Cerebral perfusion is optimized during hemodilution by both β1- and β2-adrenergic mechanisms. Antagonism of the β2-adrenoreceptor can impair cerebral vasodilation. We hypothesized that treatment with a highly β1-specific antagonist (nebivolol) would minimize the degree of cerebral hypoxia during hemodilution. Anesthetized rats were randomized to receive vehicle or nebivolol (1.25 or 2.5 mg/kg intravenously) prior to hemodilution. In vehicle-treated rats, hemodilution increased cardiac output (CO) and regional cerebral blood flow (rCBF) while microvascular brain PO2 (PBrO2) decreased. Both nebivolol doses reduced heart rate and attenuated the CO response to hemodilution. Only the higher dose of nebivolol attenuated the rCBF response to hemodilution and caused a further reduction in PBrO2. Brain hypoxic protein levels were only increased in the high dose nebivolol group. High dose nebivolol treatment resulted in drug levels near its affinity for the β2-adrenoreceptor supporting the hypothesis that cerebral perfusion is maintained by β2-dependent mechanisms during hemodilution.

Cerebral perfusion is optimized during hemodilution by both β1- and β2-adrenergic mechanisms. Antagonism of the β2-adrenoreceptor can impair cerebral vasodilation. We hypothesized that treatment with a highly β1-specific antagonist (nebivolol) would minimize the degree of cerebral hypoxia during hemodilution. Anesthetized rats were randomized to receive vehicle or nebivolol (1.25 or 2.5 mg/kg intravenously) prior to hemodilution. In vehicle-treated rats, hemodilution increased cardiac output (CO) and regional cerebral blood flow (rCBF) while microvascular brain PO2 (PBrO2) decreased. Both nebivolol doses reduced heart rate and attenuated the CO response to hemodilution. Only the higher dose of nebivolol attenuated the rCBF response to hemodilution and caused a further reduction in PBrO2. Brain hypoxic protein levels were only increased in the high dose nebivolol group. High dose nebivolol treatment resulted in drug levels near its affinity for the β2-adrenoreceptor supporting the hypothesis that cerebral perfusion is maintained by β2-dependent mechanisms during hemodilution.

Parabutoporin (PP) and opistoporin 1 (OP1) are cation, a-helical antimicrobial peptides isolated from the southern African scorpion species, Parabuthus schlechteri and Opistophthalmus carinatus, respectively. Along with their antimicrobial action against bacteria and fungi, these peptides show pore-forming properties in the membranes of mammalian cells. Pore-formation and ion selectivity in cardiac myocytes were investigated by measuring the whole cell leak current by means of the patch clamp technique. Pore-formation was observed as the induction of leak currents. Ion selectivity of the pores was indicated by the shift of the reversal potential (E,,,) upon substitution of intra (K' with CS' and CI- with aspartate) and extracellular (Na' with NMDG') ions. Results were compared with the effect of gramicidin A used as a positive control for monovalent cation selective pores. PP and OP I induced a fluctuating leak current and indicate non-selectivity of PP and OP1-induced pores. An osmotic protection assay to determine estimated pore size was performed on the cardiac myocytes. PP and OP1-induced pores had an estimate pore size of 1.38-1.78 nm in diameter. The effect of PP and OP1 on the membrane potential (MP) of a neuroblastoma cell line and cardiac myocytes was investigated. TMRM was used to mark the MP fluorescently and a confocal microscope used to record the data digitally. The resting membrane potential (RMP) of the neuroblastoma cells was calculated at -38.3 f 1.9 mV. PP (0.5 uM) and OP1 (0.5-1 uM) depolarized the entire cell uniformly to a MP of -1 1.9 k 3.9 mV and -9.4 k 1.9 mV, respectively. This occurred after 20-30 min of peptide exposure. In the case of the cardiac myocytes depolarization was induced to -39.7 f 8.4 mV and -32.6 f 5.2 mV by 0.5-1 uM PP and 1.5-2.5 uM OPl, respectively. / Thesis (M.Sc. (Physiology))--North-West University, Potchefstroom Campus, 2006.

<p>For all organisms, the ability to sense and react to noxious environments is fundamental to their survival. For multi-celled organisms this process generally involves a nervous system and an extensive network of signal transduction pathways. TRPV ion channels have been shown to participate in signal transduction in response to noxious stimuli. At the cellular level these channels function in sensing of mechanical, thermal, and osmotic stimuli, and at the organismal level they function in homeostasis and nociception. TRPV ion channels participate in nociceptive signal transduction via cation influx, but exactly how these channels function at a mechanistic level and lead to activation of the cell or induction of a specific behavior is elusive. Previous research has shown that the pore-forming unit of an ion channel is critical for channel regulation, gating, ion selectivity, and ion permeation. Various regulatory domains have been identified to date in the pore-forming unit of TRP channels and a clearer picture of channel gating is beginning to emerge, but less is known about ion permeation. </p><p>To better understand the specific domains that are critical to ion capture, selectivity, and permeation in TRPV channels, we investigated the function of these regions using the <italic>C. elegans</italic> TRPV channel OSM-9 <italic>in vivo</italic>, and the mammalian TRPV channel TRPV4 in heterologous cell culture. OSM-9 is the functional ortholog of mammalian TRPV4 and it is likely that critical domains identified in OSM-9 are functionally conserved in TRPV4 and play a similar role in other TRPV channels. OSM-9 is expressed in the ASH neurons and is responsible for all of the behaviors initiated by that cell. The stereotypical avoidance behavior mediated by ASH, in response to noxious stimuli, serves as a model for nociception in vertebrates. As OSM-9 is necessary for all of these behavioral responses, activation of ASH acts as a read-out for OSM-9 function.</p><p>Through targeted mutagenesis of the OSM-9 loop domains and transgenic expression directed to the ASH head sensory neurons in an <italic>osm-9</italic> null background, we discovered a critical role for the amino acids both N- and C- terminal to the pore helix in osmotic avoidance behavior. We confirmed the existence of a selectivity filter C-terminal to the pore helix and revealed that the turret is critical for channel function, possibly as a component of the inactivation gate.</p><p>We first identified the boundaries of the selectivity filter to be M601-F<super>609</super>. We also determined what properties of those residues were critical to Ca<super>2+</super> and Na<super>+</super> selectivity. <italic>In vivo</italic> Ca<super>2+</super> imaging strongly suggested that residues Y<super>604</super>, D<super>605</super>, and F<super>609</super> are critical for Ca<super>2+</super> entry into the cell. Patch-clamp electrophysiology of a chimeric ion channel consisting largely of rat TRPV4, but encompassing transmembranes 5 through 6 of OSM-9, revealed that OSM-9 conducts both Ca<super>2+</super> and Na<super>+</super>. Mutation Y604G disrupted both Ca<super>2+</super> and Na<super>+</super> conductance, whereas mutations Y604F and Y606A increased or maintained Na+ conductance and severely reduced Ca<super>2+</super> conductance, while maintaining avoidance behavior. Homology modeling of OSM-9, based on an alignment of OSM-9 to Kv1.2, suggests that Y<super>604</super> and F<super>609</super> serve structural roles in maintaining filter constraints. Thus, aromatic and negative residues in the OSM-9 selectivity filter are critical to ion permeation and selectivity. </p><p>Our studies involving the selectivity filter support previous research that the selectivity filter is critical for TRP channel function. We also provide evidence that the selectivity filter is critical for nocifensive animal behavior. Fewer studies, however, have investigated the TM5-pore helix linker, known as the turret. The turret is believed to function in the binding of ligands and toxins in K<super>+</super> channels, and more recently was suggested to be critical for temperature sensing in TRPV1. We investigated the function of the turret residues in several sensory submodalities of the OSM-9 channel and found that all deletions tested result in channel defects, including gain- and loss-of-function phenotypes. Several charge reversal mutations in the OSM-9 turret also resulted in partial defects. The discovery of a gain-of-function mutation indicates that the turret functions in gating. When the turret is mutated in this way, the channel is unable to enter into the inactivated state, allowing continued ion influx after repeated stimulation. The loss-of-function phenotypes indicate that the secondary structure of the turret is critical to the function of the channel, and perhaps gating. These findings, combined with the observed charge-reversal defects, support the conclusion that the turret is necessary for transducing conformational changes in response to stimuli.</p><p>Our <italic>in vivo</italic> findings on the external pore forming structures increase the understanding of ion permeation in TRP channels and clarify mechanisms of activation in nociceptor neurons <italic>in vivo</italic>. Furthermore, these studies enhance our insights into evolution of mammalian nociception in view of the established functional orthology of OSM-9 and TRPV4.</p> / Dissertation

A photolabile terpolymer containing 6-nitroveratyloxycarbonyl (NVOC) protected amine, epoxy and trimethoxysilyl functionality in 1:3:2 monomer ratio was synthesized to template glass surfaces for specific site directed coupling of non-probe oligomers and probe oligonucleotides. Non-probe oligomers were introduced to the surface to control the environment of the probes by reducing probe-to-probe and probe-to-surface interactions. The trimethoxysilyl group served as the anchoring site for the terpolymer to be covalently bound to glass and silicon wafers. Amine terminated non-probe oligomers were coupled to the epoxy sites and thiolated 19-mer SMN1 probes were directed to the deprotected amine sites via the heterobifunctional linker, sulfosuccinimidyl-4-[maleimidomethyl]cyclohexane-1-carboxylate (sulfo-SMCC). Characterization of the terpolymer was done using 1H NMR, 13C NMR, MALDI-ToF and elemental analysis. NVOC deprotection was monitored by UV absorption, and surface characterization of the bound terpolymer on silicon wafers was investigated with XPS, ToF-SIMS, ellipsometry and static contact angle. Neutral polyethylene glycol (PEG), negatively charged methacrylic acid (MAA) oligomer and dC20 oligonucleotides were used as non-probe oligomers. The probe density on the surface was estimated to be 2.2 ± 0.3 x 10^12 molecules/cm2 and the presence of the oligomers on the surface did not significantly affect probe immobilization efficiency. The mixed films were functional for target hybridization and its selectivity towards partially-mismatched targets was investigated at different solution pH, ionic strength and temperature. It was demonstrated that pH can be tuned to ameliorate non-specific adsorption and ionic strength governed the selectivity of the surfaces. Improved selectivity was achieved at high salt concentration (1 M NaCl) on PEG and dC20 mixed films at room temperature. The MAA surface did not show significant improvements in selectivity. This indicated that charge of the oligomers does not dominate control of selectivity. The results suggested that the terpolymer construct played a role in depression of the melting temperature of the hybridized duplex to within 5 to 10 oC of room temperature. With the melting temperature shifted closer to room temperature, it is possible to improve selectivity for room temperature detections of single nucleotide polymorphism.

As the number of cancer survivors continues to rise, there is an increasing need for psychological research to better understand and help individuals cope with their cancer journey. According to Socioemotional Selectivity theory (SST), shortened time perspective and mortality awareness heighten the importance of social and emotional goals. In the present analysis, SST is applied to the unmet needs of cancer survivors. This is done to provide a better understanding of the association between unmet needs of cancer survivors and the impact of such needs on the survivors' psychological well-being, especially in the case of survivor’s awareness of his/her mortality. In keeping with SST theory, we anticipated that for those with higher mortality awareness (e.g., recurrence of cancer, older age, greater mortality ratio), high unmet social and emotional needs, above else, will be associated with lower psychological well-being. Partial support was found for these hypotheses and results are discussed in terms of their contribution to a better understanding of the nature of psychological well-being of cancer survivors.

This thesis presents data which support cochlear involvement in attentional listening. It has been previously proposed that the descending auditory pathways, in particular the medial olivocochlear system, play a role in reducing the cochlea's response to noise in a process known as antimasking. This hypothesis was investigated in human subjects for its potential impact on the detection of signals in noise following auditory cues. Three experimental chapters (Chapters 3, 4 and 5) are described in this thesis. Experiments in the first chapter measured the effect of acoustic cues on the detection of subsequent tones of equal or different frequency. Results show that changes in the ability to detect signals following auditory cues are the result of both enhanced detection for tones at the cued frequency, and suppressed detection for tones at non-cue frequencies. Both effects were measured to be in the order of ~3 dB. This thesis has argued that the enhancement of a cued tone is the implicit result of an auditory cue, while suppression of a probe tone results from the expectation of a specific frequency based on accumulated experience of a listening task. The properties of enhancement support the antimasking hypothesis, however, the physiological mechanism for suppression is uncertain. In the second experimental chapter, auditory cues were replaced with visual cues (representing musical notes) whose pitch corresponded to the target frequency, and were presented to musician subjects who possessed absolute or relative pitch. Results from these experiments showed that a visual cue produces the same magnitude of enhancement as that produced by an acoustic cue. This finding demonstrates a cognitive influence on the detection of tones in noise, and implicates the role of higher centres such as those involved in template-matching or top-down control of the efferent pathways. The final experimental chapter repeated several of the experiments from the first chapter on subjects with various forms of hearing loss. The results indicate that subjects with an outer hair cell deficit (concomitant with a sensorineural hearing loss) do not exhibit an enhancement of cued frequencies or a suppression of unexpected frequencies to the same extent as the normal-hearing subjects. In addition, one subject with a long-standing conductive hearing loss (with normal cochlear function) produced an enhancement equivalent to that of the normalhearing subjects. These findings also support the role of the medial olivocochlear system and the outer hair cells in antimasking. It is the conclusion of this thesis that enhancement most likely results from a combination of changes in receptive field characteristics, at various levels of the auditory system. The medial olivocochlear system is likely to be involved in unmasking a portion of the signal at the cochlear level, which may be influenced by both acoustic reflex pathways or higher centres of the brain.

Thesis (Ph.D.)--Syracuse University, 2008. / "Publication number: AAT 3347263."

Thesis (Ph. D.)--State University of New York at Binghamton, Department of Psychology, 2009. / Includes bibliographical references.

Thesis (Ph.D.)--York University, 2004. Graduate Programme in Psychology. / Typescript. Includes bibliographical references. Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://wwwlib.umi.com/cr/yorku/fullcit?pNQ99237