Some issues in discrete approximate solution for stochastic differential equations

An evaluation method for numerical schemes of stochastic differential equations is treated. Discussing the source of errors in the discrete numerical solution, we highlight the effect of pseudo-random numbers upon the numerical solution, and point out the significance of the independencies of the series of them required in the numerical schemes. To discriminate the stochastic and deterministic parts in the errors more clearly, we propose a new two-dimensional linear test equation of multiplicative type whose analytical solution can be obtained readily. Our results are illustrated through some numerical examples.     

Molecular cloning and sequencing of two phospho-beta-galactosidase I and II genes of Lactobacillus gasseri JCM1031 isolated from human intestine

Lactobacillus (Lb.) gasseri JCM1031, which is classified into the B1 subgroup of the Lb. acidophilus group of lactic acid bacteria, characteristically produces two different phospho-beta-galactosidases (P-beta-gal) I and II in the same cytosol as reported in our previous papers [Biosci. Biotech. Biochem., 60, 139-141, 708-710 (1996)]. To clarify the functional and genetic properties of the two enzymes, the structural genes of P-beta-gal I and II were cloned and sequenced. The structural gene of P-beta-gal I had 1,446 bp, encoding a polypeptide of 482 amino acid residues. The structural gene of P-beta-gal II had 1,473 bp, encoding a polypeptide of 491 amino acid residues. The deduced relative molecular masses of 55,188 and 56,243 agreed well with the previous value obtained from the purified P-beta-gal I and II protein, respectively. Multiple alignment of the protein sequence of P-beta-gal I and II with those of P-beta-gals from 5 microorganisms had 30-35% identity on the amino acid level, but those with phospho-beta-glucosidases from 5 microorganisms had the relatively high identity of about 50%. Considering that this strain grows on lactose medium and shows no beta-galactosidase activity, and that purified P-beta-gal I and II can obviously hydrolyze o-nitrophenyl-beta-D-galactopyranoside 6-phosphate (substrate), and also the conservation of a cysteine residue in the molecule, the P-beta-gal I and II were each confirmed as a novel P-beta-gal enzyme.     

Thyroglobulin-specific T cell line from a healthy individual does not produce proinflammatory cytokines on antigenic stimulation: an implication for possible fail-safe mechanism to avoid autoimmunity

In order to investigate the regulation of autoimmune response to thyroglobulin (Tg), one of the thyroid autoantigens, we established a Tg-specific T cell line by stimulation of peripheral blood mononuclear cells from a healthy volunteer with Tg and characterized its cytokine production pattern. The Tg-specific T cell line, designated DH5D1, obtained from a limiting dilution culture bore alpha beta T cell receptor and was CD4 and CD45RO positive. Upon stimulation with Tg, DH5D1 secreted little or no titers of IL-2, TNF-alpha, and IFN-gamma, whereas activation with combination of phorbol myristate acetate and calcium ionophore produced measurable levels of these cytokines. These results indicate that the Tg-specific T cell line is not defective in its capacity to produce proinflammatory cytokines and suggest that the inability of cytokine production by autoreactive T cells of healthy individuals is one fail-safe mechanism for preventing aggression of harmful autoimmune response.     

FREE SETTLING OF A NON-SPHERICAL PARTICLE IN A STAGNANT LIQUID

The free settling behavior of the cylindrical particles made of four kinds of materials with horizontal motion in the stagnant water observed with an aid of the image sensor anemometer in the Reynolds number ranged from about 150 to 1000 was investigated in this paper. The four kinds of materials were finished into cylindrical specimens having the diameters “d” of 1.5 to 3.0 mm and the ratios of “d” to the length of specimen “1_s” of d/1_s = 1/2 to 1/3.5.

From the experimental results, the settling behavior of the particles was found to be simply expressed by the equation of a simple harmonic motion. By correcting the drag coefficient of the cylindrical particles with a correction factor which is obtained from the simple harmonic motion, the relationship between the drag coefficient and Reynolds number for the cylindrical particles was found to be parallel to that for the spherical particles.     

Efficient production of recombinant human factor VIII by co-expression of the heavy and light chains

We have developed a high-level expression system for human bloodcoagulation factor VID (FVUI) consisting of a 90 kDa heavy (H-)chainand an 80 kDa light (L-)chain. Two expression plasmids wereprepared, one expressing the H-chain and the other expressingthe L-chain. These recombinant plasmids were designed to produceeach chain linked to short additional ammo acid residues derivedfrom the FVm precursor sequence. Furthermore, Kozak's translationinitiation consensus sequence was introduced into the startcodon for the H-chain. These modifications have dramaticallyincreased the levels of expression of these chains. Chinesehamster ovary (CHO) cells co-transfected with these two recombinantplasmids were subjected to gene amplification and cloning. Thefinal cell line, designated CTC-CF8, secretes 15 IU/day/106cells of active FVm which is indistinguishable from plasma-derivedFVm in its structure and biochemical properties. This systemis suitable for large-scale production of pathogen-free recombinanthuman FVm which can be used for the treatment of haemophiliaA patients.     

Antigen-specific IgA response of NALT and cervical lymph node cells in antigen-primed rats

Three models to estimate energy requirement as a function of growth curve pattern were applied to controlled experimental data of male vs female of broilers and turkeys. The share of maintenance out of total feed requirement was 55% for the average of the three models with major divergence due to age. Comparison of the ratio between actual and estimated feed consumption reveals that the relative energy requirement was always lower in females than in males in the range of 5 to 10% for the three models, with an average of 7.7%. It appears, therefore, that in estimating the energy requirement for use in practical feeding, specific models should be assigned for males and females in both broilers and turkeys.     

Solubilization behavior ofn-octane andn-octanol in polyoxyethylated nonionic micelles

The solubilization ofn-octane andn-octanol in nonionic micelles was investigated by means of various techniques including solubilization, fluorescence and dynamic light-scattering measurements. With respect to the effect of oxyethylene chainlength of the surfactants, different solubilization behavior was observed betweenn-octane andn-octanoli.e., the solubilization ofn-octane decreases with an increase in oxyethylene chainlength, while that ofn-octanol increases. This solubilization behavior is explained from the standpoint of the volume of hydrophobic and hydrophilic regions in a micelle.     

Chaos and fractals from a forced artificial neural cell

Chaos and fractal responses from an artificial neural cell stimulated by a periodic square wave are discussed. The dynamics are described by an autonomous equation, and the one-dimensional return map is derived explicitly. The relation between the exciting pulse-width tau(1), and the excited rate gamma(e) which is the number ratio of input pulses and output pulses investigated. Mathematical evidence for gamma(e) to be Cantor function for tau(1) is given. It corresponds to fractal responses. A condition for observable chaos generation in responses from the cell is proved. This condition is described only by parameters. Some of the theoretical results are verified by laboratory experiments.     

Milbemycin derivatives: epoxidation of milbemycins

Epoxidation reactions (MCPBA epoxidation and Sharpless epoxidation) were examined as a means of chemically modifying milbemycins as part of our program for discovering anthelmintics. 8,9-Epoxy-, 14,15-epoxy-, 8,9-14,15-diepoxy-, and 3,4-8,9-14,15-triepoxymilbemycin A4 were selectively obtained from milbemycin A4 and its derivatives, in which either the C-5 and C-7 hydroxyl groups or C-5 alone were protected as appropriate by a silyl ether (in the former case) or a carbonyl group. Further silylation or epoxidation on these epoxidized compounds indicated that the configuration of each epoxide moiety of the mono- and diepoxides is in accord with that of the corresponding epoxide moiety of the triepoxide. Furthermore, in order to confirm the absolute configurations of these epoxide functionalities, an X-ray analysis of a carbamate derivative from the triepoxymilbemycin was conducted.