Morphological operators on the unit circle

Images encoding angular information are common in image analysis. Examples include the hue band of color images, or images encoding directional texture information. Applying mathematical morphology to image data distributed on the unit circle is not immediately possible, as the unit circle is not a lattice. Three approaches to solving this problem are presented. First, difference-based operators are studied (e.g., gradient, top-hat). Second, a definition of grouped circular data is suggested, and "pseudo" morphological operators, which operate only on grouped data, are introduced. Finally, processing using pixel labeling is presented, leading to the development of a cyclic opening operator. Applications for treating the hue band of color images and for finding perturbations in wood texture are given.

Overview of neuropathic pain syndromes

Patients with peripheral nerve injury often express a variety of positive sensory symptoms. Description of these symptoms can range from "painful" to "painless" to "painless but very unpleasant." Although it is widely accepted that both peripheral and central processes may play a role in the pathophysiology of these symptoms, peripheral mechanisms in particular are often overlooked. Sensitization of nociceptor unit receptors, spontaneous or stimuli-induced ectopic impulse generation, "multiplication" of impulses, and ephaptic transmission are pathophysiologic mechanisms resolved at the peripheral level that may explain the patient's symptomatology. It is important to reach an accurate diagnosis and to investigate the pathophysiology of every individual symptom. Only when this has been achieved is it possible to plan adequate symptom-oriented therapeutic strategies. In the future, therapy will be more symptom-oriented than illness-oriented, and treatment options will most likely be tailored to fit the specific constellation of symptoms expressed by a particular patient.

Prepulse inhibition of the blink reflex by laser stimuli in normal humans

The subcortical integrative effects of laser-induced activation of pain ascending tracts were examined in 11 healthy volunteers, aged 22-52 years. Subjects underwent either CO2 laser stimulation at the dorsum of the hand, electrical stimulation of digital nerves at the 3rd finger, or mechanical taps to the first dorsal interosseous space, preceding a blink reflex elicited by a supraorbital nerve electrical stimulus. The percentage inhibition induced in the R2 response of the blink reflex was similar for the three different stimulus modalities, but occurred at a different time interval. Compared to control trials, the R2 response of the test trials was a mean of 23.1% at the interval of 250 ms with laser stimuli, 17.4% at the interval of 100 ms with electrical stimuli to the 3rd finger, and 20.6% at the interval of 90 ms with a mechanical tap to the 1st interosseous space. Activation of pain receptors induces prepulse inhibition of the blink reflex at a delay corresponding to a slowly conducting pathway. The percentage inhibition is similar to that observed with other somatosensory inputs.

Quantification of D-dimer using a new fully automated assay: its application for the diagnosis of deep vein thrombosis

BACKGROUND AND OBJECTIVE

A D-dimer assay can be helpful to rule out thromboembolism provided it is sensitive, reliable, fast and easy to perform. Tests based on the ELISA methodology have a high diagnostic sensitivity, and are therefore adequate for excluding deep venous thrombosis (DVT). The drawbacks are their long assay times, unsuitability to be run on single samples and cost. New methods have been developed, based either on the same principle, by immunofiltration or by microlatex immunoturbidimetric assays which seem to reach the high sensitivity and negative predictive value (NPV) required, but allowing fast and quantitative single sample analysis. The aim of this work was to evaluate one rapid test, a fully automated quantitative assay (IL Test D-dimer, run on an ACL 7000 coagulation analyzer, Instrumentation Laboratory).

DESIGN AND METHODS

We compared the diagnostic value of IL Test for DVT with that of an ELISA (Dimertest Gold EIA Agen Biomedical Limited, Acacia Ridge, Australia). Eighty-six patients (43 men, 43 women, mean age: 61 years) showing DVT symptoms formed the population for this non-randomized controlled trial in a referral center. The diagnosis of DVT based on the clinical history, was confirmed by serial compression ultrasonography (CUS) with Doppler flow in 62 patients.

RESULTS

The IL Test D-dimer proved to be rapid, automated and well suited for individual tests with a good reproducibility in three control plasmas with different concentrations of D-dimer (coefficient of variation range 0.54-3. 87%). Its performance was comparable to that of the Dimertest Gold EIA, as indicated by the areas under the receiver operating characteristic curves (Dimertest Gold EIA 0.748; IL Test D-dimer 0.70). On the basis of kappa coefficients, there was a good concordance between the Dimertest Gold EIA and IL Test D-dimer when the receiver operating characteristic (ROC) curves suggested cut-offs were used. The sensitivity (98.3%) and NPV (88.9%) shown by IL Test D-dimer are comparable or even better than those obtained for EIA (95%, 80%, respectively).

INTERPRETATION AND CONCLUSIONS

This study shows that the new method can be included in prospective clinical trials to test the utility of D-dimer measurement in combination with other non-invasive diagnostic procedures in the management of DVT diagnosis.

[Seroepidemiological study of brucellosis in a rural endemic area]

BACKGROUND

This study investigated the prevalence of Brucella spp. antibodies in the general population in the Health Area of Tremp (Region of Pallars Jussà, Lleida). It also identified the risk factors with the presence of these.

PATIENTS AND METHODS

A total of 346 (191 men and 155 women) were studied. Information about the sex, age, location, the personal and familiar antecedents of brucellosis, occupational risk, contact with the animals and the consumption of non-hygienic dairy products was recorded. The estimation of the seroprevalence was carried out by the ELISA IgG test. The association of independent variables with the presence of antibodies was assessed by the Coombs to Brucella and the ELISA IgG tests. It was assessed by using the calculation of the analysis variance.

RESULTS

The personal antecedents, the contact with the animals and the occupational risk all showed a statistically significant relation (p < 0.05) with the Coombs and ELISA IgG tests. The familiar antecedents showed a significant relation with the ELISA IgG. The consumption of dairy products and the location showed no statistically significant relation. A seroprevalence was obtained among the researched population of 11.9%, the maximum occurred in Isona surgery (25.6%) and the minimum in Tremp (9.8%).

CONCLUSIONS

The seroprevalence is high and the epidemiological profile associated with the fact of being seropositive is associated with the profession of the study subject and it coincides with de infection mechanisms present in the area.

Value of sonography in the assessment of space-occupying lesions of the anterior nasal fossa

PURPOSE

This study was conducted to define the gray-scale, color, and power Doppler sonographic appearances and spectral analysis patterns of anterior nasal masses.

METHODS

Eight patients with anteriorly located nasal masses were referred to our hospital for CT of the paranasal sinuses. Subsequently, they were examined with a high-frequency linear-array ultrasound transducer. We performed gray-scale sonography and color and power Doppler imaging.

RESULTS

Five masses were nasal hemangiomas. The three remaining masses were a submucosal glandular cyst, a nasolabial cyst, and tuberculum septi hypertrophy. Three of the hemangiomas were histopathologically confirmed. Sonography identified the anatomic origin of all 8 lesions. On color and power Doppler imaging, the 5 hemangiomas exhibited intense vascularity that decreased with compression. Spectral analysis demonstrated arterial and venous flow within the hemangiomas, with resistance indices of 0.60-0.66 and peak systolic velocities of 6.4-18.4 cm/second. The other 3 lesions were avascular or had vascularity only at the periphery.

CONCLUSIONS

Anterior nasal fossa tumors can frequently be diagnosed by clinical examination, but specific sonographic and Doppler patterns can help to establish the anatomic origin, the local extension, and the correct diagnosis in indeterminate cases, obviating other diagnostic imaging or surgical procedures.

Six-month outcome in unstable angina patients without previous myocardial infarction according to the use of tertiary cardiologic resources. RESCATE Investigators. Recursos Empleados en el Síndrome Coronario Agudo y Tiempos de Espera

OBJECTIVES

The study assessed whether varying accessibility of patients with unstable angina (UA) to coronary angiography and revascularization determined differing usages and outcomes.

BACKGROUND

The appropriate use rate of coronary angiography and revascularization procedures in UA remains to be established.

METHODS

A total of 791 consecutive patients with UA without previous acute myocardial infarction (AMI) admitted to four reference teaching hospitals (one with tertiary facilities) were followed for six months. End points were six-month mortality and readmission for AMI, UA, heart failure, or severe ventricular arrhythmias.

RESULTS

Patients admitted to the tertiary hospital were 3.27 (95% confidence interval [CI] 2.32 to 4.62) times more likely to undergo coronary angiography after adjustment for comorbidity and severity than were those admitted to nontertiary facilities (overall six-month use rates 70.1% and 48.3%, respectively). Revascularization procedures were performed in 36.2% of patients in the tertiary hospital and 24.6% in the others (p = 0.0007); adjusted relative risk (RR) 2.37 (95% CI 1.55 to 3.63). Median delay for urgent coronary angiography was shorter in the tertiary hospital (24 h vs. 4 days, p < 0.0002). Six-month mortality and readmission rates were similar in tertiary and nontertiary hospitals: 3.9% versus 5.3% and 16.9% versus 21.2%, respectively. Adjusted RR of death or readmission for the nontertiary hospitals was 1.23 (95% CI 0.57 to 2.67).

CONCLUSIONS

The use of coronary angiography and revascularization procedures in UA patients with no previous AMI is higher in tertiary than in nontertiary hospitals, but the more selective use of these procedures in nontertiary centers does not imply worse outcome.

[The metabolic-chronotropic relation in patients with heart failure--a correlation with functional capacity]

Previous studies on chronotropic incompetence (CI) in patients with congestive heart failure (CHF) have defined it as the inability to achieve > 80% of age predicted maximum heart rate (HR) (adequacy of HR response to submaximal exercise levels not being considered). The metabolic chronotropic relation (MCR) concept proposed by Wilkoff allows the assessment of the entire chronotropic function. The value of such an approach for the evaluation of CI in patients with CHF, and its relation to exercise capacity, is unclear at present.

METHODS

We imposed maximal symptom-limited treadmill exercise testing while measuring breath-by-breath oxygen consumption, using CAEP protocol, in 25 patients (19 men), 49 +/- 10 years, all in sinus rhythm, with CHF secondary to dilated cardiomyopathy (17) or ischemic heart disease (8), NYHA class II-III. Anaerobic threshold (AT) was attained by all. No exercise was terminated due to arrhythmia or ischemia. MCR was calculated as the slope of the relation between the percentages of HR and metabolic reserves achieved at the end of each exercise stage. Using 2.0 standard deviations below the mean level of MCR in healthy controls, we defined an MCR value < 0.84 as abnormal. The parameters analysed were: age, drug therapy, fractional shortening (FS-%), resting HR (RHR-bpm), exercise duration (DUR-min), peak HR (HRp), peak oxygen consumption (VO2p-ml/kg/min), percentages of predicted maximal HR (% PMHR) and VO2 (% PMVO2), peak ventilatory equivalent for CO2 (VE/VCO2-L/min), time to AT (T-AT), and VO2 at AT (VO2-AT).

RESULTS

MCR was normal (1.01 +/- 0.18-0.86 to 1.19) in 10 patients--Group I, and abnormal (0.66 +/- 0.13-0.42 to 0.81) in 15 (60%) patients--Group II. A similar proportion of patients in both groups were taking ACE inhibitors, digoxin and amiodarone. [table: see text] CI defined as an inability to achieve a % PMHR > 80% occurred only in 6 (24%) patients, all in Group 2 (p = 0.022 versus abnormal MCR).

CONCLUSIONS

In CHF patients, CI assessed as an abnormal MCR is frequent, and relates to an impaired exercise capacity.

[Single dose of fleroxacin for the treatment of adult acute diarrhea]

The purpose of this work was to evaluate the efficacy and safety of a single dose of 400 mg of fleroxacin for the empiric antibiotic treatment of acute diarrhea in adult patients. A prospective, double-blind, placebo-controlled, randomized trial was designed. All the adult patients who consulted in our hospital for acute diarrhea from December 1994 to April 1995 were included. 72 patients were randomized to receive a single dose of fleroxacin 400 mg and 73 were placebo. Thirty-eight patients in each group were evaluable for efficacy. Between both groups there were not statistically significant differences in age, sex, number of loose stools per day at inclusion, days since the onset of symptoms up to inclusion, other symptoms than diarrhea at inclusion, percentages of bacterial pathogens and parasites isolated and symptomatic treatment indicated. At the third day since inclusion, clinical cure occurred in 72.2% of the patients receiving fleroxacin, compared with 36.4% of those receiving placebo; p = 0.002. The mean +/- SD time to cure was 2.2 +/- 1.2 days in the fleroxacin group and 3.2 +/- 2.0 days in the placebo group; p = 0.01. Twenty-eight and 16.7% of patients reported adverse effects in the fleroxacin and placebo groups respectively; p = 0.3. It is concluded that a single dose of fleroxacin 400 mg is an effective and safe alternative for the empiric antibiotic treatment of acute diarrhea in adults.

Central motor conduction time in patients with multifocal motor conduction block

The finding of conduction block (CB) within short consecutive segments along a motor nerve is a key feature of multifocal motor neuropathy (MMN). Despite their different pathogenesis, this may be the only clinical difference between some cases of MMN and the pure spinal muscular atrophy form of motor neuron disease (MND). In 12 patients with distal atrophy and fasciculations and electrophysiological evidence of CBs in the upper limbs, we measured the peripheral and central motor conduction times (PMCT and CMCT) to hand muscles. We reasoned that patients with MMN should show an abnormally prolonged PMCT with normal CMCT, whereas an increased CMCT would suggest MND. All patients had delayed F-wave latency and increased PMCT. Three patients had increased CMCT. Follow-up showed little clinical and electrophysiological change in 7 of the 9 patients with normal CMCT, and a progressive motor deficit leading ultimately to death in 1 of the 3 patients with increased CMCT. This patient's electrophysiological follow-up showed a significant decrement of the compound motor action potential to both proximal and distal stimulation points, with disappearance of earlier CBs. Autopsy revealed loss of anterior horn cells and axons of the ventral root, and degeneration of large myelinated fibers. We conclude that determining the CMCT may help in differentiating MND from MMN. Persistence of a stable clinical picture over a span of at least 1 year and lack of electrophysiological signs of involvement of upper motor neurons should both be required before establishing the diagnosis of MMN even with electrophysiological evidence of CB.

A new transthyretin variant--ATTR Arg104Cys

We report the genetic characterization of a transthyretin variant previously detected by mutation scanning employing single strand conformation polymorphism analysis in patients with peripheral neuropathies. A substitution of a thymine for cytosine resulting in the replacement of an arginine with cysteine at position 104 of the polypeptide chain was found both by DNA sequencing and restriction fragment length polymorphism analysis. The propositus presented a sensory axonal neuropathy, no neurological abnormalities in the upper limbs nor autonomic involvement. No evidence for amyloid deposition was found in either muscle and nerve biopsies. There was no history of amyloidosis in the family. This mutation might be rare in the population and future cases of the mutation will ascertain a relationship with disease.

[Should all patients with ventricular pre-excitation of the Wolff-Parkinson-White syndrome type undergo catheter ablation?]

The authors make a concise review concerning clinical, electrocardiographic and electrophysiologic risk stratification in Wolff-Parkinson-White syndrome and present the results of radiofrequency catheter ablation of atrioventricular accessory pathways. The low sensitivity of electrophysiologic criteria for the identification of a high risk profile limits their use in asymptomatic patients with a low incidence of sudden death. The greater risk of ventricular fibrillation in symptomatic patients makes radiofrequency catheter ablation the treatment of choice for these patients. Therefore, the authors do not recommend an electrophysiologic risk stratification in Wolff-Parkinson-White syndrome, but emphasize that catheter ablation should be performed in all symptomatic patients.

Activity-dependent slowing of conduction differentiates functional subtypes of C fibres innervating human skin

1. The effects of impulse activity on conduction in cutaneous C fibres have been examined in 46 microneurographic recordings from 11 normal subjects and 11 diabetic patients with normal nerve conduction. A tungsten microelectrode was inserted into a cutaneous nerve, usually the superficial peroneal close to the ankle, and intraneural microstimulation was used to identify an area of skin innervated. Three minute trains of 0.25 ms stimuli at 1, 2 and 4 Hz were then delivered to the surface of the skin, separated by intervals of 6 min with stimulation at 0.25 Hz. Slowing and block of conduction were measured from the nerve responses for up to seven C units per stimulation sequence. 2. Three types of C unit were distinguished by their responses to repetitive stimulation: type 1 units slowed progressively during the 3 min trains; slowing of type 2 units reached a plateau within 1 min; while type 3 units hardly slowed at all. Data from normal and diabetic subjects did not differ and were pooled. After 3 min at 2 Hz, the percentage increases in latency were for type 1, 28.3 +/- 9.7 (n = 63 units, mean +/- s.d.); for type 2, 5.2 +/- 1.6 (n = 14); and for type 3, 0.8 +/- 0.5 (n = 5), with no overlap. After 3 min at 4 Hz, 58 % of type 1 units (but no type 2 or 3 units) blocked intermittently. Recovery of latency after stimulation was faster for type 2 than for type 1 units, but conduction velocities of the three types were similar. 3. Type 1 units were identified as nociceptors and 7 type 2 units were identified as 'cold' fibres, activated by non-noxious cold, with no overlap in modality. None of the units tested was activated by weak mechanical stimuli or reflex sympathetic activation. 4. Spike waveforms were averaged for 18 type 1, 10 type 2 and 6 type 3 units. All units had predominantly triphasic action potentials with a major negative peak, but those of type 3 units were on average both smaller and briefer than those of type 1 and type 2 units. 5. It is concluded that repetitive electrical stimulation reliably differentiates nociceptive from cold-specific C fibres innervating human hairy skin, as has previously been shown for the rat. Cold fibres can propagate impulses continuously at much higher rates than nociceptive fibres. The nature of the type 3 units is unclear.

[Stapedectomy versus stapedotomy. Our experience]

Otosclerosis surgery has seen three well-differentiated stages of development: a) SHC fenestration; b) stapes mobilization, and c) platinectomy, a procedure introduced in 1960 by Shea. Since then, only one variation has been proposed: platinotomy. After a comparative study of platinectomy versus platinotomy, we, like other authors, concluded that platinotomy was a better technique because of the ease of execution and good functional results.

[Second primary tumors in patients with laryngeal neoplasms]

A cohort epidemiologic study of second primary tumours appeared in patients diagnosed of laryngeal neoplasms, between years 1988 and 1990, and a follow-up term of 5 years, is presented. An statistical analysis of several data to define a possible high risk group for developing primary tumours was performed for all patients.

Prevalence of diabetes in Catalonia (Spain): an oral glucose tolerance test-based population study

The goal of this study was to investigate the prevalence of diabetes mellitus and impaired glucose tolerance in the adult population of Catalonia and study their association with obesity, central obesity, hypertension and smoking habit. A random sample of 3839 subjects aged 30-89 years participated in this cross-sectional study: 2214 subjects underwent a health examination with oral glucose tolerance test (OGTT) and 1625 were interviewed by phone. Diabetes prevalence (known and unknown) in the 30-89-year-old population was 10.3%, (95% CI: 9.1-11.6). In this age group, the prevalence rates of known diabetes, unknown diabetes and impaired glucose tolerance were 6.4, 3.9 and 11.9% in men and 6.9, 3.4 and 11.9% in women. The age adjusted prevalence to the world population for the 30-64-year-old age group was 6.1% (7.1% in men and 5.2% in women).The factors significantly associated with diabetes were age, obesity, hypertension and family history of diabetes. The high ratio of previously known diabetic cases to newly discovered ones, specially in the oldest age group, suggests good levels of awareness and medical services. The prevalence in Catalonia is similar to that observed in other Mediterranean countries.

Flare and hyperalgesia after intradermal capsaicin injection in human skin

Flare and hyperalgesia after intradermal capsaicin injection in human skin. J. Neurophysiol. 80: 2801-2810, 1998. We investigated the neurovascular mechanisms that determine the flare response to intradermal capsaicin injection in humans and delineated the associated areas of mechanical and heat hyperalgesia. The flare response was monitored both visually and with infrared telethermography. The areas of mechanical and heat hyperalgesia were determined psychophysically. Thermography detected very large areas of flare. As an early event underlying the flare and before onset of the area of rubor of the skin, thermography detected the appearance of multifocal spots of increased temperature caused by dilatation of cutaneous arterioles. Repetition of capsaicin injection days apart into the same forearm induced multifocal spots of temperature elevation identical to the ones obtained in the first session, indicating dilatation of the same arterioles. Reactive hyperemia also consisted in the appearance of multifocal spots of increased temperature, which were identical to the ones reacting during the flare response, suggesting participation of the same arterioles in both events. Strips of local anesthetic placed to block cutaneous nerves prevented the spread of both the thermographic flare and associated hyperalgesia. It is inferred that the cutaneous nerve fibers responsible for the thermographic flare branch, or have coupled axons, over a long distance. The large area of flare coincided with the area of mechanical and heat hyperalgesia. Equivalence of the areas of flare and mechanical and heat hyperalgesia induced by intradermal capsaicin injection suggests that all three phenomena are the consequence of neural factors that operate peripherally.

Ectopic impulse generation and autoexcitation in single myelinated afferent fibers in patients with peripheral neuropathy and positive sensory symptoms

Microneurographic studies were performed using cutaneous nerves of 8 patients with documented peripheral neuropathy who expressed positive sensory symptoms. Intraneural recordings in single myelinated fibers revealed: (i) ectopic generation of bursts of spontaneous action potentials; (ii) ectopic generation of ongoing repetitive discharges transiently interrupted by natural stimulation of the receptive field; and (iii) repetitive discharges triggered by a preceding action potential. These results provide direct evidence of a peripheral pathophysiological basis for spontaneous and stimulus-induced paresthesias and dysesthesias in patients with peripheral neuropathy.

[Prognostic factors and etiology in patients with severe community-acquired pneumonia admitted at the ICU. Spanish multicenter study. Study Group on Severe Community-Acquired Pneumonia in Spain]

OBJECTIVE

To determine the techniques used for the etiological diagnosis of community-acquired pneumonia in patients admitted to the intensive care unit (ICU) and to describe the predominant causative organisms as well as prognostic factors of ICU mortality.

PATIENTS AND METHODS

A total of 262 patients with community-acquired pneumonia admitted to 26 ICUs between 1 November of 1991 and 31 October of 1992 were included in a prospective, open, multicenter study.

RESULTS

The diagnostic techniques most frequently used were blood culture (243 cases) and simple tracheal aspirate (166 cases). Simple tracheal aspirate (58.4%), bronchoalveolar lavage (47.7%), and protected-specimen brush (44.2%) were the techniques that showed the highest diagnostic reliability. In 220 cases, techniques considered of high diagnostic probability were employed. With the use of these procedures, the most frequent causative pathogens were Streptococcus pneumoniae (13.6%) and Legionella pneumophila (9.5%). In 100 cases (45.5%), no pathogen was isolated. A total of 88 patients (33.6%) died during the ICU stay. Predictive variables of poor outcome selected by means of a multivariate analysis were as follows: multisystemic failure (OR = 28.6; 95% CI: 12.8-65.1; p = 0.0001), APACHE II at the time of ICU admission (OR = 5.3; 95% CI: 2.5-11.3; p = 0.0001), progression and/or spread of lung infection (OR = 4.5; 95% CI: 2.4-8.4; p = 0.0001), and shock on admission (OR = 8.48; 95% CI: 4.5-15.9; p = 0.0001).

CONCLUSIONS

In 45.5% of patients with community-acquired pneumonia admitted to ICU, no causative pathogen was identified. The prognosis of these patients was influenced by the severity of disease assessed by APACHE II score and presence of multisystemic failure and shock at the time of ICU admission.

Efficacy of PdB in preventing intraoperative risk of infectious diseases

The objectives of this study were to (1) determine the number of punctures surgeons and assistants suffer during operations involving a laparotomy during the intraabdominal and closure phases; and (2) determine if the number of puncture injuries during wound closure can be reduced using a new surgical instrument (PdB) that protects the surgeon's hands and the patient's viscera against needlesticks. For the first objective, all laparotomies performed during 1 month (n = 52) were controlled, collecting the gloves used and determining the number of perforations. For the second objective, a randomized prospective controlled study, involving two series of 100 medial laparotomies, was carried out. The incidence of perforations was 29% during the intraabdominal phase and 16% during the wound closure phase. The glove perforation rate while closing medial laparotomies was 31.5% if the PdB was not used and 3% if the PdB was used (p < 0.0001). The glove perforation rate during laparotomy is significant, but with the use of the PdB this incidence can be significantly reduced.

[Nitric oxide synthase activity in nasal mucosa]

Nitric oxide (NO) plays an important regulatory role in airway function and seems to be implicated in the pathophysiology of several airway diseases. We studied the presence of NO synthase activity in human nasal mucosa and nasal polyp tissues obtained from patients undergoing septoplasty or polypectomy, respectively. NO synthase activity was quantified in tissue homogenates using citrulline release assay and was located in tissue sections using NADPH-diaphorase histochemistry. The results indicated that nasal polyps contain higher levels of total NO synthase activity than nasal mucosa tissue. In addition, nasal polyps contained mainly inducible NO synthase activity whereas all NO synthase activity detected in the nasal mucosa was in constitutive form. In both cases, NO synthase activity was localized in epithelial cells. In view of these results, we conclude that NO may be an important inflammatory mediator in the respiratory system and that the epithelium may be a source of NO production.

Intestinal gas dynamics and tolerance in humans

BACKGROUND & AIMS

Abdominal symptoms are often attributed to intestinal gas. In humans, gas production and composition have been previously investigated, but intestinal gas dynamics and tolerance remain virtually unknown. The aim of this study was to establish the relationship between intestinal gas loads, evacuation, perception of symptoms, and objective abdominal distention in healthy humans.

METHODS

A dose-response study was performed in 46 healthy subjects; intestinal gas was infused for 3 hours (0, 1, 4, 12, and 30 mL/min), and anal gas evacuation, symptom perception, and abdominal distention were measured. A mixture of gases was infused in venous proportions to minimize diffusion. Anal gas recovery and calculations of gas retention were validated using sulfur hexafluoride as a nonabsorbable gaseous marker.

RESULTS

At all of the infusion rates, gas evacuation rapidly equilibrated and paralleled gas infusion without significant differences in perception. Only 6 subjects retained >400 mL gas, and 5 of them developed abdominal distention and symptoms. By contrast, all but 4 of the 41 subjects without retention tolerated the gas loads without discomfort.

CONCLUSIONS

Intestinal gas tolerance is normally high, because expeditious gas transit and evacuation prevent gas pooling and symptoms. When this protective mechanism is insufficient, gas retention occurs, and it causes abdominal symptoms and distention.