P-NIPAM in water-acetone mixtures: experiments and simulations.

The lower critical solution temperature (LCST) of poly-N-isopropylacrylamide (p-NIPAM) diminishes when a small volume of acetone is added to the aqueous polymer solution, and then increases for further additions, producing a minimum at a certain acetone concentration. Here this behavior is observed through the variation of the hydrodynamic radius RH of p-NIPAM microgels with temperature, measured by dynamic light scattering (DLS), when adding increasing amounts of acetone in the molar fraction range of 0.00 to 0.25. This size trend of microgels with temperature is well captured by all-atom molecular dynamic simulations, which are implemented for a single 30-mer, at similar solvent and temperature conditions. Both DLS measurements and simulations indicate that the shrunken state continuously augments its size with increasing acetone content. This, in turn, leads to a minimum of the globule-to-coil transition temperature, which should correspond to the minimum of the LCST. Furthermore, density profiles, as obtained by considering a membrane arrangement of oligomers, reveal a preferential interaction of the polymer with acetone to the detriment of water. We observe how the membrane loses water content as the temperature is increased while keeping a similar amount of acetone in its interior. This competition between water and acetone for the polymer surface plays a major role in the enthalpy driven dependence of the critical temperature with acetone concentration.

[Evaluation of single kidney graft outcome in patients initially programmed for a dual kidney graft transplantation]. / Évaluation de greffons de bigreffe transplantés en monogreffe.

INTRODUCTION: Kidney transplantation is championed as the gold standard treatment for patients with end-stage kidney disease. According to the biomedical agency, there is an increasing number of patients waiting for kidney transplantation. Faced with organ shortage, the use of marginal grafts may well increase the number of available kidney grafts. Occasionally, during dual kidney graft transplantation, the poor quality of one of the two grafts, or other specific circumstances, may lead to transplantation of only one of the two grafts. We have compared patient outcome concerning single kidney transplantation from an initial dual kidney graft with respect to dual kidney graft transplantation. MATERIAL: Among 67 patients enrolled for a dual kidney graft, 39 dual kidney grafts (group 1) were compared with 12 grafts performed with only one of the two kidneys of a dual kidney graft (group 2) as well as 15 grafts performed following a classic kidney graft protocol (group 3). RESULTS: The survival of grafts was respectively for groups 1, 2 and 3 of 100%, 72,5% and 75,4% (P=0.17). The survival of patients was respectively for groups 1, 2 and 3 of 78.3%, 89.9% and 87.8% (P=0.47). CONCLUSION: Our study suggests that transplantation of a single kidney, initially proposed as dual kidney graft candidate, has satisfying results in terms of graft survival and patient mortality at the expense of poorer renal function in comparison to dual kidney graft. Indeed, there was no significant difference in the survival of patients and grafts. This seems promising taking into consideration that the aim of transplantation in elderly recipients is primarily to avoid dialysis, rather than having optimal post-transplantation kidney function. LEVEL OF EVIDENCE: 4.

Nanotribology of biopolymer brushes in aqueous solution using dissipative particle dynamics simulations: an application to PEG covered liposomes in a theta solvent.

We undertake the investigation of sheared polymer chains grafted onto flat surfaces to model liposomes covered with polyethylene glycol brushes as a case study for the mechanisms of efficient drug delivery in biologically relevant situations, for example, as carriers for topical treatments of illnesses in the human vasculature. For these applications, specific rheological properties are required, such as low viscosity at high shear rates, to improve the transport of the liposomes. Therefore, extensive non-equilibrium, coarse-grained dissipative particle dynamics simulations of polymer brushes of various lengths and shear rates are performed to obtain the average viscosity and the friction coefficient of the system as functions of the shear rate and polymerization degree under theta-solvent conditions, and we find that the brushes experience considerable shear thinning at large shear rates. The viscosity (η) and the friction coefficient (µ) are shown to obey the scaling laws η ∼ γ dot above (-0.31) and µ ∼ γ dot above (0.69) at high shear rates (γ dot above) in a theta solvent, irrespective of the degree of polymerization of brushes. These results confirm recent scaling predictions and reproduce very well trends in measurements of the viscosity at a high shear rate (γ dot above) of red blood cells in a liposome containing medium.

Scaling features of the tribology of polymer brushes of increasing grafting density around the mushroom-to-brush transition.

Nonequilibrium coarse-grained, dissipative particle dynamics simulations of complex fluids, made up of polymer brushes tethered to planar surfaces immersed in a solvent yield nonmonotonic behavior of the friction coefficient as a function of the polymer grating density on the substrates, Γ, while the viscosity shows a monotonically increasing dependence on Γ. This effect is shown to be independent of the degree of polymerization, N, and the size of the system. It arises from the composition and the structure of the first particle layer adjacent to each surface that results from the confinement of the fluid. Whenever such layers are made up of as close a proportion of polymer beads to solvent particles as there are in the fluid, the friction coefficient shows a minimum, while for disparate proportions the friction coefficient grows. At the mushroom-to-brush transition (MBT) the viscosity scales with an exponent that depends on the characteristic exponent of the MBT (6/5) and the solvent quality exponent (ν=0.5, for θsolvent), but it is independent of the polymerization degree (N). On the other hand, the friction coefficient at the MBT scales as µâˆ¼N^{6/5}, while the grafting density at the MBT scales as Γ∼N^{-6/5} when friction is minimal, in agreement with previous scaling theories. We argue these aspects are the result of cooperative phenomena that have important implications for the understanding of biological brushes and the design of microfluidics devices, among other applications of current academic and industrial interest.

A new family with frontotemporal dementia with intronic 10+3 splice site mutation in the tau gene: neuropathology and molecular effects.

Mutations in the tau gene cause familial frontotemporal dementia with parkinsonism linked to chromosome 17 characterized by filamentous tau protein deposits. Here we describe the clinical and neuropathological features of a case from a newly identified family with an intron 10+3-splice site mutation in the tau gene. The proband presented with severe personality changes and stereotyped speech followed by parkinsonian symptoms. He died at age 56 after a disease duration of approximately 6 years. At autopsy, there was marked frontotemporal degeneration with abundant tau-immunoreactive neuronal and glial inclusions widespread in the cortex and brainstem. RT-PCR analysis revealed a 3.7-fold increase of tau transcripts with exon 10, resulting in an 1.7-fold higher expression level of 4-repeat tau isoforms in soluble tau fractions when compared to control brains and exclusively 4-repeat tau isoforms in the sarcosyl-insoluble tau fractions. In accordance with the hypothesis that the overexpression leads to saturation of microtubule binding sites and an increase of unbound 4-repeat tau isoforms which assemble into filaments, the neuronal and glial inclusions in this case were exclusively composed of 4-repeat tau isoforms. The clinical and neuropathological data of this family are compared with results from the two other published families with the intron 10 + 3 mutation, the MSTD and the SOT 254 family.

[Chorion biopsy for chromosome diagnosis in the 1st trimester--discussion contribution to a new method of prenatal diagnosis]. / Die Chorionbiopsie als Mittel zur Chromosomendiagnostik im I. Trimenon--Diskussionsbeitrag zu einer neuen Methode der Pränataldiagnostik.

Biopsy of the chorion is a new possibility in prenatal diagnostics offering certain advantages over the classical puncture of the amniotic fluid during the second trimenon. The article explains the technique, possibilities of complications and ethical aspects with regard to a possible acceptance of this examination method as a routine procedure.

[Open laparoscopy in patients at risk]. / Die offene Laparoskopie bei Risikopatientinnen.

A variant of the technique of open laparoscopy is reported. The principal feature of this technique is that creation of a pneumoperitoneum is simplified. No additional instruments are required, nor sharp instruments, except for the skin incision and splitting of the fascia. The modified open laparoscopy technique was used on 23 high-risk patients in a group of 224 patients on whom laparoscopy was performed at Ludwigshafen Gynecological Clinic. The technique is discussed with reference to the literature.

[Transabdominal chorionic villi aspiration in the 1st and 2d trimester in 120 cases with reference to placental location]. / Transabdominale Zottenaspiration im 1. und 2. Trimenon in 120 Fällen unter Berücksichtigung der Placentalokalisation.

At the Gynecological Clinic of the Klinikum Ludwigshafen prenatal transabdominal diagnostic aspiration of villi was performed in 120 cases in the first and second trimesters between October 1986 and April 1988. The puncture was performed using a cannula system comprising a guide and an aspiration needle. The ultrasonographically controlled removal technique is described with special consideration of the procedure in cases with placental insertion in the posterior wall. Successful tissue removal (at least 5 mg of tissue) was achieved in 97.5% of the cases. Cytogenetic, biochemical, and molecular biologic studies were performed. The most frequent indication was to detect chromosome disorders in older mothers (74.2%). Such disorders were diagnosed in 4.2% of all cases and pregnancy was terminated in seven of them; the indications were aneuploidies, metabolic disease, or severe developmental anomalies detected by ultrasonography in normal karyotypes. In the remaining 113 pregnancies one miscarriage was seen nine weeks after aspiration of villi. On the basis of these results the abortion risk following transabdominal chorionic biopsy is 0.88% and is thus similar to that following amniocentesis.

[Early amniocentesis]. / Untersuchungen zur frühen Amniozentese.

Preliminary clinical experience with early amniocentesis is reported. Fifty-two amniocenteses were performed before the end of the 14th week following the last menstrual period. Cytogenetic and biochemical analyses (AFP, AChE) were performed. Increasing experience with amniotic fluid samples containing small-cell populations and the use of combined culture media improved the poor initial results to a 100% level, thus enabling the use of this technique for diagnostic purposes. The sampling technique and the post-procedural evolution of twelve amniocenteses in pregnant women, whose pregnancy is to be continued, are presented. The possibility of performing amniocentesis in early pregnancy is discussed with reference to anatomical aspects (amniotic and chorionic cavity).

Utilization of magnetic resonance imaging in autopsy planning with specimen preservation for thoraco-omphalopagus symmetricus conjoined twins.

Conjoined twinning is a rare obstetric event that has fascinated physicians and laypersons alike for centuries. When this event occurs, early diagnosis, close prenatal management, and the proper route of delivery will assure the best possible outcome for mother and affected infants. Magnetic resonance imaging (MRI) is used both as an ancillary technique to the sonography for the antepartum diagnosis and in the preoperative planning for the surgical separation of conjoined twins. This report describes the MRI findings in conjoined twins of the thoraco-omphalopagus symmetricus type, a condition incompatible with extrauterine life. The twins were delivered at 21 weeks gestation. The MRI was used to evaluate the anatomic nature of the internal anomalies. These findings were then used to develop an autopsy approach plan that preserved the external phenotype. After dissection, the specimen was preserved by using polyethylene glycol and ultimately prepared for use as a teaching specimen.

[Transabdominal chorionic biopsy: indications and timing of the procedure]. / Transabdominale Chorionbiopsie: Indikation und Zeitpunkt der Durchführung.

The article reports on the introduction of transabdominal chorionic biopsy in the Gynaecological Hospital of Ludwigshafen in cooperation with the Department of Human Genetics at the University of Heidelberg. After completion of a pilot study 15 diagnostic transabdominal chorionic biopsies were performed between the 15th and 23rd pregnancy week. Sampling was successful in all cases; the median estimated weight of the biopsied samples was 35 mg. Cytogenic, biochemical and molecular-genetic examinations were conducted. No complications were seen except for one subserous haematoma. Indications and time of performance are discussed. The transabdominal chorionic biopsy is easier to conduct in the 2nd trimenon than during the first, and can therefore be considered to be a favorable "entry" into the technique. Shifting the biopsy to an earlier date, namely, into the first trimenon, can be aimed at as the familiarity with the technique increases. The obvious advantages of transabdominal removal of villi compared with the transcervical method lead us to expect that in course of the time the transcervical method will be replaced by the transabdominal one. No indication for invasive prenatal diagnosis should be implied without previous detailed genetic counselling.

Screening for trisomy 21 by fetal nuchal translucency and maternal age: a multicenter project in Germany, Austria and Switzerland.

OBJECTIVE: To examine the effectiveness of screening for trisomy 21 by a combination of maternal age and fetal nuchal translucency thickness at 10-14 weeks of gestation in Germany, Austria and Switzerland. METHODS: This was a multicenter study of screening for trisomy 21 by a combination of maternal age and fetal nuchal translucency thickness at 10-14 weeks of gestation. All the sonographers involved in the study had received The Fetal Medicine Foundation Certificate of Competence in the 10-14-week scan. Fetal nuchal translucency thickness and crown-rump length were measured in 23 805 singleton pregnancies with live fetuses. In each case the risk for trisomy 21 was estimated on the basis of maternal age and fetal nuchal translucency thickness for crown-rump length with the use of The Fetal Medicine Foundation's software. The distribution of estimated risk was determined and the sensitivity and false-positive rate for a risk cut-off of 1 in 300 was calculated. RESULTS: Fetal nuchal translucency thickness was successfully measured in all 23 805 pregnancies and outcome was available in 21 959. The median maternal age was 33 (range 15-49) years and in 7935 (36.1%) the age was 35 years or greater. The median gestation at screening was 12 (10-14) weeks and the median fetal crown-rump length was 61 (range 38-84) mm. The estimated risk for trisomy 21 based on maternal age and fetal nuchal translucency thickness for crown-rump length was 1 in 300 or greater in 13.0% (2800 of 21 475) normal pregnancies, in 87.6% (184 of 210) of those with trisomy 21 and in 87.2% (239 of 274) with other chromosomal defects. CONCLUSIONS: In Germany, Austria and Switzerland the results of screening for chromosomal defects by measurement of fetal nuchal translucency thickness, in centers with appropriately qualified sonographers and using The Fetal Medicine Foundation's software, are similar to those reported in the UK using the same methodology.