Sinding-Larsen-Johansson disease. Clinical features, imaging findings, conservative treatments and research perspectives: a scoping review.

Objective: This review aims to consolidate existing research on the pathogenesis, clinical diagnosis, imaging outcomes, and conservative treatments of Sinding-Larsen-Johansson disease (SLJD), identifying literature gaps. Design: Scoping Review. Methods: A comprehensive literature search was conducted across databases including PubMed, Scopus, Medline OVID, Embase, Web of Science, and Grey literature following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) extension for scoping reviews. The quality of included studies was assessed using the Joanna Briggs Institute (JBI) checklist. Results: The body of evidence on SLJD, primarily derived from case studies, reveals limited and often conflicting data. Key findings include: (1) SLJD commonly presents as localized knee pain in physically active adolescents, particularly males, (2) ultrasound and MRI are the most effective diagnostic tools, (3) conservative treatment, which mainly focuses on activity limitation, yields positive outcomes within two to eight months. Conclusions: Our review shows that SLJD mainly affects physically active adolescents aged 9-17 years. The authors recommend conservative treatment, rest and/or cryotherapy, passive mobilization, muscle restraint, isometric exercise, and NSAIDs. Further cohort studies are necessary to refine the management and application of the SLJD treatment database.

The Impact of Liver Failure on the Immune System.

Liver failure profoundly affects the immune system, leading to dysregulation of innate and adaptive immune response. This review explores the intricate relationship between liver function and immune homeostasis. The role of the liver as a central hub in immune response initiation is elucidated, emphasizing its involvement in hepatic inflammation induction and subsequent systemic inflammation. Cytokines, chemokines, growth factors, and lipid mediators orchestrate these immune processes, serving as both prognostic biomarkers and potential therapeutic targets in liver failure-associated immune dysregulation, which might result from acute-on-chronic liver failure (ACLF) and cirrhosis. Furthermore, the review delves into the mechanisms underlying immunosuppression in liver failure, encompassing alterations in innate immune cell functions such as neutrophils, macrophages, and natural killer cells (NK cells), as well as perturbations in adaptive immune responses mediated by B and T cells. Conclusion: Understanding the immunological consequences of liver failure is crucial for developing targeted therapeutic interventions and improving patient outcomes in liver disease management.

Does Concomitant Meniscectomy or Meniscus Repair Affect Muscle Strength, Lower Extremity Balance, and Functional Tests after Anterior Cruciate Ligament Reconstruction?

Background/Objective: The effects of concomitant meniscal tears and their associated treatment on strength, lower extremity balance, and functional status after anterior cruciate ligament reconstruction (ACLR) have not been widely investigated. This study aimed to compare the functional outcomes in patients who underwent ACLR with concomitant treatment of the medial meniscus repair versus meniscectomy when returning to unrestricted physical activity. Methods: A total of 85 patients who underwent primary ACLR with combined meniscal repair (MREP; n = 39) or meniscectomy (MRES; n = 46) were assessed. The dataset included the Functional Movement ScreenTM (FMS) outcomes and single-leg balance test (SLBT) with anterior-posterior, medial-lateral, and overall stability indexes. Isokinetic knee extension and flexion strengths were tested at velocities of 60 deg·s-1 and 180 deg·s-1. The peak torque-to-body weight ratio (PT/BW) and limb symmetry index (LSI) were calculated. Results: In the functional assessment, there was no significant inter-group difference in the composite score of the FMS (MREP: 15.08 pts vs. MRES: 15.13 pts; p > 0.05). The SLBT outcomes in inter-group and inter-extremity comparisons were irrelevant (p > 0.05), too. Significant differences emerged in the inter-group comparison of the knee extension strength in the non-operated extremity at both 60 deg·s-1 and 180 deg·s-1 (p = 0.02). Inter-extremity differences were significant in both the MREP and MRES groups for knee extension and flexion at both angular velocities (all p values < 0.05). For knee extension, the LSI values ranged from 82% to 87%, and for flexion, from 77% to 84%, with no significant inter-group differences. Conclusions: Patients undergoing ACLR with concomitant meniscal repair or resection did not exhibit differences in isokinetic muscle strength, lower extremity balance, and functional tests upon returning to activity. However, participants in both groups demonstrated significant differences between the operated and non-operated extremities as far as the knee joint extensor and flexor strengths are concerned. Therefore, rehabilitation protocols should prioritize equalizing inter-extremity strength differences after the ACLR with additional treatment procedures addressing the menisci.

Knee function and quality of life in adolescent soccer players with Osgood Shlatter disease history: a preliminary study.

The aim of the study was to assess psycho-physical deficits among young athletes with history of Osgood Shlatter Disease (OSD-H) compared to adolescents without history of knee pain (Control group). Eighteen participants were recruited from a group of 80 young (U14-U17) male soccer players. Medical records, and Knee Osteoarthritis Outcome Score (KOOS) were performed from both groups. The tests were conducted to assess the anthropometric characteristics, knee and ankle range of motion (Ely's and Weight Bearing Lunge tests), and muscle power of the lower limbs (Leg Press, Single Leg Countermovement Jump, and Single Leg Hop for Distance). Results showed that overall patient-relevant outcomes following OSD (87%) were significantly lower than in the Control group (95%) (p < 0.05). Scores of the KOOS subscales revealed that Quality of Life and Function, Sports and recreational activities were significantly lower in the OSD-H group (p < 0.05). Although, there were no differences in subscale scores for Pain, Symptoms and Daily Activities. There were, also no difference between groups in range of motion angles and muscle power of the lower limbs values. The preliminary results support existing knowledge indicate that OSD may have a long-term influence on function, sports and recreational participation, and quality of life on young athletes.

Ogilvie's Syndrome in a Patient at 23 Weeks of Pregnancy: Report of a Rare Case with Successful Surgical Intervention.

BACKGROUND Ogilvie's syndrome (acute colonic pseudo-obstruction) is a syndrome characterized by symptoms suggestive of intestinal obstruction without an identifiable mechanical cause. It presents with excessive dilation of the loops of the large intestine. The treatment options include conservative management, endoscopic methods, and surgical intervention. If appropriate treatment is not implemented promptly, this syndrome can lead to life-threatening complications for the patient. Acute colonic pseudo-obstruction typically occurs in elderly individuals with numerous chronic diseases, extensive surgeries, or trauma. In younger individuals, risk factors include gynecological procedures, pregnancy, and childbirth. CASE REPORT This work presents a case of a 30-year-old woman at 23 weeks of pregnancy. She presented with persistent abdominal pain, nausea, and vomiting for several days. The patient was initially treated at the Obstetrics Clinic, where conservative management was implemented. Due to worsening symptoms after confirming pathological distension of the colon in the magnetic resonance imaging examination, she was transferred to the surgery clinic. Due to her unstable general condition and lack of improvement with conservative treatment, she was qualified for an appendectomy with the formation of a cecostomy. The performed surgical treatment led to an improvement in the patient's condition and did not have a negative impact on the further development of the child. CONCLUSIONS Ogilvie's syndrome in pregnancy is an extremely rare condition that can lead to significant complications. Its treatment requires the coordinated efforts of a multidisciplinary team of specialists. During the course of therapy, it is important to consider the limitations imposed by pregnancy on diagnostic and therapeutic methods.

Adolescents' Knowledge and Attitudes Related to Hand Eczema: A Cross-Sectional Study.

Background: Hand eczema (HE) is a common inflammatory skin disease occurring in subjects of any age. Literature data on knowledge of HE in different age-groups are scarce. Purpose: To evaluate knowledge and attitudes related to HE among adolescents. Methods: A total of 258 high school students were invited to participate in this project. A specially designed questionnaire created on the base of previous studies was used to assess adolescents' knowledge of HE. HE was self-reported answering the validated single question "Have you ever had hand eczema?" Results: Data from 243 students (94.2% response rate) were obtained for final analysis. There were 117 (48.1%) females and 126 (51.9%), males with a mean age of 16.0±1.7 years. Sixty-eight students (28%) reported a personal history of HE, and 32.8% declared having knowledge of HE. More females than males (P=0.023) declared that they knew what HE was (39.3% and 26.2%, respectively). Hand cream was used on a regular basis by 49% of adolescents. Females used hand cream more frequently (P<0.001) than males. No difference in declared knowledge of HE was found between subjects with and without a personal history of hand lesions. Students declaring having adequate knowledge of HE used hand cream more commonly (P=0.045). Conclusion: Although HE is a common disease in the general population, including adolescents, less than a third of subjects were aware of this entity. Almost half were using hand cream, but interestingly, personal history of HE did not increase the regular application of hand cream.

Alexithymia in adolescents in Poland: an important issue in the holistic approach to patients' care.

Introduction: Alexithymia is defined as a disturbed ability to identify and verbally express emotions with a limited imaginative capacity as well as externally oriented thinking. The literature on alexithymia is limited and scarce research concentrated on alexithymia in different gender groups. Aim: As alexithymia may influence the therapeutic outcome, the objective of the study was to assess the prevalence of alexithymia in adolescents in Poland, paying special attention to gender differences. Material and methods: This cross-sectional study was run on a group of 730 high school students in Poland. The mean age of this group was 17.05 ±1.18 years (age range: 15-19 years). Alexithymia was assessed with Toronto Alexithymia Scale (TAS-20). Results: Alexithymia was found in 31.0% of adolescents. 56.0% of subjects presented with signs of at least intermediate (borderline) alexithymia. Significantly more females than males suffered from alexithymia (37.0% and 20.8%, respectively; p < 0.001). TAS-20 scores were also significantly higher in females than males (55.59 ±12.32 points and 49.40 ±12.00, respectively; p < 0.001). The same phenomenon was observed for the following domains of alexithymia: difficulty in identifying feelings (DIF) and difficulty in describing feelings (DDF). However, there was no difference in gender distribution in the externally oriented thinking (EOT) domain. Conclusions: Alexithymia was shown to be common among adolescents in our country. More females than males suffer from this condition. This seems to be of importance in the holistic approach to patients' care.

Strength training program for an athlete with hemophilia A and an inhibitor while taking a new prophylactic drug treatment: a case report.

BACKGROUND: Currently, patients with hemophilia and inhibitor are being offered therapy, including a tissue factor pathway inhibitor (TFPI). The new prophylactic drug treatment may allow for new opportunities for other interventions and overall improvement in quality of life. This case report assessed the safety and effects of a strength training program in a patient with an inhibitor on a specific new study drug. DESCRIPTION: A 20-year-old patient with severe hemophilia A with an inhibitor participated in a 6-week strength training program. The strengthening program consisted of 7 exercises involving limb and trunk muscles. A qualitative assessment of movement patterns was performed using the Functional Movement Test. Dynamic balance was measured by the Y-Balance Test, whereby the power of lower extremities was measured by Counter Movement Jump. The Quality of Life Index was done by survey to assess the perceived overall quality of the patient's life. The exercise fatigue after each training was measured with the Borg scale. OUTCOMES: After the intervention during treatment with the new drug, the patient's quality of life increased, especially in terms of health and function (from 15.6 to 29.1 points), also, the power of the lower limbs increased. There were no bleeding episodes during the intervention and after a 3-month follow-up. CONCLUSION: The proposed program during the application of the new prophylactic treatment seems to be effective in improving quality of life and increasing lower limb power in a hemophilic patient with an inhibitor. However, randomized clinical trials are needed to confirm the results.

Neurological complications in patients undergoing general surgery: A literature review.

Surgical procedures are extremely burdensome for patients, as in addition to complications directly related to the intervention, they expose the patient to further complications resulting from the disturbance of key functions of homeostasis in the body's systems, particularly the circulatory, respiratory, and nervous systems. Furthermore, they may contribute to the exacerbation of symptoms of underlying chronic diseases. This paper focuses on the most common possible neurological complications that may occur after surgical procedures and includes topics such as stroke, chronic pain, neuropathy, and delirium. The risk factors for neurological deficits, their known or possible etiology, the most characteristic symptoms, and potential preventive actions are discussed. The paper analyzes articles from the PubMed, ResearchGate, and Scopus databases. A surge0on's knowledge of possible complications that may occur in the perioperative period enables early recognition and effective reduction of their negative impact on the patient's functioning and quality of life after surgery, contributing to better overall treatment outcomes.

Biological Maturation Predicts Dynamic Balance and Lower Limb Power in Young Football Players.

Biological maturation has an increasingly important role in youth sports. The aim of the study was to evaluate the relationship between dynamic balance and lower limb power and biological maturation in young football players. Seventy-two healthy, young male elite football players (age: 10 ± 2) participated in the study. Dynamic balance was assessed using a modified Star Excursion Balance Test (mSEBT). Power of the lower limbs was examined by a Countermovement Jump test (CMJ) and Single Leg Hop for Distance (SLHD). Furthermore, anthropometry and biological maturation (age, peak height velocity, and maturity offset) were assessed. There was a strong positive correlation between vertical jump (r = 0.75), distance long jump (r = 0.84), and biological maturation. A moderate positive correlation was found between dynamic balance (mSEBT COM, PL, and PM) and maturity offset. There was a significant association between mSEBT, CMJ, and SLHD (p < 0.05). Moreover, maturity offset explained 75% of vertical jump and 74% of distance long jump performance, respectively, and 12% of dynamic balance. Biological maturation should be considered when assessing athletic performance, establishing rehabilitation, and sports training in youth football players.

Facial acne causes stigmatization among adolescents: A cross-sectional study.

BACKGROUND: Stigmatization is defined as a discrediting mark which sets the person from others and hindering interpersonal relationships. Literature data on stigma in acne subjects are scarce. AIMS: This study was undertaken to assess feelings of stigmatization in adolescents with facial acne. MATERIAL/METHODS: The study was performed on 730 high-school students aged 15 to 19 years with the mean age of 17.05 ± 1.18 years. Self-reported acne was found in 74.9% of subjects. The severity of acne was self-assessed with the standardized color images based on Investigators Global Assessment (IGA). Stigmatization was studied with 6-Item Stigmatization Scale (6-ISS) and Perceived Stigmatization Questionnaire (PSQ). Additionally, quality of life (QoL) was evaluated with Dermatology Life Quality Index (DLQI). RESULTS: 58% of adolescents with acne presented with feelings of stigmatization. Within the acne population, stigmatization was significantly more common in females than in males (p < 0.001). The mean level of stigmatization according to 6-ISS was significantly higher in acne sufferers than in those free from acne (1.68 ± 2.42 points and 0.55 ± 1.50 points, respectively; p < 0.001). Feelings of stigmatization were significantly more pronounced by females than males (p < 0.001). Staring at the skin and the fact that others are not attracted to person due to skin lesions were main problems raised by the study participants with acne. 6-ISS scores correlated with acne severity (r = 0.278; p < 0.001) and both 6-ISS and PSQ scores with QoL impairment (r = 0.530; p < 0.001 and r = 0.341; p < 0.001, respectively). CONCLUSIONS: Facial acne is a highly stigmatized skin disease and requires a holistic therapeutic approach.

Association between Selected Screening Tests and Knee Alignment in Single-Leg Tasks among Young Football Players.

This study aimed to examine the relationship between knee valgus in the frontal plane projection angle (FPPA) during single-leg squat (SLS), single-leg landing (SLL), and other selected clinical tests in young athletes. Forty-three young healthy elite football players (age: 13.2 (1.7) years) that were regularly training in a local sports club participated in the study. The FPPA was assessed using 2D video analysis. The screening tests included the passive single-leg raise (PSLR), hip external and internal rotation (hip ER and IR), sit and reach test, weight-bearing lunge test (WBLT), modified star excursion balance test (mSEBT), countermovement jump (CMJ), single-leg hop for distance (SLHD), and age peak height velocity (APHV). There was a significant positive relationship between the knee valgus angles in the SLS test and the sit and reach test (r = 0.34) and a negative relationship with the hip ER ROM (r = −0.34) (p < 0.05). The knee valgus angles in the SLL were negatively associated with the hip IR (r = −0.32) and ER ROM (r = −0.34) and positive associated with the WBLT (r = 0.35) and sit and reach test (r = 0.33) (p < 0.05). Linear regression analysis showed that the results of the hip ER ROM and sit and reach tests were independent predictors of the FPPA in the SLS test (r2 = 0.11, p = 0.03 and r2 = 0.12, p = 0.02, respectively). The conducted study showed that individuals with more hip range of motion, more spine flexion extensibility, and less ankle dorsiflexion ROM may be more likely to experience high degrees of knee valgus in FPPA.

Alexithymia in Adolescents with Acne: Association with Quality of Life Impairment and Stigmatization.

Alexithymia seems to be more common among patients with skin diseases. However, studies on acne patients are very limited. We conducted this study to evaluate alexithymia in adolescents with acne. In our cross-sectional study, 730 high school students (mean age: 17.05 ± 1.18 years) were recruited. The Toronto Alexithymia Scale (TAS-20) was used to measure alexithymia, the Dermatology Life Quality Index (DLQI) was employed to study quality of life (QoL), and the 6-item Stigmatization Scale (6ISS) was used to evaluate the level of stigmatization in acne subjects. Alexithymia was found in 31% of adolescents, with similar prevalence among those with and without acne (31.3% and 30.1%, respectively). The mean scoring on the TAS-20 in patients with acne (53.1 ± 12.8 points) was not significantly different from that of the non-acne group (53.5 ± 11.9 points). However, significant correlations between TAS-20 scores and QoL assessments (r = 0.332, p < 0.001) as well as stigmatization level (r = 0.284, p < 0.001) were found. These correlations were also significant for the domains of alexithymia described as difficulty in identifying feelings (DIF) and difficulty in describing feelings (DDF), but not for externally oriented thinking (EOT). The findings clearly showed that acne does not predispose to alexithymia; however, alexithymia in acne subjects is related to impaired QoL and stigmatization.

Prevalence and quality of life of facial acne: a cross-sectional study in high school students in Poland.

Introduction: Acne is a frequent chronic inflammatory disease, which affects most commonly adolescents. It might have a negative effect on patients' well-being. Aim: To appraise the prevalence of facial acne among adolescents and to assess how acne of different clinical severity influences quality of life in this age group. Material and method: This cross-sectional study was conducted on a representative sample of individuals aged 15-19 years in high schools in Poland. A total of 730 students were included in the final analysis. Standardized photographs according to the Investigator's Global Assessment (IGA) were used for self-assessment of both the presence and severity of facial acne. The Dermatology Life Quality Index (DLQI) was employed to evaluate subjects' quality of life (QoL) impairment. Results: Facial acne was found in 547 (74.9%) respondents with no significant difference in acne prevalence among females (75.1%) and males (74.6%). The vast majority of acne individuals (90.9%) suffered from minimal and mild acne, moderate acne was reported by 7.3% and severe one by 1.8% of acne students. Acne had a small effect on QoL (DLQI mean score of 2.8 ±3.6 points); females had significantly more decreased QoL than males (3.17 ±3.74 and 1.76 ±2.69 points, respectively). QoL impairment positively correlated with the clinical severity of facial acne. Conclusions: Facial acne is a common health problem in adolescents. Although it is not very severe in the majority of subjects it significantly decreases their QoL. Therefore, acne should be treated as a serious skin condition requiring a holistic approach to the patients.

Successful Late Endoscopic Stent-Grafting in a Patient with Boerhaave Syndrome.

BACKGROUND Boerhaave syndrome is a rare esophageal injury associated with a high mortality rate of 14.8%. Immediate diagnosis and treatment have been associated with a better outcome. Surgery remains the mainstay of treatment for those who present early with widespread septic contamination. One of the most difficult dilemmas in the treatment of Boerhaave syndrome is selection of the most appropriate management for late perforations with severe septic complications. In this situation, aggressive surgical approach with esophagectomy and immediate or postponed reconstruction is usually recommended. CASE REPORT We report a patient with spontaneous esophageal rupture successfully treated by late endoscopic stent-grafting. The patient was transferred from a rural hospital after initial non-effective conservative treatment. Endoscopic stent-grafting was performed 7 days from the onset of symptoms. A self-expanding plastic stent-graft (Polyflex) used initially very early migrated to the stomach. The plastic stent-graft was then replaced by a fully covered self-expandable metal stent-graft (EndoMAXX), which was wider and equipped with anti-migration struts. Implantation of the EndoMAXX stent-graft resulted in clinical success, with the closure of esophageal rupture confirmed 8 weeks after stent-grafting. CONCLUSIONS Our case indicates that even late after spontaneous esophageal perforation, less invasive treatment by endoscopic stent-grafting with adequate drainage of septic contamination may be an attractive option for preserving the esophagus in selected patients in stable hemodynamic condition. Our case also supports implantation of wider metallic stent-grafts to seal benign esophageal perforation above the esophago-gastric junction to prevent early migration to the stomach.

Impact of Three Strengthening Exercises on Dynamic Knee Valgus and Balance with Poor Knee Control among Young Football Players: A Randomized Controlled Trial.

The observed dynamic knee valgus and the limited dynamic balance described in the literature are modifiable risk factors for injuries in athletes. Therefore, identification and appropriate prevention are crucial in managing the development of young athletes. The aim of the study was to assess the effectiveness of three exercises strengthening the muscles: gluteal medius, popliteal and tibialis posterior to reduce dynamic knee valgus and improve the dynamic balance of the lower limbs in young football players with poor knee control. A total of 134 footballers were assessed for eligibility, and finally 45 participants (age 12-15) met the inclusion criteria. Participants were assessed with 2D video kinematic analysis during single-leg squats to assess the knee valgus angles and the dynamic balance (Y-Balance Test). No significant interactions between groups (Control and Exercise) and time (baseline and after 6 week) were noted for dynamic valgus for the left and right knee (p > 0.05). For the dynamic balance, there were statistically significant results, but not clinically relevant for anterior, posteromedial, and composite direction for the right lower limbs and for the anterior direction for left lower limbs in the exercise group. However, there were no significant differences (p > 0.05) in all of the YBT scores for both lower limbs between groups. This study demonstrated that there were no statistically significant differences in dynamic knee valgus angles and dynamic balance values after 6 weeks of exercise program in young footballers with poor knee control. Future randomized trials should focus on more comprehensive exercises, where possible using biofeedback methods to improve knee kinematics.

The Relationship between Dynamic Balance and Jumping Tests among Adolescent Amateur Rugby Players. A Preliminary Study.

Rugby is a demanding contact sport. In light of research, poor balance, reduced jumping ability, muscle strength, and incorrect landing patterns might contribute to the increased risk of injury in athletes. Investigating the relationship between tests assessing these abilities might not only allow for the skillful programming of preventive training but also helps in assessing the risk of injury to athletes. Thus, the main purpose of this study was to investigate the relationship between dynamic balance, vertical and horizontal jumps, and jump-landings movement patterns. Thirty-one healthy amateur adolescent rugby players (age: 14.3 ± 1.6 years, height 171.4 ± 9.7 cm, body mass 80 ± 26 kg) participated in the study. Data were collected by the Y-balance Test (YBT), Counter Movement Jump (CMJ), Single Leg Hop for Distance (SLHD), and Landing Error Score System (LESS). Significant positive correlations were found between SLHD both legs (SLHDb) and YBT Composite both legs (COMb) (r = 0.51, p = 0.0037) and between SLHDb and CMJ (r = 0.72, p < 0.0001). A relationship was also observed between the CMJ and YBT COMb test (r = 0.51, p = 0.006). Moderate positive correlations were found between the dominant legs in SLHD and the posterolateral (r = 0.40, p = 0.027), posteromedial (r = 0.43, p = 0.014), and composite (r = 0.48, p = 0.006) directions of the YBT. These results indicate that variables that are dependent on each other can support in the assessment of injury-risk and in enhancing sports performance of young athletes.

The Role of Chloride Channels in the Multidrug Resistance.

Nowadays, one of medicine's main and most challenging aims is finding effective ways to treat cancer. Unfortunately, although there are numerous anti-cancerous drugs, such as cisplatin, more and more cancerous cells create drug resistance. Thus, it is equally important to find new medicines and research the drug resistance phenomenon and possibilities to avoid this mechanism. Ion channels, including chloride channels, play an important role in the drug resistance phenomenon. Our article focuses on the chloride channels, especially the volume-regulated channels (VRAC) and CLC chloride channels family. VRAC induces multidrug resistance (MDR) by causing apoptosis connected with apoptotic volume decrease (AVD) and VRAC are responsible for the transport of anti-cancerous drugs such as cisplatin. VRACs are a group of heterogenic complexes made from leucine-rich repetition with 8A (LRRC8A) and a subunit LRRC8B-E responsible for the properties. There are probably other subunits, which can create those channels, for example, TTYH1 and TTYH2. It is also known that the ClC family is involved in creating MDR in mainly two mechanisms-by changing the cell metabolism or acidification of the cell. The most researched chloride channel from this family is the CLC-3 channel. However, other channels are playing an important role in inducing MDR as well. In this paper, we review the role of chloride channels in MDR and establish the role of the channels in the MDR phenomenon.