Sperm ultrastructure and a new type of spermiogenesis in two species of Pimelodidae, with a comparative review of sperm ultrastructure in Siluriformes (Teleostei : Ostariophysi)

During spermiogenesis, the spermatids of the pimelodid species Pimelodus maculatus and Pseudoplatystoma fasciatum show a central flagellum development, no rotation of the nucleus, and no nuclear fossa formation, in contrast to all previously described spermatids of Teleostei. These characteristics are interpreted as belonging to a new type of spermiogenesis, named here type III, which is peculiar to the family Pimelodidae. In P. maculatus and P. fasciatum, spermatozoa possess a spherical head and no acrosome; their nucleus contains highly condensed, homogeneous chromatin with small electron-lucent areas; and a nuclear fossa is not present. The centriolar complex lies close to the nucleus. The midpiece is small, has no true cytoplasmic channel, and contains many elongate and interconnected vesicles. Several spherical to oblong mitochondria are located around the centriolar complex. The flagellum displays the classical axoneme (9 + 2) and no lateral fins. Only minor differences were observed among the pimelodid species and genera. Otherwise, spermiogenesis and spermatozoa in the two species of Pimelodidae studied exhibit many characteristics that are not found in other siluriform families, mainly the type III spermiogenesis. (C) 2007 Elsevier GmbH. All rights reserved.

Ultrastructure of the gland responsible for the synthesis of an aggregation pheromone in Rhynchophorus palmarum (L.) (Coleoptera: Curculionidae)

The ultrastructure of the glands responsible for synthesizing the aggregation pheromone rhynchophorol in the beetle Rhynchophorus palmarum (L.) was studied. Glands from live beetles were removed and examined under a light microscope using semithin sections (∼1μm) and under a transmission electron microscope (TEM) using ultrathin sections (60 nm). The glands show an alveolar structure without a reservoir and the cells making up the gland are arranged in a typical acinus pattern. The existence of two types of cells with different electron densities, secretion canaliculi, numerous mitochondria and smooth endoplasmic reticulum in abundance were observed. These latter organelles are characteristic of cells which synthetize non-proteinaceous substances and are thus, likely candidates for the producion of rhynchophorol.

Regression of the lateral oviducts during the larval-adult transformation of the reproductive system of Melipona quadrifasciata and Frieseomelitta varia

Toward the end of the larval phase (pre-pupa), the reproductive systems of Melipona quadrifasciata and Frieseomelitta varia workers are anatomically similar. Scanning electron microscopy showed that during this developmental phase the right and left ovaries are fused and form a heart-shaped structure located above the midgut. Each ovary is connected to the genital chamber by a long and slender lateral oviduct. During pupal development, the lateral oviducts of workers from both species become extremely reduced due to a drastic process of cell death, as shown by transmission electron microscopy. During the lateral oviduct shortening, their simple columnar epithelial cells show some signs of apoptosis in addition to necrosis. Cell death was characterized by cytoplasmic vesiculation, peculiar accumulation of glycogen, and dilation of cytoplasmic organelles such as mitochondria and rough endoplasmic reticulum. The nuclei, at first irregularly contoured, became swollen, with chromatin flocculation and various areas of condensed chromatin next to the nuclear envelope. At the end of the pupal phase, deep recesses marked the nuclei. At emergence, worker and queen reproductive systems showed marked differences, although reduction in the lateral oviducts was an event occurring in both castes. However, in queens the ovarioles increased in length and the spermatheca was larger than that of workers. At the external anatomical level, the reproductive system of workers and queens could be distinguished in the white- and pink-eyed pupal phase. The metamorphic function of the death of lateral oviduct cells, with consequent oviduct shortening, is discussed in terms of the anatomical reorganization of the reproductive system and of the ventrolateral positioning of adult worker bee ovaries. (C) 2000 Wiley-Liss, Inc.

Ultrastructure of Sorubim lima (Teleostei, Siluriformes, Pimelodidae) spermiogenesis

The spermiogenesis and the spermatozoon ultrastructure of Sorubim lima were studied. Our observations showed that early spermatids are round-shaped cells, have spherical nucleus with diffuse chromatin, small quantity of mitochondria and large amount of vesicles in the cytoplasm. During the differentiation process in the nucleus, chromatin compacts in a progressive and homogeneous way, and the flagellum is formed. In the cytoplasm the vesicles, that have double membranes, aggregate and fuse on the plasma membrane. The spermatozoa of 5. lima have no acrosome and show spherical nucleus with homogeneous and highly compacted chromatin, intermediary piece with mitochondria and double wall vesicles contiguous to the plasma membrane, as well as a flagellum formed by a basic axoneme (9 + 2).

Protein requirements in larvae and adults of Scaptotrigona postica (Hymenoptera: Apidia, Meliponinae): Midgut proteolytic activity and pollen digestion

The number and degree of digestion of pollen grains in the midgut and rectum, the midgut proteolytic activity and the time of pollen grain passage through the digestive tract in the stingless bee Scaptotrigona postica (Latreille) have been analyzed. The results show similar protein requirements among larvae, nurse bees and queens, as well as between forager bees and old males, but these requirements are higher in individuals from the former groups than in those from the latter. Although protein requirements have been demonstrated to vary according to a bee's activity in the colony, they are similar among bees from different castes or sexes. These changes in feeding behavior are related to the bee's function and to less competition for nourishment among individuals of the colony. It is also noted that pollen grains took between 6 and 28 h to pass through the digestive tract. Pollen grains are irregularly accumulated in the various regions of the midgut, which may reflect functional differentiation throughout the midgut. © 2001 Elsevier B.V.

Testicular ultrastructure and morphology of the seminal pathway in Prochilodus scrofa

The seminiferous tubules of Prochilodus scrofa present a coiled morphological arrangement with intertubular anastomoses and unrestricted spermatogonial distribution. The structural pattern of the seminiferous tubules is cystic, with cysts formed by cytoplasmic prolongations of Sertoli cells. Inside the cysts are observed different types of germ cells. The seminiferous tubules open individually on the ventral surface of the main testicular duct present in each testis. Each main testicular duct prolongs as a spermatic duct, fusing with the spermatic duct of the opposite side to form the common spermatic duct which opens into the urogenital papilla. The mature sperm cysts break and extravasate their content into the lumen of the seminiferous tubules from which the seminal fluid and the spermatozoa penetrate the main testicular duct, the spermatic duct and the common spermatic duct for semen ejaculation.

Targeting Plasmodium ligands on mosquito salivary glands and midgut with a phage display peptide library

Despite vast efforts and expenditures in the past few decades, malaria continues to kill millions of persons every year, and new approaches for disease control are urgently needed. To complete its life cycle in the mosquito, Plasmodium, the causative agent of malaria, has to traverse the epithelia of the midgut and salivary glands. Although strong circumstantial evidence indicates that parasite interactions with the two organs are specific, hardly any information is available about the interacting molecules. By use of a phage display library, we identified a 12-aa peptide-salivary gland and midgut peptide 1 (SM1)-that binds to the distal lobes of the salivary gland and to the luminal side of the midgut epithelium, but not to the midgut surface facing the hemolymph or to ovaries. The coincidence of the tissues with which parasites and the SM1 peptide interact suggested that the parasite and peptide recognize the same surface ligand. In support of this hypothesis, the SM1 peptide strongly inhibited Plasmodium invasion of salivary gland and midgut epithelia. These experiments suggest a new strategy for the genetic manipulation of mosquito vectorial capacity.

The ultrastructure of the pre-meiotic and meiotic stages of spermatogenesis in Plagioscion squamosissimus (Teleostei, Perciformes, Sciaenidae)

Spermatogenesis of 'corvina' P. squamosissimus starts from a stem cell that gives rise to germ cells. These cells are enveloped by Sertoli cells, forming cysts. The germ cells in the cysts are all at the same stage of development and are interconnected by cytoplasmic bridges. Spermatogonia are the largest germ cells. In the cysts, these cells differentiate into primary spermatogonia and secondary spermatogonia. The primary spermatogonia are isolated in the cyst and give rise to the secondary spermatogonia. After several mitotic divisions, they produce spermatocytes I, which can be identified by synaptonemal complexes in the nucleus. The spermatocytes I enter the first phase of meiosis to produce the spermatocytes II. These are not very frequently seen because they rapidly undergo a second phase of meiosis to produce spermatids.

Ultrastructure of the salivary glands of Pachycondyla (=Neoponera) villosa (Fabricius) (Formicidae: Ponerinae): Functional changes during the last larval instar

The cells of secretory region of the salivary glands of Pachycondyla (=Neoponera) villosa at the time of enzyme production presents the basal cellular membranes profusely folded and the intercellular junctional membranes present a few enlarged spaces. The rough endoplasmic reticulum and the Golgi bodies shift from being flat and small vesicular cisternae to enlarged vesicular cisternae according to the cell physiological state and characterize an asynchronic cell cycle. Enzymes are released into the lumen by microapocrine secretion. The stage of silk production is detected after a behavioral act, when the nurse worker separates the mature larva. At this time, the salivary gland cells present only one physiological state (synchronized secretory cycle): this state was characterized by basal cellular membrane poorly folded, intercellular junctions presenting some small spaces, rough endoplasmic reticulum compounded by flat cistenae, enlarged Golgi bodies with fibrous material inside and a few secretory vesicles containing silk, which undergo exocytosis. The silk in the lumen shows 2 forms: tactoid and flocculent material.

Cell nucleus activity during post-embryonic development of Apis melliferaL. (Hymenoptera: Apidae). Intranuclear acid phosphatase

We report nuclear acid phosphatase activity in the somatic (intra-ovariolar and stromatic) and germ cells of differentiating honey bee worker ovaries, as well as in the midgut cells of metamorphosing bees. There was heterogeneity in the intensity and distribution of electron dense deposits of lead phosphate, indicative of acid phosphatase activity in the nuclei of these tissues, during different phases of post-embryonic bee development. This heterogeneity was interpreted as a variation of the nuclear functional state, related to the cell functions in these tissues.

The ultrastructure of the guinea pig rete testis

The chambers of the rete testis (RT) of guinea pig are lined by a simple epithelium, whose cells are squamous, cubical and columnar in shape. The epithelial cells with distinct shapes were counted and the quantitative analysis of the number of these cells showed relative predominance of cubical cells. The ultrastructural observations showed predominance of membrane interdigitations among the epithelial cells. These cells present common cytoplasmic organelles. The Golgi complex polarity is typical with observation of electronlucent vesicles on the Golgi cis face closely related to rough endoplasmic reticulum (ER) lamellae, mitochondria and large number of polysomes on the Golgi trans face. These related structures present in Golgi area of RT cells suggest secretory activity which maybe occurs in the RT epithelium. Endocytotic process also occurs in the RT and this function probably concerns the uptake of substances and resorption of seminiferous fluid. Apical cilia present in RT epithelium cells are related with fluid transport and perhaps with chemoreception. Presence of spermatozoa portions enclosed into the cytoplasm of some epithelium cells has been refferred to as spermatophagy. The RT complex is mainly supported by loose connective tissue, with collagen fibres and some Leydig cells. Leydig cells are adjacent to the network channels of the septal part of the RT and apparently are able to secrete inside the RT lumen.

Intestino médio de larvas de Anticarsia gemmatalis (Hübner) (Lepidoptera: Noctuidae): estudo das células epiteliais ao microscópio de luz e eletrônico

The morphology of the midgut epithelium cells of Anticarsia gemmatalis (Hübner) larvae is described by light and transmission electron microscopy. The midgut of A. gemmatalis is the largest portion of the digestive tract, with three distinct regions: proximal, media and distal. Its wall is formed by pseudostratified columnar epithelial tissue having four cell types: columnar, goblet, regenerative, and endocrine cells. The columnar cells are numerous and long, with the apical portion showing many lengthy microvilli and the basal portion invaginations forming a basal labyrinth. The goblet cells have a large goblet-shaped central cavity delimited by cytoplasmic projections filled with mitochondria. The regenerative cells present electron-dense cytoplasm and few organelles. The endocrine cells are characterized by electron-dense secretory granules, usually concentrated in the cytoplasm basal region.

Glandular dots of Caesalpinia echinata Lam. (Leguminosae): Distribution, structure and ultrastructure

The structure and ultrastructure of immature to fully mature glandular dots in the leaf, floral organs and fruit, and their secretion components were described in Caesalpinia echinata Lam. (Leguminosae) for the first time. Data showed that glandular dots were groups of idioblasts with contents that reacted positively for both lipophilic and hydrophilic substances. Idioblasts originated from successive divisions of the ground meristem cells or mesophyll cells of an ovary of a fertilized flower. Following division, cells enlarged, the cytoplasm became denser and its content became full. No idioblasts were observed after fruit sclerification. Besides these mixed-content idioblasts, some cells in the sepals, petals and mesocarp were found to contain phenolic compounds, which probably represent a kind of constitutive defense mechanism, once the flowers and fruits become highly fitness-valued parts of the plant and can be commonly attacked. The contents of the idioblasts are released as the growth rate of the embryo increases, indicating that the plant probably diverts the precursors of secondary metabolites into the primary metabolism, at this critical time of embryo development.

Susceptibility/resistance of Anticarsia gemmatalis larvae to its nucleopolyhedrovirus (AgMNPV): Structural study of the peritrophic membrane

This investigation compares the peritrophic membrane (PM) morphology along the midgut of susceptible (SL) and resistant (RL) Anticarsia gemmatalis larvae to the AgMNPV. The PM increased the thickness from the anterior to the posterior midgut region in both insects strain; however, the intensity of FITC-WGA reaction of the PM in the RL were greater than in SL. The PM in RL was ultrastructurally constituted by several layers of fibrous/vesicular materials in comparison with the few ones in SL. Our results showed that the structure of PM in the RL could be one of the resistance barriers to AgMNPV. © 2007.