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Biomedical subjects

M L Jones

Publications and source records attributed to M L Jones.

At least 19 recordsLinked to original sources
PubMed2000

Contextual control over conditioned responding in a latent inhibition paradigm.

We used 1-, 2-, and 3-context designs to study the control exerted by contexts over freezing in rats exposed to a conditioned stimulus (CS) in advance of its pairing with a shock unconditioned stimulus. The latent inhibition observed when preexposure, conditioning, and testing occurred in the same context was attenuated if preexposure occurred in a different context to conditioning and testing. Latent inhibition (i.e., attenuated performance) was restored in a CS-specific manner if preexposure and testing occurred in the same context and conditioning in a different one. Latent inhibition was also reduced by a long retention interval but remained specific for a particular context-CS relation. Finally, CS preexposure resulted in contextual control over the expression of excitatory conditioned performance. The results are discussed in terms of memory, associative, and associative-performance models of CS-preexposure effects.

Animals↗
PubMed2000

Contextual control over conditioned responding in an extinction paradigm.

Four experiments studied contextual control over rats' freezing to conditioned stimuli (CSs) that had been paired with shock and were then extinguished. In Experiment 1, rats were exposed to a CS A-shock and a CS B-shock pairing in Context C. CS A was then extinguished in Context A, and CS B in Context B. Freezing was renewed when each CS was presented in the context where the other CS had been extinguished. In Experiments 2-4, rats were exposed to a CS A-shock pairing in A and a CS B-shock pairing in B. They were then exposed to Context C where one, both, or neither of the CSs were extinguished, or where both CSs continued to be reinforced. On test, the rats froze more to CS A than to CS B in Context A, and more to CS B than to CS A in Context B, but only if the CSs had been extinguished. Thus, after extinction, rats use contexts to regulate retrieval not only of their memory for extinction, but also of their memory for the original conditioning episode.

Aged↗
PubMed2000

The influence of orthodontic adhesive properties on the quality of orthodontic attachment.

The objective of this study was to determine the resilience, glass transition temperature (Tg), ultimate flexural strength (UFS), and penetration coefficient of 3 composite adhesives (Concise, Transbond, and Right On) and a glass ionomer cement (Fuji Ortho LC). For 25 minutes after initial set, the composite materials were significantly more resilient than Fuji Ortho LC (P = .000). Resilience values for all materials increased for up to 90 minutes after initial set, reflecting a continuation of their setting reaction. Right On remained the most resilient material at 90 minutes after initial set (P < or = .01). At 120 minutes, there was no significant difference in the resilience of Concise, Right On, and Fuji Ortho LC. However, Transbond was significantly less resilient than these materials (P < or = .01). The composite materials recorded significantly higher glass transition values (89-123 degrees C) than Fuji Ortho LC (54 degrees C). The composite materials were also significantly stronger (61-68 MPa) than Fuji Ortho LC (35 MPa) in flexion. The penetration coefficients of Concise and Transbond were significantly higher (P < or = .001) than Right On and Fuji Ortho LC. However, the relative penetration coefficients of the materials studied did not appear to influence the degree of bracket base penetration achieved by the cements. In conclusion, Fuji Ortho LC offered a reduced energy-absorbing capacity immediately after bracket placement and reduced cohesive and mechanical adhesive strength. In addition, the glass transition temperature of Fuji Ortho LC was low; this may result in compromised attachment at temperatures above 60 degrees C. Significant differences in the penetration coefficient of the materials studied have been recorded. However, the penetration of the 4 cements into a range of bracket base morphologies was uniformly good. Therefore, the differences in penetration coefficient recorded should not influence the quality of the bracket cement interface provided.

Acrylic Resins↗
PubMed2000

Endotoxin and nanobacteria in polycystic kidney disease.

BACKGROUND: Microbes have been suspected as provocateurs of polycystic kidney disease (PKD), but attempts to isolate viable organisms have failed. Bacterial endotoxin is the most often reported microbial product found in PKD fluids. We assessed potential microbial origins of endotoxin in cyst fluids from 13 PKD patients and urines of PKD and control individuals. METHODS: Fluids were probed for endotoxin and nanobacteria, a new bacterium, by the differential Limulus Amebocyte Lysate assay (dLAL), genus-specific antilipopolysaccharide (LPS) antibodies, monoclonal antibodies to nanobacteria, and hyperimmune serum to Bartonella henselae (HS-Bh). Selected specimens were also assessed by transmission electron microscopy (TEM) and nanobacterial culture methods. RESULTS: LPS or its antigenic metabolites were found in more than 75% of cyst fluids tested. Nanobacteria were cultured from 11 of 13 PKD kidneys, visualized in 8 of 8 kidneys by TEM, and immunodetected in all 13 PKD kidneys. By immunodetection, nanobacterial antigens were found in urine from 7 of 7 PKD males, 1 of 7 PKD females, 3 of 10 normal males, and 1 of 10 normal females. "Nanobacterium sanguineum" was dLAL positive and cross-reactive with antichlamydial LPS and HS-Bh. Some cyst fluids were also positive for LPS antigens from Escherichia coli, Bacteroides fragilis and/or Chlamydia, and HS-Bh, as were liver cyst fluids from one patient. Tetracycline and citrate inhibited nanobacterial growth in vitro. CONCLUSION: Nanobacteria or its antigens were present in PKD kidney, liver, and urine. The identification of candidate microbial pathogens is the first step in ascertaining their contribution, if any, to human disease.

Adult↗
PubMed2000

Initial experiences with telerehabilitation and contingency management programs for the prevention and management of pressure ulceration in patients with spinal cord injuries.

Two alternative treatment methods for preventive interventions for pressure ulcers, tele-rehabilitation and contingency management, are discussed. Telerehabilitation uses a videophone that transmits both audio and still images over a telephone line. Using this technology, the WOC nurse can interview a patient who cannot be present at a clinic because of physical condition or distance. Telerehabilitation allows the nurse to assess a patient's pressure ulcer, consult with appropriate caregivers, and make recommendations for treatment. Contingency management procedures are designed for patients with high rates of noncompliance in skin care. The patients are seen as outpatients and are compensated systematically for appropriate skin care (ie, the lack of pressure ulcers). Examples of each of these patient interventions is described, discussed, and contrasted.

Ambulatory Care↗
PubMed2000

An evaluation of the stresses generated in a bonded orthodontic attachment by three different load cases using the Finite Element Method of stress analysis.

The objective of the investigation was to develop a clinically valid three-dimensional computer model of the orthodontic bracket-cement-tooth continuum, and determine the magnitude and distribution of stresses generated by three different load cases. A three-dimensional finite element model of the bracket-cement-tooth system was constructed consisting of 15,324 nodes and 2,971 finite elements. The stresses induced in the bracket-tooth interface by a masticatory load, a peel force and a twisting couple were recorded. The maximum principal stresses resulting from occlusal and 'twisting' forces are distributed toward the lute periphery. Peel forces, applied to the bracket tie wing, are concentrated beneath the bracket stem. Twisting forces result in the highest enamel stresses. The quality of orthodontic attachment can be explained by the magnitude and distribution of major principal stresses within the cement and impregnated bracket base. Shear and shear/peel forces are most likely to induce crack propagation within the adhesive layer. However, when a twisting action is used to remove orthodontic brackets, enamel failure is most likely. A clearer insight into the complexity of the bracket-cement-tooth system has been provided by numerical and finite element investigations. Further investigations, evaluating the influence of bracket base designs and orthodontic cement physical and geometric properties are indicated. Refereed Scientific Paper

Compressive Strength↗
PubMed2000

Chlamydial development is adversely affected by minor changes in amino acid supply, blood plasma amino acid levels, and glucose deprivation.

This study has demonstrated the extreme sensitivity of Chlamydia trachomatis growing in McCoy cells to small changes in external amino acid supply. In the absence of cycloheximide, a decrease in the amino acid concentration of medium to 75% of control values was sufficient to induce the growth of enlarged chlamydial forms of reduced infectivity. Morphology became more distorted and the yield of infectious particles from inclusions declined as medium amino acid levels were further reduced. These events correlated with a general decline in intracellular amino acids, as measured by high-performance liquid chromatography, suggesting that chlamydiae require a minimum concentration of each amino acid for normal development. Cycloheximide enhanced the production of normal organisms and increased infectivity yield in media, suggesting that the drug increased the available pool of amino acids. This was supported by intracellular amino acid analyses. Aberrant forms with reduced infectivity were also induced during supply of infected cell cultures with medium containing blood plasma amino acid concentrations, supporting the proposal that nutrient levels in vivo could promote abnormal chlamydial development. Markedly abnormal forms were also observed during glucose deprivation, providing further evidence that aberrant development is a general stress-related response.

Amino Acids↗
PubMed2000

Numerical investigation of fixed orthodontic brackets.

This paper presents the results of investigations into the mechanical behaviour of fixed orthodontic brackets. Special attention has been paid to the detailed modelling of the interface between the bracket base and an adhesive by which attachment is made to the tooth surface. Properties of this interface were taken as design parameters with the aim of investigating their influence on the stress field induced during bracket removal at the end of the treatment. Stress-strain analysis was performed using a finite element program developed in-house.

Dental Cements↗
PubMed2000

Do new roles contribute to job satisfaction and retention of staff in nursing and professions allied to medicine?

BACKGROUND: Studies have suggested that job dissatisfaction is a major factor influencing nurses' and occupational therapists' intention to leave their profession. It has also been related to turnover of qualified nurses. However, literature relating to these factors among nurses and professions allied to medicine in innovative roles is scarce. AIMS: This paper considers the views of 452 nurses and 162 professionals allied to medicine (PAMs) in innovative roles, on job satisfaction, career development, intention to leave the profession and factors seen as hindering and enhancing effective working. METHODS: A self-completion questionnaire was developed as part of a larger study exploring new roles in practice (The ENRiP Study). FINDINGS: Overall there was a high level of job satisfaction in both groups (nurses and PAMs). Job satisfaction was significantly related to feeling integrated within the post-holder's own professional group and with immediate colleagues, feeling that the role had improved their career prospects, feeling adequately prepared and trained for the role, and working to protocol. Sixty-eight percent (n = 415) of respondents felt the role had enhanced their career prospects but over a quarter of respondents (n = 163; 27%) said they would leave their profession if they could. Low job satisfaction was significantly related to intention to leave the profession. CONCLUSIONS: The vast majority of post-holders in innovative roles felt that the role provided them with a sense of job satisfaction. However, it is essential that the post-holders feel adequately prepared to carry out the role and that the boundaries of their practice are well defined. Career progression and professional integration both being associated with job satisfaction.

Adult↗
PubMed1999

Protection of calves against cryptosporidiosis with immune bovine colostrum induced by a Cryptosporidium parvum recombinant protein.

The purpose of the study was to determine if immunization with a recombinant protein (rC7) of Cryptosporidium parvum would induce immune bovine colostrum that protected calves against cryptosporidiosis following oral challenge with C. parvum oocysts. Late gestation Holstein cows with low titers of antibody to the p23 antigen of C. parvum were immunized three times with 300 microg affinity purified rC7 C. parvum recombinant protein (immune cows), or left nonimmunized (control cows). Colostrum was obtained from each cow in both groups and partitioned into identical aliquots of pooled immune colostrum or pooled control colostrum. Twelve calves obtained at birth received either immune or control colostrum within the first 2 h, and again at 12 and 24 h of age. Each calf was challenged orally with 10(7) C. parvum oocysts at 12 h of age and monitored for signs of cryptosporidiosis. All six calves administered pooled control colostrum developed severe diarrhea (mean total fecal volume = 8447+/-5600 ml) and shed an average of 1.87+/-1.66 x 10(12) C. parvum oocysts. None of the six calves administered pooled immune colostrum developed diarrhea (mean total fecal volume = 740+/-750 ml, p < 0.05), and shed significantly fewer oocysts (3.05+/-2.26 x 10(9), p < 0.05). The absence of diarrhea and 2.79 log10 (99.8%) reduction in oocyst excretion indicates that immune bovine colostrum induced by immunization with C. parvum recombinant protein rC7 provided substantial protection against cryptosporidiosis in neonatal calves.

Animals↗
PubMed1999

Leukocyte subsets and neutrophil function after short-term spaceflight.

Changes in leukocyte subpopulations and function after spaceflight have been observed but the mechanisms underlying these changes are not well defined. This study investigated the effects of short-term spaceflight (8-15 days) on circulating leukocyte subsets, stress hormones, immunoglobulin levels, and neutrophil function. At landing, a 1.5-fold increase in neutrophils was observed compared with preflight values; lymphocytes were slightly decreased, whereas the results were variable for monocytes. No significant changes were observed in plasma levels of immunoglobulins, cortisol, or adrenocorticotropic hormone. In contrast, urinary epinephrine, norepinephrine, and cortisol were significantly elevated at landing. Band neutrophils were observed in 9 of 16 astronauts. Neutrophil chemotactic assays showed a 10-fold decrease in the optimal dose response after landing. Neutrophil adhesion to endothelial cells was increased both before and after spaceflight. At landing, the expression of MAC-1 was significantly decreased while L-selectin was significantly increased. These functional alterations may be of clinical significance on long-duration space missions.

Adrenocorticotropic Hormone↗
PubMed1999

The cost and value of pre-registration clinical placements for Project 2000 students.

The research outlined in this article was commissioned by the Sheffield and North Trent College of Nursing and Midwifery to explore the cost implications of pre-registration clinical placements in the context of Project 2000. The authors outline the methodology and findings of an exercise designed to collect relevant cost information which was not readily available. On the basis of these findings, they suggest that: at 1995/1996 pay and prices, clinical placements cost the education provider approximately pound 890 per student per annum; in terms of real resources, the value to service providers of the service contribution made by second- and third-year nursing and midwifery students on ward-based placements outweighs the value of the time spent by qualified staff on their supervision and education. Once the funding assumptions underlying the introduction of Project 2000 have been taken into account, second- and third-year nursing and midwifery students benefit the service provider by on average pound 3.46 for every hour they spend in an unrostered ward-based placement. The service contribution made by students in community-based clinical placements cannot free staff time in the same way as on the wards and, because qualified staff in these areas are generally more highly graded, the value of the time they spend on the supervision and education of students on placement is higher than in ward-based placements. Second- and third-year students therefore appear to cost the service provider on average pound 0.48 for each hour they spend in a community-based placement. It was not possible to determine whether this cost translates into a reduction in patient contacts.

Cost-Benefit Analysis↗
PubMed1999

Application of a subjective health and safety rating system to Iowa farm operations.

A rapid, subjective health and safety assessment tool was developed and applied to 121 farm operations visited during a cross-sectional, on-farm industrial hygiene (IH) study of the Iowa Farm Family Health and Hazard Surveillance Project (IFFHHSP). The study utilized a single field investigator who conducted visits of farm operations from August 1995 to July 1996. The farm operations visited were randomly selected from a stratified, two-stage cluster sample of Iowa farm operations. The tool developed and applied to each farm operation--the Site Rank System--was based on the average of scores assigned to four different farm characteristics, which we believed would predict the health and safety status of the farm operations. Two of these characteristics were based on an assessment of each farm's operator (operator attitude and operator practices) and the other two were based on weighted scores assigned to physical components of the farm operation (status of facilities and status of equipment). The Site Rank System was found to have been assigned consistently, but an analysis comparing the Site Rank System scores to initial in-depth medical and environmental data gathered from the visited farm operations via self-reported questionnaires showed little correlation with outcomes. However, self-reported injuries (11 total) which occurred to the principal farm operators of the farm operations visited during the on-farm IH study phase (August 1995 to July 1996) correlated with low Site Rank System scores.

Agriculture↗
PubMed1999

An evaluation of the changes in maxillary pulpal blood flow associated with orthognathic surgery.

The objective of this study was to evaluate the use of the Laser Döppler Flowmeter (LDF) in the measurement of pulpal blood flow following orthognathic surgery and to conduct an initial study of the effects of a Le Fort I osteotomy on the pulpal blood flow of the maxillary central incisors. The design consisted of a preliminary prospective controlled consecutive clinical trial undertaken at the Orthodontic Clinic, University Dental Hospital NHS Trust, Wales, 1994. The study group consisted of 15 consecutive patients who were to receive a standard advancement Le Fort I osteotomy. Seven patients who were to undergo a mandibular advancement only acted as a control. A further 20 separate patients participated in a study for the assessment of measurement error. The blood flow in relative perfusion unit v. time, was measured using a Laser Döppler Flowmeter. Measurement error for flowmeter recordings with hand-held application and custom-made splint support showed no consistent difference or significant random variation between the two methods for holding the probe against the teeth (pooled S.D. of reproducibility 1/1 = 1.91/1.39 for custom splint location as opposed to 0.96/1.07 for hand-held/fixed bracket location). For the surgical patients under investigation no significant differences for maxillary pulpal blood flow were found in the control group (mandibular osteotomy) over time. However, in the maxillary osteotomy patients there was a tendency for an initial rise in the maxillary perfusion post-surgery as measured at the central incisor pulps, followed by an overall reduction at 6 months. As an example, the mean value for the upper right central showed a significant increase in blood flow during the immediate post-operative period (P < 0.05), but at 6 months after surgery demonstrated a statistically significant overall reduction in comparison with the presurgical reading (P < 0.001). The laser Döppler flowmeter is not an easy instrument to use in the clinical assessment of pulpal blood flow. However, it would appear from these longitudinal series of readings, taken over a 6-month period on 15 patients, that the maxillary perfusion recorded at the central incisor pulps may be permanently affected in many Le Fort I osteotomy patients. For patients that already have a prejudiced blood supply this could lead to devitalization and discoloration of incisors. It is not known if this affect on the perfusion of the pulp continues beyond 6 months post-surgery.

Blood Flow Velocity↗