[Study of the right ventricle using magnetic resonance imaging]. / Estudio del ventrículo derecho mediante resonancia magnética.

Magnetic resonance (MR) imaging has proven efficacy in the study of the heart. Its clinical applications are directed primarily at the study of the left ventricle, and the right ventricle is relegated to the background. This article reviews the anatomy and physiology of the right ventricle, as well as the manifestations of most common diseases affecting this chamber of the heart: infarction, cardiomyopathy, masses, and right heart failure. Knowing the distinctive features of the right ventricle with respect to the left and the particularities of the MR imaging protocol results in better technical performance in cases in which the reason for the examination or imaging findings point to the right ventricle. The importance of the right ventricle in the management of cardiopulmonary disease is growing and MR imaging can provide clinicians with the support they need.

[Diagnosis and quantification of iron overload in the liver using MRI]. / Diagnóstico y cuantificación de la sobrecarga férrica en el hígado mediante resonancia magnética.

Hereditary hemochromatosis is the most common cause of iron overload. The diagnosis of hereditary hemochromatosis has improved since Feder et al. isolated the HFE gene in 1996 and discovered the mutations related with this disease. Nevertheless, in many cases genetic tests for hereditary hemochromatosis are negative. These cases require diagnostic confirmation by quantifying the concentration of iron in the liver (LIC); this has traditionally been accomplished by liver biopsy. Many studies have shown that it is possible to quantify LIC using MRI. However, a consensus has yet to be reached about the most appropriate technique or whether it is possible to reproduce the same methods of calculation on different MRI units. This article reviews the current state of these questions and points to possible lines to standardize this noninvasive method of quantifying LIC in the future.

Diagnóstico y cuantificación de la sobrecarga férrica en el hígado mediante resonancia magnética / Diagnosis and quantification of iron overload in the liver using MRI

La hemocromatosis hereditaria es la modalidad más frecuente de sobrecarga férrica. El diagnóstico de la misma ha mejorado desde que en 1996 Feder et al aislaron el gen HFE descubriendo las mutaciones relacionadas con la enfermedad. Sin embargo, son muchos los pacientes con estudios genéticos negativos, y que por tanto requieren una confirmación diagnóstica mediante la cuantificación de la concentración de hierro en hígado (CHH) que tradicionalmente se ha realizado mediante biopsia hepática. Muchos estudios han demostrado la posibilidad de cuantificar la CHH mediante resonancia magnética. Sin embargo, todavía no existe un consenso en cuanto a la técnica más idónea ni en cuanto a la posibilidad o no de reproducir el mismo método de cálculo en diferentes máquinas. Este artículo revisa la realidad de estas cuestiones y señala posibles líneas de futuro para estandarizar este método no invasivo de cuantificación de la CHH

Hereditary hemochromatosis is the most common cause of iron overload. The diagnosis of hereditary hemochromatosis has improved since Feder et al. isolated the HFE gene in 1996 and discovered the mutations related with this disease. Nevertheless, in many cases genetic tests for hereditary hemochromatosis are negative. These cases require diagnostic confirmation by quantifying the concentration of iron in the liver (LIC); this has traditionally been accomplished by liver biopsy. Many studies have shown that it is possible to quantify LIC using MRI. However, a consensus has yet to be reached about the most appropriate technique or whether it is possible to reproduce the same methods of calculation on different MRI units. This article reviews the current state of these questions and points to possible lines to standardize this noninvasive method of quantifying LIC in the future

[Low grade astroblastoma: pathological and magnetic resonance findings]. / Astroblastoma de baixo grau: Achados patológicos e da ressonância magnética.

INTRODUCTION: The astroblastoma is an uncommon type of glial tumour. It accounts for less than 1% of all tumours of the central nervous system. It originates in the tanicytes, ependymal cells present in the embryo and usually seen in adolescents and young adults. Radiologically it presents as a well delimited, heterogeneous tumour with a solid component which takes up contrast and is cystic, giving the same signal as cerebrospinal fluid (CSF). The pathological characteristics are of the formation of radial astroblastic pseudorosettes with perivascular hyalinization. CASE REPORT: An 18 year old woman presented with a 15 month history of motor deficit of her right limbs with occasional left frontal headache and horizontal diplopia on looking towards the left. On examination there was minimal claudication of the right limbs and bilateral papilloedema. Magnetic resonance showed a very well circumscribed left prefrontal neoplasm of heterogeneous aspect, with areas of solid and cystic appearance in the different sequences. The area of cystic appearance did not show the CSF signal in all sequences of the pulse. The tumour was totally excised. On histological study there were radial astroblastic pseudorosettes with perivascular hyalinization, with two mitoses per 10 fields of great magnification and the final diagnosis was of low grade astroblastoma. The apparently cystic portion was composed of friable gelatinous tissue. Fifteen months after her operation the patient is still asymptomatic. CONCLUSION: We report the radiological and pathological findings of a low grade astroblastoma.

Pharmacokinetics and residues of ciprofloxacin and its metabolites in broiler chickens.

The pharmacokinetic properties of ciprofloxacin and its metabolites were determined in healthy chickens after single i.v. and oral dosage of 8 mg ciprofloxacin kg(-1) bodyweight. After i.v. and oral administration, the plasma concentration-time graph was characteristic of a two-compartment open model. Mean (SD) elimination half-life and mean residence time of ciprofloxacin in plasma were 8.84 (2.13) and 8.54 (1.64) hours, respectively, after i.v. administration and 11.89 (1.95) and 13.32 (2.65) hours, respectively, after oral administration. Mean maximal plasma concentration of ciprofloxacin was 2.63 (0.20) microg ml(-1), and the interval from oral administration until maximum concentration was 0.36 (0.07) hours. The mean oral bioavailability of ciprofloxacin was found to be 69.12 (6.95) per cent. Ciprofloxacin was mainly converted to oxociprofloxacin and desethyleneciprofloxacin. Considerable kidney, liver, muscle and skin + fat tissue concentrations of ciprofloxacin and its metabolites oxociprofloxacin and desethyleneciprofloxacin were found when ciprofloxacin was administered orally (8 mg kg(-1) on 3 successive days). It was estimated that mean tissue concentrations of ciprofloxacin and its metabolites ranging between 0.011 to 0.75 microg g(-1) persisted for 5 days.

Pharmacokinetic variables and tissue residues of enrofloxacin and ciprofloxacin in healthy pigs.

OBJECTIVES: To determine pharmacokinetics of enrofloxacin and its metabolite ciprofloxacin after a single i.v. and i.m. administration of enrofloxacin and tissue residues after serial daily i.m. administration of enrofloxacin in pigs. ANIMALS: 20 healthy male pigs. PROCEDURE: 8 pigs were used in a crossover design to investigate pharmacokinetics of enrofloxacin after a single i.v. and i.m. administration (2.5 mg/kg of body weight). Twelve pigs were used to study tissue residues; they were given daily doses of enrofloxacin (2.5 mg/kg, i.m. for 3 days). Plasma and tissue concentrations of enrofloxacin and ciprofloxacin were determined. Residues of enrofloxacin and ciprofloxacin were measured in fat, kidney, liver, and muscle. RESULTS: Mean (+/-SD) elimination half-life and mean residence time of enrofloxacin in plasma were 9.64+/-1.49 and 12.77+/-2.15 hours, respectively, after i.v. administration and 12.06+/-0.68 and 17.15+/-1.04 hours, respectively, after i.m. administration. Half-life at alpha phase of enrofloxacin was 0.23+/-0.05 and 1.94+/-0.70 hours for i.v. and i.m. administration, respectively. Maximal plasma concentration was 1.17 +/-0.23 microg/ml, and interval from injection until maximum concentration was 1.81+/-0.23 hours. Renal and hepatic concentrations of enrofloxacin (0.012 to 0.017 microg/g) persisted for 10 days; however, at that time, ciprofloxacin residues were not detected in other tissues. CONCLUSIONS AND CLINICAL RELEVANCE: Enrofloxacin administered i.m. at a dosage of 2.5 mg/kg for 3 successive days, with a withdrawal time of 10 days, resulted in a sum of concentrations of enrofloxacin and ciprofloxacin that were less than the European Union maximal residue limit of 30 ng/g in edible tissues.

Groundwater flow system in the valley of Toluca, Mexico: an assay of natural radionuclide specific activities.

Natural radionuclides and physicochemical parameters have been evaluated in groundwater samples from boreholes belonging to the drinking water supply system of the Toluca City, Mexico. The results obtained for radon and radium, together with the physicochemical parameters of the studied samples, indicate a fast and efficient recharge pattern. The presence of a local and a regional groundwater flows was also observed. The local flow belongs to shallower water, recognized by its low radon content and dissolved ions, as compared with the regional, deeper groundwater flow with a longer residence time.

Pharmacokinetics of doxycycline in broiler chickens.

Doxycycline was given to two groups of eight chickens at a dose of 20 mg/kg of body weight, intravenously (i.v.) or orally. Plasma concentration was monitored serially for 12 h after each administration. Another group of 30 chickens was given 20 mg/kg orally every 24 h for 4 days, and plasma and tissue concentrations determined serially after the last administration. Concentrations of doxycycline were measured using high-performance liquid chromatography. Pharmacokinetic variables were calculated, using a two-compartment open model. The elimination half-life and the mean residence time for plasma were 6.03 +/- 0.45 and 7.48 +/- 0.38 h, respectively, after oral administration and 4.75 +/-0.21 and 2.87 +/-0.11 h, respectively, after i.v. administration. After single oral administration, doxycycline was absorbed rapidly, with T(max) of 0.35 +/- 0.02 h. Maximum plasma concentration was 54.58 +/- 2.44 mu/ml. Oral bioavailability of doxycycline was found to be 41.33 +/- 2.02%. Doxycycline was widely distributed in tissues and considerable concentrations were found following oral administration of 20 mg/kg on four successive days. The results indicate that doxycycline concentrations were cleared slowly and were at or below the accepted drug tolerance levels in the marker tissues within 5 days after dosing.