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Biomedical subjects

E Lindner

Publications and source records attributed to E Lindner.

At least 19 recordsLinked to original sources
PubMed1999

n-Alkyl fluorenyl phases in chromatography. II. Dynamic behavior and high-performance liquid chromatography applications.

The dynamic behavior of two n-hexyl fluorenyl phases (fluorene-6A [3a(Tn)(Qm)y], fluorene-6B [3b(Tn)(Qm)y]) and three n-decyl fluorenyl phases (fluorene-10A [4a(Tn)(Qm)y], fluorene-10B [4b(Tn)(Qm)y], and fluorene-10C [4c(M1)(Qm)y]) is investigated by solid-state nuclear magnetic resonance (NMR) spectroscopy using the dipolar filter technique with both 13C and 1H detection. These results are compared with those from other dynamic measurements, like the relaxation times in the rotating frame (T1pH) and the variation of the contact time (T(CH)). Additionally, another type of a fluorenyl phase [5a(Tn)(Qm)y], which has an aromatic moiety connected to the silica gel by amido couplings, was also investigated by the dipolar filter method. The solid-state NMR dynamic measurements indicate an increased mobility of the n-alkyl fluorenyl phases compared to the amido coupled fluorenyl phase. The lower the ligand density of the studied n-alkyl fluorenyl phases, the higher their mobility. The separation behavior of the respective phases in high-performance liquid chromatography was investigated with samples containing polycyclic aromatic hydrocarbons and nitro explosives. Depending on the amount of the chemically bound aromatic moiety and the length of their n-alkyl spacer groups, pi-pi interactions with the solute molecules are involved in the separation process and cause it to proceed at a different rate. Therefore, n-alkyl fluorenyl phases can be classified as mixed-mode phases.

Chromatography, High Pressure Liquid↗
PubMed1999

Chemistry in Interphases-A New Approach to Organometallic Syntheses and Catalysis.

Combining the advantages of homogeneous and heterogeneous catalysis is still a problem that has not been satisfactorily solved. Chemistry in interphases offers a new approach for overcoming the difficulties, as is described in this article. Owing to the swellable or porous matrix, an interphase represents a state which in the most favorable case is similar to that of a solution. Moreover the proper choice of a mobile hybrid copolymer enables the control of the density and accessibility of the reactive centers, which results in a distinct improvement of the activity of the catalysts (two examples are shown schematically).

Journal Article↗
PubMed1998

n-alkyl fluorenyl phases in chromatography. I. Synthesis and characterization.

A new class of silica gel-bound fluorene phases is described. The compounds are synthesized via reaction of fluorenyl lithium with omega-alkenyl bromides leading to 9-(5'-hexenyl)-9H- and 9-(9'-decenyl)-9H-fluorene (1 and 2), followed by hydrosilation reactions with different hydrosilanes. The resulting omega-functionalized silylalkyl fluorenes 3a(T0), 3b(T0), 4a(T0), 4b(T0) and 4c(M0) (Scheme 1) react with surface silanol groups of silica gel to generate the new fluorene phases 3a(Tn)(Qm)y, 3b(Tn)(Qm)y, 4a(Tn)(Qm)y, 4b(Tn)(Qm)y and 4c(M1)(Qm)y. The phases are characterized by employing 1H, 13C and 29Si solid-state nuclear magnetic resonance spectroscopy. Their applicability in high-performance liquid chromatography is proved by the Sander and Wise test (SRM 869). In contrast to conventional n-alkyl phases, pi-pi interactions are additionally involved in the separation process and, therefore, the retention times of the polycyclic aromatic hydrocarbons sample molecules depend on the ligand densities of the applied fluorene phases.

Chromatography, High Pressure Liquid↗
PubMed1997

Miniaturized ion-selective chip electrode for sensor application.

The performance of miniaturized potentiometric cells, with multilayer, planar ion-selective sensors in aqueous electrolyte solutions, human serum, urine, and whole blood, is presented. The basic steps of the fabrication with silicon technology are summarized. The effect of the contact surface between the internal reference system and the ion-sensitive membrane on the analytical characteristics of potassium- and calcium-sensitive sensors is studied. Silicone rubber-, high molecular weight PVC-, carboxylated PVC and aliphatic polyurethane (Tecoflex)-based solvent polymeric membranes were dispensed into anisotropically etched wells on silicon wafers, and the resulted planar sensors were tested in terms of their ion sensitivity (slopes of the cell voltage-pK or pCa calibration curves), long-term stability, and reproducibility. For the assay of potassium in whole blood, the miniaturized potentiometric cell was built in a flow-through manifold. To achieve the required precision, the flow conditions were optimized and the sensors calibrated periodically. The results prove the feasibility of the new sensor design and satisfy the particularly difficult requirements for the analysis of biological samples.

Biosensing Techniques↗
PubMed1994

Ion-selective membranes with low plasticizer content: electroanalytical characterization and biocompatibility studies.

High molecular weight poly(vinyl chloride) and aliphatic polyurethane (Tecoflex)-based ion selective membranes, with normal and reduced amounts of plasticizer, as well as without plasticizer, were tested with respect to their analytical properties, their biocompatibility, and cellular responses. The analytical properties of the membranes did not change significantly within a wide range of polymer to plasticizer ratios. However, the membranes with reduced plasticizer content had better adhesive properties, less anion interference, extended life time, and better biocompatibility. Using the cage implant system, the results showed that an increase of plasticizer weight percent in Tecoflex membranes correlated positively with the increase in host inflammatory response up to 14 days of implantation. The results also demonstrated that both PVC and Tecoflex-based ion-selective membranes with the most common membrane composition (1:2 polymer to plasticizer ratio) exhibited a similar acute inflammatory response, but the PVC-based membrane elicited a reduced chronic inflammatory response when compared with the Tecoflex-based membrane.

Adhesiveness↗
PubMed1994

Electroanalytical and biocompatibility studies on carboxylated poly(vinyl chloride) membranes for microfabricated array sensors.

Potassium ion-selective and pH membrane electrodes based on neutral carrier ionophores for K+ (valinomycin) and H+ (TDDA and ETH 5294), respectively, immobilized in carboxylated PVC (PVC-COOH) with normal (classical) and reduced amounts of plasticizer, were investigated with respect to their general analytical performances (linear range, slope, detection limit, selectivity, internal membrane resistance), their biocompatibility and cellular responses. The analytical performance of potassium selective electrodes was not affected by reducing the plasticizer content from 66% (m/m) to about 33% (m/m) while that of pH electrodes was significantly changed at the lower plasticizer concentration level. The adhesive properties of PVC-COOH membranes to an inert substrate such as polyimide-coated Kapton are greatly improved by reducing the plasticizer content of the membrane. In addition, as was reported earlier by this group, improved biocompatibility was observed with these membranes relative to those with increased plasticizer content. A ratio of 1:1 m/m for PVC-COOH to plasticizer is recommended for the construction of planar ISEs without massive use of internal solution.

Animals↗
PubMed1993

An analysis of dorsal root ganglia differentiation using three tissue culture systems.

The histogenesis of the dorsal root ganglia of chick embryos (ages 3 to 9 days) was followed in three different tissue culture systems. Organotypic explants included dorsal root ganglia connected to the lumbosacral segment of the spinal cord or isolated explants of the contralateral ganglia. Additionally, dissociated monolayer cultures of ganglia tissue were established. The gradual differentiation of progenitor neuroblasts into distinct populations of large ventrolateral and small dorsomedial neurons was observed in vivo and in vitro. Neurites developed after 3 days in the presence or absence of nerve growth factor in the medium. In contrast, autoradiographic analysis indicates that [3H]thymidine incorporation in neuronal cultures differed significantly from intact embryos. In vivo, the number of neuronal progenitor cells labeled with [3H]thymidine decreased in older embryos; in vitro, uptake of [3H]thymidine label was not observed in ganglionic progenitor cells regardless of the age of the donor embryo or the type of culture system. Lack of proliferation in ganglionic progenitor cells was not due to degeneration because vital staining and uptake of [3H]deoxyglucose indicated that neurons were metabolically active. Furthermore, the block in mitotic activity in vitro was limited to presumptive ganglionic neuronal cells. In the ependyma of the spinal cord segment connected to the dorsal root ganglia, neuronal progenitor cells were heavily labeled as were non-neuronal cells within both spinal cord and ganglia. Our results suggest that in vitro conditions can promote the differentiation of sensory neurons from early embryos (E3.5-4.5) without proliferation of progenitor cells.

Acetylcholinesterase↗
PubMed1988

Extraction of proteins within ultrathin-layer polyacrylamide electrophoresis (SDS-PAGE) and isoelectric focusing (PAGIF) of cryostat sections and tissue culture specimens.

Separations on a micro- and ultramicroscale by electrophoresis and isoelectric focusing of protein quantities between 10(-6) and 10(-12) g have notable interest, particularly in cytology and histology. We performed the methods of ultrathin-layer polyacrylamide horizontal electrophoresis, isoelectric focusing and protein mapping with some modifications in order to study protein extraction and applied them for cryostat sectioned muscle tissues and singular dorsal root ganglia of the chicken in tissue culture. Further we established an extraction chamber for histological specimens. The basis for ultrathin-layer electrophoresis is the ultrathin (0.12 mm-0.36 mm) polyacrylamide gel on glass plates or microscopic slides. This method allows a considerable reduction of the amount of proteins at the range of 10(-9) g and is thus appropriate for direct extraction of proteins within electrophoresis (10 min, 5 mA 200 V) or isoelectric focusing (10 min, 10 mA, 500 V) of cryostat-sections (7-20 micron thickness) or tissue culture specimens. The advantages of these techniques for extraction of soluble proteins in immunohistochemistry as well as for handling to obtain optimal resolution (compared with electrophoresis of conventional extracted proteins) will be demonstrated.

Animals↗
PubMed1987

Light-microscopic studies on spatial and temporal binding of the lectins concanavalin A, wheat-germ agglutinin and peanut agglutinin in early rat odontogenesis.

The spatial distribution and temporal expression of alpha-D-mannosyl(glucosyl)-, N-acetyl-D-glucosaminyl- and beta-D-galactosyl residues as detected by peroxidase-conjugated lectins correlated with early odontogenic events in six principal developmental stages (fetal days 13.5, 14, 15, 17, 18.5 and 19.5). The odontogenic epithelium of 13.5- and 14-day-old fetuses was characterized by strong concanavalin A (Con A) binding and between days 17 and 19.5, the stellate reticulum displayed strong peanut agglutinin (PNA) binding. Between 15 and 19.5, differentiation of dental ectomesenchyme was characterized by a rhythmic expression of terminal galactosyl residues shown by PNA-binding. At the developing dental basement membrane, there were various carbohydrate-specific regions. At days 13.5 and 14, the odontogenic basement membrane was specific for N-acetyl-D-glucosamines detected by wheat-germ agglutinin (WGA). The results suggest that the carbohydrates present at the inner dental basement membrane at days 17 to 19.5 may be involved in cell-matrix interactions during cytodifferentiation.

Animals↗
PubMed1987

Subpassaging cells on microcarriers: the importance for scaling up to production.

Optimization of microcarrier processes is dependent upon efficient, serial subcultivation routines. Established methods have been modified for a high degree of cell detachment from microcarriers, and transfer of a maximum number of viable cells from one culture to the next during the scale up process. Cultures of MRC-5 and Vero cells were studied, and cell inocula were obtained from different growth phases (i.e. exponential versus stationary) to investigate growth in subsequent cultures. Microcarrier cultures containing confluent cells were washed with EDTA-PBS and then exposed to trypsin (185 U/ml) in PBS (pH 8.0, 37 degrees C). 95-100% of the cells detached from the microcarriers with a viability greater than 95% following a 10 minute exposure to the trypsin. The presence of residual trypsin in the inoculum was investigated with respect to subsequent growth, and no significant effect was found. The methods developed at the laboratory scale (0.25 to 1.5 l cultures) were successfully applied to pilot scale (1 to 100 l cultures), and resulted in split ratios of up to 1:10 for MRC-5 cells and 1:100 for Vero cells. These results show that the modified subpassaging method and an optimal cell inoculum are vital in establishing efficient, industrial scale microcarrier processes.

Animals↗
PubMed1987

Alternatives for harvesting cells grown on microcarriers: effects on subsequent attachment and growth.

In order to facilitate the subpassaging of cells in microcarrier cultures for scaling up culture volumes, alternative procedures for harvesting cells from microcarriers were investigated. A variety of enzymes including trypsin and dextranase were tested separately and in combination to evaluate cell viability after detachment, recovery, and subsequent attachment and growth of cells following inoculation of the cells in the next microcarrier culture. Treatment of confluent microcarriers with dextranase detached cells efficiently and with high viability and in addition totally digested the dextran-based matrix of Cytodex, thus avoiding the possible need to separate the harvested cells from the microcarriers. Dextranase alone resulted in cells harvested as sheets, but if used in combination with trypsin, a single cell suspension of harvested cells was obtained.

Animals↗
PubMed1985

Microspectrophotometric and scanning microphotometric studies of carp (Cyprinus carpio L.) erythrocytes.

Carp (Cyprinus carpio) hemoglobin readily autoxidizes in blood smears. Quantification of Soret-band absorbance in individual erythrocytes by means of scanning cytophotometry therefore requires more elaborate methods of preparation of blood samples. Of the fixatives that have been tested, suspension of whole blood in isotonic salt solutions containing glutaraldehyde was most suitable. Glutaraldehyde-fixed red blood cells are totally resistant to hemolysis. In the course of fixation, hemoglobin is transformed to methemoglobin. Spectrophotometry indicated extensive similarities between glutaraldehyde-fixed carp methemoglobin and human methemoglobin. In aqueous solutions, the intensity of the Soret-peak was pH-dependent. The allosteric modifier organic polyphosphate caused an R----T transition, resulting in increased molar extinctions. Dried preparations showed Soret-spectra that were not influenced from either pH or organic polyphosphate concentration of the aqueous suspensions in which the erythrocytes had been stored. The same was true for slide preparations of cyanomethemoglobin, easily derived from methemoglobin on addition of potassium cyanide. In the absence of oxygen fresh blood cells from carp slowly transform their hemoglobin into deoxyhemoglobin. Spectra of the intermediate stages of deoxygenation, Hb4(O2)3, Hb4(O2)2 and Hb4(O2), as well as mixtures of these intermediates, could be monitored.

Animals↗
PubMed1984

[Effect of forskolin eyedrops on intraocular pressure in healthy males].

Suspensions of Forskolin in concentrations of 0.3; 0.6; and 1.0% decreased effectively the intraocular pressure of healthy subjects when instillated in the conjunctival sac. The suspensions were compared with placebo in double blind studies. The maximum effect was reached 3 hours after application of the 0.3% (22.8%) and 0.6% (27.8%) suspensions and 4 hours after the 1.0% (26.5%) suspension. The higher concentrations decreased the intraocular pressure to the same extent as the lowest concentration but the effect lasted longer: 4 hours after instillation of the 0.3% suspension, 5 hours after instillation of the 0.6% suspension and 7 hours after the 1.0% suspension. The suspensions were well tolerated. Subjective sensations like burning, itching and augmentated lacrimation were observed only in a minor amount and for a short period of time.

Adult↗
PubMed1984

Perfluorochemical perfusion of the isolated guinea pig heart.

We studied the influence of a perfluorochemical (PFC) emulsion on the ultrastructure and function of the isolated perfused guinea pig heart compared to a Krebs-Henseleit solution. The PFC perfusion enhanced the force of contraction and reduced the coronary flow rate, but had no influence on the frequency and the oxygen consumption. The positive inotropic action of K-strophanthin and isoproterenol was slightly strengthened, whereas the beta-adrenergic antagonism by propranolol and the vasodilatation by glycerol trinitrate remained unchanged. The positive chronotropic action of isoproterenol was reduced during PFC perfusion. No histological differences depending on the perfusion medium were observed. It is concluded that PFC perfusion improves the functional state of the Langendorff preparation.

Animals↗
PubMed1984

Hoe 263, a new substance with calcium channel antagonistic activity.

Hoe 263 inhibited the contraction of the potassium-depolarized pulmonary artery of the guinea pig. In this experiment it was slightly more active than verapamil. The calcium uptake of the potassium-depolarized pulmonary artery was inhibited by Hoe 263 more effectively than by prenylamine. The upstroke velocity of the potassium-depolarized papillary muscle of the guinea pig was depressed with similar concentrations of Hoe 263 and verapamil. In the (3H)-nitrendipine binding test, Hoe 263 was effective at similar concentrations as prenylamine and verapamil. The positive inotropic effect of K-strophanthin was depressed by Hoe 263 at concentrations which were comparable with those necessary for verapamil.

Animals↗
PubMed1984

L-3,4-(3-3,4-dimethoxyphenethylamino-2-hydroxypropoxy)-phenyl- crotonic acid nitrile.HCl (Hoe 224), a beta-blocking agent with high beta 1-selectivity.

L-3,4-(3-3,4-Dimethoxyphene-ethylamino-2-hydroxypropoxy)-phenyl-++ +crotonic acid nitrile X HCl (Hoe 224) has beta 1-blocking action. In the isolated left atrium of the guinea pig, the ED50 necessary to counteract the positive inotropic action of 2 ng/ml isoprenaline (isoproterenol) was determined as 10.3 ng/ml in comparison to the ED50 of propranolol 2.7 ng/ml. On the isolated right atrium of the same animal, the ED50 for inhibition of increased heart rate brought about by 2 ng/ml isoprenaline was 29.5 ng/ml in comparison to the ED50 of propranolol 13.5 ng/ml. On the isolated tracheal chain of the guinea pig 40 micrograms Hoe 224/ml also inhibited relaxation induced by 50 ng isoprenaline/ml only by 31%. The ED50 for propranolol in this experiment was 1.2 ng/ml. Therefore, Hoe 224 is a very specific beta 1-blocker. In the dog anaesthetized with pentobarbital the ED50 of Hoe 224 for depression of dp/dt increase by 0.1 mg isoprenaline/kg i.v. was determined as 85 micrograms/kg i.v. Under the same conditions, the ED50 for propranolol was 10 micrograms/kg i.v., for atenolol 17 micrograms/kg i.v., for practolol 56 micrograms/kg i.v. In the conscious dog, 1.6 mg Hoe 224/kg orally depressed the increase of dp/dt brought about by 0.1 microgram isoprenaline/kg i.v. by 50%. The beta 2-blocking effect of Hoe 224 intraarterially against vasodilating effect of 0.01 microgram isoprenaline/kg given intraarterially in the A. femoralis of anaesthetized dogs was very weak. 100 micrograms Hoe 224/kg reduced the effect of isoprenaline only by 23%, but 2 micrograms propranolol/kg intraarterially reduced this effect by 61%.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic beta-Antagonists↗