Functional reentry in cultured monolayers of neonatal rat cardiac cells.

Previous studies of reentrant arrhythmias in the heart have been performed in computer models and tissue experiments. We hypothesized that confluent monolayers of cardiac cells can provide a simple, controlled, and reproducible experimental model of reentry. Neonatal rat ventricular cells were cultured on 22-mm-diameter coverslips and stained with the voltage-sensitive dye RH-237.

Cardiomyocyte cultures with controlled macroscopic anisotropy: a model for functional electrophysiological studies of cardiac muscle.

Structural and functional cardiac anisotropy varies with the development, location, and pathophysiology in the heart. The goal of this study was to design a cell culture model system in which the degree, change in fiber direction, and discontinuity of anisotropy can be controlled over centimeter-size length scales. Neonatal rat ventricular myocytes were cultured on fibronectin on 20-mm diameter circular cover slips.

The rat arcuate nucleus integrates peripheral signals provided by leptin, insulin, and a ghrelin mimetic.

The hypothalamic circuits controlling food intake and body weight receive and integrate information from circulating satiety signals such as leptin and insulin and also from ghrelin, the only known circulating hormone that stimulates appetite following systemic injection. Activation of arcuate neurons by ghrelin and ghrelin mimetics (the growth hormone secretagogues) is augmented in 48-h-fasted rats compared with fed rats, as reflected by a greater number of cells expressing Fos protein in response to administration of the same maximally effective dose. Here we sought to determine whether this increased responsiveness in fasting might reflect or be influenced by low levels of circulating satiety factors such as leptin or insulin.

A novel algorithm for cardiac biosignal filtering based on filtered residue method.

In this paper, a new algorithm is presented for the filtering (de-noising) of cardiac bioelectrical signals. The primary target of this algorithm is the class of cardiac action potentials recorded using voltage-sensitive dyes, although the method is also applied to electrocardiographic signals. High periodicity is one of the main features of cardiac biosignals.

Decomposition of field-induced transmembrane potential responses of single cardiac cells.

In this study, we used a multi-site optical mapping system to record field-induced responses of single cells isolated from guinea pig hearts. The cells were stained with voltage sensitive dye di-8-ANEPPS and stimulated with two uniform field (S1-S2) pulses along their longitudinal axes. The first pulse (S1 = 5 ms, <10 V/cm) was applied during rest and elicited an action potential.

Spatial heterogeneity of transmembrane potential responses of single guinea-pig cardiac cells during electric field stimulation.

Changes in transmembrane voltage (V(m)) of cardiac cells during electric field stimulation have a complex spatial- and time-dependent behaviour that differs significantly from electrical stimulation of space-clamped membranes by current pulses. A multisite optical mapping system was used to obtain 17 or 25 microm resolution maps of V(m) along the long axis of guinea-pig ventricular cells (n = 57) stained with voltage-sensitive dye (di-8-ANEPPS) and stimulated longitudinally with uniform electric field (2, 5 or 10 ms, 3-62 V cm(-1)) pulses (n = 201). The initial polarizations of V(m) responses (V(mr)) varied linearly along the cell length and reversed symmetrically upon field reversal.

The inhibitory function in human progesterone receptor N termini binds SUMO-1 protein to regulate autoinhibition and transrepression.

Although most studies of progesterone receptors (PR) and their two isoforms, PR-A and PR-B, focus on transcriptional stimulation, the receptors exhibit important inhibitory properties. Autoinhibition refers to an inhibitory function located in the PR N terminus, whose deletion increases transcriptional activity at least 6-10-fold. Transrepression refers to the ability of PR-A to suppress the transcriptional activity of PR-B and other nuclear receptors, including estrogen receptors.

The yeast ADP-ribosylation factor GAP, Gcs1p, is involved in maintenance of mitochondrial morphology.

Membrane trafficking is regulated, in part, by small GTP-binding proteins of the ADP-ribosylation factor (ARF) family. ARF function depends on the controlled binding and hydrolysis of GTP. In vitro, the GTPase activity of yeast ARF proteins can be stimulated by Gcs1p.

An evaluation of complications following dental extractions using either sterile or clean gloves.

This randomized prospective study aims to evaluate any differences in the postoperative infection rate from dental extraction using either sterile or clean surgical gloves and to determine any predisposing factors that may complicate socket healing. A total of 609 patients were randomly assigned to two groups, with the operators wearing either sterile or clean gloves in performing forcep extractions. 551 patients, who had 811 extractions performed, returned for the postoperative assessment visit.

Effects of uniform electric fields on intracellular calcium transients in single cardiac cells.

Although intracellular calcium ([Ca(2+)](i)) transients in cardiac cells have been well studied in the uniformly polarized cell membrane, how these transients are modified during field stimulation when the cell membrane is nonuniformly polarized has not been investigated. In this study we characterized the effects of uniform field stimuli on [Ca(2+)](i) transients in isolated guinea pig cardiac cells. Single guinea pig cells were enzymatically isolated, loaded with the [Ca(2+)](i) fluorescent indicator fluo-3, and stimulated along their longitudinal axes with S1 or S1-S2 (S1-S2 = 50 ms) pulses.

Theoretical and experimental study of sawtooth effect in isolated cardiac cell-pairs.

Introduction: The question of how a defibrillation shock affects the myocardium far (> approximately 1 mm; the space constant of continuum tissue models) from the electrode is not fully understood. According to a long-standing, yet to be verified, hypothesis, the relatively high-resistance intercellular gap junctions may help in coupling the shock effect to the distant myocardium by redistributing the defibrillation current and creating a sawtooth pattern of polarization in which every cell undergoes hyperpolarization and depolarization. The goal of this study was to conduct an in-depth theoretical and experimental investigation of the sawtooth effect in the simplest coupled system, that of an isolated cell-pair.

Mapping the unique activation function 3 in the progesterone B-receptor upstream segment. Two LXXLL motifs and a tryptophan residue are required for activity.

Progesterone receptors (PR) contain three activation functions (AFs) that together define the extent to which they regulate transcription. AF1 and AF2 are common to the two isoforms of PR, PR-A and PR-B, whereas AF3 lies within the N-terminal 164 amino acids unique to PR-B, termed the "B-upstream segment" (BUS). To define the BUS regions that contribute to AF3 function, we generated a series of deletion and amino acid substitution mutants and tested them in three backgrounds as follows: BUS alone fused to the PR DNA binding domain (BUS-DBD), the entire PR-B N terminus linked to its DBD (NT-B), and full-length PR-B.

A case series: initial outcome of persons with multidrug-resistant tuberculosis after treatment with the WHO standard retreatment regimen in Ho Chi Minh City, Vietnam.

Few data address the outcomes of patients who have multidrug-resistant tuberculosis (MDR-TB), defined as resistance to at least isoniazid and rifampin, and who receive a standard World Health Organization (WHO) recommended retreatment regimen after relapse or failure with initial treatment. In this case series, we examined treatment outcomes of a convenience sample of 42 relapse or failure patients who had documented MDR-TB and who had received a standard WHO retreatment regimen (2SHRZE/1HRZE/5H3R3E3). One patient died of tuberculosis in the last month of treatment; the remaining 41 patients completed retreatment.

Thoughts on tamoxifen resistant breast cancer. Are coregulators the answer or just a red herring?

The antiestrogen tamoxifen is an effective treatment for estrogen receptor positive breast cancers, slowing tumor growth and preventing disease recurrence, with relatively few side effects. However, many patients who initially respond to treatment, later become resistant to treatment. Tamoxifen has both agonist and antagonist activities, which are manifested in a tissue-specific pattern.

Growth hormone (GH)-independent stimulation of adiposity by GH secretagogues.

Growth hormone secretagogues (GHSs) stimulate growth hormone (GH) secretion, which is lipolytic. Here we compared the effects of twice daily s.c.

Nuclear receptor conformation, coregulators, and tamoxifen-resistant breast cancer.

The development of tamoxifen resistance and consequent disease progression are common occurrences in breast cancers, often despite the continuing expression of estrogen receptors (ER). Tamoxifen is a mixed antagonist, having both agonist and antagonist properties. We have suggested that the development of tamoxifen resistance is associated with an increase in its agonist-like properties, resulting in loss of antagonist effects or even inappropriate tumor stimulation.

Modulated structure of La2Co1.7 from neutron and X-ray diffraction data.

An La(2)Co(1.7) crystal was investigated by single-crystal neutron and X-ray diffraction. The neutron measurement was performed with a Laue white-beam technique at 15 K and room temperature, using a large position-sensitive detector.

Virtual sources associated with linear and curved strands of cardiac cells.

Transmembrane potential (V(m)) responses in cardiac strands with different curvature were characterized during uniform electric-field stimulation with the use of modeling and experimental approaches. Linear and U-shaped strands (width 100-150 micrometer) were stained with voltage-sensitive dye. V(m) was measured by optical mapping across the width and at sites of beginning curvature.

Contact fluorescence imaging of reentry in monolayers of cultured neonatal rat ventricular myocytes.

Introduction: We present a novel contact fluorescence imaging (CFI) approach to monitor transmembrane potentials in monolayers of cultured neonatal rat ventricular cells. We apply CFI to demonstrate, for the first time, long-term recordings as well as electrical induction and termination of reentrant activity in this in vitro model.

Methods And Results: CFI was performed in confluent cell monolayers stained with di-8-ANEPPS.

Changes in electroporation thresholds of lipid membranes by surfactants and peptides.

This article reviews recent work from our laboratory that explores how chemical additives may alter the threshold of electroporation of synthetic lipid bilayers. The addition of the nonionic block copolymeric surfactant, poloxamer 188 (P188), at a concentration of 1 mM increased the electroporation thresholds of planar lipid bilayer membranes made of azolectin. For a 10-microsecond rectangular pulse, P188-treated membranes were found to have a statistically higher threshold voltage, longer latency time to rupture, and lower postpulse conductance.

Estrogen receptors alpha and beta: prevalence of estrogen receptor beta mRNA in human vascular smooth muscle and transcriptional effects.

Background: Estrogens have vascular effects through the activation of estrogen receptors (ERs). In addition to ERalpha, the first ER to be cloned, a second subtype called ERbeta has recently been discovered.

Methods And Results: Using a reverse-transcriptase polymerase chain reaction assay that employs the same primer pair to simultaneously amplify ERalpha and ERbeta transcripts, we found that ERbeta is the ER form that is predominantly expressed in human vascular smooth muscle, particularly in women.

Association of the Ku autoantigen/DNA-dependent protein kinase holoenzyme and poly(ADP-ribose) polymerase with the DNA binding domain of progesterone receptors.

Ligand-activated progesterone receptors (PR) bind to DNA at specific progesterone response elements by means of a DNA binding domain (DBD(PR)) containing two highly conserved zinc fingers. DNA-bound PRs regulate transcription via interaction with other nuclear proteins and transcription factors. We have now identified four HeLa cell nuclear proteins that copurify with a glutathionine-S-transferase-human DBD(PR )fusion protein.

Focal extracellular potential: a means to monitor electrical activity in single cardiac myocytes.

The focal extracellular potential (FEP) described in this study is an electrophysiological signal related to the transmembrane potential (V(m)) of cardiac myocytes that avoids the mechanical fragility, interference with contraction, and intracellular contact associated with conventional whole cell recording. One end of a frog ventricular myocyte was secured into a glass holding pipette. The FEP was measured differentially between this pipette and a bath pipette while the cell was voltage- or current-clamped by a third whole cell pipette.

Factors governing mechanical stimulation in frog hearts.

Because stretch-induced activation may be important in generating clinically relevant arrhythmias in the heart, we delineated the ability of different types of stretches to activate ventricular tissue. Geometrically simple sheets of frog (Rana catesbeiana) ventricular tissue were mounted to allow stretches to be applied perpendicular to one edge. Every heart could be activated by a stretch pulse (n = 25), and several parameters were varied to determine their effects on mechanical activation threshold.