4-Hydroxyphenylpyruvate dioxygenase is an iron-tyrosinate protein

A resonance Raman investigation into the blue chromophore of 4-hydroxyphenylpyruvate dioxygenase, a non-heme iron enzyme from Pseudomonas P. J. 874, reveals the presence of enhanced vibrations characteristic of tyrosinate coordination to the iron center. The excitation profiles for these features show that they are associated with the 595 nm absorption feature. EPR studies of this enzyme indicate the presence of a high-spin ferric center in a rhombic environment, as evidenced by a signal at g = 4.3 with the correct intensity for the measured iron content. This enzyme thus belongs to the emerging class of iron-tyrosinate proteins.     

Influence of fungi on growth and survival of Onychiurus armatus (Collembola) in a metal polluted soil

Summary The influence of food quantity and quality on growth and survival of Onychiurus armatus (Tullb.) in metal polluted environments has been investigated in laboratory experiments. The Collembola was reared on five species of fungi isolated from a metal polluted soil close to a brass mill in SE Sweden.Survival of O. armatus was improved when fungal biomass was continuously added in a polluted mor (1,300 ppm Zn and 200 ppm Cu), and when specimens were fed metal polluted fungi for 1, 3 and 7 days a week, only those that were starved had increased mortality. Allometric growth, on the other hand, was significantly reduced when Collembola was given surplus of metal polluted fungi, whereas growth losses caused by metals were offset by protein rich food. Hence, sufficient food quantities alone could overcome mortality losses but not growth retardation in a metal polluted environment.Feeding preference of O. armatus was not determined by the protein content of the fungi although this was beneficial for growth. Metals changed the relative palatability of fungal species, but one of the metal tolerant species, Paecilomyces farinosus, which was also protein rich, remained reasonably attractive for O. armatus also when it was metal polluted. The mechanisms by which growth and survival of O. armatus were promoted by a combination of protein and Zn/Cu rich fungi seemed to be crucial in understanding the fate of a population of this species in a metal polluted soil.     

Tritium isotope effects in the reaction catalyzed by 4-hydroxyphenylpyruvate dioxygenase from pseudomonas sp. strain P.J. 874

Tritium isotope effects in the reaction catalyzed by 4-hydroxyphenylpyruvate dioxygenase (4-hydroxyphenyl-pyruvate:oxygen oxidoreductase (hydroxylating, decarboxylating), EC 1.13.11.27) from Pseudomonas sp. strain P.J. 874 were studied with 14C- and different 3H-labelled 4-hydroxyphenylpyruvate. Tritium of ring-2,6-3H2-labelled substrate was released into water in 1:2 stoichiometry to 14CO2 formation. The tritium release from ring-3,5-3H2- and side chain-3-3H1-labelled 4-hydroxyphenylpyruvate was low as compared with 14CO2 formation. The apparent tritium isotope effects were below two, as judged by comparison of 3H/14C ratios of 4-hydroxyphenylpyruvate and homogentisate. The ratios showed no dependence on oxygen concentrations between 1 and 21% in the gas phase. Thus, a tritium assay can be used to determine the activity of 4-hydroxyphenylpyruvate dioxygenase. Apparently, none of the substrate hydrogens is involved in any rate-limiting step up to the first irreversible step. enol-4-Hydroxyphenylpyruvate was excluded as the active substrate tautomer.     

N-acetyl-p-benzoquinone imine-induced changes in the energy metabolism in hepatocytes

The effect of N-acetyl-p-benzoquinone imine (NAPQI), a reactive metabolite of acetaminophen, on the energy metabolism in isolated hepatocytes was investigated. Incubation of cells with NAPQI (400 microM) resulted in an immediate uptake into the mitochondria, followed by both reduction and glutathione conjugation of the quinone imine. These reactions were extremely rapid and were associated with depletion of the mitochondrial ATP content (greater than 80% depletion after 1 min exposure). The loss of ATP was accompanied by increases in ADP and AMP, as well as NADP. No effect on mitochondrial NAD was observed during this initial phase. Similar alterations were produced by NAPQI in the cytosolic compartment. Furthermore, incubation of hepatocytes with NAPQI inhibited oxygen consumption by nearly 90% within 10 s. In parallel to these biochemical changes, there was marked bleb formation on the surface of the hepatocytes, which was found to precede cell death (trypan blue uptake). In conclusion, our results demonstrate that during exposure of hepatocytes to NAPQI, dramatic changes in cellular energy metabolism occur. These biochemical alterations may be caused by a rapid decrease in mitochondrial function, and they may play an important role in the initiation of NAPQI-induced cytotoxicity.     

Plant survival in Iceland during periods of glaciation?

Aim The paper addresses the classical question of possible plant survival in Iceland during the last glacial period in the light of a palaeobotanical record from northern Iceland, spanning the period 11,300–9000 BP , including the Younger Dryas stadial. We review the Late Cenozoic fossil plant record, the past debate on glacial plant refugia in Iceland, and the evidence for ice-free areas during the Weichselian. Location The investigated lake sediment record comes from Lake Torfadalsvatn, which is situated in the northwestern part of the Skagi peninsula in northern Iceland. Methods The sediment chronology was constructed from the cccurrence of the Vedde Ash and the Saksunarvatn ash, two well-dated Icelandic tephras, together with the results from five AMS and conventional radiocarbon dates performed on bulk sediment samples. The vegetational reconstruction was based on detailed pollen analysis of the sediment sequence. Results The pollen analysis revealed that many of the taxa present in the area prior to the Younger Dryas stadial continued to produce pollen during that cold event. The more or less immediate reappearance of a few other pollen taxa at the Younger Dryas-Preboreal boundary suggests that these plants also survived, even if they did not produce sufficient pollen to be recorded during the Younger Dryas stadial. Main conclusions We conclude that the relatively high plant diversity found in high Arctic areas and present-day nunataks in Iceland and Greenland, together with the fact that many plant species were able to survive the Younger Dryas stadial on the Skagi peninsula, suggest that species with high tolerance for climate fluctuations also survived the whole Weichselian in Iceland. This conclusion is supported by recent palaeoclimatic data from ice-cores and deep-sea sediments, indicating that Icelandic climate during the last glacial was only occasionally slightly colder than during the Younger Dryas stadial.     

Repeated epinephrine doses during prolonged cardiopulmonary resuscitation have limited effects on myocardial blood flow: a randomized porcine study

In cases where antidiabetic monotherapy is unable to sufficiently control glucose levels in patients with type-2 diabetes, treatment needs to be intensified. Determining factors that may be predictors for the occurrence of comorbidities in these patients is essential for improving the efficacy of clinical diabetes care. The DiaRegis prospective cohort study included 3,810 type-2 diabetics for whom the treating physician aimed to intensify and optimise antidiabetic treatment due to insufficient glucose control. Treatment intensification was defined as increasing the dose of the originally prescribed drug, and/or selecting an alternative drug, and/or prescribing an additional drug. The aims were to monitor the co-morbidity burden of type-2 diabetic patients over a follow-up of two years, and to identify multivariable adjusted predictors for the development of comorbidity and cardiovascular events. A total of 3,058 patients completed the 2 year follow-up. A substantial proportion of these patients had co-morbidities such as vascular disease, neuropathy, and heart failure at baseline. After treatment intensification, there was an increased use of DPP-4 inhibitors, insulin, and GLP-1 analogues, achieving reductions in HbA1c, fasting plasma glucose, and postprandial glucose. During the 2 year period 2.5% of patients (n = 75) died, 3.2% experienced non-fatal macrovascular events, 11.9% experienced microvascular events, and 4.3% suffered onset of heart failure. Predictors for combined macro-/microvascular complications/heart failure/death were found to be age (OR 1.36; 95% CI 1.10–1.68), prior vascular disease (1.73; 1.39–2.16), and history of heart failure (2.78; 2.10–3.68). Determining the factors that contribute to co-morbidities during intensive glucose-lowering treatment is essential for improving the efficacy of diabetes care. Our results indicate that age, prior vascular disease, and heart failure constitute important predictors of poor cardiovascular outcomes in patients receiving such therapy.     

Cerebral osmoregulation of renal sodium excretion--a response analogous to thirst and vasopressin release

Studies in sheep have shown that renal excretion of sodium may be under osmoregulatory control. When sheep become dehydrated, or are infused intravenously with hypertonic saline, they increase renal Na excretion in addition to secreting vasopressin and developing a thirst. These natriuretic, antidiuretic, and dipsogenic responses to dehydration and hypertonicity can be greatly reduced by lowering the cerebrospinal fluid NaCl concentration or by prior ablation of tissue in the anterior wall of the third ventricle. Lowering of cerebrospinal fluid NaCl concentration also prevents postprandial natriuresis which normally occurs in association with a postprandial increase in plasma Na concentration and tonicity. We propose that there is a cerebral osmoregulatory control of Na excretion which may interact with volume influences from the cardiovascular system to regulate renal Na output. The effector mechanism from brain to kidney mediating such cerebral control of Na excretion is probably hormonal.     

Ectoparasites on small mammals in Iceland: Origin and population characteristics of a species-poor insular community

The Icelandic small mammal fauna is depauperated as is the associated ectoparasite fauna. Three small mammal species occur, viz. Apodemus sylvaticus L., Mus musculus L., and Rattus norvegicus Berk. ( R. rattus is probably not a regular member). The mice supposedly came to the island by settlers from the 10th century and onwards.
Apodemus and Mus from five localities altogether had seven ectoparasite species, five mites and two fleas. All species occurred on Apodemus whereas Mus was infested by four. Compared with the numbers of ectoparasite species recorded in similar studies in the Nordic countries, there are conspicuously few species in Iceland. Further, Apodemus had an overall higher infestation frequency than Mus (90% and 30%, respectively) and a higher total density of ectoparasites (3.3–20.3 and 0.5 inds/host, respectively). The density figures were high compared with those for mainland Apodemus . Especially the mite Laelaps agilis C. L. Koch and the flea Ctenophthalmus agyrtes (Heller) were common on Icelandic Apodemus . Reduced competition among parasites and/or low predator pressure on small mammals may explain the density figures obtained.
The ectoparasite species compositions on small mammals in Scandinavia and Iceland have many features in common that renders it probable that Apodemus originate from Scandinavia.     

Nutritional evaluation of the white-rot fungus Sporotrichum pulverulentum as a feedstuff to rats,pigs, and sheep

The production of single-cell protein (SCP) based on cheap carbon sources such as spent liquor from paper mills is of interest for different reasons. The White-rot fungus (Sporotrichum pulverulentum) has earlier been shown to degrade cellulose and lignin. The nutritive value of this fungus was investigated with rats, pigs, and sheep. The effect of different drying process was evaluated on rats. Experiments with piglets, growing pigs, and sheep were aimed at getting primary information on nutritive parameters with domestic animal species, Chemical analysis of S. pulverulentum showed that the sum of the amino acids corresponded to 70% and ammonia, GABA, and glucosamine to 20% of its crude protein content. Differences between drying treatments in their effect on protein digestibility were not noted. From a protein quality viewpoint, a tendency toward superiority was noted for two of the drying processes. The amino acid digestibility of S. pulverulentum was inferior to values for soybean oil meal given in textbooks. The piglet experiment confirmed the lower nutritive value of S. pulverulentum compared with soybean oil meal. in the piglet stage a content of metabolizable energy of S. pulverulentum was found which corresponded to 60% of that for soybean oil meal. With increasing age the ability of pigs to utilize the fungus increased. The limited nutritive value for monogastric animals is most certainly caused by the cell-wall structure of S. pulverulentum with poor digestibility of the carbohydrates. The experiment with sheep showed more satisfactory results than with monogastric species, with digestibility of crude protein of 82% and a content of metabolizable energy of 70% of soybean oil meal.