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Membrane Specializations (membrane + specialization)

Distribution by Scientific Domains

Life Sciences	100%

Selected Abstracts

A novel membrane specialization in the sperm tail of bug insects (heteroptera),

JOURNAL OF MORPHOLOGY, Issue 7 2009
David Mercati
Abstract The sperm tail of bug insects has 9 + 9 + 2 flagellar axonemes and two mitochondrial derivatives showing two to three crystalline inclusions in their matrix. During spermiogenesis, the axoneme is surrounded by a membrane cistern which, at sperm maturity, reduces to two short cisterns on the opposite sides of the axoneme adhering to the mitochondrial derivatives. Filamentous bridges connect the intertubular material of the axoneme to these cisterns. Such bridges, which represent a peculiar feature of bug insects, are resistant to detergent treatment, whereas part of the intertubular material and the inner content of microtubular doublets are affected by the treatment. After freeze-fracture replicas, at the insertion of the bridges to the cisternal membrane, the P-face of this membrane shows a characteristic ribbon consisting of four rows of 11 ± 1 nm staggered intramembrane particles, 13 ± 2 nm apart along each row. The bridges could be able to maintain the axoneme in the proper position during flagellar beating avoiding distortion affecting sperm motility. J. Morphol. 2009. © 2009 Wiley-Liss, Inc. [source]

Human neural stem cell grafts in the spinal cord of SOD1 transgenic rats: Differentiation and structural integration into the segmental motor circuitry

THE JOURNAL OF COMPARATIVE NEUROLOGY, Issue 4 2009
Leyan Xu
Abstract Cell replacement strategies for degenerative and traumatic diseases of the nervous system depend on the functional integration of grafted cells into host neural circuitry, a condition necessary for the propagation of physiological signals and, perhaps, targeting of trophic support to injured neurons. We have recently shown that human neural stem cell (NSC) grafts ameliorate motor neuron disease in SOD1 transgenic rodents. Here we study structural aspects of integration of neuronally differentiated human NSCs in the motor circuitry of SOD1 G93A rats. Human NSCs were grafted into the lumbar protuberance of 8-week-old SOD1 G93A rats; the results were compared to those on control Sprague-Dawley rats. Using pre-embedding immuno-electron microscopy, we found human synaptophysin (+) terminals contacting the perikarya and proximal dendrites of host , motor neurons. Synaptophysin (+) terminals had well-formed synaptic vesicles and were associated with membrane specializations primarily in the form of symmetrical synapses. To analyze the anatomy of motor circuits engaging differentiated NSCs, we injected the retrograde transneuronal tracer Bartha-pseudorabies virus (PRV) or the retrograde marker cholera toxin B (CTB) into the gastrocnemius muscle/sciatic nerve of SOD1 rats before disease onset and also into control rats. With this tracing, NSC-derived neurons were labeled with PRV but not CTB, a pattern suggesting that PRV entered NSC-derived neurons via transneuronal transfer from host motor neurons but not via direct transport from the host musculature. Our results indicate an advanced degree of structural integration, via functional synapses, of differentiated human NSCs into the segmental motor circuitry of SOD1-G93A rats. J. Comp. Neurol. 514:297,309, 2009. © 2009 Wiley-Liss, Inc. [source]

Cellular and subcellular localization of the GABAB receptor 1a/b subunit in the rat periaqueductal gray matter

THE JOURNAL OF COMPARATIVE NEUROLOGY, Issue 5 2007
Paolo Barbaresi
Abstract The inhibitory effects of ,-aminobutyric acid (GABA)ergic neurotransmission in the periaqueductal gray matter (PAG) are mediated, at least partly, by metabotropic GABAB receptor subtypes whose cellular and subcellular localization is still unknown. We performed immunohistochemical experiments with an antibody against GABAB receptor subtype 1a/b (GABABR1a/b) by using light and electron microscopy. On light microscopy, GABABR1a/b immunoreactivity (IR) was in all columns, defined by cytochrome oxidase histochemistry. Neuropil labeling was strongest in the lateral portion of dorsolateral PAG. Labeled neurons, albeit not numerous, were in ventrolateral, dorsal, and medial subdivisions and were sparser in dorsolateral PAG. Labeling was mostly on the soma of PAG neurons. Sometimes GABABR1a/b IR spread along proximal dendrites; in these cases bipolar neurons were the most common type. On electron microscopy, GABABR1a/b IR was mainly on dendrites (54.92% of labeled elements) and axon terminals (21.90%) making synapses with labeled and unlabeled postsynaptic elements. Presynaptic labeling was also on unmyelinated and myelinated axons (overall 8% of all labeled elements). Postsynaptically, GABABR1a/b IR was at extrasynaptic sites on dendritic shafts; spines were always unlabeled. On axon terminals, GABABR1a/b IR was on extrasynaptic membranes and sometimes on presynaptic membrane specializations. Of the labeled elements, 13.03% elements were distal astrocytic processes (dAsPs) surrounding both symmetric and asymmetric synapses whose pre- and postsynaptic elements were often labeled. Immunoreactive dAsPs were around the soma and dendrites of both labeled and unlabeled neurons. These findings provide insights into the intrinsic PAG organization and suggest that presynaptic, postsynaptic, and glial GABAB receptors may play crucial roles in controlling PAG neuronal activity. J. Comp. Neurol. 505:478,492, 2007. © 2007 Wiley-Liss, Inc. [source]

Synaptic specializations exist between enteric motor nerves and interstitial cells of Cajal in the murine stomach

THE JOURNAL OF COMPARATIVE NEUROLOGY, Issue 2 2005
Elizabeth A.H. Beckett
Abstract Autonomic neurotransmission is thought to occur via a loose association between nerve varicosities and smooth muscle cells. In the gastrointestinal tract ultrastructural studies have demonstrated close apposition between enteric nerves and intramuscular interstitial cells of Cajal (ICC-IM) in the stomach and colon and ICC in the deep muscular plexus (ICC-DMP) of the small intestine. In the absence of ICC-IM, postjunctional neural responses are compromised. Although membrane specializations between nerves and ICC-IM have been reported, the molecular identity of these specializations has not been studied. Here we have characterized the expression and distribution of synapse-associated proteins between nerve terminals and ICC-IM in the murine stomach. Transcripts for the presynaptic proteins synaptotagmin, syntaxin, and SNAP-25 were detected. Synaptotagmin and SNAP-25-immunopositive nerve varicosities were concentrated in varicose regions of motor nerves and were closely apposed to ICC-IM but not smooth muscle. W/WV mice were used to examine the expression and distribution of synaptic proteins in the absence of ICC-IM. Transcripts encoding synaptotagmin, syntaxin, and SNAP-25 were detected in W/WV tissues. In the absence of ICC-IM, synaptotagmin and SNAP-25 were localized to nerve varicosities. Reverse transcriptase polymer chain reaction (RT-PCR) and immunohistochemistry demonstrated the expression of postsynaptic density proteins PSD-93 and PSD-95 in the stomach and expression levels of PSD-93 and PSD-95 were reduced in W/WV mutants. These data support the existence of synaptic specializations between enteric nerves and ICC-IM in gastric tissues. In the absence of ICC-IM, components of the synaptic vesicle docking and fusion machinery is trafficked and concentrated in enteric nerve terminals. J. Comp. Neurol. 493:193,206, 2005. © 2005 Wiley-Liss, Inc. [source]