Roles of chemical mediators in the taste system

Recent advances in neural mechanisms of taste are reviewed with special reference to neuroactive substances. In the first section, taste transduction mechanisms of basic tastes are explained in two groups, whether taste stimuli directly activate ion channels in the taste cell membrane or they bind to cell surface receptors coupled to intracellular signaling pathways. In the second section, putative transmitters and modulators from taste cells to afferent nerves are summarized. The candidates include acetylcholine, catecholamines, serotonin, amino acids and peptides. Studies favor serotonin as a possible neuromodulator in the taste bud. In the third section, the role of neuroactive substances in the central gustatory pathways is introduced. Excitatory and inhibitory amino acids (e.g., glutamate and GABA) and peptides (substance P and calcitonin gene-related peptide) are proved to play roles in transmission of taste information in both the brainstem relay and cortical gustatory area. In the fourth section, conditioned taste aversion is introduced as a model to study gustatory learning and memory. Pharmacobehavioral studies to examine the effects of glutamate receptor antagonists and protein kinase C inhibitors on the formation of conditioned taste aversion show that both glutamate and protein kinase C in the amygdala and cortical gustatory area play essential roles in taste aversion learning. Recent molecular and genetic approaches to disclose biological mechanisms of gustatory learning are also introduced. In the last section, behavioral and pharmacological approaches to elucidate palatability, taste pleasure, are described. Dopamine, benzodiazepine derivatives and opioid substances may play some roles in evaluation of palatability and motivation to ingest palatable edibles.     

Modulation of motility and proliferation of glioma cells by hepatocyte growth factor

Invasive proliferation is a critical biological characteristic of gliomas. We evaluated the activities of hepatocyte growth factor (HGF) on proliferation and motility of glioma cells, comparing them with the effects of other growth factors (EGF, bFGF, PDGF-BB, TGF-beta 1). Seven primary culture lines all expressed c-met and HGF mRNA, and secreted HGF. HGF stimulated 3H-thymidine uptake of every glioma cell line (30 to 70% upregulation). Boyden chamber assay and scattering assay revealed that HGF promoted cell motility with chemokinetic and strong chemotactic activities. Concentric circle assay showed that HGF promoted two-dimensional expansion (proliferation and motility) most strongly among the growth factors studied. Further, we analyzed 23 paraffin-embedded sections of surgically resected gliomas (7 grade II, 8 grade III, and 8 grade IV) by immunohistochemistry. Expression of HGF and Met increased with malignant progression of gliomas, suggesting that gliomas stimulated their invasive proliferation by autocrine HGF production. Neurons and vasculature were HGF-positive, and Met-positive glioma cells gathered around them. The data indicate that neurons and vasculature, which are the main tracks of glioma invasion, augment chemotactic invasion and proliferation of gliomas by paracrine HGF secretion. Clearly HGF plays a critical role in invasive proliferation of glioma cells and it is therefore a candidate target of therapeutic intervention.     

Esophageal hiatal hernia after omphalocele repair

Esophageal hiatal hernias (EHH) are probably caused by congenital, traumatic, or iatrogenic factors, although the etiology remains unknown. EHHs may develop after abdominal wall closure for omphalocele or gastroschisis due to the increased intra-abdominal pressure, however, there have been few reports in the literature. We present a case of EHH developing after abdominal wall closure.     

Standard splenic volume in children and young adults measured from CT images

The number of children and adolescents with hypersplenism is increasing as the number of long-term survivors undergoing successful Kasai operation for biliary atresia increases. The aim of this study was to determine the standard splenic volume in normal children and adolescents. We measured the splenic volumes with computed tomography (CT) images obtained from 49 Japanese children, adolescents, and young adults, ranging from 9 days to 25 years of age, and from 3.0 kg to 89.0 kg of body weight. The best correlation was observed between splenic volume (SV: cm3) and body weight (BW: kg) with a power curve regression; SV = 6.516 BW0.797, r = 0.924. The splenic volume and age (AG: years) also correlated well on a power curve; SV = 41.879 AG0.411, r = 0.897. The ratio of the splenic volume to the body weight (SV/BW: cm3/kg) decreased with age; from 4.5 cm3/kg at 1 month to 2.4 cm3/kg at 25 years of age, according to an exponential curve; SV/BW = 4.473e-0.026AG, r = 0.593. The above formulas are thus considered to be clinically useful, especially in the assessment of splenic size in children with hypersplenism both before and after partial splenic embolization.     

Axin, a negative regulator of the Wnt signaling pathway, forms a complex with GSK-3beta and beta-catenin and promotes GSK-3beta-dependent phosphorylation of beta-catenin

Glycogen synthase kinase-3 (GSK-3) mediates epidermal growth factor, insulin and Wnt signals to various downstream events such as glycogen metabolism, gene expression, proliferation and differentiation. We have isolated here a GSK-3beta-interacting protein from a rat brain cDNA library using a yeast two-hybrid method. This protein consists of 832 amino acids and possesses Regulators of G protein Signaling (RGS) and dishevelled (Dsh) homologous domains in its N- and C-terminal regions, respectively. The predicted amino acid sequence of this GSK-3beta-interacting protein shows 94% identity with mouse Axin, which recently has been identified as a negative regulator of the Wnt signaling pathway; therefore, we termed this protein rAxin (rat Axin). rAxin interacted directly with, and was phosphorylated by, GSK-3beta. rAxin also interacted directly with the armadillo repeats of beta-catenin. The binding site of rAxin for GSK-3beta was distinct from the beta-catenin-binding site, and these three proteins formed a ternary complex. Furthermore, rAxin promoted GSK-3beta-dependent phosphorylation of beta-catenin. These results suggest that rAxin negatively regulates the Wnt signaling pathway by interacting with GSK-3beta and beta-catenin and mediating the signal from GSK-3beta to beta-catenin.     

Transforming growth factor-beta isoforms expressions in pulmonary adenocarcinomas as prognostic markers: an immunohistological study of one hundred and twenty patients

Congenital eye malformations were studied in a small geographical area in 212,479 consecutive births. For each of the 145 new cases studied during the period 1979 to 1994, more than 50 factors were compared in probands and in controls. The prevalence rate of congenital eye malformations was 6.8 per 10,000 for microphthalmia 1.7, anophthalmia 0.23, cataract 2.7 and coloboma 1.4 respectively. Sex ratio was 0.82. Prenatal diagnosis was performed in 18 cases and 7 cases were induced abortions. The more common types of associated malformations in the 81 affected cases (53.8%) with at least one anomaly other than an eye malformation were clubfeet, microcephaly, hydrocephaly, cleft lip/palate and facial dysmorphia. At birth infants with eye malformations and other malformations were smaller, weighted less and their head circumference was lower than in controls. Placental weight was also lower than in controls. Pregnancies with eye malformations were more often complicated by threatened abortion, oligoamnios and polyhydramnios. Mothers of children with congenital eye malformations took more often drugs during pregnancy than mothers of controls. Fathers of children with congenital eye malformations were more often exposed to occupational hazards than fathers of controls. There was a significant association between eye malformations and consanguinity of parents. The recurrence risk for first degree relatives of probands was 8.9%. First degree relatives of probands had more than three times the prevalence of non-eye malformations than controls. These results are of relevance to genetic counseling.     

Neurotoxicodynamics of the interaction between ciprofloxacin and foscarnet in mice

The potential for convulsions induced by the coadministration of ciprofloxacin (CPFX) and foscarnet (PFA) may be due not to a change in the distribution of CPFX to the brain but to a potential CPFX-induced inhibition of gamma-aminobutyric acid (GABA)-GABA(A) receptor binding in the presence of PFA.     

A low-molecular-weight inhibitor against the chemokine receptor CXCR4: a strong anti-HIV peptide T140

T22 ([Tyr5,12, Lys7]-polyphemusin II) is an 18-residue peptide amide, which has strong anti-HIV activity. T22 inhibits the T cell line-tropic (T-tropic) HIV-1 infection through its specific binding to a chemokine receptor CXCR4, which serves as a coreceptor for the entry of T-tropic HIV-1 strains. Herein, we report our finding of novel 14-residue CXCR4 inhibitors, T134 and T140, on the basis of the T22 structure. In the assays we examined, T140 showed the highest inhibitory activity against HIV-1 entry and the strongest inhibitory effect on the binding of an anti-CXCR4 monoclonal antibody (12G5) to CXCR4 among all the CXCR4 inhibitors that have been reported up to now.