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Biomedical subjects

J Knox

Publications and source records attributed to J Knox.

At least 37 records · Page 2Linked to original sources
PubMed1998

Combined stimulation of the glycine and polyamine sites of the NMDA receptor attenuates NMDA blockade-induced learning deficits of rats in a 14-unit T-maze.

The present study examined the effects of multi-site activation of the glycine and polyamine sites of the NMDA receptor on memory formation in rats learning a 14-unit T-maze task. The competitive NMDA receptor antagonist, (+/-)-3-(2-carboxypiperazine-4-yl)-propyl-1-phosphonic acid (CPP, 9 mg/kg), was used to impair learning. The objectives were two-fold: (1) to investigate the effects of independent stimulation of the strychnine-insensitive glycine site or the polyamine site; (2) to investigate the effects of simultaneous activation of these two sites. Male, Fischer-344 rats were pretrained to a criterion of 13 out of 15 shock avoidances in a straight runway, and 24 h later were trained in a 14-unit T-maze that also required shock avoidance. Prior to maze training, rats received intraperitoneal (i.p.) injections of saline, saline plus CPP, CPP plus the glycine agonist, D-cycloserine (DCS, 30 or 40 mg/kg), CPP plus the polyamine agonist, spermine (SPM, 2.5 or 5 mg/kg), or CPP plus a combination of DCS (7.5 mg/kg) and SPM (0.625 mg/kg). Individual administration of either DCS or SPM attenuated the CPP-induced maze learning impairment in a dose-dependent manner. However, the combined treatment with both DCS and SPM completely reversed the learning deficit at doses five-fold less than either drug given alone. These findings provide additional evidence that the glycine and polyamine modulatory sites of the NMDA receptor are involved in memory formation. Furthermore, the potent synergistic effect resulting from combined activation of the glycine and polyamine sites would suggest a stronger interaction between these two sites than previously considered, and might provide new therapeutic approaches for enhancing glutamatergic function.

Animals↗
PubMed1998

An evaluation of the biomechanical response of the tooth and periodontium to orthodontic forces in adolescent and adult subjects.

This study was designed to quantify the magnitude of tooth mobility in adolescents and adults, and to investigate the differences in the biomechanical response of tooth and periodontium to orthodontic forces. The initial displacement of the maxillary central incisor was measured in 50 adolescent and fifty adult patients and the biomechanical properties of the periodontium were examined using the finite element method (FEM) and supporting experimental data. The magnitude of tooth mobility was significantly greater in the adolescent group than in the adult group. By integrating the differences in tooth mobility in both subject groups with analytical tooth displacements, the Young's modulus of the periodontal ligament (PDL) was demonstrated to be greater in the adults than in the adolescent subjects. The differing biomechanical properties of the PDL in adults were demonstrated to result in almost equivalent or somewhat increased stress levels in the PDL in adult subjects. It is suggested that this might produce a reduction in the biological response of the PDL and thus lead to a delay in tooth movement in adults.

Adolescent↗
PubMed1997

Self-esteem instability and its implications for HIV prevention among gay men.

This study, using a modified State Self-Esteem Scale (SSES), examined self-esteem instability and its association with risky sexual behavior among 455 gay and bisexual men. A self-administered questionnaire included the SSES and measures of intimacy, loneliness, social support, and ways of coping. Analysis of variance showed that the self-esteem of participants who recently engaged in unprotected anal intercourse with nonprimary partners was more unstable than the self-esteem of participants who did not engage in unprotected anal intercourse. Self-esteem instability was associated with higher avoidance coping, higher loneliness, and lower social support. Episodes of self-esteem injury might motivate some gay men to engage in risky sex. HIV prevention strategies with gay men should target the quality of their interpersonal relationships and community supports.

Adaptation, Psychological↗
PubMed1997

Internal objects--a theoretical analysis of Jungian and Kleinian models.

In this paper I discuss the ways in which experimental and objective research from cognitive science and developmental psychology can help analysts evaluate the theoretical models of mental objects which we use; I indicate the ways in which such evidence tends to support models of internal objects as mental representations or developmental capacities rather than as wish-fulfilling expressions of instinctual drives. This kind of empirical evidence is not just of academic interest but also has direct clinical relevance, particularly with borderline patients; such patients' sense of identity is totally dependent on the analyst's understanding of their internal world and for this to be misunderstood by the analyst can be catastrophic. An accurate theoretical model of mental objects can therefore help analysts to contain their patients more effectively.

Adult↗
PubMed1997

Loneliness and sexual risk behavior in gay men.

This study examined loneliness in a sample of gay men and its association with unprotected anal intercourse, social support, instability of self-esteem, intimacy, and coping. A sample of 470 urban gay men completed a self-administered questionnaire. Participants scored high on Loneliness in comparison to other samples. Measures of Intimacy, Social Support, Instability of Self-esteem, monogamous relationship status, and use of Avoidance Coping predicted 58.5% of the variance in Loneliness scores. Both social and psychological variables appear to be important for understanding loneliness in this population. Men who had unprotected anal intercourse with nonprimary partners during the previous six months scored higher on Loneliness than other participants, but those who did so with primary partners scored the lowest. Episodes of unprotected anal intercourse with nonprimary partners might have been Avoidance strategies to help participants cope with loneliness or or other negative affect.

Adolescent↗
PubMed1996

Infrainguinal arterial reconstruction with nonreversed greater saphenous vein.

PURPOSE: This study was undertaken to examine the effectiveness and the possible advantages of infrainguinal arterial reconstruction with nonreversed greater saphenous vein (NRGSV) grafts. We reviewed the results achieved with 189 consecutive NRGSV bypass procedures from July 1, 1985, to August 31, 1995, and compared them with 568 consecutive in situ greater saphenous vein (INGSV) bypass procedures completed over the same interval. METHODS: NRGSV bypass procedures were performed by selecting the optimum inflow and outflow vessels and then excising the best available appropriate-length segment of greater saphenous vein. The valves were lysed with a Mills valvulotome using gentle antegrade distention with an isotonic electrolyte solution containing heparin (1000 U/500 ml) and papaverine (60 mg/500 ml). The graft was then translocated to the inflow site, where the proximal and distal anastomoses were sequentially completed, followed by a completion arteriography. RESULTS: Demographic and risk factor characteristics did not differ between patients who underwent NRGSV and those who underwent INGSV bypass. Compared with INGSV bypasses, NRGSV bypasses were more commonly secondary procedures (26% vs 8%; p < 0.001) and were more often performed for limb salvage indications (89% vs 68%; p < 0.001). NRGSV bypasses also had more distal inflow vessels (23% superficial femoral artery [SFA] and 28% popliteal artery [POP] vs 10% SFA and 1% POP; p < 0.001) and more distal outflow vessels (52% tibial and 22% pedal artery vs 47% tibial and 3% pedal artery; p < 0.001) than did INGSV bypasses. Despite the higher incidence of secondary bypass procedures and more distal outflow vessels in the NRGSV group, the overall results achieved at 5 years did not differ between the two groups. The 5-year primary patency rates were 65% +/- 5% for NRGSV and 72% +/- 3% for INGSV (p < 0.12), and the 5-year secondary patency rates were 74% +/- 5% and 82% +/- 2% (p < 0.08), respectively. Similarly, the 5-year limb salvage rate among bypass procedures performed for limb salvage indications did not differ for NRGSV (82% +/- 5%) and INGSV (90% +/- 2%; p < 0.06). CONCLUSIONS: The application of the NRGSV bypass graft preserves the INGSV's main advantage of optimal size match between artery and vein at each anastomosis, but facilitaties the tailoring of the procedure to the patients anatomy and the completion of the bypass with the shortest, best-quality conduit available. Our application of the NRGSV in a more challenging series of bypass procedures produced equivalent results to those achieved in a concurrent series of INGSV bypass procedures.

Aged↗
PubMed1996

A national survey of orthodontic facebow injuries in the UK and Eire.

There have been several reports of soft tissue injuries from orthodontic facebows in the dental and medical literature, but the magnitude of the problem in the UK and Eire has never been previously investigated. In order to obtain information, questionnaires were distributed to 1682 Dental practitioners providing orthodontic treatment in the UK and Eire. A total of 1117 (66 per cent) replied. Of these 859 (77 per cent) reported using Kloehn type facebows. Thirty-one practitioners (3.6 per cent) gave details of 33 injuries from Kloehn type facebows. The results of this questionnaire are compared and discussed with previous reports in the dental and medical literature. The relative effectiveness of extra-oral traction safety products is discussed.

Adolescent↗
PubMed1996

Managed care fundamentals: implications for health care organizations and health care professionals.

Managed care is changing our health care delivery system as radically as the computer chip has changed telecommunications. Health care professionals and organizations that do not understand managed care's implications will not be prepared for the future. For example, one implication of managed care is payment capitation, which is the transfer of financial risk from the insurer to the provider. As a result, health care providers, including occupational therapy professionals, need to be better managers of scarce resources by recognizing the cost implications among various alternative procedures while still delivering quality care. Under managed care with capitation, occupational therapists will need to learn to provide services within the parameters of a fixed budget, requiring reengineering of the therapies and processes of care and a considerable reduction in the procedures and modalities for any given treatment or therapy. As a result, patients will be required to do more for themselves, and occupational therapists will have to become better patient educators and motivators. Additionally, managed care will require changes in professional curriculums, emphasis through continuing education, and assimilation of better cost information to practitioners to facilitate decision making. Implications of managed care other than payment capitation are assigning to enrollees a gatekeeper who is responsible for limiting access to costly specialty services, practicing utilization review to audit usage patterns and provide constructive recommendations to reduce costs and improve service quality, and forming networks and associations among medical providers for developing economies of scale and providing an integrated continuum of health care services to enrollees.

Capitation Fee↗
PubMed1995

Increased survival after major thermal injury: the effect of growth hormone therapy in adults.

BACKGROUND: Advances in the management of patients with major thermal injury have resulted in a progressive increase in survival rates. We report preliminary data evaluating the safety and potential efficacy of human growth hormone (HGH) administration in a high-risk population of burned patients. METHODS: From 1989 to 1993, 69 patients sustaining major burns (defined as patient age plus percentage of body surface area with deep second- and third-degree burns > or = 90) were evaluated. Patients routinely received anti-inflammatory pharmacotherapy including antioxidants, an endotoxin binder, and cyclooxygenase blockade. Half of the 54 patients who survived more than 7 days received HGH to enhance wound healing. Injury severity, morbidity, and mortality for patients receiving HGH was compared to the 27 patients not receiving HGH. RESULTS: For the entire population (n = 69), average age was 56 +/- 23 years, body surface area burned was 58% +/- 24%, and 30% sustained smoke inhalation. Actual mortality was 41%, significantly less than the more than 70% mortality rate predicted from reported outcome data. Patients receiving HGH were well matched with the group not receiving HGH with respect to extent of injury, burn management, pharmacotherapy, and in-hospital morbidity. Mortality of the patients receiving HGH was 11%, significantly less than the 37% mortality rate of the patients without HGH (p = 0.027). CONCLUSION: Compared to standard predictors of burn mortality our small patient group appears to have an improved survival rate, suggesting that the use of anti-inflammatory agents appears safe and potentially beneficial. Patients receiving HGH exhibited minimal drug-related complications and mortality rates were improved when this population was compared with both predicted mortality rates and a well-matched control population of concurrently treated patients. Prospective blinded trials are now necessary to confirm these findings in a larger patient group.

Adolescent↗
PubMed1995

Alcohol: a drug of dreams.

In this paper I have explored the way in which regressive phantasies of fusion may be brought into being by the heavy consumption of alcohol and the cerebral changes which result, which impair the individual's capacity to digest new information and experience; change therefore has to be resisted and loss and depressive anxiety cannot be experienced and worked through, hindering individuation. Two paradigms, one based on organic brain function and the other on psychodynamic understanding are brought together and shown not to be contradictory.

Alcoholism↗
PubMed1995

Crystal bonding--an adhesive system with a future?

The primary objective of this investigation was to evaluate the crystal bonding technique and to: (1) study the effect on crystal size, coverage, and morphology of altering the concentration of lithium sulphate in a crystal growth solution; (2) investigate the potential for reattachment of brackets, following the use of the crystal growth technique; (3) assess the deterioration of the crystal growth conditioning solution with time; (4) investigate the influence of polyacrylic acid enamel pretreatment on the bond strength subsequently achieved with the crystal growth technique; and (5) confirm that the use of crystal growth solutions to attach orthodontic brackets, results in minimal enamel surface change on debond when compared to the acid etch technique. The results of the study suggest that altering the lithium sulphate concentration of the crystal growth solution results in little alteration in the size, morphology, and coverage of crystal produced. The crystal growth technique allows reattachment of orthodontic brackets with no obvious deterioration in bond strength and the crystal growth solution shows little deterioration in performance after storage for 2 years. However, the hope that the use of the crystal growth technique might be a routine and valid alternative to the acid etch technique could not be confirmed.

Acid Etching, Dental↗