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At least 793 records · Page 44Linked to original sources
PubMed1990

Structure-activity relationships on hyperglycemia by representatives of the adipokinetic/hyperglycemic hormone family in Blaberus discoidalis cockroaches.

Several members of the adipokinetic/hyperglycemic neurohormone family from several different invertebrate species have been prepared by solid-phase peptide synthesis and assayed by a modified in vivo hyperglycemic bioassay in Blaberus discoidalis cockroaches. The hypertrehalosemic hormone (HrTH) is the endogenous hypertrehalosemic factor for B. discoidalis and was the most potent peptide in the assay. The more divergent the sequence of a family member from Blaberus HrTH, the less potent was the bioanalog. Manduca adipokinetic hormone is the most divergent peptide of the family and was totally inactive in the bioassay. Locusta adipokinetic hormone I had reduced maximum activity in the assay, which suggests that Ser5 is an important residue for the transduction of the hyperglycemic response. The direct relation between bioanalog similarity to Blaberus HrTH sequence and potency suggests that the hormone and target cell receptor for HrTH have evolved to maintain an "optimal fit".

Amino Acid Sequence↗
PubMed1990

The effects of octopamine on juvenile hormone biosynthesis, electrophysiology, and cAMP content of the corpora allata of the cockroach Diploptera punctata.

Juvenile hormone production by the corpora allata of the adult female cockroach, Diploptera punctata, can be modulated by treatment with the biogenic amine, octopamine. Endogenous octopamine has been identified within the CA, using HPLC and electrochemical detection. Treatment with octopamine results in a sinusoidal, dose-dependent inhibition of JH biosynthesis by CA from day 2 virgin females, with maximal inhibition occurring at 10(-10) M and 10(-4 M. In day 4 and day 8 mated female corpora allata octopamine inhibited JH biosynthesis at 5 x 10(-5) M. Although the elevation of either cAMP or cGMP within the CA is known to be associated with an inhibition of JH biosynthesis, treatment with high concentrations of octopamine results in an increase in the level of cAMP but not cGMP. This effect is both dose- and time-dependent. Octopamine treatment also initiates changes in the passive membrane responses of the CA. Superfusion of CA with octopamine results in a pronounced hyperpolarization of CA cells and an increase in the electrotonic potential (indicative of the degree of electrical coupling between CA cells). This effect could be blocked by the octopamine receptor blocker phentolamine. Treatment with octopamine or phentolamine also blocked the hyperpolarization of CA cells normally associated with electrical stimulation of the axon tracts innervating the CA. We hypothesize that octopamine may be a natural neuromodulator of JH production by CA, regulating ion channels in CA cells themselves as well as release of the inhibitory neuropeptide, allatostatin, from the terminals within the CA.

Animals↗
PubMed1994

Immunocytochemical localization of Na+/K(+)-ATPase and V-H(+)-ATPase in the salivary glands of the cockroach, Periplaneta americana.

The acinous salivary glands of the cockroach (Periplaneta americana) consist of four morphologically different cell types with different functions: the peripheral cells are thought to produce the fluid component of the primary saliva, the central cells secrete the proteinaceous components, the inner acinar duct cells stabilize the acini and secrete a cuticular intima, whereas the distal duct cells modify the primary saliva via the transport of water and electrolytes. Because there is no direct information available on the distribution of ion transporting enzymes in the salivary glands, we have mapped the distribution of two key transport enzymes, the Na+/K(+)-ATPase (sodium pump) and a vacuolar-type H(+)-ATPase, by immunocytochemical techniques. In the peripheral cells, the Na+/K(+)-ATPase is localized to the highly infolded apical membrane surface. The distal duct cells show large numbers of sodium pumps localized to the basolateral part of their plasma membrane, whereas their highly folded apical membranes have a vacuolar-type H(+)-ATPase. Our immunocytochemical data are supported by conventional electron microscopy, which shows electron-dense 10-nm particles (portasomes) on the cytoplasmic surface of the infoldings of the apical membranes of the distal duct cells. The apically localized Na+/K(+)-ATPase in the peripheral cells is probably directly involved in the formation of the Na(+)-rich primary saliva. The latter is modified by the distal duct cells by transport mechanisms energized by the proton motive force of the apically localized V-H(+)-ATPase.

Animals↗
PubMed1990

Gastrin-cholecystokinin-like and neuroparsin-like immunoreactivities in the brain and retrocerebral neuroendocrine complex of the cockroach Blattella germanica.

Using single and double labelling techniques respectively, brain-corpora cardiaca-corpora allata complexes of the cockroach Blattella germanica have been immunohistochemically investigated with antisera raised against either the vertebrate peptide gastrin-cholecystokinin (CCK-8(s] and/or the locust neurohormone neuroparsin (NPA). Single immunolabelling with anti-CCK-8(s) reveals immunoreactive perikarya and processes in median and lateral parts of protocerebrum, optic lobes, deutocerebrum and tritocerebrum. Some fibres originating in median and lateral protocerebrum are intrinsic to the brain, whereas others terminate in the nervous areas of the corpora cardiaca. Single immunolabelling with anti-NPA reveals immunoreactive cell bodies in the median part of the protocerebrum and their processes terminate both in the nervous area of the corpora cardiaca and between the intrinsic secretory cells of this neurohaemal organ. Double immunolabelling with anti-CCK-8(s) and anti-NPA enables a description of the anatomical relations between the processes and the endings of these two neurosecretory systems.

Animals↗
PubMed1993

Structure-activity relationships in corpora allata of the cockroach Diploptera punctata: roles of mating and the ovary.

Morphometric studies were made on corpora allata of the cockroach Diploptera punctata from animals in which increasing gland size is not coupled to hormone synthesis (ovariectomized mated females; last-instar larvae) and in which gland size is coupled to hormone synthesis (normal mated and virgin females; penultimate-instar larvae). Cell number, gland volume, and juvenile hormone synthesis were measured. From electron micrographs, nuclear, cytoplasmic, and extracellular volumes; and cell membrane area were calculated; and fine structure described. Low-activity glands of ovariectomized mated females resembled high-activity glands from mated females in high cell number, large overall and cytoplasmic volume, and low nuclear-cytoplasmic ratio; they differed in having organelles typical of low-activity glands, mitochondria with dense matrices and large whorls of smooth endoplasmic reticulum. Inactive last-instar larval glands resembled mated ovariectomized female glands in increased cell number and organelles characteristic of inactive glands; however, their nuclear-cytoplasmic volume ratio was much higher. Penultimate larval glands with high activity per cell resembled active glands of normal mated females. Ovariectomy did not change morphometric parameters of virgin female glands; thus mating results in increase in size of adult female glands whereas the growing ovary is needed for changes in mitochondria and endoplasmic reticulum associated with high juvenile hormone synthesis.

Animals↗
PubMed1991

Immunocytochemical mapping of neuronal pathways from brain to corpora cardiaca/corpora allata in the cockroach Diploptera punctata with antisera against Met-enkephalin-Arg6-Gly7-Leu8.

Neuronal circuits in the brain and retrocerebral complex of the cockroach Diploptera punctata have been mapped immunocytochemically with antisera directed against the extended enkephalin, Met-enkephalin-Arg6-Gly7-Leu8 (Met-8). The pathways link median and lateral neurosecretory cells with the corpus cardiacum corpus allatum complex. In females, nerve fibres penetrate the corpora allata and varicosities or terminals, immunoreactive to Met-8, surround the glandular cells. Males differ in having almost no Met-8 immunoreactivity in the corpora allata. The corpora cardiaca of both males and females are richly supplied with Met-8 immunoreactive material, in particular in the 'cap' regions immediately adjacent to the corpora allata. A similarity in the amino-acid sequences of Met-8 and the C-terminus of the recently characterised allatostatins of D. punctata suggests that the pathways identified with the Met-8 antisera may be the same as those by which the allatostatins are transported from the brain to the corpus allatum. In comparative studies on the blowfly Calliphora vomitoria, similar neuronal pathways have been identified except that no sexual dimorphism with respect to amounts of immunoreactive material within the corpus allatum has been observed. These results suggest a possible homology in the neuropeptide regulation of the gland.

Amino Acid Sequence↗
PubMed1995

Immunocytochemical characterization of the accessory medulla in the cockroach Leucophaea maderae.

Several lines of evidence suggest that pigment-dispersing hormone-immunoreactive neurons with ramifications in the accessory medulla are involved in the circadian system of insects. The present study provides a detailed analysis of the anatomical and neurochemical organization of the accessory medulla in the brain of the cockroach Leucophaea maderae. We show that the accessory medulla is compartmentalized into central dense nodular neuropil surrounded by a shell of coarse fibers. It is innervated by neurons immunoreactive to antisera against serotonin and the neuropeptides allatostatin 7, allatotropin, corazonin, gastrin/cholecystokinin, FMRFamide, leucokinin I, and pigment-dispersing hormone. Some of the immunostained neurons appear to be local neurons of the accessory medulla, whereas others connect this neuropil to various brain areas, including the lamina, the contralateral optic lobe, the posterior optic tubercles, and the superior protocerebrum. Double-label experiments show the colocalization of immunoreactivity against pigment-dispersing hormone with compounds related to FMRFamide, serotonin, and leucokinin I. The neuronal and neurochemical organization of the accessory medulla is consistent with the current hypothesis for a role of this brain area as a circadian pacemaking center in the insect brain.

Animals↗
PubMed1984

Microbial aspects of the cockroach hindgut.

The cockroach hindgut has a complex, active microbiota, a large portion of which is associated with the chitinous gut wall. It provides a different environment from that of termites and other insects which are dependent on their hindgut microbiota for the digestion of cellulose. The pH of the midgut of Eublaberus posticus was not as high as it is in insects with a primarily cellulolytic nutrition. The hindgut of E. posticus was highly methanogenic, normal adults producing typically 10-25 mumol of methane per hour. The hindgut contained large amounts of the storage products polyphosphate and poly-beta-hydroxybutyrate. Dilution series on nonselective medium yielded 100 times more obligately anaerobic colonies than facultatively anaerobic colonies. The most common facultative isolates were Klebsiella oxytoca, Citrobacter freundii and Enterobacter agglomerans. Treatment of E. posticus with metronidazole caused a dedifferentiation of the different regions of the hindgut. One region of the hindgut is characterized by its visibly black color, a unique microbiota, and electron dense deposits in electron micrographs. Chemical determinations showed high concentrations of ferrous and sulfide ions in the region. X-ray microprobe analysis showed that some of the electron dense deposits consisted of iron, sulfur and lower amounts of copper, aluminium, and chromium associated with ruthenium red staining material. Spectra of other deposits revealed only silicon, which was not associated with ruthenium red.

Anaerobiosis↗
PubMed1988

Modulation of activity in sensory neurons and wind-sensitive interneurons by cercal displacement in the cockroach.

1. The cockroach Periplaneta americana can modify the sensory activity received by its central nervous system from the cerci, paired abdominal wind-responsive appendages. Medial displacement of the cerci produces a reduction in the number of sensory action potentials (AP's) elicited by a wind stimulus (Fig. 2) (Libersat et al. 1987; Golstein and Camhi 1988). This movement occurs naturally, for example during flying. 2. This sensory reduction is present when measured as the integral of extracellularly recorded activity as well as when counting the number of AP's larger than a threshold voltage just larger than the background noise (Fig. 2C). 3. Histological results confirm prior physiological experiments suggesting that the reduction may be produced by mechanical forces on the sensory nerve, rather than synaptically (Fig. 4). 4. The wind-response of interneurons is significantly diminished by the sensory reduction when measured either extra- or intracellularly (Figs. 5, 6). Cells affected include identified ventral and dorsal giant interneurons (GI's), which carry directional information about wind from the abdominal cerci to the more anterior portions of the nervous system, and are involved in flying (Camhi 1980; Ritzmann 1984; Comer 1985). 5. The reduction in the interneuronal response was unaffected by the elimination of input from descending central pathways, and input from a cercal chordotonal organ that senses cercal position and inhibits some of the GI's (Fig. 5). Thus, the reduction in wind-evoked sensory activity can itself account for the modulation of interneuron activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Action Potentials↗
PubMed1986

Identification of thoracic interneurons that mediate giant interneuron-to-motor pathways in the cockroach.

Paired intracellular recordings were made to identify thoracic interneurons that receive stable short latency excitation from giant interneurons (GIs). Eight metathoracic interneurons were identified in which EPSPs were correlated with GI activity which was evoked either by wind or intracellular electrical stimulation or occurred spontaneously. In all cases EPSPs in the thoracic interneurons followed GI action potentials faithfully at short latencies. EPSPs associated with GI action potentials consistently represented the upper range of amplitudes of a large sample of EPSPs recorded in the thoracic interneurons. Seven of the interneurons were correlated with activity in ventral GIs but were not correlated with activity in dorsal GIs. Four of these interneurons were part of a discrete population of interneurons whose somata are located in the dorsal posterior region of the ganglion. The eighth interneuron (designated the T cell) was positively correlated with activity in dorsal GIs. The four dorsal posterior group interneurons and the T cell were depolarized intracellularly to establish their potential for generating motor activity. In all cases evoked activity was stronger in leg motor neurons (primarily Ds and the common inhibitor) located on the side contralateral to the interneuron's soma. The results indicate that significant polysynaptic pathways exist by which GI activity can evoke motor activity. The implications of this conclusion to investigations on the cockroach escape system are discussed.

Animals↗
PubMed1989

The code for stimulus direction in a cell assembly in the cockroach.

The cockroach Periplaneta americana responds to the approach of a predator by turning away. A gentle wind gust, caused by the predator's approach, excites cercal wind receptors, which encode both the presence and the direction of the stimulus. These cells in turn excite a group of giant interneurons (GI's) whose axons convey the directional information to thoracic motor centers. A given wind direction is coded not by a single GI functioning as a labeled line, but rather by some relationship among the spike trains in an assembly of GI's. This paper analyzes the code in this assembly. It is shown that all three pairs of GI's with the largest axonal diameters respond differentially to wind from left front vs. right front (Figs, 3, 4; Table 2). Each GI encodes these angles by both the time of its first action potential, and the number of action potentials, relative to its contralateral homolog. It is shown that the behavioral discrimination cannot rely solely upon the left-right differences in the time of the first action potential. A model of the assembly code is developed that involves a comparison of the numbers of action potentials in the left vs. the right group of giant interneurons. The model is shown to account for a large number of pre-existing experimental data on direction discrimination. The model requires, however, the involvement of additional cells in the left and right groups, besides the specific GI's whose role had been tested in prior experiments. The model is then tested by further experiments designed to verify the involvement of these added cells. These experiments support the model.

Action Potentials↗
PubMed1987

Nicotinic acetylcholine receptors on a cholinergic nerve terminal in the cockroach, Periplaneta americana.

Intracellular microelectrode recording and ionophoretic application of carbamylcholine (CCh) were used to compare the cholinergic sensitivity of postsynaptic dendrites of an identified neurone with that of an identified presynaptic cholinergic axon. The axon of the lateral filiform hair sensory neurone (LFHSN) in the first-instar cockroach Periplaneta americana was found to be as sensitive to CCh as the dendritic regions of giant interneurone 3 (GI 3). The CCh response of both neurones was unaffected by replacing Ca2+ with Mg2+, confirming that the ACh receptors are present on the neurones under test. The CCh response of both neurones was mimicked by ionophoretic application of nicotine. The responses were blocked by 10(-5) M mecamylamine and 10(-6) M d-tubocurarine and were not affected by muscarinic antagonists, suggesting that the ACh receptors present on GI 3 and LFHSN are predominantly nicotinic. The muscarinic agonist oxotremorine and the antagonists atropine and quinuclidinyl benzilate had no modulatory effect on LFHSN-GI 3 synaptic transmission. The latency of the LFHSN response to CCh was consistent with the hypothesis that ACh receptors are situated on the main axon/terminal within the neuropil of the ganglion. It has previously been shown that this region of the axon does not form output synapses (Blagburn et al. 1985a). This indirect evidence indicates that presynaptic or extrasynaptic ACh receptors are present in the membrane of a cholinergic axon. LFHSN was depolarized by synaptically-released ACh after normal or evoked spike bursts, suggesting that the nicotinic ACh receptors act as autoreceptors. However, it was not possible to obtain direct evidence to support the hypothesis that these receptors modulate ACh release.

Acetylcholine↗
PubMed1994

Responsiveness of the adult cricket (Gryllus bimaculatus and Acheta domesticus) retrocerebral complex to allatostatin-1 from a cockroach, Diploptera punctata.

Brain-retrocerebral complexes of female crickets, Gryllus bimaculatus and Acheta domesticus, treated with antibody to allatostatin-1 from a cockroach, Diploptera punctata, show extensive immunoreactivity. The results suggest that allostatins or allatostatin-like molecules are produced in neurosecretory cells of the brain and are delivered to the corpora allata through nervous connections and/or via haemolymph. Radiochemical measurements of juvenile hormone III biosynthesis by isolated corpora cardiaca-corpora allata complexes from adult G. bimaculatus have been used to demonstrate an in vitro sensitivity of these glands to allatostatin-1 from D. punctata. Allatostatin-1 is a relatively potent inhibitor of juvenile hormone III biosynthesis in corpora allata of both young adult females and males. In glands taken from 3-day virgin females, 50% inhibition of hormone biosynthesis is reached at ca. 3 nmol.l-1 allatostatin-1. The inhibitory action of allatostatin-1 is rapid, dose-dependent and reversible. Addition of 200 mumol.l-1 farnesol to the incubation medium prevents inhibition of juvenile hormone III biosynthesis by allatostatin-1. Juvenile hormone III biosynthesis by isolated corpora allata of 3-day female house crickets, A. domesticus, is also susceptible to inhibition by 1 mumol.l-1 allatostatin-1.

Animals↗
PubMed1991

Immunocytochemical localization of leucomyosuppressin-like peptides in the CNS of the cockroach, Leucophaea maderae.

Immunocytochemistry was used to determine sites of synthesis and pathways for the transport of the neuropeptide, Leucomyosuppressin (pQDVDHVFLRFamide) in the cockroach, Leucophaea maderae. This study led to identification of neurons in the brain and thoracic ganglia reactive to polyclonal antibodies raised against this peptide. No immunoreactive cells were found in the subesophageal or abdominal ganglia. Although the corpus cardiacum contained no intrinsic cells immunoreactive to LMS antibodies, the periphery of this organ and that of the nervi corporis allati contain an abundance of LMS-reactive terminals.

Amino Acid Sequence↗
PubMed1979

Ion and water transport by isolated cockroach salivary glands.

When the isolated salivary glands of the cockroach Nauphoeta cinerea Oliver are stimulated by dopamine, the putative neurotransmitter, they secrete a fluid containing (mM):Na, 121; K, 47; Cl, 143. Stimulation of glands by 5-hydroxytryptamine or the neuro-transmitter evokes a secretion identical in Na composition to this. Dopamine-evoked secretion is abolished in the absence of extracellular Na. The relationship between the rates of fluid secretion and Na transport is linear. However, at very low rates of secretion the Na concentration falls. Calcium, K and Cl ions can be removed from the bathing solution without abolishing fluid secretion. Our evidence suggests that (i) the primary secretion is formed by active transport of Na in the acini, and (ii) the ionic composition of this secretion is modified by re-absorption of Na and an independent secretion of K in the ducts.

Biological Transport↗
PubMed1995

Hormonal control of sexual receptivity in cockroaches.

Many animals exhibit specific behaviors associated with sexual receptivity only when they are reproductively competent. In insects with gonadal maturation cycles, these behaviors usually coincide with ovarian maturation. In the cockroach Blattella germanica, juvenile hormone (JH), produced by the corpora allata (CA), regulates female reproductive physiology. Various experimental manipulations, including ablation of the CA, therapy with JH analogs, CA denervation, ovariectomy, and changing nutrient quality, coupled with time-lapse video recording, support the hypothesis that JH also controls female sexual receptivity. A re-examination of the role of the CA in the maturation of male sexual readiness shows that, while sexual behavior develops in the absence of JH in both B. germanica and Supella longipalpa, JH accelerates the expression of sexual readiness.

Animals↗
PubMed1977

Synthesis of ecdysone-14C and ecdysterone-14C from cholesterol-14C in cockroaches (Periplaneta americana) without molting glands.

The synthesis of molting hormone of cockroaches of which the prothoracic glands had previously been extirpated was investigated after injection of cholesterol-14C. It could be proved by means of radio thin-layer chromatography of extracts that ecdysterone and in small amounts ecdysone are synthesized in Periplaneta americana larvae without prothoracic glands. The results demonstrate that other tissues are also able to perform the molting hormone besides the molting gland itself.

Animals↗