Consistency of dogs’ reactions to threatening cues of an unfamiliar person

Reliability is one of the most important aspects of the behaviour observations measuring personality traits in animals. The most fundamental way to test reliability is the assessment of the test–retest consistency. On the other hand, in situations where social interaction between a human participant and the animal subject is at the scope of the study, the behaviour of the humans in the test situation should be restricted by a set of rules. However, if more than one experimenter participates in the observations, the similarity of the behaviour of different persons is an important aspect of the reliability of the study.In our first study we investigated the consistency of dogs’ behaviour during approach by a person in a friendly and in a threatening way, repeating the test either immediately after the first test or at least 6 months later. We found that the dogs’ sensitivity to the human's behavioural cues in this situation proved to be consistent over repetition when the second test was performed approximately 1 year after the first test, but it was not the case when the time elapsed between test occasions was a few seconds. The detailed analysis indicated that dogs performing extreme behaviour (friendly or threatening) tended to show more conservative responses than dogs showing intermediate reactions when the stranger approached threateningly. Nonetheless, the reaction of the dogs failed to be in accordance with the opinion of the owners about the dogs’ behaviour in similar situations in everyday life.In the second study we examined the consistency of the dogs’ behaviour in the same situation when confronted with two different unfamiliar persons immediately after each other. The consistency of the dogs’ response to the two experimenters was found to be reliably high.In sum, this test procedure proved to be reliable enough to be a valuable measure of a definite part of the personality characters of dogs.     

Sensitivity of transformed (phasic to tonic) motor neurons to the neuromodulator 5-HT

Long-term adaptation resulting in a 'tonic-like' state can be induced in phasic motor neurons of the crayfish, Procambarus clarkii, by daily low-frequency stimulation [Lnenicka, G.A., Atwood, H.L., 1985b. Long-term facilitation and long-term adaptation at synapses of a crayfish phasic motoneuron. J. Neurobiol. 16, 97-110]. To test the hypothesis that motor neurons undergoing adaptation show increased responses to the neuromodulator serotonin (5-HT), phasic motor neurons innervating the deep abdominal extensor muscles of crayfish were stimulated at 2.5 Hz, 2 h/day, for 7 days. One day after cessation of conditioning, contralateral control and conditioned motor neurons of the same segment were stimulated at 1 Hz and the induced excitatory post-synaptic potentials (EPSPs) were recorded from DEL(1) muscle fibers innervated by each motor neuron type. Recordings were made in saline without and with 100 nM 5-HT. EPSP amplitudes were increased by 5-HT exposure in all cases. Conditioned muscles exposed to 5-HT showed a 2-fold higher percentage of increase in EPSP amplitude than did control muscles. Thus, the conditioned motor neurons behaved like intrinsically tonic motoneurons in their response to 5-HT. While these results show that long-term adaptation (LTA) extends to 5-HT neuromodulation, no phenotype switch could be detected in the postsynaptic muscle. Protein isoform profiles, including the myosin heavy chains, do not change after 1 week of conditioning their innervating motor neurons.     

Dissociation between proliferation and antibody formation by old mouse spleen cells in response to LPS stimulation.

Both lipopolysaccharide (LPS)-induced proliferation and antibody formation by C57B1/6 spleen cells from old mice were studied by measuring thymidine incorporation and plaque-forming cells (PFCs) to the 2,4-dinitrophenyl group (DNP). There was no significant difference in the proliferative response of spleen cells from young or old mice. Anti-DNP antibody formation by spleen cells from the old mice was greatly reduced. The reduced PFC response could not explained by a shift in kinetics of the responding cells. A similar dissociation could be obtained with LPS-stimulated spleen cells from young mice by using an anti-μ serum or a low concentration of hydroxyurea in the culture medium.     

Cholinergic transmission from mechanosensory afferents to an identified nonspiking interneuron in the crayfish Procambarus clarkii girard

Pharmacological properties of excitatory synaptic transmission from mechanosensory afferents to an identifiable nonspiking interneuron of crayfish were studied by drug perfusion experiments using acetylcholine (ACh) agonists and antagonists. Application of carbachol, a general agonist of ACh, caused sustained depolarization of the interneuron and a decrease in the peak amplitude of its excitatory synaptic response to sensory stimulation on the soma side. Similar depolarization was observed during application of carbachol under the low-Ca²⁺, high-Mg²⁺ condition. The peak amplitude was also reduced by application of nicotine and tetramethylammonium, both of which also caused sustained depolarization of the inter-neuron. By contrast, perfusion of muscarinic agonists, muscarine, oxotremorine and pilocarpine, reduced the peak amplitude without affecting the membrane potential of the interneuron. Perfusion of nicotonic antagonists of ACh, d-tubocurarine and hexamethonium, caused reduction of the peak amplitude without any change in the membrane potential. A muscarinic antagonist atropine was also effective in blocking the synaptic transmission but at higher concentration than d-tubocurarine. The results suggest that the ACh receptors on the nonspiking interneuron belong to a previously characterized class of crustacean cholinergic receptors resembling the nicotinic subtype of vertebrates.     

Pigment dispersing hormone generates a circadian response to light in the crayfish, Procambarus clarkii

Photoreceptor cells have been identified as important structures in the organization of the circadian system responsible for the generation and expression of the electroretinogram (ERG) circadian rhythm. They are the structures where the circadian periodicity is expressed (effectors) and which transform information from external light signals to be conducted to the pacemaker in order to induce adjustments of the rhythm (synchronizers). After isolation, eyestalks perfused in a pigment dispersing hormone (PDH) solution, show significant changes in receptor potential (RP) amplitude and duration. Exogenous PDH injected into intact crayfish induces a migration of retinal shielding pigments to a light-adapted state. A single dose of PDH produces advances or delays in the circadian rhythm of response to light of visual photoreceptors. All these effects depend on the circadian phase of PDH application. Consequently, the determination of the action of exogenous PDH on photoreceptor cells proved to be very helpful in understanding some mechanisms underlying the circadian organization of crayfish.     

Motor unit recruitment strategy of knee antagonist muscles in a step-wise, increasing isometric contraction

The purpose of this study was to determine if differences exist between the control strategies of two antagonist thigh muscles during knee flexion and extension muscular coactivation. Surface myoelectric signal (MES) of the quadriceps (rectus femoris) and the hamstrings (semitendinosus) were obtained from both muscles while performing step-wise increasing contractions during flexion and extension with the knee at 1.57 rad of flexion (90 degrees). The median frequency of the power density spectrum, which is related to the average muscle fiber action potential conduction velocity and therefore to motor unit recruitment, was calculated from each MES. The results suggest that, in all the subjects tested, when the muscle acts as antagonist most motor units are recruited up to 50% of the maximal voluntary force, whereas when the muscle acts as antagonist motor units are recruited up to 40% of the maximal voluntary force. The force range past 40–50% of the maximal force is also characterized by differences between the agonist/antagonist.     

Predator avoidance by the freshwater snailPhysella virgata in response to the crayfishProcambarus simulans

Summary We examined predator avoidance behavior of the freshwater snailPhysella (=Physa) virgata in response to the crayfishProcambarus simulans. In both laboratory and field enclosure experiments snails crawled above the waterline for 2 h or longer, then returned to the water.Physella virgata react to chemical signals given off by crayfish actively foraging on conspecific snails; they do not react to inactive crayfish. Low dissolved oxygen, crowding, and disturbance of the sediments did not elicit crawlout behavior. Crawling above the waterline, by reducing the probability of encounter between vulnerable, thin-shelled snails and crayfish, is an adaptive response to predation.     

Neural mechanism for generating and switching motor patterns of rhythmic movements of ovipositor valves in the cricket

In adult female crickets (Gryllus bimaculatus), rhythmic movements of ovipositor valves are produced by contractions of a set of ovipositor muscles that mediate egg-laying behavior. Recordings from implanted wire electrodes in the ovipositor muscles of freely moving crickets revealed sequential changes in the temporal pattern of motor activity that corresponded to shifts between behavioral steps: penetration of the ovipositor into a substrate, deposition of eggs, and withdrawal of the ovipositor from the substrate. We aimed in this study to illustrate the neuronal organization producing these motor patterns and the pattern-switching mechanism during the behavioral sequence. Firstly, we obtained intracellular recordings in tethered preparations, and identified 12 types of interneurons that were involved in the rhythmic activity of the ovipositor muscles. These interneurons fell into two classes: ‘initiator interneurons’ in which excitation preceded the rhythmic contractions of ovipositor muscles, and ‘oscillator interneurons’ in which the rhythmic oscillation and spike bursting occurred in sync with the oviposition motor rhythm. One of the oscillator interneurons exhibited different depolarization patterns in the penetration and deposition motor rhythms. It is likely that some of the oscillator interneurons are involved in producing different oviposition motor patterns. Secondly, we analyzed oviposition motor patterns when the mecahnosensory hairs located on the inside surface of the dorsal ovipositor valves were removed. In deafferented preparations, the sequential change from deposition to withdrawal did not occur. Therefore, the switching from deposition pattern to withdrawal pattern is signaled by the hair sensilla that detect the passage of an egg just before it is expelled.     

Life-history strategies of a freshwater snail in response to stream permanence and predation: balancing conflicting demands

Summary Life-history parameters for the freshwater snail Physella virgata virgata were estimated in temporary and permanent streams with and without crayfish (known snail predators). Snails from the permanent stream with crayfish exhibited higher age and size at first reproduction, as well as higher size and age at death, compared to snail populations from both temporary streams and the permanent stream without crayfish. Life-history patterns of snails from the permanent and temporary streams without crayfish were indistinguishable, with small sizes at first reproduction and at death, as well as lower age at first reproduction and at death. The snail population from the temporary stream with crayfish showed an intermediate life-history pattern. The results suggest that snail life-history patterns vary with both predation pressure and habitat stability, exhibiting phenotypically plastic responses to the variables.     

Orientation response of arterial smooth muscle cells to mechanical stimulation

Arterial smooth muscle cells from rabbit aortic media in primary culture and subculture were grown on hydrophilized and collagen-coated silicone membranes which were then subjected to cyclic and directional stretches and relaxations at a frequency of 60 times/min. The membranes were stretched with various amplitudes ranging from 2% to 20%. Smooth muscle cells on unstretched membranes in the same incubation chamber served as controls. In long-term experiments the stretching and relaxing of the membranes was continued for several days. While the smooth muscle cells grown on unstretched membranes remained in random orientation in all experiments, the cells which underwent mechanical stimulation showed a high degree of orientation. The angle of cell orientation varied in direct relation to the stretching amplitude and became steeper in correlation to the intensity of the mechanical stimulus. The angle of cell orientation was reversible, as preoriented cells changed their orientation when another stretching amplitude was applied. To study the role of cytoskeleton in the process of cell orientation, we examined the behaviour of the intracellular actin filament system. In short-term experiments the smooth muscle cells were exposed for 3 to 12 h to cyclic and directional stretches and relaxations with an amplitude of 10%. We observed a rearrangement of the intracellular actin filament system prior to the orientation of the whole cell bodies. The present study provides evidence that stretching the artery wall by blood pulsation may result in an orientation response of the intracellular actin cytoskeleton and in the orientation of the smooth muscle cells within the media of artery walls.     

Cytoplasmic compartmental response to local mechanical stimulation of internal tissue cells

A convenient experimental system was established to test how cells derived from higher-plant internal tissues respond to mechanical stimulation. Short-term culture of tobacco ovules in vitro led to the generation of bar-shaped cells from the parenchyma tissue of the ovule funicle. These cells are still connected to the mother tissue and are almost undifferentiated. The cells are translucent, and one end protrudes from the funicle, making them easy to manipulate and observe. Mechanical stimulation tests performed on these cells indicated that the cells are less sensitive to mechanical stimulation than epidermal hair cells but still possess the ability to respond to stimulation. Interestingly, the cells showed a cytoplasmic compartmental response to the stimulation. The nucleus, some plastids, and mitochondria were organized into a responsive unit that moved in unison to the stimulated sites, whereas most of the other organelles were not notably influenced by the stimulation. This suggests that the cytoplasm is highly organized and functionally divided in response to environmental stimulation.     

T cells in G1 provide a memory-like response to secondary stimulation

The commitment of naive T cells to proliferate is a function of the strength and duration of stimuli mediated by the TCR and coreceptors. Ranges of 2-20 h of stimulation have been reported as necessary in vitro. Whether T cells actually experience uninterrupted stimulation for such long periods under physiological conditions is controversial. Here we ask whether commitment to proliferate requires continuous stimulation, or can T cells integrate intermittent periods of stimulation. T cells were stimulated for two short-term (subthreshold) periods (5-7 h) either sequentially or separated by an interval of rest. Naive lymph node T cells were able to integrate interrupted stimulation, even when the duration of rest was as long as 2 days. Furthermore, when short-term-stimulated T cells were separated by density, three populations were observed: low density blasts, intermediate density G(1) cells, and high density G(0) cells. Low density cells progressed to division without further stimulation, whereas G(0) and G(1) cells remained undivided. However, after a period of rest, a second subthreshold stimulation caused the G(1) but not the G(0) fraction to quickly proceed through the cell cycle. We conclude that noncycling T cells in the G(1) phase of the cell cycle remain in a state of readiness for prolonged periods of time, and may represent a population of memory-like effectors capable of responding rapidly to antigenic challenge.     

Directionality of antennal sweeps elicited by water jet stimulation of the tailfan in the crayfish Procambarus clarkii

Summary Directionality and intensity dependence of antennal sweeps elicited by water jet stimulation of the tailfan in tethered, reversibly blinded adult and juvenile crayfish (Procambarus clarkii) were analyzed.Resting crayfish keep their antennae at about 50° symmetrically to the longitudinal body axis (Figs. 2 bottom, and 3).In adults, tailfan stimulation elicits synchronous backward sweeps of both antennae, which increase for more caudal stimulus directions (Figs. 2–4 and 5A). Directions differing by 30°–60° are significantly distinguished (Fig. 4). The mean sweep of the ipsilateral antenna significantly overrides that of the contralateral antenna for rostrolateral stimulation at 40–200 mm/s stimulus velocity and lateral to caudolateral stimulation at 40 mm/s and thus lateralization of the stimulus is revealed (Figs. 2 top, 4 and 5A). Mean antennal sweeps at a given stimulus direction and distance increase with increasing stimulus velocity (40–250 mm/s, Fig. 5A).In juveniles, the directional dependence of antennal sweeps is reduced compared to that of adults, while a similar intensity dependence is found (Fig. 5B).The pronounced directionality of the antennal response in adult crayfish vanishes and response latencies increase after reversibly covering the tailfan with a small bag or the telson with waterproof paste (Figs. 6 and 7). Thus, tailfan and especially telson mechanoreceptors play an important role in the localization of water movements elicited by predators or prey behind the crayfish.     

Modulatory effects of ozone on THP-1 cells in response to SP-A stimulation

Ozone (O(3)), a major component of air pollution and a strong oxidizing agent, can lead to lung injury associated with edema, inflammation, and epithelial cell damage. The effects of O(3) on pulmonary immune cells have been studied in various in vivo and in vitro systems. We have shown previously that O(3) exposure of surfactant protein (SP)-A decreases its ability to modulate proinflammatory cytokine production by cells of monocyte/macrophage lineage (THP-1 cells). In this report, we exposed THP-1 cells and/or native SP-A obtained from bronchoalveolar lavage of patients with alveolar proteinosis to O(3) and studied cytokine production and NF-kappaB signaling. The results showed 1) exposure of THP-1 cells to O(3) significantly decreased their ability to express TNF-alpha in response to SP-A; TNF-alpha production, under these conditions, was still significantly higher than basal (unstimulated) levels in filtered air-exposed THP-1 cells; 2) exposure of both THP-1 cells and SP-A to O(3) did not result in any significant differences in TNF-alpha expression compared with basal levels; 3) O(3) exposure of SP-A resulted in a decreased ability of SP-A to activate the NF-kappaB pathway, as assessed by the lack of significant increase and decrease of the nuclear p65 subunit of NF-kappaB and cytoplasmic IkappaBalpha, respectively; and 4) O(3) exposure of THP-1 cells resulted in a decrease in SP-A-mediated THP-1 cell responsiveness, which did not seem to be mediated via the classic NF-kappaB pathway. These findings indicate that O(3) exposure may mediate its effect on macrophage function both directly and indirectly (via SP-A oxidation) and by involving different mechanisms.     

Hydrogen peroxide formation in cultured rose cells in response to UV-C radiation

Suspension-cultured rose ( Rosa damascena Mill. cv. Gloire de Guilan) cells irradiated with UV-C (254 nm. 558 J m⁻²) showed a transient production of H₂O₂ as measured by chemiluminescence of luminol in the presence of peroxidase (EC 1.1 1.1.7). The peak concentration of H₂O₂, which occurred at about 60–90 min after irradiation, was 8–9 μ M . The time course for the appearance of H₂O₂ matched that for UV–induced K⁺ efflux. Treatments that inhibited the UV-induced efflux of K⁺, including heat and overnight incubation with cycloheximide and diethylmaleate, also inhibited the appearance of H₂O₂. The converse was not always true, since catalase (EC 1.11.1.6. and salicylhydroxamic acid, which inhibited luminescence, did not stop K⁺ efflux. We conclude that H₂O₂ synthesis depends on K⁺ efflux. Because H₂.O₂ in the extracellular space is required for lignin synthesis in many plant tissues, we suggest that the UV–stimulated production of H₂O₂ is an integral part of a defensive lignin synthesis.