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A Arroyo

Publications and source records attributed to A Arroyo.

At least 37 records · Page 2Linked to original sources
PubMed2000

Analysis of Arabidopsis glucose insensitive mutants, gin5 and gin6, reveals a central role of the plant hormone ABA in the regulation of plant vegetative development by sugar.

Sugars have signaling roles in a wide variety of developmental processes in plants. To elucidate the regulatory components that constitute the glucose signaling network governing plant growth and development, we have isolated and characterized two Arabidopsis glucose insensitive mutants, gin5 and gin6, based on a glucose-induced developmental arrest during early seedling morphogenesis. The T-DNA-tagged gin6 mutant abrogates the glucose-induced expression of a putative transcription factor, ABI4, previously shown to be involved in seed-specific abscisic acid (ABA) responses. Thus, ABI4 might be a regulator involved in both glucose- and seed-specific ABA signaling. The characterization of the gin5 mutant, on the other hand, reveals that glucose-specific accumulation of ABA is essential for hexokinase-mediated glucose responses. Consistent with this result, we show that three ABA-deficient mutants (aba1-1, aba2-1, and aba3-2) are also glucose insensitive. Exogenous ABA can restore normal glucose responses in gin5 and aba mutants but not in gin6 plants. Surprisingly, only abi4 and abi5-1 but not other ABA-insensitive signaling mutants (abi1-1, abi2-1, and abi3-1) exhibit glucose insensitivity, indicating the involvement of a distinct ABA signaling pathway in glucose responses. These results provide the first direct evidence to support a novel and central role of ABA in plant glucose responses mediated through glucose regulation of both ABA levels by GIN5 and ABA signaling by GIN6/ABI4.

Abscisic Acid↗
PubMed2000

Variational Evaluation of the HSSH FIR Transitions: The Anomalous K-Doubling.

The roto-torsional energy levels of HSSH and DSSD up to J = 20 are evaluated variationally with a Hamiltonian expressed in terms of internal coordinates. The kinetic and potential parameters are derived from ab initio calculations with full optimization of the geometry. The calculated levels are employed for the determination of the centrifugal distortion constants. HSSH is a near-prolate symmetric rotor. The most stable C(2) conformer, calculated with MP4(SDQ)/cc-pVQZ, exhibits a 90.55 degrees dihedral angle. For J = 0, the lowest energies of HSSH and DSSD are 413.4876 cm(-1) (n = 1), 798.0304 cm(-1) (n = 2) and 1151.5773 cm(-1) (n = 3), and 304.3185 cm(-1) (n = 1), 594.2919 cm(-1) (n = 2), and 869.3508 cm(-1) (n = 3), respectively. For J = 60, the ab initio calculations allow the reproduction of the anomalous type-K doubling predicted with perturbation theory. Copyright 2000 Academic Press.

Journal Article↗
PubMed2000

alpha-synuclein promotes mitochondrial deficit and oxidative stress.

Abnormal accumulation of the presynaptic protein alpha-synuclein has recently been implicated in the pathogenesis of Alzheimer's and Parkinson's diseases. Because neurodegeneration in these conditions might be associated with mitochondrial dysfunction and oxidative stress, the effects of alpha-synuclein were investigated in a hypothalamic neuronal cell line (GT1-7). alpha-Synuclein overexpression in these cells resulted in formation of alpha-synuclein-immunopositive inclusion-like structures and mitochondrial alterations accompanied by increased levels of free radicals and decreased secretion of gonadotropin-releasing hormone. These alterations were ameliorated by pretreatment with anti-oxidants such as vitamin E. Taken together these results suggest that abnormal accumulation of alpha-synuclein could lead to mitochondrial alterations that may result in oxidative stress and, eventually, cell death.

Animals↗
PubMed2000

Interactions between ascorbyl free radical and coenzyme Q at the plasma membrane.

A role for coenzyme Q in the stabilization of extracellular ascorbate by intact cells has been recently recognized. The aim of this work was to study the interactions between reduced ubiquinone in the plasma membrane and the ascorbyl free radical, as an approach to understand ubiquinone-mediated ascorbate stabilization at the cell surface. K-562 cells stabilized ascorbate and decreased the steady-state levels of the semiascorbyl radical. The ability of cells to reduce ascorbyl free radical was inhibited by the quinone analogs capsaicin and chloroquine and stimulated by supplementing cells with coenzyme Q10. Purified plasma membranes also reduced ascorbyl free radical in the presence of NADH. Free-radical reduction was not observed in quinone-depleted plasma membranes, but restored after its reconstitution with coenzyme Q10. Addition of reduced coenzyme Q10 to depleted membranes allowed them to reduce the signal of the ascorbyl free radical without NADH incubation and the addition of an extra amount of purified plasma membrane quinone reductase further stimulated this activity. Reduction was abolished by treatment with the reductase inhibitor p-hydroximercuribenzoate and by blocking surface glycoconjugates with the lectin wheat germ agglutinin, which supports the participation of transmembrane electron flow. The activity showed saturation kinetics by NADH and coenzyme Q, but not by the ascorbyl free radical in the range of concentrations used. Our results support that reduction of ascorbyl free radicals at the cell surface involves coenzyme Q reduction by NADH and the membrane-mediated reduction of ascorbyl free radical.

Animals↗
PubMed2000

NADH and NADPH-dependent reduction of coenzyme Q at the plasma membrane.

High affinity for NADH, and low affinity for NADPH, for reduction of endogenous coenzyme Q10 (CoQ10) by pig liver plasma membrane is reported in the present work. CoQ reduction in plasma membrane is carried out, in addition to other mechanisms, by plasma membrane coenzyme Q reductase (PMQR). We show that PMQR-catalyzed reduction of CoQ0 by both NADH and NADPH is accompanied by generation of CoQ0 semiquinone radicals in a superoxide-dependent reaction. In the presence of a water-soluble vitamin E homologue, Trolox, this reduction leads to quenching of the Trolox phenoxyl radicals. The involvement of PMQR versus DT-diaphorase under the conditions of vitamin E and selenium sufficiency and deficiency was evaluated for CoQ reduction by plasma membranes. The data presented here suggest that both nucleotides (NADH and NADPH) can be accountable for CoQ reduction by PMQR on the basis of their physiological concentrations within the cell. The enzyme is primarily responsible for CoQ reduction in plasma membrane under normal (nonoxidative stress-associated) conditions.

Animals↗
PubMed1999

[Development of Escherichia coli strands resistant to quinolones in stools of patients with liver cirrhosis submitted to selective bowel decontamination].

BACKGROUND: Selective intestinal decontamination (SID) with norfloxacin in patients with cirrhosis may promote the development of quinolone-resistant (QR) gram-negative bacteria in stools. It is not known wether this fact may become a predisposing factor for the development of infections due to these bacteria. MATERIAL AND METHODS: We designed a prospective study to evaluate the incidence of Escherichia coli in stools at admission in patients with cirrhosis that had previously received norfloxacin as primary or secondary prophylaxis of spontaneous bacterial peritonitis (SBP) (group I, n = 28) vs those who did not (group II, n = 55). RESULTS: QR strains of E. coli were observed in 37.5 and in 1.47% of patients from groups I and II, respectively (p < 0.001). During admission, 36 patients underwent norfloxacin prophylaxis (group III), and 40 did not (group IV). Eleven patients from group III and one patient from group IV showed QR E. coli in stools. We observed 5 bacterial infections in group III and 14 in group IV (p = 0.0039). No patient with QR E. coli in stools developed infections due to this bacteria. CONCLUSION: The incidence of QR E. coli in stools of patients with cirrhosis is significantly increased in patients previously treated with prophylactic norfloxacin. However, this fact seems not to be associated with an increment in the prevalence of QR E. coli infections.

Aged↗
PubMed1999

Protective role of ubiquinone in vitamin E and selenium-deficient plasma membranes.

We have studied the effects of dietary depletion of vitamin E and selenium on endogenous ubiquinone-dependent antioxidant system. Deficiency induced an increase in both coenzyme Q9 and Q10 in liver tissue, reaching a maximum between 4 and 7 weeks of deficient diet consumption. Cytochrome b5 reductase polypeptide was also enriched in membranes after 5 weeks of deficient diet consumption. Substantial DT-diaphorase activity was found in deficient, but not in control plasma membranes. Deficient membranes were very sensitive to lipid peroxidation, although a great protection was observed after incubation with NAD(P)H. Our results show that liver cells can boost endogenous ubiquinone-dependent protective mechanisms in response to deficiency in vitamin E and selenium.

Animals↗
PubMed1999

Development of quinolone-resistant strains of Escherichia coli in stools of patients with cirrhosis undergoing norfloxacin prophylaxis: clinical consequences.

BACKGROUND/AIM: Norfloxacin prophylaxis decreases the incidence of bacterial infections in high-risk cirrhotic patients, but may promote the development of quinolone-resistant gram-negative bacteria in stools, and eventually lead to infections due to these bacteria. The aim of the study was to evaluate the prevalence of quinolone-resistant strains of E. coli in stools on admission, and the characteristics of any nosocomial infections. METHODS: Eighty-three consecutively hospitalized cirrhotic patients were included in this prospective study. The presence of quinolone-resistant strains of E. coli in stools on admission, and the characteristics of any nosocomial infections were recorded. RESULTS: Fourteen out of 83 patients (16.8%) showed quinolone-resistant E. coli in stools (Group I), and 69 did not (Group II). Thirteen out of 14 from Group I (92.8%) and 17/69 (24.6) from Group II had received primary or secondary prophylaxis with norfloxacin (p<0.001). During hospitalization, 12/12 (100%) of patients from Group I and 25/66 (37.8%) of patients from Group II underwent norfloxacin prophylaxis. Three bacterial infections in patients from Group I, 3 from Group II patients receiving norfloxacin and 16 from Group II patients not receiving norfloxacin were recorded (p<0.05). No infections due to quinolone-resistant E. coli were observed in patients colonized with these bacteria. Treatment with norfloxacin induced the development of quinolone-resistant E. coli in 6/14 (42.8%) patients in a mean time of 18.5+/-9.8 days. CONCLUSIONS: The development of quinolone-resistant strains of E. coli is significantly associated with previous administration of norfloxacin prophylaxis. However, in our series this fact is not associated with an increased incidence of quinolone-resistant E. coli or other gram-negative infections.

Aged↗
PubMed1999

The insulin-like growth factor system in the GT1-7 GnRH neuronal cell line.

Evidence suggests that insulin-like growth factors (IGFs; IGF-I and IGF-II) are involved in the regulation of reproductive function including the development of the gonadotropin-releasing hormone (GnRH) neuronal system and the modulation of GnRH secretory activities. To further characterize the regulatory role of the IGF system on GnRH neuronal function, we have examined the gene expression of IGF-I, IGF-II, IGF-I receptor (IGF-IR), and IGF-binding proteins (IGFBPs) in a GnRH neuronal cell line (GT1-7 cells). The relative effects of IGFs and insulin on GnRH secretion by these cells was also investigated. RT-PCR analysis demonstrated IGF-I, IGF-II and IGF-IR mRNAs in GT1-7 cells. The mRNAs for IGFBP-2, -3, -4, -5 and -6 but not IGFBP-1 were also detected. Immunoreactive protein bands for IGFBP-2, -4 and -5 but not for other IGFBPs were demonstrated by Western blot with IGFBP-5 appearing to be the most abundant IGFBP secreted by GT1-7 cells. IGFBP-5 production by GT1-7 cells was stimulated by both IGF-I and IGF-II in a dose-dependent manner with approximately equal potency, whereas insulin caused no significant effect. GnRH secretion by GT1-7 cells treated with IGF-I or IGF-II but not insulin showed an increase (80-100%) at 2 h of treatment followed by a decrease (46%) at 6 h that continued up to 24 h. We conclude that the expression of IGFs, IGF-IR and IGFBPs and their interactions in the regulation of GnRH secretion by GT1-7 cells as demonstrated by our study provide a basis for an autocrine regulatory role for the IGF system in GnRH neuronal secretory activities.

Animals↗
PubMed1999

Bioflavonoid effects on the mitochondrial respiratory electron transport chain and cytochrome c redox state.

The polyphenolic structure common to flavonoids enables them to donate electrons and exert antioxidant activity. Since the mitochondrial electron transport chain consists of a series of redox intermediates, the effect of flavonoids in a complex mixture of polyphenols, as well as related pure flavonoids, was evaluated on the rat liver mitochondrial electron transport chain. A French maritime pine bark extract (PBE), a complex mixture of polyphenols and related pure flavonoids, was able to reduce cytochrome c reversibly, possibly by donation of electrons to the iron of the heme group; the donated electrons can be utilized by cytochrome c oxidase. Among single flavonoids tested, (-)-epicatechin gallate had the greatest ability to reduce cytochrome c. In addition, PBE competitively inhibited electron chain activity in both whole mitochondria and submitochondrial particles. A 3.5-fold increase in the apparent Km value for succinate was calculated from reciprocal plots. Among the flavonoids tested, taxifolin and (-)-epicatechin gallate showed minor inhibitory effects, while (+/-)-catechin and (+)-epicatechin were ineffective. Activities of NADH-ubiquinone, succinate-ubiquinone, and ubiquinol-cytochrome c reductases were inhibited by low concentrations of PBE to a similar extent. However, inhibition of cytochrome c oxidase activity required 4-fold higher PBE concentrations. These results suggest that flavonoids reduce cytochrome c and that PBE inhibits electron transport chain activity mainly through NADH-ubiquinone, succinate-ubiquinone, and ubiquinol-cytochrome c reductases.

Animals↗
PubMed1998

Plasma membrane NADH-coenzyme Q0 reductase generates semiquinone radicals and recycles vitamin E homologue in a superoxide-dependent reaction.

We investigated the ability of plasma membrane CoQ reductase (PMQR) purified from pig liver to reduce phenoxyl radicals of a vitamin E homologue, Trolox. We report that NADH-driven one-electron reduction of CoQ0 catalyzed by PMQR produced CoQ0 semiquinone radical and CoQoH2. These in turn, recycle vitamin E homologue, Trolox, via reducing its phenoxyl radical. A significant part of NADH/PMQR-catalyzed reduction of CoQ0 (and Trolox recycling) was superoxide-dependent. Overall, our results demonstrate that PMQR in the model system used can act as an antioxidant enzyme that recycles water-soluble homologues of coenzyme Q and vitamin E.

Animals↗
PubMed1998

Vitamin E and selenium deficiency induces expression of the ubiquinone-dependent antioxidant system at the plasma membrane.

We have used a model of dietary deficiency that leads to a chronic oxidative stress to evaluate responses that are adaptations invoked to boost cellular defense systems. Long-Evans hooded rats were fed with a diet lacking vitamin E (E) and selenium (Se) for 7 wk from weaning leading to animals deficient in both nutrients (-E -Se). In the absence of an electron donor, liver plasma membranes from these rats were more sensitive to lipid peroxidation, although they contained 40% greater amounts of ubiquinone than the plasma membranes from rats consuming diets with sufficient vitamin E and Se (+E +Se). The incubation of plasma membranes with NAD(P)H resulted in protection against peroxidation, and this effect was more pronounced in -E -Se membranes. Deficiency was accompanied by a twofold increase in redox activities associated with trans plasma membrane electron transport such as ubiquinone reductase and ascorbate free radical reductase. Staining with a polyclonal antibody against pig liver cytochrome b5 reductase, which acts as one ubiquinone reductase in the plasma membrane, showed an increased expression of the enzyme in membranes from -E -Se rats. Little DT-diaphorase activity was measured in +E +Se plasma membranes, but this activity was dramatically increased in -E -Se plasma membranes. No such increase was found in liver cytosols, which contained elevated activity of calcium-independent phospholipase A2. Thus, ubiquinone-dependent antioxidant protection in +E +Se plasma membranes is based primarily on NADH-cytochrome b5 reductase, whereas additional protection needed in -E -Se plasma membranes is supported by the increase of ubiquinone levels, increased expression of the cytochrome b5 reductase, and translocation of soluble DT-diaphorase to the plasma membrane. Our results indicate that, in the absence of vitamin E and Se, enhancement of ubiquinone-dependent reductase systems can fulfill the membrane antioxidant protection.

Animals↗
PubMed1998

Pericardial fluid postmortem: Comparative study of natural and violent deaths.

Thanatochemistry is an increasingly important ancillary procedure in forensic practice. Alterations are known to take place in biochemical components during the postmortem period, particularly in the blood, and both research results and their interpretation have been the object of some controversy. For that reason, emphasis has been placed on the examination of fluids that are neither altered nor contaminated as rapidly as blood after death. This study tested the hypothesis that pericardial fluid (PF) may be a suitable medium for biochemical analysis in corpses. The study sought to determine concentrations of urea, creatinine, glucose, creatinine kinase 2, proteins, calcium, sodium, and potassium, in the pericardial fluid of corpses. The study sample was divided into two groups, natural deaths and violent deaths. Intergroup results were compared, using Mann-Whitney's U test for paired data. No significant differences were obtained between the natural death and violent death groups for the parameters studied, with the exception of urea (p < .05). Further studies are required to compare these results and create the possibility for new conclusions.

Autopsy↗
PubMed1997

Role of cytochrome b5 reductase on the antioxidant function of coenzyme Q in the plasma membrane.

Cytochrome b5 reductase purified from liver plasma membrane reduces coenzyme Q (CoQ) in reconstituted liposomes in the absence of cytochrome b5. Both CoQ and its reductase are responsible for the reduction of the ascorbate free radical at the cell surface. Thus, NADH-CoQ reductase represents a partial reaction of NADH-AFR reductase in the plasma membrane. Cytochrome b5 reductase maintains CoQ and ascorbate in their reduced state to support antioxidations. Reduced CoQ prevents lipid peroxidation in liposomes and plasma membranes. Also, oxidized CoQ can prevent lipid peroxidations in the presence of cytochrome b5 reductase and NADH. Addition of CoQ to intact cells prevents serum withdrawal-induced lipid peroxidation and apoptosis. The prevention of apoptosis by CoQ is independent of the bcl-2 protein content in the cell. Antioxidants that act at the plasma membrane as CoQ and ascorbate would represent a first barrier to protect lipids from oxidative stress and subsequent apoptosis. Cytochrome b5 reductase is then an enzyme leading this function at the plasma membrane. These data support the idea that when the plasma membrane barrier fails, bcl-2 protein would be required to prevent cell death.

Animals↗
PubMed1997

Vinorelbine as neoadjuvant chemotherapy in advanced cervical carcinoma.

PURPOSE: To evaluate the efficacy and toxicity of vinorelbine (VNB) as single-agent neoadjuvant chemotherapy in advanced cervical carcinoma (ACC). PATIENTS AND METHODS: Between December 1993 and October 1995, 43 untreated patients with stages IIB to IVA squamous cell cervical cancer were entered onto this study. Forty-two patients are assessable for response and 43 for toxicity. The median age was 46 years (range, 28 to 65). Distribution by stages (International Federation of Gynecology and Obstetrics [FIGO]) was as follows: IIB, 18 patients; IIIA, one; IIIB, 19; and IVA, five. Therapy consisted of VNB 30 mg/m2 by 20-minute intravenous (IV) infusion repeated weekly for 12 injections and followed by radical surgery if feasible or definitive radiotherapy. Both staging and response assessment were performed by a multidisciplinary team. RESULTS: One patient was considered not assessable for response. A total of 493 cycles of therapy were administered and objective remissions were observed in 19 of 42 patients (45%; 95% confidence interval, 30% to 60%). Two patients (5%) had a complete response (CR) and 17 (40%) a partial response (PR); no change (NC) was observed in 16 (38%) and progressive disease (PD) in seven (17%). Six of 19 patients (32%) who achieved objective responses (ORs) underwent surgery. The median time to failure and median survival time have not been reached yet. There were no therapy-related deaths. The dose-limiting toxicity was myelosuppression. Leukopenia occurred in 35 patients (81%) and was grade 3 or 4 in seven (17%). Twelve patients (28%) developed peripheral neuropathy, while myalgias occurred in 10 (23%). Constipation was observed in nine patients (21%), one with a prolonged ileum. Phlebitis was recorded in 18 patients (41%). In contrast, emesis and mucositis were rarely observed. No patient developed alopecia grade 3. By the end of the twelfth course of treatment, the average received dose-intensity was 85.4% of that projected. CONCLUSION: VNB is an active drug against ACC with moderate toxicity. Its activity is among the highest reported for single agents. Further evaluation in association with other agents is clearly justified.

Adult↗
PubMed1997

Inappropriate gonadotropin secretion in polycystic ovary syndrome: influence of adiposity.

In recent years, there has been uncertainty concerning the association of inappropriate gonadotropin secretion (high LH and normal FSH) and the polycystic ovary syndrome (PCOS). In the present study, we ascertained the influence of body composition on LH pulsatile parameters in 33 PCOS and 32 normal cycling (NC) women across a wide range of body mass index (BMI, 19-42 kg/m2). Twenty four-hour pulsatile parameters for serum LH (10-min sampling) and pituitary gonadotropin responses to i.v. bolus GnRH (10 micrograms) were evaluated. Fasting (0800 h) FSH and steroid hormone concentrations and 24-h mean insulin levels were determined. Insulin sensitivity (SI) was assessed by rapid i.v. glucose tolerance test in a subset of 28 PCOS and 29 NC subjects. Our results showed that BMI, an indicator of relative adiposity, had a significant negative impact on 24-h mean LH pulse amplitude (r = -0.63, P < 0.001) and the peak increment of LH in response to GnRH stimulation (r = -0.41; P = 0.02) for PCOS but not NC women. In contrast, 24-h LH pulse frequency was uniformly increased (40%) in PCOS as compared with NC women independent of BMI. In PCOS women, the blunting of pulse amplitude with increasing BMI resulted in a decline in 24-h mean LH levels (r = -0.63, P < 0.001) and the ratio of LH/FSH (r = -0.44, P = 0.02) not seen in NC. With BMI < 30 kg/m2, 24-h mean LH values for PCOS women were greater than the normal range for NC in 95% (18/19) of cases, whereas 24-h LH levels failed to discriminate PCOS from NC women in 43% (6/14) of obese (BMI > 30 kg/m2) PCOS women. Thus, the diagnostic value of LH determinations is retained for PCOS women with BMI < 30 kg/m2. For screening purposes, the mean of two LH values in samples collected at 30-min intervals was found to have a discriminatory power equal to that of the 24-h mean. These findings suggest that 1) BMI negatively influences LH pulse amplitude in PCOS women principally by an effect at the pituitary level; 2) accelerated LH pulse frequency in PCOS women is not influenced by BMI and represents a basic component of hypothalamic dysfunction in PCOS women; and 3) BMI does not influence gonadotropin secretion in normal cycling women. Thus assessments of basal LH levels and the LH/FSH ratio in hyperandrogenic anovulatory women are clinically meaningful when BMI is taken into account. Investigations to define the factor(s) that link adiposity and the attenuation of LH pulse amplitude in PCOS women would add further understanding of this complex neuroendocrine-metabolic disorder.

17-alpha-Hydroxyprogesterone↗