Jorge Ramirez | Enoi - Academia.edu (original) (raw)
Papers by Jorge Ramirez
Nucleic acids research, Jan 11, 1982
As part of a project pertaining the organization of ribosomal genes in Kinetoplastidae, we have c... more As part of a project pertaining the organization of ribosomal genes in Kinetoplastidae, we have created a data base for published sequences of ribosomal nucleic acids, with information in Spanish. As a first step in their processing, we have written a computer program which introduces the new feature of determining the length of the fragments produced after single or multiple digestion with any of the known restriction enzymes. With this information we have detected conserved SAU 3A sites: (i) at the 5' end of the 5.8S rRNA and at the 3' end of the small subunit rRNA, both included in similar larger sequences; (ii) in the 5.8S rRNA of vertebrates (a second one), which is not present in lower eukaryotes, showing a clear evolutive divergence; and, (iii) at the 5' terminal of the small subunit rRNA, included in a larger conserved sequence. The possible biological importance of these sequences is discussed.
The percent absorption of iron from four dietary sources was compared in 2018 human subjects with... more The percent absorption of iron from four dietary sources was compared in 2018 human subjects with three indicators of iron status, serum ferritin concentration, percent saturation of plasma transferrin and iron absorption from a reference dose of ferrous sulfate. Higher correlation coefficients (r) were obtained by comparing dietary iron absorption with the reference dose absorption rather than with serum ferritin;
Hydrodesulphurization (HDS) of gasoils is conventionally carried out in the petroleum industry in... more Hydrodesulphurization (HDS) of gasoils is conventionally carried out in the petroleum industry in co-current trickle bed reactors. The important disadvantage of co-current operation is that the build-up of H2S along the reactor height is detrimental to the desulphurisation reaction; this is because of inhibition effects. In this paper we examine the benefits of carrying out the HDS reaction in a
A Kluyveromyces lactis strain resistant to ethidium bromide and deficient in potassium uptake was... more A Kluyveromyces lactis strain resistant to ethidium bromide and deficient in potassium uptake was isolated. Studies on the proton-pumping activity of the mutant strain showed that a decreased H ؉ -ATPase specific activity was responsible for the observed phenotypes. The putative K. lactis PMA1 gene encoding the plasma membrane H ؉ -ATPase was cloned by its ability to relieve the potassium transport defect of this mutant and by reversing its resistance to ethidium bromide. Its deduced amino acid sequence predicts a protein 899 residues long that is structurally colinear in its full length to H ؉ -ATPases cloned from different yeasts, except for the presence of a variable N-terminal domain. By PCR-mediated amplification, we identified a transition from G to A that rendered the substitution of the fully conserved methionine at position 699 by isoleucine. We attribute to this amino acid change the low capacity of the mutant H ؉ -ATPase to pump out protons.
Applied Catalysis, 1991
The effect of fluoride incorporation on the titania support on the surface structure of promoted ... more The effect of fluoride incorporation on the titania support on the surface structure of promoted cobaltmolybdenum catalysts and their catalytic activity for thiophene hydrodesulfurization (HDS) has been studied. The relative activity between fluoride-modified and unmodified catalysts was found to be maximum and close to 5 for a fluorine content of 0.8 wt.-%. From high-resolution electron microscopy (HREM) examination of sulphided samples, the increase in HDS could be partly explained by smaller molybdenum sulphide crystallites (increase in the dispersion of the active phase). Diffuse reflectance spectroscopy (DRS) of the oxidic precursors shows that the effect of fluoride incorporation is also to increase the amount of the MO"' in tetrahedral surroundings and to enhance the part of cobalt involved in the generation of the "CO-MO-S" active phase (probably cobalt in octahedral symmetry).
Yeast, 1998
Debaryomyces hansenii showed an increased growth in the presence of either 1 KCl or 1 NaCl an... more Debaryomyces hansenii showed an increased growth in the presence of either 1 KCl or 1 NaCl and a low acidification of the medium, higher for the cells grown in the presence of NaCl. These cells accumulated high concentrations of the cations, and showed a very fast capacity to exchange either Na + or K + for the opposite cation. They showed a rapid uptake of 86 Rb + and 22 Na + . 86 Rb + transport was saturable, with K m and V max values higher for cells grown in 1 NaCl. 22 Na + uptake showed a diffusion component, also higher for the cells grown with NaCl. Changes depended on growth conditions, and not on further incubation, which changed the internal ion concentration. K + stimulated proton pumping produced a rapid extrusion of protons, and also a decrease of the membrane potential. Cells grown in 1 KCl showed a higher fermentation rate, but significantly lower respiratory capacity. ATP levels were higher in cells grown in the presence of NaCl; upon incubation with glucose, those grown in the presence of KCl reached values similar to the ones grown in the presence of NaCl. In both, the addition of KCl produced a transient decrease of the ATP levels. As to ion transport mechanisms, D. hansenii appears to have (a) an ATPase functioning as a proton pump, generating a membrane potential difference which drives K + through a uniporter; (b) a K + /H + exchange system; and (c) a rapid cation/cation exchange system. Most interesting is that cells grown in different ionic environments change their studied capacities, which are not dependent on the cation content, but on differences in their genetic expression during growth.
Yeast, 2006
In S. cerevisiae, K + transport relies principally on two structurally related membrane proteins,... more In S. cerevisiae, K + transport relies principally on two structurally related membrane proteins, known as Trk1p and Trk2p. Direct involvement in cation movements has been demonstrated for Trk1p, which is a high-affinity K + transporter. Initially described as a low-affinity K + transporter, Trk2p seems to play a minor role in K + transport, since its activity is only apparent under very specific conditions, such as in a ∆sin3 background. Here we show that growth of a ∆trk1∆sin3 double mutant, under K + -limiting conditions or at low pH, is Trk2p-dependent, and by Northern blot analysis we demonstrate that deletion of SIN3 results in transcriptional derepression of TRK2. In addition, we show that heterologous overexpression of TRK2 with the inducible GAL1 promoter bypasses Sin3p repression in a ∆trk1∆trk2 double mutant and fully restores growth under non-permissive conditions. Furthermore, kinetic experiments in a ∆trk1∆sin3 double mutant revealed a K + transporter with an apparent high affinity and a moderate capacity. Taken together, these results indicate that TRK2 encodes a functional K + transporter that, under our experimental conditions, displays distinctive kinetic characteristics.
Parasitology International, 2005
The nature of the cyanide-resistant respiration of Taenia crassiceps metacestode was studied. Mit... more The nature of the cyanide-resistant respiration of Taenia crassiceps metacestode was studied. Mitochondrial respiration with NADH as substrate was partially inhibited by rotenone, cyanide and antimycin in decreasing order of effectiveness. In contrast, respiration with succinate or ascorbate plus N,N,NV,NV-tetramethyl-p-phenylenediamine (TMPD) was more sensitive to antimycin and cyanide. The saturation kinetics for O 2 with NADH as substrate showed two components, which exhibited different oxygen affinities. The high-O 2 -affinity system (K m app = 1.5 AM) was abolished by low cyanide concentration; it corresponded to cytochrome aa 3 . The low-O 2 -affinity system (K m app = 120 AM) was resistant to cyanide. Similar O 2 saturation kinetics, using succinate or ascorbate -TMPD as electron donor, showed only the high-O 2 -affinity cyanide-sensitive component. Horse cytochrome c increased 2 -3 times the rate of electron flow across the cyanide-sensitive pathway and the contribution of the cyanide-resistant route became negligible. Mitochondrial NADH respiration produced significant amounts of H 2 O 2 (at least 10% of the total O 2 uptake). Bovine catalase and horse heart cytochrome c prevented the production and/or accumulation of H 2 O 2 . Production of H 2 O 2 by endogenous respiration was detected in whole cysticerci using rhodamine as fluorescent sensor. Thus, the CN-resistant and low-O 2 -affinity respiration results mainly from a spurious reaction of the respiratory complex I with O 2 , producing H 2 O 2 . The meaning of this reaction in the microaerobic habitat of the parasite is discussed. D
Pancreas, 1999
In pancreas, the activities of several sex steroid-transforming enzymes have been reported. Data ... more In pancreas, the activities of several sex steroid-transforming enzymes have been reported. Data have been obtained in perfused organs, total tissue homogenates, and subcellular organelles. These data, concurrent with the description of the presence of ligand-regulated steroid receptors, as well as the sexually dimorphic behavior of some pancreatic tumors, are clear evidence in support of the participation of steroid hormones in the pancreatic function. In this study, the steroidogenic ability of the pancreas was demonstrated by two different methods: (a) in tissue homogenates, by the identification of cytochrome P-450scc gene (CYP11A) transcripts after reverse transcription-polymerase chain reaction amplification (RT-PCR); and (b) in isolated mitochondria by the glutethimide-dependent inhibition of cholesterol-pregnenolone biotransformation. The results obtained in a series of independent experiments showed that (a) the pancreatic tissue possessed transcriptional activity of the CYP11A gene, although to a lesser extent than the typical steroidogenic tissues, and (b) isolated mitochondria obtained from the pancreas were able consistently to synthesize pregnenolone; furthermore, the addition of the specific inhibitor aminoglutethimide (AMG) blocked its synthesis. On the whole, these findings are interpreted as clear evidences of the activity of the cytochrome P-450scc enzymatic complex (P450scc), responsible for the transformation of cholesterol into pregnenolone and considered the first and limiting step in steroid biosynthesis.
Kidney International, 1998
Background. Intermittent oral or intravenous doses of calcitriol given two or three times per wee... more Background. Intermittent oral or intravenous doses of calcitriol given two or three times per week are commonly used to treat secondary hyperparathyroidism (2°HPT). This study was undertaken to compare the biochemical and skeletal responses to thrice weekly intraperitoneal (i.p.) versus oral doses of calcitriol in children with 2°HPT undergoing peritoneal dialysis (CCPD).
Kidney International, 1995
Calcium-regulated parathyroid hormone secretion in adynamic renal osteodystrophy. Hypercalcemia a... more Calcium-regulated parathyroid hormone secretion in adynamic renal osteodystrophy. Hypercalcemia and low serum parathyroid hormone (PTH) levels are features of the adynamic lesion (AD) of renal osteodystrophy, but there is little information about parathyroid gland function in this disorder. Therefore, the four parameter model was used to evaluate calcium-regulated PTH release in patients with either adynamic bone or secondary hyperparathyroidism (OF) as documented by bone biopsy and in normal volunteers (NL). Patients had undergone CCPD for 20 4.2 months, and all received calcium carbonate as the sole phosphate-binding agent. During two hours infusions of sodium citrate, the rate of decline in serum ionized calcium levels did not differ among groups; serum PTH levels rose from 136 38 to 342 140 pg/mI in AD and from 691 99 to 869 121 pg/mi in OF. Maximum PTH levels were 322 42% of baseline values in AD but only 146 9.7% of baseline in OF (P < 0.001), and the increase above baseline levels in AD did not differ from that in NL (300 25%, NS). During calcium infusions, serum PTH Jevels fell from 164 75 to 39 11 pg/mI in AD and from 622 76 to 171 29 pg/mi in OF; minimum serum PTH levels, expressed as a percentage of pre-infusion values, were 25 2% in AD and 26 5% in OF (NS). The slope of the sigmoidal calcium-PTH curve was less in AD than in OF (54 27 versus 127 149 pg/ml/mmol, P < 0.05), suggesting a decrease in sensitivity of the parathyroids to changes in ionized calcium; however, set point values were 1.20 0.01, 1.22 0.01 and 1.21 0.01 mmollliter in AD, OF and NL, respectively. The results indicate that abnormalities in the set point for calcium-regulated PTH release do not account for marked differences in serum PTH levels in patients with low-turnover and high-turnover skeletal lesions of renal osteodystrophy.
Kidney International, 1994
Biochemical markers of renal osteodystrophy in pediatric patients undergoing CAPD/CCPD. Serum int... more Biochemical markers of renal osteodystrophy in pediatric patients undergoing CAPD/CCPD. Serum intact PTH [1-84] levels were evaluated as a potential non-invasive method for the diagnosis of renal osteodystrophy in children treated with CAPD/CCPD. Sixty-eight bone biopsy samples were obtained from 55 patients, aged 13 5 (X SD) years, undergoing CAPD/CCPD for 29 13 months; osteitis fibrosa was present in 34 cases, mild lesions of secondary hyperparathyroidism in six, 15 had adynamic lesions, and 13 were classified as normal histology. Serum calcium levels were higher in patients with adynamic bone or normal bone histology than in those with secondary hyperparathyroidism, whereas serum phosphorus, alkaline phosphatase and PTH levels were greater in patients with osteitis fibrosa. The combination of a serum PTH level >200 pg/ml and a serum calcium value <10 mgldl was 85% sensitive and 100% specific for identifying patients with high-turnover lesions of bone. Serum PTH values <200 pg/ml were 100% sensitive but only 79% specific for patients with adynamic bone; specificity increased to 92%, however, using the combined criteria of a PTH level <150 pglml and a serum calcium level >10 mgldl. Higher serum calcium levels and serum PTH values within or below the normal range characterize patients with the adynamic lesion of renal osteodystrophy. Serum PTH levels of approximately 200 pg/mI are useful for distinguishing patients with low-turnover lesions of renal osteodystrophy from those with secondary hyperparathyroidism. Secondary hyperparathyroidism develops in most patients with chronic renal failure. Accordingly, osteitis fibrosa has been the most common histologic lesion of bone both in adults and in children undergoing hemodialysis or peritoneal dialysis [1-4]. Recent reports suggest, however, that the prevalence of lowturnover skeletal disorders, in particular the adynamic or aplastic lesion of renal osteodystrophy, has increased substantially. Thus, as many as 66% of adult patients receiving peritoneal dialysis have evidence of adynamic bone on histologic evaluation [5], and a substantial proportion of these do not have diabetes or evidence of bone aluminum deposition, factors previously recognized as causes of the adynamic lesion in patients with chronic renal failure .
Kidney International, 1994
Journal of Catalysis, 2007
The support effect was analyzed for hydrodesulfurization CoMo catalysts prepared with EDTA as the... more The support effect was analyzed for hydrodesulfurization CoMo catalysts prepared with EDTA as the chelating agent. Supports with different isoelectric points, γ -Al 2 O 3 , Al 2 O 3 -MgO, and SiO 2 , were used. Different sequences of EDTA, Co, and Mo impregnation were used to analyze whether the sequence of addition affected catalytic activity. Changing the order of addition of Co, Mo, and EDTA produced only a small effect on the catalyst HDS activity. The simultaneous impregnation of Co, Mo, and EDTA led to higher HDS activity than sequential impregnations. In contrast, changing the support nature produced important variations in catalytic activity, following the increasing order: Al 2 O 3 < SiO 2 < Al 2 O 3 -MgO. It was found that the changes in HDS activity with the type of support are related to different levels of promotion of Mo by Co, and to changes in the sulfidation patterns induced by different interactions of the active phase precursors with each support.
Journal of Bioenergetics and Biomembranes, 1994
This paper presents results of experiments designed to further purify the membrane system involve... more This paper presents results of experiments designed to further purify the membrane system involved in mitochondrial calcium transport. A partially purified extract, which transported calcium with a specific activity of l194nmol 45CaZ+/mg protein/5min, was used to obtain mouse hyperimmune serum. This serum inhibited calcium uptake both in mitoplasts and in vesicles reconstituted with mitochondrial proteins containing cytochrome oxidase. Western blot analysis of the semipurified fraction showed that the serum recognized specifically two antigens of 75 and 20 kDa. Both antibodies were purified by elution from the nitrocellulose sheets and their inhibition capacity was analyzed. The antibody that recognized the 20-kDa protein produced a higher degree of inhibition than the other one.
International Journal of Colorectal Disease, 1998
Irritable bowel syndrome is the most frequently diagnosed disorder in gastroenterology. It has be... more Irritable bowel syndrome is the most frequently diagnosed disorder in gastroenterology. It has been demonstrated with specialized motility studies that these patients compared to healthy subjects show changes in rectoanal electrical and mechanical activity and in rectoanal sensitivity. However, until now no report has been published on morphological alterations in the rectum or the internal anal sphincter. Twenty-five consecutive patients with irritable bowel syndrome (mean age 32, range 17 -47 years; 24 females) were evaluated prospectively by transrectal ultrasonography, rectal sensitivity studies, and recordings of both electrical and mechanical activity of the distal rectum and internal anal sphincter during a 2-h interdigestive period. Ten healthy volunteers (mean age 34.5, range 19 -50 years) served as a control group. Paired and non-paired Student's two-tailed t test and linear regression analysis were used. It was shown that muscle thickness of the rectum during rest (4.7 ±0.1 mm) was correlated neither with its rectal spike amplitude (0.73 ±0.1 mV) nor with rectal spike frequency (17.06 ±3.6 spike/2 h). In addition, the diameter of the internal anal sphincter (1.2 ±0.1 mm) was correlated neither with its resting pressure, nor with frequency (17.1 ±3.2/2 h), duration (14.9 ±1.5 s), or amplitude (14.1 ±1.9 mmHg), of inhibition of the spontaneous rectoanal inhibitory reflex. No correlation was found between ultrasonographic parameters and rectal distension variables (r =0.03). This study demonstrates for the first time morphological anorectal changes in patients with irritable bowel syndrome compared to healthy subjects, in addition to showing that morphological changes are independent of physiological ones. Therefore both transrectal ultrasonography to determine anorectal morphology and electromanometry to assess anorectal function are important measures in the evaluation of patients with irritable bowel syndrome.
International Journal of Colorectal Disease, 1997
Intensive Care Medicine, 2003
Objective: Evaluation of the usefulness of criteria for systemic inflammatory response syndrome (... more Objective: Evaluation of the usefulness of criteria for systemic inflammatory response syndrome (SIRS) compared with the final diagnosis of infection in patients admitted to the emergency room of two university-based hospitals. Design: Longitudinal cohort study. Setting: Hospital Universitario San Vicente de Paul and Hospital General de Medellín, Medellín, Colombia. Patients: Seven hundred thirty-four patients with suspected infection as main diagnosis for admittance into the emergency room. Measurements and results: Sensitivity, specificity, predictive values and likelihood ratios (LR) of SIRS criteria at admission were determined using, as gold standards, the diagnosis at the time of discharge based on clinical history and evolution, and microbiological confirmation of in-fection. SIRS criteria were met by 503 patients (68.5%); the discharge diagnosis of infection was found in 657 (89.4%) and 276 (37%) had microbiological confirmation. SIRS criteria exhibited a sensitivity of 69%, specificity of 35%, positive predictive value (PPV) of 90%, negative predictive value (NPV) of 12% and positive LR of 1.06. There were no differences between the two gold standards. Conclusions: The finding of two or more SIRS criteria was of little usefulness for diagnosis of infection. It is necessary to work with new criteria and probably with biological markers, in order to obtain a simple, precise and operative definition of the sepsis phenomenon.
Experimental Brain Research, 1992
mainly by input from group Ib afferents. 5. The functional implication of the results of this and... more mainly by input from group Ib afferents. 5. The functional implication of the results of this and previous studies is that input from group Ib afferents during the stance phase of walking acts to inhibit generation of flexor burst activity and to promote extensor activity. The proposal that a decline in Ib activity near the end of the stance phase is involved in regulating the stance to swing transition is discussed.
Nucleic acids research, Jan 11, 1982
As part of a project pertaining the organization of ribosomal genes in Kinetoplastidae, we have c... more As part of a project pertaining the organization of ribosomal genes in Kinetoplastidae, we have created a data base for published sequences of ribosomal nucleic acids, with information in Spanish. As a first step in their processing, we have written a computer program which introduces the new feature of determining the length of the fragments produced after single or multiple digestion with any of the known restriction enzymes. With this information we have detected conserved SAU 3A sites: (i) at the 5' end of the 5.8S rRNA and at the 3' end of the small subunit rRNA, both included in similar larger sequences; (ii) in the 5.8S rRNA of vertebrates (a second one), which is not present in lower eukaryotes, showing a clear evolutive divergence; and, (iii) at the 5' terminal of the small subunit rRNA, included in a larger conserved sequence. The possible biological importance of these sequences is discussed.
The percent absorption of iron from four dietary sources was compared in 2018 human subjects with... more The percent absorption of iron from four dietary sources was compared in 2018 human subjects with three indicators of iron status, serum ferritin concentration, percent saturation of plasma transferrin and iron absorption from a reference dose of ferrous sulfate. Higher correlation coefficients (r) were obtained by comparing dietary iron absorption with the reference dose absorption rather than with serum ferritin;
Hydrodesulphurization (HDS) of gasoils is conventionally carried out in the petroleum industry in... more Hydrodesulphurization (HDS) of gasoils is conventionally carried out in the petroleum industry in co-current trickle bed reactors. The important disadvantage of co-current operation is that the build-up of H2S along the reactor height is detrimental to the desulphurisation reaction; this is because of inhibition effects. In this paper we examine the benefits of carrying out the HDS reaction in a
A Kluyveromyces lactis strain resistant to ethidium bromide and deficient in potassium uptake was... more A Kluyveromyces lactis strain resistant to ethidium bromide and deficient in potassium uptake was isolated. Studies on the proton-pumping activity of the mutant strain showed that a decreased H ؉ -ATPase specific activity was responsible for the observed phenotypes. The putative K. lactis PMA1 gene encoding the plasma membrane H ؉ -ATPase was cloned by its ability to relieve the potassium transport defect of this mutant and by reversing its resistance to ethidium bromide. Its deduced amino acid sequence predicts a protein 899 residues long that is structurally colinear in its full length to H ؉ -ATPases cloned from different yeasts, except for the presence of a variable N-terminal domain. By PCR-mediated amplification, we identified a transition from G to A that rendered the substitution of the fully conserved methionine at position 699 by isoleucine. We attribute to this amino acid change the low capacity of the mutant H ؉ -ATPase to pump out protons.
Applied Catalysis, 1991
The effect of fluoride incorporation on the titania support on the surface structure of promoted ... more The effect of fluoride incorporation on the titania support on the surface structure of promoted cobaltmolybdenum catalysts and their catalytic activity for thiophene hydrodesulfurization (HDS) has been studied. The relative activity between fluoride-modified and unmodified catalysts was found to be maximum and close to 5 for a fluorine content of 0.8 wt.-%. From high-resolution electron microscopy (HREM) examination of sulphided samples, the increase in HDS could be partly explained by smaller molybdenum sulphide crystallites (increase in the dispersion of the active phase). Diffuse reflectance spectroscopy (DRS) of the oxidic precursors shows that the effect of fluoride incorporation is also to increase the amount of the MO"' in tetrahedral surroundings and to enhance the part of cobalt involved in the generation of the "CO-MO-S" active phase (probably cobalt in octahedral symmetry).
Yeast, 1998
Debaryomyces hansenii showed an increased growth in the presence of either 1 KCl or 1 NaCl an... more Debaryomyces hansenii showed an increased growth in the presence of either 1 KCl or 1 NaCl and a low acidification of the medium, higher for the cells grown in the presence of NaCl. These cells accumulated high concentrations of the cations, and showed a very fast capacity to exchange either Na + or K + for the opposite cation. They showed a rapid uptake of 86 Rb + and 22 Na + . 86 Rb + transport was saturable, with K m and V max values higher for cells grown in 1 NaCl. 22 Na + uptake showed a diffusion component, also higher for the cells grown with NaCl. Changes depended on growth conditions, and not on further incubation, which changed the internal ion concentration. K + stimulated proton pumping produced a rapid extrusion of protons, and also a decrease of the membrane potential. Cells grown in 1 KCl showed a higher fermentation rate, but significantly lower respiratory capacity. ATP levels were higher in cells grown in the presence of NaCl; upon incubation with glucose, those grown in the presence of KCl reached values similar to the ones grown in the presence of NaCl. In both, the addition of KCl produced a transient decrease of the ATP levels. As to ion transport mechanisms, D. hansenii appears to have (a) an ATPase functioning as a proton pump, generating a membrane potential difference which drives K + through a uniporter; (b) a K + /H + exchange system; and (c) a rapid cation/cation exchange system. Most interesting is that cells grown in different ionic environments change their studied capacities, which are not dependent on the cation content, but on differences in their genetic expression during growth.
Yeast, 2006
In S. cerevisiae, K + transport relies principally on two structurally related membrane proteins,... more In S. cerevisiae, K + transport relies principally on two structurally related membrane proteins, known as Trk1p and Trk2p. Direct involvement in cation movements has been demonstrated for Trk1p, which is a high-affinity K + transporter. Initially described as a low-affinity K + transporter, Trk2p seems to play a minor role in K + transport, since its activity is only apparent under very specific conditions, such as in a ∆sin3 background. Here we show that growth of a ∆trk1∆sin3 double mutant, under K + -limiting conditions or at low pH, is Trk2p-dependent, and by Northern blot analysis we demonstrate that deletion of SIN3 results in transcriptional derepression of TRK2. In addition, we show that heterologous overexpression of TRK2 with the inducible GAL1 promoter bypasses Sin3p repression in a ∆trk1∆trk2 double mutant and fully restores growth under non-permissive conditions. Furthermore, kinetic experiments in a ∆trk1∆sin3 double mutant revealed a K + transporter with an apparent high affinity and a moderate capacity. Taken together, these results indicate that TRK2 encodes a functional K + transporter that, under our experimental conditions, displays distinctive kinetic characteristics.
Parasitology International, 2005
The nature of the cyanide-resistant respiration of Taenia crassiceps metacestode was studied. Mit... more The nature of the cyanide-resistant respiration of Taenia crassiceps metacestode was studied. Mitochondrial respiration with NADH as substrate was partially inhibited by rotenone, cyanide and antimycin in decreasing order of effectiveness. In contrast, respiration with succinate or ascorbate plus N,N,NV,NV-tetramethyl-p-phenylenediamine (TMPD) was more sensitive to antimycin and cyanide. The saturation kinetics for O 2 with NADH as substrate showed two components, which exhibited different oxygen affinities. The high-O 2 -affinity system (K m app = 1.5 AM) was abolished by low cyanide concentration; it corresponded to cytochrome aa 3 . The low-O 2 -affinity system (K m app = 120 AM) was resistant to cyanide. Similar O 2 saturation kinetics, using succinate or ascorbate -TMPD as electron donor, showed only the high-O 2 -affinity cyanide-sensitive component. Horse cytochrome c increased 2 -3 times the rate of electron flow across the cyanide-sensitive pathway and the contribution of the cyanide-resistant route became negligible. Mitochondrial NADH respiration produced significant amounts of H 2 O 2 (at least 10% of the total O 2 uptake). Bovine catalase and horse heart cytochrome c prevented the production and/or accumulation of H 2 O 2 . Production of H 2 O 2 by endogenous respiration was detected in whole cysticerci using rhodamine as fluorescent sensor. Thus, the CN-resistant and low-O 2 -affinity respiration results mainly from a spurious reaction of the respiratory complex I with O 2 , producing H 2 O 2 . The meaning of this reaction in the microaerobic habitat of the parasite is discussed. D
Pancreas, 1999
In pancreas, the activities of several sex steroid-transforming enzymes have been reported. Data ... more In pancreas, the activities of several sex steroid-transforming enzymes have been reported. Data have been obtained in perfused organs, total tissue homogenates, and subcellular organelles. These data, concurrent with the description of the presence of ligand-regulated steroid receptors, as well as the sexually dimorphic behavior of some pancreatic tumors, are clear evidence in support of the participation of steroid hormones in the pancreatic function. In this study, the steroidogenic ability of the pancreas was demonstrated by two different methods: (a) in tissue homogenates, by the identification of cytochrome P-450scc gene (CYP11A) transcripts after reverse transcription-polymerase chain reaction amplification (RT-PCR); and (b) in isolated mitochondria by the glutethimide-dependent inhibition of cholesterol-pregnenolone biotransformation. The results obtained in a series of independent experiments showed that (a) the pancreatic tissue possessed transcriptional activity of the CYP11A gene, although to a lesser extent than the typical steroidogenic tissues, and (b) isolated mitochondria obtained from the pancreas were able consistently to synthesize pregnenolone; furthermore, the addition of the specific inhibitor aminoglutethimide (AMG) blocked its synthesis. On the whole, these findings are interpreted as clear evidences of the activity of the cytochrome P-450scc enzymatic complex (P450scc), responsible for the transformation of cholesterol into pregnenolone and considered the first and limiting step in steroid biosynthesis.
Kidney International, 1998
Background. Intermittent oral or intravenous doses of calcitriol given two or three times per wee... more Background. Intermittent oral or intravenous doses of calcitriol given two or three times per week are commonly used to treat secondary hyperparathyroidism (2°HPT). This study was undertaken to compare the biochemical and skeletal responses to thrice weekly intraperitoneal (i.p.) versus oral doses of calcitriol in children with 2°HPT undergoing peritoneal dialysis (CCPD).
Kidney International, 1995
Calcium-regulated parathyroid hormone secretion in adynamic renal osteodystrophy. Hypercalcemia a... more Calcium-regulated parathyroid hormone secretion in adynamic renal osteodystrophy. Hypercalcemia and low serum parathyroid hormone (PTH) levels are features of the adynamic lesion (AD) of renal osteodystrophy, but there is little information about parathyroid gland function in this disorder. Therefore, the four parameter model was used to evaluate calcium-regulated PTH release in patients with either adynamic bone or secondary hyperparathyroidism (OF) as documented by bone biopsy and in normal volunteers (NL). Patients had undergone CCPD for 20 4.2 months, and all received calcium carbonate as the sole phosphate-binding agent. During two hours infusions of sodium citrate, the rate of decline in serum ionized calcium levels did not differ among groups; serum PTH levels rose from 136 38 to 342 140 pg/mI in AD and from 691 99 to 869 121 pg/mi in OF. Maximum PTH levels were 322 42% of baseline values in AD but only 146 9.7% of baseline in OF (P < 0.001), and the increase above baseline levels in AD did not differ from that in NL (300 25%, NS). During calcium infusions, serum PTH Jevels fell from 164 75 to 39 11 pg/mI in AD and from 622 76 to 171 29 pg/mi in OF; minimum serum PTH levels, expressed as a percentage of pre-infusion values, were 25 2% in AD and 26 5% in OF (NS). The slope of the sigmoidal calcium-PTH curve was less in AD than in OF (54 27 versus 127 149 pg/ml/mmol, P < 0.05), suggesting a decrease in sensitivity of the parathyroids to changes in ionized calcium; however, set point values were 1.20 0.01, 1.22 0.01 and 1.21 0.01 mmollliter in AD, OF and NL, respectively. The results indicate that abnormalities in the set point for calcium-regulated PTH release do not account for marked differences in serum PTH levels in patients with low-turnover and high-turnover skeletal lesions of renal osteodystrophy.
Kidney International, 1994
Biochemical markers of renal osteodystrophy in pediatric patients undergoing CAPD/CCPD. Serum int... more Biochemical markers of renal osteodystrophy in pediatric patients undergoing CAPD/CCPD. Serum intact PTH [1-84] levels were evaluated as a potential non-invasive method for the diagnosis of renal osteodystrophy in children treated with CAPD/CCPD. Sixty-eight bone biopsy samples were obtained from 55 patients, aged 13 5 (X SD) years, undergoing CAPD/CCPD for 29 13 months; osteitis fibrosa was present in 34 cases, mild lesions of secondary hyperparathyroidism in six, 15 had adynamic lesions, and 13 were classified as normal histology. Serum calcium levels were higher in patients with adynamic bone or normal bone histology than in those with secondary hyperparathyroidism, whereas serum phosphorus, alkaline phosphatase and PTH levels were greater in patients with osteitis fibrosa. The combination of a serum PTH level >200 pg/ml and a serum calcium value <10 mgldl was 85% sensitive and 100% specific for identifying patients with high-turnover lesions of bone. Serum PTH values <200 pg/ml were 100% sensitive but only 79% specific for patients with adynamic bone; specificity increased to 92%, however, using the combined criteria of a PTH level <150 pglml and a serum calcium level >10 mgldl. Higher serum calcium levels and serum PTH values within or below the normal range characterize patients with the adynamic lesion of renal osteodystrophy. Serum PTH levels of approximately 200 pg/mI are useful for distinguishing patients with low-turnover lesions of renal osteodystrophy from those with secondary hyperparathyroidism. Secondary hyperparathyroidism develops in most patients with chronic renal failure. Accordingly, osteitis fibrosa has been the most common histologic lesion of bone both in adults and in children undergoing hemodialysis or peritoneal dialysis [1-4]. Recent reports suggest, however, that the prevalence of lowturnover skeletal disorders, in particular the adynamic or aplastic lesion of renal osteodystrophy, has increased substantially. Thus, as many as 66% of adult patients receiving peritoneal dialysis have evidence of adynamic bone on histologic evaluation [5], and a substantial proportion of these do not have diabetes or evidence of bone aluminum deposition, factors previously recognized as causes of the adynamic lesion in patients with chronic renal failure .
Kidney International, 1994
Journal of Catalysis, 2007
The support effect was analyzed for hydrodesulfurization CoMo catalysts prepared with EDTA as the... more The support effect was analyzed for hydrodesulfurization CoMo catalysts prepared with EDTA as the chelating agent. Supports with different isoelectric points, γ -Al 2 O 3 , Al 2 O 3 -MgO, and SiO 2 , were used. Different sequences of EDTA, Co, and Mo impregnation were used to analyze whether the sequence of addition affected catalytic activity. Changing the order of addition of Co, Mo, and EDTA produced only a small effect on the catalyst HDS activity. The simultaneous impregnation of Co, Mo, and EDTA led to higher HDS activity than sequential impregnations. In contrast, changing the support nature produced important variations in catalytic activity, following the increasing order: Al 2 O 3 < SiO 2 < Al 2 O 3 -MgO. It was found that the changes in HDS activity with the type of support are related to different levels of promotion of Mo by Co, and to changes in the sulfidation patterns induced by different interactions of the active phase precursors with each support.
Journal of Bioenergetics and Biomembranes, 1994
This paper presents results of experiments designed to further purify the membrane system involve... more This paper presents results of experiments designed to further purify the membrane system involved in mitochondrial calcium transport. A partially purified extract, which transported calcium with a specific activity of l194nmol 45CaZ+/mg protein/5min, was used to obtain mouse hyperimmune serum. This serum inhibited calcium uptake both in mitoplasts and in vesicles reconstituted with mitochondrial proteins containing cytochrome oxidase. Western blot analysis of the semipurified fraction showed that the serum recognized specifically two antigens of 75 and 20 kDa. Both antibodies were purified by elution from the nitrocellulose sheets and their inhibition capacity was analyzed. The antibody that recognized the 20-kDa protein produced a higher degree of inhibition than the other one.
International Journal of Colorectal Disease, 1998
Irritable bowel syndrome is the most frequently diagnosed disorder in gastroenterology. It has be... more Irritable bowel syndrome is the most frequently diagnosed disorder in gastroenterology. It has been demonstrated with specialized motility studies that these patients compared to healthy subjects show changes in rectoanal electrical and mechanical activity and in rectoanal sensitivity. However, until now no report has been published on morphological alterations in the rectum or the internal anal sphincter. Twenty-five consecutive patients with irritable bowel syndrome (mean age 32, range 17 -47 years; 24 females) were evaluated prospectively by transrectal ultrasonography, rectal sensitivity studies, and recordings of both electrical and mechanical activity of the distal rectum and internal anal sphincter during a 2-h interdigestive period. Ten healthy volunteers (mean age 34.5, range 19 -50 years) served as a control group. Paired and non-paired Student's two-tailed t test and linear regression analysis were used. It was shown that muscle thickness of the rectum during rest (4.7 ±0.1 mm) was correlated neither with its rectal spike amplitude (0.73 ±0.1 mV) nor with rectal spike frequency (17.06 ±3.6 spike/2 h). In addition, the diameter of the internal anal sphincter (1.2 ±0.1 mm) was correlated neither with its resting pressure, nor with frequency (17.1 ±3.2/2 h), duration (14.9 ±1.5 s), or amplitude (14.1 ±1.9 mmHg), of inhibition of the spontaneous rectoanal inhibitory reflex. No correlation was found between ultrasonographic parameters and rectal distension variables (r =0.03). This study demonstrates for the first time morphological anorectal changes in patients with irritable bowel syndrome compared to healthy subjects, in addition to showing that morphological changes are independent of physiological ones. Therefore both transrectal ultrasonography to determine anorectal morphology and electromanometry to assess anorectal function are important measures in the evaluation of patients with irritable bowel syndrome.
International Journal of Colorectal Disease, 1997
Intensive Care Medicine, 2003
Objective: Evaluation of the usefulness of criteria for systemic inflammatory response syndrome (... more Objective: Evaluation of the usefulness of criteria for systemic inflammatory response syndrome (SIRS) compared with the final diagnosis of infection in patients admitted to the emergency room of two university-based hospitals. Design: Longitudinal cohort study. Setting: Hospital Universitario San Vicente de Paul and Hospital General de Medellín, Medellín, Colombia. Patients: Seven hundred thirty-four patients with suspected infection as main diagnosis for admittance into the emergency room. Measurements and results: Sensitivity, specificity, predictive values and likelihood ratios (LR) of SIRS criteria at admission were determined using, as gold standards, the diagnosis at the time of discharge based on clinical history and evolution, and microbiological confirmation of in-fection. SIRS criteria were met by 503 patients (68.5%); the discharge diagnosis of infection was found in 657 (89.4%) and 276 (37%) had microbiological confirmation. SIRS criteria exhibited a sensitivity of 69%, specificity of 35%, positive predictive value (PPV) of 90%, negative predictive value (NPV) of 12% and positive LR of 1.06. There were no differences between the two gold standards. Conclusions: The finding of two or more SIRS criteria was of little usefulness for diagnosis of infection. It is necessary to work with new criteria and probably with biological markers, in order to obtain a simple, precise and operative definition of the sepsis phenomenon.
Experimental Brain Research, 1992
mainly by input from group Ib afferents. 5. The functional implication of the results of this and... more mainly by input from group Ib afferents. 5. The functional implication of the results of this and previous studies is that input from group Ib afferents during the stance phase of walking acts to inhibit generation of flexor burst activity and to promote extensor activity. The proposal that a decline in Ib activity near the end of the stance phase is involved in regulating the stance to swing transition is discussed.