[Viral genotypes in patients with hepatitis C virus infection in Medellín].
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Colombia↗
Biomedical subjects
C Alvarez
Publications and source records attributed to C Alvarez.
Characterization of distinct apoptotic changes induced by okadaic acid and yessotoxin in the BE(2)-M17 neuroblastoma cell line.
Apoptotic changes induced by okadaic acid and yessotoxin in BE(2)-M17 neuroblastoma cells have been evaluated and quantified by combining classical methods and fast and sensitive fluorimetric microplate assays. The phosphatase inhibitor okadaic acid induced rapid time- and dose-dependent apoptotic changes in this cell line, which were evident after 1h at concentrations equal or higher than 500 nM. Decreased mitochondrial membrane potential by okadaic acid (IC(50)=350 nM at 1h) was followed by cell detachment (IC(50)=400 nM at 1h), changes in total nucleic acids content (50% of controls after 1h with 1000 nM okadaic acid), caspase-3 activation (3- to 4-fold increase at 6h) and increased Annexin-V binding (1.5-fold at 6h). Yessotoxin induced similar changes in BE(2)-M17 cells, although significant differences were found in the time-course and degree of apoptotic events induced by this phycotoxin, indicating a lower potency for yessotoxin when compared with okadaic acid. This is the first report on apoptogenic activity of yessotoxin.
Annexin A5↗
Expression of E-cadherin in squamous cell carcinomas of the supraglottic larynx with correlations to clinicopathological features.
The aim of this study was to investigate the prognostic significance of E-cadherin expression in squamous cell carcinomas of the supraglottic larynx. 101 primary carcinomas were retrospectively studied. The level of E-cadherin expression was determined by immunohistochemistry. There was a significant correlation between decreased E-cadherin expression and the presence of nodal metastases (P=0.007). T-stage (P=0.025) and histological grade (P=0.043) were also associated with nodal metastases. Multivariate analysis confirmed that these three parameters were independent predictors of nodal metastases. Decreased E-cadherin expression also correlated with an increase in recurrence rates (P=0.019). However, in multivariate analysis only pathological N-stage was significantly associated with disease-specific survival. We conclude that E-cadherin is an independent predictor of nodal metastases in supraglottic squamous cell carcinomas. Determination of E-cadherin expression levels might be useful in identifying patients with clinically negative lymph nodes who are at risk of occult metastases, allowing more effective treatment strategies to be implemented.
Biomarkers, Tumor↗
Unusual complications in the Churg-Strauss syndrome.
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Abdominal Pain↗
Synthesis and characterization of a biospecific adsorbent containing bovine serum albumin as a ligand and its use for bilirubin retention.
Epoxy-activated gels from cross-linked polybutadiene-hydroxyethylmethacrylate (PB-HEMA) copolymer and epichlorohydrin (ECH) were prepared and characterized. Albumin was covalently bonded to the matrix and used as support of affinity chromatography in bilirubin (BR) retention experiments. PB-HEMA-ECH with different amounts of immobilized albumin (between 5.20 and 6.80 mg/g dry gel) were obtained. Bilirubin retention of 3.10 mg/g of these beads was observed at 5 degrees C.
Adsorption↗
Structural study of a possible neoplasia detected in Mytilus galloprovincialis collected from the Ria of Vigo (NW Spain).
Several specimens of Mytilus galloprovincialis, collected in the Ria of Vigo over a non-consecutive 2 yr period (1993 to 1994 and 1996 to 1997), presented a possible gonadal neoplasm, entailing morphologically abnormal germinal cells distributed throughout the follicle and invading the adjacent storage tissue. In some cases, affected cells were noted in gonoducts and in haemic sinusoids. Prevalence of this anomaly in the samples was 6%, and all affected individuals were found between April and June. During the rest of the year, individuals presented normal gonadal tissue.
Animals↗
Sizing the radius of the pore formed in erythrocytes and lipid vesicles by the toxin sticholysin I from the sea anemone Stichodactyla helianthus.
The radius of the pore formed by sticholysin I and II (StI, StII) in erythrocytes and sticholysin I in lipid vesicles was investigated. The rate of colloid osmotic lysis of human erythrocytes, exposed to one of the toxins in the presence of sugars of different size, was measured. The relative permeability of each sugar was derived and the pore radius estimated with the Renkin equation. The radius was similar for sticholysin I and II and was independent of the reference sugar chosen and of the toxin concentration applied. It was also the same when erythrocytes were pretreated with different toxin doses in the presence of a polyethylene glycol (PEG) large enough to prevent lysis and thereafter transferred to solutions containing oligosaccharides of different size where they did lyse at different rates. The osmometric behavior of large unilamellar vesicles (LUV) was thereafter used to estimate the toxin lesion radius in a model system. LUV transferred to a hyperosmotic solution with a certain sugar immediately shrank and then re-swelled at a rate dependent on the bilayer permeability to water and sugar. When LUV were previously permeabilized with StI, only a fraction of them, namely those not carrying pores, continued to behave as osmometers. By increasing the size of the added sugar and approaching the pore radius, the fraction of osmometric LUV increased. Relative permeabilities were derived and used to estimate a channel radius around 1.2 nm, both for sugars and for PEGs. In conclusion the sticholysin pore has a constant size independent of toxin concentration and similar in natural and artificial membranes, suggesting it has a fixed predominant structure.
Animals↗
Progesterone and 17 beta-estradiol acutely stimulate nitric oxide synthase activity in rat aorta and inhibit platelet aggregation.
The rapid non-genomic stimulatory action of progesterone (Pg) and estradiol (E2) on nitric oxide synthase (NOS) activity of endothelium intact aortic rings and its effect on platelet aggregation was investigated. First we measured the effect of the hormones on platelet aggregation when added to rat aortic strips (RAS) incubated in a PRP. RAS induced an antiaggregatory activity, which was enhanced by the presence of the hormones. The inhibitory action induced by the hormones was evoked in a dose dependent manner (10 pM-100 nM). These effects are specific for progesterone and 17-beta-estradiol, since either testosterone and 17-alpha-estradiol were devoid of activity. The hormones induced rapid responses, producing significant inhibition within 1 to 5 minutes of hormonal exposure. The addition of 10(-5) M L-NAME suppressed the antiaggregatory effect of 1 nM E2 or 10 nM Pg. Furthermore, we specifically quantified the NO generation by the 3H-citrulline technique. 10(-8) M E2 induced 2-fold increase of RAS citrulline production, while the increment induced by 10(-7) M Pg was 55% over control. Preincubation with 10(-5) M L-NAME completely suppressed the stimulatory action of 10(-9) M E2 or 10(-8) M Pg, confirming that the antiaggregatory factor released from the aortic tissue was NO. Preincubation with cycloheximide did not block the increment in NO induced by the hormones. In conclusion the present study provides for the first time evidence of acute, non-genomic effects of Pg on rat aorta NOS activity and platelet aggregation in coincidence with the results obtained with estradiol treatment.
Animals↗
Human and monkey fetal brain development of the supramammillary-hippocampal projections: a system involved in the regulation of theta activity.
The supramammillary (SUM)-hippocampal pathway plays a central role in the regulation of theta rhythm frequency. We followed its prenatal development in eight Cynomolgus monkeys (Macaca fascicularis) from embryonic day E88 to postnatal day 12 (term 165 days) and in eight human fetuses from 17.5 to 40 gestational weeks, relying on neurochemical criteria established in the adult (Nitsch and Leranth [1993] Neuroscience 55:797-812). We found that 1) SUM afferents reached the dentate juxtagranular and CA2 pyramidal cell layers at midgestation in human fetuses, earlier than in monkeys (two-thirds of gestation [E109]). They co-expressed calretinin, substance P, and acetylcholinesterase but not gamma-aminobutyric acid (GABA) or glutamic acid decarboxylase (GAD); 2) the presumed parent neurons in the monkey SUM expressed calretinin or both calretinin and substance P; 3) most of them were surrounded by GAD-containing terminals that might correspond to the septo-SUM feedback pathway (Leranth et al. [1999] Neuroscience 88:701); and 4) in addition, a large band of calretinin-labeled terminals that did not co-express substance P, GAD, or acetylcholinesterase was present in the deepest one-third of the dentate molecular layer in both the Cynomolgus monkey and human fetuses. It persisted in the adult monkey but not in adult human hippocampus; it remains questionable whether it originates in the SUM. In conclusion, the early ingrowth of the excitatory SUM-hippocampal system in human and non-human primates may contribute to the prenatal activity-dependent development of the hippocampal formation. The possibility and the functional importance of an in utero generation of hippocampal theta-like activity should also be considered.
Afferent Pathways↗
Influence of type II 5' deiodinase on TSH content in diabetic rats.
The influence of hypothalamic and pituitary type II 5'deiodinase (5'D-II) activities and T3 content on pituitary TSH content was investigated in streptozotocin (STZ)-induced diabetic rats (D). The results show, first, that hypothalamic and pituitary 5'D-II activities were lower in neonatal D rats versus control (C) rats, and the normal developmental pattern was altered. Secondly, when D and C rats were thyroidectomized (Tx) at 25 days of age (D+Tx, C+Tx), pituitary and hypothalamic 5'D-II activities increased ten days later in both populations vs. intact rats, but the percentage of increase was smaller in D+Tx than in C+Tx. The hypothalamic T3 to T4 ratios were also decreased in D+Tx animals (0.38) as compared to C+Tx rats (1.64). The hypothalamic T3 content was reduced by 30% in D as compared to C rats and by 80% in D+Tx as compared to C+Tx rats, showing a defect in hypothalamic T4 deiodination. Pituitary TSH content increased after Tx in D+Tx, but not in C+Tx. These results in diabetic rats indicate that the hypothalamic and pituitary 5'D-II activity and hypothalamic T3 content are affected by diabetes and play a role in the regulation of pituitary TSH content.
Animals↗
Effect of pH on the conformation, interaction with membranes and hemolytic activity of sticholysin II, a pore forming cytolysin from the sea anemone Stichodactyla helianthus.
Sticholysin II (St II) is a pore forming cytolysin obtained from the sea anemone Stichodactyla helianthus. Incubation of diluted St II solutions at different pHs (ranging from 2.0 to 12) slightly changes the secondary structure of the protein. These changes are particularly manifested at high pH. Similarly, the intrinsic fluorescence of the protein indicates a progressive opening of the protein structure when the pH increases from acidic (2.0) to basic (12). These modifications are only partially reversible and do not produce any significant increase in the small capacity of the protein to bind hydrophobic dyes (ANS or Prodan). Experiments carried out with model membranes show a reduced capacity of binding to egg phosphatidyl choline:sphingomyelin (1:1) liposomes both at low (2.3) and high (11.5) pH. Preincubation of the protein in the 2. 5-9.0 pH range does not modify its hemolytic activity, measured in human red blood cells at pH 7.4. On the other hand, preincubation at pH 11.5 drastically reduces the hemolytic activity of the toxin. This strong reduction takes place without measurable modification of the toxin ability to be adsorbed to the red blood cell surface. This indicates that preincubation at high pH irreversibly reduces the capacity of the toxin to form pores without a significant decrease in its binding capacity. The present results suggest that at pH > or = 10 St II experiences irreversible conformational changes that notably reduce its biological activity. This reduced biological activity is associated with a partial defolding of the protein, which seems to contradict what is expected in terms of a molten globule formalism.
Animals↗
Primary structure of two cytolysin isoforms from Stichodactyla helianthus differing in their hemolytic activity.
Sticholysin I (St-I) and sticholysin II (St-II) are cytolysins purified from the sea anemone Stichodactyla helianthus with a high degree of sequence identity (93%) but clearly differenced in their hemolytic activity. In order to go further into the structural determinants for the different behavior of St-I and St-II, we report here the complete amino acid sequences and the consensus secondary structure prediction of both proteins. The complete determination of St-II primary structure confirms the partial revision of cytolysin III amino acid sequence. All nonconservative changes between St-I and St-II are located at the N-terminal. According to our prediction these changes could be located at the same face of an alpha-helix during pore formation events and could account for the observed differences in hemolytic activity between St-I and St-II.
Amino Acid Sequence↗
Properties of St I and St II, two isotoxins isolated from Stichodactyla helianthus: a comparison.
Sticholysins I and II are two highly hemolytic polypeptides purified from the Caribbean Sea anemone Stichodactyla helianthus. Their high sequence homology (93%) indicates that they correspond to isoforms of the same hemolysin. The spectroscopic measurements show a close similarity in the secondary structure content, conformation and stability of both toxins. Exposure of the toxins to high pHs (>11), a free radical source (AAPH), urea or temperature produce permanent changes in the toxin that lead to a significant loss of HA. It is significant to note that this loss of hemolytic activity occurs when other indicators, probably with the only exception of near-UV CD spectra, barely detect changes in the protein structure. This emphasizes the sensitivity of the protein function to changes in the macromolecule conformation. The most noticeable difference between both toxins is the considerably higher activity of St II, both measured in terms of erythrocyte internal K(+) exit or hemolysis; which is related to enthalpic factors. This difference is not due to an incomplete association of St I to the membrane. We consider then that the different pore forming capacity of both toxins in erythrocytes can be explained in terms of the difference in charge of the N-terminal fragment, than can considerably reduce the St I insertion rate in the membrane probably due to the negatively charged outer leaflet of the red blood cell, without a significant reduction of its capacity to bind to the cell membrane. This electrostatic effect, together with a slightly more relaxed structure in St II, could explain the higher pore forming capacity of St II in the red blood cell membrane.
Amidines↗
Different role of insulin in GLUT-1 and -4 regulation in heart and skeletal muscle during perinatal hypothyroidism.
Two groups of hypothyroid rats were used; one group was given 2-mercapto-1-methylimidazole (MMI) treatment in the drinking water of the mothers and was killed at 2 and 4 days of life, and the other group was given similar MMI treatment and then was thyroidectomized at 5 days of life and killed at 8 or 20 days. Serum insulin, growth hormone (GH), and insulin-like growth factor I (IGF-I) were decreased in MMI-treated rats but increased in MMI-treated plus thyroidectomized rats. No significant reduction of thyroid hormones was observed in 2-day-old MMI rats. Protein and mRNA expression of GLUT-1 increased, and those of GLUT-4 decreased, in the heart in all populations independent of changes in insulin, GH, and IGF-I levels. However, GLUT-4 protein and mRNA expression in quadriceps and gastrocnemius skeletal muscles decreased at 4 days and increased at 8 and 20 days of life in parallel with insulin, GH, and IGF-I levels. GLUT-1 in the skeletal muscles seemed regulated posttranscriptionally and presented a decrease of mRNA expression in all stages studied. A differential sensitivity to insulin regulation of GLUT-1 and GLUT-4 glucose transporters seems to be one of the causes for the tissue-specific regulation of these glucose transporters in heart and skeletal muscles during the perinatal period.
Animals↗
Glucose uptake and glucose transporter proteins in skeletal muscle from undernourished rats.
Undernutrition in rats impairs secretion of insulin but maintains glucose normotolerance, because muscle tissue presents an increased insulin-induced glucose uptake. We studied glucose transporters in gastrocnemius muscles from food-restricted and control anesthetized rats under basal and euglycemic hyperinsulinemic conditions. Muscle membranes were prepared by subcellular fractionation in sucrose gradients. Insulin-induced glucose uptake, estimated by a 2-deoxyglucose technique, was increased 4- and 12-fold in control and food-restricted rats, respectively. Muscle insulin receptor was increased, but phosphotyrosine-associated phosphatidylinositol 3-kinase activity stimulated by insulin was lower in undernourished rats, whereas insulin receptor substrate-1 content remained unaltered. The main glucose transporter in the muscle, GLUT-4, was severely reduced albeit more efficiently translocated in response to insulin in food-deprived rats. GLUT-1, GLUT-3, and GLUT-5, minor isoforms in skeletal muscle, were found increased in food-deprived rats. The rise in these minor glucose carriers, as well as the improvement in GLUT-4 recruitment, is probably insufficient to account for the insulin-induced increase in the uptake of glucose in undernourished rats, thereby suggesting possible changes in other steps required for glucose metabolism.
Animals↗
Effects of long-term treatment with antipsychotics on serum leptin levels.
BACKGROUND: Abnormal regulation of the adipocyte-derived hormone leptin could play a role in body weight gain induced by antipsychotics. AIMS: To study the effects of long-term antipsychotic treatment on leptin levels in patients with schizophrenia. METHOD: Serum leptin levels were determined in 59 out-patients with chronic schizophrenia and in the same number of healthy subjects controlled by gender, age and body mass index. RESULTS: Leptin levels did not differ between patients and controls. Leptin levels in patients with schizophrenia correlated with weight gain, even after controlling for current weight, but did not show any association with clinical variables. Antipsychotic class tended to exert different effects over leptin levels (among atypicals, olanzapine induced a greater increase). CONCLUSIONS: Elevation of leptin levels induced by chronic antipsychotic treatment can be attributed to weight gain, but other mechanisms could be involved.
Adult↗
Regulation of IGF-I and -II by insulin in primary cultures of fetal rat hepatocytes.
During perinatal development, insulin and nutrients, rather than GH, regulate the IGF system. A selective primary culture of fetal rat hepatocytes has been established in our laboratory to elucidate the molecular mechanism of action of the above regulatory factors on IGF-I and -II gene expression during the late fetal period of the rat. In this model we have previously reported a regulatory role for glucose on IGF-I and -II synthesis and secretion. In the same experimental model, we now report that doses of insulin (0.1-5 microM) within the physiological range in rat fetuses during the last stages of gestation evoke an increase of IGF-I and -II mRNA abundance. Insulin regulated in a parallel manner IGF peptide secretion, and an excellent correlation was observed between IGF-I and -II mRNA and IGF-I and -II peptide levels in the conditioned media in response to the hormone. Finally, the insulin-induced rise in IGF-I and -II mRNA was not mediated by stimulation of gene transcription but by increased transcript stability. The results support the hypothesis that insulin plays a major role in IGF regulation at immature stages of development.
Animals↗
Effect of thyroxine administration on the IGF/IGF binding protein system in neonatal and adult thyroidectomized rats.
The effects of different doses of thyroxine (T(4)) delivered by injection or s.c. pellet implantation on alterations of the IGF/IGF binding protein (IGFBP) system were studied in neonatal and adult thyroidectomized (Tx) rats. Body weight, blood glucose, plasma insulin, TSH and GH and pituitary GH content, as well as serum IGF-I, IGF-II, IGFBP-1, -2 and -3 and their liver mRNA expression were assayed. Pellet implantation with the smaller dose of T(4) (1.5 microg/100 g body weight (b.w.) per day) in Tx neonatal rats decreased serum IGF-I, -II and the 30 kDa complex of IGFBPs (IGFBP-1 and -2), and increased serum IGFBP-3. Only the larger dose of T(4) (3 microg/100 g b.w. per day) recovered liver mRNA expression of IGF-I and ensured euthyroid status as shown by the normalized levels of plasma TSH. The rapid increase of body weight and serum GH after T(4) administration indicated a high sensitivity to T(4) during the neonatal period. Serum and liver mRNA expression of IGFs and plasma insulin and GH recovered in adult Tx rats after pellet implantation of 1.75 microg/100 g b.w. per day throughout 10 days. The continuous replacement of T(4) by pellet seems to be the most suitable method for thyroid rehabilitation. A very good correlation was found between insulin and IGF-II in Tx neonates treated with T(4) but not between insulin and IGF-I in Tx adults. IGFBP-2 seems to be up-regulated by T(4) deprivation in neonatal and adult rats. Finally, a good correlation as well as a partial correlation were found between IGFs and thyroid hormones in both neonatal and adult Tx populations, suggesting a direct effect in vivo of T(4) on the hepatic secretion of IGFs, as previously suggested in vitro.
Analysis of Variance↗