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Göran Pettersson

Publications and source records attributed to Göran Pettersson.

9 recordsLinked to original sources
PubMed2005

3He MRI-based assessment of posture-dependent regional ventilation gradients in rats.

A recently developed method for quantitative assessment of regional lung ventilation was employed for the study of posture-dependent ventilation differences in rats. The measurement employed hyperpolarized (3)He MRI to detect the build-up of the signal intensity after increasing numbers of (3)He breaths, which allowed for computation of a regional ventilation parameter. A group of six anesthetized rats was studied in both supine and prone postures. Three-dimensional maps of the ventilation parameter were obtained with high spatial resolution (voxel volume approximately 2 mm(3)). Vertical (dorsal-ventral) gradients of the ventilation index, defined as the regional ventilation normalized by the average ventilation within the whole lung, were investigated. Variations in the regional distribution of the ventilation parameter, as well as of the ventilation index, could be detected, depending on the posture of the rats. In supine posture, ventilation was elevated in the dependent parts of the lungs, with a linear gradient of the ventilation index of -0.11 +/- 0.03 cm(-1). In prone posture, the distribution of ventilation was more uniform, with a significantly (P < 0.001) smaller gradient of the ventilation index of -0.01 +/- 0.02 cm(-1). It is concluded that the (3)He MRI-based method can detect and quantify regional ventilation gradients in animals as small as the rat and that these gradients depend on prone or supine posture of the animal.

Administration, Inhalation↗
PubMed2004

Inhibition of the Trichoderma reesei cellulases by cellobiose is strongly dependent on the nature of the substrate.

The inhibition effect of cellobiose on the initial stage of hydrolysis when cellobiohydrolase Cel 7A and endoglucanases Cel 7B, Cel 5A, and Cel 12A from Trichoderma reesei were acting on bacterial cellulose and amorphous cellulose that were [(3)H]- labeled at the reducing end was quantified. The apparent competitive inhibition constant (K(i)) for Cel 7A on [(3)H]-bacterial cellulose was found to be 1.6 +/- 0.5 mM, 100-fold higher than that for Cel 7A acting on low-molecular-weight model substrates. The hydrolysis of [(3)H]-amorphous cellulose by endoglucanases was even less affected by cellobiose inhibition with apparent K(i) values of 11 +/- 3 mM and 34 +/- 6 mM for Cel 7B and Cel 5A, respectively. Contrary to the case for the other enzymes studied, the release of radioactive label by Cel 12A was stimulated by cellobiose, possibly due to a more pronounced transglycosylating activity. Theoretical analysis of the inhibition of Cel 7A by cellobiose predicted an inhibition analogous to that of mixed type with two limiting cases, competitive inhibition if the prevalent enzyme-substrate complex without inhibitor is productive and conventional mixed type when the prevalent enzyme-substrate complex is nonproductive.

Acetobacterium↗
PubMed2003

Synergistic cellulose hydrolysis can be described in terms of fractal-like kinetics.

A fractal-like kinetics model was used to describe the synergistic hydrolysis of bacterial cellulose by Trichoderma reesei cellulases. The synergistic action of intact cellobiohydrolase Cel7A and endoglucanase Cel5A at low enzyme-to-substrate ratios showed an apparent substrate inhibition consistent with a case where two-dimensional (2-D) surface diffusion of the cellobiohydrolase is rate-limiting. The action of Cel7A core and Cel5A was instead consistent with a three-dimensional (3-D) diffusion-based mode of action. The synergistic action of intact Cel7A was far superior to that of the core at a high enzyme-to-substrate ratio, but this effect was gradually reduced at lower enzyme-to-substrate ratios. The apparent fractal kinetics exponent h obtained by nonlinear fit of hydrolysis data to the fractal-like kinetics analogue of a first-order reaction was a useful empirical parameter for assessing the rate retardation and its dependence on the reaction conditions.

Cellobiose↗
PubMed2002

Cellobiose quinone oxidoreductase from the white rot fungus Phanerochaete chrysosporium is produced by intracellular proteolysis of cellobiose dehydrogenase.

The fungus Phanerochaete chrysosporium was grown in a 10-l automatic fermenter using cellobiose as carbon source to monitor the induction of cellobiose dehydrogenase (CDH) and cellobiose quinone oxidoreductase (CBQ) enzymes, and to search for tentative cbq and cdh genes and their transcriptional products. After 24 h of induction, CDH was detected in the culture supernatant and a protein was recognized by a specific anti-CDH polyclonal antibody in the sonicated biomass. Northern blot experiments performed with several fungal RNA samples showed, after 24 h of induction, only one single species of an mRNA transcript corresponding in size to the cdh gene (2.5 kb) The relative amount of this transcript decreased as a function of time. Southern blot experiments done with genomic DNA and database search in the recently available genome information also ruled out the presence in this strain of a separate cbq gene distinct from the cdh gene. Taken together, these results demonstrated that CBQ originates from the cdh gene. Furthermore, it is not produced by differential splicing but by a posttranslational, predominantly intracellular, proteolytic cleavage.

Alleles↗
PubMed2002

Crystal structure of the flavoprotein domain of the extracellular flavocytochrome cellobiose dehydrogenase.

Cellobiose dehydrogenase (CDH) participates in the degradation of cellulose and lignin. The protein is an extracellular flavocytochrome with a b-type cytochrome domain (CYT(cdh)) connected to a flavodehydrogenase domain (DH(cdh)). DH(cdh) catalyses a two-electron oxidation at the anomeric C1 position of cellobiose to yield cellobiono-1,5-lactone, and the electrons are subsequently transferred from DH(cdh) to an acceptor, either directly or via CYT(cdh). Here, we describe the crystal structure of Phanerochaete chrysosporium DH(cdh) determined at 1.5 A resolution. DH(cdh) belongs to the GMC family of oxidoreductases, which includes glucose oxidase (GOX) and cholesterol oxidase (COX); however, the sequence identity with members of the family is low. The overall fold of DH(cdh) is p-hydroxybenzoate hydroxylase-like and is similar to, but also different from, that of GOX and COX. It is partitioned into an FAD-binding subdomain of alpha/beta type and a substrate-binding subdomain consisting of a seven-stranded beta sheet and six helices. Docking of CYT(cdh) and DH(cdh) suggests that CYT(cdh) covers the active-site entrance in DH(cdh), and that the resulting distance between the cofactors is within acceptable limits for inter-domain electron transfer. Based on docking of the substrate, cellobiose, in the active site of DH(cdh), we propose that the enzyme discriminates against glucose by favouring interaction with the non-reducing end of cellobiose.

Amino Acid Sequence↗
PubMed2002

Quantitative measurement of regional lung ventilation using 3He MRI.

A new strategy for a quantitative measurement of regional pulmonary ventilation using hyperpolarized helium-3 (3He) MRI has been developed. The method employs the build-up of the signal intensity after a variable number of (3)He breaths. A mathematical model of the signal dynamics is presented, from which the local ventilation, defined as the fraction of gas exchanged per breath within a given volume, is calculated. The model was used to create ventilation maps of coronal slices of guinea pig lungs. Ventilation values very close to 1 were found in the trachea and the major airways. In the lung parenchyma, regions adjacent to the hilum showed values of 0.6-0.8, whereas 0.2-0.4 was measured in peripheral regions. Monte Carlo simulations were used to investigate the accuracy of the method and its limitations. The simulations revealed that, at presently attainable signal-to-noise ratios, the ventilation parameter can be determined with a relative uncertainty of <5% over a wide range of values.

Animals↗
PubMed2002

13C-angiography.

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Animals↗