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PubMed2005

[Ultrastructure of intervertebral disk in the corresponding area after internal fixation of spinal column].

OBJECTIVE: To observe ultrastructural changes of the intervertebral disk in the corresponding area after internal fixation of spinal column. METHODS: Twenty-four Japanese big ear rabbits were divided into internal fixation of spinal column group (n=12) and control group (n=12). The internal fixation model was made as follows: The spinous processes and erector spinal muscle were exposed and the T10-L3 spinous processes and the relevant two-side articular processes under the periosteum were isolated. With the help of L-shaped Kirschner wires, the steel wire was threaded through the articular of T11, T12, LI and L2, and were connected with L-shaped Kirschner wires. After 6 months of operation, the following intervertebral disk tissues were observed with transmission electron microscope: nucleus pulposus, internal anulus fibrosus and external anulus fibrosus of L1 intervertebral disk. The T12 and L2 intervertebral disk surface structure was observed horizontally and longitudinally with scanning electron microscope, respectively. RESULTS: After internal fixation of spinal column, the structural changes of cells in nucleus pulposus and internal annulus fibrosus occurred earlier than that in the external annulus fibrosus. Proteoglycan and special structure were found in nucleus pulposus and matrix of annulus fibrosus. However, the forms of special structure in nucleus pulposus and internal layer of annulus fibrosus were different. In the degeneration matrix of intervertebral disc, the proteoglycan particles and special structure were obviously decreased. CONCLUSION: Abnormal stress environment can result in the degeneration of intervertebral disk. There is a regular distribution of the special structure in nucleus pulposus and matrix of annulus fibrosus, which is related to biology behaviour of proteoglycan particles in the degeneration of intervertebral disk.

Animals↗
PubMed1996

The cell nucleus in early bovine and caprine preimplantation embryos: fine structural cytochemistry and immunoelectron microscopy.

Fine structural cytochemistry and immunocytochemistry were used to study nucleic acids and nuclear proteins in nuclear bodies (NB) of pronuclear and 2-cell bovine and caprine embryos on ultrathin sections of paraformaldehyde fixed and Lowicryl K4M or LR White embedded specimens. The most striking feature detected in some of these nuclear bodies (NBs) was the presence of non-nucleolar proteins known to be involved in pre-mRNA splicing. One category of such intranuclear bodies (showing a rather dense finely fibrillar composition and named here dense body-DB) contained the Sm-antigen (an antigen common to a major group of nucleoplasmic spliceosomal snRNPs). Another, more numerous category of NBs differed morphologically from the former one by a much looser composition of fibrillogranular elements (loose body-LB). Moreover, it showed the presence of the non-snRNP splicing factor SC-35, in addition to the Sm-antigen. Both categories of these nuclear bodies were distinguished clearly from the nucleolar precursor bodies (NPBs) by an absence of immunolabeling of NPB with antibodies against nuclear proteins involved in splicing. Moreover, the former NBs are not stained with silver, while NPBs already in pronuclei exhibit strong affinity to silver. In addition to the immunolabeling in prominent (approx. 0.2-2.0 microns) NBs, regularly occurring high concentration of snRNP was revealed in very small (approx. 0.05 micron), morphologically poorly defined areas (named here small snRNP-enriched areas-SSA), harboring moreover a set of nuclear proteins similar to that of the coiled body. Numerous observations of the presence of these small areas in nuclear bodies and in their close vicinity, in nucleoplasm, in proximity of the nuclear envelope and also in ooplasm suggested that they are possible carriers of certain nuclear proteins moving between nuclear bodies, nucleoplasm and cytoplasm. A functional relationship of all these embryonic subnuclear elements has not been elucidated so far but their mutual relation is suggested, since the NPBs and other nuclear bodies usually occur in a close association. Fine structural and immunoelectron microscopic observations further suggest a similarity of the nuclear bodies in the early ruminant embryo with specific intranuclear bodies ("snurposomes") known from Xenopus laevis oocytes. A new and striking feature emerging from these observations is a possible involvement of a group of nucleoplasmic proteins in a yet unknown way in the differentiation processes concomitant with early embryonic nucleologenesis.

Animals↗
PubMed1997

Effect of heparin on oestradiol-induced cell growth and proliferation in the uterus of ovariectomized rats.

The aim of this study was to examine the role of heparin in the realization of oestradiol (OE2) effects in the uterus. Ovariectomized rats were treated with a single injection of OE2 dipropionate (10 micrograms/rat, i.m.) along with injections of heparin (in doses of 0.4 mg/rat, i.m.). OE2 effects in the uterus were determined by measuring mitotic indices, proliferating cell nuclear antigen (PCNA)-labelling indices, DNA content, and volumes of cells, nuclei and nucleoli in luminal and glandular epithelia and stromal cells of the endometrium 24, 36 and 48 h after the injection of OE2. Heparin treatment inhibited the OE2-stimulated increase in mitotic activity and DNA content of the uterine structures, whereas OE2-induced increases in cell, nucleus and nucleolus volumes in all uterine structures tested at all the times were greatly augmented by heparin. The OE2-induced increase in PCNA-labelling index in all the cell types had a tendency to increase as the result of heparin action. In the absence of OE2, heparin had no effect on any of the uterine parameters. The effect of heparin is probably realized via changes in the mechanism of oestrogen action in the uterus. Heparin probably prevents passage of the cells from the G1- to the S-phase of the cell cycle and prolongation of the G1-phase with consequent accumulation of the cells in this phase of the cell cycle. This probably leads to reduction of mitotic activity. Furthermore, cells in G1-phase probably prolong their biosynthetic processes causing enlargement of the cell, nucleus and nucleolus volumes.

Animals↗
PubMed1980

Do neural crest cells in the pancreas differentiate into somatostatin-containing cells?

The possibility that the somatostatin cells are derived from the neurectoderm has been questioned in avian embryos. Isotopic and isochronic transplantations of the neural primordium from quail into chick embryos were made at the vagal level (somites 1 to 7). Quail and chick cells can be distinguished by the structure of their nucleus. The somatostatin cells were characterized immunocytochemically. In no case did quail cells showing the immunological reaction originate from the neural crest.

Animals↗
PubMed1999

Direct visualization of a protein nuclear architecture.

Whether the cell nucleus is organized by an underlying architecture analagous to the cytoskeleton has been a highly contentious issue since the original isolation of a nuclease and salt-resistant nuclear matrix. Despite electron microscopy studies that show that a nuclear architecture can be visualized after fractionation, the necessity to elute chromatin to visualize this structure has hindered general acceptance of a karyoskeleton. Using an analytical electron microscopy method capable of quantitative elemental analysis, electron spectroscopic imaging, we show that the majority of the fine structure within interchromatin regions of the cell nucleus in fixed whole cells is not nucleoprotein. Rather, this fine structure is compositionally similar to known protein-based cellular structures of the cytoplasm. This study is the first demonstration of a protein network in unfractionated and uninfected cells and provides a method for the ultrastructural characterization of the interaction of this protein architecture with chromatin and ribonucleoprotein elements of the cell nucleus.

Animals↗
PubMed2002

High-affinity binding sites for heparin generated on leukocytes during apoptosis arise from nuclear structures segregated during cell death.

During cell death of human cultured leukocytes (Jurkat, HL-60, THP-1, U937) and freshly prepared leukocytes, we observed a greater than 100-fold increase in the affinity of apoptotic and necrotic cells for fluorescein isothiocyanate (FITC)-heparin in comparison with live cells. Binding of FITC-heparin was reversed in the presence of high ionic strength, unlabeled heparan sulfate, and heparin and pentosan polysulfate, but not in the presence of chondroitin and dermatan sulfates. During the course of cell death, the increase in the percentage of cells positive for annexin V binding correlated with the increase in the population positive for binding FITC-heparin. Confocal microscopy demonstrated that heparin binding to dead cells was restricted to 1 or 2 small domains on the surfaces of apoptotic cells and to larger, but still discrete, areas that did not localize with chromatin on ruptured necrotic cells. The heparin-binding domains originated from the nucleus and may correspond to the ribonucleoprotein-containing structures that have recently been shown to segregate within the nucleus of cells and to move onto the cell membrane. We observed that phagocytosis of dead Jurkat cells by monocyte-derived macrophages was blocked when the heparin-binding capacity of the dead cells was saturated by the addition of pentosan polysulfate. From this we concluded that the ability of dead cells to bind to heparan sulfate proteoglycans on the surfaces of macrophages may assist in phagocytic clearance.

Apoptosis↗
PubMed2003

Targeting genes and transcription factors to segregated nuclear compartments.

With increasingly detailed images of nuclear structures revealed by advanced microscopy, a remarkably compartmentalized cell nucleus has come into focus. Although this complex nuclear organization remains largely unexplored, some progress has been made in deciphering the functional aspects of various subnuclear structures, revealing how this elaborate framework can influence gene activation. Several recent studies have helped illustrate how cells might utilize the nuclear architecture as an additional level of transcriptional control, perhaps by targeting genes and regulatory factors to specific sites within the nucleus that are designated for active RNA synthesis.

Animals↗
PubMed2000

Atomic force microscopy of the cell nucleus.

In mammals and plants, the cell nucleus is organized in dynamic macromolecular domains involved in DNA and RNA metabolism. These domains can be visualized by light and electron microscopy and their composition analyzed by using several cytochemical approaches. They are composed of chromatin or ribonucleoprotein structures as interchromatin and perichromatin fibers and granules, coiled bodies, and nuclear bodies. In plants, DNA arrangement defines chromocentric and reticulated nuclei. We used atomic force microscopy to study the in situ structure of the plant cell nucleus. Samples of the plants Lacandonia schismatica and Ginkgo biloba were prepared as for electron microscopy and unstained semithin sections were mounted on glass slides. For comparison, we also examined entire normal rat kidney cells using the same approach. Samples were scanned with an atomic force microscope working in contact mode. Recognizable images of the nuclear envelope, pores, chromatin, and nucleolus were observed. Reticulated chromatin was observed in L. schismatica. Different textures in the nucleolus of G. biloba were also observed, suggesting the presence of nucleolar subcompartments. The observation of nuclear structure in situ with the atomic force microscope offers a new approach for the analysis of this organelle at high resolution.

Animals↗
PubMed1985

[Ultrastructural study on the nucleus pulposus of the inter-vertebral disc--the behavior of the cells in the nucleus pulposus and their autolytic changes in the monkey].

Ultrastructural studies were carried out to examine the normal structure and postmortem autolytic changes of the cells and matrix of nucleus pulposus using adult monkey. Two kinds of cells were observed in the nucleus pulposus. The one was chondrocyte, which contained normal organelles and that was characterized by large halo. The halo was composed of numerous "crista like structures", that were regarded to form the matrix of nucleus pulposus. The other was notochordal cell, most of which appeared in grouping or separately, and yet had cell activity. In addition, there were the intermediate type of cells between chondrocyte and notochordal cell. The ultrastructural autolytic changes were rarely seen in the cells of 6 hours after death, but the changes in the halo and in the cytoplasm were remarkable after more than 12 hours. The autopsied nucleus pulposus for electron microscopical examination should be used within 6 hours after death in usual room temperature.

Animals↗
PubMed1999

Influences of 4-meta/MMA-TBB adhesive resin on osteodentinogenesis of transplanted rabbit dental pulp in vivo: immunohistochemical and electronmicroscopic studies.

The purpose of this study was to investigate the influence of 4-META/MMA-TBB adhesive resin (4-META resin) on osteodentinogenesis of transplanted pulp in vivo. Dental pulp was obtained from the incisors of adult rabbits. 4-META resin was applied to the pulp tissue, and the pulp tissue with 4-META resin was autotransplanted beneath the renal capsule with the pulp side touching the kidney. Pulp tissue alone was also transplanted as a control. The animals were sacrificed at 3, 7, and 14 days after the experiment, and the specimens were examined morphologically. At 3 days, proliferation of mesenchymal cells was observed, and alkaline phosphatase activity (ALP) and osteocalcin were detected throughout the entire transplanted pulp area. In the experimental case, a thin, highly electron dense zone and a granular layer were observed. Under this layer, only a cell-membrane-like structure, a cell with an unclear nucleus, a nucleus alone, and an organelle-like structure could be seen. Furthermore, an exudative layer with many neutrophils was observed, and apoptotic-body-like structures were also found in some areas. On days 7 and 14 in the control group, osteoblast-like cells had proliferated, and osteodentin formation was initiated throughout the entire transplanted pulp area. In the experimental cases at 7 and 14 days, the entire transplanted area had become osteodentin except for a thin fibrous layer under the 4-META resin. These results suggested that the components of 4-META resin such as MMA and 4-MET (A), which guide the polymerization, might cause degeneration of, but not disturb, the wound healing of the pulp tissue.

Acrylic Resins↗
PubMed2002

Expression analysis of recombinant lysyl oxidase (LOX) in myofibroblastlike cells.

Lysyl oxidase (LOX), originally known as the enzyme required for initiation of covalent cross-linking in collagens and elastin, is now known to be a member of a family of genetically related proteins. LOX, or a related protein, has also been localized intracellularly, both in association with the cytoskeleton and in the cell nucleus. To determine the structural requirements for secretion, maturation, and nuclear location of LOX in a cellular context, we have devised an homologous cell model for expression of the recombinant protein. Murine recombinant LOX was expressed in 3T6-5 myofibroblast-like cells as a 51-kD precursor, which was observed in the cytoplasm but not in the nucleus. To investigate whether potential alternative translation initiation sites were involved in specifying a nuclear form of LOX, constructs mutated or deleted for ATG(+1) were used, but alternative initiation at CTG(-315) or ATG(+418) did not lead to the expression of intranuclear forms. Residues 23 to 157 of the proregion were essential for export of the precursor, while mutation of the putative site for maturation by procollagen C-proteinase abolished processing to the mature form of the enzyme. Cross-linking of collagen, as measured by pyridinoline analysis, increased twofold with the recombinant cells, compared to non-transfected controls. This shows the specific contribution of LOX, as opposed to other genetic forms of the enzyme, to cross-linking in a cellular context.

Amino Acids↗
PubMed1988

Structure and function of barrel 'precursor' cells in trigeminal nucleus principalis.

Intracellular recording, electrical stimulation, receptive field mapping, HRP injection, and computer reconstruction techniques were used to study principalis cells in rat. They (n = 80) responded within 1.2 +/- 0.2 ms of trigeminal ganglion shocks and 69% were antidromically activated by thalamic shocks; 69% were vibrissa-sensitive, of which 80% responded to only a single vibrissa. The remainder responded only to guard hairs, skin, teeth, or nociceptors. Stained thalamic-projecting cells with one vibrissa receptive fields had stereotyped morphologies. Small somata gave rise to dendrites which extended only a short distance from the soma, where they branched extensively. Each tree was polarized, spanning no more than a hemisphere around the soma; however, there was no consistent direction of polarity. Dendritic trees extended 68 +/- 14, 95 +/- 48, and 91 +/- 29 micron in the transverse, sagittal and horizontal planes, respectively. Dendritic spines were rare, yet swellings were common. Axons never branched locally.

Action Potentials↗