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Biomedical subjects

Mark Smith

Publications and source records attributed to Mark Smith.

At least 37 records · Page 2Linked to original sources
PubMed2004

Performance of a compact adaptive-optics system.

The design of an adaptive-optics system for correction of a beam propagating through high-speed, unpredictable optical turbulence required the use of a robust controller rather than a conventional least-squares controller. We describe the 37-channel, 50-Hz adaptive-optical system and its performance (lambda/75 rms).

Journal Article↗
PubMed2004

Horizontal information flow in spoken sentence production.

In 4 experiments the authors used a variant of the picture-word interference paradigm to investigate whether there is a temporal overlap in the activation of words during sentence production and whether there is a flow of semantic and phonological information between them. Experiments 1 and 2 demonstrate that 2 semantically related nouns produce interference effects either when they are in the same or different phrases of a sentence. Experiments 3 and 4 demonstrate that 2 phonologically related nouns produce facilitation effects but only when they are within the same phrase of a sentence. The results argue against strictly serial models of multiple-word access and provide evidence of a flow of semantic and phonological information between words during sentence production.

Humans↗
PubMed2004

Three-dimensional velocity field reconstruction.

The problem of inter-slice magnetic resonance (MR) image reconstruction is encountered often in medical imaging applications, in such scenarios, there is a need to approximate information not captured in contiguously acquired MR images due to hardware sampling limitations. In the context of velocity field reconstruction, these data are required for visualization and computational analyses of flow fields to be effective. To provide more complete velocity information, a method has been developed for the reconstruction of flow fields based on adaptive control grid interpolation (ACGI). In this study, data for reconstruction were acquired via MRJ from in vitro models of surgically corrected pediatric cardiac vasculatures. Reconstructed velocity fields showed strong qualitative agreement with those obtained via other acquisition techniques. Quantitatively reconstruction was shown to produce data of comparable quality to accepted velocity data acquisition methods. Results indicate that ACGI-based velocity field reconstruction is capable of producing information suitable for a variety of applications demanding three-dimensional in vivo velocity data.

Algorithms↗
PubMed2004

Inhibition of growth by p205: a nuclear protein and putative tumor suppressor expressed during myeloid cell differentiation.

p205 belongs to a family of interferon-inducible proteins called the IFI-200 family, which have been implicated in the regulation of cell growth and differentiation. While p205 is induced in hematopoietic stem cells during myeloid cell differentiation, its function is not known. Therefore, the aim of this study was to determine the role of p205 in regulating proliferation in hematopoietic progenitor cells and in nonhematopoietic cell lines. We found that p205 localizes to the nucleus in hematopoietic and nonhematopoietic cell lines. Transient expression of p205 in murine IL-3-dependent BaF3 and 32D-C123 progenitor cell lines inhibited IL-3-induced growth and proliferation. The closely related IFI-200 family members, p204 and p202, similarly inhibited IL-3-dependent progenitor cell proliferation. p205 also inhibited the proliferation and growth of normal hematopoietic progenitor cells. In nonhematopoietic cell lines, p205 and p204 expression inhibited NIH3T3 cell colony formation in vitro, and microinjection of p205 expression vectors into NIH3T3 fibroblasts inhibited serum-induced proliferation. We have determined the functional domains of p205 necessary for activity, which were identified as the N-terminal domain in apoptosis and interferon response (DAPIN)/PYRIN domain, and the C-terminal retinoblastoma protein (Rb)-binding motif. In addition, we have demonstrated that a putative ataxia telangiectasia, mutated (ATM) kinase phosphorylation site specifically regulates the activity of p205. Taken together, these data suggest that p205 is a potent cell growth regulator whose activity is mediated by its protein-binding domains. We propose that during myelomonocytic cell differentiation, induction of p205 expression contributes to cell growth arrest, thus allowing progenitor cells to differentiate.

Amino Acid Motifs↗
PubMed2004

Assembly in vitro of tau protein and its implications in Alzheimer's disease.

Tau is a microtubule associated protein that is also the main component of the aberrant filaments that form aberrant structures like the neuropil threads or the neurofibrillary tangles, found in the brain of Alzheimer's disease patients. The assembly of tau aberrant filaments could be reproduced in vitro by using a high concentration of tau protein or, at lower protein concentrations, by adding some compounds like polyanions, fatty acids (and derivates), and others. In this mini-review a descriptive analysis of the different conditions needed for in vitro tau polymerization are summarized.

Alzheimer Disease↗
PubMed2004

Intratesticular angioleiomyoma.

Angioleiomyomas are common benign smooth muscle tumors that occur in the subcutis of the extremities and to a lesser extent, of the head and trunk. Rarely, these tumors have been reported in other deeper tissues, but never within the testis. We present what we believe to be the first report of intratesticular angioleiomyoma, occurring in a 58-year-old man with a painless testicular swelling. Orchidectomy was the treatment of choice in this patient, as there was no reliable imaging technique to clinically distinguish this benign lesion from the more common malignant intratesticular tumors.

Angiomyoma↗
PubMed2003

Physical and chemical effects on viability of the Myxobolus cerebralis triactinomyxon.

Various chemical and physical methods for destroying the triactinomyxon (TAM) stage of the myxozoan parasite Myxobolus cerebralis were tested. The fluorescent stains propidium iodide and fluorescein diacetate were used as indicators of viability. Physical variables tested included freezing, drying, high temperature, sonication, and pressure of 6.2 x 10(7) Pa (9000 psi). Chemicals evaluated included chlorine bleach, povidone-iodine, and hydrogen peroxide. Freezing or drying for 1 h was effective in killing TAMs, but pressure was not. Temperatures above 75 degrees C for at least 5 min were also effective. Sonication with a laboratory instrument cleaner for 10 to 13 min killed and ruptured TAMs, resulting in <1.9% recovery. However, among the surviving TAMs, 39 to 58% were still viable. Chlorine concentrations of 130 ppm for 10 min were also effective at temperatures ranging from ice-water to room temperature and total hardness ranging from 10 to 500 mg l(-1). Lethal concentrations of hydrogen peroxide and povidone-iodine (10% solution) were quite high: 10% for 10 min, and 50% (5000 ppm active iodine) for 60 min, respectively. The stain results indicating TAM death were verified in 2 tests in which rainbow trout Oncorhynchus mykiss were exposed to TAMs that had been either frozen for 1 h or treated with 66 ppm chlorine as sodium hypochlorite for 1 min. None of the fish exposed to the treated TAMs became infected. These results should provide disinfection guidelines to prevent transfer of M. cerebralis TAMs to uninfected areas and provide information on the risks of parasite transfer under various treatment scenarios.

Animals↗
PubMed2003

Cutaneous head and neck squamous cell carcinoma metastatic to cervical lymph nodes (nonparotid): a better outcome with surgery and adjuvant radiotherapy.

OBJECTIVE: The aim of this study is to report on the experience of treating cutaneous squamous cell carcinoma (SCC) metastatic to cervical (nonparotid) lymph nodes at the Head and Neck Unit, Westmead Hospital, Sydney, Australia. STUDY DESIGN: Retrospective chart review. METHODS: Patients diagnosed with previously untreated metastatic cutaneous SCC to cervical lymph nodes (levels I-V) and treated with radiotherapy, surgery, or surgery and adjuvant radiotherapy were identified. Relapse and outcome was analyzed using Cox regression analysis. RESULTS: Between 1980 and 2000, 74 patients were treated with curative intent. There were 59 males and 15 females, with a median age of 66 (range 37-93) years. Median duration of follow up was 48 (range 12-187) months. Fifty-two were treated with neck dissection and radiotherapy, 13 with neck dissection alone, and 9 with only radiotherapy. Most patients (85%) had an identifiable index lesion. Level I (38%) and II (36%) lymph nodes were the most often involved. In total, 25 (34%) patients developed recurrent disease, predominantly locoregional (22 of 25). Median time to recurrence was 5.2 (2-34.3) months. Increasing nodal size (> or =3 cm) (P =.01), metastatic spread to multiple nodes (P =.05), and the presence of extranodal spread (P =.01) all predicted for worse survival. Patients undergoing combined modality treatment had a lower relapse rate (15%) and a significantly better disease free survival (P =.001) compared with single modality treatment. CONCLUSION: Metastatic cutaneous SCC is uncommon but potentially lethal. Surgery and adjuvant radiotherapy remain the best practice and provide the best chance of achieving locoregional control.

Adult↗
PubMed2002

Solid-phase synthesis of beta-mannosides.

The linkage of S-phenyl 2,3-di-O-benzyl-alpha-D-thiomannopyranoside to a cross-linked polystyrene support in the form of its 4,6-O-polystyrylborinate ester is described. The activation of this polymer-supported mannosyl donor is achieved at -60 degrees C in dichloromethane in the presence of 2,4,6-tri-tert-butylpyrimidine with the combination 1-benzenesulfinyl piperidine and trifluoromethanesulfonic anhydride. Addition of the donor alcohol at -60 degrees C followed by warming to room temperature and subsequent cleavage from the resin by gentle heating in aqueous acetone yields anomerically pure 2,3-di-O-benzyl-beta-D-mannopyranosides in excellent yield. Successful, diastereoselective coupling is demonstrated with a range of primary, secondary, and tertiary glycosyl acceptors, including typical carbohydrates and threonine derivatives.

Carbohydrate Conformation↗
PubMed2002

Variations in use of tertiary cardiac services in part of North-West England.

We assess the extent to which the need for tertiary cardiac care is being met uniformly within two Health Authorities in North-West England. We analyse small-area data from 1993-1996 on standardised rates of investigation (angiography) and surgery (bypass grafts and angioplasty). Utilisation by electoral ward is shown to be related to material deprivation. Small areas in which the Asian population is high have significantly fewer angiograms and angioplasties than might be expected according to need, while there is some evidence that women do not receive the levels of bypass surgery that might be expected.

Angioplasty, Balloon, Coronary↗
PubMed2002

Formation of aberrant phosphotau fibrillar polymers in neural cultured cells.

Here we show, for the first time, the in vitro formation of filamentous aggregates of phosphorylated tau protein in SH-SY5Y human neuroblastoma cells. The formation of such aberrant aggregates, similar to those occurring in vivo in Alzheimer's disease and other tauopathies, requires okadaic acid, a phosphatase inhibitor, to increase the level of phosphorylated tau, and hydroxynonenal, a product of oxidative stress that selectively adducts and modifies phosphorylated tau. Our findings suggest that both phosphorylation and oxidative modification are required for tau filament formation. Importantly, the in vitro formation of intracellular tau aggregates could be used as a model of tau polymerization and facilitate the development of novel therapeutic approaches.

Aldehydes↗
PubMed2002

The fetal tele-ultrasound project in Queensland.

The need for access to tertiary centre experts for those living in rural and remote areas of Queensland is well recognised. With an estimated population of 3.3 million people of whom 55% live outside the capital city, Queensland is ideally suited to telemedicine, as it provides a potential opportunity to improve access to specialist care. Congenital fetal abnormalities are the major causes of perinatal morbidity and mortality. With only two Maternal Fetal Medicine Specialists in Queensland located in a major teaching hospital in Brisbane, the opportunity to use videoconferencing technology to develop a tertiary level tele-ultrasound service presented a challenge--that is, to find a technical and clinical solution to enable such a service. We report on some of our practical experiences and difficulties in establishing such a service.

Congenital Abnormalities↗