ULTRASTRUCTURE OF AN ANAPLASTIC GIANT-CELL CARCINOMA FOUND 8 YEARS AFTER OPERATION ON A PAPILLARY CARCINOMA OF THE THYROID

Light and electron microscopic studies have been made on an anaplastic giant-cell tumor that developed in a woman 8 years after an operation on the thyroid for papillary carcinoma. Many giant cells were observed in the anaplastic tumor tissue, but no follicles. Numerous tightly-packed mitochondria and abundant ribosomes were present, but there were no desmosomes. The basement membrane was not distinct.     

Block of sodium channels by tyramine and its analogue (N-feruloyl tyramine) in frog ventricular myocytes.

Pharmacological effects of tyramine and its analogue, N-feruloyl tyramine (NFT), on sodium and calcium currents in frog ventricular myocytes were examined using the whole-cell voltage-clamp technique. To improve the temporal and spatial control of the membrane potential, sodium currents (INa) were recorded in 45.5 mM [Na+]o at 10 degrees C. Both tyramine and NFT (1-100 microM) induced a concentration-dependent decrease in INa evoked from a holding potential of -80 mV without affecting a change in either the time to peak or the time constant for the falling phase of INa. Similarly the reversal potential for INa remained unchanged at a value close to that predicted from the Nernst equation. The finding that both tyramine and NFT decreased INa when activated maximally, from a holding potential of -120 mV, indicates that the amplitude of INa can be reduced independently of a change in the kinetics of the current. In addition, tyramine (100 microM) shifted the membrane potential for half maximal inactivation (Vh) of the steady-state inactivation (h infinity)-curve from -74 to -84 mV without affecting its slope. In contrast, NFT failed to affect the h infinity-curve. The calcium current (ICa) recorded in the presence of 0.3 microM TTX was not affected by either 100 microM tyramine or NFT. We concluded that tyramine directly blocks Na channel by shifting h infinity-curve and by suppressing maximum Na channel conductance, while NFT suppresses only maximum Na channel conductance.     

Clostridium sordellii phospholipase C: gene cloning and comparison of enzymatic and biological activities with those of Clostridium perfringens and Clostridium bifermentans phospholipase C

The gene encoding Clostridium sordellii phospholipase C (Csp) was cloned and expressed as a histidine-tagged (His-tag) protein, and the protein was purified to compare its enzymatic and biological activities with those of Clostridium perfringens phospholipase C (Cpa) and Clostridium bifermentans phospholipase C (Cbp). Csp was found to consist of 371 amino acid residues in the mature form and to be more homologous to Cbp than to Cpa. The egg yolk phospholipid hydrolysis activity of the His-tag Csp was about one-third of that of His-tag Cpa, but the hemolytic activity was less than 1% of that of His-tag Cpa. His-tag Csp was nontoxic to mice. Immunization of mice with His-tag Cbp or His-tag Csp did not provide effective protection against the lethal activity of His-tag Cpa. These results indicate that Csp possesses similar molecular properties to Cbp and suggest that comparative analysis of toxic and nontoxic clostridial phospholipases is helpful for characterization of the toxic properties of clostridial phospholipases.     

Induced 13C shifts by coil-supporting solvents observed in oligopeptides as model compounds of polypeptides

The origin of the chemical shift differences of carbons in polypeptides which accompany the helix-coil transition has been investigated by using oligopeptides, benzyloxycarbonyl-γ-ethyl-L -glutamyl-diethyl-L -glutamate and benzyloxycarbonyl-di-(γ-ethyl-L -glutamyl)-diethyl-L -glutamate, as models of the backbone of polypeptides. Structures of aggregates in deuterated chloroform were proposed for these oligopeptides on the basis of concentration dependence and temperature dependence of the chemical shifts of protons and carbons, and spin-lattice relaxation times. Antiparallel and/or parallel “in-register” structures for extended forms and “out-of-register” network of extended forms are coexisting in deuterated chloroform solution for these oligopeptides. From the shift for the carbons of the oligopeptides induced by organic acids, it was in ferred that down-field shifts are induced at α and amide carbons in polypeptides by organic acids. By comparing the induced shift of the carbons in the peptides with the chemical shift differences of the carbons in polypeptides which accompany the helix-coil transitions, it was found that the conformational changes play a predominant role in the origin of the chemical shift differences of the carbons in polypeptides which accompany the helix-coil transitions, it was found that the conformational changes play a predominnant role in the orgin of the chemical shift differences of amide, α, β, and γ carbons in polypeptides.     

Increased production of human immunodeficiency virus (HIV) in HIV-induced syncytia formation: An efficient infection process

Syncytia or multinucleated giant-cell formation is one of the major cytopathic effects induced by human immunodeficiency virus (HIV) infection. Cell fusion results from the strong interaction of CD4 molecules on the surface of the uninfected T cells and gp120, an external envelope glycoprotein of HIV on the infected T cells. We studied the production of HIV in fusion cells between MOLT-4 and virus-infected MOLT-4/HIV cells and found that HIV production was enhanced up to three- to fivefold, which showed a good correlation with the appearance and extent of syncytia formation. Blocking the fusion by monoclonal antibody against a binding epitope of CD4 molecule to gp120 decreased the HIV production significantly. Enhancement of HIV production was observed by more than five-fold in comparison with chronically infected cells, which were fusion free 20 hr postcocultivation. Electron microscopic observation also showed the presence of abundant HIV particles inside the fused cells and on the outer surface. AZT blocked the HIV augmentation of fused cells in coculture completely. Southern blot analysis revealed that both integrated and unintegrated HIV DNA were highly accumulated in fusion cells, as compared with fusion-free MOLT-4/HIV cells. Among unintegrated DNA, circular and linear DNA were accumulated to a similar degree. Northern blot hybridization showed that rapid enhancement of all three species of HIV-specific RNA containing genomic (9.2 kb) and subgenomic (4.3 and 1.9 kb) RNAs were found 20 hr postinfection in fusion cells. These data suggest that syncytia formation is an extremely active infection process of HIV, by which multiple rounds of reinfection might take place.     

Enhanced invasion of Tax-expressing fibroblasts into the basement membrane is repressed by phosphorylated ascorbate with simultaneous decreases in intracellular oxidative stress and NF-kappa B activation

Invasion of rat fibroblastic cells Rat-1 through Matrigel was shown to be promoted by transfection with tax gene of human T-cell leukemia virus type 1. We found that an oxidation-resistant type of vitamin C (Asc), Asc-2-O-phosphate (Asc2P), inhibited the invasion of the tax-transfected Rat-1 cells (W4 cells). Intracellular Asc (Ascin), after enzymatic dephosphorylation of administered Asc2P, was more abundant in W4 cells than in Rat-1 cells, and the ratio of dehydroascorbic acid versus Asc was increased in W4 cells but scarcely in Rat-1 cells, according to the enhanced level of intracellular reactive oxygen species (ROSin) in W4 cells. Asc2P notably repressed the increases in both ROSin and secretion of matrix metalloproteases (MMPs), but did not affect Tax protein expression in tax-transfectants. NF-kappa B activation, as evidenced by its translocation to the nucleus in W4 cells, was also repressed by Asc2P. Thus, the tax-promoted invasion together with the enhanced production of MMPs occurred with NF-kappa B activation and the increase in ROSin, both of which were effectively reduced by Asc2P. These findings indicate the therapeutic efficacy of Ascin-enriching agents for the prevention against tumor invasion in which ROSin plays a major role.     

Primary renal angiosarcoma: A case report and review of the literature

Primary renal angiosarcoma is very rare. To our knowledge, only 15 cases have been reported to date. A 77-year-old Japanese man with a unilateral kidney presented with massive hematuria followed by renal failure. A renal tumor was suspected and a left nephrectomy was performed. The histopathological diagnosis was angiosarcoma of the kidney. A hemorrhagic tumor measuring 10 × 5 cm and clotted blood was found in the modularly area. The atypical tumor cells had a sinusoidal and solid appearance, and showed Immunohistochemically positive reactions for some of the endothelial markers. The patient died about 21 months after the nephrectomy and the autopsy revealed massive metastases to the liver and retroperitoneum. One of the differential diagnoses of the case was anglomyolipoma, because the tumor cells were relatively bland in their histological appearance with entrapped fat cells in the pelvic area. Fifteen case reports with titles that included the term 'hemangiosarcoma/anglosarcoma', 'hemangioendothelloma/endothelloma' or 'vascular sarcoma' of the kidney were reviewed and compared to the present case.     

Microfilamentous type VI collagen in the hyalinized stroma of the hypertrophied ligamentum flavum

Summary Thickened ligamenta flava obtained from 14 patients with spinal canal stenosis were examined with special reference to type VI collagen. The characteristic histological finding in the thickened area was rupture of normal elastic fibre meshwork with resultant fibrosis which usually appeared hyaline. Using an immunohistological method, collagen types VI, I and III were found to be present in the hyaline matrix. Ultrastructural study revealed many microfilamentous structures of type VI collagen admixed in loosely packed, banded collagen fibres. With differential salt precipitation of pepsin-extracted collagen the existence of type VI collagen was confirmed by SDS-polyacrylamide gel electrophoresis analysis and Western blotting analysis using anti-type VI collagen antibody. Quantification of type VI collagen in pepsin-extracted crude collagen samples by an inhibition enzyme-linked immunosorbent assay showed an increasing amount of type VI collagen in the thickened ligamenta flava compared to the normal ligaments. Thus, increase of type VI collagen is the main contribution to the thickening of the ligamentum flavum. This may represent an adaptational and reparative process associated with disruption of elastic fibres.