Undifferentiated embryonal sarcoma of the liver is an aggressive mesenchymal tumor that occurs predominantly in children. Although this entity has been described for decades, its pathogenesis is still obscure. Its association with mesenchymal hamartoma has been well described on the basis of identical chromosomal abnormalities. The clinical and radiological diagnoses are often difficult, and the diagnosis of undifferentiated embryonal sarcoma of the liver is based on its histology and immunophenotype. It is essential to recognize the characteristic histologic findings and the pattern of the immunohistochemistry staining to rule out other hepatic lesions. Multimodal therapy with surgery, chemotherapy, and radiation therapy has drastically improved the prognosis of patients with undifferentiated embryonal sarcoma of the liver. This successful management requires timely diagnosis for superior outcome.

By using specific anti-ACAT-1 antibodies in immunodepletion studies, we previously found that ACAT-1, a 50-kDa protein, plays a major catalytic role in the adult human liver, adrenal glands, macrophages, and kidneys but not in the intestine. Acyl-coenzyme A:cholesterol acyltransferase (ACAT) activity in the intestine may be largely derived from a different ACAT protein. To test this hypothesis, we produced specific polyclonal anti-ACAT-2 antibodies that quantitatively immunodepleted human ACAT-2, a 46-kDa protein expressed in Chinese hamster ovary cells. In hepatocyte-like HepG2 cells, ACAT-1 comprises 85-90% of the total ACAT activity, with the remainder attributed to ACAT-2. In adult intestines, most of the ACAT activity can be immunodepleted by anti-ACAT-2. ACAT-1 and ACAT-2 do not form heterooligomeric complexes. In differentiating intestinal enterocyte-like Caco-2 cells, ACAT-2 protein content increases by 5-10-fold in 6 days, whereas ACAT-1 protein content remains relatively constant. In the small intestine, ACAT-2 is concentrated at the apices of the villi, whereas ACAT-1 is uniformly distributed along the villus-crypt axis. In the human liver, ACAT-1 is present in both fetal and adult hepatocytes. In contrast, ACAT-2 is evident in fetal but not adult hepatocytes. Our results collectively suggest that in humans, ACAT-2 performs significant catalytic roles in the fetal liver and in intestinal enterocytes. Acyl-coenzyme A:cholesterol acyltransferase (ACAT) 1 is an integral membrane protein located in the endoplasmic reticulum. It catalyzes the formation of cholesteryl esters from long

A rare form of human ACAT1 mRNA, containing the optional long 5 -untranslated region, is produced as a 4.3-kelonucleotide chimeric mRNA through a novel interchromosomal trans-splicing of two discontinuous RNAs transcribed from chromosomes 1 and 7 (Li, B. L., Li, X. L., Duan, Z. J., Lee, O., Lin, S., Ma, Z. M., Chang, C. C., Yang, X. Y., Park, J. P., Mohandas, T. K., Noll, W., Chan, L., and Chang, T. Y. (1999) J. Biol. Chem. 274, 11060 -11071). To investigate its function, we express the chimeric ACAT1 mRNA in Chinese hamster ovary cells and show that it can produce a larger ACAT1 protein, with an apparent molecular mass of 56 kDa on SDS-PAGE, in addition to the normal, 50-kDa ACAT1 protein, which is produced from the ACAT1 mRNAs without the optional long 5 -untranslated repeat. To produce the 56-kDa ACAT1, acat1 sequences located at both chromosomes 7 and 1 are required. The 56-kDa ACAT1 can be recognized by specific antibodies prepared against the predicted additional amino acid sequence located upstream of the N-terminal of the ACAT1 ORF . The translation initiation codon for the 56-kDa protein is GGC, which encodes for glycine, as deduced by mutation analysis and mass spectrometry. Similar to the 50-kDa protein, when expressed alone, the 56-kDa ACAT1 is located in the endoplasmic reticulum and is enzymatically active. The 56-kDa ACAT1 is present in native human cells, including human monocyte-derived macrophages. Our current results show that the function of the chimeric ACAT1 mRNA is to increase the ACAT enzyme diversity by producing a novel isoenzyme. To our knowledge, our result provides the first mammalian example that a trans-spliced mRNA produces a functional protein.Acyl-coenzyme A:cholesterol acyltransferase (ACAT) 1 is an intracellular enzyme that plays important roles in lipid metabolism. It catalyzes the formation of cholesteryl esters, using long-chain fatty acyl coenzyme A and cholesterol as the two substrates. In mammals, two ACAT genes have been identified (reviewed in Refs. 1-4). The first ACAT gene, acat1, was identified by isolating a human cDNA (ACAT cDNA K1) that functionally complements a Chinese hamster ovary cell mutant (clone AC29) lacking endogenous ACAT activity (5). The second ACAT gene, acat2, was identified by homology cloning, based on the nucleotide sequence of ACAT1 cDNA. The ACAT1 and ACAT2 proteins share extensive sequence homology at their C-terminal halves but not at their N-terminals. Both enzymes are integral membrane proteins. Human ACAT1 (hACAT1) contains seven transmembranes (6), whereas hACAT2 contains only two detectable transmembranes (7). A conserved histidine (His-460 in hACAT1 and His-432 in hACAT2), located within a long stretch of hydrophobic residues, may serve as an active site for ACAT catalysis (7,8). Human ACAT1 message and protein are present in many tissues and various cell types examined, including adrenal, kidney, hepatocytes, Kupffer cells, intestinal enterocytes, fibroblasts, macrophages, and neurons in the brain (5, 9 -12). In contrast, abundant ACA...

Flow cytometric reticulocyte analysis is superior to manual reticulocyte counting with respect to precision and sensitivity. Furthermore, because the fluorescence intensity of reticulocytes is directly proportional to the erythrocyte RNA content, flow cytometric analysis using thiazole orange gives a quantitative reticulocyte maturity index (RMI). Previous studies have demonstrated that the RMI parameter is the earliest indicator of bone marrow engraftment following transplantation. In the present study, we analyzed the correlation of the RMI to standard red cell parameters, reticulocyte percentage, and absolute reticulocyte count in 41 3 anemic patients. The correlation of RMI to serum erythropoietin (Epo) and serum transferrin receptor (TfR) was analyzed in a subset of anemic blood samples. We found weak correlations between the RMI and hemoglobin (rZ = 0.0411, hematocrit (r2 = 0.0381, reticulocyte percentage (r2 = 0.0781, and absolute reticulocyte count (r2 = 0.087). Stronger correlations were observed between the RMI and Epo (r2 = 0.181) and the TfR (r2 = 0.191). The results indicate that the RMI represents a cost-effective measurement of erythropoietic activity and provides an additional parameter to classify anemic patients into categories of high and low erythropoietic activity, especially in hypoproductive anemias. o 1995 Wiley-Liss, Inc.Key terms: Erythropoiesis, erythrocyte, red cell, erythropoietin, transferrin receptor, thiazole orange It has recently been shown that flow cytometric reticulocyte analysis is more precise, more sensitive, and less costly than manual reticulocyte counting ( 5,6,8,10,15, 24,28). It is likely that this method will find widespread clinical use in the future for these reasons. In addition to accurate reticulocyte enumeration, because the measured fluorescence intensity is directly proportional to the amount of RNA in the immature erythrocytes, this method has the ability to quantitate reticulocyte maturity. Although reticulocyte maturation has been studied for over a century, only the flow cytometrically derived RMI appears to allow clinical utility (18). This quantitation of RNA in the reticulocytes using fluorescence intensity of thiazole orange-stained whole blood samples, termed the reticulocyte maturity index (RMI), has been shown to be an early predictor of bone marrow engraftment in transplant patients (2,1523). The parameter has also been reported to distinguish iron deficiency anemia from anemia of chronic disease (34). A similar RMI parameter can be derived from the Sysmex R series' dedicated reticulocyte analyzers based on the fluorescence intensity of auramine 0 reticulocyte staining, which has also been reported to be an early predictor of bone marrow engraftment (3,9,19,22) and parallels the increase in circulating CD34+ cells following granulocyte colony-stim-0 1 9 9 5 Wiley-Liss, Inc.ulating factor (G-CSF) and granulocyte-macrophage colony-stimulating factor (GM-CSF) priming prior to peripheral stem cell harvesting (27,29). However, no information on the ...

We present a case of a 71 year-old woman who presented with an extrahepatic biliary obstruction and a mass in the common bile duct 45 years after cholecystectomy. Pathologic analysis revealed a bile duct neuroma. We present the preoperative imaging, operative management, pathologic diagnosis, and literature review of this rare condition.