Moulting hormone,juvenile hormone and the ultrastructure of the fat body of adult Sarcophaga bullata (Diptera)

Summary In the ovoviviparous fly, Sarcophaga bullata, vitellogenesis is cyclic; a process reflected in ultrastructural changes in the fat body cells and oenocytes. At eclosion the larval fat body has not yet completely disappeared. During vitellogenesis the fat body cells are specialized for intensive protein synthesis showing a very extensive RER and numerous invaginations of the plasma membrane. These features disappear when the eggs descend into the oviducts to complete embryogenesis. The predominant feature of the oenocytes is their very prominent SER. The fat body cells of the males are never as specialized for protein synthesis as those of the females. Feeding of ecdysterone to males for 3 or more days induces a rather extensive subcellular apparatus for protein synthesis, i.e., invaginations of the plasma membrane and an extensive RER. Juvenile hormone is completely ineffective in this respect. Both ecdysterone and juvenile hormone have pronounced but different effects on the oenocytes of males.     

Fine structure of the hemocytes and nephrocytes of Argas (Persicargas) arboreus (Ixodoidea: Argasidae)

The fine structure of the hemocytes and nephrocytes in Argas (Persicargas) arboreus is described and compared with that of similar cells in other tick species and insects. The hemocytes are of three types: prohemocytes, with a relatively undifferentiated cytoplasm lacking granular inclusions and probably serving as progenitors of the other hemolymph cell types; plasmatocytes, containing abundant mitochondria, cisternae of rough endoplasmic reticulum (RER), and free ribosomes, as well as some small granular inclusions; granulocytes, the predominant cell type in the hemolymph, containing numerous granules of variable electron density and maturity, and pseudopodia-like processes on the cell surface. Plasmatocytes and granulocytes are phagocytic and possibly also have other functions in the tick body. Cells with intermediate features appear to be in a stage of transition from plasmatocyte to granulocyte. Nephrocytes contain vacuoles enclosing fibrillar material, some electrondense granules, and moderate amounts of the active organelles—mitochondria, RER, and ribosomes. The nephrocyte is surrounded by a basal lamina and its plasma membrane infolds to form many deep invaginations coated by a fine fibrillar material. Openings to these invaginations are closed by membranous diaphragms. Coated tubular elements connect the surface invaginations with large coated vesicles, which appear to be specialized for internalization of proteins from the hemolymph. The dense granules may represent an advanced stage of condensation of ingested protein and thus may be lysosomal residual bodies, or they may develop by accumulation of secretory products.     

Sequential structural changes in the fat body of the tobacco hornworm, Manduca sexta, during the fifth larval stadium

Light and electron microscopy revealed a series of structural changes that occur in the fat body of the tobacco hornworm, Manduca sexta, during the fifth, i.e. the final, larval stadium. At each developmental stage studied, the cells of the fat body were homogeneous in structure. We found no evidence suggesting the presence of more than one type of fat body cell. Our structural data are consistent with published observations on biochemical activities of M. sexta fat body at particular developmental stages. Specific points of agreement include: (a) acquisition of Golgi complex (GC) and rough endoplasmic reticulum (RER) concomitant with the time of major protein production; (b) loss of many cellular organelles (such as GC and RER) as protein production drastically decreases; (c) accumulation of protein granules and urate granules after the onset of wandering (i.e. during the pre-pupal period); (d) accumulation of lipid and glycogen throughout the feeding period. In addition we found that (a) the plasma membrane reticular system (PMRS) developed during the period when protein secretion was great; (b) the PMRS was lost abruptly at the onset of wandering; and (c) the nucleus changed in shape from being roughly spherical to elliptoid in the pre-pupal stage. We found that the structure of M. sexta fat body is similar to that published for other Lepidoptera. However, it differs from that of Heliothis zea in that regional differences are not obviously apparent.     

Effects of Estrogen and Testosterone on Resting Energy Expenditure in Older Men

The mechanisms by which sex hormones cause changes in body composition are unclear. Sex steroid deficiency might directly reduce energy expenditure/fat oxidation and thereby predispose to increased body fat. Alternatively, sex steroid deficiency could result in lean tissue loss and thus reduced energy expenditure. Our objective was to examine the independent and combined effects of acute testosterone and estrogen withdrawal on respiratory exchange ratio (RER) and resting energy expenditure (REE) in men. The objective of the study was to examine the independent and combined effects of acute estrogen and testosterone withdrawal on RER and REE in men. A total of 54 men aged 50–80 years, BMI range of 17–35 kg/m² underwent a 3‐week eugonadal run‐in hormone‐treatment period involving suppression of endogenous sex steroids using letrozole and leuprolide acetate (Lupron) while sex steroid concentrations were maintained with transdermal testosterone (T) and estradiol (E). A second Lupron injection was then given and participants were randomized to one of the following four 3‐week treatment groups: group A (?T, ?E), group B (?T, +E), group C (+T, ?E), and group D (+T, +E). REE and RER were measured via indirect calorimetry before and after the 3‐week treatment period. Three‐week suppression and/or repletion of estrogen or testosterone did not produce changes in RER or REE within or between groups. We conclude that abrupt changes in sex steroids does not change resting substrate oxidation, indicating that changes that can be observed after more prolonged periods of deficiency are most likely due to direct effects of sex steroids on body composition.     

Histological and cytological studies on the fat body of the cockroach Nauphoeta cinerea during the first reproductive cycle

Summary The central fat body of the ovoviviparous cockroach Nauphoeta cinerea was studied during the first reproductive cycle of the female by means of light microscopy, autoradiography and electron microscopy. Comparative studies in larval stages were also undertaken. The fat body of Nauphoeta contains a large amount of lipid droplets and the remaining cytoplasm is very scarce. The cytological cyclicity of the fat body is consistent with the known biochemical rhythms of vitellogenin production. The proteosynthetic apparatus appears about 3 days after imaginal ecdysis, along with vitellogenin. The ribosomal endoplasmic reticulum (RER) shows a tremendous increase by the 7th day of the first cycle. The most active period of vitellogenin production lasts from day 7 to day 12. The proteosynthetic apparatus then returns to an inactive stage and disappears. This inactive condition lasts to the end of the gestation period. The autoradiographic results are consistent with the cytological features.Work carried out under the scientific direction of Prof. M. Lüscher of the University of Bern and supported in part by a grant from the Swiss National Science Foundation (No 3. 633.71).     

Effect of gluten on the digestive tract and fat body of Telodeinopus aoutii (Diplopoda)

Adult specimens or larvae of invertebrates used as food for vertebrates are often maintained close to gluten so they might become vectors for cereal proteins. However, the tissues and internal organs can respond differently in animals with different feeding habits. The midgut epithelium might be a first and sufficient barrier preventing uptake and effects of gluten on the whole body, while the fat body is the main organ that accumulates different xenobiotics. Good models for such research are animals that do not feed on gluten-rich products in their natural environment. The project's goal was to investigate alterations in the midgut epithelium and fat body of the herbivorous millipede Telodeinopus aoutii (Diplopoda) and analyze cell death processes activated by gluten. It enabled us to determine whether changes were intensified or reversed by adaptive mechanisms. Adult specimens were divided into control and experimental animals fed with mushrooms supplemented with gluten and analyzed using transmission electron microscopy, flow cytometry, and confocal microscopy. Two organs were isolated for the qualitative and quantitative analysis: the midgut and the fat body. Our study of the herbivorous T. aoutii which does not naturally feed on gluten containing diet showed that continuous and prolonged gluten feeding activates repair processes that inhibit the processes of cell death (apoptosis and necrosis) and induce an increase in cell viability.     

The Influence of Human Growth Hormone (GH) and Thyroxine (T4) on the Differentiation of Adipose Tissue in the Fetus

Late term fetuses from genetically obese dams have slightly larger fat cells, greater adipose tissue lipoprotein lipase (LPL) activities, elevated levels of thyroid hormones, and depressed growth hormone (GH) levels when compared to fetuses from lean dams. We have investigated the influence of thyroid hormone and GH status per se on these and other adipose tissue traits by chronically treating hypophysectomized (hypox) fetuses (day 70) between day 90 and 105 of gestation with either thyroxine (T4) or human GH. Treatment with T4 decreased body weights (P<.05), increased serum T₄ levels (P<.05), and enhanced skin and hair development (P<.05). Quantitative analysis of sections of perirenal and subcutaneous adipose tissue indicated that T₄ increased LPL activity (P<.05), slightly increased fat cell size, and more than doubled (P<.05) lipid accretion. A hypox induced deficit in fat cell cluster number in the outer layer of subcutaneous tissue was normalized by T₄ (P<.05). Conversely, human GH (hGH) treatment had no influence on body weight, increased serum hGH levels, decreased fat cell size (P<.05) and LPL activity (P<.05) but had no influence on lipid accretion. Quantitative analysis of adipose tissue sections provided direct and indirect evidence of a “critical” or “sensitive” period between 90 and 105 days, since fetal hypox at day 70 severely impeded preadipocyte recruitmentheplication during this period. Furthermore, T₄ but not GH effectively normalized this hypox-induced deficiency in preadipocyte development. Therefore, T₄ may have a major role in preadipocyte recruitmentheplication during late fetal life.     

Ultrastructure and histochemistry of the fat body of Anthonomus grandis (Coleoptera: Curculionidae)

Abstract

Metabolic demands such as growth and reproduction of insects relate directly to the fat body. This organ is responsible for the biosynthesis and storage of nutrients, and participates in the neutralization and detoxification of xenobiotics. Studies show a relationship between its ability to accumulate nutrients and activities, such as diapause and reproduction in the beetle Anthonomus grandis, an important pest of cotton plants. However, there are no detailed studies on the structure and histochemistry of the fat body in this insect. We describe the ultrastructure and histochemistry of the fat body in A. grandis and discuss some of its characteristic features. The fat body is composed of a single cell type, the trophocyte, which is a voluminous cell with a spherical or bilobed nucleus, and cytoplasm containing several lipid droplets, glycogen granules (electron-dense), and protein granules. These trophocytes have few areas of contact with each other and form lobes, enclosed by connective tissue. A high metabolic activity of the fat body is deduced by the intense histochemical staining for protein and polysaccharide compounds, demonstrating that specific processes, such as the synthesis and secretion of vitellogenin, could be a target for more specific studies on methods to control this insect.     

Unusual cell organelles during spermiogenesis in two species of gobies (Gobiidae,Teleostei)

Summary Testes of Lesuerigobius friesii and Gobius bucchichi were studied in adult reproductive fish. During the onset of spermatid development, a peculiar system of alternating rough (RER) and smooth (SER) endoplasmic reticular tubules form rings distally to the cell nucleus. The RER tubules are seen to possess up to 12 ribosomes in cross-section, whereas the SER are strongly electron-dense. Nanotubules connect these stacks of tubules to the developing head and tail of the sperm. With ripening of the sperm these tubules disintegrate within the excessive cytoplasm. It seems likely that these are special forms of Macro-Golgi System that possibly provide protamines for the developing sperm.     

Targeting of rough endoplasmic reticulum membrane proteins and ribosomes in invertebrate neurons

The endoplasmic reticulum (ER) is divided into rough and smooth domains (RER and SER). The two domains share most proteins, but RER is enriched in some membrane proteins by an unknown mechanism. We studied RER protein targeting by expressing fluorescent protein fusions to ER membrane proteins in Caenorhabditis elegans. In several cell types RER and general ER proteins colocalized, but in neurons RER proteins were concentrated in the cell body, whereas general ER proteins were also found in neurites. Surprisingly RER membrane proteins diffused rapidly within the cell body, indicating they are not localized by immobilization. Ribosomes were also concentrated in the cell body, suggesting they may be in part responsible for targeting RER membrane proteins.     

Effect of Azadirachtin on vitellogenesis of Labidura riparia (Insect Dermaptera)

This study investigates the effects of the insect growth regulator Azadirachtin (AZA) on the ultrastructure of ovaries and fat body of the earwig Labidura riparia. Ovarian development is severely reduced in AZA-injected females in a dose-dependent manner. Follicles exhibit degenerative changes, separation of follicle cells from the oocyte, and lack of pinocytotic vesicles as of yolk spheres in cortical ooplasm. Adipocytes show fragmented rough endoplasmic reticulum (RER), numerous autophagic vacuoles, multivesicular bodies, osmiophilic lipid droplets, and many large glycogen areas. Gel electrophoresis reveals that vitellogenin is absent from both fat body and hemolymph, and that vitellin is not deposited in the ovary. These pathological effects are not linked to an absence of feeding. The effect of AZA on vitellogenesis is rescuable by Juvenile hormone (JH) treatment. The inhibition of vitellogenesis by AZA is discussed on the basis of its direct cytotoxic effect as well as its interference with the neuroendocrine system.     

Cell remodeling in the fat body of an insect.

The fat body of the Lepidopteran, Calpodes ethlius, undergoes major functional changes during larval-adult metamorphosis. These changes occur in conjunction with extensive cell remodeling - a process whereby one population of cellular organelles is destroyed and replaced by another during development. Fat body organelles including mitochondria, microbodies, and RER are destroyed on a massive scale shortly before pupation (Locke and Collins, 1965; Locke and McMahon, 1971) a new populations of each are regenerated shortly after emergence of the adult. In addition, protein, lipid and RNA reserves formed shortly before pupation and multivesicular bodies formed shortly before emergence are secreted into the haemocoel during the first few days of adult life. Electron microscopic studies using tracer techniques, cytochemical and enzyme localization procedures, and sterological analyses have been undertaken to determine the time course and mechanism of organelle regeneration and the fate of reserves stored in the fat body.     

A new cell line from larval fat bodies of the bollworm, Helicoverpa armigera (Lepidoptera: Noctuidae)

Summary A new cell line, designated IOZCAS-Ha-I, was initiated from the fat body of larvae of Helicoverpa armigera (Lepidoptera: Noctuidae) in TNM-FH medium containing 10% fetal bovine serum. Spherical cells were predominant among the various cell types. The cell line showed a typical lepidopteran chromosome pattern ranging from 58 to 239 chromosomes in the majority of the cells, it was confirmed to have originated from the H. armigera by the DNA amplification-fingerprinting polymerase chain reaction (DAF-PCR) technique. The new cell line was only slightly susceptible to the multiple nucleocapsid nuclear polyhedrosis viruses (NPV) from H. armigera.     

Fine structure of the photogenous areas in the bioluminescent ophiuroidAmphipholis squamata (Echinodermata,Ophiuridea)

 Amphipholis squamata is a small bioluminescent ophiuroid whose arms are the only body part to produce light. The morphology of the arms was described paying particular attention to the spinal ganglia, viz the areas of most intense luminescence. Spinal ganglia consist of five different cell types (A–E) which were studied at different stages of the photogenous reaction. Type D cells have numerous irregularlyshaped vacuoles, widespread Golgi apparatus and well-developed rough endoplasmic reticulum (RER) that show obvious ultrastructural changes after luminescence. Type D cells appear, therefore, to be the best photocyte candidate. Type B and C cells were frequently observed in the nervous system outside spinal ganglia. Type A and E cells have not been described before. Type A cells are ciliated cells and type E cells extend long processes which are intimately associated with type D cells and epidermal ciliated cells. Both type A and type E cells could take part to the stimulation pathway that triggers luminescence. Accepted: 1 September 1996     

Effects of citronella oil (Cymbopogon winterianus Jowitt ex Bor) on Spodoptera frugiperda (J. E. Smith) midgut and fat body

The armyworm, Spodoptera frugiperda, is the principal pest of corn in Brazil. Control is achieved primarily by synthetic insecticides, which cause problems for the agro-ecosystem. Alternative methods of control are under investigation and citronella (Cymbopogon winterianus) essential oil appears to be a promising agent. We investigated the effects of citronella oil using histological, histochemical and immunohistochemical methods. The midgut of larvae treated with citronella exhibited altered epithelium including cytoplasmic protrusions, columnar cell extrusion, pyknotic nuclei, and increased periodic acid-Schiff positive granules. Regenerative cells in the epithelium of the midgut increased in number, which facilitated subsequent regeneration of this tissue. After exposure to citronella, trophocytes, the principal cell type of the fat body, possessed enlarged vacuoles and mitotic bodies, and contained reduced amounts of glycogen, lipid, and protein. Citronella oil caused morphological changes of the midgut and reduction of stored resources in the fat body, which may adversely affect insect reproduction and survival.     

Vitellogenin synthesis by the fat body of Porcellio dilatatus Brandt (Crustacea,Isopoda)

Using immunofluorescence, vitellogenin has been identified in the fat body of ovariectomized females of Porcellio dilatatus. Using immunoradiography of incubated fat body in leucine-¹⁴C-labeled medium, this organ has been demonstrated to be the synthesis site. Storage, but not synthesis, has also been proven in a particular kind of hepatopancreatic cell which might play a part in the resorption of vitellogenin excess.     

The presence of vasoactive intestinal polypeptide (VIP)-like-immunoreactive nerve fibres and VIP-receptors in the pineal gland of the Mongolian gerbil (Meriones unguiculatus)

Summary The photocytes and other endodermal cells composing the wall of the meridional canals of the comb-jelly, Mnemiopsis leidyi, were investigated by transmission electron microscopy. Although many of these cells possess distinctive features such as a ciliary apparatus, lysosome-like bodies or vacuoles, they share with photocytes the presence of a network of rough endoplasmic reticulum (RER) whose cisternae enwrap large mitochondria and are aligned along the subsurface of the plasma membrane. A stereological analysis of organelle content in photocytes confirms the prominence of the RER in these cells and a shift of RER from mitochondria to plasma membrane subsurface in photocytes induced to luminesce by the mitochondrial inhibitor dinitrophenol. Photocytes and other endodermal cells of the meridional canals are interconnected by numerous gap junctions which, among photocytes, often form symmetrical triads with cortical cisternae and mitochondria. The gap junctions and RER/mitochondria assemblages are interpreted as possible substrates for, respectively, conduction of luminescence excitation along the canals and for excitation-luminescence coupling. Neuntes occasionally make synapses with photocytes and other endodermal cells lying adjacent to the mesoglea.     

Ultrastructural features of the epidermis in turbellaria from the Lake Baikal Geocentrophora wagini (Lecithoepitheliata, Plathelminthes)

The epidermis of Geocentrophora wagini was studied using transmission electron microscopy. The turbellarian body was entirely covered by cilia, whose density was higher on the ventral surface compared with the dorsal one. In all regions examined, the epidermis was made up of a one-layered insunk epithelium. The basal matrix, underlying the epidermis, was a well developed basement membrane (BM) with bilayered structure, overlying the muscle network of circular and longitudinal fibers. The double plasma membranes, extending from the apical surface of epidermis to BM, were linked by specialized cell junctions. This suggested that epidermis had a cellular rather than a cyncytial arrangement. Each insunk epidermal cell was made of two unequal parts: a comparatively thin surface plate attached to BM by hemiadherens junctions, and a massive nucleated portion located below the body wall musculature in the parenchyma. A thin cytoplasmic bridge connected the epidermal plate with the nucleated cell body. The epidermal plates were joined by belt-like junctions along their adjacent surfaces. Inconspicuous zonula adherens (ZA) had a most apical position, and prominent septate junction was arrayed proximally to this zonula. Except ZA, cell boundaries in epidermis were frequently flanked by rows of light tubules and vesicles. In the basal half of the epithelial sheet, they were occassionally accompanied by single cisternae of rough endoplasmic reticulum (RER). The ultrastructure of the insunk cell body and that of the surface plate showed a considerable similarity. The common features were distinctive profiles of RER and GA, the presence of epitheliosomes, light tubules and vesicles, centrioles and fibrous granules. Thus, ultrastructural features allow a rather reliable identification of epidermal cells in the parenchyma, despite the absence of any visible morphological association between cell body and its epidermal plate.     

Cytomorphology and copper content of the basal cells in the midgut gland of Nautilus (Cephalopoda,Tetrabranchiata)

Summary By means of light and electron microscopical studies on Nautilus pompilius and Nautilus macromphalus, special basal cells within the alveolary enlarged terminal parts of the tubules of the midgut gland were revealed. Their abundant rough endoplasmic reticulum (RER) with enlarged cisterns synthesizes ring-shaped macromolecules that resemble the hemocyanin molecules within the bloods-paces in size and form and seem to be secreted throughout the lamina basalis, locally discharged into the adjacent blood sinus. The hypothesis that this cell type represents a site of hemocyanin synthesis was confirmed by Zeeman AAS and ASTEM analyses of the content and distribution of copper within the glandular tissue, especially the different compartments of this cell type.     

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

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.