Context of deletions and insertions in human coding sequences

We studied the dependence of the rate of short deletions and insertions on their contexts using the data on mutations within coding exons at 19 human loci that cause mendelian diseases. We confirm that periodic sequences consisting of three to five or more nucleotides are mutagenic. Mutability of sequences with strongly biased nucleotide composition is also elevated, even when mutations within homonucleotide runs longer than three nucleotides are ignored. In contrast, no elevated mutation rates have been detected for imperfect direct or inverted repeats. Among known candidate contexts, the indel context GTAAGT and regions with purine-pyrimidine imbalance between the two DNA strands are mutagenic in our sample, and many others are not mutagenic. Data on mutation hot spots suggest two novel contexts that increase the deletion rate. Comprehensive analysis of mutability of all possible contexts of lengths four, six, and eight indicates a substantially elevated deletion rate within YYYTG and similar sequences, which is one of the two contexts revealed by the hot spots. Possible contexts that increase the insertion rate (AT(A/C)(A/C)GCC and TACCRC) and decrease deletion (TATCGC) or insertion (GCGG) rates have also been identified. Two-thirds of deletions remove a repeat, and over 80% of insertions create a repeat, i.e., they are duplications.     

The muscular network of the sheep right atrium and frequency-dependent breakdown of wave propagation

The complex branching structure of the right atrium (RA) muscular network may provide the substrate for complex patterns of propagation during atrial fibrillation (AF). As AF results in some cases from stable sources in the left atrium (LA) with fibrillatory conduction toward the RA, we hypothesize that periodic input to the RA at an exceedingly high frequency results in disorganized wave propagation associated with the complex structure of the RA. Optical mapping was performed in isolated coronary-perfused sheep RA. Rhythmic pacing of Bachmann's bundle allowed well-controlled and realistic conditions for LA-driven RA. Pacing at increasingly higher frequencies led to increasing delays in activation distal to major branching sites of the Crista terminalis and pectinate bundles, culminating in spatially distributed intermittent blockade at and above approximately 6.5 Hz. At this breakdown frequency, the dominant frequencies of the RA response activity became spatially nonuniform. Such frequency-dependent changes were independent of action potential duration. Rather, the spatial boundaries between proximal and distal frequencies correlated well with branch sites of the pectinate musculature. Thus, there exists a breakdown frequency in the sheep RA below which activity is periodic throughout the atrium and above which it is fibrillation-like, consistent with the ideas that during AF, high-frequency activation initiated in the LA undergoes fibrillatory conduction toward the RA, and that sink-to-source mismatch effect at branch points of the Crista terminalis and pectinate muscles is important in determining the complexity of the arrhythmia.     

Thermodynamics of Linear Poly(pentamethylene urethane) and Poly(hexamethylene urethane) in the Range from 0 to 450 K

Summary: The thermodynamic properties – the temperature dependence of heat capacity and the temperatures and enthalpies of physical transitions – of poly(pentamethylene urethane) and poly(hexamethylene urethane) have been studied over the range 6 to 450 K by precision adiabatic vacuum and dynamic calorimetry. Their energies of combustion, Δ_cU, have been measured in a calorimeter with a static bomb and an isothermal shield. The calorimetric data were used to determine the temperature dependences of the heat capacity = f(T) for poly(pentamethylene urethane) and poly(hexamethylene urethane) in crystalline and amorphous states, to calculate the thermodynamic parameters of the glass transition and the glassy state, the thermodynamic quantities of fusion and the thermodynamic functions (T), H⁰(T) ? H⁰(0), S⁰(T) ? S⁰(0) and G⁰(T) ? H⁰(0) of the polymers for the temperature range from 0 to 450 K. The enthalpy of combustion Δ_cH⁰ and the standard thermodynamic characteristics of formation, namely, the enthalpy, Δ_fH⁰, entropy, Δ_fS⁰ and Gibbs function, Δ_fG⁰, of the substances under discussion were estimated at T = 298.15 K. The regions of thermal resistance for the tested compounds were determined calorimetrically.

Temperature dependence of of poly(pentamethylene urethane)(A) and poly(hexamethylene urethane)(A′).     

Chemotherapy of glioblastoma in rats using doxorubicin-loaded nanoparticles

Glioblastomas belong to the most aggressive human cancers with short survival times. Due to the blood-brain barrier, they are mostly inaccessible to traditional chemotherapy. We have recently shown that doxorubicin bound to polysorbate-coated nanoparticles crossed the intact blood-brain barrier, thus reaching therapeutic concentrations in the brain. Here, we investigated the therapeutic potential of this formulation of doxorubicin in vivo using an animal model created by implantation of 101/8 glioblastoma tumor in rat brains. Groups of 5-8 glioblastoma-bearing rats (total n = 151) were subjected to 3 cycles of 1.5-2.5 mg/kg body weight of doxorubicin in different formulations, including doxorubicin bound to polysorbate-coated nanoparticles. The animals were analyzed for survival (% median increase of survival time, Kaplan-Meier). Preliminary histology including immunocytochemistry (glial fibrillary acidic protein, ezrin, proliferation and apoptosis) was also performed. Rats treated with doxorubicin bound to polysorbate-coated nanoparticles had significantly higher survival times compared with all other groups. Over 20% of the animals in this group showed a long-term remission. Preliminary histology confirmed lower tumor sizes and lower values for proliferation and apoptosis in this group. All groups of animals treated with polysorbate-containing formulations also had a slight inflammatory reaction to the tumor. There was no indication of neurotoxicity. Additionally, binding to nanoparticles may reduce the systemic toxicity of doxorubicin. This study showed that therapy with doxorubicin bound to nanoparticles offers a therapeutic potential for the treatment of human glioblastoma.     

The hospital manager and game theory: chess master, poker player, or cooperative game player?

Hospital management can be seen as a game, and doctors, nurses, and health maintenance organizations are its players. The astute hospital manager realizes the interdependence of individual career strategies and the hospital's success, just as players in a game are interdependent on each other. Managers familiar with game theory may successfully transfer that knowledge to the hospital realm. They may recognize patterns and calculate outcomes like chess players, bluff other hospitals into folding services as poker players do, and cooperate with their own team to maximize productivity. Knowledge of game theory may also make the hospital manager's job.     

Graphical analysis of 2-[18F]FA binding to nicotinic acetylcholine receptors in rhesus monkey brain

External imaging of nicotinic acetylcholine receptors (nAChRs) using techniques such as PET would help to clarify the roles of these receptors in the physiology and pathology of brain function. Here we report the results of quantitative PET studies of cerebral nAChRs with 2-[(18)F]fluoro-A-85380 (2-[(18)F]FA) in rhesus monkeys. Data from dynamic PET scans were analyzed using graphical methods. Binding potential (BP) values of 2.0, 0.4, 0.3, and 0.03 observed in the thalamus (Th), cortex (Cx), striatum (Str), and cerebellum (Cb), respectively, were consistent with the pattern of alpha(4)beta(2) nAChR distribution in monkey brain. The high value of 2-[(18)F]FA-specific binding in the rhesus monkey Th and low level of that in Cb compared with nonspecific accumulation of radioactivity in these structures allowed use of Cb as a reference region for calculation of BP and volume of distribution of specific binding (VDsb) in Th by graphical methods, both with and without the plasma input function. In contrast, estimation of 2-[(18)F]FA specific binding in low-receptor-density regions such as Cx and Str required assessment of nondisplaceable volume of distribution (VDnd) in a separate study and measurement of nonmetabolized radioligand concentrations in the plasma. For accurate quantitation of 2-[(18)F]FA-specific binding by graphical analysis, PET studies should last up to 7 h due to the slow kinetics of 2-[(18)F]FA brain distribution. Further, to avoid substantial underestimation in measured BP values the doses of administered 2-[(18)F]FA should not exceed 0.1 nmol/kg body weight. The findings suggest that 2-[(18)F]FA is a promising ligand for quantitation of nAChRs in human brain.     

Characterization of the discriminative stimulus effects of GABAA receptor ligands in Macaca fascicularis monkeys under different ethanol training conditions

Rationale: Some evidence suggests an involvement of nucleus accumbens in spatial learning. However, it is controversial whether the mesoaccumbens dopaminergic pathways play a specific role in the acquisition of spatial information. Objective: The goal of these experiments was to investigate the effect of dopaminergic manipulations in the nucleus accumbens on a non-associative task designed to estimate the ability to encode/transmit spatial and non-spatial information. Methods: The effects of focal administrations of the D1 and D2 dopamine receptor antagonists, SCH 23390 (6.25, 12.5, 50 ng/side) and sulpiride (12.5, 50, 100 ng/side), respectively, and dopamine (DA; 1.25 and 2.5 μg/side) into the nucleus accumbens were studied on reactivity to spatial and non-spatial changes in an open field with objects. Results: Both SCH 23390 and sulpiride impaired reactivity to spatial change. However, several differences were found in the effects induced by the two DA antagonists. SCH 23390 did not affect locomotor activity and only slightly impaired exploration of the novel object. On the contrary, the D2 antagonist, induced a general, dose-dependent, impairment on all variables measured. Local administration of DA increased locomotor activity, but did not affect reactivity to spatial and non-spatial changes. Conclusions: These results demonstrate a facilitatory role of mesoaccumbens dopamine in the acquisition of spatial information. Moreover, they suggest that nucleus accumbens D1 DA receptors, play a more selective role in the modulation of spatial learning than accumbens D2 DA receptors. Electronic Publication     

Alemtuzumab induction in pediatric kidney transplantation

Recipient parenchymal lymphatic cells are crucial for direct and indirect pathways of allorecognition. We proposed that alemtuzumab, being infused several weeks pretransplant could eradicate peripheral lymphatic cells and promote donor‐specific tolerance. We present here a single center, retrospective review of 101 consecutive living‐donor kidney transplantations to pediatric patients aged from seven month to 18 yr, performed between September 2006 and April 2010. Immunosupression protocol included two 30 mg doses of alemtuzumab: first given 12–29 d prior to transplantation and second at the time of transplantation. Maintenance immunosupression was based on combination of low dose and wide range CNI and mycophenolate. Patients were followed for 3.8 ± 1.4 yr and protocol biopsies were taken one month, one, and three yr post transplant. The Kaplan–Meier graft and patient survival was 96% and 97% for one yr, 89% and 93% for three yr. Biopsy proven acute rejection developed in 26% patients at one yr and in 35% at two yr, no rejections occurred beyond two yr. We conclude that alemtuzumab pretreatment prior to living related donor kidney transplantation allows to reach satisfactory middle‐term results in pediatric patients with wide range and low CNI concentrations.     

Influence of tumours on normal cells and optimal chemotherapy regimens: the case of several drugs and toxicity constraints.

Cancer chemotherapy with the application of several drugs is studied. The negative and inhibiting effect of the tumour on normal cells is taken into account. Under certain hypotheses, we determine the optimal regimen that minimizes the tumour burden at the end of a fixed period of therapy while maintaining several normal cell populations above prescribed levels. More precisely, it is demonstrated that the optimal drug administration corresponds to the strategy of intensive chemotherapy.