Research Interest
- Mathematical and Computational Neuroscience
- Mathematical Physiology
- Dynamical Systems
Current Research Interests
Activity of Pancreatic Beta-Cells
Pancreatic Beta-cells are the only cells in the body that
secrete insulin, a hormone that is necessary for the uptake of glucose
by other cells. Defects in beta-cell functioning lead to diabetes,
which can result in death if not treated. The release of insulin is
controlled by many physiological variables, including the cell's
electrical activity, calcium, and nucleotide concentrations. I work in
the development and analysis of mathematical models of beta-cell
activity. This work is done in collaboration with
Artie Sherman at the
National Institutes of Health and
Les Satin at the University of Michigan
Medical School.
Hypothalamic Control of Hormone Secretion
The hypothalamus is the region of the brain that regulates the level
and timing of hormone release from endocrine glands. One such gland,
the pituitary, is located near the hypothalamus, and secretions from
this gland regulate secretions from other glands. For this reason, the
pituitary is sometimes called the "master gland". The hypothalamus
sends both stimulatory and inhibitory input to the pituitary,
resulting in neural regulation of secretion from
gonadotrophs, somatotrophs, corticotrophs, melanotrophs, and
lactotrophs. I collaborate with Marc Freeman, Joel Tabak, Arturo
Gonzalez-Iglesias, and Maurizio Tomaiuolo (all at FSU) in the
development and testing of mathematical models to help understand the
complex cellular and network
interactions involved in the secretion of prolactin from pituitary
lactotrophs. Prolactin has many roles in the body, including milk
production in the mammary gland.
Bursting Oscillations in Excitable Cells
In nerve cells, information is transmitted through electrical
impulses. Electrical impulses also cause muscles to contract and
endocrine cells to secrete hormones. Quite often, impulses are
generated as high-frequency bursts, followed by periods of quiescence.
This is particularly true in endocrine cells such as pancreatic
beta-cells. I am interested both in the dynamics of bursting (a
mathematical topic) and in the mechanisms by which
different cells generate periodic bursts of impulses (a biological
topic).
Synaptic Transmitter Release and Short-Term Plasticity
Information is processed and transmitted in nerve cells by electrical
impulses. These impulses are passed from one nerve cell to the next
through a process called synaptic transmission. In the presynaptic
cell, an impulse evokes the release of one or more chemical
neurotransmitters. These transmitters diffuse to the postsynaptic cell
and bind to transmitter receptors, resulting in a postsynaptic voltage
change. I am working on the development of mathematical models that
describe certain aspects of this process, incorporating much of the
known biophysical data. The goal is to better understand transmitter
release and the mechanisms behind the enhancement or depression of
release, i.e., synaptic plasticity. My most recent work is done in
collaboration with done in collaboration with
Artie Sherman and
Victor Matveev.
Neural Network Controlling Bird Songs
This is my most recent project, done in collaboration with
Frank Johnson,
and Wei Wu.
Song birds have a dedicated region of the brain to produce stereotyped
songs. The Johnson lab is studying how this region of the brain
controls vocalization in zebra finches. I work with Johnson and Wu to
quantify the experimental data and, in the future, to develop models
of the neural network controlling song production.
Selected Recent Publications
Helena CV, Cristancho-Gordo R, Gonzalez-Iglesias AE, Tabak J, Bertram R, Freeman ME. Systemic oxytocin induces a prolactin secretory rhythm via the pelvic nerve in ovariectomized rats. Am J Physiol Regul Integr Comp Physiol. 301(3):R676-R681. (2011)
Thompson JA, Basista MJ, Wu W, Bertram R, & Johnson F. Dual Pre-Motor Contribution to Songbird Syllable Variation. J Neurosci. 31(1), 322-330. (2011)
Sirzen-Zelenskaya A, Gonzalez-Iglesias AE, de Monvel JB, Bertram R, Freeman ME, Gerber U, Egli M. Prolactin induces a hyperpolarizing current in rat paraventricular oxytocinergic neurons. J Neuroendocrinol. (2011) [in press]
Tabak J, Mascagni M, Bertram R. Mechanism for the universal pattern of activity in developing neuronal networks. J Neurophysiol. 103:2208-2221. (2010)
Bertram R, Helena CV, Gonzalez-Iglesias AE, Tabak J, Freeman ME. A tale of two rhythms: The emerging roles of oxytocin in rhythmic prolactin release. J Neuroendocrinol. 22:778-784. (2010)
Tabak J, Gonzalez-Iglesias AE, Toporikova N, Bertram R and Freeman ME. Variations in the response of pituitary lactotrophs to oxytocin during the rat estrous cycle. Endocrinology. 151:1806-1813. (2010)
Tomaiuolo M, Bertram R, Gonzalez-Iglesias AE, Tabak J. Investigating heterogeneity of intracellular calcium dynamics in anterior pituitary lactotrophs using a combined modelling/experimental approach. J Neuroendocrinol. 22(12):1279-1289. (2010)
Matveev V, Bertram R, Sherman A. Ca2+ current versus Ca2+ channel cooperativity of exocytosis. J Neurosci. 29(39):12196-20. (2009)
Fendler B, Zhang M, Satin L, Bertram R. Synchronization of pancreatic islet oscillations by intrapancreatic ganglia: a modeling study. Biophys J. 97(3):722-9. (2009)
Helena CV, McKee DT, Bertram R, Walker AM, Freeman ME. The rhythmic secretion of mating-induced prolactin secretion is controlled by prolactin acting centrally. Endocrinology. 150(7):3245-51. (2009)
Helena CV, McKeeDT, Bertram R, Walker AM and Freeman ME. The rhythmic secretion of mating-induced prolactin secretion is controlled by prolactin acting centrally. Endocrinology. 150: 3245-3251. (2009)
Tomaiuolo M, Bertram R, Houle D. Enzyme isoforms may increase phenotypic robustness. Evolution. 62(11):2884-93. (2008)
Zhang M, Fendler B, Peercy B, Goel P, Bertram R, Sherman A, Satin L. Long lasting synchronization of calcium oscillations by cholinergic stimulation in isolated pancreatic islets. Biophys J. 95(10):4676-88. (2008)
Bertram R, Li YX. A mathematical model for the actions of activin, inhibin, and follistatin on pituitary gonadotrophs. Bull Math Biol. 70(8):2211-28. (2008)
Bertram R, Rhoads J, Cimbora WP. A phantom bursting mechanism for episodic bursting. Bull Math Biol. 70(7):1979-93. (2008)
Bertram R, Arceo RC 2nd. A mathematical study of the differential effects of two SERCA isoforms on Ca2+ oscillations in pancreatic islets. Bull Math Biol. 70(5):1251-71. (2008)
Achuthan S, Asbury T, Hu J, Bertram R, Cross TA, Quine JR. Continuity conditions and torsion angles from ssNMR orientational restraints. J Magn Reson. 191(1):24-30. (2008)
Wu W, Thompson JA,
Bertram R, and Johnson F.
A statistical method for quantifying songbird phonology and syntax.
Journal of Neuroscience Methods. vol. 174, no. 1, pp. 147-154. (2008)
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Toporikova N, Tabak J, Freeman ME and Bertram R. A-type K+ current can act as a trigger for bursting in the absence of a slow variable. Neural Computation. 20: 436-451. (2008)
Freeman ME, McKee DT, Egli M and Bertram R. Biological and mathematical modeling approaches to defining the role of oxytocin and dopamine in the control of mating-induced PRL secretion. Neurobiology of the Parental Brain. pp 235-247. (2008)
Tabak J, Toporikova N, Freeman ME and Bertram R. Low dose of dopamine may stimulate prolactin secretion by increasing fast potassium currents. Journal of Computational Neuroscience. 22: 211-222. (2007)
McKee DT, Poletini MO, Bertram R and Freeman ME. Oxytocin action at the lactotroph is required for prolactin surges in cervically stimulated ovariectomized rats. Endocrinology. 148: 4649-4657. (2007)
Egli M, Bertram R, Toporikova N, Sellix MT, Blanco, W. and Freeman ME. Prolactin secretory rhythm of mated rats induced by a single injection of oxytocin. American Journal of Physiology: Endocrinology and Metabolism. 290: E566-E572. (2006)
Bertram R, Egli M, Toporikova N and Freeman ME. A mathematical model for the mating-induced prolactin rhythm of female rats. American Journal of Physiology: Endocrinology and Metabolism. 290: E573-E582. (2006)
Bertram R, Tabak J, Toporikova N and Freeman ME. Endothelin action on pituitary lactotrophs: one receptor, many GTP-binding proteins. Science STKE. Issue 319, pp. pe4, 24 January. (2006) [DOI: 10.1126/stke.3192006pe4]