Matrix-associated regions (MARs), AT-rich DNA segments that have an affinity for the nuclear matrix, have been shown to play a role in transcriptional regulation of eukaryotic genes. The present study demonstrates that a DNA element, called L2a, which has been implicated in the transcriptional regulation of the mouse CD8a gene encoding an important T cell coreceptor, is a MAR. Moreover, the identities of two nuclear proteins, L2a-P1 and L2a-P2, previously shown to bind to the L2a element, have been determined. The L2a-P1 protein found to be present in all CD8-positive T cell lines tested is SATB1, a known MAR-binding protein. The widely expressed L2a-P2 protein is CDP/Cux, a MAR-binding protein that has been associated with repression of gene transcription. Interaction of both proteins with the L2a element was studied using the missing nucleoside approach, DNase I footprinting, and electrophoretic mobility shift assays with wild type and mutant L2a elements. The data suggest that CDP/Cux bound to the L2a element is displaced by binding of SATB1 and the accompanying conformational change in the DNA lying between the primary binding sites of SATB1 and CDP/Cux. We suggest that displacement of CDP/Cux by SATB1 favors transcription of the CD8a gene, possibly by enhancing or altering its association with the nuclear matrix.

A partir de la evaluación de las dimensiones fractales y aplicando el concepto de variabilidad y armonía matemática intrínseca celular (AMI), se desarrolló un método matemático de aplicación clínica para el diagnóstico de células preneoplásicas y neoplásicas del epitelio escamoso cervical, el cual supera el diagnóstico de ASCUS (células escamosas atípicas de significado no determinado). A partir de un método desarrollado previamente para el diagnóstico de células normales, ASCUS y L-SIL, se realizaron permutaciones estructurales fractales con los valores generales de la AMI y de variabilidad fractal para normalidad y enfermedad, buscando los prototipos generales de células normales, preneoplásicas y neoplásicas. Se midieron cinco células ASCUS y cinco cancerígenas del epitelio escamoso del cuello uterino y se encontró que para la normalidad hay 18 prototipos, mientras que para la anormalidad 44, incluyendo todos los estados de evolución hasta carcinoma.Estos resultados fueron confirmados al comparar los resultados obtenidos por las técnicas convencionales con los obtenidos por esta metodología; lo que hace pensar que se desarrolló una nueva metodología que permite diferenciar los distintos tipos de células del epitelio escamoso del cuello uterino (normales o cancerígenas).

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Previous transgenic-reporter and targeted-deletion studies indicate that the subset-specific expression of CD8αβ heterodimers is controlled by multiple enhancer activities, since no silencer elements had been found within the locus. We have identified such a silencer as L2a, a previously characterized ~220 bp nuclear matrix associating region (MAR) located ~4.5 kb upstream of CD8α. L2a transgenes driven by the E8I enhancer showed no reporter expression in thymic subsets or T cells in splenic, inguinal and mesenteric lymph node peripheral T cells. Deletion of L2a resulted in significant reporter de-repression, even in the CD4+CD8+ double positive (DP) thymocyte population. L2a contains binding sites for two MAR-interacting proteins, SATB1 and CDP. We found that that binding of these factors was markedly influenced by the content and spacing of L2a sub-motifs (L and S) and that SATB1 binds preferentially to the L motif both in vitro and in vivo. A small fraction of the transgenic CD8+ single positive (SP) thymocytes and peripheral CD8+ T cells bypassed L2a-silencing to give rise to variegated expression of the transgenic reporter. Crossing the L2a-containing transgene onto a SATB1 knockdown background enhanced variegated expression, suggesting that SATB1 is critical in overcoming L2a-silenced transcription.

DHA has been established. We propose that DHAcontaining lysophosphatidylcholine (DHA-LPC), obtained from DHA-rich eggs may be a suitable form of DHA and choline (the precursor of acetylcholine) supplementation. We evaluated the effectiveness of DHA-LPC to increase DHA and acetylcholine concentration in the brain of pups born from female rats supplemented with DHA-LPC before and during pregnancy. We also evaluated the effect of DHA supplementation on learning and memory capabilities of pups through the Skinner test for operant conditioning. Female Wistar rats received 40-day supplementation of DHA-LPC (8 mg DHA/kg b.w/daily.), before and during pregnancy. After delivery, plasma, erythrocyte, liver, and adipose tissue DHA and plasma choline were analyzed. Brains from 60 day-old pups separated into frontal cortex, cerebellum, striatum, hippocampus, and occipital cortex, were assessed for DHA, acetylcholine, and acetylcholine transferase (CAT) activity. Pups were subjected to the Skinner box test. DHA-LPC supplementation produces higher choline and liver DHA contents in the mother's plasma and increases the pups' DHA and acetylcholine in the cerebellum and hippocampus. CAT was not modified by supplementation. The Skinner test shows that pups born from DHA-LPC supplemented mothers exhibit better scores of learning and memory than the controls. Conclusion: DHA-LPC may be an adequate form for DHA supplementation during the perinatal period. KEY-WORDS: Brain acetylcholine -Choline -DHA supplementation -Lysophospholipids -Skinner box test.