Thermal Characteristics of Selected Phosphate Ores and the Effect of Inorganic Salts on Their Calcination.

Calcination of phosphate ore is one of the methods of ore processing, i.e., increasing the phosphorus content (P2O5) in the ore. However, this process is very energy-intensive and not economically justified in most cases. It can be improved by using additives to lower the required calcination temperature. In this work, several samples of phosphate ores were subjected to thermal analysis using thermogravimetry coupled with mass spectrometry (TG-MS) to study their behavior during the calcination process. Then, selected phosphate ore from the Tunisian deposit was mixed with NaCl, KNO3, or Na2CO3 and calcined in various regimes (temperature and time). Uncalcined samples, together with obtained calcinates, were also subjected to thermal analysis by TG-MS. Temperature ranges in which the mass loss occurred were defined and discussed. Appropriate models of sample weight loss were derived and visualized by using the response surface methodology. Explanations of possible processes observed during the heating of phosphate ore samples with inorganic salt addition were proposed.

Changing Face of Inflammatory Activation in Complex Coronary Artery Disease during the COVID-19 Pandemic.

INTRODUCTION: The COVID-19 pandemic has changed the immunological status of the population, indicating increased activation. The aim of the study was to compare the degree of inflammatory activation in patients admitted for surgical revascularization in the period before and during the COVID-19 pandemic. MATERIALS AND METHODS: This retrospective analysis included an analysis of inflammatory activation assessed on the basis of whole blood counts in 533 patients (435 (82%) male and 98 (18%) female) with a median age of 66 (61-71) years who underwent surgical revascularization, including 343 and 190 patients operated on in 2018 and 2022, respectively. RESULTS: The compared groups were matched by propensity score matching analysis, obtaining 190 patients in each group. Significantly higher values of preoperative monocyte count (p = 0.015), monocyte-to-lymphocyte ratio (p = 0.004) and systemic inflammatory response index (p = 0.022) were found in the during-COVID subgroup. The perioperative and 12-month mortality rates were comparable, with 1% (n = 4) in 2018 vs. 1% (n = 2) in 2022 (p = 0.911), and 5.6 % (n = 11 patients) vs. 7% (n = 13 patients) (p = 0.413), in the pre-COVID and during-COVID subgroups, respectively. CONCLUSIONS: Simple whole blood analysis in patients with complex coronary artery disease performed before and during the COVID-19 pandemic indicates excessive inflammatory activation. However, the immune variation did not interfere with one-year mortality rate after surgical revascularization.

Allogenic Adipose-Derived Stem Cells in Diabetic Foot Ulcer Treatment: Clinical Effectiveness, Safety, Survival in the Wound Site, and Proteomic Impact.

Although encouraging results of adipose-derived stem cell (ADSC) use in wound healing are available, the mechanism of action has been studied mainly in vitro and in animals. This work aimed to examine the safety and efficacy of allogenic ADSCs in human diabetic foot ulcer treatment, in combination with the analyses of the wound. Equal groups of 23 participants each received fibrin gel with ADSCs or fibrin gel alone. The clinical effects were assessed at four time points: days 7, 14, 21 and 49. Material collected during debridement from a subset of each group was analyzed for the presence of ADSC donor DNA and proteomic changes. The reduction in wound size was greater at all subsequent visits, significantly on day 21 and 49, and the time to 50% reduction in the wound size was significantly shorter in patients who received ADSCs. Complete healing was achieved at the end of the study in seven patients treated with ADSCs vs. one treated without ADSCs. One week after ADSC application, 34 proteins significantly differentiated the material from both groups, seven of which, i.e., GAPDH, CAT, ACTN1, KRT1, KRT9, SCL4A1, and TPI, positively correlated with the healing rate. We detected ADSC donor DNA up to 21 days after administration. We confirmed ADSC-related improvement in wound healing that correlated with the molecular background, which provides insights into the role of ADSCs in wound healing-a step toward the development of cell-based therapies.

Spontaneously hypertensive rats manifest deficits in emotional response to 22-kHz and 50-kHz ultrasonic playback.

Many symptoms used routinely for human psychiatric diagnosis cannot be directly observed in animals which cannot describe their internal states. However, the ultrasonic vocalizations (USV) rodents use to communicate their emotional states can be measured. USV have therefore become a particularly useful tool in brain disease models. Spontaneously hypertensive rats (SHR) are considered an animal model of attention deficit hyperactivity disorder (ADHD) and schizophrenia. However, the specifics of SHR's behavior have not been fully described and there is very little data on their USV. Recently, we developed a communication model, in which Wistar rats are exposed to pre-recorded playbacks of aversive (22-kHz) or appetitive (50-kHz) USV, and their vocal responses depend on the extent of prior fear conditioning (0, 1, 6 or 10 shocks). Here, we investigated SHR's behavior and heart rate (HR) in our communication model, in comparison to Wistar rats employed as controls. In general, SHR emitted typical USV categories, however, they contained more short 22-kHz and less 50-kHz USV overall. Moreover, fewer SHR, in comparison with Wistar rats, emitted long 22-kHz USV after fear conditioning. SHR did not show a 50-kHz playback-induced HR increase, while they showed a profound 22-kHz playback-induced HR decrease. Finally, the number of previously delivered conditioning shocks appeared to have no effect on the investigated vocal, locomotor and HR responses of SHR. The phenomena observed in SHR are potentially attributable to deficits in emotional perception and processing. A lower number of 50-kHz USV emitted by SHR may reflect observations of speech impairments in human patients and further supports the usefulness of SHR to model ADHD and schizophrenia.

[Association of antithyroid peroxidase antibodies with cardiac function in euthyroid women with type 1 diabetes mellitus - assessment with two-dimensional speckle­tracking echocardiography].

INTRODUCTION: The presence of diabetes is associated with loss of cardioprotection in premenopausal women; however, the mechanisms involved remain unknown. Autoimmune factors are suspected to play a role in cardiovascular complications, especially in type 1 diabetes (T1DM). The aim of this pilot study was to explore whether antithyroid peroxidase antibody (aTPO) as a marker of increased immune activity is related to cardiac dysfunction in young, asymptomatic women with T1DM. MATERIAL AND METHODS: Eighty-eight euthyroid women (59 with T1DM and 29 healthy controls) underwent physical examination, laboratory tests, thyroid ultrasound, and two-dimensional speckle-tracking echocardiography. According to the antiperoxidase antibodies (aTPO) titre, the T1DM women were divided into an aTPO positive (T1DM aTPO+) (n = 34) and an aTPO negative (T1DM aTPO-) (n = 25) group. The relationship between thyroid autoimmunity parameters and echocardiographic parameters was evaluated. RESULTS: Global longitudinal strain (GLS) was slightly reduced in the T1DM aTPO+ group compared to T1DM aTPO- and significantly compared to controls (p = 0.051 and p = 0.015, respectively). Although, the lower values of longitudinal strain of left ventricular were found in the majority of segments in the T1DM aTPO+ group in comparison to T1DM aTPO- and controls, significant differences were only found in the two-chamber view (specifically in the anterior segments) between the T1DM aTPO+ and T1DM aTPO- groups (p = 0.030) and in the four-chamber view (specifically in the anterolateral segments) between the T1DM aTPO+ group and controls (p = 0.021). Echocardiographic parameters of diastolic and systolic function of both ventricles were significantly correlated with parameters of thyroid autoimmunity. A logistic regression analysis showed that Hashimoto's thyroiditis (HT) duration [odds ratio (OR): 0.997, 95% confidence interval (CI): 0.995-0.999, p = 0.008), the dose of levothyroxine (OR: 0.814, 95% CI: 0.689-0.960, p = 0.013), and reduced echogenicity on thyroid ultrasound (OR: 0.309, 95% CI: 0.120-0.793, p = 0.013) had a significant influence on reduced GLS. CONCLUSIONS: Our results suggest that coexistence of aTPO with T1DM was associated with poorer myocardial function, particularly in the anterior and anterolateral segments, which may be related to an autoimmune factor. The impaired function of these segments is probably the first sign of myocardial systolic dysfunction in women with T1DM, which needs to be confirmed in further studies.

The Effect of Pre-Emptive Analgesia on the Postoperative Pain in Pediatric Otolaryngology: A Randomized, Controlled Trial.

The aim of this randomized, controlled trial was to determine whether children undergoing otolaryngological procedures (adenoidectomy, adenotonsillotomy, or tonsillectomy) benefit from pre-emptive analgesia in the postoperative period. Methods: Fifty-five children were assessed for eligibility for the research. Four children refused to participate during the first stage of the study, leaving fifty-one (n = 51) to be randomly assigned either to receive pre-emptive analgesic acetaminophen (15 mg/kg; n = 26) or a placebo (n = 25) in addition to midazolam (0.5 mg/kg) as premedication. All children were anesthetized with sevoflurane, propofol (2−4 mg/kg), and fentanyl (2 mcg/kg). Postoperative pain was assessed using the Visual Analogue Scale (VAS), the Wong−Baker Faces Pain Rating Scale, and the Face, Legs, Activity, Cry, and Consolability (FLACC) scale. The postoperative pain was measured 1, 2, 4, and 6 h after the surgery. Results: The clinical trial reported a statistically significant correlation between administering pre-emptive analgesia (acetaminophen) and reducing pain in children after otolaryngological procedures compared to placebo. The ratio of boys to girls and age were similar among the groups (p > 0.05), so the groups of children were not divided by gender or age. Conclusions: Standard pre-emptive analgesia reduced the severity of pain in the postoperative period after otolaryngological procedures in children. Acetaminophen given before surgery reduces postoperative pain in children undergoing otolaryngological procedures.

A Weighted Stochastic Conjugate Direction Algorithm for Quantitative Magnetic Resonance Images-A Pattern in Ruptured Achilles Tendon T2-Mapping Assessment.

This study presents an accurate biexponential weighted stochastic conjugate direction (WSCD) method for the quantitative T2-mapping reconstruction of magnetic resonance images (MRIs), and this approach was compared with the non-negative-least-squares Gauss-Newton (GN) numerical optimization method in terms of accuracy and goodness of fit of the reconstructed images from simulated data and ruptured Achilles tendon (AT) MRIs. Reconstructions with WSCD and GN were obtained from data simulating the signal intensity from biexponential decay and from 58 MR studies of postrupture, surgically repaired ATs. Both methods were assessed in terms of accuracy (closeness of the means of calculated and true simulated T2 values) and goodness of fit (magnitude of mean squared error (MSE)). The lack of significant deviation in correct T2 values for the WSCD method was demonstrated for SNR ≥ 20 and for GN-SNR ≥ 380. The MSEs for WSCD and GN were 287.52 ± 224.11 and 2553.91 ± 1932.31, respectively. The WSCD reconstruction method was better than the GN method in terms of accuracy and goodness of fit.

[Is thyroid autoimmunity associated with subclinical atherosclerosis in young women with type 1 diabetes mellitus?]

INTRODUCTION: It has been hypothesized that autoimmunity may contribute to cardiovascular complications and may be an important trigger for processes leading to atherosclerosis, especially in type 1 diabetes mellitus (T1DM). This pilot study aimed to answer the question of whether markers of thyroid autoimmunity are associated with increased carotid intima-media thickness (cIMT) in young, asymptomatic T1DM women. MATERIAL AND METHODS: The study population consisted of 102 women, including 72 with T1DM and 30 healthy controls. All patients had thyroid hormones within the normal range. According to the antiperoxidase antibodies (aTPO) titre, the T1DM women were divided into an aTPO-positive (T1DM aTPO+) (n = 41) and an aTPO-negative (T1DM aTPO-) (n = 31) group. In all patients, aTPO, thyroglobulin antibody (aTG) titres, thyroid-stimulating hormone (TSH), free thyroxine (FT3), free triiodothyronine (FT4), lipid parameters, glycated haemoglobin, thyroid ultrasonography, and cIMT assessment were evaluated. The association of cIMT with different risk factors related to thyroid autoimmunity was determined. RESULTS: Carotid intima-media thickness was significantly greater in T1DM aTPO+ females (0.66 ± 0.10 mm) than in T1DM aTPO- (0.59 ± 0.11 mm) and healthy controls (0.58 ± 0.10 mm) (p = 0.007, p = 0.001, respectively). In all women cIMT was significantly, positively correlated with aTPO (p = 0.005, r = 0.273), Hashimoto's thyroiditis (HT) duration (p = 0.00015, r = 0.367), levothyroxine dose per week (p = 0.006, r = 0.269), and ultrasound features of HT (p = 0.004, r = 0.281) and inversely with fT3 concentration (p = 0.014, r = -0.243) and FT3/FT4 ratio (p = 0.042, r = -0.201). A logistic regression analysis showed that HT duration (OR: 1.102, 95% CI: 1.008-1.206, p = 0.032) and a positive history family of HT (OR: 3.909, 95%CI: 1.014-15.071, p = 0.045) were risk factors for increased cIMT. However, multivariate regression analysis showed that the studied parameters related to thyroid autoimmunity are not independent risk factors for increased cIMT. CONCLUSIONS: We expanded the data on cIMT in young women with T1DM and showed that thyroid autoimmunity, and in particular the duration of exposure to anti-thyroid antibodies, despite adequate levothyroxine substitution, is associated with subclinical atherosclerosis in young women with T1DM. However, thyroid-related parameters are not independent risk factors for increased cIMT in euthyroid women.

Breakdown of Diabetic Foot Ulcer Care during the First Year of the Pandemic in Poland: A Retrospective National Cohort Study.

The COVID-19 pandemic revealed a breakdown of the system of DFU patient care. This retrospective national cohort study analyses the epidemiological status of DFU patients in relation to urgent and elective hospitalizations, amputation rates, and deaths in Poland from 2017 to 2019, and during 2020 when the COVID-19 pandemic began. The data were obtained from national medical records gathered by the National Health Fund (NHF). Discharge diagnoses were categorized according to ICD-10 and ICD-9 codes. Analysis of the data showed a statistically significant decrease in elective hospital admissions (from 29.6% to 26.3%, p = 0.001). There was a decrease in the percentage of hospitalizations related to limb-salvage procedures (from 79.4% to 71.3%, p = 0.001). The opposite tendency was observed among urgent hospital admissions (from 67.0% to 73.2%, p = 0.01), which was related to a significant increase in the number of minor amputations (from 3146 to 4269, p = 0.017). This rise was in parallel with the increase in the percentage of patients who died during hospitalization due to DFU (from 3.9% to 4.8%, p = 0.03). The number of deaths has not changed significantly (from 590.7 to 668.0, p = 0.26). The results of the conducted analyses confirm the negative tendencies in the medical care of patients with DFU during the first year of the pandemic in Poland. Changes in therapy schemes and stronger patient support following this period are necessary to avoid further complications in patients with DFU.

Temporomandibular Disk Dislocation Impacts the Stomatognathic System: Comparative Study Based on Biexponential Quantitative T2 Maps.

In this study, we aimed to assess the potential impact of temporomandibular disk displacement on anatomical structures of the stomatognathic system using biexponential T2 magnetic resonance imaging (MRI) maps. Fifty separate MRI scans of the temporomandibular joints (TMJ) of 25 patients were acquired with eight echo times. Biexponential T2 maps were created by weighted reconstruction based on Powell's conjugate direction method and divided into two groups: the TMJ without (32 images) and with (18 images) disk displacement. The disk, retrodiscal tissue, condylar bone marrow, masseter muscle, lateral and medial pterygoid muscles and dental pulp of the first and second molars were manually segmented twice. The intrarater reliability was assessed. The averages and standard deviations of the T2 times and fractions of each segmented region for each group were calculated and analysed with multiple Student's t-tests. Significant differences between groups were observed in the retrodiscal tissue, medial pterygoid muscle and bone marrow. The pulp short T2 component showed a trend toward statistical significance. The segmentation reliability was excellent (93.6%). The relationship between disk displacement and quantitative MRI features of stomatognathic structures can be useful in the combined treatment of articular disk displacement, pterygoid muscle tension and occlusive reconstruction.

Sirtuin 1, Visfatin and IL-27 Serum Levels of Type 1 Diabetic Females in Relation to Cardiovascular Parameters and Autoimmune Thyroid Disease.

The loss of cardioprotection observed in premenopausal, diabetic women may result from the interplay between epigenetic, metabolic, and immunological factors. The aim of this study was to evaluate the concentration of sirtuin 1, visfatin, and IL-27 in relation to cardiovascular parameters and Hashimoto's disease (HD) in young, asymptomatic women with type 1 diabetes mellitus (T1DM). Thyroid ultrasound, carotid intima-media thickness (cIMT) measurement, electrocardiography, and echocardiography were performed in 50 euthyroid females with T1DM (28 with HD and 22 without concomitant diseases) and 30 controls. The concentrations of serum sirtuin 1, visfatin and IL-27 were assessed using ELISA. The T1DM and HD group had higher cIMT (p = 0.018) and lower left ventricular global longitudinal strain (p = 0.025) compared to females with T1DM exclusively. In women with a double diagnosis, the sirtuin 1 and IL-27 concentrations were non-significantly higher than in other groups and significantly positively correlated with each other (r = 0.445, p = 0.018) and thyroid volume (r = 0.511, p = 0.005; r = 0.482, p = 0.009, respectively) and negatively correlated with relative wall thickness (r = -0.451, p = 0.016; r = -0.387, p = 0.041, respectively). These relationships were not observed in the control group nor for the visfatin concentration. These results suggest that sirtuin 1 and IL-27 contribute to the pathogenesis of early cardiac dysfunction in women with T1DM and HD.

Pain assessment and management in children in the postoperative period: A review of the most commonly used postoperative pain assessment tools, new diagnostic methods and the latest guidelines for postoperative pain therapy in children.

Pain is one of the most common complaints expressed by hospital patients and is the main reason they seek medical help. Pain is always subjective, so its severity should be assessed individually for each patient. The main issue with pain management in children is the difficulty involved in evaluating it. Numerous studies have developed tools that would allow for an accurate assessment of the intensity of pain in children in the postoperative period. Adequate postoperative pain assessment in pediatric patients may significantly improve their comfort and quality of life. Postoperative pain prolongs recovery and hospitalization; therefore, the severity of the pain should be part of a routine assessment. Whichever tool is applied to measure pain, it should take into account the child's age, language, ethnicity, and cognitive ability. There is no one universal method for pain assessment which is appropriate for every pediatric patient. This article provides a review of the available subjective methods of postoperative pain assessment, including new objective diagnostic methods and the latest guidelines for postoperative pain therapy in a group of pediatric patients.

Monitoring of the Achilles tendon healing process: can artificial intelligence be helpful?

PURPOSE: The aim of this study was to verify improved, ensemble-based strategy for inferencing with use of our solution for quantitative assessment of tendons and ligaments healing process and to show possible applications of the method. METHODS: We chose the problem of the Achilles tendon rupture as an example representing a group of common sport traumas. We derived our dataset from 90 individuals and divided it into two subsets: healthy individuals and patients with complete Achilles tendon ruptures. We computed approx. 160 000 2D axial cross-sections from 3D MRI studies and preprocessed them to create a suitable input for artificial intelligence methods. Finally, we compared different training methods for chosen approaches for quantitative assessment of tendon tissue healing with the use of statistical analysis. RESULTS: We showed improvement in inferencing with use of the ensemble technique that results from achieving comparable accuracy of 99% for our previously published method trained on 500 000 samples and for the new ensemble technique trained on 160 000 samples. We also showed real-life applications of our approach that address several clinical problems: (1) automatic classification of healthy and injured tendons, (2) assessment of the healing process, (3) a pathologic tissue localization. CONCLUSIONS: The presented method enables acquiring comparable accuracy with less training samples. The applications of the method presented in the paper as case studies can facilitate evaluation of the healing process and comparing with previous examination of the same patient as well as with other patients. This approach might be probably transferred to other musculoskeletal tissues and joints.

microRNA expression profile in Smooth Muscle Cells isolated from thoracic aortic aneurysm samples.

PURPOSE: Thoracic aortic aneurysm (TAA) is a cardiovascular disease characterized by increased aortic diameter, treated with surgery and endovascular therapy in order to avoid aortic dissection or rupture. The mechanism of TAA formation has not been thoroughly studied and many factors have been proposed to drive its progression; however strong focus is attributed to modification of smooth muscle cells (SMCs). Latest research indicates, that microRNAs (miRNAs) may play a significant role in TAA development - these are multifunctional molecules consisting of 19-24 nucleotides involved in regulation of the gene expression level related to many biological processes, i.e. cardiovascular disease pathophysiology, immunity or inflammation. MATERIALS AND METHODS: Primary SMCs were isolated from aortic scraps of TAA patients and age- and sex-matched healthy controls. Purity of isolated SMCs was determined by flow cytometry using specific markers: α-SMA, CALP, MHC and VIM. Real-time polymerase chain reaction (RT-PCR) was conducted for miRNA analysis. RESULTS: We established an isolation protocol and investigated the miRNA expression level in SMCs isolated from aneurysmal and non-aneurysmal aortic samples. We identified that let-7 g (0.71-fold, p = 0.01), miR-130a (0.40-fold, p = 0.04), and miR-221 (0.49-fold, p = 0.05) significantly differed between TAA patients and healthy controls. CONCLUSIONS: Further studies are required to improve our understanding of the pathophysiology underlying TAA, which may aid the development of novel, targeted therapies. The pivotal role of miRNAs in the cardiovascular system provides a new perspective on the pathophysiology of thoracic aortic aneurysms.

Normative Values for Heart Rate Variability Parameters in School-Aged Children: Simple Approach Considering Differences in Average Heart Rate.

Background: Heart rate variability (HRV) analysis is a clinical tool frequently used to characterize cardiac autonomic status. The aim of this study was to establish normative values for short-term HRV parameters by considering their main determinants in school-aged children. Methods: Five-minute electrocardiograms were taken from 312 non-athlete children (153 boys) at age of 6 to 13 years for computation of conventional time- and frequency-domain HRV parameters. Heart rate (HR), respiratory rate, age, body mass index, and sex were considered as their potential determinants. Multiple regression analysis revealed that HR was the principal predictor of all standard HRV indices. To develop their universal normative limits, standard HRV parameters were corrected for prevailing HR. Results: The HRV correction for HR yielded the parameters which became independent on both sex and HR, and only poorly dependent on age (with small effect size). Normal ranges were calculated for both time- and frequency-domain indices (the latter computed with either fast Fourier transform and autoregressive method). To facilitate recalculation of standard HRV parameters into corrected ones, a calculator was created and attached as a Supplementary Material that can be downloaded and used for both research and clinical purposes. Conclusion: This study provides HRV normative values for school-aged children which have been developed independently of their major determinants. The calculator accessible in the Supplementary Material can considerably simplify determination if HRV parameters accommodate within normal limits.

Heart Rate and Respiratory Rate Influence on Heart Rate Variability Repeatability: Effects of the Correction for the Prevailing Heart Rate.

BACKGROUND: Since heart rate variability (HRV) is associated with average heart rate (HR) and respiratory rate (RespRate), alterations in these parameters may impose changes in HRV. Hence the repeatability of HRV measurements may be affected by differences in HR and RespRate. The study aimed to evaluate HRV repeatability and its association with changes in HR and RespRate. METHODS: Forty healthy volunteers underwent two ECG examinations 7 days apart. Standard HRV indices were calculated from 5-min ECG recordings. The ECG-derived respiration signal was estimated to assess RespRate. To investigate HR impact on HRV, HRV parameters were corrected for prevailing HR. RESULTS: Differences in HRV parameters between the measurements were associated with the changes in HR and RespRate. However, in multiple regression analysis only HR alteration proved to be independent determinant of the HRV differences-every change in HR by 1 bpm changed HRV values by 16.5% on average. After overall removal of HR impact on HRV, coefficients of variation of the HRV parameters significantly dropped on average by 26.8% (p < 0.001), i.e., by the same extent HRV reproducibility improved. Additionally, the HRV correction for HR decreased association between RespRate and HRV. CONCLUSIONS: In stable conditions, HR but not RespRate is the most powerful factor determining HRV reproducibility and even a minimal change of HR may considerably alter HRV. However, the removal of HR impact may significantly improve HRV repeatability. The association between HRV and RespRate seems to be, at least in part, HR dependent.

[How much water is lost during breathing?]. / Ile wody tracimy z oddechem?

Arising from the Antoine equation and the ideal gas law, the volume of exhaled water has been calculated. Air temperature, humidity and minute ventilation has been taken into account. During physical exercise amount of exhaled H(2)O is linear, but not proportional to heart rate. And so at the heart rate of 140 bpm amount of exhaled water is approximately four times higher than during the rest and equals about 60-70 ml/h. The effect of external temperature and humidity on water lost via lungs was assessed as well. When temperature of inspired air and its humidity is 35°C an 75% respectively loss of water is 7 ml/h. Whereas when above parameters are changed to minus 10°C and 25% lung excretion of H(2)O increases up to 20 ml/h. The obtained results may become the basis for the assessment of osmolarity changes on the surface of the lower airways. The increase of which is recently considered as one of the factors responsible for exercise induced bronchospasm.