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At least 19 recordsLinked to original sources
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↗
PubMed1990

Experimental boron neutron capture therapy for melanoma: systemic delivery of boron to melanotic and amelanotic melanoma.

The boron-containing melanin precursor analogue p-boronophenylalanine (BPA) has previously been shown to selectively deliver boron to pigmented murine melanomas when administered in a single intragastric dose. If boron neutron capture therapy is to become a clinically useful method of radiation therapy for human malignant melanoma, the boron carrier must be capable of delivering useful amounts of boron to remote tumor sites (metastases) and to poorly pigmented melanomas. We have now determined the ability of BPA to accumulate in several nonpigmented melanoma models including human melanoma xenografts in nude mice. The absolute amount of boron in the nonpigmented melanomas was about 50% of that observed in the pigmented counterparts but was still selectively concentrated in the tumor relative to normal tissues in amounts sufficient for effective neutron capture therapy. Single intragastric doses of BPA resulted in selective localization of boron in the amelanotic Greene melanoma carried in the anterior chamber of the rabbit eye and in a pigmented murine melanoma growing in the lungs. The ratio of the boron concentration in these tumors to the boron concentration in the immediately adjacent normal tissue was in the range of 3:1 to 4:1. These distribution studies support the proposal that boron neutron capture therapy may be useful as a regional therapy for malignant melanoma.

Animals↗
PubMed1990

In vitro determination of uptake, retention, distribution, biological efficacy, and toxicity of boronated compounds for neutron capture therapy: a comparison of porphyrins with sulfhydryl boron hydrides.

A major problem remaining in the evaluation of boronated compounds for neutron capture therapy (NCT) is the need to know the intra- or extracellular microdistribution of boron. This is a consequence of the short range of the 10B(n,alpha)7Li reaction products (approximately 10 microns), such that biological efficacy is dependent upon intracellular distribution. In particular, if boron location is predominantly extracellular, a significant reduction in efficacy would be expected. The in vitro procedure described here was developed mainly to provide information regarding the intra- and extracellular location and concentration of boron. However, use of the technique also allows the measurement of compound uptake and retention (binding) and the determination of biological efficacy by the evaluation of survival curves obtained following irradiation with thermal neutrons. Comparison is made to results obtained with boric acid (H3(10)BO3) and to results calculated for various boron distributions. Concomitantly, an indication of compound toxicity can be obtained from the plating efficiency of unirradiated control cells. Currently, most investigators utilize in vivo systems for testing and evaluating boron uptake from various carrier molecules. Given the large number of boron compounds being synthesized and needing evaluation as to their usefulness for NCT, the in vitro technique described here is simple and advantageous for initial compound screening. In addition to sparing animal lives, it is both time and cost effective and utilizes much smaller quantities of test compound than are required for an in vivo assay. A boronated porphyrin (BOPP) evaluated by the above procedure shows an uptake and retention approximately 20 times that of sulfhydryl boron hydride monomer (BSH); the latter compound is currently being used clinically for NCT in Japan and is anticipated for use in clinical trials in the United States. If the advantages demonstrated by BOPP in these in vitro studies are validated in animal experiments, BOPP should be considered for clinical application.

Animals↗
PubMed1990

Changes in boron concentration during development and ageing of Drosophila and effect of dietary boron on life span.

Total boron concentrations in Drosophila changed during development and ageing. The highest concentration of boron was found during the egg stage followed by a decline during the larval stages. Newly emerged flies contained 35.5 ppm boron. During the adult stage the boron concentration increased by 52% by 9 weeks of age. Adding excess dietary boron during the adult stage decreased the median life span by 69% at 0.01 M sodium borate and by 21% at 0.001 M sodium borate. Lower concentrations gave small but significant increases in life span. Supplementing a very low boron diet with 0.00025 M sodium borate improved life span by 9.5%. The boron contents of young and old mouse tissues were similar to those of Drosophila and human samples. We conclude that moderate levels of dietary boron may have a general protective effect in biological systems. The mechanism of this effect at present remains unknown.

Aging↗
PubMed1991

Biological efficacy of boronated low-density lipoprotein for boron neutron capture therapy as measured in cell culture.

Low-density lipoproteins (LDLs) are known to be internalized by the cell through receptor-mediated mechanisms. There is evidence that LDLs may be taken up avidly by tumor cells to provide cholesterol for the synthesis of cell membranes. Thus, the possibility exists that LDLs may provide an ideal vehicle for the transport of boron to tumor cells for boron neutron capture therapy. A boronated analogue of LDL has recently been synthesized for possible application in boron neutron capture therapy. The analogue was tested in cell culture for uptake and biological efficacy in the thermal neutron beam at the Brookhaven Medical Research Reactor. It was found that boron concentrations 10 times higher than that required in tumors for boron neutron capture therapy were easily obtained and that the amount of uptake was consistent with a receptor-mediated binding mechanism. The measured intracellular concentration of approximately 240 micrograms 10B/g cells is significantly higher than that obtained with any other boron compound previously evaluated for possible clinical application.

Animals↗
PubMed1975

Comparative study of the activity of boric, benzene-boronic and methyl-benzene-boronic acids upon respiration, general metabolism and systemic hemodynamics of the anesthetized dog.

The authors compared the action of boric, benzene-boronic and p-methyl-benzene-boronic acids on respiration and general metabolism and on systemic hemodynamics of the anesthetized dog. They further investigated the effects on the arterial blood pressure in the rat and on the isolated rabbit heart. In the dogs, the three acids were shown to have no significant action on the systolic, diastolic and mean arterial blood pressures and a slight stimulating action on the differential arterial blood pressure. On the contrary, in the rat, all the acids were hypotensive. This action was dose dependent. In the entire animal, as well as in the isolated rabbit heart, benzene-boronic and p-methyl-benzene-boronic acids depressed the myocardial contractility. Whereas boric acid did not act on the heart contractility in situ in anesthetized dogs, it slightly stimulated the myocardial contractility of the isolated rabbit heart. The two acids seemed to be directly active on the myocardial cell. In the anesthetized dog, cardiac performances were first depressed then stimulated. Both benzene-boronic and p-methyl-benzene-boronic acids were ventilatory depressors: they reduced ventilatory output and rhythm, they first decreased then increased total O2 consumption and CO2 production.

Animals↗
PubMed1991

The toxicity of waterborne boron to Daphnia magna and Chironomus decorus and the effects of water hardness and sulfate on boron toxicity.

The concentrations of many elements, including boron, are increasing in aquatic ecosystems due to anthropogenic activities. Laboratory studies were undertaken to evaluate the toxicity of waterborne boron to two key freshwater macroinvertebrates and to evaluate the effects of water hardness and sulfate on boron toxicity. Acute toxicity evaluations of waterborne sodium tetraborate resulted in 48 h. LC50 values of 141 and 1376 mg B/L for neonate Daphnia magna and fourth instar Chironomus decorus, respectively. Chronic sublethal studies demonstrated a significant decrease in C. decorus growth rate at 20 mg B/L. Further studies showed that increasing water hardness (10.6 to 170 mg/L as CaCO3) and sulfate (10.2 to 325.4 mg SO4(-2)/L) concentrations did not affect boron toxicity to D. magna. These results, in conjunction with a review of the literature, suggest that aquatic macrophytes may be more sensitive to boron than macroinvertebrates and thus would be better choices for aquatic risk assessment evaluations for this element.

Animals↗
PubMed1992

Synthesis and in vitro evaluation of boronated uridine and glucose derivatives for boron neutron capture therapy.

The following boron-containing nucleoside and glucose derivatives have been synthesized as potential boron delivery agents for boron neutron capture therapy (BNCT): 2'-O-(o-carboran-1-ylmethyl)uridine (4a), 3'-O-(o-carboran-1-ylmethyl)uridine (4b), sodium 7-(uridin-2'-ylmethyl)dodecahydro-7,8-dicarba-++ +nido-undecaborate (5), 5'-O-(o-carboran-1-ylmethyl)uridine (9), and 3'-O-(o-carboran-1-ylmethyl)-D-glucose (13). In vitro cellular uptake studies were performed with F98 rat glioma cells. Following 16 h incubation, cellular boron concentrations were determined by direct current plasma atomic emission spectroscopy (DCP-AES). Boron concentrations ranged from 65 to 103 micrograms/g of cells for the neutral closo structures compared with 1.5 micrograms/g of cells for the charged nido species. Cellular uptake of sodium mercaptoundecahydro-closo-dodecaborate (BSH), the compound currently being used in Japan for the treatment of malignant brain tumors by BNCT, was 2 micrograms/g of cells.

Animals↗
PubMed1975

Boron neutron capture therapy of cerebral gliomas. II. Utilization of the blood-brain barrier and tumor-specific antigens for the selective concentration of boron in gliomas.

The use of the blood-brain barrier and of tumor-specific antibodies to concentrate boron selectivity in gliomas for neutron capture therapy is considered experimentally and theoretically. The time-dependent concentration of two anionic boranes, B12 H11 SH2- and B12 H11 SOSB12 H114-, in the blood, brain, and tumor of rats bearing a tumor of gliomatous origin is reported. The rate of clearance of each anionic borane from the blood is correlated with the fraction of non-protein bound anion in the plasma. The use of antibodies to carry therapeutical useful amounts of boron to tumor-specific or tumor-associated antigens on the tumor cell surface will require different numbers of boron atoms bound per antibody depending on several immunological and physical parameters. Calculations using published values of antibody-antigen association constants and of cell surface antigen densities predict that in order to obtain 10mug 10B/g tumor from 10 to over 10,000 boron-10 atoms will have to be bound per tumor antigenic site.

Animals↗
PubMed1991

[Boron neutron capture therapy of human gastric cancer by boron-containing immunoliposomes under thermal neutron irradiation].

Boron neutron capture therapy (BNCT) is based on the nuclear reaction yielding high LET Li-7 and alpha particles when boron-10 is irradiated with thermal neutrons. (Et4N)2(10)B10H10 was entrapped in 40 nm liposomes coating the monoclonal antibody, MGb 2, against human gastric cancer. There were 1.4 x 10(4) 10B atoms encapsulated and 20 molecules of MGb 2 incorporated per liposomes ELISA indicated that the immunoreactivity of antibodies on liposomes retained 80%. Preferred binding to human gastric cancer cell line SGC-7901 was observed as many as 15.1 x 10(9) 10B atoms/tumor cell, 38-fold more than that to normal human embryonic lung cell line SL 7. The fluorescent immunoliposome-stained tumor cells showed membrane-fluorescence while SL 7 cells showed no obvious fluorescence. Irradiated with thermal neutrons (0.025 eV, 3.12 x 10(11)n/cm2, gamma-ray 0.84 Gy), 10B-containing immunoliposomes pretreated SGC-7901 cells survived 27%, significantly lower than non-irradiated cells or non-pretreated cells with irradiation (P less than 0.001). The results demonstrated that boron-containing immunoliposomes could bind selectively and deliver sufficient amount of boron-10 to the target tumor cells.

Alpha Particles↗
PubMed1991

Application of boronated anti-CEA immunoliposome to tumour cell growth inhibition in in vitro boron neutron capture therapy model.

An immunoliposome containing a 10B-compound has been examined as a selective drug delivery system in boron neutron-capture therapy. Liposomes, conjugated with monoclonal antibodies specific for carcinoembryonic antigen (CEA) were shown to bind selectively to cells bearing CEA on their surface. The immunoliposomes attached to tumour cells suppressed growth in vitro upon thermal neutron irradiation and suppression was dependent upon the concentration of the 10B-compound in the liposomes and on the density of antibody conjugated to the liposomes. The results suggest that immunoliposomes containing the 10B-compound could act as a selective and efficient carrier of 10B atoms to target tumour cells in boron neutron-capture therapy.

Antibodies, Monoclonal↗
PubMed1991

Tissue disposition of boron in male Fischer rats.

Boric acid (H3BO3), an inorganic acid with widespread commercial use and consumer exposure, impairs fertility in male rodents at dose levels lower than those required to cause other adverse effects. Previous studies found a testicular lesion in adult Fischer rats fed 9000 ppm boric acid (1575 ppm boron) and slightly reduced basal serum testosterone levels. A CNS-mediated hormonal component to this lesion was suggested. Detailed data on the tissue disposition of boron in the rat, including accessory sex organs and the brain, are lacking. This study examined the tissue disposition of boron in reproductive, accessory sex organs, and other selected tissues in adult male Fischer rats fed 9000 ppm boric acid to determine if selective accumulation of boron in reproductive tissues, accessory sex organs, and/or the brain might correlate with and explain the apparent selective testicular toxicity. Adult male Fischer rats were fed 9000 ppm boric acid for up to 7 days. Animals were killed at 1, 2, 3, 4, and 7 days after the start of exposure. Plasma and excised tissues were heat-digested in acid and analyzed for boron by inductively coupled argon plasma emission spectrometry (ICAP). With the exception of adrenal glands, control boron levels in all tissues examined were below 4 micrograms/g. There was a rapid increase in plasma and tissue boron 1 day after the start of exposure (range 2- to 20-fold), with the exception of adipose tissue. With the exception of bone and adipose tissue, all soft tissues examined, including the testis, epididymis, accessory sex organs, hypothalamus, and rest of brain, appeared to reach steady-state boron levels (range 12-30 micrograms/g) by 3-4 days. Bone boron levels continued to increase up to the termination at 7 days (40-50 micrograms/g by Day 7). Bone attained the greatest concentration of boron (2- to 3-fold over plasma levels) while levels in adipose tissue were 20% of plasma levels during the 7-day exposure period. All other tissues appeared to show no appreciable accumulation of boron over plasma levels. The data suggest that neither the apparent selective testicular toxicity nor the slight CNS hormonal effect associated with boric acid exposure can be explained on the basis of selective accumulation of boron in the testis or brain/hypothalamus, respectively. Thus, the testicular toxicity is likely the result of certain biological processes that are unique to the testis and which are targets of boron exposure.

Animals↗
PubMed1992

Studies to determine whether an interaction exists among boron, calcium, and cholecalciferol on the skeletal development of broiler chickens.

Two experiments were designed to determine the effect of dietary boron on broiler cockerels and four experiments were conducted to determine whether an interaction exists among dietary boron, cholecalciferol, and calcium. The parameters measured were weight gain, feed efficiency, tibia bone ash, rickets, tibial dyschondroplasia, and plasma minerals. All experiments were conducted with tibial dyschondroplasia-inducing basal diets fed to broiler cockerels from 1 to 16 days of age. Experiments 1 and 2 had four levels of dietary boron (0, 20, 40, and 80 mg/kg (Experiment 1) and 0, 5, 10, and 20 mg/kg (Experiment 2). Boron had no effect on weight gain, feed efficiency, or plasma minerals in either experiment. In Experiment 2, increasing levels of boron had no influence on tibial dyschondroplasia but did exert a quadratic effect on bone ash with 5 and 10 mg/kg boron increasing bone ash. In Experiment 1, bone ash and the incidence of tibial dyschondroplasia were unaffected, but the severity of tibial dyschondroplasia linearly increased by increasing boron levels. Experiments 3 to 6 had a 2 x 2 x 2 factorial arrangement of treatments with calcium at .65 and .90%, cholecalciferol at 110 and 1,100 ICU/kg, and boron at 0 and 40 mg/kg (Experiments 3 to 5) or 0 and 3 mg/kg (Experiment 6). The higher levels of calcium and cholecalciferol improved weight gain, decreased the incidence of rickets, and decreased the incidence and severity of tibial dyschondroplasia. Feeding cholecalciferol at 1,100 ICU/kg increased plasma calcium and plasma dialyzable phosphorus and decreased plasma magnesium. Calcium at .90% had no effect on plasma magnesium or plasma dialyzable phosphorus and increased plasma calcium only in Experiment 4. The only response to boron in Experiments 3 to 6 was a boron effect and a boron by cholecalciferol interaction on bone ash in Experiment 3, in which boron reduced bone ash at .65% calcium and 110 ICU/kg cholecalciferol. From these experiments, there is no indication that an interaction among boron, cholecalciferol, and calcium exists in broiler cockerels.

Animal Feed↗
PubMedDate not supplied

Magnesium and methionine deprivation affect the response of rats to boron deprivation.

A series of nine experiments were done to obtain further evidence that boron might be involved in major mineral metabolism (Ca, P, and Mg), thus indicating that boron is an essential nutrient for animals. Eight factorially arranged experiments of 6-10 wk durations were done with weanling Sprague-Dawley male rats. One factorially arranged experiment was done with weanling spontaneously hypertensive rats. The variables in each experiment were dietary boron supplements of 0 and 3 micrograms g, and dietary magnesium supplements of either 200 (Experiments 1-3) or 100 (Experiments 4-9) and 400 micrograms/g. In Experiments 7 and 9, a third variable was dietary manganese supplements of 25 and 50 micrograms/g. Methionine status was varied throughout the series of experiments by supplementing the casein-based diet with methionine and arginine. Findings were obtained indicating that the severity of magnesium deprivation and the methionine status of the rat strongly influence the extent and nature of the interaction between magnesium and boron, and the response to boron deprivation. When magnesium deprivation was severe enough to cause typical signs of deficiency, a significant interaction between boron and magnesium was found. Generally, the interaction was characterized by the deprivation of one of the elements making the deficiency signs of the other more marked. The interaction was most evident when the diet was not supplemented with methionine and especially when the diet contained luxuriant arginine. Signs of boron deprivation were also more marked and consistent when the diet contained marginal methionine and luxuriant arginine. Among the signs of boron deprivation exhibited by rats fed marginal methionine were depressed growth and bone magnesium concentration, and elevated spleen wt/body wt and kidney wt/body wt ratios. Because the boron supplement of 3 micrograms/g did not make the dietary intake of this element unusual, it seems likely that the response of the rats to dietary boron in the present study were manifestations of physiological, not pharmacological, actions, and support the hypothesis that boron is an essential nutrient for the rat.

Animals↗