A mutation in aspergillus nidulans that blocks the transition from interphase to prophase

In order to develop a method for obtaining mitotic synchrony in aspergillus nidulans, we have characterized previously isolated heat-sensitive nim mutations that block the nuclear division cycle in interphase at restrictive temperature. After 3.5 h at restrictive temperature the mitotic index of a strain carrying one of these mutations, nimA5, was 0, but when this strain was subsequently shifted from restrictive to permissive temperature the mitotic index increased rapidly, reaching a maximum of 78 percent after 7.5 min. When this strain was examined electron-microscopically, mitotic spindles were absent at restrictive temperature. From these data we conclude that at restrictive temperature nimA5 blocks the nuclear division cycle at a point immediately preceding the initiation of chromosomal condensation and mitotic microtubule assembly, and upon shifting to permissive control over the initiation of microtubule assembly and chromosomal condensation in vivo through a simple temperature shift and, consequently, nimA5 should be a powerful tool for studying these processes. Electron-microscopic examination of spindles of material synchronized in this manner reveals that spindle formation, although very rapid, is gradual in the sense that spindle microtubule numbers increase as spindle formation proceeds.     

Extreme dives by free-ranging emperor penguins

We examined the incidence of extreme diving in a 3-year overwintering study of emperor penguins Aptenodytes forsteri in East Antarctica. We defined extreme dives as very deep (> 400 m) and/or very long (> 12 min). Of 137364 dives recorded by 93 penguins 264 dives reached depths > 400 m and 48 lasted > 12 min. Most (65%) very long dives occurred in winter (May–August) while 83% of the very deep dives took place in spring (September–November). The two most extreme dives (564 m depth, 21.8 min duration) were separate dives and were performed by different individual penguins. Penguins diving extremely deeply may have done so as part of their foraging strategy whereas penguins diving for very long times may have been forced to do so by changes in the sea-ice conditions.     

AMPA receptor regulation during synaptic plasticity in hippocampus and neocortex

Discovery of long-term potentiation (LTP) in the dentate gyrus of the rabbit hippocampus by Bliss and L?mo opened up a whole new field to study activity-dependent long-term synaptic modifications in the brain. Since then hippocampal synapses have been a key model system to study the mechanisms of different forms of synaptic plasticity. At least for the postsynaptic forms of LTP and long-term depression (LTD), regulation of AMPA receptors (AMPARs) has emerged as a key mechanism. While many of the synaptic plasticity mechanisms uncovered in at the hippocampal synapses apply to synapses across diverse brain regions, there are differences in the mechanisms that often reveal the specific functional requirements of the brain area under study. Here we will review AMPAR regulation underlying synaptic plasticity in hippocampus and neocortex. The main focus of this review will be placed on postsynaptic forms of synaptic plasticity that impinge on the regulation of AMPARs using hippocampal CA1 and primary sensory cortices as examples. And through the comparison, we will highlight the key similarities and functional differences between the two synapses.     

Pre-moult foraging trips and moult locations of Emperor penguins at the Mawson Coast

The movements of nine breeding adult emperor penguins Aptenodytes forsteri from two colonies, Auster (67° 23S 64° 04E) and Taylor Glacier (67° 28S 60° 54E), were determined by satellite telemetry on their pre-moult foraging trips. While preparing for their annual moult the penguins travelled for 22–38 days and reached distances of up to 618 km from the colony. Six of the nine tracked penguins were followed to three different moult locations all to the west of their breeding colonies and near other known emperor penguins colonies, such as Kloa Point (66°38S, 59°23E) and Fold Island (67°17S, 59°23E). Sea-ice conditions changed throughout the tracking period; as the birds travelled north the sea-ice contracted south.     

The Ruegeria pomeroyi acuI gene has a role in DMSP catabolism and resembles yhdH of E. coli and other bacteria in conferring resistance to acrylate

The Escherichia coli YhdH polypeptide is in the MDR012 sub-group of medium chain reductase/dehydrogenases, but its biological function was unknown and no phenotypes of YhdH(-) mutants had been described. We found that an E. coli strain with an insertional mutation in yhdH was hyper-sensitive to inhibitory effects of acrylate, and, to a lesser extent, to those of 3-hydroxypropionate. Close homologues of YhdH occur in many Bacterial taxa and at least two animals. The acrylate sensitivity of YhdH(-) mutants was corrected by the corresponding, cloned homologues from several bacteria. One such homologue is acuI, which has a role in acrylate degradation in marine bacteria that catabolise dimethylsulfoniopropionate (DMSP) an abundant anti-stress compound made by marine phytoplankton. The acuI genes of such bacteria are often linked to ddd genes that encode enzymes that cleave DMSP into acrylate plus dimethyl sulfide (DMS), even though these are in different polypeptide families, in unrelated bacteria. Furthermore, most strains of Roseobacters, a clade of abundant marine bacteria, cleave DMSP into acrylate plus DMS, and can also demethylate it, using DMSP demethylase. In most Roseobacters, the corresponding gene, dmdA, lies immediately upstream of acuI and in the model Roseobacter strain Ruegeria pomeroyi DSS-3, dmdA-acuI were co-regulated in response to the co-inducer, acrylate. These observations, together with findings by others that AcuI has acryloyl-CoA reductase activity, lead us to suggest that YdhH/AcuI enzymes protect cells against damaging effects of intracellular acryloyl-CoA, formed endogenously, and/or via catabolising exogenous acrylate. To provide "added protection" for bacteria that form acrylate from DMSP, acuI was recruited into clusters of genes involved in this conversion and, in the case of acuI and dmdA in the Roseobacters, their co-expression may underpin an interaction between the two routes of DMSP catabolism, whereby the acrylate product of DMSP lyases is a co-inducer for the demethylation pathway.     

Macroscopic spectral imaging and gene expression analysis of the early stages of melanoma

BACKGROUND: The stages of melanocytic progression are defined as atypical (dysplastic) nevus, melanoma in situ, melanoma in the radial growth phase (RGP), melanoma in the vertical growth phase (VGP), and melanoma in the metastatic growth phase (MGP). Melanoma in situ and RGP melanoma often develop in contiguous association with atypical nevi. This frequently poses a problem with respect to their early detection. Furthermore, unlike cells obtained from VGP and MGP melanomas, cells derived from melanoma in situ and RGP melanoma do not proliferate in vitro. Thus, compared to the late stages of the disease, less information is available regarding genes expressed in the early stages. MATERIALS AND METHODS: To determine whether spectral imaging, a recently developed optical imaging technique, can detect melanoma in situ and RGP melanoma arising in melanoma precursor lesions, atypical nevi in patients with a clinical history of melanoma were subjected to noninvasive macroscopic spectral imaging. To determine at what stage in the progression pathway of melanoma genes having important biological functions in VGP and MGP melanomas are activated and expressed, lesions of melanoma in situ were analyzed by immunohistochemistry and in situ hybridization for expression of some of these known molecular and immunologic markers. RESULTS: The present study demonstrates the capability of noninvasive spectral imaging to detect melanoma in situ and RGP melanoma that arise in contiguous association with atypical nevi. Furthermore, the study provides evidence that genes and antigens expressed in VGP and MGP melanoma are also expressed in melanoma in situ. CONCLUSIONS: Because of the dark and variegated pigmentation of atypical nevi, melanoma in situ and RGP melanoma that arise in these melanoma precursor lesions are often difficult to recognize and thus frequently go unnoticed. The application of new optical screening techniques for early detection of melanoma and the identification of genes expressed in the early stages of melanoma development are two important avenues in the pursuit of melanoma prevention. The investigations presented here document that macroscopic spectral imaging has the potential to detect melanoma in its early stage of development and that genes essential for the proliferation and cell adhesion of VGP and MGP melanoma are already expressed in melanoma in situ.     

Cross-reactive CD4+ T cells against one immunodominant tumor-derived epitope in melanoma patients

TCRs exhibit a high degree of specificity but may also recognize multiple and distinct peptide-MHC complexes, illustrating the so-called cross-reactivity of TCR-peptide-MHC recognition. In this study, we report the first evidence of CD4(+) T cells recognizing the same tumor peptide-epitope from NY-ESO-1, in the context of multiple HLA-DR and HLA-DP molecules. These cross-reactive CD4(+) T cells recognized not only autologous but also allogenic dendritic cells previously loaded with the relevant protein (i.e., the normally processed and presented epitope). Using clonotypic real-time RT-PCR, we have detected low frequencies of CD4(+) T cells expressing one cross-reactive TCR from circulating CD4(+) T cells of patients with stage IV melanoma either spontaneously or after immunization but not in normal donors. The maintenance of cross-reactive tumor Ag-specific CD4(+) T cells in PBLs of cancer patients required the presence of tumor Ag/epitope in the context of the MHC molecule used to prime the Ag-specific CD4(+) T cells. Our findings have significant implications for the optimization of TCR gene transfer immunotherapies widely applicable to cancer patients.     

Genome‐wide linkage analysis for human longevity: Genetics of Healthy Aging Study

Clear evidence exists for heritability of human longevity, and much interest is focused on identifying genes associated with longer lives. To identify such longevity alleles, we performed the largest genome‐wide linkage scan thus far reported. Linkage analyses included 2118 nonagenarian Caucasian sibling pairs that have been enrolled in 15 study centers of 11 European countries as part of the Genetics of Healthy Aging (GEHA) project. In the joint linkage analyses, we observed four regions that show linkage with longevity; chromosome 14q11.2 (LOD = 3.47), chromosome 17q12‐q22 (LOD = 2.95), chromosome 19p13.3‐p13.11 (LOD = 3.76), and chromosome 19q13.11‐q13.32 (LOD = 3.57). To fine map these regions linked to longevity, we performed association analysis using GWAS data in a subgroup of 1228 unrelated nonagenarian and 1907 geographically matched controls. Using a fixed‐effect meta‐analysis approach, rs4420638 at the TOMM40/APOE/APOC1 gene locus showed significant association with longevity (P‐value = 9.6 × 10^?8). By combined modeling of linkage and association, we showed that association of longevity with APOEε4 and APOEε2 alleles explain the linkage at 19q13.11‐q13.32 with P‐value = 0.02 and P‐value = 1.0 × 10^?5, respectively. In the largest linkage scan thus far performed for human familial longevity, we confirm that the APOE locus is a longevity gene and that additional longevity loci may be identified at 14q11.2, 17q12‐q22, and 19p13.3‐p13.11. As the latter linkage results are not explained by common variants, we suggest that rare variants play an important role in human familial longevity.     

Mitochondria and ageing: winning and losing in the numbers game

Mitochondrial dysfunction has long been considered a key mechanism in the ageing process but surprisingly little attention has been paid to the impact of mitochondrial number or density within cells. Recent reports suggest a positive association between mitochondrial density, energy homeostasis and longevity. However, mitochondrial number also determines the number of sites generating reactive oxygen species (ROS) and we suggest that the links between mitochondrial density and ageing are more complex, potentially acting in both directions. The idea that increased density, especially when combined with mitochondrial dysfunction, might accelerate ageing is supported by a negative correlation between mitochondrial density and maximum longevity in an interspecies comparison in mammals, and by evidence for an intimate interconnection between cellular ROS levels, mitochondrial density and cellular ageing. Recent data suggest that retrograde response, which activates mitochondrial biogenesis, accompanies cellular ageing processes. We hypothesise that increased mitochondrial biogenesis, and possibly also impaired degradation and segregation of mitochondria, if occurring as adaptation to pre-existing mitochondrial dysfunction, might aggravate ROS production and thus actively contribute to ageing.     

Iron mediates N-methyl-D-aspartate receptor-dependent stimulation of calcium-induced pathways and hippocampal synaptic plasticity

Iron deficiency hinders hippocampus-dependent learning processes and impairs cognitive performance, but current knowledge on the molecular mechanisms underlying the unique role of iron in neuronal function is sparse. Here, we investigated the participation of iron on calcium signal generation and ERK1/2 stimulation induced by the glutamate agonist N-methyl-D-aspartate (NMDA), and the effects of iron addition/chelation on hippocampal basal synaptic transmission and long-term potentiation (LTP). Addition of NMDA to primary hippocampal cultures elicited persistent calcium signals that required functional NMDA receptors and were independent of calcium influx through L-type calcium channels or α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors; NMDA also promoted ERK1/2 phosphorylation and nuclear translocation. Iron chelation with desferrioxamine or inhibition of ryanodine receptor (RyR)-mediated calcium release with ryanodine-reduced calcium signal duration and prevented NMDA-induced ERK1/2 activation. Iron addition to hippocampal neurons readily increased the intracellular labile iron pool and stimulated reactive oxygen species production; the antioxidant N-acetylcysteine or the hydroxyl radical trapper MCI-186 prevented these responses. Iron addition to primary hippocampal cultures kept in calcium-free medium elicited calcium signals and stimulated ERK1/2 phosphorylation; RyR inhibition abolished these effects. Iron chelation decreased basal synaptic transmission in hippocampal slices, inhibited iron-induced synaptic stimulation, and impaired sustained LTP in hippocampal CA1 neurons induced by strong stimulation. In contrast, iron addition facilitated sustained LTP induction after suboptimal tetanic stimulation. Together, these results suggest that hippocampal neurons require iron to generate RyR-mediated calcium signals after NMDA receptor stimulation, which in turn promotes ERK1/2 activation, an essential step of sustained LTP.