When endemic coral-reef fish species serve as models: endemic mimicry patterns in the Marquesas Islands.

This article documents several cases of widespread species, which usually mimic other widespread species throughout the Indo-Pacific, using endemic Marquesan species as a model and displaying endemic mimicry patterns. This discovery adds a new line of evidence to the uniqueness of the Marquesas Islands, which not only host a high number of endemic reef-fish species, but also endemic mimicry patterns.

Number and location of drainage catheter side holes: in vitro evaluation.

AIM: To evaluate the influence of number and location of catheter shaft side holes regarding drainage efficiency in an in vitro model. MATERIALS AND METHODS: Three different drainage catheter models were constructed: open-ended model with no side holes (one catheter), unilateral side hole model (six catheters with one to six unilateral side holes), and bilateral side hole model (six catheters with one to six bilateral side holes). Catheters were inserted into a drainage output-measuring device with a constant-pressure reservoir of water. The volume of water evacuated by each of the catheters at 10-second intervals was measured. A total of five trials were performed for each catheter. Data were analysed using one-way analysis of variance. RESULTS: The open-ended catheter had a mean drainage volume comparable to the unilateral model catheters with three, four, and five side holes. Unilateral model catheters had significant drainage volume increases up to three side holes; unilateral model catheters with more than three side holes had no significant improvement in drainage volume. All bilateral model catheters had significantly higher mean drainage volumes than their unilateral counterparts. There was no significant difference between the mean drainage volume with one, two, or three pairs of bilateral side holes. Further, there was no drainage improvement by adding additional bilateral side holes. CONCLUSION: The present in vitro study suggests that beyond a critical side hole number threshold, adding more distal side holes does not improve catheter drainage efficiency. These results may be used to enhance catheter design towards improving their drainage efficiency.

Spontaneous gallbladder pathology in baboons.

BACKGROUND: Gallbladder pathology (GBP) is a relatively uncommon, naturally occurring morbidity in both baboons and humans. METHODS: A retrospective analysis was performed on 7776 necropsy reports over a 20 year period to determine the prevalence of baboon GBP. RESULTS: Ninety-seven cases of GBP were identified, yielding a 20 year population prevalence of 1.25%. GBP is more common in adult female baboons, occurring with a female to male ratio of nearly 2:1. Among gallbladder pathologies, cholecystitis (35.1%) and cholelithiasis (29.9%) were the most prevalent abnormalities, followed by hyperplasia (16.5%), edema (15.5%), amyloidosis (5.2%), fibrosis (4.1%), necrosis (4.1%), and hemorrhage (1.0%). CONCLUSION: Many epidemiologic similarities exist between GBP in baboons and humans suggesting that the baboon may serve as a reliable animal model system for investigating GBP in humans.

Ex situ conservation of plant genetic resources: global development and environmental concerns.

Conservation of plant genetic resources is achieved by protection of populations in nature (in situ) or by preservation of samples in gene banks (ex situ). The latter are essential for users of germplasm who need ready access. Ex situ conservation also acts as a back-up for certain segments of diversity that might otherwise be lost in nature and in human-dominated ecosystems. The two methods are complementary, yet better understanding of this interrelation and the role of ex situ conservation in global environmental considerations is needed. Inclusion of ex situ conservation efforts within current environmental policies conserving global diversity would focus greater international attention on the safeguarding of these efforts.

Crop germplasm conservation and developing countries.

Loss of the genetic diversity of some of the world's crops has accelerated in recent decades, with many crops becoming increasingly susceptible to diseases, pests, and environmental stresses. A global network of gene banks has therefore been established to provide plant breeders with the genetic resources necessary for developing more resistant crops that will enable farmers to maintain high yields. Most of these gene banks now store the germplasm of only the major crops such as cereals, potatoes, and grain legumes. Cultivated varieties of these crops are conserved as well as wild species that might otherwise become extinct. Tropical cash crops such as bananas and coconuts are also important food crops in many Third World countries, and more effort needs to be made to conserve the germplasm of these crops as well as of other important plants such as plantation crops, medicinal herbs, and fruit and timber trees.

Phosphorylation-deficient G-protein-biased µ-opioid receptors improve analgesia and diminish tolerance but worsen opioid side effects.

Opioid analgesics are powerful pain relievers; however, over time, pain control diminishes as analgesic tolerance develops. The molecular mechanisms initiating tolerance have remained unresolved to date. We have previously shown that desensitization of the µ-opioid receptor and interaction with ß-arrestins is controlled by carboxyl-terminal phosphorylation. Here we created knockin mice with a series of serine- and threonine-to-alanine mutations that render the receptor increasingly unable to recruit ß-arrestins. Desensitization is inhibited in locus coeruleus neurons of mutant mice. Opioid-induced analgesia is strongly enhanced and analgesic tolerance is greatly diminished. Surprisingly, respiratory depression, constipation, and opioid withdrawal signs are unchanged or exacerbated, indicating that ß-arrestin recruitment does not contribute to the severity of opioid side effects and, hence, predicting that G-protein-biased µ-agonists are still likely to elicit severe adverse effects. In conclusion, our findings identify carboxyl-terminal multisite phosphorylation as key step that drives acute µ-opioid receptor desensitization and long-term tolerance.

A common mechanism mediates long-term changes in synaptic transmission after chronic cocaine and morphine.

The mesolimbic system is known to play a role in self-administration of opioids and psychostimulants. Although morphine and cocaine act by separate cellular mechanisms initially, the present study describes a common change in synaptic regulation of dopamine cells in the ventral tegmental area 1 week after termination of chronic treatment with either drug. Normally, D1 receptor activation augmented the amplitude of a gamma-aminobutyric acid type B (GABA(B)) inhibitory postsynaptic potential (IPSP), but in drug-experienced animals, D1 receptor activation caused an inhibition of the GABA(B) IPSP. The inhibition was blocked by adenosine A1 receptor antagonists and by agents that disrupted the metabolism of cAMP. This long-lasting dopamine-adenosine interaction may be one mechanism involved in dopamine-mediated craving and relapse to drug-seeking behaviors.

Serotonin augments the cationic current Ih in central neurons.

Serotonin (5-HT) induced a slow depolarization when superfused onto neurons of the rat brainstem nucleus prepositus hypoglossi (PH) in vitro. The depolarization was associated with a decrease in cell input resistance. In voltage clamp, 5-HT caused an inward current that activated at approximately -50 mV and was present only at potentials negative to this. With hyperpolarizing voltage-clamp steps, PH neurons exhibited a slow inward current relaxation. The properties of this conductance were consistent with the cationic, nonselective current, Ih. Bath-applied 5-HT augmented Ih. Extracellular CsCl blocked both Ih and the inward current produced by 5-HT. In addition, forskolin, isobutylmethylxanthine, and 8-bromo-cAMP mimicked the inward current seen with 5-HT. The 5-HT1 agonist 5-carboxamidotryptamine produced a similar inward current. We conclude that 5-HT excites PH neurons by augmenting Ih, probably through receptor-mediated stimulation of adenylate cyclase. As Ih is found in many types of neurons, this mechanism may be a common mode of regulating cell excitability.

Opioid inhibition of Ih via adenylyl cyclase.

Opioids are coupled through G proteins to both ion channels and adenylyl cyclase. This study describes opioid modulation of the voltage-dependent cation channel, Ih, in cultured guinea pig nodose ganglion neurons. Forskolin, PGE2, and cAMP analogs shifted the voltage dependence of activation of Ih to more depolarized potentials and increased the inward current at -60 mV. Opioids had no effect on Ih alone, but reversed the effect of forskolin on Ih. This action of opioids was blocked by naloxone. Opioids had no effect on Ih in the presence of cAMP analogs, suggesting that modulation occurs at the level of adenylyl cyclase. The shift in the voltage dependence of Ih by agents that induce inflammation (i.e., PGE2) is one potential mechanism to mediate an increased excitability. Opioid inhibition of adenylyl cyclase and subsequent inhibition of Ih may be a mechanism by which opioids inhibit primary afferent excitability and relieve pain.

A RAVE about opioid withdrawal.

Control of trafficking of g protein-linked receptors is thought to be an important regulatory mechanism for receptor signaling. Finn and Whistler test the hypothesis that agonist-induced trafficking of opioid receptors regulates the development of tolerance and dependence. The results show that measures of tolerance and withdrawal to morphine are decreased under conditions where receptors are trafficked through the endocytic/recycling pathway.

Morphine produces circuit-specific neuroplasticity in the bed nucleus of the stria terminalis.

The bed nucleus of the stria terminalis (BST) is a brain structure located at the interface of the cortex and the cerebrospinal trunk. The BST is a cluster of nuclei organized in a complex intrinsic network that receives inputs from cortical and subcortical sources, and that sends a widespread top-down projection. There is growing evidence that the BST is a key component in the neurobiological basis of substance abuse. In the present study, the regulation of excitatory inputs onto identified neurons in the BST was examined in rats treated chronically with morphine. Neurons projecting to the ventral tegmental area (VTA) were identified by retrograde transport of fluorescent microspheres and recorded in the whole-cell voltage clamp configuration in brain slices. Selective excitatory inputs to these neurons were electrically evoked with electrodes placed in the medial and lateral aspects of the dorsal BST. The chronic morphine treatment selectively increased AMPA-dependent excitatory postsynaptic currents in a subset of inputs activated by dorso-lateral stimulation in the BST. Inputs activated by medial stimulation were not affected by morphine. Likewise, the inputs to neurons that did not project to the VTA were not changed by morphine. Altogether, these results extend the understanding of neuronal circuits intrinsically sensitive to drugs of abuse within the BST.

Amphetamine selectively blocks inhibitory glutamate transmission in dopamine neurons.

Amphetamine is a highly addictive psychostimulant that promotes the release of the catecholamines dopamine and norepinephrine. Amphetamine-induced release of dopamine in the midbrain inhibits the activity of dopamine neurons through activation of D2 dopamine autoreceptors. Here we show that amphetamine may also excite dopamine neurons through modulation of glutamate neurotransmission. Amphetamine potently inhibits metabotropic glutamate receptor (mGluR)-mediated IPSPs in dopamine neurons, but has no effect on ionotropic glutamate receptor-mediated EPSCs. Amphetamine desensitizes the mGluR-mediated hyperpolarization through release of dopamine, activation of postsynaptic alpha1 adrenergic receptors, and suppression of InsP3-induced calcium release from internal stores. By selectively suppressing the inhibitory component of glutamate-mediated transmission, amphetamine may promote burst firing of dopamine neurons. Through this mechanism, amphetamine may enhance phasic release of dopamine, which is important in the neural processing of reward.

Noradrenergic modulation of the hyperpolarization-activated cation current (Ih) in dopamine neurons of the ventral tegmental area.

Alterations in the state of excitability of midbrain dopamine (DA) neurons from the ventral tegmental area (VTA) may underlie changes in the synaptic plasticity of the mesocorticolimbic system. Here, we investigated norepinephrine's (NE) regulation of VTA DA cell excitability by modulation of the hyperpolarization-activated cation current, Ih, with whole cell recordings in rat brain slices. Current clamp recordings show that NE (40 microM) hyperpolarizes spontaneously firing VTA DA cells (11.23+/-4 mV; n=8). In a voltage clamp, NE (40 microM) induces an outward current (100+/-24 pA; n=8) at -60 mV that reverses at about the Nernst potential for potassium (-106 mV). In addition, NE (40 microM) increases the membrane cord conductance (179+/-42%; n=10) and reduces Ih amplitude (68+/-3% of control at -120 mV; n=10). The noradrenergic alpha-1 antagonist prazosin (40 microM; n=5) or the alpha-2 antagonist yohimbine (40 microM; n=5) did not block NE effects. All NE-evoked events were blocked by the D2 antagonists sulpiride (1 microM) and eticlopride (100 nM) and no significant reduction of Ih took place in the presence of the potassium channel blocker BaCl2 (300 microM). Therefore, it is concluded that NE inhibition of Ih was due to an increase in membrane conductance by a nonspecific activation of D2 receptors that induce an outward potassium current and is not a result of a second messenger system acting on h-channels. The results also suggest that Ih channels are mainly located at dendrites of VTA DA cells and, thus, their inhibition may facilitate the transition from single-spike firing to burst firing and vice versa.

Ion conductances affected by 5-HT receptor subtypes in mammalian neurons.

5-Hydroxytryptamine (5-HT) has both excitatory and inhibitory actions in the CNS and PNS. The development of new 5-HT ligands has led to the expansion of 5-HT receptor subtypes into three categories: 5-HT1, 5-HT2 and 5-HT3. Each category has further subdivisions. The literature concerning the biochemical basis of this division has been reviewed recently. While this approach has elucidated many of the pharmacological properties of 5-HT receptors, it has not addressed the question of how 5-HT modulates cell excitability. Physiological studies have confirmed the existence of a multiplicity of 5-HT receptors that act through a variety of ionic mechanisms. The purpose of this review is to summarize what is known of the ionic mechanisms associated with the activation of identified mammalian 5-HT receptor subtypes, as well as some effects of 5-HT where the receptor could not be defined.

Cholinergic inhibition of ventral midbrain dopamine neurons.

Muscarinic acetylcholine receptors are common throughout the CNS. The predominant subtypes in the brain are positively coupled to phosphoinositide hydrolysis and have been found to modulate multiple conductances. Muscarinic receptor activation is most often observed to be excitatory because of suppression of various potassium conductances. Here it is reported that three distinct effects of muscarinic receptor activation can be observed in isolation from one another, depending on the duration of receptor activation and the concentration of agonist. Brief activation of muscarinic receptors, as is likely to occur with normal synaptic transmission, hyperpolarized dopamine neurons of the ventral midbrain through a calcium-activated potassium conductance. With repeated or persistent activation of muscarinic receptors, the hyperpolarizing response was entirely desensitized in the absence of any change in resting membrane potential. With sustained activation by higher concentrations of agonist, dopamine neurons were depolarized. This demonstrates that muscarinic receptors can mediate very diverse, and even opposing, postsynaptic effects on neurons depending on the pattern of acetylcholine release.

Inositol 1,4,5-triphosphate-evoked responses in midbrain dopamine neurons.

Synaptically released glutamate evokes slow IPSPs mediated by metabotropic glutamate receptors (mGluRs) in midbrain dopamine neurons. These mGluR IPSPs are caused by release of Ca(2+) from intracellular stores and subsequent activation of small-conductance Ca(2+)-activated K(+) channels (SK channels). To further investigate the intracellular mechanisms involved, the effect of photolyzing intracellular caged inositol 1,4,5-triphosphate (InsP(3)) on membrane conductance and intracellular Ca(2+) concentration ([Ca(2+)](i)) was examined in rat midbrain slices. Photolytic release of InsP(3) elicited a transient outward current and a sharp rise in [Ca(2+)](i) that lasted for approximately 5 sec. Apamin, a blocker of SK channels, abolished the InsP(3)-induced outward current without affecting the rise in [Ca(2+)](i). Depleting intracellular Ca(2+) stores with cyclopiazonic acid completely blocked both the outward current and the Ca(2+) transient elicited by InsP(3). InsP(3)-evoked Ca(2+) mobilization was not affected by blockade of ryanodine receptors with ruthenium red, whereas depleting ryanodine-sensitive Ca(2+) stores with ryanodine almost eliminated InsP(3)-induced Ca(2+) release. Increasing the size of intracellular Ca(2+) stores by means of prolonged depolarization added a late component to the outward current and a slow component to the rising phase of [Ca(2+)](i). These effects of depolarization were blocked by ruthenium red. These results show that InsP(3) activates SK channels by releasing Ca(2+) from InsP(3)-sensitive stores that also contain ryanodine receptors. Increasing intracellular Ca(2+) stores boosts InsP(3)-evoked responses by invoking Ca(2+)-induced Ca(2+) release through ryanodine receptors. This intracellular signaling pathway may play a significant role in regulating the excitability of midbrain dopamine neurons.

Roles of alpha1- and alpha2-adrenoceptors in the nucleus raphe magnus in opioid analgesia and opioid abstinence-induced hyperalgesia.

Noradrenaline and alpha-adrenoceptors have been implicated in the modulation of pain in various behavioral conditions. Noradrenergic neurons and synaptic inputs are present in neuronal circuits critical for pain modulation, but their actions on neurons in those circuits and consequently the mechanisms underlying noradrenergic modulation of pain remain unclear. In this study, both recordings in vitro and behavioral analyses in vivo were used to examine cellular and behavioral actions mediated by alpha1- and alpha2-adrenoceptors on neurons in the nucleus raphe magnus. We found that alpha1- and alpha2-receptors were colocalized in the majority of a class of neurons (primary cells) that inhibit spinal pain transmission and are excited during opioid analgesia. Activation of the alpha1-receptor depolarized whereas alpha2-receptor activation hyperpolarized these neurons through a decrease and an increase, respectively, in potassium conductance. Blockade of the excitatory alpha1-receptor or activation of the inhibitory alpha2-receptor significantly attenuated the analgesia induced by local opioid application, suggesting that alpha1-receptor-mediated synaptic inputs in these primary cells contribute to their excitation during opioid analgesia. In the other cell class (secondary cells) that is thought to facilitate spinal nociception and is inhibited by analgesic opioids, only alpha1-receptors were present. Blocking the alpha1-receptor in these cells significantly reduced the hyperalgesia (increased pain) induced by opioid abstinence. Thus, state-dependent activation of alpha1-mediated synaptic inputs onto functionally distinct populations of medullary pain-modulating neurons contributes to opioid-induced analgesia and opioid withdrawal-induced hyperalgesia.

Functional coupling between neurons and glia.

Neuronal-glial interactions play an important role in information processing in the CNS. Previous studies have indicated that electrotonic coupling between locus ceruleus (LC) neurons is involved in synchronizing the spontaneous activity. The results of the present study extend the functional electrotonic coupling to interactions between neurons and glia. Spontaneous oscillations in the membrane potential were observed in a subset of glia. These oscillations were synchronous with the firing of neurons, insensitive to transmitter receptor antagonists and disrupted by carbenoxolone, a gap junction blocker. Hyperpolarization of neurons with [Met] (5)enkephalin blocked the oscillations in glia. Selective depolarization of glia with a glutamate transporter substrate (l-alpha-aminoadipic acid) increased the neuronal firing rate, suggesting that changes in the membrane potential of glia can modulate neuronal excitability through heterocellular coupling. Dye-coupling experiments further confirmed that small molecules could be transferred through gap junctions between these distinct cell types. No dye transfer was observed between neurons and oligodendrocytes or between astrocytes and oligodendrocytes, suggesting that the junctional communication was specific for astrocytes and neurons. Finally, immunoelectron microscopy studies established that connexins, the proteins that form gap junctions, were present on portions of the plasmalemma, bridging the cytoplasm of neurons and glia in LC. This heterocellular coupling extends the mechanisms by which glia participate in the network properties of the LC in which the degree of coupling is thought to influence cognitive performance.

Release and activation of a particulate bound acid phosphatase from Tetrahymena pyriformis.

A sedimentable form of acid phosphatase (EC 3.1.3.2) from Tetrahymena pyriformis was found to be solubilized by Triton X-100. The total enzyme activity in the insoluble cell fraction increased almost 200% upon solubilization with Triton X-100 or Nonidet P-40. Removal of membrane lipids and Triton X-100 from the particulate wash solution with a chloroform extraction resulted in non-specific enzyme-protein aggregation which was reversible upon addition of Triton X-100. The results indicate that this acid phosphatase is an integral membrane protein. The pH optima for this particulate bound acid phosphatase was 3.5 with o-carboxyphenyl phosphate and 4.0 with p-nitrophenyl phosphate as substrates. The Km values of each substrate were 3.1 and 0.031 mM, respectively.

Where is the locus in opioid withdrawal?

Identification of neuroadaptations in specific brain regions that generate withdrawal is crucial for understanding and perhaps treating opioid dependence. It has been widely proposed that the locus coeruleus (LC) is the nucleus that plays the primary causal role in the expression of the opioid withdrawal syndrome. MacDonald Christie, John Williams, Peregrine Osborne and Clare Bellchambers believe that this view and the interpretation of the literature on which it is based are at best controversial. Here, they suggest an alternative view in which regions close to the LC such as the periaqueductal grey, as well as other brain structures which are independent of the LC noradrenergic system, play a more important role in the expression of the opioid withdrawal syndrome.