Impact of acidification on diatoms and chemistry of Dutch moorland pools

Old (ca 1920) and recent (1978) diatom assemblages from sixteen pristine moorland pools are compared by analysis of pH-spectra, diversity (Hill's index), (dis)similarity (number of species in common, Dyer dissimilarity) and principal component analysis. The pH-spectra of clear water pools indicate that the formerly wide range of pH (4–6) is very narrow now (3.7–4.6). No significant change of pH (ca 4.5) is observed in brown water moorland pools. Diversity significantly declines in clear water pools and has a tendency to rise in brown water pools. The number of species in common does not change. The Dyer dissimilarity significantly decreases in clear water lakes, no change is found in brown water lakes. The first principal component (PC 1) explains 61% of total variance between samples and is nearly completely determined byEunotia exigua. PC 1 has a strong positive correlation with both the absolute and relative sulfate concentration and other factors related to acidification (Ca²⁺, Al³⁺, Mg²⁺, electrical conductivity). PC1 has a negative correlation with factors characterizing humic acid waters (K MnO₄-consumption, Fe, (Na⁺ + K⁺)/ (Ca²⁺+Mg²⁺) etc.). Old samples have low scores on PC 1. Recent samples from clear waters have high scores on PC 1. The original variation, caused by regional factors, is replaced by a sulfate controled variation. The factors which are responsible for the recent differences in sulfate concentrations between pools are discussed (sulfate reduction, accumulation by dry deposition in adjacent pine forests and drought). Some observations contribute to the opinion that acidification may be considered as eutrophication and not as oligotrophication.     

Control of sorbitol metabolism in renal inner medulla of diabetic rats: regulation by substrate,cosubstrate and products of the aldose reductase reaction

Streptozotocin diabetes induces a 4-fold increase in the maximal velocity of inner medullary aldose reductase as determined in vitro but increases sorbital synthesis in intact inner medullary collecting duct (IMCD) cells only 1.3-fold [1]. In order to resolve this discrepancy we investigated the importance of intracellular factors in controlling the role of cellular sorbitol synthesis. These factors include glucose concentration, sorbitol concentration, the activity of the NADPH-regenerating pentose phosphate pathway, intracellular NADP and NADPH content, and intracellular reduced (GSH) and oxidized glutathione (GSSG). It was found that the apparent K_m of cellular sorbitol production for glucose was identical in control and diabetic rats ($\text{56 ± 18}\text{vs.}\text{59 ± 14}\text{mmol/l}\text{d}\text{-glucose}$), whereas V_max increased by 31% in diabetes. In inner medullary collecting duct cells of diabetic rats containing 146 ± 5 μmol sorbitol/g protein, sorbitol synthesis slightly lower (?15%), compared to cells which had been sorbitol-depleted prior to the experiment (87 ± 4 μmol sorbitol/g protein). However, no inhibitory effect of sorbitol (up to 200 mmol/l) was observed on aldose reductase activity in vitro. In diabetic rats the content of NADPH was about 32% lower than in the control rats (3.8 ± 0.3 vs. 5.6 ± 0.4 μmol/g protein) and the ratio of NADPH/NADP was decreased from 25.6 ± 5.1 to 8.6 ± 1.7. In homogenates of the inner medulla the activity of 6-phospho-gluconate dehydrogenase (EC 1.1.1.43) was identical in both experimental groups, so the pentose phosphate shunt seems to be unaltered. GSH content in diabetic rats was also diminished (4.2 ± 0.67 μmol/g protein vs. 7.41 ± 0.5 μmol/g protein) and the GSH/GSSG ratio fell from 92.6 to 57.4. In enzyme tests in vitro an apparent K_m of 7.3 ± 1.9 μmol/l of the aldose reductase for NADPH was found; NADP acted as competitive inhibitor with a apparent K_i of 183 ± 31 μmol/l. Aldose reductase activity was also found to be strongly inhibited by the SH-group reagent p-chloromercurybenzoesulfonate (apparent K_i = 0.85 · 10^?6 mol/l). Combining the results obtained on the properties of the aldose reductase in vitro and the observation made in the intact cells, the investigators suggest that the decrease in NADPH/ NADP ratio, as well as changes in the redox state in the cells of diabetic animals, can play a significant role in the control of sorbitol synthesis.     

Treatment of pubertal gynecomastia with the specific aromatase inhibitor anastrozole

Gynecomastia can be detected in up to 70% of boys during puberty and in about one third of adult males. An imbalance of estrogen to androgen tissue levels is believed to be the major reason for the development of gynecomastia; as a result most medical treatments so far have tried to lower the estrogen level. Five boys with pubertal gynecomastia and breast tenderness were treated for 6 months with the selective aromatase inhibitor anastrozole. Initial plasma levels of estradiol (E2), testosterone (T), androstenedione, dehydroepiandrosterone sulfate (DHEA-S) and gonadotropins were normal. DHEA-S showed a significant rise during treatment. T and androstenedione showed no significant change during treatment. E2 decreased with therapy, although to no statistically significant extent. The E2/T ratio decreased significantly during the treatment. Breast size decreased in 4 out of 5 patients, and in 1 of these 4 boys glandular breast tissue disappeared completely. The longer the duration of gynecomastia before anastrozole administration, the smaller was the reduction of breast size. Breast tenderness was resolved in all boys within 4 weeks. No adverse effects were recorded. Since the aim of medical treatment is the total disappearance of breast tissue, anastrozole, as previous aromatase inhibitors, is of limited effect. However, anastrozole seems to be of benefit for the treatment of tenderness in gynecomastia and for patients in whom surgery is particularly risky. However, as spontaneous disappearance of pubertal gynecomastia is common, further double-blinded, placebo-controlled trials are necessary before a definite conclusion can be drawn about the effectiveness and the side effects of this therapy.     

The wbbD gene of E. coli strain VW187 (O7:K1) encodes a UDP-Gal: GlcNAc{alpha}-pyrophosphate-R {beta}1,3-galactosyltransferase involved in the biosynthesis of O7-specific lipopolysaccharide

In this work, we demonstrate that the wbbD gene of the O7 lipopolysaccharide (LPS) biosynthesis cluster in Escherichia coli strain VW187 (O7:K1) encodes a galactosyltransferase involved in the synthesis of the O7-polysaccharide repeating unit. The galactosyltransferase catalyzed the transfer of Gal from UDP-Gal to the GlcNAc residue of a GlcNAc-pyrophosphate-lipid acceptor. A mutant strain with a defective wbbD gene was unable to form O7 LPS and lacked this specific galactosyltransferase activity. The normal phenotype was restored by complementing the mutant with the cloned wbbD gene. To characterize the WbbD galactosyltransferase, we used a novel acceptor substrate containing GlcNAcalpha-pyrophosphate covalently bound to a hydrophobic phenoxyundecyl moiety (GlcNAc alpha-O-PO(3)-PO(3)-(CH(2))(11)-O-phenyl). The WbbD galactosyltransferase had optimal activity at pH 7 in the presence of 2.5 mM MnCl(2). Detergents in the assay did not increase glycosyl transfer. Digestion of enzyme product by highly purified bovine testicular beta-galactosidase demonstrated a beta-linkage. Cleavage of product by pyrophosphatase and phosphatase, followed by HPLC and NMR analyses, revealed a disaccharide with the structure Gal beta1-3GlcNAc. Our results conclusively demonstrate that WbbD is a UDP-Gal: GlcNAcalpha-pyrophosphate-R beta1,3-galactosyltransferase and suggest that the novel synthetic glycolipid acceptor may be generally applicable to characterize other bacterial glycosyltransferases.     

Enzymatic basis for sialyl-Tn expression in human colon cancer cells

Sialyl-Tn antigen (SA2-6 GalNAc-Ser/Thr) is expressed as a cancer-associated antigen on the surface of cancer cells and its expression correlates with a poor prognosis in patients with colorectal and other adenocarcinomas. To understand the enzymatic basis of sialyl-Tn (STn) antigen expression, we used two clonal cell lines, LSB and LSC, derived from LS174T human colonic cancer cells. LSC cells express only the truncated carbohydrate antigen Tn (GalNAc-Ser/Thr) and sialyl-Tn on their mucin molecules, whereas LSB cells express elongated oligosaccharide chains. Both cell lines demonstrated similar activities of glycosyltransferases involved in the biosynthesis of elongated and terminal structures of complex O-glycans. However, LSC cells were unable to synthesize core 1 (Gal1-3GalNAc-) because the ubiquitous enzyme activity of UDP-Gal:GalNAc-R 3-Gal-transferase (core 1 3-Gal-transferase) was lacking. Core 1 3-Gal-transferase could not be reactivated in LSC cells by treatment with sodium butyrate or by in vivo growth of LSC cells in nude mice. In contrast, LSB cells were able to synthesize and process core 1 and core 2 (GlcNAc1-6 (Gal1-3) GalNAc-). LSC cells represent the first example of a non-hematopoietic cell line which lacks core 1 3-Gal-transferase activity. The lack of core 1 3-Gal-transferase in LSC cells explains why they are incapable of forming the common mucin O-glycan core structures and are committed to synthesizing the short Tn and STn oligosaccharides. These findings suggest that the activity of core 1 3-Gal-transferase is an important determinant of the STn phenotype of colon cancer cells.