Paul Albu

Histopatological alterations and oxidative stress in liver and kidney of Leuciscus cephalus following exposure to heavy metals in the Tur River, North Western Romania

Pollution of the aquatic environment by heavy metals is a great concern worldwide. Freshwater fish ingests various metals through gills, skin or diet. Our aim was to investigate the oxidative stress and histopathological injuries induced by Fe, Cu, Zn, Pb, Cd in the liver and kidney of Leuciscus cephalus. Fish samples were collected from two sites in the Tur River, NW Romania, in upstream and downstream of a pollution source. Metals were differently distributed in the liver and kidney of fish. The highest concentrations of Fe, Cu and Pb were found in liver, whereas Zn and Cd concentrations were the highest in kidney in specimens collected from the downstream site. The histopathological changes were associated with metal bioaccumulation, being more severe in kidney than liver. Malondialdehyde (MDA) and advanced oxidation protein products (AOPP) increased significantly in the liver and kidney of fish from downstream site compared to upstream one, whereas reduced glutathione (GSH) decreased. The activities of superoxide dismutase (SOD), catalase (CAT) and glutathione-S-transferase (GST) increased significantly in livers, whereas SOD increased in kidney. Our study revealed that liver has a higher capacity and adaptability to counteract ROS compared to kidney. The more pronounced increase of hepatic SOD, CAT and GST activities is related milder structural changes observed in liver compared to kidney, where lesions were not reduced by antioxidant defense system.

Comparative study on the thermal behavior of two similar triterpenes from birch

A comparative study on the thermal behavior of betuline and betulinic acid was performed using a TG–FTIR hyphenated technique. The comparison was focused on the kinetic of the relevant thermal-induced phenomenon. Using three different data processing strategy, that is, Friedman, Flynn–Wall–Ozawa, and nonparametric kinetic, homogeneous values for the activation energy were obtained, especially by betulinic acid. The advantages of the nonparametric kinetic method were revealed, especially by obtaining the explicit kinetic parameters of the conversion function, without any “a priori” hypothesis.

TG/DTG/DTA data used for determining the kinetic parameters of the thermal degradation process of an immunosuppressive agent: mycophenolate mofetil

Mycophenolate mofetil is a strong immunosuppressive therapeutic agent that was primely licensed to prevent rejection of transplanted organs. The decomposition reactions of pharmaceuticals, alongside other processes that occur, are important ones from both fundamental and practical point of view. The thermal stability of pharmaceuticals is important from both fundamental and clinical point of view. Kinetic analysis is one of the best method for an objective and less speculative determination of the Life Time Prediction. Following the ICTAC 2000 Protocol, the thermal behavior of mycophenolate was recorded at five different heating rates, in air atmosphere. The activation energy for the main degradation process was obtained by using four isoconversional methods of kinetic analysis: Friedman, Flynn–Wall–Ozawa, Kissinger–Akahira–Sunose and modified nonparametric kinetic methods. The obtained values of the activation energy were in a very close range.

Thermogravimetric and calorimetric studies performed on memantine hydrochloride to determine its thermal behaviour and possible drug–excipient interactions

Memantine hydrochloride is an adamantane derivative used for the treatment of moderate-to-severe Alzheimer’s disease. Pharmaceutical active compounds and the excipients are in contact with each other a period of time before the pharmaceutical formulation is used by a patient; hence, the storage conditions are very important—humidity and temperature can trigger interactions between a drug and an excipient and these interactions may affect drug bioavailability and even drug safety. For this study, TG/DTG/HF curves were recorded in air flow and they were used to determine the thermal behaviour and some indications about the compatibility of memantine, the single excipients and of the binary mixtures, while FTIR and DSC analysis of the pure compounds and the binary mixtures were used to evaluate possible interactions between the compounds.

Thermal behavior of phthalic anhydride-based polyesters Part I. Influence of the polyol on the thermal stability

A series of three phthalic polyesters with 1,2 propylene glycol, trimethylolpropane and glycerin were synthesized in a molar ratio anhydride:polyol of 1:1.25 so that a rather linear macromolecular chains were obtained with side alchyl and/or hydroxyl groups. The thermal behavior was estimated by means of the thermoanalytical curves obtained under non-isothermal conditions in dynamic air atmosphere, in order to estimate the polyol influence on the thermal stability of phthalic polyesters. A quantitative estimation of the thermal stability was possible due to a kinetic analysis using three different data processing methods. Only the modified NPK method allows a complete quantitative and objective description of the thermodegradation rate. From the three prepared polyesters, that one with glycerin presented the lowest thermal stability.

Thermal behavior of some polyurethanes reticulated by aminated maltose

Polymeric materials by polyaddition reaction between aminated maltose and methylene diisocyanate, in different molar ratio, were synthesized. Aminated maltose was obtained by functionalization at the reductive end with methylene dianiline, under soft reductive conditions. The addition reaction was certified by comparative FTIR and Raman spectra of reactants and obtained materials. The thermooxidative stability of these materials was established under non-isothermal conditions. The thermal stability decreases by increasing the isocyanate/aminated maltose molar ratio.

Thermal behaviour of the polyesters obtained with different molar ratios of carboxyl hydroxyl components

Polyesters were obtained from phthalic anhydride as acidic components and an alcoholic mixture of monoethylene glycol and n-propanol (in ratio 1:0.15). Molar ratio of the acid component versus alcohol component was 1:2, 1:1.8, 1:1.25 and 1:0.7. Obtained polyesters were characterized by: TG/DTG/Heat Flow (in synthetic air, respectively, in nitrogen atmosphere), EGA (evolved gas analysis), elemental analysis and FT-IR/UATR spectroscopy of polyesters and residues.

Influence of the nature of the chain breaker on the thermal stability of phthalic anhydride-based polyesters

Abstract This study presents the synthesis of polyesters obtained from phthalic anhydride as acidic components and one mixture of monoethylene glycol and monohydric alcohol (in ratio 1.1:0.15). Molar ratio of the acid component and alcohol component was 1:1.25. n-Propanol, n-butanol, n-octanol and isoamyl alcohol were used as monohydric alcohol. Physicochemical characterization was performed by elemental analysis, FTIR/UATR spectroscopy of polyesters and char, EGA (evolved gas analysis), thermal analysis in synthetic air and in nitrogen atmosphere.

Study of thermally induced interaction between hydroxyethylcellulose and carboxymethylcellulose with different excipients

The aim of the present paper was the study of excipient–excipient interactions. It presents the compatibility study between two polymeric compounds used in pharmaceutical technology, namely carboxymethylcellulose and hydroxyethylcellulose, with other commonly used pharmaceutical excipients, such as polyvinylpyrrolidone, sorbitol, magnesium stearate, and talc. The compatibility investigations were carried out under ambient temperature and after decomposition by FTIR spectroscopy studies and later completed by the use of thermal analysis (TG/DTG/HF) data to study the influence of temperature over stability of binary mixtures. Carboxymethylcellulose and hydroxyethylcellulose present thermal-induced interactions with sorbitol and magnesium stearate.