Sex versus asex: An analysis of the role of variance conversion.

The question as to why most complex organisms reproduce sexually remains a very active research area in evolutionary biology. Theories dating back to Weismann have suggested that the key may lie in the creation of increased variability in offspring, causing enhanced response to selection. Under appropriate conditions, selection is known to result in the generation of negative linkage disequilibrium, with the effect of recombination then being to increase genetic variance by reducing these negative associations between alleles. It has therefore been a matter of significant interest to understand precisely those conditions resulting in negative linkage disequilibrium, and to recognise also the conditions in which the corresponding increase in genetic variation will be advantageous. Here, we prove rigorous results for the multi-locus case, detailing the build up of negative linkage disequilibrium, and describing the long term effect on population fitness for models with and without bounds on fitness contributions from individual alleles. Under the assumption of large but finite bounds on fitness contributions from alleles, the non-linear nature of the effect of recombination on a population presents serious obstacles in finding the genetic composition of populations at equilibrium, and in establishing convergence to those equilibria. We describe techniques for analysing the long term behaviour of sexual and asexual populations for such models, and use these techniques to establish conditions resulting in higher fitnesses for sexually reproducing populations.

Liver Kupffer cells control the magnitude of the inflammatory response in the injured brain and spinal cord.

The CNS inflammatory response is regulated by hepatic chemokine synthesis, which promotes leukocytosis and facilitates leukocyte recruitment to the site of injury. To understand the role of the individual cell populations in the liver during the hepatic response to acute brain injury, we selectively depleted Kupffer cells (KC), using clodronate-filled liposomes, and assessed the inflammatory response following a microinjection of IL-1beta into the rat brain or after a compression injury in the spinal cord. We show by immunohistochemistry that KC depletion reduces neutrophil infiltration into the IL-1beta-injected brain by 70% and by 50% into the contusion-injured spinal cord. qRT-PCR analysis of hepatic chemokine mRNA expression showed that chemokine expression in the liver after brain injury is not restricted to a single cell population. In non-depleted rats, CXCL-10, IL-1beta, CCL-2, and MIP-1alpha mRNAs were increased up to sixfold more than in KC depleted rats. However, CXCL-1 and MIP-1beta were not significantly affected by KC depletion. The reduction in chemokine mRNA expression by the liver was not associated with decreased neutrophil mobilisation as might have been expected. These findings suggest that in response to CNS injury, KC mediated mechanisms are responsible for increasing neutrophil entry to the site of CNS injury, but that neutrophil mobilisation is dependent on other non-KC mediated events. However, the suppression of KC activity may prevent secondary damage after acute brain injury.

The relationship between trauma and beliefs about hearing voices: a study of psychiatric and non-psychiatric voice hearers.

BACKGROUND: Cognitive models suggest that distress associated with auditory hallucinations is best understood in terms of beliefs about voices. What is less clear is what factors govern such beliefs. This study aimed to explore the way in which traumatic life events contribute towards beliefs about voices and any associated distress. METHOD: The difference in the nature and prevalence of traumatic life events and associated psychological sequelae was compared in two groups of voice hearers: psychiatric voice hearers with predominantly negative beliefs about voices (PVH) and non-psychiatric voice hearers with predominantly positive beliefs about voices (NPVH). The data from the two groups were then combined in order to examine which factors could significantly account for the variance in beliefs about voices and therefore levels of distress. RESULTS: Both groups reported a high prevalence of traumatic life events although significantly more PVH reported trauma symptoms sufficient for a diagnosis of post-traumatic stress disorder (PTSD). Furthermore, significantly more PVH reported experiencing childhood sexual abuse. Current trauma symptoms (re-experiencing, avoidance and hyperarousal) were found to be a significant predictor of beliefs about voices. Trauma variables accounted for a significant proportion of the variance in anxiety and depression. CONCLUSIONS: The results suggest that beliefs about voices may be at least partially understood in the context of traumatic life events.

Immunomodulatory effects of etanercept in a model of brain injury act through attenuation of the acute-phase response.

TNF-alpha has proved to be a successful target in the treatment of many peripheral inflammatory diseases, but the same interventions worsen immune-mediated CNS disease. However, anti-TNF-alpha strategies may offer promise as therapy for non-immune CNS injury. In this study, we have microinjected IL-1beta or lipopolysaccharide (LPS) into the rat brain as a simple model of brain injury and have systemically administered the TNF-alpha antagonist etanercept to discover whether hepatic TNF-alpha, produced as part of the acute-phase response to CNS injury, modulates the inflammatory response in the brain. We report a significant reduction in neutrophil numbers recruited to the IL-1beta- or LPS-challenged brain as a result of TNF-alpha inhibition. We also show an attenuation in the levels of hepatic mRNA including TNF-alpha mRNA and of TNF-alpha-induced genes, such as the chemokines CCL-2, CXCL-5, and CXCL-10, although other chemokines elevated by the injury were not significantly changed. The reduction in hepatic chemokine synthesis results in reduced numbers of circulating neutrophils, and also a reduction in the numbers recruited to the liver as a consequence of brain injury. These findings suggest that TNF-alpha inhibitors may reduce CNS inflammatory responses by targeting the hepatic acute-phase response, and thus therapies for brain injury need not cross the blood-brain barrier to be effective.

Post-conditioning with lipopolysaccharide reduces the inflammatory infiltrate to the injured brain and spinal cord: a potential neuroprotective treatment.

Systemic infection often accompanies or precedes acute brain injury, but it remains unclear how the systemic response contributes to outcome. To examine this problem we have microinjected recombinant interleukin-1beta (IL-1beta), a cytokine associated with acute brain injury, into the rat brain parenchyma and either preceded or followed this challenge with the intravenous injection of lipopolysaccharide (LPS), which mimics systemic inflammatory response syndrome. The microinjection of IL-1beta alone into the brain parenchyma gives rise to leukocyte mobilization in the blood, and to the delayed recruitment of neutrophils and monocytes to the brain with no evidence of blood-brain barrier breakdown or overt neuronal cell death. Systemic LPS pre-conditioning resulted in a dose-dependent reduction both in the number of circulating leukocytes and in the number of leukocytes recruited to the brain parenchyma after 12 h. Surprisingly, LPS given two hours after injury was equally effective in reducing the recruitment of leukocytes to the brain, which is more relevant to the management of clinical disease. In a more clinically relevant model of spinal cord injury, intravenous LPS post-conditioning also reduced the numbers of leukocytes mobilized in the blood and recruited to the spinal cord and thus limited the breakdown of the blood-spinal cord barrier. The effects appear to be specific to LPS, as they were not observed after intravenous IL-1beta pre-conditioning. Our studies suggest that individual pro-inflammatory conditioning strategies may protect the injured central nervous system from the damaging consequences of leukocyte recruitment and may provide scope for novel therapeutic intervention.

Affinity maturation and isotype switch in clonally related anti-erythrocyte autoantibodies.

The NZB mouse is genetically predisposed to develop, at approximately 6 months of age, a spontaneous and severe autoimmune anaemia caused by production of pathogenic anti-mouse erythrocyte autoantibodies. Molecular analysis of a panel of five anti-erythrocyte monoclonal antibodies (MoAb) derived from splenocytes of unimmunized NZB mice revealed that these autoantibodies all had functionally rearranged genes from the VH J558 family of immunoglobulin genes with closest homology to germline genes H10 and H30. Owing to clustering of nucleotide differences within the CDRs, compared with the germline, it was concluded that these antibodies were most likely generated by an antigen-driven mechanism. We report here further molecular analysis of two (4.16.1 and B4.13.2) of the panel of five anti-mouse erythrocyte producing hybridomas which are apparently clonally related. Nucleotide analysis of the light chain cDNA indicated that both antibodies had closest homology to germline gene V kappa 24 and use J kappa 2 gene. Determination of the functional affinities of the MoAb reveal that B4.13.2 (IgG2a) has a > 10-fold higher affinity for mouse erythrocytes when compared to 4.16.1 (IgG1). This finding supports the view that these two autoantibodies are generated by an antigen-driven mechanism. The proposed mechanism would involve the selection and expansion of a small population of B-lymphocytes by antigen leading to isotype switch, somatic mutation and increased affinity. Our data also point to the possibility that some framework residues may be involved in the binding to antigen.

Identification of hybridomas derived from mouse CD5+ B lymphocytes by fluorescent staining for cytoplasmic CD5 expression.

The production of hybridomas derived from CD5+ B lymphocytes is important for studying the immunoglobulin gene repertoire and antibody specificity of this B-lymphocyte subpopulation. However, hybridomas derived from these lymphocytes invariably lose surface membrane expression of CD5 following hybridization. This impedes the unequivocal assignment of the generated hybridomas to the CD5+ B-lymphocyte subpopulation from unsorted, or partially sorted, cells. Recent studies have shown that mRNA transcripts of the CD5 gene and the protein product can be detected in the cytoplasm of some mouse hybridomas, indicating that although surface expression has been lost, they may have been generated from CD5+ B lymphocytes. These studies, however, have been unable to discount completely the possibility that aberrant cytoplasmic expression of the CD5 gene occurred as a direct consequence of the hybridization process. To confirm that cytoplasmic CD5 expression in the hybridomas is in fact directly related to the B-lymphocyte origin we have generated hybridomas from FACS-sorted CD5+ and CD5- murine splenic B lymphocytes, and determined their surface and cytoplasmic CD5 expression by fluorescence-activated cell sorting. Our findings reveal that all hybridomas derived from CD5+ B lymphocytes (nine hybridomas) were negative for surface but positive for cytoplasmic CD5 expression, whereas all hybridomas derived from CD5- B lymphocytes (nine hybridomas) were negative for both surface and cytoplasmic CD5 expression. This finding shows that staining for cytoplasmic CD5 expression provides an accurate method of determining the cellular origin of murine B-lymphocyte hybridomas.

Anti-mouse red blood cell monoclonal antibodies use functionally rearranged genes from the VH J558 family and are derived from the CD5- B-lymphocyte subpopulation.

The NZB mouse strain is genetically predisposed to develop, at approximately 6 months of age, a spontaneous and severe autoimmune anaemia caused by the production of pathogenic anti-mouse red blood cell (MRBC) autoantibodies. Although it is believed that the predisposition to autoimmune anaemia is multigenic in nature, the main pathogenic mechanism is attributed to anti-MRBC autoantibodies. We have generated eight anti-MRBC monoclonal antibody (mAb)-producing hybridomas derived from splenocytes of 9- and 12-month-old NZB mice with spontaneous autoimmune anaemia to dissect the molecular and cellular mechanisms resulting in the production of these pathogenic antibodies. The predominant immunoglobulin isotype was IgG2a, produced by five out of eight hybridomas (63%), while IgM, IgG1 and IgG2b were each produced by one hybridoma cell line (12%). Antigen specificity analysis of all eight hybridomas revealed that antibodies from seven out of eight hybridomas were monospecific for MRBC antigen(s). Only one hybridoma (clone 4-16-1) cross-reacted with rat RBC. None of the hybridomas produced antibodies reactive with single- or double-stranded DNA (ss- or dsDNA). Surface and cytoplasmic staining for the CD5 antigen revealed that none of the hybridomas was derived from CD5+ B lymphocytes. All hybridomas cause anaemia when implanted intraperitoneally into normal BALB/c mice. Molecular studies of five of the eight anti-MRBC mAb reveal that all use functionally rearranged genes from the VH J558 gene family. Three of these five mAb used FL16.1 DH genes while one had a CDR3 that resulted from a fusion between two DH genes (SP2.3 and SP2.2) from the SP family.

Molecular mechanisms resulting in pathogenic anti-mouse erythrocyte antibodies in New Zealand black mice.

The New Zealand black (NZB) mouse strain is genetically predisposed to develop, at approximately 6 months of age, a spontaneous and severe autoimmune anaemia caused by production of pathogenic anti-mouse erythrocyte autoantibodies. In order to investigate the molecular mechanisms which lead to anti-mouse erythrocyte autoantibody production we have generated eight anti-mouse erythrocyte MoAbs producing hybridomas from splenocytes of 9- and 12-month-old NZB with spontaneous autoimmune anaemia. IgG2a was the predominant isotype, while IgM, IgG1 and IgG2b were each produced by one hybridoma cell line. All anti-mouse erythrocyte MoAbs were characterized for their antigen specificities. None of the MoAbs cross-reacted with ss- or dsDNA or with other species' erythrocytes, with the exception of one MoAb which cross-reacted with rat erythrocytes. None of the eight hybridomas was demonstrated to express surface or cytoplasmic CD5, suggesting that they derived from CD5- B lymphocytes. All hybridomas when implanted intraperitoneally into BALB/c mice caused anaemia. In order to define the genetic basis and investigate the molecular mechanisms resulting in pathogenic anti-mouse erythrocyte autoantibody production, the pattern of immunoglobulin variable region gene use has been studied. Five of the eight MoAbs whose IgVH genes were sequenced all have functionally rearranged genes from the VH J558 gene family. There is evidence for somatic point mutations in the complementarity-determining regions (CDR) of the IgVH genes in all of these five MoAbs when compared with the closest known germline gene. We suggest that these nucleotide sequence changes are likely to reflect selection by an antigen-driven mechanism. Furthermore, the data indicate that pathogenic anti-mouse erythrocytes are not derived from 'natural' autoantibodies.

CD5 (Ly-1)-negative, conventional splenic B cells make a substantial contribution to the bromelain plaque-forming cell response in CBA and BW mice.

CD5 (Ly-1) B cells are a minor subpopulation in mouse spleen and are thought to be responsible for the production of natural autoantibodies to bromelain-treated autologous erythrocytes (Br-RBC). Here it is shown that substantial numbers of conventional, CD5-negative, splenic B cells also secrete these antibodies in CBA and (NZB x NZW)F1 mice, whereas in NZB and BALB/c mice they are all produced by the CD5 B-cell population. However, stimulation with bacterial lipopolysaccharide in vivo preferentially activates the CD5 B-cell group to anti-Br-RBC antibody secretion.

Anti-nRNP anti-nuclear antibody-secreting cells are represented in the B-lymphocyte repertoire of normal and MRL/MP-lpr/lpr lupus mice.

Spleen cells from MRL-lpr/lpr, CBA and BALB/c mice were cultured in vitro and assayed for production of anti-nuclear antibodies. Spleen cells from all species produced IgM antibodies to a nRNP (U1-RNP)-specific antigen and to double-stranded DNA (dsDNA) after stimulation with LPS. The specificity of the anti-nRNP antibodies was shown, by immunoblotting, to be directed against the 33,000 MW polypeptide of nRNP/Sm. CBA mice produced more IgM autoantibody in vitro than MRL/lpr or BALB/c mice. In contrast, IgG anti-nRNP and anti-dsDNA antibody were not produced by any of the strains. Our data show that anti-nRNP and anti-dsDNA precursor B cells are part of the normal murine immune repertoire and are not confined to the MRL/lpr strain. This suggests that the spontaneous development of anti-nRNP and anti-dsDNA antibodies associated with systemic lupus erythematosis (SLE) is dependent on clonal stimulation and removal of suppressive influences.

Immune induction of Ia antigens in activated T cells and in kidney epithelial cells in mice.

A rat monoclonal antibody against mouse Ia antigens was used to investigate the induction of Ia expression by activated T cells and renal epithelial cells during immune responses. The induction of low levels of surface Ia on activated helper and cytotoxic/suppressor T-cell phenotypes was directly demonstrated by differential fluorescence staining. Renal epithelial cells were observed to become strongly Ia-positive after primary immunization with alum-precipitated protein antigen, or after secondary challenge with the soluble antigen used for priming.

Functional differences associated with quantitative distribution of membrane immunoglobulin, Fc receptors and Ia on mouse B cells.

Murine splenic B cells were stained with antibodies against mIg, Ia or FcR and then separated on the fluorescence-activated cell sorter on the basis of quantitative differences in marker expression; that is, they were fractionated into subpopulations bearing high or low densities of the marker. The separated cells were then tested for their relative capacities for T-dependent primary and secondary antibody responses, and for lipopolysaccharide responsiveness. There was no association between the surface density of any of these markers and the ability of the cells to proliferate in response to lipopolysaccharide. However, a high level of surface Ia was associated with good primary and secondary T-dependent responses. The density of mIg or of FcR showed no association with the capacity for primary responses, but a low density of these two markers, especially FcR, was correlated with good secondary responsiveness. Thus, subpopulations of B cells selected on the basis of quantitative levels of membrane markers can also be distinguished by their functional properties.

Isolation, characterization, and regulation of the prolactin receptor.

The prolactin, or lactogenic hormone, receptor has been purified (approximately 80%) from lactating mouse liver and human term placenta by the nondenaturing zwitterionic detergent 3-[(3-cholamidopropyl)-dimethylammonio]-1-propane sulfonate and a prolactin affinity column. The isolated "core-binding unit" has a molecular weight of 37,000 +/- 2,000 daltons. It retains the specificity for lactogenic hormones and binds prolactin with an affinity (Ka = 2 to 6 X 10(9) M-1) similar to that of the receptor as it occurs in its membranous environment (Ka = 3 to 5 X 10(9) M-1). Whether this "core-binding unit" exists on the cell surface in a cryptic or active form is influenced greatly by its association with other membrane proteins and the concentration of phosphatidylcholine within its local membranous environment.

Heterogeneity of B-cells.

Two rat monoclonal antibodies, NIM-R2 and NIM-R3, were prepared that only recognize B-cells in murine secondary lymphoid tissues. Both showed differential reactivity in that they reacted most strongly with nonoverlapping populations of B-cells. They also reacted differentially with some cells of the primary lymphoid tissue, recognizing 90-95% of bone marrow cells, again in a nonoverlapping manner and with NIM-R2 accounting for twice as many cells as NIM-R3. The antibody NIM-R2, but not NIM-R3, also recognized thymocytes and red blood cells. The determinant recognized by NIM-R2 is of interest because it fluctuates at four defined stages of B-cell development: pre-B to immature B, activation of mature B, differentiation of memory cells, and differentiation of antibody-secreting cells. Particularly noteworthy was the differential reactivity of NIM-R2 with virgin and memory B-cells. Those cells that stained strongly with the antibody gave excellent primary responses, but were unable to transfer secondary responses, whereas weakly stained B-cells transferred memory, but could not generate primary antibody responses in vitro. Thus NIM-R2 recognized a cell-surface determinant that presumably decreases in density as primary B-cells differentiate into memory B-cells. A survey of sIg, I-A, Fc receptors, and major glycoproteins of B-cells from spleen, Peyer's patches, mesenteric lymph nodes, and peripheral lymph nodes failed to reveal any major differences between the cells from these different lymphoid organs.

Growth in "new" vegetarian preschool children using the Jenss-Bayley curve fitting technique.

Length and weight measurements obtained on 142 vegetarian and 229 nonvegetarian school children from a normative population were fitted to growth curves using the asymptotic nonlinear regression equation of Jenss and Bayley. All of the children were Caucasian and age ranged from a few weeks to 6 yr. The growth curves obtained for vegetarian children were from 0.5 to 1.0 kg and 1 to 2 cm lower, depending on age, sex, and diet, than were curves for reference populations of nonvegetarian children. Length was affected more than weight. Macrobiotic vegetarian children's curves were more depressed than those of the other vegetarian children, indicating that there was a good deal of heterogeneity in growth within vegetarians which was associated with dietary group characteristics. Measurements of females were more consistently affected than males, and their diets were also more far reaching with respect to animal food avoidances. The analysis of food records available provided evidence that energy intakes of the vegetarians were below recommended levels, whereas protein intakes did not appear to be limiting.