RESUMEN

Hexavalent chromium, Cr(6+), is a common and toxic pollutant in soils and waters. Reduction of the mobile Cr(6+) to the less mobile and less toxic trivalent chromium, Cr(3+), can be achieved with conventional chemical reduction technologies. Alternatively, Cr(6+) can be biochemically reduced to Cr(3+) by anaerobic microbial consortia which appear to use Cr(6+) as a terminal electron acceptor. A bioprocess for Cr(6+) reduction has been demonstrated using a packed-bed bioreactor containing ceramic packing, and then compared to a similar bioreactor containing DuPont Bio-Sep beads. An increase in volumetric productivity (from 4 mg Cr(6+)/L/h to 260 mg Cr(6+)/L/h, probably due to an increase in biomass density, was obtained using Bio-Sep beads. The beads contain internal macropores which were shown by scanning electron microscopy to house dense concentrations of bacteria. Comparisons to conventional Cr(6+) treatment technologies indicate that a bioprocess has several economic and operational advantages.

RESUMEN

Various studies suggest impact trauma may initially soften cartilage, damage subchondral bone, or a combination thereof. The initial damages are commonly thought due to excessive contact pressure generated on cartilage and the underlying bone. The objective of this research was to develop a small animal model for studying post-traumatic OA and to correlate contact pressure with tissue damage. Blunt insult was graded by dropping a rigid mass onto the hyperflexed hind limb of rabbits. Contact pressure in the patello-femoral joint was measured with pressure sensitive film. One, 3, 6, and 14 days later the animals were euthanized. Damage to cartilage and the underlying bone was assessed visually and in microscopic sections. Indentation experiments were performed on the patellar cartilage with a rigid, flat probe. Contact pressures were nonuniform over the articular surfaces and a high frequency of surface fissures were generated on the lateral facet in severe insults. The appearance of surface fissures correlated better with the magnitude of contact pressure gradients in the damage zone than the magnitude of contact pressures on the facet, per se. Blunt trauma causing surface fissures resulted in a measurable degree of softening in the patellar cartilage, especially close to the defects. Surgical intervention of the joint to insert pressure sensitive film, however, also resulted in significant softening of the cartilage.

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RESUMEN

A PC-based machine vision system has been used to continuously monitor changes in biomass concentration and to control the undesirable production of colloidal elemental sulfur (a reactor upset condition due to an excessive concentration of inhibitory sulfide substrate) in a bioreactor containing Thiobacillus denitrificans. A field of view of a video camera was established which contained regions of different background lighting. Mean values of the distribution of red, green, and blue intensity components within corresponding regions of a digital image image captured from the camera were used to monitor color changes associated with changes in biomass concentration, and to determine if the reactor was in an upset condition. The ration of red to blue intensity components was an important parameter in detecting the formation of an elemental sulfur precipitant. Using a stepper motor-driven pressure regulator, intelligent process control was performed by altering the hydrogen sulfide feed flow rate setpoint on the vision system measurements.

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The subcellular localization of adenylate cyclase (ATP pyrophosphatelyase (cyclizing), EC 4.6.1.1) in bovine corpus luteum was studied using isotonic and hypotonic homogenization and fractionation conditions. All fractions prepared were assayed for adenylate cyclase, marker enzymes and DNA. Only plasma membrane marker enzyme, 5'-nucleotidase paralleled the distribution of adenylate cyclase under both isotonic and hypotonic conditions (conditionsoth isotonic and hypotonic conditions (coefficient of correlation = 0.95). Two main fractions prepared under hypotonic conditions were subfractionated by discontinuous sucrose gradient centrifugation. The highest amount of adenylate cyclase was found in a fraction having a density approximately equal to 1.13 g/cm3. The specific activity of this fraction was 4--6 times higher than that of the homogenate. The electron microscopic study of this fraction revealed the presence of a single type of particulate material consisting of small vesicles exhibiting a typical unit membrane structure. It is concluded that this adenylate cyclase is primarily localized in the plasma membranes. Basal adenylate cyclase activity of plasma membranes was stimulated 2--3 times by luteinizing hormone (10 mug/ml), 3--4 times by prostaglandin E2 (10 mug/ml), 4--6 times by NaF (0.01 M) and two times by methanol (0.2%).

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