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Biomedical subjects

D Craig

Publications and source records attributed to D Craig.

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

Comparison of the early stages of forced unfolding for fibronectin type III modules.

The structural changes accompanying stretch-induced early unfolding events were investigated for the four type III fibronectin (FN-III) modules, FN-III(7), FN-III(8), FN-III(9), and FN-III(10) by using steered molecular dynamics. Simulations revealed that two main energy barriers, I and II, have to be overcome to initiate unraveling of FN-III's tertiary structure. In crossing the first barrier, the two opposing beta-sheets of FN-III are rotated against each other such that the beta-strands of both beta-sheets align parallel to the force vector (aligned state). All further events in the unfolding pathway proceed from this intermediate state. A second energy barrier has to be overcome to break the first major cluster of hydrogen bonds between adjacent beta-strands. Simulations revealed that the height of barrier I varied significantly among the four modules studied, being largest for FN-III(7) and lowest for FN-III(10), whereas the height of barrier II showed little variation. Key residues affecting the mechanical stability of FN-III modules were identified. These results suggest that FN-III modules can be prestretched into an intermediate state with only minor changes to their tertiary structures. FN-III(10), for example, extends 12 A from the native "twisted" to the intermediate aligned state, and an additional 10 A from the aligned state to further unfolding where the first beta-strand is peeled away. The implications of the existence of intermediate states regarding the elasticity of fibrillar fibers and the stretch-induced exposure of cryptic sites are discussed.

Amino Acid Sequence↗
PubMed2000

Should I scan or should I scope?

This paper proposes a clinical points-based method that can be used by less experienced orthopaedic surgeons who are faced with the dilemma 'Should I scan or should I scope?' By considering the history, the age of the patient and the clinical findings one can expect diagnostic performance equivalent to magnetic resonance imaging. The cost of MRI services must be considered when selecting patients for this investigation. We have suggested a threshold for requesting an MRI scan depending on the relative costs.

Journal Article↗
PubMed2000

Momentum transport from nonlinear mode coupling of magnetic fluctuations

A cause of observed anomalous plasma momentum transport in a reversed-field pinch is determined experimentally. Magnetohydrodynamic theory predicts that nonlinear interactions involving triplets of tearing modes produce internal torques that redistribute momentum. Evidence for the nonlinear torque is acquired by detecting the correlation of momentum redistribution with the mode triplets, with the elimination of one of the modes in the triplet, and with the external driving of one of the modes.

Journal Article↗
PubMed2000

Control of density fluctuations and electron transport in the reversed-field pinch

A recent study conducted on the Madison Symmetric Torus reversed-field pinch has shown that control of density fluctuations can be achieved through modification of the current density profile. Most of the power in the density fluctuations is directly associated with core-resonant resistive tearing modes. We report that, during auxiliary current drive experiments, these density fluctuations are reduced about an order of magnitude over the entire plasma cross section and the resulting electron confinement is increased eightfold.

Journal Article↗
PubMed2000

Crystal supramolecular motifs: columns of embracing Ph3PMe+ or Ph3PCI+ cations controlling formation of.

The crystal structures of (Ph3PCl)2[Cu3Cl8] (1) (triclinic, space group P1, a = 9.480(6) A, b = 10.243(8) A, c = 11.232(6) A, alpha = 86.76(4) degrees, beta = 66.62(5) degrees, gamma = 83.92(4) degrees, Z = 1) and (Ph3PMe)2[Cu3Br8] (2) (triclinic, space group P1, a = 9.795(4) A, b = 10.472(4) A, c = 11.392(4) A, alpha = 86.67(3) degrees, beta = 66.67(3)degrees, gamma = 83.14(3) degrees, Z = 1), reported here, demonstrate a new supramolecular motif for cations of the type Ph3PY+ where Y is CH3 or Cl. The crystals contain columns of cations propagated by alternating 6-fold phenyl embraces (6PE) and pseudo-6PE: the pseudo-6PE described here contains four phenyl rings and two hetero groups (Cl or CH3), and is symbolized as 4P2Y. The zigzag sequence of cations engaged in ...6P...4P2Y...6P...4P2Y... is similar to the zigzag chain of infinite 6-fold phenyl embraces (ZZI6PE) frequently adopted by Ph4P+ cations in crystals. One-dimensionally nonmolecular anion chains with repeat unit [Cu3X8] run parallel to and between the columns of cations. The coordination geometry in the [Cu3X8(2-)]1 to infinity chain has not been observed in crystals with other cations, and it is postulated that the attractive interactions between cations in the pseudo-ZZI6PE crystal supramolecular motif control the geometry of the anions through the requirement for commensurability of cation columns and anion chains.

Journal Article↗
PubMed2000

Practical logics: the shapes and lessons of popular medical knowledge and practice--examples from Vietnam and Indigenous Australia.

Popular medical knowledge and practice exist in forms that people are able to remember, and that they use to manage their daily lives. This knowledge is fundamentally practical and relates to the patterns of everyday life and the rhythms of the body. The broad "polythetic" concepts of this knowledge system are typically drawn from both dominant and other medical knowledges, and combined in pragmatic, mnemonic ways that constitute a hybrid system. Such popular medical knowledge is attuned to local, family and cultural patterns of medical and other authority, and to the personal dispositions and environmental contexts of its users. Health promoters and educators who understand these formal, embodied and familiar dimensions of popular knowledge can potentially mimic this knowledge system, making their interventions a sustainable part of everyday family life.

Australia↗
PubMed2000

Asthma management in indigenous children of a remote community using an indigenous health model.

OBJECTIVE: To describe the management of asthma in children in a remote indigenous community and the delivery of subspecialist service through the indigenous health-care model. METHODOLOGY: Children referred by indigenous health-care workers were evaluated prospectively by paediatric respiratory physicians, based on a standardized protocol, at a primary health care setting at Thursday Island, Queensland. RESULTS: Forty of the 54 children referred with a provisional diagnosis of asthma did have asthma, with 30% having persistent asthma. Only 59% of parents knew the dose of the medication prescribed and 80% had minimal knowledge of the medications. In 88% of children, the management of asthma was improved by introduction of an appropriate spacer device and changing the dose and type of medications. CONCLUSIONS: The management of children with asthma in the Torres region can be improved substantially by the use of age appropriate delivery devices and medications, and improving knowledge of asthma. Specialist delivery service to remote indigenous communities can be effectively delivered in partnership with the indigenous health service. The high proportion of persistent asthma in the Torres Straits community in comparison to urbanised Australia raises issues of inequity of appropriate medical service delivery to remote indigenous communities.

Adolescent↗
PubMed2000

Effects of an abilities-focused program of morning care on residents who have dementia and on caregivers.

OBJECTIVE: To conduct a controlled investigation to examine the effects of an abilities-focused program of morning care on the interaction behaviors and functioning of residents with dementia and on caregivers' interaction behaviors and perceptions of caregiving. DESIGN: A quasi-experimental, repeated measures design. SETTING: The study was conducted on four, nursing-home-level cognitive supports units in a geriatric care center. One of the units was randomly selected as the experimental unit; the other three served as controls. PARTICIPANTS: The final sample consisted of 40 residents (20 each in the experimental and three control groups) and 44 caregivers (16 on the experimental unit and 28 on the three control units). INTERVENTION: An educational program on delivering abilities-focused morning care, designed by the authors, was provided to caregivers on the experimental unit. MEASUREMENTS: Measures were taken at baseline and at 3 and 6 months postintervention with regard to residents' interaction behaviors, level of agitation, and level of function and to caregivers' interaction behaviors, perceived ease of caregiving, and level of stress. RESULTS: Repeated measures analysis of variance (RM-ANOVA) was used to compare the experimental and control groups in regard to changes in the outcomes over time. Results indicated that the abilities-focused program had statistically significant effects on (a) residents' personal attending and calm/functional behaviors, level of agitation, and levels of overall and social function, and (b) caregivers' verbal relevance and personal attending, relaxed, and social/flexible behaviors. CONCLUSIONS: The evidence suggests that both residents and caregivers benefit from morning care that is oriented toward the abilities of people with dementia.

Aged↗
PubMed2000

Dapsone-induced methhaemoglobinaemia: a source of diagnostic confusion.

Arterial desaturation as measured using pulse oximetry may not reflect cardiorespiratory disease; other possible causes, including certain drugs, should be sought. Within the literature, examples exist of dapsone-induced methaemoglobinaemia causing diagnostic confusion, particularly where respiratory disease is a feature. Few cases have been reported that demonstrate the potential of relatively low levels of methaemoglobinaemia to upset pulse oximetry readings. We describe three examples of dapsone-induced methaemoglobinaemia emphasising the potential for low-grade methaemoglobinaemia to cause diagnostic confusion. Widespread use of the pulse oximeter indicates this problem may occur more regularly, hence there is a need for increased awareness.

Adolescent↗
PubMed1999

Phase I trial of a recombinant vaccinia virus encoding carcinoembryonic antigen in metastatic adenocarcinoma: comparison of intradermal versus subcutaneous administration.

The principal objectives of this trial were twofold: (a) to examine the safety and relative efficacy of intradermal needle injection versus s.c. jet administration of a carcinoembryonic antigen (CEA)-encoding recombinant vaccinia virus (rV-CEA) over a limited dose range and (b) to evaluate CEA-specific immune responses or antitumor effects induced by rV-CEA vaccination. Patients were randomly assigned to one of two groups, depending upon the technique of vaccine administration. All 20 patients received two doses of 10(7) or 10(8) pfu of rV-CEA at a 4-week interval. Toxicity was limited to modest local inflammation at the inoculation site as well as low-grade fever and increased fatigue, each affecting fewer than 20% of the patients. No evidence of CEA-specific lymphoproliferation, interleukin 2 release, delayed-type hypersensitivity, or antibody response was observed. Thus, the efficacy comparison between the two administration techniques was based upon the induction of immune responses to the vaccinia virus vector. Both techniques induced vaccinia-specific lymphoproliferation, interleukin 2 release, and antibody responses of comparable magnitude and frequency as well as protected 80% of patients against pustule formation following vaccinia scarification. Thus, there is no compelling reason to recommend one administration technique over the other based upon toxicity or efficacy. We have selected s.c. jet injection for subsequent trials of rV-CEA based on the ability to accommodate larger injection volumes, enhanced standardization between clinicians, and avoidance of needles that could transmit the vaccine or blood-borne pathogens to health care workers. We recommend use of 10(8) pfu doses for subsequent trials of recombinant vaccinia virus vaccines based upon the favorable toxicity profile and more consistent local pustule formation indicative of an adequate inoculation of live virus. No objective clinical responses to the rV-CEA vaccine were observed among this population of patients with widely metastatic adenocarcinoma.

Adenocarcinoma↗
PubMed1999

Managing intractable pain with an intrathecal catheter and injection port: technique and guidelines.

The objective of our study was to describe an effective technique for the management of chronic intractable pain in patients with intermediate life expectancy or as a long-term screening device prior to implantable pump therapy. In the study, an InDura intraspinal catheter is connected to a BardPort, which is accessed transdermally. We describe our surgical technique, recommended dosage calculations, cost comparison to an implantable infusion pump, and our experience with 13 cases. In our series of 13 patients, there was one seroma and one dural leak. There were no infections, and all were functioning well in the 12 cancer patients until their deaths. One case was converted to an implantable pump. There were no malfunctions or infections of the intrathecal infusion system in the 12 cancer patients. This intrathecal drug infusion system should be considered in the treatment armamentarium for chronic intractable pain and cancer pain.

Adult↗
PubMed1997

Nitric oxide improves pulmonary vascular impedance, transpulmonary efficiency, and left ventricular filling in chronic pulmonary hypertension.

OBJECTIVE: Chronic pulmonary hypertension is difficult to treat and despite the introduction of several therapeutic options, no single therapy is universally recommended. Nitric oxide has had some role clinically in improving pulmonary hemodynamics in this setting; however, basic investigation has not been performed in an appropriate large animal model of stable pulmonary hypertension. This study was designed to examine the effects of inhaled nitric oxide on pulmonary hemodynamics in the setting of a canine model of monocrotaline pyrrole-induced chronic pulmonary hypertension and used Fourier analysis for assessment of pulmonary vascular impedance. METHODS: Sixteen mongrel dogs (22 to 25 kg) were used. Animals underwent percutaneous pulmonary artery catheterization to measure-right-sided hemodynamics before and 6 weeks after a right atrial injection of either monocrotaline pyrrole (n = 8) or placebo (n = 8). Six weeks after the injection all hearts were instrumented with an ultrasonic flow probe, sonomicrometric dimension transducers, and micromanometers. Data were collected at baseline and after nitric oxide administration. Harmonic derivation of functional data was achieved with Fourier analysis. RESULTS: Six weeks after the injection, significant increases in pulmonary artery pressure and pulmonary vascular resistance were observed in the monocrotaline pyrrole group. Nitric oxide led to significant decreases in pulmonary vascular impedance. Significant improvements in pulmonary blood flow, transpulmonary efficiency, and left ventricular filling were also observed. CONCLUSIONS: This investigation demonstrates the well-known clinical effects of nitric oxide in improving pulmonary hypertension, which were also associated with an increase in pulmonary blood flow, transpulmonary efficiency, and left ventricular filling in the setting of monocrotaline pyrrole-induced pulmonary hypertension.

Animals↗
PubMed1997

Conscious sedation.

Some patients are anxious about routine dental treatment; others, who may be able to cope with uncomplicated treatment, are worried by more unpleasant procedures such as minor oral surgery. Management approaches to anxiety vary according to its severity, the age of the patient, the degree of cooperation and the patient's medical history. Psychological approaches have been widely used and range from informal and common-sense methods to formal relaxation training and hypnosis. These techniques are safe, free from adverse effects and give the patient a sense of control. An increasing number of patients are managed with conscious sedation techniques in combination with local anaesthesia and the more severely anxious and uncooperative may require treatment under general anaesthesia. As patient awareness of the risk of anaesthesia and the availability of sedation have increased, so the popularity of conscious sedation for dentistry has increased.

Administration, Inhalation↗
PubMed1996

Total atrioventricular cardiac transplantation preserves atrial systole and ventricular diastolic filling.

BACKGROUND: Total orthotopic heart transplantation was recently introduced into clinical practice as an alternative technique for orthotopic cardiac transplantation. Total cardiac transplantation uses separate bicaval and left and right pulmonary anastomoses, whereas the standard technique of cardiac transplantation uses atrioplasty. Because the anatomic differences between total and standard orthotopic heart transplantation occur at the atrial level, this study compares atrial systolic function and biventricular filling (dV/dt) between the standard and total transplantation techniques. METHODS AND RESULTS: Forty-eight mongrel canines (23 to 31 kg) were used for 12 total and 12 standard orthotopic cardiac transplantations. Right and left ventricular (RV/LV) function and AV synchrony were analyzed with micromanometry, sonomicrometry, ultrasonic flow meters, and intraoperative echocardiography. Results are expressed as mean +/- SEM (ANOVA, paired and unpaired t tests, and chi 2 test). There were no significant differences in baseline function (pretransplantation), bypass times, and cardiac ischemic times between the two groups. Posttransplantation sinus rhythm was preserved in all total (P < 0025) and in only one standard transplantation recipient (all required atrial diastole pacing). Significant decreases in RV/LV dV/dt from 113 +/- 13 and 123 +/- 14 mL/s to 69 +/- 6 and 85 +/- 10 mL/s after transplantation were measured in the standard group. No significant changes occurred in the total group after transplantation with respect to RV/LV diastolic filling. After transplantation, left atrial contractility and relaxation (-dP/dt) decreased significantly in the standard group by 43% and 70%, respectively, whereas in the total transplantation group, there were no observed changes in left atrial contractility and-dP/dt. A significant increase in the septum to RV free wall dimension in the standard group suggests altered geometry. CONCLUSIONS: Total AV transplantation is a feasible alternative to standard cardiac transplantation and conserves both normal sinus rhythm and synchronized beating of the atria and ventricles. Ischemic and bypass times are comparable in patients undergoing either method. These data suggest that RV/LV diastolic function and geometry and atrial systole are better preserved in the total AV transplantation technique.

Animals↗
PubMed1996

Preload-recruitable stroke work relationships and diastolic dysfunction in the brain-dead organ donor.

BACKGROUND: Acute graft failure is an important cause of morbidity and mortality in cardiac transplantation, and it may be associated with myocardial changes that occur during brain death (BD). This study investigates the changes in biventricular systolic and diastolic function that occur after BD in a validated canine model. METHODS AND RESULTS: The hearts of 20 mongrel canines (23 to 31 kg) were instrumented with micromanometers, flow probes, and dimension transducers to measure minor/major axes as well as left and right ventricular (LV/RV) septum-to-free wall distances. LV/RV volumes were measured according to the shell subtraction method. LV/RV systolic function was analyzed by ventricular stroke work plotted versus end-diastolic volume during a caval occlusion (preload-independent recruitable systolic work, PRSW). The nonlinear relationships between diastatic pressure (stress) and LV/RV septum-to-free wall distances and volumes (strain) from successive diastoles during caval occlusion were used to evaluate LV/RV diastolic mechanics. The Cushing phenomenon, hyperdynamic response, and diabetes insipidus were observed in each animal after BD. Results are expressed as mean +/- SEM (P < .05 versus baseline, ANOVA, paired two-tailed Student's t test). Biventricular systolic function deteriorated significantly from baseline PRSW 6 to 7 hours after BD. The diastatic LV/RV pressure dimension relationships were significantly different after BD, indicating a decrease in ventricular chamber compliance during diastole. CONCLUSIONS: BD causes a significant loss of systolic and diastolic LV/RV function in the brain-dead, heart-beating cadaver, which may contribute to early postoperative cardiac graft failure in the recipient. These findings have significant clinical applications and may help to avoid suboptimal donor/recipient matches.

Animals↗