NITRITE REDUCTASE IN SALMONELLA TYPHIMURIUM

A nitrite reductase was identified and purified 11 -fold from the cytoplasmic fraction of Salmonella typhimurium grown anaerobically with nitrite as the sole nitrogen source. The enzyme required NADH as a cofactor and showed maximum in vitro reductase activity at pH 8.0.
S. typhimurium, grown anaerobically in glucose-limited minimal medium containing peptone and nitrite, showed shorter generation times and increased cell yields in comparison to nitrite-free cultures. The presence of nitrite had no effect on aerobic cultures. The nitrite reductase functions in a dissimilatory manner and appears to be primarily involved in physiological energy generation during anaerobic growth. The nitrite reductase may function to remove excess reducing power in the form of NADH from the cell thus increasing ATP production during the anaerobic fermentation of glucose. The formation and subsequent assimilation of ammonia from nitrite is of secondary importance to the organism.     

Spontaneous Cracking in Unfired Magnesia Compacts Upon Standing in Air

Analytical-grade magnesium oxide powder without binder was compressed hydrostatically to 50,000 lb. per sq. in. to form compacts. When exposed to moist air immediately after pressing, these compacts developed irregularly shaped cracks. Controlled tests, in which these compacts were exposed for various lengths of time to various atmospheres, indicated that in general water vapor, carbon dioxide, and residual stresses had to be present if cracking was to occur. The probable cause of the cracking was the formation of a less dense and mechanically weak basic carbonate of magnesium at crystallite surface points of high stress concentration which developed during the compacting. The adsorption of dry CO₂ at such sites prevented subsequent delayed fracture.     

MICROFLORA OF FRESH PORK SAUSAGE CASINGS. 2. Natural Casings

SUMMARY– Aerobic total plate counts on TGE Agar at 28°C varied from a level greater than 30,000 to 59,000,000 microorganisms per gram in salt-packed natural casings and from 180,000 to 23,000,000 organisms per gram in wet-packed natural casings. Both salt-packed and wet-packed casings supported similar growth patterns in selective media. 38 isolates were identified from the salt-packed casings and 53 from the wet-packed. Of the salt-packed isolates, 60.5% were of the genus Bacillus, 7.9% Pseudomonas, 15.8% Clostridium, 1.6% Micrococcus and 5.3% Gaffkya Those isolates obtained from the wet-packed casings included 62.3% Bacillus, 7.5% Pseudomonas, 7.5% Clostridium, 7.5% Micrococcus, 5.6% Proteus, 1.9% Lactobacillus and 5.7% unidentified.     

TEXTURAL CHANGES IN PRECOOKED LOBSTER (Homarus americanus) MEAT RESULTING FROM RADURIZATION FOLLOWED BY REFRIGERATED STORAGE

The textural changes of radurized precooked lobster meat were evaluated by the organoleptic chew count method and the Warner-Bratzler shear test. Significant texture toughening resulted from irradiation with 100 Krads whereas at 75 Krads the changes were not significant. The texture did not change significantly during post-irradiation storage at refrigeration temperatures.     

TOLERATION FOR PSYCHIATRIC REHABILITATION AS A FUNCTION OF COPING STYLE.

INVESTIGATED WHETHER CONTINUATION OF A PATIENT IN A COMPREHENSIVE PROGRAM OF COMMUNITY-BASED PSYCHIATRIC REHABILITATION WAS RELATED TO HIS OVERALL STYLE OF COPING BEHAVIOR. EARLY IN THE SERVICE PROGRAM, 86 EX-MENTAL-PATIENTS WERE INDEPENDENTLY RATED B8 5-7 PROFESSIONALS ON A 7-CATEGORY SCALE: FEARFUL, DEPENDENT, IMPULSIVE, SOCIALLY NAIVE, WITHDRAWN, SELF-DEPRECATORY, HOSTILE. AT THE CLOSE OF THE PROGRAM, THEY WERE CLASSIFIED INTO 3 GROUPS: 30 SS WHO COMPLETED THEIR ASSIGNED REHABILITATION PROGRAM, 30 SS WHO DROPPED OUT BEFORE COMPLETION, AND 23 SS WHO WERE ADMINISTRATIVELY TERMINATED. RESULTS INDICATE THAT THE COPING SCALE WAS A RELIABLE ASSESSMENT DEVICE. COMPLETERS WERE JUDGED AS SIGNIFICANTLY LESS IMPULSIVE AND SOCIALLY NAIVE AND SIGNIFICANTLY MORE SELF-DEPRECATORY THAN THE OTHER 2 GROUPS COMBINED; THOSE TERMINATED DIFFERED FROM DROPOUTS ONLY IN THAT THE FORMER WERE SIGNIFICANTLY MORE SOCIALLY NAIVE. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

EFFECT OF OXYGEN-ENRICHED ATMOSPHERES ON STORAGE QUALITY OF PACKAGED FRESH MEAT

SUMMARY —The extension of fresh meat shelf-life is important from both practical and theoretical points of view. Color is usually used as a measure of fresh meat quality during storage. Beef top-round slices were prepared using sanitary precautions. Meat slices were enclosed in a thermally sealed semi-rigid polyvinyl chloride tray system of special design. Face-to-face meat samples were used to compare the effects of high oxygen with normal air atmospheres. One package from each pair was evacuated and the atmosphere readjusted to approximately 90% oxygen through a septum. Packages were kept at 4 ± 0.5°C and gas chromatographic readings for CO₂, O₂ and N₂ were conducted daily. Spectrophotometric and bacteriological evaluations were made on selected pack ages during storage to determine pigment oxidation and microbial growth. Three experiments each containing six to eight pairs of samples were conducted. The generation of CO₂ was observed in two periods–the first immediately after packaging and lasting for 1–2 days, after which the CO₂ level remained approximately stable up to 8—9 days, when it again started to increase in correspondence with increased bacterial growth. There was more CO₂ produced than O₂ utilized in the stored samples. In the first stage, samples stored in oxygen-enriched atmospheres had higher O₂ uptake than samples stored in air. Microbial growth was similar in both atmospheres. Under conditions of this study, head space enrichment to about 90% oxygen prolonged acceptable meat color when compared with samples stored in an air atmosphere.     

Comparison of Growth Response by Chemostat Cultured and Batch Cultured Clostridium perfringens Cells in Various Food Substrates

A constant source of exponential phase cells of Clostridium perfringens ATCC 3624 could reduce the time required to carry out the protein quality evaluation test of Solberg et al. (1979) to 4 hr. Clostridium perfringens ATCC 3624 was grown in an anaerobic chemostat using the chemically defined medium, R&S, with glucose as the growth limiting nutrient. The dilution rate was set at 0.06 hr^?1, the pH at 7.2, and the temperature at 43°C. In the transition from a batch culture to a continuous culture an initial oscillatory cell density response was observed. In the steady state, which was continued for as long as 50 days, the cells were typical Gram positive rods, occurring singly or in chains as long as 15 rods, which were occasionally without septa. The fermentative and biochemical responses of the cells did not change. No sporulation occurred when the cells were growing in the chemostat, but spores were observed in the glucose free culture effluent after incubation at 37°C for 24 hr. When cells produced in the chemostat, were cultured in complex media they demonstrated a growth response similar to cells which had been grown in a batch culture. In defined medium the generation time for the chemostat cultured cells was decreased approximately 17%. The chemostat cultured cells can be used as inoculum for the C. perfringens protein quality assay.