Zachsia zenkewitschi (Teredinidae), a Rare and Unusual Seagrass Boring Bivalve Revisited and Redescribed.

The sea-grass borer Zachsia zenkewitschi belongs to a group of economically and ecologically important bivalves, commonly referred to as shipworms. The sole recognized representative of the genus Zachsia, this species displays an unusual life history and reproductive strategy that is now understood to include: environmental sex determination of free swimming larvae, extreme sexual and size dimorphism between males and females, internal fertilization, maintenance of often large harems of male dwarfs within a specialized cavity of the female mantle, and complex maternal care of larvae in specialized brood pouches within the gill. It is also the only shipworm species known to burrow in sea grass rhizomes rather than terrestrial wood. Although Z. zenkewitschi is rare and little studied, understanding of its biology and anatomy has evolved substantially, rendering some aspects of its original description inaccurate. Moreover, no existing type specimens are known for this species. In light of these facts, we designate a neotype from among specimens recently collected at the type location, and undertake a re-description of this species, accounting for recent reinterpretation of its life history and functional anatomy.

Dopamine release in the basal ganglia.

Dopamine (DA) is a key transmitter in the basal ganglia, yet DA transmission does not conform to several aspects of the classic synaptic doctrine. Axonal DA release occurs through vesicular exocytosis and is action potential- and Ca²âº-dependent. However, in addition to axonal release, DA neurons in midbrain exhibit somatodendritic release by an incompletely understood, but apparently exocytotic, mechanism. Even in striatum, axonal release sites are controversial, with evidence for DA varicosities that lack postsynaptic specialization, and largely extrasynaptic DA receptors and transporters. Moreover, DA release is often assumed to reflect a global response to a population of activities in midbrain DA neurons, whether tonic or phasic, with precise timing and specificity of action governed by other basal ganglia circuits. This view has been reinforced by anatomical evidence showing dense axonal DA arbors throughout striatum, and a lattice network formed by DA axons and glutamatergic input from cortex and thalamus. Nonetheless, localized DA transients are seen in vivo using voltammetric methods with high spatial and temporal resolution. Mechanistic studies using similar methods in vitro have revealed local regulation of DA release by other transmitters and modulators, as well as by proteins known to be disrupted in Parkinson's disease and other movement disorders. Notably, the actions of most other striatal transmitters on DA release also do not conform to the synaptic doctrine, with the absence of direct synaptic contacts for glutamate, GABA, and acetylcholine (ACh) on striatal DA axons. Overall, the findings reviewed here indicate that DA signaling in the basal ganglia is sculpted by cooperation between the timing and pattern of DA input and those of local regulatory factors.

5-HT(1B) receptor regulation of serotonin (5-HT) release by endogenous 5-HT in the substantia nigra.

Axonal release of serotonin (5-hydroxytryptamine, 5-HT) in the CNS is typically regulated by presynaptic 5-HT autoreceptors. Release of 5-HT in substantia nigra pars reticulata (SNr), a principal output from the basal ganglia, has seemed an interesting exception to this rule. The SNr receives one of the highest densities of 5-HT innervation in mammalian brain and yet negative feedback regulation of axonal 5-HT release by endogenous 5-HT has not been identified here. We explored whether we could identify autoregulation of 5-HT release by 5-HT(1B) receptors in rat SNr slices using fast-scan cyclic voltammetry at carbon-fiber microelectrodes to detect 5-HT release evoked by discrete stimuli (50 Hz, 20 pulses) paired over short intervals (1-10 s) within which any autoreceptor control should occur. Evoked 5-HT release exhibited short-term depression after an initial stimulus that recovered by 10 s. Antagonists for 5-HT(1B) receptors, isamoltane (1 microM) or SB 224-289 (1 microM), did not modify release during a stimulus train, but rather, they modestly relieved depression of subsequent release evoked after a short delay (< or =2 s). Release was not modified by antagonists for GABA (picrotoxin, 100 microM, saclofen, 50 microM) or histamine-H(3) (thioperamide, 10 microM) receptors. These data indicate that 5-HT release can activate a 5-HT(1B)-receptor autoinhibition of subsequent release, which is mediated directly via 5-HT axons and not via GABAergic or histaminergic inputs. These data reveal that 5-HT release in SNr is not devoid of autoreceptor regulation by endogenous 5-HT, but rather is under modest control which only weakly limits 5-HT signaling.

Presynaptic nicotinic receptors: a dynamic and diverse cholinergic filter of striatal dopamine neurotransmission.

The effects of nicotine on dopamine transmission from mesostriatal dopamine neurons are central to its reinforcing properties. Only recently however, has the influence of presynaptic nicotinic receptors (nAChRs) on dopaminergic axon terminals within striatum begun to be understood. Here, rather than simply enhancing (or inhibiting) dopamine release, nAChRs perform the role of a presynaptic filter, whose influence on dopamine release probability depends on presynaptic activity in dopaminergic as well as cholinergic neurons. Both mesostriatal dopaminergic neurons and striatal cholinergic interneurons play key roles in motivational and sensorimotor processing by the basal ganglia. Moreover, it appears that the striatal influence of dopamine and ACh cannot be fully appreciated without an understanding of their reciprocal interactions. We will review the powerful filtering by nAChRs of striatal dopamine release and discuss its dependence on activity in dopaminergic and cholinergic neurons. We will also review how nicotine, acting via nAChR desensitization, promotes the sensitivity of dopamine synapses to activity. This filtering action might provide a mechanism through which nicotine promotes how burst activity in dopamine neurons facilitates goal-directed behaviour and reinforcement processing. More generally, it indicates that we should not restrict our view of presynaptic nAChRs to simply enhancing neurotransmitter release. We will also summarize current understanding of the forms and functions of the diverse nAChRs purported to exist on dopaminergic axons. A greater understanding of nAChR form and function is imperative to guide the design of ligands with subtype-selective efficacy for improved therapeutic interventions in nicotine addiction as well as Parkinson's disease.

Assessment of effects of chromated copper arsenate (CCA)-treated timber on nontarget epibiota by investigation of fouling community development at seven European sites.

To assess the effect of the anti-marine-borer timber preservative CCA (a pressure-impregnated solution of copper, chromium, and arsenic compounds) on nontarget epibiota, fouling community development was investigated. Panels of Scots pine treated to target retentions of 12, 24, and 48 kg CCA per m3 of wood (covering the range of retentions recommended for marine use) plus untreated controls were submerged at seven coastal sites (Portsmouth, UK; La Tremblade [two sites], France; Ria Formosa, Portugal; Sagres, Portugal; Kristineberg, Sweden; Athens, Greece). The fouling community on the surfaces of the panels was assessed both qualitatively and quantitatively after 6, 12, and 18 months of exposure. Multivariate statistical methods were used to compare community structure between panel treatments. Panels treated to the three CCA loadings supported very similar fouling assemblages, which in most cases had higher numbers of taxa and individuals than assemblages on untreated panels. No detrimental effects on epibiota due to CCA preservatives were detected at any of the treatment levels at all seven exposure sites, suggesting that the range of environmental conditions at the sites had no bearing on preservative impact on fouling biota. Differences in community structure between CCA-treated and untreated panels may be due to enhanced larval settlement on CCA-treated timber by some species as a result of modifications to the surface properties of the timber by the preservative. Possible reasons for the higher numbers of certain species on the surface of CCA-treated panels are discussed.

Brain antioxidant regulation in mammals and anoxia-tolerant reptiles: balanced for neuroprotection and neuromodulation.

Reactive oxygen species (ROS) generated by mitochondrial respiration and other processes are often viewed as hazardous substances. Indeed, oxidative stress, defined as an imbalance between oxidant production and antioxidant protection, has been linked to several neurological disorders, including cerebral ischemia-reperfusion and Parkinson's disease. Consequently, cells and organisms have evolved specialized antioxidant defenses to balance ROS production and prevent oxidative damage. Research in our laboratory has shown that neuronal levels of ascorbate, a low molecular weight antioxidant, are ten-fold higher than those in much less metabolically active glial cells. Ascorbate levels are also selectively elevated in the CNS of anoxia-tolerant reptiles compared to mammals; moreover, plasma and CSF ascorbate concentrations increase markedly in cold-adapted turtles and in hibernating squirrels. Levels of the related antioxidant, glutathione, vary much less between neurons and glia or among species. An added dimension to the role of the antioxidant network comes from recent evidence that ROS can act as neuromodulators. One example is modulation of dopamine release by endogenous hydrogen peroxide, which we describe here for several mammalian species. Together, these data indicate adaptations that prevent oxidative stress and suggest a particularly important role for ascorbate. Moreover, they show that the antioxidant network must be balanced precisely to provide functional levels of ROS, as well as neuroprotection.

Dopamine-mediated volume transmission in midbrain is regulated by distinct extracellular geometry and uptake.

Somatodendritic release of dopamine (DA) in midbrain is, at least in part, nonsynaptic; moreover, midbrain DA receptors are predominantly extrasynaptic. Thus somatodendritic DA mediates volume transmission, with an efficacy regulated by the diffusion and uptake characteristics of the local extracellular microenvironment. Here, we quantitatively evaluated diffusion and uptake in substantia nigra pars compacta (SNc) and reticulata (SNr), ventral tegmental area (VTA), and cerebral cortex in guinea pig brain slices. The geometric parameters that govern diffusion, extracellular volume fraction (alpha) and tortuosity (lambda), together with linear uptake (k'), were determined for tetramethylammonium (TMA(+)), and for DA, using point-source diffusion combined with ion-selective and carbon-fiber microelectrodes. TMA(+)-diffusion measurements revealed a large alpha of 30% in SNc, SNr, and VTA, which was significantly higher than the 22% in cortex. Values for lambda and k' for TMA(+) were similar among regions. Point-source DA-diffusion curves fitted theory well with linear uptake, with significantly higher values of k' for DA in SNc and VTA (0.08--0.09 s(-1)) than in SNr (0.006 s(-1)), where DA processes are sparser. Inhibition of DA uptake by GBR-12909 caused a greater decrease in k' in SNc than in VTA. In addition, DA uptake was slightly decreased by the norepinephrine transport inhibitor, desipramine in both regions, although this was statistically significant only in VTA. We used these data to model the radius of influence of DA in midbrain. Simulated release from a 20-vesicle point source produced DA concentrations sufficient for receptor activation up to 20 microm away with a DA half-life at this distance of several hundred milliseconds. Most importantly, this model showed that diffusion rather than uptake was the most important determinant of DA time course in midbrain, which contrasts strikingly with the striatum where uptake dominates. The issues considered here, while specific for DA in midbrain, illustrate fundamental biophysical properties relevant for all extracellular communication.

Dopamine release and uptake dynamics within nonhuman primate striatum in vitro.

The putamen of the human striatum is a heterogeneous nucleus that contains the primary site of loss of dopamine (DA) in Parkinson's disease (PD). Furthermore, different functional domains of the putamen are heterogeneously susceptible to DA loss, and yet the dynamic regulation of extracellular DA concentration ([DA](o)) and comparison between domains has not been explored in the primate brain. In these studies, DA was measured in real time using fast-scan cyclic voltammetry at a carbon-fiber microelectrode in vitro in striatal sections from the common marmoset (Callithrix jacchus). [DA](o) released by a single stimulus pulse varied threefold along a ventromedial-dorsolateral axis. DA uptake was via the DA transporter (GBR12909 sensitive, desipramine insensitive). On the basis of data modeling with simulations of Michaelis-Menten kinetics, rate maximum, V(max), varied with region: both [DA](o) and V(max) were greatest in regions most vulnerable in PD. These differences were reflected in part by regional variation in DA content. [DA](o), V(max), and regional variation were two- to threefold greater than in rodent caudatoputamen. In addition, steady-state [DA](o) at physiological firing rates in primate striatum was controlled by depolarization frequency, uptake, and presynaptic autoreceptors. Furthermore, regulation of [DA](o) by these mechanisms differed significantly between limbic- and motor-associated domains. These data indicate interspecies heterogeneity in striatal DA dynamics that must be considered when extrapolating behavioral and drug responses from rodent to the primate brain. Moreover, the heterogeneity demonstrated within the primate putamen in the availability and dynamic regulation of DA may be central to understanding DA function in health, cocaine abuse, and disease.

Real-time dynamics of dopamine released from neuronal transplants in experimental Parkinson's disease.

Intrastriatal transplantation of foetal midbrain dopamine (DA) neurons ameliorates the fundamental symptoms of dopaminergic denervation in clinical and experimental parkinsonism despite providing only restricted reinnervation. To understand how DA function is restored by these grafts we used fast-scan cyclic voltammetry at a carbon-fiber microelectrode in vitro to monitor directly and in "real time" the dynamics of graft-derived DA. Simulations of Michaelis-Menten kinetics were used to model the experimental observations. We show that the concentration of DA released by a single depolarizing pulse is significantly lower in grafted than intact striata. On the other hand, the extracellular lifetime of DA in grafts is extended due to a marked reduction in the rate maximum (V(max)) for DA reuptake by the DA transporter. Moreover, variations in V(max) and release occur in parallel: where DA release is lowest, V(max) is lowest and vice versa. The consequences of these dynamics are twofold. First, during repeated depolarization at a physiological firing frequency, when net extracellular concentrations reflect DA release versus uptake, ambient levels of extracellular DA within the graft are restored to normal. Second, the protracted extracellular lifetime of DA will increase the number and extracellular sphere of its postsynaptic actions. This effect will be most prominent where DA availability (and thus V(max)) is most restricted. Thus, these data demonstrate that dopaminergic grafts restore striatal dopaminergic function with extracellular dynamics of DA that are different from those of intact striatum but which can normalize ambient DA levels and permit transmission over an extended sphere.

Effects of CCA (copper-chrome-arsenic) preservative treatment of wood on the settlement and recruitment of barnacles and tube building polychaete worms.

The effect of the anti-marine-borer treatment of wood using CCA (a pressure impregnated solution of copper, chromium and arsenic compounds) on non-target fouling animals was investigated. Panels treated to target retentions of 12, 24 and 48 kg CCA m(-3) of wood, together with untreated controls were exposed for 6, 12 and 18 months at coastal sites in Greece, Portugal, France and Sweden. General linear model (GLM) analysis revealed significant increases in numbers of certain fouling organisms (the serpulids Ficopomatus enig-maticus, Hydroides spp., Pomatoceros lamarkii and an unidentified species, three species of spirorbid, and the balanids Balanus perforatus and Elminius modestus) with increase in retention of CCA. The effect of CCA on the numbers of recruits may be due to effects on their settlement and survival, but may also be due to suppression of competitors. Significant differences in settlement density of barnacle spat occurred on newly exposed wood and on wood that had been exposed for 6 and 18 months. The relationships between settlement density and retention could be described by logarithmic curves of the form settlement density = a 1n(l + retention)+b. The effects of CCA on settlement are ascribed either to modification of wood surface chemistry leading to changes in surface charge, the availability of Cu, Cr or As at the wood surface, or to modifications to the microbial film. Barnacle settlement was between 6.5 and 14 times more intense on latewood than on earlywood, an effect that was evident in both untreated and preservative-treated wood.

Dopamine receptors--physiological understanding to therapeutic intervention potential.

There are two families of dopamine (DA) receptors, called D1 and D2, respectively. The D1 family consists of D1- and D5-receptor subtypes and the D2 family consists of D2-, D3-, and D4-receptor subtypes. The amino acid sequences of these receptors show that they all belong to a large superfamily of receptors with seven transmembrane domains, which are coupled to their intracellular signal transduction systems by G-proteins. The implications of DA receptors in neuropsychiatry and cardiovascular and renal diseases are discussed. Neuropsychiatry indications include Parkinson's disease, schizophrenia, migraine, drug dependence, mania and depression, and Gilles de la Tourette syndrome. The underlying dysfunction of dopaminergic systems and the potential benefits of dopaminergic therapy in these different indications are critically examined. With respect to the pharmacological treatment of Parkinson's disease, a range of DA agonists are in various stages of preclinical and clinical development. D2-receptor agonist activity is predominant in most effective antiparkinsonian DA agonists. However, in practice, it is difficult to treat patients for several years with DA agonists alone; therapeutic benefit is not sustained. Rather, the use of a combination of DA agonists and levodopa is considered preferable. Reports of the efficacy of DA partial agonists await confirmation, and recent clinical investigations also suggest the potential of D1 receptor agonists as antiparkinson drugs. Regarding migraine pathogenesis, clinical and pharmacological evidence suggests that DA is involved in this disorder. Most prodromal and accompanying symptoms may be related to dopaminergic activation. Several drugs acting on DA receptors are effective in migraine treatment. Furthermore, migraine patients show a higher incidence of dopaminergic symptoms following acute DA agonist administration, when compared with normal controls. In cardiology, the therapeutic benefits of DA agonists are noted in the treatment of heart failure. Low doses of DA are widely used for its specific dopaminergic effects on renal function, which are suggested to be beneficial, and for its alpha- and beta-adrenergic-mediated responses that occur with higher doses. However, studies have been unable to demonstrate that DA can prevent acute renal failure or reduce mortality. It appears that the significant progress that is being made in the molecular understanding of DA receptors will continue to have a tremendous impact in the pharmacological treatment of neuropsychiatric, cardiovascular, and renal diseases.

Dopamine is released spontaneously from developing midbrain neurons in organotypic culture.

While neuronal activity is important in CNS development, little is known of the behaviour of the actual neurotransmitters released during this period. None the less, indirect evidence has suggested that the neurotransmitter dopamine actually has a morphogenic role. This study is the first attempt to monitor directly and in real-time, the release of dopamine from midbrain neurons developing as an isolated organotypic slice culture. The observed release of dopamine was both spontaneous and synchronized and occurred with an average periodicity that is two orders of magnitude longer than the characteristic neuronal discharge activity of midbrain dopamine cells. Moreover, elevations in the extracellular concentrations of dopamine were markedly more prolonged in these and other developing systems than in axon terminal regions in mature striatum in which dopaminergic innervation is fully established. Thus, dopamine may have an action in developing circuits over spatial and temporal scales that vastly exceed those in mature, synaptic-like transmission.

Comparison of serotonin and dopamine release in substantia nigra and ventral tegmental area: region and species differences.

In this study, we compare the electrically evoked, somatodendritic release of dopamine (DA) with axonal release of serotonin (5-HT) in the substantia nigra (SN) and ventral tegmental area (VTA) in vitro by using fast-scan cyclic voltammetry with carbon-fibre microelectrodes. Furthermore, we have examined transmitter release in these regions in guinea-pig compared with rat. Somatodendritic DA was released, as shown previously, in guinea-pig VTA, SN pars compacta (SNc), and occasionally in SN pars reticulata (SNr). 5-HT was rarely released, except in SNr, where nonetheless it only contributed to <30% of amine signals. In rat midbrain, somatodendritic DA release was evoked to a similar extent as in guinea-pig. However, a clear species difference was apparent; i.e., 5-HT and DA were detected equally in rat SNc, whereas in rat SNr, 5-HT was the predominant transmitter detected. Nevertheless, electrically evoked extracellular concentrations of 5-HT in SNc and SNr were, respectively, seven- and fourfold less than DA in SNc. 5-HT release was low in all regions in neonatal rat slices before the maturation of 5-HT terminals. Hence, axonal 5-HT transmission in midbrain exhibits both species and site selectivity. Moreover, whereas somatodendritic DA release is conventionally regarded as modest compared with axon terminal release in striatum, somatodendritic DA release can result in significantly greater extracellular levels than a transmitter released from axon terminals in the same locality.

Differential autoreceptor control of somatodendritic and axon terminal dopamine release in substantia nigra, ventral tegmental area, and striatum.

Dopamine (DA) is released from somatodendritic sites of neurons in the substantia nigra pars compacta (SNc) and ventral tegmental area (VTA), where it has neuromodulatory effects. The aim of this study was to evaluate the role of D2 autoreceptor inhibition in the regulation of this somatodendritic release in each region. Fast cyclic voltammetry at carbon fiber microelectrodes was used to measure electrically evoked DA release in vitro. Furthermore, we compared D2 regulation of somatodendritic release with the more familiar axon terminal release in caudate putamen (CPu) and nucleus accumbens (NAc). Evoked DA release was TTX-sensitive at all sites. There was significant D2 autoinhibition of DA release in SNc; however, this mechanism was two- to threefold less powerful, as compared with axon terminal release in CPu. In contrast to SNc, somatodendritic release in VTA was not under significant D2 receptor control, whereas release in the respective axon terminal region (NAc) was controlled strongly by autoinhibition. Thus, these data indicate that, first, autoinhibition via D2 receptors consistently plays a less significant role in the control of somatodendritic than axon terminal DA release, and, second, even at the level of somatodendrites themselves, D2 autoinhibition displays marked regional variation. In the light of previous data indicating that DA uptake processes are also less active in somatodendritic than in terminal regions, these results are interpreted as indicating that DA transmission is regulated differently in somatodendritic zones, as compared with axon terminals, and thus may have different functional consequences.

Characteristics of electrically evoked somatodendritic dopamine release in substantia nigra and ventral tegmental area in vitro.

Somatodendritic dopamine (DA) release from neurons of the midbrain represents a nonclassical form of neuronal signaling. We assessed characteristics of DA release during electrical stimulation of the substantia nigra pars compacta (SNc) in guinea pig midbrain slices. With the use of parameters optimized for this region, we compared stimulus-induced increases in extracellular DA concentration ([DA]o) in medial and lateral SNc, ventral tegmental area (VTA), and dorsal striatum in vitro. DA release was monitored directly with carbon-fiber microelectrodes and fast-scan cyclic voltammetry. Detection of DA in SNc was confirmed by electrochemical, pharmacological, and anatomic criteria. Voltammograms of the released substance had the same peak potentials as those of DA obtained during in vitro calibration, but different from those of the indoleamine 5-hydroxytryptamine. Similar voltammograms were also obtained in the DA-rich striatum during local electrical stimulation. Contribution from the DA metabolite 3,4-dihydroxyphenylacetic acid to somatodendritic release was negligible, as indicated by the lack of effect of the monoamine oxidase inhibitor pargyline (20 microM) on the signal. Lastly, DA voltammograms could only be elicited in regions that were subsequently determined to be positive for tyrosine hydroxylase immunoreactivity (TH-ir). The frequency dependence of stimulated DA release in SNc was determined over a range of 1-50 Hz, with a constant duration of 10 s. Release was frequency dependent up to 10 Hz, with no further increase at higher frequencies. Stimulation at 10 Hz was used in all subsequent experiments. With this paradigm, DA release in SNc was tetrodotoxin insensitive, but strongly Ca2+ dependent. Stimulated [DA]o in the midbrain was also site specific. At the midcaudal level examined, DA efflux was significantly greater in VTA (1.04 +/- 0.05 microM, mean +/- SE) than in medial SNc (0.52 +/- 0.05 microM), which in turn was higher than in lateral SNc (0.35 +/- 0.03 microM). This pattern followed the apparent density of TH-ir, which was also VTA > medial SNc > lateral SNc. This report has introduced a new paradigm for the study of somatodendritic DA release. Voltammetric recording with electrodes of 2-4 microns tip diameter permitted highly localized, direct detection of endogenous DA. The Ca2+ dependence of stimulated release indicated that the process was physiologically relevant. Moreover, the findings that somatodendritic release was frequency dependent across a range characteristic of DA cell firing rates and that stimulated [DA]o varied markedly among DA cell body regions have important implications for how dendritically released DA may function in the physiology and pathophysiology of substantia nigra and VTA.

Heterogeneity of electrically evoked dopamine release and reuptake in substantia nigra, ventral tegmental area, and striatum.

Somatodendritic dopamine (DA) released in substantia nigra pars compacta (SNc) and the ventral tegmental area (VTA) may mediate extrasynaptic neuronal signaling. The concentration of extracellular DA ([DA]o) attained during somatodendritic activation will be governed by the density of release sites and properties of DA uptake. We evaluated these factors in SNc, VTA, and dorsal striatum with carbon-fiber microelectrodes and fast-scan cyclic voltammetry to monitor [DA]o during local electrical stimulation (10 Hz, 5 s) in guinea pig brain slices. Stimulated DA efflux was site specific, with significantly higher [DA]o in caudal (0.48 +/- 0.03 microM, mean +/- SE) than rostral SNc (0.16 +/- 0.01 microM), averaged over their mediolateral extents, and higher [DA]o in VTA (0.74 +/- 0.07 microM) than in medial (0.43 +/- 0.04 microM) or lateral SNc (0.29 +/- 0.05 microM), averaged rostrocaudally. Throughout SNc, evoked [DA]o correlated positively (r = 0.91) with the density of tyrosine-hydroxylase-immunoreactive cells. Modulation of evoked [DA]o by uptake was also site specific. The selective DA uptake inhibitor GBR 12909 significantly increased evoked [DA]o in caudal SNc (to 185 +/- 27%) and striatum (408 +/- 24%), but had no effect in rostral SNc or VTA. Conversely, the norepinephrine (NE) uptake inhibitor desipramine did not alter stimulated [DA]o in caudal SNc or striatum, but caused significant enhancement in rostral SNc (196 +/- 17%) and VTA (126 +/- 12%). Paroxetine, a selective 5-hydroxytryptamine uptake inhibitor had little effect in any region tested. Site-specific sensitivity to desipramine mandated evaluation of dopamine-beta-hydroxylase immunoreactivity (D beta H-ir) in midbrain. The density of filaments positive for D beta H-ir was greater in rostral SNc and VTA than in caudal SNc, suggesting DA clearance via the NE transporter in these regions. Importantly, D beta H-ir was most dense in sections rostral to SNc where no catecholamine signal was detected and no enhancement was observed with desipramine, indicating a lack of NE contribution to evoked release in any region examined. Taken together, these data confirmed that evoked somatodendritic [DA]o depends on DA cell density and on local uptake properties. Uptake was less efficient in SNc and VTA than in striatum. Moreover, enhancement of stimulated [DA]o by GBR 12909 demonstrated that evoked release from dendrites is not via reversal of the DA transporter. Lastly, the heterogeneous patterns of DA uptake within SNc and VTA were consistent with the pattern of degeneration in Parkinson's disease; less vulnerable DA cells, e.g., those in VTA, have less DA uptake than the more vulnerable cells of caudal SNc.

Subchronic inhalation toxicity of ethylbenzene in mice, rats, and rabbits.

Mice, rats, and rabbits (five/sex/group) were exposed by inhalation to ethylbenzene (EB) vapors for 6 hr/day, 5 days/week for 4 weeks (20 exposures). Rats and mice received 0, 99, 382, or 782 ppm EB while rabbits received 0, 382, 782, or 1610 ppm. No changes were evident in mortality patterns, clinical chemistries, urinalyses, or treatment-related gross/microscopic (including ophthalmologic) lesions. Rats exhibited sporadic lacrimation and salivation, as well as significantly increased liver weights at 382 and 782 ppm, and small increases in leukocyte counts at 782 ppm. Males at this exposure level also showed marginal elevations in platelet counts. In mice, females showed statistically increased absolute and relative liver weights at 382 and 782 ppm, while males had statistically increased relative liver-to-brain weight ratios only at 782 ppm. Female rabbits at the high exposure level of 1610 ppm gained weight more slowly than controls (not statistically significant); males showed a similar transient downward trend after 1 week, but showed no differences from controls at study's end. A no observed adverse effect level (NOAEL) of 382 ppm appears appropriate for rats and mice with a lowest observed adverse effect level (LOAEL) of 782 ppm. A NOAEL of 782 ppm and LOAEL of 1610 ppm are appropriate for rabbits.

HLA class I and H ferritin gene polymorphisms in normal subjects and patients with haemochromatosis.

The gene for idiopathic haemochromatosis is located on the short arm of chromosome 6 within 1 cM of the HLA-A locus. In this region there are many HLA class I genes, and there may also be a gene for the 'H' subunit of ferritin. Both HLA class I and H ferritin genes are therefore candidates for the abnormal gene in idiopathic haemochromatosis. In 15 unrelated patients the frequency of HLA-A3 was 80% compared with 24% for 600 unrelated individuals from South Wales. The most common haplotype involved is probably HLA-A3, B7. DNA was prepared from leucocytes from 12 of these patients and from 85 normal subjects. After digestion with Taq1, electrophoresis, and Southern blotting, class I sequences were detected by hybridisation to an HLA class I probe (pHLA-A). Of the 34 restriction fragments detected, 22 were polymorphic. Particular fragments correlated with the presence of HLA-A antigens A1, 2, 3, 10, 11, w19, and 28, but there was little correlation with B antigens. Restriction fragment patterns specific for haemochromatosis were not found with TaqI or during less extensive studies with other restriction enzymes. No differences in restriction fragment patterns were found between four patients and four normal subjects apparently homozygous for HLA-A3 and B7. Examination of Southern blotting patterns for genomic DNA from patients and normal subjects with a panel of 12 restriction enzymes and a probe for the H ferritin gene (pDBR-2) revealed no polymorphisms associated with either idiopathic haemochromatosis or particular HLA phenotypes. These studies provide no support for either HLA class I genes or the H ferritin gene as candidates for the haemochromatosis gene.

Lack of concordance of the Salmonella/microsome assay with the mouse dermal carcinogenesis bioassay for complex petroleum hydrocarbon mixtures.

Typical petroleum hydrocarbon mixtures were tested directly, without extraction, in the Salmonella/microsome mutagenesis assay in order to determine if the assay would be useful to predict their carcinogenic activity. The carcinogenic activity of each sample had been previously characterized in the in vivo mouse dermal carcinogenesis bioassay. The series of samples evaluated offered several advantages. They spanned a wide boiling point range, were well characterized chemically, had been tested for carcinogenic activity in a single laboratory, and varied in potency in vivo from inactive to highly active. Mutagenicity testing was performed in several well-established contract laboratories that routinely perform the assay. These laboratories were the main contracting laboratories for these assays at the time and had previously tested petroleum samples for clients. Initially, the first laboratory tested 13 samples in five strains of Salmonella typhimurium with and without rat liver S-9 (Arochlor 1254 induced), utilizing both plate and suspension techniques. None of the 13 samples exhibited a mutagenic response, even though 9 of the 13 were slightly to highly dermally carcinogenic in mice. Because of the unexpected results, it was decided to repeat the mutagenicity assays in two other laboratories. Six of the thirteen samples were selected, ranging in carcinogenic potency from negative to highly active. Again, none were mutagenic in the second contract laboratory. In a third facility, only one sample of the six exhibited a definite mutagenic response. However, the response was observed with a sample having only weak carcinogenic activity and, unusual for petroleum hydrocarbons, occurred without activation.(ABSTRACT TRUNCATED AT 250 WORDS)

Assignment of human ferritin genes to chromosomes 11 and 19q13.3----19qter.

Extracts of hamster-human and mouse-human hybrids, some with translocations involving chromosome 19, have been assayed for both human spleen ferritin (rich in L subunits) and human heart ferritin (rich in H subunits). Hybrid lines retaining part of the long arm of chromosome 19 including the region 19q13.3----19qter produced human "L" type ferritin. This confirms the previous assignment of the "ferritin gene" to chromosome 19 (Caskey et al. 1983). However, lines retaining chromosome 11 were found to contain human "H" type ferritin suggesting that the gene for the "H" subunit is on this chromosome. The presence of chromosome 6 was not necessary for the expression of either "H" or "L" type human ferritin. It thus seems unlikely that the gene for idiopathic haemochromatosis is a ferritin gene.