An ultrastructural study of abscission zone cells with special reference to the mechanism of enzyme secretion

Summary The ultrastructural changes which occur during the foliar abscission ofImpatiens sultani Hook. andColeus blumei Benth. have been described. In both cases fracture of the separation zone results from a modification of the wall and cleavage along the line of the middle lamella. This process starts at the corners of the cells and in regions rich in plasmodesmata.During the period of wall breakdown, cellular integrity is maintained and the membrane degradation described by others was not observed. Plasmolysis studies confirmed that the separation zone cells retained their selective permeability characteristics until well after wall fracture. Quantitative data are presented to show that there is an increase in the frequency of rough endoplasmic reticulum, dictyosomes and dictyosome vesicles during the period when wall-hydrolyzing enzyme secretion is occurring. These changes are interpreted as reflecting an increase in demand for the secretory machinery of the endomembrane system. The possible involvement of plasmodesmata in this process is also discussed.     

Comparative analysis of the secretion capability of early and late flagellar type III secretion substrates

A remarkable feature of the flagellar‐specific type III secretion system (T3SS) is the selective recognition of a few substrate proteins among the many thousand cytoplasmic proteins. Secretion substrates are divided into two specificity classes: early substrates secreted for hook‐basal body (HBB) construction and late substrates secreted after HBB completion. Secretion was reported to require a disordered N‐terminal secretion signal, mRNA secretion signals within the 5′‐untranslated region (5′‐UTR) and for late substrates, piloting proteins known as the T3S chaperones. Here, we utilized translational β‐lactamase fusions to probe the secretion efficacy of the N‐terminal secretion signal of fourteen secreted flagellar substrates in Salmonella enterica. We observed a surprising variety in secretion capability between flagellar proteins of the same secretory class. The peptide secretion signals of the early‐type substrates FlgD, FlgF, FlgE and the late‐type substrate FlgL were analysed in detail. Analysing the role of the 5′‐UTR in secretion of flgB and flgE revealed that the native 5′‐UTR substantially enhanced protein translation and secretion. Based on our data, we propose a multicomponent signal that drives secretion via the flagellar T3SS. Both mRNA and peptide signals are recognized by the export apparatus and together with substrate‐specific chaperones allowing for targeted secretion of flagellar substrates.     

Comparative ultrastructural analysis of diestrous and anestrous canine Grade 1 cumulus-oocyte complexes

The objective of the present study was to characterize, by means of transmission electron microscopy, immature Grade 1 cumulus-oocyte complexes (COCs) obtained from ovaries collected from bitches at diestrus and anestrus, after routine ovariohysterectomy. Cumulus-oocyte complexes were recovered after slicing the ovarian cortex and Grade 1 COCs were selected and prepared for transmission electron microscopy. All oocytes were at germinal vesicle stage in two different configurations. In 29 out of 37 COCs, oocytes presented a central or eccentric located nucleus (GVc), frequently containing a reticulated nucleolus, with a predominance of profound follicular cell processes (FCP), abundant endoplasmic reticulum (ER) and a moderated number of lipid droplets. In eight out of 37 COCs, oocytes had a peripheral located nucleus (GVp) containing small compact nucleolus, a thin perivitelline space, both superficial and profound FCP, moderate ER content and abundant lipid droplets. A higher (p<0.05) proportion of GVp was found in oocytes collected in diestrus (36.8% - 7 out of 19) than in anestrus (5.6% - 1 out of 18). In addition, distinct ultrastructure characteristics among GVc associated with estrous phase were noted. Furthermore, a number of structures, some of which had not been reported before, were present in canine prophase I oocytes at variable frequencies. The evident variation in the presence, quantity and distribution of cell organelles in canine immature Grade 1 oocytes is discussed in relation to the biological phase of the oocyte and the reproductive stage of the donor bitch.     

Comparative analysis of peripheral and localised cytokine secretion in glioblastoma patients

BACKGROUND: Malignant gliomas are the most common primary brain tumours of both children and adults. The unique aspects of their biology and anatomic site render them refractory to conventional therapeutic strategies such as surgery and chemotherapy. Significant attention has been given, recently, to immunotherapy which, although promising in preclinical studies, has not yet enhanced the survival of patients with glioblastomas. METHODS: To further understand the immunobiology of glioblastomas in clinical settings, we examined the secretion of four main cytokines in the peripheral blood and in primary cell cultures of 33 human glioblastoma patients. An ELISPOT methodology was used for the first time to examine Th1, and Th2 cytokine secretion from both peripheral lymphocytes and glioma tumour cells. RESULTS: Th1 cytokines (tumour necrosis factor (TNF-alpha), interferon (IFN-gamma) were markedly reduced compared to control levels (P=0.01 and P<0.001, respectively), whereas in contrast, Th2 (interleukin (IL)-4 and IL-10) were strongly expressed in both peripheral lymphocytes and glioma cell cultures (P=0.05 and P<0.001, respectively). CONCLUSION: This pattern indicates an 'immunosuppressive status' in glioblastomas which is related to their origination and the evasion of glioma cells from immune surveillance and could account for the failure of immunotherapy in such tumours. Furthermore, ELISPOT methodology can be used for monitoring of cytokine secretion from tumour cells, in addition to the well-established peripheral cytokine secretion.     

Comparative ultrastructural topography of the gut epithelia of some trematodes

The gut epithelia of six species of digenetic trematodes, Clonorchis sinensis, Eurytrema pancreaticum, Haematoloechus lobatus, Echinostoma hortense, Schistosoma japonicum and Fasciola hepatica, were studied with scanning and also transmission electron microscopy. Morphological differences in cytoplasmic projections of the gut of adult flukes were demonstrated stereoscopically among these species. The cytoplasmic projections vary considerably in shape, but are roughly separated into three groups by their essential forms: ribbon-shaped narrow type in C. sinensis and E. pancreaticum, broad, triangular with filamentous extensions distally and/or marginally as in F. hepatica and E. hortense, and broad, sheet-like or triangular with the distal ends blunt or rounded as in H. lobatus and S. japonicum. This character appears rather constant, without regional differences in the gut. No marked correlation was found between the gut projections of the parasites and their host or food. There are also specific discriminations in the ultrastructure of the cellular organization among the species examined.     

Comparative mitochondrial genome analysis reveals the evolutionary rearrangement mechanism in Brassica

The genus Brassica has many species that are important for oil, vegetable and other food products. Three mitochondrial genome types (mitotype) originated from its common ancestor. In this paper, a B. nigra mitochondrial main circle genome with 232,407 bp was generated through de novo assembly. Synteny analysis showed that the mitochondrial genomes of B. rapa and B. oleracea had a better syntenic relationship than B. nigra. Principal components analysis and development of a phylogenetic tree indicated maternal ancestors of three allotetraploid species in Us triangle of Brassica. Diversified mitotypes were found in allotetraploid B. napus, in which napus‐type B. napus was derived from B. oleracea, while polima‐type B. napus was inherited from B. rapa. In addition, the mitochondrial genome of napus‐type B. napus was closer to botrytis‐type than capitata‐type B. oleracea. The sub‐stoichiometric shifting of several mitochondrial genes suggested that mitochondrial genome rearrangement underwent evolutionary selection during domestication and/or plant breeding. Our findings clarify the role of diploid species in the maternal origin of allotetraploid species in Brassica and suggest the possibility of breeding selection of the mitochondrial genome.     

Osteogenesis imperfecta. Human, dog, cat, fox. Comparative analysis of the ultrastructural aspects

In the present work the authors have observed the ultrastructure of different types of cartilage and connective tissues of four different species of animals affected with osteogenesis imperfecta (man dog cat and young fox. The ultrastructural pictures demonstrate that the morphological aspects of cartilage of different species are often comparable and all cartilage tissues present the following characters: 1) Some lipid droplets inside the cytoplasm. 2) A reduction of the number and diameter of collagen fibrils. 3) A sensible increase of diameter of the alcianophilic bands that are ultrastructural representation of glycosaminoglycans. Some abnormal aspect has been seen on the connective non cartilagineus tissues.     

Comparative ultrastructural study of four reticuloendothelias viruses.

The morphology and development of four members of the reticuloendotheliosis virus group were studied by transmission electron microscopy. Virions of duck spleen necrosis virus, duck infectious anemia virus, chicken syncytial virus, and reticuloendotheliosis virus strain T are sperical with a diameter of approximately 110 nm. They are covered with surface projections about 6 nm long and 10 nm in diameter. The center-to-center distance of surface projections is about 14 nm. The budding virions contain crescent-shaped electron-dense cores 73 nm in diameter with electron-lucent centers. After release of the virions the cores apparently become condensed to 67 nm in diameter. Virions were found budding at the plasma membrane and into smooth-walled, intracytoplasmic vesicles of productively infected cells. The distribution of budding reticuloendotheliosis viruses on cells appeared random over the cell surface, and occasionally aberrant multiple forms of budding virions were observed. The virions appear to resemble mammalian leukemia and sarcoma viruses more closely than avian leukosis-sarcoma viruses.     

Comparative analysis of the mechanism of metabolism of storage compounds in the cell clock

The effect of the autooscillation period Td of various kinetic mechanisms for D in equilibrium with S exchange (D storage form of the compound S) was theoretically studied in a system of the D in equilibrium with S in equilibrium with G1 type, where G = S in equilibrium with G1 is a relaxation autooscillator. The kinetics studied were linear, hyperbolic and cooperative. With a rapid D in equilibrium S exchange all the three kinetic mechanisms were shown to yield approximately equal values of Td. However, they greatly differ in energy losses for stray substrate recirculations in the D in equilibrium S cycle: the least losses were in the case of the cooperative kinetics and the greatest in that of the linear mechanism, while the hyperbolic mechanism yielded intermediate values. The results obtained hold for any energy-dependent mechanisms of D in equilibrium S synthesis and are independent of the specific pattern of the oscillator G.     

Comparative MD analysis of the stability of transthyretin providing insight into the fibrillation mechanism

Proteins can misfold and aggregate, which is believed to be the cause of a variety of diseases, affecting very diverse organs in the body. Many questions about the nature of aggregation and the proteins that are involved in these events are still left unanswered. One of the proteins that is known to form amyloids is transthyretin (TTR), the secondary transporter of thyroxine, and transporter of retinol-binding protein. Several experimental results have helped to explain this aberrant behavior of TTR; however, structural insights of the amyloidgenic process are still lacking. Therefore, we have used all-atom MD simulation and free energy calculations to study the initial phase of this process. We have calculated the free energy changes of the initial tetramer dissociation under different conditions and in the presence of thyroxine. We show that tetramer formation is indeed only thermodynamically favorable in neutral pH conditions. We find that binding of two thyroxine molecules stabilizes the complex, and that this occurs with negative cooperativity. In addition to the energetic calculations, we have also investigated the dominant motions of the TTR and found that only the dimeric form of the protein could undergo the initial fibril formation.     

Cephalic secretion release in the male dwarf spider Oedothorax retusus (Linyphiidae: Erigoninae): An ultrastructural analysis

Secondary sexual traits in males can extend to glandular structures that play a role during courtship and mating. In dwarf spiders (Linyphiidae, Erigoninae), glandular secondary sexual traits are particularly common. Males are characterized by cephalic modifications which produce secretions that females contact with their mouthparts during courtship and/or copulation. We used the dwarf spider Oedothorax retusus as a model species to investigate if and when the contents of the glands are released during a mating sequence and if so, if the gland reservoirs are refilled after mating. To this aim, we quantitatively compared the glandular tissue on the ultrastructural level between a) inexperienced males, b) males that performed courtship, c) males immediately after copulation, and d) males three days after mating. We assessed whether the treatment groups differed in the filling state of the conducting canals and receiving canals (reservoir regions) of the glandular units. Our study shows that courting males as well as males three days after mating did not differ significantly from control (inexperienced) males in the presence of secretions. However, males exhibited significantly less secretion immediately after mating. This strongly suggests that the main function of the secretions is gustatorial courtship and not the emission of volatile pheromones for mate attraction as was previously assumed.     

Comparative ultrastructural morphometrical studies in acute leukemia.

Four hundred paramyeloblasts (from meyloblastic, promyelocytic, monoblastic and lymphoblastic types), isolated from peripheral blood of untreated leukemia patients, were studied by planimetric ultrastructural morphometry. The data of 19 parameters for these four paramyeloblastic types were compared with statistical methods. More central "scattered" heterochromatin was found from this morphometric investigation, i.e. early prophases in the lymphoblastic type of acute leukemia (these cases are more sensitive to therapy). The absolute mean values of the areas of whole cells, areas of the nucleus and nucleolus, areas of the heterochromatin and other indices show that different cell clones will undergo leukaemic transformation.     

菜蛾盘绒茧蜂畸形细胞蛋白质的合成和分泌及细胞超微结构的变化

菜蛾盘绒茧蜂 Cotesia vestalis (Haliday)是小菜蛾的重要幼虫内寄生蜂,该蜂在胚胎发育过程中由浆膜产生畸形细胞,随蜂卵孵化,释放到寄主小菜蛾的血腔中.本文运用蛋白质双向电泳技术、电子显微技术和体外培养技术对菜蛾彘绒茧蜂畸形细胞的蛋白质的合成和分泌以及细胞超微形态结构的变化进行了研究.蛋白质双向电泳图谱显示,该细胞内蛋白合成种类极为丰富,尤以分子量40.98～94.64 kDa的蛋白种类最多.但在寄生后期,畸形细胞的合成能力下降.超微形态结构发生显著变化表现在胞内细胞器数量减少,出现大量空腔,细胞表而微绒毛联合、变大,内容物外倾.随着蜂幼虫的啮出,有些细胞经历分解过程.体外培养证实,成熟畸形细胞可向培养介质中释放脂溶性物质.此外,在不同饲养温度条件下,畸形细胞伴随蜂幼虫的发育,表现为随温度升高,发育加快的趋势,表明畸形细胞的生长趋势与寄生蜂幼虫发育具有同步性.     

Quantitative ultrastructural analysis of barley sperm

Summary Complete serial ultrathin sections of seven sperm pairs, computer-assisted measurements of cell, nuclear and organelle surface areas and volumes, and three-dimensional imagery were used to demonstrate that a process of cytoplasm and organelle elimination occurs during sperm maturation in barley. The number of mitochondria per sperm cell is reduced by 50%; sperm cell surface area and volume are reduced by 30% and 51% respectively. Mean volume and surface area per mitochondrion are significantly less in mature sperms. No examples of mitochondrial fusion or degeneration were observed within sperm cells. These data, along with observations of plasma membrane apposition and vesiculation within cytoplasmic extensions containing mitochondria, support the proposition that cytoplasm and organelle loss results primarily from the formation of cytoplasmic projections that are subsequently discarded from the sperm cell body. Comparisons of the quantitative data, including the number of mitochondria, indicate that differences between sperm cells of a pair are absent to very slight. Spatial organization within the pollen grain is such that the mature sperms, as well as the sperms and vegetative nucleus, are not in close proximity.