent analog RC-160, with GH levels showing significant suppression (P less than 0.01) for more than 3 hr. Analogs RC-160-II and RC-101-I and RC-160, injected at a dose of 1.0 micrograms/100 g body wt, significantly (P less than 0.01) suppressed gastrin-releasing peptide (14-27)-stimulated serum gastrin. Analog RC-101-I was active in this test at a dose of 0.1 micrograms/100 g body wt. RC-160-II showed significant binding to somatostatin-14 receptors in all investigated tissues (human colon, human colon cancer, breast cancer, human pancreas and pancreatic cancer, human prostate and prostate cancer, and rat cerebral cortex), but there were marked variations in binding affinities among various normal and cancerous tissues. The highest affinity was found in membranes of colon cancer (Ka = 18.4 nM-1) and breast cancer (Ka = 12.46 nM-1). The binding affinity of RC-160-II to somatostatin receptors in membranes of the breast cancer was similar to that of RC-160. RC-101-I showed higher binding affinity to somatostatin-14 receptors than RC-160 in human breast, pancreatic, and prostate cancer. With the exception of breast cancer tissue, the binding affinity of RC-101-I was significantly lower than that of RC-160-II in membranes of all investigated tissues. It can be concluded that acetylated somatostatin analogs RC-101-I and RC-160-II possess prolonged and enhanced biological activities in suppressing serum GH and gastrin in rats. Significant variations in binding affinities for these analogs in different tissues and various tumors suggest that differences may exist between somatostatin receptors in normal versus malignant tissues. This raises the possibility that some of these analogs could be used more selectively in the treatment of various neoplasms.     

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.     

Coupling of polyphosphoinositide breakdown with calcium efflux in formyl-methionyl-leucyl-phenylalanine-stimulated rabbit neutrophils

Exposure of rabbit neutrophils to formyl-methionyl-leucyl-phenylalanine (FMLP) induced the efflux of 45Ca2+ from pre-labeled cells which was almost complete within 30 s. On the other hand, FMLP-induced 45Ca2+ influx did not become apparent until 60 s after stimulation. When [3H]arachidonic acid-labeled neutrophils were stimulated with FMLP, the radioactivities in phosphatidylinositol 4,5-biphosphate (TPI) and phosphatidylinositol 4-phosphate (DPI) significantly decreased in parallel with the induction of 45Ca2+ efflux. In contrast, degradation of polyphosphoinositides in [3H]glycerol-labeled neutrophils was not significant until 60 s. Taken together, these results indicate that the early degradation of polyphosphoinositides, especially of those rich in arachidonic acid is closely associated with the initial efflux of calcium in FMLP-stimulated rabbit neutrophils. The study of resynthesis of polyphosphoinositides by measuring 32Pi incorporation into these lipids is also presented.     

Intracellular accumulation of trehalose and glycogen in an extreme oligotroph,Rhodococcus erythropolis N9T-4

An extreme oligotroph, Rhodococcus erythropolis N9T-4, showed intracellular accumulation of trehalose and glycogen under oligotrophic conditions. No trehalose accumulation was observed in cells grown on the rich medium. Deletion of the polyphosphate kinase genes enhanced the trehalose accumulation and decreases the intracellular glycogen contents, suggesting an oligotrophic relationship between among the metabolic pathways of trehalose, glycogen, and inorganic polyphosphate biosyntheses.     

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.     

Effects of Controlled-Release Fertilizer on Leaf Area Index and Fruit Yield in High-Density Soilless Tomato Culture Using Low Node-Order Pinching

To further development of a simplified fertigation system using controlled-release fertilizers (CRF), we investigated the effects of differing levels of fertilizers and plant density on leaf area index (LAI), fruit yields, and nutrient use in soilless tomato cultures with low node-order pinching and high plant density during spring-summer (SS), summer-fall (SF), and fall-winter (FW) seasons. Plants were treated with 1 of 3 levels of CRF in a closed system, or with liquid fertilizer (LF) with constant electrical conductivity (EC) in a drip-draining system. Two plant densities were examined for each fertilizer treatment. In CRF treatments, LAI at pinching increased linearly with increasing nutrient supply for all cropping seasons. In SS, both light interception by plant canopy at pinching and total marketable fruit yield increased linearly with increasing LAI up to 6 m²·m⁻²; the maximization point was not reached for any of the treatments. In FW, both light interception and yield were maximized at an LAI of approximately 4. These results suggest that maximizing the LAI in SS and FW to the saturation point for light interception is important for increasing yield. In SF, however, the yield maximized at an LAI of approximately 3, although the light interception linearly increased with increasing LAI, up to 4.5. According to our results, the optimal LAI at pinching may be 6 in SS, 3 in SF, and 4 in FW. In comparing LAI values with similar fruit yield, we found that nutrient supply was 32−46% lower with the CRF method than with LF. In conclusion, CRF application in a closed system enables growers to achieve a desirable LAI to maximize fruit yield with a regulated amount of nutrient supply per unit area. Further, the CRF method greatly reduced nutrient use without decreasing fruit yield at similar LAIs, as compared to the LF method.