Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “MICROMANIPULATION”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 307 records · Page 17Linked to original sources
PubMed1998

[Microsurgery and micromanipulation in the treatment of male infertility: results of a one-year investigation].

A one-year study of 51 infertile couples, 47 couples evaluated--25 cases of testicular azoospermia and 22 cases of obstructive azoospermia. The mean age of the men in the group is 33 years (22-48 years). The follow-up period is 1-18 months. In 17 instances microsurgical epididymal sperm aspiration--MESA was made, five times testicular sperm aspiration--TESA and in 25 men testicular sperm extraction--TESE was used. In the group with testicular azoospermia it proved possible to obtain sperm in 12/25 cases, i.e. in 48%. In men with obstructive azoospermia all aspirations were successful, i.e. the yield was 100%. In this group five infants were born, another seven pregnancies are under way. Thus regardless of the etiology of male infertility 12/47 cases, i.e. 25.5%, were successfully resolved. When using differentiated evaluation of the two groups the results are as follows: in the group with testicular azoospermia one infant were born and five pregnancies are under way, i.e. 40.9%.

Adult↗
PubMed1998

Laser micromanipulation systems as universal tools in cellular and molecular biology and in medicine.

The UV-laser microbeam has been established as a valuable tool in a wide area of molecular biology as well as in medical research and applications. This system allows to cut or fuse microscopically small specimen. An important application of the cutting laser is laser microbeam microdissection (LMM) combined with laser pressure catapulting (LPC), which allows to procure single cells or small homogeneous cell areas for subsequent molecular analysis in an entirely "non-contact" manner. With LMM minute tissue areas, single cells or chromosomes are microdissected and separated from their surroundings. Subsequently, LPC ejects the dissectates directly into the cap of a sample tube without any mechanical contact. This enables the rapid procurement of homogeneous specimen from less than one up to several hundreds of micrometers in diameter without encroachment of the adjacent region. The mRNA information of the selected specimen as well as of the remaining probe are well preserved, as demonstrated with laser isolated samples from a routinely prepared tissue section of a differentiated colorectal adenocarcinoma. Reverse transcription of specific mRNA coding for cytoplasmic beta-actin and subsequent hemi-nested PCR amplification was not impaired. Any kind of tissue, as well as single cells from different sources and even subcellular structures can be captured using this laser method. Wherever homogeneous samples are required to analyze cell or chromosome-specific genetic alterations such as in cancer research or prenatal diagnosis this unique and rapid laser micropreparation method will become a key technology of great value.

Adenocarcinoma↗
PubMed1999

Flagellar arrest behavior predicted by the Geometric Clutch model is confirmed experimentally by micromanipulation experiments on reactivated bull sperm.

The central tenet of the Geometric Clutch hypothesis of flagellar beating is that the internal force transverse to the outer doublets (t-force) mediates the initiation and termination of episodes of dynein engagement. Therefore, if the development of an adequate t-force is prevented, then the dynein-switching necessary to complete a cycle of beating should fail. The dominant component of the t-force is the product of the longitudinal force on each outer doublet multiplied by the local curvature of the flagellum. In the present study, two separate strategies, blocking and clipping, were employed to limit the development of the t-force in Triton X-100 extracted bull sperm models. The blocking strategy used a bent glass microprobe to restrict the flagellum during a beat, preventing the development of curvature in the basal portion of the flagellum. The clipping strategy was designed to shorten the flagellum by clipping off distal segments of the flagellum with a glass microprobe. This limits the number of dyneins that can contribute to bending and consequently reduces the longitudinal force on the doublets. The blocking and clipping strategies both produced an arrest of the beat cycle consistent with predictions based on the Geometric Clutch hypothesis. Direct comparison of experimentally produced arrest behavior to the behavior of the Geometric Clutch computer model of a bull sperm yielded similar arrest patterns. The computer model duplicated the observed behavior using reasonable values for dynein force and flagellar stiffness. The experimental data derived from both blocking and clipping experiments are fully compatible with the Geometric Clutch hypothesis.

Animals↗
PubMed1997

Micromanipulation of chromosomes in mitotic vertebrate tissue cells: tension controls the state of kinetochore movement.

In mitotic vertebrate tissue cells, chromosome congression to the spindle equator in prometaphase and segregation to the poles in anaphase depend on the movements ofkinetochores at their kinetochore microtubule attachment sites. To test if kinetochores sense tension to control their states of movement poleward (P) and away from the pole (AP), we applied an external force to the spindle in preanaphase newt epithelial cells by stretching chromosome arms with microneedles. For monooriented chromosomes (only one kinetochore fiber), an abrupt stretch of an arm away from the attached pole induced the single attached kinetochore to persist in AP movement at about 2 microm/min velocity, resulting in chromosome movement away from the pole. When the stretch was reduced or the needle removed, the kinetochore switched to P movement at about 2 microm/min and pulled the chromosome back to near the premanipulation position within the spindle. For bioriented chromosomes (sister kinetochores attached to opposite poles) near the spindle equator, stretching one arm toward a pole placed the kinetochore facing away from the direction of stretch under tension and the sister facing toward the stretch under reduced tension or compression. Kinetochores under increased tension exhibited prolonged AP movement while kinetochores under reduced tension or compression exhibited prolonged P movement, moving the centromeres at about 2 microm/min velocities off the metaphase plate in the direction of stretch. Removing the needle resulted in centromere movement back to near the spindle equator at similar velocities. These results show that tension controls the direction of kinetochore movement and associated kinetochore microtubule assembly/disassembly to position centromeres within the spindle of vertebrate tissue cells. High tension induces persistent AP movement while low tension induces persistent P movement. The velocity of P and AP movement appears to be load independent and governed by the molecular mechanisms which attach kinetochores to the dynamic ends of kinetochore microtubules.

Animals↗
PubMed2000

Pulling chromatin fibers: computer simulations of direct physical micromanipulations.

A low-resolution molecular model, which combines the known mechanical properties of protein-free DNA with the accumulating picture of chromatosome structure, has been developed to account for the stretching of single chromatin fibers by an imposed external force. Force-extension characteristics of sets of chains accumulated by Monte Carlo sampling are consistent with recently observed findings in the non-destructive regime (<20 pN imposed force), where the structure of the chromatosome remains intact. The correspondence between simulation and the relaxation phase of the experiment limits the equilibrium entry-exit angle of linker DNA on the chromatosome to W=50(+/-10) degrees and the effective DNA linker length to L(eff)=40(+/-5) bp. The computed force-extension characteristics are relatively insensitive to other parameters of the model, precluding their accurate estimation. The introduction of an attractive potential between closely spaced nucleosomes reproduces the added initial resistance of single fibers to extension at high salt conditions. The consideration of elastic linkers also improves the fitting of assorted classical measurements of unstressed chromatin structure in solution. The overall picture of chromatin that emerges is an irregular, fluctuating, three-dimensional, zig-zag structure with intact, mechanically stable chromatosome units and deformable linkers. The modeled fiber undergoes large-scale configurational rearrangements without significant perturbation of the constituent chromatosome beads, collapsing into a highly condensed form in response to small (<2kT) inter-nucleosomal attractions.

Calibration↗
PubMed1996

Use of the CO2-laser micropoint micromanipulator for the treatment of laryngomalacia.

Between September 1989 and June 1994, 21 children (17 boys, 4 girls) with moderate to severe symptoms due to laryngomalacia underwent endoscopic surgery using the CO2-laser micropoint manipulator (shot-by-shot, 0.1 s, super-pulse, 2-3 W power; 280 microns beam; 400 mm working distance). Mean age of the children was 5 months (range, 1-11 months). The procedure was performed under high-frequency jet ventilation and consisted in the resection and/or vaporization of the aryepiglottic folds. This tissue removal could be extended to the laryngeal mucosa of the arytenoids and the lateral edge of the epiglottis. Results of surgery were excellent with normalization (8 patients) or, at worst, a very definite improvement of symptoms (4 patients). Furthermore, no complications occurred due to the technique used. These results have convinced us that the CO2-laser micropoint manipulator technique, with the "super-pulse" shooting mode and high-frequency jet ventilation, is by far superior to microsurgery with cold instruments when endoscopic treatment of laryngomalacia is indicated.

Endoscopy↗
PubMed1996

Could in vitro fertilization with a modified sperm preparation technique be an option to micromanipulations?

PURPOSE: This study evaluated the efficiency of in vitro fertilization with a modified sperm preparation technique for male infertility, to avoid systematic recourse to ICSI. METHODS: The sperm function stimulants pentoxifylline, 2-deoxyadenosine, and follicular fluid were used during the sperm preparation of IVF trials for two groups of patients: couples with long-standing infertility and previous IVF failures and couples with male-factor infertility scheduled for their first treatment. RESULTS: Forty-nine attempts were performed in the first group. The overall fertilization rate (percentage of zygotes with two pronuclei 18 hr after sperm insemination) was 30% and the clinical pregnancy rate per transfer was 33%. For the second group, 30 attempts were performed. The fertilization rate was 29.6% and the clinical pregnancy rate was 62.5% per transfer. The total number of recovered motile sperm appears to be a significant parameter: a cutoff value of 0.25 million motile sperm recovered after capacitation treatment has a good prognostic value for choosing between IVF with sperm enhancers and ICSI. CONCLUSIONS: The described modified IVF could constitute an alternative to the systematic use of ICSI.

Adult↗
PubMed1987

Analysis of cell structural and functional diversity by combination of micromanipulation and microfluorimetry.

Fluorescent molecules are widely used to study quantitative cell properties, such as density of different antigenic markers or membrane responses to various stimuli. In most cases, studies are done on bulk cell populations with a spectrofluorimeter or at the single cell level with a cytofluorograph. However, only microspectrofluorimetric techniques allow continuous recording of dynamic events undergone by individual cells. The aim of the present report was twofold: first, to describe a methodology easily accessible to cell biologists that allows simultaneous manipulation of single cells and measurements of their fluorescence properties; and second, through this methodology to study quantitative aspects of cell structure and function such as binding of a fluorescein-labeled lectin, transfer of fluorescent molecules between labeled and unlabeled cells brought in close contact, or fluorescence response of individual cells stimulated after being loaded with a potential-sensitive dye. We conclude that the understanding of many aspects of cell structure and behavior requires that individual cells be studied under dynamic conditions and for prolonged periods of time.

Animals↗
PubMed1991

Micromanipulation of mitotic chromosomes in PTK2 cells using laser-induced optical forces ("optical tweezers").

To study the potential use of optical forces to manipulate chromosome movement, we have used a Nd:YAG laser at a wavelength of 1.06 microns focused into a phase contrast microscope. Metaphase and anaphase chromosomes were exposed while being monitored by video microscopy. The results indicated that when optical forces were applied to late-moving metaphase chromosomes on the side closest to the nearest spindle pole, the trapped chromosomes initiated movement to the metaphase plate. The chromosome velocities were two to eight times the normal rate depending on the chromosome size, geometry, and trapping site. At the initiation of anaphase, a pair of chromatids could be held by the optical trap and kept motionless throughout anaphase while the other pairs of chromatids separated and moved to opposite spindle poles. As a result, the trapped chromosome either was incorporated into one of the daughter cells or was lost in the cleavage furrow, or the two chromatids eventually separated and moved to their respective daughter cells. If the trap was removed at the beginning of anaphase B, the chromosome moved back to the poles. Our experiments demonstrate that the laser-induced optical force trap is a potential new technique to study noninvasively the mitotic spindle of living cells.

Analysis of Variance↗
PubMed1987

The in vitro exposure to bovine rhinotracheitis virus of zona pellucida-micromanipulated bovine embryos with the zona pellucida damaged or removed.

One hundred and eighty-five embryos were collected from 29 superovulated donors 6 to 8 d post estrus. The zona pellucida (ZP) of these embryos was either cracked, removed mechanically or removed with acidified Tyrode's solution, or left intact. Forty-eight of 103 (47%) ZP-cracked and ZP-free embryos, exposed for 24 h to infectious bovine rhinotracheitis virus (IBRV), survived. No significant difference was found in the embryonic survival of the ZP-cracked embryos exposed to IBRV and control embryos not exposed to IBRV. However, there was a significant (P < 0.001) difference in the survival of ZP-free embryos exposed to IBRV and ZP-free embryos not exposed to IBRV (30% vs 80%).

Journal Article↗