Lobster claw motorneurons respond to contralateral sensory stimuli

Unilateral sensory stimuli in an isolated lobster claw-ganglion preparation elicits soma and axon spikes in homologous motorneurons in the ipsilateral as well as the contralateral hemiganglion. This cross excitation of the motorneurons provides a basis for bilateral reflexes in the claw and is likely mediated through interneuron(s).     

Lobster muscle and synapse respond to cortisol, a vertebrate hormone

Cortisol (0.28 mumol X L-1) applied to lobster (Homarus americanus) neuromuscular preparations produces a hyperpolarization in muscle fibers and an increase in amplitude of excitatory postsynaptic potentials. The effect appears to be surface-mediated, because of its rapid onset (within seconds). It is also Na+-K+ ATPase dependent, because ouabain blocks the effects. The effects are relatively short-lasting, and gradually subside within 15 min. The increase in excitatory postsynaptic potentials is attributed in part to increased quantal output of transmitter, and not to changes in muscle fiber membrane resistance. The effects of cortisol on neuromuscular transmission and membrane potential indicate that cortisol may have a physiological role in crustaceans.     

Culture-independent identification of microorganisms that respond to specified stimuli.

A new approach that permits culture-independent identification of microorganisms that respond to specified stimuli was developed. This approach was illustrated by examination of microorganisms that grew in response to various nutrient supplements added to soil. A thymidine nucleotide analog, bromodeoxyuridine (BrdU), and supplements were added to soil and incubated for 3 days. DNA was extracted from the soil, and the newly synthesized DNA was isolated by immunocapture of the BrdU-labeled DNA. The unique perspective this approach offers was demonstrated by comparing the microbial community structures obtained from total soil DNA and the BrdU-labeled fraction in an rRNA gene (rDNA) analysis. The traditional total DNA analysis revealed no notable differences between the treatments, whereas the BrdU-labeled DNA showed significantly different banding patterns between the nutrient supplement treatments and compared with total DNA banding patterns. PCR primers were developed to specifically amplify the intergenic region of an rDNA sequence unique to the BrdU analysis of a phosphate supplement treatment. Amplification of DNA from all treatments using these primers showed that it was unique to the phosphate treatment and that it was present in both the total DNA and BrdU-labeled DNA fractions. This result demonstrates the promise of this new strategy, because it was able to permit identification of a sequence from a phosphate-responsive organism that was not discernable in the traditional total DNA community structure analysis.     

C. elegans G protein regulator RGS-3 controls sensitivity to sensory stimuli

Signal transduction through heterotrimeric G proteins is critical for sensory response across species. Regulator of G protein signaling (RGS) proteins are negative regulators of signal transduction. Herein we describe a role for C. elegans RGS-3 in the regulation of sensory behaviors. rgs-3 mutant animals fail to respond to intense sensory stimuli but respond normally to low concentrations of specific odorants. We find that loss of RGS-3 leads to aberrantly increased G protein-coupled calcium signaling but decreased synaptic output, ultimately leading to behavioral defects. Thus, rgs-3 responses are restored by decreasing G protein-coupled signal transduction, either genetically or by exogenous dopamine, by expressing a calcium-binding protein to buffer calcium levels in sensory neurons or by enhancing glutamatergic synaptic transmission from sensory neurons. Therefore, while RGS proteins generally act to downregulate signaling, loss of a specific RGS protein in sensory neurons can lead to defective responses to external stimuli.     

Neural modification by paired sensory stimuli

With repetitive stimulation of two sensory pathways which are intact within the isolated nervous system of Hermissenda, features of a cellular conditioning paradigm were identified. Type A photoreceptors, unlike type B photoreceptors, produce fewer impulses in response to light following temporally specific pairing of light stimuli with rotation stimuli. Type A photoreceptor impulse wave-forms are also specifically changed by such stimulus regimens. These findings can be explained, at least in part, by increased inhibition of type A cells by type B cells after stimulus pairing.     

Signal transformation with pairing of sensory stimuli

Rotation of the isolated nervous system of Hermissenda in a caudal orientation causes a synaptic hyperpolarization accompanied by elimination of impulse activity during the steady-state phase of type A but not type B photoreceptors' responses to light. Rotation of the isolated nervous system in a cephalic orientation causes a synaptic depolarization with increase of impulse activity during the steady-state phase of both type A and type B photoreceptors' responses to light. These effects of rotation on photorecptors are explained by known synaptic interactions. Sufficient redundancy is found to be provided by the neural organization of the visual system and its interaction with the statocyst to preserve much of the visual information in spite of signal transformation in specific photorecptors resulting from pairing of rotation with light.     

Splenic and inguinal lymph node T cells of aged mice respond differently to polyclonal and antigen-specific stimuli.

Numerous changes have been reported to occur in T cell responsiveness of mice with increasing age. However, most of these studies have examined polyclonal stimulation of spleen cells from a limited number of mouse strains. This study investigated the influence of genetic background, source of lymphocytes, and type of stimulus on age-associated changes in T cells response. Con A-induced proliferation and IL-2 and IFN-gamma production by splenic lymphocytes (SL) was significantly greater in CBA/Ca mice compared to C57BL/6 mice, regardless of age. SL of both strains exhibited the predicted age-dependent decline in proliferative response and an increase in IFN-gamma production in response to Con A. In contrast, however, only SL from C57BL/6 mice demonstrated the predicted age-dependent decline in Con A-induced IL-2 production; Con A-induced SL of young and aged CBA/Ca mice produced comparable amounts of IL-2. Differences in age-associated responses to Con A were also observed between SL and inguinal lymph node (ILN) cells of CBA/Ca mice. In contrast to SL, ILN cells demonstrated an increased proliferative response to Con A. However, lymphokine production by Con A-stimulated ILN cells from aged CBA/Ca mice was similar to that of Con A-stimulated SL from aged CBA/Ca mice. To determine if aged ILN T cells respond similarly to polyclonal and antigen-specific stimuli, keyhole limpet hemocyanin (KLH) responses of T cells isolated from ILN of aged and young CBA/Ca mice were examined. KLH-specific T cells from aged mice cultured with KLH-pulsed macrophages (M phi) from aged mice were significantly reduced in their ability to proliferate compared to KLH-specific T cells of young mice cultured with young KLH-pulsed M phi. In contrast to the expected results, the defect was not at the level of the T cells; proliferation of young T cells cultured with aged KLH-pulsed M phi was equivalent to the proliferation of aged T cells cultured with aged M phi. These results suggest that aging has differential effects on polyclonal and antigen-specific T cell proliferation and on polyclonal stimulation of T cells isolated from different lymphoid organs and from different strains of mice.     

PGE(2) sensitizes cultured pulmonary vagal sensory neurons to chemical and electrical stimuli.

Mediators of inflammation, such as PGE(2), are known to sensitize the airways to inhaled irritants and circulating autacoids. Evidence from in vivo studies has shown the involvement of vagal pulmonary C-fiber afferents in the PGE(2)-elicited airway hypersensitivity. However, whether PGE(2) acts directly on these sensory nerves is unclear. The present study aimed to investigate whether PGE(2) has direct potentiating effects on nodose and jugular pulmonary C neurons cultured from adult Sprague-Dawley rats and, if so, determine whether the EP(2) prostanoid receptor is involved. Pulmonary neurons were identified by retrograde labeling with a fluorescent tracer 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate. Using perforated patch-clamp technique, our results showed that 1) PGE(2) pretreatment (1 microM) increased the whole cell current density elicited by capsaicin and phenylbiguanide, chemical agents known to stimulate pulmonary C fibers; 2) selective activation of the EP(2) prostanoid receptor by butaprost (3-10 microM) increased the whole cell current density elicited by capsaicin; and 3) PGE(2), as well as butaprost, increased the number of action potentials evoked by current injection. Therefore, we conclude that PGE(2) directly sensitizes vagal pulmonary C neurons to chemical and electrical stimulation. Furthermore, butaprost modulates the neurons in a manner similar to that of PGE(2), suggesting that the effects of PGE(2) are mediated, at least in part, through the EP(2) prostanoid receptor.     

Frozen-thawed human blood monocytes respond reproducibly to activation stimuli: Implications for screening of BRMs

The purpose of this study was to identify the optimal freezing conditions for human blood monocytes to allow their recovery and use forin vitro screening of activation stimuli. Human monocytes separated from buffy coats of healthy blood donors were suspended at a density of 1 × 10⁷ cells/ml in freezing medium consisting of 70% medium: 20% fetal bovine serum: 10% DMSO frozen in a stepdown freezer, and stored at –180°C. Monocytes were thawed at different times up to 4 months later. Viability was >90%. Fresh monocytes from different donors and frozen monocytes thawed at different times were incubated with different concentrations of lipopolysaccharide, muramyl tripeptide, muramyl dipeptide, or lipopeptide. Tumoricidal activity and IL-1 production of fresh monocytes varied greatly among the 5 different preparations. In contrast, the frozen monocytes (thawed at different times) produced uniform levels of antitumor activity and IL-1 production. These results show that monocytes recovered from frozen storage maintain their ability to respond to activation stimuli in a uniform and reproducible manner. Thus, the use of frozen-thawed monocytes is recommended for screening of macrophage activating agents.     

North Atlantic right whales (Eubalaena glacialis) ignore ships but respond to alerting stimuli

North Atlantic right whales were extensively hunted during the whaling era and have not recovered. One of the primary factors inhibiting their recovery is anthropogenic mortality caused by ship strikes. To assess risk factors involved in ship strikes, we used a multi-sensor acoustic recording tag to measure the responses of whales to passing ships and experimentally tested their responses to controlled sound exposures, which included recordings of ship noise, the social sounds of conspecifics and a signal designed to alert the whales. The whales reacted strongly to the alert signal, they reacted mildly to the social sounds of conspecifics, but they showed no such responses to the sounds of approaching vessels as well as actual vessels. Whales responded to the alert by swimming strongly to the surface, a response likely to increase rather than decrease the risk of collision.     

Human olfactory neurons respond to odor stimuli with an increase in cytoplasmic Ca2+.

The sense of smell allows terrestrial animals to collect information about the chemical nature of their environment through the detection of airborne molecules. In humans smell is believed to play an important role in protecting the organism from environmental hazards such as fire, gas leaks and spoiled food, in determining the flavor of foods, and perhaps in infant-parent bonding. In addition, the study of human olfaction is relevant to a number of medical problems that result in olfactory dysfunction, which can affect nutritional state, and to the study of the etiology of neurodegenerative diseases which manifest themselves in the olfactory epithelium. Although much is known about behavioral aspects of human olfaction, little is understood about the underlying cellular mechanisms in humans. Here we report that viable human olfactory neurons (HON) can be isolated from olfactory tissue biopsies, and we find that HON respond to odorants with an increase in intracellular calcium concentration ([Cai]).     

A preference for contralateral stimuli in human object- and face-selective cortex

Visual input from the left and right visual fields is processed predominantly in the contralateral hemisphere. Here we investigated whether this preference for contralateral over ipsilateral stimuli is also found in high-level visual areas that are important for the recognition of objects and faces. Human subjects were scanned with functional magnetic resonance imaging (fMRI) while they viewed and attended faces, objects, scenes, and scrambled images in the left or right visual field. With our stimulation protocol, primary visual cortex responded only to contralateral stimuli. The contralateral preference was smaller in object- and face-selective regions, and it was smallest in the fusiform gyrus. Nevertheless, each region showed a significant preference for contralateral stimuli. These results indicate that sensitivity to stimulus position is present even in high-level ventral visual cortex.     

Decoding of polymodal sensory stimuli by postsynaptic glutamate receptors in C. elegans

The C. elegans polymodal ASH sensory neurons detect mechanical, osmotic, and chemical stimuli and release glutamate to signal avoidance responses. To investigate the mechanisms of this polymodal signaling, we have characterized the role of postsynaptic glutamate receptors in mediating the response to these distinct stimuli. By studying the behavioral and electrophysiological properties of worms defective for non-NMDA (GLR-1 and GLR-2) and NMDA (NMR-1) receptor subunits, we show that while the osmotic avoidance response requires both NMDA and non-NMDA receptors, the response to mechanical stimuli only requires non-NMDA receptors. Furthermore, analysis of the EGL-3 proprotein convertase provides additional evidence that polymodal signaling in C. elegans occurs via the differential activation of postsynaptic glutamate receptor subtypes.