Instream distributions and feeding habits of two species of sleeper, <Emphasis Type="Italic">Eleotris acanthopoma</Emphasis> and <Emphasis Type="Italic">Eleotris fusca</Emphasis>, in the Teima River,Okinawa Island

The instream distributions and feeding habits of two species of sleeper, Eleotris acanthopoma and E. fusca, were studied in the Teima River on Okinawa Island, southern Japan. Both adult fishes inhabited the river, but their distribution patterns were found to be different. The distribution of E. acanthopoma was from the tidally influenced area to the lower part of the freshwater area, whereas E. fusca was distributed almost entirely in the freshwater area. They were found to coexist at the upper limit of the tidally influenced area and the lower part of the freshwater area. Their feeding habits were clearly different, although both species were carnivorous. Eleotris acanthopoma fed mainly on crabs in the tidally influenced area and on aquatic snails in the freshwater area, where they coexist with E. fusca. In contrast, E. fusca fed mainly on shrimps in the freshwater area. Their coexistence may result from the difference in their feeding habits.     

Quantification of mcrA by quantitative fluorescent PCR in sediments from methane seep of the Nankai Trough

A quantitative fluorogenic PCR method for group-specific methyl coenzyme M reductase subunit A genes (mcrA) from methanotrophic archaea was established and applied to the characterization of microbial communities in anoxic methane seep sediments at the accretionary prism of the Nankai Trough. All of the previously identified subgroups of anaerobic methanotroph (ANME) mcrA genes were detected in the cores up to 25 cm below the seafloor, but distributional patterns of mcrA genes were found to differ according to depth. These findings suggest a distinct distribution of phylogenetically and physiologically diverse methanotrophic archaea that mediate methane oxidation in the anoxic sediments. This quantification method will contribute to future investigations of methanotrophic microbial ecosystems in anoxic marine sediments.     

An ultrastructural examination of everted rat jejunum

Male, albino, Sprague-Dawley rats were sacrificed by cervical separation. Segments of jejunum were excised, everted and examined with the electron microscope. Examination of tissue fixed immediately after eversion revealed the following changes as compared to non-everted segments fixed $\text{in}$$\text{situ}$ and $\text{in}$$\text{vitro}$: 1) an increase in the length of microvilli from (mean ± S. E.) 0.991 ± 0.011μ for normal tissue to 1.389 ± 0.023μ for everted tissue, 2) an increase in width of microvilli from (mean ± S. E.) 0.089 ± 0.001μ for normal tissue to 0.097 ± 0.001μ for everted tissue, 3) an increase in length and number of lateral membrane interdigitations, and 4) the appearance of intercellular “lakes” in the lateral spaces. The above changes are in those structures hypothesized to be involved with salt and water transport across epithelia and may reflect altered transport rates $\text{in}$$\text{vitro}$ as compared to $\text{in}$$\text{vivo}$.     

On the impact of correlation between collaterally consanguineous cells on lymphocyte population dynamics

During an adaptive immune response, lymphocytes proliferate for five to twenty-five cell divisions, then stop and die over a period of weeks. Based on extensive flow cytometry data, Hawkins et al. (Proc Natl Acad Sci USA 104:5032–5037, 2007) introduced a cell-level stochastic model of lymphocyte population dynamics, called the Cyton Model, that accurately captures mean lymphocyte population size as a function of time. In Subramanian et al. (J Math Biol 56(6):861–892, 2008), we performed a branching process analysis of the Cyton Model and deduced from parameterizations for in vitro and in vivo data that the immune response is predictable despite each cell’s fate being highly variable. One drawback of flow cytometry data is that individual cells cannot be tracked, so that it is not possible to investigate dependencies in the fate of cells within family trees. In the absence of this information, while the Cyton Model abandons one of the usual assumptions of branching processes (the independence of lifetime and progeny number), it adopts another of the standard branching processes hypotheses: that the fates of progeny are stochastically independent. However, new experimental observations of lymphocytes show that the fates of cells in the same family tree are not stochastically independent. Hawkins et al. (2008, submitted) report on ciné lapse photography experiments where every founding cell’s family tree is recorded for a system of proliferating lymphocytes responding to a mitogenic stimulus. Data from these experiments demonstrate that the death-or-division fates of collaterally consanguineous cells (those in the same generation within a founding cell’s family tree) are strongly correlated, while there is little correlation between cells of distinct generations and between cells in distinct family trees. As this finding contrasts with one of the assumptions of the Cyton Model, in this paper we introduce three variants of the Cyton Model with increasing levels of collaterally consanguineous correlation structure to incorporate these new found dependencies. We investigate their impact on the predicted expected variability of cell population size. Mathematically we conclude that while the introduction of correlation structure leaves the mean population size unchanged from the Cyton Model, the variance of the population size distribution is typically larger. Biologically, through comparison of model predictions for Cyton Model parameterizations determined by in vitro and in vivo experiments, we deduce that if collaterally consanguineous correlation extends beyond cousins, then the immune response is less predictable than would be concluded from the original Cyton Model. That is, some of the variability seen in data that we previously attributed to experimental error could be due to intrinsic variability in the cell population size dynamics.      

The genera Ceratomyxa Thélohan, 1892, Leptotheca Thélohan, 1895 and Sphaeromyxa Thélohan, 1892 (Myxosporea: Bivalvulida) in gadid fish of the Northeast Atlantic

The gall-bladders of four species of gadid fish from the North Sea and Norwegian waters were examined for myxosporeans. The host species were cod Gadus morhua L. (350 examined), haddock Melanogrammus aeglefinus (L.) (592 examined), saithe Pollachius virens (L.) (205 examined) and whiting Merlangius merlangus (L.) (368 examined). Four species of myxosporeans are redescribed from these fish. Ceratomyxa arcuata Thélohan, 1892 was the most common species and was found in whiting (42.8%) and cod (0.6%). Leptotheca informis Auerbach, 1910 was found only in whiting (6.5%). L. longipes Auerbach, 1910 was found only in haddock (6.2%). Sphaeromyxa hellandi Auerbach, 1909 was found in haddock (9.1%) and whiting (0.3%). None of the saithe examined, and no cod or haddock from Norwegian waters, was infected with these myxosporeans. All four species appear to have distributions limited to the Northeast Atlantic, with S. hellandi having a more northern distribution than the other three. The validity of reports of C. arcuata, L. informis and L. longipes from outside this area is discussed.     

The Soluble Interleukin-6 Receptor Is a Mediator of Hematopoietic and Skeletal Actions of Parathyroid Hormone

Both PTH and IL-6 signaling play pivotal roles in hematopoiesis and skeletal biology, but their interdependence is unclear. The purpose of this study was to evaluate the effect of IL-6 and soluble IL-6 receptor (sIL-6R) on hematopoietic and skeletal actions of PTH. In the bone microenvironment, PTH stimulated sIL-6R protein levels in primary osteoblast cultures in vitro and bone marrow in vivo in both IL-6^+/+ and IL-6^−/− mice. PTH-mediated hematopoietic cell expansion was attenuated in IL-6^−/− compared with IL-6^+/+ bone marrow, whereas sIL-6R treatment amplified PTH actions in IL-6^−/− earlier than IL-6^+/+ marrow cultures. Blocking sIL-6R signaling with sgp130 (soluble glycoprotein 130 receptor) inhibited PTH-dependent hematopoietic cell expansion in IL-6^−/− marrow. In the skeletal system, although intermittent PTH administration to IL-6^+/+ and IL-6^−/− mice resulted in similar anabolic actions, blocking sIL-6R significantly attenuated PTH anabolic actions. sIL-6R showed no direct effects on osteoblast proliferation or differentiation in vitro; however, it up-regulated myeloid cell expansion and production of the mesenchymal stem cell recruiting agent, TGF-β1 in the bone marrow microenvironment. Collectively, sIL-6R demonstrated orphan function and mediated PTH anabolic actions in bone in association with support of myeloid lineage cells in the hematopoietic system.     

The salting-in hypothesis of post-hypertonic lysis

The phenomenon of slow cooling cryoinjury has remained one of the primary areas of research in cryobiology since the early 1950s when it was first investigated thoroughly. Lovelock demonstrated that cell death from freezing and thawing was mainly due to exposure to hypertonic solutions and the subsequent dilution back to isotonic conditions. He suggested that the cell became permeable to sodium in hypertonic conditions leading to a loading of sodium during the hypertonic exposure, which caused the cell to swell past its elastic limit during resuspension in isotonic media (post-hypertonic lysis). This idea was pursued by Zade-Oppen, Farrant, and others who were able to show that the membrane became leaky to cations in hypertonic media but they could not provide any mechanism that would cause the cell to load up with sodium (other than an exchange of extracellular sodium for intracellular potassium, leaving the cell with the same cation concentration that it started out with). In the absence of such a mechanism, predicting post-hypertonic lysis from osmotic simulations cannot be done.A simplified model is proposed in which the intracellular milieu is composed of both KCl and a proteinaceous component that normally forms many salt bridges between amino acids with fixed charges. When the intracellular salt concentration increases, the proteins are “salted in” to solution (salt bridges are replaced with ionic interactions) thereby decreasing the intracellular cation concentration. Cation channels in the plasma membrane are opened by exposure to a high salt concentration (either inside or outside the membrane) allowing extracellular sodium to take the place of the intracellular potassium that is interacting with anionic groups on the proteins. Dilution of the external medium (which also occurs during melting) causes water to move into the cells, diluting the cytoplasm. The proteins are then “salted out” of solution and release the salt back to free ions in solution. The cell has an excess of intracellular ions and may swell past its elastic limit due to water influx. A simulation engine is developed based on the model and compared to results in the literature for freeze–thaw injury in human red blood cells.