Restriction sites containing CpG show a higher frequency of polymorphism in human DNA

Unique loci in the human genome were examined with restriction enzymes in order to detect restriction fragment length polymorphisms (RFLPs). Of 31 arbitrary loci, nine were detectably polymorphic, reflecting ten polymorphic restriction sites. Nine of the ten polymorphic sites were revealed with two restriction enzymes, Msp I and Taq I, whose recognition sequences have in common the dimer sequence CpG. The cytosines in the CpG sequence are known to be frequently methylated in mammals, and the occurrence of significant variation in Msp I and Taq I sites supports the view that methylated cytosine residues are hotspots for mutation in mammalian DNA.     

Induction of activated macrophages in C3H/HeJ mice by avirulent Salmonella

A single injection of viable Salmonella typhimurium SL3235, an avirulent organism blocked in the aromatic pathway, induced the generation of activated peritoneal macrophages in three different C3H mouse strains, including macrophage-defective C3H/HeJ mice. Macrophages obtained from immunized mice were cytotoxic for B16 melanoma cells, P815 mastocytoma cells, and TU-5 fibrosarcoma cells and microbicidal in vitro for the obligate, intracellular, protozoan parasite Leishmania major. The capacity of live SL3235 to activate C3H/HeJ macrophages contrasts with the failure of live Bacillus Calmette-Guérin to induce activated macrophages in this mouse strain. Although viable SL3235 were capable of fully activating cells of both normal and defective mice, a dose-dependent difference was observed in the number of organisms necessary for induction of tumoricidal macrophages in C3HeB/FeJ (normal) and C3H/HeJ (defective) animals. As few as 80 viable SL3235 were capable of activating C3HeB/FeJ macrophages whereas 5 X 10(4) organisms were required to activate C3H/HeJ macrophages. Maximal macrophage activation occurred 7 to 10 days after SL3235 inoculation in C3H/HeJ and C3HeB/FeJ mice. Acetone-killed cells of SL3235 had some but not all of the activity of the living Salmonella. A single in vivo injection of the nonviable preparation resulted in the induction of tumoricidal macrophages in C3HeB/FeJ but not in C3H/HeJ mice, even when tested over a wide dosage range. Injection of acetone-killed cells of SL3235 did, however, result in a population of primed macrophages in C3H/HeJ mice, as explanted cells could be induced to express activated macrophage effector activities after additional treatment in vitro with either LPS or IFN-gamma. Thus, in vivo administration of viable SL3235 is, by itself, capable of eliciting the full series of steps required for activation of C3H/HeJ macrophages, whereas killed SL3235 only provides signals sufficient to prime these defective macrophages for further activation in vitro. AI 15613     

Demonstration of a beta-casomorphin immunoreactive material in the plasma of newborn calves after milk intake

Blood was collected from newborn calves before and after their first milk intake after birth; extracts of plasma were assayed by radioimmunoassay for the presence of beta-casomorphin-7 immunoreactive materials. No beta-casomorphin immunoreactivity was found in samples collected before milk ingestion; however, in samples collected after milk ingestion a beta-casomorphin-7 immunoreactive material was detected. Chromatographic characterization showed that this material was not identical with beta-casomorphin-7 but might rather represent a precursor thereof. The material proved resistant to enzymatic attack during a 30-min incubation period at 37 degrees C in the plasma of newborn calves, whereas beta-casomorphin-7 was degraded under these conditions. A physiological significance of beta-casomorphin-7 eventually cleaved from such a precursor material at any site in the newborn mammal is suggested.     

The effect of reversal of Na and K electrochemical potential gradients on the active transport of amino acids in Ehrlich ascites tumor cells

1.

1. The net uptake of α-aminoisobutyric acid (AIB) in Ehrlich ascites tumor cells has been studied under a variety of transmembrane concentration gradients of Na⁺, K⁺ and AIB itself.     

Glycosaminoglycan composition of human amniotic fluid

The glycosaminoglycan composition of human amniotic fluid between 12–21 weeks gestation has been studied by Dowex column chromatography coupled with enzymatic analyses of the specific glycosaminoglycan in each column fraction. The total uronic acid recovered from the columns consisted of “glycopeptides” (7%), hyaluronic acid (34%), nonsulfated chondroitin (14%), chondroitin-4-sulfate (13%), chondroitin-6-sulfate (20%), dermatan sulfate (5%), and heparan sulfate (6%). Based on these studies a simple screening procedure was devised to detect increased quantities of heparan sulfate and dermatan sulfate in 5–10-ml samples of amniotic fluid and tested in the antenatal diagnosis of Hurler and Hunter's syndrome. A false negative result was recorded in a Hunter fluid obtained early gestation and a false positive result recorded in a normal fluid obtained at weeks. These data suggest that the time in gestation when amniotic fluid is sampled for chemical analysis is an important variable affecting glycosaminoglycan composition in both normal and pathological pregnancies.     

Ion balance in tomato cultivars differing in salt tolerance. I. Sodium and potassium accumulation and fluxes under moderate salinity

The magnitude of sodium and potassium fluxes in Lycopersicon escutentum cuhivars Ace and Edkawi (Edkawi is considered more sait-tolerant I was evaluated in planls grown for 10 days in aerated Hoagland solution with the addition of 25 or 100 mM NaCl. Ion accumulatiun in different plant pans, ion concentration in xylem exudate. transpiration and membrane leakiness were measured. Both cultivars responded very similarly to these levels of salinity in terms of growth. No conspicuous differences in membrane leakiness were observed. Net uprake rates were calculated from ion contents data. Potassium uptake rates were lower in salinized planls than in controls, especially in cv. Aee. Potassium/sodium selectivity ratios were much higher in Edkawi than in Ace. and higher in shoot uptake rates than in xy lem exudate. This indicates that Edakw i has a higher capacity to retain potassium under salinity, a character which could contribute to its salt-tolerance.