In Vitro Packaging of UV Radiation-Damaged DNA from Bacteriophage T7

When DNA from bacteriophage T7 is irradiated with UV light, the efficiency with which this DNA can be packaged in vitro to form viable phage particles is reduced. A comparison between irradiated DNA packaged in vitro and irradiated intact phage particles shows almost identical survival as a function of UV dose when Escherichia coli wild type or polA or uvrA mutants are used as the host. Although uvrA mutants perform less host cell reactivation, the polA strains are identical with wild type in their ability to support the growth of irradiated T7 phage or irradiated T7 DNA packaged in vitro into complete phage. An examination of in vitro repair performed by extracts of T7-infected E.coli suggests that T7 DNA polymerase may substitute for E. coli DNA polymerase I in the resynthesis step of excision repair. Also tested was the ability of a similar in vitro repair system that used extracts from uninfected cells to restore biological activity of irradiated DNA. When T7 DNA damaged by UV irradiation was treated with an endonuclease from Micrococcus luteus that is specific for pyrimidine dimers and then was incubated with an extract of uninfected E. coli capable of removing pyrimidine dimers and restoring the DNA of its original (whole genome size) molecular weight, this DNA showed a higher packaging efficiency than untreated DNA, thus demonstrating that the in vitro repair system partially restored the biological activity of UV-damaged DNA.     

Dietary regulation of mammary lipogenesis in lactating rats.

The proportion of medium-chain fatty acids (C8:0, C10:0 and C12:0) in rat milk increased significantly between day 4 and day 8 of lactation and for the remainder of lactation these acids comprised 40-50mol% of the total fatty acids. The milk fatty acid composition from day 8 was markedly dependent on the presence of dietary fat and altered to include the major fatty acids of the fats (peanut oil, coconut oil and linseed oil). The distribution of fatty acids made within the gland, however, was independent of dietary lipid and C8:0, C10:0 and C12:0 acids accounted for over 70% of the fatty acids made. The rates of lipogenesis in both the mammary gland and liver determined in vivo after the administration of 3H2O were affected by the presence of dietary lipid. In the mammary gland the rate for rats fed a diet containing peanut oil for 7 days was only one fifth that for rats fed a fat-free diet. Coconut oil also suppressed lipogenesis. Both dietary fats also suppressed lipogenesis in the liver.     

Plasma levels of norethisterone measured by radioimmunoassay and gas chromatography-mass fragmentography

Assays designed to quantitate the plasma levels of norethisterone (NET) are compared. Results from radioimmunoassay were compared with those from gas chromatography-mass fragmentography which were established in 5 subjects after a 1-mg oral dose of the steroid. In general, the levels of steroid measured by radioimmunoassay were usually higher than those measured by gas chromatography-mass fragmentography; there was however a correlation coefficient of .96 (P .001). For concentrations of the steroid above 500 pg/ml, the mean overestimate by radioimmunoassay was less than 30%.     

Brugia malayi microfilaraemia in mice: a model for the study of the host response to microfilariae

Microfilariae of Brugia malayi were obtained from the peritoneal cavities of infected gerbils and were then injected intravenously into mice. A sub-periodic, nocturnal microfilaraemia was produced. The level of microfilaraemia was proportional to the number of parasites injected, with approximately 1-3% of microfilariae being found in the peripheral circulation. The duration of microfilaraemia was proportional to the number of parasites injected; it subsided by 30 days after injection of 104 microfilariae but was still present at a low level 120 days after injection of 2 x 105 microfilariae. A transient splenomegaly developed after injection of microfilariae. Histopathological examination revealed large numbers of microfilariae free in the lumens of pulmonary small blood vessels and without any accompanying inflammatory reaction. Lesser numbers of microfilariae were seen in the cardiac blood and hepatic and renal blood vessels for the first few days after injection. There was cellular proliferation in the splenic white pulp and vascular congestion of the red pulp. Microfilariae labelled with 51Cr were injected intravenously; 57% of radioactivity was found in the lungs, 8.5% in the liver and 2.9% in the spleen. Mice developed immediate hypersensitivity reactions to B. malayi antigen by 4 weeks after injection, but Arthus and delayed hypersensitivity reactions were not seen at any time. when mice which had been injected 5 months previously were challenged with a 2nd injection of microfilariae, there was an accelerated clearance of parasites over 2 weeks and a marked peripheral blood eosinophilia developed. In contrast with natural infections, in which the continuous production of microfilariae complicates assessment, this model provides a system in which factors controlling the circulation of microfilariae in the bloodstream can be studied independently.     

Social status and season of birth: a study of a metropolitan area in the southeastern United States

An analysis of live birth statistics obtained from the Health Department of Fulton County, Georgia for 1967-1977 indicated that seasonal variation in birth was significantly related to maternal social status. Mothers were assigned to social status classification on the basis of whether they lived in an upper, upper middle, lower middle, or lower socioeconomic census tract. Periodic regression analysis and analysis of variance was applied to the data. Specific findings were 1) upper status groups showed no significant variation in births; 2) upper and lower middle classes showed a similar and a significant degree of seasonal variation with depressed birth levels from January-June and elevated levels from July-December; 3) lower class birth patterns showed more seasonal variation than the other classes; 4) the periodic curve accounted for 92.3% of the monthly variation in births for the lower class, 70.6% for the lower middle class, and 64.6% for the upper middle class; 5) the relationship between social status and seasonal variation in births held for both whites and non-whites; 6) seasonal variations were somewhat more marked for non-whites than for white in the lower and lower middle class; and 7) the observed relationship held throughout the 11 year period of observation. The results were of special concern given previous studies which found that children born in September-October entered school on the average earlier than other children and did less well in school than other students. Major findings were presented in graphic and tabular form.     

Volatilization of mercury byThiobacillus ferrooxidans

Thiobacillus ferrooxidans became significantly more tolerant to mercury stress after culturing in media of increasing mercury(II) concentrations. When mercuric chloride was added to the growth medium, the resistant organisms were found to volatilize elemental mercury (Hg⁰).T. ferrooxidans may be an important factor in the natural mercury cycle, since the environments whereT. ferrooxidans is found typically contain elevated levels of heavy metals, including mercury.     

Interaction of cadmium and zinc during prenatal development in the rat

Cadmium chloride, zinc chloride, or a mixture of the two, labeled with 115m-Cd or 65-Zn was administered intraperitoneally to Wistar rats on day 9 of gestation. On day 20 fetuses of Cd-treated rats exhibited malformations, but those of rats given zinc or zinc plus cadmium did not. No radioactive cadmium was recovered in the fetuses or fetal membranes, although some was found in the placentas. Simultaneous administration of zinc did not alter the distribution of cadmium, but cadmium significantly increased the amount of zinc in the fetus and placenta. In a second experiment, cadmium or cadmium plus zinc was administered on day 9 of gestation and embryonic units were removed on days 10, 11, and 12. On day 10 cadmium was found in the embryonic unit and maternal uterus, and cadmium in both was significantly reduced by simultaneous administration of zinc. The cadmium concentration in uterus and embryonic units decreased sharply on day 11 and 12 and by day 12 did not differ in animals treated with cadmium or with cadmium plus zinc. It is concluded that cadmium reaches the placenta or embryo at an organogenetically sensitive time, and that zinc may protect the embryo by decreasing the exposure to cadmium this time.