Regulation of Th2 cell differentiation by mel-18, a mammalian polycomb group gene

Polycomb group (PcG) gene products regulate homeobox gene expression in Drosophila and vertebrates and also cell cycle progression of immature lymphocytes. In a gene-disrupted mouse for polycomb group gene mel-18, mature peripheral T cells exhibited normal anti-TCR-induced proliferation; however, the production of Th2 cytokines (IL-4, IL-5, and IL-13) was significantly reduced, whereas production of IFNgamma was modestly enhanced. Th2 cell differentiation was impaired, and the defect was associated with decreased levels in demethylation of the IL-4 gene. Significantly, reduced GATA3 induction was demonstrated. In vivo antigen-induced IgG1 production and Nippostrongylus brasiliensis-induced eosinophilia were significantly affected, reflecting the deficit in Th2 cell differentiation. Thus, the PcG gene products play a critical role in the control of Th2 cell differentiation and Th2-dependent immune responses.

Chronic intracerebroventricular administration of orexin-A to rats increases food intake in daytime, but has no effect on body weight

Orexins are recently identified neuropeptides, and have been shown to increase food intake when administered intracerebroventricularly. We examined the effects of chronic administration of orexin in rats by continuous intracerebroventricular administration by means of an osmotic minipump. Continuous administration of orexin-A (0.5 nmol/h) for 7 days in rats resulted in a significant increase in food intake in the daytime. Daytime food intake increased to 180% of the control value. However, it resulted in a slight decrease nighttime food intake as compared with vehicle-treated rats. The total amount of food intake per day was almost comparable with that of vehicle-administered rats. The gain of body weight and blood glucose, total cholesterol and free fatty acid levels were normal. Chronic orexin-A treatment did not cause obesity in rats. We observed abnormal behavior during the daytime after starting administration of orexin-A; these rats kept awake during the daytime. Our present observation showed that continuous administration of orexin-A could not overcome the regulation of energy homeostasis and body weight. However, orexin-A might be implicated in short-term, immediate regulation of feeding behavior.

Cellular senescence of angiofibroma stroma cells from patients with tuberous sclerosis

Tuberous sclerosis complex (TSC) is an autosomal dominant disorder characterized by epilepsy, mental retardation and hamartomatous lesions in multiple organs. It has been shown that the genes responsible for TSC, TSC1 and TSC2, act as tumor suppressors, but the mechanism of hamartomatous growth in several tissues is not completely understood. The TSC hamartomas are essentially benign and they rarely progress to malignant tumors. In this report, we cultured the angiofibroma stroma cells of three adult TSC patients and compared these cells with normal skin fibroblasts for their proliferative capacity, cell morphology and mitotic cycle using a stain for microtubules and the expression of the senescent associated beta-galactosidase (SA beta-Gal). Cultured angiofibroma stroma cells from TSC patients displayed several characteristics observed in human senescent fibroblasts; a low proliferative capacity, an increase in cell size, increased binucleated cells in association with abnormal cytokinesis and increased SA beta-Gal positives. Growth of facial angiofibromas in TSC may be caused by a gain in enhanced sensitivity toward some of the potential mitogens and forced multiplication without loss of the cellular senescent program; this may be the reason why TSC hamartomas rarely progress to malignancy and why the growths are limited to a finite size.

Productive infection of Epstein-Barr virus (EBV) in EBV-genome-positive epithelial cell lines (GT38 and GT39) derived from gastric tissues

We characterized the expression of Epstein-Barr virus (EBV) on two epithelial cell lines, GT38 and GT39, derived from human gastric tissues. The EBV nuclear antigen (EBNA) was detected in all cells of both cell lines. The EBV immediate-early BZLF 1 protein (ZEBRA), the early antigen diffuse component (EA-D), and one of the EBV envelope proteins (gp350/220) were expressed spontaneously in small proportions in the cells. EBNA 1, EBNA2, latent membrane protein 1, ZEBRA, and EA-D molecules were then observed by Western blotting in the cells. The lytic cycle was enhanced with treatment with 12-O-tetradecanoylphorbol-13-acetate (TPA) or n-butyrate. The virus particles were observed in the TPA treated GT38 cells by electron microscopy. Infectious EBV was detected with the transformation of cord blood lymphocytes and also with the induction of early antigen to Raji cells by the supernatants of both cells lines. A major single and minor multiple fused terminal fragments and a ladder of smaller fragments of the EBV genome were detected with a Xhol probe in both cell lines. These epithelial cells lines and viruses will be useful in studying their association with EBV in gastric epithelial cells.

Identification of Bombyx mori midgut receptor for Bacillus thuringiensis insecticidal CryIA(a) toxin

As part of a study of the mechanism by which Bacillus thuringiensis insecticidal crystal protein acts, a Bombyx mori receptor to the CryIA(a) toxin specific for lepidopterans was examined. Histological examination showed that the toxin acted on the brush-border membrane of the midgut columnar cells and broke its infolding structure, causing cell lysis. The membrane vesicles were purified, and a 175-kDa protein binding the toxin was found that accounted for some 0.015% of membrane proteins. The protein, designated BtR175, was a glycoprotein that reacted with concanavalin A. Anti-BtR antibodies inhibited the binding of toxin to membrane vesicles in vitro and decreased the effect of the toxin to silkworms in vivo. BtR175, although found in the gut, was not found in fat bodies, integument, or silk glands. These results indicated that BtR175 was the receptor protein for the insecticidal toxin. Proteins (137 and 107 kDa) binding the CryIA(a) toxin also were found in the gut membranes of Tenebrio moritor larvae, a coleopteran not sensitive to the toxin. The specificity of the toxin could not be explained only in term of the existence of its binding protein.

Accumulation of cholesterol and GM2 ganglioside in cells cultured in the presence of progesterone: an implication for the basic defect in Niemann-Pick disease type C

Cultured fibroblasts from patients with Niemann-Pick disease type C (NP-C) are characterized by lysosomal accumulation of unesterified cholesterol and a defect in intracellular trafficking of cholesterol. We have found the accumulation of GM2 ganglioside in NP-C fibroblasts [Yano T, Taniguchi M, Akaboshi S, Vanier MT, Tai T, Sakuraba H, et al. Proc Japan Acad 1996;72B:214-219]. In this communication we show that several inhibitors known to inhibit intracellular cholesterol transport, progesterone, imipramine and KN-62, elicit accumulation of not only unesterified cholesterol but also GM2 ganglioside. This finding suggests that intracellular transport of cholesterol may be coupled with that of GM2 ganglioside. The accumulation of free cholesterol and GM2 ganglioside may be a clue for understanding the basic defect of NP-C. Recently NPC1 gene is found by the positional cloning. The mechanism of accumulating of GM2 ganglioside should be further investigated by studying of the functions of NPC1 gene.

Cell growth and differentiation of a novel mouse Ito (fat-storing) cell line transformed by a temperature-sensitive mutant of simian virus 40

A novel mouse Ito (fat-storing) cell line (A640-IS) was established by transformation with a temperature-sensitive mutant of simian virus 40 (SV40) and the relationships between the expression of SV40 large T antigen and the growth, differentiation, and functions of A640-IS cells were investigated. A640-IS cells expressed large T antigen when cultured at 33 degrees C. At this temperature, the cells grew actively, assumed a fibroblastic shape, and showed few Ito cell characteristics. In contrast, when large T-antigen expression was inhibited by culture at 39 degrees C, the cells did not grow but differentiated into Ito cells as assessed by both morphological and functional characteristics. Expression of the transcription factor SCL (stem cell leukemia), which plays a role in the development and differentiation of blood cells, was observed at both 33 degrees C and 39 degrees C, although expression was greater at 33 degrees C. Therefore, opposite patterns of cell growth and the functions of differentiated cells occurred at 33 degrees C and 39 degrees C in this novel Ito cell line. Transforming growth factor beta1 stimulated A640-IS cells to produce fibronectin, collagen type III, and laminin. This unique Ito cell line provides a useful model to address important questions regarding the nature of these cells.

Establishment and characteristics of a practical and useful astrocyte cell line transformed by a temperature-sensitive mutant of simian virus 40

A practical mouse astrocyte cell line (A640-IG) was established by transformation with a temperature-sensitive mutant of simian virus 40 (SV40) and the relationship between the function of SV40 large T antigen and the growth and differentiation of A640-IG cells, which are most clearly dependent on temperature that ever established, was reported. A640-IG cells proliferated actively with expression of large T antigen when they were cultured at 33 degrees C. They had a fibroblast-like appearance, and displayed faint immunoreactivity with an antibody against glial fibrillary acidic protein (GFAP). However, when large T antigen expression ceased at 39 degrees C, the cells did not grow actively and differentiated into astrocytes as demonstrated by both their morphological and immunohistochemical characteristics. Differentiation into astrocytes was more obvious when the cells were plated on bacteriological dishes in high density. Western blotting confirmed immunohistochemical observations. A640-IG cells thus showed contrasting behaviour in terms of cell growth and differentiation depending on the temperature. This unique and practical astrocyte cell line is a useful model for investigating the mechanisms of astrocyte growth and differentiation.

Apoptosis involved in density-dependent regulation of rat fibroblastic 3Y1 cell culture

When rat 3Y1 fibroblastic cells are cultured toward confluency, the cells go through maximum cell density (overshoot) before reaching post-confluence stationary cell density. After overshooting, a number of floating cells are found in the medium. In a long-term culture, a cyclic change in cell number, an increase after each medium refreshment and subsequent cell loss within a few days has been observed so that the cell populations in the monolayer maintain post-confluence stationary cell density at a constant level. The floating cells excluded trypan blue, but they had no ability to attach to the substrate and to form colonies after being reseeded in fresh medium. They had condensed and uniformly electron-dense chromatin with sharply circumscribed edges. Their DNA contained a laddering pattern in harmony with internucleosomal cleavage. The features were those of apoptosis. When floating cells appeared, apoptotic bodies were also observed in the monolayer. Most of them were found within the cytoplasm of intact cells, suggesting that apoptotic bodies were also faded away from the culture by being rapidly engulfed by neighboring intact cells. These suggest that apoptosis and subsequent detachment from the monolayer or engulfment by neighboring intact cells, in addition to inhibition of cell division, are basic mechanisms on the process of density-dependent regulation in monolayer culture of rat 3Y1 cells.

Neutralization of human immunodeficiency virus type 1 (HIV-1) with antibody from carriers' plasma against HIV-1 protein p17

It was investigated whether human antibody against HIV-1 protein p17 (anti-p17) in HIV carriers' plasma has the ability to neutralize the infectivity of HIV. By the pretreatment of HIV-1 with anti-p17 from HIV carriers, progeny HIV-1 production from cells infected with virus pretreated with anti-p17 was suppressed and/or delayed. The neutralizing activity of anti-p17 was decreased in the presence of recombinant p17. The latter obviously masked the neutralizing activity of anti-p17. The relevant epitope(s) on p17 is located apparently on the surface of HIV virions and the binding of anti-p17 to p17 impairs the infectivity of HIV. This implies that anti-p17, if stably present in HIV carriers' plasma, may also play an important role in reducing the infectivity of HIV-1 in vivo.

A tyrosine kinase-like molecule is localized in the nuclear membrane of neurons: hippocampal behavior under stress

Protein tyrosine kinases play important roles in the development of the mammalian nervous system during embryogenesis and in the maintenance of function of the adult brain. Using a semi-nested PCR technique based on a short amino acid motif of protein tyrosine kinases, we isolated a human genomic DNA encoding a peptide whose sequence was related to known mammalian protein tyrosine kinases. The expression was examined by Northern blot analysis, and transcripts were detected almost exclusively in the brain. The corresponding cDNA was sequenced, and it was revealed that the gene designated as byk coded for a receptor-like molecule with a motif of protein tyrosine kinase. Immunohistochemical analysis demonstrated that the Byk protein was expressed in neurons and was located in the nuclear envelope. To understand the physiological significance of the Byk protein, we investigated the behavior of this molecule in the hippocampus after ischemia. Byk-like immunoreactivity disappeared from the neurons in the fields CA1 through CA3 and the dentate gyrus of the hippocampus following 20 min of ischemia. After recirculation of blood flow, neurons in the CA3 field and the dentate gyrus re-expressed Byk-like antigen but CA1 neurons did not. Interestingly, Byk-like immunoreactivity was detected in microglial cells and astrocytes in the CA1 field that were activated after ischemia. Byk could be a new tool to study the neuron-glia and glia-glia interactions.

Different sensitivity to streptolysin-O of cells in macrophage lineage

We have surveyed the sensitivity of cells in macrophage lineage to Streptolysin-O (SLO). SLO had cytotoxic activity on immature myeloid cell lines such as M1 and WEHI-3BD+. SLO was toxic to the cells after a 2-hr incubation. However, mature macrophage cell lines such as A640-BB-2, J774, and P388D1 were not sensitive to the same dose of SLO. After M1 cells were treated with leukemia inhibitory factor (LIF), a differentiation-inducer to macrophage, these cells became insensitive to SLO in one day. This cytotoxic action of SLO was inhibited by pretreatment with anti-Streptolysin-O antibody or cholesterol. These results indicate that SLO has different effects on macrophage lineage.

Purification and characterization of chitin deacetylase from Absidia coerulea

Chitin deacetylase, which releases the acetyl groups of glycol chitin was purified from a fungus, Absidia coerulea, and characterized. The enzyme was purified 516-fold to homogeneity by means of 65-80% ammonium sulfate precipitation followed by chromatography on Butyl Toyoperal-650M, Gigapite (hydroxyapatite), and DEAE Toyopearl-650M. It had an apparent molecular weight of 75 kDa both on sodium dodecyl sulfate polyacrylamide gel electrophoresis and gel filtration chromatography, indicating that the enzyme exists as a monomer. The amino-terminal sequence was determined to be Gly-Glu-Tyr-Trp-Gln-Ser-Phe-. The enzyme is active on chitooligosaccharides with more than two N-acetylglucosamine residues (chitobiose) and is able to convert the nascent chitin synthesized by chitin synthase to chitosan in vitro. When O-hydroxyethylated chitin (glycol chitin) was used as a substrate, the optimum pH for enzyme activity was 5.0 and the optimum temperature was 50 degrees C. The enzyme was heat-stable and strongly inhibited by Fe3+. Furthermore, chitin deacetylase was demonstrated to be localized near the inner face of the cell wall (periplasmic space) in the mycelia by using immunoelectron microscopy.

Immunocytochemical localization of actin in the nucleolus of rat oocytes

In order to determine the localization of actin, growing and fully grown rat oocytes were immunocytochemically examined using a post-embedding ultrastructural protein-A gold technique. In quiescent oocytes, the nucleoplasm showed slightly lower levels of actin signal when compared to the surrounding cytoplasm. The highest levels of labeling were found on nucleoli showing a reticular type morphology. In oocytes at the diakinesis stage in which nucleolar compaction had occurred, the levels of labeling increased by 5-6 times those found in quiescent oocytes. Except for conspicuous accumulation of actin under the plasma membrane, compact nucleoli had significantly higher levels of labeling when compared with those found on the general cytoplasm, while the nucleoplasm with homogeneously dispersed chromatin showed significantly lower levels of associated actin signal than the general cytoplasm. In oocytes at metaphase I, the cytoplasmic region had comparable or lower levels of labeling than the cytoplasm of oocytes at diakinesis. The meiotic spindle embedded in material with medium electron density showed a similar level of labeling as the surrounding cytoplasm. On the other hand, significantly higher levels of associated actin were observed on the chromosomes of metaphase I. The actin signals were dispersed over the chromosomes and not concentrated on a specific region. These results suggest that nuclear actin may be involved in the process of chromosome construction and also the formation of the compacted structure of the nucleolus.

Cell-cycle dependent biosynthesis and localization of p53 protein in untransformed human cells

Localization of p53 in human cultured lymphocytes and in cultured skin fibroblasts was studied by immuno-fluorescent microscopy and post-embedded immunoelectron microscopy using Lowicryl K4M. In quiescent lymphocytes, p53 was found in small amounts in both the cytoplasm and the nucleus. p53 in the nucleus was found associated with the non-chromatin structure. At 24 h or 72 h of PHA stimulation, p53 increased markedly just beneath the plasma membrane and in the nucleus, which stained diffusely with anti-p53. In resting fibroblasts, small amounts of p53 were present in both the cytoplasm and the nucleus. After 16 h of stimulation of confluent-resting fibroblasts by trypsinization and replating, a phase just prior to the initiation of DNA synthesis, p53 slightly increased in both the cytoplasm and the nucleus. Afterwards, p53 was present predominantly in the cytoplasm, closely associated with the cytoskeletal actin filaments. In mitotic cells, p53 was distributed throughout the cytoplasm. When fibroblasts were extracted with saponin, p53 was still associated with the actin filaments, as well as mitochondrial membranes and granular structures of the nuclear matrix. Our data suggest that the initial increase of p53 in cells that enter the cell cycle through G1 first bind to the actin cytoskeleton, and that some of the p53 then move into the nucleus to initiate gene activation and DNA synthesis for cell proliferation. This implies that there is some functionally significant interaction between p53 and actin in the cells.

The orientation of primary cilia during the wound response in 3Y1 cells

The behavior of the primary cilia of 3Y1 cells in the interphase was investigated by indirect immunofluorescence microscopy and transmission electron microscopy, using an antibody for tubulin. At 4.5 h after scraping a part of a confluent cell sheet, the primary cilia of cells facing the wound were located predominantly forward of the nucleus on the wounded side, and were oriented in the direction of the leading lamellae. Cytoplasmic microtubules (MTs), emanating from around the base of the cilia, were well developed in the leading lamellae on the wounded side. On the other hand, in the cells of an unperturbed area away from the wounded edge, the primary cilia remained randomly distributed near the nucleus. The position and a certain well-defined orientation of a pair of centrioles seem to play an important role for the development of cytoplasmic MTs, and consequently the orientation of the centrioles is controlled by the primary cilia.

Lysosomal glycosphingolipid storage in chloroquine-induced alpha-galactosidase-deficient human endothelial cells with transformation by simian virus 40: in vitro model of Fabry disease

Human umbilical venous endothelial cells were transformed with a temperature-sensitive mutant of simian virus 40, tsA640, and a cell line, subcultured for over 20 serial passages, was established at a temperature permissive for the virus. Treatment of transformed endothelium with 3 micrograms/ml chloroquine caused a specific reduction of alpha-galactosidase activity, without cell injury, and revealed several electron-dense materials surrounded by single unit membranes. Crystalline lamellae in lysosomes with a periodicity of 6.5 nm, which are typically seen in various tissues in Fabry disease, were produced in the presence of a glycosphingolipid mixture. These cells should be useful for in vitro pathophysiological studies on Fabry endothelium.

The spatial distribution of spindle microtubules in anaphase 3Y1 cells

The spatial distribution of the microtubules (MT) in the rat 3Y1 cells in mitosis was investigated by immunoelectron microscopy and computer-graphic reconstruction of serial thin sections. In anaphase the interzone-MT increased in number gradually with advancing phase, while the kinetochore-MT in half-spindles decreased. The interzone-MT overlapped with each other at the equatorial region of the cell, and they formed a specific structure called the 'stem bodies'. The ends of the interzone-MT opposite to the stem bodies often attached to chromosomes but not to the poles. The stem bodies were not labeled with immunogold particles of anti-alpha tubulin. Some of the stem bodies or MT which originate from stem bodies were found just beneath the plasma membrane in the equatorial region where abundant actin filaments appear showing the formation of the contractile ring and subsequently the cleavage furrow begins. On the basis of these observations it is assumed that the interzone-MT is involved both in the separation of chromosomes in anaphase and in the formation of the cleavage furrow in telophase.

Expression of glial fibrillary acidic protein (GFAP) by cultured angiofibroma stroma cells from patients with tuberous sclerosis

Large dendritic cells were cultured from facial angiofibromas of six patients with tuberous sclerosis. The cells were examined immunocytochemically for expression of selected cytoskeletal and non-structural proteins and the results compared with the staining profiles obtained with normal skin fibroblasts and normal glial cells. In similarity to normal glia, the angiofibroma stroma cells expressed glial fibrillary acidic protein (GFAP). Conversely, by analogy to fibroblasts, the abnormal stroma cells produced fibronectin and did not react with the antibody to S-100 protein. By immunogold labelling it was established that GFAP and vimentin were co-localized in intermediate filaments of the angiofibroma cells.

Establishment and characterization of a new cell line TC-YIK originating from argyrophil small cell carcinoma of the uterine cervix integrating HPV16 DNA

A new cell line, designated TC-YIK, was established from YIK-1 tumor cells, derived from argyrophil small cell carcinoma (ASCC) of the uterine cervix, and serially heterotransplanted into nude mice, integrating human papillomavirus type 16 (HPV16) DNA. The population doubling time of TC-YIK was approximately 21.6 hours at the 119th subculture. Subcutaneous injection of 1 x 10(8) TC-YIK cells into nude mice yielded a solid tumor. The cytologic appearance of TC-YIK was similar to that of YIK-1. The TC-YIK cells contained argyrophil granules and neurosecretory granules in the cytoplasm and showed positive immunohistochemical staining for neuron-specific enolase, serotonin, and chromogranin. Thus, TC-YIK retained the histochemical characteristics of ASCC. The TC-YIK cells contained HPV16 DNA in a multiple-copy integrated form and actively transcribed the integrated HPV16 genome. Amplification of the c-myc oncogene was observed in the TC-YIK cells. These data suggest that TC-YIK is a useful in vitro experimental model of ASCC and that HPV16 and c-myc may play some role in the genesis of this malignant tumor and/or maintenance of the transformed TC-YIK phenotype.

A preparation technique for observing cytoskeletons by high resolution scanning electron microscopy

The three-dimensional architecture of the cytoskeleton in cultured fibroblasts was studied using a newly devised technique for revealing cell interiors and an ultrahigh resolution scanning electron microscope, the UHS-T1. Both the cytoskeleton and membranous structures such as the plasma membrane and endoplasmic reticulum were well preserved, and we could observe the relationship between both components. Actin filaments, intermediate filaments, and microtubules were identified by immunogold staining with 5-15 nm gold particles. Actin filaments, measuring 10 nm in diameter in material not metal coated, formed thick bundles (stress fibers), sheaths or meshworks. Just beneath the plasma membrane, actin filaments could be seen in a two-dimensional network, with fibers linked laterally to the membrane. Intermediate filaments, 12 nm in diameter in uncoated material, were observed mainly in the perikaryon. Microtubules (26 nm) and clathrin-coated vesicles were also clearly seen.

The role of the vimentin intermediate filaments in rat 3Y1 cells elucidated by immunoelectron microscopy and computer-graphic reconstruction

The three-dimensional arrangement of vimentin intermediate filaments (IF) was studied in 3Y1, rat fibroblastic cell line, to elucidate its biological role in the cell. While actin filaments were observed exclusively in the superficial part of the cell, vimentin IF were found to be abundantly present in the inside of the cell where microtubules were occasionally discovered. By whole-mount immunoelectron microscopy and computer-graphic reconstruction of serial thin sections, it was observed in more detail that vimentin IF are located very close to the nucleus, endoplasmic reticulum, and mitochondria. Vimentin IF were observed to be attached to these organelles laterally or terminally. Thus, we can reasonably assume that vimentin IF are major cytoskeletal structures deep inside the cell and that they play an important role in supporting the location of the organelles. This is the first report which has visualized the three-dimensional relationship between vimentin IF and the organelles of the cell.

Heterotransplantation of argyrophil small cell carcinoma of the uterine cervix integrating HPV16 DNA into nude mice

Argyrophil small cell carcinoma of the uterine cervix (ASCC) containing human papillomavirus type 16 (HPV16) DNA has been successfully transplanted in nude mice for the first time, and we have designated the resultant cell line as YIK-1. Histology of YIK-1 was similar to that of the original tumor. The original and YIK-1 tumor cells contained argyrophil granules and neurosecretory granules in the cytoplasm, and were immunohistochemically stained positive for neuron-specific enolase, serotonin and chromogranin. Both tumors contained HPV16 DNA in a multiple-copy integrated form. Thus, YIK-1 maintains the characteristics of the original ASCC, and may therefore be useful as an animal system for experimental studies of ASCC.

Maturation of human immunodeficiency virus, strain LAV, in vitro

The budding process of human immunodeficiency virus (HIV), strain LAV, starts with the formation of a crescent electron-dense layer directly underneath the cell membrane of infected CCRF-CEM cells. After completion of the formation of the circle of inner dense layer, immature virions with an electron-lucent center are released from the cells. Serial thin sections and stereo observation of thick sections showed that most of the immature virions adjacent to the cell surface had already come off the cell and some still had very thin connections to the cell. However, on rare occasions, virions at an intermediate stage between immature stage and mature virions with bar-shaped electron-dense cores were observed. Virions with dense cores were never observed to be connected to the cell surface. These observations support the idea that the last step of the maturation of HIV occurs outside the cell and that the electron-dense core seems to develop by rearrangement and dispersion of the substance of the inner dense layer of immature virions.

Budding process and fine structure of lymphadenopathy-associated virus (LAV)

The budding process and fine structure of lymphadenopathy-associated virus (LAV), were studied by indirect immunofluorescence (IF) and electron microscopy (EM). By IF, LAV antigen was seen to be distributed focally within infected CCRF-CEM cells. Consistent with this finding, electron micrographs showed that LAV particles occurred in a focally aggregated state in a restricted area of the surface of the infected cells. LAV particles possessed bar-shaped, dense and central or eccentric cores. In addition, two or more cores were occasionally observed in one virus particle, or the cores were sometimes absent when thin sections were examined. The envelope of the virus particles had an irregular structure, although LAV particles were approximately spherical.

Actin filaments and tumorigenicity in a Fischer rat embryo fibroblast cell line (3Y1) transformed by ultraviolet-irradiated HSV

The characteristics of the cytoskeleton of a Fischer rat embryo fibroblast cell line (3Y1) transformed by ultraviolet (UV)-irradiated HSV were studied by indirect immunofluorescence using anti-actin IgG. Parental 3Y1 cells possessed well-developed actin filaments, while 3Y1 cells transformed by UV-irradiated HSV also retained well-developed actin filaments. Transformed cells were divided into 2 groups according to tumorigenicity in newborn Fischer rats; one had a strongly tumorigenic potential and the other a weakly tumorigenic potential. Tumor-derived cell lines exhibited a highly tumorigenic potential, and were also divided into 2 groups, one with well-developed actin filaments and the other without well-developed actin filaments. Our results suggested that transformation or tumor formation by HSV is a multi-step process and that morphological loss of actin filaments in the cells is not essential to the tumorigenic potential of the cells transformed by HSV.

Scanning electron microscopy of CV-1 and HeLa cells infected with herpes simplex viruses types 1 and 2

Production of virus particles in CV-1 or HeLa BU-25 cells was investigated after their infection with several strains of herpes simplex virus (HSV) types 1 and 2, especially in relation to the association of virus particles with cells, the ratio of plaque forming units (PFU) to the whole number of virus particles and the morphological characteristics of cytopathic effect (CPE). Growth curves of the viruses differed according to the combination of cells and infecting virus strains. At 20 hr p.i., the number of cell-associated or cell-free viruses ranged from 5 X 10(8) to 5 X 10(9) PFU/35 mm dish or from 5 X 10(2) to 1.5 X 10(4) PFU/cell irrelevant of virus serotype or the morphology of CPE. In the case of CV-1 cells, the ratios of the number of the virus particles to PFU ranged from 100 to 640 and/or 18 to 110, respectively, depending on the CPE of rounding type or of fusion type. In case of CPE of fusion type, a higher rate of infectious particles was observed.

Pathogenicity of newly isolated coxsackievirus B4 for mouse pancreas

Coxsackievirus B4 fresh isolates from patients with upper respiratory illness and aseptic meningitis were studied for their pathogenicity in the pancreas of SJL/J mice. Out of 12 virus isolates, 7 induced hypoglycaemia in mice 2 to 4 days after virus inoculation. All 3 isolates from faeces of patients induced hypoglycaemia in contrast to 3 viruses isolated from the cerebrospinal fluid which did not. Six isolates from throat swabs were either pathogenic (4 isolates) or non-pathogenic (2 isolates). It is concluded that at least two biologically distinct coxsackieviruses B4 prevail among humans.

In situ electron microscopic observation of negatively stained tissue culture cells contaminated with mycoplasmas

A simple, fast, and in situ method of detecting the inapparent infection of cultured cells with mycoplasmas is reported. Animal cells grown on Formvar-coated electron microscopic grids were directly fixed with glutaraldehyde, negatively stained with phosphotungstic acid and examined by transmission electron microscopy. Cells contaminated with mycoplasmas could be discriminated from uncontaminated cells. The micro-organisms in the negatively stained preparations corresponded with those revealed by thin sectioning, and the distribution of mycoplasmas in cultured cells coincided with those revealed by the Hoechst staining method. Most of the highly resolved mycoplasmas were polymorphic, and closely associated with host cells; often more than 500 organisms per host cell were seen.

Comparison of enzyme-linked immunosorbent assay, electron microscopy, and reversed passive haemagglutination for detection of human rotavirus in stool specimens

An enzyme-linked immunosorbent assay (ELISA) using microplates as solid phase, rabbit antiserum against human rotavirus Wa strain as catching antibody, and the same reagent labeled with beta-D-galactosidase as conjugate, has been developed for detection of human rotavirus antigen(s) in stool specimens from patients with acute gastroenteritis. The limit of detection of purified human rotavirus by ELISA was 15.6 ng/ml (1.56 ng/well) of viral protein. The sensitivities of ELISA, electron microscopy, and the reversed passive haemagglutination method (ROTA-CELL) were compared. ELISA was more sensitive than electron microscopy and the reversed passive haemagglutination method. The ELISA blocking assay was useful for detection of an antibody response to human rotavirus in paired sera from children in two institutions during outbreaks of rotavirus gastroenteritis.

In situ electron microscopical observation of cells infected with herpes simplex virus

Transport and release of herpes simplex virus (HSV) in an African green monkey kidney cell line (CV-1) was followed by electron microscopy for up to 24 h p.i. Transmission electron microscopy and scanning electron microscopy were employed. For the former approach, electron microscopical autoradiography of whole cultured cells and in situ thin section techniques were used. The following new observations were made. (1) Except in peripheral parts of the cells, where the cytoplasmic membrane could make a ruffling movement relatively freely, virus particles were found only on the dorsal surface of the cell and not on the surface facing the substratum. By observation of thin section in situ, it was confirmed that the virus particles within intracytoplasmic vacuoles were apparently released by a reverse phagocytic process from the cell surface adjacent to microvillus projections. (2) Progeny virus particles in the nucleus moved to the cell surface within 2 h after maturation.

Properties of a macrophage cell line transformed by simian virus 40. Morphological changes related to cell functions

A mouse macrophage clone (line nH-1) transformed by simian virus 40 (SV40) was examined by electron microscopy. In the growing phase of the cultures, NH-1 cells were non-phagocytic and SV40 T antigen-positive, and contained a large number of filament sheaths within their pseudopodia. In the late stationary phase, they became phagocytic, SV40 T antigen-negative and contained a filamentous network within their psudopodia. In addition, NH-1 cells in the late stationary phase were very similar to normal macrophages in other morphological properties.

Analysis of herpes simplex virus isolated from patients with recurrent herpes keratitis exhibiting "treatment-resistance" to 5-iodo-2'-deoxyuridine

Four strains of herpes simplex virus (HSV) were isolated from two patients with recurrent herpes keratitis who failed to respond to 5'-iodo-2'-deoxyuridine (IDU) treatment. Two of the four isolates were highly resistant to IDU in cell culture and the other two isolates were more susceptible to IDU than an HSV-1 laboratory strain. From each patient, an IDU-resistant and an IDU-susceptible virus was isolated. All 4 isolates possessed the ability to induce the thymidine kinase (TK) activity in cell lines lacking that activity. All the isolates were type 1 HSV, since the filamentous structures, recognized as a biological marker of type 2 HSV, were not observed in infected cells.

Properties of virus isolated from an epidemic of hand-foot-and-mouth disease in 1973 in the city of Matsue. Comparison with Coxsackievirus group A type 16 prototype

The virus strains isolated from clinical cases in an epidemic of hand-foot-and-mouth disease in Matsue in 1973 were characterized and its properties were compared with those of the Coxsackievirus group A type 16 (CA 16) prototype strain. The virus isolated in 1973 was similar to CA16 prototype virus with respect to morphology in electron microscopy, resistance to ether and capability to replicate in meidum containing fluorodeoxyuridine. Cross neutralization tests using guinea-pig and horse antisera revealed that there was little or no detectable common antigen between the two viruses. The two viruses also differed in heat stability of virion infectivity: the 1973-viruses were much more resistant to heat than the prototype virus. Under one-step growth conditions in Vero cell cultures, growth rate and virus yield of the 1973-viruses were lower than those of CA16, but this property was independent of incubation temperatures, pH of culture medium and other culture conditions. Several other differences in property between the 2 strains are also described. It is concluded that the epidemic in 1973 was caused by a virus whose properties differed greatly from those of the CA16 prototype.