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51.
Summary The development of acellular extrinsic fiber cementum (AEFC) has never before been studied in human teeth. We have therefore examined the initiation of AEFC in the form of a collagenous fiber fringe and its attachment to the underlying dentinal matrix, in precisely selected, erupting human premolars with roots developed to 50%–60% of their final length. Freshly extracted teeth were prefixed in Karnovsky's fixative, decalcified in EDTA and subdivided into about 10 blocks each, cut from the mesial and distal root surfaces, vertical to and along the root axis. The blocks were postfixed in osmium tetroxide, embedded in Epon and cut for light- and electron-microscopic investigation. Starting at the advancing edge of the root, within a region extending about 1 mm coronal to this edge, fibroblast-like cells were seen closely covering the external root surface. Along the first 100 m from the root edge, these cells extended cytoplasmic processes and contacted the dentinal collagen fibrils. Between these cells and the dentinal matrix, new collagen fibrils and very short collagen fibers gradually developed. Within the second 100 m from the root edge, this resulted in the formation of a cell-fiber fringe network. Newly formed fibers of the fringe were directly attached to the non-mineralized matrix containing dentinal collagen fibrils and could be distinguished from the latter by differences in fibril orientation. During the process of dentin mineralization, the transitional zone between the fiber-fringe base and the dentinal matrix, i.e., the future dentino-cemental junction, also mineralized. It is suggested that this fiber fringe is the base of AEFC, which later increases in thickness by fiber extension and subsequent mineralization.Abbreviations
AEFC
acellular extrinsic fiber cementum
-
AIFC
acellular intrinsic fiber cementum
-
CIFC
cellular intrinsic fiber cementum
-
CMSC
cellular mixed stratified cementum
-
ARE
advancing root edge
-
CP
cytoplasmic process
-
D
dentin
-
DCJ
dentinocemental junction
-
E
enamel
-
EBL
external basal lamina
-
EC
epithelial cell
-
EDTA
ethylene diaminetetraacetic acid
-
ERM
epithelial rests of Malassez
-
FF
fiber fringe
-
HRS
Hertwig's epithelial root sheath
-
IBL
internal basal lamina
-
MD
mineralized dentin
-
NMD
non-mineralized dentin
-
OB
odontoblast
-
PD
predentin
-
PL
periodontal ligament 相似文献
52.
Transmembrane diffusion of hydrophobic antimicrobial agents and cell surface hydrophobicity in Bacteroides fragilis 总被引:1,自引:0,他引:1
The transmembrane diffusion of hydrophobic antimicrobial agents, e.g. lincomycin and clindamycin, was examined in Bacteroides fragilis which is sensitive to these agents. The results showed that these agents penetrate efficiently through the outer membrane. Cell surface hydrophobicity measured by the partition assay between water and p-xylene revealed that the cell surface of B. fragilis is more hydrophobic than that of Salmonella typhimurium or Pseudomonas aeruginosa. Furthermore, treatment with low concentrations of surfactant caused cell lysis. These results suggest that the cell surface hydrophobicity in B. fragilis plays an important role in the efficient transmembrane penetration of hydrophobic compounds. This efficiency explains the susceptibility of B. fragilis to hydrophobic antimicrobial agents. 相似文献
53.
Hans-B?rje Jansson A. Jeyaprakash Gerald C. Coles Nahum Marban-Mendoza Bert M. Zuckerman 《Journal of nematology》1986,18(4):570-574
Caenorhabditis elegans and Panagrellus redivivus were investigated for surface carbohydrates using fluorescent-labelled and ferritin-labelled lectins. Rhodamine-labelled Concanavalin A was specifically located in the cephalic region of both species. Rhodamine-labelled wheat germ agglutinin was located over the entire cuticle of P. redivivus but was absent on C. elegans. Rhodamine-labelled peanut agglutinin and Limax flavus agglutinin did not label nematodes of either species. Galactose and sialic acid were not detected on either species, whereas mannose-glucose residues were specifically localized in the head areas of both species. No detectable N-acetylglucosamine occurred on C. elegans, but it was evenly distributed over the cuticle surface of P. redivivus. 相似文献
54.
55.
A hemocyte surface membrane marker (BGH1) has been identified using hemocyte-specific monoclonal antibodies (mABs) generated by somatic cell fusion methods. The BGH1 epitope was expressed on a subpopulation of circulating, glass-adherent blood cells from two strains of the snail, Biomphalaria glabrata. Approximately 40% of the circulating hemocytes from the PR albino (M-line) B. glabrata strain were BGH1?, compared to a prevalence of 10% BGH1+ cells in the 10-R2 snail strain. When hemocytes were firmly attached and spread on a glass surface, BGH1+ cells were morphologically distinguishable from BGH1? cells by their ovoid shape and the presence of short, thin filopodial projections along the ectoplasmic border. In contrast, BGH1? hemocytes were more pleomorphic and possessed long, spike-like filopodia. Moreover, the BGH1 epitope was trypsin-resistant and retained its antigenic reactivity with probe mABs following fixation with paraformaldehyde or paraformaldehyde/MeOH. Fixation with glutaraldehyde, however, significantly reduced mAB binding to the BGH1 surface epitope. There was no apparent age-dependent expression of the BGH1 determinant since circulating hemocyte populations in very young (1–2 mm) to adult (10–12 mm) snails were composed of both BGH1+ and BGH1? subpopulations. Quantitative shifts in the prevalence of epitope-bearing hemocytes between the smallest snail size class (1–2 mm) and the larger snails (3–4 and 10–12 mm) are believed to be due to a differential production and/or release of BGH1? hemocytes within the blood circulation rather than a gradual age-related change in the expression of surface antigens on individual cells. Experiments designed to assess the in vitro phagocytic capability and lysosomal acid phosphatase (APase) activity of mAB-reactive hemocytes revealed that BGH1+ cells, when compared to those lacking the surface marker, were significantly reduced in both their phagocytic and APase-producing activities. Since the PR albino strain of B. glabrata possesses a higher proportion of BGH1? hemocytes and a lower total concentration of circulating cells than do snails of the 10-R2 strain, PR albino snails are thus potentially reduced in their natural capacity to mount cellular reactions against foreign materials. 相似文献
56.
Donald M. Bers Kenneth D. Philipson Arthur Peskoff 《The Journal of membrane biology》1985,85(3):251-261
Summary Calcium binding and Na–Ca exchange activity were measured in isolated cardiac plasma membrane vesicles under various ionic conditions. A model was developed to describe the Ca binding characteristics of cardiac sarcolemmal vesicles using the Gouy-Chapman theory of the diffuse double layer with specific cation binding to phospholipid carboxyl and phosphate groups. The surface association constants used for Ca, Na, K and H binding to both of these groups were 7, 0.63, 0.3 and 3800m
–1, respectively. This model allows the estimation of surface [Ca] under any specific ionic conditions. The effects of the divalent screening cation, dimethonium, on Ca binding and Na–Ca exchange were compared. Dimethonium had no significant effect on Ca binding at high ionic strength (150mm KCl), but strongly depressed Ca binding at low ionic strength. Dimethonium had no significant effect on Na–Ca exchange (Na-inside dependent Ca influx) at either high or low ionic strength. These results suggest that the Ca sites of the Na–Ca exchanger are in a physical environment where they are either not exposed to or not sensitive to surface [Ca]. 相似文献
57.
Jean-Claude Romano 《Hydrobiologia》1985,121(1):35-43
The influence of sampling and sample treatment upon adenylic nucleotide (ATP, ADP, AMP) content of microplankton is studied. Changes in light conditions during nigh-sampling and extracting do not induce significant variations, in the adenylic nucleotide content of microplankton or in energy charge values.The contribution of zooplankton (size up to 200 µm) to microplankton adenosine values can be neglected for inshore surface waters and traditional sample volumes (about one liter). This result can been explained by the low density of zooplankton in such a small sample volume and by differences in efficiency of the extracting method used.
Impact de l'échantillonnage sur la mésure des nucléotides adényliques (ATP, ADP, AMP) du microplancton相似文献
58.
Abstract The penicillin binding proteins (PBPs) of 4 representative isolates of Haemophilus influenzae were studied using crude membrane preparations and whole cells grown to the logarithmic and stationary phases of growth. Relative binding, % of total bound, and binding affinities were compared. The PBP patterns were similar for crude membranes and whole cells for all 4 strains tested at each phase of growth. However, PBP 2 was slightly reduced and PBP 4 was markedly reduced with whole-cell labelling in comparison to crude membranes. 8 PBPs were detected in cells labelled during the logarithmic phase of growth, while 6 were detected in stationary phase cells. The pBPs 'lost' in stationary phase (PBPs 4 and 6) with apparent M r of 62 000 and 45 000, respectively, have a high affinity for ampicillin ( I 50 ≃ 0.04 μ g/ml). This suggests that these proteins may have an important role in cell growth, and are targets for β-lactam substrates. 相似文献
59.
Guatteria, Guatteriopsis, Guatteriella andHeteropetalum share the same conspicuous pollen type which is new for theSpermatophyta. It is zonoaperturate with a folded aperture region and an extremely reduced exine. First chromosome counts and karyotype analyses forGuatteriopsis (4 species investigated) andGuatteriella (1 species) are identical with those ofGuatteria (19 species seen): 2n = 28. The genome is characterized by diploidization and partly telocentric chromosomes. Sequentially Giemsa C- and fluorochrome banded chromosomes and interphase nuclei are described. The cuticular folding pattern is distinct forHeteropetalum only. Growth forms and ecology are reported for many species. The evolutionary pattern of theGuatteria group is discussed and compared with other genera and families. 相似文献
60.
Stigmatic surfaces of about 250 species from more than 100 families were examined by scanning electron microscopy. There are five main groups which differ by the amount of secretion, the morphology of the surface and the distribution of receptive cells. The types of stigmatic surfaces are often remarkably constant on the family level.Ericaceae andLiliaceae are examples for very heterogenous families. Particular interest was paid to heteromorphic (heterostylous and cleistogamous) species. In most heterostylous species there is a close morphological correlation between the stigmatic surface and the sculpture of compatible pollen. Heterostyly was established for the genusGoniolimon. The dimorphism of plants with chasmogamous and cleistogamous flowers is a phenomenon which is not comparable to the polymorphism of heterostylous forms. 相似文献