Geniposide improves insulin production and reduces apoptosis in high glucose-induced glucotoxic insulinoma cells.

Our previous work revealed that in the pancreatic ß cell line, geniposide modulated ATP production and glucose-stimulated insulin secretion (GSIS) induced by the acute stimulation of high glucose concentration. However, the effects of geniposide on functional impairment and the mass of ß-cells exposed to elevated levels of glucose remains unknown. In the present study, impaired GSIS and restrained proliferation were observed in the prolonged culture of insulinoma INS-1 cells with 33mM of glucose (high glucose). Our results indicate that the glucose-induced impairment of insulin release was significantly reverted by the inclusion of 1 or 10µM of geniposide. Moreover, induction of the phosphorylation of AMP-activated protein kinase (AMPK) was observed, which promoted the utilization of nutrient stores for energy production. AMPK phosphorylation was enhanced by an increased number of INS-1 cells, and the increased expression of AMPK downstream target heme oxygenase 1 (HO-1), under high glucose concentration. Furthermore, geniposide protected rat insulinoma cells from apoptosis in high-glucose concentrations. We have shown that these effects were associated with an increased apoptosis-related Bcl-2/BAX protein ratio. In conclusion, geniposide dose dependently improves ß-cell function and increases the proliferation of ß-cells exposed to prolonged hyperglycemia.

Roles of neutrophil gelatinase-associated lipocalin in continuous ambulatory peritoneal dialysis-related peritonitis.

INTRODUCTION: We measured the neutrophil gelatinase-associated lipocalin (NGAL) concentration in peritoneal dialysate effluent (PDE) collected following an acute episode of continuous ambulatory peritoneal dialysis (CAPD)-related peritonitis. RESULTS: NGAL concentration in PDE increased in the first 3 days after developing peritonitis and correlated well with the neutrophil count. In patients with culture-negative peritonitis, the NGAL in PDE was lower than that in patients with gram-positive or gram-negative peritonitis. Apart from providing additional diagnostic support to bacterial-induced peritonitis, measurement of NGAL in PDE may be useful to differentiate the neutrophil-dependent culture-negative peritonitis from that associated with non-bacterial or non-cellular etiologies. CONCLUSION: Human peritoneal mesothelial cell (HPMC) is another source of NGAL during peritonitis. NGAL was specifically induced in HPMC by IL-1beta. Incubation of HPMC with recombinant NGAL reversed the transforming growth factor-beta-induced up-regulation of Snail and vimentin but rescued the down-regulation of E-cadherin. Our data suggest that NGAL may exert a protective effect in modulating the epithelial-to-mesenchymal transition activated following peritonitis.

BMP-7 protects mesangial cells from injury by polymeric IgA.

Bone morphogenetic protein-7 (BMP-7) is a potential therapeutic agent for acute and chronic renal diseases. Here we found that addition of polymeric IgA, isolated from patients with IgA nephropathy, increased the synthesis of tumor necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6), transforming growth factor-beta (TGF-beta) and fibronectin in cultured human mesangial cells, effects blunted by BMP-7. When mesangial cells were cultured with both polymeric IgA and BMP-7 there was an increase in the expression of peroxisome proliferator-activated receptor-gamma (PPAR-gamma). The activation of NF kappaB and TNF-alpha synthesis induced by polymeric IgA or TNF-alpha were downregulated by BMP-7 or rosiglitazone. BMP-7 inhibited TNF-alpha release from polymeric IgA-stimulated mesangial cells by activation of PPAR-gamma but suppressed TGF-beta release by mechanisms independent of PPAR-gamma. The expression of inhibitory Smad6 and 7 was increased whereas the expression of active Smad2 and 3 was reduced in these mesangial cells by BMP-7. Our study shows that BMP-7 ameliorates IgA nephropathy-derived polymeric IgA-induced TNF-alpha and TGF-beta synthesis in human mesangial cells through multiple mechanisms involving inhibitory Smads and PPAR-gamma.

New magnetic nano-absorbent for the determination of n-octanol/water partition coefficients.

A novel and generic miniaturization methodology for the determination of partition coefficient values of organic compounds in n-octanol/water by using magnetic nanoparticles is, for the first time, described. We have successfully designed, synthesised and characterised new colloidal stable porous silica-encapsulated magnetic nanoparticles of controlled dimensions. These nanoparticles absorbing a tiny amount of n-octanol in their porous silica over-layer are homogeneously dispersed into a bulk aqueous phase (pH 7.40) containing an organic compound prior to magnetic separation. The small size of the particles and the efficient mixing allow a rapid establishment of the partition equilibrium of the organic compound between the solid supported n-octanol nano-droplets and the bulk aqueous phase. UV-vis spectrophotometry is then applied as a quantitative method to determine the concentration of the organic compound in the aqueous phase both before and after partitioning (after magnetic separation). logD values of organic compounds of pharmaceutical interest (0.65-3.50), determined by this novel methodology, were found to be in excellent agreement with the values measured by the shake-flask method in two independent laboratories, which are also consistent with the literature data. It was also found that this new technique gives a number of advantages such as providing an accurate measurement of logD value, a much shorter experimental time and a smaller sample size required. With this approach, the formation of a problematic emulsion, commonly encountered in shake-flask experiments, is eliminated. It is envisaged that this method could be applicable to the high throughput logD screening of drug candidates.

Multiwavelength spectrophotometric resolution of the micro-equilibria of cetirizine.

The acid-base properties of the antihistamine (H1 receptor antagonist) cetirizine have been studied by using a previously developed multiwavelength spectrophotometric titration method. A new computational procedure called "Two-Step-Divide-and-Conquer" (TSDC), which applied evolving factor analysis (EFA) and target factor analysis (TFA), has been derived to unravel the micro-equilibria of the triprotic zwitterionic compound from the spectral data. We have demonstrated that a single spectrophotometric titration experiment is sufficient to determine the 12 unknown microconstants and the distribution of microspecies, which are in good agreement with literature values, where available.

Multiwavelength spectrophotometric determination of acid dissociation constants part V: microconstants and tautomeric ratios of diprotic amphoteric drugs.

The acid-base equilibria of several diprotic amphoteric drugs, namely, niflumic acid, norfloxacin, piroxicam, pyridoxine and 2-methyl-4-oxo-3H-quinazoline-3-acetic acid have been characterized in terms of microconstants and tautomeric ratios. A multiwavelength spectrophotometric (WApH) titration method for determination of acid dissociation constants (pKa values) of ionizable compounds developed previously was applied for this purpose. Microspeciation was investigated by three approaches: (1) selective monitoring of ionizable group by spectrophotometry, (2) deductive method and (3) k(z) method for determination of tautomeric ratio from co-solvent mixtures. The formulation for (3) has been derived and found to invoke fewer assumptions than a reported procedure (K. Takács-Novák, A. Avdeef, K.J Box, B. Podányi, G. Szász, J. Pharm. Biomed. Anal., 12 (1994) 1369-1377). It has been shown that the WApH technique, for such types of ampholytes, is able to deduce the microconstants and tautomeric ratios which are in good agreement with literature data.

Multiwavelength spectrophotometric determination of acid dissociation constants: Part II. First derivative vs. target factor analysis.

PURPOSE: Acid dissociation constants (pKa values) denote the extent of ionization of drug molecules at different pH values, which is important in understanding their penetration through biological membranes and their interaction with the receptors. However, many drug molecules are sparingly soluble in water or contain ionization centres with overlapping pKa values, making precise pKa determination difficult using conventional spectrophotometric titration. In this work, we investigate a multiwavelength spectrophotometric titration (WApH) method for the determination of pKa values. METHODS: Spectral changes which arise during pH-metric titrations of substances with concentration of about 10(-5) M were captured by means of an optical system developed in this study. All experiments were carried out in 0.15 M KCI solution at 25 +/- 0.5 degrees C. Mathematical treatments based on the first derivative spectrophotometry procedure and the target factor analysis method were applied to calculate the pKa values from the multiwavelength absorption titration data. RESULTS: pKa values were determined by the WApH technique for six ionizable substances, namely, benzoic acid, phenol, phthalic acid, nicotinic acid, p-aminosalicylic acid and phenolphthalein. CONCLUSIONS: The pKa values measured using the WApH technique are in excellent agreement with those measured pH-metrically. We have demonstrated that the first derivative spectrophometry procedure provides a relatively simple way to visualize the pKa values which are consistent with those determined using the target factor analysis method. However, for ionization systems with insufficient spectral data obtained around the sought pKa values or with closely overlapping pKa values, the target factor analysis method outperforms the first derivative procedure in terms of obtaining the results. Using the target factor analysis method, it has been shown that the two-step ionization of phenolphthalein involves a colorless anion intermediate and a red colored di-anion.

Multiwavelength spectrophotometric determination of acid dissociation constants: Part III. Resolution of multi-protic ionization systems.

A multiwavelength spectrophotometric (WApH) titration method was applied to study several multi-protic histamine H2-receptor antagonists which involved four acid dissociation constants (pKa values) over the pH range of 2-10. Specifically, UV absorption spectra of the drug solution were acquired in the course of a pH-metric titration using an optical device based on a fibre optics dip probe, a light source and a diode array detector. Target factor analysis was utilized to deduce the pKa values from the spectral data recorded at different pH. It was noted that some of the pKa values were within mid pH range which were difficult to obtain because of insufficient absorption spectra acquired in the un-buffered region of the titration curve. With the aid of the WApH technique coupled with an optically transparent buffer, all pKa values have been successfully determined and were in excellent agreement with those measured using a conventional pH-metric method.

PH-metric log P 11. pKa determination of water-insoluble drugs in organic solvent-water mixtures.

The apparent acid dissociation constants (p(s)Ka) of two water-insoluble drugs, ibuprofen and quinine, were determined pH-metrically in acetonitrile water, dimethylformamide water, dimethylsulfoxide water, 1,4-dioxane-water, ethanol water, ethylene glycol-water, methanol water and tetrahydrofuran water mixtures. A glass electrode calibration procedure based on a four-parameter equation (pH = alpha + SpcH + jH[H+]+jOH[OH-]) was used to obtain pH readings based on the concentration scale (pcH). We have called this four-parameter method the Four-Plus technique. The Yasuda Shedlovsky extrapolation (p(s)Ka + log [H2O] = A/epsilon + B) was used to derive acid dissociation constants in aqueous solution (pKa). It has been demonstrated that the pKa values extrapolated from such solvent water mixtures are consistent with each other and with previously reported measurements. The suggested method has also been applied with success to determine the pKa values of two pyridine derivatives of pharmaceutical interest.

Multiwavelength spectrophotometric determination of acid dissociation constants Part IV. Water-insoluble pyridine derivatives.

A multiwavelength spectrophotometric (WApH) titration method for determination of acid dissociation constants (pK(a) values) of ionizable compounds developed previously was applied in the case of pyridine derivatives of pharmaceutical interest. Specifically, UV absorption spectra of the drug solution are acquired in the course of a pH-metric titration using an optical device based on a fibre optics dip probe, a light source and a diode array detector. Target factor analysis was applied to deduce the pK(a) values from the spectral data recorded at different pH. Using this technique, the pK(a) values of six pyridine derivatives were determined successfully. It was demonstrated that the WApH technique in this case outperforms conventional pH-metric methods with respect to the measurement of pK(a) values of the sparingly water soluble samples reported in this study.

Multiwavelength spectrophotometric determination of acid dissociation constants of ionizable drugs.

A multiwavelength spectrophotometric approach has been developed to determine acid dissociation constants (pKa values) of sparingly soluble drug compounds. UV absorption spectra of the drug solution are acquired using a versatile device based on a fiber optics dip probe, a light source and a photodiode array (PDA) detector while the PH and the ionic strength of the chemical system is manipulated precisely by means of a commercially available titrator. Target factor analysis (TFA) has been applied to deduce the pKa values from the multiwavelength UV absorption data recorded at different pH values. We have called this multiwavelength approach the WApH technique because the pKa results are determined from changes in Wavelength and Absorbance as a function of pH (WApH). The WApH technique is exemplified by using several pure drugs, namely, niflumic acid, nitrazepam, pyridoxine, quinine and terbutaline. The pKa values obtained agree well with those derived from pH-metric titrations. It has been demonstrated that the WApH technique is able to deduce pKa values with high accuracy even if the absorption spectra of the reacting species are very similar.

A survey of physicians' acceptance of telemedicine.

Physicians' acceptance of telemedicine is an important managerial issue facing health-care organizations that have adopted, or are about to adopt, telemedicine. Most previous investigations of the acceptance of telemedicine have lacked theoretical foundation and been of limited scope. We examined technology acceptance and usage among physicians and specialists from 49 clinical departments at eight public tertiary hospitals in Hong Kong. Out of the 1021 questionnaires distributed, 310 were completed and returned, a 30% response rate. The preliminary findings suggested that use of telemedicine among clinicians in Hong Kong was moderate. While 18% of the respondents were using some form of telemedicine for patient care and management, it accounted for only 6.3% of the services provided. The intensity of their technology usage was also low, accounting for only 6.8% of a typical telemedicine-assisted service. These preliminary findings have managerial implications.

pH-metric logP 10. Determination of liposomal membrane-water partition coefficients of ionizable drugs.

PURPOSE: To investigate a novel approach for the determination of liposomal membrane-water partition coefficients and lipophilicity profiles of ionizable drugs. METHODS: The measurements were performed by using a pH-metric technique in a system consisting of dioleylphosphatidylcholine (DOPC) unilamellar vesicles in 0.15 M KCl at 25 degrees C. The DOPC unilamellar vesicle suspension was prepared via an extrusion process. RESULTS: The liposomal membrane-water partition coefficients of eight ionizable drugs: ibuprofen, diclofenac, 5-phenylvaleric acid, warfarin, propranolol, lidocaine, tetracaine and procaine were determined and the values for neutral and ionized species were found to be in the ranges of approximately 4.5 to 2.4 and 2.6 to 0.8 logarithmic units, respectively. CONCLUSIONS: It has been shown that the liposomal membrane-water partition coefficients as derived from the pH-metric technique are consistent with those obtained from alternative methods such as ultrafiltration and dialysis. It was found that in liposome system, partitioning of the ionized species is significant and is influenced by electrostatic interaction with the membranes. We have demonstrated that the pH-metric technique is an efficient and accurate way to determine the liposomal membrane-water partition coefficients of ionizable substances.

Application of a bi-directional associative memory (BAM) network in computer assisted learning in chemistry.

A computer assisted learning software based on a bi-directional associative memory (BAM) network was developed. The software was implemented to assist students in associating the names of the elements in the periodic table with their chemical symbols. The use of the BAM facilitates the analysis and interpretation of students' responses. The software package can be modified easily as an educational tool for other disciplines.

Simultaneous multiwavelength study of the reaction of phenolphthalein with sodium hydroxide.

A photodiode array (PDA) spectrophotometer was used to study the fading reaction of phenolpthalein in dilute sodium hydroxide solution. The principal component analysis (PCA) method was employed to identify the number of light absorbing species in the kinetics system. The target factor analysis (TFA) procedure, coupled with the Broyden-Fletcher-Goldfard-Shanno (BFGS) optimization method, was applied to the observed data to deduce the rate constants and the concentration-time profile of the reaction. The internal referencing method was shown to be essential in improving the quality of data obtained by a single beam PDA spectrophotomer.