Temperature-driven coherence resonance and stochastic resonance in a thermochemical system.

We perform the stochastic analysis of a thermochemical system using a master equation which describes a chemical reaction and includes discrete and continuous temperature jumps. We study the time evolution of the system selecting the temperature of the thermostat as an easily tunable control parameter. Depending on the thermostat temperature, the system can be in an excitable, oscillatory, or stationary regime. Stochastic time series for the system temperature are generated and the distributions of interspike intervals are analyzed in the three dynamical regimes separated by a homoclinic bifurcation and a Hopf bifurcation. Different constructive roles of internal fluctuations are exhibited. A noise-induced transition is observed in the vicinity of the Hopf bifurcation. Coherence resonance and stochastic resonance are found in the oscillatory regime. In a range of thermostat temperatures, a nontrivial behavior of the highly nonlinear system is revealed by the existence of both a minimum and a maximum in the scaled standard deviation of interspike intervals as a function of particle number. This high sensitivity to system size illustrates that controlling dynamics in nanoreactors may remain a difficult task.

cAMP receptor protein from escherichia coli as a model of signal transduction in proteins--a review.

In Escherichia coli, cyclic AMP receptor protein (CRP) is known to regulate the transcription of about 100 genes. The signal to activate CRP is the binding of cyclic AMP. It has been suggested that binding of cAMP to CRP leads to a long-distance signal transduction from the N-terminal cAMP-binding domain to the C-terminal domain of the protein, which is responsible for interaction with specific sequences of DNA. The signal transduction plays a crucial role in the activation of the protein. The most sophisticated spectroscopic techniques, other techniques frequently used in structural biochemistry, and site-directed mutagenesis have been used to investigate the details of cAMP-mediated allosteric control over CRP conformation and activity as a transcription factor. The aim of this review is to summarize recent works and developments pertaining to cAMP-dependent CRP signal transduction in E. coli.

Trauma patients' desire for autonomy in medical decision making is impaired by smoking and hazardous alcohol consumption--a bi-national study.

This cross-sectional investigation studied the association between substance use and patients' desire for autonomy in medical decision making (MDM) in two trauma settings. A total of 102 patients (age 42.7 +/- 17.4 years, 70.6% male) admitted to an orthopaedic service in Warsaw, Poland, and 1009 injured patients (age 34.6 +/- 12.8 years, 62.3% male) treated in an emergency department in Berlin, Germany, were enrolled. Patients' desire for autonomy in MDM was evaluated with the Decision Making Preference Scale of the Autonomy Preference Index. Substance use (hazardous alcohol consumption and/or tobacco use) and educational level were measured. Linear regression techniques were used to determine the association between substance use and desire for autonomy in MDM. Substance use was found to be independently associated with a reduced desire by the patient for autonomy in medical decision making. No differences in patients' desire for autonomy were observed between the study sites. Empowerment strategies that encourage smokers or patients with hazardous alcohol consumption to participate in MDM may increase the effectiveness of health promotion and injury prevention efforts in this population.

Femoral neck fracture is accompanied by local changes in the content of transforming growth factor-beta1, interleukin-1beta and collagenase activity.

The aim of the study was to evaluate the relationship between the time from femoral neck fracture and the content of transforming growth factor-beta1 (TGF-beta1), interleukin-1beta (IL-1beta) and collagenase activity in bone samples of the femoral neck. The material consisted of 42 cancellous bone samples from the femoral neck collected from patients after the femoral neck fracture during hip replacement procedure. The content of TGF-beta1, IL-1beta in bone samples was measured with the use of enzyme-linked immunoassay (ELISA) and collagenase activity was measured with spectrofluorimetry. The mean content of TGF-beta1/total protein was 2.29 pg/microg (range from 0.9 to 4.0). The mean content of IL-1beta was 4.93 fg/microg (range from 1.4 to 12.5). The mean activity of collagenase was 49.08 nU/microg (range from 5.6 to 113.7). The content of TGF-beta1 and IL-1beta decreased after the injury. In case of TGF-beta1 the difference was statistically significant (p<0.05). The activity of collagenase was statistically significantly increasing in relation to time from the fracture (p<0.05). We found no correlation between the content of TGF- beta1, IL-1beta and the activity of collagenase and the age and the sex of the patients. Also, no significant discrepancies were found between the examined cytokines in relation to the bone loss of the femoral neck according to Singh's scale. These results confirm mutual changes of activity between examined cytokines in the area of fractured bone.

Age-related decrease in the activity of collagenase in the femoral head in patients with hip osteoarthritis.

The aim of the study was to evaluate the relation between the activity of collagenase in the subchondral bone of the femoral head and the age of patients with hip osteoarthritis. Thirty-two patients were enrolled into the study. The mean age was 66 (range from 37 to 80 years). Bone samples of the femoral head were harvested during total hip replacement. The activity of collagenase was measured through spectrofluorimetry. We found statistically a significant correlation between collagenase activity in the bone and age. The mean activity of collagenase in younger patients (37-68 years) was 64.17 IU/microg. In older patients (69-80 years), the mean collagenase activity was 52.26 IU/microg. In patients with hip osteoarthritis the activity of collagenase in the subchondral bone of the femoral head tended to decrease with an increase in age.

Successful eradication of methicillin-resistant Staphylococcus aureus (MRSA) intestinal carrier status in a healthcare worker--case report.

We describe bacteriophage therapy in the case of a healthcare worker whose gastrointestinal tract was colonized by methicillin-resistant Staphylococcus aureus (MRSA) with subsequent urinary tract infection caused by the same pathogen. Oral treatment with anti-MRSA phages resulted in eradication of the carrier status.

Surgical tactics in the revision of the hip prosthesis pin.

Parallel to the rise in the number of primary hip arthroplasties the number of complications is also increasing, especially aseptic loosening of cemented implants and uncemented implants with a smooth surface. The loosening of the implant is very often accompanied by the destruction of bone stock, which requires reconstruction.
On the base of 217 cases operated in the years 1997-2000 the authors present the methods of treating deficits in the proximal femur using special instruments, bone transplants, reconstructive systems, and revision prostheses. The so-called biological attitude to the problem is preferred. Operative tactics are presented in respect to bone deficits classified according to Mallory.

Principles for the management of deep infections following total hip replacement.

Current methods are presented for the management of deep infection of total hip replacements. The goal of treatment is to maintain the improvement of function gained by hip replacement. In cases without loosening, precise surgical debridement without removal of implants is indicated. Management in septic loosening depends on the general medical condition of the patient, the local bone stock, and the spread of infection. Satisfactory bone stock allows for reimplantation of a new prosthesis, prefably using antibiotic-loaded cement, after scrupulous removal of all potentially infected tissues and particles. The reimplantationcan be done as a one- or two-stage operation. In the two0stage procedure, antibiotic-loaded cement spacer can be used, but both two- and one-stage reimplantation have similar results as regards infection control. Definitive removal of the prosthesis is indicated in patients whose general medical condition is poor, who have no usable bone stock, or who present with a persistent Gram-negative bacterial infection. This procedure is not fully effective, however (infection brought under control in 83% of patients), although it does not cause significant negative effect for the functional status of this group of patients.

Outcome of revision hip arthroplasty.

Background. Clinical material collected from 1989 to 1999 from three orthopedic centers is discussed: the Orthopedic Clinic at the Center for Postgraduate Medical Education in Otwock, the Orthopedic Clinic at the Lublin Academy of Medicine, and the Orthopedic Clinic at the Warsaw Academy of Medicine.
Material and methods. During this period 511 patients with an average age of 66 were treated. The authors explain the reasons for aseptic loosening of hip prostheses, the types of implants replaced, and the methods of surgical treatment.
Analysis of results. The importance of correct surgical technique and modern cementing methods during primary arthroplasty for the duration of good prosthesis functioning is discussed. A good outcome from revision arthroplasty can be expected only when the decision to treat is made early. The authors confirm the usability of impacted camcellous allografts for revision hip arthroplasty. Complications during and after surgery are also discussed. Difficulties in the clinical and radiological evaluation of treatment outcomes caused by differing criteria used in each orthopedic treatment are also discussed in this article.
Conclusions. In the conclusion the authors propose rules for surgical treatment to reduce the number of revision procedures.

Principles for the diagnosis of infections following total hip arthroplasty.

Based on authorial material consisting of 19 patients operated in the period 1993-2000 for infections following total hip replacements, and on information from the literature, the authors discuss the suitability of various diagnostic methods. It is particularly important to diagnose infections with a slow course, without the classic clinical signs. The diagnostic criteria accepted by the Disease Control Center in Atlanta are presented, along with the radiological symptoms of latent infections and scintigraphic methods of varying sensitivity and specificity to regards to hip endoprosthesis infections. The article presents the typical changes in the value of erythrocyte precipitation and CRP concentration during the first year following a non-complicated hip arthroplasty, which has a significant impact on the interpretation of results when there is a suspicion of early infection. The decisive test for the diagnosis of a slow infection in a joint with loosened endoprosthesis with obvious clinical signs of infection is peri-operative examination of frozen scraps of the joint capsule for the presence of infiltrations of neutrophil leukocytes.

Results of therapy of infection complicating total hip replacement.

An aim of the management of infection complicating total hip arthroplasty is to control infection and maintain satisfactory hip function. In the period 1993-2000 effectives of therapy of deep injection after total hip replacement in 91 patients was assessed. Infection without loosening of endoprosthesis was diagnosed in 33 hips, septic loosening in 58. In 33 cases without loosening surgical debridement without removal of prosthesis was done with good control of infection in 25 hips. Permanent removal of prosthesis done in 42 cases resulted in recurrence of infection in 6 hips. One stage reimplantation done in 12 patients succeded in 9 hips. Two-stage reimplantation in 3 hips resulted in recurrence of infection in 2 cases. Antibiotic-embedded cement spacer (gentamycin with vancomycin) was used in I case with unsatisfactory result. Recurrent infection was observed in 13 cases of 48 hips treated without implant removal or by reimplantation of new prosthesis.

Surgical tactics in revision operations of the hip acetabulum.

Surgical tactics in acetabulum revisions is based on 2 elements. The first of these is the assessment of the patient's general health (age, clinical status, and concomitant diseases). Adequate planning makes it possible to avoid further complications, such as problems with bone transplant incorporation and subsequent mobility of the acetabulum. The second element is the assessment of bone stock deficits, especially in the acetabular ring. Although it is possible to determine the extent of bone deficits intraoperatively, in preoperative planning we use conventional X-rays, CT scans, and - in cases of advanced protrusion - angiography. The subsequent surgical technique is planned on the basis of the bone deficits as classified by Paprosky.
In the reconstruction of deficit we use different methods and implant cement or cementless acetabula, depending on the patient's age and the bone quality. In certain cases supporting metal rings, mesh, or other implants are used. To fill the deficit we implant frozen, radiated allogenic bone transplants, morselized or as solid blocks.
The revision operation is planned to reconstruct the joint axis on the same level as on the opposite side to restore the off-set. 338 patients with acetabular loosening were operated in the years 1997-2000.
The material indicates the need for the so-called biological attitude to the problem.

Growth factors and gene therapy: the prospects for treating limited cartilage defects.

The limited regenerative capacities of articular are well known. Among the many methods used to repair the joint surface, among the most innovative involve stimulating chondrocytes to grow and differentiate by local application of exogenous protein growth factors, and attempting to transfer the genes responsible for cell division and maturation. This article presents the current state of knowledge on the possibilities for the treatment of limited cartilage defects used these methods.

Methods for the isolation and culture of human articular chondrocytes.

The tissue engineering of cartilage implants may open new paths for the surgical treatment of joint surface defects. Autologous chondrocyte transplantation (ACT) has been gaining in clinical significance over the last several years. This study presents the methods used for isolation, monolayer culturing, multipication and assesment in transmission light microscopy of human chondrocytes. The tissue was gained from resected fragments of joint during total knee replacement.

Factors related to the early and late success of direct current cardioversion of chronic nonrheumatic atrial fibrillation: An echocardiographic study.

OBJECTIVES: To assess factors related to the success of restoration and one-year maintenance of sinus rhythm in chronic (more than 48 h) nonrheumatic atrial fibrillation (AF). METHODS AND RESULTS: One hundred and fifty consecutive patients aged 62+/-9 years with AF lasting 123+/-254 days were evaluated clinically with transthoracic and transesophageal echocardiography before elective direct current cardioversion. Heart chamber dimensions and left ventricular ejection fraction were measured. The presence of left atrial thrombi and spontaneous echocardiographic contrast as well as flow velocities in the left atrial appendage were assessed. The first cardioversion was followed by standardized two-step antiarrhythmic treatment including a second cardioversion, if necessary. Twenty patients (13%) spontaneously reverted to sinus rhythm (S) during anticoagulation preceding cardioversion, 81 (54%) were successfully cardioverted (Y), and in 49 (33%) cardioversion failed initially (N). No differences were noted between the two latter groups. However, S patients had smaller left atria measured in the short and long axes (42+/-4 mm, P=0.05, and 53+/-7 mm, P=0.005, respectively) than both the Y (45+/-4 and 61+/-8 mm) and the N patients (46+/-4 and 61+/-8 mm). One-year follow-up was obtained in 95 patients: 64 (67%) were in sinus rhythm while 31 (33%) had AF. Again, no initial differences predicting the maintenance of sinus rhythm were found. CONCLUSIONS: Spontaneous reversion of AF seems more likely with smaller left atria. Echocardiography, including trans-esophageal echocardiography, is unlikely to identify patients in whom attempts to restore and maintain sinus rhythm will fail or succeed.

The conformational characteristics of Congo red, Evans blue and Trypan blue.

The structures of the closely related bis-azo dyes Evans blue, Trypan blue and Congo red, which appeared to have different self-assembly properties and correspondingly different abilities to form complexes with amyloids and some other proteins, were compared in this work. Ab initio and semi-empirical methods were used to find the optimal structures and partial charge distributions of the dyes. The optimal structures were searched using different widely used programs. The structures of Congo red and evans blue were found to be planar, except for the torsion on the central diphenyl bond connecting the two halves of the dye. Both symmetrical parts of the molecules appeared very close to planarity. However, Trypan blue exhibits non planarity on the di-azo bonds, as well as on the central bond between the symmetrical parts of the dye. In a consequence, the non planarity of this molecule is higher than in the case of its isomer, Evans blue and Congo red as well. The extra rotation around the azo bonds extorted by the close proximity of the sulfonic groups may be the direct cause of its poor self-assembling and complexation properties versus Evans blue.

Carbon fiber scaffolds in the surgical treatment of cartilage lesions.

We present a new method of treatment of chondral defects of the knee with the usage of carbon fibers. The prospective study describes experience with carbon fibers used as scaffolds in the drilled lesions to enhance ingrowth of regenerative tissue. We treated 35 patients for chondral defects with that method from December 93 to June 97. Average age was 46 years (range, 19-68 years) and average follow-up was 48 months (range, 24-55 months). The results were assessed by HSS knee scale, the Wallgren-Tegner activity score, VAS (visual analogue scale to measure pain) and patients assessment of the surgery. Twenty-five (71%) of 35 patients were rated good or excellent. The most striking result was good pain relief. Early follow-up results are good, but these must be confirmed in long-term observations.

Proton magnetic resonance microimaging of human trabecular bone.

Proton magnetic resonance (1H magnetic resonance imaging (MRI)) images of human trabecular bone were acquired and discussed for two samples with different porosity. Three-dimensional 3D Spin Echo (3D SE) and Multi-Slice Multi-Echo (MSME) pulse sequences were examined. A very high slice resolution of (38 microm)2 was achieved (MSME). The intensity histograms were found useful for the characterization of the bone porosity. A spatial distribution of the spin-spin relaxation time T2 was monitored with the MSME pulse program. The work demonstrates the great potential of the proton MRI technique in the study of the trabecular bone morphology.