Capability of intensity discrimination in multiple receptor model of insect taste

A simple model in which one CNS taste neuron integrates inputsfrom multiple peripheral receptors is introduced in order toinvestigate the mechanism of acute intensity taste discriminationin flies. Information theory is applied to evaluate the acuteability of discrimination provided by the model. The presentanalysis is carried out under two statistical conditions concerningthe uncertainty of receptor response. Based on experimentaldata obtained by Smith et al. (1983), we estimate the mutualinformation entropy of the model. The numerical results obtainedhere indicate that the uncertainty observed in a single receptorresponse is dramatically reduced by the central integration.Furthermore, each of the eleven stimulus intensity levels experimentallyapplied by Smith et al., can be discriminated completely byintegrating the responses of the realistic number of receptors(33–212). Such a great improvement of the differentialsensitivity in the model resolves the discrepancy between thelow differential sensitivity of single sugar receptors (Smithet al., 1983) and the high sensitivity obtained in the feedingbehavior (Dethier and Rhoades, 1954; Dethier and Bowdan, 1984)of the blowfly.     

Molecular cloning of a non-isopeptide-selective human endothelin receptor.

We isolated several complementary DNA (cDNA) clones encoding a non-isopeptide-selective human endothelin receptor (ETBR) from a human placenta cDNA library. The clones, different in the length of their 3'-untranslated regions, encoded the same 442-amino acid protein with a transmembrane topology similar to that of other G protein-coupled receptors. The rank order of the binding of ET isopeptides (ET-1, ET-2 and ET-3) to the receptor expressed in COS-7 cells was ET-1 = ET-2 = ET-3. Northern blot analysis identified three mRNA species, 4.3 kb, 2.7 kb and 1.7 kb in size, probably generated by their use of alternative polyadenylation sites. These mRNAs were expressed in a wide variety of human tissues, at the highest level in the brain and at a significant level in cultured endothelial cells.     

Fungal toxins as a parasitic factor responsible for the establishment of fungal infections

Although the mechanism of fungal infections, particularly that of opportunistic fungus infections, has been studied extensively, much still remains to be clarified. As is the case for certain bacterial infections, it has long been assumed by numerous investigators that some toxins, enzymes and other metabolites produced in vitro as well as in vivo by pathogenic fungi or their cellular constituents might be responsible for the establishment of fungal infections. However, there are very few papers which deal with isolation and/or characterization of pathogenic fungus-derived toxins, particularly those of high molecular weight, to sufficiently meet various criteria for toxins including etiopathological ability. Likewise, it has been speculated that certain enzymes produced by pathogenic fungi are related to the pathogenesis of infections with the fungi implicated, but no direct evidence has been provided.It is commonly held by researchers concerned with medical mycology that the lowering of specific and/or nonspecific resistance of a host to pathogenic fungi is a prerequisite for the establishment of infections, particularly opportunistic infections. However, it is also accepted that if a given fungus possesses no parasite factors (e.g. toxigenicity, invasiveness and others), it would be unable to initiate infection even when the host is in a severe immunodeficient state. This is supported by our recent studies working with Saccharomyces cerevisiae and some other so-called nonpathogenic yeasts (unpublished data). Based on these considerations, the author and his co-workers have attempted to isolate several high and low molecular weight toxins in a pure state from virulent strains of Candida albicans and Aspergillus fumigatus as opportunist. Studies have also been made on the etiopathological roles of some successfully isolated toxins in infections with the fungi implicated (46).In addition to our experimental results, general concepts in fungal toxins, particularly those related to such toxins as isolated in our laboratory are outlined. Since opportunistic fungus infections have created a global problem because of their world-wide prevalence, a sharp demarcation between the so-called pathogenic and nonpathogenic fungi has become vague. Despite this situation, two terms are conventionally used throughout this paper.The author thanks Drs. H. Yamaguchi and K. Uchida, Y. Yamamoto, T. Hiratani, and Y. Nozu for their collaboration during these studies.     

Effect of temperature during preparation of rat adrenal quarters and isolated cell suspension of their ACTH responsiveness.

The effect of temperature during preparation of rat adrenal quarters or isolated adrenal cell suspension on their response to ACTH was examined through a comparison of amounts of corticosterone produced after their incubation. The response to ACTH added in vitro was considerably higher when adrenal quarters and isolated adrenal cell suspension were prepared at room temperature (25 degree C) than when prepared at ice-cold. Endogenous steroidogenesis was not affected by the temperature. It seemed unlikely that this higher response to ACTH of adrenal quarters or isolated adrenal cell suspension prepared at room temperature was due to an activation of the cells. A possibility was discussed that cooling adrenal quarters or isolated adrenal cell suspension during the preparation may create an unphysiological state in some place to related the cell membrane.     

Characterization of Avian Paramyxoviruses Isolated from Feral Ducks in Northern Japan: The Presence of Three Distinct Viruses in Nature

Seventy-eight strains of avian paramyxoviruses (PMV) were isolated from cloacal and/or tracheal swabs taken from 1,342 feral ducks, comprised of spot-bill ducks, mallards, pintails, teals, falcated teals, wigeons and buffie-heads, in Wakuya-cho, Miyagi Prefecture, Japan, between 1976 and 1979. Five and a half percent of the ducks were positive for virus. Serological and structural characterization indicated that three different avian paramyxoviruses arc prevalent in the Japanese feral duck population. The first group of PMV was Newcastle disease virus (NDV), and in vivo pathogenecity tests in embryonated chicken eggs and 1-day-old chicks revealed that all the NDV strains isolated were avirulent. The second and most prevalent strain was closely related to PMV-4, duck/Hong Kong/D3/75 strain. The viruses of the third group were recovered only from pintails. They cross-reacted antigenically with PMV-3 when antisera to the PMV-3 reference strains, turkey/Wisconsin/68 and parakeet/Netherlands/449/75, were employed. However, no cross-reaction was observed when antiserum to pintail/ Wakuya/20/78, the prototype of this group, was used. The viruses of the third group also differed in viral polypeptide profile from the reference strains of PMV-3.     

Noncanonical Transforming Growth Factor β (TGFβ) Signaling in Cranial Neural Crest Cells Causes Tongue Muscle Developmental Defects

Microglossia is a congenital birth defect in humans and adversely impacts quality of life. In vertebrates, tongue muscle derives from the cranial mesoderm, whereas tendons and connective tissues in the craniofacial region originate from cranial neural crest (CNC) cells. Loss of transforming growth factor β (TGFβ) type II receptor in CNC cells in mice (Tgfbr2^fl/fl;Wnt1-Cre) causes microglossia due to a failure of cell-cell communication between cranial mesoderm and CNC cells during tongue development. However, it is still unclear how TGFβ signaling in CNC cells regulates the fate of mesoderm-derived myoblasts during tongue development. Here we show that activation of the cytoplasmic and nuclear tyrosine kinase 1 (ABL1) cascade in Tgfbr2^fl/fl;Wnt1-Cre mice results in a failure of CNC-derived cell differentiation followed by a disruption of TGFβ-mediated induction of growth factors and reduction of myogenic cell proliferation and differentiation activities. Among the affected growth factors, the addition of fibroblast growth factor 4 (FGF4) and neutralizing antibody for follistatin (FST; an antagonist of bone morphogenetic protein (BMP)) could most efficiently restore cell proliferation, differentiation, and organization of muscle cells in the tongue of Tgfbr2^fl/fl;Wnt1-Cre mice. Thus, our data indicate that CNC-derived fibroblasts regulate the fate of mesoderm-derived myoblasts through TGFβ-mediated regulation of FGF and BMP signaling during tongue development.