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 145 records · Page 8Linked to original sources
PubMed1975

Ultrastructure of the larval corpus allatum of hyphantria cunea Drury (Insecta, Lepidoptera).

The corpora allata of the three last larval instars were studied in newly molted animals, at the beginning, middle, and end of the feeding period, and during the molt period. They were found to consist of uniform gland cells, whose ultrastructure changes in the course of the instars. In glands cells considered to be resting, the outer and inner nuclear membranes run in parallel without forming a dilated perinuclear space. Mitochondria are small, polymorphic, with an electron-dense matrix. The smooth endoplasmic reticulum (SER) appears as stacks of parallel cisternae near the nuclear envelope and in the rest of the cytoplasm, and as accumulations of twisted profiles. Occasionally, the SER takes the form of paracrystalline bodies. There are few small smooth-surfaced vesicles in the cytoplasm. In cells considered as active, a dilated perinuclear space occurs. The peripheral ends of profiles forming the SER are swollen, and numerous vesicles and vacuoles bud off from them to fill the cytoplasm. Mitochondria are large, with a more transparent matrix. The plasma membrane of gland cells located just beneath the connective tissue sheath forms numerous small invaginations. The corpora allata consist of resting cells during the molt periods. At the beginning of each instar, few active gland cells appear. In the middle of the second to last and the third to last instars, the bulk of the gland cells is active. At the end of these instars, there are both active and inactive cells. In the middle of the last instar, the gland cells are inactive or subactive, and at its end, all gland cells are completely inactive.

Activity Cycles↗
PubMed1977

The effect of diet on the ultrastructure of the mid-gut cells of Nasonia vitripennis (Walk.) (Insecta: Hymenoptera) at various ages.

The ultrastructure of mid-gut cells of female Nasonia fed on a diet of 10% sterile sucrose is described. There are extensive alterations in cell organelles, particularly the mitochondria, rough endoplasmic reticulum (R.E.R.) and lipid inclusions, when compared to similar insects fed a normal diet of dipteran pupae. A proportion of the mitochondria found in the apical cell region are enlarged in size and contain electron-dense granules. The remaining mitochondria are smaller, but also contain electron-dense granules. Cytochrome-c oxidase activity appears to be absent from the enlarged mitochondria. The R.E.R. appears reduced in many cells of the 1 day old, sugar-fed insects, however, this component fluctuates throughout the remaining life span. The lipid inclusions prominent in the 1 day old, pupae-fed insects are not present in sucrose-fed females of the same age, but lipid deposition was recorded later in the life span. There are many large residual bodies and cytolysosomes present in the old, sugar-fed insects. These changes in ultrastructure are discussed in relation to diet and longevity.

Aging↗
PubMed1977

Ultrastructural changes in midgut cells of female Aedes aegypti L. (Insecta, Diptera) after starvation or sugar diet.

The ultrastructure of the epithelial cells in the posterior part of the midgut in female Aedes aegypti was partly changed after starvation periods of 5 or 8 days. Most obvious is a drastic reduction of the amount of rough endoplasmic reticulum (rer), which is responsible for the synthesis of enzymes for blood digestion. A similar influence on rer membranes is to be observed in mosquitoes fed on sucrose solution only, without additional blood meals.

Aedes↗
PubMed1988

Morphology of neurones associated with the antennal heart of Periplaneta americana (Blattodea, Insecta).

Innervation of the antennal heart, an independent accessory circulatory motor in the head of insects, was investigated in the cockroach Periplaneta americana by use of axonal cobalt filling and transmission electron microscopy. The muscles associated with this organ are innervated by neurones located in a part of the suboesophageal ganglion, generally considered to be formed by the mandibular neuromere. Dorsal unpaired median (DUM) and paired contralateral neurones were stained. The axons of all these neurones run along the circumoesophageal connectives and through the paired nervus corporis cardiaci III into the corpora cardiaca. They pass through these organs forming fine arborizations there and exit anteriorly as a small pair of nerves which terminate at the antennal heart-dilator muscles. Numerous branches of these nerves extend beyond the lateral borders of the large transverse dilator muscle and terminate in the ampullar walls of the antennal heart. These neurosecretory fibres form neurohaemal areas which obviously release their products into the haemolymph, which is pumped into the antennae. The possible functions of the neurones associated with the antennal heart are discussed with respect to both, their role as a modulatory input for the circulatory motor and as a neurohormonal release site.

Animals↗
PubMed1978

The ultrastructure and histochemistry of the mesenteric connective tissue of the cockroach Periplaneta americana L. (Insecta, Dictyoptera).

The thick layer of collagenous connective tissue around the mesenteron of the cockroach Periplaneta americana has been examined by light microscopy, electron microscopy and histochemical techniques. This sheath, connected to the mesenteric epithelium by a basal lamina and traversed by longitudinal and circular musculature, tracheae and nerves, contains numerous collagen fibrils, elastic fibers, fibroblasts and rare hemocytes. Development starts during the first instars with the production of connective tissue material by fibroblasts. Glycosaminoglycans have been observed with the use of various histochemical reactions, in particular alcian blue staining, metachromasia and enzymatic digestion. The reactions indicate the presence of hyaluronic acid in the various instars, the appearance and increase of sulphated components during development, and the presence of neutral glycoproteins.

Animals↗
PubMed1978

The frontal ganglion of Periplaneta americana L. (Insecta): an electron microscopic and immunohistochemical study.

The frontal ganglion, part of the stomatogastric nervous system, contains about 60 to 80 neurons, 25 to 30 micron in diameter. A well developed Golgi system, producing dense-core vesicles, lysosomes, multivesicular bodies and dense bodies are abundant. Glia elements are sparsely distributed. Many nerve fibres contain granules of different size and electron density. Five groups of fibres can be distinguished: Fibres with granules of about 200 nm (type A), fibres with granules of about 160 to 170 nm (type B), fibres with granules of about 80 to 100 nm (type C) and those with synaptic vesicles of 50 nm (type D) respectively. A fifth very small type contains neither vesicles nor granules. Special attention was paid to synaptic contacts. The divergent dyad seems to be the main type in the frontal ganglion. Frequently, neurosecretory endings are observed in presynaptic position. Immunocytochemical "staining" of neurosecretory material closely corresponds to the distribution of type A fibres, as observed electron microscopically. Immunoelectrophoresis of extracts from frontal ganglia with polyspecific anti-neurosecretion-serum reveals a single precipitation line, indicating that the immunocytochemical localization of neurosecretory material is due to reaction with a specific as well as a cross-reagent anitbody.

Animals↗
PubMed1977

Ultrastructure of the myocardial cell and its membrane systems in the adult fly Calliphora erythrocephala (insecta: diptera).

Calliphora erythrocephala has cross-striated cardiac muscle cells with A, I and Z-bands. The diameters of the myosin and actin filaments are 200-250 A and 85 A respectively and the length of the myosin filaments (A-band) is approximately 1.5 micron. Usually 8-10 actin filaments surround each myosin filament. The myocardial cells show a well-developed membrane system and interior couplings. A perforated sheet of SR envelopes the myofibrils at the A-band, dilates into flattened cisternae at both A-I band levels before it merges into a three-dimensional net-work between the actin filaments of the I-bands and between the dense bodies of the discontinuous Z-discs. The T-system consists of broad flattened tubules running between the myofibrils at the A-I band levels forming dyads with the SR-cisternae. Longitudinal connections between the transverse (T-) tubules often occur. It is suggested that this well-developed SR may be an adaptation to facilitate a rapid contraction/relaxation frequency by an effective Ca2+ uptake.

Actins↗
PubMed1975

Morphometric differences in midgut epithelial cells between strains of female Aedes aegypti (L.) (Insecta, Diptera).

Midgut epithelial cells of female Aedes aegypti deriving from 2 different mosquito strains were compared morphometrically. One of the 2 strains was recently isolated from nature (East Africa). The other strain is an old laboratory strain, reared under laboratory conditions for about 30 years. The quantitative morphological comparison demonstrates, that the ultrastructural composition of the midqut epithelial cells corresponds generally in both strains. It can be shown, however, that in the old strain, compared to the new strain, the organelle amount of midgut epithelial cells is significantly reduced during the first 53 days of the mosquito's life. Parallel to decreased relative volumes of organelles and reduced surface densities of membrane systems an increase in lysosome-like structures is observed. These observations are interpreted as deterioration processes, possibly due to the long rearing in the laboratory. Therefore, care should be taken in the selection of an A.aegypti strain for any quantitative morphological or physiological investigation.

Aedes↗
PubMed1979

Synaptic connections of the nervus connectivus in the frontal ganglion of Periplaneta americana L. (Insecta). An electron microscopic and iontophoretic study.

The course of the Nervus connectivus (N.c.), its branches, and synaptic connections within the frontal ganglion (FG) were investigated electron microscopically after cobalt iontophoresis of the N.c. The subsequent treatment of ultrathin sections with Timm's method was found to be very suitable for identifying the smallest branches. In the neuropil, fibers of the N.c. form Gray-I-type synapses, but also dyads are abundant, whereby the N.c. fibers occur exclusively in postsynaptic position with neurosecretory fibers. The possible role of these relationships is discussed.

Animals↗
PubMed1979

Functional morphology of the midgut of Aedes aegypti L. (Insecta, Diptera) during blood digestion.

Morphometric analysis of the epithelial lining of the stomach of A. aegypti suggests that digestion of the first blood meal in the stomach of this species can be viewed as a series of phases that can be correlated with physiological data from the literature. In phase Ia (0-10 h after blood meal [abm]) the whorls of the rough endoplasmic reticulum unfold, the Golgi zones increase, and the basal labyrinth is enlarged. This coincides with processes of synthesis and secretion (e.g., peritrophic membrane, esterases and lipases) and transport by the stomach epithelium. In phase Ib (10-20 habm) the cellular parameters measured further increase, indicating high synthetic and secretory activities (e.g., digestive enzymes). In phase Ic (20-30 habm) cell structures involved in synthesis and secretion still exhibit high values coinciding with maximal activity of proteases in the gut. Enhanced surface area of microvilli, prominent lipid inclusions, and appearance of glycogen deposits in the gut epithelium suggest increased absorption, storage, and transport functions of the stomach cells. In phase II (30-36 habm) structural alteration points to a gradual shift from synthesis and secretion to absorption, partial storage, and transport of nutrients. In phase III (36-72 habm) the cellular apparatus is reduced concomitant with the ending of the digestive cycle. Lipid inclusions and glycogen deposits disappear from the stomach epithelium.

Aedes↗
PubMed1980

Gap junctions between germ and somatic cells in the testis of the moth, Anagasta Küehniella (Insecta: Lepidoptera).

Heterocellular gap junctions were demonstrated in germ cysts of the moth Anagasta Küehniella (Lepidoptera). They conjoin peripheral germ cells of a cyst and cells of their envelope. Their morphology differs according to the developmental stage of the germ cell involved. While gap junctional profiles are flat in cysts of gonia, in cysts of early spermatocytes they appear as button-like structures, the germ cell indenting the corresponding cyst cell. In cysts of late spermatocytes and of young spermatids, they are very numerous and often located at the extremity of conical protrusions of the germ cell. On the germ cell side, cytoplasmic microfilaments are associated with the junctional differentiation. Gap junctions are observed as being pinched off from the surface of the spermatids and, correspondingly, gap vesicles are found in the cyst cells. This, together with the fact that gap junctions are not found at later stages of development, suggests that internalization of the gap junctions might take place before elongations of the spermatids. The potential importance of these germ-somatic cell gap junctions is evaluated in light of recent physiological findings obtained by other authors on the oocyte-cumulus system and also in relation with some particularities in the development of the male germ cells in Lepidoptera.

Animals↗
PubMed1989

Formation and function of accessory nuclei in the oocytes of the bird louse, Eomenacanthus stramineus (Insecta, Mallophaga). I. Ultrastructural and histochemical studies.

In the oocytes of Eomenacanthus stramineus accessory nuclei arise by budding from the nuclear envelope. It is suggested that microtubules and the thick layer of the nuclear lamina are involved in this process. Newly formed accessory nuclei contain aggregations of fibrillogranular material. These aggregations are slightly Feulgen positive, RNA negative and stain positively with the Ag-NOR method. During later developmental stages one dense, RNA-positive inclusion appears in each accessory nucleus. These inclusions consist of an Ag-NOR-positive cortical layer and an Ag-NOR-negative core. The function of accessory nuclei in the species investigated is discussed in the light of these results.

Actins↗
PubMed1980

Histochemical and biochemical investigations concerning the function of larval oenocytes of Tenebrio molitor L. (Coleoptera, Insecta).

Larval oenocytes of Tenebrio molitor were investigated histochemically. In contrast to the lipid droplets of the fat body, they did not stain wit Sudan black. A positive reaction for lipoproteins appeared only after destructive oxidation with sodium hypochlorite. These lipoproteins are the remnants of degenerated membranes, as revealed by ultrastructural analysis. Polyphenols could be identified in th exocuticle of exuvia, and in the newly formed procuticle. Endocuticle, epidermis and oenocytes showed no staining reaction. In oenocytes a great amount of lipase is also present which could be detected with several Tweens as substrates. The significance of these lipases remains unclear, since only few glycerides are synthesized in the cells, as shown below. They may play a role in the extended membrane turnover observed in this cell type. In vitro incubation of oenocytes of the larval generation demonstrated that 14C-labeled acetate was only incorporated into the paraffin fraction. A negligible amount of the label was found in glycerides; wax esters were free of label. Larval epidermis is also capable of paraffin formation, but only to a small degree. Oenocytes of the imaginal generation located between the sternal epidermis cells of pupae and adults do not synthesize paraffins, but other more polar compounds not yet identified. Labeled waxes in cuticular lipids were detected only when 14C-acetate was injected into whole larvae, and the lipids extracted some hours later. Autoradiographs demonstrated that 14C-acetate was intensively incorporated into larval oenocytes, the rate varying in different cells. Incorporation into the epicuticle, probably into the wax layer, was clearly shown. Cuticulin and dense layer do not show an intensive label. The lamellated cuticle also seems to be impregnated with acetate derivatives.

Acetates↗
PubMed1991

Toxicity of four common pollutants to the freshwater macroinvertebrates Chironomus riparius Meigen (Insecta:Diptera) and Gammarus pulex (L.) (Crustacea: Amphipoda).

The lethal toxicities of the four pollutants 3,4-dichloroaniline (DCA), atrazine, copper, and lindane were determined for the 2nd larval instar of the insect Chironomus riparius Meigen and the juvenile stage (2nd or 3rd moult) of the crustacean Gammarus pulex (L.). Median lethal concentrations (LC50s) were determined over a 240 h test period. The order of toxicity of the test chemicals is different for each species. For C. riparius, lindane was the most toxic, followed by copper, DCA, and atrazine. During the first 96 h of exposure, the order for G. pulex was copper, lindane, then DCA and atrazine with similar LC50 values. However, at 240 h lindane replaced copper as the most toxic chemical to G. pulex. The relative sensitivity of the two species was dependent on both the toxicant and the exposure period. The lethal concentrations determined for the four chemicals are compared to the results of other toxicity studies and discussed with respect to current standard test methods.

Aniline Compounds↗
PubMed1980

Correlations between glucose-inhibition and control parameters of alpha-glucosidase kinetics in Apis mellifica haemolymph (Hymenoptera: Insecta).

Kinetics studies of haemolymph alpha-glucosidase inhibition by D. glucose led to general correlations between inhibition and control parameters, all over the honeybee development. Maximum velocities are not affected by the inhibition, while affinity constants are always significantly increased, and Hill coefficients tend to decrease, especially in for-aging adults and in prenymphs. In this later case, the 'n-type' effect tends to break the manifestation of the 'K-type' mechanism.

Animals↗