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Molecular Physiology (molecular + physiology)
Selected AbstractsMolecular physiology of SLC4 anion exchangersEXPERIMENTAL PHYSIOLOGY, Issue 1 2006Seth L. Alper Plasmalemmal Cl,,HCO3, exchangers regulate intracellular pH and [Cl,] and cell volume. In polarized epithelial cells, they contribute also to transepithelial secretion and reabsorption of acid,base equivalents and of Cl,. Members of both the SLC4 and SLC26 mammalian gene families encode Na+ -independent Cl,,HCO3, exchangers. Human SLC4A1/AE1 mutations cause either the erythroid disorders spherocytic haemolytic anaemia or ovalocytosis, or distal renal tubular acidosis. SLC4A2/AE2 knockout mice die at weaning. Human SLC4A3/AE3 polymorphisms have been associated with seizure disorder. Although mammalian SLC4/AE polypeptides mediate only electroneutral Cl,,anion exchange, trout erythroid AE1 also promotes osmolyte transport and increased anion conductance. Mouse AE1 is required for DIDS-sensitive erythroid Cl, conductance, but definitive evidence for mediation of Cl, conductance is lacking. However, a single missense mutation allows AE1 to mediate both electrogenic SO42,,Cl, exchange or electroneutral, H+ -independent SO42,,SO42, exchange. In the Xenopus oocyte, the AE1 C-terminal cytoplasmic tail residues reported to bind carbonic anhydrase II are dispensable for Cl,,Cl, exchange, but required for Cl,,HCO3, exchange. AE2 is acutely and independently inhibited by intracellular and extracellular H+, and this regulation requires integrity of the most highly conserved sequence of the AE2 N-terminal cytoplasmic domain. Individual missense mutations within this and adjacent regions identify additional residues which acid-shift pHo sensitivity. These regions together are modelled to form contiguous surface patches on the AE2 cytoplasmic domain. In contrast, the N-terminal variant AE2c polypeptide exhibits an alkaline-shifted pHo sensitivity, as do certain transmembrane domain His mutants. AE2-mediated anion exchange is also stimulated by ammonium and by hypertonicity by a mechanism sensitive to inhibition by chelation of intracellular Ca2+ and by calmidazolium. This growing body of structure,function data, together with increased structural information, will advance mechanistic understanding of SLC4 anion exchangers. [source] Molecular physiology of adventitious root formation in Petunia hybrida cuttings: involvement of wound response and primary metabolismNEW PHYTOLOGIST, Issue 3 2009Amir H. Ahkami Summary ,,Adventitious root formation (ARF) in the model plant Petunia hybrida cv. Mitchell has been analysed in terms of anatomy, gene expression, enzymatic activities and levels of metabolites. This study focuses on the involvement of wound response and primary metabolism. ,,Microscopic techniques were complemented with targeted transcript, enzyme and metabolite profiling using real time polymerase chain reaction (PCR), Northern blot, enzymatic assays, chromatography and mass spectrometry. ,,Three days after severance from the stock plants, first meristematic cells appeared which further developed into root primordia and finally adventitious roots. Excision of cuttings led to a fast and transient increase in the wound-hormone jasmonic acid, followed by the expression of jasmonate-regulated genes such as cell wall invertase. Analysis of soluble and insoluble carbohydrates showed a continuous accumulation during ARF. A broad metabolite profiling revealed a strong increase in organic acids and resynthesis of essential amino acids. ,,Substantial changes in enzyme activities and metabolite levels indicate that specific enzymes and metabolites might play a crucial role during ARF. Three metabolic phases could be defined: (i) sink establishment phase characterized by apoplastic unloading of sucrose and being probably mediated by jasmonates; (ii) recovery phase; and (iii) maintenance phase, in which a symplastic unloading occurs. [source] Somatic Gene Transfer: Implications for Cardiovascular ControlEXPERIMENTAL PHYSIOLOGY, Issue 6 2000S. Kasparov There is a great need for closer integration between physiologists and molecular biologists. These two research fields might soon form a single research discipline under the umbrella of molecular physiology. One of the areas where this interaction may be particularly fruitful is with somatic gene transfer using replication-deficient viral vectors. We applied this approach to study the central control of the cardiovascular system at the level of the nucleus of the solitary tract (NTS). We assess critically this new methodology as applied to experiments in an integrative environment (such as the whole animal). The usefulness of in vivo gene transfer is illustrated by an experiment where viral gene delivery helped to circumvent the problem imposed by an absence of a specific pharmacological blocker of the enzyme, endothelial nitric oxide synthase (eNOS). The pros and cons of using adenoviral vectors as opposed to conventional pharmacological approaches are discussed. We conclude that the use of adenoviruses to manipulate genes offers a new avenue for physiologists studying neuronal mechanisms in integrative models. [source] The molecular physiology of activity-dependent bulk endocytosis of synaptic vesiclesJOURNAL OF NEUROCHEMISTRY, Issue 4 2009Emma L. Clayton Abstract Central nerve terminals release neurotransmitter in response to a wide variety of stimuli. Because maintenance of neurotransmitter release is dependent on the continual supply of synaptic vesicles (SVs), nerve terminals possess an array of endocytosis modes to retrieve and recycle SV membrane and proteins. During mild stimulation conditions, single SV retrieval modes such as clathrin-mediated endocytosis predominate. However, during increased neuronal activity, additional SV retrieval capacity is required, which is provided by activity-dependent bulk endocytosis (ADBE). ADBE is the dominant SV retrieval mechanism during elevated neuronal activity. It is a high capacity SV retrieval mode that is immediately triggered during such stimulation conditions. This review will summarize the current knowledge regarding the molecular mechanism of ADBE, including molecules required for its triggering and subsequent steps, including SV budding from bulk endosomes. The molecular relationship between ADBE and the SV reserve pool will also be discussed. It is becoming clear that an understanding of the molecular physiology of ADBE will be of critical importance in attempts to modulate both normal and abnormal synaptic function during intense neuronal activity. [source] Comparative gene expression analysis reveals a characteristic molecular profile of the superior olivary complexTHE ANATOMICAL RECORD : ADVANCES IN INTEGRATIVE ANATOMY AND EVOLUTIONARY BIOLOGY, Issue 4 2006Hans Gerd Nothwang Abstract The superior olivary complex (SOC) is a very conspicuous structure in the mammalian auditory brainstem. It represents the first binaural processing center and is important for sound localization in the azimuth and in feedback regulation of cochlear function. In order to define molecular determinants of the SOC, which are of potential functional relevance, we have performed a comprehensive analysis of its transcriptome by serial analysis of gene expression in adult rats. Here, we performed a detailed analysis of the SOC's gene expression profile compared to that of two other neural tissues, the striatum and the hippocampus, and with extraocular muscle tissue. This tested the hypothesis that SOC-specific or significantly upregulated transcripts provide candidates for the specific function of auditory neurons. Thirty-three genes were significantly upregulated in the SOC when compared to the two other neural tissues. Thirteen encoded proteins involved in neurotransmission, including action potential propagation, exocytosis, and myelination; five genes are important for the energy metabolism, and five transcripts are unknown or poorly characterized and have yet to be described in the nervous system. The comparison of functional gene classes indicates that the SOC has the highest energy demand of the three neural tissues, yet protein turnover is apparently not increased. This suggests a high energy demand for fueling auditory neurotransmission. Such a demand may have implications on auditory-specific tasks and relate to central auditory processing disorders. Ultimately, these data provide new avenues to foster investigations of auditory function and to advance molecular physiology in the central auditory system. Anat Rec Part A, 2006. © 2006 Wiley-Liss, Inc. [source] Physiological and modelling approaches to understand water and carbon fluxes during grape berry growth and quality development: a reviewAUSTRALIAN JOURNAL OF GRAPE AND WINE RESEARCH, Issue 2010Z.W. DAI Abstract Recent advances in the understanding of the physiology of berry growth and in modelling allow simulation of fruit growth and sugar accumulation from the perspective of water and carbon balance. This review summarises present knowledge on the modelling and molecular physiology of carbon and water fluxes related to grape berry growth and quality. It focuses principally on the effects of environmental factors and cultural practices on fruit quality through their consequences on water and carbon fluxes during fruit growth. Together with ecophysiological and molecular approaches, process-based models show promising ability to aid in integrating physiological results, generating novel hypotheses and consequently providing a full picture of the control of berry growth and quality development. In the future, nitrogen and sulfur fluxes, necessary for the synthesis of secondary metabolites important for quality, should also be integrated. Modelling at the organ level should extend to metabolic content and metabolite fluxes (metabolomic and fluxomic studies). Genotypes naturally or artificially affected on a key gene or function will also be helpful to validate modelling hypotheses. [source] | ||||||||||