Search PubMed⌕ Search

Biomedical subjects

R Peters

Publications and source records attributed to R Peters.

At least 271 records · Page 15Linked to original sources
PubMed1981

Continuous fluorescence microphotolysis: A sensitive method for study of diffusion processes in single cells.

Continuous fluorescence microphotolysis is a sensitive method for the study of translational diffusion in the plasma membrane of single living cells and related systems. In this communication the conceptual basis of the method and its theoretical framework and experimental realization, as well as applications, are reported. In continuous fluorescence microphotolysis a microscopic membrane area of a single fluorescently labeled cell is irradiated by a laser beam while the fluorescence emitted from the area is monitored. The decay of the measuring signal reflects the competition of two processes: (i) the elimination of fluorophores by irreversible photolysis, and (ii) the entrance of new fluorophores into the area by diffusion. Rate constants for the two processes can be derived from the measuring data by mathematical analysis. As compared to our initial approach, fluorescence microphotolysis [Peters, R., Peters, J., Tews, K. H. & Bähr, W. (1974) Biochim. Biophys. Acta 367, 282-294], the main advantage of the method described here is an improvement of data quality and detection limit by orders of magnitude. From the practical point of view the main advantage is a simplification of the experimental setup. Results obtained by this method are encouraging and support the contention that continuous fluorescence microphotolysis may disclose new aspects of diffusion processes in biological systems.

Journal Article↗
PubMed1981

Antibodies to cell wall peptidoglycan of Staphylococcus aureus in patients with serious staphylococcal infections.

An enzyme-linked immunoassay was used to detect antibodies to the cell wall peptidoglycan of Staphylococcus aureus in human sera. All 170 sera from donors and patients with staphylococcal and nonstaphylococcal infections contained IgG antibodies to peptidoglycan; antibody levels varied with age, and transplacental transfer occurred. IgM antibodies to peptidoglycan were not found in donors and were present in only one patient with serious staphylococcal infection. Significantly elevated levels of IgG antibodies to peptidoglycan were observed in 20 (80%) of 25 patients with deep tissue infection with S. aureus but in only two (9%) of 22 patients with superficial staphylococcal infection. An increase in levels of antibodies to peptidoglycan generally coincided with an increase in level of IgG antibodies to teichoic acid. No cross-reactivity between peptidoglycan and teichoic acid was observed. Thus, staphylococcal peptidoglycan is immunogenic in humans, and testing for IgG antibodies to peptidoglycan may be useful in the diagnosis and follow-up of serious staphylococcal infections.

Antibodies, Bacterial↗
PubMed1981

Escherichia coli antibodies in opsonisation and protection against infection.

The opsonic and protective capacities of rabbit antisera against Escherichia coli O, K and core-glycolipid cell-wall antigens were compared with specific antibody titres as measured by agglutination and enzyme-linked immunosorbent assay. Anti-O antisera were opsonic and protective against two noncapsulate strains. Only anti-K antisera were opsonic and protective against a K-antigen-containing strain. In a mouse model anti-core-glycolipid antiserum was not protective against challenge even by a strain bearing only core glycolipid.

Animals↗
PubMed1981

[Variability of the dose effect in the radio-biologic experimentation on animals. Second communication: influence of breed, sex, age as well as of infections on death rates and LD 50 values (author's transl)].

As already demonstrated for Wistar rats, the radioresistance of Siv-50 male and female rats increases continually during their first months of life. Furthermore, males show a higher radioresistance than females during this period. The authors show with the same animals that a very radiosensitive rat strain can become a highly radioresistant strain after 2 1/2 years. After whole-body irradiation with 800--900 R, the increase of resistance of 85 days old males was between 62% and 68%. As a cause of this resistance increase, a mixed infection with Bordetella bronchiseptica and other germs is discussed. On the basis of literature, the authors discuss the occurrence of radioresistance increases after immunization or preconditioning with various bacterial vaccines and bacterial endotoxins.

Age Factors↗
PubMed1981

[Variability of the dose effect in the radio-biologic experimentation on animals. Third communication: Influence of breed, sex, age as well as radiation dose on body weight and survival time in days after whole-body irradiation of Wistar and Siv-50 rats (author's transl)].

After a whole-body irradiation of Wistar and Siv-50 rat males and females with 600 to 900 R, the survival times and the development of weight of the irradiated animals were determined and compared. The development of body weight was influenced by the dose administered as well as by age, sex and breed of the animals. Furthermore, the weight curves showed also characteristic analogies. During a period of 30 days after the irradiation, there are generally two phases with a considerable weight loss which are both accompanied by a reduced absorption of drinking-water and the appearance of a gastrointestinal and hemopoietic irradiation damage as well as the resulting activity increase of the pituitary gland and the cortex of the suprarenal gland. The weight recovery occurring after sublethal radiation doses is also influenced by the administered dose and the age of the animals. The dropping weight curves of dying animals are equally dependent on the administered dose. With regard to the survival time in days in dependence upon the administered dose and the age of the animals, the authors proved that the survival time of the finally dying animals becomes longer as their radioresistance increases. During the last phase of the 30 days' experimentation, females show a markedly increased death rate whereas males seem to have continually better survival chances when they are still alive at the last phase.

Age Factors↗
PubMed1980

Interactions of phagocytic and bacterial cells in patients with bacteremia caused by gram-negative rods.

The phagocytic and bactericidal functions of polymorphonuclear leukocytes and monocytes and the opsonic activity of serum from patients with gram-negative bacteremia were compared with those of cells and serum from healthy donors and control patients. Leukocytes from five of 20 patients showed diminished phagocytic capacity. Leukocytes from three of 12 patients had decreased chemotactic activity. Eleven of 37 blood culture isolates were inefficiently phagocytized after opsonization in homologous patient serum. However, in no instance was the opsonic capacity of patient serum significantly lower than that of control serum. In the serum of some patients, an increase in heat-stable opsonins was found during the course of infection. Resistance to opsonization of strains of Escherichia coli correlated with the presence of K capsular polysaccharide. It was concluded that both impaired leukocyte function and ineffective opsonization play a role in the pathogenesis of gram-negative bacteremia. Heat-stable opsonins (presumably specific antibodies) appear to be necessary for effective phagocytosis of bacilli that cause gram-negative bacteremia.

Antigens, Bacterial↗
PubMed1979

Photochemical cycle of bacteriorhodopsin studied by resonance Raman spectroscopy.

Individual species of the photochemical cycle of bacteriorhodopsin, a retinal-protein complex of Halobacteria, were studied in aqueous suspensions of the "purple membrane" at room temperature by resonance Raman (RR) spectroscopy with flow systems. Two pronounced deuterium shifts were found in the RR spectra of the all-trans complex BR-570 in H2O-D2O suspensions. The first is ascribed to C=NH+ (C=ND+) stretching vibrations of the protonated Schiff base which links retinal to opsin. The second is assigned tentatively to an "X-H" ("X-D") bending mode, where "X" is an atom which carries an exchangeable proton. A RR spectrum of the 13-cis-retinal complex "BR-548" could be deduced from spectra of the dark-adapted purple membrane. The RR spectrum of the M-412 intermediate was monitored in a double-beam pump-probe experiment. The main vibrational features of the intermediate M' in the reaction M-412 in equilibrium hv M' leads to delta BR-570 could be deduced from a photostationary mixture of M-412 and M'. Difference procedures were applied to obtain RR spectra of the L-550 intermediate and of two new long-lived species, R1'-590 and R2-550. From kinetic data it is suggested that T1'-590 links the proton-translocating cycle to the "13-cis" cycle of BR-548. The protonation and isomeric states of the different species are discussed in light of the new spectroscopic and kinetic data. It is found that conformational changes during the photochemical cycle play an important role.

Bacteriorhodopsins↗
PubMed1979

Escherichia coli K antigen in relation to serum-induced lysis and phagocytosis.

The presence of capsular polysaccharides (K antigens) and their relation to phagocytosis and sensitivity to the lytic action of serum of 26 strains of E. coli isolated from stools of healthy volunteers and from blood cultures were studied. Four of 12 strains isolated from stool cultures and 12 (86%) of the 14 strains isolated from blood cultures possessed K antigen. Three of the 12 strains isolated from stool cultures and seven of the 14 isolated from blood cultures were resistant to uptake by polymorphonuclear leucocytes; these resistant strains contained large amounts of K antigen. By contrast 10 strains, three with low amounts of K antigen and seven without detectable amounts of K antigen, were readily phagocytosed. Thus it appears that K antigen renders E. coli resistant to phagocytosis. Only four (15%) of the 26 strains were sensitive to serum lysis and there was no correlation between the presence of K antigen and the resistance to serum lysis.

Antigens, Bacterial↗
PubMed1979

Role of Escherichia coli K capsular antigens during complement activation, C3 fixation, and opsonization.

Escherichia coli strains with K capsular polysaccharides are relatively resistant to phagocytosis by polymorphonuclear leukocytes, in contrast to E. coli strains without K antigens. This inhibition of phagocytosis is related to an impaired recognition of the K+ strains by the phagocytes due to ineffective opsonization. All five strains without K antigens were readily phagocytized after opsonization in 5% normal serum, compared with no uptake of the K+ strains. Evidence is presented that the decreased opsonization of the K+ strains in normal serum is caused by a low rate of complement activation of the strains, with subsequent absence of C3b fixation or C3d fixation or both to the cell wall of the bacteria. After removal of the K+ antigens by heating of a K+ E. coli strain, the strain was able to activate complement, to bind C3b or C3d or both, and to become opsonized. Complement was then activated via the classical and alternative pathways, which was comparable to the complement consumption by K- E. coli.

Antigens, Bacterial↗