Application of higher order statistics for atrial arrhythmia classification

Atrial fibrillation (AF) and atrial flutter (AFL) are the two common atrial arrhythmia encountered in the clinical practice. In order to diagnose these abnormalities the electrocardiogram (ECG) is widely used. The conventional linear time and frequency domain methods cannot decipher the hidden complexity present in these signals. The ECG is inherently a non-linear, non-stationary and non-Gaussian signal. The non-linear models can provide improved results and capture minute variations present in the time series. Higher order spectra (HOS) is a non-linear dynamical method which is highly rugged to noise. In the present study, the performances of two methods are compared: (i) 3rd order HOS cumulants and (ii) HOS bispectrum. The 3rd order cumulant and bispectrum coefficients are subjected to dimensionality reduction using independent component analysis (ICA) and classified using classification and regression tree (CART), random forest (RF), artificial neural network (ANN) and k-nearest neighbor (KNN) classifiers to select the best classifier. The ICA components of cumulant coefficients have provided the average accuracy, sensitivity, specificity and positive predictive value of 99.50%, 100%, 99.22% and 99.72% respectively using KNN classifier. Similarly, the ICA components of HOS bispectrum coefficients have yielded the average accuracy, sensitivity, specificity and PPV of 97.65%, 98.16%, 98.75% and 99.53% respectively using KNN. So, the ICA performed on the 3rd order HOS cumulants coupled with KNN classifier performed better than the HOS bispectrum method. The proposed methodology is robust and can be used in mass screening of cardiac patients.     

Concentration of plasminogen activators and inhibitor in the human endometrium at different phases of the menstrual cycle.

The concentrations of tissue plasminogen activator (t-PA), urokinase plasminogen activator (u-PA) and plasminogen activator inhibitor (PAI-1) have been determined in endometrial curettings obtained from 46 subfertile women during proliferative, early or late secretory phases of the menstrual cycle. t-PA activity and antigen concentrations was significantly higher (P < 0.001) in late secretory endometrium than in proliferative or early secretory endometrium. Higher concentrations of PAI-1 antigen (P < 0.05) were also noted in late secretory phase than in proliferative and early secretory endometrium. However, u-PA concentration was not significantly different and no PAI activity could be demonstrated in the menstrual phases studied. Zymography studies confirmed the presence of both t-PA and u-PA in the endometrium. Ovarian hormonal patterns may therefore influence the activity of plasminogen activators especially of t-PA in the endometrium during various phases of the menstrual cycle.     

A smooth muscle Cav1.2 calcium channel splice variant underlies hyperpolarized window current and enhanced state-dependent inhibition by nifedipine

Native smooth muscle L-type Ca(v)1.2 calcium channels have been shown to support a fraction of Ca(2+) currents with a window current that is close to resting potential. The smooth muscle L-type Ca(2+) channels are also more susceptible to inhibition by dihydropyridines (DHPs) than the cardiac channels. It was hypothesized that smooth muscle Ca(v)1.2 channels exhibiting hyperpolarized shift in steady-state inactivation would contribute to larger inhibition by DHP, in addition to structural differences of the channels generated by alternative splicing that modulate DHP sensitivities. In addition, it has also been shown that alternative splicing modulates DHP sensitivities by generating structural differences in the Ca(v)1.2 channels. Here, we report a smooth muscle L-type Ca(v)1.2 calcium channel splice variant, Ca(v)1.2SM (1/8/9(*)/32/Delta33), that when expressed in HEK 293 cells display hyperpolarized shifts for steady-state inactivation and activation potentials when compared with the established Ca(v)1.2b clone (1/8/9(*)/32/33). This variant activates from more negative potentials and generates a window current closer to resting membrane potential. We also identified the predominant cardiac isoform Ca(v)1.2CM clone (1a/8a/Delta9(*)/32/33) that is different from the established Ca(v)1.2a (1a/8a/Delta9(*)/31/33). Importantly, Ca(v)1.2SM channels were shown to be more sensitive to nifedipine blockade than Ca(v)1.2b and cardiac Ca(v)1.2CM channels when currents were recorded in either 5 mM Ba(2+) or 1.8 mM Ca(2+) external solutions. This is the first time that a smooth muscle Ca(v)1.2 splice variant has been identified functionally to possess biophysical property that can be linked to enhanced state-dependent block by DHP.     

Rabs and other small GTPases in ciliary transport

The non-motile primary cilium is a single, microtubule-based hair-like projection that emanates from most, if not all, non-dividing mammalian cells. Enriched in a variety of signalling receptors and accessories, the cilium mediates crucial sensory and regulatory functions during development and postnatal tissue homoeostasis. Maintenance of ciliary morphology and function requires continuous IFT (intraflagellar transport), and recent findings have shed light on some molecular details of how ciliogenesis is dependent on targeted exocytic membrane trafficking from the Golgi. The ARL [Arf (ADP ribosylation factor)-related] small GTPase Arf4 functions in TGN (trans-Golgi network) sorting of cilia-targeted rhodopsin into carrier vesicles, while Arl6 (Arf-like 6) and Arl13b regulate aspects of ciliary transport and IFT. Ciliogenesis and ciliary functions are also regulated by small Rabs. Rab8a, in conjunction with Rab11a, and via its interaction with a multitude of proteins associated with the ciliary basal body and axoneme/membrane, appears to be critical for ciliogenesis. Rab8's close homologue Rab10 may also play a ciliogenic role in some cells. Rab23, the depletion or inactivation of which affects cilia formation, may regulate specific ciliary protein targeting and turnover, particularly those involved in Shh (Sonic hedgehog) signalling. Recent findings have also implicated Ran, a small GTPase better known for nuclear import, in ciliary targeting of the KIF17 motor protein. We highlight and discuss recent findings on how Rabs and other small GTPases mediate ciliogenesis and ciliary traffic.     

Insertional mutagenesis based on illegitimate recombination in Schizosaccharomyces pombe

An efficient insertional mutagenesis system has been developed for Schizosaccharomyces pombe based on linear PCR-generated cassettes containing selectable markers. It depends upon illegitimate recombination for integration into the genome. Various selectable markers of different sizes can be used to obtain sufficiently high transformation and integration frequencies. Based on Southern blotting, a single insertion is found in each strain and integration sites are broadly distributed in the genome. Sequence analysis of the insert junctions frequently reveals small regions of homology (4–10 bp) between the ends of the integrated cassette and the disrupted gene. The system has been used for simple genetic screens of various types and as a promoter trap for in-frame GFP fusions.     

Development of a refined ex vivo model of peritoneal adhesion formation,and a role for connexin 43 in their development

Molecular and Cellular Biochemistry - Despite many advances across the surgical sciences, post-surgical peritoneal adhesions still pose a considerable risk in modern-day procedures and are highly...     

The parasite complex ofSaissetia nigra in Malaysia

The percentage parasitism ofSaissetia nigra (Nietner) by chalcidoid parasites and the relative abundance of individual parasites were studied in the field usingHibiscus rosa-sinensis L. as the host plant. In order of abundance (on the basis of percentage recorded) the primary parasites wereAnysis saissetiae Ash.,Aneristus ceroplastae How., andMicroterys newcombi (Gir)., while the hyperparasites wereMarietta exitiosa Comp.,Cheiloneurus saissetiae Noyes & Chua andEupelmus catoxanthae Ferr. The efficiency ofA. saissetiae (the larvae of which feed on the scale eggs) to control the scale population is doubtful because it is often parasitised by all 3 hyperparasites mentioned and each larva during development causes only 58% egg mortality of the parasitised host, leaving many scale eggs unconsumed.A. ceroplastae appears to be more useful parasite because it attacks the 2nd instar scales which cause significant damage to the host plant and it is free from attack by hyperparasites.