MECHANISTIC ASPECTS OF UPTAKE AND SINUSOIDAL EFFLUX OF DIBROMOSULFOPHTHALEIN IN THE ISOLATED PERFUSED-RAT-LIVER

Using the isolated perfused rat liver technique we examined whether the accumulation and sinusoidal efflux processes of the organic anion dibromosulfophthalein (DBSP) are dependent on the intracellular ATP content, chloride concentration in the perfusion medium as well as temperature of the medium and whether they are mediated by the same or by separate carrier mechanisms. The net sinusoidal efflux rate, being the resultant of sinusoidal efflux and re-uptake, was decreased more than 50% after lowering the medium temperature from 37 to 26-degrees indicating that the efflux process is carrier-mediated. The uptake rate was decreased only 18% after lowering the medium temperature to 26-degrees. Lowering of the hepatic ATP content for more than 80% clearly decreased the DBSP uptake rate but not the sinusoidal efflux rate. These observations indicate that these opposing transport steps probably are mediated by two separate carriers. Additional evidence for this hypothesis originated from the observation that sinusoidal efflux of DBSP was decreased about 30% whereas hepatic uptake of the substrate remained unaltered after replacing chloride in the perfusion medium with gluconate. In summary, we conclude that uptake and sinusoidal efflux of DBSP are mediated by two separate carrier systems that are influenced differently by ATP depletion, temperature lowering and presence of Cl- gradients.</p

The sinusoidal efflux of dibromosulfophthalein from rat liver is stimulated by albumin, ligandin and fatty acid binding protein but not by other dibromosulfophthalein binding proteins

Organic anions can be excreted from the liver into the bile or back into the general circulation (sinusoidal efflux). It has previously been shown that the net sinusoidal efflux rate of dibromosulfophthalein from the perfused liver into the perfusate is the result of actual efflux from and reuptake into the liver, and can be strongly influenced by the presence of bovine serum albumin in the perfusion medium. The present study investigated whether the influence of albumin on the net sinusoidal efflux process is albumin-specific or whether other binding proteins could have a similar effect on the sinusoidal efflux. Using a single-pass liver perfusion technique and short-lasting (pulse) protein infusions, the stimulatory effect of a wide range of dibromosulfophthalein binding proteins on the sinusoidal efflux process were determined. These experiments showed that all the serum albumins tested as well as the liver cytosolic binding proteins fatty acid binding protein and ligandin (glutathione S-transferase) stimulated this process. The other proteins tested, bovine beta lactoglobulin-b, human gamma globulin and chicken egg lysozyme showed no stimulatory effect, despite relatively high equilibrium binding of dibromosulfophthalein. No clear-cut relationship was found between the equilibrium unbound ligand concentration as measured in perfusate and the stimulatory effect, suggesting absence of equilibrium binding in the sinusoids. Equilibrium binding of dibromosulfophthalein to chicken serum albumin and ligandin as well as the dissociation rate constants were determined in vitro with rapid filtration techniques. Pharmacokinetic modeling using a series compartment model showed that the stimulatory effect of these proteins could only be simulated accurately with higher values for both the association and dissociation rate constants compared with those determined in vitro, as was previously also found for bovine serum albumin. This may imply altered binding characteristics of the proteins during passage through the liver and/or a direct effect on the carrier-mediated efflux process. (C) Journal of Hepatology

Speech, Language and Communicative Ability in School-Aged Children with Cerebral Palsy and Speech Impairment

Abstract: The overall aim of this thesis was to explore and describe speech, language and communicative ability in school-aged children with cerebral palsy (CP) and speech impairment. The medical records of a population-based cohort of 129 children with CP born 1999–2002 in western Sweden were reviewed. Type of CP, motor functions and neuroimaging findings were analysed. Twenty-seven (21%) of the 129 children had speech impairment. Twenty-two (82%) of the 27 children took part in an assessment of speech, language, and communication skills. Consonant production, dysarthria, hypernasality and oral narratives were assessed. The children’s, the parents’, the teachers’ and the SLP’s opinions about the children’s communicative ability were also analysed. More than half of the children had severe problems with articulation of oral consonants. Speech production and non-verbal cognitive level correlated significantly and severe retelling ability problems occurred. Language ability and auditory memory correlated significantly with retelling ability. The children were mostly positive about their own communication. Parents and teachers rated them as having marked general communicative impairments. Parents’ and SLP’s ratings correlated significantly, whereas the parents and the teachers ratings did not. A comprehensive speech, language and communication test battery in which standardised tests are included is suggested for children with CP and speech impairment. The children’s own opinions and those of the key persons around them are also important to consider when planning intervention

The crystal structure of a hyperthermoactive exopolygalacturonase from Thermotoga maritima reveals a unique tetramer

The exopolygalacturonase from Thermotoga maritima is the most thermoactive and thermostable pectinase known to date. Here we present its crystal structure at 2.05A resolution. High structural homology around the active site allowed us to propose a model for substrate binding, explaining the exo-cleavage activity and specificity for non-methylated saturated galacturonate at the non-reducing end. Furthermore, the structure reveals unique features that contribute to the formation of stable tetramers in solution. Such an oligomerization has not been observed before for polygalacturonase