Effect of the rehydration medium on the recovery of freeze-dried lactic acid bacteria.

Sixteen cultures of lactic acid bacteria were freeze-dried in 10% nonfat skim milk plus 0.75 M adonitol and rehydrated by using different rehydration media. Marked variations in their capacity to repair cellular damage after freeze-drying were observed among the species and strains under consideration.     

TRH and TRH-OH in the pancreas of adult and newborn rats

TRH and its metabolite TRH-OH have been measured by specific radioimmunoassays in acid extracts of pancreas in adults and developing rats. TRH and TRH-OH immunoreactivity had the same ontogenic pattern with a maximal concentration on day 4 followed by a progressive return towards adult levels on day 20. A significant linear correlation was found between TRH levels and the TRH/TRH-OH ratio. The range of TRH/TRH-OH ratio varied from 136 +/- 1.6, at the peak of concentrations of both peptides, to 18 +/- 3.9 on day 20. Pancreatic TRH and TRH-OH had the same elution pattern as corresponding synthetic peptides both on Biogel P2 and high-pressure liquid chromatography. The origin of TRH-OH as well as its potential function need further investigations.     

Interaction of Opiates with Opioid Binding Sites in the Bovine Adrenal Medulla: I. Interaction with δ and μ Sites

In the present study we examined the interaction of opiates with the delta and mu opioid binding sites in the bovine adrenal medulla. [3H][D-Ala2, D-Leu5]-enkephalin ( [3H]DADLE) in the presence of saturating concentrations of morphiceptin was used to analyze delta site interactions, whereas either [3H]DADLE in the presence of saturation concentrations of [D-Ser2, Leu5]-enkephalin-Thr6 (DSLET) or [3H][D-Ala2, Me-Phe4, Gly5-ol]-enkephalin ( [3H]DAGO) was used for the determination of mu sites. Both binding sites were found to interact stereoselectively with opiates. The binding was affected differentially by proteolytic enzymes (trypsin, alpha-chymotrypsin, pepsin), N-ethylmaleimide, and A2-phospholipase. Kinetic and equilibrium binding studies revealed that in each case radiolabeled opiates interact with one class of binding sites, following simple second-order bimolecular kinetics. Competition for binding by opiates and opioid peptides confirmed the delta and mu selectivity of these sites. Monovalent (Na+, Li+, K+) and divalent (Mg2+, Mn2+, Ca2+) ions interacted differentially with these two binding sites: In general, monovalent cations affected preferentially the apparent number of binding sites, whereas divalent ions modified the equilibrium dissociation constant. Furthermore, positive or negative cooperativity and an apparent heterogeneity of binding sites were detected under some ionic conditions.     

Isolation and characterization of Pediococcus halophilus from salted anchovies (Engraulis anchoita)

The presence of bacteria in salted anchovies during and at the end of the curing process was investigated. Attempts to isolate bacteria under aerobic or anaerobic conditions led to the isolation of only bacteria of the genus Pediococcus which were identified as Pediococcus halophilus. The isolates correspond to a rather heterogeneous group in which some of the members differ in some biochemical tests from the types described in the literature.     

Comparison of health problems related to work and environmental measurements in two office buildings with different ventilation systems.

A cross sectional survey investigating "building sickness" was carried out in two buildings with similar populations of office workers but differing ventilation systems, one being fully air conditioned with humidification and the other naturally ventilated. The prevalence of symptoms related to work was assessed by a questionnaire administered by a doctor. A stratified, randomly selected sample of workers was seen (84% response). Building sickness includes several distinct syndromes related to work, most of which were significantly more common in the air conditioned building than the naturally ventilated building--namely, rhinitis (28% v 5%), nasal blockage and dry throat (35% v 9%), lethargy (36% v 13%), and headache (31% v 15%). The prevalence of work related asthma and humidifier fever was low and did not differ significantly between the two buildings. An environmental assessment of the offices was performed to attempt to identify possible factors responsible for the differences in the prevalence of disease. Globe temperature, dry bulb temperature, relative humidity, moisture content, air velocity, positive and negative ions, and carbon monoxide, ozone, and formaldehyde concentrations were all measured. None of these factors differed between the buildings, suggesting that building sickness is caused by other factors.     

Unusual properties of two branched RNA''s with circular and linear components.

Irradiation with ultraviolet light was used to create two nonlinear RNA molecules. Circular potato spindle tuber viroid (PSTV) RNA was crosslinked at a single site to generate a figure eight-shaped molecule; 5S rRNA from HeLa cells was transformed into an alpha-shaped molecule with a small circular element and two arms (1). Crosslinked RNA's could be separated from their untreated counterparts by electrophoresis in polyacrylamide gels containing urea. The gel mobility of crosslinked PSTV was not altered by boiling, treatment with E. coli RNase III or glyoxalation. However, mild nuclease digestion ("nicking") produced derivatives which migrated more slowly than the starting material in gels of certain polyacrylamide concentrations, but not in others. Limited nuclease digestion of crosslinked 5S rRNA did not generate any detectable products with reduced mobility in the gels tested. Thus, the ability of the "nicking assay" to reveal circular elements within nonlinear RNA's can vary depending upon the composition of the gel chosen for analysis and on the size of the circular element relative to the rest of the molecule.     

tRNA binding sites of ribosomes from Escherichia coli

70S tight-couple ribosomes from Escherichia coli were studied with respect to activity and number of tRNA binding sites. The nitrocellulose filtration and puromycin assays were used both in a direct manner and in the form of a competition binding assay, the latter allowing an unambiguous determination of the fraction of ribosomes being active in tRNA binding. It was found that, in the presence of poly(U), the active ribosomes bound two molecules of N-AcPhe-tRNAPhe, one in the P and the other in the A site, at Mg2+ concentrations between 6 and 20 mM. A third binding site in addition to P and A sites was observed for deacylated tRNAPhe. At Mg2+ concentrations of 10 mM and below, the occupancy of the additional site was very low. Dissociation of tRNA from this site was found to be rather fast, as compared to both P and A sites. These results suggest that the additional site during translocation functions as an exit site, to which deacylated tRNA is transiently bound before leaving the ribosome. Since tRNA binding to this site did not require the presence of poly(U), a function of exit site bound tRNA in the fixation of the mRNA appears unlikely. Both the affinity and stability of binding to the additional site were found lower for the heterologous tRNAPhe from yeast as compared to the homologous one. This difference possibly indicates some specificity of the E. coli ribosome for tRNAs from the same organism.     

Cytokinin-induced switch in development in excised cotyledons of radiata pine cultured in vitro

Cotyledons of Pinus radiata D. Don were cultured under shoot-forming (plus cytokinin) and elongating (minus cytokinin) conditions. Using. autoradiographic and precursor incorporation techniques, the sites and rate of macromolecular synthesis were examined during the first five days in culture. Active incorporation of ³H-thymidine, ³ H-uridine and ³H-leucine occurred. In shoot-forming cotyledons the incorporation became preferentially located in the epidermal and sub-epidermal cell layers in contact with the medium. In elongating cotyledons, in contrast, incorporation was randomly distributed, and the amount of incorporation declined with time. Biochemically, differences in DNA, RNA and total protein synthetic patterns were observed. In elongating cotyledons the rates of RNA and protein synthesis were higher during the first 48 h than in shoot-forming tissues, after which the synthetic rates were similar. Two peaks of newly formed DNA were observed in both tissues. These findings indicate that the cytokinin-induced changes in developmental pathways began within 24 h in culture.