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ABSTRACT: The original eukaryotic cells contained at least one set of double-membrane-bounded organelles (cell nucleus and mitochondria) and single-membrane-bounded organelles [endoplasmic reticulum, Golgi apparatus, lysosomes (vacuoles), and microbodies (peroxisomes)]. An increase in the number of organelles accompanied the evolution of these cells into Amoebozoa and Opisthokonta. Furthermore, the basic cells, containing mitochondria, engulfed photosynthetic Cyanobacteria, which were converted to plastids, and the cells thereby evolved into cells characteristic of the Bikonta. How did basic single- and double-membrane-bounded organelles originate from bacteria-like cells during early eukaryotic evolution? To answer this question, the important roles of the GTPase dynamin- and electron-dense rings in the promotion of diverse cellular activities in eukaryotes, including endocytosis, vesicular transport, mitochondrial division, and plastid division, must be considered. In this review, vesicle division, mitochondrial division, and plastid division machineries, including the dynamin- and electron-dense rings, and their roles in the origin and biogenesis of organelles in eukaryote cells are summarized.
International review of cell and molecular biology 02/2008; 271:97-152. · 4.48 Impact Factor
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ABSTRACT: The non-Mendelian inheritance of organellar DNA is common in most plants and animals. In the isogamous green alga Chlamydomonas species, progeny inherit chloroplast genes from the maternal parent, as paternal chloroplast genes are selectively eliminated in young zygotes. Mitochondrial genes are inherited from the paternal parent. Analogically, maternal mitochondrial DNA (mtDNA) is thought to be selectively eliminated. Nevertheless, it is unclear when this selective elimination occurs. Here, we examined the behaviors of maternal and paternal mtDNAs by various methods during the period between the beginning of zygote formation and zoospore formation. First, we observed the behavior of the organelle nucleoids of living cells by specifically staining DNA with the fluorochrome SYBR Green I and staining mitochondria with 3,3'-dihexyloxacarbocyanine iodide. We also examined the fate of mtDNA of male and female parental origin by real-time PCR, nested PCR with single zygotes, and fluorescence in situ hybridization analysis. The mtDNA of maternal origin was completely eliminated before the first cell nuclear division, probably just before mtDNA synthesis, during meiosis. Therefore, the progeny inherit the remaining paternal mtDNA. We suggest that the complete elimination of maternal mtDNA during meiosis is the primary cause of paternal mitochondrial inheritance.
Protoplasma 10/2006; 228(4):231-42. · 1.92 Impact Factor
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ABSTRACT: We studied whether the monokaryotic chloroplast (moc) mutation affects the transmission of chloroplast and mitochondrial DNA in Chlamydomonas species. We used a previously isolated moc mutant from our cell line G33, which had only one large chloroplast nucleus. To obtain zygotes, we crossed the mutant cells with wild-type cells, and mutant cells with receptive mates (females [mt+] with males [mt-]). In these zygotes, we recorded preferential dissolution of mt- parental chloroplast nuclei and fusion of the two cell nuclei. Antibiotic-resistance markers of chloroplast DNA were maternally transmitted in all crosses. PCR analysis of the cytochrome b (cob) gene sequence showed that the mitochondrial DNA was paternally transmitted to offspring. These results suggest that the moc mutation did not affect the organelle DNA transmission.
Protoplasma 11/2004; 224(1-2):107-12. · 1.92 Impact Factor
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ABSTRACT: To understand the regulatory mechanisms of chloroplast proliferation, chloroplast replication was studied in cultured leaf disks cut from plants of 25 species. In leaf disks from Brassica rapa var. perviridis, the number of chloroplasts per cell increased remarkably in culture. We examined chloroplast replication in this plant in vivo and in culture media with and without benzyladenine, a cytokinin. In whole plants, leaf cells undergo two phases from leaf emergence to full expansion: an early proliferative stage, in which mitosis occurs, and a differential stage after mitosis has diminished. During the proliferative stage, chloroplast replication keeps pace with cell division. In the differential phase, cell division ceases but chloroplast replication continues for two or three more cycles, with the number of chloroplasts per cell reaching about 60. In the leaf disks, the number of chloroplasts per cell increased from about 18 to 300 without benzyladenine, and to over 600 with benzyladenine, indicating that this cytokinin enhances chloroplast replication in cultured tissue. We also studied changes in ploidy and cell volume between in vivo cells and cells grown in culture with and without benzyladenine. Ploidy and cell volume increased in a manner very similar to that of the number of chloroplasts, suggesting a relationship between these phenomena.
Protoplasma 02/2003; 222(3-4):139-48. · 1.92 Impact Factor
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ABSTRACT: The addition of the auxin 2,4-dichlorophenoxy acetic acid (2,4-D) to tobacco Bright-Yellow-2 (BY-2) cells cultured in 2,4-D-depleted medium induced dedifferentiation of starch-storing cells into dividing cells. The changes in cell growth, starch content, organellar DNA content, and the transcript levels for the ADP-glucose pyrophosphorylase gene during the dedifferentiation of starch-storing cells were examined. Cell proliferation, decrease in starch content, and increase in DNA content began from 12–18h after 2,4-D application. RNA-gel blot analysis showed a decrease in the ADP-glucose pyrophosphorylase mRNA levels, within 6h of the addition of 2,4-D. Furthermore, experiments using aphidicolin revealed that starch degradation is linked with cell division.
Plant Cell Reports 10/2002; 21(4):289-295. · 2.27 Impact Factor
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ABSTRACT: . Changes in the distribution of organelles and organelle-DNA in Pelargonium zonale from the mature egg cell stage to the first zygotic division during the early stages of embryogenesis were investigated using electron microscopy and fluorescence microscopy. The mature egg is a large, polarized bulbous-shaped cell, tapering toward its micropylar end. The wide chalazal region has a large nucleus that is surrounded by cytoplasm containing many giant mitochondria and large amyloplasts. The mitochondria contain a large amount of mitochondrial DNA and appear as long stretched rods or complex rings, sometimes consisting of several concentric or half-concentric circles in sections. The time from pollination to cell fusion is approximately 6-9 h and it is 20-24 h until the first zygotic division. The changes in the zygote and its organelles preparatory to division occur in 3 stages. At stage 1 (6-9 h after pollination), cell fusion occurs and the zygote begins to elongate. Many vacuoles of varying size appear surrounding the nucleus. At stage 2 (9-15 h), the zygote nucleus migrates to a central position in the cell and the mitochondria form a single ring that becomes either irregularly crushed or appears as long thin strings. Amyloplasts exhibit a gradual decrease in the number of starch grains. At stage 3 (15-20 h), the vacuoles disappear, except for a few that remain in the micropylar region, and cell size decreases. Mitochondria become short, fine strings or small rings. Amyloplasts with starch grains are no longer observed, but are transformed into large proplastids. Following the first division of the zygote, approximately equal-sized apical and basal cells are formed. Short rod-shaped or small ring-shaped mitochondria are randomly distributed near the nucleus of the apical cell, whereas mitochondria in the basal cell are long and rod-shaped. In the electron microscope, two types of plastids can be distinguished: dark oval plastids originating from the sperm cell, which are observed in both the apical and basal cell, and others with a less dense, amorphous matrix, believed to originate from egg amyloplasts, which are unevenly distributed in the micropylar region of the basal cell. Fluorometry using a video-intensified microscope photon counting system reveals that, correlated with changes in mitochondrial morphology, DNA amount within the mitochondrion decreases linearly during these stages.
Sexual Plant Reproduction 01/2002; 15(1):1-12. · 1.87 Impact Factor
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ABSTRACT: During plastid division, two structures have been detected at the division site in separate analyses. The plastid-dividing ring can be detected by transmission electron microscopy as two (or three) electron-dense rings: an outer ring on the cytosolic face of the outer envelope, occasionally a middle ring in the intermembrane space, and an inner ring on the stromal face of the inner envelope. The FtsZ ring, which plays a central role in bacterial division, also is involved in plastid division and is believed to have descended to plastids from cyanobacterial endosymbiosis. The relationship between the two structures is not known, although there is discussion regarding whether they are identical. Biochemical and immunocytochemical investigations, using synchronized chloroplasts of the red alga Cyanidioschyzon merolae, showed that the plastid FtsZ ring is distinct and separable from the plastid-dividing ring. The FtsZ ring localizes in stroma and faces the inner plastid-dividing ring at the far side from the inner envelope. The FtsZ ring and the inner and outer plastid-dividing rings form in that order before plastid division. The FtsZ ring disappears at the late stage of constriction before dissociation of the plastid-dividing ring, when the constriction is still in progress. Our results suggest that the FtsZ ring;-based system, which originated from a plastid ancestor, cyanobacteria, and the plastid-dividing ring;-based system, which probably originated from host eukaryotic cells, form a complex and are involved in plastid division by distinct modes.
The Plant Cell 11/2001; 13(10):2257-68. · 8.99 Impact Factor
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ABSTRACT: In flowering plants, guidance of the pollen tube to the embryo sac (the haploid female gametophyte) is critical for successful fertilization. The target embryo sac may attract the pollen tube as the final step of guidance in the pistil. We show by laser cell ablation that two synergid cells adjacent to the egg cell attract the pollen tube. A single synergid cell was sufficient to generate an attraction signal, and two cells enhanced it. After fertilization, the embryo sac no longer attracts the pollen tube, despite the persistence of one synergid cell. This cessation of attraction might be involved in blocking polyspermy.
Science 09/2001; 293(5534):1480-3. · 31.20 Impact Factor
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ABSTRACT: FtsZ is a bacterial division protein which forms a ring at the leading edge of the cell division site. To date, a hypothesis that the plant FtsZ forms the same structure in chloroplast division is proposed, but has not been demonstrated yet. In this study, recombinant LlFtsZ (Lilium longiflorum FtsZ) protein was produced from a previously isolated ftsZ cDNA clone [Mori and Tanaka (2000) Protoplasma 214: 57] and used to raise polyclonal anti-LlFtsZ antibodies in rabbits. In immunoblot analysis with the total protein extracted from L. longiflorum leaves, purified antibodies specifically recognized LlFtsZ whose molecular mass was approximately 43 kDa. This size corresponded to that of the recombinant LlFtsZ protein lacking N-terminal sequence, which suggests that the full-length LlFtsZ translation product has a putative N-terminal signal peptide. Moreover, fluorescent and electron microscopy revealed that the anti-LlFtsZ antibodies recognized ring structures at stromal side of the constriction point of dividing chloroplasts. Here, we show direct evidence that FtsZ ring is involved in chloroplast division.
Plant and Cell Physiology 07/2001; 42(6):555-9. · 4.70 Impact Factor
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ABSTRACT: Wolbachia are intracellular symbionts mainly found in arthropods, causing various sexual alterations on their hosts by unknown mechanisms. Here we report the results that strongly suggest that Wolbachia have virus-like particles of phage WO, which was previously identified as a prophage-like element in the Wolbachia genome. Wolbachia (strain wTai) infection in an insect was detected with the antibody against Wsp, an outer surface protein of Wolbachia, by fluorescence microscopy and immunoelectron-microscopy for the first time. Virus-like particles in Wolbachia were observed by electron-microscopy. The 0.22-microm filtrate of insect ovary contained DAPI-positive particles, and PCR analysis demonstrated that a phage WO DNA passed through the filter while Wolbachia DNA were eliminated, suggesting that the DAPI-positive particles were phage WO.
Biochemical and Biophysical Research Communications 06/2001; 283(5):1099-104. · 2.48 Impact Factor
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ABSTRACT: The timing and manner of disassembly of the apparatuses for chloroplast division (the plastid-dividing ring; PD ring) and mitochondrial division (the mitochondrion-dividing ring; MD ring) were investigated in the red alga Cyanidioschyzon merolae De Luca, Taddei and Varano. To do this, we synchronized cells both at the final stage of and just after chloroplast and mitochondrial division, and observed the rings in three dimensions by transmission electron microscopy. The inner (beneath the stromal face of the inner envelope) and middle (in the inter-membrane space) PD rings disassembled completely, and disappeared just before completion of chloroplast division. In contrast, the outer PD and MD rings (on the cytoplasmic face of the outer envelope) remained in the cytosol between daughter organelles after chloroplast and mitochondrial division. The outer rings started to disassemble and disappear from their surface just after organelle division, initially clinging to the outer envelopes at both edges before detaching. The results suggest that the two rings inside the chloroplast disappear just before division, and that this does not interfere with completion of division, while the outer PD and MD rings function throughout and complete chloroplast and mitochondrial division. These results, together with previous studies of C. merolae, disclose the entire cycle of change of the PD and MD rings.
Planta 04/2001; 212(4):517-28. · 3.00 Impact Factor
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ABSTRACT: The plastid division apparatus (called the plastid-dividing ring) has been detected in several plant and algal species at the constricted region of plastids by transmission electron microscopy. The apparatus is composed of two or three rings: an outer ring in the cytosol, an inner ring in the stroma, and a middle ring in the intermembrane space. The components of these rings are not clear. FtsZ, which forms the bacterial cytokinetic ring, has been proposed as a component of both the inner and outer rings. Here, we present the ultrastructure of the outer ring at high resolution. To visualize the outer ring by negative staining, we isolated dividing chloroplasts from a synchronized culture of a red alga, Cyanidioschyzon merolae, and lysed them with nonionic detergent Nonidet P-40. Nonidet P-40 extracted primarily stroma, thylakoids, and the inner and middle rings, leaving the envelope and outer ring largely intact. Negative staining revealed that the outer ring consists of a bundle of 5-nm filaments in which globular proteins are spaced 4.8 nm apart. Immunoblotting using an FtsZ-specific antibody failed to show immunoreactivity in the fraction containing the filament. Moreover, the filament structure and properties are unlike those of known cytoskeletal filaments. The bundle of filaments forms a very rigid structure and does not disassemble in 2 M urea. We also identified a dividing phase-specific 56-kD protein of chloroplasts as a candidate component of the ring. Our results suggest that the main architecture of the outer ring did not descend from cyanobacteria during the course of endosymbiosis but was added by the host cell early in plant evolution.
The Plant Cell 04/2001; 13(3):707-21. · 8.99 Impact Factor
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ABSTRACT: We characterized the behavior of plastid (pt) and mitochondrial (mt) nucleoids during male gametogenesis in Plumbago auriculata in three dimensions. The behavior of pt-nucleoids and mt-nucleoids differed throughout male gametogenesis. Pt-nucleoids were distributed in a characteristic manner in three stages: in the early microspore, pt-nucleoids assemble around cell nucleus; in the mid-generative cell, pt-nucleoids gather at the internal side of the pollen; in the late-generative cell, pt-nucleoids aggregation turns its pole to the external side of the pollen. We also studied organelle nucleoids in the egg and the central cell by a method in which semi-thick sections of resin-embedded anthers and ovaries were observed by confocal laser scanning microscopy. The number of pt-nucleoids in the sperm cell did not differ significantly from that in the egg. These results suggest that the behavior of DNA-containing organelles is regulated strictly during male gametogenesis in P. auriculata, and that a biparental inheritance of plastids in the Plumbago embryo is more favored than was previously thought.
Protoplasma 02/2001; 216(3-4):143-54. · 1.92 Impact Factor
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ABSTRACT: Apicoplasts (apicomplexan plastids) are nonphotosynthetic, secondary endosymbiotic plastids that are found in most apicomplexans. Although these organelles are essential for parasite survival, their functions, activities, and structures are not well understood. We examined the apicoplast nucleoid of Toxoplasma gondii from a morphological aspect by high-resolution epifluorescence microscopy and electron microscopy. We found unexpectedly large amounts of DNA in the nucleoid and the presence of several division-related structures. Initially, we identified the organellar nucleoids by staining with the DNA-specific dye 4',6-diamidino-2-phenylindole. A single nucleoid was observed per apicoplast, and the fluorescent spot representing the nucleoid was bright and spherical in contrast to the weak and filamentous spot representing the mitochondrial nucleoid. We also measured the DNA content of each apicoplast nucleoid by a video-intensified microscope photon-counting system and determined that the genomic copy number was at least 25, a figure over four times greater than that reported previously. Moreover, several groups of apicoplasts had significantly higher genomic copy numbers. The DNA molecules were accurately divided into two daughter apicoplasts just before nuclear division. In addition, we examined nucleoid segregation and the division apparatus using electron microscopy. However, we failed to observe nucleoid structures, suggesting that the apicoplasts are predominantly composed of nucleoid material. In addition, we observed "cap" structures at the termini of dividing apicoplasts, a possible plastid-dividing ring, and a microbody-like granule around the constriction. These structures may be involved in apicoplast division.
Protoplasma 02/2001; 218(3-4):180-91. · 1.92 Impact Factor
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ABSTRACT: Two ftsZ homologues were isolated from the unicellular primitive red alga Cyanidioschyzon merolae (CmftsZ1 and CmftsZ2). Phylogenetic analysis revealed that CmftsZ1 is most closely related to the ftsZ genes of alpha-Proteobacteria, suggesting that it is a mitochondrial-type ftsZ gene, whereas CmftsZ2 is most closely related to the ftsZ genes of cyanobacteria, suggesting that it is a plastid-type ftsZ gene. Southern analysis indicates that CmftsZ1 and CmftsZ2 are both single-copy genes located on chromosome XIV in the C. merolae genome. Northern analysis revealed that both CmftsZ1 and CmftsZ2 are transcribed, and accumulate specifically before cell and organelle division. The results of Western analysis suggest that CmFtsZ1 is localized in mitochondria.
MGG - Molecular and General Genetics 12/2000; 264(4):452-60.
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ABSTRACT: In several cell types, an intriguing correlation exists between the position of the centrosome and the direction of cell locomotion. The centrosome is positioned between the leading edge pseudopod and the nucleus. This suggests that the polarized distribution of organelles in the cytoplasm is coupled spatially with structural and functional polarity in the cell cortex. To study cellular polarization with special interest in the roles of microtubules, we have analyzed the effects of microtubule-disrupting reagents and local laser irradiation on behaviors of both the nucleus and the centrosome in living amoebae ofPhysarum polycephalum. Physarum cells often have 2–3 pseudopods. One of the pseudopods keeps extending to become a stable leading edge while the rest retracts, a crucial step that reorients cells during locomotion. The nucleus, together with the centrosome, moves specifically toward the pseudopod that will become the leading edge. Disruption of microtubules with nocodazole randomizes positions of the nucleus, indicating the involvement of microtubules in the directional migration of the nucleus toward a specific pseudopod. The migration direction of the nucleus is reversed immediately after the UV laser is irradiated at regions between the nucleus and the future leading pseudopod. In contrast, irradiation at regions between the future tail and the nucleus does not affect nuclear migration. By immunofluorescence, we confirmed fragmentation of microtubules specifically in the irradiated region. These results suggest that the nucleus is pulled together with the centrosome toward the future leading-edge pseudopod in a microtubule-dependent manner. Microtubules seem to exert the pulling force generated in the cell cortex on the centrosome. They may serve as a mediator of shape changes initiated in the cell cortex to the organelle geometry in the endoplasm.
Protoplasma 08/2000; 211(3):172-182. · 1.92 Impact Factor
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ABSTRACT: The generative cell at anthesis in the mature pollen grain of Erythrina crista-galli (Fabaceae) was examined by 4,6-diamidino-2-phenylindole(DAPI)-fluorescence microscopy using the squash method. An unequal,
polarized distribution of DNA-containing organelles (plastids and/or mitochondria) within the generative cell was observed
in every mature pollen grain examined. Polarization of DNA-containing organelles is obvious when generative cells are freed
and assume a spherical shape soon after microspore mitosis, as revealed by fluorescence-microscopic observations of specimens
embedded in Technovit 7100 resin and thin-sectioned at different developmental stages. Early establishment of polarized localization
of organelles in young generative cells of E. crista-galli and maintenance of this unequal distribution until pollen maturation strongly suggests that the organelles may still be clustered
at pollen mitosis. Production of a dimorphic pair of sperm cells, as has been reported in Plumbago
zeylanica, was observed in some pollen tubes germinated in vitro. The differentiation of the two sperm cells is discussed in relation
to possible preferential double fertilization in angiosperms.
Sexual Plant Reproduction 03/2000; 12(5):296-301. · 1.87 Impact Factor
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Tanpakushitsu kakusan koso. Protein, nucleic acid, enzyme 03/2000; 45(2):108-15.
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ABSTRACT: Changes in the number and distribution of mitochondria in microspores and pollen grains during male gametogenesis inPharbitis nil were examined with Technovit sections stained with 3,3-dihexyloxacarbocyanine iodide. The number of mitochondria per microspore or pollen grain ofP. nil increased constantly and dramatically during male gametogenesis. During this process, mitochondria exhibited characteristic localizations: subpopulations of mitochondria covered the surface of the microspore and vegetative nuclei before and again just after postmeiotic mitosis I (9 and 5 days before flowering, respectively). The mitochondria also surrounded the generative nucleus 2 days after postmeiotic mitosis I (5 days before flowering), although the density of mitochondria on the nuclear surface was lower. Electron microscopy showed that the mitochondria were about 30 nm from the nuclear envelope and that each mitochondrion was located near a nuclear pore. The characteristic localization of mitochondria inP. nil pollen may serve as a model to analyze the mechanisms that control mitochondrial positioning within a cell and interactions between mitochondria and nuclei.
Protoplasma 02/2000; 213(1):74-82. · 1.92 Impact Factor
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T Kuroiwa
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ABSTRACT: Mitochondria and plastids contain distinct genomes and multiply by binary division of existing organelles. Mitochondrial and plastid division can be clearly separated into two main events: division of the organelle nuclei (nucleoids), and subsequent division of the rest of the organelles, the process of organellokinesis. Organellokinesis makes use of organelle dividing apparatuses such as plastid-dividing ring (PD ring) and mitochondrion-dividing ring (MD ring). The plastid-dividing apparatus (PD apparatus) is composed of three electron-dense rings (the outer, middle and inner), while the mitochondrion-dividing apparatus (MD apparatus) is a pair of electron-dense rings in cytoplasm and inner ring in the mitochondrial matrix. The behaviour of both the PD and MD apparatuses throughout organelle division in Cyanidioschyzon merolae has been studied in detail by electron microscopy. When cells enter mitosis, the inner PD ring forms first, followed by the outer and middle rings and finally the MD rings. The PD rings begin to contract before the MD rings. However, the MD rings start to contract at about 4 times the speed of the PD rings and catch up to the PD rings. The cross-sectional areas of both the outer PD and MD rings increase as contraction in the plane of division progress. This suggests that the outer rings of organelle dividing apparatuses (OD apparatus) provide the motive force for contraction. FtsZ protein is located on the bacterial contractile ring at the equator of dividing bacteria, and controls bacterial division. Since FtsZ contains a tubulin motif, and host eukaryotic organisms and chloroplasts evolved from bacteria, there is debate whether that tubulins found in the cytoskeleton and the inner or outer PD ring evolved from FtsZ protein during eukaryogenesis.
Journal of Electron Microscopy 02/2000; 49(1):123-34. · 1.31 Impact Factor
