Immunohistochemical demonstration of urotensins I and II in the caudal neurosecretory system of the Japanese charr,Salvelinus leucomaenis,retained in sea water

This paper is concerned with part of the role and function of the caudal neurosecretory system of the charr,Salvelinus leucomaenis, studied by immunohistochemistry. In order to elucidate the different histologic changes, we examined the immunoreactivities of urotenisn I (UI) and urotensin II (UII) in 3 experimental groups: the feral (river) fish, the fresh-water aquarium-, and sea water aquarium-retained fish. Coexistence of UI and UII was demonstrated in most of the smaller and larger neurons distributed in and near the urophyseal system of all 3 groups. However, some of the larger neurons were immunoreactive only to a single hormone, UI or UII. Merely a few neurons indicated no reactivity for either UI or UII. No such clearcut differences were encountered immunohistochemically in the 3 groups. Neuronal and urophysial immuno-reactivity to UI of feral and fresh-water-retained fish was slightly stronger than that of sea water-retained fish. Moreover, in sea water-retained fish, the intensity of immunoreactivity for UI was variable, and the number of neurons positive for UII only was somewhat larger than that in feral and fresh-water-retained fish. A series of UII-positive cerebrospinal fluid (CSF)-contacting neurons were seen in the ependymal and subependymal layers ventral to the central canal of the spinal cord in every group. These CSF-contacting neurons might constitute another neurosecretory system aside from the ordinary caudal neurosecretory system equipped with urophysis. In contrast to the hypothalamohypophysial neurosecretory system, the caudal neurosecretory system did not show any significant changes among the 3 groups. This suggests that urotensins I and II have no essential role in osmoregulation of the charr.     

SFA-1, a novel cellular gene induced by human T-cell leukemia virus type 1, is a member of the transmembrane 4 superfamily.

A novel cellular gene termed SFA-1 was isolated by differential hybridization of a cDNA library, using probes obtained from an adult T-cell leukemia cell line in comparison with probes obtained from normal CD4+ T cells and the MOLT-4 cell line. The mRNA of the SFA-1 gene is approximately 1.6 kb in size and encodes a protein of 253 amino acids, containing four putative transmembrane domains, a number of cysteine residues, and one potential N-glycosylation site in a major hydrophilic region between the third and fourth transmembrane domains. Expression of the SFA-1 gene was either absent or present at a low level in lymphoid cells but was up-regulated after transformation by human T-cell leukemia virus type 1 and transactivated by Tax. SFA-1 was broadly expressed in many human cell types and conserved in different species. Computer-aided comparison showed that SFA-1 had significant sequence homology and common structural features with members of the transmembrane 4 superfamily. SFA-1 antigen was detected as a 29-kDa membrane protein by immunoblotting, using anti-SFA-1 monoclonal antibody.     

Comparison of muscle force,muscle endurance,and electromyogram activity during an expedition at high altitude

Handgrip force (HF), maximal pinch force (MF), muscle endurance (ME), and the median power frequency (MdPF) of the activity shown in the electromyogram (EMG) were studied at various altitudes in eight normal healthy subjects. MF and ME were measured between the index finger and thumb, and all measurements were obtained at altitudes ranging from 610 to 4860 m during an expedition in the Qinghai Plateau in China. With the change in altitude HF, ME, and MF showed no significant change. Compared to the MdPF at 2260 m on ascent, the MdPF at other altitudes showed a significant decrease (P<0.01). Thus, we conclude that muscle performance (HF, MF, and ME) was not affected by the environment at high altitude. However, MdPF was affected and the mean MdPF at 610 m after the expedition did not recover to initial values of MdPF. We suggest these results may have been affected by fatigue and chronic exposure to the hypobaric hypoxic environment, since the members of the expedition party expressed feelings of sluggishness and fatigue after the expedition.     

EGF-Induced sustained tyrosine phosphorylation and decreased rate of down-regulation of EGF receptor in PC12h-R cells which show neuronal differentiation in response to EGF

PC12h-R cell, a subclone of PC12 cells, exhibited a neuron-like phenotype, including neurite outgrowth and increased acetylcholinesterase activity, in response to epidermal growth factor (EGF) as well as nerve growth factor (NGF). We examined the mechanism by which EGF induced the neuronal differentiation in PC12h-R cells. The EGF-induced neuronal differentiation of PC12h-R cells was not blocked by K252a, whereas that induced by NGF was. EGF induced sustained tyrosine phosphorylation of the EGF receptor in PC12h-R cells, but not in the parent PC12h cells, which do not show neuronal differentiation in response to EGF. In addition, the rate of EGF-induced down-regulation of the EGF receptor in PC12h-R cells was decreased compared with that in PC12h cells. Furthermore, we found that the duration of EGF-induced tyrosine phosphorylation of the EGF receptor in PC12h-R cells was similar to that of NGF-induced tyrosine phosphorylation of p140 ^trkA in PC12h cells. The EGF-induced phosphorylation of the EGF receptor in PC12h cells was less sustained than that of p140 ^trkA by NGF in PC12h cells. These findings suggested that the EGF-induced neuronal differentiation of PC12h-R cells is due to the sustained activation of the EGF receptor, resulting from the decreased down-regulation of the EGF receptor and that the duration of the receptor tyrosine kinase activity determines the cellular responses of PC12 cells. We concluded that sustained activation of the receptor tyrosine kinase induces neuronal differentiation, although transient activation promotes proliferation of PC12 cells. Special issue dedicated to Dr. Hans Thoenen.     

Comparison of fish assemblages among an artificial reef, a natural reef and a sandy-mud bottom site on the shelf off Iwate, northern Japan

Synopsis Fish assemblages at an artificial reef site, a natural reef site and a sandy-mud bottom site, on the shelf (depth 130 m) off Iwate Prefecture, northern Japan, were surveyed by using a bottom trammel net from May 1987 to March 1993. A total of 12 173 fishes of 48 species were recorded. Physiculus maximowiczi was dominant and comprised 69% of the total numerical abundance. Total fish number was lowest in March at all the 3 sites when P. maximowiczi migrated to deeper and warmer waters. Assemblage equitability and species diversity also varied seasonally in accordance with the abundance fluctuation of P. maximowiczi. P. maximowiczi, Alcichthys alcicornis and Hexagrammos otakii were more abundant at the artificial reef and natural reef sites, while Dexistes rikuzenius and Hemitripterus villosus were more abundant at the sandy-mud bottom site; total fish abundance was largest at the artificial reef site mainly due to the large number of P. maximowiczi. Species richness was similar among sites, but equitability, and consequently species diversity, was lowest at the artificial reef site. The main effect of the artificial reef seemed the attraction of P. maximowiczi from nearby bottoms, especially from natural rocky reefs; its large abundance determined the structure of the artificial reef fish community.     

Filial cannibalism by mouthbrooding males of the cardinal fish,Apogon doederleini, in relation to their physical condition

Synopsis Paternal brood cannibalism was observed in a population ofApogon doederleini in Shikoku Island, Japan. Of 361 egg masses mouthbrooded by males, 47 disappeared within a day of spawning. A stomach check with a syringe ascertained that they had been consumed by the males. The frequency of this cannibalism increased as the breeding season advanced. As males completed 4–7 breeding cycles in a breeding season and spent 80% of the time mouthbrooding without taking ordinary food, their physical condition deteriorated greatly late in the breeding season. We concluded that parental physical condition is an important factor in the occurrence of brood cannibalism.     

Interspecific brood-mixing in Tanganyikan cichlids

Synopsis We collected schools of young, guarded by parents, of six common cichlid species to investigate the frequency and origin of interspecific brood-mixing. The main host species were a piscivore Lepidiolamprologus elongatus and a scale-eater Perissodus microlepis; more than half of their schools included heterospecific young, accounting for 20–40% of the total young. Most of the foreign young belonged to four biparental mouth-brooders whose parents have a habit of carrying their young in their mouths. Many of these young were smaller than the largest young brooded by their own parents. We concluded that adoption of young before independence results from farming-out, a behavior by which parents actively transfer their young to foster parents.     

Expression of NADH-Dependent Glutamate Synthase in Response to the Supply of Nitrogen in Rice Cells in Suspension Culture

The effects of inorganic and organic nitrogen on the levelsof mRNA for NADH-dependent glutamate synthase (GOGAT) and theprotein were examined in rice cells in suspension culture. Asupply of NH⁺₄, NO^-₃, glutamine, or asparagine induced the accumulationof the protein and mRNA, but levels of mRNA for ferredoxin-GOGATwere hardly affected. ¹Present address: P.C. Center Wakuya-cho, Toda-gun, Miyagi,Japan.     

Simultaneous Determination of Dermatan Sulfate and Oversulfated Dermatan Sulfate in Plasma by High-Performance Liquid Chromatography with Postcolumn Fluorescence Derivatization

A chemical method for the determination of dermatan sulfate (DS) and oversulfated dermatan sulfate has been developed and applied to the pharmacokinetic study of these polysaccharides in experimental animals. The analytical procedure includes a simple preparation step of administered DS and oversulfated DS from blood plasma, HPLC for the separation and detection of DS and oversulfated DS using an Asahipak NH₂P-50 column, fluorometric reaction of the polysaccharides with guanidine in a strong alkaline medium. DS and oversulfated DS were extracted from plasma by treating it with proteinase to remove plasma proteins and recovered with endogenous plasma glycosaminoglycans by ethanol precipitation. Finally, DS and oversulfated DS were analyzed by fluorometric HPLC. The detection limits of DS and oversulfated DS were 10 and 20 ng, respectively. Furthermore, we demonstrated that artificial oversulfation of DS increased its biological half-life after intravenous administration to rats.