Global patterns of predator diversity in the open oceans.
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The open oceans comprise most of the biosphere, yet patterns and trends of species diversity there are enigmatic. Here, we derive worldwide patterns of tuna and billfish diversity over the past 50 years, revealing distinct subtropical "hotspots" that appeared to hold generally for other predators and zooplankton. Diversity was positively correlated with thermal fronts and dissolved oxygen and a nonlinear function of temperature (approximately 25 degrees C optimum). Diversity declined between 10 and 50% in all oceans, a trend that coincided with increased fishing pressure, superimposed on strong El Nino-Southern Oscillation-driven variability across the Pacific. We conclude that predator diversity shows a predictable yet eroding pattern signaling ecosystem-wide changes linked to climate and fishing. (+info)
Heavy meromyosin from skipjack tuna, Euthynus pelamis. Preparation and enzymic properties.
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A method was developed to obtain heavy meromyosin (HMM) from the tryptic digest of skipjack tuna dorsal myosin. The tuna HMM thus obtained was shown to be homogeneous on gel filtration-gel electrophoresis, and on ultracentrifugation. The sedimentation constant (S20,w) was estimated to be 6.1S for tuna HMM. The ATPase activity of tuna dorsal HMM was found to be very similar to that of rabbit skeletal HMM in many respects: KCl concentration dependence, pH dependence, effect of pCMB, kinetic parameters (Vmax and Ka) in actin activation, and Arrhenius activation energy. The only difference found between tuna HMM and rabbit HMM was in heat denaturation behavior: the ATPase activities of tuna HMM were approximately four times as sensitive to heat inactivation as those of rabbit HMM. Thus, tuna HMM should represent a good experimental material for investigations of the molecular basis of susceptibility to denaturation, and of the characteristics of fish myosins in general. A new type of heat denaturation of myosin was observed. It occurred in a very early stage of heat treatment of either tuna dorsal myosin or rabbit skeletal myosin; however, it did not occur upon heat treatment of HMM of either tuna or rabbit, and it was detectable in terms of the Mg-ATPase activity only when the activity was measured in the presence of untreated actin. (+info)
Biosensor detection of botulinum toxoid A and staphylococcal enterotoxin B in food.
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Immunoassays were developed for the simultaneous detection of staphylococcal enterotoxin B and botulinum toxoid A in buffer, with limits of detection of 0.1 ng/ml and 20 ng/ml, respectively. The toxins were also spiked and measured in a variety of food samples, including canned tomatoes, sweet corn, green beans, mushrooms, and tuna. (+info)
Some reactions of carbon monoxide and oxygen with carbodi-imide-modified cytochrome c.
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The reactivity of carbodi-imide-modified tuna and horse heart cytochromes c with the ferrous ion ligands CO and O2 has been studied. Both modified cytochromes bind one molecule of CO. Stopped-flow and flash-photolysis experiments indicate the presence of three kinetic processes in the reaction of the cytochromes with CO. The second-order rate constants associated with all three kinetic process are pH-independent being 2.8 x 10(5) M-1.s-1, 3.8 x 10(4) M-1.s-1 and 4 x 10(3) M-1.s-1 under all conditions studied. The concentration-dependence of the contributions made by each of the processes to the overall absorbance change indicates that the fast and slow kinetic phases are associated with two forms of the cytochromes which are in equilibrium, whereas the intermediate phase arises from a separate cytochrome species. The quantum yield for the photodissociation of CO from the ferrous cytochromes is unusually low. Both modified cytochromes are capable of binding and reducing O2. In the presence of excess reductant, the modified cytochromes can catalytically reduce large molar excesses of O2. In the absence of excess reducing agent, the oxy complex initially formed undergoes a pH-dependent intramolecular electron-transfer process with half-life approx. 10 min. EDC [1-ethyl-3-(3-dimethylaminopropyl)carbodi-imide]-promoted internal cross-linking is proposed to account for differences between the EDC-modified proteins and carboxymethylated cytochrome c. (+info)
Electrostatic orientation of the electron-transfer complex between plastocyanin and cytochrome c.
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To understand the specificity and efficiency of protein-protein interactions promoting electron transfer, we evaluated the role of electrostatic forces in precollision orientation by the development of two new methods, computer graphics alignment of protein electrostatic fields and a systematic orientational search of intermolecular electrostatic energies for two proteins at present separation distances. We applied these methods to the plastocyanin/cytochrome c interaction, which is faster than random collision, but too slow for study by molecular dynamics techniques. Significant electrostatic potentials were concentrated on one-fourth (969 A2) of the plastocyanin surface, with the greatest negative potential centered on the Tyr-83 hydroxyl within the acidic patch, and on one-eighth (632 A2) of the cytochrome c surface, with the greatest positive potential centered near the exposed heme edge. Coherent electrostatic fields occurred only over these regions, suggesting that local, rather than global, charge complementarity controls productive recognition. The three energetically favored families of pre-collision orientations all directed the positive region surrounding the heme edge of cytochrome c toward the acidic patch of plastocyanin but differed in heme plane orientation. Analysis of electrostatic fields, electrostatic energies of precollision orientations with 12 and 6 A separation distances, and surface topographies suggested that the favored orientations should converge to productive complexes promoting a single electron-transfer pathway from the cytochrome c heme edge to Tyr-83 of plastocyanin. Direct interactions of the exposed Cu ligand in plastocyanin with the cytochrome c heme edge are not unfavorable sterically or electrostatically but should occur no faster than randomly, indicating that this is not the primary pathway for electron transfer. (+info)
The crystal structure of bonito (katsuo) ferrocytochrome c at 2.3 A resolution. II. Structure and function.
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The structure analysis of bonito heart ferrocytochrome c was carried out at 2.3 A resolution by X-ray diffraction, and a Kendrew-type skeletal model was built up. This molecule has an overall egg shape, 35 A in height, 30 A in width and 23 A in thickness; the 5th ligand of the heme iron atom is the N-epsilon atom of the His-18 imidazole ring and the 6th is the Met-80 sulfur atom. Distinct alpha-helix regions are found between the N-terminus and reside 11, between 60 and 69, and between 90 and the C-terminus. The most distinct difference between the conformation of the present molecule and that of the horse oxidized molecule is the location of the Phe-82 phenyl ring. In the present reduced molecule, the phyenyl ring is in closer contact with the iron atom and gives influences on the character of the iron atom. Inside the molecule, at the lower part of the heme pocket, there is an extended hydrogen bond network including the propionic acid residues of the heme group. Both Phe-82 and the hydrogen bond network may play a key role in the function of this molecule. (+info)
Morganella psychrotolerans sp. nov., a histamine-producing bacterium isolated from various seafoods.
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Mesophilic Morganella morganii (n=6) and psychrotolerant M. morganii-like isolates from various seafoods (n=13), as well as clinical M. morganii isolates (n=3), were characterized by using a polyphasic approach including multi-locus sequencing. Based on the phylogenetic analysis, the 22 strains were divided into two distinct groups comprising mesophilic and psychrotolerant isolates, respectively. This classification was supported by DNA-DNA hybridization studies, whereby a psychrotolerant isolate (strain U2/3(T)) showed 41.0 and 17.8 % relatedness to the type strains of the mesophilic species Morganella morganii subsp. morganii (strain LMG 7874(T)) and Morganella morganii subsp. sibonii (strain DSM 14850(T)), respectively. Analysis of the 16S rRNA gene sequences showed a similarity of 98.6 % between mesophilic and psychrotolerant isolates. However, fragments of seven protein-encoding housekeeping genes (atpD, dnaN, gyrB, hdc, infB, rpoB and tuf) all showed less than 90.9 % sequence similarity between the two groups. The psychrotolerant isolates grew at 0-2 degrees C and also differed from the mesophilic M. morganii isolates with respect to growth at 37 degrees C and in 8.5 % (w/v) NaCl and fermentation of d-galactose. The psychrotolerant strains appear to represent a novel species, for which the name Morganella psychrotolerans sp. nov. is proposed. The type strain is U2/3(T) (=LMG 23374(T)=DSM 17886(T)). (+info)
Severe scombroid fish poisoning syndrome requiring aggressive fluid resuscitation in the emergency department: two case reports.
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Scombroid fish poisoning (scombrotoxism, scombroid ichthyotoxicosis) is a food-related illness typically associated with the consumption of dark and white meat fish. Two patients presented to the emergency department. Metilprednisone 1000 mg and ranitidine 150 mg were administered initially. A large amount of crystalloids and colloids in in combination with vasoactive drugs were required to maintain normopressure. Levels of histamine and N-methylhistamine were far above the normal mean. Carboxyhemoglobin levels were also tested to exclude a superimposition of carbon monoxide intoxication. In both cases, major symptoms occurred and were treated aggressively. Early goal directed fluid therapy corrected the DO2/VO2 unbalance, due to a distributive pattern of hypovolemic impending shock, and permitted a rapid stabilisation of both patients. It is important to recognize the syndrome as an intoxication (rather than an allergic reaction) so that the source of the toxin can be identified and further cases prevented. It is also important to investigate where the fish was cooked (i.e. in an open space vs. closed space), to exclude the possibility of a concomitant carbon monoxide intoxication, which would require transfer the patient to a hospital facility equipped with a hyperbaric chamber. (+info)