Robotic general surgery: current practice, evidence, and perspective.

BACKGROUND: Robotic technology commenced to be adopted for the field of general surgery in the 1990s. Since then, the da Vinci surgical system (Intuitive Surgical Inc, Sunnyvale, CA, USA) has remained by far the most commonly used system in this domain. The da Vinci surgical system is a master-slave machine that offers three-dimensional vision, articulated instruments with seven degrees of freedom, and additional software features such as motion scaling and tremor filtration. The specific design allows hand-eye alignment with intuitive control of the minimally invasive instruments. As such, robotic surgery appears technologically superior when compared with laparoscopy by overcoming some of the technical limitations that are imposed on the surgeon by the conventional approach. PURPOSE: This article reviews the current literature and the perspective of robotic general surgery. CONCLUSIONS: While robotics has been applied to a wide range of general surgery procedures, its precise role in this field remains a subject of further research. Until now, only limited clinical evidence that could establish the use of robotics as the gold standard for procedures of general surgery has been created. While surgical robotics is still in its infancy with multiple novel systems currently under development and clinical trials in progress, the opportunities for this technology appear endless, and robotics should have a lasting impact to the field of general surgery.

Characterization of endothelial-like cells derived from human mesenchymal stem cells.

BACKGROUND: Blood-derived endothelial progenitor cells (EPC) have been used to treat ischemic disease. However, the number of EPC that can be obtained from adult blood is limited. OBJECTIVE: To characterize endothelial-like cells obtained from human bone marrow and determine their ability to stimulate new blood vessel formation in vivo. METHODS: Mononuclear cells (MNC) were isolated from human bone marrow or umbilical cord blood and cultured in endothelial growth medium (EGM-2). Mesenchymal stem cells (MSC) were isolated from bone marrow and induced to differentiate into endothelial-like cells (MSCE), or adipocytes or osteocytes by growth in EGM-2, adipogenic or osteogenic medium. RESULTS: Cells obtained by culturing bone marrow MNC in EGM-2 formed cord- or tube-like structures when grown on Matrigel(TM) and expressed several endothelial marker proteins. However, cell morphology and the profile of endothelial marker protein expression were different from those of cord blood-derived EPC (cbEPC). Cells with a similar phenotype were obtained by differentiation of MSC into MSCE, which was accompanied by an increase of endothelial marker proteins and a diminished capacity to differentiate into adipocytes. Subcutaneous implantation of MSCE in collagen plugs in non-obese diabetic-severe combined immunodeficient (NOD-SCID) mice resulted in formation of functional blood vessels that had incorporated the MSCE. CONCLUSIONS: Our results show that MSCE and cbEPC are different cell types. The formation of functional blood vessels by MSCE, combined with high yields and a reduced capacity to differentiate into other cell types compared with MSC, makes these cells potentially useful for autologous therapy of ischemic disease.

Defining signal thresholds in DNA microarrays: exemplary application for invasive cancer.

BACKGROUND: Genome-wide or application-targeted microarrays containing a subset of genes of interest have become widely used as a research tool with the prospect of diagnostic application. Intrinsic variability of microarray measurements poses a major problem in defining signal thresholds for absent/present or differentially expressed genes. Most strategies have used fold-change threshold values, but variability at low signal intensities may invalidate this approach and it does not provide information about false-positives and false negatives. RESULTS: We introduce a method to filter false-positives and false-negatives from DNA microarray experiments. This is achieved by evaluating a set of positive and negative controls by receiver operating characteristic (ROC) analysis. As an advantage of this approach, users may define thresholds on the basis of sensitivity and specificity considerations. The area under the ROC curve allows quality control of microarray hybridizations. This method has been applied to custom made microarrays developed for the analysis of invasive melanoma derived tumor cells. It demonstrated that ROC analysis yields a threshold with reduced missclassified genes in microarray experiments. CONCLUSIONS: Provided that a set of appropriate positive and negative controls is included on the microarray, ROC analysis obviates the inherent problem of arbitrarily selecting threshold levels in microarray experiments. The proposed method is applicable to both custom made and commercially available DNA microarrays and will help to improve the reliability of predictions from DNA microarray experiments.

Decomplementation with cobra venom factor prolongs survival of xenografted islets in a rat to mouse model.

Although the involvement of complement in hyperacute rejection of xenotransplants is well recognized, its role in rejection of devascularized xenografts, such as pancreatic islets, is not completely understood. In this study, we investigated whether complement participates in the immunopathology of xeno-islet transplantation in a concordant rat to mouse model. Rat pancreatic islets were implanted under the kidney capsule of normal and cobra venom factor (CVF)-decomplementized diabetic C57BL/6 mice. Graft survival was monitored by blood glucose levels. Deposition of IgM and C3 on grafted islets in vivo or on isolated islets in vitro (after incubation with normal and decomplementized mouse serum), as well as CD4- and CD8-positive leucocyte infiltration of grafts, was checked by immunohistochemistry. In addition, complement-mediated cytotoxicity on rat islet cells was evaluated by a 3-(4, 5-dimethythiazolyl)-2.5-diphenyl-2H-tetrazolium-bromide (MTT) assay. A significant C3 deposition was found on grafted islets from the first day after transplantation in vivo, as well as on isolated islets after incubation with mouse serum in vitro. By MTT assay, complement-mediated cytotoxicity for islet cells was found. Decomplementation by CVF decreased C3 deposition on either isolated or grafted islets, delayed CD4- and CD8-positive leucocyte infiltration, led to significant inhibition of complement-mediated cytotoxicity for islet cells, and prolonged graft survival (mean survival time 21.3 versus 8.5 days; P<0.01). Our results indicate that decomplementation can prolong the survival time of devascularized xenografts across concordant species. The deposition of complement on transplanted islets may contribute to xenograft rejection by direct cytotoxicity and by promoting leucocyte infiltration.

Plasticity of Escherichia coli porin channels. Dependence of their conductance on strain and lipid environment.

The conductance properties of three members of the porin family which form channels across the outer membrane of Gram-negative bacteria were compared. With their endogenous lipopolysaccharide (LPS) bound, the closely related porins F and C from Escherichia coli reveal significantly different conductance steps and closing potentials, with values of 0.82 nS (nanosiemens) and 89 mV for F-type channels, and 0.49 nS and 158 mV for C-type pores (1 M NaCl), respectively. On the basis of their closing potentials, the two channel types can be distinguished unequivocally. If reconstituted in asolectin and extraneous LPS, porin C forms F-type in addition to C-type channels. Substitution of asolectin by mitochondrial lipids yields the native C-type pores only. Both channel types can be induced to assume the mutually other channel configuration by variation of ionic strength. A multiplicity of channel subtypes is observed by variation of the pH of the medium. The three channels within a trimer are, however, consistently of the same type. Since structural studies have revealed a single channel per monomer, the several conductance steps observed are likely to reflect distinct configurations of the same channel. Best channel recoveries were observed if endogenous LPS remained associated to porin during purification. Significant yields could nevertheless be obtained also if LPS was removed from porin and replaced with various precursors or chemically synthesized analogues. As function requires the presence of glycolipids, yet crystallization is perturbed by heterodisperse endogenous LPS, the smallest monodisperse analogues yielding good channel recovery were determined. The minimal synthetic moiety is a monoglucosaminetetraacyl compound. The characteristics of porin B from E. coli BE are shown to be indistinguishable from those of porin F. The conductance properties of this porin, refolded from random coil configuration, are indistinguishable from those exhibited by native protein. The formation of channels is thus encoded by the sequence of the mature polypeptide alone.