Development of the second-order derivative UV spectrophotometric method for direct determination of paracetamol in urine intended for biopharmaceutical characterisation of drug products

Paracetamol is a widely used nonsalicylate analgesic and antipyretic drug. The existing methods for the determination of paracetamol in biological fluids are mainly HPLC techniques, although there are some reported methods based on spectrophotometric determinations. However, all these methods involve some extraction or derivatisation procedures. In the present study the UV spectra of investigated samples were recorded over the wavelength range 220-400 nm (lambda step 0.21 nm; scan speed 60 nm/min) and second-order derivative spectra were calculated. Second-order derivative spectra of different blank urine samples displayed the presence of a zero-crossing point at 245-247 nm defined as lambdazc. The zero-order absorption spectra of paracetamol in water displays maximum absorbance at 243 nm, while in second derivative spectra, a minimum peak at 246 nm was observed. Therefore, the application of zero-crossing technique to the second-derivative UV absorption spectrum should be useful for the determination of paracetamol using 2Dlambdazc. The proposed method enables determination of total paracetamol in urine directly and simply by reading the 2Dlambdazc of the diluted samples. The obtained results were in good accordance with published data on cumulative urinary excretion after per oral administration of paracetamol obtained applying different spectrophotometric methods of determination. It could be useful for biopharmaceutical characterisation of drug products (monitoring of the levels of paracetamol in urine in bioavailability testing, for the evaluation of in vitro-in vivo correlation and screening of different formulations during drug product development).     

Neuronal nicotinic acetylcholine receptors expressed in Xenopus oocytes: role of the α subunit in agonist sensitivity and desensitization

Neuronal nicotinic acetylcholine receptors (nAChRs) were expressed in Xenopus laevis oocytes after nuclear injection of complementary deoxyribonucleic acid (cDNA) expression vectors. The two receptor subtypes 4/n1 and 3/n1 were readily distinguishable from one another by ACh sensitivity and desensitization. 3/n1 receptors showed lower ACh sensitivity and stronger desensitization than 4/n1 receptors. Furthermore, although the current/voltage relationship was very similar in both receptor subtypes, the voltage dependence of desensitization was found to be strikingly different. As the n1 subunit was unchanged, the subunits must be responsible for these functional differences. Symmetric hybrid cDNAs, 43 and 34, were constructed and functional receptors were obtained by co-injection with n1. These hybrid receptors displayed an ACh sensitivity that was mainly defined by the extracellular sequence of the subunit. In contrast, no part of the subunit was found fully to determine desensitization.     

Baculovirus expression and affinity purification of protein E2 of classical swine fever virus strain Alfort/187

The genome region encoding the major envelope glycoprotein E2 (gp55) of the classical swine fever virus (CSFV) strain Alfort/187 was cloned and sequenced. The E2 gene, either with or without additional authentic 5-terminal sequences coding for two variants of a putative signal sequence, was used to construct recombinant baculoviruses expressing the respective glycosylated and nonglycosylated E2 protein in insect cells. The signal sequences mediated glycosylation in insect cells, but no efficient secretion of the protein into the cell culture supernatant was observed. Six histidine residues introduced at the carboxy terminus of E2 allowed purification of E2 protein by Ni²⁺-chelate affinity chromatography. The proteins obtained were characterized and their immunological properties were compared by western blot analysis.     

Regeneration of the optic nerve of Xenopus laevis after argon laser injury]

Following mechanical lesion of the optic nerve (ON), lower vertebrates are capable of regeneration of the ON and regain visual function. We have studied, by light and electron microscopy, regeneration of the larval ON of Xenopus laevis after treatment with the argon laser. The laser energy is absorbed by the neurothelial pigment and provokes a burned crater and vesiculation in the interior of the ON. In contrast to the mechanically induced process, axons regenerate, after laser treatment, within the nerve and do not sprout into the neighboring tissue. The regenerating ON is not vascularized. Immediately after laser treatment, a loss of myelin, hypertrophy, phagocytic activity, and local rearrangement of glial cells are observed. After four weeks, myelination is still irregular. Glial cells have regained their normal aspect.     

Distinct risk profiles of early and advanced atherosclerosis: prospective results from the Bruneck Study

Most epidemiological surveys on risk factors of atherosclerosis were cross-sectional in design and did not consider the existence of pathologically distinct processes. The Bruneck Study is a prospective survey in the general community (age range, 40 to 79 years). The baseline examination and first reevaluation were performed in the summers of 1990 and 1995 (participation, 92%; follow-up, 96%). Carotid atherosclerosis was monitored with high-resolution duplex ultrasound. Early (incidence and/or extension of nonstenotic lesions) and advanced (incidence and/or progression of stenosis >40%) stages of atherogenesis were differentiated. The risk profile of early atherogenesis consists of traditional risk factors, such as hypertension, hyperlipidemia, and cigarette smoking (pack-years), supplemented by a variety of less well-established risk conditions, including high body iron stores, hypothyroidism, microalbuminuria, and high alcohol consumption. In contrast, the risk profile of advanced atherogenesis includes markers of enhanced prothrombotic capacity, attenuated fibrinolysis, and clinical conditions known to interfere with coagulation: high fibrinogen, low antithrombin, factor V Leiden mutation, lipoprotein(a) >0.32 g/L, high platelet count, cigarette smoking, and diabetes. Hyperlipidemia and hypertension were of only minor relevance. These findings, along with the epidemiological features of advanced atherogenesis and emergence of an elevated fibrin turnover, suggest atherothrombosis to be a key mechanism in the development of advanced stenotic atherosclerosis. Supplementary 6-category logistic regression models illustrate the changing association between major risk predictors and atherosclerosis of increasing severity and substantiate appropriateness of the 40% threshold applied for the definition of advanced stenotic atherosclerosis. Atherosclerosis is a heterogeneous process that subsumes etiologically and epidemiologically distinct disease entities. The multifactorial etiology of atherosclerosis, which goes far beyond the traditional risk factors, has not yet achieved adequate attention in clinical practice and disease prevention.     

Characterization of gait variability in multiple system atrophy and Parkinson’s disease

Journal of Neurology - Gait impairment is a pivotal feature of parkinsonian syndromes and increased gait variability is associated with postural instability and a higher risk of falls. We compared...     

Loco-regional treatments in first-diagnosis glioblastoma: literature review on association between Stupp protocol and Gliadel

Loco-regional chemotherapy with carmustine wafers (Gliadel) positioned at surgery and followed by radiotherapy has been shown to prolong survival in first-diagnosis glioblastoma, as well as concomitant radiochemotherapy with temozolomide. The combination of Gliadel with the Stupp protocol has mostly been investigated in retrospective studies. objective of this study was to review the literature of efficacy and toxicities in patients with first-diagnosis glioblastoma treated with surgery, Gliadel, radiotherapy and temozolomide chemotherapy. The data in the literature regarding the combined use of Gliadel with chemotherapy, concomitant with radiotherapy and adjuvant temozolomide for glioblastoma was analyzed and compared. The results on survival and toxicity are summarized. The combination of Gliadel and radiotherapy with temozolomide is well tolerated and may increase survival without a substantial increase in major toxicity. However, only prospective comparative studies will be able to address the issue of true advantage in survival with this combination.