[Determination of steroids in milk powder and birds' feces by high performance liquid chromatography coupled with evaporative light scattering detector]

In this paper, a new, simple and rapid method for the analysis of steroids by reversed-phase high performance liquid chromatography (HPLC) coupled with evaporative light scattering detector (ELSD) is presented. A good resolution of the 12 steroids is obtained within 35 min with a gradient elution using a binary mobile phase composed of methanol and water. The analytical column used was 2.0mm x 150mm, packed with BDS (particle size 5microm) and the mobile phase flow rate was 0.2mL/min. Nebulizer gas flow rate and drift tube temperature, the two critical parameters for determining the reproducibility and signal-to-noise ratio of ELSD were 2.00mL/min and 95 degrees C, respectively. The response of the ELSD was non-linear as a result of basic light-scattering principles, the calibration curve by plotting lnY vs lnX (Y, X stand for peak area and concentration, respectively) shows a good linearity in the range of 5-50mg/L with a correlation coefficient higher than 0.99 for individual steroid and with relative standard deviation less than 6.92%. This method has been applied to the determination of steroids in milk powder and birds' feces, solid phase extraction on reverse phase bonded C18 (5mL/500mg) was used to treat the samples efficiently. The recoveries of the steroids were between 84.0%-102.8%.

An ATP-gated cation channel with some P2Z-like characteristics in gastric smooth muscle cells of toad

1. Whole-cell and single-channel currents elicited by extracellular ATP were studied in freshly dissociated smooth muscle cells from the stomach of the toad Bufo marinus using standard patch clamp and microfluorimetric techniques. 2. This ATP-gated cation channel shares a number of pharmacological and functional properties with native rat myometrium receptors, certain native P2Z purinoceptors and the recently cloned P2X7 purinoceptor. But, unlike the last two, the ATP-gated channel does not mediate the formation of large non-specific pores. Thus, it may represent a novel member of the P2X or P2Z class. 3. Extracellular application of ATP (> or = 150 microM) elicited an inward whole-cell current at negative holding potentials that was inwardly rectifying and showed no sign of desensitization. Na+, Cs+ and, to a lesser degree, the organic cation choline served as charge carriers, but Cl- did not. Ratiometric fura-2 measurements indicated that the current is carried in part by Ca2+. The EC50 for ATP was 700 microM in solutions with a low divalent cation concentration. 4. ATP (> or = 100 microM) at the extracellular surface of cell-attached or excised patches elicited inwardly rectifying single-channel currents with a 22 pS conductance. Cl- did not serve as a charge carrier but both Na+ and Cs+ did, as did choline to a lesser extent. The mean open time of the channel was quite long, with a range in hundreds of milliseconds at a holding potential of -70 mV. 5. Mg2+ and Ca2+ decreased the magnitude of the ATP-induced whole-cell currents. Mg2+ decreased both the amplitude and the activity of ATP-activated single-channel currents. 6. ADP, UTP, P1, P5-di-adenosine pentaphosphate (AP5A), adenosine and alpha, beta-methylene ATP (alpha, beta-Me-ATP) did not induce significant whole-cell current. ATP-gamma-S and 2-methylthio ATP (2-Me-S-ATP) were significantly less effective than ATP in inducing whole-cell currents, whereas benzoylbenzoyl ATP (BzATP) was more effective. BzATP, alpha, beta-Me-ATP, ATP-gamma-S and 2-Me-S-ATP induced single-channel currents, but a higher concentration of alpha, beta-Me-ATP was required. 7. BzATP did not induce the formation of large non-specific pores, as assayed using mag-fura-2 as a high molecular mass probe.

Adhesion molecules expression in noncrescentic acute post-streptococcal glomerulonephritis

Clinicomorphological features of 11 cases of non-crescentic acute post-streptococcal glomerulonephritis (APSGN) were reviewed. Intraglomerular and interstitial leukocytes and their possible correlation with the adhesion molecules intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), and endothelial-leukocyte adhesion molecule-1 (ELAM-1/E-selectin) were investigated by an immunohistochemical method. Intraglomerular leukocytes were primarily granulocytes (11.4 +/- 10 cells/glomerular cross-section) and monocytes-macrophages (13.4 +/- 19.4 cells/glomerular cross-section). The granulocytes outnumbered monocytes-macrophages in 7 of 11 specimens. The number of intraglomerular leukocytes correlated with proteinuria at the time of renal biopsy. Intraglomerular ICAM-1 staining was strongly positive in all biopsies, especially when intraglomerular monocytes-macrophages prevailed. Expression of intraglomerular VCAM-1 and E-selectin in diseased kidneys did not differ from that in normal kidneys. Interstitial leukocytes were primarily monocytes-macrophages (158.9 +/- 96.8 cells/mm2) and T lymphocytes (102.2 +/- 63.9 cells/mm2). The number of interstitial leukocytes, especially monocytes-macrophages, correlated with serum creatinine level at the time of biopsy. Interstitial ICAM-1 staining was strongly positive on tubules, peritubular capillaries, and small vessels. The tubular positivity for ICAM-1 correlated with the number of interstitial monocytes-macrophages. Interstitial VCAM-1 and E-selectin were expressed as in normal kidney tissues. The data from this study demonstrate that APSGN is characterized by the presence of both intraglomerular and interstitial leukocyte infiltration, correlating respectively with proteinuria and serum creatinine at the time of renal biopsy. Among the adhesion molecules studied, ICAM-1 seems the most involved in leukocyte recruitment, especially in that of monocytes-macrophages.

Immunochromatographic analysis of bovine growth hormone releasing factor involving reversed-phase high-performance liquid chromatography-immunodetection

We have developed high-performance immunoaffinity chromatography (HPIAC) methods for the detection and quantitation of bovine growth hormone releasing factor (GHRF), which could also be applicable to its metabolites in biofluids. These approaches have involved a combination of IAC using immobilized antibody (Ab) to GHRF, together with reversed-phase high-performance liquid chromatography (RP-HPLC) separations of initially isolated and concentrated protein, followed by selective detection, involving on-line immunodetection (ID) schemes. ID methods involved HPIAC supports of the Ab, together with synthesized Ab-fluorescein isothiocyanate conjugates. We have demonstrated optimization methods for each step of the entire hyphenated technique (IAC-HPLC-ID), and then actually quantitated GHRF using this overall system. The minimum detectable concentration was about 1 ng/5 ml (200 ppt) with fluorescence detection (excitation wavelength, 490 nm; emission wavelength, 510-650 nm). We have also tested a single blind, spiked biological sample (bovine plasma), spiked with a known level of GHRF. Accuracy (7.4%) and precision (S.D. = +/- 22%) were quite acceptable for a double immunoassay method.

Requirement for BMP signaling in interdigital apoptosis and scale formation

Interdigital cell death leads to regression of soft tissue between embryonic digits in many vertebrates. Although the signals that regulate interdigital apoptosis are not known, BMPs--signaling molecules of the transforming growth factor-beta superfamily--are expressed interdigitally. A dominant negative type I BMP receptor (dnBMPR-IB) was used here to block BMP signaling. Expression of dnBMPR in chicken embryonic hind limbs greatly reduced interdigital apoptosis and resulted in webbed feet. In addition, scales were transformed into feathers. The similarity of the webbing to webbed duck feet led to studies that indicate that BMPs are not expressed in the duck interdigit. These results indicate BMP signaling actively mediates cell death in the embryonic limb.

The purification of human urinary kallikrein with ion-exchange radial flow membrane chromatography

A method was developed for the purification of kallikrein from human urine. The procedure consisted of three steps: ultradialysis, diethyl-(2-hydroxypropyl) aminoethyl (QAE) ion exchange radial flow membrane chromatography and affinity chromatography on aprotinin agarose. It is simple and suitable for large-scale purification. The purified product was checked by SDS-PAGE and matrix-assisted laser desorption:ionization mass spectrometery (MALDI). A single band with apparent molecular weight (MW) 42,000 in SDS-PAGE and a single monomer peak with MW33,000 in MALDI were observed, respectively. The biological activity tested by ELISA showed positive immunological identity of the purified product compared with human urinary kallikrein standard.

Perfusion immunoaffinity chromatography and its application in analysis and purification of biomolecules

Immunoaffinity cartridges have been prepared by immobilizing the monoclonal antibody to bovine growth hormone (bGH) and bovine growth hormone releasing factor (bGRF) on the streptavidin-coated perfusion media. The cartridge-immobilized antibody to bGH has been used for the analysis of standard sample of recombinant bGH (r-bGH). The cartridge immobilized bGRF has been applied for purification of the C-and N-terminal antibodies and their conjugates with horseradish peroxidase. The purity of the antibody fractions purified by bGRF cartridges has been tested by capillary zone electrophoresis. It has been shown that the immunoaffinity cartridges prepared by immobilizing the antigen offer more biological specificity for the purification of antibody than the Protein G cartridges. The stability and life time of the immunoaffinity cartridges are mainly dependent on the stability of the biomolecules immobilized on them. Immunoaffinity cartridges based on the perfusion media offer us the tools for rapid analysis and purification of antigens or antibodies as well as for determination of the biological activity between them at a very low back pressure in the columns.

Gene conversion plays the major role in controlling the stability of large tandem repeats in yeast

The genomic stability of the rDNA tandem array in yeast is tightly controlled to allow sequence homogenization and at the same time prevent deleterious rearrangements. In our study, we show that gene conversion, and not unequal sister chromatid exchange, is the predominant recombination mechanism regulating the expansion and contraction of the rDNA array. Furthermore, we found that RAD52, which is essential for gene conversion, is required for marker duplication stimulated in the absence of the two yeast type I topoisomerases. Our results have implications for the mechanisms regulating genomic stability of repetitive sequence families found in all eukaryotes.

Calcium dependence of indolactam-mediated contractions in resistance vessels

The protein kinase C activator, (-)-indolactam, has been shown to enhance reactivity of arterioles by a mechanism not requiring an increase in intracellular Ca++ (Ca++i). The aim of this study was to characterize the Ca++ requirement for indolactam-induced contraction of resistance vessels. Studies were performed in small mesenteric arteries (diameter, 260 +/- microm), using intact segments or after permeabilization with alpha-toxin (500 U/ml). Additional studies were preformed using isolated smooth muscle cells to allow electrophysiological assessment of the effect of indolactam on voltage-gated Ca++ entry. Intact and permeabilized vessel segments showed dose-dependent constriction to indolactam. Studies of Fura 2-loaded vessels and permeabilized segments maintained at low Ca++i, showed that the constriction occurred without an overt increase in Ca++i. That Ca++ was required was evident by near maximal relaxation after the removal of Ca++. Patch clamp studies indicated that indolactam potentiated voltage-gated Ca++ entry; however, nifedipine (0.5 microM) and La (0.2 or 1 mM) were relatively ineffective in reversing the contraction, indicating that voltage-gated Ca++ entry was not an absolute requirement. In intact vessel segments, the myosin light chain (MLC) kinase inhibitors, ML-7 and ML-9, reversed the indolactam contraction, suggesting the requirement of the MLC chain phosphorylation pathway. Furthermore, indolactam caused by a significant increase in MLC phosphorylation in permeabilized vessels, despite clamping of Ca++i at pCa 7.0. The data are consistent with the suggestion that the protein kinase C activator, indolactam, acts to modulate the Ca++ sensitivity of the smooth muscle contractile process such that higher than expected levels of MLC phosphorylation exist for a given level of Ca++i.

Characterization of immunochemical reaction for human growth hormone with its monoclonal antibody by perfusion protein G affinity chromatography and capillary zone electrophoresis

An extremely rapid assay technique for antibody-antigen interaction using human growth hormone and its monoclonal antibody as an example has been developed by utilizing Protein G bound to perfusion chromatography matrices. The antibody and antigen were mixed and incubated at different molar ratios by keeping the concentration of antibody constant. The mixture of antibody and antigen solution was then injected onto the Protein G column. The complex of antibody and antigen formed in the sample solution was retained on the Protein G column as was the free antibody. The peak-area and height of the retained complex and antibody linearly increased with the molar concentration of the antigen when it was not in excess of the corresponding stoichiometric amount of antibody, however, those of the retained peak were constant when the concentration of antigen was in excess of that of the antibody. The validity of this method was confirmed by the results of capillary zone electrophoresis. The method developed cannot only be used to determine the biological activity between antibody and its antigen quickly, but also to determine the stoichiometry of immunological reactions between the antibody and antigen when a stable complex of them can be formed.

Role of myosin phosphorylation and [Ca2+]i in myogenic reactivity and arteriolar tone

The aim of this study was to define the relationship between intraluminal pressure, intracellular calcium concentration ([Ca2+]i), and myosin light-chain (MLC) phosphorylation in isolated arterioles exhibiting myogenic tone. Cremaster muscles were removed from anesthetized rats, and arterioles (approximately 100-microns diam) were dissected from surrounding tissues and cannulated on glass pipettes. Vessels were warmed to 34 degrees C and initially pressurized to 70 mmHg in the absence of intraluminal flow. For [Ca2+]i measurements, vessels were loaded with 5 microM fura 2, and fluorescence emitted by excitation at 340 and 380 nm was measured. Data were considered in terms of changes in the fluorescence ratio (340/380 nm) and collected at steady-state intraluminal pressures between 30 and 170 mmHg. For measurement of MLC phosphorylation, vessels were frozen in acetone-dry ice followed by sonication in homogenizing buffer. Homogenates were separated by two-dimensional gel electrophoresis, and proteins were visualized by silver staining. MLC phosphorylation was quantitated photodensitometrically, and results are expressed as percent total 20-kDa MLC. Increasing intraluminal pressure resultedin significant constriction with increased [Ca2+]i and MLC phosphorylation. For example, the fluorescence ratio was 0.80 +/- 0.04 at 30 mmHg compared with 1.02 +/- 0.05 at 120 mmHg (n = 7 vessels); corresponding MLC-phosphorylation values were 27.7 +/- 1.6 and 39.6 +/- 3.0% (n = 6). MLC phosphorylation in arterioles superfused with 0 mM Ca(2+)-2 mM ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA) was 8.5 +/- 0.7%.(ABSTRACT TRUNCATED AT 250 WORDS)

Biomedical ultrasound beam forming

The principles of biomedical ultrasound beam forming control the quality of diagnostic imaging. Beam parameters associated with imaging quality are: (1) lateral and axial resolutions; (2) depth of field; (3) contrast and (4) frame rate. In this paper, we review some of the current beam forming techniques and their principles. We focus on trade-offs among the above four aspects of beam forming and relate them to system parameters such as aperture size, f-number (the ratio between focal length and aperture diameter), central frequency (wavelength), system bandwidth and sidelobes. Methods for steering conventional and limited diffraction beams with array transducers are also reviewed.