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Full-Text Articles in Medicine and Health Sciences

A Quantitative Visualization Tool For The Assessment Of Mammographic Risky Dense Tissue Types, Margaret R. Mccarthy Aug 2023

A Quantitative Visualization Tool For The Assessment Of Mammographic Risky Dense Tissue Types, Margaret R. Mccarthy

Electronic Theses and Dissertations

Breast cancer is the second most occurring cancer type and is ranked fifth in terms of mortality. X-ray mammography is the most common methodology of breast imaging and can show radiographic signs of cancer, such as masses and calcifcations. From these mammograms, radiologists can also assess breast density, which is a known cancer risk factor. However, since not all dense tissue is cancer-prone, we hypothesize that dense tissue can be segregated into healthy vs. risky subtypes. We propose that risky dense tissue is associated with tissue microenvironment disorganization, which can be quantified via a computational characterization of the whole breast …


Muscle Defects Lead To Skeletal Deformities In A Zebrafish Model Of Distal Arthrogryposis, Emily A. Tomak Aug 2023

Muscle Defects Lead To Skeletal Deformities In A Zebrafish Model Of Distal Arthrogryposis, Emily A. Tomak

Electronic Theses and Dissertations

Distal Arthrogryposis Type 1 (DA1) involves mild muscle weakness and limb skeletal abnormalities thought to be caused by paralysis in utero. Why the limbs are particularly affected in DA1 and the degree of paralysis that leads to these skeletal deformities in utero remains unclear. Several muscle genes are known to cause DA1, including MYLPF (myosin light chain phosphorylatable), which encodes a myosin light chain protein that binds close to the force-generating head of myosin heavy chains. The zebrafish mylpfa-/- mutant displays a phenotype consistent with DA1, including impaired myosin activity, reduced muscle force overall, and complete fin paralysis. I …


Analyzing Pseudomonas Aeruginosa With Bacteriophage Tags Using Photoacoustic Flow Cytometry, Jennifer C. Schinke Aug 2023

Analyzing Pseudomonas Aeruginosa With Bacteriophage Tags Using Photoacoustic Flow Cytometry, Jennifer C. Schinke

Electronic Theses and Dissertations

The number of daily bacterial infections is climbing and the CDC explains that this is due to the antibiotic-resistant threat in the United States. Finding a faster way of bacterial identification is necessary as it currently takes 1-4 days for a medical lab to culture and identify bacteria. Photoacoustic flow cytometry (PAFC) can be used as an alternative method resulting in swift identification within an hour (Edgar, 2019). Pseudomonas aeruginosa, cell line PA01, will be coated in up to a few hundred red dyed phages making it detectible by the photoacoustic flow cytometry system. Bacteriophages (phages) are viruses that …


Primary Cilia Of The Cardiac Neural Crest & Hedgehog-Mediated Mechanisms Of Congenital Heart Disease, Lindsey A. Fitzsimons May 2022

Primary Cilia Of The Cardiac Neural Crest & Hedgehog-Mediated Mechanisms Of Congenital Heart Disease, Lindsey A. Fitzsimons

Electronic Theses and Dissertations

Elimination of primary cilia in cardiac neural crest cell (CNCC) progenitors is hypothesized to cause a variety of congenital heart defects (CHDs), including atrioventricular septal defects, and malformations of the developing cardiac outflow tract. We present an in vivo model of CHD resulting from the conditional elimination of primary cilia from CNCC using multiple, Wnt1:Cre-loxP, neural crest-specific systems, targeting two distinctive, but critical, primary cilia structural genes: Intraflagellar transport protein 88 (Ift88) or kinesin family member 3A (Kif3a). CNCC loss of primary cilia leads to widespread CHD, where homozygous mutant embryos (MUT) display a variety of outflow tract malformations, septation …


Cannabinoids And Retinal Fibrotic Disorders., Lucy June Sloan May 2022

Cannabinoids And Retinal Fibrotic Disorders., Lucy June Sloan

Electronic Theses and Dissertations

Retinal fibrosis is detrimental to vision. Retinal pigment epithelial (RPE) cells contribute to several retinal fibrotic diseases. Upon exposure to TGF-β, a key fibrotic cytokine, RPE cells trans-differentiate to myofibroblasts marked by the integration of α-SMA fibers into F-actin stress fibers, which confer strong contractility. Myofibroblasts produce and contract the collagen-rich fibrotic scar and disrupt retinal architecture. In this study, we investigated the in vitro effects of the putative endocannabinoid compound N-oleoyl dopamine (OLDA) on TGF-β2 induced porcine RPE cell contraction and α-SMA expression. Using an in vitro collagen matrix contraction assay, we found that OLDA inhibited TGF-β2 induced contraction …


Organellar Zn2+ Homeostasis And The Role Of Trpml Channels In Neuronal Lysosome Physiology And Axonal Transport, Taylor Franklin Minckley Jan 2022

Organellar Zn2+ Homeostasis And The Role Of Trpml Channels In Neuronal Lysosome Physiology And Axonal Transport, Taylor Franklin Minckley

Electronic Theses and Dissertations

Zinc (Zn2+) is crucial for proper cellular function, and as such it is important to measure and track Zn2+ dynamics in living cells. Fluorescent sensors have been used to estimate Zn2+ content of subcellular compartments, but little is known about endolysosomal Zn2+ homeostasis. Similarly, although numerous sensors have been reported, it is unclear whether and how Zn2+ can be released from intracellular compartments into the cytosol due to a lack of probes that can detect physiological dynamics of cytosolic Zn2+. My dissertation started with comparing and characterizing different Zn2+ sensors including the …


Antioxidant Biomarkers And Nutraceutical Therapeutics In Neurodegeneration And Neurotrauma, Lilia A. Koza Jan 2022

Antioxidant Biomarkers And Nutraceutical Therapeutics In Neurodegeneration And Neurotrauma, Lilia A. Koza

Electronic Theses and Dissertations

Mild traumatic brain injury (mTBI), yielding a Glascow Coma Scale of 13-15, is the most commonly occurring severity of TBI. Pathology from mTBI consists of blood brain barrier disruption, neuroinflammation, oxidative stress, excitotoxicity, mitochondrial dysfunction, protein aggregation, axonal degeneration, and resulting neuronal death. These processes deplete the body’s endogenous antioxidant system. We report a retrospective analysis of antioxidant blood biomarkers in patients with a history of mTBI from a local sports medicine clinic, Resilience Code. We found persistent sex-specific antioxidant depletions in mTBI patients associated with worsened symptomology.

Certain populations, such as athletes, are at high risk for repetitive mTBI …


Deciphering The Perpetual Fight Between Virus And Host: Utilizing Bioinformatics To Elucidate The Host's Genetic Mechanisms That Influence Jc Polyomavirus Infection, Michael P. Wilczek Aug 2021

Deciphering The Perpetual Fight Between Virus And Host: Utilizing Bioinformatics To Elucidate The Host's Genetic Mechanisms That Influence Jc Polyomavirus Infection, Michael P. Wilczek

Electronic Theses and Dissertations

JC polyomavirus (JCPyV) is a human-specific pathogen that infects 50-80% of the population, and can cause a deadly, demyelinating disease, known as progressive multifocal leukoencephalopathy (PML). In most of the population, JCPyV persistently infects the kidneys but during immunosuppression, it can reactivate and spread to the central nervous system (CNS), causing PML. In the CNS, JCPyV targets two cell types, astrocytes, and oligodendrocytes. Due to the hallmark pathology of oligodendrocyte lysis observed in disease, oligodendrocytes were thought to be the main cell type involved during JCPyV infection. However, recent evidence suggests that astrocytes are targeted by the virus and act …


Tissue-Resident Myeloid-Derived Suppressor Cells Modulate Immune Homeostasis In Healthy Adipose., Katlin Brooke Stivers Aug 2020

Tissue-Resident Myeloid-Derived Suppressor Cells Modulate Immune Homeostasis In Healthy Adipose., Katlin Brooke Stivers

Electronic Theses and Dissertations

Our goal with this study was to gain insight into the homeostatic immune cell network in healthy adipose tissue. Specifically, we sought to determine if the immature myeloid cells found in healthy and inflamed adipose were, in fact, tissue-resident myeloid-derived suppressor cells (MDSCs). Using various in vitro and in vivo methods, we have uncovered a population of CD11bHi Ly6CHi Ly6G- MDSCs resident in healthy adipose tissue. To the best of our knowledge this is the first time that these cells have been investigated and described in healthy adipose tissue. Systemic MDSC depletion lead to the accumulation of …


Defects In Fetal Mouth Movement And Pharyngeal Patterning Underlie Cleft Palate Caused By Retinoid Deficiency., Regina Friedl May 2019

Defects In Fetal Mouth Movement And Pharyngeal Patterning Underlie Cleft Palate Caused By Retinoid Deficiency., Regina Friedl

Electronic Theses and Dissertations

Cleft palate is a common birth defect. Etiologic mechanisms of palate cleft include defects in palate morphogenesis, mandibular growth, or spontaneous fetal mouth movement. Cleft palate linked to deficient fetal mouth movement has been demonstrated directly only in a single experimental model of loss of neurotransmission. Here, using retinoid deficient mouse embryos, we demonstrate directly for the first time that deficient fetal mouth movement and cleft palate occurs as a result of mis-patterned development of pharyngeal peripheral nerves and cartilages. Retinoid deficient embryos were generated by inactivation of retinol dehydrogenase 10 (Rdh10), which is critical for production of …


Evaluating The Effects Of Antibody-Conjugated Multi-Walled Carbon Nanotubes In Combination With Microwave Irradiation, Amy Chall Jan 2019

Evaluating The Effects Of Antibody-Conjugated Multi-Walled Carbon Nanotubes In Combination With Microwave Irradiation, Amy Chall

Electronic Theses and Dissertations

Cancer remains one of the largest public health concerns of our day, particularly in developed countries where technological advances have allowed populations to live well into their eighth decade. In America, those in their 80’s have a 1 in 2 chance of developing cancer in their lifetime. Prostate cancer, specifically is the second leading cause of cancer deaths in males. Traditional cancer therapies cause high levels of toxicity to the patient due to mechanisms of action that often attack cancer cells and healthy cells alike. The holy grail of cancer research is to find a treatment that targets the cancer …


The Effect Of Wild Blueberry Bioactives On Endothelial Cell Migration And Angiogenesis: An In Vitro Mechanistic, Genomic And Proteomic Approach, Panagiotis Tsakiroglou Sep 2018

The Effect Of Wild Blueberry Bioactives On Endothelial Cell Migration And Angiogenesis: An In Vitro Mechanistic, Genomic And Proteomic Approach, Panagiotis Tsakiroglou

Electronic Theses and Dissertations

The goal of this study is to investigate the effects of wild blueberry fractions (Anthocyanins and Phenolic acids) on vascular function and physiology. More specifically the potential effects of the above fractions and their combination in physiological concentrations on endothelial cell migration, angiogenesis, gene expression and proteins synthesis of markers related to the above processes. The objectives are to study whether anthocyanins, phenolic acids and their combinations (ACNs:PAs) affect: a) cell proliferation, b) speed of endothelial cell migration, c) angiogenesis, d) gene expression of genes critical for cell migration and angiogenesis such as RAC1, RHOA, AKT1, eNOS and VEGF and …


Unfolded Protein Response Pathways In Skeletal Muscle Homeostasis., Kyle R. Bohnert Aug 2018

Unfolded Protein Response Pathways In Skeletal Muscle Homeostasis., Kyle R. Bohnert

Electronic Theses and Dissertations

Skeletal muscle mass, contractile properties, and metabolic function are regulated through the coordinated activation of multiple intracellular signaling pathways and genetic reprogramming. The endoplasmic reticulum (ER) plays a pivotal role in protein folding and calcium homeostasis in many cell types, including skeletal muscle. Disruption of calcium levels or accumulation of misfolded proteins in the ER lumen leads to stress, which results in the activation of a signaling network called the unfolded protein response (UPR). Further, recent studies have suggested that in certain conditions, UPR pathways can be activated independent of ER stress. However, the role of ER stress and the …


Deciphering The Role Of Human Arylamine N-Acetyltransferase 1 (Nat1) In Breast Cancer Cell Metabolism Using A Systems Biology Approach., Samantha Marie Carlisle Aug 2018

Deciphering The Role Of Human Arylamine N-Acetyltransferase 1 (Nat1) In Breast Cancer Cell Metabolism Using A Systems Biology Approach., Samantha Marie Carlisle

Electronic Theses and Dissertations

Background: Human arylamine N-acetyltransferase 1 (NAT1) is a phase II xenobiotic metabolizing enzyme found in almost all tissues. NAT1 can additionally hydrolyze acetyl-coenzyme A (acetyl-CoA) in the absence of an arylamine substrate. NAT1 expression varies inter-individually and is elevated in several cancers including estrogen receptor positive (ER+) breast cancers. Additionally, multiple studies have shown the knockdown of NAT1, by both small molecule inhibition and siRNA methods, in breast cancer cells leads to decreased invasive ability and proliferation and decreased anchorage-independent colony formation. However, the exact mechanism by which NAT1 expression affects cancer risk and progression remains unclear. Additionally, consequences …


The Identification And Segmentation Of Astrocytoma Prior To Critical Mass, By Means Of A Volumetric/Subregion Regression Analysis Of Normal And Neoplastic Brain Tissue, Lyn Higgins Jan 2018

The Identification And Segmentation Of Astrocytoma Prior To Critical Mass, By Means Of A Volumetric/Subregion Regression Analysis Of Normal And Neoplastic Brain Tissue, Lyn Higgins

Electronic Theses and Dissertations

As the underlying cause of Glioblastoma Multiforme (GBM) is presently unclear, this research implements a new approach to identifying and segmenting plausible instances of GBM prior to critical mass. Grade-IV Astrocytoma, or GBM, is an aggressive and malignant cancer arising from star-shaped glial cells, or astrocytes, where the astrocytes, functionally, assist in the support and protection of neurons within the central nervous system and spinal cord. Subsequently, our motivation for researching the ability to recognize GBM is that the underlying cause of the mutation is presently unclear, leading to the operative that GBM is only detectable through a combination of …


The Regulation Of Rotavirus–Infected Ht29.F8 And Ma104 Cells Treated With Arachidin 1 Or Arachidin 3, Caleb M. Witcher May 2017

The Regulation Of Rotavirus–Infected Ht29.F8 And Ma104 Cells Treated With Arachidin 1 Or Arachidin 3, Caleb M. Witcher

Electronic Theses and Dissertations

Rotavirus (RV) infections cause severe life threatening diarrhea in young children and immunocompromised individuals. Several effective vaccines have been developed for young children but are not protective against all strains of RV, and there are no anti-RV therapeutics. Our laboratory has discovered a decrease in the number of infectious simian RV particles (SA114f) in human intestinal cell line, HT29.f8 cells with the addition of either of two stilbenoids, arachidin-1 (A1) or arachidin-3 (A3). This suggests effects on the host cell and RV replication. We examined the cellular effects of human RV strain (Wa) on a human intestinal cell line (HT29.f8) …


Identification Of Cdks As Novel Targets Of Aspirin And Its Metabolites: A Potential Role In Cancer Prevention, Rakesh Dachineni Jan 2017

Identification Of Cdks As Novel Targets Of Aspirin And Its Metabolites: A Potential Role In Cancer Prevention, Rakesh Dachineni

Electronic Theses and Dissertations

Background:
The pursuit of drugs that inhibit cyclin-dependent kinases (CDKs) has been an intense area of research for more than 15 years. Till date, although multiple CDK inhibitors have been identified and few are undergoing clinical trials, only two synthetic drugs have been approved by Food and Drug Administration (FDA) for use in the treatment of cancer. These two drugs are mainly used for the treatment of metastatic breast cancer in combination with other drugs; however they have toxicity associated with their use and extends patients life not more than 24 months. Therefore, there is an urgent need for …


Endothelial Hspa12b Is A Novel Protein For The Preservation Of Cardiovascular Function In Polymicrobial Sepsis Via Exosome Mir-126, Xia Zhang Aug 2016

Endothelial Hspa12b Is A Novel Protein For The Preservation Of Cardiovascular Function In Polymicrobial Sepsis Via Exosome Mir-126, Xia Zhang

Electronic Theses and Dissertations

Sepsis is the most frequent cause of mortality in most intensive care units. Cardiovascular dysfunction is a major complication associated with sepsis, with high mortality rates up to 70%. Currently, there is no effective treatment approach for sepsis.

The integrity of the endothelium is fundamental for the homeostasis of the cardiovascular system. Sepsis induces endothelial cell injury which is the key factor for multiple organ failure. The increased expression of adhesion molecules and chemokines in endothelial cell promotes leukocytes infiltration into the tissue. The loss of tight junction proteins and increased permeability of the endothelial cells will provoke tissue hypoxia …


Microrna-186 And Metastatic Prostate Cancer., Dominique Zilpha Jones May 2016

Microrna-186 And Metastatic Prostate Cancer., Dominique Zilpha Jones

Electronic Theses and Dissertations

MicroRNA (miR) dysregulation alters cancer-associated gene expression, which contributes to cancer pathogenesis. For example, miR-186 over expression lead to enhanced proliferation and migration in pancreatic cancer cell models. However, the role of miR-186 in prostate cancer (PCa) remains controversial. Previously, miR-186-5p was up-regulated in PCa patient serum (stage III/IV) compared to controls. Furthermore, miR-186-5p was up-regulated in metastatic PCa (PC-3, MDA PCa 2b, LNCaP) relative to normal prostate epithelial cells (RWPE1). We hypothesized miR-186 inhibition will reduce aggressive PCa using metastatic cell models. To test this, we evaluated whether miR-186-5p inhibition would reduce aggressive PCa behavior and overexpression induce malignant …


Investigation Of Novel Functions For Dna Damage Response And Repair Proteins In Escherichia Coli And Humans, Benjamin A. Hilton May 2016

Investigation Of Novel Functions For Dna Damage Response And Repair Proteins In Escherichia Coli And Humans, Benjamin A. Hilton

Electronic Theses and Dissertations

Endogenous and exogenous agents that can damage DNA are a constant threat to genome stability in all living cells. In response, cells have evolved an array of mechanisms to repair DNA damage or to eliminate the cells damaged beyond repair. One of these mechanisms is nucleotide excision repair (NER) which is the major repair pathway responsible for removing a wide variety of bulky DNA lesions. Deficiency, or mutation, in one or several of the NER repair proteins is responsible for many diseases, including cancer. Prokaryotic NER involves only three proteins to recognize and incise a damaged site, while eukaryotic NER …


Role Of Transient Receptor Potential Canonical-6 (Trpc6) Channel In Metastasis Of Glioblastoma Multiforme, Rajarajeshwari Venkataraman Jan 2008

Role Of Transient Receptor Potential Canonical-6 (Trpc6) Channel In Metastasis Of Glioblastoma Multiforme, Rajarajeshwari Venkataraman

Electronic Theses and Dissertations

Glioblastoma multiforme (GBM) is one of the extremely fatal brain tumors. The main reason that makes it so lethal is its capability to invade and spread to other parts of CNS producing secondary tumors. Among other factors hypoxia, reduced oxygen availability, is linked to higher metastatic potential of cancers. Hypoxia causes numerous changes in genome and proteome of the cell. These changes help a normal cell to adapt to nutritional deficiency, but the same changes can increase the malignancy and metastasis in tumor cells. Extensive research by a number of curious scientists reveal that various pathways involving numerous proteins cross-talk …


Transcriptional Alterations During Mammary Tumor Progression In Mice And Humans, Karen Fancher Jan 2008

Transcriptional Alterations During Mammary Tumor Progression In Mice And Humans, Karen Fancher

Electronic Theses and Dissertations

Family history, reproductive factors, hormonal exposures, and subjective immunihistochemical evaluations of in situ lesions, and to a lesser extent age, remain the best clinical predictors of an individual's risk of developing breast cancer. Identification of early markers predictive of impending invasive breast cancer from in situ carcinoma is a long-term goal. The latent mammary cancer transgenic mouse model of human breast cancer, C57BL/6JTg(WapTag)1Knw (Waptag1), develops characteristic stages of tumorigenesis in a highly predictable manner: atypical hyperplasia advances to ductal carcinoma in situ (DCIS), which progresses to papillary adenocarcinomas and/or solid, invasive tumors. Microarray analyses of whole mammary glands and tumors …


Comparison Of Beta-Adrenoceptor Coupled Camp Production In Cultured Human Mononuclear Leukocytes And Myometrial Cells, Yu-Li Liu Dec 1997

Comparison Of Beta-Adrenoceptor Coupled Camp Production In Cultured Human Mononuclear Leukocytes And Myometrial Cells, Yu-Li Liu

Electronic Theses and Dissertations

$\beta\sb2$-Adrenoceptor ($\beta\sb2$-AR) agonists, such as terbutaline, are used as tocolytic agents in the treatment of preterm labor. $\beta$-Adrenoceptor stimulation relaxes myometrium through specific receptors coupled through Gs to adenylyl cyclase (AC) that catalyzes the conversion of ATP to cAMP. The purpose of this study was to compare $\beta$-adrenoceptors and cAMP production in cultured human leukocytes and myometrial cells, and to determine the importance of $\beta$-adrenoceptors and cAMP production in isoproterenol-induced myometrial relaxation. $\sp{125}$I-iodopindolol was used to assess $\beta$-adrenoceptor affinity and number cAMP levels were analyzed before and after stimulation by isoproterenol, AlF$\sb4\sp-$, forskolin, and PGE$\sb1$. Isometric recording was used to …


Microcirculation: Electrophysiological Basis For The Response Of Endothelial Cells To Inflammatory Mediators-Bradykinin, Kai Miao Dec 1994

Microcirculation: Electrophysiological Basis For The Response Of Endothelial Cells To Inflammatory Mediators-Bradykinin, Kai Miao

Electronic Theses and Dissertations

Using conventional microelectrodes, I studied the electrical basis for determining the resting V$\sb{\rm m}$ in intact EC's from hamsters. The resting V$\sb{\rm m}$ were found to be $-$40 mV for aortic EC's and $-$43 mV for vena caval EC's. The contributions of ions to the resting V$\sb{\rm m}$ of aortic EC's were compared in terms of the transference number (t$\sb{\rm ion}$). To develop a technique for in situ monitoring changes in V$\sb{\rm m}$ of postcapillary venular EC's in the hamster mesentery, a voltage-sensitive fluorescent probe, bisoxonol, was used to load the cells and the fluorescence signals were analyzed under an …


Changes In Intracellular Chloride During Osmotic Stress And L-Alanine Uptake In Mouse Hepatocytes, Kening Wang Oct 1992

Changes In Intracellular Chloride During Osmotic Stress And L-Alanine Uptake In Mouse Hepatocytes, Kening Wang

Electronic Theses and Dissertations

A stable intracellular ionic environment is necessary for hepatocytes to function normally. Thus, during hypotonic shock or L-alanine uptake, hepatocytes swell and then exhibit a regulatory volume decrease (RVD), which comprises an increase in K$\sp+$ conductance (G$\sb{\rm K}$), an increased K$\sp+$ efflux, and a hyperpolarization of transmembrane potential (V$\sb{\rm m}$). Since hepatocyte intracellular Cl$\sp-$ has been demonstrated to distribute passively with V$\sb{\rm m}$, this study is designed to test the hypothesis that the hypotonic shock- or L-alanine uptake-induced hyperpolarization of V$\sb{\rm m}$ might provide an electromotive force for the efflux of hepatocyte intracellular Cl$\sp-$, which in turn would contribute osmotically …


Molecular And Cellular Analysis Of Chlamydia Trachomatis: Persistence And Reactivation, Kimberly R. Tau May 1992

Molecular And Cellular Analysis Of Chlamydia Trachomatis: Persistence And Reactivation, Kimberly R. Tau

Electronic Theses and Dissertations

Chlamydia trachomatis (CT) is the most prevalent sexually-transmitted infection in the United States. It has been suggested that CT infections can become latent. This has not been substantiated. CT persistence was examined at the molecular and cellular level in vitro and in vivo. Penicillin treatment of CT in vitro results in abnormal inclusions and reduced recovery of infectious CT. Penicillin did not inhibit initial stages of infection, but did downregulate CT rRNA levels after 25 hours post-inoculation (p.i.). DNA amplification was employed to differentiate between a resolved infection and a persistent one. Utilizing a primer pair that amplified a 144 …


Electrophysiology, Cell Calcium, And Mechanisms Of Hepatocyte Volume Regulation, Walid E. Khalbuss Aug 1990

Electrophysiology, Cell Calcium, And Mechanisms Of Hepatocyte Volume Regulation, Walid E. Khalbuss

Electronic Theses and Dissertations

The electrophysiologic technique (Reuss, L., Proc. Natl. Acad. Sci. USA 82:6014, 1985) was modified to measure changes in steady-state hepatocyte volume during osmotic stress. Hepatocytes in mouse liver slices were loaded with tetramethylammonium ion (TMA$\sp{+}$) during transient exposure of cells to nystatin. Intracellular TMA$\sp{+}$ activity (a$\sp{\rm i}\sb{\rm TMA}$) was measured with TMA$\sp{+}$-sensitive, double-barreled microelectrodes. Loading hepatocytes with TMA$\sp{+}$ did not change their membrane potential (V$\sb{\rm m}$), and under steady-state conditions a$\sp{\rm i}\sb{\rm TMA}$ remained constant over 4 min in single impalements. Hyperosmotic solutions (50, 100, & 150 mM sucrose added to media) and hyposmotic solutions (sucrose in media reduced by …