Showing papers by "Ochsner Medical Center published in 2002"

Tumorigenesis and Aberrant Signaling in Transgenic Mice Expressing the Human Herpesvirus-8 K1 Gene

Abstract: BACKGROUND The K1 gene of human herpesvirus-8 (HHV-8; also known as Kaposi's sarcoma-associated herpesvirus) encodes a transmembrane signaling protein that elicits cellular activation events. To evaluate the potential role of K1 in HHV-8-associated pathogenesis, we produced transgenic mice expressing the HHV-8 K1 gene under the transcriptional control of the simian virus 40 promoter. METHODS Three independent heterozygous transgenic K1 mouse lines were generated from founder mice. Mouse splenic and thymic lymphocytes and tumor tissues were analyzed for the expression of cytokines involved in inflammatory and immune responses, including tumor necrosis factor-alpha (TNF-alpha), interleukin 6 (IL-6), basic fibroblast growth factor (bFGF), and interleukin 12 (IL-12); for the activation of the transcription factors nuclear factor-kappaB (NF-kappaB) and the B cell-specific transcription factor Oct-2; and for the activation of the Src and Syk family kinases, components of B-cell receptor-induced signal-transduction pathways. RESULTS Expression of bFGF was increased in K1-transgenic mice as compared with nontransgenic mice, whereas expression of TNF-alpha and IL-6 did not differ using reverse transcriptase-polymerase chain reaction. K1-transgenic mice showed substantially less serum IL-12 induction than did nontransgenic mice when challenged with a lipopolysaccharide. B lymphocytes from K1-transgenic mice but not from nontransgenic mice showed constitutive activation of NF-kappaB and Oct-2. K1 expression in human B lymphocytes stimulated NF-kappaB-dependent promoter activity. B lymphocytes from K1-transgenic mice also showed increased phosphorylation of Lyn, a Src family tyrosine kinase, and enhanced Lyn activity. Tumors in K1-transgenic mice showed features indicative of a spindle-cell sarcomatoid tumor and a malignant plasmablastic lymphoma. The pattern of cytokine, transcription factor, and Lyn kinase activity in the lymphoma was similar to that in B lymphocytes from K1-transgenic mice. CONCLUSION K1 may be involved in the activation of NF-kappaB signaling. The enhanced NF-kappaB activity in nonmalignant lymphocytes of K1 mice and its persistence in lymphoma tumors of these mice suggest that the K1 mouse may be a model of premalignancy.

Performing procedures on the newly deceased

Abstract: The report explores whether it is necessary to obtain informed consent before training procedures can be performed on the newly dead, weighing two conflicting considerations: the importance of protecting the integrity of the newly deceased with respect to family, society, and profession, and the need to educate health care providers. The report considers arguments against the need for consent, namely the benefit of having well-trained physicians, the contention that alternative models for teaching are inadequate, and the concerns that if consent were required, it rarely would be granted. These considerations are weighed against the value of respecting the sensitivities not only of families but also of medical teams, and the importance of preserving trust in the medical profession. The report concludes that performing procedures on the newly dead must proceed not randomly but rather in the context of a structured training sequence completed under close supervision, and recommends that physicians request permission from family members before performing such procedures.

Ethanol decreases the efficiency of phosphorylation of thymidine kinase in a human T-lymphocytic cell line.

Abstract: Background: Thymidine kinase (TK) and thymidylate kinase (TMPK) are the two rate-limiting enzymes in the cascade of activation of the anti-human immunodeficiency virus (HIV) drug 3′-azido-3′-deoxythymidine (AZT) to its active triphosphate form. We examined the effect of ethanol and a combination of ethanol and AZT on TK and TMPK activities in human Jurkat T cells. Methods: Jurkat T cells were exposed to 0.2 and 0.5% (v/v) ethanol concentrations alone or in combination with 5 or 10 μM AZT for 48 hr in growth medium. TK and TMPK activities were determined by measuring the conversion of [3H] substrates (thymidine or AZT for TK and thymidine monophosphate for TMPK) to their respective monophosphate or diphosphate forms. The effect of ethanol on the transcriptional activity of TK was determined by reverse transcription–polymerase chain reaction and on the growth of Jurkat cells by [3H]-thymidine incorporation and cell-cycle analysis. Results: Treatment of Jurkat cells with 0.2 and 0.5% ethanol concentrations resulted in 25 and 50% decreases (p≤ 0.05) in TK activity, respectively. No significant changes were observed in the TMPK activities. However, ethanol decreased the formation of thymidine diphosphate from thymidine in coupled TK/TMPK reactions, suggesting that decreases in TK activity could result in an overall decrease in the phosphorylation of AZT. The effect of ethanol on TK was independent of its transcript level. AZT in combination with ethanol decreased the inhibitory effect of ethanol on TK activity. However, it did not block the ethanol effect even at higher concentrations. Ethanol significantly decreased the proliferative capacity and cell cycle progression of the Jurkat cells. Conclusions: Our in vitro study in human Jurkat T cells indicates that at physiologically achievable concentrations in humans, ethanol can decrease TK activity through decreases in cell proliferation, and it suggests that ethanol ingestion in HIV-1–infected individuals could compromise activation of AZT and related drugs through decreased TK activity.