Effects of injurious compression on matrix turnover around individual cells in calf articular cartilage explants

The effects of mechanical injury on the metabolism of cartilage matrix are of interest for understanding the pathogenesis of osteoarthrosis and the development of strategies for cartilage repair. The purpose of the present study was to examine the effects of injury on matrix turnover in a calf articular cartilage explant system for which the effects of mechanical loading on cell activity and the cell-mediated pathways of matrix metabolism are already well characterized. New methods of quantitative autoradiography were used in combination with established biochemical and biomechanical techniques for the analysis of cell and matrix responses to acute mechanical injury, with particular attention to the processes of localized matrix turnover in the cell-associated matrices of individual chondrocytes. Matrix deposition and turnover around cells in control explants was spatially dependent, with the highest rates of proteoglycan deposition and turnover and the lowest rates of collagen deposition (as indicated by [3H]proline autoradiography) occurring in the pericellular matrix. Injurious compression was associated with (a) an abrupt decrease in the tensile load-carrying capacity of the collagen matrix, apparently associated with mechanical failure of the tissue, (b) a considerable but subtotal decrease in cell viability, marked by the emergence of an apparently inactive cell population interspersed within catabolically active but abnormally large cells, and (c) sustained, elevated rates of proteoglycan turnover, particularly in the cell-associated matrices of apparently viable cells, which involved the increased release of aggregating species in addition to a spectrum of degradation fragments that were also in controls. These results may represent an in vitro model for the responses of chondrocytes and the cartilage extracellular matrix to mechanical injury.     

2-Deoxy-D-glucose preferentially kills multidrug-resistant human KB carcinoma cell lines by apoptosis

The aim of this study was to determine the mechanism of cell death associated with the preferential killing of multidrug-resistant (MDR) cells by the glycolytic inhibitor 2-deoxy-D-glucose (2DG) in a range of MDR human KB carcinoma cell lines selected in different drugs. The D10 values for KB-V1, KB-C1 and KB-A1 (selected in vinblastine, colchicine and doxorubicin respectively) were 1.74, 1.04 and 0.31 mM, respectively, compared with 4.60 mM for the parental cell line (KB-3-1). The mechanism of cell death was identified as apoptosis, based on nuclear morphology, annexin V binding and poly(ADP-ribose) polymerase (PARP) cleavage. 2DG induced apoptosis in the three MDR cell lines in a dose- and time-dependent manner and did not induce necrosis. PARP cleavage was detected in KB-C1 cells within 2 h of exposure to 50 mM 2DG and slightly later in KB-A1 and KB-V1 cells. The relative levels of 2DG sensitivity did not correlate with the levels of multidrug resistance or with the reduced levels of the glucose transporter GLUT-1 in these cells. We speculate that a 2DG-stimulated apoptotic pathway in MDR KB cells differs from that in normal KB cells.     

The coalescence of H2S and CO2 bubbles in water

Coalescence times are reported for bubbles of H₂S and CO₂ formed on adjacent nozzles in water. With CO₂, times were small (1–3 ms) at pressures below 2 MPa, and rose to 20 ms at 3.4 MPa. With H₂S, the logarithm of the coalescence time was proportional to pressure, and coalescence times reached 100 ms at 1.7 MPa. Film stretching rates were calculated assuming that the film surfaces were slightly immobile. By using a form of Vrij's theory for the inherent breaking time of films of constant thickness, the effective number of immobile layers could be calculated. Since these were in the range 10^?2 to 10^?3, only a small amount of “stiffness” in the film surface is enough to cause large changes in coalescence time.     

PLUGE method of adjusting picture monitors in television studios

The PLUGE method is described, and its advantages are given. Five sets of reference conditions for setting up picture monitors are presented. Further, it is shown that the required PLUGE black level is dependent upon the value of base luminance.     

THE ESTIMATION OF RANDOM COEFFICIENT AUTOGRESSIVE MODELS. II

Abstract. In Nicholls and Quinn (1980) a procedure was proposed for the determination of strongly consistent estimates of random coefficient autoregressive models. These estimates are used here as starting values in a Newton-Raphson algorithm which is employed to obtain the maximum likelihood estimates of a class of random coefficient autoregressions. The maximum likelihood estimates are shown to be strongly consistent and to satisfy a central limit theorem. The problem of testing for the randomness of the coefficients is also briefly discussed. The results of a number of simulations are reported which illustrate the theoretical results obtained.     

Generating alternative designs for interjurisdictional natural resource development schemes in the Greater Ganges River basin

Planning for the development of regional water resources is often complicated by severe disputes. For example, in the Greater Ganges River basin, there are disagreements between India and Bangladesh over sharing the low river flows during the dry season and over controlling the potentially destructive large river flows during the monsoon. This paper illustrates an approach for providing the two riparian nations with distinct water resources plans to help solve their regional water conflicts. More specifically, a linear programming (LP) model representing a multipurpose river basin system is presented. The concept of near optimality is employed to generate a variety of solutions, in contrast to searching only for a global optimum. These solutions are grouped into similar project designs by applying a cluster analysis, which is a multivariate technique. Several project designs are graphically displayed, and their implications for national and international agreements are discussed. The range of regional alternatives available to India and Bangladesh could aid in their negotiations.An earlier version of this paper was presented at the 37th North American Meetings, Boston, November 1990.     

HeLa cells as a model to study the invasiveness and biology of Legionella pneumophila

HeLa cells were established as a model system to study the invasiveness and biology of Legionella pneumophila. In this model, invasion could be distinguished from adherence; virulent strains of L. pneumophila were adherent and invasive, whereas nonvirulent strains were adherent but poorly invasive. Invasion was rapid and did not require de novo bacterial protein synthesis, suggesting that the invasion factor is constitutively expressed by virulent strains. Entry into HeLa cells required actin polymerization and an intact microtubule cytoskeleton and was only moderately inhibited by the presence of 100 mM glucose or galactose. Intracellular replication of virulent L. pneumophila took place in ribosome-studded complex endosomes and led to the formation of free bacteria-laden vesicles presumably released from lysed HeLa cells. These free vesicles (referred to as mature vesicles) were isolated in continuous density gradients of Percoll. The bacteria contained in the isolated mature vesicles had a unique envelope structure and were highly adherent to HeLa cells, characteristics that correlated with a bright red appearance after the Giménez stain (Giménez positive). Plate-grown legionellae and replicating legionellae, harboured in complex endosomes, displayed a typical Gram-negative envelope and stained green after the Giménez stain (Giménez negative). Chronically infected cultures of HeLa cells were also established that may be a useful tool for studying long-term interactions between virulent L. pneumophila and mammalian cells. HeLa cells constitute a valuable model system that offers unique opportunities to study parasite-directed endocytosis, as well as stage specific-parasite interactions.