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Biomedical subjects

L Visser

Publications and source records attributed to L Visser.

At least 91 records · Page 5Linked to original sources
PubMed1986

Isolation of a neurotoxin from the salivary glands of female Rhipicephalus evertsi evertsi.

A quantitative study of the changes in the protein pattern of the salivary glands of female Rhipicephalus evertsi evertsi during the entire repletion process was undertaken. These results, in conjunction with the previously determined toxic phase, indicated the presence of a toxic protein. The development of a sensitive in vitro assay using a Xenopus nerve-muscle preparation, made it possible to identify toxic phases during feeding and to assay fractions of salivary gland extracts during toxin isolation. Sufficient amounts of electrophoretically and chromatographically homogeneous toxin could be obtained through the use of chromatofocusing, enabling its characterization with respect to molecular weight (68 kDa; determined by gel permeation chromatography), pI (6.00), and amino acid composition. The toxin was inactivated by pronase digestion as well as by antiserum.

Amino Acids↗
PubMed1985

Morphologic, immunologic, enzymehistochemical and chromosomal analysis of a cell line derived from Hodgkin's disease. Evidence for a B-cell origin of Sternberg-Reed cells.

Cell lines derived from Hodgkin's disease may provide a clue to the nature of Sternberg-Reed cells. In the current study, the establishment of an Epstein-Barr-virus-negative lymphoblastoid cell line, derived from the pleural fluid of a patient with the nodular sclerosis type of Hodgkin's disease, is described. The morphologic and immunologic cell marker findings indicate that this cell line is derived from Sternberg-Reed cells. The immunologic findings and a chromosomal analysis are in agreement with a B-lymphocyte origin of these cultured cells. Extrapolation of the results to Hodgkin's disease in vivo would indicate that Hodgkin's disease, like most non-Hodgkin's lymphomas, is the result of B-cell proliferation.

Antibodies, Monoclonal↗
PubMed1985

Isolation of Cowdria ruminantium by cellular affinity chromatography and detection by an enzyme-linked immunosorbent assay.

The isolation of Cowdria ruminantium by means of wheat germ lectin affinity chromatography as described in this paper permits the recovery of partially purified viable organisms under mild conditions in short time. These conclusions are based upon results of analyses of column fractions by intravenous inoculation into sheep, protein determination, electronmicroscopy and enzyme-linked immunosorbent assay. The entire purification procedure could be completed in 4-5 hours using only either infected sheep tissue or nymphae as starting material.

Animals↗
PubMed1984

Evaluation of the Venom Ex apparatus in the treatment of Egyptian cobra envenomation. A study in rabbits.

The Venom Ex cutting and suction apparatus for the initial treatment of snakebite was evaluated. Rabbits were injected with radioactive Egyptian cobra venom, and treatment with the Venom Ex followed. The fluid obtained by suction was analysed. All 8 control animals died within 4 hours; Venom Ex treatment resulted in the recovery of 7 out of 8 rabbits, after double the lethal dose of venom, providing treatment was started early. However, if treatment was delayed or if the dose of venom was high, there was a marked increase in the mortality. The amount of venom extracted was insufficient to account for the recovery of the animals. In one group of rabbits trauma was applied to the injection site without lacerating the skin and without removal of venom. About half of these animals recovered. However, this was less efficient than the Venom Ex treatment. Trauma apparently retards absorption of venom and increases survival. The possible reasons for this novel finding are discussed.

Adult↗
PubMed1983

The binding of snake venom cardiotoxins to heart cell membranes.

Cobra venom cardiotoxins have the effect, inter alia, of causing systolic arrest of the heart. We have observed significant binding in vitro of 35S-labelled cardiotoxins to mouse heart cell membranes. Part of the binding was saturable and could be displaced with homologous unlabelled cardiotoxins but not by neurotoxins or cardiotoxins inactivated by chemical modification. The specifically bound component represented more than 70% of total binding at saturation. Inclusion of Triton X-100 and NaCl in the phosphate-buffered incubation medium prevented nonspecific adsorption to centrifuge tube walls, and gave lower but more reproducible specific binding results, respectively. An apparent dissociation constant of 5 . 10(-7) M and a binding density of 500 pmol toxin/mg membrane protein were derived from the saturation isotherms.

Animals↗
PubMed1983

ELISA solid phase: partial denaturation of coating antibody yields a more efficient solid phase.

We have examined conditions which will improve the solid phase in ELISAs for HBsAg and ferritin in human serum. Sheep and rabbit antibodies were used. It was found that pre-exposure of antibody to low pH, 3 M urea and temperatures as high as 82 degrees C will enhance ELISA colour in these assays. Further experiments indicate that these conditions perturb the structure of the antibody molecules and results in the exposure of new hydrophobic regions. It is speculated that these more hydrophobic molecules can bind to regions on the plastic surface normally not coated by non-perturbed molecules.

Alkylation↗
PubMed1983

Expression of integrated viral DNA sequences outside the transforming region in eight adenovirus-transformed cell lines.

The expression of early and intermediate-early viral regions in eight adenovirus type 5 transformed cell lines was analyzed by radioimmuno-inhibition and RNA-DNA hybridization techniques. Details on the arrangement of the integrated viral DNA sequences in these cell lines have already been published (Visser, L., Wassenaar, A.D.C., Van Maarschalkerweerd, M.W. and Rozijn, T.H. (1981) J. Virol, 39, 684-693). In all cell lines tested, proteins encoded by the transforming region E1 are present. Dependent on the viral DNA content, additional early regions are expressed in most cell lines. In two of the cell lines polypeptides related to the adenoviral terminal protein, encoded by the recently described region E2b, could be detected. The viral DNA sequence encoding the body of the terminal protein mRNA is probably integrated intact, but the promoter region and at least some of the leaders are lacking in these cell lines.

Adenoviruses, Human↗
PubMed1983

Reactivity of presumed anti-natural killer cell antibody Leu 7 with intrafollicular T lymphocytes.

This report describes the presence of a T lymphocyte subpopulation in germinal centres of lymph follicles. This subpopulation is defined by reactivity with Leu 7 antibody, in addition to OKT11, OKT1, OKT3 and OKT4 positivity. The functional activity of this T lymphocyte subpopulation is a matter of discussion and has to be clarified by functional studies of purified populations of these cells.

Antibodies, Monoclonal↗
PubMed1982

Nucleotide sequence analysis of the linked left and right hand terminal regions of adenovirus type 5 DNA present in the transformed rat cell line 5RK20.

A peculiar phenomenon is observed in several adenovirus type 2 or 5 (Ad2 or Ad5) transformed cell lines: the right hand and left hand terminal regions of the viral genome present in the viral DNA insertions of these cell lines are found to be linked together. A large part of the viral DNA insertion present in the Ad5 transformed rat cell line 5RK20 has been cloned in the lambda vector Charon21A, including the segment containing the linked terminal regions. Sequence analysis of the linkage region showed a perfect homology with the Ad5 DNA sequence and a direct linkage of basepair (bp) 63 of the left hand end of the viral genome to bp 108 of the right hand end. No cellular or rearranged viral sequences were present. Our findings suggest that the joining of viral sequences into the cellular genome.

Adenoviruses, Human↗
PubMed1982

Biosynthesis, secretion and in vivo isotopic labelling of venom of the Egyptian cobra, Naja haje annulifera.

The venom glands of Elapidae differ from those of the Viperidae by lacking an expanded central lumen; the venom is stored in the tubular lumina as well as inside the cells in densely packed secretion granules. Using isotope tracer techniques, it was found that in the Egyptian cobra (Naja haje annulifera) venom is secreted both from pre-existing and from newly-formed granules. The rate of protein biosynthesis peaks at 4-9 days after venom was extracted (milked) from the glands. Highly labelled toxins (1-10 mCi/mmole protein) were isolated in good yield from the venom of snakes chronically intubated and infused i.p. with (3H)-amino acids. Repeated Fluothane (Halothane) anaesthesias and venom collections had no ill effect on venom yield. The radioactive venom and its component toxins retained full biological potency.

Amino Acids↗
PubMed1982

Sequence organization of a viral DNA insertion present in the adenovirus-type-5-transformed hamster line BHK268-C31.

The hamster cell line BHK268-C31 contains two large viral inserts which both include sequences from the left-hand end of adenovirus type 5 (Ad5) DNA. One of these viral inserts has been cloned in the lambda vector Charon 4A. Electron microscopic analysis and restriction enzyme mapping shows that the recombinant carries a 4.4-kb-long colinear segment of viral DNA, which is located between map positions 1.5 and 14.2 in the Ad5 genome. The junctions between viral DNA and flanking sequences have been sequenced and found not to show any specific features. One of the junctions is located in the E1a coding region, 573 bp from the left-hand end of the Ad5 genome, whereas the other junction is situated in the coding region for polypeptide IVa2. The promoter region as well as the cap site for the mRNAs from region E1a are thus missing from this insert and its role in viral transformation is unclear.

Animals↗
PubMed1981

1H nuclear-magnetic-resonance studies of the conformation of cardiotoxin VII2 from Naja mossambica mossambica.

The membrane toxin VII2 from the venom of Naja mossambica mossambica was investigated in aqueous solution by one-dimensional and two-dimensional high-resolution nuclear magnetic resonance (NMR) techniques at 360 MHz. The spectral characterization included identification of the complete spin systems for several amino acid residues, nuclear Overhauser effect measurements, the use of chemically induced dynamic nuclear polarization and studies of the pH dependence of the NMR spectrum. Data from homologous toxins, in particular direct lytic factor 12B from Haemachatus haemachatus, were used to establish assignments of aromatic and methyl proton resonances. From these experiments a short, triple-stranded fragment of antiparallel beta structure could be determined, which includes the residues 23-27, 43-46 and 60-62. Furthermore, the nuclear Overhauser effect measurements indicate close proximity in the protein conformation of the aromatic rings of Trp-14, Tyr-25 and Tyr-59, and the side chain of Ile-46.

Amino Acid Sequence↗
PubMed1981

Arrangement of integrated viral DNA sequences in cells transformed by adenovirus types 2 and 5.

The organization of the viral DNA sequences in 15 adenovirus-transformed cell lines was analyzed by the Southern blotting procedure. The site of adenovirus integration in the cellular genome was found not to be unique, and the viral DNA sequences involved in integration were not confined to a specific region of the adenovirus genome. Several cell lines showed simple integration patterns that demonstrated the presence of large continuous stretches of viral DNA. In four cell lines, containing sequences from both molecular ends of the viral genome, the left- and right-hand-terminal sequences appeared to be linked to each other.

Adenoviruses, Human↗
PubMed1980

Specific viral antigens in rat cells transformed by herpes simplex virus type 2 and in rat tumors induced by inoculation of transformed cells.

A rat cell line, RE1, oncogenically transformed by a herpes simplex virus type 2 ts mutant (ts 1), has been demonstrated to contain herpes simplex virus type 2-specific thymidine kinase activity, as have two of four tumors induced in rats by inoculation of these transformed cells. A high proportion of sera from tumor-bearing rats (5 of 11) have detectable antibody against herpes simplex virus thymidine kinase, and there is a correlation between enzyme activity in a tumor and antibody in "tumor sera." A proportion of tumor sera possess neutralizing activity for herpes simplex virus infectivity. Immunfluorescence studies indicate that the transformed cells express antigens which are probably induced early in herpes simplex virus type 2-productive infection.

Animals↗
PubMed1978

The synergism of cardiotoxin and phospholipase A2 in hemolysis.

The synergistic effect of exogenous cobra phospholipase A2 on the hemolysis brate of guinea pig erythrocytes by highly purified snake venom cardiotoxins was investigated. In the presence of phospholipase A2 the reaction was not only faster and had a lower activation energy but followed a sigmoidal instead of a linear time course. Similar results were obtained using porcine pancreatic phospholipase A2. Significantly, addition of even a trace of cobra phospholipase A2 (approx. 0.1%, w/w) was sufficient to bring about the full synergistic effect, emphasizing the stringent purity requirements for any meaningful investigation of cardiotoxin's own action. The possibility that the action of cardiotoxin on its own may involve the stimulation of an endogenous phospholipase is discussed in the light of the results obtained with exogenous cobra enzyme.

Animals↗