Ronald J. Przybylski, Ph.D.
Skeletal Muscle Development
biology and physiology involved in the cell-cell
interactions of skeletal myoblasts to form
multinucleated myotubes is being studied. This
is a critical step in skeletal muscle
development and regeneration after injury since
the end product is the contractile cell. The
molecular signals resulting in myoblast
recognition and then fusion appear to be calcium
regulated. Our previous studies showed that the
intracellular calcium content and the cell
surface concentration are both critical for
myoblasts to progress to the cell recognition
and cell fusion stages of development.
Currently, we are studying the cell surface
calcium sensors, calcium regulated cell surface
phosphorylation and phosphatase activity and
whether these events elicit transmembrane
signals which regulate specific genes. Further,
we are testing whether micro domains of the cell
membrane exist which are involved in these
calcium regulated cell surface events because
myoblast fusion occurs in restricted regions of
the cell membranes.
RJ., RG. MacBride and AC Kirby. Calcium
regulation of skeletal myogenesis. I. Cell
content critical to myotube formation. In Vitro
Cell and Develop. Biol. 25: 830-838,1989.
RJ., SJ Davidheiser, V Szigeti and AC Kirby.
Calcium regulation of skeletal myogenesis. II
Extracellular and cell surface effects. Cell
Calcium 15:132-142, 1994.
V Szigeti and AC Kirby. Calcium regulation of
skeletal myogenesis. IV A defined culture medium
permissive for myotube formation and the use of
the calcium antagonist lanthanum. In Vitro Cell
Develop. Biol. 22:402-406, 1986.
Bright, GR, NT
Kuo, D Chow, S Burden, C Dowe and RJ Przybylski.
Delivery of macromolecules into adherent cells
via electroporation for use in fluorescence
spectroscopic imaging and metabolic studies.
Cytometry 24:226-233, 1996.
Important Roles of Glucose and Oxygen in
birth is dependent on proper respiration and
glucose metabolism. These phenomena are tightly
interrelated to produce ATP. Our projects
include: 1) insulin regulation of glucose uptake
through the glucose transporter protein GLUT-4.
2) the basis for insulin resistance- insulin
receptor vs. intracellular signaling vs. glucose
transporter translocation; 3) the regulation of
glucose uptake by hypoxia through the glucose
transporter protein GLUT-1.
Johnston, V, V
Franzini, S Davidheiser, RJ Przybylski, and RJ
Kliegman. Insulin receptor number and binding
affinity in newborn dogs. Pediatric Res.
RJ, R Freeh, SR Vadlamudi and RM Kliegman.
Skeletal and cardiac muscle cells from insulin
resistant newborns become insulin sensitive in
cell culture. Mol. Cell Biol. 3:817, 1992.
Sasson S, EP Freener, N Boukobza-Vardi, S
Higashi, DE Moller, S Davidheiscr, RJ Przybylski
and G King. Differential regulation of glucose
transport and transporters by glucose in
vascular endothelial and smooth muscle cells.
Diabetes 42:80-89, 1993.
Kuo NT, RM Kliegman, and RJ
Przybylski. Insulin resistance in newborns:
insulin receptors, IRS- 1, phosphotidylinositol
3'-kinase and glucose transporters. Pediatric
Res 35:204, 1994.
Pichiule P, JC
Chavez, RJ Przybylski, and JC LaManna. Increase
of neuronal nitric oxide synthase during chronic
hypoxia. In: Oxygen Transport to Tissue XX
(Advances in Experimental Medicine and Biology
v.), edited by AG Hedetz and D Bruly, New York:
Plenum Press, 1998, in press.
Survival Mechanisms During and After Heart
Ischemia/reperfusion injury is an important
pathological process which is manifested
clinically as reperfusion induced arrhythmias,
myocardial stunning and an increase in the rate
of cell death. Transient, intermittent ischemia,
so-called ischemia pre-conditioning, produced
experimentally or experienced as clinical angina
promotes myocardial viability and mechanical
function during a subsequent more severe heart
attack. These events suggest that genes involved
in cell survival have enhanced expression. The
overall hypothesis that we are testing is that
preconditioning mediates a protection of the
myocardium by dramatically reducing the amount
of apoptosis (programmed cell death) that occurs
during ischemia and reperfusion. Cells
undergoing apoptosis exhibit significantly
altered ion homeostasis, gene expression, and
ultimately loss of plasma membrane integrity.
Apoptosis is regulated by the relative amounts
of apoptotic (death) and anti-apoptotic (life)
genes. Our preliminary results show that
preconditioning leads to the enhanced expression
of at least one anti-apoptotic gene and a shift
in the ratio of life and death genes to favor
life processes. We are investigating the
possible altered expression of other related
genes during experimental preconditioning and
myocardial infarcts as related to myocardial
contractility and ion homeostasis. Further, we
are investigating whether chemical mimics of
pre-conditioning used therapeutically work via
expression of apoptotic and anti-apoptotic