Biomedical subjects

H Sakai

Publications and source records attributed to H Sakai.

At least 253 records · Page 14Linked to original sources

PubMed1999

Cloning and functional expression of a novel degenerin-like Na+ channel gene in mammals.

1. A degenerate polymerase chain reaction (PCR) homology screening procedure was applied to rat brain cDNA in order to identify novel genes belonging to the amiloride-sensitive Na+ channel and degenerin (NaC/DEG) family of ion channels. A single gene was identified that encodes a protein related to but clearly different from the already cloned members of the family (18-30 % amino acid sequence identity). Phylogenetic analysis linked this protein to the group of ligand-gated channels that includes the mammalian acid-sensing ion channels and the Phe-Met-Arg-Phe-amide (FMRFamide)-activated Na+ channel. 2. Expression of gain-of-function mutants after cRNA injection into Xenopus laevis oocytes or transient transfection of COS cells induced large constitutive currents. The activated channel was amiloride sensitive (IC50, 1.31 microM) and displayed a low conductance (9-10 pS) and a high selectivity for Na+ over K+ (ratio of the respective permeabilities, PNa+/PK+ >= 10), all of which are characteristic of NaC/DEG channel behaviour. 3. Northern blot and reverse transcriptase-polymerase chain reaction (RT-PCR) analysis revealed a predominant expression of its mRNA in the small intestine, the liver (including hepatocytes) and the brain. This channel has been called the brain-liver-intestine amiloride-sensitive Na+ channel (BLINaC). 4. Corresponding gain-of-function mutations in Caenorhabditis elegans degenerins are responsible for inherited neurodegeneration in the nematode. Besides the BLINaC physiological function that remains to be established, mutations in this novel mammalian degenerin-like channel might be of pathophysiological importance in inherited neurodegeneration and liver or intestinal pathologies.

Acid Sensing Ion Channels↗

PubMed1999

Differential expression of PSP94 in rat prostate lobes as demonstrated by an antibody against recombinant GST-PSP94.

Prostate secretory protein (PSP94, 94 amino acids) is one of the most abundant proteins secreted from the prostate. Its biological role is unknown and still controversial, although it is assumed to have the potential to be a biomarker and a suppressor of prostate cancer. In order to establish an animal model to further elucidate its biological role, we expressed the mature form of rat PSP94 in Escherichia coli, using a glutathione S-transferase (GST) fusion expression vector; we generated a polyclonal rabbit antibody against the recombinant protein. The antibody specifically recognized recombinant rat PSP94 and cross-reacted only very weakly with its human homologue. Using the characterized anti-rat PSP94 antibody, we found that PSP94 was located primarily in rat prostate. Furthermore, PSP94 is present at different levels in different lobes of rat prostate, with significant levels detectable only in the lateral lobe (LP). In addition, the most abundant PSP94 expression was found in the prostate lobe secretions, and PSP94 levels in LP secretions were at least seven times higher than in secretions from the dorsal prostate (DP). The rat ventral prostate (VP) and other regions of the male accessory glands were found to be almost completely devoid of PSP94. Since most rat prostate dysplasia induced by steroid hormone treatment occurs only in dorsolateral prostate, prostate tissue-specific expression and the expression of PSP94 in dorsolateral, but not other, lobes of the prostate suggest a potential role in prostate targeting and prostate cancer development.

Animals↗

PubMed1999

Weakly bound calcium ions involved in the thermostability of aqualysin I, a heat-stable subtilisin-type protease of Thermus aquaticus YT-1.

Aqualysin I is a heat-stable protease; in the presence of 1 mM Ca(2+), the enzyme is stable at 80 degrees C and shows the highest activity at the same temperature. After gel filtration to remove free Ca(2+) from the purified enzyme sample, the enzyme (holo-aqualysin I) still bound Ca(2+) (1 mol/mol of the enzyme), but was no longer stable at 80 degrees C. On treatment of the holo-enzyme with EDTA, bound Ca(2+) decreased to about 0.3 mol/mol of the enzyme. The thermostability of holo-aqualysin I was dependent on the concentration of added Ca(2+), and 1 mM added Ca(2+) stabilized the enzyme completely, suggesting that aqualysin I has at least two Ca(2+) binding sites, i.e. stronger and weaker binding ones. Titration calorimetry showed single binding of Ca(2+) to the holo-enzyme with an association constant of 3.1 x 10(3) M(-1), and DeltaH and TDeltaS were calculated to be 2.3 and 6.9 kcal/mol, respectively, at 13 degrees C. La(3+), Sr(2+), Nd(3+), and Tb(3+) stabilized the holo-enzyme at 80 degrees C, as Ca(2+) did. These results suggest that the weaker binding site exhibits structural flexibility to bind several metal cations different in size and valency, and that the metal binding to the weaker binding site is essential for the thermostability of aqualysin I.

Binding Sites↗

PubMed1999

Complexity of terminal airspace geometry assessed by lung computed tomography in normal subjects and patients with chronic obstructive pulmonary disease.

Increases in the low attenuation areas (LAA) of chest x-ray computed tomography images in patients with chronic obstructive pulmonary disease (COPD) have been reported to reflect the development of pathological emphysema. We examined the statistical properties of LAA clusters in COPD patients and in healthy subjects. In COPD patients, the percentage of the lung field occupied by LAAs (LAA%) ranged from 2.6 to 67.6. In contrast, LAA% was always <30% in healthy subjects. The cumulative size distribution of the LAA clusters followed a power law characterized by an exponent D. We show that D is a measure of the complexity of the terminal airspace geometry. The COPD patients with normal LAA% had significantly smaller D values than the healthy subjects, and the D values did not correlate with pulmonary function tests except for the diffusing capacity of the lung. We interpret these results by using a large elastic spring network model and find that the neighboring smaller LAA clusters tend to coalesce and form larger clusters as the weak elastic fibers separating them break under tension. This process leaves LAA% unchanged whereas it decreases the number of small clusters and increases the number of large clusters, which results in a reduction in D similar to that observed in early emphysema patients. These findings suggest that D is a sensitive and powerful parameter for the detection of the terminal airspace enlargement that occurs in early emphysema.

Forced Expiratory Volume↗

PubMed1999

Lack of repetition priming effect on visual event-related potentials in schizophrenia.

BACKGROUND: The present study was designed to assess, using event-related potentials, whether aberrant semantic processing reported in schizophrenia results from primary semantic overactivation or contextual dysregulation. METHODS: The visual event-related brain potentials were compared between 9 schizophrenic subjects and 16 normal control subjects performing two kinds of semantic categorization tasks with different nontarget stimuli: 1) nontargets comprising words, pseudowords, and unpronounceable foreign letters and 2) nontargets comprising initial presenting words, immediate repetition words, and delayed repetition words. RESULTS: Schizophrenic subjects showed no evidence suggestive of a greater negative potential associated with words and pseudowords, but they did show a lack of amplitude change associated with immediately repeated words relative to that in control subjects. CONCLUSIONS: These results suggest that aberrant semantic activation in schizophrenia results mainly from a failure to utilize information from preceding words or context, and could explain the increased N400 to the congruent or related words recently reported in this disease.

Adult↗

PubMed1999

Thromboxane A2 receptor linked with the Ca2+ pathway in rat colonic crypt cells.

To clarify the presence of thromboxane A2 (TXA2) receptor in the colonic epithelium, we examined the effect of 9,11-epithio-11, 12-methano-thromboxane A2 (STA2), a stable analogue of TXA2, on intracellular free Ca2+ concentration ([Ca2+]i) of indo-1-loaded single cells in isolated rat colonic crypts by laser confocal microscopy. STA2 increased [Ca2+]i in a concentration-dependent manner with a transient peak phase and a subsequent plateau phase. The EC50 values at peak and plateau phases were 1 and 32 nM, respectively. The STA2-induced increase in [Ca2+]i was completely blocked by two selective TXA2 receptor antagonists, KW-3635 and ONO-3708. These antagonists did not affect both the basal [Ca2+]i and the carbaco-induced increase in [Ca2+]i. Prostaglandin E2 did not increase [Ca2+]i. These results indicate that the STA2-elicited increase in [Ca2+]i is mediated specifically by a TXA2 receptor in colonic crypt cells This is the first report showing the presence of a TXA2 receptor that is associated with Ca2+ mobilization in the colon.

Animals↗

PubMed1999

Stable expression of human beta1,4-galactosyltransferase in plant cells modifies N-linked glycosylation patterns.

beta1,4-Galactosyltransferase (UDP galactose: beta-N-acetylglucosaminide: beta1,4-galactosyltransferase; EC 2.4.1. 22) catalyzes the transfer of galactose from UDP-Gal to N-acetylglucosamine in the penultimate stages of the terminal glycosylation of N-linked complex oligosaccharides in mammalian cells. Tobacco BY2 cells lack this Golgi enzyme. To determine to what extent the production of a mammalian glycosyltransferase can alter the glycosylation pathway of plant cells, tobacco BY2 suspension-cultured cells were stably transformed with the full-length human galactosyltransferase gene placed under the control of the cauliflower mosaic virus 35S promoter. The expression was confirmed by assaying enzymatic activity as well as by Southern and Western blotting. The transformant with the highest level of enzymatic activity has glycans with galactose residues at the terminal nonreducing ends, indicating the successful modification of the plant cell N-glycosylation pathway. Analysis of the oligosaccharide structures shows that the galactosylated N-glycans account for 47.3% of the total sugar chains. In addition, the absence of the dominant xylosidated- and fucosylated-type sugar chains confirms that the transformed cells can be used to produce glycoproteins without the highly immunogenic glycans typically found in plants. These results demonstrate the synthesis in plants of N-linked glycans with modified and defined sugar chain structures similar to mammalian glycoproteins.

Agrobacterium tumefaciens↗

PubMed1999

Molecular cloning and expression of a stress-responsive mitogen-activated protein kinase-related kinase from Tetrahymena cells.

To identify genes responsive to cold stress, we employed the differential display mRNA analysis technique to isolate a novel gene from Tetrahymena thermophila which encodes a protein kinase of 430 amino acids. A homolog of this kinase with 90% amino acid sequence identity was also found in T. pyriformis. Both kinases contain 11 subdomains typical of protein kinases. Sequence analysis revealed that the predicted amino acid sequences resemble those of mitogen-activated protein kinase (MAPK), especially p38 and stress-activated protein kinase which are known to be involved in various stress responses. However, it should be noted that the tyrosine residue in the normally conserved MAPK phosphorylation site (Thr-X-Tyr) is replaced by histidine (Thr226-Gly-His228) in this MAPK-related kinase (MRK). The recombinant MRK expressed in Escherichia coli phosphorylated myelin basic protein (MBP) and became autophosphorylated. However, the mutated recombinant protein in which Thr226 was replaced by Ala lost the ability to phosphorylate MBP, suggesting that Thr226 residue is essential for kinase activity. The MRK mRNA transcript in T. thermophila increased markedly upon temperature downshift from 35 to 15 degrees C (0.8 degrees C/min). Interestingly, osmotic shock either by sorbitol (100-200 mM) or NaCl (25-100 mM) also induced mRNA expression of the MRK in T. pyriformis. In addition, the activity of the kinase as determined by an immune complex kinase assay using MBP as a substrate was also induced by osmotic stress. This is the first demonstration of a MAPK-related kinase in the unicellular eukaryotic protozoan Tetrahymena that is induced by physical stresses such as cold temperature and osmolarity. The present results suggest that this MRK may function in the stress-signaling pathway in Tetrahymena cells.

Amino Acid Sequence↗

PubMed1999

Characterization of free alpha- and beta-chains of recombinant macrophage-stimulating protein.

Human serum macrophage-stimulating protein (MSP) induces motile activity of murine resident peritoneal macrophages and is a growth and motility factor for epithelial cells. It belongs to the plasminogen-related family of kringle proteins, and is secreted as a single-chain, 78-kDa, biologically inactive pro-MSP. Proteolytic cleavage of pro-MSP at a single site yields active MSP, a disulfide-linked alphabeta-chain heterodimer. However cleavage of recombinant pro-MSP yielded not only the disulfide-linked heterodimer, but also free alpha- and beta-chains, indicating that some of the recombinant molecules lacked an alphabeta-chain disulfide. We purified the free chains for characterization. The beta-chain of MSP has three extra cysteines, Cys527, Cys562, and Cys672, which are not found in the plasminogen beta-chain. Disulfide bond analysis showed a Cys527-Cys562, but also a Cys588-Cys672. Coopting Cys588 by Cys672 prevented the expected formation of a disulfide between alpha-chain Cys468 and beta-chain Cys588. Concomitant studies determined structures of oligosaccharides at the three Asn-linked glycosylation sites of MSP. The oligosaccharides at the three Asn loci are heterogeneous; 11 different sugars were identified, all being sialylated fucosyl biantennary structures. We also located the pro-MSP signal peptide cleavage site at Gly18-Gln19 and the scissile bond for formation of mature MSP at Arg483-Val484.

Amino Acids↗

PubMed1999

Prognostic significance of beta-microseminoprotein mRNA expression in prostate cancer.

BACKGROUND: Human beta-microseminoprotein (beta-MSP or PSP94) is a small protein secreted by prostatic epithelial cells. We recently reported the presence of low levels of beta-MSP mRNA expression and protein in most prostate cancer tissues. METHODS: Beta-MSP and mRNA expression was examined by in situ hybridization in biopsy specimens obtained from 92 patients with prostate cancer. All tissue specimens were obtained by needle biopsies prior to treatment. All patients subsequently received endocrine therapy. To estimate the influence of beta-MSP mRNA expression and three possible prognostic factors, i.e., patient age, clinical stage, and Gleason score, on time to progression under endocrine therapy, univariate and multivariate analyses were performed using Cox's proportional hazards regression model. RESULTS: Multivariate survival analysis showed that clinical stage was the strongest prognostic factor (P = 0.006) and that beta-MSP mRNA expression was the second strongest factor (P = 0.038) in 92 patients with stage B-D disease. Analysis of only 51 patients with stage D disease showed that beta-MSP mRNA expression was the only significant prognostic indicator for progression under endocrine therapy (P = 0.003). CONCLUSIONS: The presence of cells that express the beta-MSP transcript may be a novel indicator of potentially aggressive prostate cancer.

Aged↗

PubMed1999

Synergetic activation of outwardly rectifying Cl- currents by hypotonic stress and external Ca2+ in murine osteoclasts.

1. An outwardly rectifying Cl- (ORCl) current of murine osteoclasts was activated by hypotonic stimulation. The current was characterized by rapid activation, little inactivation, strong outward rectification, blockage by DIDS and permeability to organic acids (pyruvate and glutamate). 2. The hypotonically activated ORCl current was inhibited by intracellular dialysis with an ATP-free pipette solution, but not by replacement of ATP with a poorly hydrolysable ATP analogue adenosine 5'-O-(3-thiotriphosphate). The current amplitude was reduced when intracellular alkalinity increased over the pH range 6.6-8.0. 3. Intracellular application of cytochalasin D occasionally activated the ORCl current without hypotonic stress, but inhibited activation of the ORCl current by hypotonic stimulation. The hypotonically activated ORCl current was unaffected by a non-actin-depolymerizing cytochalasin, chaetoglobosin C, but partially inhibited by deoxyribonuclease I. 4. Removal of extracellular Ca2+ inhibited activation of the ORCl current by hypotonic shock, but did not reduce the current once activated. The hypotonically activated ORCl current was partially decreased by intracellular dialysis with 20 mM EGTA. 5. With 10 mM Ca2+ in the extracellular medium, the ORCl current was activated in response to more minor decreases in osmolarity than with 1 mM Ca2+. The increased sensitivity to hypotonicity was mimicked by increasing the intracellular Ca2+ level (pCa 6.5). 6. These results suggest that hypotonic stimulation and a rise in the extracellular Ca2+ level synergistically activate the ORCl channel of murine osteoclasts, and that the activating process is modified by multiple intracellular factors (pH, ATP and actin cytoskeletal organization).

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗

PubMed1999

Enhanced shear-induced platelet aggregation in acute myocardial infarction.

BACKGROUND: Experiments under controlled flow conditions indicate that the binding of von Willebrand factor (vWF) to platelet glycoprotein (GP) Ibalpha and integrin alphaIIbbeta3 (GP IIb/IIIa complex) is crucial for aggregation at elevated shear rates. We have tested how the plasma of patients with acute myocardial infarction affects this process. METHODS AND RESULTS: Citrated plasma was obtained from 18 patients with acute myocardial infarction within 6 hours from the onset of symptoms and from 26 control subjects with chest pain syndrome without evidence of ischemia. Aggregation of normal platelets at high shear rates was significantly greater in the presence of patient than control plasma and was inhibited by both anti-GP Ibalpha and anti-alphaIIbbeta3 monoclonal antibodies. The observed values (mean+/-SD) were 47.6+/-17.8% versus 30.1+/-9.9% at 10 800 s-1 (P<0.01) and 32.9+/-14.1% versus 17.5+/-9.5% at 7200 s-1 (P<0.01), respectively, and were positively correlated with plasma vWF antigen levels and ristocetin cofactor activities. In contrast, at the lower shear rate of 1200 s-1, aggregation was similar in the presence of control or patient plasma and was not inhibited by the anti-GP Ibalpha antibody. Both vWF antigen and platelet aggregation decreased 2 weeks after the onset of myocardial infarction. CONCLUSIONS: Shear-induced platelet aggregation is enhanced in plasma in the presence of acute myocardial infarction, apparently as a result of increased vWF concentration. This may contribute to the onset of acute coronary artery thrombosis and early reocclusion after reperfusion treatment.

Adult↗

PubMed1999

The Dependence of the Apparent Contact Angles on Gravity.

We have studied theoretically the effect of gravity on the rough solid-liquid interface and have shown that its tension is enhanced by gravity when gas is adsorbed at it. As a result, the apparent contact angle on rough surfaces, which has been considered not to be influenced by gravity so far, can be raised by gravity. The calculated dependence of contact angles on gravity under the ordinary conditions of the sessile drop method is large enough to detect by experiment. The observed asymmetrical deviations from Wenzel's contact angle caused by the gas adsorption at the solid-liquid interface and by the liquid adsorption at the solid-gas interface are explained in terms of this gravitational effect. Copyright 1999 Academic Press.

Journal Article↗

PubMed1999

Prevalence of Epstein-Barr virus in oral squamous cell carcinoma.

Forty-six samples of oral squamous cell carcinoma (OSCC) were evaluated for the prevalence of Epstein-Barr virus (EBV) infection by the polymerase chain reaction (PCR), Southern blot hybridization, and in situ hybridization (ISH). EBV DNA was detected in 7 (15.2 per cent) out of 46 samples by a combination of PCR and Southern blot hybridization methods. All seven positive samples showed well-differentiated carcinoma, thus suggesting a possible relationship between EBV infection and the degree of differentiation of carcinoma tissue. Latent infection membrane protein 1 (LMP1) was detected immunohistochemically in six of the EBV-positive OSCCs. However, no signal of the EBV-encoded small RNA (EBER)-1 was demonstrated by the ISH method. No significant relationship was observed between EBV infection and lymph node metastasis. A follow-up study (range from 4.4 to 79 months; mean 34.9 months) showed no recurrence or death to occur in the EBV-positive patients, which thus suggested a good prognosis for EBV-positive OSCC patients.

Adult↗

PubMed1999

Neuronal apoptosis inhibitory protein (NAIP) may enhance the survival of granulosa cells thus indirectly affecting oocyte survival.

In mammals, the postnatal loss of more than 99% of female germ cells is due mainly to the process of ovarian follicular atresia. Atresia is known to be mediated by apoptotic granulosa cell-death. Here we show the involvement of neuronal apoptosis inhibitory protein (NAIP) in ovarian folliculogenesis in which it prevents granulosa cell-death. NAIP has been isolated in association with a neurodegenerative disorder, spinal muscular atrophy (SMA), in which it has been shown to suppress mammalian cell-death induced by a variety of stimuli (Liston et al., 1996, Nature 379:349-353). In an in situ hybridization analysis with mouse ovaries, active expression of NAIP mRNA was localized in the granulosa cells of developing follicles from the primary stage to the Graafian stages, whereas the NAIP gene was not expressed or was weakly expressed in follicles that might be undergoing atresia. Gonadotropin, which is known to inhibit apoptosis in ovarian follicles, caused a 2.4-fold increase in NAIP gene expression in the ovary. To study the role of ovarian NAIP, antisense NAIP oligonucleotides were locally delivered into the ovarian bursa. Suppression of ovarian NAIP expression with antisense oligonucleotides evoked a decrease in the number of morphologically normal ovulated oocytes, implying an indirect involvement of NAIP in germ cell development by enhancing the survival of granulosa cells. These findings suggest that gonadotropin-inducible NAIP may indirectly affect oocyte survival as a result of the inhibition of apoptotic granulosa cell-death during folliculogenesis.

Animals↗

PubMed1999

An application of meta-analysis techniques in the evaluation of adverse experiences with antihypertensive agents.

PURPOSE: To investigate the profiles of adverse events (AEs) in randomized controlled trials of antihypertensive agents therapy with the technique of meta-analysis. METHODS: A total of 620 articles were selected from MEDLINE, EMBASE, JAPIC-DOC, JMEDICINE and manual searching. Two independent reviewers examined the 620 selected articles according to the following criteria: (1) the methods of randomization, (2) making for allocating treatments, (3) therapeutic class of drugs, (4) sample sizes, (5) duration of the treatment, (6) primary endpoint, (7) reporting method for all adverse events, (8) method of monitoring AEs, and (9) incidence rates of all reported AEs. To combine the risk difference and risk ratios of incidence between CCBs and beta blockers or diuretics, the method of DerSimonian and Laird based on random effect model was applied. RESULTS: A total of 3073 patients were included in this meta-analysis of serious adverse events (SAEs). There was no significant difference in the total incidence of SAEs between CCBs and diuretics or between CCBs and beta blockers. We found that patients treated with CCBS had 0.14% fewer SAEs compared with the patients treated with diuretics. Contrarily, the patients treated with CCBs had 0.29% more SAEs compared with the patients treated with beta blockers. There was a significant difference between the patients treated with CCBs and those treated with diuretics in the symptoms with headache and oedema. With respect to the comparison between CCBs and beta blockers, flushing occurred 8.75% more frequently in the CCBs group than in the beta blockers group. CONCLUSION: A meta-analysis can be applied to safety analyses of data obtained in clinical trials if all of the RCT articles used include a complete description of adverse experiences.

Journal Article↗

PubMed1999

Regulation of synovial cell apoptosis by proteasome inhibitor.

OBJECTIVE: Recent studies have shown the importance of proteasome function in the regulation of apoptosis. This study examined whether inhibition of proteasome function mediates apoptosis of synovial cells, and whether cytokines modulate this process. METHODS: Type B synovial cells (fibroblast-like synovial cells) were cultured with tumor necrosis factor alpha (TNF alpha) or transforming growth factor beta1 (TGFbeta1), and further incubated in the presence of variable concentrations of Z-Leu-Leu-Leu-aldehyde (LLL-CHO), a proteasome inhibitor. During this process, apoptosis of synovial cells was determined by Hoechst 33258 dye staining and 51Cr release assay. The involvement of caspase cascade was examined using enzyme activity assay and blocking experiments by peptide inhibitors. The expression of pro-caspases, Bcl-2-related proteins, and X chromosome-linked inhibitor of apoptosis (XIAP) in synovial cells was examined by Western blot analysis. RESULTS: Apoptosis of cultured synovial cells was induced in a dose-dependent manner by LLL-CHO. Activation of caspase cascade through caspase-8 to caspase-3 was essential during this process. Pretreatment of synovial cells with TNF alpha significantly augmented both the activation of caspases and the proportion of apoptosis in synovial cells induced by LLL-CHO, whereas TGFbeta1 pretreatment markedly suppressed these phenomena. The ratio of the expression of Bcl-2 to Bax or Bcl-xL to Bax, and XIAP expression in synovial cells may not be directly associated with the susceptibility of synovial cells to apoptosis by LLL-CHO. CONCLUSION: Apoptosis of synovial cells was induced by inhibition of proteasome function through the activation of caspase cascade, and this process was clearly modulated by cytokines. These data provide new insight into the regulatory mechanisms controlling synovial cells in rheumatoid synovitis by proteasome inhibitors, and might be useful for the design of new therapeutic strategies in rheumatoid arthritis.

Apoptosis↗

PubMed1999

Growth potential of loose bodies: an immunohistochemical examination of primary and secondary synovial osteochondromatosis.

Histologic and immunohistochemical studies of growth potential were performed on 53 surgically removed loose bodies representing 10 cases of primary synovial osteochondromatosis, 37 bodies representing 12 cases of secondary synovial osteochondromatosis, and five bodies representing five cases of osteochondral fracture. Loose bodies in primary synovial osteochondromatosis were nodular, showing plump chondrocytes and irregular calcification, and all contained proliferative cell nuclear antigen-positive chondrocytes (labeling index: 42.5%; range: 36.0-52.0%). Other markers stained less frequently. Loose bodies in secondary synovial osteochondromatosis showed uniform chondrocytes and annular calcification surrounding core tissue. Eighteen of 37 loose bodies showed proliferative cell nuclear antigen-positive chondrocytes, mostly peripherally. Chondrocyte labeling indices were less than 5% for proliferative cell nuclear antigen and other markers, although some connective tissue cells in the outer layer were stained. Loose bodies from osteochondral fractures were composed of articular cartilage, subchondral bone, and connective tissue; cartilage was negative for markers, whereas connective tissue contained positive cells. One specimen showed cartilaginous metaplasia of connective tissue. These results suggest that loose bodies have the potential for slow growth by proliferation of chondrocytes in primary synovial osteochondromatosis and by metaplasia following proliferation of surrounding connective tissue in secondary synovial osteochondromatosis.

Adolescent↗