Properties of the intracellular transient receptor potential (TRP) channel in yeast, Yvc1

Transient receptor potential (TRP) channels are found among mammals, flies, worms, ciliates, Chlamydomonas, and yeast but are absent in plants. These channels are believed to be tetramers of proteins containing six transmembrane domains (TMs). Their primary structures are diverse with sequence similarities only in some short amino acid sequence motifs mainly within sequences covering TM5, TM6, and adjacent domains. In the yeast genome, there is one gene encoding a TRP-like sequence. This protein forms an ion channel in the vacuolar membrane and is therefore called Yvc1 for yeast vacuolar conductance 1. In the following we summarize its prominent features.     

Effect of post-mating GnRH analogue (buserelin) treatment on PGF2alpha release in ewes and ewe lambs

The objectives of this study were to determine the effects of buserelin or saline treatment on ovarian function (Experiment 1), plasma PGFM concentrations and oxytocin stimulated prostaglandin F(2alpha) (PGF(2alpha)) release (Experiment 2) in ewe lambs and ewes. Welsh Halfbred ewes (n=26) and ewe lambs (n=24) were mated to vasectomised rams at synchronised oestrus and on Day 12 post-mating each animal was injected intramuscularly either normal saline or 4 microg buserelin. In Experiment 1, plasma progesterone and oestradiol concentrations were determined in samples collected by jugular venepuncture 1h before and at 0, 2, 4, 6, 8, 24, 48 and 72 h after treatment (n=7 per treatment group). Progesterone concentrations increased (P<0.05) from 2 to 8h after buserelin treatment and returned to basal levels after 72 h, whereas oestradiol concentrations were maximal at 2h post-treatment and returned to basal levels after 24h (P<0.05). Oestradiol concentrations were lower (P<0.05) in buserelin-treated animals than controls at 72 h post-treatment. Basal and post-treatment progesterone concentrations were greater (P<0.05) in ewes than in ewe lambs but oestradiol levels were similar for both age groups. Ovulation rate, determined by laparoscopy on Day 14, was similar for both age groups (ewes 1.1; ewe lambs 1.0). Buserelin treatment induced accessory corpora lutea in ewes (4/7; 57%) but not in ewe lambs (0/7; 0%). In the Experiment 2, plasma PGFM concentrations were determined in samples collected at 20-min intervals for 6h on Day 14 and at 20-min intervals for 1h before and at 10-min intervals for 1h and then at 20-min intervals for a further 3h period after an intravenous injection of oxytocin (1IU/kg body weight) on Day 15 post-oestrus. In this experiment there were five ewe lambs and six ewes per treatment group. There was no effect of buserelin treatment or age on basal PGFM concentrations on either Day 14 or 15. Although peak PGFM concentrations tended to be lower in buserelin-treated animals, the difference was not significant (P>0.05). However, peak duration following oxytocin challenge on Day 15 post-mating was shorter (P<0.05) in control ewes compared with control ewe lambs. In conclusion, buserelin treatment given on Day 12 post-oestrus enhances luteal function more in ewes than ewe lambs and after a transitory increase, reduces oestradiol concentrations in both ewes and ewe lambs. However, buserelin treatment does not significantly attenuate the luteolytic signal.     

A class III histidine kinase acts as a novel virulence factor in Botrytis cinerea

Filamentous ascomycetes contain large numbers of histidine kinases (HK) that belong to eleven classes. Members of class III from different species were previously shown to be involved in osmoregulation and resistance to dicarboximide and phenylpyrrole fungicides. We have inactivated the gene encoding the single group III HK, BOS1, in the economically important plant pathogen Botrytis cinerea. BOS1 inactivation had pleiotropic effects on the fungus. Besides the expected osmosensitivity and resistance to fungicides, null mutants presented additional characteristics indicating that BOS1 is necessary for normal macroconidiation and full virulence. On standard culture media, null mutants very rarely formed conidiophores and those few conidiophores failed to produce conidia. This defect could be partially restored with 1 M sorbitol, suggesting that another BOS1-independent signal cascade may be involved in macroconidiation. The mutants were not found to be hypersensitive to various oxidative stresses but were more resistant to menadione. Finally, pathogenicity tests showed that bos1-null mutants were significantly reduced in the ability to infect host plants. Appressorium morphogenesis was not altered; however, in planta growth was severely reduced. To our knowledge, this is the first class III HK characterized as a pathogenicity factor in a plant-pathogenic ascomycete.     

Direct intracranial, FMRI, and lesion evidence for the causal role of left inferotemporal cortex in reading

Models of the "visual word form system" postulate that a left occipitotemporal region implements the automatic visual word recognition required for efficient reading. This theory was assessed in a patient in whom reading was explored with behavioral measures, fMRI, and intracranial local field potentials. Prior to surgery, when reading was normal, fMRI revealed a normal mosaic of ventral visual selectivity for words, faces, houses, and tools. Intracranial recordings demonstrated that the left occipitotemporal cortex responded with a short latency to conscious but also to subliminal words. Surgery removed a small portion of word-responsive occipitotemporal cortex overlapping with the word-specific fMRI activation. The patient developed a marked reading deficit, while recognition of other visual categories remained intact. Furthermore, in the post-surgery fMRI map of visual cortex, only word-specific activations disappeared. Altogether, these results provide direct evidence for the causal role of the left occipitotemporal cortex in the recognition of visual words.     

Increased adult mortality and reduced breeding success with age in a population of common guillemot Uria aalge using marked birds of unknown age

Although there is general consensus about the existence of senescence in vertebrates, empirical evidence of senescence in demographic parameters in wild populations is limited. Data on breeding success and survival of breeding common guillemots Uria aalge were collected over 20 years on the Isle of May (Scotland) using a pool of individuals marked as adults. Because the years of hatching of individuals were not known, we used the time (years) elapsed since first capture (TFC) as a measure of age. The use of this proxy did not create any bias in estimating senescence in the case of a linear decline, nor did it greatly decrease the power of a test for senescence. Breeding success declined significantly from 0.81 (95% CI: 0.77–0.84) to 0.62 (0.54–0.68) over the study period. It also varied in relation to age, initially increasing (from 0.62 (0.54–0.68) at TFC of 0 year to 0.76 (0.73–0.79) at TFC of 9 years) up to a plateau (from TFC of 9 years with 0.76 (0.73–0.79) until TFC of 13 years with 0.77 (0.74–0.79) before declining in later life to 0.70 (0.61–0.78) at TFC of 19 years). Survival was generally high and varied significantly from year to year. It also declined with TFC: survival of birds marked in 1982 decreased from 0.92 (0.85–0.96) at a TFC of 0 year to 0.88 (0.82–0.92) at a TFC of 19 years. Resighting probabilities also declined with TFC suggesting that the oldest birds do not come back to the colony to breed as regularly as younger individuals. These findings indicate that individual common guillemots on the Isle of May showed both actuarial and reproductive senescence.     

Microplitis demolitor bracovirus inhibits phagocytosis by hemocytes from Pseudoplusia includens

The braconid wasp Microplitis demolitor carries Microplitis demolitor bracovirus (MdBV) and parasitizes the larval stage of several noctuid moths. A key function of MdBV in parasitism is suppression of the host's cellular immune response. Prior studies in the host Pseudoplusia includens indicated that MdBV blocks encapsulation by preventing two types of hemocytes, plasmatocytes and granulocytes, from adhering to foreign targets. The other main immune response mediated by insect hemocytes is phagocytosis. The goal of this study was to determine which hemocyte types were phagocytic in P. includens and to assess whether MdBV infection affects this defense response. Using the bacterium Escherichia coli and inert polystyrene beads as targets, our results indicated that the professional phagocyte in P. includens is granulocytes. The phagocytic responses of granulocytes were very similar to those of High Five cells that prior studies have suggested are a granulocyte-like cell line. MdBV infection dose-dependently disrupted phagocytosis in both cell types by inhibiting adhesion of targets to the cell surface. The MdBV glc1.8 gene encodes a cell surface glycoprotein that had previously been implicated in disruption of adhesion and encapsulation responses by immune cells. Knockdown of glc1.8 expression by RNA interference (RNAi) during the current study rescued the ability of MdBV-infected High Five cells to phagocytize targets. Collectively, these results indicate that glc1.8 is a key virulence determinant in disruption of both adhesion and phagocytosis by insect immune cells.     

Melatonin in the multi-oscillatory mammalian circadian world

In mammals, the complex interaction of neural, hormonal, and behavioral outputs from the suprachiasmatic nucleus (SCN) drives circadian expression of events, either directly or through coordination of the timing of peripheral oscillators. Melatonin, one of the endocrine output signals of the clock, provides the organism with circadian information and can be considered as an endogenous synchronizer, able to stabilize and reinforce circadian rhythms and to maintain their mutual phase-relationship at the different levels of the circadian network. Moreover, exogenous melatonin, through an action on the circadian clock, affects all levels of the circadian network. The molecular mechanisms underlying this chronobiotic effect have also been investigated in rats. REV-ERB alpha seems to be the initial molecular target.     

Ageing, genetics and the somatotropic axis

Research on ageing made a big leap forward when genes regulating lifespan were discovered about a decade ago. First isolated by screening the genome of the nematode Caenorhabditis elegans, most of these genes belong to an essential signalling pathway that is highly conserved during animal evolution. Orthologous genes in vertebrate species are the families of genes coding for insulin, insulin-like growth factors (IGF) and related proteins. Intensively studied and well-known for their pivotal roles in proliferation, differentiation, survival and metabolism of most cells, we now discover their multiples functions with respect to the control of longevity and their ability to modulate the cell's responses to oxidative stress, a major cause of cellular and organismal ageing. The activity of IGF signalling in mammals depends on a complex interplay of endocrine signals that together constitute the somatotropic axis. Accordingly, several components of this hormone axis, like growth hormone or growth hormone releasing hormone receptors, regulate efficiently animal longevity, which has been elegantly demonstrated by studies performed in genetically modified mouse models. From this and other work, it becomes increasingly clear that the control of ageing is a question of hormonal regulations. We here present several of these models and discuss the respective contributions of insulin and IGF signalling to the regulation of lifespan. We review data on the Klotho gene that acts on lifespan via surprising and not yet fully understood molecular mechanisms, connecting this new, hormone-like substance to IGF and insulin signalling. We further report recent evidence showing that human lifespan might be controlled in similar ways. Finally, we shed some light on clinical GH treatment in humans, from an endocrinologist's point of view.     

Solvent participation in Serratia marcescens endonuclease complexes

The monomer and dimer of the bacterium Serratia marcescens endonuclease (SMnase) are each catalytically active and the two subunits of the dimer function independently of each other. Specific interfacial waters may play a role in stability, complex formation, and functionality. We performed molecular dynamics simulations of both a subunit of SMnase and its model built complex with DNA and analyzed the relation of the hydration sites to the catalytic mechanism. It was found that the binding of DNA has little influence on the global hydration properties of the protein, including occupancy and water residence time distributions. DNA and protein recognition in our model mainly involves direct contacts by hydrogen bond and hydrophobic interactions. Water-mediated contacts exist, but are less common. Three interior water clusters were identified for SMnase. One cluster around the active site in the monomer-DNA complex shows relatively strong interactions between hydration sites as well as between the sites and the biomolecules. The simulated cluster properties agreed well with experimental data. The magnesium ion shows ligand exchange. Although Mg2+ keeps six ligands during the entire simulation, upon the binding of DNA, Asn119 loses its coordination with Mg2+, while one nonbridging oxygen of the phosphate of a DNA residue and two oxygen atoms of the side chain of Glu127 become the ligands. Waters in a nearby cluster exchange and participate in the resolvation of groups in the presence of DNA. Water thus not only participates in the cleavage of DNA but also can stabilize the transition state and the leaving groups in our model.