Effects of diphenyl ether herbicides on porphyrin accumulation by cultured hepatocytes

Several diphenyl ether herbicides, such as acifluorfen methyl, have been previously shown to cause large accumulations of the heme and chlorophyll precursor, protoporphyrin, in plants. Lightinduced herbicidal damage is mediated by the photoactive porphyrin. Here we investigate whether diphenyl ether herbicides can affect porphyrin synthesis in rat and chick hepatocytes. In rat hepatocyte cultures, protoporphyrin, as well as coproporphyrin, accumulated after treatment with acifluorfen or acifluorfen methyl. Combination of acifluorfen methyl with an esterase inhibitor to prevent the conversion of acifluorfen methyl to acifluorfen resulted in a greater accumulation of porphyrins than caused by acifluorfen methyl or acifluorfen alone. In vitro enzyme studies of hepatic mitochondria isolated from rat and chick embryos demonstrated that protopor-phyrinogen oxidase, the penultimate enzyme of heme biosynthesis, was inhibited by low concentrations of acifluorfen, nitrofen, or acifluorfen methyl with the latter being the most potent inhibitor. These findings indicate that diphenyl ether treatment can cause protoporphyrin accumulation in rat hepatocyte cultures and suggest that this accumulation was associated with the inhibition of protoporphyrinogen oxidase. In cultured chick embryo hepatocytes, treatment with acifluorfen methyl plus an esterase inhibitor caused massive accumulation of uroporphyrin rather than protoporphyrin or coproporphyrin. Specific isozymes of cytochrome P450 were also induced in chick embryo hepatocytes. These effects were not observed in the absence of an esterase inhibitor. These results suggest that diphenyl ether herbicides can cause uroporphyrin accumulation similar to that induced by other cytochrome P450-inducing chemicals such as polyhalogenated aromatic hydrocarbons in the chick hepatocyte system.     

Calcium-sensitive cells of the pars intermedia and osmotic balance in the eel

Summary The structure of the PAS-positive calcium-sensitive (Ca-s) cells of the pars intermedia was investigated in eels kept in deionized water (DW) or fresh water (FW) supplemented with Ca²⁺ or Mg²⁺. Ca²⁺ (2mM) reduces considerably the response to DW; plasma osmolarity, Na⁺ and Ca²⁺ levels are not significantly affected. In eels adapted to DW for 21 or 28 days, showing highly stimulated Ca-s cells, an addition of CaCl₂ for 2 days inhibits the release of granules, but does not immediately block their synthesis and the mitotic activity. The nuclear area is reduced, osmolarity and plasma sodium increase, but the rise in calcium is not always significant. Magnesium, at a 10-fold greater concentration than in FW (2 mM), slightly inhibits the release of secretory granules without reducing other indicators of stimulation. In Ca-enriched FW, the Ca-s cells appear inactive. These data show that the PAS-positive cells in the pars intermedia of the eel are calcium-sensitive, similar to those of the goldfish; their role in calcium regulation is briefly discussed.     

Distribution of lipid synthesizing enzymes, 2′,3′-cyclic nucleotide 3′-phosphodiesterase,and myelin proteins in rat forebrain subfractions during development

The distribution of UDP-galactose: ceramide galactosyltransferase (CGalT) was studied in subcellular fractions of rat forebrain during development using zonal centrifugation on linear gradients. Specialized subfractions: SN 1, a microsomal fraction, SN 4, a myelin-related fraction, and purified myelin were also used for this study. For comparison, two microsomal lipid synthesizing enzymes, a myelin-specific enzyme, 2,3-cyclic nucleotide 3-phosphodiesterase and myelin proteins were measured in the same subfractions. UDP-glucose: ceramide glucosyltransferase and cerebroside sulfotransferase were confined to microsomes. CGalT was ferase and cerebroside sulfotransferase were confined to microsomes. CGalT was localized in microsomes, but also in myelin and myelin-related fractions. The developmental change in distribution of CGalT in adult animals toward myelin containing fractions could indicate that the replacement of galactosylceramide in compact myelin could be carried out in close proximity to compact myelin (mesaxon, paranodal loops) rather than in the distant oligodendrocyte perikaryon.     

Characterization ofκ-casein and keratin domains in fibrinogen

Summary Following the observation of a close sequence homology between the N-terminal moiety of the -chain of fibrinogen with large parts of-casein, the occurrence of a keratin domain in the middle section of the Achain is suggested.     

Identification of rat neurophysins: Complete amino acid sequences of MSEL- and VLDV-neurophysins

Two rat neurophysins have been purified by salt precipitation, molecular sieving and ion-exchange chromatography. The proteins, performic-acid oxidized or reduced-alkylated, have been split either by trypsin or by staphylococcal proteinase and fragments have been separated by peptide mapping. Amino acid sequences of tryptic peptides have been determined either directly or after cleaving the large fragments by subtilisin, chymotrypsin, elastase or staphylococcal proteinase and characterizing the subfragments. Tryptic peptides have been ordered through the fragments given by staphylococcal proteinase. The N-terminal sequences of both proteins have also been established by automated degradation.The two usual types of mammalian neurophysins have been identified. One neurophysin belongs to the MSEL-neurophysin family and shows 11 substitutions and a 2-residue C-terminal truncation when compared with bovine MSEL-neurophysin. The other belongs to the VLDV-neurophysin family and shows 8 substitutions when compared with bovine VLDV-neurophysin. There are 23 differences between the MSEL- and VLDV-neurophysins of the rat.     

Hybridization of a mouse T-cell lymphocyte line (HB1) with a polyoma virus-transformed mouse fibroblast line

The establishment of permanent T-lymphocyte cell lines by transformation with DNA viruses has not yet been achieved. This paper reports the successful transfer of polyoma virus genome into T-lymphocyte cells by somatic hybridization. A T-lymphocyte clone, HB₁, derived from (DBA/ 2J×AKR) spleen cells, isolated in vitro by cloning in semi-solid agar, was fused with a polyoma (Py) virus-transformed fibroblast C3HPy, clone 1. The authenticity of the hybrid C3H/HB was established by chromosome and histocompatibility antigen studies. This initial population and the various clones retained T-lymphocyte characteristics such as morphological appearance, growth properties (suspension culture) and differentiation antigen (Thy 1–2). The hybrid cell line and the various clones presented all the characteristics of Py transformation. Namely, they carried the Py genome originating from the fibroblastic parent and maintained Py virus tumour-associated antigens (TSTA, TSSA and T antigens). In most respects, this hybrid population resembled the C3HPy/C11 parent and exhibited the same tumorigenicity.     

Absence of nucleolar dominance in mouse-human heterokaryons

Autoradiographic analysis of [³H]uridine incorporation 48 h after polyethylene glycol-mediated cell fusion indicates that nucleolar RNA synthesis persists in both human and mouse nuclei in interspecific heterokaryons. The absence of nucleolar dominance in heterokaryons has been confirmed by zinc-dithizone nucleolus-specific staining, and is true even when there are considerably more nuclei of one species than of the other in the heterokaryon. Studies of actinomycin D-induced nucleolar segregation indicate that the zinc-binding proteins responsible for zinc-dithizone staining are located in a different nucleolar component than the protein responsible for silver staining.     

Effets à long terme de 4 détersifs chez le pulmoné d'eau douce Lymnaea stagnalis L.: Intoxication des adultes

Detergents added to the rearing water of the molluscLymnaea induce a sharp mortality of all the animals of each experimental group after a variable delay, depending upon the nature of the detergent and its concentration.No important perturbation of the shell growth is noted with the cationic detergent; conversely a light decrease is observed with the anionic detergents and a very severe effect is induced by a commercial washing mixture.The fecundity is always reduced by the detergents: the number of egg-masses per snail and the number of eggs per mass are diversely changed according to the products.In many cases the egg fertility is decreased and the duration of embryogenesis is increased. For each detergent the reduction of the biological yield ofLymnaea is calculated and the curves drawn allow to classify these detergents according to their chemical nature: among the anionic detergents, A has a low toxicity, B and P are characterized by higher toxicities and the cationic detergent is strongly toxic.

     

Biochemical markers in a species endangered by introgression: The red wolf

The red wolf (Canis rufus), native to much of the southeastern United States, is endangered by man's activities and by hybridization with other species of the genus Canis. The absence of diagnostic morphological markers to distinguish the red wolf from its hybrids has led to the application of the methods of biochemical genetics to this problem. The finding of a unique electrophoretically determined allele with a distribution congruent with the geographical distribution of the remaining red wolf population is reported.This research was supported by NIH Public Health Service Grants GM 19513 and CA 19311 and by the State of Texas.