Postweaning, forebrain-specific perturbation of the oxytocin system impairs fear conditioning

Oxytocin (Oxt) and vasopressin (Avp) are important for a wide variety of behaviors and the use of transgenic mice lacking the peptides or their receptors, particularly when their loss is spatially and temporally manipulated, offers an opportunity to closely examine their role in a particular behavior. We used a cued fear conditioning paradigm to examine associative learning in three lines of transgenic mice: mice that constitutively lack vasopressin 1a (Avpr1a(-/-)) or Oxt receptors (Oxtr(-/-)) and mice that have Oxt receptor loss restricted to the forebrain that begins postweaning (Oxtr(FB/FB)). Oxtr(-/-) and Avpr1a(-/-) mice have normal conditioned freezing. Oxtr(FB/FB) mice have a reduction in freezing behavior during acquisition, as well as during context and cue retention. In addition to reduction of Oxtr in the central nucleus of the amygdala, in vitro receptor autoradiography showed that the Oxtr(FB/FB) mice have significantly reduced levels of Avpr1a only in that structure. Our results show that postweaning alteration of the distribution of Oxtr receptors is critically important for fear behavior, an effect mirrored in the neural structures that mediate it. While constitutive knockouts of Oxtr and Avpr1a are useful for identifying the neural underpinnings of some behaviors, compensatory mechanisms within some circuits may obscure other behavioral roles.     

Slb/Wnt11 controls hypoblast cell migration and morphogenesis at the onset of zebrafish gastrulation

During vertebrate gastrulation, highly coordinated cellular rearrangements lead to the formation of the three germ layers, ectoderm, mesoderm and endoderm. In zebrafish, silberblick (slb)/wnt11 regulates normal gastrulation movements by activating a signalling pathway similar to the Frizzled-signalling pathway, which establishes epithelial planar cell polarity (PCP) in Drosophila. However, the cellular mechanisms by which slb/wnt11 functions during zebrafish gastrulation are still unclear. Using high-resolution two-photon confocal imaging followed by computer-assisted reconstruction and motion analysis, we have analysed the movement and morphology of individual cells in three dimensions during the course of gastrulation. We show that in slb-mutant embryos, hypoblast cells within the forming germ ring have slower, less directed migratory movements at the onset of gastrulation. These aberrant cell movements are accompanied by defects in the orientation of cellular processes along the individual movement directions of these cells. We conclude that slb/wnt11-mediated orientation of cellular processes plays a role in facilitating and stabilising movements of hypoblast cells in the germ ring, thereby pointing at a novel function of the slb/wnt11 signalling pathway for the regulation of migratory cell movements at early stages of gastrulation.     

Mixed-metal butterfly acetamidediato clusters derived from a highly reactive ruthenium oxo cluster: synthesis and characterization of [(PPh3)2N][MRu3(CO)12(η-μ3-NC(μ-O)CH3)], (M = Mn or Re)

Analogy with the isolable oxo cluster [Fe₃(CO)₉(μ₃-O)]²⁻, which is structurally interesting and synthetically useful, prompted the present attempt to synthesize its ruthenium analog. Although the high reactivity of [Ru₃(CO)₉(μ₃-O)]²⁻ (I) prevented its isolation, the reaction of this species with [M(CO)₃(NCCH₃)]⁺, where M = Mn or Re, yields [PPN][MRu₃(CO)₁₂(η²-μ₃-NC(μ-O)CH₃]⁻. The high nucleophilicity of the oxo ligand in [Ru₃(CO)₉(μ₃-O)]²⁻ (I) appears to be responsible for the conversion of acetonitrile to an acetamidediato ligand and for the instability of I. The crystal structure of [PPN][MnRu₃(CO)₁₂(η²-μ₃-NC(μ-O)CH₃)]] reveals a hinged butterfly array of metal atoms in which the acetamidediato ligand bridges the two wings with μ₃-N bonding to an Mn and two Ru atoms, and μ-O bonding to an Ru atom.     

Two dual-specific (anti-IgG and anti-dsDNA) monoclonal autoantibodies derived from the NZB/NZW F1 recognize an epitope in the hinge region

The anti-IgG properties of two dual-specific (anti-dsDNA and anti-IgG) monoclonal NZB/NZW F1-derived autoantibodies, BV 17–45 and BV 16–13, were studied to resolve the location and possible commonality of the IgG epitope. To determine if BV 17–45 and BV 16–13 recognized the same IgG epitope, the relative temperature sensitivity of the conformational IgG epitopes were evaluated using the conformational sensitive immunoassay. Comparison of the temperature sensitivity of the conformational immunoglobulin epitopes over a temperature range of 25–100°C suggested that the epitope recognized by BV 17–45 was the same as the IgG epitope recognized by BV 16–13. Further studies with papain- and pepsin-generated F(ab′)₂, Fab, and Fc fragments of BV 17–45 and BV 16–13 revealed that the dual-specific autoantibodies BV 17–45 and BV 16–13 both bound an epitope in the hinge region of the IgG molecule. The potential correlation between these studies and the pathogenic nature of dual-specific autoantibodies is discussed.     

Optical Imaging of Retinotopic Maps in a Small Songbird,the Zebra Finch

Background

The primary visual cortex of mammals is characterised by a retinotopic representation of the visual field. It has therefore been speculated that the visual wulst, the avian homologue of the visual cortex, also contains such a retinotopic map. We examined this for the first time by optical imaging of intrinsic signals in zebra finches, a small songbird with laterally placed eyes. In addition to the visual wulst, we visualised the retinotopic map of the optic tectum which is homologue to the superior colliculus in mammals.

Methodology/Principal Findings

For the optic tectum, our results confirmed previous accounts of topography based on anatomical studies and conventional electrophysiology. Within the visual wulst, the retinotopy revealed by our experiments has not been illustrated convincingly before. The frontal part of the visual field (0°±30° azimuth) was not represented in the retinotopic map. The visual field from 30°–60° azimuth showed stronger magnification compared with more lateral regions. Only stimuli within elevations between about 20° and 40° above the horizon elicited neuronal activation. Activation from other elevations was masked by activation of the preferred region. Most interestingly, we observed more than one retinotopic representation of visual space within the visual wulst, which indicates that the avian wulst, like the visual cortex in mammals, may show some compartmentation parallel to the surface in addition to its layered structure.

Conclusion/Significance

Our results show the applicability of the optical imaging method also for small songbirds. We obtained a more detailed picture of retinotopic maps in birds, especially on the functional neuronal organisation of the visual wulst. Our findings support the notion of homology of visual wulst and visual cortex by showing that there is a functional correspondence between the two areas but also raise questions based on considerable differences between avian and mammalian retinotopic representations.     

Reproductive fitness and dietary choice behavior of the genetic model organism Caenorhabditis elegans under semi-natural conditions

Laboratory breeding conditions of the model organism C. elegans do not correspond with the conditions in its natural soil habitat. To assess the consequences of the differences in environmental conditions, the effects of air composition, medium and bacterial food on reproductive fitness and/or dietary-choice behavior of C. elegans were investigated. The reproductive fitness of C. elegans was maximal under oxygen deficiency and not influenced by a high fractional share of carbon dioxide. In media approximating natural soil structure, reproductive fitness was much lower than in s tandard laboratory media. I n seminatural media, the reproductive fitness of C. elegans was low with the standard laboratory food bacterium E. coli (γ-Proteobacteria), but significantly higher with C. arvensicola (Bacteroidetes) and B. tropica (β-Proteobacteria) as food. Dietary-choice experiments in semi-natural media revealed a low preference of C. elegans for E. coli but significantly higher preferences for C. arvensicola and B. tropica (among other bacteria). Dietary-choice experiments under quasi-natural conditions, which were feasible by fluorescence in situ hybridization (FISH) of bacteria, showed a high preference of C. elegans for Cytophaga-Flexibacter-Bacteroides, Firmicutes, and β-Proteobacteria, but a low preference for γ-Proteobacteria. The results show that data on C. elegans under standard laboratory conditions have to be carefully interpreted with respect to their biological significance.     

Candidate gene analysis of metamorphic timing in ambystomatid salamanders

Although much is known about the ecological significance of metamorphosis and metamorphic timing, few studies have examined the underlying genetic architecture of these traits, and no study has attempted to associate phenotypic variation to molecular variation in specific genes. Here we report on a candidate gene approach (CGA) to test specific loci for a statistical contribution to variation in metamorphic timing. Three segregating populations (SP1, SP2 and SP3) were constructed utilizing three species of paedomorphic Mexican ambystomatid salamander, including the axolotl, Ambystoma mexicanum. We used these replicated species to test the hypothesis that inheritance of alternate genotypes at two thyroid hormone receptor loci (TRalpha, TRbeta) affects metamorphic timing in ambystomatid salamanders. A significant TRalpha*SP effect indicated that variation in metamorphic timing may be influenced by TRalpha genotype, however, the effect was not a simple one, as both the magnitude and direction of the phenotypic effect depended upon the genetic background. These are the first data to implicate a specific gene in contributing to variation in metamorphic timing. In general, candidate gene approaches can be extended to any number of loci and to any organism where simple genetic crosses can be performed to create segregating populations. The approach is thus of particular value in ecological studies where target genes have been identified but the study organism is not one of the few well-characterized model systems that dominate genetic research.     

Inositol- and folate-resistant neural tube defects in mice lacking the epithelial-specific factor Grhl-3

The neural tube defects (NTDs) spina bifida and anencephaly are widely prevalent severe birth defects. The mouse mutant curly tail (ct/ct) has served as a model of NTDs for 50 years, even though the responsible genetic defect remained unrecognized. Here we show by gene targeting, mapping and genetic complementation studies that a mouse homolog of the Drosophila grainyhead (grh) gene, grainyhead-like-3 (Grhl3), is a compelling candidate for the gene underlying the curly tail phenotype. The NTDs in Grhl3-null mice are more severe than those in the curly tail strain, as the Grhl3 alleles in ct/ct mice are hypomorphic. Spina bifida in ct/ct mice is folate resistant, but its incidence can be markedly reduced by maternal inositol supplementation periconceptually. The NTDs in Grhl3-/- embryos are also folate resistant, but unlike those in ct/ct mice, they are resistant to inositol. These findings suggest that residual Grhl3 expression in ct/ct mice may be required for inositol rescue of folate-resistant NTDs.     

Active site structure and antigen binding properties of idiotypically cross-reactive anti-fluorescein monoclonal antibodies

This report includes complete VH and V kappa nucleotide and deduced amino acid sequences of idiotypically cross-reactive monoclonal anti-fluorescein antibodies that differed greater than 10(5)-fold in affinity. High affinity monoclonal antibody 4-4-20 and intermediate affinity antibodies 10-25, 5-14, 9-40, 12-40, and 3-24 utilized greater than or equal to 90% homologous VHIIIC germ-line genes. Extensive D segment length and sequence variability were observed; however, compensatory germ-line JH4 (4-4-20 and 3-24) or JH3 (10-25, 5-14, 9-40, and 12-40) sequence lengths resulted in H chain CDR3 + FR4 to be a constant 18 amino acids. In addition, each antibody and low affinity 3-13 rearranged greater than or equal to 96% homologous V kappa II genes to J kappa 1, except for 10-25 (J kappa 5) and 3-13 (J kappa 4). Resolved crystal structure of complexed fluorescein and 4-4-20 Fab fragments revealed residues HisL27d, TyrL32, ArgL34, SerL91, TrpL96, and TrpH33 acted as hapten contact residues. Antibodies 5-14, 9-40, 12-40, and 3-24 primary structures possessed identical contact residues as 4-4-20 except for the substitution of HisL34 for ArgL34. Thus, ArgL34 was implicated in the increased affinity of monoclonal antibody 4-4-20. Finally, it was difficult to correlate extensive H chain CDR3 residue heterogeneity directly with fluorescein binding and idiotypy.     

5-HT1A receptor gene C -1019 G polymorphism and amygdala volume in borderline personality disorder

Alterations of amygdala structure and function have been repeatedly described in patients with borderline personality disorder (BPD). The aim of our study was to determine whether a functional polymorphism of the 5-hydroxytryptamine_1A receptor (5-HTR_1A) gene C −1019 G (identity number: rs6295 G/C) is associated with structural changes of the amygdala in patients with BPD. Twenty-five right-handed female inpatients with BPD according to DSM IV and 25 healthy controls matched for age, sex, handedness and educational status were enrolled. Brain volumetry of the amygdala was performed with a 1.5-T Magnetom Vision apparatus (Siemens, Erlangen, Germany) and analyzed by the software program ' brains '. Patients who have the 5-HTR_1A gene G allele had significantly smaller amygdala volumes than C/C genotype carriers ( P  = 0.02). While no difference of allelic distribution between patients and controls was detected, the described effect of 5-HTR_1A genotype on amygdala volume was found for the whole group of patients, as well as in the subgroup of patients with comorbid major depression ( P  = 0.004) but not in controls. In contrast to these subgroups of BPD patients who had significant amygdala volume differences, the mean amygdala volume of the whole group of BPD patients was not significantly different from that of controls. In summary, our study provides first evidence that 5-HTR_1A gene C −1019 G polymorphism is associated with structural changes in the limbic system of BPD patients, a finding that might be disease related and might contribute to explanation of previous discrepant results regarding amygdala volume changes in BPD. Future research is recommended to clarify possible interactions between this functional polymorphism and symptoms, course and treatment responses in this disorder.