PubMed Health⌕ Search

Biomedical subjects

M A Paz

Publications and source records attributed to M A Paz.

At least 19 recordsLinked to original sources
PubMed1994

Antisense RNA to the first N-glycosylation gene, ALG7, inhibits protein N-glycosylation and secretion by Xenopus oocytes.

N-Glycosylation has been shown to affect the rate of glycoprotein transport through the secretory pathway. In order to identify the critical components in the N-glycosylation pathway that directly influence protein secretion, we have studied the effects of downregulation of the first gene in the dolichol pathway, ALG7, on the synthesis, glycosylation and secretion of native and heterologous proteins by Xenopus laevis oocytes. Our strategy involved the use of ALG7 antisense RNA (asRNA) to lower the effective abundance of the ALG7 protein in oocytes. The results showed that there was an inverse dose-response relationship between ALG7 asRNA and the amount of glycosylated and secreted proteins. These effects were also observed for heterologously expressed rat parotid amylase. Since ALG7 asRNA did not inhibit overall protein synthesis, we conclude that downregulation of ALG7 expression directly lowered protein export.

Amylases↗
PubMed1994

Aspects of the release of superoxide by leukocytes, and a means by which this is switched off.

Although great progress has been made in understanding the respiratory burst of leukocytes that produce superoxide (O2-), it is possible that a component or components, might have been overlooked. Furthermore, O2- production and its sequels, though cardinal in bactericidal action, might ultimately be damaging to the host's own cells. It is important, therefore, that a biologic mechanism exist to turn off O2- production by stimulated leukocytes. This article offers evidence that methoxatin (PQQ), a redox-cycling orthoquinone, might be involved in O2- production by leukocytes. This is based on the fact that inhibitors of O2- production, such as diphenylene iodonium (DPI) and 4,5-dimethylphenylene diamine (DIMPDA), were shown to sequester PQQ in leukocytes, i.e., to form adducts with that substance. Addition of PQQ to cells blocked with the inhibitors partially restored O2- release. With respect to turning off cellular O2- release, a factor was observed to be released to the medium by old macrophages (14 days old, but not by those less than 7 days old). Such conditioned medium, when added to stimulated neutrophils or macrophages, blocked O2- release. This factor was sensitive to proteases, exhibited molecular sizes of 3 and 11 kDa, and its action was independent of the nature of the stimulus applied to the leukocytes. It was partially purified by column (sizing) chromatography and HPLC. It seems to be a general modulator of the release of reactive oxygen species by phagocytes and is irrespective of phagocytic cellular type, or species from which the cells were derived.

Chromatography, High Pressure Liquid↗
PubMed1992

Hydrocortisone anaphylaxis: a new case report.

In this report we describe a case of a nonatopic patient who developed an anaphylactoid reaction immediately after receiving intravenous hydrocortisone. The patient recovered after reanimation techniques and intravenous administration of atropine, epinephrine and plasma expanders. Although allergic reactions to corticosteroids appear to be rare there are a few case reports in the literature. This case is presented to draw the attention of clinicians to the occasional hazard of intravenous corticosteroid preparations, specially hydrocortisone.

Anaphylaxis↗
PubMed1992

[Prognostic predictors of left ventricular aneurysm after myocardial infarct].

We have prospectively studied the prevalence and natural history of left ventricular aneurysm in a series of 386 consecutive male patients with an acute myocardial infarction. Definition of aneurysm was angiographic and based on a single plane left ventricular angiogram. There were 52 (13.5%) left ventricular aneurysms. Mean follow-up was 57 +/- 29 months (range 40-100). During this interval, 15 of the 52 patients died (29%). Univariate analysis showed that survivors had at admission significantly less prevalence of hypercholesterolemia, previous myocardial infarction and intraventricular conduction disturbances. In addition, their Killip class was better (p less than 0.02) and the left ventricular ejection fraction was higher (p less than 0.002). The survival rates of patients with ventricular aneurysm at 1, 3 and 5 years were 88, 82 and 75%, respectively. Left ventricular end diastolic pressure, number of diseased vessels and the presence of bifascicular block were independent predictors of survival. Stratification of patients according to the risk factors allowed identification of patients with excellent prognosis (those with left ventricular end diastolic pressure less than 20 mmHg, single vessel disease and no conduction disturbances) and others with high risk of death (left ventricular end diastolic pressure greater than or equal to 20 mmHg, three vessel disease and bifascicular block). Survival at 5 years for these two groups were 81% vs 50%, respectively (p less than 0.005).

Heart Aneurysm↗
PubMed1991

Specific detection of quinoproteins by redox-cycling staining.

Quinones and related quinonoid substances catalyze redox cycling at an alkaline pH in the presence of excess glycine as reductant. With nitroblue tetrazolium and oxygen present there is concomitant reduction of the tetrazolium to formazan. This property of quinonoid compounds is used for the specific staining of quinoproteins, separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and electroblotted onto nitrocellulose. The dopa-containing vitelline proteins and the 6-hydroxydopa-containing bovine serum amine oxidase are stained with the nitroblue tetrazolium/glycinate reagent. Also, the mammalian quinoproteins, diamine oxidase and lysyl oxidase, purported to contain pyrroloquinoline quinone, tested positive in this procedure. No quinonoid components were detected in three putative pyrroloquinoline quinone-containing quinoproteins, dopamine beta-hydroxylase, lipoxygenase, and peptidylglycine-amidating monoxygenase. Redox-cycling staining therefore confirms the presence of covalently bound quinones in the copper-dependent amine oxidases, but not in two putative quinoprotein oxygenases. Clarification of the biological significance of quinolation should be facilitated by identification of quinoproteins using this approach.

Animals↗
PubMed1991

Biosynthesis and secretion of rat salivary proteins by Xenopus laevis oocytes.

Xenopus laevis oocytes injected with poly (A+) RNA isolated from rat parotid and submandibular glands synthesize and secrete salivary proteins. Amylase was identified in the media of cultured oocytes injected with rat parotid mRNA by size and immunoprecipitation with anti-human amylase serum. Secretion of the salivary proteins was detectable in the medium eight h following the parotid mRNA injection and continued in a time-dependent fashion for up to 96 h. In contrast to rat parotid slices in culture, which demonstrate a regulated pathway of secretion highly responsive to the secretagogue isoproterenol, secretion of salivary proteins by oocytes did not respond to the stimulation by isoproterenol. Though parotid mRNA is presumed to contain the templates encoding the regulated pathway of secretion, reconstitution of this pathway of secretion in oocytes was not observed in our experiments. Since Xenopus laevis oocytes secrete constitutively significant amounts of proteins when injected with salivary gland mRNA, they are a useful biological system for the analysis of secretion, processing, and function of salivary proteins.

Animals↗
PubMed1991

[Late recurrence in pheochromocytoma: need for a long term follow up].

Pheochromocytoma is a catecholamine secreting tumor which has been traditionally considered as a potentially curable cause of hypertension. However, the existence of malignant pheochromocytomas as well as the problem which the recurrence of benign pheochromocytomas present, make the eradication of this tumor more complicated. It is note worthy the difficulty in localizing recurrent pheochromocytomas as well as the prognostic interest that presents the possibility of differentiating between recurrence and metastasis. We refer the case of a female patient suffering benign adrenal pheochromocytoma, who, 10 years it was surgically removed, presented a relapse of symptoms, and was diagnosed of extra-adrenal pheochromocytoma, in Zuckerkandl organ. The importance of performing a long term post-surgical follow-up in these patients is stressed.

Adrenal Gland Neoplasms↗
PubMed1990

Soybean lipoxygenase-1 is not a quinoprotein.

Soybean lipoxygenase-1 was reinvestigated with respect to its quinoprotein nature. It has been reported previously that soybean lipoxygenase-1 contains pyrroloquinoline quinone as the organic cofactor. Because spectroscopic data were found to be inconsistent with the evidence presented in [1], we sought to reproduce the published data by carefully following the procedures described in [1] and supplementing them with new analytical results. The combined data lead us to conclude that soybean lipoxygenase-1 is not a quinoprotein.

Coenzymes↗
PubMed1989

Acid-promoted tautomeric lactonization and oxidation-reduction of pyrroloquinoline quinone (PQQ).

Acid-treatment facilitates PQQ detection by electron ionization mass spectroscopy with a molecular ion at M/e 330 and a base ion formed by triple decarboxylation at M/e 198. Other ions found probably arise through acid-catalyzed tautomeric lactonization of PQQ to PQQ-lactone (PQQL) with subsequent oxidation of PQQL and reduction of PQQ. We propose that a carboxyl group, presumably the 9-carboxyl, attacks a double bond in PQQ, reversibly converting the 4,5-orthoquinone into an 4,5-enediol and forming an isomeric lactone, PQQL, of 330 daltons. The masking of carbonyls may explain the low reactivity of PQQ with carbonyl reagents in acid. Acid-promoted tautomeric lactonization with carbonyl-masking is known to occur with fluoresceins, phenolphthalein and other compounds, but has not been recognized before with PQQ. Acid-treated PQQ demonstrates molecular and other ions derived from reduced PQQ (PQQ(2H] or its lactone at M/e 332 with a base ion at M/e 200. There is compelling evidence for a dehydrogenated lactone, PQQ(-2H)L), at M/e 328 with a base ion at M/e 196. We suggest that PQQ, in tautomeric equilibrium with PQQL, oxidizes PQQL to PQQ(-2H)L (328 daltons), with its concurrent reduction to PQQ(2H) (332 daltons). With acidified D2O, PQQ shows deuterated products with ions at M/e values consistent with lactonization and oxidation-reduction. An analytically useful quinoxaline adduct, formed from PQQ and 2,3-diaminonaphthalene (PQQ-DAN) of 452 daltons, also undergoes acid-tautomerization-lactonization and oxidation-reduction similar to PQQ showing molecular ions at M/e 450, 452 and 454 and decarboxylation-derived strong (base) ions at M/e 318, 320 and 322.(ABSTRACT TRUNCATED AT 250 WORDS)

Chemical Phenomena↗
PubMed1989

Separation and determination of alpha-amino acids by boroxazolidone formation.

Reaction of an alpha-amino acid (alpha-AA) with 1,1-diphenylborinic acid (DPBA) leads to the formation of a kinetically stable adduct at pH 2-5 in which both the alpha-amino and the alpha-carboxyl groups are bound to boron forming a cyclic mixed anhydride termed a boroxazolidone. In this adduct, the greater than N:B bond is coordinate, involving the free electron pair of nitrogen, thereby satisfying the octet rule for the second electron shell of boron (Group IIIA). Consequently, the alpha-amino function of the boroxazolidone can be primary, secondary, or tertiary, as demonstrated by boroxazolidone formation with glycine, N-methylglycine, and N,N-dimethylglycine. On reaction with DPBA, the alpha-AA moiety of N-terminal gamma-glutamyl peptides is also derivatized as demonstrated by the formation of a glutathione boroxazolidone. The 1,1-diphenylboroxazolidone adducts of alpha-AA may be separated by reversed-phase (RP)-HPLC (AA-DPBA/RP-HPLC) enabling the derivatization procedure to be used as a precolumn reaction for alpha-AA analysis. Under the conditions we describe here, DPBA is not stably reactive with the epsilon-amino group of lysine. Furthermore, it does not complex with amide bonds of the peptide backbone or to any side chains of the common amino acids. Reaction of an alpha-AA mixture with DPBA, followed by RP-HPLC (AA-DPBA/RP-HPLC) is then a simple method by which to analyze alpha-AA in a mixture with peptides and amines. Precolumn reaction with DPBA may be used to separate peptides from alpha-AA and from those peptides which contain an alpha-AA moiety. Unreacted peptides are bound only weakly to the HPLC column and thus are separated from reacted alpha-amino acids which are retained as 1,1-diphenylboroxazolidones until their selective elution. This method is particularly suited for the analysis of alpha-amino acids that are derived from post-translational modification of protein side chains.

Amino Acids↗
PubMed1989

[High-degree malignancy non-Hodgkin's lymphoma simulating a disseminated carcinoma. Presentation of 2 cases].

Highly malignant non-Hodgkin lymphomas (HM-NHL) may sometimes develop clinical features simulating an epithelial carcinoma with metastatic dissemination. Conventional histopathological study may be insufficient to differentiate between both conditions. Two patients with HM-NHL are reported with a rapid general deterioration; one of them had osteolysis and hypercalcemia. In both cases a diffuse bone marrow infiltration by large sized cells with blastic appearance was found. The initial suspected diagnosis was occult epithelial neoplasia with metastatic dissemination. The morphological study with optic microscopy and the ultrastructural analysis did not establish the origin of these cells. The definitive diagnosis was obtained by immunohistochemical techniques. In both cases, the cells were positive for the CD 45 (common leukocyte antigen) monoclonal antibody (MoAb), and for several MoAbs of lymphoid B differentiation. In one of them, the B lymphoid lineage was confirmed by monoclonal reordering of the gene that synthetises the immunoglobulin heavy chain.

Aged↗
PubMed1989

PQQ, the elusive coenzyme.

The recently discovered redox coenzyme, PQQ (methoxatin), is widely distributed. Quantitation of protein-bound PQQ has been difficult, but unique redox cycling reactions, which reflect its striking biological properties, reveal trace amounts. PQQ is a potential target for drugs.

Animals↗
PubMed1989

Methoxatin (PQQ), coenzyme for copper-dependent amine and mixed-function oxidation in mammalian tissues.

The newly discovered coenzyme PQQ can now be measured at picomole levels with redox cycling methods developed in our laboratory. PQQ-peptides have been obtained from digests of the copper quinoenzymes, diamine oxidase, lysyl oxidase and dopamine-beta-hydroxylase. PQQ is present in egg yolk and milk, suggesting its immediate availability for developing embryos and newborn animals. We suggest that PQQ, when exposed in traumatized, ischemic, inflammed or pathological tissues, may catalyze the formation of large amounts of superoxide and should be considered as a source of oxidative stress when planning pharmacotherapeutic intervention. PQQ and quinoproteins play a role in the redox metabolism and structural integrity of cells and tissues.

Amines↗
PubMed1988

The amplified detection of free and bound methoxatin (PQQ) with nitroblue tetrazolium redox reactions: insights into the PQQ-locus.

Porcine kidney diamine oxidase, a PQQ-enzyme, can be directly measured by formazan production with putrescine and nitroblue tetrazolium. This cyclic reaction in air is unaffected by superoxide dimutase, suggesting a two electron transfer between substrate-reduced PQQ-locus and nitroblue tetrazolium, without intermediate formation of superoxide. With albumin-bound PQQ and detergent-exposed PQQ-loci, glycine can be oxidized by PQQ and electrons repetitively transferred through PQQ-sites to nitroblue tetrazolium, the rate of formazan production detecting picomoles of exposed PQQ-locus. Exposed PQQ-loci are also reducible with NaCNBH3. Nitroblue tetrazolium, reoxidizes the reduced PQQ-locus with formazan production. These experiments suggest that the PQQ-locus of quinoproteins contains a [ketone-ketoimine in equilibrium with ketoamine] redox center.

Amine Oxidase (Copper-Containing)↗