PubMed Health⌕ Search

Biomedical subjects

R Spears

Publications and source records attributed to R Spears.

At least 19 recordsLinked to original sources
PubMed2003

Osteoblasts and MG-63 osteosarcoma cells behave differently when in contact with ProRoot MTA and White MTA.

AIM: To test the hypothesis that MG-63 osteosarcoma cells and primary osteoblasts react differently to ProRoot trade mark MTA (mineral trioxide aggregate) and White MTA by: (i) investigating the attachment of primary osteoblasts and MG-63 osteosarcoma cells to ProRoot trade mark MTA and White MTA; and (ii) comparing the osteogenic behaviour of both cell lines in contact with these endodontic materials. METHODOLOGY: Primary osteoblasts were harvested from foetal rat calvaria by sequential digestion and MG-63 osteosarcoma cells were purchased. Cells were exposed to ProRoot trade mark MTA and White MTA prepared according to the manufacturer's instructions. All samples and controls were prepared in quadruplicate. After 6, 9 and 13 days exposure to MTA, the cells were fixed and prepared for SEM examination. In addition, both the cell types were grown to confluence and exposed to beta-glycerophosphate and dexamethasone to assess mineralized nodule formation as a function of osteogenic behaviour. RESULTS: The number of cells on the surface of the culture dish and on top of the materials increased in all samples throughout the 3 time periods, except for White MTA where no primary osteoblasts were visible on top of the material by the end of 13 days. After exposing cells to differentiation medium nodules were observed in cultures of primary osteoblasts, but not of MG-63 osteosarcoma cells. CONCLUSIONS: Under the conditions of this study, whilst primary osteoblasts initially bound to White MTA, they did not survive on the surface by the end of 13 days. Primary osteoblasts formed mineralized nodules when exposed to differentiation medium, whilst MG-63 cells did not form nodules. As MG-63 cells do not behave osteogenically by forming mineralized nodules, and primary osteoblasts are more sensitive than MG-63 osteosarcoma cells to White MTA in cell culture, primary osteoblasts are more appropriate than MG-63 cells for testing endodontic materials in cell culture.

Aluminum Compounds↗
PubMed2003

A determination of tumor necrosis factor expression in TMJ inflammation with the use of microarray analysis.

Many different factors can lead to inflammatory changes within temporomandibular joint tissues. This investigation examined if the expression of TNF-alpha and its receptors was altered in TMJ tissues during inflammation. Adult male rats were injected bilaterally with complete Freund's adjuvant (CFA) into the TMJ or served as uninjected controls and were killed two days after CFA treatment. TMJ tissues were removed, and expression of TNF-alpha and its receptors was examined via gene microarray analysis, RT-PCR, Western blot, and ELISA. Gene microarray analysis provided evidence for changes in gene expression, notably that TNF-alpha and TNF-R1, but not TNF-R2, were significantly elevated in CFA-treated TMJ tissues. However, protein levels of TNF-alpha, TNF-R1, and TNF-R2 were all significantly increased in CFA-treated TMJ tissues. These results indicate that the pro-inflammatory cytokine TNF-alpha may play a significant role in the onset of inflammatory conditions associated with adjuvant-induced arthritis of the TMJ.

Animals↗
PubMed2001

Modulation of the inflammatory response in the rat TMJ with increasing doses of complete Freund's adjuvant.

OBJECTIVES: Acute inflammation stresses the physiological system, which must respond in order to reestablish homeostasis. The purpose of this study was to determine whether bilateral temporomandibular joint (TMJ) injections of different doses of Complete Freund's Adjuvant (CFA) produced dose-dependent changes in biologic markers of acute inflammation. The ability to establish an animal model with varying degrees of joint inflammation would allow evaluation of agents or conditions that could modulate the severity of the disease. DESIGN: The TMJs of three groups of male Sprague-Dawley rats were injected with CFA containing varying doses of Mycobacterium tuberculosis (MT). A group of non-injected and a group of saline injected rats were used as controls. Food intake, body weights, swelling and chromodacryorrhea were recorded daily. Interleukin-1 beta (IL-1 beta) and corticosterone levels were assayed and condylar cartilage thickness was measured 48 h after injections. RESULTS: Twenty-four hours post-injection, bilateral TMJ swelling and chromodacryorrhea were significantly (P< 0.05) increased following 10 microg of MT and further increased with elevated MT dose. In the CFA groups food intake was attenuated (P< 0.01) 24 and 48 h post-injection and negatively correlated with dose at 24 h. Body weight was also negatively correlated with dose. TMJ retrodiscal tissues IL-1 beta was increased (P< 0.05) in a dose-dependent manner. CFA increased corticosterone (P< 0.05), but this elevation was not dose dependent. Condylar cartilage thickness was decreased in a dose-dependent manner. CONCLUSIONS: These data suggest that an intermediate dose of CFA can be used to effect submaximal levels of TMJ inflammation that will allow experimental modulation in future studies.

Acute-Phase Reaction↗
PubMed2001

Meaning-seeking in the illusory correlation paradigm: the active role of participants in the categorization process.

The present research examines the role of categorical perception (McGarty, Haslam, Turner, & Oakes, 1993) in the illusory correlation paradigm. This approach assumes that the search for meaningful differences between two stimulus groups can lead to the illusory correlation effect. This explanation is investigated in Study 1 by presenting participants with constrained stimulus information and examining whether accentuating evaluative differences between stimuli could provide a basis for illusory correlation. Results of this study (N = 64) revealed illusory correlation effects that were related to evaluative reinterpretations of the stimuli. Study 2 (N = 19) focused on the causal relation between illusory correlation and accentuation effects, using the thinking-aloud technique. Detailed analyses of each participants' behaviour indicated that illusory correlation can arise from actively seeking intergroup differences and that reinterpretations of stimuli and the perception of illusory correlation were mutually reinforcing. Implications of these results for stereotyping processes are discussed.

Adult↗
PubMed2001

Quality of decision making and group norms.

Two studies investigated the impact of group norms for maintaining consensus versus norms for critical thought on group decisions in a modification of the biased sampling paradigm (G. Stasser & W. Titus, 1985). Both studies showed that critical norms improved the quality of decisions, whereas consensus norms did not. This effect appeared to be mediated by the perceived value of shared and unshared information: Consensus norm groups valued shared information more highly than critical groups did, and valence was a good predictor of decision outcome. In addition, the 2nd study showed that the group norm manipulation has no impact on individual decisions, consistent with the assumption that this is a group effect. Results suggest that the content of group norms is an important factor influencing the quality of group decision-making processes and that the content of group norms may be related to the group's proneness for groupthink.

Adult↗
PubMed2000

Calcitonin gene-related peptide and substance P immunoreactivity in rat trigeminal ganglia and brainstem following adjuvant-induced inflammation of the temporomandibular joint.

The immunoreactivity of two inflammatory mediators, calcitonin gene-related peptide (CGRP) and substance P, was measured in the trigeminal ganglia and brainstem to characterize an adjuvant-induced inflammation within the rat temporomandibular joint at various acute (6, 24 and 48 h) and intermediate (10 day) time intervals. Concentrations of adjuvant-related neuropeptides were compared to those in both contralateral vehicle-related tissues and non-injected controls. By 6 h, CGRP immunoreactivity in the trigeminal ganglia was significantly above that in contralateral vehicle-injected tissue. The CGRP had decreased at each of the following time-points, but remained significantly elevated at 10 days. Substance P in the ganglion on the injected side was significantly increased for all four time periods. In brainstem subnucleus caudalis, CGRP was significantly increased for all four time periods. Substance P immunoreactivity in the subnucleus caudalis was significantly increased for the initial three time periods, but by day 10 had been reduced to that of the control. These data show that the pattern of changes in neuropeptides following the induction of inflammation is different between substance P and CGRP. Moreover, the pattern of change varies between the brainstem and the trigeminal ganglion. This suggests that the two neuropeptides may have different roles in the inflammatory process, and that this process may be modulated by different mechanisms at the brainstem and ganglion.

Afferent Pathways↗
PubMed2000

How do we communicate stereotypes? Linguistic bases and inferential consequences.

The linguistic expectancy bias is defined as the tendency to describe expectancy-consistent information at a higher level of abstraction than expectancy-inconsistent information. The communicative consequences of this bias were examined in 3 experiments. Analyses of judgments that recipients made on the basis of linguistically biased information generated by transmitters indicated that behavior in expectancy-consistent messages was attributed more to dispositional and less to situational factors than behavior in expectancy-inconsistent messages. Moreover, this effect was mediated by the level of linguistic abstraction of the messages. These findings provide direct evidence for the hypothesis that recipients are sensitive to variations in linguistic abstraction in spontaneous language use because of stereotypes. Results are discussed with respect to the interpersonal aspects of stereotyping.

Adult↗
PubMed2000

Meal pattern analysis in response to temporomandibular joint inflammation in the rat.

Inflammation of the temporomandibular joint (TMJ) can alter behavioral responses such as food intake and mobilize stress hormones. The hypothesis of this study was that food intake and diurnal corticosterone analysis can be used as indicators of adjuvant-induced TMJ inflammation. Groups of rats received adjuvant or no injections at the beginning of the resting (AM) or activity (PM) phase. Forty-eight hours (early) or 6 weeks (late) after adjuvant injection, plasma corticosterone was assayed and food intake was recorded. Food intake was suppressed up to 4 days post-injection. As expected, the non-injected group showed low AM and high PM corticosterone. AM corticosterone was elevated, but PM corticosterone was attenuated in both early- and late-stage-injected rats. A computerized pair-fed experiment showed that adjuvant-induced hypophagia did not alter corticosterone levels. Meal pattern analysis revealed decreased food intake due to a decrease in the number of meals taken. Notably, meal size remained the same but meal duration increased. This model demonstrated that food intake and stress hormone analysis could be used as indicators for sequelae of adjuvant-induced TMJ inflammation.

Analysis of Variance↗
PubMed1998

Capsaicin application to the temporomandibular joint alters calcitonin gene-related peptide levels in the trigeminal ganglion of the rat.

The aim of this investigation was to determine the temporal effect of an intra-articular injection of capsaicin to the temporomandibular joint on the levels of calcitonin gene-related peptide-like immunoreactivity (CGRP-ir) in the trigeminal ganglion of the rat. The temporomandibular joints of 26 adult female rats were injected on one side with capsaicin and contralaterally with a control vehicle. Another 8 animals served as an untreated control group and received no injections. Animals were sacrificed at time intervals of 4 hours, 48 hours, 10 days, and 21 days following treatment. The trigeminal ganglia were extirpated, and CGRP-ir levels were quantified using a radioimmunoassay. Results demonstrated that when the capsaicin-treated side and the vehicle-treated side were compared, CGRP-ir levels decreased initially at 4 hours and increased at 48 hours. At 10 days, CGRP-ir levels had again dropped below control levels, followed by an increase at 21 days. CGRP-ir levels for the first two time periods investigated, which simulate an acute inflammatory state, mimic results observed in studies using limb joints, while the other time periods, which represent an intermediate and a chronic condition, respectively, suggest a more complex interaction with capsaicin-sensitive primary afferents.

Animals↗
PubMed1996

Intergroup norms and intergroup discrimination: distinctive self-categorization and social identity effects.

Manipulation of in-group and out-group norms of discrimination and fairness allowed for the operation of competing social identity principles concerning in-group bias, conformity, and group distinctiveness. The combined effects of these principles on in-group bias were first examined in a modified minimal-group setting (Study 1). Results demonstrated that participants' allocation strategies were in accord with the in-group norm. Furthermore, dissimilar norms resulted in greater use of positive differentiation allocation strategies. However, in natural groups (Study 2), more in-group bias was found when both group norms were similar and discriminatory. The results confirm the importance of in-group norms and demonstrate differences between experimental and natural groups in the applicability of competing social identity and self-categorization principles.

Adolescent↗
PubMed1996

Religiosity, gender, and the double standard.

Scottish teenagers (N = 690) participated in a survey concerning the relationship between religiosity, gender, and social judgments of sexual activity. Respondents estimated the number of sexual partners of 20-year old men and women and made evaluative judgments of sexually active men and women on positive and negative dimensions. On both tasks, evidence was obtained for the operation of a double standard. Women were expected to have fewer sexual partners than men, and their sexual activity was judged more negatively on evaluatively negative dimensions. Contrary to findings of previous studies in this area, gender differences in endorsement of the double standard were not found. Only moderate support was found for the view that religiosity contributes to different standards of sexual behavior for men and women, although religiosity had significantly greater influence on judgments made by women than on judgments made by men.

Adolescent↗
PubMed1994

The influence of personal and collective self-esteem on strategies of social differentiation.

The present study distinguished between personal self-esteem (PSE) and collective self-esteem (CSE) as determinants of in-group bias in an intergroup context. Subjects performed a group task, the product of which they subsequently evaluated ('own' group), along with solutions allegedly produced by another 'in-group' (similar nationality), and an 'out-group' (different nationality). This provided the opportunity for intragroup discrimination (own vs. in-group), and both direct (own vs. out-group) and indirect (in-group vs. out-group) strategies of intergroup discrimination. It was predicted that subjects high in CSE would differentiate more than subjects low in CSE, both directly and indirectly, but that intergroup discrimination would also result from high PSE. The relationship between the in-group and out-group was also manipulated by varying the salient out-group. It was predicted that subjects motivated to enhance social identity (high CSE) would differentiate more, directly and indirectly, when the out-group was seen as having a more competitive relationship with the in-group. Although this manipulation was unsuccessful, a follow-up suggested that the out-group predefined as less competitive was actually a more relevant comparison group in the context of the task, which is consistent with effects of this manipulation. Overall PSE and CSE were both found to influence differentiation at the intragroup and intergroup level, both independently and interactively. However, whereas high PSE led to greater positive differentiation, low CSE had this effect, and a combination of high PSE and low CSE produced the most consistent pattern of positive in-group differentiation across both out-group conditions. Possible mechanisms which account for this pattern are discussed and the relationship between dimensions of self-esteem and group differentiation is reappraised in the light of these findings.

Adult↗
PubMed1993

Natural history of coronary atherosclerosis using quantitative angiography in men, and implications for clinical trials of coronary regression. The Harvard Atherosclerosis Reversibility Project Study Group.

Previous studies of the natural history of coronary disease generally relied on estimates of percent stenosis derived from visual assessment of the coronary angiogram. In a study of 26 patients, serial quantitative angiography was performed 3 years apart to determine changes in both absolute measurements of the luminal diameter and relative percent stenosis. Initially, the mean minimal diameter of 74 coronary obstructions was 1.94 +/- 0.09 mm, the mean "normal" reference diameter was 3.06 +/- 0.11 mm, and the mean percent stenosis was 37%. At follow-up, there was a mild reduction of 0.12 +/- 0.04 mm (6%) in the minimal diameter (p < 0.005), and an increase in percent stenosis to 39% (p = 0.03). The average diameter of 85 arterial segments without a focal obstruction either initially or at follow-up showed mild but significant progression (-0.11 +/- 0.04 mm; p = 0.02). Using a minimal change of 0.27 mm in arterial diameter as a categoric variable, progression occurred in 26% of 74 arterial segments, no significant change in 65%, and regression in 9%. The only significant determinant of disease progression was the initial severity of disease. Obstructed arteries with a larger initial minimal diameter and presumably milder disease progressed more rapidly than did those with a smaller diameter (r = -0.42; p = 0.0002). There was no effect of age on the rate of progression (r = 0.02; p = NS).(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiac Catheterization↗
PubMed1993

Obtaining a durable power of attorney for health care from nursing home residents.

BACKGROUND: A durable power of attorney for health care (DPA) allows a person to appoint a surrogate decision-maker for any future period of mental incapacity. The absence of advance directives can lead to confusion and the expenditure of resources while trying to exert a substituted judgment. METHODS: The Wisconsin DPA was presented with an organized pilot program to 150 residents who had been judged by their social workers to have the capacity to make informed decisions regarding medical care. The reasons residents gave for accepting or rejecting a DPA were analyzed. RESULTS: Seventy-nine percent prepared a DPA. Reasons for signing included allowing the resident to decide who would make medical decisions and assuring that specific wishes would be carried out. Twenty-one percent did not execute a DPA. Reasons were categorized as confusion and misunderstanding regarding the legal system, mistrust, or social isolation. CONCLUSIONS: The high rate (79%) of DPA completion is probably related to individually counseling residents. However, competent residents who despite counseling do not choose to execute a DPA can have detailed advance directives ("living wills") prepared without appointing a decision-maker.

Adult↗
PubMed1992

The ultrastructural architecture of the tissue/hard-tissue replacement interface.

This investigation examined the tissue response and interfacial bonding between bone and hard-tissue replacement (HTR) using scanning (SEM) and transmission (TEM) electron microscopy. Twenty adult male Sprague-Dawley rats were anesthetized and a hole (1.0 mm deep by 2.0 mm wide) was drilled in the calvarium. Subsequently, HTR was implanted and the wound closed. The implants and surrounding tissues were removed at 7, 14, 28, and 56 days and prepared for examination by SEM or TEM. Scanning electron microscopic analysis revealed a typical inflammatory response that subsided by day 14. At that time, a fine layer of collagen fibrils (fibrous envelope) was observed covering the polymeric surface. Energy dispersive x-ray analysis (EDXA) showed no sign of mineralization. Ultrastructural analysis demonstrated that the fibrous envelope was bilaminar; it consisted of a relatively undifferentiated cellular layer adjacent to the polymer and an outer fibrous region. Scanning electron microscopic analysis of 28-day implants showed that osteoblasts had migrated onto the outer surface of the fibrous envelope and that calcification had been initiated as judged by EDXA. Electron microscopic examination confirmed previous observations of an undifferentiated cellular layer along the interfacial boundary, but also showed both macrophages and foreign-body giant cells. At 56 days, bone was observed to contact and cover the fibrous envelope surrounding the polymeric bead; however, EDXA showed that the fibrous envelope remained noncalcified. Transmission electron microscopic analysis revealed that the inner cellular layer was beginning to mature, as indicated by the presence of numerous cellular organelles. This maturation was accompanied by an increased incidence of macrophages as well as foreign-body giant cells. Within the time constraints of the experimental design, it is apparent that a bilaminar layer of cells and fibers remains between the HTR and the bone. Additional studies will be necessary, over extended time periods, to determine whether the bilaminar layer remains a constant feature between the HTR and the surrounding bone or whether this region is gradually supplanted by the ingrowing bone.

Animals↗
PubMed1992

Health beliefs and promotion of HIV-preventive intentions among teenagers: a Scottish perspective.

Beliefs concerning the spread of the human immunodeficiency virus (HIV) and preventive behaviors were examined in a sample of 351 sexually active Scottish teenagers. A postal questionnaire, including measures of variables specified by the health belief model (HBM) and preventive intentions, was employed. The relation between HBM measures and reported endorsement of HIV-preventive intentions was investigated. Results indicated that, in general, respondents intended to use condoms with new sexual partners. The majority also intended to carry condoms if they thought they might have sex with a new partner and to ask potential partners about their previous sexual history. Multiple-regression analyses showed that measures of health beliefs, gender, age, sexual experience, and previous condom use accounted for 17.8% to 24.3% of the variance in reported preventive intentions. Perceived barriers to preventive behaviors were found to be important predictors. However, the overall pattern of results raised questions concerning the adequacy of the HBM as a model of the determinants of HIV-preventive intentions, and the need for an extended model is discussed. Separate analyses were conducted for men and women and for 16- and 18-year-olds, and the implications for modeling intention formation in these subgroups are considered. The relevance of these findings to HIV-preventive campaigns is also discussed.

Adolescent↗
PubMed1992

Context and content: the impact of school-leaving and school-based health education on AIDS-relevant cognitions.

A survey examined health beliefs and intentions among 690 16-18 year-olds in Dundee. Respondents in the younger cohort (n = 363) were classified according to their educational situation (at school vs left) and self-reports of having received AIDS/HIV-relevant health education. Both remaining in school and receiving AIDS/HIV-relevant health education had independent beneficial effects, but the effects of leaving school also interacted with sex of respondent and with amount of relevant education received prior to leaving. Males' and females' reliance on mass media and other information sources diverged once they left school, indicating that males who leave school early are most likely to disregard useful or important information regarding AIDS. Consistent with this finding, leaving school reduced the difference between males' and females' intention to use condoms with a new partner. The beneficial impact of having previously received AIDS/HIV-relevant education on beliefs concerning the controllability of the epidemic and on feeling worried about everyday contact with a person with HIV/AIDS, was most marked among those who had left school. The results are discussed in terms of their implications for health education strategies.

Adolescent↗