Biomedical subjects

E Escobar

Publications and source records attributed to E Escobar.

At least 37 records · Page 2Linked to original sources

PubMed1990

Water and ion handling in the rat cecum.

The minute-by-minute net water movement (Jw) in the rat cecum was correlated with the transepithelial potential difference (PD), short-circuit current (Isc), and the unidirectional Na+, Cl-, and Rb+ fluxes, with the following results. 1) Jw was a linear function of the applied hydrostatic or osmotic transepithelial gradients (hydrostatic permeability coefficiency = 0.164 +/- 0.018 cm/s, n = 13; osmotic permeability coefficient = 0.0014 +/- 0.0002 cm/s, n = 6). 2) A fraction of this absorptive Jw (0.17 +/- 0.03 microliter.min-1.cm-2, n = 13) was independent of the presence of any osmotic, hydrostatic, or chemical gradient. 3) This fraction was Na+ dependent, associated with an amiloride-insensitive PD and net Na+ (2.37 +/- 0.68 mu eq.h-1.cm-2, n = 6) and Cl- influxes (3.45 +/- 1.46 mu eq.h-1.cm-2, n = 6), measured under short-circuit conditions. No net Rb+ movement was detected. 4) The absorptive Jw increased when HCO3- was replaced by tris(hydroxymethyl)aminomethane (Tris+) buffer or Cl- by SO4(2-). A good agreement between the observed and the expected Jw (assuming isosmotic reabsorption) was observed in the absence of HCO3-. 5) The presence of an osmotic but not a hydrostatic transepithelial gradient generated a transepithelial PD. These results show that water movement across the rat cecum in vitro is the result of a combination of hydrostatic-, osmotic-, and transport-associated transfers. Concerning this last driving force, the observed results indicate that the transport-related Jw results from the addition of an absorptive Jw, coupled to a nonelectrogenic NaCl entry, plus a secretory Jw probably coupled to HCO3- secretion.

Animals↗

PubMed1990

[The assessment of myocardial perfusion with thallium-201 in patients with a complete left His bundle-branch block].

Thallium-201 myocardial scintigraphy was used to evaluate coronary perfusion in 20 patients with left bundle branch block suspected of having coronary artery disease. Contemporary coronary arteriography was performed in 9 of these patients. Sensitivity and specificity of the method was similar to that obtained in patients without LBBB. A false positive results indicated ischemia of the interventricular septal region in a patient with normal coronary arteries, a known limitation of the method.

Aged↗

PubMed1989

Isolation and characterization of a fibrinogen-clotting enzyme from venom of the snake, Lachesis muta muta (Peruvian bushmaster).

A fibrinogen-clotting enzyme from the venom of the Peruvian bushmaster snake was purified to homogeneity by gel filtration on Sephadex G-100 followed by DEAE-cellulose ion-exchange chromatography using a linear ionic strength gradient with NaCl. The specific activity of the enzyme was 866 NIH U/mg, representing a 55-fold purification, with a recovery of 45%. The amino acid composition was Asx30, Thr14, Ser15, Glx33, Pro23, Gly22, Ala15, Val22, Cys18, Met3, Ile18, Leu23, Tyr2, Phe13, His8, Lys11, Arg11. The total carbohydrate content was 13.4%, comprised of 3.4% hexose, 8.7% hexosamine and 1.3% sialic acid. The enzyme was active against the synthetic amide substrate alpha-N-benzoyl-DL-arginine-p-nitroanilide (BAPNA) and against the ester substrates alpha-N-benzoyl-L-arginine ethyl ester (BAEE) and tosyl-L-arginine methyl ester (TAME). Kinetic parameters for TAME esterolysis were: Vmax, 135 mumoles/min/mg and Km, 2.5 x 10(-4) M. The pH optimum was 8.0. Vmax for BAPNA amidolysis was 0.363 mumoles/min/mg and Km, 7.5 x 10(-5) M. Enzyme activity was reduced by diethylpyrocarbonate and by photo-oxidation, suggesting that the enzyme is a serine protease with a histidine residue involved in the active site. The enzyme released fibrinopeptide A rapidly from purified human fibrinogen and fibrinopeptide B more slowly. Factor XIII was not activated and the clotting activity was not inhibited by heparin. A dose of 50 micrograms/kg brought about defibrinogenation in anaesthetized rats but rabbits were unaffected. A dose of 80 micrograms/kg defibrinogenated conscious rats after 5 hr. There were no hypotensive or haemorrhagic effects.

Amino Acids↗

PubMed1989

Water permeability in different epithelial barriers.

The water permeability properties of a series of epithelial barriers (the toad urinary bladder [TUB], the rat caecum [RC], the distal human colon [DHC], and the human amnion [HA] were studied in different experimental conditions. Three parameters were simultaneously determined: the water permeability coefficient in the presence of a transepithelial hydrostatic gradient (Phydr); the water permeability coefficient in the presence of an osmotic gradient (Posm); and the transepithelial potential difference (dV). All experiments were performed with the same experimental device, allowing comparison of the permeability properties of the barriers tested. The results obtained were: (1) TUB (N = 8): Phydr = 0.079 +/- 0.008 cm/s; Posm = 0.0004 +/- 0.0002 cm/s; dV = 31 +/- 5 mV; (2) TUB after ADH (N = 8): Phydr = 0.093 +/- 0.012 cm/s; Posm = 0.0065 +/- 0.0011 cm/s; dV = 52 +/- 8; (3) RC (N = 10): Phydr = 0.18 +/- 0.02 cm/s; Posm = 0.0019 +/- 0.0004 cm/s; dV = 3.9 +/- 0.1 mV; (4) RC adapted to a high K diet (N = 10): Phydr = 0.21 +/- 0.02 cm/s; Posm = 0.0018 +/- 0.0006 cm/s; dV = 4.5 +/- 0.5 mV; (5) DHC (N = 6): Phydr = 0.22 +/- 0.03 cm/s; Posm = 0.002 +/- 0.05 cm/s; dV = 15 +/- 3 mV; (6) HA (N = 10): Phydr = 0.32 +/- 0.05 cm/s; Posm = 0.0154 +/- 0.0015; dV = 0. The results show a good correlation between Phydr and dV, but not between dV and Posm or between Posm and Phydr.

Amnion↗

PubMed1989

[Myocardial perfusion during exercise and rest in coronary patients. Evaluation with a thallium 201 analog (isonitrile-technetium 99 m)].

Isonitrile-technetium, a Thallium 201 analog, was used for myocardial perfusion imaging in 12 patients with known coronary heart disease. 10-40 mCu of the isotope were injected at maximal effort during a Bruce stress test. Imaging was performed using 3 projections immediately after exercise and 24 hr later, using a gamma camera attached to a computer. Myocardial necrosis was detected with a sensitivity of 89% and specificity of 63%. Corresponding figures for stress induced ischemia were 89% and 100%. Accurate localization of ischemia or necrosis was obtained in 70% of all cases, improving to 100% in cases of total artery occlusion. These results, similar to those reported in the literature, encourage the use of Tc labeled isonitrile for myocardial perfusion imaging whenever Thallium 201 is difficult to obtain.

Adult↗

PubMed1988