Daniel R. Webster

An Organoselenium Compound Inhibits Staphylococcus aureus Biofilms on Hemodialysis Catheters In Vivo

ABSTRACT Colonization of central venous catheters (CVCs) by pathogenic bacteria leads to catheter-related bloodstream infections (CRBSIs). These colonizing bacteria form highly antibiotic-resistant biofilms. Staphylococcus aureus is one of the most frequently isolated pathogens in CRBSIs. Impregnating CVC surfaces with antimicrobial agents has various degrees of effectiveness in reducing the incidence of CRBSIs. We recently showed that organoselenium covalently attached to disks as an antibiofilm agent inhibited the development of S. aureus biofilms. In this study, we investigated the ability of an organoselenium coating on hemodialysis catheters (HDCs) to inhibit S. aureus biofilms in vitro and in vivo. S. aureus failed to develop biofilms on HDCs coated with selenocyanatodiacetic acid (SCAA) in either static or flowthrough continuous-culture systems. The SCAA coating also inhibited the development of S. aureus biofilms on HDCs in vivo for 3 days. The SCAA coating was stable and nontoxic to cell culture or animals. This new method for coating the internal and external surfaces of HDCs with SCAA has the potential to prevent catheter-related infections due to S. aureus.

Synergistic Activity of Rapamycin and Dexamethasone in vitro and in vivo in acute lymphoblastic leukemia via cell-cycle arrest and apoptosis

Activation of the mTOR pathway subsequent to phosphatase and tensin homolog (PTEN) mutation may be associated with glucocorticoid (GC) resistance in acute lymphoblastic leukemia (ALL). The combination activity of rapamycin and dexamethasone in cell lines and xenograft models of ALL was determined. Compared with either drug alone, dexamethasone+rapamycin showed significantly greater apoptosis and cell cycle arrest in some cell lines, and was more frequently seen in T-lineage cell lines with PTEN mutation. The combination significantly extended the event-free survival of mice carrying PTEN mutated xenografts. Our data suggest that PI3K/mTOR pathway inhibitors could benefit patients with PTEN mutated T-ALL.

Transforming growth factor-β effects on morphology of immature rat Leydig cells

Abstract Transforming growth factor-β (TGFβ) has been shown to regulate steroid production and DNA synthesis in rat Leydig cells. We have investigated the effects of TGFβ on the secretion of extracellular matrix (ECM) proteins and on the cytoskeleton of immature rat Leydig cells in vitro. TGFβ caused significant morphological changes in Leydig cells, which were accompanied by significant increases in secretion of fibronectin, laminin and collagen IV and rearrangement of actin filaments in TGFβ-treated cells. The cells cultured on plates pre-coated with fibronectin or fibronectin plus laminin and collagen IV, displayed morphological and cytoskeletal changes similar to those induced by TGFβ. Immunofluorescence localization studies revealed significantly higher fibronectin staining in Leydig cells in adult animals and in LH-treated immature animals than those in untreated immature animals. We conclude that TGFβ participates in the morphological differentiation of immature Leydig cells into adult Leydig cells in the rat testis by inducing the expression of ECM proteins.

Microtubules in cardiac toxicity and disease.

Microtubules (MTs) are dynamic, cytoskeletal fibers that are found in every eukaryotic cell type. MTs serve a wide range of functions, including cell division, membrane and vesicle transport, and motility. As such, MTs play pivotal roles in cardiac development and function. Agents that disrupt normal MT function, including such therapeutic agents as vincristine and paclitaxel, have also been shown to affect essential cardiac activities such as sarcomere mechanics, beat rate, and the secretion of important molecules (e.g., atrial natriuretic factor). Disease states that lead to either ischemia- or pressureoverload-induced cardiac hypertrophy also alter the microtubule cytoskeleton in several ways. A fuller understanding of the contributions of MTs to cardiac development and function will be necessary to minimize the deleterious, side effects of the therapeutic application of MT-disrupting drugs. This review summarizes current hypotheses and experimental results that demonstrate the central role of MTs in heart cell function and disease.

Decreased gap-junctional communication associated with segregation of the neuronal phenotype in the RT4 cell-line family

Abstract RT4 is a family of cell lines derived from a rat peripheral neurotumor. The RT4 family consists of a multipotential stem-cell line that spontaneously gives rise to three derivative cell types, one glial and two neuronal. The three derivative cell types are capable of further lineage-specific maturation under appropriate culture conditions. Gap-junctional communication is postulated to be important during nervous-system development by allowing and/or controlling the transmission of both electrical current and signaling molecules, which may affect growth and differentiation. Our characterization of gap-junctional communication in the RT4 cell line family revealed that: (1) the glial-derivative and the stem-cell line were extensively coupled, while the two neuronal derivatives were significantly less coupled, and (2) all of the RT4 cell lines, including the stem-cell line, expressed Cx43 mRNA and protein, and the levels were generally consistent with the observed degree of functional coupling. These observations are consistent with data from in vivo studies and establish the RT4 cell line family as a potentially useful in vitro model system for understanding the role(s) of gap-junctional communication during differentiation in the peripheral nervous system.

The ability of quaternary ammonium groups attached to a urethane bandage to inhibit bacterial attachment and biofilm formation in a mouse wound model

For proper wound healing, control of bacteria or bacterial infections is of major importance. While caring for a wound, dressing material plays a key role as bacteria can live in the bandage and keep re‐infecting the wound. They do this by forming biofilms in the bandage, which slough off planktonic bacteria and overwhelm the host defense. It is thus necessary to develop a wound dressing that will inhibit bacterial growth. This study examines the effectiveness of a polyurethane foam wound dressing bound with polydiallyl‐dimethylammonium chloride (pDADMAC) to inhibit the growth of bacteria in a wound on the back of a mouse. This technology does not allow pDADMAC to leach away from the dressing into the wound, thereby preventing cytotoxic effects. Staphylococcus aureus, Pseudomonas aeruginosa and Acinetobacter baumannii were chosen for the study to infect the wounds. S. aureus and P. aeruginosa are important pathogens in wound infections, while A. baumannii was selected because of its ability to acquire or upregulate antibiotic drug resistance determinants. In addition, two different isolates of methicillin‐resistant S. aureus (MRSA) were tested. All the bacteria were measured in the wound dressing and in the wound tissue under the dressing. Using colony‐forming unit (CFU) assays, over six logs of inhibition (100%) were found for all the bacterial strains using pDADMAC‐treated wound dressing when compared with control‐untreated dressing. The CFU assay results obtained with the tissues were significant as there were 4–5 logs of reduction (100%) of the test organism in the tissue of the pDADMAC‐covered wound versus that of the control dressing‐covered wound. As the pDADMAC cannot leave the dressing (like other antimicrobials), this would imply that the dressing acts as a reservoir for free bacteria from a biofilm and plays a significant role in the development of a wound infection.