Biomedical subjects

M Ramírez

Publications and source records attributed to M Ramírez.

At least 55 records · Page 3Linked to original sources

PubMed2001

Ex vivo expansion of umbilical cord blood (UCB) CD34(+) cells alters the expression and function of alpha 4 beta 1 and alpha 5 beta 1 integrins.

We have investigated the influence of ex vivo expansion of human CD34(+) cord blood cells on the expression and function of adhesion molecules involved in the homing and engraftment of haematopoietic progenitors. Ex vivo expansion of umbilical cord blood CD34(+) cells for 6 d in the presence of interleukin 3 (IL-3), IL-6 and stem cell factor (SCF) or IL-11, SCF and Flt-3L resulted in increased expression of alpha 4, alpha 5, beta 1, alpha M and beta 2 integrins. However, a significant decrease in the adhesion of progenitor cells to fibronectin was observed after the ex vivo culture (adhesion of granulocyte-macrophage colony-forming units (CFU-GM) was 22 +/- 4% in fresh cells versus 5 +/- 2% and 2 +/- 2% in each combination of cytokines). Incubation with the beta 1 integrin-activating antibody TS2/16 restored adhesion to fibronectin. Transplantation of ex vivo expanded umbilical cord blood CD34(+) cells was associated with an early delayed engraftment in non-obese diabetic/severe combined immunodeficient (NOD/SCID) mice. Incubation of cells with the monoclonal antibody TS2/16 before transplantation almost completely abrogated NOD/SCID repopulating ability of both fresh and expanded CD34(+) cells. The seeding efficiency of fresh and expanded CD34(+) cells was similar, but markedly reduced after incubation with the TS2/16 monoclonal antibody. Our results show that functional activation of beta 1 integrins could overcome the decreased very late antigen (VLA)-4- and VLA-5-mediated adhesion observed after ex vivo expansion of haematopoietic progenitors. However, in vivo, these effects induced an almost complete abrogation of the homing and repopulating ability of CD34(+) UCB cells.

Animals↗

PubMed2001

Plasma fatty-acid composition and antioxidant capacity in low birth-weight infants fed formula enriched with n-6 and n-3 long-chain polyunsaturated fatty acids from purified phospholipids.

OBJECTIVE: To determine whether a formula containing n-6 and n-3 long-chain polyunsaturated fatty acids (LCP) from purified phospholipids increases the content of 20:4n-6 and 22:6n-3 of plasma lipids and modifies the plasma antioxidant capacity in low-birth-weight infants. STUDY DESIGN: Seventeen infants were fed a conventional formula for low birth-weight infants (F), and 17 a formula containing n-6 and n-3 LCP from purified pig-brain phospholipids (LCP-F). Fourteen infants receiving human milk from a human milk bank were used as a reference (HM). Growth index were measured and blood samples were taken at entry and after 15 days and 30 days of feeding. RESULTS: In infants fed LCP-F the levels of 22:6n-3 in total plasma lipids and in plasma phospholipids and triglycerides were higher than in infants fed F and closer to the levels of HM group throughout the study. Docosahexaenoic acid concentration in total plasma lipids was 3.46+/-0.19 mg/dl in infants fed LCP-F and 2.08+/-0.20 in infants fed F after 15 days of feeding (P<0.001), and 3.83+/-0.30 and 2.15+/-0.20 in infants fed LCP-F and F respectively, after 30 days of feeding (P<0.001). The concentration of 20:4n-6 in the LCP-F was significantly higher than in the F group at 15 and 30 days of feeding. Plasma antioxidant capacity did not differ significantly between the study groups. CONCLUSION: Feeding low birth-weight infants a formula containing LCP phospholipids results in an increase of n-3 and n-6 LCP in plasma towards that of infants fed human milk.

Antioxidants↗

PubMed2001

Effect of valsartan on angiotensin II- and vasopressin-degrading activities in the kidney of normotensive and hypertensive rats.

Valsartan, a selective antagonist of angiotensin II at the AT(1) receptor subtype, is an efficacious, orally active, blood pressure-lowering agent used in hypertensive patients. Given that aminopeptidases (APs) play a major role in the metabolism of local peptides involved in blood pressure control, studying them helped us to understand cardiovascular control. We studied the effect of valsartan on angiotensin II- (GluAP) and vasopressin- (CysAP) degrading activities in the kidney in the rat model of renovascular hypertension, Goldblatt two-kidney one-clip. GluAP and CysAP in renal cortex and medulla exhibited different responses to hypertension and valsartan treatment. In the renal cortex, GluAP decreased in clipped and non-clipped kidneys of hypertensive animals. However, while hypertension did not affect GluAP in the clipped kidney medulla, the non-clipped kidney exhibited an increase in soluble and a decrease in membrane-bound activity. Valsartan decreased soluble GluAP in the medulla of normotensive and hypertensive animals. In the renal cortex, CysAP activity was mainly downregulated following hypertension. Valsartan decreased soluble CysAP activity in sham-operated, but not in hypertensive animals. The renal medulla showed a significant valsartan-related decreased activity in clipped and non-clipped kidneys of both sham-operated and hypertensive animals. These results suggest a functional relationship between the AT(1) receptor and vasopressin-degrading activity.

Aminopeptidases↗

PubMed2001

Laryngotracheal reconstruction in subglottic stenosis: an ancient problem still present.

BACKGROUND: Subglottic stenosis is an ancient but persistent problem as a cause of airway obstruction. The etiology and the results of surgical treatment with thyrotracheal anastomosis were reviewed. METHODS: Fifty-six patients with subglottic stenosis were studied. All were subjected to laryngotracheal reconstruction by thyrotracheal anastomosis with partial resection of the cricoid. RESULTS: Of all 56 cases of subglottic stenosis, 48 (86%) had history of previous tracheal intubation, and only 8 (14%) had different non-neoplastic obstructive processes such as scleroma, direct injury, hamartoma, and amyloidosis. Immediate results were good in all cases. After 1 year follow-up, results of thyrotracheal anastomosis were successful in 44 (91%). In 4 other cases a restenosis was observed. Eight patients were lost to follow-up. CONCLUSIONS: Subglottic stenosis is still frequent after tracheal intubation, but other causes must be considered. Laryngotracheal reconstruction with thyrotracheal anastomosis with partial cricoid resection was feasible with good results in 91% of the cases with follow-up, but this procedure must be performed by a skilled surgical team.

Adult↗

PubMed2001

Differential effects of dietary cholesterol on aminopeptidase A, B and M in the frontal cortex of male and female mice.

Although hypercholesterolemia and hypertension have been extensively associated, the regulatory mechanism underlying this relationship is poorly understood. Systemic and local renin-angiotensin systems are involved in the control of blood-pressure. Angiotensin II has been considered as the main effector peptide of renin-angiotensin system. However, other peptides derived from the metabolism of angiotensin II, as angiotensins III and IV have been shown to play significant roles. The aim of this study is to analyse the effect of dietary cholesterol on the activity of the enzymes involved in the metabolism of angiotensins II and III. Soluble and membrane-bound aminopeptidase A (aspartyl- and glutamyl-aminopeptidases), B (arginyl-aminopeptidase) and M (alanyl-aminopeptidase) activities were measured in the frontal cortex of male and female mice fed a cholesterol enriched-diet (1% cholesterol; 0.5 cholic acid). Soluble and membrane-bound aminopeptidases B and M did not change in male or female cholesterol groups. Significant increases were observed in membrane-bound aspartyl- and glutamyl-aminopeptidase activities in both cholesterol groups. Soluble aspartyl- and glutamylaminopeptidases did not change in male cholesterol group, but significant decreases were detected in female cholesterol group. Our results may indicate that the metabolism of angiotensin II to angiotensin III by aminopeptidase A is increased, but angiotensin III metabolism by aminopeptidases B and M is not modified after cholesterol intake; so cholesterol may enhance the effects of angiotensin III, at least, at the cortical level.

Aminopeptidases↗

PubMed2001

Dietary long-chain polyunsaturated fatty acids from different sources affect fat and fatty acid excretions in rats.

Several sources of long-chain polyunsaturated fatty acids (LCP) have been evaluated for infant-formula supplementation. These sources differ in their chemical structure [triglyceride (TG) or phospholipid (PL)], arrangement of fatty acids on the TG or PL backbone, fatty acid composition and presence of other lipid components. All of these characteristics influence fat digestion, may affect fat and fatty acid absorption, and hence, LCP bioavailability and metabolism in infancy. The main objective of this work was to establish the influence of different dietary LCP sources on overall fat and LCP absorption in early life. We compared fat and fatty acid excretions at weaning in rats fed control diets or diets supplemented with LCP as TG or PL. Two separate experiments were conducted. In Experiment 1, weanling rats were fed for 3 wk a control diet (C1), a diet with TG from tuna and fungal oils (TF-TG) or a diet with PL from pig brain concentrate (PB-PL). In Experiment 2, weanling rats were fed for 3 wk a control diet (C2), a diet containing egg-TG (EG-TG) or a diet containing egg-PL (EG-PL). Fat, mineral and saturated fatty acid excretions in feces were higher in rats fed PB-PL compared with those fed TF-TG diet. In Experiment 2, groups did not differ in fat and mineral excretions. However, the EG-PL group had lower fecal excretions of saturated fatty acids than the C2 and EG-TG groups. The 16:1(n-7), 18:1(n-9), 18:2(n-6) and 22:6(n-3) levels in feces were higher in the EG-TG group than in the EG-PL group. In summary, total fat and LCP excretions differed among rats fed diets supplemented with LCP from different sources.

Absorption↗

PubMed2001

Serum aminopeptidase A activity of mice is related to dietary fat saturation.

A high intake of monounsaturated fat has been proposed to be a dietary factor that can decrease the incidence of cardiovascular disease and hypertension. In addition, increasing dietary fat saturation has been shown to increase plasma total cholesterol and elevate systolic and diastolic blood pressures. We demonstrated previously that cholesterol selectively increases in vitro aminopeptidase A activity, which is related to angiotensin metabolism. In this study, we investigated the effect of different degrees of dietary fatty acid saturation on serum aminopeptidase activities in vivo. Serum total cholesterol concentrations were also measured. Five groups of male Balb/C mice were fed for 10 wk diets containing 2.4 g/100 g of sunflower oil, fish oil, olive oil, lard or coconut oil. We measured alanyl-, arginyl-, cystinyl-, pyroglutamyl-, aspartyl- and glutamyl-specific aminopeptidase activities using arylamides as substrates. Serum total cholesterol levels were higher in mice fed diets containing saturated oils (lard and coconut) than in those consuming sunflower oil, which is unsaturated. Two of the serum aminopeptidase A activities (aspartyl and glutamyl aminopeptidase) increased progressively with the degree of saturation of the dietary fatty acids; activities were significantly greater in mice fed coconut oil than in those fed sunflower or fish oil. Therefore, the substrates hydrolyzed by this activity as well as their functions may be similarly affected. These results may have some implication for the treatment of cardiovascular disease.

Aminopeptidases↗

PubMed2001

Feeding infant piglets formula with long-chain polyunsaturated fatty acids as triacylglycerols or phospholipids influences the distribution of these fatty acids in plasma lipoprotein fractions.

Several sources of long-chain polyunsaturated fatty acids (LCP) are currently available for infant formula supplementation. These oils differ in their fatty acid composition, the chemical form of the fatty acid esters [triacylglycerols (TG) or phospholipids (PL)] and presence of other lipid components. These differences may affect LCP absorption, distribution and metabolic fate after ingestion. The purpose of the present study was to evaluate the influence of different chemical forms of dietary LCP on the composition of plasma, plasma lipoproteins, liver and jejunum in infant piglets. Thirty pigs (5 d old) were bottle-fed different diets for 4 wk: a control diet (C), a diet containing LCP as TG from tuna and fungal oils (TF-TG) or a diet containing LCP as PL from egg yolk (E-PL). We measured lipid and fatty acid composition of plasma and lipoproteins, as well as lipid composition of liver and intestinal mucosa. The arachidonic and docosahexaenoic acids in HDL-PL were significantly higher in piglets fed the E-PL diet than in those fed the TF-TG diet. Opposite results were found in the LDL-PL diet. No significant differences were found between groups in TG or cholesterol concentrations of plasma or lipoproteins. Arachidonic acid in plasma PL and cholesteryl esters was significantly higher in the E-PL group than in the TF-TG group. The chemical form in which LCP esters are present in different dietary sources influences their distribution in plasma lipoproteins. This may be important for infant nutrition and suggests that not all LCP sources may be biologically equivalent.

Animal Feed↗

PubMed2001

An unusual presentation of opioid-like syndrome in pediatric valproic acid poisoning.

We report a 3-y-o boy who accidentally poisoned himself with valproic acid (VPA). Clinical features included profound coma, depressed respiration and miosis. Treatment included naloxone, gastric lavage, and activated charcoal and a saline cathartic. The patient fully recovered and was discharged 24 h after the admission. Prompt use of naloxone is advised whenever the triad of coma, pinpoint pupils and depressed respiration concur with the clinical possibility of VPA intoxication.

Child, Preschool↗

PubMed2000

Calcium-dependent modulation by ethanol of mouse synaptosomal pyroglutamyl aminopeptidase activity under basal and K(+)-stimulated conditions.

We studied the in vitro effects of ethanol (25, 50 and 100 mM) on pyroglutamyl aminopeptidase activity (pGluAP), which has been reported as thyrotrophin-releasing-hormone-degrading activity. pGluAP was measured in presence or absence of calcium, under basal and K(+)-stimulated conditions, in synaptosomes and their incubation supernatant, using pyroglutamyl-beta-naphthylamide as substrate. In basal conditions, in synaptosomes, pGluAP was inhibited by ethanol in a calcium-independent way. In the supernatant, the response differed depending on the concentration of ethanol. Depolarization with K(+) modified pGluAP in synaptosomes and supernatant depending on the presence or not of calcium. In synaptosomes, in absence of calcium, the activity was inhibited at the highest concentrations of ethanol. In contrast, in the supernatant, under depolarizing conditions, ethanol increases pGluAP in absence of calcium. These changes may be in part responsible of the behavioural changes associated to alcohol intake.

Animals↗

PubMed2000

Efficient transduction of human hematopoietic repopulating cells generating stable engraftment of transgene-expressing cells in NOD/SCID mice.

In an attempt to develop efficient procedures of human hematopoietic gene therapy, retrovirally transduced CD34(+) cord blood cells were transplanted into NOD/SCID mice to evaluate the repopulating potential of transduced grafts. Samples were prestimulated on Retronectin-coated dishes and infected with gibbon ape leukemia virus (GALV)-pseudotyped FMEV vectors encoding the enhanced green fluorescent protein (EGFP). Periodic analyses of bone marrow (BM) from transplanted recipients revealed a sustained engraftment of human hematopoietic cells expressing the EGFP transgene. On average, 33.6% of human CD45(+) cells expressed the transgene 90 to 120 days after transplantation. Moreover, 11.9% of total NOD/SCID BM consisted of human CD45(+) cells expressing the EGFP transgene at this time. The transplantation of purified EGFP(+) cells increased the proportion of CD45(+) cells positive for EGFP expression to 57. 7% at 90 to 120 days after transplantation. At this time, 18.9% and 4.3% of NOD/SCID BM consisted of CD45(+)/EGFP(+) and CD34(+)/EGFP(+) cells, respectively. Interestingly, the transplantation of EGFP(-) cells purified at 24 hours after infection also generated a significant engraftment of CD45(+)/EGFP(+) and CD34(+)/EGFP(+) cells, suggesting that a number of transduced repopulating cells did not express the transgene at that time. Molecular analysis of NOD/SCID BM confirmed the high levels of engraftment of human transduced cells deduced from FACS analysis. Finally, the analysis of the provirus insertion sites by conventional Southern blotting indicated that the human hematopoiesis in the NOD/SCID BM was predominantly oligoclonal.

Animals↗

PubMed2000

Oral administration of losartan influences aminopeptidase activity in the frontal cortex.

Although there is a brain renin-angiotensin system, its mechanisms of control are not fully understood. We studied the effect of oral administration of the AT(1) receptor antagonist losartan on brain aminopeptidase (AP) activity, which plays a major role in neuropeptide metabolism. Six AP activities, related and non-related with the angiotensin (Ang) metabolism, were measured in their soluble and membrane-bound forms in the frontal cortex of control animals and rats treated with losartan, chronically administered via the drinking water. The results demonstrate that soluble pGluAP and membrane-bound AspAP and GluAP increased significantly in losartan-treated animals, indicating that the blockade of the AT(1) receptor stimulates the activity of AP involved in the Ang metabolism. Moreover, the blockade of the AT(1) receptor induces changes not only in the brain angiotensin metabolism, but probably also in that of other neuropeptides.

Administration, Oral↗

PubMed2000

Comparative distribution of glutamyl and aspartyl aminopeptidase activities in mouse organs.

To evaluate the functional role of glutamyl and aspartyl aminopeptidases, their soluble and membrane-bound activities were measured simultaneously in several tissues of normal mice using arylamide derivatives as substrates. Although the soluble aspartyl aminopeptidase activity showed its highest levels in the testicle, the rest of the activities presented their highest levels in the kidney. Different patterns of distribution were observed for glutamyl and aspartyl aminopeptidase activities and also for soluble and membrane-bound aspartyl aminopeptidase activities. However no major differences were observed between soluble and membrane-bound glutamyl aminopeptidase activities. This unequal distribution suggests that the use of arylamide derivatives as substrates is a sensitive method that distinguishes between these enzymatic activities. The results also suggest different functions for soluble and membrane-bound aspartyl aminopeptidase activities, and for glutamyl and aspartyl aminopeptidase activities.

Adrenal Glands↗

PubMed2000

[Characteristics of Canavalia proteins].

The purpose of this work was the isolation and characterization of grain protein from five Venezuelan Genotypes (U-02, Yaracuy, Valle De La Pascua, Originally Tovar) of Jack Bean (Canavalia ensiformis). The average protein content from these genotypes was 31.37%, it ranged between 28.44% and 33.05%. The protein isolation was performed by solubility extraction procedures, showed: 84.57% of albumins, globulins and non proteic nitrogen and 15.43% of alcohol insoluble reduced glutelin (AIG). The content of anti-nutritional factors (canavanine and hemagglutination title) found in protein fractions were respectively: Albumins 1.96%, +4; globulins 0.17%, +5 and AIG 0.22%, +1. It was observed that protein fractions of genotype Tovar had the lowest canavanine values (0.79%, 0.02% and 0.00% respectively). The globulins gave the highest in vitro protein digestibility (65.20%) followed by Albumins (58.90%) and AIG (37.28%).

Albumins↗

PubMed2000

Osteopenia in Puerto Ricans with Crohn's disease.

BACKGROUND: Osteopenia has been reported in association to Inflammatory Bowel Disease, and in particular Crohn's disease. The use of corticosteroids, resection of the ileum, malabsorption, poor calcium intake, and the effect of inflammatory cytokines have all been considered as contributing factors. As Crohn's disease is more prevalent in young people, when peak bone mass is achieved, the presence of osteopenia is especially significant. OBJECTIVES: The aim of this study was to evaluate the bone density of patients with Crohn's disease in the University of Puerto Rico IBD Clinic; to determine the prevalence of osteopenia in these patients and to correlate bone mineral density with risk factors for osteopenia. METHODS: Sixty-six patients, 30 males and 36 females were included. After informed consent, demographic, clinical and metabolic data was obtained. Serum albumin, calcium, inorganic phosphorus and alkaline phosphatase were measured. Body mass index (BMI) was calculated. Bone density was determined by DEXA of the lumbar spine and femur and expressed as the Z score (standard deviations from normal correlated with sex and age). Severe osteopenia was a Z score > or = -2 and osteopenia was Z < or = -1.99 or > or = 1.01. Results were expressed in means. Pearson correlation coefficient was used for quantitative variables and Pearson chi-square for categorical values. RESULTS: Osteopenia was present in the hip in 69% and in the lumbar spine in 68%. Most patients had received steroids; the difference between treated and not treated patients was not significant. Osteopenia did not correlate with ileal resection, gender, BMI, disease characteristics or biochemical parameters. CONCLUSIONS: Low bone density was frequent in patients with Crohn's disease, but no specific risk factors could be identified. Bone density should be determined in patients with Crohn's disease in order to institute appropriate therapeutic measures.

Adult↗

PubMed2000

[Clinical experience in home care of children with tracheostomy].

BACKGROUND: Home care of tracheostomized children is considered a safe and low-cost alternative. AIM: To report the experience with tracheostomized children at the Pediatric Respiratory Unit of the Catholic University Hospital. PATIENTS AND METHODS: The records of 16 children (9 male) with tracheostomy (TQ) in home care between 1992 and 1998 were reviewed. RESULTS: The average age at the moment of TQ was 9 months (range 1-30 months) and the postoperative hospital management period was 5 months (range 1-11 months). The average age at discharge was 13 months (range 3 to 30 months). Surgical indication were upper airway obstruction (congenital or acquired subglottic stenosis in three, upper airway malformations in one, vocal cord palsy in one and tracheobronchomalacia in one) and chronic assisted ventilation (severe tracheobronchomalacia in four, pulmonary hypoplasia in two, myopathy in one, central nervous injury in one and bronchopulmonary dysplasia in one). Overall rate complications were 2 per 100 tracheostomy months during home care and 8 per 100 tracheostomy months during hospital care. No tracheostomy-related deaths were observed. A parenteral education program to teach about tracheostomy management and cardiopulmonary resuscitation was carried out. CONCLUSIONS: Tracheostomized children can be safely managed at home.

Child Health Services↗

PubMed1999

Ex vivo culture of cord blood CD34+ cells expands progenitor cell numbers, preserves engraftment capacity in nonobese diabetic/severe combined immunodeficient mice, and enhances retroviral transduction efficiency.

Ex vivo culture of hematopoietic stem/progenitor cells could potentially improve the efficacy of human placental/umbilical cord blood (CB) in clinical hematopoietic stem cell (HSC) transplantation and allow gene transduction using conventional retroviral vectors. Therefore, we first examined the effects of a 7-day period of ex vivo culture on the hematopoietic capacity of CB CD34+ cells. Medium for the ex vivo cultures contained either serum and six recombinant human hematopoietic growth factors (GFs), including Flt-3 ligand (FL), Kit ligand (KL = stem cell factor), thrombopoietin (Tpo), interleukin 3 (IL-3), granulocyte colony-stimulating factor (G-CSF), and interleukin 6 (IL-6), or a serum-free medium containing only FL, KL, and Tpo. After culture under both ex vivo conditions, the total numbers of viable cells, CD34+ cells, colony-forming cells (CFCs), and long-term culture initiating cells (LTC-ICs) were increased. In contrast, the severe combined immunodeficiency (SCID) mouse engrafting potential (SEP) of cultured cells was slightly decreased, as compared with fresh cells. Nevertheless, cultured human CB CD34+ cells were able to generate engraftment, shown to persist for up to 20 weeks after transplantation. We next tested the efficacy of retroviral transduction of cultured cells. Transduced cultured human cells were able to engraft in NOD/SCID mice, as tested 4 weeks after transplantation, and EGFP+CD34+ cells and EGFP+ CFCs were isolated from the chimeras. Thus, although additional improvements in ex vivo culture are still needed to expand the numbers and function of human HSCs, the current conditions appear to allow gene transduction into hematopoietic SCID engrafting cells, while at least qualitatively preserving their in vivo engraftment potential.

Animals↗

PubMed1999

Wine yeast fermentation vigor may be improved by elimination of recessive growth-retarding alleles.

The presence of recessive growth-retarding alleles can reduce the fitness of industrial wine yeasts. In nature, these alleles are supposed to be eliminated through "genome renewal". We emulated this process in the laboratory to increase the fermentation vigor of wine yeasts. The procedure is simply to sporulate the yeast strains and select new homozygous single-spore descendants. Most of the yeasts achieve a faster onset of fermentation when recessive deleterious genes are eliminated. The increase of the degree of homozygosity has no relation, either direct or inverse, with the fermentation vigor of the yeasts or with the quality of the resulting wine. However, in some strains in which recessive growth-retarding alleles have been eliminated, the fermentation vigor and the quality of the wine were found to be improved simultaneously.

Alleles↗