Characterization of Cardiac Time Intervals in Healthy Bonnet Macaques (Macaca radiata) by Using an Electronic Stethoscope

Nonhuman primates are used frequently in cardiovascular research. Cardiac time intervals derived by phonocardiography have long been used to assess left ventricular function. Electronic stethoscopes are simple low-cost systems that display heart sound signals. We assessed the use of an electronic stethoscope to measure cardiac time intervals in 48 healthy bonnet macaques (age, 8 ± 5 y) based on recorded heart sounds. Technically adequate recordings were obtained from all animals and required 1.5 ± 1.3 min. The following cardiac time intervals were determined by simultaneously recording acoustic and single-lead electrocardiographic data: electromechanical activation time (QS1), electromechanical systole (QS2), the time interval between the first and second heart sounds (S1S2), and the time interval between the second and first sounds (S2S1). QS2 was correlated with heart rate, mean arterial pressure, diastolic blood pressure, and left ventricular ejection time determined by using echocardiography. S1S2 correlated with heart rate, mean arterial pressure, diastolic blood pressure, left ventricular ejection time, and age. S2S1 correlated with heart rate, mean arterial pressure, diastolic blood pressure, systolic blood pressure, and left ventricular ejection time. QS1 did not correlate with any anthropometric or echocardiographic parameter. The relation S1S2/S2S1 correlated with systolic blood pressure. On multivariate analyses, heart rate was the only independent predictor of QS2, S1S2, and S2S1. In conclusion, determination of cardiac time intervals is feasible and reproducible by using an electrical stethoscope in nonhuman primates. Heart rate is a major determinant of QS2, S1S2, and S2S1 but not QS1; regression equations for reference values for cardiac time intervals in bonnet macaques are provided.Abbreviations: CTI, cardiac time intervals; QS1, electromechanical activation time; QS2, electromechanical systole; S1S2, interval between first and second heart sounds; S2S1, interval between second and first heart soundsNonhuman primates are used widely in biomedical research. Macaques and baboons are the most widely studied species.^{6,12,20,31,38,39,42,45} Macaques are anatomically similar to humans and exhibit similar cardiovascular physiology and metabolism,^{2,4,15-17,22,24,28} which make them useful as a model of left ventricular dysfunction and heart failure.^{2,23,30,32,37,44} Echocardiography has emerged as the most commonly used technique to assess left ventricular function, because it provides a variety of indices pertaining to left ventricular systolic and diastolic function. However, the availability of high-quality ultrasound equipment, transducers, technical expertise in image acquisition, and interpretation are factors that can limit the use of echocardiography in nonhuman primate research.Left ventricular function has long been assessed by using cardiac time intervals (CTI) derived by phonocardiography and carotid pulse tracings. In humans, CTI have been found highly correlated with echocardiographic, angiographic, and hemodynamic measures of left ventricular function^11,13. Low cost, ease of use, high accuracy, and excellent reproducibility have led to the frequent use of CTI in human cardiovascular research. However, electrical bioimpedence and phonocardiography with external carotid wave recordings have in large part been replaced by echocardiography as techniques to measure CTI.³⁵In recent years, electronic advances in the stethoscope have enhanced quantitative assessment of heart sounds.^5,9,33,34,43 Electronic stethoscopes are capable of recording heart sounds that can be digitally processed for display, storage, and analysis on computer. Therefore, electronic stethoscopes provide a portable low-cost alternative means to obtain CTI. Several investigators have incorporated analytical techniques to derive information pertaining to left ventricular function and pulmonary artery pressure from humans by using electronic stethoscopes.^1,5,9,43The results of several studies have led to the use of the electronic stethoscope as an alternative to the phonocardiogram, an older technology for determining CTI.^1,7,27,40 Data pertaining to the uses of CTI and electronic stethoscopes in nonhuman primates is lacking. We are unaware of a single study that has either evaluated left ventricular function by measuring CTI or has used the electronic stethoscope for cardiac assessment in monkeys. The ability to obtain CTI data and reference values may be very useful for the identification of cardiovascular abnormalities in primates. The objective of the current study was to ascertain the feasibility of determining CTI from recorded heart sounds in apparently healthy bonnet macaques (Macaca radiata). Bonnet macaques have a close physical resemblance to rhesus monkeys but are relatively smaller and lighter.²⁶     

Distinct Immune Cell Populations Define Response to Anti-PD-1 Monotherapy and Anti-PD-1/Anti-CTLA-4 Combined Therapy

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Discovery of a selective inhibitor of oncogenic B-Raf kinase with potent antimelanoma activity

BRAF(V600E) is the most frequent oncogenic protein kinase mutation known. Furthermore, inhibitors targeting "active" protein kinases have demonstrated significant utility in the therapeutic repertoire against cancer. Therefore, we pursued the development of specific kinase inhibitors targeting B-Raf, and the V600E allele in particular. By using a structure-guided discovery approach, a potent and selective inhibitor of active B-Raf has been discovered. PLX4720, a 7-azaindole derivative that inhibits B-Raf(V600E) with an IC(50) of 13 nM, defines a class of kinase inhibitor with marked selectivity in both biochemical and cellular assays. PLX4720 preferentially inhibits the active B-Raf(V600E) kinase compared with a broad spectrum of other kinases, and potent cytotoxic effects are also exclusive to cells bearing the V600E allele. Consistent with the high degree of selectivity, ERK phosphorylation is potently inhibited by PLX4720 in B-Raf(V600E)-bearing tumor cell lines but not in cells lacking oncogenic B-Raf. In melanoma models, PLX4720 induces cell cycle arrest and apoptosis exclusively in B-Raf(V600E)-positive cells. In B-Raf(V600E)-dependent tumor xenograft models, orally dosed PLX4720 causes significant tumor growth delays, including tumor regressions, without evidence of toxicity. The work described here represents the entire discovery process, from initial identification through structural and biological studies in animal models to a promising therapeutic for testing in cancer patients bearing B-Raf(V600E)-driven tumors.     

Floating-bioadhesive gastroretentive Caesalpinia pulcherrima-based beads of amoxicillin trihydrate for Helicobacter pylori eradication

Abstract

Context: An oral dosage form containing floating bioadhesive gastroretentive microspheres forms a stomach-specific drug delivery system for the treatment of Helicobacter pylori.

Objectives: To prepare and evaluate controlled release floating bioadhesive gastroretentive chitosan-coated amoxicillin trihydrate-loaded Caesalpinia pulcherrima galactomannan (CPG)-alginate beads (CCA-CPG-A), for H. pylori eradication.

Materials and methods: CCA-CPG-A beads were prepared by ionotropic gelation, using 2³ factorial design with quantity of drug, combination of CPG with sodium alginate and concentration of calcium chloride as variables. Beads facilitated mucoadhesion to gastric mucosa with floating nature caused by chitosan coating for wide distribution throughout GIT. Developed beads were evaluated for characteristics like beads size-morphology, entrapment efficiency, DSC, XRD, FTIR, swelling ratio, in vitro mucoadhesion, in vitro drug release, in vitro floating and in vitro H. pylori growth inhibition studies. CCA-CPG-A beads were studied in Wistar rats for in vivo gastric mucoadhesion, in vivo H. pylori growth inhibition studies using PCR amplification of isolated DNA, rapid urease test.

Result: Developed beads possess drug release of 79–92%, entrapment efficiency of 65–89%, mucoadhesion of 61–89%. In vivo mucoadhesion study showed more than 85% mucoadhesion of beads even after 7th hour. In vitro–in vivo growth inhibition study showed complete eradication of H. pylori.

Discussion: CPG-alginate and chitosan in beads interacts with gastric mucosubstrate surface for prolonged gastric residence with floating bioadhesion mechanism for H. pylori eradication in rats.

Conclusion: Floating bioadhesive CCA-CPG-A beads offer a promising drug delivery system for H. pylori eradication at lower dose, reduced adverse effect and enhance bioavailability.     

Enhancement of Transdermal Penetration and Bioavailability of Poorly Soluble Acyclovir Using Solid Lipid Nanoparticles Incorporated in Gel Cream

The objective of this work was to increase the amount of acyclovir in the basal epidermis, site of herpes virus simplex infection, using the solid lipid nanoparticles loaded gel cream as carriers. Solid lipid nanoparticles were prepared by high pressure homogenisation method and incorporated in a semisolid submicron gel cream. Acyclovir distribution into rat skin after topical application of solid lipid nanoparticles loaded gel cream was determined by fabricated Franz diffusion cell. The results showed that, the quantity of the acyclovir in the basal epidermis with the solid lipid nanoparticles loaded submicron gel cream was two folds times more than marketed acyclovir gel cream. This type of carrier can improve acyclovir loaded therapy since it increases drug retention in the basal epidermis.     

Development of a patient-centered video series to improve education before kidney transplantation

Background

Inadequate patient knowledge about transplantation can result in low patient satisfaction and contribute to poor clinical outcomes. The purpose of this patient-oriented research project was to develop an educational intervention for patients awaiting kidney transplantation.

Optimization of forced degradation using experimental design and development of a stability-indicating liquid chromatographic assay method for rebamipide in bulk and tablet dosage form

A novel stability-indicating RP-HPLC assay method was developed and validated for quantitative determination of rebamipide in bulk and tablet dosage form. Rebamipide (drug and drug product) solutions were exposed to acid and alkali hydrolysis, thermal stress, oxidation by hydrogen peroxide and photodegradation. Experimental design has been used during forced degradation to determine significant factors responsible for degradation and to obtain optimal degradation conditions. In addition, acid and alkali hydrolysis was performed using a microwave oven. The chromatographic method employed the HiQ sil C-18HS (250 × 4.6 mm; 5 μm) column with mobile phase consisting of 0.02 M potassium phosphate (pH adjusted to 6.8) and methanol (40:60, v/v) and the detection was performed at 230 nm. The procedure was validated for specificity, linearity, accuracy, precision and robustness. There was no interference observed of excipients and degradation products in the determination of the active pharmaceutical ingredient. The method showed good accuracy and precision (intra and inter day) and the response was linear in a range from 0.5 to 5 μg mL(-1). The method was found to be simple and fast with less trial and error experimentation by making use of experimental design. Also, it proved that microwave energy can be used to expedite hydrolysis of rebamipide.     

Topical delivery of aceclofenac from lecithin organogels: preformulation study

The purpose of this research is to evaluate the suitability of lecithin organogels containing aceclofenac for topical application. The present article focuses on the preformulation part of the whole research work. Thin layer chromatography was carried out to determine lecithin's purity. The excipients for formulating lecithin organogel were screened. Lecithin organogels are thermo reversible in nature and hence gelation temperature study was carried out to determine the temperature where Sol-Gel and Gel-Sol transformation takes place. Partition coefficient of the drug was estimated. Drug solubility in plain oil and organogel containing reverse micelles was estimated. Effect of water added on the properties of lecithin organogels such as X-ray diffraction pattern, conductivity and viscosity were determined. Microscopy of the gel sample has been carried out at different magnifications. The pseudo ternary phase diagram has been constructed to determine the organogel existence region. The permeation study of aceclofenac from different concentrations of lecithin organogels [200 mM, 300 mM and 400 mM] has been determined using cellulose acetate membrane (0.45 micro) and excised rat skin. Lecithin organogel in ethyl oleate has desired stability and consistency. A single spot on the TLC plate confirms the purity of soy lecithin to be used in organogel formation. Aceclofenac solubility was found to be more in lecithin/oil reverse micellar system as compared to its solubility in oil. The X-ray diffraction pattern confirms the incorporation of water in micellar gel network. The physical properties of organogels are affected by water incorporated and concentration of gelator. The permeation of aceclofenac through artificial membrane and excised rat skin demonstrated the same trend and were in the following order 200 mM>300 mM>400 mM. The results showed that organogel exhibits useful pharmaceutical properties.