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S K Smith

Publications and source records attributed to S K Smith.

At least 91 records · Page 5Linked to original sources
PubMed1997

Ca2+ dependence and pharmacology of large-conductance K+ channels in nonlabor and labor human uterine myocytes.

Two populations, Ca(2+)-dependent (BKCa) and Ca(2+)-independent K+ (BK) channels of large conductance were identified in inside-out patches of nonlabor and labor freshly dispersed human pregnant myometrial cells, respectively. Cell-attached recordings from nonlabor myometrial cells frequently displayed BKCa channel openings characterized by a relatively low open-state probability, whereas similar recordings from labor tissue displayed either no channel openings or consistently high levels of channel activity that often exhibited clear, oscillatory activity. In inside-out patch recordings, Ba2+ (2-10 mM), 4-aminopyridine (0.1-1 mM), and Shaker B inactivating peptide ("ball peptide") blocked the BKCa channel but were much less effective on BK channels. Application of tetraethylammonium to inside-out membrane patches reduced unitary current amplitude of BKCa and BK channels, with dissociation constants of 46 mM and 53 microM, respectively. Tetraethylammonium applied to outside-out patches decreased the unitary conductance of BKCa and BK channels, with dissociation constants of 423 and 395 microM, respectively. These results demonstrate that the properties of human myometrial large-conductance K+ channels in myocytes isolated from laboring patients are significantly different from those isolated from nonlaboring patients.

4-Aminopyridine↗
PubMed1997

Ultrastructural changes in the synthetic and secretory patterns of pulmonary surfactant following pilocarpine in vivo.

Previous studies have demonstrated that the muscarinic agonist pilocarpine stimulates the secretion of pulmonary surfactant from mammalian alveolar type II cells. The results of the present study quantify, via ultrastructural stereologic analysis, this response through 24 hours. The cytoplasmic volume density of lamellar bodies decreases significantly at 0.5 and 4 hours post-injection. This value is increased significantly at 12 hours post-injection. Elements of the secretory apparatus increase significantly at many of the post-injection times. At 12 hours post-injection many of the type II cells are quite laden with lamellar bodies, with some appearing surprisingly large. This may be a useful model for continued study of the relationship between synthesis and secretion of pulmonary surfactant.

Animals↗
PubMed1997

Evidence-based practice in perioperative nursing: a literature review and suggestions for change.

Evidence-based practice (nursing practice that relies on information generated from the results of scientific research) is widely recommended as the method of nursing practice of the future. This is particularly the method of choice in perioperative nursing. In this article the literature on evidence-based practice is reviewed with particular emphasis on the role of the perioperative nurse, research utilization, and barriers to evidence-based practice. Suggestions for change to promote evidence-based practice are also outlined.

Evidence-Based Medicine↗
PubMed1997

Expression and localization of the vascular endothelial growth factor family in ovarian epithelial tumors.

Vascular endothelial growth factor (VEGF) is an angiogenic factor secreted by various tumors, including epithelial tumors of the ovary, and is involved in tumor progression and maintenance. The significance and function of other members of the VEGF family in the ovary has not yet been elucidated. In the present study, we have defined the expression of mRNA encoding VEGF-B, VEGF-C, and placenta growth factor (PIGF), compared with that of VEGF mRNA, in normal ovary and a range of ovarian epithelial tumors. Analysis by reverse transcription-PCR indicated that mRNA encoding VEGF (isoforms 121 and 165), VEGF-B (isoforms 167 and 186), and VEGF-C, but not PIGF, were present in all ovarian tissues examined. By in situ hybridization, neither VEGF-C nor PIGF transcripts were detected in any of the samples. The expression pattern of VEGF-B mRNA was generally similar to that of VEGF mRNA, in that transcripts were readily detected in the epithelial cells of all histologic types of ovarian carcinoma, but could not be detected in normal or benign tumor epithelium. Specific differences in the expression of the two genes were noted in areas of tumor necrosis, in which the expression of VEGF mRNA, but not VEGF-B mRNA, was further enhanced, and in a sample in which VEGF-B mRNA was strongly expressed in tumor-associated macrophages that did not hybridize with the riboprobe to VEGF mRNA. These results imply that a second member of the VEGF family, VEGF-B, may play a significant role in the angiogenesis, progression, and maintenance of ovarian carcinomas.

Adult↗
PubMed1996

Vascular endothelial growth factor is produced by peritoneal fluid macrophages in endometriosis and is regulated by ovarian steroids.

Angiogenesis is important in the pathophysiology of endometriosis, a condition characterized by implantation of ectopic endometrium in the peritoneal cavity. Vascular endothelial growth factor (VEGF) is a potent angiogenic factor involved in physiological and pathological angiogenesis, and elevated levels of VEGF are found in peritoneal fluid of patients with endometriosis. Our aim was to investigate the site of expression and regulation of VEGF in endometriosis. VEGF immunoreactivity was found in tissue macrophages present in ectopic endometrium and in activated peritoneal fluid macrophages. Macrophage activation was highest in women with endometriosis, and media conditioned by peritoneal fluid macrophages from these women caused a VEGF-dependent increase in endothelial cell proliferation above that seen from normal women. Peritoneal fluid macrophages secreted VEGF in response to ovarian steroids, and this secretion was enhanced after activation with lipopolysaccharide. Peritoneal fluid macrophages expressed receptors for steroid hormones. VEGF receptors flt and KDR (kinase domain receptor) were also detected, suggesting autocrine regulation. During the menstrual cycle, expression of flt was constant but that of KDR was increased in the luteal phase, at which time the cells migrated in response to VEGF. KDR expression and the migratory response were significantly higher in patients with endometriosis. This study demonstrates that activated macrophages are a major source of VEGF in endometriosis and that this expression is regulated directly by ovarian steroids.

Adult↗
PubMed1996

Cloning, expression and genomic organization of human placental protein disulfide isomerase (previously identified as phospholipase C alpha).

Phosphoinositol-specific Phospholipase C plays an important role in transducing receptor generated signals to the rest of the cell. A cDNA encoding a phospholipase has been described (Bennett et al., 1988, Nature 334, 268-270). However it is probable that this cDNA in fact encodes a protein disulfide isomerase. Since the original work suggested that this enzyme was important in the reproductive tract we sort to clone, sequence, express and characterize the recombinant protein isolated from the placenta. We have cloned and sequenced the cDNA encoding the human homolog of this cDNA from human placenta, although the mRNA was widespread in the female reproductive tract. We have transiently expressed it in both COS cells and also 1BR fibroblasts. Cell lysates were assayed for increased phospholipase activity and protein disulfide activity. We describe the entire cDNA sequence which is highly conserved between species. We have also cloned a portion of the genomic gene and described the intron/exon boundaries. In vitro translation of this cDNA showed that it encoded a protein of 61 kD with a cleavable signal peptide. Transient expression showed the protein produced had no phospholipase activity but did show protein disulfide isomerase activity. The expression work shows that this cDNA indeed encodes a protein disulfide isomerase and not a phospholipase. The nucleotide sequence shows marked conservation of the coding and regulatory regions which may suggest that this enzyme has evolved to perform a highly specialized function.

Base Sequence↗
PubMed1996

Immunisation of sheep with an integral membrane glycoprotein complex of Haemonchus contortus and with its major polypeptide components.

Sheep were immunised against Haemonchus contortus with an integral membrane glycoprotein complex isolated from the intestines of the parasite as antigen. This antigen has been termed Haemonchus galactose-containing glycoprotein complex. Sodium dodecyl sulphate (SDS) polyacrylamide gel analysis has shown that it is composed of several polypeptides but so far these have proved refractory to separation when in the native state. However when dissociated by SDS, it was found to be as efficacious as in its native state, although it was less consistently protective when tested after being dissociated and reduced. An attempt was therefore made to identify the protective ingredient(s) of the dissociated complex by testing its major polypeptides individually after they had been separated on SDS polyacrylamide gels under non-reducing conditions. Partial protection was induced by protein bands with molecular weights of about 200 kD and less than 50 kD, but none of the individual fractions tested was as efficacious as the unseparated complex, suggesting that either more than one component was essential for a consistent effect or that the separation technique had damaged crucial protective epitopes.

Animals↗
PubMed1996

Expression of prostacyclin and thromboxane synthases in placenta and placental bed after pre-eclamptic pregnancies.

Prostacyclin and thromboxane are potent antagonistic regulators of vascular tone and platelet aggregation. In pre-eclampsia, the ratio of their metabolites is decreased. Little is known about the local regulation of intrauterine prostacyclin and thromboxane production in this condition. Placenta and placental bed biopsies were obtained from uncomplicated and pre-eclamptic pregnancies. Prostacyclin synthase (PCS) and thromboxane synthase (TXS) and their mRNA's were localized by immunohistochemistry using monoclonal antibodies and in situ hybridization. Protein and mRNA levels were quantified by immunoblot and RNase protection assay. PCS-like immunoreactivity was found in endothelial cells and leiomyocytes, whereas fetal and maternal macrophages showed positive staining for TXS. Their mRNA was localized to trophoblast and endothelium, and TXS mRNA could also be detected in macrophages. Quantitative analysis showed no significant difference in intrauterine protein or mRNA expression after pre-eclampsia. The prostacyclin and thromboxane production seems to be compartmentalized within the uteroplacental unit. The expression of their synthesizing enzymes might be regulated post-transcriptionally. Additional regulation of prostaglandin production could be metabolically or on the substrate level and requires further elucidation.

Adult↗
PubMed1996

Maternal plasma levels of vascular endothelial growth factor in normotensive pregnancies and in pregnancies complicated by pre-eclampsia.

We have measured the level of vascular endothelial growth factor (VEGF) in maternal plasma during normotensive pregnancy and in pregnancies complicated by pre-eclampsia. VEGF was measured using a competitive enzyme immunoassay. Plasma VEGF was significantly elevated (P < 0.0001) in the pre-eclamptic group (median value 32.7 ng mL-1, range 10.3-64.0), compared with the normotensive group (median value 11.7 ng mL-1, range 6.3-24.3). VEGF is a potent regulator of endothelial cell function. The increased level found in women with pre-eclampsia indicates that VEGF may be involved in the maternal endothelial cell dysfunction associated with this condition. An increase in VEGF, a potent regulator of microvascular permeability, may also contribute to the extravasation of plasma proteins and the subsequent development of proteinuria, both characteristic features of pre-eclampsia.

Adolescent↗
PubMed1996

Vascular endothelial growth factor (VEGF) concentrations are elevated in peritoneal fluid of women with endometriosis.

Active endometriosis is characterized by hypervascularization both within and surrounding the implant; therefore the presence of angiogenic factors in the peritoneal environment would be of great importance. Vascular endothelial growth factor (VEGF) is a potent angiogenic factor involved in both physiological and pathological angiogenesis. We sought to determine if VEGF was present in the peritoneal fluid of women with and without endometriosis, and to establish if differences exist between these groups. VEGF was present in all patients sampled. The fluid from patients with endometriosis contained significantly greater amounts of VEGF than controls. Cyclic variations in VEGF concentration were seen in fluid from patients with endometriosis, the VEGF concentration in proliferative phase being significantly higher than in the secretory phase. The concentration of VEGF in this fluid was also significantly higher than that found in the proliferative and secretory phases of women without endometriosis. No cyclic variations in VEGF were seen in the control group. We suggest that elevated levels of VEGF in the peritoneal fluid of patients with endometriosis may be critical in the pathogenesis of endometriosis.

Adult↗
PubMed1996

Activation of protein kinase C is required for oxytocin-induced contractility in human pregnant myometrium.

Intracellular mediators regulating the initiation of parturition are not fully understood. This study was designed to determine the possible mechanism of oxytocin-induced uterine contractility during labour. In-vitro isometric contraction studies were performed with longitudinal strips of human pregnant myometrium in the presence and absence of the protein kinase C inhibitors, staurosporine and RO 31-8220, and the tyrosine kinase inhibitor, genistein. Phospholipase D activity was measured by employing the transphosphatidylation reaction. Staurosporine significantly reduced oxytocin-stimulated contractile activity with mean activity reduced by > 50% following the addition of 10(-6) M staurosporine (P < 0.01), while addition of 10(-5) M resulted in a measured mean contractile activity of approximately 10% of the control (P < 0.001, n = 5). Similarly, uterine activity was minimal with oxytocin application following incubation with RO 31-8220, mean contractile activity being reduced by approximately 40% by the addition of 10(-7) M RO 31-8220 (P < 0.05) and by approximately 87% by the addition of either 10(-6) or 10(-5) M (P < 0.01, n = 3). Conversely, addition of genistein (10(-7) and 10(-6) M) had little effect on oxytocin-induced contractions, although at a higher concentration (10(-5) M) a significant reduction in oxytocin-induced contractile activity was observed (P < 0.01). Oxytocin evoked phospholipase D activation in a concentration- and time-dependent manner in cultured human pregnant myometrial cells (n = 4). These results indicate that activation of protein kinase C and tyrosine kinase are involved in the regulation of oxytocin-mediated myometrial contractile activity and that a coupled phospholipase D/phosphatidate phosphohydrolase pathway may play a role in the sustained stimulation of myometrial activity during labour.

Adult↗
PubMed1996

Localization of VEGF and expression of its receptors flt and KDR in human placenta throughout pregnancy.

Vascular endothelial growth factor (VEGF) is a potent secreted angiogenic growth factor. Its action is mediated through the tyrosine kinase receptors flt and KDR. We here examine, in detail, the distribution of this ligand and its receptors in human placentae throughout gestation. In the first trimester, in-situ hybridization revealed uneven distribution of flt mRNA around the villous trophoblast indicating spatial regulation. Temporal regulation of flt was observed with no flt mRNA expression detected in villi from mid-gestational placenta, while low levels were found in term villi. Extravillous trophoblast was found to contain both mRNA encoding flt and flt-like immunoreactivity throughout pregnancy. In contrast, KDR mRNA was found only in association with endothelial cells. Within the decidua the anti-flt antibody stained multiple cell types during the first trimester of pregnancy but only the extravillous trophoblast later in gestation. VEGF immunoreactivity tended to co-localize with the staining for flt. These results indicate that VEGF may exert an important role within both the placental villi and the maternal decidua in relation to the growth, differentiation and migration of trophoblast and that this is mediated primarily through the spatial and temporal regulation of the flt receptor rather than the KDR receptor.

Endothelial Growth Factors↗
PubMed1996

VEGF mRNA levels in placentae from pregnancies complicated by pre-eclampsia.

OBJECTIVE: To measure the mRNA levels of vascular endothelial growth factor and its receptor in the placenta following delivery after uncomplicated pregnancy and after pregnancies complicated by pre-eclampsia. SETTING: Rosie Maternity Hospital, Cambridge. MATERIAL: Placental biopsies were obtained following delivery by caesarean section in 23 cases of pregnancy presenting at a range of gestational ages with pre-eclampsia. These were compared with biopsies from 20 appropriately matched women with uncomplicated pregnancies. MAIN OUTCOME MEASURE: mRNA levels of vascular endothelial growth factor (VEGF) and its receptor the fins-like tyrosine kinase (flt), were quantified in total RNA isolated from placental biopsies using the RNAse protection assay. The amount of RNA was compared with that of the housekeeping gene glyceraldehyde 3-phosphate dehydrogenase (GAPDH), used as a standard. Results were expressed as arbitrary optical density units of VEGF/GAPDH and flt/GAPDH. RESULTS: In both control and pre-eclamptic women regression analysis showed that the level of mRNA encoding VEGF declined significantly with gestational age (P < 0.0001). However, levels of VEGF mRNA were significantly lower in the pre-eclamptic women compared with the control women (P < 0.023). CONCLUSIONS: This study provides evidence of an abnormality of growth factor expression in the placenta during pregnancies complicated by pre-eclampsia. Such placentae exhibit deficient growth and differentiation of terminal villi and reduced fetal capillary branching and reduced levels of VEGF could well account for these morphometric changes. This finding provides a molecular explanation for this abnormal placental development and points to VEGF as a factor in the aetiology of pre-eclampsia and its complications.

Adolescent↗
PubMed1996

Messenger RNA encoding thiol protein disulphide isomerase in amnion, chorion and placenta in human term and preterm labour.

OBJECTIVE: To investigate levels of messenger RNA (mRNA) encoding thiol protein disulphide isomerase, in human amnion, chorion and placenta during pregnancy and in relation to term and preterm labour. DESIGN: Amnion, chorion and placenta from 33 women delivered between 24 and 41 weeks of gestation were used in the study. SETTING: Reproductive Molecular Research Group, Department of Obstetrics and Gynaecology, University of Cambridge Clinical School, Rosie Maternity Hospital, Cambridge. RESULTS: Women who were delivered spontaneously before 30 weeks of gestation had higher levels of mRNA encoding thiol protein disulphide isomerase in placenta and chorion than those who were delivered spontaneously after this time (placenta (P < 0.01, chorion P < 0.01) and compared with those who were delivered by elective caesarean section before 30 weeks of gestation (placenta (P < 0.01, chorion P < 0.05). In the group in whom spontaneous labour occurred, at all gestations studied, there were increased levels of mRNA encoding thiol protein disulphide isomerase in the placenta (P < 0.001) and chorion (P < 0.001) compared with the amnion. CONCLUSION: Changes in the steady state level of mRNA encoding thiol protein disulphide isomerase may play a role in the onset of preterm labour before 30 weeks of gestation.

Adolescent↗