Quantitation of HIV-1-specific cytotoxic T lymphocytes and plasma load of viral RNA

Although cytotoxic T lymphocytes (CTLs) are thought to be involved in the control of human immunodeficiency virus-type 1 (HIV-1) infection, it has not been possible to demonstrate a direct relation between CTL activity and plasma RNA viral load. Human leukocyte antigen-peptide tetrameric complexes offer a specific means to directly quantitate circulating CTLs ex vivo. With the use of the tetrameric complexes, a significant inverse correlation was observed between HIV-specific CTL frequency and plasma RNA viral load. In contrast, no significant association was detected between the clearance rate of productively infected cells and frequency of HIV-specific CTLs. These data are consistent with a significant role for HIV-specific CTLs in the control of HIV infection and suggest a considerable cytopathic effect of the virus in vivo.     

Note: lack of influence of adherent Lactobacillus isolates on the attachment of Escherichia coli to the intestinal epithelial cells of chicken in vitro

Two Lactobacillus isolates, Lact. acidophilus I 26 and Lact. fermentum I 25, were selected, based on their poor aggregation with Escherichia coli and strong ability to adhere to ileal epithelial cells (IEC), to study in vitro interactions with E. coli O1:K1, O2:K1 and O78:K80 in an IEC radioactive-assay under the conditions of exclusion (lactobacilli and IEC, followed by the addition of E. coli), competition (lactobacilli, IEC and E. coli together) and displacement (E. coli and IEC, followed by the addition of lactobacilli). The results indicated that Lact. acidophilus I 26 and Lact. fermentum I 25 could not significantly reduce the attachment of E. coli O1:K1, O2:K1 and O78:K80 to IEC under the three conditions tested in vitro, except that the attachment of E. coli O1:K1 was slightly reduced by Lact. fermentum I 25 in the test for competition.     

Specular reflection in radiant heat transport across a spherical void

The emissivity factor for radiant heat transport across a spherical void with specular surfaces in a conducting solid is derived. To calculate the emissivity factor, the probability of all possible paths for radiation are formulated and summed. Emissivity factors for the diffuse and specular limits are compared. The resulting temperature dependence of void space radiation for several typical oxide materials is discussed.     

Nonenzymatic hydrolysis of phosphatidylcholine prepared as liposomes and mixed micelles

Nonenzymatic hydrolysis of phosphatidylcholine was investigated at several pH ranges in liposomes and mixed micelles. Phosphatidylcholine was stable to hydrolysis for 140 hr at pH 4, 7 and 10, but slowly hydrolyzed at pH 1 with a half-time of 50 hr. We conclude that phosphatidylcholine is not significantly degraded by hydrolysis under conditions typical for liposome preparation methods.     

Deformation of α-zirconium in the vicinity of 0.5 tinm

The creep behavior of specimens of α-Zr, machined from the three principal directions of a rolled slab or from swaged rod, has been studied in the temperature range 870 to 975 K, for stresses in the range 5 to 20 MPa. For a given stress and temperature, the creep rate depends on texture, being higher for specimens having their axes parallel to the longitudinal (rolling) direction than for specimens cut from either the transverse or short transverse directions. The activation energy for creep,Q _C, decreases with increasing stress, and becomes approximately equal toQ _D, the activation energy for self-diffusion, only for stresses in excess of about 20 MPa. The stress exponentn increases from 3 at low stresses to about 9 at high stresses, for the range of stresses and strain rates investigated. The results are incompatible with a simple, power-law representation of the steady-state creep rate in whichn is constant, andQ _C =Q _D, independent of stress. It is demonstrated that the data are consistent with models in which the glide process contributes to the stress and temperature dependencies of steady-state creep.     

The regulation of mouse liver ornithine decarboxylase by metabolites

The enzyme ornithine decarboxylase (L-Ornithine carboxy-lyase, EC 4.1.1.17), has been partially purified from the livers of mice subjected to partial hepatectomy (6-8 h previously). Mouse liver ornithine decarboxylase requires pyridoxal phosphate, and dithiothreitol for maximal activity. The enzyme has a pH optimum of 7.3, it is inhibited in the presence of 0.3 M phosphate, glycine, Tricine and Tris. It shows no dependence on metal ions and is inhibited by high salt concentrations, particularly ammonium salts. The kinetics of the enzyme have been studied with putrescine (and analogs), spermidine and spermine, in the presence of both high and low levels of pyridoxal phosphate. High concentrations of pyridoxal phosphate inhibit the enzyme. The enzyme is also inhibited by low concentrations of putrescine (1 mM). As the concentration of putrescine increased to 10 mM, non-competitive inhibition was observed, this could be reversed by addition of higher levels of pyridoxal phosphate. Spermidine and spermine inhibit (noncompetitively) only at high concentrations (10 mM). Ornithine inhibits at high concentrations (2 mM). Spectral studies have shown that the observed kinetics of competitive inhibition at low concentrations of polyamine changing to noncompetitive inhibition at high polyamine concentrations are due to competition between enzyme and substrate (or inhibitor) for free (non-enzyme bound) pyridoxal phosphate. Noncompetitive inhibition arises through the formation of transient Schiff base complexes between amines and free pyridoxal phosphate. It also appears that the binding of substrate to the active site takes place through Schiff base formation with enzyme bound pyridoxal phosphate.     

Effect of short wavelength illumination on the characteristic bulk diffusion length in ribbon silicon solar cells

The influence of short wavelength light on the characteristic bulk minority carrier diffusion length of the ribbon silicon photovoltaic cell has been investigated. We have measured the intensity and wavelength dependence of the diffusion length in an EFG ribbon cell, and compared it with a standard Czochralski grown silicon cell. While the various short wavelength illuminations have shown no influence on the diffusion length in the CZ cell, the diffusion lengths in the ribbon cell exhibit a strong dependence on the volume generate rate as well as on the wavelength of the superimposed lights. We have concluded that the trap-filling phenomenon at various depths in the bulk neutral region of the cell is consistent with the experimental observation.     

Immunoassayable beta-endorphin level in the plasma and CSF of heroin addicted and normal subjects before and after electroacupuncture

The present study was undertaken to evaluate if plasma or CSF beta-endorphin level can be induced to rise during the treatment of heroin addiction by electroacupuncture. Based on the examination of 30 addicts, we obtained no evidence indicating an increase of beta-endorphin level in either the plasma or the CSF after 30 min of acupuncture. In spite of this, the majority of the addicts experienced a reduction of withdrawal symptoms during treatment. Since electroacupuncture may only induce a highly localized secretion of beta-endorphin in the brain, our results cannot unequivocally exclude the possibility that this peptide is involved in mediating the action of acupuncture.     

Antioxidant activity of tea theaflavins and methylated catechins in canola oil

The present study examined the antioxidant activity of black tea theaflavins and catechin derivatives in canola oil. Oxidation was conducted at 95°C by monitoring the oxygen consumption and decreases in the linoleic and α-linolenic acids of canola oil. All were tested at a concentration of 0.5 mM. Catechins, including (−)-epicatechin, (−)-epicatechin gallate, (−)-epigallocatechin, and (−)-epigallocatechin gallate (EGCG), were more effective than theaflavins, namely, theaflavin-1, theaflavin-3-gallate, theaflavin-3′-gallate, and theaflavin-3,3′-digallate (TF₃), against the lipid oxidation of canola oil. Among the four theaflavins, TF₃ was the most effective, whereas among the four catechins, FGCG was the most potent. Under the same conditions, all theaflavins and catechins were more powerful than BHT as an antioxidant in heated canola.oil. Little or no difference in antioxidant activity was observed between each catechin and epimer pair. Methylation of the 3′-OH led to a significant loss of antioxidant activity of the catechins.