PubMed Health⌕ Search

Biomedical subjects

D Berglund

Publications and source records attributed to D Berglund.

7 recordsLinked to original sources
PubMed2005

Calcium-induced virulence factors associated with the extracellular matrix of mucoid Pseudomonas aeruginosa biofilms.

Pseudomonas aeruginosa colonizes the pulmonary tissue of patients with cystic fibrosis (CF), leading to biofilm-associated infections. The pulmonary fluid of CF patients usually contains elevated concentrations of cations and may contain the P. aeruginosa redox-active pigment pyocyanin, which is known to disrupt calcium homeostasis of host cells. Since divalent cations are important bridging ions for bacterial polysaccharides and since they may play regulatory roles in bacterial gene expression, we investigated the effect of calcium ions on the extracellular matrix constituents of P. aeruginosa biofilms. For mucoid strain P. aeruginosa FRD1, calcium addition (1.0 and 10 mM as CaCl(2)) resulted in biofilms that were at least 10-fold thicker than biofilms without added calcium. Scanning confocal laser microscopy showed increased spacing between cells for the thick biofilms, and Fourier transform infrared spectroscopy revealed that the material between cells is primarily alginate. An algD transcriptional reporter demonstrated that calcium addition caused an eightfold increase in alg gene expression in FRD1 biofilms. Calcium addition also resulted in increased amounts of three extracellular proteases (AprA, LasB, and PrpL). Immunoblots of the biofilm extracellular material established that AprA was harbored within the biofilm extracellular matrix. An aprA deletion mutation and a mutation in gene for a putative P. aeruginosa calmodulin-like protein did not significantly affect calcium-induced biofilm structure. Two-dimensional gel electrophoresis showed increased amounts of phenazine biosynthetic proteins in FRD1 biofilms and in calcium-amended planktonic cultures. Spectrochemical analyses showed that the calcium addition causes a three- to fivefold increase in pyocyanin production. These results demonstrate that calcium addition affects the structure and extracellular matrix composition of mucoid P. aeruginosa biofilms, through increased expression and stability of bacterial extracellular products. The calcium-induced extracellular matrix of mucoid P. aeruginosa consists primarily of the virulence factor alginate and also harbors extracellular proteases and perhaps pyocyanin, a biomolecule that may further disrupt cellular calcium levels.

Alginates↗
PubMed2001

Cell-cell and cell-surface interactions in an illuminated biofilm: implications for marine sediment stabilization.

Most wetted surfaces that are illuminated support a population of phototrophs. The marine sediment is no exception and there the major component of the microphytobenthic population is diatoms. These organisms are credited with stabilizing the sediment against physical disturbance by virtue of the extracellular carbohydrate polymers that they elaborate. However, diatoms synthesize and secrete several carbohydrate polymers and it is not certain which of them is involved in the stabilization process. In order to investigate this, we have constructed small glass bead-filled flow through bioreactors to mimic marine sediments. The flow rate through the bioreactors was found to reflect the physical stability of the bead bed. Thus flow rate was measured as a function of diatom growth and the production of three operationally-defined polymers, i.e., those soluble in the medium, those soluble in 0.5 M NaHCO3 at 90 degrees C and those not soluble in either solvent (matrix polymer). Growth of the diatoms did not change the hydraulic conductivity of the bioreactors. For Amphora coffeaeformis, neither did the production of medium-soluble nor NaHCO3-soluble polymers. However, matrix polymer accumulation was directly correlated with a reduction in flow (regression coefficient R2 = 0.96) and stabilization against physical disturbance. Results with species of Navicula were not as clear. Both NaHCO3-soluble and matrix polymers were involved in producing the flow reduction. In the same manner we also measured the effect of Pseudoalteromonas haloplanktis growth on bead bed hydraulic conductivity and bead bed stability. Growing alone, no effect was found, but in co-culture with a single diatom species, the bacteria reduced the diatom effect on flow through the bioreactors seen earlier, however did not reduce the extent of their growth. Confocal scanning laser microscopy of beads colonized with diatoms alone, or diatoms in co-culture with bacteria, revealed that P. haloplanktis was able to inhibit diatom adhesion to the beads. When the bacteria were present there was less matrix polymer evident. We speculate that this interference with diatom metabolic activity was either the result of less matrix polymer synthesis, or its hydrolysis by the bacteria. The results are applicable to mixed species biofilms of this type on surfaces other than sediments.

Journal Article↗
PubMed1988

Triticone A: a novel bioactive lactam with potential as a molecular probe.

Triticone A is one member of a family of novel compounds which are spirocyclic lactams produced by several plant pathogenic fungi including Drechslera tritici repentis on wheat. It undergoes racemization to form triticone B and when tested, the enantiomeric mixture causes chlorosis and necrosis on a wide range of plants. Fluorescein diacetate treated protoplasts in conjunction with various triticone treatments allowed for accurate quantitation of the biological activity of the toxin. Various physiological functions of the wheat cell are impaired including the Hill and CO2 fixation reactions in photosynthesis. In addition, triticone A inhibits enzymes that have SH functional groups as part of their active site, eg., the protease-ficin. Neither triticone C or D had any activity in the enzyme or protoplast assays. It is apparent that triticone A has some potential as a molecular probe in a variety of biological systems.

Biological Assay↗
PubMedDate not supplied

New challenges, new answers: pediatric nurse practitioners and the care of adolescents.

INTRODUCTION: Since the 1950s, patterns of morbidity and mortality among adolescents have shifted to social and environmental causes. This study examines pediatric nurse practitioners' (PNPs') self-assessed competencies in addressing the common health concerns of adolescents. METHOD: The analysis used a sample of 257 PNPs drawn from a larger national data set of 637 nurses randomly sampled from 3 nursing organizations. Factors associated with self-perceived knowledge or skill and interest in training for 28 common health concerns of adolescents were analyzed using Chi square, t test, and Pearson's correlation. Barriers and attractions to working with adolescents were also investigated. RESULTS: The greatest deficits in self-perceived knowledge or skill, as well as low interest in training and low perceived relevance to practice, were around issues of gangs, gay/lesbian/bisexual/transgender youth, HIV/AIDS, and counseling about a positive pregnancy test. Also, PNPs identified the lack of resources appropriate for adolescent referrals as the greatest barrier to working with this population. DISCUSSION: PNPs assessed their lowest competencies in some of the areas that present the greatest threats to adolescents' health and well-being. These deficits suggest needed curricular shifts in entry-level and advanced-level preparation of PNPs, as well as new priorities for continuing education.

Adolescent↗