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K Ruhnau

Publications and source records attributed to K Ruhnau.

9 recordsLinked to original sources
PubMed1994

Experiments on the possible role of leeches as vectors of animal and human pathogens: a light and electron microscopy study.

The presence and survival of pathogens inside the gut of leeches were studied by means of light and electron microscopy. In African leeches from Cameroon, blood was serologically positive for human immunodeficiency virus (HIV) and hepatitis B; blood of Hirudo medicinalis bought in German pharmacies contained up to 11 different species of bacteria. In experiments done at low (3 degrees C) and high (22 degrees, 32 degrees C) temperatures, it was shown that ingested red and white blood cells survive for long periods. The time was prolonged to at least 6 months in cases in which the leeches were stored at 3 degrees C. The same effect occurred with pathogens. Bacteriophages (viruses of bacteria) and bacteria persisted in large numbers for at least 6 months in the gut of experimentally infected leeches. Protozoan parasites such as Toxoplasma gondii, Trypanosoma brucei brucei, or Plasmodium berghei were even capable of reproducing inside the gut of the leech. In the case of Plasmodium parasites, this proceeded at low (3 degrees C) and high (22 degrees C) temperatures until all erythrocytes were used up. These parasites survived as long as the erythrocytes and lymphocytes were of good shape, i.e., around 5-6 weeks p.i. Single stages survived longer, especially at low temperatures. However, electron microscopy studies gave no hint of penetration of such pathogens into the unicellular salivary glands, which would initiate a direct transmission. Such transmission, however, is possible--many fish leeches directly transmit several blood parasites--when the leeches are squeezed during skin attachment or when they are manipulated by dropping salt solution on their backs while they are sucking. Consequently, the leech is a potential vector of many pathogens, especially in regions with an endemic spread of human and/or animal pathogens.

Animals↗
PubMed1990

Antibody mapping of functional domains in vinculin.

We have analyzed the functional domain structure of vinculin, a protein involved in linking microfilaments to the cytoplasmic face of cell membranes in animal cells. For this purpose, we used several monoclonal antibodies raised against chicken gizzard vinculin whose epitopes could be assigned to discrete regions in the vinculin sequence by immunoblotting of proteolytic fragments combined with N-terminal amino acid sequencing. Two of these antibodies induced the disruption of stress fibers and changed the number of morphology of focal contacts after microinjection in chicken embryo fibroblasts. Based on the location of its epitope in comparison with vinculin domains previously identified by other groups, we propose that one of these antibodies (15B7) interferes with the binding of vinculin to talin, the most peripheral of the microfilament proteins. The second antibody (14C10) binds within a region comprising three internal repeats and might therefore distort the inner architecture of vinculin. A third antibody (As3) inhibited the binding of F-actin to vinculin in an in vitro assay but had no effect on the microfilament system in cells. These data emphasize the role of vinculin as a key protein in microfilament-membrane linkage and support previous work on a direct interaction between vinculin and actin.

Actins↗
PubMed1989

Kinetic evidence for insertion of actin monomers between the barbed ends of actin filaments and barbed end-bound insertin, a protein purified from smooth muscle.

An actin polymerization-retarding protein was isolated from chicken gizzard smooth muscle. This protein copurified with vinculin on DEAE-cellulose and gel filtration columns. The polymerization-retarding protein could be separated from vinculin by hydroxylapatite chromatography. The isolated polymerization-retarding protein lost its activity within a few days, but was stable for weeks when it was not separated from vinculin. We termed the polymerization-retarding protein "insertin". Because of the instability of the isolated insertin, we investigated the effect of insertin-vinculin on actin polymerization. Insertin-vinculin retarded nucleated actin polymerization maximally fivefold. Polymerization at the pointed ends of gelsolin-capped actin filaments was not affected by insertin-vinculin, suggesting that insertin-vinculin binds to the barbed ends, but not to the pointed ends, of actin filaments. Retarded polymerization was observed even if the actin monomer concentration was between the critical concentrations of the ends of treadmilling actin filaments. As at this low monomer concentration the pointed ends depolymerize, monomers appeared to be inserted at the barbed ends between the terminal subunit and barbed end-bound insertin molecules. Insertin-vinculin was found not to increase the actin monomer concentration to the value of the pointed ends. These observations support the conclusion that insertin is not a barbed end-capping protein but an actin monomer-inserting protein. According to a quantitative analysis of the kinetic data, all observations could be explained by a model in which two insertin molecules were assumed to bind co-operatively to the barbed ends of actin filaments. Actin monomers were found to be inserted between the barbed ends and barbed end-bound insertin molecules at a rate of about 1 x 10(6) M-1 s-1. Insertin may be an essential part of the machinery of molecules that permit treadmilling of actin filaments in living cells by insertion of actin molecules between membranes and actin filaments.

Actins↗
PubMed1988

Rate of binding of tropomyosin to actin filaments.

The decrease of the rate of actin polymerization by tropomyosin molecules which bind near the ends of actin filaments was analyzed in terms of the rate of binding of tropomyosin to actin filaments. Monomeric actin was polymerized onto actin filaments in the presence of various concentrations of tropomyosin. At high concentrations of monomeric actin (c1) and low tropomyosin concentrations (ct) (c1/ct greater than 10), actin polymerization was not retarded by tropomyosin because actin polymerization was faster than binding of tropomyosin to actin filaments. At low actin concentrations and high tropomyosin concentrations (c1/ct less than 5), the rate of elongation of actin filaments was decreased because actin polymerization was slower than binding of tropomyosin at the ends of actin filaments. The results were quantitatively analyzed by a model in which it was assumed that actin-bound tropomyosin molecules which extend beyond the ends of actin filaments retard association of actin monomers with filament ends. Under the experimental conditions (100 mM KCl, 1 mM MgCl2, pH 7.5, 25 degrees C), the rate constant for binding of tropomyosin to actin filaments turned out to be about 2.5 X 10(6) to 4 X 10(6) M-1 S-1.

Actins↗
PubMed1988

Evidence for direct binding of vinculin to actin filaments.

The interaction of vinculin with actin filaments was investigated by methods which exclude interference by contaminating proteins which may occur in vinculin preparations. Vinculin which was blotted from SDS-polyacrylamide gels onto nitrocellulose, was stained specifically by fluorescently labeled polymeric actin (100 mM KCl, 2 mM MgCl2). Vinculin which was purified from alpha-actinin and an actin polymerization-inhibiting protein (HA1), was found to be cosedimented with polymeric actin. Maximally one vinculin molecule was cosedimented per one hundred actin filament subunits. Half maximal binding of vinculin was observed at about 0.25 microM free vinculin. Vinculin could be replaced from actin by the addition of tropomyosin.

Actins↗
PubMed1988

Characterization of the actin polymerization-inhibiting protein from chicken gizzard smooth muscle.

An actin polymerization-inhibiting protein, occurring in crude preparations of vinculin from chicken gizzard, has been found to be heterogeneous. The molecular masses of the polymerization-inhibiting peptides have been reported to range from 20 kDa to 80 kDa [Schröer, E. & Wegner, A (1985) Eur. J. Biochem. 153, 515-520]. In this paper, a 21-kDa peptide was isolated from the bulk of the other peptides by gel chromatography. The 21-kDa peptide was identified as a polymerization-inhibiting peptide by its ability to retard nucleated actin polymerization and to bind polymeric actin when it was blotted onto nitrocellulose. Antiserum raised to the 21-kDa peptide was found to react with almost all peptides of the blotted heterogeneous polymerization-inhibiting protein. The same peptides which reacted with antiserum cosedimented with polymeric actin. The major peptides of the blotted polymerization-inhibiting protein bound polymeric actin. The largest peptide which reacted with antiserum and cosedimented with polymeric actin had a molecular mass of 85 kDa. The results suggest that the preparation of polymerization-inhibiting protein contains mainly polymerization-inhibiting peptides and only some contaminants, and that all the polymerization-inhibiting peptides are proteolytic fragments stemming from a common precursor.

Actin Depolymerizing Factors↗
PubMed1984

[Diskography--myelography].

One hundred patients were submitted to a prospective, comparative study of metrizamide myelography and discography. In the 32 patients with cervical myelopathy discography yielded no additional information and was thus abandoned. The 68 patients with radiculopathy disease the following results were obtained: In view of the agreement between clinical and myelographic monosegmental findings, discography was considered unnecessary. However, in seven cases with negative myelograms it was possible to show a disc prolapse by discography. When the myelogram was pathological over several segments discography furnished additional information for the differential diagnosis between osteochondrotic or discogenic space-occupying lesions.

Female↗
PubMedDate not supplied

Cervical disk syndromes: value of metrizamide myelography and diskography.

This paper reports on the respective diagnostic values of myelography with water-soluble contrast media and diskography in a study of 100 patients examined between 1979 and 1981 and operated on because of cervical disk disease. The results of the study led to a change of the diagnostic procedures formerly applied in radicular syndromes (i.e., diskography, and then perhaps myelography) and in cervical myelopathy (myelography, rarely followed by diskography). Now cervical metrizamide myelography is always performed first. Diskography is only indicated in radicular syndromes to determine the segment causing clinical symptoms when there is a polysegmental space-occupying lesion on the myelogram in combination with a mono- or oligoradicular neurologic symptomatology; or in the case of a normal myelogram with complaints resistant to conservative treatment.

Cervical Vertebrae↗