Outcomes following mechanical ventilation in children undergoing bone marrow transplantation

Between 1976 and 1992, 869 patients <19 years of age underwent BMT at the University of Minnesota for a variety of malignant and non-malignant disorders. One hundred and ninety-six required mechanical ventilation (MV) at some time from the start of pre-BMT cyto reduction through the first year following BMT. Reasons for MV included respiratory compromise, upper airway management and non-pulmonary indications for respiratory support. In multivariate models, underlying diagnosis, receipt of HLA-mismatched marrow and the presence of acute graft-versus-host disease (aGVHD) were independent predictors of the need for MV. Indication for MV, underlying diagnosis, and presence of aGVHD were independent predictors of successful extubation. Overall survival at 2 years was 14% among MV patients and 52% among non-MV patients. While the need for MV during BMT reduces the overall likelihood of survival, 40% of children who required MV were successfully extubated; 35% of these extubated patients were long-term survivors. This outcome is better than that reported for adult BMT patients requiring respiratory support, who show survival of <5% at 6 months following BMT. Our data suggest extrapolation of outcome data from adult to pediatric patients is not appropriate and aggressive care of pediatric patients requiring respiratory support is not futile.     

Real-time trajectory generation in multi-RCCL

This article describes the design of the trajectory generator for a robot programming system called Multi-RCCL, which is a package of “C” routines for doing real-time manipulator control in a UNIX environment. RCCL has been used successfully in developing robot control applications in numerous research and industry facilities over the last several years. One of its strongest features is the ability to integrate real-time sensor control into the manipulator task specification. RCCL primitives supply the trajectory generator with target points for motions in joint or Cartesian coordinates. Other primitives allow the code developer to specify on-line functions that can modify the target points, or possibly cancel motion requests, in response to various sensor or control inputs. The design requirements of the trajectory generator are that it be able to integrate these on-line modifications into the overall robot motion and provide a smooth path between adjacent motions even when sensor inputs make the future trajectory uncertain. © 1993 John Wiley & Sons, Inc.     

Single state elastoplastic friction models

For control applications involving small displacements and velocities, friction modeling and compensation can be very important. In particular, the modeling of presliding displacement (motion prior to fully developed slip) can play a pivotal role. In this paper, it is shown that existing single-state friction models exhibit a nonphysical drift phenomenon which results from modeling presliding as a combination of elastic and plastic displacement. A new class of single state models is defined in which presliding is elastoplastic: under loading, frictional displacement is first purely elastic and then transitions to plastic. The new model class is demonstrated to substantially reduce drift while preserving the favorable properties of existing models (e.g., dissipativity) and to provide a comparable match to experimental data     

Recent developments in the hammerhead ribozyme field

Developments in the hammerhead ribozyme field during the last two years are reviewed here. New results on the specificity of this ribozyme, the mechanism of its action and on the question of metal ion involvement in the cleavage reaction are discussed. To demonstrate the potential of ribozyme technology examples of the application of this ribozyme for the inhibition of gene expression in cell culture, in animals, as well as in plant models are presented. Particular emphasis is given to critical steps in the approach, including RNA site selection, delivery, vector development and cassette construction.     

Physical design issues for very large ATM switching systems

The authors examine the physical design issues associated with terabit/second switching systems, particularly with regard to the customer access portion of the switch. They determine the physical design requirements in the areas of backplane interconnections, integrated circuit packaging, and circuit board technology and identify areas where existing- or near-future physical design technologies are inadequate to meet the requirements of this application. A new 3D interconnection architecture that solves some of the problems encountered at the backplane level is suggested. It is also suggested that multichip module technology will help meet some of the speed and density requirements at the chip packaging level. Some of the system-level consequences of the proposed model are discussed     

Ion-pair high-performance liquid chromatography for determining disaccharide composition in heparin and heparan sulphate

Rats deficient in vitamin A express low levels of P4502C7 mRNA in the liver. Administration of all-trans retinoic acid (at-RA) or growth hormone (GH) to deficient animals only partially restored the expression whereas the combined treatment returned the P4502C7 mRNA levels to that observed in normal rats. That a retinoid is the predominant inducer of P4502C7 at the cellular level is evident from studies performed with primary hepatocytes, but it became clear that GH is a prerequisite for the vitamin A effect in vivo. The at-RA induction of P4502C7 mRNA in primary rat hepatocytes was inhibited by ketoconazole, an inhibitor of P450 activity, and by cycloheximide, blocking ongoing protein synthesis. In contrast, the at-RA induction of RAR-beta2 mRNA was not affected by any of these compounds. This could indicate previously not recognized mechanisms of at-RA action. Interestingly, at-4-oxo-RA, an at-RA metabolite formed by a P450 catalyzed reaction, also induced P4502C7 mRNA. Induction of P4502C7 mRNA by the retinoic acid receptor (RAR) selective agonist TTNPB indicated that this pathway is preferred over the retinoid X receptor (RXR) pathway. In addition, analysis of RA metabolites in liver cell extracts revealed the formation of several as yet unidentified metabolites. The formation of some of these metabolites was inhibited by ketoconazole and they could therefore constitute potential inducers of CYP2C7. We suggest that metabolism of at-RA, possibly by a P450 enzyme, is an important step in the at-RA induction of P4502C7.