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Biomedical subjects

W H Wright

Publications and source records attributed to W H Wright.

12 recordsLinked to original sources
PubMed1992

Optical trapping in animal and fungal cells using a tunable, near-infrared titanium-sapphire laser.

We have compared two different laser-induced optical light traps for their utility in moving organelles within living animal cells and walled fungal cells. The first trap employed a continuous wave neodymium-yttrium aluminum garnet (Nd-YAG) laser at a wavelength of 1.06 micron. A second trap was constructed using a titanium-sapphire laser tunable from 700 to 1000 nm. With the latter trap we were able to achieve much stronger traps with less laser power and without damage to either mitochondria or spindles. Chromosomes and nuclei were easily displaced, nucleoli were separated and moved far away from interphase nuclei, and Woronin bodies were removed from septa. In comparison, these manipulations were not possible with the Nd-YAG laser-induced trap. The optical force trap induced by the tunable titanium-sapphire laser should find wide application in experimental cell biology because the wavelength can be selected for maximization of force production and minimization of energy absorption which leads to unwanted cell damage.

Aluminum Oxide↗
PubMed1991

Laser induced cell fusion in combination with optical tweezers: the laser cell fusion trap.

A single-beam gradient force optical trap was combined with a pulsed UV laser microbeam in order to perform laser induced cell fusion. This combination offers the possibility to selectively fuse two single cells without critical chemical or electrical treatment. The optical trap was created by directing a Nd:YAG laser, at a wavelength of 1.06 microns, into a microscope and focusing the laser beam with a high numerical aperture objective. The UV laser microbeam, produced by a nitrogen-pumped dye laser (366 nm), was collinear with the trapping beam. Once inside the trap, two cells could be fused with several pulses of the UV laser microbeam, attenuated to an energy of approximately 1 microJ/pulse in the object plane. This method of laser induced cell fusion should provide increased selectivity and efficiency in generating viable hybrid cells.

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↗
PubMed1991

Micromanipulation of gametes using laser microbeams.

Various microsurgical procedures at the cellular and subcellular levels using laser non-touch techniques are presented and reviewed. In these procedures, the beams of light, varying in their wavelength (range: 14 ns to continuous wave), were directed via microscopes towards the target area. Micromanipulation of human spermatozoa with a laser-generated optical trap enabled the assessment of possible effects on sperm motility and measurements of the relative force generated by each single spermatozoon. Furthermore, the optical trap also provides a new approach to the measurements of intracellular forces without physically touching the cell or its organelles, and inducing chromosome movement during cell division is also possible. Laser beams in a specific configuration are able to induce minimal superficial damage to the zona pellucida of oocytes from various species. This manipulation is aimed at increasing the fertilization rate following insemination with low-quality spermatozoa. Another intracellular application of the laser beams is the destruction of extra pronuclei in polyspermic fertilized human oocytes. These procedures require special equipment which is not commonly available. However, simpler devices may be developed if the advantages of this novel technology are demonstrated.

Fertilization↗
PubMed1991

Mid-infrared laser ablation of stratum corneum enhances in vitro percutaneous transport of drugs.

The precise removal of stratum corneum from cadaveric swine skin by a mid-infrared erbium:yttrium scandium gallium garnet laser (lambda = 2.79 microns; 250 microseconds pulse width) was assessed by electrical resistance measurements and documented by histology. The effects of stratum corneum removal by laser ablation and by adhesive tape-stripping on the in vitro penetration of 3H-hydrocortisone and 125I-gamma-interferon were determined. Excised swine skin was irradiated with laser (1 J/cm2; 31 mJ/pulse; 1 Hz; 2 mm spot diameter). For skin penetration studies, laser pulses were delivered to discrete 2-mm areas to ablate up to 12.6% of the total 3-cm2 stratum corneum diffusional area. Franz in vitro skin penetration chambers were used to measure the cumulative 48-h penetration of 3H-hydrocortisone and 125I-gamma-interferon in laser-treated and tape-stripped skin. Electrical resistance measurements and histologic studies demonstrated that 10-14 laser pulses at the above energy density were required to abolish skin resistance and selectively ablate stratum corneum without damage to adjacent dermal structures. Laser ablation of 12.6% of the surface area of stratum corneum produced a 2.8 and 2.1-times increase in permeability constant (kp) for 3H-hydrocortisone and 125I-gamma-interferon, respectively. These studies demonstrate that a pulsed mid-infrared laser can reliably and precisely remove the stratum corneum, facilitating penetration of large molecules such as 125I-gamma-interferon that cannot penetrate intact skin. This new technique may be useful for basic and clinical investigation of skin barrier properties.

Administration, Cutaneous↗
PubMed1978

The relationship between attachment height and attachment area of teeth using a digitizer and a digital computer.

Nine lower first bicuspid teeth were mounted in blocks of plastic and their roots were serially sectioned and photographed. Data from the photographs were compiled by a digitizer and a digital computer, which calculated the cumulative root surface area for each millimeter of root height. From these data, three variables, which relate root surface area to root height, were calculated. It was found that if one-half of the height of attachment to the root were lost due to periodontal disease, a mean of 61.5% of the actual attachment area to the root is lost. If a mean of 5.72 mm of root attachment height is lost, or if a mean of 60.6% of the same root height remains, only one-half of the total root attachment area remains to provide tooth support.

Bicuspid↗