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At least 775 records · Page 43Linked to original sources
PubMed1990

Localization of calcium and microfilament changes in mechanically stressed cells.

We combined fluorescence labeling, digital image processing, and micromanipulation to investigate the intracellular events induced by inflicting a mechanical stress on rat basophilic leukemia cells. Our findings were as follows: 1. Most cells displayed a localized calcium rise in response to micropipet aspiration. This represented an average threefold increase as compared to resting level, and it was observed during the first 10 s following aspiration. A slow return to initial level occurred within about 3 min. Further, this calcium rise involved a mobilization of intracellular stores, since it was not prevented by adding a calcium chelator into the extracellular medium. 2. All micropipet-aspirated cells displayed a local accumulation of microfilaments, with a preferential localization in the cell protrusions or near the pipet tips. 3. No absolute correlation was found between the localization of calcium rise and cytoskeletal accumulation. 4. Cell deformability was decreased when intracellular calcium was maintained at a constant (high or low) level with ionomycin and/or EGTA. It is concluded that cells have a general ability to respond to mechanical stimulation by a coordinated set of events. More parameters must be studied before the mechanisms of cell shape regulation are fully understood.

Actin Cytoskeleton↗
PubMed2000

Dynamics of adhesive rupture between fibroblasts and fibronectin: microplate manipulations and deterministic model.

To characterize the dynamics of cell-substrate adhesive rupture, we used a novel micromanipulation technique, in which individual fibroblasts seized on a rigid microplate were placed into contact with a fibronectin-coated flexible microplate, then pulled away. The fibronectin density (0-3000 molecules/microm2) and the pulling rate (1-10 microm/s) were controlled. The extent of the contact zone decreased to zero at a time threshold corresponding to adhesive rupture. The uniaxial force at the interface, computed from the deflection of the microplate, increased linearly with time and reached a maximum before dropping to zero. A deterministic model, focusing on the mean number of bonds between fibronectin and its membrane receptor on the cell surface, shows rapid rupture when the force reaches a critical value, in agreement with experimental observations. Increasing the ligand density and the rate of load raises the maximal force (30 200 nN), in reasonably good agreement with the model predictions. Minimization of error between experimental and simulated forces allowed identification of two physicochemical properties of the bond, i.e. its association rate constant (k(2D)on = 3 x 10(-4) microm2/s) and structural length (d = 3 nm). These results may help understand better fibroblast locomotion and interaction with the extracellular matrix.

3T3 Cells↗
PubMed2002

[Development of a jet tracheoscope. Value and possible uses in superimposed high frequency jet ventilation in endoscopic surgery of the respiratory tract].

BACKGROUND AND OBJECTIVE: Tubeless jet-ventilation offers the surgeon an unimpaired surgical field and is therefore widely used in endolaryngeal surgery. In order to permit endotracheal surgery using the same devices and instruments as those used for the larynx, we have developed special jet-tracheoscopes. Here, we report on our experience with superimposed high-frequency jet-ventilation (SHFJV) together with total intravenous anaesthesia (TIVA) in endolaryngeal and especially endotracheal surgery. PATIENTS AND METHODS: The medical reports of 172 patients (91 females, 81 males) who had undergone endolaryngeal or endotracheal surgery in SHFJV were analysed retrospectively. RESULTS: Sufficient ventilation was possible in all cases and no vitally critical situation occurred. The main indication was laryngotracheal stenosis of different origins. No significant advantages could be observed in phonosurgery. There was no difficulty in exposing the endolarynx and subglottis with the currently available laryngoscopes (five sizes). The newly developed jet-tracheoscopes (two sizes) allowed a quick and safe extension of the operating field onto the tracheal bifurcation. CONCLUSIONS: SHFJV together with TIVA enlarges the diagnostic and therapeutic options in endoscopic surgery of the respiratory tract and is in many cases the precondition for endoscopic treatment without tracheotomy. In particular, the newly developed jet-tracheoscopes widen the spectrum of endoscopic surgery and allow the use of the micromanipulator guided CO2-laser in the trachea.

Adolescent↗
PubMed1997

[In vivo cochleoscopy through the round window].

The overall aim of the present investigation was to develop a technique for endoscopic investigation of the cochlea. In the experiments reported here, the possible effect of the endoscope-called the "cochleoscope"-on the electrophysiology of the cochlea was investigated by recording the cochlear action potential (CAP) threshold tuning curve from (0.1-34 kHz). The dorsolateral bulla of anesthesized guinea pigs (with ketamine 60 mg/kg and Rompun 12 mg/kg) was opened, after which the cochleoscope was introduced under micromanipulator control through the round window membrane. Three cochleoscopes were used and had diameters of 0.29 mm, 0.7 mm and 0.89 mm, respectively, containing 2000, 3000 and 3000 fibers each. Experiments in 7 animals showed that the cochleoscope did not influence CAP thresholds. Although the present resolution of the endoscopes is limited, the basilar membrane can be clearly distinguished from the osseous spiral lamina. It is anticipated that improved resolution will allow the cochleoscope to be used for diagnostic purposes in cases of sensorineural hearing loss.

Animals↗
PubMed1998

[The CO2 laser otoscope. A new application device for paracentesis].

The CO2 laser myringotomy is a current low-pain procedure for middle-ear ventilation for secretory otitis media (SOM) that can be performed under topical anesthesia, even in children. The duration of middle-ear ventilation is essentially determined by the size of the perforation created. Perforations with a diameter greater than 2 mm ventilate the tympanic cavity for approximately 3 weeks, thus avoiding tympanic ventilation tubes. To date, the CO2 laser beam can only be reliably applied to the tymapanic membrane via a micromanipulator system coupled to an ear microscope. The CO2 laser otoscope is a new application system that markedly reduces the technical complexity of surgery and improves the mobility and availability of the system. The incorporation of a small inexpensive CO2 laser in the otoscope represents a significant development in SOM therapy.

Animals↗
PubMed1997

[Specification of cell destiny in early Caenorhabditis elegans embryo].

Embryogenesis of the nematode Caenorhabditis elegans has been described completely on a cell-by-cell basis and found to be essentially invariant. With this knowledge in hands, micromanipulated embryos and mutants have been analyzed for cell lineage defects and the distribution of specific gene products. The results challenge the classical view of cell-autonomous development in nematodes and indicate that the early embryo of C. elegans is a highly dynamic system. A network of inductive events between neighboring cells is being revealed, which is necessary to assign different developmental programs to blastomeres. In those cases where molecules involved in these cell-cell interactions have been identified, homologies to cell surface receptors, ligands and transcription factors found in other systems have become obvious.

Animals↗
PubMed2004

Microdissection and molecular manipulation of single chromosomes in woody fruit trees with small chromosomes using pomelo (Citrus grandis) as a model. I. Construction of single chromosomal DNA libraries.

Construction of single chromosomal DNA libraries by means of chromosome microdissection and microcloning will be useful for genomic research, especially for those species that have not been extensively studied genetically. Application of the technology of microdissection and microcloning to woody fruit plants has not been reported hitherto, largely due to the generally small sizes of metaphase chromosomes and the difficulty of chromosome preparation. The present study was performed to establish a method for single chromosome microdissection and microcloning in woody fruit species using pomelo as a model. The standard karyotype of a pomelo cultivar ( Citrus grandis cv. Guanxi) was established based on 20 prometaphase photomicrographs. According to the standard karyotype, chromosome 1 was identified and isolated with fine glass microneedles controlled by a micromanipulator. DNA fragments ranging from 0.3 kb to 2 kb were acquired from the isolated single chromosome 1 via two rounds of PCR mediated by Sau3A linker adaptors and then cloned into T-easy vectors to generate a DNA library of chromosome 1. Approximately 30,000 recombinant clones were obtained. Evaluation based on 108 randomly selected clones showed that the sizes of the cloned inserts varied from 0.5 kb to 1.5 kb with an average of 860 bp. Our research suggests that microdissection and microcloning of single small chromosomes in woody plants is feasible.

Blotting, Southern↗
PubMedDate not supplied

Phylogenetic affiliation of the bacteria that constitute phototrophic consortia.

The phylogenetic affiliation of epibionts occurring in three morphologically distinct types of green-colored phototrophic consortia was investigated. Intact consortia of the types "Chlorochromatium aggregatum", "C. glebulum", and a third previously undescribed type, tentatively named "C. magnum" were mechanically separated from accompanying bacteria by either micromanipulation or by chemotactic accumulation in sulfide-containing capillaries. A 540-base-pair-long fragment of the 16S rRNA gene of the epibionts was amplified employing PCR primers specific for green sulfur bacteria. DNA fragments were separated by denaturing gradient gel electrophoresis and subsequently sequenced. The results of this phylogenetic analysis indicated that the symbiotic epibionts, together with only a few free-living strains, form a cluster within the green sulfur bacterial radiation which is only distantly related to the majority of known representatives of this phylum. Consortia with identical morphology but different origin exhibited significant differences in their partial 16S rRNA gene sequences, which could be confirmed by analysis of the 16S rRNA secondary structure. The phylogenetic affiliation of the chemotrophic central rod-shaped bacterium of "C. aggregatum" and "C. magnum" was analyzed by fluorescent in situ hybridization. According to our results and contrary to earlier assumptions, the central bacterium is a member of the beta-subgroup of the Proteobacteria.

Bacteria↗
PubMed2001

Diversification of the microtubule system in the early stage of eukaryote evolution: elongation factor 1 alpha and alpha-tubulin protein phylogeny of termite symbiotic oxymonad and hypermastigote protists.

The symbiotic protists of the lower termite have been regarded as a model of early-branched eukaryotes because of their simple cellular systems and morphological features. However, cultivation of these symbiotic protists is very difficult. For this reason, these interesting protists have not been well characterized in terms of their molecular biology. In research on these organisms which have not yet been cultivated, we developed a method for retrieving specific genes from a small number of cells, through micromanipulation without axenic cultivation, and we obtained EF-1 alpha and alpha-tubulin genes from members of the Hypermastigida--the parabasalid protist Trichonympha agilis and the oxymonad protists Pyrsonympha grandis and Dinenympha exilis--from the termite Reticulitermes speratus gut community. Results of phylogenetic analysis of the amino acid sequences of both proteins, EF-1 alpha and alpha-tubulin, indicate that the hypermastigid, parabasalid, and oxymonad protists do not share a close common ancestor. In addition, although the EF-1 alpha phylogeny indicates that these two groups of protists branched at an early stage of eukaryotic evolution, the alpha-tubulin phylogeny indicates that these protists can be assigned to two diversified clades. As shown in a recent investigation of alpha-tubulin phylogeny, eukaryotic organisms can be divided into three classes: an animal--parabasalids clade, a plant--protists clade, and the diplomonads. In this study, we show that parabasalids, including hypermastigids, can be classified as belonging to the animal--parabasalids clade and the early-branching eukaryote oxymonads can be classified as belonging to the plant--protists clade. Our findings suggest that these protists have a cellular microtubule system that has diverged considerably, and it seems that such divergence of the microtubule system occurred in the earliest stage of eukaryotic evolution.

Animals↗
PubMed2005

Alignment of biological microparticles by a polarized laser beam.

The optical alignment of biological samples is of great relevance to microspectrometry and to the micromanipulation of single particles. Recently, Bayoudh et al. (J. Mod. Opt. 50:1581-1590, 2003) have shown that isolated, disk-shaped chloroplasts can be aligned in a controlled manner using an in-plane-polarized Gaussian beam trap, and suggested that this is due to their nonspherical shape. Here we demonstrate that the orientation of various micrometer-sized isolated biological particles, trapped by optical tweezers, can be altered in a controlled way by changing the plane of linear polarization of the tweezers. In addition to chloroplasts, we show that subchloroplast particles of small size and irregular overall shape, aggregated photosynthetic light-harvesting protein complexes as well as chromosomes can be oriented with the linearly polarized beam of the tweezers. By using a laser scanning confocal microscope equipped with a differential polarization attachment, we also measured the birefringence of magnetically oriented granal chloroplasts, and found that they exhibit strong birefringence with large local variations, which appears to originate from stacked membranes. The size and sign of the birefringence are such that the resulting anisotropic interaction with the linearly polarized laser beam significantly contributes to the torque orienting the chloroplasts.

Animals↗
PubMed1995

[Hodgkin cells are clonal B-cells in various stages of differentiation].

Hodgkin's disease, especially its biology and pathogenesis, has been under discussion for more than 160 years. Numerous investigations have focused on the nature and clonality of Hodgkin cells, but so far no definitive answer have been yielded by immunohistochemistry, Southern blotting and PCR. However, the use of single-cell PCR has now made it possible to answer the question of the derivation of Hodgkin cells. Using a micromanipulator, Hodgkin cells can be picked out of histological sections and B-cell specific gene rearrangements (VDJ) can be amplified. With this technique it has proved possible to demonstrate the B-cell derivation of Hodgkin cells and their clonality. Mutated immunoglobulin genes in lymphocyte-predominant Hodgkin's disease indicate a germinal center cell origin of Hodgkin cells of this type. These findings, however, do not exclude cases of Hodgkin's disease with Hodgkin cells with a T-cell genotype.

Antigens, CD↗
PubMed1997

Analysis of VH gene rearrangements from synovial B cells of patients with rheumatoid arthritis reveals infiltration of the synovial membrane by memory B cells.

The VH gene (Variable gene segments of the heavy chain locus) repertoire can be investigated by DNA analysis of rearranged immunoglobulin VH genes, which also allows for an indirect estimation of antibody selection by analysis of somatic mutations. Using a polymerase chain reaction (PCR) it is also possible to analyse these genes in small numbers of cells or even single cells. This approach was chosen to investigate germinal centre like lymphocyte follicles in the synovial membranes of two patients with rheumatoid arthritis (RA) in order to analyse the local humoral immune response in RA. Individual B-cell aggregates of synovial membrane of two patients with RA were isolated by micromanipulation from microscopic slides. VH-DH-JH (variable, diversity, and joining segments of the heavy chain locus) rearrangements in all possible VH-JH combinations were amplified from these B cell foci, cloned and subjected to sequence analysis. Sequence analysis revealed that most of the rearranged VH genes were somatically mutated with at least 1% (range 1.3-14.9%) somatic mutations and therefore were derived from antigen-selected memory B cells. Intraclonal diversity in one-third of the clones indicated the generation of memory B cells in the synovial membrane and characterized the synovial membrane as lymphatic tissue where secondary immune responses to an as yet unknown antigen take place.

Adult↗
PubMed2006

Isolation of two populations of sperm cells from the pollen tube of Torenia fournieri.

The two sperm cells of Torenia fournieri are dimorphic. The dimorphic character suggests that they might be preferentially involved in fertilization during in vivo fusion with the egg cell and central cell. To probe the mechanism of preferential fertilization, it is necessary to use the most current molecular techniques. For this purpose, populations of >1000 individuals of the two dimorphic sperm cells, Sua (unassociated with the vegetative nucleus) and Svn (associated with the vegetative nucleus) were isolated from pollen tubes that had grown out of the cut ends of the styles. The two sperm cells released from pollen tubes remained attached to one another. When the two attached sperm cells were transferred into a solution containing 0.01% cellulose, 0.01% pectinase, and 5% mannitol, the connection between the two cells disappeared, and they were easily separated using a micromanipulator. The collection of these two individual populations containing over a thousand cells will permit research on gametic recognition at the molecular level.

Cell Adhesion↗
PubMed2003

[Impact of an Er:YAG laser beam control on cut quality of non-mechanical corneal trepanation for penetrating keratoplasty].

BACKGROUND: Results of non-mechanical corneal trepanation using the excimer laser enhance the morphological and functional results for penetrating keratoplasty. Searching for alternative laser sources we assessed the impact of an automatic laser beam control for the Er:YAG solid-state laser on the cut performance and thermal damage zone in non-mechanical corneal trepanation. METHODS: We compared the cut quality of A) a manually guided laser beam, B) a semiautomatically guided laser beam and C) a fully PC-controlled laser beam positioning system (q-switched, repetition rate 5 Hz, pulse energy 65 mJ, spot size 0.7 mm) along slit aperture masks on 28 rabbit eyes using macroscopic images and histological sections (PAS staining). RESULTS: The manually guided laser beam control (A) induced the broadest thermal damage zone in the corneal stroma (19.3+/-8.7 microm) compared to the semi-automatic mode (B) (8.8+/-3.0 microm, p=0.03) and the PC-controlled laser beam control (C) (7.0+/-3.0 microm, p=0.016). CONCLUSION: The fully automatic PC-controlled laser beam positioning system for the Er:YAG solid-state laser with a small spot size and fixed low repetition rate allows a precise laser beam guidance and a significant enhancement of the cut performance compared to a manual laser beam control via micromanipulator in experimental nonmechanical corneal trepanation.

Animals↗
PubMed2004

Frictional properties of contacting surfaces in the hemelytra-hindwing locking mechanism in the bug Coreus marginatus (Heteroptera, Coreidae).

The structure and function of the hemelytra-to-hindwing locking mechanism of the bug Coreus marginatus were analysed. The system consists of a cuticular protrusion in the ventral side of the hemelytra, which locks the subcostal border of the hindwing in flight. The speed and distance slid by both surfaces against one another during flight were assessed using a combination of high-speed video recordings and a 2D geometrical model. The friction coefficient between sliding surfaces was assessed using a micromanipulator, coupled with force transducers. This was done under three experimental conditions: freshly dissected, air dried and rehydrated ethanol preserved samples. The results showed a high speed of sliding, approximately 0.18 m s(-1), with a relatively low friction coefficient (0.2 micro). There was no evident difference in the friction measured under the various treatments, with the exception of the rehydrated condition, which was lower. The surface morphology of the wing locking mechanism, namely outgrowths of one part having rounded edges, and completely flat surface on the counterpart, effectively aids in the reduction of friction at the microscopic level. The structure is effective even dry, and after being preserved in ethanol, suggesting that no cuticle secreted lubrication substance is responsible for its effectiveness. The ultrastructure presumably confers mechanical stability to the system under the high load it is subjected to in flight.

Animals↗
PubMed2006

Endoscopic surgery for hypothalamic hamartomas causing medically refractory gelastic epilepsy.

INTRODUCTION: There is increasing evidence that removal or disconnection of hypothalamic hamartomas can lead to seizure control and improvement in behavior. The purpose of this study is to report our experiences with endoscopic removal of these hamartomas. METHODS: This is a prospective review of the early outcome of 44 patients undergoing endoscopic resection utilizing frameless stereotaxis and a micromanipulator. RESULTS: All patients had normal-sized ventricles. Complete removal was possible in 14 patients, 13 of whom were seizure free at follow-up. Four patients suffered complications that have persisted for more than 3 months: One had significant hemiparesis and three had persistent difficulties with short-term memory. Postoperatively, no patient suffered a permanent hormonal deficiency. In one patient who had undergone a previous attempt at transcallosal resection, the procedure was abandoned because of the lack of internal anatomic landmarks. In a second patient, insufficient mass could be removed due to the size of the lesion and the distorted anatomy. Consequently, 1 week later, the patient underwent a transcallosal approach. CONCLUSION: In appropriately selected patients, sessile hypothalamic hamartomas can be removed completely or they can be completely disconnected from the hypothalamus with an acceptable risk. At least a year after surgery is needed to evaluate the efficacy of the procedure in terms of control of seizures and improvements in behavior and emotional ability.

Adolescent↗
PubMed1999

Migration of virus-infected neuronal cells in cerebral slice cultures of developing mouse brains after in vitro infection with murine cytomegalovirus.

To investigate the effect of murine cytomegalovirus (MCMV) infection on the developing mouse brain in vitro, we developed an infection system using cerebral slice cultures. Using a micromanipulator, the cerebral slices from mouse embryos on day 18.5 of gestation were injected in the subventricular zone with recombinant MCMV in which the lacZ gene was inserted into a late gene, and were cultured for 7 days. Viral infection, detected by beta-galactosidase reaction, was developed at the injection sites of the slices. The virus-infected spots in the slices were enhanced by adding tumor necrosis factor-alpha to the medium and inhibited by adding phosphonoacetic acid or ganciclovir. Sections from paraffin-embedded slices were subjected to immunohistochemical analyses. Neuronal cells, labeled with 5-bromo-2-deoxyuridine 24 h before cutting the slices, migrated to the cerebral cortex in the slices. Virus-infected neuronal cells expressing only the early viral antigen migrated to the cortex, whereas glial cells expressing the immediate early and late antigens tended to remain at the injected sites. The neuronal migration of infected cells was not observed in the cerebral slices from 7-day-old mice and viral infection was not detected after injection in the cerebral slices from 14- and 21-day-old mice. These results from these cerebral slices may reflect the infectious dynamics in vivo, and this system may provide a useful model for analysis of disorders of brain development caused by CMV.

Animals↗
PubMed2004

New computer-guided scanner for improving CO2 laser-assisted microincision.

The objective was to clinically test a new computer-guided scanner designed for CO2 laser-assisted microincision. The scanner-assisted beam travels across the target as a straight or curved incision line. Line length and beam penetration can be adjusted. The studied population, 155 cases, encompassed benign lesions as well as early cancers of the larynx. Operating time was compared with that required for similar operations performed with the Acuspot micromanipulator. Laser-produced coagulation thickness at the incision was measured on 41 operative specimens. The scanner-assisted incision and dissection were more accurate and required up to 30% less time than with a manually guided beam. Postoperative follow-up was straightforward. The coagulation thickness was less than 10 microm for phonomicrosurgery and less than 20 microm for other surgical procedures. The scanner-assisted incision is more accurate than that attained manually.

Humans↗