PubMed Health⌕ Search

Biomedical subjects

William Lewis

Publications and source records attributed to William Lewis.

At least 19 recordsLinked to original sources
PubMed2006

Construction and evaluation of novel fusion proteins for targeted delivery of micro particles to cellulose surfaces.

The use of IgG antibodies and fragments has been limited to specific sectors of the biotechnology industry due to the high cost of producing large batches of product necessary for alternative applications. A novel class of Camelid antibodies, known as V(HH) offer a more economical opportunity to meet a wider application in industry. In this study, we report the evaluation of four llama V(HH)-cellulose binding domain fusion proteins displaying varying formats of V(HH) and CBD domains. Proteins were characterized in a targeted particle delivery system as a method of delivering agents such as perfume to laundry in the wash cycle. Fusion proteins were shown to be stable at high pH and in the presence of a detergent base. They were also shown to bind effectively to both the designated antigen, the azo-dye reactive-red 6 (either conjugated to BSA or attached to coacervate microparticles), and cellulose. Binding strength differences were observed between the different fusion protein formats using surface plasmon resonance. The effect of key laundry ingredients was also studied. Combining the fusion proteins and particles into a delivery and deposition study generated clear microscopy evidence for bifunctionality. Confirmation of this was validated by GC-MS analysis of retained fragrance. This research, reporting the construction and characterization of a variety of fusion proteins, illustrates that the single multidomain fusion protein route offers a new technology for successful targeted delivery of encapsulated benefit agents. Furthermore, the potential to modify or select for proteins to recognize a wide range of surfaces is also possible.

Amino Acid Sequence↗
PubMed2006

Antiretroviral nucleosides, deoxynucleotide carrier and mitochondrial DNA: evidence supporting the DNA pol gamma hypothesis.

DESIGN: Nucleoside reverse transcriptase inhibitors (NRTIs) exhibit mitochondrial toxicity. The mitochondrial deoxynucleotide carrier (DNC) transports nucleotide precursors (or phosphorylated NRTIs) into mitochondria for mitochondrial (mt)DNA replication or inhibition of mtDNA replication by NRTIs. Transgenic mice (TG) expressing human DNC targeted to murine myocardium served to define mitochondrial events from NRTIs in vivo and findings were corroborated by biochemical events in vitro. METHODS: Zidovudine (3'-azido-2',3'-deoxythymidine; ZDV), stavudine (2', 3'-didehydro-2', 3'-deoxythymidine; d4T), or lamivudine ((-)-2'-deoxy-3'-thiacytidine; 3TC) were administered individually to TGs and wild-type (WT) littermates (35 days) at human doses with drug-free vehicle as control. Left ventricle (LV) mass was defined echocardiographically, mitochondrial ultrastructural defects were identified by electron microscopy, the abundance of cardiac mtDNA was quantified by real time polymerase chain reaction, and mtDNA-encoded polypeptides were quantified. RESULTS: Untreated TGs exhibited normal LV mass with minor mitochondrial damage. NRTI monotherapy (either d4T or ZDV) increased LV mass in TGs and caused significant mitochondrial destruction. Cardiac mtDNA was depleted in ZDV and d4T-treated TG hearts and mtDNA-encoded polypeptides decreased. Changes were absent in 3TC-treated cohorts. In supportive structural observations from molecular modeling, ZDV demonstrated close contacts with K947 and Y951 in the DNA pol gamma active site that were absent in the HIV reverse transcriptase active site. CONCLUSIONS: NRTIs deplete mtDNA and polypeptides, cause mitochondrial structural and functional defects in vivo, follow inhibition kinetics with DNA pol gamma in vitro, and are corroborated by molecular models. Disrupted pools of nucleotide precursors and inhibition of DNA pol gamma by specific NRTIs are mechanistically important in mitochondrial toxicity.

Animals↗
PubMed2005

Strain-dependent beta-adrenergic receptor function influences myocardial responses to isoproterenol stimulation in mice.

Recently, we showed that compared with the A/J inbred mouse strain, C57BL/6J (B6) mice have an athlete's cardiac phenotype. We postulated that strain differences would result in greater left ventricular (LV) hypertrophy in response to isoproterenol in B6 than A/J mice and tested the hypothesis that a differential response could be explained partly by differences in beta-adrenergic receptor (beta-AR) density and/or coupling. A/J and B6 mice were randomized to receive daily isoproterenol (100 mg/kg sc) or isovolumic vehicle for 5 days. Animals were studied using echocardiography, tail-cuff blood pressure, histopathology, beta-AR density and percent high-affinity binding, and basal and stimulated adenylyl cyclase activities. One hundred twenty-eight mice (66 A/J and 62 B6) were studied. Isoproterenol-treated A/J mice demonstrated greater percent increases in echocardiographic LV mass/body weight (97 +/- 11 vs. 20 +/- 10%, P = 0.001) and in gravimetric heart mass/body weight versus same-strain controls than B6 mice. Histopathology scores (a composite of myocyte hypertrophy, nuclear changes, fibrosis, and calcification) were greater in isoproterenol-treated A/J vs. B6 mice (2.8 +/- 0.2 vs.1.9 +/- 0.3, P < 0.05), as was quantitation of myocyte damage (22.3 +/- 11.5 vs. 4.3 +/- 3.5%). Interstrain differences in basal beta-AR density, high-affinity binding, and adenylyl cyclase activity were not significant. However, whereas isoproterenol-treated A/J mice showed nonsignificant increases in all beta-AR activity measures, isoproterenol-treated B6 mice had lower beta-AR density (57 +/- 6 vs. 83 +/- 8 fmol/mg, P < 0.05), percent high-affinity binding (15 +/- 2 vs. 26 +/- 3%, P < 0.005), and GTP + isoproterenol-stimulated adenylyl cyclase activity (10 +/- 1.1 vs. 5.8 +/- 1.5 pmol cAMP.mg(-1).min(-1)) compared with controls. High-dose, short-term isoproterenol produces greater macro- and microscopic cardiac hypertrophy and injury in A/J than B6 mice. A/J mice, unlike B6 mice, do not experience beta-AR downregulation or uncoupling in response to isoproterenol. Abnormalities in beta-adrenergic regulation may contribute to strain-related differences in the vulnerability to isoproterenol-induced cardiac changes.

Adenylyl Cyclases↗
PubMed2005

Infants can use distributional cues to form syntactic categories.

Nearly all theories of language development emphasize the importance of distributional cues for segregating words and phrases into syntactic categories like noun, feminine or verb phrase. However, questions concerning whether such cues can be used to the exclusion of referential cues have been debated. Using the headturn preference procedure, American children aged 1;5 were briefly familiarized with a partial Russian gender paradigm, with a subset of the paradigm members withheld. During test, infants listened on alternate trials to previously withheld grammatical items and ungrammatical items with incorrect gender markings on previously heard stems. Across three experiments, infants discriminated new grammatical from ungrammatical items, but like adults in previous studies, were only able to do so when a subset of familiarization items was double marked for gender category. The results suggest that learners can use distributional cues to category structure, to the exclusion of referential cues, from relatively early in the language learning process.

Child Language↗
PubMed2005

HIV viral protein R causes atrial cardiomyocyte mitosis, mesenchymal tumor, dysrhythmia, and heart failure.

HIV viral protein R (Vpr) affects the immunocyte cell cycle and circulates as free polypeptide in plasma of AIDS patients. Effects of Vpr on cardiomyocytes were explored using transgenic mice (TG) with Vpr targeted to cardiomyocytes by the alpha-myosin heavy-chain promoter. TG and WT littermate hearts were evaluated histopathologically, ultrastructurally, molecularly via RNA microarray analysis and quantitative RT-PCR, and functionally by cardiac magnetic resonance imaging (MRI) and electrocardiograms (ECG). Six hemizygous lines were created (Vpr(a,b,c,d,e,h)). Vpr RNA was expressed exclusively in myocardium and Vpr mRNA expression correlated with phenotypic changes. Vpr(b) exhibited the highest expression and mortality. TGs developed congestive heart failure ( approximately 8 weeks), abnormal cardiomyocyte nuclei and mitoses ( approximately 12 weeks), and became moribund ( approximately 20 weeks) with atrial mesenchymal tumors. MRI revealed four-chamber dilation, defective contraction, and atrial masses. Pathologically, cardiomegaly and atrial mesenchymal tumors occurred ( approximately 16-20 weeks). ECGs showed prolonged R-R, Q-T, and P-R intervals ( approximately 12 weeks). RNA encoding collagen and bone morphogenic protein 4, 6, and 7 were increased. Vpr targeted to cardiomyocytes caused defective contractility and atrial tumors. Since some Vpr cardiomyocytic effects resemble those found in terminally differentiated immunocytes, some pathogenetic mechanisms may be shared at the subcellular level.

Animals↗
PubMed2005

Transgenic expression of the deoxynucleotide carrier causes mitochondrial damage that is enhanced by NRTIs for AIDS.

Nucleoside reverse transcriptase inhibitors (NRTIs) are antiretrovirals for AIDS with limiting mitochondrial side effects. The mitochondrial deoxynucleotide carrier (DNC) transports phosphorylated nucleosides for mitochondrial DNA replication and can transport phosphorylated NRTIs into mitochondria. Transgenic mice (TG) that exclusively overexpress DNC in the heart tested DNC's role in mitochondrial dysfunction from NRTIs. Two TG lines were created that overexpressed the human DNC gene in murine myocardium. Cardiac and mitochondrial structure and function were examined by magnetic resonance imaging, echocardiography, electrocardiography, transmission electron microscopy, and plasma lactate. Antiretroviral combinations (HAART) that contained NRTIs (stavudine (2', 3'-didehydro-2', 3'-deoxythymidine or d4T)/lamivudine/indinavir; or zidovudine (3' azido-3'-deoxythymidine or AZT)/lamivudine/indinavir; 35 days) were administered to simulate AIDS therapy. In parallel, a HAART combination without NRTIs (nevirapine/efavirenz/indinavir; 35 days) served as an NRTI-sparing, control regimen. Untreated DNC TGs exhibited normal cardiac function but abnormal mitochondrial ultrastructure. HAART that contained NRTIs caused cardiomyopathy in TGs with increased left ventricle mass and volume, heart rate variability, and worse mitochondrial ultrastructural defects. In contrast, treatment with an NRTI-sparing HAART regimen caused no cardiac changes. Data suggest the DNC is integral to mitochondrial homeostasis in vivo and may relate mechanistically to mitochondrial dysfunction in patients treated with HAART regimens that contain NRTIs.

Acquired Immunodeficiency Syndrome↗
PubMed2005

Nucleoside reverse transcriptase inhibitors, mitochondrial DNA and AIDS therapy.

NRTIs are cornerstones of antiretroviral therapy and perhaps the most important drugs developed for AIDS treatment. Judicious use of NRTIs in the fight against HIV infection has afforded significant clinical advances in AIDS treatment. Nonetheless, it is axiomatic to expect side effects from NRTIs as well. A principal toxicity of NRTIs relates to chronic and cumulative MT in various tissues. The long-term impact of this toxicity on affected patients is not clear except in extreme cases where morbidity was severe and mortality occurred. Because of chronicity and potential for severity, NRTI MT remains an important clinical problem. Further studies will help us unravel mechanisms of NRTI MT and the natural history of mitochondrial biogenesis in humans and other mammalian systems.

Acquired Immunodeficiency Syndrome↗
PubMed2004

Cardiomyocyte-restricted peroxisome proliferator-activated receptor-delta deletion perturbs myocardial fatty acid oxidation and leads to cardiomyopathy.

Fatty acid oxidation (FAO) is a primary energy source for meeting the heart's energy requirements. Peroxisome proliferator-activated receptor-delta (PPAR-delta) may have important roles in FAO. But it remains unclear whether PPAR-delta is required for maintaining basal myocardial FAO. We show that cre-loxP-mediated cardiomyocyte-restricted deletion of PPAR-delta in mice downregulates constitutive expression of key FAO genes and decreases basal myocardial FAO. These mice have cardiac dysfunction, progressive myocardial lipid accumulation, cardiac hypertrophy and congestive heart failure with reduced survival. Thus, chronic myocardial PPAR-delta deficiency leads to lipotoxic cardiomyopathy. Together, our data show that PPAR-delta is a crucial determinant of constitutive myocardial FAO and is necessary to maintain energy balance and normal cardiac function. We suggest that PPAR-delta is a potential therapeutic target in treating lipotoxic cardiomyopathy and other heart diseases.

AMP-Activated Protein Kinases↗
PubMed2004

Mitochondrial oxidative stress in human hepatoma cells exposed to stavudine.

The toxicity of nucleoside reverse transcriptase inhibitors (NRTIs) is linked to altered mitochondrial DNA (mtDNA) replication and subsequent disruption of cellular energetics. This manifests clinically as elevated concentrations of lactate in plasma. The mechanism(s) underlying how the changes in mtDNA replication lead to lactic acidosis remains unclear. It is hypothesized that mitochondrial oxidative stress links the changes in mtDNA replication to mitochondrial dysfunction and ensuing NRTIs toxicity. To test this hypothesis, changes in mitochondrial function, mtDNA amplification efficiency, and oxidative stress were assessed in HepG2-cultured human hepatoblasts treated with the NRTI stavudine (2',3'-didehydro-2',3'-deoxythymidine or d4T) for 48 h. d4T produced significant mitochondrial dysfunction with a 1.5-fold increase in cellular lactate to pyruvate ratios. In addition, d4T caused a dose-dependent decrease in mtDNA amplification and a correlative increase in abundance of markers of mitochondrial oxidative stress. Manganese (III) meso-tetrakis (4-benzoic acid) porphyrin, MnTBAP, a catalytic antioxidant, ameliorated or reversed d4T-induced changes in cell injury, energetics, mtDNA amplification, and mitochondrial oxidative stress. In conclusion, d4T treatment elevates mitochondrial reactive oxygen species (ROS), enhances mitochondrial oxidative stress, and contributes mechanistically to NRTI-induced toxicity. These deleterious events may be potentiated in acquired immunodeficiency syndrome (AIDS) by human immunodeficiency virus (HIV) infection itself, coinfection (e.g., viral hepatitis), aging, substance, and alcohol use.

Carcinoma, Hepatocellular↗
PubMed2004

Representing the meanings of object and action words: the featural and unitary semantic space hypothesis.

This paper presents the Featural and Unitary Semantic Space (FUSS) hypothesis of the meanings of object and action words. The hypothesis, implemented in a statistical model, is based on the following assumptions: First, it is assumed that the meanings of words are grounded in conceptual featural representations, some of which are organized according to modality. Second, it is assumed that conceptual featural representations are bound into lexico-semantic representations that provide an interface between conceptual knowledge and other linguistic information (syntax and phonology). Finally, the FUSS model employs the same principles and tools for objects and actions, modeling both domains in a single semantic space. We assess the plausibility of the model by showing that it can capture generalizations presented in the literature, in particular those related to category-related deficits, and show that it can predict semantic effects in behavioral experiments for object and action words better than other models such as Latent Semantic Analysis (Landauer & Dumais, 1997) and similarity metrics derived from Wordnet (Miller & Fellbaum, 1991).

Analysis of Variance↗
PubMed2004

Cardiomyopathy, nucleoside reverse transcriptase inhibitors and mitochondria are linked through AIDS and its therapy.

Nucleoside reverse transcriptase inhibitors (NRTIs) in highly active antiretroviral therapy (HAART) bring serious side effects to light. Mitochondrial dysfunction, mtDNA replication defects and mtDNA depletion in target tissues are observed experimentally and clinical confirmation is present in some cases. Organ-specific pathological changes, particularly in the cardiovascular system, result from and are frequently attributed to HAART where NRTIs are included. Mechanisms of mitochondrial toxicity are incompletely understood, but could reasonably relate to inhibition of DNA polymerase-gamma (the enzyme responsible for mtDNA replication in eukaryotes) by pharmacologically active NRTI triphosphates. Cellular and biological implications of the pharmacologic events are addressed.

Journal Article↗
PubMed2004

Mice with cardiac-restricted angiotensin-converting enzyme (ACE) have atrial enlargement, cardiac arrhythmia, and sudden death.

To investigate the local effects of angiotensin II on the heart, we created a mouse model with 100-fold normal cardiac angiotensin-converting enzyme (ACE), but no ACE expression in kidney or vascular endothelium. This was achieved by placing the endogenous ACE gene under the control of the alpha-myosin heavy chain promoter using targeted homologous recombination. These mice, called ACE 8/8, have cardiac angiotensin II levels that are 4.3-fold those of wild-type mice. Despite near normal blood pressure and a normal renal function, ACE 8/8 mice have a high incidence of sudden death. Both histological analysis and in vivo catheterization of the heart showed normal ventricular size and function. In contrast, both the left and right atria were three times normal size. ECG analysis showed atrial fibrillation and cardiac block. In conclusion, increased local production of angiotensin II in the heart is not sufficient to induce ventricular hypertrophy or fibrosis. Instead, it leads to atrial morphological changes, cardiac arrhythmia, and sudden death.

Angiotensin II↗
PubMed2004

Risk of congestive heart failure in an elderly population treated with peripheral alpha-1 antagonists.

OBJECTIVES: To compare the risk of congestive heart failure (CHF) in elderly individuals treated with any peripheral alpha-1 antagonist for hypertension with any thiazide, test whether the risk persists in subjects without cardiovascular disease (CVD) at baseline, and examine CHF risk in normotensive men with prostatism treated with alpha antagonists. DESIGN: Prospective cohort study. SETTING: Four U.S. sites: Washington County, Maryland; Allegheny County, Pennsylvania; Sacramento County, California; and Forsyth County, North Carolina. PARTICIPANTS: A total of 5,888 community-dwelling subjects aged 65 and older. MEASUREMENTS: Adjudicated incident CHF. RESULTS: The 3,105 participants with treated hypertension were at risk for CHF; 22% of men and 8% of women took alpha antagonists during follow-up. The age-adjusted risk of CHF in those receiving monotherapy treated with alpha antagonists was 1.90 (95% confidence interval=1.03-3.50) compared with thiazides. In subjects without CVD at baseline receiving monotherapy, women taking an alpha antagonist had a 3.6 times greater age-adjusted risk of CHF, whereas men had no difference in risk. Adjustment for systolic blood pressure attenuated statistical differences in risk. There were 930 men without hypertension at risk for CHF; 5% used alpha antagonists during follow-up, with no observed increase in CHF risk. CONCLUSION: Subjects receiving alpha antagonist monotherapy for hypertension had a two to three times greater risk of incident CHF, also seen in lower-risk subjects, but differences in blood pressure control partly explained this.

Adrenergic alpha-Antagonists↗
PubMed2004

Oxidative stress in NRTI-induced toxicity: evidence from clinical experience and experiments in vitro and in vivo.

This article reviews the relationship of oxidative stress with nucleoside reverse transcriptase inhibitor (NRTI)-induced toxicity and suggests how oxi-dative stress may participate in NRTI-mediated toxicity. NRTIs are pro-drugs that require intracellular phosphorylation to their 5' triphosphates by cellular kinases to inhibit viral and mitochondrial DNA (mtDNA) replication. NRTIs in highly active antiretroviral therapy have decreased morbidity and mortality, but side effects can be limiting after prolonged use. These side effects may be linked through mitochondrial dysfunction arising from altered mtDNA replication and oxidative stress via destruction of elements of mtDNA replication, decreased oxidative phosphorylation, and cellular function. Although oxidative stress is associated with NRTI therapy, there is still debate about whether it plays a direct role in NRTI-induced toxicity. The impact of oxidative stress on cardiovascular disease is likely to increase because patients with HIV infection are living longer as a result of effective antiretroviral therapy.

Animals↗
PubMed2003

Mitochondrial dysfunction and nucleoside reverse transcriptase inhibitor therapy: experimental clarifications and persistent clinical questions.

Nucleoside reverse transcriptase inhibitors (NRTIs) in combination with other antiretrovirals (HAART) are critical in current AIDS therapy, but mitochondrial side effects have come to light with the increased use of these compounds. Clinical experience, pharmacological, cell and molecular biological evidence links altered mitochondrial (mt-) DNA replication to the toxicity of NRTIs in many tissues, and conversely, mtDNA replication defects and mtDNA depletion in specific target tissues are observed. The shared features of mtDNA depletion and energy depletion became key observations and related the clinical and in vivo experimental findings to inhibition of mtDNA replication by NRTI triphosphates in vitro. Subsequent to those findings, other observations suggested that mitochondrial energy deprivation is concomitant with or the result of mitochondrial oxidative stress in AIDS (from HIV, for example) or from NRTI therapy itself. With increased use of NRTIs, mtDNA mutations may become increasingly important pathophysiologically. One important future goal is to prevent or attenuate the side effects so that improved efficacy is achieved.

Anti-HIV Agents↗
PubMed2003

Mitochondrial toxicity of NRTI antiviral drugs: an integrated cellular perspective.

Highly active antiretroviral therapy (HAART) regimes based on nucleoside reverse transcriptase inhibitors (NRTIs) have revolutionized the treatment of AIDS in recent years. Although HAART can successfully suppress viral replication in the long term, it is not without significant toxicity, which can seriously compromise treatment effectiveness. A major toxicity that has been recognized for more than a decade is NRTI-related mitochondrial toxicity, which manifests as serious side effects such as hepatic failure and lactic acidosis. However, a lack of understanding of the mechanisms underlying mitochondrial toxicity has hampered efforts to develop novel drugs with better side-effect profiles. This review characterizes the pharmacological mechanisms and pathways that are involved in mitochondrial dysfunction caused by NRTIs, and suggests opportunities for future pharmacological research.

Amino Acid Sequence↗
PubMed2003

Use of the transgenic mouse in models of AIDS cardiomyopathy.

Heart disease in AIDS, particularly cardiomyopathy (CM), is an increasingly recognized clinical problem with as yet undefined pathogenetic mechanisms. Among the potential etiologies of AIDS CM are HIV-1 infection of cardiac myocytes and subsequent cardiac dysfunction, opportunistic infection, inflammatory reactions, cytokine effects, and cardiotoxicity of prescribed or illicit drugs. It seems probable that multiple factors may impact on the development of CM in AIDS. Transgenic mice (TG) are useful biological tools to explore mechanisms of cardiac function and disease. In AIDS models, TG offer novel ways to elucidate mechanisms of AIDS CM through combined in vivo and in vitro studies. With targeted and non-targeted TG, structural and functional effects of specific HIV-1 gene products on heart tissue may be addressed. The impact of environmental agents including therapeutics or cardiotoxins may also be defined. To address the complexity of AIDS CM using TG, an experimental approach has been employed in our laboratories to model the clinical condition. We utilize AIDS TG with generalized expression of HIV-1 gene products in CM models with combined antiretroviral regimens to define the cardiovascular effects of AIDS and its therapy on the structure and function of the murine heart. We are developing a series of cardiac specific TG bearing selected HIV-1 genes. These TG target the selected HIV-1 genes expressed in cardiac ventricular myocytes. Tissue-specific targeting of this type enables us to define structural and functional effects of specific HIV-1 gene products on the cardiac myocyte.

Acquired Immunodeficiency Syndrome↗