Mechanisms of H+ modulation of glycinergic response in rat sacral dorsal commissural neurons

Many ionotropic receptors are modulated by extracellular H+. So far, few studies have directly addressed the role of such modulation at synapses. In the present study, we investigated the effects of changes in extracellular pH on glycinergic miniature inhibitory postsynaptic currents (mIPSCs) as well as glycine-evoked currents (I-Gly) in mechanically dissociated spinal neurons with native synaptic boutons preserved. H+ modulated both the mIPSCs and I-Gly, biphasically, although it activated an amiloride-sensitive inward current by itself. Decreasing extracellular pH reversibly inhibited the amplitude of the mIPSCs and I-Gly, while increasing external pH reversibly potentiated these parameters. Blockade of acid-sensing ion channels (ASICs) with amiloride, the selective antagonist of ASICs, or decreasing intracellular pH did not alter the modulatory effect of H+ on either mIPSCs or I-Gly, H+ shifted the EC50 of the glycine concentration-response curve from 49.3 +/- 5.7 muM at external pH 7.4 to 131.5 +/- 8.1 muM at pH 5.5, without altering the Cl- selectivity of the glycine receptor (GlyR), the Hill coefficient and the maximal I-Gly, suggesting a competitive inhibition of I-Gly by H+. Both Zn2+ and H+ inhibited I-Gly. However, H+ induced no further inhibition of I-Gly in the presence of a saturating concentration of Zn2+. In addition, H+ significantly affected the kinetics of glycinergic mIPSCs and I-Gly. It is proposed that H+ and/or Zn2+ compete with glycine binding and inhibit the amplitude of glycinergic mIPSCs and I-Gly. Moreover, binding of H+ induces a global conformational change in GlyR, which closes the GlyR Cl- channel and results in the acceleration of the seeming desensitization of IGly as well as speeding up the decay time constant of glycinergic mIPSCs. However, the deprotonation rate is faster than the unbinding rate of glycine from the GlyR, leading to reactivation of the undesensitized GlyR after washout of agonist and the appearance of a rebound I-Gly. H+ also modulated the glycine cotransmitter, GABA-activated current (I-GABA). Taken together, the results support a 'conformational coupling' model for H+ modulation of the GlyR and suggest that W may act as a novel modulator for inhibitory neurotransmission in the mammalian spinal cord.

Study on the reproductive biology of Pinctada fucata (Gould) (Mollusca: Pteriidae)

Annual cycle of gonad development and spawning in pearl oyster, Pinctada ficata (Gould) in Nakhiloo, Northeast Persian Gulf, was investigated over two years from August 1994 to June 1996. Gonadal condition was assessed by staging criteria to describe gametogenic development from histological preparations of randomly collected individuals of all sizes. A bimodal gametogenic pattern with summer and autumn spawning periods was evident throughout the study. Gametogensis commenced in November-December which proceeded by major gonadal maturation during February-April. Summer spawning was observed from April to July with major spawning at the latter end. During spawning peak in July, low level of gametogensis was noticed. Gametogenic activity was picked up again in August-September which proceeded by autumn spawning from September to December. Towards the end of spawning season, incidence of gonadal inactivation increased. Minimum level of gonadal activity was observed in November. Temperature regime appears to have influential role in regulation of gametogenic and spawning processes. Gonadal development and spawning trends were similar in both sexes. P. radiaata was found to be protandrous hermaphrodite which matured as a male at shell height greater than 20 mm. Biseivality was uncommon and the sex ratio was about 1:1. Ultrastructure of gametes were investigated in the Pictada fucata (Gould). "Auxiliary cells" closely accociated with developing oocytes were observed. Each oocyte seems to be associated with only one secretory cell. which is characterized by an abundant rough endoplasmic reticulum at the onset of vitellogenesis. Contact between this cell and a developing oocytes is maintained by a desmosome-like junction which can be observed when the vitelline coat is formed. these "auxiliary or nursing cells" seem to play a tropic role in vitellogenesis, and may be involved in the formation of the vitelline coat of the oocytes. Oocytic degeneration is observed in this species, it is a continuous phenomenon of varing intensity throughout the year. The ultrastructural changes resulting in lysis of the oocyte are described. Mature spermatozoa consist of a broad, cap-shaped acrosomal vesicle, subacrosomal material, a round nucleus, two triplet substructure centrioles surrounded by four spherical mitochondria, and a flagellum anchored to the distal centriole and plasma membrane. Spermatozoa of Plucata closley resemble to those of other investigated Pteriidae. Changes in proximate composition of soft tissue and gonadal cycle of Pinctada fucata was studied. Mobilization and utilization of stored reserves are apparent during gametogenesis and gonadal maturation. Protein reserves are utilized during spermatogenesis while reserved carbohydrates form the main energy donor in oogenesis. The role of lipid as am.: energy reserve is second to that of carbohydrate.

La reproducción de la merluza en el Mar Argentino (Merlucciidae, Meluccius merluccius hubbsi) : 1. Descripción histológica del ciclo del ovario de merluza

The present paper deals on the histological description of the hake ovary made on the basis of gonad observations of 394 females during the period April 1966 March 1967. The material was obtained from weekly sampling of commercial catches carried out at the Institute of Marine Biology (Prov. Buenos Aires, Argentina). The anatomical and histological description of the standard ovary and the adopted terminology are given. The maturation process is divided into five periods, from ovocyte formation to yolked ovocyte formation, with its histological description. Ovary changes are analyzed on detail. The following conclusions were outlined: 1. Analysis demonstrated that although some specimens were totally spawned others, at the end of the spawning period, retaining a great number of ovocytes in different maturity stages. Therefore, postspawners have been classified as follows: Postspawned II : This stages is characterized by the empty ovarian structure, with ovocytes in stage II, which will remain in the resting phase untill next spawning season. Postspawned III and IV: Their main characteristics are: tissue destruction, bloody residuals and remaining ovocytes in stage III and IV, respectively. 2. Some transformations were found in ovaries of postspawned III and IV. They are classified as follows, according to its origin and structure: Developed from follicular cell membrane – a) Glandular formations, b) Epiteloid formations - Originated from remaining ovocytes, c) Ovocyte disintegration, d) Ovocyte with follicular cell infiltration. 3. All those structures derived from postpawners III and IV have a temporary character and will be reabsorbed. Their presence delay the recuperation of the organ and its reproductive functions. Consequently, the possibility of those structures acting as control mechanisms is suggested. 4. Transformations pointed out in paragraph Nº 2 prevent the possibility of consecutive spawning originated from the remaining ovocytes (II and IV). 5. No structures originated from postspawners III and IV were found during summer season. 6. Reproductive cycle of hake has been described monthly. It was observed that maturing ovaries predominate in summer (November-December).

Effects of gamma-aminobutyric acid, progesterone and ionophore A23187 on acrosome reaction of tree shrew sperm in vitro: examination of acrosome reaction with an improved fluorescence microscopy

A number of acrosome reaction (AR) initiators have been found to be effective in inducing AR of human, laboratory and domestic animal sperm. Using an improved simple fluorescence microscopy, effects of gamma-aminobutyric acid (GABA), progesterone and ionophore A23187 on sperm AR of tree shrew, a useful animal model in biomedical research, have been investigated. Spontaneous AR in 4.92-7.53% of viable sperm was observed. Complete AR in 10.31-18.25% of viable tree shrew sperm was obviously induced by 5 mu M and 10 mu M calcium ionophore A23187, 1 mM GABA, and 5 mu M progesterone, and there were no significant differences between their abilities to initiate complete AR. No significant differences of AR percentages between 1- and 2-h treatments with A23187, progesterone and/or GABA were observed. These results suggested that the responses of tree shrew sperm to these AR initiators are similar to that of human and other mammalian sperm. (C) 1997 Elsevier Science B.V.

A Structured Model of Video Reproduces Primary Visual Cortical Organisation

The visual system must learn to infer the presence of objects and features in the world from the images it encounters, and as such it must, either implicitly or explicitly, model the way these elements interact to create the image. Do the response properties of cells in the mammalian visual system reflect this constraint? To address this question, we constructed a probabilistic model in which the identity and attributes of simple visual elements were represented explicitly and learnt the parameters of this model from unparsed, natural video sequences. After learning, the behaviour and grouping of variables in the probabilistic model corresponded closely to functional and anatomical properties of simple and complex cells in the primary visual cortex (V1). In particular, feature identity variables were activated in a way that resembled the activity of complex cells, while feature attribute variables responded much like simple cells. Furthermore, the grouping of the attributes within the model closely parallelled the reported anatomical grouping of simple cells in cat V1. Thus, this generative model makes explicit an interpretation of complex and simple cells as elements in the segmentation of a visual scene into basic independent features, along with a parametrisation of their moment-by-moment appearances. We speculate that such a segmentation may form the initial stage of a hierarchical system that progressively separates the identity and appearance of more articulated visual elements, culminating in view-invariant object recognition.

The reproductive traits of brown trout (Salmo trutta fario L.) from the Yadong River, Tibet

Some key aspects of the reproductive strategy of the brown trout (Salmo trutta fario L.) in the Yadong River, Tibet, including spawning season, age at sexual maturity, fecundity and egg size, have been studied. The majority of the samples were less than 215 mm and age ranged from 1 to 4 in both sexes, indicating that the majority of the fish were younger and the pressure by overfishing was high. The spawning periodicity was determined to be between the end of October and January, mainly in November and December. The ratio of male to female brown trout population (1.29:1 with P > 0.05) suggested no sex significant differences, although males were significantly more abundant than females in October (P < 0.0001) on monthly basis. Age and size of males and females at maturity was different and males matured earlier than females. Fecundity was markedly correlated with their body weight (P < 0.001, r = 0.9255), standard length (P < 0.01, r = 0.8879), and gonad weight (P < 0.001, r = 0.9366). The mean size of mature eggs in the spawning season was: 4.0 +/- 0.45 mm and tended to increase along with the female spawners size (P < 0.001, r = 0.9641). Further researches about the brown trout population in the Yadong River should be conducted on issues such as artificial reproduction, culture, conservation, management, and restocking.

Comparative responses in rare minnow exposed to 17 beta-estradiol during different life stages

Present in the excrement of humans and animals, 17 beta-estradiol (E-2) has been detected in the aquatic environment in a range from several nanograms to several hundred nanograms per liter. In this study, the sensitivities of rare minnows during different life stages to E-2 at environmentally relevant (5, 25, and 100 ng l(-1)) and high (1000 ng l(-1)) concentrations were compared using vitellogenin (VTG) and gonad development as biomarkers under semistatic conditions. After 21 days of exposure, VTG concentrations in whole-body homogenates were analyzed; the results indicated that the lowest observed effective concentration for VTG induction was 25 ng l(-1) E-2 in the adult stage, but 100 ng l(-1) E-2 in the larval and juvenile stages. After exposure in the early life stage, the larval and juvenile fish were transferred to clean water until gonad maturation. No significant difference in VTG induction was found between the exposure and control groups in the adults. However, a markedly increased proportion of females and appearance of hermaphrodism were observed in the juvenile-stage group exposed to 25 ng l(-1) E-2. These results showed that VTG induction in the adult stage is more sensitive than in larval and juvenile stages following exposure to E-2. The juvenile stage may be the critical period of gonad development. Sex ratio could be a sensitive biomarker indicating exposure to xenoestrogens in early-life-stage subchronic exposure tests. The results of this study provide useful information for selecting sensitive biomarkers properly in aquatic toxicology testing.

The search for the IFN-gamma receptor in fish: Functional and expression analysis of putative binding and signalling chains in rainbow trout Oncorhynchus mykiss

Interferons (IFNs), consisting of three major subfamilies, type I, type II (gamma) and type III (lambda) IFN, activate vertebrate antiviral defences once bound to their receptors. The three IFN subfamilies bind to different receptors, IFNAR1 and IFNAR2 for type I IFNs, IFN gamma R1 and IFN gamma R2 for type II IFN, and IL-28R1 and IL-10R2 for type III IFNs. In fish, although many types I and II IFN genes have been cloned, little is known about their receptors. In this report, two putative IFN-gamma receptor chains were identified and sequenced in rainbow trout (Oncorhynchus mykiss), and found to have many common characteristics with mammalian type II IFN receptor family members. The presented gene synteny analysis, phylogenetic tree analysis and ligand binding analysis all suggest that these molecules are the authentic IFN gamma Rs in fish. They are widely expressed in tissues, with IFN gamma R1 typically more highly expressed than IFN gamma R2. Using the trout RTG-2 cell line it was possible to show that the individual chains could be differentially modulated, with rIFN-gamma and rIL-1 beta down regulating IFN gamma R1 expression but up regulating IFN gamma R2 expression. Overexpression of the two receptor chains in RTG-2 cells revealed that the level of IFN gamma R2 transcript was crucial for responsiveness to rIFN-gamma, in terms of inducing gamma IP expression. Transfection experiments showed that the two putative receptors specifically bound to rIFN-gamma. These findings are discussed in the context of how the IFN gamma R may bind IFN-gamma in fish and the importance of the individual receptor chains to signal transduction. (c) 2009 Elsevier Ltd. All rights reserved.

Simultaneous determination of microcystin contaminations in various vertebrates (fish, turtle, duck and water bird) from a large eutrophic Chinese lake, Lake Taihu, with toxic Microcystis blooms

This is the first to conduct Simultaneous determination of microcystin (MC) contaminations in multi-groups of vertebrates (fish, turtle, duck and water bird) from Lake Taihu with Microcystis blooms. MCs (-RR, -YR, -LR) in Microcystis scum was 328 mu g g(-1) DW. MCs reached 235 mu g g(-1) DW in intestinal contents of phytoplanktivorous silver carp, but never exceeded 0.1 mu g g(-1) DW in intestinal contents of other animals. The highest MC content in liver of fish was in Carassius auratus (150 ng g(-1) DW), followed by silver carp and Culter ilishaeformis, whereas the lowest was in common carp (3 ng g(-1) DW). In livers of turtle, duck and water bird, MC content ranged from 18 to 30 ng g(-1) DW. High MC level was found in the gonad, egg yolk and egg white of Nycticorax nycticorax and Anas platyrhynchos, suggesting the potential effect of MCs on water bird and duck embryos. High MC contents were identified for the first time in the spleens of N. nycticorax and A. platyrhynchos (6.850 and 9.462 ng g(-1) DW, respectively), indicating a different organotropism of MCs in birds. Lakes with deaths of turtles or water birds in the literatures had a considerably higher MC content in both cyanobacteria and wildlife than Lake Taihu, indicating that toxicity of cyanobacteria may determine accumulation level of MCs and consequently fates of aquatic wildlife. (C) 2009 Elsevier B.V. All rights reserved.