The plant cell wall polysaccharide rhamnogalacturonan II self-assembles into a covalently cross-linked dimer.
The location of the 1:2 borate-diol ester cross-link in the dimer of the plant cell wall polysaccharide rhamnogalacturonan II (RG-II) has been determined. The ester cross-links the apiofuranosyl residue of the 2-O-methyl-D-xylose-containing side chains in each of the subunits of the dimer. The apiofuranosyl residue in each of the two aceric acid-containing side chains is not esterified. The site of borate esterification is identical in naturally occurring and in in vitro synthesized dimer. Pb2+, La3+, and Ca2+ increase dimer formation in vitro in a concentration- and pH-dependent manner. Pb2+ is the most effective cation. The dimer accounts for 55% of the RG-II when the monomer (0.5 mM) is treated for 5 min at pH 3.5 with boric acid (1 mM) and Pb2+ (0.5 mM); at pH 5 the rate of conversion is somewhat slower. Hg2+ does not increase the rate of dimer formation. A cation's charge density and its ability to form a coordination complex with RG-II, in addition to steric factors, may regulate the rate and stability of dimer formation in vitro. Our data provide evidence that the structure of RG-II itself determines which apiofuranosyl residues are esterified with borate and that in the presence of boric acid and certain cations, two RG-II monomers self-assemble to form a dimer. (+info)
The effect of specimen processing delay on borate urine preservation.
AIM: To investigate the effect on urine culture results and their clinical interpretation of delaying the processing of urine samples in which boric acid had been used as a preservative. METHODS: 792 mid-stream specimens of urine from patients attending their general practitioner were received in borate containing plastic jars. The specimens were cultured upon receipt, stored at room temperature, and then recultured the following morning. RESULTS: After overnight delayed culture, the results were altered in 16% of samples and the clinical interpretation of these findings differed in 8% of specimens. In 28 samples (3.5%) the bacterium isolated on initial culture was not the same as that obtained by culture after overnight storage. CONCLUSIONS: Boric acid urine preservation used for overnight delayed processing of samples is associated with a significant alteration in culture results and the attendant clinical interpretation of such specimens. Rapid transportation/processing of urine specimens must remain the optimum procedure. (+info)
A new ELISA kit for measuring urinary 2-hydroxyestrone, 16alpha-hydroxyestrone, and their ratio: reproducibility, validity, and assay performance after freeze-thaw cycling and preservation by boric acid.
There is considerable controversy regarding the role of estrogen metabolites in breast cancer risk, fueled in part by the development of a rapid ELISA that is suitable for large scale investigations. An earlier version of the ELISA could detect values of the 2-hydroxyestrone (2-OHE1) and 16alpha-hydroxyestrone (16alpha-OHE1) metabolites as low as 2 ng/ml and produce consistent results in premenopausal urines. However, reproducibility was problematic in postmenopausal urines where concentrations of these compounds are much lower. In response to our concern, a new ELISA was developed with a sensitivity of 0.625 ng/ml, which we evaluated using the same pre- and postmenopausal urine samples analyzed in the earlier ELISA. In this report, we present findings on the new kit with regard to reproducibility of the 2-OHE1 and 16alpha-OHE1 measurements, comparability of results with gas chromatography-mass spectroscopy values, and with regard to the stability of the metabolites after repeated freeze-thaw cycles and after preservation by boric acid. For the most part, we found the new ELISA to be reproducible, with assay coefficients of variation ranging from 10 to 20%, and intraclass correlation coefficients (ICCs) ranging from 80 to 95% in both the pre- and postmenopausal urines. ELISA results for 16alpha-OHE1 differed from 1 day (i.e., batch) to the next, and the absolute values of the metabolites obtained by the ELISA were consistently lower than but well correlated with those obtained by gas chromatography-mass spectroscopy. Values of the 2-OHE1:16alpha-OHE1 ratio also differed between the methods, but because the range of values was not large, the magnitude of these differences was not as great. For the ratio, the correlation between methods was excellent, and the ICCs were high for both groups of women. After preservation by boric acid, values of the ratio varied according to acid concentration but not in a linear fashion. Ratio values were similar in urine samples exposed to four different freeze-thaw cycle treatments, although values for all treatments were consistently lower in one batch. Because batch-to-batch variability was not negligible, it is advisable that matched cases and controls be analyzed in the same batch. Provided this is done, the relatively low assay coefficient of variation and high ICC demonstrate that the new ELISA kit can reliably measure the 2-OHE1:16alpha-OHE1 ratio and detect small case-control differences in large population-based studies, where rapid and relatively easy laboratory methods are critical. (+info)
Treatment of recurrent vulvovaginal candidiasis.
Vulvovaginal candidiasis is considered recurrent when at least four specific episodes occur in one year or at least three episodes unrelated to antibiotic therapy occur within one year. Although greater than 50 percent of women more than 25 years of age develop vulvovaginal candidiasis at some time, fewer than 5 percent of these women experience recurrences. Clinical evaluation of recurrent episodes is essential. Patients who self-diagnose may miss other causes or concurrent infections. Known etiologies of recurrent vulvovaginal candidiasis include treatment-resistant Candida species other than Candida albicans, frequent antibiotic therapy, contraceptive use, compromise of the immune system, sexual activity and hyperglycemia. If microscopic examination of vaginal secretions in a potassium hydroxide preparation is negative but clinical suspicion is high, fungal cultures should be obtained. After the acute episode has been treated, subsequent prophylaxis (maintenance therapy) is important. Because many patients experience recurrences once prophylaxis is discontinued, long-term therapy may be warranted. Patients are more likely to comply when antifungal therapy is administered orally, but oral treatment carries a greater potential for systemic toxicity and drug interactions. (+info)
An improved method for the purification of tRNA by chromatography on dihydroxyboryl substituted cellulose.
An improved method for the rapid separation of aminoacyl-tRNA from tRNA by chromatography on dihydroxyboryl-substituted cellulose has been developed. The method relies on the selective binding of unacylated tRNA to the cell cellulose support containing dihydroxyboryl groups. This binding is the result of complex formation between the cis-diol group of the 3'-terminal ribose in tRNA and the dihydroxyboryl groups immobilized on the resin. Aminoacyl-tRNA cannot undergo borate complex formation and is not retained on the resin. The separation is carried out at near neutral pH values ensuring stability of the aminoacyl ester linkage. The aminoacyl-tRNAs are obtained in very high purity. Aminoacyl-tRNA species containing the modified nucleoside Q are also retained on dihydroxyboryl cellulose. Conditions for isolating all Q base containing tRNA species from unfractionated tRNA are described. (+info)
The preparation of simulated water samples for the purpose of bacteriological quality control.
As part of the bacteriological quality control programme of the Public Health Laboratory Service, we were asked to investigate the possibility of providing simulated water samples for distribution to the laboratories. For this purpose it was necessary to find some means whereby suspensions of coliform organisms and Escherichia coli could be kept relatively stable in number at room temperature for a period of 7-10 days. This, it was finally found, was best achieved by adding selected strains of the organisms to improved formate lactose glutamate medium (Gray, 1964) without the lactose but with added boric acid to a final concentration of 1-8%. The procedures adopted in the successful quality control programme are described. (+info)
Permeability and channel-mediated transport of boric acid across membrane vesicles isolated from squash roots.
Boron is an essential micronutrient for plant growth and the boron content of plants differs greatly, but the mechanism(s) of its uptake into cells is not known. Boron is present in the soil solution as boric acid and it is in this form that it enters the roots. We determined the boron permeability coefficient of purified plasma membrane vesicles obtained from squash (Cucurbita pepo) roots and found it to be 3 x 10(-7) +/-1.4 x 10(-8) cm s(-1), six times higher than the permeability of microsomal vesicles. Boric acid permeation of the plasma membrane vesicles was partially inhibited (30%-39%) by mercuric chloride and phloretin, a non-specific channel blocker. The inhibition by mercuric chloride was readily reversible by 2-mercaptoethanol. The energy of activation for boron transport into the plasma membrane vesicles was 10.2 kcal mol(-1). Together these data indicate that boron enters plant cells in part by passive diffusion through the lipid bilayer of the plasma membrane and in part through proteinaceous channels. Expression of the major intrinsic protein (MIP) PIP1 in Xenopus laevis oocytes resulted in a 30% increase in the boron permeability of the oocytes. Other MIPs tested (PIP3, MLM1, and GlpF) did not have this effect. We postulate that certain MIPs, like those that have recently been shown to transport small neutral solutes, may also be the channels through which boron enters plant cells. (+info)
Terconazole cream for non-Candida albicans fungal vaginitis: results of a retrospective analysis.
OBJECTIVE: Although it is FDA-approved for use in vulvovaginal candidiasis caused by non-Candida albicans species, terconazole cream has not been been studied in patients with these infections. We sought to assess the clinical and mycological efficacy of terconazole cream in women with non-C. albicans vaginitis. METHODS: The records of patients who had received a 7-day course of terconazole cream for culture-proved non-C. albicans vaginitis were reviewed. Data with regard to patient demographics, clinical and mycologic response to therapy within 1 month of treatment, and outcome with other antifungal therapies were analyzed. RESULTS: Twenty-eight patients received terconazole cream for non-C. albicans infections. Three patients did not return for follow-up. The median age was 45 years. Seven (28%) patients were nulliparous. The median duration of symptoms was 3 years. Nine patients (36%) had received terconazole within the 6 months prior to referral. Overall, there were 20 C. glabrata cases, 3 C. parapsilosis, and 2 C. lusitaniae. Fourteen (56%) patients achieved a mycologic cure; 11 (44%) noted a resolution of their symptoms. Prior terconazole use was not associated with treatment failure (P = 0.09). Ten failures received boric acid suppositories as subsequent treatment; a cure was effected in 4 (40%). Two of three patients (67%) were eventually cured with flucytosine cream. Five (20 %) patients remained uncured. CONCLUSIONS: Terconazole cream may be an appropriate first-line treatment for non C. albicans vaginitis, even in patients who have previously received the drug. (+info)