Intercellular Cavities Research Articles

In preprints: morphogens in motion.

In preprints: morphogens in motion.

Midbody-Localized Aquaporin Mediates Intercellular Lumen Expansion During Early Cleavage of an Invasive Freshwater Bivalve.

Intercellular lumen formation is a crucial aspect of animal development and physiology that involves a complex interplay between the molecular and physical properties of the constituent cells. Embryos of the invasive freshwater mussel Dreissena rostriformis are ideal models for studying this process due to the large intercellular cavities that readily form during blastomere cleavage. Using this system, we show that recruitment of the transmembrane water channel protein aquaporin exclusively to the midbody of intercellular cytokinetic bridges is critical for lumenogenesis. The positioning of aquaporin-positive midbodies thereby influences the direction of cleavage cavity expansion. Notably, disrupting cytokinetic bridge microtubules impairs not only lumenogenesis but also cellular osmoregulation. Our findings reveal a simple mechanism that provides tight spatial and temporal control over the formation of luminal structures and likely plays an important role in water homeostasis during early cleavage stages of a freshwater invertebrate species.

МОДЕЛЮВАННЯ ФІЛЬТРАЦІЙНОГО МАСОПЕРЕНОСУ В СЕРЕДОВИЩІ МІКРОПОРИСТИХ ЧАСТИНОК

Процеси фільтраційного масопереносу є важливими технологічними операціями при розділенні сумішей, екстраґуванні рідин із різних біологічних матеріалів в переробній, хімічній індустрії, фармакології та інших галузях. Структура біологічних матеріалів містить розгалужену систему вологовмістких клітин, міжклітинних полостей, мікропор, через які здійснюється масоперенос. При цьому внутрішні потоки маси спрямовані з середини мікропор вологовмістких частинок до їх поверхонь. Далі формуються проміжні (транзитні) потоки, спрямовані від зовнішніх поверхонь частинок в макропори міжчастинкового простору. В макропорах (intraparticle spaces) виникають зовнішні відтоки рідини на зовні пласту середовища. При фільтраційному переносі-відтиску у попередньо сформованому пласті мікропористих частинок біологічної природи, що піддається стискуванню, виникають внутрішні і зовнішні ґрадієнти тисків відповідно в частинках і міжчастинковому просторі, які спричинюють відтоки рідини із пласту і частинок.. Ця модель ґрунтується на відповідних рівняннях балансу маси у внутрічастинковому просторі (intraparticle spaces), включаючи міжчастинковий просторі (extraparticle spaces). Згідно такої моделі, потік рідини з мікропор intraparticle spaces розглядається як такий що є незначним у порівнянні з потоком з частинок на зовні – в макропори extraparticle spaces та потоком з extraparticle spaces назовні пласту середовища. До того ж, розглядувана модель включає припущення про псевдо статичність потоку між intraparticle spaces і extraparticle spaces. Це означає, що інтенсивність потоку – з середини частинки назовні, є пропорційною різниці тисків всередині і назовні частинки, що є дуже наближено. Методами інтеґральних перетворень Лапласа і Фур'є побудований високошвидкісний точний аналітичний розв’язок крайової задачі фільтраційного масопереносу, що включає два взаємозв’язаних типи переносу: на мікрорівні – в мікропорах вологовмістких частинок, та макрорівні – в системі макропор міжчастинкового простору в обмеженому середовищі мікропористих частинок. Шляхом розв’язання оберненої задачі з використанням експериментальних концентраційних розподілів в системі, розробленій засобами Microsoft Visual C++ розраховані профілі приведених коефіцієнтів консолідації для частинок та системи макропор і виконана перевірка моделі на адекватність.

Anatomical and histochemical studies of the abscission process on the juncture tissues between peduncle and fruit on cherry

In Japan, consumers eat cherries fresh, but their shelf life is very short. One of the problems during shelf life of fresh cherries is the separation of peduncle from fruit. However, to the best of our knowledge, no scientific information about abscission process on the juncture tissues between peduncle and fruit can be found in literature. In this study, we used cherry cultivar 'Bing', and observed abscission process anatomically and histochemically. These juncture tissues were fixed in FAA (Formalin+acetic acid+alcohol), and embedded in paraffin, cut in 15 µm and stained with toluidine blue-O, ruthenium red, zinc chloride and IKI (iodine + potassium iodide). As a result, the cells of the epidermis were broken down first, and cavities were formed. These cavities gradually spread to the inner side. At this time, in the central parenchymatous region, intercellular cavities were greatly developed. The cell walls were broken down and intercellular cavity developed within the inner wall. Finally, the peduncle was completely separated from the surface cell of the fruit tissue, and abscission occurred. The cell walls of the epidermis of peduncle were stained dark blue with zinc chloride, black with IKI, and pale red with ruthenium red. In this region, the cell walls were constituted of cellulose and starch grains, but not of pectins, so that these cell walls were broken down by pectinases. In contrast, adjacent cells in the intercellular cavities of the central parenchymatous region were not stained red, blue or black. These results indicated that they were broken down by the cell wall degrading enzymes such as cellulase and pectinase. Starch grains were consumed for energy needed for these enzyme activities in parenchymatous region as well as in epidermal region. We suggested that suppression of abscission is crucial to prolong shelf life and could be achieved by storing cherries at low temperature.

20th century changes in carbon isotopes and water-use efficiency: tree-ring-based evaluation of the CLM4.5 and LPX-Bern models

Abstract. Measurements of the stable carbon isotope ratio (δ13C) on annual tree rings offer new opportunities to evaluate mechanisms of variations in photosynthesis and stomatal conductance under changing CO2 and climate conditions, especially in conjunction with process-based biogeochemical model simulations. The isotopic discrimination is indicative of the ratio between the CO2 partial pressure in the intercellular cavities and the atmosphere (ci∕ca) and of the ratio of assimilation to stomatal conductance, termed intrinsic water-use efficiency (iWUE). We performed isotope-enabled simulations over the industrial period with the land biosphere module (CLM4.5) of the Community Earth System Model and the Land Surface Processes and Exchanges (LPX-Bern) dynamic global vegetation model. Results for C3 tree species show good agreement with a global compilation of δ13C measurements on leaves, though modeled 13C discrimination by C3 trees is smaller in arid regions than measured. A compilation of 76 tree-ring records, mainly from Europe, boreal Asia, and western North America, suggests on average small 20th century changes in isotopic discrimination and in ci∕ca and an increase in iWUE of about 27 % since 1900. LPX-Bern results match these century-scale reconstructions, supporting the idea that the physiology of stomata has evolved to optimize trade-offs between carbon gain by assimilation and water loss by transpiration. In contrast, CLM4.5 simulates an increase in discrimination and in turn a change in iWUE that is almost twice as large as that revealed by the tree-ring data. Factorial simulations show that these changes are mainly in response to rising atmospheric CO2. The results suggest that the downregulation of ci∕ca and of photosynthesis by nitrogen limitation is possibly too strong in the standard setup of CLM4.5 or that there may be problems associated with the implementation of conductance, assimilation, and related adjustment processes on long-term environmental changes.

Seagrass stems with attached roots from the type area of the Maastrichtian Stage (NE Belgium, SE Netherlands): Morphology, anatomy, and ecological aspects

Seagrasses are the only seed plants to have invaded marine environments successfully. Seagrass fossils are both rare and have received scant attention so far. However, among the limited number of plant fossils from marine strata in the Maastrichtian type area, remains of seagrasses are relatively common. The present paper provides a detailed description of the morphology and anatomy of the stems and attached roots of Thalassocharis bosquetii Debey ex Miquel, 1853, mainly on the basis of silicified material. This has enabled an interpretation of features of the abundant imprints (external moulds) among the specimens studied, inclusive of the type material. Contrary to the outcome of earlier studies, the internodes have been found to constitute leaf scars. T. bosquetii is considered to have been a seagrass, but has a complex stem anatomy, including a substantial central stele with numerous sheathed vascular bundles, an inner cortex with many small intercellular cavities, a middle cortex with distinct fibre strands, and an outer cortex with conspicuously thickened vascular bundles, each of which constricts into a thin vascular strand just below a furrow/pit on the leaf scar. The last-named feature underlies the characteristic stem surface pattern seen in Thalassocharis. The stem anatomy of T. bosquetii is clearly more complex than that of extant seagrasses, which, due to prolonged adaptation to their aquatic habitat, show a more or less reduced anatomy. As far as the complexity of the stele is concerned, T. bosquetii reminds more of some non-marine Alismatales, such as the pondweed family Potamogetonaceae and the monotypical peat bog family Scheuchzeriaceae.

Anatomical, physiological, and biochemical traits involved in the UV-B radiation response in highbush blueberry

The effects of a long-term simulated spring-summer UV-B daily course on some anatomical, physiological, and biochemical features were studied in new and old leaves of blueberry (Vaccinium corymbosum L.) cultivars Legacy, Brigitta, and Bluegold. The results show that under UV-B exposure, leaf thickness increased in Bluegold due to an increased intercellular cavities. By contrast, Brigitta maintained its leaf thickness. The net photosynthetic rate was not significantly affected by the UV-B radiation in any of the cultivars; however, Brigitta presented a better photosystem II performance, since this cultivar had more efficient photochemistry under the UV-B radiation. In addition, Brigitta also maintained enhanced total phenol and total anthocyanin content compared to the other cultivars. In conclusion, Brigitta was more resistant to the UV-B radiation than the other two cultivars.

Network model to study physiological processes of hypobaric decompression sickness: New numerical results

We have studied decompression processes when pressure changes that take place, in blood and tissues using a technical numerical based in electrical analogy of the parameters that involved in the problem. The particular problem analyzed is the behavior dynamics of the extravascular bubbles formed in the intercellular cavities of a hypothetical tissue undergoing decompression. Numerical solutions are given for a system of equations to simulate gas exchanges of bubbles after decompression, with particular attention paid to the effect of bubble size, nitrogen tension, nitrogen diffusivity in the intercellular fluid and in the tissue cell layer in a radial direction, nitrogen solubility, ambient pressure and specific blood flow through the tissue over the different molar diffusion fluxes of nitrogen per time unit (through the bubble surface, between the intercellular fluid layer and blood and between the intercellular fluid layer and the tissue cell layer). The system of nonlinear equations is solved using the Network Simulation Method, where the electric analogy is applied to convert these equations into a network-electrical model, and a computer code (electric circuit simulator, Pspice). In this paper, numerical results new (together to a network model improved with interdisciplinary electrical analogies) are provided.

Variation in mesophyll conductance among Australian wheat genotypes

CO2 diffusion from substomatal intercellular cavities to sites of carboxylation in chloroplasts (mesophyll conductance; gm) limits photosynthetic rate and influences leaf intrinsic water-use efficiency (A/gsw). We investigated genotypic variability of gm and effects of gm on A/gsw among eleven wheat (Triticum aestivum L.) genotypes under light-saturated conditions and at either 2 or 21% O2. Significant variation in gm and A/gsw was found between genotypes at both O2 concentrations, but there was no significant effect of O2 concentration on gm. Further, gm was correlated with photosynthetic rate among the 11 genotypes, but was unrelated to stomatal conductance. The effect of leaf age differed between genotypes, with gm being lower in older leaves for one genotype but not another. This study demonstrates a high level of variation in gm between wheat genotypes; 0.5 to 1.0μmolm-2s-1 bar-1. Further, leaf age effects indicate that great care must be taken to choose suitable leaves in studies of genotypic variation in gm and water-use efficiency.

Apport de la microscopie confocale in vivo et de la tomographie en cohérence optique de chambre antérieure pour l’étude des pathologies endothéliales cornéennes

To describe the appearance of various endothelial diseases with in vivo confocal microscopy and anterior chamber optical coherence tomography (AC OCT). In this study, ten patients with five different corneal endothelial pathologies were evaluated. Three patients had cornea guttata, three had corneal endothelial precipitates, two had irido-corneo-endothelial (ICE) syndrome, one had endothelial folds, and one had breaks in the Descemet membrane. All patients had bilateral ophthalmologic examinations, in vivo confocal microscopy, and AC OCT analysis. In cases of cornea guttata, AC OCT showed a finely embossed line corresponding to the empty intercellular cavities found with in vivo confocal microscopy. Corneal endothelium precipitates had the aspect of round formations suspended with the endothelium. Iris atrophy and irido-corneal synechiae resulting from ICE syndrome were precisely visualized with the AC OCT. High-resolution images of the anterior segment could be obtained using the AC OCT. Associated with in vivo confocal microscopy, these two new imaging techniques provide a precise evaluation of endothelial pathologies.

Studies of postharvest berry abscission of ‘Kyoho’ table grapes during cold storage and high oxygen atmospheres

The effects of high O 2 on catabolic enzymes and anatomical structure in abscission zones, fruit detachment force (FDF), and berry drop of grapes were investigated. ‘Kyoho’ table grapes ( Vitis vinifera x V. labrusca) were subjected to air or 80% O 2 at 0 °C in 95% relative humidity for 60 days. During storage, separation occurred at the berry-pedicel indentation and the abscission layer extended gradually from lateral phloem towards the whole phloem and pith, forming intercellular cavities and leading to berry drop. FDF declined steadily accompanied by an increase in berry drop. Grape abscission was correlated to the increases in activity of hydrolases, in particular cellulase (Cx) and polygalacturonase (PG), in abscission zones. In contrast to air storage, high O 2 inhibited Cx, PG and pectinesterase (PE) activity and the reverse for peroxidase (POD), decreased the degree of swelling and distorting of the abscission cell walls, and tended to keep berry adherence strength high and reduced berry drop. The inhibitory mechanism of high O 2 on berry drop possibly could be explained by the fact that disassembly of the abscission zone cells was delayed by a synergistic impact on degradation enzymes whose activities were affected by high O 2 levels.

An ultrastructural study of alimentary tract development in the cercariae of Diplostomum pseudospathaceum (Digenea: Diplostomidae)

Morphogenesis of the alimentary canal in developing Diplostomum pseudospathaceum cercariae has been studied using electron microscopy. The foregut primordium appears in early cercariae as a cellular cord. Later, the lumen develops within the foregut primordium, and its cells give rise to the cellular epithelium, limiting this lumen. During subsequent development, the lateral plasma membranes, separating the cells, disappear from the primary foregut epithelium as do nuclei and most of cellular organelles. These events seem to progress in several steps, and eventually, the foregut lining becomes the thin anucleate syncytial layer. In late cercariae, this layer becomes connected with nucleated cytons, producing secretory inclusions. Each of two caecal branches appears to arise from a row of large cuboid cells. The primordial gastrodermal cells are involved in synthetic and secretory activity and give rise to numerous secretory inclusions. These inclusions release their contents into the cavities which develop between adjacent primordial caecal cells. The intercellular cavities gradually increase in size and fuse to eventually form a single caecal lumen. In mature cercariae, the large caecal lumen packed with electron-dense secretory material is limited by a thin cellular gastrodermis, displaying no secretory features.

Ultrastructural Peculiarities of the Embryogenesis of the Brittle Star Amphipholis kochii (Lutken, 1972)

This paper addresses morphogenetic processes and cell differentiation during embryogenesis of the brittle star Amphipholis kochii at the ultrastructural level. The radial cleavage is not strictly determined. Embryos are covered with a thick hyaline envelope and contain numerous yolk granules and small lipid drops. Blastulae feature a thick blastoderm with extensive intercellular cavities, which are retained in the crest epithelium of late gastrulae. Embryonic cells have single cilia with long cross-striated rootlets associated with the Golgi apparatus. Depolarized cells of the primary mesenchyme with a well-developed rough endoplasmic reticulum differentiate into sclerenchyme syncytium. Gastrulation occurs by invagination. Secondary mesenchymal cells emigrate from the archenteron tip to differentiate into amebocytes, which contain a well-developed Golgi apparatus and numerous mitochondria. The endoderm is formed of cubic cells with numerous yolk granules and rare microvilli. Flattened cells of the dorsal and ventral ectoderm contain a small amount of yolk. Yolk utilization during embryogenesis occurs by intracellular lysosomal digestion with selective exocytosis of toposomes.

MORPHOLOGY AND HISTOLOGY OF THE NECTARY IN HUNGARIAN LOCAL PEAR CULTIVARS

The topography, morphology and histology of the nectary of 12 Hungarian pear cultivars in a Hungarian cultivar collection (Ujfeherto) were studied over the past 3 years. The intrafloral nectary was receptaculo-ovarial, lining the adaxial surface of the plate-like receptacle and the apical part of the ovary. The gland was automorphic on the apical part, and in some cases also on the basal part, protruding out of the receptacular tissue. A narrow zone of the nectariferous tissue stretched along the style, allowing nectar accumulation in the gap between the style and the nectary. The pear nectary was covered by a smooth cuticle, the thickness of which varied slightly between cultivars and from season to season. In the medial longitudinal section of the flower the epidermal cells were palisad-like or squareshaped, sometimes papillate. Guard cells of nectar stomata could be found either at the level of the epidermal cells (mesomorphic type) or sunken a few cell rows below the epidermis (xeromorphic type). Below the stomata, among the cells of the glandular tissue, nectar-storing intercellular cavities of varying sizes could be found. The glandular tissue consisted of small, dark-staining cells. In some cultivars the nectariferous tissue could be well distinguished from the nectary parenchyma, consisting of larger, light-staining cells. In other cultivars a mosaic-like structure could be observed, where glandular cells were mixed with parenchyma cells, with no sharp distinction between the two tissue types. In some taxa there was a correlation between the size of the nectary and nectar production, which may be important in cultivar selection.

Light-induced wilting and its molecular mechanism in epicotyls of dark-germinated pea (Pisum sativum L.) seedlings.

Possible mechanisms behind the light-induced wilting of dark-germinated pea (Pisum sativum L.) epicotyls were studied. Illumination with photosynthetically active radiation caused a fast turgor loss and wilting in the middle segments of the epicotyls accompanied by accumulation of water in the intercellular cavities. During this process, room temperature fluorescence emission spectra showed gradual bleaching of porphyrin-type pigments, which was lessened by incubating the epicotyls with excess ascorbate before illumination. Detection of singlet oxygen and lipid peroxidation products in the illuminated epicotyls suggested the occurrence of porphyrin-photosenzitized membrane damage as a cause of disordered water status and sequential wilting.

ANATOMICAL STUDIES OF THE ABSCISSION PROCESS IN THE JUNCTURE TISSUE BETWEEN THE PEDUNCLE AND SPUR ON JAPANESE PEAR FRUIT FOLLOWING ETHEPHON APPLICATION

ISHS International Symposium on Asian Pears, Commemorating the 100th Anniversary of Nijisseiki Pear ANATOMICAL STUDIES OF THE ABSCISSION PROCESS IN THE JUNCTURE TISSUE BETWEEN THE PEDUNCLE AND SPUR ON JAPANESE PEAR FRUIT FOLLOWING ETHEPHON APPLICATION

Developmental, qualitative, and ultrastructural differences between ovine and bovine embryos produced in vivo or in vitro.

The objective of this study was to compare bovine and ovine oocytes in terms of (1) developmental rates following maturation, fertilization, and culture in vitro, (2) the quality of blastocysts produced in vitro, assessed in terms of their ability to undergo cryopreservation, and (3) the ultrastructural morphology of these blastocysts. In vitro blastocysts were produced following oocyte maturation/fertilization and culture of presumptive zygotes in synthetic oviduct fluid. In vivo blastocysts were used as a control from both species. In Experiment 1, the cleavage rate of bovine oocytes was significantly higher than that of ovine oocytes (78.3% vs. 58.0%, respectively, P < 0.001). The overall blastocyst yield was similar for both species (28.7% vs. 29.0%). However, when corrected for cleavage rate, significantly more ovine oocytes reached the blastocyst stage at all time-points (36.6% vs. 50.0% on day 8, for bovine and ovine, respectively, P < 0.001). Following vitrification, there was no difference in survival between in vivo produced bovine and ovine blastocysts (72 hr: 85.7% vs. 75.0%). However, IVP ovine blastocysts survived at significantly higher rates than IVP bovine blastocysts at all time points (72 hr: 47.4% vs. 18.1%, P < 0.001). At the ultrastructural level, compared with their in vivo counterparts, IVP blastocysts were characterized by a lack of desmosomal junctions, a reduction in the microvilli population, an increase in the average number of lipid droplets and increased debris in the perivitelline space and intercellular cavities. These differences were more marked in bovine IVP blastocysts, which also displayed electron-lucent mitochondria and large intercellular cavities. These observations may in part explain the species differences observed in terms of cryotolerance. In conclusion, the quality of ovine blastocysts was significantly higher than their bovine counterparts produced under identical in vitro conditions suggesting inherent species differences between these two groups affecting embryo quality.

Anatomical Studies of the Abscission Process in the Tomato Pedicels at Flowering Stage.

The abscission process in emasculated tomato flower pedicels was investigated anatomically. Six days after emasculation, cells in the epidermal tissue in the abscission zone initially enlarged ; two days later, cells in the cortical region enlarged. Ten days after emasculation, cell enlargement spread toward the vascular bundles and then to the inner cortical parenchymatous region and to the pith. Finally, the enlarged cells separated from each other and formed large intercellular cavities ; the unpollinated flower abscised along this line from its weight 14 days after emasculation.

Structural Changes in the Abscission Zones of Pedicels at Different Ripening Stages of Tomato.

Structural changes in abscission zones on tomato pedicels were anatomically and histochemically investigated. One week after the onset of the fully ripe stage of fruit development, cells of the xylem parenchymatous region in the primary abscission zone which formed at the flower bud stage elongated longitudinally more than those of the adjacent cells. Ten days later, the elongated cells formed in the primary abscission zone, but their walls hydrolyzed in two weeks, leaving large intercellular cavities. Fruit abscission then occurred. Simultaneously, cells became lignified in the secondary cell division zone, on the proximal side of the abscission zone. No further development occurred until the fruit abscised. These results indicate that the primary abscission zone acts as the separation layer, whereas the lignified secondary cells act as the protective layer.

Technical approaches to inoculate micropropagated sugar cane plants were Acetobacter diazotrophicus

Micropropagated plantlets of sugar cane were inoculated with the N2-fixing bacterium Acetobacter diazotrophicus. Various modifications on the basic plant culture medium MS were made for the plant/bacteria association. The protocol required the inoculation of the bacteria at the end of the rooting period in a medium without hormones or vitamins, and with the concentration of sugar and mineral nutrients reduced by a factor of 10. Individual plants were inoculated with A. diazotrophicus and maintained under the appropriate light and temperature condition used for micropropagation up to 7 days. The system favored the infection and the establishment of the bacteria within the plant tissue. Bacteria colonized the plant tissue and accumulated in inter-cellular cavities and the region of lateral root emergence and also colonizes the xylem vessels. The inoculated plantlets were subsequently transferred to the acclimatization phase and after 30 days it was possible to isolate the bacteria from plant tissue. This protocol permitted studies of infection and comparison among strains.