The prevalence of tactile motion aftereffects

The present study examined the prevalence of motion aftereffects (MAEs) in the sense of touch. The effects of two types of apparatuses were tested: a ridged, spinning cylinder and an array of vibrating tactors from the Optacon, a reading aid for the blind. In the first phase of the study, 50 subjects were tested for a total of 200 trials on both stimulators. Approximately one-third of the trials with both stimulators produced reports of MAEs in either the negative (expected) direction or the positive direction relative to the adapting stimulus. With the cylinder stimulator, there were significantly more reports of positive MAEs than negative MAEs. Subjects who reported MAEs in the first phase of the experiment were tested again in the second phase of the experiment. This additional testing produced results similar to those obtained in the first phase and did not produce a substantial increase in the number of reports of MAEs. It appears that tactile MAEs are not as readily generated as visual MAEs.     

Volume-timing relationships during cough and resistive loading in the cat.

The relationship between pulmonary volume-related feedback and inspiratory (CTI) and expiratory (CTE) phase durations during cough was determined. Cough was produced in anesthetized cats by mechanical stimulation of the intrathoracic tracheal lumen. During eupnea, the animals were exposed to single-breath inspiratory and expiratory resistive loads. Cough was associated with large increases in inspiratory volume (VI) and expiratory volume (VE) but no change in phase durations compared with eupnea. There was no relationship between VI and CTI during coughing. A linear relationship with a negative slope existed between VI and eupneic inspiratory time during control and inspiratory resistive loading trials. There was no relationship between VE and CTE during all coughs. However, when the first cough in a series or a single cough was analyzed, the VE/CTE relationship had a positive slope. A linear relationship with a negative slope existed between VE and eupneic expiratory time during control and expiratory resistive loading trials. These results support separate ventilatory pattern regulation during cough that does not include modulation of phase durations by pulmonary volume-related feedback.     

Can caprine arthritis encephalitis virus (CAEV) be transmitted by in vitro fertilization with experimentally infected sperm?

For each of the five fertilization trials of the experiment, frozen semen was prepared for in vitro capacitation at a concentration of 1 × 10⁷ spz/ml and divided into three groups. One group was used as a control, while the two others were inoculated with 100 μl/ml of either culture medium from non-infected cells (placebo group) or cell culture medium containing virus at a concentration of 10⁵ TCID₅₀/ml (infected group). A total of 789 oocytes were used for IVF. For each of the five trials a group of oocytes were used as a non-infected control and were found to be caprine arthritis-encephalitis virus (CAEV) free. The other oocytes were divided in two equal batches. Oocytes in the first batch were in vitro fertilized with CAEV infected sperm (infected group) and the second batch were fertilized with CAEV non-infected sperm (placebo and control groups). After IVF, the zygotes of each group were washed 12 times. The CAEV genome was not detected (using RT-PCR) in the washing media of either the control or placebo groups from each trial. In contrast, the first three washing media from the infected group were consistently found to be positive for the CAEV genome (5/5), whereas subsequent washing media were CAEV-free (P < 0.05). Zygotes obtained using all semen groups tested negative for both the provirus and genome of CAEV. These results clearly show that the first four washes were sufficient to remove viral particles from CAEV infected fertilization media and that CAEV-free embryos can be produced by IVF using spermatozoa infected in vitro by CAEV.     

Positive and negative inotropic effects of muscarinic receptor stimulation in mouse left atria

In isolated mouse left atria, acetylcholine (ACh) produced a biphasic inotropic response; a transient decrease in developed tension was followed by an increase. Both negative and positive responses were concentration dependent and were inhibited by atropine. The negative and positive inotropic responses were also observed with a nonselective muscarinic stimulant, oxotremorine-M, but not with an M1-receptor selective stimulant, McN-A343. Pirenzepine, an M1-receptor antagonist, inhibited both negative and positive inotropic responses at high concentrations. Gallamine, an M2-receptor antagonist, inhibited the negative response. Hexahydro-siladifenidol hydrochloride, p-fluoro analog (p-F-HHSiD), an M3-receptor antagonist, inhibited the positive response with no effect on the negative phase. In pertussis toxin (PTX) treated preparations, negative inotropic response to ACh was not observed. These results suggest that the negative and positive inotropic responses to acetylcholine in mouse atria are mediated by M2 and M3 receptors, respectively. The negative phase, but not the positive phase, was mediated by a PTX-sensitive G protein.     

Is vasohibin-1 for more than angiogenesis inhibition?

Angiogenesis, a formation of neo-vessels from pre-existing ones, is regulated by the local balance between its stimulators and inhibitors. Vasohibin-1 (VASH1) was originally identified as an endothelium-derived vascular endothelial growth factor (VEGF)-inducible angiogenesis inhibitor that acts in a negative feedback manner. The expression of VASH1 has been shown in endothelial cells (ECs) in both physiological and pathological conditions associated with angiogenesis. However, recent reports indicate that VASH1 is expressed not only in ECs but also in other cell types including haematopoietic cells. The function of VASH1 may not be restricted to angiogenesis inhibition.     

Theoretical study of transmembrane and extracellular potentials under propagation block due to geometrical inhomogeneity

A mathematical model was used to study transmembrane and extracellular potentials produced by active geometrically inhomogeneous excitable structures under conditions of propagation block. The structures were electrical analogues of intact or damaged unmyelinated nerve fibres, of the soma to axon transition, or of branching axons or dendrites. It was shown that: (1) damage to a cell is equivalent to the presence of a geometrical inhomogeneity, namely of a region of increased diameter; (2) propagation block caused by a geometrical inhomogeneity, results in; (a) a sharp decrease in the calculated transmembrane potential amplitude not only for the blocked region but also before it; (b) a considerable increase in the amplitude of both the negative phase of extracellular potentials at the points of the volume conductor preceding the blocked region and the first positive phase at points in the proximity of the region; (c) a more pronounced increase in the first positive phase amplitude at small radial distances, if the geometrical inhomogeneity is short compared with the length constant (gamma); (3) the membrane damage results in recording of potentials resembling "giant" ones.     

Analysis of the role of xenogeneic antigens in the proliferation of human T cells stimulated with autologous non-T cells and phytohemagglutinin-activated T cells

Since conflicting results have been reported about the role of xenoantigens in the proliferation of T cells stimulated with autologous non-T cells, the effect of the exposure of cells to xenogeneic proteins during the isolation procedure and/or the culture period on autologous mixed lymphocyte reactions (AMLR) with non-T cells and phytohemagglutinin-activated T cells as stimulators was investigated. T and non-T cells were isolated by rosetting with 2-aminoethylisothiuronium bromide-treated sheep red blood cells (AET-SRBC), by nylon-wool nitration, and by positive or negative selection with anti-class II HLA antigens and anti-T-cell monoclonal antibodies. Isolation and cultures were performed in presence of fetal calf serum (FCS) or of autologous serum. In both types of AMLR, proliferation of responding cells did not require exposure to xenoantigens. However xenoantigens enhanced the proliferation of cells from some, although not all, the donors tested. There were differences in the degree of proliferation of the cells from the donors tested, but without correlation with the two types of AMLR. These results suggest that both types of AMLR reflect a self-recognition event and not a response to xenoantigens. However the potential interference of xenoantigens, as well as the individual variability, should be taken into account when interpreting the significance of abnormalities of AMLR in immunopathologic processes.     

Massed and spaced stimulus sequences in dimensional discrimination

In two experiments, pigeons' responding to a visual flicker-rate continuum was established by a maintained generalization procedure. For both experiments, variable-interval reinforcement was available for responses during stimuli from one half of the stimulus continuum while responses during other stimuli were extinguished. The first experiment compared gradients of dimensional stimulus control produced by randomly presented positive and negative stimuli with gradients produced by massed positive and negative stimuli. The second experiment alternated the order of massed stimulus sequences. In both cases, massing of stimulus sequences diminished positive dimensional contrast effects, without seriously disturbing discrimination between positive and negative stimuli. The results indicate that stimulus sequences can have an important role in the production of dimensional contrast effects.     

Insectivorous birds can see and smell systemically herbivore‐induced pines

Several studies have shown that insectivorous birds are attracted to herbivore‐damaged trees even when they cannot see or smell the actual herbivores or their feces. However, it often remained an open question whether birds are attracted by herbivore‐induced changes in leaf odor or in leaf light reflectance or by both types of changes. Our study addressed this question by investigating the response of great tits (Parus major) and blue tits (Cyanistes caeruleus) to Scots pine (Pinus sylvestris) damaged by pine sawfly larvae (Diprion pini). We released the birds individually to a study booth, where they were simultaneously offered a systemically herbivore‐induced and a noninfested control pine branch. In the first experiment, the birds could see the branches, but could not smell them, because each branch was kept inside a transparent, airtight cylinder. In the second experiment, the birds could smell the branches, but could not see them, because each branch was placed inside a nontransparent cylinder with a mesh lid. The results show that the birds were more attracted to the herbivore‐induced branch in both experiments. Hence, either type of the tested cues, the herbivore‐induced visual plant cue alone as well as the olfactory cues per se, is attractive to the birds.     

Synthetic heat at mild temperatures

"Synthetic heat", also known as the heat grill illusion, occurs when contact with spatially adjacent warm and cold stimuli produce a sensation of "heat". This phenomenon has been explained as a painful perception that occurs when warm stimulation inhibits cold-sensitive neurons in the spinothalamic tract (STT), which in turn unmasks activity in the pain pathway caused by stimulation of C-polymodal nociceptors (CPNs). The "unmasking model" was tested in experiment 1 by combining warm (35-40 degrees C) and cool (> or = 27 degrees C) stimuli that were too mild to stimulate CPNs. After discovering that these temperatures produced nonpainful heat, experiment 2 was designed to determine whether heat could be induced when near-threshold cooling was paired with mild warmth, and whether lowering the base temperature for cooling would increase the noxious (burning, stinging) components of heat for fixed cooling steps of 1-3 degrees C. Cooling by just 1 degrees C from a base temperature of 33 degrees C led to reports of heat on more than 1/3 of trials, and cooling by just 3 degrees C evoked heat on 75% of trials. Lowering the base temperature to 31 or 29 degrees C increased reports of heat and burning but did not produce significant reports of pain. Perception of nonpainful heat at such mild temperatures indicates either that cold-sensitive nociceptors with thresholds very similar to cold fibers innervate hairy skin in humans, or that heat can result from integration of warm fiber and cold fiber activity, perhaps via convergence on nonspecific (e.g., WDR) neurons in the STT.     

Acute Behavioral Responses to Light and Darkness in Nocturnal Mus musculus and Diurnal Arvicanthis niloticus

The term masking refers to immediate responses to stimuli that override the influence of the circadian timekeeping system on behavior and physiology. Masking by light and darkness plays an important role in shaping an organism's daily pattern of activity. Nocturnal animals generally become more active in response to darkness (positive masking) and less active in response to light (negative masking), and diurnal animals generally have opposite patterns of response. These responses can vary as a function of light intensity as well as time of day. Few studies have directly compared masking in diurnal and nocturnal species, and none have compared rhythms in masking behavior of diurnal and nocturnal species. Here, we assessed masking in nocturnal mice (Mus musculus) and diurnal grass rats (Arvicanthis niloticus). In the first experiment, animals were housed in a 12:12 light-dark (LD) cycle, with dark or light pulses presented at 6 Zeitgeber times (ZTs; with ZT0 = lights on). Light pulses during the dark phase produced negative masking in nocturnal mice but only at ZT14, whereas light pulses resulted in positive masking in diurnal grass rats across the dark phase. In both species, dark pulses had no effect on behavior. In the 2nd experiment, animals were kept in constant darkness or constant light and were presented with light or dark pulses, respectively, at 6 circadian times (CTs). CT0 corresponded to ZT0 of the preceding LD cycle. Rhythms in masking responses to light differed between species; responses were evident at all CTs in grass rats but only at CT14 in mice. Responses to darkness were observed only in mice, in which there was a significant increase in activity at CT 22. In the 3rd experiment, animals were kept on a 3.5:3.5-h LD cycle. Surprisingly, masking was evident only in grass rats. In mice, levels of activity during the light and dark phases of the 7-h cycle did not differ, even though the same animals had responded to discrete photic stimuli in the first 2 experiments. The results of the 3 experiments are discussed in terms of their methodological implications and for the insight they offer into the mechanisms and evolution of diurnality.     

Reflex facilitation during the stretch-shortening cycle.

Maximal torque during the concentric phase of a movement has been shown to be enhanced by prior eccentric muscle actions, a movement strategy referred to as the stretch-shortening cycle. Although the mechanical basis for this enhancement is well established, the neural component is not. We hypothesized that brief high-frequency bursts of spindle afferent discharge during the eccentric phase of the stretch-shortening cycle could be one mechanism for facilitating the volitional drive. To test this hypothesis, three sets of experiments were done. In the first (N=15), we demonstrated that both the peak and mean EMG of the soleus (S) and lateral gastrocnemius (LG) muscles were considerably greater during a reciprocal hopping (RHOP) task than for maximum isometric contractions (MIVCs). In the second experiment, we tested whether the dynamic nature of the RHOP or the eccentric phase of the RHOP contributed to the EMG potentiation. Peak and mean EMG produced with a concentric hop (CHOP), in which the lengthening phase of the hop was eliminated, were compared with that produced with the RHOP and MIVCs conditions (N=7). The RHOP produced greater peak EMG than either the CHOP or the MIVCs while the mean EMG for both hopping conditions was considerably more than the MIVCs. In the final experiment, we attempted to mimic the brief high-frequency burst of spindle afferent activity during the lengthening phase of the stretch-shortening cycle in the absence of muscle length changes. High-frequency (100 Hz) afferent stimulation (HFS) was delivered during MIVCs. At rest, the HFS produced negligible EMG activity but when superimposed over MIVCs produced a marked potentiation of the S EMG over values obtained during MIVCs alone. Evidence that HFS synchronizes the EMG associated with volitional activation is also provided. We conclude that a substantial but brief facilitation and possible synchronization of the neural drive is provided by the spindle afferents during the eccentric phase of the stretch-shortening cycle.     

Image analysis of in situ cell cycle related changes of PCNA and Ki-67 proliferating antigen expression

Abstract. This study reports on the proliferating cell nuclear antigen (PCNA) and Ki-67 cell cycle related expression and distribution pattern analysed in the same cells. MCF-7 cells were synchronized by mitotic detachment and triple stained for DNA, PCNA and Ki-67. The major cell type was identified on each time sample as a function of the PCNA/Ki-67 pattern, and both antigens as well as DNA were quantified. During G₁ phase, the expression of PCNA greatly increased whereas Ki-67 content decreased. During S phase, nuclear Ki-67 content continuously increased especially in the second half of this phase, mainly due to the accumulation of the antigen in the nucleoli. During G₂ phase, the antigen significantly passed into the nucleoplasm, its content continued to increase and reached its maximum in mitotic cells. Nuclear PCNA content mostly increased in the first part of S phase and sharply declined in mitotic cells as the antigen shifted to the cytoplasm. Cells showing PCNA positive Ki-67 negative labelling were observed in all time samples from the beginning of the experiment. Their nuclear size, DNA content (of G₁ cells), PCNA content (equivalent to the content of some late G, cells) and time occurrence (their percentage increased after the last late G₁ cells had disappeared) tend to indicate that these cells have left the cycle by the end of G₁ phase to enter a quiescent state. Cells coming out of mitosis split into two groups according to their Ki-67/PCNA content. The biggest fraction was PCNA negative and Ki-67 positive while the smallest showed positive staining for both antibodies. Cells of this second cohort slowly lost their 1–67 while their PCNA content increased as they moved through G₁. Concurrently, most of the cells of the first cohort (here called Q2 and Q3 cell types) lost their Ki-67 without increasing their PCNA content; then they joined cells of the second cohort by increasing their PCNA content at the end of G, phase. Some cells of this first cohort can also increase their PCNA and thus reach cells of the first cohort before the end of G₁ phase. The existence of these two main cell cohorts suggests that cells after mitosis differ in some way that make them progress dlfferently through G₁. Some cells seem to go through early G₁ (G_1a and late G₁ (G_lb) while others may come out of mitosis committed to go through the following cycle by directly entering late G₁ compartment.     

Independent aftereffects of attention and motion

In the motion aftereffect (MAE), a stationary pattern appears to move in the opposite direction to previously viewed motion. Here we report an MAE that is observed for a putatively high level of visual analysis-attentive tracking. These high-level MAEs, visible on dynamic (but not static) tests, suggest that attentive tracking does not simply enhance low-level motion signals but, rather, acts at a subsequent stage. MAEs from tracking (1) can overrule competing MAEs from adaptation to low-level motion, (2) can be established opposite to low-level MAEs seen on static tests at the same location, and (3), most striking, are specific to the overall direction of object motion, even at nonadapted locations. These distinctive properties suggest MAEs from attentive tracking can serve as valuable probes for understanding the mechanisms of high-level vision and attention.     

Similar effects of a beta-carboline and of flumazenil in negatively and positively reinforced learning tasks in mice.

Methyl beta-carboline-3-carboxylate (beta-CCM) and flumazenil (Ro15-1788) are known to be respectively an inverse agonist and an antagonist of the central benzodiazepine-receptor. Surprisingly, these two drugs have shown a similar enhancing effect in a negatively reinforced multiple-trial brightness discrimination task in mice. Thus, to evaluate the role of anxiety in this task, the action of these two drugs were compared in the same learning task with a positive or a negative reinforcement. Mice were trained for sessions of ten trials per day for six consecutive days. The sessions during the first three days took place after administration of beta-CCM (0.3 mg/kg), flumazenil (15 mg/kg) or vehicles of these drugs. A negative reinforcement (electric foot-shock) was used in a first experiment, and a positive one (food reward) in a second experiment. Results showed that, whatever the reinforcement, the two drugs enhance learning in a brightness discrimination task. The hypothesis is that flumazenil could have an inverse agonist profile in learning tasks. The question remains as to whether the flumazenil enhancing learning process results from increased arousal and/or anxiogenic factors, or from a negative modulatory influence of endogenous diazepam-like ligands for benzodiazepine receptors.     

Synthetic heat at mild temperatures

"Synthetic heat", also known as the heat grill illusion, occurs when contact with spatially adjacent warm and cold stimuli produce a sensation of "heat". This phenomenon has been explained as a painful perception that occurs when warm stimulation inhibits cold-sensitive neurons in the spinothalamic tract (STT), which in turn unmasks activity in the pain pathway caused by stimulation of C-polymodal nociceptors (CPNs). The "unmasking model" was tested in experiment 1 by combining warm (35-40°C) and cool ( &#83 27°C) stimuli that were too mild to stimulate CPNs. After discovering that these temperatures produced nonpainful heat, experiment 2 was designed to determine whether heat could be induced when near-threshold cooling was paired with mild warmth, and whether lowering the base temperature for cooling would increase the noxious (burning, stinging) components of heat for fixed cooling steps of 1-3°C. Cooling by just 1°C from a base temperature of 33°C led to reports of heat on more than 1/3 of trials, and cooling by just 3°C evoked heat on 75% of trials. Lowering the base temperature to 31 or 29°C increased reports of heat and burning but did not produce significant reports of pain. Perception of nonpainful heat at such mild temperatures indicates either that cold-sensitive nociceptors with thresholds very similar to cold fibers innervate hairy skin in humans, or that heat can result from integration of warm fiber and cold fiber activity, perhaps via convergence on nonspecific (e.g., WDR) neurons in the STT.     

Effects of intertrial reinforcers on rats' timing behavior

Two experiments were conducted to assess the effects of non-contingent intertrial interval (ITI) reinforcers on rats' discrimination of duration. In the first experiment, rats' discrimination of a 2 vs. 8 s of light was significantly disrupted when reinforcers were presented in the ITI. Disruption was not different on short (2 s) and long (8 s) trials. The second experiment showed that this disruptive effect was not specific to trials preceded by ITI reinforcers; responding on empty ITI trials run in the same session as ITI-reinforcer trials was also disrupted. This disruption however was not as great as on the ITI-reinforcer trials. The results of these experiments show that ITI reinforcers affect timing discriminations in much the same way they affect classical conditioning and delayed matching to sample. However, detailed examination of the results suggests that the deleterious effects of ITI reinforcers in these different paradigms might be produced by different rather than the same mechanism. The results also support the conclusion that pre-trial reinforcement “priming” produces disruption rather than facilitation in complex tasks.     

Effects of delays on human performance on a temporal discrimination procedure: evidence of a choose-short effect

Studies of temporal discrimination in non-human subjects have reliably shown a choose-short effect: higher matching accuracy on short-duration-sample trials than on long-duration-sample trials. This effect occurs as a function of increasing the delay between the onset of sample and comparison stimuli in a delayed matching-to-sample procedure. The present experiment investigated whether the choose-short effect could be demonstrated in human subjects under conditions which paralleled those used with non-human subjects. Subjects responded under a discrete-trial procedure in which they were required to push one of two buttons depending on the duration of a sample stimulus (a blue square on a computer monitor). Delays (0, 8, 16, and 32s) separated sample and comparison stimuli (two white boxes) and were tested both within and across several sessions. Intermediate durations (probe stimuli between 2 and 4s) were also presented. The addition of a delay between the sample and comparison stimuli produced a bias to judge intervals as short when the 8 and 32-s delays were tested across sessions and when the 0, 16, and 32-s delays were tested within the same session. Thus, the choose-short effect was produced in human subjects using the interval bisection procedure regardless of delay length.     

Direct and correlated responses to selection in a host-parasite system: testing for the emergence of genotype specificity

Genotype x environment interactions can facilitate coexistence of locally adapted specialists. Interactions evolve if adaptation to one environment trades off with performance in others. We investigated whether evolution on one host genotype traded off with performance on others in long-term experimental populations of different genotypes of the protozoan Paramecium caudatum, infected with the bacterial parasite Holospora undulata. A total of nine parasite selection lines evolving on three host genotypes and the ancestral parasite were tested in a cross-infection experiment. We found that evolved parasites produced more infections than did the ancestral parasites, both on host genotypes they had evolved on (positive direct response to selection) and on genotypes they had not evolved on (positive correlated response to selection). On two host genotypes, a negative relationship between direct and correlated responses indicated pleiotropic costs of adaptation. On the third, a positive relationship suggested cost-free adaptation. Nonetheless, on all three hosts, resident parasites tended to be superior to the average nonresident parasite. Thus genotype specificity (i.e., patterns of local adaptation) may evolve without costs of adaptation, as long as direct responses to selection exceed correlated responses.     

负性情绪对不同视野条件下工作记忆的影响

目的:研究结合延迟样本匹配任务和分视野范式,探讨负性情绪对言语和空间工作记忆的影响。方法:32名大学本科生参加实验,在中性和负性情绪图片呈现阶段,所有被试完成言语和空间工作记忆任务各160个trial。结果:言语工作记忆任务在右视野呈现时正确率较高,反应时较短,而空间工作记忆任务则在左视野呈现时表现出相似的反应优势;负性情绪状态下的工作记忆表现均优于中性情绪状态。结论:言语及空间工作记忆分别具有左、右半球的加工优势,且负性情绪对工作记忆具有促进作用。