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PubMed1989

Safety assessment of boron in aquatic and terrestrial environments.

Boron is a naturally occurring material and is used in industrial and domestic products. Its major release into the environment is through weathering processes and wastewater discharge. Boron is an essential nutrient for plants, but can above certain concentrations be toxic to aquatic and terrestrial organisms. This paper assesses the ecotoxicology and environmental safety of boron. It draws together the data for toxicological effects of boron and compares these with environmental concentrations of boron, measured in Europe and the U.S.A. Generally, environmental concentrations of boron found in surface water are below levels identified as toxic to aquatic organisms. Concentrations high enough to produce toxic effects in laboratory tests are found in areas where weathering of boron-rich formations and deposits occurs, such as in the southwestern United States. However, reproducing populations of the most sensitive species, rainbow trout, have been observed in surface waters in these regions, indicating no cause for concern. The prime concern for effects on terrestrial plants centers on the use of irrigation water with elevated levels of boron. At present, there is no evidence of widespread damage to crops resulting from this practice. In some areas, wastewater is used for irrigation and crops grown under these conditions are generally confined to those relatively insensitive to boron toxicity. Good irrigation practices will be necessary, however, in arid regions with high evapotranspiration rates and care will be needed when using wastewater, particularly in areas with naturally high boron levels. It is not anticipated that there will be any significant increase in the discharge of boron to the environment in the foreseeable future. The use of boron-containing products is expected to increase, but glass will remain the dominant market and the use of boron in detergents in Europe is expected to decrease due to the introduction of bleach activators and liquid detergents. There is a possibility that perborate may be used in detergents in the U.S.A.; however, the estimated increase in boron concentrations is likely to be environmentally insignificant.

Animals↗

PubMed1998

BORON IN PLANT STRUCTURE AND FUNCTION.

New and exciting developments in boron research in the past few years greatly contributed to better understanding of the role of boron in plants. Purification and identification of the first boron-polyol transport molecules resolved much of the controversy about boron phloem mobility. Isolation and characterization of the boron-polysaccharide complex from cell walls provided the first direct evidence for boron crosslinking of pectin polymers. Inhibition and recovery of proton release upon boron withdrawal and restitution in plant culture medium demonstrated boron involvement in membrane processes. Rapid boron-induced changes in membrane function could be attributed to boron-complexing membrane constituents. Boron may affect metabolic pathways by binding apoplastic proteins to cis-hydroxyl groups of cell walls and membranes, and by interfering with manganese-dependent enzymatic reactions. In addition, boron has been implicated in counteracting toxic effects of aluminum on root growth of dicotyledonous plants. Molecular investigations of boron nutrition have been initiated by the discovery of a novel mutant of Arabidopsis thaliana with an altered requirement for boron.

Journal Article↗

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↗

PubMed2003

Environmental boron contamination in waters of Hisarcik area in the Kutahya Province of Turkey.

Our aim was to determine boron levels in waters of rich boron mine areas in Turkey. There is a naturally occurring high level of boron in the ground waters of some parts of Turkey. Our study area is Hisarcik village in the Kutahya Province of Turkey which has a large number of boron mines. Boron occurs in combined form, usually borax (Na2B4O7 x 10H2O) and colemanite (Ca2B6O11 x 5H2O). Water samples were collected from many springs in order to determine boron concentrations and the amount of boron that is exposed to 88 samples from the drinking water (tap water), 37 from ground water and 257 from stream or pond water (surface water). Urine samples taken from 42 residents in this area were analyzed for boron and compared with its levels in drinking waters. The inductively coupled plasma/mass spectrometry (ICP/MS) method was used for the analysis of boron concentrations. Water boron contents at differing locations of this area ranged from 2.05 to 29.00 mg B/l. Mean value of boron was 10.20+/-4.08 mg B/l. Total urinary boron excretion was ranged from 0.04 to 50.70 mg B/l and mean value was 8.30+/-10.91 mg B/l. Current information on sources, occurrence, pollution potential and toxicity of environmental boron is discussed.

Boron↗

PubMed2001

Diadenosine phosphates and S-adenosylmethionine: novel boron binding biomolecules detected by capillary electrophoresis.

There is evidence that boron has a physiological role in animals and humans, but the search for boron binding biomolecules has been difficult because useful radioactive boron isotopes do not exist. To overcome this limitation we used capillary electrophoresis to identify and quantify boron binding to biomolecules by detecting the negative charge boron imparts to ligands. The effect of molecular structure and proximal electronic charges of adenosine and molecules with adenosine moieties including S-adenosylmethionine (SAM) and diadenosine polyphosphates (Ap(n)A) were compared. The boron affinity of the test species varied with the rank order SAM congruent with Ap(6)A congruent with Ap(5)A>Ap(4)A>Ap(3)A congruent with NAD(+)>Ap(2)A>NADH congruent with 5'ATP>5'ADP>5'AMP>adenosine>3'AMP congruent with 2'AMP congruent with cAMP congruent with adenine. Test species with vicinal cis-diols bound boron; species without those moieties did not. Boron binding affinity increased when proximal cationic moieties were present. Anionic moieties remote from the cis-hydroxyl binding site also positively influenced boron binding affinity. In the Ap(n)A species, cooperative complexing of boron between the terminal ribose moieties apparently occurred. In these species boron affinity greater than expected for two monocomplexes was observed and binding affinities increased as more phosphate groups (beyond three) were present separating the terminal moieties. Our results indicate that Ap(6)A, Ap(5)A, Ap(4)A, Ap(3)A, and SAM have higher affinities for boron than any other currently recognized boron ligand present in animal tissues including NAD(+).

Adenosine↗

PubMed1997

Liposomes as drug delivery vehicles for boron agents.

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 examination of the biodistribution of boron delivered by liposomes in tumor-bearing mice. Small unilamellar vesicles have been found to stably encapsulate high concentrations of water-soluble ionic boron compounds. Alternatively, lipophilic boron-containing species have been embedded within the phospholipid bilayer of liposomes, and both hydrophilic and lipophilic boron compounds have been incorporated within the same liposome formulation. The biodistribution of boron was determined at several time points over 48 hr after i.v. injection of liposomal suspensions in BALB/c mice bearing EMT6 tumors. The tumor-selective delivery of boron by the liposomes was demonstrated as tumor-boron concentrations increased for several hours post-injection. Even at the low injected doses employed (6-18 mg boron/kg body weight) therapeutic tumor boron concentrations were observed (> 30 micrograms boron/g tissue) and high tumor/blood ratios were achieved (> 5). The most favorable results were obtained with the polyhedral borane Na3[a2-B20H1-NH2CH2CH2NH2]. Liposomes encapsulating this species produced a tumor boron concentration of 45 micrograms/g tissue at 30 hr post-injection, at which time the tumor/blood boron ratio was 9.3.

Adenocarcinoma↗

PubMedDate not supplied

Boron deprivation alters rat behaviour and brain mineral composition differently when fish oil instead of safflower oil is the diet fat source.

PRIMARY OBJECTIVE: To determine whether boron deprivation affects rat behaviour and whether behavioural responses to boron deprivation are modified by differing amounts of dietary long-chain omega-3 fatty acids. RESEARCH DESIGN: Female rats were fed diets containing 0.1 mg (9 micromol)/kg boron in a factorial arrangement with dietary variables of supplemental boron at 0 and 3mg (278 micromol)/kg and fat sources of 75 g/kg safflower oil or 65 g/kg fish (menhaden) oil plus 10 g/kg linoleic acid. After 6 weeks, six females per treatment were bred. Dams and pups continued on their respective diets through gestation, lactation and after weaning. Between ages 6 and 20 weeks, behavioural tests were performed on 13-15 male offspring from three dams in each dietary treatment. The rats were euthanized at age 21 weeks for the collection of tissues and blood. METHODS AND PROCEDURES: At ages 6 and 19 weeks, auditory startle was evaluated with an acoustic startle system and avoidance behaviour was evaluated by using an elevated plus maze. At ages 7 and 20 weeks, spontaneous behaviour activity was evaluated with a photobeam activity system. A brightness discrimination test was performed on the rats between age 15 and 16 weeks. Brain mineral composition was determined by coupled argon plasma atomic emission spectroscopy. Plasma total glutathione was determined by HPLC and total cholesterol and 8-iso-prostaglandin F2alpha (8-iso-PGF2alpha) were determined by using commercially available kits. MAIN OUTCOMES AND RESULTS: Boron-deficient rats were less active than boron-adequate rats when fed safflower oil based on reduced number, distance and time of horizontal movements, front entries, margin distance and vertical breaks and jumps in the spontaneous activity evaluation. Feeding fish oil instead of safflower oil attenuated the activity response to boron deprivation. In the plus maze evaluation, the behavioural reactivity of the boron-deficient rats fed fish oil was noticeably different than the other three treatments. They made more entries into both open and closed arms and the center area and thus visited more locations. The boron-deficient rats fed fish oil also exhibited the lowest copper and zinc and highest boron concentrations in brain and the highest plasma glutathione concentration. Both boron deprivation and safflower oil increased plasma 8-iso-PGF2alpha. CONCLUSIONS: Both dietary boron and long-chain omega-3 fatty acids influence rat behaviour and brain composition and the influence of one these bioactive substances can be altered by changing the intake of the other. Brain mineral and plasma cholesterol, glutathione and 8-iso-PGF2alpha findings suggest that rat behaviour is affected by an interaction between boron and fish oil because both affect oxidative metabolism and act the cellular membrane level.

Acoustic Stimulation↗

PubMed2004

Environmental boron exposure and activity of delta-aminolevulinic acid dehydratase (ALA-D) in a newborn population.

Following boron intake, multiple effects have been observed in animal experiments. However, human data is lacking, and no data is available on the ability of boron to accumulate in fetal tissues. Positive responses in animal species suggest that developmental toxicity may be an area of concern in humans, following exposure to boron. Two hypotheses have seemed to account for the multiple effects described in scientific findings. One hypothesis is that boron is a negative regulator that influences a number of metabolic pathways by competitively inhibiting some key enzyme reactions. The other hypothesis is that boron has a role in ionic membrane transport regulations. To better understand boron potential toxicity, the present study examined the relationship between boron exposure and some key enzymes, well-known for their affinity for mineral elements, such as delta-aminolevulinic acid dehydratase (ALA-D), and two fundamental enzymes having a role in ionic membrane transport regulations (Ca-pump and Na(+)K(+)-ATPase). We investigated the potential effects of an environmental boron exposure on the activity of these enzymes in an urban population of 197 "normal" newborns. Environmental boron exposure was assessed in placental tissue. Because of the well-known inhibiting effect of lead on these enzymes, cord blood and placental lead were also analyzed. After adjustment for potential confounders, including lead, placental boron levels were negatively significantly correlated to ALA-D activity while Ca-pump and Na(+)K(+)-ATPase activities did not seem to be affected by the level of boron exposure. Given boron's ability, as a Lewis acid, to complex with hydroxyl groups, we suggest that such a mechanism would explain the inhibiting effect of boron on ALA-D.

Adult↗

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↗

PubMed2002

Determination of boron in high-purity tantalum materials by on-line matrix separation/inductively coupled plasma mass spectrometry.

A method for the determination of ultratrace amounts of boron in high-purity tantalum materials [tantalum metal, tantalum(v) oxide, tantalum pentachloride and tantalum pentaethoxide] is described. On-line anion-exchange matrix separation combined with inductively coupled plasma mass spectrometry (ICP-MS) was employed for the determination of boron at the ng g(-1) level. Tantalum materials were dissolved using HF and/or HNO3 prior to analysis. The loss of boron in the sample preparation procedure was examined as the recovery of boron by adding a definite amount of boron to each tantalum material sample before decomposition, and it was almost negligible. In an anion-exchange method using 0.1 M HF carrier solution, tantalum and boron in the sample solution were first adsorbed on a strongly basic anion-exchange resin. Next, boron was eluted from the resin with 5 M HCl, whereas tantalum was retained strongly adsorbed. The eluted boron was introduced directly into the ICP-MS system for quantitative analysis at m/z 10 and 11. Because of the long elution time of boron, the transient signal was integrated in the time range 70-300 s on the chromatogram. Although the elution of boron in the time range was ca. 40% of total boron in the sample solution injected, the determination limits (10sigma) obtained by the present method were 30, 25, 15 and 13 ng g(-1) for tantalum metal, tantalum(v) oxide, tantalum pentachloride and tantalum pentaethoxide, respectively. The method was applied to the determination of boron in commercially available high-purity tantalum materials and it was found that the concentrations of boron were in the ng g(-1)-microg g(-1) range.

Journal Article↗

PubMed1999

Boron is required for zebrafish embryogenesis

Boron is the only element known to be essential for plants, but only circumstantial evidence for essentiality exists in animals. We report here that boron is essential for the embryonic development of zebrafish (Danio rerio). Zebrafish were maintained in water with a boron concentration of 0.1 micromol l-1 or supplemented to a concentration of 45 micromol l-1 using ultrapure boric acid. Both groups were fed boron-depleted brine shrimp. This procedure depleted the boron content of the blastulas from low-boron parents to only 5 % of the boron content of the blastulas from boron-supplemented parents. Sperm from low-boron males successfully fertilized eggs from low-boron females, but 92 % of the embryos died within 10 days. The early cleavage stage of development was the most sensitive to boron deficiency. Of the fertilized embryos, 46% did not live to complete the blastula stage. Repletion of low-boron embryos during the first hour after fertilization rescued them from death. These observations provide strong evidence that boron is essential for zebrafish development.

Journal Article↗

PubMed1995

Selective boron delivery to murine tumors by lipophilic species incorporated in the membranes of unilamellar liposomes.

The nido-carborane species K[nido-7-CH3(CH2)15-7,8-C2B9H11] has been synthesized for use as an addend for the bilayer membrane of liposomes. Small unilamellar vesicles, composed of distearoylphosphatidylcholine/cholesterol, 1:1, and incorporating K[nido-7-CH3(CH2)15-7,8-C2B9H11] in the bilayer, have been investigated in vivo. The time-course biodistribution of boron delivered by these liposomes was determined by inductively coupled plasma-atomic emission spectroscopy analyses after the injection of liposomal suspensions in BALB/c mice bearing EMT6 mammary adenocarcinomas. At the low injected doses normally used (approximately 5-10 mg of boron per kg of body weight), peak tumor boron concentrations of approximately 35 micrograms of boron per g of tissue and tumor/blood boron ratios of approximately 8 were achieved. These values are sufficiently high for the successful application of boron neutron capture therapy. The bilayer-embedded boron compound may provide the sole boron source or, alternatively, a concentrated aqueous solution of a hydrophilic boron compound may also be encapsulated within the liposomes to provide a dose enhancement. Thus, the incorporation of both K[nido-7-CH3(CH2)15-7,8-C2B9H11] and the hydrophilic species, Na3[1-(2'-B10H9)-2-NH3B10H8], within the same liposomes demonstrated significantly enhanced biodistribution characteristics, exemplified by maximum tumor boron concentrations of approximately 50 micrograms of boron per g of tissue and tumor/blood boron ratios of approximately 6.

Animals↗

PubMed1980

Boronic acid inhibitors of porcine pancreatic lipase.

Porcine pancreatic lipase was inhibited by alkane and arene boronic acids. The inhibition by octadecane boronic acid was competitive when measured against the hydrolysis of dissolved tripropionin in the presence of siliconized glass beads. The value of Ki in this system was 1.34 x 10(3) molecules micron-2. The ratio of substrate to inhibitor concentrations giving 50% inhibition was in the range of 700 to 2200, indicating that lipase has a greater affinity for boronic acids than for tripropionin. Boronic acids did not interfere with the interaction of lipase with the siliconized glass/water interface, demonstrating that the binding of lipase to substrate interfaces, the first step in lipase action, was not the step at which inhibition occurred. The boronic acid binding site on lipase is at or near the active center serine since modification of this residue by diethyl p-nitrophenyl phosphate was prevented by boronic acids. Modification of the active center serine residue by diethyl p-nitrophenyl phosphate also prevented boronic acid binding. Binding of a chromophoric boronic acid, 7-nitrobenzo-2-oxa-1,3-diazolyl m-aminobenzene boronic acid, to lipase was demonstrated by equilibrium gel filtration on polyacrylamide beads (Bio-Gel P-60) in the presence of 4 mM sodium taurodeoxycholate. The complex contained 1 molecule of boronic acid per molecule of lipase and had a dissociation constant Kd of 5 x 10(-6) M. The boronic acid was not bound in the absence of taurodeoxycholate. Boronic acids are believed to be analogs of the tetrahedral intermediate in the action of lipase.

Animals↗

PubMed1998

[Boron neutron capture a a new radiotherapy model].

The boron neutron capture therapy is based on the reaction occurring with certain probability, if a thermal neutron meets the boron 10 isotope. The low energy slow neutron is captured by the nucleus and it disintegrates into Li-nucleus and He-nucleus (alpha particle). If this physical reaction occurs in a living cell that will be destroyed. If the boron neutron capture reaction could be achieved selectively in malignant cells of tumor patients, that could be an effective therapeutical modality to treat the locally growing cancers. For boron neutron capture therapy to be successful two basic conditions must be fulfilled, an appropriate neutron source must be available and the sufficient number of 10B must be delivered possibly selectively into the tumor cells by a boron compound. At present both part of this binary system are under intensive investigation, the development of the neutron source, the synthetisation and experimental testing of boron delivery agents. The development of the dosimetry, microdosimetry, the work out of the powerful tools of detection the cellular, subcellular 10B distribution, the continuous improvement of the planning system and the optimization of the boron neutron capture therapy are the main point of the research area on boron neutron capture therapy. Clinical studies and clinical application of boron neutron capture therapy are under way for the treatment of melanoma malignum and for brain tumors, with the two boron compound has been clinically tested up to now, in Japan, at two Centres in USA, and recently has been started in Europe. The authors give an overview about the principles of boron neutron capture therapy, about the result of the research on neutron sources and boron compounds, moreover about the possible application area of this new radiation modality.

Boron↗

PubMed1999

Boron deficiency causes a drastic decrease in nitrate content and nitrate reductase activity, and increases the content of carbohydrates in leaves from tobacco plants

Tobacco (Nicotiana tabacum L.) plants were used to study connections between deficiency in boron and nitrate reduction. Boron deficiency caused a substantial decrease in shoot and, particularly, root weights that resulted in a notably high shoot/root ratio in comparison to boron-sufficient plants. One of the most important effects caused by boron deficiency was the strong decrease in leaf nitrate content. Leaf contents of magnesium, calcium and, especially, potassium also declined under this deficiency, but nitrate content decreased in a higher proportion than these cations. Nitrate reductase (EC 1.6.6.1) activity of boron-deficient plants declined from the beginning of the light period; this decline did not occur in boron-sufficient plants. This fact could be attributed to the faster decrease in transcript levels of Nia, the nitrate reductase structural gene, during the light period in boron-deficient plants. Leaf protein content of boron-deficient plants also declined in the course of light periods. Boron deficiency caused an appreciable accumulation of hexoses and sucrose in leaves. This build-up of soluble sugars might correct the osmotic imbalance elicited by the low content of nitrate and cations in plants subjected to boron deficiency. Boron-deficient plants had much higher starch contents than boron-sufficient ones, and there was an inverse relationship between the contents of nitrate and starch in leaves.

Journal Article↗

PubMed2002

Imaging of fluorine and boron from fluorinated boronophenylalanine in the same cell at organelle resolution by correlative ion microscopy and confocal laser scanning microscopy.

PURPOSE: There is a clear need for a technique that provides subcellular locations of fluorine and boron atoms from fluorinated neutron capture agents because positron emission tomography is being tested as a tool for providing tumor boron concentrations in boron neutron capture therapy. EXPERIMENTAL DESIGN: Ion microscopy was used in combination with confocal laser scanning microscopy to investigate the subcellular locations of fluorine and boron from fluorinated p-boronophenylalanine (F-BPA) in human glioblastoma T98G cells. The fluorinated compound was also compared with p-boronophenylalanine (BPA) for delivery of boron after a clinically relevant 6-h exposure. Mitochondria were identified by rhodamine 123 labeling. A strict cryogenic sample preparation was used, and measurements were made in fractured freeze-dried cells. RESULTS: The nucleus, a perinuclear mitochondria-rich cytoplasmic region, and the remaining cytoplasm were the three subcellular regions identified in individual T98G cells. In cells treated with F-BPA, the mitochondria-rich perinuclear cytoplasmic region exhibited significantly lower fluorine and boron signals than the remaining cytoplasm and the nuclei. Ion microscopy observations revealed a nearly 1:1 distribution of fluorine and boron in subcellular compartments. Quantitative subcellular observations indicated that there was no significant difference in boron delivery to subcellular compartments between the F-BPA and nonfluorinated BPA. CONCLUSIONS: These observations provide the first direct evidence that fluorine and boron from fluorinated BPA are cocompartmentalized in cells and that the fluorinated compound is as efficient for boron delivery as the nonfluorinated BPA at a clinically relevant time point. These observations provide strong support for the use of F-BPA in positron emission tomography biodistribution studies for boron neutron capture therapy.

Boron↗

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↗

PubMed2006

Positive cooperativity in the cellular uptake of a boronated porphyrin.

This work was undertaken to assess the kinetics of boronated porphyrin cellular uptake, which has been reported to occur by way of the low-density lipoprotein receptors. Because of current interest in the use of boronated porphyrins in boron neutron capture therapy of tumors, this pathway was investigated for the cellular uptake of a boronated porphyrin (tetrakis-carborane-carboxylate, esters of 2,4-bis (alpha,beta-dihydroxyethyl) deuteroporphyrin IX). Boron uptake occurred even without low-density lipoprotein in the culture medium. Pre-incubation of V-79 Chinese hamster cells for 24 h in medium containing delipidized fetal bovine serum markedly increased the subsequent uptake of boron when compared with cells pre-incubated with medium containing 10% fetal bovine serum. The increased uptake was characterized by greater affinity for boronated porphyrin, compared to cells pre-incubated in 10% fetal bovine serum. Twenty-four hour preincubation of cells with increasing concentrations of LDL added to delipidized medium suppressed the up-regulation of the boron level. In contrast, incubation with added acetylated LDL did not prevent the up-regulation of boron uptake. Positive cooperativity was demonstrated by Hill and Scatchard plots. It is concluded that uptake of boronated porphyrin is characterized by positive cooperativity, that its uptake is markedly enhanced when preincubated in delipidized serum, and that significant uptake occurs even in the absence of low density lipoprotein in the medium. These data suggest a novel way for enhancing uptake of boron (and perhaps other agents) into tissues using carrier porphyrins, by increasing the number and/or affinity of cellular LDL receptors.

Animals↗