Ca2+ transport through lipid membrane by diastereomer cyclic octapeptides

Effects of the nature and orientation of a side chain in cyclic octapeptides on Ca2+ transport were examined by using cyclo[L-Lys(Z)-Sar-L-Leu-Sar]2 (C8-L), cyclo[L-Lys(Z)-Sar]4 (C8KS), and their diastereomer cyclic octapeptides, cyclo[L-Lys(Z)-Sar-D-Leu-Sar]2 (C8-D) and cyclo[L-Lys(Z)-Sar-D-Lys(Z)-Sar]2 (C8Kk). All these cyclic octapeptides were found to take a single conformation in CDCl3, and the conformation was C2-symmetric for C8-L and C8-D, and C4-symmetric for C8KS and C8Kk. They formed a complex with Ca2+. Upon complexation, C8KS accompanied isomerization of peptide bonds, but C8-D retained the arrangement of peptide bonds. The amount of Ca2+ extracted from an aqueous solution to a chloroform solution by all L cyclic octapeptide C8-L or C8KS was about twice that of Na+, but 6-8-fold smaller than that by C8-D or C8Kk including D units. These cyclic octapeptides were capable of transporting Ca2+ through a lipid membrane above the phase transition temperature, and the transport rate decreased in the order of C8Kk-C8KS greater than C8-D greater than C8-L.     

Regulation of myometrial beta 2-adrenergic receptors by progesterone and estradiol-17 beta in late pregnant rats

Rat myometrium exhibited a marked decrease in the concentration of beta 2-adrenergic receptors immediately before parturition, i.e., in the last 6 h of pregnancy. This phenomenon continued until the withdrawal of myometrial progesterone (-94% from Day 18 of pregnancy to term) and coincided with the sharp increase (+200%) of the myometrial concentration of estradiol. A linear positive correlation was found (r2 = 0.645) between the concentration of beta 2-adrenergic receptors and the log ratio of myometrial concentration of progesterone/myometrial concentration of estradiol (P/E2), suggesting a modulation of beta 2-adrenergic receptors by steroids. In rats with estrogen-dominated uteri (intact of ovariectomized late pregnant rats injected with estradiol), there was no change either in concentration or affinity of beta 2-adrenergic receptors relative to untreated control pregnant rats. In contrast, rats with progesterone-dominated uteri (intact or ovariectomized late pregnant rats treated with progesterone or ovariectomized rats) have an increased number of beta 2-adrenergic receptors, with a decreased affinity of these receptors compared to untreated control pregnant rats or to estrogen-treated rats. These results suggest that progesterone regulates the number of beta 2-adrenergic receptors in myometrium of late pregnant rats. The mechanisms by which progesterone exerts this regulation remains to be elucidated.     

Recycle use of immobilized glucoamylase by tangential flow filtration unit

Various properties of glucoamylase immobilized onto corn stover supporting material and separation of immobilized enzyme by tangential flow filtration unit were studied. Optimum pH and temperature of immobilized enzyme were 3.5 and 60 degrees C, respectively. Enzyme stability was studied in a packed-bed column. The starch conversion rate was attained at 81% for 15 days; after that, the hydrolysis rate gradually decreased. Size of supporting material proved to be an important factor, with higher activity and good loading yield resulting from smaller supporting material. Glucoamylase immobilized onto supporting material less than 44 mum was used for hydrolysis of 10% soluble starch at pH 3.5 and 40 degrees C for 3 h. Then immobilized glucoamylase was separated from the product by means of a tangential flow filtration unit using a 0.2-mum pore size Nylon 66 membrane filter. This operation was continued until 180 ml filtrate was obtained from a 260-mL starting volume. Then, the next batch was started by adding 180 mL starch substrate into the reactor. The batchwise experiments were repeated 20 times. The average filtration rate of each batch was determined and found to sharply decline during the first four batches. Thereafter, it gradually decreased from batch to batch. The cause of decreasing filtration rate appeared to be due to retrogradation of starch. The percentage of starch hydrolysis within 20 batches was in the range 89-96%. The filtration rate becomes higher if the hydrolyzation time is extended to 14 h. Resistance to filtration was also investigated. Almost all of the total resistance is related to insoluble materials, with the significant part of this from the resistance due to insoluble materials deposited on a surface of membrane and boundary layer resistance. Using a microscopic method, no microorganisms were found in the filtrate.     

The kinetics and mechanism of shear inactivation of lipase from Candida cylindracea

Shearing experiments were conducted in a stirred tank reactor with 0.1% lipase solutions of Candida cylindracea. Inactivation of the lipase solutions were observed at various shear rates from 50 to 150 s(-1) after continuous shearing for ca. 30-240 min under optimal pH and temperature conditions. However, there was no shear stress denaturation of the lipase when it was subjected to shear stresses of 0.72-109.2 kg/m/s(2) and shear rate of 100 s(-1). In the presence of polypropylene glycol, the rate of denaturation of the lipase decreased by 93%. When the lipase solution was filled to the brim, the rate of denaturation of the lipase decreased by 97% compared to that when reactor was half-filled. The rate of denaturation of the lipase decreased by 61% when probes in the fermentor were removed. There was no significant difference in the rate of denaturation of the lipase under ambient conditions compared with that in the absence of oxygen, or in the absence of free metal ions. Recovery of lipase activity from the first hour of shearing was observed at a shear rate of 150 s(-1). The native lipase and the lipase which had recovered its activity showed similar pH profiles, temperature profiles, and activation energies. Temperature was found to have no effect in the rate of shear-induced denaturation of the lipase in the range 20 to 30 degrees C during shearing at 100 s (-1)and optimal pH. Above 30 degrees C, the rate of denaturation of the lipase increased drastically as a function of temperature. The significance of the findings in the de sign of reactor systems for hydrolysis or esterification of oils by lipase will be discussed.     

Diffusivity of oxygen into carriers entrapping whole cells

The effective diffusivity of oxygen, D(e), in Ca-alginate and PVA-SbQ gels was measured using a two-chamber vessel with a membrane between the two chambers. The effect of cell density, C(c), on D(e) in Ca-alginate gels was studied. The effective diffusivity of oxygen decreased with increasing cell density, to C(c) = 170 kg dry cells/m(3) gel. The dependency of D(e) on cell density was discussed in terms of a random-pore model. The model correlated well with experimental data, i.e., kD(e)/D(0) = 0.86(1 - 1.47 x 10(-3) C(c))(2). Here, k is the partition coefficient, and D(0) is diffusivity in water.     

Kinetic model of hydrocortisone 1-en-dehydrogenation by Arthrobacter globiformis

A kinetic model of the hydrocortisone-to-prednisolone transformation by Arthrobacter globiformis is constructed using the experimental data obtained in studies of this process. Besides adequately describing experimental data, the model allows one to determine the relation between hydrocortisone oxidation and the level of endogenous substrates in bacterial cells, and the relation between the saturating concentration of hydrocortisone in the enzymic system of bacteria and the content of endogenous substrates in their cells, as well as the regulation of the transmembrane potential and the activation by the uncouplers.     

Origin of changes in electrical impedance during the growth and fermentation process of yeast in batch culture

The electrical impedance of the culture medium shows complex changes during the growth and fermentation process of yeast, and this prevents its possible application for the monitoring of certain yeast activities. Clarification of the mechanism of such changes is thus essential for practical use. As a first step toward this aim, the impedance, yeast concentration, and pH of a batch culture medium were measured using special cells with two compartments and also the usual type of cell with one compartment. In the special cells, the yeast was cultured in one compartment only. Conducting ions and nonconducting substances diffused through an intermediate porous membrane sandwiched between the two compartments. The impedances of the two compartments were measured simultaneously by the four-electrode method. The main mechanism responsible for increasing the impedance was the conducting ions produced by the yeast extract added as a nutrient to the culture broth by certain nonconducting substances during the process of growth. The increase in the yeast concentration was also a minor factor increasing the impedance. These increases surpassed the impedance decrease caused by the increase of H(+) ions produced by some accumulated acidic substances, and the impedance thus increased.     

Dynamics of plasmid maintenance in a CSTR upon square-wave perturbations in the dilution rate

The effects of forced oscillations in the dilution rate on a population of Escherichia coli K12 harboring the plasmid pBR322 in a chemostat with a nonselective medium were studied. In the constant dilution rate control experiments, the percentage of plasmid-containing cells decreased after a long lag time. Eventually, the culture approached a population consisting of 100% plasmid-free ells. However, under forced perturbations of the dilution rate, the culture maintained a mixed population of plasmid-free and plasmid-carrying cells for a longer period of ime. An unstructured model was developed to describe the above observations. Our results indicate that transient conditions created by dilution-rate perturbations provide a favorable environment for the plasmid-carrying population. In addition, experiments with different cycling frequencies suggest that adaptation by the culture to these transient conditions will reduce or totally eliminate such an advantage.     

Change of incidence of antinuclear antibodies in serum of NOD mouse with aging

Extractable nuclear antigens (ENA) were prepared from liver of C57BL/6J mouse and analyzed by SDS PAGE Western-immunoblotting techniques. Some protein components of the ENA, with molecular weights of 94 K, 65 K, 32 K, and 26 K, reacted with antinuclear antibodies in the sera of NOD mice. Incidence of antinuclear antibodies in the sera of NOD mice with aging were measured by ELISA method using the ENA as antigen. The antinuclear antibodies were not detected in young NOD mice (10 weeks old). However, the incidence increased with aging and reached 100% in the female NOD mice of 40 weeks. In the male NOD mice, the incidence of antinuclear antibodies was delayed and low in comparison with that in female.     

Detection of nuclear protein antigens to antinuclear antibodies in serum of NOD mouse

Nuclear protein antigens to the antinuclear antibodies in serum of non-obese diabetic (NOD) mice were investigated. In the serum of diabetic NOD female mice (20 weeks old), the antinuclear antibodies were detected by indirect immunofluorescence assay using frozen sections of liver of C 57 BL/6 J or NOD mice as antigen. Nuclei were separated from the liver of C 57 BL/6 J mice and solubilized. Solubilized nuclear antigens were analyzed by SDS PAGE-Western immunoblotting techniques. Nuclear protein antigens with molecular weights of 26,000, 32,000 and 65,000 showed strongly positive reactions with the antinuclear antibodies in the serum of the NOD mouse.