Absence of ethanol metabolism in "acatalatic" hepatic microsomes that oxidize drugs

When liver slices of Cs^a and Cs^b mice were incubated $\text{in}\text{vitro}$, they had similar catalase activities and equal rates of ethanol metabolism. While incubated liver homogenates and microsomes from Cs^a mice oxidized ethanol and retained catalase activity, preparations from Cs^b mice did not oxidize ethanol and lost all catalase activity. Addition of beef liver catalase restored ethanol oxidation by Cs^b microsomes. The oxidations of aniline and aminopyrine proceeded at the same rate in Cs^a and Cs^b microsomes and were inhibited by ethanol. It is evident that (a) the microsomal drug-metabolizing pathway is not involved in ethanol oxidation, and (b) the postulation of a unique microsomal ethanol-oxidizing system (“MEOS”) that is independent of microsomal catalase is unwarranted.     

The ionic structure of lecithin monolayers

Surface potentials of mixed monolayers of dicetyl phosphate and eicosanyl trimethylammonium bromide (1:1) were the same on subsolutions of 0.02 M NaCl or 0.01 M CaCl(2), which indicated that ionic phosphate does not interact with Ca(++) in the presence of a neighboring trimethylammonium group. Surface potential-pH plots of dicetyl phosphate, and of dipalmitoyl, egg, and dioleoyl lecithins showed that as the pH of the subsolution is decreased the phosphate groups in the monolayer are neutralized in the order: dicetyl phosphate > dipalmitoyl lecithin > egg lecithin > dioleoyl lecithin. The binding of cations (Na(+), Ca(++)) to the phosphate group of lecithin also showed the same order. The binding of Ca(++)) to egg phosphatidic acid monolayers, as measured by the increase in surface potential, is considerably greater than that to egg lecithin. These results suggest that there is an internal salt linkage between the phosphate and trimethylammonium groups on the same lecithin molecule. An increase in unsaturation of fatty acyl chains increases the intermolecular spacing, which reduces the ionic repulsion between polar groups, and hence strengthens the internal salt linkage. The results support the concept of a vertical rather than coplanar orientation of the phosphoryl choline group with respect to the interface. A position has been proposed for Ca(++) in the dipole lattice of lecithin from a consideration of the surface potential measurements.     

Principles and applications of luminescence spectrometry coupled to liquid chromatographic techniques

An overview is presented of the physicochemical basis of luminescence, and its application to the detection of chemicals (drugs, biomedically important compounds, environmentally active substances) in liquid chromatographic systems.     

Purification and characterization of a Ca2+/calmodulin-dependent protein kinase from rat brain

A soluble Ca2+/calmodulin-dependent protein kinase has been purified from rat brain to near homogeneity by using casein as substrate. The enzyme was purified by using hydroxylapatite adsorption chromatography, phosphocellulose ion-exchange chromatography, Sepharose 6B gel filtration, affinity chromatography using calmodulin-Sepharose 4B, and ammonium sulfate precipitation. On sodium dodecyl sulfate (NaDodSO4)-polyacrylamide gels, the purified enzyme consists of three protein bands: a single polypeptide of 51 000 daltons and a doublet of 60 000 daltons. Measurements of the Stokes radius by gel filtration (81.3 +/- 3.7 A) and the sedimentation coefficient by sucrose density sedimentation (13.7 +/- 0.7 S) were used to calculate a native molecular mass of 460 000 +/- 29 000 daltons. The kinase autophosphorylated both the 51 000-dalton polypeptide and the 60 000-dalton doublet, resulting in a decreased mobility in NaDodSO4 gels. Comparison of the phosphopeptides produced by partial proteolysis of autophosphorylated enzyme reveals substantial similarities between subunits. These patterns, however, suggest that the 51 000-dalton subunit is not a proteolytic fragment of the 60 000-dalton doublet. Purified Ca2+/calmodulin-dependent casein kinase activity was dependent upon Ca2+, calmodulin, and ATP X Mg2+ or ATP X Mn2+ when measured under saturating casein concentrations. Co2+, Mn2+, and La3+ could substitute for Ca2+ in the presence of Mg2+ and saturating calmodulin concentrations. In addition to casein, the purified enzyme displayed a broad substrate specificity which suggests that it may be a "general" protein kinase with the potential for mediating numerous processes in brain and possibly other tissues.     

Purification and properties of soybean leghemoglobin messenger RNA

Poly(A)-containing leghemoglobin mRNA from soybean root nodules has been purified 84-fold, as judged by its ability to direct the in vitro synthesis of leghemoglobin in a wheat germ system. It has a poly(A) content of 8.6% and a molecular weight, estimated by formamide gel electrophoresis, of 260 000. mRNA with a molecular weight of around 143 000 would be sufficient to code for leghemoglobin. Thus, with respect to both its poly(A) content and its unexpectedly high molecular weight, leghemoglobin mRNA is similar to mRNAs isolated from animal tissues.     

Formation of a thiamine artifact during chromatography: A single column procedure for the separation of thiamine and the thiamine mono-, di-, and triphosphate esters

Chromatography of a preparation of [¹⁴C]thiamine pyrophosphate (thiamine-PP) on Dowex 1X8 in the formate form produced an unexpected peak, X-1, which was eluted just prior to the thiamine-PP peak. An ammonium formate, pH 4.5, gradient was the eluant. Rechromatography of either peak X-1 or thiamine-PP produced the same two peaks. The radioactive specific activity per micromole labile phosphate was the same for the two peaks. Peak X-1 appears to be a thiamine compound formed in the presence of formate solutions. This procedural artifact was circumvented by the substitution of acetate for formate. By varying the pH as well as the ionic strength a single column procedure has been developed that separates thiamine and the three phosphate esters quantitatively in micromolar amounts.     

Lipochromosome mediated gene transfer: Identification and probable specificity of localization of human chromosomal material and stability of the transferents

Summary Using lipochromosomes (phospholipid-entrapped chromosomes) we have transferred the human HGPRT gene into HGPRT deficient mouse cells (A9) with a frequency of approximately 1×10⁻⁵ (Mukherjee et al., Proc. Natl. Acad. Sci. USA 75: 1361–1365; 1978). Two other genes located on the long arm of the human X-chromosome were also expressed in two independently derived populations of transferents (A9/GT3 and A9/GT4). We report here the chromosomal and enzymatic composition of human HGPRT-positive clones from each subpopulation analyzed in detail with alkaline Giemsa-11 staining. All the clones expressed human PGK and HGPRT, but one (A9/GT4C6) lacked human G6PD. In each of four clones examined microscopically, a small piece of presumptive human chromatin was visible in the karyotypes of most cells. The chromatin fragment was free or attached in each cell of an individual clone. When integrated, the human chromosomal fragment in each clone appeared associated with the centromere of the same telocentric A9 chromosome (No. 6 by Q-banding). These data suggest that: (a) substantial human chromosomal fragments can be transferred into recipient cells using the lipochromosome technique; (b) clones from human HGPRT positive A9 transferent subpopulations may or may not possess other human X-linked markers; (c) the stability of lipochromosomally transferred genes varied from clone to clone and stability is generally poor in the absence of continuous selection pressure (e.g., HAT); (d) when multiple X-linked human genes were transferred to mouse cells a cytologically detectable human chromosomal fragment was identified free or attached to a host chromosome; and (e) integration of transferred human chromosomal material into mouse chromosomes may occur at preferential site(s) in the recipient genome. This research was sponsored in part by the Office of Health and Environmental Research U.S. Department of Energy under Contract W-7405-eng-26 with the Union Carbide Corporation.     

Phosphorylation of microtubule-associated protein-2 in GH3 cells. Regulation by cAMP and by calcium.

The rat pituitary cell line GH3 contains a high molecular weight microtubule-associated protein with properties characteristic of microtubule-associated protein-2 (MAP-2). The 280-kDa protein is selectively immunoprecipitated by antibodies to authentic bovine brain MAP-2 and is phosphorylated at appropriate sites by cAMP-dependent protein kinase (cAMP kinase) and multifunctional Ca2+/calmodulin-dependent protein kinase (CaM kinase). Although MAP-2 is a minor cellular constituent, it can be immunoprecipitated from [32P]Pi-labeled GH3 cells and shown to contain a high level of basal phosphorylation. Vasoactive intestinal peptide, forskolin, 3-isobutyl-1-methylxanthene, or cholera toxin, treatments which increase cellular cAMP levels, or dibutyryl cAMP stimulate phosphorylation of specific sites on MAP-2 without significantly increasing its high state of basal phosphorylation. Phosphopeptide mapping reveals that the sites phosphorylated by cAMP kinase in vitro are the same sites whose phosphorylation in situ increases following stimulation of GH3 with agents that activate cAMP kinase. Increasing intracellular Ca2+ levels in GH3 cells also stimulates phosphorylation of MAP-2 but at sites distinct from those phosphorylated following treatment with cAMP inducing agonists. Phosphopeptide mapping indicates that the sites phosphorylated by CaM kinase in vitro are the same sites whose phosphorylation in situ increases following Ca2(+)-mediated stimulation. We conclude that activation of cAMP- and Ca2(+)-based signaling pathways leads to phosphorylation of MAP-2 in GH3 cells and that cAMP kinase and CaM kinase mediate phosphorylation by these pathways, respectively.