The electrocardiogram of Macaca fascicularis

Electrocardiograms from 16 male cynomolgus monkeys (Macaca fascicularis) were studied. Standard and augmented limb leads (I, II, III, aVR, aVL, aVF) were obtained with the animals restrained in a sitting position. Normal electrocardiographic parameters were determined, including PR and QT intervals; P, QRS, and T wave axes; P and QRS wave widths. Voltages in all standard and augmented limb leads were lower than previously reported for similar size monkeys.     

Modulation of Xenopus oocyte-expressed phospholemman-induced ion currents by co-expression of protein kinases.

Phospholemman (PLM), the major sarcolemmal substrate for phosphorylation by cAMP-dependent kinase (PKA) protein kinase C (PKC) and NIMA kinase in muscle, induces hyperpolarization-activated anion currents in Xenopus oocytes, most probably by enhancing endogenous oocyte currents. PLM peptides from the cytoplasmic tail are phosphorylated by PKA at S68, by NIMA kinase at S63, and by PKC at both S63 and S68. We have confirmed the phosphorylation sites in the intact protein, and we have investigated the role of phosphorylation in the regulatory activity of PLM using oocyte expression experiments. We found: (1) the cytoplasmic domain is not essential for inducing currents in oocytes; (2) co-expression of PKA increased the amplitude of oocyte currents and the amount of PLM in the oocyte membrane largely, but not exclusively, through phosphorylation of S68; (3) co-expression of PKA had no effect on a PLM mutant in which all putative phosphorylation sites had been inactivated by serine to alanine mutation (SSST 62, 63, 68, 69 AAAA); (4) co-expression of PKC had no effect in this system; (5) co-expression of NIMA kinase increased current amplitude and membrane protein level, but did not require PLM phosphorylation. These findings point to a role for phosphorylation in the function of PLM.     

Marked differences in tissue-specific expression of chitinases in mouse and man.

Two distinct chitinases have been identified in mammals: a phagocyte-specific enzyme named chitotriosidase and an acidic mammalian chitinase (AMCase) expressed in the lungs and gastrointestinal tract. Increased expression of both chitinases has been observed in different pathological conditions: chitotriosidase in lysosomal lipid storage disorders like Gaucher disease and AMCase in asthmatic lung disease. Recently, it was reported that AMCase activity is involved in the pathogenesis of asthma in an induced mouse model. Inhibition of chitinase activity was found to alleviate the inflammation-driven pathology. We studied the tissue-specific expression of both chitinases in mice and compared it to the situation in man. In both species AMCase is expressed in alveolar macrophages and in the gastrointestinal tract. In mice, chitotriosidase is expressed only in the gastrointestinal tract, the tongue, fore-stomach, and Paneth cells in the small intestine, whereas in man the enzyme is expressed exclusively by professional phagocytes. This species difference seems to be mediated by distinct promoter usage. In conclusion, the pattern of expression of chitinases in the lung differs between mouse and man. The implications for the development of anti-asthma drugs with chitinases as targets are discussed.     

3H]-MRE 2029-F20, a selective antagonist radioligand for the human A2B adenosine receptors

MRE 2029-F20 [N-benzo[1,3]dioxol-5-yl-2-[5-(2,6-dioxo-1,3-dipropyl-2,3,6,7-tetrahydro-1H-purin-8-yl)-1-methyl-1H-pyrazol-3-yloxy]-acetamide] is a selective antagonist ligand of A2B adenosine receptors. For use as a radioligand, 1,3-diallyl-xanthine, the precursor of [3H]-MRE 2029-F20, was synthesized, and tritiated on the allyl groups. [3H]-MRE 2029-F20 bound to human A2B receptors expressed in CHO cells showed a KD value of 1.65+/-0.10 nM and Bmax value of 36+/-4 fmol/mg protein. [3H]-MRE2029-F20 represents a useful tool for the pharmacological characterization of human A2B adenosine receptor subtype.     

Presence of functional sarcoplasmic reticulum in the developing heart and its confinement to chamber myocardium

During development fast-contracting atrial and ventricular chambers develop from a peristaltic-contracting heart tube. This study addresses the question of whether chamber formation is paralleled by a matching expression of the sarcoplasmic reticulum (SR) Ca(2+) pump. We studied indo-1 Ca(2+) transients elicited by field stimulation of linear heart tube stages and of explants from atria and outflow tracts of the prototypical preseptational E13 rat heart. Ca(2+) transients of H/H 11+ chicken hearts, which constitute the prototypic linear heart tube stage, were sensitive to verapamil only, indicating a minor contribution of Ca(2+)-triggered SR Ca(2+) release. Outflow tract transients displayed sensitivity to the inhibitors similar to that of the linear heart tube stages. Atrial Ca(2+) transients disappeared upon addition of ryanodine, tetracaine, or verapamil, indicating the presence of Ca(2+)-triggered SR Ca(2+) release. Quantitative radioactive in situ hybridization on sections of E13 rat hearts showed approximately 10-fold higher SERCA2a mRNA levels in the atria compared to nonmyocardial tissue and approximately 5-fold higher expression in compact ventricular myocardium. The myocardium of atrioventricular canal, outflow tract, inner curvature, and ventricular trabecules displayed weak expression. Immunohistochemistry on sections of rat and human embryos showed a similar pattern. The significance of these findings is threefold. (i) A functional SR is present long before birth. (ii) SR development is concomitant with cardiac chamber development, explaining regional differences in cardiac function. (iii) The pattern of SERCA2a expression underscores a manner of chamber development by differentiation at the outer curvature, rather than by segmentation of the linear heart tube.     

Inactivation of the Sema5a gene results in embryonic lethality and defective remodeling of the cranial vascular system

The semaphorins are a large family of proteins involved in the patterning of both the vascular and the nervous systems. In order to analyze the function of the membrane-bound semaphorin 5A (Sema5A), we generated mice homozygous for a null mutation in the Sema5a gene. Homozygous null mutants die between embryonic development days 11.5 (E11.5) and E12.5, indicating an essential role of Sema5A during embryonic development. Mutant embryos did not show any morphological defects that could account for the lethality of the mutation. A detailed analysis of the vascular system uncovered a role of Sema5A in the remodeling of the cranial blood vessels. In Sema5A null mutants, the complexity of the hierarchically organized branches of the cranial cardinal veins was decreased. Our results represent the first genetic analysis of the function of a class 5 semaphorin during embryonic development and identify a role of Sema5A in the regional patterning of the vasculature.     

Retinitis pigmentosa: rapid neurodegeneration is governed by slow cell death mechanisms

For most neurodegenerative diseases the precise duration of an individual cell''s death is unknown, which is an obstacle when counteractive measures are being considered. To address this, we used the rd1 mouse model for retinal neurodegeneration, characterized by phosphodiesterase-6 (PDE6) dysfunction and photoreceptor death triggered by high cyclic guanosine-mono-phosphate (cGMP) levels. Using cellular data on cGMP accumulation, cell death, and survival, we created mathematical models to simulate the temporal development of the degeneration. We validated model predictions using organotypic retinal explant cultures derived from wild-type animals and exposed to the selective PDE6 inhibitor zaprinast. Together, photoreceptor data and modeling for the first time delineated three major cell death phases in a complex neuronal tissue: (1) initiation, taking up to 36 h, (2) execution, lasting another 40 h, and finally (3) clearance, lasting about 7 h. Surprisingly, photoreceptor neurodegeneration was noticeably slower than necrosis or apoptosis, suggesting a different mechanism of death for these neurons.     

Ebstein’s anomaly may be caused by mutations in the sarcomere protein gene MYH7

Ebstein’s anomaly is a rare congenital heart malformation characterised by adherence of the septal and posterior leaflets of the tricuspid valve to the underlying myocardium. Associated abnormalities of left ventricular morphology and function including left ventricular noncompaction (LVNC) have been observed. An association between Ebstein’s anomaly with LVNC and mutations in the sarcomeric protein gene MYH7, encoding β-myosin heavy chain, has been shown by recent studies. This might represent a specific subtype of Ebstein’s anomaly with a Mendelian inheritance pattern. In this review we discuss the association of MYH7 mutations with Ebstein’s anomaly and LVNC and its implications for the clinical care for patients and their family members.