Flavor and Texture of Cottage Cheese Made by Direct-Acid-Set and Culture Methods 1

Consumers were asked to indicate a flavor and texture preference for one of two creamed and salted small-curd cottage cheeses made by direct-acid-set or conventional short-set culture methods. When a commercial starter distillate flavor was added to direct-acid-set cheese, its flavor and texture were preferred over cheese made by the culture method. Conversely, when flavor was not added to the direct-acid-set cheese, consumers preferred the flavor and texture of the cultured product. Differences among mean flavor or texture scores of three age groups were not significant (< 20, 20-40, > 40). Preferences for texture appeared to be biased by flavor.

Metabolism and covalent binding of benzo[alpha]pyrene in human peripheral lung

Short-term organ cultures of peripheral lung from lung cancer patients metabolise benzo[alpha]pyrene to ethylacetate-soluble metabolites, which covalently bind to tissue macromolecules. The nature and quantities of metabolites formed and the extent of covalent binding are dependent upon the time of incubation, the substrate concentration and interindividual variability in the metabolic activity of the lung. Individuals whose lungs rapidly metabolise the carcinogen exhibit more extensive further metabolism of primary metabolites and higher levels of covalent binding. Certain striking differences in the relative retention in the tissue or release into the extra-cellular medium of different metabolites have been found as illustrated by the observation that the ratio of 7,8-dihydro-7,8-dihydroxybenzo[alpha]-pyrene to 9,10-dihydro-9,10-dihydroxybenzo[alpha]pyrene was always significantly higher in the tissue than in the extracellular medium.

Importance of conjugation reactions in determining the qualitative nature of polycyclic aromatic hydrocarbon-DNA interactions

Polycyclic aromatic hydrocarbons are metabolically activated by microsomal enzymes to reactive metabolites which covalently bind to DNA. The qualitative and quantitative nature of the hydrocarbon-deoxyribonucleoside adducts formed are markedly dependent on the balance of the oxidative and conjugating enzymes present in the activation system. Thus, utilising rat liver microsomes, to metabolically activate benzo(a)pyrene, the major hydrocarbon-deoxyribonucleoside adduct formed is due to metabolic activation of 9-hydroxybenzo(a)pyrene. In striking contrast to this when isolated rat hepatocytes are used to metabolically activate [3H]-benzo(a)pyrene, 9-hydroxybenzo(a)pyrene is conjugated primarily with UDPglucuronic acid and the major hydrocarbon-deoxyribonucleoside adduct formed is due to further metabolism of 7,8-dihydro-7,8-dihydroxybenzo(a)pyrene. Thus the balance and nature of conjugating enzymes present in a tissue will, by determining the nature and amounts of adducts formed, also modulate the biological susceptibility of a particular tissue or cell. In this regard it may be of particular interest that whereas in isolated rat hepatocytes and short-term organ cultures of rodent lung and trachea conjugation with UDPglucuronic acid is quantitatively the major route of conjugation, with short-term organ culture of human lung, sulphate ester conjugation of phenolic substrates appears to be a major route of metabolism. Thus in vivo or in microsome or cell mediated mutagenesis assays of polycyclic aromatic hydrocarbons the susceptibility of a particular cell or tissue will be dependent in part on the relative activities of the oxidative and conjugating enzymes.

Large interindividual variations in metabolism of benzo(alpha)pyrene by peripheral lung tissue from lung cancer patients

A very large variation (44-fold) was observed in the ability of short-term organ cultures of peripheral lung tissue from lung-cancer patients to metabolize the environmental carcinogen benzo(alpha)pyrene to organic solvent-soluble metabolites. The amounts of benzo(alpha)pyrene (2 microM) metabolized ranged from little (1%) to almost total (96.2%) metabolism within 24 h of culture. Previous work by Kellerman et al. (1973) has suggested a relationship between susceptibility to lung cancer and the indicibility of aryl hydrocarbon hydroxylase activity in cultured human lymphocytes. The metabolic fate of carcinogenic polycyclic aromatic hydrocarbons in the respiratory tract in vivo is undoubtedly more closely mimicked by short-term organ culture of human lung than by cultured lymphocytes. Thus the very wide interindividual variation observed in pulmonary metabolism of benzo(alpha)pyrene in this study and the large variations in covalent binding to human bronchial DNA observed by Harris et al. (1976) strongly suggest that there may be little basis for screening humans for variations in lymphocyte aryl hydrocarbon hydroxylase activity as a means of assessing their susceptibility to lung cancer.

The influence of dose on the pattern of conjugation of phenol and 1-naphthol in non-human primates

1. The pattern of conjugation of phenol and 1-naphthol was investigated in several primates; three Old World species (rhesus, cynomolgus, patas monkeys), two New World species (capuchin, tamarin), and two prosimians (bushbaby, tree shrew). 2. Following intra-muscular phenol or 1-naphthol (10 mg/kg), sulphation was the major conjugation in the Old World monkeys and prosimians, whereas glucuronidation predominated in the New World species. 3. In rhesus and cynomolgus monkeys, sulphation decreased as dose increased, but remained the major conjugation with both substrates at dose levels of 0.01 to 25 mg/kg. 4. In the capuchin, the conjugation pattern of phenol changed markedly as dose increased; at 0.01 and 1 mg/kg sulphation was the major conjugation, whereas at 10 and 25 mg/kg glucuronidation predominated. With 1-naphthol only small amounts of sulphate were excreted; glucuronic acid conjugation was the major metabolism at all four dose levels. 5. The importance of considering both substrate and dose when making inter-species comparisons, particularly with man, is discussed.

Undernutrition and immunity: smallpox vaccination in chronically starved, undernourished subjects and its immunologic evaluation

This study illustrates the specific immune response of chronically starved, undernourished adults after inoculation of live smallpox vaccine. It produced no adverse effect, and major vaccinial reaction was observed in all. 63% of undernourished individuals showed a fourfold or greater rise of the neutralizing antibody titre. In contrast, only 9% of normal healthy subjects could show similar response. However, the prevaccination titre was much lower in the undernourished group than in the control group, and the postvaccination titre also remained persistently lower in the former than in the latter group. Furthermore, whereas the specific humoral antibody response in the undernourished subjects was partially adequate, the development of specific cellular immunity against vaccinia was remarkably poor, indicating that smallpox vaccination in these subjects might be less effective against variola infection. This observed profound effect of chronic starvation and severe undernutrition on the immune apparatus was possibly multifactorial, protein depletion being the most important factor, as proved by the significantly low serum albumin level. The significantly low peripheral blood lymphocyte count and spectacular unresponsiveness to many antigens in these individuals suggested profound depression of the thymolymphatic system. Further, the significantly low level of neutralizing antibody in the malnourished subjects suggested that the formation of this protective antibody might necessitate the cooperation of T lymphocytes.