Exposure to Contaminated River Water is Associated with Early Hatching and Dysregulation of Gene Expression in Early Life Stages of the Endangered Copper Redhorse (Moxostoma hubbsi)

The copper redhorse (Moxostoma hubbsi) is an endangered fish that spawns exclusively in the Richelieu River (Quebec, Canada). Tributaries of the Richelieu are contaminated with high levels of current-use pesticides, which may impact early-life stage (ELS) copper redhorse and other native fishes. We assessed the effects of exposure to contaminated river water on ELS copper redhorse and river redhorse (Moxostoma carinatum), a related fish that shares the copper redhorse's spawning grounds and nursery habitat. A riverside flow-through system was used to expose copper and river redhorse embryos (1000 each) to Richelieu River water or laboratory water as a control. Fish were maintained until 14 days posthatch, and water samples were taken daily for chemical analysis. Following a heavy rain event, concentrations of two neonicotinoid pesticides, clothianidin and thiamethoxam, exceeded water quality guidelines for aquatic life (20 ng/L). Using nontargeted screening, we tentatively identified an additional 24 pharmaceutical and personal care products and 23 pesticides in river water. Effects of river water on ELS fish were observed in both species, but the copper redhorse appeared to be more sensitive. Fish exposed to river water hatched 10.7 (copper redhorse) and 2.4 (river redhorse) cumulative degree days earlier than controls. Copper redhorse survival was significantly lower in river water (73 ± 16%) compared to laboratory water (93 ± 3%), whereas river redhorse survival was similar between treatments (84 ± 6% and 89 ± 4%, respectively). Sequencing of copper redhorse larvae RNA revealed 18 differentially expressed genes (DEGs) following 14 days of exposure to river water. Eight up-regulated DEGs were linked to immune function and injury response, and seven down-regulated DEGs were involved with digestion and nutrient absorption. The present study provided valuable data on the effects of ELS exposure to a real-world mixture of contaminants in two fish species of concern. Environ Toxicol Chem 2022;41:1950-1966. © 2022 SETAC.

Biological markers to establish a relationship between the health status of the St. Lawrence River yellow perch (Perca flavescens) with a gradient of anthropogenic disturbances

Since the mid-1990s, the decline of the yellow perch population of Lake Saint-Pierre (hereinafter LSP) in Quebec, Canada has been the subject of several research programs. The combined effect of habitat deterioration, the presence of invasive species, and poor water quality negatively affected the yellow perch population in this lake. In 2013, we sampled yellow perch (larvae, juveniles and adults) at six sites along the St. Lawrence River representing a gradient of increasing human influences from upstream to downstream and measured several biomarkers including retinoid compounds (vitamin A). In the most contaminated sites (LSP, north and south shores), we found that retinoid stores were decreased in all three stages of development. To corroborate these results and to test other biomarkers, we once again sampled yellow perch (adults only) from the same sites. Results from our 2014 and 2015 samplings confirmed that LSP yellow perch appeared to be at a disadvantage compared to fish from upstream populations. Individuals from LSP have lower acetylcholinesterase (AChE) activity as well as lower retinoid levels in liver and plasma. These fish were also marked by lower levels of antioxidants such as lycopene and vitamin E. A discriminant analysis of this set of results confirmed that the yellow perch of the LSP could be easily discriminated from those of the other sites (2014 and 2015) on the basis of liver retinoid and, to a lesser extent, of the liver tocopherol and protein concentration of the muscle, as well as AChE activity and DROH (all-trans-3,4-dehydroretinol) measured in plasma.

A major release of urban untreated wastewaters in the St. Lawrence River (Quebec, Canada) altered growth, reproduction, and redox status in experimentally exposed Daphnia magna

In 2015, five billion liters of untreated urban wastewater (UWW) were released into the St. Lawrence River (Quebec, Canada) over the course of four days in order to repair the Montreal's sewer interceptor network related to the city's primary wastewater treatment plant. The UWW discharge originated mainly from household, industrial, and hospital sources. The objective of this study was to investigate the toxicological effects of this unprecedented punctual UWW release on aquatic invertebrates to gather information that could help understand the potential impacts to the receiving environment of overflow episodes occurring during heavy rain events. Water samples were collected at four impacted and non-impacted sites during and four weeks after the release. The freshwater crustacean Daphnia magna were experimentally exposed to surface water collected from UWW-impacted sites for 13 days and analyzed for life-history endpoints and suitable biomarkers related to oxidative stress (i.e., catalase, superoxide dismutase, lipid peroxidation, and glutathione-s-transferase) and reproduction (chitinase). Results indicated that D. magna growth and reproduction were significantly increased by exposure to UWWs. These effects were correlated with an increase in chitinase activity, which is primarily controlled by reproductive hormones and involved in growth, suggesting potential impacts on these processes. Results also indicated that some UWW samples might have caused oxidative stress during the release but that it was overcome by antioxidant defenses and did not lead to cellular damage. Overall, current results contribute to a better understanding of the biological impacts of UWW to aquatic invertebrates for a better stormwater management.

Trends of persistent organic pollutants in ringed seals (Phoca hispida) from the Canadian Arctic

Ringed seals (Phoca hispida) have been used as bioindicator species of environmental contamination in Canada since the 1970s. In the present study, seals were harvested during subsistence hunts in four regions of the Canadian Arctic: Beaufort Sea, Arctic Archipelago, Hudson Bay, and coastal Labrador. An extensive suite of persistent organic pollutants (POPs) was determined in seal blubber collected for multiple years between 1972 and 2016. Results from this long-term study indicate geographical differences in the contaminant concentrations in seals and the significant general decrease of most POPs, including polychlorinated biphenyls (PCBs), dichlorodiphenyltrichloroethane (DDT) and related compounds, chlordanes (CHL), and hexachlorocyclohexanes (HCH) over time in ringed seals. The highest decrease rates (up to -9.1%/year for α-HCH) were found in seals from the Hudson Bay region where all chemicals investigated have significantly decreased since 1986. Significant increases in concentrations of hexachlorobenzene (HCB) in seals from Labrador and β-HCH in Sachs Harbour, NT and Arctic Archipelago were observed. Site-specific and contaminant-specific associations between climate pattern (i.e., Arctic Oscillation, North Atlantic Oscillation, and Pacific/North American pattern) and mean ice-coverage (total, first-year ice, and old-ice) were found at sites with the longest time trend data (i.e., Arviat, Sachs Harbour/Ulukhaktok and Resolute Bay). Overall, results suggest that North American and international regulations have led to the long-term reduction of most POPs in Canadian Arctic ringed seals by reducing emissions from primary sources. However, other sources of legacy compounds (e.g., environmental reservoirs) as well changes in food web composition and structure in relation to climate changes could also be influencing the very slow rates of decline, or stable levels, of contaminants found in seals at some sites. Further work is warranted to discern between co-variation of climate changes and contaminant concentrations and cause-and-effect relationships.

Inhibition of platelet aggregation ex vivo is repressed in apolipoprotein E deficient mice

In the present study, we assessed whether the endogenous platelet inhibitory mechanisms are altered in the early to moderate stages of the atherosclerotic process. Apolipoprotein E deficient mice (ApoE-/-), a mouse model of atherosclerosis, and their wild-type (WT) counterparts were used to assess agonist-stimulated synthesis of prostacyclin (PGI₂), inhibition of platelet aggregation ex vivo, and intra-platelet cAMP levels. Basal U46619 and ADP -induced platelet aggregation in vitro were increased in ApoE-/- mice at 18-20 weeks in comparison with 8-10 weeks of age. Systemically administered endothelin-1 (ET-1) or bradykinin (BK) inhibited platelet aggregation in a similar fashion in 8- to 10-week-old ApoE-/- and WT mice, but not in the ApoE-/- mice at 18-20 weeks of age, although both peptides maintained their capacity to increase plasma levels of the PGI₂. Intravenous infusion of PGI₂ also failed to inhibit platelet aggregation ex vivo in 18- to 20-week-old ApoE-/- mice. Interestingly, both BK and PGI₂ retained their ability to increase intraplatelet cAMP in WT and ApoE-/- mice. Our results suggest that a loss of activity of endogenous inhibitorymechanisms could contribute to the increased platelet reactivity in ApoE-/- mice, and that this phenomenon occurs early in the intermediate stage of the atherosclerotic process.

Spatial and temporal trends of alternative flame retardants and polybrominated diphenyl ethers in ringed seals (Phoca hispida) across the Canadian Arctic

Concentrations of alternative flame retardants and polybrominated diphenyl ethers (PBDEs) were analyzed in ringed seal (Phoca hispida) blubber collected across the Canadian Arctic during subsistence hunts between 1998 and 2013. More than 80% of sampled animals were females and juvenile males. The highest mean ΣPBDE concentrations (sum of 13 congeners) were found in seals from Nain (Nunatsiavut) as well as Inukjuaq and Arviat (Hudson Bay) and the lowest mean levels were found in seals from Lancaster Sound. BDE-47 and -99 were the predominant PBDE congeners quantified in ringed seals. The most frequently detected non-PBDE flame retardants were polybrominated biphenyl 101 (BB-101, 57% of samples analyzed for this chemical), hexabromocyclododecane (HBCDD; 38%), hexabromobenzene (HBB, 30%), and 2-ethylhexyl-2,3,4,5-tetrabromobenzoate (EHTeBB, 23%). The relative trophic position of seals, estimated using stable isotopes, did not vary over time and did not influence flame retardant blubber concentrations. The relative carbon source increased over time at Arviat and Resolute Bay and weak relationships were observed with ΣPBDEs in blubber of seals. ΣPBDEs increased significantly from 1998 to 2008 in ringed seals from East Baffin and subsequently decreased in recent years. PBDE levels at other sites fluctuated slightly over time. HBCDD concentrations increased at several sites over the past decade. The presence of flame retardants in ringed seals suggests their persistence and their continuous inputs in the Canadian Arctic environment. Monitoring and research on the effects of these contaminants in seals are warranted given the importance of this species in Arctic marine food webs and for local communities.

Production of morphologically derived words in the semantic variant of primary progressive aphasia: preserved decomposition and composition but impaired validation

Although there is growing interest in inflectional morphology in semantic variant primary progressive aphasia (svPPA), derivational morphology has rarely been studied in this population. This study reports the performance of N.G., a 72-year-old-woman with svPPA in a verb production task designed to entail morphological processing (composition, decomposition) and self-appraisal of her productions. N.G. demonstrated an over-reliance on morphological processing and failures in her appraisal of root/affix combinations that resulted in the production of morphological paraphasias and neologisms. Her performance in lexical decision of verbs and pseudo-verbs points to the involvement of semantic impairment in these difficulties.

Improving verb anomia in the semantic variant of primary progressive aphasia: the effectiveness of a semantic-phonological cueing treatment

The semantic variant of primary progressive aphasia (svPPA) is known to affect the comprehension and production of all content words, including verbs. However, studies of the treatment of anomia in this disorder focused on relearning object names only. This study reports treatment of verb anomia in an individual with svPPA. The semantic-phonological cueing therapy resulted in significant improvement in naming abilities, for treated verbs only. This case study demonstrates that improvement in verb-naming abilities may be possible in svPPA. The almost complete maintenance of the treatment's effects in the patient 4 weeks after the end of the therapy also suggests improvements may be durable, at least in the short term, for some individuals with svPPA.

High salt-induced hypertension in B2 knockout mice is corrected by the ETA antagonist, A127722

BACKGROUND AND PURPOSE

The contribution of endothelin-1 (ET-1) in a B2KO mouse model of a high salt-induced arterial hypertension was investigated.

EXPERIMENTAL APPROACH

Wild-type (WT) or B2KO mice receiving a normal diet (ND) or a high-salt diet (HSD) were monitored by radiotelemetry up to a maximum of 18 weeks. At the 12th week of diet, subgroups under ND or HSD received by gavage the ETA antagonist A127722 during 5 days. In addition, blood samples were collected and, following euthanasia, the lungs, heart and kidneys were extracted, homogenized and assayed for ET-1 by RIA. In a separate series of experiments, the ETA antagonist, BQ123 was tested against the pressor responses to a NOS inhibitor L-N(G)-nitroarginine methyl ester (L-NAME) in anaesthetized WT and B2KO mice.

KEY RESULTS

In B2KO, but not WT mice, 12 weeks of HSD triggered a maximal increase of the mean arterial pressure (MAP) of 19.1 ± 2.8 mmHg, which was corrected by A127722 to MAP levels found in B2KO mice under ND. Significant increases in immunoreactive ET-1 were detected only in the lungs of B2KO mice under HSD. On the other hand, metabolic studies showed that sodium urinary excretion was markedly reduced in B2KO compared with WT mice under ND. Finally, BQ123 (2 mg·kg(-1)) reduced by 50% the pressor response to L-NAME (2 mg·kg(-1)) in B2KO, but not WT mice under anaesthesia.

CONCLUSIONS AND IMPLICATIONS

Our results support the concept that functional B2 receptors oppose high salt-induced increments in MAP, which are corrected by an ETA receptor antagonist in this mouse model of experimental hypertension.

Role of capsular polysaccharide in Group B Streptococccus interactions with dendritic cells

Group B Streptococcus (GBS) type III is an important agent of life-threatening invasive infections. Albeit the immune system plays a dual role in development and protection against disease, mechanisms leading to an efficient immune response against GBS remain obscure. Mouse bone marrow-derived dendritic cells (DCs) and primary spleen DCs were used to evaluate GBS capacity to modulate the functions of these important antigen-presenting cells. The role of capsular polysaccharide (CPS), one of the most important GBS virulence factors, in bacterial-DC interactions was evaluated by using a non-encapsulated mutant. Phagocytosis assays, confocal and electron microscopy showed that DCs efficiently internalize encapsulated GBS, but the latter possesses strong intracellular survival capacity. GBS devoid of CPS was internalized and killed at higher and faster rates than encapsulated GBS early after infection. Among several cytokines tested, GBS internalization was required for modulation of IL-12, IL-10 and CXCL10 pathways. In contrast, GBS induced DC expression of co-stimulatory molecules in a phagocytosis-independent manner. Finally, the production of pro-inflammatory and Th1 cytokines by GBS-stimulated DCs was differentially modulated by CPS expression, depending on DC origin. Our data suggest multiple mechanisms involved in GBS modulation of DC functions, which were selectively regulated by the presence of CPS.

The MAPK signaling cascade is a central hub in the regulation of cell cycle, apoptosis and cytoskeleton remodeling by tripeptidyl-peptidase II

Tripeptidyl-peptidase II (TPPII) is a serine peptidase highly expressed in malignant Burkitt's lymphoma cells (BL). We have previously shown that overexpression of TPPII correlates with chromosomal instability, centrosomal and mitotic spindle abnormalities and resistance to apoptosis induced by spindle poisons. Furthermore, TPPII knockdown by RNAi was associated with endoreplication and the accumulation of polynucleated cells that failed to complete cell division, indicating a role of TPPII in the cell cycle. Here we have applied a global approach of gene expression analysis to gain insights on the mechanism by which TPPII regulates this phenotype. mRNA profiling of control and TPPII knockdown BL cells identified one hundred and eighty five differentially expressed genes. Functional categorization of these genes highlighted major physiological functions such as apoptosis, cell cycle progression, cytoskeleton remodeling, proteolysis, and signal transduction. Pathways and protein interactome analysis revealed a significant enrichment in components of MAP kinases signaling. These findings suggest that TPPII influences a wide network of signaling pathways that are regulated by MAPKs and exerts thereby a pleiotropic effect on biological processes associated with cell survival, proliferation and genomic instability.

PCB concentrations in lake trout (Salvelinus namaycush) are correlated to habitat use and lake characteristics

This study considers the importance of lake trout habitat as a factor determining persistent organochlorine (OC) concentration. Lake trout is a stenothermal, cold water species and sensitive to hypoxia. Thus, factors such as lake depth, thermal stratification, and phosphorus enrichment may determine not only which lakes can support lake trout but may also influence among-lake variability in lake trout population characteristics including bioaccumulation of OCs. A survey of 23 lakes spanning much of the natural latitudinal distribution of lake trout provided a range of lake trout habitat to test the hypothesis that lake trout with greater access to littoral habitat for feeding will have lower concentrations of OCs than lake trout that are more restricted to pelagic habitat. Using the delta13C stable isotope signature in lake trout as an indicator of influence of benthic littoral feeding, we found a negative correlation between lipid-corrected delta13C and sigmaPCB concentrations supporting the hypothesis that increasing accessto littoral habitat results in lower OCs in lake trout. The prominence of mixotrophic phytoplankton in lakes with more contaminated lake trout indicated the pelagic microbial food web may exacerbate the biomagnification of OCs when lake trout are restricted to pelagic feeding. A model that predicted sigmaPCB in lake trout based on lake area and latitude (used as proximate variables for proportion of littoral versus pelagic habitat and accessibility to littoral habitat respectively) explained 73% of the variability in sigmaPCBs in lake trout in the 23 lakes surveyed.

Interleukin-10-induced MARCH1 mediates intracellular sequestration of MHC class II in monocytes

IL-10 is a potent anti-inflammatory cytokine interfering with antigen presentation by inducing the intracellular sequestration of MHC class II (MHC-II) molecules. Here we studied the contribution of membrane-associated RING-CH (MARCH) ubiquitin ligase family members to the IL-10-induced down-regulation of MHC-II molecules. We found that MARCH1 and MARCH8 proteins are the most potent family members for the down-regulation of MHC-II surface expression in transfected cells, but only MARCH1 mRNA expression is strongly induced by IL-10 in human primary monocytes. We detected mono- and poly-ubiquitinated forms of MHC-II molecules both in IL-10-treated monocytes and in cells transfected with MARCH1. We also show direct interaction between MHC-II and MARCH1 molecules in co-immunoprecipitation assays. Finally, we found that siRNA-mediated knockdown of MARCH1 reverses IL-10-induced MHC-II down-regulation in primary monocytes. Thus, the immunosuppressive effect of IL-10 on antigen presentation is mediated through induced expression of MARCH1.

Modulation of the phagosome proteome by interferon-gamma

Macrophages are immune cells that function in the clearance of infectious particles. This process involves the engulfment of microbes into phagosomes where these particles are lysed and degraded. In the current study, we used a large scale quantitative proteomics approach to analyze the changes in protein abundance induced on phagosomes by interferon-gamma (IFN-gamma), an inflammatory cytokine that activates macrophages. Our analysis identified 167 IFN-gamma-modulated proteins on phagosomes of which more than 90% were up-regulated. The list of phagosomal proteins regulated by IFN-gamma includes proteins expected to alter phagosome maturation, enhance microbe degradation, trigger the macrophage immune response, and promote antigen loading on major histocompatibility complex (MHC) class I molecules. A dynamic analysis of IFN-gamma-sensitive proteins by Western blot indicated that newly formed phagosomes display a delayed proteolytic activity coupled to an increased recruitment of the MHC class I peptide-loading complex. These phagosomal conditions may favor antigen presentation by MHC class I molecules on IFN-gamma-activated macrophages.

LeishmaniaAntigens Are Presented to CD8+T Cells by a Transporter Associated with Antigen Processing-Independent Pathway In Vitro and In Vivo

CD8+ T cells are generated in response to Leishmania major (Lm) or Toxoplasma gondii parasitic infections, indicating that exogenously delivered Ag can be processed for presentation by MHC class I molecules. We show that presentation of Lm nucleotidase (NT)-OVA is TAP independent in vivo and in vitro, and is inhibited by chloroquine, but not by proteasome inhibitors. In contrast, the presentation of T. gondii P30-OVA relies on the TAP/proteasome pathway. Presentation of OVA- or rNT-OVA-coated beads also bypassed TAP requirement above a certain Ag threshold. TAP was also dispensable for the presentation of wild-type Lm Ags to primed CD8+ T cells in vitro. Finally, in vivo priming of CD8+ T cells involved in acquired resistance to Lm was not compromised in TAP-deficient mice. Thus, Leishmania Ags appear to be confined to an intraphagosomal processing pathway that requires higher concentrations of Ags, suggesting that these parasites may have evolved strategies to impair the efficient endoplasmic reticulum-based, TAP-dependent cross-presentation pathway to avoid or delay CD8+ T cell priming.

Phagocytosis: the convoluted way from nutrition to adaptive immunity

Phagocytosis, the process by which cells internalize large particulate materials from their milieu and sequester them in phagosomes, plays a role in a variety of cell functions ranging from nutrition in ameba to innate and adaptive immunity in mammals. Recent findings revealed unexpected characteristics of phagosomes, highlighting how this complex organelle may have evolved, from Dictyostelium to human, to become a key player in our ability to mount an efficient immune response against a variety of intracellular pathogens.

Leishmania donovani lipophosphoglycan disrupts phagosome microdomains in J774 macrophages

Clearance of pathogens by phagocytosis and their killing in phagolysosomes is a key aspect of our innate ability to fight infectious agents. Leishmania parasites have evolved ways to survive and replicate in macrophages by inhibiting phagosome maturation and avoiding the harsh environment of phagolysosomes. We describe here that during this process Leishmania donovani uses a novel strategy involving its surface lipophosphoglycan (LPG), a virulence factor impeding many host functions, to prevent the formation or disrupt lipid microdomains on the phagosome membrane. LPG acts locally on the membrane and requires its repetitive carbohydrate moieties to alter the organization of microdomains. Targeting and disruption of functional foci, where proteins involved in key aspects of phagolysosome biogenesis assemble, is likely to confer a survival advantage to the parasite.

Phagosomes are competent organelles for antigen cross-presentation

The ability to process microbial antigens and present them at the surface of cells is an important aspect of our innate ability to clear infections. It is generally accepted that antigens in the cytoplasm are loaded in the endoplasmic reticulum and presented at the cell surface on major histocompatibility complex (MHC) class I molecules, whereas peptides present in endo/phagocytic compartments are presented on MHC class II molecules. Despite the apparent segregation of the class I and class II pathways, antigens from intracellular pathogens including mycobacteria, Escherichia coli, Salmonella typhimurium, Brucella abortus and Leishmania, have been shown to elicit an MHC class-I-dependent CD8+ T-cell response, a process referred to as cross-presentation. The cellular mechanisms allowing the cross-presentation pathway are poorly understood. Here we show that phagosomes display the elements and properties needed to be self-sufficient for the cross-presentation of exogenous antigens, a newly ascribed function linked to phagocytosis mediated by the endoplasmic reticulum.

Leiomyosarcoma of urinary bladder following cyclophosphamide therapy: report of two cases

Leiomyosarcoma of urinary bladder is rare, although it is the most common mesenchymal tumor in adults. We report two cases of this tumor following cyclophosphamide therapy. The first case is from a 53-year-old man with Wegener's granulomatosis treated for 6 years with cyclophosphamide. He presented with painless hematuria, and the initial biopsy of the bladder tumor revealed a malignant spindle cell neoplasm. A final diagnosis of leiomyosarcoma was made on radical cystoprostatectomy. The second example is from a 21-year-old man who had received cyclophosphamide in early infancy for a bilateral retinoblastoma. He also presented with painless hematuria, and a bladder tumor was resected transurethrally and diagnosed as leiomyosarcoma. He underwent partial cystectomy two months later. Cyclophosphamide, when used for a neoplastic or non-neoplastic condition, is associated with an increased risk of developing bladder cancer. The distribution of histologic subtypes differs from that seen in spontaneous bladder tumors. A review of the literature shows an increased proportion of squamous cell carcinomas and sarcomas, especially leiomyosarcomas in cyclophosphamide exposed patients. Acrolein, a cytotoxic metabolite of cyclophosphamide excreted in urine, is regarded as the most likely causative agent.

Phosphatidylinositol 3-kinase controls human intestinal epithelial cell differentiation by promoting adherens junction assembly and p38 MAPK activation

The signaling pathways mediating human intestinal epithelial cell differentiation remain largely undefined. Phosphatidylinositol 3-kinase (PI3K) is an important modulator of extracellular signals, including those elicited by E-cadherin-mediated cell-cell adhesion, which plays an important role in maintenance of the structural and functional integrity of epithelia. In this study, we analyzed the involvement of PI3K in the differentiation of human intestinal epithelial cells. We showed that inhibition of PI3K signaling in Caco-2/15 cells repressed sucrase-isomaltase and villin protein expression. Morphological differentiation of enterocyte-like features in Caco-2/15 cells such as epithelial cell polarity and brush-border formation were strongly attenuated by PI3K inhibition. Immunofluorescence and immunoprecipitation experiments revealed that PI3K was recruited to and activated by E-cadherin-mediated cell-cell contacts in confluent Caco-2/15 cells, and this activation appears to be essential for the integrity of adherens junctions and association with the cytoskeleton. We provide evidence that the assembly of calcium-dependent adherens junctions led to a rapid and remarkable increase in the state of activation of Akt and p38 MAPK pathways and that this increase was blocked in the presence of anti-E-cadherin antibodies and PI3K inhibitor. Therefore, our results indicate that PI3K promotes assembly of adherens junctions, which, in turn, control p38 MAPK activation and enterocyte differentiation.

Intestinal epithelial cell differentiation involves activation of p38 mitogen-activated protein kinase that regulates the homeobox transcription factor CDX2

The intracellular signaling pathways responsible for cell cycle arrest and differentiation along the crypt-villus axis of the human small intestine remain largely unknown. p38 mitogen-activated protein kinases (MAPKs) have recently emerged as key modulators of various vertebrate cell differentiation processes. In order to elucidate further the mechanism(s) responsible for the loss of proliferative potential once committed intestinal cells begin to differentiate, the role and regulation of p38 MAPK with regard to differentiation were analyzed in both intact epithelium as well as in well established intestinal cell models recapitulating the crypt-villus axis in vitro. Results show that phosphorylated and active forms of p38 were detected primarily in the nuclei of differentiated villus cells. Inhibition of p38 MAPK signaling by 2-20 microm SB203580 did not affect E2F-dependent transcriptional activity in subconfluent Caco-2/15 or HIEC cells. p38 MAPK activity dramatically increased as soon as Caco-2/15 cells reached confluence, whereas addition of SB203580 during differentiation of Caco-2/15 cells strongly attenuated sucrase-isomaltase gene and protein expression as well as protein expression of villin and alkaline phosphatase. The binding of CDX2 to the sucrase-isomaltase promoter and its transcriptional activity were significantly reduced by SB203580. Pull-down glutathione S-transferase and immunoprecipitation experiments demonstrated a direct interaction of CDX3 with p38. Finally, p38-dependent phosphorylation of CDX3 was observed in differentiating Caco-2/15 cells. Taken together, our results indicate that p38 MAPK may be involved in the regulation of CDX2/3 function and intestinal cell differentiation.

Characterization of oxalate oxidase and cell death in Al-sensitive and tolerant wheat roots

Several genes including oxalate oxidase (Oxo) are up-regulated in Triticum aestivum L. root tips exposed to Al. To better understand the function of Oxo during Al exposure, the protein level and enzyme activity were measured. The data indicate that both Oxo protein and activity are increased proportionally to the level of root growth inhibition (RGI). A high level of Oxo expression may result in excess H(2)O(2) production which could become toxic and induce cell death. However, the timing of H(2)O(2) production (observed after 24 h) indicates that it cannot be the primary cause of cell death first observed after 8 h. Moreover, at Al concentrations resulting in 50% RGI, we did not observe any cell death in the sensitive cultivar while a punctated pattern of death involving small groups of cells was found in the tolerant cultivar. This pattern was maintained for several days in the tolerant cultivar, suggesting the involvement of a cell death mechanism aimed at replacing epidermal cells intoxicated with Al while root growth is maintained. The accelerated epidermal cell turnover may represent a new detoxification mechanism helping to protect deeper cell layers of the meristematic and elongation zone essential for root growth.

Somatostatin inhibits Akt phosphorylation and cell cycle entry, but not p42/p44 mitogen-activated protein (MAP) kinase activation in normal and tumoral pancreatic acinar cells

Somatostatin, or its structural analog SMS 201-995 (SMS), is recognized to exert a growth-inhibitory action in rat pancreas, but the cellular mechanisms are not completely understood. This study was undertaken to evaluate the effect of SMS on p42/p44 MAP kinases and phosphatidylinositol 3-kinase activation and to analyze expression of some cell cycle regulatory proteins in relation to pancreatic acinar cell proliferation in vivo (rat pancreas), as well as in the well-established tumoral cell line AR4-2J. We herein report that: 1) SMS inhibits caerulein-induced pancreatic weight and DNA content and abolishes epidermal growth factor (EGF)-stimulated AR4-2J proliferation; 2) SMS only moderately reduces the stimulatory effect of caerulein on p42/p44 MAP kinase activities in pancreas and has no effect on EGF-stimulated MAP kinase activities in AR4-2J cells; 3) SMS repressed caerulein-induced Akt activity in normal pancreas; 4) SMS has a strong inhibitory action on cyclin E expression induced by caerulein in pancreas and EGF in AR4-2J cells and as expected, the resulting cyclin E-associated cyclin-dependent kinase (cdk)2 activity, as well as pRb phosphorylation, are blunted by SMS treatment in both models; and 5) SMS suppresses mitogen-induced p27(Kip1) down-regulation, as well as marginally induces p21(Cip) expression. Thus, our data suggest that somatostatin-induced growth arrest is mediated by inhibition of phosphatidylinositol 3-kinase pathway and by enhanced expression of p21(Cip) and p27(Kip1), leading to repression of pRb phosphorylation and cyclin E-cdk2 complex activity.

Cadmium uptake by Caco-2 cells: effects of Cd complexation by chloride, glutathione, and phytochelatins

Short-term cadmium uptake by the highly differentiated TC7 clone of enterocytic-like Caco-2 cells was studied as a function of Cd speciation. For low metal concentrations and with a constant free [Cd(2+)] = 43 nM, initial uptake rates of (109)Cd increased linearly as a function of increasing concentration of chlorocomplexes (Sigma[(109)CdCl(2-n)(n)]) over the range from 0 to 250 nM. When normalized as a function of the metal concentration, the absorption rate for the chlorocomplexes was less than that estimated for uptake of the free Cd(2+) cation. Metal absorption decreased upon organic ligand addition in the exposure media, but much less than predicted from the assumption that only inorganic metal species would be transported. Under exposure conditions where the concentration of each of the inorganic species was kept constant, (109)Cd uptake increased with increasing concentrations of cadmium glutathione ((109)Cd-GSH) or phytochelatin ((109)Cd-hmPC(3)) complexes. A specific system of very high affinity but low capacity has been characterized for (109)Cd-GSH transport, whereas accumulation data increased linearly with (109)Cd-hmPC(3) up to 6 microM. Comparison among uptake data for 0.3 microM inorganic (109)Cd, (109)Cd-GSH, or (109)Cd-hmPC(3) yields the following accumulation ratios: Cd-GSH/Cd(inorg) = 0.2; Cd-hmPC(3)/Cd(inorg) = 0.5. These results clearly show that Cd(2+) is not the exclusive metal species participating in Cd absorption, though, for comparable Cd concentrations, its contribution to transport would be more important than that of other species. Cadmium bound to thiol-containing peptides may be absorbed via transport systems that differ from those involved in absorption of the inorganic metal species.

Regulation of extrathymic T cell development and turnover by oncostatin M

Chronic exposure to oncostatin M (OM) has been shown to stimulate extrathymic T cell development. The present work shows that in OM transgenic mice, 1) massive extrathymic T cell development takes place exclusively the lymph nodes (LNs) and not in the bone marrow, liver, intestines, or spleen; and 2) LNs are the sole site where the size of the mature CD4+ and CD8+ T cell pool is increased (6- to 7-fold). Moreover, when injected into OM transgenic mice, both transgenic and nontransgenic CD4+ and CD8+ T cells preferentially migrated to the LNs rather than the spleen. Studies of athymic recipients of fetal liver grafts showed that lymphopoietic pathway modulated by OM was truly thymus independent, and that nontransgenic progenitors could generate extrathymic CD4+CD8+ cells as well as mature T cells under the paracrine influence of OM. The progeny of the thymic-independent differentiation pathway regulated by OM was polyclonal in terms of Vbeta usage, exhibited a phenotype associated with previous TCR ligation, and displayed a rapid turnover rate (5-bromo-2'-deoxyuridine pulse-chase assays). This work suggests that chronic exposure to OM 1) discloses a unique ability of LNs to sustain extrathymic T cell development, and 2) increases the number and/or function of LN niches able to support seeding of recirculating mature T cells. Regulation of the lymphopoietic pathway discovered in OM transgenic mice could be of therapeutic interest for individuals with thymic hypoplasia or deficient peripheral T cell niches.

Sensitivity and specificity of a multi-antigen ELISA test for the serological diagnosis of tuberculosis

A new serological assay (DETECT-TB, BioChem ImmunoSystems), using three recombinant proteins and two synthetic peptides for the detection of the anti-Mycobacterium tuberculosis IgG, was evaluated using a panel of serum specimens collected from 100 tuberculosis (TB) patients and 270 controls, in comparison with a homemade ELISA test using purified protein derivative (PPD) as antigen. DETECT-TB presented a higher sensitivity (75%) compared to PPD-ELISA (56%; P < 0.01), while the specificity of each assay was similar (DETECT-TB 97%; PPD-ELISA 100%; P > 0.80). Receiver operating characteristics (ROC) analysis obtained with these data confirmed the higher level of performance of DETECT-TB in comparison with PPD-ELISA. Considering the rapidity, cost-effectiveness and simplicity of this assay, its use may provide useful clinical information aiding in the rapid diagnosis of difficult TB cases.

Evidence for an intracellular barrier to cadmium transport through Caco-2 cell monolayers

109Cd transport was studied in the highly differentiated TC7 clone of the enterocytic-like Caco-2 cells grown on filters. Accumulation curves for 0.3 microM 109Cd over 12 h from the apical (AP) or the basal (BL) sides revealed a three-step mechanism involving: 1) a zero-time accumulation Ao; 2) a fast process Af(t1/2 < or = 10 min); and 3) a slow process of uptake As (5 h < or = t1/2 < or = 10 h) responsible for the major cellular levels of 109Cd. The relative contribution of adsorption to total accumulation is greater for short exposure times (< or = 35%), but is no longer significant after the exposure times needed to reach equilibrium. Transepithelial transport was less than 4% of the cellular level at 12 h. A negligible but specific binding onto the BL surface of the filters was characterized. Saturable systems of accumulation with comparable affinities (Km = 2.5+/-0.5 and 5.4+/-0.4 microM) but distinct capacities (Vmax = 8.9+/-1.2 and 312+/-22 pmol/min/mg protein) were identified at the AP and BL cell membranes, respectively. Efflux studies revealed that Cd accumulation is only partially reversible, with an exclusive metal release at the same side. A 2-h exposure on both sides simultaneously failed to demonstrate any competition for cellular accumulation: uptake was additive relative to AP and BL uptake values. These data suggest that Af leads to an accumulation of loosely bound Cd, whereas As represents irreversible intracellular binding processes. We conclude that Cd transport occurs exclusively by a transcellular route and that saturation of the intracellular high-capacity binding sites is the rate-limiting step in Cd absorption.

Attenuation of haptoglobin gene expression by TGFbeta requires the MAP kinase pathway

In addition to important roles in the regulation of cell growth and cell restitution, both pro- and anti-inflammatory effects have been ascribed to TGFbeta in intestinal epithelial cells. However, the mechanisms involved in TGFbeta-dependent anti-inflammatory activities remain to be determined. In the rat intestinal epithelial cell line IEC-6, TGFbeta attenuated the glucocorticoid-dependent increases in mRNA levels of the acute phase protein gene haptoglobin, and of C/EBP isoforms beta and delta. Supershift assays demonstrated a TGFbeta-mediated decrease in the binding of C/EBP isoforms beta and delta to the haptoA and haptoC C/EBP DNA-binding sites from the haptoglobin promoter. Mutations of both HaptoA and HaptoC sites abolished the glucocorticoid-dependent activation and the TGFbeta-mediated attenuation of the haptoglobin promoter, as assessed by transient transfection assays. TGFbeta induced p42/p44 MAP kinase activities. Treatment with the MEK 1/2 inhibitor PD 98059 abolished TGFbeta attenuation. These results suggest that C/EBP isoforms are involved both in the glucocorticoid-dependent induction and in the TGFbeta-mediated attenuation of haptoglobin expression. Furthermore, p42/p44 MAP kinases may function in a TGFbeta-dependent signaling pathway leading to attenuation of haptoglobin expression.

Isolation and characterization of wheat aluminum-regulated genes: possible involvement of aluminum as a pathogenesis response elicitor

Using differential screening of a root tip cDNA library prepared from an Al-tolerant wheat cultivar (Triticum aestivum L. cv. Atlas-66) exposed to Al, we have isolated and characterized several wheat aluminum-regulated (War) cDNAs. Sequence comparison revealed that genes up-regulated by Al correspond to peroxidase (war4.2), cysteine proteinase (war5.2), phenylalanine-ammonia lyase (war7.2), and oxalate oxidase (war13.2). Two wheat cultivars that differ in their level of tolerance (cv. Atlas-66: tolerant, and cv. Fredrick: sensitive) were used to evaluate the relationship between the accumulation of War mRNAs and Al toxicity, as measured by root growth inhibition (RGI). The mRNA accumulation was modulated to similar levels in both cultivars compared at equivalent RGIs. This indicates that War mRNA accumulation is associated with the toxicity of Al rather than with the cultivar's tolerance. It appears that most of the genes found to be up-regulated by Al share homologies with genes induced by pathogens. This suggests that Al may act as an elicitor of a pathogenesis-related transduction pathway. The potential functions of the up-regulated war genes in cell wall strengthening and Al trapping are discussed.

Heterogeneous antibody responses in tuberculosis

Antibody responses during tuberculosis were analyzed by an enzyme-linked immunosorbent assay with a panel of 10 protein antigens of Mycobacterium tuberculosis. It was shown that serum immunoglobulin G antibodies were produced against a variety of M. tuberculosis antigens and that the vast majority of sera from tuberculosis patients contained antibodies against one or more M. tuberculosis antigens. The number and the species of serologically reactive antigens varied greatly from individual to individual. In a given serum, the level of specific antibodies also varied with the antigen irrespective of the total number of antigens recognized by that particular serum. These findings indicate that person-to-person heterogeneity of antigen recognition, rather than recognition of particular antigens, is a key attribute of the antibody response in tuberculosis.

In vitro expression of MMP-2 and MMP-9 in glioma cells following exposure to inflammatory mediators

Progression of glioma is associated with local degenerative processes which are attributed to the activity of gelatinases. As glioma cells are candidate for secretion of these enzymes, we have studied in vitro the potential of cytokines (interleukin-1alpha (IL-1), tumor necrosis factor-alpha (TNFalpha) and transforming growth factor-beta (TGFbeta2)) to regulate the expression of gelatinase A and B (Gels A and B, respectively) in two glioma cells of human (A172) and rat origin (C6). We showed that IL-1 and TNFalpha both induced gene expression and protein secretion of Gel B in both cell lines, as revealed by RT-PCR and gelatin zymography, respectively. In C6 cells, TNFalpha had no effect on Gel A constitutive expression while IL-1 increased its production, but only at high doses. We have also demonstrated that TGFbeta2 inhibited both IL-1- or TNFalpha-induced gene expression and Gel B production in a dose-dependent manner but had no effect on Gel A secretion. The effect of TGFbeta2 on Gel B secretion was reversed by phorbol myristate acetate (PMA). Taken together, these data suggest that IL-1, TNFalpha and TGFbeta2 tightly regulate Gel B secretion in glioma cells, an enzyme which is believed to play an important role in the local invasion of brain tissue by tumor cells.

Accumulation of an acidic dehydrin in the vicinity of the plasma membrane during cold acclimation of wheat

Expression of the acidic dehydrin gene wcor410 was found to be associated with the development of freezing tolerance in several Gramineae species. This gene is part of a family of three homologous members, wcor410, wcor410b, and wcor410c, that have been mapped to the long arms of the homologous group 6 chromosomes of hexaploid wheat. To gain insight into the function of this gene family, antibodies were raised against the WCOR410 protein and affinity purified to eliminate cross-reactivity with the WCS120 dehydrin-like protein of wheat. Protein gel blot analyses showed that the accumulation of WCOR410 proteins correlates well with the capacity of each cultivar to cold acclimate and develop freezing tolerance. Immunoelectron microscope analyses revealed that these proteins accumulate in the vicinity of the plasma membrane of cells in the sensitive vascular transition area where freeze-induced dehydration is likely to be more severe. Biochemical fractionation experiments indicated that WCOR410 is a peripheral protein and not an integral membrane protein. These results provide direct evidence that a subtype of the dehydrin family accumulates near the plasma membrane. The properties, abundance, and localization of these proteins suggest that they are involved in the cryoprotection of the plasma membrane against freezing or dehydration stress. We propose that WCOR410 plays a role in preventing the destabilization of the plasma membrane that occurs during dehydrative conditions.

Accumulation of an acidic dehydrin in the vicinity of the plasma membrane during cold acclimation of wheat

Expression of the acidic dehydrin gene wcor410 was found to be associated with the development of freezing tolerance in several Gramineae species. This gene is part of a family of three homologous members, wcor410, wcor410b, and wcor410c, that have been mapped to the long arms of the homologous group 6 chromosomes of hexaploid wheat. To gain insight into the function of this gene family, antibodies were raised against the WCOR410 protein and affinity purified to eliminate cross-reactivity with the WCS120 dehydrin-like protein of wheat. Protein gel blot analyses showed that the accumulation of WCOR410 proteins correlates well with the capacity of each cultivar to cold acclimate and develop freezing tolerance. Immunoelectron microscope analyses revealed that these proteins accumulate in the vicinity of the plasma membrane of cells in the sensitive vascular transition area where freeze-induced dehydration is likely to be more severe. Biochemical fractionation experiments indicated that WCOR410 is a peripheral protein and not an integral membrane protein. These results provide direct evidence that a subtype of the dehydrin family accumulates near the plasma membrane. The properties, abundance, and localization of these proteins suggest that they are involved in the cryoprotection of the plasma membrane against freezing or dehydration stress. We propose that WCOR410 plays a role in preventing the destabilization of the plasma membrane that occurs during dehydrative conditions.

Ammonium acid urate crystal formation in adult North American stone-formers

Although ammonium acid urate (AAU) stones are endemic in Asia, pure AAU calculi have almost disappeared from industrialized countries and clinical pathophysiologic relevance of sporadic stones containing AAU crystals is currently unknown. We reviewed 1,396 crystallographic stone analyses performed in our institution over a 10-year period. Prevalence of stones containing AAU crystals and predominantly AAU stones were 3.1% and 0.2%, respectively. In more than two thirds of cases, AAU crystals represented less than 10% of stone crystal composition. No pure AAU stone was found. According to crystalline predominance, 42%, 35%, and 12% of these calculi were uric acid, infectious, and calcium oxalate stones, respectively. AAU crystals were detected as discrete intercrystalline or peripheral deposits in 74.4% of stones. In only one calculus was AAU crystals detected in the nucleus. The hospital charts of 37 patients who presented with 43 calculi containing AAU crystals were also reviewed. The mean age was 53.1 +/- 16.6 years. Fifty-seven percent of calculi were upper urinary tract stones and 43% were bladder stones. Upper urinary tract calculi were more frequently uric acid stones, followed by infectious and calcium oxalate stones. Lower urinary tract calculi were more frequently infectious stones, followed by uric acid stones. Upper urinary tract stones were passed spontaneously in 13 patients and removed surgically in nine patients. Nine of these subjects were idiopathic recurrent stone formers who had passed other calculi with no trace of AAU crystal. Fifty-seven percent of lower urinary tract stones were associated with documented bladder dysfunction. In conclusion, although AAU-containing urolithiases are occasionally seen in our population, predominantly or primarily AAU stones are exceptional. AAU crystal formation usually appears as a minor and secondary phenomenon of no primary pathophysiologic relevance in stone formation.

Gene expression during cold acclimation in strawberry

To elucidate the molecular basis of cold acclimation in strawberry (Fragaria x anannassa), we have begun studies to identify genes associated with low temperature (LT) acclimation. Differential screening of a cDNA library prepared from cold-acclimated strawberry plants allowed us to isolate several cDNAs showing differential expression at LT. Northern analysis showed that the transcript level of Fcor1 (Fragaria Cold-Regulated) peaked after 2 days of LT exposure while that of Fcor2 peaked after 2 weeks. On the other hand, the level of Fcor3 transcript decreased within 24 hours of LT exposure and remained low during the 8 weeks acclimation period. Fcor1 and Fcor2 are expressed in all tissues while Fcor3 is specific to leaves. The Fcor1-encoded protein has a compositional bias for leucine, isoleucine, glycine, proline and serine. This protein shares homology with the proteins encoded by blt101, a LT-responsive gene from barley, and ESI3, a gene induced by salt stress in Lophopyrum. The FCOR2 protein is rich in lysine, leucine, valine, alanine and arginine, and shows no homology with any known gene products. The partial Fcor3 cDNA clone encodes a polypeptide that shows a very high identity with the spinach PSI subunit V and with the PSI PsaG polypeptide from barley. The level of Fcor1 transcript accumulation is correlated with the freezing tolerance of the strawberry cultivars used in our study. This suggests that Fcor1 may be useful as a molecular marker to select for this trait in resulted species of the Rosaceae family.

Caco-2 cell line used as an in vitro model to study cadmium accumulation in intestinal epithelial cells

109Cd uptake was studied using the highly differentiated TC7 clone of Caco-2 cells as a model of human enterocyte function. Intracellular accumulation of 0.3 microM 109Cd involved a rapid and a slow uptake phase, which resulted in complete equilibration (t(1/2) = 17.3 +/- 1.3 min) with an apparent in-to-out distribution ratio (alphae) of 11.6 +/- 0.8. The amplitude of the rapid phase (U0) and the rate of the slow phase (V) were similarly reduced in the less differentiated PF11 clone, but comparable alphae values were observed at equilibrium. In both clones, the t(1/2) and alphae values increased and decreased, respectively, upon addition of unlabeled Cd to the uptake media. In TC7 cells, 109Cd uptake at 1 min (U1) was unaffected by Ca concentrations four order of magnitude in excess, but both U0 and V demonstrated similar sensitivities to unlabeled Cd, Zn and sulfhydryl-reactive agents. Only U0 disappeared when EDTA was present in the wash solutions. U1 showed saturation kinetics and the data were found compatible with a model assuming rapid initial Cd binding and transport through a unique transport protein (Km = 3.8 +/- 0.7 microM). Cd efflux kinetics demonstrated partial reversibility in EDTA-containing solutions, suggesting that the taken up Cd might be both tightly and loosely bound to intracellular binding sites. However, the displacement of 109Cd measured at 65 min failed to reveal this heterogeneity: the data were found compatible with a model equation assuming the presence of one class of high-capacity high-affinity binding sites. We conclude that a slow-transport fast-intracellular binding mechanism of Cd uptake best accounts for these results and that Cd transport most likely involves a carrier-type of protein unrelated to Ca absorption.

Synergistic and selective stimulation of gelatinase B production in macrophages by lipopolysaccharide, trans-retinoic acid and CGP 41251, a protein kinase C regulator

The production of gelatinase B by macrophages is relevant in the immunological and migratory functions of macrophages. CGP 41251, an inhibitor of protein kinase C (PKC), was found to stimulate the expression of gelatinase B in macrophages, as shown by the study of two different monocytic/macrophagic cell lines, mouse RAW 264.7 and human THP-1 cells. When human monocytes and rat peritoneal macrophages were treated with CGP 41251, insignificant increases of 10 and 25% were obtained. This can possibly be due to the presence of contaminating cells in these two enriched populations, since the CGP 41251 treatment of non-macrophagic cell lines inhibited their PMA-induced gelatinase B production. Taken together, these results suggest that the stimulatory effect of CGP 41251 is specific to cells of the monocytic lineage. Using RAW 264.7 cells as a model, the effect of CGP 41251 is additive to that obtained using lipopolysaccharide (LPS) and phorbol 12-myristate 13-acetate (PMA), as revealed by gelatin zymography and Northern blot analysis. The stimulatory effect of CGP 41251 on gelatinase B production in RAW 264.7 was: (a) inhibited by calphostin C (as is the LPS-induced response), indicating a PKC-dependence; (b) inhibited by dexamethasone (as opposed to the LPS-induced response); and (c) enhanced by addition of trans-retinoic acid (RA). In fact, RA can induce gelatinase B production, either alone or in synergy with LPS and/or CGP 41251, since the combination of the three agents gives the highest gelatinase B response, at both the protein and the mRNA levels. This represents an important observation considering the RA is now being tested as an anti-cancer agent and proposed for prevention studies.

Differential modulation of natural and adaptive immunity in Fischer rats exposed for 6 weeks to 60 Hz linear sinusoidal continuous-wave magnetic fields

Two separate, independent experiments were conducted to evaluate the effect of 60 Hz linearly polarized, sinusoidal, continuous-wave magnetic fields (MFs) on immune system performances in rats born and raised under these fields. Each experiment lasted for 6 weeks. A total of 96 animals, divided into groups of eight animals each, was exposed for 20 h/day to MFs of different intensities, i.e., sham (< 0.02 microT) and 2, 20, 200, and 2000 microT. Another group of animals, which was housed in a separate room, served as cage controls (CC). These animals were exposed to ambient MFs of < 0.02 microT. The following immune responses were evaluated in both experiments total T and B cells; CD4+ and CD8+ subpopulation and natural killer (NK) cell activity in splenic lymphocytes; hydrogen peroxide (H2O2), nitrous oxide (NO), and tumor necrosis factor (TNF) production by peritoneal macrophages. Our results show that a 6 week exposure to MFs induced a significant decrease in the number of CD5+, CD4+, and CD8+ populations. These changes were even more significant in rats that were exposed to fields of 2000 microT. A lower, although significant, decrease in the CD5+ population was also observed in animals that were exposed to fields of 200 microT. Linear regression analysis demonstrated a dose effect with MF intensity. B lymphocyte (Ig+ cell) populations also showed a 12% decrease (P < .05) in the groups that were exposed to fields of 20 and 200 microT. However, these results were not significant, and no relation with MF intensities could be demonstrated. In contrast, evaluation of splenic NK cell activity revealed a 50% increase (P < .05) in animals that were exposed to fields of 2000 microT. No significant results were obtained from the evaluation of TNF activity and NO secretion in peritoneal macrophages. Phorbol 12-myristate 13-acetate (PMA)-stimulated and net H2O2 productions for a minor subpopulation of peritoneal cells showed positive dose-response correlations by linear regression analysis. Taken together, our results suggest that an in vivo exposure of rats for 6 weeks to 60 Hz MFs can induce significant immunological perturbations on effector cells of both natural and adaptive immunity in a dose-dependent fashion.

Expression of the cold-induced wheat gene Wcs120 and its homologs in related species and interspecific combinations

Low-temperature response was measured at the whole plant and at the molecular level in wheat–rye amphiploids and in other interspecific combinations. Cold tolerance of interspecifics whose parents diverged widely in hardiness levels resembled the less hardy higher ploidy level wheat parent. Expression of the low-temperature induced Wcs120 gene of wheat (Triticum aestivum L. em. Thell.) has been associated with freezing tolerance and was used here to study mRNA and protein accumulation in interspecific and parental lines during cold acclimation. Northern and Western analyses showed that homologous mRNAs and proteins were present in all the related species used in the experiments. Cold-tolerant rye (Secale cereale L.) produced a strong mRNA signal that was sustained throughout the entire 49-day cold-acclimation period. The wheats produced a mRNA signal that had diminished after 49 days of low-temperature exposure. The wheat–rye triticales did not exhibit the independent accumulation kinetics of the cold-tolerant rye parent but, rather, more closely resembled the wheat parent in that the mRNA signal was greatly diminished after 49 days of low-temperature exposure. The influence of the rye genome was manifest in slightly greater mRNA and protein accumulation in earlier stages of acclimation. Protein accumulations in the triticales were also maintained to a somewhat greater extent than found in the wheats at the end of the 49-day acclimation period. Protein accumulations in the wheat-crested wheatgrass (Agropyron cristatum L. Gaertner) interspecific resembled that of the wheat parent. The influence of the higher ploidy level wheats of the expression of homologous gene families from wheat-related hardy diploids in interspecific combinations may in part explain the poor cold tolerance observed.Key words: cold tolerance, transcription, protein accumulation, alien gene expression, Triticeae.

Immunolocalization of freezing-tolerance-associated proteins in the cytoplasm and nucleoplasm of wheat crown tissues

A protein family associated with the development of freezing tolerance in wheat has been identified. This protein family is Gramineae-specific and coordinately regulated by low temperature. Antibodies directed against the 50 kDa (WCS120) protein recognize at least 5 members of this family. Using these antibodies, the cellular content and location of this protein family was determined in cold-acclimated wheat seedlings. Western analyses of subcellular fractions indicated the presence of all members of the family in the cytosolic and purified nuclear fractions. These proteins accumulated to 0.9% of soluble proteins after 21 days of cold acclimation in winter wheat. This represents a cellular concentration of 1.34 microM. Immunohistochemical localization showed that these proteins are highly expressed in the vascular transition zone. No detectable expression was found in mature xylem, in the shoot apical meristem or lateral root primordia. This differential tissue expression suggests that the sensitive cells near the regions where water tends to freeze first require a higher amount of these proteins. This observation is consistent with the fact that regrowth after freezing stress is highly dependent on the viability of this region of the crown. Electron microscopy analysis using immunogold labelling showed that these proteins are present in the cytoplasm and in the nucleoplasm. They are not found in cell walls or other organelles. In vitro cryoprotective assays indicated that the WCS120 protein (PD50 of 10 micrograms ml-1 or 0.2 microM) are as effective as BSA and sucrose (at 250 mM) against freezing denaturation of lactate dehydrogenase. These results suggest that this protein family may be involved in a general mechanism of protection in the soluble fraction of the cell. Their presence in the nucleoplasm may also suggest a possible protective function of the transcriptional machinery. The high hydrophilicity, the abundance and stability of these proteins to boiling suggest that they may provide a particular micro-environment needed for cell survival in the sensitive vascular transition zone during freezing stress.