Effects on cardiorespiratory fitness of moderate-intensity training vs. energy-matched training with increasing intensity

Introduction

The present study investigated the role of training intensity in the dose-response relationship between endurance training and cardiorespiratory fitness (CRF). The hypothesis was that beginners would benefit from an increase in training intensity after an initial training phase, even if the energy expenditure was not altered. For this purpose, 26 weeks of continuous moderate training (control group, CON) was compared to training with gradually increasing intensity (intervention group, INC) but constant energy expenditure.

Methods

Thirty-one healthy, untrained subjects (13 men, 18 women; 46 ± 8 years; body mass index 25.4 ± 3.3 kg m-2; maximum oxygen uptake, VO2max 34 ± 4 ml min-1 kg-1) trained for 10 weeks with moderate intensity [3 days/week for 50 min/session at 55% heart rate reserve (HRreserve)] before allocation to one of two groups. A minimization technique was used to ensure homogeneous groups. While group CON continued with moderate intensity for 16 weeks, the INC group trained at 70% HRreserve for 8 weeks and thereafter participated in a 4 × 4 training program (high-intensity interval training, HIIT) for 8 weeks. Constant energy expenditure was ensured by indirect calorimetry and corresponding adjustment of the training volume. Treadmill tests were performed at baseline and after 10, 18, and 26 weeks.

Results

The INC group showed improved VO2max (3.4 ± 2.7 ml kg-1 min-1) to a significantly greater degree than the CON group (0.4 ± 2.9 ml kg-1 min-1) (P = 0.020). In addition, the INC group exhibited improved Vmax (1.7 ± 0.7 km h-1) to a significantly greater degree than the CON group (1.0 ± 0.5 km h-1) (P = 0.001). The reduction of resting HR was significantly larger in the INC group (7 ± 4 bpm) than in the CON group (2 ± 6 bpm) (P = 0.001). The mean heart rate in the submaximal exercise test was reduced significantly in the CON group (5 ± 6 bpm; P = 0.007) and in the INC group (8 ± 7 bpm; P = 0.001), without a significant interaction between group and time point.

Conclusion

Increasing intensity leads to greater adaptations in CRF than continuing with moderate intensity, even without increased energy expenditure. After 26 weeks of training in the moderate- and higher-intensity domain, energy-matched HIIT elicited further adaptations in cardiorespiratory fitness. Thus, training intensity plays a crucial role in the dose-response relationship between endurance training and fitness in untrained but healthy individuals.

Clinical Trial Registration

https://www.drks.de/DRKS00031445, identifier DRKS00031445.

Patterns and influencing factors of exercise attendance of breast cancer patients during neoadjuvant chemotherapy

BACKGROUND

Performing 2-3 exercise sessions/week may relieve therapy-related side effects of breast cancer patients (BRCA) and improve their quality of life. However, attendance to the exercise sessions is often impaired. Thus, we investigated patterns and possible influencing factors of attendance to an aerobic (AT) or resistance training (RT) intervention in BRCA during neoadjuvant chemotherapy.

METHODS

BRCA (N = 122) were randomly allocated to supervised AT or RT twice weekly during neoadjuvant chemotherapy (18 ± 4 weeks). Attendance was calculated individually and group-wise per training week as the percentage of the performed sessions out of the prescribed sessions. Possible influencing factors were investigated using multiple regression analyses.

RESULTS

Mean individual attendance was 44.1% ± 29.3% with no significant differences between the groups. Group-wise attendance was highest in the first 6 weeks of training with ≥ 60% for AT and ≥ 50% for RT, but decreased over the course of the intervention accompanying chemotherapy. Significantly higher attendance was associated with not having vs. having nausea (ß =  - 14.57; p = 0.007) and not having vs. having pain (ß =  - 12.07; p = 0.12), whereas fatigue did not show any association (ß =  - 0.006; p = 0.96). Having been randomized into a preferred intervention group (48.8%) showed no association with attendance. Yet, patients' rating of the exercise intervention as "good"/ "very good" (58.7%) was significantly associated with higher attendance (p = 0.01).

CONCLUSION

For both exercise interventions, group-wise attendance/training week decreased during chemotherapy despite good intervention ratings. While some patients never started, others trained almost constantly twice weekly. The study revealed that patients who are nauseous or experience pain may need more support to attend more exercise sessions. Trial Registration Clinicaltrials.gov: NCT02999074 from May 6, 2016.

Maintenance of Aerobic or Resistance Training After an Exercise Intervention Among Breast Cancer Patients After Neoadjuvant Chemotherapy

BACKGROUND

Exercise interventions have been shown to be beneficial for cancer patients regarding various treatment-related side effects and quality of life. For sustainable effects, patients should continue the training. Therefore, we investigated the maintenance of an exercise training in breast cancer patients, reasons for (dis)continuation, and explored possible influencing factors.

METHODS

The investigation is based on a 3-arm randomized intervention trial comparing aerobic and resistance training (19 [4]) during or after neoadjuvant chemotherapy among breast cancer patients. About 2 years after breast surgery, 68 patients (age 52 [11] y) provided information about training continuation, self-reported reasons of (dis)continuation, sociodemographics, employment status, age, and body mass index. Training continuation was investigated with Kaplan-Meier analyses.

RESULTS

The intervention was rated as good or very good by 88.1% of participants. Nevertheless, 52.9% discontinued the training directly, but half of them changed to different types of exercise. Reasons for discontinuation included lack of time and long travel distance to the training facility. The median continuation was 19.0 months (Q1, Q3: 5.5, 36.0) with no statistically significant difference between the intervention groups. Younger, better educated, partnered patients tended toward longer training continuation.

CONCLUSIONS

The majority of patients continued exercising after the end of intervention. However, a nonnegligible number discontinued training immediately or after few months. Practical, social, and financial support for a transition to an adequate training that is affordable and feasible in the patient's daily life might foster training maintenance. Especially patients who are less educated, elderly, or living alone may need more support to continue exercising.

Prehabilitative high-intensity interval training and resistance exercise in patients prior allogeneic stem cell transplantation

Physical capacity prior allogeneic stem cell transplantation (allo-HCT) has been shown as a relevant prognostic factor for survival after transplant. Therefore, we evaluated feasibility and preliminary efficacy of a high-intensity interval training (HIIT) and moderate to high-intensity resistance exercise (RE) to increase physical capacity in patient's prior allo-HCT. In this multicentre single arm pilot study, a supervised exercise program was performed twice weekly for 4-12 weeks prior allo-HCT, depending on the individual time remaining. Outcomes were feasibility (recruitment, adherence, safety), physical capacity (cardiorespiratory fitness [VO2peak], muscle strength) and patient reported outcomes (physical functioning, fatigue). Thirty patients were intended, 16 could be included, and 14 completed post intervention assessment (75% male, 55 ± 11 years). The study was stopped early due to a low recruitment rate. Nine patients (64%) reached the initial minimum planned number of eight exercise sessions. Individual adherence was high with 92% for HIIT and 85% for RE. 87% of all performed exercise sessions were completed without complaints and VO2peak increased significantly from 20.4 to 23.4 ml/kg/min. The low recruitment rate suggests that initiation of the intervention concept immediately before allo-HCT is feasible only in a small number of patients. In particular, the timeframe directly prior allo-HCT seems too short for exercise interventions, although the exercise program was designed to improve outcomes in a very short time frame. HIIT and RE were feasible, effective and well accepted by the included patients.

Physical activity-related health competence and symptom burden for exercise prescription in patients with multiple myeloma: a latent profile analysis

The purpose of this study is to ensure best possible supply of exercise therapy to patients with multiple myeloma (MM); it is helpful to identify patient groups with similar symptom burden and physical activity-related health competences (PAHCO). Latent profile analyses (LPA) of MM patients were used to identify profiles of patients with similar PAHCO and symptom burden. Analysis of variance was applied to investigate group differences in important covariates. N = 98 MM patients (57% male, age 64 ± 9 years) could be assigned to three distinct PAHCO profiles: 46% were patients with high PAHCO, 48% patients with moderate, and 5% were patients with low PAHCO. The mean probability to be assigned to a certain profile was over 99%. The first group showed significant higher physical activity (PA) and lower comorbidities. Regarding symptom burden, three different profiles exist, including group one (32% of patients) with very low symptom burden, profile two (40%) with medium symptom burden, and group three (15%) with very high symptom burden (mean probability ≥ 98%). Patients in profile one had a lower number of treatment lines compared to the other profiles. Patients who were assigned to the high PAHCO profile were more likely to display a milder symptoms profile. In this exploratory analysis, we identified different patient profiles for PAHCO and symptom burden that may be used to individualize exercise recommendations and supervision modalities in MM patients. PAHCO and symptom burden level may be used to stratify MM patients in order to provide more personalized and effective exercise counseling. The profiles require individualized exercise recommendations and different supervision modalities, including educational instructions tailored particularly to every patient's needs, according to their PAHCO and symptom profile. TRIAL REGISTRATION NUMBER: NCT04328038.

Does Higher Intensity Increase the Rate of Responders to Endurance Training When Total Energy Expenditure Remains Constant? A Randomized Controlled Trial

BACKGROUND

Standardized training prescriptions often result in large variation in training response with a substantial number of individuals that show little or no response at all. The present study examined whether the response in markers of cardiorespiratory fitness (CRF) to moderate intensity endurance training can be elevated by an increase in training intensity.

METHODS

Thirty-one healthy, untrained participants (46 ± 8 years, BMI 25.4 ± 3.3 kg m^-2 and [Formula: see text]O_2max 34 ± 4 mL min^-1 kg^-1) trained for 10 weeks with moderate intensity (3 day week^-1 for 50 min per session at 55% HR_reserve). Hereafter, the allocation into two groups was performed by stratified randomization for age, gender and VO_2max response. CON (continuous moderate intensity) trained for another 16 weeks at moderate intensity, INC (increased intensity) trained energy-equivalent for 8 weeks at 70% HR_reserve and then performed high-intensity interval training (4 × 4) for another 8 weeks. Responders were identified as participants with VO_2max increase above the technical measurement error.

RESULTS

There was a significant difference in [Formula: see text]O_2max response between INC (3.4 ± 2.7 mL kg^-1 min^-1) and CON (0.4 ± 2.9 mL kg^-1 min^-1) after 26 weeks of training (P = 0.020). After 10 weeks of moderate training, in total 16 of 31 participants were classified as VO_2max responders (52%). After another 16 weeks continuous moderate intensity training, no further increase of responders was observed in CON. In contrast, the energy equivalent training with increasing training intensity in INC significantly (P = 0.031) increased the number of responders to 13 of 15 (87%). The energy equivalent higher training intensities increased the rate of responders more effectively than continued moderate training intensities (P = 0.012).

CONCLUSION

High-intensity interval training increases the rate of response in VO_2max to endurance training even when the total energy expenditure is held constant. Maintaining moderate endurance training intensities might not be the best choice to optimize training gains. Trial Registration German Clinical Trials Register, DRKS00031445, Registered 08 March 2023-Retrospectively registered, https://www.drks.de/DRKS00031445.

Nasolacrimal intubation in transcanalicular endoscopic dacryoplasty: a long-term follow-up study

Nowadays, transcanalicular endoscopic dacryoplasty represents the majority of lacrimal duct surgery procedures performed in adults in specialised centers. However, there are still hardly any data available regarding the intra- and postoperative care, particularly regarding the duration of silicone tube intubation (STI). Our aim was to evaluate the relation between tube duration and recurrence of symptoms in patients who underwent transcanalicular microdrill dacryoplasty (MDP) in a long-term setting. Medical records of 576 adult patients after MDP were retrospectively reviewed. A total of 256 eyes of 191 patients could be included. The median follow-up time was 7.83 [7.08; 9.25] years. In 57.0% of the cases there was still full resolution of symptoms at the time of the survey. The median duration of the STI was 6 [3.00; 6:00] months. When distinguishing between a tube duration < 3 months and ≥ 3 months there was a significant difference in the long-term success rate (< 3 months: 38%; ≥ 3 months: 61%; p = 0.011). In conclusion, an early removal of the STI (< 3 months) after transcanalicular MDP seems to be associated with a higher incidence of recurrence of symptoms. This should be considered in the intra- and postoperative care of patients following this minimally invasive first-step procedure.

Effects of exercise mode and intensity on patient-reported outcomes in cancer survivors: a four-arm intervention trial

PURPOSE

The aim of this study was to compare the effects of different exercise modes (aerobic, resistance) and intensity prescriptions (standard, polarized, undulating) on patient-reported outcomes (PROs) in cancer survivors.

METHODS

107 breast or prostate cancer survivors (52% females, age 58 ± 10 years, 6-52 weeks after primary therapy) performed one out of four training programs, two sessions/week, over 12 weeks: work rate-matched vigorous intensity aerobic training (AT_Standard, n = 28) and polarized intensity aerobic training (AT_Polarized, n = 26) as well as volume-matched moderate intensity resistance training (RT_Standard, n = 26) and daily undulating intensity resistance training (RT_Undulating, n = 27). Health-related quality of life (HRQoL, EORTC-QLQ-C30) and cancer-related fatigue (CRF, MFI-20) were assessed at baseline, at the end of intervention and after a 12-week follow-up without further prescribed exercise.

RESULTS

Over the intervention period, HRQoL-function-scales of the EORTC-QLQ-C30 improved over time (p = .007), but no group*time interaction was observed (p = .185). Similarly, CRF values of the MFI-20 improved over time (p = .006), but no group*time interaction was observed (p = .663). When including the follow-up period and pooling the AT and the RT groups, HRQoL-function-scales developed differently between groups (p = .022) with further improvements in RT and a decline in AT. For CRF no significant interaction was found, but univariate analyses showed a non-significant trend of more sustainable effects in RT.

CONCLUSIONS

AT and RT with different work rate-/volume-matched intensity prescriptions elicits positive effects on HRQoL and CRF, without one regimen being significantly superior to another over the intervention period. However, RT might result in more sustainable effects compared to AT over a follow-up period without any further exercise prescription.

CLINICAL TRIAL REGISTRATION

The study was registered at clinicaltrials.gov (NCT02883699).

Feasibility of High-Intensity Resistance Training Sessions in Cancer Survivors

ABSTRACT

Schlüter, K, Schneider, J, Rosenberger, F, and Wiskemann, J. Feasibility of high-intensity resistance training sessions in cancer survivors. J Strength Cond Res 36(9): 2643-2652, 2022-Moderate-intensity resistance training (MIRT) is regarded as safe in cancer survivors (CS), but for high-intensity resistance training (HIRT), evidence is lacking. Hence, in the current exploratory analyses, single sessions of HIRT are compared with MIRT regarding safety and feasibility. Twenty-three of 24 included CS (14 breast and 10 prostate CS, 61.6 ± 9.5 years, body mass index 27.0 ± 4.3 kg·m -2 , 6-52 weeks after end of primary therapy) started a 12-week resistance training (RT) with a daily undulating periodization model including HIRT (90% of 1 repetition maximum [1RM]) and MIRT (67% 1RM) sessions. Parameters of safety (adverse events [AEs] and training-related pain), feasibility (physical and mental exhaustion, sensation of effort, enjoyment, and dropout rate), and adherence were assessed. An alpha level of 0.05 was applied for analyses. Nineteen of 23 training starters (83%) completed all sessions. Fourteen minor AEs occurred. A significantly higher increase for physical exhaustion appeared in HIRT ( p < 0.001). For 18% (HIRT) and 19% (MIRT) of the sessions, training-related pain was reported with no significant difference between intensities. In total, 34% of HIRT and 35% of MIRT sessions were perceived as overstraining or partly overstraining with no significant difference between intensities, but enjoyment (median and quartiles on a 1-7 scale) was high for both (HIRT = 5 [5;6] and MIRT = 5 [4,6]). Our analysis indicates that HIRT sessions do not differ from MIRT sessions concerning safety or feasibility, but training-related pain should be monitored. RT protocols incorporating high-intensity training loads can be applied safely in breast and prostate CS.

Design of a multinational randomized controlled trial to assess the effects of structured and individualized exercise in patients with metastatic breast cancer on fatigue and quality of life: the EFFECT study

Background

Many patients with metastatic breast cancer experience cancer- and treatment-related side effects that impair activities of daily living and negatively affect the quality of life. There is a need for interventions that improve quality of life by alleviating fatigue and other side effects during palliative cancer treatment. Beneficial effects of exercise have been observed in the curative setting, but, to date, comparable evidence in patients with metastatic breast cancer is lacking. The aim of this study is to assess the effects of a structured and individualized 9-month exercise intervention in patients with metastatic breast cancer on quality of life, fatigue, and other cancer- and treatment-related side effects.

Methods

The EFFECT study is a multinational, randomized controlled trial including 350 patients with metastatic breast cancer. Participants are randomly allocated (1:1) to an exercise or control group. The exercise group participates in a 9-month multimodal exercise program, starting with a 6-month period where participants exercise twice a week under the supervision of an exercise professional. After completing this 6-month period, one supervised session is replaced by one unsupervised session for 3 months. In addition, participants are instructed to be physically active for ≥30 min/day on all remaining days of the week, while being supported by an activity tracker and exercise app. Participants allocated to the control group receive standard medical care, general written physical activity advice, and an activity tracker, but no structured exercise program. The primary outcomes are quality of life (EORTC QLQ-C30, summary score) and fatigue (EORTC QLQ-FA12), assessed at baseline, 3, 6 (primary endpoint), and 9 months post-baseline. Secondary outcomes include physical fitness, physical performance, physical activity, anxiety, depression, pain, sleep problems, anthropometric data, body composition, and blood markers. Exploratory outcomes include quality of working life, muscle thickness, urinary incontinence, disease progression, and survival. Additionally, the cost-effectiveness of the exercise program is assessed. Adherence and safety are monitored throughout the intervention period.

Discussion

This large randomized controlled trial will provide evidence regarding the (cost-) effectiveness of exercise during treatment of metastatic breast cancer. If proven (cost-)effective, exercise should be offered to patients with metastatic breast cancer as part of standard care.

Trial registration

ClinicalTrials.govNCT04120298. Registered on October 9, 2019.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13063-022-06556-7.

Exercise Recommendation for People With Bone Metastases: Expert Consensus for Health Care Providers and Exercise Professionals

PURPOSE

Exercise has been underutilized in people with advanced or incurable cancer despite the potential to improve physical function and reduce psychosocial morbidity, especially for people with bone metastases because of concerns over skeletal complications. The International Bone Metastases Exercise Working Group (IBMEWG) was formed to develop best practice recommendations for exercise programming for people with bone metastases on the basis of published research, clinical experience, and expert opinion.

METHODS

The IBMEWG undertook sequential steps to inform the recommendations: (1) modified Delphi survey, (2) systematic review, (3) cross-sectional survey to physicians and nurse practitioners, (4) in-person meeting of IBMEWG to review evidence from steps 1-3 to develop draft recommendations, and (5) stakeholder engagement.

RESULTS

Recommendations emerged from the contributing evidence and IBMEWG discussion for pre-exercise screening, exercise testing, exercise prescription, and monitoring of exercise response. Identification of individuals who are potentially at higher risk of exercise-related skeletal complication is a complex interplay of these factors: (1) lesion-related, (2) cancer and cancer treatment-related, and (3) the person-related. Exercise assessment and prescription requires consideration of the location and presentation of bone lesion(s) and should be delivered by qualified exercise professionals with oncology education and exercise prescription experience. Emphasis on postural alignment, controlled movement, and proper technique is essential.

CONCLUSION

Ultimately, the perceived risk of skeletal complications should be weighed against potential health benefits on the basis of consultation between the person, health care team, and exercise professionals. These recommendations provide an initial framework to improve the integration of exercise programming into clinical care for people with bone metastases.

Acceptability and Feasibility of a Guided Biopsychosocial Online Intervention for Cancer Patients Undergoing Chemotherapy

Chemotherapy is a physically and psychologically highly demanding treatment, and specific Internet-based interventions for cancer patients addressing both physical side effects and emotional distress during chemotherapy are scarce. This study examined the feasibility and acceptability of a guided biopsychosocial online intervention for cancer patients undergoing chemotherapy (OPaCT). A pre-post, within-participant comparison, mixed-methods research design was followed. Patients starting chemotherapy at the outpatient clinic of the National Center for Tumor Diseases in Heidelberg, Germany, were enrolled. Feasibility and acceptability were evaluated through intervention uptake, attrition, adherence and participant satisfaction. As secondary outcomes, PHQ-9, GAD-7, SCNS-SF34-G and CBI-B-D were administered. A total of N = 46 patients participated in the study (female 76.1%). The age of participants ranged from 29 to 70 years (M = 49.3, SD = 11.3). The most prevalent tumour diseases were breast (45.7%), pancreatic (19.6%), ovarian (13.1%) and prostate cancer (10.8%). A total of N = 37 patients (80.4%) completed the OPaCT intervention. Qualitative and quantitative data showed a high degree of participant satisfaction. Significant improvements in the SCNS-SF34 subscale 'psychological needs' were found. Study results demonstrate the feasibility and acceptability of the intervention. The results show that OPaCT can be implemented well, both in the treatment process and in participants' everyday lives. Although it is premature to make any determination regarding the efficacy of the intervention tested in this feasibility study, these results suggest that OPaCT has the potential to reduce unmet psychological care needs of patients undergoing chemotherapy.

Different endurance exercises modulate NK cell cytotoxic and inhibiting receptors

PURPOSE

Induction of IDO depends on the activation of AhR forming the AhR/IDO axis. Activated AhR can transcribe various target genes including cytotoxic and inhibiting receptors of NK cells. We investigated whether AhR and IDO levels as well as activating (NKG2D) and inhibiting (KIR2DL1) NK cell receptors are influenced by acute exercise and different chronic endurance exercise programs.

METHODS

21 adult breast and prostate cancer patients of the TOP study (NCT02883699) were randomized to intervention programs of 12 weeks of (1) endurance standard training or (2) endurance polarized training after a cardiopulmonary exercise test (CPET). Serum was collected pre-CPET, immediately post-CPET, 1 h post-CPET and after 12 weeks post-intervention. Flow cytometry analysis was performed on autologous serum incubated NK-92 cells for: AhR, IDO, KIR2DL1 and NKG2D. Differences were investigated using analysis-of-variance for acute and analysis-of-covariance for chronic effects.

RESULTS

Acute exercise: IDO levels changed over time with a significant increase from post-CPET to 1 h post-CPET (p = 0.03). KIR2DL1 levels significantly decreased over time (p < 0.01). NKG2D levels remained constant (p = 0.31). Chronic exercise: for both IDO and NKG2D a significant group × time interaction, a significant time effect and a significant difference after 12 weeks of intervention were observed (IDO: all p < 0.01, NKG2D: all p > 0.05).

CONCLUSION

Both acute and chronic endurance training may regulate NK cell function via the AhR/IDO axis. This is clinically relevant, as exercise emerges to be a key player in immune regulation.

Exercise for individuals with bone metastases: A systematic review

BACKGROUND

Exercise has the potential to improve physical function and quality of life in individuals with bone metastases but is often avoided due to safety concerns. This systematic review summarizes the safety, feasibility and efficacy of exercise in controlled trials that include individuals with bone metastases.

METHODS

MEDLINE, Embase, Pubmed, CINAHL, PEDro and CENTRAL databases were searched up to July 16, 2020.

RESULTS

A total of 17 trials were included incorporating aerobic exercise, resistance exercise or soccer interventions. Few (n = 4, 0.5%) serious adverse events were attributed to exercise participation, with none related to bone metastases. Mixed efficacy results were found, with exercise eliciting positive changes or no change. The majority of trials included an element of supervised exercise instruction (n = 16, 94%) and were delivered by qualified exercise professionals (n = 13, 76%).

CONCLUSIONS

Exercise appears safe and feasible for individuals with bone metastases when it includes an element of supervised exercise instruction.

Vertebral fracture during one repetition maximum testing in a breast cancer survivor: A case report

RATIONALE

One repetition maximum (1-RM) testing is a standard strength assessment procedure in clinical exercise intervention trials. Because no adverse events (AEs) are published, expert panels usually consider it safe for patient populations. However, we here report a vertebral fracture during 1-RM testing.

PATIENT CONCERNS

A 69-year-old breast cancer survivor (body-mass-index 31.6 kg/m2), 3 months after primary therapy, underwent 1-RM testing within an exercise intervention trial. At the leg press, she experienced pain accompanied by a soft crackling.

DIAGNOSIS

Imaging revealed a partially unstable cover plate compression fracture of the fourth lumbar vertebra (L4) with a vertical fracture line to the base plate, an extended bone marrow edema and a relative stenosis of the spinal canal.

INTERVENTIONS

It was treated with an orthosis and vitamin D supplementation. Another imaging to exclude bone metastases revealed previously unknown osteoporosis.

OUTCOMES

The patient was symptom-free 6.5 weeks after the event but did not return to exercise.

CONCLUSION

This case challenges safety of 1-RM testing in elderly clinical populations.

LESSONS

Pre-exercise osteoporosis risk assessment might help reducing fracture risk. However, changing the standard procedure from 1-RM to multiple repetition maximum (x-RM) testing in studies with elderly or clinical populations would be the safest solution.

Feasibility and suitability of a graded exercise test in patients with aggressive hemato-oncological disease

Purpose

Physical activity promises to reduce disease-related symptoms and therapy-related side effects in patients suffering from aggressive lymphoma (L) or acute leukemia (AL). For an efficient training program, determination of patients’ physical capacity with a purposive exercise test is crucial. Here, we evaluated the feasibility and suitability of a graded exercise test (GXT) frequently applied in patients suffering from solid tumors by assessing whether patients achieved criteria for maximal exercise testing according to the American College of Sports Medicine (ACSM).

Methods

The GXT was performed by 51 patients with an aggressive L or AL prior to the start or in the earliest possible phase of high-dose chemotherapy, following a recommended protocol for cancer patients, starting at 20 Watts (W), with an increase of 10 W/min until volitional exhaustion. Subsequently, we investigated whether the following ACSM criteria were fulfilled: (1) failure of heart rate to increase despite increasing workload, (2) post-exercise capillary lactate concentration ≥ 8.0 mmol L⁻¹, (3) rating of perceived exertion at exercise cessation > 17 on the 6–20 Borg Scale.

Results

Out of 51 patients, two, six, and 35 participants met the first, second, and third criterion, respectively. No relevant relationships between the completion of the criteria and patients’ characteristics (e.g., gender, age) were found.

Conclusion

Although results of this study suggest a general feasibility of the applied GXT, the ACSM criteria were not met by the majority of the participants. Therefore, this study raises doubts about the suitability of the GXT protocol and the ACSM criteria for this group of patients.

Exercise intensity prescription in cancer survivors: ventilatory and lactate thresholds are useful submaximal alternatives to VO2peak

PURPOSE

Most studies with cancer survivors use percentages of peak oxygen uptake (VO2peak) for intensity prescription. Lactate or ventilatory thresholds might be useful submaximal alternatives, but this has never been investigated. Therefore, we aimed at comparing three training sessions prescribed using %VO2peak (reference), lactate thresholds, and ventilatory thresholds in terms of meeting the vigorous-intensity zone, physiological, and psychological responses.

METHODS

Twenty breast (58 ± 10 years) and 20 prostate cancer survivors (68 ± 6 years), 3.6 ± 2.4 months after primary therapy, completed a maximal cardiopulmonary exercise test and three vigorous training sessions in randomized order: 38 min of cycling at 70% VO2peak (M-VO2peak), 97% of individual anaerobic lactate threshold (M-IAT), and 67% between ventilatory thresholds 1 and 2 (M-VT). Heart rate (HR), blood lactate concentration (bLa), perceived exertion, and enjoyment were assessed.

RESULTS

Cancer survivors exercised at 75 ± 23, 85 ± 18, and 79 ± 19 W during M-VO2peak, M-IAT, and M-VT (p > .05). Sessions could not be completed in 3, 8, and 6 cases. Session completers showed HR of 82 ± 7, 83 ± 9, and 84 ± 8 %HRpeak and bLa of 3.7 ± 1.9, 3.9 ± 0.9, and 3.9 ± 1.5 mmol·l-1, which was not different between sessions (p > .05). However, variance in bLa was lower in M-IAT compared to M-VO2peak (p = .001) and to M-VT (p = .022).

CONCLUSION

All intensity prescription methods on average met the targeted intensity zone. Metabolic response was most homogeneous when using lactate thresholds.

IMPLICATIONS FOR CANCER SURVIVORS

Submaximal thresholds are at least as useful as VO2peak for intensity prescription in cancer survivors. Overall, slightly lower percentages should be chosen to improve durability of the training sessions.

Long-term outcome of transcanalicular microdrill dacryoplasty: a minimally invasive alternative for dacryocystorhinostomy

Background/Aim

Dacryocystorhinostomy (DCR) remains the gold standard therapy for nasolacrimal duct obstruction (NLDO), but is invasive and does not maintain the physiology of the lacrimal pathway. With transcanlicular microdrill dacryoplasty (MDP), there is a minimally invasive alternative surgical approach. This study aimed to present this modern lacrimal duct surgery technique and to evaluate its long-term success rate in a large study population.

Methods

The medical records of 1010 patients with acquired NLDO were retrospectively reviewed. Adult patients who had undergone transcanalicular MDP were included. The evaluation included the following parameters: age, gender, success rate, complication rate, obstruction grade and patient satisfaction. Long-term results regarding patient satisfaction and success rate were evaluated by a telephone survey. Only a complete resolution of symptoms was defined as success.

Results

793 eyes of 576 patients after transcanalicular MDP could be included in the study. The mean follow-up time was 8.7±0.9 years. Initial surgical success rate was 84.0%. At the time of the follow-up, 57.5% (n=229) still had full resolution of symptoms. The mean patient satisfaction with the procedure was 6.9±3.2 out of 10 points. Heavy bleeding occurred in two cases only (0.25%).

Conclusion

This is the first study to show the success rate of microendoscopic lacrimal duct surgery after such a long follow-up period and in such a large study population. Transcanalicular MDP is a minimally invasive technique with a very low complication rate and can be used as an alternative procedure before performing more invasive lacrimal duct surgery such as DCR.

Influencing factors of cardiorespiratory fitness in allogeneic stem cell transplant candidates prior to transplantation

PURPOSE

Cardiorespiratory fitness (CRF) seems to be prognostic prior to allogeneic stem cell transplantation (allo-HSCT). Influencing factors of CRF in allo-HSCT candidates have not been studied so far. Aim was to identify potentially influencing factors on CRF.

METHODS

To assess CRF, a maximal cardiopulmonary exercise test (CPET) was performed on average 2.6 ± 7.2 days prior to admission. A regression analysis was conducted, with the following predictors: gender, age, body mass index (BMI), time between last therapy and allo-HSCT (t_Therapies), number of cardiotoxic therapies (n_Cardiotox), number of transplantations (n_Transplantations), comorbidity index (HCT-CI), hemoglobin level of the last 3 months (area under the curve), and physical activity.

RESULTS

A total of 194 patients performed a CPET. VO_2peak was significantly reduced compared with reference data. In total, VO_2peak was 21.4 ml/min/kg (- 27.5%, p < 0.05). Men showed a significant larger percentage difference from reference value (- 29.1%, p < 0.05) than women (- 24.4%). VO_2peak was significantly (p < 0.05) influenced by age (β = - 0.11), female gender (β = - 3.01), BMI (β = - 0.44), n_Cardiotox (β = - 0.73), hemoglobin level (β = 0.56), and physical activity prior to diagnosis (β = 0.10).

CONCLUSIONS

Our study demonstrates a decreased CRF indicating the potential need of prehabilitative exercise. We revealed some influencing factors on CRF. Those patients could benefit the most from exercise.

Prospective PED-study of intravitreal aflibercept for refractory vascularized pigment epithelium detachment due to age-related macular degeneration: morphologic characteristics of non-responders in optical coherence tomography

Purpose

The aim of this study was to investigate the outcomes of a fixed intravitreal aflibercept regimen in patients with vascular pigment epithelium detachment (vPED) secondary to age-related macular degeneration with refractory subretinal fluid.

Methods

A prospective, interventional case series involved 20 eyes of 20 patients with refractory subretinal fluid and vPED treated with at least three injections of intravitreal anti-VEGF prior to study inclusion. After study inclusion, patients were treated with three injections of intravitreal aflibercept 2 mg/0.05 mL monthly followed by injections every 8 weeks. Best-corrected visual acuity (BCVA) and spectral-domain optical coherence tomography (SD-OCT) were evaluated at all visits. Fluorescein angiography and indocyanine green angiography were performed at baseline and quarterly. Primary outcomes were effectivity of a fixed treatment as measured in change in BCVA, PED greatest linear diameter (GLD), and PED height from baseline to month 12. In an additional post hoc analysis, vPED patients were differentiated into two groups: (1) vPED lesions that showed persistence of subretinal fluid throughout 1 year of treatment and (2) vPED lesions that showed complete resolution of subretinal fluid at least at one of the monthly performed OCT volume scans. Reflectivity values were determined in the subretinal pigment epithelium (RPE) compartment in OCT scans at baseline, month 6 and 12.

Results

A total of 18 patients completed the study protocol. The mean age was 74.8 ± 10.6 years, and six patients were female. The median BCVA of all patients was 72.0 ± 8.0 EDTRS letters at baseline and 72.5 ± 9.5 EDTRS letters at 12-month follow-up (p = 0.7420). The median PED height in all patients as measured in the OCT images significantly decreased from 372.0 ± 140.0 μm to 149.0 ± 142.0 μm after 12 months of treatment (p = 0.0020). Persistent subretinal fluid was present at every OCT control in six patients (group 1). Twelve patients showed resolution of subretinal fluid at least at one OCT control (group 2). Reflectivity values in the sub-RPE compartment in OCT scans were 41.48 ± 4.48 (group 1) and 42.62 ± 12.34 (group 2) at baseline (p = 0.854) and 65.88 ± 6.74 and 50.87 ± 14.11 at month 12 (p = 0.038).

Conclusions

Intravitreal aflibercept in refractory vPED leads to a significant reduction in PED height and disease activity as well as preservation of BCVA over 1 year. Persistent subretinal fluid was present in PED lesions with high values of reflectivity under the RPE, suggesting both a diffusion barrier and an increasing fibrovascular maturization of the choroidal neovascularization.

Trial registration

ClinicalTrials.gov Identifier: NCT03370380

Do we underestimate maximal oxygen uptake in cancer survivors? Findings from a supramaximal verification test

Cancer survivors demonstrate a reduced maximal oxygen uptake, which is clinically relevant in terms of overall survival. However, it remains uncertain whether they attain their "true maximal oxygen uptake" in a cardiopulmonary exercise test (CPET). In the present study, a supramaximal verification bout (Verif) was applied in cancer survivors to confirm attainment of maximal oxygen uptake. Seventy-five participants (age, 61 ± 12 years; n = 43 females with breast cancer and n = 32 males with prostate cancer, 6-52 weeks after primary therapy) performed a CPET on a cycle ergometer and a Verif at 110% peak power output. As verification criterion, maximal oxygen uptake in Verif should not exceed maximal oxygen uptake in CPET by >3%. On average, maximal oxygen uptake was significantly lower in Verif compared with CPET (1.60 ± 0.38 L·min^-1 vs. 1.65 ± 0.36 L·min^-1, p = .023). On the individual level, n = 51 (68%) satisfied the verification criterion, whereas n = 24 (32%) demonstrated a higher maximal oxygen uptake in Verif. n = 69 (92%) fulfilled ≥2 secondary criteria for maximal exhaustion in the CPET. While maximal oxygen uptake was not underestimated in the CPET on average, one-third of cancer survivors did not attain their true maximal oxygen uptake. Verif appears feasible and beneficial to confirm true maximal oxygen uptake in this population. Furthermore, it might be more reliable than secondary criteria for maximal exhaustion. Novelty In about one-third of cancer survivors, maximal oxygen uptake is underestimated by a CPET. This underestimation of maximal oxygen uptake is not necessarily indicated by secondary criteria for maximal exhaustion. A supramaximal verification bout appears feasible and helpful for the determination of maximal oxygen uptake in cancer survivors.

Repeated testing for the assessment of individual response to exercise training

Observed response to regular exercise training differs widely between individuals even in tightly controlled research settings. However, the respective contributions of random error and true interindividual differences as well as the relative frequency of nonresponders are disputed. Specific challenges of analyses on the individual level as well as a striking heterogeneity in definitions may partly explain these inconsistent results. Repeated testing during the training phase specifically addresses the requirements of analyses on the individual level. Here we report a first implementation of this innovative design amendment in a head-to-head comparison of existing analytical approaches. To allow for comparative implementation of approaches we conducted a controlled endurance training trial (1 yr walking/jogging, 3 days/wk for 45 min with 60% heart rate reserve) in healthy, untrained subjects ( n = 36, age = 46 ± 8 yr; body mass index 24.7 ± 2.7 kg/m2; V̇o2max 36.6 ± 5.4). In the training group additional V̇o2max tests were conducted after 3, 6, and 9 mo. Duration of the control condition was 6 mo due to ethical constraints. General efficacy of the training intervention could be verified by a significant increase in V̇o2max in the training group ( P < 0.001 vs. control). Individual training response of relevant magnitude (>0.2 × baseline variability in V̇o2max) could be demonstrated by several approaches. Regarding the classification of individuals, only 11 of 20 subjects were consistently classified, demonstrating remarkable disagreement between approaches. These results are in support of relevant interindividual variability in training efficacy and stress the limitations of a responder classification. Moreover, this proof-of-concept underlines the need for tailored methodological approaches for well-defined problems.

NEW & NOTEWORTHY This work reports a first implementation of a repeated testing training trial for the investigation of individual response. This design amendment was recently proposed to address specifically the statistical requirements of analyses on the individual level. Moreover, a comprehensive comparison of previously published methods exemplifies the striking heterogeneity of existing approaches.

The reliability of fat

The exercise intensity eliciting maximal fat oxidation (Fat(max)) is typically determined during an incremental test. Its reproducibility, however, has not been thoroughly investigated so far. To address this issue, 21 healthy subjects (23.5+/-1.7 years; BMI 22.4+/-1.8 kg/m(2); VO(2peak) 47.4+/-11.3 mL/min/kg) carried out two identical cycling tests to determine Fat(max) after an initial incremental baseline test. The duration of each of five stages during the Fat(max) tests was 6 min. The first stage equalled the first increase in blood lactate during the baseline test; the highest stage corresponded to a respiratory exchange ratio of 1.00. Between these intensities the other three stages were distributed evenly. Fat(max) was 28.0+/-8.6 L/min (59.2+/-18.1% VO(2peak)) in the first test and 29.8+/-10.5 L/min (62.9+/-22.2% VO(2peak)) in the second one. There was no significant difference between both Fat(max) determinations [number of stage: P=0.31; total VO(2): P=0.20; VO(2) utilized for fat oxidation (VO(2Fat)): P=0.33]. Linear correlation coefficients between tests were r=0.84 (total VO(2); P<0.001) and r=0.83 (VO(2Fat); P<0.001). However, Bland-Altman plots revealed wide 95% limits of agreement of 0.91 L/min (total VO(2)) and 0.32 L/min (VO(2Fat)). In conclusion, spontaneous intraindividual variability in Fat(max) appears too large to recommend the use of this parameter for the prescription of training intensity.

Physiological characteristics of badminton match play

The present study aimed at examining the physiological characteristics and metabolic demands of badminton single match play. Twelve internationally ranked badminton players (eight women and four men) performed an incremental treadmill test [VO(2peak = )50.3 +/- 4.1 ml min(-1) kg(-1) (women) and 61.8 +/- 5.9 ml min(-1) kg(-1) (men), respectively]. On a separate day, they played a simulated badminton match of two 15 min with simultaneous gas exchange (breath-by-breath) and heart rate measurements. Additionally, blood lactate concentrations were determined before, after 15 min and at the end of the match. Furthermore, the duration of rallies and rests in between, the score as well as the number of shots per rally were recorded. A total of 630 rallies was analysed. Mean rally and rest duration were 5.5 +/- 4.4 s and 11.4 +/- 6.0 s, respectively, with an average 5.1 +/- 3.9 shots played per rally. Mean oxygen uptake (VO(2)), heart rate (HR), and blood lactate concentrations during badminton matches were 39.6 +/- 5.7 ml min(-1) kg(-1) (73.3% VO(2peak)), 169 +/- 9 min(-1) (89.0% HR(peak)) and 1.9 +/- 0.7 mmol l(-1), respectively. For a single subject 95% confidence intervals for VO(2) and HR during match play were on average 45.7-100.9% VO(2peak) and 78.3-99.8% HR(peak). High average intensity of badminton match play and considerable variability of several physiological variables demonstrate the importance of anaerobic alactacid and aerobic energy production in competitive badminton. A well-developed aerobic endurance capacity seems necessary for fast recovery between rallies or intensive training workouts.

Running 8000 m Fast or Slow: Are There Differences in Energy Cost and Fat Metabolism?

PURPOSE

To compare energy requirements and substrate use for running a given distance fast versus slow under field conditions.

METHODS

Ten males and four females who were moderately endurance trained (32 +/- 6 yr; 71 +/- 11 kg; body mass index: 22.7 +/- 2.3 kg x m(-2); VO2max: 62.0 +/- 6.0 mL x min(-1) x kg(-1); individual anaerobic threshold [IAT]: 13.7 +/- 1.4 km x h(-1)) performed an incremental running protocol to determine IAT. Subsequently, two 8000-m runs at 70 and 95% IAT were performed on separate days in randomized order on an indoor track. Energy expenditure (EE) was measured by means of a portable metabolic device (indirect calorimetry). A meaningful difference in EE was defined as >10%.

RESULTS

EE was significantly greater during the 95% IAT run than during the 70% IAT run (2650 +/- 276 and 2554 +/- 348 kJ, respectively). However, this difference was only 3.8 +/- 4.8%. Including measurements up to 10 min postexercise, the difference rose to 5.1 +/- 4.7% (95% IAT: 2830 +/- 301 kJ; 70% IAT: 2692 +/- 368 kJ). There was no significant difference between the absolute amounts of fat oxidized during the runs (70% IAT: 26 +/- 5 g; 95% IAT: 20 +/- 5 g). During the 95% IAT run, significantly more carbohydrates were metabolized than during the 70% IAT run (108 +/- 14 and 90 +/- 5 g, respectively). The difference in EE between the two runs increased from the first to the third part of the running distance (first: no significance; second: P < 0.01; third: P < 0.001).

CONCLUSION

Energy requirements for a commonly run distance in recreational endurance training differ significantly but not relevantly between slow and fast speeds. However, increasing total running distance might lead to larger differences.

Heterogeneity determination and purification of commercial hen egg-white lysozyme

Hen egg-white lysozyme (HEWL) is widely used as a model protein, although its purity has not been adequately characterized by modern biochemical techniques. We have identified and quantified the protein heterogeneities in three commercial HEWL preparations by sodium dodecyl sulfate polyacrylamide gel electrophoresis with enhanced silver staining, reversed-phase fast protein liquid chromatography (FPLC) and immunoblotting with comparison to authentic protein standards. Depending on the source, the contaminating proteins totalled 1-6%(w/w) and consisted of ovotransferrin, ovalbumin, HEWL dimers, and polypeptides with approximate M(r) of 39 and 18 kDa. Furthermore, we have obtained gram quantities of electrophoretically homogeneous [> 99.9%(w/w)] HEWL by single-step semi-preparative scale cation-exchange FPLC with a yield of about 50%. Parallel studies of crystal growth kinetics, salt repartitioning and crystal perfection with this highly purified material showed fourfold increases in the growth-step velocities and significant enhancement in the structural homogeneity of HEWL crystals.

Repartitioning of NaCl and protein impurities in lysozyme crystallization

Nonuniform precipitant and impurity incorporation in protein crystals can cause lattice strain and, thus, possibly decrease the X-ray diffraction resolution. To address this issue, a series of crystallization experiments were carried out, in which initial supersaturation, NaCl concentration, protein purity level and crystallized fraction were varied. Lysozyme and protein impurities, as well as sodium and chloride were independently determined in the initial solution, supernatant and crystals. The segregation coefficients for Na(+) and Cl(-) were found to be independent of supersaturation and NaCl concentration, and decreased with crystallized fraction/crystal size. Numerical evaluation of the extensive body of data, based on a nucleation-growth-repartitioning model, suggests a core of approximately 40 micro m in which salt is incorporated in much greater concentrations than during later growth. Small crystals containing higher amounts of incorporated NaCl also had higher protein impurity contents. This suggests that the excess salt is associated with the protein impurities in the core. X-ray topography revealed strain fields in the center of the crystals comparable in size to the inferred core. The growth rates of crystals smaller than 30-40 micro m in size were consistently 1.5-2 times lower than those of larger crystals, presumably due to higher chemical potentials in the core.

A novel adaptor protein orchestrates receptor patterning and cytoskeletal polarity in T-cell contacts

Recognition of antigen by T cells requires the formation of a specialized junction between the T cell and the antigen-presenting cell. This junction is generated by the recruitment and the exclusion of specific proteins from the contact area. The mechanisms that regulate these events are unknown. Here we demonstrate that ligand engagement of the adhesion molecule, CD2, initiates a process of protein segregation, CD2 clustering, and cytoskeletal polarization. Although protein segregation was not dependent on the cytoplasmic domain of CD2, CD2 clustering and cytoskeletal polarization required an interaction of the CD2 cytoplasmic domain with a novel SH3-containing protein. This novel protein, called CD2AP, is likely to facilitate receptor patterning in the contact area by linking specific adhesion receptors to the cytoskeleton.

Effects of microheterogeneity in hen egg-white lysozyme crystallization

In earlier sodium dodecylsulfate-polyacylamide gel electrophoresis (SDS-PAGE) studies it has been found that commonly utilized commercial hen egg-white lysozyme (HEWL) preparations contained 0.2-0.4 mol% covalently bound dimers. Here it is shown, using high-performance capillary electrophoresis (HPCE), that HEWL contains, in addition, two differently charged monomers in comparable amounts. To explore the origin of these microheterogeneous contaminants, purified HEWL (PHEWL) has been oxidized with hydrogen peroxide (0.0026-0.88 M) at various pH levels between 4.5 and 12.0. Optical densitometry of oxidized PHEWL (OHEWL) bands in SDS-PAGE gels shows that hydrogen peroxide at 0.88 M in acetate buffer pH 4.5 increased the amount of dimers about sixfold over that in commercial HEWL. OHEWL had, in addition to one of the two monomer forms found in HEWL and PHEWL, three other differently charged monomer forms, each of them representing about 25% of the preparation. SDS-PAGE analysis of OHEWL yielded two closely spaced dimer bands with Mr = 28000 and 27500. In addition, larger HEWL oligomers with Mr = 1.7 million and 320000 were detected by gel-filtration fast protein liquid chromatography with multiangle laser light scattering detection. Non-dissociating PAGE in large pore size gels at pH 4.5 confirmed the presence of these large oligomers in HEWL and OHEWL. Increased microheterogeneity resulted in substantial effects on crystal growth and nucleation rate. On addition of 10 microgram-1 mg ml-1 OHEWL to 32 mg ml-1 HEWL crystallizing solutions, both the number and size of forming crystals decreased roughly proportionally to the concentration of the added microheterogeneity. The same effect was observed in HEWL solutions on addition of 0.03-0.3 M hydrogen peroxide. Repartitioning of the dimer during crystallization at various temperatures between 277 and 293 K was analyzed by SDS-PAGE. The crystals contained </= 25%(w/w) of the oligomers in the solution, with no apparent temperature dependence of the repartitioning.

X-ray Topography of Tetragonal Lysozyme Grown by the Temperature-Controlled Technique

Growth-induced defects in lysozyme crystals were observed by white-beam and monochromatic X-ray topography at the National Synchrotron Light Source (NSLS) at the Brookhaven National Laboratory (BNL). The topographic methods were non-destructive to the extent that traditional diffraction data collection could be performed to high resolution after topography. It was found that changes in growth parameters, defect concentration as detected by X-ray topography, and the diffraction quality obtainable from the crystals were all strongly correlated. In addition, crystals with fewer defects showed lower mosaicity and higher diffraction resolution as expected.

Adenine nucleotide-induced inhibition of binding of sulphonylureas to their receptor in pancreatic islets

1. The effects of the Mg complex of adenosine 5'-triphosphate (MgATP) on binding of sulphonylureas to microsomes obtained from mouse pancreatic islets were examined. 2. MgATP inhibited the binding of both glibenclamide and tolbutamide to microsomes. 3. Binding of [3H]-glibenclamide inhibited by MgATP was not further diminished by Mg(2+)-bound adenosine 5'-(beta, gamma-imidotriphosphate) (AMP-PNP) or free adenosine 5'-diphosphate (ADP). Higher concentrations of MgAMP-PNP induced a partial reversal of the inhibitory effect of MgATP on [3H]-glibenclamide binding. 4. The apparent dissociation constant (K'D) for binding of [3H]- glibenclamide remained constant when 5. Extracellular ADP did not markedly stimulate insulin release from mouse pancreatic islets. 6. It is concluded that sulphonylureas and cytosolic nucleotides exert their inhibitory effects on the K-ATP-channels of beta-cells by binding to different sites. The binding properties of the sulphonylurea receptor seem to be modulated by protein phosphorylation.

Tolbutamide-sensitivity of the adenosine 5'-triphosphate-dependent K+ channel in mouse pancreatic B-cells

The patch-clamp technique was used to examine the tolbutamide-sensitivity of the adenosine 5'-triphosphate (ATP)-dependent K+ channel in mouse pancreatic B-cells. When studied at 37 degrees C in cell-attached membrane patches, this channel had a single-channel conductance of 88 pS and was half-maximally inhibited by 2.2 mumol/l tolbutamide in the presence of 3 mmol/l D-glucose and 10 mumol/l nifedipine. The tolbutamide-induced decrease in the amplitude of the single-channel currents indicated that the membrane potential was sufficiently depolarized for initiation of insulin release by 30 but not by 10 mumol/l of tolbutamide. Using 300 mumol/l diazoxide to open the ATP-dependent K+ channels already closed by 3 mmol/l D-glucose alone, it was demonstrated that initiation of insulin release requires closure of more than 98% of all ATP-dependent K+ channels. In excised inside-out membrane patches, the K+ channel-blocking potency of tolbutamide was maximally enhanced by 0.3 mmol/l adenosine 5'-diphosphate (ADP) at the cytoplasmic side. This ADP effect required the presence of Mg2+. Inhibition of K+ channel activity by ATP, ADP (Mg2(+)-free) or their non-hydrolyzable analogues adenylyl-imidodiphosphate (AMP-PNP) and alpha, beta methylene adenosine 5'-diphosphate (AMP-CP) was not accompanied by enhancement of tolbutamide-sensitivity. The results suggest that cytosolic MgADP controls tolbutamide-sensitivity by interaction with a receptor site not identical with the site mediating channel closure and that this control plays a role in the intact B-cell.