Showing papers by "Uppsala University published in 1988"

Glutathione transferases--structure and catalytic activity.

Abstract: The glutathione transferases are recognized as important catalysts in the biotransformation of xenobiotics, including drugs as well as environmental pollutants. Multiple forms exist, and numerous transferases from mammalian tissues, insects, and plants have been isolated and characterized. Enzymatic properties, reactions with antibodies, and structural characteristics have been used for classification of the glutathione transferases. The cytosolic mammalian enzymes could be grouped into three distinct classes--Alpha, Mu, and Pi; the microsomal glutathione transferase differs greatly from all the cytosolic enzymes. Members of each enzyme class have been identified in human, rat, and mouse tissues. Comparison of known primary structures of representatives of each class suggests a divergent evolution of the enzyme proteins from a common precursor. Products of oxidative metabolism such as organic hydroperoxides, epoxides, quinones, and activated alkenes are possible "natural" substrates for the glutathione transferases. Particularly noteworthy are 4-hydroxyalkenals, which are among the best substrates found. Homologous series of substrates give information about the properties of the corresponding binding site. The catalytic mechanism and the active-site topology have been probed also by use of chiral substrates. Steady-state kinetics have provided evidence for a "sequential" mechanism.

Exchange of phosphorus across the sediment-water interface

Abstract: In this article, principles of phosphorus retention and phosphorus release at the sediment-water interface in lakes are reviewed. New results and hypotheses are discussed in relation to older models of phosphorus exchange between sediments and water. The fractional composition of sedimentary phosphorus is discussed as a tool for interpretation of different retention mechanisms. Special emphasis is given to the impact of biological, particularly microbial, processes on phosphorus exchange across the sediment-water interface and to the significance of biologically induced CaCO3 precipitation to phosphorus retention in calcareous lakes.

Female choice selects for male sexual tail ornaments in the monogamous swallow

Abstract: Male secondary sexual ornaments are widespread among polygynous animals1 where they apparently arise through female choice and differential mating success of males2–5. Darwin1 and Fisher2 suggested that female choice should also select for extravagant male ornaments in monogamous birds because female preference for ornamented males should result in earlier breeding which would increase male reproductive success by enhancing the quality and/or the quantity of offspring raised each year. In such cases female reproductive success should be positively related to body condition6 and a heritable component of the time of breeding should be affected by stabilizing selection7. Female preferences for orna-mented males would be favoured by sexual selection because such choosy females would have a greater probability of bearing orna-mented sons with an increased chance of pairing up early. I report here that in the monogamous swallow, Hirundo rustica, males with experimentally elpngated tail ornaments obtain mates more quickly than males with shorter tails, and enjoy increased reproductive output in one breeding season. Such males are also preferred by females seeking extra-pair-bond copulations. Thus male sexual ornaments may also be maintained by female mate choice in monogamous species.

Pollination in Dianthus deltoides (Caryophyllaceae): effects of habitat fragmentation on visitation and seed set

Abstract: I analyse the effects of habitat fragmentation on the pollination success of a perennial, butterfly-pollinated, caryophyllaceous herb, the maiden pink, Dianthus deltoides L. The study was conducted in July 1986 and July 1987 at two different sites in southwest Sweden, an undisturbed “mainland” site and a fragmented site consisting of “habitat islands” within a heavily utilized agricultural area The fragmented area had a lower diversity and abundance of both flowering plants and flower-visiting insects. Dianthus flowers received fewer visits in the fragmented area than in the mainland area, and the seed set was much lower. Hand pollination increased seed set up to 4.1 times in the fragmented area, but no significant differences were found between hand-pollinated and control flowers at the mainland site. There were no differences between the two sites in standing crop of nectar, ovule number per flowers, or seed set of bagged flowers, band-pollinated flowers, and hand-pollinated fertilized flowers Thus, the difference in natural seed set between the two sites can be explained by differences in pollinator service. Resumen: Analize los efectos de fragmentacion de habitat sobre el exito de polinizacion de la hierba perenne, “caryophyllacedes, Dianthus deltoides L.” que es polinada por mariposas. Este estudio fue conducido en julio de 1986 y 1987 en dos diferentes lugares en el suroeste de Suecia, en un lugar pristino del continente y en un lugar fragmentado compuesto de “islas de habitat” dentro una area agricola summente utilizada. La area fragmentada tuvo una diversidad mas baja y una menor abunduncia de plantas florecentes y de insectos tipo visitantes de flores Las flores “Dianthus” recibieron menos visitas en las areas de habitat fragmentada que en la area del continente aun no modificado. La siembra tambien era mas baja. Polinizacion por mano aumento la siembra 4.1 veces mas en la area fragmentada, pero niguna diferencia significante fue encontrada entre las flores polinadas por mano y en el control en el lugar del continente. No bubo diferencias en cosechas paradas del nectar, numero de ovule por flor, o la siembra de flores de bolsas, flores polinadas por mano, y las flores fertilizadas y polinadas por mano, entre los dos lugares. Asi, la diferencia entre la siembra natural de los dos lugares puede ser explicado por las diferencias en el servicio de polinizacion.

Refined structure of human carbonic anhydrase II at 2.0 A resolution.

Abstract: The structure of human erythrocytic carbonic anhydrase II has been refined by constrained and restrained structure–factor least-squares refinement at 2.0 A resolution. The conventional crystallographic R value is 17.3%. Of 167 solvent molecules associated with the protein, four are buried and stabilize secondary structure elements. The zinc ion is ligated to three histidyl residues and one water molecule in a nearly tetrahedral geometry. In addition to the zinc-bound water, seven more water molecules are identified in the active site. Assuming that Glu-106 is deprotonated at pH 8.5, some of the hydrogen bond donor–acceptor relations in the active site can be assigned and are described here in detail. The Oγ1 atom of Thr-199 donates its proton to the Oe1 atom of Glu-106 and can function as a hydrogen bond acceptor only in additional hydrogen bonds.

The evolution of flowers with deep corolla tubes

Abstract: Some plants have evolved flowers of extraordinary depth, a phenomenon which puzzled Darwin1. Darwin suggested that the evolution of deep flowers could be a response to a kind of 'race' with pollinating insects: the length of the tongues of pollinating insects could increase as a result of a general size increase, or because it increased their nectar foraging efficiency. As this occurred, plants with relatively shallow flowers could be disadvantaged since pollen transfer, which is effected by physical contact between the pollinator and the anthers or stigma of the plant, could be reduced when the insect tongue is long relative to flower depth. This could lead to the evolution of increasing flower depth which in turn could drive the evolution of a further increase in insect tongue length. Various predictions of Darwin's proposal were tested here for orchid species with deep flowers that are pollinated by moths. It was found that insects do indeed insert their probosces no further than necessary to obtain nectar; that an experimental reduction in flower depth reduces both the male and female components of fitness; and that in natural populations there is a correlation between flower depth and female fitness measured by fruit set. These results all support Darwin's hypothesis to explain the evolution of flower depth.

Elevated CSF levels of substance P and high incidence of Raynaud phenomenon in patients with fibromyalgia: new features for diagnosis.

Abstract: In 30 patients with diagnosed fibromyalgia, the CSF level of immunoreactive substance P (SP) was investigated. Compared to normal values (9.6 +/- 3.2 fmol/ml), all the patients had elevated CSF levels of SP (36.1 +/- 2.7 fmol/ml, range 16.5-79.1 fmol/ml). Anamnestic information from the patients revealed that 53.3% had Raynaud/Raynaud-like phenomenon localized in the fingers, the toes or both. Although SP levels did not differ significantly in patients with or without the Raynaud phenomenon, elevated activity may be present in the peripheral branches of SP neurons which could be responsible for the last (rubor) phase of the triphasic Raynaud's phenomenon. SP levels were significantly higher in patients who were smokers (40.1 +/- 2.7 fmol/ml, range 25.3-64.1 fmol/ml), compared to patients who were non-smokers (29.2 +/- 5.0 fmol/ml, range 16.5-79.1 fmol/ml). We propose elevated CSF levels of SP and the Raynaud phenomenon as characteristic features for fibromyalgia with potential as diagnostic markers of the disease and further that smoking might be an aggravating factor for its pathogenesis or development.

Expression of the beta-nerve growth factor gene in hippocampal neurons

Abstract: In situ hybridization with complementary DNA probes for nerve growth factor (NGF) was used to identify cells containing NGF messenger RNA in rat and mouse brain. The most intense labeling occurred in hippocampus, where hybridizing neurons were found in the dentate gyrus and the pyramidal cell layer. The neuronal identity of NGF mRNA-containing cells was further assessed by a loss of NGF-hybridizing mRNA in hippocampal areas where neurons had been destroyed by kainic acid or colchicine. RNA blot analysis also revealed a considerable decrease in the level of NGF mRNA in rat dentate gyrus after a lesion was produced by colchicine. This lesion also caused a decrease in the level of Thy-1 mRNA and an increase in the level of glial fibrillary acidic protein mRNA. Neuronal death was thus associated with the disappearance of NGF mRNA. These results suggest a synthesis of NGF by neurons in the brain and imply that, in hippocampus, NGF influences NGF-sensitive neurons through neuron-to-neuron interactions.

Histopathological classification of nonantral gastric endocrine growths in man.

Abstract: Recently, the gastric endocrine system has been recognized as the origin of benign and malignant tumors in pernicious anemia. It has also been found that the gastric endocrine cells respond to permanent elevation of serum gastrin levels induced by changes in acid secretion in response to surgical procedures, drug therapy and age. Therefore, a definition of nonantral gastric endocrine hyperplasia (simple or diffuse, linear or chain-forming, micronodular, adenomatoid), dysplasia (enlarging or fusing micronodules, microinvasion, nodular growth) and neoplasia (intramucosal carcinoid, invasive carcinoid) is presented. The individual entities are illustrated, together with the literature discussed and the techniques for their identification presented.

Application of prazosin is associated with an increase of insulin sensitivity in obese patients with hypertension

Abstract: The aim of this study was to determine whether insulin sensitivity measured by the euglycaemic insulin clamp technique is lower in patients with primary hypertension than in matched healthy control subjects, and whether this sensitivity was affected after 12 weeks of antihypertensive treatment with the alpha 1-adrenoceptor blocking drug prazosin. Twelve moderately obese normoglycaemic patients (four men), with hypertension not previously treated with pharmacological agents and diastolic blood pressure above 100 mm Hg, and 12 healthy matched control subjects participated. Supine blood pressure decreased 12/5 mmHg (p<0.01) and standing blood pressure 14/9 mmHg (p=0.001) during prazosin treatment (mean dosage 5.3±1.6 mg/day (SD)). During euglycaemic insulin clamp studies the control subjects showed a higher mean glucose uptake than the untreated hypertensive patients (7.5±1.0 and 5.8±1.9 mg·kg b.w.−1·min−1, respectively, p<0.01). During prazosin treatment there was no significant difference between the hypertensive patients and the control subjects in this respect (6.6±2.8 and 7.5±1.0, respectively, p=0.21). During prazosin treatment, however, the disappearance rate of glucose decreased during the intravenous glucose tolerance test (from 1.7±0.9 to 1.3±0.6, p<0.02) and the area under the glucose concentration-time curve decreased by 38% (from 473±119 to 294±99, p<0.001). The peak insulin concentration decreased from 55±35 to 46±32 mU/l (p<0.006) and the area under the insulin concentration-time curve was suppressed by 38% (from 2368±1597 to 1479±940, p<0.01). This study shows that treatment of moderately obese hypertensive patients with prazosin is associated with an increase of the insulin-mediated glucose disposal and a decrease of the insulin response to an intravenous glucose load.

Uncoupling of Somatic and Otolith Growth Rates in Arctic Char (Salvelinus alpinus) as an Effect of Differences in Temperature Response

Abstract: Experiments were conducted to study the effect of temperature, fish size, and somatic growth rate on mean daily otolith growth rate in Arctic char (Salvelinus alpinus) fry fed maximum rations. Long...

Rat beta-nerve growth factor sequence and site of synthesis in the adult hippocampus.

Abstract: A rat b-nerve growth factor (NGF) genomic sequence encoding the entire 3′ exon of preproNGF was cloned, and its nucleotide sequence was determined. Rat NGF shows very high homology with other known NGFs in both the prepropeptide and the 3′ untranslated regions. The presumptive signal sequence, the cysteine residues important for tertiary structure, possible glycosylation sites, and dibasic amino acids required for proteolytic cleavage to mature NGF are conserved across species. Comparison of the hydrophobicity plots and amino acid sequences revealed an evolutionary divergent domain on the external surface of NGF, which may account for the poor immunologic crossreactivities of the various NGFs. In situ hydridization with a rat-specific oligodeoxynucleotide indicated high levels of NGF mRNA synthesis in both hippocampal granule and pyramidal cell layers. These results are consistent with one role for NGF in the CNS as a neuronally released, retrogradely transported neurotrophic factor for basal forebrain cholinergic neurons.

Risk factors for type 2 (non-insulin-dependent) diabetes mellitus. Thirteen and one-half years of follow-up of the participants in a study of Swedish men born in 1913

Abstract: This report presents data on antecedents of Type 2 (non-insulin-dependent) diabetes mellitus in a homogeneous sample of randomly selected 54-year-old men from an urban Swedish population with a diabetes incidence of 6.1% during 13.5 years of follow-up. The increased risk leading to diabetes for those in the top quintile compared to the lowest quintile of the distribution of statistically significant risk factors were: body mass index = 21.7, triglycerides = 13.5, waist-to-hip circumference ratio = 9.6, diastolic blood pressure = 6.7, uric acid = 5.8, glutamic pyruvic transaminase = 3.9, bilirubin = 3.2, blood glucose = 2.7, lactate = 2.4 and glutamic oxaloacetic transaminase = 2.0. Those with a positive family history of diabetes had 2.4-fold higher risk for developing diabetes than those without such a history. In a multivariate analysis glutamic pyruvic transaminase, blood glucose, body mass index, bilirubin, systolic blood pressure, uric acid and a family history of diabetes were all significantly associated with the development of diabetes. Our study demonstrates the great importance of adiposity and body fat distribution for the risk of diabetes. A number of established risk factors for coronary heart disease are risk factors for diabetes as well. Disturbed liver function and increased levels of lactate are early risk factors for diabetes - presumably indicators of the presence of impaired glucose tolerance and/or hyperinsulinaemia.

Pharmacokinetics and bioavailability of reduced and oxidized N-acetylcysteine.

Abstract: The pharmacokinetics and bioavailability of N-acetylcysteine (NAC) have been determined after its intravenous and oral administration to 6 healthy volunteers. According to a randomized cross-over design each subject received NAC 200 mg i.v. and 400 mg p.o., and blood samples were collected for 30 h. Reduced NAC had a volume of distribution (VSS) of 0.59 l.kg-1 and a plasma clearance of 0.84 l.h-1.kg-1. The terminal half-life after intravenous administration was 1.95 h. The oral bioavailability was 4.0%. Based on total NAC concentration, its volume of distribution (VSS) was 0.47 l.kg-1 and its plasma clearance was 0.11 l.h-1.kg-1. The terminal half-life was 5.58 h after intravenous administration and 6.25 h after oral administration. Oral bioavailability of total NAC was 9.1%.

Site-specific recombination promotes linkage between trimethoprim- and sulfonamide resistance genes. Sequence characterization of dhfrV and sulI and a recombination active locus of Tn21

Abstract: A new gene for trimethoprim resistance, dhfrV, found in several plasmid isolates with different characteristics, was sequenced and found to correspond to a peptide of 157 amino acids showing 75% similarity with the previously characterized, drug resistant dihydrofolate reductase of type I. The sequenced surroundings of dhfrV in plasmid pLMO20, were found to be almost identical with genetic areas surrounding resistance genes in transposon Tn21 and in R plasmid R388. The trimethoprim resistance genes of pLMO20 and R388 and the spectinomycin resistance gene of Tn21 could be regarded as having been inserted, by recombination, into an evolutionary older structure containg the sulfonamide resistance gene, sulI. The latter gene was sequenced and found to correspond to a peptide of 279 amino acids and with a molecular weight of 30126 daltons. The inserted genes were found to be governed by a promoter situated in the highly conserved structure and also controlling expression of sulI. The insertion points of the different resistance genes were precisely defined, and at the 3′ ends of the inserted genes inverted repeats allowing the formation of stem and loop structures were found. Similar structures were found at the 3′ ends of the antibiotic resistance genes in Tn7, which could indicate similar recombination mechanisms to be effective in the evolutionary construction of all these different resistance elements.

Bioavailability of different phosphorus forms in freshwater systems

Abstract: The recent literature on the bioavailability of different forms of P in freshwater systems is reviewed. Bioavailable P is defined as the sum of immediately available P and the P that can be transformed into an available form by naturally occurring processes. Methods used to estimate the bioavailable P pool, which vary between studies largely depending on the time perspective applied, are critically evaluated. Most studies on particulate P aim to determine the potentially available P pool. Potential bioavailability of particulate P is normally analysed in bioassays with algal yield determinations and the available P fraction is characterized from interpretations of results of sequential chemical extractions. NaOH-extractable P is in most studies the most algal-available P fraction. For soil samples and tributary water particulate matter, NaOH-P has often been found to be equal to algal extractable P. In other studies depletions of NaOH-P have accounted for the algal P uptake, but only a minor proportion of the fraction has been utilized. Organic P in lake water particulate matter and bed sediments of eutrophic lakes can also be algal-available to a significant extent.

July temperatures in europe from pollen data, 6000 years before present.

Abstract: Mean July temperatures across Europe 6000 years before present were reconstructed from palynological data by the transfer function method. Reconstructed summer temperatures were warmer than those at present over most of Europe with the greatest heating, more than 2°C, in the midcontinent and the far north. This pattern is explained by high summer insolation and a weak zonal insolation gradient 6000 years before present and the effective heating of the landmass relative to ocean and coastal areas. A strong land-sea pressure gradient may in turn have increased westerly air flow into southern Europe, which is consistent with cooler reconstructed summer temperatures in the Mediterranean region, and reduced the environmental lapse rate in the central European mountains.