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M Lechuga

Publications and source records attributed to M Lechuga.

7 recordsLinked to original sources
PubMed2006

Simplified spectrophotometric method using methylene blue for determining anionic surfactants: applications to the study of primary biodegradation in aerobic screening tests.

In the present work, we propose a simplified spectrophotometric method for determining anionic surfactants, based on the formation of the ionic pair anionic surfactant-methylene blue (AS-MB). This method, in relation to the conventional analytic procedure, considerably reduces not only the quantity of chloroform used in extracting the ionic pair formed, but also the time and the quantity of sample necessary to perform the assay, eliminating the filtration stage. The method has been simplified by displacing the transfer equilibrium of the ionic pair AS-MB towards the organic phase, augmenting the volumetric relationship of chloroform/sample. The method proposed has been applied in the study of primary biodegradation kinetics of linear alkylbenzenesulfonate (LAS).

Alkanesulfonic Acids↗
PubMed1994

Effect of the in vivo treatment with the synthetic steroid 17 beta-methoxy-17-methyl-(5 alpha)-1 H'-androstane-(3,2-c) pyrazole (17MM) on the in vitro formation of DHT in the epididymis of the rat.

Adult male Sprague-Dawley rats were injected subcutaneously (s.c.) for 21 days either with the synthetic steroid 17 beta-methoxy-17-methyl-(5 alpha)-1 H'-androstane-(3,2-c) pyrazole (17MM) at two dose levels (0.1 and 1 mg/kg/day) or with the vehicle used to dilute the steroid. At autopsy, caput epididymes and ventral prostates were removed and incubated in vitro. The effect on the 5 alpha-reductase (5 alpha-R) activity was evaluated by measuring the amounts of DHT formed from 14C-testosterone (14C-T) used as the substrate. The in vivo administration of 17MM at the dose of 0.1 mg/kg/day resulted in a significant decrease in the formation of DHT at the level of the epididymis, while there was no effect on the prostate. The dose of 1 mg/kg/day did not induce any modification in the formation of DHT in either organ. The determination of serum LH showed that the treatment with either dose did not alter serum LH titers. These findings suggest that the in vivo treatment with 17MM lowers the in vitro formation of DHT from T at the epididymal, but not at the prostatic level and consequently suggests a selective inhibitory effect of 17MM on the 5 alpha-R present in the epididymis.

5-alpha Reductase Inhibitors↗
PubMed1992

Selective inhibition of the 5 alpha-reductase of the rat epididymis.

The effect of several synthetic steroids belonging either to the 4-aza-3-oxo-steroid family or to androstene and androstane derivatives was investigated "in vitro" on the epididymal as well as prostatic 5 alpha-reductase activity. For this purpose rat caput epididymis and prostate were incubated with the different steroidal compounds at molar concentrations of 10(-7), 10(-6), and 10(-5) in the presence of labelled testosterone as substrate. The steroids 4-MA (17 beta, N,N-diethyl-carbamoyl-4-aza-5 alpha-androstan-3-one) and 4-OH-A (4-hydroxy-androstenedione), already known to be effective 5 alpha-reductase inhibitors at the level of the prostate, have been used as reference molecules. The 5 alpha-reductase activity was evaluated by measuring pg of dihydrotestosterone (DHT) formed in 2 h of incubation by mg of tissue. The steroids A, B, C, F, G and I inhibit the formation of DHT in the rat epididymis although to different extents; they are also equally effective on the formation of DHT in the rat prostate. The steroids D, E, H and L are devoid of any inhibitory property on the formation of DHT in both the rat epididymis and prostate. The most interesting results were obtained with compound M which exhibits a dose-dependent and significant inhibitory effect on the formation of DHT in the epididymis, but it is inactive at the level of the prostate. These findings suggest that it is possible (a) to selectively interfere with the 5 alpha-reductase of the epididymis without affecting that present in the prostate, and (b) consequently to envisage new ways to regulate male fertility.

3-Oxo-5-alpha-Steroid 4-Dehydrogenase↗
PubMed1975

Genetical studies in nontraumatic retinal dialysis.

1. The retinal periphery was explored with binocular indirect ophthalmoscopy and scleral depression in members of the families of patients with detachment due to retinal disinsertions and 30 pedigrees have been thus obtained. 2. A genetic causation of this disease is postulated, based in the concentration of cases in some of the sibships studied (33% of the sibships with 2 or more siblings); furthermore, the disease was demonstrated in two identical twins and was absent in two fraternal twins. 3. The sex incidence was similar and the vast majority of affected individuals had normal parents, suggesting an autosomal recessive mode of inheritance for at least some of the cases.

Diseases in Twins↗