The proximal femoral nail antirotation (PFNA) in the treatment of proximal femoral fractures

Proximal femoral fractures, especially in elderly persons with osteoporosis, present a challenge for the traumatologist. While the dynamic hip screw (DHS) became the implant of choice for the treatment of stable fractures, the ideal implant for the treatment of unstable fractures remains an issue. In our experience, Proximal Femoral Nail Antirotation (PFNA) is an excellent device for osteosynthesis as it can be easily inserted, it provides angular and rotational stability and allows early weight bearing on the affected limb. Between February 2007 and August 2009, 76 patients underwent the PFNA fixation for proximal femoral fractures (15 men and 61 women). Forty seven fractures were pertrochanteric, 14 subtrochanteric, 2 pathological and 5 ipsilateral trochanteric and diaphyseal fractures whereas in 8 cases the PFNA was used in reosteosynthesis. The mean age of patients was 73.4 years (range 22-91 years). The fractures were reduced on a traction table and the implant was inserted using minimally invasive technique. Four patients developed superficial postoperative wound infection. No cases of implant breakage have been recorded; there was one cut-out; delayed union was noted in three patients. The majority of patients regained their pre-injury mobility status. The PFNA is an excellent implant for stabilisation of both trochanteric and complex combination fractures as well as an exceptional device for reosteosynthesis. It is easily inserted with few intra- and postoperative complications and allows early weight bearing on the affected limb as well as quicker rehabilitation of patients.     

Experimental determination of group flux control coefficients in metabolic networks

Grouping of reactions around key metabolite branch points can facilitate the study of metabolic control of complex metabolic networks. This top-down Metabolic Control Analysis is exemplified through the introduction of group (flux, as well as concentration) control coefficients whose magnitudes provide a measure of the relative impact of each reaction group on the overall network flux, as well as on the overall network stability, following enzymatic amplification. In this article, we demonstrate the application of previously developed theory to the determination of group flux control coefficients. Experimental data for the changes in metabolic fluxes obtained in response to the introduction of six different environmental perturbations are used to determine the group flux control coefficients for three reaction groups formed around the phosphoenolpyruvate/pyruvate branch point. The consistency of the obtained group flux control coefficient estimates is systematically analyzed to ensure that all necessary conditions are satisfied. The magnitudes of the determined control coefficients suggest that the control of lysine production flux in Corynebacterium glutamicum cells at a growth base state resides within the lysine biosynthetic pathway that begins with the PEP/PYR carboxylation anaplorotic pathway. Copyright 1998 John Wiley & Sons, Inc.     

Identification of linear viscoelastic constitutive models

Accelerations induce in the brain mechanical stresses that may explain the loss of consciousness feared by fighter pilots. In this study, the brain is modelled as a multi-domain structure and a finite element method is used to identify the constitutive law parameters of each domain and then to analyse the stress level in the brain. The loading and observed strain rates induced by hypergravity seem to indicate a quasi-static behaviour of the brain structure. A general procedure has been developed to characterise the behaviour of a structure including several domains. Each of them is assumed to be isotropic and homogeneous with a linear viscoelastic behaviour. These constitutive laws were identified using only the displacements of several nodes on the envelope discarding the displacements between domains at the interaction surfaces. These interfaces may be buried inside the structure and not connected with the external surface. Two validation examples are proposed to show the reliability and effectiveness of the method.     

Variability and familial transmission of constitutive heterochromatin of human chromosomes evaluated by the method of linear measurement

Summary Using the method of linear measurement, the lengths of constitutive heterochromatin of chromosomes 1, 9, 16, and Y were determined in 125 unrelated individuals, and in 30 members of ten families. The method used eliminates the variations in the C-band length due to different degrees of contraction of chromosomes in different mitoses, and enables the size of heterochromatin blocks to be expressed. It was found that the distribution of C-band lengths in the group of 125 individuals was normal, i.e., Gaussian, for all four classes of chromosomes measured. On the basis of length distribution and by computing the P₁, P₁₀, P₉₀ and P₉₉ percentiles, the actual numerical limits could be proposed for the five-step evaluation of heterochromatin length according to the Paris Conference (1971), Supplement (1975), for chromosomes 1, 9, 16, and in a preliminary way also for Y. When applying the proposed limits to data obtained in the present study, 165 C-band variants could be identified among the 125 individuals.In ten families, C-block lengths of the chromosomes transmitted from parents to progeny could be determined in 63 cases. The mean difference in C-band length of transmitted chromosomes, as measured in parents and in children, was 0.46×10^-7 m. An analysis was carried out to detect the factors upon which the magnitude of this difference depends, and to define what differences are attributable to methodological errors. The results revealed that the difference rises slightly with the increasing length of the measured C block. Three degrees, defined by concrete ranges of difference in C-block length, were proposed for expressing the probability that the compared chromosomes had been transmitted.The study further attests to the effectiveness of the method of constitutive heterochromatin measurement for paternity testing. In our set of ten families, the comparison of C-band lengths of chromosomes 1, 9, 16, and Y led to rejection of paternity in 64% of unrelated individuals; excluding the Y chromosome, the percentage decreased to 61. As many as 47% of the individuals were rejected by a difference higher than two units (i.e., transmission of the compared chromosome highly improbable).     

Adenosine causes a biphasic response in the ovine fetal placental vasculature

We have reported in a previous study that adenosine infusion causes fetal placental vascular resistance to increase after 2 min. To determine whether this action is followed by a more prolonged vasodilation, we studied 7 mature fetal lambs. At surgery, catheters were inserted into the fetal hindlimb arteries and veins. After a five day recovery period, control blood flow measurements were made by radiolabeled microsphere technique immediately after an infusion of 0.9% NaCl, (vehicle, 1.03 ml.min-1) into a fetal vein for 2 min. Within 5 min of the control blood flow measurement, adenosine (10 mg/min) was infused for 2 min. Blood flow measurements were repeated 5, 10, 15, 20 and 30 min after the end of the infusion period. Fetal arterial blood pressure dropped from 50 +/- 1 to 34 +/- 5 mmHg immediately after the adenosine infusion and returned to the control value within 5 min after the infusion. No further blood pressure response was detected. However, placental vascular resistance fell from 0.334 +/- 0.040 to 0.269 +/- 0.027 (P less than 0.05) at the 15 min measurement, remained low through the 20 min measurement (P less than 0.001) and was not different from control levels 30 min after the adenosine infusion. We conclude that the fetal placental vasculature responds to systemic adenosine infusion in a biphasic manner. The immediate reaction to adenosine is a transient vasoconstriction in the fetal placental vasculature followed by vasodilation 15 to 20 min after the initial exposure to adenosine.     

Experimental study and constitutive modeling of the viscoelastic mechanical properties of the human prolapsed vaginal tissue

In this paper, the viscoelastic mechanical properties of vaginal tissue are investigated. Using previous results of the authors on the mechanical properties of biological soft tissues and newly experimental data from uniaxial tension tests, a new model for the viscoelastic mechanical properties of the human vaginal tissue is proposed. The structural model seems to be sufficiently accurate to guarantee its application to prediction of reliable stress distributions, and is suitable for finite element computations. The obtained results may be helpful in the design of surgical procedures with autologous tissue or prostheses.     

Transient state isoelectric focusing. Experimental determination of apparent diffusion coefficients in polyacrylamide gels

A photoelectric scanning assembly utilizing uv absorption optics and an on-line digital data acquisition and processing system has been used to follow kinetically zone spreading during the defocusing stage (absence of electric field) of transient state isoelectric focusing (TRANSIF) in polyacrylamide gels. Measurement of the variance (σ²) of a diffusing zone as a function of time yields a linear relationship, the slope of which corresponds to the apparent diffusion coefficient (D) of the protein. A linear relationship is also obtained when the logarithm of the apparent diffusion coefficients (logD) are plotted vs acrylamide concentration (T). This relationship can be used to extrapolate D to zero gel concentration. The apparent diffusion coefficient measured in this way is significantly larger than the true diffusion coefficient. The slope of the plot logD vs T, designated C_R, is expected to be a measure of molecular size related to the retardation coefficient in polyacrylamide gel electrophoresis.     

Effects of hydrocarbon additions on gas-liquid mass transfer coefficients in biphasic bioreactors

The effects of aliphatic hydrocarbons (n-hexadecane andn-dodecane) on the volumetric oxygen mass transfer coefficient (k _L a) were studied in flat alveolar airlift reactor and continuous stirred tank reactors (CSTRs). In the flat alveolar airlift reactor, high aeration rates (>2 vvm) were required in order to obtain efficient organic-aqueous phase dispersion and reliablek _L a measurements. Addition of 1% (v/v)n-hexadecane orn-dodecane increased thek _l a 1.55-and 1.33-fold, respectively, compared to the control (superficial velocity: 25.8×10⁻³ m/s, sparger orifice diameter: 0.5 mm). Analysis of the gas-liquid interfacial areaa and the liquid film mass transfer coefficientk _L suggests that the observedk _L a increase was a function of the media's liquid film mass transfer. Addition of 1% (v/v)n-hexadecane orn-dodecane to analogous setups using CSTRs led to ak _L a increase by a factor of 1.68 and 1.36, respectively (superficial velocity: 2.1×10⁻³ m/s, stirring rate: 250 rpm). These results propose that low-concentration addition of oxygen-vectors to aerobic microbial cultures has additional benefit relative to incubation in purely aqueous media.     

Characterization of human chromosomal constitutive heterochromatin

The constitutive heterochromatin of human chromosomes is evaluated by various selective staining techniques, i.e., CBG, G-11, distamycin A plus 4,6-diamidino-2-phenylindole-2-HCl (DA/DAPI), the fluorochrome D287/170, and Giemsa staining following the treatments with restriction endonucleases AluI and HaeIII. It is suggested that the constitutive heterochromatin could be arbitrarily divided into at least seven types depending on the staining profiles expressed by different regions of C-bands. The pericentromeric C-bands of chromosomes 1, 5, 7, 9, 13-18, and 20-22 consist of more than one type of chromatin, of which chromosome 1 presents the highest degree of heterogeneity. Chromosomes 3 and 4 show relatively less consistent heterogeneous fractions in their C-bands. The C-bands of chromosomes 10, 19, and the Y do not have much heterogeneity but have characteristic patterns with other methods using restriction endonucleases. Chromosomes 2, 6, 8, 11, 12, and X have homogeneous bands stained by the CBG technique only. Among the chromosomes with smaller pericentric C-bands, chromosome 18 shows frequent heteromorphic variants for the size and position (inversions) of the AluI resistant fraction of C-band. The analysis of various types of heterochromatin with respect to specific satellite and nonsatellite DNA sequences suggest that the staining profiles are probably related to sequence diversity.     

Experimental characterization and constitutive modeling of the biomechanical behavior of male human urethral tissues validated by histological observations

This work aims at observing the mechanical behavior of the membranous and spongy portions of urethrae sampled on male cadavers in compliance with French regulations on postmortem testing, in accordance with the Scientific Council of body donation center of Grenoble. In this perspective, a thermostatic water tank was designed to conduct ex vivo planar tension tests in a physiological environment, i.e., in a saline solution at a temperature of \(37 \pm 1\) \({^{\circ }}\hbox {C}\). In order to observe the anisotropy of the tissues, the samples were tested in two directions. Tests consisting of a series of load–unload cycles of increasing amplitudes were performed to highlight their viscous behavior. The results were then discussed according to the microstructure of tissue, which was investigated using different staining methods and histological analysis. The observed behaviors were then fitted using an anisotropic hyperelastic or a visco-hyperelastic matrix–fiber model.     

High-throughput microplate assay for the determination of drug partition coefficients

Partition coefficients (K(p)) of drugs between the phospholipid bilayer and the aqueous phase provide useful information in quantitative structure-activity relationship studies. Hexadecylphosphocholine (HePC) micelles, composed of a zwitterionic hydrophilic surface and a hydrophobic core, mimic the biomembranes and have several advantages over other lipid structures to assess K(p) values. Their preparation is easy, fast and avoids the use of toxic organic solvents, and the output has fewer spectroscopic interferences. Here, we describe a high-throughput microplate protocol for assessing the K(p) of drugs using HePC micelles as membrane models and derivative spectrophotometry as the detection technique. Moreover, the time-consuming data treatment to assess K(p) values is easily performed by a dedicated Excel routine developed here and described in detail. The K(p) values of nonsteroidal anti-inflammatory drugs (acemetacin, clonixin, diclofenac and indomethacin) were determined to show the simplicity of the method and to validate this protocol, which provides K(p) values (n = 3) of two drugs in ～ 2 h.     

The determination of local cell membrane diffusion coefficients

Solutions applicable to the measurement of cell membrane diffusion coefficients are derived using an approximate integral method.     

Fate determination of fetal Leydig cells

Leydig cell (LC) is one of the most important somatic cell types in testis, which localized in the interstitium between seminiferous tubules. The major function of Leydig cells is to produce steroid hormone, androgens. LC differentiation exhibits a biphasic pattern in rodent testes, which are divided into two different temporal mature populations, fetal Leydig cells (FLCs) and adult Leydig cells (ALCs). FLCs are transiently present in fetal testes and undergo involution or degeneration after birth. FLCs are completely devoid and replaced by ALCs in adult testes. Comparing to ALCs, FLCs display unique morphology, ultrastructure and functions. The origin of FLCs has been debated for many years, but it is still a mystery. Many factors have been reported regulating the specification, proliferation and differentiation of FLCs. FLCs degenerate in a few weeks postnatally, however, the underlying mechanism is still unknown. In this review, we will focus on the fate determination of FLCs, and summarize the resent progress on the morphology, ultrastructure, function, origin and involution of FLCs.