A comprehensive chemoselective and enantioselective 2D-HPLC set-up for fast enantiomer analysis of a multicomponent mixture of derivatized amino acids

A feasibility study on the fast enantioselective two-dimensional HPLC separation of racemic amino acid derivatives is presented. The method involves the on-line coupling of a narrow-bore C18 RP column in the first dimension to a short enantioselective column based on nonporous 1.5 microm particles modified with quinidine carbamate as chiral selector in the second dimension. Conceptually, the system was designed to enable both time-controlled repeated transfer of fractions of the eluate and detector-controlled transfer of selected fractions from column 1 to column 2. To avoid volume overloading of the second chiral column, a narrow-bore reversed phase column was installed in the first dimension. Due to the fast (less than 1.5 minutes) enantiomer separation that occurs in the second dimension, the overall analysis time for the two-dimensional separation of a mixture of nine racemic 3,5-dinitrobenzoyl amino acids was optimized at 16 minutes.

How to increase inflow in liver transplantation

Liver transplantation (LTx) has become the treatment of choice for selected cases of benign and malignant liver disease. Despite becoming increasingly safer in recent years this procedure still incurs several serious postoperative complications. The most significant surgical complications are related to surgical technique, particularly the reconstruction and/or anastomosis of the hepatic artery. Arterial hypoperfusion may lead to graft failure, sepsis, or ischemic biliary lesions. In this review we focus on the Achilles' heel of LTx: the hepatic artery. We provide transplant surgeons with an overview of the technical options that are available to increase arterial inflow and subsequently improve patient outcome. We exemplify some of the discussed techniques using a liver transplant case with an eventful postoperative course because of arterial complications.

Immunosuppressive standards in simultaneous kidney?pancreas transplantation

Simultaneous pancreas-kidney transplantation is an established procedure for patients with type I diabetes and end-stage renal disease. Continuous advances in the operation techniques with consequent reduction of perioperative morbidity and mortality and the introduction of modern immunosuppressive agents improved not only patients but also graft survival and significantly decreased rejection episodes of both kidney and pancreas grafts. Availability of a variety of new immunosuppressants in the clinical routine and increasing experience of the transplant specialists allowed further developments of therapeutic schemes with application of induction and maintenance immunosuppressive protocols. In this article, we summarize the current status of immunosuppressive regimens in simultaneous pancreas and kidney transplantation.

[Autoimmune pancreatitis--a surgical disease?]

The term autoimmune pancreatitis (AIP) describes a nonalcoholic, chronic lymphoplasmocytic pancreatitis. The lymphoplasmocytic infiltration is characterized by periductal localization of predominantly CD4-positive T cells, fibrosis, and acinar atrophy, frequently resulting in stenosis of the main pancreatic and distal common bile ducts. Imaging studies often reveal a diffuse narrowing of the pancreatic main duct and swelling of the pancreatic head wrongly suggesting the presence of a malignant tumor. Clinical signs include mild abdominal pain, jaundice, recurrent episodes of acute pancreatitis, and even new-onset diabetes mellitus. Additionally, AIP can be associated with other autoimmune diseases such as Sjögren's syndrome, primary sclerosing cholangitis, chronic inflammatory bowel diseases, and retroperitoneal fibrosis. Serological markers include autoantibodies and increased levels of gamma globulin and especially IgG4. Steroids seem to be effective in improving clinical symptoms as well as in the resolution of pancreatic and bile duct narrowing. This distinguishes AIP from other forms of pancreatitis and from pancreatic neoplasms. Further studies of the underlying pathophysiologic mechanisms, prognosis, and new diagnostic tools are needed to provide adequate and effective treatment in the future. In this article, we summarize the current knowledge about AIP and present 17 cases that underwent surgical resection at our institution from 2003 to 2004.

Selectivity Tuning of Serially Coupled (S,S)Whelk-O 1 and (R,R)Whelk-O 1 Columns in HPLC

The selectivity tuning of two columns coupled in series is investigated in chiral high-performance liquid chromatography. Two columns with reversal enantioselectivities [(R,R) Whelk-O 1 and (S,S) Whelk-O 1] are coupled in series via a T connector. Selectivity of such a column series is tuned by varying the mobile phase flows in the individual columns. The flow ratio necessary for the required selectivity is calculated on the basis of retention factors measured on the individual columns. The performance of this method for adjusting the required selectivity is studied by the separation of enantiomers of alkoxy substituted esters of phenylcarbamic acid. It is demonstrated that the change of the mobile phase flows in the individual columns enables change in the elution order of enantiomers.

Selectivity tuning in chiral dual column gas chromatography

The enantioselective tuning of two columns coupled in series is investigated in chiral high-resolution gas chromatography. Two columns with opposite enantioselectivities (Chirasil-L-Val and Chirasil-D-Val) are coupled in series via a T connector, and the relative retention of enantiomers chromatographed on the system is changed by varying the individual carrier gas flow rates in the coupled columns. The flow-rate ratio necessary for the required selectivity is calculated on the basis of the measured retention factors on the individual columns. The performance of this method for adjusting selectivity is studied by the separation of enantiomers of the N-TFA-O-methyl esters of six amino acids. It is demonstrated that the change of the coupling point carrier gas pressure, at the constant inlet and outlet pressures, may change the enantioselectivity of the given column series to such an extent that the enantiomer elution order may be reversed.

CD2AP and p130Cas localize to different F-actin structures in podocytes

Mice lacking the 80-kDa CD2-associated protein (CD2AP) develop progressive renal failure that starts soon after birth with proteinuria and foot process effacement by unknown mechanisms. CD2AP has been identified and cloned independently by virtue of its interaction with the T cell protein CD2 and with the docking protein p130Cas. In the present study we examined the localization of CD2AP and p130Cas in the mouse glomerulus and in cultured podocytes. In glomeruli, CD2AP and p130Cas immunofluorescence were observed in podocytes, where they colocalized with F-actin in foot processes. In addition, p130Cas was strongly expressed in mesangial cells. Immunoelectron microscopy demonstrated that CD2AP was present in podocyte foot processes without a prevailing localization. In cultured podocytes, p130Cas was enriched at sites of focal adhesions, where it colocalized like vinculin with F-actin at stress fiber ends. In contrast, CD2AP colocalized with F-actin at the leading edge of lamellipodia and in small spots, which were unevenly distributed in the cytoplasm. The spot-shaped F-actin structures were also stained by antibodies against the actin nucleation Arp2/3 complex and cortactin, both contributing to dynamic actin assembly. Moreover, CD2AP spots in cultured podocytes were in close spatial association with actinin-4, but not actinin-1. Our results suggest that CD2AP and p130Cas, which both colocalize with F-actin in podocytes in situ, possess different functions. Whereas p130Cas is found in focal adhesions, CD2AP seems to be involved in the regulation of highly dynamic F-actin structures in podocyte foot processes.

Influence of buffer zone concentrations on efficiency in partial filling micellar electrokinetic chromatography

The potential of counter pressure-moderated partial filling micellar electrokinetic chromatography (PF-MEKC) was investigated in this work. Plate numbers of homologous omega-phenylalcohols were measured in a two-plug PF-MEKC system varying the concentrations and hence the ionic strengths of the background buffer compared to the sodium dodecyl sulfate-containing separation buffer and the counter pressure on the cathodic buffer reservoir. It was observed that plate numbers are strongly influenced by both the buffer concentrations and the counter pressure. Highest plate numbers were obtained with a buffer system where the concentrations are adjusted such that the electroosmotic flow velocities in both zones are equal. Differences in the local electroosmotic flow velocities of the zones caused by different buffer concentrations are responsible for tremendously reduced plate numbers. The efficiency drop is explained in several models by the formation of an intersegmental pressure which produces a parabolically shaped laminar flow component in both zones. Thus, the electroosmotic plug-like flow profile is distorted and the efficiency is reduced. The effect of counter pressure on efficiency turned out to be very complex in dependence on the buffer system applied.

Moderation of the electroosmotic flow in capillary electrophoresis by chemical modification of the capillary surface with tentacle-like oligourethanes

The surface chemistry of the inner wall of fused-silica capillaries is one important means to control the magnitude as well as the direction of the electroosmotic flow and the adsorption activity. A method was developed to change the surface characteristics of fused-silica capillaries by binding tentacle-like oligourethane groups onto the inner surface. The electroosmotic flow at a buffer pH of 6-9 was reduced by 15 to 40% compared to that in a bare fused-silica tubing, dependent on the type of coating. Sample adsorption is diminished at the same time resulting in a separation of proteins with higher resolution and good migration time precision. At a pH below 4.5 the electroosmotic flow is reversed into the anodic direction, which offers further possibilities for the separation of positively charged analytes as demonstrated for the separation of aromatic and biogenic amines.

Role of phosphodiesterases in the regulation of endothelial permeability in vitro

Neutrophil-derived hydrogen peroxide (H2O2) is believed to play an important role in the pathogenesis of vascular injury and pulmonary edema. H2O2 time- and dose-dependently increased the hydraulic conductivity and decreased the selectivity of an endothelial cell monolayer derived from porcine pulmonary arteries. Effects of H2O2 on endothelial permeability were completely inhibited by adenylate cyclase activation with 10(-12) M cholera toxin or 0.1 microM forskolin. 10(-8) M Sp-cAMPS, a cAMP-dependent protein kinase A agonist, was similarly effective. The phosphodiesterase (PDE) inhibitors motapizone (10(-4) M), rolipram (10(-6) M), and zardaverine (10(-8) M), which specifically inhibit PDE-isoenzymes III, IV, and III/IV potently blocked H2O2-induced endothelial permeability when combined with 10(-6) M prostaglandin E1. Overall cellular cAMP content and inhibition of H2O2 effects on endothelial permeability were poorly correlated. H2O2 exposure resulted in a rapid and substantial decrease in endothelial cAMP content. The analysis of the PDE isoenzyme spectrum showed high activities of isoenzymes II, III, and IV in porcine pulmonary endothelial cells. The data suggest that adenylate cyclase activation/PDE inhibition is a powerful approach to block H2O2-induced increase in endothelial permeability. This concept appears especially valuable when endothelial PDE isoenzyme pattern and PDE inhibitor profile are matched optimally.

[Examples for using capillary gas chromatography with wide bore columns in occupational health]

Wide bore capillary columns (0.4-0.75 mm ID) can be easily and inexpensively installed in packed column GCs. The analytical advantages cause an expanding market for such capillaries and interconverting hardware kits. It is illustrated with some examples that often individual exposition levels can be determined exactly only by using capillary columns: ethylbenzene may be separated from the C8-isomers also in complex mixtures, the marker PBN for rubber smoke expositions can be determined with 30 min sampling time, the detection sensitivity of the FID is sufficient also for chlorinated pesticides and the analyses of high-boiling compounds profit by the high phase ratio of wide bore capillary columns. A single capillary column substitutes a variety of different packed columns, so saving time and money and protecting the analyst from failures and frustrating compromises.