Basolateral membranes of Aplysia californica foregut epithelia contain an ATP-dependent Na /K transporter (Na /K pump or Na /K -ATPase). This Na /K pump accounts for both the intracellular Na electrochemical potential (μ̄) being less than the extracelluar Na and the intracellular K being more than the extracellular K . Also, K channel activity resides in both luminal and basolateral membranes of the Aplysia foregut epithelial cells. Increased activity of the Na /K pump, coupled to luminal and basolateral membrane depolarization altered the K transport energetics across the basolateral membrane to a greater extent than the alteration in K transport energetics across the luminal membrane. These results suggest that K transport, either into or out of the Aplysia foregut epithelial cells, is rate-limiting at the basolateral membrane.

The circadian clock is entrained to the diurnal alteration of environmental conditions such as light and temperature, but the molecular mechanism underlying the entrainment is not fully understood. In the present study, we employed a differential display-based screening for a set of genes that are induced by light in the chick pineal gland, a structure of the central clock entrainable to both light and temperature changes. We found that the level of the mRNA encoding chicken heat shock protein 90 α (cHSP90α) was rapidly elevated in the pineal gland within a 5-min exposure of chicks to light. Furthermore, the pineal cHsp90α mRNA was expressed rhythmically under both 12-hr light/12-hr dark (LD) cycles and constant dark (DD) conditions. The total amount of the pineal cHSP90α protein was, however, kept at nearly constant levels under LD cycles, and immunohistochemical analyses of the pineal cHSP90α showed invariable localization at the cytoplasm throughout the day. In vivo measurement of the chick pineal temperature demonstrated its light-dependent and time-of-day-dependent change, and the profile was very similar to that of the pineal cHsp90α mRNA level. These observations suggest that the in vivo temperature change regulates the expression of temperature-responsive genes including cHsp90α in the pineal gland. The temperature change may induce a phase-shift of the pineal clock, thereby facilitating its efficient entrainment to environmental LD cycles.

This study aims to give an integrative description of the correlation of physiological parameters of osmoregulation and the habitats of the four common Uca species in Taiwan. Uca arcuata inhabits areas close to fresh water in the upper beach. Uca formosensis is only found in the areas near the mean high water of spring tide where there is a clear dry-wet transition within a single semilunar cycle. Uca vocans is found in the lower intertidal zone. Uca lactea, the most widely distributed species, can easily be found on most muddy sand shores. The number of gills was observed and histological sectioning performed on each species. The range of salinity in which the fiddler crabs maintained their hemolymph osmolality without any significant change (i.e. osmoregulatory homeostasis) and the gill Na , K -ATPase activity were determined by transferring individuals to different salinity tanks. The results suggest that U. formosensis and U. lactea can sustain a wider range of salinity change through both modification in gill morphology and Na , K -ATPase activity. Uca arcuata can regulate in a hypo-osmotic condition and U. vocans tends to be a weak-osmoregulator.

The antigenic structure of the bovine rhodopsin molecule was investigated by using a bovine rhodopsin-specific monoclonal antibody designated Rh29. Competition assay with sealed intact disks and broken disks indicated that the antibody-binding region was localized in the intradiscal surface. An antigenic peptide obtained by a cyanogene bromide cleavage of rhodopsin was purified and determined as residues 2–39 in the amino acid sequence.

Further analysis suggested that the antigenic determinant included at least residues 21–25. These results were consistent with the structural model for membrane topology of rhodopsin. The antigenicity of the rhodopsin was compared among several states. The antibody bound to both ammonyx LO-solubilized unbleached and bleached rhodopsin. In contrast, upon membrane-embedded rhodopsin, unbleached one was 100-times less antigenic than bleached one. The results suggested that the segment around the determinant of membrane-embedded rhodopsin should undergo a structural change upon absorption of light.

Rh29 detected a band corresponding to bovine, porcine and octopus opsins in immunoblotting. Protein blot of crayfish rhabdome did not show any reactive band. These bands except for crayfish reacted with concanavalin A as well. The N-terminal structure may, therefore, conserved between mammal and erthropoda and diverge between them and cepharopoda.

Asexual worms of fissiparous strain of the planarian Dugesia ryukyuensis switch from asexual to sexual reproduction, if they are fed with sexually mature worms of Bdellocephala brunnea. This suggests that the sexually mature worms have a sexualizing substance(s) that induces the sexuality in the asexual worms. Here, we found by analysis of the sexualization that the cessation of the fission, namely their asexual reproduction, occurs immediately after the acquisition of sexuality. This result suggests that the downstream mechanisms induced by the putative sexualizing substance in B. brunnea become responsible for the cessation of fission. We also found that the decapitation triggers fission in the worms even after the acquisition of sexuality if they are not sexually mature, while the fully sexualized worms never fission even though they are decapitated. This result suggests that the cessation of fission takes place via at least two steps: (1) the mechanisms associated with the cephalic system; (2) other mechanisms independent of cephalic control.

Asexual worms of an exclusively fissiparous strain (the OH strain) of the planarian Dugesia ryukyuensis keep developing hermaphroditic reproductive organs and eventually undergo sexual reproduction instead of asexual reproduction, namely fission, if they are fed with sexually mature worms of an exclusively oviparous planarian, Bdellocephala brunnea, suggesting that the sexually mature worms has a sexualizing substance(s). The fully sexualized worms no longer need the feeding on sexual worms to maintain the sexuality. Here, we demonstrate that the sexualized worms produce enough of their own sexualizing substance similar to that contained in B. brunnea. In case of surgical ablation of the sexualized worms, the fragments with sexual organs regenerate to become sexual, while those without sexual organs, namely head fragments, regenerate to return to the asexual state. The asexual regenerants from the sexualized worms are also fully sexualized by being fed with B. brunnea. Additionally, it was reported that head region in sexually mature worms lacks the putative sexualizing substance necessary for complete sexualization (Sakurai, 1981). These results suggest that the fragments without sexual organ lack enough of an amount of the putative sexualizing substance and the sexuality is maintained by the sexualizing substance contained in the sexualized worms.

Spermatogenesis was histologically examined in non-breeding male of the naked mole rat (Heterocephalus glaber) using a light microscopy. Spermatogonia, spermatocytes and spermatids were confirmed in the seminiferous tubules. However, the spermatogenesis was disordered, and many spermatocytes and spermatids were sloughing. Sperms could not be seen in the lumen of the tubules. The characteristic accumulation of interstitial cells was the most noteworthy. In the immunohistochemistry for cytochrome P450 side-chain cleavage enzyme, immunoreactions were not entirely distributed in each interstitial cell, although positive reactions were scattered in the interstitial cell-mass. The findings indicate that few interstitial cells act as a testosterone-synthesizing apparatus in the characteristic structure with accumulated cell-mass. From the immunohistochemical data we suggest the possibility that spermatogonia and Sertoli cells may secrete 17β-estradiol. We also suggest that 17β-estradiol from spermatogonia and Sertoli cells may inhibit the interstitial cells from synthesizing and secreting testosterone and may suppress the later stages of the spermatogenesis to induce apoptosis of germ cells. The TUNEL methods demonstrated that cell death occurred in some spermatocytes in non-breeding males.

Levels of urinary progesterone and estradiol-17β were measured twice a week in a female dugong, Dugong dugon, in captivity for two years from April 1996 to April 1998. The dugong showed 14 ovarian cycles during the period of study. Concentrations of progesterone ranged from 0.01ng/mg creati-nine (Cr) to 1.94ng/mg Cr and the length of estrous cycle was 53.6±8.6 (mean±SEM) days based on intervals of urinary progesterone peak-to-peak measurements. Concentrations of urinary estradiol-17β ranged from 0.9pg/mgCr to 23.7pg/mgCr, and tended to peak just prior to elevations of progesterone during the first year of study. This is the first report demonstrates that the ovulatory cycle of the dugong is about 50 days. The present findings suggest that measurement of urinary progesterone is a useful method to detect ovarian cycle of the dugong in captivity.

Short photoperiod induces physiological changes connected to the wintering of the tundra vole, Microtus oeconomus. The aim of the present study was to investigate the effects of continuous melatonin treatment on selected hormones and enzyme activities associated with energy metabolism in the species. Liver, kidney, and muscle glycogen concentrations and glycogen phosphorylase activities, as well as liver and kidney glucose-6-phosphatase and lipase esterase activities were determined. Plasma leptin, ghrelin, thyroxine, testosterone, cortisol, and melatonin concentrations were also measured. Exogenous melatonin stimulated gluconeogenesis, increased glycogen stores, and reduced fat mobilization in kidneys. Melatonin treatment also increased the food intake of the voles. This may have been mediated via elevated ghrelin levels of the melatonin-treated animals, as ghrelin is known to increase appetite of rodents. Winter metabolism of the species does not seem to require accumulation of fat or extra stores of liver or muscle glycogen. On the contrary, successful wintering of the tundra vole presumably depends on continuous food availability.

Hyperthermia of fetal rats is known to cause malformations of various organs including brain. The present study was carried out to investigate the effect of the hyperthermia-induced brain damages on the development of the adenohypophysis. Mother rats of Day 9.5 of pregnancy were anesthetized and immersed in hot water (43°C) for 15 min. At Day 21.5 of gestation, fetuses were removed by caesarian section and examined for exencephaly. Hyperthermal stress induced varying degrees of exencephaly in 36% of surviving fetal rats. In extreme cases a considerable part of head was lost. Even in those fetuses with severe brain deformities, the hypophysial stalk and neural lobe were present though they were markedly underdeveloped. In exencephalic fetuses, no immunoreactive vasopressin was detected in the neural lobe of the hypophysis. Immunohistochemical examination of the adenohypophysis showed that exencephaly caused a marked decrease in the number of growth hormone (GH)-producing cells. Other types of hormone-producing cells appeared to be unaffected by brain anomaly. The reason for a decreased population of GH cells in exencephalic fetuses is discussed in relation to their adrenocortical hypotrophy.

Pogonophores are tube worms that live in reducing deep-sea waters where sunlight does not penetrate. They are highly adapted for their special habitat in lacking guts and possessing endosym-biotic chemosynthetic bacteria. Because of these peculiar characteristics, it is not yet clear whether they should be classified as annelids or not. Electron-microscopic observations of sections of a Japanese pogonophore (Oligobrachia mashikoi) show that the body wall has circular and longitudinal muscular systems. These muscular systems, however, differ from the annelid (Branchiura sowerbyi) in these ways: (1) The outer circular muscle of the pogonophore was constructed of smooth muscle cells. In contrast, that of the annelid was composed of obliquely-striated muscle cells, even though the cells were small and bore undeveloped characteristics. (2) The inner longitudinal muscle of the pogonophore was constructed of undeveloped obliquely-striated muscle cells, whereas that of the annelid was composed of well-developed ones. These observations suggest that this pogonophore can not be classified as an annelid, although many previous studies have placed pogonophores in that phylum.

Organisms sometimes change their phenotype to maximize fitness according to local environments. If the frequency of the broad-headed “cannibal” morph in the larvae of the salamander Hynobius retardatus has been evolutionarily maintained at a certain level within a population as a result of local adaptation, variations in its frequency should be found among different populations with environmental variation. We investigated whether variations in the frequency of the broad-headed morph were present in 2 different populations, Nopporo (a low-density population) and Erimo (a high-density population), by raising larvae from the respective populations under the same experimental conditions. The occurrence rate of the broad-headed “cannibal” morph was significantly different between the 2 populations when examined with different experimental larval densities. These results suggest that the reaction norm with respect to the frequency of the broad-headed morph is different between the Nopporo and Erimo populations. Because the local populations are assumed to be selected for under different environments, the different reaction norm might have evolved in response to different selection pressures.

Several mechanisms of fish ontogenetic dietary shifts, which have important ecological implications, have been proposed. We studied the mechanism of dietary shifts of a benthophagous fish Goniistius zonatus, focusing on the effect of foraging on calcareous algal mat, one of its main feeding substrates, through comparison between two local populations (Morode and Arakashi) with different feeding ecology. The studied fish (11–29 cm SL) fed on various kinds of small invertebrates inhabiting the substrates, using a suctorial feeding mode without visual discrimination towards individual prey. At Morode, gut contents of small fish consisted of more epifaunal and less infaunal organisms than those of large fish, that is, mainly small crustaceans in small fish, and many invertebrates other than crustaceans in large fish. By contrast, at Arakashi, gut contents consisted mostly of epifaunal crustaceans regardless of fish size, i.e., fish showing no dietary shifts. At Morode, G. zonatus took foods mostly from thick calcareous algal mat, whereas fish foraged mainly on thin algal mat and bare rocks at Arakashi, the difference being due to the local differences in the substrate component. The algal mat of Morode harbored much larger amount of infaunal animals than any substrates of Arakashi. At Morode, large fish more forcefully and deeply thrust the mouth into thick algal mat than small fish, and was likely to suck up more infaunal prey using great suctorial force. The comparison clearly indicates that the dietary shifts of G. zonatus at Morode resulted from size-related efficiency in straining foods from heterogeneous micro-topography of thick algal mat.