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At least 19 recordsLinked to original sources

PubMed2001

The smoke detector principle. Natural selection and the regulation of defensive responses.

Defenses, such as flight, cough, stress, and anxiety, should theoretically be expressed to a degree that is near the optimum needed to protect against a given threat. Many defenses seem, however, to be expressed too readily or too intensely. Furthermore, there are remarkably few untoward effects from using drugs to dampen defensive responses. A signal detection analysis of defense regulation can help to resolve this apparent paradox. When the cost of expressing an all-or-none defense is low compared to the potential harm it protects against, the optimal system will express many false alarms. Defenses with graded responses are expressed to the optimal degree when the marginal cost equals the marginal benefit, a point that may vary considerably from the intuitive optimum. Models based on these principles show that the overresponsiveness of many defenses is only apparent, but they also suggest that, in specific instances, defenses can often be dampened without compromising fitness. The smoke detector principle is an essential foundation for making decisions about when drugs can be used safely to relieve suffering and block defenses.

Anxiety↗

PubMedDate not supplied

[Features of differential inhibition in choice between alimentary and defensive response].

Instrumental defensive (avoidance/escape) and alimentary responses (reinforced with palatable food) in dogs were conditioned by the same stimulus (6-Hz light flashes). Differential inhibition for these responses (0.6-Hz flashes) was formed in unalterable series. Later on, alternative experiments with choice between reinforcements were carried out. In both of experimental series, the degree of alimentary excitability (hunger, satiation) was changed. Numbers of responses to differential and positive conditioned stimuli and their latencies were calculated. Under condition of choice (electrodes on a leg and a pedal in front of a dog) the response depended on a dominant motivation. The dogs differed in the degree of motivation dominance. Differential inhibition was less perfect in unalterable experimental series with dominant motivation. Under conditions of choice between alimentary and defensive reinforcements, the response to the differential stimuli depended on the balance between these motivations: two days of hunger increased the number of alimentary responses, defensive responses prevailed after satiation.

Animals↗

PubMed2003

Differential expression of genes encoding calmodulin-binding proteins in response to bacterial pathogens and inducers of defense responses.

Calmodulin (CaM) plays an important role in sensing and transducing changes in cellular Ca2+ concentration in response to several biotic and abiotic stresses. Although CaM is implicated in plant-pathogen interactions, its molecular targets and their role in defense signaling pathway(s) are poorly understood. To elucidate the signaling pathways that link CaM to defense responses, we screened a cDNA library constructed from bean leaves undergoing a hypersensitive response (HR) with radiolabeled CaM isoforms. A total of 26 putative CBPs were identified. Sequencing of the cDNAs revealed that they represent 8 different genes. They are homologues of previously identified CaM-binding proteins (CBPs) in other systems. However, some CBPs are novel members of known CBP families. The proteins encoded by these clones bound CaM in a Ca2+-dependent manner. To determine if these CBPs are involved in plant defense responses, we analyzed their expression in bean leaves inoculated with compatible, incompatible and nonpathogenic bacterial strains. Expression of three CBPs including an isoform of cyclic nucleotide-gated channels (PvCNGC-A) and two hypothetical proteins (PvCBP60-C and PvCBP60-D) was induced whereas the expression of two other isoforms of CNGCs (PvCNGC-B and PvCNGC-C) was repressed in response to incompatible pathogens. The expression of the rest, a small auxin up RNA (PvSAUR1) and two hypothetical proteins (PvCBP60-A and PvCBP60-B), was not changed. The expression of most of the pathogen-regulated genes was also affected by salicylic acid, jasmonic acid, hydrogen peroxide and a fungal elicitor, which are known to induce defense responses. Our results strongly suggest that at least five bean CBPs are involved in plant defense responses.

Bacteria↗

PubMed2004

Methyl jasmonate-induced ethylene production is responsible for conifer phloem defense responses and reprogramming of stem cambial zone for traumatic resin duct formation.

Conifer stem pest resistance includes constitutive defenses that discourage invasion and inducible defenses, including phenolic and terpenoid resin synthesis. Recently, methyl jasmonate (MJ) was shown to induce conifer resin and phenolic defenses; however, it is not known if MJ is the direct effector or if there is a downstream signal. Exogenous applications of MJ, methyl salicylate, and ethylene were used to assess inducible defense signaling mechanisms in conifer stems. MJ and ethylene but not methyl salicylate caused enhanced phenolic synthesis in polyphenolic parenchyma cells, early sclereid lignification, and reprogramming of the cambial zone to form traumatic resin ducts in Pseudotsuga menziesii and Sequoiadendron giganteum. Similar responses in internodes above and below treated internodes indicate transport of a signal giving a systemic response. Studies focusing on P. menziesii showed MJ induced ethylene production earlier and 77-fold higher than wounding. Ethylene production was also induced in internodes above the MJ-treated internode. Pretreatment of P. menziesii stems with the ethylene response inhibitor 1-methylcyclopropene inhibited MJ and wound responses. Wounding increased 1-aminocyclopropane-1-carboxylic acid (ACC) oxidase protein, but MJ treatment produced a higher and more rapid ACC oxidase increase. ACC oxidase was most abundant in ray parenchyma cells, followed by cambial zone cells and resin duct epithelia. The data show these MJ-induced defense responses are mediated by ethylene. The cambial zone xylem mother cells are reprogrammed to differentiate into resin-secreting epithelial cells by an MJ-induced ethylene burst, whereas polyphenolic parenchyma cells are activated to increase polyphenol production. The results also indicate a central role of ray parenchyma in ethylene-induced defense.

Acetates↗

PubMed2003

Small GTPase 'Rop': molecular switch for plant defense responses.

The conserved Rho family of GTPases (Rho, Rac, and Cdc42) in fungi and mammals has emerged as a key regulator of diverse cellular activities, such as cytoskeletal rearrangements, programmed cell death, stress-induced signaling, and cell growth and differentiation. In plants, a unique class of Rho-like proteins, most closely related to mammalian Rac, has only been found and termed 'Rop' (Rho-related GTPase from plant [Li et al. (1998) Plant Physiol. 118, 407-417; Yang (2002) Plant Cell 14, S375-S388]). ROPs have been implicated in regulating various plant cellular responses including defense against pathogens. It has been shown that ROPs, like mammalian Rac, trigger hydrogen peroxide production and hence the 'oxidative burst', a crucial component associated with the cell death, most likely via activation of nicotinamide adenine dinucleotide phosphate oxidase in both monocotyledonous and dicotyledonous species. Recent studies have established that ROPs also function as a molecular switch for defense signaling pathway(s) linked with disease resistance. As discerning the defense pathway remains one of the priority research areas in the field of plant biology, this review is therefore particularly focused on recent progresses that have been made towards understanding the plant defense responses mediated by ROPs.

Amino Acid Sequence↗

PubMed1994

Response-specific inhibition during general facilitation of defensive responses in Aplysia.

Siphon responses of Aplysia have been used to examine the neural basis of nociceptive behavioral inhibition. The authors tested the response specificity and functional significance of this inhibition. Video analysis showed that strong tail-nerve shock decreased the duration of siphon constriction evoked by weak siphon shock. Tail-nerve shock also caused the appearance of a novel flaring response to the test stimulus, which resembled the siphon response to tail-nerve shock. Novel flaring responses were expressed to both mechanical and electrical siphon stimuli. Tailshock facilitated another defensive response, inking, during the period of inhibited siphon constriction. Tailshock also facilitated tail contractions evoked by weak contralateral tail stimulation during this period. These results indicate that inhibition is not generalized across defensive responses and is specific to siphon responses that interfere with directed ink ejection toward an injured site.

Animals↗

PubMed1996

Kainic acid versus carbachol induced emotional-defensive response in the cat.

The emotional-defensive response (EDR) and accompanied neurotoxic and electroencephalographic (EEG) effects induced by injection of kainic acid (KA, 0.1; 0.2 microgram) into the midbrain periaqueductal grey region (PAG) and antero-medial hypothalamus (AMH) in the cat were examined and compared with EDR and accompanied neurotoxic and EEG effects induced by injection of cholinergic agent, carbachol (CCH), into the same sites. The injections of KA (0.2 microgram) into the PAG induced EDR which closely resembled the defense behavior typically observed after administration of CCH. However, in contrast to CCH-induced EDR, the defensive response induced by KA was found to be accompanied by EEG symptoms of epileptiform activity in the limbic cortex and a massive cell loss in the site of injection. It is proposed that KA-induced EDR and seizure activity may have resulted from the activation of different cell populations localized either in the vicinity of the injection (i.e., PAG region) and in the area remote from the injection loci, the limbic cortex. KA induced activation of PAG neuronal network would trigger the 'local response' (emotional-defensive response) and produce a remote effect-epileptiform activity.

Agonistic Behavior↗

PubMed2004

Genome-wide analysis of defense-responsive genes in bacterial blight resistance of rice mediated by the recessive R gene xa13.

Defense responses triggered by dominant and recessive disease resistance (R) genes are presumed to be regulated by different molecular mechanisms. In order to characterize the genes activated in defense responses against bacterial blight mediated by the recessive R gene xa13, two pathogen-induced subtraction cDNA libraries were constructed using the resistant rice line IRBB13--which carries xa13--and its susceptible, near-isogenic, parental line IR24. Clustering analysis of expressed sequence tags (ESTs) identified 702 unique expressed sequences as being involved in the defense responses triggered by xa13; 16% of these are new rice ESTs. These sequences define 702 genes, putatively encoding a wide range of products, including defense-responsive genes commonly involved in different host-pathogen interactions, genes that have not previously been reported to be associated with pathogen-induced defense responses, and genes (38%) with no homology to previously described functional genes. In addition, R-like genes putatively encoding nucleotide-binding site/leucine rich repeat (NBS-LRR) and LRR receptor kinase proteins were observed to be induced in the disease resistance activated by xa13. A total of 568 defense-responsive ESTs were mapped to 588 loci on the rice molecular linkage map through bioinformatic analysis. About 48% of the mapped ESTs co-localized with quantitative trait loci (QTLs) for resistance to various rice diseases, including bacterial blight, rice blast, sheath blight and yellow mottle virus. Furthermore, some defense-responsive sequences were conserved at similar locations on different chromosomes. These results reveal the complexity of xa13-mediated resistance. The information obtained in this study provides a large source of candidate genes for understanding the molecular bases of defense responses activated by recessive R genes and of quantitative disease resistance.

Chromosomes, Plant↗

PubMed1976

Scopolamine: effects on fear or defense responses in the rat.

In previous research scopolamine reduced fear or defense responses of rats to a cat, and removal of the rats' olfactory bulbs had the same effect. This suggested that scopolamine might have affected defense responses by blocking olfactory perception of the stimulus cat. The present experiments studied this possibility and explored further the effects of scopolamine on defense responses of the hooded rat. In Experiment 1 rats treated with scopolamine were found to be responsive to olfactory cues from a cat. When cat smell, but not a cat, was present in the apparatus, scopolamine-treated rats showed a large and significant suppression of food consumption. In Experiment 2 the effects of scopolamine on defense responses were shown to be generalizable to an inanimate stimulus, mechanical robot. Scopolamine caused significantly less freezing and avoidance and significantly shorter latencies to drink in the presence of the robot. One of the primary findings of the present research is that scopolamine has now been shown to reduce the defensive response of freezing in a variety of stimulus situations. This finding was thought to have important implications for the literature relating anticholinergic drugs and avoidance behavior.

Animals↗

PubMed2004

The transcriptional innate immune response to flg22. Interplay and overlap with Avr gene-dependent defense responses and bacterial pathogenesis.

Animals and plants carry recognition systems to sense bacterial flagellin. Flagellin perception in Arabidopsis involves FLS2, a Leu-rich-repeat receptor kinase. We surveyed the early transcriptional response of Arabidopsis cell cultures and seedlings within 60 min of treatment with flg22, a peptide corresponding to the most conserved domain of flagellin. Using Affymetrix microarrays, approximately 3.0% of 8,200 genes displayed transcript level changes in flg22 elicited suspension cultures and seedlings. FLARE (Flagellin Rapidly Elicited) genes mostly encode signaling components, such as transcription factors, protein kinases/phosphatases, and proteins that regulate protein turnover. Approximately 80% of flg22-induced genes were also up-regulated in Arabidopsis seedlings treated with cycloheximide. This suggests that many FLARE genes are negatively regulated by rapidly turned-over repressor proteins. Twenty-one tobacco Avr9/Cf-9 rapidly elicited (ACRE) cDNA full-length sequences were used to search for their Arabidopsis orthologs (AtACRE). We identified either single or multiple putative orthologs for 17 ACRE genes. For 13 of these ACRE genes, at least one Arabidopsis ortholog was induced in flg22-elicited Arabidopsis suspension cells and seedlings. This result revealed a substantial overlap between the Arabidopsis flg22 response and the tobacco Avr9 race-specific defense response. We also compared FLARE gene sets and genes induced in basal or gene-for-gene interactions upon different Pseudomonas syringae treatments, and infer that Pseudomonas syringae pv tomato represses the flagellin-initiated defense response.

Arabidopsis↗

PubMed2003

Pain and the defense response: structural equation modeling reveals a coordinated psychophysiological response to increasing painful stimulation.

The defense response theory implies that individuals should respond to increasing levels of painful stimulation with correlated increases in affectively mediated psychophysiological responses. This paper employs structural equation modeling to infer the latent processes responsible for correlated growth in the pain report, evoked potential amplitudes, pupil dilation, and skin conductance of 92 normal volunteers who experienced 144 trials of three levels of increasingly painful electrical stimulation. The analysis assumed a two-level model of latent growth as a function of stimulus level. The first level of analysis formulated a nonlinear growth model for each response measure, and allowed intercorrelations among the parameters of these models across individuals. The second level of analysis posited latent process factors to account for these intercorrelations. The best-fitting parsimonious model suggests that two latent processes account for the correlations. One of these latent factors, the activation threshold, determines the initial threshold response, while the other, the response gradient, indicates the magnitude of the coherent increase in response with stimulus level. Collectively, these two second-order factors define the defense response, a broad construct comprising both subjective pain evaluation and physiological mechanisms.

Adolescent↗

PubMed2003

ACD6, a novel ankyrin protein, is a regulator and an effector of salicylic acid signaling in the Arabidopsis defense response.

The previously reported Arabidopsis dominant gain-of-function mutant accelerated cell death6-1 (acd6-1) shows spontaneous cell death and increased disease resistance. acd6-1 also confers increased responsiveness to the major defense signal salicylic acid (SA). To further explore the role of ACD6 in the defense response, we cloned and characterized the gene. ACD6 encodes a novel protein with putative ankyrin and transmembrane regions. It is a member of one of the largest uncharacterized gene families in higher plants. Steady state basal expression of ACD6 mRNA required light, SA, and an intact SA signaling pathway. Additionally, ACD6 mRNA levels were increased in the systemic, uninfected tissue of Pseudomonas syringae-infected plants as well as in plants treated with the SA agonist benzothiazole (BTH). A newly isolated ACD6 loss-of-function mutant was less responsive to BTH and upon P. syringae infection had reduced SA levels and increased susceptibility. Conversely, plants overexpressing ACD6 showed modestly increased SA levels, increased resistance to P. syringae, and BTH-inducible and/or a low level of spontaneous cell death. Thus, ACD6 is a necessary and dose-dependent activator of the defense response against virulent bacteria and can activate SA-dependent cell death.

Ankyrins↗

PubMed1979

Physostigmine: effects on fear or defense responses in the rat.

Previous research had shown that the anticholinergic drug, scopolamine, decreased innate defensive responses of rats to a live cat or mechanical robot, and that the effects of scopolamine were attributable to actions of the drug on the central nervous system. In the present research, the anticholinesterase, physostigmine, which increases central cholinergic activity, caused an increase in the defense responses of male hooded rats. Physostigmine caused significantly more freezing and significantly more suppression of feeding and suppression of time near the aversive stimulus (ROBOT). Dose-response curves showed a positive, linear relationship between dose (0.025, 0.05, 0.1 and 0.2 mg/kg) of physostigmine and defense responses. The present results could not be attributed to general response suppression since the effects of physostigmine were situation-specific, i.e., the drug had no significant effect on behavior in the non-aversive or NO ROBOT condition. The present results were taken as further evidence of the involvement of cholinergic activity in the mediation of defense responses. The effects of cholinergic and anticholinergic drugs on the observable defense response of freezing were thought to have important implications for the large literature relating these drugs and avoidance responding.

Aggression↗

PubMed2006

Modified cyclodextrins are chemically defined glucan inducers of defense responses in grapevine cell cultures.

In grapevine (Vitis vinifera L.), defense responses after microbial infection or treatment with elicitors involve accumulation of phytoalexins, oxidative burst, and the synthesis of pathogenesis-related proteins. Oligosaccharide fractions from fungal or algal cell walls efficiently induce the defense responses, but a detailed analysis of the elicitor-plant cell surface interaction at the molecular level is precluded by the lack of chemically pure oligosaccharide elicitors. A grapevine liquid cell culture system was used to examine the properties of cyclodextrins (CDs) as inducers of defense responses. This work shows that the chemically pure heptakis(2,6-di-O-methyl)-betaCD caused a dramatic extracellular accumulation of the phytoalexin resveratrol and changes in peroxidase activity and isoenzymatic pattern. Other modified CDs tested on several grapevine cell lines resulted in different eliciting capacities of CDs and different sensibilities of the cell lines. The spent medium of elicited cultures was shown to disturb Botrytis cinerea growth in a plate assay.

Botrytis↗

PubMed2005

Proteomics of Rac GTPase signaling reveals its predominant role in elicitor-induced defense response of cultured rice cells.

We have previously shown that a human small GTPase Rac homolog, OsRac1, from rice (Oryza sativa) induces cascades of defense responses in rice plants and cultured cells. Sphingolipid elicitors (SEs) have been similarly shown to activate defense responses in rice. Therefore, to systematically analyze proteins whose expression levels are altered by OsRac1 and/or SE treatment, we performed a differential display analysis of proteins by the use of two-dimensional gel electrophoresis and mass spectrometry. A total of 271 proteins whose expression levels were altered by constitutively active (CA)-OsRac1 or SE were identified. Interestingly, of 100 proteins that were up-regulated by a SE, 87 were also induced by CA-OsRac1, suggesting that OsRac1 plays a pivotal role in defense responses induced by SE in cultured rice cells. In addition, CA-OsRac1 induces the expression of 119 proteins. Many proteins, such as pathogenesis-related proteins, SGT1, and prohibitin, which are known to be involved in the defense response, were found among these proteins. Proteins involved in redox regulation, chaperones such as heat shock proteins, BiP, and chaperonin 60, proteases and protease inhibitors, cytoskeletal proteins, subunits of proteasomes, and enzymes involved in the phenylpropanoid and ethylene biosynthesis pathways were found to be induced by CA-OsRac1 or SE. Results of our proteomic analysis revealed that OsRac1 is able to induce many proteins in various signaling and metabolic pathways and plays a predominant role in the defense response in cultured rice cells.

Cells, Cultured↗

PubMedDate not supplied

Amygdala and periaqueductal gray lesions only partially attenuate unconditional defensive responses in rats exposed to a cat.

Defensive responses to a cat were observed in rats given excitotoxic lesions of the central nucleus of the amygdala (ACe), dorsolateral periaqueductal gray (dlPAG), ventral periaqueductal gray (vPAG), or sham lesions. Rats were placed adjacent to a compartment containing a cat. Sham-lesioned rats avoided the area nearest the cat and preferred the area furthest away from the cat. They also exhibited numerous defensive responses including, climbing, escape from the apparatus, and freezing. Rats with lesions of the ACe reacted like the sham lesioned rats by preferring the area of the apparatus furthest from the cat, however they climbed and escaped significantly less than sham lesioned rats. Avoidance of the area adjacent to the cat was attenuated in rats with lesions of the vPAG. Climbing along the walls of the apparatus was also attenuated in rats with lesions of the vPAG. Escapes from the apparatus were not significantly reduced by lesions of the vPAG and dlPAG. Thus, ACe lesions attenuated climbing and eliminated escapes, but did not impair locomotion of the rat away from the cat.

Aggression↗

PubMed1984

Role of the hemigiant neurons in the crayfish defense response.

The medial and lateral hemigiant neurons of the crayfish were isolated in the circumesophageal connective and electrically stimulated to examine their ability to elicit a defense response. In contrast to previous reports, neither a defense response nor any other thoracic or abdominal movements were observed following stimulation of either hemigiant. Small fibers that lie adjacent to the hemigiants in the circumesophageal connective evoked defense responses when they were electrically stimulated. Two types of defense responses could be evoked by stimulation of small fibers.

Animals↗

PubMed1995

Inhibition of ascorbate peroxidase by salicylic acid and 2,6-dichloroisonicotinic acid, two inducers of plant defense responses.

In recent years, it has become apparent that salicylic acid (SA) plays an important role in plant defense responses to pathogen attack. Previous studies have suggested that one of SA's mechanisms of action is the inhibition of catalase, resulting in elevated levels of H2O2, which activate defense-related genes. Here we demonstrate that SA also inhibits ascorbate peroxoidase (APX), the other key enzyme for scavenging H2O2. The synthetic inducer of defense responses, 2,6-dichloroisonicotinic acid (INA), was also found to be an effective inhibitor of APX. In the presence of 750 microM ascorbic acid (AsA), substrate-dependent IC50 values of 78 microM and 95 microM were obtained for SA and INA, respectively. Furthermore, the ability of SA analogues to block APX activity correlated with their ability to induce defense-related genes in tobacco and enhance resistance to tobacco mosaic virus. Inhibition of APX by SA appears to be reversible, thus differing from the time-dependent, irreversible inactivation by suicide substrates such as p-aminophenol. In contrast to APX, the guaiacol-utilizing peroxidases, which participate in the synthesis and crosslinking of cell wall components as part of the defense response, are not inhibited by SA or INA. The inhibition of both catalase and APX, but not guaiacol peroxidases, supports the hypothesis that SA-induced defense responses are mediated, in part, through elevated H2O2 levels or coupled perturbations of the cellular redox state.

Ascorbate Peroxidases↗