Sulfate reduction and S-oxidation in a moorland pool sediment

In an oligotrophic moorland pool in The Netherlands, S cycling near the sediment/water boundary was investigated by measuring (1) SO₄ ^2– reduction rates in the sediment, (2) depletion of SO₄ ^2– in the overlying water column and (3) release of³⁵S from the sediment into the water column. Two locations differing in sediment type (highly organic and sandy) were compared, with respect to reduction rates and depletion of SO₄ ^2– in the overlying water.Sulfate reduction rates in sediments of an oligotrophic moorland pool were estimated by diagenetic modelling and whole core³⁵SO₄ ^2– injection. Rates of SO₄ ^2– consumption in the overlying water were estimated by changes in SO₄ ^2– concentration over time in in situ enclosures. Reduction rates ranged from 0.27–11.2 mmol m^–2 d^–1. Rates of SO₄ ^2– uptake from the enclosed water column varied from –0.5, –0.3 mmol m^–2 d^–1 (November) to 0.43–1.81 mmol m^–2 d^–1 (July, August and April). Maximum rates of oxidation to SO₄ ^2– in July 1990 estimated by combination of SO₄ ^2– reduction rates and rates of in situ SO₄ ^2– uptake in the enclosed water column were 10.3 and 10.5 mmol m^–2 d^–1 at an organic rich and at a sandy site respectively.Experiments with³⁵S^2– and³⁵SO₄ ^2– tracer suggested (1) a rapid formation of organically bound S from dissimilatory reduced SO₄ ^2– and (2) the presence of mainly non SO₄ ^2–-S derived from reduced S transported from the sediment into the overlying water. A³⁵S^2– tracer experiment showed that about 7% of³⁵S^2– injected at 1 cm depth in a sediment core was recovered in the overlying water column.Sulfate reduction rates in sediments with higher volumetric mass fraction of organic matter did not significantly differ from those in sediments with a lower mass fraction of organic matter.Corresponding author     

Enzymological characterization of a putative canine analogue of primary hyperoxaluria type 1.

This paper concerns an enzymological investigation into a putative canine analogue of the human autosomal recessive disease primary hyperoxaluria type 1 (alanine:glyoxylate/serine:pyruvate aminotransferase deficiency). The liver and kidney activities of alanine:glyoxylate aminotransferase and serine:pyruvate aminotransferase in two Tibetan Spaniel pups with familial oxalate nephropathy were markedly reduced when compared with a variety of controls. There were no obvious deficiencies in a number of other enzymes including D-glycerate dehydrogenase/glyoxylate reductase which have been shown previously to be deficient in primary hyperoxaluria type 2. Immunoblotting of liver and kidney homogenates from oxalotic dogs also demonstrated a severe deficiency of immunoreactive alanine:glyoxylate aminotransferase. The developmental expression of alanine:glyoxylate/serine:pyruvate aminotransferase was studied in the livers and kidneys of control dogs. In the liver, enzyme activity and immunoreactive protein were virtually undetectable at 1 day old, but then increased to reach a plateau between 4 and 12 weeks. During this period the activity was similar to that found in normal human liver. The enzyme activities and the levels of immunoreactive protein in the kidneys were more erratic, but they appeared to increase up to 8 weeks and then decrease, so that by 36 weeks the levels were similar to those found at 1 day. The data presented in this paper suggest that these oxalotic dogs have a genetic condition that is analogous, at least enzymologically, to the human disease primary hyperoxaluria type 1.     

Enxymological characterization of a putative canine analogue of primary hyperoxaluria type 1

This paper concerns an enzymological investigation into a putative canine canalogue of the human autosomal recesive disease primary hyperoxaluria type 1 (alanine:glyoxylate / serine:pyruvate aminotransferase deficiency). The liver and kidney activities of alanine:glyoxylate aminotransferase and seribe:pyruvate aminotransferase in two Tibetan Spaniel pups with familial oxalate nephripathy were markedly reduced when compared with a variety of controls. There were no obvious deficiencies in a number of other enzymes including d-glycerate dehydrogenese / glyoxylate reductase which have been shown previously to be deficient in primary hyperoxaluria type 2. Immunoblotting of liver and kidney homogenates from oxalotic dogs also demonstrated a severe deficiency of immunoreactive alanine:glyoxylate aminotransferase. The developmental expression of alanine:glyoxylate / serine:pyruvate aminotransferase was studied in the livers and kidneys of control dogs. In the liver, enzyme activity and immunoreactive protein were virtually undetectable at 1 day old, but then increased to reach a plateau between 4 and 12 weeks. During this period the activity was similar to that found in normal humanb liver. The enzyme activities and the levels of immunoreactive protein in the kidneys were more erratic, but they appeared to increase up to 8 weeks and then decrease, so that by 36 weeks the levels were similar to those found at 1 day. The data presented in this paper suggest that these oxalotic dogs have a genetic condition that is anlogous, at least enzymologically, to the human disease primary hyperoxaluria type 1.     

The disulfide bonded ring of iso-rANP, unlike that of rANP, has potent cardiovascular activity

Iso-atrial natriuretic peptide (iso-rANP), a 45 amino acid peptide with a disulfide bond between residues 23 and 39, is a newly discovered second atrial hormone with considerable homology with rat atrial natriuretic peptide (rANP). We have reported that iso-rANP(1-45) has effects similar to rANP in anesthetized rats in causing hypotension, a decrease in heart rate, and an increase in urine flow and electrolyte excretion. In the present experiments, we found that, unlike the ring peptide of rANP (rANP(105-121)), bolus injections of the ring peptide of iso-rANP (iso-rANP(23-39)) had considerable effects on the circulation but only small effects on the kidney, compared with iso-rANP(1-45). However, the effects of iso-rANP(23-39) in causing hypotension and decreasing heart rate were transient compared with those of iso-rANP(1-45). When we substituted a glycine for arginine into the ring portion of iso-rANP at position 36, so that there were only three amino acids different from the ring of rANP, biological activity of iso-rANP(23-39) was retained. In our bioassay system, all of the circulatory effects and most of the renal effects of rANP are mediated via vagal sensory afferents. We found that the effects of the ring peptide of iso-rANP on the circulation and the kidney were unchanged following vagotomy. The results indicate that iso-rANP(23-39) mediates at least some biological effects by membrane receptor mechanisms different from those of rANP and that the ring portion of iso-rANP probably contributes to nonvagally mediated responses of iso-rANP(1-45).     

Structural similarities among enzyme pterin binding sites as demonstrated by a monoclonal anti-idiotypic antibody

BALB/c mice were immunized with a synthetic co-factor of the aromatic amino acid hydroxylases, 6,7-dimethyl-5,6,7,8-tetrahydropterin, conjugated to albumin. Hybridoma cell lines isolated from the immunized mice secreted monoclonal antibodies reacting specifically with the pterin molecule and monoclonal antibodies which were found to bind phenylalanine hydroxylase. Several lines of evidence were consistent with the anti-phenylalanine hydroxylase antibodies being anti-idiotype antibodies mimicking the pterin molecule and binding to the pterin binding site of phenylalanine hydroxylase. (a) An anti-idiotype monoclonal antibody, NS7, when reimmunized into mice produced anti-pterin antibodies consistent with NS7 being an internal image anti-idiotypic antibody. (b) NS7 antibody was prevented from binding to phenylalanine hydroxylase when a competitive inhibitor of phenylalanine hydroxylase enzyme activity, 6,7-dimethyl-7,8-dihydropterin, was bound to phenylalanine hydroxylase. (c) NS7 antibody was shown to bind to a wide range of pterin-requiring enzymes: phenylalanine, tyrosine and tryptophan hydroxylases, dihydropteridine reductase, dihydrofolate reductase, and sepiapterin reductase. Thus the NS7 antibody has successfully mimicked a common portion of the pterin cofactors utilized by these enzymes and demonstrated structure homology in their pterin binding sites despite their diverse function and little amino acid sequence homology except among the three aromatic amino acid hydroxylases.     

Stoichiometry of a half-turnover of band 3, the chloride transport protein of human erythrocytes

The kinetics of human red blood cell Cl transport have been studied under nonequilibrium conditions to determine whether or not an outward Cl gradient can recruit the transport protein from an inward-facing to an outward-facing configuration. Three kinds of evidence are consistent with this outward recruitment. First, the initial net Cl efflux into a Cl-free phosphate medium is independent of the intracellular Cl concentration in the range 20-170 mM. Second, an outward Cl gradient strongly enhances the inhibitory potency of DNDS (4,4'-dinitro-2,2'-stilbene disulfonate), which suggests that DNDS binds primarily to outward-facing states. Finally, we have estimated the number of Cl ions transported during the putative outward recruitment. Resealed red cell ghosts containing only 70 muM 36Cl were resuspended at 0 degrees C in a Cl-free, HCO3-free Na2SO4 medium. In the first 10 s, or approximately 10(6) Cl ions per ghost, followed by a much slower further loss of Cl. The rapid loss of 10(6) Cl ions per ghost, which is abolished by pretreatment with DIDS (4,4'-diisothiocyano-2,2'-stilbene disulfonate), appears to represent the Cl that is transported during the first half-turnover of the transport cycle. These data are strong evidence that the influx and efflux events in the catalytic cycle for anion transport do not take place simultaneously, and that the stoichiometry of the transport cycle is close to one pair of anions exchanged per band 3 monomer.     

The R-type lipopolysaccharides of Neisseria meningitidis

The lipopolysaccharides of all the different serogroups of Neisseria meningitidis are of the "R" type despite the morphologically smooth appearance and the demonstrated virulence of the organisms from which they were derived. This was confirmed when each of the lipopolysaccharides was found to be devoid of detectable O-antigen side chains, giving only a low "molecular" weight core oligosaccharide when subjected to mild acid hydrolysis. The cores were modified by dephosphorylation and subjected to sugar and methylation analysis by gas-liquid chromatography. Although all the different cores contained identical components (glucose, galactose, glucosamine, heptose, and 2-keto-3-deoxyoctonate) they could be separated into three distinct categories according to their galactose:glucose ratios. These categories are typified by the cores obtained from groups A, C, and 29-e which have galactose:glucose ratios of 1:2, 2:2, and 2:1, respectively. The modified cores were methylated and analyzed by gas chromatography--mass spectrometry and on the basis of differences in the derived methylated sugars the cores could again be divided into the same three categories as above. This structural diversity also results in some serological specificity as demonstrated by the complete serogroup specificity of the group A lipopolysaccharide.     

Partition zone penetration by chymotrypsin, and the localization of the chloroplast flavoprotein and photosystem II.

1. Chymotrypsin treatment of chloroplast membranes inactivates Photosystem II. The inactivation is higher when the activity is measured under low intensity actinic light, suggesting that primary photochemistry is preferentially inactivated. 2. Membrane stacking induced by Mg2+ protects Photosystem II against chymotrypsin inactivation. When the membranes are irreversible unstacked by brief treatment with trypsin, Mg2+ protection against chymotrypsin inactivation of Photosystem II is abolished. 3. The kinetics of inactivation by chymotrypsin of Photosystem II indicates that membrane stacking slows down, but does not prevent, the access of chymotrypsin to Photosystem II, which is mostly located within the partition zones. 4. It is concluded that a partition gap exists between stacked membranes of about 45 A, the size of the chymotrypsin molecule. 5. The kinetics of inhibition of the chloroplast flavoprotein, ferredoxin-NADP reductase, bt its specific antibody is not affected by membrane stacking. This indicates that this enzyme is located outside the partition zones.     

A novel role for macrophage: antigen discrimination of distinct carbohydrate bonds.

Velocity sedimentation-derived subpopulations of peritoneal exudate macrophages have been pulsed with a variety of TNP-coupled carbohydrate/protein antigens and investigated for their ability to present those antigens in immunogenic form to whole spleen cell populations. The data presented indicate that while no difference is seen in the ability of the various subpopulations examined to present protein antigens for an antibody response, different cells are certainly involved in the antigen handling of carbohydrate antigens for an antibody response. Moreover, it seems that individual macrophage subpopulations can only interact with certain subpopulations of B lymphocytes to induce antibody responses to the same immunogenic determinants.