Citations

We have compared cytoplasmic extracts from chicken DU249 cells at various stages along the apoptotic pathway. Extracts from morphologically normal “committed stage” cells induce apoptotic morphology and DNA cleavage in substrate nuclei but require ongoing caspase activity to do so. In contrast, extracts from frankly apoptotic cells induce apoptotic events in added nuclei in a caspase-independent manner. Biochemical fractionation of these extracts reveals that a column fraction enriched in endogenous active caspases is unable to induce DNA fragmentation or chromatin condensation in substrate nuclei, whereas a caspase-depleted fraction induces both changes. Further characterization of the “execution phase” extracts revealed the presence of an ICAD/DFF45 (inhibitor of caspase-activated DNase/DNA fragmentation factor)- inhibitable nuclease resembling CAD, plus another activity that was required for the apoptotic chromatin condensation. Despite the presence of active caspases, committed stage extracts lacked these downstream activities, suggesting that the caspases and downstream factors are segregated from one another in vivo during the latent phase. These observations not only indicate that caspases act in an executive fashion, serving to activate downstream factors that disassemble the nucleus rather than disassembling it themselves, but they also suggest that activation of the downstream factors (rather than the caspases) is the critical event that occurs at the transition from the latent to active phase of apoptosis.

We present results of a strong laser field interacting with a two-center system. The two centers consist of a donor and acceptor pair which are coupled by Fœrster–Dexter resonance energy transfer. The donor molecule is the indole chromophore in indolylethylenediaminetetraacetic acid (indolyl-EDTA) which chelates the lanthanide ion acceptor holmium (Ho3+). The changes in the donor lifetime consequent upon excitation of the acceptor were examined. Excitation of the lanthanide acceptor with a second laser field resulted in the appearance of a substantially increased lifetime component. This additional (new) lifetime component is on the order of a second, compared with the original nanosecond lifetime of the donor in its complex with the acceptor. This new component is not attributable to the spontaneous lifetime of the acceptor. Rather, we propose that the large lifetime is due to the interaction of the donor with the excited state acceptor.

Abnormalities of fatty acid metabolism are recognized to play a significant role in human disease, but the mechanisms remain poorly understood. Long-chain acyl-CoA dehydrogenase (LCAD) catalyzes the initial step in mitochondrial fatty acid oxidation (FAO). We produced a mouse model of LCAD deficiency with severely impaired FAO. Matings between LCAD +/− mice yielded an abnormally low number of LCAD +/− and −/− offspring, indicating frequent gestational loss. LCAD −/− mice that reached birth appeared normal, but had severely reduced fasting tolerance with hepatic and cardiac lipidosis, hypoglycemia, elevated serum free fatty acids, and nonketotic dicarboxylic aciduria. Approximately 10% of adult LCAD −/− males developed cardiomyopathy, and sudden death was observed in 4 of 75 LCAD −/− mice. These results demonstrate the crucial roles of mitochondrial FAO and LCAD in vivo .

Ectomesenchymomas (EM) are rare malignant neoplasms usually consisting of rhabdomyosarcoma (RMS) with a neural component. Only 21 cases have been previously reported. Here we extend the clinicopathologic spectrum of EM by describing our findings in 15 cases. Only 5 patients were infants; 10 were ≤3 years old and 5 were ≥6 years old. No male predilection was observed; 7 were female. The originating institutional diagnoses were; RMS (12), undifferentiated sarcoma (1), or EM (2), suggesting underdiagnosis of this entity. The primary tumor sites included external genital (5), pelvis/abdomen (6), head and neck (3), and extremity (1). The size of the primary neoplasm was usually ≥5 cm at diagnosis but dissemination only occurred in a minority. Local infiltration was not uncommon. These neoplasms were typically multilobate, thinly encapsulated, hemorrhagic, and necrotic. Light microscopic features were highly variable, but embryonal RMS with scattered or clustered ganglion cells, often in lacunae, was characteristic. In some cases, primitive neuroblastic or neuroectodermal areas were found and/or a component of alveolar RMS was seen. Focal anaplasia was occasionally observed. Mitotic activity appears higher than previously appreciated and some necrosis was invariably present. Electron microscopy was performed in 11 cases, which confirmed skeletal muscle ± neural differentiation. Cytogenetic studies performed in five cases revealed no specific abnormality. Monoclonal neuron-specific enolase was the best marker of ganglion cells and primitive neural elements. MIC-2 (CD99) membrane expression was not definitively present in any of the six cases examined. A number of the above parameters appear to be of some prognostic significance, but overall, these neoplasms appear to have a similar outcome as would be predicted for their RMS element alone (exclusive of any neural component), with respect to the RMS subtype, age of the patient, and anatomic location of the neoplasm.

Rhabdomyosarcoma (RMS) is the most common soft tissue sarcoma of childhood, and 75% of such cases in the United States are reviewed at the Pathology Center for the Intergroup Rhabdomyosarcoma Study Group (IRSG). The first four generations of IRSG therapeutic trials (IRS I–IV) and supportive pathologic studies have generated a new International Classification of Rhabdomyosarcoma (ICR) that offers new morphologic concepts to the practicing pathologist. The objective of this report is to clearly define emerging histopathologic categories of RMS as defined by the ICR, and to emphasize correlative immunohistochemical or molecular studies. Emerging ICR variants of RMS place the patient in widely divergent prognostic categories (superior, botryoid or spindle cell variants; poor, solid alveolar or diffusely anaplastic variants). The cardinal histopathologic features of the ICR combined with results of studies of fusion genes seen with t(1;13) and t(2;13) will help delineate therapeutic subgroups of RMS for the fifth generation (IRS V) of IRSG studies. Consequently, it is imperative for the practicing pathologist to be familiar with the practical workup and diagnosis of RMS in childhood.