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Biomedical subjects

S J Taylor

Publications and source records attributed to S J Taylor.

At least 73 records · Page 4Linked to original sources
PubMed1997

Cost implications in the management of induction of labour.

For many years the standard treatment of induction of labour has been amniotomy followed by intravenous oxytocin. More recently prostaglandin E2 (PGE2; dinoprostone), in various preparations, has been used to both ripen the cervix before amniotomy and administration of oxytocin, and to induce labour on its own. Since the acquisition cost of PGE2 is approximately 15 times that of oxytocin, it is important to justify the use of PGE2. In this paper, literature from 1970 to 1996 has been reviewed and outcomes following the use of PGE2, plus amniotomy and oxytocin if necessary, have been compared with outcomes following the use of amniotomy plus oxytocin alone. No significant differences in the mode of delivery and no serious adverse effects in mothers or babies were detected. Three economic analyses of these approaches to induction of labour have been reviewed. While under certain conditions there may be some cost savings associated with the use of PGE2, neither of the studies reviewed showed substantial, reliable cost savings. Further research is required to identify the patients who would gain most benefit from the use of PGE2.

Dinoprostone↗
PubMed1996

Cell cycle-dependent activation of Ras.

BACKGROUND: Ras proteins play an essential role in the transduction of signals from a wide range of cell-surface receptors to the nucleus. These signals may promote cellular proliferation or differentiation, depending on the cell background. It is well established that Ras plays an important role in the transduction of mitogenic signals from activated growth-factor receptors, leading to cell-cycle entry. However, important questions remain as to whether Ras controls signalling events during cell-cycle progression and, if so, at which point in the cell-cycle it is activated. RESULTS: To address these questions we have developed a novel, functional assay for the detection of cellular activated Ras. Using this assay, we found that Ras was activated in HeLa cells, following release from mitosis, and in NIH 3T3 fibroblasts, following serum-stimulated cell-cycle entry. In each case, peak Ras activation occurred in mid-G1 phase. Ras activation in HeLa cells at mid-G1 phase was dependent on RNA and protein synthesis and was not associated with tyrosine phosphorylation of Shc proteins and their binding to Grb2. Significantly, activation of Ras and the extracellular-signal regulated (ERK) sub-group of mitogen-activated protein kinases were not temporally correlated during G1-phase progression. CONCLUSIONS: Activation of Ras during mid-G1 phase appears to differ in many respects from its rapid activation by growth factors, suggesting a novel mechanism of regulation that may be intrinsic to cell-cycle progression. Furthermore, the temporal dissociation between Ras and ERK activation suggests that Ras targets alternate effector pathways during G1-phase progression.

3T3 Cells↗
PubMed1996

Src and the control of cell division.

The finely tuned mechanisms that control cell cycle progression go awry in cancer, pointing to proto-oncogene products as important players in cell-cycle regulation. One such proto-oncoprotein, c-Src, has previously been directly implicated, based on its requirement for growth factor-stimulated DNA synthesis. Roche et al. have now shown that c-Src or its close relatives are also required for cell division to occur. The demonstration of essential functions for the Src family at multiple points in the cell cycle raises important questions about the normal and transforming activities of these and other proto-oncoproteins.

Animals↗
PubMed1995

Raf-1 is activated during mitosis.

The Raf-1 serine/threonine kinase transmits proliferative and developmental signals to downstream effectors in the mitogen-activated protein kinase cascade. Studies to date have concentrated on its role in growth factor-mediated activation of the cell cycle. We show here that Raf-1 kinase activity is also highly stimulated during mitosis, with an attendant distinctive electrophoretic mobility shift due to hyperphosphorylation. These results suggest that Raf-1 may play a role in traversal of at least two distinct phases of the cell cycle.

3T3 Cells↗
PubMed1995

Autophosphorylation of purified c-Src at its primary negative regulation site.

The phosphorylating and transforming activities of c-Src are negatively regulated by phosphorylation at Tyr-527 near its carboxyl terminus. Previous studies have indicated that c-Src preferentially autophosphorylates Tyr-416, a residue in the middle of the catalytic domain, in vitro, and that Tyr-527 is phosphorylated by the carboxyl-terminal Src kinase, Csk. However, indirect evidence suggests that c-Src may also autophosphorylate Tyr-527 as part of a negative feedback loop. While some in vivo evidence suggests that Tyr-527 can be autophosphorylated in an intermolecular interaction, it has not previously been possible to directly demonstrate significant autophosphorylation in vitro. Here we show that c-Src purified from recombinant bacteria can autophosphorylate Tyr-527 to high levels in vitro when incubated with sufficiently high concentrations of ATP (KM(Mg2+/ATP) approximately equal to 20 microM) that are well above those that have been used previously. In vitro Tyr-527 autophosphorylation can occur both as an intra- and intermolecular interaction; higher enzyme concentrations are required for intermolecular Tyr-527 phosphorylation than for Tyr-416 autophosphorylation. These results support the possibility that, like G-proteins, c-Src can switch itself off in vivo by its own enzymatic activity.

Escherichia coli↗
PubMed1995

Identification of a mouse p21Cdc42/Rac activated kinase.

We have isolated a novel member of the mammalian PAK (p21 activated kinase) and yeast Ste20 serine/threonine kinase family from a mouse fibroblast cDNA library, designated mPAK-3. Expression of mPAK-3 in Saccharomyces cerevisiae partially restores mating function in ste20 null cells. Like other PAKs, mPAK-3 contains a putative Cdc42Hs/Rac binding sequence and when transiently expressed in COS cells, full-length mPAK-3 binds activated (GTP gamma S (guanosine 5'-3-O-(thio-triphosphate)-bound) glutathione S-transferase (GST)-Cdc42Hs and GST-Rac1 but not GST-RhoA. As expected for a putative target molecule, mPAK-3 does not bind to an effector domain mutant of Cdc42Hs. Furthermore, activated His-tagged Cdc42Hs and His-tagged Rac stimulate mPAK-3 autophosphorylation and phosphorylation of myelin basic protein by mPAK-3 in vitro. Interestingly, the amino-terminal region of mPAK-3 contains potential SH3-binding sites and we find that mPAK-3, expressed in vitro and in vivo, shows highly specific binding to the SH3 domain of phospholipase C-gamma and at least one SH3 domain in the adapter protein Nck. These results raise the possibility of an additional level of regulation of the PAK family in vivo.

3T3 Cells↗
PubMed1995

Functional interaction between c-Src and its mitotic target, Sam 68.

The c-Src tyrosine kinase phosphorylates and binds to a 68-kDa RNA-binding protein in mitotic cells. We have examined the mechanism and functional consequence of the interaction of c-Src with this protein, Sam 68 (Src associated in mitosis, 68 kDa). In whole cell homogenates, Sam 68 was the predominant substrate and binding partner of overexpressed c-Src. Mitotic, tyrosine-phosphorylated Sam 68 bound selectively to recombinant SH2 domains with significantly different affinities (c-Src approximately Ras GTPase activating protein > p85 alpha (amino-terminal) > Grb2 >> p85 alpha (COOH-terminal)). In vitro translated Sam 68 also bound selectively to recombinant SH3 domains, with the highest affinity for the Src and p85 alpha SH3 domains. SH3 binding was inhibited by specific Sam 68 peptides. In vitro translated Sam 68 bound directly to immobilized poly(U), and this was inhibited by binding of Src and p85 SH3 domains to Sam 68. The results suggest that the selection of Sam 68 as a mitotic target by c-Src is the result of highly specific interaction with SH2 and SH3 domains and that this interaction may modulate the RNA binding activity of Sam 68.

3T3 Cells↗
PubMed1995

Comparison of growth rates of bovine retinal and brain microvascular pericytes in different oxygen concentrations in vitro.

BACKGROUND: The hyperoxic injury of the microcirculation in the central nervous system appears to be specific to the retina in premature mammals. Oxygen tensions in normal adult mammalian retina and brain vary between nearly 0 and 90 mmHg. This study sought to compare the in vitro replication of retinal and brain microvascular pericytes in normal glucose medium and in 1%, 5% and 20% oxygen (equivalent to 15 mmHg, 35 mmHg and 150 mmHg, respectively). METHODS: A preliminary study, using oxygen microelectrodes, confirmed that the pericellular oxygen tension of pericytes, cultured in medium under air, was within 13 mmHg of the tension of the gas phase above the media. Pericytes were highly enriched by magnetic antibody cell sorting with the anti-pericyte monoclonal antibody (3G5) to 95% to 99% purity, to remove cell contaminants which may have invalidated the mitogenic assay. RESULTS: Mitogenic assays showed that brain pericytes replicated faster than their counterparts from retina (P < 0.0001, averaged for data from all culture conditions using three-way ANOVA). Reduction of oxygen tension from 150 to 15 mmHg led to significantly increased replication of retinal pericytes (P = 0.01), but an insignificant increase for brain pericytes. CONCLUSIONS: We have found that pericytes from the brain and retina cultured conventionally in fetal calf serum consume a relatively low amount of oxygen. Decreasing the oxygen tension to 1% (15 to 20 mmHg) increased the replication of retinal pericytes but not brain pericytes in normal glucose concentrations and in fetal calf serum. That retinal pericyte replication is sensitive to variation in oxygen tensions, indicates that the retinal microvascular cells have a unique biological response. This growth sensitivity to oxygen may be important in the pathogenesis of retinopathy of prematurity.

Animals↗
PubMed1994

An RNA-binding protein associated with Src through its SH2 and SH3 domains in mitosis.

The tyrosine kinase activity of c-Src is stimulated during mitosis by dephosphorylation of its regulatory tyrosine residue. This is associated with increased accessibility of its Src homology-2 (SH2) domain for binding a phosphotyrosine-containing peptide. But physiological targets of activated c-Src in mitosis have not yet been identified. Here we report that a 68K protein (p68) becomes tyrosine-phosphorylated and physically associates with Src during mitosis in mouse fibroblasts. p68 independently binds the Src SH2 and SH3 domains in vitro and both domains are required for p68 phosphorylation and binding in vivo. p68 is closely related to the p62 protein that is associated with the Ras GTPase-activating protein (GAP) and selectively binds, directly or indirectly, polyribonucleotides. Because the Src SH3 domain also binds heterogeneous nuclear ribonucleoprotein K, these results raise the intriguing possibility that c-Src may regulate the processing, trafficking or translation of RNA in a cell-cycle-dependent manner.

3T3 Cells↗
PubMed1994

Enzyme-catalysed kinetic resolution of 4-endo-hydroxy-2-oxabicyclo[3.3.0]oct-7-en-3-one and employment of the pure enantiomers for the synthesis of anti-viral and hypocholestemic agents.

The endo-hydroxylactone (+/-)-(1) was resolved by enantioselective acetylation using Candida cylindracea lipase or preferentially Pseudomonas fluorescens lipase (pfl). Alternatively the corresponding butyrate (+/-)-(3) was hydrolysed with pfl to give the ester (+)-(1S,4R,5S)-(3) and the alcohol (-)-(1R,4S,5R)-(1). The latter compound was converted into carbovir (-)-(1R,4S)-(12) while the ester (+)-(3) was transformed into the delta-lactone (+)-(3R,5S)-(18). The exo-hydroxylactone (+/-)-(2) was resolved less efficiently by a trans-esterification process employing pfl and vinyl acetate.

Anticholesteremic Agents↗
PubMed1994

Direct interaction of v-Src with the focal adhesion kinase mediated by the Src SH2 domain.

The recently described focal adhesion kinase (FAK) has been implicated in signal transduction pathways initiated by cell adhesion receptor integrins and by neuropeptide growth factors. To examine the mechanisms by which FAK relays signals from the membrane to the cell interior, we carried out a series of experiments to detect potential FAK interactions with proteins containing Src homology 2 (SH2) domains that are important intracellular signaling molecules. Using v-Src-transformed NIH3T3 cells, we showed that FAK was present in the immune-complex precipitated by anti-Src antibody, suggesting potential interaction of FAK with v-Src in vivo. We also showed potentially direct interaction of FAK with v-Src in vivo using the yeast two-hybrid system. Using recombinant FAK expressed in insect cells and bacterial fusion proteins containing Src SH2 domains, we showed direct binding of FAK to the Src SH2 domain but not to the SH3 domain in vitro. A kinase-defective mutant of FAK, which is not autophosphorylated, did not interact with the Src SH2 domain under the same conditions, suggesting the involvement of the FAK autophosphorylation sites. Treatment of FAK with a protein-tyrosine phosphatase decreased its binding to the Src SH2 domain, whereas autophosphorylation in vitro increased its binding. These results confirm the importance of FAK autophosphorylation sites in its interaction with SH2 domain-containing proteins. Taken together, these results suggest that FAK may mediate signal transduction events initiated on the cell surface by kinase activation and autophosphorylation that result in its binding to other key intracellular signaling molecules.

3T3 Cells↗
PubMed1994

The psychosocial and clinical status of younger women with early rheumatoid arthritis: a longitudinal study with frequent measures.

A longitudinal study of 75 young women (median age 43 yr) with early RA was performed with psychological, clinical and functional status measured every 4 months for up to 44 months. The aim was to describe functional changes, and to estimate the association between psychosocial variables and function in the early years after diagnosis. Function was measured by the Stanford Health Assessment Questionnaire (HAQ) and improved on average by about 10% per year with most improvement occurring over the first year. Pain and psychosocial variables also improved over time. There was still a residual improvement in HAQ with time of about 4% per year not accounted for by changes in these measured variables. When examined over time, psychosocial variables were as important as disease and pain in determining function. The results suggest interventions based on the importance of maintaining social relationships could impact on function.

Adolescent↗
PubMed1993

The cell cycle and c-Src.

The activity of the proto-oncogene encoded c-Src product is tightly regulated in vivo. In recent years, a model has emerged of how this regulation is achieved. In particular, protein kinases and phosphatases that are potential regulators of c-Src activity in the cell cycle have been identified and characterized.

Amino Acid Sequence↗
PubMed1993

Primary sequence analysis and representation techniques in carbohydrates.

Sequence similarity calculations of carbohydrates present several problems which must be addressed if a computer implementation is to be achieved. These problems range from the computational representation of the complex carbohydrate structure to the method by which the comparison of residue and linkage is to be made. This paper therefore discusses the form of this representation and how two or more carbohydrates can be meaningful compared. An example set of results using this approach is presented and discussed to illustrate how similarity comparison can show relationships between carbohydrates, features that are otherwise hidden by the sheer volume of data which must be considered.

Algorithms↗
PubMed1993

Myristylation is required for Tyr-527 dephosphorylation and activation of pp60c-src in mitosis.

The chicken proto-oncoprotein c-Src is phosphorylated by p34cdc2 during mitosis concomitant with increased c-Src tyrosine kinase activity. On the basis of indirect evidence, we previously suggested that this is caused by partial dephosphorylation at Tyr-527, the phosphorylation of which suppresses c-Src kinase activity. In support of this hypothesis, we now show that treatment of cells with a protein tyrosine phosphatase inhibitor, sodium vanadate, blocks the mitotic increase in Src kinase activity. Also, we show that an amino-terminal mutation that prevents myristylation (and membrane localization) of c-Src does not interfere with the p34cdc2-mediated phosphorylations but blocks both mitotic dephosphorylation of Tyr-527 (in kinase-defective Src) and stimulation of c-Src kinase activity. Furthermore, in unsynchronized cells, the kinase activity of nonmyristylated c-Src is suppressed by 60% relative to wild-type c-Src, presumably because of increased Tyr-527 phosphorylation. Consistent with this, the Tyr-527 dephosphorylation rate measured in cell homogenates is much higher for wild-type, myristylated c-Src than for nonmyristylated c-Src. Tyr-527 phosphatase activity was primarily associated with the nonsoluble subcellular fraction. These findings suggest that the phosphatase(s) that acts on Tyr-527 is membrane bound and indicate that membrane localization of c-Src is necessary for its mitotic activation by dephosphorylation of Tyr-527.

Animals↗