The potential aminopeptidase activity (APA) vis-a-vis important ecological parameters of surface and bottom waters of Uranouchi Inlet (Japan), a semi-enclosed eutrophic coastal ecosystem, were studied on a weekly to biweekly basis from mid-August 1996 to early November 1997. The aim of this study was to investigate the main factors regulating the annual and seasonal dynamics of APA in the inlet. APA was estimated in short-term incubations as the V, , of the rate of enzymatic hydrolysis of a fluorophore 7-L-leucyl-4-methyl couomarinylarnide under conditions close to those of in situ. The water column structure at the study site changed considerably during the study period as the ecological parameters such as temperature, dissolved oxygen (DO), nutrient contents, and bacterial abundance exhibited pronounced seasonal stratification (May to September). When the water column was mixed (October to March), surface and bottom waters possessed similar APA . But when the water column became stratified, pronounced differences became apparent, with surface water showing considerably higher APA. On extreme days, surface water possessed as much as -20 times higher APA than that of bottom water. Thus, APA of surface water demonstrated strong seasonality and varied by almost 40-fold compared to that of bottom water, which varied only about 12-fold during the study period. Notably, bacterial abundances of both waters showed limited seasonality and varied only -3-fold during the same period. These results imply that changes in APA are not merely a function of bacterial abundance but rather more of per-cell activity. On an annual basis, APA in both waters were positively correlated (p < 0.001) with temperature and bacterial abundance, and negatively correlated with s M i t y (p c 0.001 for surface and p < 0.01 for bottom water) but were not correlated (p > 0.05) with DO, chlorophyll a (p < 0.05; only for surface water), inorganic or organic forms of nitrogen (DIN, DON) or inorganic phosphorous (DIP) contents. Furthermore, when the water column was mixed, APA correlated strongly with temperature (p < 0.001; r = 0.87), and marginally (p < 0.05) with DIN (r = 0.43) and DIP (r = 0.40) content but not with DO (p > 0.05) content. In contrast, when the water column became stratified, APA correlated only marginally with temperature (0.01 c p < 0.05; r = 0.33) but strongly with DO (p c 0.001; r = 0.73), and negatively (p c 0.001) with DIN (r = -0.61) and DIP (r = -0.70) content. DON content did not show any correlation (p > 0.05) with APA regardless of whether the water column was mixed or stratified. These correlations suggest that temperature played a critical role in regulating the APA when the water column was mixed (October to March), and DO or inorganic nutrient contents (May to September) when the water colun~n was stratified.

Semen Quality of Industrial Workers Occupationally Exposed to Chromium: Sunil KUMAR, et al. Reproductive Toxicology and Histochemistry Division, National Institute of Occupational Health (ICMR), India-A total of sixty-one subjects occupationally exposed to chromium in an industry which manufactures chromium sulphate and fifteen control subjects from a nearby industry which does not manufacture any chromium related compounds were studied. The history of each subject was recorded on pre-designed form through interview and a routine medical examination was carried out. Blood samples (5-6 ml) were collected for the estimation of chromium and semen samples were collected for semen analysis and the determination of copper and zinc levels in the seminal plasma. Clinical examination revealed nasal perforation in 10 subjects (out of 61) in the exposed group as compared to none in the control group. A significantly higher level of chromium was observed in the blood of the exposed workers as compared to the control. The concentration of zinc in seminal plasma was lower while the level of copper was higher in the exposed group as compared to the control. However, these changes were not statistically significant. S t a t i s t i c a l l y s i g n i f i c a n t h i g h e r n u m b e r s o f morphologically abnormal sperms were noticed in the exposed group with respect to the control. Further analysis of the data indicated that about 53% of the exposed subjects showed less than 30% normal forms as compared to 10% in control subjects. However, no significant alterations in semen volume, liquefaction time, mean pH value, sperm viability, concentration or motility, were noticed between chromium exposed and unexposed workers. The data also indicates that exposure to chromium has some effect on human sperm as a significant positive correlation (r=0.301) was observed between percentages of abnormal sperm morphology and blood chromium levels (p=0.016) after pooling all the data of the control and exposure groups. (J Occup Health 2005; 47: 424-430)

No abstract

Two semi-intensive grow-out trials of Nile tilapia, Oreochromis niloticus (L.), each consisting of seven mixed feeding schedules (rhythmic presentation of high and low protein) and two constant, a high-protein and the other low-protein feeding schedules, were carried out simultaneously for 60 days. Mixed feeding schedules were achieved, in Trial 1, by alternating the presentation of a high feed ration (H; 2.3% body weight (BW)) with a low feed ration (L; 1.5% BW) of a single diet A (crude protein content 33%), and in Trial 2, by alternating the presentation of diet Awith diet B of a relatively low protein content (crude protein content 22%). In both trials, signi¢cant improvements in protein utilization parameters, such as apparent protein conversion e⁄ciency and protein e⁄ciency ratio against continuously high protein feeding were obtained because of the adoption of mixed feeding schedules without any signi¢cant decline in the growth parameters such as net ¢sh yield or daily weight gain. In both trials, the mixed feeding schedule ensuring 2 days of high followed by 3 days of low protein presentation, viz. 2H/3L of Trial 1 and 2A/3B of Trial 2 performed the best. Improvement in nutrient utilization in both trials was comparable; however, at existing market prices cost saving because of adoption of mixed feeding schedules was greater in Trial 1.

The potential aminopeptidase activity (APA) in surface sediment (0-1 cm), and important ecological factors of a eutrophicated inlet were monitored for one and a half years on a weekly to biweekly basis to elucidate the fluctuations in extracellular hydrolysis of protein during an annual cycle, and main regulating factors on an annual and/or a seasonal basis. APA was estimated in sediment slurry prepared with unamended bottom water, as the V max of the rate of the enzymatic hydrolysis of a coumarine derivative fluorophore at in situ temperatures. APA varied 5-6 fold during the study period with highest values (225-275 nmole AMC h -1 g -1 dry weight) during September-October or early June when the temperature was 22-28°C and dissolved oxygen concentrations (DO) (2-4 mg L -1 ) in overlying bottom water were high, and much lower values (ca. 50 nmoles AMC h -1 g -1 dry weight) in July-August or December-February. On an annual basis, APA correlated only marginally (p < 0.05; r = 0.25) with the protein content of the surface sediment and not at all with any other variables. However, it showed highly significant correlations (p < 0.001) with temperature (r = 0.81), and protein content (0.65) in mid December-early June, when temperatures were relatively low (ca. 12-22°C) and DO was abundant (ca. 2-6 mg L -1 ) in overlying bottom water.