Down-regulation of the macrophage lineage through interaction with OX2 (CD200)

OX2 (CD200) is a broadly expressed membrane glycoprotein, shown here to be important for regulation of the macrophage lineage. In mice lacking CD200, macrophage lineage cells, including brain microglia, exhibited an activated phenotype and were more numerous. Upon facial nerve transection, damaged CD200-deficient neurons elicited an accelerated microglial response. Lack of CD200 resulted in a more rapid onset of experimental autoimmune encephalomyelitis (EAE). Outside the brain, disruption of CD200-CD200 receptor interaction precipitated susceptibility to collagen-induced arthritis (CIA) in mice normally resistant to this disease. Thus, in diverse tissues OX2 delivers an inhibitory signal for the macrophage lineage.

Cryptomonad algae are evolutionary chimaeras of two phylogenetically distinct unicellular eukaryotes

Although it is widely accepted that the plastids of plants and algae originated as endosymbionts, the details of this evolutionary process are unclear. It has been proposed that in organisms whose plastids are surrounded by more than two membranes, the endosymbiont was a eukaryotic alga rather than a photosynthetic prokaryote. The DNA-containing nucleomorph of cryptomonad algae appears to be the vestigial nucleus of such an algal endosymbiont. Eukaryotic-type ribosomal RNA sequences have been localized to a nucleolus-like structure in the nucleomorph. In support of the hypothesis that cryptomonads are evolutionary chimaeras of two distinct eukaryotic cells, we show here that Cryptomonas phi contains two phylogenetically separate, nuclear-type small-subunit rRNA genes, both of which are transcriptionally active. We incorporate our rRNA sequence data into phylogenetic trees, from which we infer the evolutionary ancestry of the host and symbiont components of Cryptomonas phi. Such trees do not support the thesis that chromophyte algae evolved directly from a cryptomonad-like ancestor.

A molecular phylogeny of the marine red algae (Rhodophyta) based on the nuclear small-subunit rRNA gene

A phylogeny of marine Rhodophyta has been inferred by a number of methods from nucleotide sequences of nuclear genes encoding small subunit rRNA from 39 species in 15 orders. Sequence divergences are relatively large, especially among bangiophytes and even among congeners in this group. Subclass Bangiophycidae appears polyphyletic, encompassing at least three lineages, with Porphyridiales distributed between two of these. Subclass Florideophycidae is monophyletic, with Hildenbrandiales, Corallinales, Ahnfeltiales, and a close association of Nemaliales, Acrochaetiales, and Palmariales forming the four deepest branches. Cermiales may represent a convergence of vegetative and reproductive morphologies, as family Ceramiaceae is at best weakly related to the rest of the order, and one of its members appears to be allied to Gelidiales. Except for Gigartinales, for which more data are required, the other florideophyte orders appear distinct and taxonomically justified. A good correlation was observed with taxonomy based on pit-plug ultrastructure. Tests under maximum-likelihood and parsimony of alternative phylogenies based on structure and chemistry refuted suggestions that Acrochaetiales is the most primitive florideophyte order and that Gelidiales and Hildenbrandiales are sister groups.

Fusarium polycaprolactone depolymerase is cutinase

Polycaprolactone (PCL), a synthetic polyester, is degraded by a variety of microorganisms, including some phytopathogens. Many phytopathogens secrete cutinase, a serine hydrolase that degrades cutin, the structural polymer of the plant cuticle. We compared wild-type strains and a cutinase-negative gene replacement mutant strain of Fusarium solani f. sp. pisi (D. J. Stahl and W. Schäfer, Plant Cell 4:621-629, 1992) and a wild-type strain of Fusarium moniliforme to show that Fusarium cutinase is a PCL depolymerase. The wild-type strains, but not the mutant strain, (i) degraded PCL and used it as a source of carbon and energy, (ii) showed induction of secreted PCL depolymerase and an esterase activity of cutinase when grown in the presence of cutin, and (iii) showed induction of PCL depolymerase and an esterase activity of cutinase when grown in the presence of a hydrolysate of PCL, which contains PCL oligomers that are structurally similar to the natural inducers of cutinase. These results together with other details of regulation and conditions for optimal enzyme activity indicate that the Fusarium PCL depolymerase, required for degradation and utilization of PCL, is cutinase.

Continuous intrathecal hydromorphone and clonidine for intractable cancer pain

The use of hydromorphone and clonidine, delivered intrathecally by an implanted infusion pump, is described in a patient with intractable cancer pain. The patient was a 48-year-old woman with uterine cervical cancer-related pain that was poorly responsive to conventional oral narcotics. Hydromorphone was used because of the patient's history of morphine intolerance. When progressive intrathecal hydromorphone dosages were required, intrathecal clonidine (an alpha 2 adrenergic agonist) was infused concomitantly. Intrathecal hydromorphone and clonidine successfully controlled this patient's pain without the necessity to resort to destructive neurosurgery.

Selective responding of nucleus accumbens core and shell dopamine to aversively conditioned contextual and discrete stimuli

Dopamine transmission within the nucleus accumbens has been implicated as a neurochemical substrate of associative learning processes. It has been suggested that the acquisition of classically conditioned fear to a specific environment, or context, differs fundamentally from the development of conditioned fear to a discrete stimulus, such as a light or a tone. In this study, we assessed extracellular dopamine in the rat nucleus accumbens shell and core during the expression of a conditioned fear response. Animals were aversively conditioned to either a context or a tone and extracellular dopamine was measured in the nucleus accumbens shell and core by in vivo microdialysis over the next 2 days as animals were returned first to the conditioning chamber (day 1: context test), and subsequently as animals were again returned to the chamber and presented with the conditioned tone stimulus (day 2: tone test). Dopamine levels in the core were significantly higher in the Context-Shock group compared to the Tone-Shock group during the 30-min exposure to context while dopamine levels in the nucleus accumbens shell did not differ significantly during the context test between groups. In contrast, extracellular dopamine in the shell but not the core of Tone-Shock animals increased significantly during presentation of the tone. Dopamine in both the shell and core remained unchanged during the tone test in the Context-Shock groups.These data suggest distinct roles for shell and core dopamine transmission in the expression of a conditioned emotional response. While dopamine increased in the shell primarily during the presentation of a discrete tone conditioned stimulus, core dopamine responded more to a contextual conditioned stimulus. These results may reflect differences in either the type of information acquired or the salience of the learned associations which are formed to a context vs. a discrete tone cue.

A computer controlled analysis of freezing behaviour

The conditioned freezing response in rats has been much used both by psychologists and neuroscientists to investigate the behavioural effects of brain lesions and of changes in motivational state. The primary advantage of the freezing response is that it can be used without motivational manipulations such as food or water deprivation. Previously, freezing has been measured by a human observer either from video recordings or during the test sessions themselves. But these methods of data collection have potential disadvantages. In the present paper, we describe a new, computer controlled, automated procedure for assessing conditioned freezing. Each conditioning chamber contains a mini-video camera. Behaviour is analysed on-line by means of a programme which compares every two adjacent seconds of video tape to generate a screen representing the percentage difference between them. A difference of <0.05% (50 pixels) is classified as a freezing response. Experiments are described in which we measure conditioned freezing and its development over time, in response to contextual cues and to a discrete tone which had been paired with foot shock. We demonstrate our apparatus and methods of data analysis to be sensitive to: number of tone-shock pairings, rat strain and tone pre-exposure.

Lesion of the habenular efferent pathway produces anxiety and locomotor hyperactivity in rats: a comparison of the effects of neonatal and adult lesions

Recent studies have implicated the habenula in modulating states of arousal and chronic responses to stress. We examined whether lesion of the habenula efferent pathway, the fasciculus retroflexus (FR), at either 3 (P3) or 70 (P70) days of age affects stress-related anxiety (elevated plus-maze test) and activity levels (open-field test) in rats tested as adults. Both P3- and P70-lesioned rats showed chronically elevated plasma levels of corticosterone. Rats receiving FR lesions as neonates (P3) exhibited greater open arm avoidance on the elevated plus-maze than controls 2 months postoperatively, suggesting a heightened state of anxiety. In contrast, P70-lesioned rats behaved similarly to controls on the plus-maze, but showed increased locomotion and increased grooming in the open field, effects not observed in P3-lesioned rats. When an additional stressful condition was imposed (5 days of social isolation plus 24 h food deprivation) before testing, both FR-lesion groups showed an attenuation of the normal behavioral responses (decreased open-arm entries/time in open arms, increased freezing). The effects of FR lesions on activity and behavioral indices of anxiety may be due to disruption of lateral habenular projections to dopaminergic neurons in the ventral tegmentum and/or projections to regions containing high concentrations of benzodiazepine receptors, the median and dorsal raphe and dorsal periaqueductal gray. Behavioral differences observed as a function of lesion age suggest differential capabilities of P3- and P70-lesioned rats to utilize compensatory mechanisms to correct FR lesion-induced deficits.

The prognosis of small primary breast cancers

The Nottingham Prognostic Index (NPI) is an integrated prognostic index used to predict patient survival for women with invasive breast cancer. The index is based on invasive tumour size, histological lymph node stage and tumour grade. The value of such an index has been questioned in small invasive breast cancers and it has been suggested that size is the only necessary prognostic determinant. The aims of this study were to determine the extent of regional lymph node involvement and survival in women with small invasive breast cancers and to assess the value of the NPI. Between 1976 and 1994, 2684 women aged < or = 70 years were treated for primary operable invasive breast cancers of < or = 5 cm in maximum diameter, of which 318 measured < or = 1 cm. Follow-up data were evaluated to determine histological factors important in predicting survival outcomes in women with cancers < or = 1 cm in diameter and comparing their survival according to the NPI with all women treated for primary operable breast cancers < or = 5 cm in maximum diameter. Histological lymph node involvement was demonstrated in 56/318 (18%) of cancers of < or = 1 cm in diameter. Significant survival differences were demonstrated for small breast cancers according to lymph node stage, vascular invasion and histological tumour grade. Only lymph node stage and histological tumour grade were independent prognostic indicators using a multivariate Cox model. The survival curves for small tumours stratified by the NPI were similar to those of cancers up to 5 cm in diameter. The results indicate that lymph node staging and histological grading are still important prognostic determinants for breast cancers < or = 1 cm in diameter. An axillary node staging procedure should be performed for all invasive breast cancers < or = 1 cm in diameter. The NPI remains relevant for small breast cancers.

Pain induces adaptations in ventral tegmental area dopamine neurons to drive anhedonia-like behavior

The persistence of negative affect in pain leads to co-morbid symptoms such as anhedonia and depression-major health issues in the United States. The neuronal circuitry and contribution of specific cellular populations underlying these behavioral adaptations remains unknown. A common characteristic of negative affect is a decrease in motivation to initiate and complete goal-directed behavior, known as anhedonia. We report that in rodents, inflammatory pain decreased the activity of ventral tegmental area (VTA) dopamine (DA) neurons, which are critical mediators of motivational states. Pain increased rostromedial tegmental nucleus inhibitory tone onto VTA DA neurons, making them less excitable. Furthermore, the decreased activity of DA neurons was associated with reduced motivation for natural rewards, consistent with anhedonia-like behavior. Selective activation of VTA DA neurons was sufficient to restore baseline motivation and hedonic responses to natural rewards. These findings reveal pain-induced adaptations within VTA DA neurons that underlie anhedonia-like behavior.

Pharmacologic responses and spectral analyses of spontaneous fluctuations in heart rate and blood pressure in SHR rats

The aim of this experiment was to characterize patterns of autonomic control in spontaneously hypertensive (SHR) and normotensive Wistar-Kyoto (WKY) rats by measuring effects of pharmacologic blockers and using power spectral analysis of heart rate variability (HRV) and blood pressure variability (BPV). Resting HRs and BPs were recorded during a 20-min baseline period and over two 20-min periods of sequential autonomic blockade. On one day, animals received atropine followed by atenolol and on the following day, the drug order was reversed. Power spectrum analyses were performed on 30-s blocks of data throughout each of the three 20-min treatment periods (baseline, single blocker, combined blockade) and HRV and BPV were computed over low and high frequency bands. Increases in HR after atropine were significantly (approx. 40%) smaller in SHR rats than in WKYs. This held true even when animals were pretreated with atenolol. In contrast, decreases in HR following atenolol were similar in the two strains. These results indicate that SHRs have reduced vagal tone, but similar cardiac sympathetic tone compared to WKY rats. Virtually all HRV, over both low and high frequency bands, and in both strains, was inhibited by atropine. SHRs had significantly less high frequency HRV which is consistent with the conclusion that they have reduced cardiac vagal activity when compared with WKYs. BPV was not affected by atropine or atenolol but was inhibited by an alpha-receptor (phentolamine). BPV within both the low and high frequency bands was significantly greater in SHRs, suggesting that sympathetic tone to the vasculature is greater in SHR rats.

Differential involvement of dopamine in the shell and core of the nucleus accumbens in the expression of latent inhibition to an aversively conditioned stimulus

Latent inhibition, the process whereby pre-exposure to a conditioned stimulus without consequence impairs subsequent learning of an association between the conditioned stimulus and an unconditioned stimulus, is reportedly disrupted in both amphetamine-treated rats and in acute schizophrenics. This has led to the suggestion that disruptions in latent inhibition model some of the cognitive impairments associated with hyperactive dopamine transmission as it is expressed in schizophrenic patients. Specifically, fluctuations in dopamine neurotransmission within the nucleus accumbens have been implicated in the mediation of latent inhibition; however, it has not been established whether these dopamine-mediated effects occur in the shell or core subregion of the nucleus. In the present study, 48h after conditioned stimulus-pre-exposed and non-pre-exposed animals experienced 10 pairings of tone and footshock, we measured extracellular levels of dopamine in the shell and core during the expression of latent inhibition to an aversively conditioned tone using in vivo microdialysis. Our results show that pre-exposure to the tone eliminated the conditioned release of dopamine in the shell of the nucleus accumbens and resulted in an attenuated conditioned freezing response to the tone conditioned stimulus. In contrast, dopamine release in the core was not affected by pre-exposure to the tone. These data suggest that it is specifically the shell of the nucleus accumbens in which alterations of dopaminergic tone, whether pharmacologically induced in rodents or the result of disease in humans, may act to disrupt latent inhibition.

Putative steroidal pheromones in the round goby, Neogobius melanostomus: olfactory and behavioral responses

To identify potential hormonal pheromones of the round goby (Neogobius melanostomus), a species recently introduced to the Great Lakes, we used electro-olfactogram (EOG) recording to examine olfactory responsiveness to more than 100 steroids and prostaglandins. Neogobius detected free and conjugated 18-, 19- and 21-carbon steroids, but did not detect prostaglandins. EOG cross-adaptation, used to determine if Neogobius can discriminate the detected compounds at the sensory level, suggested that the detected steroids act on four classes of olfactory receptor mechanisms named (according to the most potent ligand for each): estrone, 17 beta-estradiol-3 beta-glucuronide, etiocholanolone, and dehydroepiandrosterone-3-sulfate. Although none of the detected steroids induced reproductive behaviors, exposure to steroids from three of the four receptor classes (estrone, 17 beta-estradiol-3 beta-glucuronide, or etiocholanolone) increased ventilation rate in males, whereas only etiocholanolone increased ventilation rate in females. Using the ventilation increase as a behavioral bioassay of steroid detection, behavioral cross-adaptation studies in males demonstrated that steroids discriminated at the sensory level are also discriminated behaviorally. These findings suggest the round goby may use steroids as putative pheromones.

Airway somatosensory deficits and dysphagia in Parkinson's disease

BACKGROUND

Individuals with Parkinson's disease (PD) often experience substantial impairment of swallow control, and are typically unaware of the presence or severity of their impairments suggesting that these individuals may also experience airway sensory deficits. However, the degree to which impaired swallow function in PD may relate to airway sensory deficits has yet to be formally tested.

OBJECTIVE

The purpose of this study was to examine whether airway sensory function is associated with swallow impairment in PD.

METHODS

Eighteen PD participants and 18 healthy controls participated in this study and underwent endoscopic assessment of airway somatosensory function, endoscopic assessment of swallow function, and clinical ratings of swallow and disease severity.

RESULTS

PD participants exhibited abnormal airway somatosensory function and greater swallow impairment compared with healthy controls. Swallow and sensory deficits in PD were correlated with disease severity. Moreover, PD participants reported similar self-rated swallow function as healthy controls, and swallow deficits were correlated with sensory function suggesting an association between impaired sensory function and poor self-awareness of swallow deficits in PD.

CONCLUSIONS

These results suggest that control of swallow is influenced by airway somatosensory function, that swallow-related deficits in PD are related to abnormal somatosensation, and that swallow and airway sensory function may degrade as a function of disease severity. Therefore, the basal ganglia and related neural networks may play an important role to integrate airway sensory input for swallow-related motor control. Furthermore, the airway deficits observed in PD suggest a disintegration of swallow-related sensory and motor control.

Selective aortic arch perfusion during cardiac arrest: a new resuscitation technique

STUDY OBJECTIVES

To demonstrate the technique of selective aortic arch perfusion during cardiac arrest and to observe the hemodynamic effects of volume infusion and aortic epinephrine administration.

DESIGN

Sequential series, nonrandomized, noncontrolled.

TYPE OF PARTICIPANTS

Fourteen mongrel dogs weighing 21 to 36 kg.

INTERVENTIONS

Animals had midaortic arch pressure, right atrial pressure, and descending aortic arch balloon occlusion catheters placed. After ten minutes of ventricular fibrillation, balloon inflation and aortic arch infusions were initiated as follows: group 1 (six), 30 mL/kg/min of 0.9% NaCl for two minutes; group 2 (four), 30 mL/kg/min of oxygenated lactated Ringer's with 2 mg/L epinephrine for two minutes, followed by CPR; and group 3 (four), 20 mL/kg/min of oxygenated perfluorochemicals with 4 mg/L epinephrine for one minute, then CPR.

MEASUREMENTS AND MAIN RESULTS

Midaortic arch pressure, right atrial pressure, and coronary perfusion pressure each rose significantly in all groups. Midaortic arch pressure and coronary perfusion pressure increases were greater in groups 2 and 3 than in group 1. In groups 1 and 2, right atrial pressure increases at end-selective aortic arch perfusion were excessive as midaortic arch pressure and right atrial pressure increased linearly and similarly after 20 to 30 seconds. In groups 2 and 3, CPR-diastolic midaortic arch pressure and coronary perfusion pressure after selective aortic arch perfusion were good and similar to midaortic arch pressure and coronary perfusion pressure at end-selective aortic arch perfusion.

CONCLUSION

Selective aortic arch perfusion is technically feasible, but excessive right atrial pressure increases limit maximal infusion rates and volumes. Selective aortic arch perfusion infusates with epinephrine produce greater midaortic arch pressure and coronary perfusion pressure during infusion than infusate without epinephrine. Controlled studies are needed to determine if selective aortic arch perfusion improves resuscitation outcome.

Activation of dopaminergic neurotransmission in the medial prefrontal cortex by N-methyl-d-aspartate stimulation of the ventral hippocampus in rats

Many behavioral functions-including sensorimotor, attentional, memory, and emotional processes-have been associated with hippocampal processes and with dopamine transmission in the medial prefrontal cortex (mPFC). This suggests a functional interaction between hippocampus and prefrontal dopamine. The anatomical substrate for such an interaction is the intimate interconnection between the ventral hippocampus and the dopamine innervation of the mPFC. The present study yielded direct neurochemical evidence for an interaction between ventral hippocampus and prefrontal dopamine transmission in rats by demonstrating that subconvulsive stimulation of the ventral hippocampus with N-methyl-d-aspartate (NMDA; 0.5 mug/side) activates dopamine transmission in the mPFC. Postmortem measurements revealed that bilateral NMDA stimulation of the ventral hippocampus, resulting in locomotor hyperactivity, increased the homovanillic acid/dopamine ratio, an index of dopamine transmission, in the mPFC; indices of dopamine transmission in any of five additionally examined forebrain regions (amygdala, nucleus accumbens shell/core, lateral prefrontal cortex, caudate putamen) were unaltered. In vivo microdialysis measurements in freely moving rats corroborated the suggested activation of prefrontal dopamine transmission by demonstrating that unilateral NMDA stimulation of the ventral hippocampus increased extracellular dopamine in the ipsilateral mPFC. The suggested influence of the ventral hippocampus on prefrontal dopamine may be an important mechanism for hippocampo-prefrontal interactions in normal behavioral processes. Moreover, it indicates that aberrant hippocampal activity, as found in neuropsychiatric diseases, such as schizophrenia and mood disorders, may contribute to disruption of certain cognitive and emotional functions which are extremely sensitive to imbalanced prefrontal dopamine transmission.

Maternal involvement in the development of cardiovascular phenotype

Over the past 20 years, laboratory studies of genetically defined animal models of human essential hypertension have provided valuable information on the pathophysiology of this disturbance in cardiovascular regulation. Relatively fewer studies have examined the impact of preweaning factors on the developing cardiovascular system of hypertensive animals. In our laboratory studies, we have utilized two inbred genetically hypertensive models: the spontaneously hypertensive (SHR) rat and its Wistar/Kyoto (WKY) normotensive control strain as well as the Dahl hypertension-sensitive (SS/Jr) and hypertension-resistant (SR/Jr) strains. To manipulate the preweaning maternal environment, we have employed the technique of reciprocal cross-fostering of litters between hypertensive and matched normotensive mothers. Our findings to date point to the maternal environment as a powerful influence on the development of high blood pressure in genetically hypertensive rats. In general, hypertensive rats reared by normotensive foster mothers have significant reductions in arterial blood pressure in adulthood. Thus, the progression of hypertensive disease is not strictly predetermined by genotypic factors. Rather, a genetic predisposition to hypertension interacts with preweaning environmental factors to determine an animal's cardiovascular phenotype in adulthood.

Latent inhibition, but not prepulse inhibition, is reduced during withdrawal from an escalating dosage schedule of amphetamine

The enhanced locomotor and stereotypic responses of the rat to repeated amphetamine (AMPH) administration are considered to be an animal model of positive schizophrenic symptoms. In contrast, behaviors observed during withdrawal from repeated AMPH are believed to model depression or anxiety. In the present study, the authors tested whether AMPH withdrawal might also elicit behaviors consistent with animal models of schizophrenia, specifically, disruptions in latent inhibition (LI) of 2-way active avoidance and prepulse inhibition (PPI) of startle. Rats treated with escalating doses of AMPH (6 days, 1-5 mg/kg ip) or saline were tested for LI and PPI during withdrawal. LI was eliminated by prior AMPH treatment in rats tested at 4, 13, and 28 days of withdrawal. In contrast, PPI did not differ between AMPH and control groups. These results support an interrelationship between repeated-AMPH and LI-disruption, but not PPI-disruption, models of schizophrenia.

Amphetamine withdrawal does not produce a depressive-like state in rats as measured by three behavioral tests

Administration of amphetamine (AMPH) can induce symptoms of psychosis in humans and locomotor sensitization in rats; in contrast, withdrawal from a period of AMPH intake is most often associated with symptoms of human endogenous depression. The aim of this study was to determine whether AMPH withdrawal produces a depressive-like state in rats. The present study examined the effects of withdrawal from an escalating-dose AMPH schedule (ESC; three daily injections over 6 days, 1-5 mg/kg, i.p.) and an intermittent-dose AMPH schedule (INT; one daily injection over 6 days, 1.5 mg/kg, i.p.) on animals' performance in three behavioral paradigms related to depression: the Porsolt swim test, the learned helplessness assay and operant responding for sucrose on a progressive ratio schedule. ESC and INT AMPH withdrawal had no effect on any of these tests or on stress responsiveness as measured by increased plasma levels of corticosterone (CORT) and adrenocorticotropin following the swim test, although basal CORT levels were higher in AMPH-withdrawn animals compared to controls. Finally, we confirmed the presence of locomotor sensitization for both AMPH schedules after 30 days of withdrawal. Our results suggest that the ability of AMPH withdrawal to produce symptoms of depression may not be evident in all behavioral screens for depressive symptoms in the rat.

Increased conditioned fear response and altered balance of dopamine in the shell and core of the nucleus accumbens during amphetamine withdrawal

It has been suggested that neuroadaptations within the nucleus accumbens (NAC) dopaminergic (DA) projection contribute to the negative affect associated with psychostimulant withdrawal. The present study assessed the effects of amphetamine (AMPH) withdrawal on behavioral and NAC DA responses to conditioned fear stress. Animals injected with escalating-dose AMPH (1-5mg/kg, three injections/day, 6 days) or saline (SAL) acquired a tone-shock association on withdrawal day 3 and were tested for extinction of conditioned freezing to the tone on withdrawal day 4. Extracellular levels of NAC shell and core DA were monitored using in vivo microdialysis on both days. AMPH-withdrawn animals exhibited more conditioned freezing than SAL animals during both acquisition and extinction. During acquisition, DA increased more in the shell than the core of the NAC in both AMPH and SAL groups. During extinction to the tone, shell DA increased in SAL- but not AMPH-treated animals, whereas core DA activity was greater in AMPH than SAL animals. These data demonstrate that AMPH withdrawal alters the balance between shell and core DA transmission while increasing the behavioral expression of conditioned fear. Such drug-induced neuroadaptations in the NAC stress response may be involved in the exacerbation of negative emotions associated with drug withdrawal and stimulant-induced psychosis.

Maternal behavior of spontaneously hypertensive and Wistar-Kyoto normotensive rats: effects of reciprocal cross-fostering of litters

Maternal behavior of spontaneously hypertensive (SHR) and Wistar-Kyoto (WKY) normotensive dams rearing either their natural pups or pups of the opposite strain was assessed when pups were 4-6 days of age. Consistent with previous reports, SHR dams caring for their natural pups were observed nursing and licking their pups more often than WKY dams and were away from their pups less often. The behavior of dams rearing cross-fostered pups demonstrated that this strain difference in patterns of maternal behavior is dependent on pup type. Mothers of both strains shifted their behavior in the direction of the opposite strain's maternal behavior pattern when caring for cross-fostered pups. This shift was most pronounced in SHR dams caring for WKY pups. These data suggest that alterations in patterns of maternal behavior produced by cross-fostering may play an important role in cross-fostering effects on the physiological development of SHRs previously reported.

The acquisition, retention and reversal of spatial learning in the morris water maze task following withdrawal from an escalating dosage schedule of amphetamine in wistar rats

Two experiments were carried out to evaluate the effects of amphetamine withdrawal in rats on spatial learning in the water maze. A schedule of repeated d-amphetamine administration lasting for 6 days, with three injections per day (1-5 mg/kg, i.p.), was employed. Experiment 1 demonstrated that amphetamine withdrawal did not impair the acquisition of the water maze task (third to fourth withdrawal days), but amphetamine-withdrawn rats made more target-zone visits and reached the former location of the platform quicker than controls during the probe test (fifth withdrawal day). In experiment 2, retention of the location of the escape platform was assessed in animals having been pre-trained on the water maze task before treatment. On the third withdrawal day, retention of the former platform location was assessed in a probe test. Retention was only clearly seen in the measure of target zone visits, and performance did not differ between groups. Next, the animals were trained to escape to a new location in the water maze on withdrawal days 4-5. A reversal effect could be discerned across the first four trials, as evident by the animals' tendency to search in the former target quadrant. This interfered with the new learning, but amphetamine-withdrawn animals appeared to overcome it more rapidly than saline-treated controls. This finding is consistent with the view that amphetamine withdrawal can enhance behavioural switching, which could be expressed as a reduction of proactive interference during learning; and, it is in line with our previous finding that latent inhibition is also attenuated during amphetamine withdrawal.

Laparoscopic common bile duct exploration: evolution of a new technique

Laparoscopic exploration of the common bile duct (CBD) with a choledochoscope or a stone basket during laparoscopic cholecystectomy was attempted in 60 patients and was successful in 56. The cystic duct was used for entry to the CBD in 46 patients and in 14 a choledochotomy was performed. Of 51 patients with confirmed common duct stones, 38 had complete laparoscopic clearance (75 per cent). In 13 patients the duct was not cleared or was only partially cleared, of whom four went on to have clearance by postoperative percutaneous choledochoscopy down a cystic duct or T-tube track. Two patients with cystic duct tubes passed their remaining stones spontaneously. One patient had open exploration and six required endoscopic retrograde cholangiopancreatography. Of nine patients without stones, choledochoscopy was impossible in three patients whose cholangiogram was later considered to be normal. In five patients stones were excluded by choledochoscopy and in one patient laparoscopic choledochoscopy was undertaken to better define abnormal biliary anatomy; this helped to avoid major bile duct injury. Choledochoscopy was easier with the smaller 3.6-mm ureteroscope but stone removal was more difficult when the basket was too small for the stones, the cystic duct too small relative to stone size or the number of stones was too great. Successful stone clearance was proportional to the level of effort expended, and was limited by operating time and equipment.

The lobster parasite Anophryoides haemophila (Scuticociliatida: Orchitophryidae): nuclear 18S rDNA sequence, phylogeny and detection using oligonucleotide primers

We have determined the nucleotide sequence of the nuclear gene encoding small-subunit ribosomal ribonucleic acid of the ciliate Anophryoides haemophila, a parasite of the American lobster Homarus americanus. The gene is 1763 bp in length, and has a guanosine-plus-cytosine content of 43.9%. Inferred phylogenetic frameworks strongly support the monophyly of the scuticociliates, and suggest that order Scuticociliatida should be elevated to at least subclass rank. Oligonucleotide probes based on A. haemophila ssurDNA can discriminate between DNAs of A. haemophila and other investigated hymenostome ciliates, and effectively prime polymerase chain reaction-based detection of A. haemophila deoxyribonucleic acid against at least a 1600-fold excess of total deoxyribonucleic acid from H. americanus. GENBANK/U51554

Protistan parasite QPX of hard-shell clam Mercenaria mercenaria is a member of Labyrinthulomycota

Biomass of the protistan parasite QPX (quahaug parasite X) of hard-shell clam Mercenaria mercenaria was enriched from in vitro culture. The nuclear gene encoding the 18S RNA of the small-subunit ribosomal (ssu-rDNA) was recovered using the polymerase chain reaction (PCR) and sequenced. Phylogenetic analysis clearly showed that QPX is a member of phylum Labyrinthulomycota, within which it appears as a specific relative of Thraustochytrium pachydermum. These results confirm the provisional assignment of QPX to the Labyrinthulomycota made previously on the basis of morphological and ultrastructural characters found in some, but not all, geographic isolates.