Hyperpolarization moves S4 sensors inward to open MVP,a methanococcal voltage-gated potassium channel

MVP, a Methanococcus jannaschii voltage-gated potassium channel, was cloned and shown to operate in eukaryotic and prokaryotic cells. Like pacemaker channels, MVP opens on hyperpolarization using S4 voltage sensors like those in classical channels activated by depolarization. The MVP S4 span resembles classical sensors in sequence, charge, topology and movement, traveling inward on hyperpolarization and outward on depolarization (via canaliculi in the protein that bring the extracellular and internal solutions into proximity across a short barrier). Thus, MVP opens with sensors inward indicating a reversal of S4 position and pore state compared to classical channels. Homologous channels in mammals and plants are expected to function similarly.     

Modelling spinal circuitry involved in locomotor pattern generation: insights from deletions during fictive locomotion

The mammalian spinal cord contains a locomotor central pattern generator (CPG) that can produce alternating rhythmic activity of flexor and extensor motoneurones in the absence of rhythmic input and proprioceptive feedback. During such fictive locomotor activity in decerebrate cats, spontaneous omissions of activity occur simultaneously in multiple agonist motoneurone pools for a number of cycles. During these 'deletions', antagonist motoneurone pools usually become tonically active but may also continue to be rhythmic. The rhythmic activity that re-emerges following a deletion is often not phase shifted. This suggests that some neuronal mechanism can maintain the locomotor period when motoneurone activity fails. To account for these observations, a simplified computational model of the spinal circuitry has been developed in which the locomotor CPG consists of two levels: a half-centre rhythm generator (RG) and a pattern formation (PF) network, with reciprocal inhibitory interactions between antagonist neural populations at each level. The model represents a network of interacting neural populations with single interneurones and motoneurones described in the Hodgkin-Huxley style. The model reproduces the range of locomotor periods and phase durations observed during real locomotion in adult cats and permits independent control of the level of motoneurone activity and of step cycle timing. By altering the excitability of neural populations within the PF network, the model can reproduce deletions in which motoneurone activity fails but the phase of locomotor oscillations is maintained. The model also suggests criteria for the functional identification of spinal interneurones involved in the mammalian locomotor pattern generation.     

Non-heparan sulfate-binding interactions of endostatin/collagen XVIII in murine development.

Knobloch syndrome is characterized by a congenital generalized eye disease and cranial defect. Pathogenic mutations preferentially lead to a deletion or functional alteration of collagen XVIII's most C-terminal endostatin domain. Endostatin can be released from collagen XVIII and is a potent inhibitor of angiogenesis and tumor growth. We show differential expression of binding partners for endostatin, vascular endothelial growth factor (VEGF), and the collagen XV endostatin homologue in murine embryonal development using a set of alkaline phosphatase fusion proteins. Consistent with the human phenotype, vascular mesenchyme in the developing eye was identified as endostatin's primary target. While endostatin predominantly bound to blood vessels, the VEGF164 affinity probe labeled nonvascular tissues such as forebrain, hindbrain, the optic nerve, and the surface ectoderm of the future cornea. Strikingly increased staining specificity was observed with a non-heparin/heparan sulfate-binding endostatin probe. In contrast, elimination of the heparan sulfate binding site from VEGF led to complete loss of binding. The collagen XV endostatin homologue showed a highly restricted binding pattern. Oligomerization with endogenous endostatin was ruled out by use of collagen XVIII knockout mice. Our data provide strong evidence that collagen XVIII's C-terminal endostatin domain harbors a prominent tissue-binding site and that binding can occur in the absence of heparan sulfates in situ.     

No association between the Pro197Leu polymorphism in the glutathione peroxidase (GPX1) gene and schizophrenia

OBJECTIVE: Oxidative stress such as free radical-mediated neuronal dysfunction may be involved in the pathophysiology of schizophrenia. The human glutathione peroxidase (GPX1) is a selenium-dependent enzyme, which plays an important role in the detoxification of free radicals. We therefore hypothesized that the GPX1 gene, which is located on chromosome 3p21.3, may be involved in the pathophysiology of schizophrenia. The aim of this study is to examine whether a potentially functional polymorphism, a proline (Pro) to leucine (Leu) substitution at codon 197 (Pro197Leu) of the human GPX1 gene, is associated with susceptibility to schizophrenia. METHODS: We genotyped the Pro197Leu polymorphism in a total of 113 nuclear families that had a proband with schizophrenia. Genetic association was tested using the transmission disequilibrium test (TDT), the sib transmission disequilibrium test (STDT), and the family-based association test (FBAT). RESULTS: The minor allele (Leu) frequency was calculated to be 0.282. We could not find significant transmission disequilibrium of the alleles for the Pro197Leu polymorphism in the GPX1 gene in association with the presence of schizophrenia in our family sample (TDT, chi2=0.03, degrees of freedom=1, P=0.86; combined TDT-STDT, Z'=-0.052, P=0.47; FBAT, Z=0.000, P=1.000). CONCLUSION: The results of this study suggest that the GPX1 polymorphism is unlikely to be associated with susceptibility to schizophrenia.     

Specific and nonspecific immune factors in dental plaque fluid and saliva from young and old populations.

Separate samples of supragingival dental plaque overtly free of blood were centrifuged to obtain the free fluid phase (plaque fluid). Bound protein was eluted from the plaque bacteria and matrix by washing the plaque with a low-pH buffer. The plaque fluid, low pH eluate, and whole saliva were assayed for immunoglobulins A, G, and M, the third component of complement, lysozyme, lactoferrin, and lactoperoxidase. Concentrations of total protein and albumin were also determined. Antibody reactive with specific plaque bacteria was detected by indirect immunofluorescent microscopy. Specific and nonspecific immune proteins were present in plaque fluid from adult subjects at significantly greater concentrations than in their saliva, which suggests that these proteins are concentrated in dental plaque. The results indicate that both saliva and gingival exudate contribute to the immunological proteins found in the free fluid phase of dental plaque. The observation that immunoglobulin A antibody reactive with plaque bacteria could be detected in plaque fluid suggests that a wide variety of immunological reactions may occur in the dental plaque. These potential interactions between host, plaque bacteria, and their products could serve to influence the plaque flora and its ability to induce disease.     

Duplication 18q syndrome

Some variation in the phenotype of patients with dup(18q) is recognized. Our patient has the phenotype described for dup(18qter).     

Unlocking the secrets of galectins: a challenge at the frontier of glyco-immunology

Over the last decade, we have witnessed an explosion of information regarding the function of glycoconjugates, carbohydrate-binding proteins, and the elucidation of the sugar code. This progress has yielded not only important insights into fundamental areas of glycobiology but has also influenced other fields such as immunology and molecular medicine. A family of galactoside-binding proteins, called galectins, has emerged recently as a novel kind of bioactive molecules with powerful, immunoregulatory functions. Different members of this family have been shown to modulate positively or negatively multiple steps of the inflammatory response, such as cell-matrix interactions, cell trafficking, cell survival, cell-growth regulation, chemotaxis, and proinflammatory cytokine secretion. To introduce a comprehensive overview of these new advances, here we will explore the molecular mechanisms and biochemical pathways involved in these functions. We will also examine the role of these proteins in the modulation of different pathological processes, such as chronic inflammation, autoimmunity, infection, allergic reactions, and tumor spreading. Understanding the intimate mechanisms involved in galectin functions will help to delineate selective and novel strategies for disease intervention and diagnosis.