Elongated Vesicles Research Articles

The Lami pyroclastic succession (Lipari, Aeolian Islands): A clue for unravelling the eruptive dynamics of the Monte Pilato rhyolitic pumice cone

The Lami succession piled up during the explosive activity of the Monte Pilato on Lipari Island (Central Aeolian Arc, Italy). It comprises a repetitive alternation of fall and pyroclastic density current beds, which define 13 Units separated by fine ash beds. Despite the homogeneous rhyolitic composition the juveniles fragments show strong textural heterogeneities from highly vesicular pumice to dense black obsidians. The pumice types are termed: i) “tube”, which shows elongated tubular vesicles, ii) “frothy”, highly vesicular with large, sub-rounded vesicles, and iii) agglomerated and welded. Two types of obsidian pyroclasts are recognized: i) aphyric black obsidian, and ii) grey obsidian showing spherulitic texture. All these pyroclastic types occur throughout the stratigraphic succession, and mixed in the same bed. They account for changing physical conditions along the conduit, which is hypothesised to be filled by a melt plug during the eruption of 12 out of 13 Units. The strong textural heterogeneities of the juvenile fragments testify for the existence of differential shear rates, which can be explained though two shear mechanism: i) simple shear, producing horizontal zonation of texture in the conduit with black obsidians along the conduit walls passing to tube and frothy pumice to the centre, and ii) pure shear, producing a vertical zonation in the conduit, with black obsidians at the top overlying frothy pumice. Agglomerated and welded pumice of Unit 13 is thought to represent the portion of magma heated by a batch of hotter melt that entered the magma chamber and triggered the eruption. The deposits of Unit 13 represent a unique case of spatter accretion due to accumulation of hot, low-viscous rhyolitic pumice fragments, emplaced from pyroclastic fountaining.

Evaluation of Percutaneous Absorption of Naproxen from Different Liposomal Formulations

The present study concerns the percutaneous absorption of naproxen (NPX), as model anti-inflammatory drug, included in liposome formulations constituted of different lipids: stratum corneum lipids (SCL) and phosphatidylcholine/cholesterol (PC/CHOL). Liposome dispersions were produced using two different methods: reverse-phase evaporation (REV) and thin layer evaporation (TLE). Morphology and dimensions of the disperse phase were characterized by cryo-transmission electron microscopy (cryo-TEM) and photon correlation spectroscopy, respectively. X-ray diffraction was employed to determine the structural organization of the vesicles. In vitro diffusion was studied by Franz cell on liposome dispersions viscosized by carbomer. Tape stripping was performed to investigate in vivo the performance of differently composed liposomes as NPX delivery system. Cryo-TEM showed spherical vesicles and bigger irregular elongated nanoparticles for TLE SCL liposomes. REV resulted in spherical and elongated multilamellar vesicles. Also X-ray diffraction evidenced L alpha or L beta multilamellar vesicles for PC/CHOL and SCL liposome respectively. The in vitro study showed a lower NPX flux for SCL with respect to PC/CHOL liposome. Tape stripping corroborate the in vitro findings regarding SCL, suggesting that liposomes create a drug reservoir mixing with SC lipids, whilst PC/CHOL liposome promoted NPX permeation through the skin. Liposome lipid composition seems to affect NPX permeation through the skin.

Pelagodinium gen. nov. and P. béii comb. nov., a Dinoflagellate Symbiont of Planktonic Foraminifera

The taxonomic status of the free-living stage of the dinoflagellate Gymnodinium béii, symbiont of the foraminifer Orbulina universa, was reassessed on the basis of detailed morpho-genetic analyses. Electron microscopy observations revealed previously undescribed morphological features of the cell that are important for species recognition. The presence of a single elongated apical vesicle (EAV) ornamented with a row of small knobs, absent in species of the genus Gymnodinium, calls into question the current taxonomic position of the symbiont. The presence of a type E extraplastidial eyespot, the arrangement of the amphiesmal vesicles in series and the absence of trichocysts confirm the affiliation with other symbiotic dinoflagellates and certain genetically related non-symbiotic genera, all belonging to the order Suessiales. The arrangement of the series of vesicles of the analyzed strain is unique within the Suessiales, and the ultrastructure of the pyrenoid is different from other symbiotic dinoflagellates. A large subunit (LSU) rDNA phylogenetic analysis confirmed that the analyzed pelagic symbiont clusters in an independent, well-supported clade within the Suessiales with other sequences of symbiotic dinoflagellates extracted from planktonic foraminifera. Hence a novel genus, Pelagodinium gen. nov., is erected for this pelagic, symbiotic dinoflagellate, and Gymnodinium béii is reclassified as Pelagodinium béii.

Caecincola longiscens n. sp. (Digenea: Cryptogonimidae) from the White Crappie, Pomoxis annularis, in Mississippi, U.S.A.

A new cryptogonimid trematode is described from the white crappie, Pomoxis annularis Rafinesque, 1818, collected from Lake Chotard, an oxbow lake directly connected to the Mississippi River in Issaquena County, and from a small ephemeral oxbow periodically connected with the Pascagoula River in Jackson County, both in Mississippi, U.S.A. Caecincola longiscens n. sp. is characterized by having an elongated body with a length to width ratio of 5.5–7.5:1, tandem testes, an elongated tubular seminal vesicle, and vitelline follicles confined to the hindbody.

Characterization of juvenile pyroclasts from the Kos Plateau Tuff (Aegean Arc): insights into the eruptive dynamics of a large rhyolitic eruption

Silicic pumices formed during explosive volcanic eruptions are faithful recorders of the state of the magma in the conduit, close to or at the fragmentation level. We have characterized four types of pumices from the non-welded rhyolitic Kos Plateau Tuff, which erupted 161,000 years ago in the East Aegean Arc, Greece. The dominant type of pumice (>90 vol.%) shows highly elongated tubular vesicles. These tube pumices occur throughout the eruption. Less common pumice types include: (1) “frothy” pumice (highly porous with large, sub-rounded vesicles), which form 5–10 vol.% of the coarsest pyroclastic flow deposits, (2) dominantly “microvesicular” and systematically crystal-poor pumices, which are found in early erupted, fine-grained pyroclastic flow units, and are characterized by many small (<50 μm in diameter) vesicles and few mm-sized, irregular voids, (3) grey or banded pumices, indicating the interaction between the rhyolite and a more mafic magma, which are found throughout the eruption sequence and display highly irregular bubble shapes. Except for the grey-banded pumices, all three other types are compositionally identical and were generated synchronously as they are found in the same pyroclastic units. They, therefore, record different conditions in the volcanic conduit leading to variable bubble nucleation, growth and coalescence. A total of 74 pumice samples have been characterized using thin section observation, SEM imagery, porosimetry, and permeametry. We show that the four pumice types have distinct total and connected porosity, tortuosity and permeability. Grey-banded pumices show large variations in petrophysical characteristics as a response to mingling of two different magmas. The microvesicular, crystal-poor, pumices have a bimodal bubble size distribution, interpreted as reflecting an early heterogeneous bubble nucleation event followed by homogeneous bubble nucleation close to fragmentation. Finally, the significant differences in porosity, tortuosity and permeability in compositionally identical tube and frothy pumices are the result of variable shear rates in different parts of the conduit. Differential shear rates may be the result of either: (1) pure shear, inducing a vertical progression from frothy to tube and implying a relatively thick fragmentation zone to produce both types of pumices at the same time or (2) localized simple shear, inducing strongly tubular vesicles along the wall and near-spherical bubbles in the centre of the conduit and not necessarily requiring a thick fragmentation zone.

Morphological observations on a lipid-based drug delivery system during in vitro digestion

The in vitro digestion of a self nano-emulsifying drug delivery system (SNEDDS) was visualized by cryogenic transmission electron microscopy (Cryo-TEM). The dynamic lipolysis model, simulating the environment of the gastrointestinal tract in fasted conditions, was used for this purpose. The results revealed that micelles are present during the entire lipolysis process. Oil droplets from the self nano-emulsifying drug delivery system are transformed to spherical or elongated unilamellar vesicles as lipolysis progresses. Low numbers of bilamellar and open vesicles were detected. After 50% hydrolysis a decrease in the number of unilamellar vesicles and oil droplets was observed. Furthermore, the electrical properties of the oil droplets were investigated by measuring their ζ-potential values as a function of time. An increase (in absolute values) to the ζ-potential of the hydrolyzing SNEDDS droplets observed versus time implying (binding or incorporation) of the micelles to the surface. The current data emphasize that Cryo-TEM combined with the in vitro dynamic lipolysis model can offer useful information on the formation of the various colloid phases during in vitro digestion of lipid-based formulations. Furthermore, it can provide a better understanding of the in vivo behavior of these systems, as well the solubilization of lipophilic drug compounds, offering new insights for designing and optimizing oral lipid-based formulations and possibly predicting their in vivo behavior. Such methodology can be a useful tool for the strategic development of lipid-based formulations.

Effect of the Headgroup Structure on the Aggregation Behavior and Stability of Self-Assemblies of Sodium N-[4-(n-Dodecyloxy)benzoyl]-l-aminoacidates in Water

Three amino acid-derived chiral surfactants, sodium N-[4-(n-dodecyloxy)benzoyl]-L-leucinate (SDBL), sodium N-[4-(n-dodecyloxy)benzoyl]-L-isoleucinate (SDBIL), and sodium N-[4-(n-dodecyloxy)benzoyl]-L-threoninate (SDBT), were synthesized, and their aggregation behavior was studied in aqueous solution. Surface tension, fluorescence probe, dynamic light scattering, nuclear magnetic resonance (NMR), gel permeation chromatography, circular dichroism, and optical as well as transmission electron microscopic techniques were utilized to characterize the self-assemblies formed by the amphiphiles. Results of these studies reveal that the surfactants have a very low critical aggregation concentration (cac) and they form spherical vesicles spontaneously in dilute aqueous solution. The mean diameters of the vesicles were measured to be in the range of 130-190 nm. 1H NMR spectra indicated hydrogen bonding between the amide groups near the surfactant headgroup, which is one of the driving forces for vesicle formation. The vesicle formation is more favored at a pH of about 7.0. The amphiphiles also form chiral helical aggregates at relatively higher concentrations as indicated by circular dichroism spectra. The stability of the vesicles was also evaluated with respect to the surfactant concentration, pH, temperature, and aging. The vesicles have a tendency to transform into elongated vesicles (closed tubules) or rodlike micelles with an increase of the surfactant concentration and/or pH. On the basis of the results obtained from different studies, phase diagrams for all three water/amphiphile systems have been constructed. The studies have further shown that the stereogenic center at the amino acid side chain has a significant effect on the aggregation properties of the amphiphiles and on the stability of the self-assemblies.

A Comparative Ontogenic Study of Urinary Bladder: Impact of the Epithelial Differentiation in Embryonic and Newborn Rats

The present study aimed to show the cellular and subcellular distribution of glycogen content during the differentiation of urothelial cells from simple cuboidal to stratified transitional epithelium. Bladder samples were taken from rat embryos on the 15th to 19th days and newborn at 21st day. During the development of the bladder, the formation of fusiform vesicles, asymmetric unit membrane (AUM) and microridges were examined with staining with haematoxylin-eosin and periodic acid Schiff for light microscope and periodic acid-thiocharbohydrazide-silver proteinate for transmission electron microscope. The topographical changes of luminal differentiation were examined with the scanning electron microscope. The urothelium was simple cuboidal from 15th till the 17th days of gestation. Glycogen content was present in the cytoplasm till the 18th day of gestation. At the early stage (16th day) of gestation, the apical surface contains microvilli that points the undifferentiated cells. The density of microvilli decreased and ropy microridges appeared at the 17th day of gestation. The small discoid vesicles lined with AUM developed at the apical cytoplasm of the surface cells at the 17th day of gestation. After this stage, both the density of microridges and large and elongated fusiform vesicles increased. The differentiation of the urothelium begins with the formation of the round and small vesicles, continues with the formation of the AUM and at the final stage there is a decrease in both glycogen content and the appearance of the microridges at the luminal surface of the urothelial cells.

Spermiogenesis and introsperm ultrastructure of Scoloplax distolothrix (Ostariophysi: Siluriformes: Scoloplacidae)

AbstractSpermiogenesis in scoloplacids is characterized by initial lateral development of the flagellum, nuclear rotation, medial nuclear fossa formation, complex centriolar migration, and cytoplasmic channel formation. The scoloplacid spermiogenesis is similar to those found in Diplomystidae, the most primitive siluriform family. The scoloplacid spermatozoa have all the main characteristics of introsperm. They exhibit a conic head, a symmetric midpiece, a medial flagellum, and no acrosome. The conic forward‐elongated nuclei contain homogeneous chromatin. The thin extremity of the nuclei is strongly curved and along its internal face there is a well‐developed membranous compartment. The centrioles are completely inside the medial nuclear fossa, perpendicular to each other and with an electron‐dense material between them. In a cross view of the midpiece, the mitochondria form a ring surrounding internally the cytoplasmic channel, and in a longitudinal view they are organized in a row along it. Several elongated vesicles are distributed peripherally, mainly concentrated in the mid‐piece basal region. The flagellum contains the classical axoneme (9 + 2) and has two lateral projections or fins. The spermatozoa of scoloplacids share several characteristics with those of Auchenipteridae. Since these two families are not phylogenetically related this similarity seems to be due to convergence once both families are, until now, the only known siluriform families with introsperm.

Parvalbumin-like immunostaining in the cat inferior colliculus. Light and electron microscopic investigation

The presence of the calcium-binding protein parvalbumin (PV) was studied in neuronal elements of the cat's inferior colliculus (IC) by means of light and electron microscopic immunocytochemistry. Immunostaining of PV was detected in all three main parts of the IC. Several subtypes of large neurons that differed in size and shape were immunostained, comprising approx. 15% of the total number of PV-containing neurons. Approx. half of the labeled neurons were medium sized. Two types of small neurons were found to be PV synthesizing, and comprised approx. 35% of the total PV-containing population. Ultrastructurally, many dendrites were heavily immunolabeled, and the reaction product was present in dendritic spines as well. Several types of synaptic boutons contained reaction product, and terminated on both labeled and unlabeled postsynaptic targets forming asymmetric and symmetric synapses. Approx. 70% of all PV-immunolabeled terminals contained round synaptic vesicles and formed asymmetric synapses. The majority of these boutons were of the “large round” type and corresponded to the terminals of cochlear nuclei. A lower number were of the “small round” type, and were probably corticotectal terminals. The remaining 30% of PV-containing terminals contained pleomorphic or elongated vesicles and formed symmetric synapses. These terminals corresponded with “P” and “F1” bouton types. Part of these boutons appeared to arise from nuclei of the lateral lemniscus and the superior olive, and a certain percentage likely represented endings of inhibitory interneurons.

Primary clinopyroxene spherulites in basaltic lavas from the Pacific–Antarctic Ridge

Fresh glassy basaltic andesite samples recovered from the northern part of the Pacific–Antarctic Ridge contain abundant spherulites consisting of arrays of closely packed clinopyroxene fibers. The spherulites frequently enclose elongated vesicles that are tear drop-shaped or tailed. The long axes of the elongated vesicles were found to be always parallel to the orientation of the surrounding crystal fibers. In several cases, elongated vesicles having different orientations are hosted by a single spherulite. The existence of elongated vesicles provides unequivocal evidence that a significant proportion of the clinopyroxene fibers must have crystallized directly from a supercooled liquid at temperatures above the glass transition. Moreover, the absence of fractures within the spherulites and the surrounding glass as well as the observed nucleation of clinopyroxene fibers at vesicle walls are interpreted to be consistent with a primary origin of the clinopyroxene spherulites. Based on these textural observations it has to be concluded that spherulites do not represent a diagnostic texture for the devitrification of volcanic glass that occurs below the glass transition temperature.

Biogenesis and exocytosis of Weibel-Palade bodies.

Vascular endothelial cells contain typical, elongated vesicles, the so-called Weibel-Palade bodies, which serve as a storage compartment for von Willebrand factor (VWF), a plasma protein that plays an essential role in controlling the adhesion and aggregation of platelets at sites of vascular injury. Upon activation of endothelial cells by agonists such as thrombin, epinephrine or histamine, the Weibel-Palade bodies fuse with the plasma membrane and release their contents into the blood circulation. This process provides an adequate means by which endothelial cells can actively participate in controlling the arrest of bleeding upon vascular damage. Besides VWF, Weibel-Palade bodies contain a subset of other proteins, including interleukin-8 (IL-8), P-selectin and endothelin. Similar to VWF, these proteins are transported to the outside of the cell upon stimulation and may control local or systemic biological effects, including inflammatory and vasoactive responses. Apparently, endothelial cells are able to create a storage pool for a variety of bioactive molecules which can be mobilised upon demand. Endothelial cells that are deficient of VWF synthesis are not only unable to form Weibel-Palade bodies, but also lack the ability to store IL-8 or P-selectin or release these proteins in a regulated manner. It thus appears that VWF not only plays a prominent role in controlling primary haemostasis, but also may modulate inflammatory processes through its ability to target inflammatory mediators to the regulated secretion pathway of the endothelium.

Dynorphin induced magnetic ordering in lipid bilayers as studied by 31P NMR spectroscopy

Lipid bilayers of dimyristoyl phosphatidylcholine (DMPC) containing opioid peptide dynorphin A(1–17) are found to be spontaneously aligned to the applied magnetic field near at the phase transition temperature between the gel and liquid crystalline states ( T m=24°C), as examined by 31P NMR spectroscopy. The specific interaction between the peptide and lipid bilayer leading to this property was also examined by optical microscopy, light scattering, and potassium ion-selective electrode, together with a comparative study on dynorphin A(1–13). A substantial change in the light scattering intensity was noted for DMPC containing dynorphin A(1–17) near at T m but not for the system containing A(1–13). Besides, reversible change in morphology of bilayer, from small lipid particles to large vesicles, was observed by optical microscope at T m. These results indicate that lysis and fusion of the lipid bilayers are induced by the presence of dynorphin A(1–17). It turned out that the bilayers are spontaneously aligned to the magnetic field above T m in parallel with the bilayer surface, because a single 31P NMR signal appeared at the perpendicular position of the 31P chemical shift tensor. In contrast, no such magnetic ordering was noted for DMPC bilayers containing dynorphin A(1–13). It was proved that DMPC bilayer in the presence of dynorphin A(1–17) forms vesicles above T m, because leakage of potassium ion from the lipid bilayers was observed by potassium ion-selective electrode after adding Triton X-100. It is concluded that DMPC bilayer consists of elongated vesicles with the long axis parallel to the magnetic field, together with the data of microscopic observation of cylindrical shape of the vesicles. Further, the long axis is found to be at least five times longer than the short axis of the elongated vesicles in view of simulated 31P NMR lineshape.

Author Index

Volcanic glasses with minor mafic mineral fragments, such as biotite and hornblende, found in deep-sea sediments of the South China Sea Basin (SCSB) have been clearly identified as eruptive products of the Youngest Toba Tuff (YTT), northern Sumatra, Indonesia. The tephra layer occurs between marine oxygen isotopic event 5.1 (79.3 ka) and event 4.22 (64.1 ka), with an interpolated age of 74.0 ka, which is in good consistence with previous radiometric dating (73–75 ka) and ice-core dating (71±5 ka) of the YTT. The tephra consists predominantly of bubble-wall shards with minor elongated vesicles of pumice fragments. Geochemical characteristics of the tephra, such as high total alkali content, high 87Sr/86Sr ratio and uniformity of their compositions, all suggest that the recovered tephra is of the Youngest Toba Tuff. This finding supports an extended dispersal of coarse (>63 μm) glass shards over 1500 km northeast of the Toba caldera, a direction opposite to what previously conceived. While providing a better documentation of the distribution extent of the Toba ash, this report points to the need to re-estimating the eruptive volume of the YTT and re-evaluating its environmental impact.

Newly discovered eastern dispersal of the youngest Toba Tuff

Volcanic glasses with minor mafic mineral fragments, such as biotite and hornblende, found in deep-sea sediments of the South China Sea Basin (SCSB) have been clearly identified as eruptive products of the Youngest Toba Tuff (YTT), northern Sumatra, Indonesia. The tephra layer occurs between marine oxygen isotopic event 5.1 (79.3 ka) and event 4.22 (64.1 ka), with an interpolated age of 74.0 ka, which is in good consistence with previous radiometric dating (73‐75 ka) and ice-core dating (71 ^ 5 ka) of the YTT. The tephra consists predominantly of bubble-wall shards with minor elongated vesicles of pumice fragments. Geochemical characteristics of the tephra, such as high total alkali content, high 87 Sr/ 86 Sr ratio and uniformity of their compositions, all suggest that the recovered tephra is of the Youngest Toba Tuff. This finding supports an extended dispersal of coarse (.63 mm) glass shards over 1500 km northeast of the Toba caldera, a direction opposite to what previously conceived. While providing a better documentation of the distribution extent of the Toba ash, this report points to the need to reestimating the eruptive volume of the YTT and re-evaluating its environmental impact. q 2000 Elsevier Science B.V. All rights reserved.

Conformation and Dynamics of Melittin Bound to Magnetically Oriented Lipid Bilayers by Solid-State 31P and 13C NMR Spectroscopy

The conformation and dynamics of melittin bound to the dimyristoylphosphatidylcholine (DMPC) bilayer and the magnetic orientation in the lipid bilayer systems were investigated by solid-state 31P and 13C NMR spectroscopy. Using 31P NMR, it was found that melittin-lipid bilayers form magnetically oriented elongated vesicles with the long axis parallel to the magnetic field above the liquid crystalline-gel phase transition temperature ( T m = 24°C). The conformation, orientation, and dynamics of melittin bound to the membrane were further determined by using this magnetically oriented lipid bilayer system. For this purpose, the 13C NMR spectra of site-specifically 13C-labeled melittin bound to the membrane in the static, fast magic angle spinning (MAS) and slow MAS conditions were measured. Subsequently, we analyzed the 13C chemical shift tensors of carbonyl carbons in the peptide backbone under the conditions where they form an α-helix and reorient rapidly about the average helical axis. Finally, it was found that melittin adopts a transmembrane α-helix whose average axis is parallel to the bilayer normal. The kink angle between the N- and C-terminal helical rods of melittin in the lipid bilayer is ∼140° or ∼160°, which is larger than the value of 120° determined by x-ray diffraction studies. Pore formation was clearly observed below the T m in the initial stage of lysis by microscope. This is considered to be caused by the association of melittin molecules in the lipid bilayer.

Neural connections of the pineal organ in the primitive bony fish Acipenser baeri : A carbocyanine dye tract‐tracing study

The pineal organ of the sturgeon (Acipenser baeri; Chondrostei) consists of an elongated terminal vesicle and a long stalk that runs to the region of the posterior commissure. In order to investigate the neural connections of the pineal organ of the surgeon, a fluorescent indocarbocyanine (DiI) was applied to the pineal stalk of paraformaldehyde-fixed brains. This application strongly labeled the pineal tracts (right and left), which form an extensive bilateral projection to the brain. The fibers of these tracts could be followed to their different targets in the brain, namely the preoptic region, the rostral habenulae, the medial subhabenular and retrohabenular (post- and subcommissural) region, the medial thalamus, the dorsal hypothalamus, the pretectal area, and medial and dorsolateral tegmental mesencephalic regions (interstitial nucleus of Cajal, oculomotor nucleus, mesencephalic reticular area, nucleus profundus mesencephali, and central gray). A few fibers reach the interpeduncular nucleus and the rostral optic tectum. Pinealofugal fibers branched profusely, and some of them crossed the midline ventrally in the optic chiasma, the postoptic commissure, the conspicuous preinfundibular commissure or, occasionally, the mesencephalic tegmentum. In addition to pinealofugal fibers, this type of DiI application labeled a few cells, here interpreted as pinealopetal neurons, in the posthabenular-dorsomedial thalamic region and the central gray of the mesencephalon. The wide distribution of pinealofugal projections in sturgeon is reminiscent of that in the lamprey. Comparison of the present findings with those of other authors in teleosts, amphibians, and reptiles also suggests that there has been a reduction in the number of pineal projections in these lines.

Neural connections of the pineal organ in the primitive bony fish Acipenser baeri: a carbocyanine dye tract-tracing study.

The pineal organ of the sturgeon (Acipenser baeri; Chondrostei) consists of an elongated terminal vesicle and a long stalk that runs to the region of the posterior commissure. In order to investigate the neural connections of the pineal organ of the surgeon, a fluorescent indocarbocyanine (DiI) was applied to the pineal stalk of paraformaldehyde-fixed brains. This application strongly labeled the pineal tracts (right and left), which form an extensive bilateral projection to the brain. The fibers of these tracts could be followed to their different targets in the brain, namely the preoptic region, the rostral habenulae, the medial subhabenular and retrohabenular (post- and subcommissural) region, the medial thalamus, the dorsal hypothalamus, the pretectal area, and medial and dorsolateral tegmental mesencephalic regions (interstitial nucleus of Cajal, oculomotor nucleus, mesencephalic reticular area, nucleus profundus mesencephali, and central gray). A few fibers reach the interpeduncular nucleus and the rostral optic tectum. Pinealofugal fibers branched profusely, and some of them crossed the midline ventrally in the optic chiasma, the postoptic commissure, the conspicuous preinfundibular commissure or, occasionally, the mesencephalic tegmentum. In addition to pinealofugal fibers, this type of DiI application labeled a few cells, here interpreted as pinealopetal neurons, in the posthabenular-dorsomedial thalamic region and the central gray of the mesencephalon. The wide distribution of pinealofugal projections in sturgeon is reminiscent of that in the lamprey. Comparison of the present findings with those of other authors in teleosts, amphibians, and reptiles also suggests that there has been a reduction in the number of pineal projections in these lines.

Expression and Secretion of Barley Cysteine Endopeptidase B and Cellobiohydrolase I in Trichoderma reesei

Localization of expression and secretion of a heterologous barley cysteine endopeptidase (EPB) and the homologous main cellobiohydrolase I (CBHI) in a Trichoderma reesei transformant expressing both proteins were studied. The transformant was grown on solid medium with Avicel cellulose and lactose to induce the cbh1 promoter for the synthesis of the native CBHI and the recombinant barley protein linked to a cbh1 expression cassette. Differences in localization of expression between the two proteins were clearly indicated by in situ hybridization, indirect immunofluorescence, and immunoelectron microscopy. In young hyphae, native-size recombinant epb mRNA was localized to apical compartments. In older cultures, it was also seen in subapical compartments but not in hyphae from the colony center. The recombinant EPB had a higher molecular weight than the native barley protein, probably due to glycosylation and differential processing in the fungal host. As was found with its transcripts, recombinant EPB was localized in apical and subapical compartments of hyphae. The cbh1 mRNA and CBHI were both localized to all hyphae of a colony, which suggests that the endogenous CBHI was also secreted from these. In immunoelectron microscopy, the endoplasmic reticulum and spherical vesicles assumed to contribute to secretion were labeled by both CBHI and EPB antibodies while only CBHI was localized in elongated vesicles close to the plasma membrane and in hyphal walls. The results indicate that in addition to young apical cells, more mature hyphae in a colony may secrete proteins.

From coiled tubules to a secretory canaliculus: a new model for membrane transformation and acid secretion by gastric parietal cells

The acid-secreting gastric parietal cell has a unique secretory membrane system. This membrane system exists in an inactive (non-secreting) and an active (secreting) form. The current accepted model to explain the transformation events associated with the conversion of the non-secreting membrane to the secreting membrane, and vice versa, invokes membrane recycling of elongated vesicle structures. However, recent studies employing cryopreparation have shown that the non-secreting membrane in these cells is actually a complex network of helically coiled tubules. Here, we present an alternative model to explain how the membrane in parietal cells is activated to secrete HCI.