Biomedical subjects

P Oliver

Publications and source records attributed to P Oliver.

At least 37 records · Page 2Linked to original sources

PubMed2000

Reactive oxygen species mediate tumor necrosis factor alpha-converting, enzyme-dependent ectodomain shedding induced by phorbol myristate acetate.

Ectodomain shedding of cell surface membrane-anchoring proteins is an important process in a wide variety of physiological events(1, 2). Tumor necrosis factor alpha (TNF-alpha) converting enzyme (TACE) is the first discovered mammalian sheddase responsible for cleavage of several important surface proteins, including TNF-alpha, TNF p75 receptor, L-selectin, and transforming growth factor-a. Phorbol myristate acetate (PMA) has long been known as a potent agent to enhance ectodomain shedding. However, it is not fully understood how PMA activates TACE and induces ectodomain shedding. Here, we demonstrate that PMA induces both reactive oxygen species (ROS) generation and TNF p75 receptor shedding in Mono Mac 6 cells, a human monocytic cell line, and l-selectin shedding in Jurkat T-cells. ROS scavengers significantly attenuated PMA-induced TNF p75 receptor shedding. Exogenous H2O2 mimicked PMA-induced enhancement of ectodomain shedding, and H2O2-induced shedding was blocked by TAPI, a TACE inhibitor. Furthermore, both PMA and H2O2 failed to cause ectodomain shedding in a cell line that lacks TACE activity. By use of an in vitro TACE cleavage assay, H2O2 activated TACE that had been rendered inactive by the addition of the TACE inhibitory pro-domain sequence. We presume that the mechanism of TACE activation by H2O2 is due to an oxidative attack of the pro-domain thiol group and disruption of its inhibitory coordination with the Zn++ in the catalytic domain of TACE. These results demonstrate that ROS production is involved in PMA-induced ectodomain shedding and implicate a role for ROS in other shedding processes.

ADAM Proteins↗

PubMed2000

Activation of tumor necrosis factor-alpha-converting enzyme-mediated ectodomain shedding by nitric oxide.

Ectodomain shedding of cell surface proteins is an important process in a wide variety of physiological and developmental events. Recently, tumor necrosis factor-alpha-converting enzyme (TACE) has been found to play an essential role in the shedding of several critical surface proteins, which is evidenced by multiple developmental defects exhibited by TACE knockout mice. However, little is known about the physiological activation of TACE. Here, we show that nitric oxide (NO) activates TACE-mediated ectodomain shedding. Using an in vitro model of TACE activation, we show that NO activates TACE by nitrosation of the inhibitory motif of the TACE prodomain. Thus, NO production activates the release of cytokines, cytokine receptors, and adhesion molecules, and NO may be involved in other ectodomain shedding processes.

ADAM Proteins↗

PubMed2000

Requirement of endogenous stem cell factor and granulocyte-colony-stimulating factor for IL-17-mediated granulopoiesis.

IL-17 is a novel, CD4+ T cell-restricted cytokine. In vivo, it stimulates hematopoiesis and causes neutrophilia consisting of mature granulocytes. In this study, we show that IL-17-mediated granulopoiesis requires G-CSF release and the presence or induction of the transmembrane form of stem cell factor (SCF) for optimal granulopoiesis. However, IL-17 also protects mice from G-CSF neutralization-induced neutropenia. G-CSF neutralization completely reversed IL-17-induced BM progenitor expansion, whereas splenic CFU-GM/CFU-granulocyte-erythrocyte-megakaryocyte-monocyte was only reduced by 50% in both Sl/Sld and littermate control mice. Thus, there remained a significant SCF/G-CSF-independent effect of IL-17 on splenic granulopoiesis, resulting in a preservation of mature circulating granulocytes. IL-17 is a cytokine that potentially interconnects lymphocytic and myeloid host defense and may have potential for therapeutic development.

3T3 Cells↗

PubMed2000

In vivo effects of CGP-12177 on the expression of leptin and uncoupling protein genes in mouse brown and white adipose tissues.

OBJECTIVE: To assess the effect of chronic treatment with CGP-12177 a beta3-adrenergic receptor (AR) agonist with beta2/beta1-AR antagonist action, on the expression of the leptin gene and of genes coding for uncoupling proteins (ucp1, ucp2 and ucp3) in brown and white adipose tissues. DESIGN: NMRI mice received a daily subcutaneous injection of CGP-12177 at a dose of 0.05, 0.2, 0.5 or 1 mg/kg for 15 days. The specific levels of the mRNAs of interest were analysed in interscapular brown adipose tissue (BAT) and in two white adipose tissue (WAT) depots, inguinal (IWAT) and epididymal (EWAT). RESULTS: No changes in food intake or body weight were detected at any dose of CGP-12177. In the two WAT depots, the treatment led to enhanced expression of ucp1 and ucp3, but not of ucp2. In BAT, low doses (0.05 and 0.2 mg/kg) led to a decreased expression of the three ucp genes, whereas a slight stimulatory effect on the three ucp genes was elicited with a high dose (1 mg/kg). Treated animals displayed increased expression of leptin in BAT and, to a lesser extent, in IWAT, but not in EWAT. CONCLUSION: The results reveal that simultaneous stimulation of the expression of certain ucp genes and the leptin gene can be achieved, and suggest that adrenergic regulation of the leptin gene and of genes of the ucp family in adipose tissues is the result of complex interactions between the different beta-AR pathways.

Adipose Tissue↗

PubMed2000

Keeping families of heroin addicts together: results of 13 months' intake for community detoxification and rehabilitation at a family centre for drug users.

BACKGROUND: Heroin addiction is a major public health problem affecting both the addicted individuals and their children, who have been shown to have poor social, educational and health status and to be at higher risk of abuse than their peers. Whilst the antenatal effects of parental drug use and the overall poor outcomes for these children have been widely studied, there has been little emphasis on the effectiveness of treatment interventions and even less emphasis on evaluating the effect on children of the standard treatments aimed at their parents' drug use. OBJECTIVES: The aim of the present study was to evaluate the effect on heroin-addicted parents and their children of a family-based drug treatment intervention using a records-based methodology, and to identify any factors at admission which may influence outcome. This study is a pilot for a prospective Europe-wide study using a similar methodology prospectively in several treatment modalities. METHODS: A retrospective cohort study was carried out using existing clinical and residential record data. The setting was a residential family centre run by the charity Phoenix House in Sheffield, UK, offering a 6-month (180 days) family-based programme for heroin addicts including community detoxification overseen by primary care specialist doctors and residential rehabilitation. All adults and children who entered the centre between July 1997 and July 1998 were included in the study (26 adults and 33 children, in 23 family groups). An analysis was made of clinical records and records kept on the adults and children by the clinicians and staff at the centre. The main outcome measures for the adults were length of stay and reason for departure (treatment complete, early planned discharge, unplanned discharge, eviction); and for the children were reason for departure and discharge destination (with parent or taken into care). RESULTS: Mean length of stay was 110 days, and only 11 children (33%) and nine adults (35%) completed 150 days or more. Length of stay was found to be significantly correlated with parental age at admission (P < 0.01). Twelve children (37%) and nine adults (35%) were deemed to have completed treatment successfully. Of the remainder, 14 children (42%) and 11 adults (42%) left because of definite treatment failure. Successful treatment completion was found to be correlated with increased parental age (Pearson's r = 0.612, P = 0. 001). Poly-drug users were significantly less likely to complete treatment successfully (Fisher's exact test, P = 0.012). Twenty children were in the care of their parents on admission, and 24 were able to go home with their parents. There was no association between residence with parents pre- and post-admission (McNemar's chi-squared test = 1.6, P > or = 0.1). CONCLUSIONS: Whilst overall high rates of treatment success are not expected in abstinence-based programmes, the outcomes for the adults in this setting are comparable with published results in other residential settings, and there is some evidence that some families may have stayed together who might otherwise have been separated. Older adults who were not poly-drug users had significantly better outcomes. The records-based methodology proved successful, but centres need to keep detailed and preferably long-term records on children if their outcomes are to be evaluated more fully.

Adult↗

PubMed2000

Phase I-II study of high dose epirubicin plus cisplatin in unresectable non-small-cell lung cancer: searching for the maximal tolerated dose.

The purpose of this study was to search for the maximal tolerated dose of cisplatin in the cisplatin plus high-dose epirubicin combination for patients with non-small-cell lung cancer. The following range of cisplatin dosages were tested in a phase I study: 75, 90, 105, and 120 mg/m2 in combination with epirubicin 120 mg/m2 every 3 weeks. Eligibility consisted of previously untreated stage IIIb or IV non-small-cell lung cancers, Eastern Cooperative Oncology Group Performance Status less than or equal to 2, age less than or equal to 70 years, measurable disease, adequate blood counts, chemistry, cardiac function, and no brain metastasis. The maximal tolerated dose was defined as the dose level of cisplatin for which two of three patients or three of six patients developed one or more limiting toxicities during the first course of therapy. Afterward, the maximal tolerated dose of cisplatin was adopted in a subsequent phase II study. Three centers enrolled 42 patients: 18 in phase I and 24 in phase II. The maximal tolerated dose was almost reached at the last dose level (i.e., 120 mg/m2). Taking into account the total duration of the treatment, the real dose intensity for patients treated at the fourth dose level (120 mg/m2) did not differ from that of the third dose level (105 mg/m2). The latter dosage was therefore considered as the maximal tolerated one. In the subsequent phase II study, the median number of cycles received per patient was three (range: one to eight). Fifty percent required a dose reduction of either epirubicin, cisplatin, or both. The main toxicity was neutropenia, resulting in 10 episodes of febrile grade IV neutropenia requiring readmission. Other toxicities were mild to moderate. There was no toxic-related death. On intent-to-treat analysis, 10 patients (33%) achieved an objective response. Among them were three complete responders. Median survival was 8 months. We observed neither detraction nor improvement of quality of life as assessed using the European Organization for Research and Treatment of Cancer QLQ-C30-LC13. Given every 3 weeks in combination with epirubicin 120 mg/m2, the maximal tolerated cisplatin dose is 105 mg/m2. This combination yields activity in non-small-cell lung cancer.

Adult↗

PubMed1999

Brown adipose tissue response to cafeteria diet-feeding involves induction of the UCP2 gene and is impaired in female rats as compared to males.

Noradrenaline-dependent brown adipose tissue (BAT) thermogenesis is activated by the cold and excess energy intake, largely depends on the activity of the uncoupling protein 1 (UCP1), and is mediated mainly through the beta3-adrenoceptor (beta3-AR). We investigated the expression of ucp2, a gene that encodes a putative UCP1-like uncoupling protein, along with that of ucp1 and beta3-ar, in the interscapular BAT (IBAT) of male and female rats chronically fed a cafeteria diet. After 3 months on this diet, male rats attained a 34% excess body mass and showed IBAT hypertrophy and increased IBAT thermogenic potential, in terms of both UCP1 and UCP2 mRNA expression (both by 1.6-fold), UCP1 protein expression (by 1.75-fold) and GDP binding to IBAT mitochondria (by 2.2-fold); female rats attained a larger excess body weight (50%) and their IBAT, although hypertrophied, showed no signs of increased thermogenic potential per gram of tissue. Interestingly, the IBAT of female rats was already activated compared to males. Treatment of mouse brown adipocytes in primary culture with noradrenaline also triggered a dose-dependent increase of the levels of UCP1 mRNA and UCP2 mRNA. Retroregulatory down-regulation of the beta3-AR mRNA levels was found in the two models used. The results support a physiological role for UCP2, along with UCP1, in rodent BAT thermogenesis.

Adipose Tissue, Brown↗

PubMed1999

MDM2 oncogene as a target for cancer therapy: An antisense approach.

The MDM2 oncogene is amplified or overexpressed in human cancers. It has also been suggested that MDM2 levels are associated with poor prognosis of several human cancers. The MDM2 oncoprotein binds to the p53 tumor suppressor protein and serves as a negative regulator of p53. The p53 tumor suppressor also has an important role in cancer therapy, with p53-mediated apoptosis being a major mechanism of action for many clinically used cancer chemotherapeutic agents and radiation therapy. Therefore, the negative regulation of p53 by MDM2 may limit the magnitude of p53 activation by DNA damaging agents, thereby limiting their therapeutic effectiveness. The investigators hypothesize that, by inhibiting MDM2 expression, the MDM2 oncoprotein level will be reduced and the MDM2 negative feedback inhibition of p53 will be diminished, resulting in a significant increase of functional p53 levels that will modulate p53-mediated therapeutic effects. The overall objective of the present study was to investigate the functions of MDM2 oncogene in tumor growth and the potential value of MDM2 as a drug target for cancer therapy. The role of MDM2 in tumor growth is determined by inhibiting MDM2 expression in in vivo models of human cancers. The in vivo synergistically therapeutic effects of MDM2 inhibition and DNA damaging agents were also evaluated. Significant in vitro antitumor activities were found in cell lines, human osteosarcoma SJSA and choriocarcinoma JAR, in a time-, concentration-, and sequence-dependent manner. Following i.p. administration of anti-MDM2 antisense oligonucleotides, in vivo antitumor activity was observed in nude mice bearing SJSA and JAR xenografts in a dose-dependent manner. Moreover, in vivo synergistically therapeutic effects of MDM2 inhibition and DNA damaging agents adriamycin and 10-hydroxycamptothecin were observed. This study should provide the basis for future development of anti-MDM2 antisense oligonucleotides as cancer therapeutic agents used alone or in combination with conventional chemotherapeutics.

Animals↗

PubMed1998

Stem cell factor improves the repopulating ability of primitive hematopoietic stem cells after sublethal irradiation (and, to a lesser extent) after bone marrow transplantation in mice.

Bone marrow transplantation (BMT) and sublethal irradiation (XRT) cause profound long-term damage to hematopoietic stem cells. We used the competitive repopulation assay in mice to test the ability of granulocyte-macrophage colony-stimulating factor (GM-CSF) and stem cell factor (SCF), cytokines given in clinical settings to enhance marrow recovery after XRT or BMT and to protect the marrow repopulating ability of primitive hematopoietic stem cells (PHSC) after these modalities. The repopulating ability of exhaustible multilineage progenitors (EMP) was also tested after these modalities, with or without cytokines. Repopulating abilities of EMP and PHSC were significantly reduced after XRT or BMT; PHSC were preferentially affected. Administration of SCF to C57B6/J mice after XRT resulted in improved EMP and PHSC repopulating ability, although progenitor numbers--repopulating units--were not completely returned to control levels. Whether given as a single dose or multiple doses, GM after XRT did protect PHSC function from the deleterious effects of XRT, but this was not a significant effect. SCF caused an increase in PHSC repopulating ability after BMT, but this too was not a significant difference. GM after BMT had little effect. SCF administration before XRT led to severe impairment of PHSC function with very little or no stem cell activity observed. Therefore, timing of its administration is an important consideration since preadministration of the cytokine before XRT can be extremely harmful to PHSC function.

Animals↗

PubMed1998

The uncoupling protein, thermogenin.

The uncoupling protein (UCP) or thermogenin is a 33 kDa inner-membrane mitochondrial protein exclusive to brown adipocytes in mammals that functions as a proton transporter, allowing the dissipation as heat of the proton gradient generated by the respiratory chain and thereby uncoupling oxidative phosphorylation. Thermogenesis (heat production) in brown adipose tissue, which is activated in response to cold exposure or chronic overeating, depends largely on UCP activity. Norepinephrine, released from sympathetic terminals and acting via beta-adrenoceptors and cAMP, is the main positive regulator of both UCP synthesis and activity. Brown fat thermogenesis plays a critical role in thermoregulation and in overall energy balance, at least in rodents. Manipulation of thermogenesis, whether through UCP or through analogous uncoupling proteins, could be an effective strategy against obesity.

Adipose Tissue, Brown↗

PubMed1998

2-Methoxyestradiol, an endogenous metabolite of 17beta-estradiol, inhibits adipocyte proliferation.

The effects of 2-methoxyestradiol (2ME), a naturally occurring mammalian metabolite of 17beta-estradiol, on adipocyte growth has been investigated in mouse brown adipose tissue precursor cells developed in primary culture. 2ME inhibits brown adipocyte proliferation in a dose-response manner (IC50 = 1.7 x 10(-6) M for DNA synthesis), with much higher potency than its hormone precursor 17beta-estradiol, and cells acquire the typical differentiated morphology--more round with a higher content of triglycerides. 2ME causes similar effects in the immortal brown adipocyte tumor-derived hibernoma cell line HIB 1B and the immortal 3T3-F442A white adipocyte line. These findings suggest a possible role for 2ME in adipocyte proliferation, and probably in the differentiation process, entering the cells in the adipogenic program.

2-Methoxyestradiol↗

PubMed1996

Disparities in access to family planning services in Jamaica.

In order to improve the effectiveness and subtainability of the family planning programme, the National Family Planning Board has devised a strategy to shift users to longer-acting methods and increase the role of the private sector. To design interventions, a better understanding of existing services was thought to be necessary. This study examines the distribution of family planning service delivery points in Jamaica and the services offered by the public and private sectors through an examination of records and questionnaire interviews. The study found that, because of the concentration of private sector providers-the main outlets for longer-acting methods-in urban areas, rural areas had poor access to these methods. Because rural areas are not attractive to private sector providers, the public sector should recognize the need to continue to serve these areas.

Delivery of Health Care↗

PubMed1994

Targeted disruption of the apolipoprotein C-III gene in mice results in hypotriglyceridemia and protection from postprandial hypertriglyceridemia.

Using gene targeting in embryonic stem cells, we have generated mice lacking apolipoprotein C-III (ApoC-III). Homozygous mutant animals show absence of ApoC-III protein and no expression of ApoC-III mRNA in the liver or in the intestine. Expression of the neighboring genes, coding for apolipoprotein A-I and apolipoprotein A-IV, are not altered in the liver but are reduced in the intestine. This suggests that these three genes share a tissue-specific element for intestinal expression and that insertion of an additional promoter for the neomycin-resistant gene into the locus affects interaction between the tissue-specific element and the promoter of the individual gene. Fasted plasma triglyceride levels in the homozygous mutants are reduced to about 70% of normal, while heterozygotes have values intermediate between those of the homozygous mutants and wild types. Plasma levels of total cholesterol and of high density lipoprotein cholesterol in homozygotes are consistently lower than those in normal mices but the reduction does not reach statistical significance. A fat meal test showed that postprandial hypertriglyceridemia is abolished in homozygotes lacking ApoC-III. The homozygous mutants also clear chylomicrons faster than wild type controls. These data indicate that ApoC-III modulates the catabolism of triglyceride-rich lipoproteins and plays a role in the postprandial management of triglycerides.

Animals↗

PubMed1994

The effect of user fees on the utilization of family planning services. A clinical study.

A new fee structure was introduced to the Advanced Training and Research in Fertility Management Unit in 1992. The study looked at the effect of the new fees on attendance and the choice of contraceptive methods through an examination of clinical records and a questionnaire survey. There was a decline in attendance of roughly 28 per cent between 1992 and 1993. The decline affected mainly new clients and those who accepted injectables. A reduction in the price of injectables is suggested since the fee for this short-term method is more in line with those charged for long-term and permanent methods.

Family Planning Services↗

PubMed1994

Show, no show and sterilization.

The study investigates the factors involved in the decision of a sample of women to break appointments for sterilizations at the Fertility Management Unit of the University of the West Indies. A case control study involved 50 women who did not show up (no-shows) and an equal number who did show up (shows) over the same period. The no-shows had spent a shorter time in their current union than the shows, and some had no children for their partners at the time the appointments were made. Marriage was the single most important event that would encourage the no-shows to consider sterilization in the future. As long as poor women see child bearing as a precondition for financial assistance from spouses, they will hesitate to give up this capability.

Adult↗

PubMed1993

TGF alpha deficiency results in hair follicle and eye abnormalities in targeted and waved-1 mice.

To explore the physiological roles of transforming growth factor alpha (TGF alpha), we disrupted the mouse gene by homologous recombination in embryonic stem cells. Homozygous mutant mice were viable and fertile, but displayed pronounced waviness of the whiskers and fur, accompanied by abnormal curvature, disorientation, and misalignment of the hair follicles. Homozygous and, to a lesser extent, heterozygous mice displayed eye abnormalities of variable incidence and severity, including open eyelids at birth, reduced eyeball size, and superficial opacity. Histological examination revealed eyelid and anterior segment dysgenesis, corneal inflammation and scarring, and lens and retinal defects. Although TGF alpha deficiency affected skin and eyes, wound healing in these tissues was not impaired. Similar hair and eye defects have been previously associated with the recessive mutation waved-1 (wa-1), and Northern analysis revealed reduced expression of TGF alpha in wa-1 mice. Crosses between wa-1 homozygotes and TGF alpha-targeted mice confirmed that wa-1 and TGF alpha are allelic.

Alleles↗

PubMed1993

Lethal thalassemia after insertional disruption of the mouse major adult beta-globin gene.

Thalassemias are hereditary anemias caused by mutations that disturb the normal 1:1 balance of alpha- and beta-globin chains that form hemoglobin. We have disrupted the major adult beta-globin gene (b1) in mouse embryonic stem cells by using homologous recombination to insert selectable sequences into the gene. Mice homozygous for this insertional disruption of the b1 gene (Hbbth-2/Hbbth-2) are severely anemic and die perinatally. In contrast, approximately 60% of mice homozygous for deletion of the same gene (Hbbth-1/Hbbth-1) survive to adulthood and are much less anemic [Skow, L. C., Burkhart, B. A., Johnson, F. M., Popp, R. A., Goldberg, S. Z., Anderson, W. F., Barnett, L. B. & Lewis, S. E. (1983) Cell 34, 1043-1052]. These different phenotypes have implications for the control of beta-globin gene expression.

Animals↗

PubMed1993

Purification, characterization, crystallisation and X-ray analysis of selenomethionine-labelled hydroxymethylbilane synthase from Escherichia coli.

Hydroxymethylbilane synthase (HMBS) catalyses the conversion of porphobilinogen into hydroxymethylbilane, a linear tetrapyrrolic intermediate in the biosynthesis of haems, chlorophylls, vitamin B12 and related macrocycles. In the course of an investigation of the crystal structure of this enzyme, we intended to follow a new strategy to obtain the X-ray phase information, i.e. the collection of multiwavelength anomalous diffraction data from a crystal of a seleno-L-methionine (SeMet)-labelled variant of the protein. We have expressed and purified HMBS from Escherichia coli (34268 Da) in which all (six) methionine (Met) residues are replaced by SeMet. Complete replacement, as shown by amino acid composition analysis and by electrospray mass spectrometry, was achieved by growing the Met-requiring mutant E. coli PO1562 carrying the plasmid pPA410 in a medium containing 50 mg/l SeMet as the sole source of Met. [SeMet]HMBS exhibits full enzyme activity, as reflected by unchanged steady-state kinetic parameters relative to native enzyme. Rhombohedral crystals of [SeMet]HMBS could be grown at the pH optimum (7.4) of the enzyme (solutions containing 30 mg/ml protein, 0.4 mM EDTA, 20 mM dithiothreitol, 3 M NaCl and 15 mM Bristris-propane buffer were equilibrated by vapour diffusion at 20 degrees C against reservoirs of saturated NaCl). However, being very thin plates, these crystals were not suitable for X-ray analysis. Alternatively, rectangular crystals were obtained at pH 5.3 using conditions based on those reported for wild-type HMBS [sitting drops of 50 microliters containing 6-7 mg/ml protein, 0.3 mM EDTA, 15 mM dithiothreitol, 10% (mass/vol.) poly(ethylene glycol) 6000 and 0.01% NaN3 in 0.1 M sodium acetate were equilibrated by vapour diffusion at 20 degrees C against a reservoir of 10-20 mg solid dithiothreitol]. X-ray diffraction data of the crystals were complete to 93.8% at 0.21 nm resolution and showed that [SeMet]HMBS and native HMBS crystallise isomorphously. A difference Fourier map using FSeMet-Fnative and phases derived from the native structure, which has recently been determined independently by multiple isomorphous replacement, showed positive difference peaks centered at or close to where the sulphur atoms of the Met side chains appear in the native structure. In addition, paired positive/negative peaks in the difference map near the cofactor of HMBS indicate conformational differences in the active site, probably due to differences in the state of oxidation of the cofactor in the two crystalline samples.

Amino Acids↗