The effects of exposure to sediment-associated tri-
n-butyltin chloride (TBT) and triphenyltin chloride (TPhT) were examined in the euryhaline European flounder,
Platichthys flesus (L.). The effects ...were quantified by measuring the changes in sodium efflux, Na
+/K
+-ATPase activity and the numbers, areas and distribution of chloride cells in the gills of freshwater-adapted fish, following a rapid transfer to seawater. After transfer, the Na
+/K
+-ATPase activity and the sodium efflux significantly increased in both the TPhT and control groups but not in the TBT group. However, Na
+/K
+-ATPase activity and the sodium efflux in the TPhT group had returned to pre-salinity transfer levels by day 15 after the initial exposure to TPhT. Morphological changes in the numbers and areas of chloride cells, known to be associated with seawater adaptation, took place in the control group, i.e. there was a significant reduction in the number of lamellar chloride cells accompanied by an increase in the number of interlamellar chloride cells. There was a reduction in the numbers of lamellar chloride cells in the TBT-exposed group following transfer to seawater but the mean number was significantly higher than the control group by the end of the experiment. In the TPhT-exposed group, the reduction was not significantly different to that seen in the control group. By the end of the experiment, both organotin-exposed groups had significantly lower mean numbers of interlamellar chloride cells than the control group. Before transfer to seawater, the mean areas of lamellar and interlamellar chloride cells of all three groups were not significantly different. On transfer, the mean areas of lamellar chloride cells in the control group became significantly smaller than the mean areas of the organotin groups. There was no significant difference in the mean areas of interlamellar chloride cells in the control and TBT groups between the start and finish of the experiment but there was a significant increase in the mean area of TPhT-treated animals at the end of the experiment when compared to the control group. The results presented in this study lead to the conclusion that tri-
n-butyltin chloride and triphenyltin chloride in sediments are capable of significantly disrupting both the physiological as well as morphological components of ionic regulatory functions of an estuarine fish, at concentrations currently found in estuarine sediments.
We have investigated the origin of intraepithelial lymphocytes (IEL) populations in the murine gut, using reconstitution experiments in which the presence of thymus-derived cells of host or donor ...origin is rigorously controlled: RAG-/- mutant mice which have no T cells, were injected either with the bone marrow (BM) cells of nude mice or with selected peripheral lymph node (LN) T cells of euthymic mice. In thymectomized RAG-/- mice, injection of BM cells from nude mice led, after 2 mo, to the development of a peripheral B cell compartment and to the appearance, in the gut, of IEL bearing homodimeric CD8 alpha chains and either gamma/delta or alpha/beta TCR. In RAG-/- mice with a thymus, a similar injection led to complete lymphoid reconstitution, with the additional appearance in the gut of CD4+, CD8 alpha/beta+ or CD4+CD8 alpha/alpha+ IEL, all bearing alpha/beta TCR. In contrast, injection of LN T cells into these mice reconstituted a gut IEL population made of CD4+, CD8 alpha/beta+, or CD4+ CD8 alpha/alpha+ cells, all bearing alpha/beta TCR; CD8 alpha/alpha+ TCR-gamma/delta+ or alpha/beta+ IEL were not observed. These results demonstrate that the thymus and/or thymic-derived peripheral T cells are absolutely required for the generation of CD4+, CD8 alpha/beta+, and CD4+CD8 alpha/alpha+ IEL, which are thus thymus dependent. In contrast, TCR+ CD8 alpha/alpha+ IEL appear in the absence of the thymus, and thus are thymus independent.
We showed in a recent study that topical retinyl palmitate prevented UV-B–induced DNA damage and erythema in humans. Given that retinyl palmitate is a precursor of retinoic acid, the biological form ...of vitamin A that acts through nuclear receptors, we wondered whether these protective effects toward UV-B exposure were either receptor dependent or linked to other properties of the retinoid molecule such as its spectral properties. We determined the epidermal retinoid profile induced by topical retinoic acid in hairless mice and analyzed its effect on markers of DNA photodamage (thymine dimers) and apoptosis following acute UV-B exposure; we compared these effects to those induced by other natural topical retinoids (retinaldehyde, retinol and retinyl palmitate) which do not directly activate the retinoid receptors. We then analyzed the direct action of these retinoids on UV-B–induced DNA damage and apoptosis in cultured A431 keratinocytes. Topical retinoic acid significantly decreased (≈50%) the number of apoptotic cells, as well as the formation of thymine dimers in the epidermis of mice exposed to acute UV-B. Interestingly, the other topical retinoids decreased apoptosis and DNA damage in a similar way. On the other hand, neither retinoic acid nor the other retinoids interfered with the apoptotic process in A431 keratinocytes exposed to UV-B, whereas DNA photodamage was slightly decreased. We conclude that the decrease of apoptotic cells in hairless mouse epidermis following topical retinoids and UV-B irradiation reflects a protection of the primary targets of UV-B (DNA) by a mechanism independent of the activation of retinoid nuclear receptors, rather than a direct inhibition of apoptosis.
The effects of exposure ot sediment-associated tri-n-butyltin chloride (TBTCl) were examined in the euryhaline European flounder, Platichthys flesus (L.). The effects wree quantified by measuring the ...changes in sodium efflux; Na+/K+ -ATPase activity; and the numbers, areas, and distribution of chloride cells in the gills of freshwater-adapted fish, following a rapid transfer to seawater.
The effect of the water pool size (ω°) on the average number of the probe molecules located at the interface and on the monophotonic ionization yield has been examined in anionic and cationic reverse ...micelles, using tetramethylbenzidine (TMB) as an easily photoionizable solute. The main conclusions of the present study are as follows: (1) The number of molecules located at the interface parallels that of the square radius of the water pool and partly depends on the compactness of the interface. (2) Owing to the high concentration of the counterions, the variations of the electrical potential remain low, when ω° increases from 18 to 40, although the fraction of free water increases significantly. (3) The charge separation efficiency (Y TMB + ) varies as the fraction of free water in the water pool. Such Y TMB + variations are interpreted in changes in the fundamental energy of the excess electron at the interface with ω°. (4) The comparison of Y TMB + values, obtained in the present work with previous data in direct micelles, points out the influence of the sign of the curvature radius on the photoionization reaction.
Irreversible electroporation (IRE) is a novel form of tissue ablation that uses high-current electrical pulses to induce pore formation of the cell lipid bilayer, leading to cell death. The safety of ...IRE for ablation of hepatocellular carcinoma (HCC) has been established. Outcome data for ablation of HCC by IRE are limited, but early results are encouraging and suggest equivalency to the outcomes obtained for thermal ablation for appropriately selected, small (<3 cm) tumors. Long-term oncologic efficacy and histopathologic response data have not been published, and therefore, application of IRE for the treatment of HCC should still be viewed with caution.
Dityrosine formation, via radiolytic production of N3{square root} and TyrO{square root} free radicals by gamma and pulse radiolysis, has been studied in buffered water and direct micellar solutions ...of tyrosine. Steady-state studies (60Co) allowed, for the first time, the determination of dityrosine yield in the different systems. It is shown that, whatever the interfacial charge is, micelles exert an efficient protection against tyrosine oxidation when compared to aqueous solutions. Such an effect is related to a different location of the reactants in the different media.
Most gut intraepithelial cells (IEL) of the mouse are T cells that bear CD8 molecules, present either as alpha-beta chain heterodimers (CD8 beta+) or as alpha chain homodimers (CD8 beta-). All CD8 ...beta+ IEL bear alpha/beta T cell receptors (TCR); CD8 beta- IEL bear either alpha/beta or gamma/delta TCR and are considered to be a thymus-independent (TI) population, probably arising locally from a small fraction of CD3- IEL containing the recombinant activating gene RAG proteins. Here we report that TI CD8 beta- IEL, whether bearing alpha/beta or gamma/delta TCR, contain, in normal mice, mRNAs for both zeta and Fc epsilon RI gamma chains. These chains are present in their CD3-TCR complexes as homo- or heterodimers. In contrast, only zeta chain mRNA and homodimers are found in gut CD8 alpha/beta+ IEL and in peripheral T lymphocytes. Intestinal CD3- precursor cells contain only gamma chain, and CD3- IL-2R+ thymocyte precursors only zeta chain mRNAs. Only very primitive thymocyte precursors contain detectable gamma chain mRNA, and it thus appears that Fc epsilon RI gamma chain use is switched off at a very early stage during thymocyte differentiation. Thus, T cell differentiation in the gut epithelium differs from that occurring in the thymus, from which CD8 beta+ IEL appear to derive. Use of different TCR transducing modules and CD8 accessory molecules between the TI and the thymus-derived T cell populations provides an explanation for their difference in reactivity to antigenic stimulations and thus in selection of repertoires.
Abstract
The variability of predominant Mycoplasma bovis surface antigens in the presence of specific immune pressure was analyzed in an in vitro assay to determine if M. bovis could escape immune ...destruction. We have shown that serum antibodies from immunized or experimentally infected calves and monoclonal antibodies which specifically react with previously characterized or as yet undefined major M. bovis membrane surface proteins cause repression of expression or shortening of the target protein, or induce switching to expression of an antigenically distinct variant protein. We have further demonstrated that removal of the inducing antibody results in reversion to the original phenotype. These results suggest that the level of expression and the length of M. bovis surface antigens in the host is modulated by cognate antibodies. According to the surface antigenic variation systems, random selection of preexisting variants resistant to antibody-mediated inhibition or direct regulation of gene expression may be means by which this organism evades host immune defences.
Exosomes are small vesicles secreted by different immune cells and which display anti‐tumoral properties. Stimulation of RBL‐2H3 cells with ionomycin triggered phospholipase D2 (PLD2) translocation ...from plasma membrane to intracellular compartments and the release of exosomes. Although exosomes carry the two isoforms of PLD, PLD2 was enriched and specifically sorted on exosomes when overexpressed in cells. PLD activity present on exosomes was clearly increased following PLD2 overexpression. PLD2 activity in cells was correlated to the amount of exosome released, as measured by FACS. Therefore, the present work indicates that exosomes can vehicle signaling enzymes.
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