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W F Bauer

Publications and source records attributed to W F Bauer.

7 recordsLinked to original sources
PubMed1995

11B nuclear magnetic resonance studies of the interaction of borocaptate sodium with serum albumin.

The interaction between borocaptate sodium, Na2B12H11SH (BSH), and three types of serum albumin--bovine, human and dog (BSA, HSA and DSA)--has been investigated quantitatively using 11B NMR. The 11B chemical shifts and relaxation rates of BSH were studied with various concentrations of serum albumin (1-5%, w/v) at 295-310 degrees K. Correction of the longitudinal relaxation rate (R1) due to protein viscosity effects was accomplished. The corrected R1 values were analyzed mathematically using a saturation function and linear regression. The linewidths of 11B resonances, which are related to the spin-spin relaxation rates (R2), were also measured. The binding fractions (P), the number of binding sites (NBS), and the binding constants (Kb) of BSH at various concentrations of the three types of serum albumin (1-5%, w/v) were determined at 295 and 310 degrees K. We speculate that the nature of this interaction may be electrostatic.

Animals↗
PubMed1994

Biodistribution of boron in dogs with spontaneous intracranial tumors following borocaptate sodium administration.

Borocaptate sodium (Na2B12H11SH) is a potentially useful compound for boron neutron capture therapy of intracranial tumors. Tumor and normal tissue boron concentrations were evaluated in 30 dogs with naturally occurring intracranial tumors after i.v. borocaptate sodium infusion (55 mg boron/kg). Postmortem tissue boron concentrations were measured for three postinfusion time periods (2, 6, and 12 h) by inductively coupled plasma atomic emission spectroscopy. Mean boron concentrations for extracerebral tumors were 40.6 +/- 16.9 (2 h; n = 8), 25.9 +/- 11.7 (6 h; n = 5), and 8.6 +/- 4.5 micrograms boron/g (12 h; n = 6). Mean boron concentrations for intracerebral tumors were 30.6 +/- 17.5 (2 h; n = 7) and 2.9 +/- 1.8 micrograms boron/g (6 h; n = 4). Mean tumor boron concentrations were lower at longer postinfusion times. The tumor:normal brain boron concentration ranged from 0.8 to 19.8. Tumor:blood boron concentrations were less than one for all but three dogs and ranged from 0.04 to 1.4. Mean peritumor boron concentrations were highly variable but exceeded that of normal brain in 10 of 20 dogs. In some dogs, the mean peritumor boron concentration was similar to or exceeded the tumor boron concentration. Distant or contralateral normal brain had consistently low boron concentrations. Some cranial and systemic tissues had high boron concentrations, indicating substantial extravascular boron. The spontaneous animal tumors provided a realistic spectrum of data and enabled extensive sampling of diseased and normal tissues. The biodistribution of boron from borocaptate sodium administration was partially favorable because of high tumor boron concentrations. Empirical radiation dose tolerance studies should be used to determine the impact of the unfavorably high boron concentration of blood and some cranial tissues.

Adenoma↗
PubMed1992

Borocaptate sodium: a potential boron delivery compound for boron neutron capture therapy evaluated in dogs with spontaneous intracranial tumors.

Borocaptate sodium (Na2B12H11SH) is a boron-carrying compound under consideration for use in boron neutron capture therapy. The biodistribution of boron from borocaptate sodium administration will partly determine boron neutron capture therapy efficacy and normal tissue radiation tolerance. The biodistribution of boron was determined in 30 dogs with spontaneous intracranial tumors at 2, 6, or 12 hr after intravenous borocaptate sodium infusion. Blood and tissue boron concentrations were measured using inductively coupled plasma atomic emission spectroscopy. Mean tumor boron concentration (mean +/- standard error) was 35.9 +/- 4.6 (n = 15), 22.5 +/- 6.0 (n = 9), and 7.0 +/- 1.1 micrograms of boron per g (n = 6) at 2, 6, and 12 hr, respectively, after borocaptate sodium infusion. Peritumor boron concentrations were elevated above that of normal brain in half of the dogs. Normal brain boron concentration (mean +/- standard error) was 4.0 +/- 0.5, 2.0 +/- 0.4, and 2.0 +/- 0.3 micrograms of boron per g at 2, 6, and 12 hr after infusion, respectively. Some cranial and systemic tissues, and blood, had high boron concentration relative to tumor tissue. Geometric dose sparing should partly offset these relatively high normal tissue and blood concentrations. Borocaptate sodium biodistribution is favorable because tumor boron concentrations of recommended magnitude for boron neutron capture therapy were obtained and there was a high tumor-to-normal brain boron concentration ratio.

Animals↗
PubMed1992

Model studies directed toward the boron neutron-capture therapy of cancer: boron delivery to murine tumors with liposomes.

The successful treatment of cancer by boron neutron-capture therapy (BNCT) requires the selective concentration of boron-10 within malignant tumors. The potential of liposomes to deliver boron-rich compounds to tumors has been assessed by the examination of the biodistribution of boron delivered by liposomes in tumor-bearing mice. Small unilamellar vesicles with mean diameters of 70 nm or less, composed of a pure synthetic phospholipid (distearoyl phosphatidylcholine) and cholesterol, have been found to stably encapsulate high concentrations of water-soluble ionic boron compounds. The hydrolytically stable borane anions B10H10(2-), B12H11SH2-, B20H17OH4-, B20H19(3-), and the normal form and photoisomer of B20H18(2-) were encapsulated in liposomes as their soluble sodium salts. The tissue concentration of boron in tumor-bearing mice was measured at several time points over 48 h after i.v. injection of emulsions of liposomes containing the borane anions. Although the boron compounds used do not exhibit an affinity for tumors and are normally rapidly cleared from the body, liposomes were observed to selectively deliver the borane anions to tumors. The highest tumor concentrations achieved reached the therapeutic range (greater than 15 micrograms of boron per g of tumor) while maintaining high tumor-boron/blood-boron ratios (greater than 3). The most favorable results were obtained with the two isomers of B20H18(2-). These boron compounds have the capability to react with intracellular components after they have been deposited within tumor cells by the liposome, thereby preventing the borane ion from being released into blood.

Animals↗
PubMedDate not supplied

Macroscopic geometric heterogeneity effects in radiation dose distribution analysis for boron neutron capture therapy.

Calculations of radiation flux and dose distributions for boron neutron capture therapy (BNCT) of brain tumors are typically performed using sophisticated three-dimensional analytical models based on either a homogeneous approximation or a simplified few-region approximation to the actual highly heterogeneous geometry of the irradiation volume. Such models should be validated by comparison with calculations using detailed models in which all significant macroscopic tissue heterogeneities and geometric structures are explicitly represented as faithfully as possible. This paper describes such a validation exercise for BNCT of canine brain tumors. Geometric measurements of the canine anatomical structures of interest for this work were performed by dissecting and examining two essentially identical Labrador retriever heads. Chemical analyses of various tissue samples taken during the dissections were conducted to obtain measurements of elemental compositions for the tissues of interest. The resulting geometry and tissue composition data were then used to construct a detailed heterogeneous calculational model of the Labrador head. Calculations of three-dimensional radiation flux distributions pertinent to BNCT were performed for this model using the TORT discrete-ordinates radiation transport code. The calculations were repeated for a corresponding volume-weighted homogeneous-tissue model. Comparison of the results showed that peak neutron and photon flux magnitudes were quite similar for the two models (within 5%), but that the spatial flux profiles were shifted in the heterogeneous model such that the fluxes in some locations away from the peak differed from the corresponding fluxes in the homogeneous model by as much as 10%-20%. Differences of this magnitude can be therapeutically significant, emphasizing the need for proper validation of simplified treatment planning models.

Animals↗