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Biomedical subjects

L Ohman

Publications and source records attributed to L Ohman.

At least 55 records · Page 3Linked to original sources
PubMed1990

Neutrophil killing of two type 1 fimbria-bearing Escherichia coli strains: dependence on respiratory burst activation.

The production of reactive oxygen metabolites by neutrophils is thought to play a key role in host defense against invading microorganisms. In this study, the generation of oxygen metabolites induced by two uropathogenic Escherichia coli strains, ABU2 and PN7, and their subsequent killing in neutrophils were investigated. Both strains were grown to promote type 1 (mannose-sensitive) fimbria formation, but they differ with respect to other surface structures. When interacting with human neutrophils, the ABU2 bacteria adhered to and were phagocytized by the neutrophils, whereas PN7 bacteria adhered to the neutrophils but resisted phagocytosis. Both strains induced a pronounced neutrophil chemiluminescence response. However, when the intracellular and extracellular parts of the oxidative response were separated, we found that the predominant part of the response was of intracellular origin with the ABU2 bacteria as prey, whereas a large fraction of the response induced by the PN7 bacteria was extracellular. The general opinion is that production of reactive oxygen metabolites should be intraphagosomal to minimize the tissue-damaging effects of the metabolites and to optimize their bactericidal effects. However, since the surface-adherent bacteria (the PN7 cells) are killed in an aerobic but not an anaerobic milieu, whereas the ingested bacteria (the ABU2 cells) are killed in both aerobic and anaerobic milieu, we propose that extracellularly generated oxygen metabolites are of importance in killing E. coli strains that can resist neutrophil engulfment.

Aerobiosis↗
PubMed1987

Bacterial virulence versus host resistance in the urinary tracts of mice.

The relative contributions of host resistance and bacterial virulence were analyzed in a mouse model for ascending urinary tract infection. The congenic mouse strains C3H/HeJ and C3H/HeN were used in parallel. They differ in their reactivity to lipopolysaccharide (LPS) and susceptibility to experimental urinary tract infection. C3H/HeJ cells are susceptible to infection and are nonresponders to LPS (Lpsd Lpsd), whereas C3H/HeN cells respond to LPS and are resistant to infection (Lpsn Lpsn). The Escherichia coli pyelonephritis isolate GR-12, serotype O75K5, expressing adhesins specific for globoseries glycolipids (P fimbriae) and for mannosides (type-1 fimbriae), and its derivatives deficient in these factors were used, either singly or in combination, to establish experimental infections. In C3H/HeN mice, the relative persistence of E. coli was inversely proportional to its phagocytosis in vitro. Loss of the O75 and K5 antigens increased the tendency toward hydrophobic interaction, promoted phagocytosis, and reduced persistence in the kidneys. This was not the case in C3H/HeJ mice, in which O75- and K5- serotypes persisted in the same extent as did the parent strain. The total number of bacteria recovered from the kidneys of C3H/HeJ mice was about 1,000-fold higher than the number recovered from kidneys of C3H/HeN mice 24 h after infection. Previous studies have demonstrated a delayed influx of polymorphonuclear leukocytes into the urinary tracts of C3H/HeJ mice. The results are consistent with the hypothesis that phagocyte activation through LPS is a major defense mechanism against E. coli in the kidney, a property in which C3H/HeJ mice are deficient.

Animals↗
PubMed1986

The kinetics of peritoneal clearance of Escherichia coli and Bacteroides fragilis and participating defense mechanisms.

In a study using pigs, we delineated the dynamic character and the interplay of defense mechanisms that operate in the peritoneal cavity and their effectiveness against Escherichia coli and Bacteroides fragilis. The bacteria were extensively cleared during the first three hours. The concentration of both organisms in the peritoneal fluid decreased by up to 300,000-fold, and the final concentration was a function of the inoculum given. Clearance efficiency did not differ between a bolus dose and prolonged bacterial administration. Peritoneal absorption was a major eliminating mechanism during the first three hours but was limited to bacterial concentrations exceeding approximately 10(9) colony-forming units per milliliter of peritoneal fluid. Intraperitoneal elimination started immediately and continued for approximately six hours. Thereafter, residual bacteria were not eliminated, even though the defense capacity was intact. Prolonged bacterial administration, however, protracted the period for active bacterial destruction.

Animals↗
PubMed1986

Bacterial clearance and granulocyte response in experimental peritonitis.

Clearance kinetics of Escherichia coli and Bacteroides fragilis from the peritoneal cavity and functional properties of peritoneal and blood polymorphonuclear leukocytes (PMNL) were studied in pigs. The bacteria, approximately 10(10) colony forming units (CFU) of each species, were intraperitoneally injected. Blood and peritoneal exudate were sampled regularly during 24 hr for bacterial quantification and PMNL analysis. The peritoneal concentration of both species fell rapidly in the first 3 hr and then stabilized. Approximately 10(2) CFU/ml remained after 24 hr. Chemotaxis, phagocytosis, and metabolic activation of the peritoneal PMNL showed little change. In some pigs a second bacterial dose was injected 6 hr after the first dose and gave an identical clearance pattern. Exhaustion of the local defence capacity thus was excluded as cause of the impaired bacterial elimination.

Animals↗
PubMed1985

Studies on immunity against Escherichia coli K13 with monoclonal anti-K13 and anti-anti-K13.

The structural basis for the cross-reactivity between the Escherichia coli K13, K20 and K23 capsular polysaccharides is the----)-beta-ribofuranosyl-(1----7)-beta-2-keto-3-deoxyoctonate polymer. Monoclonal antibodies against E. coli K13 which require O-acetyl-2-keto-3-deoxyoctonate for binding were further investigated. Such antibodies, of both the IgG and the IgM isotype, opsonized E. coli K13 in vitro and protected against intraperitoneal infection in mice as well as ascending pyelonephritis in rats. A monoclonal IgG1 anti-idiotype, specific for the K13 polysaccharide combining site of a protective IgM idiotype, primed for protection against intraperitoneal infection with live E. coli K13 following K13 injections at four as well as 12 weeks of age, the K13 polysaccharide alone did not immunize and protect. The monoclonal anti-K13 idiotype only primed for protection at four weeks of age. These findings suggest a strong effect of a single idiotype on the outcome of a bacterial infection.

Animals↗
PubMed1985

Mannose-specific and hydrophobic interaction between Escherichia coli and polymorphonuclear leukocytes--influence of bacterial culture period.

The influence of culture period on mannose-specific and hydrophobic properties of the bacterial surface and on bacteria/polymorphonuclear leukocyte (PMNL) interaction was studied. Four E. coli strains, PN7 (01:K1), ABU2 (ON:K14), CU9 (06:K14) and CU13 (08:KN) and two Salmonella typhimurium strains 395 MR10 and 395 MS, well characterized according to physicochemical surface properties, presence of type 1 fimbriae and interaction with PMNL, were used in the study. The results show that with prolonged culture period, the liability to hydrophobic interaction increases, the agglutination-strength of mannose-specific maltobionamide liposomes increases, while the agglutination-titer with guinea-pig erythrocytes remains constant. Furthermore, the mannose-specific association with and metabolic activation of PMNL is augmented, while the ingestion is unchanged. In addition, our results demonstrate differences in sensitivity between the methods used to detect exposure of mannose-specific structures on the surface of bacteria, and that the culture condition is important for bacterial surface properties. It thus appears that the culture conditions have a great influence on the surface properties of E. coli bacteria and the interaction with phagocytic cells.

Escherichia coli↗
PubMed1985

Effect of monosaccharides and ethyleneglycol on the interaction between Escherichia coli bacteria and Octyl-Sepharose.

Combined effects of monosaccharides and reduced surface tension of the medium were studied in relation to the hydrophobic binding of Escherichia coli bacteria, with and without mannose-specific structures. Hydrophobic binding was analyzed by hydrophobic interaction chromatography on Octyl-Sepharose. The results showed that ethyleneglycol, as well as mannose, reduced the hydrophobic interaction of the bacteria with mannose-specific structures. This effect was potentiated by combining ethyleneglycol and mannose. No other monosaccharides tested (galactose and fucose) had any effect on the hydrophobic interaction of bacteria with mannose-specific structures. These results further strengthen the hypothesis that the mannose-specific interaction of Escherichia coli bacteria is, at least in part, mediated by hydrophobic forces.

Adhesiveness↗
PubMed1984

The effect of monoclonal antibodies against Escherichia coli type 1 pili and capsular polysaccharides on the interaction between bacteria and human granulocytes.

Monoclonal antibodies against Escherichia coli type 1 pili and the K13 capsular polysaccharide strongly influenced the interaction between human polymorphonuclear leucocytes (PMNL) and E. coli 06:K13:H1. Bacteria with type 1 pili, associated with the neutrophils, caused a metabolic activation but were not ingested. Addition of monoclonal antibodies to type 1 pili resulted in increased association, but also phagocytosis and metabolic activation of the granulocytes. Monoclonal antibodies against the K13 polysaccharide strongly stimulated phagocytosis, especially of the type 1 piliated bacteria, suggesting a synergistic effect between binding of type 1 pili and the Fc part of the capsular antibodies to the PMNL. Addition of D-mannose inhibited the opsonization of type 1 piliated E. coli 06:K13:H1 in the presence of both type 1 pilus antibodies and capsular antibodies. Monoclonal anti-idiotypic (anti-anti-capsular) antibodies reduced the association with the PMNL of the bacteria preopsonized with anti-capsular antibodies. The bacterial ingestion and the metabolic activation of the PMNL were also reduced, suggesting a role for anti-idiotypic antibodies in specific modulation of inflammation.

Antibodies, Anti-Idiotypic↗
PubMed1983

Effects of lateral suprasylvian visual cortex lesions on visual localization, discrimination, and attention in cats.

Experiments were carried out to begin to define the behavioral functions of the lateral suprasylvian (LS) visual area of the cat's cortex. Behavioral tasks were chosen for analysis on the basis of previous suggestions in the literature concerning possible functions of LS cortex and its afferent pathways. These tasks included the ability of cats to orient the head and eyes to a stimulus presented in particular locations in the visual field, the ability to learn successive reversals of a two-choice visual pattern discrimination, and the ability to maintain or shift attention between relevant or irrelevant visual form and brightness cues. Eight cats were trained on each of these tasks. Four of the cats then received bilateral lesions of LS cortex, including the AMLS and PMLS regions, and the remaining 4 cats were used to assess normal retention. The LS cortex lesions had no significant effect upon performance of any of the behaviors tested. Thus, this region of cortex appears to play no essential role in simple brightness, form, and pattern discrimination performance, visual reversal learning, maintaining and shifting visual attention, or orienting the head and eyes to stimuli in the visual field. These results are discussed in relation to previous lesion studies involving large regions of the cat's extrastriate cortex and studies in other species. Possible functions of LS cortex, based upon recent electrophysiological studies, are suggested.

Animals↗
PubMed1982

Interaction between human polymorphonuclear leukocytes and two different strains of type 1 fimbriae-bearing Escherichia coli.

Two type 1 fimbriae-bearing strains of Escherichia coli, ABU2 (ON:K14) and PN7 (O1:K1), with different underlying physicochemical surface properties were compared for their capacity to interact with human polymorphonuclear leukocytes. Both strains attached strongly to neutrophils in a mannose-sensitive manner. One of the strains, ABU2, with a surface exposing weak negative charge and liability to hydrophobic interaction, was efficiently ingested (65%) and caused a release of reactive oxidative metabolites (chemiluminescence) and lysosomal enzymes. The other strains, PN7, exposing a hydrophilic, negatively charged K antigen and hydrophilic uncharged smooth lipopolysaccharide, resisted phagocytosis (only 25% were ingested) but nevertheless caused a release of reactive oxidative metabolites and lysosomal enzymes to a greater extent than did phagocytosed strain ABU2. These results show that attachment mediated by type 1 fimbriae does not ultimately lead to ingestion. Whether the attached bacteria are being ingested or not depends on their underlying physicochemical surface properties. Furthermore, if the bacteria remain extracellularly attached, they may potentiate the inflammatory process.

Adhesiveness↗
PubMed1982

Absorption of topically applied hydrocortisone from the eye of the rhesus monkey.

Blood samples were collected from anaesthetized monkeys during one h a) after topical application of an eyedrop of hydrocortisone acetate suspension, b) after topical application of a drop of the vehicle alone, and c) after no application at all. Radioimmunoassay (RIA) showed a rapid and similar increase of hydrocortisone plasma levels in all 3 kinds of experiments. RIA revealed that in monkeys the anaesthetic procedure alone was sufficient to cause a considerable increase of endogenous hydrocortisone levels overshadowing any systemic absorption of topical hydrocortisone. Using tritiated hydrocortisone instead a rapid increase of systemic absorption after topical application was found. A plasma concentration of 1% of the dose was found one min after topical instillation increasing to a maximum of 6-7% at 30 min. The half time of the show phase of elimination was about 19 h.

Absorption↗
PubMed1982

Rapid regression of pituitary tumours during bromocriptine treatment of women with hyperprolactinaemia.

Four hyperprolactinaemic women with large pituitary adenomas with suprasellar extension were given primary tumour therapy with bromocriptine. The treatment resulted in rapid tumour regression in all the women, as verified by repeated computerized tomography (CT) scans. Pronounced visual field defects were present in three of the four women before treatment. All of them had marked improvement of vision within a few days after the initiation of bromocriptine therapy and they regained normal or nearly normal visual fields during the treatment. The raised serum prolactin concentrations decreased to normal levels in all the women. Thus, medical treatment with bromocriptine can induce rapid tumour regression in patients with hyperprolactinaemia and large pituitary tumours.

Adenoma↗
PubMed1982

Five cases of Campylobacter jejuni/coli bacteremia.

During a 3-year period (1977-1979) 5 cases of Campylobacter jejuni/coli (CJC) bacteremia were observed in the south of Sweden. Four of the 5 patients had diarrhoea and 3 of 4 patients tested showed a serological response to a homologous strain. This accumulation of bacteremia cases may be explained from the short duration between the onset of high fever (less than 38.5 degrees C) and obtaining blood cultures, and the use of blind subcultures in the laboratory procedures.

Aged↗
PubMed1981

Physicochemical surface properties of Escherichia coli strains isolated from different types of urinary tract infections.

Escherichia coli strains isolated from three groups of patients with urinary tract infections, such as acute pyelonephritis, acute cystitis, and asymptomatic bacteriuria, were analyzed with respect to their physicochemical surface properties by means of polymer two-phase partitioning in dextran-polyethylene glycol systems and hydrophobic interaction chromatography on Octyl-Sepharose. Strains causing acute pyelonephritis constituted a homogenous group which, depending on the growth conditions, demonstrated smooth-type lipopolysaccharide, elevated negative charge, and liability to hydrophobic interaction, whereas strains isolated from acute cystitis and asymptomatic bacteriuria showed a more heterogenous pattern.

Adolescent↗
PubMed1980

17 beta-estradiol levels in blood and cerebrospinal fluid after ocular and nasal administration in women and female rhesus monkeys (Macaca mulatta).

17 beta-estradiol was applied ocularly to menstruating and postmenopausal women. The absorption by blood was measured. A rapid increase of both estradiol and estrone was seen with higher plasma levels in the menstruating group, possibly due to a better conjunctival circulation. Twenty-one rhesus monkeys were given estradiol suspension or solution ocularly or nasally. The absorption by blood and cerebrospinal fluid was measured and compared to intravenous injection of 0.5 mg estradiol. Estradiol increased in plasma after 1'. Maxima were reached at 15'. Estradiol solution gave higher plasma levels than estradiol suspension. At 5' they amounted to the levels found after i.v. injection. The estradiol levels in cerebrospinal fluid never exceeded the corresponding plasma levels and were generally low. The increase in cerebrospinal fluid was thought to be secondary to the raised plasma levels.

Administration, Intranasal↗