Voltammetric assay of the anthelmintic veterinary drug nitroxynil in bulk form and formulation at a mercury electrode.

The electrochemical behavior of the anthelmintic veterinary drug nitroxynil at the mercury electrode was studied in a series of Britton-Robinson universal buffer of pH 1.9-11 containing 20% (v/v) ethanol using dc-polarography cyclic voltammetry and controlled-potential coulometry. The voltammograms exhibited two irreversible cathodic steps over the pH range 1.9-10.2; the height of the first step is double that of the second one. Controlled-potential coulometry in the B-R universal buffer of pH 1.9-10 at a mercury pool working electrode revealed the consumption of four and two electrons via the first and second reduction steps, respectively, which attributed to reduction of the NO2 group to the hydroxylamine stage (first step), and then to the amine stage (second step). Three voltammetric analytical procedures including dc-polarography, differential-pulse adsorptive stripping voltammetry and square-wave adsorptive stripping voltammetry were optimized for the direct determination of bulk nitroxynil. The three proposed procedures were applied for analysis of bulk nitroxynil with limits of detection of 3 x 10(-5), 1.31 x 10(-8) and 8.4 x 10(-10)M and limits of quantification of 1 x 10(-5), 4.36 x 10(-8) and 2.80 x 10(-9)M, respectively. The three procedures were successfully applied to the determination of nitroxynil in formulation (Dovenix, 25% nitroxynil injection solution) without the necessity for sample pretreatment and/or time-consuming extraction steps prior to the analysis.

Beta-catenin expression in benign and malignant pilomatrix neoplasms.

BACKGROUND: Beta-catenin is a 92-kDa protein, initially identified as a coprecipitating species with the E-cadherin cell-cell adhesive complex. It plays a role in signal transduction in the Wnt signalling pathway and has been identified as an oncogene in colon cancer and melanoma. Exon 3 beta-catenin-activating mutations were found in 75% of cases of pilomatricoma (PM). Previous studies have shown that nuclear and/or cytoplasmic staining may correlate with beta-catenin gene mutation. OBJECTIVES: Because the immunohistochemical expression of beta-catenin in the nucleus or the cytoplasm correlates with beta-catenin mutation, we studied the immunohistochemical profile of beta-catenin expression in normal scalp hair follicles and in PM and pilomatrix carcinoma (PC). METHODS: We reviewed 21 cases of PM and five cases of PC using immunohistochemical staining with commercially available antibody in a standard fashion on formalin-fixed paraffin-embedded tissue samples. RESULTS: All 26 tumours displayed both nuclear and cytoplasmic staining in the basaloid cells with focal membranous staining. Shadow cells were negative in all tumours. Normal control sections from the scalp displayed nuclear reactivity of the matrical cells, mostly concentrated in the supramatrical zone of hair follicles. Membranous staining was present along the intercellular junctions of the epidermis and along the outer and inner root sheaths of hair follicles. We have found similar patterns of beta-catenin nuclear and cytoplasmic expression in both PM and PC. CONCLUSIONS: Despite the shared beta-catenin expression, the biological behaviour of PM and PC is markedly different. These two tumours probably share the activation of a common cellular pathway that could be related to their shared method of keratinization or a shared dysfunction of the cellular adhesion complex and consequently tumorigenesis. To the best of our knowledge, this is the first report on the beta-catenin immunohistochemical expression profile in PC.

Thomsen-Friedenreich (T) antigen: a possible tool for differentiating sebaceous carcinoma from its simulators.

The Thomsen-Friedenreich (T) antigen is a cryptic glycoprotein, referred to as tumor antigen or cancer-associated antigen because it is absent or masked by some carbohydrates in normal tissues, but present in many human cancers. The latter include gastrointestinal, lung, pancreatic, mammary, and some ovarian carcinomas. Cancer cells frequently undergo incomplete glycosylation resulting in the appearance of precursor structures that normally would be absent like the case with the T antigen. T antigen can be detected by several different reagents including monoclonal antibodies and several plant lectins-e.g., Arachis hypogea (peanut agglutinin). The aim of the current study was to evaluate the expression of T antigen in sebaceous carcinoma and to compare it with its simulators. The authors studied the immunohistochemical expression of T antigen in 45 skin biopsy and excisional specimens obtained from the archives of their dermatopathology laboratories, including 8 cases of sebaceous carcinoma, 15 cases of sebaceous adenoma, 9 cases of sebaceoma, 1 case of basal cell carcinoma with sebaceous differentiation, and 12 cases of basal cell carcinoma with cytologic atypia. Sebaceous carcinoma was unique in expressing a strong, diffuse cytoplasmic T antigen reactivity (7 of 8 cases) along the immature basaloid cells and the intermediate cells. However, sebaceous adenoma, sebaceoma, and basal cell carcinomas expressed negative reaction in the basaloid cells and mild reactivity in the intermediate cells. Mature sebocytes showed a strong reaction in all cases. The authors concluded that T antigen expression may be a helpful tool in differentiating sebaceous carcinoma from other sebaceous lesions that may simulate it histologically.

Polarographic behaviour of loratadine and its direct determination in pharmaceutical formulation and human plasma by cathodic adsorptive stripping voltammetry.

The polarographic behaviour of the antihistaminic drug loratadine has been investigated in B.R. buffer solution of different pH values. Contradictory to that mentioned before in a previously published work, loratadine is electro-active at the mercury electrode. In B.R. buffer solution of pH values > or =6 it is reduced via a single 2-electrons irreversible wave corresponding to saturation of carbon-nitrogen double bond of the pyridine ring. The electrode reaction pathway was proposed and discussed. A sensitive differential pulse stripping voltammetric method based on controlled adsorptive accumulation of loratadine on a hanging mercury drop electrode has been developed for its direct determination at nanomolar concentrations without nitration of the drug. The optimized conditions for the direct cathodic adsorptive stripping voltammetric determination of the drug are: 0.1 M sodium hydroxide solution as a supporting electrolyte, accumulation potential, -1.2 V; accumulation time, 30 s; scan rate, 2-5 mV x s(-1) and pulse amplitude 100 mV. The proposed procedure was applied for the assay of loratadine in pharmaceutical formulation and human plasma. The average recoveries were 99.32-99.44 and 100.33-102.99% with the RSD 0.27-0.42 and 0.39-0.90% in pharmaceutical formulation and human plasma, respectively. The limits of detection of 1.60x10(-7) and 1.25x10(-7) M loratadine were found in pharmaceutical formulation and human plasma, respectively.

Hypopigmented mycosis fungoides in childhood and adolescence.

We present a case of purely hypopigmented mycosis fungoides of 8-years duration in an 18-year-old woman who responded readily to psoralen plus ultraviolet A (PUVA) treatment. The literature pertaining to hypopigmented mycosis fungoides is reviewed.

Simultaneous determination of Cd, Pb, Cu, Sb, Bi, Se, Zn, Mn, Ni, Co and Fe in water samples by differential pulse stripping voltammetry at a hanging mercury drop electrode.

A highly sensitive and selective voltammetric procedure is described for the simultaneous determination of eleven elements (Cd, Pb, Cu, Sb, Bi, Se, Zn, Mn, Ni, Co and Fe) in water samples. Firstly, differential pulse anodic stripping voltammetry (DPASV) with a hanging mercury drop electrode (HMDE) is used for the direct simultaneous determination of Cd, Pb, Cu, Sb and Bi in 0.1 M HCI solution (pH = 1) containing 2 M NaCl. Then, differential pulse cathodic stripping voltammetry (DPCSV) is used for the determination of Se in the same solution. Zn is subsequently determined by DPASV after raising the pH of the same solution to pH 4. Next, the pH of the medium is raised to pH 8.5 by adding NH3/NH4Cl buffer solution for the determination of Mn by DPASV. Ni and Co are determined in the same solution by differential pulse adsorptive stripping voltammetry (DPAdSV) after adding DMG (1 x 10(-4) M). Finally, 1 x 10(-5) M 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP) is added to the solution for the determination of Fe by DPAdSV. The optimal conditions are described. Relative standard deviations and relative errors are calculated for the eleven elements at three different concentration levels. The lower detection limits for the investigated elements range from 1.11 x 10(-10) to 1.05 x 10(-9)M, depending on the element determined. The proposed analysis scheme was applied for the determination of these eleven elements in some ground water samples.