The epithelial cells of the choroid plexuses secrete cerebrospinal fluid (CSF), by a process which involves the transport of Na + , Cl -and HCO 3 -from the blood to the ventricles of the brain. The unidirectional transport of ions is achieved due to the polarity of the epithelium, i.e. the ion transport proteins in the blood-facing (basolateral) membrane are different to those in the ventricular (apical) membrane. The movement of ions creates an osmotic gradient which drives the secretion of H 2 O. A variety of methods (e.g. isotope flux studies, electrophysiological, RT-PCR, in situ hybridization and immunocytochemistry) have been used to determine the expression of ion transporters and channels in the choroid plexus epithelium. Most of these transporters have now been localized to specific membranes. For example, Na + -K + ATPase, K + channels and Na + -2Cl --K + cotransporters are expressed in the apical membrane. By contrast the basolateral membrane contains Cl --HCO 3 exchangers, a variety of Na + coupled HCO 3 -transporters and K + -Cl -cotransporters. Aquaporin 1 mediates water transport at the apical membrane, but the route across the basolateral membrane is unknown. A model of CSF secretion by the mammalian choroid plexus is proposed which accommodates these proteins. The model also explains the mechanisms by which K + is transported from the CSF to the blood. Keywordschoroid plexus; blood-cerebrospinal fluid barrier; epithelial cells; ion transport; ion channels; Na + -K + ATPaseThe cerebrospinal fluid (CSF) is a major part of the extracellular fluid of the CNS. The CSF fills the ventricles of the brain, the spinal canal and the subarachnoid space ( Fig. 1), and in humans has a total volume of approximately 140 ml. The CSF is separated from neuronal tissue by the ependyma (which lines the ventricles and canals), and the pia (which covers the external surface of the brain). The composition of the CSF does, however, influence neuronal activity, notably in the central chemoreceptors of the medulla oblongata which control respiration by responding to changes in CSF pH.The CSF has a number of important functions. It helps provide mechanical support for the brain, i.e. the brain "floats" in the CSF reducing its effective weight by more than 60% (Segal, 1993). CSF also acts as a drainage pathway for the brain, by providing a "sink" into which products of metabolism or synaptic activity are diluted and subsequently removed * Corresponding author. Tel: +44-161-275-5463; fax: +44-161-275-5600. E-mail address: peter.d.brown@man.ac.uk (P. D. Brown).. Abbreviations:CFTRcystic fibrosis transmembrane conductance regulator CSF cerebrospinal fluid. Europe PMC Funders Group Europe PMC Funders Author ManuscriptsEurope PMC Funders Author Manuscripts (Segal, 1993). The CSF may also be an important route by which some nutrients reach the CNS . A final putative role for the CSF is that it acts as a route of communication within the CNS, i.e. it carries hormones and transmitters between different areas of the brain ....

CD22 is a surface glycoprotein of B lymphocytes that is rapidly phosphorylated on cytoplasmic tyrosines after antigen receptor cross-linking. Splenic B cells from mice with a disrupted CD22 gene were found to be hyperresponsive to receptor signaling: Heightened calcium fluxes and cell proliferation were obtained at lower ligand concentrations. The mice gave an augmented immune response, had an expanded peritoneal B-1 cell population, and contained increased serum titers of autoantibody. Thus, CD22 is a negative regulator of antigen receptor signaling whose onset of expression at the mature B cell stage may serve to raise the antigen concentration threshold required for B cell triggering.

Accelerated development of the secondary immune response may be attributable in part to the rapid delivery of antigen to lymphoid follicles by circulating antibody elicited on primary immunization. Here we provide evidence indicating that the nonspecific IgM present in naive mice (natural antibody) plays a role in the acceleration of the primary response. Targeted deletion of the Ig s polyadenylation site by use of Cre recombinase allowed the creation of mice that, although harboring a normal number of B cells expressing surface IgM, completely lacked serum IgM while retaining the other Ig isotypes. These mice retained a broadly normal B lymphocyte distribution (although containing a somewhat expanded peritoneal B1a subset) but exhibited substantial delays in mounting affinity-matured IgG responses to T cell-dependent antigens. The T cell-independent response, however, was augmented. The data indicate that the IgM present before antigen challenge (as well, possibly, as that elicited immediately after immunization) accelerates maturation of the primary response, presumably by complexing with the antigen and facilitating lymphocyte activation and͞or antigen trapping.

The activation-induced deaminase/apolipoprotein B-editing catalytic subunit 1 (AID/APOBEC) family comprises four groups of proteins. Both AID, a lymphoid-specific DNA deaminase that triggers antibody diversification, and APOBEC2 (function unknown) are found in all vertebrates examined. In contrast, APOBEC1, an RNA-editing enzyme in gastrointestinal cells, and APOBEC3 are restricted to mammals. The function of most APOBEC3s, of which there are seven in human but one in mouse, is unknown, although several human APOBEC3s act as host restriction factors that deaminate human immunodeficiency virus type 1 replication intermediates. A more primitive function of APOBEC3s in protecting against the transposition of endogenous retroelements has, however, been proposed. Here, we focus on mouse APOBEC2 (a muscle-specific protein for which we find no evidence of a deaminating activity on cytidine whether as a free nucleotide or in DNA) and mouse APOBEC3 (a DNA deaminase which we find widely expressed but most abundant in lymphoid tissue). Gene-targeting experiments reveal that both APOBEC2 (despite being an ancestral member of the family with no obvious redundancy in muscle) and APOBEC3 (despite its proposed role in restricting endogenous retrotransposition) are inessential for mouse development, survival, or fertility.

In this study, we address the hypothesis that it is possible to exploit genetic/functional variation in parental Chinese hamster ovary (CHO) cell populations to isolate clonal derivatives that exhibit superior, heritable attributes for biomanufacturing--new parental cell lines which are inherently more "fit for purpose." One-hundred and ninety-nine CHOK1SV clones were isolated from a donor CHOK1SV parental population by limiting dilution cloning and microplate image analysis, followed by primary analysis of variation in cell-specific proliferation rate during extended deep-well microplate suspension culture of individual clones to accelerate genetic drift in isolated cultures. A subset of 100 clones were comparatively evaluated for transient production of a recombinant monoclonal antibody (Mab) and green fluorescent protein following transfection of a plasmid vector encoding both genes. The heritability of both cell-specific proliferation rate and Mab production was further assessed using a subset of 23 clones varying in functional capability that were subjected to cell culture regimes involving both cryopreservation and extended sub-culture. These data showed that whilst differences in transient Mab production capability were not heritable per se, clones exhibiting heritable variation in specific proliferation rate, endocytotic transfectability and N-glycan processing were identified. Finally, for clonal populations most "evolved" by extended sub-culture in vitro we investigated the relationship between cellular protein biomass content, specific proliferation rate and cell surface N-glycosylation. Rapid-specific proliferation rate was inversely correlated to CHO cell size and protein content, and positively correlated to cell surface glycan content, although substantial clone-specific variation in ability to accumulate cell biomass was evident. Taken together, our data reveal the dynamic nature of the CHO cell functional genome and the potential to evolve and isolate CHO cell variants with improved functional properties in vitro.

The Kobayashi score (KS) predicts intravenous immunoglobulin (IVIG) resistance in Japanese children with Kawasaki disease (KD) and has been used to select patients for early corticosteroid treatment. We tested the ability of the KS to predict IVIG resistance and coronary artery abnormalities (CAA) in 78 children treated for KD in our UK centre. 19/59 children were IVIG non-responsive. This was not predicted by a high KS (11/19 IVIG non-responders, compared with 26/40 responders, had a score ≥4; p=0.77). CAA were not predicted by KS (12/20 children with CAA vs 25/39 with normal echo had a score ≥4; p=0.78). Low albumin and haemoglobin, and high C-reactive protein were significantly associated with CAA. The KS does not predict IVIG resistance or CAA in our population. This highlights the need for biomarkers to identify children at increased risk of CAA, and to select patients for anti-inflammatory treatment in addition to IVIG.

Full-length Aβ1-42 and Aβ1-40, N-truncated pyroglutamate Aβ3-42 and Aβ4-42 are major variants in the Alzheimer brain. Aβ4-42 has not been considered as a therapeutic target yet. We demonstrate that the antibody NT4X and its Fab fragment reacting with both the free N-terminus of Aβ4-x and pyroglutamate Aβ3-X mitigated neuron loss in Tg4-42 mice expressing Aβ4-42 and completely rescued spatial reference memory deficits after passive immunization. NT4X and its Fab fragment also rescued working memory deficits in wild type mice induced by intraventricular injection of Aβ4-42. NT4X reduced pyroglutamate Aβ3-x, Aβx-40 and Thioflavin-S positive plaque load after passive immunization of 5XFAD mice. Aβ1-x and Aβx-42 plaque deposits were unchanged. Importantly, for the first time, we demonstrate that passive immunization using the antibody NT4X is therapeutically beneficial in Alzheimer mouse models showing that N-truncated Aβ starting with position four in addition to pyroglutamate Aβ3-x is a relevant target to fight Alzheimer’s disease.

Multiple DNA polymerases exist in eukaryotes. Polymerases alpha, delta and epsilon are mainly responsible for chromosomal DNA replication in the nucleus and are required for proliferation. In contrast, the repair polymerases beta and eta are not essential for cellular proliferation in yeast or mice, but a lack of either polymerase can lead, respectively, to defects in base excision repair or the ability to replicate past lesions induced by ultraviolet (UV) radiation [1-3]. Here, we have focused on polymerase zeta. This was first described as a non-essential product of the yeast REV3/REV7 genes involved in UV-induced mutagenesis, and was later implicated in trans-lesion synthesis [4,5]. Unlike in yeast, the mouse homologue (mRev3) was found to be essential for life. Homozygous mutant mice died in utero. Mutant embryos were considerably reduced in size at day 10.5 of development and usually aborted around day 12.5. It is likely that this block reflects a need for mRev3 in proliferative clonal expansion (rather than in the production of a particular cell type) as mutant blastocysts showed greatly diminished expansion of the inner cell mass in culture. Thus, mRev3 could be required to repair a form of externally induced DNA damage that otherwise accumulates during clonal expansion or, consistent with the high homology shared between its Rev7 partner and the mitotic checkpoint gene product Mad2 [6], mRev3 might play a role in cell proliferation and genomic stability even in the absence of environmentally induced damage.