Transformation of leukotriene A4 methyl ester to leukotriene C4 monomethyl ester by cytosolic rat glutathione transferases

Six major basic cytosolic glutathione transferases from rat liver catalyzed the conversion of leukotriene A4 methyl ester to the corresponding leukotriene C4 monomethyl ester. Glutathione transferase 4-4, the most active among these enzymes, had a Vmax of 615 nmol X min-1 X mg protein-1 at 30 degrees C in the presence of 5 mM glutathione. It was followed in efficiency by transferase 3-4 which had a Vmax of 160 nmol X min-1 X mg-1 under the same conditions. Transferases 1-1, 1-2, 2-2 and 3-3 had at least 30 times lower Vmax values than transferase 4-4.     

Comparative trial of treatment with Prioderm lotion and Kwellada shampoo in children with head lice.

The safety and efficacy of treatment with a new pediculicide lotion, Prioderm (0.5% malathion in isopropanol), were compared with those of treatment with Kwellada (1% lindane) shampoo in a randomized trial of children with head lice. The children''s scalps were examined for live lice immediately, 7 days and 4 to 6 weeks following treatment. To determine the in-vitro ovicidal effect of treatment, samples of hair with nits were removed before and immediately following treatment; the subsequent rates of hatching were compared. No live lice were present immediately following either treatment. At 7 days after treatment 2 of the 29 children treated with Prioderm lotion and 4 of the 33 children treated with Kwellada shampoo were infested with live lice, whereas at 4 to 6 weeks after treatment 5 and 3 children respectively were infested. The initial effectiveness of treatment was 93% in the children treated with Prioderm lotion and 88% in those treated with Kwellada shampoo; however, a large difference in efficacy could have been missed owing to the small number of children in the study. Both preparations demonstrated in-vitro ovicidal activity, but neither totally abolished post-treatment hatching. No side effects were reported from either preparation. Because ovicidal activity was incomplete two treatments with the same pediculicides should be given about 7 days apart.     

A mechanism for the formation of inside-out membrane vesicles. Preparation of inside-out vesicles from membrane-paired randomized chloroplast lamellae

Inside-out thylakoid membrane vesicles can be isolated by aqueous polymer two-phase partition of Yeda press-fragmented spinach chloroplasts (Andersson, B. and Åkerlund, H.-E. (1978) Biochim. Biophys. Acta 503, 462–472). The mechanism for their formation has been investigated by studying the yield of inside-out vesicles after various treatments of the chloroplasts prior to fragmentation. No inside-out vesicles were isolated during phase partitioning if the chloroplasts had been destacked in a low-salt medium prior to the fragmentation. Only in those cases where the chloroplast lamellae had been stacked by cations or membrane-paired by acidic treatment did we get any yield of inside-out vesicles. Thus, the intrinsic properties of chloroplast thylakoids seem to be such that they seal into right-side out vesicles after disruption unless they are in an appressed state. This favours the following mechanism for the formation of inside-out thylakoids. After press treatment, a ruptured membrane still remains appressed with an adjacent membrane. Resealing of such an appressed membrane pair would result in an inside-out vesicle.If the compartmentation of chloroplast lamellae into appressed grana and unappressed stroma lamellae is preserved by cations before fragmentation, the inside-out vesicles are highly enriched in photosystem II. This indicates a granal origin which is consistent with the proposed model outlined. Inside-out vesicles possessing photosystem I and II properties in approximately equal proportions could be obtained by acid-induced membrane-pairing of chloroplasts which had been destacked and randomized prior to fragmentation. Since this new preparation of inside-out thylakoid vesicles also exposes components derived from the stroma lamellae it complements the previous preparation.It is suggested that fragmentation of paired membranes followed by phase partitioning should be a general method of obtaining inside-out vesicles from membranes of various biological sources.     

L-3-Phosphoglyceric acid,formed by ribulose-1,5-bisphosphate carboxylase,is the primary substrate for photorespiration: Experimental test of a hypothesis

Preparations of RuBP carboxylase are shown to carry out an oxygen dependent decarboxylation of L-3-phosphoglyceric acid. The product of this reaction is probably phosphoglycollate. L-3-phosphoglyceric acid, formed by RuBP carboxylase is therefore proposed to be the primary substrate for photorespiration.     

Periodate oxidation and alkaline degradation of heparin-related glycans

Heparin, heparan sulphate, and various derivatives thereof have been oxidised with periodate at pH 3.0 and 4° and at pH 7.0 and 37°. Whereas oxidation under the latter conditions destroys all of the nonsulphated uronic acids, treatment with periodate at low pH and temperature causes selective oxidation of uronic acid residues. The reactivity of uronic acid residues depends on the nature of neighbouring 2-amino-2-deoxyglucose residues. d-Glucuronic acid residues are susceptible to oxidation when flanked by N-acetylated amino sugars, but resistant when adjacent residues are either unsubstituted or N-sulphated. L-Iduronic acid residues in their natural environment (2-deoxy-2-sulphoamino-d-glucose) are resistant to oxidation, whereas removal of N-sulphate groups renders a portion of these residues periodate-sensitive. Oxidised uronic acid residues in heparin-related glycans may be cleaved by alkali, producing a series of oligosaccharide fragments. Thus, periodate oxidation-alkaline elimination provides an additional method for the controlled degradation of heparin.     

Effect of Mg2+ and spermine on the kinetics of Ca2+ transport in rat-liver mitochondria

Plots relating the initial rate of mitochondrial Ca²⁺ transport to the Ca²⁺ concentration (kinetic plots) have a hyperbolic shape in a Ca²⁺ concentration range of 2.5–100 µM as measured in sucrose or KCl media. In the presence of Mg²⁺ or a polyamine spermine, which both are competitive inhibitors of Ca²⁺ binding to low affinity sites at the membrane surface, the shape of the plots becomes sigmoidal. At higher concentrations of these agents linear kinetic plots are obtained as measured in a sucrose medium. In a KCl medium the sigmoidality of the kinetic plots is enhanced by an increase in the Mg²⁺ or spermine concentration. It is suggested that Mg²⁺ and spermine affect the kinetics of Ca²⁺ transport by interfering with Ca²⁺ binding to low affinity sites of the membrane surface and that the binding of Ca²⁺ to these sites is the first step of the mitochondrial Ca²⁺ transport.     

LSD and related drugs as DA antagonists: Receptor-mediated effects on the synthesis and turnover of DA

We have earlier shown that d-lysergic acid diethylamide, LSD and its 2-bromo derivative, BOL like the dopamine (DA) antagonists haloperidol increased the rate of the $\text{in vivo}$ tyrosine hydroxylation in the striatum measured as the accumulation of DOPA after decarboxylase inhibition.Now we have found that several agents structurally similar to LSD increase the $\text{in vivo}$ tyrosine hydroxylation in the striatum. Psilocybin (50 mg/kg i.p.) and N,N-dimethyltryptamine (50 mg/kg i.p.) caused a short-lasting increase of DOPA accumulation, while mescaline (10 – 100 mg/kg i.p.) did not increase the DOPA accumulation. A marked increase of DOPA accumulation was observed after the 5-hydroxytryptamine (5-HT) antagonist cyproheptadine. The effects of LSD and structurally related drugs on the DOPA accumulation in the striatum appear to be mediated via DA antagonism at receptor level. However, these agents may control the DOPA accumulation via other receptors than DA receptors e.g. 5-HT receptors. A control of DOPA accumulation via receptors other than DA receptors appears to be predominant after treatment with N,N-dimethyltryptamine or psilocybin.     

Gene fusion vectors based on the gene for staphylococcal protein A

Two plasmid vectors, containing the gene coding for staphylococcal protein A and adapted for gene fusion, have been constructed. These vectors will allow fusion of any gene to the protein A gene, thus giving hybrid proteins which can be purified, in a one-step procedure, by IgG affinity chromatography. As an example of the practical use of such vectors, the protein A gene has been fused to the lacZ gene of Escherichia coli. E. coli strains containing such plasmids produce hybrid proteins with both IgG binding and β-galactosidase activities. The hybrid protein(s) can be immobilized on IgG-Sepharose by its protein A moiety with high efficiency without losing its enzymatic activity and they can be eluted from the column by competitive elution with pure protein A. The fused protein(s) also binds to IgG-coated microtiter wells which means that the in vivo product can be used as an enzyme conjugate in ELISA tests.     

Cell to cell communication and pH in the frog lens

Fiber cells of the lens are electrically and diffusionally interconnected through extensive gap junctions. These junctions allow fluxes of small solutes to move between inner cells and peripheral cells, where the majority of transmembrane transport takes place. We describe here a method utilizing two intracellular microelectrodes to measure the cell to cell resistance between fiber cells at any given distance into the intact lens. We also use ion-sensitive microelectrodes to record intracellular pH at various depths in the intact lens. We find that gap junctions connecting inner fiber cells differ in pH sensitivity as well as normal coupling resistance from those connecting peripheral cells. The transition occurs in a zone between 500 and 650 microns into the lens. Fiber cells peripheral to this zone have a specific coupling resistance of 1.1 omega cm2, whereas those inside have a specific coupling resistance of 2.7 omega cm2. However, when the cytoplasm of fiber cells is acidified by bubbling with CO2, peripheral cells uncouple and the cell to cell resistance goes up more than 40-fold, whereas junctions inside this zone are essentially unaffected by changes in intracellular pH. In a normal frog lens, the intracellular pH in fiber cells near the lens surface is 7.02, a value significantly alkaline to electrochemical equilibrium. Our data suggest that Na/H exchange and perhaps other Na gradient-dependent mechanisms in the peripheral cells maintain this transmembrane gradient. Deep in the lens, the fiber cell cytoplasm is significantly more acidic (pHi 6.81) due to influx of hydrogen across the inner fiber cell membranes and production of H+ by the inner fiber cells. Because of the normally acid cytoplasm of interior fiber cells, their loss of gap junctional sensitivity to pH may be essential to lens survival.     

The Binding Properties of the Particulate and Solubilized Sulfonylurea Receptor from Cerebral Cortex Are Modulated by the Mg2+ Complex of ATP

Glibenclamide closes an ATP-sensitive K+ channel (K-ATP channel) by interaction with the sulfonylurea receptor in the plasma membrane of pancreatic B cells and thereby initiates insulin release. Previous studies demonstrated that the Mg2+ complex of ATP decreases glibenclamide binding to the sulfonylurea receptor from pancreatic islets. The aim of the present study was to examine the effect of adenine and guanine nucleotides on binding of sulfonyl-ureas to the cerebral sulfonylurea receptor. For this purpose, binding properties of the particulate and solubilized site from rat or pig cerebral cortex were analyzed. Maximum recovery of receptors in detergent extracts amounted to 40-50%. Specific binding of [3H]glibenclamide to the solubilized receptors corresponded well to specific binding to microsomes. In microsomes and detergent extracts, the Mg2+ complexes of ATP, ADP, GTP, and GDP inhibited binding of [3H]glibenclamide. These effects were not observed in the absence of Mg2+. In detergent extracts, Mg-ATP (300 microM) reduced the number of high-affinity sites for [3H]-glibenclamide by 52% and increased the dissociation constant for [3H]glibenclamide by eightfold; Mg-ATP was half-maximally effective at 41 microM. Alkaline phosphatase accelerated the reversal of Mg-ATP-induced inhibition of [3H]glibenclamide binding. The data suggest similar control of the sulfonylurea receptor from brain and pancreatic islets by protein phosphorylation.