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Biomedical subjects

M W Berns

Publications and source records attributed to M W Berns.

At least 19 recordsLinked to original sources
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↗
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↗
PubMed1992

Laser vs. suture nerve anastomosis.

The repair of injured or transected nerves is frequently encountered in head and neck surgery. Recently, CO2 lasers with milliwatt capability and micrometer spot sizes have been developed that may be used in nerve anastomosis. A comparative study was performed between microsuture and CO2 laser repair of transected sciatic nerves in rats. Nerve regeneration was measured in terms of morphology, electrophysiology, and function. Histologic studies revealed no difference in the size and number of regenerated axons, although there was less scar tissue formation at the anastomotic site with the laser repair. EMG and nerve conduction velocity were similar for the two repair methods. Functional recovery, as determined objectively using measurements of gait footprints, showed no difference between suture and laser repair. Laser-repaired nerves did have a higher dehiscence rate, although this problem can probably be prevented by splinting the rats postoperatively. However, laser repair was faster and simpler than suture repair and required less manipulation of the nerve. This study shows laser repair of peripheral nerves is possible with results comparable to conventional microsuture neurorrhaphy. Laser nerve anastomosis may be an effective alternative to suture nerve repair.

Anastomosis, Surgical↗
PubMed1992

Acute ultrastructural changes of cornea after excimer laser ablation.

Corneal ultrastructural changes induced by an argon fluoride excimer laser using different parameters were investigated. Twenty-eight rabbit corneas were ablated at light doses per pulse and repetition rates ranging from 25-800 mJ/cm2 and 1-100 Hz, respectively, at four different total light doses (25-150 J/cm2). Transmission electron microscopy showed that corneal ablations done at subthreshold light doses per pulse with repetition rates higher than 30 Hz and with an exposure more than 100 sec caused significant surface coagulation and an increase in pseudomembrane thickness. These changes were not observed in ablations done above threshold light doses per pulse, regardless of repetition rate and exposure time. However, repetition rates as high as 80 Hz caused damage to the endothelium and Descemet's membrane at the same ablation depth that did not cause such damage using repetition rates under 40 Hz. It appears that high repetition rates used during excimer laser corneal surgery may cause irreversible damage to the cornea.

Animals↗
PubMed1992

Ab-interno neodymium:YAG versus erbium:YAG laser sclerostomies in a rabbit model.

This study was undertaken to determine whether thermally-induced tissue necrosis was a factor in ab-interno contact-laser sclerostomy failure. A rabbit model was used to compare the continuous-wave Neodymium (Nd):YAG with the pulsed Erbium (Er):YAG laser with respect to such failure. Laser energy was focused into a fused-silica fiber optic (400 microns) for the Nd:YAG laser (12 W; 3 to 5 seconds), and into a single-crystal, uncladded sapphire fiber optic (250 microns) for the Er:YAG laser (7 to 8 mJ; 250 microseconds; 6 to 8 pulses). The Nd:YAG and Er:YAG lasers required from 21 to 35 J and from 42 to 64 mJ, respectively, to create the sclerostomies. Filtering blebs and intraocular pressure reduction lasted longer (log-rank test; P less than .03) and surgical complications were fewer in the Er:YAG group than in the Nd:YAG group. By creating sclerostomies with minimal thermal damage, the Er:YAG laser may offer significant clinical advantages over lasers producing larger thermal effects.

Animals↗
PubMed1991

Thoracoscopic carbon dioxide laser treatment of bullous emphysema.

A new technique of thoracoscopic laser ablation of pulmonary bullae suitable for patients with multiple bullae and diffuse emphysema was developed and assessed in 22 patients. 20 of 22 patients survived. Pre-operative and postoperative functional evaluation is available for the 11 patients followed up for more than a month; at 1 to 3 months postoperatively there were increases in FVC (mean 2.0 litres pre-operatively to 2.7 litres postoperatively, p less than 0.001), in FEV1 (0.74 to 1.06 litres, p = 0.01), and in maximum exercise treadmill times (5.4 min to 8.0 min, p less than 0.01). Postoperative air leaks lasted a mean of 13 days and usually resolved spontaneously. Other complications were bleeding (1 patient) and unilateral acute lung injury (1 patient). These results suggest that selected patients with diffuse emphysema and pulmonary bullae may benefit from thoracoscopic carbon dioxide laser ablation.

Cysts↗
PubMed1991

Photodynamic therapy of spontaneous cancers in felines, canines, and snakes with chloro-aluminum sulfonated phthalocyanine.

This is the first report on the photodynamic treatment with a second-generation sensitizer, chloro-aluminum sulfonated phthalocyanine (CASPc) of spontaneously arising tumors and on the photodynamic therapy (PDT) of snake neoplasms. Each of 10 cats, 2 dogs, and 3 snakes presenting with a variety of tumor types (squamous cell carcinoma, mast cell malignant tumor, and mixed carcinoma/sarcoma) was given an intravenous injection of 1 mg of CASPc per kilogram body weight 48 hours prior to irradiation with 675-nm light. Some larger tumors (greater than 1.5 cm deep) were surgically debulked prior to PDT. No significant systemic toxicity or skin photosensitization was observed in any animal. The tumor responses were comparable to those seen with conventional cryotherapy, hyperthermia, or surgery. PDT with CASPc of these cases led to 67% (12 of 18) complete response, 22% (4 of 18) partial response, and 11% (2 of 18) no response (less than 50% reduction in tumor size). Four cases could not be evaluated. Since the overall tumor response to CASPc is very good, and the problem of skin photosensitivity is nonexistent, it is expected that using CASPc-PDT to eradicate human tumors would also yield comparable results. Further studies with long-term follow-up are necessary to optimize the use of CASPc-PDT in veterinary and human medicine.

Animals↗
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

Laser trabecular ablation (LTA).

As part of a pilot study for glaucoma surgery, the use of 3 infrared solid state lasers with 4 fiber optic delivery systems to ablate human trabecular meshwork was investigated. Laser trabecular ablation (LTA) was attempted with the Erbium:YAG (2.94 microns), Erbium:YSGG (2.79 microns), and Holmium:YSGG (2.1 microns) lasers. Laser energy was delivered as a single pulse (250 microseconds) by tissue fiber optic contact with low hydroxyl-fused silica (200 and 500 microns), zirconium fluoride (250 microns), or sapphire (250 microns) fiber optics. Total energy required and thermal effects decreased as laser wavelength increased. LTA was best achieved at 2.94 microns (4 mJ total energy; energy densities = 8.2-12.7 J/cm2; pulse length 250 microseconds) with average thermal damage zones of 5.3-10.3 +/- 1.3-2.4 microns (means +/- SDs) to contiguous structures. This finding has potential applications in the surgical treatment of open-angle and congenital glaucoma and may minimize failure rates seen in other types of surgery on the trabecular meshwork where disrupted trabecular meshwork is not removed.

Aluminum Oxide↗
PubMed1991

Selectivity, efficiency, and surface characteristics of hard dental tissues ablated with ArF pulsed excimer lasers.

Lasers are finding expanding applications in the field of dentistry. Cutting in soft tissue, hard dental material ablation, caries removal, and root canal therapy are only a few examples of dental laser uses. In this article, the application of short pulse ArF excimer laser to ablation of dentin and enamel is investigated. In particular, the effect of laser pulse repetition rates (PRR) and fluence levels on the efficiency of the ablation process and on the average thermal response of ablated surfaces is investigated. Ablation of dentin was found to be considerably more efficient than the ablation of enamel and depends exponentially on the laser fluence. Both dentin and enamel surfaces showed an increase in surface temperature with repetition rate. At lower PRR, however, temperature increases are very small. Surface temperature was also found to increase with laser fluence, although this increase is very small at laser PRR of 5 Hz or less. Tissue ablation rates were found to be comparable to or better than other nanosecond lasers, and left smooth surfaces, free of thermal damage. Microscopic examination of the ablated surface shows no crack formation, charring, discoloration, or any other thermal damage. The ablated surfaces appear to be very smooth, highly polished, and glossy looking as if they were subjected to thermal melting. This observation is indeed confirmed under scanning electron microscopy (SEM), where evidence of localized melting of the tissue is observed. Furthermore, a close SEM examination of the dentin surface reveals a selectively ablated intertubular dentin, while the remaining pillar-like dentin tubules are sealed off with fused peritubular dentin. At all fluence levels and PRR, the first three to four pulses impinging on an untreated enamel surface produced unusually large plumes of debris which were different in size, texture, and fluorescence emission characteristics from the ablation products of subsequent pulses. It is believed that these different ablation characteristics are a consequence of the pulsed ArF laser's ability to selectively remove residual matter from the more resistant enamel surface.

Acid Etching, Dental↗