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Biomedical subjects

L Engstrand

Publications and source records attributed to L Engstrand.

At least 55 records · Page 3Linked to original sources
PubMed1999

pH-dependent binding of Helicobacter pylori to pig gastric mucins.

A microtiter-based assay was developed to study the binding of Helicobacter pylori to pig gastric mucins purified by density-gradient centrifugation in CsCl/4 M guanidinium chloride. Binding of H. pylori was observed over the 'mucin' band as well as with 'low-density' components in the gradients, and binding to the latter was more pronounced when incubations were performed at 37 degrees C as compared to 20 degrees C. At a lower pH, binding of H. pylori (strain SVA 40) to the 'high-density' mucins from pig antrum was increased but binding to the 'low-density' ones was decreased. Binding of the P466 strain (Le(b)-specific) was mainly associated with the 'mucin' band, whereas the MO19 strain reacted preferentially with the 'low-density' components. In summary, H. pylori may bind to gastric mucins and the binding is influenced by temperature, pH and the repertoire of bacterial adhesins.

Adult↗
PubMed1999

The morphological transition of Helicobacter pylori cells from spiral to coccoid is preceded by a substantial modification of the cell wall.

The peptidoglycan (murein) of Helicobacter pylori has been investigated by high-performance liquid chromatography and mass spectrometric techniques. Murein from H. pylori corresponded to the A1gamma chemotype, but the muropeptide elution patterns were substantially different from the one for Escherichia coli in that the former produced high proportions of muropeptides with a pentapeptide side chain (about 60 mol%), with Gly residues as the C-terminal amino acid (5 to 10 mol%), and with (1-->6)anhydro-N-acetylmuramic acid (13 to 18 mol%). H. pylori murein also lacks murein-bound lipoprotein, trimeric muropeptides, and (L-D) cross-linked muropeptides. Cessation of growth and transition to coccoid shape triggered an increase in N-acetylglucosaminyl-N-acetylmuramyl-L-Ala-D-Glu (approximately 20 mol%), apparently at the expense of monomeric muropeptides with tri- and tetrapeptide side chains. Muropeptides with (1-->6)anhydro-muramic acid and with Gly were also more abundant in resting cells.

Cell Wall↗
PubMed1999

Evaluation of human seroreactivity to Bartonella species in Sweden.

Among the species that compose the expanding genus Bartonella, thus far only B. henselae and B. quintana have reportedly been isolated from humans in Europe. To evaluate the prevalence of Bartonella infection in Sweden, we conducted a retrospective serological examination of 126 human serum samples. These samples were analyzed for antibodies to B. henselae, B. quintana, and B. elizabethae. Serum samples from 100 blood donors, who spanned the ages of 20 to 60 and had no apparent clinical signs of illness, were also studied as a control group. An immunoglobulin G indirect fluorescence antibody assay revealed 4 and 8.3% Bartonella positivity rates for the blood donor and patient group, respectively, when a cutoff titer of >/=64 was chosen. Among the blood donors, four were seropositive to B. elizabethae; one of these also had concordant positive titer to B. henselae. In the patient group, 14 serum samples were positive against Bartonella spp. These serum specimens represented nine patients. In three of these seropositive patients, paired serum samples displayed a fourfold increase in antibody titer to at least one of the three antigens. These three patients are discussed. In this report we also present a case study of a 60-year-old Swedish male with fatal myocarditis. Postmortem serological analysis revealed a high titer against B. elizabethae. PCR and nucleotide sequencing of the myocardial tissue from this patient, and of liver tissue from one of the other three patients, showed sequences similar to B. quintana. The age, geographical origin, animal contacts, and serological response pattern to the different Bartonella antigens differed among the four patients. This study substantiates the presence of Bartonella spp. in Sweden, documents the seroreactivity to three Bartonella antigens in Swedish patients, and reports the first two cases of B. quintana-like infections in Sweden.

Adolescent↗
PubMed1999

Adherent surface mucus gel restricts diffusion of macromolecules in rat duodenum in vivo.

The aim of this study was to investigate the permeability of the adherent mucus gel layer in rat duodenum in vivo to macromolecules applied in the lumen. Rats were anesthetized with thiobarbiturate, and the duodenum was perfused with isotonic NaCl solution containing large-molecular-size secretagogues. Effects on mucosal HCO(-)(3) secretion and blood-to-lumen (51)chromium-labeled EDTA clearance were used as indexes that compounds had migrated across the mucus layer. Exposure to a low concentration of papain (10 U/100 ml) for 30 min removed the mucus layer without damage to the epithelium and induced or markedly enhanced HCO(-)(3) secretory responses to cholera toxin (molecular mass of 85 kDa) or glucagon (3.5 kDa). Water extracts from a VacA cytotoxin (89 kDa) producing Helicobacter pylori strain, but not from a toxin-negative isogenic mutant, caused a small increase in HCO(-)(3) secretion but only after the mucus layer had been removed by papain. The duodenal surface mucus gel thus significantly restricts migration of macromolecules to the duodenal surface. Release of bacterial toxins at the cell-mucus interface may enhance or be a prerequisite for their effects on the gastrointestinal mucosa.

Animals↗
PubMed1998

Co-twin study of the effect of environment and dietary elements on acquisition of Helicobacter pylori infection.

The rate of Helicobacter pylori infection is inversely related to socioeconomic status, and childhood is thought to be the major acquisition period. The authors investigated the importance of childhood environment in the acquisition of H. pylori infection. A cross-sectional study was conducted of monozygotic and dizygotic twins who were reared apart or reared together. Three hundred twins from a subregistry of the Swedish Twin Registry were studied. H. pylori status was evaluated by using an enzyme-linked immunosorbent assay for anti-H. pylori immunoglobulin G. Socioeconomic status during childhood was assessed on the basis of the density of the living conditions and the economic situation of the family that reared the twins. Current socioeconomic status was estimated by using a scale that combined income and education. Dietary elements that were studied included fat and fiber intake and ascorbic acid consumption. The density of the childhood home was consistently found to be significantly associated with the acquisition of H. pylori infection (p = 0.04). Among monozygotic twins reared apart and discordant for H. pylori status, affected twins were raised in homes under poorer socioeconomic conditions than those of their unaffected co-twins (p = 0.02). Additionally, infected twins consumed more ascorbic acid than their unaffected co-twins (p = 0.04). The finding of an effect of socioeconomic status during childhood on the acquisition of H. pylori among monozygotic twins who were reared apart and had an identical genetic makeup but not a common environment confirms the hypothesis that childhood acquisition of H. pylori infection is linked to hygiene practices.

Adult↗
PubMed1998

Helicobacter pylori adhesin binding fucosylated histo-blood group antigens revealed by retagging.

The bacterium Helicobacter pylori is the causative agent for peptic ulcer disease. Bacterial adherence to the human gastric epithelial lining is mediated by the fucosylated Lewis b (Leb) histo-blood group antigen. The Leb-binding adhesin, BabA, was purified by receptor activity-directed affinity tagging. The bacterial Leb-binding phenotype was associated with the presence of the cag pathogenicity island among clinical isolates of H. pylori. A vaccine strategy based on the BabA adhesin might serve as a means to target the virulent type I strains of H. pylori.

Adhesins, Bacterial↗
PubMed1998

Biological strategies expressed by different Streptococcus pyogenes strains: an explanation of the epidemiology.

The numerous reports in the last ten years on the serious diseases caused by Streptococcus pyogenes indicate the continued significance of this pathogen. Furthermore, clinical studies and modern techniques have yielded new information on S. pyogenes and its pathogenic mechanisms. Although much still remains to be discovered about the biology of S. pyogenes, two different strategies--the 'epidemic' and the 'endemic' strategy--can be seen in the interaction of different S. pyogenes strains with the human host. The challenges posed by these two groups of bacteria are also outlined.

Disease Outbreaks↗
PubMed1998

Presence of Helicobacter species DNA in Swedish water.

Municipal water, treated waste-water and well-water from all 25 counties in Sweden were analysed for the presence of Helicobacter spp. DNA. Bacteria were concentration by immunomagnetic separation. Culture, Gram staining and urease tests were performed before lysis of bacteria. Two polymerase chain reaction (PCR) assay with high sensitivity (adhesin and 16S rRNA) were followed by Helicobacter spp. specific hybridization. Nine of 24 private wells, three of 25 municipal tapwater and three of 25 wastewater samples were positive for both PCR assays. Positive municipal and waste-water samples were positive for counties. Non-specificity of PCR methods due to the presence of unknown bacteria within the genus helicobacter cannot be totally ruled out. Thus, the clinical significance of findings Helicobater spp. DNA in drinking water needs to be further evaluated.

DNA, Bacterial↗
PubMed1998

Extracts of Helicobacter pylori reduce gastric mucosal blood flow through a VacA- and CagA-independent pathway in rats.

BACKGROUND: Helicobacter pylori may interfere with gastroduodenal protective mechanisms. Such effects could be due to a direct interaction with gastric epithelial cells but also to the action of a wide range of secreted and membrane-bound virulence factors. Our aim was to study the acute effects of water extracts produced from H. pylori on gastric mucosal blood flow and acid secretion and to relate them to VacA and CagA activity. METHOD: Extracts were produced from strains 88-23 and A5, both wild type; A5VacA, an isogenic mutant lacking expression of the vacuolating cytotoxin (VacA) and the immunodominant antigen (CagA); and Escherichia coli strain ATCC-25922. Bacterial extracts were applied on the exteriorized gastric corporal mucosa in inactin-anaesthetized rats after removal of as much as possible of the mucus layer, during intravital microscopy. Blood flow was measured by means of laser-Doppler flowmetry. RESULTS: All H. pylori extracts, including the extract from 88-23 heated to 100 degrees C for 30 min, significantly reduced blood flow by 15%-19%, whereas E. coli had no significant effect on blood flow. CONCLUSION: A factor or a combination of factors, other than VacA and CagA released from H. pylori, might compromise the natural defence of the gastric corporal mucosa by reducing mucosal blood flow. The factor is heat-stable and lacking or less potent in E. coli.

Animals↗
PubMed1998

Virulence and colonization-associated properties of Helicobacter pylori isolated from children and adolescents.

Helicobacter pylori isolates from 32 children and adolescents were characterized with respect to putative virulence and colonization-associated properties. Only 3 of the subjects had duodenal ulcer. All but 2 of the remaining 29 had various degrees of chronic gastric inflammation. No significant correlation between degree of inflammation and presence of the cag-pathogenicity island, cytotoxin production, vacA alleles associated with cytotoxin expression, and binding ability to the Lewis(b) (Le[b]) oligosaccharide was found. Only 4 isolates expressed the Le(b)-specific adhesin, of which 3 were also cag region-positive. This is in contrast to adults with gastritis or peptic ulcer disease (or both), in whom most of the H. pylori isolates bind Le(b). In an in situ binding assay H. pylori were less able to adhere to gastric surface mucous cells in biopsies taken from children compared with adults, suggesting a lower expression of the Le(b) oligosaccharide in the children.

Adolescent↗
PubMed1998

Cancer-associated strains of Helicobacter pylori stimulate DNA synthesis in IEC-6 cells.

OBJECTIVE: To determine whether water extracts of Helicobacter pylori strains, which express CagA, can influence DNA synthesis in untransformed intestinal epithelial cells in vitro. DESIGN: We used water extracts produced from H. pylori strains (A, B, C), collected from gastric mucosa of gastric cancer patients. Strain A was CagA+/VacA+ whereas strains B and C were CagA+/VacA-. Water extracts from Helicobacter mustelae and Escherichia coli were used as controls. METHODS: IEC-6 cells (small intestinal epithelial cell line from germ-free rats) were incubated with various concentrations of the bacterial extracts for 24 h. The cells were labelled with [3H]methylthymidine for 4 h and thereafter processed for autoradiography. DNA synthesis was evaluated by the labelling index (LI%). RESULTS: Water extracts from CagA-positive strains of H. pylori, with or without the capacity to produce vacuolating toxins, increased the LI in a dose-related manner (P < 0.05). The water extracts of E. coli significantly increased the LI (P < 0.001), whereas the water extracts of H. mustelae did not affect DNA synthesis. CONCLUSIONS: Cancer-associated, CagA-positive strains of H. pylori stimulate DNA synthesis in epithelial cells in vitro, independently of their ability to produce VacA toxin. Our findings suggest that unknown mitogenic components of H. pylori may contribute to the increased cell proliferation observed in the histological stages preceding gastric cancer.

Animals↗
PubMed1998

Rapid PCR detection of Helicobacter pylori-associated virulence and resistance genes directly from gastric biopsy material.

We have developed a PCR-based method to detect macrolide resistance and the virulence gene cagA in Helicobacter pylori within 24 h, thereby improving the lengthy process of culture-based approaches. Total DNA was prepared directly from stomach biopsy specimens. The procedure proved to be rapid and reliable and could be utilized for diagnostic purposes.

Antigens, Bacterial↗
PubMed1998

Helicobacter pylori stimulates DNA synthesis in a small intestinal cell line in vitro.

BACKGROUND: Helicobacter pylori, which causes gastritis and peptic ulcer, seems to be an important factor in the pathogenesis of gastric cancer and MALT lymphoma. Thus our aim was to examine whether H. pylori influences DNA synthesis in epithelial cells in vitro. METHODS: Sonicated and water extracts of H. pylori (cytotoxic strains NCTC 11637, 88-23 and A5, and a noncytotoxic isogenic mutant of A5, A5 vac A) were diluted to a final concentration of 1/1,000, 1/100, 1/50 and 1/10. Water extracts of Escherichia coli were used as reference. IEC-6 cells were incubated during 24 h with fragments of H. pylori or extracts of the concentrations described above. The cells were labeled with 3H-methylthymidine for 4 h and processed for autoradiography. DNA synthesis was evaluated by the labeling index (LI). RESULTS: The LI% of controls was 15.6 +/- 5.1%. All the water extracts and sonicated strains of H. pylori increased the LI% in a dose-dependent manner (p < 0.001). The highest concentrations of the sonicated strains tended to reduce the LI%, although these values were still higher than those of the control group. The water extracts of E. coli increased the LI% in a dose-dependent manner (p < 0.0001). CONCLUSION: H. pylori stimulates DNA synthesis in epithelial cells in vitro, but no association was found with the presence of cytotoxin production. Our results suggest that hitherto unknown components of H. pylori may contribute to the increase in cell proliferation observed in gastritis and to the development of MALT lymphoma and gastric cancer.

Animals↗
PubMed1997

Urinary nitrite: more than a marker of infection.

OBJECTIVES: The bacteriostatic gas nitric oxide (NO) is formed when nitrite is acidified. Infected urine may contain considerable amounts of nitrite as a result of bacterial nitrate reductase activity, and detection of nitrite in urine is routinely used in the diagnosis of bacterial cystitis. We sought to determine whether NO was generated from acidified nitrite-containing urine. Furthermore, we also studied the growth of the urinary pathogen Escherichia coll in acidified nitrite-containing urine. METHODS: Urine, collected from healthy control subjects or from patients with infected nitrite-containing urine, was acidified and incubated in a closed syringe with varying amounts of nitrite added. After 30 minutes, the headspace gas was removed and immediately injected into a chemiluminescence NO analyzer. In addition, NO was measured in urine collected from healthy control subjects after ingestion of vitamin C. Bacterial growth was measured continuously in control urine for 10 hours after incubation for 2 hours in acidic urine with varying concentrations of nitrite added. RESULTS: Large amounts of NO were released from infected nitrite-containing urine after mild acidification. NO was also released from acidified control urine if nitrite was added, and this release was greatly potentiated in the presence of vitamin C. Furthermore, the growth of E. coli was markedly reduced by the addition of nitrite to acidified urine. CONCLUSIONS: We propose that nitrite-producing bacteria induce their own death in acidic urine by supplying substrate for generation of bacteriostatic compounds such as NO. This mechanism might explain why urinary acidification and vitamin C may be effective in the treatment of bacteriuria.

Escherichia coli↗
PubMed1997

Is the sanctuary where Helicobacter pylori avoids antibacterial treatment intracellular?

The sanctuary site where Helicobacter pylori evades antimicrobial therapy is unknown, but considerable data exist about an intracellular location for H pylori. Ten H pylori-infected volunteers received standard triple antimicrobial therapy for 2 weeks. Gastric mucosal biopsy specimens were obtained with jumbo forceps on therapy days 0, 3, 14, and 42. Hematoxylin-eosin staining was used for classification of gastritis and the Genta stain for the visualization of H pylori. Immunohistochemical staining was used to detect HLA-DR antigens, human heat shock protein (HSP60), and the bacterial HSP60 antigen. Bacterial HSP60 was expressed on the mucosal surface and within epithelial cells. No such expression of human HSP60 was found, which supports a bacterial origin for the intracellular HSP60. Coexpression of bacterial HSP60 and HLA-DR was always observed, indicating an ongoing local immune response. Infection was cleared on day 14, but when examined 4 weeks after completion of therapy, Genta staining indicated that only five volunteers remained free of H pylori. However, results of immunohistochemical staining were negative at this time for only two volunteers. Disappearance of intracellular expression of bacterial HSP60 remained after therapy and correlated with the intensity of chronic inflammatory cell infiltration. These data are consistent with the intracellular localization of H pylori having a role in inflammation and as a protective strategy against extracellular antibacterial activity.

Adult↗