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.     

Chemotaxonomic significance of the xanthomonadins,novel brominated aryl-polyene pigments produced by bacteria of the genus Xanthomonas

The cell pigments produced by strains of Xanthomonas spp. (including representatives of all five presently recognized taxospecies of these phytopathogenic bacteria) have been isolated as isobutyl esters, purified, and characterized in terms of electronic absorption, chromatographic and co-chromatographic, and mass spectrometric properties. This comparative examination reveals that these bacteria produce brominated aryl-polyene pigments which are given the trivial name xanthomonadins. The several xanthomonadins usually occur as mixtures which have been resolved by chromatography and sorted into several Pigment Groups, thus enabling a more rational approach in our on-going systematic study of their exact chemical structures and biosynthesis. From what is presently known, some of the xanthomonadins might differ from xanthomonadin I, the exact structure of which has previously been determined in material from Xanthomonas juglandis ICPB XJ103, by their being monobrominated (rather than dibrominated, as is xanthomonadin I), by their having the equivalent of one methyl group less than does xanthomonadin I, and/or in other ways. The pigments of Xanthomonas ampelina (a little known and possibly questionable member of this genus) seem somewhat different from the pigments of the other Xanthomonas spp. The ability to form these distinctive xanthomonadin pigments is a useful chemotaxonomic marker for the genus Xanthomonas, since such pigments are not known to be formed by taxonomically or ecologically adjacent bacteria. Sufficient characterization of this assemblage of xanthomonadin pigments is presented so that they can be isolated and identified routinely on the basis of the aforementioned properties.     

Correlation between active rosette formation and delayed cutaneous hypersensitivity in experimental allergic encephalomyelitis

The effect of encephalitogenic myelin basic protein, BP, on active rosette-forming T cells (ARFC) was compared to that of nonencephalitogenic peptide S42, a synthetic analogue of the tryptophan region of BP. Depression of ARFC by these antigens was reversible within 24 h after a second dose of the antigen into the skin, or after in vitro incubation of lymphocytes with the sensitizing antigen (Ag-ARFC). The ratio of Ag-ARFC to ARFC rose with time following the sensitization but fell shortly before the clinical onset of experimental allergic encephalomyelitis in animals sensitized with BP. In contrast, the Ag-ARFC/ARFC ratios for animals sensitized with peptide S42 reached plateau levels from which they did not drop. The kinetics of the Ag-ARFC/ARFC responses paralleled those for delayed-type skin hypersensitivity (DTH) in the respective animals. The DTH responses rose following sensitization and fell shortly after the appearance of clinical signs of EAE. The results of this study provide in vitro and in vivo evidence for sensitization to myelin basic protein, and focus attention on the ARFC as a measure for an immunologically active cell population which may be quantitated by antigenic stimulation.Abbreviations used in this report EAE experimental allergic encephalomyelitis - DTH delayed-type skin hypersensitivity - ARFC active rosette-forming T cells - Ag-ARFC antigen-stimulated active rosette-forming T cells - TRFC total rosette-forming T cells     

Fossil Robinia wood from the western United States

A collection of petrified wood from the Lower Pliocene Ogallala Formation in western Oklahoma was examined. All specimens appear to be of the same taxon and exhibit features of extant Robinia species. To date, four fossil wood species of Robinia have been described. The relationship of Robinioxylon zuriensis Falqui to Robinia is doubtful because of the lack of diagnostic critical features. The remaining three, Robinia alexanderi Webber, Robinia breweri Prakash, Barghoorn and Scott, and Robinioxylon zirkelii (Platen) Müller-Stoll and Mädel do show affinity to Robinia and all have been noted as structurally similar to R. pseudoacacia. The Oklahoma woods and these three fossil species show considerable overlap in quantitative features and are identical in qualitative features. Examination of different sections (and specimens) of extant Robinia pseudoacacia wood reveals quantitative and qualitative variation similar to that found amongst the petrified woods. Robinia alexanderi, Webber, R. breweri Prakash, Barghoorn and Scott, R. zirkelii (Platen) Müller-Stoll and Mädel, and the Oklahoma specimens are considered to be conspecific as the differences between these fossil wood species are no different from those accounted for by variation within a single living species, R. pseudoacacia.     

Transfer of purified herpes virus thymidine kinase gene to cultured mouse cells.

Treatment of Ltk^?, mouse L cells deficient in thymidine kinase (tk), with Bam I restriction endonuclease cleaved DNA from herpes simplex virus-1 (HSV-1) produced tk⁺ clones with a frequency of 10^?6/2 μg of HSV-1 DNA. Untreated cells or cells treated with Eco RI restriction endonuclease fragments produced no tk+ clones under the same conditions. The thymidine kinase activities of four independently derived clones were characterized by biochemical and serological techniques. By these criteria, the tk activities were found to be identical to HSV-1 tk and different from host wildtype tk. The tk⁺ phenotype was stable over several hundred cell generations, although the rate of reversion to the tk^? phenotype, as judged by cloning efficiency in the presence of bromodeoxyuridine, was high (1–5 × 10^?3). HSV-1 DNA Bam restriction fragments were separated by gel electrophoresis, and virtually all activity, as assayed by transfection, was found to reside in a 3.4 kb fragment. Transformation efficiency with the isolated fragment is 20 fold higher per gene equivalent than with the unfractionated total Bam digest. These results prove the usefulness of transfection assays as a means for the bioassay and isolation of restriction fragments carrying specific genetic information. Cells expressing HSV-1 tk may also provide a useful model system for the detailed analysis of eucaryotic and viral gene regulation.     

Histone mRNAs contain blocked and methylated 5′ terminal sequences but lack methylated nucleosides at internal positions

Histone mRNA, labeled with ³²P or ³H-methionine during the S phase of partially synchronized HeLa cells, was isolated from the polyribosomes and purified as a “9S” component by sucrose gradient sedimentation. We identified two types of 5′ terminals, m⁷G(5′)pppN^mpN and m⁷G(5′)pppN^m-pN^mpN, in which the first methylated nucleoside is 7-methylguanosine, the second is either N⁶,2′-O-dimethyladenosine, 2′-O-methyladenosine, or 2′-O-methylguanosine, and the third is 2′-O-methyluridine, 2′-O-methylcytidine, or 2′-O-methyladenosine. Approximately 1.7% of the ³²P label was present in the 5′ terminal structures. Assuming a similar specific radioactivity for all phosphates, this percentage corresponds to an average of one terminal per 335 nucleotides. Histone mRNA differed from bulk polyadenylylated mRNA of HeLa cells in lacking significant amounts of 2′-O-methyluridine or 2′-O-methylcytidine in the second position of the 5′ terminal oligonucleotide and in lacking N⁶-methyladenosine residues at internal positions.     

Regulation by the H-2 gene complex of delayed type hypersensitivity

Identity at the major histocompatibility complex (MHC) was essential for successful transfer of delayed type hypersensitivity (DTH) in mice. The regions of the MHC involved differed according to the antigen used for sensitization. In the case of fowl gamma globulin (FGG), identity atI-A was necessary, whereas with dinitrofluorobenzene (DNFB), identity at theK, I, orD region was sufficient. These different genetic constraints probably reflect differences in the mechanisms by which antigens are presented to T lymphocytes. Cells from sensitized (CBA×C57BL)F₁ mice transferred DTH to FGG into parental-strain mice, but transfer was more effective in C57BL than in CBA with the same cell dose. This phenomenon is governed by the MHC, since there was better transfer intoH-2 ^b than intoH-2 ^k mice, regardless of their backgrounds. It may reflect the activity of an Ir gene-dependent process. Cells of one genotype (e.g., CBA), sensitized in chimeric mice derived from two MHC-incompatible strains (CBAC57BL), transferred DTH to both strains. These results do not support the notion that the genetic constraint observed in DTH transfer may be a result of the necessity for sensitized T and stimulator cells to match an identical MHC-coded cell interaction molecule. Rather, they favor the hypothesis that T cells recognize antigen, not as a naked determinant, but in close association with products of genes of the MHC.     

Active transport of alpha-aminoisobutyric acid in freshly prepared rat hepatocytes

The transport of alpha-aminoisobutyric acid in freshly prepared rat liver cells was saturable and exhibited a K_t of 13.9 × 10^?3M and a_max of 28.6 umoles/ml intracellular fluid/30 min. The system required the presence of sodium and was sensitive to ouabain. Anaerobiosis, 2,4-dinitrophenol and low temperature suppressed the uptake of the amino acid. Efflux studies also indicated that the majority of the intracellular amino acid was rapidly exchangeable and therefore probably present in the cell water in a free state. It is suggested that alpha-aminoisobutyric acid is transported into isolated rat hepatocytes by an active carrier system.     

Biosynthesis of eugenol and cinnamic aldehyde in Cinnamomum zeylanicum

Incorporation of [¹⁴C]-phenylalanine and [¹⁴C]-methionine into cinnamon cuttings suggests that synthesis of eugenol from phenylalanine involves exchange of the terminal carbon in the side chain with that from a donor molecule such as methionine whereas synthesis of cinnamic aldehyde incorporates phenylalanine in toto.