Application of mesenchymal stromal cell sheets to prevent medication-related osteonecrosis of the jaw with titanium implants in rats

Medication-related osteonecrosis of the jaw (MRONJ) is an intractable adverse event. Dental implants are one of the triggering factors of MRONJ, and implant therapy with low MRONJ risk is required. This study aimed to investigate a rat model of MRONJ induced by extraoral placement of titanium materials and the use of mesenchymal stromal cell (MSCs) sheets to prevent MRONJ. Eight-week-old male rats were administered zoledronate and dexamethasone thrice weekly until killing. A week after drug initiation, a titanium screw and a plate were placed on the left buccal side of the mandible. Allogeneic bone marrow-derived MSC sheets were co-grafted with the titanium plates in the MSC sheet ( +) group. Six weeks after titanium placement, the rats were killed, and their excised mandibular bones were subjected to micro-computed tomography (CT) analysis. Histological analysis was performed after the titanium implants were removed. Empty lacunae visualized on hematoxylin and eosin staining were used as evidence of bone necrosis. Bone necrosis was reduced in the MSC sheet ( +) group. Tartrate-resistant acid phosphatase (TRAP) staining revealed a decreased number of TRAP-positive cells in areas with a large number of empty lacunae in the MSC sheet (-) group. Micro-CT analyses demonstrated that the bone volume fraction (BV/TV) was not significantly different between the MSC sheet (-) and ( +) groups. We conclude that MRONJ can be triggered by a titanium placement in rats, and grafting of allogeneic MSC sheets has the potential to prevent MRONJ.

Application of cell-sheet engineering for new formation of cementum around dental implants

Periodontal disease involves the chronic inflammation of tooth supporting periodontal tissues. As the disease progresses, it manifests destruction of periodontal tissues and eventual tooth loss. The regeneration of lost periodontal tissue has been one of the most important subjects in periodontal research. Since their discovery, periodontal ligament stem cells (PDLSCs), have been transplanted into periodontal bony defects to examine their regenerative potential. Periodontal defects were successfully regenerated using PDLSC sheets, which were fabricated by cell sheet engineering in animal models, and for which clinical human trials are underway. To expand the utility of PDLSC sheet, we attempted to construct periodontal tissues around titanium implants with the goal of facilitating the prevention of peri-implantitis. In so doing, we found newly formed cementum-periodontal ligament (PDL) structures on the implant surface. In this mini review, we summarize the literature regarding cell-based periodontal regeneration using PDLSCs, as well as previous trials aimed at forming periodontal tissues around dental implants. Moreover, the recent findings in cementogenesis are reviewed from the perspective of the formation of further stable periodontal attachment structure on dental implant. This mini review aims to summarize the current status of the creation of novel periodontal tissue-bearing dental implants, and to consider its future direction.

Periodontal regeneration with autologous periodontal ligament-derived cell sheets - A safety and efficacy study in ten patients

Background

Periodontitis results in the destruction of tooth-supporting periodontal tissues and does not have the ability to heal spontaneously. Various approaches have been introduced to regenerate periodontal tissues; however, these approaches have limited efficacy for treating severe defects. Cytotherapies combine stem cell biology and tissue engineering to form a promising approach for overcoming these limitations. In this study, we isolated periodontal ligament (PDL)-derived cells from patients and created cell sheets with “Cell Sheet Engineering Technology”, using temperature responsive culture dishes, in which all the cultured cells can be harvested as an intact transplantable cell sheet by reducing the temperature of the culture dish. Subsequently, the safety and efficacy of autologous PDL-derived cell sheets were evaluated in a clinical setting.

Methods

A single-arm and single-institute clinical study was performed to verify the safety and efficacy of autologous PDL-derived cell sheets in patients with periodontitis. Wisdom teeth were extracted from patients diagnosed with chronic periodontitis, ranging in age from 33 to 63 years (mean [±SD], 46 ± 12), and periodontal tissues were scraped for cell sources. Three-layered PDL-derived cell sheets were constructed using temperature-responsive culture dishes and transplanted in an autologous fashion following standard flap surgeries. Bony defects were filled with beta-tricalcium phosphate granules. Clinical variables were evaluated at baseline, 3 months, and 6 months. Cone-beam computed tomography was performed at baseline and 6 months. Additionally, mid-long-term follow-up has been performed with patients’ agreements.

Results

Our method was found to be safe and no severe adverse events were identified. All the findings, including reduction of periodontal probing depth (mean ± SD, 3.2 ± 1.9 mm), clinical attachment gain (2.5 ± 2.6 mm), and increase of radiographic bone height (2.3 ± 1.8 mm), were improved in all 10 cases at 6 months after the transplantation. These therapeutic effects were sustained during a mean follow-up period of 55 ± 19 months, and there were no serious adverse events.

Conclusions

The results of this study validate the safety and efficacy of autologous PDL-derived cell sheets in severe periodontal defects, and the stability of this efficacy during mid-long-term follow up. This cytotherapeutic approach, based on cell sheet engineering, offers an innovative strategy to treat the recognized unmet need of treating severe periodontal defects.

In Vivo Periodontium Formation Around Titanium Implants Using Periodontal Ligament Cell Sheet

Osseointegrated implants have been recognized as being very reliable and having long-term predictability. However, host defense mechanisms against infection have been known to be impaired around a dental implant because of the lack of a periodontal ligament (PDL). The purpose of our experimental design was to produce cementum and PDL on the implant surface adopting cell sheet technology. To this aim we used PDL-derived cells, which contain multipotential stem cells, as the cell source and we cultured them on an implant material constituted of commercially pure titanium treated with acid etching, blasting, and a calcium phosphate (CaP) coating to improve cell attachment. Implants with adhered human PDL cell sheets were transplanted into bone defects in athymic rat femurs as a xenogeneic model. Implants with adhered canine PDL-derived cell sheets were transplanted into canine mandibular bone as an autologous model. We confirmed that PDL-derived cells cultured with osteoinductive medium had the ability to induce cementum formation. The attachment of PDL cells onto the titanium surface with three surface treatments was accelerated, compared with that onto the smooth titanium surface, at 40 min after starting incubation. Results in the rat model showed that cementum-like and PDL-like tissue was partly observed on the titanium surface with three surface treatments in combination with adherent PDL-derived cell sheets. On the other hand, osseointegration was observed on almost all areas of the smooth titanium surface that had PDL-derived cell sheets, but did not have the three surface treatments. In the canine model, histological observation indicated that formation of cementum-like and PDL-like tissue was induced on the titanium surface with surface treatments and that the PDL-like tissue was perpendicularly oriented between the titanium surface with cementum-like tissue and the bone. Results demonstrate that a periodontal-like structure was formed around a titanium implant, which is similar to the environment existing around a natural tooth. The clinical application of dental implants combined with a cell sheet technique may be feasible as an alternative implant therapy. Furthermore, application of this methodology may play an innovative role in the periodontal, prosthetic, and orthodontic fields in dentistry.

The role of Tsukushi (TSK), a small leucine-rich repeat proteoglycan, in bone growth

INTRODUCTION

Endochondral ossification is one of a key process for bone maturation. Tsukushi (TSK) is a novel member of the secreted small leucine-rich repeat proteoglycan (SLRP) family. SLRPs localize to skeletal regions and play significant roles during whole phases of bone development. Although prior evidence suggests that TSK may be involved in the regulation of bone formation, its role in skeletal development has not yet been elucidated.

METHODS

In the present study, we examined TSK's function during bone growth by comparing skeletal growth of TSK deficient (TSK-/-) mice and wild type (WT) mice. And an in vitro experiment using siRNA transfection of a chondrogenic cell line was performed.

RESULTS

TSK-/- mice exhibited decreased weight and short stature at 3 weeks of age due to decreased longitudinal bone growth coupled with low bone mass. Furthermore, an in vitro experiment using siRNA transfection into a chondrogenic cell line revealed that decreased TSK expression induced down-regulation of key chondrogenic marker gene expression and up-regulation of mid-to-late chondrogenic markers gene expression.

CONCLUSIONS

Our results reveal that TSK regulates bone elongation and bone mass by modulating growth plate chondrocyte function and consequently, overall body size.

Creation and Transplantation of an Adipose-derived Stem Cell (ASC) Sheet in a Diabetic Wound-healing Model

Artificial skin has achieved considerable therapeutic results in clinical practice. However, artificial skin treatments for wounds in diabetic patients with impeded blood flow or with large wounds might be prolonged. Cell-based therapies have appeared as a new technique for the treatment of diabetic ulcers, and cell-sheet engineering has improved the efficacy of cell transplantation. A number of reports have suggested that adipose-derived stem cells (ASCs), a type of mesenchymal stromal cell (MSC), exhibit therapeutic potential due to their relative abundance in adipose tissue and their accessibility for collection when compared to MSCs from other tissues. Therefore, ASCs appear to be a good source of stem cells for therapeutic use. In this study, ASC sheets from the epididymal adipose fat of normal Lewis rats were successfully created using temperature-responsive culture dishes and normal culture medium containing ascorbic acid. The ASC sheets were transplanted into Zucker diabetic fatty (ZDF) rats, a rat model of type 2 diabetes and obesity, that exhibit diminished wound healing. A wound was created on the posterior cranial surface, ASC sheets were transplanted into the wound, and a bilayer artificial skin was used to cover the sheets. ZDF rats that received ASC sheets had better wound healing than ZDF rats without the transplantation of ASC sheets. This approach was limited because ASC sheets are sensitive to dry conditions, requiring the maintenance of a moist wound environment. Therefore, artificial skin was used to cover the ASC sheet to prevent drying. The allogenic transplantation of ASC sheets in combination with artificial skin might also be applicable to other intractable ulcers or burns, such as those observed with peripheral arterial disease and collagen disease, and might be administered to patients who are undernourished or are using steroids. Thus, this treatment might be the first step towards improving the therapeutic options for diabetic wound healing.

Allogeneic Transplantation of Periodontal Ligament-Derived Multipotent Mesenchymal Stromal Cell Sheets in Canine Critical-Size Supra-Alveolar Periodontal Defect Model

Periodontitis is a chronic inflammatory disease that induces the destruction of tooth-supporting tissues, followed by tooth loss. Although several approaches have been applied to periodontal regeneration, complete periodontal regeneration has not been accomplished. Tissue engineering using a combination of cells and scaffolds is considered to be a viable alternative strategy. We have shown that autologous transplantation of periodontal ligament-derived multipotent mesenchymal stromal cell (PDL-MSC) sheets regenerates periodontal tissue in canine models. However, the indications for autologous cell transplantation in clinical situations are limited. Therefore, this study evaluated the safety and efficacy of allogeneic transplantation of PDL-MSC sheets using a canine horizontal periodontal defect model. Canine PDL-MSCs were labeled with enhanced green fluorescent protein (EGFP) and were cultured on temperature-responsive dishes. Three-layered cell sheets were transplanted around denuded root surfaces either autologously or allogeneically. A mixture of β-tricalcium phosphate and collagen gel was placed on the bone defects. Eight weeks after transplantation, dogs were euthanized and subjected to microcomputed tomography and histological analyses. RNA and DNA were extracted from the paraffin sections to verify the presence of EGFP at the transplantation site. Inflammatory markers from peripheral blood sera were quantified using an enzyme-linked immunosorbent assay. Periodontal regeneration was observed in both the autologous and the allogeneic transplantation groups. The allogeneic transplantation group showed particularly significant regeneration of newly formed cementum, which is critical for the periodontal regeneration. Serum levels of inflammatory markers from peripheral blood sera showed little difference between the autologous and allogeneic groups. EGFP amplicons were detectable in the paraffin sections of the allogeneic group. These results suggest that allogeneic PDL-MSC sheets promoted periodontal tissue regeneration without side effects. Therefore, allogeneic transplantation of PDL-MSC sheets has a potential to become an alternative strategy for periodontal regeneration.

Improved enzymatic treatment for accurate cell counting from extracellular matrix-rich periodontal ligament cell sheets

PURPOSE

The objective of this study was to establish a method for accurate cell counting from matrix-rich cell sheets in the clinical setting.

MATERIALS AND METHODS

Human periodontal ligament (HPDL) cells were obtained from healthy donors to prepare PDL cell sheets. To obtain single cell suspensions, the cell sheets were treated with three different enzymatic formulations: collagenase alone, trypsin-ethylenediaminetetraacetic acid (EDTA) alone, and a combination of collagenase and trypsin-EDTA. After cell dispersion, cell numbers and cell survival rates were measured. To evaluate damage to the cell surfaces from the enzymes, the dispersed cells were analyzed by a flow cytometer with an anti-alkaline phosphatase antibody.

RESULTS

Treatment with collagenase alone or trypsin-EDTA alone dispersed few cells from HPDL cell sheets. In contrast, combined treatment with collagenase and trypsin-EDTA successfully produced a large amount of single cells from cell sheets. Flow cytometry analysis showed that single cells obtained by combined use of collagenase and trypsin-EDTA preserved alkaline phosphatase epitopes on the cell surfaces.

CONCLUSIONS

Cell sheets rich with extracellular matrix were dispersed via combined treatment with collagenase and trypsin-EDTA without destroying the expression of cell surface markers. The results suggest that this method would be useful for determining the accurate cell number of cell sheets for cell therapies and should also be applicable for other kinds of matrix-rich cell sheets.

Comparison of different tissue-derived stem cell sheets for periodontal regeneration in a canine 1-wall defect model

Cytotherapeutic approaches have been investigated to overcome the limitations of existing procedures for periodontal regeneration. In this study, cell sheet transplantation was performed using three kinds of mesenchymal tissue (periodontal ligament, alveolar periosteum, and bone marrow)-derived cells to compare the differences between cell sources in a canine severe defect model (one-wall intrabony defect). Periodontal ligament cells (PDLCs), iliac bone marrow mesenchymal stromal cells (BMMSCs), and alveolar periosteal cells (APCs) were obtained from each dog; a total of four dogs were used. Three-layered cell sheets of each cell source supported with woven polyglycolic acid were autologously transplanted to the denuded root surface. One-wall intrabony defects were filled with a mixture of β-tricalcium phosphate (β-TCP) and collagen. Eight weeks after the transplantation, periodontal regeneration was significantly observed with both newly formed cementum and well-oriented PDL fibers more in the PDLC group than in the other groups. In addition, nerve filament was observed in the regenerated PDL tissue only in the PDLC group. The amount of alveolar bone regeneration was highest in the PDLC group, although it did not reach statistical significance among the groups. These results indicate that PDLC sheets combined with β-TCP/collagen scaffold serve as a promising tool for periodontal regeneration.

Validation of human periodontal ligament-derived cells as a reliable source for cytotherapeutic use

AIM

Periodontal ligament (PDL) is a reliable cell source for periodontal regeneration. In this study, an optimal protocol for the extraction, expansion, and characterization of human PDL (hPDL) cells was examined for clinical trials.

MATERIALS AND METHODS

hPDL tissues were obtained from 41 surgically extracted teeth and digested with enzymes. Human adipose-derived stem cells (hADSCs), bone marrow-derived mesenchymal stem cells (hBMMSCs), and gingival fibroblasts (hGFs) were used for comparison. For each sample, the proliferative capacity, colony-forming ability, alkaline phosphatase activity, differentiation ability, the cell surface antigens, gene expression, and regenerative potential were examined.

RESULTS

hPDL cells were more successfully extracted with collagenase/dispase [29/30 (96.7%)] than with trypsin/EDTA [8/11 (72.7%)], and exhibited osteogenic potential both in vitro and in vivo. The proliferation of hPDL cells was rapid at a low cell density. hPDL cells frequently differentiated into cementoblastic/osteoblastic lineage (∼60%). In contrast, their adipogenic and chondrogenic potentials were lower than those of hADSCs and hBMMSCs. Some genes (NCAM1, S100A4, and periostin) were preferentially expressed in hPDL cells compared with those of hBMMSCs and hGFs. Immunohistochemical studies revealed the expressions of S100A4 and periostin in hPDL tissue.

CONCLUSION

A protocol for the successful cultivation and validation of hPDL cells is proposed for clinical settings.

Periodontal ligament cell sheet promotes periodontal regeneration in athymic rats

AIM

The primary goal of periodontal treatment is regeneration of the periodontium. Current theories suggest that the periodontal ligament (PDL) cells have the capacity to participate in restoring connective and mineralized tissues, when appropriately triggered. We evaluated whether human PDL cell sheets could reconstruct periodontal tissue.

MATERIAL AND METHODS

To obtain the cell sheet, human PDL cells were cultured on temperature-responsive culture dishes with or without osteogenic differentiation medium. The cell sheets were transplanted on periodontal fenestration defects of immunodeficient rats. Forty rats were divided in two groups: in one group, cell sheets cultured with control medium were transplanted and in the other, cell sheets cultured with osteogenic differentiation medium were transplanted. The defects were analysed histologically and histomorphologically after healing.

RESULTS

Most of the experimental group exhibited a new cementum-like layer and new attachment of collagen fibres to the layer. Histomorphological analyses indicated significant periodontal regeneration. The control group revealed dense extracellular matrix and fibre formation, but an obvious cementum layer was not observed.

CONCLUSIONS

Transplanted PDL cell sheets cultured with osteogenic differentiation medium induced periodontal regeneration containing an obvious cementum layer and Sharpey's fibres. Thus, the method could be feasible as a new therapeutic approach for periodontal regeneration.

Periodontal regeneration with multi-layered periodontal ligament-derived cell sheets in a canine model

Periodontal regeneration has been challenged with chemical reagents and/or biological approaches, however, there is still no sufficient technique that can regenerate complete periodontium, including alveolar bone, cementum, and well-oriented collagen fibers. The purpose of this study was to examine multi-layered sheets of periodontal ligament (PDL)-derived cells for periodontal regeneration. Canine PDL cells were isolated enzymatically and expanded in vitro. The cell population contained cells capable of making single cell-derived colonies at an approximately 20% frequency. Expression of mRNA of periodontal marker genes, S100 calcium binding protein A4 and periostin, was observed. Alkaline phosphatase activity and gene expression of both osteoblastic/cementoblastic and periodontal markers were upregulated by osteoinductive medium. Then, three-layered PDL cell sheets supported with woven polyglycolic acid were transplanted to dental root surfaces having three-wall periodontal defects in an autologous manner, and bone defects were filled with porous beta-tricalcium phosphate. Cell sheet transplantation regenerated both new bone and cementum connecting with well-oriented collagen fibers, while only limited bone regeneration was observed in control group where cell sheet transplantation was eliminated. These results suggest that PDL cells have multiple differentiation properties to regenerate periodontal tissues comprising hard and soft tissues. PDL cell sheet transplantation should prove useful for periodontal regeneration in clinical settings.

PTEN activity could be a predictive marker of trastuzumab efficacy in the treatment of ErbB2-overexpressing breast cancer

Trastuzumab is the only HER2/neu-directed therapy to have received Food and Drug Administration approval for the treatment of patients with metastatic breast cancer. The efficacy of trastuzumab depends on the HER2/neu status of the tumour and the patient's prior treatment, but even when patients are selected on the basis of HER2/neu gene amplification, the single-agent response rate ranges from 12 to 30% and few patients respond to trastuzumab monotherapy. Here, we propose PTEN as a predictive biomarker for trastuzumab efficacy. Human breast cancer SKBR3 and drug-resistant SKBR3/R cells were investigated. We also examined clinical samples from patients who had been treated with trastuzumab and analysed the relationship between trastuzumab efficacy and PTEN level. The PI3K/Akt signalling pathway was observed to be highly active in the drug-resistant cells, and their level of PTEN was low. Delivery of antisense PTEN duplex siRNA significantly decreased the trastuzumab chemosensitivity of parental SKBR3 cells, and marked activation of Akt signalling pathway was also recognised. Moreover, immunohistochemical investigation revealed that trastuzumab treatment was remarkably successful in cells with elevated PTEN expression. Along with the immune-system-associated cytotoxic mechanism, several mechanisms have been proposed for the effect of trastuzumab. PTEN activity might play an important and major role in its HER2/PI3K/Akt-mediated antitumour effect, and could be a useful biomarker for predicting the efficacy of trastuzumab in the treatment of breast cancer.

Identification of Dof proteins with implication in the gibberellin-regulated expression of a peptidase gene following the germination of rice grains

Type III carboxypeptidase (CPD3) is one of the hydrolytic enzymes whose expression is up-regulated by gibberellins (GA) in the aleurones of germinated cereal grains. A number of pyrimidine boxes and a sequence resembling the gibberellic acid response element (GARE) are observed in the region upstream of the transcription initiation site of the CPD3 gene, showing a characteristic of cereal GA-responsive genes. Transient gene expression assays in germinated rice aleurone demonstrated that the CPD3 promoter was able to confer hormonally responses on the expression of the reporter gene. By southwestern screening, several cDNAs encoding the Dof class proteins were isolated from a rice aleurone library. Each mRNA accumulation for five novel members of Dof proteins (OsDof1--5) occurs with a different time course and in a tissue-specific manner following the germination of grains. Of these, the expression of the OsDof3 gene is abundant in aleurones where it precedes that of the CPD3 gene, implying that this is an early response gene of GA. The OsDof3 protein, expressed in Escherichia coli, selectively bound AAAG motifs of the pyrimidine boxes through the DNA-binding activity of its Dof domain. Co-expression experiments in aleurones suggested that the OsDof3 protein should play a regulatory role in the expression of the CPD3 gene under the control of GA.

The glycosylphosphatidylinositol-anchored phosphatase from Spirodela oligorrhiza is a purple acid phosphatase

We recently presented clear evidence that the major low-phosphate-inducible phosphatase of the duckweed Spirodela oligorrhiza is a glycosylphosphatidylinositol (GPI)-anchored protein, and, to our knowledge, is the first described from higher plants (N. Morita, H. Nakazato, H. Okuyama, Y. Kim, G.A. Thompson, Jr. [1996] Biochim Biophys Acta 1290: 53-62). In this report the purified 57-kD phosphatase is shown to be a purple metalloenzyme containing Fe and Mn atoms and having an absorption maximum at 556 nm. The phosphatase activity was only slightly inhibited by tartrate, as expected for a purple acid phosphatase (PAP). Furthermore, the protein cross-reacted with an anti-Arabidopsis PAP antibody on immunoblots. The N-terminal amino acid sequence of the phosphatase was very similar to those of Arabidopsis, red kidney bean (Phaseolus vulgaris), and soybean (Glycine max) PAP. Extracts of S. oligorrhiza plants incubated with the GPI-specific precursor [3H]ethanolamine were treated with antibodies raised against the purified S. oligorrhiza phosphatase. Radioactivity from the resulting immunoprecipitates was specifically associated with a 57-kD band on sodium dodecyl sulfate-polyacrylamide gels. These results, together with previous findings, strongly indicate that the GPI-anchored phosphatase of S. oligorrhiza is a PAP.

Organ-specific and hormone-dependent expression of genes for serine carboxypeptidases during development and following germination of rice grains

Several cDNA clones encoding either serine carboxypeptidases or related proteins of Oryza sativa L. were identified, and the abundance of the corresponding mRNA in immature and germinated grains was examined. The deduced amino acid sequence of each cDNA included key sequences, such as a pentapeptide (G-X-S-X-G/A) that is conserved among many serine carboxypeptidases, and the putative protein products were classified as two general and one novel type of cereal serine carboxypeptidases. Two general types exhibited considerable homology to type I and type III carboxypeptidases of cereal plants. The novel type encoded a serine carboxypeptidase-like protein that was very similar to type III carboxypeptidases of barley and wheat but had slight differences in both the N- and the C-terminal sequences. The mRNAs of each of these carboxypeptidases were observed in immature grains, and they decreased during maturation. The abundance of mRNA for each class of carboxypeptidase increased again following germination with the same time course and in a tissue-specific manner. The mRNAs for type I and type III-like carboxypeptidases were abundant in germinated embryos composed of leaf, root, and scutellum, whereas the mRNA for type III carboxypeptidase was conspicuous in endosperm that contained the aleurone layer. Altered amounts of mRNA in deembryonated half-grains in response to phytohormones, such as gibberellic acid and abscisic acid, were only detectable in the case of type III carboxypeptidase. Southern blot analysis using rice genomic DNA revealed the simple organization of each gene for these three classes of carboxypeptidases.

Phylogenetic subtypes of human T-lymphotropic virus type I and their relations to the anthropological background

Isolates of human T-lymphotropic virus type I (HTLV-I) were phylogenetically analyzed from native inhabitants in India and South America (Colombia and Chile) and from Ainu (regarded as pure Japanese descendants from the preagricultural "Jomon" period). Their genomes were partially sequenced together with isolates from Gabon in central Africa and from Ghana in West Africa. The phylogenetic tree was constructed from the sequence data obtained and those of previously reported HTLV-I isolates and simian T-lymphotropic virus type I (STLV-I) isolates. The heterogeneity of HTLV-I was recently recognized, and one major type, generally called the "cosmopolitan" type, contained Japanese, Caribbean, and West African isolates. The phylogenetic tree constructed in the present study has shown that this cosmopolitan type can be further grouped into three lineages (subtypes A, B, and C). Subtype A consists of some Caribbean, two South American, and some Japanese isolates, including that from the Ainu, in addition to an Indian isolate, and subtype B consists of other Japanese isolates in addition to another Indian isolate, suggesting that there might be at least two ancestral lineages of the Japanese HTLV-I. Subtype A implies a close connection of the Caribbean and South American natives with the Japanese and thereby a possible migration of the lineage to the American continent via Beringia in the Paleolithic era. Subtype C consists of the West African and other Caribbean isolates, indicating that not all but part of the Caribbean strains directly originated from West Africa probably during the period of slave trade. The tree also has shown that the HTLV-I isolate from Gabon in central Africa forms a cluster with STLV-I from a chimpanzee, suggesting a possible interspecies transmission between man and the chimpanzee in the past. No specific clustering was observed in the tree in relation to manifestations of the disease such as adult T-cell leukemia and HTLV-I-related neurological disorders. Thus, the topology of the phylogenetic tree reflects the movement of people carrying the virus in the past.

A new aspect of tolbutamide metabolism in the rabbit: the role of 1-butyl-3-(p-formylphenyl)sulphonylurea

We investigated the metabolism of tolbutamide by using synthetic 1-butyl-3-(p-formylphenyl)sulphonylurea (ATB), an intermediate in the metabolic pathway of tolbutamide. ATB (40 mg kg-1) administered intravenously to rabbits was oxidized to 1-butyl-3-(p-carboxyphenyl)sulphonylurea (CTB) and also reduced to 1-butyl-3-(p-hydroxymethylphenyl)sulphonylurea (HMTB). Therefore, it is likely that in the metabolism of tolbutamide, the oxidation of HMTB to ATB involved the reverse reaction, suggesting the reduction of ATB to HMTB. The oxidation of ATB to CTB was inhibited by disulfiram pretreatment. ATB was detected in the blood following intravenous administration of HMTB in rabbits pretreated with disulfiram. These results, confirm that ATB is an intermediate in the oxidative metabolism of tolbutamide in the rabbit.

Dinucleotide repeat polymorphism at the apolipoprotein AII locus--phenotyping from peripheral blood and hair

The genomes of eukaryotes including humans contain very short simple sequence repeats such as (dA-dC)n and (dG-dT)n. Recently, these repeats have been reported to exhibit marked length polymorphism due to wide variation in their reiteration numbers. We report here dinucleotide repeat polymorphism at the apolipoprotein AII locus in Japanese subjects. The informativeness in Japanese was as high as in Caucasians (PIC value and heterozygosity of 0.67 and 0.72, respectively), but their allele frequencies were different with statistical significance. We also discuss the advantages of using dinucleotide repeat polymorphisms in forensic science, demonstrating determination of phenotype from not only a single hair root but also a short hair shaft.

Effects of cytosine methylation at restriction sites on deoxyribonucleic acid (DNA) typing

The effects of endogenous 5-methylcytosines on deoxyribonucleic acid (DNA) fingerprints were studied. Analysis with methylation-sensitive restriction endonuclease Sau3AI and its methylation-insensitive isoschizomer MboI showed some differences in the patterns generated as a result of 5-methylcytosines at the recognition sites. Moreover, a few bands of sperm DNA did not match those of blood DNA from the same individual, a phenomenon only observed in the digests of methylation-sensitive endonucleases. These findings indicate the unsuitability of methylation-sensitive restriction endonucleases for DNA fingerprinting and other forms of DNA typing, because of the tissue-specific status of the methylation.

Human-specific sequences: isolation of species-specific DNA regions by genome subtraction

Uniqueness is fundamental to the individuality of species, and this in turn is based on the uniqueness of their genomes. For the purpose of resolving the genetic basis of human uniqueness, we describe here the isolation of human-specific sequences using the technique of genome subtraction, i.e., competitive reassociation of genomic DNAs between two very closely related species. One such sequence, HS5, was found to be present only in the human genome and absent in the genomes of non-human primates including chimpanzees, the species most closely related to humans.

Probe walking: development of novel probes for DNA fingerprinting

The tandem repeat of a 28-base-pair (bp) sequence downstream of the human c-Ha-ras-1 oncogene was studied as a probe for DNA fingerprinting. Multiple hypervariable patterns were observed by Southern hybridization at low stringency. The patterns were specific to individuals, indicating the availability of the 28-bp repeat as a probe for DNA fingerprinting. Moreover, we cloned the tandem repeat of a 33-bp sequence, which cross-hybridized with the 28-bp repeat. This 33-bp repeat detected another set of hypervariable restriction fragments by Southern hybridization at the same stringency. These results suggests that 'probe walking' can be employed to develop novel probes that provide different DNA fingerprints.

Generalized view of Gaussian pulse-transmission characteristics in single-mode optical fibers

A generalized view of Gaussian pulse-transmission characteristics in single-mode optical fibers is presented. With this generalization, it becomes possible to describe manner. Gaussian pulse-transmission characteristics in a unified manner.

130-km-long fault location for single-mode optical fiber using 1.55-microm Q-switched Er(3+):glass laser

An optical-time-domain reflectometer has been constructed with a 1.55-microm Er(3+):glass laser, a TeO(2) acousto-optical directional coupler, and a cooled Ge P-I-N photodiode. With it, a maximum detectable fault-location length of 130 km for single-mode optical fiber has been successfully achieved at a 1.55microm wavelength.

Output-stabilized high-repetition-rate 1.545-microm Q-switched Er:glass laser

A newly developed Q-switched Er:glass laser with a long pulse length, suitable for fiber-fault location, is described. A specially prepared athermal rod has made it possible to operate at a 5-Hz repetition rate. A feedback-stabilized Q-switching method involving fluorescence monitoring has been applied to this three-level laser system. A +/-3% power stability (standard deviation) has been obtained for a 1-microsec pulse with a 2-mJ output energy.

Efficient arc lamps for optical pumping of neodymium lasers

A krypton arc lamp with high conversion efficiency has been obtained by increasing Kr pressure. The conversion efficiency of a lamp at 8 atm is about 1.2-1.5 times as high as that of a lamp used at 2 atm, depending on the operating electrical input. The high pressure Kr arc lamp and Nd: YAG rod were set in a prolate ellipsoidal cavity. Laser power of 73 W was obtained at an input of 2.63 kW for a slope efficiency of 3.5%.