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Biomedical subjects

R Linke

Publications and source records attributed to R Linke.

At least 91 records · Page 5Linked to original sources
PubMed1992

Identification of neuronal connections by means of electron microscopic immunocytochemistry.

For many years neuroanatomical research has focused on the tracing of connections between populations of neurons in the central nervous system. With the development of immunocytochemical procedures employing antibodies against transmitters, transmitter-synthesizing enzymes and various neuropeptides, it has become possible to study the chemical characteristics of nerve cells. By combining tracer techniques and immunocytochemical approaches the transmitter identity of a projection can be determined. Moreover, electron microscopic double-labeling procedures allow the identification of the target cells of immunocytochemically characterized presynaptic terminals. This way, by the immunocytochemical identification of transmitters or neuropeptides in defined projection neurons, a more functional interpretation of neuroanatomical data has become possible. In the present report, these combinations of techniques are demonstrated by describing recent studies of cholinergic septohippocampal projection neurons.

Animals↗
PubMed1991

Generalized amyloidosis from beta 2-microglobulin, with caecal perforation after long-term haemodialysis.

A 73-year-old man with chronic renal failure of undetermined aetiology had received haemodialysis for 12 years when he died of acute purulent peritonitis due to caecal perforation. Amyloid deposits detected in a cystic bone lesion in the left hip had caused a pathological fracture 17 days before death. At autopsy, extensive amyloid deposits were found in the osteoarticular system, in the cartilaginous surface and the capsular tissue of joints, ligaments, vertebral discs and bone. In addition, vascular amyloid deposits were diagnosed in the heart, kidneys, testes, lungs, skin and in the gastrointestinal tract. A special feature of this case were interstitial amyloid deposits forming a fine-meshed structure in the myocardium and plate-like deposits in the gastrointestinal tract. Immunohistochemically, all these deposits reacted strongly with antibody to human beta 2-microglobulin but showed no reaction with antibodies to AA, A-lambda, A-kappa and AF. The present case demonstrates that extra-osteoarticular manifestations of AB-amyloidosis can cause serious complications.

Aged↗
PubMed1990

[Serum level and organ deposits of beta 2-microglobulin in dialysis patients].

In radioimmunological estimation of beta 2-microglobulin (beta 2m) significant higher serum values were found in 36 dialysis patients (44.4 +/- 20.3 mg/l) in comparison with healthy probands (1.5 +/- 0.2 mg/l). A significant relation to the duration of dialysis, diuresis, symptoms of the musculo-skeletal system, but not to radiologic changes or bone biopsy findings could be seen. Post mortem examinations carried out in 21 dialysis patients revealed AB-amyloid deposits in synovial tissue of different joints (particularly shoulder and hip joint) or intervertebral discs in eight patients (age 48 to 73 years, dialysis duration less than four years) without correlation to serum beta 2m level or radiographically suspect areas. In the tissue of cervical spine or intervertebral discs of two patients suffering from destructive spondylarthropathy no amyloid could be detected. These results suggest that AB-amyloid may occur in elderly patients early in the course of hemodialysis and may be asymptomatic in most cases.

Aged↗
PubMed1990

Kinetics of interaction of nucleotides with nucleotide-free H-ras p21.

A method is described for the convenient preparation of substantial quantities of nucleotide-free p21 or of 1:1 complexes with nucleotides other than GDP. The nucleotide-free protein has been used for kinetic studies of the binding of GDP and GTP, making use of the fluorescent analogues 3'-(methylanthraniloyl)-2'-deoxy-GDP and -GTP. Stopped-flow studies have led to the formulation of a two-step binding mechanism for both GDP and GTP, involving initial rapid but weak binding of the nucleotide followed by a relatively slow (10-20 s-1 at 25 degrees C; 3-5 s-1 at 5 degrees C) quasi-irreversible isomerization reaction. By use of a nonequilibrium competition method, guanosine and GMP have been shown to interact weakly but significantly with p21 (dissociation constants of 153 and 29 microM, respectively). The presence of guanosine or GMP at the active site of p21 leads to a marked stabilization of p21 against spontaneous denaturation when compared with the nucleotide- and nucleoside-free protein.

Guanosine↗
PubMed1990

Optic nerves in plethodontid salamanders (amphibia, urodela): neuroglia, fiber spectrum and myelination.

In five species of lungless salamanders, family Plethodontidae, which all show highly developed visual abilities, the ultrastructure of the optic nerve was investigated and the total number of retinal ganglion cell axons, the percentage of myelinated axons, and the volume densities of glia and axons were determined. More than 80% of all axons were smaller than 0.4 micron and only 2-3% were larger than 0.8 micron. In individual nerves the degree of myelination varied between 1 and 9% which is in the range reported for other amphibian species. The miniaturized and highly paedomorphic species Batrachoseps attenuatus was an exception because only very few or even no myelinated axons were present in the nerve, which is unique among gnathostome vertebrates. The five investigated species had total numbers of axons ranging from 26,000 in Batrachoseps attenuatus to about 50,000 in Plethodon jordani. These numbers are the lowest found among vertebrates with an elaborated visual system. The amount of glial material in the optic nerve varied between 25 and 50%, with larger nerves possessing more glia than smaller ones. Ultrastructural analysis revealed that the optic nerve of each species contained both astrocytes and oligodendrocytes, although often in immature form. In Batrachoseps attenuatus the glia showed features of both astrocytes and oligodendrocytes which reflect an undifferentiated state.

Animals↗
PubMed1990

Bradykinin antibodies: new developments.

Because all antibodies to bradykinin described to date more or less cross-react with larger and smaller bradykinin derivatives, the aim of the present study was the induction of a specific antibody against bradykinin. A bradykinin derivative, containing a Cys residue at position 6 instead of Ser, was linked to BSA by using a new heterobifunctional cross-linking reagent, the N-maleimido-6-aminocaproyl ester of 1-hydroxy-2-nitro-4-benzenesulfonic acid (mal-sac-HNSA). The Cys6-bradykinin derivative conjugated via the SH group to BSA was used to elicit bradykinin-specific antibodies in rabbits. After the fifth booster injection, the cross-reactivity of this antiserum with kallidin is 4 X 10(-3) when compared with bradykinin. The cross-reactivity of the de-Arg1-bradykinin derivative was 2 X 10(-4), indicating that the antibody requires the free N-terminus. The cross-reactivity of bradykinin and de-Arg9-bradykinin was nearly identical. However, de-Arg9-de-Phe8-bradykinin has a binding of 6 X 10(-3). From these data, it can be concluded that due to the ring-like structure of bradykinin, the coupling of bradykinin in the center of the molecule will elicit an antiserum that needs both the free N-terminal as well as the C-terminal phenylalanine and arginine residues for antibody recognition.

Amino Acid Sequence↗
PubMed1990

[Unusual primary cutaneous localized amyloidosis].

The case of a 41-year-old female patient with an unusual type of primary localized cutaneous amyloidosis is reported. Clinical examination revealed lesions typical for macular cutaneous amyloidosis, while histology and histochemistry, in contrast, revealed the presence of nodular amyloidosis of the skin with deposition of lambda light chain amyloid.

Adult↗
PubMed1989

Morphology of retinal ganglion cells in lungless salamanders (fam. Plethodontidae): an HRP and Golgi study.

The family Plethodontidae consists of nearly two-thirds of all living urodeles; most of them possess highly developed visual abilities. We investigated the morphology of retinal ganglion cells (RGCs) in four representative species by means of the horseradish peroxidase method in flatmounts and in transverse sections and with the Golgi method in transverse sections. In flatmount preparations, four classes of RGCs were found, differing in dendritic arborization, dendritic field size, and stratification pattern of dendrites in the inner plexiform layer (IPL). Class-1 cells had small dendritic fields (29-44 microns 2) and arborized throughout the entire depth of the IPL. Class-2 cells had medium to large dendritic fields (75-206 microns 2) and mostly arborized in two or three laminae or in a diffuse fashion in the IPL. Class-3 cells had medium to large dendritic fields (72-200 microns 2) but sparse dendritic arborization. They only arborized in the proximal lamina of the IPL. Class-4 cells had large dendritic fields (273-626 microns 2) and branched in the most sclerad stratum of the IPL. No large differences in intraspecific soma size of the different RGC classes were detected (although interspecific soma size varied to a considerable degree) and no "giant" cells typically found in other vertebrate retinas were present. The results suggest that, with respect to the pattern of arborization and stratification of dendrites, lungless salamanders possess morphological classes of RGC similar to those found in frogs, but the morphology of RGCs in lungless salamanders seems to be simplified in comparison to frog RGCs. This simplification might be a consequence of paedomorphosis.

Animals↗
PubMed1989

Crystallization and preliminary X-ray analysis of the human c-H-ras-oncogene product p21 complexed with GTP analogues.

The catalytic domain (amino acid residues 1 to 166) of the human ras-oncogene product p21 complexed with the GTP analogues beta,gamma-imido-GTP (GMPPNP), beta,gamma-methylene-GTP (GMPPCP), and guanosine-5'-(gamma-thiotriphosphate) (GTP gamma S) have been been crystallized. Crystals of the GMPPNP and GMPPCP complexes are well suited for high resolution X-ray crystallography. They belong to space group P3(1)21 (or its enantiomorph P3(2)21) with unit cell axes a=b=40.3 A and c = 162.2 A.

Base Sequence↗
PubMed1988

Fibrin-fibronectin compounds in human ovarian tumor ascites and their possible relation to the tumor stroma.

Covalently linked heterogeneous fibrin-fibronectin compounds were detected in ascitic fluid of 31 patients with advanced ovarian cystadenocarcinoma by means of enzyme-linked immunosorbent assay techniques, immunoaffinity chromatography, and Western blot analysis. Deposition of fibrin and fibronectin could also be demonstrated immunohistochemically in Carnoy-fixed tissue sections. Fibrin and fibronectin were found in the tumor stroma within tumor nests and more prominently in stroma surrounding the tumor nests. The association of fibrin and fibronectin was especially pronounced in the stroma surrounding the tumor islands. Fibronectin was also found to be associated with stroma cells. Areas within the tumor stroma showed superimposed staining for both fibrin and fibronectin supporting the assumption that the covalently linked fibrin-fibronectin conjugates found in ascitic fluid may stem from the provisional tumor stroma by proteolytic release.

Ascitic Fluid↗
PubMed1988

Miniaturization, genome size and the origin of functional constraints in the visual system of salamanders.

During their evolution, many species of lungless salamanders (fam. Plethodontidae) have experienced a great increase in genome size and consequently in the size of their cells, including sensory receptors and neurons. In addition, some have become extremely miniaturized. The consequences of these events and the morphological compensatory processes are studied in the visual system of juvenile and adult salamanders.

Animals↗
PubMed1985

Amyloid fibrils derived from V-region together with C-region fragments from a lambda II-immunoglobulin light chain (HAR).

Amyloid fibril proteins were isolated from the spleen of a patient with IgD(lambda)-plasmocytoma by extraction and gel filtration in 5M guanidine hydrochloride. The molecular mass of the predominant polypeptide chain was approximately 5000 Da. Its complete amino-acid sequence was elucidated by stepwise automated degradation of the carboxymethylated polypeptide chain and by structural studies of tryptic and thermolysinolytic cleavage products. The length of the polypeptide chain was 58 to 59 residues and it was homologous to the amino acids in positions 8 through 65 of the variable part of an lambda-type immunoglobulin light chain, which was most closely related to the lambda II subgroup. The N-terminal sequence of this amyloid fibril protein proved to be heterogeneous, indicating cleavage after the amino acids in positions 7 and 8. Peptides from the constant part of the lambda-chain were unexpectedly found in the tryptic digest of the denatured amyloid protein HAR. One polypeptide derived from the constant region was separated from the main component by high performance liquid chromatography. Its amino-acid sequence commenced at position 111 and could be traced in 41 steps. In this case, at least two constant region fragments were shown to be constituents of the amyloid fibril protein. The association of fragments from the variable as well as the constant region is discussed with respect to amyloid formation.

Amino Acid Sequence↗
PubMed1977

Cross reactivity of rabbit antibodies against purified animal enzymes. Comparison of enzymes of human and animal origin, II.

Enzyme preparations used for quality control of enzyme activity determinations in clinical chemistry should be very similar to human enzymes. Antibodies against e.g. porcine enzymes show cross reactivity with the corresponding human enzymes, indicating partial identity of the enzyme proteins. As the enzyme-antibody precipitates retain catalytic activity the similarity between the enzyme proteins is not limited to the catalytic sites.

Animals↗