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S Smith

Publications and source records attributed to S Smith.

At least 91 records · Page 5Linked to original sources

mSprouty2 inhibits FGF10-activated MAP kinase by differentially binding to upstream target proteins.

Murine Sprouty2 (mSpry2) is a conserved ortholog of Drosophila Sprouty, a gene that inhibits several tyrosine kinase receptor pathways, resulting in net reduction of mitogen-activated protein (MAP) kinase activation. However, the precise mechanism mediating mSpry2 function as a negative regulator in tyrosine kinase growth factor pathways that regulate diverse biological functions remains incompletely characterized. Fibroblast growth factor 10 (FGF10) is a key positive regulator of lung branching morphogenesis and induces epithelial expression of mSpry2 adjacent to mesenchymal sites of FGF10. Herein, we demonstrate that FGF10 stimulation of mouse lung epithelial cells (MLE15) overexpressing mSpry2 results in both mSpry2 tyrosine phosphorylation and differential binding of mSpry2 to several key upstream target proteins in the MAP kinase-activating pathway. Thus FGF receptor (FGFR) activation results in increased association of mSpry2 with growth factor receptor-binding protein 2, suc-1-associated nuerotrophic factor target 2, and Raf but decreased binding to protein tyrosine phosphatase 2 and GTPase-activating protein 1, resulting in a net reduction of MAP kinase activation. mSpry2 also spatially translocates to the plasma membrane and intracellular membrane structures in response to FGF10 stimulation. Our data demonstrate novel intracellular mechanisms mediating mSpry2 function as a negative regulator of uncontrolled FGF-induced MAP kinase signaling.

Amino Acid Sequence↗

Cerebellar responses during anticipation of noxious stimuli in subjects recovered from depression. Functional magnetic resonance imaging study.

BACKGROUND: Subjects recovered from depression have a substantial risk for recurrence of depression, suggesting persistent abnormalities in brain activity. AIMS: To test whether women recovered from depression show abnormal brain activity in functional magnetic resonance imaging (fMRI) during a conditioning paradigm with a noxious pain stimulus. METHOD: Ten unmedicated women who had recovered from major depression and eight healthy control women each received either noxious hot or non-noxious warm stimuli, the onset of which was signalled by a specific coloured light during 3-tesla echo planar imaging-based fMRI. RESULTS: Similar patterns of brain activation were found during painful stimulation for both patients and healthy controls. However, relative to healthy controls, subjects recovered from depression showed a reduced response in the cerebellum during anticipation of the noxious stimulus compared with anticipation of the non-noxious stimulus. CONCLUSIONS: Our data suggest that abnormal cerebellar function could be a marker of vulnerability to recurrent depression. This could provide a new target for therapeutic interventions.

Adult↗

Abnormal bone architecture and biomechanical properties with near-lifetime treatment of rats with PTH.

Skeletal effects are described for near-lifetime treatment of young, female rats with recombinant human PTH (1-34) (PTH). Rats (5-8 wk of age) were administered 0, 5, 30, or 75 microg/kg x d sc PTH for up to 2 yr, as part of an oncogenicity evaluation, which is required by regulatory agencies for potential chronic therapies. Proliferative lesions were observed in the skeleton as described in Vahle et al. (1 ); in this paper, we describe the quantitative bone data for this study. In the appendicular skeleton, PTH stimulated trabecular and endocortical mineral apposition to the near exclusion of marrow spaces at 5 microg/kg, with some periosteal apposition at 30 microg/kg, followed by considerable periosteal apposition and altered geometry at 75 microg/kg. Increased bone mass was observed for all treatment groups that substantially exceeded normal levels attained by vehicle controls and exceeded skeletal efficacy reported previously for similar doses in shorter-term studies. Dose-dependent increases in osteocalcin levels and a linear increase in wet weight of femora were observed for the entire treatment duration, suggesting nearly continuous PTH stimulation of osteoblasts and skeletal growth throughout life. Histology showed many osteocytes and prominent osteoblasts, but a conspicuous absence of osteoclasts. Morphometry showed a lack of distinction between trabecular and cortical bone. Biomechanics of vehicle controls showed that optimal mechanical integrity for the normal skeleton is observed at about 11 months of age. PTH greatly strengthened and stiffened vertebra and femora; however, the midshaft showed reduced toughness and increased brittleness with treatment, which was not the case for vertebra. Related studies of 6 and 9 months duration showed that the optimal duration for PTH skeletal efficacy was about 6 months in rats, based on toughness, strength, ultimate displacement, and architecture, especially for cortical bone. Therefore, treatment duration is an under appreciated aspect of PTH pharmacology; and PTH skeletal effects are a complex function of dose and duration. Comparative analyses showed that short-term treatment (6 months or less) is more advantageous than near-lifetime treatment, because PTH stimulates skeletal growth throughout life, resulting in abnormal architecture and untoward biomechanical properties in rats.

Absorptiometry, Photon↗

Mutational status of overexpressed p16 in head and neck cancer: evidence for germline mutation of p16/p14ARF.

Inactivation of the p16 tumor suppressor gene is a common phenomenon in squamous cell carcinoma of the head and neck (SCCHN). Less commonly described is the observation of p16 overexpression in SCCHN. Since overexpression of p16 is a potent predictor of outcome in other cancers, we were interested in determining the level of expression of p16 in our SCCHN specimens as a prerequisite to later prognostic studies. We were also interested in determining the mutational status of p16 in these tumors, in order to determine whether the combination of overexpression and gene alteration may predict a different clinical outcome from overexpression alone. A total of 84 specimens of SCCHN were selected for study. These specimens were obtained from all major sites within the oral cavity, oropharynx, pharynx and larynx. The level of expression of p16 in SCCHN specimens was measured by semi-quantitative RT-PCR. In 35 cases, RNA was also isolated from matched normal tissue obtained from a negative tumor margin. In the other 49 cases, the expression level was compared with the level of expression measured in pooled normal RNA obtained from 10 specimens of normal epithelial tissue. Overexpression of p16 was documented when the level of expression in the tumor specimen was 2-fold or greater above the level of expression found in normal tissue. A total of 46 specimens demonstrated overexpression of p16 (55%). All specimens demonstrating overexpression were then subject to sequence analysis. Thirty specimens (65%) showed p16-specific gene alterations, ranging from intragenic deletions to single point mutations, and 15 of these cases concomitantly affect p14ARF. A single specimen demonstrated a silent point mutation within the p16 reading frame. This mutation produces a stop codon at residue 85 in the context of the p14ARF reading frame, predicting premature termination of p14ARF within a previously determined nucleolar localization signal. This observation suggests that in some cases at least, p14ARF may be a selective target for alteration, independently of p16. Analysis of a normal tissue specimen obtained from a negative tumor margin, and a blood sample obtained approximately five years after surgery indicate that this p14ARF-specific alteration may represent a germline mutation.

Carcinoma, Squamous Cell↗

Allantoin formation and urate and glutathione exchange in human muscle during submaximal exercise.

Seven males performed two exhaustive cycling bouts (EX1 and EX2) at a work-rate of 90% of maximal oxygen uptake, separated by 60 min. During EX1 there was a significant accumulation of urate (from 0.16 +/- 0.02 to 0.27 +/- 0.03 micromol/kg d.w.) and allantoin (from 0.39 +/- 0.05 to 0.69 +/- 0.14 micromol/kg d.w.) in the muscle. An uptake of urate was observed in early recovery from EX1 (0-9 min: 486 +/- 136 micromol; p <.05). There was no exchange of total glutathione or cysteine over the muscle either during or after exercise, and muscle and plasma total glutathione remained unaltered (p <.05). The glycogen levels were lowered by 40% at the onset of EX2, yet the level of oxidative stress in EX1 and EX2 was similar as evidenced by a similar increase in muscle allantoin in both exercise bouts. The data suggest that urate is utilized as antioxidant in human skeletal muscle and that reactive oxygen species are formed in muscle during intense submaximal exercise. No net exchange of glutathione appears to occur over the muscle either at rest, during exercise or in recovery. Moreover, when an exhaustive exercise bout is repeated with lowered glycogen levels, the level of oxidative stress is not different than that of the first bout.

Adenosine Triphosphate↗

The care of HIV-infected adults in rural areas of the United States.

OBJECTIVE: This study describes the population of HIV-infected adults receiving care in rural areas of the United States and compares HIV care received in rural and urban areas. METHODS: Interviews were conducted with a nationally representative sample of 367 HIV-infected adults receiving health care in rural areas and 2806 HIV-infected adults receiving health care in urban areas of the contiguous United States. RESULTS: We estimate that 4800 HIV-infected persons received medical care in rural areas during the first half of 1996. Patients in rural HIV care were more likely than patients in urban HIV care to receive care from providers seeing few (<10) HIV-infected patients (38% vs. 3%; p <.001). Rural care patients were less likely than urban care patients to have taken highly active antiretroviral agents (57% vs. 73%; p <.001) or Pneumocystis carinii pneumonia prophylactic medication when indicated (60% vs. 75%; p =.006). CONCLUSIONS: Few American adults received HIV care in rural areas of the United States. Our findings suggest ongoing disparities between urban and rural areas in access to high-quality HIV care.

Adult↗

Trithorax and dCBP acting in a complex to maintain expression of a homeotic gene.

Trithorax (Trx) is a member of the trithorax group (trxG) of epigenetic regulators, which is required to maintain active states of Hox gene expression during development. We have purified from Drosophila embryos a trithorax acetylation complex (TAC1) that contains Trx, dCBP, and Sbf1. Like CBP, TAC1 acetylates core histones in nucleosomes, suggesting that this activity may be important for epigenetic maintenance of gene activity. dCBP and Sbf1 associate with specific sites on salivary gland polytene chromosomes, colocalizing with many Trx binding sites. One of these is the site of the Hox gene Ultrabithorax (Ubx). Mutations in either trx or the gene encoding dCBP reduce expression of the endogenous Ubx gene as well as of transgenes driven by the bxd regulatory region of Ubx. Thus Trx, dCBP, and Sbf1 are closely linked, physically and functionally, in the maintenance of Hox gene expression.

Acetylation↗

Argon plasma coagulation for rectal bleeding after prostate brachytherapy.

PURPOSE: To better define the efficacy and safety of argon plasma coagulation (APC), specifically for brachytherapy-related proctitis, we reviewed the clinical course of 7 patients treated for persistent rectal bleeding. Approximately 2-10% of prostate cancer patients treated with 125I or 103Pd brachytherapy will develop radiation proctitis. The optimum treatment for patients with persistent bleeding is unclear from the paucity of available data. Prior reports lack specific dosimetric information, and patients with widely divergent forms of radiation were grouped together in the analyses. METHODS AND MATERIALS: Seven patients were treated with APC at the Veterans Affairs Puget Sound Health Care System and the University of Washington from 1997 to 1999 for persistent rectal bleeding due to prostate brachytherapy-related proctitis. Four patients received supplemental external beam radiation, delivered by a four-field technique. A single gastroenterologist at the Veterans Affairs Puget Sound Health Care System treated 6 of the 7 patients. If the degree of proctitis was limited, all sites of active bleeding were coagulated in symptomatic patients. An argon plasma coagulator electrosurgical system was used to administer treatments every 4-8 weeks as needed. The argon gas flow was set at 1.6 L/min, with an electrical power setting of 40-45 W. RESULTS: The rectal V100 (the total rectal volume, including the lumen, receiving the prescription dose or greater) for the 7 patients ranged from 0.13 to 4.61 cc. Rectal bleeding was first noticed 3-18 months after implantation. APC (range 1-3 sessions) was performed 9-22 months after implantation. Five patients had complete resolution of their bleeding, usually within days of completing APC. Two patients had only partial relief from bleeding, but declined additional APC therapy. No patient developed clinically evident progressive rectal wall abnormalities after APC, (post-APC follow-up range 4-13 months). CONCLUSIONS: Most patients benefited from APC, and no cases of clinically evident progressive tissue destruction were noted. Although APC appears to be efficacious and safe in the setting of the rectal doses described here, caution is in order when contemplating APC for brachytherapy patients.

Argon↗

Factors influencing student nurses in their choice of a rural clinical placement site.

INTRODUCTION: Rural health and government bodies have identified the need for greater numbers of health professionals in rural and remote health care settings. Providing students with the opportunity to experience a rural clinical placement has been suggested as one strategy for future health professionals to gain familiarity with the rural workplace and an awareness of the employment opportunities available in these areas. Although substantial numbers of student nurses have participated in a rural undergraduate clinical placement program at Queensland University of Technology, Australia, since 1996, available places remain unfilled. This study aimed to investigate the factors influencing student nurses in their choice of a rural or metropolitan clinical placement. METHODS: This study utilised a descriptive survey design. In the 24-item questionnaire, questions related to demographics, previous experience of a rural lifestyle, previous work experience and issues of importance regarding the clinical placement experience. All final-year Bachelor of Nursing students in the year 2000 (n = 212) were included in the sample, with a 65% response rate for the pre-test (n = 137). Frequency distributions, chi2 analysis (for nominal data) and ANOVA (for interval data) were used to describe differences between the characteristics of students choosing a rural or remote placement and students choosing a metropolitan placement. RESULTS: Findings demonstrated that possession of a rural background, previous work experience in a rural community and family, financial and/or employment commitments all influenced students' choice of undertaking a rural clinical placement. CONCLUSION: Students who have previously lived and/or worked in a rural area are more likely to choose a rural setting for clinical placements or postgraduate employment. However, the value of rural clinical placements as a method of increasing awareness of employment opportunities in the rural setting is considerable. Family, financial and employment commitments should be considered in the development of recruitment and retention strategies for health professionals to rural areas.

Journal Article↗

Paclitaxel and carboplatin adjuvant therapy alone or with radiotherapy for resected nonsmall cell lung carcinoma: a feasibility study of the Minnie Pearl Cancer Research Network.

BACKGROUND: The objective of this study was to determine the feasibility and toxicity of paclitaxel and carboplatin given in the adjuvant setting alone for patients with resected Stage IB disease and combined with radiotherapy for patients with resected Stages II and IIIA disease and selected patients with Stage IIIB and IV disease (Revised International System for Staging of Lung Cancer). METHODS: One hundred two patients with resected nonsmall cell lung carcinoma were treated in the postoperative period with 3 courses of paclitaxel 200 mg/m(2) intravenously (i.v.) over 1 hour and carboplatin area under the curve of 6 i.v. every 3 weeks for 3 courses. Patients with Stage IB received no further therapy, and those with higher stages also subsequently received radiotherapy plus concurrent weekly paclitaxel and carboplatin over 6 weeks. The median age was 61 years, with 56 men and 46 women, and the predominant histologic type was adenocarcinoma. Twenty pneumonectomies, 80 lobectomies, and 2 other procedures were performed. Ninety percent of the patients (92 of 102) received all 3 courses of adjuvant paclitaxel and carboplatin (84% received full doses). Seventy-three percent received full doses of radiotherapy and concurrent weekly chemotherapy (49 of 67 patients), and 14 others received greater than 75% of the radiotherapy and concurrent chemotherapy. RESULTS: Toxicity of the chemotherapy was mild with only three hospitalizations for neutropenia and fever and no treatment-related deaths. Severe hypersensitivity occurred in six patients (6%). Concurrent radiation therapy and weekly chemotherapy also was well tolerated with the exception of Grade 3-4 esophagitis observed in 27% (17 of 67 patients). Follow-up was short with a median of 10 months, and 65% of all patients remained progression free. CONCLUSIONS: Three courses of paclitaxel and carboplatin is tolerable, feasible, and can be delivered in most patients in the adjuvant setting. Subsequently, in higher stage patients, concurrent postoperative radiation therapy and weekly paclitaxel and carboplatin is well tolerated and delivered in most patients. Definitive prospective randomized Phase III adjuvant trials are warranted.

Adult↗

A placebo-controlled trial of gabapentin in spinal muscular atrophy.

OBJECTIVE: To evaluate the efficacy of gabapentin in increasing muscle strength of patients with spinal muscular atrophy (SMA). BACKGROUND: Preclinical data in experimental models of motor neuron disease suggest a neuroprotective effect of gabapentin. METHODS: Gabapentin (1200 mg), or placebo, was administered three times daily in a randomized, double-blind trial for 12 months. The primary outcome measure was the average percent change from baseline, based on the measurement of strength in four muscles (elbow flexion and hand grip bilaterally) for each patient. Drug efficacy was examined by comparing the percent change in strength for patients on drug vs. placebo. Secondary efficacy variables included: forced vital capacity (FVC), SMA functional rating scale (SMAFRS), and mini-Sickness Impact Profile (SIP). RESULTS: Eighty-four patients, with type II or III SMA, were enrolled at eight sites across the United States. There were no differences in baseline features. There was no difference between the placebo and drug groups in any outcome measure. CONCLUSIONS: This study demonstrates the feasibility of this trial design and provides data for the design of future clinical trials in SMA.

Acetates↗

HSV and glycoprotein J inhibit caspase activation and apoptosis induced by granzyme B or Fas.

HSV-1 inhibits apoptosis of infected cells, presumably to ensure that the infected cell survives long enough to allow completion of viral replication. Because cytotoxic lymphocytes kill their targets via the induction of apoptosis, protection from apoptosis could constitute a mechanism of immune evasion for HSV. Several HSV genes are involved in the inhibition of apoptosis, including Us5, which encodes glycoprotein J (gJ). Viruses deleted for Us5 showed defects in inhibition of caspase activation after Fas ligation or UV irradiation. Transfected cells expressing the Us5 gene product gJ were protected from Fas- or UV-induced apoptosis, as measured by morphology, caspase activation, membrane permeability changes, or mitochondrial transmembrane potential. In contrast, caspase 3 activation in mitochondria-free cell lysates by granzyme (gr)B was inhibited equivalently by Us5 deletion and rescue viruses, suggesting that gJ is not required for HSV to inhibition this process. However, mitochondria-free lysates from transfected cells expressing Us5/gJ were protected from grB-induced caspase activation, suggesting that Us5/gJ is sufficient to inhibit this process. Transfected cells expressing Us5/gJ were also protected from death induced by incubation with purified grB and perforin. These findings suggest that HSV has a comprehensive set of immune evasion functions that antagonize both Fas ligand- and grB-mediated pathways of CTL-induced apoptosis. The understanding of HSV effects on killing by CTL effector mechanisms may shed light on the incomplete control of HSV infections by the immune system and may allow more rational approaches to the development of immune modulatory treatments for HSV infection.

Animals↗

Mapping the functional topology of the animal fatty acid synthase by mutant complementation in vitro.

An in vitro mutant complementation approach has been used to map the functional topology of the animal fatty acid synthase. A series of knockout mutants was engineered, each mutant compromised in one of the seven functional domains, and heterodimers generated by hybridizing all possible combinations of the mutated subunits were isolated and characterized. Heterodimers comprised of a subunit containing either a beta-ketoacyl synthase or malonyl/acetyltransferase mutant, paired with a subunit containing mutations in any one of the other five domains, are active in fatty acid synthesis. Heterodimers in which both subunits carry a knockout mutation in either the dehydrase, enoyl reductase, keto reductase, or acyl carrier protein are inactive. Heterodimers comprised of a subunit containing a thioesterase mutation paired with a subunit containing a mutation in either the dehydrase, enoyl reductase, beta-ketoacyl reductase, or acyl carrier protein domains exhibit very low fatty acid synthetic ability. The results are consistent with a model for the fatty acid synthase in which the substrate loading and condensation reactions are catalyzed by cooperation of an acyl carrier protein domain of one subunit with the malonyl/acetyltransferase or beta-ketoacyl synthase domains, respectively, of either subunit. The beta-carbon-processing reactions, responsible for the complete reduction of the beta-ketoacyl moiety following each condensation step, are catalyzed by cooperation of an acyl carrier protein domain with the beta-ketoacyl reductase, dehydrase, and enoyl reductase domains associated exclusively with the same subunit. The chain-terminating reaction is carried out most efficiently by cooperation of an acyl carrier protein domain with the thioesterase domain of the same subunit. These results are discussed in the context of a revised model for the fatty acid synthase.

Alcohol Oxidoreductases↗

Differences in patterns of activation of MAP kinases induced by oncogenic ras-p21 and insulin in oocytes.

Oncogenic ras (Val 12-containing)-p21 protein induces oocyte maturation by a pathway that is blocked by peptides from effector domains of ras-p21, i.e., residues 35-47 (that block Val 12-p21-activated raf) and 96-110 and 115-126, which do not affect the ability of insulin-activated cellular p21 to induce maturation. Oncogenic p21 binds directly to jun-N-terminal kinase (JNK), which is blocked by the p21 96-110 and 115-126 peptides. This finding predicts that oncogenic p21, but not insulin, induces maturation by early and sustained activation of JNK. We now directly confirm this prediction by showing that oncogenic p21 induces activating phosphorylation of JNK (JNK-P) and of ERK (MAP kinase) (MAPK-P), whose levels correlate with oocyte maturation. p21 peptides 35-47 and 96-110 block formation of JNK-P and MAPK-P, further confirming this correlation and suggesting, unexpectedly, that raf-MEK-MAPK and JNK-jun pathways strongly interact on the oncogenic p21 pathway. In contrast, insulin activates only low levels of JNK-P, and, surprisingly, we find that insulin induces only low levels of MAPK-P, indicating that insulin and activated normal p21 utilize MAP kinase-independent signal transduction pathways.

Animals↗