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Biomedical subjects

S Rankin

Publications and source records attributed to S Rankin.

At least 37 records · Page 2Linked to original sources
PubMed1997

The surface contraction waves of Xenopus eggs reflect the metachronous cell-cycle state of the cytoplasm.

Activated Xenopus laevis eggs undergo a series of surface contractions in response to cell-cycle progression but fall to cleave unless the sperm centrosome is present. These surface contraction waves (SCWs) begin at the animal pole and progress around the egg, occur every cell cycle and precede cleavage [1] [2] [3]. The SCWs are biphasic, comprising a relaxation phase (SCWa) and a contraction phase (SCWb). To investigate how these events are linked to the underlying cell cycle, we studied the temporal and spatial relationship between the SCWs and previously characterized biochemical markers of cell-cycle progression. We found that the relaxation phase was a response to activated maturation-promoting factor (MPF). In contrast, the contraction phase required inactivation of MPF and was blocked when MPF activity was maintained at elevated levels. We also found that a wave of MPF activity traveled within the cell from the animal to the vegetal hemisphere. Taken together, these experiments suggest that the SCWs are a local response to a wave of MPF activation and inactivation. The egg cytoplasm, therefore, is metachronous in terms of cell-cycle progression; multiple cell-cycle states are present and spatially distinct within the egg at the same time.

Animals↗
PubMed1997

Implantable cardioverter defibrillators: physical and psychosocial outcomes.

BACKGROUND: The long-term outcomes of living with an implantable cardioverter defibrillator are an important consideration in recovery. However, little is known about physical and psychosocial outcomes beyond 1 year after implantation. OBJECTIVE: To describe the long-term physical and psychosocial adaptation of persons who have had an implantable cardioverter defibrillator for approximately 2 years or more. METHODS: This nonexperimental cross-sectional study used telephone interviews to ascertain the responses of 80 recipients of implantable cardioverter defibrillators to physical and psychosocial questionnaires to explore the long-term outcomes of living with the devices. Subjects eligible for inclusion were selected from the files of an arrhythmia clinic. RESULTS: Hierarchical regression analysis showed that subjects who are not emotional are likely to be more physically active, especially if they are young and male, and that subjects who tend to be emotional are likely to be psychologically distressed and have poorer social and domestic adaptation. Furthermore, use of emotions was a positive predictor of psychological distress and poor social and domestic adaptation. Subjects reported the use of both emotion- and problem-focused coping. Subjects' scores on physical and psychosocial functioning were comparable to scores reported in the literature for patients who have had myocardial infarction or dysrhythmia. CONCLUSIONS: Emotional responses to distress were predictive of little physical activity and psychological distress. Furthermore, young recipients of implantable cardioverter defibrillators and men were predicted to be physically active. Persons who have had an implantable cardioverter defibrillator for approximately 2 years or more can anticipate that their physical and psychosocial functioning will be similar to that of patients who have myocardial infarction or dysrhythmia.

Adaptation, Psychological↗
PubMed1996

Requirement for phosphatidylinositol 3'-kinase activity in platelet-derived growth factor-stimulated tyrosine phosphorylation of p125 focal adhesion kinase and paxillin.

The role of phosphatidylinositol 3'-kinase (PI 3'-kinase) activity in platelet-derived growth factor (PDGF)-stimulated tyrosine phosphorylation of focal adhesion kinase (p125FAK) and paxillin has been examined. The tyrosine phosphorylation of p125FAK and paxillin in response to PDGF was markedly inhibited by wortmannin in a dose-dependent manner. PDGF-stimulated PI 3'-kinase activity, membrane ruffle formation, and tyrosine phosphorylation of p125FAK and paxillin were all inhibited by the same low concentrations of wortmannin (>90% inhibition at 40nM). In contrast, tyrosine phosphorylation of p125FAK and paxillin in response to bombesin, endothelin, and phorbol 12,13-dibutyrate was not inhibited by wortmannin in these cells. Furthermore, LY294002, an inhibitor of PI 3'-kinase structurally unrelated to wortmannin, also inhibited PDGF-stimulated p125FAK tyrosine phosphorylation. PDGF was shown to stimulate the tyrosine phosphorylation of p125FAK in porcine aortic endothelial (PAE) cells transfected with the wild type PDGF-beta receptors, but not in PAE cells transfected with PDGF-beta receptors in which the PI 3'-kinase binding sites (Tyr-740/751) were replaced by phenylalanine. PDGF-stimulated, PI 3'-kinase-dependent tyrosine phosphorylation of p125FAK was not inhibited by rapamycin, and thus it was dissociated from the activation of p70 S6 kinase, previously identified as a molecular downstream target of PI 3'-kinase. Thus, we have identified a PI 3'-kinase-dependent signal transduction pathway in the action of PDGF, which leads to the phosphorylation of p125FAK and paxillin.

3T3 Cells↗
PubMed1996

Effects of homology, size and exchange of the meiotic segregation of model chromosomes in Saccharomyces cerevisiae.

In most eukaryotic organisms, chiasmata, the connections formed between homologous chromosomes as a consequence of crossing over, are important for ensuring that the homologues move away from each other at meiosis I. Some organisms have the capacity to partition the rare homologues that have failed to experience reciprocal recombination. The yeast Saccharomyces cerevisiae is able to correctly partition achiasmate homologues with low fidelity by a mechanism that is largely unknown. It is possible to test which parameters affect the ability of achiasmate chromosomes to segregate by constructing strains that will have three achiasmate chromosomes at the time of meiosis. The meiotic partitioning of these chromosomes can be monitored to determine which ones segregate away from each other at meiosis I. This approach was used to test the influence of homologous yeast DNA sequences, recombination intiation sites, chromosome size and crossing over on the meiotic segregation of the model chromosomes. Chromosome size had no effect on achiasmate segregation. The influence of homologous yeast sequences on the segregation of noncrossover model chromosomes was negligible. In meioses in which two of the three model chromosomes experienced a crossover, they nearly always disjoined at meiosis I.

Chromosome Mapping↗
PubMed1996

Managing hypovolaemic shock.

This poster has been designed to impart information which was gathered for a seminar as part of an Anaesthetic Nursing Course. It looks at the research which has been compiled on this subject, both in the Nursing and the Medical fields and illustrates the recommendations made by these pieces of research. The poster also depicts the breakdown of fluid compartments in the body and the physiological transference of fluids within the body in times of crisis. There is another section in the poster which explains the differences between certain fluids which are typically used during hypovolaemic resuscitation and the reasons for using these particular fluids. A version of a table designed by the American College of Surgeons, (Advanced Trauma Life Support, ATLS), which is recommended in some of the research on this topic is also shown in the poster and is very useful as a guide to what should happen in the hypovolaemic situation.

Fluid Therapy↗
PubMed1996

Haemostasis.

There are many different methods and techniques used to achieve this in operating theatres, day procedure units and general practice surgeries around the country. I am aware that some of the methods which I am going to mention may not be available in all work areas but they are techniques which are synonymous with achieving haemostasis and are methods which you may want implemented in your area. So let me outline the topics I intend to look at in this session. First of all I would like to briefly outline the basic physiology behind coagulation, the body's natural response to bleeding. Then, I would like to mention a few drugs which can affect haemostasis and also look at the use of electrosurgery in achieving haemostasis. I would then intend to look at a few other techniques which are used such as suturing, tourniquets and pressure dressings.

Anticoagulants↗
PubMed1995

Phage conversion in Salmonella enterica serotype Enteritidis: implications for epidemiology.

A model system for the study of phage conversion of Salmonella enterica serotype Enteritidis is reported. Temperate phages 1,2,3 and 6 from the phage typing scheme were used to convert several individually recognized phage types into others. Phage type 4 was converted to PT8, PT6a to PT4, PT6a to PT7, PT13 to PT13a and PT15 to PT11; some new phage lysis patterns were also detected. This model was used to examine the relationships between phage types within a previously defined clonal lineage, SECLIII, to establish whether or not Enteritidis like Salmonella enterica serotype Typhi and Salmonella enterica serotype Paratyphi B possessed type determining phages. We were able to convert PT1 to PT20, and PT15 to PT11.

Animals↗
PubMed1994

Botulinum C3 exoenzyme blocks the tyrosine phosphorylation of p125FAK and paxillin induced by bombesin and endothelin.

In this study we examined the role of rho p21 in neuropeptide-stimulated tyrosine phosphorylation. Intact Swiss 3T3 cells were treated with the Clostridium botulinum C3 exoenzyme which specifically ADP ribosylates and inactivates rho p21. C3 exoenzyme treatment of cells caused a marked decrease in both bombesin- and endothelin-stimulated tyrosine phosphorylation of multiple proteins, including p125 focal adhesion kinase (FAK) and paxillin. Our results suggest that rho p21 is a component of the signal transduction pathway linking seven transmembrane domain receptors with tyrosine phosphorylation and cytoskeletal events.

3T3 Cells↗
PubMed1994

Platelet-derived growth factor modulation of focal adhesion kinase (p125FAK) and paxillin tyrosine phosphorylation in Swiss 3T3 cells. Bell-shaped dose response and cross-talk with bombesin.

In the present study, we have identified several proteins in Swiss 3T3 cells that are phosphorylated on tyrosine in response to platelet-derived growth factor (PDGF) and exhibit an unusual bell-shaped dose-response curve with a maximum at 5 ng/ml platelet-derived growth factor (PDGF). These proteins include two that are associated with focal adhesions, namely the focal adhesion kinase (p125FAK), a novel cytosolic tyrosine kinase, and paxillin. At low concentrations of PDGF (1-5 ng/ml), these proteins are the predominant tyrosine-phosphorylated species. At 30 ng/ml PDGF, however, there was no stimulation of their phosphorylation over control levels. In contrast, tyrosine phosphorylation of previously described substrates of the PDGF receptor tyrosine kinase, namely the p21ras GTPase-activating protein, p120, phosphatidyl inositol 3' kinase, and phospholipase C gamma exhibited sigmoidal dose-response curves with PDGF and were all efficiently phosphorylated on tyrosine at 30 ng/ml PDGF. Cytochalasin D, which disrupts the actin cytoskeleton, completely inhibited the tyrosine phosphorylation of p125FAK and paxillin by PDGF. Examination of the actin cytoskeleton after stimulation of cells with different concentrations of PDGF revealed that at 5 ng/ml PDGF, actin appears in stress fibers and in membrane ruffles, while at 30 ng/ml, PDGF disrupts the actin cytoskeleton. Bombesin stimulates actin stress fiber formation with no evidence of disruption of stress fibers at high concentrations. When cells were stimulated with bombesin (10 nM) in the presence of 30 ng/ml PDGF, however, the actin cytoskeleton was completely disrupted. Further, the tyrosine phosphorylation of both p125FAK and paxillin induced by bombesin (10 nM) was completely prevented when cells were stimulated with bombesin in the presence of 30 ng/ml PDGF. We propose that the inhibitory limb in the bell-shaped dose-response curve of PDGF and the novel cross-talk between PDGF and bombesin on tyrosine phosphorylation may be explained by the ability of PDGF at 30 ng/ml to disrupt the actin cytoskeleton.

3T3 Cells↗
PubMed1992

The integrin-binding domain of invasin is sufficient to allow bacterial entry into mammalian cells.

Yersinia pseudotuberculosis is able to enter normally nonphagocytic host cells by multiple pathways, the most efficient of which is mediated by invasin, a 986-amino-acid bacterial outer membrane protein. It has previously been shown that the C-terminal 192 amino acids of invasin are sufficient to bind mammalian cells. To determine if additional regions of the invasin protein are necessary to promote entry, we developed a novel assay that tests the ability of various invasin derivatives to confer on Staphylococcus aureus the ability to enter animal cells. We determined that the 192-amino-acid cell-binding region of invasin, when used to coat the bacterial cell surface, was also sufficient to promote cellular penetration. These results suggest that the simple binding of invasin to its receptors is sufficient to mediate entry and that the bacterium plays a largely passive role in the entry process.

Adhesins, Bacterial↗
PubMed1991

Metastatic carcinoma in the neck: a clinical, radiological, scintigraphic and pathological study.

This study was undertaken to compare clinical evaluation of the neck with 99mTc(v) DMSA planar scintigraphy and computerized tomography (CT) in patients with head and neck carcinoma. Twenty-six patients were studied and in all but one the neck was previously untreated. A total of 31 neck dissections were performed and the specimens examined histopathologically. CT was approximately as accurate (71%) as clinical examination (68%) and more accurate than 99mTc(v) DMSA planar scintigraphy (48%) in predicting which necks contained metastatic carcinoma. Overall, 13% of necks had their staging correctly changed by 99mTc(v) DMSA scintigraphy compared with 10% for CT. Although scintigraphy upstaged 13% of clinically N0 necks compared to 6% for CT, it was less sensitive and specific than either clinical examination or CT. 99mTc(v) DMSA planar scintigraphy has no role to play in the investigation of patients with metastatic carcinoma to include the clinically N0 neck.

Adenocarcinoma↗
PubMed1990

Estrogen receptors, progestin receptors and DNA synthesis in the macaque endometrium during the luteal-follicular transition.

We have suggested that in the nonhuman primate endometrium, stromal cells might play a role in mediating the effects of estrogen on the epithelium, especially during the luteal-follicular transition (LFT) when target cells normally escape from the inhibitory influence of progesterone (P). We now report that like estrogen receptors (ER), endometrial progestin receptors (PR) are detectable only in stromal cells until the fifth day of the LFT. With a technique that combined immunocytochemistry and autoradiography on the same sections, we characterized the cellular distribution of ER or PR coincidentally with the localization of [3H]thymidine taken up in vitro by endometria from monkeys undergoing an LFT. DNA synthesis in the glands of the upper endometrium was E2-dependent, but the distribution of [3H]thymidine was not positively correlated with the presence of ER or PR. Readministration of P to animals on days 3 or 4 of the LFT significantly reduced the [3H]thymidine labeling index of the glandular epithelium and caused stromal ER to decline, but P did not block the eventual appearance of ER in epithelial cells on day 5 of the LFT. Thus, E2 stimulated DNA synthesis in epithelial cells that lacked ER, and P suppressed DNA synthesis in these cells even though PR was only detected in the stroma when P treatment began. These data are consistent with a role for endometrial stromal cells in mediating the effects of E2 and P on the epithelium during the LFT.

Animals↗