Role Of Cysts Research Articles

The GRA17 Parasitophorous Vacuole Membrane Permeability Pore Contributes to Bradyzoite Viability.

The Toxoplasma gondii parasitophorous vacuole membrane (PVM) offers protection from the host immune system but is also a barrier for uptake of nutrients from the host. Previously, we showed that GRA17 mediates the tachyzoite PVM permeability to small molecules. During the conversion from tachyzoites to encysted bradyzoites, the PVM become the cyst membrane that is the outer layer of the cyst wall. Little is known about how small molecules, such as nutrients, enter cysts. To characterize GRA17's role in cysts, we deleted GRA17 in the type II ME49 cyst-forming strain. ME49Δgra17 parasites have reduced growth and formed grossly enlarged “bubble vacuoles,” which have reduced PVM small molecule permeability. ME49Δgra17 parasites formed cysts in vitro at rates comparable to the wild-type, but the viability of the bradyzoites inside these cysts was significantly reduced compared to wild-type bradyzoites. Genetic complementation of ME49Δgra17 with GRA17 expressed from the endogenous or tachyzoite-specific SAG1 promoter recovered the viability of bradyzoites. Complementation with the bradyzoite-specific SRS9 promoter drastically increased the viability of bradyzoites, demonstrating the importance of GRA17 in regulating bradyzoite viability inside cysts. Mice infected with a high dose of ME49Δgra17 parasites did not contain parasites in their brain nor did mice infected with ME49Δgra17 complemented with GRA17 expressed from a bradyzoite-specific promoter. Our results suggest that the ME49Δgra17 strain is avirulent and is cleared before it can reach the brain and that GRA17 not only plays an important role during acute infections but is also needed for viability of bradyzoites inside cysts.

Mouse oocytes differentiate through organelle enrichment from sister cyst germ cells.

Oocytes differentiate in diverse species by receiving organelles and cytoplasm from sister germ cells while joined in germline cysts or syncytia. Mouse primordial germ cells form germline cysts, but the role of cysts in oogenesis is unknown. We find that mouse germ cells receive organelles from neighboring cyst cells and build a Balbiani body to become oocytes, whereas nurselike germ cells die. Organelle movement, Balbiani body formation, and oocyte fate determination are selectively blocked by low levels of microtubule-dependent transport inhibitors. Membrane breakdown within the cyst and an apoptosis-like process are associated with organelle transfer into the oocyte, events reminiscent of nurse cell dumping in Drosophila We propose that cytoplasmic and organelle transport plays an evolutionarily conserved and functionally important role in mammalian oocyte differentiation.

Functional differentiation of small heat shock proteins in diapause‐destined Artemia embryos

Encysted embryos of Artemia franciscana cease development and enter diapause, a state of metabolic suppression and enhanced stress tolerance. The development of diapause-destined Artemia embryos is characterized by the coordinated synthesis of the small heat shock proteins (sHsps) p26, ArHsp21 and ArHsp22, with the latter being stress inducible in adults. The amounts of sHsp mRNA and protein varied in Artemia cysts, suggesting transcriptional and translational regulation. By contrast to p26, knockdown of ArHsp21 by RNA interference had no effect on embryo development. ArHsp21 provided limited protection against stressors such as desiccation and freezing but not heat. ArHsp21 may have a non-essential or unidentified role in cysts. Injection of Artemia adults with amounts of ArHsp22 double-stranded RNA less than those used for other sHsps killed females and males, curtailing the analysis of ArHsp22 function in developing embryos and cysts. The results indicate that diapause-destined Artemia embryos synthesize varying amounts of sHsps as a result of differential gene expression and mRNA translation and also suggest that these sHsps have distinctive functions.

The clinical significance of biochemical failure in the first 2 years in patients treated with neo-adjuvant androgen deprivation and radiotherapy for prostate cancer

Lyme disease remains a controversial illness. The controversy is based on a profound disagreement over the existence of persistent infection with the Lyme spirochete, Borrelia burgdorferi, and the ability of this persistent infection to cause chronic symptoms in patients who are untreated or undertreated for the initial spirochetal disease. In this article, we summarize evidence from animal models, human studies and in vitro experiments that support persistent spirochetal infection as the cause of chronic Lyme disease. Specifically, the role of cysts and biofilms in this process is outlined, and the need for better treatment options for patients with chronic Lyme disease is defined.

MUC5AC in juvenile conjunctival nevus

To evaluate the possible role of cysts with mucins and inflammatory cells in rapid-growing juvenile conjunctival nevus. This was a case-control study at a university-based referral clinic. Seventeen conjunctival melanocytic lesions surgically excised from patients aged <20 years between 2001 and 2009 were examined by hematoxylin-eosin, periodic acid-Schiff, MUC5AC, and Alcian blue staining. The clinical signs of the affected patients and the histological findings were characterized. Eleven patients (3 girls and 8 boys; mean age 13.72 ± 3.60 years) underwent excision of a conjunctival nevus that had grown rapidly within a recent 6-month period. We found a significantly higher number of prominent cysts with mucins in the rapid-growing specimens than in the stable-growing control specimens (n = 6; 33.7 ± 19.9 vs. 0.9 ± 0.9%, P = 0.0005). However, the numbers of inflammatory cells were not statistically significantly different (42.17 ± 15.46 vs. 45.55 ± 16.31, P = 0.683). The period of rapid growth of juvenile conjunctival nevus is not a malignant clinical sign. Although it might correlate with enlarged cysts lined by goblet cells associated with mucin secretions, the number of inflammatory cells remains relatively stable over time.

Shell-bound iron dependant nitric oxide synthesis in encysted Artemia parthenogenetica embryos during hydrogen peroxide exposure

Artemia is a tiny marine crustacean, serves as an excellent tool in both basic and applied aspects of stress biology research. In the current manuscript, we report that Artemia parthenogenetica embryos (cysts), in diapause stage, undergo iron transition changes when exposed to chemical diapause deactivation stimulus (hydrogen peroxide). X-ray surface analysis of A. parthenogenetica embryos exposed to H(2)O(2) showed significant transitional changes in iron, as seen in cyst cross-sections. Electron paramagnetic resonance study revealed that upon H(2)O(2) exposure, increased nitric oxide (NO) production was observed in non-decapsulated cysts (ND), but not in decapsulated cysts (DC) (shell-removed cysts). Spin trapping studies also showed an increase in hydroxyl radical formation in NDs exposed to H(2)O(2) through Fenton-like reaction. On the contrary, exposure of DCs to H(2)O(2) did not induce hydroxyl radical formation. Taken together, results from the present study indicate a key role of cyst shell-bound iron and reactive oxygen species on successful diapause termination in eukaryotic extremophile animal model, such as Artemia.

Intact fetal ovarian cord formation promotes mouse oocyte survival and development

BackgroundFemale reproductive potential, or the ability to propagate life, is limited in mammals with the majority of oocytes lost before birth. In mice, surviving perinatal oocytes are enclosed in ovarian follicles for subsequent oocyte development and function in the adult. Before birth, fetal germ cells of both sexes develop in clusters, or germline cysts, in the undifferentiated gonad. Upon sex determination of the fetal gonad, germ cell cysts become organized into testicular or ovarian cord-like structures and begin to interact with gonadal somatic cells. Although germline cysts and testicular cords are required for spermatogenesis, the role of cyst and ovarian cord formation in mammalian oocyte development and female fertility has not been determined.ResultsHere, we examine whether intact fetal ovarian germ and somatic cell cord structures are required for oocyte development using mouse gonad re-aggregation and transplantation to disrupt gonadal organization. We observed that germ cells from disrupted female gonad prior to embryonic day e13.5 completed prophase I of meiosis but did not survive following transplantation. Furthermore, re-aggregated ovaries from e13.5 to e15.5 developed with a reduced number of oocytes. Oocyte loss occurred before follicle formation and was associated with an absence of ovarian cord structure and ovary disorganization. However, disrupted ovaries from e16.5 or later were resistant to the re-aggregation impairment and supported robust oocyte survival and development in follicles.ConclusionsThus, we demonstrate a critical window of oocyte development from e13.5 to e16.5 in the intact fetal mouse ovary, corresponding to the establishment of ovarian cord structure, which promotes oocyte interaction with neighboring ovarian somatic granulosa cells before birth and imparts oocytes with competence to survive and develop in follicles. Because germline cyst and ovarian cord structures are conserved in the human fetal ovary, the identification of genetic components and molecular mechanisms of pre-follicle stage germ and somatic cell structures may be important for understanding human female infertility. In addition, this work provides a foundation for development of a robust fetal ovarian niche and transplantation based system to direct stem cell-derived oocyte differentiation as a potential therapeutic strategy for the treatment of infertility.

Morphology and germination characteristics of the cysts of Chattonella ovata (Raphidophyceae), a novel red tide flagellate in the Seto Inland Sea, Japan

To elucidate the mechanism of bloom outbreaks of Chattonella ovata (Raphidophyceae), we investigated the cysts of C. ovata and succeeded in finding them from the bottom sediments of Hiroshima Bay. The morphology of the cysts was mostly hemispherical in shape, with a diameter of ca. 30 μm and height of ca. 20 μm. The cysts were usually adhering to solid materials, such as diatom frustules, yellow-greenish in color and had several dark brown grains. The cyst wall was smooth and had no ornamentation. Because the morphological characteristic of the cysts was in general agreement with those of Chattonella antiqua and Chattonella marina, it was difficult to differentiate the cysts of these three species. Germination of the cysts of C. ovata was observed at temperatures from 17.5 to 30 °C, but not at 15 °C or below. The number of the germinated cysts increased with increasing temperature and the optimum temperature for germination was 30 °C. Although cysts of C. antiqua and C. marina germinated at temperatures from 15 to 30 °C, optimum temperature of germination was 22.5 °C. The lower limit and optimum temperatures for germination of C. ovata cysts was higher than for C. antiqua and C. marina. The role of cysts in the population dynamics of C. ovata is discussed.

Acanthamoeba isolates belonging to T1, T2, T3, T4 but not T7 encyst in response to increased osmolarity and cysts do not bind to human corneal epithelial cells

Acanthamoeba is an opportunistic protozoan that is widely distributed in the environment and can cause human infections. The life cycle of Acanthamoeba consists of an infective trophozoite form. However under harsh environmental conditions trophozoites differentiate into a double-walled, metabolically inactive and resistant cyst form. Research in Acanthamoeba has mostly focussed on the infective trophozoite form and its pathogenic mechanisms. In this study, we used Acanthamoeba isolates belonging to T1, T2, T3, T4, T7 genotypes and studied their cysts properties. We determined that food deprivation stimulates encystment in Acanthamoeba isolates belonging to T1, T2, T3, T4 and T7 genotypes in a sodium dodecyl sulfate (SDS)-resistant manner. In addition, increase in osmolarity triggered encystment in T1, T2, T3, T4 isolates (SDS-resistant) but T7 failed to encyst (SDS-labile). Adhesion assays revealed that Acanthamoeba cysts belonging to T1, T2, T3, T4, and T7 genotypes exhibited no and/or minimal binding (<5%) to the host cells. Fluorescein-labelled lectins showed that all Acanthamoeba isolates tested exhibited binding to concanavalin A, indicating the expression of mannosyl- and/or glucosyl-residues. Role of cysts in the transmission of infection is discussed further.

Bloom dynamics of toxic Alexandrium species in the northeastern U.S

Coastal waters of the northeastern U.S. are subject to recurrent outbreaks of paralytic shellfish poisoning (PSP) caused by toxic dinoflagellates in the genus Alexandrium. PSP is not uniform across the large region, but instead reflects Alexandrium growth and toxin accumulation in five separate habitats or zones defined by circulation patterns and the discontinuous distribution of the dinoflagellates. Each of these habitats has a unique set of environmental and oceanographic forcings that determine the timing and extent of bloom development and transport and that regulate the extent of genetic exchange with adjacent populations. Several habitats (e.g. the southwestern Gulf of Maine, Massachusetts Bay, and Georges Bank) are linked hydrographically and may share the same Alexandrium population via large‐scale transport in a. coastal current, whereas the other two habitats (eastern Maine and southern salt ponds‐embayments) seem to be isolated and have little or no hydrographic or genetic linkage to adjacent regions during bloom seasons. My paper provides an overview of the regional ecology and oceanography of Alexandrium through a focus on these five subpopulations. Issues that relate to PSP and Alexandrium dynamics throughout the world are highlighted, including species dispersal, the role of cysts and “initiation zones” in bloom development, and the influence of large‐ and small‐scale hydrography on population development and transport. The ability of Alexandrium to colonize multiple habitats and to persist over a large region is emphasized in recognition of the adaptability and resilience of this important organism.

The role of cysts on population dynamics of Scrippsiella spp. (Dinophyceae) in Onagawa Bay, northeast Japan

The seasonal behavior of both vegetative cells and cysts of dinophytes Scrippsiella spp., mostly S. trochoidea, which is the dominant group among dinoflagellate populations in Onagawa Bay on the northeastern coast of Honshu, Japan, was investigated between 1990 and 1992. The germination of the cysts after 8 d incubation under favorable laboratory conditions was examined using the extinction dilution method. Incessant germination occurred throughout the year, but the germination ratio (no. of germinable cysts/total cysts) varied seasonally with a marked fluctuation during summer when vegetative cells in the water column were abundant. Although such fluctuation largely reflects the variable flux of newly deposited immature cysts produced by the vegetative cells, the regulation of germination caused by a lowered saturation of dissolved oxygen (DO) under thermally stratified conditions was also suggested. During winter, while the cysts germinated in the laboratory, vegetative cells were not found in the water column. These facts suggest that germination in situ is regulated by low temperature in winter and possibly by lowered DO and by cyst age as well in summer. Such regulation prevents simultaneous germination of all the cysts, which is disadvantageous for the population because it would be more difficult to survive adverse conditions such as successive nutrient depletion and higher grazing risk.