Production of stable anti-digoxin Fv in Escherichia coli.

We have created a bacterial expression-export system and have used it to express (14 mg l-1) the variable region fragment (Fv) of an anti-digoxin antibody (26-10) in Escherichia coli. The expression-export plasmid contains a T7 promoter and the E. coli signal sequences ompA [Movva et al., J. biol. Chem. 255, 27-29 (1980)] and phoA [Inouye et al., J. Bacteriol. 149, 434-439 (1982)] fused to heavy chain (VH) and light chain (VL) variable region sequences to generate an artificial cistron. The 26-10 Fv protein made using this system was soluble, unlike many other expression systems which produce insoluble proteins in the form of inclusion bodies. The 26-10 VH and VL proteins were cleaved at their mature N-termini and exported into the bacterial periplasm where they could be easily extracted and affinity purified on ouabain-Sepharose. 26-10 Fv bound to digoxin with similar affinity and specificity as the whole 26-10 antibody (Ka for Fv, 1.3 x 10(9) M-1, Ka for IgG, 7 x 10(9) M-1). 26-10 Fv appears to be remarkably stable in comparison with other Fv fragments. The half-life for chain dissociation of 26-10 Fv was 48 hr compared to the reported 1.5 hr half-life of McPC603 Fv. We present the proton NMR spectra of the 26-10 Fv as preliminary evidence that this expression-export system can be used to facilitate the analysis of the solution structure of 26-10 Fv by NMR.     

Optically active vinyl polymers containing fluorescent groups, 2. Synthesis of optically active vinyl carbazole derivatives

Synthesis and characterization of (S)-3-sec-butyl-9-vinylcarbazole ( 7 ), (S)-9-(2-methylbutyl)-2-vinylcarbazole ( 14 ), and (S)-9-(2-methylbutyl)-3-vinylcarbazole ( 18 ) are described in detail.     

Myoblasts fail to stimulate T cells but induce tolerance

Recent interest in myoblast transfer and in the use of myoblastsas vehicles in gene therapy has made it important to understandthe potential immunogenicity of allogeneic or neoantlgen-expresslngmyoblasts. Given the problems of producing a pure populationof myoblasts, In this study we used a tumour-derived musclecell line (TE671), with phenotyplc features of myoblasts, whichwe transfected to express HLA-DR1. However, this cell line wasunable to stimulate either established HLA-DR1-specific alloreactlveT cell clones or a primary alloresponse. Nor could it presenthaemagglutlnln peptide HA 306–324 to DR1-restricted, HA306–324-speciflc T cell clones or lines. Indeed, prelncubatlonwith DR1-expressing TE671 and HA 306–324 rendered suchT cells tolerant as Judged by their subsequent inability toproliferate in response to a DR1⁺ B cell line plus peptide HA306–324. These results imply that myoblasts do not providecostlmulatory signals, and are therefore unlikely to stimulateallospeclfic T cells following myoblasts transplantation orto initiate neoantlgen-speclfic immune responses following Invivo transfection.     

The impact of testing accommodations on MCAT scores: descriptive results.

PURPOSE: Medical College Admission Test (MCAT) examinees with disabilities who receive accommodations receive flagged scores indicating nonstandard administration. This report compares MCAT examinees who received accommodations and their performances with standard examinees. METHOD: Aggregate history records of all 1994-2000 MCAT examinees were identified as flagged (2,401) or standard (297,880), then further sorted by race/ethnicity (broadly identified as underrepresented minority and non-URM, at the time of testing) and gender. Those with flagged scores were also classified by disability (LD = learning disability, ADHD = attention deficit hyperactivity disorder, LD/ADHD = learning disability and attention deficit hyperactivity disorder, and Other = other disability) and type of accommodation. Mean MCAT scores were calculated for all groups. A group of 866 examinees took the MCAT first as a standard administration and subsequently with accommodations. In a separate analysis, their two sets of scores were compared. RESULTS: Less than 1% of examinees (2,401) had accommodations; of these, 55% were LD, 17% ADHD, 5% LD/ADHD, and 23% Other. Extended time was the most frequently provided accommodation. Mean flagged scores slightly exceeded mean standard scores on all MCAT sections. Examinees who retook the MCAT with accommodations after a standard administration increased their scores by six points, quadrupling the average gain Standard-Standard retest cohort from another study. CONCLUSION: The small but statistically significant different higher flagged scores may reflect either appropriate compensation or overly generous accommodations. Extended time had a positive impact on the scores of those who retested with this accommodation. The validity the flagged MCAT in predicting success in medical school is not known, and further investigation is underway.     

Electron microscopic analysis of two-dimensional crystals of the Ca2+-transport ATPase — a freeze-fracture study

Summary Two distinct forms of Ca²⁺-ATPase crystals have been analysed in sarcoplasmic reticulum (SR) membranes. The E₁-type crystals, induced by Ca²⁺ or lanthanide ions, consist of single chains of ATPase monomers, and the E₂-type crystals, induced by vanadate ions, consist of dimer chains. Using improved freeze-fracture techniques we have obtained high-resolution images of complementary surface replicas of SR membranes containing these crystal forms. In E₁ crystals, the concave fracture (P) faces display obliquely oriented rows of intramembrane particles (IMPs) spaced at - 6–7 nm along both crystal axes, while the convex fracture (E) faces show corresponding rows of pits. In E₂ crystals, regular arrays of oblique parallel ridges with spacing of - 10.5–11 nm appear on the P-faces and complementary grooves or furrows on the E-faces. In many instances the ridges break up into elongated particles repeating every 5.5 nm. When the direction of the shadow is almost parallel to the axis of the ridges, these 9.5 nm particles can be resolved into two domains, which represent intramembranous contacts between the two monomers of the two adjacent dimer chains. Complementary grooves on the E-faces can also be resolved into rows of pits complementary to the particles of the ridges on the P-faces. In the control SR membranes, randomly dispersed IMPs and corresponding pits are observed on the P- and E-faces, respectively. The data suggest that transport of Ca²⁺ involves significant structural changes of the enzyme molecule, reflected in the ATPase-ATPase interactions both on the cytoplasmic surface and in the lipid bilayer.     

Computational fluid dynamics modeling of impeller designs for the HeartQuest left ventricular assist device

To finalize the design of the next generation of the HeartQuest left ventricular assist device, a suitable impeller had to be designed and tested. The new prototype was based on calculations and test results of previous designs, but required several changes to decrease the size. For most pump designs, this is a simple matter of altering impeller geometry and rotational speed to achieve the desired pressure rise and flow rate. However, this particular pump was limited by housing geometry and the magnetic bearings that support the impeller. Without much freedom in the overall impeller size, the only parameters open to the designers were the blade profiles and the rotating speed. Rather than build several candidates and test them in a rig at enormous cost, computational models of several designs were tested and analyzed. This not only saved money, but also sped up the development time for the project. The computer models were developed in TASCflow, a computational fluid dynamics software package from AEA Technologies. This paper analyzes the data from several of the selected models, paying close attention to pumping performance and general trends from specific design changes.     

Dose-intensive therapy for extensive-stage small cell lung cancer and extrapulmonary small cell carcinoma: long-term outcome.

Treatment for extensive-stage small cell lung cancer (ES SCLC) or extrapulmonary small cell carcinoma (EPSC) is typically palliative. We set out to determine progression-free survival (PFS) and overall long-term survival of ES SCLC and EPSC patients, physiologically aged < or = 60 years, responding to first-line chemotherapy followed by high-dose combination alkylating agents with hematologic stem cell support. Patients in first-line chemotherapy response underwent stem cell collection (marrow, peripheral blood progenitor cells, or both) followed by high-dose therapy with 1 of 2 regimens: CBP (cyclophosphamide, cisplatin, and carmustine) or ICE (ifosfamide, carboplatin, and etoposide) with or without etanidazole. Involved-field radiotherapy was given to selected patients with oligometastatic disease distributed in sites allowing for reasonable radiation ports, and prophylactic cranial radiotherapy was given upon recovery to patients in complete response (CR) or near-CR. A total of 36 patients were treated. Of 29 patients with ES SCLC, 6 (21%) had achieved CR, 18 near-CR, and 5 partial response prior to high-dose therapy. Of 7 patients with EPSC, 3 (43%) had achieved CR, 3 had achieved near-CR, and 1 had progression of disease prior to high-dose therapy. Thirteen ES SCLC patients received high-dose CBP. Of the remaining 23 patients with SCLC or EPSC, 17 were treated with ICE and 6 with ICE plus etanidazole, a hypoxic cell sensitizer. Treatment-related mortality was 11% (4 of 36 patients). For all patients, the median event-free survival (EFS) was 5 months. The 2- and 5-year survivals after intensification were 12% (95% confidence interval [CI], 5%-31%) and 9% (95% CI, 3%-27%), respectively. Of the 30 patients in or near CR prior to high-dose therapy, 5 remain continuously progression-free (2 ES SCLC, 3 EPSC) for a median of 55 months (range, 1-96 months) after high-dose therapy. By multivariate analysis, factors associated with more favorable EFS were the use of a more aggressive induction regimen (ICE), and the EPSC histology. These factors were also associated with more favorable overall survival. Other factors associated with more favorable overall survival were the use of short induction therapy (< or = 4 cycles) and younger age (<50 years). Except for high-dose ICE with etanidazole, the use of high-dose systemic therapy in ES SCLC and EPSC was associated with low treatment-related morbidity and mortality over the past 5 years. Late complications were infrequent, and most patients returned to full-time work and activity, barring disease recurrence. Nonetheless, few patients with ES SCLC have progression-free long-term survival. We conclude that high-dose therapy is not indicated as an approach for ES SCLC, except as part of an investigative trial. Conversely, 3 of the 7 patients with EPSC remain relapse-free (range, 1-96 months), warranting further phase II evaluation of this approach in this population.     

An interactive, microcomputer-based karyotype analysis system for phylogenetic cytotaxonomy

A versatile and practical semi-automatic computerized system of karyotype analysis has been developed for phylogenetic cytotaxonomy for under $4,000. The modular software system is designed for use solely with a small 8-bit microcomputer and requires virtually no custom made hardware. The system interacts with the operator and greatly augments the speed and accuracy of cytotaxonomic investigations.