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81.
Platelet-activating factor (PAF) has been implicated as one of the mediators of cardiac anaphylaxis. This phospholipid has been shown to have numerous effects on a variety of tissues, including the heart. Among these effects are alterations in the resting potential and generation of arrhythmias at very low concentrations. This suggests that PAF may modulate the activity of the background, inwardly-rectifying potassium current (IK1). Thus, the effects of PAF on IK1 were examined at the single channel level. Ventricular cells were isolated from adult guinea pig hearts and single channel currents recorded from cell-attached patches. PAF had substantial effects on the single channel currents at sub-nanomolar concentrations (10–11 to 10–10 M). PAF initially caused flickering of the channels, followed by a gradual prolonged depression of channel activity. Since these potassium channels play a major role in determining the resting potential and excitability of the cardiac cell, the effects of PAF on IK1 may play a major role in the deleterious electrophysiological actions of PAF on the heart.Abbreviations IK1 Inwardly-rectifying background potassium current - Lyso-PAF Lyso-platelet-activating factor - PAF Platelet-activating factor  相似文献   
82.
Five genomic clones containing ribosomal DNA repeats from the gymnosperm white spruce (Picea glauca) have been isolated and characterized by restriction enzyme analysis. No nucleotide variation or length variation was detected within the region encoding the ribosomal RNAs. Four clones which contained the intergenic spacer (IGS) region from different rDNA repeats were further characterized to reveal the sub-repeat structure within the IGS. The sub-repeats were unusually long, ranging from 540 to 990 bp but in all other respects the structure of the IGS was very similar to the organization of the IGS from wheat, Drosophila and Xenopus.  相似文献   
83.
Chemical entities designed to noncovalently interact with predetermined partners have fashioned a new paradigm in chemical biology. Fluorocarbons are extremely promising as supramolecular synthons toward these objectives. Bioorthogonal noncovalent interactions provide a way to modulate self-assembled systems in environments where such control has hitherto not been possible. Fluorocarbons have now found applications in self-assembly as well as proteomics, biomolecule purification and in the creation of microarray platforms. Other self-assembly motifs with similar attributes might be exploited using the same general approach.  相似文献   
84.
Centrifugal dehydration force (CDF) and rehydration isotherm (RHI) methods were used to measure and characterize hydration fractions in rabbit psoas skeletal muscle. The CDF method assessed fluid flow rate from rabbit muscle and hydration capacity of the fractions. Bulk and multiple non-bulk water fractions were identified. The non-bulk water was divisible into the following fractions: two outer non-bulk fractions, a main chain proteins backbone or double water bridge fraction, and a single water bridge fraction. The total non-bulk water amounts to about 85% of the total water in the muscle. The sizes of the water fractions (in g water/g dry mass) agree with a recently proposed molecular stoichiometric hydration model (SHM) applicable to all proteins in and out of cells (Fullerton GD, Cameron IL. Water compartments in cells. Methods Enzymol, 2007; Cameron IL, Fullerton GD. Interfacial water compartments on tendon/collagen and in cells. In: Pollack GH, Chin WC, editors. Phase transitions in cells. Dordrecht, The Netherlands: Springer, 2008). Age of the rabbit significantly slowed the flow rate of the outer non-bulk water fraction by about 50%. Also, muscle of the older rabbit (26 weeks vs. 12 weeks old) had less bulk water and less outer non-bulk water but the same amount of main chain backbone water compared to muscle of the younger rabbit. Increase in time post-mortem from 30min to 4h resulted in rigor mortis and a significantly slower flow rate of water from the outer non-bulk water fraction, which is attributed to muscle contraction, increased packing of contractile elements and increased obstructions to flow of fluid from the muscle fibers.  相似文献   
85.
Apportioning trace fossils to producers is significant for palaeoecological and palaeoenvironmental studies. A tracemaker is usually attributed through the comparison of the morphology of the trace to the body plans of modern and extinct animals. However, hypotheses of tracemaker identifications may be tested with the use of further methods. This contribution aims to evaluate the potential tracemakers of a trackway‐dominated ichnofauna preserved in the siltstone–claystone rhythmites of the Pennsylvanian Rio do Sul Formation in the southern Brazil. These deposits are typical of the deglaciation phase of the Late Palaeozoic Ice Age of Gondwana in the Paraná Basin. Thus, the parameters applied in this work are as follows: (1) functional analyses of the traces to infer the biomechanics of the locomotion of the producer; and (2) neoichnology, whereby modern traces whose producers are known are compared to those of the ichnofauna in question. The conclusions obtained with these methods strongly support millipedes as the producers of Diplichnites gouldi and Diplopodichnus biformis. The malacostracan crustacean‐related ichnogenera are Umfolozia sinuosa and Gluckstadtella elongata, produced by syncarids or peracarids, while isopods are suggested as the tracemakers of Glaciichnium isp. and Protovirgularia dichotoma. In terms of branchiopod crustaceans, Cruziana problematica is attributed to notostracans. Helminthoidichnites tenuis, Mermia carickensis and Treptichnus pollardi are considered traces produced by insect larvae. The palaeobiology of the tracemakers that produced the ichnofauna preserved in the rhythmites of the Rio do Sul Formation permits inferences that terrestrial (millipedes) and aquatic (crustaceans and insect larvae) animals colonized the sediments. This conclusion points to a dynamic depositional environment, with changing physical and chemical parameters conditioning the biota.  相似文献   
86.
Therapeutics development for triplet repeat expansion diseases   总被引:5,自引:0,他引:5  
The underlying genetic mutations for many inherited neurodegenerative disorders have been identified in recent years. One frequent type of mutation is trinucleotide repeat expansion. Depending on the location of the repeat expansion, the mutation might result in a loss of function of the disease gene, a toxic gain of function or both. Disease gene identification has led to the development of model systems for investigating disease mechanisms and evaluating treatments. Examination of experimental findings reveals similarities in disease mechanisms as well as possibilities for treatment.  相似文献   
87.
Canonically, 'mirror neurons' are cells in area F5 of the ventral premotor cortex that are active during both observation and execution of goal-directed movements. Recently, cells with similar properties have been observed in a number of other areas in the motor system, including the primary motor cortex. Mirror neurons are a part of a system whose function is thought to involve the prediction and interpretation of the sensory consequences of our own actions as well as the actions of others. Mirror-like responses are relevant to the development of brain-machine interfaces (BMIs) because they provide a robust way to map neural activity to behavior, and because they represent high-level information about goals and intentions that may have utility in future BMI applications.  相似文献   
88.
Over the last decade, unusually high losses of colonies have been reported by beekeepers across the USA. Multiple factors such as Varroa destructor, bee viruses, Nosema ceranae, weather, beekeeping practices, nutrition, and pesticides have been shown to contribute to colony losses. Here we describe a large-scale controlled trial, in which different bee pathogens, bee population, and weather conditions across winter were monitored at three locations across the USA. In order to minimize influence of various known contributing factors and their interaction, the hives in the study were not treated with antibiotics or miticides. Additionally, the hives were kept at one location and were not exposed to potential stress factors associated with migration. Our results show that a linear association between load of viruses (DWV or IAPV) in Varroa and bees is present at high Varroa infestation levels (>3 mites per 100 bees). The collection of comprehensive data allowed us to draw a predictive model of colony losses and to show that Varroa destructor, along with bee viruses, mainly DWV replication, contributes to approximately 70% of colony losses. This correlation further supports the claim that insufficient control of the virus-vectoring Varroa mite would result in increased hive loss. The predictive model also indicates that a single factor may not be sufficient to trigger colony losses, whereas a combination of stressors appears to impact hive health.  相似文献   
89.
Gill morphometrics of the three thresher shark species (genus Alopias) were determined to examine how metabolism and habitat correlate with respiratory specialization for increased gas exchange. Thresher sharks have large gill surface areas, short water–blood barrier distances, and thin lamellae. Their large gill areas are derived from long total filament lengths and large lamellae, a morphometric configuration documented for other active elasmobranchs (i.e., lamnid sharks, Lamnidae) that augments respiratory surface area while limiting increases in branchial resistance to ventilatory flow. The bigeye thresher, Alopias superciliosus, which can experience prolonged exposure to hypoxia during diel vertical migrations, has the largest gill surface area documented for any elasmobranch species studied to date. The pelagic thresher shark, A. pelagicus, a warm‐water epi‐pelagic species, has a gill surface area comparable to that of the common thresher shark, A. vulpinus, despite the latter's expected higher aerobic requirements associated with regional endothermy. In addition, A. vulpinus has a significantly longer water–blood barrier distance than A. pelagicus and A. superciliosus, which likely reflects its cold, well‐oxygenated habitat relative to the two other Alopias species. In fast‐swimming fishes (such as A. vulpinus and A. pelagicus) cranial streamlining may impose morphological constraints on gill size. However, such constraints may be relaxed in hypoxia‐dwelling species (such as A. superciliosus) that are likely less dependent on streamlining and can therefore accommodate larger branchial chambers and gills. J. Morphol. 276:589–600, 2015. © 2015 Wiley Periodicals, Inc.  相似文献   
90.
Mitogens activate cell signaling and gene expression cascades that culminate in expression of cyclin D1 during the G(0)-to-G(1) transition of the cell cycle. Using cell cycle arrest in response to oxidative stress, we have delineated a dynamic program of chromatin trafficking of c-Fos and Fra-1 required for cyclin D1 expression during cell cycle reentry. In serum-stimulated lung epithelial cells, c-Fos was expressed, recruited to chromatin, phosphorylated at extracellular signal-regulated kinase 1- and 2 (ERK1,2)-dependent sites, and degraded prior to prolonged recruitment of Fra-1 to chromatin. Immunostaining showed that expression of nuclear c-Fos and that of cyclin D1 are mutually exclusive, whereas nuclear Fra-1 and cyclin D1 are coexpressed as cells traverse G(1). Oxidative stress prolonged the accumulation of phospho-ERK1,2 and phospho-c-Fos on chromatin, inhibited entry of Fra-1 into the nucleus, and blocked cyclin D1 expression. After induction of the immediate-early gene response in the presence of oxidative stress, inhibition of ERK1,2 signaling promoted degradation of c-Fos, recruitment of Fra-1 to chromatin, and expression of cyclin D1. Our data indicate that termination of nuclear ERK1,2 signaling is required for an exchange of Fra-1 for c-Fos on chromatin and initiation of cyclin D1 expression at the G(0)-to-G(1) transition of the cell cycle.  相似文献   
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