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At least 91 records · Page 5Linked to original sources
PubMed1982

Spindle microtubules and their mechanical associations after micromanipulation in anaphase.

Micromanipulation of living grasshopper spermatocytes in anaphase has been combined with electron microscopy to reveal otherwise obscure features of spindle organization. A chromosome is pushed laterally outside the spindle and stretched, and the cell is fixed with a novel, agar-treated glutaraldehyde solution. Two- and three-dimensional reconstructions from serial sections of seven cells show that kinetochore microtubules of the manipulated chromosome are shifted outside the confusing thicket of spindle microtubules and mechanical associations among microtubules are revealed by bent or shifted microtubules. These are the chief results: (a) The disposition of microtubules invariably is consistent with a skeletal role for spindle microtubules. (b) The kinetochore microtubule bundle is composed of short and long microtubules, with weak but recognizable mechanical associations among them. Some kinetochore microtubules are more tightly linked to one other microtubule within the bundle. (c) Microtubules of the kinetochore microtubule bundle are firmly connected to other spindle microtubules only near the pole, although some nonkinetochore microtubules of uncertain significance enter the bundle nearer to the kinetochore. (d) The kinetochore microtubules of adjacent chromosomes are mechanically linked, which provides an explanation for interdependent chromosome movement in "hinge anaphases." In the region of the spindle open to analysis after chromosome micromanipulation, microtubules may be linked mechanically by embedment in a gel, rather than by dynein or other specific, cross-bridging molecules.

Anaphase↗
PubMed2001

Monozygotic twinning after assisted reproductive techniques: a phenomenon independent of micromanipulation.

A 3 year retrospective analysis was conducted of pregnancies achieved after various assisted reproductive treatment modalities in our infertility practice, to calculate and compare the rates of monozygotic twinning (MZT). A total of 731 pregnancies achieved after various assisted reproduction treatments were reviewed. Gonadotrophin therapy for induction of ovulation and controlled ovarian hyperstimulation (COH) yielded 129 clinical pregnancies. Conventional IVF yielded 139 pregnancies. IVF and intracytoplasmic sperm injection (ICSI) with or without assisted hatching (AH) yielded 463 pregnancies, all during the same time period. The rates of multiple pregnancy (monozygotic and dizygotic) twins and triplets were recorded. MZT was found in 1.5% of ovulation induction or COH pregnancies (2/129). The incidence of MZT after conventional IVF was 0.72% (1/139). After IVF-ICSI/AH, MZT was found in 0.86% (4/463). The overall rate of MZT was 0.95% (7/731). Five cases were dizygotic triplets and two cases were monozygotic twins. We found the rate of MZT after assisted reproduction treatment increased more than two-fold over the background rate in the general population. Dizygotic triplets were found more often than monozygotic twins. The rate of MZT was consistently increased, irrespective of treatment modality or micromanipulation. This may signify that the aetiology of increased MZT after assisted reproduction is the gonadotrophin treatment rather than in-vitro conditions, micromanipulation, or multiple embryo transfer.

Adult↗
PubMed1963

TRANSFORMATION OF BACILLUS SUBTILIS TO MOTILITY AND PROTOTROPHY: MICROMANIPULATIVE ISOLATION OF BACTERIA OF TRANSFORMED PHENOTYPE.

Stocker, B. A. D. (Stanford Medical Center, Palo Alto, Calif.). Transformation of Bacillus subtilis to motility and prototrophy: micromanipulative isolation of bacteria of transformed phenotype. J. Bacteriol. 86:797-804. 1963.-A nonmotile (nonflagellated, fla(-)) try(-) strain of Bacillus subtilis was transformed to fla(+) and to try(+) by wild - type deoxyribonucleic acid (DNA) at comparable rates. Bacteria of fla(+) phenotype were recognized by their motility approximately 3 hr after uptake of DNA, and bacteria of try(+) phenotype at about the same time by their elongation into filaments in a medium lacking tryptophan. Of phenotypically transformed bacteria of each sort isolated by micromanipulation, the majority produced only transformed progeny, a mixture of transformed and untransformed, or a mixture of two kinds of transformant. Some produced only untransformed progeny, or progeny transformed only at a locus linked to that concerned in their phenotypic transformation. In a few clones, some partial heterozygotes were present even ten generations after DNA uptake. In nonmotile clones derived from motile isolates, the unilinear transmission of motility to one to four descendants was detected; it is attributed to persistence of a corresponding number of units of some product of an unincorporated fla(+) gene, probably flagella or cell walls each carrying several flagella. No pedigrees indicating unilinear transmission of an unincorporated fla(+) gene were observed.

Bacillus subtilis↗
PubMedDate not supplied

The impact of the measuring distance on laser-Doppler measurements of the microcirculation in human nasal mucosa. A study of rhinostereometry and micromanipulator-guided laser-Doppler flowmetry.

Fourteen healthy volunteers were examined using rhinostereometry (RSM) and micromanipulator-guided laser-Doppler flowmetry (LDF) on the inferior turbinate and nasal septum. There were significant differences of the flowmetry readings at different distances from the mucosal surface within 0-1.0 mm. Changes in LDF values due to a change in distance between probe and mucosa seem to be an important artefact that will influence the flowmetry, especially if the probe is fixed to the framework of the nose (i.e. the skull) and if the congestive status of the mucosa changes. This can be a problem especially during intranasal challenges with substances that influence congestion. These artefacts can be eliminated by using an RSM-guided micromanipulator that allows the probe to follow changes in congestion.

Adult↗
PubMedDate not supplied

Studies of spontaneous fluctuations in congestion and nasal mucosal microcirculation and the effects of oxymetazoline using rhinostereometry and micromanipulator guided laser Doppler flowmetry.

The mucosa of the inferior turbinate was studied using rhinostereometry and micromanipulator-guided laser Doppler flowmetry in 10 healthy volunteers. First, spontaneous fluctuations were studied measuring congestion and multiple microcirculatory parameters simultaneously every 2 minutes. The subjects were then challenged with oxymetazoline using the same measuring technique studying the effects of the challenge during 12 minutes. There were spontaneous variations in congestion of up to 2.1 mm and variations in perfusion from 38% to 175% of average. There was no correlation between congestion in itself, or change in congestion, to perfusion or any other microcirculatory parameter. After challenge with oxymetazoline there was a rapid decrease in perfusion at 3 minutes after which there were no significant changes. The congestion decreased gradually throughout the procedure. Because congestion reflects the filling of the venous sinusoids and the flowmetry the state of the superficial vessels, we conclude that there are spontaneous short-term fluctuations in the sympathetic tone with independent actions on the different vessels. After challenge with a sympathomimetic drug, there was a decrease in both swelling and flow, but not synchronized. The combination of rhinostereometry and micromanipulator-guided laser Doppler flowmetry is a useful tool to study the dynamics of intranasal challenge reactions.

Depression, Chemical↗
PubMed1991

Micromanipulation in a center for reproductive medicine.

Several variations of micromanipulation of the female gamete (zona drilling, zona cracking, ooplasmic sperm injection, partial zona dissection) have been applied recently to human IVF to overcome severe male factor. Of the first 16 cycles attempted using partial zona dissection, one pregnancy resulted leading to a normal term delivery. Careful removal of the coronal cells, as well as stepwise removal of sucrose postpartial zona dissection, will facilitate this procedure and greatly reduce potential damage to the oocyte by pH, mechanical, or thermal injury. Micromanipulation has become a routine service offered in our program in cases where the likelihood of a poor IVF outcome is either known or suspected, and also serves as a replacement for simple reinsemination in cases of failed fertilization.

Adult↗
PubMed1988

[A floating hydraulic micromanipulator for microelectrode research on brain neurons].

The article describes a simple floating hydraulic micromanipulator of original construction which works in positive-positive pressure and provides maximum stability of the microelectrode tip concerning the neuron in the moving brain. This work is achieved by fixing of the micromanipulator on the hinged suspension bracket and by setting of it on the surface of the object with the help of bearing site. Breathing and vascular brain moving don't influence the neuron activity lead.

Animals↗
PubMed1984

[Compact micromanipulator for the chronic extracellular recording of neuronal activity in restrained and freely moving animals].

A design of a compact micromanipulator giving possibility to introduce the microelectrode into unlimited depth of the brain and to realize the penetration of it into the narrow area of trepanized cranial of the animal several times has been worked out and described. Small size and mass of the design allow to set up several micromanipulators on the cranial of different experimental animals and to record the neuronal activity of the different brain structures simultaneously.

Animals↗
PubMed1993

Can severe male factor infertility be treated without micromanipulation?

OBJECTIVE: To present data on IVF in severe male factor infertility using modified IVF laboratory methods and to compare them with the reported data of gamete micromanipulation. DESIGN: Retrospective, not randomized. SETTING: University of California, Irvine, Center for Reproductive Health. PATIENTS: Seventy-one patients with severe oligoasthenozoospermia defined as total motile count in the pretreatment sample of < 5 x 10(6). Two groups were identified, group I with total motile count between 1.5 and 5 x 10(6) and group II with total motile count < 1.5 x 10(6). INTERVENTIONS: Treatment of the semen samples with mini-Percoll and the modification of standard IVF techniques. These modifications include insemination with larger numbers of sperm, the use of culture tubes for insemination of oocytes, and pooling oocytes together in one or more culture tubes. MAIN OUTCOME MEASURES: Fertilization and pregnancy rates (PRs). Additionally, the number of patients achieving cryopreservation and patients with previous failure to fertilize are specified. RESULTS: Eighty percent of the patients achieved fertilization with an overall rate of 38% per oocyte. Fifty-three ETs were performed and 23 clinical pregnancies (43% per transfer and 35% per cycle) were achieved. Fifty percent of the patients had excess embryos for cryopreservation. In group I the fertilization rate was 54% with a PR of 56% per transfer and 48% per cycle. In group II the fertilization rate was 25% with a PR per transfer of 32% and 24% per cycle. Of 28 patients who had previous failure of fertilization, 25 fertilized and 8 pregnancies were established. CONCLUSIONS: These data demonstrate that by the modification of standard laboratory methods for IVF, monospermic fertilization, cleavage, and a high clinical PR can be achieved in cases of severe male factor infertility without having to resort to micromanipulation.

Adult↗
PubMed1983

Motorized teleguided stereotactic micromanipulator for vitreous microsurgery.

A recently developed motorized stereotactic micromanipulator enhances the precision of the procedure, the comfort of the surgeon, and the safety of the patient during vitreous surgery. It can accommodate almost any type of vitreous surgical instrument by means of special adapters. The system is moved by the action of electrical motors remotely controlled by the surgeon operating a joystick on a separate control unit. Electrical reversal of motion, obtained by flipping a switch, allows observation through an altered version of the Panfundoscope that provides a 160 degrees inverted fundus view during all phases of the operation. In addition to improving many aspects of present vitreous surgical procedures, this stereotactic system may initiate the development of still finer surgical methods that cannot be performed with the free hand.

Fluorescein Angiography↗
PubMed2001

Indirect micromanipulation of single molecules in water-in-oil emulsion.

Based on real-time observation and micromanipulation, analytical methods for single DNA molecules have been under development for some time. Precise manipulation, however, is still difficult because single molecules are too small for conventional techniques. We have developed a chemical reaction system that uses water droplets in oil as containers of materials. The water droplets can be manipulated by optical force. The manipulation of the water droplets permits the fusion of two selected droplets. This process corresponds to mixing of different samples. We designate this system as "w/o (water-in-oil emulsion) microreactor system", and each droplet can be thought of as a "microreactor". In this system, single molecules can be manipulated readily, as a molecule can be contained in a microm-sized microreactor. The microreactor utilizes extremely small quantities of samples, therefore, reactions are rapid, as diffusion times in the microreactor are very short. The manipulation technique of the microreactors based on optical force has been applied to induce fusion between microreactors loaded with DNA and YOYO, a fluorescent dye that binds to DNA. This fusion induced a rapid binding of YOYO.

Benzoxazoles↗
PubMed2004

Mechanical properties of desiccated ragweed pollen grains determined by micromanipulation and theoretical modelling.

The mechanical properties of desiccated ragweed pollen grains were determined using a micromanipulation technique and a theoretical model. Single pollen grains with a diameter of approximately 20 microm were compressed and held, compressed and released, and compressed to rupture at different speeds between two parallel surfaces. Simultaneously, the force being imposed on the pollen grains was measured. It has been found that the rupture force of pollen grains increased linearly with their displacement at rupture on average, but was independent of their diameter. The mean rupture force was 1.20 +/- 0.03 mN, and mean deformation (the ratio between the displacement and diameter) at rupture was 22 +/- 0.6%. Single pollen grains were modeled as a capsule with a core full of air and a non permeable wall. A constitutive equation based on Hookean law was used to determine the mechanical property parameters Eh (product of the Young's modulus and wall thickness), and the mean value of Eh of desiccated pollen gains was estimated to be 1653 +/- 36 N/m.

Ambrosia↗
PubMed1995

Micromanipulation of statoliths in gravity-sensing Chara rhizoids by optical tweezers.

Infrared laser traps (optical tweezers) were used to micromanipulate statoliths in gravity-sensing rhizoids of the green alga Chara vulgaris Vail. We were able to hold and move statoliths with high accuracy and to observe directly the effects of statolith position on cell growth in horizontally positioned rhizoids. The first step in gravitropism, namely the physical action of gravity on statoliths, can be simulated by optical tweezers. The direct laser microirradiation of the rhizoid apex did not cause any visible damage to the cells. Through lateral positioning of statoliths a differential growth of the opposite flank of the cell wall could be induced, corresponding to bending growth in gravitropism. The acropetal displacement of the statolith complex into the extreme apex of the rhizoid caused a temporary decrease in cell growth rate. The rhizoids regained normal growth after remigration of the statoliths to their initial position 10-30 micrometers basal to the rhizoid apex. During basipetal displacement of statoliths, cell growth continued and the statoliths remigrated towards the rhizoid tip after release from the optical trap. The resistance to statolith displacement increased towards the nucleus. The basipetal displacement of the whole complex of statoliths for a long distance (>100 micrometers) caused an increase in cell diameter and a subsequent regaining of normal growth after the statoliths reappeared in the rhizoid apex. We conclude that the statolith displacement interferes with the mechanism of tip growth, i.e. with the transport of Golgi vesicles, either directly by mechanically blocking their flow and/or, indirectly, by disturbing the actomyosin system. In the presence of the actin inhibitor cytochalasin B the optical forces required for acropetal and basipetal displacement of statoliths were significantly reduced to a similar level. The lateral displacement of statoliths was not changed by cytochalasin B. The results indicate: (i) the viscous resistance to optical displacement of statoliths depend mainly on actin, (ii) the lateral displacement of statoliths is not impeded by actin filaments, (iii) the axially directed actin-mediated forces against optical displacement of statoliths (for a distance of 10 micrometers) are stronger in the basipetal than in the acropetal direction, (iv) the forces acting on single statoliths by axially oriented actin filaments are estimated to be in the range of 11-110 pN for acropetal and of 18-180 pN for basipetal statolith displacements.

Actins↗
PubMed1992

In vitro fertilization and gamete micromanipulation in the lowland gorilla.

PURPOSE: Our purpose was to utilize current reproductive technologies to treat an infertile female lowland gorilla. RESULTS: Following pituitary down-regulation with a gonadotropin releasing hormone agonist and follicular stimulation with human menopausal gonadotropins, transrectal ultrasound-guided aspiration of ovarian follicles yielded nine oocytes. Following failed fertilization with both epididymal and electroejaculated sperm, zona dissection and sperm injection were performed and produced one embryo, which was cryopreserved. Immature oocytes were obtained from ovarian sections and were either cultured in vitro or cryopreserved. CONCLUSIONS: This report demonstrates that in vitro fertilization techniques, including pituitary suppression, ultrasound-guided aspiration, micromanipulation, and cryopreservation, can be used to assist reproduction in the lowland gorilla.

Animals↗
PubMed1992

The YAG laser used in micromanipulation to transect the zona pellucida of hamster oocytes.

PROBLEM: Since there has been no reported use of the YAG laser to micromanipulate oocytes, our purpose was to study whether (1) a YAG laser could be used to open the zona pellucida of hamster oocytes; (2) human sperm could reach the ooplasm and (3) under sperm penetration assay conditions, sperm would bind and penetrate the ooplasm. RESULTS: A YAG 100 laser was used at 10 W and 0.4-sec pulse width to open eight of eight ooplasm oocytes. The opening in the zonae was 0.25 to 1.0 rad (10 to 40 microns). For the initial eight oocytes and two parallel controls, the coarse appearance of the ooplasm was unchanged after 3 days. Next, in 11 of 12 manipulated oocytes, the sperm clustered at the opening of the zona. When 16 more oocytes were opened and exposed to sperm in sperm penetration assay conditions, each ooplasm bound sperm. There was no penetration noted. Each manipulation time was < 1 min. To clarify the laser effect, oocytes were exposed to laser energy then utilized as the interactive surface in the sperm penetration assay. It was found that only 20% bound sperm with no penetration. CONCLUSION: While the time factor compares favourably with other methods of zona opening, further study needs to be performed to minimize effect to the exposed oocyte.

Animals↗
PubMed1997

Treatment variables in relation to oocyte maturation: lessons from a clinical micromanipulation-assisted in vitro fertilization program.

OBJECTIVE: In an effort to understand the mechanism underlying the improved pregnancy rate observed in IVF cycles when gonadotropin-releasing hormone analogues (GnRH-a) are applied, we investigated a possible relationship between treatment variables and oocyte nuclear maturity. DESIGN: Nuclear maturity was retrospectively assessed in cumulus-free, denuded oocytes, obtained from women undergoing micromanipulation-assisted IVF treatment following controlled ovarian hyperstimulation with GnRH-a and menotropins. SETTING: The setting was the infertility and IVF unit of a tertiary academic medical center. PARTICIPANTS: Two hundred twenty-one patients underwent 435 treatment cycles. MAIN OUTCOME MEASURE: This was the proportion of germinal vesicle-intact immature (GVII) oocytes. RESULTS: One hundred fifty-four of the 3520 oocytes studied (4.4%) were in the GVII stage. These oocytes were found in 66 of the treatment cycles (15.2%) and in 54 of the patients (24.4%). Cycles in which GVII oocytes were detected did not differ from those in which all the aspirated oocytes were mature in the following respects: patient age, type and duration of infertility, controlled ovarian hyperstimulation protocol and time of ovum pickup. However, the GVII group was characterized by a significantly higher peak estradiol level, as well as a higher number of mature follicles visualized sonographically (diameter, > 14 mm) and oocytes retrieved. CONCLUSIONS: Comparing the present findings with previously published data, it appears that the inclusion of GnRH-a in the stimulation regimen is associated with a lower proportion of immature oocytes. A higher occurrence of oocyte-nuclear immaturity is apparently associated with a significantly better ovarian response to stimulation. The high incidence of immature oocytes observed in patients with normospermic partners and low fertilization rates in previous cycles may suggest that the fertilization failure in some of these cases is due to oocyte, rather than sperm, dysfunction.

Adult↗
PubMed2005

An improved method for single cell isolation of prokaryotes from meso-, thermo- and hyperthermophilic environments using micromanipulation.

This study presents an improved system that enables isolation of single viable prokaryotic cells from a mixture of cells. The system is based on an inverted microscope, a microinjector and a micromanipulator. The isolated cell is captured in a microcapillary from a volume of 400 mul and transferred to an appropriate growth medium. Validation of the system was performed using two fluorescent strains: Pseudomonas putida expressing red fluorescent protein (DsRed), and Escherichia coli expressing green fluorescent protein (GFP). A mixture (100:1) of the constructed fluorescent strains was subjected to isolation experiments and nine out of ten individually isolated cells yielded axenic cultures of E. coli. Upon construction and validation, the system was used to isolate and subsequently cultivate axenic cultures of the thermophilic Archaeon Metallosphaera sedula and the hyperthermophilic Archaeon Sulfolobus solfataricus from enriched hot spring samples. The high efficiency of single-cell isolation and cultivation demonstrated over a range of temperatures-90% (30 degrees C), 85% (70 degrees C) and 95% (80 degrees C)-from different environments is probably due to the elimination of osmotic stress and limitation of temperature fluctuations during the isolation process, as a result of the large sample volume from which the cells are isolated.

Archaea↗