PubMed Health⌕ Search

Biomedical subjects

H Bobo

Publications and source records attributed to H Bobo.

9 recordsLinked to original sources
PubMed1994

High-flow microinfusion: tissue penetration and pharmacodynamics.

High-flow microinfusion provides a means for delivering macromolecules to large volumes of brain in easily obtainable time intervals. Slowly degraded approximately 180-kDa macromolecules, delivered at a constant volumetric flow rate of 3 microliters/min into homogeneous brain tissue (e.g., gray matter), would penetrate to a 1.5-cm radius in 12 h. The predicted concentration profile is relatively flat until it declines precipitously at the flow front. Hence, tissues are dosed rather uniformly, providing control over the undesired toxicity that may occur with alternative methods that depend on large concentration gradients for tissue transport. The penetration advantage of high-flow (convective) over low-flow (diffusive) microinfusion has been assessed at fixed pharmacodynamic effect. A 12-h high-flow microinfusion of a macromolecule degraded with a characteristic time of 33.5 h would provide 5- to 10-fold increases in volume over low-flow infusion and total treatment volumes > 10 cm3. Slower degradation rates would result in larger treatment volumes; more rapid degradation rates would reduce the volume but still favor convective over diffusive administration. This technique may be applicable to a variety of diagnostic and therapeutic agents such as radioimmunoconjugates, immunotoxins, enzymes, growth factors, and oligonucleotides.

Animals↗
PubMed1992

Measurement of thymidine replacement in patients with high grade gliomas, head and neck tumors, and high grade sarcomas after continuous intravenous infusions of 5-iododeoxyuridine.

Based upon the radiation sensitization properties of the halogenated pyrimidines, 5-iododeoxyuridine (IdUrd) and 5-bromodeoxyuridine, long term i.v. infusions of halogenated pyrimidines in conjunction with fractionated radiation therapy have been evaluated in the treatment of a variety of human malignancies. While clinical studies have attempted to measure the halogenated pyrimidine incorporation, few have successfully related tumor response to the incorporation of IdUrd by the tumor. The present study reports the continuous IdUrd labeling index (number of cells labeled) and the IdUrd corrected replacement (percentage of thymidine replacement in the labeled cells of the population) from the tumors of 17 patients who received continuous infusions of IdUrd (1000 mg/m2/24 h). The tumors treated included four high grade gliomas, five head and neck tumors, four high grade sarcomas, and five other tumors of varying types. Less than 25% of the cells in three of four gliomas incorporated IdUrd after 5-7-day IdUrd infusion time. Corrected replacement for the gliomas ranged from 0 to 4%. In contrast, 63-85% of the cells in the head and neck biopsies were labeled with IdUrd after 3-7-day IdUrd infusions suggesting that these large tumors (3-12 cm diameter) have a high fraction of dividing cells. Corrected replacements values for the head and neck tumor patients ranged from 2.9 to 26.3%. The high grade sarcomas also demonstrated a high percentage of IdUrd labeled cells (57-79%) with three patients having corrected replacements of 7.5-14.2%. The continuous labeling and thymidine replacement data for four patients from whom serial biopsies were taken during IdUrd infusion demonstrated both an increasing IdUrd replacement and continuous labeling index with an increasing duration of IdUrd infusion. The clinical response of both the high grade glioma and head and neck tumor patients indicate that the IdUrd replacement and labeling data may provide some important predictive information with regard to the successful use of the halogenated pyrimidines in clinical radiation trials.

Animals↗
PubMed1992

Effect of intra-arterial cisplatin and 1,3-bis(2chloroethyl)-1-nitrosourea (BCNU) dosage on radiographic response and regional toxicity in malignant glioma patients: proposal of a new method of intra-arterial dosage calculation.

The frequency of both neurologic toxicity and therapeutic response due to intra-arterial (IA) chemotherapy is decreased by dose reduction. A method to individualize IA drug dosage is needed to provide each patient with the safest, most effective dose. Most trials of IA chemotherapy for malignant glioma have used body surface area (BSA) to calculate dosage; but brain size and arterial distribution do not correlate well with BSA. Fixed doses of cisplatin and BCNU were used in combination to perform 35 IA infusions in 20 malignant gliomas patients. Doses modified by the number of major intracranial vessels supplied by the infused artery were used in 34 infusions in 19 patients. Patients receiving 150 to 200 mg CP and 300 mg BCNU had an incidence of neurologic deficit of 5.6% if greater than or equal to 3 vessels were supplied by the infused artery compared to 42% for those with only 2 vessels. This crude dose modification maintained efficacy while reducing neurologic toxicity. Further refinement is possible using well established intra-arterial pharmacokinetic principles. Intra-arterial dosing based on volume flow at the site of infusion would yield a more reproducible exposure of the infused capillary bed to a drug than methods currently in use. More consistent drug exposure should reduce toxicity due to over dosing and treatment failure due to under dosing.

Adult↗
PubMed1992

Long-term follow-up on National Cancer Institute Phase I/II study of glioblastoma multiforme treated with iododeoxyuridine and hyperfractionated irradiation.

PURPOSE: We report the results of the final phase I/II program in glioblastoma (GBM) multiforme patients using only hyperfractionated irradiation and intravenous iododeoxyuridine (IdUrd). METHODS: For a decade we investigated halogenated pyrimidine radiosensitizers in an effort to exploit the potential for differential uptake of thymidine analogs between proliferating tumor and normal brain tissues. Trials began with bromodeoxyuridine (BrdUrd) but were changed to IdUrd when the latter proved less photosensitizing. A series of dose-escalating pilot trials led to treatment at a maximum-tolerated dose (MTD) of IdUrd of 1,000 mg/m2/d for two separate 14-day courses, one during the initial radiation field and one during the cone down. The radiotherapy also evolved over time and was hyperfractionated in all cases reported. Over 5 years we accrued 45 patients into the final hyperfractionated, 1,000 mg/m2/d scheme. We report here results on only the patients with minimum follow-up of 1 year (90% had at least 2 years of follow-up) or until death. RESULTS: The results do not indicate a significant benefit for use of sensitizers, as compared with other contemporary and aggressive types of radiation treatment. The median survival has been 11 months, with a 2-year actuarial survival of 9%. As yet, there are no survivors at 3 years. Tumor biopsies at craniotomy showed relatively low sensitizer incorporation. CONCLUSION: The failure of radiosensitizers combined with radiation therapy to show major benefit may be due to patient selection but appears also to be related to the combined problems of poor drug penetration/uptake into tumor, tumor-cell heterogeneity, and a high inherent cellular radioresistance of GBM.

Adult↗
PubMed1990

Multiple pterygium syndrome: neuromuscular findings in a case.

A woman with multiple congenital joint deformities and webbing (multiple pterygium syndrome) is described. The electrophysiologic study revealed normal sensory and motor nerve conduction velocities. However, the compound muscle action potential amplitude and the voluntary motor unit size were reduced, suggesting a decrease in the number of muscle fibers. The muscle biopsy was otherwise unremarkable histologically and histochemically. Possible explanations for these findings are discussed.

Adult↗
PubMed1987

Intracranial BCNU.

Explore the source record for details and available documents.

Brain Neoplasms↗
PubMed1986

Inaccurate pressure readings for subarachnoid bolts.

The subarachnoid bolt has been used extensively to monitor intracranial pressure in a variety of conditions. We have had two patients who had subarachnoid bolts in place that were thought to be functional in whom evidence of increased pressure was present. In one case, the patient had Reye's syndrome with seizure activity, decerebrate posturing, fixed and dilated pupils, and cardiac arrest. Although autopsy revealed evidence of cerebellar and uncal herniation, verifying the presence of pressure cones, the subarachnoid bolt pressure was never elevated and had a good wave form. In the other case, the patient developed an epidural hematoma postoperatively while a subarachnoid bolt was in place. The subarachnoid bolt was measuring pressures of less than 15 mm Hg with a good wave form despite clinical and, subsequently, computed tomographic evidence of an evolving mass. The use of a pressure monitor such as the subarachnoid bolt should not replace frequent clinical assessment of the patient.

Adult↗
PubMedDate not supplied

Intracranial aneurysms in a child with recurrent atrial myxoma.

Subarachnoid hemorrhage and formation of intracranial aneurysms occurred in an adolescent with recurrent atrial myxomas without a history of cerebral embolic infarction. Myxomatous intracranial aneurysm is a potentially lethal complication in children.

Adolescent↗