Extracellular proteases of Aspergillus flavus. Fungal keratitis, proteases, and pathogenesis

To get a better understanding of the possible role of proteases in the pathogenesis of fungal keratitis, the extracellular proteases of a clinical isolate of Aspergillus flavus, from a severe case of keratitis, were identified and partially characterized. This strain, designated CU226/88, was grown with a variety of substrates as nitrogen sources, under conditions that would be expected to derepress the production of extracellular proteases. When grown on minimal medium with milk protein as a nitrogen source, the fungus appeared to produce primarily a metalloprotease, which has a zinc cofactor. When grown with insoluble collagen or elastin as a nitrogen source, a serine protease and cysteine protease, as well as the metalloprotease, are produced. Strain CU226/88 can grow with collagen, but not elastin, as the sole source of carbon as well as nitrogen. It is possible that the collagenase activity is a mediator of the severe corneal destruction caused by this isolate.

The nature of an intragenic suppressor of the Escherichia coli dnaA508 temperature-sensitive mutation

Escherichia coli strain E508 (dnaA508) is temperature-sensitive for dnaA function. A mutant with an intragenic suppressor of the dnaA508 mutation, called PR1, has been isolated. The suppressor mutation(s) allow initiation of DNA synthesis at 42 degrees C and, like dnaA cold-sensitive mutants, PR1 grows poorly at 32 degrees C. Two-dimensional gel analysis indicates that DnaA protein is overproduced in PR1. Transcriptional analysis indicates two to three times the number of dnaA and dnaN transcripts in PR1, as compared to a wild-type dnaA+ strain. The dnaA gene from PR1 has been cloned and found to complement the original dnaA508 mutation, as well as dnaA46, but not dnaA5. Sequencing of the dnaAPR1 gene reveals three separate base changes, two of which result in nonconservative amino acid substitutions and the third is a change in the start codon from GTG to ATG.

Cell populations of tendon: a simplified method for isolation of synovial cells and internal fibroblasts: confirmation of origin and biologic properties

Tendons transmit the force of muscle contraction to bone to effect limb movement. Special structural and biological properties of tendon have developed to facilitate force transmission. The tendon has a complex organization of cells surrounding the collagen bundles inside tendon as well as at the tendon surface. Internal cells may act to maintain the bulk of the collagen in tendon. External cells in the epitenon may provide lubrication for tendon gliding. To develop better understanding of these processes and the roles the cell populations play, we isolated cells from the surface and interior of tendon and studied them in vitro. Flexor tendons from 8-week-old white Leghorn chickens were separated into two distinct cell populations: the outer synovial cells and the fibroblasts more internal in tendon. These cell populations were discernible by their locations in the intact tendon, determined by sequential enzymatic and physical release from their substrata. Initially, some cells eluted in Hanks' salt solution (HSS) (population 1); then synovial cells were released after a 2-min treatment with 0.5% collagenase (population 2). Next, a population of synovial cells was released in high yield by treatment with 0.25% trypsin (step III, population 3). Step III, population 3 cells were used as synovial cells (SCs). Next, a population of SCs and fibroblasts were released by scraping with a rubber policeman (population 4). Subsequently, fibroblasts were released after incubation with 0.5% collagenase (population 5). A more direct procedure (procedure 2) to isolate the synovial and internal tendon cells involved treatment in 0.5% collagenase followed by sedimentation at 900 g. Cells that sedimented were largely fibroblasts, whereas the cells that remained at the top of the tube were largely SCs. Cells designated as SCs, isolated by procedure 2, most likely contained surface cells from epitenon and internal interfascicular cells from endotenon and paratenon. Surface tendon cells separated by sequential enzymatic and physical release from their substrata (by procedure 1) had all the following characteristics: distinct subpopulations of cells based on morphology; presence of cytoplasmic, lipid-containing vesicles; decreased sensitivity to trypsin; and reduced generation time as compared with that of internal fibroblasts. Conversely, the internal fibroblasts (IFs) appeared to represent a more uniform population based on morphological characteristics.

Reversal of ethanol induced body dehydration with prolonged consumption in rats

Ethanol induced negative water balance has been previously inferred from fluid turnover rates upon initial exposure followed by restored normal fluid balance with prolonged exposure. The first two experiments of the present investigation noted hypovolemia and carcass dehydration during the initial few days of forced choice maintenance on 10% ethanol with recovery to near normal levels of intravascular volume and carcass water after 2 months of forced consumption. A third experiment attempted to test whether the alcohol induced dehydration could be corrected with the administration of exogenous ADH.