Cellular glutathione levels may exceed vitamin C levels by 10-fold, generating the question about the real antioxidant role that low intracellular concentrations of vitamin C can play in the presence of a vast molar excess of glutathione. We characterized the metabolism of vitamin C and its relationship with glutathione in primary cultures of human endothelial cells oxidatively challenged by treatment with hydrogen peroxide or with activated cells undergoing the respiratory burst, and analyzed the manner in which vitamin C interacts with glutathione to increase the antioxidant capacity of cells. Our data indicate that: (i) endothelial cells express transporters for reduced and oxidized vitamin C and accumulate ascorbic acid with participation of glutathione-dependent dehydroascorbic acid reductases, (ii) although increased intracellular levels of vitamin C or glutathione caused augmented resistance to oxidative stress, 10-times more glutathione than vitamin C was required, (iii) full antioxidant protection required the simultaneous presence of intracellular and extracellular vitamin C at concentrations normally found in vivo, and (iv) intracellular vitamin C cooperated in enhancing glutathione recovery after oxidative challenge thus providing cells with enhanced survival potential, while extracellular vitamin C was recycled through a mechanism involving the simultaneous neutralization of oxidant species. Therefore, in endothelial cells under oxidative challenge, vitamin C functions as an essential cellular antioxidant even in the presence of a vast molar excess of glutathione.Human cells contain two important water soluble antioxidants, vitamin C and the tripeptide glutathione (L-␥-glutamyl-L-cysteinyl-glycine). Vitamin C plays an important physiological role in cells as a reducing agent and antioxidant, free radical scavenger, and enzyme cofactor (1, 2). Glutathione is the most abundant non-protein thiol in mammalian cells and participates in multiple functions central to the physiology of cells, acting as a reducing agent, antioxidant, and free-radical scavenger and is involved in the metabolism and detoxification of xenobiotics, and alterations in GSH levels and metabolism have been associated with different human diseases (3, 4). Glutathione and vitamin C show a strong functional interdependence in vivo. Disruption of glutathione metabolism in vivo in rats and guinea pigs by treatment with buthionine-(SR)-sulfoximine (BSO), 5 a potent and specific glutathione synthesis inhibitor, revealed that the dysfunction and mortality associated with glutathione deficiency can be ameliorated by vitamin C supplementation (3, 5). Inversely, glutathione ester supplementation can protect or delay the effects of a vitamin C-free diet in newborn rats and guinea pigs unable to synthesize vitamin C (3, 6).Although a functional relationship between glutathione and vitamin C has been clearly established in rats and guinea pigs, we know little about how they cooperate in providing human cells with potent antioxidant defense mechan...

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Flow cytometry (FCM) was implemented in 2008 at the Pontificia Universidad Javeriana and later at the Hospital Universitario San Ignacio to examine special samples of patients with hematological malignancies and solid tumors other than bone marrow and peripheral blood for diagnosis and monitoring. This study describes the main findings of special sample evaluation over a six-year period. In all, 1070 samples of body fluids from patients with benign and malignant diseases were examined by FCM. These samples were stabilized with TransFix TM and stained with six-color immunophenotyping panels. Samples included cerebrospinal fluid, bronchoalveolar lavage, pleural fluid, pericardial fluid and ascite fluid from patients with acute and chronic leukemia, myelodysplastic syndromes, lymphomas, myeloma, autoimmune diseases, immunodeficiencies and solid tumors, among others. Flow cytometry provided important information for the classification and detection of minimal numbers of tumor cells in leukemia and lymphoma cases. This work represents the first national report describing FCM implementation in special samples for diagnosis and clinical monitoring of patients with malignant and benign pathologies. Consequently, over the last decade, use of commercially available cell stabilization solutions has been recommended. These solutions can preserve PB and cerebrospinal fluid (CSF) samples over time periods greater than one week after collection [4, 8 -9]. This stabilization preserves cellularity and integrity of both cell surface and intracellular antigens [9].

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Central nervous system infiltration by acute leukemia is a poor prognosis variable, and conventional cytology is the gold standard for its diagnosis; the technique is highly specific but not sensitive. To improve the diagnosis, flow cytometry has been used in different studies, showing greater sensitivity in the detection of leukemic cells. This study aimed to evaluate the presence of tumor cells by flowcytometry and conventional cytology, in cerebrospinal fluid from patients with acute leukemia as well as its relationship with clinical and biological parameters. In total, 156 CSF samples from 55 children with acute leukemia were studied. We found the following results: FCM-/CC- 131/156; FCM+/CC- 19/156; FCM-/CC+ 0; FCM+/CC+ 1/156; FC-/CC suspicious 1/156; and FCM+/CC suspicious 4/156. Patients with B-cell acute lymphoblastic leukemia and FCM+ showed a lower response to steroid-treatment, abnormal karyotype, neurological symptoms, and worse relapsefree survival. Patients with T-cell acute lymphoblastic leukemia and FCM+ demonstrated association with thrombocytopenia. In conclusion, flow cytometry has greater sensitivity for the detection of tumor infiltration in cerebrospinal fluid, a finding that correlates with prognostic parameters in patients with acute leukemia.

Se trata de un paciente pediátrico diagnosticado con una leucemia linfoblástica aguda (LLA) de precursores B, con dos poblaciones de blastos diferentes caracterizadas mediante citometría de flujo (una población tiene un inmunofenotipo asociado a células Pre-B y otra población corresponde a LLA-B común). El análisis genético en médula ósea reportó la presencia de t(9;22) (q34;q11) con BCR-ABL, hiperdiploidía de DNA (>50 cromosomas) y trisomía del cromosoma 5. Dada la complejidad genética, el paciente fue monitorizado semanalmente mediante citometría de flujo con persistencia de la población tumoral correspondiente a LLA-B común, hasta su eventual remisión.