Cell death was examined by studying the spinal cords of rats subjected to traumatic insults of mild to moderate severity. Within minutes after mild weight drop impact (a 10 gm weight falling 6.25 mm), neurons in the immediate impact area showed a loss of cytoplasmic Nissl substances. Over the next 7 d, this lesion area expanded and cavitated. Terminal deoxynucleotidyl transferase (TdT)-mediated deoxyuridine triphosphate-biotin nick end labeling (TUNEL)-positive neurons were noted primarily restricted to the gross lesion area 4-24 hr after injury, with a maximum presence at 8 hr after injury. TUNEL-positive glia were present at all stages studied between 4 hr and 14 d, with a maximum presence within the lesion area 24 hr after injury. However 7 d after injury, a second wave of TUNEL-positive glial cells was noted in the white matter peripheral to the lesion and extending at least several millimeters away from the lesion center. The suggestion of apoptosis was supported by electron microscopy, as well as by nuclear staining with Hoechst 33342 dye, and by examination of DNA prepared from the lesion site. Furthermore, repeated intraperitoneal injections of cycloheximide, beginning immediately after a 12.5 mm weight drop insult, produced a substantial reduction in histological evidence of cord damage and in motor dysfunction assessed 4 weeks later. Present data support the hypothesis that apoptosis dependent on active protein synthesis contributes to the neuronal and glial cell death, as well as to the neurological dysfunction, induced by mild-to-moderate severity traumatic insults to the rat spinal cord.

Biochemistry. In the article ''Identification by mass spectrometry of the phosphorylated residue responsible for activation of the catalytic domain of myosin I heavy chain kinase, a member of the PAK͞STE20 family'' by Joanna Szczepanowska, Xiaolong Zhang, Christopher J. Herring, Jun Qin, Edward D. Korn, and Hanna Brzeska, which appeared in number 16, August 5, 1997, of Proc. Natl. Acad. Sci. USA (94,(8503)(8504)(8505)(8506)(8507)(8508), the authors wish to note that in Fig. 3, the ions of m͞z 1345.3 and 1247.1 were incorrectly identified as b 13 and b 13 ⌬ , respectively, produced by cleavage of the peptide AS(Pi)VVGTTYW-MAPEVVK between E and V (Fig. 3 Inset). In fact, these ions are b 12 and b 12 ⌬ , produced by cleavage of the peptide between P and E. This correction has no effect on the conclusion that the phosphorylated residue is serine. Also, in Table 2, reference numbers 22-24 should be 21-23 (the reference in the legend is cited correctly) and the MIHCK sequence is from residue 624 to residue 638.Cell Biology. In the article ''Subtraction hybridization identifies a transformation progression-associated gene PEG-3 with sequence homology to a growth arrest and DNA damageinducible gene'' by Zao

The temporal evolution of cerebral infarction was examined in rats subjected to transient occlusion of both common carotid arteries and the right middle cerebral artery. After severe (90-min) ischemia, substantial right-sided cortical infarction was evident within 6 h and fully developed after 1 day. After mild (30-min) ischemia, no cortical infarction was present after 1 day. However, infarction developed after 3 days; by 2 weeks, infarction volume was as large as that induced by 90-min ischemia. These data suggest that infarction after mild focal ischemia can develop in a surprisingly delayed fashion. Some evidence of neuronal apoptosis was present after severe ischemia, but only to a limited degree. However, 3 days after mild ischemia, neurons bordering the maturing infarction exhibited prominent TUNEL staining, and DNA prepared from the periinfarct area of ischemic cortex showed internucleosomal fragmentation. Furthermore, pretreatment with 1 mg/kg cycloheximide markedly reduced infarction volume 2 weeks after mild ischemia. These data raise the possibility that apoptosis, dependent on active protein synthesis, contributes to the delayed infarction observed in rats subjected to mild transient focal cerebral ischemia.

Abstract-We created knock-in mice in which a deletion of 3 base pairs coding for K210 in cardiac troponin (cTn)T found in familial dilated cardiomyopathy patients was introduced into endogenous genes. Membrane-permeabilized cardiac muscle fibers from mutant mice showed significantly lower Ca 2ϩ sensitivity in force generation than those from wild-type mice. Peak amplitude of Ca 2ϩ transient in cardiomyocytes was increased in mutant mice, and maximum isometric force produced by intact cardiac muscle fibers of mutant mice was not significantly different from that of wild-type mice, suggesting that Ca 2ϩ transient was augmented to compensate for decreased myofilament Ca 2ϩ sensitivity. Nevertheless, mutant mice developed marked cardiac enlargement, heart failure, and frequent sudden death recapitulating the phenotypes of dilated cardiomyopathy patients, indicating that global functional defect of the heart attributable to decreased myofilament Ca 2ϩ sensitivity could not be fully compensated by only increasing the intracellular Ca 2ϩ transient. We found that a positive inotropic agent, pimobendan, which directly increases myofilament Ca 2ϩ sensitivity, had profound effects of preventing cardiac enlargement, heart failure, and sudden death. These results verify the hypothesis that Ca 2ϩ desensitization of cardiac myofilament is the absolute cause of the pathogenesis of dilated cardiomyopathy associated with this mutation and strongly suggest that Ca 2ϩ sensitizers are beneficial for the treatment of dilated cardiomyopathy patients affected by sarcomeric regulatory protein mutations. (Circ Res. 2007;101:185-194.)Key Words: dilated cardiomyopathy Ⅲ troponin Ⅲ mutation Ⅲ calcium sensitivity Ⅲ knock-in mouse D ilated cardiomyopathy (DCM) is a disorder of cardiac muscle characterized by cardiac enlargement and systolic dysfunction and accounts for more than 10 000 deaths annually by heart failure and sudden death in the United States. 1-3 DCM is known to result from nongenetic insults, such as viruses, alcohol, toxins, and immunologic injury; however, recent genetic studies have revealed that mutations in genes for cytoskeletal (dystrophin, desmin, ␦-sarcoglycan), nuclear envelope (tafazzin and lamin A/C), and sarcomeric (cardiac actin, ␤-cardiac myosin heavy chain, ␣-tropomyosin, cardiac myosin-binding protein C, titin/connectin, cardiac troponin [cTn]T, cTnI, and cTnC) proteins are important causes of DCM, 4 and the incidence of the inherited DCM is thought to be 20% to 35%. [5][6][7] Cardiac muscle contraction is regulated through Ca 2ϩ binding to cardiac troponin complex localized on the thin filaments, 8 and DCM-causing mutations in troponin complex are associated with a malignant phenotype with a high incidence of premature cardiac death and heart transplantation. 9 Cardiac troponin complex consists of 3 components of distinct structure and function, cTnT, cTnI, and cTnC. cTnT has a structural role in anchoring troponin complex to the thin filaments through its binding to tropomyosin, cTnI inhibits the interaction ...