Spike Characteristics Research Articles

PRODUCTION AND CYTOGENETIC STUDY OF INTERGENERIC HYBRIDS BETWEEN Triticum aestivum AND Agropyron desertorum

Through embryo culture, intergeneric hybrids were produced between common wheat, Triticum aestivum cv. Chinese Spring (CS) (2n= 6x = 42, AABBDD) and crested wheatgrass, Agropyron desertorum (2n =4x =28, PPPP) for the first time. Their F_2 and BC_1 seeds have also been successfully obtained by selfing and backcrossing with wheat in F_1 hybrids. The seedlings of all F_1 hybrids tended to resemble their female parent, but they had more tillers, and their spike characteristics were between their parents. Average meiotic chromosome pairing at MI of F_1 hybrids was: 6.62Ⅰ+ 8.20RingⅡ+ 4.16RodⅡ+0.57Ⅲ+ 0.35Ⅳ+0.06Ⅴ+ 0.03Ⅵ. The successful experience of hybridization of common wheat with A. desertorum, the reason for the high level of chromosome pairing and self-fertility in the F_1 hybrids were discussed. The F_2 and BC_1 seeds obtained in F_1 hybrids are of great importance to theory and practice.

Hybridization between Triticum aestivum L. and Agropyron michnoi Roshev.

Intergeneric hybrids between Triticum aestivum cv 'Chinese Spring' (2n=6x=42, AABBDD) and Agropyron michnoi Roshev. (2n=4x=28, PPPP) were obtained by embryo culture. Their spike characteristics were similar to those of common wheat but, unlike their parents, they were long-awned. The average meiotic chromosome pairing at MI of F1 hybrids was: 6.39 I +3.75 rodII+8.64 ringII+0.81 III+0.30 IV+0.04 V, the bivalent and multivalent formation of which was much higher than expected from the genomic formulae. It is especially worthwhile to note that the F1 hybrids were self-fertile, self set being 0.15%, and seeds were easily obtained from the backcross of f1 plants with hexaploid and tetraploid wheats; here the seed set was more than 20.0%. The polyploid taxa and the position of A. Michnoi in Agropyron are discussed.

Source modelling of the rolandic focus

In rolandic epilepsy, consideration of the stereotyped ictal symptomatology suggests that the epileptic zone is likely to be in the same cortical structure in different patients. Routine EEG tracings of the interictal spike activity suggests a deep Sylvian fissure location. On the basis of the predominantly tangential potential field at the peak spike negativity seen in this group of patients, the inferior bank of the Sylvian fissure appears to be a good candidate. Without invasive studies, little refinement to this rather imprecise localization can be made as there is neither neurologic deficit nor lesion to provide a marker on radiological imaging. However, the application of source modelling technique using a simple single-dipole spherical head model has resulted in improved understanding of the generator behaviour, and facilitated the generation of new ways of analyzing spikes (e.g., stability index). Review of newer quantitative approaches including matrix and singular value decomposition of the dataset, spatial-temporal constrained source estimates etc. suggest other fruitful approaches. At least in some patients with partial epilepsy, the source characteristics of interictal scalp spikes appear to contain information of the ictal generator. Under certain circumstances, such derived information which is not otherwise available from routine electrophysiology may influence clinical management and prognosis. This is an additional bonus to the primary objectives of quantification and data reduction.

Two Types of EEG Spikes in the Kindled Rabbit Hippocampus

The characteristics of interictal EEG spikes were studied in the rabbit hippocampus. After kindling for 2-4 weeks, rabbits were anesthetized and curarized for acute experiments. There were two types of EEG spikes in the kindled hippocampus; one (B) had its source in the stimulated side, and the other (A) in the contralateral side. In addition, compound EEG spikes (C) were observed that consisted basically of B and A spikes. Intracellular counterparts of A and B spikes were generally a depolarization-hyperpolarization sequence in the CA1 pyramidal cells. On the other hand, counterparts of the C spikes were initial depolarization with a superposed spike burst followed by relatively shorter lasting hyperpolarization which seemed to indicate an enhancement of excitation during the kindling process.

Shading and Thinning Effects on Multi‐ and Standard‐Floret Winter Wheat

Grain set in a crop is related to many factors, including genotype and assimilate supply. This study was conducted to examine differences in grain set in two winter wheat (Triticum aestivum L.) cultivars differing in spike characteristics. The multiflorous cultivar Benni and the standard floret cultivar Houser were investigated in field studies at Elora and Woodstock, Ontario, Canada. In 1984, three 50% of full daylight shading treatments were imposed (PRE: a 2 wk period prior to anthesis; POST: 2 wk following anthesis; PRE + POST: 2 wk prior to anthesis plus the 1 wk following anthesis). In 1985, a postanthesis thinning treatment (THIN), in which stem number was reduced by 50%, was added. In 1984, Houser had reduced total aboveground biomass and grain yields per meters squared with the PRE and PRE + POST treatments. Grain yield reduction was associated with reduced kernel number per meters squared. For Benni in 1984, shading treatments affected neither total biomass nor grain yield. In 1985, all shading treatments reduced total biomass and grain yield for Houser, while treatments PRE and PRE + POST reduced total biomass and treatments PRE + POST and THIN reduced grain yield for Benni. Grain yield reduction for Houser was associated with reduced kernel weight for all treatments and reduced kernel and spike numbers per meters squared for treatment PRE + POST. Reduced grain yield for Benni was associated with reduced kernel numbers for treatments PRE + POST and THIN and spike numbers for treatment PRE + POST. The responses, usually manifest in a similar aboveground biomass production under different shade conditions, suggest that some internal limitation was present.

Composed Dynamic Topography for Spike and Sharp Wave

We reported two kinds of dynamic topographies. In one, an interspike interval histogram and a computerized topography of the EEG basic activity were composed. In the other, spike and sharp wave characteristics were composed of an isopotential topography. These topographies enabled us to observe serial changes in epileptic discharge dynamically by 1 msec.

Pressure spikes in elastohydrodynamics-some elastic considerations

Starting with the one-dimensional form of the Reynolds lubrication equation with a Barus fluid it is argued that the pressure spike characteristic of heavily loaded metallic contacts is closely logarithmic but not singular. Using results from rigid wedge indentation theory the implications upon the deformation and stress distribution within the contacting surfaces are examined. In particular, the surface stress concentration (principal shear stress) is examined and found to be less than the hertzian value for contacts operating in practical regions of parameter space. The influence of the familiar operating parameters g 3 and g 4 upon the spike's properties is also investigated.

Effects of Shading on Winter Wheat Yield, Spike Characteristics, and Carbohydrate Allocation1

Light intensity has variable effects on plant morphology, carbohydrate allocation, and yield. This study tested whether shading ‘Vona’ winter wheat (Triticum aestivum L.) altered allocation and spike characteristics that contribute to final grain yield under field conditions (Nunn clay loam, Aridic Argiustolls). The shaded treatment consisted of 50% ambient light reduction from 1 week before booting through the first week of grain fill (6 weeks total). Plants harvested were partitioned into stem, leaf blades by position on culm, and spike components. At maturity, spikes were divided into individual spikelets by position on the rachis. Carbon‐14‐labeled tracer was applied 24 h prior to each harvest. Shading significantly decreased spike weights for the later samplings, but had little effect on leaf or stem weights. Despite high spike sink activity and increasing spike size, when carbohydrates were limiting, photosynthate partitioning to spikes was not increased. Greater tiller mortality resulted in fewer culms per plant (and fewer spikes per plant) in shaded treatments. Shading altered spike morphology by decreasing the number and weight of kernels per spikelet and, therefore, total spikelet and spike weight; the number of grain‐bearing spikelets was unaffected. Spikelets were decreased most at the lower central portion of the spike, contrasting with other studies that found decreases in the upper half or basal portion of the spike. The combined effects of shading resulted in 32% lower yield, due mostly to lower spike density, but also to decreased kernel number and size.

Phase shift effects of the I-V characteristics of zero-field current spikes in long Josephson junctions

In this paper we analyse the length dependence of the zero-field current spikes (Z.F.S.) which appear in the I-V current voltage characteristics of long Josephson tunnel junctions. ZFS are described in terms of travelling fluxons. The presence of the bias current, losses and in particular of the boundary conditions is discussed: in the absence of magnetic fields fluxons are reflected either at the junction edges or for antifluxon collisions. The generated phase shift effects are dominant with respect to the variations of the power balance condition. Taking into account the phase shift and the limit of the Lorentz fluxon contraction, we derive an analytical approximate expression of the mean velocity in one-dimensional, intermediate length, overlap junctions. A rather good agreement is obtained comparing our theoretical analysis with several experimental ZFS I-V characteristics.

The characteristics of type IV-associated spikes at metric wavelengths

Out of 120 solar type IV events recorded at the Trieste Astronomical Observatory, we have selected 15 groups of spike bursts. We analyze their properties, concentrating on the characteristics of their polarization. We find that the polarization of the spikes varies over a wide range, but that within a particular group of spikes it remains almost constant. Sometimes groups of spikes with different degrees of polarization occur almost contemporaneously, probably indicating that more than one source is active at nearly the same time.

Variability in the characteristics of pontogeniculooccipital spikes during paradoxical sleep

An important criterion for identifying paradoxical sleep is the presence of a peculiar waveform recorded in the pons, lateral geniculate body, and visual cortex during that sleep state. These waveforms, termed PGO waves, have long been viewed as having large and constant amplitudes, an initial negative deflection in the visual cortex, and not being dependent on the levels of background illumination. Waveforms recorded during wakefulness have different characteristics, and these have been used to differentiate the waking state from paradoxical sleep. The present study demonstrated that most PGO waves have highly variable amplitudes during paradoxical sleep and that only a small fraction conform to the stereotypic wave characteristics of constant and large amplitudes and the presence of initial negative deflections. These findings argue against the criteria commonly used to differentiate PGO waves during paradoxical sleep from the eye movement potentials recorded in wakefulness.

Variation in durum wheat populations from three geographical origins. I. Material and spike characteristics

Sixteen durum wheat landraces. i.e. 6 from Algeria, 5 from Ethiopia and 5 from Italy were analysed in order to ascertain the amount of variation for all 11 spike characters. For each population the differences among spike progenies were significant for all the observed characters. Principal component analysis showed that 4 factors accounted for 80% of the total variation. Component 1 accounted for 32% of the total variation and was associated with spike width, spike density, number of kernels per spikelet and kernel weight. Component 2 accounted for 24% of the total variation and was associated with number of fertile spikelets, total number of spikelets and spike length. In a scatter diagram of all 1127 spike progenies for the first two principal components, the material from Ethiopia and Italy clustered at two opposite sides, while the material from Algeria had the largest swarm and overlapped the other two groups of material. Differences among populations from the same origin were found. The ecological and anthropological causes that may have played a role in the creation of the observed variation in the examined populations, are discussed.

Electrophysiological properties of neocortical neurons in vitro.

1. Intracellular recordings were obtained from neurons of the guinea pig sensorimotor cortical slice maintained in vitro. Under control recording conditions input resistances, time constants, and spiking characteristics of slice neurons were well within the ranges reported by other investigators for neocortical neurons in situ. However, resting potentials (mean of -75 mV) and spike amplitudes (mean of 93.5 mV) were 10-25 mV greater than has been observed in intact preparations. 2. Current-voltage relationships obtained under current clamp revealed a spectrum of membrane-rectifying properties at potentials that were subthreshold for spike generation. Ionic and pharmacologic analyses suggest that subthreshold membrane behavior is dominated by voltage-sensitive, very slowly inactivating conductances to K+ and Na+. 3. Action potentials were predominantly Na+ dependent under normal conditions but when outward K+ currents were reduced pharmacologically, it was possible, in most cells, to evoke a non-Na+-dependent, tetrodotoxin-(TTX) insensitive spike, which was followed by a prominent depolarizing after-potential. Both of these events were blocked by the Ca2+ current antagonists, Co2+ and Mn2+. 4. A small population of neurons generated intrinsic, all-or-none burst potentials when depolarized with current pulses or by synaptic activation. These cells were located at a narrow range of depths comprising layer IV and the more superficial parts of layer V. 5. Spontaneous excitatory synaptic potentials appeared in all neurons. Spontaneous inhibitory events were visible in only about 10% of the cells, and in those cases apparently reversed polarity at a level slightly positive to resting potential. Stimulation of the surface of the slice at low intensities evoked robust and usually concurrent excitatory and inhibitory synaptic potentials. Unitary inhibitory postsynaptic potentials (IPSPs) reversed at levels positive to rest. Stronger stimulation produced a labile, long-duration, hyperpolarizing IPSP with a reversal potential 15-20 mV negative to the resting level. 6. Neocortical neurons in vitro retain the basic membrane and synaptic properties ascribed to them in situ. However, the array of passive and active membrane behavior observed in the slice suggests that cortical neurons may be differentiated by specific functional properties as well as by their extensive morphological diversity.

A Hybrid Between Agropyron trachycaulum and A. desertorum1

An interspecific hybrid between Agropyron trachycaulum (2n = 28) as female and A. desertorum (2n = 28) was obtained by controlled crossing in a greenhouse, followed by embryo culture. The purposes of this study were to describe the morphology and cytology of this new hybrid. Most vegetative and spike characteristics of the hybrid were intermediate between those of the parent species. The allopolyploid A. trachycaulum, designated SSHH, regularly formed 14 bivalents at meiotic Metaphase I, and A. desertorum, designated CCCC, behaved as an autotetraploid, with an average configuration of 8.4II and 2.8IV. The hybrid, 2n = 28, represented by the formula SHCC provided a new genome combination and genetic background in which to study pairing of the three genomes. An average of 9.24I, 8.62II, 0.47III and 0.031V per cell was observed with a range of 6 to 12 bivalents (47% closed). Seven bivalents were attributed to autosyndetic pairing of A. desertorum genomes. Trivalents may have been formed from S chromosomes associated with a CC bivalent. Additional bivalents must have been formed by associations between the S and H genomes of A. trachycaulum. This indicates that these chromosomes may be sufficiently homologous (homoeologous) to enable pairing to occur in certain genetic backgrounds.

Neural basis of amplitude-spectrum representation in auditory cortex of the mustached bat.

Neural basis of amplitude-spectrum representation in auditory cortex of the mustached bat.

SOME CHARACTERISTICS OF HEXAPLOID TRITICALE SUBSTITUTION LINES INVOLVING THE A-, B-, AND D-GENOME CHROMOSOMES OF WHEAT

Three hexaploid (2n = 6x = 42) triticale lines (× Triticosecale Wittmack) were synthesized in which a specific chromosome of either the A or B genomes was replaced by a homoelogous chromosome of the D genome of wheat (Triticum aestivum L. em Thell.). Two of the substitutions involved the B genome [substitution lines 1D(1B)R-4 and 6D (6B)R-5] and the third involved the A genome [4D(4A)R-1]. Polyacrylamide gel electrophoresis of gliadin proteins produced distinct differences in banding patterns between the three substitutions and provided a definitive method for the identification of specific chromosome substitutions in triticale. Plant and spike characteristics of the substitution triticales were similar to those of the control (unsubstituted) triticale. Substitution 6D(6B)R-5 exhibited extremely low fertility and was difficult to maintain. The substitution 4D(4A), on the other hand, appeared to have no effect on fertility, while substitution 1D(1B) reduced fertility by almost one-half of that of the control triticale. Chromosome pairing in substitution 4D(4A)R-1 was regular whereas 1D(1B)R-4 exhibited an average of five univalents/cell at MI. Limited seed supply prevented a meiotic study of 6D(6B)R-5. Flour proteins of the three substitution triticales ranged from 15.8% for 4D(4A)R-1 to 18.0% for 6D(6B)R-5. A comparison of the three substitutions for amino acid composition indicated that line 6D(6B)R-5 was 25% higher in methionine than the control, while in substitution 4D(4A)R-1 methionine content was reduced by 53%.

Surface and deep EEG correlates of surgical outcome in temporal lobe epilepsy.

Interictal and ictal EEG characteristics derived from limited surface montages and medial temporal lobe sites were compared with long-term seizure relief following anterior temporal lobectomy in 52 epileptics. Patients were classified into one of four surgical outcome groups, ranging from seizure free to no clinical improvement. For each patient, interictal records were analyzed according to deep and surface spike characteristics and background activity. Ictal records were analyzed according to the proportion of episodes initiated in a unilateral or bilaterally synchronous fashion, the proportion of surface or deep onsets, the variability of onset location, and the morphology of seizures onsets. Interictal EEG variables that correlates with surgical outcome included: (a) various types of bilaterally synchronous surface/deep spikes; (b) diffuse background slowing; (c) sharp waves; and (d) the presence of multiple independent deep spike patterns in the lobe chosen for resection. Relevant ictal EEG variables included: (a) episodes initiated in a bilaterally synchronous fashion; (b) variability in seizure onset location; (c) the proportion of precisely focal onsets from deep sites; (d) the proportion of surface onsets; and (e) the proportion of onsets from the side chosen for resection. Multivariate analysis of these data with linear, stepwise, discriminate analysis and adaptive, nonlinear, distribution-free pattern recognition demonstrated that: (a) both interictal and ictal EEG characteristics can independently predict surgical outcome at levels significantly better than chance; (b) ictal and interictal EEG data contain nonredundant information for making such predictions; and (c) nonlinear pattern recognition techniques are capable of deriving the most accurate rules for predicting the effects of surgery.

Computer-aided quantification of EEG spike and sharp wave characteristics

This work presents data from detailed, computer-aided analysis of pertinent electrographic characteristics of well-defined EEG spikes and sharp waves. The data show morphological differences between spikes obtained from different subjects, spikes from different electrode montages, as well as between monophasic and biphasic spikes, and between spikes and sharp waves.

Quantitative measurements of epileptic spike morphology in the human EEG

A previously developed method of automatic recognition and quantification of interictal epileptic activity was used to measure morphological characteristics of spikes or sharp waves (SSWs). Each SSW was divided into first and second half-waves. The amplitude, duration and slope near the apex, were measured for each half-wave; values were averaged over all SSWs of one channel. Statistical comparisons determined the asymmetry of SSWs for that channel, in amplitude, duration and slope. 317 active EEG channels from 49 patients were analyzed. Patients were divided into those with unilateral and those with bilateral abnormalities. In most channels we found the expected asymmetry in amplitude (76%) and duration (70%), the second half-wave being significantly larger and longer than the first. The reverse was never found (remaining cases showed no significant asymmetry). Slope asymmetry was found in 30% of channels, the second slope being most frequently the steepest. This unexpected finding was confirmed by careful visual examination. The usual concept that spikes have a steeper first half-wave probably originates in the frequent asymmetry in duration and amplitude, but was not confirmed for the slope. A few differences were found in the distribution of asymmetries between patients with unilateral and patients with bilateral abnormalities.

Intermediate Wheatgrasses of Iran1

Geographic distribution, morphology, cytology, and fertility were studied in 247 collections of the intermediate wheatgrass complex (Agropyron intermedium (Host) Beauv., A. trichophorum (Link) Richt., and A. pulcherrimum Grossh.) collected in Iran and grown at Logan, Utah. This group of grasses is the most widespread Agropyron complex in Iran, occurring at altitudes of 500 to 2,700 m in the Alborz and Zagros mountain ranges and in semiarid plateau regions north of 30° N Lat. A 2,735‐plant population was extremely diverse in vegetative and spike characteristics. Plant breeders will find ample variation in these collections for significant improvement in forage and seed production. Of 234 plants, 93% had a chromosome number of 2n=42, and the remainder were 2n=41, 43, 45, and 52. Chromosome pairing at metaphase I averaged 0.60I, 20.19II, 0.05III, 0.20IV, 0.002V, and 0.008VI per cell in 1,926 cells. Pairing was in harmony with the hypothesis that intermediate wheat grasses are segmental autoallohexaploids. Open‐pollination fertility of 247 plants ranged from 0.0 to 72.8 seeds per spike and averaged 35.5. Self‐fertility of the same plants ranged from 0.0 to 44.4 seeds per spike and averaged 5.7. Occasional plants were highly self‐fertile, a condition previously unknown in these grasses. The spike characteristics that separate A. intermedium, A. trichophorum, and A. pulcherrimum taxonomically, i.e., pubescent vs. glabrous lemmas and awns vs. awnlessness, segregated in the population as if they were simply inherited traits. The three taxa cannot be separated on the basis of geographic distribution, ecological adaptation, cytological characteristics, or reproductive behavior. Consequently, all should be treated as a single species, A. intermedium.