Gene expression profiling in the developing rat brain exposed to ketamine

Ketamine, a non-competitive N-methyl-d-aspartate (NMDA) receptor antagonist, is associated with accelerated neuronal apoptosis in the developing rodent brain. In this study, postnatal day (PND) 7 rats were treated with 20 mg/kg ketamine or saline in six successive doses (s.c.) at 2-h intervals. Brain frontal cortical areas were collected 6 h after the last dose and RNA isolated and hybridized to Illumina Rat Ref-12 Expression BeadChips containing 22,226 probes. Many of the differentially expressed genes were associated with cell death or differentiation and receptor activity. Ingenuity Pathway Analysis software identified perturbations in NMDA-type glutamate, GABA and dopamine receptor signaling. Quantitative polymerase chain reaction (Q-PCR) confirmed that NMDA receptor subunits were significantly up-regulated. Up-regulation of NMDA receptor mRNA signaling was further confirmed by in situ hybridization. These observations support our working hypothesis that prolonged ketamine exposure produces up-regulation of NMDA receptors and subsequent over-stimulation of the glutamatergic system by endogenous glutamate, triggering enhanced apoptosis in developing neurons.

Novel anti-prostate cancer curcumin analogues that enhance androgen receptor degradation activity

The androgen receptor (AR) plays a crucial role in the physiological and pathological functions of androgen. As a transcription factor, the AR modulates androgen activity by regulating the transcription of target genes that are involved in numerous physiological functions and pathological disorders, such as acne vulgaris, androgenetic alopecia, benign prostate hyperplasia (BPH), and prostate cancers. Although many natural and synthetic curcumin analogues have been reported to possess anticancer activity through a common cytotoxic property against proliferating tumor cells, none has been reported to inhibit cancer cell growth through a more specific mechanism or target in the cancer cells. Recently, new curcumin analogues were studied extensively regarding their synthesis, structure-activity (i.e., anticancer activity) relationships, and mechanism of action. These compounds, such as ASC-J9 and its analogues (3 and 4), have now been shown to inhibit prostate cancer proliferation through a novel mechanism of enhancing AR degradation.

Use of two-year disease-free survival (DFS) as a primary endpoint in stage III adjuvant colon cancer trials with fluoropyrimidines with or without oxaliplatin or irinotecan: New data from 12,676 patients from MOSAIC, X-ACT, PETACC-3, NSAPB C-06 and C-07, and C89803

4011

Background: The ACCENT group previously validated DFS with 3 years (yr) median follow-up (f-up) based on 20,898 pts from trials testing 5-FU based regimens (rx) (3yr DFS) as an endpoint to predict overall survival with 5 yr median f-up (5yr OS) (Sargent, JCO 2005). ACCENT further proposed (1) 2yr DFS predicts 5yr OS, (2) a stronger relationship between DFS and OS in stage III pts (Sargent JCO 2007) and (3) 6 or 7 yrs are necessary to demonstrate DFS and OS association in future trials due to extended survival following recurrence (de Gramont ASCO 2008). The relationship between endpoints in more recent trials with oral fluoropyrimidines, oxaliplatin, and irinotecan is unknown. Methods: Concordance between 2 and 3yr DFS, and 5 and 6yr OS was examined in 6 randomized phase III trials from 1997–2002. Individual data for 12,676 pts was analyzed; 2 trials tested oxaliplatin, 2 irinotecan, and 2 oral rx vs 5-FU/LV control. Association between DFS and OS hazard ratios (HRs) via weighted least squares (WLS), and concordance between predicted and actual within-trial HRs, were calculated overall and for stage III pts. Results: Overall association between 3 yr DFS and 5 yr OS HRs was reduced compared to the prior ACCENT analysis (Table). In stage III pts, the association between DFS and OS HRs remained strong. Observed 5 and 6yr OS HRs were predicted accurately by 2yr DFS overall and in stage III pts (within 95% prediction limits in all trials). In all pts, DFS HRs were more highly associated with 6 vs 5yr OS HRs. Conclusions: In recent trials in stage III pts, DFS HRs based on 2yr median f-up are highly predictive of 5 and 6yr OS HRs. In all pts the association between DFS and OS HRs is stronger for 6yr OS, but 7yr follow-up may be required. These data support 3yr DFS as a primary endpoint for modern stage III trials, and indicate that 2yr DFS would also be an appropriate primary endpoint.

[Table: see text]

[Table: see text]

Symptom burden in cancer survivors: A report from the American Cancer Society's studies of cancer survivors

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Background: Cancer survivors may have persistent symptoms as a result of the cancer or the late effects of cancer treatment, although few studies have assessed symptom burden after completion of cancer therapy. We described symptom burden and risk factors for high symptom burden in a population-based sample of cancer survivors. Methods: Cancer survivors were drawn from 11 state cancer registries and surveyed by telephone or mail approximately 1 year after diagnosis; 3697 respondents completed the Modified Rotterdam Symptom Checklist (RSCL-M) and Profile of Mood States-37 (POMS-37). Factor analyses were used to generate composite scores from RSCL-M and POMS-37.Two-step cluster analyses using these composite scores were performed to identify cancer survivors with high symptoms. Results: Six composite scores (pain, nausea/vomiting, fatigue, poor bowel and bladder control, weight loss, and unspecified symptoms) were generated for physical symptoms (RSCL-M). Five composite scores (anxious/depressed, miserable, energetic, exhausted, and annoyed) were generated for mental symptoms (POMS-37). Cluster analyses revealed that 20% of survivors reported both high physical and high mental symptoms. Multivariate logistic regression revealed risk factors associated with high physical and high mental symptoms: younger than 55, household income lower than $40,000, high school or lower education level, unemployed when diagnosed with cancer, lack of health insurance, distant cancer, one or more comorbid conditions, diagnosis of lung cancer, and previous chemotherapy. Conclusions: One of five cancer survivors in this survey belonged to a group with high physical and mental symptoms, which were associated with certain risk factors. These findings will help clinicians and researchers identify subgroups of survivors most likely to report high symptoms and therefore most in need of symptom management. The high symptoms reported by survivors without insurance may have policy implications.

No significant financial relationships to disclose.

Health-related quality of life indicators and overall quality of life: Results from a cluster analysis on baseline EORTC QLQ-C30 data from 6,739 cancer patients

e20576

Background: Increasingly randomized controlled trials in cancer research include Health-related Quality of Life (HRQoL) alongside traditional biomedical outcome measures. The majority of these trials focus on a general cancer HRQoL measure. The objective of this meta-analysis was to identify which HRQoL indicators influence a patient's overall quality of life, in order to better understand the changes in such a generic scale. Methods: Retrospective pooling of 29 European Organisation for Research and Treatment of Cancer (EORTC) clinical trials, among 10 cancer sites, yielded baseline EORTC QLQ-C30 data for a total of 6,739 patients. A cluster analysis, using Ward's method, was performed to determine how the 15 HRQoL indicators, and the Global Health scale (GH) in particular, cluster overall and by cancer characteristics. Cronbach's alpha coefficient (α) was used to measure internal consistency. Dendrograms of the HRQoL indicators were plotted for each cancer type. Results: Three main clusters emerged: a physical function related cluster (physical functioning, role functioning, fatigue and pain, α = 0.83), a psychological function related cluster (emotional functioning, cognitive functioning and insomnia, α = 0.64) and a gastrointestinal cluster (nausea and vomiting and appetite loss, α = 0.68). The GH scale was found to be part of the physical function cluster in the overall dataset (α = 0.85). This result was reproduced for both metastatic and non-metastatic patients. When looking across the 10 different cancer sites, the GH scale was mainly linked with a physical component in brain, head and neck, lung, melanoma, ovarian, pancreatic and prostate cancer. However, in breast and testicular cancer, GH was more strongly associated with the emotional scales. Conclusions: This study shows that the GH scale of the EORTC QLQ-C30 is most strongly linked with a patient's physical status. This result is consistent across stage of disease and most cancer sites. The different results seen in patients with breast and testicular cancer deserve additional investigation.

No significant financial relationships to disclose.

A sperm GPI-anchored protein elicits sperm-cumulus cross-talk leading to the acrosome reaction

The acrosome reaction has long been thought to be induced by the zona pellucida. Here we report the identification and function of a novel human sperm glycosylphosphatidylinositol (GPI)-anchored membrane protein, NYD-SP8. The release of the protein during sperm-egg interaction and its binding to the cumulus, the first layer of egg investment, elicits cross-talk between the gametes and produces calcium dependant release of progesterone, which lead to the acrosome reaction. An in vivo mouse model of NYD-SP8 immunization is also established showing a reduced fertility rate. Thus, contrary to accepted dogma, our study demonstrates for the first time that, prior to reaching the zona pellucida, sperm may release a surface protein that acts on the cumulus cells leading to the acrosome reaction, which may be important for determining the outcome of fertilization.

IGF-1 regulation of type II collagen and MMP-13 expression in rat endplate chondrocytes via distinct signaling pathways

OBJECTIVE

Abnormal maturation and ossification of the endplate chondrocytes play a central role in the pathogenesis of degenerative disorders of the cervical spine. It is widely held that insulin like growth factor-1 (IGF-1) stimulates chondrocyte proliferation and inhibits chondrocyte terminal differentiation both in vitro and in vivo. However, the mechanism underlying such regulation is not fully understood. The present study aimed to determine the role of IGF-1 on the mRNA expression of collagen type II, alpha 1 (Col2a1) and matrix metallopeptidase 13 (MMP-13) in rat endplate chondrocytes. The possible pathways that transduce IGF-1 effects such as phosphatidylinositol-3 (PI-3)-kinase (PI3K) and mitogen activated protein kinase (MAPK) were also investigated in these cells.

METHODS

Cultured endplate chondrocytes harvested from rat cervical spines were treated with IGF-1 (100ng/ml), and the changes in Col2a1 and MMP-13 mRNA were monitored with real-time polymerase chain reaction (PCR). MMP-13 activity was also assayed. Activation of signaling proteins was evaluated by western blot analysis. Cells were also treated with pharmacological agents that block PI3K and MAPK signaling pathways.

RESULTS

IGF-1 increased Col2a1 mRNA expression in rat endplate chondrocytes in a time- and dose-dependent manner. IGF-1 treatment resulted in a fourfold increase of Col2a1 mRNA with the effect maximizing at 24h. In contrast, IGF-1 treatment for 24h caused a roughly 50% reduction in MMP-13 mRNA. Similar effects were seen on the protein levels of type II collagen (col2) and MMP-13. Consistent with these results, IGF-1 also repressed MMP-13 activity. IGF-1 activated both the PI3K and the extracellular signal-regulated kinase (ERK) pathways as evidenced by phosphorylation of either Akt or ERK1/2 (respectively). The PI3K inhibitor Wartmannin significantly inhibited the IGF-1 effect on Col2a1 mRNA expression but did not affect IGF-1-induced repression of MMP-13 expression. In contrast, the ERK/MAPK inhibitor PD98059 significantly inhibited the effect of IGF-1 on MMP-13 mRNA repression and enhanced IGF-1-induced Col2a1 mRNA expression.

CONCLUSIONS

In rat endplate chondrocytes the PI3K pathway mainly transduces IGF-1 effect on col2 expression while the ERK pathway mediates IGF-1 effect on MMP-13 expression.

Clinical analysis of nervous system involvement in ANCA-associated systemic vasculitides

OBJECTIVE

To assess the clinical features of nervous system (NS) involvement in patients with ANCA-associated vasculitides (AAV), including microscopic polyangiitis (MPA), Wegener's granulomatosis (WG), and Churg-Strauss syndrome (CSS).

METHODS

One hundred and seventy-nine patients admitted to Peking Union Medical College Hospital from 1995 to 2008, including 93 cases of MPA, 61 cases of WG, and 25 cases of CSS, were enrolled in this study. Medical charts including demographic data, clinical features, laboratory findings, treatments and outcomes were systematically reviewed.

RESULTS

NS involvements were observed in 36.6% of MPA, 50.8% of WG, and 76.0% of CSS patients. Peripheral neuropathy predominated in each type of AAV. In CSS and MPA, the majority was mononeuritis multiplex and distal symmetrical polyneuropathy, whereas, differently, 64.5% of WG patients with NS involvement had cranial neuropathy. Central nervous system (CNS) involvement accounted for 21.1%, 29.4%, and 32.3% of neuropathy respectively in CSS, MPA and WG patients, including arachnoid hemorrhage, cerebrovascular neuro-pathy, meningitis, and diffuse brain damage. 157 (87.7%) AAV patients responded to treatment with high dose of prednisone plus immunosuppressants. Thirteen (14.0%) MPA and four (6.6%) WG patients died. The leading causes of death were diffuse alveolar hemorrhage (DAH) (6, 35.3%) and infection (6, 35.3%). No patient died directly of neuropathy.

CONCLUSION

NS involvement was common in AAVs and the characteristic of NS involvement was different among MPA, WG and CSS patients. DAH and infection instead of NS damage remained the leading causes of death in AAVs.

Taxonomy of the Streptomyces strain ZG0656 that produces acarviostatin alpha-amylase inhibitors and analysis of their effects on blood glucose levels in mammalian systems

AIMS

To clarify the taxonomic status of strain ZG0656 and analyse the effects of its acarviostatin products on blood glucose levels in mammalian systems.

METHODS AND RESULTS

Our program to screen for new alpha-amylase inhibitors led to the isolation of strain ZG0656. The polyphasic taxonomic study revealed that strain ZG0656 represents a novel variation of Streptomyces coelicoflavus, for which we propose the name S. coelicoflavus var. nankaiensis. Four chemically distinct alpha-amylase inhibitors, acarviostatins I03, II03, III03 and IV03, were isolated from strain ZG0656. Acarviostatins III03 and IV03 are both novel oligomers. All four acarviostatins are mixed noncompetitive porcine pancreas alpha-amylase inhibitors. Acarviostatin III03 is the most potent alpha-amylase inhibitor known to date. Moreover, in the in vitro and in vivo experiments, acarviostatins III03 showed significant inhibition of starch hydrolysis and glucose transfer to blood.

CONCLUSIONS

Strain ZG0656 is a novel variation of S. coelicoflavus, whose products are novel effective alpha-amylase inhibitors. Among the products, acarviostatins III03 could significantly depress blood glucose levels in mammalian systems and be developed towards a possible therapeutic agent for diabetes.

SIGNIFICANCE AND IMPACT OF THE STUDY

Acarviostatin III03 is the most potent alpha-amylase inhibitor known to date. The oligomer will benefit the research on the relationship between alpha-amylase and various inhibitors and will offer more choices in diabetes treatments.

Influence of mitochondrial enzyme deficiency on adult neurogenesis in mouse models of neurodegenerative diseases

Mitochondrial defects including reduction of a key mitochondrial tricarboxylic acid cycle enzyme alpha-ketoglutarate-dehydrogenase complex (KGDHC) are characteristic of many neurodegenerative diseases. KGDHC consists of alpha-ketoglutarate dehydrogenase, dihydrolipoyl succinyltransferase (E2k), and dihydrolipoamide dehydrogenase (Dld) subunits. We investigated whether Dld or E2k deficiency influences adult brain neurogenesis using immunohistochemistry for the immature neuron markers, doublecortin (Dcx) and polysialic acid-neural cell adhesion molecule, as well as a marker for proliferation, proliferating cell nuclear antigen (PCNA). Both Dld- and E2k-deficient mice showed reduced Dcx-positive neuroblasts in the subgranular zone (SGZ) of the hippocampal dentate gyrus compared with wild-type mice. In the E2k knockout mice, increased immunoreactivity for the lipid peroxidation marker, malondialdehyde occurred in the SGZ. These alterations did not occur in the subventricular zone (SVZ). PCNA staining revealed decreased proliferation in the SGZ of E2k-deficient mice. In a transgenic mouse model of Alzheimer's disease, Dcx-positive cells in the SGZ were also reduced compared with wild type, but Dld deficiency did not exacerbate the reduction. In the malonate lesion model of Huntington's disease, Dld deficiency did not alter the lesion-induced increase and migration of Dcx-positive cells from the SVZ into the ipsilateral striatum. Thus, the KGDHC subunit deficiencies associated with elevated lipid peroxidation selectively reduced the number of neuroblasts and proliferating cells in the hippocampal neurogenic zone. However, these mitochondrial defects neither exacerbated certain pathological conditions, such as amyloid precursor protein (APP) mutation-induced reduction of SGZ neuroblasts, nor inhibited malonate-induced migration of SVZ neuroblasts. Our findings support the view that mitochondrial dysfunction can influence the number of neural progenitor cells in the hippocampus of adult mice.

Utility of QuantiFERON-TB Gold in-tube testing for latent TB infection in HIV-infected individuals

SETTING

Urban inner city human immunodeficiency virus (HIV) clinic.

OBJECTIVE

To evaluate tuberculin skin testing (TST) and QuantiFERON-TB Gold (QFT-G) testing in an HIV-infected population relative to the presence of risk factors for latent tuberculosis infection (LTBI).

DESIGN

Cross-sectional analysis of the response of a whole blood gamma interferon release assay to early secreted antigenic target 6 (ESAT-6) and culture filtrate protein 10 (CFP-10) antigens and TST relative to known risk factors for LTBI.

RESULTS

Of 207 subjects enrolled, four were excluded due to missing data and three specimens yielded discordant results. Ten specimens were indeterminate due to inadequate response to mitogen. All indeterminate results occurred in subjects with CD(4) counts <200 cells/mm(3). Eleven QFT-G results and 13 TST results were positive. The concordance between TST and QFT-G was poor (kappa 0.38). QFT-G results were more likely than TST to be associated with risk factors for LTBI.

CONCLUSIONS

QFT-G, but not TST, showed a statistically significant association between the number of risk factors for LTBI and a positive result (OR 1.6). QFT-G testing may be more useful than TST in individuals with HIV infection.

Symptom burden and survival outcome: 3 cycles versus 6 cycles of chemotherapy in advanced NSCLC

17054

Background: Improving survival and quality of life is the primary treatment goal for patient with advanced NSCLC receiving palliative chemotherapy. The optimal treatment duration remains to be determined, and there are few studies that examine longitudinal symptom burden in this population. Methods: We prospectively collected self-reported symptom data from advanced stage NSCLC patients receiving chemotherapy. Symptom data was collected weekly utilizing the MD Anderson Symptom Inventory (15 symptoms) pre chemotherapy until therapy discontinuation or up to 26 weeks. Principal components analysis of symptoms measures with a Varimax rotation were used to identify symptom clusters. A piecewise linear mixed-effect regression model was used to estimate the changes over time in symptom severity, and Cox modeling was used for data analysis. Results: Data from 102 subjects were available for analysis. Chemotherapy was primarily discontinued because of tumor progression or a decline in the patient's functional status. Seventy patients received only 2 cycles of chemotherapy, while 46 and 29 patients received 4 and 6 cycles of chemotherapy, respectively. Four clusters of symptoms were identified prior to therapy, including: general symptoms (such as pain, fatigue, sleeping disturbance), GI distress (nausea, vomiting, lack of appetite & constipation), affective symptoms (sadness & distress) and specific disease related symptoms (coughing & shortness of breath). In patients who received = 3 cycles of chemotherapy, a rapid increased in symptom severity was observed, compared to those who received > 3 cycles (P<.05). Patients who received =3 cycles of chemotherapy demonstrated shorter survival compared to those who received > 3 of chemotherapy (HR=9.9, CI=4–22.7, P<.001). Conclusion: Patients with advanced NSCLC who received more than 3 cycles of chemotherapy demonstrated more stable symptom burden and longer survival compared to those who received = 3 cycles of chemotherapy.

No significant financial relationships to disclose.

Palliative chemotherapy and cancer-related fatigue in advanced NSCLC patients

6622

Background: Cancer-related fatigue is one the most severe and prevalent symptoms in patients with advanced-stage non- small cell lung cancer (NSCLC). Whether palliative chemotherapy causes additional fatigue, beyond that which is caused by the disease itself, is unknown. Methods: Study subjects were 88 patients with advanced NSCLC who were treated with platinum-based chemotherapy at The University of Texas M. D. Anderson Cancer Center. Fatigue severity and other symptoms were measured weekly using the 0–10 rating scales of the M. D. Anderson Symptom Inventory (MDASI). Using mixed-effect modeling, we assessed fatigue severity over time of receiving chemotherapy. Results: Over the time of this longitudinal symptom assessment study, fatigue severity was overwhelmingly higher than all other symptoms. We observed no significant impact on fatigue severity by age, sex, or race/ethnicity variation; however, there was a significant difference in fatigue severity using longitudinal analysis between patients who discontinued chemotherapy within 0–6 week vs beyond 12 weeks (P<.05), and within 6–12 weeks vs beyond 12 weeks (P<0.01). By each cycle of chemotherapy, the fatigue pattern showed a consistent trend of reduced severity at day 0–3, a fatigue peak on day 5–6 (P<.05), then unchanged during days 7–21. Fatigue was most severe during the first cycle. Discussion: Cancer-related fatigue was the most severe symptom in the study sample, especially for patients only able to receive 2–4 cycles of chemotherapy. However, patients who received over 4 cycles of chemotherapy had a stable level of fatigue, which indicates that continued chemotherapy does not increase fatigue. Additional analysis demonstrated that fatigue was at it's lowest immediately following chemotherapy, possibly related to the use of steroids in conjunction with chemotherapy administration.

No significant financial relationships to disclose.

Density-driven segregation in vertically vibrated binary granular mixtures

Segregation in vertically vibrated binary granular mixtures with the same size is studied experimentally. The partially segregated state occurring in this system is observed carefully. We find that the characteristic of the partially segregated state is that the lighter particles tend to rise and form a pure layer on the top of the system while the heavier particles and some of the lighter ones stay at the bottom and form a mixed layer. The ratio of the thickness of the pure top layer to that of the whole system can be taken as an order parameter, which describes the degree of the segregation quantitatively and is useful in the investigation of the system. By use of it, we find that the segregation state is only dependent on the density ratio of the two kinds of particles. The dependent of the segregation on the vibration frequency is also studied by use of this order parameter, and finally, two typical phase diagrams are given.

Responses of the mitochondrial alpha-ketoglutarate dehydrogenase complex to thiamine deficiency may contribute to regional selective vulnerability

Thiamine-dependent enzymes are diminished in multiple neurodegenerative diseases. Thiamine deficiency (TD) reduces the activity of thiamine dependent-enzymes [e.g., the alpha-ketoglutarate dehydrogenase complex (KGDHC)], induces regional selective neurodegeneration and serves as a model of a mild impairment of oxidative metabolism. The current experiments tested whether changes in KGDHC protein subunits (E1k, E2k and E3) or activity or message levels underlie the selective loss of neurons in particular brain regions. Thus, TD-induced changes in these variables in the brain region most vulnerable to TD [the sub-medial thalamic nucleus (SmTN)] were compared to those in a region that is relatively resistant to TD (cortex) at stages of TD when the neuron loss in SmTN is not present, minimal or severe. Impaired motor performance on rotarod was apparent by 8 days of TD (-32%) and was severe by 10 days of TD (-97%). At TD10, the overall KGDHC activity measured by an in situ histochemical staining method declined 52% in SmTN but only 20% in cortex. Reductions in the E2k and E3 mRNA in SmTN occurred as early as TD6 (-28 and -18%, respectively) and were more severe by TD10 (-61 and -66%, respectively). On the other hand, the level of E1k mRNA did not decline in SmTN until TD10 (-48%). In contrast, TD did not alter mRNA levels of the subunits in cortex at late stages. Western blots and immunocytochemistry revealed different aspects of the changes in protein levels. In SmTN, the immunoreactivity of E1k and E3 by Western blotting increased 34 and 40%, respectively, only at TD8. In cortex, the immunoreactivity of the three subunits was not altered. Immunocytochemical staining of brain sections from TD10 mice indicated a reduction in the immunoreactivity of all subunits in SmTN, but not in cortex. These findings demonstrate that the response of the KGDHC activity, mRNA and immunoreactivity of E1k, E2k and E3 to TD is region and time dependent. Loss of KGDHC activity in cortex is likely related to post-translational modification rather than a loss of protein, whereas in SmTN transcriptional and post-translational modifications may account for diminished KGDHC activity. Moreover, the earlier detection in TD induced-changes of the transcripts of KGDHC indicates that transcriptional modification of the two subunits (E2k and E3) of KGDHC may be one of the early events in the cascade leading to selective neuronal death.

Hydrogen Dynamics in Na3AlH6: A Combined Density Functional Theory and Quasielastic Neutron Scattering Study

Understanding the elusive catalytic role of titanium-based additives on the reversible hydrogenation of complex hydrides is an essential step toward developing hydrogen storage materials for the transport sector. Improved bulk diffusion of hydrogen is one of the proposed effects of doping sodium alanate with TiCl3, and here we study hydrogen dynamics in doped and undoped Na3AlH6 using a combination of density functional theory calculations and quasielastic neutron scattering. The hydrogen dynamics is found to be vacancy mediated and dominated by localized jump events, whereas long-range bulk diffusion requires significant activation. The fraction of mobile hydrogen is found to be small for both undoped and doped Na3AlH6, even at 350 K, and improved hydrogen diffusion as a result of bulk-substituted titanium is found to be unlikely. We also propose that previously detected low-temperature point defect motion in sodium alanate could result from vacancy-mediated sodium diffusion.