Contributions of Astrocyte and Neuronal Volume to CA1 Neuron Excitability Changes in Elevated Extracellular Potassium

Rapid increases in cell volume reduce the size of the extracellular space (ECS) and are associated with elevated brain tissue excitability. We recently demonstrated that astrocytes, but not neurons, rapidly swell in elevated extracellular potassium (∧[K+]o) up to 26 mM. However, effects of acute astrocyte volume fluctuations on neuronal excitability in ∧[K+]o have been difficult to evaluate due to direct effects on neuronal membrane potential and generation of action potentials. Here we set out to isolate volume-specific effects occurring in ∧[K+]o on CA1 pyramidal neurons in acute hippocampal slices by manipulating cell volume while recording neuronal glutamate currents in 10.5 mM [K+]o + tetrodotoxin (TTX) to prevent neuronal firing. Elevating [K+]o to 10.5 mM induced astrocyte swelling and produced significant increases in neuronal excitability in the form of mixed α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)/N-methyl-D-aspartate (NMDA) receptor mEPSCs and NMDA receptor-dependent slow inward currents (SICs). Application of hyperosmolar artificial cerebrospinal fluid (ACSF) by addition of mannitol in the continued presence of 10.5 mM K+ forced shrinking of astrocytes and to a lesser extent neurons, which resisted swelling in ∧[K+]o. Cell shrinking and dilation of the ECS significantly dampened neuronal excitability in 10.5 mM K+. Subsequent removal of mannitol amplified effects on neuronal excitability and nearly doubled the volume increase in astrocytes, presumably due to continued glial uptake of K+ while mannitol was present. Slower, larger amplitude events mainly driven by NMDA receptors were abolished by mannitol-induced expansion of the ECS. Collectively, our findings suggest that cell volume regulation of the ECS in elevated [K+]o is driven predominantly by astrocytes, and that cell volume effects on neuronal excitability can be effectively isolated in elevated [K+]o conditions

Modern meat: the next generation of meat from cells

Modern Meat is the first textbook on cultivated meat, with contributions from over 100 experts within the cultivated meat community. The Sections of Modern Meat comprise 5 broad categories of cultivated meat: Context, Impact, Science, Society, and World. The 19 chapters of Modern Meat, spread across these 5 sections, provide detailed entries on cultivated meat. They extensively tour a range of topics including the impact of cultivated meat on humans and animals, the bioprocess of cultivated meat production, how cultivated meat may become a food option in Space and on Mars, and how cultivated meat may impact the economy, culture, and tradition of Asia

Role of Myostatin in oxidative stress in skeletal muscle

Skeletal muscle is a metabolically active tissue that is highly susceptible to wasting via oxidative stress. Oxidative stress, caused by excessive generation of reactive oxygen species, leads to skeletal muscle wasting during various diseases including cancer, diabetes and sarcopenia via various signaling molecules including TNF-α, NADPH oxidase, NF-κB, MAPKs and IL-6. However, the exact mechanism involved in oxidative stress-induced muscle wasting is not known. In the recent years, Myostatin, a member of the TGF-β superfamily and a negative regulator of skeletal muscle growth and development, has been identified as a potent inducer of muscle wasting. Here, in this thesis using various in vitro and in vivo approaches, I present that Myostatin acts as a pro-oxidant leading to skeletal muscle wasting. Firstly, this thesis demonstrates that Myostatin induces reactive oxygen species in skeletal muscle cells through TNF-α signaling via NF-κB and NADPH oxidase. In addition, Myostatin and TNF-α are components of a ‘feed forward’ loop in which Myostatin triggers reactive oxygen species generation via TNF-α and the elevated TNF-α in turn stimulates Myostatin expression. The sustained reactive oxygen species production leads to increased proteasomal-mediated degradation of proteins resulting in skeletal muscle wasting. Genetic inactivation of Myostatin in young and aged mice increased the basal Antioxidant Enzyme levels and lowered NF-κB levels, thus offering resistance to oxidative stress. Since aged Myostatin-/- mice also have lower levels of NF-κB in the muscle, I propose that Myostatin would be a good candidate to target during sarcopenia. To further understand Myostatin signaling of NF-κB and reactive oxygen species, Smad3-/- mice was used as a model since Smads are crucial downstream targets of Myostatin. Recently, our laboratory showed that Smad3-/- mice have pronounced muscle atrophy which was attributed to the increased Myostatin levels in these mice. Hence, I investigated if Smad3-/- mice have increased reactive oxygen species and our results indicated that indeed these mice have elevated oxidative stress in skeletal muscle. Inactivation of Myostatin in the absence of Smad3 partially alleviates the oxidative stress. Even though, increased Myostatin in Smad3-/- mice induced excessive reactive oxygen species, NF-κB signaling was not activated in these mice. This led us to propose that Smad3 is necessary for Myostatin-induced oxidative stress via NF-κB. Reactive oxygen species generation by Myostatin in mice lacking Smad3 was by activation of complex signaling pathways that include p38, ERK MAPK and crosstalk with the JAKs and STATs. Activation of these signaling cascades increased TNF-α, NADPH oxidase and Xanthine oxidase levels resulting in exaggerated reactive oxygen species production in Smad3-/- muscles. The excessive reactive oxygen species generated led to increased binding of CHOP transcription factor to MuRF1 promoter resulting in enhanced muscle atrophy. To advance our understanding of the effect of Myostatin-induced reactive oxygen species in skeletal muscle, a type 1 diabetes mouse model via Streptozotocin administration was used. During type 1 diabetes, there is pronounced muscle wasting due to excessive oxidative stress also leading to DNA damage. In the recent years, Myostatin has been shown to be up-regulated during Streptozotocin-induced type 1 diabetes in rodents. Since I showed that Myostatin can cause oxidative stress in muscle cells leading to protein degradation, I wanted to investigate if Myostatin can induce DNA damage also. Using an integrative approach from cell cultures to mice, I show that Myostatin can induce DNA damage via p63/REDD1 pathway in skeletal muscle. Moreover, inhibition/inactivation of Myostatin partially rescued DNA damage by regulating DNA damage/repair mechanisms. Additionally, our results also demonstrate that hypoinsulinemia during type 1 diabetes increased Myostatin levels via FoxA2. In conclusion, the data presented in this thesis indicates that Myostatin is a pro-oxidant that can induce oxidative stress leading to skeletal muscle wasting, by not only increasing protein degradation but by also causing DNA damage.DOCTOR OF PHILOSOPHY (SBS

Desmoplastic ameloblastoma

The most common odontogenic neoplasm, it accounts for only 1% of all jaw tumors. A variant of Ameloblastoma- Desmoplastic type is known for its unique features and propensity to recur. A 44 year old male patient, report with a swelling in anterior part of lower jaw. Radiograph reveals a mixed radiopaque and radiolucent lesion. Histopathology shows features of Desmoplastic ameloblastoma

Molecular targets of cancer cachexia: opportunities for pharmanutritional approaches

Cancer cachexia is a complex syndrome of progressive weight loss especially devastating to skeletal muscle and adipose tissue. In about 30% of cancer patients, cachexia is the most common cause of death. Often cachexia is accompanied with loss of appetite, inflammation and insulin resistance. Several inflammatory cytokines including Tumor Necrosis Factor-α (TNF-α) and Interleukin-6 (IL-6) are known to be involved in cachexia. Besides the humoral factors, the tumoral factors such as Proteolysis Inducing Factor (PIF) play a role in inducing cachexia. Recently, our laboratory discovered that Myostatin, a Transforming Growth Factor-β (TGF-β) superfamily member, is abundantly secreted by C26 tumor cells. Previously others and our laboratory have established Myostatin as a pro-cachectic factor inducing muscle wasting through up-regulation of muscle-specific E3 ligases, Atrogin-1 and MuRF1, and enhanced activity of the ubiquitin-proteasome pathway. Myostatin has also been shown to induce Reactive Oxygen Species (ROS), TNF-α and IL-6. Collectively, these results indicate that Myostatin is a potential target of cancer cachexia and antagonism of Myostatin would be beneficial during cancer cachexia. On the nutrition front, nutrients like Omega-3 fatty acids, Leucine and l-Carnitine have been shown to be beneficial during cancer cachexia. Based on the above findings, we propose that a combination of Myostatin antagonist and Omega-3 fatty acids or Leucine or l-Carnitine may have potential to improve muscle mass during cancer cachexia

Retinoic acid is abundantly detected in different depots of adipose tissue by sers

Retinoic acid (RA) is essential for early developmental processes and stem cell differentiation, but less is known about its contributions to adult tissues and stem cells including adipose tissue. We previously demonstrated that many genes involved in RA synthesis and downstream pathway are differentially expressed in adipose-derived stem cells (ASCs) from visceral fat compared to those from subcutaneous fat, leading to changes in their early adipogenic functions. In order to study potential contributions of RA in adipose tissue, we measured tissue RA levels using a technique based on surface-enhanced Raman spectroscopy (SERS). The data indicate heretofore underappreciated abundance of endogenous RA in mouse adipose tissue compared to other tissues and dynamic changes of RA concentrations after high fat diet feeding. Our results lay the foundation for further investigation on the functional role of RA in adipose tissue development and metabolism

Retinoic acid is abundantly detected in different depots of adipose tissue by sers

Retinoic acid (RA) is essential for early developmental processes and stem cell differentiation, but less is known about its contributions to adult tissues and stem cells including adipose tissue. We previously demonstrated that many genes involved in RA synthesis and downstream pathway are differentially expressed in adipose-derived stem cells (ASCs) from visceral fat compared to those from subcutaneous fat, leading to changes in their early adipogenic functions. In order to study potential contributions of RA in adipose tissue, we measured tissue RA levels using a technique based on surface-enhanced Raman spectroscopy (SERS). The data indicate heretofore underappreciated abundance of endogenous RA in mouse adipose tissue compared to other tissues and dynamic changes of RA concentrations after high fat diet feeding. Our results lay the foundation for further investigation on the functional role of RA in adipose tissue development and metabolism

Morquio’s Syndrome: A Case Report of Two Siblings

Morquio syndrome or MPS IVA is a rare type of lysosomal storage disease associated with highly specific dental abnormalities. We present two siblings with enamel hypoplasia and skeletal abnormalities. A diagnosis of mucopolysaccharidosis type IVA was reached based on the clinical, radiographic, and dental findings of the patients. The dental findings are useful diagnostic aid for the early diagnosis of this debilitating disorder

Efficient synthesis of out-of-core algorithms using a nonlinear optimization solver

We address the problem of efficient out-of-core code generation for a special class of imperfectly nested loops encoding tensor contractions. These loops operate on arrays too large to fit in physical memory. The problem involves determining optimal tiling and placement of disk I/O statements. This entails a search in an explosively large parameter space. We formulate the problem as a non-linear optimization problem and use a discrete constraint solver to generate optimized out-of-core code. Measurements on sequential and parallel versions of the generated code demonstrate the effectiveness of the proposed approach.