Stochasticity of the transfer of reactant molecules between nano-reactors affecting the reversible association A + B ⇆ C.

Theoretical analysis and computer simulations (Monte Carlo and numerical integration of differential equations) indicate that the statistical effect of a small number of reacting molecules is affected by transfer of reagent molecules between nanoreactors (droplets in this study). As a model reaction, a simple reversible association A + B ⇆ C was chosen, which was studied previously without reagent transfer processes. For sufficiently fast exchange of reactant molecules and a sufficiently high number of nanoreactors, the studied systems virtually do not differ from large volume systems if overall kinetics and thermodynamics of the chemical process are concerned. However, if either reagent molecule exchange is not fast or the number of exchanging nanoreactors is low, then the stochastic effect is clearly visible, influencing the kinetics of reaching reaction equilibrium. In systems with a low number of nanoreactors, the apparent (average) equilibrium constant is affected as well. The distribution of reactant molecules in the nanoreactors is governed by stochastic processes, dependent on stochastic rate constants of all processes, chemical as well as physical (transfer of molecules outside and into droplets). When accumulation of reactant molecules in the continuous phase cannot be neglected, then the partition coefficients of reactants between the continuous and dispersed phases have to be taken into account. Distributions of reactant molecules described in the paper for systems composed of few nanoreactors can be especially important for some biochemical processes in living cells or devised corresponding artificial reactors. If the reactant molecules predominate in a continuous phase, then the kinetics and overall conversion of reversible association may be significantly affected by the presence of the dispersed phase and its catalytic behavior can be observed. It has been shown that Monte Carlo simulations, applying a devised simple algorithm, give reliable results, allowing theoretical studies of nanoscale-droplet systems.

Chain length distributions in linear polyaddition proceeding in nano-scale small volumes without mass transfer.

Computer simulations (Monte Carlo and numerical integration of differential equations) and theoretical analysis show that the statistical nature of polyaddition, both irreversible and reversible one, affects the way the macromolecules of different lengths are distributed among the small volume nano-reactors (droplets in this study) at any reaction time. The corresponding droplet distributions in respect to the number of reacting chains as well as the chain length distributions depend, for the given reaction time, on rate constants of polyaddition kp and depolymerization kd (reversible process), and the initial conditions: monomer concentration and the number of its molecules in a droplet. As a model reaction, a simple polyaddition process (M)1+(M)1⟶⟵(M)2, (M)i+(M)j⟶⟵(M)i+j was chosen, enabling to observe both kinetic and thermodynamic (apparent equilibrium constant) effects of a small number of reactant molecules in a droplet. The average rate constant of polymerization is lower than in a macroscopic system, depending on the average number of reactant molecules in a droplet. The apparent equilibrium constants of polymerization Kij=[(M)i+j]¯/([(M)i]¯[(M)j]¯) appear to depend on oligomer/polymer sizes as well as on the initial number of monomer molecules in a droplet. The corresponding equations, enabling prediction of the equilibrium conditions, were derived. All the analyzed effects are observed not only for ideally dispersed systems, i.e. with all droplets containing initially the same number of monomer (M)1 molecules, but also when initially the numbers of monomer molecules conform the Poisson distribution, expected for dispersions of reaction mixtures.

Statistical effects related to low numbers of reacting molecules analyzed for a reversible association reaction A + B = C in ideally dispersed systems: An apparent violation of the law of mass action.

Theoretical analysis and computer simulations (Monte Carlo and numerical integration of differential equations) show that the statistical effect of a small number of reacting molecules depends on a way the molecules are distributed among the small volume nano-reactors (droplets in this study). A simple reversible association A + B = C was chosen as a model reaction, enabling to observe both thermodynamic (apparent equilibrium constant) and kinetic effects of a small number of reactant molecules. When substrates are distributed uniformly among droplets, all containing the same equal number of substrate molecules, the apparent equilibrium constant of the association is higher than the chemical one (observed in a macroscopic-large volume system). The average rate of the association, being initially independent of the numbers of molecules, becomes (at higher conversions) higher than that in a macroscopic system: the lower the number of substrate molecules in a droplet, the higher is the rate. This results in the correspondingly higher apparent equilibrium constant. A quite opposite behavior is observed when reactant molecules are distributed randomly among droplets: the apparent association rate and equilibrium constants are lower than those observed in large volume systems, being the lower, the lower is the average number of reacting molecules in a droplet. The random distribution of reactant molecules corresponds to ideal (equal sizes of droplets) dispersing of a reaction mixture. Our simulations have shown that when the equilibrated large volume system is dispersed, the resulting droplet system is already at equilibrium and no changes of proportions of droplets differing in reactant compositions can be observed upon prolongation of the reaction time.

Functional evaluation of treatment outcome in fractures of the cervical spine.

Introduction. Fractures of the cervical spine are becoming more and more frequent, which is causing the number of disabled persons to increase. Proper handling of the patient on the scene of the accident, proper transport to the hospital, and the correct interpretation of indications for surgical intervention can contribute to reducing the number of complications and improving treatment outcome.
Material and method. Our research involved 132 patients, 86 men and 46 women, operated as a result of traumatic injury to the spine and spinal cord with neurological deficits of varying degree. The patients were evaluated neurologically before surgery and divided into three groups on the deficits discovered. Their functional status was tested by means of the Functional Independence Measure (FIM) before surgery (Exam I), one week after surgery (Exam II), and approximately 6 months after surgery (Exam III).
Results. Improvement occurred in our patients in all the measured parameters, depending on the preoperative status of the patient. The greatest improvement in respect to functional independence was gained by those patients who prior to surgery presented with the largest neurological deficits; however, due to the very low preoperative level of functioning exhibited by these patients their condition, even after considerable improvement, was less than fully satisfactory. Somewhat less improvement took place in the patients with a moderate level of neurological deficit, while the least improvement occurred in the patients who presented with minimal neurological deficits. The condition of the patients in this last group was close to normal.
Conclusions. The proposed surgical method in many cases facilitated a rapid return to health; within only a few days after surgery these patients obtain more complete sphincter control, greater motor capability, more self-sufficiency, and better social functioning. The treatment outcomes are dependent on the patient's preoperative status.

Sustained delivery and expression of DNA encapsulated in polymeric nanoparticles.

Sustained release polymeric gene delivery systems offer increased resistance to nuclease degradation, increased amounts of plasmid DNA (pDNA) uptake, and the possibility of control in dosing and sustained duration of pDNA administration. Furthermore, such a system lacks the inherent problems associated with viral vectors. Biodegradable and biocompatible poly(DL-lactide-co-glycolide) polymer was used to enacapsulate pDNA (alkaline phosphatase, AP, a reporter gene) in submicron size particles. Gene expression mediated by the nanoparticles (NP) was evaluated in vitro and in vivo in comparison to cationic-liposome delivery. Nano size range (600 nm) pDNA-loaded in poly(DL-lactide-co-glycolide) polymer particles with high encapsulation efficiency (70%) were formulated, exhibiting sustained release of pDNA of over a month. The entrapped plasmid maintained its structural and functional integrity. In vitro transfection by pDNA-NP resulted in significantly higher expression levels in comparison to naked pDNA. Furthermore, AP levels increased when the transfection time was extended, indicating sustained activity of pDNA. However, gene expression was significantly lower in comparison with standard liposomal transfection. Seven days after i.m. injections in rats, naked pDNA and pDNA-NP were found to be significantly more potent (1-2 orders of magnitude) than liposomal pDNA. Plasmid DNA-NP treatment exhibited increased AP expression after 7 and 28 days indicating sustained activity of the NP.

Application of the CPM splint in the continuing care of patients with injuries to the cervical and thoracic spine.

The paper presents the authors' experience in the application of CPM (continuous passive motion) splints in the rehabilitation of patients with injuries to the cervical and thoracic spine. The observation period averages 3-4 weeks. The authors discuss the construction principles of the splint, the relevant treatment methods, and the advantages if the CPM splint. The results achieved by patients with para- and tetraplegia are presented.

The process of active rehabilitation for SCI patients.

The growth in motor vehicle traffic and the lack of due caution when jumping into shallow water are the primary reasons for trauma to the spine and spinal cord. These injuries prove to have a profound impact on both patients and families. Once the patient has been brought out of post-traumatic and post-operative shock there follows a lengthy process of rehabilitation and adaptation to the hardships of daily life. The authors present various ways of adapting to altered circumstances and techniques for obstacle course exercises.

Pregnancy, labor, and puerperium in a 38-year old patient with transverse post-traumatic spinal cord injury.

Pregnancy co-existing with a complete transverse spinal cord lesion is a very rare case not commonly encountered in everyday clinical practice. The management of pregnancy, delivery, and puerperium poses great difficulties requiring interdisciplinary solutions. The authors present the course of delivery and puerperium in a woman with transverse SCI following traumatic injury to Th4-Th5.

Fixation of the cervical spine using a titanium plate.

Surgery of the cervical spine has been developing since the early twentieth century, but significant progress began with the appearance of the anterior approach, thanks to Bailley, Bedgley and Cloward, who developed a special set of instruments to facilitate operations using the anterior approach. In 1967 Haftek became the first surgeon to perform this operation in Poland; since that time the anterior approach has come to be in more and more general use. The first goal of the operation is to remove fragments of bone and intervertebral discs compressing the spinal cord; the second goal is to achieve good fixation of the operated segment of the cervical spine. In the earlier period external immobilization was applied, using campolite collars, Florida collars, Schanz collars, or HALO stabilizers. Currently immobilizing is done with titanium plates, which are well suited to the purpose of internal fixation of the spine.

Surgical treatment of pathologiesof the craniocervical functions.

Spinal fractures at the craniocervical function require surgical treatment. Surgical can be preceded by direct traction of the cranium in order to set the fragments prior to fixation. This paper presents various methods of fixation from the posterior titanium loops.

Fixation of high thoracic spine fractures. A case report.

Fractures of the thoracic spine are very frequently accompanied by spinal cord compression syndromes, including symptoms that would indicate complete severance of the spinal cord. The indicates a very small reverse of space, especially in the upper and middle segments of the thoracic spine. Even a few millimeters of dislocation among the fragments of broken vertebrae can disrupt the proper anatomical relations and produce neurological deficits. Early intervention - in the form of complete immobilization of the damaged spinal segment, the administration of Solu-Medrol in a dosage consistent with the NASCIS II recommendations, and early surgical treatment with full decompression of the nerve elements - can lead to improvement. Despite the natural splinting provided by the ribs and the sternum, the thoracic spine requires good fixation after the decompression operation, followed in short order by intensive rehabilitation.

Problems in treating bedsores in patients with significantly limited motor activity.

Bedsores are a treatment problem often encountered in patients with spinal injuries and other bedridden patients. It may occur in patients who do not receive proper nursing care. Failure to observe nursing standards may result in neglect, potentially leading to the death of the patient. The authors describe the pathomechanism of bedsores, preventive measures against bedsores in daily nursing practice, and methods of treatment.

[Exocrine pancreatic function and gastric mucosa and duodenal mucosa in patients with chronic kidney failure]. / Czynnosc zewnatrzwydzielnicza trzustki i blony sluzowej zoladka i dwunastnicy u chorych na przewlekla niewydolnosc nerek.

Uraemic pancreatopathy is frequently observed in patients with chronic renal failure. The aim of the study was to assess some parameters of exocrine pancreatic function in uraemic patients maintained on intermittent haemodialyses. Elevated serum amylase activity was found in these patients. The most significant finding was the low bicarbonate output in duodenal content after secretin-cerulein stimuli, comparable with that obtained in patients with chronic pancreatitis. It indicates pancreatic exocrine defect in uraemic patients. A fall in protein output and lower amylase activity in duodenal content was also observed in haemodialyzed patients after stimulation. Low basal acid output (BAO) and enhanced maximal (MAO) and peak (PAO) acid outputs were found in uraemic patients after pentagastrin stimulation. Gastritis and duodenitis were frequently diagnosed in endoscopic and histopathological examinations in these patients. In patients with chronic renal failure even without clinical signs of pancreatic, laboratory findings of exocrine pancreatic abnormalities are reported. It may be the cause of uraemic pancreatopathy.

Gastric and pancreatic functions in haemodialyzed patients.

The aim of this work was to assess gastric acid secretion in relation to morphological and histological changes in the gastric mucosa as well as prevalence of Helicobacter pylori in chronically haemodialyzed uraemic patients. Exocrine pancreatic functions after secretin-cerulein test were also studied. In haemodialyzed patients low basal gastric acid output was found, whereas peak output after pentagastrin stimulation did not differ significantly when compared to controls. Endoscopy of gastric and duodenal mucosa revealed inflammatory changes in the majority of patients, described histologically as chronic gastritis with duodenitis. Helicobacter pylori antigen was detected in the serum of 45% of uraemic patients. Serum amylase activity was elevated in haemodialyzed patients relative to controls. Although clinically asymptomatic, haemodialyzed patients exhibited various degrees of gastrointestinal mucosal abnormalities and impairment in exocrine pancreatic functions, mainly low stimulated bicarbonate and protein output as well as low electrolyte concentrations in duodenal content.

[Jumper's knee]. / "Kolano skoczka" (jumper's knee).

A series of 30 athletes aged about 16 years on an average, exposed to activities putting a strain on the patellar tendon during training has been examined. They were involved in competitive sports for 3 years on an average. In 27 per cent of them jumpers knee symptoms have been found.

[A case of Sinding-Larsen-Johansson and Osgood-Schlatter disease in both knees]. / Przypadek choroby Sinding-Larsen-Johanssona oraz choroby Osgood-Schlattera obu kolan.

A case of simultaneous occurrence of two types of aseptic bone necrosis in both knees is presented. The knees of 12 years old hurdle runner became markedly painful after 5 months of competing. The pain has disappeared after 3 months of rest and physical therapy. Radiographic assessment carried out 2 years later demonstrated full remodelling of bony tissue.