Social amnesia in mice lacking the oxytocin gene.

The development of social familiarity in rodents depends predominantly on olfactory cues and can critically influence reproductive success. Researchers have operationally defined this memory by a reliable decrease in olfactory investigation in repeated or prolonged encounters with a conspecific. Brain oxytocin (OT) and vasopressin (AVP) seem to modulate a range of social behaviour from parental care to mate guarding. Pharmacological studies indicate that AVP administration may enhance social memory, whereas OT administration may either inhibit or facilitate social memory depending on dose, route or paradigm. We found that male mice mutant for the oxytocin gene (Oxt-/-) failed to develop social memory, whereas wild-type (Oxt+/+) mice showed intact social memory. Measurement of both olfactory foraging and olfactory habituation tasks indicated that olfactory detection of non-social stimuli is intact in Oxt-/- mice. Spatial memory and behavioural inhibition measured in a Morris water-maze, Y-maze, or habituation of an acoustic startle also seemed intact. Treatment with OT but not AVP rescued social memory in Oxt-/- mice, and treatment with an OT antagonist produced a social amnesia-like effect in Oxt+/+ mice. Our data indicate that OT is necessary for the normal development of social memory in mice and support the hypothesis that social memory has a neural basis distinct from other forms of memory.

Identification of a subpopulation of metastatic breast cancer patients with very high HER2 expression levels and possible resistance to trastuzumab.

BACKGROUND: Patients with metastatic breast cancer (MBC) overexpressing HER2 (human epidermal growth factor receptor 2) are currently selected for treatment with trastuzumab, but not all patients respond. PATIENTS AND METHODS: Using a novel assay, HER2 protein expression (H2T) was measured in formalin-fixed, paraffin-embedded primary breast tumors from 98 women treated with trastuzumab-based therapy for MBC. Using subpopulation treatment effect pattern plots, the population was divided into H2T low (H2T < 13.8), H2T high (H2T ≥ 68.5), and H2T intermediate (13.8 ≤ H2T < 68.5) subgroups. Kaplan-Meier (KM) analyses were carried out comparing the groups for time to progression (TTP) and overall survival (OS). Cox multivariate analyses were carried out to identify correlates of clinical outcome. Bootstrapping analyses were carried out to test the robustness of the results. RESULTS: TTP improved with increasing H2T until, at the highest levels of H2T, an abrupt decrease in the TTP was observed. KM analyses demonstrated that patients with H2T low tumors [median TTP 4.2 months, hazard ratio (HR) = 3.7, P < 0.0001] or H2T high tumors (median TTP 4.6 months, HR = 2.7, P = 0.008) had significantly shorter TTP than patients whose tumors were H2T intermediate (median TTP 12 months). OS analyses yielded similar results. CONCLUSIONS: MBC patients with very high levels of H2T may represent a subgroup with de novo resistance to trastuzumab. These results are preliminary and require confirmation in larger controlled clinical cohorts.

Organ dose and inherent uncertainty in helical CT dosimetry due to quasiperiodic dose distributions.

PURPOSE: The purpose of this study was to characterize relative magnitudes of peripheral dose modulations present in helical MDCT resulting from variation in x-ray tube starting position and phantom position relative to isocenter using a novel methodology that employs direct dosimetric measurements and knowledge of scan geometry. The magnitudes of potential dose savings to specific radiosensitive tissues related to the phase of the quasiperiodic dose distribution are also quantified and compared to similar Monte Carlo based studies. METHODS: For this study, a Siemens SOMATOM Sensation 16 helical MDCT scanner and a tomographic adult anthropomorphic phantom from the University of Florida phantom series were used for all scans. In addition, a plastic scintillator-based fiber-optic-coupled dosimetry system was used to record real-time axial dosimetric measurements. These direct measurements were used to derive cumulative point doses and tissue doses for helical MDCT using different pitch values and surface to isocenter distances. RESULTS: Cumulative point doses and doses for the lens of the eye and thyroid showed strong variation with both the phase of the dose distribution and phantom positioning relative to isocenter. Depending on the phantom positioning relative to isocenter, individual in-phantom cumulative point dose values were shown to vary anywhere from 0 to 25% lower than the maximum value for scans of pitch 1, and greater than 60% for scans of pitch 1.5. Reduction in total tissue dose to the lens of the eye (thyroid) varied from 0 to 20% (4%) lower than the maximum value for pitch 1, and from 59 (14%) to 71% (19%) lower than the maximum value for scans using pitch 1.5. These values are similar to those found in previous Monte Carlo based studies. The reduction in average total tissue dose between the extremes (+/- 3 cm from nominal) of phantom positioning relative to isocenter for the eye (thyroid) was 16% (13%) for pitch 1, and 14% (12%) for pitch 1.5. CONCLUSIONS: As recent Monte Carlo simulations have shown, there exists an inherent uncertainty when performing dose measurements within a phantom during helical MDCT scans. The periodic dose distributions in helical MDCT means that low resolution sampling of local phantom doses could result in dose measurement aliasing. For reliable results, these considerations should be accounted for in helical MDCT phantom dosimetry studies. The variability in surface dose has a strong dependence on phantom positioning relative to isocenter. Dose to tissues such as the lens of the eye and thyroid can be minimized by positioning patients, so these tissues are closer to isocenter because the decrease in x-ray intensity due to beam divergence dominates the increases resulting from increased primary beam exposure overlap. Of course, this dose decrease would have to be balanced against any diminished image quality resulting from misalignment of the patient with the bowtie filter. Additionally, significantly reduced dose to small radiosensitive tissues such as the lens of the eye could occur if it were possible to shift the phase of the periodic dose distribution present in helical MDCT. These dose reductions would come at no cost to image quality.

Widespread expression of BDNF but not NT3 by target areas of basal forebrain cholinergic neurons.

Brain-derived neurotrophic factor (BDNF) and neurotrophin-3 (NT3) are homologs of the well-known neurotrophic factor nerve growth factor. The three members of this family display distinct patterns of target specificity. To examine the distribution in brain of messenger RNA for these molecules, in situ hybridization was performed. Cells hybridizing intensely to antisense BDNF probe were located throughout the major targets of the rat basal forebrain cholinergic system, that is, the hippocampus, amygdala, and neocortex. Strongly hybridizing cells were also observed in structures associated with the olfactory system. The distribution of NT3 mRNA in forebrain was much more limited. Within the hippocampus, labeled cells were restricted to CA2, the most medial portion of CA1, and the dentate gyrus. In human hippocampus, cells expressing BDNF mRNA are distributed in a fashion similar to that observed in the rat. These findings point to both basal forebrain cholinergic cells and olfactory pathways as potential central targets for BDNF.

An M2 muscarinic receptor subtype coupled to both adenylyl cyclase and phosphoinositide turnover.

To investigate whether a particular receptor subtype can be coupled to multiple effector systems, recombinant M2 muscarinic receptors were expressed in cells lacking endogenous receptor. The muscarinic agonist carbachol both inhibited adenylyl cyclase and stimulated phosphoinositide hydrolysis. The stimulation of phosphoinositide hydrolysis was significantly less efficient and more dependent on receptor levels than the inhibition of adenylyl cyclase. Both responses were mediated by guanine nucleotide binding proteins, as evidenced by their inhibition by pertussis toxin; the more efficiently coupled adenylyl cyclase response was significantly more sensitive. Thus, individual subtypes of a given receptor are capable of regulating multiple effector pathways.

Primary structure and biochemical properties of an M2 muscarinic receptor.

A partial amino acid sequence obtained for porcine atrial muscarinic acetylcholine receptor was used to isolate complementary DNA clones containing the complete receptor coding region. The deduced 466-amino acid polypeptide exhibits extensive structural and sequence homology with other receptors coupled to guanine nucleotide binding (G) proteins (for example, the beta-adrenergic receptor and rhodopsins); this similarity predicts a structure of seven membrane-spanning regions distinguished by the disposition of a large cytoplasmic domain. Stable transfection of the Chinese hamster ovary cell line with the atrial receptor complementary DNA leads to the binding of muscarinic antagonists in these cells with affinities characteristic of the M2 receptor subtype. The atrial muscarinic receptor is encoded by a unique gene consisting of a single coding exon and multiple, alternatively spliced 5' noncoding regions. The atrial receptor is distinct from the cerebral muscarinic receptor gene product, sharing only 38% overall amino acid homology and possessing a completely nonhomologous large cytoplasmic domain, suggesting a role for the latter region in differential effector coupling.

Immediate cardiovascular effects of the Taser X26 conducted electrical weapon.

STUDY OBJECTIVES: To evaluate the immediate cardiac and cardiovascular effects of Taser X26 conducted electrical weapon (CEW) exposure in human volunteers, including heart rhythm, rate and blood pressure. METHODS: Volunteer police officers participating in CEW training and testing each underwent a 5, 3 and 1 s exposure to the Taser X26 CEW. Continuous electrocardiogram (ECG) monitoring was performed before, during and after each exposure. Blood pressures were measured at rest before and within 1 minute after each exposure. Paired sample t-test analysis and confidence interval calculations were performed. RESULTS: 84 Taser exposures were monitored among 28 subjects (24 men, four women) with an average age of 34 years (range 24-46, SD 5.6). No cardiac dysrhythmias or aberrantly conducted beats were seen. Mean heart rate increased by 10.9 beats per minute (bpm) (95% CI 8.2 to 13.7) from 121.7 to 132.6 (p<0.001). The QRS and QTc cardiac intervals did not change significantly. Mean blood pressure increased from 138.6/82.8 mm Hg at rest to 145.8/85.6 mm Hg after the standard 5-s CEW discharge. CONCLUSION: CEW exposure produced no detectable dysrhythmias and a statistically significant increase in heart rate. Overall, Taser CEW exposure appears to be safe and well tolerated from a cardiovascular standpoint in this population. This study increases the cumulative human subject experience of CEW exposure with continuous ECG monitoring and includes 28 full 5-s exposures.

Evidence that brain-derived neurotrophic factor is a trophic factor for motor neurons in vivo.

The neurotrophins nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), and neurotrophin-3 (NT-3) act upon populations of neurons that express specific receptors. The present study demonstrates that BDNF rescues motor neurons from degeneration and may also play a role in the normal physiology of these cells. BDNF is expressed in the local environment and in muscle targets of motor neurons; muscle expression is up-regulated by denervation. The alpha motor neurons express the gene encoding p145trkB, a receptor involved in BDNF signal transduction, whereas a subset of motor neurons express p75NGFR. BDNF is transported selectively to alpha motor neurons from skeletal muscles. Finally, BDNF prevents motor neuron death in the axotomized facial nucleus of the neonatal rat. The effects of BDNF on motor neurons raise the possibility that some neurotrophins may be useful in treating patients with motor neuropathies and amyotrophic lateral sclerosis.

Primary structure and biological activity of a novel human neurotrophic factor.

During development, each tissue receives and maintains a number of specific neuronal projections that are adequate to sustain its function. The mechanism by which this intricate process occurs is not well understood, but it has been proposed that diffusible neurotrophic factors derived from the target tissue may be involved. Here we describe the identification of a novel human protein that is important for the growth, differentiation, and survival of primary sympathetic and placode-derived sensory neurons. This polypeptide, designated neuronotrophin-3, has a broad tissue distribution and is structurally related to both nerve growth factor and brain-derived neurotrophic factor. Its unique range of trophic and differentiation-inducing activities suggests that it is likely to play a wide role in defining the fate and function of nerve cells during development.

BDNF mRNA is decreased in the hippocampus of individuals with Alzheimer's disease.

In recent years, nerve growth factor (NGF) has gained attention as a potential therapeutic agent for Alzheimer's disease (AD). To study the expression of NGF and its homologs, brain-derived neurotrophic factor (BDNF) and neurotrophin 3 (NT-3), postmortem samples of hippocampus from AD and control donors were examined by in situ hybridization. Hybridization signal for BDNF, but not NGF or NT-3, was decreased in samples of hippocampus from donors with AD. Decreased transcript abundance of BDNF mRNA in hippocampi of individuals with AD was verified by an RNAase protection assay. These results suggest the possibility that decreased expression of BDNF may contribute to the progression of cell death in AD.

Neurotrophin-5: a novel neurotrophic factor that activates trk and trkB.

In vertebrates, the formation and maintenance of neuronal connections are subject to regulation by multiple target-derived, diffusible (neurotrophic) factors. Here we describe the identification and characterization of a novel neurotrophic factor designated neurotrophin-5 (NT-5). NT-5 is structurally related to nerve growth factor and is expressed in embryonic as well as adult tissues. Recombinant NT-5 promotes the survival of peripheral sensory and sympathetic neurons and induces differentiation of the pheochromocytoma cell line PC12. NT-5 activates two trk-related tyrosine kinase receptors and shares these receptors with other neurotrophins. Activation of multiple receptors may permit a single neurotrophin to control target innervation by distinct neuronal populations. Receptor sharing could enable neurotrophic factors emanating from distinct targets to cooperate in regulating neurons with multiple connections.

Cloning of AL-1, a ligand for an Eph-related tyrosine kinase receptor involved in axon bundle formation.

REK7 is an Eph-related tyrosine kinase receptor expressed exclusively in the nervous system, predominantly in hippocampus and cortex. A soluble REK7-IgG fusion protein, produced to analyze the biological role of REK7, prevents axon bundling in cocultures of cortical neurons with astrocytes, a model of late stage nervous system development and differentiation. Using REK7-IgG as an affinity reagent, we purified and cloned a novel REK7 ligand called AL-1, a GPI-linked protein homologous to other members of an emerging ligand family. Membrane attachment of AL-1 appears necessary for receptor activation, since REK7 on cortical neurons is efficiently activated by transfected cells expressing GPI-linked AL-1, but not by soluble AL-1. Consistent with this, soluble AL-1 blocks axon bundling. Our findings, together with the observation that both molecules are expressed in the brain, suggest a role in the formation of neuronal pathways, a crucial feature of nervous system development and regeneration.

Vascular cell adhesion molecule-1 and the integrin VLA-4 mediate adhesion of human B cell precursors to cultured bone marrow adherent cells.

Adhesion of B cell precursors to accessory cells in the bone marrow microenvironment may be required for normal early B cell development. Human bone marrow B cell precursors adhere more avidly than mature B cells to bone marrow-derived fibroblasts. To determine the mechanism of this adhesion, expression of adhesion proteins on human B precursor cells and cell lines was measured by flow cytometry. The very late antigen (VLA) integrins VLA-4 and VLA-5 were the only adhesion proteins expressed at higher levels in B cell precursors than mature B cells. Antibodies to the alpha and beta chains of VLA-4, but not VLA-5, significantly blocked binding to bone marrow-derived fibroblasts of immature B cells and cell lines. Although fibronectin is a ligand for VLA-4, anti-fibronectin antibody and a soluble fibronectin fragment containing the VLA-4 binding domain did not block adhesion, suggesting that VLA-4 is involved in adhesion of B cell precursors, but not as a fibronectin receptor. Vascular cell adhesion molecule-1 (VCAM-1), the other known counterreceptor for VLA-4, was identified on bone marrow-derived fibroblasts, and anti-VCAM-1 significantly blocked adhesion of normal B cell precursors to bone marrow-derived fibroblasts, indicating that VLA-4/VCAM-1 interactions are important in adhesion of B cell precursors to the bone marrow microenvironment.

The Mouse Genome Database (MGD): integrating biology with the genome.

The Mouse Genome Database (MGD) is one component of the Mouse Genome Informatics (MGI) system (http://www.informatics.jax.org), a community database resource for the laboratory mouse. MGD strives to provide a comprehensive knowledgebase about the mouse with experiments and data annotated from both literature and online sources. MGD curates and presents consensus and experimental data representations of genetic, genotype (sequence) and phenotype information including highly detailed reports about genes and gene products. Primary foci of integration are through representations of relationships between genes, sequences and phenotypes. MGD collaborates with other bioinformatics groups to curate a definitive set of information about the laboratory mouse and to build and implement the data and semantic standards that are essential for comparative genome analysis. Recent developments in MGD discussed here include an extensive integration of the mouse sequence data and substantial revisions in the presentation, query and visualization of sequence data.

Conversion disorder in a pediatric transgender patient.

Somatoform disorders are difficult to diagnosis and often present as a neurological illness in pediatric populations. Conversion disorder is the somatoform disorder most commonly seen in children, particularly adolescents, who have anxiety related to sexual behaviors and orientation. In a transgender patient, the risk of conversion disorder is even higher. The patient described in this article presented with multiple neurological symptoms that disappeared after she began presenting herself as a male. There is a significant need for research into somatoform disorders as well as research into the transgender population.

Regulation of learning by EphA receptors: a protein targeting study.

EphA family receptor tyrosine kinases and their ephrin-A ligands are involved in patterning axonal connections during brain development, but until now a role for these molecules in the mature brain had not been elucidated. Here, we show that both the EphA5 receptor and its ephrin-A ligands (2 and 5) are expressed in the adult mouse hippocampus, and the EphA5 protein is present in a phosphorylated form. Because there are no pharmacological agents available for EphA receptors, we designed recombinant immunoadhesins that specifically bind to the receptor binding site of the ephrin-A ligand (antagonist) or the ligand binding site of the EphA receptor (agonist) and thus target EphA function. We demonstrate that intrahippocampal infusion of an EphA antagonist immunoadhesin leads to impaired performance in two behavioral paradigms, T-maze spontaneous alternation and context-dependent fear conditioning, sensitive to hippocampal function, whereas activation of EphA by infusion of an agonist immunoadhesin results in enhanced performance on these tasks. Because the two behavioral tasks have different motivational, perceptual, and motor requirements, we infer the changes were not caused by these performance factors but rather to cognitive alterations. We also find bidirectional changes in gene expression and in electrophysiological measures of synaptic efficacy that correlate with the behavioral results. Thus, EphA receptors and their ligands are implicated as mediators of plasticity in the adult mammalian brain.

Functional diversity of muscarinic receptor subtypes in cellular signal transduction and growth.

The regulation of cellular signal transduction and growth by four human muscarinic acetylcholine receptor (mAChR) subtypes has been studied comparatively. The four mAChRs fall into two functional sub-groups, based on their primary effects on second messenger formation; two of the receptors strongly inhibit adenylyl cyclase activity, whereas the other two strongly stimulate PI hydrolysis. Studies on mAChR regulation of two cellular events involved in cellular growth regulation, the transcription of proto-oncogene c-fos and DNA synthesis, indicate that these events are efficiently activated by those mAChRs which couple primarily to phospholipase C.

Adhesive interactions of normal and leukemic human CD34+ myeloid progenitors: role of marrow stromal, fibroblast, and cytomatrix components.

Adhesive interactions between CD34+ myeloid progenitors, cytomatrix components, and marrow fibroblast and stromal monolayers are described and compared to the binding interactions of the CD34+ myeloid leukemic cell lines KG1a and KG1. Both normal precursors and their leukemic counterparts showed adhesion to marrow stroma and fibroblasts. CD34+ myeloid progenitors bound to the extracellular matrices of marrow stromal cell and fibroblast monolayers and to laminin and fibronectin to a lesser extent than to cellular stromal layers. These adhesive interactions were not inhibited by polyclonal antibodies to laminin or fibronectin, nor by 1 mM Arg-Gly-Asp-Ser (RGDS)-containing peptides. Also, although both normal and leukemic cells expressed the CD18 antigen, binding of these cells to stroma was not inhibited by blocking anti-CD18 monoclonal antibodies. Finally, KG1a adhesion was not blocked in the presence of anti-CD54 (ICAM) antibody, nor was it blocked when galactosyl or mannosyl pyranosides were added. KG1a binding was trypsin sensitive and enhanced in the presence of neuraminidase. These studies serve to characterize adhesive properties of normal and leukemic myeloid progenitors and begin to establish interactions important for the lodgement of early progenitor cells in human marrow.

Homologous regulation of brain oxytocin receptors.

Specific receptors for oxytocin have been identified in rat forebrain. Previous studies have demonstrated that in select regions, these receptors are dependent on heterologous induction by gonadal steroids. To investigate whether brain oxytocin receptors are homologously regulated by oxytocin, we measured oxytocin receptor binding after hypothalamic paraventricular nucleus lesions, repeated central injections of oxytocin, and continuous central infusion of oxytocin via osmotic minipump. Neither lesions of the paraventricular nucleus nor repeated oxytocin injections altered the binding of the selective oxytocin receptor ligand [125I]OTA [125I] d(CH2)5[Tyr(Me)2,Thr4,Tyr-NH2(9)] ornithine vasotocin, as measured by in vitro receptor autoradiography. After 10 days of continuous oxytocin infusion by osmotic minipump, oxytocin receptor binding decreased in every target field by at least 50%. This decrease appeared to represent a down-regulation of receptors and not displacement by exogenous peptide, as it persisted for at least 24 h after pump removal, and binding remained reduced in the presence of a saturating concentration of [125I] OTA. Reduction of oxytocin receptors in response to increased oxytocin release may represent an important physiological mechanism for the regulation of central oxytocin neurotransmission.

Human seminal relaxin is a product of the same gene as human luteal relaxin.

Unlike that of other species, which have only one gene encoding relaxin, the human genome contains two nonallelic genes for relaxin, designated H1 and H2, which encode markedly different relaxin peptides. Whereas human relaxin gene H2 is selectively expressed in the ovary, no ovarian expression of gene H1 has been detected. Since relaxin is actively produced in the human male, it is possible to postulate divergent gene expression of relaxin in the male and female. We examined this question directly through the structural determination of human seminal relaxin and its comparison with the structure of human luteal relaxin. Partially purified relaxin, prepared from pooled human seminal plasma which had been delipidated by extraction with acid acetone and hexane, subjected to two cycles of HPLC and an additional purification step by ion-exchange chromatography, was further purified by immunoaffinity chromatography, using a monoclonal antibody to the H2 relaxin A chain which cross-reacts with synthetic H1 relaxin, followed by an additional HPLC step performed on a C4 reverse-phase column. The recovered, purified relaxin was then analyzed by N-terminal gas-phase sequencing and fast atom bombardment mass spectroscopy for determination of the amino acid sequence and molecular ions of the A and B chains, respectively. The results demonstrate that the structure of the predominant relaxin in human semen plasma is derived from the product of the H2 gene, consisting of a N-terminal pyroglutamic acid A-24 A chain and a mixture of B-26 and B-27 B chains. With the exception of degradation of the seminal relaxin B chain C-terminus, this structure is identical to the structure of human luteal relaxin. Therefore, both human seminal and luteal relaxin are products of the H2 gene.