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Biomedical subjects

R Cardenas

Publications and source records attributed to R Cardenas.

At least 19 recordsLinked to original sources
PubMed2005

Cell motility and local viscoelasticity of fibroblasts.

Viscoelastic changes of the lamellipodial actin cytoskeleton are a fundamental element of cell motility. Thus, the correlation between the local viscoelastic properties of the lamellipodium (including the transitional region to the cell body) and the speed of lamellipodial extension is studied for normal and malignantly transformed fibroblasts. Using our atomic force microscopy-based microrheology technique, we found different mechanical properties between the lamellipodia of malignantly transformed fibroblasts (H-ras transformed and SV-T2 fibroblasts) and normal fibroblasts (BALB 3T3 fibroblasts). The average elastic constants, K, in the leading edge of SV-T2 fibroblasts (0.48 +/- 0.51 kPa) and of H-ras transformed fibroblasts (0.42 +/- 0.35 kPa) are significantly lower than that of BALB 3T3 fibroblasts (1.01 +/- 0.40 kPa). The analysis of time-lapse phase contrast images shows that the decrease in the elastic constant, K, for malignantly transformed fibroblasts is correlated with the enhanced motility of the lamellipodium. The measured mean speeds are 6.1 +/- 4.5 microm/h for BALB 3T3 fibroblasts, 13.1 +/- 5.2 microm/h for SV-T2 fibroblasts, and 26.2 +/- 11.5 microm/h for H-ras fibroblasts. Furthermore, the elastic constant, K, increases toward the cell body in many instances which coincide with an increase in actin filament density toward the cell body. The correlation between the enhanced motility and the decrease in viscoelastic moduli supports the Elastic Brownian Ratchet model for driving lamellipodia extension.

Animals↗
PubMed2001

Effect of tauroursodeoxycholate and S-adenosyl-L-methionine on 17beta-estradiol glucuronide-induced cholestasis.

BACKGROUND/AIMS: S-adenosyl-L-methionine (SAMe) and tauroursodeoxycholate (TUDC) exert an additive ameliorating effect on taurolithocholate (TLC)-induced cholestasis. The aims were to investigate the protective effect of SAMe on 17beta-estradiol-glucuronide (17betaEG) cholestasis and to find out whether SAMe and TUDC may exert an additive, ameliorating effect. METHODS: Hepatocyte couplet function was assessed by canalicular vacuolar accumulation (cVA) of cholyllysylfluorescein (CLF). Cells were co-treated with 17betaEG and SAMe, TUDC, or both (protection study), or treated with 17betaEG and then with SAMe, TUDC or both (reversion study) before CLF uptake. Couplets were also co-treated with SAMe and dehydroepiandrosterone (DHEA), a competitive substrate for the sulfotransferase involved in 17betaEG detoxification. The effects of 17betaEG, SAMe and TUDC were also examined on intracellular distribution of F-actin. RESULTS: Both SAMe and TUDC significantly protected against, and reversed, 17betaEG-induced cholestasis, but their effects were not additive. DHEA abolished the protective effect of SAMe. 17BetaEG did not affect the uptake of CLF into hepatocytes at the concentrations used, and also, it did not affect the intracellular distribution of F-actin. CONCLUSIONS: 17BetaEG does not affect the uptake of CLF into hepatocytes. SAMe and TUDC protect and reverse 17betaEG-induced cholestasis, but without an additive effect. Protection by SAMe may involve facilitating the sulfation of 17betaEG.

Actins↗
PubMed2001

Visualization of the transport of primary and secondary bile acids across liver tissue in rats: in vivo study with fluorescent bile acids.

BACKGROUND/AIMS: Lysyl fluorescein conjugated bile acid analogues (LFCBAA) closely parallel their natural counterparts. To assess LFCBAA as a tool for the visualization of bile acid transport within liver tissue. METHODS: Wistar rats were administered physiological concentrations of the primary bile acid analogue cholyllysyl fluoroscein (CLF) and of the secondary bile acid analogue lithocholyllysyl fluorescein (LLF) and serial liver biopsies were taken at fixed intervals. Both compounds were also injected retrogradely into the biliary tree. Frozen sections were examined by fluorescence microscopy. RESULTS: Both CLF and LLF were rapidly taken up from sinusoidal blood but differed significantly in their hepatic handling. CLF was rapidly transported into bile, whereas LLF transport was slower and produced significantly more bile duct fluorescence. LLF clearance showed a lobular gradient with last remaining bile acid being confined largely to zone 3. Both compounds were avidly taken up by cholangiocytes after injection intravenously or retrogradely into the biliary tree. CONCLUSIONS: Visualization of LFCBAA by fluorescence microscopy may yield further information regarding hepatobiliary bile acid localization during studies of physiological and pathological mechanisms involved in transport of bile acids. The presence of both compounds within cholangiocytes strongly suggests that they may undergo a degree of chole-hepatic recirculation.

Animals↗
PubMed2000

Molecular cloning and expression of a type-two somatostatin receptor in goldfish brain and pituitary.

Somatostatin (SRIF or SS) exerts diverse inhibitory actions through binding to specific receptors. In this study, a SRIF receptor cDNA was cloned and sequenced from goldfish brain using PCR and cDNA library screening. The cDNA encodes a 380-amino acid goldfish type-two SRIF receptor (designated as sst(2)), with seven putative transmembrane domains (TMD) and YANSCANP motif in the seventh TMD, a signature sequence for the mammalian SRIF receptor (sst) family. In addition, the amino acid sequence of the receptor has 61-62% homology to mammalian sst(2), 41-47% homology to other mammalian sst subtypes and 41-43% homology to recently identified fish sst(1) and sst(3) receptors. Both SRIF-14 and [Pro(2)]SRIF-14, two of the native goldfish SRIF forms, but not a putative goldfish SRIF-28, significantly inhibited forskolin-stimulated adenosine 3':5'-cyclic monophosphate (cAMP) release in COS-7 cells transiently expressing goldfish sst(2), suggesting functional coupling of the receptor to adenylate cyclase. None of the three peptides affected inositol phosphate production in the same receptor expression system. Northern blot showed that mRNA for the sst(2) receptor is widely distributed in goldfish brain, and highly expressed in the pituitary. The decrease in pituitary sst(2) mRNA levels following estradiol implantation suggests the presence of a negative feedback mechanism on sst(2) gene expression.

Amino Acid Sequence↗
PubMed2000

Characterization and distribution of somatostatin binding sites in goldfish brain.

Somatostatin (SRIF) binding sites were characterized in goldfish brain. Binding of (125)I-[Tyr(11)]-SRIF-14 to a brain membrane preparation was found to be saturable, reversible, and time-, temperature-, and pH-dependent. Binding was also displaceable by different forms of SRIF. Under optimal conditions (22 degrees C, pH 7.2), the equilibrium binding of (125)I-[Tyr(11)]-SRIF-14 to goldfish brain membranes was achieved after 60 min incubation. Analysis of saturable equilibrium binding revealed a one-site model fit with K(a) of 1.3 nM. SRIF-14, mammalian SRIF-28, and salmon SRIF-25 displaced (125)I-[Tyr(11)]-SRIF-14 binding with similar affinity, whereas other neuropeptides, e.g., substance P, were unable to displace (125)I-[Tyr(11)]-SRIF-14. Autoradiography studies demonstrated that (125)I-[Tyr(11)]-SRIF-14 binding sites are found throughout the goldfish brain. A high density of (125)I-[Tyr(11)]-SRIF-14 binding sites was found in the forebrain, including the nucleus preopticus, nucleus preopticus periventricularis, nucleus anterioris periventricularis, nucleus lateralis tuberis, nucleus dorsomedialis thalami, nucleus dorsolateralis thalami, nucleus ventromedialis thalami, and nucleus diffusus lobi inferioris. In midbrain, (125)I-[Tyr(11)]-SRIF-14 binding sites were found in the optic tectum. The facial and vagal lobes and the mesencephalic-cerebellar tract were found to have a high density of binding sites. This study provides the first characterization and distribution of specific binding sites for SRIF in a fish brain.

Animals↗
PubMed2000

Biphasic changes in nitric oxide generation in hemodialyzed patients with end-stage renal disease treated with recombinant human erythropoietin.

BACKGROUND: Use of recombinant human erythropoietin (rHuEpo) in patients with end-stage renal disease (ESRD) improves anemia and reduces the need for blood transfusions. However, one third of patients on rHuEpo develop hypertension, aggravation of preexistent hypertension, or other complications. Nitric oxide (NO) plays a role in blood pressure (BP) regulation. Whether rHuEpo treatment in ESRD is accompanied by alterations in NO production was explored in patients undergoing hemodialysis. METHODS: Of 121 consecutive patients in a hemodialysis clinic, 107 were treated with rHuEpo and 14 were untreated. Plasma was collected before and after hemodialysis for quantification of nitrite and nitrate (NOx). Findings were correlated with various routinely monitored parameters. RESULTS: Predialysis NOx levels were lower in the treated than the untreated group; postdialysis NOx levels were virtually the same. Thus, the change was less in the treated group. Urea reduction ratios (URR) and ultrafiltrate volumes were similar. The mean predialysis systolic BP was higher in the treated group than in the untreated group. The dose of rHuEpo did not correlate with the plasma NOx or the predialysis BPs. No correlation was found between NOx levels and Hb or gender. Of the 107 treated patients, 12 had an increased postdialysis NOx without differences in ultrafiltrate volumes or URR. This group had higher total serum calcium levels, faster pulses, and greater BP reductions than other treated patients. No difference was found in the use of calcium-channel blockers and serum phosphorus and intact parathyroid hormone concentrations did not differ significantly among these groups. CONCLUSIONS: Intermittently hemodialyzed ESRD patients treated with rHuEpo accumulate less NOx in the plasma before dialysis but generate more NOx during dialysis than untreated patients. About 11% of treated patients generated excessive amounts of NOx, thereby maintaining plasma concentrations at the predialysis level or higher. This group experienced significant hemodynamic consequences characteristic of the excessive action of NO.

Blood Pressure↗
PubMed2000

Somatostatin family of peptides and its receptors in fish.

Somatostatin (SRIF or SS) is a phylogenetically ancient, multigene family of peptides. SRIF-14 is conserved with identical primary structure in species of all classes of vertebrates. The presence of multiple SRIF genes has been demonstrated in a number of fish species and could extend to tetrapods. Three distinct SRIF genes have been identified in goldfish. One of these genes, which encodes [Pro2]SRIF-14, is also present in sturgeon and African lungfish, and is closely associated with amphibian [Pro2,Met13]SRIF-14 gene and mammalian cortistatin gene. The post-translational processing of SRIF precursors could result in multiple forms of mature SRIF peptides, with differential abundance and tissue- or cell type-specific patterns. The main neuroendocrine role of SRIF-14 peptide that has been determined in fish is the inhibition of pituitary growth hormone secretion. The functions of SRIF-14 variant or larger forms of SRIF peptide and the regulation of SRIF gene expression remain to be explored. Type 1 and type 2 SRIF receptors have been identified from goldfish and a type 3 SRIF receptor has been identified from an electric fish. Fish SRIF receptors display considerable homology with mammalian counterparts in terms of primary structure and negative coupling to adenylate cyclase. Although additional types of receptors remain to be determined, identification of the multiple gene family of SRIF peptides and multiple types of SRIF receptors opens a new avenue for the study of physiological roles of SRIF, and the molecular and cellular mechanisms of SRIF action in fish.

Amino Acid Sequence↗
PubMed1999

Hemodialysis hypotension: interaction of inhibitors, iNOS, and the interdialytic period.

Hypotension during hemodialysis in end-stage renal disease (ESRD) not explained by excessive ultrafiltration has been linked to an apparent increase in the synthesis of nitric oxide (NO). The authors tested whether the induction of NO synthase (iNOS) by cytokines or differences in the concentrations of inhibitors of NOS or both could account for variability in the amount of NO synthesized during hemodialysis. Plasma levels of an inhibitor of NOS, asymmetric dimethylarginine (ADMA), L-arginine, the substrate for NOS, the end-products N02+N03, iNOS activity in circulating buffy coat cells, and their interdialytic changes were measured in 10 patients during three treatments. Predialysis (0') levels of ADMA were markedly elevated with a mean of 0.008+/-0.002 micromol/mL of deproteinized plasma, compared to controls where ADMA is present in trace amounts. ADMA levels from 30 minutes to the end of dialysis correlated directly with the drop in blood pressure (BP), with levels being much higher in patients with severe hypotension. Postdialysis ADMA levels correlated directly with the 0' systolic BP and the drop in BP at the next dialysis treatment. NOS activity was detected in two thirds of the predialysis buffy coat samples, and appeared to increase as dialysis progressed. 0' iNOS activity correlated inversely with the 0' BP, but activities did not differ based on percent drop in BP. iNOS activity in the 0' samples correlated inversely with the time since the last dialysis, reflecting the greater accumulation of dialyzable inhibitors of NOS as the interval is prolonged. The interdialytic change in iNOS activity correlated inversely with the drop in BP. The isoform detected immunochemically in the buffy coat samples had an Mr of 130 kDa and was reactive with antihuman iNOS. Thus, iNOS is already induced in the cells of the buffy coat in many intermittently hemodialyzed ESRD subjects, but its expression may be masked by inhibitors. After 60 minutes of dialysis (too brief a time for the de novo induction of iNOS,) the appearance of or increase in iNOS activity suggests that an inhibitor had been removed. Because ADMA levels are associated with higher predialysis systolic BPs that result in a greater severity of hypotension, reduction in ADMA concentrations would appear to play a major role in the resumption of NO synthesis by various isoforms.

Adult↗
PubMed1996

Endogenous reactive oxygen metabolites mediate sublethal endothelial cell dysfunction during reoxygenation.

PURPOSE: Endothelial cells (EC) secrete vasoactive eicosanoids, which maintain organ blood flow. Because EC are a major source of eicosanoids, we studied the effects of reoxygenation on EC prostacyclin production. METHODS: Bovine aortic EC cultures were exposed to 2 hours of normoxia, then 1 hour of hypoxia (PO2 = 10 +/- 3.5 mm Hg), followed by 1.5 hours of reoxygenation in either normal medium or medium plus either superoxide dismutase (SOD, 300 units/ml), catalase (1200 units/ml), allopurinol (5.0 x 10(-4) mol/L), or dinitrophenol (10(-4) mol/L). RESULTS: Prostacyclin production decreased to 40% (p < 0.05) of basal prostacyclin production after 1 hour of hypoxia. EC reoxygenated with control medium recovered to 48% of basal prostacyclin production. EC reoxygenated in SOD resulted in recovery (p < 0.05) to 154% of basal prostacyclin production after 60 minutes. Catalase treatment resulted in recovery to 105% (p < 0.05) of basal prostacyclin production within 30 minutes of reoxygenation. Allopurinol treatment resulted in 77% recovery (p < 0.05) of basal prostacyclin production only during 30 minutes of reoxygenation. Dinitrophenol treatment resulted in significant (> or = 85%, p < 0.05) sustained recovery of basal prostacyclin production at 30, 60, and 90 minutes of experimental reperfusion. CONCLUSIONS: The hypoxia-induced decrease in EC prostacyclin does not recover during reoxygenation. Catalase/SOD allowed return to baseline prostacyclin production during reoxygenation, implicating reactive oxygen metabolites as mediators of decreased eicosanoid biosynthesis. Recovery of prostacyclin production after 60 minutes reoxygenation with dinitrophenol but not allopurinol suggests a mitochondrial origin of the oxygen metabolites responsible for decreased prostacyclin biosynthesis.

Analysis of Variance↗
PubMed1996

Pigment cholelithiasis induced by vitamin A and its prevention by butylated hydroxytoluene.

We previously reported on the induction by vitamin A of gallstones, rich in calcium and phosphate, in hamsters. On the other hand, it has been reported that the phenolic antioxidant butylated hydroxytoluene (BHT) potentiates the hepatotoxicity of vitamin A. In the present work we have tested the effect of BHT on the lithogenicity of vitamin A and on bile composition. The urinary excretion of calcium and phosphate was determined to assess a possible asymptomatic bone resorption due to vitamin A toxicity, and/or an effect of BHT on the homeostasis of calcium and phosphate. Three groups of 18 male hamsters were fed with the following diets for 70 days: Group 1, Purina Nutricubes (DB); Group 2, DB + 25,000 IU% retinol acetate (DL); Group 3, DL + 500 mg% BHT. Vitamin A (Group 2) induced gallstones in 78% of the animals, increased bile flow and biliary phosphate and calcium concentrations, and reduced those of bile salt, cholesterol and phospholipid. BHT (Group 3) reduced gallstone frequency to 5.5%, and decreased biliary phosphate, calcium and lipids toward more normal concentrations. Vitamin A alone or with BHT did not significantly affect food intake or urinary excretion of calcium and phosphate.

Animals↗
PubMed1991

Stability and fluctuations of the potato carboxypeptidase A protein inhibitor fold: a molecular dynamics study.

A 120ps non-inertial solvent (NIS) molecular dynamics (MD) trajectory of the potato carboxypeptidase A protein inhibitor (PCI) was calculated and analyzed. It is shown that, in spite of a very low content of regular secondary structure, the PCI fold has a large degree of stability, judged from the fairly good agreement between the average MD and X-ray structures. The N-terminal and C-terminal regions behave differently, both in their isoatomic positional shifts with respect to the X-ray structure, and in atomic fluctuation pattern. Positional shifts up to 9A are detected in the exposed N-terminal region as it folds back on the inhibitor's core. This large deviation is most likely caused by the absence of the receptor protein or by the lack of supporting solvent molecules. In contrast, the C-terminal region, which is the primary contact site with the enzyme, has an average structure similar to the X-ray conformation; this feature is probably due to a hydrogen bond network to the central core of PCI. The C-terminal tail shows larger fluctuations than the core. The secondary contact site retains its structure in this simulation. The results evidence an intrinsically stable PCI fold which favors a spatially well defined, fairly flexible, structuration of the primary and secondary contact sites that optimizes PCI's interaction with its target enzyme.

Binding Sites↗
PubMed1991

A molecular dynamics study of a model built Pro-36-Gly mutant derived from the potato carboxypeptidase A inhibitor protein.

A 120ps molecular dynamics (MD) trajectory was calculated and analyzed for a putative Pro-36-Gly mutant of the potato carboxypeptidase A (CPA) protein inhibitor (PCIm). The mutant protein's fold shows a large degree of stability, judged from its low alpha-carbon r.m.s. deviation from the X-ray structure of the wild type PCI (PCIw). The N-terminal tail of PCIm differs slightly less from the X-ray structure than it does in PCIw, while the mutant's C-terminal tail (the primary contact site with CPA) and residues 13-17 present deviations as they approach each other. Differences in fluctuation pattern exist between PCIm and PCIw in residues 2-4 (the N-terminal tail), 13-17, 22-23, 28-31 (the secondary contact site with CPA) and 37-38 (the C-terminal tail); the latter region is rigidified in PCIm. Results show that the MD method is able to sense local perturbative effects produced by amino acid substitutions in flexible regions of protein molecules. The simulation suggests that the conformation of the C-terminal tail is less favorable for interaction with the target protein in the mutant than it is in the wild type protein. The Pro-36-Gly mutant is predicted to be a less potent inhibitor.

Carboxypeptidases↗
PubMed1989

Circulating colony-forming units of granulocytes and monocytes/macrophages in systemic lupus erythematosus.

In systemic lupus erythematosus (SLE) patients, in vitro bone marrow (BM) colony-forming units of granulocytes and monocytes/macrophages (CFU-GM) are decreased, suggesting that granulomonopoietic failure may play an important role in the mechanism of peripheral blood (PB) depletion of neutrophils and monocytes. No information concerning CFU-GM in PB of patients with SLE is available. The present study was undertaken in order to determine whether SLE itself and the inactive or active stage of disease would modify the number of GFU-GM in PB samples from 20 treatment-free SLE women, 12 inactive and eight active. CFU-GM growth was significantly decreased in both inactive (P = 0.018) and active (P = 0.008) SLE patients as compared with controls (n = 8). The difference in CFU-GM growth between SLE groups was not significant. These results indicate that the number of circulating CFU-GM is significantly reduced in patients with SLE regardless of disease activity or remission.

Female↗
PubMed1982

Measurement of right and left ventricular ejection fractions by gated equilibrium scintigraphy using Fourier functional images.

Left and right ventricular ejection fractions (LVEF and RVEF) were calculated by gated equilibrium scintigraphy in 28 normal controls and in 21 patients with heart disease. Regions of interest (ROIs) for the ventricles were assigned on the amplitude and phase Fourier images. Two methods of preprocessing of data were compared. In Method 1 the resolution was improved and the statistical noise was reduced, while in Method 2 only the statistical noise was reduced. There were no differences between the results of the two methods for the left ventricle. The mean LVEF for normal subjects was 0.63 +/- 0.06. For the right ventricle, Method 1 showed higher sensitivity in detecting reduced RVEF in pathological situations. The mean RVEF by Method 1 for normal controls was 0.56 +/- 0.07, which is significantly different (p less than 0.001) than that found by Method 2 (0.36 +/- 0.05), and similar to those reported by others employing the firstpass method. The results show the usefulness of the phase Fourier image and the importance of a suitable preprocessing of data for determining RVEF by gated equilibrium scintigraphy.

Adolescent↗