Combined resection of coronary and innominate artery aneurysms.

Coexistent aneurysms of the coronary and inominate arteries are extremely rare. We present the case of a 28-year-old male with an aneurysm of the left anterior descending coronary artery and an aneurysm of the inominate artery presenting with hoarseness and severely depressed left ventricular function (ejection fraction of 25%). He underwent successful surgical resection of both aneurysms. The inominate artery aneurysm was excised and the brachiocephalic trunk was reconstructed off-pump. The coronary artery aneurysm was excised and distal aorto-coronary bypass grafting was done on cardiopulmonary bypass.

Post-translational modifications in circadian rhythms.

The pace has quickened in circadian biology research. In particular, an abundance of results focused on post-translational modifications (PTMs) is sharpening our view of circadian molecular clockworks. PTMs affect nearly all aspects of clock biology; in some cases they are essential for clock function and in others, they provide layers of regulatory fine-tuning. Our goal is to review recent advances in clock PTMs, help make sense of emerging themes, and spotlight intriguing (and perhaps controversial) new findings. We focus on PTMs affecting the core functions of eukaryotic clocks, in particular the functionally related oscillators in Neurospora crassa, Drosophila melanogaster, and mammalian cells.

A role for casein kinase 2 in the mechanism underlying circadian temperature compensation.

Temperature compensation of circadian clocks is an unsolved problem with relevance to the general phenomenon of biological compensation. We identify casein kinase 2 (CK2) as a key regulator of temperature compensation of the Neurospora clock by determining that two long-standing clock mutants, chrono and period-3, displaying distinctive alterations in compensation encode the beta1 and alpha subunits of CK2, respectively. Reducing the dose of these subunits, particularly beta1, significantly alters temperature compensation without altering the enzyme's Q(10). By contrast, other kinases and phosphatases implicated in clock function do not play appreciable roles in temperature compensation. CK2 exerts its effects on the clock by directly phosphorylating FREQUENCY (FRQ), and this phosphorylation is compromised in CK2 hypomorphs. Finally, mutation of certain putative CK2 phosphosites on FRQ, shown to be phosphorylated in vivo, predictably alters temperature compensation profiles effectively phenocopying CK2 mutants.

Fully codon-optimized luciferase uncovers novel temperature characteristics of the Neurospora clock.

We report the complete reconstruction of the firefly luciferase gene, fully codon optimized for expression in Neurospora crassa. This reporter enhances light output by approximately 4 log orders over that with previously available versions, now producing light that is visible to the naked eye and sufficient for monitoring the activities of many poorly expressed genes. Time lapse photography of strains growing in race tubes, in which the frq or eas/ccg-2 promoter is used to drive luciferase, shows the highest levels of luciferase activity near the growth front and newly formed conidial bands. Further, we have established a sorbose medium colony assay that will facilitate luciferase-based screens. The signals from sorbose-grown colonies of strains in which the frq promoter drives luciferase exhibit the properties of circadian rhythms and can be tracked for many days to weeks. This reporter now makes it possible to follow the clock in real time, even in strains or under conditions in which the circadian rhythm in conidial banding is not expressed. This property has been used to discover short, ca. 15-h period rhythms at high temperatures, at which banding becomes difficult to observe in race tubes, and to generate a high-resolution temperature phase-response curve.

Circadian rhythmicity by autocatalysis.

The temperature compensated in vitro oscillation of cyanobacterial KaiC phosphorylation, the first example of a thermodynamically closed system showing circadian rhythmicity, only involves the three Kai proteins (KaiA, KaiB, and KaiC) and ATP. In this paper, we describe a model in which the KaiA- and KaiB-assisted autocatalytic phosphorylation and dephosphorylation of KaiC are the source for circadian rhythmicity. This model, based upon autocatalysis instead of transcription-translation negative feedback, shows temperature-compensated circadian limit-cycle oscillations with KaiC phosphorylation profiles and has period lengths and rate constant values that are consistent with experimental observations.

The Drosophila type II receptor, Wishful thinking, binds BMP and myoglianin to activate multiple TGFbeta family signaling pathways.

Wishful thinking (Wit) is a Drosophila transforming growth factor-beta (TGFbeta) superfamily type II receptor most related to the mammalian bone morphogenetic protein (BMP) type II receptor, BMPRII. To better understand its function, we undertook a biochemical approach to establish the ligand binding repertoire and downstream signaling pathway. We observed that BMP4 and BMP7, bound to receptor complexes comprised of Wit and the type I receptor thickveins and saxophone to activate a BMP-like signaling pathway. Further we demonstrated that both myoglianin and its most closely related mammalian ligand, myostatin, interacted with a Wit and Baboon (Babo) type II-type I receptor complex to activate TGFbeta/activin-like signaling pathways. These results thereby demonstrate that Wit binds multiple ligands to activate both BMP and TGFbeta-like signaling pathways. Given that myoglianin is expressed in muscle and glial-derived cells, these results also suggest that Wit may mediate myoglianin-dependent signals in the nervous system.

Role of endothelin-1 in genesis of coronary artery disease.

BACKGROUND: The endothelial cells produce the most potent vasoconstrictor known as endothelin-1. Elevated plasma levels of endothelin have been associated with coronary artery disease, essential hypertension and heart failure. The aims of the present study were, to compare the plasma endothelin-1 levels in coronary artery disease patients and healthy controls, to confirm endothelin-1 as surrogate marker for coronary artery disease and to compare the presence of endothelin-1 like immunoreactivity in aortic and internal mammary artery specimens obtained during coronary artery bypass graft surgery. METHODS AND RESULTS: The circulating levels of endothelin-1 were determined by enzyme-linked immunoassay in patients of coronary artery disease (n=145) and compared with healthy controls (n=70). Tissue endothelin-1 immunoreactivity was examined by immunohistochemical method in aortic and internal mammary artery tissue specimens obtained from 20 patients of coronary artery disease during coronary artery bypass grafting to understand the role of endothelin in atherosclerosis. Significantly higher levels (p < 0.001) of endothelin-1 were observed in all patients of coronary artery disease as compared to healthy controls. The immunoreactivity of endothelin-1 was localized to endothelial cell layer in internal mammary artery whereas in aortic specimens, in addition to endothelial cell layer, immunoreactivity was seen in the cytoplasm of smooth muscle cells of intima and media. CONCLUSIONS: The significant increase in plasma endothelin-1 in coronary artery disease cases as compared to healthy subjects and presence of tissue endothelin-1 immunoreactivity in smooth muscle cells of intimal as well as medial layers of aorta confirms the role of endothelin-1 as a surrogate marker of atherosclerosis.

TGF-beta and the Smad signal transduction pathway.

Transforming growth factor beta (TGF-beta) superfamily members are important regulators of many diverse developmental and homeostatic processes and disruption of their activity has been implicated in a variety of human diseases ranging from cancer to chondrodysplasias and pulmonary hypertension. TGF-beta family members signal through transmembrane Ser-Thr kinase receptors that directly regulate the intracellular Smad pathway. Smads are a unique family of signal transduction molecules that can transmit signals directly from the cell surface receptors to the nucleus, where they regulate transcription by interacting with DNA binding partners as well as transcriptional coactivators and corepressors. In addition, more recent evidence indicates that Smads can also function both as substrates and adaptors for ubiquitin protein ligases, which mediate the targeted destruction of intracellular proteins. Smads have thus emerged as multifunctional transmitters of TGF-beta family signals that play critical roles in the development and homeostasis of metazoans.