Influence of melatonin on bovine pulmonary vascular and bronchial airway smooth muscle tone

The influence of melatonin on tension of isolated bovine pulmonary vascular and bronchial smooth muscle rings were examined in these experiments. Melatonin caused a dose-dependent relaxation of precontracted (30 mM KCl) pulmonary artery and vein, although the effect is greater in arterial smooth muscle. This relaxant response was blocked by preincubating vessels with antagonists of vasoactive intestinal peptide or Substance P. In bronchial smooth muscle, melatonin caused a small contractile response. These experiments demonstrate that in response to melatonin the pulmonary vasculature relaxes, while in airway smooth muscle the reverse, constriction, occurs. It is hypothesized that nocturnal exaggeration of asthma may, in part, be due to changes in circulating levels of melatonin.     

Human balance and posture control during standing and walking

The common denominator in the assessment of human balance and posture is the inverted pendulum model. If we focus on appropriate versions of the model we can use it to identify the gravitational and acceleration perturbations and pinpoint the motor mechanisms that can defend against any perturbation.

We saw that in quiet standing an ankle strategy applies only in the A/P direction and that a separate hip load/unload strategy by the hip abd/adductors is the totally dominant defence in the M/L direction when standing with feet side by side. In other standing positions (tandem, or intermediate) the two mechanisms still work separately, but their roles reverse. In the tandem position M/L balance is an ankle mechanism (invertors/evertors) while in the A/P direction a hip load/unloading mechanism dominates.

During initiation and termination of gait these two separate mechanisms control the trajectory of the COP to ensure the desired acceleration and deceleration of the COM. During initiation the initial acceleration of the COM forward towards the stance limb is achieved by a posterior and lateral movement of the COP towards the swing limb. After this release phase there is a sudden loading of the stance limb which shifts the COP to the stance limb. The COM is now accelerated forward and laterally towards the future position of the swinging foot. Also M/L shifts of the COP were controlled by the hip abductors/adductors and all A/P shifts were under the control of the ankle plantar/dorsiflexors. During termination the trajectory of both COM and COP reverse. As the final weight-bearing on the stance foot takes place the COM is passing forward along the medial border of that foot. Hyperactivity of that foot's plantarflexors takes the COP forward and when the final foot begins to bear weight the COP moves rapidly across and suddenly stops at a position ahead of the future position of the COM. Then the plantarflexors of both feet release and allow the COP to move posteriorly and approach the COM and meet it as quiet stance is achieved. The inverted pendulum model permitted us to understand the separate roles of the two mechanisms during these critical unbalancing and rebalancing periods.

During walking the inverted pendulum model explained the dynamics of the balance of HAT in both the A/P and M/L directions. Here the model includes the couple due to the acceleration of the weight-bearing hip as well as gravitational perturbations. The exclusive control of A/P balance and posture are the hip extensors and flexors, while in the M/L direction the dominant control is with the hip abductors with very minor adductor involvement. At the ankle the inverted pendulum model sees the COM passing forward along the medial border to the weight-bearing foot. The model predicts that during single support the body is falling forward and being accelerated medially towards the future position of the swing foot. The model predicts an insignificant role of the ankle invertors/evertors in the M/L control. Rather, the future position of the swing foot is the critical variable or more specifically the lateral displacement from the COM at the start of single support. The position is actually under the control of the hip abd/adductors during the previous early swing phase.

The critical importance of the hip abductors/adductors in balance during all phases of standing and walking is now evident. This separate mechanism is important from a neural control perspective and clinically it focuses major attention on therapy and potential problems with some surgical procedures. On the other hand the minuscule role of the ankle invertors/evertors is important to note. Except for the tandem standing position these muscles have negligible involvement in balance control.     

Role of endothelin in the exercise intolerance of chronic heart failure

In conclusion, plasma levels of the endothelialderived vasoconstrictor endothelin-1 (but not those of other neurohormonal vasoconstrictor factors), measured during exercise correlated closely with objective variables of exercise capacity in patients with heart failure. These findings suggest that endothelin-1 may contribute to exercise intolerance in patients with heart failure, perhaps by limiting the ability of the peripheral vasculature to dilate during exercise.     

Reflective practice: a critique of the work of Argyris and Schön

The seminal work of Argyris and Schon on action theories, technical rationality and reflective practice is reviewed, it is argued that their work reflects important inconsistencies between their theorizing and the pedagogical interventions they implemented/recommended The implications of the results of these inconsistencies, which appear mirrored in nurse-education programmes in the United Kingdom and Australia, are discussed Tentative suggestions for the provision of a more adequate practical pedagogy are included     

Bifurcation properties of the two process model

Abstract Daan's two process model is known to be one of the most powerful models, covering various situations from free-running to sleep deprivation. In this study, bifurcation properties of the model dynamics as function of a gap, D , between the threshold processes are clarified using a circle map. As a function of D , we will show that the model has the different types of the mutual entrainment regions that are intervened by the tangent bifurcation. The variable behavior of human circadian rhythm is suggested to be systematically understood based on the bifurcation properties of the two process model.     

Efficacy and Costs of Patient-controlled Analgesia versus Regularly Administered Intramuscular Opioid Therapy

Background: Many studies have shown in the efficacy of patient-controlled analgesia (PCA). However, it is not clear whether PCA has clinical or economic benefits in addition to efficient analgesia. The current study was designed to evaluate these issues by comparing PCA with regularly administered intramuscular injections of opioids after hysterectomy.

Methods: This prospective study included 126 patients who underwent abdominal hysterectomy and were randomly assigned to receive PCA or regularly timed intramuscular injections of morphine during a period of 48 h. Doses were adjusted to provide satisfactory analgesia in both treatment groups. Pain at rest and with movement, functional recovery, drug side effects, and patient satisfactory were measured using rating scales and questionnaires. The costs of PCA and intramuscular therapy were calculated based on personnel time and drug and material requirements.

Results: Comparable analgesia was observed with the two treatment methods, with no significant differences in the incidence of side effects or patient satisfaction. The medication dosage had to be adjusted significantly more frequently in the intramuscular group than in the PCA patients. The PCA did not favor a faster recuperation time compared with intramuscular therapy in terms of times of ambulation, resumption of liquid and solid diet, passage of bowel gas, or hospital discharge. The results of the economic evaluation, which used a cost-minimization model and sensitivity analyses, showed that PCA was more costly than regular intramuscular injections despite the fact that no costs for the pump were included in the analyses. Cost differences in nursing time favoring PCA were offset by drug and material costs associated with this type of treatment.     

Insights from latent partition analysis into categories inherent in wellness-illness

How health–disease is perceived or conceptualized is important for nursing research There is increasing evidence that individual representations are important in constructing the experience of health–disease What is the personal saliency of health–disease for the individual? To explore the patterns of meaning inherent in health–disease, a card sort was undertaken among 15 healthy individuals and 15 individuals with chronic renal disease Both groups were given 28 cards to sort twice once for when they felt ‘well’ and again for when they felt ‘ill’ The theoretical basis underlying the items of the card sort was a model of wellness-illness being developed Latent partition analysis was used to cluster the concepts from each data set followed by multi-dimensional scaling to analyse the structure of the intercategory probability estimates A possible unidimensional pattern of meaning (harmony) emerged for the ‘well’ data and a two-dimensional pattern (disharmony and optimism) for the ‘ill’ data This represents a preliminary step in the development of a theoretical model that would permit assessment of the meaning of health–disease for the individual     

Effect of minimizing preoperative fasting on perioperative blood glucose homeostasis in children

Two hundred healthy, unpremedicated children, ages 1–10 years, scheduled for elective outpatient surgery were studied in order to examine the effect of minimizing preoperative fasting on perioperative blood glucose concentrations in paediatric patients. None of the patients ingested solids after midnight. On the day of surgery, the children were assigned to one of two groups. Group A children (n= 113) were not allowed any liquids for at least 6 h prior to surgery (NPO). Children in Group B (n= 87) ingested 10 ml·kg^?1 of apple juice 2–4 h prior to the induction of anaesthesia. All patients received lactated Ringer's solution intraoperatively, unless BG at induction was < 50 mg·dl^?1 (2.8 m·mol·l^?1) in which case dextrose 2.5% in lactated Ringer's solution was administered. None of the patients who received apple juice was hypoglycaemic during induction of anaesthesia. However, two children in the NPO group had blood glucose values ± 50 mg·dl^?1 (2.8 m·mol·l^?1) at the time of induction of anaesthesia. Thirteen (11%) patients in Group A and 6 (7%) patients in Group B showed either no change or a further decrease in their postoperative BG concentration as compared with their induction values. Two of 43 patients in Group A and 2 of 41 patients in Group B had gastric fluid volumes > 0.4 ml/kg. All patients in both groups had gastric pH < 2.5. This study shows that gastric fluid volume and pH following a 2–4 h fast are not different from the values measured in children who were subjected to a traditional fasting period of 6 h or longer. Moreover, apple juice consumed 2–4 h prior to surgery neither buffers gastric pH nor does it modify intraoperative glucose homeostasis in children.     

Cross-calibration of liquid and solid QCT calibration standards: Corrections to the UCSF normative data

Quantitative computed tomography (QCT) has been shown to be a precise and sensitive method for evaluating spinal bone mineral density (BMD) and skeletal response to aging and therapy. Precise and accurate determination of BMD using QCT requires a calibration standard to compensate for and reduce the effects of beam-hardening artifacts and scanner drift. The first standards were based on dipotassium hydrogen phosphate (K₂HPO₄) solutions. Recently, several manufacturers have developed stable solid calibration standards based on calcium hydroxyapatite (CHA) in water-equivalent plastic. Due to differences in attenuating properties of the liquid and solid standards, the calibrated BMD values obtained with each system do not agree. In order to compare and interpret the results obtained on both systems, cross-calibration measurements were performed in phantoms and patients using the University of California San Francisco (UCSF) liquid standard and the Image Analysis (IA) solid standard on the UCSF GE 9800 CT scanner. From the phantom measurements, a highly linear relationship was found between the liquid- and solid-calibrated BMD values. No influence on the cross-calibration due to simulated variations in body size or vertebral fat content was seen, though a significant difference in the cross-calibration was observed between scans acquired at 80 and 140 kVp. From the patient measurements, a linear relationship between the liquid (UCSF) and solid (IA) calibrated values was derived for GE 9800 CT scanners at 80 kVp (IA=[1.15×UCSF]-7.32). The UCSF normative database for women and men obtained with the liquid standard was corrected for use with the solid standard. Proper procedures for cross-calibrating QCT measurements and the appropriate uses of normative data are discussed.