Positive evidence against human hippocampal involvement in working memory maintenance of familiar stimuli

Subjects (n = 40) performed a delayed item recognition task for visually presented letters with three set sizes (1, 3 or 6 letters). Accuracy was close to ceiling at all set sizes, so we took set size as a proxy for WM load (i.e. the amount of information being maintained in WM). Functional magnetic resonance imaging (fMRI) signal associated with the delay period increased in a nearly linear fashion with WM load in the left inferior frontal gyrus/anterior insula (possibly Broca's area, BA 44/45), right anterior insula, bilateral caudate, bilateral precentral gyrus (BA 6), bilateral middle frontal gyrus (BA 9/46), bilateral inferior parietal lobule (with foci in both BA 39 and 40), left superior parietal lobule (BA 7), medial frontal gyrus (BA 6), anterior cingulate gyrus (BA 32) and bilateral superior frontal gyrus (BA 8). These results lend support to the idea that at least some of the cortical mechanisms of WM maintenance, potentially rehearsal, exhibit a scaling with WM load. In contrast, the delay-related fMRI signal in hippocampus followed an inverted U-shape, being greatest during the intermediate level of WM load, with relatively lower values at the lowest and highest levels of WM load. This pattern of delay-related fMRI activity, orthogonal to WM load, is seemingly not consonant with a role for hippocampus in WM maintenance of phonologically codable stimuli. This finding could possibly be related more to the general familiarity of the letter stimuli than their phonological codability per se.     

Dissociating the roles of right ventral lateral and dorsal lateral prefrontal cortex in generation and maintenance of hypotheses in set-shift problems

Although patient data have traditionally implicated the left prefrontal cortex (PFC) in hypothesis generation, recent lesion data implicate right PFC in hypothesis generation tasks that involve set shifts (lateral transformations). To test the involvement of the right prefrontal cortex in a hypothesis generation task involving set shifts, we scanned 13 normal subjects with fMRI as they completed Match Problems (a classic divergent thinking task) and a baseline task. In Match Problems subjects determined the number of possible solutions for each trial. Successful solutions are indicative of set shifts. In the baseline condition subjects evaluated the accuracy of hypothetical solutions to match problems. A comparison of Match Problems versus baseline trials revealed activation in right ventral lateral PFC (BA 47) and left dorsal lateral PFC (BA 46). A further comparison of successfully versus unsuccessfully completed Match Problems revealed activation in right ventral lateral PFC (BA 47), left middle frontal gyrus (BA 9) and left frontal pole (BA 10), thus identifying the former as a critical component of the neural mechanisms of set-shift transformation. By contrast, activation in right dorsal lateral PFC (BA 46) covaried as a function of the number of solutions generated in Match Problems, possibly due to increased working memory demands to maintain multiple solutions 'on-line', conflict resolution, or progress monitoring. These results go beyond the patient data by identifying the ventral lateral (BA 47) aspect of right PFC as being a critical component of the neural systems underlying lateral transformations, and demonstrate a dissociation between right VLPFC and DLPFC in hypotheses generation and maintenance.     

Striatal dopamine and working memory

Recent studies have emphasized the importance of dopamine projections to the prefrontal cortex (PFC) for working memory (WM) function, although this system has rarely been studied in humans in vivo. However, dopamine and PFC activity can be directly measured with positron emission tomography (PET) and functional magnetic resonance imaging (fMRI), respectively. In this study, we examined WM capacity, dopamine, and PFC function in healthy older participants in order to test the hypothesis that there is a relationship between these 3 factors. We used the PET tracer 6-[18F]fluoro-L-m-tyrosine to measure dopamine synthesis capacity in the striatum (caudate, putamen), and event-related fMRI to measure brain activation during different epochs (cue, delay, probe) of a WM task. Caudate (but not putamen) dopamine correlated positively with WM capacity, whereas putamen (but not caudate) dopamine correlated positively with motor speed. In addition, delay-related fMRI activation in a left inferior prefrontal region was related to both caudate dopamine and task accuracy, suggesting that this may be a critical site for the integration of WM maintenance processes. These results provide new evidence that striatal dopaminergic function is related to PFC-dependent functions, particularly brain activation and behavioral performance during WM tasks.     

Physiological dysfunction of the dorsolateral prefrontal cortex in schizophrenia revisited

Evidence implicates subtle neuronal pathology of the prefrontal cortex (PFC) in schizophrenia, but how this pathology is reflected in physiological neuroimaging experiments remains controversial. We investigated PFC function in schizophrenia using functional magnetic resonance imaging (fMRI) and a parametric version of the n-back working memory (WM) task. In a group of patients who performed relatively well on this task, there were three fundamental deviations from the 'healthy' pattern of PFC fMRI activation to varying WM difficulty. The first characteristic was a greater magnitude of PFC fMRI activation in the context of slightly impaired WM performance (i.e. physiological inefficiency). The second was that the significant correlations between behavioral WM performance and dorsal PFC fMRI activation were in opposite directions in the two groups. Third, the magnitude of the abnormal dorsal PFC fMRI response was predicted by an assay of N-acetylaspartate concentrations (NAA) in dorsal PFC, a measure of neuronal pathology obtained using proton magnetic resonance spectroscopy. Patients had significantly lower dorsal PFC NAA than controls and dorsal PFC NAA inversely predicted the fMRI response in dorsal PFC (areas 9, 46) to varying WM difficulty - supporting the assumption that abnormal PFC responses arose from abnormal PFC neurons. These data suggest that under certain conditions the physiological ramifications of dorsal PFC neuronal pathology in schizophrenia includes exaggerated and inefficient cortical activity, especially of dorsal PFC.     

Prefrontal selection and medial temporal lobe reactivation in retrieval of short-term verbal information

Both the prefrontal cortex (PFC) and medial temporal lobe (MTL) are involved in memory retrieval. Here we distinguish between their roles by manipulating demand for interference resolution and reactivation of maintained information. Subjects were tested on a letter working memory task with distractors. When the memory delay was interrupted with letter distractors, there was higher activity in the middle frontal gyrus at retrieval compared to when the delay was interrupted by number distractors, suggesting the role of the PFC in interference resolution. By contrast, activity in the parahippocampal gyrus did not differ between the two conditions. The two structures were then compared using the dataset of our previous study on memory reactivation, where subjects performed a letter working memory task with arithmetic distractors or non-distractors. The activity in the parahippocampal gyrus at retrieval was higher when distractors interrupted rehearsal than when the intervening task was non-distracting and subjects continued to rehearse, suggesting the role of the MTL in reactivating the stored information. By contrast, the activity in the middle frontal gyrus did not differ between the two conditions. Taking these results together, we have shown the double dissociation between the PFC and MTL in memory retrieval.     

Age-related differences in brain activity underlying working memory for spatial and nonspatial auditory information

We used functional magnetic resonance imaging and a 1-back task to assess working memory (WM) for spatial (sound location) and nonspatial (sound category) auditory information in younger and older adults. A mixed block-event-related design was used to measure sustained activity during each task block and transient activity to targets (repetitions of location or category). In both groups, there was increased sustained activity for category WM in left anterior temporal cortex and inferior prefrontal cortex (PFC) and increased activity for location WM in right inferior parietal cortex and dorsal PFC. There were no reliable age differences in this pattern of activity. Older adults had more sustained activity than younger adults in left PFC during both tasks, suggesting that additional PFC recruitment in older adults reflects nonspecific engagement of frontally mediated task-monitoring processes. Both groups showed lower transient than sustained activity in auditory cortex bilaterally; however, older adults showed smaller target-related reductions of activity during the category task. A greater reduction of activity to category targets in left auditory cortex was associated with better performance on this task in older adults, suggesting that a failure to modulate activity appropriately when a stimulus is repeated, or when a particular feature of the stimulus is repeated, could lead to reduced ability to detect this repetition.     

Concurrent performance of two working memory tasks: potential mechanisms of interference

When two tasks are performed simultaneously, performance often deteriorates, with concomitant increases in reaction time and error rate. Three potential neurophysiological mechanisms behind this deterioration in performance have been considered here: (i) dual-task performance requires additional cognitive operations and activation of cortical areas in addition to those active during single-task performance; (ii) two tasks interfere if they require activation of the same part of cortex; and (iii) cross-modal inhibition causes interference between two tasks involving stimuli from different sensory modalities. Positron emission tomography was used to measure regional cerebral blood flow (rCBF) during performance of an auditory working memory (WM) task, a visual WM task, both WM tasks (dual task) and a control condition. Compared to the control condition, the auditory and visual WM tasks activated sensory-specific areas in the superior temporal gyrus and occipital pole respectively. Both WM tasks also activated overlapping parts of cortex in the dorsolateral prefrontal, inferior parietal and cingulate cortex. There was no separate cortical area which was activated only in the dual task, and thus no area which could be associated with any dual task specific cognitive process such as task-coordination or divided attention. Decrease in rCBF in one WM task did not overlap with the areas of rCBF increase in the other WM task. However, an inhibitory mechanism could not be ruled out, since the rCBF increase in sensory specific areas was smaller in the dual- task condition than in the single-task conditions. The cortical activity underlying WM was to a large extent organized in a non-sensory specific, or non-parallel, way, and the results are consistent with the hypothesis that concurrent tasks interfere with each other if they demand activation of the same part of cortex.      

Enhanced catecholamine synthesis in the prefrontal cortex after traumatic brain injury: implications for prefrontal dysfunction

Traumatic brain injury (TBI)--induced dysfunction of the prefrontal cortex causes many high-level cognitive deficits, including working memory (WM) dysfunction. WM lies at the core of many high-level functions, yet the cellular and molecular mechanisms underlying its dysfunction are poorly understood. Lesion and pharmacological studies in rodents have implicated the medial prefrontal cortex (mPFC), which includes the prelimbic/infralimbic (PL/IL) cortices, in WM tasks. These studies have shown that optimal levels of catecholamine neurotransmission are critical for normalcy of WM function, suggesting that alterations in their synthesis may play a role in WM dysfunction. Using the cortical impact injury model of traumatic brain injury which reproducibly causes working memory deficits in rodents, we have measured the protein levels and activity of tyrosine hydroxylase (TH), the rate-limiting enzyme for catecholamine biosynthesis, and tissue dopamine (DA) and norepinephrine (NE) levels in microdissected PL/IL tissues. Our results show that TBI increases TH protein levels, its activity and tissue DA and NE content in the PL/IL. These findings suggest that altered catecholamine signaling within the PL/IL may contribute to impaired PFC function, and may have implications in the design and implementation of strategies to alleviate prefrontal dysfunction in brain injury patients.     

Parieto-frontal interactions in visual-object and visual-spatial working memory: evidence from transcranial magnetic stimulation.

This study aimed to investigate whether transcranial magnetic stimulation (TMS) can induce selective working memory (WM) deficits of visual-object versus visual-spatial information in normal humans. Thirty-five healthy subjects performed two computerized visual n-back tasks, in which they were required to memorize spatial locations or abstract patterns. In a first series of experiments, unilateral or bilateral TMS was delivered on posterior parietal and middle temporal regions of both hemispheres after various delays during the WM task. Bilateral temporal TMS increased reaction times (RTs) in the visual-object, whereas bilateral parietal TMS selectively increased RTs in the visual-spatial WM task. These effects were evident at a delay of 300 ms. Response accuracy was not affected by bilateral or unilateral TMS of either cortical region. In a second group of experiments, bilateral TMS was applied over the superior frontal gyrus (SFG) or the dorsolateral prefrontal cortex (DLPFC). TMS of the SFG selectively increased RTs in the visual-spatial WM task, whereas TMS of the DLPFC interfered with both WM tasks, in terms of both accuracy and RTs. These effects were evident when TMS was applied after a delay of 600 ms, but not one of 300 ms. These findings confirm the segregation of WM buffers for object and spatial information in the posterior cortical regions. In the frontal cortex, the DLPFC appears to be necessary for WM computations regardless of the stimulus material.     

Molecular markers in stored kidneys using perfluorocarbon-based preservation solution: preliminary results

BACKGROUND: Delayed graft function (DGF) is a problem in kidney transplantation and cold ischemia has been identified as a risk factor. Perfluorocarbons (PFC) have an enhanced ability to dissolve and release oxygen. We evaluated histologically and a number of molecular changes induced by ischemia in stored kidneys with University of Wisconsin (UW) and PFC-based preservation solutions (PFC-UW). MATERIALS AND METHODS: ACI rats were used as kidney donors. UW (control group) or PFC-UW (study group) preservation solutions were used for kidney perfusion. All kidneys were stored at 4 degrees C for 12, 24, and 36 hours. After this time, intragraft histologic evaluation as well as mRNA HO-1 and iNOS levels were also analyzed. RESULTS: In the kidneys stored at 24 hours, mRNA HO-1 levels were elevated in the study group when compared with the control and mRNA iNOS was decreased. CONCLUSION: We observed overexpression of HO-1 and underexpression of iNOS in the kidney tissue stored with PFC-UW solution at 24 hours. These preliminary data suggest that increasing oxygen delivery by PFC added to the perfusion solution triggers cytoprotective mechanism in kidney transplantation.     

Effects of Sleeve Gastrectomy on Nonalcoholic Fatty Liver Disease in an Obese Rat Model

Background/Aim

Laparoscopic sleeve gastrectomy (SG) is an increasingly used bariatric surgery, which is reported to be effective for nonalcoholic fatty liver disease (NAFLD). Recently, activation of farnesoid X receptor (FXR), which is a nuclear receptor of bile acid (BA), was reported to contribute to the resolution of NAFLD. However, it is unclear whether SG has an effect on expression of FXR in the liver. We aimed to investigate the expression of FXR and its related factors in the liver after SG and to clarify the relationship between changes in FXR expression and NAFLD in an obese rat model.

Methods

Thirty male Zucker fatty rats were divided into three groups: sham-operated (SO) control, pair-fed (PF) control, and SG. Eight weeks after the surgery, metabolic parameters, plasma levels of total BA and liver enzymes, liver triglyceride (TG) content, and mRNA expression of FXR and its related factors, such as small heterodimer partner (SHP) and peroxisome proliferator-activated receptor α (PPARα), were measured.

Results

Metabolic parameters in the SG group were significantly improved compared with the SO group. Liver enzymes and TG were significantly lower in the SG group than in the SO group. Plasma levels of BA were significantly higher in the SG group than in the SO and PF groups. mRNA expression of FXR, SHP, and PPARα in the liver was significantly higher in the SG group than in the SO group.

Conclusions

These results suggest that the effects of SG on NAFLD should be associated with the expression of the FXR pathway in the liver in a Zucker fatty rat model.

     

Analogical reasoning and prefrontal cortex: evidence for separable retrieval and integration mechanisms

The present study examined the contributions of prefrontal cortex (PFC) subregions to two component processes underlying verbal analogical reasoning: semantic retrieval and integration. Event-related functional magnetic resonance imaging data were acquired while subjects performed propositional analogy and semantic decision tasks. On each trial, subjects viewed a pair of words (pair 1), followed by an instructional cue and a second word pair (pair 2). On analogy trials, subjects evaluated whether pair 2 was semantically analogous to pair 1. On semantic trials, subjects indicated whether the pair 2 words were semantically related to each other. Thus, analogy--but not semantic--trials required integration across multiple retrieved relations. To identify regions involved in semantic retrieval, we manipulated the associative strength of pair 1 words in both tasks. Anterior left inferior PFC (aLIPC) was modulated by associative strength, consistent with a role in controlled semantic retrieval. Left frontopolar cortex was insensitive to associative strength, but was more sensitive to integration demands than was aLIPC, consistent with a role in integrating the products of semantic retrieval to evaluate whether distinct representations are analogous. Right dorsolateral PFC exhibited a profile consistent with a role in response selection rather than retrieval or integration. These findings indicate that verbal analogical reasoning depends on multiple, PFC-mediated computations.     

Segregation of areas related to visual working memory in the prefrontal cortex revealed by rTMS

The functional organization of working memory (WM) in the human prefrontal cortex remains unclear. Storage and processing functions might be segregated in ventral and dorsal areas of the prefrontal cortex, respectively. If so, storage functions might be spared, irrespective of informational domain, following damage or dysfunction in dorsolateral areas. Alternatively, WM and prefrontal function in general might be segregated according to informational domains (e.g. spatial versus object-based information). In the present study we used repetitive transcranial magnetic stimulation (rTMS) to directly test these competing hypotheses. We applied rTMS to transiently and selectively disrupt the function of the dorsomedial, dorsolateral or ventral prefrontal cortex in normal human volunteers performing either a spatial or a face-recognition delayed-response task. Performance in the spatial task was impaired by rTMS of the dorsomedial prefrontal cortex. Performance in the face-recognition (non-spatial) task was impaired by rTMS of the ventral prefrontal cortex. Transient disruption of the dorsolateral prefrontal cortex affected performance in both tasks. These findings provide evidence of domain-specific segregation of WM functions in widely separated areas of prefrontal cortex.     

How to regulate emotion? Neural networks for reappraisal and distraction

The regulation of emotion is vital for adaptive behavior in a social environment. Different strategies may be adopted to achieve successful emotion regulation, ranging from attentional control (e.g., distraction) to cognitive change (e.g., reappraisal). However, there is only scarce evidence comparing the different regulation strategies with respect to their neural mechanisms and their effects on emotional experience. We, therefore, directly compared reappraisal and distraction in a functional magnetic resonance imaging study with emotional pictures. In the distraction condition participants performed an arithmetic task, while they reinterpreted the emotional situation during reappraisal to downregulate emotional intensity. Both strategies were successful in reducing subjective emotional state ratings and lowered activity in the bilateral amygdala. Direct contrasts, however, showed a stronger decrease in amygdala activity for distraction when compared with reappraisal. While both strategies relied on common control areas in the medial and dorsolateral prefrontal and inferior parietal cortex, the orbitofrontal cortex was selectively activated for reappraisal. In contrast, the dorsal anterior cingulate and large clusters in the parietal cortex were active in the distraction condition. Functional connectivity patterns of the amygdala activation confirmed the roles of these specific activations for the 2 emotion regulation strategies.     

Neuro-functional differences associated with arithmetic processing in Turner syndrome

Turner syndrome (TS) is a neurogenetic disorder characterized by the absence of one X chromosome in a phenotypic female. Individuals with TS are at risk for impairments in mathematics. We investigated the neural mechanisms underlying arithmetic processing in TS. Fifteen subjects with TS and 15 age-matched typically developing controls were scanned using functional MRI while they performed easy (two-operand) and difficult (three-operand) versions of an arithmetic processing task. Both groups activated fronto-parietal regions involved in arithmetic processing during the math tasks. Compared with controls, the TS group recruited additional neural resources in frontal and parietal regions during the easier, two-operand math task. During the more difficult three-operand task, individuals with TS demonstrated significantly less activation in frontal, parietal and subcortical regions than controls. However, the TS group's performance on both math tasks was comparable to controls. Individuals with TS demonstrate activation differences in fronto-parietal areas during arithmetic tasks compared with controls. They must recruit additional brain regions during a relatively easy task and demonstrate a potentially inefficient response to increased task difficulty compared with controls.     

The neural correlates of declining performance with age: evidence for age-related changes in cognitive control

The neural system involved in cognitive control includes the anterior cingulate cortex (ACC) and the lateral prefrontal cortex (PFC). Neural activity within these structures is sensitive to aging. We investigated the hypothesis that decline in performance with age results in increased cognitive control, as indexed by greater activity within the ACC and lateral PFC. Using positron emission tomography we measured neural activity during a range of verbal decision-making tasks in 16 subjects aged 37-83 years. Conditions were separated behaviorally on the basis of their sensitivity to aging. This allowed the comparison of age-dependent and age-independent conditions, revealing the neural correlates of age-dependent decline in performance. We then modeled the relationship between age, decision type, performance, and frontal lobe activity. ACC activity was independently predicted by age and decision-making accuracy, indicating that in older individuals ACC response is more sensitive to declining performance. We also found strong functional connectivity between the ACC and lateral PFC and observed that activation of the lateral PFC was qualitatively different over time in different age groups. Thus, the ACC and lateral PFC show distinct responses to age-related decline in decision-making performance. This suggests that greater cognitive control is employed as individuals age and their performance declines.     

Effect of oxygenated perfluorocarbons on isolated rat pancreatic islets in culture

One impediment for a wider application of islet transplantation is the limited number of donor pancreata for islet isolation. A more efficient utilization of available organs could in part alleviate this problem. Perfluorocarbons (PFCs) have a high oxygen solubility coefficient and maintain high oxygen partial pressures for extended time. They serve also as oxygen "reservoirs" for harvested organs in pancreas organ transplantation. The aim of this study was to test whether the use of PFCs could also be beneficial for the secretory activity and overall viability of cultured purified islets before transplantation. Purified rat islets were cultured in static conditions with or without oxygen-saturated PFCs for 1 or 7 days. Cell death and apoptosis were assessed by trypan blue staining, DNA strand breaks, and caspase 3/7 activity. mRNA levels of insulin and ICA512/IA-2, a membrane marker of secretory granules (SGs), were quantitated by real-time PCR, whereas insulin content and secretion were measured by RIA. Polypyrimidine tract binding protein (PTB), which promotes SG biogenesis, was assessed by Western blotting. The number of SGs and the ultrastructural appearance of beta5-cells were analyzed by cryoimmunoelectronmicroscopy for insulin. Various parameters, including caspase activity, insulin and ICA512/IA-2 mRNA levels, PTB expression, number of secretory granules, and ultrastructural appearance did not significantly differ between control and PFC-cultured islets. On the other hand, PFC culture islets showed significantly increased DNA fragmentation and a reduced insulin stimulation index at both time points compared to control islets. While advantageous for the transport of human harvested organs, the use of PFH in the culture may be comparable to and/or not provide advantage over conventional protocols for culture of islets for transplantation.     

Synaptic basis of persistent activity in prefrontal cortex in vivo and in organotypic cultures

Persistent activity is observed in many cortical and subcortical brain regions, and may subserve a variety of functions. Within the prefrontal cortex (PFC), neurons transiently maintain information in working memory via persistent activity patterns; however, the mechanisms involved are largely unknown. The present study used intracellular recordings from deep layer PFC neurons in vivo and patch-clamp recordings from PFC neurons in organotypic brain slice cultures to examine the ionic mechanisms underlying persistent activity states evoked by various inputs. Persistent activity had consistent features regardless of the initiating stimulus; it was driven by non-NMDA glutamate receptors yet consisted of an initial GABA mediated component, followed by a prolonged synaptically mediated inward current that maintained the sustained depolarization on which rode many asynchronous GABA-mediated events. The stereotyped nature of the multiple-component persistent activity pattern reported here might be a common feature of interconnected cortical networks but within PFC could be related to the persistent activity required for working memory.     

Bursting of prefrontal cortex neurons in awake rats is regulated by metabotropic glutamate 5 (mGlu5) receptors: rate-dependent influence and interaction with NMDA receptors

Metabotropic glutamate 5 (mGlu5) receptors have been recently implicated in prefrontal cortex (PFC)-dependent executive functions because inhibition of mGlu5 receptors impairs working memory and worsens cognitive-impairing effects of NMDA receptor antagonists. To better understand the mechanisms by which mGlu5 receptors influence PFC function, we examined the effects of selective mGlu5 receptor antagonist 2-methyl-6-(phenylethynyl)-pyridine (MPEP), given alone or in combination with the NMDA receptor antagonist MK801, on ensemble single unit activity in the medial PFC (mPFC) of behaving rats. MPEP decreased the spontaneous burst activity of the majority of mPFC neurons. This inhibition was selective for the most active cells because greater decreases were observed in neurons with higher baseline firing rates. MPEP augmented the effects of MK801 on burst activity, variability of spike firing and random spike activity. These findings demonstrate that in awake animals mGlu5 receptors regulate the function of PFC neurons by two related mechanisms: (i) rate-dependent excitatory influence on spontaneous burst activity; and (ii) potentiation of NMDA receptor mediated effects on firing rate and burst activity. These mechanisms support the idea that modulation of mGlu5 receptors may provide a pharmacological strategy for fine-tuning the temporal pattern of firing of PFC neurons.     

Ameliorating Small Bowel Injury Using a Cavitary Two-Layer Preservation Method with Perfluorocarbon and a Nutrient-Rich Solution

The aim of this study was to improve small bowel (SB) quality during cold storage by combining two proven preservation strategies involving perfluorocarbon (PFC) and a novel luminal amino acid-rich solution. Rodent SB was flushed vascularly with UW solution and flushed luminally as follows: Group 1 (control)--no luminal flush, stored in UW; Group 2--luminal UW solution, stored in PFC; Group 3--luminal amino-acid (AA) solution, stored in PFC; and Group 4--luminal AA solution, stored in AA solution. Energetics, histology and mucosal function/electrophysiology were assessed over 24 h at 4 degrees C. ATP was consistently greater in Groups 2-4 than in the Control Group. Groups 3 and 4 exhibited significantly greater ATP, ATP/ADP ratios and energy charge levels after 12-h storage than in the other Groups. Histologic injury was generally lower in the AA-treated tissues (Groups 3 and 4); after 24 h, only minor epithelial clefting (Park's median grade 2) was present in Group 4; and consistent transmural infarction (grade 8) was evident in Groups 1 and 2. Combined treatment with luminal amino acid solution and oxygenated storage solution (PFC or AA solution) significantly improves energetics and mucosal function. This strategy may have implications for successful SB preservation in the clinic.