Guillermo Saez - Academia.edu (original) (raw)

Papers by Guillermo Saez

Research paper thumbnail of Antioxidant activities and oxidative stress byproducts in human hypertension

…, 2003

The objective was to study oxidative status, antioxidant activities, and reactive oxygen species ... more The objective was to study oxidative status, antioxidant activities, and reactive oxygen species byproducts in whole blood and mononuclear peripherals cells and their relationship with blood pressure. Sixty-six hypertensive patients and 16 normotensive volunteers as a control ...

Research paper thumbnail of Oxidative Stress and DNA Damage in Human Gastric Carcinoma: 8-Oxo-7'8-dihydro-2'-deoxyguanosine (8-oxo-dG) as a Possible Tumor Marker

We characterized the oxidative stress (OS) status by the levels of reduced/oxidized glutathione (... more We characterized the oxidative stress (OS) status by the levels of reduced/oxidized glutathione (GSH/GSSG), malondialdehyde (MDA) and the mutagenic base 8-oxo-7'8-dihydro-2'-deoxyguanosine (8-oxo-dG) in human gastric carcinoma (HGC) samples and compared the results with normal tissue from the same patients. We also OPEN ACCESS analyzed 8-oxo-dG in peripheral mononuclear cells (PMNC) and urine from healthy control subjects and in affected patients in the basal state and one, three, six, nine and twelve months after tumor resection. The levels of DNA repair enzyme mRNA expression (hOGG1, RAD51, MUYTH and MTH1) were determined in tumor specimens and compared with normal mucosa. Tumor specimens exhibited increased levels of MDA and 8-oxo-dG compared with normal gastric tissue. GSH levels were also increased, while GSSG levels remained stable. DNA repair enzyme mRNA expression was induced in the tumor tissues. Levels of 8-oxo-dG were significantly elevated in both urine and PMNC of gastric cancer patients compared with healthy controls. After gastrectomy, the levels of the damaged base in urine and PMNC decreased progressively to values close to those found in the healthy population. The high levels of 8-oxo-dG in urine may be related to the increased induction of DNA repair activity in tumor tissue, and the changes observed after tumor resection support its potential use as a tumor marker.

Research paper thumbnail of Glucose formation from methylglyoxal in rat hepatocytes

Biochemical Society Transactions, 1985

Research paper thumbnail of Human and Methodological Sources of Variability in the Measurement of Urinary 8-Oxo-7,8-dihydro-2′-deoxyguanosine

Antioxidants & Redox Signaling, 2013

Aims: Urinary 8-oxo-7,8-dihydro-2¢-deoxyguanosine (8-oxodG) is a widely used biomarker of oxidati... more Aims: Urinary 8-oxo-7,8-dihydro-2¢-deoxyguanosine (8-oxodG) is a widely used biomarker of oxidative stress. However, variability between chromatographic and ELISA methods hampers interpretation of data, and this variability may increase should urine composition differ between individuals, leading to assay interference. Furthermore, optimal urine sampling conditions are not well defined. We performed inter-laboratory comparisons of 8-oxodG measurement between mass spectrometric-, electrochemical-and ELISA-based methods, using common within-technique calibrants to analyze 8-oxodG-spiked phosphate-buffered saline and urine samples. We also investigated human subject-and sample collection-related variables, as potential sources of variability. Results: Chromatographic assays showed high agreement across urines from different subjects, whereas ELISAs graphic assays. Excretion rates in timed 'spot' samples showed strong correlations with 24 h excretion (the 'gold' standard) of urinary 8-oxodG (r p 0.67-0.90), although the associations were weaker for 8-oxodG adjusted for creatinine or specific gravity (SG). The within-individual excretion of 8-oxodG varied only moderately between days (CV 17% for 24 h excretion and 20% for first void, creatinine-corrected samples). Innovation: This is the first comprehensive study of both human and methodological factors influencing 8-oxodG measurement, providing key information for future studies with this important biomarker. Conclusion: ELISA variability is greater than chromatographic assay variability, and cannot determine absolute levels of 8-oxodG. Use of standardized calibrants greatly improves intra-technique agreement and, for the chromatographic assays, importantly allows integration of results for pooled analyses. If 24 h samples are not feasible, creatinine-or SG-adjusted first morning samples are recommended.

Research paper thumbnail of The production of free radicals during the autoxidation of cysteine and their effect on isolated rat hepatocytes

Biochimica et Biophysica Acta (BBA) - General Subjects, 1982

Autoxidizing cysteine has been shown to produce thiyi and hydroxyl radicals. Hydrogen peroxide in... more Autoxidizing cysteine has been shown to produce thiyi and hydroxyl radicals. Hydrogen peroxide increased the yield of both radicals which was inhibited by catalase but stimulated by copper/zinc superoxide dismutase. This effect is due to increased hydrogen peroxide production by copper/zinc superoxide dismutase as a result of superoxide dismutation. The production of superoxide radicals could not be detected probably because of its low reactivity, however, measurement of oxygen uptake and reduction of ferricytochrome c by autoxidizing cysteine clearly implicate the involvement of super oxide radicals. The production of hydroxyl radicals is postulated to proceed through a Fenton reaction, however, this may not necessarily be metal ion controlled. Autoxidizing cysteine disrupts the integrity of heptocytes causing release of glutathione, adenosine triphosphate and lactate dehydrogenase indicating that it is of little use as a therapeutic agent.

Research paper thumbnail of Antioxidant activities and oxidative stress byproducts in human hypertension

…, 2003

The objective was to study oxidative status, antioxidant activities, and reactive oxygen species ... more The objective was to study oxidative status, antioxidant activities, and reactive oxygen species byproducts in whole blood and mononuclear peripherals cells and their relationship with blood pressure. Sixty-six hypertensive patients and 16 normotensive volunteers as a control ...

Research paper thumbnail of Oxidative Stress and DNA Damage in Human Gastric Carcinoma: 8-Oxo-7'8-dihydro-2'-deoxyguanosine (8-oxo-dG) as a Possible Tumor Marker

We characterized the oxidative stress (OS) status by the levels of reduced/oxidized glutathione (... more We characterized the oxidative stress (OS) status by the levels of reduced/oxidized glutathione (GSH/GSSG), malondialdehyde (MDA) and the mutagenic base 8-oxo-7'8-dihydro-2'-deoxyguanosine (8-oxo-dG) in human gastric carcinoma (HGC) samples and compared the results with normal tissue from the same patients. We also OPEN ACCESS analyzed 8-oxo-dG in peripheral mononuclear cells (PMNC) and urine from healthy control subjects and in affected patients in the basal state and one, three, six, nine and twelve months after tumor resection. The levels of DNA repair enzyme mRNA expression (hOGG1, RAD51, MUYTH and MTH1) were determined in tumor specimens and compared with normal mucosa. Tumor specimens exhibited increased levels of MDA and 8-oxo-dG compared with normal gastric tissue. GSH levels were also increased, while GSSG levels remained stable. DNA repair enzyme mRNA expression was induced in the tumor tissues. Levels of 8-oxo-dG were significantly elevated in both urine and PMNC of gastric cancer patients compared with healthy controls. After gastrectomy, the levels of the damaged base in urine and PMNC decreased progressively to values close to those found in the healthy population. The high levels of 8-oxo-dG in urine may be related to the increased induction of DNA repair activity in tumor tissue, and the changes observed after tumor resection support its potential use as a tumor marker.

Research paper thumbnail of Glucose formation from methylglyoxal in rat hepatocytes

Biochemical Society Transactions, 1985

Research paper thumbnail of Human and Methodological Sources of Variability in the Measurement of Urinary 8-Oxo-7,8-dihydro-2′-deoxyguanosine

Antioxidants & Redox Signaling, 2013

Aims: Urinary 8-oxo-7,8-dihydro-2¢-deoxyguanosine (8-oxodG) is a widely used biomarker of oxidati... more Aims: Urinary 8-oxo-7,8-dihydro-2¢-deoxyguanosine (8-oxodG) is a widely used biomarker of oxidative stress. However, variability between chromatographic and ELISA methods hampers interpretation of data, and this variability may increase should urine composition differ between individuals, leading to assay interference. Furthermore, optimal urine sampling conditions are not well defined. We performed inter-laboratory comparisons of 8-oxodG measurement between mass spectrometric-, electrochemical-and ELISA-based methods, using common within-technique calibrants to analyze 8-oxodG-spiked phosphate-buffered saline and urine samples. We also investigated human subject-and sample collection-related variables, as potential sources of variability. Results: Chromatographic assays showed high agreement across urines from different subjects, whereas ELISAs graphic assays. Excretion rates in timed 'spot' samples showed strong correlations with 24 h excretion (the 'gold' standard) of urinary 8-oxodG (r p 0.67-0.90), although the associations were weaker for 8-oxodG adjusted for creatinine or specific gravity (SG). The within-individual excretion of 8-oxodG varied only moderately between days (CV 17% for 24 h excretion and 20% for first void, creatinine-corrected samples). Innovation: This is the first comprehensive study of both human and methodological factors influencing 8-oxodG measurement, providing key information for future studies with this important biomarker. Conclusion: ELISA variability is greater than chromatographic assay variability, and cannot determine absolute levels of 8-oxodG. Use of standardized calibrants greatly improves intra-technique agreement and, for the chromatographic assays, importantly allows integration of results for pooled analyses. If 24 h samples are not feasible, creatinine-or SG-adjusted first morning samples are recommended.

Research paper thumbnail of The production of free radicals during the autoxidation of cysteine and their effect on isolated rat hepatocytes

Biochimica et Biophysica Acta (BBA) - General Subjects, 1982

Autoxidizing cysteine has been shown to produce thiyi and hydroxyl radicals. Hydrogen peroxide in... more Autoxidizing cysteine has been shown to produce thiyi and hydroxyl radicals. Hydrogen peroxide increased the yield of both radicals which was inhibited by catalase but stimulated by copper/zinc superoxide dismutase. This effect is due to increased hydrogen peroxide production by copper/zinc superoxide dismutase as a result of superoxide dismutation. The production of superoxide radicals could not be detected probably because of its low reactivity, however, measurement of oxygen uptake and reduction of ferricytochrome c by autoxidizing cysteine clearly implicate the involvement of super oxide radicals. The production of hydroxyl radicals is postulated to proceed through a Fenton reaction, however, this may not necessarily be metal ion controlled. Autoxidizing cysteine disrupts the integrity of heptocytes causing release of glutathione, adenosine triphosphate and lactate dehydrogenase indicating that it is of little use as a therapeutic agent.