TOXICITY OF 1, 2-DIMETHYLHYDRAZINE IN MICE: EFFECT OF DIET AND DEVELOPMENT OF TOLERANCE

The effect of diet on the lethality of 1, 2-dimethylhydrazine (DMH) injections was investigated using Swiss mice. Mortality was highest when mice were fed a nutrient-diluted/high-fat diet, was intermediate with a nutrient-diluted/low-fat diet and was lowest with laboratory chow. Wheat bran was not protective. Mice developed tolerance to DMH after receiving several injections of progressively increasing dose.     

ANXIETY AS A FUNCTION OF TAKING THE MMPI.

TO INVESTIGATE ANXIETY PRODUCED BY TAKING A PERSONALITY TEST, 44 COLLEGE SS WERE RANDOMLY ASSIGNED TO 1 OF 3 GROUPS: A CONTROL GROUP WHICH WROTE AN ESSAY, "WHO AM I?"; A GROUP WHICH TOOK AN ELEMENTARY FORM OF AN ACHIEVEMENT TEST (IOWA TEST OF BASIC SKILLS), THEN WROTE THE ESSAY; AND A GROUP WHICH TOOK A PERSONALITY INVENTORY (MMPI), THEN WROTE THE ESSAY. CONTENT ANALYSIS, EMPLOYING THE GENERAL INQUIRER SYSTEM, REDUCED THE ESSAYS TO QUANTITATIVE TAG SPECIFIC CONCEPTS WHICH DISCLOSED STATISTICALLY RELIABLE DIFFERENCES ON 21 OF THE 83 TAGS (P $MS .05). AS HYPOTHESIZED, THE MMPI GROUP DISPLAYED MORE ANXIETY AS A FUNCTION OF THE TEST EXPERIENCE THAN DID EITHER OF THE OTHER 2 GROUPS. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Postmortem Loss of Carnitine from Skeletal Muscle of Pork and Beef

The carnitine content of beef muscle postmortem was more than twofold higher than the content of pork muscle. For both pork and beef, carnitine was distributed among the fractions, free carnitine ? short-chain acylcarnitine > long-chain acylcarnitine concentration. Based on total carnitine content, the only loss of carnitine from pork muscle occurred as a result of cooking. Cooking also reduced total carnitine content of beef muscle. In addition, total carnitine content of the beef steaks was lower after thawing. Time in the retail case did not influence carnitine content.     

ALGAL GLYCEROL PRODUCTION: INITIAL GLYCEROL SYNTHESIS KINETICS

A review of previous work has allowed presentation of a unified conceptual model relating the important biochemical mechanisms involved in regulating glycerol production in halophilic algae. Experimental results on the initial rate of glycerol synthesis are reported which are used to indicate sodium transport may be the rate limiting step. These and other related results are discussed in relation to the model, and to algal glycerol process considerations.     

Casein Inhibition of Clostridium perfringens Growth and Exoprotease Production

Growth of C. perfringens strain 3624 on a defined medium containing ANRC Reference Casein as the nitrogen source was investigated. Gas production, monitored manometrically as an index of growth, indicated a depressed growth response of the organism in the casein-containing medium. Increased growth response resulting from pepsin treatment of the casein was largely due to the enzyme serving as a nitrogen source. Chelation of iron by casein was not responsible for the growth inhibition. Casein suspended in complete medium was not inhibitory to the organism. Growth studies indicated that native casein was not available as a nitrogen source to the organism. Acid hydrolyzed casein and commercial casein hydrolysate served as suitable nitrogen sources for growth of the organism, however exoprotease production was repressed in both media as well as in medium containing native casein as the sole nitrogen source. C. perfringens strain 3624 produced exoprotease in the completely defined medium containing synthetic amino acids, indicating the possible presence of an amino acid or a metabolite, not produced in the casein-containing medium which functioned to derepress the enzyme synthesizing mechanism.     

MOLECULAR PROPERTIES OF POST-MORTEM MUSCLE. 9. Effect of Temperature and pH on Tropomyosin-Troponin and Purified α-Actinin from Rabbit Muscle

SUMMARY– A study was done on the effects of in vitro storage of purified α-actinin, troponin, tropomyosin, and the tropomyosin-troponin complex on the activity of these protein fractions in the ATPase and superprecipitation assays. Storage was done at various combinations of temperatures between 0 and 40°C and pH values between 5.7 and 7.0. Even after 40 hr of storage, activities of purified tropomyosin and the tropomyosin-troponin complex were not affected by any combination of temperature and pH included in this study, but activities of purified α-actinin and troponin were almost completely lost after 16 hr at 40°C and pH 5.7. Storage for 40 hr at low pH (5.7) and low temperatures (0°C) did not affect the activity of either α-actinin or troponin, but 40 hr of storage at high temperatures (40°C) and neutral pH caused some loss in activity for both these proteins. This loss of activity caused by 40°C, pH 7.0 storage was much more noticeable in the case of troponin than in the case of α-actinin. Storage periods of 40 hr or longer were required before any loss of α-actinin activity could be detected at pH 7.0 and 40°C. Since most meat animal carcasses are chilled soon after exsanguination and attain muscle temperatures of 25°C or lower before the pH falls below 6.2, it is probable that α-actinin and tropomyosin-troponin activity remain almost unchanged in meat handled through normal market channels. However, myofibrillar tissue in those porcine animals whose musculature undergoes a very rapid post-mortem decline in pH so that values of 5.7 or less are reached while muscle temperatures are still 37°C or higher may lose much of its α-actinin and tropomyosin-troponin activity during the first 24 hr post-mortem.     

Direct measurement of hydraulic properties in developing berries of Vitis vinifera L. cv Shiraz and Chardonnay

Berries of Vitis vinifera L. cv Shiraz can undergo weight loss during later stages of ripening. Existing published views on how weight loss occurs are based on changes in capacity of the vascular system to import water during development (McCarthy and Coombe, Australian Journal of Grape and Wine Research, 5, 17–21, 1999). One important element of these views is the proposed cessation of water flow through the xylem after veraison. We have now measured the water flow into berries of Shiraz and Chardonnay as they develop using the pressure probe and the high pressure flow meter (HPFM). The pressure probe connected to the pedicel of individual berries provided measurements of single berry hydraulic conductance. By systematic excision of tissue segments of the berry and pedicel we determined where in the pathway hydraulic conductance changed during development. The HPFM was used on whole bunches showing that berries (including pedicels) represent parallel high hydraulic resistances and that the hydraulic resistance of the bunch axis was rather small. The hydraulic conductance per berry could be determined from excision experiments. There was close agreement between the pressure probe and HPFM measurements. Both showed a ten‐fold reduction in hydraulic conductance of whole berries from veraison to full ripeness. Shiraz had hydraulic conductances that were 2‐ to 5‐fold higher than those for Chardonnay. Shiraz maintained a higher hydraulic conductance past 90 days after flowering than Chardonnay. The decrease in hydraulic conductance occurred in both the distal and proximal parts of the berry for both varieties. The pressure probe also provided measurements of the xylem pressure that non‐transpiring berries could develop. These pressures were –0.2 to –0.1 MPa until veraison and increased to zero when the juice osmotic potential reached about –3 MPa in Chardonnay and –4 MPa in Shiraz. The results suggest values of the reflection coefficient of the osmotic barrier around the xylem vessels of about 0.1–0.2 at veraison decreasing to 0 at harvest. It is suggested that in addition to changes in xylem anatomy, aquaporins in berry membranes may play a role in regulating hydraulic conductance. Water movement from the berry back to the parent vine via the xylem (backflow) may be an important component of berry weight loss in Shiraz, particularly if the phloem ceases functioning at high osmotic potentials near maximum weight. Backflow could account for a weight loss of 43 mg per day in Shiraz berries for a relatively small gradient of 0.1 MPa.     

Fiber in Breakfast Cereals

Ready-to-eat breakfast cereals were surveyed and their fiber contents were determined by the neutral-detergent fiber (NDF) method (AACC first approval method 32–20). The samples were bought in local markets except for 135 samples representing 15 brands that were obtained directly from the manufacturer. Eighty-one brands of cereal totaling 410 samples were tested. Average NDF values ranged from 0–31%. The distribution of average NDF values indicates that 75.3% of the brands contained less than 5% fiber. Nested analysis of variance of fiber values shows that more than 99% of the variance can be attributed to differences among brands.