Dr BALLARD, Heather Janet 白思雅
- BSc, PhD (University of Leeds)
- Associate Professor (Senior Lecturer)
- Deputy Director of the Institute of Cardiovascular Science & Medicine
- Cardiovascular physiology
- Control of skeletal muscle blood flow
- Cardiovascular responses to exercise or systemic hypoxia
- ATP and adenosine release in skeletal muscle
Dr. Ballard obtained her BSc and PhD from the University of Leeds. Upon graduation she spent 3 years in a junior Faculty position at the University of Newcastle upon Tyne, followed by a brief spell in the pharmaceutical industry, before joining the University of Hong Kong as a Lecturer in 1988. She was promoted to Senior Lecturer/Associate Professor in 1997.
Dr. Ballard is committed to excellence in both teaching and research: she served the Faculty as Assistant Dean for Education & Student Affairs from 2004-2010 and is currently the Deputy Director of the Institute of Cardiovascular Science & Medicine.
Our research is focused on the mechanisms that regulate blood flow, particularly in the skeletal muscle circulation, which undergoes large flow changes in the transition from rest to exercise. We also study the interaction between central and peripheral control mechanisms of flow regulation in situations such as exercise or systemic hypoxia.
Our recent work investigates the mechanism of ATP release from the skeletal muscle cells: ATP is an important mediator of exercise hyperaema: it activates afferent nerves in the exercise pressor reflex, and is the substrate for extracellular formation of the important local vasodilator, adenosine. The rate of ATP release from skeletal muscle cells is the strongest determinant of the rate of adenosine formation in the muscle interstitial space.
We have shown that ATP release from skeletal muscle is dependent on activation of the cystic fibrosis transmembrane conductance regulator (CFTR): exercise lowers the intracellular pH of muscle cells, and pH-lowering elevates the intracellular cAMP concentration, resulting in Protein-Kinase-A-dependent activation of CFTR. However, ATP is not released through CFTR itself: CFTR interacts with other proteins in the muscle cell membrane so that CFTR activation brings about the opening of a separate ATP release pore.
Co-immunoprecipitation experiments show that CFTR associates with connexin-43 and pannexin-1 in the muscle cell membrane, and current experiments are directed towards identifying the mechanism of the interaction between them. Another current focus is on the upstream signaling pathway that links the muscle contractions and low pH to the elevation of cAMP in the muscle cell.
Experimental approaches employed in my laboratory range from studies of integrated mammalian physiology down to single cell systems, enzyme studies in fractionated cells and molecular methods.
Techniques include interstitial microdialysis, in vivo pressure and flow measurements, HPLC, spectrophotometric assays, various gas- or ion-sensitive electrodes, confocal microscopy, intracellular pH/ion measurements using fluorescent dyes, immunostaining, RNA interference, and protein overexpression in cultured cell models.
- Le GY, Essackjee HC, Ballard HJ. (2014) Intracellular adenosine formation and release by freshly-isolated vascular endothelial cells from rat skeletal muscle: effects of hypoxia and/or acidosis. Biochemical and Biophysical Research Communications. 450: 93-98. 4 citations
- Tu J, Lu L, Cai W, Ballard HJ. (2012) cAMP/Protein Kinase A activates Cystic Fibrosis Transmembrane Conductance Regulator for ATP release from rat skeletal muscle during low pH or contractions in vivo. PLoS One 7(11): e50157. doi: 10.1371/journal.pone.0050157. I.F. 4.09 (1 yr.), 4.54 (5 yr.); 10 citations.
- Tu J, Le GY, Ballard HJ. (2010) Involvement of the cystic fibrosis transmembrane conductance regulator in the lactic-acid-induced increase in interstitial ATP in rat soleus muscle. Journal of Physiology 588: 4563-4578. I.F. 5.14 (1 yr.), 4.98 (5 yr.); 20 citations; this paper is highlighted in a Perspective Article by Frederic Becq on pp. 4605-4606 of the same volume.
- Das R, Balonan L, Ballard HJ, Ho S. (2008) Chronic hypoxia inhibits the antihypertensive effect of melatonin on pulmonary artery. International Journal of Cardiology 126: 340-345. I.F. 7.08 (1 yr.), 4.11 (5 yr.); 10 citations.
- Liu J, Kam KWL, Borchert GH, Kravtsov GM, Ballard HJ, Wong TM. (2006) Further study on the role of HSP70 on Ca2+ homeostasis in rat ventricular myocytes subjected to simulated ischemia. American Journal of Physiology 290: C583-C591. I.F. 4.33 (1 yr.), 3.98 (5 yr.); 31 citations.
- Yeung EW, Balnave CD, Ballard HJ, Bourreau J-P, Allen DG. (2002) Development of T-tubular vacuoles in eccentrically-damaged mouse muscle fibres. Journal of Physiology 540, 581-592. I.F. 4.72 (1 yr.), 4.93 (5 yr.); 44 citations.
- Mo FM, Ballard HJ. (2001) The effect of systemic hypoxia on interstitial and blood adenosine, AMP, ADP and ATP in dog skeletal muscle. Journal of Physiology 536, 593-603. I.F. 4.72 (1 yr.), 4.93 (5 yr.); 57 citations.
- Cheng B, Essackjee HC, Ballard HJ. (2000) Evidence for control of adenosine metabolism in rat oxidative skeletal muscle by changes in pH. Journal of Physiology 522, 467-477. I.F. 4.72 (1 yr.), 4.93 (5 yr.); 31 citations; Journal of Physiology “Most-read article” in July 2010)
- Mo FM, Ballard HJ. (1997) Intracellular lactate controls adenosine output from canine gracilis muscle during moderate systemic hypoxia. American Journal of Physiology 272, H318-H324. I.F. 3.63 (1 yr.), 3.86 (5 yr.); 11 citations.
- Ballard HJ. (1991) The influence of lactic acid on adenosine release from skeletal muscle in anaesthetised dogs. Journal of Physiology 433, 95 - 108. I.F. 4.72 (1 yr.), 4.93 (5 yr.); 27 citations.
- Faculty Teaching Medal (2002)
- Deputy Director, The Institute of Cardiovascular Science & Medicine (2011-2015)
- Honorary Secretary, The Institute of Cardiovascular Science & Medicine (1999-2003 & 2007-2011)
- Assistant Dean (Education & Student Affairs) (2004-2010)
- Chairman, MBBS Cardiovascular System Block Planning Group (1997-2016)
- Chairman, MBBS Cardiopulmonary and Renal System Block Planning Group (2016-present)
- Co-Chairman, Working Group on the review of whole-class sessions in the MBBS curriculum (2009-2010)
- Chairman, Working Group on the Bachelor of Pharmacy (2006-2009)
- Faculty representative, Senate Discontinuation Committee (2008-2011)
- Faculty representative, Curriculum Development Committee (2004-2008)
- Year 1 Assessment Coordinator, Assessment sub-committee, MBBS Curriculum Committee (2000-2010)
- Course coordinator, graduate course “Advances in Cardiovascular Physiology” (2007-present)
- Course coordinator, B Pharmacy courses “Anatomy, Physiology & Pathophysiology I and II” (2015-present)