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Biomedical subjects

S A Lewis

Publications and source records attributed to S A Lewis.

At least 109 records · Page 6Linked to original sources
PubMed1991

Expression, processing, and assembly of foot-and-mouth disease virus capsid structures in heterologous systems: induction of a neutralizing antibody response in guinea pigs.

Plasmids containing the foot-and-mouth disease virus structural protein precursor (P1) and 3C protease genes or the P1 gene alone were expressed in Escherichia coli. A recombinant baculovirus containing the P1 gene was also generated and expressed in Spodoptera frugiperda cells. Expression of the P1 and 3C genes in E. coli resulted in efficient synthesis and processing of the structural protein precursor and assembly into 70S empty capsids. This material reacted with neutralizing monoclonal antibodies which recognize only conformational epitopes and elicited a significant neutralizing antibody response in vaccinated guinea pigs. Expression of the P1 gene in E. coli resulted in synthesis of an insoluble product, whereas in insect cells infected with the recombinant baculovirus a soluble product was synthesized. Both soluble and insoluble P1 reacted with a 12S-specific monoclonal antibody, but only soluble P1 elicited a neutralizing antibody response in guinea pigs.

Animals↗
PubMed1991

A spectroscopic method for assessing confluence of epithelial cell cultures.

We describe a convenient nonelectrophysiological technique for assessing cell proliferation and subsequent tight junction formation for epithelial monolayers grown on permeable supports. The method involves the use of phenol red (PR), a standard pH indicator in most cell culture media. In addition, we report a systematic error in a commercially available system for measuring transepithelial electrical properties. Briefly, the flux of PR across the epithelium was measured from the serosal solution into the mucosal solution. The mucosal solution was first replaced with a PR-free solution and then collected at timed intervals. The PR concentration was measured using a spectrophotometer set at the isosbestic point for PR (479 nm). PR flux was then calculated and used as an index of the permeability of the epithelium to PR. This method was tested using the renal epithelial cell line A6. After cell seeding, PR flux decreased in two phases: an initial large decrease, associated with cell growth and monolayer confluence, and a second decrease associated with tight junction formation [assessed by measuring transepithelial conductance (Gt)]. In addition to monitoring tight junction formation, PR flux measurements were also used to estimate the net movement of solution by the epithelial cells between the mucosal and serosal compartments. For convenience, Gt was initially measured in culture dishes using a commercially available "chopstick" electrode system. However, the chopstick system yielded Gt values that were on average 51% lower than values for the same preparations when measured in standard Ussing-type chambers. The discrepancy was due to a nonuniform current field produced by the chopstick electrodes.

Cell Division↗
PubMed1991

Characterization of proteins and immunogens released by adult Schistosoma mansoni.

The proteins released in vitro by metabolically radiolabeled adult Schistosoma mansoni were identified by 2-dimensional gel electrophoresis. To determine the origin of these proteins, adult worms were fractionated into surface membrane, tegument, and remaining body components, and the electrophoretic patterns of the proteins in the 3 fractions were compared to those of the released proteins. The immunogens present in these fractions then were identified by immunoprecipitation with sera from humans infected with S. mansoni. This analysis indicated that essentially all of the proteins released from the worm were immunogenic, whereas most of the major membrane and tegumental proteins were not reactive with the immune sera. Thus, it appears that the adult worm is defended against immune attack by detection of the host's antibody response against released proteins rather than against proteins-exposed on the worm's surface.

Animals↗
PubMed1990

Doppler echocardiographic evaluation of left ventricular diastolic function after percutaneous transluminal coronary angioplasty for unstable angina pectoris or acute myocardial infarction.

The effect of percutaneous transluminal coronary angioplasty (PTCA) on left ventricular (LV) diastolic function has not been systematically investigated in patients treated for unstable angina or ischemia after acute myocardial infarction (AMI). To assess the relation between reduction of stenosis severity and improvement in diastolic function in this setting, 42 patients with either unstable angina (n = 22) or post-AMI ischemia (n = 20) were serially monitored by Doppler echocardiography 8 +/- 5 hours before and 2 +/- 1 days after PTCA. Doppler LV filling indexes included isovolumic relaxation time, mitral deceleration time, E/A peak velocity ratio and atrial filling fraction. Eighteen aged-matched control subjects served to establish normal values for comparison. Before PTCA, both groups exhibited abnormal diastolic function demonstrated by prolonged isovolumic relaxation time and mitral deceleration time, decreased E/A ratio and increased atrial filling fraction. After PTCA isovolumic relaxation time and deceleration time decreased 18 +/- 28 (p less than 0.005) and 33 +/- 43 ms (p less than 0.002) in the unstable angina group and 18 +/- 23 (p less than 0.003) and 14 +/- 34 ms (difference not significant), respectively, in the post-AMI ischemia group. An increase in E/A ratio and a decrease in atrial filling fraction occurred in both groups; however, these changes were significant only in patients with post-AMI ischemia (+21%, p less than 0.03 and -11.4%, p less than 0.005, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Clinical and angiographic recurrence following PTCA for nonacute total occlusions: comparison of one- versus five-minute inflations.

To assess potential efficacy of longer inflations to reduce restenosis, 49 patients with nonacute total occlusions were randomized into two groups after successful guide wire passage across the occlusive stenosis. Twenty-one group I patients had all inflations less than 1 minute, while 28 group II patients received at least one inflation of 5 minutes' duration. There was no significant difference between group I and group II patients in mean age (56 +/- 3 versus 57 +/- 2 years), percent male sex (76% versus 68%), or frequency of left anterior descending (LAD) percutaneous transluminal coronary angioplasty (PTCA) (33% versus 32%), p = NS for all. All lesions post PTCA were less than or equal to 50% stenosed and no patient had coronary artery bypass surgery (CABG). Mean post PTCA stenosis was 29 +/- 2% for group I versus 33 +/- 2% for group II, p = NS. Clinical follow-up was available for all patients 8 +/- 0.6 months after PTCA. Recurrent symptoms were present in 8 of 21 (38%) group I patients compared with 12 of 28 (43%) patients in group II, p = NS. Angiographic follow-up was available in 32 patients (65%), with confirmation of restenosis in seven (33%) group I patients and in 11 (39%) group II patients, p = NS. In conclusion, this prospective study suggests that recurrence rates following successful PTCA of nonacute total occlusions is not modified by 5-minute versus 1-minute inflations.

Angiography↗
PubMed1990

Bluetongue virus: surface exposure of VP7.

The exposed proteins of bluetongue virus serotype 17 were determined using surface labeling and reactivity with monoclonal antibodies. Iodination of amino groups predominantly labeled VP2; however, iodination of tyrosine residues labeled both VP2 and VP5, with VP7 labeled to a significantly lesser degree. To investigate the exposure of VP7 on the intact virion further, monoclonal antibodies that reacted with this protein were used. At least two antibodies, reacting with different epitopes on VP7, bound to intact virions, as determined by adsorption of infectious particles, electron microscopic observation of antibody-bound virus, and co-sedimentation of antibody and virus. Surface iodination of viral cores was used to show that VP7 and VP3 are major exposed proteins on these particles. We conclude that a major core protein, VP7, has at least two epitopes exposed on the virus surface.

Antibodies, Monoclonal↗
PubMed1990

Mercury levels in the plumage of red-billed gulls Larus novaehollandiae scopulinus of known sex and age.

Samples of 4-8 small body feathers were taken from 27 chicks and 35 adult red-billed gulls caught at their nests on the Kaikoura Peninsula, New Zealand, in December 1988. The adults had been ringed as chicks and were of known ages from 2 to 15 years old. Analysis of total mercury in the feather samples showed that levels were independent of sex and age in adults. Mean fresh weight concentration in adult body feathers was 2.4 microg g(-1). The lack of age accumulation of mercury in gull feathers contrasts with the well known age related accumulation of mercury in tissues of fish and marine mammals, but agrees with predictions of recent studies on mercury dynamics in birds. Mercury levels in chick feathers were about 80% of levels in adult feathers.

Journal Article↗
PubMed1990

Effect of hyperosmotic challenge on basolateral membrane potential in rabbit urinary bladder.

In the rabbit urinary bladder, serosal hyperosmotic challenge (SHOC) with either 33 mM NaCl or 66 mM mannitol caused basolateral membrane potential (Vbl) to initially depolarize from -52.6 +/- 1.6 to -48.4 +/- 1.4 mV, followed by a recovery of Vbl to -57.5 +/- 1.3 mV after 13.7 +/- 1.0 min. The voltage recovery was dependent on both serosal HCO3- and Cl-, and in the absence of both, Vbl depolarized to -11.6 +/- 1.5 mV and the ratio of apical-to-basolateral resistance (Ra/Rbl) decreased from 21.0 +/- 3.4 to 8.3 +/- 3.1. This decrease in Ra/Rbl and consequent depolarization of Vbl is caused by a decrease in basolateral K+ conductance. Replacement of serosal Cl- with NO3- or SCN- followed by SHOC caused a sustained depolarization of Vbl to -32.5 +/- 4.4 and -40.9 +/- 0.9 mV, respectively. However, when Br- was used to replace Cl-, voltage recovery occurred but was slowed (24.0 +/- 2.7 min) and reduced in magnitude (-47.5 +/- 3.5 mV). Addition of amiloride (1 mM) or niflumic acid (100 microM), but not bumetanide (1 microM), to the serosal bathing solution inhibited voltage recovery causing Vbl to depolarize to -36.3 +/- 2.6 and -41.5 +/- 4.5 mV, respectively. Serosal addition of ouabain after SHOC caused Vbl to depolarize by 10.8 +/- 0.9 mV in 2 min. We speculate that the SHOC-induced initial depolarization of Vbl is a loss of Ba2(+)-sensitive K+ conductance caused by cell shrinkage. The subsequent repolarization/hyperpolarization of Vbl is caused by an enhanced basolateral membrane Na+ pump current and a reappearance of the Ba2(+)-sensitive K+ conductance. The parallel operation of Na(+)-H+ and Cl(-)-HCO3- exchanges will then supply Na+ for the pump current and, via cellular accumulation of Na+, K+, and Cl-, might result in a partial recovery of cell volume and thus Ba2(+)-sensitive K+ conductance.

Amiloride↗
PubMed1990

Vectorial secretion of a kallikrein-like enzyme by cultured renal cells. I. General properties.

Urinary kallikreins are proteolytic enzymes known to be secreted by distal nephron tubules. In this study, we demonstrate (using the chromogenic tripeptide substrate S 2266) that the renal cell line A6 from Xenopus laevis secretes a kallikrein-like enzyme. Secretion is present only when the cells are grown on filters, and enzyme is secreted only into the apical membrane bathing solution. Enzyme secretion consists of two components, one soybean trypsin inhibitor (SBTI) sensitive (SSBTI) and the other insensitive to SBTI (ISBTI). Both enzymes were inhibited by aprotinin, a kallikrein-like enzyme inhibitor. Using a bioassay, only the ISBTI enzyme produced a hypotensive effect on blood pressure and is thus a kallikrein-like enzyme. The apical membrane of cells grown on filters contains both enzyme species, whereas the basolateral membrane contains only the ISBTI (kallikrein-like) enzyme. Both enzymes were present in the apical membrane of cells grown on plastic. Initiation of enzyme secretion occurred after the cells formed electrically tight monolayers and the increase in membrane activity always preceded enzyme secretion. Using an irreversible inhibitor of the apical membrane-bound enzymes, the turnover rate for the SSBTI and ISBTI enzymes (cells on filters) was 3 and 7 h, respectively. Because the recovery of enzyme secretion was proportional to the recovery of membrane-bound enzyme activities, this suggests that enzyme secretion is due to the release of membrane-bound enzyme.

Animals↗
PubMed1990

Reversible segmental left ventricular dysfunction after coronary angioplasty.

Patients with chronic segmental myocardial dysfunction may demonstrate improvement after coronary revascularization. To evaluate the early effects of percutaneous transluminal coronary angioplasty (PTCA) on resting left ventricular segmental function, we obtained serial two-dimensional echocardiograms 1.1 +/- 0.9 days before and 3.1 +/- 2 days after elective PTCA in 40 patients. Echocardiograms were reviewed in a blind fashion; left ventricular segmental wall motion was analyzed in four short-axis views, and a score was assigned to each region (0, normal; 1, hypokinetic; and 2, akinetic). Abnormal regional wall motion was present in 20 of the patients before PTCA. Summed segment scores in these 20 patients showed an improvement in regional wall motion from 4.5 +/- 2.5 to 1.6 +/- 2.1 (p less than 0.01) after successful PTCA. Similar results were obtained when the patients were divided into those with or without a previous myocardial infarction. Improvement occurred in the seven patients without a previous myocardial infarction; the summed segment score decreased from 4.2 +/- 3.4 to 0.86 +/- 1.6 (p less than 0.05) after PTCA. Ten of the 13 patients with a prior myocardial infarction demonstrated improvement in wall motion after PTCA; the summed segment scores decreased 54% (p less than 0.001). Of the 260 segments analyzed in the study, 180 were normal before and after PTCA. Forty-nine of the 69 hypokinetic segments were normal, and 10 of 12 akinetic segments were hypokinetic after successful coronary revascularization. There was no deterioration in wall motion after PTCA.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1989

Organization of microtubules in dendrites and axons is determined by a short hydrophobic zipper in microtubule-associated proteins MAP2 and tau.

Here we report that the microtubule-associated proteins MAP2 and tau share two separable functional domains. One is the microtubule-binding site which serves to nucleate microtubule assembly; the second is a short C-terminal alpha-helical sequence which can crosslink microtubules by means of a hydrophobic zipper interaction into dense stable parallel arrays characteristic of axons or dendrites. Thus, interactions between molecules of a single type are capable of drastically reorganizing microtubules and completely suppressing their dynamic properties.

Animals↗
PubMed1989

Simultaneous left ventricular and ascending aortic pressure measurements via single artery access for assessment of aortic stenosis.

In order to determine the reliability of a single arterial access technique for hemodynamic assessment of aortic stenosis, data obtained from this method was compared with that from dual arterial access in 13 patients. A 59 cm long, 8 Fr. Mullins Transseptal Sheath (MTS) was placed in the ascending aorta (AA) and a 5 Fr. pigtail catheter advanced through the MTS (using a hemostatic "Y" adapter) into the left ventricle for simultaneous pressure recordings. Another 5 Fr. pigtail catheter (PTC) was advanced in the AA from the contralateral femoral artery. Peak pressures, AA pressure-tracing characteristics, mean gradients, and the aortic valve area using tracings from the MTS and the PTC were compared. Peak pressures 120 +/- 8 vs. 119 +/- 8 mmHg (r = .998), "T" time .16 +/- .01 vs. .15 +/- .01 sec. (r = .913), "U" time .36 +/- .02 vs. .36 +/- .02 sec. (r = .983), mean gradients 38.4 +/- 6.1 vs. 39.6 +/- 6.9 mmHg (r = .990) and the AV area .78 +/- .08 vs. 79 +/- .08 cm2 (r = .994) were similar. Therefore, this single arterial technique provides data comparable to the traditional dual access system for hemodynamic assessment of aortic stenosis.

Aged↗
PubMed1989

Study of the performance of 5 French and 7 French catheters in coronary angiography: a functional comparison.

The functional efficacy of a conventional 7F (high flow) coronary catheter (hand injection) was compared with a 5F (high flow) catheter using hand and powered injection in 29 patients with ischemic heart disease. Patients were randomized to 5F or 7F catheters as the initial catheter. Consecutive comparative coronary angiograms were performed in the 15 degrees right anterior oblique (RAO) view using Judkin's technique. Visual diagnostic grade (Grade 1 = Diagnostic, Grade 2 = Equivocal, Grade 3 = Nondiagnostic), vessel filling, vessel density (using a densitometer and corrected for background), streaming, and dislodgement were all evaluated independently by two experienced angiographers with correlation of results. Mean diagnostic grade (1.31 +/- 0.48) was significantly better with the 7F compared to 5F (hand) 1.72 +/- 0.81 and 5F (power) 2.00 +/- 0.71 (P less than or equal to 0.05) for each. Streaming was seen in 55% of injections with 5F (hand) versus 88.5% with 5F (power) and 20.7% with 7F. Measured vessel density was not different for the two catheters. Coronary injection dislodgement occurred significantly more often with 5F power injections than with hand injection of either catheter. Finally, in 6 (30%) of 20 patients in which the 5F was randomly the second catheter used, the operator had to revert to the 7F catheter in order to obtain adequate images. In conclusion, angiographic quality is reduced with 5F catheters compared to 7F high flow in certain patients. Thus, to achieve optimal diagnostic angiograms, larger lumen catheters may be required during certain procedures initially begun with 5F catheters.

Blood Flow Velocity↗
PubMed1989

Use of ionophores in epithelia: characterizing membrane properties.

In this chapter we have described the use of antibiotics for studying epithelial membrane resistances and permeabilities, as well as active and passive transport processes. We placed particular emphasis on sources of artifacts that could result in erroneous determination of any of the above parameters, as well as methods for assessing such artifacts (where possible). Although the number of possible artifacts seems large, it is not our intention to dissuade researchers from using this probe of epithelial function, but rather to point out how data might be incorrectly interpreted.

Animals↗
PubMed1989

The microtubule binding domain of microtubule-associated protein MAP1B contains a repeated sequence motif unrelated to that of MAP2 and tau.

We report the complete sequence of the microtubule-associated protein MAP1B, deduced from a series of overlapping genomic and cDNA clones. The encoded protein has a predicted molecular mass of 255,534 D and contains two unusual sequences. The first is a highly basic region that includes multiple copies of a short motif of the form KKEE or KKEVI that are repeated, but not at exact intervals. The second is a set of 12 imperfect repeats, each of 15 amino acids and each spaced by two amino acids. Subcloned fragments spanning these two distinctive regions were expressed as labeled polypeptides by translation in a cell-free system in vitro. These polypeptides were tested for their ability to copurify with unlabeled brain microtubules through successive cycles of polymerization and depolymerization. The peptide corresponding to the region containing the KKEE and KKEVI motifs cycled with brain microtubules, whereas the peptide corresponding to the set of 12 imperfect repeats did not. To define the microtubule binding domain in vivo, full-length and deletion constructs encoding MAP1B were assembled and introduced into cultured cells by transfection. The expression of transfected polypeptides was monitored by indirect immunofluorescence using anti-MAP1B-specific antisera. These experiments showed that the basic region containing the KKEE and KKEVI motifs is responsible for the interaction between MAP1B and microtubules in vivo. This region bears no sequence relationship to the microtubule binding domains of kinesin, MAP2, or tau.

Amino Acid Sequence↗