Biomedical subjects

C A Bolger

Publications and source records attributed to C A Bolger.

6 recordsLinked to original sources

PubMed1984

Hematoporphyrin derivative photoradiation therapy of the rat 9L gliosarcoma brain tumor model.

The distribution of hematoporphyrin derivative (HPD) in the rat 9L gliosarcoma intracerebral brain tumor model at 4, 24, 48, and 72 hours after intravenous administration was evaluated using a digital video fluorescence microscopy technique. Maximum tissue fluorescence in the normal brain was observed at 4 hours, whereas maximum fluorescence in the tumor regions occurred at 24 hours. Although the fluorescence counts suggested that there was significant uptake of HPD within the tumors when compared to normal brain, only 33% to 44% of each of the eight tumors surveyed showed fluorescence. In response to a laser light dose (633 nm) of 30 J/cm2, six rats that had been sensitized with HPD had a patchy coagulation necrosis involving up to 70% of the total tumor volume. In contrast, four rats given HPD only or exposed to laser only had no areas of necrosis, as observed on histological examination. In a group of 30 rats, no prolongation of survival was observed in response to photoradiation therapy.

Animals↗

PubMed1984

Effect of microsurgical and carbon dioxide and argon laser resection on recurrence of the intracerebral 9L rat gliosarcoma.

The intracerebral 9L rat brain tumor was resected from 38 rats with the use of standard microsurgical techniques, the carbon dioxide laser, or the argon laser. The extent of resection was evaluated by histological examination, and the effect on survival of the three methods was compared. All three methods achieved histologically verifiable gross total resection, and tumor recurrence after resection by all three methods occurred at the same rate.

Animals↗

PubMed1983

Diagnosis of acute nerve compression in the cat with high frequency nerve trains evoked responses.

High frequency nerve trains were evaluated from above and below the site of compression before, during, and after acute compression of the sciatic nerves of six adult cats. Acute nerve compression reduced the ability of axons to conduct high frequency impulse trains: the longer the compression, the lower the frequency of impulses that could be conducted through the region of compression without a decrement in latency and amplitude. Possible mechanisms for alterations of nerve trains and the possible clinical and experimental use of nerve trains analysis are discussed.

Acute Disease↗

PubMed1982

Evaluation of misonidazole peripheral neurotoxicity in rats by analysis of nerve trains evoked response.

The clinical use of misonidazole and other nitroimidazole radiosensitizing agents is limited by the peripheral and central neurotoxicity that is produced in animals and humans. In a blinded study, rats treated with misonidazole at either 100 mg/kg or 300 mg/kg, 5 days/week for 3 weeks, were evaluated for peripheral neurotoxicity using nerve trains evoked responses. Only one rat treated at a dose of 100 mg/kg developed symptoms and signs of neurotoxicity, while all rats treated at 300 mg/kg developed these signs and symptoms. Nerve trains analysis made possible a diagnosis of neurotoxicity before overt clinical signs appeared. This test is non-invasive and may be useful for evaluating patients receiving nitroimidazole radiosensitizers as part of a radiation therapy regimen.

Animals↗

PubMed1982

Comparison of the brain tissue response in rats to injury by argon and carbon dioxide lasers.

This study compares the acute and chronic response of brain tissue to injury by equal power density, focused argon (Ar) and carbon dioxide (CO2) laser beams. A cortical incision from 0.2-second laser pulses of 12.5 X 10(3) W/cm2 power density was made in the exposed cortex of 32 rats using either the CO2 or the Ar laser. The brains were examined at intervals from 1/2 hour to 1 month after injury. Histologically, all brain incisions were sharply demarcated hemispheroidal defects with a vaporized center bordered by a zone of coagulation necrosis surrounded by edema. The laser incisions were found to be of equal depth (less than 1 mm). The average cortical surface diameter of the CO2 laser incision was 0.86 mm for a focused beam spot size 0.45 mm in diameter, compared with 0.65 mm with the Ar laser, which had a focused beam spot size 0.15 mm in diameter. In both incisions, some delayed depth effect was observed. A progression of the tissue necrosis by approximately 17% was observed during the first 24 hours after injury. During the first 4 hours after injury, the Evans blue blood-brain barrier defect (EBBD) surrounding the cortical incisions averaged 5.80 mm2 for the CO2 incision and 0.888 mm2 for the Ar incision. In both types of brain incision, the EBBD appeared to resolve by 24 hours after injury. At 1 month after injury, a core of coagulation necrosis surrounded by mild fibrillary gliosis was observed. At the power density and focused beam spot sizes used, there was no significant difference in the overall brain tissue response to Ar and CO2 laser lesions.

Animals↗

PubMed1982

Spinal cord pathways mediating somatosensory evoked potentials.

Using a CO2 laser, discrete thoracic spinal cord lesions were made in cats anesthetized with ketamine and xylazine (Rompun). Differences in cortical somatosensory evoked potentials (SEP's) produced with high-intensity stimulation (20 times the motor threshold) of each posterior tibial nerve determined for nine different combinations of unilateral spinal cord lesions. The results of these studies show that nerve fibers in the ipsilateral dorsal column, the ipsilateral dorsal spinocerebellar tract, and the contralateral ventrolateral tracts with respect to the side of leg stimulation, contribute to cortical SEP's. A lesion of the dorsal spinocerebellar tract affected only the early waves (less than 30 msec) of the SEP from leg stimulation ipsilateral to the side of the lesion, whereas a solitary lesion of the ventrolateral tract caused changes primarily in the amplitude of later waves (greater than 30 msec) of the SEP produced by contralateral leg stimulation. Lesions involving one-half of the dorsal column caused changes in the amplitude of both the early and late waves produced by stimulation ipsilateral to the side of the lesion. The effects of various combinations of lesions on the cortical SEP's were not additive, which indicates significant interaction between afferent pathways. These findings suggest that high-intensity peripheral nerve stimulation, which activates both C and A fibers, could be used intraoperatively to assess spinal cord function with more accuracy than the current practice of using a stimulus strength of twice the motor threshold. The importance of using anesthetic agents that do not depress cortical activity (which may affect the later components of the SEP) is also emphasized.

Animals↗