[A Case of Autoimmune Acquired Factor XIII Deficiency Diagnosed from Recurrent Postoperative Bleeding]

The patient was a 79-year-old man with ureteroileal anastomotic stricture after a Bricker ileal conduit. Endourological treatment of stenosis was performed via percutaneous nephrostomy and ileal conduit. The patient experienced lower abdominal pain on the following day, and computed tomographic (CT) scan showed hematoma retention around the kidney and active bleeding from the renal artery branches. Transarterial embolisation (TAE) was performed and the bleeding was controlled. Two days later, there was a sudden progression of anemia and CT showed an increase in hematoma around the kidney. We subsequently performed nephrectomy for hemostasis. Five days later, the anemia progressed further. There was hematoma retention in the retroperitoneal cavity, and emergency laparotomy hemostasis was performed. Routine coagulation test results were normal. Heavy bleeding was observed several days after TAE and the possibility of coagulation factor XIII deficiency was considered. Factor XIII deficiency was confirmed by a low factor XIII activity level. The patient was given plasma-derived factor XIII. After receiving factor XIII replacement, factor XIII activity remained unchanged and the patient continued to bleed. Thereafter, a cross-mixing test was performed and the patient was diagnosed with autoimmune acquired factor XIII deficiency. Cortical steroids were administered to remove the factor XIII inhibitor. Steroid administration showed a rapid increase in factor XIII activity, and bleeding symptoms were no longer observed. In cases of serious bleeding of unknown cause with a normal coagulation profile, acquired factor XIII deficiency should be suspected and factor XIII activity measured.

Epitope mismatch at HLA-DRB1 associates with reduced relapse risk in cord blood transplant for standard-risk hematological malignancy

BACKGROUND

Cord blood transplantation (CBT) is an attractive therapeutic option for patients with hematological malignancies. CBT tolerates HLA mismatches between donors and recipients, but which HLA mismatches generate graft-versus-tumor (GVT) effects is unknown.

OBJECTIVE

Given that HLA molecules contain epitopes comprising polymorphic amino acids that determine their immunogenicity, we investigated associations between epitope-level HLA mismatches and relapse following single-unit CBT.

STUDY DESIGN

A total of 492 patients with hematological malignancies who received single unit, T cell replete CBT were included in this multi-center retrospective study. HLA epitope mismatches (EM) were quantified using HLA matchmaker software from donor and patient HLA-A, B, C and DRB1 allele data. Patients were dichotomized by median EM value and divided into groups transplanted in complete/partial remission (standard stage: 62.4%) and others (advanced stage: 37.6%).

RESULTS

Median EM numbers in the graft-versus-host direction (GVH-EM) at HLA-class I and HLA-DRB1 were 3 (range, 0-16) and 1 (range, 0-7), respectively. Higher HLA-class I GVH-EM increased non-relapse mortality (NRM) in the advanced stage group (adjusted hazard ratio [HR], 2.12; p=0.021), with no significant advantage for relapse in either stage. On the other hand, higher HLA-DRB1 GVH-EM was associated with better disease-free survival in the standard stage group (adjusted HR, 0.63; p=0.020), which was attributed to lower relapse risk (adjusted HR, 0.46; p=0.014). These associations were also observed even within HLA-DRB1 allele-mismatched transplants in the standard stage group, indicating that EM might have impacts on relapse risk independently of allele mismatch. High HLA-DRB1 GVH-EM did not increase NRM in either stage.

CONCLUSIONS

High HLA-DRB1 GVH-EM may lead to potent GVT effects and favorable prognosis following CBT especially in the patients transplanted in the standard stage. This approach may facilitate appropriate unit selection and improve the overall prognosis of patients with hematological malignancies who receive CBT.

Coexistence of HLA and KIR ligand mismatches as a risk factor for viral infection early after cord blood transplantation

Viral infection is one of the lethal adverse events after cord blood transplantation (CBT). Human leukocyte antigen (HLA) and killer immunoglobulin-like receptor (KIR) ligand divergences can increase the risk of viral infection due to conflicting interactions between virus-infected cells and immune cells. However, the relationship between these disparities and the frequency of viral infection after CBT remains to be evaluated. Herein, we have conducted a retrospective multicenter study to assess the effect of HLA and KIR ligand mismatches on viral infections after CBT. The study included 429 patients, among which 126 viral infections occurred before day 100. Viral infection was significantly associated with poorer overall survival (OS; hazard ratio [HR] 1.74, p < 0.01). Patients harboring ≥3 mismatches in the HLA allele and inhibitory KIR ligand mismatches (HLA & KIR mismatches) had a significantly greater prevalence of viral infection (HR 1.66, p = 0.04). Thus, patients with HLA & KIR mismatches had poorer outcomes in terms of non-relapse mortality (HR 1.61, p = 0.05). Our study demonstrates the unfavorable impacts of HLA & KIR mismatches on viral infections and non-relapse mortality after CBT. Evaluating the viral infection risk and performance of an appropriate and early intervention in high-risk patients and optimizing the graft selection algorithm could improve the outcome of CBTs.

Combined Cohesin-RUNX1 Deficiency Synergistically Perturbs Chromatin Looping and Causes Myelodysplastic Syndromes

STAG2 encodes a cohesin component and is frequently mutated in myeloid neoplasms, showing highly significant comutation patterns with other drivers, including RUNX1. However, the molecular basis of cohesin-mutated leukemogenesis remains poorly understood. Here we show a critical role of an interplay between STAG2 and RUNX1 in the regulation of enhancer-promoter looping and transcription in hematopoiesis. Combined loss of STAG2 and RUNX1, which colocalize at enhancer-rich, CTCF-deficient sites, synergistically attenuates enhancer-promoter loops, particularly at sites enriched for RNA polymerase II and Mediator, and deregulates gene expression, leading to myeloid-skewed expansion of hematopoietic stem/progenitor cells (HSPC) and myelodysplastic syndromes (MDS) in mice. Attenuated enhancer-promoter loops in STAG2/RUNX1-deficient cells are associated with downregulation of genes with high basal transcriptional pausing, which are important for regulation of HSPCs. Downregulation of high-pausing genes is also confirmed in STAG2-cohesin-mutated primary leukemia samples. Our results highlight a unique STAG2-RUNX1 interplay in gene regulation and provide insights into cohesin-mutated leukemogenesis. SIGNIFICANCE: We demonstrate a critical role of an interplay between STAG2 and a master transcription factor of hematopoiesis, RUNX1, in MDS development, and further reveal their contribution to regulation of high-order chromatin structures, particularly enhancer-promoter looping, and the link between transcriptional pausing and selective gene dysregulation caused by cohesin deficiency.This article is highlighted in the In This Issue feature, p. 747.

Splenic mass in a case of CALR-mutated essential thrombocythemia

We report here an intrasplenic large mass in an elderly case of essential thrombocythemia (ET)-myelofibrosis. Laparoscopic splenectomy revealed extramedullary hematopoiesis (EMH) and a type 1 CALR gene mutation (CALR-c.1092_1143del52) in the splenic mass. It remains to be determined if CALR-mutated ET has an increased tendency to develop mass-forming EMH.

Molecular pathogenesis of disease progression in MLL-rearranged AML

Leukemic relapse is frequently accompanied by progressively aggressive clinical course. To understand the molecular mechanism of leukemic relapse, MLL/AF9-transformed mouse leukemia cells were serially transplanted in C57BL/6 mice (N = 96) by mimicking repeated recurrences, where mutations were monitored by exome sequencing (N = 42). The onset of leukemia was progressively promoted with advanced transplants, during which increasing numbers of somatic mutations were acquired (P < 0.005). Among these, mutations in Ptpn11 (p.G60R) and Braf (p.V637E) corresponded to those identified in human MLL-AML, while recurrent mutations affecting Msn (p.R295C) were observed only in mouse but not in human MLL-AML. Another mutated gene of interest was Gnb2 which was reported to be recurrently mutated in various hematological neoplasms. Gnb2 mutations (p.G77R) were significantly increased in clone size (P = 0.007) and associated with earlier leukemia onset (P = 0.011). GNB2 transcripts were significantly upregulated in human MLL-AML compared to MLL-negative AML (P < 0.05), which was supported by significantly increased Gnb2 transcript induced by MLL/AF9 overexpression (P < 0.001). In in vivo model, both mutation and overexpression of GNB2 caused leukemogenesis, and downregulation of GNB2 expression reduced proliferative potential and survival benefit, suggesting a driver role of GNB2. In conclusion, alterations of driver genes over time may play an important role in the progression of MLL-AML.

Integrated molecular analysis of adult T cell leukemia/lymphoma

Adult T cell leukemia/lymphoma (ATL) is a peripheral T cell neoplasm of largely unknown genetic basis, associated with human T cell leukemia virus type-1 (HTLV-1) infection. Here we describe an integrated molecular study in which we performed whole-genome, exome, transcriptome and targeted resequencing, as well as array-based copy number and methylation analyses, in a total of 426 ATL cases. The identified alterations overlap significantly with the HTLV-1 Tax interactome and are highly enriched for T cell receptor-NF-κB signaling, T cell trafficking and other T cell-related pathways as well as immunosurveillance. Other notable features include a predominance of activating mutations (in PLCG1, PRKCB, CARD11, VAV1, IRF4, FYN, CCR4 and CCR7) and gene fusions (CTLA4-CD28 and ICOS-CD28). We also discovered frequent intragenic deletions involving IKZF2, CARD11 and TP73 and mutations in GATA3, HNRNPA2B1, GPR183, CSNK2A1, CSNK2B and CSNK1A1. Our findings not only provide unique insights into key molecules in T cell signaling but will also guide the development of new diagnostics and therapeutics in this intractable tumor.

Epstein-Barr virus-positive diffuse large B-cell lymphoma of the elderly complicated by the onset of acute myeloid leukemia

We herein describe the case of a 62-year-old woman who presented with anemia and an 8-month history of weight loss. Bone marrow aspiration showed increased myeloblasts. The histopathology findings of biopsy specimens of the right cervical lymph node and intestinal mass indicated B-lymphoproliferative disorder (B-LPD) with Hodgkin lymphoma-like morphologic features and polymorphous diffuse large B-cell lymphoma (DLBCL), respectively. In addition, both types of lymphoma cells were positive for Epstein-Barr virus (EBV)-encoded small RNA-1. The patient was diagnosed with EBV-associated B-LPD and simultaneous acute myeloid leukemia (AML). This is the first case of a patient diagnosed with simultaneous EBV-positive DLBCL of the elderly and AML.

Acute renal failure associated with systemic polyoma BK virus activation in a patient with peripheral T-cell lymphoma

Renal dysfunction associated with polyoma BK virus (BKV) reactivation usually occurs in the setting of profound immunosuppression related to renal transplantation and hematopoietic stem cell transplantation. However, it has been rarely described as a complication during the course of conventional chemotherapy. Here, we report a case of BKV-associated acute renal failure developed in a patient suffering from refractory peripheral T-cell lymphoma, not otherwise specified. After repetitive cycles of salvage chemotherapy, the patient developed fever and urinary frequency, rapidly followed by anuria that necessitated the emergent institution of hemodialysis. Cytologic examination of the urine revealed the presence of decoy cells and positive immunostaining for polyomavirus simian virus 40 antigen. High levels of BKV were detected in urine and plasma with quantitative real-time polymerase chain reaction, strongly suggesting that his renal failure was due to polyoma virus-associated nephropathy. This rare complication should be kept in mind in case of unexplained renal failure developed in immunodeficient patients undergoing cytotoxic chemotherapy.

Glycogen synthase kinase-3beta and p38 phosphorylate cyclin D2 on Thr280 to trigger its ubiquitin/proteasome-dependent degradation in hematopoietic cells

Cyclin D2 plays an important role in regulation of hematopoietic cell proliferation by cytokines and is implicated in oncogenesis of various hematopoietic malignancies. However, mechanisms regulating cyclin D2 stability and its expression level have remained to be known. Here, we demonstrate that interleukin-3 signaling stabilizes cyclin D2 by inhibition of glycogen synthase kinase-3beta (GSK3beta) through Janus kinase2-dependent activation of phosphatidylinositol 3'-kinase (PI3K)/Akt signaling pathway in hematopoietic 32Dcl3 cells. On the other hand, osmotic stress was shown to induce a rapid proteasomal degradation of cyclin D2, which was mediated by activation of p38. GSK3beta and p38 was demonstrated to phosphorylate cyclin D2 on Thr280 in vitro, while a cyclin D2 mutant with this residue substituted with Ala was found to be resistant to ubiquitination and proteasome-dependent degradation in 32Dcl3 cells. Inhibition of the PI3K pathway or induction of osmotic stress also caused a rapid proteasomal degradation of cyclin D2 in primary leukemic or myeloma cells. These results indicate that cyclin D2 expression in normal and malignant hematopoietic cells is regulated by ubiquitin/proteasome-dependent degradation that is triggered by Thr280 phosphorylation by GSK3beta or p38, which is induced by inhibition of the PI3K pathway or by osmotic stress, respectively.

Pharmacological evidence of cholinergic involvement in adult hippocampal neurogenesis in rats

In adult hippocampus, neural progenitor cells give rise to neurons throughout life, and the neurogenesis is modulated by various intrinsic and extrinsic factors. Recent reports showed that lesion of septal cholinergic nuclei projecting to hippocampus suppressed the survival of newborn cells in the dentate gyrus (DG) of hippocampus. Here, we studied whether pharmacological treatment to activate or inhibit the cholinergic system could modulate adult hippocampal neurogenesis. 5'-Bromo-2'-deoxyuridine (BrdU) was injected to label dividing cells before the drug treatment. Immunohistochemical analysis was performed in normal rats chronically treated with an acetylcholinesterase inhibitor donepezil or a muscarinic acetylcholine receptor blocker scopolamine for four weeks. Donepezil increased, but scopolamine decreased, the number of BrdU-positive cells in the DG as compared with the control. Neither drug altered the percentage of BrdU-positive cells that were also positive for a neuronal marker neuronal nuclei, nor net population of proliferative cells labeled with proliferating cell nuclear antigen. We also found that donepezil enhanced, and scopolamine suppressed, the expression level of phosphorylated cAMP response element binding protein (CREB), which is related to cell survival, in the DG. These results indicate that donepezil enhances and scopolamine suppresses the survival of newborn cells in the DG via CREB signaling without affecting neural progenitor cell proliferation and the neuronal differentiation. This is the first evidence that pharmacological manipulation of the cholinergic system can modulate adult hippocampal neurogenesis.

Functional analysis of microtubule-binding domain of bovine MAP4

Bovine microtubule-associated protein 4 (MAP4) consists of an amino-terminal projection domain and a carboxyl-terminal microtubule-binding domain. The carboxyl-terminal domain of MAP4 is further divided into three subdomains: a region rich in proline and basic residues (Pro-rich region), a region containing four repeats of an assembly-promoting (AP) sequence, which consists of 22 amino acid residues (AP sequence region), and a hydrophobic tail region (Tail region). The subdomain structure of MAP4 microtubule binding domain is similar to those of other MAPs (MAP2 and tau). In order to study the function of each subdomain per se of bovine MAP4 microtubule-binding domain, we purified a series of truncated fragments of MAP4, expressed in Escherichia coil. Binding affinity of the PA4T fragment (containing the Pro-rich region, the AP sequence region and the Tail region) is only four times higher than that of the A4T fragment (containing the AP sequence region and the Tail region), while the microtubule nucleating activity of the PA4T fragment is far greater. We propose that the Pro-rich region promotes the nucleation of microtubule assembly. The A4 fragment (corresponding to the AP sequence region) stimulated the assembly of tubulin into coldstable amorphous aggregates. The AP sequence region of MAP4 failed to promote microtubule assembly. On the other hand, the fragment has an activity to stimulate microtubule elongation. The function of the MAP4 Tail region is not clear at present. The A4T fragment (containing the AP sequence region and the Tail region) promote both microtubule nucleation and elongation step, but the A4 fragment only promotes microtubule elongation, suggesting that the Tail region is indispensable for the nucleation step. However, the fragment containing only the Tail region could not bind to microtubule. Although MAP4 was considered to be long, thin and flexible molecule, never the Tail region may contribute to be the proper folding of MAP4, and/or may interact with other molecules. We concluded that both the Pro-rich region and the AP sequence region take part in the promotion of tubulin polymerization, and that the former is important for the lateral protofilament-protofilament interaction, and the latter is important for the longitudinal affinity between each tubulin dimer in a protofilament.

Hippocampal Damage Disrupts Eyeblink Conditioning in Mice Lacking Glutamate Receptor Subunit δ2

Cerebellar long-term depression (LTD) at the parallel fiber-Purkinje cell synapses has been proposed to be a neural substrate for classical eyeblink conditioning. Mutant mice lacking the glutamate receptor subunit δ2 (GluRδ2), in which the cerebellar LTD is disrupted, exhibited a severe impairment in the delay eyeblink conditioning with a temporal overlap of CS and US. However, they learned normally trace and delay conditioning without CS-US overlap, suggesting a learning mechanism which does not require the cerebellar LTD.In the present study, we tested possible involvement of the hippocampus in this cerebellar LTD-independent learning. We examined effects of scopolamine and hippocampal lesion on the delay conditioning without CS-US overlap. TheGluRδ2 mutant mice that received scopolamine or aspiration of the dorsalhippocampus together with its overlying cortex exhibited a severe impairment in learning, while the control mutant mice that received saline or aspiration of the overlying cortex learned normally. In contrast, wild-type mice that received either treatment learned as normally as the control wild-type mice. These results suggest that the hippocampus is essential in the cerebellar LTD-independent learning in the GluRδ2 mutant mice, indicating a newrole of hippocampus in the paradigm with a short trace interval.

The actin-depolymerizing factor destrin has an actin-stabilizing domain

Destrin is a 19 kDa actin-depolymerizing protein of the ADF-cofilin family. Destrin was digested with trypsin to a structurally stable 9.2 kDa fragment that contains the actin-binding sequence. The purified 9.2 kDa fragment has an actin filament stabilizing activity, rather than an actin filament depolymerizing activity. The deleted region is probably essential for the actin filament depolymerizing activity of intact destrin. Surprisingly, the 9.2 kDa fragment also has an assembly-promoting activity in the absence of ATP.

Hyperpolarizing shift by quinine in the steady-state inactivation curve of delayed rectifier-type potassium current in bullfrog sympathetic neurons

Whole-cell recordings were made from dissociated bullfrog sympathetic neurons to examine the actions of quinine (1-100 microM) on the steady-state activation and inactivation curves of a delayed rectifier-type potassium current (I(K)). Quinine (EC50 approximately 8 microM) caused a hyperpolarizing shift (approximately 31 mV with 30 microM) in the inactivation curve of I(K) without significantly affecting its activation curve. Quinine (20 microM) was without effects on the voltage-dependence of a rapidly-inactivating A-type potassium current (I(A)). It is concluded that quinine can selectively modulate the voltage-dependence of I(K) in amphibian autonomic neurons.

Purification and characterization of a new, ubiquitously distributed class of microtubule-associated protein with molecular mass 250 kDa

A heat-stable microtubule-associated protein (MAP) with relative molecular mass 250 000, termed 250-kDa MAP, was purified from bovine adrenal cortex. It is classified as a MAP subspecies distinct from MAP1, MAP2, tau, and MAP4, as judged from its electrophoretic mobility, heat stability and immunoreactivity. Purified 250-kDa MAP was able to bind to taxol-stabilized microtubules, although it lacked the ability to polymerize purified tubulin into microtubules. Western-blot analysis showed that this MAP was expressed ubiquitously in mammalian tissues. Immunofluorescence microscopy revealed that polyclonal antibodies raised against 250-kDa MAP stained many punctate structures in the cytoplasm of cultured cells. Blurry cytosolic staining was also observed. Judging from the result of nocodazole treatment, the punctate structures were associated with the microtubule network throughout the cytoplasm, while cytosolic 250-kDa MAP colocalized with free tubulin. Under electron microscopy, 250-kDa MAP has the appearance of a hollow sphere of about 12 nm diameter.

Effects of lanthanides on voltage-dependent potassium currents in bullfrog sympathetic neurons

The effects of lanthanides (La(3+), Gd(3+), Lu(3+) and Sm(3+)) on voltage-dependent potassium currents were studied in dissociated bullfrog sympathetic neurons. A-type current (I(A)) and M-type current (I(M)) were blocked by lanthanides (0.1-30 microM) with I(M) being much less sensitive to these ions than I(A). The order of potency was Gd(3+)>/=Lu(3+) approximately La(3+) approximately Sm(3+) for I(A) and Gd(3+)&z.Gt;Lu(3+) approximately La(3+)>Sm(3+) for I(M). The I(M) block occurred independently of its activation kinetics while the I(A) block was associated with a positive shift of the activation and inactivation curves. Gd(3+) (100 microM) blocked the delayed rectifier-type current (I(K)) by less than 20%; Lu(3+), La(3+) and Sm(3+) (100 microM for each) were without effect on I(K). It is concluded that I(A) was the most sensitive to lanthanides, and Gd(3+) was the most potent for all the currents in amphibian autonomic neurons.

Cytokine-inducing macromolecular glycolipids from Enterococcus hirae: improved method for separation and analysis of its effects on cellular activation

Previously, we showed that several minor macromolecular glycolipids accounting for less than 5% of the lipoteichoic acid (LTA) fraction from Enterococcus hirae ATCC 9790 possess cytokine-inducing activity, whereas the purified LTA does not. In other words, the immunobiological activity of the LTA fraction reported in the 1980s was not attributable to LTA itself, but to other glycolipids coexisting in the fraction. In the present study, we improved the procedure of separation of the active glycolipids and evaluated their effects on cellular activation. The immunobiologically active glycolipids were separated from the crude glycolipid fraction obtained by hot phenol-water extraction of the cells. The total yield of active glycolipids was about fivefold higher than that separated by the previous method. Interleukin-6-inducing activities of the active glycolipids from 1,25-dihydroxy vitamin D(3)-differentiated human monocytic leukemia cells, THP-1, were inhibited by anti-CD14 mAbs in a dose-dependent manner. Macrophages from Toll-like receptor (TLR)-2-deficient or -4-deficient mice completely lacked the ability to produce tumor necrosis factor-alpha on stimulation with active glycolipids. These observations indicated that the cellular activation by the active glycolipids from E. hirae is mediated by CD14 and by both TLR2 and TLR4.

Mechanisms underlying the M-current block by barium in bullfrog sympathetic neurons

Whole-cell/voltage-clamp recordings were made from dissociated bullfrog sympathetic neurons to examine the channel blocking actions of barium (3-2000 microM) on an M-type potassium current (I(M)). Barium (IC(50) approximately 105 microM) blocked I(M) without affecting the 50%-activation voltage ( approximately -35 mV) and the slope factor ( approximately 11 mV) of the activation curve. The results indicate that the barium block is independent of the kinetics of I(M).

Microtubule-binding property of microtubule-associated protein 2 differs from that of microtubule-associated protein 4 and tau

The microtubule-binding domains of microtubule-associated protein (MAP) 2, MAP4, and tau are structurally similar [Aizawa, H., Emori, Y., Murofushi, H., Kawasaki, H., Sakai., H., and Suzuki, K. (1990) J. Biol. Chem. 265, 13849-13855]. To compare the microtubule-binding mechanisms of the three MAPs, we performed a quantitative competition analysis using the three MAPs and the microtubule-binding domain fragment of MAP4 (PA4T fragment). The two-cycled microtubule protein fraction from bovine brain contains MAP1, MAP2, MAP4, and tau. When an excess of the PA4T fragment was added to the microtubule protein fraction, MAP4 and tau were completely released from the microtubules, while MAP1 remained bound. MAP2 was only partially released from the microtubules. The competition between MAP2 and MAP4 was further analyzed using purified MAP2, the PA4T fragment, and tubulin. About half of the MAP2 was still bound to the microtubules, even in the presence of an excess amount of the PA4T fragment. The microtubule-binding mechanisms of MAP2 and MAP4 seem to be different, in spite of their similar primary structures.

A novel cytokine-inducing glycolipid isolated from the lipoteichoic acid fraction of Enterococcus hirae ATCC 9790: a fundamental structure of the hydrophilic part

Previously, we showed that quantitatively minor several glycolipids totaling only less than 5% of the lipoteichoic acid (LTA) fraction from Enterococcus hirae ATCC 9790 possessed cytokine-inducing activity, whereas the major component (over 90%) did not [Suda et al. (1995) FEMS Immun Med Microbiol 12:97-112]. The major inactive component was shown to have the chemical structure as was proposed for the LTA by Fischer [Hashimoto et al. (1997) J Biochem 121:779-86], suggesting that so-called LTA is not a cytokine-inducing component in the Gram-positive bacteria. In the present paper, the structure of the hydrophilic part of one of the cytokine-inducing glycolipid tentatively named GL4 is elucidated. GL4 was first subjected to hydrolysis with aqueous HF to give a polysaccharide and a mixture of low molecular weight products. The polysaccharide was composed mainly of highly branching mannan as concluded from NMR and MS analyses of its acetolysis products. The low molecular weight products consisted of phosphate and glycerol, suggesting the presence of a poly(glycerophosphate) structure in the original GL4. From these observations, the hydrophilic part of GL4 was shown to consist of mannose-rich polysaccharide and poly(glycerophosphate), the latter being bound to the former by a phosphodiester linkage.

A new model for microtubule-associated protein (MAP)-induced microtubule assembly. The Pro-rich region of MAP4 promotes nucleation of microtubule assembly in vitro

The microtubule-binding domains of microtubule-associated protein (MAP) 2, tau, and MAP4 are divided into three distinctive regions: the Pro-rich region, the AP sequence region and the tail region (Aizawa, H., Emori, Y., Murofushi, H., Kawasaki, H., Sakai., H., and Suzuki, K. (1990) J. Biol. Chem. 265, 13849-13855). Electron microscopic observation showed that the taxol-stabilized microtubules alone and those mixed with the A4T fragment (containing the AP sequence region and the tail region) had a long, wavy appearance, while those mixed with the PA4T fragment (containing the Pro-rich region, the AP sequence region, and the tail region) or the PA4 fragment (containing the Pro-rich region and the AP sequence region) were shorter and straighter. Stoichiometries of the binding between the fragments and the tubulin dimers were approximately between 1 and 2, suggesting that not all of the AP sequences in the AP sequence region bound to tubulin. Binding affinity of the PA4T fragment is only four times higher than that of the A4T fragment, while the microtubule nucleating activity of the PA4T fragment is far greater. Based on these results, we propose that the nucleation of microtubule assembly is promoted by the bridging activity of the Pro-rich region in the MAPs.

A lipoteichoic acid fraction of Enterococcus hirae activates cultured human monocytic cells via a CD14-independent pathway to promote cytokine production, and the activity is inhibited by serum components

To elucidate the cellular activation mechanisms of lipoteichoic acid (LTA) compared with those of lipopolysaccharide (LPS), a quantitatively major LTA fraction, QM-1M, was prepared from hot phenol-water extracts of Enterococcus hirae (ATCC 9790) by hydrophobic octyl-Sepharose chromatography and by ion-exchange membrane (QMA-Mem Sep 1010) chromatography as a 60% 1-propanol- and 1 M NaCl-eluted fraction. Unlike the reference Escherichia coli LPS, QM-1M did not demonstrate any ability to induce cytokines in a human whole blood culture system in this study, whereas QM-1M induced a few cytokines such as interleukin (IL)-8 and tumor necrosis factor-alpha in human monocytic THP-1 cell and human peripheral mononuclear cell (PBMC) cultures in the absence of serum. Fetal calf and human sera decreased the above cytokine induction by QM-1M in THP-1 and PBMC cultures, whereas sera increased activities of the reference LPS. IL-8 induction in the absence of serum in response to QM-1M was demonstrated to proceed through a CD14-independent pathway unlike the reference LPS.

Myelodysplastic syndrome resembling chronic myeloproliferative disorders in clinicopathological aspects

We report on a patient with myelodysplastic syndrome (MDS) which resembled chronic myeloproliferative disorder (CMPD). A 67-year-old male was admitted to our hospital in June 1990. A diagnosis of refractory anemia with excess of blasts in transformation (RAEB-T) was based on the peripheral blood and bone marrow findings on admission. However, since thrombocytosis and bone marrow fibrosis was noted, the patient was diagnosed as MDS with myelofibrosis. Low-dose cytosine arabinoside therapy was performed. Although complete remission could not be achieved, a high quality of life could be maintained by appropriate transfusion. In January 1993, the patient was readmitted because of a marked increase in mature neutrophils, showing a moderate increase of blasts, chromosomal aberration (46,XY,12p-) and hepatosplenomegaly; but no fibrosis of bone marrow was observed. These findings suggested that neoplastic proliferation at the level more differentiated to granulocytic lineage occurred at the terminal stage and that his clinical feature was located between MDS and CMPD. This case may be important in considering various aspects of MDS.

Human natural resistance-associated macrophage protein is a new type of microtubule-associated protein

Natural resistance-associated macrophage protein 1 (NRAMP1) is a putative membrane protein that dominates natural resistance to infection. An NRAMP1-glutathione S-transferase fusion protein was used to test the ability of the NRAMP1 NH2-terminal domain to bind to taxol-stabilized microtubules. Co-sedimentation analysis showed that the fusion protein binds to microtubules. Although the NH2-terminal domain of the NRAMP1 molecule has structural homology with the Pro-rich region of microtubule-associated protein 4 (MAP4), the presence of the MAP4 microtubule-binding domain fragment had little effect on the binding of the fusion protein to microtubules.

Evidence for structural differences between the two highly homologous actin-regulatory proteins, destrin and cofilin

The amino acid sequences of destrin and cofilin are very similar (84% homology) throughout the entire range of proteins, but they have different functions. In this study, we constructed a new cofilin expression plasmid, which had high expression frequency, and the structures of destrin and cofilin were analyzed by limited proteolysis and circular dichroism (CD). When destrin was digested by trypsin, two fragments of 17.0 kDa and 9.2 kDa were obtained, whereas only one 8.4 kDa fragment was obtained from cofilin. In spite of the overall sequence homology, an N-terminal amino acid sequence analyses of the fragments revealed the cleavage sites on destrin and cofilin to be different. These results suggest that destrin and cofilin differ in their overall tertiary folds. Cofilin showed activity similar to destrin at high pH values, although no pH-dependent structural change in cofilin was confirmed by using limited proteolysis and CD.

PKA and MPF-activated polo-like kinase regulate anaphase-promoting complex activity and mitosis progression

Ubiquitin-mediated proteolysis is the key to cell cycle control. Anaphase-promoting complex/cyclosome (APC) is a ubiquitin ligase that targets cyclin B and factors regulating sister chromatid separation for proteolysis by the proteasome and, consequently, regulates metaphase-anaphase transition and exit from mitosis. Here we report that Cdc2-cyclin B-activated Polo-like kinase (Plk) specifically phosphorylates at least three components of APC and activates APC to ubiquitinate cyclin B in the in vitro-reconstituted system. Conversely, protein kinase A (PKA) phosphorylates two subunits of APC but suppresses APC activity. PKA is superior to Plk in its regulation of APC, and Plk activity peaks whereas PKA activity is falling at metaphase. These results indicate that Plk and PKA regulate mitosis progression by controlling APC activity.

The 'assembly-promoting sequence region' of microtubule-associated protein 4 failed to promote microtubule assembly

In order to study the function of the bovine MAP4 microtubule-binding domain (the assembly-promoting (AP) sequence region), a fragment corresponding to the AP sequence region was prepared using an Escherichia coli expression system. When the fragment was mixed with purified tubulin at 37 degrees C, the fragment caused a time- and dose-dependent turbidity increase, and the fragment bound to tubulin. However, the products were cold-stable, and amorphous aggregates were observed by electron microscopy. Using axonemes as the seeds for microtubule assembly, the microtubule-elongating activity of the fragment was examined. A dose-dependent turbidity increase of the sample was observed, and electron microscopic observation revealed that microtubules were dose-dependently elongated from the axonemes. Consequently, the AP sequence region does not nucleate microtubules, but elongates them.

Cell cycle-dependent expression and spindle pole localization of a novel human protein kinase, Aik, related to Aurora of Drosophila and yeast Ipl1

Mutations in Aurora of Drosophila and related Saccharomyces cerevisiae Ipl1 kinase are known to cause abnormal chromosome segregation. We have isolated a cDNA encoding a novel human protein kinase of 402 amino acids with a predicted molecular mass of 45.9 kDa, which shares high amino acid identities with the Aurora/Ipl1 protein kinase family; hence the cDNA is designated as aik (aurora/IPL1-related kinase). Amino acid sequence of C-terminal kinase domain of Aik shares 86, 86, 72, 59, and 49% identity with those of Xenopus XLP46APK and XLP46BPK, mouse STK-1, Aurora of Drosophila, and yeast Ipl1, respectively, whereas N-terminal domain of Aik shares high homology only with those of XLP46APK and XLP46BPK. Northern and Western blotting analyses revealed that Aik is expressed highly in testis and various proliferating cells including HeLa cells. In HeLa cells, the endogenous levels of aik mRNA and protein contents are tightly regulated during cell cycle progression. Both of these levels are low in G1/S, accumulate during G2/M, and reduce rapidly after mitosis. Its protein kinase activity is also enhanced at mitosis as inferred by exogenous casein phosphorylation. Immunofluorescence studies using a specific antibody have shown that Aik is localized to the spindle pole during mitosis, especially from prophase through anaphase. These results strongly suggest that Aik is a novel member of a protein kinase family possibly involved in a centrosome function(s) such as chromosome segregation or spindle formation.

Structural feature of the major but not cytokine-inducing molecular species of lipoteichoic acid

Previously, lipoteichoic acid (LTA) of Enterococcus hirae was found to exhibit definite cytokine-inducing activity but synthetic specimens which share the fundamental structural principles proposed for LTA had no corresponding activity. We also showed recently that several minor components totally less than 5% of the LTA fraction from E. hirae ATCC 9790 possessed the activity, whereas the major component (over 90%) did not [Suda, Y., Tochio, H., Kawano, K., Takada, H., Yoshida, T., Kotani, S., and Kusumoto, S. (1995) FEMS Immun. Med. Microbiol. 12, 97-112]. In the present study, the structure of the major component of LTA was studied in an attempt to elucidate the reason for the lack of the activity in the synthetic compounds. The major component of the LTA was first digested by hydrofluoric acid hydrolysis to cleave phosphodiester linkages present. The hydrolysis products were separated and characterized by means of NMR and MS. The linkage positions of the original phosphodiesters were determined from the NMR spectra of an alkali-treated product without hydrofluoric acid degradation. The compound was proved to consist of 1,3-linked poly(glycerophosphate) and a lipid anchor, Glc(alpha1-2)Glc(alpha1-3)acyl(2)Gro, the former being linked to the 6-position of the distal glucose of the latter. The 2-position of the glycerol residues in the glycerophosphate part were substituted by oligoglucose esterified partially with alanine. The gross structure elucidated here thus coincides with the previous conclusion described by Fischer [Fischer, W. (1990) in Glycolipids, Phosphoglycolipids and Sulfoglycolipids (Kates, M., ed.) pp. 123 234, Plenum Press, New York]. Thus, the molecular species with this so-called "LTA structure" is not responsible for the cytokine-inducing activity.

Multiple thoracic disc herniations: case report and review of the literature

The incidence of intervertebral disc herniation in the thoracic region of the spine is much less than in the cervical or lumbar areas, and multiple thoracic disc herniations are rare. We described a 33-year-old man with two-level thoracic disc herniation, who exhibited features of spinal cord compression. Magnetic resonance imaging and computed tomographic myelography demonstrated anterior compression of the spinal cord due to disc herniation at T4/5 and T7/8 levels. Through an anterolateral approach, these discs were removed and interbody fusion was performed using autogenous bone grafts. Excellent results were obtained.

Purification and partial characterization of a novel human platelet aggregation factor in the extracellular products of Streptococcus mitis, strain Nm-65

A human blood platelet aggregation factor was purified from the extracellular products (ECP) of Streptococcus mitis, strain Nm-65 by sequential chromatography on DEAE-Sepharose CL-6B, hydroxyapatite and Superdex 75 columns. The purified factor (S. mitis-derived human platelet aggregation factor, Sm-hPAF) gave a single band with a molecular weight of 66 kDa on SDS-polyacrylamide gel electrophoresis (SDS-PAGE). Sm-hPAF showed a peak absorption at 278 nm and an isoelectric point of around 8.5. Chemical analyses revealed that Sm-hPAF contained no sugars and that its first 15 amino-terminal amino acid residues were H-DEQGNRPVETENIAR. Platelet aggregation activity of Sm-hPAF was abolished by heating at 45 degrees C for 10 min. Platelet aggregation by Sm-hPAF was accompanied by a release of prostaglandin E2 (PGE2) in a dose-dependent manner. The platelet aggregation was not inhibited by either prostaglandin E1 (PGE1) or Gly-Arg-Gly-Asp-Ser (GRGDS), that inhibit the platelet aggregation induced by collagen. Twenty (77%) platelet rich-plasma (PRP) specimens derived from 26 healthy volunteers were aggregated by Sm-hPAF, but the remaining 6 (23%) were not reactive. A preliminary study suggested the presence of an inhibitory factor against Sm-hPAF in the plasma from a non-reactive donor.

Induction of lymphocytes cytotoxic to oral epithelial cells by Streptococcus mitis superantigen

The preparation of a superantigenic fraction F-2 from the culture supernatant of Streptococcus mitis 108, a fresh isolate from human tooth surfaces, was reported previously. Now, to determine the possible pathogenic role of the superantigen in oral mucosal diseases, we examined the cytotoxic effects of human peripheral blood T-cells activated with F-2 on human oral epithelial cells. T-cells activated with F-2 were cytotoxic to the human squamous carcinoma HO-1-N-1 cells derived from the oral mucosa, similar to those activated with Staphylococcus aureus enterotoxin B (SEB). This cytotoxic effect was increased in a dose-dependent manner by the addition of the respective stimulant, F-2 or SEB, to the cytotoxic assay system. F-2 endowed mainly CD8+ T-cells with cytotoxic activity. Pretreatment with human interferon gamma increased the sensitivity of the HO-1-N-1 cells to the cytotoxic effects of F-2-activated T-cells. The F-2-activated T-cells were also cytotoxic to human keratinocytes derived from gingiva. There was no correlation between the degree of cytotoxicity and the levels of tumor necrosis factor alpha in co-cultures of F-2-activated T-cells and HO-1-N-1 cells. A double-chamber plate experiment revealed no cytotoxic effects when the F-2-activated T-cells were separated from the HO-1-N-1 cells. Supernatants of the co-cultures of target and effector cells were not cytotoxic to HO-1-N-1 cells. These findings suggest that the cytotoxic effects of the F-2-activated T-cells on HO-1-N-1 cells were mediated not by soluble factors but by the direct interaction between the activated T-cells and the target cells. The cytotoxicity of the F-2-activated T-cells against HO-1-N-1 cells was markedly inhibited by monoclonal antibodies (MAbs) against CD11a and CD54, but was only slightly inhibited by MAbs against human leukocyte antigen (HLA)-DR and CD2. Thus, the interaction between lymphocyte-function-associated antigen-1 (LFA-1) and intercellular adhesion molecule-1 (ICAM-1) was crucial for the F-2-dependent T-cell-mediated cytotoxicity against oral epithelial cells, while HLA-DR and CD2 molecules are not necessarily involved in the cytotoxicity observed.

Cytokine-inducing glycolipids in the lipoteichoic acid fraction from Enterococcus hirae ATCC 9790

Five high molecular weight glycolipids capable of stimulating human peripheral whole-blood cell cultures to cause interleukin 6 (IL-6) and tumor necrosis factor (TNF)-alpha induction were isolated from one of the lipoteichoic acid fractions (LTA-2) extracted from Enterococcus hirae ATCC 9790 (Tsutsui et al., (1991) FEMS Microbiol. Immunol. 76, 211-218) by a combination of hydrophobic interaction and anion-exchange chromatographies. This purification procedure resulted in a remarkable increase in the cytokine-inducing activities on the weight basis of isolated glycolipids (a maximum of 36- and 17-fold increases of IL-6 and TNF-alpha induction, respectively). The total yield of these bioactive glycolipids amounted to 6 wt% of the parent LTA-2 fraction, while the recovery rate in terms of the cytokine-inducing activities was estimated to be sufficient. The chemical composition and the profile, using SDS-PAGE, revealed that all of the isolated bioactive components were high molecular weight glycolipids, which were distinct from each other and from the parent LTA-2 fraction. These findings suggest that the IL-6 and TNF-alpha-inducing activities previously noted in the parent LTA-2 fraction are not attributable to a chemical entity, the structure of which had been proposed elsewhere (Fischer, W. (1990) in Glycolipids, Phosphoglycolipids and Sulfoglycolipids (Kates, M. ed.) pp. 123-234, Plenum Press, New York), but to the other high molecular weight glycolipids described here.

Oral immunoadjuvant activity of lipophilic derivatives of N-acetylglucosaminyl-beta(1-->4)-N-acetylmuramyl-L-alanyl-D-isoglutamin yl-(L)- 2,6-meso-diaminopimeric acid-(D)-amide

Twenty-four kinds of the acylated, amidated or esterified derivatives of N-acetylglucosaminyl (GlcNAc)-beta(1-->4)-N-acetylmuramyl (MurNAc)-L-alanyl (Ala)-D-isoglutaminyl (isoGln)-(L)-meso-2,6-diaminopimeric acid (A2pm)-(D)-amide (GMP3-A) which were prepared by chemical modifications of an enzymatic hydrolysate of Lactobacillus plantarum cell-wall peptidoglycans were examined for oral adjuvant activity by gastric intubation with bovine serum albumin (BSA) in liposomes into BALB/c mice. The gastric intubation of GlcNAc-beta(1-->4)-MurNAc-L-Ala-D-isoGln-(L)- stearoyl-(D)-meso-A2pm-(D)-amide-(L)-O-octyl, -nonyl and -dodecyl esters exhibited the most marked oral adjuvant activity in terms of enhanced production of serum anti-BSA IgG antibody. Some derivatives showed a less marked adjuvanticity and others were totally inactive. Thus the oral adjuvanticity of test lipophilic derivatives of GMP3-A in liposomes was dependent upon their chemical structure.

Immunopathological activities of extracellular products of Streptococcus mitis, particularly a superantigenic fraction

Previously, we prepared extracellular products, fractions F-1 and F-2 of Streptococcus mitis 108, an isolate from the tooth surface of an infant, and showed that F-1 exhibited inflammatory cytokine-inducing activities. In the present study, we present evidence that fraction F-2 induced human T-cell proliferation in the presence of irradiated human peripheral blood mononuclear cells and selectively activated T cells bearing V beta 2 and V beta 5.1 in the T-cell receptor. F-1, on the other hand, stimulated human gingival fibroblasts to support the T-cell proliferation in the same way as human gamma interferon or Prevotella intermedia lipopolysaccharide (LPS). Fraction F-1 also primed gingival fibroblasts to support the production of interleukin-2 and gamma interferon by the T cells upon stimulation with F-2. Human gingival fibroblasts stimulated with fraction F-1, like those stimulated by P. intermedia LPS and human gamma interferon, exhibited human leukocyte antigen (HLA)-DR mRNA expression and cell surface HLA-DR molecules as detected by enzyme-linked immunosorbent assay. An anti-HLA-DR monoclonal antibody inhibited T-cell proliferation in response to F-2, probably through inactivating the accessory function of HLA-DR-bearing fibroblasts. T cells activated with F-2 in the presence of irradiated peripheral blood mononuclear cells exhibited definite cytotoxic effects against fibroblasts and squamous carcinoma cells originating from human oral tissues. These findings are strongly suggestive of an association of extracellular products of viridans streptococci with pathogenesis of oral mucosal diseases, particularly those disorders in gingiva which are accompanied by heavy infiltration of T cells.

A variant form of cyclin-dependent kinase 2 (Cdk2) in a malignantly transformed rat thyroid (FRTL-Tc) cell line

Cyclin-dependent kinase 2 (Cdk2) controls the transition from the G1 to the S phase in the mammalian cell cycle. We found by immunoblotting that anti-Cdk2 antibodies recognize three Cdk2 proteins (of 33, 34 and 39 kDa) in FRTL-5 and FRTL-Tc cells (malignantly transformed FRTL cells). Although 33 kDa protein is a phosphorylated form of 34 kDa protein previously reported, the nature of 39 kDa protein is unknown. In order to determine the nature of this protein, we screened a FRTL-5 cDNA library. Two cDNA clones of the rat homologue (rat Cdk2-alpha and -beta) of human Cdk2 were isolated. The open reading frame of rat Cdk2-alpha cDNA encoded a protein with 428 amino acids and has a high degree of conservation with human Cdk2. The calculated molecular weight of Cdk2-alpha protein is 33892 Da. The rat Cdk2-beta cDNA was identical to Cdk2-alpha cDNA except that it had extra 144 bp; this coincided with insertion of 48 amino acids into Cdk2-alpha protein between Met 196 and Val 197. The calculated molecular weight of Cdk2-beta protein is 39087 Da. Northern blot analysis indicated that the sizes of rat Cdk2-alpha and -beta mRNAs are approximately 2.5 kb and 3.0 kb, respectively. Partial proteolytic mapping showed that Cdk2-beta gene product is 39 kDa Cdk2 in the immunoblotting. We also found that Cdk2-beta protein binds to cyclin A and suc1 proteins. During G1-S phase in FRTL-Tc cells, Cdk2-alpha protein level is constant, but is gradually phosphorylated. In contrast, the level of Cdk2-beta protein increases through the S phase and decreases at the early G2 phase. These results suggest that a variant form of Cdk2 protein might be required for entry into the S phase of the cell cycle in FRTL-Tc cells.

Effect of sterilization on bone morphogenetic protein

Demineralized bone matrix and bone morphogenetic protein have been used clinically to accelerate bone regeneration. However, the best method of sterilization has been the subject of controversy. Some investigators have used ethylene oxide, but others have reported that doses adequate for sterilization destroyed the osteoinductivity of demineralized bone matrix and that gamma irradiation was less harmful in this respect. We used partially purified bone morphogenetic protein and type-I collagen to investigate the effects of sterilization by ethylene oxide and gamma irradiation on the activity of bone morphogenetic protein. Osteoinductivity was reduced considerably after sterilization by gamma irradiation at 2.5 Mrad and by ethylene oxide at 37 degrees C for 4 hours and at 55 degrees C for 1 hour; however, the reduction induced by ethylene oxide at 29 degrees C for 5 hours was about half of the control values. This study showed that ethylene oxide at 29 degrees C for 5 hours can be used clinically for sterilization of bone morphogenetic protein. We also investigated the effect of gamma irradiation on bone morphogenetic protein and the collagen carrier separately and found that collagen was far more labile than bone morphogenetic protein.

A study of the complications induced by conventional and disposable contact lenses

We reviewed the charts of 23,068 patients (45,580 eyes) who were prescribed contact lenses in order to investigate the incidence of corneal complications in Japan. This population of patients included wearers of various types of conventional contact lenses as well as disposable extended wear lenses and daily disposable lenses. The rate of corneal complications and 95% confidence interval for each lens group were: polymethylmethacrylate (PMMA) lenses, 15.8% (358 of 2,267 eyes, 14.3-17.3%); rigid gas permeable lenses, 10.5% (3,191 of 30,459 eyes, 10.2-10.8%); acrylelastomer lenses, 7.2% (nine of 124 eyes, 2.7-11.7%); HEMA lenses 8.5% (534 of 6,261 eyes, 7.8-9.2%); high water content lenses, 4.0% (103 of 2,591 eyes, 3.6-4.4%); weekly disposable lenses, 4.9% (146 of 2,985 eyes, 4.1-5.7%); and daily disposable lenses, 2.5% (22 of 893 eyes, 1.5-3.5%). PMMA lenses had a significantly higher rate of corneal complications compared with other lenses, whereas the daily disposable lens had a significantly lower rate for the same. The majority of corneal complications for all types of lenses consisted of superficial punctate keratopathy, and there were no cases of corneal ulcers.

Cytokine induction by extracellular products of oral viridans group streptococci

During an etiological study of Kawasaki disease (mucocutaneous lymph node syndrome [MCLS]), we found that dominant viridans streptococcal strains on tooth surfaces and in the throat of both MCLS patients and non-MCLS control children formed erythrogenic and biologically active, extracellular products. In this study, we demonstrated that erythrogenic culture supernatant concentrates of representative strains (two Streptococcus mitis and two Streptococcus oralis), when injected intravenously, induced serum tumor necrosis factor alpha, interleukin-6 (IL-6), and gamma interferon in muramyldipeptide- or Propionibacterium acnes-primed C3H/HeN mice. The concentrates also induced tumor necrosis factor alpha, IL-6, and thymocyte-activating factor (essentially IL-1) in murine peritoneal macrophage, human monocyte, and human whole-blood cultures. An erythrogenic, heat-labile extracellular protein fraction (F-1) that was concentrated from the culture supernatants of a representative S. mitis strain exhibited the above-mentioned cytokine-inducing activity. This partially purified F-1 fraction also induced thymocyte-activating factor and IL-6 in human umbilical vascular endothelial cell and gingival fibroblast cultures.

Electron microscopy of calcification during high-density suspension culture of chondrocytes

Chondrocyte cultures grown in centrifuge tubes with intermittent centrifugation differentiate into hypertrophic chondrocytes and form calcification. We examined chondrocytes cultured in this system electron microscopically. Rat growth-plate chondrocytes were seeded in a plastic centrifuge tube and cultured in the presence of Eagle's minimum essential medium supplemented with 10% fetal bovine serum and 50 micrograms of ascorbic acid per ml. Specimens were examined by using electron microscopy and selected-area electron-diffraction techniques. In the early stage of culture, a few chondrocytes were scattered and extracellular matrices were not observed. In the middle stage of the cultures, the chondrocytes resembled proliferative cells. Matrix vesicles appeared to be budding from the cell surfaces of chondrocytes and were observed sparsely in the extracellular matrices, which were well formed around the chondrocytes. Matrix vesicles increased substantially during the following cultures. In the mature stage of the cultures, crystal formation related to matrix vesicles was observed. In the 33-day cultures, several masses of calcified matrix were formed and it was confirmed to be apatite by selected-area electron diffraction analysis. The chondrocytes appeared hypertrophic during this same stage. The 56-day culture was similar to the 33-day culture. It was concluded that this culture system provides an extracellular-matrix mineralization which is produced by chondrocytes per se.