Larval fat body cells die during the early pupal stage in the frame of metamorphosis remodelation in Bombyx mori.

Division of Life Sciences, Graduate School of Natural Science and Technology, Kanazawa University, Kakumamachi, Kanazawa 920-1192, Japan.
Journal of insect physiology (Impact Factor: 2.24). 12/2011; 57(12):1715-22. DOI: 10.1016/j.jinsphys.2011.09.013
Source: PubMed

ABSTRACT In holometabolus insects, morphology of the larval fat body is remodeled during metamorphosis. In higher Diptera, remodeling of the fat body is achieved by cell death of larval fat body cells and differentiation of the adult fat body from primordial cells. However, little is known about remodeling of the fat body at pupal metamorphosis in Lepidoptera. In this study, we found that cell death of the larval fat body in Bombyx mori occurs at shortly after pupation. About 30% of the fat body cells underwent cell death on days 1 and 2 after pupation. The cell death involved genomic DNA fragmentation, a characteristic of apoptosis. Surgical manipulation and in vitro culture of fat body cells revealed that 20-hydroxyecdysone and juvenile hormone had no effect on either initiation or progression of cell death. During cell death, a large increase in activity of caspase-3, a key enzyme of cell death, was observed. Western blot analysis of the active form of caspase-3-like protein revealed that the length of caspase-3 of B. mori was much larger than that of caspase-3 in other species. The results suggest that larval fat body cells of B. mori are removed through cell death, which is mediated by a caspase probably categorized in a novel family.

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: In holometabolous insects the fall to zero of the titer of Juvenile Hormone ends its still poorly understood "status quo" mode of action in larvae. Concurrently it initiates metamorphosis of which the programmed cell death of all internal tissues that actively secrete proteins, such as the fat body, midgut, salivary glands, prothoracic glands etc is the most drastic aspect. These tissues have a very well developed rough endoplasmic reticulum, a known storage site of intracellular Ca(2+). A persistent high [Ca(2+)]i is toxic, lethal and causal to apoptosis. Metamorphosis becomes a logical phenomenon if analyzed from: 1. the causal link between calcium toxicity and apoptosis; 2. the largely overlooked fact that at least some isoforms of Ca(2+)-ATPases have a binding site for farnesol-like endogenous sesquiterpenoids (FRS). The Ca(2+)-ATPase blocker thapsigargin, like JH a sesquiterpenoid derivative, illustrates how absence of JH might work. The Ca(2+)-homeostasis system is concurrently extremely well conserved in evolution and highly variable, enabling tissue-, developmental-, and species specificity. As long as JH succeeds in keeping [Ca(2+)]i low by keeping the Ca(2+)-ATPases pumping, it acts as the " the status quo" hormone. When it disappears, its various inhibitory effects are lifted. The electrical wiring system of cells, in particular in the regenerating tissues, is subject to change during metamorphosis. The possibility is discussed that in vertebrates an endogenous farnesol-like sesquiterpenoid, probably farnesol itself, acts as a functional, but hitherto completely overlooked Juvenile anti-aging "Inbrome", a novel concept in signaling.
    General and Comparative Endocrinology 01/2014; · 2.82 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Hintergrund Die Altersbestimmung von juvenilen Schmeißfliegen ist ein wichtiges Werkzeug zur Eingrenzung der minimalen Leichenliegezeit. Der vorliegende Beitrag präsentiert morphologische und histologische Landmarken der über 50% der juvenilen Entwicklung beanspruchenden Puppen für die beiden in Deutschland wichtigsten Arten Calliphora vicina und Lucilia sericata. Methoden Die Aufzucht erfolgte bei 25°C. Die Puppen wurden 24-stündlich entnommen und gewogen oder abgetötet; das Puparium der abgetöteten Individuen wurde entfernt und die Puppe fotografiert. Puppen wurden in Formalin fixiert und histologische Präparate (7 µm, HE-Färbung) zur Analyse der Zellkernvolumina und Adipozyten sowie der allgemeinen histologischen Merkmale angefertigt. Ergebnisse Zehn morphologische Landmarken wurden definiert und ein signifikanter Gewichtsverlust im Verlauf der Metamorphose beobachtet. Die Zellkerne zeigten eine Volumenreduktion von bis zu 25,3% während des ersten Tages der Histolyse; die Zahl der Fettzellen reduzierte sich um bis zu 52,4%. Schlussfolgerungen Morphologische Merkmale von Puppen der Arten C. vicina und L. sericata erlauben es, die Wachstumsrate bei einer Umgebungstemperatur von 25°C auf den Tag genau einzugrenzen. Histologische Parameter können die Ergebnisse bestätigen oder sogar verbessern.
    Rechtsmedizin 12/2012; 22(6). · 0.63 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The transformation from a lepidopteran caterpillar to a non-feeding pupa and adult moth involves complete remodeling and restructuring of the insect and its organs. The synthesis of smart-nano particles (SP1 and SP2) by the larval fat body and the reuptake of these proteins by the fat body shortly before pupation seem to be a common process in the life cycle of all holo-metabolous insects. Insect fat body has been considered a single tissue with multiple and diverse metabolic functions, which are easily distinguished through appearance in different location by microscopic studies and electronmicrograph. Further fine structural changes were observed in both peripheral fat body tissue (PF) and perivisceral fat body tissues (PFV) under electron mircograph. The structural integrity of the PF was consistently maintained during final instars but showed changes towards the beginning of the spinning period. In addition, program cell death (PCD) in peripheral fat body was well characterized by chromatin condensation, cytoplasmic budding, appearance of giant autophagic vacuoles, the disappearance of the smooth endoplasmic reticulum and intercellular channels, and the fragmentation of the cytoplasm into membrane-bound bodies by morphological examination and DNA fragmentation by agarose gel electrophoresis. The metamorphosis of holometabolous insects, virtually all organs and tissue changes and < br />adult-specific proteins are expressed, while production of larval- and pupal-specific proteins is terminated. The selective uptake of smart protein or storage proteins into PVF was clearly visible in electron mircrograph. The number and size of the smart protein nano-particles granules reached a maximum about the time of the larval-pupal transformation. During the pupation, the smart protein granules were abundant in PVF. Basically there are three kinds of smart nano-particles which are distinguishable as hexmeric, amorphous, ellipsoid shape (0.5μm -1μm), while multivesicular bodies (MVB) are large < br />(3-5μm). The appearance of smart storage protein granules in the perivisceral fat body was further confirmed by immunogold labeling analysis. It has been proposed that a functional shift of the fat body take place at the end of the last larval stage, from biosynthetic organ (PF) to storage organs (PVF) and the present EM data support this hypothesis. Physiological links between the amino acids stored in smart nano-particles /storage protein later undergo proteolytic cleavage to supply amino acids resources necessary for the completion of adult development and also for egg production.
    Current microscopy contributions to advances in science and technology, First Edition edited by A.Mendez-Vilas, 07/2012: chapter Volume 1: pages 168-178; Formatex Research Center., ISBN: ISBN-13 Vol. 1: 978-84-939843-5-9