PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Insecta”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 91 records · Page 5Linked to original sources
PubMed1988

Further experimental evidence for the involvement of ecdysone in the control of meiotic reinitiation in oocytes of Locusta migratoria (Insecta, Orthoptera).

Ecdysone has recently been shown to be able to trigger meiotic reinitiation in vitro in submature oocytes of Locusta. In the present study we have experimentally depressed (by 60-70%) ecdysone biosynthesis in the ovaries of adult females by rearing them on a diet with a modified sterol profile. Mature oocytes from such females fail to undergo normal reinitiation, but when incubated in vitro, can be induced to break their meiotic arrest by the addition of exogenous ecdysone. These results lend further support to the hypothesis that in Locusta, ovarian ecdysone is involved in the control of meiotic reinitiation.

Animals↗
PubMed1989

A monoclonal antibody against an adult-specific cuticular protein of Tenebrio molitor (Insecta, Coleoptera).

To study the sequential expression of the epidermal program in the mealworm Tenebrio molitor, monoclonal antibodies were prepared against the water-soluble proteins from preecdysial adult cuticle. Among the 16 clones obtained, one of them (named K2F6) recognized a 20-kDa antigen, found only in adult extracts but not in the larval or pupal ones, as revealed by immunoblot analysis. Our results strongly suggest an epidermal origin for this protein. The monoclonal antibody K2F6 fails to react with water-soluble proteins from fat body and hemolymph taken during the deposition of the 20-kDa antigen. Electron microscopic immunogold localization of this antigen showed that it is secreted, just after epicuticle deposition, in the 30 first-deposited preecdysial lamellae of sternal and elytral cuticles only. The sclerotizing process, which modifies the physicochemical properties of these cuticles, does not prevent the immunoreaction. When the expression of the adult program was inhibited by application of a juvenile hormone analog (ZR 515), the water-soluble proteins from different pupal-adult intermediates were never recognized by the monoclonal antibody K2F6 using immunoblot analysis. These results support the conclusion that this 20-kDa antigen is a protein specific for the sclerotized cuticle of the adult stage.

Animals↗
PubMed1992

What are and what are not imaginal discs: reevaluation of some basic concepts (Insecta, Holometabola).

Some general aspects of the concept of imaginal discs in the Holometabola are reevaluated. Their monolayer character and continuity with the surrounding epidermis are confirmed. Studies on the imaginal discs of the silkworm (Bombyx mori) and data from the literature show that the discs and their peripodial cells produce cuticle during larval life, as well as at metamorphosis. In B. mori it is demonstrated that adult and larval antennae are produced by the same cells or their progeny. The results also suggest that segments of the typically three-segmented larval antenna of Holometabola are not scape, pedicel, and one-segmented flagellum; at least segments 2 and 3 are of flagellar origin. Based on these and some additional facts it is argued that: (1) No larval organs are "replaced" at metamorphosis, but strict "sequential homology" is always maintained. (2) Imaginal discs are not undifferentiated structures destined to form the adult after larval breakdown, cannot be unambiguously defined, and do not represent qualitatively different epidermal structures. Classical imaginal discs (invaginated and present also in pre-final larval instars) arose several times independently and were not present in the larvae of ancestral Holometabola. (3) Since the disc cells are not undifferentiated and "embryonic" (if these words have a defined meaning at all), it is unreasonable to expect that the processes taking place in discs at metamorphosis would differ fundamentally from those occurring in other diploid metamorphosing epidermal cells.

Animals↗
PubMed1985

Studies on the toxicity of some carbamate fungicides in Drosophila melanogaster Meig. (Insecta, Diptera).

This paper reports the effects of three commercial powders mixed into the diet, Dithane M-45 (mancozeb 80%), Pomarsol (thiram 80%) and Peltar (maneb 50% and methyltiophanate 25%) on survivorship of adults Drosophila and on the progeny. With wild-type adults (Oregon), fungicides were added to the diet at the rate recommended on the label. The mean lifespan was reduced by 42.5% (Pomarsol), 50% (Dithane M-45), and 83% (Peltar). For larvae of two strains (Oregon and triploid) intoxicated with Dithane M-45 and Peltar, a linear relationship was demonstrated between the doses and the percentage of the progeny reduction. The calculated doses inducing a 50% reduced progeny (PR50) are in the range of 400 to 700 ppm. With Pomarsol in the range of 500 to 1500 ppm and for the both strains, the progeny was decreased by about 60%. A very reduced size and a leg paralysis was observed with each toxic powder for Oregon and triploid flies. It appears that a triploid stock of chromosomes does not significantly modify the reaction of the flies.

Animals↗
PubMed1988

Characterization of three hydroxylases involved in the final steps of biosynthesis of the steroid hormone ecdysone in Locusta migratoria (Insecta, Orthoptera).

It is most generally accepted that the last three enzymatic reactions in the biosynthetic pathway of ecdysone are, in this order, the hydroxylations at positions C-25, C-22 and C-2. Using high specific activity tritiated ecdysone precursors (2,22,25-trideoxyecdysone, 2,22-dideoxyecdysone and 2-deoxyecdysone) we have characterized the hydroxylases involved in these reactions, in the major biosynthetic tissue of ecdysone, i.e. the prothoracic glands. We show that C-2 hydroxylase is a mitochondrial oxygenase which differs from conventional cytochrome P-450-dependent monooxygenases by its relative insensitivity to CO. In contrast, C-22 and C-25 hydroxylases appear as classical cytochrome P-450 monooxygenases; C-22 hydroxylase is a mitochondrial enzyme whereas our data point to a microsomal localization of the C-25 hydroxylase.

Animals↗
PubMed1976

Morphometric comparison of the midgut epithelial cells in male and female Aedes aegypti L. (Insecta, Diptera).

Midgut epithelial cells of male and female Aedes aegypti, 3 days after emergence, were compared morphometrically. The results of the present investigation concerning the female, are in good agreement with those of a previous study (Hecker et al., 1974), demonstrating that morphometric investigation of midgut epithelia in A. aegypti can successfully be reproduced, and that the mosquito strain used did not show quantitative morphological changes due to laboratory rearing. In males, the cells of the anterior (A) and posterior part (P, 'stomach') of the midgut differ in their quantitative composition. Higher values are found for the microvilli and for the basal labyrinth in the A-part. On the other hand a higher volume density of the mitochondria is present in the P-part. No significant differences are found in the A-part between males and females. Significant differences, however, are present in the P-part. Distinctly more rer in the female stomach can be correlated with the synthesis of enzymes for blood digestion, which are absent in the male. In addition, the more complex functions of the female P-part are also reflected by higher values for other organelles and membrane systems (e.g. mitochondria, basal labyrinth).

Aedes↗
PubMed1991

Morphine analgesia, tolerance and addiction in the cricket Pteronemobius sp. (Orthoptera, Insecta).

The escape reaction time (ERT) of the cricket Pteronemobius sp. from the heated box begins at 48 degrees and increases with temperature until 56 degrees C, beyond which there is no further increase. The ERT (2.2 +/- 1.39 s) from the hot box at 54 degrees C is used as a model for studying the analgesic effects of opiates. Results of the present paper show that the ERT did not change after injecting the insect in the abdominal haemocoel with 0.9% saline solution, but ERT increased when 0.32, 0.52 or 0.69 mg/g of morphine is injected in the same place. The maximum ERT increase is reached at 90 min after drug injection, and the drug effect disappears 3 h after the injection. At 90 min after drug injections, the dose of 0.50 mg/g of morphine produces 50% of ERT increase, and it is referred to as the median analgesic dose (D50). 1.05 mg/g of morphine produces an ERT longer than 30 s that results in an irreversible damage to the insect. Sixty-four micrograms/g of naloxone given in addition to D50 of morphine fully blocked the effect of morphine during its 3-h action. However, more than 64 micrograms/g of naloxone alone also increase the ERT in the cricket, similar to what has been described for vertebrates. Four daily morphine injections of D50 decreased ERT in such a way that, at the fourth day, the ERT is similar to the ERT produced by saline solution; i.e., tolerance is shown. The suppression of daily morphine injections of D50 during the fifth day produced a hyperresponse to vibration (big jumps) not shown in the case of the injections of saline solution; i.e., addiction is shown.

Analgesia↗
PubMed1988

Brain RNA synthesis and the retention of learning through metamorphosis in Tenebrio obscurus (Insecta: Coleoptera).

1. Neurochemical events associated with the retention of learning through metamorphosis in the tenebrionid beetle, Tenebrio obscurus, were investigated. 2. Retention of learning of a complex maze task was demonstrated for this species. 3. Learning was accompanied by a significant increase in RNA synthesis within the corpora pedunculata of both larval and adult stages of this holometabolous insect. 4. The implications of these results to the development of the insect CNS during various life cycle stages and the conservation of neural organization within those brain regions associated with the consolidation and storage of experiential information are discussed.

Animals↗
PubMed1990

Sheathed nuclear division in primary spermatocytes of Orgyia antiqua (Lepidoptera, Insecta).

The restructuring of spermatocytes during the first meiotic division is examined in the moth Orgyia antiqua (Lymantriidae, Lepidoptera) using transmission electron microscopy. Particular emphasis was placed on the behaviour of the perispindle membrane system. These membranes develop from layers of smooth endoplasmic reticulum wrapped around the prophase I nucleus and are retained until early telophase I. The original nuclear envelope is dissolved in metaphase I. Polar fenestrae in the perispindle membrane stacks are filled with numerous irregular membrane elements. The formation of new nuclear envelopes around the daughter nuclei takes place inside the perispindle membrane system. Finally, the membrane stacks rupture concomitantly with spindle elongation in late telophase I. Thus, division of primary spermatocytes in Orgyia antiqua has a surprising degree of similarity with the so-called closed mitosis. This mode of division is typical for many protozoa, algae and fungi. In the pertinent cells, the original nuclear envelope persists around the spindle area during nuclear division. In order to distinguish the closed mitosis from the situation in Orgyia antiqua spermatocytes, the term 'sheathed nuclear division' is suggested for the latter.

Animals↗
PubMed1985

Functional multiplicity and structural correlations in the hemoglobin system of larvae of Chironomus thummi thummi (Insecta, Diptera): Hb components CTT I, CTT II beta, CTT III, CTT IV, CTT VI, CTT VIIB, CTT IX and CTT X.

Larvae of the dipteran insect Chironomus thummi thummi that burrow in fresh-water muds, contain at least 12 hemoglobin (Hb) components of which the functional properties have not been systematically documented, although their amino acid sequences have been elucidated, showing mutually distinct primary structures. We isolated eight components (the monomeric Hbs CTT I, CTT III and CTT IV and the dimeric Hbs CTT II beta, CTT VI, CTT VIIB, CTT IX and CTT X) and measured in each O2 affinity and cooperativity and their pH dependence, and the effects of temperature, NaCl and ATP. The O2 affinities, Bohr- and temperature effects of the isohemoglobins are discussed in relation to mode of life and the microenvironmental conditions to which the larvae are subjected in nature, and with regard to the molecular mechanisms underlying the Hb-oxygenation reactions.

Animals↗
PubMed1990

Low allozyme variability in Bactrocera albistrigata (Insecta: Diptera: Tephritidae) from Peninsular Malaysia.

1. Population samples of Bactrocera albistrigata from Peninsular Malaysia were analyzed for 12 to 14 gene-enzyme systems comprising 15-18 loci. 2. Three loci, aMDH, PGD and PGM, were polymorphic. 3. Anodal malate dehydrogenase and phosphogluconate dehydrogenase were represented by two alleles each, while phosphoglucomutase was represented by three alleles. 4. Phosphoglucomutase had a higher heterozygosity than anodal malate dehydrogenase and phosphogluconate dehydrogenase. 5. B. albistrigata was characterized by low genetic variability, as measured by the proportion of polymorphic loci and heterozygosity.

Alleles↗
PubMed1986

Neurons reactive to antibodies against serotonin in the stomatogastric nervous system and in the alimentary canal of locust and crickets (Orthoptera, Insecta).

Immunoreactive neurons in the stomatogastric nervous system and in the alimentary tract of the locust Schistocerca gregaria and the crickets Gryllus bimaculatus and Acheta domesticus have been examined using antibodies against serotonin (5-hydroxytryptamine; 5-HT). For comparative anatomical analysis cobalt chloride infusion was applied. The innervation of the visceral muscles was studied electron microscopically. In all three species the majority of the 5-HT-immunoreactive cell bodies of the stomatogastric nervous system occur in the frontal ganglion in which 30-40% of the total number of cell bodies react with anti-5-HT. In the occipital ganglion only two to four cell bodies (1-2%) are 5-HT-immunoreactive. Single immunoreactive cell bodies were observed in the ventricular ganglia in only a few preparations. The 5-HT-immunoreactive neurons in the frontal ganglion are pseudounipolar or multipolar. The main process of the 5-HT-immunoreactive neurons of the frontal ganglion descend along the entire stomatogastric nervous system. Some arborizations of these processes ascend into the brain and others supply the neuropil of all stomatogastric ganglia. Side branches leave the stomatogastric nervous system and form a plexus along the surface of the entire intestinal tract from where 5-HT-immunoreactive fibers supply: all muscle layers of the muscularis; the external dilator muscles of the foregut and probably some somatic muscles, neurohaemal organs and Malpighian tubules (excretory system). Serotonin-immunoreactive fibers further proceed into salivary gland and the retrocerebral complex (corpora cardiaca and corpora allata). The retrocerebral glandular complex and the hindgut receive additional immunoreactive neurons from the central nervous system. Electron microscopic analysis of nerves innervating the muscle layers of the alimentary tract revealed one type of 5-HT-immunoreactive and one or two types of non-5-HT-immunoreactive fibers. All fiber types contact the sarcolemma of muscle fibers without any obvious synaptic membrane specializations. The 5-HT-immunoreactive fibers are in some regions in close contact with the haemolymph. These regions can be regarded as sites of neurohormonal release. The distribution of serotonin-immunoreactive neurons suggests that 5-HT acts as a neurotransmitter and/or modulator on intestinal muscles and some somatic muscles and glandular cells, and as a neurohormone released from neurohaemal sites into the body fluid.

Animals↗