Smaller Spikes Research Articles

Carex delongii (Cyperaceae), a new sedge from Russia

While performing vegetation surveys in the southern part of the Lena delta, a new species of Carex from section Phacocystis has been found. Morphologically, Carex delongii sp. nov. is most close to C. cespitosa and C. minuta but differs from the former in smaller inflorescences, shorter pistillate spikes, narrow and soft leaves, oblong-ovoid (vs. ovoid) utricles; from the latter, it is distinguished by having smaller spikes and larger utricles. This relationship is also confirmed by molecular data. A detailed description of Carex delongii, its comparison with related species, illustrations, characteristics of habitat and phylogenetic position are reported.

STORAGE CHARACTERISTICS OF SPIKES AND GRAINS OF BREAD WHEAT CULTIVARS

This study was conducted to identify the storage characteristics of spikes of five bread wheat cultivars (Abu-Ghraib3, IPA-99, Boohooth-22, Al-Rashid and Al-Wafeer). These spikes were gathered and compacted in cubic box (25×25×25 cm) with different weight masses (0, 3, 6 and 9 kg container -1). A laboratory experiment was carried out in the Seed Technology Laboratory, Department of Field Crop Sciences, College of Agricultural Engineering Sciences-University of Baghdad. Results revealed significant differences among cultivars, masses levels and their interaction for all studied characters. Abu-Ghraib3 gave the highest mean of spikes number and less mean for the broken spikes and shuttered grains. While Al-Wafeer gave the highest mean of total grains weight resulted from spikes shuttering and grains space. However, Al-Rashid gave the highest mean of broken spikes, shuttered grains and replacement percentage in the container. Increasing the weight masses imposed on the gathered spikes in the container increased all studied characters. It can be concluded that the varieties were different in their spikes morphological characteristics as smaller spikes sizes the less losses resulted from spikes pressure.

PROPER ORTHOGONAL DECOMPOSITION: A TOOL TO STUDY THE UNDERLYING PHYSICS OF TURBULENCE

Wall bounded turbulence have been investigated by many authors to understand the underlying physics, experimentally as well as numerically with different techniques and methods. Enormous studies are reported in the literature in the field of turbulence to get the insight of near wall structure in a broad spectrum of Reynolds number. To recognize the contribution of different turbulent scales in a flow a well-known technique, Proper Orthogonal decomposition (POD) is used. Dynamical behaviour of coherent structure in a turbulent channel flow submitted to high temperature gradient is investigated via proper orthogonal decomposition (POD). The turbulent data is generated using thermal large eddy simulation (TLES) of channel flow at Re = 180 for two values of temperature ratio between hot and cold wall. The POD technique is applied to fluctuating part of the velocity to study the temporal evolution of the most energetic modes. It is observed that dominant flow structures are elongated in streamwise direction which further distorted due to the interaction with bean shaped propagating modes. The plotted average energy E(t) as a function of non-dimensional time shows a constant level of fluctuating energy with one little peak at t+ = 1000, all other smaller spikes are showing constant fluctuations about mean line. This behavior at quantitatively describe the role of temperature stratification which stabilizes the roll mode energy and prevent them from breakup into smaller scales thus affects the interaction process during turbulent burst event resulting in a chugging or relaminarizing phenomenon. It is observed that thermal stratification decreases the bursting rate by slowing the breaking mechanism of streamwise elongated modes to larger number of bean shaped modes which results in relaminarization of the flow near hot wall.

Rungia daklakensis(Acanthaceae), a New Species from Vietnam

Rungia daklakensis D.V. Hai, Y.F. Deng & Joongku Lee sp. nova (Acanthaceae) is described and illustrated from Vietnam. It is morphologically closely related to R. pierrei, from which it differs by the bifariously pubescent stem, shape and pubescence of leaves, smaller spikes, much bigger sterile bracts, glabrous calyx and glabrous capsules. Colour photographs, description and an identification key to Vietnamese species of Rungia are provided.

Mysterious abrupt carbon-14 increase in coral contributed by a comet

A large and sudden increase in radiocarbon (14C) around AD 773 are documented in coral skeletons from the South China Sea. The 14C increased by ~ 15‰ during winter, and remain elevated for more than 4 months, then increased and dropped down within two months, forming a spike of 45‰ high in late spring, followed by two smaller spikes. The 14C anomalies coincide with an historic comet collision with the Earth's atmosphere on 17 January AD 773. Comas are known to have percent-levels of nitrogen by weight, and are exposed to cosmic radiation in space. Hence they may be expected to contain highly elevated 14C/12C ratios, as compared to the Earth's atmosphere. The significant input of 14C by comets may have contributed to the fluctuation of 14C in the atmosphere throughout the Earth's history, which should be considered carefully to better constrain the cosmic ray fluctuation.

ENHANCING THE YIELD OF HIGH-DENSITY ELECTRODE ARRAYS THROUGH AUTOMATED ELECTRODE SELECTION

Recently developed CMOS-based microprobes contain hundreds of electrodes on a single shaft with inter-electrode distances as small as 30 μm. So far, neuroscientists needed to select electrodes manually from hundreds of electrodes. Here we present an electronic depth control algorithm that allows to select electrodes automatically, hereby allowing to reduce the amount of data and locating those electrodes that are close to neurons. The electrodes are selected according to a new penalized signal-to-noise ratio (PSNR) criterion that demotes electrodes from becoming selected if their signals are redundant with previously selected electrodes. It is shown that, using the PSNR, interneurons generating smaller spikes are also selected. We developed a model that aims to evaluate algorithms for electronic depth control, but also generates benchmark data for testing spike sorting and spike detection algorithms. The model comprises a realistic tufted pyramidal cell, non-tufted pyramidal cells and inhibitory interneurons. All neurons are synaptically activated by hundreds of fibers. This arrangement allows the algorithms to be tested in more realistic conditions, including backgrounds of synaptic potentials, varying spike rates with bursting and spike amplitude attenuation.

Recruitment in Retractor Bulbi Muscle During Eyeblink Conditioning: EMG Analysis and Common-Drive Model

To analyze properly the role of the cerebellum in classical conditioning of the eyeblink and nictitating membrane (NM) response, the control of conditioned response dynamics must be better understood. Previous studies have suggested that the control signal is linearly related to the CR as a result of recruitment within the accessory abducens motoneuron pool, which acts to linearize retractor bulbi muscle and NM response mechanics. Here we investigate possible recruitment mechanisms. Data came from simultaneous recordings of NM position and multiunit electromyographic (EMG) activity from the retractor bulbi muscle of rabbits during eyeblink conditioning, in which tone and periocular shock act as conditional and unconditional stimuli, respectively. Action potentials (spikes) were extracted and classified by amplitude. Firing rates of spikes with different amplitudes were analyzed with respect to NM response temporal profiles and total EMG spike firing rate. Four main regularities were revealed and quantified: 1) spike amplitude increased with response amplitude; 2) smaller spikes always appeared before larger spikes; 3) subsequent firing rates covaried for spikes of different amplitude, with smaller spikes always firing at higher rates than larger ones; and 4) firing-rate profiles were approximately Gaussian for all amplitudes. These regularities suggest that recruitment does take place in the retractor bulbi muscle during conditioned NM responses and that all motoneurons receive the same command signal (common-drive hypothesis). To test this hypothesis, a model of the motoneuron pool was constructed in which motoneurons had a range of intrinsic thresholds distributed exponentially, with threshold linearly related to EMG spike amplitude. Each neuron received the same input signal as required by the common-drive assumption. This simple model reproduced the main features of the data, suggesting that conditioned NM responses are controlled by a common-drive mechanism that enables simple commands to determine response topography in a linear fashion.

Physiological differences between neurons in layer 2 and layer 3 of primary visual cortex (V1) of alert macaque monkeys

The physiological literature does not distinguish between the superficial layers 2 and 3 of the primary visual cortex even though these two layers differ in their cytoarchitecture and anatomical connections. To distinguish layer 2 from layer 3, we have analysed the response characteristics of neurons recorded during microelectrode penetrations perpendicular to the cortical surface. Extracellular responses of single neurons to sweeping bars were recorded while macaque monkeys performed a fixation task. Data were analysed from penetrations where cells could be localized to specific depths in the cortex. Although the most superficial cells (depth, 145-371 microm; presumably layer 2) responded preferentially to particular stimulus orientations, they were less selective than cells encountered immediately beneath them (depth, 386-696 microm; presumably layer 3). Layer 2 cells had smaller spikes, higher levels of ongoing activity, larger receptive field activating regions, and less finely tuned selectivity for stimulus orientation and length than layer 3 cells. Direction selectivity was found only in layer 3. These data suggest that layer 3 is involved in generating and transmitting precise, localized information about image features, while the lesser selectivity of layer 2 cells may participate in top-down influences from higher cortical areas, as well as modulatory influences from subcortical brain regions.

Roles of Subthreshold Calcium Current and Sodium Current in Spontaneous Firing of Mouse Midbrain Dopamine Neurons

We used a preparation of acutely dissociated neurons to quantify the ionic currents driving the spontaneous firing of substantia nigra pars compacta neurons, isolated from transgenic mice in which the tyrosine hydroxylase promoter drives expression of human placental alkaline phosphatase (PLAP) on the outer surface of the cell membrane. Dissociated neurons identified by fluorescent antibodies to PLAP showed firing properties similar to those of dopaminergic neurons in brain slice, including rhythmic spontaneous firing of broad action potentials and, in some cells, rhythmic oscillatory activity in the presence of tetrodotoxin (TTX). Spontaneous activity in TTX had broader, smaller spikes than normal pacemaking and was stopped by removal of external calcium. Normal pacemaking was also consistently silenced by replacement of external calcium by cobalt and was slowed by more specific calcium channel blockers. Nimodipine produced a slowing of pacemaking frequency. Pacemaking was also slowed by the P/Q-channel blocker omega-Aga-IVA, but the N-type channel blocker omega-conotoxin GVIA had no effect. In voltage-clamp experiments, using records of pacemaking as command voltage, cobalt-sensitive current and TTX-sensitive current were both sizeable at subthreshold voltages between spikes. Cobalt-sensitive current was consistently larger than TTX-sensitive current at interspike voltages from -70 to -50 mV, with TTX-sensitive current larger at voltages positive to -45 mV. These results support previous evidence for a major role of voltage-dependent calcium channels in driving pacemaking of midbrain dopamine neurons and suggest that multiple calcium channel types contribute to this function. The results also show a significant contribution of subthreshold TTX-sensitive sodium current.

The effect of raft lipid depletion on microvilli formation in MDCK cells, visualized by atomic force microscopy

We have investigated whether raft lipids of Madin–Darby canine kidney (MDCK) cells play any role in microvilli maintenance using a combination of atomic force microscopy (AFM) and laser scanning confocal microscopy. MDCK cells were treated to reduce the amount of sphingolipids, cholesterol, or both and subsequently imaged, in buffer solution, using AFM. It was observed that inhibition of either sphingolipid or cholesterol biosynthesis led to a reduction in the number of microvilli on the surface of MDCK cells. However, this effect was not uniform across the monolayer, with some cells resembling those in untreated controls. The subsequent extraction of cholesterol from cells grown in the presence of inhibitors led to a further reduction in microvilli on the surface of the cells and, in some cases, resulted in monolayers devoid of full length microvilli. Significantly, smaller spikes were observed on the surface of the smoother cells.

A novel aspect of photodynamic action: induction of recurrent spikes in cytosolic calcium concentration.

Effects of photodynamic action of gadolinium porphyrin-like macrocycle B (PLMGdB) on cytosolic Ca2+ concentration, [Ca2+]c, was investigated in isolated rat pancreatic acini. The PLMGdB alone or light alone (2 min) had no effect on [Ca2+]c. Cell-bound PLMGdB upon brief (0.5-2.0 min) light activation triggered recurrent spikes in [Ca2+]c. At lower PLMGdB concentration (100 nM) the spikes continued during the whole period of monitoring [Ca2+]c. At a higher concentration of 500 nM, the spikes continued for the first 40 min, followed by a gradual increase in basal [Ca2+]c upon which smaller spikes were superimposed. At 1 microM, the spikes continued for the first 20 min, after that spiking gradually degenerated into a plateau phase. In many aspects, photodynamically triggered spikes resembled spikes generated by physiological concentrations of cholecystokinin. The spikes triggered by photodynamic action were likely to be the result of the ignition of a physiological "chain reaction", because functional inositol-1,4,5-trisphosphate (IP3) receptors were required for spiking to occur. Two-aminoethoxydiphenylborate, an inhibitory modulator of IP3-triggered Ca2+ release from intracellular stores, effectively inhibited photodynamically generated spikes. Therefore photodynamic action appears to be able to permanently transfix a physiological process, leading to long-lasting pharmacological or therapeutic effects.

Burst activities of cremasteric motor units.

Electromyographic activities of the ipsilateral cremaster muscle evoked by electrical stimulation of either the thigh or the penis were analyzed for latencies and burst durations. Response latencies were 30 ms on thigh stimulation and 30-35 ms on penile stimulation. With the increase in stimulus intensity the latencies decreased to 30 ms in both cases. The changes were stepwise, indicating the switching between different reflex arcs. The burst duration on thigh stimulation was about 50 ms, and that for penile stimulation was 45 ms. Impulses producing the burst consisted of larger and smaller spikes, and this indicates the grouping of motor units for wing tonic and phasic units. The results suggest the existence of parallel neuronal circuitries for the spinal cremasteric reflex, and it is expected to provide a clue for evaluating the clinical significance of the cremasteric reflex.

Single pulses of cytoplasmic calcium associated with phagocytosis of individual zymosan particles by macrophages

We have measured cytosolic free calcium levels ([Ca ++] i) in individual macrophages during the phagocytosis of single zymosan particles. We report here that the contact of a macrophage with zymosan results in a rapid transient elevation of [Ca ++] i. Each [Ca ++] i pulse is symmetrical lasting for up to 30 seconds. In contrast, macrophage spreading is associated with repetitive [Ca ++] i spiking occuring in salvos of up to four smaller spikes, each lasting for between 8 and 18 seconds. These qualitative and kinetic differences might suggest that the role of [Ca ++] i in phagocytosis is distinct from its role in spreading.

Visual responses of nucleus isthmi in a teleost fish ( Lepomis macrochirus)

Extracellular electrical activity was recorded from the nucleus isthmi of the bluegill sunfish ( Lepomis macrochirus) in response to brief flashes produced by red light emitting diodes, and other visual stimuli. Metal microelectrodes detected positive spikes outside the nucleus, and negative spikes inside. Spikes of a continuous range of amplitudes up to 1 mV occurred in bursts, spontaneously and visually triggered. The highest amplitude spikes were triggered by the appearance or movement of stimuli throughout the visual field of the contralateral eye. Smaller spikes were triggered by stimuli throughout both visual fields. However, all spiking activity habituated with repeated stimulation in one region of the field. Stimulating at 12 widely spaced positions within the visual field of one eye yielded no consistent differences in the numbers of large spikes evoked. Different penetrations within and around the nucleus also gave uniform distributions of spike numbers. Thus no visuotopic organization was evident. The large spike response evoked by contralateral field stimulation was partially inhibited by a competing stimulus presented to the ipsilateral eye.

Response of wheat cultivars to dates of sowing under dryland conditions

SUMMARYField experiments made for 4 years between 1976–7 and 1979–80 in a semi-arid environment of north-west India showed that the productivity of dryland unirrigated wheat can be increased considerably by adjusting the date of sowing to conducive atmospheric temperatures. Sowing in the middle of November when daily mean temperatures ranged between 19 and 21 °C produced yields ranging between 2·6and 3·5t/ha (averaged over the 4 years) compared with 1·4–3·3 t/ha obtained from the crop sown by mid-October when the daily mean temperature ranged between 24 and 26 °C. The tall cultivar C 306, a derivative of winter x spring wheat cross, could withstand sowing at higher temperatures (mid-October) more than the spring wheats. High temperatures prevailing during the seedling stage of spring wheats shortened their vegetative growth and initiated early differentiation. Night temperatures above 13 °C coupled with day temperatures of 33–35 °C in the last fortnight of October adversely affected the tillering of spring wheats sown on 15 October and produced smaller spikes with few fertile spikelets.

A cementless system of total hip prosthesis. Experimental studies on total hip prosthesis in dogs.

It is essential that the prosthetic material should not be harmful to the human body, it should be strictly fitted to the body and it should have sufficient durability. To investigate those conditions of an artificial joints as mentioned above, it is important to have experimental studies using a model of the artificial joint in animals instead of a simulator. The authors have developed their own total hip prosthesis for a dog since 1970. These prostheses were fixed to the bone without bone cement. These dogs were killed periodically from 8 weeks to 3 years after surgery of total hip replacement. Not only were pathohistological studies on the joint capsule and bony tissue of the femur surrounding the prosthesis performed, but also scanning electron microscopic examination on capsule and the surface of the prosthetic head were performed. The results were excellent. Ther was no loosening or wear when the new type of acetabular socket with large spikes was used. On the other hand, in the case of the old type socket with its smooth surface and smaller spikes, loosening of the socket and prosthetic stem occurred within one year after surgery.

An electrophysiological study of parapodial innervation patterns in Aplysia fasciata.

ABSTRACT Studies have been made of the patterns of parapodial innervation in Aplysia fasciata and A. depilans using electrophysiological methods. Sensory fibres are chiefly found in the main parapodial nerves. The areas innervated by these nerves overlap somewhat and such overlapping extends to the branches of individual parapodial nerves. Responses to mechanical stimulation of the parapodial surface gives rise to varying sizes of spike, the smaller spikes being usually more slowly adapting, the larger being highly phasic. Although the general pattern of innervation is common to all specimens there are wide variations in detail. Electrical stimulation of parapodial nerves produces mechanical contractions which are associated with responses in some of the sensory fibres. Usually the afferent units which are stimulated in this way have sensory fields within overlapping areas supplied by the two branches. Such proprioceptive feedback responses usually declined with repetition.

The action of tetrodotoxin on the frog's isolated muscle spindle.

AbstractTetrodotoxin in concentrations of 0.8–1.0 × 10‐7 g/ml completely blocked conducted activity of the afferent nerve of isolated frog muscle spindle without affecting the receptor potential. Development of block was characterized by an increase in threshold of the nerve, a gradual delay of the onset of the impulse response and a reduction and decomposition of the individual action potentials into smaller spikes. The spike decomposition appeared to be due to a de‐synchronization of the conducted activity in the branched afferent terminals. After block by tetrodotoxin for up to 20 min the normal response could be restored by washing the preparation with Ringer's solution. The blocking action of tetrodotoxin was delayed and reduced by increasing calcium; removal of calcium had the opposite effect. Tetrodotoxin (1000 ng/ml) had no significant effect on the receptor potential. With low sodium plus tetrodotoxin the receptor potential was reduced by about 50 %; this reduction was reversed by addition of normal sodium. It is suggested that the sodium carrying system of the generator potential differs from that underlying the regenerative activity.