Analysis of the unique hamster cell tropism of ecotropic murine leukemia virus PVC-211

PVC-211 murine leukemia virus (MuLV) is a neuropathogenic variant of Friend MuLV (F-MuLV). Previous studies from our laboratory demonstrated that unlike the parental F-MuLV, PVC-211 MuLV can infect rat brain capillary endothelial cells efficiently and that it has acquired genetic changes responsible for its expanded cellular tropism. To determine if PVC-211 MuLV also has expanded its host range, we tested its infectivity on Chinese hamster ovary-derived CHO-K1 cells, which are generally resistant to ecotropic MuLV. The results indicated that PVC-211 MuLV, but not F-MuLV, was highly infectious for CHO-K1 cells. Studies using glycosylation inhibitors and glycosylation mutants of CHO-K1 cells, as well as interference studies, suggested that PVC-211 MuLV has acquired the ability to interact with the ecotropic MuLV receptor on CHO-K1 cells that has undergone glycosylation-dependent modification. Using chimeric viruses between PVC-211 MuLV and F-MuLV, we were able to localize the viral genetic element crucial for CHO-K1 cell tropism within the env gene of PVC-211 MuLV and show that glycine at position 116 and lysine at position 129 of the envelope glycoprotein SU were important. These viral determinants also appear to confer tropism for other hamster cells resistant to ordinary ecotropic MuLVs. Further studies on the interaction between PVC-211 MuLV and the receptor on hamster cells may provide novel insights into the molecular mechanisms for receptor recognition and binding by viral envelope glycoproteins.     

A shallow high-resolution seismic reflection study of dudley ridge, south-east missouri

Dudley Ridge is an arcuate, north-trending terrace remnant of Wisconsinan (late Quaternary) outwash in the Western Lowlands of southeast Missouri. The ridge, an elongate topographic bulge, is approximately 12 km long and 2 km wide with up to 5 m of relief. Previous workers have attributed the ridge to fluvial erosion, or to a combination of fluvial erosion and tectonic deformation during the late Quaternary. The Commerce geophysical lineament, which is a major northeast-trending basement feature, is located a few kilometers to the southeast, and swarms of paleoliquefaction and possible neotectonic deformations have been reported in nearby areas of the Western Lowlands.To test the tectonic hypothesis, in 1994 and 1995 we acquired two west–east high-resolution seismic reflection profiles along the crest and western flank of Dudley Ridge to determine whether Paleozoic, Cretaceous and shallow Quaternary strata are faulted or folded. Profile SPB-1 shows several near-vertical faults indicative of at least three periods of movement: Paleozoic to middle Mesozoic; late Cretaceous to Tertiary; and early to late Wisconsinan (late Quaternary). Profile SPB-2 shows three ambiguous fault-like features which cut Cretaceous and Quaternary reflectors, but cannot be interpreted unequivocally to extend down into the Paleozoic section.These new seismic reflection data are interpreted to show that at least three major periods of faulting have disrupted Paleozoic, Cretaceous and Quaternary strata beneath Dudley Ridge, with the most recent faulting being early to late Wisconsinan in age and producing about 6–8 m (8–10 ms) of near-vertical displacement. Because Quaternary reflectors cannot be resolved above about 30–40 ms, the seismic data alone do not reveal whether or not the Wisconsinan deformation affected the surface of Dudley Ridge or whether the faults may have died out as they propagated up through the soft, saturated Wisconsinan outwash. However, the presence of the Farmdale Geosol beneath lower terraces adjacent to Dudley Ridge and the geosol’s apparent absence, or near-total truncation, beneath modern soils on Dudley Ridge suggest that one or more periods of tectonic bulging and accelerated erosion may have occurred between the Farmdale Interstadial and the Holocene about 25,000–10,000 years before present.     

Sensor-guided micro assembly of active micro systems by using a hot melt based joining technology

This article presents (the most) recent results of the subprojects B4 and B8 of the Collaborative Research Center 516—Design and Manufacturing of Active Micro Systems—which are concerned with the assembly of active micro systems. While subproject B4 investigates sensor guided assembly processes, subproject B8 develops suitable assembly techniques on the basis of non-viscous adhesive systems (hot melts). Process development focuses on the suitability for automation, process times and the applicability of batch processes. The article discusses certain hot melt application techniques that are suitable for batch production, a sensor-guided assembly system as well as different approaches for heat conduction in an automated assembly process for hot melt coated micro components.     

Assessment of the blade skew and the through flow velocity gradients in hydrodynamic torque converters

The well established one-dimensional mean flow approach in the analysis of hydrodynamic torque converters has been supplemented by equations regarding the balance in the transverse direction of the flow path. By these equations the validity of the design mean flow path can be considered as well as the impact of the skew of the blades. Also additional information about the flow is obtained in the form of through flow velocity gradients, which allows a refined calculation of the performance to be undertaken.     

Ontogeny of vesicular monoamine transporter mRNAs VMAT1 and VMAT2. I. The developing rat central nervous system

We used in situ hybridization histochemistry to study the expression of the mRNA of the two vesicular monoamine transporters (VMAT1 and VMAT2) during embryonic and postnatal development of the central nervous system (CNS) in the rat. In the adult rat, VMAT2 mRNA is present exclusively in monoaminergic cell groups of the CNS and VMAT1 mRNA was reported to be present in the adrenal medulla and certain intestinal epithelial cells. In contrast to the above, the expression of VMAT1 mRNA has previously never been detected in the central nervous system. This study shows the first evidence that both transporter molecules are expressed in CNS during ontogenesis. We here demonstrate four main expression patterns detected during development: 1. VMAT2 mRNA expression in monoaminergic neurons of the brainstem beginning as early as embryonic day E13. 2. Expression of VMAT2 mRNA in all major sensory relay nuclei of central nervous system. 3. Co-expression of VMAT1 and VMAT2 mRNA in most limbic structures, basal ganglia, as well as in some hypothalamic nuclei. 4. Exclusive expression of VMAT1 mRNA in the neocortical subventricular zone, in the amygdala at early (E15-18) and late (P1-P28) timepoints, the granular cell layer of cerebellum, and in several brainstem motor nuclei. Based on their distribution during development we suggest that monoamines, released in a controlled fashion, might affect wiring of sensory and also motor circuits. VMAT1 mRNA expression may reflect a specific effect of monoamines in glial differentiation and cerebellar granule cell migration and/or differentiation.     

Receptor up-regulation, internalization, and interconverting receptor states. Critical components of a quantitative description of N-formyl peptide-receptor dynamics in the neutrophil

High resolution kinetic data of the binding of fluorescent peptide to the N-formyl peptide receptor of neutrophils at 37 degrees C has allowed for the development of a ligand binding model that predicts statistically larger binding rate constants than those previously reported for intact neutrophils. The new model accounts for ligand association and dissociation, receptor up-regulation, ligand-receptor complex internalization, a change in receptor affinity, and the quenching of internalized fluorescent ligand. We determined that receptor up-regulation is both agonist- and temperature-induced and is inhibited by both phenylarsine oxide and pertussis toxin treatment. Model fits of ligand association to pertussis toxin-treated cells show that while receptor up-regulation was inhibited, rate constants for ligand binding, receptor affinity conversion, and internalization of ligand-receptor complexes were unaffected. Results suggest Gi-protein-mediated receptor up-regulation and Gi-protein-independent receptor affinity conversion. Simulation of ligand infusion using our model gives insight into the quantitative and dynamic relationship between the low affinity ligand-receptor complex and the actin polymerization response.     

cAMP signaling mechanisms with aging in rats

This work focuses on the maize root as a one-membrane osmo-diffusive converter of free energy. Energy expenditures of the root on water transport by radial route as well as on xylem water uptake, occurring according to the principle of osmotic root pressure, are analyzed. The so-called practical method of osmo-diffusive energy conversion (Kargol 1990, 1993) and experimental data taken from the work by Steudle et al. (1987) were employed, including coefficients of filtration (Lpr), reflection (sigma) and permeation (omega) of the maize root treated as a one-membrane model system. It is shown a.o. that the energy efficiency of the root does not depend (within a certain concentration interval) on the concentration of a given solute in solution into which the root is placed. This suggests a certain independence of environmental conditions. The efficiency is different for different dissolved substances contained in the solution.     

Wear Properties of Alumina/Aluminum Composites with Interpenetrating Networks

The tribological behavior of an A1₂O₃/AI composite against a steel and an alumina was investigated in pin-on-disk wear tests using unlubricated conditions in air. Various composite compositions of aluminum contents ranging from 0 to 28 vol% were investigated over a variety of contact loads and sliding speeds. Wear rate and friction force were continuously monitored during testing. Following completion of the test, pin weight loss and the profile of the wear tracks were determined. Scanning electron microscopy accompanied by EDAX analysis was used to investigate the worn surfaces and the wear debris. The wear behavior of the composites with a low metal content (<15%) during sliding against steel and alumina was found to be comparable to the wear of pure alumina. Wear occurred either on the steel or apparently simultaneously on the pin and alumina disk. With higher Al contents, wear shifts to the composite, the wear rate increases abruptly and is accompanied by fracture of the A1₂O₃ matrix. Wear appears to occur in the composite when the mechanical strain in the composite, near the contact surface, as a result of frictional loads, exceeds the fracture strain of the alumina matrix.