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At least 1,783 records · Page 99Linked to original sources
PubMed2004

The dissipative contribution of myosin II in the cytoskeleton dynamics of myoblasts.

We have determined the microrheological response of the actin meshwork for individual cells. We applied oscillating forces with an optical tweezer to a micrometric bead specifically bound to the actin meshwork of C2 myoblasts, and measured the amplitude and phase shift of the induced cell deformation. For a non-perturbed single cell, we have shown that the elastic and loss moduli G' and G'' behave as power laws f (alpha) and f (beta) of the frequency f (0.01<f <50 Hz), alpha and beta being in the range 0.15-0.35. This demonstrates that the dissipation mechanisms in a single cell involve a broad and continuous distribution of relaxation times. After adding blebbistatin, an inhibitor of myosin II activity, the exponent of G' decreases to about 0.10, and G'' becomes roughly constant for 0.01<f<10 Hz. The actin meshwork appears less rigid and less dissipative than in the control experiment. This is consistent with an inhibition of ATPase and reduction of the gliding mobility of myosin II on actin filaments. In this frequency range, the actomyosin activity appears as an essential mechanism allowing the cell to adapt to an external mechanical stress.

Animals↗
PubMed2005

Acto-myosin cytoskeleton dependent viscosity and shear-thinning behavior of the amoeba cytoplasm.

The mechanical behavior of the human parasite Entamoeba histolytica plays a major role in the invasive process of host tissues and vessels. In this study, we set up an intracellular rheological technique derived from magnetic tweezers to measure the viscoelastic properties within living amoebae. The experimental setup combines two magnetic fields at 90 degrees from each other and is adapted to an inverted microscope, which allows monitoring of the rotation of pairs of magnetic phagosomes. We observe either the response of the phagosome pair to an instantaneous 45 degrees rotation of the magnetic field or the response to a permanent uniform rotation of the field at a given frequency. By the first method, we concluded that the phagosome pairs experience a soft viscoelastic medium, represented by the same mechanical model previously described for the cytoplasm of Dictyostelium discoideum [Feneberg et al. in Eur Biophys J 30(4):284-294 2001]. By the second method, the permanent rotation of a pair allowed us to apply a constant shear rate and to calculate the apparent viscosity of the cytoplasm. As found for entangled polymers, the viscosity decreases with the shear rate applied (shear-thinning behavior) and exhibits a power-law-type thinning, with a corresponding exponent of 0.65. Treatment of amoeba with drugs that affect the actin polymer content demonstrated that the shear-thinning behavior of the cytoplasm depends on the presence of an intact actin cytoskeleton. These data present a physiologic relevance for Entamoeba histolytica virulence. The shear-thinning behavior could facilitate cytoplasm streamings during cell movement and cell deformation, under important shear experienced by the amoeba during the invasion of human tissues. In this study, we also investigated the role of the actin-based motor myosin II and concluded that myosin II stiffens the F-actin gel in living parasites likely by its cross-linking activity.

Actins↗
PubMed1999

Recurrent failure of pronucleus formation after intracytoplasmic sperm injection.

We report on a couple with complete fertilization failure in three consecutive trials of intracytoplasmic sperm injection. Some of the unfertilized oocytes were fixed and decondensed sperm heads were found in all of them. It is not clear whether specific defects of the oocyte, abnormalities of sperm chromatin, or a combination of factors are responsible for the observed failure to develop pronuclei.

Adult↗
PubMed1997

Shared DNA sequences between the X and Y chromosomes in the tammar wallaby - evidence for independent additions to eutherian and marsupial sex chromosomes.

Marsupial sex chromosomes are smaller than their eutherian counterparts and are thought to reflect an ancestral mammalian X and Y. The gene content of this original X is represented largely by the long arm of the human X chromosome. Genes on the short arm of the human X are autosomal in marsupials and monotremes, and represent a recent addition to the eutherian X and Y. The marsupial X and Y apparently lack a pseudoautosomal region and show only end-to-end pairing at meiosis. However, the sex chromosomes of macropodid marsupials (kangaroos and wallabies) are larger than the sex chromosomes of other groups, and a nucleolus organizer is present on the X and occasionally the Y. Chromosome painting using DNA from sorted and microdissected wallaby X and Y chromosomes reveals homologous sequences on the tammar X and Y chromosomes, concentrated on the long arm of the Y chromosome and short arm of the X. Ribosomal DNA sequences were detected by fluorescence in situ hybridization on the wallaby Xp but not the Y. Since no chiasmata have been observed in marsupial sex chromosomes, it is unlikely that these shared sequences act as a pseudoautosomal region within which crossing over may occur, but they may be required for end-to-end associations. The shared region of wallaby X and Y chromosomes bears no homology with the recently added region of the eutherian sex chromosomes, so we conclude that independent additions occurred to both sex chromosomes in a eutherian and macropodid ancestor, as predicted by the addition-attrition hypothesis of sex chromosome evolution.

Animals↗
PubMed2006

Laser microdissection combined with immunohistochemistry on serial thin tissue sections: a method allowing efficient mRNA analysis.

Laser microdissection (LMD) with subsequent reverse transcription-PCR analysis is a powerful histochemical technique subserving the molecular characterization of specific cell types. We developed an efficient method for selective sampling of specific cell populations using immunohistochemistry coupled with LMD. The cerebral cortex of adult rats was cut into serial thin sections. Some sections were immunostained for parvalbumin. The adjacent sections were mounted on Cell Support Film for LMD and stained with neutral red. By comparison of the two adjacent sections, neuronal profiles representing parts of parvalbumin-immunopositive somata were identified in the neutral red-stained sections. These neuronal profiles were safely captured with LMD and analyzed on reverse transcription-PCR using extracted RNA. The method presented here can be applied to cell-type-specific characterizations using fixed cells under RNase-free conditions.

Animals↗
PubMed1997

Laser-assisted patch clamping: a methodology.

Laser microsurgery can be used to perform both cell biological manipulations, such as targeted cell ablation, and molecular genetic manipulations, such as genetic transformation and chromosome dissection. In this report, we describe a laser microsurgical method that can be used either to ablate single cells or to ablate a small area (1-3 microns diameter) of the extracellular matrix. In plants and microorganisms, the extracellular matrix consists of the cell wall. While conventional patch clamping of these cells, as well as of many animal cells, requires enzymatic digestion of the extracellular matrix, we illustrate that laser microsurgery of a portion of the wall enables patch clamp access to the plasma membrane of higher plant cells remaining situated in their tissue environment. What follows is a detailed description of the construction and use of an economical laser microsurgery system, including procedures for single cell and targeted cell wall ablation. This methodology will be of interest to scientists wishing to perform cellular or subcellular ablation with a high degree of accuracy, or wishing to study how the extracellular matrix affects ion channel function.

Cell Fusion↗
PubMed2002

Beta-catenin expression and allelic loss at APC in sporadic colorectal carcinogenesis.

beta-catenin is involved in E-cadherin-mediated cell adhesion, intracellular signal transduction, and also interacts with adenomatous polyposis coli (APC) protein. We previously found that 31% of colorectal adenomas and 84% of carcinomas showed reduced membranous staining of beta-catenin, while 46% of adenomas and 79% of carcinomas displayed beta-catenin nuclear expression. Importantly, a reciprocal relationship between reduced membranous and increased nuclear beta-catenin expression was demonstrated in the development from adenoma to carcinoma. To clarify whether this relates to an abnormality of the APC gene ( APC), we have now studied allele loss in microdissected tissues from 74 adenomas and 21 carcinomas (sporadic cases, previously immunostained for beta-catenin) by analysis of the microsatellites D5S346, D5S82 and D5S299. Fifty-five tumors (57.8%) showed allele loss at APC (no difference between adenomas and carcinomas). Thirty-one of these 55 (31/55, 56.4%) displayed both increased nuclear localization and reduced membranous staining of beta-catenin, and thirteen tumors (13/55, 23.6%) manifested either nuclear expression without changes in membranous expression or reduced membranous staining without nuclear expression (9 and 4 cases, respectively), while 11 (11/55, 20.0%) preserved normal membranous expression. Adenomas and carcinomas showing both nuclear and reduced membranous expression of beta-catenin, compared with those with normal membranous expression, tended to show allele loss ( P<0.01). In addition, 24 (24/95, 25.6%) tumors showed a change in the pattern of beta-catenin expression, but did not exhibit allele loss. These results suggest that although there may be a number of mechanisms responsible for changes in beta-catenin expression in colorectal tumors, dysfunction of APC may be the major cause of this phenomenon.

Adenoma↗
PubMed2002

Immunohistomorphologic and molecular cytogenetic analysis of a carcinosarcoma of the urinary bladder.

Carcinosarcomas of the urinary bladder are malignant biphasic tumors with an epithelial and a spindle cell component. For the histogenesis of the two components, a biclonal and a monoclonal origin are discussed. We present the immunomorphology and molecular cytogenetics of such a case. The immunohistology of biopsies of the urinary bladder revealed a poorly differentiated urothelial carcinoma (GIII) and a co-existing pleomorphic, spindle cell leiomyosarcoma (GIII). The two components were microdissected and further analyzed for gains and losses of chromosomal material using comparative genomic hybridization. In addition, loss of heterozygosity analyses were included. The tumor components revealed as overlapping core aberrations losses on the short arm of chromosome 9 and on the long arm of chromosome 11. However, both components showed additional aberrations exclusively detected in one of the components. The occurrence of overlapping aberrations strongly argues for a monoclonal origin of this tumor with a common ancestor. The additional aberrations of the components point to an independent and divergent course of tumor progression in both components.

Aged↗
PubMed2002

Detection of gene expression of vascular endothelial growth factor and flk-1 in the renal glomeruli of the normal rat kidney using the laser microdissection system.

The recent development of the laser microdissection (LMD) technique enables one to target particular tissues or cells for gene or protein analyses. The purpose of this study was to detect local mRNA expression of vascular endothelial growth factor (VEGF) and its receptor, flk-1, in the glomeruli of normal rat kidneys using the LMD system. Frozen sections of the kidney of 8-week-old male Wistar rats were made. The glomeruli were dissected from the frozen sections with the LMD system, and total RNA was extracted from 200 glomeruli in each kidney. Reverse-transcription polymerase chain reaction (RT-PCR) revealed the local mRNA expression of three isoforms of VEGF, flk-1 and GAPDH in the glomeruli. Moreover, the real-time PCR was performed to evaluate the experimental condition for quantification of VEGF and flk-1 mRNA expression using this system, and the results showed that at least 10 glomeruli might be needed for quantifying local VEGF mRNA expression. However, cDNA from 200 glomeruli was not enough for quantitative evaluation of flk-1 mRNA with this system. These results demonstrate the reproducibility of the analysis of mRNA expression in the renal glomeruli using the LMD system and also suggest that the application of the LMD technique will provide information to further our understanding of the mechanisms involved in kidney diseases.

Angiogenesis Inducing Agents↗
PubMed2001

Estrogen receptor-alpha and C-ERBB-4 expression in breast carcinomas.

The presence of estrogen receptors (ERs) in breast carcinomas is important for clinical response to endocrine therapy. However, the cellular mechanisms following ER activation are not fully understood. It has been indicated that expression of the ER is associated with the expression of c-erbB-4. To address this question, 103 breast carcinoma samples were studied using reverse transcriptase polymerase chain reaction (RT-PCR) analysis after application of a microselection method for RNA isolation. Total RNA for RT-PCR was isolated from 20-microm-thick frozen sections, which were made from microselected areas. Paraffin blocks from 98 of these 103 tumors were also immunohistochemically examined. Significant associations between ER-alpha and c-erbB-4 mRNA and protein expressions were found in the present study with both methods. One-fourth of the tumors did not express ER-alpha (22%, 24%, and 26% with chemical binding, immunohistochemistry, and RT-PCR, respectively). About one-half of the ER-alpha negative tumors did not express c-erbB-4 on both mRNA and protein levels (48% with RT-PCR and 46% with immunohistochemistry, P=0.001 for both methods). The endocrine therapy responsive breast cancer cell lines MCF-7 and T47-D were positive for both ER-alpha and c-erbB-4 expression, while the endocrine therapy nonresponsive breast cancer cell lines MDA-MD-231 and SK-BR-3 were not. Thus, we confirm the association between the expression of ER-alpha and c-erbB-4 mRNA and protein in breast carcinomas, indicating a role for c-erbB-4 in estrogen signal transduction.

Breast Neoplasms↗
PubMed2001

Identification of syt-ssx fusion transcripts in both epithelial and spindle cell components of biphasic synovial sarcoma in small tissue samples isolated by membrane-based laser microdissection.

In order to confirm the presence of SYT-SSX fusion gene in epithelial and spindle cell components of synovial sarcoma, we performed a nested reverse transcriptase-polymerase chain reaction (RT-PCR) using microbeam microdissection of membrane-mounted native tissue (MOMeNT) technique applied on formalin-fixed, paraffin-embedded tumor specimens from two biphasic synovial sarcomas and a control tissue of adamantinoma. Small targeted portions of either an epithelial or spindle cell component of the tumor tissue were microdissected together with the supporter membrane, by using an ultraviolet (337-nm) pulsed laser microbeam coupled into a robot-stage microscope with infinity optics. The SYT-SSX fusion transcript was detected in epithelial and spindle cell components of both biphasic synovial sarcomas, but not in the control tissue. Southern blot analysis also confirmed that the detected messages were derived from the SYT-SSX fusion gene. In conclusion, the microbeam MOMeNT is a useful method for isolating selected small portions from tissue sections. The SYT-SSX fusion gene is present in both cellular components of biphasic synovial sarcoma and is involved in oncogenesis of the synovial sarcoma rather than in morphologic epithelial differentiation. Therefore, in spite of the variable proportions of each component, our results confirm that the synovial sarcoma is of monoclonal origin.

Adult↗
PubMed2001

Piffalls in diagnostic molecular pathology--significance of sampling error.

Today, molecular diagnostic tests are widely used in clinical medicine with polymerase chain reaction (PCR)-based techniques being of particular interest. In tissue specimens, however, false-positive and false-negative results can be obtained if pathomorphological and processing aspects are not considered. We therefore studied the impact of tissue sampling in three widely used diagnostic tests: (1) assessment of clonality in B-cell non-Hodgkin's lymphoma, (2) analysis of microsatellite instability (MSI) in colorectal neoplasia, and (3) demonstration of mycobacterium tuberculosis. Tissue sections of routinely formalin-fixed and paraffin-embedded diagnostic specimens were taken, and the significance of sampling was systematically investigated using laser microdissection or processing of the entire section. PCR analyses were done according to standard protocols. False-positive pseudo-monoclonality was obtained in small gastrointestinal biopsies and in laser microdissected lymph follicles of non-neoplastic tonsils. False negativity (pseudo-stability) could be demonstrated in a case with hereditary rectal adenoma if whole tissue sections were taken without microdissection of the most dysplastic subareas. Demonstration of mycobacteria failed in tissue sections of a formalin-fixed lymph node that was positive after complete digestion or in fresh frozen material of the same patient. In diagnostic molecular pathology, sampling error is an important source of false-positive and false-negative results, particularly if disease- and tissue-specific morphological features, such as sample size, type of fixation, and intralesional heterogeneity, are ignored.

Clone Cells↗
PubMed2002

Oligoclonality of a "composite" gastric diffuse large B-cell lymphoma with areas of marginal zone B-cell lymphoma of the mucosa-associated lymphoid tissue type.

We analyzed a case of oligoclonal Helicobacter pylori-associated, primary gastric diffuse large B-cell lymphoma (DLBCL) with areas of extranodal marginal zone B-cell lymphoma (MZBL) of mucosa-associated lymphoid tissue (MALT) type in a 61-year-old male patient. The patient had two separate tumors, in the corpus and in the antrum, each showing two morphologically distinct components (DLBCL and MZBL of MALT type). To determine the clonal relationship between the large- and small-cell components, we microdissected four samples from morphologically distinct tumor components at both tumor sites. PCR analysis revealed rearranged immunoglobulin heavy chain (IgH) genes of different sizes in three of the four microdissected samples. Cloning and sequencing of the PCR products displayed different IgH gene rearrangements in the two small cell components of the antrum and the corpus. A third genuinely differently rearranged IgH gene was found in the large-cell components of both antrum and corpus. Our results suggest that in primary gastric DLBCL with areas of MZBL of MALT type, the small-cell component may comprise more than one tumor clone. Furthermore, the large-cell component may evolve independently from coexisting MZBL.

Amino Acid Sequence↗
PubMed2001

Beta-catenin mutations in sporadic fundic gland polyps.

Fundic gland polyp (FGP) is the most common gastric polyp. It occurs sporadically or in association with familial adenomatous polyposis (FAP). FAP patients carry germline mutations of the adenomatous polyposis coli (APC) gene, and previous studies have revealed frequent somatic mutations of the APC gene in FGPs associated with FAP. Although inactivation of the APC gene contributes to histogenesis of FGPs associated with FAP, this rarely happens in sporadic cases. Loss of the APC gene promotes abnormal accumulation of beta-catenin, and mutation of GSK-3 beta phosphorylation sites in the beta-catenin gene can have a similar effect. To elucidate the contribution of beta-catenin gene mutation to the histogenesis of sporadic FGP, we analyzed beta-catenin gene mutation in exon 3 in 45 FGP lesions obtained from 35 patients. Somatic mutations were found in 29 lesions: 28 were missense mutations and one was an in-frame deletion. All of the missense mutations were confined to the former two serine residues of the GSK-3 beta phosphorylation sites and their flanking residues (codons 32, 33, 34, 37). Analysis in cases with multiple FGPs revealed a different mutation in each lesion, indicating their multicentric origin. Therefore, a significant proportion of sporadic FGPs have genetic alterations involving beta-catenin stabilization, as did FAP-associated FGPs.

Adult↗
PubMed2001

Cell surface events during resealing visualized by scanning-electron microscopy.

The function of exocytosis during plasma membrane resealing might be to facilitate the flow of surface lipid over the disruption site and/or to add defect-spanning "patches" of internal membrane across it. Scanning-electron-microscopic visualization of large plasma membrane disruptions in sea urchin eggs is here used to distinguish between these two possibilities. Disruptions were induced by shear stress in the presence and absence of resealing-permissive levels of external Ca2+, and the eggs were fixed at various intervals thereafter for microscopic processing. In eggs fixed immediately (<1 s) after shearing in the absence of Ca2+, a condition which prevents resealing, disruption sites were filled with a uniform population of spherical vesicles (approximately 1 microm in diameter). In eggs fixed immediately after shearing at a resealing-permissive level of Ca2+, disruption sites were filled with a highly heterogeneous population of enlarged vesicles, some being more than 10 microm in diameter and many having irregular profiles and/or appearing to be joined to one another. In eggs fixed 2 s or 5 s post-shearing, the continuity of these large vesicles with one another and the surface membrane began to obscure individual vesicle identities. Single "apertures" of discontinuity over disruption sites, the predicted morphology of a flow-based resealing mechanism, were not observed at any time point (1-5 s) during the interval required for completion of resealing. These observations provide strong confirmation that "patching" of large disruptions mediates their resealing.

Animals↗
PubMed2004

A new molecular biology approach in morphology: basic method and application of laser microdissection.

Our understanding of the role played by specific genes in various diseases is advanced as elucidation of the human genome progresses. One important step in this process is profiling gene expression so as to understand the roles of specific genes and the role of the translated protein. Profiling of the gene should also include tissue generation and an explanation of the mechanism of the disease. A useful technique in achieving this goal is the laser microdissection (LMD) method, which can draw genetic information from tissues of individual patients. We describe herein our technique using a special film which we developed and laser microdissection by the Palm Co. With this LMD method, RNA was extracted from carcinoma tissue and genetic analysis was carried out. LMD is equivalent to pathological diagnosis, and it is necessary to do dissection for accurate diagnosis. It seems to make clear gene pathological diagnosis possible in the future.

Gene Expression Profiling↗
PubMedDate not supplied

Small round cell tumor with biphenotypic differentiation and variant of t(21;22)(q22;q12).

A 14-year-old boy presented with a soft tissue swelling on the outer aspect of his left upper arm. Examination of the tumor by light microscopy showed a small round cell tumor with a rare focus of myogenic differentiation. Myogenic differentiation was confirmed on ultrastructural examination by immunohistochemistry and reverse transcriptase polymerase chain reaction (RT-PCR). Conventional G-banding and fluorescent in situ hybridization (FISH) demonstrated a complex variant of t(21;22)(q22;q12). By RT-PCR, the EWS-ERG fusion transcript was defined as type 9e. This tumor was unusual in that it showed characteristics of myogenic and neural differentiation, and contained a rearrangement of the EWS gene consistent with a diagnosis of Ewing's sarcoma. This supports the hypothesis that a class of biphenotypic childhood sarcomas, with features of myogenic and neural differentiation, exists that may be related to the Ewing's sarcoma family of tumors.

Adolescent↗