Biomedical subjects

G Oster

Publications and source records attributed to G Oster.

At least 55 records · Page 3Linked to original sources

PubMed1998

Force generation in RNA polymerase.

RNA polymerase (RNAP) is a processive molecular motor capable of generating forces of 25-30 pN, far in excess of any other known ATPase. This force derives from the hydrolysis free energy of nucleotides as they are incorporated into the growing RNA chain. The velocity of procession is limited by the rate of pyrophosphate release. Here we demonstrate how nucleotide triphosphate binding free energy can rectify the diffusion of RNAP, and show that this is sufficient to account for the quantitative features of the measured load-velocity curve. Predictions are made for the effect of changing pyrophosphate and nucleotide concentrations and for the statistical behavior of the system.

Adenosine Triphosphatases↗

PubMed1998

Strong precursor-pore interactions constrain models for mitochondrial protein import.

Mitochondrial precursor proteins are imported from the cytosol into the matrix compartment through a proteinaceous translocation pore. Import is driven by mitochondrial Hsp70 (mHsp70), a matrix-localized ATPase. There are currently two postulated mechanisms for this function of mHsp70: 1) The "Brownian ratchet" model proposes that the precursor chain diffuses within the pore, and that binding of mHsp70 to the lumenal portion of the chain biases this diffusion. 2) The "power stroke" model proposes that mHsp70 undergoes a conformational change that actively pulls the precursor chain through the pore. Here we formulate these two models quantitatively, and compare their performance in light of recent experimental evidence that precursor chains interact strongly with the walls of the translocation pore. Under these conditions the simulated Brownian ratchet is inefficient, whereas the power stroke mechanism seems to be a plausible description of the import process.

Adenosine Triphosphatases↗

PubMed1998

The economics of hypercholesterolemia and lipid-lowering therapy: a brief historical tour.

The first formal economic evaluation of a lipid-lowering intervention was conducted almost 20 years ago. The field exploded in the mid-1980s following the publication of findings from the Lipid Research Clinics Coronary Primary Prevention Trial (LRC-CPPT), in which the bile-acid sequestrant, cholestyramine, was reported to reduce the incidence of coronary artery disease in adults with significant elevations in cholesterol. Almost all of the early pharmacoeconomic studies that followed focused on this agent. Later in the decade, the introduction of lovastatin, the first 3-hydroxy-3 methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor (or "statin"), revolutionized the treatment of hypercholesterolemia, as it was significantly more effective than earlier agents (as were the other statins that followed it). Pharmacoeconomic studies of the statins generally have reported that, despite their higher cost, they are significantly more cost-effective than bile acid sequestrants. Recent long-term clinical trials, such as the West of Scotland Coronary Prevention Study (WOSCOPS) and the Scandinavian Simvastatin Survival Study (4S), have provided firm evidence of the benefits of the statins in both the primary and secondary prevention of coronary artery disease. Formal economic evaluations were incorporated into most of these end-point studies-in contrast to morbidity and mortality trials of earlier lipid-lowering agents-and results from these evaluations are just now becoming available. The availability of primary economic data derived directly from large-scale, long-term clinical trials raises important questions about the future role of modeling in this area.

Journal Article↗

PubMed1998

Predictors of a medical-offset effect among patients receiving antidepressant therapy.

OBJECTIVE: Characteristics of patients receiving antidepressant therapy were examined to identify factors that may be associated with a medical-offset effect. METHOD: In a retrospective study, the authors analyzed claims data from a large health insurer in New England. The study subjects included 1,661 persons initiating treatment for depression with selective serotonin reuptake inhibitors or tricyclic antidepressants between July 1991 and June 1993. RESULTS: Patients with anxiety disorders, coronary heart disease, cancer, and chronic fatigue syndrome and those remaining on their initial regimens of antidepressant therapy for at least 6 months were more likely to experience significant reductions in the costs of medical care services. The number of visits to mental health providers had no effect on the costs of medical services. CONCLUSIONS: Specific comorbid conditions and sustained use of antidepressant drugs may be associated with a medical-offset effect for patients receiving treatment for depression.

Adult↗

PubMed1998

Potential economic benefits of lower-extremity amputation prevention strategies in diabetes.

OBJECTIVE: To estimate the potential economic benefits of selected strategies from published literature--educational interventions, multidisciplinary clinics, and insurance coverage for therapeutic shoes--to reduce the incidence of lower-extremity amputation among individuals with diabetes. RESEARCH DESIGN AND METHODS: We developed a model to estimate the expected incidence and associated costs of lower-extremity amputation in a hypothetical cohort of 10,000 people with diabetes. Prevention strategies were assumed to be targeted at individuals with a history of foot ulcer, and benefits were estimated over a period of 3 years. RESULTS: The total potential economic benefits (discounted at 5%) of strategies to reduce amputation risk ranged from $2.0 to $3.0 million ($2,900 to $4,442 per person with a history of foot ulcer) over 3 years. Benefits were highest for educational interventions. Most benefits were found to accrue among individuals aged > or = 70 years. CONCLUSIONS: Strategies to reduce the risk of lower-extremity amputation may generate substantial economic benefits and should be a standard component of routine diabetes care. Benefits may best be achieved through a partnership of government, private payers, health care service providers and producers, and individuals with diabetes.

Age Factors↗

PubMed1997

A cisternal maturation mechanism can explain the asymmetry of the Golgi stack.

Morphological data suggest that Golgi cisternae form at the cis-face of the stack and then progressively mature into trans-cisternae. However, other studies indicate that COPI vesicles transport material between Golgi cisternae. These two observations can be reconciled by assuming that cisternae carry secretory cargo through the stack in the anterograde direction, while COPI vesicles transport Golgi enzymes in the retrograde direction. This model provides a mechanism for cisternal maturation. If Golgi enzymes compete with one another for packaging into COPI vesicles, we can account for the asymmetric distribution of enzymes across the stack.

Animals↗

PubMed1997

Protein turbines. I: The bacterial flagellar motor.

The bacterial flagellar motor is driven by a flux of ions between the cytoplasm and the periplasmic lumen. Here we show how an electrostatic mechanism can convert this ion flux into a rotary torque. We demonstrate that, with reasonable parameters, the model can reproduce many of the experimental measurements.

Bacterial Physiological Phenomena↗

PubMed1996

Use of terfenadine and contraindicated drugs.

OBJECTIVE: To assess changes in concurrent use of products containing terfenadine and contraindicated macrolide antibiotics (erythromycin, clarithromycin, troleandomycin) and imidazole antifungals (ketoconazole, itraconazole) following reports of serious drug-drug interactions and changes in product labeling. DESIGN: Retrospective review of computerized pharmacy claims. SETTING: A large health insurer in New England. PATIENTS: Health plan members with 1 or more paid pharmacy claims for products containing terfenadine between January 1990 and June 1994. MAIN OUTCOME MEASURES: Among persons with paid claims for terfenadine in any given month, percentage with a prescription for any contraindicated drug that alternatively was dispensed on the same day as ("same-day dispensing") or had therapy days that overlapped those of ("overlapping use") a prescription for terfenadine. RESULTS: Concurrent use of terfenadine and contraindicated drugs declined over the study period. The rate of same-day dispensing declined by 84% from an average of 2.5 per 100 persons receiving terfenadine in 1990 to 0.4 per 100 persons during the first 6 months of 1994, while the rate of overlapping use declined by 57% (from 5.4 to 2.3 per 100 persons). Most cases involved erythromycin. CONCLUSIONS: Despite substantial declines following reports of serious drug-drug interactions and changes in product labeling, concurrent use of terfenadine and contraindicated macrolide antibiotics and imidazole antifungals continues to occur.

Anti-Bacterial Agents↗

PubMed1996

Cholesterol-reduction intervention study (CRIS): a randomized trial to assess effectiveness and costs in clinical practice.

BACKGROUND: The 1988 US National Cholesterol Education Program Expert Panel Report recommended initial treatment with niacin or bile acid sequestrants, followed by other agents if needed, to lower low-density lipoprotein cholesterol (LDL-C) levels in hypercholesterolemic patients who require drug therapy. It is unknown how the effectiveness and costs of such an approach ("stepped care") compare in typical clinical practice to those of initial therapy with lovastatin. PATIENTS AND METHODS: We randomly assigned 612 patients, aged 20 to 70 years, who met 1988 National Cholesterol Education Program guidelines for drug treatment of elevated LDL-C level and had not previously used cholesterol-lowering medication, to either a stepped-care regimen or initial therapy with lovastatin (both n=306). The study, conducted at Southern California Kaiser Permanente, was designed to approximate typical practice: provider compliance with treatment plans was encouraged but not enforced, and patients paid for medication as they customarily would. RESULTS: At 1 year, the decline in mean LDL-C level was significantly greater among patients assigned to initial treatment with lovastatin (22% vs 15% for stepped care; P<.001), as was the number who attained goal LDL-C level (</= 4.14 mmol/L [</= 160 mg/dL], or </= 3.36 mmol/L [</= 130 mg/dL] if coronary heart disease or two or more risk factors were present) (40% vs 24%; P<.001). The increase in mean high-density lipoprotein cholesterol levels was significantly greater in the stepped-care group, however (8% vs 1% for lovastatin; P<.001). Patients who were randomized to stepped care were more likely to report substantial bother caused by side effects (30% vs 16% for lovastatin; P<.001) and discontinuation of therapy at 1 year (28% vs 18%, respectively; P<.01). Costs of care were $333 higher per patient in the lovastatin group ($786 vs $453; P<.001). CONCLUSIONS: A stepped-care regimen beginning with niacin is less costly than initial therapy with lovastatin, but also less effective in lowering LDL-C level. While it is more effective in increasing high-density lipoprotein cholesterol levels, the tolerability of such a regimen may be a problem.

Adult↗

PubMed1996

Estimated effects of reducing dietary saturated fat intake on the incidence and costs of coronary heart disease in the United States.

OBJECTIVES: To estimate the effects of reducing dietary saturated fat intake on the incidence and economic costs of coronary heart disease (CHD) in the United States. DESIGN: Modeling techniques and data from secondary sources, including the Framingham Heart Study and the second and third National Health and Nutrition Examination Surveys, were used to estimate the effects on CHD incidence and associated costs of reducing dietary saturated fat intake as a percent of total energy by one to three percentage points. SUBJECTS: Persons aged 35 to 69 years who have total cholesterol levels of 5.17 mmol/L or higher and are currently free of CHD. RESULTS: Approximately 3 million first-time coronary events are estimated to occur over a 10-year period among persons with total cholesterol levels exceeding 5.17 mmol/L. Reducing saturated fat intake by one to three percentage points would reduce CHD incidence by 32,000 to 99,700 events and yield combined savings in medical expenditures and lost earnings ranging from $4.1 to $12.7 billion over 10 years (estimates in 1993 US dollars). CONCLUSION: Population-based interventions to encourage Americans to reduce dietary intake of saturated fat may prevent tens of thousands of cases of CHD and save billions of dollars in related costs.

Adult↗

PubMed1996

Cell motility driven by actin polymerization.

Certain kinds of cellular movements are apparently driven by actin polymerization. Examples include the lamellipodia of spreading and migrating embryonic cells, and the bacterium Listeria monocytogenes, that propels itself through its host's cytoplasm by constructing behind it a polymerized tail of cross-linked actin filaments. Peskin et al. (1993) formulated a model to explain how a polymerizing filament could rectify the Brownian motion of an object so as to produce unidirectional force (Peskin, C., G. Odell, and G. Oster. 1993. Cellular motions and thermal fluctuations: the Brownian ratchet. Biophys. J. 65:316-324). Their "Brownian ratchet" model assumed that the filament was stiff and that thermal fluctuations affected only the "load," i.e., the object being pushed. However, under many conditions of biological interest, the thermal fluctuations of the load are insufficient to produce the observed motions. Here we shall show that the thermal motions of the polymerizing filaments can produce a directed force. This "elastic Brownian ratchet" can explain quantitatively the propulsion of Listeria and the protrusive mechanics of lamellipodia. The model also explains how the polymerization process nucleates the orthogonal structure of the actin network in lamellipodia.

Actins↗

PubMed1996

A multinational economic evaluation of rhDNase in the treatment of cystic fibrosis.

Economic evaluations of pharmaceuticals are increasingly being conducted in conjunction with randomized phase III clinical trials to meet the demand for pharmacoeconomic data when new products are launched. While the need for such data is often global, the trials in which relevant information may be collected are often conducted in only one or a limited number of countries. A critical issue is how data from pivotal clinical trials in one setting can serve as the basis for pharmacoeconomic evaluations in others. We address this issue and report on four economic evaluations that we undertook in conjunction with a recent U.S. phase III clinical trial of recombinant human deoxyribonuclease (rhDNase), which is used to improve pulmonary function in patients with cystic fibrosis (CF). The objective of these evaluations was to estimate the potential impact of rhDNase therapy in France, Germany, Italy, and the United Kingdom on the direct costs of medical care for the treatment of respiratory tract infections (RTIs) in patients with CF. Analyses of economic impact were undertaken both with and without adjustment for differences in practice patterns between the United States and the countries of interest. Our findings suggest that rhDNase therapy may reduce the cost of RTI-related care by between US$600 and US$1,100 over a 24-week period; the cost of rhDNase is not included in these figures, as a price was unavailable when our analyses were undertaken. Despite methodologic challenges, economic evaluations that meet the information needs of decision makers in diverse countries can nonetheless be undertaken in conjunction with phase III clinical trials.

Clinical Trials, Phase III as Topic↗

PubMed1996

The benefits and risks of over-the-counter availability of nicotine polacrilex ("nicotine gum").

Nicotine polacrilex ("nicotine gum") is effective in helping persons to quit smoking cigarettes. Because many persons try to quit without formal assistance, it may be an appropriate product for over-the-counter (OTC) purchase. Some smokers, however, might use such a product in lieu of more effective methods of cessation, and still others might use it to cope with enforced periods of nicotine abstinence (eg, at the work place) and thereby delay their decision to quit. The study's objective was to assess the public health benefits and risks of OTC availability of nicotine gum. A Markov model was developed and used to contrast two alternative policy scenarios: one in which nicotine gum was assumed to remain available only by prescription, and another in which it was assumed to be made available for OTC purchase. Various data sources were used to estimate the model, including the Health Promotion and Disease Prevention Supplement to the 1991 National Health Interview Survey and the 1986 Adult Use of Tobacco Survey. Primary outcome measures included the numbers of persons who would try to quit smoking, the numbers who would use various methods of smoking cessation, including OTC nicotine gum, and the numbers of current adult smokers who would be abstinent at the end of 10 years. Findings suggest that an average of 3 million persons each year would use OTC nicotine gum. As a consequence of OTC availability, an additional 450,000 smokers would be abstinent at the end of 10 years. These results are sensitive to assumptions regarding the effectiveness of OTC nicotine gum, as well as to the effect of OTC availability on the use of other methods of smoking cessation. The number of persons who would quit smoking, however, increases under a fairly wide range of assumptions. Over-the-counter availability of nicotine gum may confer significant public health benefits.

Adolescent↗

PubMed1995

Cost-effectiveness of enoxaparin vs low-dose warfarin in the prevention of deep-vein thrombosis after total hip replacement surgery.

BACKGROUND: Enoxaparin sodium, a low-molecular-weight heparin, was recently approved for use in the United States to prevent deep-vein thrombosis after total hip replacement surgery. Its cost-effectiveness relative to prophylaxis with low-dose warfarin sodium is unknown. METHODS: A decision-analytic model was developed to compare two strategies of prophylaxis for deep-vein thrombosis with a strategy of not using prophylaxis in a hypothetical cohort of 10,000 patients undergoing total hip replacement surgery. For each of these strategies, we estimated the expected number of cases of confirmed deep-vein thrombosis or pulmonary embolism, the expected number of thromboembolic deaths, and the expected costs of venous thromboembolic care, including prophylaxis, diagnosis, and treatment. Data were drawn primarily from the published literature. RESULTS: Compared with no prophylaxis, the use of low-dose warfarin would be expected to reduce the number of cases of confirmed deep-vein thrombosis from about 1000 (per 10,000 patients) to 420 and the number of thromboembolic deaths from about 250 to 110. Expected costs of care related to deep-vein thrombosis also would be reduced from approximately $530 to $330 per patient. Prophylaxis with enoxaparin would be expected to reduce further the number of cases of confirmed deep-vein thrombosis and the number of thromboembolic deaths (to 250 and 70, respectively) but increase costs of care by approximately $50 per patient. The cost-effectiveness of enoxaparin (relative to low-dose warfarin) is estimated to be approximately $12,000 per death averted. CONCLUSION: Although enoxaparin is more costly than low-dose warfarin, its cost-effectiveness in total hip replacement compares favorably with that of other generally accepted medical interventions.

Cost-Benefit Analysis↗

PubMed1995

Health-related quality of life in patients with advanced prostate cancer: a multinational perspective.

To explore the value of antiandrogen therapy for advanced prostate cancer, two clinical trials of similar design were recently conducted in six countries throughout Europe. A total of 550 patients with previously untreated metastatic prostate cancer were randomized either to treatment with an antiandrogen or castration. While time to treatment failure, objective tumour response and survival were expected to be similar between study treatments, their effects on health-related quality of life (HRQOL) were expected to differ and were therefore a focus of concern in this trial. To assess these effects, we developed a brief self-administered patient questionnaire covering 10 domains of HRQOL (general health perceptions, pain, emotional well-being, vitality, social functioning, physical capacity, sexual interest, sexual functioning, activity limitation and bed disability), which we translated from English into several other languages. In this paper, we describe the development, content and translation of this survey instrument and report on its reliability and validity in six countries based on data collected for the first 487 patients to complete questionnaires at study entry.

Activities of Daily Living↗

PubMed1995

A randomized trial to assess effectiveness and cost in clinical practice: rationale and design of the Cholesterol Reduction Intervention Study (CRIS).

To compare the effectiveness and costs of two alternative approaches to the treatment of hypercholesterolemia, a prospective randomized trial is being undertaken at Southern California Kaiser Permanente, a large health maintenance organization. Six hundred and twelve patients with postdiet LDL cholesterol (LDL-C) levels in the range of 190-230 mg/dl (or 160-230 mg/dl for those with coronary heart disease or two or more coronary risk factors) were randomized to a stepped-care regimen (initial treatment with niacin followed by other agents if needed) or to initial use of lovastatin, an HMG-CoA reductase inhibitor. All patients are being followed for 1 year. The study seeks to approximate conditions of typical clinical practice: provider compliance with these plans of treatment is encouraged but not enforced and patients pay for medication as they customarily would. Principal outcomes of interest include the proportion of participants who achieve goal LDL-C at one year, the mean change in total cholesterol and LDL-C levels between baseline and the end of follow-up, and the costs of cholesterol-lowering therapy.

Adult↗

PubMed1995

Rotary DNA motors.

Many molecular motors move unidirectionally along a DNA strand powered by nucleotide hydrolysis. These motors are multimeric ATPases with more than one hydrolysis site. We present here a model for how these motors generate the requisite force to process along their DNA track. This novel mechanism for force generation is based on a fluctuating electrostatic field driven by nucleotide hydrolysis. We apply the principle to explain the motion of certain DNA helicases and the portal protein, the motor that bacteriophages use to pump the genome into their capsids. The motor can reverse its direction without reversing the polarity of its electrostatic field, that is, without major structural modifications of the protein. We also show that the motor can be driven by an ion gradient; thus the mechanism may apply as well to the bacterial flagellar motor and to ATP synthase.

Adenosine Triphosphatases↗

PubMed1995

Effects of recombinant human DNase therapy on healthcare use and costs in patients with cystic fibrosis.

OBJECTIVE: To assess the effects of recombinant human DNase (rhDNase) therapy on the cost of treating respiratory tract infections (RTIs) in patients with cystic fibrosis. DESIGN: We prospectively documented the use of healthcare services among 968 patients with cystic fibrosis who participated in a recent Phase III double-blind, multicenter, clinical trial in which patients were assigned randomly to receive either rhDNase 2.5 mg once daily, rhDNase 2.5 mg twice daily, or placebo. All patients were followed for 24 weeks. Data from secondary sources were used to estimate a total cost of RTI-related care (excluding the cost of study therapy) for each trial participant, based on observed levels of resource use. MAIN OUTCOME MEASURES: Number of RTI-related hospital admissions, days of RTI-related outpatient antibiotic therapy (intravenous and oral), and total costs of RTI-related care (excluding the cost of study therapy). RESULTS: Patients randomized to receive rhDNase once daily averaged 0.15 fewer RTI-related hospital admissions (0.41 vs 0.56 for placebo; p < 0.05) and 1.5 fewer days of RTI-related outpatient intravenous antibiotic therapy (2.9 vs 4.4; p < 0.05). Patients randomized to receive rhDNase twice daily had 0.14 fewer hospital admissions (p < 0.01), but no reduction in outpatient intravenous antibiotic therapy. Compared with placebo, the cost of treating RTIs over 24 weeks was $814-1682 less among patients receiving rhDNase. CONCLUSIONS: rhDNase therapy reduced the costs of treating RTIs in patients with cystic fibrosis; assuming once-daily dosing, these savings would offset about one-third of the cost of such therapy.

Anti-Bacterial Agents↗