PubMed Health⌕ Search

Biomedical subjects

G B Chapman

Publications and source records attributed to G B Chapman.

At least 19 recordsLinked to original sources
PubMed2001

Time preferences for the very long term.

Many important decisions concern outcomes delayed by decades or centuries. Whereas some economists have argued that inter-generational discount rates should be lower than intra-generational rates, three experiments found that inter- and intra-generational discount rates were quite similar. Experiment 1 found that discount rates for long delays (30-900 years) were lower than those for shorter delays (1-30 years) but that, holding delay constant, discount rates for outcomes occurring to future generations were similar to those for outcomes occurring to the present generation. Experiment 2 compared inter-generational discount rates for three different types of outcomes and found similar discount rates for saving lives, improving health, and financial benefits. Experiment 3 found similar inter-generational discounting of life-saving programs that benefit people close to or distant from the decision maker. These studies indicate that the discount rate applied to outcomes occurring to future generations depends on the length of the time delay but not on other factors.

Adult↗
PubMed2001

A fallacy of the multiplicative QALY model for low-quality weights in students and patients judging hypothetical health states.

OBJECTIVES: In quality-adjusted life-years (QALY) models, it is customary to weigh life-years with quality of life via multiplication. As a consequence, for positive health states a longer duration has more QALYs than a shorter duration (i.e., longer is better). However, we have found that for poor health states, many prefer to live only a limited amount of time (i.e., longer is worse). Such preferences are said to be maximum endurable time (MET). In the present contribution, the following questions are asked: a) How low does the utility have to be in order for a MET to arise? and b) Do MET preferences occur when patients judge hypothetical health states? METHODS AND RESULTS: We reanalyzed data from 176 students for the hypothetical health states of "living with migraines" and "living with metastasized cancer." For utilities smaller than 0.7 (ranging from 0 to 1), the MET preference rate was larger than 50%. High MET preference rates were also found in two new studies on migraine and esophageal cancer patients, who evaluated hypothetical health states related to their disease. CONCLUSIONS: We discuss the interpretation of the MET preferences and the preference reversal phenomenon. Standard QALY models imply that longer is better. However, we find that more often, longer is worse for poorly evaluated health states. Consider the following question: are 3 years with a weight of 0.3 equally as valuable as 1 year with a weight of 0.9? Our results suggest that the 3-year period may be less valuable because for poor health, many will prefer a 1-year over a 3-year period.

Adult↗
PubMed2001

What counts as a decision? Predictors of perceived decision making.

We examined lay perceptions of what counts as a decision. Eighty-six subjects read 10 scenarios that described clear decisions (e.g., choosing a graduate school), clear "nondecisions" (e.g., an accidental wrong turn), or ambiguous actions (e.g., eating a donut when on a diet or allowing someone else to make the decision). The subjects rated each scenario as to whether the actor had made a decision and also rated six other attributes. The scenarios were rated as clearly illustrating a decision if the actor engaged in a lot of thought and did not act reflexively. Consideration of consequences and having alternatives were moderately related to decision ratings, whereas having self-control problems and the influence of physiological drives showed little relationship with decision ratings. Thus, lay concepts of decision making differ from decision theory in that thoughtful, intentional behavior is more important in defining a decision than are decision theoretic components, such as alternatives and consequences.

Adult↗
PubMed2001

Value for the future and preventive health behavior.

Many everyday decisions require trade-offs between immediate and delayed benefits. Although much research has assessed discounting of delayed outcomes by using hypothetical scenarios, little research has examined whether these discounting measures correspond to real-world behavior. Three studies examined the relationship between scenario measures of time preference and preventive health behaviors that require an upfront cost to achieve a long-term benefit. Responses to time preference scenarios showed weak or no relationship to influenza vaccination, adherence to a medication regimen to control high blood pressure, and adherence to cholesterol-lowering medication. The finding that scenario measures of time preference have surprisingly little relationship to actual behaviors exemplifying intertemporal trade-offs places limits on the applications of time preference research to the promotion of preventive health behavior.

Adult↗
PubMed2000

YC-1, a benzyl indazole derivative, stimulates vascular cGMP and inhibits neointima formation.

The pathobiologic process of arterial stenosis following balloon angioplasty continues to be an enigmatic problem in clinical settings. This research project investigates the ability of YC-1, a benzyl indazole derivative that sensitizes sGC/cGMP, to stimulate endogenous cGMP and attenuate balloon injury-induced neointima (NI) formation in the rat carotid artery. Northern and Western blot analyses revealed enhanced acute expression of iNOS and inducible heme oxygenase (HO-1) mRNA and protein in the injured artery. The contralateral uninjured artery also demonstrated acute HO-1 mRNA and protein induction without detectable iNOS expression. Perivascular application of YC-1 immediately following injury significantly stimulated acute vessel wall cGMP compared to untreated controls. YC-1 treated sections demonstrated significant reduction in NI area (-74%), NI area/medial wall area (-72%), and NI thickness (-76%) 2 weeks post-injury. These results directly implicate YC-1 as a potent new therapeutic agent capable of reducing post-angioplasty stenosis through endogenous CO- and/or NO-mediated, cGMP-dependent processes.

Angioplasty, Balloon↗
PubMed2000

Transmission electron microscope study of bacterial morphotypes on the anterior dorsal surface of human tongues.

The human tongue has been the subject of many cytological and histological studies. When a literature search disclosed no reports of the ultrastructure of the morphotypes of bacteria residing on the tongue's surface, a transmission electron microscope study of ultrathin sections of bacteria obtained by scraping eight human tongues was undertaken. The scrapings from the anterior dorsal tongue surfaces, processed conventionally for electron microscope study, revealed 33-35 different bacterial morphotypes. Several of the morphotypes were unique to a tongue. Morphotype differences were also related to donor characteristics such as smoking, tongue site, location in centrifuge pellet, diet, and medications. The predominant morphotypes were Gram-positive cocci. These preliminary findings suggest that the microbiota of the human tongue and variations in that microbiota, related to physical condition, lifestyle, medications, and dietary preferences, merit more attention from anatomists.

Adult↗
PubMed2000

Physiological cyclic stretch causes cell cycle arrest in cultured vascular smooth muscle cells.

Smooth muscle cells (SMC) are the major cellular component of the blood vessel wall and are continuously exposed to cyclic stretch due to pulsatile blood flow. This study examined the effects of a physiologically relevant level of cyclic stretch on rat aortic vascular SMC proliferation. Treatment of static SMC with serum, platelet-derived growth factor, or thrombin stimulated SMC proliferation, whereas exposure of SMC to cyclic stretch blocked the proliferative effect of these growth factors. The stretch-mediated inhibition in SMC growth was not due to cell detachment or increased cell death. Flow cytometry analysis revealed that cyclic stretch increased the fraction of SMC in the G(0)/G(1) phase of the cell cycle. Stretch-inhibited G(1)/S phase transition was associated with a decrease in retinoblastoma protein phosphorylation and with a selective increase in the cyclin-dependent kinase inhibitor p21, but not p27. These results demonstrate that cyclic stretch inhibits SMC growth by blocking cell cycle progression and suggest that physiological levels of cyclic stretch contribute to vascular homeostasis by inhibiting the proliferative pathway of SMC.

Animals↗
PubMed1999

Occurrence of mast cells within bundles of myelinated and unmyelinated nerves in the rat tongue.

The rat tongue has been the subject of many cytological studies, both purely descriptive and experimental. To assess the suitability of the organ for additional cytological and histological senior research thesis projects, light and transmission electron microscope studies of thin and ultrathin sections, respectively, were conducted. Several samples from the anterior dorsal surface of the tongue of a male rat (Sprague-Dawley) were processed conventionally for light and electron microscope study. About 170 sections, each approximately 1 x 1 mm in area and 1.0 microm thick, collected from 12 adjacent areas, all including the mucosa, of a tongue were studied in the light microscope. Numerous mast cells were observed scattered throughout the submucosal region, adjacent to nerve bundles, blood vessels, and skeletal muscle, and up to six bundles each consisting of many myelinated and unmyelinated nerve processes were seen per section. Single, double, and quadruple myelinated nerve processes were also seen. Several of the multiple, mixed nerve bundles contained a mast cell. Mast cells were not found within the endoneurium or perineurium of exclusively myelinated processes. Ultrathin sections adjacent to the thin sections containing mast cells within the nerve bundles were sought and studied in the transmission electron microscope to confirm the identification of these mast cells. Mast cells occur within bundles containing both myelinated and unmyelinated nerves in the rat tongue, and this is an apparently previously unreported event. Furthermore, no clear evidence has been found in the literature of such specific mast cell distribution in other parts of the animal body. Single, double, and quadruple myelinated nerve processes were noted, but none contained a mast cell.

Animals↗
PubMed1999

Predictors of influenza vaccine acceptance among healthy adults.

BACKGROUND: Previous studies investigating predictors of influenza vaccine acceptance have focused on high-risk patients or health care workers. Few studies have examined flu shot acceptance among healthy adults in workplace settings, even though influenza vaccine is recommended for this group as well. METHODS: Two studies investigated predictors of flu vaccine acceptance in workplace samples of healthy adults. In the first study, 79 university employees were interviewed, while in the second, 435 corporate employees completed a questionnaire. RESULTS: In the first study, flu shot acceptance was predicted by perceived effectiveness of the vaccine (r = 0.36), perceived likelihood of vaccine side effects (r = -0.32), and having received the shot in the previous year (r = 0.25). In the second study, flu shot acceptance was again predicted by perceived effectiveness (r = 0.49), likelihood of side effects (r = -0.31), and previous flu shot (r = 0.66) and was also related to older age (r = 0.10) and to predicted percentage of co-workers who also received the shot (r = 0.24). CONCLUSIONS: The current studies indicate that predictors of vaccine acceptance among healthy adults are similar to those identified in studies of high-risk patient populations and health care workers.

Adolescent↗
PubMed1999

Rationality in medical treatment decisions: is there a sunk-cost effect?

OBJECTIVE: To assess residents' propensity to display the sunk-cost effect, an irrational decision-making bias, in medical treatment decisions; and to compare residents' and undergraduates' susceptibility to the bias in non-medical, everyday behaviors. DESIGN: Cross-sectional, in-person survey. SETTING: Louisiana State University, two locations: Medical Center-Baton Rouge and Main Campus-Psychology Department. PARTICIPANTS: Internal medicine and family practice residents (N = 36, Mdn age = 27) and college undergraduates (N = 40, Mdn age = 20). MEASUREMENTS AND MAIN RESULTS: Residents evaluated medical and non-medical situations that varied the amount of previous investment and whether the present decision maker was the same or different from the person who had made the initial investment. They rated reasons both for continuing the initial decision (e.g., stay with the medication already in use) and for switching to a new alternative (e.g., a different medication). There were two main findings: First, the residents' ratings of whether to continue or switch medical treatments were not influenced by the amount of the initial investment (p's>0.05). Second, residents' reasoning was more normative in medical than in non-medical situations, in which it paralleled that of undergraduates (p's<0.05). CONCLUSIONS: Medical residents' evaluation of treatment decisions reflected good reasoning, in that they were not influenced by the amount of time and/or money that had already been invested in treating a patient. However, the residents did demonstrate a sunk-cost effect in evaluating non-medical situations. Thus, any advantage in decision making that is conferred by medical training appears to be domain specific.

Adult↗
PubMed1999

A multi-attribute model of prostate cancer patient's preferences for health states.

Multi-attribute utility theory (MAUT) provides a way to model decisions involving trade-offs among different aspects or goals of a problem. We used MAUT to model prostate cancer patients' preferences for their own health state and we compared this model to patients' global judgments of health state utility. 57 patients with prostate cancer (mean age = 70) at two Chicago Veterans Administration health clinics were asked to evaluate health states described in terms of five health attributes affected by prostate cancer: pain, mood, sexual function, bladder and bowel function, and fatigue and energy. Each attribute had three levels that were used to form three clinically realistic health state descriptions (A = high, B = moderate, C = low). A fourth personalized health description (P) matched the patient's current health. We first measured patients' preferences using time trade-off (TTO) judgments for the three health states (A, B, and C) and for their own current health state (P). The TTO for the patient's own health state (P) was standardized by comparing it to TTO judgments for states A and C. We next constructed a multi-attribute model using the relative importance of the five attributes. The MAU scores were moderately correlated with the TTO preference judgments for the personalized state (Pearson r = 0.38, N = 57, p < 0.01). Thus, patients' preference judgments are moderately consistent and systematic. MAUT appears to be a potentially feasible method for evaluating preferences of prostate cancer patients and may prove helpful in assisting with patient decision making.

Aged↗
PubMed1998

Flow resistance and drag forces due to multiple adherent leukocytes in postcapillary vessels.

Computational fluid dynamics was used to model flow past multiple adherent leukocytes in postcapillary size vessels. A finite-element package was used to solve the Navier-Stokes equations for low Reynolds number flow of a Newtonian fluid past spheres adhering to the wall of a cylindrical vessel. We determined the effects of sphere number, relative geometry, and spacing on the flow resistance in the vessel and the fluid flow drag force acting to sweep the sphere off the vessel wall. The computations show that when adherent leukocytes are aligned on the same side of the vessel, the drag force on each of the interacting leukocytes is less than the drag force on an isolated adherent leukocyte and can decrease by up to 50%. The magnitude of the reduction depends on the ratio of leukocyte to blood vessel diameter and distance between adherent leukocytes. However, there is an increase in the drag force when leukocytes adhere to opposite sides of the vessel wall. The increase in resistance generated by adherent leukocytes in vessels of various sizes is calculated from the computational results. The resistance increases with decreasing vessel size and is most pronounced when leukocytes adhere to opposite sides of the vessel.

Biophysics↗
PubMed1996

Temporal discounting and utility for health and money.

In 3 experiments, choices for hypothetical amounts of future health and money showed that, contrary to normative discounted utility theory, the temporal discount rate, or annual percentage increase in value needed to offset a delay, differed for the 2 domains. Domain independence, defined as the low correlation between health and money discount rates relative to the consistency within each domain, was not due to different utility functions for health and money. Consistent with other research, these results suggest that decision domain affects the cognitive processes used. Despite this domain difference, there were some similarities between the 2 domains. Both health and money decisions revealed that discount rates were larger for short delays, small magnitudes, and gains as compared with losses.

Adult↗
PubMed1995

New inclusion body in a rat renal cell.

BACKGROUND AND METHODS: In an effort to review ultrastructural features of cells in the kidney of a male rat, transmission electron microscopy was used to study ultrathin sections. RESULTS: One light cell in a collecting tubule contained a 2.3-microns long linear array of electron-dense asymmetric structures in a granular zone of greater electron density than the general cytoplasm. This inclusion body could be interpreted to consist of a parallel array of 100-150-nm x 24-nm electron-dense rodlets, or a parallel array of 100-150-nm x 67-nm tubules. The inclusion showed no association with any cell organelle. The origin, chemical nature, frequency of occurrence, and functional significance of this inclusion are unknown. CONCLUSIONS: Although this inclusion body somewhat resembles previously described inclusions or granules, the differences in dimensions, frequency, and relation to other cell structures suggest it is a new observation.

Animals↗
PubMed1995

Clinical reasoning about new symptoms despite preexisting disease: sources of error and order effects.

BACKGROUND: Previous work that studied the evaluation of new, atypical symptoms in patients with preexisting diseases indicated that physicians largely ignored the past medical history and therefore erred in their diagnoses, when compared to a Bayesian analysis. Other studies have shown that the order in which information is presented to a decision maker can affect the inferences drawn, again contrary to a Bayesian standard. OBJECTIVES: The aim of the study was to investigate the source of disparity between clinical judgment and Bayesian analysis and to investigate the effect of alternative orders of presenting information on diagnostic conclusions. METHODS: Two groups of family physicians received a written clinical scenario. One group was given the past medical history before the history of present illness, the physical exam, and the laboratory data. The second group learned about the past medical history after all other clinical information had been presented. Judgments of test accuracy and probably diagnosis were collected at several points to identify the source of any diagnostic error. RESULTS: For both groups, the major source of error was in estimating the prior probability of disease, not in estimating the accuracy of a diagnostic test or updating opinions following receipt of test results. Although both groups of physicians received the same information, they came to markedly different conclusions about the most likely diagnosis. The group given the past medical history at the beginning of the scenario considered this information much less significant than did the group who received it at the end. CONCLUSIONS: Family physicians deviate from a Bayesian standard of reasoning by wrongly specifying prior probabilities and by being influenced by the order in which clinical information is presented.

Bayes Theorem↗
PubMed1992

The occurrence of disporous Bacillus thuringiensis cells.

Ultrathin sections of sporulating Bacillus thuringiensis were examined in a transmission electron microscope. Less than 1% of the about 2,000 approximately sagittal sections of the bacterial cells examined contained two endospores per cell. This finding clarifies the majority of textbook and research reports (which tend to be ambiguous), contradicts several of the most recent textbook reports, and confirms three unillustrated textbook reports, in relation to the occurrence of disporous bacilli. Electron microscopic evidence of the observation is presented, apparently for the first time.

Bacillus thuringiensis↗
PubMed1991

Ultrastructural study of the blood cells of the beluga whale, Delphinapterus leucas.

General cytological and ultrastructural features of cells found in the peripheral blood of three captive beluga whales (Delphinapterus leucas) are described. We noted all major peripheral cell types common to the circulation of mammalian species, including polymorphonuclear neutrophils, eosinophils, basophils, lymphocytes, and monocytes, as well as myelocytes, erythroblasts, and plasma cells. Platelets and two populations (normal and hypochromic) of red blood corpuscles were observed.

Animals↗