Papillomaviruses: different genes have different histories

Papillomaviruses (PVs) infect stratified squamous epithelia in vertebrates. Some PVs are associated with different types of cancer and with certain benign lesions. It has been assumed that PVs coevolved with their hosts. However, recently it has been shown that different regions of the genome have different evolutionary histories. The PV genome has a modular nature and appeared after the addition of pre-existent blocks. This order of appearance in the PV genome is evident today in the different evolutionary rates of the different genes, with new genes--E5, E6 and E7--diverging faster than old genes--E1, E2, L2 and L1. Here, we propose an evolutionary framework aiming to integrate genome evolution, PV biology and epidemiology of PV infections.     

Ras proteins: different signals from different locations

Ras signalling has classically been thought to occur exclusively at the inner surface of a relatively uniform plasma membrane. Recent studies have shown that Ras proteins interact dynamically with specific microdomains of the plasma membrane as well as with other internal cell membranes. These different membrane microenvironments modulate Ras signal output and highlight the complex interplay between Ras location and function.     

Paramyxoviruses: different receptors - different mechanisms of fusion

Paramyxovirus-mediated membrane fusion usually requires an interaction between the viral-attachment and -fusion proteins. The mechanism by which this interaction regulates fusion differs between paramyxoviruses that bind to sialic acid-containing receptors and those that recognize specific proteins. The recently solved structure of the globular head of the measles virus hemagglutinin suggests that this difference might be related to the location of the receptor-binding sites on the attachment proteins of the two classes of paramyxoviruses.     

Three different human tumor cell lines contain different oncogenes

We have obtained foci of transformed mouse cells after transfection of human DNA from colon and bladder carcinoma cell lines and a promyelocytic leukemia cell line. These foci can be shown to contain a large number of human DNA sequences by use of highly repetitive human DNA sequence probes. Cell DNA from primary foci can be used in a subsequent cycle of transfection resulting in secondary foci that contain relatively little human DNA. Secondary foci appear to contain only the human sequences proximal to those responsible for the transformed phenotype. A set of characteristic DNA restriction fragments is found in common among secondary foci derived from each tumor cell line DNA. Comparison of the common DNA fragments found in secondary foci derived from three different human tumor cell lines indicates that these three cell lines contain three different transforming genes.     

FlgM proteins from different bacteria exhibit different structural characteristics

Intrinsically disordered proteins (IDPs) are a unique class of proteins that do not require a stable structure for function. The importance of IDPs in many biological processes has been established but there remain unanswered questions about their evolution and conservation of their disordered state within a protein family. Our group has been studying the structural similarities among orthologous FlgM proteins, a model class of IDPs. We have previously shown that the FlgM protein from the thermophile Aquifex aeolicus has more structure at A. aeolicus' physiological temperature (85 °C) than is observed for the Salmonella typhimurium FlgM, suggesting that the disordered nature of FlgM varies among organisms and is not universally conserved. In this work, we extend these studies to the FlgM proteins from Escherichia coli, Pseudomonas aeruginosa, Proteus mirabilis, and Bacillus subtilis. We demonstrate that the B. subtilis, E. coli, and S. typhimurium FlgMs exist in a premolten globule-like conformation, though the B. subtilis FlgM is in a more compacted conformation than the other two. The P. aeruginosa and P. mirabilis FlgM proteins exist in a currently unknown conformation that is not either coil-like or premolten globule-like. The P. aeruginosa FlgM appears to contain more weak intramolecular contacts given its more compacted state than the P. mirabilis FlgM. These results provide experimental evidence that members of the same protein family can exhibit different degrees of disorder, though understanding how different disordered states evolve in the same protein family will require more study.     

Two rheologically different gastric mucus secretions with different putative functions

Previous work has shown the presence of different mucin gene products and glycosylated species in gastric mucus secretions, however, the functional relevance of these differences is unclear. This study aimed to investigate rheologically, differences in the gel behaviour within gastric mucus samples using a pig model. Rheological measurements were made on a Bohlin CVO50 rheometer. Mucins were characterised by antigenicity, lectin reactivity and proteolytic fragmentation patterns. Two distinct mucus gel secretions, one compliant with and the other resistant to shear stress, were removed from the gastric mucosa. The two gels had different rheological behaviour profiles and exhibited structural differences in their constituent mucins. The shear-compliant mucus was located superficially to the adherent shear-resistant mucus layer and was shown not to be a proteolytic product of the latter. This study has demonstrated that there are two rheologically distinct mucus gel secretions with structural/compositional differences in the stomach. Rheological properties suggest that the adherent, shear-resistant gel could provide the mucus barrier in vivo while the shear-compliant gel could act primarily as a lubricant.     

Melittin peptides exhibit different activity on different cells and model membranes

Melittin (MLT) is a lytic peptide with a broad spectrum of activity against both eukaryotic and prokaryotic cells. To understand the role of proline and the thiol group of cysteine in the cytolytic activity of MLT, native MLT and cysteine-containing analogs were prepared using solid phase peptide synthesis. The antimicrobial and cytolytic activities of the monomeric and dimeric MLT peptides against different cells and model membranes were investigated. The results indicated that the proline residue was necessary for antimicrobial activity and cytotoxicity and its absence significantly reduced lysis of model membranes and hemolysis. Although lytic activity against model membranes decreased for the MLT dimer, hemolytic activity was increased. The native peptide and the MLT-P14C monomer were mainly unstructured in buffer while the dimer adopted a helical conformation. In the presence of neutral and negatively charged vesicles, the helical content of the three peptides was significantly increased. The lytic activity, therefore, is not correlated to the secondary structure of the peptides and, more particularly, on the propensity to adopt helical conformation.     

Hypothalamic control of energy balance: different peptides, different functions

Energy balance is maintained via a homeostatic system involving both the brain and the periphery. A key component of this system is the hypothalamus. Over the past two decades, major advances have been made in identifying an increasing number of peptides within the hypothalamus that contribute to the process of energy homeostasis. Under stable conditions, equilibrium exists between anabolic peptides that stimulate feeding behavior, as well as decrease energy expenditure and lipid utilization in favor of fat storage, and catabolic peptides that attenuate food intake, while stimulating sympathetic nervous system (SNS) activity and restricting fat deposition by increasing lipid metabolism. The equilibrium between these neuropeptides is dynamic in nature. It shifts across the day-night cycle and from day to day and also in response to dietary challenges as well as peripheral energy stores. These shifts occur in close relation to circulating levels of the hormones, leptin, insulin, ghrelin and corticosterone, and also the nutrients, glucose and lipids. These circulating factors together with neural processes are primary signals relaying information regarding the availability of fuels needed for current cellular demand, in addition to the level of stored fuels needed for long-term use. Together, these signals have profound impact on the expression and production of neuropeptides that, in turn, initiate the appropriate anabolic or catabolic responses for restoring equilibrium. In this review, we summarize the evidence obtained on nine peptides in the hypothalamus that have emerged as key players in this process. Data from behavioral, physiological, pharmacological and genetic studies are described and consolidated in an attempt to formulate a clear statement on the underlying function of each of these peptides and also on how they work together to create and maintain energy homeostasis.     

Fungal growth on different insulation materials exposed to different moisture regimes

Commercially available paper, flax, glass wool and rock wool insulation materials were tested for sensitivity to moisture and the ability of fungi to grow on them under different moisture regimes. Three levels of moisture were used, ambient, simulated rain and water holding capacity. After wetting, the materials were inoculated with a mixture of fungi and incubated at 26°C in boxes with high moisture levels for 4 weeks. The greatest degree of fungal growth was observed on paper and flax insulation materials initially conditioned to ambient moisture levels. Paper and flax insulation were strongly affected by moisture, with all treatments showing losses in dry mass of approx. 20%, except for paper subjected to simulated rain treatment in which the loss was 39%. Glass and rock wools were not sensitive to moisture and were resistant to fungal degradation, showing only traces of fungal growth and minimal loss in dry mass over 4 weeks.     

Multiculturalism and AIDS: different communities mean different educational messages required

Having a multitude of different ethnic communities forces Canada''s AIDS educators to use many different methods to deliver their messages. These range from an AIDS bingo game that has been used to educate natives in northern Manitoba to attempts to take AIDS education to the streets of Toronto. With AIDS education, reports Olga Lechky, one message definitely does not fit all.     

Mussel beds on different types of structures support different macroinvertebrate assemblages

Abstract Artificial structures, such as seawalls, pilings and pontoons, are common features of urban estuaries. They replace natural structures or add to the amount of hard substratum in an area and provide habitats for many fish and invertebrates. Previous work has concentrated on fish or on the invertebrates that occupy the primary substratum of artificial structures. Mussels often grow on different types of structures (pontoons, pilings, seawalls and natural reefs) and provide a secondary substratum for other organisms to inhabit. Counting and identifying organisms associated with mussel beds is traditionally done to species level, which is very time‐consuming. To save time, organisms in this study were identified to coarse levels of taxonomic resolution (a mix of taxa, such as class, order, family and genus), which showed similar patterns to those when particularly speciose and abundant groups were identified to species. This study tests hypotheses that the distribution and abundance of mobile and sessile organisms that inhabit mussel beds will differ among natural and various types of artificial structures. When the associated assemblages of mussel beds from different types of structures and from different locations were examined, assemblages varied according to the type of structure they inhabited and its location. Assemblages associated with mussels on pontoons differed consistently from those on other types of structures. Patterns in the assemblages were also consistent through time. These data show that the types and amounts of artificial structures added to an environment can affect the types, distribution and abundances of organisms living in biogenic habitats.