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PubMed1993

Fish optic nerve oligodendrocytes support axonal regeneration of fish and mammalian retinal ganglion cells.

Segments from adult fish and rat retinae were explanted on myelin-marker expressing oligodendrocytes derived from the regenerating goldfish optic nerve. Fish axons grew in high density and even rat retinal axons regenerated to considerable length on the surface of the fish oligodendrocytes, suggesting that this type of fish glia has axon-growth promoting surface components that exert their influence across species boundaries. One interesting surface component of the fish oligodendrocytes as demonstrated here is the E 587 antigen, which is related to the L1 family of cell adhesion molecules. In long term cocultures of oligodendrocytes and retinal axons, the fish glial cells were found to enwrap rat axons. This suggests that the oligodendrocytes of the regenerating goldfish optic nerve/tract may, despite striking differences, represent the equivalent to mammalian optic nerve oligodendrocytes.

Animals↗
PubMed1978

Further scanning electron microscope studies of lizard auditory papillae.

The papillae basilares of 12 species of lizards from seven different families were studied by SEM. The iguanids, Sceloporus magister and S. occidentalis, have typical "iguanid type" papillae with central short-ciliated unidirectional hair cell segments and apical and basal long-ciliated bidirectional hair cell segments. These species of Sceloporus are unique among iquanids in that the bidirectional segments consist of but two rows of hair cells. The agamids, Agama agama and Calotes nigrolabius, have an "agamid-anguid type" papilla consisting of an apical short-ciliated unidirectional segment. Agama agama is unusual in having a few long-ciliated hair cells at the apical end of the apical short-ciliated segment. The agamid, Uromastix sp., has an "iguanid type" papilla with a central short-ciliated unidirectional segment and apical and basal bidirectional segments. The anguid, Ophisaurus ventralis, has an "iguanid" papillar pattern with the short-ciliated segment centrally located. All the short-ciliated hair cells of the above species are covered by a limbus-attached tectorial network or cap and the long-ciliated hair cells, only by loose tectorial strands. The lacertids, Lacerta viridis and L. galloti, have papillae divided into two separate segments. The shorter apical segment consists of opposingly oriented, widely separated short-ciliated cells covered by a heavy tectorial membrane. The apical portion of the longer basal segment consists of unidirectionally oriented hair cells, while the greater part of the segment has opposingly oriented hair cells. The xantusiids, Xantusia vigilis and X. henshawi, have papillae made up of separate small apical segments and elongated basal segments. The apical hair cells are largely, but not exclusively, unidirectional and are covered by a heavy tectorial cap. The basal strip is bidirectional and the hair cells are covered by sallets. The kinocilial heads are arrowhead-shaped. The papilla of the cordylid, Cordylus jonesii, is very similar to that of Xantusia except that the apical segment is not completely separated from the basal strip. The papilla of the Varanus bengalensis is divided into a shorter apical and a longer basal segment. The hair cells of the entire apical and the basal three quarters of the basal segment are opposingly oriented, not with reference to the midpapillary axis but randomly to either the neural or abneural direction. The apical quarter of the basal segment contains unidirectional, abneurally oriented hair cells. The entire papilla is covered by a dense tectorial membrane. The functional correlations of the above structural variables are discussed.

Animals↗
PubMed1984

Control of cell division by sex factor F in Escherichia coli. I. The 42.84-43.6 F segment couples cell division of the host bacteria with replication of plasmid DNA.

The F plasmid of Escherichia coli was used to study the genetic background of the control circuit in the bacteria that co-ordinates DNA replication and cell division of the host cells. When DNA replication of the F plasmid was blocked by growing cells carrying an amber-suppressible replication-defective F plasmid mutant under restrictive conditions, the cells continued to divide for about one generation until F plasmid was supposedly diluted to one copy per cell, and then they stopped dividing and formed non-septated filamentous cells. These observations suggest that completion of a round of replication is a necessary and sufficient condition of F DNA synthesis in the cell division of F+ bacteria; i.e. cell division of the F+ bacteria is coupled with DNA replication of the F plasmid. The observation that Giemsa-stainable materials in the filamentous cells were clustered in the center indicates that partitioning of chromosomal DNA (and presumably of F plasmid DNA) is also coupled with plasmid DNA replication. The function necessary for this coupling is carried by the 42.84-43.6 F (BamHI-PstI) segment, which is located outside the region essential for replication of the F plasmid. The nucleotide sequence demonstrates the existence of two open reading frames in this region, which encode polypeptides of 72 and 101 amino acids, respectively. These two reading frames are most likely to be transcribed as a single polycistronic message in the direction from the BamHI site at 42.84 F to the PstI site at 43.6 F. The expression of this "operon" is likely to be controlled by plasmid DNA replication.

Base Sequence↗
PubMed1994

Segment and cell type lineage restrictions during pharyngeal arch development in the zebrafish embryo.

In zebrafish, the segmental series of pharyngeal arches is formed predominantly by two migratory cell types, neural crest and paraxial mesoderm, which arise in the early embryo. Neural crest cells migrate ventrally out of the neuroepithelium and into the arches to form cartilage, neurons, glia and pigment cells. Surrounding mesoderm generates muscles and endothelia. We labeled individual pharyngeal precursor cells with fluorescent dyes and found that their clonal progeny were confined to single segments and generated single cell types. When a neural crest or mesodermal cell was marked before migration into the pharynx, its progeny dispersed but generally remained confined to a single arch primordium. Such segmental restrictions arose first in the most rostral arches, mandibular and hyoid, and progressed caudally. The phenotypes of progeny generated by single cells were examined in the mandibular arch. Clones derived from premigratory neural crest cells generally did not contribute to more than one cell type. Further, the progenitors of some cell types were spatially separated in the premigratory crest. In particular, neurogenic crest cells were situated further laterally than cells that generate cartilage and connective tissues, while pigment and glial cell progenitors were more evenly distributed. Based on these results we suggest that arch precursors may be specified as to their eventual fates before the major morphogenetic movements that form the arch primordia. Further, cell movements are restricted during segmentation establishing a group of arch precursors as a unit of developmental patterning, as in the fashion of vertebrate rhombomeres or segmental lineage compartments in Drosophila.

Animals↗
PubMed1996

Prokaryotic expression of an immediate-early gene of human herpesvirus 6 and analysis of its viral antigen expression in human cells.

Segments of an immediate-early (1E) protein (1E03; 958 amino acids (aa)), encoded by clone pSTY03, of human herpesvirus 6 (HHV-6) variant B strain HST were expressed as beta-galactosidase fusion proteins in Escherichia coli. Using Western blot analysis, and the serum of a patient having high titer anti-HHV-6 antibodies, an antigenic region of the IE03 protein was mapped between residues 340 and 505 (pUE03IE-M). The fusion protein expressed in E. coli harboring plasmid pUE03IE-M was purified after electrophoresis in SDS-PAGE, and then immunized in mice to obtain a monospecific antibody. Monospecific antibody raised against the fusion protein reacted with IE03 protein species with apparent molecular weights of 155 and 170 kDa, and was detected as granular fluorescence in nuclei of infected cells by an immunofluorescence antibody test. Furthermore, this antibody reacted only with HHV-6 variant B, but did not react with HHV-6 variant A. The IE03 protein was confirmed to be an IE protein, since the synthesis of this protein was observed in infected cells that were first treated with cycloheximide, which was then replaced with actinomycin D. Further, it was also detected as early as 4 h after infection.

Animals↗
PubMedDate not supplied

Preferential binding of imaginal disk cells to embryonic segments of Drosophila.

Cell recognition and selective adhesion may be important in pattern formation; such processes in Drosophila melanogaster could be responsible for the maintenance of segment boundaries, the morphogenesis of metamorphosing imaginal disks, and the paths of axon outgrowth during neurogenesis. As cells from different imaginal disks of Drosophila are able to recognize and sort out from one another, we decided to investigate whether these larval cells could recognize and bind to the epidermis of intact embryos. We report here that imaginal disk cells bind preferentially to the epidermis of the embryonic segments from which they are derived: thoracic disk cells to thoracic segments and genital disk cells to abdominal segments. Furthermore, thoracic disk cells recognize and bind, without preference, to all segments of the homoeotic mutant Df(3R)P9 (ref. 6). We conclude, therefore, that cells of the same segmental origin have similar recognition properties at different developmental stages.

Animals↗
PubMed1986

An iterative region-growing process for cell image segmentation based on local color similarity and global shape criteria.

An image segmentation process was derived from an image model that assumed that cell images represent objects having characteristic relationships, limited shape properties and definite local color features. These assumptions allowed the design of a region-growing process in which the color features were used to iteratively aggregate image points in alternation with a test of the convexity of the aggregate obtained. The combination of both local and global criteria allowed the self-adaptation of the algorithm to segmentation difficulties and led to a self-assessment of the adequacy of the final segmentation result. The quality of the segmentation was evaluated by visual control of the match between cell images and the corresponding segmentation masks proposed by the algorithm. A comparison between this region-growing process and the conventional gray-level thresholding is illustrated. A field test involving 700 bone marrow cells, randomly selected from May-Grünwald-Giemsa-stained smears, allowed the evaluation of the efficiency, effectiveness and confidence of the algorithm: 96% of the cells were evaluated as correctly segmented by the algorithm's self-assessment of adequacy, with a 98% confidence. The principles of the other major segmentation algorithms are also reviewed.

Biometry↗
PubMed1993

Brain-type creatine kinase in photoreceptor cell outer segments: role of a phosphocreatine circuit in outer segment energy metabolism and phototransduction.

Different isoforms of creatine kinase, an important enzyme of vertebrate energy metabolism, were localized in bovine photoreceptor cells, with particular emphasis on the identification and quantification of the brain-type isoform within the outer segment compartment. Using immunofluorescence and immunoelectron microscopy, brain-type creatine kinase was shown to be present in bovine photoreceptor cell outer and inner segments. The presence of this isoenzyme in rod outer segments was additionally confirmed by immunoblotting and immunolabeling of isolated rod outer segments. The content of creatine kinase in rod outer segments was quantified by measuring creatine kinase activity after membrane disruption with detergent. The ATP regeneration potential provided by the creatine kinase in isolated, washed bovine rod outer segments was 1.2 +/- (0.4) i.u. mg-1 rhodopsin. This value was calculated to be at least an order of magnitude larger than that necessary to replenish the energy required for cGMP resynthesis in rod outer segments, and high enough to regenerate the entire ATP pool of rod outer segments within the time span of a photic cycle. A mitochondrial creatine kinase isoenzyme was located within the ellipsoid portions of bovine rod and cone inner segments by immunofluorescence microscopy and, using immunogold staining, was specifically localized in the mitochondria clustered within bovine rod and cone inner segments. These results suggest that vertebrate photoreceptor cells contain a functional phosphocreatine circuit. Outer segment creatine kinase may play an important role in phototransduction by providing energy for the visual cycle, maintaining high local ATP/ADP ratios and consuming protons produced by enzymes located in the outer segment.

Adenosine Triphosphate↗
PubMed2000

Drosophila homologs of transcriptional mediator complex subunits are required for adult cell and segment identity specification.

The origins of specificity in gene expression are a central concern in understanding developmental control. Mediator protein complexes regulate transcriptional initiation, acting as modular adaptors linking specific transcription factors to core RNA polymerase II. Here, we identified the Drosophila homologs of 23 human mediator genes and mutations of two, dTRAP240 and of dTRAP80 (the putative fly homolog of yeast SRB4). Clonal analysis indicates a general role for dTRAP80 necessary for cell viability. The dTRAP240 gene is also essential, but cells lacking its function are viable and proliferate normally. Clones reveal localized developmental activities including a sex comb cell identity function. This contrasts with the ubiquitous nuclear accumulation of dTRAP240 protein in imaginal discs. Synergistic genetic interactions support shared developmental cell and segment identity functions of dTRAP240 and dTRAP80, potentially within a common complex. Further, they identify the homeotic Sex combs reduced product, required for the same cell/tissue identities, as a functional partner of these mediator proteins.

Amino Acid Sequence↗
PubMed2004

Combining intensity, edge and shape information for 2D and 3D segmentation of cell nuclei in tissue sections.

We present a region-based segmentation method in which seeds representing both object and background pixels are created by combining morphological filtering of both the original image and the gradient magnitude of the image. The seeds are then used as starting points for watershed segmentation of the gradient magnitude image. The fully automatic seeding is done in a generous fashion, so that at least one seed will be set in each foreground object. If more than one seed is placed in a single object, the watershed segmentation will lead to an initial over-segmentation, i.e. a boundary is created where there is no strong edge. Thus, the result of the initial segmentation is further refined by merging based on the gradient magnitude along the boundary separating neighbouring objects. This step also makes it easy to remove objects with poor contrast. As a final step, clusters of nuclei are separated, based on the shape of the cluster. The number of input parameters to the full segmentation procedure is only five. These parameters can be set manually using a test image and thereafter be used on a large number of images created under similar imaging conditions. This automated system was verified by comparison with manual counts from the same image fields. About 90% correct segmentation was achieved for two- as well as three-dimensional images.

Automation↗
PubMed1979

Neutrophil marrow profiles in patients with rheumatoid arthritis and neutropenia.

Neutrophil marrow cellularity was determined in 14 neutropenic patients with rheumatoid arthritis (RA) from measurements of neutrophil-normoblast ratios in marrow biopsies and ferrokinetic estimates of marrow normoblasts. A marrow profile was developed for each patient comprising the numbers of promyelocytes and myelocytes, of metamyelocytes and bands, and of segmented neutrophils in whole marrow. In each case a maturation ratio was calculated by dividing the number of metamyelocytes and bands by the number of promyelocytes and myelocytes. The physiologic marrow response to loss of neutrophils from circulation was assumed to be an increase in promyelocytes and myelocytes due to proliferation and influx, a reduction in segmented cells due to early release, and a normal maturation ratio. The results were interpreted in the light of the 95% confidence limits for data previously obtained from 13 normal subjects: in patients with neutropenia reduced or basal numbers of promyelocytes and myelocytes were interpreted as absence of the anticipated proliferative response; increased numbers of marrow segmented cells were attributed to failure of release; a low maturation ratio was assessed to reflect intramedullary cell loss. The pattern in two patients with Felty's syndrome was consistent with a physiological response to neutrophil destruction. The other 12 patients had neutrophil marrow abnormalities. Seven patients with Felty's syndrome and four patients without splenomegaly had absolute or relative hypoplasia of neutrophil marrow or low maturation ratios. One patient with a normal spleen size had an increased number of marrow segmented cells yet failed to mobilize cells normally in response to dialysis coil-activation of C3. Abnormalities of neutrophil marrow may contribute to neutropenia in RA irrespective of the presence of splenomegaly. Recognition of neutrophil marrow abnormalities in these patients may be of value in prognosis and management.

Adult↗
PubMed1988

Rift Valley fever virus M segment: cell-free transcription and translation of virus-complementary RNA.

A cell-free system has been used to study gene expression of the M segment RNA of the Phlebovirus Rift Valley fever virus (RVFV). RVFV sequence-containing plasmids were used to synthesize M segment mRNA-like transcripts. These transcripts were then translated in vitro in the absence or presence of microsomal membranes. Cell-free translation of a transcript which closely resembled authentic M segment mRNA (RNA-7) yielded a primary translation product of 133 kilodaltons (kDa), the size expected of a polypeptide encompassing the entire open reading frame (ORF) of the M segment. When translations were conducted in the presence of microsomal membranes, this primary protein was cotranslationally processed to yield the two viral glycoproteins, G1 and G2, as well as proteins of 78, 21, and 14 kDa. With one exception, these in vitro processed polypeptides comigrated with M segment-encoded proteins found in RVFV-infected cell lysates. A polypeptide corresponding to the in vitro 21-kDa protein was not detected in vivo. To investigate translational initiation and processing of the protein products of the M segment, additional transcripts were generated in which varying portions of the amino-terminal "preglycoprotein" region of the M segment ORF were deleted. Translation results indicated that the 78- and 21-kDa proteins were initiated from the first methionine codon of the ORF, and the 14-kDa polypeptide began from the second in-phase ATG. These products and a major portion of the preglycoprotein region sequence were not required for the proper synthesis and processing of the viral glycoproteins in vitro. In light of these results, possible expression strategies used by this Phlebovirus M segment RNA are discussed.

Bunyaviridae↗
PubMedDate not supplied

A morphologist's perspective on terminal growth and segmentation.

When approaching the study of terminal growth and segmentation, comparative morphology provides an important guide to formulate questions. There are often problems in unambiguously identifying the axis along which we wish to study terminal (often, actually, subterminal) growth, especially when the trunk axis is posteriorly prolonged in an appendage (as with the tail of vertebrates), or when the polarity of the "external animal" is other than the polarity of the "internal animal," as in polypoid bilaterians. We cannot ignore that the rear end of the main body axis is possibly defined very early in development in some groups, for example, arthropods, whereas in others, vertebrates, for example, it is defined much later. We cannot think of segmentation as always corresponding to the sequential posterior addition of new units, thus ignoring the widespread occurrence of double segmentation. A more subtle problem is represented by the overlapping of different processes, all of them contributing to elongating the body, such as segmentation, cell proliferation, cell rearrangement, and cell growth. Within a segmented trunk, cell proliferation and differentiation may go on in parallel from as many growth points as there are groups of regularly spaced cells. The main consequence, however, is not so much to expedite elongation as to reduce the disparity of metabolic conditions, gene expression patterns and "relative age" of different body districts, otherwise possibly troublesome within the limited space of the embryo.

Animals↗
PubMed1999

Enhanced expression of fas ligand (CD95L) on T cells after segmental allergen provocation in asthma.

BACKGROUND: Little is known about the termination of the T-cell driven inflammation found in patients with allergic asthma. OBJECTIVE: Because signals delivered through Fas/Fas ligand can lead to T-cell apoptosis, we investigated the expression of Fas and Fas ligand on peripheral blood- and bronchoalveolar lavage fluid (BALF)-derived T cells and the percentage of apoptotic BALF cells in asthma. METHODS: Nine atopic subjects with mild asthma and 9 control subjects underwent segmental sham and allergen challenge. Flow cytometry was used to determine the T-cell expression of Fas and Fas ligand, and the terminal dUTP nick end labeled technique was applied to detect apoptotic BALF cells. RESULTS: In asthmatic and control subjects almost all T cells in the BALF expressed Fas antigen without changes after saline or allergen challenge. A small percentage of T cells in BALF expressed the Fas ligand. In asthmatic subjects, but not in control subjects, there was a significant increase in Fas ligand after allergen challenge (CD3: 0.8% +/- 0.6% [baseline] vs 3.2% +/- 1.2% [allergen challenge]; CD4: 1.8% +/- 0.0% vs 4.3% +/- 1.8%; CD8: 2.8% +/- 2.4% vs 9.1% +/- 4.8%) but not after saline challenge, with a significant correlation to the percentage of BALF eosinophils. Apoptotic BALF cells were localized exclusively in macrophages at a very low frequency (0.03% to 0.15%) and without changes after saline or allergen challenge in both groups. CONCLUSION: In asthma there is an upregulation of Fas ligand on T cells in BALF after allergen challenge. Because there is no evidence for increased apoptosis, this phenomenon may reflect antigen-induced T-cell activation rather than apoptosis.

Adult↗
PubMed1957

The structure and concentration of solids in photoreceptor cells studied by refractometry and interference microscopy.

Fragments of freshly obtained retinas of several vertebrate species were studied by refractometry, with reference to the structure of the rods and cones. The findings allowed a reassessment of previous descriptions based mainly on fixed material. The refractometric method was used also to measure the refractice indices and to calculate the concentrations of solids and water in the various cell segments. The main quantitative data were confirmed by interference microscopy. When examined by the method of refractometry the outer segments of freshly prepared retinal rods appear homogeneous. Within a few minutes a single eccentric longitudinal fiber appears, and transverse striations may develop. These changes are attributed to imbibition of water and swelling in structures normally too small for detection by light microscopy. The central "core" of outer segments and the chromophobic disc between outer and inner segments appear to be artifacts resulting from shrinkage during dehydration. The fresh outer segments of cones, and the inner segments of rods and cones also are described and illustrated. The volumes, refractive indices, concentrations of solids, and wet and dry weights of various segments of the photoreceptor cells were tabulated. Rod outer segments of the different species vary more than 100-fold in volume and mass but all have concentrations of solids of 40 to 43 per cent. Cone outer segments contain only about 30 per cent solids. The myoids, paraboloids, and ellipsoids of the inner segments likewise have characteristic refractive indices and concentrations of solids. Some of the limitations and particular virtues of refractometry as a method for quantitative analysis of living cells are discussed in comparison with more conventional biochemical techniques. Also the shapes and refractive indices of the various segments of photoreceptor cells are considered in relation to the absorption and transmission of light. The Stiles-Crawford effect can be accounted for on the basis of the structure of cone cells.

Histological Techniques↗