The photosynthetic response to a shift in the chlorophyll a to chlorophyll B ratio of chlorella

The chlorophyll a:b ratio was shifted in Chlorella vannielii by varying the illuminance under which the cells were cultured—the ratio increased from 2.9, 3.0, 4.0, and 4.8 to 6.2, respectively, at 100, 300, 900, 2,700 and 6,000 foot candles. The 6,000-foot candle cells retained an optimal growth rate at the chlorophyll a:b ratio of 6.2 which was the upper limit of normal growth. Comparisons were made between the 300-and 6,000-foot candle cultures to determine the significance to the photosynthetic mechanism of a shift in the chlorophyll a:b ratio.     

CIRCUS MOVEMENTS OF LIMULUS AND THE TROPISM THEORY

1. Under laboratory conditions Limulus from 20 to 60 mm. in diameter are positively phototropic, and execute circus movements towards the normal side, when the median and the opposite lateral eyes are removed or covered. 2. The phototropism of Limulus may be modified or obliterated by (a) fright, (b) hunger, (c) stereotropism, (d) photokinesis, and (e) unknown stimuli. 3. Quantitative measurements of the paths of animals doing circus movements demonstrate that the amount of turning varies directly with the light intensity as follows: for 8,000 candle meters the degrees turned per centimeter were 6.73; for 2,000 candle meters, 5.23; and for 900 candle meters, 4.78. In other words, the diameter of the circle varies inversely with the light intensity. 4. The rate of locomotion per minute also varies directly with the light intensity, being 178 cm. for 8,000 candle meters, 167 for 2,000, and 157 for 900. 5. These reactions are satisfactorily explained by the tropism theory.     

Variations in electroencephalographic alpha activity under conditions of differential lighting and auditory feedback

The electroencephalographic alpha activity of 13 college students was monitored under conditions of darkness or dim light for six sessions, and for a seventh under the opposite condition. Auditory feedback was given for the presence of alpha activity during a 5-min orientation period, and then during ten 2-min trial periods. The results indicated that: (1) alpha production in the presence of feedback did not exceed initial eyes-closed base line production; (2) introducing feedback immediately enhances alpha activity, rather than increasing production gradually; (3) under certain circumstances, dim light is sufficient to suppress alpha; and (4) after many sessions of alpha production in darkness, subjects maintain a given amount of alpha even when visual stimulation is present.     

Interaction of air ions and bactericidal vapours to control micro-organisms

AIMS: The aim of this study was to investigate the antibacterial activity of candles containing specific-antibacterial compounds, such as essential oils and their constituent compounds. The importance of the ionization products from the flame and the aerial concentration of the volatile compounds were investigated. METHODS AND RESULTS: Agar plates inoculated with Escherichia coli (DH5alpha) or Staphylococcus aureus (NCTC strain number 8532) were exposed in a large air-tight chamber to candle flames combined with the volatile bactericidal compounds beta-pinene and orange oil. A steady decline in E. coli numbers was observed over time because of the effect of a candle flame. This was significantly increased by the addition of volatile oils. The number of S. aureus colonies was not reduced by a plain candle, but significant reductions were caused following exposure to beta-pinene and orange oil candles. As aerial concentration of the volatiles was increased the viability of E. coli and S. aureus declined. Ionization products from the flame made a significant contribution to the observed effects, as intercepting the ions on a grounded grid over the agar plates allowed at least 20% more cells to survive. CONCLUSIONS: This study demonstrates the antibacterial properties of ionization products from a candle flame, and that this effect can be significantly increased by the addition of specific-antibacterial compounds, such as orange oil and beta-pinene. The role of both the ionization products from the candle flame and the concentration of volatile compounds released are important to the effect. SIGNIFICANCE AND IMPACT OF THE STUDY: The technique described here offers a new and novel technique for reducing the concentration of bacteria on surfaces.     

Does EEG activity during painful stimulation mirror more closely the noxious stimulus intensity or the subjective pain sensation?

Abstract

Background: Many researchers have tried to investigate pain by studying brain responses. One method used to investigate pain-related brain responses is continuous electroencephalography (EEG). The objective of the current study is to add on to our understanding of EEG responses during pain, by differentiation between EEG patterns indicative of (i) the noxious stimulus intensity and (ii) the subjective pain sensation.

Methods: EEG was recorded during the administration of tonic experimental pain, consisting of six minutes of contact heat applied to the leg via a thermode. Two stimuli above pain threshold, one at pain threshold and two non-painful stimuli were administered. Thirty-six healthy participants provided a subjective pain rating during thermal stimulation. Relative EEG power was calculated for the frequency bands alpha1, alpha2, beta1, beta2, delta, and theta.

Results: Whereas EEG activity could not be predicted by stimulus intensity (except in one frequency band), subjective pain sensation could significantly predict differences in EEG activity in several frequency bands. An increase in the subjective pain sensation was associated with a decrease in alpha2, beta1, beta2 as well as in theta activity across the midline electrodes.

Conclusion: The subjective experience of pain seems to capture unique variance in EEG activity above and beyond what is captured by noxious stimulus intensity.     

光照对棕色田鼠和昆明小鼠活动性的影响

光照对啮齿动物的行为格局和活动节律有着重要的影响。本研究以比较生物学方法,以光照强度和鼠种两个因素,在实验室内利用动物行为监视系统,以焦点动物取样法( Focus animal sampling) ,在＜ 20 Lux、200 Lux、800 Lux 和1 600 Lux 等4 个水平的光照强度下,监测和记录棕色田鼠和昆明小鼠的移动和静止行为,并在实验结束时测定实验动物的体重; 在800 Lux 光照强度下,设置正常( 12L∶ 12D) 和全黑( 0L∶ 24D) 两种光照时间,连续12 h监测并记录实验动物的行为。采用双因素方差分析方法对数据进行统计分析。结果表明:1) 光强与鼠种对静止行为存在显著交互作用,棕色田鼠的静止行为与光强间存在显著的负相关关系,而昆明小鼠的静止行为则与光强无显著的相关; 2) 光强对两种动物移动行为的影响与静止行为表现方式相反; 3) 在12 h的光暴露条件下,棕色田鼠的相对活动显著强于昆明小鼠; 4) 光强对两种动物体重的影响不同,棕色田鼠体重与光强呈正相关关系,昆明小鼠与光强呈负相关关系,但差异不显著。本研究进一步验证了地面鼠与地下鼠对光强适应的差别。     

The effect of light intensity on hydrogen production by sulfur-deprived Chlamydomonas reinhardtii

The effect of light intensity on hydrogen production by sulfur-deprived Chlamydomonas reinhardtii was studied in situ using either long- or short-term experiments, or alternatively, with samples withdrawn from the photobioreactor. Overall hydrogen production by S-deprived culture was shown to depend on the light intensity and to exhibit regions of light limitation and light inhibition. The optimal incident light intensity for hydrogen production was independent of the method of sulfur deprivation or the initial acetate concentration in the medium (12-34 mM). However, it varied with the Chl concentration and the thickness of the photobioreactor. To calculate the average light intensity in the photobioreactor under different experimental conditions, a special mathematics approach was developed. The optimal average light intensity for H(2) production appeared to be 30-40 microE m(-2)s(-1) and was independent of the Chl or acetate concentrations and the method of S deprivation. The inhibitory effect of high light intensity was related to the enhanced O(2) evolution activity during the photosynthetic stage of sulfur deprivation and to the high activity of photosystem II at the beginning of the H(2)-production phase. Data support the major role of photosystem II in supplying reductants through photosystem I to the hydrogenase throughout the H(2)-production phase.     

Attention and regulation of EEG alpha-attenuation responses

Two experiments with 16 normal adults of both sexes tested the hypothesis that inattention to a biofeedback display is associated with increased variability of those physiological processes that had been regulated by the biofeedback. Each experiment was a repeated-measures-on-independent-subjects-design. Dependent variables were the time durations and the mean rms power of two mutually exclusive segments of the parietal-occipital EEG: alpha and not-alpha segments. Independent variables were combination of counting tasks and instructions to look at, listen to, and count visual and auditory flashes and clicks. The durations of alpha and not-alpha segments were controlled or regulated by means of an alpha-contingent visual feedback stimulus, Attention to the feedback stimulus was challenged by instructions to count other, noncontingent stimuli. Control of alpha and not-alpha segments was least for conditions of (1) “sham” feedback, and (2) feedback with instructions to count noncontingent auditory clicks, which were presented 3/sec while the feedback visual stimuli were occurring. A new EEG test of attention and distraction was suggested.     

Tobias Mayer--experiments on visual acuity (1755)

The pioneering experimental work of Tobias Mayer (1723-1762) on visual acuity, published in 1755 in Latin, is presented in English translation. Mayer distinguished between two kinds of visual acuity, the one (30 arc sec) for single objects seen against a uniform background, the other (1 arc min) for more complex objects such as gratings, grids, or checkerboards. Strong illumination did not improve visual acuity. For targets seen in the light of a candle, the visual angle needed for resolution was inversely proportional to the cube root of the distance of the candle and therefore to the sixth root of 'brightness'. The historical significance of Mayer's work on visual acuity is briefly outlined.     

Behavioural studies on the lesser sandeel Ammodytes marinus (Raitt) II. The effect of light intensity on activity

The behaviour of the lesser sandeel, Ammodytes marinus (Raitt), has been investigated at light intensities of 1, 10, 100 and 1000 lux, using a photographic method of recording activity. The level of swimming activity was high at 1000 and 100 lux, declining to a very low level at 1 lux. It was concluded that this was due to the limiting effect of light on feeding. The threshold light intensity for swimming activity in the tank was estimated as being approximately 20 lux but it was considered that in the area of the sandeel fishing grounds the threshold might be higher than this, in the region of 100 lux. The number of hours light per day above 20 and 100 lux at a depth of 15 m in the area of the Outer Dowsing sandbank (53°30'N, 01°00'E) was estimated for the various months of the year. It was shown that during the winter the light intensity does not normally reach 100 lux and only exceeds 20 lux for a few hours each day. It is suggested that this could limit swimming activity and accessibility at this time of year. Measurements were made of the penetration of light into sand and it was concluded that fish which are buried might be able to detect light, possibly via the pineal gland.     

Auditory and visual prepulse inhibition in mice: parametric analysis and strain comparisons

Prepulse inhibition (PPI) is a multimodal phenomenon where the prepulse and the startling stimulus can be presented in either the same or the different sensory modalities. The aim of the present study was to characterize intramodal and cross-modal PPI in mice. We first examined the effects of varying prepulse intensity and prepulse duration on auditory and visual PPI in three inbred mouse strains C57BL/6J, 129S2 and BALB/cByJ mice. Increasing the intensity (5-15 dB above the background) and the duration (1-25 milliseconds) of the acoustic prepulse increased auditory PPI, and maximum level of inhibition was reached with each prepulse intensity at specific prepulse duration (between 5 and 15 milliseconds). Varying the intensity (30-300 lux) and the duration (1-25 milliseconds) of the light flashes had similar impact on visual PPI level (optimal durations between 1 and 10 milliseconds). There were also marked strain differences in PPI performances, with 129S2 and BALB/cByJ mice displaying the highest and the lowest scores of auditory PPI, respectively. In contrast, opposite strain ranking was obtained for visual PPI. The temporal expression of PPI was then studied in the same mouse strains using a wide range of interstimulus intervals (2-2000 milliseconds between the prepulse offset and the pulse onset). The time-course of the auditory and the visual PPI were relatively comparable (bell-shaped curve) with optimal lead-times between 10 and 100 milliseconds, but the shape of the temporal function varied between the mouse strains depending on the prepulse modality. These findings demonstrate that PPI has many physiological and genetic determinants that vary greatly across temporal and intensity domain, as well as stimulus modality.     

A disjunctive analysis of neonatal approach stimulus prepotence

Preliminary results of a disjunctive procedure developed to ascertain the relative attractiveness for domestic chicks of auditory and visual stimuli are promising. A detailed account of the procedure and initial results is presented. Seventy-two Canadian Athens random bred chicks were tested at 24 or 36 h posthatch. A repetitive tone (4 per sec, 50 msec duration, 500 Hz) served as the auditory stimulus, and a flickering light (3.5 flashes per sec, 0.8 foot candle) served as the visual stimulus. An age-dependent change in the attractiveness of auditory and visual stimuli obtained with the disjunctive procedure. No change in stimulus preference obtained when the stimuli were presented individually.     

Spatial firing patterns of auditory neuron network modelling by computer simulation

This communication examines, in digital computer simulated network, input signals and response patterns established at excitatory neurons' level i.e. the membrane potential of neuron soma. It is restricted to spatial patterns of the auditory neuron networks and time factor for nervous conduction and transmission is neglected compared with long maintained membrane potentials of neuron somas. The model analyzes the change in the spatial patterns of the membrane potential in the two dimensional networks of the auditory system. In order to evaluate the contribution of the various parameters, it is started that the simplest model has only one parameter, lateral inhibition. The other parameters are then added, one at a time, to successive models. The lateral inhibition is a necessary condition in the auditory nervous system if any sharpening of the response areas in the single neurons is to occur. A necessary condition for the validity of the model is that it should be applicable to the other senses such as vision and chemical patterns, taste. The threshold feature of auditory neurons aids in producing a sharpening in the neuron of the auditory relay nuclei. It does this clipping the spatial response patterns in one dimensional arrays of excitatory neurons. Recurrent inhibition seems a necessary condition in the sensory nervous system that any kinds of input signals are to be preserved over a wide range of stimulus intensity. In other words, this network has a wide dynamic range against any kinds of input signals. A simple self-recurrent negative feedback does not contribute to the sharpening, but more complex socalled averaged type does. A neuron network is capable of responding stably to stimuli with a wide range of intensity and with any kind of spatial patterns if there is a simple negative feedback mechanism. When there is no negative feedback, input signals soon disappear or saturate in the neuron network. Therefore, recurrent inhibition is the most important mechanism. Spontaneous activity appears to aid in the sharpening by providing a kind of contrast, that is by reducting the amount of activity in neurons adjacent to the excitatory area. Moreover, the effect of spontaneous activity in the model seems to make repples around the excitatory area and suggests that an introduction of activity at any stage of the networks, from whatever source for example reticulum formation and thalamus, might appreciably alter the response patterns at subsequent neuron network. This suggests that the mechanism of the consciousness that might be controlled by the thalamus and or reticular formation. These two dimensional neuron networks may be expanded to three dimensional neuron networks. The former might simulate the auditory nervous system while the latter might simulate the visual system.     

rTMS Induced Tinnitus Relief Is Related to an Increase in Auditory Cortical Alpha Activity

Chronic tinnitus, the continuous perception of a phantom sound, is a highly prevalent audiological symptom. A promising approach for the treatment of tinnitus is repetitive transcranial magnetic stimulation (rTMS) as this directly affects tinnitus-related brain activity. Several studies indeed show tinnitus relief after rTMS, however effects are moderate and vary strongly across patients. This may be due to a lack of knowledge regarding how rTMS affects oscillatory activity in tinnitus sufferers and which modulations are associated with tinnitus relief. In the present study we examined the effects of five different stimulation protocols (including sham) by measuring tinnitus loudness and tinnitus-related brain activity with Magnetoencephalography before and after rTMS. Changes in oscillatory activity were analysed for the stimulated auditory cortex as well as for the entire brain regarding certain frequency bands of interest (delta, theta, alpha, gamma). In line with the literature the effects of rTMS on tinnitus loudness varied strongly across patients. This variability was also reflected in the rTMS effects on oscillatory activity. Importantly, strong reductions in tinnitus loudness were associated with increases in alpha power in the stimulated auditory cortex, while an unspecific decrease in gamma and alpha power, particularly in left frontal regions, was linked to an increase in tinnitus loudness. The identification of alpha power increase as main correlate for tinnitus reduction sheds further light on the pathophysiology of tinnitus. This will hopefully stimulate the development of more effective therapy approaches.     

Light and Nitrate Requirements for Induction of Nitrate Reductase Activity in Hordeum vulgare

The importance of light to the induction of nitrate reductase activity in barley (Hordeum vulgare L.) was studied. Activity in etiolated leaves in darkness stayed at a low endogenous level even while large amounts of nitrate were actively accumulated. Light was required for any increase in activity, though the requirement may be satisfied to a limited extent before nitrate is available. Nitrate reductase activity was induced in the dark in green leaves which had not previously had nitrate but were supplied nitrate at the beginning of the dark period. If the nitrate then made available was sufficient, nitrate reductase activity increased until the effect of the previous light treatment was exhausted. Activity then decreased even though nitrate uptake continued. Upon returning the leaves to light, enzymatic activity increased again, as expected. Nitrate uptake was eliminated as an experimental variable by giving dark-grown plants nitrate, then detaching the leaves for induction studies. Under these conditions light saturation occurred between 3600 and 7700 lux at exemplary periods of illumination. At intensities of 3600 lux and above, activity increased sharply after a 6-hour lag period. As light intensity was decreased below 3600 lux the lag period became longer. Thus, when sufficient nitrate was available, the extent of induction of nitrate reductase activity was regulated by light.     

Extended exposure to continuous low intensity light abolishes the photosensitivity of retinal dopamine neurons

Male Sprague-Dawley rats were divided into 2 groups. One group (experimental) was housed for 6 months in continuous low intensity light while the other (control) was exposed to standard 14 hr light: 10 hr dark cyclic lighting conditions for the entire time. For both the control and experimental groups the light intensity was 350-700 Lux. After 6 months, the experimental rats were returned to cyclic lighting. At one week and again at 2 months the light aversion behavior of all rats was tested in a light/dark test box. The experimental rats chose the dark side of the box only 58% of the time while control animals preferred the dark 79% of the time. Since rats normally are nocturnal and avoid light, these results suggest that the experimental rats may have permanently lost a functionally significant portion of the ability to detect light. After the second behavioral test all rats were dark adapted and 15 hr later the effect of short term (30 or 60 min) exposure to light on DA turnover in one retina from each rat was assessed. The other retina from each rat was fixed and examined histologically. Light significantly enhanced the alpha methyl-p-tyrosine induced decline of DA in the retinas of the control rats but exerted no similar effect in the experimental animals. The retinal DA contents of the experimental rats were substantially depleted. Histological examination suggested that the outer nuclear layers of the experimental retinas were more severely damaged than those from rats exposed to continuous light for 4 months but still contained a few pycnotic photoreceptor nuclei and nearly normal looking inner neural layers. These results indicate that extended exposure to light eventually abolishes light aversion behavior and at this time there is also a loss of the photosensitivity of the dopaminergic amacrine neurons.     

A rapid form of activity-dependent recovery from short-term synaptic depression in the intensity pathway of the auditory brainstem

Short-term synaptic plasticity acts as a time- and firing rate-dependent filter that mediates the transmission of information across synapses. In the avian auditory brainstem, specific forms of plasticity are expressed at different terminals of the same auditory nerve fibers and contribute to the divergence of acoustic timing and intensity information. To identify key differences in the plasticity properties, we made patch-clamp recordings from neurons in the cochlear nucleus responsible for intensity coding, nucleus angularis, and measured the time course of the recovery of excitatory postsynaptic currents following short-term synaptic depression. These synaptic responses showed a very rapid recovery, following a bi-exponential time course with a fast time constant of ~40 ms and a dependence on the presynaptic activity levels, resulting in a crossing over of the recovery trajectories following high-rate versus low-rate stimulation trains. We also show that the recorded recovery in the intensity pathway differs from similar recordings in the timing pathway, specifically the cochlear nucleus magnocellularis, in two ways: (1) a fast recovery that was not due to recovery from postsynaptic receptor desensitization and (2) a recovery trajectory that was characterized by a non-monotonic bump that may be due in part to facilitation mechanisms more prevalent in the intensity pathway. We tested whether a previously proposed model of synaptic transmission based on vesicle depletion and sequential steps of vesicle replenishment could account for the recovery responses, and found it was insufficient, suggesting an activity-dependent feedback mechanism is present. We propose that the rapid recovery following depression allows improved coding of natural auditory signals that often consist of sound bursts separated by short gaps.     

Rapid change in articulatory lip movement induced by preceding auditory feedback during production of bilabial plosives

Background

There has been plentiful evidence of kinesthetically induced rapid compensation for unanticipated perturbation in speech articulatory movements. However, the role of auditory information in stabilizing articulation has been little studied except for the control of voice fundamental frequency, voice amplitude and vowel formant frequencies. Although the influence of auditory information on the articulatory control process is evident in unintended speech errors caused by delayed auditory feedback, the direct and immediate effect of auditory alteration on the movements of articulators has not been clarified.

Methodology/Principal Findings

This work examined whether temporal changes in the auditory feedback of bilabial plosives immediately affects the subsequent lip movement. We conducted experiments with an auditory feedback alteration system that enabled us to replace or block speech sounds in real time. Participants were asked to produce the syllable /pa/ repeatedly at a constant rate. During the repetition, normal auditory feedback was interrupted, and one of three pre-recorded syllables /pa/, /Φa/, or /pi/, spoken by the same participant, was presented once at a different timing from the anticipated production onset, while no feedback was presented for subsequent repetitions. Comparisons of the labial distance trajectories under altered and normal feedback conditions indicated that the movement quickened during the short period immediately after the alteration onset, when /pa/ was presented 50 ms before the expected timing. Such change was not significant under other feedback conditions we tested.

Conclusions/Significance

The earlier articulation rapidly induced by the progressive auditory input suggests that a compensatory mechanism helps to maintain a constant speech rate by detecting errors between the internally predicted and actually provided auditory information associated with self movement. The timing- and context-dependent effects of feedback alteration suggest that the sensory error detection works in a temporally asymmetric window where acoustic features of the syllable to be produced may be coded.     

Behavioral and hormonal correlates of social dominance in stable and disrupted groups of male domestic fowl

An experiment was conducted to determine the behavioral and hormonal correlates of social dominance in stable and disrupted groups of male domestic fowl (Gallus domesticus). In addition, the relative importance of visual and auditory cues in the maintenance of dominance status in this species was assessed. Alpha roosters were removed from their six-bird home pens for 1 week, and placed in either (1) and adjacent pen in visual contact with penmates, (2) and adjacent pen where visual, but not auditory, contact was prevented, or (3) a different building where they were in visual and auditory isolation. Dominance rank, aggressive activity, and crowing frequency were intercorrelated during the premove period. There was a significant increase in both aggression and crowing among the males remaining in the home pen following removal of the alpha male, except in the treatment in which males were still in visual contact with the removed alpha, in which only aggression increased. Increases in crowing frequency were also noted in alpha males. High levels of aggression occurred when alpha males were returned except in those pens in which visual contact had been maintained. Visual cues thus appear to be more important than auditory cues alone with respect to the maintenance of dominant social status in roosters. There were no clear correlations between behavioral variables and plasma androgen or corticosterone levels in either the stable or disrupted flocks, and no consistent changes in the levels of these hormones as a result of experimental manipulation; several possible explanations for this finding are discussed.     

Effect of larval ontogeny, turbulence and light on prey attack rate and swimming activity in herring larvae

The effects of ontogeny (larval size), light and turbulence on the attack rate and swimming activity (proportion of time swimming and duration of swimming bout) of herring larvae (15-28 mm TL) have been investigated. Emphasis was put on the experimental design in order to create a set-up where the turbulence intensity distribution could be accurately measured as well as controlled in the entire experimental tank.Both larval size (ontogeny) and light had a significant positive effect on prey attack rate. Likewise, an intermediate increase in turbulence had a positive effect on prey attack rate, but this effect was dependent of light intensity and larval size.At low light (1.5 μE m² s⁻¹) intermediate turbulence increased the prey attack rate significantly for larger larvae (26 and 28 mm), while at high light (18 μE m² s⁻¹) intermediate turbulence had only a significant positive effect on the attack rate of smaller larvae 20 and 23 mm.In general, our data show a dome-shaped response of turbulence on attack rate and a U-shaped response of turbulence on swimming activity.For herring larvae >20 mm, the maximum (attack rate) and minimum (swimming activity) response of turbulence were found at intermediate turbulence intensities (energy dissipation rates between 7∗10⁻⁸ and 1∗10⁻⁶ W/kg). The highest turbulence level tested (8∗10⁻⁶ W/kg) showed only negative effects, as attack rates where at the lowest and swimming activity at the highest.Swimming activity increased with larval size or light, and decreased at intermediate turbulence. Compared to turbulent intensities under natural conditions this implies that larger herring larvae at 10 m depth have to be exposed to wind speeds of more than 17 m/s before negative effects on attack rate and swimming activity occurs.