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Biomedical subjects

S Rice

Publications and source records attributed to S Rice.

At least 19 recordsLinked to original sources
PubMed2001

Kinetics of the AHL regulatory system in a model biofilm system: how many bacteria constitute a "quorum"?

Acylated homoserine lactones (AHLs) regulate a wide variety of phenotypes in Gram-negative bacteria. Most research suggests that AHL-mediated phenotypes are not expressed in populations until late logarithmic phase or stationary phase. Here, we model how the concentration of AHLs inside bacterial cells and in a biofilm changes over time as a function of population growth rate, diffusion of AHLs and the rate of autoinduction. Our theoretical results show that the concentration of AHLs inside a single bacterium (and by implication induction of a phenotype) has a non-trivial behaviour over time, and often exhibits a rapid increase early in population growth. This rapid increase is followed by a plateau, followed by another rise in the concentration of AHLs, to a second plateau. High concentrations of AHLs inside the bacterial cell early in population growth are positively affected by slow diffusion rates out of the cell and the biofilm, slow bacterial growth rates and fast autoinduction. In contrast, fast growth rates, slow autoinduction rates and high diffusion rates result in a high concentration plateau in stationary phase. More generally, the density-dependent nature of AHL regulation can be viewed as a trade-off between factors that dilute intracellular concentrations of AHLs (diffusion out of the cell, cell division), and those that increase concentrations (a slowing or restriction of diffusion or growth, or autoinduction). These results suggest that expression of AHL-mediated phenotypes can occur at relatively low cell densities and low external/environmental AHL concentrations.

4-Butyrolactone↗
PubMed2001

Treatment demands and differential treatment of patients with cystic fibrosis and their siblings: patient, parent and sibling accounts.

Cystic fibrosis (CF) is a progressive disease with no known cure. Advances in diagnosis and treatment have resulted in patients living longer and thus families live with the illness for longer. Treatments are becoming increasingly demanding and are largely performed in the family home. Mothers are often reported to experience greater stress and poorer adjustment than mothers of well children or population norms. Patients and siblings are also reported to display adjustment difficulties. Siblings have rarely been included in research designs. This qualitative study investigates the impact of CF and treatment on eight patients, eight mothers, one father and eight siblings. A family systems perspective was adopted. Each individual was interviewed independently using semistructured interviews. Patients and siblings were aged between 9 and 21 years. Qualitative analyses revealed high levels of non-adherence (intentional and unintentional) and parental involvement in treatment, minimal involvement of siblings, and preferential treatment towards patients. Demanding treatment, coupled with the progressive nature of CF, promote high levels of parental involvement for younger children as well as older teenagers, often due to attempted or actual non-adherence. Siblings may receive less attention while patients' needs take priority. Future development of a measure of adherence suitable for children and adolescents should take into account different motivations for non-adherence, particularly regarding the level of personal control over adherence to treatment. In addition, the potential impact of having a brother or sister with CF should not be underestimated and the needs of siblings should not go unnoticed.

Adaptation, Psychological↗
PubMed2001

Rapid screening: a comparative study.

Although rapid screening of negative and inadequate cervical smears is a quality assurance requirement for all UK laboratories, there has been little attempt to standardize the method and laboratories make use of a number of different techniques and times. The aim of this study was to assess the sensitivity of these various techniques by measuring their ability to pick out known false-negative smears. Completed questionnaires from 123 laboratories across England revealed that 52% of laboratories use a "step" technique, 19% use "turret", 15% use random paths and 34% attempt to rescreen the whole slide quickly. Twenty-two percent of laboratories use a mixture of techniques. Timings are also variable, with the majority of laboratories allowing screeners to review slides at a pace decided by themselves but usually between 1 and 2 min. The study involved 120 participants who performed a total of 24 000 rapid screens. The results showed that, of the 90 abnormal slides used in the study, 62 cases (69%) were identified as abnormal or needing review by more than 50% of participants. Overall rapid screening picked out 58% of high-grade squamous abnormalities, 59% of low-grade abnormalities and 72% of glandular lesions. Step screening performed best, followed by whole slide/random and then turret. One minute was the optimum time and there was a significant fall in performance once individuals attempted to rescreen large numbers (>50). The most significant finding was the marked variation in the performance of individuals using the same slide sets.

Diagnostic Errors↗
PubMed2000

Paclitaxel sensitivity of breast cancer cells with constitutively active NF-kappaB is enhanced by IkappaBalpha super-repressor and parthenolide.

The transcription factor nuclear factor-kappaB (NF-kappaB) regulates genes important for tumor invasion, metastasis and chemoresistance. Normally, NF-kappaB remains sequestered in an inactive state by cytoplasmic inhibitor-of-kappaB (IkappaB) proteins. NF-kappaB translocates to nucleus and activates gene expression upon exposure of cells to growth factors and cytokines. We and others have shown previously that NF-kappaB is constitutively active in a subset of breast cancers. In this study, we show that constitutive activation of NF-kappaB leads to overexpression of the anti-apoptotic genes c-inhibitor of apoptosis 2 (c-IAP2) and manganese superoxide dismutase (Mn-SOD) in breast cancer cells. Furthermore, expression of the anti-apoptotic tumor necrosis factor receptor associated factor 1 (TRAF1) and defender-against cell death (DAD-1) is regulated by NF-kappaB in certain breast cancer cells. We also demonstrate that NF-kappaB-inducible genes protect cancer cells against paclitaxel as MDA-MB-231 breast cancer cells modified to overexpress IkappaBalpha required lower concentrations of paclitaxel to arrest at the G2/M phase of the cell cycle and undergo apoptosis when compared to parental cells. The effect of NF-kappaB on paclitaxel-sensitivity appears to be specific to cancer cells because normal fibroblasts derived from embryos lacking p65 subunit of NF-kappaB and wild type littermate embryos were insensitive to paclitaxel-induced G2/M cell cycle arrest. Parthenolide, an active ingredient of herbal remedies such as feverfew (tanacetum parthenium), mimicked the effects of IkappaBalpha by inhibiting NF-kappaB DNA binding activity and Mn-SOD expression, and increasing paclitaxel-induced apoptosis of breast cancer cells. These results suggest that active ingredients of herbs with anti-inflammatory properties may be useful in increasing the sensitivity of cancers with constitutively active NF-kappaB to chemotherapeutic drugs. Oncogene (2000) 19, 4159 - 4169

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed2000

Homing and engraftment potential of Sca-1(+)lin(-) cells fractionated on the basis of adhesion molecule expression and position in cell cycle.

Engraftment potential of hematopoietic stem cells (HSCs) is likely to be dependent on several factors including expression of certain adhesion molecules (AMs) and degree of mitotic quiescence. The authors investigated the functional properties and engraftment potential of Sca-1(+)lin(-) cells subfractionated on the basis of expression, or lack thereof, of CD11a, CD43, CD49d, CD49e, or CD62L and correlated that expression with cell cycle status and proliferative potential of engrafting fractions. Donor-derived chimerism in mice receiving CD49e(+) or CD43(+) Sca-1(+)lin(-) cells was greater than that in mice receiving cells lacking these 2 markers, while Sca-1(+)lin(-) cells positive for CD11a and CD62L and bright for CD49d expression mediated minimal engraftment. AM phenotypes enriched for engraftment potential contained the majority of high proliferative potential-colony forming cells, low proliferative potential-colony forming cells, and cells providing rapid in vitro expansion. Cell cycle analysis of AM subpopulations revealed that, regardless of their bone marrow repopulating potential, Sca-1(+)lin(-) AM(-) cells contained a higher percentage of cells in G(0)/G(1) than their AM(+) counterparts. Interestingly, engrafting phenotypes, regardless of the status of their AM expression, were quicker to exit G(0)/G(1) following in vitro cytokine stimulation than their opposing phenotypes. When engrafting phenotypes of Sca-1(+)lin(-) AM(+) or AM(-) cells were further fractionated by Hoechst 33342 into G(0)/G(1) or S/G(2)+M, cells providing long-term engraftment were predominantly contained within the quiescent fraction. These results define a theoretical phenotype of a Sca-1(+)lin(-) engrafting cell as one that is mitotically quiescent, CD43(+), CD49e(+), CD11a(-), CD49d(dim), and CD62L(-). Furthermore, these data suggest that kinetics of in vitro proliferation may be a good predictor of engraftment potential of candidate populations of HSCs. (Blood. 2000;96:1380-1387)

Animals↗
PubMed2000

Role of the kinesin neck linker and catalytic core in microtubule-based motility.

Kinesin motor proteins execute a variety of intracellular microtubule-based transport functions [1]. Kinesin motor domains contain a catalytic core, which is conserved throughout the kinesin superfamily, followed by a neck region, which is conserved within subfamilies and has been implicated in controlling the direction of motion along a microtubule [2] [3]. Here, we have used mutational analysis to determine the functions of the catalytic core and the approximately 15 amino acid 'neck linker' (a sequence contained within the neck region) of human conventional kinesin. Replacement of the neck linker with a designed random coil resulted in a 200-500-fold decrease in microtubule velocity, although basal and microtubule-stimulated ATPase rates were within threefold of wild-type levels. The catalytic core of kinesin, without any additional kinesin sequence, displayed microtubule-stimulated ATPase activity, nucleotide-dependent microtubule binding, and very slow plus-end-directed motor activity. On the basis of these results, we propose that the catalytic core is sufficient for allosteric regulation of microtubule binding and ATPase activity and that the kinesin neck linker functions as a mechanical amplifier for motion. Given that the neck linker undergoes a nucleotide-dependent conformational change [4], this region might act in an analogous fashion to the myosin converter, which amplifies small conformational changes in the myosin catalytic core [5,6].

Adenosine Triphosphatases↗
PubMed2000

The effect of nonscreening smears on screening smear results: a statistical analysis with its implications for the NHS cervical screening programme.

This is a statistical analysis of individual NHS Cervical Screening Programme laboratories screening smear 'pick-up' rates (defined here as percentage low grade and percentage high grade of total adequate smears for ages 20-64 years derived from general practitioners and community clinics) in relation to their nonscreening smear workload proportion (here defined as percentage nonscreening smears of total laboratory workload from all sources for all ages). This was achieved by the use of three one way ANOVA models in order to receive a complete overview of the results. The models were applied to the following: (1) Laboratories with a total workload of less than 15000 general practitioner (GP) and community clinic smears; (2) laboratories with a total workload of greater than 15000 GP and community smears and; (3) all laboratories (i.e. a combination of 1 and 2). The 'test' groups within each of these models comprised three subgroups based on the percentage of laboratory workload that consisted of smears from a nonscreening source. This figure ranged from 2.8% to 82.6%. The subgroups were divided so as to contain approximately the same number of laboratories in each one (172 laboratories in total, 42 with workload < 15000 and 130 with > 15000). The results show that laboratories high and low grade pick-up rates have a positively correlated but variable relationship with the proportion of their workload that consists of nonscreening smears. The results show significance overall at the 5% level for high grade and the 10% level for low grade (high grade at P = 0.045 and low grade at P = 0.071). Significance for laboratories viewing less than 15000 screening smears at the 1% level (high grade P = 0.006 and low grade P = 0.005). They show no significance, however, for laboratories viewing more than 15000 screening smears (high grade P = 0.457 and low grade P = 0.622). There is an intriguing possibility that a greater exposure to abnormal smears results in a greater tendency to detect them. The current data provides no evidence to support the NHS Executive's use of 15000 as a designated figure when quality monitoring and service provision becomes a specific issue. The closure or amalgamation of laboratories with workloads less than this would appear to have no scientific evidence base.

Adult↗
PubMed2000

Gastric adenocarcinoma with a yolk sac component: a case report and review of the literature.

Gastric yolk sac tumors (YST) are very rare and are mainly reported in elderly people. We present a case of a 36-year-old man with a poorly differentiated gastric cancer showing a mixture of adenocarcinoma and yolk sac tumor that metastasized to Virchow's node. Both biopsies, Virchow's node and gastric tumor, contained areas of adenocarcinoma and yolk sac tumor that stained strongly positive for alpha fetoprotein (AFP) by the immunohistochemistry method. A high level of serum AFP (38,200 ng/mL) was also noted in this case. The response to chemotherapy in this case of mixed gastric yolk sac tumor and adenocarcinoma was not as favorable as would be expected in a pure primary germ cell tumor.

Adenocarcinoma↗
PubMed2000

Hematology analyzers.

Explore the source record for details and available documents.

Clinical Laboratory Information Systems↗
PubMed1999

A structural change in the kinesin motor protein that drives motility.

Kinesin motors power many motile processes by converting ATP energy into unidirectional motion along microtubules. The force-generating and enzymatic properties of conventional kinesin have been extensively studied; however, the structural basis of movement is unknown. Here we have detected and visualized a large conformational change of an approximately 15-amino-acid region (the neck linker) in kinesin using electron paramagnetic resonance, fluorescence resonance energy transfer, pre-steady state kinetics and cryo-electron microscopy. This region becomes immobilized and extended towards the microtubule 'plus' end when kinesin binds microtubules and ATP, and reverts to a more mobile conformation when gamma-phosphate is released after nucleotide hydrolysis. This conformational change explains both the direction of kinesin motion and processive movement by the kinesin dimer.

Adenosine Triphosphatases↗
PubMed1999

Quorum-sensing cross talk: isolation and chemical characterization of cyclic dipeptides from Pseudomonas aeruginosa and other gram-negative bacteria.

In cell-free Pseudomonas aeruginosa culture supernatants, we identified two compounds capable of activating an N-acylhomoserine lactone (AHL) biosensor. Mass spectrometry and NMR spectroscopy revealed that these compounds were not AHLs but the diketopiperazines (DKPs), cyclo(DeltaAla-L-Val) and cyclo(L-Pro-L-Tyr) respectively. These compounds were also found in cell-free supernatants from Proteus mirabilis, Citrobacter freundii and Enterobacter agglomerans [cyclo(DeltaAla-L-Val) only]. Although both DKPs were absent from Pseudomonas fluorescens and Pseudomonas alcaligenes, we isolated, from both pseudomonads, a third DKP, which was chemically characterized as cyclo(L-Phe-L-Pro). Dose-response curves using a LuxR-based AHL biosensor indicated that cyclo(DeltaAla-L-Val), cyclo(L-Pro-L-Tyr) and cyclo(L-Phe-L-Pro) activate the biosensor in a concentration-dependent manner, albeit at much higher concentrations than the natural activator N-(3-oxohexanoyl)-L-homoserine lactone (3-oxo-C6-HSL). Competition studies showed that cyclo(DeltaAla-L-Val), cyclo(L-Pro-L-Tyr) and cyclo(L-Phe-L-Pro) antagonize the 3-oxo-C6-HSL-mediated induction of bioluminescence, suggesting that these DKPs may compete for the same LuxR-binding site. Similarly, DKPs were found to be capable of activating or antagonizing other LuxR-based quorum-sensing systems, such as the N-butanoylhomoserine lactone-dependent swarming motility of Serratia liquefaciens. Although the physiological role of these DKPs has yet to be established, their activity suggests the existence of cross talk among bacterial signalling systems.

4-Butyrolactone↗
PubMed1998

Delayed targeting of cytokine-nonresponsive human bone marrow CD34(+) cells with retrovirus-mediated gene transfer enhances transduction efficiency and long-term expression of transduced genes.

Primitive hematopoietic progenitor cells (HPCs) are potential targets for treatment of numerous hematopoietic diseases using retroviral-mediated gene transfer (RMGT). To achieve high efficiency of gene transfer into primitive HPCs, a delicate balance between cellular activation and proliferation and maintenance of hematopoietic potential must be established. We have demonstrated that a subpopulation of human bone marrow (BM) CD34(+) cells, highly enriched for primitive HPCs, persists in culture in a mitotically quiescent state due to their cytokine-nonresponsive (CNR) nature, a characteristic that may prevent efficient RMGT of these cells. To evaluate and possibly circumvent this, we designed a two-step transduction protocol using neoR-containing vectors coupled with flow cytometric cell sorting to isolate and examine transduction efficiency in different fractions of cultured CD34(+) cells. BM CD34(+) cells stained on day 0 (d0) with the membrane dye PKH2 were prestimulated for 24 hours with stem cell factor (SCF), interleukin-3 (IL-3), and IL-6, and then transduced on fibronectin with the retroviral vector LNL6 on d1. On d5, half of the cultured cells were transduced with the retroviral vector G1Na and sorted on d6 into cytokine-responsive (d6 CR) cells (detected via their loss of PKH2 fluorescence relative to d0 sample) and d6 CNR cells that had not divided since d0. The other half of the cultured cells were first sorted on d5 into d5 CR and d5 CNR cells and then infected separately with G1Na. Both sets of d5 and d6 CR and CNR cells were cultured in secondary long-term cultures (LTCs) and assayed weekly for transduced progenitor cells. Significantly higher numbers of G418-resistant colonies were produced in cultures initiated with d5 and d6 CNR cells compared with respective CR fractions (P < .05). At week 2, transduction efficiency was comparable between d5 and d6 transduced CR and CNR cells (P > .05). However, at weeks 3 and 4, d5 and d6 CNR fractions generated significantly higher numbers of neoR progenitor cells relative to the respective CR fractions (P < .05), while no difference in transduction efficiency between d5 and d6 CNR cells could be demonstrated. Polymerase chain reaction (PCR) analysis of the origin of transduced neoR gene in clonogenic cells demonstrated that mature progenitors (CR fractions) contained predominantly LNL6 sequences, while more primitive progenitor cells (CNR fractions) were transduced with G1Na. These results demonstrate that prolonged stimulation of primitive HPCs is essential for achieving efficient RMGT into cells capable of sustaining long-term in vitro hematopoiesis. These findings may have significant implications for the development of clinical gene therapy protocols.

Adult↗
PubMed1998

An intensive weight loss programme in established type 2 diabetes and controls: effects on weight and atherosclerosis risk factors at 1 year.

The efficacy, safety, and effect on cardiovascular risk factors of two intensive weight loss programmes in overweight Type 2 diabetic subjects were studied. The patients were recruited from hospital diabetic clinics and control obese subjects from the community. Obese (BMI >30) patients with Type 2 diabetes mellitus and controls were offered intensive conventional diabetic advice or a very low calorie diet. Weekly 2 h sessions were conducted in two day-room areas of adjacent medical wards of Torbay Hospital. Non-diabetic and diabetic very low calorie diet groups reduced BMI by 6 and 5 kg m(-2), respectively, at 1 year. Waist-hip ratios (-0.06 and -0.05) were also reduced (p = 0.04 and p = 0.01), while HDL/total cholesterol ratios increased (+0.04 and +0.06, p = <0.01). Transient changes in blood pressure and antioxidant vitamin status occurred in the intensive conventional diet group. Fourteen of diabetic very low calorie diet subjects discontinued insulin and oral hypoglycaemic agents for the whole year, and psychological well-being transiently improved. Substantial weight loss and improvement in cardiovascular risk factors could be maintained for 1 year in Type 2 diabetic patients by the use of a very low calorie diet.

Adult↗
PubMed1998

Transduction of recombinant human erythropoietin receptor cDNA into daughter progenitors derived from single CD34(3+) cord blood cells changes the differentiation profile of daughter progenitors.

In this study, we tested the capacity to change the differentiation profile of progenitor cells by retroviral-mediated transduction of EpoR cDNA into one of the paired daughter cells derived from single CD34(3+) CB cells. Our results show that for the non-viral-treated daughter cells, the majority (99.6%) formed the same colony type. However, with cells transduced with viral vectors, 7.1% of the daughter cells transduced with the EpoR cDNA formed either a burst forming unit-erythroid (BFU-E) or a colony-forming unit-granulocyte, macrophage, erythroid, megakaryocyte (CFU-GEMM) colony compared to the other daughter cell transduced with viral supernatant lacking EpoR cDNA, which formed either a colony-forming unit granulocyte-macrophage (CFU-GM) or a high proliferative potential-colony forming cell (HPP-CFC) colony. Expression of the transduced EpoR cDNA was confirmed in individual colonies by RT-PCR analysis. These results substantiate in a more rigorous fashion our previous results that it is possible to change the Epo-responsive differentiation profile of progenitor cells by transduction into these cells of an EpoR cDNA and this change was apparent only in daughter cells derived from single CD34(3+) kit+ cells transduced with EpoR cDNA.

Antigens, CD↗
PubMed1998

The myeloid zinc finger gene (MZF-1) delays retinoic acid-induced apoptosis and differentiation in myeloid leukemia cells.

The myeloid zinc finger gene, MZF-1, is a hematopoietic transcription factor expressed in developing myeloid cells. To characterize further the role of MZF-1 in myelopoiesis, we used retroviral gene transduction to overexpress MZF-1 in HL-60 cells to produce HL-60-MZF-1 cells. HL-60 cells respond to retinoic acid (RA) with growth inhibition, granulocytic differentiation and apoptosis. However, HL-60-MZF-1 cells exposed to RA continue to proliferate in response to RA as evidenced by a higher percentage of cells in S phase, higher peak cell counts, and later peak cell counts. Morphologic differentiation of the RA-induced HL-60-MZF-1 cells is delayed with half as many of the HL-60-MZF-1 cells compared to the wild-type HL-60 cells that are differentiated after 3 days of RA, although both cells types responded with 80-95% mature granulocytes after 6 days of RA. Apoptosis was delayed in the MZF-1 transduced cells as measured by internucleosomal DNA fragmentation patterns, the terminal transferase end labeling reaction (TUNEL), and quantitation of fragmented DNA by the diphenylamine reaction. Several markers of differentiation were identical in both HL-60 and HL-60-MZF-1 cells including CD11b, CD33, CD34, CD13, CD16 and CD14. However, following 6 days of RA, only half as many HL-60-MZF-1 cells expressed CD18 compared to the wild-type HL-60 cells. Expression of the bcl-2 proto-oncogene transcript and protein was higher in the HL-60-MZF-1 cells compared to wild-type HL-60s and expression persisted for 5 days following RA in the HL-60-MZF-1 cells compared to only 3 days in the parental HL-60 cells suggesting that bcl-2 may contribute to the inhibition of apoptosis. Overexpression of MZF-1 had no effect on PMA-induced monocyte/macrophage differentiation of HL-60 cells. Together these findings indicate that MZF-1 can stimulate cell proliferation and delay RA-induced differentiation and apoptosis in HL-60 cells. MZF-1 may function in a similar role in myelopoiesis allowing myeloid precursors to expand their numbers before going on to terminally differentiate.

Antineoplastic Agents↗