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.     

Cloning and sequencing of Schizosaccharomyces pombe DNA topoisomerase I gene, and effect of gene disruption.

We cloned the structural gene topl+ for Schizosaccharomyces pombe DNA topoisomerase I (topo I) by hybridization. An eight-fold increase of topo I relaxing activity was obtained in S. pombe cells transformed with multicopy plasmid with topl+ insert. Nucleotide sequence determination showed a hypothetical coding frame interrupted by two short introns, encoding a 812 residue polypeptide (M.W. 94,000), 43 residues longer than and 47% homologous to Saccharomyces cerevisiae topo I. We show that the topl (null) strain made by gene disruption is viable, although its generation time is 20% longer than that of wild type. The topl locus is mapped in the long arm of chromosome II, using the Leu+ marker integrated with the cloned topl+ sequence. We constructed a double mutant topl (null) top2 (ts) and found its defective phenotype similar to that of previously obtained topl (heat sensitive) top2 (ts). The other double mutant topl (null) top2 (cs), however, was lethal. Our results suggest that topl+ gene of S. pombe is dispensable only if topo II activity is abundant.     

numb, a gene required in determination of cell fate during sensory organ formation in Drosophila embryos

Neurons and support cells of each sensory organ in Drosophila embryos are most likely derived from a single precursor cell. This cell lineage is affected in numb mutants. Morphological alterations of sensory structures, as well as changes in the number of cells expressing cell type-specific markers, indicate that sensory neurons in numb mutant embryos are transformed into lineage-related nonneuronal support cells. Thus the numb gene controls the fate of progeny derived from sensory organ precursors. The numb gene has been isolated by the plasmid rescue method. The structure of its predicted product is discussed.     

Involvement of inositol 1,4,5-trisphosphate in Ca2+ influx in thrombin stimulated human platelets

By incubating platelets at low temperature (10 degrees C), the relationship between Ca2+ mobilization and formation of inositol 1,4,5-trisphosphate (IP3) in thrombin stimulated platelets could be precisely investigated. In the presence of 1 mM EGTA, time dependent changes in the intracellular free calcium concentration [( Ca2+]i) were closely related to those in IP3 formation. Time course of the influx of external Ca2+, estimated by delta [Ca2+]i obtained by subtracting [Ca2+]i in the presence of 1 mM EGTA from that in the presence of 1 mM CaCl2 was also very similar to that of IP3 formed. Furthermore, the increase in delta [Ca2+]i was extremely well correlated with the amount of IP3 formed (Y = 49X - 34, r = 0.99). Thus, these data indicate that IP3 might be involved not only in intracellular Ca2+ mobilization but in Ca2+ influx of human platelets stimulated by thrombin.     

Calyculin A and okadaic acid: inhibitors of protein phosphatase activity

Calyculin A and okadaic acid induce contraction in smooth muscle fibers. Okadaic acid is an inhibitor of phosphatase activity and the aims of this study were to determine if calyculin A also inhibits phosphatase and to screen effects of both compounds on various phosphatases. Neither compound inhibited acid or alkaline phosphatases, nor the phosphotyrosine protein phosphatase. Both compounds were potent inhibitors of the catalytic subunit of type-2A phosphatase, with IC50 values of 0.5 to 1 nM. With the catalytic subunit of protein phosphatase type-1, calyculin A was a more effective inhibitor than okadaic acid, IC50 values for calyculin A were about 2 nM and for okadaic acid between 60 and 500 nM. The endogenous phosphatase of smooth muscle myosin B was inhibited by both compounds with IC50 values of 0.3 to 0.7 nM and 15 to 70 nM, for calyculin A and okadaic acid, respectively. The partially purified catalytic subunit from myosin B had IC50 values of 0.7 and 200 nM for calyculin A and okadaic acid, respectively. The pattern of inhibition for the phosphatase in myosin B therefore is similar to that of the type-1 enzyme.     

A newly established human acute lymphoblastic leukemia cell line with characteristics of the earliest B-cell maturation

A new human acute lymphoblastic leukemia (ALL) cell line, designated HBL-3, was established from the bone marrow of a patient with non-T-ALL. The HBL-3 cell line expressed B4 (CD 19), BA-1 (CD 24) and HLA-DR antigens, but not surface immunoglobulin (SIg) or cytoplasmic immunoglobulin (CIg). The cell line lacked the common acute lymphoblastic leukemia antigen (CALLA) and antigenic markers characteristic of T-cell and myeloid cell lineages. The HBL-3 cells had structural rearrangements of both the homologous chromosome 9s, including a translocation with chromosome 1 which has been reported in a patient with common ALL. The cell line had rearranged immunoglobulin heavy chain genes but retained germ-line κ light chain genes and germ-line T-cell receptorβ- and γ-chain genes. The HBL-3 cell line was strongly positive for terminal deoxynucleotidyl transferase (TdT). These findings indicate that the HBL-3 cell line is derived from the earliest B-cell committed to B-cell lineage.     

Characteristics of various synthetic peptide calpain inhibitors and their application for the analysis of platelet reaction

Calpeptin (a cell permeable synthetic peptide calpain inhibitor) inhibited the generation of thromboxane B2 (TxB2) by the direct inhibition on Tx synthetase in platelets at the concentrations more than 30 microM. Calpeptin, its analogues and E-64d (EST) were further examined with regard to cell permiability and inhibitory spectra. Among all compounds, only calpeptin inhibited the degradation of substrate proteins of calpain with negligible effect on TxB2 generation in intact platelets at the concentrations less than 30 microM. These concentrations of calpeptin did not inhibit the platelet aggregation, the elevation of [Ca2+], nor the formation of inositol 1,4,5-trisphosphate (IP3) in thrombin or collagen activated platelets. These results indicate that calpain dose not participate in the process of platelet activation induced by thrombin or collagen.     

1H NMR studies of deuterated ribonuclease HI selectively labeled with protonated amino acids

Summary Two-dimensional (2D)¹H NMR experiments using deuterium labeling have been carried out to investigate the solution structure of ribonuclease HI (RNase HI) fromEscherichia coli (E. coli), which consists of 155 amino acids. To simplify the¹H NMR spectra, two fully deuterated enzymes bearing several prototed amino acids were prepared from an RNase HI overproducing strain ofE. coli grown in an almost fully deuterated medium. One enzyme was selectively labeled by protonated His, He. Val. and Leu. The other was labeled by only protonated His and Ile. The 2D¹H NMR spectra of these deuterated R Nase H1 proteins, selectively labeled with protonated amino acids, were much more simple than those of the normally protonated enzyme. The simplified spectra allowed unambiguous assignments of the resonance peaks and connectivities in COSY and NOESY for the side-chain protons. The spin-lattice relaxation times of the side-chain protons of the buried His residue of the deuterated enzyme became remarkably longer than that of the protonated enzyme. In contrast, the relaxation times of the side-chain protons of exposed His residues remained essentially unchanged.     

Immunohistochemical evidence of progestin target cells in the pituitary gland of ovariectomized rat

Progestin (P) target cells were identified in the pituitary gland of gonadectomized female rats which had been primed with estrogen (E). P staining was localized using the immunohistochemical avidin-biotin-peroxidase (ABP) complex method. Dark brown precipitates were primarily found over the cytoplasm of cells in the pars distalis, but not in the pars intermedia nor in the pars nervosa. The majority of P-sensitive cells in the pars distalis were identical with luteotrophs, a few being lactotrophs. These observations suggest a role of P in the regulation of production and secretion of gonadotrophins in the pituitary glands of female rats.     

Water-soluble glucans from the seed of Coix lacryma-jobi var. ma-yuen

The water-soluble major polysaccharides from the seed of Coix lacryma-jobi var. ma-yuen eluted as a broad peak by gel filtration on Sepharose CL-2B. The mixture (CS-Glucan) was resolved into 7 glucans by HPLC on the column of Asahi-Pak GS-510 + GS-320. Similarities were observed between M, shown in the gel filtration profile and the elution volume in HPLC. Methylation analysis indicated that the ethanol-fractionated CS-glucan contained 4-O- and 4,6-di-O-substituted glucosyl residues. ¹H and ¹³C NMR data accorded with the results of methylation analysis, and the glycosidic linkages were shown to have an α-configuration. Thus, CS-glucan contained (1 → 4) linked α-d-glucans to which are attached glucosyl side chains at O-6 of the main chain in a similar way to amylopectin. Each purified glucan was shown to have different absorption maxima ( > 550 nm or 530 nm) in the iodine reaction. The results of the methylation analysis and of the pullulanase digestion suggest that the 550 nm-glucan has a lower branching frequency and shorter side chains than the 530 nm-glucan. Although CS-glucan was found to have weak anti-complementary activity, HPLC-purified > 550 nm-glucan was found to be more potent than the 530 nm-glucan. Thus CS-glucan is highly heterogeneous, and the glucans which form a tight complex when tested with iodine, generally tend to have considerable anti-complementary activity.