Decreased catalase activity is the underlying mechanism of oxidant susceptibility in glucose-6-phosphate dehydrogenase-deficient erythrocytes

Historically, it has been theorized that the oxidant sensitivity of glucose-6-phosphate dehydrogenase (G6PD)-deficient erythrocytes arises as a direct consequence of an inability to maintain cellular gluthione (GSH) levels. This study alternatively hypothesizes that decreased NADPH concentration leads to impaired to catalase activity which, in turn, underlies the observed oxidant susceptibility. To investigate this hypothesis, normal and G6PD-deficient erythrocytes and hemolysates were challenged with a H₂O₂-generating agent. The results of this study demonstrated that catalase activity was severely impaired upon H₂O₂ challenge in the G6PD-deficient cell whiel only decrease was observed in normal cells. Supplmentation of either normal or G6PD-deficient hemolysates with purified NADPH was found to significantly (P < 0.001) inhibit catalase inactivation upon oxidant challenge while addition of NADP⁺ had no effect. Analysis of these results demonstrated direct correlation between NADPH concentration and catalase activity (r = 0.881) and an inverse correlation between catalase activity and erythrocyte oxidant sensitivity (r = 0.906). In contrast, no correlation was found to exist between glutathione concentration (r = 0.170) and oxidant sensitivity. Analysis of NADPH/NADPt ration in acatalasemic mouse erythrocytes demonstrated that NADPH maintenance alone was not sufficient to explain oxidant resistance, and that catalase activity was required. This study supports the hypothesis that impaired catalase activity underlies the enhanced oxidant sensitivity of G6PD-deficient erythrocytes and elucidates the importance of NADPH in the maintenance of normal catalase activity.     

EFFECTS OF FERTILIZATION ON EPICUTICULAR WAX MORPHOLOGY OF NEEDLE LEAVES OF DOUGLAS FIR,PSEUDOTSUGA MENZIESII (PINACEAE)

Fertilized stands of Pseudotsuga menziesii were found to have glaucous needles. We investigated the morphological and quantitative characteristics of the epicuticular waxes of needles of fertilized and control trees. Glaucousness was caused by ornate tubular epicuticular wax. Dipping needles in chloroform, which dissolves waxes, eliminated the glaucous appearance. Based on cryostage scanning electron microscopic observations, the epicuticular waxes in the nonstomatal region were much more ornate on the needles of the fertilized trees (experimental needles) than in unfertilized trees (control needles). The stomatal region in both experimental and control needles showed similarly ornate waxes. Quantities of waxes were similar in experimental and control needles. The glaucousness was not the result of greater quantities of wax; rather, fertilization altered wax morphology in the nonstomatal regions.     

A high-pressure liquid chromatographic method for measuring 3', 5'-cyclic AMP in brain.

A method is described for the estimation of adenosine 3′,5′-monophosphate (3′,5′-cyclic AMP) in rat brain by high-pressure liquid chromatography (HPLC). The nucleotide is purified initially by being passed through two columns, alumina and AG-1X2. The peak in HPLC was identified by a number of methods. Optimum parameters for HPLC were obtained by using 1 mm KH₂PO₄ buffer, pH 4.8, at a flow rate of 57 ml/hr at room temperature. Using this technique the concentration of 3′,5′-cyclic AMP in rat brain was found to be 2.53 ± 0.40 nmol/g (mean ± SD, n = 5).     

Sexual development of patients with isochromosomes for the long arm of the X chromosome

Summary The sexual development of 14 girls with non-mosaic monocentric 46,X,iXq karyotype was studied. Seven out of eight girls were found to have immature secondary sexual characteristics and amenorrhoea, a finding greatly contrasting with that in Triplo-X girls. The relative ineffectiveness of the isochromosome Xq in maintaining fertility may be due to the absence of one short arm, which probably also carries a gonadal determinant. Alternatively, the presence of two inactivation sites on one isochromosome may render the gonadal determinants inactive at an important stage in gonadal development.     

Crystallization of preliminary electron diffraction study to 3.7 A of DNA helix-destabilizing protein gp32*I.

A two-dimensionally large and thin crystal has been obtained from gp32¹I, a proteolytically digested product of a DNA helix-destabilizing protein coded by gene 32 in bacteriophage T4. High-resolution electron diffraction patterns (~3.7Å) are recorded from both unstained and stained protein crystals embedded in glucose. The crystal is of orthorhombic space group with $\text{a = 62.9}\text{A}\text{?}\text{and}\text{b = 47.3}\text{A}\text{?}$.     

Role of calcium in the initiation of fast axonal transport of protein: Effects of divalent cations

Fast axonal transport of [³H]protein has been examined in bullfrog primary afferent neurons incubated in media supplemented with divalent cations that can act as agonists or antagonists of calcium ions. Incubation in calcium-free medium (CFM) had no effect on the rate of transport, but reduced the amount of transported [³H]protein by 40–60% relative to transport in the contralateral preparation maintained in normal medium. Preparations incubated in CFM supplemented with 1.8 mM SrCl₂ (equimolar to the CaCl₂ concentration in normal medium) carried out transport at control levels. Incubation conditions in which primary afferent somata were exposed to the Sr²⁺-medium while nerve trunks were maintained in CFM also supported normal transport. By contrast, selective exposure of nerve trunks to Sr²⁺-medium, and somata to CFM resulted in a reduced level of transport similar to that observed when the whole preparation was incubated in CFM. The depression of transport resulting from incubation in CFM was shown to be reversible when preparations were transferred from CFM to either Sr²⁺-supplemented CFM or to normal medium. By contrast to the effects of Sr²⁺, Ba²⁺ (up to 18 mM) did not substitute for Ca²⁺ in the transport process. When normal medium was supplemented with calciumantagonist cations, the amount of transport was depressed (Co²⁺ > Mn²⁺ >> Mg²⁺), with no concomitant effect on the rate of transport. Results of studies with Co²⁺, as well as those with Sr²⁺, suggest that a major locus of action of these cations is within the neuronal soma at a step subsequent to protein synthesis, and prior to the onset of protein translocation via the transport system. Thus, it is inferred that these divalent cations affect a calcium-dependent step that occurs during the initiation phase of fast axonal transport.     

Transbilayer distribution and mobility of phosphatidylinositol in human red blood cells

The present studies describe the distribution of phosphatidylinositol (PI) within the membrane bilayer of the human red blood cell (RBC) as well as its transbilayer mobility. The membrane bilayer distribution was determined by measuring the hydrolysis of PI in the exterior leaflet of the RBC membrane using a PI-specific phospholipase C and by extraction of PI from the exterior leaflet using bovine serum albumin. The transbilayer mobility of PI was measured by following the fate of radiolabeled PI which was first incorporated into the outer leaflet of the RBC membrane. Our results indicate that PI is asymmetrically distributed in the membrane, with approximately 80% located in the inner and 20% in the outer leaflet of the bilayer. The rate of transbilayer mobility of PI is similar to that for certain molecular species of phosphatidylcholine and much slower than that reported for the aminophospholipids in the RBC membrane.