Reversed-phase liquid chromatographic investigation of UV-absorbing low-molecular-weight compounds in saliva

The reversed-phase mode of high-performance liquid chromatography was used to determine the intra- and inter-individual levels of UV-absorbing low-molecular-weight compounds in saliva. Many of the compounds known to occur in serum were also found in saliva; however, concentrations in saliva are lower. Both the intra- and inter-individual levels of these compounds vary significantly; in most cases, the inter-individual variance is 2–3 times the intra-individual variance.

Caffeine and its metabolites in saliva are also reported. A greater number of metabolites were found in the saliva of habitual coffee drinkers. After caffeine was administered orally, paraxanthine, theobromine, theophylline, 1-methylxanthine, and 1-methyluric acid were found in the saliva of an individual who did not drink coffee regularly. In this subject, the serum half-life for caffeine was 3.49 h and the saliva half-life was 3.27 h. The half-life of caffeine in an habitual coffee drinker who had refrained from caffeine products for four days was 4.39 h.     

Both strands of polyoma DNA are replicated discontinuously with ribonucleotide primers in vivo

Nascent polyoma DNA molecules were isolated after pulse-labeling of infected murine 3T6 cells with [3H]thymidine. The extent of digestion of these DNA molecules by spleen exonuclease was increased by exposure to alkali or RNase, suggesting that ribonucleotides were present at or near the 5' terminal of the newly synthesized pieces of DNA. Intermediates shorter than 300 nucleotides were hybridized to the separated strands of restriction enzyme fragments of the polyoma genome: 2.5 to 3-fold more radioactivity was found in the strand whose synthesis is necessarily discontinuous (the lagging strand) than in the strand whose synthesis is potentially continuous (the leading strand) than in the strand whose synthesis is potentially continuous (the leading strand). Separation of the strands of [5'-32P]DNA molecules showed that the excess [3H]thymidine in lagging-strand molecules was not simply the result of an increased number of molecules. Therefore, assuming equivalent efficiencies of labeling, lagging-strand pieces must be slightly longer than those with leading-strand polarity. The presence of ribonucleotides on the 5' termini of molecules with both leading- and lagging-strand polarity was demonstrated by (i) release of 32P-ribonucleoside diphosphates upon alkaline hydrolysis of [5'-32P]DNA separated according to replication polarity and (ii) the change in the degree of self-annealing of nascent molecules upon preferential degradation of DNA molecules possessing initiator RNA moieties by spleen exonuclease. We conclude that replication of polyoma DNA in vivo occurs discontinuously on both sides of the growing fork, using RNA as the major priming mechanism.     

Comparison of high-performance liquid chromatographic serum profiles of humans and dogs

The sera of 30 healthy male beagles were analyzed by reversed-phase high-performance liquid chromatography. The profiles were compared with those obtained from the sera of 30 healthy human donors. The chromatograms of each group were very reproducible; however, there were characteristic differences between the two groups. The compounds observed in both the human and canine profiles were identified as creatinine, uric acid, tyrosine, hypoxanthine, xanthine, kynurenine, inosine and tryptophan. Compounds present only in the canine profiles were identified as cytindine, riboflavin and 5-methylcytidine. Compounds present only in the human profiles include uridine, guanosine, hippuric acid and the dietary dependent compounds theobromine and caffeine. The compounds present in both human and canine sera were quantitated and compared statistically. The amounts of these compounds were very similar, except for uric acid.     

The single tryptophan residue of human placental lactogen. Effects of modification and cleavage on biologic activity and protein conformation

In order to define further the chemical features of the human placental lactogen (hPL) molecule responsible for its lactogenic activity, two derivatives of the hormone were prepared by treatment with BNPS-skatole (2-nitrophenylsulfenyl)-3-methyl-3'-bromoindolenine). At a molar ratio of reagent to hPL of 7:1, a derivative was produced in which the single tryptophan was completely oxidized. At higher ratios, a second derivative was formed in which the peptide chain was cleaved at the tryptophan residue and the two resulting fragments remained bound by the disulfide bond between Cys53 and Cys165. Oxidation of the single tryptophan resulted in reduced immunologic activity, reduced helical content as measured by circular dichroism below 240 nm, and changes in the near-UV circular dichroic spectrum, each indicating a change in the conformation of the hPL molecule. Nevertheless, this derivative retained 20% of its ability to bind to lactogenic receptors and 40 to 50% of its ability to stimulate N-acetyllactosamine synthetase in vitro. Cleavage at the tryptophan was not complete, but the loss of immunologic and biologic activity was equivalent to the degree of cleavage, indicating that the cleaved derivative was completely inactive. In addition, separation of the cleaved fragments from intact hormone followed by recombination did not generate any immunologic or biologic activity. We conclude that the single tryptophan of hPL is not essential for the biologic activity of hPL. It is likely that the reduced activity associated with modification or cleavage at the tryptophan residue is due to changes in the conformation of the molecule.     

The length of the Y chromosome in Nubian males and its location in metaphase spreads

Summary A total of 242 metaphase plates from the peripheral blood of Nubian males living near Aswan, Egypt were studied with respect to the length of the Y chromosome and its location in metaphase spreads. The length of the Y was similar to that found in American Negroes, and the Y chromosome was peripherally located in 79 of the 242 cells.     

Independent temporal expression of two N-substituted aminoacyl-tRNA hydrolases during the development of Artemia salina.

Encysted embryos of the crustacean Artemia salina contain an enzymatic activity which hydrolyzes N-acetylphenylalanyl-tRNA to N-acetylphenylalanine and tRNA. The enzyme apparently does not hydrolyze other free or N-substituted aminoacyl-tRNAs. The levels of this enzyme do not significantly change during embryonic and early larval development. In contrast, an unspecific hydrolase active on several N-substituted aminoacyl-tRNAs is practically absent in the encysted embryos and during embryogenesis and appears abruptly during larval development. The independent temporal expression of these two hydrolases during Artemia salina differentiation makes this organism siuitable for the study of the physiological role of these enzymes.     

Human chromosomes. Evidence for autosomal sexual dimorphism.

The karyotypes of 100 males and 100 females, each assembled by the trypsin banding method, are examined in a study designed to investigate sex differences among autosomes. It is shown that female autosomes are consistently longer than those of the males, with respect to both the short and long arm measurements. In addition, discriminant analysis is used to distinguish between the male and female karyotypes. We find that, using autosomal measurements alone, this can be done with a high probability of success.