Fatty acid binding protein is a major determinant of hepatic pharmacokinetics of palmitate and its metabolites

Disposition kinetics of [H-3] palmitate and its low-molecular-weight metabolites in perfused rat livers were studied using the multiple-indicator dilution technique, a selective assay for [H-3] palmitate and its low-molecular-weight metabolites, and several physiologically based pharmacokinetic models. The level of liver fatty acid binding protein (L-FABP), other intrahepatic binding proteins (microsomal protein, albumin, and glutathione S-transferase) and the outflow profiles of [H-3] palmitate and metabolites were measured in four experimentalgroups of rats: 1) males; 2) clofibrate-treated males; 3) females; and 4) pregnant females. A slow-diffusion/bound model was found to better describe the hepatic disposition of unchanged [H-3] palmitate than other pharmacokinetic models. The L-FABP levels followed the order: pregnant female > clofibrate-treated male > female > male. Levels of other intrahepatic proteins did not differ significantly. The hepatic extraction ratio and mean transit time for unchanged palmitate, as well as the production of low-molecular-weight metabolites of palmitate and their retention in the liver, increased with increasing L-FABP levels. Palmitate metabolic clearance, permeability-surface area product, retention of palmitate by the liver, and cytoplasmic diffusion constant for unchanged [H-3] palmitate also increased with increasing L-FABP levels. It is concluded that the variability in hepatic pharmacokinetics of unchanged [H-3] palmitate and its low-molecular-weight metabolites in perfused rat livers is related to levels of L-FABP and not those of other intrahepatic proteins.

Hepatic pharmacokinetics of taurocholate in the normal and cholestatic rat liver

1 The disposition kinetics of [H-3] taurocholate ([H-3]TC) in perfused normal and cholestatic rat livers were studied using the multiple indicator dilution technique and several physiologically based pharmacokinetic models. 2 The serum biochemistry levels, the outflow profiles and biliary recovery of [H-3] TC were measured in three experimental groups: (i) control; (ii) 17α-ethynylestradiol (EE)-treated (low dose); and (iii) EE-treated (high dose) rats. EE treatment caused cholestasis in a dose-dependent manner. 3 A hepatobiliary TC transport model, which recognizes capillary mixing, active cellular uptake, and active efflux into bile and plasma described the disposition of [H-3]TC in the normal and cholestatic livers better than the other pharmacokinetic models. 4 An estimated five- and 18-fold decrease in biliary elimination rate constant, 1.7- and 2.7-fold increase in hepatocyte to plasma efflux rate constant, and 1.8- and 2.8-fold decrease in [H-3]TC biliary recovery ratio was found in moderate and severe cholestasis, respectively, relative to normal. 5 There were good correlations between the predicted and observed pharmacokinetic parameters of [H-3]TC based on liver pathophysiology (e.g. serum bilirubin level and biliary excretion of [H-3]TC). In conclusion, these results show that altered hepatic TC pharmacokinetics in cholestatic rat livers can be correlated with the relevant changes in liver pathophysiology in cholestasis.

Reduced hepatic extraction of palmitate in steatosis correlated to lower level of liver fatty acid binding protein

Nonalcoholic fatty liver disease is the most common of all liver diseases. The hepatic disposition [H-3]palmitate and its low-molecular-weight metabolites in perfused normal and steatotic rat liver were studied using the multiple indicator dilution technique and a physiologically based slow diffusion/bound pharmacokinetic model. The steatotic rat model was established by administration of 17alpha-ethynylestradiol to female Wistar rats. Serum biochemistry markers and histology of treated and normal animals were assessed and indicated the presence of steatosis in the treatment group. The steatotic group showed a significantly higher alanine aminotransferase-to-aspartate aminotransferase ratio, lower levels of liver fatty acid binding protein and cytochrome P-450, as well as microvesicular steatosis with an enlargement of sinusoidal space. Hepatic extraction for unchanged [H-3]palmitate and production of low-molecular-weight metabolites were found to be significantly decreased in steatotic animals. Pharmacokinetic analysis suggested that the reduced extraction and sequestration for palmitate and its metabolites was mainly attributed to a reduction in liver fatty acid binding protein in steatosis.

Assessing the cellular transmembrane electrical potential difference on the hepatic uptake of palmitate

Understanding the driving forces for the hepatic uptake of endogenous and exogenous substrates in isolated cells and organs is fundamental to describing the underlying hepatic physiology/pharmacology. In this study we investigated whether uptake of plasma protein-bound [H-3]-palmitate across the hepatocyte wall is governed by the transmembrane electrical potential difference (PD). Uptake was studied in isolated hepatocytes and isolated perfused rat livers (IPL). Protein-binding and vasoactive properties of the different perfusates were determined using in vitro heptane/buffer partitioning studies and the multiple indicator dilution (MID) technique in the IPL, respectively. Altering hepatocyte PD by perfusate ion substitution resulted in either a substantial depolarization (-14 +/- 1 mV, n = 12, mean +/- S.E., substituting choline for Na+) or hyperpolarization (-46 +/- 3 mV, n = 12, mean +/- S.E., substituting nitrate for Cl-). Perfusate ion substitution also affected the equilibrium binding constant for the palmitate-albumin complex. IPL studies suggested that, other than with gluconate buffer, hepatic [H-3]-palmitate extraction was not affected by the buffer used, implying PD was not a determinant of extraction. [H-3]-Palmitate extraction was much lower (p < 0.05) when gluconate was substituted for Cl- ion. This work contrasts with that for the extraction of [H-3]-alanine where hepatic extraction fraction was significantly reduced during depolarization. Changing the albumin concentration did not affect hepatocyte PD, and [H-3]-palmitate clearance into isolated hepatocytes was not affected by the buffers used. MID studies with vascular and extravascular references revealed that, with the gluconate substituted buffer, the extravascular volume possibly increased the diffusional path length thus explaining reduced [H-3]-palmitate extraction fraction in the IPL.

Hepatic pharmacokinetics of propranolol in rats with adjuvant-induced systemic inflammation

Systemic inflammation is known to affect drug disposition in the liver. This study sought to relate and quantitate changes in hepatic pharmacokinetics of propranolol with changes in hepatic architecture and physiology in adjuvant-treated rats. Transmission electron microscopy was used to assess morphological changes in mitochondria and lysosomes of adjuvant-treated rat livers. The disposition of propranolol was assessed in the perfused rat liver using the multiple indicator dilution technique. Hepatic extraction and mean transit time were determined from outflow-concentration profiles using a nonparametric method. Kinetic parameters were derived from a two-phase physiologically based organ pharmacokinetic model. Possible relationships were then explored between the changes in hepatic drug disposition and cytochrome P-450 activity and iron concentration. Adjuvant treatment induced the appearance of mitochondrial inclusions/tubularization and irregularly shaped lysosomes in rat livers. Livers from adjuvant-treated rats had (relative to normal) significantly higher alpha(1)-acid glycoprotein (orosomucoid) and iron tissue concentrations but lower cytochrome P-450 content. The hepatic extraction, metabolism, and ion trapping of propranolol were significantly impaired in adjuvant-treated rats and could be correlated with altered iron store and cytochrome P-450 activity. It is concluded that adjuvant-induced systemic inflammation alters hepatocellular morphology and biochemistry and consequently influences hepatic disposition of propranolol.

Osmolarity effects on observed insect cell size after baculovirus infection are avoided using growth medium for sample dilution

Rates of cell size increase are an important measure of success during the baculovirus infection process. Batch and fed batch cultures sustain large fluctuations in osmolarity that can affect the measured cell volume if this parameter is not considered during the sizing protocol. Where osmolarity differences between the sizing diluent and the culture broth exist, biased measurements of size are obtained as a result of the cell osmometer response. Spodoptera frugiperda (Sf9) cells are highly sensitive to volume change when subjected to a change in osmolarity. Use of the modified protocol with culture supernatants for sample dilution prior to sizing removed the observed error during measurement.

Adolescents' perceptions of social status: Development and evaluation of a new indicator

Objective. Eliminating health disparities, including those that are a result of socioeconomic status (SES), is one of the overarching goals of Healthy People 2010. This article reports on the development of a new, adolescent-specific measure of subjective social status (SSS) and on initial exploratory analyses of the relationship of SSS to adolescents' physical and psychological health. Methods. A cross-sectional study of 10 843 adolescents and a subsample of 166 paired adolescent/mother dyads who participated in the Growing Up Today Study was conducted. The newly developed MacArthur Scale of Subjective Social Status (10-point scale) was used to measure SSS. Paternal education was the measure of SES. Indicators of psychological and physical health included depressive symptoms and obesity, respectively. Linear regression analyses determined the association of SSS to depressive symptoms, and logistic regression determined the association of SSS to overweight and obesity, controlling for sociodemographic factors and SES. Results. Mean society ladder ranking, a subjective measure of SES, was 7.2 ± 1.3. Mean community ladder ranking, a measure of perceived placement in the school community, was 7.6 ± 1.7. Reliability of the instrument was excellent: the intraclass correlation coefficient was 0.73 for the society ladder and 0.79 for the community ladder. Adolescents had higher society ladder rankings than their mothers (µteen = 7.2 ± 1.3 vs µmom = 6.8 ± 1.2; P = .002). Older adolescents' perceptions of familial placement in society were more closely correlated with maternal subjective perceptions of placement than those of younger adolescents (Spearman's rhoteens

Mapping glider habitat in dry eucalypt forests for Montreal Process indicator 1.1: Fragmentation of forest types

Accurate habitat mapping is critical to landscape ecological studies such as required for developing and testing Montreal Process indicator 1.1e, fragmentation of forest types. This task poses a major challenge to remote sensing, especially in mixedspecies, variable-age forests such as dry eucalypt forests of subtropical eastern Australia. In this paper, we apply an innovative approach that uses a small section of one-metre resolution airborne data to calibrate a moderate spatial resolution model (30 m resolution; scale 1:50 000) based on Landsat Thematic Mapper data to estimate canopy structural properties in St Marys State Forest, near Maryborough, south-eastern Queensland. The approach applies an image-processing model that assumes each image pixel is significantly larger than individual tree crowns and gaps to estimate crown-cover percentage, stem density and mean crown diameter. These parameters were classified into three discrete habitat classes to match the ecology of four exudivorous arboreal species (yellowbellied glider Petaurus australis, sugar glider P. breviceps, squirrel glider P. norfolcensis , and feathertail glider Acrobates pygmaeus), and one folivorous arboreal marsupial, the greater glider Petauroides volans. These species were targeted due to the known ecological preference for old trees with hollows, and differences in their home range requirements. The overall mapping accuracy, visually assessed against transects (n = 93) interpreted from a digital orthophoto and validated in the field, was 79% (KHAT statistic = 0.72). The KHAT statistic serves as an indicator of the extent that the percentage correct values of the error matrix are due to ‘true’ agreement verses ‘chance’ agreement. This means that we are able to reliably report on the effect of habitat loss on target species, especially those with a large home range size (e.g. yellow-bellied glider). However, the classified habitat map failed to accurately capture the spatial patterning (e.g. patch size and shape) of stands with a trace or sub-dominance of senescent trees. This outcome makes the reporting of the effects of habitat fragmentation more problematic, especially for species with a small home range size (e.g. feathertail glider). With further model refinement and validation, however, this moderateresolution approach offers an important, cost eff e c t i v e advancement in mapping the age of dry eucalypt forests in the region.

Lysine requirements of pre-lay broiler breeder pullets: Determination by indicator amino acid oxidation

The indicator amino acid oxidation (IAAO) method allows the determination of amino acid requirements under conditions of low growth rate as found in pre-laying broiler breeder pullets. Cobb 500 breeder pullets (20 wk old; 2290 +/- 280 g, n = 4) were adapted (6 d) to a pelleted, purified control diet containing all nutrients at greater than or equal to 110% of NRC recommendations. After recovery from surgery for implantation of a jugular catheter, each bird was fed, in random order, test diets containing one of nine levels of lysine (0.48, 0.96, 1.92, 2.88, 3.84, 4.80, 7.68, 9.60 and 14.40 g/kg of diet). Indicator oxidation was determined during 4-h primed (74 kBq/kg body), constant infusions (44 kBq (.) h(-1) (.) kg body(-1)) of L-[1-C-14]phenylalanine. Using the breakpoint of a one-slope broken-line model, the lysine requirement was determined to be 4.88 +/- 0.96 g/kg of diet or 366 +/- 72 mg (.) hen(-1) (.) d(-1) with an upper 95% Cl of 6.40 g/kg of diet or 480 mg (.) hen(-1) (.) d(-1). IAAO allows determination of individual bird amino acid requirements for specific ages and types of birds over short periods of time and enables more accurate broiler breeder pullet diet formulation.

The effect of adsorption, filter material and point of dilution on antibiotic elimination by haemofiltration - An in vitro study of levofloxacin

We studied an in vitro model of continuous venous-venous haemofiltration (CVVH), into which levofloxacin 100 mg was infused, to determine levofloxacin adsorption and to determine the effect of filter material and point of dilution (pre- or post-filter) on sieving coefficient. Mean (standard deviation; S.D.) adsorption was 18.7 (5.3) mg for the polyamide filter and 40.2 (2.0) mg for the polyacrylonitrile (PAN) filter (P < 0.001). Post-dilution resulted in a minor, but statistically significant, decrease in sieving coefficient (pre-dilution 0.96 (S.D. 0.10), post-dilution 0.88 (S.D. 0.11) with the PAN filter. These data indicate that the variability in published values for levofloxacin sieving coefficient are not due to variation in point of dilution or membrane type (PAN or polyamide). Significant adsorption of levofloxacin onto PAN filters occurs. (C) 2004 Elsevier B.V. and the International Society of Chemotherapy. All rights reserved.

The jigsaw sign. A reliable indicator of congenital aetiology in os odontoideum

There is evidence in the literature for both a congenital and a post-traumatic aetiology for os odontoideum. In no series published to date has CT been used to aid in the diagnosis. This is a prospective study of the history of trauma and presence of diagnostic features on CT of 18 consecutive cases with os odontoideum. Our objective was to derive clinically useful radiological features enabling accurate differentiation between congenital and post-traumatic aetiologies. A mid-sagittal CT reconstruction of the atlanto-dens joint was obtained. Hypertrophy of the anterior arch of the atlas was quantified by measurement of the arch-peg-area ratio. The presence of dysplastic features (a positive jigsaw sign) of the atlanto-axial joint were noted. These included narrowing of the cartilage space and interdigitation of the two joint surfaces. A history of a potential traumatic aetiology was only obtained in one of the 18 (6%) in our series. A significant elevation of the arch-peg ratio was found when comparing this series to 85 controls. And a positive jigsaw sign was observed in 75% of cases. These features were not seen in paediatric cases of atlanto-axial instability, including odontoid non-union. In conclusion, an elevated arch-peg ratio and the presence of a jigsaw sign are sensitive and specific diagnostic criteria for os odontoideum. This series supports a congenital aetiology for this condition.