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Biomedical subjects

R Boyd

Publications and source records attributed to R Boyd.

At least 37 records · Page 2Linked to original sources
PubMed2001

Orthodontic treatment of a mildly crowded malocclusion using the Invisalign System.

The 35-year-old male patient was treated at the University of the Pacific, San Francisco U.S.A., as part of an on-going study investigating the feasibility of the Invisalign System of tooth movement. The study called for 40 subjects, 10 with minor, 15 with moderate and 15 with severe tooth deviation. This patient fell into the "moderate" degree-of-difficulty category, due to the position of the maxillary incisors. Treatment time with the initial series of aligners was 14 months. Treatment objectives were met, with the exception of adequate anterior overbite.

Adult↗
PubMed2001

Built for speed, not for comfort. Darwinian theory and human culture.

Darwin believed that his theory of evolution would stand or fall on its ability to account for human behavior. No species could be an exception to his theory without imperiling the whole edifice. The ideas in the Descent of Man were widely discussed by his contemporaries although they were far from being the only evolutionary theories current in the late nineteenth century. Darwin's specific evolutionary ideas and those of his main followers had very little impact on the social sciences as they emerged as separate disciplines in the early Twentieth Century. Not until the late twentieth century were concerted, sophisticated efforts made to apply Darwinian theory to human behavior. Why such a long delay? We argue that Darwin's theory was rather modern in respects that conflicted with Victorian sensibilities and that he and his few close followers failed to influence any of the social sciences. The late Twentieth Century work takes up almost exactly where James Baldwin left off at the turn of the century.

Behavior↗
PubMed2000

Glucocorticoid production in the murine thymus.

Glucocorticoid hormones are known to act as important modulatory factors in the development of autoimmune diseases, and to play an important role in thymic T-cell selection. There seems to be a finely balanced equilibrium between the apoptosis-inducing effects of glucocorticoid and T cell receptor ligand binding. Here we are investigating whether glucocorticoid-induced T cell apoptosis is mainly dependent on circulating glucocorticoid levels or if the thymus itself is able to produce glucocorticoids. To this end, we attempted to demonstrate enzyme activities of the whole set of steroidogenic enzymes for the synthesis of glucocorticoids in murine thymic tissue. We isolated steroidogenic organelles from thymic tissue, incubated these with radioactive (precursor) steroids in vitro, and visualized the resulting products by thin-layer chromatography. Our results show that the thymus possesses all enzymes and cofactors required for glucocorticoid production. However, an intact thymic architecture is necessary for glucocorticoid production, since 11beta-hydroxylase was not detected in irradiated thymi or in a thymic epithelial cell line. The results of these experiments show that the whole glucocorticoid metabolism takes place within the thymus. This finding provides the biochemical basis for the in situ effects of glucocorticoid hormones on thymocyte development and selection.

Animals↗
PubMed2000

Cheap talk when interests conflict.

Most evolutionary analyses of animal communication suggest that low-cost signals can evolve only when both the signaller and the recipient rank outcomes in the same order. When there is a conflict of interest between sender and receiver, honest signals must be costly. However, recent work suggests that low-cost signals can be evolutionarily stable, even when the sender and the receiver rank outcomes in different orders, as long as the interest in achieving coordination is sufficiently great. In this paper, we extend this body of work by analysing a game theory model that shows that low-cost signals can evolve when there are conflicts of interest and no interest in coordination, as long as individuals interact repeatedly. We also present an empirical example indicating that female rhesus macaques, Macaca mulatta, use honest, low-cost, vocal signals to facilitate interactions when conflicts of interest exist. Copyright 2000 The Association for the Study of Animal Behaviour.

Journal Article↗
PubMed2000

Regulation of chicken haemopoiesis by cytokines.

The continuous production, control and functional activation of blood cells involves a complex series of cellular events in which a small population of stem cells generates large numbers of mature cells. The survival, proliferation and development of these cells is strictly dependent on extracellular signals, among these are polypeptide regulators generally known as cytokines. While a large number of mammalian cytokines with proliferative and inhibitory effects have been described in detail, it is surprising that comparatively little is known of the avian system. Given the success of human cytokines as a model, the ability to manipulate the chicken haemopoietic and lymphopoietic systems by precise application of purified cytokines provides a rational approach to defence against disease. As a general caveat, an increased awareness of the existence of regulatory networks and the likelihood that these regulators were designed to function most effectively when acting in combination, will provide an understanding into the regulation of haemopoiesis and hence find application in both clinical and agricultural research.

Animals↗
PubMed2000

Witnessed resuscitation by relatives.

Witnessed resuscitation is the process of active 'medical' resuscitation in the presence of family members. Witnessed resuscitation though not as yet wide spread in practice is becoming established. Early reports of programs designed to promote such a process first appeared in the early 1980s. More recent work appears to show both public support and a desire for inclusion in the resuscitation process. Some research has been produced that indicates both satisfaction and psychological benefit for those relatives enabled to witness. Limited work only, exists pertaining to the effects on health care providers and these reports currently do not show any significant deleterious effects. Approval of witnessed resuscitation programs is not universal amongst all groups of health care workers. Concerns about the ethics of witnessed resuscitation and its medico-legal implications have been raised. The quality of the initial witnessed resuscitation reports is however variable and there is a great need for further work to validate the initial findings particularly in the areas of psychological stressors in staff and risk management implications.

Attitude of Health Personnel↗
PubMed2000

Analgesic effects of botulinum toxin A: a randomized, placebo-controlled clinical trial.

Postoperative pain in children with spastic cerebral palsy (CP) is often attributed to muscle spasm and is difficult to manage using opiates and benzodiazepines. Adductor-release surgery to treat or prevent hip dislocation in children with spastic CP is frequently performed and is often accompanied by severe postoperative pain and spasm. A double-blinded, randomized, placebo-controlled clinical trial of 16 patients (mean age 4.7 years) with a mainly spastic type of CP (either diplegic or quadriplegic in distribution) was used to test the hypothesis that a significant proportion of postoperative pain is secondary to muscle spasm and, therefore, might be reduced by a preoperative chemodenervation of the target surgical muscle by intramuscular injection of botulinum toxin A (BTX/A). Compared with the placebo, BTX/A was found to be associated with a reduction in mean pain scores of 74% (P<0.003), a reduction in mean analgesic requirements of approximately 50% (P<0.005), and a reduction in mean length of hospital admission of 33% (P<0.003). It was concluded that an important component of postoperative pain in the patient population is due to muscle spasm and this can be managed effectively by preoperative injection with BTX/A. These findings may have implications for the management of pain secondary to muscle spasm in other clinical settings.

Botulinum Toxins, Type A↗
PubMed2000

Secondary conditions and women with physical disabilities: a descriptive study.

OBJECTIVE: To examine secondary conditions and their relationship to life satisfaction in women with physical disabilities. DESIGN: Survey research. SETTING: Metropolitan Philadelphia. PARTICIPANTS: Women aged 18 to 65 years with self-reported functional limitations associated with neurologic, neuromuscular, brain, sensory, arthritic, spinal cord, orthopedic, or other chronic conditions. MAIN OUTCOME MEASURES: Secondary conditions, health status, functional status, and life satisfaction. RESULTS: In the past year, an average of 12 +/- 6.1 (SD) secondary conditions were experienced. Fatigue, mobility, physical deconditioning, spasticity, and joint pain were reported most frequently, followed by depression, chronic pain, access problems, weight problems, and isolation. In comparing women with multiple sclerosis (MS) and those with other disabling conditions, women with MS had higher secondary conditions problem index (SCPI) scores for bladder, bowel, and sexual dysfunction than women in the mixed disability group. Other secondary conditions with the highest SCPI scores remained similar. Self-reported emotional health status and SCPI scores were the only significant predictors of life satisfaction. CONCLUSION: Secondary conditions influence health status and quality of life for women with physical disabilities. Despite differences among disability groups in terms of the type of secondary conditions, common secondary conditions experienced by most women may be amenable to non-disability-specific health promotion programs.

Activities of Daily Living↗
PubMed2000

The relationship of 2 professional occlusal indexes with patients' perceptions of aesthetics, function, speech, and orthodontic treatment need.

The aim of this study was to determine the relationship between patients' perceptions of orthodontic treatment need and need as determined with professionally derived indexes, namely the dental aesthetic index and the index of orthodontic treatment need. This study was undertaken at orthodontic offices in San Francisco, Calif. The pretreatment study casts of 50 consecutive patients, presenting for orthodontic treatment, were objectively assessed with these indexes by 2 examiners trained and calibrated in their use. Patients were asked to complete a questionnaire consisting of 4 questions addressing appearance, function, speech, and treatment need, using either a 5-point Likert scale or a yes/no response. The professionally derived indexes showed that statistically significant correlations existed between the aesthetic component and dental health component (r = 0.46; P <.01), the aesthetic component and dental aesthetic index (r = 0.54; P <.01), and the dental health component and dental aesthetic index (r = 0.46; P <.01). Statistically significant correlations were also found for subjective assessments between biting/chewing and speech (r = 0.31; P <.05), between speech and the aesthetic component (r = -0.39; P <. 01) and the dental aesthetic index (r = 0.34; P <.05), and between the aesthetic component and appearance (r = -0.28; P <.05). Logistic regression analysis after dichotomization (treatment/no treatment need) confirmed that the aesthetic component was the only statistically significant factor (odds ratio, 0.57; 95% confidence limits 0.34 to 0.97).

Adolescent↗
PubMed2000

Does witnessed cardiopulmonary resuscitation alter perceived stress in accident and emergency staff?

The aim of this study was to ascertain if the presence of patients' relatives during cardiopulmonary resuscitation altered perceived symptoms of stress in accident and emergency personnel participating in resuscitation attempts. An anonymous structured questionnaire survey of all accident and emergency staff participating in non-traumatic adult cardiopulmonary resuscitation was designed to elicit symptoms of an acute stress reaction within 24 hours based on ICD-10 diagnostic criteria. One hundred and fourteen staff replies were received, a reply rate of 89%. Twenty-five replies had two or more symptoms of an acute stress reaction. The grade or role of the staff member had no influence on the presence of stress symptoms. There was no difference in rates of reporting between staff resuscitating in the presence or absence of relatives. It is concluded that the presence of relatives witnessing resuscitation attempts does not affect self-reported stress symptoms in staff participating in resuscitation attempts.

Acute Disease↗
PubMed1999

ChT1, an Ig superfamily molecule required for T cell differentiation.

The thymus is colonized by circulating progenitor cells that differentiate into mature T cells under the influence of the thymic microenvironment. We report here the cloning and function of the avian thymocyte Ag ChT1, a member of the Ig superfamily with one V-like and one C2-like domain. ChT1-positive embryonic bone marrow cells coexpressing c-kit give rise to mature T cells upon intrathymic cell transfer. ChT1-specific Ab inhibits T cell differentiation in embryonic thymic organ cultures and in thymocyte precursor cocultures on stromal cells. Thus, we provide clear evidence that ChT1 is a novel Ag on early T cell progenitors that plays an important role in the early stages of T cell development.

Amino Acid Sequence↗
PubMed1999

Development, organization and function of the thymic medulla in normal, immunodeficient or autoimmune mice.

Thymopoiesis is initiated by the colonisation of the epithelial rudiment with blood-borne hemopoietic precursors. Their subsequent differentiation to the functionally mature T cell subsets is exquisitely linked to sequential interaction with a diverse array of thymic epithelial cells which form discrete microenvironments. The development and organisation of the epithelium, however, is in turn controlled by thymocyte subsets. In particular the medulla organization depends upon activating signals provided by mature thymocytes to epithelial and dendritic cells. These signals are lacking in RelB-deficient mice leading to the disorganization of the corticomedullary junction and abnormal negative selection despite normal thymocyte maturation. This thymic stromal cell architecture phenotype is found in autoimmune diseases suggesting that abnormalities in the establishment of medullary microenvironments might be linked to the development of autoimmunity.

Animals↗
PubMed1999

High- or low- technology measurements of energy expenditure in clinical gait analysis?

The repeatability of energy-expenditure measurements were studied in five children and four adults without disabilities using the Cosmed K4 (high technology). The ability to detect change in measurements was compared between this instrument and the Physiological Cost Index (PCI; low technology). The results of repeatability (95% range) for oxygen cost were 13.1% in children and 13% in adults. In contrast, the SD of PCI was 6 to 72% of the mean in adults and wider in children (91%; 95% range). The validity of PCI as an outcome measure was questioned. In addition, 177 children with motor disability were prospectively studied using the Cosmed K4. Previous experience with the Cosmed K2 (intermediate technology) helped to develop a practical and repeatable protocol for testing children with disability using the Cosmed K4. The protocol commenced with 5 minutes of rest to achieve baseline values of heart rate and oxygen consumption, followed by 10 minutes of continuous walking at a self-selected speed on a 10-metre level oval walking track. The test concluded with 5 minutes of rest to monitor the return to baseline values. Ninety-one percent of the children with disability quickly reached a steady-state of oxygen consumption and carbon-dioxide production. The carbon-dioxide sensor in the Cosmed K4 has enabled a new group of severely involved children with cerebral palsy (9%) to be defined. These children have been termed 'physiologically marginal ambulators'.

Adult↗