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PubMed2003

Cytoplasmic dynein in fungi: insights from nuclear migration.

Cytoplasmic dynein is a microtubule motor that mediates various biological processes, including nuclear migration and organelle transport, by moving on microtubules while associated with various cellular structures. The association of dynein with cellular structures and the activation of its motility are crucial steps in dynein-dependent processes. However, the mechanisms involved remain largely unknown. In fungi, dynein is required for nuclear migration. In budding yeast, nuclear migration is driven by the interaction of astral microtubules with the cell cortex; the interaction is mediated by dynein that is probably associated with the cortex. Recent studies suggest that budding yeast dynein is first recruited to microtubules, then delivered to the cortex by microtubules and finally activated by association with the cortex. Nuclear migration in many other fungi is probably driven by a similar mechanism. Recruitment of dynein to microtubules and its subsequent activation upon association with cellular structures are perhaps common to many dynein-dependent eukaryotic processes, including organelle transport.

Biological Transport↗
PubMed2005

Cellular fine structures and histochemical reactions in the tissue of a cypress twig preserved in Baltic amber.

A twig of a cypress plant preserved for ca. 45 Myr in Baltic amber was analysed by light and electron microscopy. Cross-sections of the whole plant showed an almost intact tissue of the entire stem and leaves, revealing, to our knowledge, the oldest and most highly preserved tissue from an amber inclusion reported so far. The preparations are based on a new technique of internal imbedding, whereby the hollow spaces within the inclusion are filled with synthetic resin which stabilizes the cellular structures during the sectioning procedure. Cytological stains applied to the sections reacted with cell walls and nuclei. A strong green auto-fluorescence of the cuticle and the resin canals in the leaves was observed. Transmission electron micrographs revealed highly preserved fine structures of cell walls, membranes and organelles. The results were compared with taxonomically related recent Glyptostrobus and Juniperus plants.

Amber↗
PubMed1998

Genetic pattern, histological structure, and cellular phenotype in early and advanced gastric cancers: evidence for structure-related genetic subsets and for loss of glandular structure during progression of some tumors.

Gastric cancer shows remarkable heterogeneity in histological pattern, cellular phenotype, and genotype. Tumor subsets identified by varying procedures have shown limited reciprocal correlation and have failed to provide a sound rationale for the characterization and classification of all tumors. Based on a case series of 130 gastric cancers that covered both early (70 cases) and advanced (60 cases) stages and that represented most histological types and structural patterns, this study investigated (1) microsatellite instability and p53 gene mutation by means of PCR-based molecular techniques and (2) p53 protein accumulation or tumor cell immunophenotype by means of immunoperoxidase procedures. It was found that microsatellite instability and p53 gene mutation involve two distinct subsets of both early and advanced-stage glandular (intestinal) cancer, and that, contrastingly, they leave purely diffuse cancers unaffected. Mixed cancers, namely, those in which glandular admixed with diffuse growths, showed scarce microsatellite instability at all stages, whereas prominent p53 gene mutation and p53 protein accumulation was limited to the advanced stage alone. No significant correlation was found between tumor cell immunophenotype and either genotype or histotype, although some correlation with particular structural patterns was detected. Comparison of intramucosal with invasive growths within any given tumor suggested that invasive cancers with diffuse-type growth arise in part from mucosal cancers of glandular or mixed structure through progressive loss of intercellular junctional systems. It is concluded that at least two genetically distinct subsets of glandular cancer, one with microsatellite instability and the other with p53 lesions, should be separated both from purely diffuse cancer and, at least in the advanced stage, from mixed cancer. Available evidence suggests distinct clinicopathologic profiles for such tumor entities.

Aged↗
PubMed2000

Effects of RNA secondary structure on cellular antisense activity.

The secondary and tertiary structures of a mRNA are known to effect hybridization efficiency and potency of antisense oligonucleotides in vitro. Additional factors including oligonucleotide stability and cellular uptake are also thought to contribute to antisense potency in vivo. Each of these factors can be affected by the sequence of the oligonucleotide. Although mRNA structure is presumed to be a critical determinant of antisense activity in cells, to date little direct experimental evidence has addressed the significance of structure. In order to determine the importance of mRNA structure on antisense activity, oligonucleotide target sites were cloned into a luciferase reporter gene along with adjoining sequence to form known structures. This allowed us to study the effect of target secondary structure on oligonucleotide binding in the cellular environment without changing the sequence of the oligonucleotide. Our results show that structure does play a significant role in determining oligonucleotide efficacy in vivo. We also show that potency of oligonucleotides can be improved by altering chemistry to increase affinity for the mRNA target even in a region that is highly structured.

Animals↗
PubMed1994

Partial outlet obstruction of the rabbit bladder results in changes in the mitochondrial genetic system.

In the rabbit, partial outlet obstruction of the urinary bladder results in significant changes in the physiology, cellular structure, and cellular metabolism of that organ. One of the most striking changes observed is a 50% decrease in oxidative metabolism. Here we investigate whether the function of the mitochondrial (mt) genetic system is altered in rabbit bladder tissue following partial outlet obstruction. Southern analyses of total DNA prepared from bladder tissue excised as a function of time after initiation of partial outlet obstruction showed that the relative number of copies of the mt genome decreases as much as 10-fold during the first 7 d after obstruction, and that this attenuated mt genome copy number is maintained until at least 14 d post-obstruction. Northern analyses, in contrast, showed that mt COII and cytochrome b transcript levels initially decrease but recover to control levels by about 5 d after obstruction; that level is maintained through 14 d post-obstruction. Enzymatic analysis of cytochrome oxidase and NADH cytochrome c reductase activities in obstructed bladder tissue gave results which paralleled the pattern in the mt RNA analyses. Surprisingly, transcript levels for the mt-related nuclear COIV gene rapidly decreased to about 50% of control levels following obstruction and remained there until 14 d post-obstruction. These results indicate that partial outlet obstruction of the rabbit bladder leads to significant changes in the status and expression of the mt genetic system in bladder tissue.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Transduction of the gravity stimulus in the root statocyte.

The amyloplasts of root statocytes are considered to be the perceptors of gravity. However, their displacement and the starch they contain are not required for gravisensing. The mechanism of the transduction of gravistimulus remains therefore controversial. It is well known that the amplitude of the stimulus is dependent upon the intensity of the acceleration and the inclination of the root with respect to gravity. This strongly supports the hypothesis that the stimulus results in a mechanical effect (pressure or tension) on a cellular structure. Three cellular components are proposed as possible candidates for the role of transducer: the actin filaments, the endoplasmic reticulum and the plasma membrane with its ion channels. Recent results obtained in the frame of the IML 1 Mission of Spacelab show that the endoplasmic reticulum should rather be responsible for the termination of the stimulus. The contacts of amyloplasts with the distal ER could therefore be involved in the regulation of root growth.

Actin Cytoskeleton↗
PubMed1984

Ultrastructure of normal, metaplastic, and abnormal human uterine cervix: use of montages to study the topographical relationship of epithelial cells.

The ultrastructure of the entire thicknesses of normal and abnormal human uterine cervical epithelia is studied with the use of slit-type grids. In four normal squamous epithelial specimens, basic similarities in the maturational sequence were apparent; however, significant variation in the progression of differentiation was also obvious. Because of this variation, it was not possible to always correlate cellular structure with cellular location within the epithelial strata. Four normal specimens containing combinations of squamous, columnar, and metaplastic cells show variations in the topographical relationships of these cells and stages in the transition of reserve to squamous cells in metaplastic zones. The presence of cells with features characteristic of squamous and columnar epithelia suggests a bipotentiality of reserve cells. Six abnormal specimens share several morphologic features, which usually, but not regularly, vary quantitatively with the extent of abnormality. Because of the inconsistent gradation of cellular features with lesion severity, it was essential that numerous ultrastructural parameters be considered in order to evaluate the extent of abnormality. Cellular features peculiar to individual specimens include edema, keratinization, phagocytic squamous cells, and cells similar in appearance to koilocytes described in condylomas. Electron micrograph montages of extensive unobstructed areas of normal and abnormal cervices and higher-magnification micrographs of cell components provide improved documentation of the variation in morphology of normal and abnormal epithelia. Use of montages also results in a clear view of ultrastructural changes accompanying the transition from normal to abnormal cervical epithelium.

Basement Membrane↗
PubMedDate not supplied

Protein profiling of human pancreatic islets by two-dimensional gel electrophoresis and mass spectrometry.

Completion of the human genome sequence has provided scientists with powerful resources with which to explore the molecular events associated with disease states such as diabetes. Understanding the relative levels of expression of gene products, especially of proteins, and their post-translational modifications will be critical. However, though the pancreatic islets play a key role in glucose homeostasis, global protein expression data in human are decidedly lacking. We here report the two-dimensional protein map and database of human pancreatic islets. A high level of reproducibility was obtained among the gels and a total of 744 protein spots were detected. We have successfully identified 130 spots corresponding to 66 different protein entries and generated a reference map of human islets. The functionally characterized proteins include enzymes, chaperones, cellular structural proteins, cellular defense proteins, signaling molecules, and transport proteins. A number of proteins identified in this study (e.g., annexin A2, elongation factor 1-alpha 2, histone H2B.a/g/k, heat shock protein 90 beta, heat shock 27 kDa protein, cyclophilin B, peroxiredoxin 4, cytokeratins 7, 18, and 19) have not been previously described in the database of mouse pancreatic islets. In addition, altered expression of several proteins, like GRP78, GRP94, PDI, calreticulin, annexin, cytokeratins, profilin, heat shock proteins, and ORP150 have been associated with the development of diabetes. The data presented in this study provides a first-draft reference map of the human islet proteome, that will pave the way for further proteome analysis of pancreatic islets in both healthy and diabetic individuals, generating insights into the pathophysiology of this condition.

Adult↗
PubMed2000

Glial-defined rhombomere boundaries in developing Xenopus hindbrain.

The vertebrate central nervous system is characterized by regional specialization, which arises during early development and contributes to patterning the emerging central nervous system (CNS). In the hindbrain, rhombomeres demarcate nonoverlapping regions of the CNS that give rise to distinct neural structures. The cellular structures that define boundaries between adjacent rhombomeres are as yet unclear. However, in certain species the boundary regions between discrete CNS regions appear to be defined by specialized glial cells. Here, we show that in developing Xenopus, DM gamma, a membrane protein of the proteolipid protein family, is expressed in a subset of radial glia. During development, DM gamma transcripts are first expressed in presumptive glial cells throughout the hindbrain, but later become confined to the ventricular zone at rhombomere centers, whereas the protein is exclusively expressed in radial glial cell processes that occupy the rhombomere boundary regions. Likewise, early in development vimentin and glial fibrillary acidic protein are extensively coexpressed in hindbrain radial glia but subsequently define distinct rhombomere domains: vimentin remains localized in radial glia at the rhombomere boundary regions, whereas expression of glial fibrillary acidic protein becomes restricted to the centers. Moreover, radial glial processes at the boundary region are distinguishable from those at the center region; the processes of the boundary region radial glia extend upward in a fan-shaped arrangement and are encircled by the processes from the center glia. These data suggest that an early event in determining rhombomere topology is the specification of both morphologically and biochemically distinct subsets of radial glia.

Animals↗
PubMed1998

[Etiology and pathogenesis of acute pancreatitis].

The theory of pancreatic gland autodigestion by pancreatic enzymes assumed by Chiari 1886 as the crucial moment in the pathogenesis of acute pancreatitis (AP) remains accepted so far. The appearance of mutations of cationic trypsinogen gene on the 7th chromosome in several families with hereditary AP, supports the significance of trypsin in the initiation of AP. The generally recognized etiologic factors of AP include the biliary tract disease and alcohol. Opie in his "Common Channel theory" assumed that the impacted gallstone in the ampulla of Vater could cause a permanent obstruction and subsequently AP. Later clinical studies have confirmed that a short-term block of the common pancreatic duct caused by migrating gallstones is associated with onset of AP. Chronic consumption of alcohol evokes subclinical pancreatic disturbances already prior to the onset of AP. PAP (pancreatic associated protein) being the marker of pancreatic inflammation was significantly increased in chronic alcoholism without signs of AP. Many pathophysiological concepts and effective therapeutic procedures which were successful in the animal studies have not turned out to be appropriate in man. The destruction of both cellular structure and cellular connections is an early event in the development of experimental AP. There is much evidence that free oxygen radicals and the disturbances of microcirculation determine the severeness of AP. The roles of NO (nitric oxide) and kinins remain to be clarified cytokins a interleukin 2 (IL2) and interleukin 10 (IL10) had a protective effect in experimental AP. In humans the antagonist of PAF (platelet activating factor) had reduced the occurrence of organ failure. There is hope, that this knowledge, will lead to new therapeutic possibilities.

Acute Disease↗
PubMed2002

Subfailure damage in ligament: a structural and cellular evaluation.

Subfailure damage in ligaments was evaluated macroscopically from a structural perspective (referring to the entire ligament as a structure) and microscopically from a cellular perspective. Freshly harvested rat medial collateral ligaments (MCLs) were used as a model in ex vivo experiments. Ligaments were preloaded with 0.1 N to establish a consistent point of reference for length (and strain) measurements. Ligament structural damage was characterized by nonrecoverable difference in tissue length after a subfailure stretch. The tissue's mechanical properties (via stress vs. strain curves measured from a preloaded state) after a single subfailure stretch were also evaluated (n = 6 pairs with a different stretch magnitude applied to each stretched ligament). Regions containing necrotic cells were used to characterize cellular damage after a single stretch. It should be noted that the number of damaged cells was not quantified and the difference between cellular area and area of fluorescence is not known. Structural and cellular damage were represented and compared as functions of subfailure MCL strains. Statistical analysis indicated that the onset of structural damage occurs at 5.14% strain (referenced from a preloaded length). Subfailure strains above the damage threshold changed the shape of the MCL stress-strain curve by elongating the toe region (i.e., increasing laxity) as well as decreasing the tangential modulus and ultimate stress. Cellular damage was induced at ligament strains significantly below the structural damage threshold. This cellular damage is likely to be part of the natural healing process in mildly sprained ligaments.

Algorithms↗
PubMed2003

Dynamics and mechanics of the microtubule plus end.

An important function of microtubules is to move cellular structures such as chromosomes, mitotic spindles and other organelles around inside cells. This is achieved by attaching the ends of microtubules to cellular structures; as the microtubules grow and shrink, the structures are pushed or pulled around the cell. How do the ends of microtubules couple to cellular structures, and how does this coupling regulate the stability and distribution of the microtubules? It is now clear that there are at least three properties of a microtubule end: it has alternate structures; it has a biochemical transition defined by GTP hydrolysis; and it forms a distinct target for the binding of specific proteins. These different properties can be unified by thinking of the microtubule as a molecular machine, which switches between growing and shrinking modes. Each mode is associated with a specific end structure on which end-binding proteins can assemble to modulate dynamics and couple the dynamic properties of microtubules to the movement of cellular structures.

Animals↗
PubMed1975

[Role of cations and surface membrane proteins in the adhesion of rat liver parenchymal cells. I. Effect of dirrerent perfusion periods on the structure of cellular junctions].

Electronmicroscopic study of the structure of the rat liver cell junctions in the normal conditions and after 90 min. perfusion by the physiological solution showed 4 kinds of specialized junctions between the hepatocytes with typical structure: tight junction, gap junction, intermediate junction, and desmosomes. The long perfusion does not cause visible changes in the contact structure or the sizes of the intercellular space. The preservation of the tight junction after the long perfusion is demonstrated by the lanthanum tracer: lanthanum is never found in the tight junction and in the bile capillary. Lanthanum reveales globular structure of the middle layer of the gap junction.

Animals↗
PubMed2004

Dynactin.

Dynactin is a multisubunit protein complex that is required for most, if not all, types of cytoplasmic dynein activity in eukaryotes. Dynactin binds dynein directly and allows the motor to traverse the microtubule lattice over long distances. A single dynactin subunit, p150Glued, is sufficient for both activities, yet dynactin contains several other subunits that are organized into an elaborate structure. It is currently believed that the bulk of the dynactin structure participates in interactions with a wide range of cellular structures, many of which are cargoes of the dynein motor. Genetic studies verify the importance of all elements of dynactin structure to its function. Although dynein can bind some membranous cargoes independently of dynactin, establishment of a fully functional dynein-cargo link appears to depend on dynactin. In this review, I summarize what is presently known about dynactin structure, the cellular structures with which it associates, and the intermolecular interactions that underlie and regulate binding. Although the molecular details of dynactin's interactions with membranous organelles and other molecules are complex, the framework provided here is intended to distill what is presently known and to be of use to dynactin specialists and beginners alike.

Animals↗
PubMed2001

Ultrastructural features of the midgut epithelium of females Lutzomyia intermedia (Lutz & Neiva, 1912) (Diptera: Psychodidae: Phlebotominae).

A morphological study of the midgut of Lutzomyia intermedia, the primary vector of cutaneous leishmaniasis, in southeast Brazil, was conducted by light, scanning and transmission electron microscopy. The midgut is formed by a layer of epithelium of columnar cells on a non-cellular basal lamina, under which there is a musculature, which consists of circular and longitudinal muscular fibers. A tracheolar network is observed surrounding and penetrating in the musculature. Females were examined 12, 24, 48, 72 h and 5 days following a blood meal and were analyzed comparatively by transmission electron microscopy with starved females. In starved females, the epithelium of both the anterior and posterior sections of the midgut present whorl shaped rough endoplasmic reticulum. The posterior section does not present well-developed cellular structures such as mitochondria. Observations performed at 12, 24, 48 and 72 h after the blood meal showed morphological changes in the cellular structures in this section, and the presence of the peritrophic matrix up to 48 h after the blood meal. Digestion is almost complete and a few residues are detected in the lumen 72 h after blood feeding. Finally, on the 5th day after the blood meal all cellular structures present the original feature resembling that seen in starved sand flies. Morphometric data confirmed the morphological observations. Mitochondria, nuclei and microvilli of midgut epithelial cells are different in starved and blood fed females. The mitochondria present a similar profile in the epithelium of both the anterior and posterior section of the midgut, with higher dimension in starved females. The cell microvilli in the posterior section of the midgut of starved females are twice the size of those that had taken a blood meal. We concluded that there are changes in the midgut cellular structures of L. intermedia during the digestion of blood, which are in agreement with those described for other hematophagous diptera.

Animals↗
PubMed1983

Time-lapse microcinematographic and phase contrast studies on the cell reformation of Chirocephalus yolk granules in vitro.

In this article we report on a time-lapse microcinematographic and phase contrast study of the cell reformation of yolk granules which were isolated from mature oocytes in the genital sac of the middle female intersex of Chirocephalus nankinensis. The observations on yolk granules were made in fixed positions and the morphological changes of cell reformation were continuously recorded in vitro. The transformation of yolk granules into cellular structures may be tentatively described as follows: At the early stages in culture, it can be seen that the granular or bubbly structures gradually appear within the hyaloid and homogeneous yolk granules; the appearance of yolk granules gradually changes from elliptical into round shape. With further transformation, their appearances in general take the shape of oblate spheroids, their size is smaller than before and inside the yolk granules their granular and bubbly structures become more and more obvious. Finally, the nuclear and cellular structures can be seen in these transforming yolks. By means of time-lapse microcinematographic and phase contrast examinations in fixed positions, single yolk granules obtained from the mature oocyte with little amounts of adhering cytoplasm are continuously recorded and have been shown to occur, steadily and gradually build up cellular structures by self-organization and self-assembly. Up to the present, we have cultured these kinds of cellular organizations repeatedly. Therefore, it can be concluded that the existence of cell reformation on the basis of yolk granules according to the dynamic morphological changes is an objective reality.

Animals↗
PubMed1982

Accelerated aging of fasted Drosophila. Preservation of physiological function and cellular fine structure by thiazolidine carboxylic acid (TCA).

Thiazolidine carboxylic acid (TCA) is a natural liver metabolite whose Mg-salt increased lifespan of flies and mice (Miquel and Economos, 1979, Exp. Geront. 14: 279). We studied the physiological and cellular fine structural effects of various concentrations of TCA in the food of male Drosophila. Flies on 0.3% TCA at 27 degrees C had a reduced oxygen consumption rate (about 20% less than controls) at 3 wks of age while their mating capacity and speed of mating were preserved; the flies lived in various experiments 20-30% longer than controls. Apparently TCA improved the metabolic efficiency of the flies (possibly from less "waste" of energy due to improved mitochondrial coupling). However, flies on 0.9% TCA had a reduced mating capacity and lifespan (:toxicity) while at 0.1% TCA was ineffective. A similar dose-response relationship was found in young flies treated with TCA for 1 week and then deprived of food and water, a procedure found to induce accelerated physiological aging. TCA at the 0.3% and 0.6% level reduced the speed of development and the size of the enclosed flies. Electron microscopic investigation of wing muscle showed that 0.3% TCA had a protective effect on cellular fine structure. Though in starved controls (40% survivors after 24 hours of starvation) there was a total absence of glycogen granules, and a striking shrinkage and densification of mitochondria, TCA to a large extent protected muscle cells from these effects of starvation.

Aging↗
PubMed1976

[Structure and cellular organization of the osphradium of Limnea stagnalis L].

Light microscopy was used to study the structure and cellular organization of the osphradial organ of the pulmonary mollusque L. stagnalis. The osphradium unites the epithelial canal and the ganglion consisting of two cell populations. On the internal surface of the V-shaped osphradial canal there are three zones of cells: secretory, villous and epithelial. The villous zone of the canal is related with sensory bipolar and multipolar neurons of the ganglion. The irritation percepted by these cells seems to be transferred through numerous zones of neuropile to large unipolar neurons of the ganglion cortical layer.

Animals↗