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C Bahr

Publications and source records attributed to C Bahr.

At least 19 recordsLinked to original sources
PubMed2006

Novel sequence variants in the human xylosyltransferase I gene and their role in diabetic nephropathy.

AIMS: Decreased content of heparan sulphate proteoglycans (HSPGs) is a characteristic of the glomerular basement membrane (GBM) in diabetes and contributes to the development of diabetic nephropathy (DN). Xylosyltransferase I (XT-I) is the chain-initiating enzyme involved in the biosynthesis of HSPGs. This study investigated a possible association between XYLT-I sequence variants and susceptibility to DN. METHODS: Screening of all XYLT-I exons was performed in 74 caucasians with Type 1 diabetes (48 with and 26 without DN) and in 13 non-diabetic control subjects using denaturing high-performance liquid chromatography. RESULTS: Fifteen XYLT-I sequence variants were identified. Of these, six were previously unknown. There were significant differences in the allele frequencies of the three polymorphisms (c.343G-->T (p.A115S), IVS3+10C-->T, IVS3+30G-->C) in Type 1 diabetic patients and healthy controls. CONCLUSIONS: The occurrence of DN is independent of the XYLT-I variants detected in our study. However, three XYLT-I polymorphisms may be linked to Type 1 diabetes. Since we have previously proposed that one of these polymorphisms was not associated with Type 1 diabetes (Schön S et al. Kidney Int 2005; 68: 1483-1490), larger-scale analysis is clearly necessary to pinpoint the significance of this mutation.

Adult↗
PubMed2001

Structure of freely suspended chiral smectic films as determined by x-ray reflectivity and optical ellipsometry.

We report on a combined x-ray reflectivity and optical ellipsometry study of freely suspended smectic (Sm) films of a chiral liquid crystalline compound with the phase sequence Sm-A-Sm-C(*)(alpha)-Sm-C*-Sm-C(*)(gamma)-Sm-C(*)(A). Using tilt magnitude profiles from x-ray reflectivity as input to model the average optical properties obtained by ellipsometry, tilt direction profiles are also obtained. In this way realistic models can be elaborated for the various types of chiral Sm-C films. We find that the surface layers are more tilted than the interior layers due to surface interactions and finite size effects. For the ferrielectric Sm-C(*)(gamma) phase the tilt direction profile corresponds to a three-layer helix, in agreement with the clock model of chiral Sm-C phases. In thin films the surface interactions suppress the bulk helix structure of the Sm-C(*)(alpha) phase and a Sm-C(*)(A)-like structure is formed with an anticlinic layer-by-layer alternation of the tilt directions.

Journal Article↗
PubMed2001

X-ray reflectivity study of smectic wetting and prewetting at the free surface of isotropic liquid crystals.

We study the structures of free-surface-wetting layers above the isotropic to smectic-A transition of three liquid-crystal compounds that show different kinds of growth of the wetting film as the bulk transition is approached: layer-by-layer, continuous, and continuous with prewetting. The smectic-A surface phase of the layer-by-layer compound consists of well-defined layers and possesses a sharp boundary to the isotropic bulk phase, whereas in the two continuous compounds sinusoidal density oscillations with a continuously decaying amplitude are found. In the continuous case with prewetting, the wetting film below the prewetting transition does not show an essential difference to the continuous case without prewetting.

Journal Article↗
PubMed2000

Surface plasmon resonance study of the spreading of a liquid-crystal smectic- a droplet on a gold substrate.

We report a study of the spreading of liquid-crystal smectic- A droplets which completely wet a gold substrate. After the initial spreading of a molecular precursor layer, the droplets develop a complex terraced structure consisting of several monolayers and one bilayer spreading at different rates. During the late stage of spreading the droplet height decreases via a series of layer-by-layer shrinkages until a final state is reached which consists of a single dense monolayer.

Journal Article↗
PubMed2000

Wetting behavior above the liquid-crystal-isotropic transition in a homologous series

An ellipsometric study of the wetting behavior at the free surface above the isotropic to nematic or isotropic to smectic-A transition of nine homologous compounds with even alkyl chain lengths n in the range from four to twenty carbon atoms is presented. All compounds show a pretransitional increase of the nematic or smectic surface coverage as the bulk isotropic to liquid-crystal transition is approached from above. The behavior of the nematic compounds (n=4 to 10) can be interpreted, within the framework of a Landau model, as complete wetting. In short nematic homologs the divergence of the nematic coverage is strongly reduced by a decrease of the nematic susceptibility of the isotropic phase. The elastic coefficient L of the Landau model shows a pronounced increase with increasing n, resulting in the occurrence of a discontinuous prewetting transition in the shortest smectic homolog (n=12) that is still describable by the nematic Landau model. In the longer smectic homologs (n=14 to 20), layering steps appear in the pretransitional increase of the coverage. The results indicate probable partial wetting for the longest homolog, whereas for the other smectic compounds the distinction between complete and partial wetting is difficult on the basis of ellipsometry.

Journal Article↗
PubMed2000

Ellipsometric studies of synclinic and anticlinic arrangements in liquid crystal films

The molecular arrangements in liquid crystal freestanding films are studied when smectic C* surface ordering occurs above the bulk smectic A to smectic C* transition temperature. Details of the resulting structures are resolved using ellipsometry. The behavior of the film is compound dependent. Below a critical electric field, either a synclinic or anticlinic structure may be present depending on the magnitude of the bulk spontaneous polarization. A model is presented in which the low-field anticlinic arrangement results from the interaction between polarization fluctuations at the two surfaces.

Journal Article↗
PubMed1999

[Standard technique of breast reduction surgery with vertical scar].

In 1991, we started to use a new surgical technique for breast reduction with a single vertical scar incision as developed by Marchac, Lassus, and Lejour. The operative procedure wsa changed step-by-step according to the following significant modifications: Simultaneous liposuction is carried out only in the presence of extensive axillary fatty tissue. The undermining of the glandular tissue is limited to the extension of glandular resection. The number of glandular sutures is significantly reduced. A central fixating suture to the pectoral fascia is performed only in the presence of extreme ptosis. The positioning of the nipple-areola complex represents the final step of the reduction procedure after the resection of the glandular tissue. Based on our experience with more than 800 breast reductions, this technique is considered to be a safe standard procedure for nearly all breast sizes.

Cicatrix↗
PubMed1999

Temperature difference between bulk and surface transition in freely suspended smectic films.

We report an ellipsometric study of freely suspended films of a chiral liquid-crystal compound possessing the phase sequence smectic-C-smectic-A-isotropic with a very broad (67 K) smectic-A phase range. We observe a smectic-C-smectic-A surface transition which is situated more than 60 K above the bulk smectic-C-smectic-A transition temperature. Possible reasons for this unusually large temperature shift are discussed.

Journal Article↗
PubMed1999

Structure of the chiral smectic-C(*)(alpha) phase.

Ellipsometric measurements of freely suspended films of a chiral liquid-crystal compound possessing the phase sequence smectic-A-smectic-C(*)(alpha)-smectic-C* have been conducted in order to elucidate the structure of the smectic-C(*)(alpha) phase. The measured ellipsometric quantities Delta and Psi are compared with values, which were calculated for model films using the 4x4 matrix method. Our results confirm, for the compound under investigation, predictions of a phenomenological model [M. Cepic and B. Zeks, Mol. Cryst. Liq. Cryst. 263, 61 (1995)] according to which the smectic-C(*)(alpha) phase is characterized by a short-pitch helical structure.

Journal Article↗
PubMed1996

[Indications for arterialization of tissue].

Data from 69 arterialized venous flaps and transplants were reviewed and showed on overall complication rate of 18.6%. Possible hemodynamic mechanisms include, among others, the opening of macro- and microvenous interconnecting pathways with in the perivenous areolar tissue and pressure-induced insufficiency of venouf valves. The use of arterialized venous flaps increases the plastic surgeon's armamentarium if standard local or distant flap procedures are not possible, and the use of a vein to provide arterial inflow into an amputated body part presents a suitable alternative if arteries are not available and venous congestion is controlled.

Adult↗
PubMed1993

Lower-extremity amputation. Incidence, risk factors, and mortality in the Oklahoma Indian Diabetes Study.

Oklahoma Indians with NIDDM (n = 1012) underwent a baseline examination in 1972-1980. The incidence of and risk factors for first lower-extremity amputation were estimated. The mortality rates of amputees using data from 875 patients who had no previous history of amputation and who underwent follow-up examination between 1987 and 1991 are presented. The mean age of the 875 patients was 51.6 +/- 10.8 yr, and the mean duration of diabetes was 6.6 +/- 6.1 yr. After a mean follow-up time of 9.9 +/- 4.3 yr, the incidence rate of first LEA among diabetic Oklahoma Indians was 18.0/1000 person-yr. The incidence rate was two times higher in men than in women. In both sexes, significant risk factors (P < 0.05) were retinopathy and duration of diabetes. Fasting plasma glucose, use of insulin, and systolic blood pressure were significant for men only. For women, plasma cholesterol and diastolic blood pressure were additional risk factors. Compared with the mortality rate of 33.5/1000 person-yr among nonamputees, the rate among amputees was 55.5/1000 person-yr. The 5-yr survival rate after first amputation was 40.4%. For the amputees, the most common causes of death were diabetes (37.3%), cardiovascular disease (29.1%), and renal disease (7.3%). The incidence and mortality rates in diabetic Oklahoma Indians were higher than those reported in Pima Indians and other diabetic populations. To lower the incidence of lower-extremity amputation in this high-risk population, preventive action through education, foot care programs, and early detection of lesions must be intensified.

Adult↗