Cyclin-dependent kinase 2 (cdk2) plays a critical role in the G1- to S-phase checkpoint of the cell cycle. Adult cardiomyocytes are believed to withdraw from the cell cycle. To determine whether forced overexpression of cdk2 results in altered cell-cycle regulation in the adult heart, we generated transgenic mice specifically overexpressing cdk2 in hearts. Transgenic hearts expressed high levels of both cdk2 mRNA and catalytically active cdk2 proteins. Cdk2 overexpression significantly increased the levels of cdk4 and cyclins A, D3, and E. There was an increase in both DNA synthesis and proliferating cell nuclear antigen levels in the adult transgenic hearts. The ratio of heart weight to body weight in cdk2 transgenic mice was significantly increased in neonatal day 2 but not in adults compared with that of wild-type mice. Analysis of dispersed individual adult cardiomyocytes showed a 5.6-fold increase in the proportion of smaller mononuclear cardiomyocytes in the transgenic mice. Echocardiography revealed that transgenic heart was functionally normal. However, adult transgenic ventricles expressed beta-myosin heavy chain and atrial natriuretic factor. Surgically induced pressure overload caused an exaggerated maladaptive hypertrophic response in transgenic mice but did not change the proportion of mononuclear cardiomyocytes. The data suggest that overexpression of cdk2 promotes smaller, less-differentiated mononuclear cardiomyocytes in adult hearts that respond in an exaggerated manner to pressure overload.

Nkx2.5 and Nkx2.6 are murine homologs of Drosophila tinman. Their genes are expressed in the ventral region of the pharynx at early stages of embryogenesis. However, no abnormalities in the pharynges of embryos with mutations in either Nkx2.5 or Nkx2.6 have been reported. To examine the function of Nkx2.5 and Nkx2.6 in the formation of the pharynx, we generated and analyzed Nkx2.5 and Nkx2.6 double-mutant mice. Interestingly, in the double-mutant embryos, the pharynx did not form properly. Pharyngeal endodermal cells were largely missing, and the mutant pharynx was markedly dilated. Moreover, we observed enhanced apoptosis and reduced proliferation in pharyngeal endodermal cells of the double-mutant embryos. These results demonstrated a critical role of the NK-2 homeobox genes in the differentiation, proliferation, and survival of pharyngeal endodermal cells. Furthermore, the development of the atrium was less advanced in the doublemutant embryos, indicating that these two genes are essential for both pharyngeal and cardiac development.

Among Han nationality Chinese and living in the northern area of the Yellow River, 120 patients suffering from Beh^et's disease and 100 unrelated healthy individuals were typed for histocompatibility antigens (HLA)-A,-B,-C, and-DR and-DQ antigens. HLA-DR and DQ typing was performed on B-lymphocyte separated with Lympho-B-Kwik. The HLA-antisera were provided by llth IHWC. Bf alleles and C4 allotypes were determined by immunofixation agarose-gel electrophoresis. HLA-B51 was found in 67/120 (55.83%) patients and in 12/100 (12%) controls, the Chi-square and relative risk values were 45.54 and 9.27, respectively (p < 0.0005). C4AQo frequency was significantly increased in the patient group. In the complete form group HLA-B51 was observed more frequently (62.79%). No significant differences of other HLA antigens, frequencies, Bf or B4 alleles were found between the groups.

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1 In the present experiments, we investigated the eects of methylecgonidine (MEG) on nitric oxide (NO) production in cultured neonatal rat cardiomyocytes. Incubation of cultured cardiomyocytes with carbachol or MEG for 48 h signi®cantly enhanced NO production. No release was increased from 1.48+0.13 mM (mg protein) 71 for control to 5.73+0.19 mM (mg protein) 71 for 1 mM carbachol treated cells (P50.001). In addition, incubation with 1 mM MEG enhanced NO production to 5.55+0.28 mM (mg protein) 71. The eects of MEG on NO production were concentrationdependent. The muscarinic antagonist atropine prevented the enhancement of NO production induced by carbachol or MEG. Compared to MEG-induced NO production, cocaine was much less potent. 2 The enhancement of NO production by carbachol or MEG was even greater in cultured cardiomyocytes transfected with the M 2 cDNA. After 48-h incubation with 1 mM carbachol or 1 mM MEG, NO production was increased by 6.5 and 6.7 fold, respectively, in cardiomyocytes overexpressing M 2 receptors. Coincubation with atropine or N G -nitro-L-arginine methyl ester abolished the enhancement of NO production. In contrast, NO production enhanced by carbachol or MEG in M 1 -or M 3 -transfected cardiomyocytes was similar to the level in non-transfected cells. 3 Western blot analysis showed that the protein levels of M 1 , M 2 , and M 3 were signi®cantly increased in cardiomyocytes transfected with the receptor cDNAs, but MEG had no eect on the expressions. It is interesting that both carbachol and MEG caused a signi®cant increase in constitutive endothelial NO synthase (eNOS) only in M 2 -transfected cardiomyocytes, not in nontransfected, M 1 -or M 3 -transfected cells. Again, atropine blocked the MEG-produced induction of eNOS. 4 Our data demonstrate that MEG signi®cantly enhanced NO production in cultured cardiomyocytes and that the enhancement of NO production may result from MEG stimulation of muscarinic M 2 receptors.

The present study investigated whether genistein, a broad-spectrum tyrosine kinase inhibitor, could increase the myofilament Ca2+ sensitivity and partially reverse postischemic depressed myocardial function. Left ventricular papillary muscles were isolated from adult Wistar rats and loaded with the Ca2+ indicator, aequorin. The use of fluorocarbon immersion with hypoxia simulated a model of ischemia. Myofilament responsiveness to Ca2+ was evaluated from force-[Ca2+], relationship recorded during tetani in papillary muscles. Protein levels of troponin I (Tnl) were measured in postischemic papillary muscles with the Western blot technique. Isometric contraction was depressed during the period of ischemia and remained low after 60 min of reoxygenation without a corresponding significant change of peak [Ca2+], in the control group (n = 7). In contrast, the depression of isometric contraction was ameliorated during ischemia in muscle preparations in the presence of genistein (2 μM; n = 8), and postischemic depressed myocardial contractility partially recovered after a 60-min reperfusion. The myofilament Ca2+ responsiveness was significantly increased in papillary muscles in the presence of genistein. Protein levels of Tnl were reduced in postischemic papillary muscles, whereas genistein partially restored decreased protein levels of Tnl. Our results reveal that genistein produces an effective attenuation of postischemic depressed myocardial function and improves myofibrillar Ca2+ responsiveness in rat myocardium.

Type I and type II macrophage scavenger receptors (MSR) have six structurally distinct domains. MSR are known to mediate a wide range of ligand recognition, endocytosis, phagocytosis and macrophage adhesion. Expression of mutated receptors in various cultured cells and analysis using synthetic peptides indicate that two coiled-coil domains, α-helical coiled-coil domain (domain IV) and collagen-like domain (domain V) mediate these functions. Domain IV is essential for the trimerization of MSR and EDTA-resistant adhesion function. Domain V is essential for the wide range of ligand recognition. Cooperation of these two domains is also essential for the cellular function of MSR including pH-dependent ligand dissociation.

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