A semimechanistic mathematical model for growth of Rhizopus oligosporus in a model solid-state fermentation system

A Semimechanistic mathematical model is developed which describes the growth of Rhizopus oligosporus in a model solid-state fermentation system. Equations are presented for the release of glucoamylase, the diffusion of glucoamylase, the hydrolysis of starch, the generation and diffusion of glucose, and the uptake of glucose and conversion into new biomass. Good agreement of the model with the experimental data was obtained only after the glucoamylase diffusivity and the maximum specific glucose uptake rate were altered from their originally determined values. The model recognizes the distributed nature of the solid-state fermentation and therefore is able to predict the concentration profiles of the system components within the substrate. The model provides an insight into the possible rate-limiting steps in solid-state fermentation-the generation of glucose within the substrate and the resulting availability of glucose at the surface.     

Immunohistochemical distribution of MAM-3 and MAM-6 antigens in developing salivary glands of the human fetus

Summary The immunohistochemical expression of MAM-3 and MAM-6 antigens was studied in developing human fetal salivary gland removed at autopsy of 22 normal fetuses of varying maturity (10–40 weeks of gestation). The onset of functional maturation in the fetal gland was seen at 21 weeks of gestational maturity. The acini and ducts then underwent distinct alterations in antigen expression with growth and maturation until the late developmental stage (33–40 weeks of gestation) when they resemble the adult salivary gland. The role of maturing duct cells in histogenesis of salivary gland tumours is discussed.     

Determination of total and active immobilized enzyme distribution in porous solid supports

The total and active immobilized enzyme (IME) distributions in porous supports are studied both theoretically and experimentally. In order to determine experimentally the enzyme distribution profiles within a single particle, we construct a diffusion cell containing controlled-pore glass particles such that the cell would mimic a large pellet support. Our purpose is to study the interplay between the diffusion process within the interparticle void space and immobilization process in the controlled-pore glass particles onto the evolution of the (total and active) enzyme distributions. A mathematical model is developed to describe the interaction of various processes within the diffusion cell. The immobilized enzymes are determined for a system of trypsin and controlled-pore glass particles. The total amount of enzymes are determined by the amino acid analysis, and the active fraction is obtained by an active-site titration. The experimentally measured total IME profiles compare very well with that predicted by the model. The determined active enzyme profile is found to be nonuniform one, and it represents about 40% of the total enzyme immobilized in the support particles.     

Effects of excess selenomethionine on selenium status indicators in pregnant long-tailed macaques (Macaca fascicularis)

Forty pregnant long-tailed macaques were treated daily for 30 d with 0, 25, 150 or 300 μg selenium as L-selenomethionine/kg body weight. Erythrocyte and plasma selenium and glutathione peroxidase specific activities, hair and fecal selenium, and urinary selenium excretion were increased by and were linearly related to L-selenomethionine dose. Hair selenium was most sensitive to L-selenomethionine dose, with an 84-fold increase in the 300 μg selenium/(kg-d) group relative to controls (r=0.917). Daily urinary selenium excretion (80-fold,r=0.958), plasma selenium (22-fold,r=0.885), erythrocyte selenium (24-fold,r=0.920), and fecal selenium (18-fold,r=0.911) also responded strongly to L-selenomethionine. Erythrocyte and plasma glutathione peroxidase specific activities increased 154% and 69% over controls, respectively. Toxicity was associated with erythrocyte selenium >2.3 μg/mL, plasma selenium >2.8 μg/mL, and hair selenium >27 μg/g. Plasma, erythrocyte, and hair selenium concentrations may be useful for monitoring and preventing the toxicity of L-selenomethionine administered to humans in cancer chemoprevention trials.     

Plant regeneration of NaCl-pretreated cells from long-term suspension culture of rice (Oryza sativa L.) in high saline conditions

Cells of a 2-year-old suspension culture of rice (Oryza sativa L.), grown under 1.5% NaCl stress for 3 months, gave rise to plants through embryogenesis in different saline conditions. The high regeneration potential (59.6%) on salt-free medium decreased rapidly with increasing concentration of salt in the regeneration medium. At 1.25% NaCl, healthy shoots were developed in 14.9% of the cultures. Under 1.5% salt stress, embryo formation and embryo germination (6.1%) was observed but further development into plants was inhibited. Cells not pretreated with salt produced plants at a low frequency (2.6–4.2%) both in salt-free and low saline condition (0.75–1% NaCl). Cells pretreated for 3 months with 0.75% salt did not give rise to plants on all tested media. Plants regenerated from the salt-stressed cultures were transferred to soil and grew to maturity in a greenhouse.Abbreviations BA 6-benzyladenine - CH casein hydrolysate - 2,4-D 2,4-dichlorophenoxyacetic acid - NAA 1-naphthaleneacetic acid     

Biophysical correlates of lysophosphatidylcholine- and ethanol-mediated shape transformation and hemolysis of human erythrocytes. Membrane viscoelasticity and NMR measurement

The effects of monopalmitoylphosphatidylcholine (MPPC or lysophosphatidylcholine) and a series of short-chain primary alcohols (ethanol, 1-butanol and 1-hexanol) on cell shape, hemolysis, viscoelastic properties and membrane lipid packing of human red blood cells (RBCs) were studied. For MPPC, the effective membrane concentration to induce the formation of stage 3 echinocytes (8 x 10(6) molecules per cell) was one order of magnitude lower than that needed to induce 50% hemolysis (7 x 10(7) molecules per cell). In contrast, short-chain alcohols induced both shape changes and hemolysis within close concentration range (2.5 x 10(8) to 3.5 x 10(8) molecules per cell). Viscoelastic properties of the RBCs were studied by micropipette aspiration and correlated with shape change. Ethanol-treated RBCs showed a decrease in membrane elastic modulus and an increase in membrane viscosity in the recovery phase at the early stage of shape change. MPPC-treated cells showed the same type of viscoelastic changes, but these were not observed until the formation of stage 2 echinocytes. High-resolution solid-state 13C nuclear magnetic resonance technique was applied to study membrane lipid packing in the ghost membrane by following the chemical shift of hydrocarbon chains. Both MPPC and ethanol caused the 13C-NMR chemical shift to move upfield, indicating that membrane lipids were expanded due to the intercalation of these exogenous molecules. Using data obtained from model compounds, we convert values of chemical shift into a lipid packing parameter, i.e., number of gauche bonds for fatty acyl hydrocarbon chains. Approximately 10(8) interacting molecules per cell are required to induce a detectable change of lipid packing by both MPPC and ethanol. The results indicate that homolysis occurs at a smaller surface area for MPPC- than ethanol-treated RBCs. Our findings suggest that progressive changes in the molecular packing in the membrane lead eventually to hemolysis, but the mode responsible for shape transformation varies with these amphipaths.     

Measurement of 2-deoxyglucose and 2-deoxyglucose 6-phosphate in tissues

The enzymatic methods previously described for 2-deoxyglucose (DG) and 2-deoxyglucose 6-phosphate have been refined and adapted to measurements of brain samples ranging from 50 mg wet weight to less than a microgram dry weight. Procedures for preparing such samples for assay are described. Analytical properties of the enzymes employed are given together with means for overcoming their possible short comings. Emphasis is placed on information useful for employing DG to assess rapid changes in glucose metabolism.     

Flavonoids of Derris araripensis

Nineflavonoids: a dihydrochalcone,a flavone,four 3-methylflavonols,a flavanone, a 3-methylflavanonol and a flavan were isolated from the roots of Derris araripensis. Eight of these compounds are reported for the first time. Structures were established by spectral analysis and chemical degradation.     

An improved enzymatic cycle for nicotinamide-adenine dinucleotide phosphate.

We describe the use of column chromatography on the nonpolar adsorbent. Amberlite XAD-2, and on silanized silica gel in the desalting and partial purification of cobalamins. These techniques are both simpler and more versatile than phenol extraction, without sacrificing efficiency. In addition, a solvent system for thin-layer chromatography on silanized silica gel is described which rapidly separates naturally occurring cobalamins.