Biology & Neuroscience Spring 2008 Thesis Defenses

by Paul Heideman | January 31, 2008

Biology Department thesis defense events are also listed in the Biology Events Calendar.

Vinny Roggero (Master’s Defense, Allison)
Tuesday, April 15th
1pm, Small Hall TBA

Andy Speidell (Griffin)
The Effects of Cirazoline and Clonidine on the Firing Rates of Thermally Classified Neurons in the Anterior Hypothalamus of the Rat
Friday, April 18th
2pm, Millington 119

Terence Imbery (Neuroscience, Griffin)
An Analysis of COX-2 Derived PGE2 in the Alpha-1 and Alpha-2 Adrenoreceptor-Mediated Responses of Thermally Classified Neurons in the Anterior Hypothalamus
Tuesday, April 22nd
2pm, TBA

Connie Gibbons (Heideman)
The Effect of Diet on Reproductive Inhibition in Photoresponsive White-Footed Mice (Peromyscus leucopus)
Thursday, April 24th
12pm, Morton Room 4

Kristin Mahalak (Heideman)
Use of Non-Native Macroalgal Habitat by Hatchery-Reared and Wild Blue Crab Juveniles
Friday, April 25th
9am, Small 240

Chris Johnstone (Master’s Defense, Case)
The Vascular Flora of the Totuskey Creek Watershed
Friday, April 25th
3pm, Millginton 119

Stephen Schworer (Bradley)
Correlation of NIS mRNA levels with radioiodide uptake in mammary tumors and non-tumor mammary glands of MMTV-infected mice
Tuesday, April 29th
10am, Millington 108

Saji Perera (Swaddle)
Tuesday, April 29th
11am, Morton 302

Daniel Teasley (Saha)
Transcription factor coexpression with GABAergic and glycinergic terminal differentiation genes
Tuesday, April 29th
1pm, Millington 108

Amy Dapper (Gilchrist)
Tuesday, April 29th
2pm, Millington 123

Brittany Johnson (Saha)
Wednesday, April 30th
9am, Millington 108

Drew Hughes (Saha)
Wednesday, April 30th
2pm, Millington 108

Ben Winer (Wawersik)
The development of time of flight second ion mass spectroscopy to investigate biological tissue
Saturday, May 10th
10am, Millington 108

Kellyn Carrierfenster (Saha)
Thursday, May 1st
12pm, Millington 108

Abigail Brunner (Allison)
Thursday, May 1st
1pm, Millington 117

Abstract:
Previous studies have proved that during a lipopolysaccharide (LPS) challenge, norepinephrine (NE) levels in the preoptic area of the mammalian hypothalamus (PO/AH) rise and are correlated with an increase in core body temperature. Whole animal studies have revealed that selective activation of the α1- and α2-adrenergic receptors (ARs) can, respectively, induce a hyperthermic or hypothermic thermoregulatory response. Therefore, we hypothesize that in accordance with established models of neural thermoregulation, firing rate responses to the α1-AR agonist Cirazoline and the α2-AR agonist Clonidine should differ with respect to thermosensitivity of the neuron. To characterize these responses, single-unit recordings of neurons in rat hypothalamic tissue preparation were made. Neurons were classified as either warm sensitive or temperature insensitive through manipulations in local temperature. This was followed by treatment of the neuron with either Cirazoline or Clonidine. As hypothesized, the majority of insensitive neurons increased their firing rate when exposed to Cirazoline and decreased their activity when introduced to Clonidine. When warm sensitive neurons were treated with Cirazoline, all responded with a decrease in activity, while most increased their firing rate during treatment with Clonidine.

Return to top

Abstract:
In vivo evidence demonstrates that the initial febrigenic signal from the periphery is communicated to the anterior hypothalamus (AH), the thermoregulatory center of the brain, via ascending projections of the hepatic vagus nerve. The subsequent release of Norepinephrine (NE) in the AH is a key intermediary of the febrile response, resulting in two distinct phases mediated by a1 and a 2 adrenoreceptors (AR). Activation of the a1 AR produces a PGE2-independent rise in body temperature, whereas a2 activation yields a biphasic response; hypothermia followed by a PGE2-dependent temperature increase (Feleder et al., 2007). What remains unknown is how these ARs modify the firing rate of thermoregulatory neurons within the AH to drive these phases and which cyclooxygenase (COX) isozyme is responsible for PGE2 production. The action of NE in the AH was tested in the present study with the selective COX-2 inhibitor Meloxicam (.1-10 µM) by recording single-unit activity of AH neurons in a tissue slice preparation from the adult male rat, in response to temperature and the selective a1 AR agonist Cirazoline (1 µM) or the selective a2 AR agonist Clonidine (1 µM). All neurons were classified as either warm sensitive or temperature insensitive. Warm sensitive neurons responded to Cirazoline with a decrease in firing rate, while temperature insensitive neurons showed a firing rate increase. These findings strengthen the role of the a1 AR in quickly driving set-point temperature into a hyperthermic range to initiate fever in a PGE2- independent fashion. In contrast, warm sensitive neurons responded to Clonidine with an increase in firing rate, while temperature insensitive neurons showed a firing rate decrease. This indicates the a2 AR may initially be driving an opposing hypothermia, but COX-2 inhibition eliminated late phase responses after a2 AR activation, suggesting that PGE2 from this pathway is responsible for sustaining the fever initiated by a1 AR.

Return to top

Chris Johnstone(Master’s Defense, Case)
The Vascular Flora of the Totuskey Creek Watershed
Friday, April 25th
3pm, Millginton 119

Abstract:
The vascular flora of the lower Totuskey Creek watershed, Richmond County, Virginia was surveyed from 2005 to 2007. The county is one of five which form the Northern Neck Peninsula, the northernmost peninsula on the coastal plain of Virginia. The peninsula is bound by the Potomac River to the north, and the Rappahannock River to the south. Numerous habitats were surveyed within the study site encompassing 50 square miles in the eastern portion of Richmond County. These habitats included upland mixed hardwood forest, pine/mixed hardwood forest, successional pine stands, ravines, creek banks, fresh and brackish marshes, stream flood plains, ponds, roadsides, fields, and powerline cuts.

A total of 672 plant taxa were collected and represent 125 families and 399 genera. One hundred forty-six taxa are new records to Richmond County while 16 of these are new records to the Northern Neck. Two species previously thought not to occur north of the Middle Peninsula, Eupatorium saltuense and Quercus laurifolia, are now documented on the Northern Neck from Richmond County. Nearly half (48.7%) of the native flora is distributed west beyond the Mississippi River but falls short of the Pacific Coast. Another 20.8% of the flora is non-native.

With the assistance of relatively new floristic data from studies on the Northern Neck, an analysis of regional floristic similarity indicates the Northern Neck is more similar to the Middle and Lower peninsulas of Virginia than previous results indicated. The flora of the coastal plain of Maryland appears the most distinct among the floras considered. The proportion of southern species decreases in a northerly direction across these same areas, while the proportion of northern species fails to change in a north-south direction.

Return to top

Connie Gibbons (Heideman)
The Effect of Diet on Reproductive Inhibition in Photoresponsive White-Footed Mice (Peromyscus leucopus)
Thursday, April 24th
12pm, Morton Room 4

Abstract:
Variation in reproduction is a characteristic of many different species. Reproductive variation can be caused by genetic variation, phenotypic plasticity, or a combination of both factors. The genes of an animal set up reaction norms, which include phenotypically plastic responses to different environmental cues. One environmental cue that has a powerful effect on reproductive variation in many mammalian species is photoperiod. Animals that are reproductively responsive to photoperiod demonstrate suppressed reproductive capacity in short, winter-like photoperiods. A second environmental cue that has a powerful effect on reproduction is food availability. The importance of food availability in reproductive variability is unsurprising, because increased energy is required for reproductive activity. Previous studies have shown that reduced food availability can result in suppressed reproduction. This study tests whether an abundance of high quality food can also effect reproductive variation. In this study, we tested reproductively photoresponsive male white-footed mice, Peromyscus leucopus, to determine if a high fat diet could overcome the reproductive suppression usually seen in short day photoperiods. This study also tested whether P. leucopus provided with a high fat diet consumed more kilocalories than mice provided with a defined control diet. Our results indicated increased caloric intake and gonad mass in mice provided with a high fat diet, but not to statistically significant levels.

Return to top

Kristin Mahalak (Heideman)
Use of Non-Native Macroalgal Habitat by Hatchery-Reared and Wild Blue Crab Juveniles
Friday, April 25th
9am, Small 240

Abstract:
Seagrass beds are thought to be the preferred nursery habitat for juvenile blue crabs, Callinectes sapidus, increasing both survival and growth in early molt stages. Degradation of this structured nursery habitat and a drastic decline in spawning stock due to natural and fishing mortality having many scientists concerned about the Chesapeake Bay's blue crab population. This study looked to determine how a non-native macroalga, Gracilaria spp. may function as an alternative nursery habitat for juvenile crabs and how it may help to increase release success of hatchery-reared individuals as part of stock enhancement efforts. Approximately, ~28,000 hatchery-reared blue crab juveniles were released near the mouth of the York River in an unvegetated mud cove enhanced with ~3600 L of Gracilaria spp. Sampling was conducted in two areas of the cove using a basket apparatus. The number and size (carapace width-CW) of crabs were measured during each sampling. The crabs collected during sampling were sent to the Center of Marine Biotechnology in Baltimore, MD and identified as hatchery-reared or wild using genetic analysis. Densities of crabs in each site suggest Gracilaria in the mud cove had a carrying capacity of ~4-8 crabs m-2. Genetic analysis determined that a number of hatchery-reared crabs remained within the mud cove for the entire study period. Mean carapace width for hatchery-reared cohort increased from 7.15mm(SE+/- 0.0581) to 6.6mm(SE+/- 1.93). In addition, settlement of wild juvenile recruits in the Gracilaria was observed in early August. These findings suggest that the non-native macroalgae Gracilaria spp. serves as an alternative nursery habitat for blue crab juveniles and release of hatchery-reared juveniles into habitats containing Gracilaria spp. may help to increase post-release success.

Return to top

Stephen Schworer (Bradley)
Correlation of NIS mRNA levels with radioiodide uptake in mammary tumors and non-tumor mammary glands of MMTV-infected mice
Tuesday, April 29th
10am, Millington 108

Abstract:
We have developed an in vivo non-invasive gamma camera imaging system which uses ¹²⁵I to detect functional iodide metabolism in mammary tumors. Iodide metabolism in these tumors is mediated by the sodium iodide symporter. The quantity and pattern of radioiodide uptake varies between mammary tumors. We have previously shown that localization of NIS protein expression reflects the radioiodide uptake in gamma camera images. In this study, we investigate whether expression levels of NIS mRNA in mammary tumors correlate with ¹²⁵I uptake pattern shown in gamma camera images. Our hypothesis is that NIS function in mammary tumors and non-tumor mammary glands is regulated primarily at the transcriptional level. To test this hypothesis, we quantified NIS mRNA levels using TaqMan real-time RT-PCR, and constructed a cRNA standard curve for quantification. The ratio of NIS to the housekeeping gene β-actin was compared to the intensity and pattern of mammary tumor radioiodide uptake as imaged by the gamma camera. In MMTV tumors, our results suggest that NIS is under both transcriptional and post-transcriptional control in this model for breast cancer. In separate tumors, we observed both positive correlation and no correlation between NIS mRNA level and radioiodide uptake. We also found that NIS mRNA levels were increased in non-palpable tumors in correlation with increases in radioiodide uptake, suggesting that an upregulation of NIS mRNA occurs in early tumor development.

Return to top

Daniel Teasley (Saha)
Transcription factor coexpression with GABAergic and glycinergic terminal differentiation genes
Tuesday, April 29th
1pm, Millington 108

Abstract:
The adoption of neurotransmitter phenotype is a crucial step in thedevelopment of the nervous system. Ca2+ transients have been shown to play a critical role by modulating neurotransmitter phenotype specification during differentiation. The mechanisms by which this occurs remain unclear, but given that Ca2+ affects terminal differentiation gene expression, transcription factors may be regulated by the Ca2+ transients. As a first necessary step in elucidating the effects of Ca2+ on transcription factors in neuronal development, we have characterized the coexpression patterns of transcription factors with terminal differentiation genes to provide a baseline for future studies. We have found that the transcription factors xDlx2 and xDlx5 colocalize extensively with both xGAD67 and xVIAAT in the telencephalon and diencephalon in very similar patterns. xPitx2 is coexpressed moderately with both xGAD67 and xGAT1 in the midbrain, and xPtf1a colocalizes moderately with xGAD67 in the retina. Xbh1 colocalizes extensively with xGlyT1 in the retina. Interestingly, xPitx2 is expressed mutually exclusive to xGAD67 and xGAT1 in the diencephalon with virtually no colocalization. Similarly, Xbh1 is expressed in a mutually exclusive pattern to xGAD67 and xVIAAT in the midbrain. All of these observations lead to several conclusions, among them that the similar coexpression patterns observed for xGAD67, xGAT1, and xVIAAT with several transcription factors suggest that the GABAergic terminal differentiation genes are all subject to similar transcriptional regulatory mechanisms. Furthermore, the mutually exclusive expression patterns observed suggest that either negative regulatory mechanisms or signaling mechanisms play a role in the specification of GABAergic terminal differentiation genes in certain regions of the central nervous system. Finally, overlap observed in transcription factor expression patterns, a transcription factor binding site analysis, and the variability of transcription factor expression along the anterior-posterior axis suggest that inhibitory neurotransmitter phenotype specification is controlled by multiple transcription factors in a combinatorial fashion.