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Soil phosphates exchange oxygen atoms rapidly with soil water once recycled by intracellular enzymes, thereby approaching an equilibrium δ18OP signature that depends on ambient temperature and the δ18OW signature of soil water. We hypothesized that in the topsoil, phosphates reach this equilibrium δ18OP signature even if amended by different fertilizers. In the subsoil, however, there might be phosphates with a smaller δ18OP value than that represented by the isotopic equilibrium value, a condition that could exist in the case of limited biological P cycling only. We tested these hypotheses for the HCl-extractable P pool of the Hedley fractionation scheme of arable soil in Germany, which integrates over extended time-scales of the soil P cycle. We sampled several types of fertilizer, the surface soil that received these fertilizer types and composites from a Haplic Luvisol depth profile under long-term agricultural practice. Organic fertilizers had significantly smaller δ18OP values than mineral fertilizers. Intriguingly, the fields fertilized organically also tended to have smaller δ18OP signatures than other types of surface soil, which calls into question full isotopic equilibrium at all sites. At depths below 50 cm, the soil δ18OP values were even depleted relative to the values calculated for isotopic equilibrium. This implies that HCl-extractable phosphates in different soil horizons are of different origins. In addition, it supports the assumption that biological cycling of P by intracellular microbial enzymes might have been relatively inefficient in the deeper subsoil. At depths of 50-80 cm, there was a transition zone of declining δ18OP values, which might be regarded as the first evidence that the degree of biological P cycling changed at this depth interval. [ABSTRACT FROM AUTHOR]

The binding of palladium to organic ligands was studied in leaves from contaminated endive. The palladium-treated plants contained 8.7 ngPd/g referring to wet weight. After a cell breakdown in buffer the resulting homogenate was separated into supernatant and pellet by centrifugation and the distribution of palladium was determined. The liquid fraction contained 40% of the total palladium and was further separated by ultrafiltration. This technique revealed that 23% of total palladium was present as high molecular weight species (>10kDa). After concentration, the high molecular weight fraction was further investigated by gel permeation chromatography (GPC). By this method only one elution range for palladium was observed. The size range of the GPC used was about 20-8000 kDa for globular proteins. The palladium elution maximum was detected in the range of about 160kDa. The determinations of palladium were performed by total-reflection X-ray fluorescence after palladium separation and preconcentration. [ABSTRACT FROM AUTHOR]

Reports on the uptake of automobile catalyst emitted palladium by European eels, Anguilla anguilla following experimental exposure to road dust. Analytical problems in detecting palladium in small biological samples; Total-reflection X-ray fluorescence analysis after co-precipitation of palladium with mercury; Uptake of traffic related palladium by European eels.

To investigate the regulation of lg switch recombination, we have constructed mice with a 56 kb VDJμδγ1 transgene. This transgene included an anti-nitrophenyl VDJ segment, Sμ, Cμ, Cδ, Iγ1, Sγ1, Cγ1 and the Cγ1 membrane exons from the murine Igha haplotype. Two founder lines were produced, with very similar characteristics. Transgenic B cells expressed normal amounts of Cμ (which is >95% transgenic), Cδ and other cell surface markers, and normal amounts of VDJ and Cμ RNA. γ1 germline transcription of the transgenes is properly regulated since stable transcripts were not expressed in B cells treated with lipopolysaccharide (LPS) alone, nor in thymus or non-lymphoid tissues, but were expressed after treatment of B cells with LPS+IL-4 or CD40L+IL-4. B cells from both lines of transgenic mice expressed transgenic γ1a after in vitro culture with CD40L+IL-4, but not after culture with CD40L alone. However, the CD40L+IL-4 induced IgG1 precursor frequency is much lower for VDJμδγ1 transgenic B cells (1:240-760) than for non-transgenic B cells (1:9). Analysis of DNA from transgenic hybridomas indicated that switch recombination can take place in switch (S) regions, but can also take place outside S regions. These results indicate that targeting of switch recombinase to S regions must include regulation beyond the S regions themselves and correct germline transcription. This additional regulation might include cis-acting elements or appropriate spacing or arrangement of the recombining elements. [ABSTRACT FROM PUBLISHER]

Mutations in Bruton's tyrosine kinase (Btk) gene, in mice, result in reduced numbers and responses of peripheral B cells. Surface Ig-mediated signaling is defective in Btk mutant B cells as they do not proliferate upon slg cross-linking and lack thymus-independent (TI) type II responses. Signals through sIg and CD40 play a critical role in B cell maturation. To investigate the consequences of the lack of both Btk and CD40 on B cell development and function, mice were generated that were homozygous for targeted mutations in the Btk and the CD40 genes (BtkMCD40M). The CD40 mutation (CD40M) had a synergistic effect on the BtkM defects. In BtkMCD40M mice the number of B cells was reduced 3- to 4-fold compared to BtkM mice and mature B cells (IgMlow/IgDhigh) were virtually absent; serum levels of all Ig isotypes were diminished; and antibody responses to TI-I TI-II and thymus-dependent antigens were impaired. Furthermore, although wild-type BtkM and CD40M mice produced germinal centers in response to TI-I antigen, the BtkMCD40M mice did not. Maturational and functional B cell defects in BtkMCD40M mice may result from a combination of intrinsic B cell defects, lack of CD40L-dependent T cell help and microenvironmental defects. These data suggest that signals through Btk and CD40 are necessary for the production and maintenance of the mature B cell. [ABSTRACT FROM AUTHOR]

Animal models substantially contribute to the understanding of the pathogenesis of various human diseases, including those associated with genetic defects. Our study investigated the characteristics of antibody responses elicited by T-dependent and T-independent antigens in mice rendered k-deficterrt by targeted deletion of the JC gene segments. It is known that in normal murine species the k repertoire dominates the antibody repertoire (k/λratio = 95:5). Our results indicate that the k gene deletion causes the alternative usage of λ1 (93%) and λ2 (7%) light chains, confirming previous studies demonstrating that in k-deficlent mice all B cells express IGλ receptors. The anti-trinitrophenylbenzene (TUP) response in K−/− mice was compensated for by α1 and α2 bearing Igs. However, isoelectric focusing analysis of anti-TNP antibodies showed a considerably more restricted pattern of α anti-TNP antibodies in K−/− as compared with κ antibodies in normal mice. No major differences were observed in the affinity for the hapten of κ orα1 or α2 mAbs obtained from 129/Sv and K−/− mice. Furthermore, κ1 and κ2 chains can reconstitute the expression of an Idiotype (460ld) borne on κ anti-TNP antibodies. The 460ld was detected both in polyclonal and monoclonal anti-TNP antibodies obtained from K−/− mice. Our results clearly showed that the κ anti-TNP repertoire is compensated by the α repertoire even though the latter is clonally restricted in K−/− mice. [ABSTRACT FROM PUBLISHER]

The immunoglobulin light chain Vκ1 gene family is polymorphic in murine inbred strains and this family has been subdivided into five sub-groups (Vκ1A–E). The Vκ1A sub-group contributes to ∼ 2% of the total serum immunoglobulin light chains in several mouse strains. However, It has been reported that this sub-group Is absentin New Zealand Black (NZB) mouse serum. Amino acid sequencing of myeloma proteins from this inbred mouse has shown that they belong to the Vκ1B sub-group. We report here the structure of nine functional germllne genes from NZB mice thathave high homologies to the Vκ1 A, Vκ1B, Vκ1C, and Vκ1D sub-groups. In addition, a novel germlinegene representing the prototype of a new sub-group (designated Vκ1F) has been Identified. We have Isolated different Vκ1 germline genes from a single restriction fragment length polymorphism (RFLP) fragment, as well as Identical Vgenes from two different RFLP migrating bands. Therefore, the complexity of the genes encoding the immunoglobulin variable region cannot be determined solely by RFLP analysis. Nucleotide sequence analysis of 16 Vκ1 genes which code for NZB autoantlbodies indicate that they belong to five different Vκ1 sub-groups with five hybridomas (31%)expressing the Vκ1A sub-group. Comparison of the sequences of Vκ1 genes expressed in hybridomas with corresponding germllne genes shows no somatic mutations [ABSTRACT FROM PUBLISHER]

Vaccine development targeting rapidly evolving pathogens such as HIV-1 requires induction of broadly neutralizing antibodies (bnAbs) with conserved paratopes and mutations, and in some cases, the same Ig-heavy chains. The current trial-and-error search for immunogen modifications that improve selection for specific bnAb mutations is imprecise. Here, to precisely engineer bnAb boosting immunogens, we use molecular dynamics simulations to examine encounter states that form when antibodies collide with the HIV-1 Envelope (Env). By mapping how bnAbs use encounter states to find their bound states, we identify Env mutations predicted to select for specific antibody mutations in two HIV-1 bnAb B cell lineages. The Env mutations encode antibody affinity gains and select for desired antibody mutations in vivo. These results demonstrate proof-of-concept that Env immunogens can be designed to directly select for specific antibody mutations at residue-level precision by vaccination, thus demonstrating the feasibility of sequential bnAb-inducing HIV-1 vaccine design., (© 2024. The Author(s).)