Effects of Liming on an Acid—Sensitive Southern Appalachian Stream

Laurel Branch (Tennessee, U.S.A.), an acid-sensitive stream in the southern Appalachian Mountains, was limed as a part of the Acid Precipitation Mitigation Program funded by the U.S. Fish and Wildlife Service. Objectives were (1) to evaluate the effectiveness of stream liming by means of a hydropowered doser design, and (2) to monitor stream response(s) to increased pH and alkalinity. Precipitation in the region was documented to be acidic, with a mean pH of 4.54 in 1987. Preliming evaluations conducted from 1986 through 1988 depicted Laurel Branch as soft (hardness less than 5 mg/L CaCO₃, pH 6.2–6.6), dilute (ionic strength less than 400 μeq/L), and lightly buffered (alkalinity less than 100 μeq/L). Because of the apparent relationship between flow and water chemistry, Laurel Branch was considered susceptible to episodic acidification caused by storms. In June 1989, a hydro–powered limestone doser was installed to treat the lower 3 km of the stream. Approximately 8.2 tonnes of crushed limestone were added during an 18–month treatment phase that concluded in December 1990. Technical and design problems with the doser reduced efficiency and limited the scale of liming through much of the first 6 months of operation. Design modifications and equipment upgrades in late 1989 corrected most of the problems and improved doser performance in 1990. No substantial chemical or biological changes were detected within the treated reach of Laurel Branch as a result of liming. Time–series statistical analyses showed small but significant changes in total alkalinity (10 μeq/L average increase) and dissolved calcium at all limed sites. pH (as hydrogen ion) increased 0.16 and 0.13 units at two limed sites that were 1 km and 2 km below the doser, respectively. At the lowermost limed site 3 km below the doser, a significant decrease in pH was detected which was probably flow-related. Mean length of age–0 (juvenile) and age-1 rainbow trout increased marginally during liming, suggesting improved fish growth, but increases were not significant. Densities of an acid-sensitive macrobenthic taxon (Baetis spp.) increased during liming, whereas densities of an acid-tolerant taxon (Leuctra spp.) remained unchanged. In general, observed biological changes were considered minimal; they were judged unrelated to liming but rather of seasonal and/or spatial origin. The regional drought of 1987 and 1988 was considered a confounding factor. With most of the baseline data collected during these years, vastly differing hydrology in 1989 and 1990 (“wet” years regionally) became problematic and may have distorted some responses and masked others. It is also possible that biological responses may have been delayed because of the small magnitude of chemical changes, particularly pH and alkalinity. A calcium mass budget estimated that up to 62% of the calcium added was accounted for in chemistry data from limed sites, with increases most visible in the spring and summer of 1990. Results indicated that, although the Laurel Branch watershed does receive acidic precipitation, current biological communities show high levels of integrity and little apparent degradation related to acidification. If watershed buffering capabilities are depleted from continued acidic deposition, however, stream biota may be at risk in the future.     

Angiotensin stimulates cortisol biosynthesis in human adrenal cells in vitro

Adrenal glands obtained from patients undergoing therapeutic adrenalectomy were used to study the effects of angiotensin on human adrenal steroidogenesis. It was observed that angiotensin stimulated cortisol biosynthesis. Although this has been demonstrated to occur in canine and bovine adrenals, angiotensin-induced cortisol biosynthesis has not been established in man. The possibility that angiotensin merely stimulated glomerulosa cells to secrete precursor steroids which accumulated in the medium and then diffused into fasciculata cells to provide substrate for cortisol biosynthesis was excluded by demonstrating that 3β-hydroxy-5-pregnen-20-one (pregnenolone) and progesterone (the only pertinent precursors) did not accumulate in angiotensinstimulated cell suspensions. In addition, angiotensin stimulated cortisol biosynthesis in a fasciculata cell suspension in which angiotensin did not stimulate aldosterone production. Therefore, in human adrenal cell suspensions angiotensin appeared to act directly to stimulate cortisol synthesis by fasciculata cells. In normal subjects pre-treated with dexamethasone, angiotensin infusions failed to stimulate an increase in plasma cortisol. The physiological importance of angiotensin as a regulator of cortisol secretion remains, therefore, to be established.     

Protein inactivation in amorphous sucrose and trehalose matrices: effects of phase separation and crystallization

Trehalose is the most effective carbohydrate in preserving the structure and function of biological systems during dehydration and subsequent storage. We have studied the kinetics of protein inactivation in amorphous glucose/sucrose (1:10, w/w) and glucose/trehalose (1:10, w/w) systems, and examined the relationship between protein preservation, phase separation and crystallization during dry storage. The glucose/trehalose system preserved glucose-6-phosphate dehydrogenase better than did the glucose/sucrose system with the same glass transition temperature (T_g). The Williams-Landel-Ferry kinetic analysis indicated that the superiority of the glucose/trehalose system over the glucose/sucrose system was possibly associated with a low free volume and a low free volume expansion at temperatures above the T_g. Phase separation and crystallization during storage were studied using differential scanning calorimetry, and three separate domains were identified in stored samples (i.e., sugar crystals, glucose-rich and disaccharide-rich amorphous domains). Phase separation and crystallization were significantly retarded in the glucose/trehalose system. Our data suggest that the superior stability of the trehalose system is associated with several properties of the trehalose glass, including low free volume, restricted molecular mobility and the ability to resist phase separation and crystallization during storage.