Morphological variation between non‐native lake‐ and stream‐dwelling pumpkinseed Lepomis gibbosusin the Iberian Peninsula

The objective of this study was to test if morphological differences in pumpkinseed Lepomis gibbosus found in their native range (eastern North America) that are linked to feeding regime, competition with other species, hydrodynamic forces and habitat were also found among stream‐ and lake‐ or reservoir‐dwelling fish in Iberian systems. The species has been introduced into these systems, expanding its range, and is presumably well adapted to freshwater Iberian Peninsula ecosystems. The results show a consistent pattern for size of lateral fins, with L. gibbosus that inhabit streams in the Iberian Peninsula having longer lateral fins than those inhabiting reservoirs or lakes. Differences in fin placement, body depth and caudal peduncle dimensions do not differentiate populations of L. gibbosus from lentic and lotic water bodies and, therefore, are not consistent with functional expectations. Lepomis gibbosus from lotic and lentic habitats also do not show a consistent pattern of internal morphological differentiation, probably due to the lack of lotic–lentic differences in prey type. Overall, the univariate and multivariate analyses show that most of the external and internal morphological characters that vary among populations do not differentiate lotic from lentic Iberian populations. The lack of expected differences may be a consequence of the high seasonal flow variation in Mediterranean streams, and the resultant low‐ or no‐flow conditions during periods of summer drought.     

The effects of huwentoxin-I on the voltage-gated sodium channels of rat hippocampal and cockroach dorsal unpaired median neurons

Huwentoxin-I (HWTX-I) is a 33-residue peptide isolated from the venom of Ornithoctonus huwena and could inhibit TTX-sensitive voltage-gated sodium channels and N-type calcium channels in mammalian dorsal root ganglion (DRG) neurons. However, the effects of HWTX-I on mammalian central neuronal and insect sodium channel subtypes remain unknown. In this study, we found that HWTX-I potently inhibited sodium channels in rat hippocampal and cockroach dorsal unpaired median (DUM) neurons with the IC₅₀ values of 66.1 ± 5.2 and 4.80 ± 0.58 nM, respectively. Taken together with our previous work on DRG neurons (IC₅₀ ≈ 55 nM), the order of sodium channel sensitivity to HWTX-I inhibition was insect central DUM ? mammalian peripheral > mammalian central neurons. HWTX-I exhibited no effect on the steady-state activation and inactivation of sodium channels in rat hippocampal and cockroach DUM neurons.     

Traveling EEG slow oscillation along the dorsal attention network initiates spontaneous perceptual switching

An ambiguous figure such as the Necker cube causes spontaneous perceptual switching (SPS). The mechanism of SPS in multistable perception has not yet been determined. Although early psychological studies suggested that SPS may be caused by fatigue or satiation of orientation, the neural mechanism of SPS is still unknown. Functional magnetic resonance imaging (fMRI) has shown that the dorsal attention network (DAN), which mainly controls voluntary attention, is involved in bistable perception of the Necker cube. To determine whether neural dynamics along the DAN cause SPS, we performed simultaneous electroencephalography (EEG) and fMRI during an SPS task with the Necker cube, with every SPS reported by pressing a button. This EEG–fMRI integrated analysis showed that (a) 3–4 Hz spectral EEG power modulation at fronto-central, parietal, and centro-parietal electrode sites sequentially appeared from 750 to 350 ms prior to the button press; and (b) activations correlating with the EEG modulation traveled along the DAN from the frontal to the parietal regions. These findings suggest that slow oscillation initiates SPS through global dynamics along the attentional system such as the DAN.     

From neurodevelopment to neurodegeneration: the interaction of neurofibromin and valosin-containing protein/p97 in regulation of dendritic spine formation

Both Neurofibromatosis type I (NF1) and inclusion body myopathy with Paget''s disease of bone and frontotemporal dementia (IBMPFD) are autosomal dominant genetic disorders. These two diseases are fully penetrant but with high heterogeneity in phenotypes, suggesting the involvement of genetic modifiers in modulating patients'' phenotypes. Although NF1 is recognized as a developmental disorder and IBMPFD is associated with degeneration of multiple tissues, a recent study discovered the direct protein interaction between neurofibromin, the protein product of the NF1 gene, and VCP/p97, encoded by the causative gene of IBMPFD. Both NF1 and VCP/p97 are critical for dendritic spine formation, which provides the cellular mechanism explaining the cognitive deficits and dementia found in patients. Moreover, disruption of the interaction between neurofibromin and VCP impairs dendritic spinogenesis. Neurofibromin likely influences multiple downstream pathways to control dendritic spinogenesis. One is to activate the protein kinase A pathway to initiate dendritic spine formation; another is to regulate the synaptic distribution of VCP and control the activity of VCP in dendritic spinogenesis. Since neurofibromin and VCP/p97 also regulate cell growth and bone metabolism, the understanding of neurofibromin and VCP/p97 in neurons may be applied to study of cancer and bone. Statin treatment rescues the spine defects caused by VCP deficiency, suggesting the potential role of statin in clinical treatment for these two diseases.     

Chemical phenotypes of P2X2 purinoreceptor immunoreactive cell bodies in the area postrema

Purines such as adenosine 5'-triphosphate (ATP) act as extracellular messengers through specific purinergic receptors. Three different classes of purinergic receptors have been identified and termed P1, P2X, and P2Y. The purinergic receptor subunit P2X2 is a ligand-gated ion channel that is widely expressed by neurons in the CNS. In the brainstem medulla oblongata, the ionotropic P2X2 receptor (P2X2R) is enriched in the area postrema (AP). Two different antisera to P2X2R were used to determine the chemical nature of P2X2R immunoreactive cell bodies in the rat AP, an area lacking a blood-brain barrier. Subcellularly, P2X2R immunoreactivity was located to the periphery of individual cell bodies. The majority of P2X2R-immunoreactive cells were shown to contain tyrosine hydroxylase (TH) (63.5 ± 7.7%) and dopamine β-hydroxylase (61.5 ± 5.1%). Phenylethanolamine N-methyltransferase (PNMT)-containing cells were not detected in the AP, supporting a noradrenergic nature of P2X2R cells in the AP. There were no P2X2R-immunoreactive cells in the AP that contained the GABA-synthesizing enzyme glutamic acid decarboxylase 65. Only single vesicular glutamate transporter 2-immunoreactive cell bodies that were not P2X2R-positive were demonstrated in the AP. Some P2X2R-positive cells in the AP were immunoreactive for the neuropeptides substance P and pituitary adenylate cyclase-activating polypeptide, whereas dynorphin-, enkephalin-, or cholecystokinin-positive cells were not P2X2R-immunoreactive. Presence of P2X2R in a majority of noradrenergic cells of the AP implies that ATP may have a regulatory action on neuronal noradrenaline release from the AP, a circumventricular organ with a strategic position enabling interactions between circulating substances and the central nervous system.     

Neonatal fluoxetine exposure alters motor performances of adolescent rats

Growing evidence from human and animal studies has shown adverse consequences of maternal usage of antidepressants in their newborn babies. To study the effects of early antidepressant exposure on motor function later in life, we treated neonatal rat pups with fluoxetine (FLX), a selective serotonin reuptake inhibitor (SSRI)-type antidepressant, from the day of birth to postnatal day 4 and examined motor performance during adolescence. FLX-treated rats had reduced locomotor activities in an open field and poorer motor performance on an accelerating rotarod compared to the control group of saline-treated animals. Nevertheless, the poorer motor performance largely improved after repetitive practices. To elucidate the structural alterations in the motor system, we examined the structure of neurons in motor-related brain regions. The shape, density, and soma size of cerebellar Purkinje cells were comparable in the two groups, however, density of dendritic spine in medial spiny neurons of striatum and Layer 5 pyramidal neurons in the primary motor cortex (M1) were reduced in FLX-rats. Furthermore, the basilar dendrites in M1 Layer 5 neurons had reduced dendritic complexity than those of the control animals. The impaired dendritic structure in striatal and cortical neurons in FLX-treated rats might account for their poorer motor performances. Together, the structure and function of the motor system are affected by early FLX exposure, the long-term effects of early exposure to SSRI-type antidepressants should be concerned.     

Sardine early survival, physical condition and stress after introduction to captivity

The main factors that affect early survival, physical damage and stress reactions of sardine Sardina pilchardus after live capture and introduction to captivity were examined. A total of 2800 sardines were captured alive from commercial purse seiners in five trials off southern Portugal and monitored for 4 weeks in aquaculture tanks. Survival rates varied considerably between trials (from <20 to >80% after a month), with most deaths occurring in the first 5 days. Sardine early survival was affected by factors related to conditions at sea (catch composition, sea temperature and transportation density), during introduction to captivity (magnitude of thermal shock, land transportation duration and use of antibacterial treatment) and, possibly, their interaction. Physical damage was related to the probability of dying, with fish that died during the first week showing significantly higher scale loss and larger caudal fin erosion that those that were alive in the same period. For all stress variables measured (blood haematocrit, cortisol, glucose and ions in the plasma), the most extreme values were attained during introduction to captivity or in the first hours after. After 2 weeks in captivity, most variables had returned to levels close to those observed at the onset of purse-seine fishing, suggesting that maintenance conditions were adequate to permit a rapid recovery from fishing and transport stress.     

Tegumental ultrastructure of adult Gynaecotyla squatarolae (Digenea: Microphallidae)

Gynaecotyla squatarolae (Digenea: Microphallidae) adult flukes were recovered from experimental chicks at day 4-6 post-infection and their tegumental ultrastructure was observed with a scanning electron microscopy. They were pyriform in shape, and their anterior halves were concaved ventrally. The whole body surface was covered with tegumental spines, which were wide and 16-17 digitated between oral and ventral suckers. The density of spines and number of digits decreased posteriorly. The oral sucker was subterminal and the excretory pore was at the posterior end of the worm. Two ventral suckers were similar in appearance and protruded near midline of the worm. The genital atrium was dextral to the small ventral sucker. The dorsal surface was covered with tegumental spines, but the spines were sparser than on the ventral surface. On the middle portion of the dorsal surface, a small opening presumed to be the Laurer's canal was seen. From these findings, it has been confirmed that the adult G. squatarolae has unique characteristics in the surface ultrastructure.     

Neuropeptide FF2 receptor distribution in the human brain. An immunohistochemical study

Human neuropeptide FF2 (hFF2) receptor has been postulated to mediate central autonomic regulation by virtue of its ability to bind with high affinity to many amidated neuropeptides. In the present immunohistochemical study, we identified hFF2 positive neurons in the forebrain and medulla oblongata of individuals, who died suddenly of mechanical trauma or hypothermia. Morphologically, these neurons demonstrated features identified with both projection neurons and interneurons. In the forebrain, the highest density of hFF2 expressing neurons was observed in the anterior amygdaloid area and dorsomedial hypothalamic nucleus, especially in its caudal part. A lesser density of hFF2 neurons was identified in the ventromedial hypothalamic nucleus, lateral and posterior hypothalamic areas whereas few cells were visualized in the paraventricular hypothalamic nucleus, perifornical nucleus, horizontal limb of the diagonal band, ventral division of the bed nucleus of the stria terminalis, nucleus basalis of Meynert and ventral tegmental area. In the medulla, significant numbers of hFF2 neurons were observed in the dorsal motor nucleus of vagus and to a lesser extent in the area of catecholaminergic cell groups, A1/C1. These data provide first immunohistochemical evidence of hFF2 localization in the human brain, which is consistent with that reported for tissue distribution of FF2 mRNA and FF2 binding sites within the brain of a variety of mammalian species. The distribution of hFF2 may help in identifying the role of amidated neuropeptides in the human brain within the context of central autonomic and neuroendocrine regulation.