Structure and packing of microfibrils in collagen

X-ray diffraction, patterns suggest that the five-stranded microfibrils in the collagen of rat tail tendon are supercoiled and packed together on a square lattice with a statistical distribution of axial displacements between nearest neighbours.     

Incidence of the aerobactin iron uptake system among Escherichia coli isolates from infections of farm animals

To assess the importance of aerobactin-mediated iron uptake as a bacterial virulence determinant in animal infections, a total of 576 strains of Escherichia coli isolated from cattle, chickens, sheep and pigs were screened by colony hybridization to determine the presence of the aerobactin genetic determinants, and by a bioassay to detect aerobactin secretion in iron-limited conditions. Results obtained by the two complementary methods correlated well. The incidence of the aerobactin system was very high among septicaemia isolates, particularly those from cattle and chickens, an observation that strongly suggests an important role for this mechanism of iron assimilation in pathogenesis. On the other hand, the incidence of the aerobactin system among mastitis strains was not significantly higher than among faecal isolates from healthy animals. No classical enterotoxigenic E. coli strains tested carried the aerobactin genetic determinants. Although most strains that produced aerobactin were also able to make colicin V, the fact that the two characteristics existed separately in a significant minority of isolates suggested that colicin testing alone could not be reliably used to determine the presence of the aerobactin system.     

Metacestode-induced depression of the production of, and response to, sex pheromone in the intermediate host Tenebrio molitor

Hymenolepis diminuta infection of Tenebrio molitor is associated with an impairment of vitellogenesis and a reduction in host fecundity. In this communication the effect of infection upon an additional aspect of host reproduction, the initiation of mating behavior, has been examined. Copulatory release pheromone, extracted from control virgin females 6-7 days old, was shown to stimulate a positive mating response in 88% of 5- to 6-day-old control males; however, only a 56% response was elicited by pheromone from infected females. In addition, parasitization adversely effected male response to pheromone from control females. A significant (P less than 0.001) depression of copulatory response occurred in infected 6- to 7-day-old males (age of peak response) although this effect was not sustained in older beetles. The possibility that an endocrine interaction between metacestodes and host may mediate these effects is discussed in the light of our knowledge of the role of host juvenile hormone in controlling both pheromone production and vitellogenesis in T. molitor.     

Anno genominis XX: 20 years of Arabidopsis genomics

Twenty years ago, the Arabidopsis thaliana genome sequence was published. This was an important moment as it was the first sequenced plant genome and explicitly brought plant science into the genomics era. At the time, this was not only an outstanding technological achievement, but it was characterized by a superb global collaboration. The Arabidopsis genome was the seed for plant genomic research. Here, we review the development of numerous resources based on the genome that have enabled discoveries across plant species, which has enhanced our understanding of how plants function and interact with their environments.

The publication of the Arabidopsis genome sequence 20 years ago has had an enormous impact on the global plant science community.     

Collagen-fibronectin interactions in normal and rous sarcoma virus-transformed avian tendon cells: Possible mechanisms for increased extracellular matrix turnover after transformation

Summary Using gelatin, casein, and fibronectin as substrates and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), we have identified protein-degrading enzymes in both normal and Rous sarcoma virus-transformed primary avian tendon cells. Although there are some consistent differences in the profile of the gelatinolytic activities (mainly metalloproteinases) between normal and transformed cells, the amounts of fibronectin-degrading activities seem to be comparable. In vitro studies reported here demonstrate that the degradation of fibronectin is partially and specifically inhibited by gelatin and collagen. We therefore propose that the abundant collagen present in normal tendon cells protects fibronectin against degradation. Conversely, in transformed cells, where collagen levels are drastically reduced, fibronectin may be more accessible to degradation. Thus differences in the steady-state levels of fibronectin on normal and transformed cells may be, at least in part, a consequence of changes in collagen levels. This work was supported by the Office of Health and Environmental Research, Office of Energy Research, U.S. Department of Energy, Washington, D.C., under contracts DE-AC03-76-SF00098 and DE-AC03-76-SF01012.     

Conformational homologies among cytokines: Interleukins and colony stimulating factors

Some 30 cytokine amino acid sequences (mainly interleukins, colony stimulating factors and tumor necrosis factors) have been examined for evidence of secondary structure as well as longer-range interactions of a type likely to lead to stable α-helical bundles. Most, though not all, of the cytokines examined have a high predicted α-helical content (40–60%) and quasi-repeating heptads containing i/i+3 apolar periodicities. This major subset of the cytokines is predicted to be characterized by molecules in which 4-α-helical bundles with an average length of 25Å are the most marked conformational features. Based on these conclusions, we suggest structures for huG-CSF, huGM-CSF and muIL-5 in which defined loop segments at the ends of helical bundles are the most likely sites for binding and recognition by specific cell receptors. As such, they provide a means for testing or refining the three working models we have defined, using currently available methods of site-directed substitution and deletion mutagenesis, as well as synthetic peptides corresponding to the proposed loop sequences and the use of monoclonal antibodies of defined epitopic specificity. The structure arrived at for huGM-CSF is consistent with the limited data currently available concerning the residues which are important for binding and activity.