|The zinc finger protein Zfr1p is localized specifically to conjugation junction and required for sexual development in Tetrahymena thermophila.|
Xu, J; Tian, H; Wang, W; Liang, A
Conjugation in Tetrahymena thermophila involves a developmental program consisting of three prezygotic nuclear divisions, pronuclear exchange and fusion, and postzygotic and exconjugant stages. The conjugation junction structure appears during the initiation of conjugation development, and disappears during the exconjugant stage. Many structural and functional proteins are involved in the establishment and maintenance of the junction structure in T. thermophila. In the present study, a zinc finger protein-encoding gene ZFR1 was found to be expressed specifically during conjugation and to localize specifically to the conjugation junction region. Truncated Zfr1p localized at the plasma membrane in ordered arrays and decorated Golgi apparatus located adjacent to basal body. The N-terminal zinc finger and C-terminal hydrophobic domains of Zfr1p were found to be required for its specific conjugation junction localization. Conjugation development of ZFR1 somatic knockout cells was aborted at the pronuclear exchange and fusion conjugation stages. Furthermore, Zfr1p was found to be important for conjugation junction stability during the prezygotic nuclear division stage. Taken together, our data reveal that Zfr1p is required for the stability and integrity of the conjugation junction structure and essential for the sexual life cycle of the Tetrahymena cell.
|Nociceptive afferents to the premotor neurons that send axons simultaneously to the facial and hypoglossal motoneurons by means of axon collaterals.|
Dong, Y; Li, J; Zhang, F; Li, Y
It is well known that the brainstem premotor neurons of the facial nucleus and hypoglossal nucleus coordinate orofacial nociceptive reflex (ONR) responses. However, whether the brainstem PNs receive the nociceptive projection directly from the caudal spinal trigeminal nucleus is still kept unclear. Our present study focuses on the distribution of premotor neurons in the ONR pathways of rats and the collateral projection of the premotor neurons which are involved in the brainstem local pathways of the orofacial nociceptive reflexes of rat. Retrograde tracer Fluoro-gold (FG) or FG/tetramethylrhodamine-dextran amine (TMR-DA) were injected into the VII or/and XII, and anterograde tracer biotinylated dextran amine (BDA) was injected into the caudal spinal trigeminal nucleus (Vc). The tracing studies indicated that FG-labeled neurons receiving BDA-labeled fibers from the Vc were mainly distributed bilaterally in the parvicellular reticular formation (PCRt), dorsal and ventral medullary reticular formation (MdD, MdV), supratrigeminal nucleus (Vsup) and parabrachial nucleus (PBN) with an ipsilateral dominance. Some FG/TMR-DA double-labeled premotor neurons, which were observed bilaterally in the PCRt, MdD, dorsal part of the MdV, peri-motor nucleus regions, contacted with BDA-labeled axonal terminals and expressed c-fos protein-like immunoreactivity which induced by subcutaneous injection of formalin into the lip. After retrograde tracer wheat germ agglutinated horseradish peroxidase (WGA-HRP) was injected into VII or XII and BDA into Vc, electron microscopic study revealed that some BDA-labeled axonal terminals made mainly asymmetric synapses on the dendritic and somatic profiles of WGA-HRP-labeled premotor neurons. These data indicate that some premotor neurons could integrate the orofacial nociceptive input from the Vc and transfer these signals simultaneously to different brainstem motonuclei by axonal collaterals.Full Text Article
|Sphingosine kinase 1 regulates the expression of proinflammatory cytokines and nitric oxide in activated microglia.|
D Nayak,Y Huo,W X T Kwang,P N Pushparaj,S D Kumar,E-A Ling,S T Dheen
Microglial activation has been implicated as one of the causative factors for neuroinflammation in various neurodegenerative diseases. The sphingolipid metabolic pathway plays an important role in inflammation, cell proliferation, survival, chemotaxis, and immunity in peripheral macrophages. In this study, we demonstrate that sphingosine kinase1 (SphK1), a key enzyme of the sphingolipid metabolic pathway, and its receptors are expressed in the mouse BV2 microglial cells and SphK1 alters the expression and production of proinflammatory cytokines and nitric oxide in microglia treated with lipopolysaccharide (LPS). LPS treatment increased the SphK1 mRNA and protein expression in microglia as revealed by the RT-PCR, Western blot and immunofluorescence. Suppression of SphK1 by its inhibitor, N, N Dimethylsphingosine (DMS), or siRNA resulted in decreased mRNA expression of TNF-alpha, IL-1beta, and iNOS and release of TNF-alpha and nitric oxide (NO) in LPS-activated microglia. Moreover, addition of sphingosine 1 phosphate (S1P), a breakdown product of sphingolipid metabolism, increased the expression levels of TNF-alpha, IL-1beta and iNOS and production of TNF-alpha and NO in activated microglia. Hence to summarize, suppression of SphK1 in activated microglia inhibits the production of proinflammatory cytokines and NO and the addition of exogenous S1P to activated microglia enhances their inflammatory responses. Since the chronic proinflammatory cytokine production by microglia has been implicated in neuroinflammation, modulation of SphK1 and S1P in microglia could be looked upon as a future potential therapeutic method in the control of neuroinflammation in neurodegenerative diseases.