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Biomedical subjects

N Fox

Publications and source records attributed to N Fox.

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

Empowering research: statistical power in general practice research.

BACKGROUND: Statistical power is a measure of the extent to which a study is capable of discerning differences or associations which exist within the population under investigation, and is of critical importance whenever a hypothesis is tested by statistics. Conventionally, studies should reach a power level of 0.8, such that four times out of five a false null hypothesis will be rejected by a study. Statistical power may most easily be increased by increasing sample size. OBJECTIVE: We aimed to assess the level of statistical power of general practice research. METHODS: A total of 1422 statistical tests in 85 quantitative original papers in the British Journal of General Practice were analysed for statistical power. RESULTS: The median power of tests analysed was 0.71, representing a slightly greater than two-thirds likelihood of rejecting false null hypotheses. Of 85 studies, 37 (44%) attained power of 0.8 or more. Ten studies had power of more than 0.99 suggesting 'over-powering'. Twenty-one of the papers surveyed (25%) had a likelihood of gaining significant results poorer than that obtained by tossing a coin when a null hypothesis is false. CONCLUSION: While achieving higher power than studies in similar surveys of other disciplines, the power of general practice research falls short of the 0.8 convention. Adequate power is essential so that effects which exist are not missed. Recommendations are made concerning power calculations prior to the start of research and reporting of results in journal articles.

Bias↗
PubMed1997

Program of All-inclusive Care for the Elderly (PACE): an innovative model of integrated geriatric care and financing.

OBJECTIVES: The Program of All-inclusive Care for the Elderly (PACE) is a long-term care delivery and financing innovation. A major goal of PACE is prevention of unnecessary use of hospital and nursing home care. SETTING: PACE serves enrollees in day centers and clinics, their homes, hospitals and nursing homes. Beginning at On Lok in San Francisco, the PACE model has been successfully replicated across the country. In 1995, PACE was fully operational in 11 cities in nine states. PARTICIPANTS: To enroll in PACE, a person must be 55 years of age or older, be certified by the state as eligible for care in a nursing home and live in the program's defined geographical catchment area. PACE participants are ethnically diverse. In 1995, the average PACE enrollee was 80.0 years old and had an average of 7.8 medical conditions and 2.7 dependencies in Activities of Daily Living. A significant number have bladder incontinence (55%). Many enrollees (39%) live alone in the community, and 14% have no means of informal support. INTERVENTION: Medicare and Medicaid waivers allow delivery of services beyond the usual Medicare and Medicaid benefits. The PACE service delivery system is comprehensive, uses an interdisciplinary team for care management, and integrates primary and specialty medical care. PACE receives monthly capitation payments from Medicare and Medicaid. Patients ineligible for Medicaid pay privately. RESULTS: Outcomes of PACE programs have been positive. There has been steady census growth, good consumer satisfaction, reduction in use of institutional care, controlled utilization of medical services, and cost savings to public and private payers of care, including Medicare and Medicaid. However, starting up a PACE program requires substantial time and capital, and the model has not yet attracted large numbers of older middle income adults. CONCLUSION: The growing number of older people in the United States challenges healthcare providers and policy makers alike to provide high quality care in an environment of shrinking resources. The PACE model's comprehensiveness of health and social services, its cost-effective coordinated system of care delivery, and its method of integrated financing have wide applicability and appeal.

Aged↗
PubMed1996

Thrombopoietin stimulates colony-forming unit-megakaryocyte proliferation and megakaryocyte maturation independently of cytokines that signal through the gp130 receptor subunit.

Thrombopoietin (Tpo), the ligand for the c-Mpl receptor, is a major regulator of megakaryopoiesis. Treatment of mice with Tpo raises the platelet count fourfold within a few days. Conversely, c-mpl knock-out mice have platelet counts that are 15% that of normal. The subunit structure of the c-Mpl receptor is not fully understood. Some cytokines that stimulate megakaryopoiesis (IL-6, IL-11, leukemia inhibitory factor, and oncostatin M) bind to receptors that use gp130 as a signal transduction subunit. For these reasons, we determined whether gp130 function was required for Tpo-induced signal transduction. Murine marrow cells were cultured in semi-solid media in the presence of Tpo or IL-3, with or without a neutralizing anti-gp130 monoclonal antibody (RX187) or a soluble form of c-Mpl receptor (soluble Mpl) that blocks Tpo bioactivity, and the numbers of colony-forming unit-megakaryocyte (CFU-Meg) colonies were counted on day 5. Murine marrow cells were also cultured in suspension under serum-free conditions for 5 days, and megakaryocyte DNA content was measured by flow cytometry, as an index of nuclear maturation. The addition of RX187 did not block Tpo-induced CFU-Meg colony growth nor CFU-Meg nuclear maturation in suspension culture. However, IL-3-induced CFU-Meg colony growth and megakaryocyte nuclear maturation decreased in the presence of RX187. Soluble Mpl completely ablated Tpo-induced CFU-Meg growth, and partially blocked IL-3-stimulated CFU-Meg growth. Thus the effects of Tpo on megakaryopoiesis in vitro do not depend on cytokines that signal through gp130. Furthermore, it is unlikely that gp 130 serves as a beta chain for the c-Mpl receptor, as Tpo signalling is unimpaired in the presence of RX187. In contrast, the effects of IL-3 on CFU-Meg growth are mediated in part through Tpo and through gp130-signalling cytokines.

Animals↗
PubMed1996

Do dentists refer orthodontic patients inappropriately?

One concern to both providers and consumers of orthodontic treatment is the length of new patient consultation waiting lists. A possible reason for the excessive length of these lists could be unnecessary referral of patients. This research project aimed to identify whether inappropriate referrals for new patient orthodontic consultations were a significant problem. The study was carried out in two FHSA areas in the north of England in two stages. The first part of the study involved an evaluation of GDP referral patterns to orthodontic secondary care providers. In the second part, information on the patients referred by the dentists was collected. We concluded that there was a marked variation in referral rates between the dentists and many patients were referred unnecessarily. Importantly, there was no association between dentists' referral rate and the number of inappropriate referrals made. It appears that referral guidelines for orthodontic treatment are necessary and they should be directed at all general dental practitioners.

Adolescent↗
PubMed1996

Transgenic model for the discovery of novel human secretory non-pancreatic phospholipase A2 inhibitors.

Transgenic mice were created which overexpress human secretory non-pancreatic phospholipase A2 (sPLA2) pansomatically as a potential disease and drug-testing model. The mice were produced using a DNA construct in which the inducible mouse metallothionein gene promoter drives expression of a human sPLA2 minigene. High levels of sPLA2 were detected in several tissues by immunofluorescence localization. Expression in the testes caused hypospermia and male infertility. Circulating catalytically active sPLA2 could be induced to levels observed in patients undergoing a systemic inflammatory response but had no detectable effect on the mice. Therefore, these results suggest that sPLA2 hyperphospholipasemia alone may have only limited pathophysiological consequences. We further show that 3-[3-acetamide-1-benzyl-2-ethylindolyl-5-oxy]propane phosphonic acid LY311727), a potent new inhibitor of phospholipase A2 catalysis developed by our group, dramatically suppresses the circulating enzyme activity in these animals whereas 3-[3-acetamide-1-benzyl-2-propylindolyl-5-oxy]propane phosphonic acid (LY314024), a substantially less potent LY311727 analog, is without effect. These later results thus motivate the further development of this compound as a potential new therapeutic agent and valuable research tool.

Animals↗
PubMed1996

The effect of thrombopoietin on the proliferation and differentiation of murine hematopoietic stem cells.

In this study, we explored whether thrombopoietin (Tpo) has a direct in vitro effect on the proliferation and differentiation of long-term repopulating hematopoietic stem cells (LTR-HSC). We previously reported a cell separation method that uses the fluorescence-activated cell sorter selection of low Hoescht 33342/low Rhodamine 123 (low Ho/low Rh) fluorescence cell fractions that are highly enriched for LTR-HSC and can reconstitute lethally irradiated recipients with fewer than 20 cells. Low Ho/low Rh cells clone with high proliferative potential in vitro in the presence of stem cell factor (SCF) + interleukin-3 (IL-3) + IL-6 (90% to 100% HPP-CFC). Tpo alone did not induce proliferation of these low Ho/low Rh cells. However, in combination with SCF or IL-3, Tpo had several synergistic effects on cell proliferation. When Tpo was added to single growth factors (either SCF or IL-3 or the combination of both), the time required for the first cell division of low Ho/low Rh cells was significantly shortened and their cloning efficiency increased substantially. Moreover, the subsequent clonal expansion at the early time points of culture was significantly augmented by Tpo. Low Ho/low Rh cells, when assayed in agar directly after sorting, did not form megakaryocyte colonies in any growth condition tested. Several days of culture in the presence of multiple cytokines were required to obtain colony-forming units-megakaryocyte (CFU-Mk). In contrast, more differentiated, low Ho/high Rh cells, previously shown to contain short-term repopulating hematopoietic stem cells (STR-HSC), were able to form megakaryocyte colonies in agar when cultured in Tpo alone directly after sorting. These data establish that Tpo acts directly on primitive hematopoietic stem cells selected using the Ho/Rh method, but this effect is dependent on the presence of pluripotent cytokines. These cells subsequently differentiate into CFU-Mk, which are capable of responding to Tpo alone. Together with the results of previous reports of its effects on erythroid progenitors, these results suggest that the effects of Tpo on hematopoiesis are greater than initially anticipated.

Animals↗
PubMed1996

Oral fluconazole compared with bladder irrigation with amphotericin B for treatment of fungal urinary tract infections in elderly patients.

Fungal urinary tract infections are increasingly prevalent in the elderly in acute and chronic care settings. This randomized trial compares the efficacy and safety of oral fluconazole with the efficacy and safety of bladder irrigation with amphotericin B for treatment of funguria (> or = 10,000 cfu/mL of urine) in 109 hospitalized elderly patients. A second treatment course was given for persistent funguria. Indwelling bladder catheters were present in 69% of the patients. While Candida albicans was the predominant isolate from catheterized patients, C. albicans, Candida tropicalis, and Torulopsis glabrata were recovered from noncatheterized patients. Two days after completion of treatment, funguria was eradicated in 96% of the patients treated with amphotericin B and 73% of those treated with fluconazole (P < .05). At 1 month after study enrollment, the mortality rate associated with all causes was greater among patients who were treated with amphotericin B bladder irrigation than among those who received oral fluconazole therapy (41% vs. 22%, respectively; P < .05); this finding suggests that local therapy may be associated with poorer survival. The proportion of patients without funguria at 1 month after study enrollment was similar in the two treatment groups (84%, amphotericin B group; 80%, fluconazole group). A few minor and mild adverse events occurred.

Administration, Oral↗
PubMed1996

Factors influencing the uptake of orthodontic treatment.

The aim of this investigation was to evaluate the factors that influenced the uptake of orthodontic treatment for patients who were referred for orthodontic treatment to two types of orthodontic treatment provider; a fee per item and hospital service. The following data were collected: (i) basic demographic data; (ii) the need for orthodontic treatment as measured by IOTN; and (iii) the outcome of the consultation. The data analysis with logistic regression revealed that the following variables had a predictive effect on the uptake of treatment: (i) the need for orthodontic treatment; and (ii) the patient's gender. Most of the patients that were referred and accepted for treatment had a definite need for orthodontic treatment.

Adolescent↗
PubMed1996

Massage therapy reduces anxiety and enhances EEG pattern of alertness and math computations.

Twenty-six adults were given a chair massage and 24 control group adults were asked to relax in the massage chair for 15 minutes, two times per week for five weeks. On the first and last days of the study they were monitored for EEG, before, during and after the sessions. In addition, before and after the sessions they performed math computations, they completed POMS Depression and State Anxiety Scales and they provided a saliva sample for cortisol. At the beginning of the sessions they completed Life Events, Job Stress and Chronic POMS Depression Scales. Group by repeated measures and post hoc analyses revealed the following: 1) frontal delta power increased for both groups, suggesting relaxation; 2) the massage group showed decreased frontal alpha and beta power (suggesting enhanced alertness); while the control group showed increased alpha and beta power; 3) the massage group showed increased speed and accuracy on math computations while the control group did not change; 4) anxiety levels were lower following the massage but not the control sessions, although mood state was less depressed following both the massage and control sessions; 5) salivary cortisol levels were lower following the massage but not the control sessions but only on the first day; and 6) at the end of the 5 week period depression scores were lower for both groups but job stress score were lower only for the massage group.

Adult↗
PubMed1995

Thrombopoietin, the Mp1 ligand, is essential for full megakaryocyte development.

The development of megakaryocytes (MKs) from their marrow precursors is one of the least understood aspects of hematopoiesis. Current models suggest that early-acting MK colony-stimulating factors, such as interleukin (IL) 3 or c-kit ligand, are required for expansion of hematopoietic progenitors into cells capable of responding to late-acting MK potentiators, including IL-6 and IL-11. Recently, the Mp1 ligand, or thrombopoietin (Tpo), has been shown to display both MK colony-stimulating factor and potentiator activities, at potencies far greater than that of other cytokines. In light of these findings, we tested the hypothesis that Tpo is absolutely necessary for MK development. In this report we demonstrate that neutralizing the biological activity of Tpo eliminates MK formation in response to c-kit ligand, IL-6, and IL-11, alone and in combination, but that these reagents only partially reduce MK formation in the presence of combinations of cytokines including IL-3. However, despite the capacity of IL-3 to support the proliferation and initial stages of MK differentiation, elimination of Tpo prevents the full maturation of IL-3-induced MK. These data indicate that two populations of MK progenitors can be identified: one that is responsive to IL-3 but can fully develop only in the presence of Tpo and a second that is dependent on Tpo for both proliferation and differentiation. Thus, our results strongly suggest that Tpo is the primary regulator of MK development and platelet production.

Animals↗
PubMed1995

Amyloid formation in response to beta cell stress occurs in vitro, but not in vivo, in islets of transgenic mice expressing human islet amyloid polypeptide.

BACKGROUND: Human, but not mouse, islet amyloid polypeptide (IAPP) is amyloidogenic. Transgenic mice overexpressing human IAPP in the beta cells of the islets of Langerhans should be useful in identifying factors important for the deposition of IAPP as insoluble amyloid fibrils. MATERIALS AND METHODS: Transgenic mice expressing human IAPP were examined using several experimental models for the production of persistent hyperglycemia, as well as for the overstimulation and/or inhibition of beta cell secretion. Obesity was induced by aurothioglucose. Persistent hyperglycemia was produced by long-term administration of glucocorticosteroids or by partial pancreatectomy. Inhibition of normal beta cell exocytosis by diazoxide administration, with or without concurrent dexamethasone injections, was carried out to increase crinophagy of secretory granules. The human IAPP gene was also introduced into the ab and ob mouse models for diabetes. Finally, isolated islets cultivated in vitro at high glucose concentration were also examined. RESULTS: No amyloid deposits were found in the pancreata of any of the animals, either by light microscopy after Congo red staining or by electron microscopy after immunogold labeling with antibodies specific for human IAPP. Aurothioglucose treatment resulted in increased numbers of granules in the beta cell and the appearance of large lysosomal bodies without amyloid. However, islets from db and ob mice expressing human IAPP cultivated in vitro in the presence of glucocorticosteroid and/or growth hormone, were found to contain extracellular amyloid deposits reacting with antibodies to human IAPP. CONCLUSIONS: Oversecretion of human IAPP or increased crinophagy are not sufficient for amyloid formation. This indicates that other factors must influence amyloid deposition; one such factor may be the local clearance of IAPP.

Amyloid↗
PubMed1993

Human islet amyloid polypeptide transgenic mice as a model of non-insulin-dependent diabetes mellitus (NIDDM).

To model islet amyloidogenesis in NIDDM and explore the glucoregulatory role of islet amyloid polypeptide (IAPP), we have created transgenic mice containing a rat insulin-I promoter-human IAPP fusion gene. Expression of human IAPP was localized to the islets of Langerhans, anterior pituitary and brain in transgenic animals; blood IAPP levels were elevated 5-fold while fasting glucose levels remained normal. Amyloid deposits have not been detected in transgenic islets suggesting that other co-existing abnormalities in NIDDM may be required for the formation of islet amyloid. These animals provide a unique model for exploring this hypothesis and other proposed functions of IAPP.

Amyloid↗
PubMed1993

Guidelines for the recording and quantitative analysis of electroencephalographic activity in research contexts.

Developments in technologic and analytical procedures applied to the study of brain electrical activity have intensified interest in this modality as a means of examining brain function. The impact of these new developments on traditional methods of acquiring and analyzing electroencephalographic activity requires evaluation. Ultimately, the integration of the old with the new must result in an accepted standardized methodology to be used in these investigations. In this paper, basic procedures and recent developments involved in the recording and analysis of brain electrical activity are discussed and recommendations are made, with emphasis on psychophysiological applications of these procedures.

Action Potentials↗
PubMed1993

Tissue-specific and beta-adrenergic regulation of the mitochondrial uncoupling protein gene: control by cis-acting elements in the 5'-flanking region.

Uncoupling protein (UCP) gene expression is tightly restricted to thermogenic brown adipocytes and is rapidly activated by norepinephrine released after cold exposure. To identify cis-acting regulatory elements controlling this gene, a region encompassing 4.5 kilobases of DNA upstream of the transcription start site was analyzed using hybrid UCP-chloramphenicol acetyltransferase reporter gene constructs. Evidence for the presence of both tissue-specific and beta-adrenergic response elements in this 4.5-kilobase region was obtained by comparing the expression of these reporter genes in transfected brown adipocytes (in vitro differentiated), brown preadipocytes, white adipocytes, and Chinese hamster ovary (CHO) cells and from experiments in transgenic animals. Deletion analyses in transfected cells indicated that the minimal region exhibiting promoter activity and tissue specificity is located between -157 and -57 base pairs (bp). A 211-bp activator element located between -2494 and -2283 bp was necessary for full expression in brown adipocytes. This element also activated expression of the homologous -157-bp promoter and expression of a heterologous promoter in both brown adipocytes and CHO cells. A second region, downstream of the activator and possibly located between positions -400 and -157 bp, inhibited the UCP promoter in CHO cells. In mice transgenic for a chloramphenicol acetyltransferase reporter gene containing these elements, expression was both tissue specific and regulatable by environmental temperature changes. These results indicate that both positive and negative cis-acting elements participate in the regulation of UCP gene expression.

Adipose Tissue, Brown↗
PubMed1992

Hibernoma formation in transgenic mice and isolation of a brown adipocyte cell line expressing the uncoupling protein gene.

Transgenic mice were produced containing the adipocyte-specific regulatory region from the adipocyte P2 (aP2) gene linked to the simian virus 40 transforming genes. Most of the transgenic mice developed brown fat tumors (hibernomas) in their interscapular brown adipose tissue. Hibernoma formation was noticeable in some of the mice as early as 1 day after birth and most of the mice developed very large tumors by 1 month of age. All of the tumor tissue expressed the brown fat-specific uncoupling protein (UCP) gene as well as the aP2 gene. Several of the tumors have been used to establish cultured cell lines and at least one of these lines can be induced to differentiate into brown adipocytes. The cultured adipocytes express mRNA for UCP upon stimulation with N6,O2'-dibutyryladenosine 3',5'-cyclic monophosphate, norepinephrine, isoproterenol or D7114, a beta 3 adrenergic agonist. Thus, regulation of the key thermogenic gene UCP can now be studied in an established cell line.

Adipose Tissue, Brown↗
PubMed1991

The cost of hospitalization for the late complications of diabetes in the United States.

Estimates of the cost of diabetes should take into account the development of complications. Patient records identified from the 1987 National Hospital Discharge Survey were used to evaluate the risk of hospitalization due to late complications. Hospitalization for diabetic nephropathy reached a peak of 6.74/1000 between the ages of 45 and 54 years, compared to 0.14 to 1.80/1000 in controls. Diabetic patients less than or equal to 45 years of age were 46 times more likely to be hospitalized due to neuropathy. The risk of cardiovascular complications is high, with a greater incidence of arterial than venous disorders. Diabetic patients were 22 times more likely to be admitted for skin ulcers/gangrene, 15 times more likely due to peripheral vascular disease, and 10 times due to atherosclerosis. The risk of cerebrovascular accident and heart disease was 6 to 10 times greater in diabetic patients. Seventy-five per cent of diabetic cardiovascular disorders are myocardial infarction or chronic ischaemia. Hospitalization from renal complications occurs at younger ages than in the general population. Ophthalmic complications increase with age. Diabetic complications account for 2% of the total hospital admissions in the US in 1987. The total cost of the treatment of late diabetic complications was estimated at +5091 million (cardiovascular 74%; renal diseases 10%; nephropathy 3.6%; ophthalmic disorders 1.5%; other unspecified diseases 10%).

Age Factors↗