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M Ramírez

Publications and source records attributed to M Ramírez.

At least 91 records · Page 5Linked to original sources
PubMed1998

Mature human hematopoietic cells in donor bone marrow complicate interpretation of stem/progenitor cell assays in xenogeneic hematopoietic chimeras.

Xenogeneic hematopoietic chimeras have been used to assay the growth and differentiation of human stem/progenitor cells. The presence of human hematopoietic cells in immunodeficient mice transplanted with human marrow cells may be caused by proliferation and differentiation of early stem/progenitor cells and/or proliferation of mature cells. Unpurified human marrow mononuclear cells, T cell-depleted, or stem/progenitor cell-enriched (CD34+ or CD34+CD38-) populations were injected into sublethally irradiated NOD/LtSz scid/scid (NOD/SCID) mice. High levels of human cells were detected in mice (hu/mu chimeras) transplanted with each of the above human marrow populations. Large numbers of mature human T lymphocytes were found in marrow, spleens, and thymuses from hu/mu chimeras that had been transplanted with unpurified human mononuclear marrow cells. Human immunoglobulin was detected in sera from these chimeras, and some exhibited a clinical syndrome suggestive of graft-versus-host disease. In contrast, in hu/mu chimeras that had received T cell-depleted or stem/progenitor cell-enriched populations, multilineage hematopoiesis (myeloid, B lymphoid, and progenitor cells by immunophenotype) was detected but T lymphocytes and human immunoglobulin were not; in addition, no human cells were detected in the thymuses. Thus, injection of adult human marrow cells into immunodeficient mice can result in hematopoietic chimerism for at least 3 months after transplant. However, the types of cells present in hu/mu chimeras differ depending on the human cell population transplanted. This should be taken into account when hematopoietic chimeras are used to assess human stem/progenitor cell function.

ADP-ribosyl Cyclase↗
PubMed1998

In vivo engraftment potential of clinical hematopoietic grafts.

BACKGROUND: Quantitative assays are needed to characterize the multilineage engraftment potential of clinical hematopoietic grafts. After we observed a dose-response relationship between the number of human hematopoietic cells transplanted into nonobese diabetic-scid/scid (NOD/SCID) mice and the number of human CD45+ cells recovered in the chimeras' marrows and spleens, we sought to develop a multiple linear regression model that allows quantitative comparisons of human cell engraftment in vivo. METHODS: We used this NOD/SCID xenotransplant model to compare the engraftment potential of cord blood vs. adult marrow or mobilized blood, after either of 2 commonly used clinical graft engineering procedures: CD34+ cell selection or T cell depletion. RESULTS: The engraftment per transplanted cell was > 20 fold higher for cord blood cells, as compared to hematopoietic cells from adults. However, there was no difference in engraftment per CD34+ cell transplanted between marrow and mobilized blood. Levels of human cell engraftment from all sources could be increased by administration of human hematopoietic growth factors to human/mouse chimeras after transplantation. Correlation analysis of the number of human CD13+ myeloid cells and CD19+ B lymphoid cells in the chimeras' marrows 8 weeks after transplantation provided evidence that almost all the human myeloid and B lymphoid cells were derived from the same primitive precursor cells. CONCLUSIONS: These findings and assay may be useful in the development of clinical hematopoietic cell therapies.

Adult↗
PubMed1998

[Outbreak of schistosomiasis in a group a travellers returning from Burkina Faso].

BACKGROUND: Schistosomiasis in Spain is always an imported disease mainly presented in travellers from endemic areas with a history of having bathed in fresh water and in immigrants from these areas. A group of travellers presenting infection by schistosomes following an 8-day journey to Burkina Faso. PATIENTS AND METHODS: The travellers, residents of Gran Canaria (Spain), who had bathed in fresh water were studied by schistosomiasis serology and parasitologic examination in stools and urine. RESULTS: A total of 29 travellers were studied, 20 (69%) of whom were considered to be infected, on presenting positive serology and/or coproparasitologic examination. Fourteen of the infected patients presented clinical symptomatology compatible with the Katayama syndrome, while 6 were asymptomatic. The mean time to appearance of the symptoms was 27 days and these were most frequently fever, headache, neck pain, diarrhea and arthromyalgia together with eosinophilia achieving a mean value of 3,513 eosinophils/microliter. All the infected travellers presented positive serology and in 5 eggs of a Schistosoma mansoni were observed in stools. All the infected patients were treated with praziquantel. CONCLUSIONS: Limited exposure by bathing in fresh water in this group of travellers led to a high rate of infection. The diagnosis of schistosomiasis should be considered in any traveller from an endemic area with a history of having bathed in fresh water. In the case of an outbreak, investigation of all the travellers who had bathed is recommendable given that the infection may be asymptomatic.

Adult↗
PubMed1997

Renal aminopeptidase activities in animal models of hypertension.

Aminopeptidase activity (AP) has been implicated in the metabolism of renal and circulating vasoactive peptides. This activity is involved in the pathogenia of hypertension, essentially in spontaneously hypertensive rats. However, no other animal models, which develop hypertension by other different ways, have been used to study the possible role of aminopeptidase activity. To investigate the role of this activity in the pathogenesis of hypertension, angiotensinase A activity (glutamyl-AP and aspartyl-AP), aminopeptidase M activity (alanyl-AP), aminopeptidase B activity (arginyl-AP), pyroglutamyl-AP, and cystinyl-AP were measured in the serum and kidney of two experimental animal models of renovascular hypertension: Goldblatt two-kidney one clip (G2K-1C) and low renal mass rats (LRM). No differences were found in serum levels of AP in LRM or G2K-1C in comparison with their respective controls. In LRM rats there was a significant decrease in membrane-bound angiotensinase A (glutamyl-AP), arginyl-AP and alanyl-AP activities. In G2K-1C rats there was a significant decrease in soluble and membrane-bound angiotensinase A activity (aspartyl-AP). Our results suggest that AP activities play a role in the regulation of renal vasoactive peptides, and respond differently depending on the cause of hypertension.

Aminopeptidases↗
PubMed1997

Hypoxanthine uptake at the fetal side of human placenta proceeds through a nucleobase-preferring carrier and a non-saturable process.

Uptake and metabolism of hypoxanthine by human placenta were studied using the single-circulation paired-tracer technique. In isolated cotyledons perfused through the fetal (basal) circulation, at mean pressures of 31.7 +/- 4.0 mmHg and mean flow rates maintained at 5.5 +/- 0.15 ml/min, the [3H]hypoxanthine uptake was 36 +/- 2.4 per cent (16.5 +/- 1.1 pmol/g wet weight). Hypoxanthine uptake was significantly inhibited by unlabelled (mM) hypoxanthine (0.5), adenine (0.5), guanine (0.5) and papaverine (15.0), but was unaffected by nitrobenzylthioinosine (0.01). Adenosine failed to inhibit hypoxanthine uptake. The kinetic analysis of hypoxanthine uptake showed it to be partially mediated by a saturable (apparent K(m) = 12.1 +/- 1.85 microns; Jmax = 7.1 +/- 0.52 nmol/min) and Na(+)-dependent mechanism. A greater fraction of hypoxanthine influx proceeded through a non-saturable process. Thin layer chromatographic analysis of venous perfusate after the intra-arterial injection of [3H]hypoxanthine showed a negligible degradation of nucleobase. These overall results show that hypoxanthine uptake at the fetal side of human placenta occurs by a saturable plus a non-saturable process. The carrier showed specificity for nucleobases and high affinity-low capacity for hypoxanthine. Since the fetal blood concentration of hypoxanthine is normally low, its uptake would be mediated by the high affinity transport system. Because the non-saturable mechanism can be operative at high concentrations of hypoxanthine, it may have primary importance to clear the nucleobase coming from the fetus during intrauterine hypoxia.

Adenine↗
PubMed1997

[Biopharmaceutical studies of similar theophylline products in the national market].

BACKGROUND: Theophylline has a narrow therapeutic margin, therefore it should be formulated as a sustained release pharmaceutical form. In Chile there are several brands of sustained release theophylline forms that have not been tested. AIM: To perform in vitro release-dissolution studies of sustained release theophylline forms commercialized in Chile. MATERIALS AND METHODS: Five sustained release products were studied according to the specifications of the seventh supplement of The United States Pharmacopoeia Convention. Release and dissolution rates were compared with a rapid release aminophylline form. The identity, validation and active principle content of each product was also studied. RESULTS: All the studied forms complied with the quality requirements of the USP XII. The dissolution rate constants of the products at pH 6 ranged from 0.0583 to 0.2130, compared with 7.1 for the rapid release form. The dissolution of all products, except one, was pH dependent. CONCLUSIONS: These results underscore the need to systematically study the quality of pharmaceutical products, considered similar, whose differences could have potential risks for patients.

Bronchodilator Agents↗
PubMed1996

Pyroglutamyl peptidase I levels and their left-right distribution in the rat retina and hypothalamus are influenced by light-dark conditions.

To evaluate the effects of light and darkness on pyroglutamyl peptidase I activity (pGluPI) and its left-right distribution, pGluPI was measured bilaterally in the retina and hypothalamus under selected light-dark schedules. Rats under a 12 h light-dark cycle were divided into four experimental groups. After the end of the 12 h dark period, the animals were kept two additional hours in darkness (group 1), or light (group 2). After the end of the 12 h light period, the animals were kept two additional hours in darkness (group 3), or light (group 4). Experiments were done in light or darkness depending on the 2 h period. In the retina, a previous 12 h light period led to higher values of enzyme activity than dark periods. Left-right predominance, however, depended on the previous 2 h period: the light period led to left predominance, whereas right predominance was found after the 2 h dark period. In the hypothalamus, a left predominance was found only in group 3. These results demonstrate that environmental light conditions influence pGluPI activity in the rat retina and hypothalamus.

Adaptation, Ocular↗
PubMed1996

Identification and characterisation of two transcriptional repressor elements within the coding sequence of the Saccharomyces cerevisiae HXK2 gene.

A well-defined set of isogenic yeast strains has been constructed whereby each strain contains a different HXK2::lacZ gene fusion integrated at the URA3 locus. These HXK2::lacZ fusions differ in the amount of the HXK2 gene (encoding hexokinase 2 isoenzyme) that is fused to the lacZ reporter gene. Comparison of the beta-galactosidase activities of each strain during growth on glucose or ethanol revealed that some part of the coding region between +39 and +404 bp is involved in repressing gene expression in a carbon source dependent manner. A series of deletions of this HXK2 coding region were constructed and fused upstream of a minimal CYC1::lacZ promoter. beta-Galactosidase activities on glucose or ethanol growth yeast calls revealed that two different regulatory elements are present in this DNA region. Gel mobility shift analysis and in vitro DNase I footprinting have shown that proteins bind specifically to two downstream repressor sequences (DRS1 located from +140 to +163 and DRS2 located between +231 and +251) that influence the rate of HXK2 transcription when ethanol is used as carbon source by Saccharomyces cerevisiae. We identified and partially purified a 18 kDa protein that binds specifically to synthetic double-stranded oligonucleotides containing the (A/C)(A/G)GAAAT box sequence. Our data suggest that p18 synthesis is under the control of genes involved in glucose repression (MIG1 = CAT4) and glucose derepression (SNF1 = CAT1).

Base Sequence↗
PubMed1996

Molecular analysis of the promoter region of the hexokinase 2 gene of Saccharomyces cerevisiae.

lacZ fusions of the hexokinase 2 gene promoter were constructed and a deletion analysis was performed in order to identify the cis-acting regulatory elements of the promoter that controls hexokinase 2 gene expression. Expression of the hexokinase 2 gene is induced by glucose and around 40-fold repressed by ethanol. This repression seems to be mediated mainly by a repression element located within the coding region of the hexokinase 2 gene, between +39 and +404 bp from the ATG start codon. A second repressing element for ethanol growing cells was located between -455 bp and -254 bp. A synergistic effect on repression of transcription, when ethanol is the carbon source used for growth, was demonstrated by experiments in which both repressing elements were simultaneously removed. The finding of regulatory sequences in the coding region of the hexokinase 2 gene stimulates a search for regulatory elements in the coding region of other yeast genes.

Cloning, Molecular↗
PubMed1996

Tnk1: a novel intracellular tyrosine kinase gene isolated from human umbilical cord blood CD34+/Lin-/CD38- stem/progenitor cells.

Degenerate PCR was employed to identify novel tyrosine kinase genes from an enriched population of human umbilical cord blood hematopoietic stem/progenitor cells. One novel tyrosine kinase gene, designated Tnk1, was cloned. The sequence of the complete Tnk1 coding region predicts a 72 kD protein. Comparison of Tnk1 to available sequences in protein databases reveals that it is most homologous to Ack, an intracellular tyrosine kinase which associates with the GTP-bound form of p21cdc42Hs. Like Ack, Tnk1 consists of an N-terminal kinase domain, a putative SH3 domain immediately C-terminal to the kinase domain, and a proline-rich C-terminal region. Analysis of Tnk1 mRNA expression demonstrates that Tnk1 is expressed in all cord blood, bone marrow and adult blood sub-populations, as well as in most of the leukemia cell lines examined (16 of 20). Hybridization to fetal multi-tissue Northern blots detected several different Tnk1 transcripts in all fetal tissues examined. In contrast, a single Tnk1 transcript was detected in only five of 16 adult tissues examined (prostate, testis, ovary, small intestine and colon). Fluorescence in situ hybridization (FISH) analysis of metaphase chromosomes localized the Tnk1 gene to the short arm of chromosome 17 (17p13.1), near the p53 locus. Thus, Tnk1 is a novel tyrosine kinase that may be involved in signalling pathways utilized broadly during fetal development, more selectively in adult tissues and in cell of the lymphohematopoietic system.

ADP-ribosyl Cyclase↗
PubMed1996

Chimerism after allogeneic hematopoietic cell transplantation in childhood acute lymphoblastic leukemia.

Leukemic relapse after allogeneic bone marrow transplantation or allogeneic peripheral blood progenitor cell transplantation arises normally from residual malignant host hematopoiesis. The lack of specific tumor markers in acute lymphoblastic leukemia presents a problem for detection of residual disease post-infusion. In the present prospective study, we used PCR amplification of variable numbers of tandem repeat genetic regions for close follow-up of chimeric status in order to try to distinguish those patients at high risk of relapse. We found that chimeric status evolution was different between the long-term surviving patients and relapsed patients. The former showed either donor chimerism (DC) or transient mixed chimerism (tMC), while the latter always showed a recipient-growing MC (r.gMC). In addition, we found that complete substitution of hematopoiesis was achieved better with radiation-containing regimens, and that chronic graft-versus-host disease never appeared in MC patients. We conclude that very close follow-up of serial samples can facilitate the early detection of those leukemic children with a poor outcome after hematopoietic cell transplantation.

Adolescent↗
PubMed1996

Developmental changes of soluble and membrane-bound aspartate aminopeptidase activities in rat brain.

Specific soluble and membrane-bound aspartyl-naphthylamide hydrolyzing activities were assayed in brain subcellular fractions from rat fetuses (19-20 days of gestation), and from 1-week-old and 1-, 5- and 24-month-old rats. Both enzymatic activities showed a heterogeneous distribution, with highest concentrations mainly in the microsomal fraction. Membrane-bound activity was in most cases higher than soluble activity. With the exception of soluble activity in the nuclear and microsomal fractions, significant age-related changes were observed in all fractions for both enzymatic activities. Soluble activity showed a homogeneous developmental profile in most of the fractions, with the lowest levels in 1-month-old rats and the highest in 1-week and 5-month-old animals. However, changes in the microsomal fraction did not follow the pattern displayed by the rest of the fractions. No clear developmental profile in specific membrane-bound activity was observed, each fraction exhibiting a different sequence of changes. Whereas in 24-month-old-rats there was a significant increase in activity in homogenate, nuclear and microsomal fractions, a significant decrease was observed in the synaptosomal fraction. These results may reflect the functional status of the endogenous substrates of the enzymes.

Aging↗
PubMed1996

[Subcellular distribution of leucine aminopeptidase during the development and aging of rat brains].

INTRODUCTION: The aminopeptidases are considered to be enzymes which can regulate the activity of various neuropeptides. However, their precise function has not yet been fully determined. OBJECTIVE: With a view to studying the function of these enzymes at the cerebral level, the subcellular distribution of soluble leucine aminopeptidase from left and right cerebral hemisphere, in rats of different pre-natal and post-natal ages was determined as described in this paper. MATERIALS AND METHODS: The activity of soluble leucine aminopeptidase was determined fluorimetrically in the sub-cellular fractions obtained from the left and right cerebral hemispheres of rats of different pre-natal and post-natal ages: fetuses (of 19-21 days gestation), 1 week, 1, 5 and 24 months of age. RESULTS: No differences were observed between the cerebral hemispheres at any of the ages studied. However, significant differences were seen in the evolutionary behaviour of the two hemispheres. At all ages, except 24 months, there were significant differences between the fractions. In the fetuses, most activity was seen at the level of the synaptosomal raw fraction and least in the microsomal. At 1-week-old, the highest levels were seen at a microsomal level. In rats of 1 and 5 months of age, the highest levels were detected at synaptosomal level. With regard to the evolution with age, in the homogenate, nuclear fraction, cytosol and mitochondrial fraction a similar profile was observed, with a decrease after birth and an increase at one month, being stable at the other ages. At a synaptosomal level the profile is similar, although the differences are much more marked, with a drastic decrease in activity at two years of age. By contrast, the microsomal fraction showed a very different evolutionary profile with an increase after birth, becoming stable at later ages. CONCLUSIONS: The activity of soluble leucine aminopeptidase shows a heterogeneous subcellular distribution together with significant differences during cerebral development and ageing. The behaviour of this enzyme may reflect the functional state of its neuropeptide substrates.

Age Factors↗
PubMed1996

Detección de Escherichia coli toxigénica (LT) mediante la reacción en cadena de la polimerasa [The detection of toxigenic Escherichia coli (LT) by the polymerase chain reaction].

In this paper it is described the detection enteroxigenic Escherichia coli LT (+). This method is based on the amplification of a DNA fragment of 400 pairs of bases by polymerase chain reaction (PRC). The oligonucleotides were designed by the authors and the characteristic patterns were observed when the samples were submitted to an electrophoresis in an Agarose gel at 2%. The PCR had positive results with the strains of Escherichia coli 0:149 K; 88 (LT+) collection and with 20 strains isolated from patients with acute diarrhea. Negative results were found in Escherichia coli 0:101 K:99 NM (ST+), Vibrio cholerae 01 and Aeromonas hydrophila.

Aeromonas hydrophila↗
PubMed1995

Dietary nucleotides enhance plasma lecithin cholesterol acyl transferase activity and apolipoprotein A-IV concentration in preterm newborn infants.

The activity of lecithin cholesterol acyl transferase (LCAT), a key enzyme in lipoprotein metabolism, is low in newborn preterm infants. It has been suggested that a normal gastrointestinal function might be necessary to induce a postnatal increase of LCAT activity because apoproteins A-I and A-IV (apoA-I and apoA-IV) synthesized in considerable amounts in the intestine are known activators of LCAT. Dietary nucleotides have been reported to enhance intestinal growth and maturation; therefore, we hypothesized that nucleotide supplementation to formulas for preterm infants may influence LCAT activity. To investigate this hypothesis, two groups of preterm infants were fed either a nucleotide-free formula or a nucleotide-supplemented formula during the first month of life. The plasma LCAT activity, plasma levels of apoA-I and apoA-IV, plasma cholesteryl esters, and plasma fatty acid composition of cholesteryl esters and phospholipids were then determined. Infants receiving nucleotides had higher LCAT activities and apoA-IV levels than those receiving the nucleotide-free formula for a few weeks. The changes in apoA-IV levels were highly correlated with those of the LCAT activities. However, there were no significant correlations between changes in LCAT activity and plasma cholesteryl esters or phospholipids. These findings indicate that nucleotide supplementation to formulas for preterm infants may improve dietary lipid tolerance by enhancing plasma LCAT activity, probably as a result of an increase in apoA-IV plasma concentrations; they also suggest that nucleotides may enhance apoA-IV synthesis in the intestine during the neonatal period.

Apolipoprotein A-I↗
PubMed1995

G-CSF after autologous bone marrow transplantation for malignant diseases in children. Spanish Working Party for Bone Marrow Transplantation in Children.

The use of recombinant human granulocyte-stimulating factor (G-CSF) has been shown to effectively accelerate granulocytic recovery after autologous bone marrow transplantation (BMT) in adults. The experience, however, is limited in children. We evaluated the hematopoietic reconstitution in 41 consecutive children undergoing autologous BMT for hematologic malignancies (21 acute lymphoblastic leukemia, five non-Hodgkin's lymphoma) and solid tumours (seven neuroblastoma, two brain tumor, three Ewing's sarcoma, two Wilms' tumor, one rhabdomyosarcoma). Their ages ranged from 2 to 16 years (mean 7.2 years). rhG-CSF was given at a dose of 10 micrograms/kg/day i.v. in a 2h infusion from day +1 until +28 or until the absolute neutrophil count (ANC) was > 1 x 10(9)/L. These patients were compared with a similar historical control group of 38 children who did not receive rhG-CSF after autologous BMT. The number of cells infused was similar in both groups. At the dose and schedule used in the present study, rhG-CSF was well tolerated and no side-effects were observed. The number of cell infused was similar in both groups. At the dose and schedule used in the present study, rhG-CSF was well tolerated and no side-effects were observed. Our data show that rhG-CSF accelerates engraftment and reduces the number of febrile days and antibiotic use. Furthermore, patients who were treated had less infections.

Adolescent↗