Phloem mobility of fluorescent xenobiotics in Arabidopsis in relation to their physicochemical properties

The transport of a range of fluorescent probes within the rootphloem of Arabidopsis thaliana has been imaged using the confocallaser scanning microscope. The phloem mobility of these probesand their subsequent subcellular distribution in the cells ofthe ‘unloading zone’, close to the root tip, arediscussed in relation to a structure-activity relations (SAR)model. This is a generalized model describing the interactionof low molecular weight xenobiotics with living cells, basedon the physicochemical properties of the former. The work demonstratesthat the model can be used to predict the phloem mobility ofxenobiotics, but only partly predicts the subcellular distributionof phloem-mobile probes following unloading. The potential useof phloem-mobile fluorescent probes as physiological indicatorsis discussed. Key words: Arabidopsis, confocal laser scanning microscopy (CLSM), fluorescent probes, phloem transport, xenobiotic transport     

News from the Biological Stain Commission No. 11

The 11th issue of News from the Biological Stain Commission (BSC) provides our first impressions of the REACH and ECHA programs. We intend to give a more thorough account of what these important programs actually mean in later editions of News from the Biological Stain Commission. Under the heading of Regulatory Affairs, the Biological Stain Commission's International Affairs Committee presents information from the opening session of the meeting of the International Standards Organization ISO/TC 212 Clinical laboratory testing and in vitro diagnostic test systems held on 2-4 June 2010 in Seoul, Republic of Korea.     

A Simple Assay Procedure for Mixtures of Hematoxylin and Hematein

A simple and rapid method for the simultaneous quantitative analysis of mixtures of hematoxylin and hematein uses the molar extinction coefficients of the pure substances calculated by Lalor and Martin (1959). Absorbance measurements of the samples dissolved in methanol are made at wavelengths of 292 nm and 445 nm, the wavelengths of maximum absorption of hematoxylin and hematein respectively. The hematoxylin absorbance at 292 nm is corrected for the presence of hematein.

Using this method it was found that of 12 commercial samples labelled “hematoxylin” all contained at least 90% of the compound. Hematein contents of these samples fell in the range 0.1% to 6.8%. In 9 commercial samples labelled “hematein” the hematein contents fell in the range 1.2% to 90.7%. The hematoxylin contents of these samples fell in the range of 1.0% to 82.7%.

This paper describes also a chromatographic method for the identification of hematein and its oxidation products.     

Understanding Romanowsky staining. I: The Romanowsky-Giemsa effect in blood smears

Normal blood smears were stained by the standardised azure B-eosin Y Romanowsky procedure recently introduced by the ICSH, and the classical picture resulted. The effects of varying the times and temperature of staining, the composition of the solvent (buffer concentration, methanol content, & pH), the concentration of the dyes, and the mode of fixation were studied. The results are best understood in terms of the following staining mechanism. Initial colouration involves simple acid and basic dyeing. Eosin yields red erythrocytes and eosinophil granules. Azure B very rapidly gives rise to blue stained chromatin, neutrophil specific granules, platelets and ribosome-rich cytoplasms; also to violet basophil granules. Subsequently the azure B in certain structures combines with eosin to give purple azure B-eosin complexes, leaving other structures with their initial colours. The selectivity of complex formation is controlled by rate of entry of eosin into azure B stained structures. Only faster staining structures (i.e. chromatin, neutrophil specific granules, and platelets) permit formation of the purple complex in the standard method. This staining mechanism illuminates scientific problems (e.g. the nature of 'toxic' granules) and assists technical trouble-shooting (e.g. why nuclei sometimes stain blue, not purple).     

Fractional clearance of urate: validation of measurement in spot-urine samples in healthy subjects and gouty patients

Introduction

Hyperuricemia is the greatest risk factor for gout and is caused by an overproduction and/or inefficient renal clearance of urate. The fractional renal clearance of urate (FCU, renal clearance of urate/renal clearance of creatinine) has been proposed as a tool to identify subjects who manifest inefficient clearance of urate. The aim of the present studies was to validate the measurement of FCU by using spot-urine samples as a reliable indicator of the efficiency of the kidney to remove urate and to explore its distribution in healthy subjects and gouty patients.

Methods

Timed (spot, 2-hour, 4-hour, 6-hour, 12-hour, and 24-hour) urine collections were used to derive FCU in 12 healthy subjects. FCUs from spot-urine samples were then determined in 13 healthy subjects twice a day, repeated on 3 nonconsecutive days. The effect of allopurinol, probenecid, and the combination on FCU was explored in 11 healthy subjects. FCU was determined in 36 patients with gout being treated with allopurinol. The distribution of FCU was examined in 118 healthy subjects and compared with that from the 36 patients with gout.

Results

No substantive or statistically significant differences were observed between the FCUs derived from spot and 24-hour urine collections. Coefficients of variation (CVs) were both 28%. No significant variation in the spot FCU was obtained either within or between days, with mean intrasubject CV of 16.4%. FCU increased with probenecid (P < 0.05), whereas allopurinol did not change the FCU in healthy or gouty subjects. FCUs of patients with gout were lower than the FCUs of healthy subjects (4.8% versus 6.9%; P < 0.0001).

Conclusions

The present studies indicate that the spot-FCU is a convenient, valid, and reliable indicator of the efficiency of the kidney in removing urate from the blood and thus from tissues. Spot-FCU determinations may provide useful correlates in studies investigating molecular mechanisms underpinning the observed range of efficiencies of the kidneys in clearing urate from the blood.

Trial Registration

ACTRN12611000743965