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.

[Electroresectoscopy in submucous fibroids, intrauterine adhesions and uterine malformation treatment]. / Zastosowanie elektroresektoskopu w leczeniu miesniaków podsluzówkowych, przegród i zrostów wewnatrzmacicznych.

182 hysteroscopic operations with electroresectoscope use performed in Ist Department of Obstetrics and Gynaecology (Warsaw) between 1996-1999 were analyzed. Myomectomy was performed in 117 patients, resection of uterine septum in 25 and deliberation of intrauterine adhesions in 40 patients. Abnormal bleeding and infertility were the main indications for hysteroscopy. In 70% of patients normalization of menstrual bleeding was obtained and 24% of patients got pregnant. In 3 cases uterine wall perforation was noted, increased uterine bleeding was observed in 7 patient and there was only one case of fluid overload.

Comparison of Hysterosalpingography with Laparoscopy and Chromopertubation

We compared two methods of determining tubal patency. Between January 1, 1993, and December 31, 1994, 55 women were evaluated for infertility by laparoscopy and chromopertubation and either traditional hysterosalpingogram (HSG; group 1, 25 patients, 16 primary, 9 secondary infertility) or a mixture of Hy-Co-Sy with Echovist (group 2, 30 patients, 14 primary, 16 infertility). In group 1 HSG showed 64% bilateral patency, 8% unilateral patency, and 28% bilateral occlusion; laparoscopy and chromopertubation showed 72%, 8%, and 20%, respectively. Identical findings were present in 92% of women, with method sensitivity and specificity of 100% and 89.4%, respectively. One case of allergic reaction occurred. In group 2, rates with Hy-Co-Sy and Echovist were 63.3% bilateral patency, 23.3% unilateral, and 13.3% bilateral occlusion; laparoscopy and chromopertubation results were 83.3%, 10%, and 6.7%, respectively. Identical findings were present in 86.7% of patients, with method sensitivity and specificity of 100% and 84.9%, respectively. No side effects were noted. The high sensitivity of both methods suggest that either one is of value in primary assessment of tubal patency, as neither requires general anesthesia and both may precede laparoscopy of hysteroscopy.

[Evaluation of selected parameters of lymphocyte activity in umbilical blood. I. Natural cytotoxicity]. / Ocena wybranych parametrów aktywnosci limfocytów krwi pepowinowej. I. Naturalna cytotoksyczno-s-c (NK).

Natural cytotoxic activity in the umbilical blood was estimated in 52 healthy newborns. Mononuclear cells were isolated from the umbilical blood using Boym's method. The mean natural cell cytotoxicity in the examined group was 7.05 +/- 0.9 (SD).

[Clinical analysis of patients surgically treated for cancer in the body of the uterus]. / Analiza kliniczna pacjentek operowanych z powodu raka trzonu macicy.

107 patients, aged 40 to 87, after surgical intervention with diagnosis of uterine corpus cancer were clinically examined. 68.1 percent of them were 51 to 70 year old women. 20.5 percent had been never pregnant, and 22.47 been pregnant for one time. In 93.2 percent, corpus cancer was revealed after menopause. Among risk factors, there was observed: diabetes mellitus in 7.4%, hypertension in 35.5%, and obesity in 78% of cases. It was stated interdependence between the depth of uterine infiltration, parametrium metaplastic focuses, adnexa metaplastic focuses, cervix infiltration and decrease of adenocarcinoma maturity. The concord between biopsy and clinical stage I degree was stated in 86 percent of cases.

Patient-interactive, computer-controlled neurological stimulation system: clinical efficacy in spinal cord stimulator adjustment.

Over the past 20 years, continuing technical advances have rendered spinal cord stimulation an easily implemented low-morbidity technique for the management of chronic intractable pain in properly selected patients. Percutaneous methods for the insertion of arrays of multiple epidural electrodes, which are driven by noninvasively programmable "multichannel" implanted devices, have been among the most important of these technical improvements. The same implanted electronics may be used with peripheral nerve or intracerebral electrodes. If the capabilities of this new hardware are to be used to full advantage, a major investment of time and effort is required to adjust the system postoperatively for optimum effect. Ideally, these adjustments should be based upon psychophysical data, obtained in a manner that minimizes influences such as potential operator bias or stimulus presentation-order effects. These requirements have been met by the development of a computerized system designed for direct patient interaction and for greater ease of operation than the standard external devices used with these implants. The system has been tested clinically in 25 patients with spinal cord stimulation for pain. It rapidly tests the available electrode combinations and stimulus pulse parameters at a rate comparable to or greater than that of a skilled human operator using the standard device. It records detailed graphic data and patient analog ratings at varying thresholds and implements "pain drawing" methods with novel input and analytical techniques. This patient-interactive computerized system has proved to be safe and effective clinically. The time required by the average patient working with this system to adjust the stimulator is comparable to or less than the time required by the same patient working with a physician's assistant. Psychophysical data collected by the system may be correlated with clinical observations. Ongoing development will permit delivery of novel pulse sequences and protocols to assess the mechanisms by which stimulation affords relief from pain.

Ten-year follow-up on the performance of a telemetric intracranial pressure sensor.

A permanently implanted epidural sensor has permitted long term telemetric intracranial pressure monitoring in selected neurosurgical patients. The sensor, consisting only of an inductance and a pressure-sensitive capacitance, has been implanted in 127 patients. Of these 127 patients, 13 have continued to have the sensor in place for 4 to 9 years (average, 6.8 +/- 0.44 years). The remaining patients were lost to follow-up or the sensor was removed. The sensor has been evaluated from the standpoint of accuracy, longevity, safety, and stability. Longevity was proven by successful monitoring over periods of years (in 1 patient, at least 9 years). The sensor has been a safe tool; the only morbidity has been two asymptomatic perisensor blood clots in 2 patients. There have been no infections in any of the 127 cases. The stability of the sensor was evaluated by measuring base line drift over time. This rate was 1.0 +/- 0.2 mm H2O/day. Causes of the drift and possible solutions are discussed, and the sensor is compared to other epidural telemetric monitoring systems.