Is 10 min post heparin bolus ACT, alongside aPTT monitoring, predictive for CRRT filter survival?

OBJECTIVE

When using heparin anticoagulation for continuous renal replacement therapy (CRRT), the main challenge is to tailor the dosage to patient response. This study aimed to determine if the first activated thromboplastin time (aPTT) (measured after 3 hours post heparin bolus) can be a predictor for CRRT filter survival and if the first activated clotting time-low range (ACT-LR) (10 min post heparin bolus) can be predictive for subtherapeutic or therapeutic first aPTT.

MATERIALS AND METHODS

An unfractionated heparin (UF) anticoagulation protocol was used in CRRT and heparin monitoring was performed by aPTT and ACT-LR. Extracorporeal therapy was analyzed and filter survival was assessed for general risk factors, especially coagulation tests. For statistical analysis, Logrank tests, ROC curve analysis, and the Kaplan-Meier chart for survival evaluations were utilized.

RESULTS

Using the pLogrank test, the overall survival for the CRRT procedure was 47.8 hours (p=0.04), and no clotting events occurred during the first 12 hours for all examined therapies. Multivariate analysis for filter survival prediction to estimate 48 hours of CRRT revealed statistical relevance for Age (<60 years), BMI (<25.9), and INR (>1.3), with negative statistical significance for lipids, triglycerides, and fibrinogen. aPTT (180 min) values greater than 57 sec were shown to be predictive of 48-hour filter survival, and similar findings were obtained for aPTT measured at 6 hours. ACT-LR samples assessed 10 minutes after the initial heparin bolus was shown to be predictive of 48-hour filter survival (cutoff > 218 sec; p=0.04). When ACT prediction potential for therapeutic aPTT values was evaluated, ACT-LR 10 min (cut off > 200 sec.), ACT-LR 60 min (cut off > 186 sec.), and ACT-LR 180 min (cut off > 182 sec.) were found to be predictive.

CONCLUSIONS

Based on this study and its sample size, ACT-LR can be a complimentary assessment to aPTT for monitoring anticoagulation with heparin on CRRT.

Could diastolic perfomance parameters be earlier markers for cardiotoxicity in high risk cancer patients?

Introduction

Survival after chemotherapy in cancer patients can be affected by several factors, including cardiotoxicity. Identification of high-risk patients and early diagnosis of cardiotoxicity would allow preventive therapies that would mitigate its effect. Although troponin I (hsTnI) and NT-proBNP have shown their usefulness, there still is incomplete data regarding the time and frequency of their testing.

Aims

The goal of our study was to identify new diagnostic biomarkers for early diagnosis of cardiotoxicity and analyze their predictive value for outcome.

Methods

We included 68 female patients with breast cancer treated with trastuzumab, who underwent clinical, biological and echocardiographic evaluation and signed informed consent. We performed biomarker testing (NT-proBNP, hsTnI, Gal 3 and GDF-15) and echocardiography at inclusion and on the day of the first chemotherapy course (after trastuzumab was administered).The patients was follow for 1 years and cardiovascular events was noted.

Results

The study group included middle-aged women (34.5±8.4). Although changes in the biomarker levels after the first chemotherapy course were found, these were not statistically significant. The more interesting aspect is that we found some markers increased (NTproBNP 11.12±2.9 vs 16.25±3.17, p=0.12, hsTnI 147.75±32.88 vs 151.09±34.67, p=0.74,) while other decreased (Gal-3 2300.92±982.26 vs 2193.53±377.69, p=0.78, GDF-15- 1014.09±1689 vs 1006±1662, p=0.76). Echocardiography showed no significant differences in systolic performance parameters – ejection fraction (EF) and global longitudinal strain (GLS) – but a significant change in left ventricular end-diastolic filling pressure (LVEDP) estimated by the e/e' ratio (5.68±5.63 vs 10.05±4.42, p=0.000. The LVEDP increase was correlated to NTproBNp (r=0.712, p=0.000) and Gal3 (r=0.44, p=0.009) variability. Univariate analysis showed that only NTproBNP variability predicts 16.3% of the LVEDP variability between the two moments, but the NTproBNP and LVEDP could predict the cardiovascular events during the 1-year follow-up.

Conclusion

Changes in diastolic performance – e/e' ratio – occur early after chemotherapy and correlate with the variability of serum natriuretic peptides.

Funding Acknowledgement

Type of funding source: Public grant(s) – EU funding. Main funding source(s): Partnership for the transfer of knowledge in biogenomics applications in oncology and related fields - BIOGENONCO, Project co-financed by FEDR through Competitiveness Operational Programme 2014–2020, contract no. 10/01.09.2016.

Assessing Suffering in Experimental Pain Models

Abstract. Although suffering is a central issue in pain, there is only little research on this topic. The aim of this study was to assess suffering in an experimental context using various stimulation methods and durations, and to examine which psychological or psychophysiological measures covary with pain-related suffering. Twenty-one healthy volunteers participated in two experiments in which we used tonic thermal and phasic electric stimuli with short and long stimulus durations. The participants rated pain intensity, unpleasantness, and pain-related suffering on separate visual analog scales (VAS) and completed the Pictorial Representation of Illness and Self Measure (PRISM), originally developed to assess suffering in chronic illness. We measured heart rate, skin conductance responses (SCRs), and the electromyogram (EMG) of the musculus corrugator supercilii. For both heat and electric pain, we obtained high ratings on the suffering scale confirming that suffering can be evoked in experimental pain conditions. Whereas pain intensity and unpleasantness were highly correlated, both scales were less highly related to suffering, indicating that suffering is distinct from pain intensity and unpleasantness. Higher suffering ratings were associated with more pronounced fear of pain and increased private self-consciousness. Pain-related suffering was also related to high resting heart rate, increased SCR, and decreased EMG during painful stimulation. These results offer an approach to the assessment of suffering in an experimental setting using thermal and electric pain stimulation and shed light on its psychological and psychophysiological correlates.

The impact of 0.5% chlorhexidine oral decontamination on the prevalence of colonization and respiratory tract infection in mechanically ventilated patients. Preliminary study

AIMS

To determine the effect of Chlorhexidine (CHX) 0.5% oral decontamination on the incidence of colonization/infection of lower respiratory tract in critically ill mechanically ventilated patients.

METHODS

The study was conducted in the multidisciplinary ICU. 30 patients, mechanically ventilated for at least 48 hours, were included. The oral care was performed every 6 hours (6 h CHX group) or 12 hours (12 h CHX group). Tracheal samples were collected every day and the mucosal plaque score (MPS) was also assessed.

RESULTS

The MPS score averages were between 3.8 and 6 in the 6 hours CHX group and between 3.6 and 5 in the 12 hours CHX group. There was no positive association between MPS score and frequency of CHX decontamination (p= 0.898). For 60% of patients in 6 h CHX group and for 40% of patients in 12 h CHX group, colonization did not develop until leaving the study. No significant difference were found between groups with respect to frequency of colonization based on its time of onset (p= 0.523). There is a relationship between the isolation of MRSA and CHX oral decontamination at 12 hours (<phi c =0.392, p=0.032).

CONCLUSIONS

In our preliminary study, no signifficant differences were found between 6 or 12 hour CHX oral decontamination with respect to MPS score and colonization. However, MRSA is vulnerable to 6 hours CHX decontamination. Larger sample size studies are required to determine the efficacy of CHX in the prevention of colonization or respiratory tract infections in mechanically ventilated patients.

Arterial compliance in hypertension and heart failure

The purpose of this paper is to investigate the relation between the presence and degree of arterial compliance impairment and, respectively, the clinical conditions of systemic hypertension and/or heart failure. We investigated 19 patients with hypertension, without heart failure (group A), 13 patients with hypertension and heart failure class NYHA II (group B), 10 patients with coronary heart disease and heart failure class NYHA II (group C) and 7 control patients without clinically relevant cardio-vascular diseases (group D). Compliance was evaluated with a Complior device, by measuring carotid femoral and carotid-radial pulse-wave velocities (PWV). Carotid-radial PWV did not differ significantly between the various groups (10.8 +/- 2, 10.6 +/- 0.9, 9.5 +/- 1.5 and 9.9 +/- 1.6 m/s, for groups A, B, C and D, respectively). Carotid-femoral PWV, in group A hypertensive p without heart failure, was 13.1 +/- 2.9 m/s, significantly higher as compared to group C p with coronary heart disease and heart failure (10.5 +/- 2.4 m/s, p = 0.02), as well as compared to group D controls (9.8 +/- 2.6, p = 0.02). Group B p, with heart failure associated to hypertension, had a carotid-femoral PWV of 13.5 +/- 3.9 m/s, similar to the one found in group A hypertensive p without heart failure. When comparing groups B and C p with heart failure, we noted that the carotid-femoral PWV was significantly (p = 0.04) increased in hypertensive p, as compared to those with coronary heart disease. In conclusion, the results of our study confirm the impairment of arterial compliance, in hypertensive patients. The carotid-femoral, but not the carotid-radial PWV, were useful for identifying impaired compliance in these patients. Heart failure, associated to hypertension, was not accompanied by a supplemental deterioration of arterial compliance. In fact, our study could not confirm the decrease of arterial compliance, in heart failure patients, as compared to controls. This study suggests the importance of hypertension, with its structural arterial wall changes, in the genesis of arterial compliance impairment.

Interferon alpha treatment of chronic hepatitis C in HIV-infected patients receiving zidovudine: efficacy, tolerance and response related factors

BACKGROUND/AIMS

In our area most of the human immunodeficiency virus (HIV) infected patients are intravenous drug users; HIV and hepatitis C virus infections often coexist in these patients. Due to the repercussions of both infections, we designed a trial to evaluate the efficacy, response-related factors and tolerance during an eight-month regime of recombinant interferon alpha-2b on hepatitis C virus infection.

METHODOLOGY

We included 79 patients in an open, prospective and multicentric trial with zidovudine and interferon alpha-2b. Response to interferon treatment was evaluated by biochemical and histopathological criteria.

RESULTS

A complete response (alanine aminotransferase normalization) was obtained in 57.4% of patients. The significant response-related factors were: degree of histopathological activity, CD4+ cell number and initial leukocyte number.

CONCLUSIONS

Recombinant interferon therapy seems to be effective for chronic hepatitis C in HIV infected patients; the best response was in those with active chronic hepatitis and CD4+ cell counts > or = 200/mm3. General tolerance was variable, although side effects were not different from those seen in non-HIV patients. The most common side effect was flu-like syndrome (constitutional manifestations), with no interference on treatment continuity; however, hematological toxicity prevents the indiscriminate use of interferon.

A comparative study of mast cells and eosinophil leukocytes in the mammalian testis

The existence of a physiological integration between the immune and endocrine systems has long been recognized. In spite of the abundant literature data on the presence of cells of the immune system in the testis, mast cells and eosinophil leukocytes have received little attention. We have studied the presence, distribution and numbers of mast cells and eosinophils in the testes of 12 mammalian species. Mast cells were frequently found in equine (stallion, ass and mule) and human testis, whereas eosinophils were nearly absent. On the contrary, eosinophils were abundant in the hare testis, while mast cells were lacking. Both cells types were present in high numbers in swine (wild and domestic boar) testis. Otherwise, mast cells and eosinophils were absent from the testicular parenchyma of several species (rat, dog, cat, bull and deer), although they were present, in most cases, around blood vessels in the tunica albuginea. The presence of high numbers of mast cells and/or eosinophil leukocytes in the testicular parenchyma of some species suggest a role for these cells in local regulatory pathways.

Psychoneuroimmunological correlates of persisting sciatic pain in patients who underwent discectomy

Patients suffering from persisting sciatic pain 8 weeks following discectomy were compared with patients displaying low complaints and healthy, pain-free volunteers regarding their interleukin-6 (IL-6) levels, morning cortisol levels and degree of psychological distress. Whereas serum concentrations of IL-6 were measured by collecting blood samples between 0945 and 2400 h in intervals of 45 min, morning cortisol levels were obtained by sampling saliva on five ensuing measurements, beginning immediately after awakening. In addition, questionnaires aimed at measuring depressive mood, somatic symptoms, coping and chronic stress were filled out by the subjects. The patients with ongoing pain displayed significantly elevated IL-6 levels and an attenuated elevation of cortisol secretion after awakening compared to the two other groups. Patients with persisting pain were also suffering more frequently from depressive mood and ongoing work-related strains. In addition, maladaptive coping strategies were favoured by these patients. The presented data support the hypothesis that the persistence of pain in many of the concerned patients may significantly be related to dysfunctional reciprocal relations between neural, endocrine and immune function.

Vaccination against hepatitis B virus in Spain: a cost-effectiveness analysis

A cost-effectiveness analysis was made to determine the effectiveness of the following strategies of mass immunization with the new recombinant vaccine against the hepatitis B virus in Spain: vaccination of adolescents, newborns, both populations, and vaccination plus passive immunization of newborns of HBsAg positive mothers. Decision trees supported on Markov models with Monte Carlo simulation have been used for the calculation of costs of the disease, and a mathematical model of differential equations was used for the simulation of the potential effectiveness of vaccination. The costs considered were those associated with the vaccination and travel of subjects, diagnosis, and treatment of the disease. The results are presented as additional cost or saving per case of infection prevented. In all assumptions, results showed that the most effective strategy for mass vaccination was the combination of vaccinating all adolescents together with active and passive immunization of children born to HBsAg positive mothers.

Morphine, 5-HT2 and 5-HT3 receptor antagonists reduce c-fos expression in the trigeminal nuclear complex following noxious chemical stimulation of the rat nasal mucosa

Noxious chemical stimulation of the rat nasal mucosa induces the expression of the immediate early gene c-fos in trigeminal brainstem neurons. In the present study, we applied the irritant mustard oil (1%) into the left nostril of urethane anesthetized rats. Immunohistochemical methods were used to evaluate the expression of Fos protein in the trigeminal subnuclei interpolaris and caudalis and to test the effects of putative analgesics that might depress synaptic transmission in neurons related to nociception. For this purpose, morphine (3 mg/kg and 10 mg/kg), the 5-HT2 antagonist ketanserin (0.5 mg/kg and 5 mg/kg) and the 5-HT3 antagonist ICS 205-930 (0.1 mg/kg and 1 mg/kg) were administered intravenously prior to noxious stimulation. Pretreatment with any of the three compounds reduced Fos-like immunoreactivity. The effect of morphine was reversible with naloxone. The reduction of the expression of Fos-like immunoreactivity by exogenous morphine speaks in favour of an opioidergic link in the modulation of orofacial pain in the trigeminal nuclei. The effects of the 5-HT receptor antagonists are most likely mediated via 5-HT2 and 5-HT3 receptors located on primary afferent fibres.

Induction of c-Jun and suppression of CREB transcription factor proteins in axotomized neurons of substantia nigra and covariation with tyrosine hydroxylase

In adult rats, the expression of transcription factor proteins c-Jun and CREB and their colocalization with tyrosine hydroxylase (TH) were investigated in neurons of the substantia nigra compacta (SNC) axotomized by stereotaxic unilateral transection of the medial forebrain bundle (MFB). Axotomized SNC neurons were identified by injection of the retrograde tracer horseradish-peroxidase-coupled-gold (HRP-gold) into the ipsilateral striatum 5 days prior to MFB transection. Nuclear c-Jun immunoreactivity (IR) appeared 36 h after MFB transection in SNC neurons, was maximal after 5 days, and declined after 10 days. c-Jun-IR was visible in HRP-gold-labeled SNC neurons, demonstrating that c-Jun is in fact expressed in axotomized neurons. The constitutively expressed CREB (calcium/cAMP response element-binding protein, syn. CREB-1) was present in apparently all neuronal and glial cells in the brains of untreated rats including those SNC neurons that coexpressed TH. Three days following MFB transection, the nuclear CREB-IR disappeared in the axotomized SNC neurons labeled by TH-IR and was almost completely absent after 20 days in this neuronal population. The TH-IR rapidly declined 5 days after MFB transection, and 10 and 100 days post-axotomy the number of TH-labeled neurons was reduced by 52 and 80%, respectively. During this period, the majority of surviving TH positive neurons coexpressed c-Jun but were immunonegative for CREB. Between 3 and 60 days following MFB transection, the number of CREB-labeled glial cell nuclei increased in the ipsilateral substantia nigra by about 80%. Concomitantly, expression of GFAP, a marker protein for astrocytes, was also enhanced whereas nuclear c-Jun-, JunD-, and c-Fos-IR did not change in glial cells. These findings demonstrate that c-Jun can be expressed in axotomized neurons during the absence of CREB and suggest a role of c-Jun in the transcriptional control of the TH gene.

Responses of rat medullary dorsal horn neurons following intranasal noxious chemical stimulation: effects of stimulus intensity, duration, and interstimulus interval

1. Most quantitative examinations of nociception are performed with thermal or mechanical stimuli. Because nociceptive processing mechanisms may depend on the modality of the stimuli, comparable studies on chemonociception are necessary. 2. We examined the activity of chemonociceptive medullary dorsal horn neurons in halothane-anesthetized rats. For controlled noxious chemical stimulation, defined CO2 pulses were applied to the nasal mucosa. The effects of stimulus intensity, duration, and interstimulus interval (ISI) were tested by performing three different CO2 stimulation protocols (see below). 3. The recorded neurons were characterized by intranasal and facial stimuli of different modalities. The cells received input from intranasal A delta- and/or C-fibers. All tested neurons also responded to other intranasally applied irritants, e.g., mustard oil. Furthermore, the units were sensitive to intranasal high-threshold mechanical stimulation and to facial mechanical stimulation. According to the properties of their facial mechanoreceptive fields, the units were classified as wide dynamic range (WDR) or nociceptive specific (NS) neurons. The majority of the cells also responded to facially applied noxious heat stimuli, so that most of the recorded neurons were found to be multimodal. Some of the neurons, in addition, had convergent input from primary afferents innervating the maxillary tooth pulps or the cornea and periorbital structures. 4. In the first stimulation protocol we presented four different CO2 concentrations (25, 50, 75, and 100%; stimulus duration 2 s). In total, each concentration was applied 10 times (2 trains of 5 stimuli). Stimulus response functions (SRFs) were computed with average responses to identical stimuli. All but 2 of the 23 tested neurons displayed enhanced responses after stimulation with increasing intensities. In general, WDR cells (n = 15) discharged more vigorously to the same CO2 concentration than NS cells (n = 8). WDR neurons discriminated more reliably between stimulus intensities in the low to moderate range (25-50% CO2) than NS cells. Both categories of neurons, however, discriminated equally well in the moderate- to high-intensity range (50-75% CO2). The discriminatory capacity of WDR and NS neurons was reduced in the highest concentration range (75-100% CO2). The proportion of NS neurons significantly discriminating between these intensities tended to be higher compared with WDR neurons when stimuli were applied with long ISIs (120 s). 5. To examine the effects of the duration of the ISI, identical test sequences were performed with ISIs of 30 and 120 s. (ABSTRACT TRUNCATED AT 400 WORDS)

N-substituted pyrazino[2,3-c][1,2,6]thiadiazine 2,2-dioxides. A new class of diuretics

The synthesis and evaluation of a new class of diuretic agents derived from the pyrazino[2,3-c][1,2,6]thiadiazine 2,2-dioxide ring system are described. Preliminary structure-activity relationships indicate that the nature and location of the substituents at different positions of the heterocycle are crucial for activity. Thus, a novel synthetic methodology has been developed to selectively introduce the desired substituents at different positions. From the study of the pharmacological properties (dose-response curves, duration of action, and acute toxicity) of the most active compounds, 4-amino-1,7-diethyl-6-methylpyrazino[2,3-c][1,2,6]thiadiazine++ + 2,2-dioxide (9) was selected for further investigation. Compound 9 (C10H15N5O2S) crystallizes in space group P21/a with unit cell dimensions a = 16.482 (1), b = 9.3484 (3), c = 8.333 (3) A, beta = 103.003 (3) degrees, Z = 4.

Protons selectively induce lasting excitation and sensitization to mechanical stimulation of nociceptors in rat skin, in vitro

In ischemic and in inflamed tissues, pH levels down to 5.4 have been measured, and this local acidosis may contribute to pain and hyperalgesia in disease states. To evaluate the role of acid pH in nociception, we have studied identified primary afferents in a rat skin-saphenous nerve preparation in vitro where the receptive fields can be superfused at the highly permeable corium side with controlled solutions. The nerve endings were exposed to CO2-saturated synthetic interstitial fluid (SIF;pH 6.1) and to carbogen-gassed SIF phosphate buffered to different acid pH levels (5 min duration, 10 min intervals). Mechanical thresholds were repeatedly tested in a "blind" fashion by von Frey hair stimulation. Low-threshold mechanosensitive A beta- (n = 12) and A delta-fibers (n = 11) were not excited or sensitized by acid pH levels. In 24 of 96 nociceptor type C- and A delta-fibers, irregular low-frequency discharge with poor response characteristics was induced. However, a distinct subpopulation of mechanoheat sensitive, "polymodal" C-units (n = 25; 38%) showed stimulus-related responses increasing with proton concentration and encoding the time course of the pH change. Threshold levels were found to range from pH 6.9 to 6.1; mean maximum discharge was at pH 5.2. All such fibers responded to CO2 as well as to phosphate-buffered solution at the same pH 6.1. The CO2 responses, however, displayed significantly shorter latencies and more pronounced dynamic phases. The carboanhydrase blocker acetazolamide markedly delayed and reduced the CO2 responses. Prolonged application of acid pH (30 min) evoked nonadapting activity irrespective of oxygen supply. Many, but certainly not all, fibers sensitive to protons were also driven by capsaicin (10(-6) M, 10(-5) M) and vice versa. Repeated or prolonged treatment with low pH induced a significant and lasting decrease of the mechanical (von Frey) thresholds in almost all C-fibers tested (from 35 to 16 mN, on average), and this occurred whether or not a fiber was excited by protons. The sensitizing effect was more pronounced the higher the initial von Frey thresholds (0.75 rank correlation). This sensitization to mechanical stimulation was in contrast to the combined action of other inflammatory mediators, bradykinin, 5-HT, histamine and prostaglandin E2. In conclusion, we suggest that pH sensitivity of nociceptors may be an important source of pain and hyperalgesia.

Controlled noxious chemical stimulation: responses of rat trigeminal brainstem neurones to CO2 pulses applied to the nasal mucosa

The nasal mucosa of halothane-anesthetized rats was stimulated with defined CO2 pulses. Recordings were performed from single trigeminal brainstem neurons to characterize their responses to this controlled chemical irritation. All cells examined with this stimulus displayed graded discharges to increasing concentrations of CO2. Enhanced responses were obtained in a group of neurons when the duration of the interstimulus interval was increased. The application of chemical irritants, notably mustard oil or acetic acid induced vigorous ongoing discharges in all cells tested. The CO2 stimulation method described here thus provides an ideal model for the quantitative physiological and pharmacological examination of chemically induced nociception.

c-FOS-like immunoreactivity in rat brainstem neurons following noxious chemical stimulation of the nasal mucosa

It has previously been shown that noxious and non-noxious peripheral stimuli induce c-fos expression in spinal dorsal horn neurons. In the present study we have examined the expression of c-fos in brainstem neurons following noxious chemical stimulation of the respiratory region of the nasal mucosa. In urethane-anaesthetized rats we injected mustard oil or applied CO2 pulses to the right nasal cavity. In control animals we applied paraffin oil or a continuous flow of air. A further group of control animals was anaesthetized and not subjected to any experimental treatment. Two hours after the first stimulus the rats were perfused with 4% phosphate-buffered paraformaldehyde. Brainstem sections were incubated with primary antiserum against the FOS protein and processed according to the ABC method. Only the mustard oil-treated rats had obvious signs of rhinitis and displayed FOS-positive cells in laminae I and II of the subnucleus caudalis and in the subnucleus interpolaris of the trigeminal brainstem nuclear complex as well as in the medullary lateral reticular nucleus. These areas are known to be involved in the processing of nociceptive information. Although CO2 pulses applied to the nasal mucosa are known to evoke pain sensations in man we did not observe any FOS-positive neurons in trigeminal and reticular brainstem areas of CO2-treated rats. This lack of c-fos expression probably results from the fact that unlike mustard oil, CO2 did not induce any apparent inflammatory reactions. In all animals c-fos expression was found in the nucleus of the solitary tract and in the area postrema. Staining in these areas might partly result from factors related to anaesthesia, changed respiration parameters and stress. Since the mustard oil-treated rats displayed the highest levels of immunoreactivity in the nucleus of the solitary tract and in the area postrema, additional effects specifically related to nociceptive input are very likely.

Central projections of trigeminal primary afferents innervating the nasal mucosa: a horseradish peroxidase study in the rat

The respiratory region of the nasal mucosa is innervated by the ethmoidal nerve. Chemical nociceptive stimulation of this area leads to upper airway reflexes that prevent access of noxious substances to the respiratory tract and the lungs. In the present study we examined the localization of the cell bodies of the respective primary afferent fibres within the trigeminal ganglion, as well as their central projections. In 25 rats a horseradish peroxidase-wheat germ agglutinin gel was applied to the right nasal cavity. The animals were killed after 48-72 h. For visualization of the tracer the tissue was processed according to the tetramethylbenzidine method. In the trigeminal ganglion almost all labelled cell bodies were localized in a medial band immediately caudal to the entrance of the ophthalmomaxillary branch. Transganglionic projections to the trigeminal brainstem nuclear complex were only localized in the superficial laminae of the subnucleus caudalis and in the subnucleus interpolaris, areas known to be involved in processing of nociceptive information. An additional labelled terminal field was observed in the interstitial subnucleus of the nucleus tractus solitarius, which is involved in respiratory control. These results are in favour of the hypothesis that the ethmoidal nerve in rat constitutes the afferent limb of protective upper airway reflexes since it transmits mainly nociceptive information.

Tubular sodium handling in cirrhotic patients with ascites as analysed by the renal lithium clearance method

The proximal and distal sodium reabsorption were calculated from lithium clearance in 21 healthy controls and 24 cirrhotic patients with ascites after 4 days under a sodium-restricted diet. The values of fractional lithium clearance were lower in patients than in controls (7.37 +/- 0.87 vs. 18.13 +/- 1.76%, P less than 0.001). Fractional proximal sodium reabsorption was increased in patients compared with controls (92.8 +/- 1.1 vs. 81.8 +/- 1.7%, P less than 0.001). No differences were found in fractional distal sodium reabsorption between controls and patients (96.9 +/- 0.8 vs. 98.6 +/- 0.1%). When patients were separated into two subgroups according to their sodium balance, it was found that fractional distal sodium reabsorption was increased in patients whose balance remained positive, compared with patients on a negative sodium balance (98.99 +/- 0.26 vs. 94.11 +/- 1.50%, P less than 0.05). In addition, the natriuretic response to a specific dose of spironolactone was higher in patients on positive sodium balance compared with patients on negative sodium balance (per cent increase in natriuresis after spironolactone 300 mg day-1: 355.24 +/- 73.98 vs. 84.21 +/- 15.8%, P less than 0.01). We conclude that proximal sodium reabsorption is increased in cirrhotics with ascites. In addition, distal sodium reabsorption is enhanced only in those patients which exhibit avid sodium retention.

Responses of nociceptive SI neurons in monkeys and pain sensation in humans elicited by noxious thermal stimulation: effect of interstimulus interval

1. Twenty-six nociceptive neurons in the primary somatosensory cortex (SI) of anesthetized monkeys were responsive to noxious thermal stimulation applied to the face. Thermode temperature increased from a base line of 38 degrees C to temperatures ranging from 44 to 49 degrees C (T1). After a period of 5 s, the temperature increased an additional 1 degree C (T2). The neuronal responses to noxious thermal stimuli were compared when the interstimulus interval (ISI) was 30 or 180 s. 2. A linear regression analysis was applied to the stimulus-response functions of neuronal responses to T1 stimuli obtained at ISIs of 180 s. Based on the slopes and linear regression coefficients of these stimulus-response functions, two populations of nociceptive neurons were identified. The neuronal responses of one population of nociceptive SI neurons (WDR1) to T1 stimuli were characterized by steep slopes and high regression coefficients, whereas the other population (WDR2) had flatter slopes and lower regression coefficients. WDR1 neurons responded with monotonic increases in neuronal activity as the stimulus intensity increased. However, the peak frequency of WDR2 neurons often reached a plateau below 47 degrees C. Both WDR1 and WDR2 neurons had receptive fields that encompassed one or two divisions of the trigeminal nerve. 3. The T1 neuronal responses of WDR1 neurons were significantly suppressed when thermal stimuli were delivered with ISIs of 30 s. The T1 neuronal responses of WDR2 and the T2 responses of both WDR1 and WDR2 neurons were not significantly different when ISIs of 30 and 180 s were used. The T1 thresholds of WDR1 and WDR2 neurons were significantly higher when stimuli were delivered with ISIs of 30 s compared with ISIs of 180 s. 4. Most nociceptive SI neurons were located in layers III and IV of area 1-2. In a number of instances, multiple nociceptive neurons were found in the same microelectrode penetration. 5. The humans' intensity of pain sensation paralleled the neuronal responses of nociceptive SI neurons. With the use of a similar paradigm as in the monkey experiments, increases in T1 and T2 temperatures resulted in monotonic increases in pain ratings and change in pain sensation, respectively. However, the intensity of pain sensation to T1 temperatures was suppressed by ISIs of 30 s. Neither ISI produced statistically significant changes in the intensity of pain sensation to T2 stimuli. 6. These data demonstrate that manipulations that alter the intensity of pain sensation also produce concomitant changes in the responsiveness of nociceptive SI neurons.(ABSTRACT TRUNCATED AT 400 WORDS)

The detection and perceived intensity of noxious thermal stimuli in monkey and in human

1. The magnitude of the sensations produced by small increases in thermal stimuli superimposed on noxious levels of heat stimulation was studied by the use of a simple reaction-time task. Noxious thermal stimuli were presented on the face of three monkeys, the forearm volar surface of three monkeys, and the face of four human subjects. The subject, either monkey or human, initiated a trial by pressing an illuminated button. Subsequently, a contact thermode increased in temperature from a base line of 38 degree C to temperatures of 44, 45, 46, or 47 degrees C (T1). After a variable time period lasting between 4 and 10 s, the thermode temperature increased an additional 0.1, 0.2, 0.4, 0.6, or 0.8 degrees C (T2). The subject was required to release the button as soon as the T2 stimulus was detected. Detection latency, expressed as its reciprocal, detection speed, was defined as the time interval between the onset of T2 and the release of the button. 2. The monkeys' detection speed to stimuli presented on the upper lip was dependent on the intensity of both T1 and T2. Increases in the intensity of T2 between 0.1 and 0.8 degrees C produced faster detection speeds. In general, as the intensity of T1 increased, the detection speed increased to identical T2 stimuli. The monkeys' T2-detection threshold was also dependent on the intensity of T1. 3. The psychophysical functions obtained from stimulation of the monkey's face were compared with those obtained from the volar surface of the monkey's forearm. Whereas the T2 thresholds obtained from stimulation of the monkey's forearm and face were similar, the psychophysical functions obtained from stimulation of the face were significantly steeper than those obtained from stimulation of the forearm. 4. The humans' detection speed of T2 stimuli presented on the face was monotonically related to the intensity of T2 and was dependent on the level of T1. The psychophysical functions obtained from the human's face were equivalent to those obtained from the monkey's faces. 5. A cross-modality matching procedure was used to examine the perceived intensity of pain sensation produced by T2 stimuli in human subjects. The magnitude estimates of these stimuli were dependent on the level of T1, as well as the intensity of T2. Detection speed, plotted as a function of the estimated magnitude of pain, independent of T1 and T2 temperature, was best fit by a logarithmic function.(ABSTRACT TRUNCATED AT 400 WORDS)

Spinal lamina I projection neurons in the rat: collateral innervation of parabrachial area and thalamus

A major ascending nociceptive pathway from spinal lamina I to the mesencephalon has previously been reported in the cat, rat and monkey. In the present paper, we have used single and double retrograde labeling techniques to describe this projection system and its collateralization to the thalamus in the rat. Injections of wheat germ agglutinin-horseradish peroxidase into the pontomesencephalic parabrachial area labeled cell bodies bilaterally in lamina I and deeper laminae of the spinal cord. Bilateral lesions of the dorsolateral funiculi at thoracic levels reduced labeling of lamina I neurons caudal to the lesions. Combined injections of fluorescent retrograde tracers into the lateral thalamus and parabrachial area resulted in double labeling of projection neurons in lamina I, lamina IV VIII and the lateral spinal nucleus of the cervical and lumbar enlargements. Double-labeled neurons were especially abundant in lamina I. Thus, we have demonstrated a major lamina I projection through the dorsolateral funiculi to the parabrachial area with significant collateralization to the thalamus. Moreover, since more than 80% of retrogradely labeled lamina I spinothalamic tract cells had collaterals to the parabrachial area we have indirectly demonstrated the presence of a dorsolateral funicular pathway for lamina I spinothalamic neurons in the rat. More lamina I neurons were retrogradely labeled from midbrain injections as compared to thalamic injections. The significance of these findings rest on previous work in this and other laboratories and concerns the understanding of spinal nociceptive mechanisms. Lamina I projection neurons are primarily nociceptive-specific in their response properties and have been shown to project to both the midbrain and thalamus via the dorsolateral funiculus in a number of species. The role of this projection system in nociceptive transmission may lie in its ability to distribute precise information to multiple brain stem sites which in turn activate autonomic or affective responses or descending pain modulatory mechanisms.

SI nociceptive neurons participate in the encoding process by which monkeys perceive the intensity of noxious thermal stimulation

The activity of primary somatosensory (SI) cortical nociceptive neurons was recorded while the monkeys performed a psychophysical task in which they detected small increases in skin temperature superimposed on noxious levels of thermal stimulation. The detection latency to these stimuli, expressed as detection speed, was used as a measure of the perceived intensity of sensation. Two-thirds of the neurons that responded to noxious thermal stimulation increased their discharge in response to graded increases in stimulus intensity. The remaining neurons responded to noxious thermal stimulation, but did not grade their response with the intensity of the stimulus. The response of SI nociceptive neurons that encode the intensity of noxious thermal stimulation was significantly correlated with the monkey's detection speed. We conclude that SI nociceptive neurons are involved in the encoding process by which monkeys perceive the intensity of noxious thermal stimulation.

Selective excitation by capsaicin of mechano-heat sensitive nociceptors in rat skin

The effect of close-by arterial injections of capsaicin on single afferent fibers of the saphenous nerve was studied on 82 units from control rats and on 44 units from rats pretreated with capsaicin (total dose 200 mg/kg applied subcutaneously under anesthesia 3 days before the experiment). In control rats low doses of capsaicin selectively excited mechano-heat sensitive cutaneous nociceptors (polymodal C fiber nociceptors and MH-A delta nociceptors). The median threshold dose for polymodal nociceptors was 0.1 micrograms. Repeated injections of capsaicin in near-threshold doses evoked reproducible effects without obvious signs of desensitization. In contrast A delta high-threshold mechanoreceptors, hair follicle receptors, cold receptors and C fiber mechanoreceptors were not excited by capsaicin even at doses of 5 micrograms. These high doses activated, however, some SA-II mechanoreceptors after a time lag, probably due to increased tissue turgor induced by plasma extravasation. Systemic capsaicin pretreatment of adult rats resulted in a selective decrease in the proportion of polymodal nociceptors among the afferent C-units, and an increment in the threshold dose of capsaicin of the responding polymodal nociceptors. It is concluded that in the adult rat capsaicin exerts a selective stimulatory and blocking effect on cutaneous mechano-heat sensitive nociceptors conducting both in the C fiber and A delta fiber range.

Measurement of the analgesic effects of aspirin with a new experimental algesimetric procedure

Using controlled long lasting noxious squeeze stimuli applied to the interdigital webs we have tried to develop experimental methods allowing us to measure the effects of peripherally acting analgesics. In the present double-blind cross-over study with 12 subjects we tested the effects of aspirin (1000 and 1500 mg) vs. placebo on subjective pain induced by alternately applied 12 N (Newton) and 8 N stimuli. During the sessions blood samples were taken in regular intervals to measure acetylsalicylate (ASA)- and salicylate (SA)-plasma levels. Analyses of variance were computed with several psychophysical parameters. Both the '12 N' and the '8 N' ratings discriminated between placebo and aspirin, however, only the ratings obtained from the stronger stimuli discriminated between two doses of aspirin. Subsequently we computed analyses of covariance with the ASA- and SA-plasma levels as covariates. Significant (negative) correlations of pain ratings and SA-plasma levels were found for the high dose of aspirin, but there were no significant correlations of ASA levels and ratings.

Discharge patterns of afferent cutaneous nerve fibers from the rat's tail during prolonged noxious mechanical stimulation

Feedback controlled constant force stimuli of 4, 6 and 8 N intensities and of 120 s duration were applied to the receptive fields of cutaneous afferent fibers in the rat's tail. Two types of nociceptive units showed sustained discharges during these stimuli: "polymodal" unmyelinated C-units (MH-C units, N = 18, c.v. 0.5-0.9 m/s) and high-threshold mechanoreceptive A-delta-units (HTM-units, N = 10, c.v. 1.9-11.2 m/s). In addition two classes of sensitive low threshold mechanoreceptors, SA I (N = 6) and SA II (N = 5) units, responded to the prolonged mechanical stimuli. At the onset of a noxious pressure, 11 of the 18 polymodal nociceptors exhibited dynamic responses (lasting about 10 s) which were followed by slowly adapting tonic discharges that lasted for the duration of the stimuli. The remaining polymodal C-fiber units (8/18) did not show dynamic discharges at 4 and 6 N. Phasic and tonic discharges were positively correlated with stimulus strength. The HTM-units encoded stimulation intensity mainly by their dynamic discharges. The tonic discharges of these units displayed faster adaptation rates with stronger mechanical stimuli, i.e. encoding of stimulation intensity became progressively weaker during the tonic phase. The discharges of sensitive SA I and SA II units with A beta axons were not positively correlated with the strength of noxious pressure stimuli. Tonic discharge rates of SA I units were negatively correlated to stimulus strength, whereas SA II units usually stopped firing in the course of a stimulus and became reversibly irresponsive to mechanical stimulation. Possible afferent mechanisms underlying the induction of pain by sustained noxious mechanical stimulation are discussed.

Vascular reactions correlated with pain due to cold

Psychophysical experiments with healthy volunteers were conducted to study the relationships between cold pain and blood perfusion of the skin. By means of a thermode the left middle finger was cooled to a constant temperature near 0 degrees C for 45 min. During this stimulation period, the subject regularly rated the pain on an electronically controlled visual analogue scale. Two variables of vascular reactions were measured: the finger photoplethysmogram of the cooled finger and the thermal flux at the skin surface of this finger. Cross correlograms computed between these noninvasive physiologic parameters of blood flow and the pain ratings revealed that pain intensity and degree of vasoconstriction were strongly correlated. The implications of these findings for the peripheral nociceptor mechanism of cold pain are discussed. We conclude that the nociceptors for this type of pain are most probably situated in deeper skin structures and that they are excited by temperatures ranging approximately from 3 to 20 degrees C.