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Biomedical subjects

M W Berns

Publications and source records attributed to M W Berns.

At least 91 records · Page 5Linked to original sources
PubMed1994

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.

Aged↗
PubMed1993

Scanning electron microscopy and thermal characteristics of dentin ablated by a short-pulse XeCl excimer laser.

The interaction of a short pulse XeCl excimer laser radiation with human dentin was investigated. The dependence of surface temperatures and temperature gradients into the treated teeth on laser parameters such as fluence (0.5J/cm2-7J/cm2), pulse repetition rate (1Hz-35Hz), and spot size (0.004cm2-0.12cm2) was studied. Additionally, the effect of fluence and pulse repetition rate on dentin microstructure was studied using scanning electron microscopy (SEM). It is demonstrated that this "cold ablation" excimer laser can result in significant thermal modification in the dentin surfaces. Changes include the formation of melted dentin grains, which uniformly cover the surface and the exposed dentin tubules. Maximum temperatures of the ablated surfaces, however, remained relatively low at most laser parameters used. Also, the immediate neighborhood of the root canal was essentially undisturbed at most laser parameters. These observations suggest that with the appropriate choice of parameters XeCl lasers can be effective in producing surface structures that may prove useful in enhancing bond strength or other applications in dentistry, without exposing tooth pulp to significant temperature elevation.

Absorption↗
PubMed1993

Effects of pulse width on erbium:YAG laser photothermal trabecular ablation (LTA).

An erbium (Er):YAG laser can remove trabecular meshwork (TM) by photothermal ablation with minimal contiguous thermal damage. A variable pulse width Er:YAG laser was used to investigate the effect of varying pulse width on ablation of human TM. Trabecular photothermal ablation was performed on tissue obtained from eye bank eyes at pulse widths of 50, 150, and 250 microseconds, with energy held constant at 4 mJ. At this energy, a single laser pulse was sufficient for full-thickness ablation of TM. Laser energy was delivered through a 200-microns diameter optical fiber held in apposition to the tissue sample, which was immersed in physiologic saline. High-speed photography of the resultant steam bubbles also was performed. Light microscopy and scanning electron microscopy of TM ablated at 50 microseconds revealed the greatest variability in size (0-140 microns) of the full-thickness ablated areas and demonstrated blast effects, tissue shredding and < or = 10 microns thermal damage. At 150 microseconds, the full-thickness ablated areas were more consistent size (115-120 microns), showed no blast effects and 10 to 20 microns thermal damage. At 250 microseconds, the largest ablations were found (180-220 microns) and showed no blast damage; however, a significant amount of thermal damage (< or = 50 microns) was evident. The steam bubbles produced by the laser energy were largest at 50 microseconds and did not begin to collapse until well over twice the original pulse interval. At 150 and 250 microseconds, the steam bubbles were successively smaller and dissipated at the end of the laser pulse.(ABSTRACT TRUNCATED AT 250 WORDS)

Humans↗
PubMed1993

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.

Animals↗
PubMed1993

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.

Animals↗
PubMed1993

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.

Animals↗
PubMed1993

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.

Animals↗
PubMed1993

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.

Animals↗
PubMed1993

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.

Female↗
PubMed1993

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.

Anaphase↗
PubMed1992

Carbon dioxide laser ablation combined with doxorubicin hydrochloride treatment for vaginal fibrosarcoma in a dog.

The combined use of CO2 laser ablation and doxorubicin hydrochloride (30 mg/m2) administered twice, 4 weeks apart, resulted in complete remission of vaginal fibrosarcoma in a 10-year-old Miniature Poodle. The tumor had redeveloped when only CO2 ablation was used for treatment and doxorubicin hydrochloride alone has had marginal influence on fibrosarcomas; however, use of both treatments in this dog resulted in a 20-month, disease-free period. This treatment combination was minimally traumatic to the dog, easily accomplished, and effective, and it allowed retention of the normal anatomy and function of the urogenital tract.

Animals↗
PubMed1992

Photodynamic therapy of experimental subchoroidal melanoma using chloroaluminum sulfonated phthalocyanine.

Although photodynamic therapy has shown great promise for the treatment of a variety of malignant neoplasms, the role of this new therapeutic modality in the clinical management of intraocular tumors remains incompletely understood. This study examines the effects of photodynamic therapy using chloroaluminum sulfonated phthalocyanine on Greene hamster melanoma transplanted into the subchoroidal space in rabbits. Twenty-four hours after intravenous administration of chloroaluminum sulfonated phthalocyanine (5 mg/kg), tumors were irradiated with 675 nm of light at total light doses of 7 to 60 J/cm2. The results show that tumor growth was arrested at total light doses of 22 to 60 J/cm2. At total light doses of 15 to 21 J/cm2, tumor growth was initially arrested. However, regrowth of these tumors was apparent within 7 days. Total light doses of less than 15 J/cm2 showed no response. Complications of photodynamic therapy, such as intraretinal or subretinal hemorrhages and retinal detachment, were seen only in animals who received total light doses in excess of 43 J/cm2.

Aluminum↗
PubMed1992

Glucose administration combined with photodynamic therapy of cancer improves therapeutic efficacy.

Both the scope and the levels of activity in basic research and in the clinical applications of PDT, have grown enormously during the past few years. Several studies have examined the synergism of hyperthermia and chemotherapeutic agents in combination with PDT to enhance tumor eradication. The present study investigates the synergism of glucose administration combined with phototherapy. The results of this study suggest that glucose administration is simple and well tolerated, and combined with PDT produces a larger percentage of animals cured than using PDT alone. Furthermore, the results indicate that this approach requires lower amounts of light and might enable dosage reduction of photosensitizer for optimal response, with minimal side effects, to the treatment of cancer.

Adenocarcinoma↗
PubMed1992

Demonstration of synergistic effects of hyperthermia and photodynamic therapy using the chick chorioallantoic membrane model.

The chick chorioallantoic membrane (CAM) model was used to study vascular effects of photodynamic therapy (PDT) and hyperthermia (HPT) and the synergism of these modalities. The CAM is a convenient medium for monitoring the modifications of the vasculature. It is possible to view the CAM and to examine structural changes of individual blood vessels in real time. Moreover, the CAM is a closed system which lends itself to mathematical modeling of the temporal and spatial temperature profile and in which HPT can be performed quantitatively and to a selected depth, using different lasers. A porphyrin-type photosensitizer solution was applied to areas of the CAM, defined by teflon O-rings placed on the surface. Uptake dynamics of the sensitizer into the CAM was determined by analyzing its fluorescence in vivo. The CAM area was irradiated with a dual-wavelength laser system composed of a dye laser at 644 nm (to induce PDT) and a CO2 laser at 10.6 microns (to bring about HPT). Damage to the CAM vasculature, due to combined PDT+HPT, was compared to the outcome of the separate modalities, and a synergistic effect of about 40% was observed.

Allantois↗