首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 0 毫秒
1.
过量氟对大鼠下切牙釉原蛋白表达的影响   总被引:1,自引:0,他引:1  
目的研究过量氟对大鼠下切牙釉原蛋白表达的影响,探讨氟斑牙的发病机制。方法选择6只Wistar大鼠,随机分成实验组和对照组。实验组每日饲以F-质量浓度为100mg/L的氟化水,对照组饲以蒸馏水,两组均用常规饲料喂养8周。饲养8周后处死大鼠,利用实时定量聚合酶链反应(PCR)观察过量氟对大鼠下切牙釉原蛋白表达的影响。结果实验组大鼠下切牙釉原蛋白的表达低于对照组(P<0.05)。结论过量氟可能通过抑制釉原蛋白的表达来影响釉质发育。  相似文献   

2.
目的 分离、培养和纯化大鼠切牙颈环上皮细胞,观察牙釉蛋白在大鼠切牙颈环上皮细胞中的表达情况.方法 取出生2d的威斯塔大鼠牙胚颈环组织,培养原代混合细胞,纯化颈环上皮细胞,将细胞进行抗牙釉蛋白免疫细胞化学染色.结果 牙釉蛋白在培养且纯化的颈环上皮细胞中呈强阳性表达,对照组呈阴性表达.结论 大鼠切牙颈环上皮细胞具有向成釉细胞分化的潜能.  相似文献   

3.
Previous of the sympathetic nerve supply of the rat mandibular incisor pulp have shown conflicting results. Here, the neurovascular control of the rat lower incisor pulp was investigated by stimulating the tooth crown and the cervical sympathetic trunk electrically and monitoring blood-flow changes in the pulp by laser Doppler flowmetry. In addition the presence of noradrenaline (NA) in the pulp and gingiva was examined biochemically in untreated and sympathectomized animals by high-performance liquid chromatography. The tissue concentrations of NA in the pulp were 11-fold greater than those of gingiva. Surgical sympathectomy significantly reduced the NA content in the pulp by 76%. Monopolar electrical stimulation of teeth (25–50 μA) for 1 min resulted in a frequency-dependent reduction followed by an increase in pulpal blood flow. At 16 Hz the reduction in blood flow was 65% and the subsequent increase was 9%. After intravenous administration of the -adrenoceptor antagonist phentolamine, the stimulation-induced reduction in pulpal blood flow was diminished by 94% while the increase was significantly enhanced (from 9 to 40%). Infusion of the β-adrenoceptor antagonists propranolol and timolol significantly reduced this increase in blood flow by 53 and 55%, respectively. Preganglionic sympathetic nerve stimulation also induced a frequency-dependent reduction followed by a slight increase in pulpal blood flow. This reduction in blood flow was almost abolished after -adrenergic blockade and there was no subsequent increase. These findings suggest that there are sympathetic nerve fibres in rat incisor pulp and that they are activated upon monopolar electrical stimulation of teeth resulting in -and β-adrenoceptor mediated blood-flow responses.  相似文献   

4.
ABSTRACT – The electron microprobe technique was used to study the accumulation of iron in rat incisor ameloblasts as well as the subsequent release of iron from the cells and deposition into the outer layer of the enamel. Starting about 3 mm from the developing end, a gradual accumulation of iron occurred in the ameloblasts. At a stage where the iron content of the cells had reached a maximal level, and the calcium content of the adjacent hard tissue had reached the level of mature enamel, the initial incorporation of iron in the enamel was seen. In the iron incorporation zone the iron content of the enamel increased from less than 0.1 % to about 9 % and the iron content of the ameloblasts was gradually reduced. Concomitant with the increase of iron in the enamel, a decrease of the calcium content was observed in the same region, indicating a withdrawal of calcium from the enamel. Since the incorporation of iron occurs at a stage where the enamel is highly mineralized, the processes involved can hardly be explained as an interaction with the organic matrix. The key to the understanding of these processes should therefore be sought in the adjacent cell layer.  相似文献   

5.
ABSTRACT – The contents of Ca and P in developing enamel of the continuously growing rat incisor were examined by the electron microprobe. A longitudinally sectioned, epoxy res-in-embedded maxillary incisor from a 5-month-old rat was analyzed by linear scans across the enamel at intervals from the growing end. Near the growing end, concentrations of approximately 2 % Ca and 1 % P were found close to the ameloblast-enamel junction, increasing to 18 % Ca and 9 % P near the dentino-enamel junction. With increasing distance from the growing end, a successive increase of the mineral content was observed, together with a leveling out of the concentration gradients from the enamel surface to the amelo-dentinal junction seen at earlier stages of mineralization. Mature enamel contained about 35 % Ca and 17 % P. The results were discussed in the light of previous electron microscopic observations of the same specimen material. It was concluded that in analysis of mineralized tissues in an early stage of development, the mineral content as found by the electron microprobe technique can be considered a valid approximation of the true situation. This technique may also be applied to the study of hard tissues in varying stages of demineralization.  相似文献   

6.
Porphyromonas gingivalis has been implicated as a major pathogen in periodontitis. To determine the role of T cells in the regulation of this disease, a method was developed for the generation and characterization of rat T-cell clones with antigen specificity to P. gingivalis whole cells. The clones studied so far demonstrated a T-helper (Th) phenotype W3/13+, W3/25+, OX8− and OX22−. These T-cell clones proliferated in vitro in response to P. gingivalis, but not to other bacteria (Prevotella intermedia, Actinobacillus actinomycetemcomitans, Wolinella recta, Fusobacterium nucleatum, Streptococcus sanguis). Limiting dilution analysis showed W3/25+, OX8− T cells preferentially respond to P. gingivalis, rather than W3/25−, OX8+ T cells. P. gingivalis-reactive W3/25+ T cells belonged to the OX22− population, suggesting that the OX22− T cells may represent memory cells. All clones tested produced interferon γ, but not interleukin 2. The cloned T-cell F1 significantly enhanced P. gingivalis-specific antibody production (p < 0.03). The availability of these cloned T cells should bring new insight into the mechanism by which T cells regulate oral health and periodontal disease.  相似文献   

7.
Hamster enamel protein extracts were analyzed by RP-HPLC and the isolated fractions by SDS-and Western blotting using polyclonal antibodies against recombinant mouse amelogenin and anti-peptide antibodies against the mouse exon 4-encoded sequence. Total RNA was extracted from enamel organ epithelia and, using a 3′ rapid amplification of cDNA ends (3′ RACE) technique, the coding regions for three different amelogenin isoforms were cloned along with the 3′ non-coding region. DNA sequencing revealed that the hamster amelogenin isoforms are 180, 73 and 59 amino acids in length, respectively. The 59-residue amelogenin corresponds to the leucine-rich amelogenin protein (LRAP), the 73-residue amelogenin corresponds to LRAP with the inclusion of the exon 4-encoded sequence, while the 180-residue amelogenin is the most abundant amelogenin isoform. Edman degradation was performed on purified hamster amelogenin, which provided the amino acid sequence in the region encoded by the 5′ PCR amplification primer used in cloning. Therefore, the entire derived amino acid sequence of hamster amelogenin was revealed. The hamster amelogenin amino acid sequence was aligned with all its known homologues. Hamster differs from rat and mouse amelogenin at only three amino acid positions. Southern blot analysis using a panel of restriction enzymes gave the same pattern for hamster DNA obtained from males and females, suggesting that in hamster, as in mouse, amelogenin is expressed from a single gene located on the X chromosome.  相似文献   

8.
Nineteen 8-week-old female Sprague-Dawley rats were used to observe macroscopically the direction of tooth movements following removal of approximal contacts. In 10 rats, under anaesthesia, approximal contact between the second and third right maxillary molars (M2–M3) was removed by grinding. These animals and a control group of nine rats were housed with normal diet and water ad libitum for 7 weeks. After killing, the skulls of all animals wre removed, dried, and fixed in a standardized position on a Horsley-Clarke type stereotaxic frame. Using a micromanipulator graduated to 1/100 mm and mobile in three orthogonal directions, distances between the teeth (M1 or M3) and some bone structures that served as landmarks were measured. These measurements showed the direction of tooth movements in the experimental approximal space. After statistical analysis of the data, the results showed that the approximal space between M2 and M3 was closed by both a distal drift of M1-M2 and a mesial migration of M3. It was concluded that, in the rat, a mesial drift exists that can be induced by the loss of approximal contact. This movement is distinct from the distal physiological dental migration classically described in histological studies.  相似文献   

9.
abstract — With adenylyl-imidodiphosphate as a specific substrate, adenyl cyclase has been demonstrated at the plasma membranes of all epithelial cells except the ameloblasts in the enamel organ of rat incisors. Hydrolysis of the substrate was found to be stimulated by 10 mM sodium fluoride in the incubation medium.  相似文献   

10.
abstract — Previous studies have shown that the pigmented surface layer of rat incisor enamel contains up to 30% iron but have left the question open as to whether iron is bound to the hydroxyapatite crystals or is present as a separate crystalline phase. Maxillary incisors from adult rats were demineralized for an extended period of time in EDTA. An insoluble membranous structure representing the remaining superficial portion of the enamel was collected and analyzed in the electron microprobe. The analyses showed that the demineralization procedure had removed calcium and phosphorus nearly completely, whereas the iron content of the surface layer had not been appreciably reduced. Electron microscopic examination of these specimens showed that the residual material contained electron-dense particles whose size, form and orientation indicated that they were remnants of the original crystal population. Several other demineralized and undemineralized specimens were also examined electron microscopically. The results indicate that iron is not present as a separate particulate phase but is, probably, bound to the surface of hydroxyapatite crystals.  相似文献   

11.
A 99.5 per cent pure aluminium step-wedge served as reference for evaluating the radiopacity of 55 anterior and posterior composites. The radiopacity of all materials evaluated was compared with the radiopacity of human enamel and human dentine of equivalent sample thickness. Seventeen composites exhibited a radiopacity significantly greater than that of enamel. Some composites intended for posterior use lack the radiopacity required for posterior composite restorations.  相似文献   

12.
These effects were examined with and without pretreatment of animals with reserpine and the adrenergic antagonists prazosin (1), yohimbine (2) and propranolol (β). The effects of clonidine on glandular concentrations of norepinephrine and dopamine also were examined. These effects were compared with those of xylazine, a presynaptic 2-adrenergic agonist. A single, high dose of clonidine followed by an overnight fast caused marked increases in calcium content and acinar secretory granules in the submandibular and sublingual glands, similar to those caused by reserpine. However, the calcium content of the parotid gland was not altered by clonidine. although there seemed to be a modest increase in acinar secretory granules. The clonidine-induced increase in submandibular calcium content could not be attributed to any adrenergic receptor activity since it was not blocked by either - or β-adrenergic antagonists. Unlike reserpine, clonidine did not affect catecholamine concentrations in the parotid and submandibular glands. Pretreatment with reserpine did not significantly alter the clonidine-induced increase in submandibular calcium content. It is likely that the greater accumulation of acinar secretory granules is related to the increased calcium stores of the glands in clonidine- and/or reserpine-treated rats. The large differences in calcium content among the three glands might be attributable, in part, to differences in the calcium-binding capacity of their secretory granules. Possible mechanisms for the clonidine effects on salivary-gland calcium include disturbances in membrane-associated pools or gating mechanisms for calcium, which need further study.  相似文献   

13.
Leucine-rich amelogenin peptide (LRAP) is an alternately spliced amelogenin. LRAP is known to bind to hydroxyapatite, and has been shown to signal mesenchymal cells to proliferate, but its function in enamel formation is unclear. The purpose of this study was to determine the calcium-binding properties and structure of recombinant human LRAP (rLRAP) compared with full-length amelogenin (rH174). rLRAP and rH174 were synthesized in Escherichia coli and purified by affinity chromatography and reverse-phase high-performance liquid chromatography. Calcium binding was measured by isothermal titration calorimetry (ITC) at pH 7.5 and 25°C, and raw data were analyzed by origin 7.0 software. The structure of rLRAP was analyzed by nuclear magnetic resonance (NMR) and circular dichroism (CD) in the absence or presence of Ca2+, pH 7.5 and 4.0, at 25°C. Thermodynamic values showed that rLRAP had a Ca2+-binding affinity ≈ 6.4-times greater than rH174. NMR and CD data revealed that rLRAP was randomly coiled, and that this structure was not altered by Ca2+, which bound to rLRAP and rH174 via ionic interactions. Unlike r174 ( β -spiral), rLRAP had a random-coiled structure. The calcium binding and structural differences between rLRAP and rH174 suggest that these proteins have different functions in enamel biomineralization.  相似文献   

14.
15.
abstract — The enamel of rat incisors is characterized by a pigmented, iron-rich surface layer. The Fe content and degree of mineralization of this enamel layer in rats fed an Fe-deficient diet were studied using the electron microprobe. Four groups of eight 24-day-old rats were fed a milk diet, Fe-fortified milk diet, Cu-fortified milk diet, and Fe+Cu-fortified milk diet, respectively, for 10 weeks. At the end of the experimental period, incisor pigmentation was markedly reduced in the animals fed the Fe-deficient diets. Close to the enamel surface, the Fe content averaged 1.9% in the midsagittal area, as opposed to 9.9% Fe in the controls. Variation of Cu supply had no effect on hemoglobin values or Fe content of incisor enamel. In a second experiment, rats were fed a milk diet with and without Fe supplementation. Nearly colorless incisors from animals sacrificed after 16 weeks on the milk diet contained 1.9% Fe (range 1.4–2.5%) close to the enamel surface. In this region, the Ca content averaged 33.7% and P 17.2%. Normally orange-colored incisors from animals receiving the Fe-supplemented diet contained, in the same region, 9.9% Fe (9.3–10.5%), 28.9% Ca, and 16.0% P. While pigmentation and Fe content of incisor surface enamel were markedly reduced as a result of the Fe-deficient diet, the Ca and P contents had increased to values similar to those found in non-pigmented subsurface enamel. The Ca/P weight ratio of incisor surface enamel was 1.96 in the iron-deficient animals and 1.81 in the controls.  相似文献   

16.
The ultimate loads required to extract three mandibular molars in the dissected jaw were examined after elimination of the antagonistic teeth for up to 64 days. The ultimate loads in the experimental first and second molars decreased rapidly in the first few days, while those in the third molar remained low during the same period in both experimental and control groups. The ultimate loads in all three molars of the experimental animals then increased gradually towards the end of the experiment at rates similar to those in controls. Maximum relative reductions of the ultimate load were observed within the first 8 days in all three molars. An increase in the length of roots was also found in all hypofunctional molars. Daily rates of root elongation ranged from 13 to 19 μm/day in the control and from 18 to 26 μm/day in the experimental molars during the whole experiment. The greatest value (80 μm/day) was obtained during the first 8 days in the third molars of both control and experimental animals. Thus the mechanical strength of the periodontal ligament estimated in vitro may be increased by the development of teeth and by non-functional occlusal contacts with the opposing gingiva-covered alveolar ridge deprived of its tooth crowns. The ligament of the third molar was apparently immature at the beginning of the experiment.  相似文献   

17.
目的 探讨人釉原蛋白(AM)全长及其N端酪氨酸富集段(TRAP)、C端亮氨酸富集段(LRAP)体外自组装的动态过程及其在羟磷灰石(HA)晶体形成中的作用.方法 体外重组、纯化人AM全长及其功能片段TRAP、LRAP,在三氨基甲烷(Tris-HCl)中配制成100μg·mL-1、pH=8的蛋白溶液,室温孵育1~15 mi...  相似文献   

18.
abstract — The present report describes a new method for rapidly and gently isolating the enamel organ of the rat incisor for use in histologic studies. Incisors from 3-month-old rats were fixed by perfusion with glutaraldehyde or formaldehyde. The jaws were trimmed, and, using a technique that controlled the fracture of the alveolar bone, the enamel organ was denuded along its entire length. After 3 d in an EDTA solution, the denuded enamel organ could be isolated in three parts. The apical cone representing the growing end of the incisor was cut off. The intermediate portion adjacent to the thick, immature enamel was separated from the dentin by blunt dissection, and the remaining part on the mature enamel was readily lifted away from the tooth surface. The specimens were dehydrated, taking special precautions against twisting due to shrinkage, and embedded in polyester wax. Sections of such enamel organs show excellent cellular preservation with no disruption of histologic relationships.  相似文献   

19.
The rat mandible has been used to study fractures, ridge augmentation, bone defects, and the effects of cryosurgery, all of which affect the structural properties of the mandible. The only previously described mechanical test of the rat mandible used three-point bending with a piece of foam placed between the lingual surface of the mandible and the support. The accuracy and reproducibility of this test were not determined. Two different, three-point bending tests for characterizing the structural properties of the rat mandible have now been evaluated. Acrylic specimens representing three different-sized mandibles were tested in three-point bending with either potted ends or foam interposed between the specimen and the outer load points. Flexural stiffness and failure load were compared against data from a conventional three-point bending test. In addition, five paired halves of 90- and 210-day-old rat mandibles were tested either with interposed foam or with potted ends and the mean coefficients of variation of the stiffness and failure loads were determined. Failure loads of the acrylic specimens with the potted and foam methods were significantly higher (50 and 10%, respectively; p < 0.05) than with the conventional method. The stiffness of the acrylic specimens with the potted and foam methods was significantly different (75% higher and 21% lower, respectively; p < 0.05) than with the conventional test. In addition, there was no difference between the coefficient of variation in stiffness (26 + 11%) or failure load (10 + 4%) measured with the foam test and the comparable values (16 + 11%) and (18 + 13%) in the potted test. Thus it appears that the foam test more accurately reflects the stiffness and failure load of the acrylic specimens than the potted test. Although there was no difference in the coefficients of variation in the potted and foam tests, the technical difficulties associated with potting indicate that the foam test is a better method for testing the structural properties of the rat mandible. The objective of this experiment was to establish a method for accurately measuring the structural properties of the rat mandible and for detecting differences in structural properties between different treatment groups.  相似文献   

20.
On the formation of amelogenin microribbons   总被引:3,自引:0,他引:3  
We recently reported the remarkable spontaneous self-assembly and hierarchical organization of amelogenin 'microribbons' and their ability to facilitate oriented growth of apatite crystals in vitro . In a letter of correction we communicated the finding that the X-ray diffraction pattern reported in our original report was that of cellulose contaminant and not amelogenin microribbon. We have re-evaluated our data and confirmed the protein nature of the microribbons using Fourier transform infrared and Raman microspectroscopy. Some microribbons were remarkably similar in their morphology to that of cellulose fibers. The size distribution of amelogenin microribbons was wider, particularly in width and length, and generally smaller than those originally reported. Here we present additional detailed information on the formation of a series of intermediate hierarchical structures of amelogenin assemblies prior to the formation of microribbon. The most significant finding was that full-length amelogenin nanospheres had a tendency to assemble into collinear arrays whose function is assumed to be critical at the initial stage of enamel mineral deposition. The present data gives an insight into the step-by-step assembly process of amelogenin from nanometer scale molecules to micrometer scale organized structures that can be used as templates for controlled and oriented growth of apatite mineralization in vitro .  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号