Sulfate Peak Research Articles

Reduction of atherosclerosis by administration of dehydroepiandrosterone. A study in the hypercholesterolemic New Zealand white rabbit with aortic intimal injury.

Dehydroepiandrosterone (DHEA) is an endogenous steroid that blocks carcinogenesis, retards aging, and exerts antiproliferative properties. In vitro, it is a potent inhibitor of glucose-6-phosphate dehydrogenase, the first committed step of the pentose phosphate pathway. In man, serum levels of DHEA and its sulfate peak in early adulthood and drop markedly with age. Epidemiologic evidence indicates that low levels of DHEA or its sulfate conjugate are linked to an increased risk of developing cancer or of death from cardiovascular disease. Like cancer, atherosclerosis is a proliferative process characterized by both initiation and promotion phases. This similarity provided a framework in which to study the antiatherogenic effects of DHEA. Rabbits were randomly assigned to four groups. Two groups of rabbits received aortic endothelial injury by balloon catheter and were fed a 2% cholesterol diet for 12 wk. DHEA, 0.5%, was incorporated into the diet of one group receiving the 2% cholesterol diet and endothelial injury and also into the diet of one of the control groups. Animals were killed after 12 wk and aortas, hearts, and livers were studied. Plasma samples were analyzed for total cholesterol, VLDL, LDL, HDL, triglycerides, DHEA, and DHEA-sulfate levels. The atherogenic insult resulted in severe atherosclerosis in animals not treated with DHEA. In those receiving DHEA there was an almost 50% reduction in plaque size (P = 0.006), inversely related to the serum level of DHEA attained. Fatty infiltration of the heart and liver were also markedly reduced. These beneficial actions were not attributable to differences in body weight gain, food intake, total plasma cholesterol or distribution of cholesterol among the VLDL, LDL, or HDL fractions. The results show that high levels of plasma DHEA inhibit the development of atherosclerosis and they provide an important experimental link to the epidemiologic studies correlating low DHEA-sulfate plasma levels with an enhanced risk of cardiovascular mortality.

Investigation of the negative sulphate peaks obtained in the analysis of high-concentration chloride solutions by ion chromatography

The object of this work was to detect reliably 0.5 mg l–1 of sulphate in 10 g l–1 of chloride (the maximum amount that could be analysed) in order that 2–3 mg l–1 of sulphate could be detected in oil reservoir formation waters, which contain, typically, 40–60 g l–1 of chloride. When a solution containing 10 g l–1 of chloride was subjected to ion chromatography a small positive peak followed by a small negative peak occurred where the sulphate peak should have been. This made the detection and quantification of less than 2 mg l–1 of sulphate in 10 g l–1 of chloride uncertain. Investigation showed that the phenomenon was caused by sulphate contamination at the 0.01–0.02 mg l–1 level in the eluent. The use of a high-capacity anion-exchange pre-column to clean up the eluent eliminated the problem and allowed the desired detection limit to be achieved.

Ion-exchange chromatography of anions with tiron as eluent

The characteristics of Tiron (1,2-dihydroxybenzene-3,5-disulfonic acid and its sodium salt) solution as an eluent for anions in ion-exchange chromatography was investigated with conductivity and UV absorbance detectors. Tiron (acid and sodium salt) has such a strong affinity for the anion exchanger that the concentration in the eluent can be made lower than that of benzene carboxylates, such as phthalate, which have been used similarly. Tiron acid exhibited an unusual effect which increased the sensitivity with a conductivity detector. The water dip was not observed, and a big ghost peak appeared near the sulfate peak. Tiron salt did not produce a ghost peak, and was better for highly sensitive detection in indirect photometric chromatography than phthalate, because of a better balance between UV absorptivity and elution ability. Because Tiron forms stable chelates with many metal ions, pretreatment with a cation-exchange resin is necessary for real samples such as tap water.

Proteoglycan synthesis by skeletal muscle undergoing bone matrix-directed transformation into cartilage in vitro.

Myoblasts and fibroblasts of embryonic skeletal muscle reproducibly form chondrocytes when cultured on demineralized bone in vitro. The transformation occurs in 3 morphologically defined phases, with disappearance of the myoblast phenotype preceding the appearance of fibroblast-like cells and finally chondrocytes. Proteoglycan synthesis in these cultures was investigated by labeling at prechondrogenic (5 days) and postchondrogenic (6-12 days) stages with (35S)sulfate and [6-3H]glucosamine. Labeled material elutes from associative Sepharose CL-2B columns as two major included peaks, which correspond to proteoglycan monomer and a material of lower molecular size. Control cultures, cultured upon gels of type I collagen, fail to synthesize monomer-like material and contain solely a material of lower molecular size. Demineralized bone-derived monomer was rechromatographed under dissociative conditions in an attempt to detect the presence of small aggregates. Again, only a single peak of sulfate and glucosamine-labeled material appears. The data further show that the monomer resembles that of embryonic cartilage in glycosaminoglycan chain size (Mr = 8.6-12.2 X 10(3] and composition (mainly chondroitin 4-sulfate). Aggregated monomer forms a shoulder of the monomeric peak and comprises only 5% of the sulfated material. Fifteen to thirty-four per cent of the monomer elutes as aggregate after addition of rooster comb hyaluronic acid (HA). Failure to aggregate appears to be related to endogenous synthesis of short chain HA. Synthesis of long chain HA may constitute a rate-limiting step in chondrogenesis. Material of lower molecular size, from cultures grown on demineralized bone, bind to exogenous HA, whereas the elution pattern of sulfated material from control cultures remains essentially unchanged. These latter data suggest that proteoglycans of low hydrodynamic size may participate in the early formation of proteoglycan aggregate.

Temporal Changes in a Pink Feedlot Lagoon

Temporal changes in a feedlot drainage lagoon with a predominance of the phototrophic purple sulfur bacterium, Thiopedia rosea, were investigated during a 3-year period. The surface protein and bacteriochlorophyll concentrations, which indirectly measure T. rosea abundance, peaked annually during the fall months and coincided with the intensity of pink coloration. Surface bacteriochlorophyll concentration correlated with pH, alkalinity, and protein. The pH range was optimal for the survival of T. rosea. Surface sulfide concentration, which increased over the winter and early spring, reached low levels during the fall months. The most striking pattern to emerge was the marked increase in sulfate concentration that occurred each fall and winter. The protein peaks, which preceded the sulfate peaks, were indicative of the sulfate concentrations that would follow. During 1977 and 1978, the lagoon was essentially anaerobic and provided adequate growth conditions for T. rosea. Above-average precipitation during early 1979 raised the water level and altered the chemistry of the lagoon. Dissolved oxygen was higher during the final year, and, concurrently, concentrations of bacteriochlorophyll declined. Aeration of the lagoon resulted in a decrease in T. rosea.

On the nature of the diurnal variation of sulfates at rural sites in the Eastern United States

During the summer of 1976, sulfate samples were collected for 29 days at two rural sites in the eastern U.S. Other pollutant parameters, including ozone and sulfur dioxide levels, and meteorological factors such as temperature, humidity, and wind speed, were obtained. Two types of distinct diurnal patterns were observed. In the first type, a peak was observed in mid-afternoon at about the time of the ozone maximum. The second pattern, a nocturnal sulfate peak, occurred on calm nights when surface transport was not occurring, and was most pronounced on clear nights when ground fog developed. (14 graphs, 22 references, 5 tables)