ABSTRACT
Although synchronized oscillations are found in a variety of systems and living organisms in nature, there has been no report on technologically important materials. We have observed by a fluorescence microscope that a large number of carbon nanotubes (CNTs) dispersed in an aqueous mixture of the surfactant and dye execute synchronized oscillations spontaneously. The movement was quantified to give a power spectrum, revealing a single, sharp synchronization peak at 20 Hz. It was found not to be affected nor created by external vibrations. The surfactant concentration dependence demonstrates that the Kuramoto model is applicable to describe the CNT synchronization. It is always associated with the power-law noise, indicating the presence of complex heterogeneous networks. These results suggest a highly cooperative form of the sparse CNT network connected with variable linkages.
ABSTRACT
Patients with depression showed a decrease in plasma and cerebrospinal fluid allopregnanolone (ALLO). But antidepressants increased the contents of ALLO in the rat brain. We examined the antidepressant-like effects of infusion of ALLO into the cerebral ventricle, hippocampus, amygdala, nucleus accumbens, or prefrontal cortex of learned helplessness (LH) rats (an animal model of depression). Of these regions, infusions of ALLO into the cerebral ventricle, the CA3 region of hippocampus, or the central region of amygdala exerted antidepressant-like effects. Infusion of ALLO into the hippocampal CA3 region or the central amygdala did not produce memory deficits or locomotor activation in the passive avoidance and open field tests. It is well documented that ALLO exerts its effects through GABA receptors. Therefore, we examined the antagonistic effects of flumazenil (a GABA receptor antagonist) on the antidepressant-like effects of ALLO. Coinfusion of flumazenil with ALLO into the hippocampal CA3 region, but not into the central amygdala, blocked the antidepressant-like effects of ALLO. However, coinfusion of (+)MK801 (an NMDA receptor antagonist), but not cycloheximide (a protein synthesis inhibitor), blocked the antidepressant-like effects of ALLO in the central amygdala. These results suggest that ALLO exerts antidepressant-like effects in the CA3 region of hippocampus through the GABA system and in the central region of amygdala, dependently on the activation of the glutamatergic mechanisms.
Subject(s)
Amygdala/drug effects , CA3 Region, Hippocampal/drug effects , Helplessness, Learned , Pregnanolone/administration & dosage , Receptors, GABA/drug effects , Receptors, N-Methyl-D-Aspartate/drug effects , Amygdala/physiology , Animals , Antidepressive Agents/pharmacology , Avoidance Learning/drug effects , CA3 Region, Hippocampal/physiology , Depression/drug therapy , Disease Models, Animal , Dizocilpine Maleate/administration & dosage , Drug Combinations , Flumazenil/administration & dosage , GABA Antagonists/administration & dosage , Humans , Injections, Intraventricular , Male , Nucleus Accumbens/drug effects , Nucleus Accumbens/physiology , Prefrontal Cortex/drug effects , Rats , Rats, Sprague-Dawley , Receptors, N-Methyl-D-Aspartate/antagonists & inhibitorsABSTRACT
Narp (neuronal activity-regulated pentraxin) is a secreted immediate early gene product functioning as a cluster factor for the AMPA receptor subtype of glutamate receptors. This study was designed to examine the effects of acute administration of methamphetamine (MAP) on the Narp gene in rat brain using reverse transcription - polymerase chain reaction (RT-PCR). Acute administration of MAP [4.6 mg/kg, intraperitoneally (i.p.)] increased Narp mRNA in the prefrontal cortex, whereas the same treatment with MAP decreased Narp mRNA in the hippocampus. Therefore, Narp gene could be involved in the MAP-induced effects.
Subject(s)
C-Reactive Protein , Central Nervous System Stimulants/pharmacology , Hippocampus/drug effects , Hippocampus/metabolism , Methamphetamine/pharmacology , Nerve Tissue Proteins , Prefrontal Cortex/drug effects , Prefrontal Cortex/metabolism , RNA, Messenger , Animals , C-Reactive Protein/drug effects , C-Reactive Protein/genetics , C-Reactive Protein/metabolism , Central Nervous System Stimulants/administration & dosage , Drug Administration Schedule , Male , Methamphetamine/administration & dosage , Nerve Tissue Proteins/drug effects , Nerve Tissue Proteins/genetics , Nerve Tissue Proteins/metabolism , RNA, Messenger/drug effects , RNA, Messenger/genetics , RNA, Messenger/metabolism , Rats , Rats, Wistar , Reverse Transcriptase Polymerase Chain ReactionABSTRACT
The spermatozoa of Phallusia (Ascidia) nigra have an elongated head (approximately 5 µm in length) in which a nucleus and a single mitochondrion are located side by side. There is no midpiece. The apex of the head is wedge-shaped. Acrosomal vesicles (approximately 55-65 nm in diameter) and moderately electron-dense material (MEDM) are present between the plasmalemma and the nuclear membranes in the anterior tip of the head. The MEDM occupies a central position and three or four acrosomal vesicles are seen in a line alongside it. The acrosomal vesicles disappear as the sperm makes contact with the surface of the chorion. Gamete fusion most likely occurs between a small process extending from the peripheral margin of the sperm apex and the egg surface, resulting in incorporation of the sperm into the egg from the anterior region of its head.
ABSTRACT
An acrosome reaction occurs by fusion between the acrosomal outer membrane and the plasmalemma enclosing the acrosome in Ciona intestinalis spermatozoa. The fusion seems to proceed along the peripheral margin of the acrosome, which causes vesiculation. The membrane bound vesicle formed by this process is probably shed by the sperm. The acrosomal inner membrane is exposed and becomes a part of the plasmalemma enclosing the anterior region of the sperm head. During this process, any acrosomal substance might be released through the opening formed by membrane fusion. The acrosome reaction most likely occurs in C. intestinalis spermatozoa, via vesiculation, in fundamentally the same way as observed in mammalian spermatozoa.
ABSTRACT
An acrosome-like structure has been recognized at the apex of mature spermatozoa of both Pyura haustor and Styela plicata. The acrosome-like structure of P. haustor is a slightly depressed ellipsoid, approximately 90 nm × 80 nm × 50 nm, in length, width and height, respectively, while that of S. plicata is an antero-posteriorly elongated, flattened vesicle, approximately 200 nm × 100 nm × 50 nm, in length, width and height, respectively. During spermiogenesis, two vesicles (50-80 nm in diameter) are found in a blister at the apex of early spermatids of both species. These vesicles, presumably derived from the Golgi apparatus, contain moderately electron-dense material. In late spermatids, these two vesicles appear to fuse to form an acrosome-like structure. Because of its extremely reduced size and the paucity of its contents, it is unlikely that the acrosome-like structure of these sperm contain a significant amount of chorion lysin(s). A well developed Golgi apparatus and many Golgi vesicles of various sizes are found in the cytoplasm of spermatids in both P. haustor and S. plicata. It is hypothesized that ascidian spermatozoa contain a poorly developed acrosome, and that the chorion lysin(s) are intercalated into the plasmalemma enclosing the sperm head.
