Unitary giant synapses embracing a single neuron at the convergent site of time-coding pathways of an electric fish, Gymnarchus niloticus

Phase-locking neurons in the electrosensory lateral line lobe (ELL) of a weakly electric fish, Gymnarchus niloticus, fire an action potential in response to each cycle of the sinusoidal electrosensory signal (350-500 Hz) created by the fish's own electric organ. The exact firing times of the phase-locking neurons are altered (time-shifted) by capacitance of electrolocation objects or by electric organ discharges of other individuals. The magnitude of the time shifts depends on the location of the neurons' receptive field on the skin; thus, time disparities arise between the firing of phase-locking neurons. To compute these disparities, there should be a site where these phase-locking neurons converge. In this study we morphologically identified a novel cell type, which we named the "ovoidal cell", that receives the convergent projections of phase-locking neurons in the inner cell layer (ICL) of the ELL. We labeled these neurons with biocytin and examined them by light and electron microscopy. The giant cells and the S-type primary afferents, two types of phase-locking neurons, respectively terminate on the soma via chemical synapses and on the dendrite of the ovoidal cells via mixed synapses. Each terminal of the giant cells embraces the soma of an ovoidal cell, covering as much as 84% of the somatic membrane. The giant cell terminals and ovoidal cell somata were immunoreactive to SV2, a synaptic vesicle protein, but the S-afferent terminals were not, even though they contain numerous synaptic vesicles. The dendrite of the ovoidal cells also contacts the pyramidal cells of the ICL, which are known to be sensitive to time disparities. The anatomical connections of the phase-locking neurons to the ovoidal cells strongly suggest that they are involved in computing time disparity.     

Axonogenesis in the medaka embryonic brain

In order to know the general pattern of axonogenesis in vertebrates, we examined axonogenesis in the embryonic brain of a teleost fish, medaka (Oryzias latipes), and the results were compared with previous studies in zebrafish and mouse. The axons and somata were stained immunocytochemically using antibodies to a cell surface marker (HNK-1) and acetylated tubulin and visualized by retrograde and anterograde labeling with a lipophilic dye. The fiber systems developed correlating with the organization of the longitudinal and transverse subdivisions of the embryonic brain. The first axons extended from the synencephalic tegmentum, forming the first fiber tract (fasciculus longitudinalis medialis) in the ventral longitudinal zone of the neural rod, 38 hours after fertilization. In the neural tube, throughout the entire brain two pairs of longitudinal fiber systems, one ventral series and one dorsal or intermediate series, and four pairs of transverse fiber tracts in the rostral brain were formed sequentially during the first 16 hours of axon production. In one of the dorsal longitudinal tracts, its branch retracted and disappeared at later stages. One of the transverse tracts was found to course in the telencephalon and hypothalamus. The overall pattern of the longitudinal fiber systems in medaka brain is similar to that in mouse, but apparently different from that in zebrafish. We propose that a ventral tract reported in zebrafish partially belongs to the dorsal fiber system, and that the longitudinal fiber systems in all vertebrate brains pass through a common layout defined by conserved genetic and developmental programs.     

Isolated cranial neuropathy associated with anti-glycolipid antibodies

We describe seven patients with isolated cranial neuropathy in whom serum anti-glycolipid antibodies were detected. Trigeminal sensory neuropathy was found in four patients, who had exhibited symptoms for 2 months to 4 years. The other three patients showed facial nerve palsy with or without ophthalmoparesis. Temporal profile analysis of anti-glycolipid antibodies revealed that titers of anti-glycolipid IgM antibodies against GM2 and LM1 gradually decreased in patients having chronic trigeminal sensory neuropathy. In patients with acute trigeminal sensory neuropathy, elevation of anti-LM1 antibody titers continued over 12 months although anti-GalNAc-GD1a antibody disappeared. On the other hand, titers of anti-glycolipid antibodies rapidly decreased in patients with acute facial nerve palsy with or without ophthalmoparesis. We conclude that anti-glycolipid antibodies may play an important role in the development of isolated cranial neuropathy in some patients.     

Pharmacogenetic roles of CYP2C19 and CYP2B6 in the metabolism of R- and S-mephobarbital in humans

OBJECTIVES AND METHODS: We assessed the relationship between the metabolism of R- and S-mephobarbital (MPB) and genetic polymorphisms of cytochrome P450 (CYP) 2C19 and CYP2B6. Nine homozygous extensive metabolizers (homo-EMs, 2C19*1/2C19*1) of CYP2C19, ten heterozygous EMs (hetero-EMs, 2C19*1/2C19*2, 2C19*1/2C19*3) and eleven poor metabolizers (PMs, 2C19*2/2C19*2, 2C19*3/2C19*3, 2C19*2/2C19*3) recruited from a Japanese population, received an oral 200 mg-dose of racemic MPB. Blood and urine samples were collected, and R-MPB, S-MPB and the metabolites, phenobarbital (PB) and 4'-hydroxy-MPB, were measured. Each subject was also genotyped for CYP2B6 gene. RESULTS: The mean area under the plasma concentration-time curve (AUC) of R-MPB was 92-fold greater in PMs than in homo-EMs. R/S ratios for AUC of MPB were much higher in PMs than in EMs (homo- and hetero-). The cumulative urinary excretion of 4'-hydroxy-MPB up to 24 h postdose was 21-fold less in PMs than in homo-EMs. The metabolic ratio of AUCPB/(AUCS-MPB + AUCR-MPB) was higher in PMs than in EMs (homo- and hetero-). In addition, this metabolic ratio was lower in the carriers of CYP2B6*6 compared with that in its non-carriers. CONCLUSIONS: Our results indicate that the 4'-hydroxylation of R-MPB is mediated via CYP2C19 and that the rapid 4'-hydroxylation of R-MPB results in a marked difference in the pharmacokinetic profiles between R-MPB and S-MPB in the different CYP2C19 genotypic individuals. In addition, a minor fraction of the interindividual variability in PB formation from MPB may be explainable by the CYP2B6*6 allele.     

Adrenomedullin concentrations in early 2nd-trimester amniotic fluid: relation to preterm delivery and fetal growth at birth

OBJECTIVE: The purpose of this study was to evaluate whether adrenomedullin concentrations in the early 2nd-trimester amniotic fluid predict preterm delivery or fetal growth at birth. METHODS: The adrenomedullin concentrations in early 2nd-trimester amniotic fluid were measured in 70 pregnancies with term delivery and in 3 pregnancies with preterm delivery. Total and free adrenomedullin concentrations were measured from early 2nd-trimester amniotic fluid samples using an immunoradiometric assay. RESULTS: The amniotic fluid total adrenomedullin concentrations in women with preterm delivery were significantly higher (129.7 +/- 19.6 fmol/ml) than those in women with term delivery (92.5 +/- 28.2 fmol/ml; p < 0.05). There were no significant differences for amniotic fluid free adrenomedullin concentrations and free/total adrenomedullin ratios between the two groups. Total or free adrenomedullin concentrations in the early 2nd-trimester amniotic fluid showed an inverse correlation both with birth weight (r = 0.27, p < 0.05, and r = 0.21, p < 0.05) and height (r = 0.30, p < 0.05, and r = 0.28, p < 0.05). There were no correlations between placental weight and total or free adrenomedullin concentrations in the early 2nd-trimester amniotic fluid. CONCLUSIONS: These results suggest that adrenomedullin concentrations in the early 2nd-trimester amniotic fluid might be related to further in utero fetal growth and that high levels of adrenomedullin in the early 2nd-trimester amniotic fluid may be involved in the occurrence of preterm delivery.     

Developmental toxicity of estrogenic chemicals on rodents and other species

ABSTRACT  Antenatal sex-hormone exposure induces lesions in mouse reproductive organs, which are similar to those in humans exposed in utero to a synthetic estrogen, diethylstilbestrol. The developing organisms including rodents, fish and amphibians are particularly sensitive to exposure to estrogenic chemicals during a critical window. Exposure to estrogens during the critical period induces long-term changes in reproductive as well as non-reproductive organs, including persistent molecular alterations. The antenatal mouse model can be utilized as an indicator of possible long-term consequences of exposure to exogenous estrogenic compounds including possible environmental endocrine disrupters. Many chemicals released into the environment potentially disrupt the endocrine system in wildlife and humans, some of which exhibit estrogenic activity by binding to the estrogen receptors. Estrogen responsive genes, therefore, need to be identified to understand the molecular basis of estrogenic actions. In order to understand molecular mechanisms of estrogenic chemicals on developing organisms, we are identifying estrogen responsive genes using cDNA microarray, quantitative RT-PCR, and differential display methods, and genes related to the estrogen-independent vaginal changes in mice induced by estrogens during the critical window. In this review, discussion of our own findings related to endocrine distuptor issue will be provided.     

Molecular alterations of h-warts/LATS1 tumor suppressor in human soft tissue sarcoma

h-warts/LATS1 is a human homolog of the Drosophila warts tumor suppressor gene, which functions as a component of the mitotic apparatus. LATS1-deficient (Lats1(-/-)) mice have been reported to develop ovarian stromal tumors and soft tissue sarcomas. We investigated the status of the h-warts/LATS1 in 50 human soft tissue sarcomas to address its potential function as a tumor suppressor in human sarcoma development. In our RT-PCR assay, 7 (14%) (3 of 4 myxoid liposarcomas, 3 of 7 leiomyosarcomas, 1 of 9 malignant fibrous histiocytomas) of 50 sarcomas examined had no or a reduced expression of the h-warts/LATS1, indicating down-regulated gene expression. We further analyzed alterations of the h-warts/LATS1 in these seven sarcomas. Using microsatellite markers for chromosome 6q23-25.1, to which the h-warts/LATS1 is localized, an allelic loss of this locus was detected in one leiomyosarcoma, in which a missense point mutation of the h-warts/LATS1 was detected by PCR single-strand conformation polymorphism. Clusters of CpG dinucleotides in a 5' putative promoter region were hypermethylated in the other six sarcomas. Our data suggest that the molecular alterations of the h-warts/LATS1 could be of pathologic importance in human sarcomagenesis.     

A case of pseudo-Bartter's syndrome induced by long-term ingestion of furosemide delivered orally through health tea

A 32-year-old woman with a three-year history of muscle weakness and hypokalemia, was admitted to our hospital because of hypokalemic periodic paralysis. Clinical and laboratory findings were consistent with Bartter's syndrome. Although she denied any ingestion of diuretics substantial quantities of furosemide were detected in her urine. She had been drinking health tea which contained about 90 mg of furosemide per teabag daily for five years. Four years after discontinuation of drinking the tea, the hypokalemia was completely ameliorated, but poor renal concentration ability is still present. We conclude that is a case of pseudo-Bartter's syndrome that was caused by long-term ingestion of the health tea supplemented illegally with furosemide, and suspect that such cases may be observed more frequently than currently thought.