Seasonal dynamics of fish assemblage structures in a surf zone on an exposed sandy beach in Japan

Seasonal dynamics in fish assemblage structure, comprising postlarval to early adult stages, in the surf zone on an exposed sandy beach on the Kashimanada coast were studied over a 2-year period. A total of 32 species and two higher group taxa were found. In terms of abundance, Salangichthys ishikawae, Mugil cephalus cephalus, Plecoglossus altivelis altivelis, and Engraulis japonicus were the four most dominant species. The results of cluster analysis and canonical correspondence analysis using 12 dominant species in terms of abundance revealed that water temperature and wind factor (wind speed × wind direction) had significant independent associations on species occurrence patterns for 11 species; that is, occurrence of 11 species was significantly related to water temperature and occurrence of 7 species was related to wind factor. Two species (S. ishikawae and P. altivelis altivelis) showed clear monthly increases in size, consequently suggesting their use of the surf zone as a nursery area. In contrast, M. cephalus cephalus and E. japonicus showed few increases in standard length, indicating their use of the surf zone only in their postlarval and/or juvenile stage. It is suggested that numerous fish species use the surf zone as shelter and/or a nursery area, even in the harsh conditions of an exposed sandy beach with great wave action.     

Depression of gustatory receptor potential in frog taste cell by parasympathetic nerve-induced slow hyperpolarizing potential

Parasympathetic nerve (PSN) innervates taste cells of the frog taste disk, and electrical stimulation of PSN elicited a slow hyperpolarizing potential (HP) in taste cells. Here we report that gustatory receptor potentials in frog taste cells are depressed by PSN-induced slow HPs. When PSN was stimulated at 30 Hz during generation of taste cell responses, the large amplitude of depolarizing receptor potential for 1 M NaCl and 1 mM acetic acid was depressed by approximately 40% by slow HPs, but the small amplitude of the depolarizing receptor potential for 10 mM quinine-HCl (Q-HCl) and 1 M sucrose was completely depressed by slow HPs and furthermore changed to the hyperpolarizing direction. The duration of the depolarizing receptor potentials depressed by slow HPs prolonged with increasing period of PSN stimulation. As tastant-induced depolarizing receptor potentials were increased, the amplitude of PSN-induced slow HPs inhibiting the receptor potentials gradually decreased. The mean reversal potentials of the slow HPs were approximately -1 mV under NaCl and acetic acid stimulations, but approximately -14 mV under Q-HCl and sucrose stimulations. This implies that when a slow HP was evoked on the same amplitude of depolarizing receptor potentials, the depression of the NaCl and acetic acid responses in taste cells was larger than that of Q-HCl and sucrose responses. It is concluded that slow HP-induced depression of gustatory depolarizing receptor potentials derives from the interaction between gustatory receptor current and slow hyperpolarizing current in frog taste cells and that the interaction is stronger for NaCl and acetic acid stimulations than for Q-HCl and sucrose stimulations.     

Establishment of LC-MS methods for the analysis of palmitoylated surfactant proteins

The surfactant proteins (SPs), SP-B and SP-C, are important components of pulmonary surfactant involved in the reduction of alveolar surface tension. Quantification of SP-B and SP-C in surfactant drugs is informative for their quality control and the evaluation of their biological activity. Western blot analysis enabled the quantification of SP-B, but not SP-C, in surfactant drugs. Here, we report a new procedure involving chemical treatments and LC-MS to analyze SP-C peptides. The procedure enabled qualitative analysis of SP-C from different species with discrimination of the palmitoylation status and the artificial modifications that occur during handling and/or storage. In addition, the method can be used to estimate the total amount of SP-C in pulmonary surfactant drugs. The strategy described here might serve as a prototype to establish analytical methods for peptides that are extremely hydrophobic and behave like lipids. The new method provides an easy measurement of SP-C from various biological samples, which will help the characterization of various experimental animal models and the quality control of surfactant drugs, as well as diagnostics of human samples.     

Fractal dimension analysis and mathematical morphology of structural changes in actin filaments imaged by electron microscopy

In this work, we examined structural changes of actin filaments interacting with myosin visualized by quick freeze deep-etch replica electron microscopy (EM) by using a new method of image processing/analysis based on mathematical morphology.In order to quantify the degree of structural changes, two characteristic patterns were extracted from the EM images. One is the winding pattern of the filament shape (WP) reflecting flexibility of the filament, and the other is the surface pattern of the filament (SP) reflecting intra-molecular domain-mobility of actin monomers constituting the filament. EM images were processed by morphological filtering followed by box-counting to calculate the fractal dimensions for WP (D_WP) and SP (D_SP). The result indicates that D_WP was larger than D_SP irrespective of the state of the filament (myosin-free or bound) and that both parameters for myosin-bound filaments were significantly larger than those for myosin-free filaments. Overall, this work provides the first quantitative insight into how conformational disorder of actin monomers is correlated with the myosin-induced increase in flexibility of actin filaments along their length as suggested by earlier studies with different techniques. Our method is yet to be improved in details, but promising as a powerful tool for studying the structural change of protein molecules and their assemblies, which can potentially be applied to a wide range of biological and biomedical images.     

Influences of weight loss on monocytes and T-cell subpopulations in male judo athletes

The purpose of this study was to examine weight loss effects on immune function in judo athletes. Six elite male Japanese judo athletes (20.3 ± 0.4 years) were enrolled in this study. They completed usual weight loss programs during 2 weeks preceding an actual competition. Subjects noted the appearance of upper-respiratory tract infection (URTI) symptoms during the study period. Blood samples were obtained at 40 (baseline period: BL) and 3 (weight loss period: WL) days before and 1 day after the competition (AC). The CD3, CD4, CD8, CD56CD3, CD28CD4, CD28CD8, and Toll-like-receptor-4 (TLR-4) CD14 cells were counted by using flow cytometer analysis. The 6 subjects reported 1 headache, 3 runny nose conditions, and 1 coughing instance during the WL. The CD3, CD4, CD8, and CD28CD4 cell counts were significantly lower at WL than at BL (p ≤ 0.05); they reverted to the baseline value at AC. The TLR-4CD14 cells were significantly fewer at WL (p ≤ 0.05); they remained fewer than they had been at BL, even at AC. These results suggest that 2 weeks of weight loss before a competition can impair cell-mediated immune function and induce high susceptibility to URTI in judo athletes. Coaches, support staff, and athletes should monitor athletes' weight loss, hydration status, appearance of URTI symptoms, and immunocompetence such as lymphocytes and monocytes to prevent the physical condition from becoming worse.