Zachary Walls | East Tennessee State University (original) (raw)

Papers by Zachary Walls

... Page 4. The dissertation of Zachary Floyd Walls is approved. Jon M. Fukuto ... ... Bob and Li... more ... Page 4. The dissertation of Zachary Floyd Walls is approved. Jon M. Fukuto ... ... Bob and Linda Wink - for doing so much during this last leg. Meg O'Neil - for being a good friend when I needed one the most. Randy Slates - the consummate wingman. ...

Journal of the American Pharmacists Association

Journal of Drug Targeting

Abstract The use of peptides in drug development has been hampered by their poor pharmaceutical p... more Abstract The use of peptides in drug development has been hampered by their poor pharmaceutical properties, most notably their inability to reliably permeate biological membranes and lack of targeting. To overcome these disadvantages, the AMino acid Intracellular Delivery SysTem (AMIDST) was developed. This modular peptide-based delivery system confers cellular permeability and organelle-specific targeting for therapeutic peptides. As demonstrated in this study, the delivery of a HER2-binding peptide to the secretory organelles of breast cancer cells resulted in intracellular sequestration, a reduction in downstream signalling, and reduced viability compared to the delivery of a control peptide. Given its modular design and ease of production, AMIDST has the potential to enhance the use of peptides as therapeutic agents.

Age and Ageing

the development of an objective and comprehensive drug-based index of physical function for older... more the development of an objective and comprehensive drug-based index of physical function for older adults has the potential to more accurately predict fall risk. the index was developed using 862 adults (ages 57-85) from the National Social Life, Health, and Aging Project (NSHAP) Wave 1 study. The index was evaluated in 70 adults (ages 51-88) from a rehabilitation study of dizziness and balance. the prevalence among 601 drugs for 1,694 side effects was used with fall history to determine the magnitude of each side effect&amp;#39;s contribution towards physical function. This information was used to calculate a Medication-based Index of Physical function (MedIP) score for each individual based on his or her medication profile. The MedIP was compared to the timed up and go (TUG) test as well as drug counts using receiver operating characteristic (ROC) analysis. The associations between various indices of physical function and MedIP were calculated. within the NSHAP data set, the MedIP was better than drug counts or TUG at predicting falls based on ROC analysis. Using scores above and below the cutpoint, the MedIP was a significant predictor of falls (OR = 2.61 [95% CI 1.83, 3.64]; P &amp;lt; 0.001). Using an external data set, it was shown that the MedIP was significantly correlated with fall number (P = 0.044), composite physical function (P = 0.026) and preferred gait speed (P = 0.043). the MedIP has the potential to become a useful tool in the healthcare and fall prevention of older individuals.

Journal of geriatric physical therapy (2001), Jan 10, 2017

The adverse effects of drugs may influence results on tests of mobility and balance, but the drug... more The adverse effects of drugs may influence results on tests of mobility and balance, but the drug-specific impact is not identified when using these tests. We propose that a quantitative drug index (QDI) will assist in assessing fall risk based on these tests, when combined with other fall risk variables. Fifty-seven community-dwelling older adults who could walk independently on a treadmill and had Mini-Mental State Examination (MMSE) scores equal to or greater than 24 participated. Mobility and balance outcome measures included the Balance Evaluation Systems Test (BESTest), Berg Balance Scale (BBS), Timed Up and Go (TUG) and cognitive dual task TUG (TUGc). Fall history, current drug list, and Activity-Specific Balance Confidence (ABC) scale scores were also collected. Body mass index (BMI) was calculated. The QDI was derived from the drug list for each individual, and based on fall-related drug adverse effects. Multiple linear regression analyses were conducted using age, BMI, and...

Education for Health, 2016

Background: The aim of this study was to design and evaluate a laboratory activity based on scien... more Background: The aim of this study was to design and evaluate a laboratory activity based on scientific inquiry to educate first-year pharmacy students in the U.S. about vaccination theory and the attributes of common pathogens. Methods: The laboratory activity had two principal sections. The first consisted of an interactive game during which students rolled a die to determine outcomes based on a set of predetermined criteria. In the second section, students generated and tested hypotheses about vaccine theory using a computer simulation that modeled disease transmission within a large population. In each section students were asked to evaluate epidemiological data and make inferences pertinent to vaccination effectiveness. Results: Mean scores on a knowledge-based assessment given immediately before and immediately after the activity increased from 46% to 71%. Discussion: A laboratory activity designed to stimulate scientific inquiry within pharmacy students enabled them to increase their knowledge of common vaccines and infectious diseases.

Engineering in Translational Medicine, 2013

Molecular pharmaceutics, Jan 25, 2016

Liposomal doxorubicin is a clinically important drug formulation indicated for the treatment of s... more Liposomal doxorubicin is a clinically important drug formulation indicated for the treatment of several different forms of cancer. For doxorubicin to exert a therapeutic effect, it must gain access to the nucleus. However, a large proportion of the liposomal doxorubicin dose fails to work because it is sequestered within endolysosomal organelles following endocytosis of the liposomes due to the phenomenon of ion trapping. Listeriolysin O (LLO) is a pore-forming protein that can provide a mechanism for endosomal escape. The present study demonstrates that liposomal coencapsulation of doxorubicin with LLO enables a significantly larger percentage of the dose to colocalize with the nucleus compared to liposomes containing doxorubicin alone. The change in intracellular distribution resulted in a significantly more potent formulation of liposomal doxorubicin as demonstrated in both the ovarian carcinoma cell line A2780 and its doxorubicin-resistant derivative A2780ADR.

Bioconjugate Chemistry, Feb 1, 2008

RNA detection and quantitation is a common necessity in modern molecular biology research. Most m... more RNA detection and quantitation is a common necessity in modern molecular biology research. Most methods, however, are complex and/or time-intensive. Presented here is a BRET (bioluminescene resonance energy transfer)-based method that can accomplish the task of RNA identification quickly and easily. By conjugating BRET enzymes to two different oligonucleotides that are complementary to the same target sequence, probes were developed that could detect RNA using a solution-based assay. This assay was optimized for spacer length between the binding sites (found to be 10 nucleotides), and sensitivity was determined to be 1 microg for a specific species of RNA within a mixed population. Specificity of the assay was assessed using in vitro transcribed cRNA and found to be statistically siginificant ( p = 3.11 x 10 (-6), ANOVA, multiple range test). This assay represents a possibility for a less technically demanding, streamlined alternative to canonical RNA assays.

Optical Fibers and Sensors for Medical Diagnostics and Treatment Applications IX, 2009

We present the design and fabrication of an implantable fluorescence biosensor suitable for conti... more We present the design and fabrication of an implantable fluorescence biosensor suitable for continuously monitored, freely-moving in vivo rodent studies. The GaAs-based semiconductor sensor incorporates an un-cooled photodetector with a 670nm vertical-cavity surface-emitting laser (VCSEL) optimized for sensing fluorescent Cy5.5 dye. For filtering unwanted spectra, a combination of physical and spectral blocking layers yields OD5 excitation rejection at the detector. The sensor detects near-IR fluorescent Cy5.5 molecules in vitro at 100nM concentration (in a 100µL volume) with linear response for concentrations up to 25µM. In a preliminary study in a living mouse, subcutaneously injected dye (1µM Cy5.5 in 50µL) was detected. This technology has the potential to enable new studies of living systems in applications that require long-term, continuous fluorescence sensing.

Molecular Pharmaceutics, 2010

Human valacyclovirase (hVACVase) is a prodrug-activating enzyme for amino acid prodrugs including... more Human valacyclovirase (hVACVase) is a prodrug-activating enzyme for amino acid prodrugs including the antiviral drugs valacyclovir and valganciclovir. In hVACVase-catalyzed reactions, the leaving group of the substrate corresponds to the drug moiety of the prodrug, making the leaving group effect essential for the rational design of new prodrugs targeting hVACVase activation. In this study, a series of valine esters, phenylalanine esters and a valine amide were characterized for the effect of the leaving group on the efficiency of hVACVase-mediated prodrug activation. Except for phenylalanine methyl and ethyl esters, all of the ester substrates exhibited a relatively high specificity constant (k cat /K m ), ranging from 850 to 9490 mM -1 ·s -1 . The valine amide Val-3-APG exhibited significantly higher K m and lower k cat values compared to the corresponding ester Val-3-HPG, indicating poor specificity for hVACVase. In conclusion, the substrate leaving group has been shown to affect both binding and specific activity of hVACVasecatalyzed activation. It is proposed that hVACVase is an ideal target for α-amino acid ester prodrugs with relatively labile leaving groups, while it is relatively inactivate towards amide prodrugs.

Molecular imaging of gene expression is currently hindered by the lack of a generalizable platfor... more Molecular imaging of gene expression is currently hindered by the lack of a generalizable platform for probe design. For any gene of interest, a probe that targets protein levels must often be generated empirically. Targeting gene expression at the level of mRNA, however, would allow probes to be built on the basis of sequence information alone. Presented here is a class of generalizable probes that can image pre-mRNA in a sequence-specific manner, using signal amplification and a facile method of delivery. Methods: Pre-trans-splicing molecules (PTMs) were engineered to capitalize on the phenomenon of spliceosomemediated RNA trans-splicing. Using a modular binding domain that confers specificity by base-pair complementarity to the target pre-mRNA, PTMs were designed to target a chimeric target mini gene and trans-splice the Renilla luciferase gene onto the end of the target. PTMs and target genes were transfected in cell culture and assessed by luciferase assay, reverse-transcriptase polymerase chain reaction, Western blot, and rapid analysis of 59 cDNA ends. PTMs and target genes were also assessed in vivo by hydrodynamic delivery in mice. Results: Efficiency and specificity of the trans-splicing reaction were found to vary depending on the binding domain length and structure. Specific trans-splicing was observed in living animals (P 5 0.0862, Kruskal-Wallis test). Conclusion: Described here is a model system used to demonstrate the feasibility of spliceosomemediated RNA trans-splicing for imaging gene expression at the level of pre-mRNA using optical imaging techniques in living animals. The experiments reported here show proof of principle for a generalizable imaging probe against RNA that can amplify signal on detection and be delivered using existing gene delivery methodology.

An amino acid ester derivative of luciferin (valoluc) was synthesized to mimic the transport and ... more An amino acid ester derivative of luciferin (valoluc) was synthesized to mimic the transport and activation of valacyclovir. This molecule was characterized in vitro for specificity and enzymatic constants, and then assayed in two different, physiologically-relevant conditions. It was demonstrated that valoluc activation is sensitive to the same cellular factors as valacyclovir and thus has the potential to elucidate the dynamics of amino acid ester prodrug therapies in a functional, high-throughput manner.

Spliceosome-mediated RNA trans-splicing (SMaRT) provides an effective means to reprogram mRNAs an... more Spliceosome-mediated RNA trans-splicing (SMaRT) provides an effective means to reprogram mRNAs and the proteins they encode. SMaRT technology has a broad range of applications, including RNA repair and molecular imaging, each governed by the nature of the sequences delivered by the pre-trans-splicing molecule. Here, we show the ability of SMaRT to optically image the expression of an exogenous gene at the level of pre-mRNA splicing in cells and living animals. Because of the modular design of pre-trans-splicing molecules, there is great potential to employ SMaRT to image the expression of any arbitrary gene of interest in living subjects. In this report, we describe a model system that demonstrates the feasibility of imaging gene expression by trans-splicing in small animals. This represents a previously undescribed approach to molecular imaging of mRNA levels in living subjects. mRNA repair gene correction reporter