Matthew C.E. Gwee

Bio: Matthew C.E. Gwee is an academic researcher from National University of Singapore. The author has contributed to research in topics: Venom & Cimetidine. The author has an hindex of 19, co-authored 57 publications receiving 1363 citations.

Autonomic effects of some scorpion venoms and toxins

Abstract: 1. The autonomic effects of venoms and toxins from several species of scorpions, including the Indian red scorpion Mesobuthus tamulus, the Chinese scorpion Buthus martensi Karsch and the Israeli scorpion Leiurus quinquestriatus quinquestriatus, all belonging to Buthidae, and the Asian black scorpions Heterometrus longimanus and Heterometrus spinifer, belonging to Scorpionidae, are reviewed. 2. The effects of the venoms of M. tamulus and L. q. quinquestriatus on noradrenergic and nitrergic transmission in the rat isolated anococcygeus muscle revealed that both venoms mediated their pharmacological effects via a prejunctional mechanism involving the activation of voltage-sensitive sodium channels with consequent release of neurotransmitters that mediate target organ responses, similar to the effects mediated by other alpha-scorpion toxins. 3. Two new toxins, Makatoxin I and Bukatoxin, were purified to homogeneity from the venom of B. martensi Karsch. Determination of their complete amino acid sequences confirmed that both toxins belonged to the class of alpha-scorpion toxins. The effects of both toxins on noradrenergic and nitrergic transmission in the rat anococcygeus muscle provided firm evidence that their pharmacological actions also closely resembled those mediated by other alpha-scorpion toxins on neuronal voltage-sensitive sodium channels. 4. The venoms of H. longimanus and H. spinifer were found to have high concentrations of noradrenaline (1.8 +/- 0.3 mmol/L) and relatively high concentrations of acetylcholine (79.8 +/- 1.7 micromol/L) together with noradrenaline (146.7 +/- 19.8 micromol/L), respectively, which can account for their potent direct cholinergic and noradrenergic agonist actions in the rat anococcygeus muscle. 5. Our studies confirmed that the rat anococcygeus muscle is an excellent nerve-smooth muscle preparation for investigating the effects of bioactive agents on noradrenergic and nitrergic transmission, as well as the direct agonist actions of these agents on post-synaptic alpha-adrenoceptors and M3 muscarinic cholinoceptors. Although many studies, including our own, have documented that scorpion venoms and toxins mediate their primary effects via a prejunctional mechanism that leads to the marked release of various autonomic neurotransmitters, our studies have shown that there are exceptions to this generally accepted phenomenon. In particular, we have provided firm evidence to show that the venoms from H. longimanus and H. spinifer do not have such a prejunctional site of action but, instead, the venoms mediate their autonomic effects through direct agonist actions on post-junctional muscarinic M3 cholinoceptors and alpha-adrenoceptors.

Globalization of Problem-based Learning (PBL): Cross-cultural Implications

Abstract: Problem-based learning (PBL) is essentially a learning system design that incorporates several educational strategies to optimize student-centered learning outcomes beyond just knowledge acquisition. PBL was implemented almost four decades ago as an innovative and alternative pathway to learning in medical education in McMaster University Medical School. Since then, PBL has spread widely across the world and has now been adopted globally, including in much of Asia. The globalization of PBL has important cross-cultural implications. Delivery of instruction in PBL involves active peer teaching-learning in an open communication style. Consequently, this may pose an apparent serious conflict with the Asian communication style generally dominated by a cultural reticence. However, evidence available, especially from the PBL experience of some senior Korean medical students doing an elective in the University of Toronto Medical School and the cross-cultural PBL experience initiated by Kaohsiung Medical University, strongly suggests creating a conducive and supportive learning environment for students learning in a PBL setting can overcome the perceived cultural barriers; that is, nurture matters more than culture in the learning environment. Karaoke is very much an Asian initiative. The Karaoke culture and philosophy provide a useful lesson on how to create a conducive and supportive environment to encourage, enhance and motivate group activity. Some key attributes associated with Asian culture are in fact consistent with, and aligned to, some of the basic tenets of PBL, including the congruence between the Asian emphasis on group before individual interest, and the collaborative small group learning design used in PBL. Although there are great expectations of the educational outcomes students can acquire from PBL, the available evidence supports the contention the actual educational outcomes acquired from PBL do not really match the expected educational outcomes commonly intended and specified for a PBL program. Proficiency in the English language can pose serious problems for some Asian medical schools, which choose to use English as the language for discussion in PBL tutorials. A novel approach that can be applied to overcome this problem is to allow students to engage in discussions using both their native language as well as English, a highly successful practice implemented by the University of Airlangga, Surabaya, Indonesia. As PBL is a highly resource-intensive pedagogy, Asian medical educators need to have a clear understanding of the PBL process, philosophy and practice in order to be able to optimize the educational outcomes that can be derived from a PBL curriculum.

The Pharmacological Basis of Therapeutics

Abstract: The Pharmacological Basis of Therapeutics A Textbook of Pharmacology, Toxicology and Therapeutics for Physicians and Medical Students. By Prof. Louis Goodman and Prof. Alfred Gilman. Pp. xiii + 1383. (New York: The Macmillan Company, 1941.) 50s. net.

Neurotoxins Affecting Neuroexocytosis

Abstract: Nerve terminals are specific sites of action of a very large number of toxins produced by many different organisms. The mechanism of action of three groups of presynaptic neurotoxins that interfere directly with the process of neurotransmitter release is reviewed, whereas presynaptic neurotoxins acting on ion channels are not dealt with here. These neurotoxins can be grouped in three large families: 1) the clostridial neurotoxins that act inside nerves and block neurotransmitter release via their metalloproteolytic activity directed specifically on SNARE proteins; 2) the snake presynaptic neurotoxins with phospholipase A(2) activity, whose site of action is still undefined and which induce the release of acethylcholine followed by impairment of synaptic functions; and 3) the excitatory latrotoxin-like neurotoxins that induce a massive release of neurotransmitter at peripheral and central synapses. Their modes of binding, sites of action, and biochemical activities are discussed in relation to the symptoms of the diseases they cause. The use of these toxins in cell biology and neuroscience is considered as well as the therapeutic utilization of the botulinum neurotoxins in human diseases characterized by hyperfunction of cholinergic terminals.

The Toxicogenomic Multiverse: Convergent Recruitment of Proteins Into Animal Venoms

Abstract: Throughout evolution, numerous proteins have been convergently recruited into the venoms of various animals, including centipedes, cephalopods, cone snails, fish, insects (several independent venom systems), platypus, scorpions, shrews, spiders, toxicoferan reptiles (lizards and snakes), and sea anemones. The protein scaffolds utilized convergently have included AVIT/colipase/prokineticin, CAP, chitinase, cystatin, defensins, hyaluronidase, Kunitz, lectin, lipocalin, natriuretic peptide, peptidase S1, phospholipase A2, sphingomyelinase D, and SPRY. Many of these same venom protein types have also been convergently recruited for use in the hematophagous gland secretions of invertebrates (e.g., fleas, leeches, kissing bugs, mosquitoes, and ticks) and vertebrates (e.g., vampire bats). Here, we discuss a number of overarching structural, functional, and evolutionary generalities of the protein families from which these toxins have been frequently recruited and propose a revised and expanded working definition...