Identification of Mytilus spp. and Pecten maximus in Irish Waters by Standard PCR of the 18S rDNA Gene and Multiplex PCR of the 16S rDNA Gene

Two molecular protocols for the identification of mussel and scallop have been developed using specific primers targeting the mitochondrial 16S ribosomal DNA gene and the nuclear 18S ribosomal DNA gene. Primers for the mitochondrial 16S ribosomal DNA gene in multiplex polymerase chain reaction (PCR) protocols yielded diagnostic DNA fragments for the mussels Mytilus edulis, Mytilus galloprovincialis, and the hybrid Mytilus edulis/galloprovincialis (335 bp), the king scallop Pecten maximus (382 bp) and the black scallop Mimachlamys varia (398 bp). DNA from the queen scallop Aequipecten opercularis showed no consistent PCR amplification of the 16S rDNA gene. Primers for the nuclear 18S rDNA gene in standard PCR protocols yielded similar-sized, diagnostic DNA fragments (approx. 190 bp) for the mussels Mytilus edulis, Mytilus galloprovincialis, and the hybrid Mytilus edulis/galloprovincialis, the king scallop Pecten maximus, the black scallop Mimachlamys varia, and the queen scallop Aequipecten opercularis. Both protocols have been tested with Mytilus spp., P. maximus, and 6 other bivalve species from a wide range of locations in Irish and European waters. Cross reaction of the specific primers with DNA template from any of the 6 other bivalve species was not observed. Rapid DNA extraction using FTA Card technology and the16S rDNA primers allowed for the detection of at least 10 mussel larvae in a subsample of natural plankton.     

Hedgehog signaling is required for cranial neural crest morphogenesis and chondrogenesis at the midline in the zebrafish skull

Neural crest cells that form the vertebrate head skeleton migrate and interact with surrounding tissues to shape the skull, and defects in these processes underlie many human craniofacial syndromes. Signals at the midline play a crucial role in the development of the anterior neurocranium, which forms the ventral braincase and palate, and here we explore the role of Hedgehog (Hh) signaling in this process. Using sox10:egfp transgenics to follow neural crest cell movements in the living embryo, and vital dye labeling to generate a fate map, we show that distinct populations of neural crest form the two main cartilage elements of the larval anterior neurocranium: the paired trabeculae and the midline ethmoid. By analyzing zebrafish mutants that disrupt sonic hedgehog (shh) expression, we demonstrate that shh is required to specify the movements of progenitors of these elements at the midline, and to induce them to form cartilage. Treatments with cyclopamine, to block Hh signaling at different stages, suggest that although requirements in morphogenesis occur during neural crest migration beneath the brain, requirements in chondrogenesis occur later, as cells form separate trabecular and ethmoid condensations. Cell transplantations indicate that these also reflect different sources of Shh, one from the ventral neural tube that controls trabecular morphogenesis and one from the oral ectoderm that promotes chondrogenesis. Our results suggest a novel role for Shh in the movements of neural crest cells at the midline, as well as in their differentiation into cartilage, and help to explain why both skeletal fusions and palatal clefting are associated with the loss of Hh signaling in holoprosencephalic humans.     

Co-infection of Mycobacterium tuberculosis and Mycobacterium leprae in human archaeological samples: a possible explanation for the historical decline of leprosy

Both leprosy and tuberculosis were prevalent in Europe during the first millennium but thereafter leprosy declined. It is not known why this occurred, but one suggestion is that cross-immunity protected tuberculosis patients from leprosy. To investigate any relationship between the two diseases, selected archaeological samples, dating from the Roman period to the thirteenth century, were examined for both Mycobacterium leprae and Mycobacterium tuberculosis DNA, using PCR. The work was carried out and verified in geographically separate and independent laboratories. Several specimens with palaeopathological signs of leprosy were found to contain DNA from both pathogens, indicating that these diseases coexisted in the past. We suggest that the immunological changes found in multi-bacillary leprosy, in association with the socio-economic impact on those suffering from the disease, led to increased mortality from tuberculosis and therefore to the historical decline in leprosy.     

Sex determination in the monoecious species cucumber is confined to specific floral whorls

In unisexual flowers, sex is determined by the selective repression of growth or the abortion of either male or female reproductive organs. The mechanism by which this process is controlled in plants is still poorly understood. Because it is known that the identity of reproductive organs in plants is controlled by homeotic genes belonging to the MADS box gene family, we analyzed floral homeotic mutants from cucumber, a species that bears both male and female flowers on the same individual. To study the characteristics of sex determination in more detail, we produced mutants similar to class A and C homeotic mutants from well-characterized hermaphrodite species such as Arabidopsis by ectopically expressing and suppressing the cucumber gene CUCUMBER MADS1 (CUM1). The cucumber mutant green petals (gp) corresponds to the previously characterized B mutants from several species and appeared to be caused by a deletion of 15 amino acid residues in the coding region of the class B MADS box gene CUM26. These homeotic mutants reveal two important concepts that govern sex determination in cucumber. First, the arrest of either male or female organ development is dependent on their positions in the flower and is not associated with their sexual identity. Second, the data presented here strongly suggest that the class C homeotic function is required for the position-dependent arrest of reproductive organs.     

Control of secondary metabolite congener distributions via modulation of the dissolved oxygen tension

Many secondary metabolites, including various polyketides, require complex enzymatic pathways for modification into their final biologically active forms. Limitation of the dissolved oxygen supplied during cultivation of various microbial strains can decrease the activity of cytochrome P-450 monooxygenases required for the processing of pathway intermediates into their final forms, resulting in the accumulation of these intermediates as the primary products. Here, a generalized oxygen-limited cultivation strategy is specifically demonstrated with a myxobacterial strain engineered to heterologously express the epothilone polyketide synthase (PKS) gene cluster under either an excess (the dissolved oxygen tension is maintained at 50% of saturation) or a depleted (no residual dissolved oxygen detected) level of oxygenation during cultivation. Cultivation of this myxobacterial strain with excess oxygenation resulted in the production of epothilones A and B as the primary products, while cultivation of this same strain under depleted oxygenation resulted in the production of epothilones C and D as the primary products. Additionally, the peak cell density in the oxygen-depleted cultivations was 60% higher than that observed in oxygen-excess cultivations. Finally, an active EpoK epoxidase was found to catalyze the production of a novel epothilone (Epo506) with an unexpected structure during the cultivation of another myxobacterial strain expressing a genetically modified epothilone PKS under excess oxygenation. The structure of Epo506 was determined by high-resolution mass spectrometry and one- and two-dimensional NMR.     

Elimination of terminal complement intermediates from the plasma membrane of nucleated cells: the rate of disappearance differs for cells carrying C5b-7 or C5b-8 or a mixture of C5b-8 with a limited number of C5b-9

We have previously shown that multiple complement (C) channels are required for lysis of a nucleated cell in contrast to the single channel requirement for erythrocytes. To further investigate this multichannel requirement for nucleated cells, we examined the stability of terminal C complexes in the plasma membrane of Ehrlich ascites tumor cells. Ehrlich cells bearing C5b-7 or C5b-8 with or without C9 were incubated at 37 degrees C or 0 degree C for various time intervals before converting the remaining complexes to lytic C5b-9 channels. C5b-7, C5b-8, and C5b-8 in the presence of a limited number of C5b-9 complexes disappeared functionally from the plasma membrane at 37 degrees C, with initial half-lives of 31, 20, and 10 min, respectively. Disappearance of these complexes did not occur at 0 degree C, nor did disappearance occur at 37 degrees C when formed on sheep erythrocytes. The fate of C5b-8 complexes on the surface of Ehrlich cells was traced with colloidal gold particles bound to C5 determinants on C5b-8 with the use of immunoelectron microscopy. Colloidal gold could be seen on the cell surface after specific binding to cells carrying C5b-8 sites at 0 degree C. After incubating these cells at 37 degrees C, gold particles were internalized into the cell continuously via endocytic vesicles. It is postulated that terminal C complexes may stimulate or accelerate the removal of these complexes from the cell surface.     

Responses of the blister beetle Hycleus apicicornis to visual stimuli

Insect attraction to host plants may be partly mediated by visual stimuli. In the present study, the responses of adult Hycleus apicicornis (Guér.) (Coleoptera: Meloidae) to plant models of different colours, different combinations of two colours, or three hues of blue of different shapes are compared. Single‐colour models comprised the colours sky blue, bright green, yellow, red, white and black. Sky blue (reflecting light in the 440–500 nm region) is the most attractive, followed by white, which reflects light over a broader range (400–700 nm). On landing on sky blue targets, beetles exhibit feeding behaviour immediately. When different hues of blue (of different shapes) are compared, sky blue is preferred over turquoise, followed by dark blue, indicating that H. apicicornis is more attracted to lighter hues of blue than to darker ones. No significant differences are found between the three shapes (circle, square and triangle) tested, suggesting that reflectance associated with colour could be a more important visual cue than shape for host location by H. apicicornis. The preference of H. apicicornis for sky blue can be exploited in designing an attractive trap for its management.     

The Fixation and Saccade P3

Although most instances of object recognition during natural viewing occur in the presence of saccades, the neural correlates of objection recognition have almost exclusively been examined during fixation. Recent studies have indicated that there are post-saccadic modulations of neural activity immediately following eye movement landing; however, whether post-saccadic modulations affect relatively late occurring cognitive components such as the P3 has not been explored. The P3 as conventionally measured at fixation is commonly used in brain computer interfaces, hence characterizing the post-saccadic P3 could aid in the development of improved brain computer interfaces that allow for eye movements. In this study, the P3 observed after saccadic landing was compared to the P3 measured at fixation. No significant differences in P3 start time, temporal persistence, or amplitude were found between fixation and saccade trials. Importantly, sensory neural responses canceled in the target minus distracter comparisons used to identify the P3. Our results indicate that relatively late occurring cognitive neural components such as the P3 are likely less sensitive to post saccadic modulations than sensory neural components and other neural activity occurring shortly after eye movement landing. Furthermore, due to the similarity of the fixation and saccade P3, we conclude that the P3 following saccadic landing could possibly be used as a viable signal in brain computer interfaces allowing for eye movements.