Search PubMed⌕ Search

Biomedical subjects

P Berthold

Publications and source records attributed to P Berthold.

At least 37 records · Page 2Linked to original sources
PubMed1991

Orientation in birds. Satellite tracking: a new method in orientation research.

The study of bird migration by satellite tracking began in the 1980s, after transmitters had become sufficiently small to allow the monitoring of larger migrating species. The initial studies in this direction were all successful with respect to establishing this method (Section 2) of elucidating new migration patterns and various aspects of orientation. These pilot studies are summarized in Section 3, Table 1, Figures 1-4. We believe that studies on avian orientation and navigation will, in general, greatly benefit from satellite tracking if some prerequisites are fulfilled and adequate experiments planned (Section 4). In future studies, smaller transmitters with increased life expectancies are needed, and possible effects of these transmitters on bird behaviour must be examined. Considerable improvement of satellite tracking in avian orientation research is to be expected, along with the development of a new generation of satellites allowing communication between satellites and transmitters (Sections 4, 5).

Animals↗
PubMed1991

Orientation in birds. Spatiotemporal programmes and genetics of orientation.

A number of migratory bird species have endogenous annual rhythms that regulate the entire annual cycle, including migration. Moreover, captive migrants display inherited migrational activity; this could theoretically also be used by free-living migrants as a time programme for migration. Finally, this heritable migrational activity is oriented in a seasonally appropriate direction, even in naive birds. These characteristics should enable inexperienced migrants isolated from contact with experienced conspecifics, to utilize a heritable vector-navigation programme to migrate from the breeding grounds to the winter quarters. That is, migrants should reach goal areas they have never experienced by migrating in programmed directions, for as long a period as the genetically fixed time programme for migrational activity induces them to do so. The time course of migration, as established by trapping stations, theoretical influences of environmental variables on migration programmes, and also compensatory behaviour and backup measures, are discussed. The present evidence supports the view that a large number of migrants are essentially brought to their wintering areas by vector-navigation systems.

Animals↗
PubMed1991

Structure and function of the B and D genes of the Actinobacillus actinomycetemcomitans leukotoxin complex.

The Actinobacillus actinomycetemcomitans leukotoxin gene complex, consisting of four genes, has been cloned and the sequence of the AaLtC and AaLtA genes reported. The present paper details the sequences of the AaLtB and AaLtD genes which, like AaLtC and AaLTA, are also homologues of genes found in other cytolytic toxin complexes of several other Gram-negative bacterial pathogens. When tested in a recombinant expression system, the AaLtB and/or AaLtD genes are required for the translocation and insertion of the A. actinomycetemcomitans leukotoxin (AaLtA) into the cell membrane of Escherichia coli.

Actinobacillus↗
PubMed1990

Leukocidal activity of staphylococci isolated from human periodontal lesions.

Staphylococci isolated from subgingival samples of patients with advanced periodontitis were tested for leukocidal activity. Intact organisms, bacterial sonicates or bacterial culture supernatants were incubated with human neutrophils that had been prelabeled with 51chromium. The majority of Staphylococcus aureus periodontal isolates provoked dose-dependent extracellular release of the radiolabel. By contrast, other strains of staphylococci had marginal or no demonstrable leukocidal activity. Leukocidal activity was heat-sensitive and was neutralized by horse anti-leukocidin antibodies. The results indicate that S. aureus colonizing human periodontal lesions elaborate a leukocidin that may conceivably destroy neutrophils that emigrate into the gingival region. This could adversely affect the overall status of this antimicrobial defense system in the gingival area and contribute to the pathogenicity of S. aureus as well as other potential periodontopathic organisms.

Chromium Radioisotopes↗
PubMed1990

Effects of cations and osmotic protectants on cytolytic activity of Actinobacillus actinomycetemcomitans leukotoxin.

Actinobacillus actinomycetemcomitans leukotoxin permeabilized the plasma membrane of HL-60 promyelocytic leukemia cells, resulting in colloid osmotic lysis. These events were associated with efflux of 51chromium (from prelabeled cells), influx of propidium iodide, and ultrastructural evidence of cellular damage. Target cell lysis was inhibited by procedures which may interfere with the initial interaction of the toxin with the plasma membrane. For example, washing cultures (to dilute and remove toxin) or the addition of monoclonal antibodies (to neutralize toxin) or trypsin (to inactivate toxin) limited lysis when undertaken within the first 5 min of the reaction. The extent of injury was also diminished when radiolabeled HL-60 cells were exposed to toxin in the presence of unlabeled, toxin-sensitive cells (e.g., HL-60 cells or human neutrophils) or certain toxin-resistant target cells (e.g., human K562 erythroleukemia cells). This suggests that the association of the toxin with the cell membrane may not be sufficient to cause lysis without activation of additional effector mechanisms. The addition of specific trivalent (e.g., La3+) or divalent (e.g., Ca2+ and Zn2+) cations to toxin-treated cells appeared to enhance their capacity to repair or minimize the extent of toxin-mediated membrane damage. Depending on size, certain saccharides served as osmotic protectants: maltose almost completely inhibited radiolabel release, while smaller molecules provided correspondingly less protection. The results imply that the leukotoxin has membranolytic activity, producing pores in target cells with a functional diameter approximately the size of maltose (0.96 nm).

Actinobacillus↗
PubMed1989

Saliva-mediated aggregation of Enterococcus faecalis transformed with a Streptococcus sanguis gene encoding the SSP-5 surface antigen.

The interaction of a high-molecular-weight salivary glycoprotein (agglutinin) with Streptococcus sanguis M5 leads to the formation of bacterial aggregates. We have previously shown that the SSP-5 surface antigen from S. sanguis M5 binds the salivary agglutinin and therefore may be involved in the aggregation process. Here we report the transformation of a nonaggregating Enterococcus faecalis strain with the SSP-5 gene and show that the protein is expressed on the cell surface and confers an aggregation-positive phenotype. E. faecalis S161 protoplasts were transformed with pAM401 EB-5, a shuttle vector containing the S. sanguis SSP-5 gene, resulting in the isolation of E. faecalis S161EB-5. Crude cell extracts from this transformant and from S. sanguis M5 were analyzed by Western blotting. Extracts from S. sanguis M5 possessed peptides of 190 and 205 kilodaltons that reacted strongly with polyclonal antibodies against the recombinant SSP-5 antigen. E. faecalis S161EB-5 contained only the 190-kilodalton immunoreactive protein, suggesting that the antigen may be processed differently in E. faecalis S161EB-5. The parent strain, E. faecalis S161, did not react with this antibody preparation. Immunogold labeling of intact E. faecalis S161EB-5 and S. sanguis M5 with anti-SSP-5 immunoglobulin G showed that both organisms expressed similar levels of the antigen. Both organisms formed visible aggregates upon incubation with salivary agglutinin. These results suggest that the SSP-5 antigen may mediate both the binding of agglutinin to S. sanguis M5 and the subsequent formation of bacterial aggregates.

Agglutinins↗
PubMed1988

Ultrastructure of the flagellar basal body complex of Centipeda periodontii.

The morphology and insertion of the flagellar basal body complex into the cell wall of Centipeda periodontii was studied by electron microscopy of both negatively and positively stained specimens. Freshly harvested cells were examined either after treatment with 0.2% sodium dodecyl sulfate (SDS) for 2 min and negatively stained with phosphotungstic acid, or after treatment according to standard electron microscopy procedures that included positive staining. Small numbers of flagella were dislocated from the cell body after treatment with SDS. The flagella demonstrated an unusual basal body structure: five rings were attached to a rod in a three-ringed (distal) and two-ringed (proximal) patterns; ring diameters produced a distinctive hourglass shape. The cell envelope was typical for gram-negative bacteria with a cytoplasmic membrane and an outer membrane separated by a peptidoglycan layer. Basal body length and cell wall width were in general agreement, approximately 29 nm. Cell wall width exceeded dimensions previously reported for Escherichia coli; this was attributed to an unusually thick peptidoglycan layer.

Flagella↗
PubMed1988

Killing of human myelomonocytic leukemia and lymphocytic cell lines by Actinobacillus actinomycetemcomitans leukotoxin.

The purified leukotoxin of Actinobacillus actinomycetemcomitans kills human leukemic cell lines (e.g., HL-60, U937, and KG-1) and human T- and B-cell lines (e.g., JURKAT, MOLT-4, Daudi, and Raji) in a dose- and time-dependent manner. The 50% effective doses for these cell lines are similar to those established for human polymorphonuclear leukocytes and monocytes. In contrast, other human and nonhuman tumor cell lines are not susceptible to the leukotoxin. These human leukemia and lymphoid cell lines will serve as useful model systems with which to study the molecular specificity and mechanism(s) of action of the actinobacillus leukotoxin.

Actinobacillus↗
PubMed1987

Immunosuppressive effects of Centipeda periodontii: selective cytotoxicity for lymphocytes and monocytes.

We have examined soluble sonic extracts prepared from several strains of Centipeda periodontii for their ability to alter human lymphocyte function. These organisms were isolated from subgingival plaque of patients with periodontal disease. We found that sonicates from several, but not all, strains of C. periodontii caused a dose-dependent inhibition of lymphocyte responsiveness to concanavalin A, phytohemagglutinin, pokeweed mitogen, and formalinized Staphylococcus aureus. Inhibition was associated with a concomitant decrease in cell viability assessed by trypan blue exclusion, 51Cr release, and electron microscopy. The maximal number of dead cells was observed 20 to 24 h after exposure to the sonic extract. Susceptible cells include human lymphocytes (both B and T), monocytes, and erythrocytes, whereas polymorphonuclear cells, murine L-929 fibroblasts, and sheep erythrocytes were not affected. Preliminary characterization of the cytotoxic activity indicates that it is heat labile and trypsin sensitive and has an Mr of 60,000. It has been proposed that impaired host defense may play a pivotal role in the pathogenesis of periodontal diseases. The data presented in this paper suggest that immunosuppression (local or systemic or both) could be initiated by C. periodontii. This immunosuppression may alter the nature and consequences of host-parasite interactions, thereby enhancing the pathogenicity of C. periodontii itself or some other opportunistic organism.

Bacteria, Anaerobic↗
PubMed1984

Helical flagellation in Centipeda periodontii, a gram-negative, anaerobic bacillus from periodontitis lesions.

The insertion pattern of flagellation of Centipeda periodontii was determined from electron micrographs of negatively stained cells treated with various detergents to remove their outer cell wall layer(s) selectively. The best results were obtained with 0.2% sodium dodecyl sulphate and a treatment time of 1-2 min. Detergent-treated cells displayed a unique helical pattern of flagellation which we designate as helicotrichous (Gk n. helix, helix + Gk n. thrix, hair). Flagella originated from an electron-dense region approximately 180 nm wide, which spiraled around the cell body. The length of the insertion path averaged 2.6 micron per 360 degrees turn; its periodicity was 2.5 micron. An average of 19 flagella were inserted per 1 micron length of the electron-dense region. The effects of cell division and branching on flagellation were also examined.

Bacteria, Anaerobic↗
PubMed1983

Immunoperoxidase labeling of Streptococcus mutans for scanning electron microscopy.

The application of an immunoperoxidase method to labeling of Streptococcus mutans subsp. sobrinus for scanning electron microscopy is described. Bacteria from four separate cultures were fixed in 2.5% buffered glutaraldehyde solution. The specimens were treated in accordance with an indirect immunolabeling procedure using a rabbit anti-S. mutans subsp. sobrinus gamma-globulin. Labeled bacteria were equipped with a layer of small, distinct globules of horse-radish peroxidase reaction product. Bacteria exposed to control incubations were not equipped with this layer.

Bacteriological Techniques↗