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PubMed1979

Milky spots (Taches laiteuses) as structures which trap asbestos in mesothelial layers and their significance in the pathogenesis of mesothelial neoplasia.

The UICC standard sample of asbestos, crocidolite, was injected subcutaneously into the flanks of CBA/lac mice. Asbestos fibres were found in milky spots in the serosal cavities more than 442 days after the injection, in the form of either naked fibres or asbestos bodies. Milky spots were the only structure in which asbestos fibres were observed in the mesothelial layer. The fact that asbestos fibres were found in the liver, spleen, kidney, brain, etc., in addition to milky spots, suggested that they were transported by the blood stream throughout the body. This assumption was confirmed by the similar distribution of asbestos after intravenous administration. The vascular and cellular structure of milky spots is such that they are particularly likely to trap blood-borne asbestos fibres. Hyperplastic changes were observed in milky spots after both subcutaneous and intravenous administration of asbestos in mice. The possible involvement of milky spots in the genesis of tumors of the mesothelium following exposure of animals to asbestos is discussed.

Animals↗
PubMed2005

Functional MRI using molecular imaging agents.

Contrast agents for magnetic resonance imaging (MRI) have recently been used as cellular-level probes of neural function. New in vivo labeling strategies now enable researchers to follow plasticity of brain activation patterns and cellular structure over time. On the horizon is the prospect that molecular imaging agents specifically designed for functional imaging (fMRI) on a relatively fast timescale could offer an alternative to conventional hemodynamics-based approaches. Development of several MRI sensors has defined principles by which imaging agents for "molecular fMRI" can be constructed; application of engineered sensors for cellular-level correlates of neuronal activity would allow researchers to combine the noninvasiveness of MRI with spatial resolution of tens of microns and temporal resolution of 100ms or less. Facilitated by advances in imaging-agent delivery methods and model systems appropriate for high-resolution neuroimaging, novel molecular imaging strategies continue to potentiate MRI as a tool for mechanistic investigation of neural systems.

Animals↗
PubMed1996

Glycosomes--the organelles of glycogen metabolism.

This article reviews the data concerning the electron microscopical interpretation of glycogen. It demonstrates that glycogen in the cell is associated with the enzymes involved in its metabolism and that the glycogen-protein complex forms morphologically distinct cell organelles called glycosomes. Glycogen can be visualized in the electron microscope (EM) by histochemical procedures, or by negative staining, but it does not react with heavy metals such as uranium and lead. The protein component of glycosomes, stainable by heavy metals, appears in EM as 20-30 nm granules. While biochemical findings have long indicated the association of glycogen and protein in the cell, morphological interpretation traditionally defined the protein component of glycosomes as particles of glycogen. Accordingly, the term alpha or beta particles, introduced to define particles of glycogen, became subsequently applied to the protein component visible in sections stained by heavy metals. The history of microscopic research reveals the conditions which led to such interpretation. Morphological analysis of the reaction of glycosomes to the acids shows that glycosomes deposited free in the cytosol (lyoglycosomes) are acid labile, whereas the others (desmoglycosomes), intimately associated with different cellular structures, are acid-resistant. These 2 groups correspond to lyo- and desmoglycogen distinguished in early biochemical studies on the basis of their different resistance to the cold trichloroacetic acid. The theory of glycosomes provides a new paradigm which clarifies numerous unexplained data in the microscopic literature on glycogen, and opens a vast field for the research on the cellular metabolism of glycogen, with the use of modern molecular and cellular biology techniques.

Animals↗
PubMed1997

Natural resistance to infection with intracellular pathogens: the Nramp1 protein is recruited to the membrane of the phagosome.

The Nramp1 (natural-resistance-associated macrophage protein 1) locus (Bcg, Ity, Lsh) controls the innate resistance or susceptibility of mice to infection with a group of unrelated intracellular parasites which includes Salmonella, Leishmania, and Mycobacterium. Nramp1 is expressed exclusively in professional phagocytes and encodes an integral membrane protein that shares structural characteristics with ion channels and transporters. Its function and mechanism of action remain unknown. The intracellular localization of the Nramp1 protein was analyzed in control 129/sv and mutant Nramp1-/- macrophages by immunofluorescence and confocal microscopy and by biochemical fractionation. In colocalization studies with a specific anti-Nramp1 antiserum and a panel of control antibodies directed against known cellular structures, Nramp1 was found not to be expressed at the plasma membrane but rather localized to the late endocytic compartments (late endosome/lysosome) of resting macrophages in a Lamp1 (lysosomal-associated membrane protein 1)-positive compartment. Double immunofluorescence studies and direct purification of latex bead-containing phagosomes demonstrated that upon phagocytosis, Nramp1 is recruited to the membrane of the phagosome and remains associated with this structure during its maturation to phagolysosome. After phagocytosis, Nramp1 is acquired by the phagosomal membrane with time kinetics similar to Lamp1, but clearly distinct from those of the early endosomal marker Rab5. The targeting of Nramp1 from endocytic vesicles to the phagosomal membrane supports the hypothesis that Nramp1 controls the replication of intracellular parasites by altering the intravacuolar environment of the microbe-containing phagosome.

Animals↗
PubMed1989

Proteolysis and cell death.

Cell death can occur by a number of different mechanisms, some of which are associated with significant protein degradation. L-cells in monolayer culture were labelled with 14C-leucine and 3H-thymidine and placed in a cold chase medium for each experiment. General cellular necrosis, induced by either repeated freeze-thawing or NaCN, rapidly disrupted cellular structure, but produced only small amounts of acid soluble 14C over a period of 24 h. Selective cell death was produced by adding 5 mM thymidine to growing tissue cultures. With such treatment, cell death became manifest only after a 24 h lag period and progressively more intense in the next 48 h. The process was characterized first by cellular enlargement and protein accumulation, followed by the formation and release of eosinophilic hyaline bodies from cell cytoplasm. These bodies were often found adjacent to the plasma membranes of viable cells, as well as within cellular vacuoles. Biochemical studies indicated that proteolysis was significantly increased; this proteolysis, but not cell death, was prevented by NH4Cl. Cell death, formation of eosinophilic hyaline bodies, and proteolysis were prevented by cycloheximide. Cell cultures that manifest cell turnover, i.e. selective cell death, apoptosis-type, will show increased amounts of vacuolar proteolysis, which may be confused with accelerated protein turnover occurring in the vacuolar system.

Ammonium Chloride↗
PubMedDate not supplied

A genetic abnormality of cardiac myocytes from the blind mutant (RC) chick heart: abnormalities of cardiac structure and choline transport.

A new genetic cardiomyopathy was identified in a blind mutant avian strain. Cardiac myocytes were cultured from 7-day-old chick embryos from Rhode Island Red chickens and from another strain of this species that has been identified to have several abnormalities, the most striking of which is blindness. Cardiac myocytes were maintained in tissue culture. Morphologically, in culture, the cardiac myocyte from the blind mutant strain assumed a spherical shape and showed abnormalities of sarcolemmal membrane compared to control myocytes from heterozygous animals. Choline uptake and metabolism were examined, using [methyl 3H] choline, because it is a sarcolemmal transport process and choline is metabolised to phosphatidylcholine, an important phospholipid for cellular structure and function. Choline uptake through the active transport process was markedly and significantly reduced in the mutant cells compared to control cells, while choline metabolism to phosphatidylcholine was not significantly altered. These results demonstrate a new abnormality of cardiac myocytes, a cardiomyopathy that can be studied in cell culture and one with abnormalities of cellular choline transport.

Animals↗
PubMedDate not supplied

[Peroxidase and human thyroid hormone synthesis disorders (author's transl)].

Thyroid peroxidase in involved in several steps of the biosynthesis of thyroid hormone utilizing H2O2: peroxidation of iodide to iodine, iodination of thyroglobulin (Tg) and coupling reaction leading to T4 and T3 formation. The peroxidase enzyme appears to be an heme protein containing a protoporphyrin IX, with binding sites for both iodide and tyrosine. Although the peroxidase is present in numerous cellular structure, iodination activity occurs primarily if not only at all, at the apical cell border. Lack of peroxidase activity or abnormal peroxidase has been described in isolated cases of congenital goiter with organification defect and a positive perchlorate test. However no change in enzymatic activity has been found in patients with Pendred's syndrome as compared to normal tissue. The deficiency of hormone synthesis observed in various benign diffuse thyroid disorders in certainly not due to a lack of peroxidase activity. In treated hyperthyroid patients, a high cellular activity is observed, especially at the apical cell border. In euthyroid patients with diffuse sporadic goiter, an increase of peroxidase activity is also observed. However, the cytochemical localization of the enzyme in goitrous thyroid gland shows that the peroxidase activity is mostly visualized around numerous lipoid structures; being concentrated in this particular site, the enzyme might preferentially oxidize lipids and consequently be less available for hormone synthesis. In euthyroid hot nodule, the peroxidase activity is normal. In cold nodule, a discrepancy between iodide oxidation and protein iodination has been found, suggesting that iodide peroxidation and iodination of tyrosine residues of Tg are two relatively independent processes although thyroid peroxidase catalyses both reactions. In contrast with the benign pathological conditions, the peroxidase activity is lower than normal in thyroid cancerous tissue.

Humans↗
PubMed1994

Tensin: a potential link between the cytoskeleton and signal transduction.

Cytoskeletal proteins provide the structural foundation that allows cells to exist in a highly organized manner. Recent evidence suggests that certain cytoskeletal proteins not only maintain structural integrity, but might also be associated with signal transduction and suppression of tumorigenesis. Since the time of the discovery of tensin, a fair amount of data has been gathered which supports the notion that tensin is one such protein possessing these characteristics. In this review, we discuss recent studies that: (1) elucidate a role for tensin in maintenance of cellular structure and signal transduction; (2) implicate tensin as the anchor for actin filaments at the focal adhesion; (3) describe the phosphorylation of tensin; (4) describe potential targets for its Src homology region 2 domain; (5) describe the association between tensin and the nuclear protein p130; and (6) demonstrate that increased tensin expression in a cell line appears to reduce its transformation potential.

Actin Cytoskeleton↗
PubMed1986

A morphometric analysis of the redistribution of organelles in columella cells of horizontally-oriented roots of Zea mays.

In order to determine what structural changes in graviperceptive cells are associated with onset of root gravicurvature, the redistribution of organelles in columella cells of horizontally-oriented, graviresponding roots of Zea mays has been quantified. Root gravicurvature began by 15 min after reorientation, and did not involve significant changes in the (i) volume of individual columella cells or amyloplasts, (ii) relative volume of any cellular organelle, (iii) number of amyloplasts per columella cell, or (iv) surface area of cellular location of endoplasmic reticulum. Sedimentation of amyloplasts began within 1 to 2 min after reorientation, and was characterized by an intensely staining area of cytoplasm adjacent to the sedimenting amyloplasts. By 5 min after reorientation, amyloplasts were located in the lower distal corner of columella cells, and, by 15 min after reorientation, overlaid the entire length of the lower cell wall. No consistent contact between amyloplasts and any cellular structure was detected at any stage of gravicurvature. Centrally-located nuclei initially migrated upward in columella cells of horizontally-oriented roots, after which they moved to the proximal ends of the cells by 15 min after reorientation. No significant pattern of redistribution of vacuoles, mitochondria, dictyosomes, or hyaloplasm was detected that correlated with the onset of gravicurvature. These results indicate that amyloplasts and nuclei are the only organelles whose movements correlate positively with the onset of gravicurvature by primary roots of this cultivar of Zea mays.

Cell Nucleus↗
PubMed2003

Application of in situ reverse trancriptase-polymerase chain reaction (RT-PCR) to tissue microarrays.

Detection of disease-associated gene transcripts in primary disease tissues is frequently confounded by the presence of non-involved cell types. Alternative methods of detecting gene expression directly within tissues involve either the generation of antibodies, which can be a lengthy process and may suffer from lack of specificity, or amplification of reverse-transcribed cDNA in tissue sections (in situ RT-PCR). The latter method is highly specific and enables detection of transcripts in the cells originally responsible for their synthesis, but is highly destructive of tissue structures and can be carried out on only one or a few sections per experiment, resulting in low reproducibility. In this study, in situ RT-PCR was applied for the first time to commercially available tissue section microarrays enabling the examination of up to 70 different samples simultaneously. Modifications to the technique are detailed that preserved visible tissue and cellular structures and improved transcript detection whilst preventing significant generation of artefacts.

Journal Article↗
PubMed1976

[Nuclei and fields of the rabbit hypothalamus].

Common features and distinctions in the structure of certain fields of the rabbit hypothalamus were established on the basis of cytoarchitectonical and cytological analysis. It has been shown that there are three types of nerve cells in the nuclei and fields of the hypothalamus which can be referred to somato-, cyto- and karyochromic elements of the nervous system in accordance with the Nissl classification. All the cellular structures of the hypothalamus can be divided into heteromorphic and isomorphic types. The medial and lateral hypothalamic fields of all the rostro-caudal length of the hypothalamus are referred to the first type. The hypothalamic nuclei occupying its basal part are referred to the second type. On the basis of the obtained data concerning the neuronal composition of the fields and nuclei of the hypothalamus, it can be divided into three zones: the medial zone, including 3 medial hypothalamic fields disposed along the 3d ventricle; the lateral zone comprizing two a lateral hypothalamic fields occupying its lateral parts along its all length and the basal zone including hypothalamic nuclei disposed mainly in the ventral part of the hypothalamus.

Animals↗
PubMed1993

The alpha-helical rod domain of human lamins A and C contains a chromatin binding site.

We examined regions of human lamins A and C involved in binding to surfaces of mitotic chromosomes. An Escherichia coli expression system was used to produce full-length lamin A and lamin C, and truncated lamins retaining the central alpha-helical rod domain (residues 34-388) but lacking various amounts of the amino-terminal 'head' and carboxy-terminal 'tail' domains. We found that lamin A, lamin C and lamin fragments lacking the head domain and tail sequences distal to residue 431 efficiently assembled into paracrystals and strongly associated with mitotic chromosomes. Furthermore, the lamin rod domain also associated with chromosomes, although efficient chromosome coating required the pH 5-6 conditions needed to assemble the rod into higher order structures. Biochemical assays showed that chromosomes substantially reduced the critical concentration for assembly of lamin polypeptides into pelletable structures. Association of the lamin rod with chromosomes was abolished by pretrypsinization of chromosomes, and was not seen for vimentin (which possesses a similar rod domain). These data demonstrate that the alpha-helical rod of lamins A and C contains a specific chromosome binding site. Hence, the central rod domain of intermediate filament proteins can be involved in interactions with other cellular structures as well as in filament assembly.

Animals↗
PubMed1993

Correlative light and electron microscopy of the same sections embedded in HPMA, Quetol 523 and MMA.

Semithin sections, cut from tissues stained with acid and basic dyes after embedding in 2-hydroxypropyl methacrylate, Quetol 523 and methyl methacrylate, showed cytoplasmic components at a high resolution by light microscopy. These same sections could then be viewed, after osmium tetroxide, uranyl and lead staining, by the electron microscope. These sections had a number of inherent advantages: they could be observed with a light microscope; they facilitated analysis of cellular structures in the identical sites, and they were frequently the optimum thickness to provide three-dimensional information. We clearly established the structural detail of this same-section correlative light-electron microscopy approach by showing that the coloured materials observed in such sections of cells followed the distribution of fine structures within the same sections as determined by electron microscopy. In some instances the fidelity of the correlation between the distribution of the coloured area and cytoplasmic components in identical cells of the same section revealed significant details which could not visualized in thin sections. This technique, therefore, provided a simple and useful solution to many problems that require the localization of cellular components in identical cells selected previously by light microscopy.

Animals↗
PubMed1974

Cytologic studies of hematopoietic cells by interference contrast (Nomarski) optics.

Nucleoli and other cytologic structures of mature and immature, normal and leukemic hematopoietic cells can be readily and clearly visualized when such material is examined by interference contrast microscopy. Optimum results are dependent upon the use of fresh, unfixed, unstained, briefly dried blood or bone marrow smears mounted in isotonic or near isotonic solutions of low refractive index. By this approach, fixation artifacts are avoided and cellular structures can be seen which may not be visible by any other technic. The methodology and findings, particularly with relation to nucleoli of normal and leukemic leukocytes, are discussed.

Blood Cells↗
PubMed1998

Registration of serial sections of mouse liver cell nuclei.

Image registration of biological tissue is essential for 3D reconstruction, which is important for visualizing and quantifying the 3D relationships between internal structures of an object. The biological role of DNA organization, which is an extremely complex 3D architecture within the cell nucleus, has come into focus since it has become clear that the chromatin structure in itself functions as a regulator of DNA. Thus, 3D reconstruction of cell nuclei based on consecutive series of high-resolution ultrathin slices may provide new information about the chromatin structure and its organizational changes during carcinogenesis. This work focuses mainly on the problem of registering successive serial transmission electron micrographs of ultrathin sections of mouse liver cell nuclei to analyse the 3D chromatin structure. A five-step semiautomatic interactive registration method is proposed. The first two steps of the procedure correct the rotation and translation components by using the phase correlation. The third, fourth and fifth steps correct the global distortion, employing a point mapping method based on different ways of selecting the control points. In step three, the control points were automatically computed by phase correlating corresponding subimages of the reference and sensed image. A semiautomatic method is used in the fourth step to select the control points, i.e. an automated method for computing the centre of mass of manually identified anatomical structures in neighbouring slices. For the sections which could not be properly corrected by the four steps, a final step is introduced, where control points are manually selected in the reference and sensed images. An algorithm is proposed to examine the spatial distribution of selected control points. Four sets of serial sections of mouse liver cell nuclei, each with approximately 100 sections, are registered by the proposed method and also registered manually for the comparison of registration accuracy. Artificial X-Z and Z-Y sections of registered series were visually compared for the smoothness of the nuclear membrane. To quantify the registration accuracy and the extent of registration, the correlation coefficient (C) and the overlap index (Co) were computed over the registered structure of interest. In addition to the visual comparison and the comparison of C and Co, the registered serial sets were compared by 3D GLCM-based texture features in the Z direction. The results demonstrate that the proposed semiautomatic registration technique achieved accurate results comparable to the manual registration. The proposed registration method relies only on the operator for rough pinpointing of cellular structures. Therefore, it should provide better reproducibility, and allow the user to operate the system faster and in a more relaxed manner than in a manual registration.

Algorithms↗
PubMed1977

Cytoarchitecture and acetylcholinesterase activity of the amygdaloid nuclei in the dog.

The cellular structure and distribution of histochemically demonstrated acetylcholinesterase (AChE) activity were studied in the amygdaloid body of 9 dogs. Cytoarchitectonic observations were made in series of paraffin and celloidin sections stained with cresyl violet. For the demonstration of the acetylcholinesterase activity, modifications of Koelle method were used. The general pattern of morphological structure of the dog's amygdaloid body is similar to that in other mammalian species. The corticomedial group of the nuclei was characterized generally by cytoarchitectonic uniformity of small, lightly stained cells and low intensity of the AChE reaction, except for the nucleus of the lateral olfactory tract and the lateral part of the central nucleus. The latter showed further differentiation in both cellular arrangement and distribution of AChE activity and may be divided into three subdivisions. The basolateral group of nuclei was characterized by higher differentiation of the cellular arrangement and distribution of the AChE activity. The highest enzyme activity was observed in the basal magnocellular nucleus. These findings support the homology of particular amygdaloid nuclei in various mammalian species.

Acetylcholinesterase↗
PubMed2002

The cytoskeleton and gravitropism in higher plants.

The cellular and molecular mechanisms underlying the gravitropic response of plants have continued to elude plant biologists despite more than a century of research. Lately there has been increased attention on the role of the cytoskeleton in plant gravitropism, but several controversies and major gaps in our understanding of cytoskeletal involvement in gravitropism remain. A major question in the study of plant gravitropism is how the cytoskeleton mediates early sensing and signal transduction events in plants. Much has been made of the actin cytoskeleton as the cellular structure that sedimenting amyloplasts impinge upon to trigger the downstream signaling events leading to the bending response. There is also strong molecular and biochemical evidence that the transport of auxin, an important player in gravitropism, is regulated by actin. Organizational changes in microtubules during the growth response phase of gravitropism have also been well documented, but the significance of such reorientations in controlling differential cellular growth is unclear. Studies employing pharmacological approaches to dissect cytoskeletal involvement in gravitropism have led to conflicting results and therefore need to be interpreted with caution. Despite the current controversies, the revolutionary advances in molecular, biochemical, and cell biological techniques have opened up several possibilities for further research into this difficult area. The myriad proteins associated with the plant cytoskeleton that are being rapidly characterized provide a rich assortment of candidate regulators that could be targets of the gravity signal transduction chain. Cytoskeletal and ion imaging in real time combined with mutant analysis promises to provide a fresh start into this controversial area of research.

Actins↗
PubMed2005

Effects of coiling on the micromechanics of the mammalian cochlea.

The cochlea transduces sound-induced vibrations in the inner ear into electrical signals in the auditory nerve via complex fluid-structure interactions. The mammalian cochlea is a spiral-shaped organ, which is often uncoiled for cochlear modelling. In those few studies where coiling has been considered, the cochlear partition was often reduced to the basilar membrane only. Here, we extend our recently developed hybrid analytical/numerical micromechanics model to include curvature effects, which were previously ignored. We also use a realistic cross-section geometry, including the tectorial membrane and cellular structures of the organ of Corti, to model the apical and basal regions of a guinea-pig cochlea. We formulate the governing equations of the fluid and solid domains in a curvilinear coordinate system. The WKB perturbation method is used to treat the propagation of travelling waves along the coiled cochlear duct, and the O(1) system of the governing equations is solved in the transverse plane using finite-element analysis. We find that the curvature of the cochlear geometry has an important functional significance; at the apex, it greatly increases the shear gain of the cochlear partition, which is a measure of the bending efficiency of the outer hair cell stereocilia.

Animals↗