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A Tejedor

Publications and source records attributed to A Tejedor.

At least 19 recordsLinked to original sources
PubMed2003

Automatic quantification of viability in epithelial cell cultures by texture analysis.

Quantification of live cells in phase contrast microscopy images allows in vivo assessment of the viability of cultured cells. An automatic screening procedure seems advisable because of the large number of cells that must be counted to achieve reasonable accuracy. This paper presents a method that quantifies necrosis in cell cultures by texture analysis of microscope images. The image is divided into regions of equal size that are classified by means of a segmentation algorithm based on texture analysis into three categories: live cells, necrotic cells and background. The classification uses three discriminant functions, built from parameters derived from the histogram and the co-occurrence matrix and calculated by performing an initial stepwise discriminant analysis on 21 sample images from a training set. The areas occupied by live and necrotic cells and number of live cells have been obtained for primary cellular cultures in intervals of 48 h during 2 weeks. The results have been compared with those obtained by an experienced observer, showing a very good correlation (Pearson's coefficient 0.95, kappa 0.87, N= 1600). A method has been developed that provides an accuracy similar to that provided by an expert, while allowing a much higher number of fields to be counted.

Cell Culture Techniques↗
PubMed2001

Prevalence of hypertension in renal disease.

BACKGROUND: Hypertension (HTN) is very frequent in patients with renal disease and its prevalence increases as renal failure progresses. METHODS: We studied the prevalence of HTN in 1921 patients with different nephropathies. Patients on dialysis and renal transplant patients were not included in the study. HTN was defined as SBP>140 and/or DBP>90 mmHg, or requiring antihypertensive therapy. RESULTS: The prevalence of HTN in the total group of patients with renal diseases was 60.5%, but this prevalence varied widely depending upon the type of underlying nephropathy. The prevalence of HTN was practically universal in patients with renal vascular disease (93%) and in patients with established diabetic nephropathy (87%), and 74% of the patients with polycystic kidney disease, 63% of the patients with chronic pyelonephritis and 54% of the patients diagnosed with glomerulonephritis were hypertensive. The prevalence of HTN in patients with renal insufficiency (80%) is significantly higher than that in patients without renal insufficiency (43% P<0.001). In a multiple logistic regression analysis, the independent risk factors defining HTN in renal patients were: renal failure, age, the presence of diabetes, hypertriglyceridaemia and proteinuria. Antihypertensive treatment consisted of diet alone in 4% of the patients, one drug in 45%, two drugs in 36%, three medications in 13% and more than three drugs in 2.5%. The angiotensin-converting enzyme (ACE) inhibitors were the most frequently prescribed drug (39% of the patients treated in monotherapy) followed by calcium channel blockers (27%), diuretics (18%) and beta-blockers (9%). The most common combined therapy was a diuretic plus an ACE inhibitor. The percentage of patients with BP controlled according to current recommendations for renal patients (BP<130/85) was very low; SBP in only 49% and DBP in 24%. Control of both was only achieved in 10% of the patients. CONCLUSIONS: There is a high prevalence of HTN in renal patients, which depends on the type of nephropathy and the degree of renal failure. Other independent risk factors for HTN in patients with renal disease are: advanced age, the presence of diabetes, hypertriglyceridaemia and the severity of proteinuria. BP control in renal patients is quite poor and should be improved to reduce progression of the renal disease.

Blood Pressure↗
PubMed2000

Role of vascular endothelial growth factor (VEGF) in endothelial cell protection against cytotoxic agents.

Autocrine expression of VEGF has been detected in endothelial cells under hypoxia or oxidative stress. However, the functional significance of this VEGF autocrine expression remains undefined. To analyze the role of autocrine VEGF in the endothelial response against injury, cultured bovine aorta endothelial cells (BAEC) were challenged with potentially cytotoxic substances with different chemical structure and pharmacologic properties, namely cytochalasin D (CyD), hydrogen peroxide (H2O2) and cyclosporine A (CsA). Our results revealed that: i. In particular conditions, exposure to potentially cytotoxic agents as CyD, H2O2 or CsA results in significant BAEC cytoprotection rather than injury. ii. The response to the 3 agents is shifted to a cell damaging pattern in the presence of a specific anti VEGF monoclonal antibody (mAb). iii. CyD and H2O2 markedly stimulate the autocrine expression of VEGF mRNA and VEGF protein. In conclusion, the present study reveals a protective mechanism of endothelial cells against injury involving autocrine VEGF production. Moreover, the occurrence of a significant increase in VEGF expression accompanying this defensive mechanism is further disclosed.

Amino Acid Sequence↗
PubMed1999

Sperm-lectin agglutination combined with swim-up leads to an efficient selection of highly motile, viable and heterogeneous ram spermatozoa.

Lectins, high molecular weight glycoproteins with different sugar-binding specificity, are able to agglutinate different cell types. The recovery of high-quality spermatozoa can be facilitated by the agglutination induced by the lectin binding. The objective of this study was to combine sperm-lectin agglutination with a dextran/swim-up procedure for developing a new selection technique for ram spermatozoa. To study sperm quality, cell viability (plasma membrane integrity), the HOS-test response and progressive individual motility were assessed. Simultaneously, centrifugal countercurrent distribution (CCCD) in an aqueous two-phase system was carried out to analyze sperm surface heterogeneity. Semen from 3 mature Saltz rams was pooled, and 0.5-mL aliquots were incubated with 4 fluorescein-labelled lectins (ECL, JAC, PSA, RCA). Then, a dextran solution was gently added and overlaid with medium. The top layer of the medium containing the spermatozoa was collected and replaced by careful addition of fresh medium. The incubation sequence was repeated 3 times at 10-min intervals. The consecutive 4 top layers obtained were pooled to give the swim-up combined sample. The highest rate of improvement in sperm quality was obtained after incubation with RCA, with a 50% increase in progressive individual motility, 21.6% in HOS value and 39.5% in viability. Total cell recovery was 64% (1.56x10(9) cells), with a viable cell recovery rate of 86%. The obtained sample showed 82% motility, 80% HOS score and 77% viability, up from the pre-swim-up values of 51, 60 and 57 %, respectively. Comparative CCCD analysis revealed a very high heterogeneous population in the RCA/swim-up sample obtained, while a much more homogeneous population was obtained in the sample after the dextran/swim-up procedure previously developed byus With this simple method, a large proportion of highly-motile spermatozoa with preserved plasma membrane and high heterogeneity can be obtained. These results strongly suggest that this selection procedure could result in a high fertility rate.

Animals↗
PubMed1998

Isolated kidney controlled perfusion with true physiological pulsatile waveform.

A computer controlled perfusion system has been developed to study the behavior of perfused kidneys in several conditions. The system is designed to perform kidney perfusions at constant pressure and low temperature (about 4 degrees C). We compared 2 types of perfusion pumps, a classical roller pump widely used in hemodialysis circuits and a vacuum powered tubular pump with active valves developed by our group and able to produce a flow pattern very similar to the pulse wave in the human circulatory system. In this preliminary study, we show the hydrodynamics obtained with both pumps in isolated hypothermic kidneys perfused with this system. The different flow patterns with both pumps seem to determine differences in the preservation conditions of the kidney.

Animals↗
PubMed1997

Characteristics of thoracic duct lymph in multiple organ dysfunction syndrome.

OBJECTIVE: To investigate the presence of endotoxin, bacteria, and potential humoral and cellular mediators in thoracic duct lymph and peripheral blood in patients with severe refractory multiple organ dysfunction. DESIGN: Convenience sample. SETTING: General intensive care unit of a university hospital. PATIENTS: Two men and 2 women were studied after a mean of 7.25 days (range, 6-9 days) of multiple organ dysfunction syndrome. The primary injury was thoracic in 1 patient and abdominal in 3 patients. INTERVENTION: The thoracic duct was cannulated with a 7F catheter and samples of lymph and peripheral blood were obtained. MAIN OUTCOME MEASURES: Simultaneous lymph and serum levels of lipopolysaccharide, tumor necrosis factor alpha, interleukin-1 beta, and interleukin-6, and activation markers on T lymphocytes. RESULTS: Lipopolysaccharide and cytokine levels were low in lymph and serum, except for a mean lymph-to-serum ratio of 53.4 for interleukin-1 beta. There was phenotypical evidence of intense polyclonal T-lymphocyte activation in both lymph and peripheral blood with increased lymph-to-peripheral blood ratios. Increased percentages in lymph of CD45RA + CD45RO + lymphocytes were observed. In 1 patient, Proteus mirabilis grew simultaneously in lymph, pancreatic necrosis fluid, and a central venous catheter tip. All simultaneous blood cultures were negative. CONCLUSIONS: Our results provide evidence of the participation of the gut-associated lymphatic tissue in the pathogenesis of the multiple organ dysfunction syndrome, suggesting that T-cell activation and cytokine production occur at the gut level. Future studies are needed to confirm and extend our findings.

Female↗
PubMed1995

Long-term follow-up of 6-8 mm brachioaxillary polytetrafluorethylene grafts for hemodialysis.

Eight millimeter expanded polytetrafluoroethylene (e-PTFE) grafts, tapered to 6 mm at the arterial site, are used by our group in the upper arm in order to avoid midgraft stenosis observed with other graft sizes. Long-term results (1-12 years) on 157 6-8 mm brachioaxillary e-PTFE grafts (Gore-Tex) are analyzed. Early failure was found in 4 grafts (2.5%). The rate of late complications was 0.37 episodes per graft-year. Steal syndrome, found in 4 cases (2.5%), was successfully treated in 3 cases by graft banding. Neither midgraft nor arterial anastomotic stenosis was observed in the 63 grafts requiring surgical thrombectomy or fistulography. The primary patency rates were 73%, 53%, and 41% at 1, 3, and 5 years, respectively. The secondary patency rates were 91%, 80%, and 72% at 1, 3, and 5 years, respectively. Comparison between both curves by the log rank test was significant (p < 0.001) expressing the efficiency of rescue surgery. We conclude that a 6-8 mm graft can be successfully used for dialysis in the brachioaxillary position.

Adolescent↗
PubMed1995

Could cytoplasmic concentration gradients for sodium and ATP exist in intact renal cells?

In renal cells, the Na+ pump maintains a transmembrane concentration gradient for sodium ensuring the net reabsorption of sodium with or without cotransported species. This process requires a significant fraction of the ATP turnover of proximal tubules and thick ascending limbs. To understand the potential regulatory influences of Na+ and ATP on the activity of the Na+ pump in these nephron segments, the apparent kinetics of the membrane-bound Na+-K+ ATPase and of the cellular Na+ pump were studied in different preparations of dog proximal tubules and thick ascending limbs (tubular suspensions, tissue homogenates, and basolateral membrane vesicles) obtained from dog kidney cortex and red medulla. Two determinant kinetic parameters, i.e., the apparent Michaelis constant (Km) and the saturating concentrations for sodium and ATP, were compared with the intracellular concentrations of Na+ and ATP measured under physiological conditions. In both types of tubules, the apparent Km value for Na+ (5-15 mM) is set well below the measured mean intracellular concentration of sodium (50-60 mM), suggesting that the Na+ pump should be saturated by sodium ions under normal conditions. Nevertheless, a modest increment of the Na concentration in the vicinity of the pump, obtained by equilibrating the intra- and extra-cellular sodium concentrations at various extracellular [Na+] with nystatin, increases the activity of the Na+ pump in intact cortical tubules and thick ascending limbs, even when the extracellular [Na+] is set at the estimated intracellular [Na+], demonstrating that the pump is not saturated by sodium in situ. Similarly, the kinetics of the renal Na+ pump as a function of the ATP concentration suggested that the pump should be saturated by ATP in physiological conditions, since in both tissues the cellular ATP level (3-6 mM) is higher than the concentration required to achieve saturation of this activity (< 2.5 mM). However, in renal cortical tubules, the steady-state intracellular [Na+] is affected by modest changes of ATP concentration, suggesting that the Na+ pump is not functionally saturated by ATP. Our data suggest that concentration gradients for Na+ and ATP may exist in the cytosol of renal cells. These gradients would be related to the polarity of sodium transport and of the ATP-consuming and ATP-regenerating processes in intact cells.(ABSTRACT TRUNCATED AT 400 WORDS)

Adenosine Triphosphate↗
PubMed1994

Primary renal lymphoma: report of 3 cases and review of the literature.

Primary renal lymphoma is a controversial entity. Only 29 cases have been reported since 1980. Diagnostic criteria are not well established. We report here 3 new cases and review the literature. Primary renal lymphoma was considered on the basis of uni- or bilateral nonobstructive nephromegaly with or without renal failure. In all cases, the diagnosis was made after renal biopsy. Extrarenal abdominal involvement was excluded by imaging techniques. The role of staging laparotomy remains controversial. Chemotherapy is the treatment of choice, but the prognosis is poor. We propose a clinical definition of primary renal lymphoma in order to achieve a better management of the disease.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1993

Metabolic cost of bafilomycin-sensitive H+ pump in intact dog, rabbit, and hamster proximal tubules.

Bafilomycin A1 is a specific inhibitor of the brush-border membrane-bound H(+)-adenosinetriphosphatase (H(+)-ATPase) of the kidney cortex with no effect on the mitochondrial ATP synthetase or on the basolateral Na(+)-K(+)-ATPase activities. Bafilomycin A1 is thus a useful tool to estimate the contribution of the activity of the H(+)-ATPase to the cellular ATP turnover in a suspension of proximal tubules containing largely S1 and S2 segments. In dog proximal tubules incubated under control conditions, we found that 81% of the respiration is directly related to ATP synthesis, i.e., is sensitive to oligomycin (phosphorylative respiration). Of this amount, 29% is inhibited by 5 x 10(-7) M bafilomycin A1 alone and 90-95% by the combination of bafilomycin plus ouabain. These results indicate that the H(+)-ATPase activity is a significant energy-requiring process in dog proximal tubules. If bafilomycin is added after a 5- to 7-min preincubation with 1 mM ouabain, then the bafilomycin-sensitive ATP turnover is larger, reaching 44% of total phosphorylation. This may suggest that the H+ pump is stimulated by the indirect inhibition of the Na+/H+ exchanger produced by the exposure of tubules to ouabain. The contribution of the bafilomycin-sensitive H+ pump to the cell ATP turnover is also increased by acidification of the extracellular medium. In rabbit and hamster proximal tubules, the bafilomycin-sensitive ATP requirement involves only 5 and 10%, respectively, of the total ATP turnover. These results demonstrate that the metabolic cost of proton secretion by the membrane-bound H(+)-ATPase in suspensions of proximal tubules may be considerable but varies significantly from species to species.

Adenosine Triphosphate↗
PubMed1992

Substrate-induced modulation of ATP turnover in dog and rabbit proximal tubules.

In dog proximal tubules in suspension, the addition of glucose increased significantly the ouabain-sensitive fraction of respiration, a response suppressed by phlorizin. The addition of alpha-methyl-D-glucoside (alpha-MG) had a modest effect and 3-O-methyl-D-glucoside (3-O-MG) had no effect. The different stimulation of the Na+,K(+)-ATPase activity elicited for each hexose could be explained by a different increment of net transepithelial flux of sodium induced by the sodium: hexose cotransport. This flux is a direct function of the transport characteristics of both luminal and antiluminal membranes of proximal cells for these sugars: glucose is rapidly transported by both membranes (allowing a large transepithelial flux of glucose: sodium) while alpha-MG is poorly transported by the basolateral, and 3-O-MG by the luminal, membrane of the dog proximal tubule (allowing a small transepithelial flux of hexoses and sodium). However the overall tubular respiration of dog proximal tubules was not increased by glucose addition because the increment in the ouabain-sensitive fraction was accompanied by a reciprocal decrement in an ouabain-insensitive but oligomycin- or N',N' dicyclohexylcarbodiimide (DCCD)-sensitive (or in the bafilomycin-sensitive) component of respiration. This component reflects the activity of a large BBM-bound H(+)-ATPase found in this species. The intracellular pH of dog proximal tubules in suspension was measured using the proton-sensitive fluorescent probe 2',7'-bis-2-(carboxyethyl)-5, (and 6)-carboxyfluorescein. Glucose application significantly alkalinized the cells. In contrast, other substrates such as lactate or acetate simultaneously acidified the cells and increased the ouabain-insensitive phosphorylative respiration of dog tubules. These observations suggest that a modulation of the activities of both the sodium and most probably the proton pump is elicited by substrate availability in suspensions of proximal tubules.

Adenosine Triphosphate↗
PubMed1991

Effects of endothelin on in vitro renin secretion.

The ability of endothelin-1 (ET-1) to directly inhibit renal renin secretion in the presence of a renin stimulator is unknown, as is the mechanism of action of any renin inhibition. Thus direct effects of ET-1 on renin secretion were investigated in two distinct preparations: rat kidney cortical slices and isolated juxtaglomerular cells (JGC). In rat kidney cortical slices, ET-1 reduced basal renin release by 20 (P less than 0.05) and 44% (P less than 0.005) at 10(-9) and 10(-8) M, respectively. To test the efficacy of ET-1 as a renin inhibitor, experiments were performed in the presence of the renin stimulator isoproterenol (10(-5) M). Addition of isoproterenol to cortical slices increased renin release by 97% (P less than 0.001); ET-1 (10(-8) M) limited this increase in renin release by isoproterenol by 80% (P less than 0.05). Similar effects were observed in JGC as ET-1 (10(-8) M) significantly reduced basal renin secretion by 26% (P less than 0.05). In isolated JGC, isoproterenol increased renin secretion by 151% (P less than 0.001); ET-1 (10(-8) M) significantly reduced this stimulated increase in renin secretion by 68%. The mechanism of renin inhibition was examined by testing the effects of the intracellular calcium buffer 1,2-bis(2-aminophenoxy) ethane-N,N,N',N'-tetraacetic acid (BAPTA; 10(-6) M) in JGC. BAPTA alone increased renin secretion in JGC by 116% (P less than 0.01); when the combination of (10(-6) M) BAPTA and ET-1 (10(-8) M) were tested in the JGC, renin secretion still increased significantly (by 78%, P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Affinity Labels↗