Effects of the Ebbinghaus figure on grasping are not only due to misjudged size

It is not evident how the small effects of the flankers of the Ebbinghaus figure on peak grip aperture (PGA) should be interpreted. One interpretation is that the flankers influence the estimated size, which in turn influences the grasp. If this interpretation is correct, then only the size-dependent aspects of the grasping movement should depend on the spatial positions of the flankers. An alternative interpretation is that the effect on grip aperture is caused by a change in judgement of the required precision, in which case various aspects of the grasping movement could be influenced by the size and position of the flankers. We presented subjects with a display consisting of a central disk surrounded by four large or small flankers. The array of circular flankers could be rotated by 45°. There were two tasks: to reproduce the perceived size of the central disk, and to grasp the central disk. As in other studies, the reproduced size and the PGA were both influenced by the size of the flankers. The effect on reproduced size settings was independent of the flankers spatial position. Nevertheless, the flankers position did influence the final grip aperture and the grip orientation at PGA and at movement offset. Because the flankers changed more than only the PGA, we conclude that the effect of the flankers on prehension cannot only be because of misjudgement of the size of the central disk.     

Persistence of hepatitis B antigen in Culex quinquefasciatus (Diptera: Culicidae)

Groups of wild-caught Culex quinquefaciatus Say, previously tested for the presence of hepatitis B surface antigen (HBsAg), were tested for the presence of hepatitis B e antigen (HBeAg). This antigen was detected at low levels in blood-fed, half-gravid, and gravid groups. A colony of Cx. quinquefasciatus was established in the laboratory and tested for the persistence of HBsAg and HBeAg. Five days after feeding on blood infected with HBsAg and HBeAg, 9 of 20 (45%) pools of Cx. quinquefasciatus were HBeAg-positive and 5 of 20 (25%) pools were HBeAg-positive; low levels of HBsAg and HBeAg were still detectable 28 d after the infective meal in 2 of 20 (10%) and 1 of 20 (5%) pools, respectively. A crude protease extract was prepared from colony mosquitoes, and the effect of this extract on HBsAg and HBeAg present in human serum was tested in vitro. After 20 h, tests for both antigens were still strongly positive. Low levels of HBsAg were detected in ovaries 7 d after infection. Salivary glands were HBsAg- and HBeAg-negative.     

Cell adhesion-related proteins as specific markers of sponge cell types involved in allogeneic recognition

Sponge immunocyte identification is of interest to comparative immunologists since characterizing these cells will allow investigations into the mechanisms of non-self recognition in the oldest animal phylum. Here, we report that polyclonal antibodies raised against the core protein of a proteoglycan involved in cell adhesion in the marine sponge Microciona prolifera are specific markers for archaeocytes, the totipotent sponge cells. Archaeocytes are mobilized upon allogeneic contact and they accumulate in the contact zone. A second type of cell, the gray cells, are specifically recognized by monoclonal antibodies raised against CD44, a hyaluronan receptor. Gray cells do also accumulate in the contact area. Specific staining of a third sponge cell type, the rhabdiferous cells, shows that these do not accumulate upon allografting. These specific cell markers allow tracking of archaeocytes and gray cells, and show that they play an active role in sponge allogeneic reactions.     

Computer-assisted prenatal aneuploidy screening for chromosome 13, 18, 21, X and Y based on multiplex ligation-dependent probe amplification (MLPA)

In routine prenatal diagnostics we used a commercial multiplex ligation-dependent probe amplification (MLPA) kit for aneuploidy screening for chromosomes 13, 18, 21, X and Y. We present the results of 1593 consecutive prenatal samples analysed and diagnosed prior to knowledge of the G-banding analysis during 8-month routine use of computer-assisted MLPA aneuploidy screening. In total, 27 aneuploidies were detected. There were no false positive results while two false negative results could be explained by a placental mosaicism and a partial monosomy, respectively. In total, 3.2% of the samples were inconclusive. We conclude that automatic computer assisted MLPA is a rapid, simple and reliable method for detection of aneuploidies in prenatal diagnostics.     

Ultrastructure and chromogranin A immunogold labelling of ECL cell carcinoids

Poorly differentiated neuroendocrine cells can be difficult to recognise. Sensitive methods are needed to label cells that have lost their ultrastructural features and have reduced concentrations of neuroendocrine markers. In gastric neoplasms, enterochromaffin-like cells might dedifferentiate and lose their characteristic granules and secretory vesicles, making detection of such cells increasingly difficult. However, chromogranin A (CgA) immunogold labelling could provide sensitive and specific detection of gastric neuroendocrine cells. We present ultrastructural findings, CgA immunogold labelling as well as conventional immunohistochemical findings of two human enterochromaffin-like cell carcinoids. Electron-dense granules of poorly differentiated cells were less intensely labelled than granules in well-differentiated cells. Granules with atypical shape as well as punctuate granules previously found in neuroendocrine neoplasms were also CgA labelled. The CgA labelling efficacy after antigen retrieval in an alkaline solution was higher after heating in an autoclave at 135 degrees C compared to a microwave at 100 degrees C for both granules and secretory vesicles without significant deterioration of the ultrastructure. In conclusion, the use of CgA immunogold labelling could ensure a specific classification of cells with neuroendocrine granules and be a supplement to immunohistochemical examination of poorly differentiated tumours.     

On the morphology and life-history ofDerogenes varicus (Müller, 1784) Looss, 1901 (Trematoda,Hemiuridae)

Summary The cystophorous cercaria ofDerogenes varicus (Müller, 1784) Looss, 1901 (=Cercaria appendiculata Pelseneer, 1906) develops in rediae inNatica spp. The cercaria is able to swim by undulating its furcate appendage. The free-swimming cercaria is eaten by calanoid or harpactacoid copepods. Mechanical pressure of the mouth limbs of the copepod causes the evagination of the long delivery tube, which in free-swimming cercariae is coiled up in the caudal vesicle. The cercarial body is pressed through the delivery tube and injected into the body cavity of the copepod.ImmatureD. varicus were found in the stomachs of 0-group plaice and dab fed uponCalanus finmarchicus (Gunnerus) containing two-week old metacercariae. Gobies became infected by eating infected harpactacoid copepods. If gobies with immatureD. varicus were given to a cod they matured in this fish, and matureD. varicus were positively transferred from one cod to another.The cercaria is redescribed, and the different developmental stages are described using the scanning electron microscope.Previous records ofD. varicus from invertebrate hosts are given.     

Separation of ECHO virus type 6 antigens by centrifugation in caesium chloride density gradients

Summary ECHO virus 6 particles separated by caesium chloride density gradient centrifugation were studied by electron microscopy. Particles in fractions of a density of 1.33 g/cm³, carrying peak infectivity and N antigenicity, appeared in the electron microscope as complete virions. The diameter was found to be 25 m. Particles in fractions of a density of 1.30 g/cm³, carrying H antigenicity, appeared as more or less empty capsids. This was true for the naturally occurring H antigen as well as for H antigen obtained by heat treatment.