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Biomedical subjects

J Tulip

Publications and source records attributed to J Tulip.

47 records · Page 3Linked to original sources
PubMed1986

Bactericidal action of carbon dioxide laser radiation in experimental dental root canals.

The ability of a carbon dioxide laser to sterilize the root canal of human teeth has been investigated. Three oral bacteria, Streptococcus sanguis, Streptococcus mutans, and Actinomyces viscosus, and three other bacteria, Bacillus cereus, Staphylococcus aureus, and Pseudomonas aeruginosa were used as experimental organisms. Exposure of cells on glass slides to laser radiation showed there was little difference in the exposure required to kill these six organisms. Complete recovery of bacteria from the root canal was initially a problem and was only achieved when bacterial manipulations and removal were carried out in rapid succession, within 5 min of inoculation. However, the geometry of the instrumented canal and the laser alignment were major factors in achieving consistent cell death of oral bacteria in the root canals. Using sets of 10 teeth, four repeated exposures of 10 W for 1 s was found to sterilize 4 or more of the teeth.

Actinomyces↗
PubMed1986

In vitro photoradiation therapy of the rat 9L gliosarcoma.

The authors have investigated various factors involved in the photoradiation treatment of 9L glioma cells. The cells were grown in tissue culture and exposed to light from a laser source that allowed accurate quantitation of the light energy. Cell death was determined following treatment using the trypan blue exclusion test. It was shown that the treatment is very wavelength-dependent following the absorption spectrum of hematoporphyrin derivative (HPD). The absorption peaks in the lower part of the spectrum are more efficient than those of higher wavelengths. Photoradiation therapy is more effective the higher the concentration of HPD. Intensity of light is a very important factor in calculating the total dose of light necessary for this treatment.

Animals↗
PubMed1986

Treatment of Dunning R3327-AT rat prostate tumors with photodynamic therapy in combination with misonidazole.

Fischer X Copenhagen rats bearing Dunning R3327-AT tumors were treated with hematoporphyrin derivative and red light (630 nm from an argon-driven dye laser) alone or in combination with the hypoxic cell radiosensitizer, misonidazole (MISO). In vitro studies had suggested that hypoxia might significantly decrease the cytotoxicity of photodynamic therapy (PDT) and labeling with [14C]MISO had revealed a significant fraction of viable hypoxic cells in this tumor. PDT alone resulted in a growth delay of 8.8 days but no tumor cures were observed. The administration of MISO (i.p. at 0.5 mg/g) 33 min prior to PDT resulted in an average growth delay of 15.2 days and tumor cures (local control at 33 days) in 20% of animals treated. If MISO at a similar dosage was administered 30 min after PDT an average growth delay of 16.3 days was measured and tumor cure was observed in 70% of the animals treated. These results suggest that the hypoxic cell fraction in R3327-AT tumors might be a limitation to their curability by PDT. The addition of MISO and/or other hypoxic cell cytotoxic agents to PDT procedures may provide an effective means of treating PDT-resistant hypoxic cells in solid tumors.

Animals↗
PubMed1985

Photoradiation therapy of 9L-gliosarcoma in rats: hematoporphyrin derivative (types I and II) followed by laser energy.

Suspensions of 9L-gliosarcoma cells were inoculated into the brain or flank of rats and photoradiation therapy (PRT) was applied to the resulting tumors. The PRT consisted of hematoporphyrin derivative (HpD), type I or II, followed by single-fiber laser energy 24, 48, or 72 h later. Necrotic foci in brain tumors were most numerous following laser exposure 24 h after HpD; they were more than twice as common, and with less damage to healthy tissue, after HpD II than after HpD I with the same laser dose. Neither lifespan nor the final weight of brain tumor was affected by the type of HpD or whether PRT was applied once or twice. In rats with flank tumor, multiple PRT (up to X 4) did not delay tumor growth; also, 11 of 12 PRT-treated flank tumors grew after implantation at various sites in healthy rats. We conclude that HpD II is a more effective photosensitizer than HpD I. However, the value of PRT will be limited until a lethal dose of laser energy can be delivered throughout a tumor without destroying vital healthy tissue.

Animals↗
PubMed1985

Penetration of hematoporphyrin derivative into rat brain and intracerebral 9L glioma tissue.

Brain and glioma tissue levels of tritiated hematoporphyrin derivative (3H-HPD) were measured in normal and 9L intracerebral glioma-bearing rats at 24 hours following administration of 3H-HPD 2-20 mg/kg and at 24-120 hours after 3H-HPD 10 mg/kg. Levels of 3H-HPD in blood, liver, spleen and muscle were also measured. Tissue levels of 3H-HPD increased progressively as the dose was increased. In animals given 10 mg/kg, gradual decreases in tissue levels occurred between 24 and 72 hours but thereafter remained stable. The 3H-HPD level in gliomas was consistently 2-3 X greater than in brain tissue, despite changes in dosage and time interval. High levels of activity were measured in normal brain tissue at all dosage levels, and subsequent clearance of the 3H-HPD from brain, glioma, and other tissues was slow; at 120 hours after administration of 10 mg/kg, approximately 50% of the 24 hour level was still present. These results indicate that although a dose- and time-independent preferential uptake of hematoporphyrin derivative occurs in intracerebral gliomas, persistent high levels may be present in the surrounding brain. The disadvantages of using hematoporphyrin derivative rather than its individual components in studies of HPD uptake and photosensitization in the brain are discussed.

Animals↗
PubMed1984

Interstitial applications of laser irradiation in hematoporphyrin derivative-photosensitized Dunning R3327 prostate cancers.

Two prostate tumour models (Dunning R3327H and AT) were tested in rats to see if they were sensitive to hematoporphyrin-photoradiation therapy (HPD-PRT). The R3327H tumours were irradiated by implantation of a single fiber optic and the R3327 AT tumours were treated with implantation of four fiber optics simultaneously. Thermal measurements made at the tip of the fiber and up to 1 cm from the tip indicated temperature rises from 1.5 degree C to 20 degrees C at the tip and 0 degree to 8 degrees C distal to the tip, with power densities ranging from 100 mW to 500 mW. The R3327H tumour was controlled up to 8 weeks post-HPD-PRT, when the initial tumour size was 400-500 mm3. The R3327 AT tumours also respond to the HPD-PRT but a significant laser-induced thermal rise in the tumour is suspected.

Animals↗
PubMed1984

Effects of photoradiation therapy on normal rat brain.

Laser photoradiation of the brain via an optical fiber positioned 5 mm above a burr hole was performed after the injection of hematoporphyrin derivative (HpD) in 33 normal rats and 6 rats with an intracerebral glioma. Normal rats received HpD, 5 or 10 mg/kg of body weight, followed by laser exposure at various doses or were exposed to a fixed laser dose after the administration of HpD, 2.5 to 20 mg/kg. One control group received neither HpD nor laser energy, and another was exposed to laser energy only. The 6 rats bearing an intracranial 9L glioma were treated with HpD, 5 mg/kg, followed by laser exposure at various high doses. The temperature in the cortex or tumor was measured with a probe during laser exposure. The rats were killed 72 hours after photoradiation, and the extent of necrosis of cerebral tissue was measured microscopically. In the normal rats, the extent of brain damage correlated with increases in the dose of both the laser and the HpD. In all 6 glioma-bearing rats, the high laser doses produced some focal necrosis in the tumors but also damaged adjacent normal brain tissue. We conclude that damage to normal brain tissue may be a significant complication of high dose photoradiation therapy for intracranial tumors.

Animals↗
PubMed1982

Segmental irradiation of the bladder with neodymium YAG laser irradiation.

The Neodymium YAG laser energy source can be readily adapted for cystoscopic use by some simple modifications of existing urologic equipment. Both the fiberoptic resectoscope and a deflecting cystourethroscope have been adapted for this purpose. Fixation of the fiber tip 1 cm. from the target and use of a divergent beam of 36 degrees allows the delivery of standardized dosage to a relatively large bladder tissue volume. Animal experiments involving 35 mongrel dogs established that repetitive overlapping doses of 200 joules ech can successfully treat a large area of bladder resulting in a full thickness bladder wall injury. This technique has been used in 4 high risk patients with infiltrating bladder cancer without adverse sequelae. The ability to reliably produce a full thickness lesion may give this modality a therapeutic advantage over conventional cautery techniques especially for the treatment of residual infiltrative carcinoma.

Aluminum↗
PubMedDate not supplied

Experimental laser phototherapy of the Morris 7777 hepatoma in the rat.

The tumoricidal effect of the activation of hematoporphyrin derivative (HpD), by an argon-ion-dye-laser (wavelength 630 nm), was investigated in the Buffalo rat bearing subcutaneous implants of the Morris 7777 hepatoma. Tumor growth was monitored by measuring the tumor volume with constant force calipers. In control animals and those that were pretreated with HpD alone (10 or 20 mg per kg by i.p. injection) or laser light alone (2,000 J at 100 mW), a predictable exponential growth pattern of the cancer was observed. Animals were pretreated with HpD (10 mg per kg by i.p. injection) 48 hr prior to the fiberoptic, intratumor delivery of laser radiation (2,000 J at 100 mW), when the tumor had reached a volume greater than 1.5 cm3. Forty-eight hours after combined laser and HpD treatment, the hepatoma underwent coagulation necrosis, and the tumor volume rapidly increased from a mean value of 1.8 +/- 0.7 cm3 S.D. to a value of 5.8 +/- 1.5 cm3 S.D., compared with a mean of 3.7 +/- 0.7 cm3 S.D. in animals who had not received laser phototherapy. Rats treated with HpD and laser light survived longer (mean survival time 48 +/- 12 days S.D.) than did the other animals treated with the laser alone or HpD alone (mean survival time 31 +/- 16.5 S.D.). Tissue biodistribution studies with tritiated hematoporphyrin derivative, given with doses of 10 and 20 mg per kg of HpD, showed higher concentrations of the dye in the liver, kidneys and spleen than in the tumor at 48 hr after administration of the dye.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

Optical dosimetry for interstitial photodynamic therapy.

An approach to photodynamic treatment of tumors is the interstitial implantation of fiber optic light sources. Dosimetry is critical in identifying regions of low light intensity in the tumor which may prevent tumor cure. We describe a numerical technique for calculating light distributions within tumors, from multiple fiber optic sources. The method was tested using four translucent plastic needles, which were placed in a 0.94 X 0.94 cm grid pattern within excised Dunning R3327-AT rat prostate tumors. A cylindrical diffusing fiber tip, illuminated by 630 nm dye laser light was placed within one needle and a miniature light detector was placed within another. The average penetration depth in the tumor region between the two needles was calculated from the optical power measured by the detector, using a modified diffusion theory. Repeating the procedure for each pair of needles revealed significant variations in penetration depth within individual tumors. Average values of penetration depth, absorption coefficient, scattering coefficient, and mean scattering cosine were 0.282 cm, 0.469 cm-1, 250 cm-1 and 0.964, respectively. Calculated light distributions from four cylindrical sources in tumors gave reasonable agreement with direct light measurements using fiber optic probes.

Adenocarcinoma↗