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Biomedical subjects

H Rink

Publications and source records attributed to H Rink.

At least 37 records · Page 2Linked to original sources
PubMed1996

A new combination of protecting groups and links for encoded synthetic libraries suited for consecutive tests on the solid phase and in solution.

A strategy for high-throughput evaluation of combinatorial compound libraries is reported, which circumvents the necessity to test complex mixtures. The method is based on a new combination of protecting groups, solid-phase linker and tags. The bulk of the library first undergoes a binding assay with the components grafted on beads. A selection of beads carrying strong ligands is stripped from the labelled target and distributed into microvessels. The ligands are cleaved and rinsed into microeluates. Subsequently, a more detailed characterization with a functional assay in solution determines the best performers, which are identified through the peptidic tag left behind on the corresponding mother bead.

Chemistry, Organic↗
PubMed1995

[1H-MR spectroscopic imaging in patients with clinically diagnosed Alzheimer's disease].

PURPOSE: To detect regional differences in accompanying metabolic changes, 1H-Magnetic Resonance Spectroscopic Imaging (MRSI) was performed in 16 patients with Alzheimer's disease (AD); the clinical diagnosis was based upon DSM-III-R and NINCDS-ADRDA guidelines. METHODS: In the hippocampal region metabolic maps of the local distribution of N-acetylaspartate (NAA), choline (Cho), creatine compounds (P(Cr)) and lactate were determined. Ratios of Cho/NAA, (P)Cr/NAA and Cho/(P)Cr calculated from selected hippocampal spectra were compared to those from healthy volunteers (n = 17). RESULTS: AD patients demonstrated an increase of Cho/NAA and (P)Cr/NAA ratios caused by increased choline compounds and decreased NAA. These alterations were observed in 11/12 cases in the hippocampal and in 7/12 in the temporo-occipital region. Hippocampal Cho/NAA ratios (0.56 +/- 0.19) were significantly elevated compared with controls (0.33 +/- 0.04; p < 0.0001). CONCLUSION: The observed elevation of choline compounds in the hippocampus supports the hypothesis that alterations in the cholinergic system play an important role in Alzheimer's disease. The observed reduction of NAA is due to neuronal degeneration.

Aged↗
PubMed1995

Basic biochemical parameters of one hundred cataractous lenses from Egyptian patients.

Cataractous lenses from an extended population of 100 Egyptian patients whose age, sex and case history had been recorded, were collected and classified morphologically. After determination of the lens wet weights, lenses were microsectioned and basic parameters such as wet weight, dry weight, water content and contents of water-soluble and water-insoluble crystallins of the samples were determined. The data obtained document moderate as well as drastic changes of the investigated parameters along with aging and cataractogenesis, and extend our knowledge from small numbers of hitherto investigated human lenses to a considerably high number of cases.

Adult↗
PubMed1995

Distribution of water-soluble crystallins in microsectioned cataractous lenses from one hundred Egyptian patients.

Morphologically classified lenses from 100 cataract patients from the Mansoura Eye Hospital (Egypt) were microdissected and the crystallin composition and distribution were analyzed by thin-layer isoelectric focusing (IEF). The IEF profiles of cataractous lenses were compared with each other, with those of sclerotic lenses and with a normal lens profile. The alterations in the composition of high-molecular-weight (HMW)-, alpha-, beta H-, beta L-, beta s-, and gamma-crystallins along with normal aging, are superimposed by pronounced cataract-related changes which are different for the various types of cataracts. The general feature includes a continuous loss of gamma-, beta s- and beta L-crystallins of higher IEPs and an increase of HMW material. This is highly pronounced in the nucleus of nuclear cataractous lenses. In cortical cataractous lenses, changes start in the cortical layers. No differences could be observed between alterations in Caucasian lenses and this extended Egyptian lens population.

Adult↗
PubMed1993

Changes in interactions in complexes of hirudin derivatives and human alpha-thrombin due to different crystal forms.

The three-dimensional structures of D-Phe-Pro-Arg-chloromethyl ketone-inhibited thrombin in complex with Tyr-63-sulfated hirudin (ternary complex) and of thrombin in complex with the bifunctional inhibitor D-Phe-Pro-Arg-Pro-(Gly)4-hirudin (CGP 50,856, binary complex) have been determined by X-ray crystallography in crystal forms different from those described by Skrzypczak-Jankun et al. (Skrzypczak-Jankun, E., Carperos, V.E., Ravichandran, K.G., & Tulinsky, A., 1991, J. Mol. Biol. 221, 1379-1393). In both complexes, the interactions of the C-terminal hirudin segments of the inhibitors binding to the fibrinogen-binding exosite of thrombin are clearly established, including residues 60-64, which are disordered in the earlier crystal form. The interactions of the sulfate group of Tyr-63 in the ternary complex structure explain why natural sulfated hirudin binds with a 10-fold lower K(i) than the desulfated recombinant material. In this new crystal form, the autolysis loop of thrombin (residues 146-150), which is disordered in the earlier crystal form, is ordered due to crystal contacts. Interactions between the C-terminal fragment of hirudin and thrombin are not influenced by crystal contacts in this new crystal form, in contrast to the earlier form. In the bifunctional inhibitor-thrombin complex, the peptide bond between Arg-Pro (P1-P1') seems to be cleaved.

Amino Acid Sequence↗
PubMed1993

Contributions from hydration of carboxylate groups to the spectrum of water-polypeptide proton-proton Overhauser effects in aqueous solution.

Nuclear Overhauser effects (NOE) were measured between water protons and protons of the glutamic acid side chain of the bicyclic decapeptide c-[Arg-Arg-Cys-Asn-Ala-Glu-Ala-Cys-Lys-Gly] in aqueous solution. Positive NOEs were observed between the gamma CH2 group of Glu and the water resonance, with similar NOE intensities at pH 2.0 and pH 6.3 in both the laboratory frame and the rotating frame of reference. These results indicate that the residence times of the hydration water molecules near the side-chain methylene protons are shorter than 500 ps for both the charged form and the uncharged form of Glu, and hence comparable to the water residence times near uncharged amino acid side chains. Furthermore, this study shows that the acidic proton in protonated carboxylic acid groups is not likely to interfere with the observation of polypeptide-hydration water NOEs, which is in contrast to the hydroxyl protons of the side chains of serine, threonine and tyrosine.

Algorithms↗
PubMed1993

DNA strand break induction and rejoining and cellular recovery in mammalian cells after heavy-ion irradiation.

The induction of intracellular DNA strand breaks by X rays and various heavy charged particles was measured by the alkaline unwinding and alkaline and neutral filter elution techniques. No variations in strand break induction were found between the different cell lines under investigation. For a given particle, both the LET and the particle energy determined the efficiency to induce DNA lesions. RBE values for the total amount of induced strand breaks were always less than 1. For DNA double-strand breaks (DSBs), RBE values only slightly greater than 1 were determined for particle radiation with an LET around 300 keV/microns. Intracellular DSB/SSB ratios were found to be equivalent to data reported for in vitro systems using radioprotective conditions [Christensen et al., Int. J. Radiat. Biol. 22, 457-477, 1972; Taucher-Scholz et al., Adv. Space Res. 12(2-3), (2)73-(2)80, 1992]. Strand break rejoining as an indicator of cellular repair processes was detected even after high-LET irradiation (LET < or = 10,000 keV/microns). However, both the half-times of rejoining and the fraction of residual DNA breaks increased with the atomic number of the particle. After particle irradiation with LET values beyond 10,000 keV/microns, no rejoining of DNA strand breaks was found.

Animals↗
PubMed1992

Cellular kinetics of prednimustine versus chlorambucil plus prednisolone in vitro.

Intracellular concentrations of prednimustine (PM), chlorambucil (CLB), phenylacetic acid mustard (PAAM) and prednisolone (P) were measured in different experimental tumor cell lines that had been incubated with either PM or CLB + P. For intracellular analytical determination, we modified a high-pressure liquid chromatographic method for the detection of these substances in plasma. Intact PM could be detected in the intracellular compartment of the incubated tumor cells. PM-incubated cells from PM-injected rats exhibited a higher intracellular concentration-time integral (PAAM) and longer concentration-time profiles for drugs with alkylating capacity than did cells exposed to the CLB + P mixture or to CLB. PAAM was not detectable after incubation of cells with PM, whereas in CLB-incubated cells the AUC of PAAM exceeded that of the parent drug CLB. Our in vitro results therefore favour the concept of a facilitated intracellular uptake and an increased antiproliferative effect for PM versus CLB and CLB + P.

Animals↗
PubMed1992

X-ray induced DNA strand break induction and rejoining in cultured bovine lens epithelial cells.

DNA strand break induction and rejoining in cultured bovine lens epithelial cells were measured by the alkaline unwinding technique followed by hydroxyapatite chromatography. DNA damage is described in terms of dose effect curves for unwinding immediately after irradiation (0 min) and for unwinding after a recovery period (30 min). The dose effect curves obtained are purely exponential with D0 values of 29.3 Gy (0 min) and 138 Gy (30 min), respectively. Rejoining data are given in terms of rejoining enhancement curves with half-times for overall rejoining being in the range from 4 to 10 min, independent of the dose. Kinetics of strand breaks are also presented in terms of decay curves, which are best described by the sum of three exponential components. The half-times of these components have been determined as tau(I) approximately 2 min, tau(II) approximately 15 min and tau(III) approximately 500 min. These components of damage decay curves are discussed in relation to cell killing.

Animals↗
PubMed1992

Comparison of DNA strand break induction in CHO cells measured by alkaline elution and by fluorometric analysis of DNA unwinding (FADU).

DNA damage in X-irradiated CHO cells was measured by alkaline filter elution and compared to fluorometric analysis of DNA unwinding (FADU). The FADU method proved to be as sensitive as the alkaline filter elution technique in detecting X-ray induced DNA breaks. Strand break induction was also measured after treatment with four radical generating chemicals (hydrogen peroxide, bleomycin, mitomycin C and methyl viologen) using the FADU technique.

Animals↗
PubMed1991

Procalcitonin NH2-terminal cleavage peptide has no mitogenic effect on normal human osteoblast-like cells.

The NH2-terminal cleavage peptide of procalcitonin (N-proCT) recently was reported to be a bone cell mitogen (Burns DM et al., Proc Natl Acad Sci USA 86:9519-9523, 1989). We have investigated the effect of N-proCT on the proliferation of normal human cells that have the phenotype of mature osteoblasts (hOB cells). N-proCT treatment for 24, 48, or 96 h in concentrations from 1 nM to 1 microM did not significantly increase [3H]thymidine uptake (means ranged from -19% to 38% of control, no significant differences) in hOB cells (6-10 cell strains per experiment) plated at four different densities. However, the hOB cells responded significantly to treatment with transforming growth factor beta (3 ng/ml), bovine insulin (300 micrograms/ml), or 30% fetal calf serum, which were included in all experiments as positive controls. The [3H]thymidine uptake data were confirmed in a direct cell count experiment tested at 96 h. Thus our data do not support the hypothesis that N-proCT is a potent mitogen for normal human osteoblasts.

Calcitonin↗
PubMed1991

Radiation sensitivity of cultured bovine lens epithelial cells.

The radiosensitivity of cultured bovine lens epithelial cells was measured. Data are given as survival curves for immediate plating (IP) and delayed plating (LP) after a recovery period of 48 h and for plating of cells irradiated in the exponential stage of growth (Exp). The survival curves obtained are strongly exponential, showing no shoulders in the low-dose range, with D37 values of 1.38 (Exp), 2.08 (IP) and 3.28 (LP), respectively. Data of in vitro radiosensitivity are discussed in relation to lens radiosensitivity in vivo. The study was possible by introducing poly-L-lysine hydrobromide coating of culture dishes.

Animals↗
PubMed1990

'Antiflammins': two nonapeptide fragments of uteroglobin and lipocortin I have no phospholipase A2-inhibitory and anti-inflammatory activity.

The 'antiflammin' nonapeptides P1 and P2 [(1988) Nature 335, 726-730] were synthesized and tested for inhibition of phospholipase A2 and release of prostaglandin E2 and leukotriene C4 in stimulated cells in vitro, and in vivo for anti-inflammatory activity in rats with carrageenan-induced paw oedema. Porcine pancreatic phospholipase A2 was not inhibited at concentrations of 0.5-50 microM. Prostaglandin E2 and leukotriene C4 release by mouse macrophages stimulated with zymosan or ATP was not affected up to a concentration of 10 microM, nor was prostaglandin release by interleukin 1 beta-stimulated mesangial cells and angiotensin II-stimulated smooth muscle cells. Both peptides exhibited no anti-inflammatory activity in carrageenan-induced rat paw oedema after topical (250 micrograms/paw) or systemic administration (1 or 4 mg/kg s.c.). These results do not support the claim of potent phospholipase A2-inhibitory and anti-inflammatory activity of the 'antiflammins' P1 and P2.

Amino Acid Sequence↗
PubMed1990

Preparation of monoclonal antibodies to hirudin and hirudin peptides. A method for studying the hirudin--thrombin interaction.

A panel of four monoclonal antibodies was obtained against hirudin, a potent and specific inhibitor of thrombin, by immunizing three groups of mice with protein conjugates made of recombinant desulfatohirudin (group I) or two synthetic peptides representing the C-terminal sequences 40-65 (group II) and 52-65 (group III) of hirudin. Only the monoclonal antibody 4049-83-12, obtained from the group I of mice, showed high affinity for hirudin (Kd of 0.6 nM) and in vitro neutralizing properties. The anti-peptide monoclonal antibodies bound hirudin with lower affinity (Kd of 1.5-7 nM) and showed lower neutralizing capacities. An epitope analysis performed by competitive ELISA using various hirudin analogues and by limited proteolysis of the hirudin-antibody complex revealed that the binding domains of all the anti-peptide antibodies were located close to the C-terminus of hirudin, since the bond between Glu-61 and Glu-62 was not cleaved by the V8 staphylococcal protease in the presence of these antibodies. The epitope of the antibody 4049-83-12 was strictly conformation-dependent, it recognized neither S-carboxymethylated hirudin nor any peptides of hirudin. The cleavage of the bond between Glu-43 and Gly-44 by V8 protease, as well as the cleavage of the bond between Lys-47 and Pro-48 by lysyl endopeptidase, was prevented by the binding of the antibody 4049-83-12 to hirudin. The possibility that this epitope overlapped with a region of hirudin involved in the binding to thrombin is discussed.

Animals↗
PubMed1990

The structural elements of hirudin which bind to the fibrinogen recognition site of thrombin are exclusively located within its acidic C-terminal tail.

Six lysyl residues of human thrombin (LysB21, LysB52, LysB65, LysB106, LysB107 and LysB154) have been previously shown to participate in the binding site of hirudin, a thrombin-specific inhibitor [(1989) J. Biol. Chem. 264, 7141-7146]. In this report, we attempted to delineate the region of hirudin which binds to these basic amino acids of thrombin. Using the N-terminal core domains (r-Hir1-43 and r-Hir1-52) derived from recombinant hirudins and synthetic C-terminal peptides (Hir40-65 and Hir52-65)--all fragments form complexes with thrombin--we are able to demonstrate that the structural elements of hirudin which account for the shielding of these 6 lysyl residues are exclusively located within the acidic C-terminal region. Since hirudin C-terminal peptides were shown to bind to a non-catalytic site of thrombin and inhibit its interaction with fibrinogen [(1987) FEBS Lett. 211, 10-16], our data consequently imply that these 6 lysyl residues are constituents of the fibrinogen recognition site of thrombin.

Amino Acid Sequence↗
PubMed1990

SCE-measurements as tool for evaluation of drug-induced chromosomal disorders.

A staining procedure that detects sister chromatid exchanges has been used to examine the response of chromosomes in cultured human fibroblasts to a series of chemical and physical mutagens. The test represents a sensitive and reproducible method for detecting mutagenicity on the chromosome level. It provides a powerful method for the detection of environmental mutagens and can be used in ocular toxicity studies.

Bleomycin↗
PubMed1989

Distribution of clobetasone in rabbit eye tissues after topical application.

This study describes the bioavailability of Clobetasone, which is topically applied as an anti-inflammatory drug. Right eyes of Chinchilla rabbits received Clobetasone eye drops 3 times daily over a period of consecutive 14 days. 30 min up to 96 h after the last application animals were killed at different times and the eyes removed immediately. Nine different eye tissue samples were prepared for Clobetasone estimation by radioimmunoassay (RIA) using 3H-labeled Clobetasone and an antibody directed against Clobetasone. Results indicate that Clobetasone penetrates relatively fast into the different eye tissues. The concentrations are different in the various tissues and show a relationship to the distance from cornea to vitreous. Concentrations decline in the following order: cornea greater than conjunctiva, sclera, iris (200 ng/g) greater than lens, vitreous, aqueous humour (5-15 ng/g). In all samples investigated Clobetasone levels decrease with time. No accumulation of the drug has been measured at any time. Clobetasone levels in the left, untreated eye, indicate that the compound has a small systemic resorption.

Administration, Topical↗