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At least 163 records · Page 9Linked to original sources
PubMed1993

The influence of a low-boron diet and boron supplementation on bone, major mineral and sex steroid metabolism in postmenopausal women.

An increase in dietary intake of B from 0.25 to 3.25 mg/d has been reported to increase plasma oestradiol and testosterone and decrease urinary Ca excretion in postmenopausal women. Consequently, it is suggested that the higher level of B intake could reduce bone loss associated with the menopause and cessation of ovarian function. The present study was designed to investigate the effect of a B supplement on bone mineral absorption and excretion, plasma sex steroid levels and urinary excretion of pyridinium crosslink markers of bone turnover in healthy postmenopausal volunteers. The women were accommodated in a metabolic unit, given a low-B diet (LBD; 0.33 mg/d) for 3 weeks and were asked to take a B supplement of 3 mg/d in addition to the LBD for a further 3 weeks. Changing B intake from 0.33 to 3.33 mg/d had no effect on minerals, steroids or crosslinks. However, the LBD appeared to induce hyperabsorption of Ca since positive Ca balances were found in combination with elevated urinary Ca excretion. This phenomenon may have inhibited or obscured any effect of B.

Bone and Bones↗
PubMed2001

Evaluation of the potential of p-boronophenylalaninol as a boron carrier in boron neutron capture therapy, referring to the effect on intratumor quiescent cells.

C57BL mice bearing EL4 tumors and C3H / He mice bearing SCC VII tumors received 5-bromo-2'-deoxyuridine (BrdU) continuously for 5 days via implanted mini-osmotic pumps to label all proliferating (P) cells. Three hours after oral administration of l-p-boronophenylalanine-(10)B (BPA), or 30 min after intraperitoneal injection of sodium borocaptate-(10)B (BSH) or l-p-boronophenylalaninol (BPA-ol), a newly developed (10)B-containing alpha-amino alcohol, the tumors were irradiated with thermal neutron beams. For the combination with mild temperature hyperthermia (MTH) and / or tirapazamine (TPZ), the tumors were heated at 40 degrees C for 30 min immediately before neutron exposure, and TPZ was intraperitoneally injected 30 min before irradiation. The tumors were then excised, minced and trypsinized. The tumor cell suspensions thus obtained were incubated with cytochalasin-B (a cytokinesis blocker), and the micronucleus (MN) frequency in cells without BrdU labeling ( = quiescent (Q) cells) was determined using immunofluorescence staining for BrdU. Meanwhile, 6 h after irradiation, tumor cell suspensions obtained in the same manner were used for determining the apoptosis frequency in Q cells. The MN and apoptosis frequency in total (P + Q) tumor cells were determined from tumors that were not pretreated with BrdU. Without TPZ or MTH, BPA-ol increased both frequencies most markedly, especially for total cells. However, as with BPA, the sensitivity difference between total and Q cells was much larger than with BSH. On combined treatment with both MTH and TPZ, this sensitivity difference was markedly reduced, similarly to when BPA was used. MTH increased the (10)B uptake of all (10)B-compounds into both tumor cells. BPA-ol has good potential as a (10)B-carrier in neutron capture therapy, especially when combined with both MTH and TPZ.

Administration, Oral↗
PubMed1981

Boron content of plasma and urine as indicators of boron intake in cattle.

Yearling beef heifers were offered drinking water (0.8 mg of B/L of water) to which 0, 15, 30, 60, or 120 mg of B/L of water was added for 10-day periods. Feed and water consumption were unaffected by treatments. There were no overt signs of toxicosis. Increased B ingestion increased plasma and urine B concentrations. The percentage of renally filtered B that was excreted was increased with the 30, 60, and 120 mg of B/L of water treatments, and B clearance exceeded endogenous creatinine clearance with these treatments. Ingesting increased amounts of B was associated with decreased plasma PO4(-3) concentration and increased renal clearance and urinary excretion of PO4(-3). The B status of cattle can be predicted from plasma or urine B concentrations. Results indicated that prediction can be made from the B/creatinine ratio of urine. With an induced urine sample, the equation for predicting B ingestion is Y = -67.79 + 976.74X - 141.91X2 (r = 0.96; Syx = 121.57) where Y is B in milligrams per 100 kg of body weight per day, and X is the ratio of urine B (mg/L of urine) to creatinine (mg/L of urine).

Animals↗
PubMed2001

The Influence of Excess Ammonia on the Mechanism of the Reaction of Boron Trichloride with Ammonia-An Ab Initio Molecular Dynamics Study This work was supported by the Deutsche Forschungsgemeinschaft in the framework of the Sonderforschungsbereich 408 "Anorganische Festkörper ohne Translationssymmetrie". We thank Mauro Boero from the Joint Research Center for Atom Technology, Tsukuba (Japan) for the reoptimization of the Martins-Troullier pseudopotentials for boron and chlorine, as well as the John-von-Neumann-Institut für Computing, Jülich, for making computer time available to us.

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Journal Article↗
PubMed2001

Fragment mode analysis and its application to the vibrational normal modes of boron trichloride-ammonia and boron trichloride-pyridine complexes.

A method for expressing quantitatively the vibrational normal modes of a molecule in a basis set consisting of the normal vibrations (plus translations and rotations) of its constituent fragments is presented. The method is illustrated by describing the vibrational modes of BCl3-NH3 and BCl3-pyridine electron donor-acceptor complexes in terms of motions of BCl3 and either NH3 or pyridine. These complexes show examples of mixing between modes located on different fragments, mixing between modes of one fragment due to symmetry lowering, and the transformation of six fragment translations/rotations into vibrations of the complex. Although perturbation theory has been proposed to explain such examples of mode mixing, calculations imply that interactions between fragments of both complexes are too strong for perturbation theory to be generally applicable. In addition, the transformation of fragment rotations and/or translations into vibrations of the composite molecule will always occur and cannot be understood in detail by using perturbation theory. For the BCl3-pyridine complex, a band observed at 1107 cm(-1) is re-assigned as a combination of C-H in-plane bending and a ring-breathing mode of the pyridine fragment.

Ammonia↗