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Results for “Morphological Characterization”

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PubMed2000

Phenotypic profiles of cultured glomerular cells following repeated cycles of hydrocarbon injury.

BACKGROUND: The glomerulus has been implicated as a target of hydrocarbon injury in vitro and in vivo. In the present studies, the phenotypic profiles of cultured rat glomerular cells (GCs) following repeated cycles of hydrocarbon injury were evaluated. Cultured GCs were incubated for 24 hours with benzo[a]pyrene (BaP; 3 micromol/L), a prototypical polycyclic aromatic hydrocarbon, and were allowed to recover overnight before two additional cycles of chemical challenge during serial propagation in vitro. At the end of this regimen, control cultures were characterized by predominance of fusiform cells that grew in "hills and valleys," while GCs subjected to hydrocarbon injury displayed an epithelial morphology characterized by a rounded, polygonal shape clearly distinct from that normally exhibited by glomerular mesangial cells (GMCs) in culture. METHODS: Indirect immunofluorescent detection of cell markers was conducted to identify cells of mesenchymal or epithelial origin. Measurements of DNA synthesis and cell number were performed to determine proliferative capacities of the different cell types in response to hydrocarbon challenge. RESULTS: Immunofluorescence studies revealed that control GC cultures contained mostly alpha-smooth muscle (SM) actin-positive cells, with a few (5.1% +/- 2.6) E-cadherin-positive cells occasionally identified. In contrast, BaP-treated cultures exhibited a mixed cell population in which E-cadherin-positive cells were predominant (66.6% +/- 4.1). Single-cell cloning of naive cultures of GCs yielded four clones, three of which exhibited a fusiform morphology and were alpha-SM actin positive (SCC 1 through SCC 3) and one (SCC 4E) that exhibited epithelial characteristics similar to those found in hydrocarbon-treated cultures. Immunofluorescence studies showed that epithelial cells in hydrocarbon-treated cultures, as well as SCC 4E-derived clones, were vimentin positive and cytokeratin negative, characteristics similar to glomerular visceral epithelial cells (GVECs). DNA synthesis and cell proliferation in clone SCC 1 were decreased following acute BaP challenge, while growth rates in SCC 4E-derived clones were unaffected by hydrocarbon injury. Repeated cycles of hydrocarbon challenge in clonal populations yielded different profiles of DNA synthesis, with significant decreases in SCC 1 and no changes in SCC 4E. CONCLUSIONS: These observations suggest that hydrocarbon injury induces differential responses in cells of the glomerulus, resulting in inhibition of GMCs and selective growth advantage of GVECs. These alterations are reminiscent of critical events described in the pathogenesis of focal segmental glomerulosclerosis and raise important questions about the pathogenesis of hydrocarbon-induced nephropathies.

Actins↗

PubMed1992

Characterization of early and late endocytic compartments of the transferrin cycle. Transferrin receptor antibody blocks erythroid differentiation by trapping the receptor in the early endosome.

We describe a detailed morphological characterization of the endocytic pathway in differentiating chicken erythroblasts transformed by a temperature-sensitive mutant of avian erythroblastosis virus (AEV). These cells express high levels of transferrin receptors (TfR) when induced to differentiate at 42 degrees C. Biochemical analysis showed that most (approximately 90%) of the internalized 125I-Tf recycled within approximately 30 min while a smaller fraction of 125I-Tf required up to 2 h for recycling. By immunocytochemistry, the bulk of Tf and TfR was localized at the plasma membrane and in tubuloreticular early endosomes. This structure contained coated buds that labelled with an antibody specific for the clathrin light chain. Decreasing amounts of both Tf and TfR were detected in two distal compartments, spherical endosome vesicles resembling multivesicular bodies and the prelysosomal compartment (PLC) enriched in cation-independent mannose 6-phosphate receptor. As shown by fluorescent (FITC-Tf) labelling of living cells, the movement of Tf/TfR complex into these late structures was accompanied by a significant drop in pH from about 6, the value displayed by early endosomes, to values below pH 5.0. Since no detectable 125I-Tf degradation was observed during a 4 h period we believe that the Tf/TfR detected in these late endocytic structures avoids degradation and recycles back to the cell surface. The addition of an anti-TfR monoclonal antibody to the culture medium of these cells blocks their differentiation. Under this condition the antibody-TfR complex was trapped in an early endosome compartment that enlarged to more than twice its normal size. However, this condition did not affect the transport kinetics of horseradish peroxidase from the medium to the PLC.

Alpharetrovirus↗

PubMed1993

Characterization of calretinin-immunoreactive structures in the striatum of the rat.

Previous observations have shown that the striatum contains a population of neurones that display immunoreactivity for calretinin. In order to morphologically characterize these neurones, sections of the rat striatum were immunostained to reveal calretinin and examined at both light and electron microscopic levels. The striatum contained a small population of calretinin-immunoreactive neurones, which were of medium-size (9-17 microns) and possessed few aspiny, infrequently branching dendrites which tapered to become very thin processes in their most distal portions. Although the calretinin-immunoreactive neurones were homogeneously distributed in the frontal plane, there was a marked rostrocaudal gradient with a much greater density of cells in the rostral than in the caudal parts of the striatum. At the ultrastructural level, calretinin-immunoreactive neurones were seen to possess an indented nucleus and to receive synaptic input from at least three types of boutons. In addition to the calretinin-immunoreactive neurones, the striatum also contained axons and terminal boutons that displayed immunoreactivity for calretinin. At least two types of immunoreactive terminals were identified, those forming symmetrical synaptic specialisations and those forming asymmetrical synaptic specialisations. Approximately 50% formed asymmetrical contacts with spines and 30% formed symmetrical synaptic contact with dendritic shafts. In an attempt to further chemically characterize the calretinin-containing neurones, double pre-embedding immunocytochemistry for calretinin and parvalbumin or choline acetyltransferase was carried out and calretinin immunocytochemistry was combined with histochemistry for NADPH-diaphorase. Analysis of these double-stained sections revealed that the population of calretinin-immunoreactive neurones was distinct from the populations of neurones containing parvalbumin, choline acetyltransferase or NADPH-diaphorase. It is concluded that: (1) on the basis of distribution, morphology, chemistry, ultrastructure and afferent synaptic input, the calretinin-immunoreactive neurones are distinct from the major classes of neurones that have been previously recognised in the striatum; (2) calretinin-immunoreactive terminals are heterogeneous and are probably derived from local calretinin-containing neurones and possibly other sources.

Animals↗

PubMed1995

Ultrastructural characterization of neurons recorded intracellularly in vivo and injected with lucifer yellow: advantages of immunogold-silver vs. immunoperoxidase labeling.

Immunoperoxidase labeling of lucifer yellow provides a sensitive method for morphological characterization of neurons recorded intracellularly in vitro or in vivo. However, the reaction product is often so dense that it obscures ultrastructural details necessary for the analysis of synaptic contacts onto individually filled neurons. In the present study, we describe a silver intensification procedure using 1 nm gold labeling of lucifer yellow as an optimal means for immunocytochemically identifying single physiologically characterized neurons at the ultrastructural level. Single neurons in the frontal cortex of anesthetized rats were impaled in vivo and filled with lucifer yellow. The brains were then perfused with an acrolein fixative. Single vibratome sections through the recording site were reacted with a rabbit antibody directed against lucifer yellow followed by goat anti-rabbit 1 nm gold-labeled IgG and silver intensified. For comparison, additional sections were processed for immunoperoxidase detection of lucifer yellow. Labeled sections were processed for light microscopy or embedded in plastic for electron microscopy. The immunogold-silver label as well as peroxidase reaction product of lucifer yellow was readily detected in cell bodies, proximal and distal dendrites, and spines. However, in contrast to immunoperoxidase, the immunogold-silver reaction did not obscure subcellular organelles. Most importantly, the synaptic junctions formed by afferents to the filled neuron were more easily identifiable following the immunogold-silver procedure. This clear visualization of postsynaptic densities is essential for examining synaptic circuitry between afferents and physiologically characterized neurons.

Animals↗

PubMed2005

A novel xyloglucan from seeds of Afzelia africana Se. Pers.--extraction, characterization, and conformational properties.

This paper is the first multi-scale characterization of the xyloglucan extracted from seeds of the African tree Afzelia africana Se. Pers. It describes the extraction and characterization of this polysaccharide in terms of both primary monosaccharide and oligosaccharide composition. It also includes a study of the seed morphology. Morphological characterization includes optical, transmission, and scanning electron microscopy. The polysaccharide exists in thickened cell walls of the cotyledonary cells, and the extracted xyloglucan is structurally quite similar to those from tamarind seed and detarium. Nevertheless there are some subtle differences in the fine structure, particularly in the oligomeric xyloglucan composition. The chain flexibility of the polysaccharide is also discussed in the light of our recent measurements reported elsewhere [Biomacromolecules2004, 5, 2384-2391].

Carbohydrate Conformation↗

PubMed2005

Haloaleurodiscus mangrovei gen. sp. nov. (Basidiomycota) from mangrove forests in Japan.

Haloaleurodiscus gen. nov. (Homobasidiomycetes) is described from Japanese mangrove forests with one species H. mangrovei sp. nov. The genus is morphologically characterized by having resupinate basidioma, nodose-septate hyphae, sulphoaldehyde-positive gloeocystidia, dendrohyphidia and amyloid basidiospores with minute warts. These morphological features are similar to those of Aleurodiscus s. lat., but H. mangrovei differs from the Aleurodiscus primarily in occurring in white pocket-rot and is not closely related based on ribosomal DNA sequence analyses. Molecular data suggest that this species is phylogenetically placed in the root of the 'Peniophorales' clade. In addition, ecological and physiological features of the species are provided.

Basidiomycota↗

PubMed2002

High levels of chromosome aberrations correlate with impaired in vitro radiation-induced apoptosis and DNA repair in human B-chronic lymphocytic leukaemia cells.

PURPOSE: To investigate the relationship between the susceptibility of B-chronic lymphoid leukaemia (B-CLL) cells to DNA damage-induced apoptosis, the kinetics of DNA strand-break rejoining, and chromosome damage after exposure to ionizing irradiation. MATERIALS AND METHODS: Lymphocytes from B-CLL patients were gamma-irradiated in vitro with 0.2-5 Gy and stimulated by Staphylococcus aureus cowan I (SAC I) for estimation of chromosomal damage. Induction of apoptosis after irradiation was studied in 50 patients by two methods: morphological characterization of apoptotic cells after fluorescent staining (Hoechst), and specific quantification of mono- and oligonucleosomes in cytoplasmic cell fractions (ELISA assay). Morphological chromosome damage was scored in the first cell generation after irradiation (13 patients). In parallel, the kinetics of DNA single-strand break rejoining were investigated by the alkaline comet assay (12 patients). RESULTS: Ionizing irradiation did not induce apoptosis in lymphocytes from a subset of B-CLL patients. The results suggest that B-CLL cells resistant to radiation-induced apoptosis could repair DNA strand-breaks more rapidly and showed a higher level of chromosome aberrations than radiation-sensitive B-CLL cells. CONCLUSION: Each of three biological effects observed (apoptosis, kinetics of DNA single-strand-break repair, chromosomal damage) might be explained by different modifications occurring in irradiated B-CLL cells. Their convergence strongly suggests that resistance to apoptotic death initiation by DNA damage may be impeded by a rapid engaging of the DNA repair mechanisms. The higher level of chromosome aberrations observed in these cells suggests that the type of DNA repair system involved may generate inaccurate repair.

Apoptosis↗

PubMed2005

[FDG (18 fluorodeoxyglucose) positron emission tomography and breast cancer].

Positron emission tomography (PET) is a metabolic radionuclide imaging method in which a tracer labeled with a positron emitter is detected with a dedicated system. 18F-fluorodeoxyglucose (FDG) accumulates in tumor cells because of their increased glycolytic activity, and is thus widely used as a tracer in oncology. This increased metabolic activity precedes morphologic modifications, making FDG-PET a very useful tool for detecting and staging cancer. It can also be used to characterize morphologic changes, differentiating not only between benign and malignant lesions, but also between viable tumor cells and areas of necrosis and/or fibrosis induced by treatments. Being a whole-body examination, it allows malignancies to be staged in a single procedure. Systems combining PET and CT (computed tomography) offer improved performance, providing both metabolic and anatomical data. This technique appears to be useful for initial breast cancer staging, especially of locally advanced forms and suspected recurrences (increase of isolated tumor marker). Early studies of PET evaluation of responses to hormonal and/or cytotoxic therapies have also given very promising results. However, this technique does not seem sufficiently sensitive to be included in the initial screening or diagnosis of primary tumors, owing to its limited resolution (about 5 mm) and its restricted availability. This approach is poorly sensitive when used for axillary assessment, but offers good specificity.

Breast Neoplasms↗

PubMed1984

[Morphological criteria of the malignancy of pheochromocytoma].

Morphological features of the chromaffin tissue tumours removed surgically were studied in detail. The complex of the histological and cytological signs characterizing morphological criteria of the pheochromocytoma malignancy is recommended to be used in the everyday diagnostic practice. It is suggested that pheochromocytomas should be divided into the three main variants which seem to be stages of the neoplastic process: so-called benign, borderline malignant, and malignant tumours. The latter may be metastasizing or without visible metastasis but having all the features of morphological malignancy identical to those in the metastasizing neoplasms. The group of the borderline malignant pheochromocytoma is of importance not only theoretically but practically as well, since it complements our concepts of the neoplastic process dynamics and in many cases may be the indication of the possible prognosis of the disease.

Adolescent↗

PubMed2005

Physicochemical characterization of vibriophage N5.

Phage N5 is one of the phages of Vibrio cholerae serovar O1 biotype El Tor (Ghosh, A. N., Ansari, M. Q., and Dutta, G. C. Isolation and morphological characterization of El Tor cholera phages. J. Gen. Virol. 70: 2241-2243, 1989). In the present communication the growth curve, molecular weight and confirmation of the genome, partial denaturation map and restriction endonuclease digestion pattern have been determined. Partial denaturation map indicates that the genome has non-permuted / invariant sequence. Presence of cohesive ends has also been documented.

Bacteriophages↗

PubMed2005

[Morphology of neutrophils in centarians].

Recently, centenarians are involved in many research programs as they are believed to represent so-called successful aging. The aim of the study was to characterize morphological alterations observed in neutrophils from their peripheral blood. The study involved 40 centenarians (group B--34 females and 6 males) as well as 40 young healthy subjects aged 20-30 years (group K--35 females and 5 males). The study is a part of the Polish Centanarians Program coordinated by the International Institute of Molecular and Cell Biology in Warsaw. In this study, the morphometry of neutrophils from blood smear was performed in all studied subjects. Additionally, in centenarians, the relationship between observed alteration and serum level of vitamin B12 and folic acid was analyzed. Both the mean size of granulocytes and the mean value of neutrophil lobe counts were higher in group B vs group K (15.5 +/- 0.6 mm and 13.9 +/- 0.7 mm; p<0.0001 and 4.01 +/- 0.7 and 3.2 +/- 0.2; p<0.0001). Chromatin chips and toxic granules in cytoplasm were observed more often in centenarians as well (39/40 vs 20/40--p<0.0001 and 40/40 vs. 23/40--p<0.0001; respectively). In centenarians, there was no relationship between the presence of morphological alterations in granulocytes and the serum level of vitamin B12 and folic acid. In conclusion, morphological alterations were very common in studied centenarians. Detailed analysis of biochemical parameters and clinical status is necessary to answer the question about their pathomechanism.

Adult↗

PubMed2003

A review of morphological techniques for detection of peroxisomal (and mitochondrial) proteins and their corresponding mRNAs during ontogenesis in mice: application to the PEX5-knockout mouse with Zellweger syndrome.

In the era of application of molecular biological gene-targeting technology for the generation of knockout mouse models to study human genetic diseases, the availability of highly sensitive and reliable methods for the morphological characterization of the specific phenotypes of these mice is of great importance. In the first part of this report, the role of morphological techniques for studying the biology and pathology of peroxisomes is reviewed, and the techniques established in our laboratories for the localization of peroxisomal proteins and corresponding mRNAs in fetal and newborn mice are presented and discussed in the context of the international literature. In the second part, the literature on the ontogenetic development of the peroxisomal compartment in mice, with special emphasis on liver and intestine is reviewed and compared with our own data reported recently. In addition, some recent data on the pathological alterations in the liver of the PEX5(-/-) mouse with a peroxisomal biogenesis defect are briefly discussed. Finally, the methods developed during these studies for the localization of mitochondrial proteins (respiratory chain complexes and MnSOD) are presented and their advantages and pitfalls discussed. With the help of these techniques, it is now possible to identify and distinguish unequivocally peroxisomes from mitochondria, two classes of cell organelles giving by light microscopy a punctate staining pattern in microscopical immunohistochemical preparations of paraffin-embedded mouse tissues.

Animals↗

PubMed2004

T2 mapping: an efficient MR quantitative technique to evaluate spontaneous cartilage repair in rat patella.

OBJECTIVE: To evaluate the ability of T2 mapping on an 8.5 T imager to characterize morphologically and quantitatively spontaneous repair of rat patellar cartilage following full thickness defect. METHODS: Patellar cartilage defects were created in 24 rats knees on D0. Eight rats per time-point were killed on D20, D40 and D60 after surgery. T2 maps of repair tissue in patellar defects were obtained from eight different axial spin echo images on an 8.5 T imager. Global, superficial and deep T2 values were evaluated in spontaneous repair tissues (3x8 right patellae) vs the opposite patellae (3x8 left patellae) of the same animals. MR data were compared with macroscopic and histological studies. RESULTS: T2 map was able to identify morphologically three types of repair tissue observed macroscopically and histologically: 'total', 'partial' and 'hypertrophic' repair tissue. 'Total' and 'partial' repair tissues were characterized by global T2 values almost similar to controls, whereas 'hypertrophic' repair tissues were characterized by T2 global values higher than controls. Zonal variation between superficial and deep T2 values observed in controls was not depicted in repair tissue before D60. CONCLUSION: T2 map is able to characterize quantitatively and qualitatively rat patellar cartilage repair, and thus can be promoted, as a non invasive technique, in clinical longitudinal studies of articular cartilage repair.

Animals↗

PubMed2005

Three novel Pax6 alleles in the mouse leading to the same small-eye phenotype caused by different consequences at target promoters.

PURPOSE: To characterize three new mouse small-eye mutants detected during ethylnitrosourea mutagenesis programs. METHODS: Three new mouse small-eye mutants were morphologically characterized, particularly by in situ hybridization. The mutations were mapped, and the candidate gene was sequenced. The relative amount of Pax6-specific mRNA was determined by real-time PCR. Reporter gene analysis used Crygf and Six3 promoter fragments in front of a luciferase gene and HEK293 cells as recipients. RESULTS: The new mutations--ADD4802, Aey11, and Aey18--were mapped to chromosome 2; causative mutations have been characterized in Pax6 (Aey11: C-->T substitution in exon 8, creating a stop codon just in front of the homeobox; ADD4802: G-->A substitution at the beginning of intron 8 changes splicing and leads to an altered open reading frame and then to a premature stop codon; Aey18: G-->A exchange in the last base of intron 5a leads also to a splice defect, skipping exons 5a and 6). Real-time PCR indicated nonsense-mediated decay in Pax6Aey11 and Pax6Aey18 mutants but not in Pax6ADD4802. This result is supported by the functional analysis of corresponding expression constructs in cell culture, where the Aey11 and Aey18 alleles did not show a stimulation of the Six3 promotor or an inhibition of the Crygf promoter (as wild-type constructs do). However, the Pax6ADD4802 allele stimulated both promoters. CONCLUSIONS: Together with functional analysis in a reporter gene assay and immunohistochemistry using Pax6 antibodies, it is suggested that the Pax6Aey11 and Pax6Aey18 alleles act through a loss of function, whereas ADD4802 represents a gain-of-function allele.

Alleles↗

PubMed2006

Immunochemical, ultrastructural and electrophysiological investigations of bone-derived stem cells in the course of neuronal differentiation.

Numerous reports have highlighted the use of mesenchymal stem cells (MSC) for tissue engineering because of the capacity of the cells to differentiate along the osteogenic, chondrogenic or adipogenic pathway. As MSC also display neuronal morphologies under appropriate culture conditions, the differentiation capacity of stem cells seems to be more complex than initially thought, but it requires careful characterization of the cells. This is especially the case because recently it has been suggested that neuronal differentiation of stem cells is only an artifact. Here, we investigate the sequence of ultrastructural changes of bone-derived stem cells during neuronal induction and compare these data with immunocytochemical and electrophysiological properties of the cells. For further comparative analyses, stem cells were incubated with non-neurologically inducing stressors. The stem cells were harvested from human osseous debris and were characterized morphologically, immunocytochemically and by using FACS. After 6 h of neuronal induction, the cells had assumed neuronal morphologies and expressed neuron-specific enolase, beta-III-tubulin, neurofilament-H and HNK-1, while only a subpopulation expressed CD15 and synaptophysin. However, electrical signaling could not be detected, neither spontaneously nor after electrical stimulation. Nevertheless, transmission electron microscopy revealed cellular features of neuritogenesis and synaptogenesis in the course of neuronal induction and suggested that the cells have features similar to those observed in immature neurons. Based upon the results, it can be concluded that neuronal induction had initiated the early steps of neuronal differentiation, while exposure of the cells to non-neurological stressors had caused necrotic alterations.

Bone and Bones↗

PubMed2005

Evidence of apoptotic effects of 2,4-D and butachlor on walking catfish, Clarias batrachus, by transmission electron microscopy and DNA degradation studies.

Apoptosis or programmed cell death is characterized morphologically by chromatin condensation, cell shrinkage, fragmentation of the nucleus and cytoplasm, and consequently formation of apoptotic bodies. It has also been best characterized by the cleavage of DNA into nucleosomal size fragments of 180-200 bp or multiples of the same. Contrary to this, under extreme conditions, the cells were found to show adaptive response to apoptosis and unable to regulate their own death; necrosis is therefore predominantly observed. In the present study, we showed induction of apoptosis in Clarias batrachus due to sublethal concentration of 2,4-D and butachlor at multiple exposure time. The first phase of the study involved light microscopy (LM) and transmission electron microscopy (TEM) for ultrastructural abnormalities of the germinal tissues. While, in the second phase of the study, DNA degradation of blood and hepatic tissue was resolved on agarose gel electrophoresis. In histopathological studies, large numbers of stage II oocytes were noted for nuclear blebbing irrespective of the test chemical. Some of the butachlor-exposed oocytes showed vacuolation and electron dense cytoplasm along with thickened nuclear envelope, having close association with the lysosomes on the cytoplasmic side. Some oocytes undergo nuclear blebbing having inner dense core and translucent cytoplasm. Leydig cells were slightly hypertrophied and few appeared pycnotic, a process involving necrotic changes in which the cell nuclei were characterized by rounding up and condensation resulting in hyperchromatic staining or pycnosis. In testicular tissue, spermatogonial nuclei had irregular large clumps of heterochromatin adjoining the nuclear membrane indicating initial stage of apoptotic cell death. Electrophoretic separation resulted in a ladder pattern of blood DNA and smear like pattern of hepatic DNA. These results indicate that the above herbicides are able to induce apoptosis both at molecular as well as cytological level. A reference dose or safety factor approach to calculate risk of human exposure to both chemicals is still awaited.

2,4-Dichlorophenoxyacetic Acid↗

PubMed1984

Use of cell culture to identify human precancer.

In the United States, colon cancer is the most common form of internal cancer in both sexes. Prevention of the disease depends on early diagnosis of polyps or pre-cancerous lesions. The response of normal human colon fibroblasts ( CRL1459 ) was used to identify individuals with clinical pre-cancer. Their plasma induced transformation associated morphology characterized by the retraction of cellular processes, cell rounding and eventual detachment from the vessel surface. Those plasma samples which induced a transformation associated morphology contained significantly increased levels of protease as shown by casein hydrolysis (Bio-Rad, CA). We are using hyperproteinasemia as a biomarker to identify individuals with polyps who have hereditary adenomatosis of the colon and rectum (ACR). We are currently evaluating cell cultures versus biochemical assays as a means for early detection of precancerous tumors in the general population. The findings of a tumor associated protease in clinical precancer, and its effect on cell cultures support our proposal that protease activity promotes tumor progression in ACR and may represent the gene defect in this hereditary disease.

Actins↗

PubMed1998

patufet, the gene encoding the Drosophila melanogaster homologue of selenophosphate synthetase, is involved in imaginal disc morphogenesis.

Proliferation in imaginal discs requires cell growth and is linked to patterning processes controlled by secreted cell-signalling molecules. To identify new genes involved in the control of cell proliferation we have screened a collection of P-lacW insertion mutants that result in lethality in the larval/pupal stages, and characterized a novel gene, patufet (ptuf). Inactivation of ptuf by a P element insertion in the 5' untranslated region leads to aberrant imaginal disc morphology characterized by a reduction in mass of discs and disorganization of disc cells where no folding or patterning can be detected. Moreover, apoptotic cells can be observed in these small and abnormal mutant discs. To examine the role of ptuf we have studied its clonal behaviour in genetic mosaics generated by mitotic recombination. The mutation causes reduced cell viability, smaller cell size and stops vein differentiation. Non-autonomous effects, such as abnormal differentiation of wild-type cells surrounding the clones, are also observed. We have cloned the ptuf gene of Drosophila melanogaster and found that it encodes a selenophosphate synthetase, which is the first identified in insects. Mutant flies transformed with the full-length cDNA show complete reversion of lethality and disc phenotype. Northern blot analysis and in situ hybridization indicate that the ptuf gene is expressed in imaginal discs as well as at different stages of development. The synthesis of selenoproteins by the selenophosphate synthetase, the role of selenoproteins in the maintenance of the oxidant/antioxidant balance of the cell and its possible implications in imaginal disc morphogenesis are discussed.

Amino Acid Sequence↗