Apolipoprotein E and diets: a case of gene-nutrient interaction?

Apolipoprotein E has key functions in lipoprotein metabolism, and polymorphisms in the apolipoprotein E gene are associated with distinct lipoprotein patterns. The possibility of gene-nutrient interactions for apolipoprotein E has been addressed in many studies. Although results have generally been mixed, the indications for such an interaction have been more common in studies employing a metabolic challenge. Studies directly designed to examine apolipoprotein E gene-nutrient interactions are needed.     

Role of the 2-amino group of deoxyguanosine in sequence recognition by EcoRI restriction and modification enzymes.

The dG residues within the EcoRI recognition sequence of ColE1 DNA have been selectively replaced with dI. Methylation of the altered sequence by the EcoRI modification enzyme is extremely slow as compared with methyl transfer to the natural recognition site. Since the affinity of the modification enzyme for the dI-containing sequence is considerably less than that for the natural sequence, we have concluded that the 2-amino group of dG has an important role in DNA site recognition by this enzyme. In contrast, the altered site is subject to cleavage by EcoRI endonuclease at rates essentially identical with those observed with the natural sequence. These results strongly suggest that the two enzymes utilize different contacts within the EcoRI site and are consisted with our conclusion (Rubin, R. A., and Modrich, P. (1977) J. Biol. Chem. 252, 7265-7272) that the two proteins interact with their common recognition sequence in different ways.     

The differential protection by WR2721 of skin versus growing cartilage following irradiation in weanling rats

The potential for radioprotection of growing cartilage by the thiophosphate WR2721 was evaluated in weanling rats using single fractions of irradiation. Protection of acute skin toxicity was monitored simultaneously. Single doses of 600, 1200, 1800, or 2400 cGy were administered to the left tibia of CrL:CD(SD)BR female rats in groups of 12. Identically treated groups were injected with 310 mg/kg WR2721 (2/3 the determined LD50/30) in a concentration of 26 mg/ml intraperitoneally 15 min prior to irradiation. Rats untreated or given WR2721 without radiation served as control groups. Radiographs of the irradiated and unirradiated tibiae for each animal were obtained weekly to the date of sacrifice at 80 days following the initial treatment. Skin toxicity was assessed weekly starting on the second week using Moulder's scale (J.E. Moulder, J.J. Fischer, and A. Casey, Radiology 115, 465-470 (1975]. No significant difference in bone growth as measured by tibial lengths for the WR2721-treated or untreated animals was observed. Skin toxicity including moist desquamation occurred in irradiated limbs and was substantially less in rats treated with WR2721. As opposed to previous work with cysteamine, WR2721 as administered had no significant radioprotective effect on tibial growth in weanling rats but substantially reduced the accompanying skin toxicity.     

The relationship between passive smoking and child health: methodologic criteria applied to prior studies

Most studies investigating the relationship between passive smoking and child health have found a significant effect on respiratory illness and lung function. The wide range of findings is based on diverse types of studies which use multiple criteria for respiratory illness, smoke exposure, and outcome variables. The aim of this review is to examine these studies in an attempt to focus attention on methodological criteria which relate to the strength of the association and likelihood of a causal relationship between passive smoking and child health. We examined 30 studies and judged their strength by examining (1) data collection, (2) surveillance bias, (3) definition of amount of smoking, (4) definition of illness, (5) detection bias, (6) outcome variables, and (7) control for confounding variables. Poor scores were noted in the use of "blinded" data collectors (37 percent of possible score), use of multiple specific outcome variables (51 percent), and definition of the quantity of smoking (56 percent). Good scores were noted in the detection of illnesses (98 percent), recall by study subjects of symptoms of illness (71 percent), control for confounding variables (81 percent), and definition of illnesses (86 percent). The range of scores for the studies was from 44 percent to 89 percent (of the total possible score). While a few well-designed studies demonstrate a significant effect of passive smoking on child health, most studies had significant design problems that prevent reliance on their conclusions. Thus, many questions remain, and future studies should consider important methodological standards to determine more accurately the effect of passive smoking on child health.     

Characterization of the calcium sensitivity of differentiation in SCC-13 human squamous carcinoma cells

Summary The sensitivity to calcium of the human squamous carcinoma cell line, SCC-13, was demonstrated and characterized. Cultures grown to confluence in the presence of 0.2 to 2 mM calcium had approximately 10-fold higher levels of particulate transglutaminase activity and envelope competence than those grown in low calcium (0.025 to 0.05 mM) medium. Raising the calcium from 0.025 to 1.8 mM induced expression of this enzyme and of competence over the course of a week. Conversely, for cultures grown to confluence in 1.8 mM calcium, subsequent reduction of calcium to 0.025 mM resulted in a substantial decline in transglutaminase over a similar time period. Immunoprecipitable transglutaminase was clearly identifiable in cultures grown in 1.8 mM calcium-containing medium but not in those grown in low calcium medium or in the presence of retinoic acid, suggestive of regulation at the level of mRNA accumulation or translation rather than posttranslational modification. This research was supported by Public Health Service grant AR 27130 from the National Institute of Arthritis, Musculoskeletal and Skin Diseases, Bethesda, MD, and National Research Service postdoctoral fellowship ES 05336 from the National Institute of Environmental Health Sciences, Research Triangle Park, NC.     

Protective effect of casein toward Salmonella typhimurium in acid-milk

Lactic acid is the inhibitory agent in yoghurt responsible for the inhibition of Salmonella typhimurium. Casein, however, may exert a protective effect toward the survival of the salmonella in acid-milk products. Salmonella typhimurium was found to die-off 21.2% more rapidly in 18-h yoghurt-whey than in 18-h yoghurt at 37 degrees C with a pH of 3.85 and 1.42% lactic acid. When casein was added to yoghurt-whey, the die-off rate of the salmonellas was reduced to that found in yoghurt. The rate remained unchanged when 4.8% sodium caseinate was added to the whey. When 0 to 14% casein was added to the acid-whey the die-off rate changed from 9.7 to 24.0 min/log reduction of cells, respectively. There was a direct correlation between the increase in casein concentration and length of survival of the salmonellas. At a pH of 3.85, 4.2 or 4.5, the die-off rate was 6.5, 13.0 or 40 min/log reduction of cells in milk containing 1.42% lactic acid, and was 4.0, 10.0 or 33.3 min/log reduction, respectively, in whey with 1.42% lactic acid. Thus, the protective effect of casein toward Salm. typhimurium increased as the pH increased. This indicated that casein exerts a protective effect on Salm. typhimurium in acid dairy products and the degree of protection depends on the casein concentration, the form of the casein molecule and the pH.     

Inactivation of Naegleria gruberi cysts by chlorinated cyanurates.

The resistance of Naegleria gruberi cysts to chlorine in the presence of cyanuric acid was compared at pH 5 and 7. An amperometric membrane electrode was used to measure HOCl concentrations independently of the chlorinated cyanurate species, thus permitting an analysis of the role of free chlorine versus chlorinated cyanurates in cyst inactivation. In the presence of cyanuric acid, the products of the HOCl residual and the contact time required for 99% cyst inactivation were 8.5 mg . min/liter and 13.9 mg . min/liter at pH 5 and 7, respectively. The Watson's Law coefficients of dilution (n) were 1.3 and 1.6 at pH 5 and 7, respectively. The results strongly suggest that HOCl is the predominant cysticide with no measurable cysticidal effect of the chlorinated cyanurate species.