Low-speed purification of human placental nuclei.

A simple method for the purification of human placental nuclei is described. Nuclei were isolated by homogenizing tissue in standard saline citrate solution in the presence of zinc chloride to stabilize the nuclear membranes, NP40 as non-ionic detergent and sodium bisulphite for inhibition of proteolytic activity. Nuclei purification was achieved by low-speed centrifugation through a discontinuous sucrose gradient. The purified nuclei were evaluated by morphological criteria using phase contrast and electron microscopy. The extent of contamination by cytoplasmic debris was estimated by Papanicolaou's staining technique. Biochemical criteria include measurements of alkaline phosphatase activity as a plasma membrane enzyme marker and DNA-dependent RNA polymerase activity for the functional integrity of nuclear components. Transcriptionally active nuclei were obtained but the yield of nuclei was low; however, this low yield is compensated by the high degree of purity, the simplicity of the method and the functional and morphological integrity of the purified nuclei.

Analysis of 16 cystic fibrosis mutations in Mexican patients.

We carried out molecular analysis of 80 chromosomes from 40 unrelated Mexican patients with a diagnosis of cystic fibrosis. The study was performed in two PCR steps: a preliminary one to identify mutation delta F508, the most frequent cause of cystic fibrosis worldwide, and the second a reverse dot-blot with allele-specific oligonucleotide probes to detect 15 additional common mutations in the Caucasian population. A frequency of 45% for delta F508 was found, making it the most common in our sample of Mexican patients. Another five mutations (G542X, 3,849 + 10 kb C-->T, N1303K, SN549N, and 621 + 1 G-->T) were detected, and those accounted for 11.25%. The remaining mutations (43.75%) were undetectable with the methodology used.

Urinary delta-aminolevulinic acid as a biological indicator throughout penicillamine therapy in lead intoxication.

A group of 121 patients with occupational lead exposure was studied. Saturnism was confirmed in 42 of them. Patients were given D-penicillamine in doses of 0.75 and 1.5 g/day. Urinary delta-aminolevulinic acid was selected as a toxicity biological indicator; its concentrations were quantified daily during therapy. Urinary delta-aminolevulinic acid is considered a good biological indicator throughout penicillamine therapy and also in the detection of lead intoxication. Likewise, the chelating test is considered an excellent method to confirm the diagnosis of lead poisoning.

[Determination of delta aminolevulinic acid in urine in a population exposed to lead]. / Determinación del ácido delta. Aminolevulínico urinario en población expuesta a plomo

Uninary levels of delta-aminolevulinic acid (ALA) were determined in 93 workers exposed to lead. Control groups were made up of 32 employees of the same factories of test group and of 24 patients with no history of lead exposure. In the first group, urinary concentration of ALA was 28.55 mg/1; it was 3.36 mg/1 in the second group and 2.98 mg/1 in the other control group. Differences between workers and controls were statistically significant.

Population genetics in the state of Nuevo León, Mexico. II. Genetic markers, frequencies and their possible association with chromosome damage in workers exposed to lead.

In order to find out genetic variability and its possible association with chromosomic damage, we studied the ABO, Rh and MN blood groups as well as the ability to taste PTC, ear lobe type and mid-digital hair, in 77 workers exposed to lead oxides. 23 people who worked near the source of lead (internal control) and 20 people not exposed to lead (external control). From each person a blood sample was taken for chromosome analysis in cultured lymphocytes and for lead determination, at the same time an urine sample was taken for delta-aminolevulinic acid (ALA) determinations; at the same time an urine sample increased chromosome damage, blood lead levels and urinary ALA, were found as compared with both controls. Differences were statistically significant. As for genetic marker frequencies differences were found only for the Rh factor, between the internal control and both the external control and exposed workers. No significant association was found between genetic markers and chromosome damage. Association was observed between blood lead levels, and urinary ALA with some genetic markers like ABO and MN blood groups and ear lobe type.

A modified spectrophotometric assay for porphobilinogen deaminase: its application in the detection of both carriers and patients with acute intermittent porphyria.

A spectrophotometric method for porphobilinogen deaminase assay in erythrocytes is described. This test is determinant for the definite diagnosis of acute intermittent porphyria. In the method described, delta-aminolevulinic acid is used as substrate. Mercaptoethanol and zinc ions are introduced to maintain delta-aminolevulinic acid dehydratase in optimal conditions and to guarantee the in vitro production of porphobilinogen. An incubation temperature of 45 degrees C leads to the production of uroporphyrins, which are measured spectrophotometrically at 405 nm, giving reproducible results. The assay can be performed easily in any clinical laboratory and is valuable for detecting both patients and carriers of acute intermittent porphyria.

Zinc is associated with the beta subunit of DNA-dependent RNA polymerase of Bacillus subtilis.

The Bacillus subtilis DNA-dependent RNA polymerase holoenzyme and core enzyme each contain approximately two atoms of zinc per molecule. When the dissociated subunits of the enzyme are passed through a blue dextran-Sepharose affinity column, only the beta subunit binds to the column. The total zinc content of the enzyme is tightly bound to the beta subunit. Dialysis studies suggest that the two zinc ions differ in the strength of their association with the beta subunit. The presence of zinc in beta is consistent with several other lines of evidence which indicate that this subunit is dirrectly involved in phosphodiester bond formation. The blue dextran-Sepharose column procedure should be useful in future studies of the dissociation and reassociation of the enzyme since the method is rapid and provides excellent recovery of the beta subunit as well as the alpha and beta' subunits of the RNA polymerase.

El cromosoma Philadelphia ocurre en la celula totipotencial: trombocitosis primaria t (9q+; 22q-). / The pluripotential stem cell may present the Philadelphia-chromosome: primary thrombocythemia t (9q+; 22q-)

La trombocitosis primaria es un sindrome mieloproliferativo maligno diferente a la leucemia granulocitica cronica. Hasta la fecha, solo se ha descrito un caso de trombocitosis primaria con la translocacion cromosomica: t (9q+; 22q-).Se describe aqui otro caso de trombocitosis primaria con cromosoma Philadelphia (Phl+), que ademas desarrollo finalmente leucemia aguda mieloide, ocurrencia poco frecuente. Se discute el hallazgo en las celulas de la alteracion cromosomica encontrada que sugiere que el evento (Phl+) no ocurre en las celulas de la serie granulocitica sino probablemente en la celula madre totipotencial