The impact of right atrium and left atrium reverse remodeling for functional regurgitation of atrioventricular valve among patients who were underwent ablation for atrial fibrillation

Background

Atrial fibrillation (AF) is a risk factor of Regurgitation of Atrioventricular Valve and Regurgitation of Atrioventricular Valve is improved after ablation for AF. However, Mechanism of improvement of Tricuspid regurgitation (TR) and Mitral regurgitation (MR) after ablation for AF were unclear.

Methods

The one hundred fifty-seven cases consecutive patients who were underwent ablation for persistent AF were examined in this study. These patients were performed Holter ECG and Echocardiography 6 months after ablation for persistent AF. The area of the Right Atrium (RA), Left Atrium (LA), diameter of the tricuspid valve anulus and Mitral valve annulus, were measured by echocardiography at before and 6 months after ablation for AF. The reverse remodeling index (RRI) was defined as divided post area of RA and LA by pre area of RA and LA. The Improved group was defined as one or more than regurgitation grade improvements.

Results

TR improved in 56 cases (35.7%) of 157 cases and MR improved in 25 (16.6%) cases of 157 cases. The ratio of improved TR was significantly higher than ratio of improved MR (p<0.01). The difference in tricuspid annulus diameter before and after ablation for AF was significantly longer in TR improved group than in TR non-improved group. (4.9±5.3 mm vs 1.6±5.4 mm, p<0.01). The RRI of RA in TR improved group was significantly smaller than in TR non-improved group (0.73±0.19 vs 0.89±0.26 p<0.01). The difference in mitral annulus diameter before and after ablation for AF was not significant differences between MR improved group and MR non-improved group. The RRI of LA in MR improved group was significantly smaller than in MR non-improved group (0.79±0.22 vs 0.90±0.25 p<0.01). The RRI of RA was significantly smaller than RRI of LA among patients who were able to maintain sinus rhythm after ablation for persistent AF (0.79±0.23 vs 0.85±0.24 p=0.04).

Conclusion

Reverse remodeling of RA was higher than Reverse remodeling of LA among patients who were able to maintain sinus rhythm after ablation for persistent AF and Reverse remodeling of RA and LA were important factors of improvement of TR and MR after ablation for persistent AF. These results considered to be the cause why the improvement rate of TR was higher than the Improvement rate of MR after persistent AF.

Funding Acknowledgement

Type of funding sources: None.

Development of a fast response neutron detector for the supersonic FRC collision process

The collisional merging experiments of the field-reversing configuration (FRC) at supersonic/Alfvénic velocities have been performed in the FRC Amplification via Translation-Collisional Merging device only in Japan. This experiment may excite shockwaves and cause particle acceleration. To obtain supporting evidence of particle acceleration by shockwaves, we have proposed to observe neutrons originating from the D-D fusion reaction of accelerated non-thermal particles. A plastic scintillation detector has been developed for the supersonic/Alfvénic collision/merging FRC experiment. The developed neutron detector has sufficient performance of neutron sensitivity and nanosecond response time. In the collisional merging process, we obtained a signal that could be considered a neutron, which is not predicted by the adiabatic compression process in the two-dimensional magnetohydrodynamics simulation.

Tau oligomerization: a role for tau aggregation intermediates linked to neurodegeneration

Intracellular accumulation of filamentous tau proteins is a defining feature of neurodegenerative diseases, including Alzheimer's disease, progressive supranuclear palsy, corticobasal degeneration, Pick's disease, and frontotemporal dementia with Parkinsonism linked to chromosome 17, all known collectively as tauopathies. Tau protein is a member of microtubule (MT)-associated proteins. Tau is a highly soluble and natively unfolded protein dominated by a random coil structure in solution. It is believed that aberrant modifications of tau, including phosphorylation, truncation, and conformational changes, induce filamentous aggregation. However, the mechanism underlying the conversion of tau protein from a soluble state to one of insoluble aggregates still remains elusive. The importance of tau aggregation intermediates (e.g. tau dimer, tau multimer, and granular tau oligomer) in disease pathogenesis was suggested by recent studies. Here, we review the latest developments in tracking the structural changes of tau protein and discuss the utility improving our understanding of tau aggregation pathway leading to human tauopathies.

Molecular chaperone-mediated tau protein metabolism counteracts the formation of granular tau oligomers in human brain

Intracellular accumulation of filamentous tau proteins is a defining feature of neurodegenerative diseases termed tauopathies. The pathogenesis of tauopathies remains largely unknown. Molecular chaperones such as heat shock proteins (HSPs), however, have been implicated in tauopathies as well as in other neurodegenerative diseases characterized by the accumulation of insoluble protein aggregates. To search for in vivo evidence of chaperone-related tau protein metabolism, we analyzed human brains with varying degrees of neurofibrillary tangle (NFT) pathology, as defined by Braak NFT staging. Quantitative analysis of soluble protein levels revealed significant positive correlations between tau and Hsp90, Hsp40, Hsp27, alpha-crystallin, and CHIP. An inverse correlation was observed between the levels of HSPs in each specimen and the levels of granular tau oligomers, the latter of which were isolated from brain as intermediates of tau filaments. We speculate that HSPs function as regulators of soluble tau protein levels, and, once the capacity of this chaperone system is saturated, granular tau oligomers form virtually unabated. This is expressed pathologically as an early sign of NFT formation. The molecular basis of chaperone-mediated protection against neurodegeneration might lead to the development of therapeutics for tauopathies. (c) 2007 Wiley-Liss, Inc.

Hard tissue formation in subcutaneously transplanted rat dental pulp

While dental pulp appears to be able to form mineralized matrices that do not always resemble dentin, the precise characteristics of the hard tissue and the mechanism of its induction remain unknown. Therefore, we evaluated hard tissue induced by transplantation of pulp into subcutaneous tissue. Seven days after transplantation, initial hard tissue was formed at the inner periphery of the pulp. After 14 days, this hard tissue expanded inwardly. Mineralized matrix was immunopositive for osteocalcin, osteopontin, and bone sialoprotein, but negative for dentin sialoprotein. Transplantation of GFP-labeled pulp into wild-type rats showed these formative cells to have been derived from the transplant. TEM observation revealed apatite crystals within necrotic cells and matrix vesicles at the initial stage of calcification. These results indicate that pulp cells possess the ability to form a bone- or cementum-like matrix. Calcification of the matrix may occur in necrotic cells and matrix vesicles, followed by collagenous calcification.

Efficacy of gemtuzumab ozogamicin on ATRA- and arsenic-resistant acute promyelocytic leukemia (APL) cells

Acute promyelocytic leukemia (APL) cells express a considerable level of CD33, which is a target of gemtuzumab ozogamicin (GO), and a significantly lower level of P-glycoprotein (P-gp). In this study, we examined whether GO was effective on all-trans retinoic acid (ATRA)- or arsenic trioxide (ATO)-resistant APL cells. Cells used were an APL cell line in which P-gp was undetectable (NB4), ATRA-resistant NB4 (NB4/RA), NB4 and NB4/RA that had been transfected with MDR-1 cDNA (NB4/MDR and NB4/RA/MDR, respectively), ATO-resistant NB4 (NB4/As) and blast cells from eight patients with clinically ATRA-resistant APL including two patients with ATRA- and ATO-resistant APL. The efficacy of GO was analyzed by (3)H-thymidine incorporation, the dye exclusion test and cell cycle distribution. GO suppressed the growth of NB4, NB4/RA and NB4/As cells in a dose-dependent manner. GO increased the percentage of hypodiploid cells significantly in NB4, NB4/RA and NB4/As cells, and by a limited degree in NB4/MDR and NB4/RA/MDR cells. Similar results were obtained using blast cells from the patients with APL. GO is effective against ATRA- or ATO-resistant APL cells that do not express P-gp, and the mechanism of resistance to GO is not related to the mechanism of resistance to ATRA or ATO in APL cells. Leukemia (2005) 19, 1306-1311. doi:10.1038/sj.leu.2403807; published online 26 May 2005.

Fibrinogens Kosai and Ogasa: Bbeta15Gly-->Cys (GGT-->TGT) substitution associated with impairment of fibrinopeptide B release and lateral aggregation

We found two heterozygous dysfibrinogenemias, designated fibrinogen Kosai and fibrinogen Ogasa. Kosai was associated with arteriosclerosis obliterans but Ogasa showed no bleeding or thrombotic tendencies. The plasma fibrinogen concentrations from the two propositi (Ogasa and Kosai) were much lower when determined by the thrombin-time method (0.94 and 1.06 g L(-1), respectively) than when determined by the immunological method (2.87 and 2.72 g L(-1), respectively). We performed DNA sequencing and functional analyses to clarify the relationship between the structural and functional abnormalities. Genetic analysis of PCR-amplified DNA from the propositi identified the heterozygous substitution Bbeta15Gly-->Cys (GGT-->TGT). Western blotting analysis of purified fibrinogen revealed the existence of albumin-fibrinogen complexes. Functional analyses indicated that compared with the normal control, the propositi's fibrinogen released only half the normal amount of fibrinopeptide B and showed markedly impaired polymerization. In addition, the observation of thinner fibers in fibrin clots (by scanning electron microscopy) indicated markedly defective lateral aggregation in the variant fibrinogens. The impaired functions may be due to the substitution of Cys for Bbetao15Gly plus the existence of some additional disulfide-bonded forms.

Arsenic trioxide therapy for relapsed or refractory Japanese patients with acute promyelocytic leukemia: need for careful electrocardiogram monitoring

Recent studies have shown that arsenic trioxide (As(2)O(3)) can induce complete remission in patients with acute promyelocytic leukemia (APL). We tested the efficacy and safety of As(2)O(3) for the treatment of patients with APL who had relapsed from or become refractory to all-trans retinoic acid (ATRA) and conventional chemotherapy in a prospective study. As(2)O(3) at a dose of 0.15 mg/kg was administered until the date of bone marrow remission to a maximum of 60 days. In patients who achieved complete remission (CR), one additional course of As(2)O(3) was administered using the same dose for 25 days. Of 14 patients, 11 (78%) achieved CR. Six of 10 patients who achieved CR showed disappearance of PML-RARalpha transcript by RT-PCR assay. The duration of As(2)O(3)-induced CR ranged from 4 to 22 months (median, 8 months) at a median follow-up of 17 months. Adverse events included 13 electrocardiogram abnormalities (13 QTc prolongation, eight ventricular premature contraction, four nonsustained ventricular tachycardia and two paroxysmal supraventricular tachycardia), seven nausea and vomiting, four pruritus, three peripheral neuropathy, three fluid retention and one APL differentiation syndrome. Four patients received antiarrhythmic agents. Hyperleukocytosis developed in five patients and in three cytotoxic drugs were necessary. Other adverse events were relatively mild. As(2)O(3) treatment is effective and relatively safe in relapsed or refectory patients with APL. Cardiac toxicities in patients with QTc prolongation should be carefully monitored.

Cellular events at the onset of physiological root resorption in rabbit deciduous teeth

For elucidation of how physiological root resorption of deciduous teeth is initiated, the cellular events that occur surrounding the root of rabbit deciduous teeth before and at the onset of physiological root resorption were observed by means of light and electron microscopy. In addition, the cytodifferentiation of odontoclasts during the initial phase of this root resorption was evaluated by histochemical staining of tartrate-resistant acid phosphatase (TRAP) activity as a marker odontoclasts and their precursors. The present investigation was focused on the physiological root resorption of the deciduous lower second molar of rabbits from Day 0-5 postnatally. At birth, the deciduous molar had not erupted yet, and no TRAP-positive cell could be found surrounding the tissue adjacent to the root of the deciduous tooth. TRAP-positive mononuclear cells were initially detected in the coronal portion of the dental follicle of the permanent tooth at Day 1 postnatally. Ultrastructurally, these mononuclear cells had moderate numbers of mitochondria and short-strand rough endoplasmic reticulum, as well as scattered free ribosomes throughout their cytoplasm. TRAP-positive mononuclear cells then appeared in the cementoblast layer immediately adjacent to the surface of the deciduous roots. These mononuclear cells projected cytoplasmic extensions between the cementoblasts and made contact with the cementum. At that time, cell-cell contact was frequently observed between these mononuclear cells and cementoblasts. During 3-5 days postnatally, the number of TRAP-positive multinucleate odontoclasts on the root surface gradually increased. They had well-developed ruffled borders and made typical resorption lacunae on the root surface of the deciduous tooth. During this early postnatal period, neither inflammatory cells nor necrotic tissue could be observed surrounding the deciduous root. This study demonstrates that the dental follicle of the permanent tooth as well as the connective tissue adjacent to the deciduous root might play important role in site- and time-specific recruitment, development, and activation of odontoclasts before and at the onset of physiological root resorption.

Enhanced neurofibrillary degeneration in transgenic mice expressing mutant tau and APP

JNPL3 transgenic mice expressing a mutant tau protein, which develop neurofibrillary tangles and progressive motor disturbance, were crossed with Tg2576 transgenic mice expressing mutant beta-amyloid precursor protein (APP), thus modulating the APP-Abeta (beta-amyloid peptide) environment. The resulting double mutant (tau/APP) progeny and the Tg2576 parental strain developed Abeta deposits at the same age; however, relative to JNPL3 mice, the double mutants exhibited neurofibrillary tangle pathology that was substantially enhanced in the limbic system and olfactory cortex. These results indicate that either APP or Abeta influences the formation of neurofibrillary tangles. The interaction between Abeta and tau pathologies in these mice supports the hypothesis that a similar interaction occurs in Alzheimer's disease.

Temporal changes in the distribution and number of macrophage-lineage cells in the periodontal membrane of the rat molar in response to experimental tooth movement

In order to evaluate the possible role of macrophages in the remodelling of periodontal tissue in response to tooth movement, temporal changes in the number and distribution of macrophage-lineage cells in the periodontal membrane of the rat molar tooth after experimental tooth movement were examined immunohistochemically using four anti-rat monoclonal antibodies: ED1 (anti-monocyte/macrophage-lineage cells and dendritic cells), ED2 (anti-resident macrophages), KI-M2R (anti-tissue macrophages), and OX6 (anti-class II molecules). The right maxillary first molar tooth of Wistar rats was moved mesially by a closed-coil spring for 1, 3, 5, or 7 days. Sham-treated rats wearing an inactivated appliance for each experimental period and entirely untreated rats were used as controls. Alternate horizontal serial cryostat sections were cut and incubated with antibodies to ED1, ED2, KI-M2R, and OX6. In addition, cells immunopositive for each monoclonal antibody in the periodontal membrane during tooth movement were analysed on the tension and pressure sides. In the control rats, large numbers of cells positively stained with each monoclonal antibody were distributed throughout the periodontal membrane surrounding the distobuccal root. At 1 day after experimental tooth movement, the number of immunopositive cells obtained with all four monoclonal antibodies decreased as compared with those of the control on the mesial/pressure side. During the later experimental time periods, ED1- and OX6-positive cells in the periodontal membrane of this side were significantly increased in number compared with controls, whereas the density and distribution pattern of cells positive with ED2 or KI-M2R remained unchanged. On the mesial/pressure side, which underwent hyalinization, a marked accumulation of OX6- and ED1-reactive cells, but not of ED2- or KI-M2R-reactive cells, was frequently observed in the area of the hyalinized tissue at 5-7 days after the start of tooth movement. On the distal/tension side, no particular change in the distribution of immunopositive cells obtained with any antibody was detected throughout the experimental periods, with the exception that there was a significant increase in the number of ED1-positive cells and in of OX6-positive cells at 1 and 7 days, respectively, after the start of tooth movement. These results suggest that after the start of tooth movement OX6- and ED1-positive cells, which are mostly exudative macrophages, but not ED2- and KI-M2R-positive cells, i.e., resident macrophages, may be actively engaged in bone resorption and the remodelling of tissues on the pressure side of the periodontal membrane.

Multiple myeloma expressing CD19(+)CD56(-) phenotype

A 70-year-old woman presented with monoclonal gammopathy, pancytopenia, and renal insufficiency, which were initially refractory to combination chemotherapy by VMMD (vincristine, ranimustine, melphalan, and dexamethasone) and MP (melphalan and prednisolone) regimens. The myeloma cells, which consisted of 73% of bone marrow nucleated cells, expressed CD38(+), CD19(+), CD56(-), CD45(-), CD49e(-), and MPC-1(+) phenotypes by flow cytometric analysis and showed the rearranged immunoglobulin heavy chain (IgH) gene by Southern blotting. By immunostaining, the myeloma cells were positive for cytoplasmic immunoglobulin light chain kappa. These results suggest that myeloma cells can express CD19(+)CD56(-), the phenotype considered to be expressed on only normal plasma cells.

Apolipoprotein E allele-dependent antioxidant activity in brains with Alzheimer's disease

Thiobarbituric acid-reactive substances (TBARS), an index of lipid peroxidation, were assayed in postmortem brain. Basal TBARS levels were increased and oxidative stimulation produced more TBARS in AD relative to control brains. In addition, apolipoprotein E isoforms showed differing antioxidant activities, with E2 > E3 > E4, suggesting that the lowest antioxidant activity of E4 could contribute to its association with AD.

Missense point mutations of tau to segregate with FTDP-17 exhibit site-specific effects on microtubule structure in COS cells: a novel action of R406W mutation

Missense and splicing point mutations have been found in the tau gene in families with frontotemporal dementia with parkinsonism linked to chromosome 17 (FTDP-17). Of these mutations, we examined four exonic missense point mutations (G272V, P301L, V337M and R406W) in 3-repeat or 4-repeat tau isoform on the transfection experiment. The effects of two mutations (G272V or P301L) on microtubules were subtle whereas those of two other mutations (V337M or R406W) were dramatically significant when these two mutations were constructed into 3-repeat tau but not into 4-repeat tau. The R406W mutation induced an alternation of microtubules to form dotted or fragmented forms retaining colocalization of tau with tubulin whereas the V337M mutation predominantly disrupted microtubule networks and diminished colocalization of tau and tubulin. The effect of the mutations on microtubules were thus site-dependent and isoform-dependent. Tau with R406W mutation was found to be colocalized with tubulin without filamentous structures on confocal views, suggesting that the carboxyl region of tau played a different role from tubulin-binding domain on microtubule assemble. Another abnormal property was identified in tau with R406W mutation that failed to suffer phosphorylation. Thus, diverse effects of tau mutations on microtubules may explain the various clinicopathologies of FTDP-17 and related tauopathies.

The tau mutation (val337met) disrupts cytoskeletal networks of microtubules

The missense point mutation found in the tau gene, which was segregated in a family with frontotemporal dementia with parkinsonism linked to chromosome 17 (FTDP-17), has proved to be the causal molecule for widely spread dementia diseases. Here we examined the effects of the tau mutation using confocal analysis. When wild-type tau cDNA was introduced into cells, extensive cell processes and well-developed thick bundles of microtubules were induced. On the other hand, when altered tau cDNA with the mutation (valine337-methionine) was introduced, cell lost processes and microtubule networks resulted in more round cell shape but showed intact mitochondria or endoplasmic reticulum. We conclude that the tau mutation primarily affects the microtubules and resultantly causes the loss of cellular organization and function due to microtubule disruption.

A high incidence of apolipoprotein E epsilon4 allele in middle-aged non-demented subjects with cerebral amyloid beta protein deposits

We examined the apolipoprotein E (ApoE) genotypes of 19 middle-aged non-demented subjects with cerebral amyloid beta protein (Abeta) deposits, and compared the results with those of 16 patients with sporadic Alzheimer's disease (AD) and those of 34 age-matched controls. The frequency of the ApoE epsilon4 allele was higher (P = 0.0256) in these 19 subjects (0.211) than in controls (0.059), and was close to that in AD patients (0.281). This result suggests that middle-aged non-demented subjects with cerebral Abeta deposits are at high risk of developing AD, and that the diffuse Abeta deposits in these cases represent an early stage of AD pathology. We speculate that in the majority of late-onset sporadic AD patients, cerebral Abeta deposition commences when these patients are in their forties or fifties, and that the pathological process progresses gradually, taking 20 to 30 years for clinical manifestation of dementia.

Ultrastructural features of odontoclasts that resorb enamel in human deciduous teeth prior to shedding

Three dental hard tissues, i.e., cementum, dentin, and enamel, are resorbed by multinucleated cells referred to as "odontoclasts." These cells have morphological and functional characteristics similar to those of bone-resorbing osteoclasts. However, concerning enamel resorption, which is a process that may occur during tooth eruption, satisfactory ultrastructural data on odontoclastic resorption are still lacking. Ultrastructural and histochemical characteristics of odontoclasts resorbing enamel of human deciduous teeth prior to shedding were examined by means of light microscopy and transmission and scanning electron microscopy. Odontoclasts that that resorbed enamel were tartrate-resistant acid phosphatase (TRAP)-positive multinucleated giant cells that were essentially the same as those that resorbed dentin and cementum. Ultrastructurally, they had numerous mitochondria, lysosomes, and free polysomes in their cytoplasm. In addition, they were characteristically rich in large cytoplasmic vacuoles containing enamel crystals in the cytoplasm opposite the ruffled border. Although they extended a well-developed, ruffled border against enamel surface, a clear zone--an area typically devoid of organelles--was rarely seen in these cells. In many cases, the cells were in very close contact with the enamel surface by the peripheral part of their cytoplasm. The enamel prisms at the resorption surface contained more loosely packed and electron-lucent enamel crystals compared with those of unresorbed, intact enamel. Furthermore, numerous thin needle- or plate-like enamel crystals that were liberated from the enamel matrix were found in the extracellular channels of the ruffled border and in various-sized cytoplasmic vacuoles in their cytoplasm. The superficial layer of the enamel matrix undergoing odontoclastic resorption stained positively with toluidine blue and for TRAP activity. The results of the present study suggest that odontoclasts resorbing enamel secrete acids as well as organic components, including hydrolytic enzymes, into the resorption zone underlying their ruffled border and that they phagocytose crystals that have been liberated from the partially demineralized enamel matrix by acids, subsequently dissolving them intracellularly.

Quantitative evaluation of newly formed bone in the alveolar wall surrounding the root during the initial stage of experimental tooth movement in the rat

By using a chronological lead-labelling technique and computer image analysis the volume of this newly formed bone was evaluated. Rat maxillary first molars were moved mesially by a fixed, closed coil-spring appliance for 6 days using three different magnitudes of initial tensile force (27, 60 and 136 g). Sham-treated rats wearing an inactivated appliance were used for the control study. All animals were injected twice intraperitoneally with lead-disodium EDTA, 3 hr before the beginning and 3 hr before the end of treatment. The unit volumes of newly formed bone (mm3/mm2) were assessed with reference to lead-labelling lines in the alveolar walls of the root socket by computer image analysis. In the control group, two distinct lead-labelling lines indicated continuous bone formation on the mesial side of the root sockets, but only a jagged line was found on the distal side. After experimental mesial tooth movement, only a single lead line could be found on the mesial/pressure side of the root sockets; on the distal/tension side, a wide layer could be detected between the two lead lines. The volume of newly formed bone on the distal/tension side in the experimental groups was significantly greater than that in the control group. However, there was no significant difference in the volumes of newly formed bone among the three experimental groups. The study demonstrates that the volume of newly formed bone in the alveolar walls during the initial stage of tooth movement can be quantified and that the magnitude of the tensile force of tooth movement may not influence directly the volume of newly formed bone in the alveolar wall on the tension side.

[Hereditary spherocytosis associated with severe hypophosphatemia in patients recovering from aplastic crisis]

This is a report about two cases of hereditary spherocytosis complicated by severe hypophosphatemia, while recovering from aplastic crisis. Case #1: A 31-year-old male, who had jaundice and splenomegaly since the age of 15 and who has a son diagnosed with hemolytic anemia, was admitted because of fever lymphadenopathy, and jaundice. A diagnosis of hereditary spherocytosis was made based on microspherocytes observed in his peripheral blood smear. After admission, the anemia became more serious for a few days and he was considered suffering from bone marrow aplastic crisis. His serum phosphorus level fell to 0.5 mg/dl on the second day, but it rapidly returned to normal as reticulocyte counts rose. Case #2: A 29-year-old male with known transient jaundice and splenomegaly suffered from fever, anemia and jaundice, but recovered two weeks later. Laboratory examination revealed positive human Parvovirus B19 (HPV-B19) DNA, anti-HPV-19 IgM and IgG-antibody. His serum phosphorus level fell to 1.2 mg/dl on the eighth day, but it rose in the same manner as seen in case #1. The fall in serum phosphorus is probably due to its shift to the erythroblasts during erythroid hyperplasia.

Amyloid-beta-protein isoforms in brain of subjects with PS1-linked, beta APP-linked and sporadic Alzheimer disease

To determine whether similar abnormalities of various soluble full-length and N-terminal truncated Abeta peptides occur in postmortem cerebral cortex of affected PS1 mutation carriers, we examined the amounts of two amyloid species ending at residue 40 or at residues 42(43) using sandwich ELISA systems. Our results indicate that PS1 mutations effect a dramatic accumulation in brain of the highly insoluble potentially neurotoxic long-tailed isoforms of the Abeta peptide such as Abeta1-42(43) and Abetax-42(43). This enhancing effect of PS1 mutation on Abetax-42(43) deposition was highly similar to that of a betaAPP mutation (Val717Ile) but the effects on Abetax-40 production were significantly different between these two causal genes. In contrast to previous studies of soluble Abeta in plasma and in supernatants from cultured fibroblasts of subjects with PS1 mutations, our studies also show that there is an increase in insoluble Abetax-40 peptides in brain of subjects with PS1 mutations.

Presenilin 1 cleavage is a universal event in human organs

A panel of antibodies raised against various regions of human presenilin 1(PS1)--the amino-terminal domain, the domain between the transmembrane domains 1 and 2, the cleavage-site, loop domains, or carboxyl-terminal domain--was prepared to analyze PS1 in human tissues. We observed the predominance of two fragments (28-kDa NH2 and 18-kDa COOH fragments) in various tissues, including cerebral cortices. In addition to these two fragments, we found a previously unidentified amino-terminal fragment of PS1 with Mr 14 kDa in the lungs, spleen, pancreas, and testes. Using a sensitive ELISA for PS1, we measured the amount of PS1 species in tissues and found high contents of PS1 fragment in the testes. Our data show that common and unique processing pathways of PS1 occur in a tissue-dependent manner. It is likely that cleavage at the loop structure of PS1 to produce a functional form is a common event in human organs.

Variable deposition of amyloid beta-protein (A beta) with the carboxy-terminus that ends at residue valine40 (A beta 40) in the cerebral cortex of patients with Alzheimer's disease: a double-labeling immunohistochemical study with antibodies specific for A beta 40 and the A beta that ends at residues alanine42/threonine43 (A beta 42)

Amyloid beta-protein (A beta) deposits in the cerebral cortices of patients with Alzheimer's disease (AD) were investigated immunohistochemically to determine their carboxy terminal sequences. Antibodies specific for A beta terminating at residue valine40 (A beta 40) and at residues alanine42/threonine43 (A beta 42) were used. Virtually all parenchymal A beta deposits were positive for A beta 42. Many of these deposits were also partially or completely labeled for A beta 40. The degree of A beta 40 labeling varied from area to area within a given brain and from AD case to AD case. In contrast to parenchymal deposits, A beta 40 labeled essentially all the vascular deposits which constitute amyloid angiopathy (AA), with A beta 42 occurring variably in some of these deposits. Occasional AA was found, however, in which A beta 42 predominated or was exclusively deposited. Such a diversity of A beta species, both in brain parenchyma and in AA, suggests that multiple C-terminal processing mechanisms occur in the cell types responsible for these deposits.

Proteolytic processing of presenilin-1 (PS-1) is not associated with Alzheimer's disease with or without PS-1 mutations

Cerebral presenilin-1 protein (PS-1) is normally composed of the amino-terminal fragment (NTF) with Mr 28 kDa and the carboxy-terminal fragment (CTF) with 18 kDa. We analyzed human PS-1 in brains with early-onset familial Alzheimer's disease (FAD) with and without PS-1 mutations to study whether mutated PS-1 was abnormally metabolized. Cerebral PS-1 were found to be cleaved into two fragments of NTF and CTF independently of the occurrence of PS-1 mutation in human brains. A small portion of PS-1 was recently found to suffer another processing by caspase-3, an apoptosis-related cysteine protease. In contrast to the recent finding that the Volga-German mutation on presenilin-2 (PS-2) affects the increasing caspase-3 PS-2 fragment, the PS-1 mutation did not cause a significant change in PS-1 fragmentation. We conclude that PS-1 fragmentation and other (probably caspase-3-mediated) digestion following apoptosis occur independently of PS-1 mutations.

A subset of senile dementia with high incidence of the apolipoprotein E epsilon2 allele

There is a subset of very elderly patients with senile dementia in whom abundant neurofibrillary tangles are present, mainly in the hippocampal region, without a significant number of senile plaques. In a retrospective neuropathological examination of 239 dementia patients, 14 were found to have this type of senile dementia. The apolipoprotein E epsilon2, epsilon3, and epsilon4 allele frequencies in this patient group were 0.39, 0.50, and 0.11, respectively. Such a high frequency of the epsilon2 allele suggests that this type of dementia is distinct from Alzheimer's disease not only from a neuropathological but also from a genetic viewpoint.

Assignment of Alzheimer's presenilin-2 (PS-2) gene to 1q42.1 by fluorescence in situ hybridization

Presenilin-2 (PS-2) was suggested to be localized on 1q31-42 based on linkage analysis and cDNA cloning. The final identification of PS-2 as the causal gene for early-onset familial Alzheimer's disease in Voga-German pedigrees was concluded based on the point mutation found in the candidate cDNA isolated from this familial AD. We present evidence of its physical genome mapping of PS-2 on chromosome 1q42.1 by fluorescence in situ hybridization method.

Abnormal gel-electrophoretic behavior of presenilin 1 and it's fragment

Presenilin 1 (PS-1) is the main causal gene of familial Alzheimer's disease. In this report, we describe the abnormal behavior of PS-1 in gel electrophoresis in the presence of SDS. Freshly in vitro synthesized PS-1 was identified as a single molecule with the molecular size of 43,000 on SDS gels but was found to disappear after incubation at 37 degrees C for 24 hr due to the formation of aggregates. Intermediate aggregates with M(r) 74,000 and 100,000 were formed before the final aggregate which was retained at the top of the gel. Thus the amount of 43,000-protein species of PS-1 was found to decrease on gels with a concomitant increase in the amount of 74,000/100,000 proteins. Similar abnormality was seen in PS-1 expressed in COS cells transfected with PS-1 cDNA. Moreover, cellular PS-1 was strongly suggested to be cleaved into the fragments with M(r) approximately 20,000 in COS and CHO cells. Fragmentation of cellular PS-1 was not affected by the missense point mutation of Ala260Val on PS-1 which was identified in a pedigree with familial Alzheimer's disease.

Assignment of Alzheimer's presenilin-1 (PS-1) gene to 14q24.3 by fluorescence in situ hybridization

Presenilin-1 (PS-1) was suggested to be localized on 14q24.3 based on linkage analysis and cDNA cloning. The final identification of PS-1 as the causal gene for Alzheimer's disease (AD) was concluded based on finding of the point mutations in the candidate cDNA linked with pedigrees with early-onset familial AD. We present evidence of its physical genome mapping of PS-1 by fluorescence in situ hybridization method.

Amyloid beta protein and its 3-kDa fragment are present in the axoplasm fraction of the white matter in human brain

Production of the soluble amyloid beta-protein (A beta) precedes abnormal accumulation of A beta amyloid in the brains of subjects with Alzheimer's disease. To determine the cellular source and generating mechanisms of soluble A beta in the human brain, we separated an axoplasm fraction from the cerebral white matter and analyzed it. The axoplasm fraction contained secretory isoforms of beta-amyloid precursor protein (APP) and 11.5 kDa A beta-bearing carboxyl-terminal fragments (CTFs) of APP. Furthermore, soluble 4 kDa A beta and 3 kDa fragments of A beta (p3) were obtained from the axoplasm fraction. These results suggest that amyloidogenic 4 kDa A beta is intracellularly produced in cerebral neurons and carried through the axons in human brain.

Identification and characterization of presenilin I-467, I-463 and I-374

We cloned a novel isoform of presenilin I (presenilin I-374) besides previously published presenilin I-467 and I-463 in human lymphocytes. Presenilin I-463 was identical to presenilin I-467 except a 12 bp nucleotides deletion in its amino terminal region. Another isoform, presenilin I-374 was produced by an alternative splicing with an additional exon consisting of 92 bp nucleotides (exon 11), which resulted in the frame shift with a stop codon to generate a truncated presenilin consisting of 374 amino acids. The transcripts for presenilin I-467/463 was ubiquitously detected while that for presenilin I-374 was selectively detected in liver, spleen, kidney. Abnormal behavior of presenilin I on gel electrophoresis was found with affinity-purified antibodies against presenilin I.

Cytodifferentiation of the odontoclast prior to the shedding of human deciduous teeth: an ultrastructural and cytochemical study

BACKGROUND

In human deciduous teeth, odontoclastic resorption takes place at the pulpal surface of the coronal dentine prior to shedding, and this resorption shows clear time-related histological changes (Sahara et al., 1992).

METHODS

Using this phenomenon as an observation system, we examined the cytodifferentiation of human odontoclasts by light and electron microscopy. For a histochemical marker of odontoclast differentiation and function, tartrate-resistant acid phosphatase (TRAP) activity was determined by light and electron microscopic enzyme histochemistry.

RESULTS

As root resorption neared completion, TRAP-positive mononuclear cells were initially detected in the pulp chamber. They had abundant mitochondria, small lysosomes, and moderately developed rough endoplasmic reticulum throughout their cytoplasm. In these mononuclear cells, TRAP activity was localized in compartments of the biosynthetic pathway, i.e., in cisternae of the endoplasmic reticulum and Golgi lamellae, as well as small lysosomes. The TRAP-positive mononuclear cells first made contact with the predentine surface by their elongated cellular processes. After attachment, they spread out along the predentine surface and developed specialized membrane structures, clear zones, and ruffled borders. Next, they fused with each other on the predentine surface and formed typical multinucleate odontoclasts. After termination of their resorption function, the odontoclasts lost their ruffled borders and became detached from the resorbed surface. Most of the detached odontoclasts had numerous large pale vacuoles and secondary lysosomes and appeared to be in the process of degeneration.

CONCLUSIONS

The present study demonstrates that: (1) odontoclasts differentiated from TRAP-positive mononuclear cells, which presumably originate from circulating progenitor cells, (2) membrane specialization of odontoclasts, i.e., development of a clear zone and ruffled border, is induced following their contact with the resorption surface, (3) multinucleation of odontoclasts takes place only after their attachment to the resorption surface, (4) mature multinucleate odontoclasts can resorb predentine as well as dentine in the same way as osteoclasts resorb bone, and (5) at the end of the resorption, odontoclasts gradually lose their ruffled borders and become detached from the resorbed surface.

Modified amyloid beta protein ending at 42 or 40 with different solubility accumulates in the brain of Alzheimer's disease

Serial extraction study of Alzheimer's disease (AD) and control brains revealed 4, 3.7 and 3 kD amyloid beta protein (A beta) species accumulated in AD brains. In the fractions extracted with TBS, 10% SDS and formic acid, considerable amounts of A beta species were recovered in SDS fractions besides TBS and formic acid fractions. Immunoblotting with several site-specific antibodies confirmed not only the presence of 4 kD A beta starting at the first amino acid of A beta but also 2 smaller A beta species with modification of their amino-termini in the highly resolutional Tris/Tricine gel system. A beta solubility using these solvents was associated with both modification of the amino-terminus and length of carboxyl-terminus of A beta. Especially, a large amount of modified A beta was found to be accumulated as forms with different solubility in AD brains.

APP717 missense mutation affects the ratio of amyloid beta protein species (A beta 1-42/43 and a beta 1-40) in familial Alzheimer's disease brain

We have biochemically purified A beta from brains of two unrelated familial Alzheimer's disease (FAD) pedigrees with the APP717 mutation (Val-->Ile) and from two sporadic Alzheimer's disease (AD) brains and characterized them by means of mass spectrometry and enzyme-linked immunosorbent assay. We observed two types of amyloid beta protein (A beta), the short-tail form (A beta 1-40) and the long-tail form (A beta 1-42/43), in sporadic AD and FAD brains, and found that the ratio of the long-tail form of A beta (A beta 1-42/43) to total A beta was increased in FAD brains. These in vivo results were confirmed in vitro using cultured cells transfected with three kinds of APP cDNAs bearing the APP717 mutations (Val-->Ile, Gly, or Phe). Taken together with the hypothesis that A beta 1-42/43 functions as a "seed" that increases the kinetics of amyloid fibril formation (Jarrett, J. T., and Lansbury, P. T., Jr. (1993) Cell 73, 1055-1058), we conclude that the APP717 missense mutation does not create new A beta species but promotes the increased accumulation of A beta 1-42/43 in the brain, which results in the enhancement of amyloid fibril formation from soluble A beta. These findings provide a causal relationship between this FAD genotype and the pathological phenotype of A beta deposition and senile plaque formation.

Biochemical evidence for the long-tail form (A beta 1-42/43) of amyloid beta protein as a seed molecule in cerebral deposits of Alzheimer's disease

We measured the amounts of total A beta, A beta 1-40 and A beta 1-42/43 in brain tissues using a newly developed ELISA assay and found that the amounts of insoluble A beta 1-42/43 and insoluble A beta 1-40 were linearly related to the amount of A beta deposits or total insoluble A beta at their lower and higher concentrations, respectively. In an experiment to characterize the A beta species in brain homogenates with buffered saline, we unexpectedly detected soluble A beta which was derived from the insoluble amyloid deposits in brain tissue, indicating reversible depolymerization of A beta from insoluble amyloid deposits. To confirm this finding, we performed 5 consecutive washes of insoluble precipitates of AD brains with buffered saline. Both species of A beta were found in all 5 supernatant fractions and their amounts were gradually decreased. The ratio of A beta 1-42/43 to A beta 1-40 was increased with the numbers of washes, indicating that A beta 1-40 existed in an exposed manner as compared to A beta 1-42/43. Thus the present finding is the first biochemical evidence that A beta 1-40 was the predominant species involved in the reversible exchanging reaction on seeding A beta 1-42/43 between the soluble and the insoluble forms (amyloid fibrils).

Racemization: its biological significance on neuropathogenesis of Alzheimer's disease

Amyloid beta protein (A beta) in neuritic plaques of Alzheimer's disease has been found to be racemized and/or isomerized at their Asp residues. To elucidate the effect of racemization on the aggregation properties of A beta, we synthesized three kinds of A beta peptides in which D-Asp was substituted for L-Asp residues, i.e, normal A beta 1-40, [D-Asp7]A beta 1-40 and [D-Asp23]A beta 1-40. The aggregation and fibril formation of each peptide was examined by means of spectrofluorometry and electron microscopy. Of the three peptides, normal A beta showed the gradual increase of aggregation while [D-Asp7]A beta 1-40 and [D-Asp23] A beta 1-40 showed more enhanced aggregation at the final stage when the fibril formations were detected in all peptides solutions by electron microscopy. A comparative immunohistochemical study by anti-racemized A beta antibody and anti-A beta 1-42/43 antibody further showed the in vivo incorporation of D-Asp in senile plaques of Alzheimer's disease brains, which may be involved in plaque formation at the later stage than the deposition of the longer form of A beta (A beta 1-42/43). Taken together with the recent accumulated evidence on the aggregation mechanisms of A beta, the data presented here suggest that racemization may occur after the amyloid fibril formation but enhance the aggregation process by shifting the equilibrium of A beta from the soluble form to the insoluble form in Alzheimer's disease.

Odontoclastic resorption of the superficial nonmineralized layer of predentine in the shedding of human deciduous teeth

Resorption by odontoclasts of a superficial nonmineralized layer of predentine that occurs in prior to the shedding of human deciduous teeth was studied by light and electron microscopy. As resorption of the tooth roots neared completion, multinucleate cells appeared on the predentine surface of the coronal dentine between the degenerated odontoblasts, excavated characteristic resorption lacunae in the nonmineralized predentine. These multinucleate cells had the same ultrastructural characteristics as odontoclasts and histochemical demonstration of tartrate-resistant acid phosphatase activity in the multinucleate cells revealed intense staining in numerous small granules identified as lysosomes. Occasionally, the multinucleate cells simultaneously resorbed both nonmineralized and calcospherite-mineralized matrix in the predentine. The study demonstrates that multinucleate odontoclasts can resorb nonmineralized predentine matrix in vivo, probably in the same way as they resorb demineralized organic matrix in the resorption zone underlying their ruffled border.

Okadaic acid enhances abnormal phosphorylation on tau proteins

Tau proteins are one of the microtubule-associated proteins (MAPs) and show promoting activity on microtubule assembly. Tau proves to be the major constituent of Alzheimer's paired helical filaments, in which tau is found to be different from normal tau in that it is abnormally phosphorylated. To examine the effect of the abnormal phosphorylation on microtubule assembly, we obtained abnormally phosphorylated tau that was made in vitro by hyperphosphorylation with ATP or with ATP and okadaic acid, a drug inhibiting phosphatase, mainly 1 and 2A. We confirmed the biochemical properties of abnormally phosphorylated tau based on its retarded gel mobility and immunoreactivity to anti-PHF. We found that abnormally phosphorylated tau was able to promote the polymerization of microtubules but showed less activity as compared with normally phosphorylated tau. This effect of ATP on abnormal phosphorylation of tau was enhanced when okadaic acid was added in the phosphorylation reaction mixture during microtubule assembly. It is of significance that phosphatase activity as well as kinase activity are involved in the formation of abnormal tau. The present evidence suggests the simultaneous occurrence of microtubule disassembly and the pathogenesis of paired helical filaments following the abnormal phosphorylation of tau.

A histological study of the exfoliation of human deciduous teeth

For clarification of the histological details of the shedding of human deciduous teeth, exfoliated and extracted deciduous teeth were examined by light and electron microscopy. After the roots were completely resorbed, the dentogingival junction migrated along the inner resorbing surface and finally reached the pulpal surface of the crown. At the same time, the gingival epithelium also proliferated and migrated under the crown of the deciduous tooth in such a way that part of it lined the residue of the pulp and another part lined the surface overlying the erupting successional tooth. This phenomenon took place from various sides of the tooth surface. Therefore, just before exfoliation, the migrated gingival epithelium formed narrow necks of tissue, and the crown was only superficially attached to the gingiva by them. The final shedding of the tooth appeared to occur by a tearing of these narrow tissue regions. The results of the present study suggest that the dento-gingival junction as well as gingival epithelium play important roles in the process of exfoliation of human deciduous teeth.

Cementum-like tissue deposition on the resorbed pulp chamber wall of human deciduous teeth prior to shedding

In the later stage of exfoliation in human deciduous teeth, odontoclastic resorption takes place at the pulpal surface of the coronal dentin. However, this resorption does not continue until the teeth are shed, and the resorbed pulp chamber wall is usually repaired by cementum-like tissue deposition. In this study, we examined the formation and characteristics of the cementum-like hard tissue on the resorbed dentin surface in the pulp chamber of deciduous teeth prior to shedding. The site and degree of deposition of newly formed cementum-like tissue on the resorbed pulp chamber wall varied from tooth to tooth. Furthermore, they also showed compositional and structural variations. Generally, however, the matrix of the cementum-like tissue was composed of intrinsic collagen fibers, acellular or cellular. There was a tendency for acellular cementum-like tissue to be deposited on small and shallow resorption bays, whereas the cellular type was found on larger and deeper ones. In both cases, the surface of the deposited cementum-like tissue on the resorbed dentin surface usually became flat. However, unlike the cementum repair of resorbed areas on the root surface, no acellular extrinsic fiber cementum-like tissue was found on the resorption pulp chamber wall. Although the role of the repair of the resorbed pulp chamber wall with cementum-like tissue deposition just before shedding is unknown, it might play some role in the retention of deciduous teeth until shedding.

Odontoclastic resorption at the pulpal surface of coronal dentin prior to the shedding of human deciduous teeth

Histological and histochemical observations of more than 150 extracted human deciduous teeth revealed that, prior to shedding, odontoclastic resorption as a rule takes place at the pulpal surface of coronal dentin. We also found that this phenomenon occurs in all kinds of deciduous teeth. The process of this internal resorption of coronal dentin of deciduous teeth clearly showed time-related histological changes. During the time the roots were actively being resorbed, the pulpal tissue retained its normal structure. However, when root resorption neared completion, inflammatory cells started to gradually infiltrate into the pulp, and odontoblasts began to degenerate. After that, multinucleate odontoclasts appeared, and resorption proceeded from the predentin to the dentin. The odontoclastic activity was initially detected only on the pulpal surface at the bottom areas of the crown. It gradually spread towards the pulpal horn regions along the wall of the pulp chamber. However, this internal resorption of coronal dentin did not continue until the teeth were finally shed. After the elimination of resorption, the resorbed dentin surface was repaired by a cementum-like deposition or covered with fibrous connective tissue.