[Single and 2-week repeated intravenous dose toxicity studies of disodium mercaptoundecahydro-closo-dodecaborate in rats]

Disodium mercaptoundecahydro-closo-dodecaborate (BSH) is a boron compound used in Boron Neutron Capture Therapy for malignant brain tumors. Intravenous single and 2-week repeated dose toxicity studies of BSH were performed in Sprague-Dawley rats. In the single-dose study, BSH was administered at doses of 100, 300 or 600 mg/kg. Death occurred within 10 min (acute type) or from 5 hr to 2 days (delayed type) after dosing in the 600 mg/kg group. No differences in mortality by sex and dosing speed were observed. Major causes of death were considered to be circulatory disorder in acute death and renal injury in delayed death. The renal injury was observed in the 300 and 600 mg/kg groups. In the 2-week repeated dose study, BSH was administered at doses of 30, 100 or 300 mg/kg/day for 14 days. Body weight gain was suppressed in the 100 and 300 mg/kg groups. One male in the 300 mg/kg group died due to renal and pulmonary lesions at day 8. Slight anemia was observed in the 300 mg/kg group. Pathologically, the kidney showed tubular regeneration with increase of weight in the 300 mg/kg. From these results, the NOAEL of BSH is 30 mg/kg/day.

Serum and urinary boron levels in rats after single administration of sodium tetraborate

The pharmacokinetics of boron was studied in rats by administering a 1 ml oral dose of sodium tetraborate solution to several groups of rats (n=20) at eleven different dose levels ranging from 0 to 0.4 mg/100 g body weight as boron. Twenty-four-hour urine samples were collected after boron administration. After 24 h the average urinary recovery rate for this element was 99.6+/-7.9. The relationship between boron dose and excretion was linear (r=0.999) with a regression coefficient of 0.954. This result suggests that the oral bioavailability (F) of boron was complete. Another group of rats (n=10) was given a single oral injection of 2 ml of sodium tetraborate solution containing 0.4 mg of boron/100 g body wt. The serum decay of boron was followed and found to be monophasic. The data were interpreted according to a one-compartment open model. The appropriate pharmacokinetic parameters were estimated as follows: absorption half-life, t1/2a=0.608+/-0.432 h; elimination half-life, t1/2=4.64+/-1.19 h; volume of distribution, Vd = 142.0+/-30.2 ml/100 g body wt.; total clearance, Ctot=0.359+/-0.0285 ml/min per 100 g body wt. The maximum boron concentration in serum after administration (Cmax) was 2.13+/-0.270 mg/l, and the time needed to reach this maximum concentration (Tmax) was 1.76+/-0.887 h. Our results suggest that orally administered boric acid is rapidly and completely absorbed from the gastrointestinal tract into the blood stream. Boric acid in the intravascular space does not have a strong affinity to serum proteins, and rapidly diffuses to the extravascular space in proportion to blood flow without massive accumulation or binding in tissues. The main route of boron excretion from the body is via glomerular filtration. It may be inferred that there is partial tubular resorption at low plasma levels. The animal model is proposed as a useful tool to approach the problem of environmental or industrial exposure to boron or in cases of accidental acute boron intoxication.

Disposition and tissue distribution of boron after infusion of borocaptate sodium in patients with malignant brain tumors

PURPOSE

In the frame of the Czech boron neutron capture therapy (BNCT) project, a clinical Phase I study of borocaptate sodium [Na2B12H11SH (BSH)] as the boron-10 delivery agent was performed to obtain data on disposition and tissue distribution of boron after an infusion of this compound, as well as to establish an optimal protocol for BNCT of malignant cerebral tumors.

METHODS AND MATERIALS

The kinetics of boron disposition after an infusion of borocaptate sodium (25 mg/kg body wt over the period of 1 h) was studied in a group of 10 patients with astrocytoma or glioblastoma of cerebral hemispheres using a modification of the Soloway-Messer colorimetric method. The boron content of tissues (tumor, healthy brain, dura mater, muscle, skin, and cranial bone) removed during the operation performed with latencies varying between 3 and 18 h was investigated by atomic emission spectrometry.

RESULTS

Compartmental analysis of boron blood concentrations has shown that in the majority of patients (four males and three females), the concentration decline can be adequately described by a two-compartment pharmacokinetic model (i.e., by a biexponential relationship). The calculated half-lives of the initial (fast) phase of the concentration decline varied between 0.85 and 3.65 h, whereas the half-life values for the terminal (slow) phase ranged between 22.2 and 111.8 h. However, in the remaining three patients (all females), the goodness of fit of the boron concentration data was significantly better when a pharmacokinetic model with three compartments was assumed. In these patients, therefore, an additional ultrafast phase with a half-life varying between 17 and 37 min was detected in the beginning of the boron blood concentration decline. On the other hand, in one of these patients, the half-life of the terminal phase was found to be 415 h (i.e., more than 17 days). Such a long persistence in the body is explained by the very high value of the total distribution volume, indicating extensive binding of BSH in peripheral tissues. Another reason may be enterohepatic recycling of BSH.

CONCLUSION

Tumor-to-blood ratios higher than 1.5, which are necessary for an effective outcome of BNCT, can be obtained only if the time interval elapsing between the onset of surgery and termination of BSH infusion is at least 12 h.

A round-robin determination of boron in botanical and biological samples

The accurate determination of boron (B) at trace and ultratrace concentrations is an important step toward establishing the role of B in biological functions. However, low-level B concentrations are difficult to determine accurately, especially for many botanical and biological matrices. A round-robin study was conducted to assess analytical agreement for low-level B determinations. Ten experienced research groups from analytical laboratories extending across Europe, Asia, and the US participated in this study. These groups represent a cross-section of academic, commercial, and government facilities. The researchers employed both ion-coupled plasma and neutron techniques in the study. Results from this round-robin study indicate good agreement between participating laboratories at the mg/kg level, but at the lowest levels, microg/kg, only three laboratories participated, and agreement was poor. By encouraging discussion among scientists over these data, the secondary goal of this round-robin study is to stimulate continued improvement in analytical procedures and techniques for accurate low-level B determinations. Furthermore, it is intended to encourage the development of a variety of low-level (low mg/kg and microg/kg) B certified reference samples in biological and botanical matrices. The results from the round-robin analyses were compiled and are summarized in this article.

Blood boron concentrations in pregnant rats fed boric acid throughout gestation

Timed-mated Sprague-Dawley rats (28 to 32/group) were exposed to boric acid (BA) in the diet from Gestational Day (GD) 0 to 20. Dietary concentrations of added BA (0%, 0.025%, 0.050%, 0.075%, 0.100%, or 0.200%) yielded average daily intakes equivalent to 0, 3, 6, 10, 13, or 25 mg boron/kg body weight/d. Dams and their fetuses were evaluated for evidence of maternal or developmental toxicity, as reported previously. At termination on GD 20, maternal whole blood was collected in heparinized Vacutainer tubes, stored frozen (-20 degrees C), and subsequently prepared by a high-temperature alkaline ashing procedure for analysis of boron by inductively coupled plasma optical emission spectrometry. Increasing dietary concentrations of BA were positively associated with whole blood boron concentrations in confirmed pregnant rats, specifically 0.229 +/- 0.143, 0.564 +/- 0.211, 0.975 +/- 0.261, 1.27 +/- 0.298, 1.53 +/- 0.546, or 2.82 +/- 0.987 micrograms boron/g whole blood (mean +/- SD) for the control through high-dose groups. Maternal blood boron concentrations were positively correlated with indices of maternal dietary intake of boron and with embryo/fetal toxicity observed at 0.100% and 0.200% BA in the diet reported previously. Thus, blood boron concentrations of 1.27 +/- 0.298 and 1.53 +/- 0.546 micrograms boron/g were associated with the no-observed-adverse-effect level (10 mg boron/kg/d) and lowest-observed-adverse-effect level (13 mg boron/kg/d) for developmental toxicity reported previously.

Determination of trace boron in microsamples of biological tissues

A benign-by-design method for the determination of boron (B) in microsamples of biological tissues was developed. This is a simple, automated, microdigestion method. Use of reagents and generation of waste are minimized, and the use of toxic/hazardous reagents is eliminated as compared to currently available B methodology. Microsamples are accommodated by the method; 100-400 mg samples were used in this study. B is determined by inductively coupled plasma atomic emission spectrometry (ICPAES) at 249.678 nm. The instrument detection limit for B is 0.01 microgram/mL. Interference studies have been investigated for 21 common elements. Over 250 analyses of standard reference materials were analyzed during the study duration. Recoveries for a series of biological tissues, both plant and animal, ranged from 82-104%.

[Preliminary study on the effects of Nd-Fe-B magnet on trace elements in rhesus monkeys]

Three adult rhesus monkeys were selected. Two of them were fixed with Nd-Fe-B magnets on the palates respectively. Nd-Fe-B magnet was not used in one monkey. Blood was drawn from all monkeys. Ten kinds of trace elements in blood were measured. The result showed that there was no quantitative difference in ten kinds of trace elements between the experimental and control animals.

Pharmacokinetics and boron uptake of BSH (Na2B12H11SH) in patients with intracranial tumors

We evaluated retrospectively the pharmacokinetics and boron uptake of BSH (mercaptoundecahydrododecarborate) for Boron Neutron Capture Therapy (BNCT) in 123 patients undergoing craniotomy for intracranial tumors. The pharmacokinetics revealed that BSH could move easily from blood to the peripheral organs; it was retained there and elimination was very slow. BSH after intra-arterial infusion (i.a.) was found to move into the peripheral organs more easily than after intra-venous (i.v.) infusion. In patients with malignant glioma, the average values of boron concentration in tumor and the tumor to blood ratio (T/B ratio) after i.a. infusion were 26.8 +/- 19.5 micrograms/g (range, 6.1-104.7 micrograms/g) and 1.77 +/- 1.30 (range, 0.47-6.65) respectively. On the other hand, after i.v. infusion the values were 20.9 +/- 12.2 micrograms/g (range, 7.0-39.7 micrograms/g) and 1.30 +/- 0.65 (range, 0.61-2.94) respectively. The differences are not statistically significant. Boron uptake in malignant glioma was about three times higher than low grade glioma. We found a good correlation between boron uptake and time interval from BSH infusion, and 15-20 hours after BSH infusion the boron concentration in tumor was above 20 micrograms/g 10B in 69% of the malignant glioma patients; T/B ratio was above one in 75%, and above two in 44% of them. We recommend intra-venous infusion of BSH clinically since it is safer, and results in sufficient boron concentration in tumor, and the planned irradiation might be optimal around 15-20 hours after the BSH infusion for treating malignant glioma.

Serum boron concentration from inhabitants of an urban area in Japan. Reference value and interval for the health screening of boron exposure

Boron (B) levels were determined in the serum of 980 healthy inhabitants living in an urban area of Japan by means of inductively coupled plasma emission spectrometry (ICPES). The results showed a log-normal distribution of serum B for both sexes, although there are age-related differences. In male subjects, serum B increases rapidly up to 49 yr of age, reaching a plateau between ages 50 and 69 yr old, followed by a gradual increase up to 70 yr or older. Female subjects exhibit a gradual increase up to the age of 70 yr old. The reference value for male and female subjects was 79.8 micrograms/L and 67.9 micrograms/L, and the reference interval was 33.3-191.2 micrograms/L and 29.5-154.9 micrograms/L, respectively. The obtained reference value and interval of the nonexposed group may be useful for health screening for B exposure, either for people living in regions with high levels of B in the environment, or for workers who are exposed to this element.

Boron diffusion across the dialysis membrane during hemodialysis

To investigate the movement of boron across the dialysis membrane, serum and dialysate boron levels of long-term hemodialysis (HD) patients (n = 17) were determined using inductively coupled plasma emission spectrometry in both the inlet and the outlet side of the dialyzer. Results revealed that 77.8% of the serum boron in the inlet side of the dialyzer was filterable and 94.4% of filterable boron was actually filtered during HD. Boron dialysance was found to be 138.6 +/- 16.1 ml/min, and this value was higher than the clearance value of blood urea nitrogen (not significant), phosphorus and creatinine (p < 0.001). It is concluded that HD is effective in eliminating serum boron even at low concentrations, and boron can be classified as an element that is easily diffusible across the dialysis membrane. There seems to be relatively little relation of boron to serum constituents of macromolecules that are reported to have a major impact on the diffusion of trace elements across the HD membrane.

Hemodialysis effect on serum boron level in the patients with long term hemodialysis

Serum and dialysate boron levels in 17 patients with long term hemodialysis (HD) were determined by inductively coupled plasma emission spectrometry (ICPES). Serum boron level was compared with the value of age matched 467 healthy controls and the relationship between serum and dialysate boron level was analyzed. The results showed that serum boron level was significantly higher at the beginning of HD, and lower at the completion of HD in comparison with controls. Although the dialysate was contaminated with trace boron, HD resulted in an excessive decrease of serum boron, rather than boron exposure from the dialysate. Boron hemodialyzability was almost proportional to the gradient of the boron level at the beginning of HD and it could be controlled by the adjustment of the gradient. In conclusion, the serum boron level was very much disturbed in long term HD patients. If boron excess in serum at the beginning of HD, or deficiency at the completion of HD may contribute to the complications of HD patients, fine adjustment and close surveillance of the gradient should be taken into account.

Synthesis of a nickel tetracarboranylphenylporphyrin for boron neutron-capture therapy: biodistribution and toxicity in tumor-bearing mice

Nickel-2,3,7,8,12,13,17,18-octaacetic acid-5,10,15,20-tetra-[3-carboranyl-methoxyphenyl]-porphyrin octamethylester (NiTCP) was given in a Cremophor EL, a polyethoxylated castor oil, and propylene glycol emulsion to BALB/c mice bearing transplanted s.c. KHJJ mammary carcinomas. A total dose of 244 microg NiTCP/gram body weight (gbw) (54 microg B/gbw) was given in 6 i.p. injections over a 32 hr period. Observations of behavior and changes in body weight and chemical and hematological blood tests indicated little or no toxicity from NiTCP over a period of 6-90 hr after injections. Boron concentrations near tumor margins were 160-180 microg B/g at 41-90 hr after the last injection. Tumor:normal brain boron concentration ratios reached approx. 10:1 and tumor:blood ratios reached approx. 250:1 after 4 days. There was no evidence of thrombocytopenia or other potentially important toxicities. Our findings place NiTCP among the leading candidates for pre-clinical experiments aimed toward improvement upon the compounds being tested for boron neutron-capture therapy of glioblastoma multiforme.

Analysis of 10B by PIGE with factor analytical gamma-ray peak identification

Studying the biodistribution of boronated compounds for B neutron capture therapy (BNCT) requires the accurate detection of low levels of boron (10B) in biological samples. Proton induced gamma-ray emission analysis (PIGE) of 10B was found to be viable in a study of low density lipoprotein (LDL), in tissue and blood samples. However, the method is sensitive to Na present in the samples and can therefore not be used for accurate measurements of 10B concentrations below 5 ppm in samples containing Na. PIGE can be considered to be an appropriate reference method for chemical B analysis. The factor analytical method presented here is the most objective way to separate Na and B peaks from each other, and the factorizing method can be applied in different forms of spectral analysis.

Monitoring of blood-10B concentration for boron neutron capture therapy using prompt gamma-ray analysis

The aim of the present study was to monitor the blood-10B concentration of laboratory dogs receiving boron neutron capture therapy, in order to obtain optimal agreement between prescribed and actual dose. A prompt gamma-ray analysis system was developed for this purpose at the High Flux Reactor in Petten. The technique was compared with inductively coupled plasma-atomic emission spectrometry and showed good agreement. A substantial variation in 10B clearance pattern after administration of borocaptate sodium was found between the different dogs. Consequently, the irradiation commencement was adjusted to the individually determined boron elimination curve. Mean blood-10B concentrations during irradiation of 25.8 +/- 2.2 micrograms/g (1 SD, n = 18) and 49.3 +/- 5.3 micrograms/g (1 SD, n = 17) were obtained for intended concentrations of 25 micrograms/g and 50 micrograms/g, respectively. These variations are a factor of two smaller than irradiations performed at a uniform post-infusion irradiation starting time. Such a careful blood-10B monitoring procedure is a prerequisite for accurately obtaining such steep dose-response curves as observed during the dog study.

Plasma boron and the effects of boron supplementation in males

Recently, a proliferation of athletic supplements has been marketed touting boron as an ergogenic aid capable of increasing testosterone. The effect of boron supplementation was investigated in male bodybuilders. Ten male bodybuilders (aged 20 to 26) were given a 2.5-mg boron supplement, while nine male bodybuilders (aged 21 to 27) were given a placebo for 7 weeks. Plasma total and free testosterone, plasma boron, lean body mass, and strength measurements were determined on day 1 and day 49 of the study. A microwave digestion procedure followed by inductively coupled argon plasma spectroscopy was used for boron determination. Twelve subjects had boron values at or above the detection limit with median value of 25 ng/ml (16 ng/ml lower quartile and 33 ng/ml upper quartile). Of the ten subjects receiving boron supplements, six had an increase in their plasma boron. Analysis of variance indicated no significant effect of boron supplementation on any of the other dependent variables. Both groups demonstrated significant increases in total testosterone (p < 0.01), lean body mass (p < 0.01), and one repetition maximum (RM) squat (p < 0.001) and one RM bench press (p < 0.01). The findings suggest that 7 weeks of bodybuilding can increase total testosterone, lean body mass, and strength in lesser-trained bodybuilders, but boron supplementation affects these variables not at all.

Essentiality of boron for healthy bones and joints

Since 1963, evidence has accumulated that suggests boron is a safe and effective treatment for some forms of arthritis. The initial evidence was that boron supplementation alleviated arthritic pain and discomfort of the author. This was followed by findings from numerous other observations epidemiologic and controlled animal and human experiments. These findings included a) analytical evidence of lower boron concentrations in femur heads, bones, and synovial fluid from people with arthritis than from those without this disorder; b) observation evidence that bones of patients using boron supplements are much harder to cut than those of patients not using supplements; c) epidemiologic evidence that in areas of the world where boron intakes usually are 1.0 mg or less/day the estimated incidence of arthritis ranges from 20 to 70%, whereas in areas of the world where boron intakes are usually 3 to 10 mg, the estimated incidence of arthritis ranges from 0 to 10%; d) experimental evidence that rats with induced arthritis benefit from orally or intraperitoneally administered boron; e) experimental evidence from a double-blind placebo-boron supplementation trial with 20 subjects with osteoarthritis. A significant favorable response to a 6 mg boron/day supplement was obtained; 50% of subjects receiving the supplement improved compared to only 10% receiving the placebo. The preceding data indicate that boron is an essential nutrient for healthy bones and joints, and that further research into the use of boron for the treatment or prevention of arthritis is warranted.

Effects of boron supplementation on bone mineral density and dietary, blood, and urinary calcium, phosphorus, magnesium, and boron in female athletes

The effects of boron supplementation on blood and urinary minerals were studied in female college students--17 athletes and 11 sedentary controls--over a one-year period. The athletes had lower percent body fat and higher aerobic capacities than sedentary controls. Athletic subjects consumed more boron in their normal diets than sedentary subjects; all other dietary measures were similar between the two groups. The athletes showed a slight increase in bone mineral density, whereas the sedentary group showed a slight decrease. Serum phosphorus concentrations were lower in boron-supplemented subjects than in subjects receiving placebos, and were lower at the end of the study period than during baseline analysis. Activity depressed changes in serum phosphorus in boron-supplemented subjects. Serum magnesium concentrations were greatest in the sedentary controls whose diets were supplemented with boron, and increased with time in all subjects. A group x supplement interaction was observed with serum magnesium; exercise in boron-supplemented subjects lowered serum magnesium. In all subjects, calcium excretion increased over time; in boron-supplemented subjects, boron excretion increased over time. In all subjects, boron supplementation affected serum phosphorus and magnesium, and the excretion of urinary boron.

Response of rat skin to boron neutron capture therapy with p-boronophenylalanine or borocaptate sodium

The effects of boron neutron capture irradiation employing either BPA or BSH as neutron capture agents has been assessed using the dorsal skin of Fischer 344 rats. Pharmacokinetic studies, using prompt gamma spectrometry, revealed comparable levels of boron-10 (10B) in blood and skin after the intravenous infusion of BSH (100 mg/kg body wt.). The 10B content of blood (12.0 +/- 0.5 micrograms/g) was slightly higher than that of skin (10.0 +/- 0.5 micrograms/g) after oral dosing with BPA. Biphasic skin reactions were observed after irradiation with the thermal neutron beam alone or in combination with BPA or BSH. The time of onset of the first phase of the skin reaction, moist desquamation, was approximately 2 weeks. The time at which the second-wave skin reaction, dermal necrosis, became evident was dose-related and occurred after a latent interval of > or = 24 weeks, well after the acute epithelial reaction had healed. The incidence of both phases of skin damage was also dose-related. The radiation doses required to produce skin damage in 50% of skin sites (ED50 values) were calculated from dose-effect curves and these values were used to determine relative biological effectiveness (RBE) and compound biological effectiveness (CBE) factors for both moist desquamation and dermal necrosis. It was concluded on the basis of these calculations that the microdistribution of the two neutron capture agents had a critical bearing on the overall biological effect after thermal neutron activation. BSH, which was possibly excluded from the cytoplasm of epidermal cells, had a low CBE factor value (0.56 +/- 0.06) while BPA, which may be selectively accumulated in epidermal cells had a very high CBE factor (3.74 +/- 0.7). For the dermal reaction, where vascular endothelial cells represent the likely target cell population, the CBE factor values were comparable, at 0.73 +/- 0.42 and 0.86 +/- 0.08 for BPA ad BSH, respectively.

The pharmacokinetics of p-Boronophenylalanine.fructose in human patients with glioma and metastatic melanoma

PURPOSE

To study the biodistribution of p-Boronophenylalanine in patients undergoing surgery for intracranial tumors or metastatic melanoma.

METHODS AND MATERIALS

D,L-p-Boronophenylalanine was administered as boronophenylalanine.fructose in an intravenous bolus 1-4 h before the operation. Blood samples were collected for 24 h from the time of administration of the compound, and the blood boron elimination parameters were determined. For the glioma patients tumor samples were obtained and skin, dura, periosteum, and surrounding brain samples were collected whenever possible. For the metastatic melanoma patients tumor, fat, skin, and muscle were collected. Determination of the boron content was performed using inductively coupled plasma-atomic emission spectrometry. Twelve melanoma patients and six glioma patients participated in the study. The melanoma patients included four cases of cutaneous metastatic melanoma, six cases of metastatic melanoma to the lymph nodes and two cases of cerebral metastasis.

RESULTS

The results for the metastatic melanoma patients are encouraging with an average tumor:blood boron concentration ratio and standard deviation of about 4.4 +/- 3.2 and a maximum value of 10 for the cerebral metastasis. The glioma patients involved high grade glioma for which the tumor:blood ratio was 2.2 +/- 1.2.

CONCLUSION

The tumor:blood ratios for melanoma fulfil requirements for epithermal boron neutron capture therapy for cerebral melanoma metastases, whereas those for high grade glioma do not.

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.

Dietary boron modifies the effects of vitamin D3 nutrition on indices of energy substrate utilization and mineral metabolism in the chick

An experiment was designed to test part of the hypothesis that physiologic amounts of dietary boron enhance utilization of or, alternatively, compensate for, inadequate concentrations of active vitamin D metabolites to normalize energy substrate utilization and mineral metabolism. Day-old cockerel chicks were fed a ground corn, high-protein casein, corn oil-based diet (< or = 0.18 mg B/kg) supplemented with physiologic amounts of boron (as orthoboric acid) at 0 (non-PSB) or 1.4 (PSB) mg/kg and vitamin D3 (as vitamin D3 powder in corn endosperm carrier) at 3.13 (inadequate, IVD) or 15.6 (adequate, AVD) micrograms/kg. After 26 days, IVD decreased food consumption and plasma calcium concentrations and increased plasma concentrations of glucose, beta-hydroxybutyrate, triglycerides, triiodothyronine, cholesterol, and alkaline phosphatase activity. In the IVD chicks, PSB returned plasma glucose and triglycerides to concentrations exhibited by the AVD chicks and increased food consumption in both IVD and AVD chicks. Histologic findings suggested that PSB enhanced maturation of the growth plate. A ninefold increase in dietary boron yielded only a two-fold increase in plasma boron concentration and no increase in femur boron concentration, which suggests that boron is under homeostatic control. The findings suggest that boron acts on at least three separate metabolic sites because it compensates for perturbations in energy substrate utilization induced by vitamin D3 deficiency, enhances major mineral content in bone, and, independently of vitamin D3, enhances some indices of growth cartilage maturation.

Boron neutron capture therapy of intracerebral melanoma using boronophenylalanine as a capture agent

A rat brain tumor model has been developed utilizing nude rats and the human melanoma cell line MRA 27. For pharmacokinetic and tissue distribution studies, 2 10(5) MRA 27 cells were implanted intracerebrally (i.c.), and 30 days later, 120 mg of 10B-enriched L-boronophenylalanine were injected i.p. into nude rats. 10B concentrations in the tumor, blood, and normal brain were 23.7, 9.4, and 8.4 micrograms/g, respectively, 6 h following administration. For therapy experiments, tumor bearing rats were irradiated at the Brookhaven Medical Research Reactor 30 days following implantation. The median survival time was 44 days for untreated rats, 76 days for those receiving a physical dose of 2.7 Gy, and 93 days for those receiving 3.6 Gy. Animals receiving both 10B-L-boronophenylalanine and physical doses of 1.8, 2.7, or 3.6 Gy (total tumor physical doses of 5.0, 7.5, or 10.1 Gy) had median survival times of 170, 182, and 262 days, respectively. Forty % of rats that received the highest tumor dose (10.1 Gy) survived > 300 days. In a replicate experiment 21% of animals that had received L-boronophenylalanine and irradiation (total tumor physical dose of 10.1 Gy) were alive 220 days after therapy. In a parallel study, animals that were irradiated with gamma photons from a 137Cs source with 12 Gy or 2.0 Gy 9 delivered to the head had median survival times of 86 and 79 days, respectively, compared to 47 days for untreated animals. Our results indicate that boron neutron capture therapy is effective against i.c. melanoma in a rodent model and suggest that large animal studies are warranted to further assess its efficacy.

The effect of boron supplementation on lean body mass, plasma testosterone levels, and strength in male bodybuilders

The effect of boron supplementation was investigated in 19 male bodybuilders ages 20-27 years. Ten were given a 2.5-mg boron supplement while 9 were given a placebo every day for 7 weeks. Plasma total and free testosterone, plasma boron, lean body mass, and strength measurements were determined on Days 1 and 49 of the study. Plasma boron values were significantly (p < 0.05) different as the experimental group increased from (+/- SD) 20.1 +/- 7.7 ppb pretest to 32.6 +/- 27.6 ppb posttest, while the control group mean decreased from 15.1 +/- 14.4 ppb pretest to 6.3 +/- 5.5 ppb posttest. Analysis of variance indicated no significant effect of boron supplementation on any of the dependent variables. Both groups demonstrated significant increases in total testosterone, lean body mass, 1-RM squat, and 1-RM bench press. The findings suggest that 7 weeks of bodybuilding can increase total testosterone, lean body mass, and strength in lesser trained bodybuilders, and that boron supplementation had no effect on these measures.

Microwave digestion preparation and ICP determination of boron in human plasma

A microwave digestion procedure, followed by Inductively Coupled Argon Plasma Spectroscopy, is described for the determination of boron (B) in human plasma. The National Institute of Standards and Technology (NIST) currently does not certify the concentration of B in any substance. The NIST citrus leaves 1572 (CL) Standard Reference Material (SRM) and wheat flour 1567a (WF) were chosen to determine the efficacy of digestion. CL and WF values compare favorably to those obtained from an open-vessel, wet digestion followed by ICP, and by neutron activation and mass spectrometric measurements. Plasma samples were oxidized by doubled-distilled ultrapure HNO3 in 120 mL PFA Teflon vessels. An MDS-81D microwave digestion procedure allows for rapid and relatively precise determination of B in human plasma, while limiting handling hazards and sources of contamination.

Regulation of lithium and boron levels in normal human blood: environmental and genetic considerations

Blood lithium levels may be both genetically and environmentally regulated. The genetic component is evidenced mainly from studies in twins who were either normal or had a manic-depressive disorder. An environmental contribution is adduced from the relationship between the blood lithium level and the amount of the element ingested. No such information is available for boron, another element present in ultra trace amounts in human blood. Unusually high levels of lithium and boron in the waters of northern Chile offer an opportunity to study the genetic and environmental regulation of these elements in the blood of healthy subjects. Samples of blood (n = 40) and water (n = 47) were collected at seven locations in the province of Tarapaca. Most of the healthy subjects were Aymara who had been resident in the respective communities for at least 3 years. The samples were transported to Canada and then freeze-dried. Neutron irradiation was performed in a highly thermalized flux to induce the reactions 6Li (n, alpha) t and 10B (n,7Li) alpha. Assays of 6Li and 10B were conducted in a static mass spectrometer by measurement, respectively, of 3He, produced from decay of tritium, and 4He from alpha-particles. Lithium concentrations in water and blood exhibited a linear relationship, as did the boron concentrations in these fluids. Because some of the individual subjects (n = 15) were first-degree relatives, a genetic component to the regulation of blood levels was explored. The variance in blood levels of lithium and boron was significantly greater between than within families (p < 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)