Quantum theory of Cherenkov beam instabilities in plasma

A quantum theory of stimulated Cherenkov emission of longitudinal waves by an electron beam in an isotropic plasma is presented. The emitted radiation is interpreted as instability due to the decay of the de Broglie wave of a beam electron. Nonrelativistic and relativistic nonlinear quantum equations for Cherenkov beam instabilities are obtained. A linear approximation is used to derive quantum dispersion relations and to determine the instability growth rates. The mechanisms for nonlinear saturation of quantum Cherenkov beam instabilities are investigated, and the corresponding analytic solutions are found.     

Studying sperm motility in marine fish: an overview on the state of the art

This contribution reviews existing literature and some new own findings on teleost sperm motility and factors controlling it, emphasizing selected marine species. In marine teleosts with external fertilization (halibut, turbot, sea bass, hake, cod and tuna serving as examples), mainly the osmolality controls sperm motility: movement is activated by transfer from the seminal fluid into sea water, representing a large upward step in osmolality. The exception are flatfishes (such as halibut or turbot) where CO₂ is responsible for flagellar immotility in seminal fluid. In all cases, the duration of motility is short and limited to minutes ranges due to partial exhaustion of the ATP energy and to increase of internal ionic concentration as suggested by studies with de‐membranated/ATP reactivated flagellae. In this overview, we compare motility characteristics (percentage of active spermatozoa, velocity, linearity), flagellar waves parameters (wave length and amplitude, number of waves) and energy content (respiration and ATP concentration) within species where these data have been established. All parameters show a rapid decrease after activation; therefore progressive forward movement needed by the sperm to effectively reach the egg surface, is limited to a short initial period following activation. In two species (turbot and sea bass) the rapid decrease of sperm motility is reflected by a corresponding decrease of the fertilizing ability. Exposure to external environments (sea water) at activation also leads to local defects of the sperm flagella posing additional limitations on motility duration. However, minor flagellar damages as well as energetic exhaustion are reversible: after a resting period in a non‐swimming solution at the end of the motility period, spermatozoa can be re‐activated for a second motility period. From these results and from additional data obtained from de‐membranated/ATP re‐activated spermatozoa, a paradigm has been developed which establishes a link between external osmolality (sea water), internal ionic concentration and control of axonemal activity.     

Broadening of Plasmonic Resonance Due to Electron Collisions with Nanoparticle Boundary: а Quantum Mechanical Consideration

We present a quantum mechanical approach to calculate broadening of plasmonic resonances in metallic nanostructures due to collisions of electrons with the surface of the structure. The approach is applicable if the characteristic size of the structure is much larger than the de Broglie electron wavelength in the metal. The approach can be used in studies of plasmonic properties of both single nanoparticles and arrays of nanoparticles. Energy conservation is insured by a self-consistent solution of Maxwell's equations and our model for the photon absorption at the metal boundaries. Consequences of the model are illustrated for the case of spheroid nanoparticles, and results are in good agreement with earlier theories. In particular, we show that the boundary-collision broadening of the plasmonic resonance in spheroid nanoparticles can depend strongly on the polarization of the impinging light.     

Sperm flagellar motion maintained by ADP

Bull and human sperm which are dissected or impaled retain wave motion in the presence of 10 mM ADP. Unlike ATP-induced motility which must be mechanically initiated, ADP-induced motility requires no initiation. The activity observed appears similar to that of intact cells. Flagellar segments which are detached from the head and middle piece are capable of sustaining coordinated motility. Asymmetric motion resembling a ciliary beat can also be exhibited by free flagellar segments.     

P物质尾核微量注射抑制小鼠胃肌电活动和胃运动

本文观察了小鼠尾核微量注射Ｐ物质或乙酰胆碱对胃肌电和胃运动的ｍ影响;并初步探讨了两者作用的关系。用双极康铜导线引导胃窦部肌电;用水囊连接压力换能器记录胃窦部运动。上述信息经生物电放大器和载波放大器放大后,由四道记录仪描记曲线,同时输入微机进行采集、贮存和处理。计算出注药前后每分钟胃肌电快波、慢波和胃运动波的频率和总幅度的变化百分数。结果如下：尾核注射ＳＰ或ＡＣｈ胃电快波和胃运动呈明显的抑制效应。用     

A preliminary study of oscillating electromagnetic field effects on human spermatozoon motility

Some effects of extremely low frequency electromagnetic fields (ELF-EMFs) on human spermatozoa are reported. Significant increases in the values of the motility and of the other kinematic parameters have been observed when spermatozoa were exposed to an ELF-EMF with a square waveform of 5 mT amplitude and frequency of 50 Hz. By contrast, a 5 mT sine wave (50 Hz) and a 2.5 mT square wave (50 Hz) exposure did not produce any significant effect on sperm motility. The effects induced by ELF-EMF (50 Hz; 5 mT) during the first 3 h of exposure persisted for 21 h after the end of the treatment. These results indicate that ELF-EMF exposure can improve spermatozoa motility and that this effect depends on the field characteristics.     

Motility of the spirochete Leptospira

Spirochetes are a group of bacteria with a unique ultrastructure and a fascinating swimming behavior. This article reviews the hydrodynamics of spirochete motility, and examines the motility of the spirochete Leptospira in detail. Models of Leptospira motility are discussed, and future experiments are proposed. The outermost structure of Leptospira is a membrane sheath, and within this sheath are a helically shaped cell cylinder and two periplasmic flagella. One periplasmic flagellum is attached subterminally at either end of the cell cylinder and extends partway down the length of the cell. In swimming cells, each end of the cell may assume either a spiral or a hook shape. Translational cells have the anterior end spiral shaped, and the posterior end hook shaped. In the model of Berg et al., the periplasmic flagella are believed to rotate between the sheath and the cell cylinder. Rotation of the anterior periplasmic flagellum causes the generation of a gyrating spiral-shaped wave. This wave is believed sufficient to propel the cells forward in a low-viscosity medium. The cell cylinder concomitantly rolls around the periplasmic flagella in the opposite direction--which allows the cell to literally screw through a gel-like viscous medium without slippage. This model is presented, and it is contrasted to previous models of Leptospira motility.     

多巴胺参与P物质对胃肌电活动和胃运动的毒蕈碱抑制效应

我们以前的工作表明尾核注射Ｐ物质能抑制胃肌电快波和胃运动,该效应是通过胆碱能Ｍ受体介导的。本文观察到Ｐ物质的抑胃效应可分别被尾核注射Ｐ物质抗血清、Ｐ物质受体拮抗剂［Ａｒｇ＾６,Ｄ－Ｔｒｉｐ＾７,ＭｅＰｈｅ＾８］－ＳＰ６－１１以及多巴胺Ｄ２受体了民剂氟哌啶醇所消除;尾核注射多巴胺对胃肌电快波和胃运动也有抑制作用,且能被尾核注射氟哌啶醇以及阿托品所阻断。据此,我们高想尾核Ｐ物质可能是通过多巴胺Ｄ２受体     

Reversing invasion in bistable systems

In this paper, we discuss a class of bistable reaction-diffusion systems used to model the competitive interaction of two species. The interactions are assumed to be of classic “Lotka–Volterra” type and we will consider a particular problem with relevance to applications in population dynamics: essentially, we study under what conditions the interplay of relative motility (diffusion) and competitive strength can cause waves of invasion to be halted and reversed. By establishing rigorous results concerning related degenerate and near-degenerate systems, we build a picture of the dependence of the wave speed on system parameters. Our results lead us to conjecture that this class of competition model has three “zones of response”. In the central zone, varying the motility can slow, halt and reverse invasion. However, in the two outer zones, the direction of invasion is independent of the relative motility and is entirely determined by the relative competitive strengths. Furthermore, we conjecture that for a large class of competition models of the type studied here, the wave speed is an increasing function of the relative motility.     

Motility activation and metabolism characteristics of spermatozoa of the black-lip-pearl oyster Pinctada margaritifera var: cumingii (Jameson, 1901)

Motility of Pinctada margaritifera (Linnaeus, 1758); var: cumingii (Jameson, 1901) (P. margaritifera) spermatozoa collected from gonads are not immediately activated at spawning in seawater (SW) but motility occurs when spermatozoa are transferred into alkaline seawater (pH ranging from 9.0 to 11.4). This motility-activating effect of alkaline pH is reversed when pH is shifted back to more acidic values. In both cases, activity of sperm (% motile cells) increases gradually after alkaline pH activation then lasts for several minutes. The characteristics of these fully motile spermatozoa are described in details at the level of flagella: the wave amplitude and wave-length range 5 to 6 μm and 15 μm respectively, while the flagellar beat frequency is approximately 49 Hz. The velocity of sperm displacement is from 220 to 230 μm/sec. The general swimming pattern is almost circular: the head trajectories describe portions of circles intercalated with small linear segments. Spermatozoa saved in natural seawater at 4°C retain potent motility for several days and can be subsequently activated by alkaline seawater. Respiration and ATP concentration were measured in 3 conditions: regular seawater (pH 7.8), artificial diluent (pH 8.2), and alkaline Tris-buffered seawater (pH 10.5). Results show that sperm respiration rates are higher whereas ATP levels are lower in the latter two media.     

Distinct Ca2+ channels maintain a high motility state of the sperm that may be needed for penetration of egg jelly of the newt,Cynops pyrrhogaster

Activation state of sperm motility named “hyperactivation” enables mammalian sperm to progress through the oviductal matrix, although a similar state of sperm motility is unknown in non‐mammalian vertebrates at fertilization. Here, we found a high motility state of the sperm in the newt Cynops pyrrhogaster. It was predominantly caused in egg jelly extract (JE) and characterized by a high wave velocity of the undulating membrane (UM) that was significantly higher at the posterior midpiece. An insemination assay suggested that the high motility state might be needed for sperm to penetrate the egg jelly, which is the accumulated oviductal matrix. Specific characteristics of the high motility state were completely abrogated by a high concentration of verapamil, which blocks the L‐type and T‐type voltage‐dependent Ca²⁺ channels (VDCCs). Mibefradil, a dominant blocker of T‐type VDCCs, suppressed the wave of the UM at the posterior midpiece with separate wave propagation from both the anterior midpiece and the posterior principal piece. In addition, nitrendipine, a dominant L‐type VDCC blocker, weakened the wave of the UM, especially in the anterior midpiece. Live Ca²⁺ imaging showed that, compared with the intact sperm in the JE, the relative intracellular Ca²⁺ level changed especially in the anterior and posterior ends of the midpiece of the blocker‐treated sperm. These suggest that different types of Ca²⁺ channels mediate the intracellular Ca²⁺ level predominantly in the anterior and posterior ends of the midpiece to maintain the high motility state of the newt sperm.     

Evidence for outer hair cell driven oscillatory fluid flow in the tunnel of corti

Outer hair cell (OHC) somatic motility plays a key role in mammalian cochlear frequency selectivity and hearing sensitivity, but the mechanism of cochlear amplification is not well understood and remains a matter of controversy. We have visualized and quantified the effects of electrically evoked OHC somatic motility within the gerbil organ of Corti using an excised cochlear preparation. We found that OHC motility induces oscillatory motion of the medial olivocochlear fibers where they cross the tunnel of Corti (ToC) in their course to innervate the OHCs. We show that this motion is present at physiologically relevant frequencies and remains at locations distal to the OHC excitation point. We interpret this fiber motion to be the result of oscillatory fluid flow in the ToC. We show, using a simple one-dimensional hydromechanical model of the ToC, that a fluid wave within the tunnel can travel without significant attenuation for distances larger than the wavelength of the cochlear traveling wave at its peak. This ToC fluid wave could interact with the cochlear traveling wave to amplify the motion of the basilar membrane. The ToC wave could also provide longitudinal coupling between adjacent sections of the basilar membrane, and such coupling may be critical for cochlear amplification.     

The effect of ouabain on membrane potential and flagellar wave in ejaculated bull spermatozoa.

Ejaculated bull spermatozoa were exposed to various concentrations of ouabain to ascertain the effect on membrane potential, intracellular concentrations of sodium and potassium and motility. Membrane potenital, measured by electrophysiological methods, decreased. Intracellular potassium decreased and intracellular sodium increased. Progressive motility decreased. In addition, the motility change produced by ouabain was identified as a decrease both in beat frequency and in wave amplitude.     

Cyclic adenosine 3',5' monophosphate, calcium and protein phosphorylation in flagellar motility

cAMP and calcium are two important regulators of sperm flagellar motility. cAMP stimulates sperm motility by activating cAMP-dependent protein kinase and catalyzing the phosphorylation of sperm proteins. The stimulation of sperm motility by cAMP appears to be at two different levels. Evidence has been presented to suggest that cAMP-dependent phosphorylations may be required in order for motility to be initiated. In addition, cAMP-dependent phosphorylation appears to modulate specific parameters of motility resulting in higher beat frequency or greater wave amplitude. Calcium, on the other hand, when elevated intracellularly to 10(-6) M or higher, inhibits flagellar motility. The calcium-binding protein, calmodulin, appears to mediate a large number of effects of calcium on motility. Evidence suggests that calcium-calmodulin may be involved at the level of the membrane to pump calcium out of the flagellum. In addition, calcium-calmodulin may be involved in the control of axonemal function by regulating dynein ATPase and myosin light chain kinase activities. The identification of cAMP-dependent protein kinase, calmodulin and myosin light chain kinase in the sperm head suggests that cAMP and calcium-dependent phosphorylations are also involved in the control of the fertilization process, i.e., the acrosome reaction, in a manner similar to that known for the control of stimulus/secretion coupling. Finally, the effects of cAMP on flagellar motility are mediated by protein phosphorylation while the effects of calcium on motility are also in part, mediated by effects on protein phosphorylation.     

Developmental regulation of spine and filopodial motility in primary visual cortex: reduced effects of activity and sensory deprivation

Dendritic protrusions are highly motile during postnatal development. Although spine morphological plasticity could be associated with synaptic plasticity, the function of rapid spine/filopodial motility is still unknown. To investigate the role of spine motility in the development of the visual cortex and its relation with critical periods, we used two-photon imaging of neurons from layers receiving visual input in developing mouse primary visual cortex and compared motility between control and visually deprived animals. Spine and filopodia motility was prominent during early synaptogenesis (P11-P13) but greatly decreased after P15. This "switch" was coincident with a 2.5-fold increase in protrusion density and spine formation. Spine motility was not regulated during the critical period for monocular deprivation (P19-P34). Moreover, delaying the critical period by dark rearing did not delay the normal developmental decrease of spine motility, but caused a modest further reduction in motility at P28-P35. Dark rearing and enucleation also mildly reduced spine motility before eye opening and dark rearing reduced the proportion of filopodia. We conclude that (1) rapid spine motility is not related to critical period plasticity, but is likely to play a role in early synaptogenesis, and (2) neuronal activity stimulates spine motility during synaptogenesis and promotes the appearance of dendritic filopodia.     

十二指肠内胆盐对胃肌电和运动的影响及其神经...

Changes of gastric myoelectric fast wave, slow wave and gastric motility were studied after intraduodenal infusion of sodium taurocholate (ST) in an attempt to search the concerned neuromechanism. Frequency and total amplitude of the fast wave and slow wave of gastric myoelectric activity and of gastric contractile wave were recorded every five minutes before and after intraduodenal infusion of ST under the background action of various drugs. The frequency and amplitude were expressed in percentage change of the respective premedication value. After intraduodenal infusion of ST (n = 10) the frequency and the amplitude of fast wave and gastric contractile wave were suppressed. Blocking anesthesia of celiac plexus, reserpinization and intravenous infusion of carbachol could eliminate the inhibition induced by ST, which could be partly eliminated by intravenous infusion of propranolol but not affected by phentolamine at all. The results demonstrate that intraduodenal infusion of bile salt suppresses the fast wave of gastric myoelectric activity and gastric motility, most probably controlled by efferent sympathetic adrenergic fibres through beta-receptor.     

Two anti-radial spoke monoclonal antibodies inhibit Chlamydomonas axonemal motility by different mechanisms

In the 9 + 2 axoneme, radial spokes are structural components attached to the A-tubules of the nine outer doublet microtubules. They protrude toward the central pair microtubule complex with which they have transient but regular interactions for the normal flagellar motility to occur. Flagella of Chlamydomonas mutants deficient in entire radial spokes or spoke heads are paralyzed. In this study the importance of two radial spoke proteins in the flagellar movement is exemplified by the potent inhibitory action of two monoclonal antibodies on the axonemal motility of demembranated-reactivated Chlamydomonas models. We show that one of these proteins is localized on the stalk of the radial spokes, whereas the other is a component of the head of the same structure and most likely correspond to radial spoke protein 2 and 1, respectively. Fine motility analysis by videomicrography further indicates that these two anti-radial spoke protein antibodies at low concentration affect motility of demembranated-reactivated Chlamydomonas by changing the flagellar waveform without modifying axonemal beat frequency. They also modify wave amplitude differently during motility inhibition. This brings more direct evidence for the involvement of both radial spoke stalk and head in the fine tuning of the waveform during flagellar motility.     

Characterisation of three cDNA clones encoding different mRNAs for the precursor to the small subunit of wheat ribulosebisphosphate carboxylase.

We have isolated and sequenced three cDNA clones for the nuclear-encoded precursor to the small subunit of the chloroplast enzyme, ribulose-1,5-bisphosphate carboxylase of wheat. The nucleotide sequences of these clones are different, indicating that they are probably derived from three different mRNAs. This finding is consistent with the proposal that this polypeptide is encoded by a multigene family in wheat, in support of similar data reported by Broglie et al. (Bio/Technology 1:55-61, 1983). We deduce that the mature small subunit polypeptide is comprised of 128 amino acids and that its precursor contains an N-terminal transit peptide sequence. The sequences of both the mature small subunit and its transit peptide differ at several positions from those determined by Broglie et al, (1983) from a different wheat cultivar. Different wheat cultivars might therefore contain different small subunit polypeptides. A comparison of nucleotide and amino acid sequences of the small subunit from wheat, pea, soybean and spinach shows that these sequences are not highly conserved, particularly between monocotyledon and dicotyledon species.     

A selective effect of Ni2+ on wave initiation in bull sperm flagella

Bull sperm that are extracted with 0.1% Triton X-100 and restored to motility with Mg2+-ATP lose coordination and stop swimming in the presence of 0.5 mM NiSO4. Although spontaneous coordination of flagellar waves is lost after exposure to Ni2+, other functions of the flagellum remain intact. The capacity for wave propagation along the flagellum is maintained together with the capacity for microtubular sliding. Wave motility can be restored to Ni2+-inhibited sperm by inducing a permanent bend onto the flagellum by micromanipulation. In the absence of such intervention, the loss of wave coordination is complete and irreversible. Ni2+-inhibited demembranated cells that are kept active by maintaining a bend in the flagellum exhibit a normal beat frequency. Both intact and demembranated sperm can retain spontaneous wave production at considerably slower rates of motion than Ni2+-inhibited cells. Short segments from the distal tip of the flagellum contain only the 9 + 2 microtubular axoneme. These short segments are able to propagate imposed bends even in the presence of Ni2+. In addition to wave propagation Ni2+-treated sperm can be shown to exhibit a normal sliding tubule phenomenon by direct assay. Although Ni2+-treated cells have a functional sliding tubule mechanism, and consequently the axoneme can propagate bends, it appears that these retained functions are not sufficient to cause spontaneous bend initiation. Our findings show that bend initiation is inhibited by Ni2+, and therefore is an independent process separate from the sliding tubule mechanism responsible for wave propagation.     

Effects of osmolality on sperm morphology, motility and flagellar wave parameters in Northern pike (Esox lucius L.)

Northern pike (Esox lucius L.) spermatozoa are uniflagellated cells differentiated into a head without acrosome, a midpiece and a flagellar tail region flanked by a fin structure. Total, flagellar, head and midpiece lengths of spermatozoa were measured and show mean values of 34.5, 32.0, 1.32, 1.17 μm, respectively, with anterior and posterior widths of the midpiece measuring 0.8 and 0.6 μm, respectively. The osmolality of seminal plasma ranged from 228 to 350 mOsmol kg⁻¹ (average: 283.88 ± 33.05). After triggering of sperm motility in very low osmolality medium (distilled water), blebs appeared along the flagellum. At later periods in the motility phase, the tip of the flagellum became curled into a loop shape which resulted in a shortening of the flagellum and a restriction of wave development to the proximal part (close to head). Spermatozoa velocity and percentage of motile spermatozoa decreased rapidly as a function of time postactivation and depended on the osmolality of activation media (P < 0.05). In general, the greatest percentage of motile spermatozoa and highest spermatozoa velocity were observed between 125 and 235 mOsmol kg⁻¹. Osmolality above 375 mOsmol kg⁻¹ inhibited the motility of spermatozoa. After triggering of sperm motility in activation media, beating waves propagated along the full length of flagella, while waves appeared dampened during later periods in the motility phase, and were absent at the end of the motility phase. By increasing osmolality, the velocity of spermatozoa reached the highest value while wave length, amplitude, number of waves and curvatures also were at their highest values. This study showed that sperm morphology can be used for fish classification. Sperm morphology, in particular, the flagellar part showed several changes during activation in distilled water. Sperm motility of pike is inhibited due to high osmolality in the seminal plasma. Osmolality of activation medium affects the percentage of motile sperm and spermatozoa velocity due to changes in flagellar wave parameters.