Assessing alternative models of individualism and collectivism: A confirmatory factor analysis

Six alternative structural models of individualism-collectivism are reviewed and empirically compared in a confirmatory factor analysis of questionnaire data from an Australian student sample (N=340). Central to the debate about the structure of this broad social attitude are the issues of (I) polarity (are individualism and collectivism bipolar opposites, or orthogonal factors?) and (2) dimensionality (are individualism and collectivism themselves higher-order constructs subsuming several more specific factors and, if so, what are they?). The data from this Australian sample support a model that represents individualism and collectivism as a higher-order bipolar factor hierarchically subsuming several bipolar reference-group-specific individualisms and collectivisms. Copyright (C) 2001 John Wiley & Sons, Ltd.

Glycosphingolipids modulate renal phosphate transport in potassium deficiency

Background. Potassium (K) deficiency (KD) and/or hypokalemia have been associated with disturbances of phosphate metabolism The purpose of the present study was to determine the cellular mechanisms that mediate the impairment of renal proximal tubular Na/Pi cotransport in a model of K deficiency in the rat. Methods. K deficiency in the rat was achieved by feeding rats a K-deficient diet for seven days. which resulted in a marked decrease in serum and tissue K content. Results. K deficiency resulted in a marked increase in urinary Pi excretion and a decrease in the V-max of brush-border membrane (BBM) Na/Pi cotransport activity (1943 95 in control vs. 1183 +/- 99 pmol/5 sec/mg BBM protein in K deficiency. P < 0.02). Surprisingly. the decrease in Na/Pi cotransport activity was associated with increases in the abundance of type I (NaPi-1). and type II (NaPi-2) and type III (Glvr-1) Na/Pi protein. The decrease in Na/Pi transport was associated with significant alterations in BBM lipid composition, including increases in sphingomyelin. glucosylceramide. and ganglioside GM, content and a decrease in BBM lipid fluidity. Inhibition of glucosylceramide synthesis resulted in increases in BBM Na/Pi cotransport activity in control and K-deficient rats. The resultant Na/Pi cotransport activity in K-deficit nt rats was the same as in control rats (1148 +/- 52 in control + PDMP vs. 11.52 +/- 61 pmol/5 sec/mg BBM protein in K deficiency + PDMP). These changes in transport activity occurred independent of further changes in BBM NaPi-2 protein or renal cortical NaPi-2 mRNA abundance. Conclusion. K deficiency in the rat causes inhibition of renal Na/Pi cotransport activity by post-translational mechanisms that are mediated in part through alterations in glucosylceramide content and membrane lipid dynamics.

Differential perturbation of neuronal and glial glutamate transport systems in retinal ischaemia

Glutamate is the major excitatory neurotransmitter in the retina and is removed from the extracellular space by an energy-dependent process involving neuronal and glial cell transporters. The radial glial Muller cells express the glutamate transporter, GLAST, and preferentially accumulate glutamate. However, during an ischaemic episode, extracellular glutamate concentrations may rise to excitotoxic levels. Is this catastrophic rise in extracellular glutamate due to a failure of GLAST? Using immunocytochemistry, we monitored the transport of the glutamate transporter substrate, D-aspartate, in the retina under normal and ischaemic conditions. Two models of compromised retinal perfusion were compared: (1) Anaesthetised rats had their carotid arteries occluded for 7 days to produce a chronic reduction in retinal blood flow. Retinal function was assessed by electroretinography. D-aspartate was injected into the eye for 45 min, Following euthanasia, the retina was processed for D-aspartate. GLAST and glutamate immunocytochemistry. Although reduced retinal perfusion suppresses the electroretinogram b-wave, neither retinal histology, GLAST expression, nor the ability of Muller cells to uptake D-aspartate is affected. As this insult does not appear to cause excitotoxic neuronal damage, these data suggest that GLAST function and glutamate clearance are maintained during periods of reduced retinal perfusion. (2) Occlusion of the central retinal artery for 60 min abolishes retinal perfusion, inducing histological damage and electroretinogram suppression. Although GLAST expression appears to be normal. its ability to transport D-aspartate into Muller cells is greatly reduced. Interestingly, D-aspartate is transported into neuronal cells, i.e. photoreceptors, bipolar and ganglion cells. This suggests that while GLAST is vitally important for the clearance of excess extracellular glutamate, its capability to sustain inward transport is particularly susceptible to an acute ischaemic attack. Manipulation of GLAST function could alleviate the degeneration and blindness that result from ischaemic retinal disease. (C) 2001 Elsevier Science Ltd, All rights reserved.

Human GC-AG alternative intron isoforms with weak donor sites show enhanced consensus at acceptor exon positions

It has been previously observed that the intrinsically weak variant GC donor sites, in order to be recognized by the U2-type spliceosome, possess strong consensus sequences maximized for base pair formation with U1 and U5/U6 snRNAs. However, variability in signal strength is a fundamental mechanism for splice site selection in alternative splicing. Here we report human alternative GC-AG introns (for the first time from any species), and show that while constitutive GC-AG introns do possess strong signals at their donor sites, a large subset of alternative GC-AG introns possess weak consensus sequences at their donor sites. Surprisingly, this subset of alternative isoforms shows strong consensus at acceptor exon positions 1 and 2. The improved consensus at the acceptor exon can facilitate a strong interaction with U5 snRNA, which tethers the two exons for ligation during the second step of splicing. Further, these isoforms nearly always possess alternative acceptor sites and always possess alternative acceptor sites and exhibit particularly weak polypyrimidine tracts characteristic of AG-dependent introns. The acceptor exon nucleotides are part of the consensus required for the U2AF(35)-mediated recognition of AG in such introns. Such improved consensus at acceptor exons is not found in either normal or alternative GT-AG introns having weak donor sites or weak polypyrimidine,tracts. The changes probably reflect mechanisms that allow GC-AG alternative intron isoforms to cope with two conflicting requirements, namely an apparent need for differential splice strength to direct the choice of alternative sites and a need for improved donor signals to compensate for the central mismatch base pair (C-A) in the RNA duplex of U1 snRNA and the pre-mRNA. The other important findings include (i) one in every twenty alternative introns is a GC-AG intron, and (ii) three of every five observed GC-AG introns are alternative isoforms.

Post-transcriptional regulation of the GLI1 oncogene by the expression of alternative 5 ' untranslated regions

The oncogene GLI1 is involved in the formation of basal cell carcinoma and other tumor types as a result of the aberrant signaling of the Sonic hedgehog-Patched pathway. In this study, we have identified alternative GLI1 transcripts that differ in their 5' untranslated regions (UTRs) and are generated by exon skipping. These are denoted (alpha -UTR, beta -UTR, and gamma -UTR according to the number of noncoding exons possessed (three, two, and one, respectively). The alpha- and beta -UTR forms represent the major Gli1 transcripts expressed in mouse tissues, whereas the gamma -UTR is present at relatively low levels but is markedly induced in mouse skin treated with 12-O-tetradecanoylphorbol 13-acetate, Transcripts corresponding to the murine beta and gamma forms were identified in human tissues, but significantly, only the gamma -UTR form was present in basal cell carcinomas and in proliferating cultures of a keratinocyte cell line. Flow cytometry analysis determined that the gamma -UTR variant expresses a heterologous reporter gene 14-23-fold higher than the alpha -UTR and 5-13-fold higher than the beta -UTR in a variety of cell types. Because expression of the gamma -UTR variant correlates with proliferation, consistent with a role for GLI1 in growth promotion, up-regulation of GLI1 expression through skipping of 5' noncoding exons may be an important tumorigenic mechanism.

Rearrangement of diflunisal acyl glucuronide into its beta-glucuronidase-resistant isomers facilitates transport through the small intestine to the colon of the rat

Many non-steroidal anti-inflammatory drugs (NSAIDs) which form acyl glucuronide conjugates as major metabolites have shown an antiproliferative effect on colorectal tumors. This study assesses the extent to which rearrangement of an acyl glucuronide metabolite of a model NSAID into beta -glucuronidase-resistant isomers facilitates its passage through the small intestine to reach the colon. Rats were dosed orally with diflunisal (DF), its acyl glucuronide (DAG) and a mixture of rearrangement isomers (iso-DAG) at 10 mg DF equivalents/kg. The parent drug DF appeared in plasma after all doses, with maximum concentrations of 20.5 +/- 2.5, 28.8 +/- 8.3 and 11.0 +/- 1.6 mug DF/ml respectively, obtained at 3.8 +/- 0.3, 3.6 +/- 1.8 and 7.5 +/- 0.9 hr after the DF, DAG and iso-DAG doses respectively. At 48 hr, 16.2 +/- 3.3, 19.8 +/- 0.8 and 42.9 +/- 10.1% of the doses respectively were recovered in feces, with less than or equal to 1% remaining in the intestine. About half of each dose was recovered as DF and metabolites in 48 hr urine: for DF and DAG doses, the majority was in the first 24 hr urine. whereas for iso-DAG doses, recoveries in the first and second 24 hr periods were similar. The results show that hydrolysis of both DAG and iso-DAG, and absorption of liberated DF, occur during passage through the gut, but that these processes occur more slowly and to a lesser degree for iso-DAG. The intrinsic hydrolytic capacities of various intestinal segments (including contents) towards DAG and iso-DAG were obtained by incubating homogenates under saturating concentrations of DAG/iso-DAG at 37 degreesC. Upper small intestine, lower small intestine, caecum and colon released 2400, 3200, 9200 and 22800 mug DF/hr/g tissue plus contents respectively from DAG substrate, and 18, 10, 140 and 120 mug DF/hr/g tissue plus contents respectively from iso-DAG substrate. The much greater resistance of iso-DAG to hydrolysis appears attributable to its resistance to beta -glucuronidases. The data suggest that in rats dosed with DF, DAG excreted in bile would be substantially hydrolysed in the small intestine and liberated DF reabsorbed, but that portion which rearranges to iso-DAG would likely reach the colon. (C) 2001 Elsevier Science Inc. All rights reserved.

Synthesis of an analog of the thyroid hormone-binding protein transthyretin via regioselective chemical ligation

Transthyretin is an essential protein responsible for the transport of thyroid hormones and retinol in human serum and is also implicated in the amyloid diseases familial amyloidotic polyneuropathy and senile systemic amyloidosis. Its folding properties and stabilization by ligands are of current interest due to their importance in understanding and combating these diseases, Here we report the solid phase synthesis of the monomeric unit of a transthyretin analog (equivalent to 127 amino acids) using t-Boc chemistry and peptide ligation and its folding to form a functional 54-kDa tetramer, The monomeric unit of the protein was chemically synthesized in three parts (positions 1-51, 54-99, and 102-127) and ligated using a chemoselective thioether ligation chemistry. The synthetic protein was folded and assembled to a tetrameric structure in the presence of transthyretin's native ligand, thyroxine, as shown by gel filtration chromatography, native gel electrophoresis, transthyretin antibody recognition, and thyroid hormone binding. Other folding products included a high molecular weight aggregate as well as a transient dimeric species. This represents one of the largest macromolecules chemically synthesized to date and demonstrates the potential of protein chemical synthesis for investigations of protein-ligand interactions.

Solution techniques for transport problems involving steep concentration gradients: application to noncatalytic fluid solid reactions

Some efficient solution techniques for solving models of noncatalytic gas-solid and fluid-solid reactions are presented. These models include those with non-constant diffusivities for which the formulation reduces to that of a convection-diffusion problem. A singular perturbation problem results for such models in the presence of a large Thiele modulus, for which the classical numerical methods can present difficulties. For the convection-diffusion like case, the time-dependent partial differential equations are transformed by a semi-discrete Petrov-Galerkin finite element method into a system of ordinary differential equations of the initial-value type that can be readily solved. In the presence of a constant diffusivity, in slab geometry the convection-like terms are absent, and the combination of a fitted mesh finite difference method with a predictor-corrector method is used to solve the problem. Both the methods are found to converge, and general reaction rate forms can be treated. These methods are simple and highly efficient for arbitrary particle geometry and parameters, including a large Thiele modulus. (C) 2001 Elsevier Science Ltd. All rights reserved.

Influence of seaward boundary condition on contaminant transport in unconfined coastal aquifers

Contaminant transport in coastal aquifers is complicated partly due to the conditions at the seaward boundary including seawater intrusion and tidal variations of sea level. Their inclusion in modelling this system will be computationally expensive. Therefore, it will be instructive to investigate the consequence of simplifying the seaward boundary condition by neglecting the seawater density and tidal variations in numerical predictions of contaminant transport in this zone. This paper presents a comparison of numerical predictions for a simplified seaward boundary condition with experimental results for a corresponding realistic one including a saltwater interface and tidal variations. Different densities for contaminants are considered. The comparison suggests that the neglect of the seawater intrusion and tidal variations does not affect noticeably the overall migration rate of the plume before it reaches the saltwater interface. However, numerical prediction shows that a more dense contaminant travels further seaward and part of the solute mass exits under the sea if the seawater density is not included. This is not consistent with the experimental result, which shows that the contaminant travels upwards to the shoreline along the saltwater interface. Neglect of seawater density, therefore, will result in an underestimation of the exit rate of solute mass around the coastline and fictitious migration paths under the seabed. For a less dense contaminant, neglect of seawater density has little effect on numerical prediction of migration paths. (C) 2001 Elsevier Science B.V. All rights reserved.

Comments on alternative calculations of the broadening of spectral lines of neutral sodium by H-atom collisions

With the exception of the sodium D-lines, recent calculations of line broadening cross sections for several multiplets of sodium by Leininger et al (Leininger T, Gadea F X and Dickinson A 2000 J. Phys. B: At. Mol. Opt. Phys. 33 1805) are in substantial disagreement with cross sections interpolated from the tables of Anstee and O'Mara (Anstee and O'Mara 1995 Mon. Not. R. Astron. Soc. 276 859) and Barklem and O'Mara (Barklem P S and O'Mara B J 1997 Mon. Not. R. Astron. Soc. 290 102). The discrepancy is as large as a factor of 3 for the 3p-4d multiplet. The two theories are tested by using the results of each to synthesize lines in the solar spectrum. It is found that generally the data from the theory of Anstee, Barklem and O'Mara produce the best match to the observed solar spectrum. It is found, using a simple model for reflection of the optical electron by the potential barrier between the two atoms, that the reflection coefficient is too large for avoided crossings with the upper states of subordinate lines to contribute to line broadening, supporting the neglect of avoided ionic crossings by Anstee, Barklem and O'Mara for these lines. The large discrepancies between the two sets of calculations is a result of an approximate treatment of avoided ionic crossings for these lines by Leininger et al (Leininger T, Gadea F X and Dickinson A 2000 J. Phys. B: At. Mol. Opt. Phys. 33 1805).

Mating behaviour and alternative oviposition sites for male eggs in the heteronomous hyperparasitoid Coccophagus gurneyi Compere (Hymenoptera : Aphelinidae)

The aphelinid parasitoid Coccophagus gurneyi Compere has unusual sex-related host relationships. Females are diploid and develop internally within mealybugs Pseudococcus calceolariae (Maskell). Males, in contrast, are haploid and hyperparasitic, developing on primary parasitoid larvae within the mealybugs. Furthermore, males have been claimed to be capable of either internal or external development, depending on the precise site of deposition of the haploid egg. This diversity of developmental pathways could indicate the existence of a sibling-species complex. We therefore quantified the mating and ovipositional behaviour of C. gurneyi, for comparison with that of an undescribed sibling species. We also checked whether the females deposit male eggs in alternative sites. The pattern of mating was found to be typical of mating behaviour in Coccophagus spp. and was consistent among all mating pairs, suggesting that the colony comprised one species. Further, the mating behaviour was significantly different from that of the undescribed sibling species. The site of male egg deposition varied and is apparently dictated by two factors; whether the mealybug is parasitised and, if so, the size of the parasitoid it contains. If the mealybugs were unparasitised or if the parasitoids within the mealybugs were small (< 0.53 mm), male eggs were deposited within the mealybug haemocoel. If the parasitoids were large (> 1.05 mm), male eggs were deposited within the parasitoids. These results support the claim of alternate host relationships and developmental pathways within males of C. gurneyi.

Cloning and gastrointestinal expression of rat hephaestin: relationship to other iron transport proteins

The membrane-bound ceruloplasmin homolog hephaestin plays a critical role in intestinal iron absorption. The aims of this study were to clone the rat hephaestin gene and to examine its expression in the gastrointestinal tract in relation to other genes encoding iron transport proteins. The rat hephaestin gene was isolated from intestinal mRNA and was found to encode a protein 96% identical to mouse hephaestin. Analysis by ribonuclease protection assay and Western blotting showed that hephaestin was expressed at high levels throughout the small intestine and colon. Immunofluorescence localized the hephaestin protein to the mature villus enterocytes with little or no expression in the crypts. Variations in iron status had a small but nonsignificant effect on hephaestin expression in the duodenum. The high sequence conservation between rat and mouse hephaestin is consistent with this protein playing a central role in intestinal iron absorption, although its precise function remains to be determined.

Transport of endosomal early antigen I in the rat sciatic nerve and location in cultured neurons

Early endosomal antigen I (EEAI) is known to be a marker of early endosomes and in cultured hippocampal neurons it preferentially localizes to the dendritic but not the axonal compartment. We show in cultured dorsal root ganglia and superior cervical ganglia neurons that EEAI localizes to the cell bodies and the neurites of both sensory and sympathetic neurons. We then show in vivo using a ligated rat sciatic nerve that EEAI significantly accumulates on the proximal side and not on the distal side of the ligation. This suggests that EEAI is transported in the anterograde direction in axons either as part of the homeostatic process or to the nerve ligation site in response to nerve injury. NeuroReport 12:281-284 (C) 2001 Lippincott Williams & Wilkins.