LK peptide side chain dynamics at interfaces are independent of secondary structure

Real-time observation of the ultrafast motions of leucine side chains within model peptides at the water–air interface with representative folds – α-helix, 3₁₀-helix, β-strand – show that interfacial dynamics are mostly determined by surface interactions.

Single-site laparoscopic (SSL) cholecystectomy in human cadavers using a novel percutaneous instrument platform and a magnetic anchoring and guidance system (MAGS): reestablishing the "critical view"

INTRODUCTION

SSL introduces ergonomic challenges while establishing the critical view during dissection of the Triangle of Calot (TOC). This study investigates the use of a novel percutaneous instrument platform and MAGS in performing SSL cholecystectomy with a technique that closely mimics four-port cholecystectomy.

METHODS

SSL cholecystectomy was performed on four female cadavers via a 15-18-mm incision made at the umbilicus for introduction of these devices and the working port. MAGS comprises an internal effector with a retractable monopolar cautery hook coupled across the abdominal wall to an external magnet held by the surgeon. The novel grasper was introduced percutaneously in the RUQ and comprises a 3-mm transabdominal shaft mated to a 5-mm end effector intracorporeally. Retraction was accomplished using the percutaneous grasper to manipulate the fundus and a standard 5-mm grasper at the umbilicus for the infundibulum. Dissection was performed by using a combination of the MAGS and a standard Maryland dissector. Total procedure time, time from procedure start to obtain a critical view of the TOC and clipping and dividing the cystic duct/artery, time for dissection of the gallbladder from the liver bed, and thickness of the abdominal wall at the umbilicus were measured.

RESULTS

The critical view was obtained in each case, and all four procedures were completed successfully. Mean procedure time was 40 (range, 33-51) min; time from procedure start to obtaining the critical view and clipping and dividing the cystic duct/artery was 33 (range, 28-38) min, and time for dissection of the gallbladder from the liver bed was 6.7 (range, 3-13) min. The mean abdominal wall thickness was 1.9 (range, 1.5-2) cm.

CONCLUSIONS

The use of a novel graspers and MAGS overcomes the limitations of SSL cholecystectomy and improves surgeon dexterity. Making SSL feel more like traditional laparoscopy will enable a wider adoption of this procedure in the community.

Comparative structural and functional analysis of photoreceptor neurons of Rho-/- mice reveal increased survival on C57BL/6J in comparison to 129Sv genetic background

To explore the possible influence of defined genetic backgrounds on photoreceptor viability and function in mice carrying a targeted disruption of the rhodopsin gene, the severities of retinopathies in Rho-/- mice on C57BL/6J and 129Sv congenic backgrounds were compared by light microscopy and electroretinography and qualitatively by in situ end labeling of DNA in apoptotic photoreceptor nuclei of retinal sections. Cone photoreceptor viability and function were shown to deteriorate more slowly on the C57BL/6J background in comparison to that of the 129Sv, with significantly greater numbers of outer nuclear layer nuclei in the retinas of C57BL/6J mice at 3 and 4 months of age. Both amplitude and waveform features of the ERG were shown to be remarkably different in the two strains, indicating an approximately 6-fold difference in C57BL/6J Rho-/- mice compared to 129Sv Rho-/- mice at 80 days. Thus, in comparison with the 129Sv strain, genetic modifiers appear to constitute a component of the C57BL/6J background, the expression of which significantly protects cone photoreceptors from apoptotic death in a mutation-induced murine retinopathy. The differences in phenotype revealed in this study are sufficient in principle to provide a basis for comparisons to be made between QTLs in light-induced and mutation-induced systems.

Adaptability in the workplace: development of a taxonomy of adaptive performance

The purpose of this research was to develop a taxonomy of adaptive job performance and examine the implications of this taxonomy for understanding, predicting, and training adaptive behavior in work settings. Two studies were conducted to address this issue. In Study 1, over 1,000 critical incidents from 21 different jobs were content analyzed to identify an 8-dimension taxonomy of adaptive performance. Study 2 reports the development and administration of an instrument, the Job Adaptability Inventory, that was used to empirically examine the proposed taxonomy in 24 different jobs. Exploratory factor analyses using data from 1,619 respondents supported the proposed 8-dimension taxonomy from Study 1. Subsequent confirmatory factor analyses on the remainder of the sample (n = 1,715) indicated a good fit for the 8-factor model. Results and implications are discussed.

Does computerizing paper-and-pencil job attitude scales make a difference? New IRT analyses offer insight

The measurement equivalence of 2 scales of the Job Descriptive Index (JDI; P. C. Smith, L. M. Kendall, & C. L. Hulin, 1969), the Supervisor Satisfaction scale and the Coworker Satisfaction scale, was examined across computerized and paper-and-pencil administrations. In this study, employees in 2 organizations (N = 1,777) were administered paper-and-pencil versions of the scales, and employees in a third organization (N = 509) were administered a computerized version. A newly developed item response theory (IRT) technique for examining differential test functioning (N. S. Raju, W. J. van der Linden, & P. F. Fleer, 1995) was used to examine measurement equivalence across media. Results support the measurement equivalence of the JDI Supervisor and Coworker scales across administration media. The implications of these findings for both practitioners and organizational researchers are discussed.

The Perceptions of Fair Interpersonal Treatment Scale: development and validation of a measure of interpersonal treatment in the workplace

The Perceptions of Fair Interpersonal Treatment (PFIT) scale was designed to assess employees' perceptions of the interpersonal treatment in their work environment. Analyses of the factor structure and reliability of this new instrument indicate that the PFIT scale is a reliable instrument composed of 2 factors: supervisor treatment and coworker treatment. It was hypothesized that the PFIT scale would be positively correlated with job satisfaction variables and negatively correlated with work withdrawal, job withdrawal, experiences of sexual harassment, and an organization's tolerance of sexual harassment. Results based on 509 employees in a private-sector organization and 217 female faculty and staff members at a large midwestern university supported these hypotheses. Arguments that common method variance and employees' dispositions are responsible for the significant correlations between the PFIT scale and other job-related variables were eliminated. The implications of these results are discussed.

Turbidimetric studies of Limulus coagulin gel formation

The turbidity during trypsin-induced coagulin gel formation was studied over a range of wavelengths. The range of wavelengths used (686-326 nm) also made it possible to investigate the dependence of turbidity on wavelength (the wavelength exponent). Using the results from that work, and structural information on coagulin and the coagulin gel from other studies, a model gel-forming system was designed that consists of species for which the turbidity can be calculated relatively simply. These species include small particles (small in all dimensions relative to the wavelength of incident light); long rods and long random coils (particles that are large in just one dimension relative to the wavelength of incident light); and reflective regions (aggregated material that is large in more than one dimension relative to the wavelength of incident light). The turbidimetric characteristics of the real coagulin gel-forming system are compared with those of the model system.

Scatter factor and hepatocyte growth factor: activities, properties, and mechanism

Scatter factor (SF) was first identified as a fibroblast-derived protein which disperses (i.e., "scatters") cohesive colonies of epithelium. SF-like proteins were found in human smooth muscle cell conditioned medium, amniotic fluid, and placental tissue. SFs markedly stimulate migration of epithelial, carcinoma, and vascular endothelial cell types at picomolar concentrations. Hepatocyte growth factors (HGFs) were originally described as platelet- and serum-derived proteins which stimulate hepatocyte DNA synthesis. Partial amino acid sequence data for mouse and human SFs indicate significant homology with HGFs. We used biological, biochemical, and immunological assays to evaluate and compare the activities, properties, and mechanisms of action of mouse SF, human SF (fibroblast or placenta derived), and recombinant human HGF (hrHGF). We report the following findings: (a) mouse SF exhibits species-related differences in biological activities relative to the human factors; (b) human SF and hrHGF show significant overlap in biological activities (i.e., hrHGF stimulates motility of multiple normal and carcinoma cell types, whereas human SF stimulates DNA synthesis in several normal cell types); (c) the three factors contain common antigenic determinants; and (d) all three proteins stimulate rapid phosphorylation of tyrosine residues on the c-met protooncogene protein product (the putative receptor for HGF) and on another protein with Mr 110,000. A few biological and immunological differences between human SFs and hrHGF were observed. These may reflect minor variations in amino acid sequence or posttranslational modification related to the sources of the factors. Taken as a whole, our findings suggest that by structural, functional, immunological, and mechanistic criteria, human SF and human HGF are essentially identical.

Tumor necrosis factor stimulates epithelial tumor cell motility

Cellular motility is a critical function in embryonic development, tissue repair, and tumor invasion. We used assays of scattering (epithelial colony dispersion), cell migration, and cell invasion to study cytokine-regulated motility in epithelial and carcinoma cell lines. Tumor necrosis factor (TNF) stimulated motility in 12 of 14 cell lines in one or more assay systems. The motility-stimulating activity of TNF did not correlate with its antiproliferative activity. In lines whose migration was stimulated by both TNF and scatter factor (SF), a fibroblast-derived cytokine which stimulates epithelial cell motility, saturating concentrations of TNF plus SF induced greater migration than either agent alone. Anti-TNF monoclonal antibody blocked TNF- but not SF-stimulated motility. While various other factors (basic fibroblast growth factor, interleukin 6, interleukin 2, colony-stimulating factor 1) had little or not motility-stimulating activity, phorbol-12-myristate-13-acetate (PMA), a tumor-promoting phorbol ester, scattered and/or stimulated migration in all cell lines studied. Combinations of saturating concentrations of TNF plus PMA or of SF plus PMA induced greater migration than did any agent alone. These findings suggest that (a) carcinoma cell motility may be mediated by multiple biochemical pathways and (b) TNF stimulates epithelial motility by a mechanism different from that of SF and PMA. In vivo, TNF might enhance invasiveness of some carcinomas or stimulate epithelial wound healing.

A novel trypsin inhibitor from the hemolymph of the horseshoe crab Limulus polyphemus

Trypsin inhibitory activity from the hemolymph of Limulus polyphemus was found to co-purify with coagulogen (the clottable protein in blood coagulation) after acidification, ammonium sulfate precipitation, and gel filtration. Limulus trypsin inhibitor (LTI) was separated from coagulogen by ion-exchange chromatography on carboxymethyl-Sephadex. LTI is an inhibitor of trypsin (Ki = 3.3 nM) on both high and low molecular weight substrates. It also inhibits chymotrypsin but has little or no effect on thrombin, thermolysin, pepsin, or papain, nor does LTI inhibit the proteolytic cascade produced in endotoxin-stimulated Limulus amoebocyte lysate coagulation. Electrophoresis under nonreducing conditions on denaturing polyacrylamide gel yields a doublet migrating with an estimated Mr of 20,000. Under reducing conditions, a single broad band migrates with an estimated Mr of 15,000. The native structure is a monomer of moderate asymmetry with a molecular weight of 16,300 and a so20,w = 1.5(5), as determined by analytical ultracentrifugation. The amino acid composition of LTI yields a calculated molecular weight of 15,680 and a calculated partial specific volume of 0.71(7) ml/g. LTI does not contain methionine, tryptophan, or detectable levels of reducing carbohydrate. The NH2-terminal sequence (V-S-P-P-F-I-K-Q-T-K-F-S-T-X-F-L-G-X-S-S) consists primarily of hydrophobic amino acid residues. Comparison of the amino acid composition and amino-terminal sequence of LTI with those of other known protease inhibitors reveals no significant similarity to other trypsin inhibitors. The novel physical characteristics suggest that LTI represents a new type of protease inhibitor.

Scatter factor stimulates migration of vascular endothelium and capillary-like tube formation

Scatter factors (SFs) are heat- and trypsin-sensitive cytokines secreted by fibroblastic and vascular smooth muscle cell lines which stimulate motility of normal epithelium, carcinoma cells, and vascular endothelium. Human and mouse SFs have been purified and identified as 90 kD heterodimeric proteins consisting of heavy (58 kD) and light (31 kD) disulfide-bonded subunits. Partial amino acid sequence data from SF-derived tryptic peptides indicate marked sequence homology with hepatocyte growth factors, suggesting a common multigene family. In this chapter we describe the regulation by SF of vascular endothelial cell chemotaxis and chemokinesis; migration from microcarrier beads to flat surfaces; invasion through porous filters coated with reconstituted basement membrane; secretion of plasminogen activator; and in vitro capillary-like tube formation on a basement membrane surface.

Influence of cimetidine on pharmacokinetics of propranolol

Whole-blood propranolol concentrations were estimated for 12 hours after a single 80 mg oral dose was given in six patients taking cimetidine and two weeks after they had stopped the drug. Mean blood propranolol concentrations were higher throughout the sampling period when the patients were taking cimetidine than when they were not, and the difference was statistically significant between one and four hours (p less than 0.05). The mean relative bioavailability of propranolol, measured as the area under the concentration time curve, was significantly higher when the patients were taking cimetidine (p less than 0.025). The mean increase in bioavailability was 136.5 +/- 57.6%, and the results were consistent in each subject. It is concluded from these results that cimetidine reduces the hepatic first-pass extraction of propranolol.