Assisted hatching in mouse embryos using a noncontact Ho:YSGG laser system

PURPOSE

A noncontact holmium:yttrium scandium gallium garnet (Ho:YSGG) laser system has been designed and tested for the micromanipulation of mammalian embryos. The purpose of this preliminary investigation was to determine the effectiveness of this laser for assisted hatching and evaluate its impact on embryo viability. The Ho:YSGG system, utilizing 250-microsecond pulses at a wavelength of 2.1 microns and 4 Hz, was used to remove a portion of the zona pellucida (ZP) of two- to four-cell FVB mouse embryos.

RESULTS

In the first experiment there was no difference in blastocyst production or hatching rates following laser or conventional assisted hatching (LAH or AH, respectively) in contrast to control embryos cultured in a 5% CO2 humidified air incubator at 37 degrees C. In the second experiment a blastocyst antihatching culture model was employed and LAH-treated embryos were cultured in a serum-free HTF medium (HTF-o). Blastocyst formation was not influenced by LAH treatment and hatching was increased (P < 0.01) from 4 to 60% compared to HTF-o control group.

CONCLUSIONS

These preliminary data demonstrate the utility and nontoxic properties of the Ho:YSGG laser system for quick and precise ZP drilling.

1-Methyl-4-phenylpyridinium (MPP+) inhibits mitochondrial oxygen consumption mediated by succinate as well as malate in rat pheochromocytoma PC12 cells

When rat pheochromocytoma PC12 cells are cultured with 1 mM 1-methyl-4-phenylpyridinium (MPP+), the number of viable cells decreases to one third in 4 days while the number increases ten-fold without MPP+. Oxygen consumption by mitochondria in the presence of malate is inhibited about 80% by the treatment of the cells with MPP+ for 4 days. Unexpectedly, succinate-dependent oxygen consumption is also inhibited to essentially the same extent as malate-dependent one. These results suggest that the impairment of the respiration mediated by succinate as well as malate is important as a mechanism of MPP(+)-induced cell death.

Anion transport function of mouse erythroid band 3 protein (AE1) does not require acylation of cysteine residue 861

Cys-861 of mouse band 3 is equivalent to Cys-843 of human band 3, the only acylated cysteine residue in the anion exchanger AE1 of the red blood cell (Hamasaki et al. (1992) Progress Cell Res. 2, 65-71). Mutation of Cys-861 to serine or methionine caused no significant changes of band 3-mediated anion exchange as measured after expression of the appropriate cRNAs in Xenopus oocytes. Susceptibility to inhibition of transport by 4,4'-dinitrostilbene-2,2'-disulfonate and PCMBS was not affected. We conclude that palmitoylation is not an absolute requirement for the successful execution the anion transport function by the hydrophobic domain of band 3 in the plasma membrane.

Preferential heme transport through endoplasmic reticulum associated with mitochondria in rat liver

The transport of de novo synthesized protoheme into the conventional microsomal fraction and endoplasmic reticulum associated with mitochondria (MAER) was studied by injecting amino[14C]levulinic acid (ALA) into phenobarbital-treated rats to evaluate the role of MAER in the trafficking of heme between mitochondria and endoplasmic reticulum. In mitochondria, the specific radioactivity of the radiolabeled heme reached a maximum level at 4 min after the injection of 14C-ALA. The specific radioactivity in cytosol was about 2-fold lower than that in microsomes, suggesting that the cytosolic pathway of the heme transport from mitochondria to endoplasmic reticulum is not predominant, because the specific radioactivity of heme in cytosol should be higher than that in microsomes if heme is transported mainly through cytosol. MAER showed higher specific radioactivity than the conventional microsomal fraction up to 4 min and thereafter the specific radioactivities in MAER and the conventional microsomal fraction became nearly the same. The extents of decrease in cytochrome P-450 and the radioactivity in microsomes by the treatment with allylisopropylacetamide which destroyed cytochrome P-450 but not cytochrome b5, were essentially the same, suggesting that most of the radiolabeled heme in microsomes was incorporated into cytochrome P-450. These results suggest that MAER is a preferential site for the protoheme transport from mitochondria to endoplasmic reticulum.

Identification of 1-hydroxypyrene glucuronide as a major pyrene metabolite in human urine by synchronous fluorescence spectroscopy and gas chromatography-mass spectrometry

Humans are exposed to polycyclic aromatic hydrocarbons (PAHs) from various occupational, environmental, medicinal and dietary sources. The measurement of specific PAH metabolites, particularly 1-hydroxypyrene, in human urine treated with deconjugating enzymes (e.g. beta-glucuronidase) has been extensively used as a means of assessing recent exposure to PAHs. We have examined pyrene metabolites in human urine prior to enzymatic deconjugation in order to determine the relative proportions of conjugated and unconjugated pyrene metabolites. The analytical method utilized immunoaffinity chromatography, high performance liquid chromatography (HPLC) and the complementary techniques of synchronous fluorescence spectroscopy (SFS) and gas chromatography-mass spectrometry (GC-MS) to measure pyrene-containing metabolites. SFS analysis of immunoaffinity-purified urine samples showed fluorescence spectra characteristic of the pyrene moiety (using wavelength differences of 34 nm, 54 nm and 102 nm). These spectra are produced by several PAHs containing the pyrene moiety. HPLC analysis with fluorescence detection indicated that the major fluorescent metabolite in immunoaffinity-purified urine was much more polar than simple hydroxylated metabolites of pyrene (1-hydroxypyrene) or benzo[a]pyrene (benzo[a]pyrene-diols or -tetrols). Following digestion with beta-glucuronidase, this metabolite co-chromatographed with authentic 1-hydroxypyrene and exhibited fluorescence spectra characteristic of 1-hydroxypyrene, suggesting that the major metabolite was a glucuronide conjugate of 1-hydroxypyrene. This was subsequently confirmed by GC-MS analysis of trimethylsilyl derivatives of the major metabolite; both 1-hydroxypyrene and glucuronic acid were detected independently as derivatized products. Since 1-hydroxypyrene glucuronide is approximately 5-fold more fluorescent than 1-hydroxypyrene, it may provide a more sensitive biomarker for assessing exposure to pyrene in mixtures of PAHs.

Phosphatidic acid induces the release of beta-glucuronidase but not lactoferrin from electropermeabilized human neutrophils

We studied the degranulation reaction of electropermeabilized human neutrophils induced by 1,2-didecanoyl-3-sn-phosphatidic acid (PA10). PA10 dose-dependently induced the release of beta-glucuronidase, an enzyme of azurophil granules, but did not induce the release of lactoferrin, a protein of specific granules. The enzyme release by PA10 absolutely required Ca2+, ATP, and Mg2+ and the concentrations for the half-maximal response were 2.5 microM, 60 microM, and 0.25 mM, respectively. Although Ca2+ alone at concentrations higher than 10 microM induced the release of both beta-glucuronidase and lactoferrin, the extents of the release were far less than that of the beta-glucuronidase release by PA10. Phorbol myristate acetate (PMA) and 1-oleoyl-2-acetyl-sn-glycerol induced the release of lactoferrin alone at concentrations of Ca2+ below 0.5 microM while they induced the release of both beta-glucuronidase and lactoferrin at higher Ca2+ concentrations, indicating that the degranulation induced by PA10 is not mediated by diacylglycerol which might be formed from PA. The degranulation reactions induced by PA10 and PMA were dose-dependently inhibited by staurosporine and calphostin C, protein kinase C inhibitors, although no direct activation of protein kinase C by PA10 was observed. The extent of the beta-glucuronidase release by PA10 was not enhanced by the addition of PMA. Propranolol, which inhibits protein kinase C as well as phosphatidic acid phosphohydrolase, strongly inhibited the degranulation reactions induced by PA10 and PMA. Ethanol, a metabolic modulator of phospholipase D, and cyclic AMP did not affect the degranulation reactions by PMA and PA10.(ABSTRACT TRUNCATED AT 250 WORDS)

Red blood cell band 3. Lysine 539 and lysine 851 react with the same H2DIDS (4,4'-diisothiocyanodihydrostilbene-2,2'-disulfonic acid) molecule

The band 3 protein of the red blood cell membrane catalyzes anion exchange that is inhibited by the stilbenedisulfonate derivative H2DIDS (4,4'-diisothiocyanodihydrostilbene-2,2'-disulfonic acid). There is one H2DIDS binding site per 95,000-Da band 3 polypeptide. The single bound H2DIDS molecule can react covalently with 2 different lysine residues. The 2 lysines that react covalently with H2DIDS have been localized directly by sequencing fragments of human band 3 from cells labeled with [3H]H2DIDS. The most rapid covalent reaction is with Lys-539, in agreement with site-directed mutagenesis studies. The slower reaction is with Lys-851, which is known to be the primary site of binding of another anion transport inhibitor, pyridoxal phosphate (Kawano et al., 1988). These results indicate that the protein is folded to bring these 2 residues into close enough proximity to react covalently with the same H2DIDS molecule. In addition to defining the residues that react with H2DIDS, these studies have also defined new in situ proteolytic cleavage sites in band 3.

Characterization of NAD(P)H-dependent ubiquinone reductase activities in rat liver microsomes

Exogenous ubiquinone-10 was efficiently reduced by rat liver microsomes in the presence of NADH and NADPH under anaerobic conditions. Ubiquinone-10 reduced under anaerobic conditions was rapidly re-oxidized by the re-aeration. The reduction and re-oxidation were not observed when the reactions were carried out with the boiled microsomes or without microsomes, suggesting that the reactions were enzymatically catalyzed by the electron transport system(s) from NAD(P)H to O2 through the ubiquinone. The Km and Vmax of the reductase activity for NADH were 0.4 mM and 1.7 nmol/min per mg of protein, and those for NADPH were 19 microM and 2.1 nmol/min per mg of protein, respectively. The NADH-dependent oxidoreduction system was different from the NADPH-dependent system because of the following observations; (1) rotenone inhibited only the NADH-dependent ubiquinone-10 reductase, (2) dicoumarol inhibited the NADPH-dependent ubiquinone-10 reduction more potently than the NADH-dependent reduction and (3) the activity oxidizing the reduced ubiquinone-10 in the presence of NADH was less than that in the presence of NADPH. Endogenous ubiquinone-9 was also reduced and re-oxidized in essentially the same manner as exogenous ubiquinone-10. Thus, ubiquinone-10 oxidoreductase in rat liver microsomes acts on endogenous ubiquinone-9.

A structural study of the membrane domain of band 3 by tryptic digestion. Conformational change of band 3 in situ induced by alkali treatment

Nine peptides derived from the transmembrane domain of band 3 were purified and sequenced. All of the sequences agreed completely with deduced sequences from cDNA of human erythroid band 3. Five peptides, KS-1 to KS-5, were released from the band 3 molecule when alkali-stripped membranes were digested with trypsin, while four other peptides, KM-6 to KM-9, were obtained following subsequent urea treatment. This indicates that at least 13 new in situ cleavage sites were demonstrable by these procedures, that the released peptides are parts of hydrophilic connector loops, and that the other peptide portions constitute membrane-spanning helices. The topological designations are consistent with the hydropathy prediction of murine band 3 according to Passow ((1986) Rev. Physiol. Biochem. Pharmacol. 103, 61-203). One mol of histidine residue was found/mole of KS-1, KS-2, KS-4, and KM-6. The conformation of band 3 in situ was apparently changed by alkali treatment of erythrocyte membranes, i.e. the amount of KS-1, KS-2, and KS-4 peptides released by trypsin treatment increased as NaOH concentration was raised from 10 to 100 mM. Similarly, [3H]dihydro-4,4'-diisothiocyanostilbene-2,2'-disulfonic acid was found to bind to band 3 in membranes treated with 10 mM NaOH as well as to band 3 in white ghosts, but not to membranes treated with 100 mM NaOH. In addition, alkali treatment of membranes tended to increase the amount of band 3 cross-linked by 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS). The conformational change in band 3 by alkali treatment was also supported by the interaction of antibodies against peptides released by trypsin. The release of KS-1, KS-2, and KS-4 from the membrane was strongly inhibited by pretreating the erythrocyte membrane with DIDS, suggesting that the DIDS-band 3 complex which is in the outward facing form, is more compact and becomes resistant to trypsin compared to band 3 without DIDS.

Succinate-dependent lipid peroxidation and its prevention by reduced ubiquinone in beef heart submitochondrial particles

When succinate and ADP-Fe3+ chelate were added to beef heart submitochondrial particles pretreated with 2-thenoyltrifluoroacetone, an inhibitor of succinate dehydrogenase of the mitochondrial respiratory chain, the formation of malondialdehyde was observed. No formation was observed without the pretreatment. Oxaloacetate competitively inhibited the malondialdehyde formation with an apparent Ki of 3.4 microM. The malondialdehyde formation seemed to be initiated at the location between the p-hydroxymercuribenzoate-sensitive site and the 2-thenoyltrifluoroacetone-sensitive site of the succinate dehydrogenase because it was inhibited by the mercurial. Ubiquinone-10 was rapidly destroyed during the malondialdehyde-forming reaction when it was in the oxidized form, while the ubiquinone was not destroyed and the malondialdehyde formation was abolished when about 50% of the ubiquinone in the particles was in the reduced state. These observations suggest that the succinate-dependent peroxidation is strongly controlled by the redox state of ubiquinone.

Ubiquinone biosynthesis by mitochondria, sonicated mitochondria, and mitoplasts of rat liver

Ubiquinone was biosynthesized when rat liver mitochondria were incubated with S-adenosyl-L-methionine, solanesyl diphosphate, and [U-14C]p-hydroxybenzoate. The intermediates of ubiquinone biosynthesis but not ubiquinone were accumulated in mitochondria incubated without S-adenosyl-L-methionine and the accumulated intermediates were converted to ubiquinone by the addition of the methyl group donor and an excess of cold p-hydroxybenzoate. No solaneylated compounds except nonaprenyl p-hydroxybenzoate were found in sonicated mitochondria, while the biosynthesis of ubiquinone was observed in the sonicated preparation of mitochondria in which the intermediates accumulated. The results indicate that the initial decarboxylation reaction is completely abolished and the subsequent reactions of hydroxylation and methylation are not completely inhibited by the sonication treatment and therefore the decarboxylation reaction is the next step after nonaprenylation of p-hydroxybenzoate. Mitoplasts could biosynthesize ubiquinone with activity comparable to that of intact mitochondria, suggesting that components of the outer membrane and the intermembranous space of mitochondria are not involved in ubiquinone biosynthesis.

Evidence that the decarboxylation reaction occurs before the first methylation in ubiquinone biosynthesis in rat liver mitochondria

Biosynthesis of ubiquinone-9 was studied by incubating rat liver mitochondria with p-hydroxy[U-14C]benzoate, solanesyl diphosphate and S-adenosyl-L-methionine. When methylation reactions were inhibited by replacing S-adenosyl-L-methionine with S-adenosyl-L-homocysteine, nonaprenyl p-hydroxybenzoate and three other labeled peaks, designated as P1, P2 and P3 according to their retention times on HPLC, were observed. No carboxyl group was present in P1, P2 or P3 because the radioactivities disappeared when p-hydroxy[U-14C]benzoate was replaced by p-hydroxy[carboxyl-14C]benzoate. Compound P2 seemed to be hydroxylated but not methylated because its radioactivity markedly diminished under anaerobic conditions and the radioactivity was not incorporated into the compound from S-adenosyl-L-[methyl-3H]methionine, suggesting that P2 is 6-hydroxynonaprenylphenol. The complete correspondence of the retention times of P2 and chemically synthesized 6-hydroxynonaprenylphenol on HPLC further confirmed this possibility. P2 was a precursor of ubiquinone-9 because the radioactivity of the compound was incorporated into ubiquinone when incubated with mitochondria. The results suggest that the decarboxylation may occur prior to the first methylation in the ubiquinone biosynthesis in rat liver mitochondria, though it has been generally considered that in eukaryotes the first methylation precedes the decarboxylation.

The role of Ca2+ and Ca2+-activated phospholipid-dependent protein kinase in degranulation of human neutrophils

The degranulation reactions of human neutrophils induced by 1-oleoyl-2-acetylglycerol (OAG), phorbol 12-myristate 13-acetate (PMA), and calcium ionophore A23187 or their combinations, were studied. OAG in the absence of the Ca2+-ionophore A23187 stimulated the releases of both lysozyme and lactoferrin, constituents of the specific granules, but did not stimulate the release of beta-glucuronidase, an enzyme of the azurophil granules. Electron microscopy revealed a selective decrease in the numbers of the specific granules in this case. The combined effects of A23187 at a concentration higher than 0.1 microM and OAG were essentially additive. W-7, known to be an inhibitor of both Ca2+-activated phospholipid-dependent protein kinase (C-kinase) and calmodulin, inhibited the degranulation induced by OAG or PMA, while it inhibited the reaction induced by A23187 less markedly. The release of lysozyme reached a plateau at about 0.1 microM A23187 and increased again at higher concentrations of A23187. The observations suggest that degranulation can be induced by the activation of the C-kinase, and the degranulation by A23187 at low concentrations may be due to the activation of the C-kinase; the effects of A23187 at high concentrations, however, could not be explained only in terms of the activation of the C-kinase.

Keshan disease: an endemic cardiomyopathy in China

Keshan disease is an endemic cardiomyopathy in China. Morphologically, the condition is characterized by multifocal necrosis and replacement fibrosis of the myocardium, resulting in acute or chronic heart failure. Some patients with Keshan disease show the clinical features of congestive (dilated) cardiomyopathy, but the pathologic features of the two conditions are different. The etiology of Keshan disease remains unknown. It is likely that numerous agents work synergistically to cause the disease.

Kinetics of superoxide formation by respiratory chain NADH- dehydrogenase of bovine heart mitochondria

Formation of superoxide anions (O2-) by bovine heart NADH-dehydrogenase preparation (Complex I) supported by an NADH- or NADPH-generating system was studied kinetically. Both NADH- and NADPH-dependent superoxide-forming activities of Complex I were biphasic in double reciprocal plots. The NADH-dependent reaction had two sets of kinetic parameters: One Km value for NADH was 10 times higher than the other one, and the Vmax of the reaction with high Km was about 4 times higher than that of the reaction with low Km. Similar Vmax values were obtained for the NADPH-dependent reactions but the Km values were a thousand times higher than those of the NADH-dependent reactions. The plots of the NADH-dependent activity of rotenone-treated submitochondrial particles were also biphasic. The double reciprocal plots of NADH- and NADPH-dependent 2,6-dichlorophenolindophenol (DCIP) reductase activities of Complex I were linear and the plots of the superoxide-forming activities against the DCIP reductase activities were biphasic. These results indicate that the biphasic double reciprocal plots of the superoxide-forming activities against reduced coenzymes are not caused by interaction between reduced coenzymes and the NADH-dehydrogenase but are due to the presence of at least two superoxide-forming sites in the respiratory chain NADH-dehydrogenase.