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.