The influence of positive selection on RAG expression in thymocytes

The expression of recombination activating gene (RAG) products, responsible for T cell receptor (TcR) gene rearrangement, is shut off during positive selection of thymocytes. The precise stage at which this down-regulation occurs remains somewhat controversial. We have analyzed RAG-1 expression in thymocytes of TcR transgenic mice carried on selecting versus non-selecting genetic backgrounds, both by in situ hybridization on thymus sections and by polymerase chain reaction amplification of RNA from sorted cells. The data from several transgenic lines indicate that RAG expression is already reduced in immature, cortical, CD4⁺CD8⁺ cells in the presence of positively selecting major histocompatibility complex molecules, although complete shut-off is not achieved until the mature, medullary, single-positive stage. This finding has practical and theoretical significance for studies on the mechanism of positive selection.     

肝癌患者肝动脉导管栓塞后消化系统病变的观察

应用B超对168例施行肝动脉导管栓塞(TAE)治疗的肝癌患者进行了胆囊、胰腺和脾脏的动态观察,并对其中有明显上腹部疼痛的34例进行了胃镜对照检查。结果发现TAE后胆囊病变最常见(123/168),占73.2％;其次为胃、十二指肠病变,占15.5％(26/168);胰腺病变为1.2％(2/168);未见脾脏病变。结果表明TAE后的消化系统并发症并非少见。     

转小鼠金属硫蛋白基因集胞藻6803及其野生藻培养

通过摇瓶培养考察转小鼠金属硫蛋白基因集胞藻６８０３及其野生藻的光合自养培养过程中碳源浓度、氮源浓度和光照度对这两种藻生长的影响。野生藻的最适生长碳源浓度（０．０５－０．５ｇ／Ｌ）比转基因藻的最适生长碳源浓度（０．０２－０．０５ｇ／Ｌ）高。氮源浓度对转基因藻和野生藻的影响趋势相同。在０．３－４．５ｇ／Ｌ范围内,随着氮源浓度的增高,藻体生长的最大细胞浓度降低。转基因藻生长的最佳光照度为１５００ｌｘ,野     

Potentiation of glutamatergic agonist-induced inositol phosphate formation by basic fibroblast growth factor is related to developmental features in hippocampal cultures: neuronal survival and glial cell proliferation

We investigated the modulation by growth factors of phospholipase C (PLC)-linked glutamate receptors during in vitro development of hippocampal cultures. In defined medium, glial cells represent between 3 and 14% of total cell number. When we added basic fibroblast growth factor (bFGF) 2 h after plating, we found: (i) a neuroprotection from naturally occurring death for up to 5 days; (ii) a proliferation of glial cells from day 3; and (iii) a potentiation of quisqualate (QA)-induced inositol phosphate (IP) formation from 1 to 10 days in vitro (DIV) and 1S, 3R-amino-cyclopentane-1,3-dicarboxylate (ACPD) response from 3 to 10 DIV. The antimitotic cytosine-beta,D-arabinofuranoside (AraC) blocked glial cell proliferation induced by bFGF, but not neuroprotection. Under these conditions, the early potentiation of the QA response (1-3 DIV) was not changed, while the ACPD and late QA response potentiations were prevented (5-10 DIV). Epidermal growth factor was not neuroprotective but it induced both glial cell proliferation and late QA or ACPD potentiation. Surprisingly, the early bFGF-potentiated QA-induced IP response was blocked by 6, 7-dinitro-quinoxaline-2,3-dione (DNQX), suggesting the participation of ionotropic (RS)-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA)/kainate (KA) receptors. The delayed bFGF-potentiated ACPD-induced IP response is inhibited by (S)-alpha-methyl-4-carboxyphenylglycine (MCPG), indicating possible activation of glial metabotropic receptors. These results suggest that, in hippocampal cultures, bFGF modulates AMPA and metabotropic glutamate receptors linked to the IP cascade, possibly in relation to the regulation of neuronal survival and glial cell proliferation, respectively.     

EDWARD COTLIER AND ROBERT WEINREB, EDITORS Retinoblastoma in Transgenic Mice: Models of Hereditary Retinoblastoma

Retinoblastoma, the most common intraocular malignancy in childhood, has served as a paradigm for the study of genetic mechanisms of oncogenesis. The retinoblastoma susceptibility gene RB1 was the first tumor suppressor gene to be cloned, and genetic and molecular biologic studies of this tumor have greatly expanded the understanding of the mechanics of tumorigenesis. Human retinoblastoma has essentially no naturally occurring animal counterpart. The development of transgenic murine models of retinoblastoma have created an experimental tool for manipulation of a tumor gene system in vivo. These models have also enabled studies of new therapeutic modalities. This review outlines the development of the transgenic murine models of retinoblastoma, together with the genetic mechanisms of retinoblastoma origin. Current therapeutic innovations developed by means of the transgenic models are described.     

The effects of cyclosporin A,tamoxifen, and medroxyprogesterone acetate on the enhancement of Adriamycin cytotoxicity in primary cultures of human breast epithelial cells

Summary Adriamycin (Adr), the single most active agent used in the treatment of breast cancer, may become ineffective as treatment progresses due to the development of multidrug resistant (MDR) tumors. A major mechanism associated with MDR is increased P-glycoprotein (Pgp) expression. This study examined the abilities of the anti-estrogen tamoxifen (TAM) and the progestin medroxyprogesterone acetate (MPA) as well as cyclosporin A (CsA), a known resistance modifier, to enhance the cytotoxic effects of Adr on human breast epithelial cells (HBEC) in primary culture. Pgp and estrogen receptor (ER) expression were determined in each of the cultures by immunocytochemical assays using the monoclonal antibodies C219 and H222 Sp, respectively. The Adr-sensitive, Pgp-, ER+ MCF-7 cell line and the Adr-resistant, Pgp+, ER-MCF7-AdrR cell line were used as controls. Primary cultures were categorized as HBEC from tissues with or without previous chemotherapy. Pgp was detected in 1 of the 15 cell cultures from tissues without previous chemotherapy and in 5 of the 6 cell cultures from tissues previously exposed to chemotherapy. Incubation with either CsA or MPA plus Adr enhanced Adr toxicity in Pgp+ but not Pgp- cell cultures, whereas TAM had no effect on the sensitivity of any of the cultures. Of the 21 primary cultures of HBEC, 3 were ER+. There was no correlation between the enhancement of Adr cytotoxicity and ER status. The data suggest that MPA as well as CsA may be useful as modifying agents in overcoming Pgp-associated multidrug resistance.     

Effects of 1α,25-dihydroxy-vitamin D3 and calcipotriol on organotypic cultures of outer root sheath cells: a potential model to evaluate antipsoriatic drugs

In the human hair follicle, outer root sheath (ORS) cells constitutively express the hyperproliferation-associated keratins 6, 16 and 17 instead of keratins 1 and 10 found in interfollicular epidermis. In organotypic cultures, ORS cells form a stratified epithelium which in many respects resembles psoriatic skin: it has a hyperplastic tissue architecture and a poorly developed granular layer, and expresses hyperproliferation-associated keratins. Therefore, we studied the effects of the antipsoriatic compounds 1,25-dihydroxy-vitamin D₃ (1,25-(OH)₂-D₃) and its synthetic derivative calcipotriol on cultured ORS cells. In monolayer cultures, 10^–6 M 1,25-(OH)₂-D₃ or calcipotriol completely blocked ORS cell proliferation. This inhibitory effect was substantially reduced at 10^–8 M. Incubation of organotypic ORS cultures with both vitamin D analogues resulted in a marked thinning of the living cell compartment concomitant with a thickening of the horny layer. A reduced expression of differentiation markers such as keratins 10,16 and 17, involucrin and filaggrin paralleled the thinning of the stratum Malpighi. As determined by quantification of BrdU-positive cells, ORS cell proliferation was apparently not affected by the vitamin D analogues, indicating that these compounds mainly operate by accelerating the differentiation pathway within the suprabasal living cell compartment. No alteration in the expression of the 6- and 1-integrin chains was found.     

Virology studies and cell lines for prostate cancer

Immunological and biochemical probes for viral genomes and products, growth in cell culture, co-culture methods to activate latent genomes, use of activating agents, and electron microscopy have been used in efforts to demonstrate RNA viruses in prostate cancer. Despite findings of C-type particles and p30 antigens, the role of RNA viruses appears to be secondary, with activation of the virogene being a relatively uncommon occurrence. No compelling evidence for Herpes II or cytomegalovirus as etiologic agents has emerged, despite their common presence in the urogenital tract. Though the search for integration of fragments of viral genome into host DNA is still in progress, it appears unlikely that these viruses would account for a significant number of prostate carcinomas. Progress has been achieved in developing simple, reliable, primary culture methods for human prostatic tissue, using explants or dispersed cells. Three cell lines, all from metastatic foci, have been established, are characterized, and are available for distribution. One neonatal cell strain retains many properties of normal prostate.     

The influence of external sodium and potassium on lithium uptake by primary brain cell cultures at ‘therapeutic’ lithium concentration

The ionic regulating of lithium homeostasis and steady-state intra: extracellular lithium distribution in the brain can be approached by experimental methods using intact nerve cells in vitro. Primary cultures prepared from chick embryonic brain were applied to study the effect of extracellular sodium and potassium on the lithium uptake of nerve cells at therapeutic lithium concentration (1.5 mM). Lithium influx and the level of steady-state intracellular lithium were significantly reduced by increasing the external sodium concentration. At physiological extracellular sodium level, the steady-state content of lithium in the brain cells was about half of that observed in the presence of 10 mM sodium in the incubation media and the value of the intra: extracellular lithium distribution ratio was below 1. External potassium (0.5–3 mM) strongly inhibited lithium uptake of the nerve cells. Ouabain (10^-4 M) had no effect on this potassiumsensitive lithium uptake in Tyrode media. Sodium influx studied by isotope tracer methodology was higher in cultures preloaded with lithium as compared to that of the controls. It can be concluded that sodium and potassium ions, at physiological concentrations, significantly influence lithium uptake as well as the intra: extracellular lithium distribution in brain cell cultures.