Some aspects of organization and histochemistry of the embryo sac ofScilla sibirica sato

Summary The present investigation deals with some of the organizational and histochemical aspects of the embryo sac ofScilla sibirica. Both the synergids and egg cell are invested by PAS-positive complete walls. The filiform apparatus comprises an elaborate system of fibrillar projections, showing extensive ramifications. The micropylar region of the embryo sac wall from where the filiform apparatus originates is composed of three distinct layers. On a histochemical basis it may be surmised that, unlike the egg cell, the synergids are metabolically very active. Two kinds of wall ingrowths (i) massive and highly branched very much akin to the filiform apparatus, and (ii) small tuberculate wall projections, are unique to the antipodal cells of S.sibirica. Small tuberculate projections have also been observed along the wall of the central cell adjacent to the nutrient-rich nucellar cells. The antipodals and the central cell show the presence of starch grains and abundant total proteins. All the cell types in the embryo sac ofS. sibirica are structurally so organized as to meet the requirements of its nutrition during pre- and postfertilization development. The presence of abundant PAS-positive granular substance in the cells of nucellar epidermis probably establishes a gradient which assists in the pollen tube growth.     

Anti-Predator behaviour of naïve compared experienced juvenile roach

Juvenile roach Rutilus rutilus without any previous contact with predatory fishes reacted to the presence of alarm substances more intensively than fish with previous experience. Among several types of behavioural response observed, some, such as hiding, were not registered in experienced fish. The most pronounced difference between the two juvenile fish categories was manifested in feeding. Naïve fish used more time for feeding than experienced ones. The experiment showed that alarm substance originating from small and young and medium roach induced a stronger reaction than the substance extracted from large and oldéê fish.     

The pore of the leaf cavity of Azolla species: teat cell differentiation and cell wall projections

The differentiation of the specialized secretory teat cells of the leaf cavity pore of Azolla species was investigated at the ultrastructural level with emphasis on their peculiar cell wall projections. The results indicated that the projections are formed as soon as the teat cells complete their differentiation and that their production is principally associated with changes in endoplasmic reticulum profiles. The number of projections increases with the teat cell age and is stimulated under salt and P deficiency stresses. Salt stress also promotes their emergence on Azolla species that under normal conditions do not produce projections. Cytochemical tests on different Azolla species showed that the projection composition is almost identical: proteins, acidic polysaccharides, and pectin are always detected. This study revealed that Azolla teat cell projections differ fundamentally from other types of hitherto described cell wall projections that are considered as remnant structures from cell separation. In contrast, in Azolla teat cells projections are actively produced and compounds are excreted by an exocytotic mechanism. The possible role of the projections in the symbiosis of Azolla spp. with Anabaena azollae is discussed.     

Effects of steroid hormones and other substances on alarm substance cells and mucous cells in the epidermis of the European minnow, Phoxinus phoxinus (L.), and other Ostariophysi (Pisces)

The alarm substance cells and mucous cells of various species of Ostariophysi do not react uniformly to treatment with androgen and other steroid hormones. This indicates that the mechanism controlling formation of alarm substance is not uniform in the Ostariophysi and three exist at least two such mechanisms, one of which is operated by androgens and perhaps other steroid hormones of the gonads. Steroid hormones from the adrenal cortex proved ineffective. In the European minnow, anti-androgen (androcur®, cyproteroneacetate) had an efrect opposite to that of androgen, while androgen treatment upon this species led to an increase in the size of mucous cells and a reduction in the alarm substance cells. The epidermis of androgen-treated European minnows contained neither alarm substance cells nor alarm substance, and skin extracts of such fish proved ineffective in behaviour experiments upon fish schools. The effect of further hormone treatments are discussed and the reactions of the European minnow are compared to those of other species.     

Epidermal 'alarm substance' cells of fishes maintained by non-alarm functions: possible defence against pathogens, parasites and UVB radiation

Many fishes possess specialized epidermal cells that are ruptured by the teeth of predators, thus reliably indicating the presence of an actively foraging predator. Understanding the evolution of these cells has intrigued evolutionary ecologists because the release of these alarm chemicals is not voluntary. Here, we show that predation pressure does not influence alarm cell production in fishes. Alarm cell production is stimulated by exposure to skin-penetrating pathogens (water moulds: Saprolegnia ferax and Saprolegnia parasitica), skin-penetrating parasites (larval trematodes: Teleorchis sp. and Uvulifer sp.) and correlated with exposure to UV radiation. Suppression of the immune system with environmentally relevant levels of Cd inhibits alarm cell production of fishes challenged with Saprolegnia. These data are the first evidence that alarm substance cells have an immune function against ubiquitous environmental challenges to epidermal integrity. Our results indicate that these specialized cells arose and are maintained by natural selection owing to selfish benefits unrelated to predator-prey interactions. Cell contents released when these cells are damaged in predator attacks have secondarily acquired an ecological role as alarm cues because selection favours receivers to detect and respond adaptively to public information about predation.     

Socializing makes thick-skinned individuals: on the density of epidermal alarm substance cells in cyprinid fish, the crucian carp (Carassius carassius)

In cyprinid fish, density of epidermal club cells (i.e. alarm substance cells) has been found to vary between lakes with different predator fauna. Because predators can be labelled with chemical cues from prey, we questioned if club cell density could be controlled indirectly by predators releasing prey cues. In particular, we suspected a possible feedback mechanism between chemical alarm signals and their cellular source. We raised crucian carp singly and in groups of four. For both rearing types, fish were exposed to skin extracts of either conspecifics or brown trout (without club cells), and provided either low or high food rations. Independent of rearing type, condition factor and club cell density increased with food ration size, but no change was found in club cell density following exposure to conspecific alarm signals. However, the density of club cells was found significantly higher for fish raised in groups than for fish raised alone. We conclude that an increased condition factor results in more club cells, but crucian carp may also possess an awareness of conspecific presence, given by higher club cell densities when raised in groups. This increase in club cell density may be induced by unknown chemical factors released by conspecifics.     

Fluoreszenzmikroskopischer Nachweis des Schreckstoffes in den Schreckstoffzellen der Elritze,Phoxinus phoxinus (L.) (Cyprinidae,Ostariophysi, Pisces)

Zusammenfassung Die Schreckstoffzellen der Elritze,Phoxinus phoxinus (L.), zeigen nach Gefriertrocknung der Haut eine Eigenfluoreszenz. Diese wird bei 360–380 nm maximal angeregt; das Emissionsmaximum liegt bei ca. 515 nm. Die Fluoreszenz einer Schreckstoffzelle wird mit der Fluoreszenz des isolierten Schreckstoffes mikrospektralphotofluorimetrisch verglichen: die Emissions-maxima liegen nur 10 nm voneinander entfernt. Die Kurven relativer Fluoreszenzintensität verlaufen weitgehend gleichartig. Dies zeigt, daß der Schreckstoff tatsächlich den Schreckstoffzellen entstammt.

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Fluorescence microscopical demonstration of the alarm substance in the alarm substance cells of the European minnow,Phoxinus phoxinus (L.) (cyprinidae, ostariophysi, pisces)

Summary The alarm substance cells of the European minnow,Phoxinus phoxinus (L.), are autofluorescent after freeze-drying of the skin (Fig. 1). Their autofluorescence is maximally excited at 360–380 nm; the maximum of emission lies at about 515 nm. The fluorescence of an alarm substance cell is compared with the autofluorescence of the isolated alarm substance by means of a microspectro-photofluorometer. The maxima of emission are only about 10 nm apart. The curves of relative fluorescence intensity are almost identical (Fig. 3). These results show that the alarm substance actually comes from the alarm substance cells.

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Mit Unterstützung durch die Deutsche Forschungsgemeinschaft.     

Die Schreckstoffzellen von Phoxinus phoxinus und Morulius chrysophakedion (Cyprinidae,Ostariophysi, Pisces)

Zusammenfassung Die Untersuchung der Histochemie und der Ultrastruktur der Schreckstoffzellen von Phoxinus phoxinus und Morulius chrysophakedion (Cyprininae, Cyprinidae, Cypriniformes, Ostariophysi) führte zu übereinstimmenden Ergebnissen. Unmittelbar perinucleär sind Ribosomen, Mitochondrien und ein Golgikomplex nachweisbar, von dem ein Netzwerk tubulärer Systeme ausgeht. Histochemisch sind in unmittelbarer Kernnähe gelegentlich Glykogengranula, stets ein deutlicher RNS-Gehalt und die Aktivitäten der Succinatdehydrogenase, der Lactatdehydrogenase, in einigen Zellen der Glucose-6-phosphat-dehydrogenase darstellbar. Im gesamten Cytoplasma der Schreckstoffzelle ist die Aktivität der Leucinaminopeptidase vorhanden, deren Maximum ebenfalls in Kernnähe vorliegt. Nur im kernfernen Cytoplasma wurden Proteine und diastaseresistente Polysaccharide nachgewiesen. Aus den Ergebnissen geht hervor, daß die Schreckstoffzellen sekretorisch tätig sind; vermutlich handelt es sich bei dem spezifischen Sekret um ein kleinmolekulares Protein.

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The alarm substance cells of Phoxinus phoxinus and Morulius chrysophakedion (Cyprinidae, Ostariophysi, Pisces)Histochemical and electron microscopical study

Summary The histochemical studies of the alarm substance cells from Phoxinus phoxinus and Morulius chrysophakedion (Cyprininae, Cyprinidae, Cypriniformes, Ostariophysi) are in total agreement with the results of the ultrastructural investigations. Perinuclear ribosomes, mitochondria, and a golgi complex are demonstrated. A tubular network radiates from the golgi complex. Histochemically, glycogen granula can occasionally be demonstrated in proximity to the nucleus. Consistently a strong RNA reaction as well as succinic-dehydrogenase activity, lactic-dehydrogenase activity, and in some cells glucose-6-phosphatedehydrogenase activity can be shown. In the cytoplasm of the alarm substance cell leucyl-aminopeptidase activity exists; its maximum lies in vicinity of the nucleus. Proteins and diastase-resistant polysaccharides are found only in cytoplasm not directly adjacent to the nucleus. The results indicate that the alarm substance cells show a secretory activity. It is assumed that the specific secrete is a protein of low molecular weight.

Mit Unterstützung durch die Deutsche Forschungsgemeinschaft.     

Localization of octopaminergic neurones in insects

This paper reviews data on the localization of octopaminergic neurones revealed by immunocytochemistry in insects, primarily the locusts Schistocerca gregaria and Locusta migratoria, cricket Gryllus bimaculatus, and cockroach Periplaneta americana. Supporting evidence for their octopaminergic nature is mentioned where available. In orthopteran ventral ganglia, the major classes of octopamine-like immunoreactive (-LI) neurones include: (1) efferent dorsal and ventral unpaired median (DUM, VUM) neurones; (2) several intersegmentally projecting DUM interneurones in the suboesophageal ganglion; other DUM interneurones are probably GABAergic; (3) a pair of anterior median cells in the prothoracic ganglion; (4) a single pair of ventral cells in most thoracic and some other ganglia; these appear to be plurisegmentally projecting interneurones. Eight categories of octopamine-LI neurones occur in the orthopteran brain. The basic projections of three types are described here: one class project to the optic lobes to form wide field projections. Another type descends to cross into the tritocerebral commissure and may invade the contralateral brain hemisphere. A further class is the median neurosecretory cells with axons in the nervi corpori cardiaci I. Available data for the honey bee Apis mellifera and moth Manduca sexta indicate that the octopamine-LI cell types found in orthopterans also occur in holometabolous insects. Immunocytochemical evidence suggests that some octopaminergic DUM cells contain an FMRFamide-related peptide and the amino acid taurine as putative cotransmitters.     

Microscopic identification of novel cell types in the integument of larval lake sturgeon,Acipenser fulvescens

Osmoregulation, respiration, nutrient/mineral transport, and defense mechanisms are all evident in the integument of fish. The role of the integument in these physiological processes is particularly important during early life history in larval fishes, as functional systems such as the gills and gastrointestinal tract are not fully developed. Using a variety of microscopy techniques, we describe the morphology of keratinocytes, mitochondria rich cells, ciliated cells and mucous cells of the skin, yolk sac, and gills. The cytology we observed was similar to previous studies describing the integument of larval fish, however, we have also identified two novel cell types on the integument of larval Lake Sturgeon, Acipenser fulvescens, between 9 and 34 days post fertilization. Our detailed analysis included a multifaceted microscopy approach using scanning electron, transmission electron, and light microscopy to elucidate the histology of the tissue and cellular morphology in addition to quantification and distribution of these novel cell types. The first cell type had a characteristic ampullary shape with a central cavity and a pore opening at the surface. The second, located on the free surface of the epidermis, had an uneven plasma membrane surface. Based on the abundance of secretory vesicles, organelles necessary for protein synthesis, and the lack of neural connection in both cell types, we propose these cells to be involved in the release of semiochemicals that may act as a pheromone, alarm substance, or chemical defense mechanism. J. Morphol. 277:86–95, 2016. © 2015 Wiley Periodicals, Inc.     

A small particulate component of the cytoplasm

A particulate component of small dimensions (100 to 150 A) and high density is described in the ground substance of the cytoplasm of mammalian and avian cells. In many cell types that seem to have in common a high degree of differentiation, the new component is preferentially associated with the membrane of the endoplasmic reticulum; whereas in other cell types, characterized by rapid proliferation, it occurs more or less freely distributed in the ground substance of the cytoplasm. In the Discussion an attempt is made to integrate the observations presented in this paper with the already available cytological, histochemical, and cytochemical information.     

An immunohistochemical study of the GnRH neuron morphology and topography in the adult female rabbit hypothalamus

The morphology and distribution of immunoreactive (GnRH) neural elements in the hypothalamus of the adult nulliparous female rabbit were examined. Approximately 1,000 GnRH cells (range 890-1136) were counted in the right half of the hypothalamus. Two distinct GnRH cell types were observed: GnRH cells with rough or spiny contours accounted for 64% of the total immunoreactive cells, and smooth-contoured cells represented 34% of the total. The majority of immunoreactive neural elements were found in the anterior hypothalamus. GnRH cells and processes were located primarily in the ventral and medial anterior hypothalamus forming an inverted V pattern. Processes were followed from the medial preoptic area and suprachiasmatic nucleus to the infundibular stem. Extrahypothalamic projections of GnRH cells were observed. Immunoreactive fibers were also found to contact the ependymal lining of the third ventricle. It is concluded that two morphologically distinct GnRH cell types exist and have a broad distribution in the rabbit hypothalamus. The functional significance of these cell types requires further study.     

Induction of fascin spikes in breast cancer cells by activation of the insulin-like growth factor-I receptor

Insulin-like growth factor-I receptor (IGF-IR) signaling contributes to the formation of mammary carcinomas and has chiefly been studied with regard to the proliferative and anti-apoptotic effects of IGF-IR signaling. However, IGF-IR activation also affects the actin cytoskeleton and alterations in cell migratory behavior are of known importance for the malignant conversion and metastasis of epithelial cells. The actin-binding protein fascin is found in cell projections and spikes that are involved in the locomotion of mesenchymal cells. Fascin expression is typically low in normal epithelial cells, but is markedly upregulated in several types of carcinomas. Here, we also demonstrate increased fascin expression in breast carcinoma cell lines and adopt MCF-7 human mammary carcinoma cells that over-express wild-type or kinase-inactivated forms of the IGF-IR as a model system to test the hypothesis that IGF-IR activation induces fascin projections. We show that the time-dependent dissociation of cell colonies that occurs upon receptor activation by IGF-I involves the formation of dynamic, fascin-containing lateral cell projections that co-localize with ruffling membranes in association with protrusive activity and cell migratory phenotype. The molecular mechanism of these effects is completely dependent on IGF-IR tyrosine kinase activity and is mediated by a phosphatidylinositol (PI) 3-kinase-dependent process. In demonstrating transduction of fascin spike assembly by activation of a peptide growth factor receptor, these novel data reveal a wide role for fascin spikes in cell motility and provide new insight into the complex effects of IGF-IR signaling on actin cytoskeletal organization.     

Ultrastructure of the Protonephridia in the Dorvilleid Polychaete Apodotrocha progenerans (Annelida)

The achaetous dorvilleid polychaete Apodotrocha progenerans Westheide & Riser, 1983, possesses several pairs of segmentally arranged protonephridia. They consist of a blindly ending terminal cell and three tubule (emission) cells. The terminal cell is a flame bulb with unusual filtration area consisting of interdigitated pedicel-like projections. Each cell has its own tuft of flagella; and the emission channel is intracellular. The tube-shaped 'seamless' cells are slotted into each other like water-pipes.     

A SMALL PARTICULATE COMPONENT OF THE CYTOPLASM

A particulate component of small dimensions (100 to 150 A) and high density is described in the ground substance of the cytoplasm of mammalian and avian cells. In many cell types that seem to have in common a high degree of differentiation, the new component is preferentially associated with the membrane of the endoplasmic reticulum; whereas in other cell types, characterized by rapid proliferation, it occurs more or less freely distributed in the ground substance of the cytoplasm. In the Discussion an attempt is made to integrate the observations presented in this paper with the already available cytological, histochemical, and cytochemical information.     

ACTIVE TRANSPORT BY THE CECROPIA MIDGUT : II. Fine Structure of the Midgut Epithelium

A morphological basis for transcellular potassium transport in the midgut of the mature fifth instar larvae of Hyalophora cecropia has been established through studies with the light and electron microscopes. The single-layered epithelium consists of two distinct cell types, the columnar cell and the goblet cell. No regenerative cells are present. Both columnar and goblet cells rest on a well developed basement lamina. The basal portion of the columnar cell is incompletely divided into compartments by deep infoldings of the plasma membrane, whereas the apical end consists of numerous cytoplasmic projections, each of which is covered with a fine fuzzy or filamentous material. The cytoplasm of this cell contains large amounts of rough endoplasmic reticulum, microtubules, and mitochondria. In the basal region of the cell the mitochondria are oriented parallel to the long axes of the folded plasma-lemma, but in the intermediate and apical portions they are randomly scattered within the cytoplasmic matrix. Compared to the columnar cell, the goblet cell has relatively little endoplasmic reticulum. On the other hand, the plications of the plasma membrane of the goblet cell greatly exceed those of the columnar cell. One can distinguish at least four characteristic types of folding: (a) basal podocytelike extensions, (b) lateral evaginations, (c) apical microvilli, and (d) specialized cytoplasmic projections which line the goblet chamber. Apically, the projections are large and branch to form villus-like units, whereas in the major portion of the cavity each projection appears to contain an elongate mitochondrion. Junctional complexes of similar kind and position appear between neighboring columnar cells and between adjacent columnar and goblet cells as follows: a zonula adherens is found near the luminal surface and is followed by one or more zonulae occludentes. The morphological data obtained in this study and the physiological information on ion transport through the midgut epithelium have encouraged us to suggest that the goblet cell may be the principal unit of active potassium transport from the hemolymph to the lumen of the midgut. We have postulated that ion accumulation by mitochondria in close association with plicated plasma membranes may play a role in the active movement of potassium across the midgut.     

Goblet cell membrane differentiations in the midgut of a lepidopteran larva.

So-called goblet cells are present in the midgut of lepidopteran larvae. They are thought to be involved in the active transport of potassium out of the haemolymph and into the gut lumen. A number of plasma membrane differentiations within the goblet cell cavity has been investigated using conventional staining, lanthanum tracer and freeze-etch techniques. Of particular interest are junction-like inter- and intra-membrane differentiations found on the villus-like cytoplasmic projections present at the apical tip of the goblet cell cavities. These cytoplasmic projections appear to act as a valve; in some cases they seem to close off the top of the goblet cell cavity, so isolating it from the gut lumen, while in other cases they are spread apart leaving a wide channel from the cavity into the lumen. The junction-like structures on these cytoplasmic projections are different in structure from the septate-type junctions which seal the midgut cells together at their apical borders, and the 2 types are present on the same plasma membrane, often within one micron of each other. The need for a different type of junction may possibly be related to the fact that it occurs between 2 areas of the same plasma membrane. The morphology of this unusual junction-like structure is discussed and 2 diagrams are presented to illustrate our interpretation of its structure.     

Photoreceptor cells and neural elements with long axonal processes in the pineal organ of the lamprey,Lampetra japonica,identified by use of the horseradish peroxidase method

Summary Horseradish peroxidase (HRP) was applied to the transected end of the pineal tract of the lamprey, Lampetra japonica. Distinct reaction products of HRP were observed in 2 types of cell other than ganglion cells. The first type of cell protrudes a knob-like process into the pineal lumen. This type of cell was clearly identified by electron microscopy as a photoreceptor cell; its outer segment was connected to the ellipsoid through a sensory cilium. The other type of cell was located among photoreceptor and supporting cells. The processes of these cells were thin and slender, and they obviously did not represent photoreceptor, supporting, or conventional ganglion cells. The present results indicate that, in the lamprey, some of the photoreceptor cells of the pineal organ project their axon-like processes toward the posterior commissure, but that there is also another type of cell displaying long axonal projections. HRP-containing cells were distributed randomly over the pineal organ and were occasionally also observed in the parapineal organ.     

Epithelial bridging of the primary palate: II. In vitro model mimics in vivo behavior

Previously, Forbes et al. [J Craniofac Genet Dev. Biol, 9:271-284, 1989] and Millicovsky et al. [Am J Anat 164:29-44, 1982], demonstrated that some of the epithelial cells of the primary palate formed extensive projections, bridging the medial and lateral nasal prominences. These connections are thought to aide in the fusion process by facilitating union of the prominences, a process known as secondary fusion [Millicovsky et al., 1982]. In order to study the epithelial cell and its behavior more closely an in vitro model was established [Gibson et al.: J Craniofac Genet Dev Biol, 1989], where epithelial cells in culture were shown to produce many of the morphologic characteristics observed in vivo. In the present study, an in vitro model is discussed which reproduces the epithelial projections observed in vivo. Epithelial cells, previously characterized, were obtained from the primary palate of 13-day-old rat embryos and sub-cultured as explants. Comparisons were made with the epithelial bridging observed in vivo of two species of animals. The results indicated sub-cultured epithelium as isolated cells, at either low or high density, rarely formed bridges. Primary cultures of epithelial explants also infrequently formed projections. However, sub-cultures of epithelial explants, plated as small clusters of cells with intervening spaces between cell groups, demonstrated extensive epithelial bridging. Epithelial projections did not form from cells that were directly attached to the plastic culture dish; only superficial, elevated cells formed projections. Significantly, the connections that occurred between explants did not attach to the plastic substratum. Instead, they appeared as line connections suspended by the medium. With time, the number of projections increased and epithelial cells could be seen along the projections forming an epithelial bridge. This study established a model of epithelial bridging in vitro for analysis of a process which has been shown to be an integral part of primary palate fusion.     

The unusual microtubule polarity in teleost retinal pigment epithelial cells

In cells of the teleost retinal pigment epithelium (RPE), melanin granules disperse into the RPE cell's long apical projections in response to light onset, and aggregate toward the base of the RPE cell in response to dark onset. The RPE cells possess numerous microtubules, which in the apical projections are aligned longitudinally. Nocodazole studies have shown that pigment granule aggregation is microtubule-dependent (Troutt, L. L., and B. Burnside, 1988b Exp. Eye Res. In press.). To investigate further the mechanism of microtubule participation in RPE pigment granule aggregation, we have used the tubulin hook method to assess the polarity of microtubules in the apical projections of teleost RPE cells. We report here that virtually all microtubules in the RPE apical projections are uniformly oriented with plus ends toward the cell body and minus ends toward the projection tips. This orientation is opposite that found for microtubules of dermal melanophores, neurons, and most other cell types.