Showing papers by "Tulane University published in 1987"

False Hopes and Best Data: Consent to Research and the Therapeutic Misconception

Abstract: To maintain a therapeutic misconception is to deny the possibility that there may be major disadvantages to participating in clinical research that stem from the nature of the research process itself. It could be argued that the research project has been peer-reviewed for scientific merit and approved for ethical acceptability by an institutional review board (IRB), the problem of the therapeutic misconception is not significant enough to warrant intervention. The neutral explainer would be responsible to the IRB and would be trained to emphasize those aspects of the research situation about which the IRB has the greatest concern. This approach might be especially appropriate when the investigator is also the subject's treating physician and the methodology used is likely to be interpreted as therapeutic in intent. The unique aspects of clinical research include the goal of creating generalizable knowledge; the techniques of randomization; and the use of a study protocol, control groups, and double-blind procedures.

The effect of surface macrotexture and hydroxylapatite coating on the mechanical strengths and histologic profiles of titanium implant materials.

Abstract: A mechanical and histological evaluation of uncoated and hydroxylapatite-coated titanium implant materials was performed. Cylindrical implants of uncoated commercially pure (CP) titanium and hydroxylapatite-coated Ti-6Al-4V alloy were studied using a transcortical model, with implants evaluated after periods of 3, 5, 10, and 32 weeks. All implants had a surface macrotexture consisting of a series of semicircular annular grooves, approximately 750 micron in maximum depth. The attachment characteristics of interface shear stiffness and interface shear strength were determined by mechanical push-out testing. Nondecalcified histologic and microradiographic techniques, with implants in situ, were used to evaluate the response to the implant materials and the presence of the surface macrotexture. Mechanical testing results indicated that the hydroxylapatite-coated implants exhibited significantly greater values of maximum interface shear strength than the uncoated implants after all time periods. Interface shear stiffness was also significantly greater at all time periods for the hydroxylapatite-coated implants as compared to the uncoated implants. Histological evaluation after 3 weeks revealed an osteoid layer covering on all areas coated with the hydroxylapatite material; mineralization of this layer appeared to be complete after 10 weeks. In all cases, longer-term implants demonstrated mineralization of interface bone directly onto the hydroxylapatite coating, and in no case was a fibrous layer observed between the hydroxylapatite coating and the interface bone. Sections from the uncoated CP titanium implants revealed a thin fibrous layer present in nearly all areas. Only isolated regions of direct bone-implant apposition were observed for the uncoated implants. The presence of this fibrous tissue layer, however, apparently did not adversely affect the development of considerable attachment strength. The results from this study indicate that the hydroxylapatite coating can significantly increase the attachment strength of implants which rely upon bone apposition for fixation. In addition, the hydroxylapatite coating provides an osteophilic surface for bone deposition, and allows for a more rapid development of implant-bone attachment.

Interleukin-1 stimulates ACTH release by an indirect action which requires endogenous corticotropin releasing factor.

Abstract: The present study was performed in order to clarify the mechanism by which interleukin-1 (IL-1) activates the hypothalamic-pituitary-adrenal (H-P-A) axis. The iv administration of IL-1 into freely moving, conscious rats significantly elevated the plasma levels of ACTH. This ACTH response to IL-1 was, however, completely abolished by preinjection of 0.5 ml rabbit antiserum generated against rat CRF, but not by normal rabbit serum (NRS). The IL-1-induced ACTH release did not seem to be caused by a general stress effect of IL-1 because plasma PRL levels, another indicator of a stress response, were not altered by the injection of IL-1. These results suggest that IL-1 acts centrally in the brain to stimulate the secretion of CRF, thereby eliciting ACTH release, and that a direct action of IL-1 on the pituitary gland is unlikely.

Beyond negative affectivity: Measuring stress and satisfaction in the workplace.

Abstract: Stress researchers frequently use self-report measures to assess stress, health, psychological adjustment, and subjective dissatisfaction. We present evidence demonstrating that all of these variables are highly intercorrelated and reflect a common underlying factor of Negative Affectivity (NA). NA is a stable and pervasive personality dimension-high NA individuals report more stress, distress and physical complaints, even in the absence of any objective stressor or health problem. Thus, NA may operate as a substantial nuisance factor in many areas of research. To circumvent its influence, investigators can use non-subjective measures of stress and health. Finally, we present a two-factor model of stress and satisfaction that includes, in addition to NA, the independent factor of Positive Affectivity (PA), a trait reflecting positive feelings about oneself and one's life.

Diagnosis of Cutaneous and Mucocutaneous Leishmaniasis in Colombia: A Comparison of Seven Methods

Abstract: Seven methods of diagnosing leishmaniasis were compared in 177 patients presenting with lesions of the skin (165) or mucosa (12) in Tumaco and Cali, Colombia. The three methods of visualizing amastigotes in tissue samples (histological staining of tissue sections, impression smears of punch biopsies, and smears of dermal scraping from slits in the lesion margins) were less sensitive than the four Leishmania isolation methods (aspiration of lesion border cultured in biphasic media, aspirate inoculated into hamster nasal tissue, culture of punch biopsy macerate, and hamster inoculation of macerate). The aspirate-culture and biopsy-hamster methods employed in this study proved most sensitive of the four methods for the recovery of parasites. The combined overall sensitivity of the 7 methods was 67% for all enrolled patients and 75% for Montenegro skin test-positive patients. The individual sensitivities for the methods for all patients and Montenegro-positive positive, patients, respectively, were: histopathology 14% and 16%, impression smear 19% and 21%, dermal scraping 22% and 26%, aspirate-culture 58% and 64%, aspirate-hamster 38% and 41%, biopsy-culture 50% and 55%, and biopsy-hamster 52% and 57%. All methods were less sensitive in lesions of greater than 6 months duration than in lesions of more recent onset. Mucosal lesions were best diagnosed by the culture or hamster inoculation of a macerated mucosal biopsy. The diagnosis by inoculation of hamsters was achieved within 2 to 12 weeks, a mean of 34.5 days. Promastigotes were seen on Senekjie's medium within 3-8 days.(ABSTRACT TRUNCATED AT 250 WORDS)

Free fatty acids block growth hormone (GH) releasing hormone-stimulated GH secretion in man directly at the pituitary.

Abstract: Increases in plasma FFA levels inhibit GH responses to a variety of pharmacological and physiological stimuli. To gain further insight into the mechanism by which FFA exert their effect, we studied the plasma GH responses to GHRH-(1-44) (1 microgram/kg, iv) in normal subjects in whom plasma FFA levels were raised by a lipid-heparin infusion (250 mL 10% Intralipid plus 2500 U heparin). Paired tests were performed in 10 normal subjects, with and without lipid-heparin pretreatment. Lipid-heparin infusion from -30 to 120 min increased mean FFA levels from 0.41 +/- 0.03 (+/- SEM) to 3.12 +/- 0.40 mmol/L at 120 min. The mean plasma GH levels after GHRH administration were lower at all times; however, the values were significantly different (P less than 0.05) only at the later times (45, 60, and 90 min). When considered individually, an all or none pattern was observed; 5 subjects had no plasma GH response to GHRH, and 5 had no reduction. To investigate the time relationships between the FFA peak and subsequent GH blockade, a different protocol of paired tests was performed with GHRH with or without a different lipid-heparin infusion protocol. Lipid-heparin was infused from -90 to 0 min, with an additional heparin pulse at -15 min, to obtain a higher and earlier (0 min) FFA increase. FFA increased from 1.06 +/- 0.19 to 11.61 +/- 0.83 mmol/L at zero time. The GHRH-induced GH secretory peak (15.8 +/- 3.5 ng/ml) at 15 min was completely blocked (0.9 +/- 0.2 ng/ml), and the mean plasma GH levels were also lower at 30, 45, and 60 min. To determine whether the FFA-induced blockade of GH secretion was exerted in the pituitary, a series of in vitro studies was conducted using monolayer cultures of rat anterior pituitary glands, with GHRH concentrations of both 10(-10) and 10(-8) M and 10(-5) M forskolin to stimulate GH release. Both caprylic and oleic acid inhibited basal GH release and GHRH- or forskolin-induced GH release. PRL release was not altered, nor were toxic actions noted on the cells. In conclusion, FFA are able to block GH secretion directly at the pituitary level.

The endocrine mechanisms of crustaceans

Abstract: The basic plan of the crustacean endocrine system 1 The endocrine structures 2 X-organ-sinus gland complex 2 Postcommissural organ 3 Pericardial organ 3 Y -o rg a n .... ....... .. ...... ......... ... ......... 3 Androgenic gland 4 O vary 4 Mandibular organ 4 The roles of hormones 5

Distributive and procedural justice in the workplace

Abstract: The interrelatedness of procedural and distributive justice has implications for organizational practice, especially in the area of performance appraisal. I explore these implications by first describing how procedures can influence perceptions of distributive justice: Procedural improprieties can bring to mind the possibility that a more just outcome might have been obtained if only more acceptable practices had been followed. Next I discuss a second form of interrelatedness — how distributive consequences can influence perceptions of procedural justice — by suggesting that the fairness of a procedure can be assessed in terms of its “expected-value” (typical or most probable) outcome. These points are illustrated by a discussion of howvoice, or the opportunity for employees to contribute information during the performance appraisal process, can affect both appraisal accuracy and perception of fairness.

The Sound of Leadership: Presidential Communication in the Modern Age

Abstract: Why did Gerald Ford speak in public once every six hours during 1976? Why did no president spreak in Massachusetts during one ten-year period? Why did Jimmy Carter conduct public ceremonies four times more often than Harry Truman? Why are television viewers two-and-a-half times more likely to see a president speak on the nightly news than to hear him speak? "The Sound of Leadership" answers these questions and many more. Based on analysis of nearly 10,000 presidential speeches delivered between 1945 and 1985, this book is the first comprehensive examination of the ways in which presidents Truman through Reagan have used the powers of communication to advance their political goals. This communication revolution has produced, Roderick P. Hart argues, a new form of governance, one in which public speech has come to be taken as political action. Using a rhetorical appraoch, Hart details the features of this new American presidency by carefully examining when and where presidents spoke in public during the last four decades and what they said. Even though presidents have been speaking more and more, Hart reveals, they have been saying less and less. Rather than leading the nation, the modern president usually offers only the hollow "sound" of leadership. Written with great flair and acuteness, "The Sound of Leadership" will become a standard guide to the voices of modern presidential politics.

Limb Development and Regeneration

Abstract: Experiments on developing and regenerating vertebrate limbs have led to the idea that pattern formation and growth control are causally linked. The mechanism by which position-specific growth occurs is termed intercalation, and evidence is presented that implicates intercalation in the initiation, maintenance and cessation of growth during limb formation. We conclude that among the variety of cell types present in limbs, only fibroblasts have been shown to possess the positional information necessary for intercalation. Hence we propose that the limb pattern is generated by intercalation between fibroblasts to give rise to a connective tissue scaffold, which in turn dictates the positioning and morphogenesis of all of the differentiated cell types of the limb. Finally, we review evidence that regenerative failure among higher vertebrates is linked to defects in the intrinsic cellular mechanisms of growth control (intercalation) and conclude that progress towards the goal of stimulating regenerative limb outgrowth in non-regenerating vertebrates will be contingent upon a better understanding of these intrinsic mechanisms.

Surgical repair of Achilles tendon ruptures

Abstract: We evaluated the surgical results of 42 consecutive patients with spontaneous rupture of the Achilles ten don treated from 1973 to 1984 to determine the causes of rupture and to evaluate our treatment methods. Patients were divided into early and late repair groups and their charts reviewed to determine common clinical features. A new method of repair with early functional range of motion exercises before casting was used and compared to other techniques in common use. Thirty- one patients were contacted for long-term followup (average, 4.7 years). Twenty-three of these patients returned for intensive reevaluation and Cybex testing.We found a high incidence of gout (14.3%) and previous steroid injections (7.1 %) in our patients. Good results were obtained from the four surgical methods used. There were no reruptures and only 7% of the patients experienced minor wound problems. Patients treated with early functional range of motion exercises averaged 12.5° more dorsiflexion at the time of cast removal and ...

Relative effects of procedural and distributive justice on employee attitudes.

Abstract: This study investigated the relative influence of two aspects of fairness, procedural and distributive justice, on two employee attitudes: organizational commitment and satisfaction with pay. Hierarchical regression analysis of data from 36 employees from one organization indicated that the variance in organizational commitment was uniquely associated with procedural factors, whereas the variance in satisfaction with pay was uniquely associated with distributive factors. Thibaut and Walker's (1975) pioneering studies of procedural justice examined the alternative dispute-resolution models used most frequently in legal settings. A number of their investigations concerned the objective functioning of these competing models of the legal process; that is, an examination of how actual decisions varied as a result of using different procedures. At the same time, they also noted the importance of other considerations. However, this kind of information about what actually happens can provide, in our opinion, only a partial basis for selecting a dispute-resolution model to serve a particular purpose. It is also necessary to know how each of the possible procedural choices is perceived and evaluated by persons subject to the process and by other persons who may at some future time have their rights decided in a similar setting. This subjective measure is crucial because one of the major aims of the legal process is to resolve conflicts in such a way as to bind up the social fabric and encourage the continuation of productive exchange between individuals. (p. 67) This passage emphasizes that favorable subjective evaluations of dispute-resolution methods - perceptions of procedural fairness are central to the operation of the legal system. l.ndeed, such evaluations areessential to theallegiance, commitment, and loyalty of citizens necessary for a society grounded in law. Continued support for the legal system hinges on the perceived fairness of the Procedures used to make judgments. The present study addresses an analogous situation in business organizations. Many decisions in such organizations (e.g., promotions, raises) involve judging people, a process typicaliy called Performance appraisai. We are interested in the perceived procedural justice of performance appraisals. We suggest that these Perceptions have a strong impact on the level of commitment

Mycotoxins, mycotoxicoses, mycotoxicology and Mycopathologia

Abstract: Mycotoxins are fungal poisons. This definition does not stipulate whether fungi are the targets of poisoning or are the producers of the poisons. The following is suggested as a useful working definition: Mycotoxins are natural products produced by fungi that evoke a toxic response when introduced in low concentration to higher vertebrates and other animals by a natural route. Some mycotoxins have multiple effects, and may cause phytotoxic and antimicrobial syndromes in addition to animal toxicity. By convention, mushroom and yeast poisons are usually excluded from discussions of mycotoxins. The eclectic nature of the discipline and the international scope of the problem has attracted scientists from many different backgrounds. The publishers and editors of Mycopathologia intend for this journal to become a major forum for mycotoxin research.

The Elastic Properties of a Human Mandible

Abstract: This paper is a report on a study of the elastic properties of the human mandible. Using a continuous-wave ultrasound technique, we determined the elastic constants of ten small specimens taken fro...

Gentamicin enhanced production of hydrogen peroxide by renal cortical mitochondria

Abstract: Agents that affect mitochondrial respiration have been shown to enhance the generation of reactive oxygen metabolites. On the basis of the well-demonstrated ability of gentamicin to alter mitochondrial respiration (stimulation of state 4 and inhibition of state 3), it was postulated that gentamicin may enhance the generation of reactive oxygen metabolites by renal cortical mitochondria. The aim of this study was to examine the effect of gentamicin on the production of hydrogen peroxide (measured as the decrease in scopoletin fluorescence) in rat renal cortical mitochondria. The hydrogen peroxide generation by mitochondria was enhanced from 0.17 +/- 0.02 nmol . mg-1 . min-1 (n = 14) in the absence of gentamicin to 6.21 +/- 0.67 nmol . mg-1 . min-1 (n = 14) in the presence of 4 mM gentamicin. This response was dose dependent with a significant increase observed at even the lowest concentration of gentamicin tested, 0.01 mM. Production of hydrogen peroxide was not increased when gentamicin was added to incubation media in which mitochondria or substrate was omitted or heat-inactivated mitochondria were used. The gentamicin-induced change in fluorescence was completely inhibited by catalase (but not by heat-inactivated catalase), indicating that the decrease in fluorescence was due to hydrogen peroxide. Thus this study demonstrates that gentamicin enhances the production of hydrogen peroxide by mitochondria. Because of their well-documented cytotoxicity, reactive oxygen metabolites may play a critical role in gentamicin nephrotoxicity.

The clinical and immunologic responses of normal human volunteers to low dose hookworm (Necator americanus) infection.

Abstract: Five normal human volunteers were exposed to approximately 50 infective larvae of Necator americanus and were observed for the development of clinical signs or symptoms and for changes in blood eosinophil levels, IgG antibody titers, total and parasite-specific IgE, and lymphocyte blastogenic responses for 6-10 weeks Bronchoalveolar lavage was performed on four subjects prior to infection and at times when larval migration through the pulmonary tree was likely Eggs were demonstrated in the stools of four volunteers who remained untreated for more than 6 weeks; one volunteer had to be treated at day 40 because of severe gastrointestinal symptoms All others also complained of abdominal pain and flatulence between days 35-40 All volunteers developed marked blood eosinophilia which peaked between days 38-64 and ranged from 1,350-3,828 eosinophils/mm3 Small increases in total and parasite-specific IgE and IgG were noted in some volunteers One volunteer showed a significant lymphocyte blastogenic response With the exception of mucosal erythema, bronchoalveolar lavage results were unremarkable Our data indicate that a single small inoculum of hookworm larvae is capable of producing significant transient gastrointestinal morbidity and marked blood eosinophilia but does not induce other prominent T cell- and B cell-dependent immune responses

Role stress, physical symptomatology, and turnover intentions: A causal analysis of three alternative specifications

Abstract: SUMMARY Causal relationships involving role stressors, physical symptomatology, and turnover intentions were examined within three alternative specifications. These specifications stemmed from Beehr and Newman's (1978) and Schuler's (1982) models of role stress and Locke's (1976) theory of job satisfaction. The results, derived from LISREL VI analyses, indicate that a revised Schuler model is the most plausible specification. Findings are discussed in terms of implications for understanding role stress and employee withdrawal.

Chapter 9 Theory of public goods

Abstract: Publisher Summary This chapter discusses the class of goods that has come to be known as “public goods” or “collective goods” A distinctive characteristic of such goods is that they are not used up in the process of being consumed or utilized as an input in a production process To be considered public, a good must also be of interest to more than one consumer or firm Otherwise, the fact that the consumption possibilities of others are undiminished is irrelevant The chapter presents the derivation and interpretation of the efficiency conditions for pure public goods The positive issues of the way the private market arrangements provide for public goods are discussed in the chapter The chapter describes alternative mechanisms for making public goods decisions within the public sector Public goods are of particular relevance to public policy, because they tend to be inefficiently provided by private arrangements, such as the market mechanism The category of public “goods” is considered as opposed to public “bads” Because they are not used up in the act of consumption of production, the marginal cost of extending service to additional users is zero Private provision of the good, however, necessitates revenues from users to defray the cost of producing the good Such charges usually lead some potential users to forgo consumption, creating a deadweight efficiency loss

Women in Communication Studies: A Typology for Revision.

Abstract: Five conceptualizations of women dominate contemporary research practices in communication studies: Womanless Communication; Great Women Communicators; Woman as Other; The Politics of Woman as Other; Women as Communicators. Each conceptualization is examined to show the implicit assumptions that perpetuate the exclusion of women's communication from research practices and findings. The inclusion of female experience in communication studies demands collaborative and critical attention to the politics of conducting research.

Social distance regarding male and female homosexuals.

Abstract: Four hypotheses were tested by having American undergraduates respond to a Guttman scale of social distance toward male and female homosexuals. Respondents had higher degrees of discomfort toward same-sex homosexuals than toward opposite-sex homosexuals. Results indicated comfort around homosexuals to be negatively associated with the frequency of religious participation and positively associated with having had a friend who was believed to be homosexual. Having been subject to sexual advance did not appear to be related to discomfort regarding homosexuals. Scale scores were compared to levels of agreement with a variety of stereotypic statements. Sex differences regarding social distance toward both male and female homosexuals were examined.

Self-isolation and insect pollination in the primitive angiosperms: New evaluations of older hypotheses

Abstract: A review of the literature, compiled over the past 40 years suggests new directions for theories discussing the evolution of reproductive isolation and entomophily in angiosperms. Data on breeding systems suggests that the protoangiosperms may have developed gametophytic self-incompatibility. Protogyny is probably ancestral to protandry and herkogamy. Although the proto-flowers were bisexual wide variation in the number of sexual organs within proto-flowers probably led to labile sexuality and early trends towards dicliny. Beetle-pollination in extant relicts appears too specialized to represent an ancestral condition. Rather, the proto-flowers may have been generalist entomophiles incorporating some beetles,Plecoptera, thrips, micropterigid moths and proto-dipterans into their fluctuating spectra of opportunistic pollinators. Bee-pollination is probably polyphyletic in origin evolving repeatedly from angiosperms showing these generalist syndromes. There is still no correlation between primitive bees (especiallyColletidae) and the relictual angiosperms. Pollen that is usually retained within the anthers following dehiscence and the presence of staminal filaments and styles characterizes most of the flowers of those relictual angiosperms pollinated by specialized, modernApoidea.

Bioassays of nutrient limitation in a tropical rain forest soil

Abstract: Six speices of shrubs and one large herb with contrasting life history patterns were used as bioassays of nutrient availability in a Costa Rican lowland rain forest soil. Growth responses of the herb (Phytolacca rivinoides, Phytolaccaceae) confirmed soil measurements indicating high availability of N and potentially limiting levels of P, K, Mg and Ca. Growth responses of the shrub species (Miconia spp., Melastomataceae and Piper spp., Piperaceae) to a complete nutrient fertilizer were generally less than that of Phytolacca. Lack of a strong shrub response to +P fertilization is probably due to mycorrhizal associations and slower growth rates of woody species. In general, increased growth did not occur at the expense of phenolic production in the leaves. The results emphasize that assessment of specific nutrient limitations to plant growth vary depending on species selected for the bioassay, even among species from the same community.