Development of labellar taste hairs in the blowfly,Calliphora vicina (Insecta,Diptera)

Summary The early development of taste sensilla has been studied with special emphasis on cilia, dendrite, and pore formation.In the 39-h stage (the first stage investigated) differentiation of sensilla is already under way. The mechanisms of differentiation of dendrites (39–48 h) deviate from the mechanisms described for differentiation of true cilia. In taste hairs the centrioles meet in the tip of the narrowed apical region of the sensory neuron. Together they sink deeper into this region and line up coaxially, thus forming the basal body complex. Thereafter, lateral contacts between this complex and the plasma membrane of the neuron are established. Formation of open connections between the trichogen lumen of the hair and the environment, or the dendrite lumen, was not observed.Electrophysiological data indicate that the sensilla become functional from 3 days before emergence onwards.List of Abbreviations B Basal body complex - bc Basal compartment - bs Basal sheath - bl Basement lamina - D Dendrite(s) - EPC Non-sensillar epithelial cells - ES Ecdysial sheath - GERL Granular endoplasmatic reticulum-lysosomes - HS Hemolymph space - P Protrusions - PRN Prospective receptor neuron - RER Rough endoplasmatic reticulum - RN Receptor neuron - n Neck - THC Thecogen cell - TOC Tormogen cell - TRC Trichogen cell - TRS Trichogen sprout     

A specialized trophospongium in large neurons of Leptodora (Crustacea)

Summary A specialized type of trophospongium has been described in large nerve cells of the cerebral ganglion of the planktonic crustacean Leptodora kindtii. It consists of three parts (Fig. 6). The first is, as a rule, long; it is composed of an infolding of the plasma membrane of the neuron, an intercellular space and a slender process of a glial cell. The second segment from the end of the glial process to the beginning of the X-body is always short; it is characterized by the presence of a desmosome-like junction. The third part consists of a labyrinth of cisternal spaces lined by membranes which are continuous with the infoldings of the surface membrane of the nerve cell.This investigation was supported by U.S.P.H.S. Grant NB 02145-04. The skillful assistance of Mrs. Cynthia Jones, Mr. Stanley Brown and Mr. Douglas Gasner in different phases of this work is gratefully acknowledged.     

Ultrastructure of the Malpighian Tubule Cells in the Mosquito Larvae, Anopheles sinesis

Ultrastructure of epithelial cells constituting the Malpighian tubule of Anopheles sinesis last instar larvae was observed with electron microscope. Malpighian tubule consists of four long and narrow tubule structures with principal cells in typical absorptive cells and regenerative cells forming the simple epithelium. Apical plasma membrane of the principal cell is differentiated into microvilli with one mitochondrion in each microvilli. Basal plasma membrane had extreme infolding to form a canaliculi and a well developed mitochondria was attached in the infoldings. And, rER, ribosomes, and vacuoles were well developed inside the cells. However, there were two main cell types depending on the differentiation of cell organelles. Type 1 cell was cubic, forming the distal portion of Malpighian tubule. The length of microvilli was approximately 4 μm and the basal infoldings were introjected to the depth of 2 μm inside the cell. On the other hand, Type II cell that formed the main proxinal portion was a low squamous type cells with shorter 2 μm of microvilli and the basal infoldings were introjected to the depths of 4 μm inside the cell. As for vacuoles scattered inside the cells, they were regularly observed in both Type I and II and the Type II cells had better developed cellular organelles. Although regenerative cells were extremely small, their cellular organelles were developed and their overall electron density was high that they appeared darker than the principal cells.     

Fine structure of the functional mesonephros in the eight-day chick embryo

An electron microscopic study of the functional mesonephros in the 8-day chick embryo revealed the following features of the nephron: Proximal tubule cells. Nuclei are spherical and basally oriented. Mitochondri are round or elongate with clear-cut cristae. Intramitochondrial granules occur sporadically. The Golgi complex, lying adjacent to the nucleus in apical cytoplasm, consists of flattened lamellae and associated secretion droplets. The cytoplasm is filled with ribosomes which occasionally are spiral in arrangement. Characteristic microvilli project from the apical end of cells. Basal regions of the cells are bounded by a homogeneous basement membrane. Adjacent epithelial cells are separated at their base by wide intercellular spaces. Interdigitating processes between cells are common in this area. At their apices, cells are joined by junctional complexes. Distal tubule cells. Nuclei are round and centrally located. Microvilli are sparse and usually absent. When present, they are short and blunt. Cells are closely allied at their base and joined tightly at their apices. Interdigitating processes are not as prevalent as in proximal tubules. Infoldings of the plasma membrane are prominent and compartmentalize mitochondria. Glomerulus. Endothelial cells are elongate, bordering the capillary lumen, and their membranes contain definite slit-pores. Epithelial pedicels extend from the cell body, intergiditate with each other and rest on the capillary basement membrane. The latter consists of three layers resembling those in adults. The similarity in the fine structural characteristics between chick mesonephros and adult metanepros corroborates the holonephric theory of vertebrate kidney evolution.     

Ultrastructure of the metanephridial system in Aeolosoma bengalense (Annelida)

Summary The excretory system of Aeolosoma bengalense has been examined by light and electron microscopy. The system consists of seven serially arranged paris of metanephridia and six pairs of podocytes (referring to the first zoid of an animal chain). The podocytes surround blood spaces of the alimentary canal forming dorsoventrally running loops that emerge on both sides of it. The two elements of the system have a correlative position, each podocyte extending in close proximity to the funnel of a metanephridium. Only in the region of the first metanephridia are podocytes lacking. The nephrostome of the metanephridia consists of two cells, an inner one, the terminal duct cell, and an outer one enwrapping it, called the mantle cell. Nephrostomal cilia that extend into the coelomic space arise exclusively from the rim of the mantle cell whereas those of the terminal duct cell arranged on its luminal surface protrude into the canal forming a flame. The nephridial canal is ciliated throughout and is either intra- or extracellular. Its initial loops aggregate to form a compact organ, the nephridial body. The middle part of the duct constitutes a loop that ascends at each side of the alimentary canal where it is in intimate contact with its blood spaces. Ultrastructural features of the duct cells suggest a reabsorptive function in two regions, the nephridial body and the uppermost part of the loop. The terminal part of the duct passes through the nephridial body and opens ventrolaterally. Generally, the transverse vascular loops at the gut consist of one podocyte each. In the oesophageal region, where only one pair of podocytes is present, the loops connect the dorsal with the ventral longitudinal vessel. Three pairs of podocytes are present in the dilated region of the intestine emerging from its lateral wall and joining the median ventral vessel or blood spaces near by. In the hind gut, where two pairs of podocytes occur, the loops arise from the dorsolateral part and enter directly the ventral vessel. Cytological features of podocytes resemble those of other animals. The results are discussed on the basis of current theories on the function and the phylogenetic significance of excretory systems in the Annelida.Abbreviations bl basal lamina - bs blood space - bv blood vessel - cf ciliary flame - ci cilia - co connection of the vascular loop with the intestinal blood space - cu cuticle - db dense body - dc duct cell - di dictyosome - za zonula adhearens - dv dorsal vessel - ecb epicuticular body - ev endocytotic vesicle - ic intestinal cell - ici inner cilia - iv intestinal vessel - lm longitudinal muscle - mc mantle cell - mg midgut - mi mitochondrion - mv microvilli - nu nucleus - oci outer cilia - oe oesophagus - pc podocyte - pe pedicel - pel primary elongation of the podocyte - sm slit membrane - tc terminal duct cell - ve vesicle with heterogeneous contents - vv ventral vessel     

Organization of statocysts in the Otoplanidae (Plathelminthes): an ultrastructural analysis with implications for the phylogeny of the Proseriata

Summary The statocyst of otoplanids is enveloped by a bipartite capsule which consists of two different extracellular matrices. This capsule encircles three different types of aciliary cells: several peripherally located flattened parietal cells, one central statolith forming cell (lithocyte) and two clusters of accessory cells. Intracapsular lumina exist which are different from extracapsular intercellular spaces. The accessory cells most probably represent those structures that are mainly involved in nervous conduction. These cells extend cytoplasmatic processes towards different peripheral regions of the statocyst where processes of outer nerve cells penetrate the capsule. The statocyst does not seem to represent a more evolved equilibrium receptor system but may function as a relatively simple aciliary sense organ suitable for positive geotactic behaviour. The otoplanid statocyst corresponds to statocysts in other lithophorous proseriates but not to statocysts in other taxa of the free-living Plathelminthes. The monophyly of a taxon Lithophora within the Proseriata is corroborated by this autapomorphic characteristic.Abbreviations ac accessory cell(s) - c capsule of the statocyst - ce cerebrum - ci cephalic intestine - co capsule opening - cp cell process(es) of accessory cell(s) and cell(s) containing filaments - ecm extracellular matrix - fc cell(s) containing filaments - ic intercellular spaces within the capsule - mc muscle cell(s) - n lobed nucleus of the lithocyte - nac nucleus (nuclei) of accessory cell(s) - nc nerve cell(s) - npc nucleus (nuclei) of parietal cell(s) - pc parietal cell(s) - s statolith - sc statolith cell (lithocyte)     

Ultrastructural investigations on the labral glands of Daphnia obtusa (Crustacea,Cladocera)

The labral glands of Daphnia consist of three distinct functional units on each side: (1) several cells at the base of the head, (2) two large cells at the base of the labrum and one large cell (cell A) in the median part of the labrum and (3) one large cell (cell B) in the median part of the labrum. These gland cells do not form a syncytium, contrary to reports by previous investigators. With the exception of cell B, they have a well-developed rough endoplasmic reticulum and many active Golgi complexes. The Golgi activity changes during the molt cycle. The Golgi activity of the cells of the head base is different from that of the large cells of the labrum. Since clear exocytotic phenomena were not observed, the secretion can be assumed to flow into the hemolymph after accumulation in the enlarged intercellular spaces. Cell B has a distinctive cytoplasmic ultrastructure the function of which is not yet understood. The four large cells of the labrum are in contact with a duct cell (or several duct cells) characterized by a deep infolding of the plasma membrane. This delimits a narrow lumen, which contains no secretion. No passage of substance is visible from the gland cells to the duct cell(s).     

Structural changes ofNoetia ponderosa red blood cell membranes during cell volume regulation in reduced salinities: A freeze fracture study

Summary Changes in molluscan blood cell membrane structure coincided with changes in membrane amino acid permeability during cell volume regulation. Blood cells were freeze fractured after the free amino acid permeability of their membranes had been altered by modifying the extracellular Ca²⁺ and intracellular ATP levels and the membrane particles examined for changes in size, number/area and distribution. Test substances that altered the divalent cation or ATP levels also altered membrane particle densities, but not size or distribution, of freeze fractured blood cells. Those test substances (Ca²⁺-free seawater, DNP, low temperature) that inhibited volume regulation and the FAA efflux caused decreased membrane particle density, while those test substances (Co²⁺, Mn²⁺) that potentiated volume regulation and the FAA efflux increased the number of membrane particles/unit area. These changes in membrane particle density appear to result from the changes in surface area due to the treatment effects on cell volume, so that the number of membrane particles per cell remained constant. Therefore, altered membrane FAA permeability is associated with altered membrane particle density, but the effect of this structural alteration on membrane permeability is not clear.Abbreviations FAA free amino acid - DMSO dimethylsulfoxide - DNP dinitrophenol - ASW artificial seawater     

Freeze-substitution of dehydrated plant tissues: Artefacts of aqueous fixation revisited

Summary This investigation assessed the extent of rehydration of dehydrated plant tissues during aqueous fixation in comparison with the fine structure revealed by freeze-substitution. Radicles from desiccation-tolerant pea (Pisum sativum L.), desiccation-sensitive jackfruit seeds (Artocarpus heterophyllus Lamk.), and leaves of the resurrection plantEragrostis nindensis Ficalho & Hiern. were selected for their developmentally diverse characteristics. Following freeze-substitution, electron microscopy of dehydrated cells revealed variable wall infolding. Plasmalemmas had a trilaminar appearance and were continuous and closely appressed to cell walls, while the cytoplasm was compacted but ordered. Following aqueous fixation, separation of the plasmalemma and the cell wall, membrane vesiculation and distortion of cellular substructure were evident in all material studied. The sectional area enclosed by the cell wall in cortical cells of dehydrated pea and jackfruit radicles and mesophyll ofE. nindensis increased after aqueous fixation by 55, 20, and 30%, respectively. Separation of the plasmalemma and the cell wall was attributed to the characteristics of aqueous fixatives, which limited the expansion of the plasmalemma and cellular contents but not that of the cell wall. It is proposed that severed plasmodesmatal connections, plasmalemma discontinuities, and membrane vesiculation that frequently accompany separation of walls and protoplasm are artefacts of aqueous fixation and should not be interpreted as evidence of desiccation damage or membrane recycling. Evidence suggests that, unlike aqueous fixation, freeze-substitution facilitates reliable preservation of tissues in the dehydrated state and is therefore essential for ultrastructural studies of desiccation.Abbreviations LM light microscopy - TEM transmission electron microscopy - CF conventional (aqueous) fixation - FS freeze-substitution - ER endoplasmic reticulum     

Ultrastructure of the jugular body of Rana pipiens

Summary The jugular bodies in adult Rana pipiens, are surrounded by a capsule of mesothelium and connective tissue, and their parenchyma consists of cell cords arranged in a sinusoidal network. The cell cords are formed by irregular reticular cells, showing numerous filaments and joined together by zonulae adhaerents. The intercellular spaces are filled by reticular fibres and free cells. These latter are small and medium lymphocytes, lymphoblasts, and developing and mature plasma cells. Additionally, free macrophages, neutrophils and acidophils also occur. Sinusoidal blood vessels show thin walls with numerous filaments and pinocytotic vesicles. They exhibit a discontinuous basement membrane, and tight junctions frequently occur between endothelial cells. Occasionally, lymphatic vessels are found and the innervation is principally vasomotor, although nerve endings appear remarkably near reticular cells and lymphocytes. The jugular bodies of adult R. pipiens are plasma cell and antibody-forming organs, whose functional significance is discussed in relation to their ultrastructural organization.     

The protocerebral neurosecretory system and associated cerebral neurohemal area of Acheta domesticus

Summary A comparison of rectal morphology and ultrastructure is made between a freshwater (A. aegypti) and salt water (A. campestris) species of mosquito larvae, and between A. campestris larvae producing hyper- and hyposmotic urine.The epithelium of A. aegypti contains one cell type characterized by infolding of both the apical and basal membranes, straight lateral borders, and evenly distributed mitochondria.The rectum of A. campestris contains distinct anterior and posterior regions, each made up of a single cell type. These two regions can be distinguished on the basis of cell thickness, depth of apical infolding and distribution of mitochondria. The anterior region is similar to the rectum of A. aegypti, while the posterior region is considered unique to the salt-water species and hence probably is associated with the formation of hyperosmotic urine.In A. campestris, the apical (rather than lateral or basal) membranes are probably the site of hyperosmotic urine production. Two possible mechanisms for this process are discussed.This work was supported by operating grants from the National Research Council of Canada.     

Thin-blooded Antarctic fishes: a rheological comparison of the haemoglobin-free icefishes Chionodraco kathleenae and Cryodraco antarcticus with a red-blooded nototheniid, Pagothenia bernacchii

The icefishes (family Channichthyidae) comprise a unique group of teleost fishes endemic to Antarctic and sub-antarctic seas. All members of the family totally lack haemoglobin. Haematological parameters and viscosity were determined for blood from 11 specimens of two channichthyid species (Chionodraco kathleenae Regan, 1914; Cryodraco antarcticus Dollo, 1900), and 14 specimens of a red-blood Antarctic nototheniid species (Pagothenia bernacchii (Boulenger, 1902)), captured near the Italian research station at Terra Nova Bay, Ross Sea, Antarctica. Channichthyid blood contained only a small number of non-pigmented cells (10 000-40 000 cells μI^?1, depending on species) in contrast to nototheniid blood (360 000-450 000 cells μI^?1 in unstressed specimens). Blood viscosity was measured by cone plate viscometry over a range of shear rates (11.3-450s ^?1), at six temperatures between – 1.8°C and + 15°C. At the ambient Antarctic seawater temperature of – 1.8° C, and at low shear rate (22.5 s^?1), the viscosity of channichthyid blood was relatively low (3.99 ± 0.40 cP) compared with blood taken from unstressed P. bernacchii, which was about 25% more viscous (4.91 ± 0.59 cP). The viscosity of channichthyid blood was almost independent of shear rate, approximating an ideal Newtonian fluid, while the viscosity of nototheniid blood was much more dependent upon both shear rate and temperature, increasing sharply at low shear rates and low temperatures. Viscosity of nototheniid blood varied with haematocrit, which was in turn strongly influenced by stress. Blood samples taken from P. bernacchii under moderate stress induced by handling during acute caudal venepuncture had haematocrit values in the range 15–20% and viscosities of 8-l0cP, while undisturbed specimens sampled through a venous cannula yielded haematocrits of 8–10%. The viscosity of nototheniid plasma did not differ significantly from that of channichthyid whole blood or channichthyid plasma. The higher viscosity of nototheniid blood is attributable to cell content, and in stressed specimens possibly also to adrenergic swelling of erythrocytes. The absence of erythrocytes in channichthyid blood avoids the great increases in viscosity which are induced in corpusculate blood by sub-zero seawater temperatures.     

Changes in Amino Acid Transport During Red Cell Maturation

We studied amino acid transport in sheep red blood cells (RBCs) as a function of cell maturation. Transport of amino acids is decreased strikingly in the mature mammalian RBC compared to the immature reticulocyte. Blood obtained 5-6 days after massive bleeding was fractionated on dextran gradients. In the mature erythrocyte amino acids are taken up only slowly, and in the normal experimental interval (60 min) the concentration in the cell does not reach that of the medium. In contrast, the reticulocyte-rich (top) fraction (50-90% reticulocytes) accumulates certain amino acids, particularly histidine, methionine, and leucine. The underlying process is ATP-independent and Na⁺-insensitive, and has properties consistent with exchange diffusion, i.e., accelerated uptake or efflux when unlabeled solute is present on the trans side. The process is apparent not only in intact cells but also in resealed ghosts. The decrease in activity of amino acid transport is a function of red cell maturation. Thus it can be shown that (a) separation of cells according to their density 1, 2, and 3 weeks after bleeding leads to progressively lower amino acid transport activity with increasing cell density; and (b) during in vitro long-term incubation at 37°C of reticulocyte-rich, unfractionated blood (5–10% reticulocytes), amino acid transport decreases while red cell integrity is maintained, as evidenced by the retention of a normal K⁺ gradient and the absence of hemolysis. The progressive loss is seen with resealed ghosts as well as with intact cells. Not all the amino acids examined participate in this exchange process. The most actively exchanged are histidine, leucine, methionine, and phenylalanine. Glycine, proline, arginine, and a-amino isobutyric acid do not participate in the exchange process.     

Long-term influence of adjuvant therapy on natural killer cell activity in breast cancer

Summary Unstimulated IFN- and IL2-stimulated (NK) cell activities were investigated in patients with breast cancer who had received either local radiotherapy alone or adjuvant chemotherapeutic treatment with CMF combined with radiotherapy 12 to 18 months previously. When tested against the primarily NK-sensitive K562 cell line, patients who had received adjuvant chemotherapeutic treatment with CMF were shown to have a significantly decreased unstimulated and IFN-stimulated NK cell activity, as compared to both patients after radiotherapy only (P<0.002) and P<0.005, respectively) and healthy control persons (P<0.05). The former group of patients also had a significantly decreased IFN-stimulated NK cell activity, when tested against the primarily NK-insensitive Chang hepatoma cell line, as compared to patients after radiotherapy only (P<0.005) and healthy controls (P<0.05). Moreover, patients after radiotherapy only proved to have a significantly increased unstimulated (P<0.01) and IFN-stimulated NK cell activity (K562: P<0.05; Chang hepatoma cell line: P<0.05), as compared to healthy control individuals. In contrast, no difference in IL2-stimulated NK cell activity was detected. The investigation for the expression of CD3 and/or Leu 19 antigens as phenotypic markers of cells with non-MHC restricted cytotoxicity showed a significantly lower percentage of cells with the CD3+ phenotype in patients with breast cancer, irrespective of the chosen post-operative treatment, as compared to healthy controls (P<0.01). Finally, patients with breast cancer who had received radiotherapy only had a significant trend towards an increased percentage of CD³+/Leu 19+ PMNC, as compared to both patients after CMF treatment (P<0.05) and healthy controls (P<0.025). We conclude that patients with breast cancer vary on a long-term basis in their NK activity and in the phenotype of their PMNC depending on their post-operative adjuvant management.Abbreviations NK natural killer cells - IFN interferon - IL 2 interleukin 2 - CMF cyclophosphamide, methotrexate, fluorouracil - ER oestrogen receptor - PMNC peripheral blood mononuclear cells - MHC major histocompatibility complex - CTL cytotoxic T lymphocytes     

Ultrastructural study of different types of callus from leaf expiants ofAesculus hippocastanum L.

Summary The cell ultrastructure in three types of callus obtained from leaf explants ofAesculus hippocastanum L. has been studied. Remarkable differences have been shown between the cells of the forerunner E₁ callus and those of the callus arising from it, according to the culture conditions.The peculiar characteristics of E₁ are the scarcity of intercellular spaces and the occurrence of autophagic vacuoles in the cells.An embryogenic friable callus (E₂) is formed in time when E₁ is maintained on solid culture medium. The E₂ cells show cytological features typical of a higher metabolic level and contain starch. Diffused middle lamella digestion leads to the detachment of small embryogenic cell aggregates consisting of vacuolated parenchymatous-like cells and small meristematic cells which may be regarded as embryoids initials.Shaking E₁ in the same liquid medium and subsequent culture on solid medium lead to the differentiation of a non-embryogenic callus (NE), whose cells are very large and highly vacuolated, devoid of starch and with organelle-rich cytoplasm. The NE callus shows a high degree of growth, but does not attain embryogenic competence in time.Abbreviations c cell - cr crystal - cw cell wall - d dictyosome - er endoplasmic reticulum - m mitochondrion - mb microbody - n nucleus - p plastid - s starch - v vacuole     

Coupling of RNA polymerase III assembly to cell cycle progression in Saccharomyces cerevisiae

Assembly of the RNA polymerases in both yeast and humans is proposed to occur in the cytoplasm prior to their nuclear import. Our previous studies identified a cold-sensitive mutation, rpc128-1007, in the yeast gene encoding the second largest Pol III subunit, Rpc128. rpc128-1007 is associated with defective assembly of Pol III complex and, in consequence, decreased level of tRNA synthesis. Here, we show that rpc128-1007 mutant cells remain largely unbudded and larger than wild type cells. Flow cytometry revealed that most rpc128-1007 mutant cells have G1 DNA content, suggesting that this mutation causes pronounced cell cycle delay in the G1 phase. Increased expression of gene encoding Rbs1, the Pol III assembly/import factor, could counteract G1 arrest observed in the rpc128-1007 mutant and restore wild type morphology of mutant cells. Concomitantly, cells lacking Rbs1 show a mild delay in G1 phase exit, indicating that Rbs1 is required for timely cell cycle progression. Using the double rpc128-1007 maf1Δ mutant in which tRNA synthesis is recovered, we confirmed that the Pol III assembly defect associated with rpc128-1007 is a primary cause of cell cycle arrest. Together our results indicate that impairment of Pol III complex assembly is coupled to cell cycle inhibition in the G1 phase.     

Podocytes in bivalve molluscs: Morphological evidence for ultrafiltration

Summary In representatives from a survey of three major taxa of bivalves the pericardial glands were found in two distinct positions. In protobranches (Acila castrensis) and filibranch bivalves (Glycymeris subobsoleta, Chlamys hastata, Pecten caurinus, Placopecten magellanicus, Mytilus edulis andMytilus californianus) the pericardial glands are located on the auricular surface. In heterodonts (Mercenaria mercenaria, Clinocardium nuttallii andMya arenaria) the pericardial glands are found in an anterodorsal position to the pericardial cavity.The sites of ultrafiltration are described. They consist of podocytes with basally extending pedicels forming an interdigitating network apposed to a basal lamina. Other characteristics of this ultrafiltration barrier described are anionic sites on the basal lamina and presence of substructural components within the ultrafiltration slits between pedicels.The pathway for the ultrafiltrate in protobranchs and filibranchs is from the hemocoel through the basal lamina, through the ultrafiltration slits of the pedicel network, into the urinary spaces between the podocyte cell bodies and into the pericardial cavity. The pathway for the ultrafiltrate in heterodonts is from the hemocoel through the basal lamina, through the ultrafiltration slits of the pedicel network, into urinary spaces between the podocyte cell bodies, into the lumen of the pericardial gland tubules and into the pericardial cavity.All podocyte cells have electron dense granules, Golgi apparatus and vacuoles associated with their cytoplasm. Heterodont species have microvilli on the cell surfaces of the podocytes apposed to urinary spaces.In all cases the morphological sites of ultrafiltration were associated with the pericardial glands of the heart-pericardial complex.     

Measurement of blood volume in the elasmobranch fish Scyliorhinus canicula following acute and long‐term salinity transfers

A technique using ⁵¹chromium‐labelled erythrocytes was used to measure blood volume in Scyliorhinus canicula following long‐term and acute salinity transfers. Basal whole‐blood volume was 5·6 ± 0·2 ml 100 g^?1 (mean ±s .e .), this increased (6·3 ± 0·2 ml 100 g^?1) following +14 day acclimation to 80% sea water (SW) and decreased (4·6 ± 0·2 ml 100 g^?1) following acclimation to 120% SW. These changes were shown to be primarily due to changes in plasma volume, with no significant changes in extrapolated red‐cell volume being demonstrated. Blood volume was also measured in the same animals during 10 h acute transfer to 100% SW. Plasma volume in S. canicula during acclimation from 80% SW was significantly reduced (4·5 ± 0·3 ml 100 g^?1) after 6 h of transfer to 100% SW. Blood volume in animals during acclimation from 120% SW was significantly increased (4·8 ± 0·2 ml 100 g^?1) after 4 h of acute transfer. The osmoregulatory implications of these different timeframes during hyposaline and hypersaline transfer are discussed, along with the importance of this in vivo technique as context for in vitro studies with haemo‐dynamic stimuli.     

Ultrastructure of transitional epithelium of man

Summary Blocks of human normal renal pelvis and ureter obtained at the time of surgery were fixed in glutaraldehyde and osmium with or without ruthenium red, for electron microscopic observations. The transitional epithelium is arranged in three cell layers: basal, intermediate and superficial. All epithelial cells show numerous microvilli and contain the characteristic vesicles of transitional epithelium, bundles of cytoplasmic filaments, microtubules and numerous free ribosomes. The epithelial extracellular compartment is notably large and appears as an intricate, tridimensional network of canaliculi and cisternae which are wider in the intermediate and superficial layers and in which microvilli and cytoplasmic folds of vicinal cells are often attached or interdigitated. At these sites there are desmosomes.The surface of all transitional epithelial cells is covered by a fibrillar mucous coat which is more developed at the plasmalemma of the free border of luminal cells in which microvilli are also seen. Ruthenium red stains selectively the plasmalemma and the mucous coat of the free surface of the epithelium, indicating the presence of an acid polysaccharide. With this technic (Luft, 1965), it is observed, radiating from the plasmalemma, branching filaments which measure 100 Å in diameter forming a zone of varying density which is about 400 m wide and which corresponds, at the light microscopic level, to the luminal border of the transitional epithelial cells in which a sialomucin has been identified. The slender filaments have a beaded appearance. At the free border, superficial cells are attached by functional complexes in which tight junctions seal the epithelial intercellular space, which is opened at the level of the basement membrane where only desmosomes are observed.The ultrastructure of human transitional epithelium of urinary tract resembles the duct cells of the salt gland of certain marine birds (Fawcett, 1962) and the amphibian epidermis (Farquhar and Palade, 1965) in which there are active processes of transport. The mucous surface coat, selectively stained by the ruthenium red, contains a sialomucin (Monis and Dorfman, 1965, 1967).The ultrastructure and histochemistry of the mucous fluffy coat of man transitional epithelium and the observations of Porter and Tamm (1955), on the ultrastructure of preparations of the Tamm and Horsfall mucoprotein (1952) are bases for suggesting that transitional epithelium of urinary tract of man is the site of biosynthesis of certain urinary mucoids. Present investigations are directed to obtain evidence to substantiate this hypothesis.General Abbreviations B basal cell - E exfoliating cell - I intermediate cell - L lumen - S superficial cell - SC surface coat - bm basement membrane - ci cell infolding - d desmosome (macula adhaerens) - f fibroblast - fi cytoplasmic filaments - is intercellular space - jc junctional complex - ly lysosome - lym lymphocyte - mt microtubules - m mitochondria - mv microvilli - n nucleus - r ribosomes - rv round vesicle - zo zonula occludens - za zonula adherens Dr. Monis wishes to thank Dr. E. De Robertis for the use of the electron microscope facilities of the Instituto de Anatomía General y Embriologia, Facultad de Medicina, Universidad de Buenos Aires. — Prof. E. Trabucco and Dr. R. J. Borzone (Cátedra de Clinica Genitourinaria de la Facultad de Medicina, Universidad de Buenos Aires) generously supplied the specimens which were the bases of this study. — Thanks are due to Mrs. A. M. Novara and Mrs. Defilippi-Novoa for efficient technical help and to Miss Rosa Gentile for secretarial assistance. Photomicrography by Mr. M. A. Saenz.Dr. Zambrano is investigator (CNICT).     

Ultrastructure of the Bacterial Symbiotes in the Pharyngeal Diverticulum of Dacus oleae (Gmelin) (Trypetidae; Diptera)

Abstract The ultrastructure of the bacterial symbiotes in the pharyngeal diverticula of adult olive flies [Dacus oleae (Gmelin)] was examined. The diverticulum was an extension of the foregut formed by a row of epithelial cells bounded by an inner layer of cuticle. Towards the hemolymph, the epithelial cells showed an infolding of their basement membrane while adjacent to the cuticular lining, the cells contained a zone of extensive membrane proliferation. The diverticula were packed with bacterial rods which possessed elongate filamentous and short catenulate appendages. The function of these appendages is unknown. They did not resemble fimbriae (pili), flagella or prosthecae described from other bacteria.