Cell differentiation in the embryonic midgut of the tobacco hornworm, Manduca sexta

Design, Characterization and SAR Studies of Novel Bioactive Benzylideneacetophenone Derivatives as Insecticidal Agents against Spodoptera frugiperda (Lepidoptera: Noctuidae)

Unintentional environmental effects brought on by insecticides encourage the creation of safer substitutes. A very polyphagous migrating lepidopteran pest species in Africa called S. Frugiperda causes terrible damage. In the current paper, treatment of 4-acetylphenyl 4-methylbenzenesulfonate with different aromatic aldehydes in the presence of NaOH afforded benzylideneacetophenones. The structure of the newly prepared compounds were proved by different spectroscopic techniques such as IR, 1 H-NMR, 13 C NMR, and elemental analysis. We looked at the association between contact with S. frugiperda and stricture reaction to examine their harmful effect. Additionally, S. frugiperda was used for testing the newly created compounds for their ability to kill insects. The majority of substances have been proven to be effective and promising. It has been found that 4-[3-(4-Methylphenyl)prop-2-enoyl]phenyl-4-methyl benzenesulfonate (4) was the most active with an LC50 =3.46 mg/L of 2nd instar larvae and LC50 =9.45 mg/L of 4th instar larvae. Moreover, some of biological and histopathological aspects of the synthesized products were investigated under laboratory conditions.

Ultrastructural differentiation of plasma membrane and cell junctions in the hindgut cells is synchronized with key developmental transitions in Porcellio scaber

Differentiation of transporting epithelial cells during development of animal organisms includes remodelling of apical and basal plasma membranes to increase the available surface for transport and formation of occluding junctions, which maintain a paracellular diffusion barrier. This study provides a detailed ultrastructural analysis of apical and basal plasma membrane remodelling and cell junction formation in hindgut cells during late embryonic and early postembryonic development of the crustacean Porcellio scaber. Hindgut cells in late-stage embryos are columnar with flat apical and basal plasma membranes. In early-stage marsupial mancae the hindgut cells begin to acquire their characteristic dome shape, the first apical membrane folding is evident and the septate junctions expand considerably, all changes being probably associated with the onset of active feeding. In postmarsupial mancae the apical labyrinth is further elaborated and the septate junctions are expanded. This coincides with the transition to an external environment and food sources. First basal infoldings appear in the anterior chamber of early-stage marsupial mancae, but in the papillate region they are mostly formed in postmarsupial mancae. In molting late-stage marsupial mancae, the plasma membrane acquires a topology characteristic of cuticle-producing arthropod epithelia and the septate junctions are considerably reduced.

Ultrastructure of alimentary tract formation in embryos of two insect species: Melasoma saliceti and Chrysolina pardalina (Coleoptera, Chrysomelidae)

Embryogenesis of the alimentary tract in two chrysomelid species (Chrysolina pardalina and Melasoma saliceti) is described. The embryonic development of both species lasts 7days at room temperature. Stomodaeum and proctodaeum invaginate at the anterior and posterior ends of the germ band. Together with the ectodermal tissue the endoderm cells also enter into the embryo. The anterior and posterior parts of the alimentary tract wedge into the yolk in the form of conical structures. The endodermal cells remain at the yolk surface and start migration over the yolk mass as two lateral bands of cells. The endoderm is always accompanied by mesoderm. On the fifth day of development the endodermal cells together with the mesoderm layer spread over the ventral and dorsal sides of the yolk mass and form the single layered primordium of the midgut epithelium. On the sixth day of development a basal lamina appears between the endoderm and the mesoderm cells and differentiation of both tissues starts. The endodermal epithelium cells change shape from flat to cuboidal and eventually into columnar. Mesoderm cells differentiate into muscle and tracheae. On the 7thday of development stomodaeum and proctodaeum become lined with cuticle and the midgut becomes covered with microvilli. The yolk cells populating the yolk mass do not contribute to midgut formation in the species studied.

Morphological evidence for proliferative regeneration of the Anopheles stephensi midgut epithelium following Plasmodium falciparum ookinete invasion

Ookinetes are motile invasive stages of the malaria parasite that enter the midgut epithelium of the mosquito vector via an intracellular route. Ookinetes often migrate through multiple adjacent midgut epithelial cells, which subsequently undergo apoptosis/necrosis and are extruded from the midgut epithelium into the midgut lumen. Hundreds of ookinetes may simultaneously invade the midgut epithelium, causing destruction of an appreciable proportion of the total number of midgut epithelial cells. However, there is little evidence that ookinete invasion of the midgut epithelium per se is detrimental to the survival of the mosquito vector implying that efficient mechanisms exist to restore the damaged midgut epithelium following malaria parasite infection. Proliferation and differentiation of precursor stem cells could replace the midgut epithelial cells destroyed and lost as a consequence of ookinete invasion. Although the existence of so-called "regenerative" cells within the mosquito midgut epithelium has long been recognized, there has been no previously published evidence for proliferation/differentiation of these putative precursor midgut epithelial cells in mature adult female mosquitoes. In the current study, examination of Giemsa-stained histological sections from Anopheles stephensi mosquito midguts infected with the human malaria parasite Plasmodium falciparum provided morphological evidence that regenerative cells undergo division and subsequent differentiation into normal columnar midgut epithelial cells. Furthermore, the number of these putatively proliferating/differentiating regenerative cells was significantly higher in P. falciparum-infected compared to uninfected mosquitoes, and was positively correlated with both the level of malaria parasite infection and midgut epithelial cell destruction. The loss of invaded midgut epithelial cells associated with intracellular migration by ookinetes, therefore, appears to trigger, and to be compensated by, proliferative regeneration of the mosquito midgut epithelium.

Ultrastructural studies of midgut epithelium formation inLepisma saccharina L. (Insecta, Zygentoma)

At the end of embryogenesis of Lepisma saccharina L. (Insecta, Zygentoma), when the stomodaeum and proctodaeum are completely formed, the midgut epithelium is replaced by the primary midgut, a yolk mass is surrounded by a cell membrane. Midgut epithelium formation begins in the 1st larval stage. Energids migrate toward the yolk periphery and aggregate just beneath the cell membrane. They are gradually enclosed by cell membrane folds of the primary midgut. Single cells are formed. Succeeding energids join just formed cells. Thus, groups of cells, regenerative cell groups, are formed. Their number gradually increases. The external cells of the regenerative cell groups transform into epithelial cells and their basal regions spread toward the next regenerative cell groups. Epithelial cells of neighboring regenerative cell groups join each other to form the epithelium. At the end of the 2nd larval stage, just before molting, degeneration of newly the formed epithelium begins. Remains of organelles and basal membrane occur between the regenerative cell groups. The new epithelium is formed from the regenerative cell groups, which are now termed stem cells of the midgut epithelium.

Patch-clamp study of the apical membrane of the midgut of Manduca sexta larvae: direct demonstration of endogenous channels and effect of a Bacillus thuringiensis toxin

The patch-clamp technique was applied to the apical membrane of epithelial midgut cells of a lepidoptera, Manduca sexta L. Access to the apical membrane, the main target site of Bacillus thuringiensis (Bt) toxins, was achieved by using freshly isolated larval midgut preparations mounted onto holding glass pipettes. The epithelial cells retained their functional integrity, as evidenced by the magnitude of intracellular potentials recorded with microelectrodes. With standard 32 mM K(+) solution in the bath and the patch-clamp pipette, endogenous channel activity was detected in about 50% of experiments, mainly in moulting larvae and larvae that had been kept at reduced temperature for at least two days prior to the experiments. In both cell-attached and inside-out patch-clamp configurations, different types of channel were observed, with conductances varying between about 5 and 50 pS and different conducting properties. Addition of trypsin-activated Cry1Ac Bt toxin in the patch-clamp pipette triggered, after a delay, large conductances of a few nanosiemens. This is the first study allowing exploration, in the intact midgut, of the properties of apical membrane channels and the direct interaction between the apical membrane of epithelial cells and pathogenic agents such as Bt toxins.

The role of stem cells in midgut growth and regeneration

The Manduca sexta (L.) [Lepidoptera: Sphingidae] and Heliothis virescens (F.) [Lepidoptera: Noctuidae] midguts consist of a pseudostratified epithelium surrounded by striated muscle and tracheae. This epithelium contains goblet, columnar, and basal stem cells. The stem cells are critically important in that they are capable of massive proliferation and differentiation. This growth results in a fourfold enlargement of the midgut at each larval molt. The stem cells are also responsible for limited cell replacement during repair. While the characteristics of the stem cell population vary over the course of an instar, stem cells collected early in an instar and those collected late can start in vitro cultures. Cultures of larval stem, goblet, and columnar cells survive in vitro for several mo through proliferation and differentiation of the stem cells. One of the two polypeptide differentiation factors which have been identified and characterized from the culture medium has now been shown to be present in midgut in vivo. Thus the ability to examine lepidopteran midgut stem cell growth in vitro and in vivo is proving to be effective in determining the basic features of stem cell action and regulation.

Sequence of a 17 kDa vacuolar H(+)-ATPase proteolipid subunit from insect midgut and Malpighian tubules

A 0.4 kb polymerase chain reaction (PCR) product obtained from cDNA made from the midgut and Malpighian tubules of fifth instar larvae of Heliothis virescens was used to screen a larval midgut and Malpighian tubules cDNA library. Four clones were obtained, one of 1.9 kb and others of 1.4 kb. The 1.9 kb clone encodes a 17.2 kDa protein which is highly homologous to other vacuolar ATPases proteolipids. Putative N-glycosylation and DCCD binding sites were observed at amino acid residues 83 and 139, respectively.

Cell-cell communication correlates with pattern formation in molting Manduca midgut epithelium

The midgut epithelium of larval Manduca sexta is constructed of single goblet cells surrounded by a one-cell-thick reticulum of columnar cells. This pattern is expanded at each molt by the addition of new cells. Between molts, these epithelial cells are not dye coupled, even though gap junctions are present. Proliferating stem cells are dye coupled in small groups early in the molt. Then, at mid-molt, the whole epithelium temporarily becomes dye coupled. This is when the new (expanded) pattern is being established. Later, at the end of the molt, the epithelium returns to the non-coupled state. These results suggest that cell communication via gap junctions may play a role in cell patterning.

Primary structure of V-ATPase subunit B from Manduca sexta midgut

The amino acid sequence of a vacuolar-type ATPase (V-ATPase) subunit B has been deduced from a cDNA clone isolated from a Manduca sexta larval midgut library. The library was screened by hybridization with a labeled cDNA encoding subunit B of Arabidopsis thaliana tonoplast V-ATPase. The M. sexta V-ATPase subunit B consists of 494 amino acids with a calculated M(r) of 54,902. The amino acid sequence deduced for V-ATPase subunit B of M. sexta is between 98% and 76% identical with that of seven other V-ATPase subunits B and greater than 52% identical with three archaebacterial ATPase subunits B.

Molecular cloning and characterization of the B subunit of a vacuolar H(+)-ATPase from the midgut and Malpighian tubules of Helicoverpa virescens

Using the polymerase chain reaction (PCR) a 0.8-kb product was amplified from cDNA made from the midgut and Malpighian tubules of fifth instar larvae of Helicoverpa virescens. This 0.8-kb PCR product was then used to isolate a clone of the B subunit of the V-type ATPase from a cDNA library made from the same tissues. The cDNA clone encodes for a protein of 55 kDa which shows very high amino acid homology to other known B subunits of V-type ATPases. The transcript size of the B subunit in the midgut of H. virescens was 2.3 kb, and a transcript of identical size was also detected in the Malpighian tubules. Northern blot analysis revealed the presence of a homologous transcript of 2.6 kb in the midgut of Manduca sexta and PCR analysis also confirmed the presence of such a transcript in the Malpighian tubules and the nervous system of M. sexta, and in the midgut Malpighian tubules of Culex quinquefasciatus. The presence of the V-type ATPase in the Malpighian tubules of lepidopteran insects suggests that the transport of ions across the cell membrane in this tissue is also probably driven by a similar process as that observed in the midgut of these insects.