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Biomedical subjects

J A Parrish

Publications and source records attributed to J A Parrish.

At least 37 records · Page 2Linked to original sources
PubMed1987

Cytotoxicity and mutagenicity of low intensity, 248 and 193 nm excimer laser radiation in mammalian cells.

The cytotoxicity of 193 and 248 nm excimer laser radiation was compared to that produced by a germicidal lamp (predominantly 254 nm) using Chinese hamster ovary cells (CHO), and a human diploid fibroblast line, AG-1522A. Excimer laser radiation at 248 nm (3.5 X 10(2) w/m2) and germicidal radiation (5.3 X 10(-5) w/m2) caused toxicity in both cell lines, with the AG-1522A cells (D37 = 7-8 J/m2) being slightly more sensitive than the CHO cells (D37 = 11 J/m2). Incident 193 nm radiation was less cytotoxic than 248 nm to AG-1522A and CHO cells with D37 values of 18 and 85 J/m2, respectively. The mutagenic potential of UV excimer radiation at 193 and 248 nm was evaluated using the hypoxanthine guanine phosphoribosyl transfer assay system with CHO cells. Excimer laser radiation at 248 nm induced mutation in proportion to dose (1.7 X 10(-5) resistant colonies per survivor per J/m2 incident radiation) up to 14 J/m2, similar to results reported for 254 nm light. However, excimer laser radiation at 193 nm did not cause mutation greater than the dark control. The decreased cytotoxicity and mutagenicity of 193 nm radiation may be due to the shielding of the nucleus by cytoplasmic and membrane components or to the formation of different DNA photoproducts. These differences between 193 and 248 nm radiation may be important in choosing an excimer wavelength for ablation in biological systems.

Animals↗
PubMed1987

Fragmentation of biliary calculi with tunable dye lasers.

The feasibility of using lasers to fragment biliary calculi was examined in vitro. Flashlamp-pumped tunable dye lasers were coupled to small-diameter flexible quartz fibers that were placed in direct contact with biliary calculi. The minimum laser energy necessary to damage a calculus was measured for wavelengths between 450 and 700 nm and for pulse durations between 0.8 and 360 microseconds. This threshold energy increased with increasing wavelength but was not significantly affected by pulse duration. Cholesterol stones had uniformly higher thresholds than pigmented ones. When a repetitively pulsed laser was used, complete fragmentation required fewer than 500 pulses and fragments were predominantly less than 2 mm. The pulsed dye laser can effectively fragment biliary calculi when transmitted through a small-diameter quartz fiber and may be useful as a tool for fragmenting retained common duct stones.

Cholelithiasis↗
PubMed1987

The pulsed dye laser for fragmenting urinary calculi.

The properties of a laser which effect stone fragmentation have been studied. The pulsed dye laser emitting at 504 nm. in one microsecond duration pulses appears to be the optimum out of a wide range of parameters tested. The laser is coupled to a 200 micron core fiber; this complete with its cladding has a total diameter of only 0.25 mm. Most calculi are fragmented by a series of pulses of up to 30 mJ. The system is used by firing bursts of pulses with the fiber actually in contact with the stone. The result is a very controlled fragmentation which is particularly suited to use in the confines of the ureter. This modality of treatment utilises less energy than ultrasound or electrohydraulic probes to fragment a stone and the very fine, flexible fiber represents a considerable miniaturization.

Calcium Oxalate↗
PubMed1987

An assessment of the pulsed dye laser for fragmenting calculi in the pig ureter.

The pulsed dye laser was used to fragment ureteric calculi in 10 pig ureters, compared to electrohydraulic disintegration in six pig ureters. The stones were impacted in the proximal ureter and approached by rigid ureteroscopy. Four ureters did not have stones impacted but had ureteroscopes passed. The stones were fragmented and the particles left to pass spontaneously. The degree of inflammatory reaction was graded at the site of fragmentation as well as in the middle and lower ureter. The degree of inflammation seen at the site of fragmentation was significantly less in the laser group than in the electrohydraulic group (p = 0.0027). It was noted that the degree of inflammation seen in the lower ureter was significantly greater than that seen at the site of fragmentation (p = 0.01), and that this grade of inflammation correlated well with the size of ureteroscope used (p = 0.0026). Further, the degree of dilatation of the ureter and pelvicalyceal system was significantly greater when the larger calibre ureteroscope had been used (p = 0.0056) ranging up to hydronephrosis with flattening of the papillae. If there is any parallel which can be drawn between the pig ureter and the human ureter then it suggests that ureteroscopy is more significant than the modality of fragmentation used. The contribution of the laser may therefore be more by the miniaturization of instrumentation which will be made possible than by any advantage it may have as a fragmenter.

Animals↗
PubMed1987

Pulsed dye laser fragmentation of ureteral calculi: initial clinical experience.

The pulsed dye laser, emitting at wavelengths of 504 nm. for 1 microsecond. at a frequency of 5 Hz. transmitted via a 250 mu in diameter silicon-coated quartz fiber, was passed into the ureter through the working channel of a 9.5F rigid ureteroscope. Seventeen patients with ureteral calculi too large to be extracted directly, who were unable to be treated by extracorporeal shock wave lithotripsy or who otherwise would have required transureteral or percutaneous ultrasonic stone removal, underwent attempted stone fragmentation by pulsed dye laser application. Of the 17 calculi 16 were fragmented to spontaneously passable or easily extractable fragments. There was no significant ureteral injury, thermal or otherwise, attributable to laser energy action. At 3-month followup 15 of the 17 ureters had improved and 2 showed evidence of ureterscopic injury. The mechanism of stone fragmentation by laser is small volume "shock wave" formation.

Coloring Agents↗
PubMed1987

Controlled removal of human stratum corneum by pulsed laser.

A new method is presented for controlled removal of the stratum corneum of human skin. An excimer laser (193 nm wavelength, 14 ns pulsewidth) was used to remove stratum corneum from in vitro human skin samples by an ablative process. The tritiated water (3H2O) permeability constant and electrical resistance of skin samples were measured in a diffusion chamber apparatus to quantify the enhancement of skin permeability. Each laser pulse ablates about a micrometer of stratum corneum, which allows controlled removal of tissue. The maximum specific enhancement of the 3H2O permeability constant obtained after complete stratum corneum removal depends on the laser pulse energy used. The most gentle laser ablation, achieved with a radiant exposure of 70 mJ/cm2 per pulse, produced a 124-fold enhancement, which is comparable to that achieved after stratum corneum removal by tape-stripping or removal of epidermis by mild heat treatment. Rapid tissue ablation occurred at higher radiant exposures of 170-480 mJ/cm2 per pulse, but only a 45-fold enhancement of permeability was achieved. The precision with which stratum corneum can be ablated using excimer laser pulses may allow further basic research on the internal structure of stratum corneum and on the re-epithelization in controlled wounds. The technique may prove useful clinically to enhance percutaneous transport in applications such as topical delivery of drugs, patch testing, and percutaneous blood gas monitoring.

Adult↗
PubMed1987

Prolongation of murine skin allograft survival by the systemic effects of 8-methoxypsoralen and long-wave ultraviolet radiation (PUVA).

Systemic administration of the photoactive drug 8-methoxypsoralen to a group of mice bearing cutaneous allografts, followed by exposure to long-wave ultraviolet radiation (UVA, 320-400 nm) (PUVA) daily for 14 days at a site distant from the allograft, significantly increased the survival time of the allografts. This effect was seen both in donor-recipient combinations that differ at the major histocompatibility complex and in those differing only at minor histocompatibility loci. Treatment with 8-methoxypsoralen or long-wave UV radiation alone was ineffective in prolonging allograft survival, as were doses of mid-wave UV radiation (UVB, 280-320 nm) that produced greater inflammation than the PUVA protocol. Allografted, PUVA-treated animals also demonstrated decreased alloantigen reactivity against donor-strain spleen cells during the period of treatment by cytotoxicity assays. Allografts of skin in the murine system are highly immunogenic and are generally rejected faster than organ allografts; thus PUVA treatment appears to exert a potent effect on prolonging allograft survival. The systemic nature of the effect and the fact that adverse side effects from PUVA are largely limited to the skin suggest that PUVA might have a role in clinical organ transplantation management.

Animals↗
PubMed1987

Ultrastructure: effects of melanin pigment on target specificity using a pulsed dye laser (577 nm).

It has been shown recently that brief pulses of 577 nm radiation from the tunable dye laser are absorbed selectively by oxyhemoglobin. This absorption is associated with highly specific damage to superficial vascular plexus blood vessels in those with lightly pigmented (type I-II) skin. To determine whether pigmentary differences in the overlying epidermis influence this target specificity, we exposed both type I (fair) and type V (dark) normal human skin to varying radiant exposure doses over 1.5-microsecond pulse durations from the tunable dye laser at a wavelength of 577 nm. Using ultrastructural techniques, we found in type I skin that even clinical subthreshold laser exposures caused reproducible alterations of erythrocytes and adjacent dermal vascular endothelium without comparable damage to the overlying epidermis. In contrast, degenerated epidermal basal cells represented the predominant form of cellular damage after laser exposure of type V skin at comparable doses. We conclude that epidermal melanin and vascular hemoglobin are competing sites for 577 nm laser absorption and damage, and that the target specificity of the 577 nm tunable dye laser is therefore influenced by variations in epidermal pigmentation. This finding is relevant to the clinical application of the tunable dye laser in the ablative treatment of vascular lesions. We also found on ultrastructure that the presence of electron-lucent circular structures of approximately 800 A in diameter were observed only at and above clinical threshold doses in those with type I skin and at the highest dose of 2.75 J/cm2 in type V skin. It has been proposed that these structures might be heat-fixed molds of water vapor. Both this and ultrastructural changes of epidermal basal cells demonstrate mechanisms responsible for alteration of tissue after exposure to 577 nm, which are discussed.

Animals↗
PubMed1987

Unscheduled DNA synthesis in human skin after in vitro ultraviolet-excimer laser ablation.

DNA damage repaired by the excision repair system and measured as unscheduled DNA synthesis (UDS) was assessed in freshly excised human skin after 193 and 248 nm ultraviolet (UV)-excimer laser ablative incisions. Laser irradiation at 248 nm induced DNA damage throughout a zone of cells surrounding the ablated and heat-damaged area. In contrast, with 193 nm irradiation UDS was not detected in cells adjacent to the ablated area, even though DNA strongly absorbs this wavelength. Our results suggest that the lack of UDS after 193 nm irradiation is due to: "shielding" of DNA by the cellular interstitium, membrane, and cytoplasm, DNA damage that is not repaired by excision repair, or thermal effects that either temporarily or permanently inhibit the excision repair processes.

Adult↗
PubMed1987

The pulsed dye laser: its use at 577 nm wavelength.

The ability to increase laser-induced cutaneous blood vessel damage selectivity is dependent upon optimizing various intrinsic laser parameters. Varying the laser emission wavelength, pulse duration, and/or incident energy dosage allows the clinician potential improvement in the laser treatment of cutaneous small blood vessel processes such as port-wine hemangioma and telangiectasia. The pulsed dye laser at 577 nm and a pulse duration of 300 to 400 microseconds, incorporates desired laser parameters into its design. Clinical evaluation of the therapeutic outcome with this laser reveals favorable results while significantly minimizing potential adverse side effects.

Hemangioma↗
PubMed1987

Tunable pulsed dye laser for the treatment of benign cutaneous vascular ectasia.

A tunable pulsed dye laser emitting at 577 nm and 360 microseconds pulse width was used to treat benign cutaneous vascular ectasias other than port wine stain in 77 patients. Except for leg telangiectasias (34 patients), the overall response was excellent. Forty-two of forty-five patients with hemangiomas, spider nevi, angioma serpiginosum, venous lakes or facial telangiectasias showed excellent results after 1-4 consecutive treatments. Scarring was observed in none of the patients. These results confirm previous data on the use of the tunable dye laser in the treatment of port wine stain, and suggest that 577 nm wavelength and 360 microseconds pulse width allow the selective photothermolysis of vascular cutaneous ectasias with better clinical results than previously reported.

Adult↗
PubMed1987

[Selective photothermolysis: contribution to the treatment of flat angiomas (port wine stains) by laser].

Since 1962, lasers have been used in dermatology and have become the first choice in the treatment of superficial, vascular ectasia. Lasers are unique sources of light; they are coherent, monochromatic, collimated and intense. By careful selection of wavelength, pulse duration, and intensity, it is often possible to selectively confine a laser effect to a specific histologic structure in tissue, depending upon the tissue properties. The ideal treatment of Port Wine Stains (PWS) should irreversibly damage the ectatic vessels but minimize heating of the epidermis and superficial dermis. A theory, called selective photothermolysis, predicts the optimal combination of laser parameters of achieving this ideal treatment of PWS to be a wavelength of 577 nm, a pulse duration of 0.35-10 msec, and an energy per surface area of about 7-8 J/cm2. Laser wavelength: The wavelength of 577 nm is preferred because it: maximizes the selective absorption by hemoglobin, minimizes absorption by epidermal melanin, provides sufficient depth of penetration in the blood to coagulate 0.1 mm vessels allows penetration of light into dermis up to 1 mm. Laser pulse duration: A pulse-width in the range of 0.35-10 msec allows the temperature elevation to be uniform inside the vessel and to be confined to the vessel area. Shorter pulses superheat the red blood cells causing explosive boiling and hemorrhage. Longer pulses allow heat to diffuse away from vessels, requiring greater energies per pulse to achieve vessel damage. An increased energy per pulse increases the risk of excessive damage to surrounding tissue.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1986

Tunable dye laser (577 nm) treatment of port wine stains.

Despite steady improvement in the laser treatment of port wine stains (PWS), hypertrophic scarring remains a serious side-effect in approximately 10% of patients. The tunable dye laser (577 nm) has been shown to cause selective vascular destruction in normal and PWS skin. We have treated ten patients using a tunable dye laser (577 nm, 300 mu sec) resulting in clearing of the PWS without any evidence of hypertrophic scarring. Treatment requires no anesthesia or wound care, and there were no postoperative infections.

Adolescent↗
PubMed1986

Contribution of topical tar oil to ultraviolet B phototherapy for psoriasis.

A bilateral comparison study of twenty-two outpatients with psoriasis assessed clearing experience and remission time on halves of the body to which tar oil and oil vehicle (an emollient) were applied twice daily. In addition, both sides were treated three times a week with suberythemogenic doses of ultraviolet B radiation. Of the eighteen patients who complied with the protocol, fourteen (78%) had clearing. There was no significant difference between body halves with regard to the number of treatments to clearing, the dose of ultraviolet B to clearing, or the remission time (p greater than 0.2, all comparisons). Our data indicate with 95% confidence that using tar oil in conjunction with ultraviolet B phototherapy reduces the average total ultraviolet B dose required for clearing by a maximum of 9%, in comparison with using oil vehicle and ultraviolet B. These findings suggest that there is insufficient evidence for substantial clinical benefit to recommend tar oil use in conjunction with outpatient ultraviolet B phototherapy for psoriasis.

Adult↗
PubMed1986

Effect of continued ultraviolet B phototherapy on the duration of remission of psoriasis: a randomized study.

Phototherapy using sunburn spectrum ultraviolet radiation (UVB) is now a frequently utilized treatment for psoriasis that is extensive or has not responded to topical preparations. Four university centers performed a prospective randomized clinical trial to compare remission times of patients with psoriasis who continued UVB phototherapy after initial clearing with this therapy and patients whose UVB phototherapy was discontinued within 3 weeks of clearing. As assessed by life table methods, the time to flare after initial clearing for patients on UVB maintenance therapy was significantly longer than for patients who discontinued UVB within 3 weeks after initial clearing. Our data suggest that continuing UVB phototherapy after initial clearing contributes to the duration of disease control and is justified for many patients.

Actuarial Analysis↗
PubMed1986

Selective ablation of atheromas using a flashlamp-excited dye laser at 465 nm.

Ablation of human atheromas with laser pulses that had only a small effect on normal artery tissue was shown in vitro in air and under saline using 1-mu sec pulses at 465 nm from a flashlamp-excited dye laser. At this wavelength, there is preferential absorption in atheromas due to carotenoids. The threshold fluence for ablation was 6.8 +/- 2.0 J/cm2 for atheromas and 15.9 +/- 2.2 J/cm2 for normal aorta tissue. At a fluence of 18 J/cm2 per pulse, the ablated mass per unit of energy ranged from 161 to 370 micrograms/J for atheromas and from 50 to 74 micrograms/J for normal aorta tissue. Ablation products consisted of cholesterol crystals, shredded collagen fibers, and small bits of calcific material. Most debris was less than 100 micron in diameter, but a few pieces were as large as 300 micron. High-speed photography of ablation in air suggested explosive ejection of debris, caused by vapor formation, at speeds on the scale of 300 m/sec. Histological analysis showed minimal thermal damage to residual tissue. These data indicate that selective laser ablation of atheromas is possible in vitro.

Arteriosclerosis↗