Further evidence that the 3’Untranslated Region of the CHOP mRNA possesses mRNA destabilizing effect

Poster presentation - Theme 1: Cell biologyThe transcription regulatory factor known as Chop is commonly induced to express in stressed cells. In most cases, the expression of CHOP is associated with apoptosis. Although the regulation of CHOP expression at the transcriptional level has been studied to considerable details, the involvement of post-transcriptional mechanism such as mRNA stability has not been much addressed. We previously provided indirect evidence that the 3’UTR of CHOP mRNA had an mRNA destabilizing effect. The objective of this study was to provide more direct evidence to support this hypothesis. A reporter plasmid was constructed so as to express an EGFP mRNA that has its original ...postprin

The induction of p21/WAF1/CIP1 expression by the specific kappa opioid receptor agonist is independent of MAPK and PKC

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The biochemical mechanism of hypoxia-induced mobilization of glycogen in cultured cancer cell

Conference Theme: Cancer and metabolismPoster Presentation: P37BACKGROUND: Metabolic reprogramming is one of the strategies adopted by cancer cells to survive hypoxic conditions. Recent findings suggest that hypoxic cancer cells derive the energy that they need through glycolysis using glucose mobilized from intracellular glycogen reserve. Glycogen phosphorylase (GP) is the major rate-determining enzyme for glycogen mobilization in many normal cells under the condition of starvation or physical exercise. The lysosomal alpha-glucosidase (GAA) has also been implicated in glycogen mobilization since deficiency of this enzyme is known to result in Glycogen Storage Disease Type II (Pompe disease). Although a role for GP in the mobilization of glycogen by cancer cells depleted of oxygen had been demonstrated, whether a similar role for GP (and GAA) could be demonstrated under deprivation of both glucose and oxygen is not yet known. This issue is addressed in this study by examining the intracellular level of glycogen in the absence and presence of pharmacological inhibitors of GP and/or …published_or_final_versio

The enzymatic mechanism mediating the breakdown of glycogen in hypoxic tumor cells

Poster presentation - Theme 2: Cancer & other diseasesGlycogen has been recently implicated as a major source of metabolic fuel for hypoxic tumor cells. The biochemical mechanism underlying the breakdown of glycogen to produce the substrate for glycolysis though is not fully understood. The aim of this study is to demonstrate the potential role of glycogen phosphorylase or α-glucosidase in mediating breakdown of intracellular glycogen in hypoxic tumor cells. The deprivation of glucose in normoxic tumor cells over a period of 6 hours resulted in marked reduction of intracellular glycogen level. Imposing hypoxia (1% O2) on these cells during ...postprin

Design, Development and Evaluation of Biochemistry Virtual Laboratory for Blended Learning

This paper examines students’ reflection on the design and development of a prototype biochemistry virtual laboratory (vLab) at the University of Hong Kong. Second year students from the MBBS programme were divided into two groups. One group (non-vLab) took part in the original didactic lecture while the other group (vLab) joined in the trial blended virtual lab learning session. The learning outcomes were evaluated by a post-lab knowledge comprehension quiz and the class performances were analyzed. In addition, students’ perceptions toward blended vLab learning experience were evaluated by questionnaires. The group with the vLab experience achieved higher quiz results. However, their evaluation and feedback with regard to the vLab learning experience were rather critical, which provided valuable insights for further improvements on the instructional design.published_or_final_versio

The biological effect of fenretinide in nasopharyngeal carcinoma cells

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Lithium ion alters Ins(1,4,5)P3 production and mobilisation of intracellular free calcium in k-agonist stimulated rat ventricular myocytes

The effect of lithium ion on the generation of inositol phosphates and the mobilisation of intracellular free calcium in isolated adult rat ventricular myocytes stimulated with k-agonist was studied. Dynorphin1-13 stimulated an increase in the levels of Inositol 1,4,5-trisphosphate (InsP3) and intracellular free calcium ([Ca2+ ]i). Preincubation of the ventricular myocytes with lOmM Li+ for 20 minutes prior to stimulation by dynorphin1-13 reduce the increase of both InsP3 and [Ca2+]i. This effect of Li+ was not seen if 5mM inositol was also present during preincubation. It is concluded that (1) the inhibition of the k-agonist stimulated increase in InsP3 and [Ca2+]i, in Li+-pretreated ventricular myocytes was a result of a depletion of intracellular inositol, due probably to the inhibition by Li+ of inositol monophosphatase which participates in the recycling of intracellular inositol, and (2) the k-agonist induced increase in [Ca2+]i is a consequence of the production of InsP3 since altering the kinetics of production of this compound also altered [Ca2+]i.published_or_final_versio

An unexpected journey of a suction catheter in a preterm neonate

Foreign bodies are extremely rare in preterm neonates. The majority are iatrogenic. We describe a neonate of 27 weeks gestation who was found to have an 18 mm long suction catheter at the right main bronchi after resuscitation in another hospital. It was first detected by chest X-ray after endotracheal intubation. Repeat X-ray revealed the catheter moved to the stomach and migrated to the lower gastrointestinal tract in a few hours. The patient was treated conservatively and the catheter was passed out on day 14. Newborn resuscitation may result in iatrogenic foreign body in neonates. Serious complications such as respiratory compromise, perforations or abscess may occur. Early referral to a specialized tertiary center with pediatric surgical service is recommended. We hope our experience demonstrated the importance of preventing iatrogenic foreign body in clinical setting. Access to endoscopic instrumentation for foreign body removal in preterm neonates should be available at all times.published_or_final_versio

Functional significance of the 3’-UTR in the mRNA of the stress-inducible protein CHOP/Gadd153

Poster Presentation: no. P-H041How translation is regulated by the 3’-untranslated region (3’-UTR) of many messenger RNA is presently not fully understood. This issue is addressed in this study with regard to those mRNA species that are specifically expressed in stressed cells, as exemplified by the stress-inducible CHOP/Gadd153 mRNA. A human genomic fragment with DNA sequence corresponding to the entire 3’-UTR plus an additional 500bp immediately downstream from the polyadenylation site of CHOP/Gadd153 mRNA was cloned into the pEGFP-C1 plasmid. The transcription of this pEGFP-CHOP plasmid in HeLa cells produced two mRNA transcripts due to utilization of either the polyA-signal of the CHOP/Gadd153 gene or the pEGFP-C1 plasmid itself. The EGFP protein level in the pEGFP-CHOP transfected cells was several-fold lower than cells expressing the control (pEGFP-C1). The deletion of the first 171bp from the 5’-end of the ...postprin

Intracellular Reactive Oxygen Species enhances the survival of cells under the conditions of ER stress

Symposium URL at http://www.biochem.hku.hk/postgraduate/symposium2011/Poster Presentation: P-H027An increase in reactive oxygen species (ROS) level in cells that are in a state of stress has been known for a very long time but the underlying functional significance is as yet uncertain. We have addressed this issue by examining the role played by ROS in instances of endoplasmic reticulum (ER) stress in HeLa cells. The treatment of these cells with tunicamycin resulted in sustained increase in intracellular level of ROS that is susceptible to quenching by either N-acetylcysteine (NAc) or dithiolthreitol (DTT), but not by ascorbic acid. The reduction of the availability of folding substrates through inhibition of protein synthesis with cycloheximide resulted in complete absence of tunicamycin-induced phosphorylation of PERK and the splicing of XBP-1, but the increase in ROS level and eIF2α phosphorylation was still observed. The quenching of ROS in tunicamycin-treated cells resulted in partial reduction of eIF2α phosphorylation but otherwise had no effects on the extent of stress-induced inhibition of global protein synthesis, the phosphorylation of PERK and the splicing of XBP. More importantly, significant increase in caspase activities and cell death was observed when tunicamycin was added to cells in the simultaneous presence of NAc or DTT, or to cells that over-expressed catalase to remove intracellular hydrogen peroxide. Our experiments rather unexpectedly reveal that there is a lack of correlation between protein folding and ROS production in ER-stressed cells and that ROS may function to lengthen the period of cellular survival under the condition of continuous stress.postprintThe 2011 Hong Kong Inter-University Biochemistry Postgraduate Symposium, Hong Kong, 11 June 2011