Biomedical subjects
L Leiva
Publications and source records attributed to L Leiva.
Casein kinase II is a major protein phosphorylating activity in the nuclei of Xenopus laevis oocytes.
The nuclei of Xenopus laevis oocytes contain kinases capable of phosphorylating endogenous and exogenous proteins using either ATP or GTP as phosphoryl donors. These enzymes are much more active with casein and phosvitin as substrates than with histones or protamines. The protein phosphorylating activity of oocyte nuclear extracts is not regulated by cyclic nucleotides, phorbol esters, calmodulin and calcium, or phospholipids. However, the casein phosphorylating activity can be greatly enhanced by the polyamines spermine or spermidine and drastically inhibited by heparin. Fractionation of the nuclear casein kinase activities by DEAE-Sephadex chromatography and glycerol gradient centrifugation indicate that the nuclei contain enzymes with the properties of casein kinases I and II as characterized in other species. Oocyte casein kinase I (Mr 37,000) is specific for ATP as phosphoryl donor, is only slightly inhibited by 10 micrograms/ml heparin, and is not significantly stimulated by polyamines. Casein kinase II (Mr 135,000) can use both ATP and GTP as substrates, and is very sensitive to heparin inhibition and polyamine stimulation. The fact that low concentrations of heparin (10 micrograms/ml) can inhibit a large percentage of the endogenous phosphorylation of nuclear extracts or of whole nuclei indicates that casein kinase II is probably the major protein phosphorylating activity of these oocyte organelles.
[Effects of iodine deficiency during intrauterine and early postnatal life on DNA synthesis in liver and brain of rats].
Iodine deficiency during intrauterine and early postnatal life of the rat produces a transient decrease in the DNA content of brain and cerebellum, which is spontaneously recovered without replacement therapy. Results of the study revealed that DNA synthesis measured through thymidine-H3 incorporation to DNA, was increased at 21 days of life in liver, brain and cerebellum, indicative of a higher activity of DNA synthesis. This prolongation of the critical period of brain cell multiplication in iodine deficient rats, suggests, therefore, an alteration of brain maturation.
Expression of the cutaneous lymphocyte-associated antigen in circulating T cells in drug-allergic reactions.
BACKGROUND: Mechanisms underlying the production of delayed cutaneous reactions to drugs are poorly characterized. The cutaneous lymphocyte-associated antigen (CLA) is a skin-homing T cell receptor that defines T lymphocytes associated with the cutaneous immune response. We studied the percentage and activation phenotype of circulating CLA+ T cells in drug allergic patients and healthy controls. METHODS: PBMCs were isolated from heparinized venous blood by Ficoll density gradient. Lymphocytes were stained for flow cytometry with anti-CLA, anti-CD3 and anti-HLA-DR mAbs. Five-parameter analysis was performed on an Ortho Cytoron Absolute flow cytometer. RESULTS: We found increased percentages of circulating CLA+ T cells in drug-allergic patients compared to controls. Moreover, CLA+ T cells from drug-allergic individuals expressed a higher percentage of the T cell activation marker HLA-DR. CONCLUSIONS: These results suggest that CLA+ T cells may play a role in the pathology of delayed cutaneous reactions to drugs. Further studies are in progress to elucidate the role of skin-homing T cells in allergic reactions to drugs.
[Etiology of growth retardation in children of adolescent mothers].
The influence of some nutritional and hormonal factors in the growth failure detected in children of teenage mothers belonging to medium-low socioeconomic level (SEL) was studied. They were compared with children of mothers older than twenty years of the name SEL. Only growth retarded children of teenage mothers had significant delay in bone age, compared with chronological age (14.8 +/- 4.1 vs 18.2 +/- 2.2 months respectively). Children with growth failure had significantly lower plasma Zn (85.7 +/- 13.3 vs 94.6 +/- 17.9 micrograms/dl), Cu (106.2 +/- 32.5 vs 122.0 +/- 13.8 micrograms/dl) and hemoglobin (Hb) (11.7 +/- 2.1 vs 12.8 +/- 2.1 micrograms/dl) levels. No differences in plasmatic levels of thyrotropin, thyroid hormones and response of growth hormone to L-Dopa stimulation were detected in comparison with those of children with normal stature. We concluded that etiological factors of growth failure were similar in children of teenage and adult mothers according to the parameters analyzed. The increased prevalence of growth failure in children of teenage mothers may be due to a greater impact of the analyzed factors.
[Prevalence of endemic goiter among school children of central and southern Chile].
The prevalence of endemic goiter was evaluated during 1986 in 1,015 school age children from basic public schools of Santiago and Temuco, Chile. The prevalence of goiter, defined by WHO's standards was 7.6% as a whole, without differences related to children's geographical origin. A greater prevalence of goiter, in females than in males, which increased with age, was detected. Prevalence of endemic goiter decreased from year 1982 to year 1986 from 18.8% to 7.4% in similar samples of school children from Santiago. This change may be due to preventive iodination of table salt.
[Pubertal characteristics of school girls in the Metropolitan region].
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[Evaluation of height during puberal development].
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[Growth and development of children of adolescents of middle-low socioeconomic class. II: 30 months of life].
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