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PubMed2002

Differential involvement of Ca(2+) channels in survival and neurite outgrowth of cultured embryonic cockroach brain neurons.

The contribution of voltage-gated calcium channels (VGCC) to the development of cultured embryonic cockroach brain neurons was assessed using pharmacological agents. VGCC currents were recorded using the patch-clamp technique and were found to be blocked dose-dependently by micromolar concentrations of mibefradil. The activation and inactivation properties of the calcium channels enable a sizeable calcium current to flow at rest (about -30 and -20 mV in high-potassium culture media). As expected, the cytoplasmic-free calcium concentration was found to rise when the extracellular potassium concentration was raised from 3 to 15 and 30 mM. The effects of VGCC blockers and calcium chelators were different in fresh and in mature cultures in which the neurons were connected to each other to form a defined network. In fresh cultures, the two non-selective VGCC blockers (verapamil and mibefradil) induced a dose-dependent cell death that was proportional to their blocking effect on I(Ba). This effect could not be prevented by addition of fetal calf serum to the culture medium. A similar effect was obtained using intra- or extracellular calcium chelating agents (10 microM BAPTA-AM or 10 mM EGTA). Quite unexpectedly, blockade of the P/Q-like (omega-Aga WA-sensitive) component of the calcium current by 500 nM of omega-AgaTx IVA had no lethal effect, suggesting that the corresponding channels are not involved in the survival mechanism. As expected from their lack of effect on I(Ba), isradipine, nifedipine, and omega-CgTx GVIA did not induce cell death. When the neurons started growing neurites, their sensitivity to calcium channel blockade by mibefradil decreased, indicating a correlation between neurite outgrowth and resistance to calcium depletion. In mature cultures, the neurons became resistant to mibefradil, verapamil, and BAPTA-AM. However, these agents, as well as omega-AgaTx IVA, had a significant inhibitory effect on the increase in diameter of the connectives that linked adjacent clusters of neurons. This effect has been shown to result, in the case of mibefradil, from an inhibition of neurite outgrowth characterized by a significant reduction of the number of primary neurites and secondary branchings but not to a significant modification of the diameter of individual neurites. These results support the view that, as in vertebrates, calcium influx through VGCC plays an important role in survival and neurite outgrowth of cultured embryonic insect neurons. The differential contribution of the P/Q-like and R-like (omega-Aga WA-sensitive) calcium channels in these processes is discussed.

Animals↗
PubMed1998

Contractile responses to allergen and cholinergic stimulation in bronchus and trachea of cockroach allergen-sensitized guinea pigs.

Airway hyperreactivity is a hallmark of asthma. Yet, the role of allergic sensitization in the hyperreactivity remains controversial. This study examined the effects of airborne cockroach allergen (CRa) sensitization on the contractility of bronchial (BSM) and tracheal (TSM) smooth muscle rings to cholinergic stimulations, and to specific antigen, in vitro. Guinea pigs were actively immunized with CRa, 5 mg (high dose, HD), 0.5 mg (low dose, LD), or saline aerosols (2x/day, 5 days/week, for 4 weeks) and challenged by CRa inhalation 5 days after last exposure. Twenty-four hours postchallenge, the contractions of the TSM and BSM to electrical field stimulation (EFS), acetylcholine (ACh), and to CRa were measured in vitro. In addition, the contraction to these stimuli were also examined in the passively sensitized TSM with the sera of CRa-immunized guinea pigs. The contractile responses of actively immunized and passively sensitized tissues to EFS and ACh were very similar to those of control tissues. CRa induced dose-dependent contractions in both actively immunized and passively sensitized, but not in control, tissues. The CRa-induced contraction was stronger in the HD group than in the LD group (p<0.0001). Leukotriene C4/D4 receptor antagonist LY-171883 inhibited the CRa-induced contraction by 86% in actively immunized TSM, and by 9% in the passively sensitized TSM. Pyrilamine inhibited the contraction by 57% in actively immunized TSM and 70% in passively sensitized TSM. The results indicate that CRa sensitization does not cause increased airway smooth muscle contractility to cholinergic stimulations, but induces antigen-specific contractions in vitro. Leukotrienes appear to play a significant role in the CRa-specific contractions, more in the actively immunized than those in the passively sensitized tissues, while histamine exerts a moderate effect on the CRa-induced contractions.

Acetophenones↗
PubMedDate not supplied

Molecular cloning of German cockroach (Blattella germanica) allergens.

Allergens produced by cockroaches (CRs) are an important cause of IgE antibody responses and asthma. Using molecular cloning and nucleic acid hybridization techniques, we have identified and sequenced several important allergens produced by the German CR (Blattella germanica) and studied their expression in the American CR (Periplaneta americana). Principal allergens include Bla g 2 (36-kD protein) and Bla g 4 (21-kD protein), to which 60-70% of CR-allergic patients make IgE antibodies. Bla g 2 is only expressed by B. germanica, whereas DNA encoding Bla g 4 is present in P. americana, but is not transcribed into mRNA. Sequence homology searches have identified Bla g 2 as an aspartic protease and Bla g 4 as a calycin. Other CR allergens that have been cloned include a glutathione transferase and a troponin. These studies will enable recombinant allergens to be expressed and used to investigate the role of CR allergens in asthma.

Allergens↗
PubMed1996

Experimental asthma developed by room air contamination with cockroach allergen.

To study the asthmatogenic effect of certain airborne elements of the home environment, we studied a group of guinea pigs exposed to aerosolized cockroach allergen (CRa) and side-stream cigarette (S-SC) smoke. Four groups of guinea pigs were exposed to aerosols, either saline or CRa, for 4 weeks, after a sham or S-SC smoke pretreatment. Anaphylactic antibodies were measured by passive cutaneous anaphylaxis (PCA) assay and by skin test. Animals were challenged with aerosol CRa on day 35, and lung function and leukotrienes (LTB4 and LTC4/D4) were measured. Skin tests were positive on days 21 and 29. The antibodies were heat-stable, IgG1a-like antibodies (PCA titers 1:2-18). The CRa challenge caused an immediate reduction in both the maximal expiratory flow rate at 50% of the lung capacity and respiratory compliance. The decreased lung function continued for up to 6 h (p < 0.0001). LTB4 and LTC4/D4 were elevated (p < 0.0001) in the sensitized animals at the corresponding times of reduced lung function. S-SC smoke did not affect the CRa sensitization; instead, a protective effect on the CRa-induced bronchospasms was noted. Thus, the study indicates that a simple airborne CRa exposure without an adjuvant sensitizes guinea pigs, and that the animals respond to antigen challenge with CRa-specific airway obstructions.

Aerosols↗
PubMed1985

Circadian rhythms in the electroretinogram of the cockroach.

Circadian regulation of the amplitude of the electroretinogram (ERG) of the cockroach Leucophaea maderae was investigated. Two components of the ERG exhibited circadian rhythms in amplitude. Interestingly, the peak amplitudes for the two rhythms were approximately 12 hr out of phase. The dominant corneal negative potential (the "sustained component") exhibited maximum amplitude during the subjective night. A second corneal negative potential (the "off-transient") was at a maximum during the subjective day. Intensity-response curves of the sustained component were measured at both the peak and trough of the rhythm. The results showed that the circadian rhythm in amplitude reflected a sensitivity change equivalent to 0.2-0.6 log unit of intensity. An effort was also made to identify the anatomical locus of the pacemaking oscillator for the ERG rhythm in a series of lesion experiments. Neural isolation of the optic lobe from the midbrain by bisection of the optic lobe proximal to the distal edge of the lobula had no effect on the circadian rhythm of ERG amplitude. Bisection of the optic lobe distal to the lobula abolished the ERG amplitude rhythm. These results suggest that the pacemaker is located in the optic lobe near the lobula; that its motion continues in the absence of neural connections with the rest of the nervous system; and that its regulation of ERG amplitude depends on neural pathways in the optic lobe.

Animals↗
PubMed1987

Serotonin phase-shifts the circadian rhythm of locomotor activity in the cockroach.

Serotonin, a putative neurotransmitter in insects, was found to cause consistent phase shifts of the circadian rhythm of locomotor activity of the cockroach Leucophaea maderae when administered during the early subjective night as a series of 4-microliters pulses (one every 15 min) for either 3 or 6 hr. Six-hour treatments with dopamine also caused significant phase shifts during the early subjective night, but 3-hr treatments with dopamine had no phase-shifting effect. Other substances tested in early subjective night (norepinephrine, octopamine, gamma-aminobutyric acid, glutamate, carbachol, histamine, tryptophan, tryptamine, N-acetyl serotonin, or 5-hydroxyindole-3-acetic acid) did not consistently cause phase shifts. The phase-shifting effect of serotonin was found to be phase-dependent. The phase response curve (PRC) for serotonin treatments was different from the PRC for light. Like light, serotonin caused phase delays in the late subjective day and early subjective night, but serotonin did not phase-shift rhythms when tested at phases where light causes phase advances.

Animals↗
PubMed1993

Photoperiodic time measurement and a graded response in a cockroach.

Almost exclusively, photoperiodic insects respond to a given photoperiod in one of two ways: a "long-day" response or a "short-day" response. Intermediate responses occur only at a very restricted range of photoperiods (often less than 30 min) and are generally population phenomena rather than intermediate responses of individuals. In contrast, individuals of the wood roach, Parcoblatta pennsylvanica, show intermediate responses over a broad range of photoperiods. We examined the effect of constant light, constant darkness, and photoperiods ranging from 10 to 18 hr of light per 24 hr on growth rate as measured by weight gain, and found a robust photoperiodic response. Nymphs raised in photoperiods with light periods (photophases) from 0 to 12 hr gained little weight, whereas those in LD 18:6 were almost 15 times heavier. This is the first report of a photoperiodic response curve for a cockroach. Interestingly, there was a linear relationship between the duration of the photophase and weight gain over a broad range of photoperiods (LD 12:12 to LD 18:6; r2 = 0.99). Statistical analysis showed that the intermediate responses were attributable to individuals' growing at an intermediate rate. Another interesting observation was that all larval stages appeared to be capable of perceiving and responding to photoperiodic signals. The results of further experiments using non-24-hr photoperiods were consistent with the existence of a circadian component in the photoperiodic time measurement in this species.

Analysis of Variance↗
PubMed1993

Circadian control of visual information processing in the optic lobe of the giant cockroach Blaberus giganteus.

Extracellular spike activity from three different types of visual interneurons found in the optic lobe of the giant cockroach Blaberus giganteus was recorded. The spike rate of all three types of neurons fluctuated in a circadian manner in constant darkness (DD). Two types, so-called "on" neurons (ON1 and ON2), responded exclusively to stationary light stimuli. A static light pulse elicited a sustained component in ON1, whereas in ON2 only a brief transient response was observed. In ON1 neurons, responsiveness was high during the subjective night and low during the subjective day. The responsiveness of ON2 neurons had a peak during a few hours around subjective dusk and a smaller peak in the later subjective night. The third neuron type recorded consisted of a directionally selective motion-detecting (DSMD) neuron. The pure intensity response and the motion response of the DSMD neuron were high during the subjective day and low during the subjective night. The results show that visual interneurons in the optic lobes are influenced differently by the circadian oscillator system. It is suggested that the mode of circadian control depends on the role a neuron plays in the process of visual information processing.

Animals↗
PubMed1992

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.

Animals↗
PubMed1985

Unusual structural features and assembly of gap and pleated septate junctions in embryonic cockroach CNS.

Junctional assembly in the developing CNS in cockroach embryos has been studied during the last half of neurogenesis. Atypical linear tracts of gap junctions are found to develop between attenuated cytoplasmic glial cell processes and their overlying perineurial cells during the last third of development. During both perineurial and glial gap-junctional formation, 13 nm E face (EF) intramembrane particles (IMPs), such as are characteristic of arthropod gap junctions, are seen initially as free IMPs; these then become arranged in loose irregular clusters or alignments and finally are aggregated in plaques. P face ridges (or EF grooves), typical of tight junctions, are found on the same perineurial membrane face as assembling gap-junctional PF pits (or EF particles). Pleated separate junctions also develop between adjacent perineurial processes during the last third of embryogenesis; these form by the apparent migration of individual 8 nm PF IMPs into meandering rows, which then become aligned in numerous orderly parallel stacks. Although all these junctions occur on the same perineurial membrane face, the IMPs that form the different junctional types never appear to be confused during junctional assembly. The cues to signal the advent of these precise patterns, however, are unknown.

Animals↗
PubMed2003

Repeatability of standard metabolic rate and gas exchange characteristics in a highly variable cockroach, Perisphaeria sp.

For natural selection to take place several conditions must be met, including consistent variation among individuals. Although this assumption is increasingly being explored in vertebrates, it has rarely been investigated for insect physiological traits, although variation in these traits is usually assumed to be adaptive. We investigated repeatability (r) of metabolic rate and gas exchange characteristics in a highly variable Perisphaeria cockroach species. Although this species shows four distinct gas exchange patterns at rest, metabolic rate (r=0.51) and the bulk of the gas exchange characteristics (r=0.08-0.91, median=0.42) showed high and significant repeatabilities. Repeatabilities were generally lower in those cases where the effects of body size were removed prior to estimation of r. However, we argue that because selection is likely to act on the trait of an animal of a given size, rather than on the residual variation of that trait once size has been accounted for, size correction is inappropriate. Our results provide support for consistency of variation among individuals, which is one of the prerequisites of natural selection that is infrequently tested in insects.

Animals↗
PubMed2004

Antennal movements reveal associative learning in the American cockroach Periplaneta americana.

Using antennal movements as an indicator of learning and retention, an associative learning paradigm has been developed to investigate associative memory between visual and olfactory stimuli. Experiments were performed on the restrained cockroach Periplaneta americana, which normally moves its antennae towards a localized odor source. Such "antennal projection responses" (APRs) are exploited to demonstrate long-term memory, where an APR is elicited by a conditioned stimulus (CS; green light point source) paired with a spatially coincident odor [the unconditioned stimulus (US)]. Association of the CS with the US is established after five trials. Before training, a visual cue alone does not elicit an APR. This behavior is elicited by a visual cue only after pairing it with an odor stimulus. The acquired APR to the green light cue persists for up to 72 h, indicative of long-term memory. This paradigm is thus suitable for future studies of neural correlates of learning and memory on restrained animals.

Animals↗
PubMed2004

Spatial learning in the restrained American cockroach Periplaneta americana.

Spatial learning abilities were tested in restrained cockroaches by observing antennal projection responses towards the positions of a learned visual cue perceived monocularly by one eye in the context of a second stimulus provided to the contralateral eye. Memory of the position of the conditioning stimulus relative to the contralateral reference stimulus was tested by altering the relative positions of the two stimuli. Memory of the conditioning stimulus is retained if the angle between the conditioning stimulus and the contralateral reference stimulus is maintained. The results suggest that during learning the insect recognizes spatial relationships between the conditioning stimulus and the contralateral reference stimulus. Possible mechanisms, such as retinotopic matching versus angular matching, are discussed.

Animals↗
PubMed2004

Dopaminergic and serotonergic innervation of cockroach salivary glands: distribution and morphology of synapses and release sites.

The paired salivary glands in the cockroach are composed of acini with ion-transporting peripheral P-cells and protein-secreting central C-cells, and a duct system for the modification of the primary saliva. Secretory activity is controlled by serotonergic and dopaminergic neurons, whose axons form a dense plexus on the glands. The spatial relationship of release sites for serotonin and dopamine to the various cell types was determined by anti-synapsin immunofluorescence confocal microscopy and electron microscopy. Every C-cell apparently has only serotonergic synapses on its surface. Serotonergic and dopaminergic fibres on the acini have their release zones at a distance of approximately 0.5 microm from the P-cells. Nerves between acinar lobules may serve as neurohaemal organs and contain abundant dopaminergic and few serotonergic release sites. Some dopaminergic and serotonergic release sites reside in the duct epithelium, the former throughout the duct system, the latter only in segments next to acini. These findings are consistent with the view that C-cells respond exclusively to serotonin, P-cells to serotonin and dopamine, and most duct cells only to dopamine. Moreover, the data suggest that C-cells are stimulated by serotonin released close to their surface, whereas P-cells and most duct cells are exposed to serotonin/dopamine liberated at some distance.

Animals↗
PubMed1984

Growth and ion-specificity of excitability in regenerating cockroach giant interneurones.

The effects of lesions on cockroach giant interneurones (GIs) were studied to investigate the transient, Ca-dependent, action potentials which have been reported to appear near the tips of regenerating GIs (Meiri, Spira & Parnas, 1981). We were unable to repeat these observations. Ligation of connectives, before cutting, delayed the degenerative changes in segments of GIs that were separated from their cell bodies. The short-term injury response (which was normally observed on cutting while recording close to the site of lesion) was not recorded when the axon was ligated. The effect of cutting GIs at different distances from their cell bodies was also investigated. There was no apparent relation between the response of GIs to a lesion and the site of the lesion. Sprouting of GIs was observed both at the tip of the axon and also at sites some distance from the lesion. No changes of the cell body or its dendritic tree in the terminal ganglion were seen but sprouting was observed in other ganglia.

Action Potentials↗
PubMed1987

Motor activity during searching and walking movements of cockroach legs.

1. Rhythmic motor activity may be recorded in the legs of cockroaches during the execution of several different types of behaviour that involve leg movements. It was examined in detail during searching and walking. 2. During walking, motor activity always consisted of a series of bursts separated by silent periods. During searching, it was usually continual, but modulated in frequency. 3. Sometimes, the motor pattern recorded from a searching leg was burst-like rather than modulated. In these cases, it could nevertheless be reliably distinguished from the motor pattern recorded during walking by a simple analysis of the burst pattern. 4. An analysis of the motor pattern recorded during righting indicated that this pattern was more like that for walking than that for searching. Therefore, searching is not simply walking that lacks certain periodic sensory input due to leg contact with the ground. 5. It is concluded that walking and searching can be reliably distinguished from one another on the basis of an analysis of a record of motor activity in a single leg muscle only. An ability to distinguish between similar types of behaviour on the basis of the motor pattern may prove useful in a variety of experiments.

Animals↗
PubMed1988

Ionic currents in neurones cultured from embryonic cockroach (Periplaneta americana) brains.

Neurones isolated from embryonic cockroach brains were maintained in culture for up to 8 weeks. A single patch electrode was used to record voltage changes in response to injected current, membrane ionic currents under whole-cell voltage-clamp conditions or single-channel currents from isolated membrane patches. The voltage changes in response to injected current that depolarized the cell indicated increases in membrane permeability to calcium and potassium. These observations were confirmed using a voltage clamp. The potassium current observed in the youngest cultures turned on with a delay and was blocked by tetraethylammonium (TEA) and 4-aminopyridine (4-AP). Two kinds of decrease in the outward potassium current were observed. One may be associated with extracellular potassium accumulation, inactivation of the potassium channel or inactivation of a calcium channel. The other appears to be a voltage-dependent inactivation. The magnitude of the calcium permeability appeared to increase as the cultures developed, being most prominent in cultures more than 2 weeks old. Single-channel conductance measured from an analysis of records from six isolated membrane patches ranged from 15 to 110 pS. Except for one channel, the probability of the channels being open did not change appreciably with membrane potential. Our results suggest that much of the increase in potassium permeability may be due an increase in intracellular calcium level.

Animals↗
PubMed1988

Motor activity in the stump of an amputated leg during free walking in cockroaches.

1. A rhythmic pattern of motor activity was recorded in the stump of an amputated leg during free walking in cockroaches. 2. During relatively rapid walking, extensor (depressor) and flexor (elevator) muscles in the intact coxa of the amputated leg showed one burst of activity during each cycle of bursting in an adjacent, intact leg. However, during slower walking these muscles could show two or three bursts of activity during each cycle of bursting in an intact leg. 3. Motor bursts in the stump of an amputated leg showed features similar to those of bursts recorded from intact legs. Burst duration increased with an increase in period, and the bursts generally showed consistent timing (phase) relative to bursts in most of the intact legs. 4. The motor pattern recorded in a stump was very like that recorded in an intact leg during walking, and unlike that recorded during searching for a foothold (defined in the text). It is concluded that after the amputation of most of a leg, motor neurones innervating muscles in the stump of the amputated leg continue to be driven by the interneurones that normally drive the intact leg during walking. Analysis of the motor pattern in the stump may therefore reveal important features of the locomotor control system.

Amputation Stumps↗