Test of the negative feedback hypothesis of colony size sensing in social insects.

Social insects can sense colony size-even without visual information in a dark environment. How they achieve this is yet largely unknown. We empirically tested a hypothesis on the proximate mechanism using ant colonies.

Understanding the mechanism of CO-Assisted electrospray ionization for parameter optimization in supercritical fluid chromatography mass spectrometry.

Supercritical fluid chromatography (SFC) is often coupled with electrospray ionization mass spectrometry (ESI-MS) for analyte detection because of its detection capability to a wide range of chemical properties. However, MS sensitivity is highly dependent on the chromatographic conditions, so that it is important to understand the ionization mechanism to determine the optimal chromatographic conditions. The ionization mechanism in SFC/ESI-MS is different to that of liquid chromatography because of the use of CO as a mobile phase.

Solid-phase microextraction- probe electrospray ionization devices for screening and quantitating drugs of abuse in small amounts of biofluids.

Probe electrospray ionization (PESI) is an ambient ionization mass spectrometry technique (AIMS) that is primarily used in qualitative studies, though researchers have recently combined it with sample preparation for the quantitative analysis of various analytes in biological matrices. This study presents a method that integrates solid-phase microextraction with PESI for direct coupling to a triple quadrupole mass spectrometer, and examines its ability to quantitate drugs of abuse. Intra- and inter-probe reproducibility experiments were conducted to assess the stability and reproducibility of the extraction-phase-coated PESI probes (coating length: 2 mm; coating thickness: 6.

Development of a novel comprehensive analytical method for volatile compounds using supercritical fluid chromatography/mass spectrometry with a highly cross-linked styrene divinylbenzene polymer-based column.

Analytical techniques to determine volatile compounds such as flavor, aroma, and fragrances are in high demand due to their wide range of applications in industry, the chemical properties of them are very diverse. Supercritical fluid chromatography (SFC) is capable of high speed, high peak capacity separation and has a high separation coverage. It is also an advantageous for preparative purifications due to its unique mobile phase conditions.

Importance of optimizing chromatographic conditions and mass spectrometric parameters for supercritical fluid chromatography/mass spectrometry.

Supercritical fluid chromatography/mass spectrometry (SFC/MS) has great potential in high-throughput and the simultaneous analysis of a wide variety of compounds, and it has been widely used in recent years. The use of MS for detection provides the advantages of high sensitivity and high selectivity. However, the sensitivity of MS detection depends on the chromatographic conditions and MS parameters.

What Kind of Capsule Endoscope Is Suitable for a Controllable Self-Propelling Capsule Endoscope? Experimental Study Using a Porcine Stomach Model for Clinical Application (with Videos).

Background: We have been developing the Self-Propelling Capsule Endoscope (SPCE) that allows for controllability from outside of the body and real-time observation. What kind of capsule endoscope (CE) is suitable for a controllable SPCE is unclear and a very critical point for clinical application. We compared observing ability of three kinds of SPCEs with different viewing angles and frame rates.

Memory block: a consequence of conflict resolution.

Food deprivation for 1 day in the pond snail Lymnaea stagnalis before aversive classical conditioning results in optimal conditioned taste aversion (CTA) and long-term memory (LTM) formation, whereas 5-day food deprivation before training does not. We hypothesize that snails do in fact learn and form LTM when trained after prolonged food deprivation, but that severe food deprivation blocks their ability to express memory. We trained 5-day food-deprived snails under various conditions, and found that memory was indeed formed but is overpowered by severe food deprivation.

The Yerkes-Dodson law and appropriate stimuli for conditioned taste aversion in Lymnaea.

The pond snail Lymnaea stagnalis can learn conditioned taste aversion and then consolidate it into long-term memory (LTM). A high-voltage electric shock was used as the unconditioned stimulus, where we have previously used KCl. We varied the strength of both the conditioned and unconditioned stimuli to determine whether the so-called Yerkes-Dodson law prevailed.

An increase in insulin is important for the acquisition conditioned taste aversion in Lymnaea.

Conditioned taste aversion (CTA) in Lymnaea is brought about by pairing a sucrose solution (the conditioned stimulus, CS) with an electric shock (the unconditioned stimulus, US). Following repeated CS-US pairings, CTA occurs and it is consolidated into long-term memory (LTM). The best CTA is achieved, if snails are food-deprived for 1 day before training commences.

What are the elements of motivation for acquisition of conditioned taste aversion?

The pond snail Lymnaea stagnalis is capable of being classically conditioned to avoid food and to consolidate this aversion into a long-term memory (LTM). Previous studies have shown that the length of food deprivation is important for both the acquisition of taste aversion and its consolidation into LTM, which is referred to as conditioned taste aversion (CTA). Here we tested the hypothesis that the hemolymph glucose concentration is an important factor in the learning and memory of CTA.

Paired pulse ratio analysis of insulin-induced synaptic plasticity in the snail brain.

Insulin's action in the brain can directly alter cognitive functioning. We have recently shown that molluscan insulin-related peptides are upregulated following a conditioned taste aversion (CTA) training procedure. In addition, when mammalian insulin is superfused over the isolated Lymnaea stagnalis central nervous system, it elicits long-term synaptic enhancement at the monosynaptic connection between the cerebral giant cell and the buccal 1 (B1) motor neuron.

Involvement of insulin-like peptide in long-term synaptic plasticity and long-term memory of the pond snail Lymnaea stagnalis.

The pond snail Lymnaea stagnalis is capable of learning taste aversion and consolidating this learning into long-term memory (LTM) that is called conditioned taste aversion (CTA). Previous studies showed that some molluscan insulin-related peptides (MIPs) were upregulated in snails exhibiting CTA. We thus hypothesized that MIPs play an important role in neurons underlying the CTA-LTM consolidation process.

Memory trace in feeding neural circuitry underlying conditioned taste aversion in Lymnaea.

Background: The pond snail Lymnaea stagnalis can maintain a conditioned taste aversion (CTA) as a long-term memory. Previous studies have shown that the inhibitory postsynaptic potential (IPSP) evoked in the neuron 1 medial (N1M) cell by activation of the cerebral giant cell (CGC) in taste aversion-trained snails was larger and lasted longer than that in control snails. The N1M cell is one of the interneurons in the feeding central pattern generator (CPG), and the CGC is a key regulatory neuron for the feeding CPG.

Multiple subtypes of serotonin receptors in the feeding circuit of a pond snail.

In the central nervous system of the pond snail Lymnaea stagnalis, serotonergic transmission plays an important role in controlling feeding behavior. Recent electrophysiological studies have claimed that only metabotropic serotonin (5-HT(2)) receptors, and not ionotropic (5-HT(3)) receptors, are used in synapses between serotonergic neurons (the cerebral giant cells, CGCs) and the follower buccal motoneurons (the B1 cells). However, these data are inconsistent with previous results.

Does conditioned taste aversion learning in the pond snail Lymnaea stagnalis produce conditioned fear?

In conditioned taste aversion (CTA) training performed on the pond snail Lymnaea stagnalis, a stimulus (the conditional stimulus, CS; e.g., sucrose) that elicits a feeding response is paired with an aversive stimulus (the unconditional stimulus, US) that elicits the whole-body withdrawal response and inhibits feeding.

Learning-Dependent Gene Expression of CREB1 Isoforms in the Molluscan Brain.

Cyclic AMP-responsive element binding protein1 (CREB1) has multiple functions in gene regulation. Various studies have reported that CREB1-dependent gene induction is necessary for memory formation and long-lasting behavioral changes in both vertebrates and invertebrates. In the present study, we characterized Lymnaea CREB1 (LymCREB1) mRNA isoforms of spliced variants in the central nervous system (CNS) of the pond snail Lymnaea stagnalis.

Raphe modulation of the pre-Bötzinger complex respiratory bursts in in vitro medullary half-slice preparations of neonatal mice.

Spontaneous respiratory bursts which begin in the pre-Bötzinger complex were recorded from the hypoglossal (XIIth) nerve rootlets of in vitro slices prepared from newborn mice. First, we examined the respiratory bursts before and after a midline or para-midline transection which spared the caudal raphe nuclei: the raphe obscurus and raphe pallidus. After a midline transection, the respiratory bursts in both half-slices were desynchronized and had slightly decreased amplitudes and frequencies.

Spontaneous respiratory rhythm generation in in vitro upper cervical slice preparations of neonatal mice.

Isolated upper cervical slice preparations were prepared from neonatal mice to examine whether spontaneous respiratory activity could be generated in the preparations. By using brainstem-spinal cord preparations, we first recorded from the cervical C1-C2 and C4 ventral roots rhythmic bursts which were synchronized with respiratory burst activity of the hypoglossal (XIIth) nerve. Following transection just above the C1 segment, smaller and slower rhythmic bursts still persisted in the C1/C2 ventral roots and these were synchronized with those in the C4 ventral root.

Contrary effects of octopamine receptor ligands on behavioral and neuronal changes in locomotion of lymnaea.

The pond snail Lymnaea stagnalis moves along the sides and bottom of an aquarium, but it can also glide upside down on its back below the water's surface. We have termed these two forms of locomotion "standard locomotion" and "upside-down gliding," respectively. Previous studies showed that standard locomotion is produced by both cilia activity on the foot and peristaltic contraction of the foot muscles, whereas upside-down gliding is mainly caused by cilia activity.

Glutamate transporters in the central nervous system of a pond snail.

Previous studies on glutamate (GLU) and its receptors in the pond snail Lymnaea stagnalis have suggested that GLU functions as a neurotransmitter in various behaviors, particularly for generation of feeding rhythm. The uptake mechanism of GLU is not yet known in Lymnaea. In the present study, we characterized the GLU transporters and examined their functions in the feeding circuits of the central nervous system (CNS) in Lymnaea.

Upside-down gliding of Lymnaea.

The pond snail Lymnaea stagnalis can often be observed moving upside down on its back just below the surface of the water. We have termed this form of movement "upside-down gliding." To elucidate the mechanism of this locomotion, we performed a series of experiments involving behavioral analyses and microscopic observations.

Speed of back-swimming of Lymnaea.

The pond snail, Lymnaea stagnalis, can locomote on its back utilizing the surface tension of the water. We have called this form of movement 'back-swimming'. In order to perform this behavior, the snail must flip itself over on its back so that its foot is visible from above.

One-trial conditioned taste aversion in Lymnaea: good and poor performers in long-term memory acquisition.

In the majority of studies designed to elucidate the causal mechanisms of memory formation, certain members of the experimental cohort, even though subjected to exactly the same conditioning procedures, remember significantly better than others, whereas others show little or no long-term memory (LTM) formation. To begin to address the question of why this phenomenon occurs and thereby help clarify the causal mechanism of LTM formation, we used a conditioned taste aversion (CTA) procedure on individuals of the pond snail Lymnaea stagnalis and analyzed their subsequent behavior. Using sucrose as an appetitive stimulus and KCl as an aversive stimulus, we obtained a constant ratio of ;poor' to ;good' performers for CTA-LTM.

Involvement of medullary GABAergic and serotonergic raphe neurons in respiratory control: electrophysiological and immunohistochemical studies in rats.

In the present study we first examined the possible involvement of the putative neurotransmitters gamma-aminobutyric acid (GABA) and serotonin (5-HT) in raphe-induced facilitatory or inhibitory effects on the respiratory activity of rats. Secondly, we investigated the possibility of spinal projections of GABAergic and serotonergic neurons from the medullary raphe nuclei to the phrenic motor nucleus (PMN). We observed that an intravenous (i.

Altered gene activity correlated with long-term memory formation of conditioned taste aversion in Lymnaea.

The pond snail Lymnaea stagnalis is capable of learning conditioned taste aversion (CTA) and then consolidating that learning into long-term memory (LTM) that persists for at least 1 month. LTM requires de novo protein synthesis and altered gene activity. Changes in gene activity in Lymnaea that are correlated with, much less causative, memory formation have not yet been identified.