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Biomedical subjects

U Schramm

Publications and source records attributed to U Schramm.

At least 37 records · Page 2Linked to original sources
PubMed1995

P-glycoprotein-mediated secretion of a fluorescent cyclosporin analogue by teleost renal proximal tubules.

The transport of a fluorescent cyclosporin analogue was measured in killifish (Fundulus heteroclitus) proximal tubules by means of epifluorescence microscopy and digital image analysis. Renal cells rapidly accumulated the cyclosporin analogue from the medium and attained steady state within 60 min; luminal fluorescence increased over the first 60-90 min. At steady state, luminal fluorescence intensity was two to three times higher than cellular. Cellular fluorescence intensity was a linear function of medium substrate concentration and was not affected by any treatment used. In contrast, luminal fluorescence exhibited a saturable component as the medium concentration of the cyclosporin was increased. Secretion into the lumen was blocked by metabolic inhibitors, vanadate, other cyclosporins, such as cyclosporin A and cyclosporin G, and substrates for P-glycoprotein (verapamil, vinblastine, and quinine) but not by substrates for the renal organic anion or organic cation transport systems, such as p-aminohippurate or tetraethylammonium. The data are consistent with the fluorescent cyclosporin analogue entering proximal tubule cells by simple diffusion and then being pumped into the tubular lumen by P-glycoprotein.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1995

[Normal variation of arterial liver supply in mesenterico-celiacography].

Progress in operative techniques in surgery of the upper abdomen necessitates extensive preoperative diagnostic studies. Mesenterico-coeliacography along with CAT-SCAN form the basis for effective operative planning. In the angiography, the clinician is often confronted by variations in the arterial supply of the liver. These variations of the norm which are scarcely mentioned in anatomical textbooks must be carefully taken into consideration by the surgeon. In order to clarify the operative significance of these variations, we have conducted a retrospective study of the angiographies of the truncus coeliacus as well as of the arteria mesenterica superior. We found variations in 25.5% of 204 angiographies. The incidence of deviant and accessory hepatic arteries was 33.8% and of variations in the truncus coeliacus was 6.7%. These variations of the norm are discussed as to clinical and embryological aspects.

Angiography↗
PubMed1994

Functional morphology of the nictitating membrane in the domestic cat.

Morphological differences between the corneal and palpebral surfaces of the nictitating membrane of the domestic cat were examined using histology, histochemistry and the scanning electron microscope. Both surfaces are covered by one or two layers of epithelial cells. The epithelium contains numerous goblet cells, particularly on the palpebral side. These cells revealed binding sites for six lectins as well as positive PAS reactivity, and alcianophilia at both pH 2.5 and pH 3.5. Numerous lymph follicles located on the corneal side make the epithelium look like lymphoepithelial tissue. Accumulations of lymphatic tissue may also be found on the palpebral side. Scanning electron micrographs showed microvilli on the epithelial surfaces. The function of the cat nictitating membrane is discussed on the basis of our findings and those of other authors. Movements of the nictitating membrane alternate between active and passive phases of gliding. The membrane as a whole effectively protects the nasal portion of the bulb from dust, dehydration and pathogens.

Animals↗
PubMed1993

Saturation mutagenesis in Escherichia coli of a cloned Xanthomonas campestris DNA fragment with the lux transposon Tn4431 using the delivery plasmid pDS1, thermosensitive in replication.

A system allowing transposon mutagenesis of cloned DNA fragments in Escherichia coli with Tn4431, which carries the promotorless luciferase (lux) operon of Vibrio fischeri, has been developed. The transposon delivery plasmid, pDS1, based on an IncF replicon, is thermosensitive in replication and mobilizable to many Gram-negative bacteria. We used pDS1 for Tn4431-saturation mutagenesis of a 10-kb DNA fragment of Xanthomonas campestris pv. campestris (X.c.c.) in E. coli and showed that the expression of the lux operon was dependent on orientation and location of the transposon. Transfer of a specific Tn4431 insertion to X.c.c. allowed the determination of the bioluminescence phenotype in planta.

Cloning, Molecular↗
PubMed1993

[Comparative experimental studies of mechanical and holmium laser synovectomy].

The goal of this study was to evaluate tissue reactions in rabbit knees following laser synovectomy using a holmium:YAG laser (wavelength: 2.1 microns) and to compare these results with those found after conventional mechanical abrasion treatment. Chronic arthritis was immunologically induced in one knee joint each of 48 rabbits. Twelve served as controls, 12 were sham-operated, 12 were exposed to laser radiation, and 12 others were treated according to conventional methods. In the laser group, a pulse length of 1 ms at a repetition rate of 3 Hz resulted in a pulse energy of 600 mJ. After periods of 1 day, 1 week and 1 and 3 months, respectively, three animals from each group were sacrificed and the synovialis was examined macroscopically and histologically using light and electron microscopy. Edema, acute inflammation, and coagulation necrosis occurred immediately following laser therapy. After 1 week, the synovial layer showed slight fibrosis, which was comparable to that found in the controls. One month later the surface appeared to be smooth. The mechanical abrasion caused hemorrhage and necrosis. Fibrosis was pronounced in all capsular layers, and after 3 months the surface appeared coarse and villous in this group. Based on these preliminary findings, holmium-laser synovectomy may offer an alternative to existing therapeutic techniques in the treatment of rheumatoid arthritis. The arthroscopic approach could prevent additional capsular fibrosis associated with mechanical irritation.

Animals↗
PubMed1993

Fluorescent derivatives of bile salts. III. Uptake of 7 beta-NBD-NCT into isolated hepatocytes by the transport systems for cholyltaurine.

Uptake of 7 beta-NBD-NCT ([N-[7-(4-nitrobenzo-2-oxa-1,3-diazol)]-7 beta-amino-3 alpha,12 alpha-dihydroxy-5 beta-cholan-24-oyl)-2'-aminoethanesulfonate) in isolated rat liver hepatocytes occurs by saturable transport without being superimposed by simple diffusion. The dependency of flux rate of uptake on the concentration of 7 beta-NBD-NCT in the presence of Na+ (143 mM) and with Na+ depletion (1 mM) is best described by the assumption of two simple transport systems. Maximal flux rates of uptake Jn and half-saturation constants KT for 7 beta-NBD-NCT are in presence of Na+ for transport system 1 J1(Na+ 143) = 0.15 +/- 0.03 nmol/(min.mg protein) and KT1(Na+ 143) = 3.5 +/- 0.5 microM and for transport system 2 J2(Na+ 143) = 1.0 +/- 0.1 nmol/(min.mg protein) and KT2(Na+ 143) = 190 +/- 25 microM, and in case of Na+ depletion J1(Na+ 1) = 0.1 +/- 0.03 nmol/(min.mg protein), KT1(Na+ 1) = 3.0 +/- 0.5 microM, and J2(Na+ 1) = 0.85 +/- 0.9 nmol/(min.mg protein) and KT2(Na+ 1) = 195 +/- 27 microM. Uptake of 7 beta-NBD-NCT by both transport systems is competitively inhibited by cholyltaurine in the presence of Na+ and with Na+ depletion. Two transport systems are likewise involved in the uptake of cholyltaurine in the presence of Na+ as well as in case of Na+ depletion. Their kinetic parameters are in presence of Na+ J'1(Na+ 143) = 1.55 +/- 0.14 nmol/(min.mg protein) and K'T1(Na+ 143) = 16.1 +/- 3.0 microM, and J'2(Na+ 143) = 0.51 +/- 0.05 nmol/(min.mg protein) and K'T2(Na+ 143) = 38.0 +/- 4.1 microM, and in case of Na+ depletion J'1(Na+ 1) = 0.10 +/- 0.02 nmol/(min.mg protein), K'T1(Na+ 1) = 7.7 +/- 1.2 microM, and J'2(Na+ 1) = 0.40 +/- 0.03 nmol/(min.mg protein) and K'T2(Na+ 1) = 41.0 +/- 4.2 microM. Uptake of cholyltaurine by both transport systems is competitively inhibited by 7 beta-NBD-NCT in the presence of Na+ as well as in case of Na+ depletion. In both cases the inhibition constants are practically identical with the KT values for uptake of 7 beta-NBD-NCT. Photoaffinity labeling of isolated hepatocytes using 7,7-ACT (400 microM) resulted in the irreversible inhibition of uptake of both bile salts to similar extents, confirming the kinetic data that 7 beta-NBD-NCT is a true analogue of cholyltaurine.

Affinity Labels↗
PubMed1992

Holmium-laser synovectomy of immune synovitis in rabbits.

Holmium-laser synovectomy was carried out to remove allergically inflamed synovial membranes in rabbit knee joints. The healing process was then investigated at different periods. Left knee joints of 12 rabbits were exposed to Ho:YAG-laser radiation at a wavelength of 2.1 microns, pulse energy of 600 mJ, pulse length of 1 ms, and repetition rate of 3 Hz. Twelve others were treated conventionally and 12 served as controls. After 1 day, 1 week, and 1 and 3 months, respectively, 3 animals from each group were sacrificed and the synovialis grossly and microscopically examined. Coagulation necrosis, inflammation, and edema resulted following laser therapy. After 1 week, the synovial layer consisted of a scarlike formation of fibers and within 1 month, its surface appeared smooth. The mechanical abrasion caused hemorrhage and necrosis. Fibrosis developed in the capsular layers, and after 3 months, the surface appeared coarse and villous. Based on these preliminary findings, holmium-laser synovectomy may offer an alternative method to existing therapeutic techniques.

Aluminum Silicates↗
PubMed1992

Aggregation substance of Enterococcus faecalis mediates adhesion to cultured renal tubular cells.

The sex pheromone system of Enterococcus faecalis is a unique, highly efficient plasmid collection mechanism for this species. A crucial role in this system is played by an adhesin called aggregation substance which enables the cell-cell contact between donor and recipient strains. The existence of the amino acid motif Arg-Gly-Asp-Ser in the adhesin prompted us to look for a possible binding of E. faecalis cells expressing aggregation substance to eucaryotic cells. We were able to show that the adhesin mediated binding to cultured renal tubular cells (porcine cell line LLC-PK1) via light microscopic, electron microscopic, and enzyme-linked immunosorbent assay-based studies. Synthesis of the adhesin was induced by some component(s) of serum. These data are interpreted to mean that aggregation substance is an adhesin mediating not only cell-cell contact between different E. faecalis strains but also binding of E. faecalis to eucaryotic cells, and therefore it might contribute to virulence.

Amino Acid Sequence↗
PubMed1992

SEM studies on unmanageable hair.

The manageability of the hair is dependent on the surface composition of the hair shaft. Exogenously caused damage leads to unmanageability by massive superficial defects in the hair cuticle. The symptoms of trichorrhexis nodosa and trichoptilosis are present, and superficial horny scales are bent up and curve under in tunnel-like fashions. Appropriate hair care can improve these defects. Endogenous damage to the hair leading to unmanageability is characterized by spiral furrows along the shaft. It can not usually be improved by the use of care products. The examples presented in the paper demonstrate that exogenous and endogenous causes of unmanageability are characterized by different alterations in the hair shaft.

Hair↗
PubMed1991

Demonstration of a molybdenum- and vanadium-independent nitrogenase in a nifHDK-deletion mutant of Rhodobacter capsulatus.

In Rhodobacter capsulatus there exists, in addition to a conventional Mo-containing nitrogenase, a second, Mo-indendent nitrogenase which was demonstrated in wild-type cells as well as in cells of a nifHDK- mutant. To construct this R. capsulatus mutant, a 4-kb BglII-HindIII fragment encompassing nifK, nifD and most of the nifH coding region was substituted by an interposon coding for kanamycin resistance. The alternative nitrogenase is repressed by molybdenum. Mo concentration greater than 1 ppb in the growth medium prevented diazotrophic growth of nifHDK- cells and the expression of nitrogenase activity. The Mo-independent nitrogenase was maximally derepressed in activated carbon-treated media which contained less than 0.05 ppb Mo, high concentrations of iron (1 mM ferric citrate) and serine as N source. Under N2-fixing and optimal Mo-deficient conditions, nifHDK- cells grew with a doubling time of 9 h. The highest activity achieved with whole cells was 1.2 nmol ethylene.min-1.mg protein-1. Vanadium neither stimulated nor inhibited growth and activity. The alternative nitrogenase reduced acetylene to both ethylene and ethane. With whole cells (nifHDK-) the proportion of ethane varied over 2-5% depending on the amount of residual traces of Mo in the medium. The addition of Mo to a growing, nitrogenase-active culture resulted in a slow decrease of total activity but also in a simultaneous increase of ethane production up to 40%. In contrast, cell-free extracts and the purified enzyme did not show any or only very little ethane formation (0-0.4%). Both enzyme components appeared to be very labile proteins. Component 2 lost almost all its activity during cell breakage. With component 1 in crude extracts, if complemented with the stable component 2 of the Mo-nitrogenase from Xanthobacter autotrophicus, a recovery of 50% of the original whole cell activity could be achieved. During purification, component 1 (from the nifHDK- mutant) remained remarkably stable. The partially purified component 1 had a pH optimum (acetylene reduction) of 7.8-8.0, relatively high affinity to acetylene (Km = 0.055 mM) and was analyzed to contain 20 mol Fe atoms/mol protein, 0.2 mol Mo atoms and negligible amounts of V, W and Re. The dithionite-reduced dinitrogenase appeared to be ESR-silent. The results indicate that the alternative nitrogenase of R. capsulatus is not a vanadium enzyme but rather a heterometal-free Fe-nitrogenase or a nitrogenase with an as-yet-unidentified heterometal atom.

Chromatography, Gel↗
PubMed1991

The acinar location of the sodium-independent and the sodium-dependent component of taurocholate uptake. A histoautoradiographic study of rat liver.

The acinar location of tritium-labelled taurocholate taken up from sodium-containing and sodium-free perfusion media in isolated perfused rat liver was made visible by means of histoautoradiography on cryoslices at low, medium and high bile salt concentrations. In antegrade perfusion studies, in the presence of sodium, with taurocholate concentrations of 1 and 20 microM, respectively, the silver grain label was mainly restricted to acinar zones 1. At an 80 microM concentration, zones 2 and 3 were also labelled but with decreasing intensities towards the terminal hepatic venules. At 120 microM taurocholate, all acinar zones were nearly equally labelled. In the absence of sodium, antegrade liver perfusions with 1, 20 and 120 microM taurocholate resulted in an almost homogenous labelling of all acinar zones and retrograde perfusions in a silver grain density slightly decreasing towards the terminal portal venules. The results indicate that hepatocytes of all acinar zones are capable of taking up taurocholate by both a sodium-dependent and a sodium-independent pathway. The contribution of the sodium-independent uptake to the overall uptake of taurocholate increases with increasing zonal recruitment at higher concentrations. The sodium-dependent uptake, however, is always dominant.

Animals↗
PubMed1991

P300 response of hippocampus analyzed by means of multielectrodes in cats.

Event-related potentials (ERPs) of the cat hippocampus were investigated by means of multielectrodes in various layers of the hippocampus. The experimental and mathematical procedures were the same as those in the companion report (Başar-Eroglu et al., in press a). It is shown that the most ample N200-P300 complex was recorded close to the CA3 region of the hippocampus.

Animals↗
PubMed1991

Fluorescent derivatives of bile salts. I. Synthesis and properties of NBD-amino derivatives of bile salts.

In order to visualize bile salt transport, fluorescent bile salt derivatives were synthesized by introduction of the relatively small fluorescent 4-nitrobenzo-2-oxa-1,3-diazol (NBD)-amino group in either the 3-, 7-, or 12-position of the steroid structure, thus providing a complete set of diastereomeric derivatives, 3 alpha-NBD-amino-7 alpha,12 alpha-dihydroxy-5 beta-cholan-24-oic acid, 3 beta-NBD-amino-7 alpha,12 alpha-dihydroxy-5 beta-cholan-24-oic acid, 7 alpha-NBD-amino-3 alpha,12 alpha-dihydroxy-5 beta-cholan-24-oic acid, 7 beta-NBD-amino-3 alpha,12 alpha-dihydroxy-5 beta-cholan-24-oic acid, 12 alpha-NBD-amino-3 alpha,7 alpha-dihydroxy-5 beta-cholan-24-oic acid, 12 beta-NBD-amino-3 alpha,7 alpha-dihydroxy-5 beta-cholan-24-oic acid, as well as their taurine conjugates. Their optical properties with absorption maxima at about 490 nm and emission maxima at 550 nm make them suitable for fluorescent microscopic studies. Fluorescence of the NBD-derivatives is strongly dependent on polarity of the solvent, on the concentration of the bile salt derivatives, and only slightly on temperature.

Bile Acids and Salts↗
PubMed1991

Fluorescent derivatives of bile salts. II. Suitability of NBD-amino derivatives of bile salts for the study of biological transport.

Interaction of unconjugated and taurine-conjugated NBD-amino-dihydroxy-5 beta-cholan-24-oic acids bearing the fluorophor in the 3 alpha, 3 beta, 7 alpha, 7 beta, 12 alpha, or 12 beta position with albumin results in a small hypsochromic shift of the emission maximum and an increase in quantum yield, suggesting binding by hydrophobic interactions. The different unconjugated fluorescent bile salt derivatives are metabolized by intact rat liver in different ways. The unconjugated 3 beta-NBD-amino derivative is completely transformed to its taurine conjugate and secreted as such, whereas the 3 alpha-NBD-amino derivative is completely transformed to a polar fluorescent compound not identical with its taurine conjugate. The unconjugated 7 alpha- and 7 beta-NBD-amino derivatives are only partially conjugated with taurine and mainly secreted in unmetabolized form. The unconjugated 12 alpha- and 12 beta-NBD-amino derivatives are not at all transformed to their taurine conjugates, but are partially metabolized to unidentified compounds. They are predominantly secreted as the unmetabolized compounds. In contrast to the unconjugated derivatives, all taurine-conjugated fluorescent bile salt derivatives are secreted into bile unmetabolized. With the exception of the 3 alpha-compound, all synthesized taurine-conjugated fluorescent derivatives interfere with the secretion of cholyltaurine. Differential photoaffinity labeling studies using (7,7-azo-3 alpha,12 alpha- dihydroxy-5 beta-cholan-24-oyl)-2'-[2'-3H(N)]aminoethanesulfonate as a photolabile derivative revealed that in liver cells all fluorescent bile salt derivatives interact with the same polypeptides as the physiological bile salts. The hepatobiliary transport of taurine-conjugated NBD-amino bile salt derivatives is, due to hydrophobic interactions, accompanied by an increase in fluorescence intensity which is favorable for the study of biological bile salt transport by fluorescence microscopy.

Albumins↗