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S J Myers

Publications and source records attributed to S J Myers.

At least 19 recordsLinked to original sources
PubMed1999

Src family kinase activation in glycosphingolipid-rich membrane domains of endothelial cells treated with oxidised low density lipoprotein.

Extraction of ECV304 endothelial cells in 1% Triton X-100 at 4 degrees C resulted in a detergent-insoluble pellet that contained 90% of the caveolin, 78% of the src family kinases and 99% of the annexin II. When detergent-treated cells were loaded beneath a 10-30% sucrose gradient the caveolin and a large proportion of the cellular cholesterol floated at a density of 1.09 g/cm3, characteristic of caveolae and glycosphingolipid-rich membranes. With extended centrifugation the src family kinases, which were initially associated with this floating material, sedimented to the bottom of the gradient. Annexin II remained on the bottom of the gradient under both centrifugation conditions. After 24-h incubation with oxidised low density lipoprotein (oxLDL) about 7.5% of the total sterol in the cells was replaced by 7-ketocholesterol, the major oxysterol found in oxLDL. The majority of this 7-ketocholesterol was found in the light membrane fraction on sucrose gradients. Under these conditions src kinase activity more than doubled in the Triton-resistant fraction, without changes in the concentration of src kinase protein. Introducing oxysterols directly into the medium bathing ECV304 cells for 1 h also modulated the activity of src family kinases in the detergent-resistant membranes. An elevation in activity was observed for 7-ketocholesterol while 7alpha-hydroxycholesterol, 7alpha-hydroxycholesterol and cholesterol epoxide all produced decreases in the background level of src kinase activity. We conclude that 7-ketocholesterol and possibly other components of oxLDL can equilibrate into glycosphingolipid-rich membranes and increase the activity of src kinases, possibly by interaction with caveolin.

Animals↗
PubMed1998

Transcriptional regulation of the GluR2 gene: neural-specific expression, multiple promoters, and regulatory elements.

To understand how neurons control the expression of the AMPA receptor subunit GluR2, we cloned the 5' proximal region of the rat gene and investigated GluR2 promoter activity by transient transfection. RNase protection and primer extension of rat brain mRNA revealed multiple transcription initiation sites from -340 to -481 bases upstream of the GluR2 AUG codon. The relative use of 5' start sites was different in cortex and cerebellum, indicating complexity of GluR2 transcript expression among different sets of neurons. When GluR2 promoter activity was investigated by plasmid transfection into cultured cortical neurons, cortical glia, and C6 glioma cells, the promoter construct with the strongest activity, per transfected cell, was 29.4-fold (+/- 3.7) more active in neurons than in non-neural cells. Immunostaining of cortical cultures showed that >97% of the luciferase-positive cells also expressed the neuronal marker MAP-2. Evaluation of internal deletion and substitution mutations identified a functional repressor element I RE1-like silencer and functional Sp1 and nuclear respiratory factor-1 (NRF-1) elements within a GC-rich proximal GluR2 promoter region. The GluR2 silencer reduced promoter activity in glia and non-neuronal cell lines by two- to threefold, was without effect in cortical neurons, and could bind the RE1-silencing transcription factor (REST) because cotransfection of REST into neurons reduced GluR2 promoter activity in a silencer-dependent manner. Substitution of the GluR2 silencer by the homologous NaII RE1 silencer further reduced GluR2 promoter activity in non-neuronal cells by 30-47%. Maximal positive GluR2 promoter activity required both Sp1 and NRF-1 cis elements and an interelement nucleotide bridge sequence. These results indicate that GluR2 transcription initiates from multiple sites, is highly neuronal selective, and is regulated by three regulatory elements in the 5' proximal promoter region.

Animals↗
PubMed1997

Organization and differential expression of the human monocyte chemoattractant protein 1 receptor gene. Evidence for the role of the carboxyl-terminal tail in receptor trafficking.

Two forms of the monocyte chemoattractant protein-1 receptors (the type A monocyte chemoattractant protein 1 (MCP-1) receptor CCR-2A and the type B MCP-1 receptor (CCR-2B) have been recently cloned and found to differ only in their terminal carboxyl tails. Here, we report that the two isoforms are alternatively spliced variants of a single MCP-1 receptor gene. Sequencing of the gene revealed that the 47-amino acid carboxyl tail of CCR2B was located in the same exon as the seven transmembrane domains of the receptor, and the 61-amino acid tail of CCR2A was in a downstream exon. Examination of freshly isolated human monocytes by reverse transcriptase-polymerase chain reaction revealed that CCR2B was the predominant isoform and that message levels of both CCR2A and CCR2B decreased as the monocytes differentiated into macrophages. In stably transfected cell lines, CCR2B trafficked well to the cell surface, but CCR2A was found predominantly in the cytoplasm. Equilibrium binding studies revealed that those CCR2A receptors that successfully trafficked to the cell surface bound MCP-1 with high affinity (Kd = 310 pM), similar to CCR2B. In signaling studies, both CCR2A and CCR2B mediated agonist-dependent calcium mobilization, as well as inhibition of adenylyl cyclase. Creation of chimeras between CCR2A and the human thrombin receptor revealed that the cytoplasmic retention of CCR2A was due to its terminal carboxyl tail. Progressive truncation of the carboxyl tail indicated that a cytoplasmic retention signal(s) was located between residues 316 and 349. These data indicate that the alternatively spliced form of the human MCP-1 receptor (CCR2A) binds MCP-1 with high affinity and is a functional receptor and that expression at the cell surface is controlled by amino acid sequences located in the terminal carboxyl tail.

Amino Acid Sequence↗
PubMed1995

Signal transduction and ligand specificity of the human monocyte chemoattractant protein-1 receptor in transfected embryonic kidney cells.

We have examined the ligand specificity and signal transduction pathways of a recently cloned receptor for monocyte chemoattractant protein-1 (MCP-1). In human 293 cells stably transfected with the MCP-1 receptor, MCP-1 bound specifically with high affinity (Kd = 260 pM) and induced a rapid mobilization of calcium from intracellular stores. The closely related chemokines MIP-1 alpha, MIP-1 beta, RANTES, interleukin 8 (IL-8), and Gro-alpha were inactive at concentrations as high as 300 nM. Activation of the MCP-1 receptor potently inhibited adenylyl cyclase with an IC50 = 90 pM. Activation of the MIP-1 alpha/RANTES receptor also mediated inhibition of adenylyl cyclase activity but with a different pharmacological profile: MIP-1 alpha (110 pM, IC50), RANTES (140 pM), MIP-1 beta (10 nM), and MCP-1 (820 nM). Mobilization of intracellular calcium and inhibition of adenylyl cyclase were blocked by pertussis toxin, suggesting that the MCP-1 receptor coupled to G alpha i. These results demonstrate that the MCP-1 receptor binds and signals in response to picomolar concentrations of MCP-1 in a highly specific manner. Signaling was manifested as mobilization of intracellular calcium and inhibition of adenylyl cyclase and was mediated by a pertussis toxin-sensitive G-protein(s).

Adenylyl Cyclase Inhibitors↗
PubMed1994

Molecular cloning and functional expression of two monocyte chemoattractant protein 1 receptors reveals alternative splicing of the carboxyl-terminal tails.

Monocyte chemoattractant protein 1 (MCP-1) is a member of the chemokine family of cytokines that mediate leukocyte chemotaxis. The potent and specific activation of monocytes by MCP-1 may mediate the monocytic infiltration of tissues in atherosclerosis and other inflammatory diseases. We have isolated cDNAs that encode two MCP-1-specific receptors with alternatively spliced carboxyl tails. Expression of the receptors in Xenopus oocytes conferred robust mobilization of intracellular calcium in response to nanomolar concentrations of MCP-1 but not to related chemokines. The MCP-1 receptors are most closely related to the receptor for the chemokines macrophage inflammatory protein 1 alpha and RANTES (regulated on activation, normal T expressed and secreted). The identification of the MCP-1 receptor and cloning of two distinct isoforms provide powerful tools for understanding the specificity and signaling mechanisms of this important chemokine.

Alternative Splicing↗
PubMed1994

Licensed midwife-attended, out-of-hospital births in Washington state: are they safe?

The safety of out-of-hospital births attended by midwives who are licensed according to international standards has not been established in the United States. To address this issue, outcomes of births attended out of hospital by licensed midwives in Washington state were compared with those attended by physicians and certified nurse-midwives in hospital and certified nurse-midwives out of hospital between 1981 and 1990. Outcomes measured included low birthweight, low five-minute Apgar scores, and neonatal and postneonatal mortality. Associations between attendant and outcomes were measured using odds ratios to estimate relative risks. Multivariate analysis using logistic regression controlled for confounding variables. Overall, births attended by licensed midwives out of hospital had a significantly lower risk for low birthweight than those attended in hospital by certified nurse-midwives, but no significant differences were found between licensed midwives and any of the comparison groups on any other outcomes measured. When the analysis was limited to low-risk women, certified nurse-midwives were no more likely to deliver low-birthweight infants than were licensed midwives, but births attended by physicians had a higher risk of low birthweight. The results of this study indicate that in Washington state the practice of licensed nonnurse-midwives, whose training meets standards set by international professional organizations, may be as safe as that of physicians in hospital and certified nurse-midwives in and out of hospital.

Adult↗
PubMed1992

Spinal cord arteriovenous malformation in a person with congenital lymphatic abnormalities.

Spinal cord arteriovenous malformations have been described in association with a variety of congenital diseases affecting the vasculature, including Klippel-Trenaunay-Weber syndrome, Rendu-Osler-Weber syndrome and others, but rarely in association with lymphatic abnormalities. We report the case of a young man with congenital lymphedema and arteriovenous malformations of one lower extremity and a spinal cord arteriovenous malformation. Awareness of the possible presence of a central nervous system arteriovenous malformation in individuals with pre-existing arteriovenous and lymphatic abnormalities may be helpful in their diagnosis and management.

Abnormalities, Multiple↗
PubMed1991

Dural spinal cord arteriovenous malformation.

After multiple hospital admissions and an inpatient rehabilitation stay, a 68-year-old woman was transferred to our rehabilitation facility with a paraparesis of unknown etiology. Previous studies included four CT scans and three MRIs which did not demonstrate the lesion. A myelogram was noncharacteristic. The correct diagnosis, confirmed by selective angiography, was ultimately contingent upon recognition of the clinical features and natural history of dural spinal cord arteriovenous malformations (SCAVM). The unusual combination of this multitude of nondiagnostic imaging studies in the uncommon dural SCAVM served to delay diagnosis and treatment. Such delay may have great functional consequences. This report illustrates the importance of suspecting SCAVM and recognizing its features. Emphasis is placed on the physiatrist's role in assuring proper diagnosis to expedite a timely treatment and to obtain the best functional outcome. A brief review of the classification, clinical features, pathophysiology, diagnosis, and prognosis of SCAVM is presented.

Aged↗
PubMed1990

Molecular biology of mammalian amino acid receptors.

The amino acid receptor proteins are ubiquitous transducers of most excitatory and inhibitory synaptic transmission in the brain. In July 1987 two reports appeared describing the molecular cloning of a pair of subunits of the GABAA receptor (7) and one subunit of the glycine receptor (13). These papers sparked wide interest and led quickly to the concept of a ligand-gated receptor-ion channel superfamily that includes nicotinic acetylcholine receptors as well as certain amino acid receptors. The identification of additional subunits of each receptor followed; with the recent cloning of a kainate receptor subunit (14), only the NMDA receptor remains elusive. Several disciplines have been brought to bear on these receptor clones, including in situ hybridization and functional expression in Xenopus laevis oocytes and mammalian cell lines. In this review we compare cloning strategies that have been used for amino acid receptors and discuss structural similarities among the receptor subunits. Two findings that have arisen from molecular cloning and expression of these receptors receive special attention. First, the molecular heterogeneity of GABAA receptors is larger than expected from pharmacological studies of native receptors. Second, although the native receptors are thought to be heterooligomers, much like the model proposed for the nicotinic receptors, some individual amino acid receptor subunits can form functional receptor channels, presumably in a homomeric configuration. This review focuses, therefore, on what we have learned from cloning efforts about amino acid receptors and what might lie ahead in this field.

Amino Acid Sequence↗
PubMed1990

Unlicensed midwifery practice in Washington state.

We examined the role of unlicensed midwives in Washington State by questioning mothers of infants born out-of-hospital with an unlicensed person in attendance. Only a small proportion of the state's births (0.11 percent) were attended by unlicensed midwives. Unlicensed midwives attended 7 percent of home births, licensed midwives and certified nurse-midwives attended 69 percent. Mothers chose unlicensed midwives because they had religious beliefs in common, or because they were the only providers available who would attend a home birth.

Adolescent↗
PubMed1983

A correlational study of cardiovascular autonomic functioning and unipolar depression.

Cardiovascular autonomic functioning was assessed in 22 drug-free inpatients diagnosed by DSM-III criteria as having a unipolar depression. Sympathetic cholinergic, alpha- and beta-adrenergic activity were assessed via the measurement of forearm blood flow (FBF), digital blood flow (DBF), and the cardiac pre-ejection period (PEP), respectively. These parameters were correlated with total Hamilton score (HT) (using partial correlations to control for extraneous autonomic variables) to identify the specific autonomic correlates of unipolar depression. Significant negative correlations were found between HT and supine FBF and significant positive correlations between HT and PEP. Large effect-size, negative correlations (which approached significance) were found between HT and DBF. It is concluded that there is a specific autonomic profile of unipolar depression, characterized by a decrease in central sympathetic cholinergic outflow, coupled with increases in alpha-adrenergic and decreases in beta-adrenergic activity. Further, this profile is not merely a static hallmark of depression but covaries with the severity of the depression, independent of other autonomic activity.

Aged↗
PubMed1982

A model of clinical pain. Technique for evaluation of analgesic agents.

A method is described utilizing repetitive electrical stimulation for the production of long-term continuous pain which approaches the quality of clinical pain. This technique provides for on-line monitoring of actual power delivered to the subject. Incremental stimuli of high and low intensities were randomly superimposed on continuous painful background electrical stimulation. Subjects were studied in a triple crossover design with acupuncture, codeine and baseline treatments. Data were evaluated by Sensory Decision Theory (SDT) procedures. The codeine compound significantly raised the response criterion to higher intensity stimuli but did not effect perception of low intensity stimuli, indicating an analgesic but not an anesthetic effect. No significant differences were found between control and acupuncture results for either pain discriminability or pain report criterion. The results are discussed with regard to the physiological effects of electrical stimulation and the merits of this new stimulation technique.

Acupuncture Therapy↗
PubMed1978

Past history and degree of depression in paraplegic individuals.

The purpose of this study was to attempt to collect sufficient data to substantiate the clinical impression that the degree of depression in the paraplegic and his past history are correlated. It was hypothesised that the poorer the past history, the greater the degree of depression in paraplegic individuals. This study was conducted on ten paraplegic subjects from the Spinal Cord Clinic at Columbia Presbyterian Medical Center, Department of Rehabilitation Medicine, based on data obtained from the administration and scoring of the Depression Scale (D-scale) of the Minnesota Multiphasic Personality Inventory (MMPI) and by the clinical observation by the consulting psychiatrist with the Spinal Injury Clinic. Past history was assumed measurable as 'favourable' to 'poor' by the use of an original questionnaire. The results of this investigation suggested a relationship between a paraplegic individual's past history and the degree of depression. The study was deemed significant in presentation of an original past history questionnaire and in the prediction of future difficulties in the rehabilitation of paraplegics so that preventive measures could be instituted.

Achievement↗
PubMed1977

Paraplegia following trauma in a patient with kyphosis.

The reported incidence of paraplegia following acute spinal trauma in patients with kyphosis is very low. One such case is presented here and discussed. Although deterioration of spinal cord function in patients with kyphosis who have not sustained trauma is treated by surgical decompression and stabilization of the spine, a more conservative approach may be beneficial in those patients with a history of trauma. Thus, the treatment appears to follow that now recommended for acute spinal injuries in patients with a premorbidly normal spine.

Humans↗