Wall-thickness and midwall-radius variations in ventricular mechanics.

A fluid-fiber-collagen stress tensor is used to describe the rheology of the left ventricle of the heart. Linear theory is used to find the equilibrium solutions for the end-diastolic and end-systolic states of general axisymmetric shapes that are small perturbations of a thick-walled finite cylinder. The general problem can be studied by superposing the effects of variable midwall radius but constant wall thickness with those of variable wall thickness but constant midwall radius. A Fourier series representation is used to describe the midwall radius and thickness functions. Numerical calculations are performed to determine the deformed geometry and spatial distributions of tissue pressure, stresses, and fiber strains. The calculations proved to be highly accurate when compared to an analytical solution obtained for the special case of no fibers. The results show significant longitudinal differences when compared to results for the cylindrical geometry, with more sensitivity to variation in wall thickness than to variation in midwall radius.     

Altered regulation of in-vivo coagulation in orthopedic patients prior to knee or hip replacement surgery.

Up to 20% of patients develop venographically proven deep-vein thrombosis after elective orthopedic surgery even under the cover of heparin or low molecular weight heparin. The extent to which the chronic inflammation of osteoarthritis requiring elective orthopedic surgery alters in-vivo coagulation and whether any specific alteration influences the development of postoperative thrombosis are unknown. This study compared the concentrations of activated factor VII (FVIIa), tissue factor pathway inhibitor (TFPI), activated factor X (FXa)-TFPI, thrombin-antithrombin, and prothrombin fragment 1+2 (F1+2) in plasmas of 535 healthy individuals (ages 17-76) with those in the preoperative plasmas of 306 arthritis patients (ages 30-92) scheduled for elective knee or hip replacement surgery. C-reactive protein was also measured in the plasmas of approximately 15% of the participants. Age-adjusted concentrations of FVIIa, F1+2, and C-reactive protein were higher in patients than controls, while the concentrations of thrombin-antithrombin, TFPI and FXa-TFPI were similar. Chronic inflammation in the patients was thus associated with increased coagulation in vivo. Without compensatory increases in the concentrations of TFPI (natural inhibitor of prothrombinase), the elevated concentrations of FVIIa in the preoperative plasmas and the trauma associated with surgery may enhance the risk for developing postoperative deep-vein thrombosis.     

Bereavement therapy with adolescents: facilitating a process of spiritual growth

TOPIC: Bereavement therapy as a catalyst for spiritual growth. PURPOSE: This study aims to review the literature and reflect on the bereavement therapy undertaken with two adolescents who had been bereaved during childhood. SOURCES: Research articles and books identified through a combination of electronic and manual searches. CONCLUSIONS: It would appear that grief therapy could facilitate spiritual growth in such circumstances. Further in-depth studies are required to identify how typical or atypical this experience is, and to contribute to the evidence base for working with bereaved children and adolescents.     

Rapid Immunofluorescence Microscopy for Diagnosis of Melioidosis

An immunofluorescent (IF) method that detects Burkholderia pseudomallei in clinical specimens within 10 min was devised. The results of this rapid method and those of an existing IF method were prospectively compared with the culture results for 776 specimens from patients with suspected melioidosis. The sensitivities of both IF tests were 66%, and the specificities were 99.5 and 99.4%, respectively.     

Use of a violence risk assessment tool in an acute care hospital: effectiveness in identifying violent patients.

This study examined the use and effectiveness of the Alert assessment form. The form is part of the Alert system, used by one large acute care hospital to identify patients with a propensity for violence. All reported incidents of patient violence from August 1, 2003, through December 31, 2004, were included in patient charts. One hundred seventeen violent patient charts were reviewed and compared with 161 non-violent patient charts, randomly chosen from the same time period. Overall use of the Alert assessment form for violent and non-violent patients was 75.7% and 35.4%, respectively. The assessment form was found to have moderate sensitivity (71%) and high specificity (94%). It is reasonably effective in identifying potentially violent or aggressive patients when it is used according to protocol. Efforts to improve the tool are warranted, as is evaluation of its benefit in settings with low prevalence of violence. Also, greater effort must be taken to prevent violence once an aggressive patient has been identified.     

Neurochemical mechanisms mediating the behavioral and cognitive effects of nicotine

Data are reviewed, largely from experiments in the authors'laboratory, that suggest three modes of action of systemic nicotine in producing three different types of effect upon behavior and cognitive function. (1) Preexposure of a stimulus without consequence makes it harder subsequently to form associations to that stimulus, a form of selective attention known as latent inhibition. Latent inhibition is blocked by nicotine, an effect that is apparently mediated by a nicotine-induced increase in dopamine release in the nucleus accumbens. (2) A single dose of nicotine proactively increases the partial reinforcement extinction effect measured several weeks later: that is, resistance to extinction is decreased by nicotine in animals that have been trained on a continuous reinforcement schedule, and increased in animals trained on a partial reinforcement schedule. This effect appears to be due to increased synthesis of tyrosine hydroxylase in the cell bodies of noradrenergic neurons in the locus coeruleus, followed by axonal transport to the hippocampus and increased synthesis and release of noradrenaline in that structure. (3) Nicotine improves vigilance in animals with cognitive deficits due to destruction of the forebrain cholinergic projection system, either as a consequence of excitotoxic lesions of the nuclei of origin of this system or after prolonged alcohol consumption; and also in human subjects with Alzheimer's disease (in which this system undergoes degeneration). This effect is most likely due to an action at denervated cholinergic synapses in the hippocampus and neocortex. © 1994 Wiley-Liss, Inc.