2-Amino-3-methylimidazo[4,5-f]quinoline (IQ), a carcinogenic pyrolysate, induces chromosomal aberrations in Chinese hamster lung fibroblasts in vitro

The ability of 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) to induce chromosomal aberrations (CAs) in Chinese hamster lung fibroblast (CHL/IU) cells in vitro was examined. On incubation with rat S9 (2.5-10%, v/v) for 3 h, followed by a recovery culture period of 21 h, IQ caused significant induction of CAs at a concentration 20 micrograms/ml, but had less effect at 40 micrograms/ml. With longer recovery culture times such as 27-33 h, however, IQ was much more effective at 40 micrograms/ml. No significant induction was observed with 1 or 6 h treatments followed by 23 or 18 h recovery cultures, respectively. On incubation without S9, only weak CA induction by IQ was observed. These results show that IQ is a clastogen and that its clastogenic effect varied with the experimental conditions, such as the time of exposure and the time of recovery culture. The cell cycle perturbation effect is suggested to be one of the critical factors for the detection of the clastogenic potential of IQ.

[MR imaging during arteriography (MR arteriography) in the detection of hepatocellular carcinoma]

MR imaging during arteriography was performed to evaluate the clinical utility to patients with hepatocellular carcinoma. After a conventional hepatic arteriography, the patients were transferred to the MR unit and MR arteriography was obtained with the gradient echo technique synchronously starting manual injection of Gd-DTPA diluted with normal saline into the hepatic artery using 5-F Cobra angiographic catheter. The tumors showed high signal intensity relative to surrounding normal parenchyma and a clear liver-to-lesion contrast was obtained. Especially in one case, a conventional hepatic arteriography did not show the recurrent mass, however it was demonstrated as a high signal intensity area on MR arteriography. Therefore, this new technique seemed to be useful for the detection of hepatocellular carcinoma.

Improved enzyme immunoassay for human basic fibroblast growth factor using a new enhanced chemiluminescence system

An enhanced chemiluminescence reaction has been incorporated into an enzyme immunoassay (EIA) for human basic fibroblast growth factor (hbFGF). We developed a new luminol derivative, designated L-012 and a new enhancer, 4-(4-hydroxyphenyl)thiazole. Using these compounds, the detection limit of hbFGF was improved to 0.1 pg/assay, which was 10-20 and 2 times better than the o-phenylenediamine colorimetric and luminol chemiluminescence assays, respectively. The average concentration of bFGF in sera from 25 normal volunteers was 5.9 pg/ml. On the other hand, serum bFGF levels were elevated in renal, lung and brain tumor patients. The data presented here indicate that the serum bFGF level could be a useful diagnostic marker for these tumors. Furthermore, these new compounds could easily be applied to any other EIA that uses horse radish peroxidase to improve sensitivity.

Molecular diversity of calpastatin in human erythroid cells

According to differences in mobility on SDS-polyacrylamide gel electrophoresis, calpastatins (inhibitor proteins of the calcium-dependent proteinase calpain) are classified into the tissue type (100-120 kDa) and the erythrocyte type (70 kDa), which lacks the amino-terminal domains (domains L and 1). We investigated the molecular diversity of calpastatin in human hematopoietic cells by Western-blot analysis and by the reverse-transcription-polymerase-chain reaction method. While the mononuclear and polymorphonuclear cells in peripheral blood showed the tissue type (110 and 114 kDa), a cell line of erythroid cells (JK-1) showed both the tissue type (110 kDa) and the erythrocyte type (70 kDa) at approximately equal ratios. When the lysate of JK-1 cells was incubated in the presence of ATP, the 110-kDa form was degraded much faster than the 70-kDa form. In human erythrocytes, the 110-kDa form was identified as the tissue type by an antibody recognizing domain L, and this form was also present in addition to the predominant 70-kDA form. JK-1 cells, as well as nucleated cells in peripheral blood, contained calpastatin mRNA with exon-3-deleted. Glioblastoma and fibroblast cell lines expressed the nondeleted calpastatin mRNA in addition to the deletion type, and they showed bands corresponding to 117 kDa as well as 110 and 114 kDa. The 117-kDa band was detectable by an anti-exon 3 peptide antibody. These results suggest that diversity among the tissue type calpastatins is caused by both alternative splicing and post-translational processing whereas the apparent conversion from the tissue type to the erythrocyte type is caused by proteolytic processing.

Characterization of a novel biphenotypic leukemia cell line, TA-1, with myeloperoxidase and inducible cytoplasmic mu chain: altered rearrangement patterns of antigen receptor genes

A novel biphenotypic cell line carrying t(9;11)(p22;q23), TA-1, was established from the peripheral blood of a patient with acute undifferentiated leukemia. The TA-1 cells simultaneously expressed lymphoid (CD19, CD20) and myeloid characteristics (CD13, CD33, myeloperoxidase) on the same cells. When the cells were treated with tetraphorbol acetate, cytoplasmic mu chain was induced and the fluorescence intensity of CD13 was increased. These findings suggested that TA-1 cells have a bidirectional maturation capacity, as well as biphenotypic features. Molecular analysis disclosed differences in the rearranged bands, corresponding to one allele of the immunoglobulin heavy chain gene (IgH) and the T cell antigen receptor gamma gene (TCR gamma), between the non-cultured cells and the cell line, while showing identical rearranged patterns of another allele of both these genes and the TCR beta gene. These results suggest that the non-cultured cells and the established cell line have the same clonal origin and that the latter is a clonal descendant of the former.

Requirement of different subdomains of calpastatin for calpain inhibition and for binding to calmodulin-like domains

Calpain requires Ca2+ for both proteolysis of its substrates and interaction with its endogenous inhibitor, calpastatin. The mechanism of inhibition of calpain by calpastatin has remained unsolved, although Nishimura and Goll [J. Biol. Chem. 266, 11842-11850 (1991)] reported that autolyzed calpain fragments containing calmodulin-like domains (CaMLDs) bound to an immobilized calpastatin column. We investigated the correlation between CaMLD-binding and calpain inhibition using immobilized columns of gene-engineered CaMLDs derived from the human mu-calpain large subunit and various recombinant calpastatin mutants. Among the four internally repetitive inhibitory domains of calpastatin, each having conserved regions A, B, and C, only domains 1 and 4 showed the binding activity. The region B deletion mutant of domain 1, retaining the CaMLD-binding ability, no longer had the calpain inhibition activity, and became susceptible to proteolysis. In contrast, a synthetic oligopeptide of region B with moderate calpain inhibition activity did not bind to the column. Domain 3 acquired the binding ability on substitution of region A with that of domain 1. These results suggest that calpain inhibition and binding to the CaMLDs are not correlated or mediated by different subdomains of calpastatin.

[Usefulness of 2D FLASH multislice dynamic MR imaging for evaluation of parametrial invasion in cervical carcinoma]

Twenty seconds and 3 minutes after starting rapid injection of Gd-DTPA, multislice dynamic (MD) images were obtained with the 2 dimension fast low-angle shot (2D FLASH) technique. Four of 5 cervical carcinomas showed high signal intensity in the early dynamic phase (20 seconds), so they were readily distinguished from the myometrium that were not enhanced in the same phase. For evaluation of parametrial invasion, MD study showed better contrast between the tumor and the parametrium than did T2-weighted images because the tumor demonstrated a high signal intensity similar to that of the parameterium on T2-weighted images. MD images were able to scan the entire tumor especially in progressive cases and to evaluate the hemodynamics of the tumor. Therefore, MD imaging seemed to be useful for evaluation of parametrial invasion in cervical carcinomas.

Developmental expression of trkB and low-affinity NGF receptor in the rat retina

Brain-derived neurotrophic factor (BDNF) promotes the survival of retinal ganglion cells, but these effects are dependent on the developmental stages, and a number of retinal ganglion cells are eliminated during pre- and neonatal stages. We have examined the expression of BDNF receptors, trkB and low-affinity nerve growth factor receptor (LNGFR), in the rat retina during these period using Northern blot analysis. The expression of trkB and LNGFR displayed two peaks during embryonic day 17 (E17) through postnatal day 1 (P1), and during P14-P17, indicating that it may play an important role in neuronal development and neuronal cell death.

[Evaluation of early MR imaging of the liver in rabbits after ethanol injection]

Seven days after ethanol injection, MR images of the liver in 5 rabbits were evaluated by T1, T2-weighted SE and TURBO-FLASH dynamic images. Necrotic area was visualized as low-intensity on T1-weighted images and high-intensity on T2-weighted images. These findings were similar to the tumor that was not treated, so it is necessary to be careful for evaluation of therapeutic efficacy. Necrotic area was not meanwhile enhanced on TURBO-FLASH dynamic images, therefore, dynamic study seemed to be useful for therapeutic efficacy after ethanol injection.

Extension of optic nerve fibers on genetically modified cells producing brain-derived neurotrophic factor

Since brain-derived neurotrophic factor (BDNF) promotes the survival of retinal ganglion cells (RGCs), we transfected a rat BDNF cDNA into rat fibroblasts, and retinal fragments of rat embryos were cultured on cell monolayers of these cells. Retinal fragments showed enhanced neurite extension on BDNF-transfected cells compared with that on control cells. The degree of the neurite extension, however, decreased depending upon the embryonic stages. These results suggest that fibroblasts genetically modified to produce BDNF might be a promoter of neurite extension by RGCs, but this does not apply to the RGCs of late embryonic stages.

Characterization of ribosomal frameshifting for expression of pol gene products of human T-cell leukemia virus type I

For study of the pol gene expression of human T-cell leukemia virus type I (HTLV-I), RNA was transcribed in vitro from proviral DNA and translated in rabbit reticulocyte lysates. This cell-free translation resulted in two major translation products representing the Gag and Gag-Pro polyproteins. By contrast, the Gag-Pro-Pol polyprotein could be readily observed only when translation was performed with mutant mRNA in which the protease (pro) reading frame was aligned to gag to eliminate the frameshifting event in the gag-pro overlap. The results indicated that two independent ribosomal frameshifting events are required for expression of the HTLV-I pol gene product. Studies with mutant DNAs facilitated the characterization of the primary structure of the HTLV-I mRNA responsible for the ribosomal frameshift in the pro-pol overlap and demonstrated that the frameshift occurs at the signal sequence UUUAAAC. Direct amino acid sequencing of the transframe protein localized the site of the frameshift to the asparagine codon AAC.

Possible activity of acidic fibroblast growth factor as a progression factor rather than a transforming factor

Acidic and basic fibroblast growth factors (aFGF and bFGF) are mitogens for mesoderm- and neuroectoderm-derived cells. The facts that FGF-related proteins are oncogenic and that FGFs are expressed in a variety of tumor cell lines or tumor tissues suggest the transforming activities of FGFs. To examine such an activity of aFGF, we introduced a human aFGF expression vector into two populations of Rat-1 cells; one was non-transformed (nRat-1), the other was partially-transformed (tRat-1). tRat-1 cells transfected with aFGF cDNA formed larger colonies in soft agar and produced larger and more malignant tumors in nude mice than those of parental cells. In contrast, nRat-1 cells transfected with aFGF cDNA neither formed colonies in soft agar nor produced tumors in nude mice. Our results suggest that high expression of aFGF may enhance a tumorigenic potential of Rat-1 cells rather than confer such a potential de novo.

The presence of antibodies to purified p24gag protein of HTLV-I in sera of patients with systemic lupus erythematosus (SLE)

Sera of patients with systemic lupus erythematosus (SLE) were tested for their reactivity to HTLV-I by western blotting (WB). Seven (18%) of 40 SLE serum samples reacted to the p24gag protein of HTLV-I by WB using purified gag antigens. The specificity of anti-p24gag antibodies in the SLE sera was confirmed by competitive inhibition on WB. Two of the seven patients were shown to be HTLV-I carriers, because HTLV-I infected T cell lines were easily established from their peripheral blood mononuclear cells (PBMC). Except for these two carrier patients, the gag proteins were not detected in the lysates of PBMC by WB using anti-p24gag and anti-p19gag monoclonal antibodies. The gag and pX genes of HTLV-I were not detected by PCR in PBMC of the SLE patients, with the exception of the 2 HTLV-I carrier patients. These results show no direct involvement of HTLV-I in the etiology of SLE. However, the existence of a specific antibody to p24gag in the sera of some of the noncarrier SLE patients suggests a crossreactivity to either unknown viruses or some autoantigens.

Phosphorylation of the Rex protein of human T-cell leukemia virus type I

Rex protein, the posttranscriptional regulator of human T-cell leukemia virus type I (HTLV-I), is required for the control of viral structural protein expression and virus replication. Rex is a phosphoprotein found predominantly in the cell nucleolus, whose function is thought to be regulated by its nucleolar localization and phosphorylation. Therefore, we investigated the in vivo phosphorylation of Rex protein in more detail. Phosphorylation of Rex occurred in all HTLV-I-infected cell lines examined in vivo, primarily at serine residues and to a very small extent at threonine residues. Treatment of cells with 12-O-tetradecanoylphorbol-13-acetate (TPA) led to significant but transient enhancement of the incorporation of [32P]orthophosphate into Rex protein. N-terminal truncation of Rex protein abolished TPA-dependent phosphorylation. Chymotryptic digestion of phosphorylated Rex yielded two phosphopeptides. In vivo phosphorylation sites were identified as serine residues 70 and 177 and threonine residue 174. Serine 70 was a TPA-dependent phosphorylation site within a regulatory domain. We have already shown that the protein kinase C inhibitor H-7 (1-(5-isoquinolinylsulfonyl)-2-methylpiperazine) specifically blocked accumulation of viral unspliced gag-pol mRNA. Therefore, the phosphorylation at serine 70 may be involved in the regulation of Rex function in response to extracellular stimuli.

Expression of calpain II gene in human hematopoietic system cells infected with human T-cell leukemia virus type I

We examined the distribution of calpains I and II in human hematopoietic system cell lines by Western and Northern blot analyses and enzyme activity assay. Expression of calpain I, a low Ca(2+)-requiring cysteine protease, was observed in all human T-cell lines tested. By contrast, expression of calpain II, a high Ca(2+)-requiring form, in human T-cells was closely correlated with human T-cell leukemia virus type I (HTLV-I) infection, which is known to result in the expression of adult T-cell leukemia-associated antigens, interleukin-2 (IL-2) receptor alpha, and Ca(2+)-dependent cell proliferation. Specific expression of calpain II in HTLV-I-infected cells occurred at the mRNA level. Furthermore, expression of calpain II in human natural killer-like cells was augmented by HTLV-I pX gene transfection. In HTLV-I-infected cells, the trans-acting transcriptional activation of the long terminal repeat and control elements for the IL-2 receptor alpha, c-fos, and granulocyte-macrophage colony-stimulating factor genes by the Tax from the pX gene is already known. Our results suggest that the similar trans-activation occurs to the calpain II gene in HTLV-I-infected hematopoietic system cells.

Transforming activity and the level of Tax protein: effect of one point mutation in HTLV-I tax gene

The transcriptional trans-activator molecule of HTLV-I, Tax, is known to transform rodent fibroblasts. A revertant clone expressing Tax was obtained by treating transformed Rat-I cells harboring a single copy of the tax gene with a mutagen. Sequence analysis of the tax gene of the revertant clone revealed that it had one point mutation at codon 12(CTT----TTT), resulting in a change from Leu to Phe. The colony-forming efficiencies of the cells transfected with the mutant tax gene (mu71 tax) were significantly lower than those transfected with the wild-type by the soft-agar method. This difference was shown to be due to the instability of mu71 Tax.

Maturational stage specific immunoglobulin heavy chain gene rearrangements, determined by D and D upstream region gene structures

In 43 cases of various B-cell lineage tumors, precise gene structures of rearranged immunoglobulin heavy chain (IgH) were studied. By Southern-blot analysis of D upstream (5'D) gene of IgH, biallelic rearrangement structures, D-J or V-D-J, were determined and consequently maturational stage specific IgH rearrangement patterns were investigated. B-precursor ALL cases (especially stage IV of Nadler's criteria) have V-D-J rearranged IgH genes on both alleles. In contrast, most of the mature B-cell malignancies, excluding multiple myeloma, have IgH genotype of D-J/V-D-J. In addition, in case of D-J/V-D-J, the D gene used in D-J joining has been speculated by Southern-blot of D genes. So, these approaches for inquiring precise structures of rearranged IgH genes are supposed to provide new information of lymphocyte differentiation and leukemogenesis.

Commitment reversion model of unrestricted cell growth

Through the analysis of accumulated experimental data of cell growth, a model of unrestricted cell growth is presented here. This model is based hypothetically on the cellular commitment to senescence as in the previously presented commitment theory. Cells are divided into 3 types, namely uncommitted cells, committed cells and terminal cells. The division of an uncommitted cell produces an uncommitted cell itself and a committed cell of the first generation. This committed cell goes through a limited number of cell divisions until the cells become non-dividing terminal cells. It is hypothesized that during a committed cell division, there is a very small probability that an uncommitted cell may be generated. With computer simulations, it is estimated that a committed cell of the first generation may divide around 30 times until they become non-dividing terminal cells, and that the probability of an uncommitted cell regeneration for each committed cell division may be 2(-H). This hypothesis may possibly clarify some aspects of the biological phenomena of cell growth, which can not be explained by the previous commitment theory, such as the growth pattern of cultured diploid cells, cancer initiation and promotion, and cancer progression and metastasis.

Analysis of C5b-8 binding sites in the C9 molecule using monoclonal antibodies: participation of two separate epitopes of C9 in C5b-8 binding

C5b-8 binding sites in C9 were examined using mAbs raised against C9. Among 16 mAbs, two, designated P40 and X197, blocked C9-mediated EAC1-8 lysis. C9 pretreated with the mAbs failed to bind to EAC1-8 at 4 degrees C. In addition, the mAbs became inaccessible to the C9 that had been incorporated into EAC1-8 at 4 degrees C. These findings suggest that C9 binding to EAC1-8, but not its membrane spanning or polymerization, is blocked by mAbs. By immunoblotting analysis using alpha-thrombin proteolytic fragments derived from C9 [a N-terminal fragment of mol. wt 25,000 (C9a) and a C-terminal one of mol. wt 37,000 (C9b)] and tryptic fragments of C9 (mol. wts 53,000 (C9a') and 20,000 (C9b')), the epitopes of P40 and X197 were mapped to the N-terminal and C-terminal regions of C9b, respectively. Both P40 and X197 bound to the C9 polymerized with Zn2+ in the fluid phase, whereas X197 but not P40 reacted with the membrane attack complex (MAC) formed on membranes. The results suggest that two distinct epitopes are involved in C9 binding to EAC1-8, and behave in a different manner for globular C9 bound to EAC1-8 at 4 degrees C, C9 assembled in MAC, or poly-C9 induced by Zn2+. These mAbs may be useful in clarifying the conformational states of C9 and in analyzing the molecular interaction between C9 and its inhibitors.

Successful twenty-four-hour lung preservation with donor core cooling and leukocyte depletion in an orthotopic double lung transplantation model

Donor core cooling with cardiopulmonary bypass is a valid method of clinical lung preservation. However, organ ischemia with this method is still limited to short-term intervals. Since circulating leukocytes participate in postischemic injury through the release of oxygen-derived free radicals, we examined whether leukocyte depletion by mechanical filtration could extend ischemic tolerance of the lung during preservation and subsequent double lung transplantation. Bovine donor lungs were preserved by donor core cooling (10 degrees to 15 degrees C) with cardiopulmonary bypass. Donor lungs were removed, stored in 4 degrees C donor blood for 24 hours, and transplanted. Graft function was studied for 6 hours after transplantation. Group 1 animals (n = 6) underwent standard cardiopulmonary bypass with whole blood for donor and recipient procedures. In group 2 (n = 6), leukocyte filters were incorporated into the cardiopulmonary bypass circuit in both donor and recipient operations. In group 2 recipient animals leukocyte counts decreased to 3% of mean baseline values and remained low during the experiment. Postischemic lung function (assessed by systemic arterial oxygenation, pulmonary artery pressure, pulmonary vascular resistance, airway pressure, lung water content, and end-point histologic characteristics) was significantly better preserved in the animals with leukocyte depletion. Leukocyte depletion by mechanical filtration in both donor and recipient improves the ischemic tolerance of the lung beyond that provided by donor core cooling alone, resulting in excellent lung function after 24 hours of ischemia.

Intranuclear topological distribution of HIV-1 trans-activators

Subcellular localization of human immunodeficiency virus type I (HIV-1) Tat and Rev was examined using a confocal laser scanning microscope (CLSM). In transfected COS-7 cells, Tat resided exclusively in the perinocleolar region, while Rev infiltrated fully into the nucleoli. The chimeric Tat in which the nucleolar targeting signal was replaced by that of Rev, which retains trans-acting activity of Tat, remained still in the perinucleolar region as wild-type Tat. Perinucleolar distribution of Tat protein suggests the existence of a novel nucleolar architecture that affects transcription.

[ATL and its virus]

A retrovirus called Human T cell leukemia virus type 1 (HTLV-1) is a causative agent of adult T cell leukemia (ATL). A cultured cell line called MT-2, produces constitutively HTLV-1. The characteristics of HTLV-1 produced from MT-2 has been extensively investigated. The molecular mechanism of ATL leukemogenesis by HTLV-1 is discussed.