Effects of acute exposure to dispersed oil and burned oil residue on long-term survival, growth, and reproductive development in polar cod (Boreogadus saida).

The present study investigates the potential long-term physiological effects on maturing polar cod (Boreogadus saida), an Arctic key species, after an acute exposure (48 h) to environmentally realistic concentrations of either mechanically dispersed oil (MDO), chemically dispersed oil (CDO) or burned oil residues (BO) (N = 58-60 per treatment). Following exposure, fish were monitored in a common tank supplied with clean water for a seven-month period coinciding with the period of reproductive development. Females exposed to BO residues were more frequently found in an earlier phase of gonadal maturation compared to unexposed females while no effects of different oil spill response (OSR) actions were seen in the reproductive development of males. Mechanically and chemically dispersed oil induced a transient short-term reduction in growth in the first week post-exposure. Overall, no significant long-term effects of exposure were seen in growth or mortality. Ultimately, this study provides information for the assessment of population consequences of different OSR actions as part of a net environmental benefit analysis.

A Pleistocene ice core record of atmospheric O2 concentrations.

The history of atmospheric O2 partial pressures (Po2) is inextricably linked to the coevolution of life and Earth's biogeochemical cycles. Reconstructions of past Po2 rely on models and proxies but often markedly disagree. We present a record of Po2 reconstructed using O2/N2 ratios from ancient air trapped in ice. This record indicates that Po2 declined by 7 per mil (0.7%) over the past 800,000 years, requiring that O2 sinks were ~2% larger than sources. This decline is consistent with changes in burial and weathering fluxes of organic carbon and pyrite driven by either Neogene cooling or increasing Pleistocene erosion rates. The 800,000-year record of steady average carbon dioxide partial pressures (Pco2) but declining Po2 provides distinctive evidence that a silicate weathering feedback stabilizes Pco2 on million-year time scales.

Global carbon sinks and their variability inferred from atmospheric O2 and delta13C.

Recent time-series measurements of atmospheric O2 show that the land biosphere and world oceans annually sequestered 1.4 +/- 0.8 and 2.0 +/- 0.6 gigatons of carbon, respectively, between mid-1991 and mid-1997. The rapid storage of carbon by the land biosphere from 1991 to 1997 contrasts with the 1980s, when the land biosphere was approximately neutral. Comparison with measurements of delta13CO2 implies an isotopic flux of 89 +/- 21 gigatons of carbon per mil per year, in agreement with model- and inventory-based estimates of this flux. Both the delta13C and the O2 data show significant interannual variability in carbon storage over the period of record. The general agreement of the independent estimates from O2 and delta13C is a robust signal of variable carbon uptake by both the land biosphere and the oceans.

OCEANOGRAPHY: Tracer from the Sky.

The rate of marine photosynthesis is of great importance for the global carbon cycle but is difficult to measure from environmental properties or in vitro. In this Perspective, Bender highlights a study by Luz and Barkan, who exploit the anomalous isotopic composition of molecular oxygen to determine the gross rate of photosynthesis in seawater. The method allows much longer time scales and larger spatial scales to be covered than with traditional oceanographic techniques.

Congenital knee dislocation in a 49,XXXXY boy.

We report on a 12 year old mentally retarded boy who presented at birth with bilateral knee dislocations, dislocation of the right hip, and general joint laxity. Cytogenetic studies showed a 49,XXXXY karyotype. Hyperlaxity of joints is known to occur in 49,XXXXY patients, but congenital knee dislocation has not been reported. Rarely in 49,XXXXY and 49,XXXXX syndromes Larsen-like features may be seen. Patients with congenital joint dislocation or laxity, combined with other malformations, especially if psychomotor development is delayed, should be karyotyped to exclude chromosomal abnormalities.

Preparation and purification of microplasmin.

A catalytically active, human microplasmin was produced by incubation of [Lys]plasmin in buffer at pH 11.0 for up to 12 hr. The microplasmin was purified by affinity chromatography that used lysine-Sepharose and soybean trypsin inhibitor-Sepharose columns. It is homogeneous and pure by electrophoretic analysis in NaDodSO4/polyacrylamide gels and by gel filtration on a Superose 12 column. The molecular weight of the microplasmin determined by NaDodSO4 gel electrophoresis is 29,000 and 26,500 under reducing condition, whereas the molecular weight of native plasmin is 76,500. Microplasmin consists mainly of the ligh (B) chain of native human plasmin and possesses one active site per protein molecule when titrated with p-nitrophenyl p'-guanidinobenzoate. Microplasmin hydrolyzes the peptide substrate NH2-D-Val-Leu-Lys-p-nitroanilide (S-2251) with a Km of 0.361 +/- 0.017 mM and a kcat of 40.3 +/- 3.3 s-1 at pH 7.4 and 37 degrees C, whereas native plasmin has a Km of 0.355 +/- 0.002 mM and a kcat of 27.9 +/- 0.3 s-1 under the same conditions.

Structure and formation of microplasmin.

The structure of human microplasmin, prepared from plasmin in alkaline solution, has been studied. Microplasmin consists of two polypeptide chains connected by disulfide bonds. One polypeptide is the B chain of plasmin consisting of 230 amino acids, and the other peptide is the COOH-terminal portion of the A chain of plasmin consisting of 31 amino acid residues. Microplasmin has a molecular weight of 28,635, calculated from its primary sequence. It is slightly more positively charged than plasminogen and is a more hydrophobic molecule. The proposed scheme for the formation of microplasmin involves autolysis at specific peptide bonds and scrambling of especially sensitive disulfide bonds in alkaline solution.

Thermal and pH stability of "beta-benzyme".

The thermal and pH stability of "beta-benzyme", an artificial chymotrypsin based on beta-cyclodextrin, has been studied and compared with the stability of real chymotrypsin. Artificial chymotrypsin is vastly superior to real chymotrypsin with regard to both temperature and pH stability. The reasons for this increased stability are discussed.

Evolution of the ratio of strontium-87 to strontium-86 in seawater from cretaceous to present.

A detailed record of the strontium-87 to strontium-86 ratio in seawater during the last 100 million years was determined by measuring this ratio in 137 well-preserved and well-dated fossil foraminifera samples. Sample preservation was evaluated from scanning electron microscopy studies, measured strontium-calcium ratios, and pore water strontium isotope ratios. The evolution of the strontium isotopic ratio in seawater offers a means to evaluate long-term changes in the global strontium isotope mass balance. Results show that the marine strontium isotope composition can be used for correlating and dating well-preserved authigenic marine sediments throughout much of the Cenozoic to a precision of +/-1 million years. The strontium-87 to strontium-86 ratio in seawater increased sharply across the Cretaceous/Tertiary boundary, but this feature is not readily explained as strontium input from a bolide impact on land.

Synthesis and evaluation of a miniature organic model of chymotrypsin.

An artificial chymotrypsin, with all the features of the real chymotrypsin, namely a binding site (from cyclodextrin) attached to a catalytic site containing an imidazolyl group, a carboxylate group and a hydroxyl group, has been synthesized. This artificial chymotrypsin has a molecular weight of only 1,365 while the real enzyme has a molecular weight of 24,800. However, from preliminary measurements, both the real and artificial enzymes have approximately the same catalytic activity (both rate and binding constants).

Inhibition of porcine elastase and anhydroelastase by boronic acids.

Porcine pancreatic elastase binds and is inhibited by the arylboronic acids with Ki values on the order of 10(-4)M, binding tighter than butaneboronic acid or methaneboronic acid. The pH dependence of the Ki values shows two pK values, pK1 = 6.8, assigned to enzyme ionization, and pK2, assigned to inhibitor ionization. The substituent effect of the arylboronic acids on Ki, investigated by a Hammett plot, suggests that the boron atom of the inhibitor interacts strongly with a nucleophilic site of elastase and probably forms an enzyme-bound tetrahedral structure. Anhydroelastase was formed by the removal of active site Ser-OH of elastase. Anhydroelastase has a much reduced affinity for the arylboronic acids or specific aldehyde inhibitors than the native enzyme, agreeing with the tetrahedral postulate.

Fluorine magnetic resonance studies of fluorine-substituted benzoyl chymotrypsins.

The fluorine magnetic resonance spectra of 4-fluorobenzoyl and 3,5-di(trifluoromethyl)benzoyl-alpha-chymotrypsins and the corresponding methyl esters were determined. An unusually large downfield displacement of the chemical shift (-10 ppm) was observed for the 4-fluorobenzoyl-alpha-chymotrypsin compared to the free acid in water. The shift of the ethyl ester was displaced upfield on going from a partly aqueous solvent to dioxane or methanol. The line broadening of the fluorine resonance of the 3,5-di(trifluoromethyl)benzoyl-alpha-chymotrypsin was minimal and there was no evidence of two peaks in the spectrum. The resonance was displaced only slightly downfield from the corresponding acid in water. Unusual chemical shifts for fluorinated acylchymotrypsins have been reported for other acyl groups and they appear to be unrelated to the anomalous deacylation rates observed for some fluorine substituted acylenzymes.

Kinetics of subtilisin and thiolsubtilisin.

Subtilisin is a bacterial serine protease with a broad specificity in the S1 subsite. It has been very extensively studied using a variety of kinetic and physical techniques. A chemical derivative, thiolsubtilisin, has been subjected to similar studies in order to analyze the effects of the OH to SH conversion on enzyme activity. The native structure of thiolsubtilisin is indicated by a variety of physical techniques. Oligopeptides bind nearly equally well to both enzymes, and a peptide chloromethylketone is much more reactive to thiolsubtilisin than to subtilisin. Both enzymes have a similar level of activity towards activated nonspecific amides and esters. However, thiolsubtilisin is inactive towards highly specific peptide amides and esters. Thiolsubtilisin also does not show good binding to boronic and arsonic acids. The observation that these transition state analog inhibitors bind poorly to thiolsubtilisin while other compounds bind nearly equally well to both enzymes suggests that thiolsubtilisin may not be able to stabilize the transition state during acylation by specific substrates.

Upwelling of hydrothermal solutions through ridge flank sediments shown by pore water profiles.

High calcium ion and low magnesium ion concentrations in sediment pore waters in cores from the Galápagos Mounds Hydrothermal Field on the flank of the Galápagos Spreading Center are believed to be due to a calcium-magnesium exchange reaction between circulating seawater and basement basalt. The nonlinearity of the calcium ion and magnesium ion gradients indicates that these discharging hydrothermal solutions on the ridge flank are upwelling at the rate of about 1 centimeter per year through the pelagic sediments of the Mounds Field and at about 20 centimeters per year through the hydrothermal mounds themselves.

Ageing of alpha-chymotrypsin: Cannibalistic and hydroxide ion reactions.

The loss of catalytic activity (irreversible denaturation) of alpha-chymotrypsin (EC 3.4.21.1) as a function of pH between 6 and 13 is described. Around neutrality the irreversible denaturation is second order with respect to enzyme. At high pH, the irreversible denaturation is first order with respect to enzyme and also with respect to hydroxide ion. The first- or second-order dependency on enzyme concentration has been shown both by the time course of denaturation and by the effect of enzyme concentration on the rate of denaturation. The first-order dependency on hydroxide ion was shown by a plot of the logarithm of the rate constant vs. pH. These enzyme inactivations are peptide bond cleavages at all pH values. From the kinetics, the irreversible denaturation can be described as a cannibalistic reaction of two enzyme molecules around neutrality or as a reaction of one enzyme molecule plus one hydroxide ion at high pH.

Elimination of cannibalistic denaturation by enzyme immobilization or inhibition.

The cannibalistic denaturation of alpha-chymotrypsin (EC 3.4.21.1) around neutral pH can be eliminated by immobilization (insolubilization) of the enzyme or by inhibition by specific reversible inhibitors, but the high-pH denaturation cannot be. The denaturation of the immobilized enzyme at high pH follows first-order kinetics, just as the denaturation of the soluble enzyme does. These results lend credence to the description of the denaturation of chymotrypsin as cannibalistic around neutrality and due to a hydroxide ion reaction at high pH; this interpretation followed from kinetic arguments given in the previous article [Wu, H.-L., Wastell, A. & Bender, M. L. (1981) Proc. Natl. Acad. Sci. USA 78, 4116-4117]. Elimination of denaturation around neutrality by immobilization may be the reason why membrane-bound enzymes are so common in vivo.

Thermal structure of the deep pacific ocean in the early pliocene.

The thermal structure of the Pacific Ocean between water depths of about 1 and 4.5 kilometers is estimated from the oxygen isotopic ratio of benthonic foraminifera from deep-drilled and piston cores of early Pliocene age (about 3 to 5 million years ago). The ratio of oxygen-18 to oxygen-16 in the early Pliocene at each site varies by an average of only +/- 0.12 per mil (1 standard deviation). A plot of the oxygen isotopic ratio against modern bottom-water temperature is adequately fit by a line having a slope of - 0.26 per mil per degree Celsius (the equilibrium temperature dependence of calcite-water fractionation), suggesting that the temperature gradient of the Pacific Ocean during the early Pliocene was similar to that of today.