Chronic overcrowding decreases cytoplasmic free calcium levels in T lymphocytes of aged CBA/CA mice

Intracellular calcium concentration is a sensitive marker of the homeostasis of living cells, and its increase is an essential step of T lymphocyte activation. Changes in the environment provoke an adaptive stress-response of the organism. In our present work we have investigated the effect of chronic overcrowding on resting and lectin-stimulated cytoplasmic free calcium concentration of splenic T lymphocytes from young and aged CBA/CA mice (50 animals total). The animals were kept under ‘normal’ (68 cm²/animal) or ‘overcrowded’ (22 cm²/animal) conditions for 3 months. Young animals showed no change in resting and stimulated calcium after overcrowding. T cells from aged mice, however, displayed significantly smaller levels of both resting and lectin-stimulated intracellular calcium concentration (p<0.01 each), as compared to those of the non-stressed, aged animals. This inadequate adaptation in the calcium metabolism of T lymphocytes may significantly contribute to the diminished immune response of the aged in stress.     

Viral infection associated with mortality in the oyster Crassostrea gigas Thunberg]

Virus particles and their morphogenesis have been observed in the cytoplasm of connective cells in the Japanese Oyster Crassostrea gigas. This virus seems to be similar to those described in the Portuguese Oyster Crassostrea angulata when high rates of mortality were recorded in 1970-1973 and those found in gill disease of this species.     

Growth inhibitory effect of Hcc-1/CIP29 is associated with induction of apoptosis, not just with G2/M arrest

No Abstract. .Received 4 March 2005, accepted: 26 April 2005     

Newly synthesized elastin is associated with neoplastic epithelial cells in human mammary carcinoma

Summary Indirect immunofluorescence with a purified antiserum to human foetal elastin has identified newly synthesized elastin on the membranes of neoplastic epithelial cells in human mammary carcinoma.This research was supported by a project grant from the Medical Research Council, London.     

Enhanced susceptibility of T lymphocytes to oxidative stress in the absence of the cellular prion protein

The cellular prion glycoprotein (PrP^C) is ubiquitously expressed but its physiologic functions remain enigmatic, particularly in the immune system. Here, we demonstrate in vitro and in vivo that PrP^C is involved in T lymphocytes response to oxidative stress. By monitoring the intracellular level of reduced glutathione, we show that PrP^−/− thymocytes display a higher susceptibility to H₂O₂ exposure than PrP^+/+ cells. Furthermore, we find that in mice fed with a restricted diet, a regimen known to increase the intracellular level of ROS, PrP^−/− thymocytes are more sensitive to oxidative stress. PrP^C function appears to be specific for oxidative stress, since no significant differences are observed between PrP^−/− and PrP^+/+ mice exposed to other kinds of stress. We also show a marked evolution of the redox status of T cells throughout differentiation in the thymus. Taken together, our results clearly ascribe to PrP^C a protective function in thymocytes against oxidative stress.     

In vitro proliferation of human large granular lymphocytes with v-raf/v-myc recombinant retrovirus

The effect of infection with a retrovirus carrying v-raf/v-myc oncogenes (J2 virus) on the in vitro proliferation of human large granular lymphocytes (LGL) was investigated. LGL infected with J2 virus (J2LGL), unlike uninfected cells, grew with a proliferation peak eight days after infection. Such cells retained the morphology and functional properties typical of LGL. Furthermore, 5% of J2LGL produced virus the day after infection, whereas non-virus production was detectable five days later. These data indicate that J2 virus provides a transient mitogenic signal for LGL.     

Dephosphorylation and inactivation of Akt/PKB is counteracted by protein kinase CK2 in HEK 293T cells

Akt (PKB) is a critical kinase in cell-survival pathways. Its activity depends on the phosphorylation of Thr308 and Ser473, by PDK1 and mTORC2, respectively. We found that Akt can be further stimulated through phosphorylation of Ser129 by another kinase, CK2. Here we show that phosphorylation of Akt at Ser129 also facilitates its association with Hsp90 chaperone, thus preventing Thr308 dephosphorylation. This is supported by the following observations: (1) phospho-Thr308 decreases when Ser129 is mutated to alanine, (2) this decrease is abolished by cell treatment with okadaic acid (to inactivate PP2A) or geldanamycin (to inactivate Hsp90), (3) phosphorylation of Ser129 neither enhances the activity of PDK1 nor hampers the in vitro activity of PP2A on Thr308, but increases the Hsp90 association to Akt. These data support the view that the antiapoptotic potential of CK2 is at least in part mediated by its ability to maintain Akt in its active form.     

Rosette formation by human T and B lymphocytes in the presence of adrenergic and cholinergic drugs

Summary It was shown that adrenergic drugs, which increase the intracellular levels of cAMP, inhibit the rosette formation by T-lymphocytes, but stimulate the rosettes produced by B-lymphocytes. Cholinergic drugs, which increase the levels of cGMP, on the contrary, stimulate the formation of rosettes by T-lymphocytes but inhibit those produced by B-lymphocytes.Acknowledgments. This investigation was supported by Grant from National Council for Scientific and Technological Development (CNPq), Rio de Janeiro, Brazil.     

Studies on the relationships between biotin and the behaviour of B and T lymphocytes in the guinea-pig

Summary In biotin-deficient guinea-pigs the number of circulating neutrophils is increased; lymphocytes carrying B and T markers are decreased. Incubation with biotin increases significantly the number of lymphocytes carrying B and T markers, from biotin-deficient guinea-pigs; no increase was observed when the lymphocytes from normal guinea-pigs were incubated.     

Rosette formation by human T and B lymphocytes in the presence of adrenergic and cholinergic drugs.

It was shown that adrenergic drugs, which increase the intracellular levels of cAMP, inhibit the rosette formation by T-lymphocytes, but stimulate the rosettes produced by B-lymphocytes. Cholinergic drugs, which increase the levels of cGMP, on the contrary, stimulate the formation of rosettes by T-lymphocytes but inhibit those produced by B-lymphocytes.     

Lactacystin-induced apoptosis of cultured mouse cortical neurons is associated with accumulation of PTEN in the detergent-resistant membrane fraction

The tumor suppressor function of PTEN is attributed to its phospholipid phosphatase activity that dephosphorylates the plasma membrane phosphatidylinositol-(3,4,5)-triphosphate [PtdIns(3,4,5)P₃]. Implicit in this notion is that PTEN needs to be targeted to the plasma membrane to dephosphorylate PtdIns(3,4,5)P₃. However, the recruitment of PTEN to the plasma membrane is not fully understood. Here, we demonstrate PTEN accumulation in the detergent-insoluble fraction of neuronal cells in response to treatment by the proteasome inhibitor lactacystin. First, lactacystin induces apoptosis and the activation of caspase-3 in cultured cortical neurons. Second, PTEN undergoes proteolysis to form a truncated 50-kDa form that lacks parts of its C-terminal tail. Third, the truncated PTEN is stably associated with the detergent-insoluble fraction in which the plasma membrane marker protein flotillin-1 resides. Taken together, our results suggest that truncation and accumulation of PTEN to the detergent-insoluble membrane fraction are two events associated with the apoptotic signals of the proteasome inhibitor in cortical neurons.Received 24 March 2004; received after revision 26 May 2004; accepted 5 June 2004     

Alpha 1-adrenergic stimulation of ketogenesis and fatty acid oxidation is associated with inhibition of lipogenesis in rat hepatocytes

The effect of norepinephrine on fatty acid synthesis (3H2O incorporation into fatty acids), on fatty acid oxidation to CO2 and on ketogenesis was studied in isolated hepatocytes of fed rats. After incubation with norepinephrine (50 microM), lipogenesis was lower (5.7 +/- 1.1 nmoles 3H2O incorporated into fatty acids/mg dry weight/30 min) than in controls (7.5 +/- 1.7; n = 6, p less than 0.02). In contrast, (1-14C) palmitate conversion into total ketone bodies was increased to 10.9 +/- 1.8 nmoles/mg/30 min with norepinephrine, vs 8.5 +/- 1.6 in controls (p less than 0.05), and more (1-14C) palmitate was converted to 14CO2 with norepinephrine than in controls (1.48 +/- 0.10 nmoles/mg/30 min vs 1.06 +/- 0.11, p less than 0.05). The inhibitory effect of norepinephrine on lipogenesis was abolished by addition of the alpha 1-receptor blocker prazosin, but not by alpha 2 or beta-blockers. The results demonstrate that the ketogenic effect of norepinephrine is coupled with an inhibitory effect on lipogenesis which may be explained by diminished activity of acetyl-CoA carboxylase, diminished formation of malonyl-CoA and decreased activity of carnitine palmitoyl transferase I.     

Thyroid hormone receptor-mediated regulation of the methionine adenosyltransferase 1 gene is associated with cell invasion in hepatoma cell lines

The thyroid hormone T₃ regulates differentiation, growth, and development. We demonstrated that methionine adenosyltransferase 1A (MAT1A) was positively regulated by T₃ identified by cDNA microarray previously. The expression of the MAT1A was upregulated by T₃ in hepatoma cell lines overexpressing thyroid hormone receptors (TRs). Additionally, these findings indicate that MAT1A may be regulated by CCAAT/enhancer binding protein (C/EBP). The critical role of the C/EBP binding sites was confirmed by the reporter or chromatin immuno-precipitation (ChIP) assay. In addition, C/EBP was upregulated in hepatoma cells after T₃ treatment and ectopic expression of MAT1A inhibited cell migration and invasion in J7 hepatoma cells. Conversely, knockdown of MAT1A expression increased cell migration. Together, these findings suggest that the expression of the MAT1A gene is mediated by C/EBP and is indirectly upregulated by T₃. Finally, TR was downregulated in a small subset of hepatocellular carcinoma cells concomitantly reduced the expression of C/EBPα and MAT1A.