Nitric oxide synthase activity in tissues of the blowfly Chrysomya megacephala (Fabricius, 1794).

Although insects lack the adaptive immune response of the mammalians, they manifest effective innate immune responses, which include both cellular and humoral components. Cellular responses are mediated by hemocytes, and humoral responses include the activation of proteolytic cascades that initiate many events, including NO production. In mammals, nitric oxide synthases (NOSs) are also present in the endothelium, the brain, the adrenal glands, and the platelets. Studies on the distribution of NO-producing systems in invertebrates have revealed functional similarities between NOS in this group and vertebrates. We attempted to localize NOS activity in tissues of na?ve (UIL), yeast-injected (YIL), and saline-injected (SIL) larvae of the blowfly Chrysomya megacephala, using the NADPH diaphorase technique. Our findings revealed similar levels of NOS activity in muscle, fat body, Malpighian tubule, gut, and brain, suggesting that NO synthesis may not be involved in the immune response of these larval systems. These results were compared to many studies that recorded the involvement of NO in various physiological functions of insects.     

Protein detection in spermatids and spermatozoa of the butterfly Euptoieta hegesia (Lepidoptera).

This study was undertaken to detect protein components in both sperm types of the butterfly Euptoieta hegesia. These spermatozoa possess complex extracellular structures for which the composition and functional significance are still unclear. In the apyrene sperm head, the proteic cap presented an external ring and an internal dense content; basic proteins were detected only in external portions. In the tail, the paracrystalline core of mitochondrial derivatives and the axoneme are rich in proteins. The extratesticular spermatozoa are covered by a proteic coat, which presented two distinct layers. In eupyrene spermatozoa, acrosome and nucleus were negatively stained, probably because of their high compaction. In the tail, there is no paracrystalline core and the axoneme presented a very specific reaction for basic proteins. The lacinate and reticular appendages are composed of cylindrical sub-units and presented a light reaction to E-PTA and a strong reaction to tannic acid. A complex proteic coat also covers the extratesticular spermatozoa. We found similarities between both extratesticular coats, indicating a possible common origin. Both spermatozoon types are rich in proteins, especially the eupyrene appendages and the extratesticular coats. We believe that both coats are related to the sperm maturation and capacitation processes.     

Age-related changes in the avian primary lymphoid organs (thymus and bursa of Fabricius)

The avian primary lymphoid organs, the thymus and the bursa of Fabricius, undergo age-dependent changes leading in some cases to the complete atrophy of the organ. Nevertheless, the timetable of the involutive process as well as the consequences in the structure and functionality of the organs vary largely in the time frame and structural changes among species. On the other hand, and in contrast with the large body of literature reporting the structural and functional changes in mammalian primary lymphoid organs, the age-dependent changes in avian thymus and bursa of Fabricius are scarce, fragmentary, and heterogeneous. This article reviews the current literature on this topic, and focuses primarily on the involution of the bursa of Fabricius.     

Foreword: the Cosslett festschrift (Ellis Cosslett).

A method for the detection and characterization of clusters of particles observed in section with the electron microscope is presented. Cluster analysis is performed by the division method described by Berthet et al. (1976). Starting from a single cluster, profiles from each electron micrograph are successively classified in sets containing an increasing number of clusters. The decrease in the mean free distance, Λ, between profiles in the clusters, is used for terminating the subdivision procedure. The function relating the mean free distance with the number of clusters is evaluated in each subdivision set. The actual number of clusters is selected on the basis of the slope of that function, at a point where Λ has a value close to the average profile diameter. The method assumes a convex shape for the clusters; the salient feature is that it provides a physical delineation of clusters in the section. Hence, an evaluation of some characteristics of clusters in the three-dimensional sample may be obtained by using standard stereological procedures. Characterization of the volume to which the individual particles of a population are eventually restricted can as a result be performed. Practical problems in the acquisition of the data needed for cluster analysis are discussed and a system using for that purpose a Quantimet 720 image analyser in a basic configuration, connected on line with a PDP 11/10 minicomputer, is presented. Application of the method is illustrated by the analysis of lysosomes in cultured hepatoma (HTC) cells, at the end of mitosis and during the S phase. Cluster analysis shows that in mitotic cells, lysosomes are confined within 3·7% of the total cellular volume, while in cells actively synthesizing DNA they are grouped in clusters representing 5·7% of the cellular volume. Moreover, the average number of particles per cluster falls from a minimum of thirteen at mitosis to only six at the S phase.     

Sensilla and secretory glands in the antennae of a primitive ant: Dinoponera lucida (Formicidae: Ponerinae)

Morphology of the antennae of the female workers of the ponerine ant Dinoponera lucida was examined by light and scanning electron microscopy. In several antennomers, we found secretory gland cells of class I and III. Class III gland cells release their secretion through single pores in the antennal surface, whereas class I secretory cells are seen as tall epidermal cells close to the cuticle. Both gland types have weak reaction for total proteins and neutral polysaccharides. Six distinct sensilla types were observed: trichodea, chaetica, campaniform, basiconica, placodea, and coeloconica. The possible sensory functions of these sensilla and the gland functions are discussed.     

Ultrastructure of proteoglycans in the tectorial membrane

The ultrastructure of proteoglycans (PGs) in the tectorial membrane (TM) of the mature chinchilla cochlea was investigated using the cationic dye Cuprolinic blue. When used at a high critical electrolyte concentration, Cuprolinic blue has been shown specifically to bind to the glycosaminoglycan residues of sulfated PGs. After Cuprolinic blue treatment, PGs were observed in the TM which were represented as rod-shaped, electron-dense structures. A perifibrillar, primarily orthogonal, array of PGs was associated with the type A protofibrils. These PGs were distributed in 50 nm intervals along the length of the type A protofibrils. A less common orientation was parallel to the axis of the type A protofibrils. PGs did not appear to be associated with the type B protofibrils. Based upon previous results by other investigators, the TM contains types II and IX collagen, and it appears likely that the type A protofibrils are composed of collagen type II. PGs visualized in the TM in this study thus may represent the glycosaminoglycan residue of type IX collagen which is associated with the type II collagen fibrils. Alternatively, the TM PGs may be small dermatan or chondroitin sulfate PGs.     

An ultrastructural study of spermiogenesis in two species of Sitophilus (Coleoptera: Curculionidae).

The spermiogenesis of Sitophilus zeamais and Sitophilus oryzae, the maize and the rice weevil, respectively, was studied by light microscopy and scanning and transmission electron microscopy. Sitophilus spp. is the most widespread and destructive primary pest of stored cereals in the world. The spermiogenesis occurs within cysts. There are approximately 256 germ line cells per cyst. Inside each cysts, all the spermatids are in the same stage of maturation. The ultrastructure of the spermatozoa of S. zeamais and S. oryzae is similar to that described for other beetles. The head is formed by a three-layered acrosome with the perforatorium, the acrosomal vesicle, the extra-acrosomal layer and the nucleus. The flagellum has the typical axoneme formed by a 9+9+2 microtubules arrangement, two mitochondrial derivatives and two accessory bodies. The typical pattern for Curculionidae spermatozoa described here may provide useful information for future phylogenetic analysis of the superfamily Curculionoidea.     

Ultrastructure of Paneth cells in the intestine of various mammals

Paneth cells in the following species were observed under an electron microscope: human, rhesus monkey, hare, guinea pig, rat, nude rat, mouse, golden hamster, and insect feeder bat. Secretory granules containing homogeneous electron-dense materials were observed in the Paneth cells of humans, monkeys, hares, guinea pigs, and bats; mouse Paneth-cell granules were bipartite (central core and peripheral halo), and the Paneth cells in rats and golden hamsters had secretory granules showing various electron densities. In humans, monkeys, and bats, immature granules near the Golgi apparatus sometimes showed bipartite substructure. The number and size of secretory granules were also diverse among various animal species. Some lysosome-like bodies were commonly observed in peri- or supranuclear regions, though the size and shape of the bodies differed from cell to cell. In apical cytoplasm, small clear vesicles (100–200 nm diameter) were more-or-less observed in all species examined, and it was especially note that rat Paneth cells contained many clear vesicles. Small dense-cored vesicles (150–200 nm diameter) were rare. It is unlikely that the various ultrastructural features of Paneth cells correlate with the phylogenetical classification.     

Ultrastructure research in biology before the introduction of the electron microscope

Techniques used by the authors for preparing wood samples for the scanning electron microscope are detailed. Topics covered include: procedures for cutting, cleaning, dehydrating, mounting and storage of the specimens.     

Angiogenesis in endocrine glands: special reference to the expression of vascular endothelial growth factor

Recent studies have shown that several angiogenic growth factors are produced and secreted by normal endocrine cells and are increased in pathological states of endocrine glands, including inflammation, hyperplasia, and neoplasia. Expression of corresponding receptors on epithelial cells and/or endothelial cells enables these angiogenic factors to influence growth and function of the endocrine tissues by auto- or paracrine mechanisms. Some of the angiogenic factors are also considered to be involved in angiogenesis, which is a critical process in tumor formation and progression. Vascular endothelial growth factor (VEGF) is regarded as one of most important angiogenic factors with specific effects on endothelial cell growth and vascular permeability, and is isolated from a variety of normal and neoplastic endocrine cells. In this article, recent studies on angiogenic factors, especially on expression of VEGF, are reviewed in the field of endocrine systems.     

Ultrastructure of the mammalian pinealocyte under natural and experimental conditions: quantitative aspects.

This review briefly summarizes data accumulated on the quantitative aspects of the ultrastructure of the mammalian pinealocyte. Quantitative changes have been demonstrated under natural and experimental conditions in pinealocyte cell organelles in various species. Special attention is paid to two cytoplasmic components most frequently studied by means of quantitative electron microscopy, namely, dense-core vesicles and "synaptic" ribbons.     

Ultrastructure of cyst shell and underlying membranes of three strains of the brine shrimp Artemia (Branchiopoda: Anostraca) from South India

The cyst of Artemia has shell and membranous coverings over the embryo. The membranous coverings have special adaptive features to allow the physical changes accompanying repeated hydration and dehydration cycles that might occur and adversely influence postembryonic development. Whole and slices of cryptobiotic cysts were processed for electron microscopy to study the internal details and to compare the morphological architecture of three Artemia strains of South India. Surface topography of scanning electron microscopic (SEM) studies revealed distinct button shaped structures on the cyst of Puthalam strain. Transmission electron microscopic (TEM) studies of the cysts displayed the conventional pattern of anostracan crustaceans with outer cortex and alveolar layer, cuticular membranes, and the cytoplasmic inclusions namely nucleus, yolk droplets, lipoid bodies, and mitochondria. The prominent wavy outer cortex layer of Puthalam cysts corroborates the results of SEM studies.     

Microsporogenesis in tetraploid accessions of Brachiaria nigropedata (Ficalho & Hiern) Stapf (Gramineae).

The genus Brachiaria (Trin.) Griseb. has achieved considerable importance to cattle production systems, as a result of the good production and adaptation of a few cultivars to poor and acid soils of the Brazilian savannas. Many of its species and accessions are polyploid and apomictic, which limits direct hybridization. To assist the breeding program, cytogenetic characterization has been undertaken on the accessions of Brachiaria collection at the Embrapa Beef Cattle Research Center. In this study, chromosome number and meiotic behavior are reported for the Brachiaria nigropedata (Ficalho & Hiern) Stapf collection. The 20 available accessions are tetraploid (2n = 4x = 36). Chromosomes paired preferentially as bivalents, but quadrivalents were found in high frequencies in some cells. Meiotic behavior was, in general, irregular, and varied among accessions. Most accessions presented more than 20% of abnormal tetrads. The most common meiotic abnormalities were those related to irregular chromosome segregation due to polyploidy, leading to micronuclei formation in the tetrad stage. A low frequency of other meiotic abnormalities such as the absence of cytokinesis, chromosome stickiness, cell fusion, anaphase bridges, and chromosome transfer among microsporocytes were also recorded in some accessions. Limitations of these accessions for use in hybridization programs are discussed.     

Cytochemical localization of acid phosphatase in Stigeoclonium tenue (Chaetophorales, Chlorophyceae).

Nonspecific acid phosphatases are a group of enzymes whose activity increases the availability of exogenous and endogenous orthophosphate either through extra- or intracellular hydrolysis of phosphate compounds. Our study demonstrates the activity of acid phosphatases in the filamentous freshwater alga Stigeoclonium tenue. These enzymes were detected following a cerium-based method in which cerium was used as an orthophosphate-capture reagent. In thalli from S. tenue from the natural environment, acid phosphatases were found in the longitudinal cell wall, plasmalemma, and vacuole. In thalli from Bold's Basal Medium culture, these enzymes were found mainly in the plasmalemma; they were scarce in the cell wall. In the thalli grown in phosphate-enriched culture medium, enzymes were found only in the plasmalemma. The low availability of orthophosphate in the medium seems to induce the transport of these enzymes to the cell wall. Its abundance, on the contrary, seems to attenuate this response without affecting the localization of acid phosphatases in the plasmalemma.