Wave of cortical actin polymerization in the sea urchin egg

The distribution of actin filaments in the cortical layer of sea urchin eggs during fertilization has been investigated by light microscopy using fluorescently labeled phallotoxins. The cortical layer of both whole eggs and cortices isolated on a glass surface was examined. In cortices of unfertilized eggs, numerous fluorescent spots were seen, which may correspond to short actin filament cores in microvilli. After insemination, one of the sperm-attaching points on the egg surface first became strongly fluorescent. This fluorescence grew around the point of sperm penetration with the growth of the fertilization cone. Then, the cortical layer of the egg around the fertilization cone became strongly fluorescent and the fluorescence propagated in a wavelike manner over the entire cortex. The mechanism of the propagation of actin polymerization is discussed.     

Localization and possible function of 20 kDa actin-modulating protein (actolinkin) in the sea urchin egg

We have previously described a novel actin-capping protein, a 20,000-molecular weight protein (20K protein)-actin complex (20K-A) isolated from sea urchin eggs. In the present study, the localization and possible function of this 20K protein were investigated. The 20K protein was localized in the sea urchin egg cortex. Its distribution in the cortex as revealed by immunofluorescence microscopy did not change during or after fertilization up to the first mitosis, but it was concentrated to some extent in the cleavage furrow region. Exogenously added actin polymerized on the cortex isolated from unfertilized egg; however, actin did not polymerize on the cortex extracted with 0.6 M KCl, that is, the cell membrane, which lost the 20K protein. The cell membrane preincubated with 20K-A restored the activity to grow actin filaments. When decorated with myosin subfragment 1, almost all the actin filaments showed the arrowhead configuration pointing away from the membrane, indicating that they were connected to the membrane at their barbed ends. These results strongly suggest that the 20K protein connects actin filaments to the plasma membrane of sea urchin eggs. Because of this property we call this protein "actolinkin".     

Separation of RRBC-RFC and non-rosette forming cells (non-RFC) of guinea pig T-cell populations and their functional difference. 1. Response of RRBC-RFC and non-RFC to either Con-A or LPS.

Guinea pig lymph node cells suspension (LNC-O) was filtered through a glass wool column and the effluent (LNC-G) was further filtered through a nylon column. In this effluent (LNC-NE) about 30 per cent of the lymphocytes was identified as non-rosette forming cells (non-RFC). The non-RFC fraction was separated from LNC-NE fraction by Ficol-Conray specific gravity centrifugation or effluent cells reacted previously to rabbit red blood cells (RRBC). The upper layer after centrifugation, designated non-RFC fraction, was separated. In this fraction 96% of the cells were lymphocytes and about 95% of them were non-RFC, which lacked receptors for rabbit red blood cells (RRBC) or EAC and detectable surface immunoglobulin by conventional techniques. Though the response of the lymphocytes in the non-RFC fraction to mitogenic (Con-A, LPS) or antigenic stimulation was lower in comparison with that in RFC-rich fraction, the response of non-RFC to ConA exceeded the response to LPS. These facts suggest that at least a portion of the non-RFC may be cells from the T-cell line.     

Effects of aldose reductase inhibitor (ONO-2235) on human erythrocyte sorbitol concentrations in 75 g oral glucose tolerance tests

In order to evaluate the effects of the aldose reductase inhibitor, ONO-2235, on the short-term response of human erythrocyte sorbitol to hyperglycemia in vivo, eleven diet-treated Type 2 (non-insulin-dependent) diabetic patients were studied twice in 75 g oral glucose tolerance tests - with and without ONO-2235 (200 mg p.o.) premedication. The erythrocyte sorbitol concentrations increased with the increments of blood glucose and erythrocyte glucose concentrations in the test performed without ONO-2235. The erythrocyte sorbitol response in the test performed with administration of ONO-2235 30 min prior to glucose load was lower than that in the test performed without ONO-2235 (F = 5.782, P less than 0.05). No significant differences were found between the two tests in blood glucose and erythrocyte glucose concentrations (F = 0.092, P = 0.761; F = 0.029, P = 0.860, respectively). It is concluded that human erythrocyte sorbitol concentrations change promptly in response to rapid changes in erythrocyte glucose concentrations and that administered ONO-2235 is effective in inhibiting the human erythrocyte sorbitol pathway in man.     

Myosin-II reorganization during mitosis is controlled temporally by its dephosphorylation and spatially by Mid1 in fission yeast

Cytokinesis in many eukaryotes requires an actomyosin contractile ring. Here, we show that in fission yeast the myosin-II heavy chain Myo2 initially accumulates at the division site via its COOH-terminal 134 amino acids independently of F-actin. The COOH-terminal region can access to the division site at early G2, whereas intact Myo2 does so at early mitosis. Ser1444 in the Myo2 COOH-terminal region is a phosphorylation site that is dephosphorylated during early mitosis. Myo2 S1444A prematurely accumulates at the future division site and promotes formation of an F-actin ring even during interphase. The accumulation of Myo2 requires the anillin homologue Mid1 that functions in proper ring placement. Myo2 interacts with Mid1 in cell lysates, and this interaction is inhibited by an S1444D mutation in Myo2. Our results suggest that dephosphorylation of Myo2 liberates the COOH-terminal region from an intramolecular inhibition. Subsequently, dephosphorylated Myo2 is anchored by Mid1 at the medial cortex and promotes the ring assembly in cooperation with F-actin.     

Morphological features of an endangered Japanese strain of Cyprinus carpio: reconstruction based on seven SNP markers

Morphological analyses of 183 specimens of Japanese common carp Cyprinus carpio (171 from Lake Biwa and 12 from nursery ponds) using genetic hybrid indices demonstrated that the typical native Japanese strain of C. carpio has a more elongate body, more branched dorsal‐fin rays, fewer and shorter gill rakers, more developed pneumatic bulb, more coiled pneumatic duct, longer posterior swimbladder and shorter intestine than the typical introduced C. carpio. These results provide a basis for a better understanding of the ecological characteristics and taxonomic status of the endangered Japanese strain of C. carpio.     

Measurement of Mesoscale Conformational Dynamics of Freely Diffusing Molecules with Tracking FCS

Few techniques are suited to probe the structure and dynamics of molecular complexes at the mesoscale level ($～$100–1000 nm). We have developed a single-molecule technique that uses tracking fluorescence correlation spectroscopy (tFCS) to probe the conformation and dynamics of mesoscale molecular assemblies. tFCS measures the distance fluctuations between two fluorescently labeled sites within an untethered, freely diffusing biomolecule. To achieve subdiffraction spatial resolution, we developed a feedback scheme that allows us to maintain the molecule at an optimal position within the laser intensity gradient for fluorescence correlation spectroscopy. We characterized tFCS spatial sensitivity by measuring the Brownian end-to-end dynamics of DNA molecules as short as 1000 bp. We demonstrate that tFCS detects changes in the compaction of reconstituted nucleosome arrays and can assay transient protein-mediated interactions between distant sites in an individual DNA molecule. Our measurements highlight the applicability of tFCS to a wide variety of biochemical processes involving mesoscale conformational dynamics.     

Ten simple rules for establishing a mentorship programme

In recent years, a wide variety of mentorship programmes targeting issues that cannot be addressed through traditional teaching and learning methods alone have been developed. Mentoring plays significant roles in the growth and development of both mentors and mentees, and the positive impacts of mentoring have been well documented. Mentorship programmes are therefore increasingly being implemented in a wide variety of fields by organisations, academic institutes, businesses, and governments. While there is a growing body of literature on mentoring and mentorship programmes, gaining a clear overview of the field is often challenging. In this article, we therefore provide a concise summary of recommendations to consider when designing and establishing mentorship programmes. These recommendations are based on the collective knowledge and experiences of 4 different emerging and established mentorship programmes and can be adapted across various mentorship settings or contexts.     

Acrosomal ATPase in starfish and bivalve mollusk spermatozoa

ATPase activity was found in acrosomes of starfish and bivalve mollusk spermatozoa, using a cytochemical method with electron microscopy. The activity was located in central material of the starfish acrosome and in material lining the acrosomal membrane of the Mytilus acrosome, as well as in the basal part of the starfish acrosome. The ATPase activity in the former material was preferably activated by Ca²⁺, while that in the starfish basal material was preferably activated by Mg²⁺. Both types of activity persisted during and after the acrosome reaction. ATPase activity was also observed in the region of the axial filament complex of the flagella, in centrioles and in a basal matrix. ATPase in the acrosome also hydrolysed other nucleoside triphosphates. However, there was no detectable phosphatase activity, and little pyrophosphatase or 5′-nucleotidase activity. Evidence was obtained that adenylate kinase may be included in the acrosome. A possible role of the ATPase activity in the acrosome reaction is discussed.