A peritoneal mesothelioma in a captive aardwolf (Proteles cristatus)

A 10-year-old male aardwolf (Proteles cristatus) was presented abdominal distention and emaciation for 3 months. Physical examination revealed firm abdominal masses with effusions. Cytologic assessment of the effusion showed uniform round tumor cells with a surface brush border. Necropsy showed white velvety masses covering the peritoneal surface of the liver, gall bladder, stomach, omentum, mesentery, spleen, intestine, abdominal wall and diaphragm. Histologic examination demonstrated papillary projections, lined with cuboidal tumor cells supported by fibrous connective tissue cores, arising from the serosa of visceral organs. Cytoplasmic vacuolation and a surface brush border were evident on some cells under light microscopy. Tumor cells stained positive for both cytokeratin (AE1/AE3) and vimentin. Electron microscopy showed prominent surface microvilli, rough endoplasmic reticulum, mitochondria and desmosomes in tumor cells. This may be the first reported case of peritoneal mesothelioma in a captive wild aardwolf.     

Amplification effect and mechanism of action of ET-1 in U-46619-induced vasoconstriction in pig skin

The aim of this study was to investigate if a low concentration of endothelin-1 (ET-1; 8 x 10(-10) M) may amplify the skin vasoconstrictor effect of other vasoactive substances in the pathogenesis of skin vasospasm. Pig skin flaps (6 x 16 cm) were perfused with Krebs buffer equilibrated with 95% O(2) and 5% CO(2) at 37 degrees C and pH 7.4. Skin perfusion pressure measured by a pressure transducer and skin perfusion assessed by the dermofluorometry technique were used for assessment of skin vasoconstriction. We observed that ET-1 (8 x 10(-10) M) significantly amplified the concentration-dependent (10(-7)-10(-5) M) skin vasoconstrictor effect of norepinephrine. More importantly, we observed for the first time that this low concentration of ET-1 also amplified the concentration-dependent (10(-8)-10(-6) M) skin vasoconstrictor effect of the thromboxane A(2) mimetic U-46619, and this amplification effect of ET-1 was completely blocked by the protein kinase C (PKC) inhibitor chelerythrine (5 x 10(-6) M). Conversely, the PKC activator phorbol 12,13-dibutyrate (10(-7) M) amplified the vasoconstrictor effect of U-46619. Furthermore, the sensitivity of the skin vasculature to the vasoconstrictor effect of extracellular Ca(2+) in U-46619-induced skin vasoconstriction was significantly enhanced in the presence of 8 x 10(-10) M ET-1. Finally, the cyclooxygenase inhibitor indomethacin (5 x 10(-6) M) did not affect the amplification effect of ET-1 on U-46619-induced skin vasoconstriction. We conclude that a low concentration of ET-1 can amplify the skin vasoconstrictor effect of U-46619 independent of endogenous cyclooxygenase products, and the mechanism may involve activation of PKC and increase in sensitivity of the contractile apparatus to Ca(2+) in smooth muscle cells.     

Successful molecular dynamics simulation of the zinc-bound farnesyltransferase using the cationic dummy atom approach

Farnesyltransferase (FT) inhibitors can suppress tumor cell proliferation without substantially interfering with normal cell growth, thus holding promise for cancer treatment. A structure-based approach to the design of improved FT inhibitors relies on knowledge of the conformational flexibility of the zinc-containing active site of FT. Although several X-ray structures of FT have been reported, detailed information regarding the active site conformational flexibility of the enzyme is still not available. Molecular dynamics (MD) simulations of FT can offer the requisite information, but have not been applied due to a lack of effective methods for simulating the four-ligand coordination of zinc in proteins. Here, we report in detail the problems that occurred in the conventional MD simulations of the zinc-bound FT and a solution to these problems by employing a simple method that uses cationic dummy atoms to impose orientational requirement for zinc ligands. A successful 1.0 ns (1.0 fs time step) MD simulation of zinc-bound FT suggests that nine conserved residues (Asn127alpha, Gln162alpha, Asn165alpha, Gln195alpha, His248beta, Lys294beta, Leu295beta, Lys353beta, and Ser357beta) in the active site of mammalian FT are relatively mobile. Some of these residues might be involved in the ligand-induced active site conformational rearrangement upon binding and deserve attention in screening and design of improved FT inhibitors for cancer chemotherapy.     

Expression of functional soluble human alpha-globin chains of hemoglobin in bacteria

Individual, soluble human alpha-globin chains were expressed in bacteria with exogenous heme and methionine aminopeptidase. The yields of soluble alpha chains in bacteria were comparable to those of recombinant non-alpha chains expressed under the same conditions. Molecular mass and gel-filtration properties of purified recombinant alpha chains were the same as those of authentic human alpha chains. Biochemical and biophysical properties of isolated alpha chains were identical to those of native human alpha chains as assessed by UV/vis, circular dichroism (CD), and nuclear magnetic resonance (NMR) spectroscopy which contrasts with previous results of refolded precipitated alpha chains made in the presence of heme in vitro (M. T. Sanna et al., J. Biol. Chem. 272, 3478-3486, 1997). Mixtures of purified, soluble recombinant alpha-globin and native beta-globin chains formed heterotetramers in vitro, and oxygen- and CO-binding properties as well as the heme environment of the assembled tetramers were experimentally indistinguishable from those of native human Hb A. UV/vis, CD, and NMR spectra of assembled Hb A were also the same as those of human Hb A. These results indicate that individual expressed alpha chains are stable in bacteria and fold properly in vivo and that they then can assemble with free beta chains to form hemoglobin heterotetramers in vivo as well as in vitro.     

Overexpression of beta-catenin induces apoptosis independent of its transactivation function with LEF-1 or the involvement of major G1 cell cycle regulators

beta-Catenin promotes epithelial architecture by forming cell surface complexes with E-cadherin and also interacts with TCF/LEF-1 in the nucleus to control gene expression. By DNA transfection, we overexpressed beta-catenin and/or LEF-1 in NIH 3T3 fibroblasts, corneal fibroblasts, corneal epithelia, uveal melanoma cells, and several carcinoma cell lines. In all cases (with or without LEF-1), the abundant exogenous beta-catenin localizes to the nucleus and forms distinct nuclear aggregates that are not associated with DNA. Surprisingly, we found that with time (5-8 d after transfection) cells overexpressing beta-catenin all undergo apoptosis. LEF-1 does not need to be present. Moreover, LEF-1 overexpression in the absence of exogenous beta-catenin does not induce apoptosis, even though some endogenous beta-catenin moves with the exogenous LEF-1 into the nucleus. TOPFLASH/FOPFLASH reporter assays showed that full-length beta-catenin is able to induce LEF-1-dependent transactivation, whereas Arm beta-catenin totally abolishes the transactivating function. However, Arm beta-catenin, containing deletions of known LEF-1-transactivating domains, has the same apoptotic effects as full-length beta-catenin. Overexpressed beta-catenin also induces apoptosis in cells transfected with nuclear localization signal-deleted LEF-1 that localizes only in the cytoplasm. Thus, the apoptotic effects of overexpressed exogenous beta-catenin do not rely on its transactivating function with nuclear LEF-1. Overexpressed delta-catenin, containing 10 Arm repeats, induces only minor apoptosis, suggesting that the major apoptotic effect may be due to domains specific to beta-catenin as well as to Arm repeats. The absence of p53, Rb, cyclin D1, or E2F1 does not affect the apoptotic effect of overexpressed beta-catenin, but Bcl-x(L) reduces it. We hypothesize that in vivo apoptosis of cells overexpressing beta-catenin might be a physiological mechanism to eliminate them from the population.     

Second mutations rescue point mutant of the Na(+)/H(+) exchanger NHE1 showing defective surface expression

We studied the effect of point mutation within the putative 11th transmembrane domain (TM11) of the Na(+)/H(+) exchanger NHE1 on the plasma membrane expression. Of the 19 mutants tested, two mutants (Tyr454 or Arg458 replaced by Cys) were retained in the endoplasmic reticulum. Interestingly, Y454C was expressed on the cell surface when one of the endogenous cysteine residues at position 8, 133, 421, or 477 was substituted with alanine. Random mutagenesis at Cys8 and its surrounding residues in the cytosolic N-tail revealed that replacement of Cys8 with Ala was the only identified single residue mutation that rescued Y454C. These results suggest that the abnormal conformation of the region of TM11 containing the Y454C mutation is compensated by the second mutation within other domains such as the N-tail. This approach may provide evidence for the interdomain interaction in NHE1.     

Synthesis of the same two proteins prior to larval diapause and pupation in the spruce budworm,Choristoneura fumiferana

Spruce budworm larvae produce large quantities of two proteins (Choristoneura fumiferana diapause associated proteins 1 and 2, CfDAP1 and CfDAP2) that are diapause related. These proteins appeared soon after hatching and increased in abundance, reaching maximum levels by four days into the 1st instar, and they remained at high levels until three days after the termination of diapause. These two proteins were purified to homogeneity and their NH2-terminal sequences were obtained. Oligonucleotide primers designed on the basis of these NH2-terminal sequences were used in RT-PCR to isolate the cDNA fragments coding for these proteins. These PCR fragments were then used as probes to isolate the cDNAs that contained the complete coding region. The 2.5kb mRNAs coding for these proteins started to appear 24hr after hatching and large quantities of these mRNAs were detected in 1st instar and 2nd instar larvae until the 2nd instar larvae entered diapause. Low levels of these mRNAs were detected in the 2nd instar larvae that were preparing to enter diapause, in those that were in diapause as well as in those that terminated diapause. Low levels of CfDAP1 mRNA were also detected on days 1 and 2 after ecdysis to the 3rd instar. However, no CfDAP1 and CfDAP2 mRNAs could be detected during the 4th and 5th instar larval stages. The mRNAs reappeared 24hr after the 5th instar larvae molted into the 6th instar and increased to reach maximum levels by 60hr after ecdysis. The mRNA levels remained high until 156hr after ecdysis into the 6th instar (36-48hr before pupal ecdysis), after which they disappeared once again. Immunocytochemical analyses showed that CfDAP1 protein was present in 2nd and 6th instar larval fat body but not in 5th instar larval fat body. Thus, the same two genes were expressed for the first time before C. fumiferana larvae entered diapause and for a 2nd time before pupation.     

Multiple variants and a differential splicing pattern of kinectin in human hepatocellular carcinoma.

To extend the search for hepatocellular carcinoma (HCC) associated antigens with immunogenicity for clinical applications, we constructed a cDNA expression library using resected human HCC tissue sample and screened it by serological analysis of recombinant cDNA expression library (SEREX) with autologous and allogeneic sera. A total of 24 distinct antigens were isolated and kinectin was the antigen most frequently identified. We found that kinectin was alternatively spliced at four sites and obtained all eight theoretical forms of variant, six by SEREX and two by RT-PCR, from the different splicing combinations of the last three sites. In addition, the splicing patterns of four sites were analyzed. Variant containing D2 was overexpressed in cancerous tissues and this alteration may be tumor associated. The four splicing sites, the variants generated by alternative splicing, and the humoral immune response in HCC patients, may help to analyze the role of kinectin in human HCC cell biology.