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Trainees of Distinction

 

Jennifer Catalano

Mentor: Avi Gnatt

Research Areas: Toxicology/Genomics

I am working on a project in collaboration with the US Army to study the toxic effects of organophosphates and various organic solvents on the nervous system. I am using a cell culture model system, in combination with cDNA microarray technology to study altered gene expression after exposure to particular compounds of interest. These results are confirmed with classical methods such as RT-PCR. The toxicants studied are models for chemical and biological weapons to which soldiers might be exposed; it is hoped that this work will benefit them in combat situations.


 
 

Tony Gover

Mentor: Danny Weinreich

Research Area: Neuropharmacology

My research interests include synaptic physiology related to nerve terminal plasticity and novel methods to study this physiology. A recent past study I completed with Dr. Tom Abrams looked at synaptic plasticity between the sensory and motor neurons that are responsible for the defensive withdrawal reflex in Aplysia. We wanted to know what mechanisms of synaptic depression occurred at this synapse. Using a combination of computer simulations and electrophysiological studies we found a novel mechanism of synaptic depression. We found that homosynaptic depression at this synapse was a consequence of release-independent silencing of presynaptic nerve terminals. This active switching off of release sites contributes to behavioral habituation, the ignoring of stimuli with little behavioral importance.

My current research, and thesis project, is conducted in the lab of Dr. Danny Weinreich. It focuses on free calcium dynamics and regulation in sensory nerve terminals of the cornea. Calcium is an important regulator of several sensory nerve terminal functions. Substantial indirect evidence suggests calcium is important for nerve terminal excitation, sensitization and desensitization to several sensory stimuli. It is also necessary for the release of trophic factors and inflammatory mediators from peripheral sensory nerve terminals. The cornea offers unique advantages for direct measurements of calcium in sensory nerve terminals. These include: a high density of sensory nerve terminals, nerve terminals traveling within a few microns of the corneal surface, and an absence of myelination and blood vessels. With this preparation we should be able to provide new and fundamental knowledge about calcium dynamics in sensory nerve terminals.

Publications from Weinreich Lab

Lancaster E, Oh EJ, Gover T, and Weinreich D. (2002) Calcium and calcium-activated currents in vagotomized rat primary vagal afferent neurons. J Physiology. 540:543-556.

Gover TD, Jiang XY, and Abrams TW. (2002) Persistent, exocytosis-independent silencing of release sites underlies homosynaptic depression at sensory synapses in Aplysia. J Neuroscience 22:1942-55.

Carr MJ, Gover TD, Weinreich D, and Undem BJ. (2001) Inhibition of mechanical activation of guinea-pig airway afferent neurons by amiloride analogues. British J Pharmacology 133:1255-62.


 
 

Dmitry N. Grigoryev

Mentor: Angela Brodie

Research Area: Oncopharmacology

During my doctorate training in Pharmacology and Experimental Therapeutics, I received vigorous training in modern oncopharmacology. In Dr. Angela Brodie’s laboratory I was initially involved in breast cancer research. I studied potencies of new inhibitors on aromatase enzyme activity in human placental microsomes. Then, for my thesis research, I studied prostate cancer with Dr. Brodie as an advisor. My research involved pre-clinical evaluation of effects of new androgen synthesis compounds on hormone responsive prostate cancer. During this research I learned and developed a range of novel techniques for screening and evaluating new anticancer therapeutic compounds in vitro and in vivo.

Publications from Brodie Lab

Grigoryev, D.N. , Long, B.J., Njar, V.C.O., and Brodie, A.M.H. (2000) Pregnenolone stimulates LNCaP prostate cancer cell growth via the mutated androgen receptor: implications for the treatment of prostate cancer. J. Steroid Biochem. Molec. Biol. 75:1-10.

Grigoryev, D.N. , Long, B.J., Njar, V.C.O., Liu, Y., Nnane, I.P., and Brodie, A.M. (1999) Effects of new 17a-hydroxylase/C17,20-lyase inhibitors on the growth of LNCaP prostate cancer cells in vitro and in vivo. Br. J. Cancer, 81, 622-630.

Grigoryev, D.N. , Kato, K., Njar, V.C.O., Long, B.J., Ling, Y-Z., Wang, X., Mohler, J, and Brodie, A.M.H. (1999) Cytochrome P450c17-expressing Escherichia coli as a first-step screening system for P450 17a-hydroxylase-C17,20-lyase inhibitors. Analytical Biochemistry, 267: 319-330.

Subsequent Positions

2000-present: CRTA Fellow, NIH, National Cancer Center
1999: Post-Doctoral Fellow, VA Medical Center, Baltimore


 
 

Kim Moore

Mentor: Danny Weinreich

Research Area: Neuropharmacology

My dissertation research in Dr. Danny Weinreich’s lab focused on communication between the immune and nervous systems. Immunologically sensitized guinea pigs exposed to aerosolized antigen are often used as a model for allergic airway inflammation. ‘Challenge’ of the animals with the sensitizing antigen activates mast cells, resulting in the release of a plethora of preformed (granular stored, e.g. histamine and serotonin) and newly synthesized (e.g. arachadonic acid metabolites) inflammatory mediators. Utilizing this model, we identified inflammation-induced changes in the tachykinin responsiveness of vagal afferents (nodose ganglion neurons). Nodose neurons acutely isolated from normal guinea pigs are unresponsive to tachykinins. In sharp contrast, following airway inflammation, tachykinin application depolarizes ~80% of nodose neurons. In vitro, up-regulation or ‘unmasking’ of tachykinin receptors can occur within minutes and is independent of new protein synthesis, suggesting that the receptors are present but not functional in control nodose neurons. Pharmacological analysis revealed that 5-HT3 receptor activation, calcium/calmodulin, and nitric oxide are requisite for the unmasking process. Finally, antagonism of 5-HT3 receptors during in vitro antigenic activation of nodose ganglia significantly reduced the percentage of tachykinin responsive neurons, confirming that 5-HT3 receptor activation is essential for allergic inflammation–induced receptor unmasking. Receptor unmasking is a novel mechanism of primary afferent neuron sensitization. Since it is likely that other G-protein coupled receptors may be modulated by immune mediators in a similar fashion, these principles may also be applied to other receptor systems to enhance our overall comprehension of inflammation-induced synaptic plasticity.

Publications from Weinreich Lab

Moore, K. A., Cohen, A. S., Kao, J. P. Y. and Weinreich, D. Ca2+ - induced Ca2+ release mediates a slow post spike hyperpolarization in rabbit vagal afferent neurons. Journal of Neurophysiology, 79:688-694, 1998.

Moore, K. A., Taylor, G. E. and Weinreich, D. Serotonin unmasks functional NK-2 receptors in vagal sensory neurones of the guinea pig. Journal of Physiology (London), 514:111-124, 1999.

Moore, K. A., Undem, B. J. and Weinreich, D. Airway inflammation in vivo unmasks NK-2 tachykinin responses in primary vagal afferents. American Journal of Respiratory and Critical Care Medicine, 161:232-236, 2000.

Moore, K. A., Oh, E. J. and Weinreich, D. Serotonin mediates allergic inflammation-induced unmasking of functional NK-2 tachykinin receptors. Journal of Applied Physiology, in press, 2002.

Subsequent Positions

1999-2001: Post-Doctoral Fellow., Harvard Medical School
2001- present: Post-Doctoral Fellow, University of California San Francisco


 
 

Chiadi U. Onyike

Mentor: Tom Abrams

Research Area: Cell Signaling

In my research, I studied the molecular mechanisms by which Ca2+ allosterically modulates transmitter stimulation of adenylyl cyclase. Earlier studies had suggested that during classical conditioning, the dually-regulated Ca2+/calmodulin(CaM)-sensitive adenylyl cyclase plays a critical role in detecting the temporal relationship between paired stimuli. This model proposes the enzyme as an associative molecular integrator that is stimulated by activity in the sensory neurons of the conditioned stimulus (CS) pathway in Aplysia, as well as by modulatory neurotransmitter. When modulatory transmitter release (triggered by the unconditioned stimulus, US) is paired with Ca2+ influx (during activity in the sensory neuron triggered by the CS) in the temporally appropriate CS-US sequence, the result is an increase in cAMP synthesis, a greater cAMP rise than would occur with the presentation of either stimulus alone. This increase in cAMP acts to strengthen the synaptic connections from neurons of the CS pathway.

Two broad questions arise out of this model: Why would simultaneous presentation of the stimuli not be optimally effective in activating the adenylyl cyclase? Can the activation properties of this enzyme account for the temporal requirement for stimulus pairing? I explored these questions using native adenylyl cyclase derived from Aplysia CNS membranes, and the recombinant type I adenylyl cyclase from mammalian brain amplified in High-Five cells using the baculovirus vector expression system. Our data suggested that both the Aplysia and mammalian CaM-sensitive adenylyl cyclase show a substantial delay in the stimulatory response to a Ca2+ pulse. This delay appears to be the result of a rapid transient direct inhibitory effect by Ca2+, as well as the slow time course of activation by CaM. In addition there is a persistence of the CaM stimulation of the adenylyl cyclase after Ca2+ levels have dropped which appears almost entirely due to the slow uncoupling of CaM from the enzyme (free CaM in solution has no memory for Ca2+). These findings support the prediction that optimal activation requires the arrival of the modulatory transmitter after the initial rise in Ca2+, when CaM-mediated stimulation has begun. This delay in the stimulatory response to Ca2+/CaM may contribute to the requirement in conditioning that presentation of the CS precede presentation of the US.

Publications from Abrams lab

Onyike CU, Lin AH, and Abrams TW. (1998). Persistence of the interaction of calmodulin with adenylyl cyclase: implications for integration of transient Ca2+ stimuli.. J. Neurochemistry. 71:1298-1306.

Lin, AH, Onyike CU and Abrams TW. (1998). Sequence-dependent interactions between transient calcium and transmitter stimuli in activation of mammalian brain adenylyl cyclase. Brain Research. 800:300-307.

Subsequent Positions

1997-2000: Resident & Chief Resident, Department of Psychiatry, Johns Hopkins Hospital
2000-2002: Research Fellow in Psychiatric Epidemiology, Department of Mental Hygiene, Bloomberg School of Public Health, Johns Hopkins University
2000-2002: Clinical Fellow, Department of Psychiatry, Johns Hopkins Hospital
2000-present: Director, Psychiatric Emergency Services, Department of Psychiatry, Johns Hopkins Hospital
2002-present: Assistant Professor, Department of Psychiatry, Johns Hopkins Hospital


 
 

Dana Perkins

Mentor: Laure Aurelian

Research Area: Neurovirology

In my graduate research I discovered that one of the Herpes Simplex Virus 2 (HSV-2) genes, called ICP10 PK, has anti-apoptotic activity in neurons, i.e., it promotes neuron survival. Specifically, protects primary neuronal cultures from apoptosis (a sequence culminating in cell death) that is induced by virus infection, oxidative stress, neurotrophic factor deprivation and innate genetic defects that lead to apoptosis. In order to deliver ICP10 PK to the brain, I used a replication-deficient HSV-2 vector (constructed in our laboratory) instilled intranasally in mice. ICP10 PK was expressed in the hippocampus and related limbic structures and infected mice were free of inflammation and neurological impairments, suggesting that ICP10 PK can be used as a therapeutic for neurological disorders that involve apoptosis (such as Alzheimer's disease or Down syndrome) and can be safely and efficiently delivered by peripheral administration of an HSV-2 vector.

Awards

Winner of the 2nd Annual Research Paper Contest for Graduate Students, organized by the American Society for Microbiology, Maryland Branch, 2002.

Winner of the National Collegiate Inventors Competition (organized by the U.S. Patent and Trademark Office and the National Inventors Hall of Fame), 2001. Title of invention: “Gene therapy of Alzheimer’s disease using a herpes simplex virus vector”.

Patent co-author: “Anti-apoptotic activity of HSV-2 gene ICP10 PK”. International Patent Application filed on July, 2001.

Publications from Aurelian Lab

Perkins, D., Pereira, E.F.R., Gober, M., Yarowsky, P., and Aurelian, L. 2002. The Herpes Simplex Virus Type 2 gene R1 PK (ICP10 PK) blocks apoptosis in hippocampal neurons involving activation of the MEK/MAPK survival pathway. J.Virol. 76: 1435-1449

Perkins, D., Yu, Y., Bambrick, L., Yarowsky, P.J. and Aurelian, L. 2002. Expression of the Herpes Simplex Virus Type 2 Protein ICP10 PK protects neurons from apoptosis due to serum deprivation or genetic defects. Exp. Neurol. 174: 118-122

Perkins, D., Gyure, K., Pereira, E.F.R., and Aurelian, L. 2002. Encephalitis caused by Herpes Simplex Virus Type 1 has an apoptotic component involving activation of c-Jun N-terminal kinase. J. NeuroVirol. Submitted