Fate of Selenium in Soils at a Seleniferous Site Recorded by High Precision Se Isotope Measurements.

Selenium poisoning is a significant health problem in parts of Punjab, India, which is an area of intense agricultural productivity. To determine the complex soil dynamics that control distribution of Se in this area, we measured concentrations and δ(82/76)Se of bulk Se and individual Se pools in four soil profiles. This was compared against δ(82/76)Se of crops and groundwater used for irrigation. The isotopic composition of bulk Se and component Se pools reveal spatial heterogeneity. The bulk δ(82/76)Se show progressively lower values with increasing soil depth indicating the preferential migration of isotopically lighter Se downward through the soil profile. The δ(82/76)Se of water-soluble Se is isotopically heavier than δ(82/76)Se of adsorbed Se, suggesting Se isotope fractionation by reduction prior to scavenging by reactive minerals in the soil. The organically bound Se is isotopically lighter than water-soluble Se and correlates with the C/N ratio at different soil depths. Thus, Se immobilization by redox cycling controls the biogeochemical Se cycle in the soil. Se isotope ratios help to trace biochemical processes of Se in agricultural seleniferous soils and provide an important assessment for better soil management mitigating Se concentrations of ecotoxicological levels.

Deep origin and hot melting of an Archaean orogenic peridotite massif in Norway.

The buoyancy and strength of sub-continental lithospheric mantle is thought to protect the oldest continental crust (cratons) from destruction by plate tectonic processes. The exact origin of the lithosphere below cratons is controversial, but seems clearly to be a residue remaining after the extraction of large amounts of melt. Models to explain highly melt-depleted but garnet-bearing rock compositions require multi-stage processes with garnet and clinopyroxene possibly of secondary origin. Here we report on orogenic peridotites (fragments of cratonic mantle incorporated into the crust during continent-continent plate collision) from Otrøy, western Norway. We show that the peridotites underwent extensive melting during upwelling from depths of 350 kilometres or more, forming a garnet-bearing cratonic root in a single melting event. These peridotites appear to be the residue after Archaean aluminium depleted komatiite magmatism.

Minimal health impact from exposure to diet-sourced cadmium on a population in central Jamaica.

Elevated concentrations of naturally occurring Cd have been found mainly in the bauxitic soils of central Jamaica at levels up to 100-1,000 times higher than typical worldwide averages. Some food crops cultivated on these soils absorb significant amounts of Cd. Autopsy studies of kidney Cd concentrations confirm elevated human exposure, and some long-term residents in central Jamaica exceed the general population average by a factor of two. Diet studies have ascertained that a population in central Jamaica is at risk of being exposed to Cd levels in excess of the Provisional Tolerable Weekly Intake (PTWI) set by the WHO of 7 µgCd/kg bodyweight/week, and the EU TWI of 2.5 µgCd/kg bodyweight/week. Elevated levels of urine cadmium (U-Cd) and beta-2 microglobulin (ß2-MG) concentrations were confirmed with a strong correlation between soil Cd and the U-Cd. Also, higher ß2-MG concentrations (>200µg/g creatinine) were found in the population with U-Cd concentrations greater than 2.5µg/L. While this identification is often taken to indicate impairment in the reabsorption capacity of the renal tubules leading to renal disease, there is no evidence in the mortality records of enhanced deaths in central Jamaica compared with the general population resulting from renal disease or diabetes related complications. The highest median age of death in the island is found in Manchester, the parish with the highest average Cd concentration. While we have identified a possible Cd linked renal dysfunction, significant indications of morbidity are not present in the general population.

In situ S-isotope compositions of sulfate and sulfide from the 3.2 Ga Moodies Group, South Africa: A record of oxidative sulfur cycling.

Sulfate minerals are rare in the Archean rock record and largely restricted to the occurrence of barite (BaSO4 ). The origin of this barite remains controversially debated. The mass-independent fractionation of sulfur isotopes in these and other Archean sedimentary rocks suggests that photolysis of volcanic aerosols in an oxygen-poor atmosphere played an important role in their formation. Here, we report on the multiple sulfur isotopic composition of sedimentary anhydrite in the ca. 3.22 Ga Moodies Group of the Barberton Greenstone Belt, southern Africa. Anhydrite occurs, together with barite and pyrite, in regionally traceable beds that formed in fluvial settings. Variable abundances of barite versus anhydrite reflect changes in sulfate enrichment by evaporitic concentration across orders of magnitude in an arid, nearshore terrestrial environment, periodically replenished by influxes of seawater. The multiple S-isotope compositions of anhydrite and pyrite are consistent with microbial sulfate reduction. S-isotope signatures in barite suggest an additional oxidative sulfate source probably derived from continental weathering of sulfide possibly enhanced by microbial sulfur oxidation. Although depositional environments of Moodies sulfate minerals differ strongly from marine barite deposits, their sulfur isotopic composition is similar and most likely reflects a primary isotopic signature. The data indicate that a constant input of small portions of oxidized sulfur from the continents into the ocean may have contributed to the observed long-term increase in Δ33 Ssulfate values through the Paleoarchean.

Climate control on banded iron formations linked to orbital eccentricity.

Astronomical forcing associated with Earth's orbital and inclination parameters ("Milankovitch" forcing) exerts a major control on climate as recorded in the sedimentary rock record, but its influence in deep time is largely unknown. Banded iron formations, iron-rich marine sediments older than 1.8 billion years, offer unique insight into the early Earth's environment. Their origin and distinctive layering have been explained by various mechanisms, including hydrothermal plume activity, the redox evolution of the oceans, microbial and diagenetic processes, sea level fluctuations, and seasonal or tidal forcing. However, their potential link to past climate oscillations remains unexplored. Here we use cyclostratigraphic analysis combined with high-precision uranium-lead dating to investigate the potential influence of Milankovitch forcing on their deposition. Field exposures of the 2.48-billion-year-old Kuruman Banded Iron Formation reveal a well-defined hierarchical cycle pattern in weathering profile that is laterally continuous over at least 250 kilometres. The isotopic ages constrain the sedimentation rate at 10 m/Myr and link the observed cycles to known eccentricity oscillations with periods of 405 thousand and about 1.4 to 1.6 million years. We conclude that long-period, Milankovitch-forced climate cycles exerted a primary control on large-scale compositional variations in banded iron formations.

Influence of mammary tumor progression on phenotype and function of spleen and in situ lymphocytes in mice.

Peripheral immunity to an immunogenic chemically induced mouse mammary adenocarcinoma has been demonstrated in the syngeneic host, i.e., BALB/c mice, by several in vivo and in vitro cell-mediated immune assays. Analysis of the responsiveness of the immune cells within the in situ population may prove to be more indicative of the actual interactions between host and tumors. A centrifugal elutriation procedure was used to isolate tumor-infiltrating lymphocytes. A fluorescence-activated cell sorter revealed that most in situ cells were of the T-cell lineage as determined by the absence of surface immunoglobulin (sIg) and the presence of the Thy 1.2 antigen on their surfaces, while in mice with large tumors there were 27.4% Thy 1.2+ and 47.9% sIg+ cells Further studies using fluorescein-conjugated monoclonal anti-Lyt 1 or anti-Lyt 2 antibodies revealed a decrease in the levels of Lyt 1+ cells and an increase in the percentage of Lyt 2+ lymphocytes in the spleens of mice bearing large tumors. Within the Thy 1.2+ population infiltrating mammary tumors, the proportion of lymphocytes presenting the Lyt 1 marker was decreased in comparison to that of spleens of normal mice (0.58 vs. 0.83). At the same time the relative proportions of Lyt 2+ cells within the Thy 1.2+ population was increased in the in situ population (0.50) compared to those of spleens of normal mice (0.28). Examination of the functional abilities of the in situ lymphocytes (ISL) revealed that ISL derived from small tumors responded to the T-cell mitogens phytohemagglutinin (PHA) and concanavalin A (Con A), although at lower levels than those of the splenocytes of the animals from which they were obtained. Responses to PHA were lost rapidly in ISL from large tumors, whereas Con A responses were more durable. In contrast to the spleen cells of tumor bearers, ISL failed to respond to tumor-associated antigens (TAA) at any stage of the disease. The changes in the subsets of T-cells in the spleens of tumor-bearing mice and in ISL may provide an explanation for the decreased activation of ISL by mitogens and for the lack of responsiveness to TAA observed in the splenocytes of mice with large tumors and in the ISL isolated from the mammary adenocarcinomas.

Dependence of initiation of an innocent bystander cytotoxicity reaction on the association of viral antigens and tumor cell membranes in mice.

In chemically induced mouse mammary tumors in BALB/c mice, no murine mammary tumor virus (MuMTV) antigens could be detected in the tumor cell membranes. In contrast, in mammary tumors of spontaneous appearance in BALB/cfC3H mice neonatally infected with MuMTV, viral antigens could be detected by immunofluorescence. Specific activation of immune spleen lymphocytes in vitro by homologous tumor cell membrane preparations resulted in an innocent bystander cytotoxicity reaction in BALB/c mice bearing either the chemical- or virus-induced mammary tumors. Non-tumor bearers did not respond in this reaction. The cytotoxicity effector cell was a nylon-adherent Thy 1.2+, Lyt 1+, Lyt 2+ lymphocyte. Induction of the reaction in the chemically induced mammary tumor bearers was related to tumor-associated antigens, but in the mice with MuMTV-induced tumors, it was possible that all responses were solely due to viral antigens. Biochemical analyses using immunoprecipitation techniques indicated that the major external glycoprotein of MuMTV (gp52) was present in the tumor cell membrane preparations. Preincubation of the cell membranes of virus-induced tumors with anti-MuMTV completely blocked the capacity of this preparation to induce the cytotoxicity. Preabsorption of the anti-MuMTV with purified MuMTV removed all the blocking activity of these sera, indicating that the antigenic determinants recognized were of viral origin. However, purified MuMTV failed by itself to elicit the innocent bystander cytotoxicity. This observation indicates that an association with membranes was necessary for the viral antigens to initiate and/or effect this cell-mediated immune reaction.

Induction of "innocent bystander" cytotoxicity in nonimmune mice by adoptive transfer of L3T4+ Lyt-1+2- mammary tumor immune T-cells.

Spleen cells from BALB/c mice, bearing a syngeneic mammary adenocarcinoma, nonspecifically lyse xenogeneic target cells following in vitro reexposure to mammary tumor-associated antigens. The effectors of this reaction have been shown to be Thy-1+ Lyt-1+2+ nylon-adherent cells. Tumor-immune spleen cells are also able to induce nonimmune spleen cells to express nonspecific cytotoxicity. Studies were undertaken to determine whether this inducer activity is mediated by the effector population or by a functionally distinct subset. Cell separation studies demonstrated that the inducers and effectors of innocent bystander cytotoxicity can be separated based upon the property of adherence to nylon wool. Further examination of the nylon-nonadherent inducer population indicated that the phenotype is L3T4 + Lyt-1+2-. By flow cytometry the inducer subset was shown to express a higher density of Thy 1 antigen than that expressed by the cytotoxic effectors. When adult thymectomized mice were implanted with mammary tumors, nonspecific effectors were not generated. In contrast, spleen cells from the same experimental animals were able to induce nonspecific cytotoxicity in normal mice following adoptive transfer of their spleen cells. Thus, these data support the conclusion that during the course of mammary tumor growth, at least two functionally and phenotypically distinct cell populations interact for the expression of "innocent bystander" cytotoxicity.

Characterization of the effector cells mediating an "innocent bystander" cytotoxicity reaction induced by a syngeneic mammary adenocarcinoma in mice.

Spleen cells from BALB/c mice bearing a syngeneic mammary adenocarcinoma nonspecifically destroy xenogeneic targets following in vitro induction with mammary tumor-associated antigens. Studies were undertaken to characterize the effector cell population(s) mediating this "innocent bystander" cytotoxicity reaction. Fractionation experiments using phagocyte-depleted spleen cells revealed that the effector population was adherent to nylon wool columns. Flow cytometric analysis of the nylon-adherent cells revealed the presence of a minor population of Thy 1.2+ cells. Following treatment of the nylon-adherent cells with anti-Thy 1.2 and complement, the cytotoxic activity was abolished. Furthermore, when those cells expressing the Thy 1.2 antigen were positively selected by cell sorting, they were able to mediate the cytotoxic reaction. In contrast, nylon-adherent Thy 1.2-negative cells were unable to mediate the reaction following selection by cell sorting. Depletion studies with anti-Lyt 1 or anti-Lyt 2 and complement also abolished this cytotoxic response. Additional studies demonstrated that nylon-adherent spleen cells from mammary tumor-bearing mice were not able to lyse natural killer cell-sensitive targets. These data suggest that the cells which effect tumor antigen-induced "innocent bystander" cytotoxicity, or their activated precursors, are nylon-adherent Thy 1.2+, Lyt 1+2+ T-cells.

Emergence of a B lymphocyte population with ADCC effector function in mammary tumor bearing mice.

Differential expression of antibody dependent cellular cytotoxicity (ADCC) effectors was studied in normal Balb/cCrgI mice and those bearing a chemically induced 7, 12 dimethylbenzanthracene mammary adenocarcinoma. Depletion of macrophages from normal mouse splenocytes by Sephadex G-10 columns resulted in elimination of ADCC. Further separation of the normal G-10 nonadherent splenocytes on nylon wool columns did not result in any population with significant cytotoxicity. However, Balb/c mice bearing mammary tumors showed enhanced levels of ADCC which were not eliminated by macrophage removal. Lymphocytes from tumor bearers further separated on nylon wool yielded nonadherent and adherent populations both capable of effecting significant ADCC. Treatment of the nylon nonadherent cells of both normal and tumor bearing mice with anti-asialo GM1 (AGM1) and complement decreased the ADCC responses. The same treatment only marginally affected cytotoxic levels of nylon adherent cells from tumor bearers, indicating that these effectors are primarily of non-NK lineage. In addition, G-10 nonadherent, nylon adherent cells from tumor bearers separated on a fluorescence activated cell sorter based on the presence of surface immunoglobulins (slg) revealed that both the slg- and slg+ (98% pure) sorted cells were capable of functioning in ADCC. To determine whether in the tumor mice the 2% of slg- cells present in the slg+ sorted population were the ADCC effectors, mixing experiments were done in which up to 10% of slg- cells from tumor bearers were added to nylon adherent cells from normal mice. No significant increases in ADCC levels were found over that of normal mice. These experiments indicate that the 2% slg- cells were not the ADCC effectors nor were they inducing normal B cells to exert this type of cytotoxic reaction in vitro. To further substantiate the B cell lineage of the slg+ ADCC effectors, surface immunoglobulins were removed with protease treatment. After a 36 hr incubation, 92% of the cells had regenerated their slg. The results presented in this paper demonstrate that various splenic lymphoreticular populations from tumor bearers possess an enhanced cytolytic activity against antibody coated target cells. Among these is a unique nylon adherent slg+ cell that is capable of functioning as an ADCC effector.

Improved allograft survival using highly enriched populations of rat islets.

A method is described for the purification of islets before the cells are placed in tissue culture, thus permitting the transplantation of islets cultured for three days against major histocompatibility barriers without adjuvant immunosuppression. Mixed lymphocyte culture reactions were carried out with three rat strain combinations and the in vitro responses were correlated with the in vivo survival of islet allografts. These results showed that islet allograft acceptance is independent of the degree of histoincompatibility between different rat strains.

Splenic alterations during mammary tumorigenesis: diverse effects on different immune parameters.

An evaluation of various parameters of the immune system was undertaken in Balb/c mice transplanted with a syngeneic mammary adenocarcinoma. Increasing tumor burdens resulted in a depression of some cell mediated immune functions. In contrast, an augmentation of humoral responses was observed in tumor-bearing mice. A defect in the immunoregulatory mechanism did not appear to be responsible for the elevated humoral response as revealed in suppressor cell experiments. However, flow cytometric analysis of T and B lymphocyte levels in the spleens of mice with mammary tumors indicated that the numbers of Thy 1.2 positive cells were greatly diminished while there was only a slight increase in the proportion of cells bearing surface immunoglobulin. These splenic alterations accompanying tumor growth might be responsible for the altered immune responses observed in tumor-bearing animals.

Treatment of a murine leukemia with chlorambucil bound monoclonal antibodies.

Mice bearing a murine T cell leukemia (P388) were treated with a battery of monoclonal antibodies specific for normal T cell differentiation antigens. Therapy was evaluated during the early course of disease by DNA cell cycle analysis and recovery of leukemia cells from tumor bearing mice. This form of therapy was shown to be ineffective. However, treatment with chlorambucil bound monoclonal antibodies was shown to be effective in reducing the number of leukemia cells undergoing DNA synthesis and mitosis, in addition to diminishing the tumor burden as compared to control mice. The potential benefits of this form of therapy are discussed.

B cell subsets in spleens of BALB/c mice: identification and isolation of MMTV-expressing and MMTV-responding subpopulations.

The DNA of BALB/c mice contains two genomic- and one subgenomic-size MMTV proviruses that appear to be preferentially expressed in their spleen cells, although intact MMTV virions cannot be detected in the tissues of these mice. This retrovirus antigen expression is restricted to a subpopulation of B lymphocytes, as determined by double label immunofluorescence studies. Nylon-adherent, SIg-positive spleen lymphocytes from BALB/c mice are capable of being stimulated by purified MMTV in lymphocyte transformation assays. Two possibilities were explored: the MMTV-positive cells are the responders to MMTV in the blastogenesis assay, or there exists two B lymphocyte subsets, one expressing the MMTV antigen(s) and the other responding to the virus. Depletion of MMTV-positive, nylon-adherent cells with anti-MMTV and complement resulted in no significant change in the blastogenesis to MMTV, indicating that the MMTV-negative lymphocytes are the responders in this reaction. These results were confirmed by positive selection experiments by using a fluorescence-activated cell sorter. Two populations of nylon-adherent cells, on the basis of the presence or absence of MMTV antigen in their surfaces, were obtained by a two-way sorting procedure and were used in lymphocyte transformation assays. MMTV-expressing lymphocytes were found to be nonresponsive to MMTV antigens, although high levels of [3H]thymidine incorporation were observed in the MMTV-negative, nylon-adherent cell cultures exposed to MMTV. These data indicate that in normal BALB/c mice, expression of endogeneous retrovirus genetic information is restricted to a nylon-adherent spleen cell subset that is different from the one responding in blastogenesis to the viral antigens.

Selective action of alkylating agents against cells participating in suppression of antibody responses.

The effect of several alkylating agents on the induction and expression of specific suppressor cell activity induced by supraoptimal immunization (SOI) with (4 x 10(9) ) SRBC was studied. Splenocytes taken 8-28 days after SOI and transferred to normal syngeneic recipients together with optimal dose of (3 x 10(8) ) SRBC caused 70-90% suppression. By contrast splenocytes harvested 2 days after SOI did not exert a significant suppressive effect. Treatment of donor mice with 30 mg/kg BCNU, CCNU, or MeCCNU, 8 mg/kg Melphalan or as much as 200 mg/kg Cy 2 days before SOI uniformly had no effect on the subsequent development of suppressor cells. By contrast, different drugs had diverse effects when injected after SOI: both BCNU and Cy injected 2 days post SOI alleviated suppression, whereas CCNU, MeCCNU and Melphalan injected 2 days post SOI were without effect. Another diversity between BCNU and Cy was noticed when the administration of drugs was delayed further. While Cy alleviated suppression 12 days post SOI, BCNU was ineffective at this time. Dose response and time course studies revealed that the effect of Cy was most severe when injected 2 days post SOI and gradually diminished with the passage of time after SOI. These results have been discussed in the light of the current concepts of multiple cell participation in the induction and expression of suppressor cell function.

Thymic involution and thymocyte phenotypic alterations induced by murine mammary adenocarcinomas.

A profound thymic atrophy has been observed in mice bearing large adenocarcinomas of the mammary gland. Only 2 to 5% of thymocytes remained 4 wk after tumor implantation. Although there is a slight decrease in the overall percentages of Thy-1+ cells in tumor bearers, the majority of the remaining cells are of a Thy-1 low phenotype. There was a lower percentage of double positive (CD4+, CD8+) cells, an increase of CD4+ CD8- thymocytes, similar percentages of CD4- CD8+ cells and double negative (CD4- CD8-) thymocytes in tumor-bearing mice. In addition, an increased percentage of CD3 cells could be detected in these animals. These results indicate that proportionally less immature thymocytes are present in the atrophic thymuses of mammary tumor bearers. Enhanced levels of glucocorticoids are known to produce similar effects on the thymus. However, adrenalectomy of mice followed by tumor implantation did not result in reversal of the thymic atrophy. Furthermore, a study of serum corticosterone levels in tumor bearers indicated no significant changes during tumorigenesis. A study of several parameters of bone marrow (BM) populations indicate that there is an increase in cells of the granulocyte-macrophage lineage and a decrease in lymphocytes induced by tumor-derived granulocyte macrophage-CSF. An alteration of prothymocytes in the BM is not the main cause of the thymic atrophy because BM cells from normal and tumor-bearing mice reconstituted irradiated normal mice equally well. There was no preferential recruitment of double positive cells to the spleen as indicated by no significant differences in the levels of T cells of immature phenotype including the CD4+ CD8+ population in the spleens of tumor bearers. Because no major changes were observed in tumor bearers, either at their capacity to repopulate the thymus or at the patterns of subsequent redistribution of thymocytes, it was postulated that the thymic atrophy may be caused by a direct or indirect effect of the tumor or tumor-associated factor(s). Intrathymic injections of tumor cells into young normal recipient mice resulted in a significant reduction of the thymus weight and cellularity. These data suggest that mammary tumors can secrete factor(s) that are capable of severely impairing the normal development of cells of the T cell lineage.

Lymphoreticular cells isolated by centrifugal elutriation from a mammary adenocarcinoma. I. Characterization of an in situ lymphocyte suppressor population by surface markers and functional reactivity.

The procedure of centrifugal elutriation was evaluated as a means of purifying large numbers of in situ lymphocytes from enzymatically disaggregated mouse mammary tumors. The eluate obtained at a flow rate of 3.0 ml/min was optimal for high levels of lymphocyte recovery with low levels of contaminating tumor cells, polymorphonuclear leukocytes, and macrophages. The majority of the tumor infiltrating lymphocytes (90%) expressed the Thy 1.2 antigen, while less than 5% possessed surface immunoglobulin. Further analysis of the T lymphocyte population was accomplished by flow cytometric analysis of in situ lymphocytes stained with fluorescein-conjugated monoclonal anti-Lyt 2 antibodies. The results of such studies reveal an increase in the levels of Lyt 2+ lymphocytes within the in situ population. To determine whether these Lyt 2+ cells were functionally active as suppressor cells, the ISL1 were mixed with spleen cells from tumor bearers and then tested for their ability to respond to mitogen and TAA-induced blast transformation of tumor-bearer spleen cells. Removal of macrophages from ISL by Sephadex G-10 columns did not alter the suppression. Treatment with monoclonal anti-Lyt 1 antibody and complement did not affect the inhibition observed. However, treatment of ISL with anti-Lyt 2+ monoclonal antibody and complement resulted in the elimination of the suppressor cell activity. We concluded that within the tumor-infiltrating lymphoreticular cells there is a population of Thy 1.2+ Lyt 2.2+ lymphocytes responsible for the suppression of mitogen and tumor-antigen-induced blastogenesis.