Parameter-free testing of the shape of a probability distribution

The Kolmogorov-Smirnov test determines the consistency of empirical data with a particular probability distribution. Often, parameters in the distribution are unknown, and have to be estimated from the data. In this case, the Kolmogorov-Smirnov test depends on the form of the particular probability distribution under consideration, even when the estimated parameter-values are used within the distribution. In the present work, we address a less specific problem: to determine the consistency of data with a given functional form of a probability distribution (for example the normal distribution), without enquiring into values of unknown parameters in the distribution. For a wide class of distributions, we present a direct method for determining whether empirical data are consistent with a given functional form of the probability distribution. This utilizes a transformation of the data. If the data are from the class of distributions considered here, the transformation leads to an empirical distribution with no unknown parameters, and hence is susceptible to a standard Kolmogorov-Smirnov test. We give some general analytical results for some of the distributions from the class of distributions considered here. The significance level and power of the tests introduced in this work are estimated from simulations. Some biological applications of the method are given.

Innexins in the lobster stomatogastric nervous system: cloning, phylogenetic analysis, developmental changes and expression within adult identified dye and electrically coupled neurons

Gap junctions play a key role in the operation of neuronal networks by enabling direct electrical and metabolic communication between neurons. Suitable models to investigate their role in network operation and plasticity are invertebrate motor networks, which are built of comparatively few identified neurons, and can be examined throughout development; an excellent example is the lobster stomatogastric nervous system. In invertebrates, gap junctions are formed by proteins that belong to the innexin family. Here, we report the first molecular characterization of two crustacean innexins: the lobster Homarus gammarus innexin 1 (Hg-inx1) and 2 (Hg-inx2). Phylogenetic analysis reveals that innexin gene duplication occurred within the arthropod clade before the separation of insect and crustacean lineages. Using in situ hybridization, we find that each innexin is expressed within the adult and developing lobster stomatogastric nervous system and undergoes a marked down-regulation throughout development within the stomatogastric ganglion (STG). The number of innexin expressing neurons is significantly higher in the embryo than in the adult. By combining in situ hybridization, dye and electrical coupling experiments on identified neurons, we demonstrate that adult neurons that express at least one innexin are dye and electrically coupled with at least one other STG neuron. Finally, two STG neurons display no detectable amount of either innexin mRNAs but may express weak electrical coupling with other STG neurons, suggesting the existence of other forms of innexins. Altogether, we provide evidence that innexins are expressed within small neuronal networks built of dye and electrically coupled neurons and may be developmentally regulated.

Synaptogenesis in the giant-fibre system of Drosophila: interaction of the giant fibre and its major motorneuronal target

The tergotrochanteral (jump) motorneuron is a major synaptic target of the Giant Fibre in Drosophila. These two neurons are major components of the fly's Giant-Fibre escape system. Our previous work has described the development of the Giant Fibre in early metamorphosis and the involvement of the shaking-B locus in the formation of its electrical synapses. In the present study, we have investigated the development of the tergotrochanteral motorneuron and its electrical synapses by transforming Drosophila with a Gal4 fusion construct containing sequences largely upstream of, but including, the shaking-B(lethal) promoter. This construct drives reporter gene expression in the tergotrochanteral motorneuron and some other neurons. Expression of green fluorescent protein in the motorneuron allows visualization of its cell body and its subsequent intracellular staining with Lucifer Yellow. These preparations provide high-resolution data on motorneuron morphogenesis during the first half of pupal development. Dye-coupling reveals onset of gap-junction formation between the tergotrochanteral motorneuron and other neurons of the Giant-Fibre System. The medial dendrite of the tergotrochanteral motorneuron becomes dye-coupled to the peripheral synapsing interneurons between 28 and 32 hours after puparium formation. Dye-coupling between tergotrochanteral motorneuron and Giant Fibre is first seen at 42 hours after puparium formation. All dye coupling is abolished in a shaking-B(neural) mutant. To investigate any interactions between the Giant Fibre and the tergotroachanteral motorneuron, we arrested the growth of the motorneuron's medial neurite by targeted expression of a constitutively active form of Dcdc42. This results in the Giant Fibre remaining stranded at the midline, unable to make its characteristic bend. We conclude that Giant Fibre morphogenesis normally relies on fasciculation with its major motorneuronal target.

Nasal continuous positive airway pressure devices do not maintain the set pressure dynamically when tested under simulated clinical conditions

STUDY OBJECTIVES

Nasal continuous positive airway pressure (CPAP) is standard therapy for obstructive sleep apnea syndrome. The effective nasal mask pressure may be adversely affected by factors that increase system resistance (eg, long tubing and/or water condensation) and by dynamic variables (breathing frequency [f] and tidal volume [VT]). The present study was conducted in order to assess the performance of CPAP machines throughout a range of simulated clinical conditions.

DESIGN

Four currently used CPAP machines were tested at settings of 5, 10, 15, and 20 cm H(2)O using a pulmonary waveform generator to produce VTs of 0.4, 0.8, and 1.2 L at frequencies of 10, 20, and 30 breaths/min. Machines were tested under five conditions: 6-foot and 12-foot tubing, with and without an in-line humidifier, and 12-foot tubing with humidifier and water condensation.

MEASUREMENTS

Maximum and minimum mask pressure measurements were obtained during five respiratory cycles for each dynamic variable under each of the five conditions and CPAP settings (180 experiments on each of four CPAP models).

RESULTS

Using typical clinical parameters (VT, 0.4 L and 0.8 L; f, 10 breaths/min and 20 breaths/min; and CPAP, 5 to 15 cm H(2)O), mask pressure consistently varied above and below the set point when additional tubing and/or a humidifier were added to the system (0.7 to 2.9 cm H(2)O below and 0.5 to 1.0 cm H(2)O above the set pressure). Water condensation caused large pressure deviations (inspiratory pressure ranged from 3.5 to 5.6 cm H(2)O below set pressure, and expiratory pressure ranged from 0.7 to 3.5 cm H(2)O above set pressure).

CONCLUSIONS

Therapy and compliance could be adversely affected because some CPAP machines in current use do not maintain constant continuous mask pressure when tested using simulated conditions, especially when water condenses in the tubing.

Two engrailed-related genes in the cockroach: cloning, phylogenetic analysis, expression and isolation of splice variants

engrailed-related genes have been isolated in numerous taxa. Within the insects, some species have a single engrailed-related gene whilst others have two copies, raising the question of when and how often gene duplications have occurred. Here we report the cloning, in the cockroach Periplaneta americana, of two engrailed-related genes Pa-en1 and Pa-en2. By comparing conserved domains and by carrying out a phylogenetic analysis, we conclude that these two genes are likely to be the product of a recent duplication in the cockroach lineage. Pa-en1 and Pa-en2 are co-expressed during early embryogenesis and their segmental pattern of expression appears in an anterior-posterior progression. We have also isolated potential splice variants of Pa-en2 which lack some regulatory domains. The roles these splice variants may play in regulating developmental processes are discussed.

Two Drosophila innexins are expressed in overlapping domains and cooperate to form gap-junction channels

Members of the innexin protein family are structural components of invertebrate gap junctions and are analogous to vertebrate connexins. Here we investigate two Drosophila innexin genes, Dm-inx2 and Dm-inx3 and show that they are expressed in overlapping domains throughout embryogenesis, most notably in epidermal cells bordering each segment. We also explore the gap-junction-forming capabilities of the encoded proteins. In paired Xenopus oocytes, the injection of Dm-inx2 mRNA results in the formation of voltage-sensitive channels in only approximately 40% of cell pairs. In contrast, Dm-Inx3 never forms channels. Crucially, when both mRNAs are coexpressed, functional channels are formed reliably, and the electrophysiological properties of these channels distinguish them from those formed by Dm-Inx2 alone. We relate these in vitro data to in vivo studies. Ectopic expression of Dm-inx2 in vivo has limited effects on the viability of Drosophila, and animals ectopically expressing Dm-inx3 are unaffected. However, ectopic expression of both transcripts together severely reduces viability, presumably because of the formation of inappropriate gap junctions. We conclude that Dm-Inx2 and Dm-Inx3, which are expressed in overlapping domains during embryogenesis, can form oligomeric gap-junction channels.

Gap-Junctional communication between developing Drosophila muscles is essential for their normal development

Recent experiments have demonstrated that a family of proteins, known as the innexins, are structural components of invertebrate gap junctions. The shaking-B (shak-B) locus of Drosophila encodes two members of this emerging family, Shak-B(lethal) and Shak-B(neural). This study focuses on the role of Shak-B gap junctions in the development of embryonic and larval muscle. During embryogenesis, shak-B transcripts are expressed in a subset of the somatic muscles; expression is strong in ventral oblique muscles (VO4-6) but only weak in ventral longitudinals (VL3 and 4). Carboxyfluorescein injected into VO4 of wild-type early stage 16 embryos spreads, via gap junctions, to label adjacent muscles, including VL3 and 4. In shak-B2 embryos (in which the shak-B(neural) function is disrupted), dye injected into VO4 fails to spread into other muscles. In the first instar larva, when dye coupling between muscles is no longer present, another effect of the shak-B2 mutation is revealed by whole-cell voltage clamp. In a calcium-free saline, only two voltage-activated potassium currents are present in wild-type muscles; a fast IA and a slow IK current. In shak-B2 larvae, these two currents are significantly reduced in magnitude in VO4 and 5, but remain normal in VL3. Expression of shak-B(neural) in a shak-B2 background fully rescues both dye coupling in embryonic muscle and whole-cell currents in first instar VO4 and 5. Our observations show that Shak-B(neural) is one of a set of embryonic gap-junction proteins, and that it is required for the normal temporal development of potassium currents in some larval muscles.

Double-stranded RNA interference shows that Engrailed controls the synaptic specificity of identified sensory neurons

The transcription factor Engrailed (En) controls the topography of axonal projections by regulating the expression of cell-adhesion molecules [1] [2] [3] [4] but it is not known whether it also controls the choice of individual synaptic target cells. In the cercal sensory system of the larval cockroach (Periplaneta americana), small numbers of identified wind-sensitive sensory neurons form highly specific synaptic connections with 14 identified giant interneurons [5] [6], and target-cell choice is independent of the pattern of axonal projections [6]. En is a putative positional determinant in the array of cercal sensory neurons [7]. In the present study, double-stranded RNA (dsRNA) interference [8] was used to abolish En expression. This treatment changed the axonal arborisation and synaptic outputs of an identified En-positive sensory neuron so that it came to resemble a nearby En-negative cell, which was itself unaffected. We thus demonstrate directly that En controls synaptic choice, as well as axon projections.

Null mutation in shaking-B eliminates electrical, but not chemical, synapses in the Drosophila giant fiber system: a structural study

Mutations in the Drosophila shaking-B gene perturb synaptic transmission and dye coupling in the giant fiber escape system. The GAL4 upstream activation sequence system was used to express a neuronal-synaptobrevin-green fluorescent protein (nsyb-GFP) construct in the giant fibers (GFs); nsyb-GFP was localized where the GFs contact the peripherally synapsing interneurons (PSIs) and the tergotrochanteral motorneurons (TTMns). Antibody to Shaking-B protein stained plaquelike structures in the same regions of the GFs, although not all plaques colocalized with nsyb-GFP. Electron microscopy showed that the GF-TTMn and GF-PSI contacts contained many chemical synaptic release sites. These sites were interposed with extensive regions of close membrane apposition (3.25 nm +/- 0.12 separation), with faint cross striations and a single-layered array of 41-nm vesicles on the GF side of the apposition. These contacts appeared similar to rectifying electrical synapses in the crayfish and were eliminated in shaking-B2 mutants. At mutant GF-TTMn and GF-PSI contacts, chemical synapses and small regions of close membrane apposition, more similar to vertebrate gap junctions, were not affected. Gap junctions with more vertebratelike separation of membranes (1.41 nm +/- 0.08) were abundant between peripheral perineurial glial processes; these were unaffected in the mutants.

Drosophila Shaking-B protein forms gap junctions in paired Xenopus oocytes

In most multicellular organisms direct cell-cell communication is mediated by the intercellular channels of gap junctions. These channels allow the exchange of ions and molecules that are believed to be essential for cell signalling during development and in some differentiated tissues. Proteins called connexins, which are products of a multigene family, are the structural components of vertebrate gap junctions. Surprisingly, molecular homologues of the connexins have not been described in any invertebrate. A separate gene family, which includes the Drosophila genes shaking-B and l(1)ogre, and the Caenorhabditis elegans genes unc-7 and eat-5, encodes transmembrane proteins with a predicted structure similar to that of the connexins. shaking-B and eat-5 are required for the formation of functional gap junctions. To test directly whether Shaking-B is a channel protein, we expressed it in paired Xenopus oocytes. Here we show that Shaking-B localizes to the membrane, and that its presence induces the formation of functional intercellular channels. To our knowledge, this is the first structural component of an invertebrate gap junction to be characterized.

Regeneration of cercal filiform hair sensory neurons in the first-instar cockroach restores escape behavior

Neural regeneration in the escape circuit of the first-instar cockroach is described using behavioral analysis, electrophysiology, intracellular staining, and electron microscopy. Each of the two filiform hairs on each of the animal's cerci is innervated by a single sensory neuron, which specifically synapses with a set of giant interneurons (GIs) in the terminal ganglion. These trigger a directed escape run. Severing the sensory axons causes them to degenerate and perturbs escape behavior, which is restored to near normal after 4-6 days. Within this time, afferents regenerate and reestablish arborizations in the terminal ganglion. In most cases, regenerating afferents enter the cercal glomerulus and re-form most of the specific monosynaptic connections they acquired during embryogenesis, although their morphology deviates markedly from normal; these animals reestablish near normal escape behavior. In a few cases, regenerating afferents remain within the cercus or bypass the cercal glomerulus, and thereby fail to re-form synapses with GIs; these animals continue to exhibit perturbed escape behavior. We conclude that in most cases, specific synapses are reestablished and appropriate escape behavior is restored. This regeneration system therefore provides a tractable model for the establishment of synaptic specificity in a simple neuronal circuit.

Mutations in shaking-B prevent electrical synapse formation in the Drosophila giant fiber system

The giant fiber system (GFS) is a simple network of neurons that mediates visually elicited escape behavior in Drosophila. The giant fiber (GF), the major component of the system, is a large, descending interneuron that relays visual stimuli to the motoneurons that innervate the tergotrochanteral jump muscle (TTM) and dorsal longitudinal flight muscles (DLMs). Mutations in the neural transcript from the shaking-B locus abolish the behavioral response by disrupting transmission at some electrical synapses in the GFS. This study focuses on the role of the gene in the development of the synaptic connections. Using an enhancer-trap line that expresses lacZ in the GFs, we show that the neurons develop during the first 30 hr of metamorphosis. Within the next 15 hr, they begin to form electrical synapses, as indicated by the transfer of intracellularly injected Lucifer yellow. The GFs dye-couple to the TTM motoneuron between 30 and 45 hr of metamorphosis, to the peripherally synapsing interneuron that drives the DLM motoneurons at approximately 48 hr, and to giant commissural interneurons in the brain at approximately 55 hr. Immunocytochemistry with shaking-B peptide antisera demonstrates that the expression of shaking-B protein in the region of GFS synapses coincides temporally with the onset of synaptogenesis; expression persists thereafter. The mutation shak-B2, which eliminates protein expression, prevents the establishment of dye coupling shaking-B, therefore, is essential for the assembly and/or maintenance of functional gap junctions at electrical synapses in the GFS.

Identified octopaminergic neurons provide an arousal mechanism in the locust brain

1. Habituation is the declining responsiveness of a neural circuit (or behavior) to repetitive stimulation. Dishabituation (or arousal) can be brought about by the sudden presentation of an additional, novel stimulus. A clear example of arousal in the locust is provided by the visual system: the habituated response of the descending contralateral movement detector (DCMD) interneuron to repetitive visual stimuli can be dishabituated by a variety of other visual and tactile stimuli. 2. Application of octopamine to the locust brain and optic lobes dishabituates the DCMD in a manner similar to the effect of visual and tactile stimulation. 3. The locust CNS contains two pairs of octopamine-immunoreactive cells, the protocerebral medulla 4 (PM4) neurons, that could potentially mediate this dishabituation effect; PM4 neurons arborize in the optic lobe, they contain octopamine, and they respond to the same visual and tactile stimuli that dishabituate the DCMD. 4. To investigate whether PM4 activity dishabituates the DCMD, we recorded intracellularly from one of the PM4 neurons while recording extracellularly from the DCMD. When the PM4 neuron is injected with hyperpolarizing current to render it completely inactive, the DCMD exhibits its characteristic habituation to a moving visual stimulus. However, depolarizing the PM4 neuron, to produce action potentials at approximately 20 Hz, significantly increases the number of DCMD action potentials per stimulus. 5. The PM4 neurons may therefore play an important role in dishabituating the DCMD to novel stimuli. This effect is presumably mediated by PM4 neurons releasing endogenous octopamine within the optic lobe.

Expression of engrailed in an array of identified sensory neurons: comparison with position, axonal arborization, and synaptic connectivity

engrailed (en) is expressed in the posterior region of embryonic segments and appendages of the cockroach, Periplaneta americana. By 23% of embryogenesis En immunoreactivity is apparent in the dorsal half of the cercus, appendages of segment A11. By 40% of development, En staining is present in the dorsomedial half of the cercus. The nucleus of the medial filiform hair sensory neuron (M), born in this region, expresses en strongly. Staining is never seen in the lateral neuron (L). En is expressed in M as the sensory axons enter the terminal ganglion and begin to form their different arborizations and synaptic connections. This pattern of expression persists through development to the second instar. In mutant animals with supernumerary filiform hair sensilla, En immunoreactivity is only seen in the medial neurons. In second-instar and adult cerci en expression is also seen in medially located neurons. We compared the levels of En staining in the array of 25 second instar neurons with their position, axonal arbor type, and synaptic connections. Staining intensity correlates with distance from the cercal midline, suggesting that en is regulated by other circumferential positional determinants. The expression of en does not correlate with the formation of an M-type arbor. Although 10 to 12 sensory neurons that express en form synapses with giant interneuron 5, the correlation is not precise. These results suggest that, if En does form part of a combinatorial system of positional information in the cercus, its actions are modulated by other gene products.

Exercise-induced QRS changes (Athens QRS score) in patients with coronary artery disease: a marker of myocardial ischemia

Previous studies have shown a good correlation between exercise-induced changes of Q-, R-, and S-waves (Athens QRS score) and the number of the obstructed coronary arteries. The present study was undertaken to test the hypothesis that abnormal Athens QRS score is related to exercise-induced myocardial ischemia. Patients who had exercise radionuclide ventriculography (n = 150) or thallium-201 scintigraphy (n = 124) within 1 month of cardiac catheterization were studied. Athens QRS score was calculated based on the exercise-induced changes of the Q-, R-, and S-waves. Changes in Athens QRS score were compared to the number of obstructed coronary arteries, segmental contraction abnormalities, and exercise-induced myocardial perfusion defects. Athens QRS score and coronary artery disease: The Athens QRS score was decreased as the number of obstructed coronary arteries increased (normal coronary arteries 3.7 mm, confidence interval 1.0 to 3.9, one vessel disease 1.2 mm, two vessel disease -0.6 mm, three vessel disease -1.3 mm, p < 0.001). Athens QRS score and segmental contraction abnormalities: The Athens QRS score decreased as the number of segmental contraction abnormalities increased (no segmental contraction abnormalities 2.5 mm, confidence interval 1.0 to 3.9, one segmental contraction abnormality -0.4 mm, two segmental contraction abnormalities -1.5 mm, three segmental contraction abnormalities -2.6 mm, p < 0.001). Athens QRS score and reversible myocardial perfusion defects: The Athens QRS score was decreased as the number of exercise-induced myocardial perfusion defects increased (no perfusion defect 2.4 mm, confidence interval 0.9 to 3.9, one perfusion defect -0.7 mm, two perfusion defects -2.6 mm, three perfusion defects -3.3 mm, p < 0.001). Abnormal values of the Athens QRS score were better correlated with the number of exercise-induced segmental contraction abnormalities or the myocardial perfusion defects than the number of obstructed coronary arteries (p < 0.001). Exercise-induced changes in Athens QRS score were directly related to the number of obstructed coronary arteries, to exercise-induced segmental contraction abnormalities and to exercise-induced myocardial perfusion defects. However, Athens QRS score changes were more closely related to the number of exercise-induced segmental contraction abnormalities or to the exercise-induced myocardial perfusion defects than to the number of obstructed coronary arteries. The data suggest that exercise-induced QRS changes, Athens QRS score are related to exercise-induced myocardial ischemia.

Naltrexone use in the treatment of anorexia nervosa and bulimia nervosa

Our auto-addiction model suggests that opiate blockade may be therapeutically useful in anorexia nervosa and bulimia nervosa. Naltrexone was administered to out-patient subjects in double-blind clinical trials with randomized cross-over designs. Reduction in binge-purge symptomatology was evident in the naltrexone period over placebo for 18 out of 19 subjects with either bulimia or anorexia nervosa of the bulimic subtype. In every case, the decoding of drug or placebo double blinding confirmed the assessments of both the investigator and the subjects, based on the blind analysis of the data and on their therapeutic response, respectively. Statistical analysis done on the total population and two diagnostic subgroups found highly significant differences.

Analysis of the peptide content of the locust vasopressin-like immunoreactive (VPLI) neurons

Isolated cell bodies of the locust vasopressin-like immunoreactive (VPLI) neurons, analyzed by HPLC separation and radioimmune assay, contain three arginine vasopressin-like peptides: a previously identified monomer (Fl, Cys-Leu-Ile-Thr-Asn-Cys-Pro-Arg-Gly-NH2) and its antiparallel homodimer (F2), but also the previously unreported parallel homodimer (PDm). VPLI neuron activity significantly reduces the level of cAMP in the CNS. Of the three synthetic peptides, only the monomer (F1, 10(-8) and 10(-6) M) is capable of inhibiting a forskolin-stimulated increase in cAMP in isolated neural membranes. The antiparallel (F2) and parallel dimers (PDm) of this peptide have no effect on this second messenger.

Cellular colocalization of diuretic peptides in locusts: a potent control mechanism

Locust abdominal ganglia are shown to colocalize Locusta-diuretic peptide-, leucokinin I-, and lysine vasopressin-like immunoreactivity in posterior lateral neurosecretory cells. Extracts of abdominal ganglia were partially purified by RP-HPLC then dot immunoassay screened with the same antisera used for immunocytochemistry. Locusta-diuretic peptide-like immunoreactive material coeluted with synthetic Locusta-diuretic peptide, and leucokinin-like immunoreactive material coeluted with locustakinin. Lysine vasopressin-like material eluted in fractions that also showed Locusta-diuretic peptide and leucokinin I immunoreactivity. The diuretic activity of synthetic Locusta-diuretic peptide and locustakinin is demonstrated, and they are shown to act at least additively to promote Malpighian tubule fluid secretion. The immunoreactive neurosecretory cells are assumed to express at least these two peptides, and a model for promoting fluid secretion is proposed.

Pharmacological analysis of the cholinergic input to the locust VPLI neuron from an extraocular photoreceptor system

1. The brain of the locust contains an extraocular photoreceptor (EOP), which provides the major synaptic excitation to the vasopressin-like immunoreactive (VPLI) interneuron of the suboesophageal ganglion. Although the precise location of the EOP remains unknown, its activity can be determined indirectly by intracellular recording from the VPLI neuron. The excitatory drive to the VPLI neuron occurs only in darkness and is absent in the light. 2. The EOP is preferentially sensitive to light of wavelength 494 +/- 7 (SD) nm (blue-green) and has an absorption spectrum characteristic of a rhodopsin-like photopigment. 3. In the presence of high divalent saline (20 mM Ca2+ and Mg2+), the VPLI neuron receives excitatory input in the light. This indicates that the excitatory input to the VPLI neuron is from a tonically active descending input, which normally is inhibited by the light-induced activation of the presynaptic EOP. 4. Stimulation of the connectives while recording the resultant excitatory postsynaptic potential (EPSP) evoked in VPLI shows that the descending input projects beyond the suboesophageal ganglion, extending as far as the metathoracic ganglion. 5. Pharmacological analysis shows that the descending input to the VPLI neuron is cholinergic: acetylcholine (ACh) strongly depolarizes the neuron and eserine, an ACh esterase inhibitor, markedly potentiates the synaptic excitation of the VPLI neuron. 6. Nicotinic and muscarinic receptor antagonists show that the excitation of VPLI consists of two pharmacologically discrete components. Nicotinic ACh receptors mediate a fast depolarization, whereas muscarinic ACh receptors evoke a more sustained depolarization. Accordingly, both a fast and slow depolarization can be evoked selectively in VPLI by direct application of either nicotine or muscarine. 7. Voltage-clamp analysis shows that the fast EPSP evoked current is similar to that produced by nicotine in that it decreases linearly with membrane depolarization. The current associated with the sustained depolarization is similar to that evoked by muscarine, increasing nonlinearly with membrane depolarization. 8. Activity of the descending input, or application of muscarine, lowers the spike-initiation threshold of the VPLI neuron, thereby increasing its excitability. 9. It is concluded that the presence of two ACh receptor subtypes act synergistically to allow continuous activity of the VPLI neuron for sustained periods (i.e., throughout the hours of darkness).

Comparative anatomy of serotonin-like immunoreactive neurons in isopods: putative homologues in several species

It is now commonly accepted that the arthropod nervous system has evolved only once, and so homologies between crustacean and insect nervous systems can be meaningfully sought. To do this, we have examined the distribution of serotonin (5-hydroxytryptamine)-like immunoreactive neurons in the central nervous system (CNS) of four common British isopods. Two species of terrestrial woodlouse, Oniscus asellus and Armadillidium vulgare, the littoral sea slater, Ligia oceanica, and the aquatic water hoglouse, Asellus meridianus, all possess approximately 40 pairs of serotonin-like immunoreactive neurons, distributed throughout the CNS in a very similar pattern. Interspecific homology is clearly suggested. Serotonin-like immunoreactive neurons in the first (T1) and fourth (T4) thoracic ganglia are particularly prominent in each of the four species studied. Whole-mount immunohistochemistry shows that the pair of T1 neurons have large dorsolateral cell bodies and prominent neurites that project medially and then anteriorly, whereas the pair of T4 neurons have ventrolateral cell bodies and neurites that bifurcate to form a thin axon projecting anteriorly to terminate in T3 and a thick medial axon that projects posteriorly into the abdominal neuromeres of the terminal ganglion. Intracellular cobalt staining of these neurons reveals more of their arborizations: the T1 neurons send three processes anteriorly, which arborize in the brain and exist from the CNS via peripheral nerves, whereas the T4 neurons contribute considerably to the extensive pattern of serotonin-like immunoreactive fibres in T3-T6 ganglia. The overall pattern of serotonin-like immunoreactive neurons in the isopods is similar to that in decapod crustacea, and a number of putative homologies can be assigned. It is more difficult to homologize the isopod serotonin-like immunoreactive neurons with those in the insect CNS, but some stained brain and thoracic neurons share common cell body positions and axon trajectories in isopods, decapods, and insects and may therefore be homologous.

A good eye for arthropod evolution

Insect and crustacean lineages diverged over 500 Myr ago, and there are continuing uncertainties about whether they evolved from a common arthropod ancestor or, alternatively, they evolved independently from annelid worms. Despite the diversity of their limbs and lifestyles, the nervous systems of insects and crustaceans share many common features both in development and in function. Cellular and molecular embryology techniques reveal good evidence for homologies in the developing segmental ganglia. In the visual system, this seemingly common programme of insect and crustacean CNS development culminates in common adult neural function. Comparisons of the cellular anatomy and physiology of animals as diverse as flies and crayfishes indicate that the neural circuits in the lamina of their optic lobe have been inherited largely unchanged from a common ancestor with good compound eyes.

Localization of Locusta-DP in locust CNS and hemolymph satisfies initial hormonal criteria

Locusta-diuretic peptide (Locusta-DP) is a potent stimulant of fluid secretion and cyclic AMP production by locust Malpighian tubules. In this study, a polyclonal antiserum raised to the C-terminus of Locusta-DP reveals a wide distribution of immunoreactive cell bodies and processes throughout the CNS, and endings in two important neurohemal release sites: the corpora cardiaca and the perivisceral organs. HPLC fractionation of CNS, neurohemal structures, and hemolymph reveals immunoreactive material that coelutes with synthetic Locusta-DP and stimulates cyclic AMP production by locust tubules. The identity of the immunoreactive and biologically active material is confirmed as authentic Locusta-DP by mass spectrometry.

Cardiac catheterization and coronary angiography using 5 French preformed (Judkins) catheters from the percutaneous right brachial approach: a comparative analysis with the femoral approach

This study describes a method for the performance of cardiac catheterization using 5 French preformed Judkins catheters from a percutaneous right brachial approach, and compares that technique to the more traditional percutaneous right femoral approach with 6 French catheters. One hundred consecutive patients requiring diagnostic left heart catheterization and selective coronary angiography were randomized according to femoral versus brachial arterial technique. Procedural efficiency, radiation exposure, and diagnostic film quality favored the femoral approach, while patient comfort, hemostasis time, time to ambulation, and decreased need for post-procedure nursing care favored the brachial approach. No differences were identified in complications. Cardiac catheterization from a right brachial artery percutaneous approach with 5 French preformed catheters has both advantages and disadvantages when compared with a more traditional femoral approach with 6 French catheters. Multiple factors should be considered before selecting an approach to diagnostic cardiac catheterization and each patient should be individually evaluated for determination of the optimal technique.

Morphology of the vasopressin-like immunoreactive (VPLI) neurons in many species of grasshopper

It has previously been shown that the pair of vasopressin-like immunoreactive (VPLI) neurons of the locust, Locusta migratoria, have cell bodies on the ventral midline of the suboesophageal ganglion and extensive arborisations in all ganglia of the central nervous system. In the present study, we have stained vasopressin-like immunoreactive neurons in 16 additional species of grasshopper, and consistently find this pair of extensive neurons: we assume these to be interspecies homologues. However, the anatomy of these neurons falls into two morphological types: the first, typified by Schistocerca gregaria, has most of its processes distributed in dorsal and lateral neuropil of all ganglia; the second, typified by Locusta migratoria, is equally extensive in its arborisation, but the distribution of branches is shifted peripherally into the optic lobes and the proximal portions of peripheral nerves. It has been suggested that the peripheral fibres in Locusta migratoria are neurohaemal organs for the release of a vasopressin-like diuretic peptide. Our sample of 17 Acridoid species has deliberately selected animals from very different habitats, but our extensive survey of VPLI anatomy shows that peripheral fibres are only present in species from the subfamily Oedipodinae (of which Locusta migratoria is a member) and that no peripheral fibres are present in any of the species from the 4 other subfamilies of the Acridoidea that we have examined. The presence of peripheral fibres is therefore determined by phylogeny and not by habitat. The absence of peripheral VPLI fibres in most grasshopper species examined in this study probably means that the release of putative diuretic hormone from VPLI to control water homeostasis cannot be a conserved function of this ubiquitous neuron. In contrast, the extensive central arborisations and rare antigenicity, which are highly conserved features of the VPLI neuron in all those grasshoppers we have examined, suggests that any conserved role is more likely to be central. A central role for the VPLI neuron has yet to be determined.

A comparison of the effects of two putative diuretic hormones from Locusta migratoria on isolated locust malpighian tubules

Previous work has shown that a peptide related to arginine vasopressin is present in the suboesophageal ganglion of the locust, Locusta migratoria. This peptide was determined to be an anti-parallel dimer of the nonapeptide Cys-Leu-Ile-Thr-Asn-Cys-Pro-Arg-Gly-NH2 and was reported to stimulate cyclic AMP production and fluid secretion in a combined Malpighian tubules and midgut preparation from locusts. For these reasons the peptide has been called the arginine-vasopressin-like insect diuretic hormone (AVP-like IDH). Recently, a second diuretic peptide (Locusta-DP), which is related to corticotropin releasing factor, has been identified: this is a potent stimulant of fluid secretion and cyclic AMP production by isolated locust tubules. Because water balance in insects is likely to be controlled by a cocktail of hormones acting on both Malpighian tubules and hindgut, this study directly compares the activity of these two peptides in fluid secretion and cyclic AMP production bioassays on one target organ, the isolated Malpighian tubule of Locusta migratoria. Locusta-DP was synthesised directly, whereas the dimeric AVP-like IDH was obtained by oxidation of a synthetic nonapeptide monomer. Products were separated by RP-HPLC and their structures unequivocally confirmed by enzymatic digestion, sequence analysis and electrospray mass spectrometry. We show that Locusta-DP causes strong stimulation of fluid secretion and cyclic AMP production, whereas the AVP-like IDH has no effect in either assay. These findings are discussed in the light of recent work on the anatomy and physiology of the vasopressin-like immunoreactive (VPLI) neurones in the suboesophageal ganglion of Locusta migratoria, the proposed source of the AVP-like peptide.

Ectopic sensory neurons in mutant cockroaches compete with normal cells for central targets

The cercus of the first instar cockroach, Periplaneta americana, bears two filiform hairs, lateral (L) and medial (M), each of which is innervated by a single sensory neuron. These project into the terminal ganglion of the CNS where they make synaptic connections with a number of ascending interneurons. We have discovered mutant animals that have more hairs on the cercus; the most typical phenotype, called “Space Invader” (SI), has an extra filiform hair in a proximo-lateral position on one of the cerci. The afferent neuron of this supernumerary hair (SIN) “invades the space” occupied by L in the CNS and makes similar synaptic connections to giant interneurons (GIs). SIN and L compete for these synaptic targets: the size of the L EPSP in a target interneuron GI3 is significantly reduced in the presence of SIN. Morphometric analysis of the L afferent in the presence or absence of SIN shows no anatomical concomitant of competition. Ablation of L afferent allows SIN to increase the size of its synaptic input to GI3. Less frequently in the mutant population, we find animals with a supernumerary medical (SuM) sensillum. Its afferent projects to the same neuropilar region as the M afferent, makes the same set of synaptic connections to GIs, and competes with M for these synaptic targets. The study of these competitive interactions between identified afferents and identified target interneurons reveals some of the dynamic processes that go on in normal development to shape the nervous system.

Correlation of filiform hair position with sensory afferent morphology and synaptic connections in the second instar cockroach

An attempt is made to relate the distribution of filiform hairs on the cercus of the second instar cockroach, Periplaneta americana, to the morphology and patterns of synaptic connectivity of their afferents. We studied the most distal 25 of the 39 filiform hairs which are commonly present. Filiform afferent arborizations were stained by cobalt filling from the cell body in the cercus. Three fundamental arbor types were found, two similar to those of the first instar medial (M) and lateral (L) afferents, and a third, novel type. L-type arbors could be divided into four subtypes. The most obvious correlate of arbor type is the circumferential position of the hair on the cercus. The proximodistal position of the sensillum within each cercal segment is also a determinant of its arbor. By comparison of hair positions and afferent morphologies, we were able to ascribe homologies between the second instar hairs and members of adult longitudinal hair columns. The patterns of monosynaptic connections between afferents and giant interneurons (GIs) 1, 2, 3, 5, and 6 were determined by recording synaptic potentials in GIs evoked by direct mechanical displacement of individual filiform hairs. Latency from stimulus onset to the rise phase of the first excitatory postsynaptic potential (EPSP) was used as the criterion of monosynapticity. The EPSP amplitudes of the two original L and M afferents are halved in the second instar, in the absence of a significant decrease in GI input resistance. The other afferents can be divided into two basic classes: those which input to GI5 (M-type), and those which input to GI3 and GI6 (L-type). The former is correlated with a central or medial position, while the latter is associated with a group of afferents situated laterally on the cercus. In segments 3 and 4, input to GIs 1 and 2 also correlates with a medial cercal position, however, in the more proximal segments 5 and 6, afferents at all positions input to these interneurons. The occurrence of afferents of identical morphology and similar connectivity in equivalent positions in different segments suggests that each sensory neuron is determined by its two-dimensional position within a segment. The presence of afferents with the same morphology which display proximodistal differences in synaptic connectivity, and of other afferents which have M-type connectivity despite L-type morphology, means that anatomy is generally a poor predictor of synaptic connectivity.

Positional information determines the anatomy and synaptic specificity of cockroach filiform hair afferents using independent mechanisms

Mutant first instar cockroaches (Periplaneta americana) with supernumerary filiform hair sensilla on their cerci were used to study the effects of cell body position on axonal morphology and synaptic connections. The wild-type cercus has two hairs, one lateral (L) and the other medial (M), each with an underlying sensory neuron. Silver-intensified cobalt fills show that the supernumerary lateral neuron (SIN) in the mutant has the same shape of arborization as L, and electrophysiological recording shows that it forms synaptic connections with the same subset of giant interneurons (GIs) as L in the terminal ganglion: GI3 and GI6. The supernumerary medial neuron (SuM) has the same axonal morphology as M and synapses with the same GIs as does M: ipsilateral GIs 1 and 2 and contralateral GIs 1, 2, 3, 5 and 6. In 0.1% of approximately 8000 animals screened, a supernumerary hair arose on the cercal midline (C hair). The C neuron sends its axon to the CNS in the same branch of the cercal nerve as the L and SIN, and has a similar arborization. However, the C neuron forms synapses with the same GIs as do M and SuM. Electron microscopy of horseradish peroxidase-injected neurons was used to confirm that the C afferent forms a monosynaptic connection to GI2. It was concluded that the position of the sensory neuron cell body does control its axonal morphology and synaptic connectivity, but that these characteristics are produced by independent mechanisms.

The vasopressin-like immunoreactive (VPLI) neurons of the locust, Locusta migratoria. II. Physiology

The two vasopressin-like immunoreactive (VPLI) neurons of the locust, Locusta migratoria, have cell bodies in the suboesophageal ganglion and extensive arborizations throughout the CNS. One of the two peptides responsible for AVP-like immunoreactivity is a vasopressin-related peptide with putative 'diuretic hormone' properties. These neurons also have FLRF-like immunoreactivity, probably due to the FMRF-amide-related peptide. SchistoFLRF-amide, isolated from Schistocerca gregaria. This peptide has cardioinhibitory activity and a dual potentiation/inhibition of slow motoneuron induced muscle-twitch tension. Although haemolymph AVP-like peptide titre fluctuates under various conditions, the mechanism that regulates neurohaemal release of this peptide is not understood. Very little is known of the release of SchistoFLRF-amide. We have used intracellular recording from VPLI neurons in vivo to reveal synaptic inputs that lead to changes in their level of spiking activity, and probably, release of both the AVP-like peptides and SchistoFLRF-amide. This pair of neurosecretory cells has a major, common excitatory input whose sustained rate of activity is inversely related to light intensity; VPLI spiking activity, driven by this input, is greater in the dark than in light. This input is from a pair of descending brain interneurons. Their light-sensitivity persists after ablation of compound eyes, optic lobes and ocelli, showing them to be part of an extra-ocular photoreceptor system. Attempts to record from, and individually stain, the descending neuron have been unsuccessful, although its axon location and diameter in the circumoesophageal connective have been determined. Possible locations for its cell body have been identified; one region, close to the pars intercerebralis, is known to be photosensitive in some insects. Mechanosensory stimuli also lead to brief increases in VPLI spiking activity via the descending interneuron, though this modality rapidly habituates. We detect no changes in VPLI spiking activity that consistently correlate with the osmolality of perfusion salines; such changes might have been expected from their previously proposed role in water homeostasis. Alternative roles for VPLI cells are discussed.

The vasopressin-like immunoreactive (VPLI) neurons of the locust, Locusta migratoria. I. Anatomy

Antiserum to arginine-vasopressin has been used to characterise the pair of vasopressin-like immunoreactive (VPLI) neurons in the locust. These neurons have cell bodies in the suboesophageal ganglion, each with a bifurcating dorsal lateral axon which gives rise to predominantly dorsal neuropilar branching in every ganglion of the ventral nerve cord. There are extensive beaded fibre plexuses in most peripheral nerves of thoracic and abdominal ganglia, but in the brain, the peripheral plexuses are reduced while neuropilar branching is more extensive, although it generally remains superficial. An array of fibres runs centripetally through the lamina-medulla chiasma in the optic lobes. Lucifer Yellow or cobalt intracellular staining of single VPLI cells in the adult suboesophageal ganglion shows that all immunoreactive processes emanate from these two neurons, but an additional midline arborisation (that was only partially revealed by immunostaining) was also observed. Intracellularly staining VPLI cells in smaller larval instars, which permits dye to reach the thoracic ganglia, confirms that there is no similar region of poorly-immunoreactive midline arborisation in these ganglia. It has been previously suggested that the immunoreactive superficial fibres and peripheral plexuses in ventral cord ganglia serve a neurohaemal function, releasing the locust vasopressin-like diuretic hormone, F2. We suggest that the other major region of VPLI arborisation, the poorly immunoreactive midline fibres in the suboesophageal ganglion, could be a region where VPLI cells receive synaptic input. The function of the centripetal array of fibres within the optic lobe is still unclear.

Effects of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine in the dog: effect of pargyline pretreatment

Adult beagle dogs of either sex were injected with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-HCl (2.5 mg/kg, i.v.) alone or after pretreatment with pargyline (5.0 mg/kg, s.c., twice), with pargyline alone, or were uninjected. Groups were killed 2 h, 3 weeks, or 3 months after injection, and several brain areas were assayed for biogenic amines and their synthetic and degradative enzymes. MPTP caused a massive and permanent loss of striatal dopamine, tyrosine hydroxylase, and 3,4-dihydroxyphenylalanine decarboxylase activities and the loss of cells within the substantia nigra pars compacta. Dopamine and norepinephrine also were depleted to various degrees in cortex, olfactory bulb, and hypothalamus; however, dopamine beta-hydroxylase activity in cortex was normal. There was no cell loss in the ventral tegmental area or locus ceruleus. The activities of monoamine oxidase (MAO)-A and MAO-B in cortex and caudate were not affected by MPTP. Despite a permanent loss of the nigrostriatal system, the dogs exhibited only a transient hypokinesia lasting 1-2 weeks. Pargyline pretreatment prevented the loss of striatal dopamine and cells from the substantia nigra, but did not prevent a prolonged but reversible decrease in the concentration of dopamine metabolites. It is argued that this apparent inhibition of MAO is due not to suicide inactivation of the enzyme by MPTP, but to reversible inhibition by accumulation of the pyridinium metabolite, 1-methyl-4-phenylpyridinium, selectivity in aminergic terminals.

The tritocerebral commissure 'dwarf' (TCD): a major GABA-immunoreactive descending interneuron in the locust

The minor branch of the tritocerebral commissure of the locust, Locusta migratoria, contains only two axons which are from interneurons in the brain descending to the ventral cord ganglia. The smaller of these two neurons, the tritocerebral commissure dwarf (TCD), is immunoreactive to GABA, suggesting that it may be an inhibitory interneuron. We have exploited the accessibility of its axon in the commissure, first, to fill it with cobalt to define its morphology, and second, to record its input characteristics. It has a cell body and arborization of fine branches in the deutocerebrum of the brain, its axon passes contralateral through the tritocerebral commissure and it forms bilateral arborizations in the suboesophageal and three thoracic ganglia. It receives mechanosensory input from many regions of the ipsilateral body and head, and it is sensitive to illumination levels, generally showing greater spontaneous activity in the dark. It is one of the largest GABA-immunoreactive descending interneurons in the locust, suggesting it plays a prominent role in behaviour. Since it is easily accessible for physiological recording, its roles in circuits for particular components of behaviour should be amenable to investigation.

The development of amine substituted analogues of MPTP as unique tools for the study of MPTP toxicity and Parkinson's disease

We are currently developing amino-substituted MPTP analogues as useful probes for understanding the mechanism of MPTP toxicity and Parkinson's disease. One analogue, 4'-amino MPTP, induces a loss of striatal dopamine and is thus a suitable substitute for MPTP. This probe will be used as a histologically fixable MPTP which can be used to answer detailed anatomical questions concerning the sites of MPTP, MPP+ uptake and storage. In addition, antibodies have been raised against MPTP and MPP+ in rabbits using diazo-linked bovine serum albumin conjugates. The antibodies have been characterized with regard to their recognition of relevant structural analogues using an enzymelinked immunoassay (ELISA) procedure. Antibodies to MPTP detected MPTP in mouse brain extracts derived from as little as 5 micrograms of tissue. The antibodies will be used for immunohistochemical localization of 4'-NH2-MPTP and 4'-NH2-MPP+ in brain, as well as probes for the screening of parkinsonian brain tissue for any MPTP- or MPP+-like materials which might exist.

1-Methyl-4-phenylpyridine (MPP+) induces oxidative stress in the rodent

MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) produces an irreversible parkinsonism in primates. Recent evidence suggests metabolism of MPTP to 1-methyl-4-phenylpyridine (MPP+) is required for toxicity. We have proposed that MPP+ may play a central role in the toxicity of MPTP, but direct assessment of the effects of MPP+ in brain is difficult. Therefore, we have sought to define the mechanism of peripheral MPP+ toxicity in the rat and mouse. Systemically administered MPP+ produced its major pathology in the lung and was typified by perivascular edema. An increase in plasma glutathione disulfide concentrations also resulted, suggesting that MPP+ in analogy to paraquat produces oxidative stress. In addition, the lethality of MPP+ in the mouse was increased by dietary selenium deficiency. These results define in both pathological and chemical terms the potent systemic toxicity of MPP+ and suggest that MPP+, because of its high concentration in primate brain, has the potential to play an important role in the CNS toxicity of MPTP.

Receptive fields of cricket giant interneurones are related to their dendritic structure

The structural relationship between the afferent projection and the dendrites of the interneurones was examined in the cercal-to-giant interneurone system of the cricket using intracellular recording and dye injection techniques. The physiology of the sensory neurones beneath the cercal filiform hairs was investigated by placing a recording pipette over the end of a cut hair and using movements of the pipette to characterize the directionality of the receptor. Most of the filiform receptors could be classified as belonging to one of four major types. Each type is sensitive to a different wind direction and is confined to particular regions of the cercus. The location of the terminal arborizations of each type of sensory cell was revealed by staining with cobalt chloride. Single cells were stained reliably by placing a dye-filled pipette over a cut hair. Each physiological receptor type arborizes in a different region of the central nervous system. Therefore the neuropile is functionally divided according to wind direction. The dendrites of three identified interneurones were examined in the context of this afferent projection. It was found that each of these neurones has dendrites in regions of neuropile corresponding to different wind directions. By searching for unitary synaptic potentials in identified interneurones, it was possible to show a strong correlation between anatomical overlap of primary afferent and interneurone and the existence of a synaptic connexion. Further, when there was no overlap, no synaptic potentials were seen. Therefore the over-all excitatory receptive field of an interneurone could be predicted by examining its dendritic structure. Each of the three identified interneurones examined in this study was found to have a directional response that matched the response predicted on the basis of its anatomy.

Transplantation of cricket sensory neurons to ectopic locations: arborizations and synaptic connections

The cerci (abdominal sensory appendages) of crickets were transplanted to a leg stump after amputating the leg. Single identifiable cercal afferents were stained and found to regenerate into the host thoracic ganglia. A given neuron always arborizes in the same area of neuropil of the foreign ganglion and is distinctive in this property from other identified neurons. Taken as a whole, the results show that the afferents from the ectopic cercus are spatially ordered, the destination of a particular afferent within the ganglion being correlated with the location of its sensory cell body on the cercal surface. This is the case for the pro-, meso-, and metathoracic ganglion and the topography of these ectopic projections bears some resemblance to the normal projections found in the terminal ganglion. Thus the insect segmental ganglion seems to possess a set of markers which are interpretable by all afferent neurons, and this organization is repeated in each ganglion. The ectopic afferents make functional synaptic connections with intersegmental interneurons, one of which is described anatomically here. However, the ectopic afferents do not, as had previously been reported, make functional connections with the medial giant or lateral giant interneuron (the normal targets of cercal sensory neurons in the terminal ganglion).

Sensory projections from the wind-sensitive head hairs of the locust Schistocerca gregaria. Distribution in the central nervous system

The neurones from the wind-sensitive hairs on the locust head have been filled with cobalt chloride and intensified with silver. All the neurones project through the brain to the suboesophageal ganglion, some continue to the prothoracic ganglion and a few as far as the mesothoracic ganglion. Three different types of projection are described and a regrouping is proposed of Weis-Fogh's five hair fields into three areas. The distribution of the neurones from these areas is described in relation to other structures in the ganglion and is discussed in relation to the function of the hair fields in stability control and grooming.