An in vitro model for videoimaging of human bladder smooth muscle cell contractions

Knowledge regarding human bladder smooth muscle cell (SMC) physiology is very limited. Only a few specific medical therapies for bladder disorders have therefore been established. The objective of this study was to develop a model for videomicroscopy of bladder SMC contractions. Cells were isolated from human cystoprostatectomy specimens and cultured in a modified EMEM medium. These cells were identified as SMCs by means of immunohistochemistry. For videomicroscopy, the culture flasks were coated with a viscous agent to allow cell contraction. Contractions were visualized by means of a cell culture microscope with a time-lapse videosystem. For cholinergic stimulation of the cells, acetylcholine, in concentrations ranging from 100 μM to 10 mM, was applied. The percentage of contracting cells within the observation field was evaluated for quantitative analysis. In control experiments without contractile stimulant 6% of the cells were observed to contract. Stimulation with acetylcholine induced a significant dose-dependent increase to 47% in contracting cells. These results demonstrated that videomicroscopy is an appropriate tool to investigate the contraction mechanisms of bladder SMCs. This model offers the possibility of studying drug effects on the human detrusor in vitro. Received: 16 September 1999 / Accepted: 1 May 2000     

Cell length measurements in longitudinal smooth muscle strips of the pig urinary bladder

Summary In this study the length of smooth muscle cells in muscle bundles of pig urinary bladder wall was determined after dissection in Tyrode buffers with different calcium concentrations ([Ca²⁺]). Previous studies have shown that the length of isolated smooth muscle cells decreases with an increase in [Ca²⁺] in the buffer. Unlike the results in isolated cells, no significant differences in length were found between cells in strips subjected to different [Ca²⁺]. Cells in bundles dissected from filled bladders were significantly larger than those dissected from emptied bladders. Cells in strips from emptied bladders dissected in 1.8 mM Ca²⁺-Tyrode buffer were shorter than those obtained in Ca²⁺-free buffer. From the measurements it was concluded that: (1) Cell length in intact tissue is directly related to tissue length; series elastic structures external to the cells do not allow significant shortening of the cells. (2) Passive parallel elasticity outside the cells accounts for passive shortening when bladders are emptied manually. (3) Cell length is not related to empty bladder weight. (4) A positive relation exists between empty bladder weight and bladder capacity.     

引导性骨再生中成骨细胞来源的实验观察

目的 研究 长管骨引导性骨再生成骨细胞来源,进一步完善引导性骨再生理论。方法 将４２只成年雄性新西兰兔在双侧桡骨中段制作标准骨缺损不愈合模型,用硅胶膜呈管状包囊一侧骨缺损,另一侧作为对照侧。１只兔术后１￣１２周分别于每周进行Ｘ线检查;３０只兔,随机分为６组,分别于术后３天、１、２、３、４、５周外死取材,分别进行常规ＨＥ染色,ＳＰ方法ＢＭＰ、ＢＧ抗体的免疫组化染以。结果 隔膜在骨缺损局部生成隔离密闭     

重组人骨形态发生蛋白-2缓释微球对成骨细胞的作用

目的　探讨甲基丙烯酸缩水甘油酯右旋糖酐 (dex GMA)重组人骨形态发生蛋白(rhBMP 2 )凝胶微球 (rhBMP2 dex HM )对成骨细胞的生物学作用。方法　将单纯rhBMP 2 (A组 )、空白dex GMA凝胶微球dex HM (B组 )和rhBMP2 dex HM (C组 )加入成骨细胞培养液中 ,用细胞计数法、噻唑蓝比色法 (MTT法 )、流式细胞仪观察细胞增殖情况 ,并检测成骨细胞上清液中骨钙素 (BGP)含量。结果　培养 1～ 2d后 ,3组细胞计数、吸光度 (A)值差异无统计学意义 (P >0 .0 5 ) ;4～ 6d时A、C组细胞计数和A值开始高于B组 ,但A、C组间差异无统计学意义 (P >0 .0 5 ) ;培养 6～ 8d后 ,C组明显高于其他组 ,差异有统计学意义 (P <0 .0 1)。14d后 ,A、B、C 3组细胞数分别为 (2 2 .97± 0 .2 3 )、(13 .89± 0 .5 7)和 (3 2 .46± 0 .67)× 10 4个细胞 /ml,差异有统计学意义(P <0 .0 1)。流式细胞仪检测结果显示 ,培养 2d后 ,A组的G2 /M +S期百分数最高 ;6～ 8d后 ,C组的G2 /M +S期百分数最高。成骨细胞上清液中BGP含量 ,C微球组最高 ,其次为A组。结论　rhBMP 2 dex HM可以较长时间持续释放活性rhBMP 2 ,作为rhBMP 2的缓释载体 ,可以明显促进成骨细胞增殖和分化。     

Differential modulation of RANKL isoforms by human osteoarthritic subchondral bone osteoblasts: influence of osteotropic factors

BACKGROUND: Osteoarthritis (OA) is the most common human joint disease. Recent studies suggest that an abnormal subchondral bone metabolism is intimately involved in the genesis of this disease. Bone remodelling is tightly regulated by a molecular triad composed of OPG/RANK/RANKL. RANKL exists as 3 isoforms: RANKL1, 2, and 3. RANKL1 and 2 enhance osteoclastogenesis whereas RANKL3 inhibits this phenomenon. We previously reported that human OA subchondral bone osteoblasts can be discriminated into two subgroups according to their level of PGE2 [low (L) or high (H)]. Moreover, we also showed that L-OA osteoblasts express higher levels of total RANKL compared to H-OA osteoblasts. In this study, we investigated the level of membranous RANKL, comparing L- and H-OA subchondral bone osteoblasts, as well as its modulation by osteotropic factors. The impact of the modulation of RANKL1 and 3 on the membranous RANKL level was also studied. METHODS: Gene expression was determined using real-time PCR for RANKL1 and semi-quantitative PCR for RANKL3. Membranous RANKL was measured by flow cytometry. The modulation of membranous RANKL and RANKL isoforms was monitored on the L- and H-OA osteoblasts and also following treatment with osteotropic factors, including vitamin D3 (50 nM), IL-1beta (100 pg/ml), TNF-alpha (5 ng/ml), PGE2 (500 nM), PTH (100 nM), IL-6 (10 ng/ml) and IL-17 (10 ng/ml). RESULTS: Membranous RANKL levels were significantly increased in L-OA osteoblasts compared to normal (p<0.01) and H-OA (p<0.05). The gene expression level of the RANKL1 profile was reminiscent of the membranous RANKL level. Although RANKL3 gene expression was lower on the H-OA osteoblasts than on normal and L-OA osteoblasts (p<0.03), the overall outcome favoured RANKL1. Treatment with the tested factors showed a significant increase in membranous RANKL on the L-OA osteoblasts, with the exception of PTH and IL-17. Interestingly in this subpopulation, the RANKL3 gene expression level was significantly increased upon PTH and IL-17 treatment. No effect of the tested osteotropic factors was found on the H-OA. CONCLUSION: Our findings showed that the normal, L- and H-OA subchondral bone osteoblasts differentially express membranous RANKL and RANKL isoforms, and that treatment with osteotropic factors generally favours increased membranous localization of RANKL on L-OA compared to H-OA osteoblasts. This phenomenon appears to take place through differential modulation of each RANKL isoform.     

Formation of bone by isolated,cultured osteoblasts in millipore diffusion chambers

Summary Osteoblast-like and osteoclast-like cells freed from neonatal calvaria by sequential enzymatic digestion after 6–7 days in culture were placed in diffusion chambers and implanted in the peritoneal cavities of CD-1 mice. About half of the chambers also contained a dead calvarium to test for the need of an “inducer.” After 20 days, 11 of 18 chambers containing the osteoblast-like cells formed large foci of mineralized bone that corresponded to alkaline phosphatase activity throughout the chambers. Moreover, only type I (i.e., bone) collagen was formed. Occasional deposits of bone were found in only 3 of 22 chambers containing the osteoclast-like cells. The presence of dead bone did not affect any of the results. These data confirm the osteoblast-like nature of the isolated cell populations and demonstrate that these cells retain their differentiated function in culture.     

A possible role for nitric oxide in the regulation of human ureteral smooth muscle tone in vitro

There is ample evidence that nitric oxide (NO) is an important neurotransmitter in many tissues of the urogenital tract. The aim of the present study was to examine the possible role of NO in ureteral relaxation. Human ureteral rings were mounted in organ bath chambers and precontracted with KCl. Increasing doses of the NO donor linsidomine (SIN-1) were added with and without prior blockade of the NO/cGMP pathway by methylene blue and protein kinase (PK) inhibitors Rp-8-pCPT-cGMPS and Rp-8-CPT-cAMPS. Electrical field stimulation (EFS) was done before and after incubation with L-NOARD (N ^G-nitro-L-arginine) and TTX (tetratodoxin). For detection of neuronal NO synthase (NOS), ureters were stained immunohistochemically. Ureteral strips were dose dependently relaxed by SIN-1; preincubation with methylene blue and protein kinase G inhibitor significantly reduced the SIN-1-induced relaxations. No effects of L-NOARG and TTX on EFS-induced tone alterations were found. NOS-positive neuronal axons and nerve-ending-like structures were found in the muscular layers. Our in vitro findings suggest that ureteral relaxation may involve the NO pathway.     

海绵体脱细胞基质和平滑肌细胞相容性的研究

目的探讨海绵体脱细胞基质（ACCM）与人脐动脉平滑肌细胞（HUASMCs）的相容性。方法以1％的Triton-X100与0．1％NH3H2O制备ACCM。异体肌肉内埋植实验评价ACCM的生物相容性。分离培养HUASMCs，噻唑蓝（MTT）法测定ACCM浸提液对HUASMCs增殖的影响。将3—5代的HUASMCs接种ACCM，共培养3、5、10d后观察HUASMCs与ACCM复合情况。结果ACCM无细胞残留，异体肌肉内埋植实验证实ACCM生物相容性良好。浸提液实验显示体外培养第4天和第6天，浸提液组A值明显高于对照组（P〈0．05）。HUASMCs能渗人ACCM内部，并分化形成平滑肌柬。结论ACCM与HUASMCs相容性良好，两者复合有望构建组织工程海绵体平滑肌。     

联合成骨细胞移植促进骨髓移植小鼠的造血功能重建

目的 探讨联合成骨细胞移植对骨髓移植小鼠造血功能重建的影响.方法 Balb/c小鼠60只,取其中18只制备移植用骨髓有核细胞和成骨细胞.将其余42只小鼠分为3组.单纯移植组:小鼠18只,仅进行骨髓移植(BMT);联合移植组:18只,进行BMT的同时每只小鼠输入成骨细胞2×106个;正常对照组:小鼠6只,不做任何处理,仅作为移植前的正常对照.移植组小鼠在全身照射(TBI)预处理后4 h经尾静脉注入骨髓细胞2×106个.移植后第7、14和21天,分别处死移植组小鼠6只,对小鼠的外周血细胞和骨髓单个核细胞(BMMNC)进行计数,采用流式细胞术测定BMMNC中CD34+细胞的百分比,使用HPIAS-1000高清晰度彩色病理图像系统测量骨髓造血组织面积,采用免疫组化染色法测定骨髓组织微血管密度(MVD).结果 移植后第7天,单纯移植组和联合移植组小鼠外周血细胞计数及BMMNC数均明显低于正常对照(P＜0.01).第21天时联合移植组小鼠白细胞、红细胞及BMMNC数明显恢复,血小板数已接近正常对照组;单纯移植组小鼠外周血细胞数和BMMNC数虽然有所恢复,但其恢复程度明显弱于联合移植组.移植后第7、14和21天,联合移植组外周血细胞计数及BMMNC数均明显高于同期单纯移植组(P＜0.01或P＜0.05).移植后第7、14、21天,单纯移植组和联合移植组小鼠骨髓造血组织面积、BMMNC中CD34+细胞百分比及骨髓组织MVD均明显低于正常对照组(P＜0.01),但联合移植组均高于同期单纯移植组(P＜0.01或P＜0.05).结论 联合成骨细胞移植能有效促进骨髓移植小鼠骨髓造血系统的重建.

Abstract：

Objective To explore the effects of cotransplantation with osteoblasts on hematopoietic reconstitution in mice after bone marrow transplantation (BMT). Methods The typical model of syngeneic BMT was established. 18 Balb/c mice were used to prepare the bone marrow nuclear cells and osteoblasts for BMT. The 42 Balb/c mice were randomly divided into 3 group:normal group (6 mice, without any treatment), the single BMT group ( 18 mice, given 2 × 106 bone marrow nuclear cells/each mouse) and the cotransplantation group of HSC with osteoblaats (18 mice,given 2 × 106 bone marrow nuclear cells and osteoblasts/each mouse). The following factors were measured on day 7, 14, 21 after BMT: peripheral blood cells, bone marrow mononuclear cells (BMMNC), the percentage of CD34+ cells in BMMNC (assayed by flow cytometry), the hematopoietic tissue changes (detected by HPIAS-1000 image analysis system) and micro vascular density (MVD) of bone marrow tissue (with immunohistochemistry). Results The levels of periphral WBC, RBC, PLT, BMMNC in the contransplantation group were higher than those in the single BMT group (P＜0. 01 or P＜0. 05). In the contransplantation group, the percentage of CD34+ cells in BMMNC, the hematopoietic tissue area and the MVD of bone marrow were also higher than the single BMT group on the 7th, 14th, 21st day after BMT(P＜0.01 or P＜0.05). Conclusion Cotransplantation with osteoblasts could significantly promote hematopoietic reconstruction in mice after BMT. Cotransplantation may represent a promising means of achieving higher engraftment rate after BMT.     

Pancreatic duct obstruction itself induces expression of alpha smooth muscle actin in pancreatic stellate cells

BACKGROUND: Pancreatic stellate cells (PSCs) are thought to be responsible for pancreatic fibrosis. Although fibrosis is a major characteristic of chronic pancreatitis (CP) induced by pancreatic duct obstruction, it is unclear whether pancreatic duct obstruction itself activates PSCs. METHODS: To test the hypothesis that pancreatic duct obstruction activates PSCs, clinical and experimental analyses were performed using alpha smooth muscle actin (alpha-SMA) as a marker of their activation. In clinical analysis, surgical specimens from the patients with pancreatic cancer or cancer of the papilla Vater were classified into two groups with or without duct obstruction. alpha-SMA expression was examined on these specimens, and the difference between two groups was evaluated. In animal experiment, duct ligation-induced pancreatitis was developed in rats by ligating the secondary pancreatic duct in duodenal segment, and the expression of alpha-SMA was examined. RESULTS: In clinical analysis, the specimens from the pancreas with duct obstruction (14 cases) expressed alpha-SMA significantly stronger than those from the pancreas without duct obstruction (7 cases). All specimens in the former expressed alpha-SMA, but 4 specimens from the latter did not at all (P < 0.05). In animal experiment, alpha-SMA expression was detected 7 days after the ligation and was increased on the 10th day. CONCLUSIONS:We can assume that pancreatic duct obstruction itself activates PSCs. This mechanism may play roles in the development of CP from multiple origins.     

塞来昔布抑制骨髓间充质干细胞的增殖和成骨诱导分化

目的 探讨非甾体类抗炎药塞来昔布对人骨髓间充质干细胞(hBMSCs)增殖和分化成骨的影响.方法 骨髓取自1名健康男性,采用Ficoll-Paque密度梯度离心分离hBMSCs,并进行体外扩增.在细胞增殖和诱导过程中加入不同浓度(12.5、25.0、50.0、100.0 μmol/L)的塞来昔布,采用细胞计数试剂盒(CCK8)方法测定塞来昔布对hBMSCs增殖的影响.使用地塞米松、维生素C等试剂诱导hBMSCs分化成骨,在hBMSCs成骨过程中加入100 μmol/L塞来昔布,通过碱性磷酸酶(ALP)活性分析、钙定量分析等方法测定塞来昔布对hBMSCs成骨的影响,通过Western blot方法检测塞来昔布对hBMSCs分化成骨关键转录因子Runx2表达的影响.结果 塞来昔布的作用呈现剂量依赖性.12.5～100.0 μmol/L塞来昔布对hBMSCs细胞增殖均有抑制作用,该作用随着药物浓度的增加而增强.大剂量的塞来昔布抑制hBMSCs分化成骨中的碱性磷酸酶和钙沉积,并抑制转录因子Runx2的表达.结论 塞来昔布抑制hBMSCs增殖和成骨分化,并与剂量成正相关.长时间使用,尤其是大剂量使用塞来昔布的患者应考虑到其对成骨分化的抑制作用.     

常用麻醉性镇痛药对家兔支气管平滑肌腺苷酸环化酶和磷酸二酯酶活力的影响

常用麻醉性镇痛药吗啡、哌替啶和芬太尼对家兔离体支气管平滑肌腺苷酸环化酶（ＡＣ）和磷酸二酯酶（ＰＤＥ）活力的影响，结果表明：吗啡可使ＡＣ的活性由对照组的１５．９９１１±０．８５７９ｕ降至１５．０４６３±０．７９８９ｕ，Ｐ＜０．０５．在吗啡加纳络酮组，这种对ＡＣ的抑制作用依然存在。芬太尼使ＰＤＥ的活性由对照组的３．４８９２±０．７１２３ｕ上升至４．３０５４±０．７６７４ｕ，Ｐ＜０．０５。实验结果提示：（１）吗啡可减少支气管平滑肌中的ｃＡＭＰ生成，芬太尼可增加ｃＡＭＰ的降解，致使ｃＡＭＰ含量减少，这可能与其增加支气管平滑肌张力的作用有关；（２）吗啡对支气管平滑肌ＡＣ的抑制作用不受纳络酮的影响，提示该作用可能不是通过阿片受体起作用的，作用焦点可能在Ｇ－蛋白或催化亚单位。     

Nitric oxide mediates relaxation in rabbit and human corpus cavernosum smooth muscle

Summary We investigated in vitro the relaxant effect of exogenous acetylcholine (ACh) and electric-field stimulation (EFS) on rabbit and human corpus cavernosum smooth muscle strips (CC) precontracted with phenylephrine. The effects of EFS and ACh were monitored alone, after muscarinic receptor blockade and after inhibition of nitric oxide (NO) formation with l-N-nitroarginine (l-NOARG). In rabbit und human CC, both atropine and l-NOARG abolished the relaxant effects of ACh. The relaxant effects of EFS, however, were only slightly reduced by atropine to 97.5±17.5% in human CC and to 89.0±6.1% in rabbit CC. l-NOARG further reduced the EFS effects to 0.8±1.7% in human CC and to 16.2±8.7% in rabbit CC. In strips obtained from impotent patients with diabetes mellitus, the relaxant effects appeared to be significantly less than in strips from nondiabetic impotent men. Tetrodotoxin blocked the relaxant EFS effects in human and rabbit strips completely. The data indicate the important role of NO in cholinergically induced relaxation of cavernous smooth muscle in rabbits and humans. Our findings support the idea of NO as the nonadrenergic noncholinergic neurotransmitter in penile erection in both species. Rabbit erectile tissue might serve as an in vitro animal model for further investigation.     

醛固酮诱导大鼠主动脉平滑肌细胞凋亡

目的 观察醛固酮在体内能否诱导主动脉平滑肌细胞凋亡.方法 将24只SD大鼠随机分为3组,每组8只:(1)空白溶剂设为对照组;(2)醛固酮组;(3)醛固酮+血管扩张剂组.渗透泵内分别注入醛固酮(1 μg/h)或空白溶剂,然后埋于大鼠背部皮下.肼苯哒嗪[25 mg/(kg·d)]溶于引用水,每日灌胃1次.8周后脱氧核苷酸末端转移介导的缺口末端标记法(TUNEL)检测凋亡的主动脉平滑肌细胞.结果 醛固酮组和醛固酮+血管扩张剂组大鼠主动脉TUNEL阳性的平滑肌细胞分别占(18.0±1.5)％和(16.5±2.0)％,与对照组(4.7±1.0)％比较,差异有统计学意义(P＜0,05);后两组之间差异无统计学意义(P＞0.05).结论 醛固酮在体内可以直接诱导主动脉平滑肌细胞凋亡.     

Direct inhibitory effect of erythromycin on human alimentary tract smooth muscle

BACKGROUND: Erythromycin was found to stimulate motor activity in the upper gastrointestinal tract. However, in several smooth muscle preparations, it also elicited an inhibitory effect. Our aim was to study the effect of erythromycin in various human alimentary tract smooth muscles. METHODS: Using force measurements, we assessed the effect of erythromycin on electrically and chemically evoked contractions of isolated muscle strips of human gallbladder, small intestine, and colon. RESULTS: The muscarinic receptor agonist carbachol evoked contraction in gallbladder, ileum, and colonic smooth muscle that were reduced by erythromycin at 10(-4) M to 72% +/- 24%, 77% +/- 22%, and 76% +/- 22% of control values, respectively. Erythromycin did not affect contractions evoked by noncholinergic agents. Erythromycin's inhibitory effects were not altered by nerve blockade, indicating a direct muscle effect. Eryrthromycin also reduced contractions evoked by electrical stimulation at frequencies of 5, 10, and 20 Hz in the human gallbladder, ileum, and colon preparations. These contractions were reduced by erythromycin in a reversible and dose-dependent manner. CONCLUSIONS: Erythromycin antagonized direct cholinergic effects on various smooth muscles from the human alimentary tract in a concentration-dependent manner.     

Qtracker体外标记兔成骨诱导分化后细胞的初步研究

目的 探讨Qtracker体外标记兔成骨诱导分化后细胞的特点及可行性.方法 抽取3个月龄健康新西兰大白兔骨髓,贴壁培养骨髓基质干细胞(BMSCs),传至第3代后向成骨细胞诱导,并做鉴定.Qtracker分别以1、2、4、8、16和32 nmol/10~6细胞的浓度标记成骨诱导分化后细胞,分别记为A、B、C、D、E、F组;未标记的细胞作为空白对照组(G组).分别利用荧光显微镜计数和流式细胞术两种方法枪测标记阳性率,台盼蓝拒染法检测标记后细胞存活率,甲基噻唑基四唑(MTT)法观察Qtracker染料对细胞增殖的影响.结果 兔BMSCs经诱导后能向成骨细胞诱导分化.经Qtracker标记后,荧光显微镜下胞浆呈绿色荧光.随着标记浓度的增加,A、B、C、D、E、F组细胞标记阳性率逐渐增高,于8 nmol/10~6细胞的浓度标记时,在荧光显微镜下计数,标记率可达到(93.58±2.08)%;通过流式细胞仪检测,其标记率为(95.24±1.31)%,经两种方法测定,D、E、F组间标记率差异均无统计学意义(P>0.05),且与其他各组比较差异均有统计学意义(P<0.05);G组各时间点标记阳性率均为0.以不同浓度标记后各组细胞存活率均在96%以上,且各组之间差异无统计学意义(P>0.05).标记Qtracker后对细胞的增殖无影响(P>0.05).结论 Qtracker可用于兔成骨诱导分化后细胞的体外标记,在浓度为8 nmol/10~6细胞下可得到最佳的标记率,且其对成骨诱导分化后细胞的增殖无明显影响.     

苯肾上腺素对体外培养人前列腺平滑肌细胞增殖及凋亡的作用

目的探讨苯肾上腺素（PE）对体外培养人前列腺平滑肌细胞增殖及凋亡的作用。方法将原代培养得到的3—5代人前列腺平滑肌细胞随机分组，各组加入浓度为0．1μmol／L～100μmol／L的PE和／或10μmol／L a1受体阻滞剂酚妥拉明（Ph），以噻唑蓝（MTT）检测细胞增殖情况．原位凋亡法（TUNEL）检测细胞凋亡情况。结果PE浓度大于1μmol／L时对前列腺平滑肌细胞有诱导增殖和抗凋亡作用（P均〈0.05），并且存在浓度依赖性。r分别为0．90和-0．893（P均〈0．05）；10μmol／L Ph能够拮抗PE的诱导增殖和抗凋亡作用（P〈0．01）。结论PE可以通过a1受体信号传导途径诱导体外前列腺平滑肌细胞增殖增加和凋亡减少。     

Cyclo-oxygenase products of arachidonic acid metabolism in rat osteoblasts in culture

Summary The metabolism of arachidonic acid to its cyclo-oxygenase products was studied in monolayer cultures of osteoblast-rich rat calvarial cells and of clonal cell lines from a rat osteogenic sarcoma, enriched in the osteoblast phenotype. Prostanoids were measured by radioimmunoassay after extraction of media and fractionation by high pressure liquid chromatography. In both normal and malignant osteoblasts the major cyclo-oxygenase product was 6-oxo-prostaglandin F_1α, the hydration product of prostacyclin, with lesser amounts of prostaglandin E₂ and prostaglandin F_2α. No significant thromboxane B₂ was detected. Prostaglandins are thought to have a local role in the regulation of bone resorption. These results point to the possible importance of prostacyclin either in bone resorption or in some other local function, e.g., regulation of bone blood flow.     

Radioautographic visualization of3H-fucose incorporation into glycoprotein by osteoblasts and its deposition into bone matrix

Summary The elaboration of bone matrix glycoprotein by osteoblasts of alveolar bone was investigated by radioautography after the intravenous injection of³H-fucose into young rats. At selected times after injection, animals were sacrificed by intracardiac perfusion and demineralized specimens were prepared for light and electron microscope radioautography. At 5 and 10 min after injection, when the blood fucose level was high, silver grains were restricted to the spheroidal and cylindrical saccules of the Golgi apparatus. At 20 min membrane-limited secretory granules were also labeled. By 35 min, the blood fucose level had dropped and silver grains were detected over the apical cortical cytoplasm, in association with secretory granules located therein. Some grains were present over osteoblast processes and the adjacent prebone matrix. By 4 h most of the silver grains had left the cell. At that time they were observed over prebone, adjacent to osteoblast processes, as well as over the prebone-bone junction where a distinct band of label was noted. In demineralized preparations an electron-dense granular material was present at the prebone-bone junction in association with collagen fibrils. These findings provide evidence that osteoblasts in alveolar bone synthesize fucose-containing glycoprotein and indicate that the addition of³H-fucose occurs in the Golgi apparatus. The glycoprotein passes to the apical cortical cytoplasm by way of membrane-limited secretory granules, is exteriorized, and accumulates at the site where prebone transforms into bone (the prebone-bone junction). Since this is also the site of the calcification front, the deposition of labeled glycoprotein may be related to the deposition of bone mineral.