Synergetic effects of Ca2+ and Cu2+ on phase transition in phosphatidylserine membranes

In complexes of divalent metals with large exchange rate constant (K_H2O) of the coordinated H₂O, such as Ca²⁺ and Cu²⁺, the cubic structure in the ligand field is usually unstable and conformation changes are easily induced. We observed the molecular motion of phosphatidylserine (PS) in an amphipathic solvent (water / methanol / chloroform) by ¹H-NMR and ESR using Ca²⁺ and / or Cu²⁺, which has a similar K_H2O to that of Ca²⁺. We found that Ca²⁺ did not hinder the molecular movements of PS. However, Cu²⁺ reduced the movements of both headgroups and the double bonds in the fatty acids of PS. By addition of both Ca²⁺ and Cu²⁺, phase transition to a soft solid phase in the PS membrane was observed at room temperature. The results indicate that the headgroups are clustered in two-dimensional network with each ligand field displaced from the aqueous phase to the water / oil interface. The structure changes of the polar headgroups after the binding of divalent cations are considered to trigger the phase transition of this acidic phospholipid membrane.     

Myosin light chain kinases and phosphatase in mitosis and cytokinesis

At mitosis, cells undergo drastic alterations in morphology and cytoskeletal organization including cell rounding during prophase, mitotic spindle assembly during prometaphase and metaphase, chromatid segregation in anaphase, and cytokinesis during telophase. It is well established that myosin II is a motor responsible for cytokinesis. Recent reports have indicated that myosin II is also involved in spindle assembly and karyokinesis. In this review, we summarize current understanding of the functions of myosin II in mitosis and cytokinesis of higher eukaryotes, and discuss the roles of possible upstream molecules that control myosin II in these mitotic events.     

Haplostomides hawaiiensis,new species (Copepods: Cyclopoida: Ascidicolidae), associated with the ascidian Polyclinum constellatum at Honolulu,Hawaii

An ascidicolid copepod, Haplostomides hawaiiensis, is described on the basis of females obtained from the compound ascidian Polyclinum constellatum collected in Keehi Lagoon, Honolulu, Hawaii. The features that separate H. hawaiiensis from other species of the genus include an elongate body with dorsal curvature and indistinct tagmosis, and a combination of characters of cephalic appendages (antenna with 2 spines, mandible with 3 setae, maxillule with 7 setae and maxilla with 2 setae) and thoracic appendages (legs 1–4 with 1 seta on protopod and 2 spines and 1 seta on exopod). Haplostomides hawaiiensis appears to be most closely related to H. hibernicus (T. & A. Scott, 1895) which occurs in compound ascidians from European seas. This is the first copepod associate of an ascidian to be reported from Hawaii.     

Simple, Quantitative Assay for Both Xenotropic Murine Leukemia and Ecotropic Feline Leukemia Viruses

A cat cell line carrying the genome of a murine sarcoma virus developed discrete foci in linear response to infection with feline leukemia virus or xenotropic murine C-type virus.     

Comparative deposition and clearance of various nickel compounds exposed by inhalation in rats

Wistar male rats were exposed to three types of nickel compounds, NiO(G), NiO(B), and Ni₃S₂, for 6 h/d, 5 d/wk for 6 mo. The solubility of these chemicals to saline solution was 0.3 ppm for NiO(G), 3.5 ppm for NiO(B), and 310 ppm for Ni₃S₂. Controls were exposed to clean air under similar conditions. Some rats were sacrificed 24 h after the termination of the final repeated exposure, and the remaining rats were kept for a 12-mo clearance period before sacrifice. There was no significant difference in body weight between exposed rats and controls and also no significant differences in organs weights, except for lungs in the case of Ni₃S₂, between exposed rats and controls. Nickel concentration in the lungs just after the exposure to nickel compounds was the highest when compared to other organs. The apparent deposition fractions (%) in the lungs were 0.5 ± 0.1 for NiO(G), 1.0 ± 0.3 for NiO(B), and 0.5 ± 0.1 for Ni₃S₂., After the clearance period, there were no significant differences in organ weights, except for the lungs in case of Ni₃S₂, between the exposed rats and the controls. During the 12 mo of clearance, 82% of deposited NiO(G), 73% of NiO(B), and 98% of Ni₃S₂ were cleared from lungs.     

Immunohistochemistry and nerve lesion experiments on the methionine-enkephalin immunopositive neurons in the small intestine of the bullfrog (Rana catesbeiana)

Summary Nerve elements in the small intestine of the bullfrog. Rana catesbeiana, were studied by immunohistochemistry with anti-methionine enkephalin antisera and by nerve lesion experiments, using laser irradiation. Methionine-enkephalin immunopositive nerve fibers occur in the myenteric plexus, circular muscle layer, submucosa, and mucosa. Immunopositive nerve cell bodies in the myenteric plexus have dendrite-like and a long axon-like processes. In the froglet (3 months after metamorphosis), these axon-like processes lead posteriorly in the nerve strand of the myenteric plexus. Some bifurcate, one branch continuing posteriorly, the other doubling back to lead anteriorly; both form terminal varicose fibers in the circular muscle layer. Nerve lesion experiments, in the adult bullfrog, resulted in accumulations of methionine-enkephalin immunoreactivity at the oral and hinder edges of the laser-irradiated necrotic area; there were sprouting and nonsprouting immunopositive stumps. It is suggested that bidirectional flow of methionine-enkephalin in the myenteric plexus is mediated via the anterior and posterior branches of the axon-like process. The difference in sprouting behavior of immunopositive nerve fiber stumps, after nerve lesion, is discussed with reference to regional differences of the axon-like process.