Structure of the abdominal receptor responsive to internally applied pressure in the blood-feeding insect,Rhodnius prolixus

Summary The sensory receptor responsive to pressure applied internally to the ventral abdominal body wall of the blood-feeding insects, Rhodnius prolixus, is a single sense cell containing, at its distal end, a cilium enclosed within a scolopale, a densely staining structure characteristic of insect scolopidial sensilla. A small spherical structure lies within a dilation near the midregion of the cilium, and contains nine heavily staining bodies, the position of each corresponding to a pair of microtubules in the cilium. Proximal to the dilation, the microtubules are organized in a ring of nine pairs with one microtubule of each pair associated with dyneinlike arms. Dastal to the dilation a central pair of microtubules is present, but dyneinlike arms are absent. The scolopale cell, which gives risc to the scolopale, has cytoplasmic invaginations that form an elaborate array of extracellular compartments surrounding the body wall of the sense cell. These compartments may serve to dampen high frequency vibrations permitting the receptor to respond to pressure exerted by touch, an attribute in keeping with the receptor's proposed function of detecting abdominal distension related to the size and movement of the stomach.     

The use of clip cages to restrain insects reduces leaf expansion systemically in Rumex obtusifolius

Abstract. 1. Clip cages have been used widely by experimental ecologists to contain insects on plants.
2. Under controlled conditions, the effect of applying clip cages alone and clip cages and the chrysomelid beetle Gastrophysa viridula on systemic leaf expansion of Rumex obtusifolius was investigated. Treatments were applied to the fully expanded fourth leaf and expansion of leaf 8 was measured over a period of 22 days.
3. The application of clip cages reduced the rate at which leaf area increased and led to reductions in final leaf areas.
4. Clip cages have systemic effects on plant development and these effects are sustained even after the clip cage is removed. Investigators should take this into account in designing experiments.     

Active human erythropoietin expressed in insect cells using a baculovirus vector: A role for N-linked oligosaccharide

Biologically active recombinant human erythropoietin has been expressed at high levels in an insect cell background. Expression involved the preparation of a human erythropoietin cDNA, the transfer of this cDNA to the Autographa californica nuclear polyhedrosis virus (AcNPV) genome under the polyhedrin gene promoter, and the subsequent infection of Spodoptera frugiperda cells with recombinant AcNPV. Erythropoietin cDNA was prepared through the expression of the human erythropoietin gene in COS cells using pSV2 and the construction of a COS cell cDNA library in bacteriophage Lambda GT10. Prior to transfer to the AcNPV genome, erythropoietin cDNA isolated from this library was modified at the 3′-terminus in order to replace genomic erythropoietin for SV40 cDNA derived from pSV2. Transfer of this cDNA to AcNPV and the infection of S. frugiperda cells with cloned recombinant virus led to the secretion of erythropoietin: based on bioassay, rates of hormone secretion (over 40 U/ml per h) were 50-fold greater than observed for COS cells. The purified recombinant product possessed full biological activity (at least 200000 U/mg), but was of lower M_r (23000) than human erythropoietin produced in COS cells (30000) or purified from urine (30000 to 38000). This difference was attributed to the glycosylation of erythropoietin in S. frugiperda cells with oligosaccharides of only limited size. Further removal of N-linked oligosac-charides from this M_r 23000 hormone using N-Glycanase yielded an apo-erythropoietin (M_r 18000) which possessed substantially reduced biological activity. These results indicate that glycosylation, but not the normal processing of oligosaccharides to complex types, is required for the full hormonal activity of human erythropoietin during red cell development.     

Constancy of ascending projections in the metamorphosing brain of the meal-beetle Tenebrio molitor L. (Insecta: Coleoptera)

Summary The fate of ascending projections of thoracic interneurons in the metamorphosing brain of Tenebrio molitor is described. Persistent brain neurons were identified and their fate is described during metamorphosis. The projection sites of ascending elements are invariable throughout metamorphosis both in quantitative and in qualitative terms. Some of these ascending neurons are serotonin-immunoreactive and this set of neurons maintains a constant projection site within the metamorphosing brain. The alterations in the projection sites of these and other ascending neurons in the ventral nerve cord were analysed experimentally. The central projection sites of these persistent ascending neurons are not important for the maintenance of their nerve cord projections throughout metamorphosis. Experimental deletion of ascending neurons which project into the suboesophageal ganglion varies the shape of persistent central neurons.     

The midline metathoracic ear of the praying mantis,Mantis religiosa

Summary The praying mantis, Mantis religiosa, is unique in possessing a single, tympanal auditory organ located in the ventral midline of its body between the metathoracic coxae. The ear is in a deep groove and consists of two tympana facing each other and backed by large air sacs. Neural transduction takes place in a structure at the anterior end of the groove. This tympanal organ contains 32 chordotonal sensilla organized into three groups, two of which are 180° out of line with the one attaching directly to the tympanum. Innervation is provided by Nerve root 7 from the metathoracic ganglion. Cobalt backfills show that the auditory neuropile is a series of finger-like projections terminating ipsilaterally near the midline, primarily near DC III and SMC. The auditory neuropile thus differs from the pattern common to all other insects previously studied.     

Evidence and bioassay for diuretic factors in the nervous system of larvalHeliothis virescens

Summary Diuretic factors were studied in the central nervous system of larvae of the tobacco budworm,Heliothis virescens, using [¹⁴C]urea as a sensitive indicator for water movement through isolated Malpighian tubules. The assay required Na⁺ and a pH of 6.0–6.2 for maximum activity. Malpighian tubules had high secretory activity in feeding larvae of the fifth instar, but the activity declined during the burrowing-digging stage that preceded pupation. Malpighian tubules from starved larvae showed a greater response to extracts of nervous tissues than did tubules from feeding larvae, and extracts showed a dose-response relationship with fluid secretion. Diuretic activity was distributed throughout all parts of the central nervous system with the brain having the most activity. Brain extracts increased fluid secretion by in vitro Malpighian tubules by more than 3-fold and doubled the rate of dye clearance from the hemolymph in vivo. Diuretic activity in nervous tissue extracts was unaffected by boiling but sensitive to proteases. Fluid secretion by in vitro tubules was increased by cAMP, dbcAMP, theophylline, octopamine and dopa. These studies provide evidence for the presence of diuretic factors in the central nervous system ofH. virescens larvae and describe a sensitive bioassay for these factors.Abbreviations AR activation ratio - cAMP cyclic AMP - dbcAMP dibutyryl cyclic AMP - dbcGMP dibutyryl cyclic GMP - Dopa dihydroxyphenylalanine - 5-HT 5-hydroxytryptamine - L1 larval instar - VCNS ventral central nervous system     

Neural activity pattern is not necessary for the development of adult ultrastructure in katydid (Neoconocephalus robustus) singing muscles

Summary The singing muscles of the katydid Neoconocephalus robustus develop adult ultrastructure late in the last nymphal instar and during the first few days of adult life. The ultrastructural changes during early adulthood were not affected by unilateral axotomy shortly after the adult molt. Both denervated and innervated muscles developed adult proportions of mitochondria, myofibril, and sarcoplasmic reticulum and transverse tubules.     

Isolation and structure of corazonin, a cardioactive peptide from the American cockroach

Corazonin, a new cardioaccelerating peptide, has been isolated from the corpora cardiaca of the American cockroach, Periplaneta americana, and its structure determined to be Glp-Thr-Phe-Gln-Tyr-Ser-Arg-Gly-Trp-Thr-Asn-amide. The peptide stimulated heart beat at concentrations as low as 0.2 nM, which makes it the most potent insect cardioactive neuropeptide.     

Acetylcholinesterase activity in antennal receptor neurons of the sphinx moth Manduca sexta

Summary We have used a cytochemical technique to investigate the distribution of acetylcholinesterase (AChE) activity in the antenna of the sphinx moth Manduca sexta. High levels of echothiophate-insensitive (presumably intracellular) AChE activity were found in six different types of antennal receptors localized in specific regions of the three antennal segments of the adult moth. Mechanosensory organs in the scape and pedicel, the Böhm bristles and Johnston's organ, are innervated by AChE-positive neurons. In each annulus of the antennal flagellum, AChE-positive neurons are associated with six sensilla chaetica and a peg organ, probably a sensillum styloconicum. At least 112 receptor neurons (8–10 per annulus) innervating the intersegmental membranes between the 14 distalmost annuli also exhibit high levels of echothiophate-resistant AChE. In addition, each annulus has more than 30 AChE-positive somata in the epidermis of the scale-covered (back) side of the flagellum, and 4 AChE-positive somata reside within the first annulus of the flagellum. Since none of the olfactory receptor neurons show a high level of echothiophateresistant AChE activity, and all known mechanoreceptors are AChE-positive, apparently intracellular AChE activity in the antenna correlates well with mechanosensory functions and is consistent with the idea that these cells employ acetylcholine as a neurotransmitter.