Research Interests:
Control of the volume of
surface liquid which covers the pulmonary epithelium is critical for normal
mucociliary clearance and for efficient gas exchange. The role that active
transepithelial ion transport plays as a driving force for liquid movement
across the pulmonary airways is currently under study. We measure the
bioelectric properties of isolated bronchi and bronchioles as correlates of
active ion transport activity. We then use selective transport inhibitors
and stimulators to determine which transport pathways are present and how
these processes are regulated. In persons afflicted with cystic fibrosis
(CF), a molecular defect in an epithelial chloride channel is present that
leads to a myriad of pathological problems, the most critical of which
involves secretion of thickened, dehydrated mucus into the airways. A major
focus of our research is to determine how such defects in chloride ion
transport are mechanistically related to the development of the symptoms
observed in cystic fibrosis patients. Our findings suggest that fluid
secretion from the submucosal glands of the trachea and bronchial airways
is disrupted in CF, leading to the production of a highly concentrated
mucus that is poorly cleared from the airways by cough or by mucociliary
transport. We use techniques for measuring liquid secretion, mucociliary
transport, and ciliary beat frequency to determine the importance of
interactions between periciliary fluid, mucus, and cilia at the airway
surface for maintaining normal ciliary clearance. We also model important
aspects of CF lung disease in porcine isolated lungs by perfusing the
vasculature with selective inhibitors of anion secretion. We are now
expanding our studies by exploring new ways to model CF lung disease
including use of in vitro (siRNA) and in
vivo (screening non-humam animal populations for mutant CFTR)
approaches. We believe that our findings are of great importance for
understanding the underlying cause of CF lung disease and for development
of effective treatments.
If you would like to know
more about my work, or if you are interested in graduate or post-graduate
studies in my laboratory, please feel free to e-mail me at sballard@usouthal.edu.
Currently (8/05), I have
an opening for a post-doctoral fellow. Click here to
see the job description.
If you are interested in this position, please contact me by
e-mail.
Selected
Publications:
 Ballard, S.T., J.D.
Fountain, S.K. Inglis, and A.E. Taylor. Chloride
secretion across distal airway epithelium: relationship to submucosal gland
distribution. Am. J. Physiol. 268:L526-L531, 1995.
Corboz, M.R., S.T.
Ballard, S.K. Inglis, and A.E. Taylor. Tracheal
microvascular responses to inhibition of nitric oxide synthesis in
anesthetized rats. Am. J. Respir. Crit Care Med. 154:1382-1386, 1996.
Corboz, M.R., S.T.
Ballard, S.K. Inglis, and A.E. Taylor. Beta-adrenergic
stimulation of the tracheal microvasculature in anesthetized rats. Am.
J. Respir. Crit. Care Med. 153:1093, 1996.
Inglis, K.I., M.R.
Corboz, A.E. Taylor, and S.T. Ballard. Regulation
of ion transport across porcine distal bronchi. Am. J. Physiol.
14:L279-L297, 1996.
Corboz, M.R., S.T.
Ballard, S.K. Inglis, and A.E. Taylor. Dilatory
effect of furosemide on tracheal arterioles and venules. Am. J. Respir.
Crit Care Med. 156:478-483, 1997.
Inglis, S.K., M.R.
Corboz, A.E. Taylor, and S.T. Ballard. Effect
of anion transport inhibition on mucus secretion by airway submucosal
glands. Am. J. Physiol. 272:L372-L377, 1997.
Inglis, S.K., M.R.
Corboz, A.E. Taylor, and S.T. Ballard. In
situ visualization of bronchial submucosal glands and their secretory
response to acetylcholine. Am. J. Physiol. 272:L203-L210, 1997.
Corboz, M.R., and
S.T. Ballard. "Intravital microscopy: airway circulation," in
Methods in Pulmonary Research, eds. S. Uhlig and A.E. Taylor,
Birkauser-Verlag, Basel, 1998.
Inglis, S.K., M.R.
Corboz, and S.T. Ballard. Effect
of anion secretion inhibitors on mucin content of airway submucosal gland
ducts. Am J. Physiol. 274:L762-L766, 1998.
Trout, L., M. King,
W. Feng, S.K. Inglis, and S.T. Ballard. Inhibition
of airway liquid secretion and its effects on the physical properties of
airway mucus. Am. J. Physiol. 274:L258-L263, 1998.
Trout, L., J.T.
Gatzy, and S.T. Ballard. Contribution
of chloride and bicarbonate transport to acetylcholine-induced liquid
secretion in porcine bronchial epithelium. Am. J. Physiol.
275:L1095-L1099, 1998.
Ballard, S.T., L.
Trout, Z. Bebok, E.J. Sorscher, and A. Crews. CFTR involvement in chloride, bicarbonate and liquid
secretion by airway submucosal glands. Am. J. Physiol. 277:L694-L699,
1999.
Corboz, M.R., S.T.
Ballard, H. Gao, J.N. Benoit, S.K. Inglis, and A.E. Taylor. Differential effects of furosemide on porcine vascular and
bronchial smooth muscle. J. Appl. Physiol. 89:1360-1364, 2000.
Crews,
A., A.E. Taylor, and S.T. Ballard. Liquid
transport properties of tracheal epithelium. J. Appl.
Physiol.91:797-802, 2001.
Trout,
L., M.R. Corboz, and S.T. Ballard.
Mechanism
of substance P-induced liquid secretion across porcine bronchial epithelium. Am. J. Physiol. 281:L639-L645,
2001.
Ballard,
S.T., L. Trout, A. Mehta, and S.K. Inglis. Liquid
secretion inhibitors reduce mucociliary transport in glandular airways. Am. J. Physiol. 283:L329-L335,
2002.
Trout,
L., M.I. Townsley, A. Bowden, and S.T. Ballard. Disruptive
effects of anion secretion inhibitors on airway mucus morphology in
isolated perfused pig lungs.
J. Physiol. 549.3:845-853, 2003.
Ballard,
S.T. and S.K. Inglis. Liquid
secretion properties of airway submucosal glands. J. Physiol. 556.1:1-10, 2004.
Ballard,
S.T. Airway liquid secretion
and cystic fibrosis lung disease.
News in Physiology
54:22-23, 2004.
Ballard,
S.T., L. Trout, S.K. Inglis, and J. Garrison. Ionic mechanism of forskolin-induced liquid secretion by
porcine bronchi. (in review)
Ballard
S.T., J.C. Parker, and C.R. Hamm.
Restoration of mucociliary transport in the fluid-deplete trachea by
surface-active substances. (in
review)
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