Organization of fimbriate cells in colonies of Escherichia coli strain 3040

Immunofluorescence staining with fimbria-specific antibodies was used to study the organization of fimbriate cells in colonies of Escherichia coli strain 3040. The strain has both type-1 and S fimbriae and shows fast phase variation between the fimbrial types. Colonies stained in sectors whose length and number per colony were dependent on the fimbrial phase of progeny cells. It is proposed that such sectors result from fimbrial phase variation.     

Complementation and regulatory interaction between two cloned fimbrial gene clusters of Escherichia coli strain KS71

Summary Complementation experiments with cloned DNA fragments encoding either the KS71A, the KS71B or the KS71C fimbriae of the pyelonephritogenic Escherichia coli strain KS71 were used to localise the P-fimbrillin genes and to demonstrate regulatory interactions between the cloned genes. The structural genes of the KS71A and KS71B fimbriae were located within a common 1.1 kilobase pair ClaI-SmaI fragment, and it was shown that the gene clusters for these fimbriae could complement each other in trans. The gene cluster encoding the KS71C fimbriae did not complement for the other KS71 fimbriae. A DNA fragment, located near the KS71A fimbrillin gene, was found to enhance the production of the KS71B fimbriae in trans.     

Relationship between serum lipids, lipoproteins and pseudocholinesterase during organophosphate poisoning in rabbits

The activities of serum pseudocholinesterase, lecithin: cholesterol acyltransferase (LCAT) and gamma-glutamyltransferase in rabbits were investigated before and after dichlorvos administration in vivo. The effects of this organophosphate on some serum lipids and lipoprotein fractions were also determined. LCAT activity remained almost unaffected after organophosphate administration. However, serum gamma-glutamyltransferase and pseudocholinesterase activities markedly decreased. Dichlorvos markedly lowered both serum low density lipoprotein (LDL) and cholesterol contents, whereas high density lipoprotein (HDL) concentration increased and very low density lipoprotein (VLDL) remained unaffected. Triglycerides as well as esterified fatty acids increased significantly but the statistical changes in free fatty acid concentrations were not significant, because individual variations in fatty acid concentrations were high.     

Cytological evidence for somatic diploidization in dikaryotic cells ofArmillariella mellea

Dikaryotic hyphae isolated from basidiocarps ofArmillariella mellea are unstable in aseptic culture and change into monokaryotic hypae. During monokaryotization the nuclei of a dikaryon fuse and fusion nucleus immediately divides resulting in two uninucleate cells, from which the monokaryotic mycelium originates. Similar fusion of two nuclei takes place in matings of compatible singlespore isolates. It is concluded that the resulting monokaryotic mycelium is diploid.     

Thermoregulation during rest and exercise in the cold in pre- and early pubescent boys and in young men.

Eight minimally dressed pre- and early pubescent boys (age 11-12 yr) and 11 young adult men (age 19-34 yr) rested for 20 min and exercised on a cycle ergometer for 40 min at approximately 30% of their maximum oxygen consumption (VO2max) at 5 degrees C. To quantify the added increase in metabolic rate because of cold, a separate test was carried out at 21 degrees C at rest and at equal work rates as in the cold. Both groups were similar in subcutaneous fat thickness and VO2max per kilogram body weight. Rectal temperature increased slightly during the exposure to the cold, but no significant difference was observed between the boys and men. In the cold, the boys had lower skin temperatures than the adults in their extremities but not in the trunk. The boys increased their metabolic rates in the cold more than did the men. As a result, the boys maintained their core temperature as effectively as the adults. Similar age-related differences in thermoregulatory responses to cold were observed when two boys and two men with equal body sizes were compared. Our results suggest that there may be maturation-related differences in thermoregulation in the cold between children and adults.     

Comparison of some enrichment broths and growth media for the isolation of thermophilic campylobacters from surface water samples

Three different enrichment broths and two selective growth media were compared for isolating thermophilic campylobacters by combined membrane filtration and enrichment techniques from surface waters of different physical, chemical and bacteriological characteristics. Fifty-two strains of campylobacters were isolated from total of 1668 cultures. The various broth/medium combinations did not affect the dominance of C. jejuni over C. coli (total 49 C. jejuni and three C. coli). The most efficient combinations of enrichment broth and growth media were either Oosterom broth/blood-free charcoal-cefoperazone-deoxycholate agar (CCDA) medium or blood-free charcoal-cefoperazone-deoxycholate (CCD) broth/CCDA medium. Modified Preston broth (sheep blood instead of horse blood) with either of the growth media gave significantly lower yields although it suppressed efficiently the growth of contaminants. Skirrow medium had lower selectivity than CCDA medium and gave slightly lower isolation rate. Enrichment time (24 or 48 h) did not affect the isolation frequency of campylobacters but longer enrichment time increased the growth of contaminants. Prefiltration through membranes of pore sizes 5.0 and 1.2 microns decreased the growth of contaminants. However, these membranes retain campylobacters and must be cultured to avoid underestimation. From more polluted waters campylobacters were isolated most frequently with CCD broth and CCDA medium.     

Type V collagen as the target for type-3 fimbriae, enterobacterial adherence organelles

Tissue-binding specificity of the type-3 fimbriae of pathogenic enteric bacteria was determined using frozen sections of human kidney. A wild-type Klebsiella sp. strain and the recombinant strain Escherichia coli HB101(pFK12), both expressing type-3 fimbriae, as well as the purified type-3 fimbriae effectively bound to sites at or adjacent to tubular basement membranes, Bowman's capsule, arterial walls, and the interstitial connective tissue. Bacterial adherence to kidney was decreased after collagenase treatment of the tissue sections. Recombinant strains expressing type-3 fimbriae specifically adhered to type V collagen immobilized on glass slides, whereas other collagens, fibronectin or laminin did not support bacterial adherence. In accordance with these findings, specific binding of purified type-3 fimbriae to immobilized type V collagen was demonstrated. Specific adhesion to type V collagen was also seen with the recombinant strain HB101(pFK52/pDC17), which expresses the mrkD gene of the type-3 fimbrial gene cluster in association with the pap-encoded fimbrial filament of E. coli, showing that the observed binding was mediated by the minor lectin (MrkD) protein of the type-3 fimbrial filament. The interaction is highly dependent on the conformation of type V collagen molecules since type V collagen in solution did not react with the fimbriae. Specific binding to type V collagen was also exhibited by type-3 fimbriate strains of Yersinia and Salmonella, showing that the ability to use type V collagen as tissue target is widespread among enteric bacteria.     

A computational algorithm to simulate disorganization of collagen network in injured articular cartilage

Cartilage defects are a known risk factor for osteoarthritis. Estimation of structural changes in these defects could help us to identify high risk defects and thus to identify patients that are susceptible for the onset and progression of osteoarthritis. Here, we present an algorithm combined with computational modeling to simulate the disorganization of collagen fibril network in injured cartilage. Several potential triggers for collagen disorganization were tested in the algorithm following the assumption that disorganization is dependent on the mechanical stimulus of the tissue. We found that tensile tissue stimulus alone was unable to preserve collagen architecture in intact cartilage as collagen network reoriented throughout the cartilage thickness. However, when collagen reorientation was based on both tensile tissue stimulus and tensile collagen fibril strains or stresses, the collagen network architecture was preserved in intact cartilage. Using the same approach, substantial collagen reorientation was predicted locally near the cartilage defect and particularly at the cartilage–bone interface. The developed algorithm was able to predict similar structural findings reported in the literature that are associated with experimentally observed remodeling in articular cartilage. The proposed algorithm, if further validated, could help to predict structural changes in articular cartilage following post-traumatic injury potentially advancing to impaired cartilage function.