On an automatic delineator for arterial blood pressure waveforms

Arterial blood pressure waveforms contain rich pathophysiological information; hence receive much attention in cardiovascular health monitoring. To assist computerized analysis, an automatic delineator was proposed for the fiducial points of arterial blood pressure waveforms, namely their onsets, systolic peaks and dicrotic notches. The presented delineator characterizes arterial blood pressure waveforms in a beat-by-beat manner. It firstly seeks the pairs of inflection and zero-crossing points, and then utilizes combinatorial amplitude and interval criteria to select the onset and systolic peak. Once a new beat is settled, the delineator seeks the derivative backward to locate the dicrotic notch in the preceding beat. In a nutshell, the delineator is based on the combinatorial analysis of arterial blood pressure waveforms and their derivatives. Three open databases, with an additional subset database, were utilized for delineator validation and performance evaluation. In terms of beat detection, the delineator achieved an average error rate 1.14%, sensitivity 99.43% and positive predictivity 99.45%. As to dicrotic notch detection, it performed well with an error rate 6.83%, sensitivity 96.53% and positive predictivity 96.64%.     

Bacterial Tethering Analysis Reveals a “Run-Reverse-Turn” Mechanism for Pseudomonas Species Motility

We have developed a program that can accurately analyze the dynamic properties of tethered bacterial cells. The program works especially well with cells that tend to give rise to unstable rotations, such as polar-flagellated bacteria. The program has two novel components. The first dynamically adjusts the center of the cell''s rotational trajectories. The second applies piecewise linear approximation to the accumulated rotation curve to reduce noise and separate the motion of bacteria into phases. Thus, it can separate counterclockwise (CCW) and clockwise (CW) rotations distinctly and measure rotational speed accurately. Using this program, we analyzed the properties of tethered Pseudomonas aeruginosa and Pseudomonas putida cells for the first time. We found that the Pseudomonas flagellar motor spends equal time in both CCW and CW phases and that it rotates with the same speed in both phases. In addition, we discovered that the cell body can remain stationary for short periods of time, leading to the existence of a third phase of the flagellar motor which we call “pause.” In addition, P. aeruginosa cells adopt longer run lengths, fewer pause frequencies, and shorter pause durations as part of their chemotactic response. We propose that one purpose of the pause phase is to allow the cells to turn at a large angle, where we show that pause durations in free-swimming cells positively correlate with turn angle sizes. Taken together, our results suggest a new “run-reverse-turn” paradigm for polar-flagellated Pseudomonas motility that is different from the “run-and-tumble” paradigm established for peritrichous Escherichia coli.     

Physiological analysis on oscillatory behavior of glucose-insulin regulation by model with delays

Despite temporally forced transmission driving many infectious diseases, analytical insight into its role when combined with stochastic disease processes and non-linear transmission has received little attention. During disease outbreaks, however, the absence of saturation effects early on in well-mixed populations mean that epidemic models may be linearised and we can calculate outbreak properties, including the effects of temporal forcing on fade-out, disease emergence and system dynamics, via analysis of the associated master equations. The approach is illustrated for the unforced and forced SIR and SEIR epidemic models. We demonstrate that in unforced models, initial conditions (and any uncertainty therein) play a stronger role in driving outbreak properties than the basic reproduction number R₀, while the same properties are highly sensitive to small amplitude temporal forcing, particularly when R₀ is small. Although illustrated for the SIR and SEIR models, the master equation framework may be applied to more realistic models, although analytical intractability scales rapidly with increasing system dimensionality. One application of these methods is obtaining a better understanding of the rate at which vector-borne and waterborne infectious diseases invade new regions given variability in environmental drivers, a particularly important question when addressing potential shifts in the global distribution and intensity of infectious diseases under climate change.     

Synthesis and antimicrobial activity of N¹-benzyl or N¹-benzyloxy-1,6-dihydro-1,3,5-triazine-2,4-diamines

The emergence and spread of multidrug-resistant strains of Staphylococcus aureus and Mycobacterium tuberculosis are generating a threat to public health worldwide. In the current study, a series of N(1)-benzyl and N(1)-benzyloxy-1,6-dihydro-1,3,5-triazine-2,4-diamine derivatives were synthesized and investigated for their antimicrobial activity against S. aureus, and Mycobacterium smegmatis which is taxonomically related to M. tuberculosis. Most of the compounds exhibited good activity against M. smegmatis as determined by comparison of diameters of the zone of inhibition of test compounds and standard antibiotics. Compound 7o showed potent antimycobacterial activity against M. smegmatis without mammalian DHFR inhibition liability. The results from this study indicate that 1-benzyl derivatives of 1,6-dihydro-1,3,5-triazine-2,4-diamines may be used as lead compounds for the discovery of antimycobacterial agents.     

First report of paralytic shellfish poisoning (PSP) caused by Alexandrium tamiyavanichii in Kuantan Port,Pahang, East Coast of Malaysia

Harmful algal bloom (HAB) is a proliferation of algae, which naturally produce biotoxins and cause harmful effects to humans, the environment and organisms associated with it. Paralytic shellfish poisoning (PSP) was reported for the first time in Kuantan Port, Pahang, Malaysia, in November 2013, followed by a second episode in August 2014. The toxicity level reported during the second event was as high as 3500 μg of STX equiv./100 g shellfish. Ten people were hospitalized with PSP symptoms after consuming contaminated shellfish. This study was conducted at Kuantan Port to identify the organisms responsible for these events. Water samples were collected monthly for a period of 12 months beginning in September 2014. HAB species were identified based on their morphology using light and fluorescence microscopes, and their classification was supported by molecular evidence based on internal transcribed spacer (ITS) sequences. Monthly cell abundance of Alexandrium tamiyavanichii was measured at four sampling stations. Toxin production by three strains isolated from the area was determined using HPLC. Our results revealed the presence of several HAB species, including the PSP‐producing species A . tamiyavanichii . The highest cell density of A . tamiyavanichii was 840 cells L^?1. The presence of GTX components was detected in these strains. However, other toxin components could not be determined. This study reported, for the first time, the presence of PSP‐producing A . tamiyavanichii on the Pahang coast of east Peninsular Malaysia and confirmed that the PSP events in Kuantan Port were attributable to this species. The presence of this species further indicates that several safety measures need to be considered to safeguard public health, particularly in Pahang coastal waters.     

Three-Directional Evaluation of Mitral Flow in the Rat Heart by Phase-Contrast Cardiovascular Magnetic Resonance

Purpose

Determination of mitral flow is an important aspect in assessment of cardiac function. Traditionally, mitral flow is measured by Doppler echocardiography which suffers from several challenges, particularly related to the direction and the spatial inhomogeneity of flow. These challenges are especially prominent in rodents. The purpose of this study was to establish a cardiovascular magnetic resonance (CMR) protocol for evaluation of three-directional mitral flow in a rodent model of cardiac disease.

Materials and Methods

Three-directional mitral flow were evaluated by phase contrast CMR (PC-CMR) in rats with aortic banding (AB) (N = 7) and sham-operated controls (N = 7). Peak mitral flow and deceleration rate from PC-CMR was compared to conventional Doppler echocardiography. The accuracy of PC-CMR was investigated by comparison of spatiotemporally integrated mitral flow with left ventricular stroke volume assessed by cine CMR.

Results

PC-CMR portrayed the spatial distribution of mitral flow and flow direction in the atrioventricular plane throughout diastole. Both PC-CMR and echocardiography demonstrated increased peak mitral flow velocity and higher deceleration rate in AB compared to sham. Comparison with cine CMR revealed that PC-CMR measured mitral flow with excellent accuracy. Echocardiography presented significantly lower values of flow compared to PC-CMR.

Conclusions

For the first time, we show that PC-CMR offers accurate evaluation of three-directional mitral blood flow in rodents. The method successfully detects alterations in the mitral flow pattern in response to cardiac disease and provides novel insight into the characteristics of mitral flow.     

On-site rapid detection of toxic <Emphasis Type="Italic">Alexandrium tamiyavanichii</Emphasis>: integrating the species-specific hydrolysis probe in insulated isothermal polymerase chain reaction (iiPCR)

On-site investigation of phytoplankton samples is important for rapid detection of harmful algal species and for early warning of harmful algal bloom. Molecular detection method by DNA amplification in a portable insulated isothermal PCR (iiPCR) device provides a simple and rapid detection based on fluorescent probe within an hour of reaction time. The assay was developed for a paralytic shellfish toxin-producing dinoflagellate Alexandrium tamiyavanichii. The assay presents the data as positive or negative on the presence or absence of A. tamiyavanichii cells, with a limit of detection (LOD) at five target cells per reaction. While the assay is incapable to accurately quantify cell density, it exhibits high detection accuracy and strongly correlated with quantitative PCR (qPCR) data. The user repeatability of iiPCR assay was evaluated; the results showed that no significant differences in the assay run by different operators. Field applicability of the assay was further validated by environmental samples. Despite the shortcoming of the assay, the overall performance of the assay to detect cells, its low-cost effectiveness, and portability for on-site detection, iiPCR has proven its potential as an early screening tool for harmful algae monitoring.