John Chi Wang Ho

The University of Hong Kong, Hong Kong, Hong Kong

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Publications (3)9.18 Total impact

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    ABSTRACT: Recent studies have described the bacterial community residing in the guts of giant pandas, together with the presence of lignocellulolytic enzymes. However, a more comprehensive understanding of the intestinal microbial composition and its functional capacity in giant pandas remains a major goal. Here, we conducted a comparison of bacterial, fungal and homoacetogenic microbial communities from fecal samples taken from two geriatric and two adult captive giant pandas. 16S rDNA amplicon pyrosequencing revealed that Firmicutes and Proteobacteria are the most abundant microbiota in both geriatric and adult giant pandas. However, members of phylum Actinobacteria found in adult giant pandas were absent in their geriatric counterparts. Similarly, ITS1 amplicon pyrosequencing identified developmental changes in the most abundant fungal classes from Sordariomycetes in adult pandas to Saccharomycetes in geriatric pandas. Geriatric pandas exhibited significantly higher abundance of a potential probiotic fungus (Candida tropicalis) as compared to adult pandas, indicating their importance in the normal digestive physiology of aged pandas. Our study also reported the presence of a lignocellulolytic white-rot fungus, Perenniporia medulla-panis, and the evidence of novel homoacetogens residing in the guts of giant pandas.
    PLoS ONE 01/2014; 9(1):e79902. · 3.53 Impact Factor
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    ABSTRACT: In mammals, the neuropeptide galanin exerts a variety of physiological roles in the neuroendocrine system through its interactions with three galanin receptor subtypes (GalR1, GalR2 and GalR3). However, little is known about the characteristics of galanin receptors in birds, and it is only recently that avian GalR1 and a novel GalR1-like receptor were first identified in chickens. In this study, we report the cDNA cloning and characterization of the other two chicken galanin receptors, the galanin type II receptor (cGalR2) and a novel GalR2-like receptor (GalR2-L), which share high degrees of similarity in sequence identity, gene structure and signaling properties. cGalR2 and cGalR2-L cDNAs encode two putative receptors of 371 and 370 amino acids, in which they show considerable amino acid sequence identities (65-67%, and 53-55%, respectively) with the mammalian GalR2. RT-PCR assays revealed that cGalR2 and cGalR2-L mRNA were widely expressed in the adult chicken tissues including the whole brain, intestine, lung, ovary, pituitary and different regions of the oviduct. As assayed with different luciferase reporter systems, chicken galanin (cGal 1-29) and human galanin-like peptide (hGALP 1-60) were demonstrated to stimulate the luciferase activities in Chinese hamster ovary cells expressing cGalR2 and cGalR2-L through the activations of cAMP/PKA, Ca(2+)/calcineurin and MAPK/ERK signaling pathways, hence suggesting that both receptors are functionally coupled to the G(s) and G(q) proteins. Furthermore, the previously identified cGalR1 and cGalR1-L were found to be solely coupled to the G(i/o) proteins, and the hGALP (1-60) exhibited only a low potency to cGalR1, cGalR1-L, cGalR2 and cGalR2-L activations.
    General and Comparative Endocrinology 09/2012; 179(2):305-12. · 2.82 Impact Factor
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    ABSTRACT: Galanin is a multi-functional neuropeptide that is widely distributed in the mammalian central nervous system and peripheral tissues. It exerts multiple physiological functions through interaction with 3 known G protein-coupled receptors (GPCR), namely, galanin type I, II and III (GalR1, 2 and 3) receptors, which have only been identified in mammals. In this study, we reported the cloning and characterization of chicken galanin type I receptor (GalR1) and a novel galanin receptor with considerable homology to chicken GalR1, which herein is designated as galanin type I-like receptor (GalR1-L). Chicken GalR1 and GalR1-L full-length cDNAs were cloned from chicken brain and small intestine tissue, respectively. The former encodes a protein of 357 amino acids that shares 84-86% amino acid sequence identities with its mammalian counterparts, whereas the latter encodes a 363-amino acid protein with comparatively lower identities (55-56%) to the mammalian GalR1. Using reverse transcription (RT)-PCR assays, we examined the expression of both receptors in adult chicken tissues. Both receptors were found to be widely distributed in the tissues examined, including brain, small intestine, kidney, ovary, pancreas, pituitary and spleen. Interestingly, cGalR1 expression was detected in different regions of chicken oviduct, while cGalR1-L expression was restricted to the vagina. Using a pGL3-CRE luciferase reporter system, chicken galanin peptide (1-29) was demonstrated to inhibit both basal and forskolin-stimulated luciferase activities, in dose-dependent manners, through the cAMP-mediated signaling pathway in Chinese hamster ovary (CHO) cells expressing either cGalR1 or cGalR1-L, thus suggesting the functional couplings of both receptors to G(i) proteins. Together, the characterization of chicken GalR1 and GalR1-L provides a better understanding of the physiological roles of galanin in avian species.
    General and Comparative Endocrinology 10/2010; 170(2):391-400. · 2.82 Impact Factor