Different culture media containing methyldopa for melanin production by Cryptococcus species / Avaliação de diferentes meios de cultura contendo metildopa para a produção de melanina por espécies de Cryptococcus

INTRODUCTION: Melanin production by species of Cryptococcus is widely used to characterize C. neoformans complex in mycology laboratories. This study aims to test the efficacy of methyldopa from pharmaceutical tablet as a substrate for melanin production, to compare the production of melanin using different agar base added with methyldopa, and to compare the melanin produced in those media with that produced in Niger seed agar and sunflower seed agar by C. neoformans, C. laurentii, and C. albidus. Two isolates of each species, C. neoformans, C. laurentii, and C. albidus, and one of Candida albicans were used to experimentally detect conditions for melanin production. METHODS: The following media were tested: Mueller-Hinton agar (MHA), brain and heart infusion agar (BHIA), blood agar base (BAB), and minimal medium agar (MMA), all added with methyldopa, and the media Niger seed agar (NSA) and sunflower seed agar (SSA). RESULTS: All isolates grew in most of the culture media after 24h. Strains planted on media BAB and BHIA showed growth only after 48h. All isolates produced melanin in MMA, MHA, SSA, and NSA media. CONCLUSIONS: Methyldopa in the form pharmaceutical tablet can be used as a substrate for melanin production by Cryptococcus species; minimal medium plus methyldopa was more efficient than the BAB, MHA, and BHIA in the melanin production; and NSA and SSA, followed by MMA added with methyldopa, were more efficient than other media studied for melanin production by all strains studied.

INTRODUÇÃO: A produção de melanina por espécies de Cryptococcus é uma característica amplamente utilizada em laboratórios de micologia para caracterização do complexoC. neoformans. O objetivo deste estudo foi verificar a eficácia da metildopa na forma farmacêutica de comprimido, como substrato para a produção de melanina por Cryptococcus, comparar diferentes bases de meios de cultura acrescidas de metildopa para produção de melanina e comparar o pigmento produzido nestes meios com o produzido em ágar Níger e ágar girassol por C. neoformans, C. laurentii e C. albidus. MÉTODOS: Foram testados dois isolados de cada uma das espécies, C. neoformans, C.laurentii e C.albidus, e um de C. albicans para avaliar a produção de melanina nos meios de cultura ágar Müeller-Hinton (MH), ágar brain heart infusion (BHI), ágar base sangue (BS), meio mínimo (MM), todos acrescidos de metildopa, e ainda ágar girassol e ágar Níger. RESULTADOS: Todos os isolados cresceram na maioria dos meios após 24h. O crescimento nos meios BS e BHI somente ocorreu após 48h. Todos os isolados produziram melanina nos meios MM, MH, girassol e Niger. CONCLUSÕES: A metildopa de origem farmacêutica pode ser utilizada como substrato para a produção de melanina por espécies de Cryptococcus; o MM acrescido de metildopa mostrou-se mais eficiente na produção de melanina do que os meios BS, MH e BHI; ágar girassol e ágar Níger seguidos de MM acrescido de metildopa foram os mais eficientes na produção de melanina pelos isolados estudados.

comparative study of a new spectrophtometeric assay of alpha-methyldopa tablets manufactured by different companies

Many spectrophotometeric methods have been described for the determination of alpha-Methyldopa powder and tablets. However, most of these methods suffer from extraction, heating, time consuming for developing colour. The objective of this study is to eliminate previous factors and to determine a simple and sensitive Spectrophtometeric method. A simple, and sensitive Spectrophtometeric method is proposed for the analysis of reference standard and four commercial brands of alpha-Methyldopa. The method is based on the oxidation of alpha-Methyldopa by 0.25% K2CrO4, followed by oxidative coupling with 0.5% sulphanilic acid, to yield greenish-yellow product having maximum absorbance at 400 nm, and the absorptions were taken after 5 minutes. The system obeyed Beer's law over the concentration 10-175 mcg/ml. The relationship between absorbance and concentration was linear by applying regression linear equation. We calculated the concentration of the drug from the calibration curve. The common excipients and additives did not interfere with their determinations. The results obtained by the proposed method were compared statistically with official method [USP]. There were no significant differences in precision between them [p = 0.011]. The method was successfully used for the determination of alpha- methyldopa powder and tablets

Effects of the antihypertensive drugs Ó-methyldopa and hydralazine on the performance of spontaneously hypertensive rats in the elevated plus-maze

The effects of antihypertensive drugs on the performance of spontaneously hypertensive rats (SHR) in the elevated plus-maze were determined. Male SHR (3 months old) were submitted to long-term treatment (15 days) with Ó-methyldopa (ÓMD, 5g/l, N = 10) and hydralazine (HYD, 100 mg/l, N = 10) given orally, diluted in water. After the drug treatment, the performance of the rats in the plus-maze was observed for 5 min in a single test and mean arterial pressure (MAP) and heart rate (HR) were then measured. The antihypertensive drugs reduced MAP significantly (mean ñ SEM:CON = 176.2 ñ 5.2, ÓMD = 157.8 ñ 4.6 and HYD = 150 ñ 4.4 mmHg) and only ÓMD increased HR significantly (mean ñ SEM:CON = 391.7 ñ 13.8, ÓMD = 453.3 ñ 14 and HYD = 368.8 ñ 18.9 bpm). The ÓMD group presented a lower total number of entries (mean ñ SEM:CON = 12.7 ñ 0.7, ÓMD = 8.7 ñ 0.9 and HYD = 12 ñ 0.9) and spent less time in the open arms than the CON (N = 10) and HYD groups (mean ñ SEM:CON = 0.69 ñ 0.04, ÓMD = 0.48 ñ 0.07 and HYD = 0.65 ñ 0.06 s). ÓMethyldopa acts centrally and hydralazine acts peripherally. The behavioral change of SHR treated with Ó-methyldopa suggests that hypertension seems to be related to central nervous dysfunctions that are affected by an antihypertensive drug with central noradrenergic action

Influence of clonidine, methyldopa and propranolol on acute toxicity of fenitrothion in mice.

The effect of pretreatment with clonidine, methyldopa and propranolol, and of atropine was studied in mice on acute toxicity of fenitrothion, the active ingredient of TIK-20. Atropine significantly decreased and propranolol somewhat decreased the fenitrothion induced death in mice. Clonidine and methyldopa somewhat increased the percentage mortality due to fenitrothion.

Efecto de la alfa metildopa sobre el corazón en la hipertensión renovascular / Effect of alpha methyldopa on heart in renovascular hypertension

Resultados previos mostraron que la hipertrofia cardíaca (HC) y la respuesta contráctil al Isoproterenol (I) en el modelo 2R Ic, se normalizagba tres semanas sdespués del descenso de la presión arterial (PA) por el declipado de la arteria renal. En el presente trabajo se estudió el efecto de la Alfa Metidopa (aMD) sobre la PA, HC y la respuesta al I. Con ese propósito, a 43 ratas macho Wistar, de 280 gramos, se las dividió en: a) Grupo Control (C) (n = 24). Luego de tres semanas de control de PA, a 17 de ellas se les administró aMD per os a la dosis de 100 mg/kg/día durante 21 días (C alta). b) Grupo clip (K) (n = 19), a los que se les colocó un clip de plata en la arteria renal izquierda. Luego de tres semanas de hipertensión a (n = 9) (K alfa) se les administró aMD en forma similar a C Alfa. La respuesta al I se evaluó a los 21 a C y K y a los 42 días a C alfa y K alfa. A tal fin, previa anestesia se canularon la carótida, la arteria y vena femorales y se registró la frecuencia cardíaca (FC), la presión arterial media (PAM), la presión sistólica y diastólica de ventrículo izquierdo y la DP/DT + MAX en condiciones basales, y luego de dosis unicas crecientes de I. Al finalizar la experiencia se determinó el peso biventricular (PC) y se normalizó por el peso corporal (pc). La PA aumentó en K (p < 0,05): 179 ñ 2,3 vs C 125 ñ 2,9 y con aMD descendió: C alfa 111 + 2,5 y K alfa 151,7 ñ 6 (p < 0,05). EIPC (g) con aMD fue menor en C alfa (p < 0,05) 0,69 ñ 0,04 vs 0,78 ñ 0,05 y en K alfa...

Characterization of alpha-adrenoceptors involved in central thermoregulation in rabbits.

Intracerebroventricular (icv) injection of methyldopa induced body temperature changes in the rabbits. The dose of 100 micrograms/kg did not produce any significant change on body temperature whereas 250 micrograms/kg of the drug induced hyperthermia. Higher dose of 500 micrograms/kg produced initial hypothermia which was followed by hyperthermia. On further increase of the dose to 1 mg/kg, consistent hypothermia was evident. Prazosin, a specific post-synaptic alpha 1 adrenoceptor blocker, induced hypothermia whereas piperoxan (presynaptic alpha 2 antagonist) produced hyperthermia. The pretreatment with prazosin, blocked the hyperthermic response of methyldopa. The initial hypothermia by 500 micrograms/kg of methyldopa was also potentiated. The pretreatment with piperoxan completely blocked the hypothermia but had no effect on hyperthermic response of methyldopa. Pretreatment of rabbits with both prazosin and piperoxan completely blocked the hypothermia as well as hyperthermic response of methyldopa. Thus it appeared that both presynaptic alpha 2 and postsynaptic alpha 1 adrenoceptors are involved in central thermoregulation in rabbits.

Beta blockade and anticonvulsant activity of propranolol.

Racemic and dextro forms of propranolol were equipotent in their anticonvulsant activity in normal rats by the MES test. In an attempt to determine any difference in the anticonvulsant activity of the two forms a variety of adrenergic agents were used, viz. phenoxybenzamine, reserpine, alphamethyl dopa and acetazolamide. There was no difference between the two forms, in the absence or presence of several adrenergic drugs employed. However, racemic but not dextro propranolol reduced MET, in normal as well as in nialamide primed rats.