Snapper (Pagrus auratus) leucocyte proliferation is synergistically enhanced by simultaneous stimulation with LPS and PHA

Important channels of communication between mammalian leucocytes have long been recognised. Here, data are reported that suggest similar integrations may occur between snapper leucocytes upon mitogen stimulation. Cell surface immunoglobulin (IgM) expression was used in conjunction with intracellular fluorescence staining and flow cytometry to differentiate proliferating peripheral blood leucocyte subsets (PBLs). Independent activation using phytohaemagglutinin (PHA) or lipopolysaccharide (LPS) drove both mIg(-)and mIg(+)cells into cycle. It is not known if the proliferation of mIg(+)cells was mediated by a mutually exclusive effect of the mitogen on each cell population, cognate cellular interaction or a soluble growth factor. Simultaneous activation of PBLs with PHA and LPS consistently induced significantly more cells to proliferate than the sum of proliferating cells stimulated solely with PHA or LPS. Together, the results suggest that different leucocyte subsets have the capability to influence their respective responses to mitogenic stimulation. Therefore, like in the mammalian immune system, communication may occur between snapper leucocyte subsets.     

Rhythmic changes in metabolism of dopamine in the chick retina: the importance of light versus biological clock

Rhythmic changes in dopamine (DA) content and metabolism were studied in retinas of chicks that were adapted to three different lighting conditions: 12-h light : 12-h dark (LD), constant darkness (DD) and continuous light (LL). Retinas of chicks kept under LD conditions exhibited light-dark-dependent variations in the steady-state level of DA and the two metabolites of DA, i.e. 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanilic acid (HVA). Concentrations of DA, DOPAC and HVA were high in light hours and low in dark hours of the LD illumination cycle. In retinas of chicks kept under DD, the content of DA, DOPAC and HVA oscillated in a rhythmic manner for 2 days, with higher values during the subjective light phase than during the subjective dark phase. The amplitudes of the observed oscillations markedly and progressively declined compared with the amplitudes recorded under the LD cycle. In retinas of chicks kept under LL conditions, levels of DA, DOPAC and HVA were similar to those found during the light phase of the LD cycle. Changes in the retinal contents of DA and HVA did not exhibit pronounced daily oscillations, while on the first day of LL the retinal concentrations of DOPAC were significantly higher during the subjective light phase than during the subjective dark phase. Acute exposure of chicks to light during the dark phase of the LD cycle markedly increased DA and DOPAC content in the retina. In contrast, light deprivation during the day decreased the retinal concentrations of DA and DOPAC. It is suggested that of the two regulatory factors controlling the level and metabolism of DA in the retina of chick, i.e. light and biological clock, environmental lighting conditions seem to be of major importance, with light conveying a stimulatory signal for the retinal dopaminergic cells.     

Genomic organization and expression profile of the human and mouse <Emphasis Type="Italic">WAVE</Emphasis> gene family

The WAVE gene family, which contains three members, has been shown to play a major role in the actin polymerization and cytoskeleton organization processes. We have identified the WAVE3 gene from Chromosome (Chr) 13q12, as being involved in one of the breakpoints of a t(1:13)(q21:q12) reciprocal translocation, in a patient with ganglioneuroblastoma (Sossey-Alaoui et al. 2002; Oncogene 21: 5967–5974). We have also reported the cloning of the mouse Wave3. During our analysis of the human gene map, we also noted that WAVE2 maps to Chr region lp35-36, which frequently undergoes loss of heterozygosity and deletion in advanced stage neuroblastoma. These data clearly indicate a possible involvement of the WAVE genes in the pathogenesis of neuroblastoma. In this study, we report the complete genomic organization and expression profile of the three human WAVE genes and their mouse orthologs. We show that the WAVE genes have distinctive expression patterns in both adult and fetal human and mouse tissues. We also show a high level of conservation between these genes, in both the nucleotide and protein sequences. We finally show that the genomic structure is highly conserved among these genes and that the mouse Wave genes map to chromosome regions that have synteny in the human genome. The gene content in these syntenic regions is also conserved, suggesting that the WAVE genes are derived from a common ancient ancestor by genome duplication. The genomic characterization and expression analysis of the WAVE genes provide the basis towards understanding the function of these genes. It also provides the first steps towards the development of mouse models for the role of the WAVE genes in actin and cytoskeleton organization in general, and in the development of neuroblastoma in particular.     

Competitive exclusion and coexistence of universal grammars

Universal grammar (UG) is a list of innate constraints that specify the set of grammars that can be learned by the child during primary language acquisition. UG of the human brain has been shaped by evolution. Evolution requires variation. Hence, we have to postulate and study variation of UG. We investigate evolutionary dynamics and language acquisition in the context of multiple UGs. We provide examples for competitive exclusion and stable coexistence of different UGs. More specific UGs admit fewer candidate grammars, and less specific UGs admit more candidate grammars. We will analyze conditions for more specific UGs to outcompete less specific UGs and vice versa. An interesting finding is that less specific UGs can resist invasion by more specific UGs if learning is more accurate. In other words, accurate learning stabilizes UGs that admit large numbers of candidate grammars.     

Exposure to Thiodan results in lipofuscin accumulation in hepatocytes of the freshwater catfish Tandanus tandanus

We investigated the effect of time after pulse exposure to 1.0 microg l(-1) endosulfan (applied as Thiodan) on endosulfan residues in the liver and ultrastructural changes in the hepatocytes of the freshwater catfish Tandanus tandanus. Time after exposure did not affect the mean residue level in the liver. After exposure to endosulfan, residues in the liver were 227.47 microg kg(-1) after 1 d and 282.83 microg kg(-1) after 28 d; residues in the bile were 313.97 microg kg(-1) after 1 d and 334.53 microg kg(-1) after 28 d. At the end of 28 d exposure, lipofuscin was present in up to 69% of hepatocytes of fish containing residues of endosulfan, but absent from control fish. There was a statistically significant increase in the percentage of pyknotic nuclei and altered rough endoplasmic reticulum 28 d after exposure. The mean percentage of cells with altered endoplasmic reticulum ranged from 12.93% (Day 1) to 7.50% (Day 28) for control fish, while for exposed fish it increased from 14.30% (Day 1) to 35.00% (Day 28). The mean percentage of cells with pyknotic nuclei increased from 1.1 to 2.1% in control fish and from 3.8 to 9.6% in exposed fish. Other ultrastructural changes included increased ultrastructural heterogeneity, progressive vacuolation and fractionation of rough endoplasmic reticulum, accumulation of lysosomes and residual bodies, intranuclear inclusions and pseudoinclusions, membrane whorls and myelinated bodies. Protracted senescence was one of the main features of endosulfan toxicity to T. tandanus hepatocytes.     

Daxx overexpression in T-lymphoblastic Jurkat cells enhances caspase-dependent death receptor- and drug-induced apoptosis in distinct ways

The role of Daxx, in particular, its ability to promote or hinder apoptosis, still remains controversial. In order to elucidate the functional relevance of Daxx in apoptosis signaling of malignant lymphocytes, Jurkat T-cells were stably transfected with a Daxx-expressing vector or with the respective Daxx-negative control vector. We thus demonstrate that ectopic expression of Daxx substantially increases the rate of apoptosis upon incubation with death receptor agonists such as Fas and TRAIL as well as upon incubation with the cytotoxic drug doxorubicin (DOX). Analysis of the molecular changes induced in the extrinsic and intrinsic apoptosis pathways reveals that augmentation of apoptosis by Daxx overexpression is conveyed by distinctly different mechanisms. Although enforced apoptosis caused by ectopic Daxx expression is caspase-dependent in both cases, major differences between Fas/TRAIL-induced apoptosis and doxorubicin-induced apoptosis are observed in expression patterns of X-linked inhibitor of apoptosis (XIAP), p53, Bid, ZIP kinase, and prostate apoptosis response gene 4 (Par-4). Moreover, we could show that addition of a CD95 blocking antibody to the clones treated with doxorubicin was able to increase apoptosis as compared to doxorubicin treatment alone and was accompanied by an enhancement of the mitochondrial branch of apoptosis. In conclusion, we here outline the major molecular mechanisms underlying the apoptosis-promoting effect of Daxx in neoplastic lymphocytes and demonstrate fundamental molecular differences elicited by the overexpression of Daxx in the extrinsic and intrinsic signaling pathways.