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102
result(s) for
"Baxter, Melissa"
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Directed differentiation of human embryonic stem cells toward chondrocytes
by
Soncin, Francesca
,
Lowe, Emma T
,
Kimber, Susan J
in
631/532/1360
,
631/61/2320
,
631/61/51/1844
2010
Degeneration of articular cartilage in the joints may be amenable to tissue engineering solutions. Oldershaw
et al
. present an efficient, chemically defined protocol for differentiating human ES cells to chondrocyte-like cells.
We report a chemically defined, efficient, scalable and reproducible protocol for differentiation of human embryonic stem cells (hESCs) toward chondrocytes. HESCs are directed through intermediate developmental stages using substrates of known matrix proteins and chemically defined media supplemented with exogenous growth factors. Gene expression analysis suggests that the hESCs progress through primitive streak or mesendoderm to mesoderm, before differentiating into a chondrocytic culture comprising cell aggregates. At this final stage, 74% (HUES1 cells) and up to 95–97% (HUES7 and HUES8 cells) express the chondrogenic transcription factor SOX9. The cell aggregates also express cell surface CD44 and aggrecan and deposit a sulfated glycosaminoglycan and cartilage-specific collagen II matrix, but show very low or no expression of genes and proteins associated with nontarget cell types. Our protocol should facilitate studies of chondrocyte differentiation and of cell replacement therapies for cartilage repair.
Journal Article
Optic nerve regeneration in larval zebrafish exhibits spontaneous capacity for retinotopic but not tectum specific axon targeting
by
Baxter, Melissa
,
Harvey, Beth M.
,
Granato, Michael
in
Animals
,
Animals, Genetically Modified
,
Apoptosis
2019
In contrast to mammals, retinal ganglion cells (RGC) axons of the optic nerve even in mature zebrafish exhibit a remarkable capacity for spontaneous regeneration. One constraint of using adult zebrafish is the limited ability to visualize the regeneration process in live animals. To dynamically visualize and trace the degree of target specific optic nerve regeneration, we took advantage of the optical transparency still preserved in post developmental larval zebrafish. We developed a rapid and robust assay to physically transect the larval optic nerve and find that by 96 hours post injury RGC axons have robustly regrown onto the optic tectum. We observe functional regeneration by 8 days post injury, and demonstrate that similar to adult zebrafish, optic nerve transection in larval zebrafish does not prominently induce cell death or proliferation of RGC neurons. Furthermore, we find that partial optic nerve transection results in axonal growth predominantly to the original, contralateral tectum, while complete transection results in innervation of both the correct contralateral and 'incorrect' ipsilateral tectum. Axonal tracing reveals that although regenerating axons innervate the 'incorrect' ipsilateral tectum, they successfully target their topographically appropriate synaptic areas. Combined, our results validate post developmental larval zebrafish as a powerful model for optic nerve regeneration, and reveal intricate mechanistic differences between axonal growth, midline guidance and synaptic targeting during zebrafish optic nerve regeneration.
Journal Article
Increased ventriculostomy infection rate with use of intraventricular tissue plasminogen activator: A single-center observation
by
Fabiano, Andrew J.
,
Baxter, Melissa S.
,
Gruber, Thomas J.
in
Aneurysm
,
Antibiotics
,
Cerebral Hemorrhage - drug therapy
2013
Intraventricular tissue plasminogen activator (alteplase) has been advocated for prevention of vasospasm in aneurysmal subarachnoid hemorrhage and treatment of traumatic or spontaneous intraventricular hemorrhage. External ventricular drain (EVD) insertion is often performed to manage increased intracranial pressure and hydrocephalus associated with these disease states. EVD-related ventriculitis is a serious infection with an up to 50% mortality rate.
We assessed the EVD infection rate in patients receiving intraventricular alteplase over a 12-month period. Patients were divided into intraventricular alteplase and non-intraventricular alteplase groups; ventriculitis rates were compared.
EVDs were placed in 93 patients. Six of 7 (86%) patients who received intraventricular alteplase developed ventriculitis versus 4 of 86 (5%) patients in the non-intraventricular alteplase group (p<0.0001).
Intraventricular alteplase use may increase ventriculitis risk. Currently, we reserve intraventricular alteplase for patients with EVDs obstructed by hematoma accompanied by increased intracranial pressure.
Journal Article
Carotid artery stenting outcomes: do they correlate with antiplatelet response assays?
2014
Objective Limited data exist regarding the use of antiplatelet response assays during neuroendovascular intervention. We report outcomes after carotid artery stenting (CAS) based on aspirin and P2Y12 assays. Methods We retrospectively identified patients who had aspirin and P2Y12 assays at the time of stenting. Aspirin (325 mg) and clopidogrel (75 mg) were started 7–10 days pre-intervention. If not possible, aspirin (650 mg) and clopidogrel (600 mg) loading doses were given pre-intervention. Assays were checked on postoperative day 0/1. Outcomes included neurological ischemic sequela at 30 days, 1 and 2 years, as well as 30 day death/hemorrhage/myocardial infarction. Results 449 patients were included. Mean P2Y12 reaction unit (PRU) values were higher in patients with an ipsilateral ischemic event (stroke/transient ischemic attack (TIA)) or stroke (alone) at 1 and 2 years than in patients with no events: ischemic event versus no event at 1 year, 252 vs 202 (p=0.008); stroke versus no stroke at 1 year, 252 versus 203(p=0.029); ischemic event versus no event at 2 years, 244 vs 203 (p=0.047); stroke versus no stroke at 2 years, 243 versus 203 (p=0.082). Ischemic event free survival (stroke/TIA, p=0.0268) and overall survival (p=0.0291) post-CAS were longer in patients with PRU ≤198 compared with an initial threshold of PRU ≤237. Mean PRU values were higher in patients who died from all causes at 30 days than in survivors (p=0.031). No correlation was found between lower PRU values and hemorrhage. Aspirin reaction units did not correlate with outcome. Conclusions PRU ≤198 may be associated with a lower incidence of ischemic neurological sequela and death post-CAS. Prospective studies are needed to validate the relationship between antiplatelet assays and outcomes post-CAS.
Journal Article
The use of faecal microbiota transplant as treatment for recurrent or refractory Clostridium difficile infection and other potential indications: joint British Society of Gastroenterology (BSG) and Healthcare Infection Society (HIS) guidelines
by
Marsden, Gemma L
,
Colville, Alaric
,
Settle, Christopher
in
Clinical trials
,
Clostridium difficile
,
Cytomegalovirus
2018
Interest in the therapeutic potential of faecal microbiota transplant (FMT) has been increasing globally in recent years, particularly as a result of randomised studies in which it has been used as an intervention. The main focus of these studies has been the treatment of recurrent or refractory Clostridium difficile infection (CDI), but there is also an emerging evidence base regarding potential applications in non-CDI settings. The key clinical stakeholders for the provision and governance of FMT services in the UK have tended to be in two major specialty areas: gastroenterology and microbiology/infectious diseases. While the National Institute for Health and Care Excellence (NICE) guidance (2014) for use of FMT for recurrent or refractory CDI has become accepted in the UK, clear evidence-based UK guidelines for FMT have been lacking. This resulted in discussions between the British Society of Gastroenterology (BSG) and Healthcare Infection Society (HIS), and a joint BSG/HIS FMT working group was established. This guideline document is the culmination of that joint dialogue.
Journal Article
Omega-3 fatty acid ethyl esters do not improve clopidogrel associated P2Y12 inhibition in stroke patients
by
Baxter, Melissa
,
Mehta, Bijal K.
,
Kamal, Haris
in
Cerebrovascular disease
,
clopidogrel
,
Fatty acids
2015
The specific action of omega-3 fatty acid ethyl esters (OFA) in preventing cerebrovascular disease remains unknown, but research has demonstrated multiple possible mechanisms. In addition to altering lipid profiles, OFA may inhibit platelet aggregation. Clopidogrel inhibits platelets via the P2Y12 receptor. OFA may alter clopidogrel-associated platelet-inhibition via a possible combined effect on P2Y12 inhibition. To determine if OFA affects clopidogrel associated P2Y12 platelet receptor inhibition by comparing the percentage of responders in patients with cerebrovascular disease who were taking clopidogrel with or without OFA. We retrospectively reviewed data from adult patients with cerebrovascular disease or cerebral aneurysms and taking clopidogrel, who were seen at a single hospital between March 2010 to September 2011. We included 438 subjects in the study. For the 67 subjects who received loading doses of both clopidogrel and OFA, 71.6% had a P2Y12 inhibition response more than 20%, which is considered a positive response. For the 55 subjects who received just clopidogrel load, 67.2% of subjects were responders. There were 70.4% responders in the 274 subjects who were taking 75 mg of clopidogrel alone at home, and 73.8% responders in the 42 subjects who were taking both clopidogrel and OFA at home. However, these percentage differences were not statistically significant. This study did not find additional P2Y12 platelet inhibition when patients were given OFA, either given as a loading dose or taking it daily.
Journal Article
Derivation of Man-1 and Man-2 research grade human embryonic stem cell lines
by
Kimber, Susan J.
,
Mckay, Tristan R.
,
Oldershaw, Rachel A.
in
Adaptation, Physiological - drug effects
,
Animal Genetics and Genomics
,
Animals
2010
We report here the derivation of two new human embryonic stem cell lines, Man-1 and Man-2, and their full characterization as novel pluripotent stem cell lines. Man-1 was derived from an embryo surplus to requirement from routine IVF, while Man-2 was obtained from an oocyte classified as failed to fertilise and subsequently chemically activated. We report the characterisation of pluripotency and the differentiation potential of these lines. Work is in progress to establish novel methods of stem cell derivation and culture, which will avoid the use of xenobiotics and be relevant to clinical production of human embryonic stem cell lines. Both newly derived human embryonic stem cell lines will be available for the research community from the UK Stem Cell Bank (http://www.ukstemcellbank.org.uk).
Journal Article
Concise Review: Workshop Review: Understanding and Assessing the Risks of Stem Cell‐Based Therapies
by
Sethu, Swaminathan
,
Stacey, Glyn
,
Cross, Michael J.
in
Adult stem cells
,
Autologous stem cell transplantation
,
Cell- and Tissue-Based Therapy - adverse effects
2015
Although it is important that stem cell therapies are advanced into the clinic, their safety must be continually evaluated. This review, the result of an Innovative Medicines Initiative SafeSciMET workshop with support from the UK Regenerative Medicine Platform, held at the University of Liverpool, outlines the known risks of stem cell therapeutics and discusses how they can be assessed and managed through preclinical and clinical trials to ensure the safest possible development of new products. The field of stem cell therapeutics is moving ever closer to widespread application in the clinic. However, despite the undoubted potential held by these therapies, the balance between risk and benefit remains difficult to predict. As in any new field, a lack of previous application in man and gaps in the underlying science mean that regulators and investigators continue to look for a balance between minimizing potential risk and ensuring therapies are not needlessly kept from patients. Here, we attempt to identify the important safety issues, assessing the current advances in scientific knowledge and how they may translate to clinical therapeutic strategies in the identification and management of these risks. We also investigate the tools and techniques currently available to researchers during preclinical and clinical development of stem cell products, their utility and limitations, and how these tools may be strategically used in the development of these therapies. We conclude that ensuring safety through cutting‐edge science and robust assays, coupled with regular and open discussions between regulators and academic/industrial investigators, is likely to prove the most fruitful route to ensuring the safest possible development of new products.
Journal Article