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Biomedical subjects

J S Erickson

Publications and source records attributed to J S Erickson.

16 recordsLinked to original sources
PubMed2004

Monte Carlo simulations on the effect of substrate geometry on adsorption and compression.

Canonical Monte Carlo simulations were used to study the adsorption and compression of fluid layers on model substrates with cubic, (111) fcc, and graphite geometries. The effect of the relative size of the fluid and substrate molecules on adsorption was considered for strong molecule-surface interactions. In the case of monolayer formation, it was found that the surface geometry and the size of the adsorbate molecules had a significant effect on the structure of the adsorbed layer. These structures varied from well-ordered, commensurate layers to liquid-like structures. Lateral compression was observed for certain fluid to substrate molecule sizes. For the interactions studied in this work, it was found that maximum lateral compression occurred on the cubic surface when adsorbate molecules had a diameter approximately 15% larger than the substrate diameter. In the case of multilayer formation, it was found that second and higher adsorbed layers could compress into the adsorbed layers below them. For cubic substrates, the interlayer compression was predicted analytically with reasonable accuracy, with maximum interlayer compression found for fluid diameters approximately 90% the size of substrate molecule diameters.

Journal Article↗
PubMed2004

Lattice gas 2D/3D equilibria: chemical potentials and adsorption isotherms with correct critical points.

A priori information is used to derive the chemical potential as a function of density and temperature for 2D and 3D lattice systems. The functional form of this equation of state is general in terms of lattice type and dimensionality, though it contains critical temperature and critical density as parameters which depend on lattice type and dimensionality. The adsorption isotherm is derived from equilibrium between two-dimensional and three-dimensional phases. Theoretical predictions are in excellent agreement with grand canonical Monte Carlo simulations.

Journal Article↗
PubMed1990

Intracoronary urokinase for intracoronary thrombus accumulation complicating percutaneous transluminal coronary angioplasty in acute ischemic syndromes.

Intracoronary urokinase was used to treat flow-limiting intracoronary thrombus accumulation that complicated successful percutaneous transluminal coronary angioplasty (PTCA) during acute ischemic syndromes in 48 patients who were followed up through the acute phase of their illness. The study group comprised 10 patients with unstable angina pectoris, 18 patients with an evolving acute myocardial infarction, and 20 patients with postinfarction angina. The initial mean percent coronary diameter stenosis for the entire population was 95 +/- 7% and decreased with initial PTCA to 41 +/- 20% (p less than 0.001), with improved corresponding coronary flow by Thrombolysis in Myocardial Infarction trial (TIMI) grade. However, thrombus accumulation then resulted in a significant increase in percent diameter stenosis to 83 +/- 17% (p less than 0.001); a corresponding significant reduction in coronary flow also occurred by TIMI grade. After administration of intracoronary urokinase (mean dose, 141,000 units; range, 100,000-250,000 units during an average period of 34 minutes), with additional PTCA, mean percent diameter stenosis significantly decreased to 34 +/- 17% (p less than 0.001); a correspondingly significant improvement in mean coronary flow by TIMI grade occurred to 2.9 +/- 0.2. Overall, the angiographic success rate was 90%. There were no ischemic events requiring repeat PTCA and no procedure-related myocardial infarctions or deaths before hospital discharge. One patient was referred for urgent coronary artery bypass graft surgery after a successful PTCA. Plasma fibrinogen levels were obtained in 15 patients, and in no patient was the level below normal for our laboratory.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Echocardiographic and clinical predictors for outcome of elective cardioversion of atrial fibrillation.

Previous studies have suggested that success of elective direct-current cardioversion for atrial fibrillation (AF) can be predicted from clinical features and M-mode echocardiographic left atrial diameter. We evaluated clinical variables as well as M-mode and 2-dimensional echocardiographic measurements of atrial size in 85 patients undergoing electrical cardioversion for AF. Of 65 patients who were initially converted to sinus rhythm, 45 (69%) and 38 (58%) remained in sinus rhythm at 1 and 6 months, respectively. No historical feature predicted initial success, although patients with cardiomyopathy or pulmonary disease underlying their AF had significantly lower success rates compared with those having other etiologies. Furthermore, no M-mode or 2-dimensional echocardiographic measurements of atrial size predicted initial success of cardioversion. Maintenance of sinus rhythm at 1 month was related to short duration of AF before cardioversion (less than 3 months vs greater than 12 months, p less than 0.05). Left atrial area and long axis dimension by 2-dimensional echocardiography were significantly larger in patients remaining in sinus rhythm than in those who had reverted to AF at 1 month (28 +/- 7 vs 24 +/- 5 cm2 and 65 +/- 9 vs 59 +/- 8 mm, respectively, both p less than 0.05), but overlap was great. No significant difference in atrial dimensions was noted at 6-month follow-up. It appears that, although no clinical or echocardiographic variable predicts initial success for cardioversion of AF, duration of AF does predict maintenance of sinus rhythm 1 month after initial success.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1980

Biological properties of human interferon fractions obtained by blue sepharose chromatography.

Human interferons of lymphoid and nonlymphoid origins were segregated into several fractions by virtue of their elution properties from Blue Sepharose. According to desorption of the main portion of antiviral activity, three major classes could be discerned: 1. Leukocyte interferons eluting predominantly in 0.5 M NaCl buffer, 2. Lymphoblastoid interferons eluting mostly in 1 M NaCl buffer, and 3. Cell culture-derived fibroblast and bladder carcinoma interferons requiring ethylene glycol in addition to 1 M NaCl for elution. Desorption behavior from Blue Sepharose did not necessarily correlate with the presence of specific antigenic markers and no consistent segregation of Le and F antigens in individual fractions was observed. All fractions exhibited comparable activity in heterologous sheep and homologous human cells. Therefore, no distinctive biological features could be associated with multiple interferon species isolated by Blue Sepharose chromatography.

Antigens↗
PubMed1979

Molecular species of interferon induced in mouse L cells by Newcastle disease virus and polyriboinosinic-polyribocytidylic acid.

Interferons were stimulated in mouse L cells by Newcastle disease virus (NDV) or by polyriboinosinic-polyribocytidylic acid poly(rI).poly(rC). These were fractionated by sequential affinity chromatography on bovine plasma albumin (BPA)-Sepharose and on omega-carboxypentyl (CH)-Sepharose. Based on their interaction with CH-Sepharose, interferon induced by NDV was resolved into three major bands of activity (L/NDV-1,2,3) and poly(rI).poly(rC)-interferon into two (L/rI:rC-1,2). These interferon components were purified to a specific activity of 3 X 10(7) to 4 X 10(7) units/mg protein by antibody affinity chromatography and examined by electrophoresis in SDS-polyacrylamide gels. A total of five molecular species was thus identified for NDV-induced interferon and three for poly(rI).poly(rC) induced interferon, as summarized in Table 1. We conclude from our observations that mouse interferons can be produced by L cells in multiple forms with specific physiochemical properties and in proportions determined by the type of agent employed for induction.

Animals↗
PubMed1973

N-hexyl-O-glucosyl sphingosine, an inhibitor of glucosyl ceramide -glucosidase.

A synthetic analog of glucocerebroside, N-hexyl-O-glucosyl sphingosine, was found to inhibit the glucosidase in rat spleen that hydrolyzes glucocerebroside. At a concentration of 1 micro m, the analog inhibited the enzyme by 48%. The mode of action appeared to be competitive, probably aided by tight binding of the amine group to a carboxyl group near the enzyme's active site. Increasing or decreasing the chain length of the n-alkyl group attached to the nitrogen atom led to decreased effectiveness. The inhibitory effect was maximal at pH 7.0, but it was still considerable at the enzyme's optimal pH, 5.0. It is suggested that the compound may be useful for inducing an animal model of Gaucher's disease.

Alkanes↗