Comparison between titrimetric and spectrophotometric methods for quantification of vitamin C.

Vitamin C is usually quantified by titrimetric or chromatographic methods. However, these methods have limitations: food color interferes with the titrimetric method and the chromatographic method is costly. The aim of this study was to compare a spectrophotometric method, based on reduction of cupric ions in the presence of cuproine complex, with a titrimetric method, based on reduction of 2,6-dicholorophenolindophenol. Linearity, precision, accuracy, and limits of detection (LOD) and quantification (LOQ) were evaluated using a standard vitamin C solution. Both methods were also applied for AA quantification in industrialized orange and pineapple juices. The methods were precise and accurate when applied to the standard solution. The spectrophotometric method was more sensitive, with lower values for LOD (0.002mgmL-1) and LOQ (0.010mgmL-1), and more accurate with error less than 5% while results from the titrimetric method were affected by the juice color, which generated errors in excess of 15%.

DNA polymerase I in constitutive stable DNA replication in Escherichia coli.

We examined the effects of mutations in the polA (encoding DNA polymerase I) and polB (DNA polymerase II) genes on inducible and constitutive stable DNA replication (iSDR and cSDR, respectively), the two alternative DNA replication systems of Escherichia coli. The polA25::miniTn10spc mutation severely inactivated cSDR, whereas polA1 mutants exhibited a significant extent of cSDR. cSDR required both the polymerase and 5'-->3' exonuclease activities of DNA polymerase I. A similar requirement for both activities was found in replication of the pBR322 plasmid in vivo. DNA polymerase II was required neither for cSDR nor for iSDR. In addition, we found that the lethal combination of an rnhA (RNase HI) and a polA mutation could be suppressed by the lexA(Def) mutation.

Histiocitosis X. Informe de 45 casos. / Histiocytosis X.Report of 45 cases

Con el objeto de determinar las caracteristicas clinico-evoluativas y terapeuticas los casos de histiocitosis X vistos en el Instituto Nacional de Pediatria DIF, de la ciudad de Mexico, se revisa el periodo 1970-1979. Se encuentran 45 casos de histiocitosis S (frecuencia 1:4333 pacientes pediatricos; y 1:388 pacientes dermatologicos) en sus tres formas clinicas: Enfermedad de Letterer-Siwe 15. Enfermedad de Hand-Schuller-Christian 22, y granuloma eosinofilo del hueso 8. Habia lesiones cutaneas en el 57% de los casos, pero su frecuencia variada con las formas clinicas Asi estaban presentes en el 93% de los casos de E.L.S. y en el 63% de los E.H.S.C.; y ausentes en los de granuloma eosinofilo del hueso.Los cuadros simulando dermatitis seborreica fueron los habituales, siguiendoles las purpuras, intertrigos y ulceraciones. En ningun paciente estas lesiones precedieron al cuadro clinico general

Histiocitosis X. Informe de 45 casos. / Histiocytosis X.Report of 45 cases

Con el objeto de determinar las caracteristicas clinico-evoluativas y terapeuticas los casos de histiocitosis X vistos en el Instituto Nacional de Pediatria DIF, de la ciudad de Mexico, se revisa el periodo 1970-1979. Se encuentran 45 casos de histiocitosis S (frecuencia 1:4333 pacientes pediatricos; y 1:388 pacientes dermatologicos) en sus tres formas clinicas: Enfermedad de Letterer-Siwe 15. Enfermedad de Hand-Schuller-Christian 22, y granuloma eosinofilo del hueso 8. Habia lesiones cutaneas en el 57% de los casos, pero su frecuencia variada con las formas clinicas Asi estaban presentes en el 93% de los casos de E.L.S. y en el 63% de los E.H.S.C.; y ausentes en los de granuloma eosinofilo del hueso.Los cuadros simulando dermatitis seborreica fueron los habituales, siguiendoles las purpuras, intertrigos y ulceraciones. En ningun paciente estas lesiones precedieron al cuadro clinico general

Neuroichthyosis with hypogonadism (Rud's syndrome).

Rud's syndrome is a neuroichthyosis with hypogonadism, associated with mental deficiency and epilepsy. Short stature is a frequent component of the syndrome. The primary genetic defect and the pattern of inheritance have not yet been determined. A typical patient is presented, with mental deficiency, short stature, pypoacusia, muscular atrophy, tylosis, pseudoacanthosis nigricans and endocrine disturbances. The neuroichthyosis with hypogonadism must be considered Rud's syndrome. A classification of neuroichthyosis is proposed. In a first group is neuroichthyosis with hypogonadism, in the second group is neuroichthyosis with spasticity and in the third group, neuroichthyosis without hypogonadism or spasticity.