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PubMed2003

Phenotypic diversity of oral C. albicans isolated on single and sequential visits in an HIV-infected Chinese cohort.

HIV-infected individuals maintain multiple oral C. albicans strains over time that are thought to undergo microevolution in terms of both phenotypic and genotypic features. To study this phenomenon, a 12-month prospective study was conducted in a cohort of 16 HIV-infected ethnic Chinese individuals with (A) and without (B) symptoms of oropharyngeal candidiasis to evaluate the phenotype distribution among oral C. albicans isolates during disease progression. Oral rinse samples were obtained and up to five C. albicans colony-forming units were selected per each visit, during the one year period of multiple visits. The isolates were phenotyped using two commercially available biotyping kits, the API 20C system, API ZYM system, and a plate test for resistance to boric acid. A total of 261 C. albicans strains in group A were differentiated into 67 biotypes, while 42 biotypes were seen amongst the 182 isolates from group B. The major biotypes in the two groups were similar and were in decreasing order of prevalence J1R, J1S, J6S, J6R, J2S, K1S, J10R, K1R, and K6R; 48 different biotypes were seen in group A and 24 in group B, with some uniquely represented in each group, leading to a significant association between the prevalence of the biotypes J1S and J2S and symptomatic candidiasis (p<0.05). Taken together this study illustrates the wide phenotypic spectrum of oral C. albicans associated with HIV-infection.

Adult↗
PubMed2003

Contact sensitivity to calcium hypochlorite.

Eusol (an abbreviation for Edinburgh University solution), consisting of aqueous boric acid and calcium hypochlorite, is widely used in the management of open wounds left to heal by secondary intention (1).

Adolescent↗
PubMed2000

Biotypes of oral Candida albicans isolated from AIDS patients and HIV-free subjects in Thailand.

This study was conducted to examine biotypes and antifungal susceptibility patterns of oral Candida albicans isolated from HIV-infected patients, HIV-free patients with candidiasis and healthy subjects. All isolates were biotyped using a typing system based on enzyme profiles, carbohydrate assimilation patterns and boric acid resistance. Thirty-eight biotypes were found amongst 218 oral C. albicans isolates. The major biotype found was A1S, which accounted for 32.6% of all isolates, and this biotype was the most common in all groups. There was a greater variety of biotypes of C. albicans in the HIV-infected group than in the other groups; however, there was no statistically significant difference between the groups. The minimum inhibitory concentrations (MICs) of a total of 118 isolates were determined for amphotericin B and for ketoconazole using the National Committee for Clinical Laboratory Standards (NCCLS) broth macrodilution method and the E-test. When the antifungal susceptibility patterns among the groups were compared, a statistically significant difference was found only with amphotericin B. The median MIC of amphotericin B in the HIV-infected group was higher than in the healthy group (P=0.013, NCCLS method; P=0.002, E-test). However, this difference in sensitivity was not restricted to any sub-type investigated. Our results showed that the biotype patterns of C. albicans isolates that colonize HIV-infected patients are similar to those of HIV-free subjects, and there is no relationship between antifungal susceptibility patterns and the biotypes.

AIDS-Related Opportunistic Infections↗
PubMed1990

Use of masking agents in the determination of lead in tap water by flame atomic absorption spectrometry with flow injection pre-concentration.

The selectivity of immobilised 8-hydroxyquinoline for lead is shown to be improved by the use of masking agents during pre-concentration, prior to determination by flame atomic absorption spectrometry. Interference by iron, copper, aluminium and zinc is suppressed by including triethanolamine, thiourea, fluoride, acetylacetone or cyanide in the buffer as masking agents. Species such as iron or copper can completely prevent the pre-concentration of lead. This is shown to be overcome by using a buffer consisting of 0.2 M boric acid, 2% triethanolamine, 2% thiourea and 2% acetylacetone, even when the interfering species is in a 200-fold excess over lead. Recoveries from tap water samples, to which various amounts of lead had been added, ranged from 94 to 108%. Results of analyses of tap water samples using this method were in good agreement with those obtained by electrothermal atomic absorption spectrometry.

Indicators and Reagents↗
PubMed1996

Determination of isotope enrichments of magnesium in microwave-digested biological samples by thermal ionization mass spectrometry using a direct loading technique.

The isotope ratios of magnesium were determined in isotopically normal and 26 Mg-enriched samples of human blood, blood plasma, urine and faeces and bovine muscle. The measurements were made with a magnetic sector, thermal ionization mass spectrometer (TIMS) equipped with a multiple ion collector system for simultaneous detection of the ion currents. The samples were decomposed using microwave digestion with HNO3 and HCI. Without further chemical treatment, the mineralized samples were deposited together with silica gel and boric acid on rhenium filaments, which served as thermal ionization source filaments. This method, called the direct loading technique (DLT), results in stable ion signals of the magnesium isotopes with isotope ratios indistinguishable from those of natural Mg standards within experimental error. Fractionation-corrected 26 Mg/24 Mg ratios of natural Mg standards were determined with a relative external precision of 0.02%. The magnesium recoveries for all of the analysed matrices were > or = 97%; 26 Mg was added to calibrated sample solutions to produce isotopic enrichments within a range typically appearing in samples of human tracer studies. Linear regression analysis of measured versus expected per 1000 (/1000) enrichments yields y = 0.998x + 0.79. The DLT described here is a simpler and quicker method than other methods reported hitherto. It has the advantage of avoiding magnesium separation and purification steps prior to TIMS analysis for all of the analysed biological samples and thus reduces contamination and guarantees optimum magnesium recovery. The reported method improves the applicability of stable isotopes of magnesium in human tracer studies.

Animals↗
PubMed2006

Ferromagnetic ordering in a new nickel polyborate NiB12O14(OH)10.

A new nickel polyborate, NiB12O14(OH)10 was synthesized using boric acid as a flux. This material has two-dimensional borate layers with a quasi-square lattice of Ni2+. The Ni2+ ions locate in the plane of the two-dimensional layer, bridged through BnO(n+1) chains in the plane and connected with the three-membered ring borate groups out of the plane. The dc and ac magnetic susceptibility, magnetization and specific heat measurements show that this material undergoes a weak ferromagnetic phase transition at Tc = 5.8 K. At T < Tc, a metamagnetic phase transition is observed at about 5 T, associated by a spin-flop, suggesting the ferromagnetic ordering is induced by an antiferromagnetic interaction. A broad maximum in the ac susceptibility at TM = 23-24 K indicates an intermediate short-range ordering.

Journal Article↗
PubMed2002

Plant aquaporins: multifunctional water and solute channels with expanding roles.

There is strong evidence that aquaporins are central components in plant water relations. Plant species possess more aquaporin genes than species from other kingdoms. According to sequence similarities, four major groups have been identified, which can be further divided into subgroups that may correspond to localization and transport selectivity. They may be involved in compatible solute distribution, gas-transfer (CO2, NH3) as well as in micronutrient uptake (boric acid). Recent advances in determining the structure of some aquaporins gives further details on the mechanism of selectivity. Gating behaviour of aquaporins is poorly understood but evidence is mounting that phosphorylation, pH, pCa and osmotic gradients can affect water channel activity. Aquaporins are enriched in zones of fast cell division and expansion, or in areas where water flow or solute flux density would be expected to be high. This includes biotrophic interfaces between plants and parasites, between plants and symbiotic bacteria or fungi, and between germinating pollen and stigma. On a cellular level aquaporin clusters have been identified in some membranes. There is also a possibility that aquaporins in the endoplasmic reticulum may function in symplasmic transport if water can flow from cell to cell via the desmotubules in plasmodesmata. Functional characterization of aquaporins in the native membrane has raised doubt about the conclusiveness of expression patterns alone and need to be conducted in parallel. The challenge will be to elucidate gating on a molecular level and cellular level and to tie those findings into plant water relations on a macroscopic scale where various flow pathways need to be considered.

Journal Article↗
PubMed1997

Capillary electrophoresis of r-hirudin and a polyethylene glycol derivative of r-hirudin (PEG-hirudin).

UNLABELLED: Recombinant (r-) hirudins and PEG-hirudin are currently tested for anticoagulant therapy. For their concentration measurement, radioimmunoassay and HPLC methods are available. The separation of r- and PEG-hirudin is currently performed by HPLC. However, the sensitivity of the method is low. Capillary electrophoresis is a rapid, selective technique that requires low sample amounts. Our aim was the development of a capillary electrophoresis method to measure r- and PEG-hirudin. The results are as follows: In a borate solution (0.3% boric acid and 0.4% sodium tetraborate, pH 9.5) r-hirudin was separated from PEG-hirudin in a purified system using a fused silica capillary (50 cm long and 75-micron i.d. and reversed polarity). A neutral capillary with a 20 mM tricine buffer (pH 8.0, field strength 500 V/cm) was also effective in resolving r- from PEG-hirudin. A linear correlation was found between the peak area and the concentration between 20 micrograms/mL and 10 mg/mL for hirudin (r2 = 0.99) and between 1.25 and 10 mg/mL for PEG-hirudin (r2 = 0.99). In human plasma mixtures, r- and PEG-hirudin were completely separated. The linear correlation between the peak area and the concentration was r2 = 0.99. CONCLUSION: In a fused silica capillary, r- and PEG-hirudin are separated in a purified system. Capillary electrophoresis which is performed in a neutral capillary, resolves r- from PEG-hirudin in a purified system, in plasma and in urine. The sensitivities of the methods are comparable. Capillary electrophoresis separates r- from PEG-hirudin and may be applied to biologic systems to measure the concentration and purity of r- and PEG-hirudin.

Electrophoresis, Capillary↗
PubMed1983

Whole-body irradiation of deuterated mice by the 10B(n, alpha)7Li reaction.

Specific pathogen-free mice, 8-12 wk of age, were supplied with either acidified tap water or acidified 30 atom % 2H2O in tap water. Thirteen days later, when body water deuterium was about 20 atom %, mice were irradiated either by neutrons or by x-rays after intraperitoneal injection of boric acid. Mortality from whole-body neutron-boron radiation, unlike mortality from whole-body x-radiation, was not lowered by such deuteration. Time intervals to death of neutron-irradiated mice were compatible with the gastrointestinal syndrome. Neither species nor numbers of colonic bacteria were measurably altered by deuteration alone. Because the toxic, nonlethal range of deuterium substitution for aqueous hydrogen in mammals is approximately 1/5th to 1/3rd, these results indicate that partial deuteration of human tissues would improve neutron capture therapy of deep tumors. Neutron penetration would be enhanced and damage to normal tissues from photons would be decreased. The number of deuterium recoils due to neutron capture by hydrogen would also be decreased.

Animals↗
PubMed1991

Formation of phosphatidylinositol 3-phosphate by isomerization from phosphatidylinositol 4-phosphate.

We have synthesized phosphatidylinositol 3-phosphate from phosphatidylinositol 4-phosphate by using diisopropylcarbodiimide to promote migration of the 4-phosphate via a cyclic phosphodiester intermediate. The product was isolated by a thin-layer chromatographic method that depends on the ability of phosphatidylinositol 4-phosphate, but not phosphatidylinositol 3-phosphate, to form complexes with boric acid. The final yield of the procedure was 8% phosphatidylinositol 3-phosphate, which was approximately 80% pure. The product was shown to be phosphatidylinositol 3-phosphate by the following criteria: (i) cochromatography with an authentic standard on borate thin-layer chromatography, (ii) cochromatography of the deacylated product with glycerophosphoinositol 3-phosphate on high-performance liquid chromatography, (iii) conversion of the product to phosphatidylinositol by homogeneous phosphatidylinositol 3-phosphate 3-phosphatase, and (iv) deacylation and deglyceration of the product to a compound that comigrates with inositol 1,3-bisphosphate on high-performance liquid chromatography. The availability of mass amounts of phosphatidylinositol 3-phosphate will allow further elaboration of reactions in this recently discovered pathway of phosphatidylinositol metabolism.

Autoradiography↗
PubMed1995

Mechanism of protein modification by glyoxal and glycolaldehyde, reactive intermediates of the Maillard reaction.

The role of glyoxal and glycolaldehyde in protein cross-linking and N epsilon-(carboxymethyl)lysine (CML) formation during Maillard reaction under physiological conditions was investigated. Incubation of bovine serum albumin with these reagents lead to rapid formation of C-2-imine cross-links and CML. Initial CML formation rate from glyoxal was not dependent on oxidation, suggesting an intramolecular Cannizzaro reaction. CML formation from glucose/lysine or Amadori product of both was strongly dependent on oxidation. Blocking of Amadori product by boric acid totally suppressed CML formation from Amadori product, but only by 37% in the glucose/lysine system. Trapping of glyoxal with aminoguanidine hardly suppressed CML formation from Amadori product, whereas it blocked 50% of CML production in the glucose/lysine system. While these results would support a significant role for glucose autoxidation in CML formation, the addition of lysine to a glucose/aminoguanidine incubation system catalyzed glyoxal-triazine formation 7-fold, thereby strongly suggesting that glucose autoxidation is not a factor for glyoxal-mediated CML formation. Based on these results, it can be estimated that approximately 50% of the CML forming in a glucose/lysine system originates from oxidation of Amadori product, and 40-50% originates from a pre-Amadori stage largely independent from glucose autoxidation. This step may be related to the so-called Namiki pathway of the Maillard reaction.

Acetaldehyde↗
PubMed2004

Noncanonical DNA elements in the lamin B2 origin of DNA replication.

DNA replication origins of eukaryotes lack linear replicator elements but contain short (dT)(n) (dA)(n) sequences that could build mutually equivalent unorthodox structures. Here we report that the lamin B2 origin of DNA replication adopts an alternative form characterized by unpaired regions CTTTTTTTTTTCC/GGAAAAAAAAAAG (3900-3912) and CCTTTTTTTTC/GAAAAAAAAGG (4141-4151). Both unpaired regions are resistant to DNase and except in central parts of their homopyrimidine strands are sensitive to single strand-specific chemicals. Interactions that protect central pyrimidines probably stabilize the bubble-like areas. Because DNA fragments containing either one or both bubbles migrate in TBM (89 mm Tris base, 89 mm boric acid, and 2 mm MgCl(2)) PAGE even faster than expected from their linear size, interacting regions are expected to belong to the same molecule. In an origin fragment containing a single bubble, free homopyrimidine strand can only interact with Hoogsteen hydrogen bonding surfaces from a complementary double stranded sequence. Indeed, this origin fragment reacts with triplex preferring antibody. In competition binding experiments control double stranded DNA or single stranded (dT)(40) do not affect origin-antibody interaction, whereas TAT and GGC triplexes exert competitive effect. Because the chosen fragment does not contain potential GGC forming sequences, these experiments confirm that the lamin B2 origin adopts a structure partly composed of intramolecular TAT triads.

Base Sequence↗
PubMed2002

Microbiological evaluation of a commercial transport system for urine samples.

The aim of this study was to evaluate a commercial tube prepared with boric acid, sodium formate and sorbitol (Hemogard Vacutainer tubes, Becton-Dickinson, HG tubes). Fourteen bacterial strains were incubated in urine in HG tubes and conventional tubes. During a 24-h period, most of the microorganisms grew readily in conventional tubes at room temperature, whereas the bacterial counts were comparatively unchanged when chilled or kept in HG tubes. The bacterial counts of Alcaligenes faecalis and lactobacilli decreased by two 10 logarithms in the HG tubes, at room temperature. Experiments were also performed with the addition of various antibiotics. Ciprofloxacin caused a decrease in E. coli counts regardless of type of tube used, while the HG tubes and the conventional tubes kept chilled conserved bacterial counts upon challenge with fosfomycin, trimethoprim or mecillinam. Bedside cultures from 154 outpatients were sampled and divided into three tubes. One conventional tube was sent to our laboratory by ordinary chilled transport. Another conventional tube and one HG tube were transported to the laboratory without chilling. Cultures were performed upon arrival at the laboratory and then 24, 48 and 72 h after primary sampling. Within 24 h of sampling, no significant differences in bacterial counts were observed between chilled conventional tubes and the HG tubes at room temperature. However, in the HG tubes a significant change in enterococcal counts was noted within 48 h.

Anti-Bacterial Agents↗
PubMed2000

A method for determining fumonisin B1 in corn using immunoaffinity column clean-up and thin layer chromatography/densitometry.

A method for determining fumonisin B1 (FB1) in corn was developed and the clean-up optimized in order to give an extract suitable for one-dimensional thin layer chromatographic (TLC) analysis. FB1 was extracted with a solution of methanol:water (80:20, v/v), purified through an immunoaffinity column and separated on a C18 reversed phase TLC plate. The FB1 was visualized with 0.1 mol/l sodium tetraborate, 0.40 mg/ml fluorescamine in acetonitrile and 0.01 mol/l boric acid:acetonitrile (2:3, v/v) for fluorescence detection, and quantified by densitometric analysis. Water, acetonitrile:water (1:1 v/v) and acetonitrile:water (4:1 v/v) were evaluated as TLC solvents for running both standards and samples together with derivatization procedures aimed at improving separation, resolution, sensitivity and linearity. The mean recovery for FB1 for spiked samples was found to be 85% and the linear equation of standard calibration curve by densitometric analysis gave an r2 value higher than 0.99. The maximum coefficient of variation for replicate analysis of spiked samples was 19%. The absolute amount of FB1 standard detectable on a TLC plate was 2 ng, giving a detection limit for the method of 0.1 mg/kg. The method has been shown to be robust in the application of FB1 monitoring in corn (214 samples) collected in different regions of the country. FB1 was detected in 99% of these samples in the range of 0.2 to 6 mg/kg.

Carboxylic Acids↗
PubMed1987

RBE of a thermal neutron beam and the 10B(n, alpha)7Li reaction on cultured B-16 melanoma cells.

The RBE of a thermal neutron beam and the 10B(n, alpha)7Li reaction were determined in cultured B-16 melanoma cells. The Kyoto University Research Reactor (KUR) was used as a thermal neutron source which had a very low contamination of gamma-rays and fast neutrons. The cells were irradiated with the beam in the presence or absence of 10B-boric acid. The absorbed dose from the neutron capture reaction to the cells was calculated by a method of Kitao (1975). Survival curves in both conditions had no shoulder and Do values were 0.506 or 0.604 Gy in the presence or absence of 5 micrograms 10B/ml-medium, respectively. The Do value of the 10B(n, alpha)7Li reaction was also estimated at 0.466 Gy, assuming each component of radiation was additive. The RBEs of the KUR thermal neutron beam and the 10B(n, alpha)7Li reaction relative to 60Co gamma-rays were estimated as 4.62 and 6.01 at 0.1 surviving fraction, respectively. Using these results, we calculated the absorbed dose from the 10B-compound and estimated the specific accumulation in the cultured cells of 10B-compounds which we have previously reported but not quantified (Nakanishi et al. 1980, Ichihashi et al. 1982).

Cell Line↗
PubMed1989

Lethal effect and potentially lethal damage recovery in cultured mammalian cells irradiated by neutron-capture beams.

Cell killing and potentially lethal damage (PLD) recovery in Hela cells were examined after irradiation in suspension using a 10B neutron-capture beam. Thermal-neutron irradiation in the medium containing from 0.09 to 9 mM boron-10 (0.9-90 micrograms/g 10B, 90 per cent enriched boric acid) resulted in steeper survival curves than in the boron-free medium. The relative biological effectiveness (r.b.e.), expressed as the Do ratio, increased from 2.2 +/- 0.1 for the control without boron-10 to 5.4 +/- 0.3 in the medium containing 0.9 mM boron-10. The r.b.e. value was 5.2 +/- 0.5 at a boron-10 concentration of 9 mM, and did not increase when the boron-10 concentration was increased from 0.9 to 9 mM. It was suggested that the observed plateau of r.b.e. at boron-10 concentrations higher than 0.9 mM was due to the dominancy of the 10B(n, alpha)7Li reaction for dose accumulation. PLD recovery after the neutron irradiation containing 0.9 mM boron-10 was not observed, while a small effect was observed after irradiation in the thermal neutron beam, although much less than after gamma rays. The results show that the neutron-capture beam is an excellent beam for radiotherapy if the boron-10 concentration in tumour cells could be elevated to about 1 mM.

Boron↗
PubMed1996

Comet assay study of DNA damage and repair of tumour cells following boron neutron capture irradiation with fast d(14) + Be neutrons.

We compared the amount of radiation-induced DNA damage and the extent of DNA repair in human melanoma cells (MeWo) using the 'comet assay' after neutron, boron neutron capture and X-irradiation. Using a colony-forming assay it was shown earlier that lethal effects in tumour cells treated with fast neutrons may be increased by the neutron capture reaction 10B(n, alpha)7Li. The effectiveness of boron neutron capture in killing tumour cells depends on the number of 10B atoms delivered to the tumour, the subcellular distribution of 10B and the thermal neutron fluence at the side of the tumour. Using the 'comet assay' the DNA damage of fast neutrons (mean energy 5.8 MeV) was shown to be significantly greater than for the same absorbed dose of X-rays. The presence of 600 ppm 10B (boric acid H5 10BO3) in the cell medium during irradiation with d(14) + Be neutrons in a phantom enhances the DNA damage by 20% compared with neutron irradiation alone. After DNA damage induction by neutrons and neutron capture of boron, the DNA repair capacity of the MeWo cells is significantly reduced in comparison with X-irradiation resulting in proportionally more residual DNA damage after 180 min of repair time.

Boron Neutron Capture Therapy↗