Assisted hatching in mouse embryos using a noncontact Ho:YSGG laser system

PURPOSE

A noncontact holmium:yttrium scandium gallium garnet (Ho:YSGG) laser system has been designed and tested for the micromanipulation of mammalian embryos. The purpose of this preliminary investigation was to determine the effectiveness of this laser for assisted hatching and evaluate its impact on embryo viability. The Ho:YSGG system, utilizing 250-microsecond pulses at a wavelength of 2.1 microns and 4 Hz, was used to remove a portion of the zona pellucida (ZP) of two- to four-cell FVB mouse embryos.

RESULTS

In the first experiment there was no difference in blastocyst production or hatching rates following laser or conventional assisted hatching (LAH or AH, respectively) in contrast to control embryos cultured in a 5% CO2 humidified air incubator at 37 degrees C. In the second experiment a blastocyst antihatching culture model was employed and LAH-treated embryos were cultured in a serum-free HTF medium (HTF-o). Blastocyst formation was not influenced by LAH treatment and hatching was increased (P < 0.01) from 4 to 60% compared to HTF-o control group.

CONCLUSIONS

These preliminary data demonstrate the utility and nontoxic properties of the Ho:YSGG laser system for quick and precise ZP drilling.

Root canal preparation using the second harmonic KTP:YAG laser: a thermographic and scanning electron microscopic study

Thermal and microstructural events resulting from KTP laser use during root canal preparation were investigated in 30 extracted single-rooted human teeth. In the first section of this study, thermal events occurring on the root surfaces of 18 teeth during and after exposure of the root canal were measured using thermography. A variety of parameters were used to determine settings that would be effective without causing thermal damage to the periodontal ligament. In the second section of the study, root canals of 12 teeth exposed to KTP laser irradiation at parameters derived from section 1 were evaluated using Scanning electron microscopy. KTP laser application at a power setting of 3 W, an exposure time of 2 s, and a frequency of 5 Hz, applied five times, removed smear layer and debris from the root canal surface at temperatures below the thermal injury threshold for periodontal tissue.

Rat reproductive performance following photodynamic therapy with topically administered Photofrin

A rat animal model was used for comparing the photodynamic efficacy of two formulations of topically administered Photofrin in the uterus: 0.7 mg/kg Photofrin and 0.7 mg/kg Photofrin + 4% Azone, a penetration-enhancing agent. Uterine structure and reproductive performance were evaluated following illumination with 80 J/cm2 of 630 nm light. Fluorescence microscopy was employed to determine drug localization in frozen uterine sections at various times after drug administration. Functionality studies demonstrated a significant reduction in the number of implantations per treated uterine horn compared to controls. The mean number of implantations decreased systematically on increasing the interval between Photofrin administration and light application. At 72 h, 0.88 +/- 0.52 gestational sacs per rat were recorded with Photofrin therapy, compared with 8.1 +/- 1.12 (P = 0.01) on the untreated side, indicating nearly complete loss of reproductive capability. Similar results were achieved after only 3 h treatment with Photofrin + Azone (0.38 +/- 0.26 sacs per rat versus 7.5 +/- 1.07 on the untreated side; P = 0.01). This indicates that the effect of Photofrin can be enhanced either by extending the drug incubation period from 3 to 72 h or by adding the penetration-enhancing drug Azone. Fluorescence pharmacokinetic studies suggest that both forms of topically administered Photofrin are diffusely distributed throughout the endometrium at virtually the same rate. However, Azone may enhance the selectivity of photodynamic therapy by facilitating drug targeting to critical endometrial structures.

Photomedicine of the endometrium: experimental concepts

Gynaecological photomedicine offers new diagnostic and therapeutic methods based on the interaction of light with the reproductive organs. One example is photodynamic therapy (PDT) in which photosensitizers are applied systemically or topically for selective endometrial ablation. Several studies describing the potential use of PDT for this application are reviewed. Basic experimental and clinical aspects of PDT, such as photosensitizer types, application modes, irradiation parameters, optical properties of tissues and photodegradation of photosensitizers are discussed.

Thermal effects of CO2 laser on the pulpal chamber and enamel of human primary teeth: an in vitro investigation

BACKGROUND AND OBJECTIVE

Thermal effects of direct exposure of the pulp chamber to CO2 laser irradiation were evaluated and potentially safe parameters for its clinical application were determined.

STUDY DESIGN/MATERIALS AND METHODS

Using conventional methods, the pulp chambers of freshly extracted primary cuspids were exposed and then subjected to CO2 laser irradiation at the following parameters: 2, 4, 6, 8, 10, 15, and 20 Watts power settings; 0.76 mm diameter spot size; total energy densities between 4-1,058 J/cm2; exposure time between .01-60 s. Exposures in the continuous wave mode were performed in some specimens. In others, single firings of a .01 s pulse duration and a 1 s pulse interval were conducted. Temperature measurements were conducted using a thermocouple and thermal camera.

RESULTS

Significant statistical differences in maximum temperature rise on enamel were observed in groups that received total energy densities > or = 8 J/cm2 (P < or = 0.01); within the pulp chambers these were observed in groups that used > or = 44 J/cm2 (P < or = 0.01).

CONCLUSION

Parameters appropriate for pulpotomy were observed at energy densities up to 176 J/cm2 in the continuous wave mode and 264 J/cm2 using single pulses, wherein temperature rises below 5.5 degrees C were recorded on tooth surface.

Photodynamic laser cyclodestruction with chloroaluminum sulfonated phthalocyanine (CASPc) or Photofrin (PII) vs. Nd:YAG laser cyclodestruction in a pigmented rabbit model

BACKGROUND AND OBJECTIVE

To investigate Photofrin (PII) and CASPc for photodynamic therapy (PDT) of the ciliary body in rabbits.

STUDY DESIGN/MATERIALS AND METHODS

PII (10 mg/kg) or CASPc (1 mg/kg) was given by ear vein. Pharmacokinetics were studied in frozen sections by fluorescence microscopy (CCD camera based low light detection system with digital image processing) at 1 and 24 h (8 rabbits; 16 eyes). Laser light was delivered (argon pumped dye laser; 630 and 675 nm; 8 rabbits; 16 eyes) by contact fiberoptic. To compensate for iris attenuation, irradiance was 125 mW/cm2 (20, 40, 80, or 160 J/cm2). Controls (4 rabbits; 8 eyes) received laser light without photochemicals (OD) and for comparison, continuous wave Nd:YAG laser by fiberoptic (0.8-1.2J; OS).

RESULTS

Localization studies showed intravascular distribution with some selective ciliary body distribution at 24 h (PII > CASPc). Rabbits treated with PII or CASPc exhibited variable amounts of gross ciliary body edema, infarction, and necrosis by 24-48 h. This response was not seen in PDT control tissues; damage was seen in the iris and ciliary body, with partial vacuolization of the pigment epithelium.

CONCLUSION

PDT may offer a more selective approach to ciliary body destruction. A small but significant thermal effect was seen during PDT from melanin photon uptake with damage to iris and ciliary body. Thermal damage and potential interaction with ocular visual pigments may limit use of these photochemicals and wavelengths for PDT of the ciliary body.

Effect of freezing on the relative escape force of sperm as measured by a laser optical trap

OBJECTIVE

To determine the possible effect of freezing on sperm escape force as measured by laser trap.

DESIGN

Controlled clinical study.

SETTING

Normal volunteers, academic setting.

PATIENTS

Normal, healthy volunteers.

INTERVENTION

Sperm selection, freezing and thawing. Measurement of relative (sperm) escape force before and after freezing.

MAIN OUTCOME MEASURE

Comparison of escape force as a measurement of freezing effects.

RESULTS

Wide individual variations noted, with some individuals showing significant increases or decreases. The relative escape force in fresh (76.1 +/- 31.1 mW) and in frozen-thawed samples (75.6 +/- 40.0 mW) were similar.

CONCLUSION

Freezing does not affect the relative escape force of normal sperm. Any possible detrimental effect of freezing on sperm may be related to other sperm functions.

Differential vascular response to laser photothermolysis

Individual blood vessels in the chick choriallantoic membrane were selectively coagulated through photothermolysis, using pulsed laser irradiation at 585 nm. Pulse durations were chosen to be 0.45 ms and 10 ms, which correspond to the thermal relaxation times in blood vessels of 30 microns and 150 microns diameter, respectively. The short pulses, at a light fluence F = 3 Jcm-2, caused permanent occlusion of vessels of 40 microns diameter or less, whereas larger caliber vessels (60-120 microns) required F = 4-5 Jcm-2. The long-duration pulses, at F = 7 Jcm-2, caused coagulation of the larger diameter vessels; the small-caliber vessels and capillaries showed resistance to photothermolysis and required multiple exposures to achieve coagulation. The fluence versus diameter (F versus d) relationship for coagulation was calculated for the two pulse durations. The energy deposited in a cylindrical absorber of diameter d by an optical field, incident perpendicular to the vessel, was expressed analytically and compared with the energy required to coagulate a blood vessel of the same lumen dimeter. When thermal diffusion is incorporated into the model, our findings can be accounted for quantitatively. This information will be of use for improving the laser treatment of port wine stains and other vasculopathies. A surprising observation was that arterioles were damaged at lower incident energy densities than venules having the same lumen diameter, despite the fact that absorbance in oxygen-rich and oxygen-poor blood is the same at 585 nm.

Photodynamic destruction of endometrial tissue with topical 5-aminolevulinic acid in rats and rabbits

OBJECTIVE

The goal of this study was to determine the optimal parameters for photodynamic endometrial destruction with topically applied 5-aminolevulinic acid, a precursor for the endogenous synthesis of the fluorescent photosensitizer protoporphyrin IX.

STUDY DESIGN

5-Aminolevulinic acid pharmacokinetics were measured in rat and rabbit models by analyzing tissue frozen sections 3 to 12 hours after topical administration. Dose-response studies were conducted for 100 to 400 mg/ml 5-aminolevulinic acid. Photodynamic therapy was performed intraluminally, and tissue morphologic features were evaluated 3 and 7 days after treatment.

RESULTS

Peak fluorescence was observed 3 hours after topical administration. Glandular fluorescence significantly exceeded stromal and myometrial in all studies, particularly for 200 mg/ml 5-aminolevulinic acid. Histologic studies revealed persistent epithelial destruction with minimal regeneration.

CONCLUSION

Topical 5-aminolevulinic acid photodynamic therapy can be used for highly effective, long-lasting destruction of endometrial epithelium. However, optical dosimetry can vary, particularly in the rabbit model, and this appears to have an impact on long-term reepithelialization.

Benzoporphyrin derivative: a potent photosensitizer for photodynamic destruction of rabbit endometrium

OBJECTIVES

To determine the optimal pharmacokinetic characteristics for photodynamic endometrial destruction using topically applied benzoporphyrin derivative and to evaluate long-term morphologic effects in a rabbit model.

METHODS

Benzoporphyrin derivative pharmacokinetics were measured by analyzing frozen tissue sections 1.5-12 hours following topical administration. Photodynamic therapy was induced intraluminally 1.5 hours after drug application, and tissue morphology was evaluated by light and scanning electron microscopy 1 and 4 weeks after treatment.

RESULTS

The highest glandular and stromal fluorescence was observed 1.5 hours after topical administration. Relative fluorescence of the endometrial glands significantly exceeded that of stroma and myometrium mainly at 1.5 and 3 hours (P < .0001). Histology revealed persistent epithelial destruction with minimal regeneration. Stroma resembled scar tissue in the majority of sections. The bordering myometrium was loosened and invaded by connective tissue.

CONCLUSION

Topically applied benzoporphyrin derivative can be used for highly effective, long-lasting photodynamic destruction of rabbit endometrium. However, optical dosimetry can vary, particularly in the rabbit model, and this appears to affect long-term reepithelialization.

Relative force of human epididymal sperm

OBJECTIVE

To assess the relative escape force of human epididymal sperm using a laser generated optical trap and compare it with that of human ejaculated sperm.

DESIGN

Evaluation of the relative force generated by epididymal and ejaculated sperm using an 800-nm laser-generated optical trap system (titanium-sapphire, model 899-01; Coherent Innova, Palo Alto, CA).

SETTING

University-based facility at the Beckman Laser Institute and Medical Clinic and Center for Reproductive Health, University of California, Irvine.

INTERVENTIONS

A total of 2,720 sperm from 28 samples were randomly analyzed. Fifteen were ejaculated samples (1,650 sperm) obtained from men with proven fertilization, and 13 were epididymal samples (1,070 sperm) aspirated microsurgically from patients with obstructive azoospermia. An optical trap equipped with the 100x Neofluar objective was used to analyze an average of 100 sperm per patient.

MAIN OUTCOME MEASURES

Determination of mean relative escape force values in milliwatts for epididymal and ejaculated sperm samples.

RESULTS

The mean relative escape force for epididymal sperm was 32.4 mW, significantly lower than ejaculated sperm, which was 85.1 mW. By correlating epididymal sperm relative force with fertilization in vitro at an arbitrary cutoff value of 30 mW, it was found that no fertilization occurred if a sample had < 13% of sperm at that value.

CONCLUSIONS

[1] The average relative escape force of the epididymal sperm was found to be 60% weaker than that of ejaculated sperm. [2] It is demonstrated that the noncontact laser optical trap is a sensitive tool that can evaluate single sperm force as a new physiological parameter.

Directed movement of chromosome arms and fragments in mitotic newt lung cells using optical scissors and optical tweezers

A pulsed-laser microbeam at 532 nm wavelength (optical scissors) and a laser-induced optical trap at 1064 nm wavelength (optical tweezers) have been successively combined to dissect and manipulate chromosomes in live newt lung epithelial cells. These preliminary experimental results demonstrated that chromosome fragments dissected by laser microbeam surgery, regardless of their size, could be easily pulled or rotated by optical forces when positioned at the periphery of the mitotic spindle. In addition, chromosome arms which were not subjected to laser microsurgery also could be moved with the optical tweezers at the spindle periphery. In our previous study on rat kangaroo kidney cells (PTK2), this degree of facilty in manipulating chromosome movement was not possible, most likely due to the close proximity of the intermediate filament "cage" to the spindle. It is concluded herein that optical scissors and tweezers can be used in combination to study the interaction of chromosomes with the mitotic spindle in cells where the peripheral regions of the spindle are unobstructed by intermediate filaments. This can be performed on newt cells, where the diameter of the cage can be substantially larger than the diameter of the spindle.

Parametric study of the forces on microspheres held by optical tweezers

Optical-trapping forces exerted on polystyrene microspheres are predicted and measured as a function of sphere size, laser spot size, and laser beam polarization. Axial and transverse forces are in good and excellent agreement, respectively, with a ray-optics model when the sphere diameter is ≥ 10 µm. Results are compared with results from an electromagnetic model when the sphere size is ≤ 1 µm. Axial trapping performance is found to be optimum when the numerical aperture of the objective lens is as large as possible, and when the trapped sphere is located just below the chamber cover slip. Forces in the transverse direction are not as sensitive to parametric variations as are the axial forces. These results are important as a first-order approximation to the forces that can be applied either directly to biological objects or by means of microsphere handles attached to the biological specimen.

Thoracoscopic laser ablation of pulmonary bullae. Radiographic selection and treatment response

The purpose of this study was to develop objective preoperative selection methods for predicting outcome in patients undergoing thoracoscopic laser ablation of emphysematous pulmonary bullae. Initial radiographic presentation was correlated with physiologic function both before and after the operation in 24 patients entered into a prospective clinical protocol for evaluation of carbon dioxide laser treatment of emphysematous pulmonary bullae. Nineteen surviving patients underwent follow-up evaluation 1 to 3 months after the operation. Pulmonary function test results showed improvements in spirometry (forced vital capacity increased 0.82 +/- 0.125 L, forced expiratory volume in 1 second increased 0.36 +/- 0.07 L, and maximum voluntary ventilation increased 11.69 +/- 2.6 L/m; p < 0.002); airway resistance decreased by 0.9 +/- 0.35 cm of water/L per second, and specific conductance increased 0.019 +/- 0.006 L/cm H2O per second (p < 0.02). Lung volumes improved (residual volume decreased 1.25 +/- 0.23 L, p < 0.001) without significant change in resting gas exchange. Quantitative radiographic grading of extent of preoperative pulmonary bullae correlated well with response to laser treatment in patients with preoperative and postoperative studies. Patients with large bullae accompanied by crowding of adjacent lung structures, upper lobe predominance, and minimal underlying emphysema had greatest improvement in pulmonary function results with laser bullae ablation (p < 0.05). However, some patients with multiple smaller bullae and diffuse emphysema also demonstrated objective improvement after operation. Quantitative radiographic analysis of the extent of bullous disease and the degree of associated emphysema can be used to determine short-term postoperative pulmonary response and may be useful in selecting future thoracoscopic laser bullae ablation candidates. Additional follow-up will be necessary to further improve selection criteria and help define the long-term role of thoracoscopic laser treatment of bullous emphysema.

Exposure of human spermatozoa to the cumulus oophorus results in increased relative force as measured by a 760 nm laser optical trap

Spermatozoa change their movement characteristics in response to different environmental conditions. To investigate the relative force of spermatozoa exhibiting different motility patterns, a laser optical trap was used. A laser beam at 760 nm was directed through a microscope objective and focused above the spermatozoa to create a three-dimensional optical trap. Spermatozoa were trapped at 300 mW, and laser power was reduced until spermatozoa could escape. The force generated by the flagellar movement was proportional to the laser power at which the spermatozoa escaped from the trap. Three motility patterns were studied: linear, hyperactivated, and cumulus-related. Mean escape power for spermatozoa displaying linear motility was 59.5 +/- 43 mW, for hyperactivated motility 122.3 +/- 67 mW (P < 0.0001) and for cumulus-related motility 200.6 +/- 44.2 mW (P < 0.0001). In this study, we showed that human spermatozoa generated more relative force upon exposure to the cumulus mass. The combination of small-amplitude lateral head displacement and higher relative force may produce a 'drilling' effect which is synergistic with the enzymatic digestion of the cumulus matrix during the fertilization process.

Astral and spindle forces in PtK2 cells during anaphase B: a laser microbeam study

Rat kangaroo kidney epithelium (PtK2) cells develop prominent asters and spindles during anaphase B of mitosis. It has been shown that severing the spindle at early anaphase B in living PtK1 cells results in a dramatic increase in the rate of pole-pole separation. This result suggested that the asters pull on the spindle poles, putting tension on the spindle, while the spindle acts as a governor, limiting the rate of pole separation. To further test these inferences, we used a UV-laser microbeam to damage one of the two asters in living PtK2 cells at early anaphase B and monitored the effects on individual spindle pole movements, pole-pole separation rates and astral microtubules (MTs). Irradiation at the estimated position of a centrosome greatly reduced its array of astral MTs and nearly stopped the movement of the irradiated pole, whereas the sister pole retained its normal array of astral MTs and actually accelerated. Control irradiations, either close to the estimated position of the centrosome or beside the spindle at the equator, had little or no effect on either spindle pole movements or astral MTs. These results support the inferences that during anaphase B in living PtK cells, the central spindle is under tension generated by pulling forces in the asters (presumably MT-mediated) and that the spindle generates counterforces that limit the rate of pole separation. The results also suggest that the central spindle in living PtK cells may be able to generate a pushing force.

Zona opening with 308 nm XeCl excimer laser improves fertilization by spermatozoa from long-term vasectomized mice

Spermatozoa from long-term vasectomized mice have greatly reduced fertilizing ability in vivo and in vitro, which makes this a useful animal model for male factor infertility. The purpose of this study was to evaluate the 308 nm XeCl excimer laser for opening the zona pellucida to enhance the fertilization rate with spermatozoa from vasectomized males. Inseminating zona-intact (control) oocytes with 5 x 10(6) spermatozoa/ml resulted in only 6% fertilization and 33.3% development to the blastocyst stage; zona-opened oocytes showed significant improvement with 31.5% fertilization, 90% cleavage to the 2-cell stage, and 72.2% blastocyst formation. Out of the 130 oocytes in the experimental group, zona ablation was performed successfully on 127 and only three were damaged. These results suggest that laser micromanipulation for assisted fertilization potentially offers a simplified and precise method for mechanical zona cutting.

Effect of administration route and estrogen manipulation on endometrial uptake of Photofrin porfimer sodium

OBJECTIVE

Our purpose was to evaluate the influence of the route of drug administration and target tissue vascularity on the distribution of a photosensitizer, Photofrin porfimer sodium, in the uterus.

STUDY DESIGN

The study was divided in two phases. In phase I 80 mature female rats were hormonally suppressed and then stimulated with estrogen. They were randomized to receive intravenous, intraperitoneal, or intrauterine Photofrin and killed 3, 6, 24, or 48 hours later. Drug distribution and levels were then determined. In phase II 40 female rats were randomized to receive hormonal stimulation, suppression, both, or neither. All received intrauterine Photofrin and were killed 24 hours later. Statistical analysis was performed with the unpaired t test and the two-way analysis of variance.

RESULTS

Intrauterine administration was determined to be the simplest and most effective method of delivery because it provided for optimal uptake and distribution (p = 0.05) within the uterus, at lower doses.

CONCLUSIONS

Selective localization of photosensitizer within the target tissue suggests that highly selective photodynamic destruction of endometrial tissue can be achieved. Furthermore, the combination of intrauterine administration of photosensitizer with estrogen adjuvant may minimize the most debilitating side effect of Photofrin, cutaneous phototoxicity.

Optical trapping for chromosome manipulation: a wavelength dependence of induced chromosome bridges

Using a tunable titanium-sapphire laser, we have compared different wavelengths (from 700 to 840 nm) for their utility in optical trapping of chromosomes in mitotic rat kangaroo Potorous tridactylus (PtK2) cells. It was found that irradiation with a near-infrared light induces the sticking together of chromosome shoulders. The attached chromatids failed to separate, or separated with significant delay and formed a chromosome bridge during anaphase. Using this bridge (and induced c-mitosis) as a reference, we compared the action of different wavelengths (from 700 to 840 nm). Chromosomes were irradiated at metaphase and the cells were observed until the end of cytokinesis. Chromosomes were irradiated for different periods of time, using 130 mW of power at the objective focal plane. The biological responses observed after optical trapping were: (1) normal cell division, (2) formation of a temporary chromosome bridge, (3) formation of a permanent chromosome bridge, (4) complete blockage of chromosome separation (c-mitosis). The chromosomes were found to have a maximal sensitivity to 760-765 nm light and minimal sensitivity to 700 and 800-820 nm light. Cells with chromosomes irradiated for a long time, using wavelength 760-765 nm, generally were incapable of going through anaphase and remained in c-mitosis. We conclude that the optimal wavelengths for optical trapping are 700 and 800-820 nm.

Micromanipulation of chromosomes in PTK2 cells using laser microsurgery (optical scalpel) in combination with laser-induced optical force (optical tweezers)

An optical scalpel and optical tweezer have been combined to perform intracellular microsurgery and micromanipulation in vivo. When only laser microsurgery was performed on metaphase chromosomes, the dissected sister chromatid fragments drifted off to either the side of the spindle or completely off the spindle. At anaphase the fragments separated and the two arms generally moved to their respective daughter cells. When the chromosome arm was cut during anaphase A and B, the distal chromosome fragment separated from the rest of the chromosome and moved toward the pole, following the proximal chromosome fragment. Distal chromosome fragments laser-dissected during metaphase were held together throughout anaphase using the optical trap. Optical trapping of dissected chromosome fragments during anaphase A and B inhibited movement of the chromosome fragment to its pole. As a result, the trapped chromosome fragments were (1) incorporated into the opposite daughter cell, (2) lost in the cleavage furrow during cytokinesis, or (3) eventually incorporated into the correct daughter cell. These results indicate that optical traps are effective in holding laser-dissected chromosome fragments throughout mitosis. This new tool should be useful for studies on chromosome movement and cell genetics.

Ab-interno erbium (Er):YAG laser sclerostomy with iridotomy in Dutch cross rabbits

An ab-interno technique using a pigmented rabbit model has been developed that uses a pulsed erbium:YAG laser to create an iridotomy with a sclerostomy through the same corneal incision. Laser energy was delivered with an articulated arm terminating in side-firing (850 or 650 microns OD) or end-firing (850 or 400 microns OD) fiber optic endoprobes, which allowed iridotomies and sclerostomies, respectively, to be created. Initially, sclerostomies (8-10, 8 mJ/300 microseconds pulses) and basal iridotomies (1-3, 4 mJ/200 microseconds pulses) were created with the larger probes. Problems encountered with this technique included corneal decompensation and rapid formation of peripheral anterior synechiae with occlusion of sclerostomies. The smaller endoprobes were then used to create mid-peripheral iridotomies and sclerostomies utilizing the same energy parameters. Sclerostomies created in this manner remained patent in the first postoperative week until the animals were sacrificed to obtain material for histologic study.