[Update: Clinical imaging of cartilage-part 2 : Aspects helpul in daily clinical practice]. / Update: Klinische Knorpelbildgebung ­ Teil 2 : In der Klinik hilfreiche Aspekte.

BACKGROUND: Imaging-based analysis of articular cartilage and its defects as well as the radiologist have to live up to the more and more specific clinical questions arising from increasing experience with cartilage-dedicated therapies. MATERIALS AND METHODS: Based on the currently available literature and experience from clinical routine, imaging findings relevant for lesion analysis will be summarized and illustrated by specific pathologies. RESULTS: Local aspects and topographic distribution of bone marrow edema pattern (BMEP), careful analysis of the cartilage surface and of the subchondral plate as well as the patient's clinical and biomechanical context are essential for image analysis. Formal grading is helpful to communicate imaging findings, but in itself is not sufficient for a comprehensive analysis. Assessing the stability of a lesion is important for therapy planning. Imaging is helpful to this end, but can be challenging and requires consideration of the arthroscopic and histologic perspective especially when dealing with juvenile osteochondral lesions. DISCUSSION: In order to maximize the therapeutic and prognostic relevance of findings from cartilage imaging, radiologists need to be sensitive to-often very subtle-imaging clues but at the same time we need to be aware of the limitations of our methods.

[Update: clinical imaging of cartilage-part 1 : Technical aspects]. / Update: Klinische Knorpelbildgebung ­ Teil 1 : Technische Aspekte.

BACKGROUND: In order to answer clinical therapy-oriented questions, reliable and consistent depiction of articular cartilage across technical platforms is necessary. MATERIALS AND METHODS: Technical standards and developments in cartilage imaging are summarized based on current literature and experience from clinical daily routine. RESULTS: Clinical questions that need to be answered relate to cross-sectional extent, depth, differentiating cartilaginous from bony components of a lesion and to the lesion's location within the compartment. If present, displaced fragments, concomitant meniscal, ligamentous and/or degenerative lesions should be identified. To date, magnetic resonance imaging (MRI) is the workhorse of cartilage imaging and is largely based on moderately T2-weighted and also proton-density (PD)-weighted fat-suppressed turbo-spin-echo sequences. Direct MR- and CT-arthrography are the gold standard to evaluate thin cartilage layers. Recent advances in coil and MR sequence design, increased availability of 3T-MR scanners and more and more sophisticated acceleration techniques allow for better spatial resolution and more robust image contrast at acceptable scan times. DISCUSSION: As abundant as current developments in clinical routine cartilage imaging may be, the radiologist must carefully select the approach best suited to answering the clinical questions.

Hard X-ray index of refraction tomography of a whole rabbit knee joint: A feasibility study.

We report results of the computed tomography reconstruction of the index of refraction in a whole rabbit knee joint examined at the photon energy of 51keV. Refraction based images make it possible to delineate the bone, cartilage, and soft tissues without adjusting the contrast window width and level. Density variations, which are related to tissue composition and are not visible in absorption X-ray images, are detected in the obtained refraction based images. We discuss why refraction-based images provide better detectability of low contrast features than absorption images.

[Organ and function preservation in urethral cancer]. / Organ- und Funktionserhalt beim Urethralkarzinom.

Primary urethral carcinomas are rare tumors that can occur both in men and women. Histological patterns of these tumors are mixed, urothelial tumors occur as well as squamous cell tumors or adenocarcinomas.There are different clinical factors that define clinical prognosis, and the 1- and 5-year cancer-free survival is 75% and 54%. Therapy of locally limited disease is surgical resection, and organ-preserving treatment is possible if negative frozen sections prove complete surgical resection. However, in men a perineal urethrostomy might be necessary, and in women there is a high risk of urinary incontinence if more than 2 cm of the distal urethra is resected.In case of locally advanced tumors or tumors of the proximal urethra, a radical urethrectomy with supravesical urinrary diversion is necessary. In some cases neoadjuvant (radio-)chemotherapy may be an option.

[Post-treatment rehabilitation after autologous chondrocyte implantation: State of the art and recommendations of the Clinical Tissue Regeneration Study Group of the German Society for Accident Surgery and the German Society for Orthopedics and Orthopedic Surgery]. / Nachbehandlung bei der autologen Chondrozytentransplantation: Eine Bestandsaufnahme und Empfehlung der AG Klinische Geweberegeneration der DGU/DGOOC.

BACKGROUND: Over the course of the past two decades autologous chondrocyte implantation (ACI) has become an important surgical technique for treating large cartilage defects. The original method using a periostal flap has been improved by using cell-seeded scaffolds for implantation, the matrix-based autologous chondrocyte implantation (mb-ACI) procedure. MATERIAL AND METHODS: Uniform nationwide guidelines for post-ACI rehabilitation do not exist. A survey was conducted among the members of the clinical tissue regeneration study group concerning the current rehabilitation protocols and the members of the study group published recommendations for postoperative rehabilitation and treatment after ACI based on the results of this survey. RESULTS: There was agreement on fundamentals concerning a location-specific rehabilitation protocol (femoral condyle vs. patellofemoral joint). With regard to weight bearing and range of motion a variety of different protocols exist. Similar to this total agreement on the role of magnetic resonance imaging (MRI) for postsurgical care was found but again a great variety of different protocols exist. CONCLUSIONS: This manuscript summarizes the recommendations of the members of the German clinical tissue regeneration study group on postsurgical rehabilitation and MRI assessment after ACI (level IVb/EBM).

[MRI based volumetric assessment of knee cartilage after ACL-reconstruction, correlated with qualitative morphologic changes in the joint and with clinical outcome. Is there evidence for early posttraumatic degeneration?]. / MRT-basierte Knorpelvolumetrie nach Kreuzbandersatzplastik in Korrelation mit qualitativen Gelenkveränderungen und dem klinischen Outcome. Gibt es Hinweise auf frühzeitige posttraumatische degenerative Veränderungen?

PURPOSE: The purpose of this study was to analyze potential quantitative and qualitative changes of the knee cartilage and joint indicative of early posttraumatic OA 4 years after ACL-reconstruction and to correlate the MRI-findings with the clinical outcome (CO). MATERIALS AND METHODS: 1.5 T MRI-scans were performed on 9 patients post-op and 4 years later. Using a high-resolution T 1-w-fs-FLASH-3D-sequence cartilage volume (cVol) and thickness (mTh) were quantified. Using standard PD-w fs and T 1-w sequences qualitative changes of the joint structures were analyzed based on the WORMS-score. CO was rated by an orthopaedic surgeon using Lysholm-score, OAK-score, Tegner-activity-score (TAS), and Arthrometer KT-1000 testing. RESULTS: Mean changes of cVol were -1.8 % (range: -5.9 %; + 0.7 %) and of mTh -0.8 % (range: -3.0 %; + 1.1 %). No significant change (95 %-CI) could be identified for any compartment. Three patients developed new peripatellar ostheophytes, acute trauma related changes mostly decreased. Mean outcome of Lysholm-score and OAK-score were 90 pts and 86 pts, mean TAS was 4.3 pts. Average maximum tibial translation reached 5.2 mm comparing to 6.7 mm on the healthy contralateral side. CONCLUSION: Despite a tendency towards decreased cVol and mTh 4 years after ACL-reconstruction qMRI revealed no significant cartilage loss. Newly developing osteophytes did not match with the observed good CO. This small pilot study motivates future quantitative and qualitative-structural MRI-based assessment of articular cartilage and other joint structures in order to improve diagnostic tools for the detection of early OA.

Development and validation of a new method for the radiologic measurement of the tibial slope.

PURPOSE: The posterior tibial slope has a huge influence on the kinematics of the knee. In several orthopedic interventions such as high tibial osteotomy and unicondylar or bicondylar knee replacement changing, the tibial slope can result in altered knee mechanics. Therefore, an exact preoperative measurement of the posterior tibial slope is mandatory. Several methods are used on conventional radiographs and CT scans, but until now there is no standard validated method. The aim of this study was to compare several methods and imaging techniques to measure the posterior tibial slope and to establish a standard and reliable measurement method by radiography. METHODS: Fourteen knees (seven cadavers) were scanned by a 64-slice CT, a 3T-MRI, and true lateral radiographs were performed. The anatomical references (TPAA = tibial proximal anatomical axis; ATC = anterior tibial cortex; PTC = posterior tibial cortex) and the new computed reference (MPA = mean of PTA and ATC) were compared by short as well as long radiographs, CT scan and MRI. The influence of a malrotation in radiographs of the knees was also analyzed. RESULTS: CT scan and MRI are suitable for the measurement of the medial and lateral posterior tibial slopes, the results of the radiographs varied depending on the method used. The new method (MPA) showed the best correlation to the CT scan (r = 0.997), even on short radiographs (10 cm distal the joint line). CONCLUSION: The measurement of the posterior tibial slope on a short lateral radiograph using the MPA is a reliable method and should be established as a standard. LEVEL OF EVIDENCE: Diagnostic study, Level II.

[Locoregional deformation pattern of the patellar cartilage after different loading types - high-resolution 3D-MRI volumetry at 3 T in-vivo]. / Lokoregionäre Deformationsmuster im Patellarknorpel nach unterschiedlichen Belastungsparadigmen - hochauflösende 3-D-MR-Volumetrie bei 3 T in vivo.

PURPOSE: To analyze locoregional deformation patterns indicative of contact areas in patellar cartilage after different loading exercises. MATERIALS AND METHODS: 7 healthy patellae were examined in-vivo before and immediately after standardized loading (kneeling, squatting or knee bends) and after 90 minutes of rest using a sagittal 3D-T1-w FLASH WE sequence (22 msec/ 9.8 msec/ 15°/ 0.3 × 0.3 × 1.5 mm³) at 3 T. After cartilage segmentation and 3D reconstruction, voxel-based and global precision errors (PR) were calculated. The former were used to determine significant differences in local cartilage thickness. Voxel-based 2σ-thickness difference maps were calculated to visualize locoregional deformation patterns. Global changes in volume (Vol), mean thickness (mTh) and cartilage-bone-interface area (CBIA) were calculated. RESULTS: The voxel-based PR depended on cartilage thickness (D) ranging from 0.12 - 0.35 mm. For D ≥ 1 mm the RF was < 0.31 mm (< voxel size), and for D ≥ 2 mm, the RF was < 0.22 mm. The global PR was 83 mm³ (2.4 %) for Vol, 0.06 mm (2.0 %) for mTh and 16 mm² (1.4 %) for CBIA. The focal cartilage deformation equaled 14 % of the local thickness reduction. The deformation areas were oval and located in the peripheral medial (more vertically oriented, all exercises) and caudo-lateral (more horizontally oriented, kneeling and knee bends) aspects of the patella and were least pronounced in knee bends. Significant changes for Vol/mTh ranged from 2.1 to 3.7 %. CONCLUSION: This MRI-based study is the first to identify in-vivo voxel-based patellar cartilage deformation patterns indicating contact and loading zones after kneeling and squatting. These zones are anatomically and functionally plausible and may represent areas where stress induced degeneration and subsequent OA can originate. The data may facilitate understanding of individual knee loading properties and help to improve and validate biomechanical models for the knee.

New observations from MR velocity-encoded flow measurements concerning diastolic function in constrictive pericarditis.

OBJECTIVE: To assess diastolic function in patients with constrictive pericarditis (CP) by using velocity-encoded flow measurements at the atrioventricular valves and to evaluate whether conclusions regarding increased ventricular pressure can be drawn. METHODS: Twenty-two patients with CP and 20 healthy subjects were examined on a 1.5-T MR system. In addition to evaluation of pericardial thickness, ventricular volumes and septal movement, velocity-encoded flow measurements were performed at the level of the atrioventricular valves for assessment of diastolic function. Amplitudes of the e- and a-waves were measured and e- to a-wave ratios were calculated. The correlation of transtricuspid e- to a-wave ratios and right ventricular end-diastolic pressures (RVEDP) was calculated. RESULTS: Right ventricular volumes were significantly smaller in patients with CP (p < 0.001). Abnormal septal movement was detected in all patients except one with CP and in none of the healthy subjects. In patients with CP mean transtricuspid e- to a-wave ratios were significantly smaller compared with healthy subjects. Individual transtricuspid e- to a-wave ratios were highly correlated with RVEDP (r = 0.6, p = 0.01). CONCLUSIONS: An elaborate MR examination can identify patients with CP. Velocity-encoded flow measurements with calculation of transtricuspid e- to a-wave ratios are a valuable tool for detection of diastolic dysfunction in patients with CP. The value of e- to a-wave ratios may indicate elevated RVEDP.

[Diagnostic algorithm in cystic renal masses]. / Diagnostischer Algorithmus bei zystischen Nierenläsionen.

Cystic renal lesions can be classified as either simple or complicated cysts, which might occur as solitary as well as multifocal lesions. The Bosniak classification (I-IV), which characterizes renal cysts on the basis of ultrasound or computer tomographic criteria, is very useful for further decision-making about the therapeutic approach. The method of choice for diagnosis of renal cysts is ultrasound. Besides the conventional B-mode ultrasound, contrast enhanced ultrasound with SonoVue provides a promising new technique for distinguishing cysts according to the Bosniak classification. This review describes cystic renal lesions with emphasis on the etiology and significance of these pathologies in a methodological comparison of conventional B-mode, contrast enhanced ultrasound and computer tomography.

[Modern sonography in the diagnosis of acute abdomen]. / Moderne Sonographie zur Diagnostik des akuten Abdomens.

Acute abdomen is a serious clinical situation and prompt imaging is mandatory so that appropriate therapeutic measures can be taken. Multiple diseases can present with the clinical signs and symptoms of acute abdomen. Ultrasound is widely available and can be performed expeditiously. Recently, major technical innovations in ultrasound technology were introduced which greatly enhanced the diagnostic accuracy in the evaluation of acute abdomen. Contrast-enhanced ultrasound is among these valuable innovations. In this article the application of modern ultrasound techniques for the diagnosis of the most common causes of acute abdomen is outlined, which may be due to diseases of the gastro-intestinal tract, parenchymal organs in the upper abdomen as well as vascular disorders. Moreover, the diagnostic efficacy and the value as compared to other imaging modalities are analyzed.

[Ultrasound imaging of the abdominal aorta]. / Ultraschallbildgebung der Aorta abdominalis.

Abnormalities of the abdominal aorta and the visceral vessels can represent a diagnostic challenge in patients with both acute and chronic clinical symptoms. In addition to the primary conventional examination using color-coded duplex ultrasound, contrast-enhanced ultrasound (CEUS) with low mechanical index (low MI) may contribute to achieving a precise diagnosis. CEUS is a new and promising method in the diagnosis and follow-up of aortic and visceral artery lesions. Color-coded duplex ultrasound and CEUS with SonoVue(R) allow a rapid and non-invasive diagnosis especially in critically ill patients as these methods can readily be applied at the bedside. In this article the contribution of color-coded duplex ultrasound and CEUS as compared to multi-slice computed tomography angiography (MS-CTA) in various pathologies of the abdominal aorta and the visceral arteries will be addressed.

[Imaging of endoleaks after endovascular aneurysm repair (EVAR) with contrast-enhanced ultrasound (CEUS)]. / Kontrastmittelverstärkter Ultraschall im Follow-up nach endovaskulärer Stentversorgung eines infrarenalen Bauchaortenaneurysmas.

Endoleaks following endovascular aneurysm repair (EVAR) are common and present a diagnostic challenge in the follow-up after EVAR. Contrast-enhanced ultrasound (CEUS) is a promising new method for the diagnosis and follow-up of endoleaks. CEUS with SonoVue allows a rapid and non-invasive diagnosis in the follow-up after EVAR. The sensitivity and specificity of conventional ultrasound compared to the multislice CT angiography is estimated to be 33-63% and 63-93%, respectively. These values can be increased through the use of CEUS in up to 98-100% (sensitivity) and 82-93% (specificity). This article describes the etiology, classification and importance of different types of endoleaks. The value of CEUS in this clinical scenario will be discussed.

[Current developments in vascular ultrasound]. / Aktuelle Entwicklungen in der vaskulären Sonographie.

Ultrasound plays a central role in the diagnostic imaging of venous and arterial vessels, especially for the assessment or exclusion of arteriosclerotic vessel obstructions as well as venous or arterial thrombosis. Due to its excellent patient acceptance and its broad availability, ultrasound is considered the standard method of choice for vascular imaging. New techniques and methods have greatly enhanced its diagnostic accuracy, the most notable of which are the B-flow technique, a variant of Doppler signal read-out for reduction of artifacts in duplex sonography, as well as other techniques, such as tissue harmonic imaging, the cross-beam technique and the speckle-reduction technique, which employ different echo processing methods for contrast improvement and enhanced delineation of body structures adjacent to the vessels. The introduction of contrast enhanced ultrasound represents an important advancement and has brought a substantial improvement in sensitivity. This article describes and discusses these new techniques and methods of vascular ultrasound diagnostics with respect to their diagnostic value.

Contrast-enhanced ultrasound versus conventional ultrasound and MS-CT in the diagnosis of abdominal aortic dissection.

PURPOSE: To evaluate the diagnostic results of different ultrasound techniques: B-scan, color-coded Doppler sonography (CCDS) and contrast-enhanced ultrasound in the diagnosis of abdominal aortic dissection in comparison to multislice computed tomography (MS-CT). MATERIALS AND METHODS: Between March 2006 and December 2008, 35 patients (28 males, 7 females) with a mean age of 58 years (range 37-87 years) with abdominal aortic dissection and 15 patients (11 males, 4 females) with a mean age of 53 years (range 42-78 years) without abdominal aortic dissection as a control group were examined with B-scan, CCDS and contrast-enhanced ultrasound (CEUS) after injection of 1.0-1.2 cc of SonoVue (Bracco, Italy). The examinations were performed using a Sequoia 512 (Siemens/Acuson, Mountain View) system with CPS software. Standardized MS-CTA using a 16 or 64 row scanner (Somatom Sensation 16 or 64, Siemens Medical Systems, Forchheim, Germany) served as the reference standard. RESULTS: The sensitivity of B-scan and CCDS for detecting abdominal aortic dissections were both 23/35 (68%); for contrast-enhanced ultrasound it was 34/35 (97%). Dissection membrane, differentiation of true and false lumen and flow direction within the true and false lumen were better detected by CEUS than by CCDS. The lack of angle dependence of the US probe and lack of flow and pulsations artifacts in CEUS made the examination procedure easier. All findings were confirmed by MS-CT. CONCLUSION: With contrast-enhanced ultrasound, diagnostic accuracy sensitivity and specificity for the diagnosis of abdominal aortic dissections is improved as compared to B-scan and CCDS. Dissection membrane and flow within the true and false lumen are clearly differentiated by CEUS. Thus CEUS is a promising alternative for patients whose condition does not allow an examination by CTA.

Local topological analysis of densitometer-generated scan images of the proximal femur for differentiation between patients with hip fracture and age-matched controls.

SUMMARY: We evaluate densitometer-generated scan images of the proximal femur with respect to topological properties of bone mineral distribution patterns in selected regions of interest. In a population of 100 post-menopausal women, the method has a highly discriminative potential with a performance superior to standard densitometry. Results vary with anatomical location within the proximal femur. INTRODUCTION: The objectives of the study were to evaluate densitometer-generated scan images of the proximal femur with respect to topological properties of bone mineral distribution patterns in selected regions of interest, to test the ability for differentiation between post-menopausal women hip fracture and controls, and to compare results with standard bone densitometry. MATERIALS AND METHODS: We used dual-energy X-ray absorptiometry (DXA) to measure the femoral bone mineral density (BMD) of 100 post-menopausal women (73.4 +/- 12.2), 50 of whom had a recent hip fracture. Local bone mineral distribution in the scanner-generated images was analyzed in the standard DXA-regions of interest (ROIs; femoral neck, the shaft, the trochanteric area; and the total hip) using an optimized, local topological parameter MF2D. Performance of topological analysis and BMD was tested by receiver-operator characteristic and discriminant analysis. RESULTS: Area under the curve (AUC) for correct differentiation between patients with and without fractures by BMD in the different ROIs ranged from 0.64 to 0.71; AUC of regional density-pattern analysis varied between 0.79 and 0.84. Using multivariate statistical models, between 71% and 84% of patients were correctly identified as fracture/non-fracture cases by regional topological analysis, whereas BMD reached levels from 58% to 68%. CONCLUSION: Our analysis indicates that identification of patients with hip fracture by regional evaluation of density patterns varies with anatomical location within the proximal femur. In our study population, performance of the novel parameter was superior to densitometry.

Contrast enhanced ultrasound eases interpretation of an unclear renal tumor in addition to CT, MRI and histological findings--a case report in a young patient.

Renal cancer represents accounts for approximately 3% of all adult malignancies with a rising incidence. Incidental diagnosis is mostly based upon ultrasound (US). US and Computed tomography (CT) are the standard imaging modalities for detecting renal cell cancer (RCC). Differentiation between malignant and benign renal tumors is of utmost importance. Contrast enhanced ultrasound (CUS) seems to be a promising new diagnostic option for diagnosis and preoperative treatment planning for patients with renal cancer. It is an additional examination to baseline ultrasound and CT. We report a case of a 37-year-old woman with a papillary renal cell cancer in which CUS helped to differentiate dignity of the tumor. CUS is an additional examination to baseline ultrasound and CT. It is a less invasive technique than contrast enhanced CT and shows even slight tumor blood flow. In addition it may allow a more rapid diagnosis, because of its bedside availability.

[T2 relaxation time in patellar cartilage--global and regional reproducibility at 1.5 tesla and 3 tesla]. / T2-Relaxationszeit am Patellaknorpel--Globale und regionale Reproduzierbarkeit bei 1,5 Tesla und 3 Tesla.

PURPOSE: Evaluation of the global and regional reproducibility of T2 relaxation time in patellar cartilage at 1.5 T and 3 T. MATERIALS AND METHODS: 6 left patellae of 6 healthy volunteers (aged 25 - 30, 3 female, 3 male) were examined using a fat-saturated multiecho sequence and a T1-w 3D-FLASH sequence with water excitation at 1.5 Tesla and 3 Tesla. Three consecutive data sets were acquired within one MRI session with the examined knee being repositioned in the coil and scanner between each data set. The segmented cartilage (FLASH sequence) was overlaid on the multiecho data and T2 values were calculated for the total cartilage, 3 horizontal layers consisting of a superficial, intermedial and deep layer, 3 facets consisting of a medial, median (ridge) and lateral facet (global T2 values) and 27 ROIs/MRI slices (regional T2 value). The reproducibility (precision error) was calculated as the root mean square average of the individual standard deviations [ms] and coefficients of variation (COV) [%]. RESULTS: The mean global reproducibility error for T2 was 3.53 % (+/- 0.38 %) at 1.5 Tesla and 3.25 % (+/- 0.61 %) at 3 Tesla. The mean regional reproducibility error for T2 was 8.62 % (+/- 2.61 %) at 1.5 Tesla and 9.66 % (+/- 3.37 %) at 3 Tesla. There was no significant difference with respect to absolute reproducibility errors between 1.5 Tesla and 3 Tesla at a constant spatial resolution. However, different reproducibility errors were found between the cartilage layers. One third of the data variability could be attributed to the influence of the different cartilage layers, and another 10 % to the influence of the separate MRI slices. CONCLUSION: Our data provides an estimation of the global and regional reproducibility errors of T2 in healthy cartilage. In the analysis of small subregions, an increase in the regional reproducibility error must be accepted. The data may serve as a basis for sample size calculations of study populations and may contribute to the decision regarding the level of detail of an evaluation of study data.

Contrast-enhanced ultrasound in detection and follow-up of an infrarenal abdominal aortic aneurysm with aorto-caval fistula and endovascular treatment.

An aorto-caval fistula is a rare complication of a symptomatic or ruptured infrarenal aortic aneurysm having a frequency of 3-6%. Patients typically present with clinical signs of diffuse abdominal pain associated with increasing venous congestion and tachycardia, rapid cardiopulmonary decompensation with acute dyspnea, and an audible machinerylike bruit. Perioperative mortality is high, ranging from 20% to 60%. We report a case of an endovascular aortic repair in a patient with a symptomatic infrarenal aortic aneurysm and an aorto-caval fistula. Contrast-enhanced ultrasound seems to be a promising new diagnostic option for the diagnosis and preoperative treatment planning for patients with abdominal aortic aneurysms with rupture into the inferior vena cava. It is in addition to computed tomography angiography. It might allow a more rapid and noninvasive diagnosis, especially for patients in intensive care because of its bedside availability. Because the examination is dynamic, additional information about blood flow between the aorta and inferior cava vein can be evaluated.

The control of mitochondrial respiration in yeast: a possible role of the outer mitochondrial membrane.

Mitochondrial respiration in yeast (S. cerevisiae) is regulated by the level of glucose in the medium. Glucose is known to inhibit respiration by repressing key enzymes in the respiratory chain. We present evidence that the early events in this inhibition include the closure of VDAC channels, the primary pathway for metabolite flow across the outer membrane. Aluminum hydroxide is known to inhibit the closure of VDAC. Addition of aluminum acetylacetonate to yeast cells, which should elevate the aluminum hydroxide concentrations in the cytoplasm, caused the inhibition of cell respiration by glucose to be delayed for up to 100 min. No significant effect of aluminum was observed in cells grown on glycerol. Yeast cells lacking the VDAC gene were also unresponsive to the addition of aluminum salt in the presence of glucose. Therefore, the closure of VDAC channels may be an early step in the inhibition of the respiration of yeast by glucose.