Biochemical changes in oyster tissues and hemolymph during long-term air exposure

The Pacific oyster Crassostrea gigas is a sessile bivalve that inhabits the intertidal zone and therefore frequently exposed to air during the tidal cycle. It is highly adaptive to hypoxic conditions. We have studied the physiological state of oysters during long-term exposure to air. The oysters became hypoxic when exposed to air or hypoxic seawater. The 50% lethal time of oysters exposed to air at 4, 15 and 20°C was 47.8, 15.9 and 12.2 days, respectively. The hemolymph pH decreased by day 3; however, it showed a slight increase by day 5 at both 4 and 20°C. The adenylate energy charge (AEC) values decreased rapidly on the first day of air exposure in the adductor muscle, mantle, gill and body trunk, and these decreases were accompanied by decreases in ATP concentrations and increases in AMP concentrations. The AEC values in all of the tissues had fallen to below 30% by day 50 of air exposure at 4°C. These data suggest that the energy state of oysters deteriorates rapidly with air exposure. Consequently, AEC values may be useful indices of the physiological state of the oyster during long-term exposure to air.     

Pharmacokinetic disposition and arthropathic potential of oral ofloxacin in dogs

We examined the relation between the pharmacokinetic disposition and arthropathic potential of ofloxacin, a new quinolone antibacterial agent, using both male immature (3-month-old) and mature (18-month-old) beagles. Ofloxacin was orally administered to these dogs at 20 mg/kg once daily for 8 consecutive days, and the animals were killed 2 h after the last treatment. Serum ofloxacin concentrations were repeatedly measured on days 1 and 7 by use of high-performance liquid chromatography (HPLC), and pharmacokinetic parameters were calculated. In addition, on day 8, the drug concentrations in the joint synovial fluid and humeral and femoral condyles were measured. Clinico-pathological tests of blood and serum or histopathological examination of bone specimens were also performed. Arthropathy was macroscopically observed in the cartilage surface of all immature dogs, but not in mature dogs. There were, however, no noticeable differences in pharmacokinetic parameters between the two age groups of dogs or between single and 7-day treatments. In contrast to the occurrence of arthropathic lesions, the synovial fluid and condylar drug concentrations in immature dogs was equal to or lower than those in mature dogs, suggesting that the pharmacokinetic disposition of ofloxacin may not be essential for cartilage lesions.     

cDNA cloning and characterization of two gelatinases from Japanese flounder

SUMMARY: Toughness is one of the most important elements that define the commercial value of the raw meat of fish. Degradation of the extracellular matrix is thought to be a cause of postmortem tenderization of fish meat. A previous study has suggested that this tenderization is caused mainly by metalloproteinases. The present study seeks to identify the proteinase(s) involved in tenderization; hence, cloned cDNA of two gelatinases from Japanese flounder, which showed high homology with mammalian matrix metalloproteinase (MMP)-2 and MMP-9, were designated as jfMMP-2 and jfMMP-9 , respectively. Northern blot analysis revealed that jfMMP-2 mRNA was expressed almost ubiquitously in adult tissues including the brain, muscle, gill, heart, gut, kidney, spleen, testis, and ovary. In contrast, the expression of jfMMP-9 mRNA was observed in those tissues which were abundant in blood cells, such as kidney, spleen, heart, and gill. Both recombinant proteins (jfMMP-2 and jfMMP-9) produced with the COS-7 cell system exhibited gelatin-degrading activity that was sensitive to 1,10-phenanthroline, a typical metalloproteinase inhibitor.