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C Cells (c + cell)
Selected AbstractsAbundance and production of bacteria, and relationship to phytoplankton production, in a large tropical lake (Lake Tanganyika)FRESHWATER BIOLOGY, Issue 6 2009STEPHANE STENUITE Summary 1. Abundance and bacterial production (BP) of heterotrophic bacteria (HBact) were measured in the north and south basins of Lake Tanganyika, East Africa, during seasonal sampling series between 2002 and 2007. The major objective of the study was to assess whether BP can supplement phytoplankton particulate primary production (particulate PP) in the pelagic waters, and whether BP and particulate PP are related in this large lake. HBact were enumerated in the 0,100 m surface layer by epifluorescence microscopy and flow cytometry; BP was quantified using 3H-thymidine incorporation, usually in three mixolimnion layers (0,40, 40,60 and 60,100 m). 2. Flow cytometry allowed three subpopulations to be distinguished: low nucleic acid content bacteria (LNA), high nucleic acid content bacteria (HNA) and Synechococcus -like picocyanobacteria (PCya). The proportion of HNA was on average 67% of total bacterial abundance, and tended to increase with depth. HBact abundance was between 1.2 × 105 and 4.8 × 106 cells mL,1, and was maximal in the 0,40 m layer (i.e. roughly, the euphotic layer). Using a single conversion factor of 15 fg C cell,1, estimated from biovolume measurements, average HBact biomass (integrated over a 100-m water column depth) was 1.89 ± 1.05 g C m,2. 3. Significant differences in BP appeared between seasons, especially in the south basin. The range of BP integrated over the 0,100 m layer was 93,735 mg C m,2 day,1, and overlapped with the range of particulate PP (150,1687 mg C m,2 day,1) measured in the same period of time at the same sites. 4. Depth-integrated BP was significantly correlated to particulate PP and chlorophyll- a, and BP in the euphotic layer was on average 25% of PP. 5. These results suggest that HBact contribute substantially to the particulate organic carbon available to consumers in Lake Tanganyika, and that BP may be sustained by phytoplankton-derived organic carbon in the pelagic waters. [source] The balance between photosynthesis and grazing in Antarctic mixotrophic cryptophytes during summerFRESHWATER BIOLOGY, Issue 11 2002William Marshall SUMMARY 1. Grazing and photosynthetic contributions to the carbon balance of planktonic, mixotrophic cryptophytes in Lakes Fryxell and Hoare in the Taylor Valley, Antarctica were measured during November and December 2000. 2. The cryptophytes never became entirely photosynthetic, although carbon derived from grazing decreased in December. Individual grazing rates ranged between 5.28 and 10.08 bacteria cell,1 day,1 in Lake Fryxell and 0.36,11.76 bacteria cell,1 day,1 in Lake Hoare. Grazing rates varied temporally and with depth in the water column. In Lake Fryxell, which is a meromictic lake, highest grazing occurred just above the chemocline. Individual photosynthetic rates ranged from 0.23 to 1.35 pg C cell,1 h,1 in Lake Fryxell and 0.074 to 1.08 pg C cell,1 h,1 in Lake Hoare. 3. Carbon acquisition by the cryptophyte community gained through grazing ranged between 8 and 31% during November in Lake Fryxell, dropping to between 2 and 24% in December. In Lake Hoare grazing contributed 12,21% of the community carbon budget in November and 1,28% in December. Around 4% of the carbon acquired from grazing and photosynthesis was remineralised through respiration. 4. Mixotrophy is probably a major survival strategy for cryptophytes in the extreme lakes of the Dry Valleys, because perennial ice-cover severely limits light penetration to the water column, whereas these phytoflagellates are not normally mixotrophic in lower latitude lakes. The evidence suggests that mixotrophy may be a mechanism for supplementing the carbon budget, as well as a means of acquiring nutrients for growth. [source] FATTY ACIDS IN PHOTOTROPHIC AND MIXOTROPHIC GYRODINIUM GALATHE-ANUM (DINOPHYCEAE)JOURNAL OF PHYCOLOGY, Issue 2000J.E. Adolf Fatty acids were measured in G. galatheanum grown either phototrophically, or mixotrophically with Storeatula major (Cryptophyceae) as prey. G. galatheanum, like many photosynthetic dinoflagellates, contains high amounts of n-3 long-chain-polyunsaturated fatty acids (LC-PUFA) such as docosahexaenoic acid (DHA, 22:6n-3) and the hemolytic toxic fatty acid 18:5n-3. We hypothesize that a benefit of phagotrophy in G. galatheanum is the acquisition of precursor linolenic acid (18:3n-3) that fuels LC-PUFA synthesis. Phototrophs grew at 0.37 d,1, while mixotrophs grew at 0.40 d,1 with a feeding rate of 0.62 d,1. Photosynthesis was lower in mixotrophs (3.7 pg C cell,1 h,1) than phototrophs (4.9 pg C cell,1 h,1). DHA levels were higher in mixotrophs [3.7 (+/, 0.11) pg cell,1] than phototrophs [3.0 (+/, 0.16) pg cell,1] and prey [0.4 (+/, 0.01) pg cell,1]. 18:5n,3 levels [1.7 (+/, 0.03) pg cell,1] were similar in phototrophs and mixotrophs. An intermediate in n-3 LC-PUFA synthesis, 20:4n-3, accumulated in mixotrophs [0.6 (+/, 0.27) pg cell,1] relative to phototrophs (not detected) and prey [0.03 (+/, 0.002) pg cell,1]. Low ratios of linolenic acid to DHA in phototrophic G. galatheanum (0.14) relative to mixotrophic G. galatheanum (0.29) and prey (2.14) are consistent with substrate limitation of LC-PUFA synthesis in phototrophs. Accumulation of 20:4n-3 suggests incomplete conversion of linolenic acid to DHA, possibly due to conditions in batch culture. We conclude that precursors for n-3 LC-PUFA biosynthesis in G. galatheanum may be acquired through ingestion of S. major, and may partially control feeding/photosynthesis in mixotrophic populations. [source] Ecological implications of biomass and morphotype variations of bacterioplankton: an example in a coastal zone of the Northern Adriatic Sea (Mediterranean)MARINE ECOLOGY, Issue 2 2005Rosabruna La Ferla Abstract This study had the objective of quantifying the variability in abundance, cell volume, morphology and C content of a natural bacterioplankton community in a coastal zone of the North Adriatic Sea during two periods (February and June) of two consequent years (1996 and 1997). We used epifluorescence microscopy with Acridine Orange staining procedures and a microphotographic technique. Low variability in bacterial abundance (range 0.3,3.1 × 105 cells ml,1) occurred between summer and winter periods. Conversely, the cell volume and the calculated carbon content changed greatly with warm and cold periods (ranges: 0.015,0.303 ,m3 and 5.83,42.17 fg C cell,1, respectively). Elongated bacteria were dominant while coccoid cells prevailed only in February 1997. Biomass showed high variability (range 0.12,10.21 ,g C l,1) whilst the abundance did not show noticeable differences among the sampling periods. As a consequence, quantification of bacterial biomass based solely on cell abundance must be considered with caution because the true biomass could depend on variability in cell volumes and morphotypes. [source] Immunohistochemical analysis of thyroid-specific transcription factors in thyroid tumorsPATHOLOGY INTERNATIONAL, Issue 5 2006Ping Zhang Thyroid transcription factor 1 (TTF1), thyroid transcription factor 2 (TTF2) and paired box gene 8 (Pax8) are demonstrated to play a crucial role for the differentiation and organogenesis of thyroid follicular cells. Their roles in thyroid carcinogenesis are not very clear. Because dedifferentiation is a common process in thyroid carcinogenesis, thyroid-specific transcription factors seem also to be involving in thyroid carcinogenesis. The purpose of the present paper was to investigate their expression in a broad spectrum of follicular cell tumors in different degrees of differentiation, from well-differentiated benign follicular adenoma to anaplastic carcinoma. Medullary (C cell) carcinoma was also included in the investigation. Results of immunohistochemical staining showed that nuclear localization of these transcription factors was gradually decreased corresponding to the progressive dedifferentiation of thyroid tumors. Also, abnormal cytoplasmic accumulation of TTF2 and Pax8 was detected in many tumors samples, which may indicate a subtle regulation mechanism on the function of these transcription factors. In conclusion, abnormal expression of TTF1, TTF2 and Pax8 was closely related to thyroid tumorigenesis. [source] Ultrastructural and antigenic properties of neural stem cells and their progeny in adult rat subventricular zoneGLIA, Issue 2 2009Alexandre I. Danilov Abstract Neural stem cells (NSCs) in the subventricular zone (SVZ) continuously generate olfactory bulb interneurons in the adult rodent brain. Based on their ultrastructural and antigenic properties, NSCs, transient amplifying precursor cells, and neuroblasts (B, C, and A cells, respectively) have been distinguished in mouse SVZ. Here, we aimed to identify these cell types in rat SVZ ultrastructurally and at the light microscopy level, and to determine the antigenic properties of each cell type using gold and fluorescence immunolabeling. We found astrocytes with single cilia (NSCs, correspond to B cells) and neuroblasts (A cells). We also observed mitotic cells, ependymal cells, displaced ependymal cells, and mature astrocytes. In contrast, transient amplifying precursor cells (C cells) were not detected. The NSCs and neuroblasts had epidermal growth factor receptor (EGFR) and platelet-derived growth factor receptor alpha (PDGFR,) expressed on the ciliary apparatus and were the only cell types incorporating the proliferation marker BrdU. Throughout mitosis, EGFR and PDGFR, were associated with the microtubule of the mitotic spindle. Ependymal and displaced ependymal cells also expressed EGFR and PDGFR, on their cilia but did not incorporate BrdU. Our findings indicate that the NSCs in adult rat SVZ give rise directly to neuroblasts. During mitosis, the NSCs disassemble the primary cilium and symmetrically distribute EGFR and PDGFR, among their progeny. © 2008 Wiley-Liss, Inc. [source] A Dominant Negative Cadherin Inhibits Osteoblast Differentiation,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 12 2000Su-Li Cheng Abstract We have previously indicated that human osteoblasts express a repertoire of cadherins and that perturbation of cadherin-mediated cell-cell interaction reduces bone morphogenetic protein 2 (BMP-2) stimulation of alkaline phosphatase activity. To test whether inhibition of cadherin function interferes with osteoblast function, we expressed a truncated N-cadherin mutant (NCad,C) with dominant negative action in MC3T3-E1 osteoblastic cells. In stably transfected clones, calcium-dependent cell-cell adhesion was decreased by 50%. Analysis of matrix protein expression during a 4-week culture period revealed that bone sialoprotein, osteocalcin, and type I collagen were substantially inhibited with time in culture, whereas osteopontin transiently increased. Basal alkaline phosphatase activity declined in cells expressing NCad,C, relative to control cells, after 3 weeks in culture, and their cell proliferation rate was reduced moderately (17%). Finally,45Ca uptake, an index of matrix mineralization, was decreased by 35% in NCad,C-expressing cells compared with control cultures after 4 weeks in medium containing ascorbic acid and ,-glycerophosphate. Similarly, BMP-2 stimulation of alkaline phosphatase activity and bone sialoprotein and osteopontin expression also were curtailed in NCad,C cells. Therefore, expression of dominant negative cadherin results in decreased cell-cell adhesion associated with altered bone matrix protein expression and decreased matrix mineralization. Cadherin-mediated cell-cell adhesion is involved in regulating the function of bone-forming cells. [source] Potentiation of PGE2 -mediated cAMP production during neuronal differentiation of human neuroblastoma SK-N-BE(2)C cellsJOURNAL OF NEUROCHEMISTRY, Issue 2 2001Se-Young Choi The prostaglandin-evoked cAMP production was studied in human neuroblastoma SK-N-BE(2)C cells during neuronal differentiation induced by all- trans retinoic acid. The incubation with 5 µm all- trans retinoic acid for 4,6 days promoted neurite outgrowth of cells. After differentiation, prostaglandin E2 (PGE2)-induced cAMP production was dramatically increased, whereas forskolin- and AlF -induced cAMP productions were not changed. The increase reached maximum after 4-days of incubation with all- trans retinoic acid. The differentiation caused an increase in the maximal response and a decrease in the half-maximal effective concentration of the PGE2 -induced cAMP production. In addition, the binding of [3H]PGE2 to membrane receptors was enhanced in differentiated cells. However, the order of potency of the various prostaglandins (PGE1 = PGE2 > PGD2 = PGF2, = PGI2) in cAMP production did not change during the differentiation, suggesting that mainly E-prostanoid (EP) receptors were involved. Butaprost, an EP2 receptor specific agonist, increased the cAMP level in a concentration dependent manner and had a similar potentiating effect on cAMP production as PGE2 upon differentiation. Northern blot analysis using the human cDNA probes shows that the EP2 mRNA level was about seven times higher in differentiated cells, while the dopamine ,-hydroxylase (DBH) mRNA completely disappeared. Our results, thus, suggest that elevated gene expression of the prostanoid EP2 receptor results in an increase in the PGE2 -evoked cAMP production in SK-N-BE(2)C cells during neuronal differentiation. [source] Mitochondrial localization of DJ-1 leads to enhanced neuroprotectionJOURNAL OF NEUROSCIENCE RESEARCH, Issue 1 2009Eunsung Junn Abstract Mutations in DJ-1 (PARK7) cause recessively inherited Parkinson's disease. DJ-1 is a multifunctional protein with antioxidant and transcription modulatory activity. Its localization in cytoplasm, mitochondria, and nucleus is recognized, but the relevance of this subcellular compartmentalization to its cytoprotective activity is not fully understood. Here we report that under basal conditions DJ-1 is present mostly in the cytoplasm and to a lesser extent in mitochondria and nucleus of dopaminergic neuroblastoma SK-N-BE(2)C cells. Upon oxidant challenge, more DJ-1 translocates to mitochondria within 3 hr and subsequently to the nucleus by 12 hr. The predominant DJ-1 species in both mitochondria and nucleus is a dimer believed to be the functional form. Mutating cysteine 106, 53, or 46 had no impact on the translocation of DJ-1 to mitochondria. To study the relative neuroprotective activity of DJ-1 in mitochondria and nucleus, DJ-1 cDNA constructs fused to the appropriate localization signal were transfected into cells. Compared with 30% protection against oxidant-induced cell death in wild-type DJ-1-transfected cells, mitochondrial targeting of DJ-1 provided a significantly stronger (55%) cytoprotection based on lactate dehydrogenase release. Nuclear targeting of DJ-1 preserved cells equally as well as the wild-type protein. These observations suggest that the time frame for the translocation of DJ-1 from the cytoplasm to mitochondria and to the nucleus following oxidative stress is quite different and that dimerized DJ-1 in mitochondria is functional as an antioxidant not related to cysteine modification. These findings further highlight the multifaceted functions of DJ-1 as a cytoprotector in different cellular compartments. © 2008 Wiley-Liss, Inc. [source] Adult human spinal cord harbors neural precursor cells that generate neurons and glial cells in vitroJOURNAL OF NEUROSCIENCE RESEARCH, Issue 9 2008C. Dromard Abstract Adult human and rodent brains contain neural stem and progenitor cells, and the presence of neural stem cells in the adult rodent spinal cord has also been described. Here, using electron microscopy, expression of neural precursor cell markers, and cell culture, we investigated whether neural precursor cells are also present in adult human spinal cord. In well-preserved nonpathological post-mortem human adult spinal cord, nestin, Sox2, GFAP, CD15, Nkx6.1, and PSA-NCAM were found to be expressed heterogeneously by cells located around the central canal. Ultrastructural analysis revealed the existence of immature cells close to the ependymal cells, which display characteristics of type B and C cells found in the adult rodent brain subventricular region, which are considered to be stem and progenitor cells, respectively. Completely dissociated spinal cord cells reproducibly formed Sox2+ nestin+ neurospheres containing proliferative precursor cells. On differentiation, these generate glial cells and ,-aminobutyric acid (GABA)-ergic neurons. These results provide the first evidence for the existence in the adult human spinal cord of neural precursors with the potential to differentiate into neurons and glia. They represent a major interest for endogenous regeneration of spinal cord after trauma and in degenerative diseases. © 2008 Wiley-Liss, Inc. [source] Diagnostic and surgical dilemmas in hereditary medullary thyroid carcinomaTHE LARYNGOSCOPE, Issue 7 2009Shawn M. Allen MD Abstract Medullary thyroid carcinoma (MTC) is a rare malignancy arising from the parafollicular C cells within the thyroid gland. The majority of cases are sporadic, but at least 30% are hereditary in nature. Inherited forms of MTC occur as familial MTC or as a manifestation of multiple endocrine neoplasia type 2. Early diagnosis and aggressive surgical management, including prophylactic thyroidectomy, improve the prognosis of patients with hereditary MTC. Several issues regarding the diagnosis and treatment of MTC remain controversial. Genetic penetrance and virulence are variable. We present an index case of familial MTC to illustrate common difficulties in the initial diagnosis and dilemmas in the surgical approach, followed by a review of current literature relevant to the management of hereditary MTC. Laryngoscope, 2009 [source] Predictive value of pentagastrin test for preoperative differential diagnosis between C-cell hyperplasia and medullary thyroid carcinoma in patients with moderately elevated basal calcitonin levelsCLINICAL ENDOCRINOLOGY, Issue 1 2010F. Milone Summary Background and Objectives, Medullary thyroid carcinoma (MTC) is a calcitonin (CT)-secreting neuroendocrine tumour originating from thyroid C cells. Serum CT concentrations are helpful in the early detection of MTC, while it is still unclear whether they can be used also for the differential diagnosis between MTC and C-cell hyperplasia (CCH), a precancerous condition in familial MTCs but with unclear clinical significance in sporadic MTCs. Nowadays, surgery is recommended in all patients with basal or pentagastrin (PG)-stimulated CT value of 100 pg/ml or more, without discriminating if they are affected with MTC or CCH only. The objective of this study was to investigate the utility of the PG test for CT in distinguishing CCH from MTC before surgery. Patients and Methods, Sixteen of 20 patients with thyroid nodules and basal CT levels between 15 and 100 ng/l had a positive PG test (>100 ng/l PG CT peak) and form the basis of the data analysis. A diagnosis of MTC was histologically proved on surgical samples in seven patients and of CCH in nine other patients. Four patients with neither FNAB nor PG test consistent with a diagnosis of MTC did not undergo thyroidectomy. Results, A peak of CT of 275 ng/l after PG was able to significantly distinguish patients with MTC from patients with CCH, with 100% sensitivity and 89% specificity (P = 0·002). PG-stimulated calcitonin levels >275 ng/l had a positive predictive value (PPV) value for diagnosis of MTC of 100%, and PG-stimulated calcitonin levels <275 had a PPV for the diagnosis of CCH of 89%. Conclusions, A CT cut-off after PG of 275 ng/l is suggested to be highly predictive in distinguishing CCH from MTC before surgery, and this may be helpful in selecting patients for thyroid surgery. [source] | |||||||||||||||||||||||||