Antiproliferative and antibiofilm potentials of endolichenic fungi associated with the lichen Nephroma laevigatum.

AIMS: The objective of this study was to explore the diversity of endolichenic fungi from Nephroma laevigatum and to investigate their antiproliferative and antibiofilm potential. METHODS AND RESULTS: Forty-six isolates were obtained and identified by DNA barcoding. They belonged to genera Nemania, Daldinia, Peziza and Coniochaeta. Six strains belonging to the most represented species were selected and tested for their antiproliferative and antibiofilm activities. Extracts were analysed by reversed-phase HPLC. Activities against fungal and bacterial biofilm were evaluated using tetrazolium salt (XTT) assay and crystal violet assay respectively. Antiproliferative responses of extracts were determined by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Apoptosis induction by two extracts was observed in two cell lines (HT-29 and PC-3) via morphological changes, pro-apoptotic and anti-apoptotic proteins analysis (Western blotting) and DNA fragmentation. Four extracts displayed activities against Candida albicans biofilm with IC50 values ranging from 25 to 200 µg ml-1 . All extracts were inactive against Staphylococcus aureus and Pseudomonas aeruginosa biofilms. The most active isolates against human colorectal (HT-29 and HCT116) and prostate (PC-3 and DU145) cancer cell lines were Nemania serpens (NL08) and Nemania aenea var. aureolatum (NL38) with IC50 values ranging from 13 to 39 µg ml-1 . These extracts induced an apoptotic process through activation of caspases 8 and 3, poly(ADP-ribose) polymerase cleavage and DNA fragmentation. CONCLUSIONS: Selected crude fungal extracts have antiproliferative and antibiofilm activities. Data suggest that this antipoliferative effect is due to apoptosis process. This is the first report showing the effects of endolichenic fungi from N. laevigatum. SIGNIFICANCE AND IMPACT OF THE STUDY: This study highlights the therapeutic potential of endolichenic fungi metabolites as sources for drug discovery programmes.

Candida albicans interaction with Gram-positive bacteria within interkingdom biofilms.

Candida albicans is a commensal of the human body and an opportunistic pathogen frequently responsible for nosocomial bloodstream infections. Most of these infections are linked to the development of a biofilm in or on implanted medical devices. C. albicans cells have the capacity to interact with bacteria within biofilms, especially by the way of chemical or metabolic indirect interactions and/or direct physical contacts involving specifically the yeast or hyphal form of the fungal cell, or more rarely involving both forms. According to the species, C. albicans-bacteria interactions can be antagonistic or synergistic, competitive or not. The polymicrobial nature of biofilms may deeply influence the physiopathology of infections as well as the efficiency of antimicrobial agents. The present review aims to focus on the current knowledge of interactions between C. albicans and major Gram-positive bacteria such as Staphylococcus aureus, coagulase negative Staphylococcus, Streptococcus spp. and Clostridium spp. within biofilms. A better understanding of this complicated, fast-paced world of multi-kingdom biofilms will contribute to develop new effective ways to fight biofilm-related infections.

Persistent STAT5 activation in myeloid neoplasms recruits p53 into gene regulation.

STAT (Signal Transducer and Activator of Transcription) transcription factors are constitutively activated in most hematopoietic cancers. We previously identified a target gene, LPP/miR-28 (LIM domain containing preferred translocation partner in lipoma), induced by constitutive activation of STAT5, but not by transient cytokine-activated STAT5. miR-28 exerts negative effects on thrombopoietin receptor signaling and platelet formation. Here, we demonstrate that, in transformed hematopoietic cells, STAT5 and p53 must be synergistically bound to chromatin for induction of LPP/miR-28 transcription. Genome-wide association studies show that both STAT5 and p53 are co-localized on the chromatin at 463 genomic positions in proximal promoters. Chromatin binding of p53 is dependent on persistent STAT5 activation at these proximal promoters. The transcriptional activity of selected promoters bound by STAT5 and p53 was significantly changed upon STAT5 or p53 inhibition. Abnormal expression of several STAT5-p53 target genes (LEP, ATP5J, GTF2A2, VEGFC, NPY1R and NPY5R) is frequently detected in platelets of myeloproliferative neoplasm (MPN) patients, but not in platelets from healthy controls. In conclusion, persistently active STAT5 can recruit normal p53, like in the case of MPN cells, but also p53 mutants, such as p53 M133K in human erythroleukemia cells, leading to pathologic gene expression that differs from canonical STAT5 or p53 transcriptional programs.

Effect of age and long-term stress experience on adaptation to stress analgesia in mature rats: role of opioids.

The effects of aging and previous long-term stress on development of tolerance to stress-induced analgesia were evaluated in male Sprague-Dawley rats exposed to intermittent cold water swims (ICWS) in 2 degrees C water (eighteen 10-s exposure, three/min) on 15 consecutive days. Analgesia was measured by the tail-flick test prior to and 30 min after ICWS. In young rats (4 months), tolerance developed faster and asymptotic tolerance was acquired sooner and was more complete than in older rats (15-16 months). Previous long-term exposure (but not the age at which it occurred) accelerated the development and acquisition of asymptotic tolerance to reexposure. Naltrexone (10 mg/kg, ip) partially and completely reversed tolerance to ICWS analgesia in 4- and 9-10-month-old rats, respectively, results suggesting that the opioids are involved in ICWS-analgesia tolerance in both young and old mature rats. In young animals, a second mechanism, naltrexone-insensitive, may be responsible for at least some of the differences in ICWS tolerance found between young and old mature adult rats.

Refinement of the alpha aminooleic acid bioprosthetic valve anticalcification technique.

BACKGROUND: Aminooleic acid treatment has been demonstrated to prevent porcine valve calcification and to protect valvular hemodynamic function. Initial enthusiasm was tempered by histologic studies of these AOA valves, which showed cuspal hematomas, structural loosening, and surface roughening. This prompted a systematic review of the AOA treatment process. Unsolubilized particles of alpha aminooleic acid present in the treatment solution were identified as the cause of mechanical abrasion of valve cusps during processing. These particles were eliminated with a revamped protocol, which included filtration of the AOA solution before valve preparation. METHODS: Porcine aortic valve cusps treated with this modified AOA protocol (AOA II) were studied in a rat subdermal implant model of mineralization. A juvenile sheep trial was then used to confirm the antimineralization effects of AOA II on glutaraldehyde-fixed porcine aortic roots in a circulatory model of accelerated calcification. RESULTS: Retrieved AOA II-treated cusps from the subdermal model were markedly less calcified than control cusps (AOA II, 1 +/- 0, 17 +/- 4, 23 +/- 6, and 17 +/- 10 versus control, 189 +/- 14, 251 +/- 16, 250 +/- 14, and 265 +/- 10 mg calcium/mg sample at 4, 8, 12, and 16 weeks, respectively; p < 0.0001). Morphologic examination of the AOA II cusps of the valves retrieved from the sheep demonstrated freedom from the structural loosening, surface roughening, and hematoma formation that had limited the utility of the original AOA preparation technique. Cusps from AOA II-treated porcine roots had significantly less calcium than control cusps (AOA II, 5.5 +/- 3.0 mg/g; control, 91.2 +/- 19.5 mg/g; p = 0.0004). The aortic walls had similar levels of calcification (AOA II, 156 +/- 73 mg/g; control, 159 +/- 10 mg/g; p = not significant). CONCLUSIONS: These data suggest that the modified AOA technique warrants further evaluation as an antimineralization treatment for glutaraldehyde-fixed porcine bioprostheses.

Peripheral mechanisms of olfactory discrimination of complex mixtures by the spiny lobster: no cell types for mixtures but different contributions of the cells to the across neuron patterns.

Toward understanding mechanisms of olfactory discrimination, we have examined the existence of cell types and the role of cells in the coding of odorant quality in the olfactory organ of the spiny lobster. The results consisted of responses of 30 antennular chemoreceptor cells to 8 behaviorally discriminable complex stimuli--4 natural extracts and 4 artificial mixtures, each at 3 concentrations. Multidimensional scaling and cluster analysis failed to identify unequivocal cell types, but rather suggested a continuum of cellular response profiles. The lack of cell types suggests that the code for the quality of natural odorants in this system is a population code. The distribution of cells along the response continuum was based on any of many features of their response profiles. The most effective stimulus (= best stimulus) and the least effective stimulus (= least stimulus), two features of the response profiles, could only partially explain the differences in response profiles of cells. Nonetheless, cells with different response profiles were shown to have different functions in odorant coding. Most cells contribute to some degree to the discrimination of any two stimuli, but a cell's contribution to the discrimination of two stimuli is usually disproportionally robust when those two stimuli produce very different responses in that cell.

Non-reciprocal cross-adaptation of spiking responses of individual olfactory receptor neurons of spiny lobsters: evidence for two excitatory transduction pathways.

Single-unit spiking responses of 72 olfactory receptor neurons (ORNs) in the olfactory organ of the spiny lobster Panulirus argus were recorded extracellularly during presentation of a set of seven odorant stimuli (adenosine-5'-monophosphate, ammonium chloride, betaine, L-cysteine, L-glutamate, D,L-succinate and taurine) and analyzed in order to evaluate the response specificities of single ORNs and the independence of receptor sites. Individual ORNs often had narrow excitatory response spectra, but the most excitatory compound was different from neuron to neuron. These results suggest that these compounds can exert most of their excitatory effects through relatively independent receptor site types. To determine the relative independence of excitatory transduction processes in single ORNs for these stimuli, single-unit spiking responses of these neurons under conditions of self- and cross-adaptation were analyzed. The results demonstrate extensive cross-adaptation between pairs of the seven stimuli. When averaged across all neurons and all cross-adaptation conditions, cross-adaptation resulted in a mean reduction of 81% of the unadapted response. However, there were differences in the degree and pattern of adaptation for different pairs of compounds and for different neuron types (defined by most excitatory or 'best' chemical). For a given neuron type, there were significant levels of non-reciprocal cross-adaptation: neurons cross-adapted more when adapted to their best chemical than when adapted to their non-best chemicals. These results suggest the existence of two excitatory transduction pathways within an olfactory receptor neuron: one pathway activated exclusively by the best chemical and a second pathway activated by a broader spectrum of chemicals.

Effects of stimulating the subcoeruleus-parabrachial region on the non-noxious and noxious responses of T1-T5 spinothalamic tract neurons in the primate.

The effects of electrical stimulation of the subcoeruleus-parabrachial (SC-PB) region on the discharge rate of upper thoracic spinothalamic tract (STT) neurons were investigated in 21 monkeys anesthetized with alpha-chloralose. STT cells were antidromically activated from the medial thalamus (MT) and the ventral posterior lateral nucleus (VPL) and received viscerosomatic convergent input from the cardiopulmonary sympathetic afferents and the left chest-forearm region. Stimulation of the SC-PB region inhibited the activity of all 30 STT neurons studied in the T1-T5 regions of the spinal cord. The minimum average current required to decrease the discharge rate of 22 cells exhibiting spontaneous activity was 89 +/- 10 microA (100 Hz, 100 microseconds duration). Currents as high as 300 microA completely inhibited the activity of most cells. Examination of the importance of frequency of stimulation from the SC-PB area on 8 cells revealed that impulses of at least 40 Hz (208 +/- 37 microA, 100 microseconds duration) were necessary to inhibit the spontaneous activity by 60%. Higher frequencies produced greater degrees of inhibition. Stimulation of the SC-PB region also inhibited the response of 23 of 23 neurons excited by noxious pinch and 11 of 11 wide dynamic range cells stimulated by innocuous input such as blowing or brushing hair. No differences in the inhibition produced by SC-PB stimulation on cells projecting to VPL (n = 20), MT (n = 5), or both VPL and MT (n = 5) were observed. These results demonstrate that the SC-PB region may be an important brainstem site for descending inhibition of both noxious and innocuous somatic input to upper thoracic STT cells in the primate.

A physiological and pharmacological analysis of the electrodermal response in the rat.

Electrodermal responses (EDR) of the sympathetic-cholinergic sudomotor system were elicited in the footpads of the hindpaws of anesthetized rats. The most reactive CNS loci were caudal to the region of the posterior hypothalamus. Peripherally evoked responses were elicited by electrical stimulation of the decentralized tibial nerve. The amplitude of these evoked EDR was stable over time and both the centrally and peripherally elicited responses were frequency-dependent. Atropine (200 micrograms/kg) depressed the EDR elicited by both peripheral and central stimulation whereas hexamethonium (20 mg/kg) only inhibited the central EDR. Clonidine had no effect on the EDR evoked at the periphery but produced a significant dose-dependent depressant effect on the centrally evoked EDR; this effect was partially antagonized by yohimbine (0.75 mg/kg). It is suggested that the rat is a suitable species for the use of the sudomotor system in the investigation of adrenergic agents which are thought to have a central sympatho-inhibitory action.

Cold water stress analgesia in rats: differential effects of naltrexone.

Cold water swim (CWS, 2 degrees C, 3.5 min) decreases the responsiveness to nociceptive stimuli in rats. The influence of various parameters of the CWS condition on stress-induced analgesia were evaluated by means of naltrexone effects. Naltrexone dose-dependently (but significantly only at high doses--21 mg/kg) partially antagonized 3.5 minute continuous CWS analgesia. Its effect was proportional to the duration of CWS. Naltrexone (14 mg/kg) significantly antagonized intermittent CWS-analgesia (18 10-sec exposures, 3/min) and enhanced the analgesia induced by 60 consecutive exposures (1 sec each, 12/min). These results demonstrate that naltrexone differentially affects CWS-analgesia, depending on specific parametric conditions of the stressor. In addition to activation of a non-specific naltrexone-insensitive analgesia-inducing system (not reduced by the drug in all the conditions studied) there appear to be three naltrexone sensitive systems: (1) a non-opioid analgesia-inducing system which mediates continuous CWS-analgesia; (2) an opioid analgesia-inducing system, involved in intermittent CWS-analgesia; and (3) a naltrexone-sensitive system which opposes the analgesic effect of 60 consecutive exposures. Thus, a highly specific relationship exists between certain parameters of the cold water stressor and the nature of the mechanisms which subserve the induced analgesia.

Amide cross-linking: an alternative to glutaraldehyde fixation.

BACKGROUND AND AIMS OF THE STUDY: A new fixation method for bioprosthetic tissues is being developed, which does not utilize the standard glutaraldehyde treatment. This method, referred to as Ultifix, uses a coupler and a coupling enhancer with or without one or more coupling agents. It fixes the tissue by linking the amine and the carboxyl moieties through amide bonds either directly, or indirectly when coupling agents form bridges. The amide bonds thus formed are more stable than the Schiff-base bonds formed by glutaraldehyde. All compounds used during the fixation process and their by-products are water-soluble, and are easily removed by washing. In addition, the by-products are not toxic, as opposed to glutaraldehyde, which induces toxic reactions after implantation. The tests described in the manuscript were specifically aimed at evaluating the cross-linking efficacy of the process on heart valve tissues, as well as their resistance to calcification in the rat model. METHODS: Porcine aortic roots and porcine pericardium were fixed using the coupling agents 1,6-hexane diamine (DIA) and suberic acid (SUA) in the presence of the coupler 1-ethyl-3(-3 dimethyl aminopropyl) carbodiimide hydrochloride (EDC) and the coupling enhancer N-hydroxysulfosuccinimide (sulfo-NHS). The tissues were then evaluated for their resistance to thermal denaturation, to enzymatic digestion, and to calcification when implanted subdermally in rats for two, four, eight and 16 weeks. RESULTS: The results demonstrate that the cusps and the wall of porcine aortic roots, and porcine pericardium, are as well stabilized and as cross-linked by Ultifix as they are by the standard glutaraldehyde method. In addition, the cusps of the porcine aortic root and the porcine pericardium, but not the wall of the porcine aortic root, calcify minimally and significantly less when implanted subdermally for up to 16 weeks in three week old rats than the control material fixed with glutaraldehyde. CONCLUSION: The Ultifix process of cross-linking bioprosthetic heart valves may thus be a good alternative to the standard glutaraldehyde process of fixation, with increased durability and without toxic effects.

A comparison between glutaraldehyde and diepoxide-fixed stentless porcine aortic valves: biochemical and mechanical characterization and resistance to mineralization.

As previously reported, we found that the fixation rate and thermal denaturation (shrink) temperature of the diepoxide-fixed tissue could be controlled by varying the concentration of the fixative as well as by adding alcohol and/or sodium chloride to the solution. In contrast to prior experience, however, we now found that the epoxide-fixed leaflets exhibited significantly higher resistance to mineralization compared to controls, but only when the tissue had not been exposed to phosphate ion.

Naltrexone antagonizes the biobehavioral adaptation to cold water stress in rats.

The reported studies on the development of tolerance to the analgesic effects of stress have been mostly concerned with the involvement of opioid or non-opioid substances in stress-induced analgesia (SIA). To further investigate the processes involved in SIA tolerance, rats were exposed to forced intermittent cold water swim (ICWS, 18 exposures, 3/min, 10 sec each) on 16 consecutive days. On days 15 and 16, they were injected prior to swim with saline and naltrexone (10 mg/kg), respectively. During swim, three types of readily identifiable behaviors were observed. They may be characterized by immobility and horizontal floating (Type I), intensive activity and escape attempts (Type II), and passivity and "behavioral despair" (Type III). In the acute condition, only Type II and Type III appear in sequence. In the chronic condition, the sequence of behaviors is: Type I, Type II, and Type III. Thirty minutes after swim, analgesia, core temperature, and degree of inactivity were measured. With chronic exposure, tolerance developed to the analgesia, core hypothermia and hypoactivity induced by the ICWS. Type I behavior appeared on day 3 or 4 and persisted throughout the chronic treatment. Type II behavior did not adapt. Naltrexone (10 mg/kg) antagonized the adaptive aspect of all those variables where adaptation or tolerance were found (analgesia, hypoactivity, core hypothermia, and Type I behavior) but had no effect on Type II behavior where no adaptation was observed. It is suggested that the endorphins have a functional role in the behavioral and and physiological adaptation to aversive stressful environmental situations.

Intermittent cold water stress-analgesia in rats: cross-tolerance to morphine.

Continuous cold water swim ( CCWS , 3.5 min, 2 degrees C) induces a non-opiate type of analgesia since 14 mg/kg of naltrexone or 20 mg/kg of naloxone only partially antagonize this stress-induced analgesia (SIA) and since there is no cross-tolerance between CCWS and morphine-analgesia. Intermittent cold water swim ( ICWS ) analgesia is significantly antagonized by naltrexone (14 mg/kg). These studies suggested that CCWS -analgesia is mediated by non-opioid systems, while ICWS -analgesia acts through a system that also mediates morphine analgesia. The hypothesis that ICWS -analgesia shares a common opioid pathway with morphine-analgesia, but not with CCWS -analgesia, was further tested by cross-tolerance studies in rats. The results showed a complete cross-tolerance to morphine analgesia in ICWS -tolerant animals,, but no cross-tolerance in animals. This suggests that morphine- and ICWS -analgesia partially share a common pathway, ICWS acting probably at levels "downstream" from the opiate-sensitive site, while CCWS induces analgesia by acting on a different system which is not mediated by opioids.

Effect of AOA on glutaraldehyde-fixed bioprosthetic heart valve cusps and walls: binding and calcification studies.

Alpha-aminooleic acid (AOA), a potent, non-toxic and biocompatible anticalcification agent, has been shown to be effective for glutaraldehyde-fixed valves in rat and juvenile sheep models, and is used for the treatment of Medtronic heart valve bioprostheses currently in clinical trials. In the pre-clinical sheep study of a stentless aortic root, the treatment with AOA prevented calcification of the cusps, but not of the wall. The experiments described in this manuscript were designed to investigate a possible relationship between the binding of AOA and the differential treatment efficacy in the cusp and the wall, and to improve the anticalcification effect of the AOA treatment in the wall. Glutaraldehyde-fixed porcine roots were treated with [14C]-AOA for binding studies, and with non-radioactive AOA for calcification studies for rat subdermal implants. The results indicate that a) the AOA treatment did reduce wall calcification, but only temporarily, b) the low efficacy of the AOA treatment on the wall was probably due to the limited penetration of AOA, and c) increasing the volume of the AOA solution during treatment significantly increased the content of AOA in the wall, and significantly decreased wall calcification. This study suggests that AOA efficacy in the wall may be hindered because of the physical characteristics of the wall, and that wall calcification may be prevented by developing methods aimed at increasing AOA penetration into the wall.

[Diagnosis of malnutrition in the elderly by dual energy absorptiometry]. / Diagnostic de la dénutrition chez les personnes âgées par l'absorptiométrie biénergétique.

OBJECTIVES: Denutrition is a frequent condition in elderly persons and may have major consequences. A noninvasive investigation, whole body dual energy X-ray absorptiometry, should allow, by direct measurement of body composition, early and reliable diagnosis of denutrition. This study was conducted to elaborate a diagnostic tool using this exam and to test its validity. PATIENTS AND METHODS: A global index of denutrition was proposed combining anthropometric, biological criteria, and the Mini Nutritional Assessment scale. Two agreement analyses were made between classical diagnostic criteria of nutritional status and body fat and fat free mass assessed by anthropometry and absorptiometry. An association between nutritional status and body absorptiometric composition were studied with univariate analysis followed by a multivariate logistic regression model. This model allowed an elaboration of a nutritional absorptiometric index (NAI). RESULTS: One hundred one elderly subjects were included. Twenty-three were considered to be in a state of denutrition. Agreement was poor between anthropometric and biological diagnostic criteria of denutrition. It was good between the different masses assess by anthropometry and absorptiometry. Subjects in a state of denutrition had significantly lower body fat and lower fat free mass. The fat free mass index (fat free mass divided by the square height) and body fat were entered into a logistic model and composed the NAI, which showed good diagnostic validity in terms of specificity and sensitivity. DISCUSSION: Absorptiometry appears to be a simple reliable diagnostic tool for assessing denutrition in elderly persons in routine practice. Further studies are required and should lead to a confirmation of the interest of these absorptiometric indexes.

Neural coding of quality of complex olfactory stimuli in lobsters.

1. Extracellular responses to complex biologically relevant stimuli were recorded from 30 primary olfactory cells from excised antennules of spiny lobsters. The stimulus types were natural extracts of crab, mullet, oyster, and shrimp and artificial mixtures of crab, mullet, oyster and shrimp based on the chemical composition of the related extracts. All stimulus types were presented at the following three concentrations: 0.005, 0.05, and 0.5 mM. 2. The responses were expressed as number of spikes per 5 s. Response magnitude increased significantly as a function of concentration. It was significantly greater for the natural extracts than for the related artificial mixtures but was not significantly different among stimulus types within either natural extracts or artificial mixtures. 3. The cells were broadly tuned to all stimuli. Tuning slightly, but significantly, broadened as a function of stimulus concentration. 4. Multidimensional scaling (MDS) was used to evaluate similarities and dissimilarities among stimuli based on population responses. The artificial mixtures and the natural extracts were analyzed separately. Dimensionality of spatial configuration was based on the following three criteria: stress values, squared correlation values, and relevance to quality coding. 5. When applied to the original data, MDS distributed the stimuli in a two-dimensional space where the location of each stimulus was based mainly on stimulus concentration. The results of a simple standardization procedure showed that this distribution resulted mostly from the significant effect of concentration on one of the two features of population responses, which is the absolute magnitude. This standardization procedure equalized the three concentrations in terms of absolute magnitude of evoked response. Consequently, the neural population responses of the 12 stimuli (4 types X 3 concentrations) could be compared based only on their across-neuron patterns (ANPs) (relative amount of activity across neurons). 6. When stress and squared correlation values were used as criteria for dimensionality, the configuration of the artificial mixtures space was best derived from dimensions 1, 2, and 3 of the three-dimensional resolution. When relevance to quality coding was used, the configuration of the artificial mixtures space was best derived from dimensions 1, 3, and 4 of the four-dimensional resolution. Whether stress and squared correlation values or relevance to quality coding were used, the four types of stimuli occupied nonoverlapping spaces.(ABSTRACT TRUNCATED AT 400 WORDS)

Chronic stress, aging and morphine analgesia: chronic stress affects the reactivity to morphine in young mature but not old rats.

The effect of chronic stress on analgesic responsiveness to morphine was studied in mature rats of different ages. Chronic stress consisted of eighteen 10-sec exposures (three/min) in 2 degrees C water for 54 consecutive days. From day 20, at 4-day intervals, the rats were not stressed but instead given i.p. injections of, sequentially: 10, 0 (saline), 5, (2 mg/kg of naltrexone) + 10, 2.5, 1, 20 and 10 mg/kg of morphine sulfate. On these days, tail-flick latencies were measured before and 5, 10, 15, 30, 60, 120 and 180 min after morphine injection. The responsiveness to morphine was significantly altered by exposure to chronic stress in young, mature rats (4 months) as compared to control rats. A dose of 10 mg/kg of morphine induced a diphasic response. Initial increased tail-flick reflexes (at 5 min after injection) were followed by slight but nonsignificant decreased responses to the tail-flick test. At 30 min, the dose-response curve was shifted to the right. No alteration of the response to morphine was observed in older rats (15-17 months) exposed to chronic stress, unless they had been submitted to chronic stress at 4 months of age. In addition, the response after a second exposure to chronic stress to morphine was highly dependent on, and similar to, the age-dependent response after a first exposure. These results demonstrate that the endogenous opiate system can be altered by exposure to chronic stress even after maturation has occurred and that this alteration has long-term effects on the reactivity to morphine.

Independent components of the neural population response for discrimination of quality and intensity of chemical stimuli.

The responses of a population of 30 olfactory receptor cells from spiny lobsters to 8 behaviorally relevant complex types of stimuli at 0.005, 0.05 and 0.5 mM were analyzed using multidimensional scaling to evaluate their potential for coding quality and intensity. A discrimination index was derived from the resulting stimulus coordinates, which takes into account the response similarities within type/concentration and the response dissimilarities between types/concentrations. The results indicate that quality and intensity can be discriminated by separate components of the response of the population of neurons: quality by the pattern of responses produced across the neuronal population, and intensity by the absolute response magnitude.

Effects of intracardiac bradykinin on T2-T5 medial spinothalamic cells.

Effects of injecting bradykinin (2 micrograms/kg) into the left atrium on spinothalamic tract neurons projecting to medial thalamus (M-STT cells), to the ventral posterior lateral nucleus of the thalamus (L-STT cells), or to both (LM-STT cells) were examined in 18 monkeys (Macaca fascicularis) anesthetized with alpha-chloralose. Bradykinin increased cell activity in 11/16 M-STT cells, 10/15 L-STT cells, and 4/7 LM-STT cells. One M-STT cell was inhibited. Peak responses to bradykinin of the three cell groups were not different. LM-STT cells began to respond and reached peak responses slightly earlier than the other two groups. Six M-STT, four L-STT, and two LM-STT cells became entrained to the cardiac cycle during their responses to bradykinin. Responses to bradykinin were not dependent on the type of somatic input or cell location. Responding cells most often received A delta- and C-fiber sympathetic input, but some responding cells had only A delta-input. These results demonstrate that in addition to L-STT cells STT cells projecting to the medial thalamus respond to a potentially noxious cardiac stimulus. These cells may participate in the motivational-affective component of cardiac pain.