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1.
Enzyme-assisted photosensitization with rose Bengal acetate induces structural and functional alteration of mitochondria in HeLa cells 总被引:4,自引:4,他引:0
Bottone MG Soldani C Fraschini A Alpini C Croce AC Bottiroli G Pellicciari C 《Histochemistry and cell biology》2007,127(3):263-271
Rose Bengal acetate (RB-Ac) can be used as a fluorogenic substrate for photosensitization of cells both in vivo and in vitro:
once inside the cells, RB-Ac is converted into photoactive rose Bengal (RB) molecules which redistribute dynamically in the
cytoplasm and, upon irradiation by visible green light, can damage organelles such as the endoplasmic reticulum, the Golgi
apparatus, and the cytoskeleton. Recently, evidence has been provided that mitochondria may also be affected. The aims of
the present study were to describe RB-induced photodamage of mitochondria in single HeLa cells and to define, on a quantitative
basis, the effects of photosensitization on their morphofunctional features. HeLa cell cultures were exposed to 10−5 M RB-Ac for 60 min and then irradiated with a light emitting diode at 530 nm (total light dose, 1.6 J/cm2). After irradiation, the cells were transferred to a drug-free complete medium and allowed to grow for 24–72 h. Using conventional
and confocal fluorescence microscopy, transmission electron microscopy, and flow cytometry, we demonstrate that, in photosensitized
cells, mitochondria undergo structural and functional alterations which can lead cells to apoptosis. Interestingly, in our
system some cells were able to survive 72 h post-treatment and to recover, exhibiting the same mitochondrial structure, distribution
and inner membrane potential as those in untreated controls. Taking into account that the photoactive molecules redistribute
dynamically inside the cell upon RB-Ac administration, it may be hypothesized that cells can be differently affected by irradiation,
depending on the relative amount and organelle location of the photosensitizer. 相似文献
2.
Maria Grazia Bottone Cristiana Soldani Annunzia Fraschini Anna Cleta Croce Giovanni Bottiroli Tania Camboni Anna Ivana Scovassi Carlo Pellicciari 《Histochemistry and cell biology》2009,131(3):391-399
Photosensitization of tumor cells after incubation with Rose Bengal acetate (RB-Ac) induces multiple organelle photodamage
followed by apoptotic cell death. We used immunocytochemical techniques in multicolor fluorescence microscopy to elucidate
whether this occurs through the simultaneous activation of different apoptotic pathways, in HeLa cells. We detected in situ
the activated forms of caspases 9 and 3, and the translocation from the mitochondria to the nucleus of the apoptosis inducing
factor; DNA electrophoretic techniques were also used to assess the occurrence of nuclear DNA cleavage into either high- or
low-molecular-weight fragments. Both the caspase-dependent and caspase-independent apoptotic pathways are activated. The genomic
DNA is degraded into high molecular weight molecules only, without the formation of oligonucleosome-sized fragments. The ability
of RB-Ac to induce the simultaneous release of apoptogenic signals from different photodamaged organelles makes it an especially
powerful cytotoxic agent. 相似文献
3.
C. Pellicciari M. Giagnacovo B. Cisterna M. Costanzo A. C. Croce G. Bottiroli M. Malatesta 《Histochemistry and cell biology》2013,139(6):863-871
Photodynamic therapy is a moderately invasive therapeutic procedure based on the action of photosensitizers (PSs). These compounds are able to absorb light, and dissipate energy through photochemical processes leading to the production of oxidizing chemical species (singlet oxygen, free radicals or reactive oxygen species) which can damage the cell molecular structures eventually inducing cell death. To increase the entering through the plasma membrane, a PS with suitable chemical structure can be modified by addition of chemical groups (e.g., acetate or phosphate): this affects both the fluorescence emission and of the photosensitizing properties of the native PS. The modified compounds behave as fluorogenic substrates (FSs), since inside the cell the bound groups can be enzymatically removed and the fluorescence and photosensitizing properties of the native molecules are restored. With the aim to detect the subcellular localization of photoactive molecules at transmission electron microscopy, we loaded cultured HeLa cells with two different FSs, Rose Bengal acetate (RB-Ac) or Hypocrellin B acetate (HypB-Ac), and took advantage of the photophysical properties of the intracellularly restored PS molecules to obtain the photoconversion of diaminobenzidine (DAB) into an electrondense product. We demonstrated that RB-Ac and HypB-Ac are mostly internalized by endocytosis, and are converted into the native PSs already at the cell surface. Endocytosed PS molecules apparently follow the endosomes–lysosome route, being found in endosomes, lysosomes and multivescicular bodies; PS molecules were also detected in the cytosol. This ultrastructural localization of the photoactive molecules is fully consistent with the multiorganelle photodamage observed after irradiation in culture of RB-Ac- or HypB-Ac-loaded cells. Due to the very short half-life of the oxidizing chemical species and their limited mobility, DAB deposits do localize in close proximity of the very place where photoactive molecules elicited the production of reactive oxygen species upon light irradiation. Therefore, DAB photoconversion promises to be a suitable tool for directly visualizing in single cells the PS molecules at high resolution, helping to elucidate their mode of penetration into the cell as well as their dynamic intracellular redistribution and organelle targeting. 相似文献
4.
Bienertia sinuspersici Akhani has an unusual mechanism of C4 photosynthesis which occurs within individual chlorenchyma cells. To perform C4, the mature cells have two cytoplasmic compartments consisting of a central (CCC) and a peripheral (PCC) domain containing
dimorphic chloroplasts which are interconnected by cytoplasmic channels. Based on leaf development studies, young chlorenchyma
cells have not developed the two cytoplasmic compartments and dimorphic chloroplasts. Fluorescent dyes which are targeted
to membranes or to specific organelles were used to follow changes in cell structure and organelle distribution during formation
of C4-type chlorenchyma. Chlorenchyma cell development was divided into four stages: 1—the nucleus and chloroplasts occupy much
of the cytoplasmic space and only small vacuoles are formed; 2—development of larger vacuoles, formation of a pre-CCC with
some scattered chloroplasts; 3—the vacuole expands, cells have directional growth; 4—mature stage, cells have become elongated,
with a distinctive CCC and PCC joined by interconnecting cytoplasmic channels. By staining vacuoles with a fluorescent dye
and constructing 3D images of chloroplasts, and by microinjecting a fluorescence dye into the vacuole of living cells, it
was demonstrated that the mature cell has only one vacuole, which is traversed by cytoplasmic channels connecting the CCC
with the PCC. Immunofluorescent studies on isolated chlorenchyma cells treated with cytoskeleton disrupting drugs suspended
in different levels of osmoticum showed that both microtubules and actin filaments are important in maintaining the cytoplasmic
domains. With prolonged exposure of plants to dim light, the cytoskeleton undergoes changes and there is a dramatic shift
of the CCC from the center toward the distal end of the cell. 相似文献
5.
When studying the kinetics of DNA synthesis, growth and cell division inEscherichia coli B/r after irradiation with different doses of UV-radiation (254 nm) we could demonstrate, by means of pulse incorporation
of3H-thymidine, a lag in DNA synthesis after the irradiation. The relative rate of the restored DNA synthesis (related to the
number of viable cells) was higher than in the non-irradiated culture. After 3 h the rate of DNA synthesis settled at a constant
value, which was identical with the control rate up to the “critical dose” of 20 J/m2. The irradiated cell population is heterogenous and contains basically two categories of cells — surviving and non-surviving.
Cells of both types contribute to DNA synthesis restored after the lag period to a different extent. During the first hour
after the irradiation even the nonviable portion of the population,i.e. cells that do not form colonies but are still penicillin-sensitive, is involved in the DNA synthesis. 相似文献
6.
Bernd Fischer Manfred Lambertz Christa Hegele-Hartung 《In vitro cellular & developmental biology. Animal》1992,28(5):337-347
Rabbit morulae and blastocysts were cultured in conventional culture media [Ham’s F10 or BSM II supplemented with bovine serum
albumin (BSA) or serum] or in Ham’s medium supplemented with synchronous or asynchronous uterine flushings, mostly for 2 days,
and afterwards investigated by light and electron microscopy and by autoradiography. Ultrastructure and cell proliferation
differed considerably between cultured embryos and noncultured controls. Cultured embryos displayed more dead cells. They
were developmentally retarded (predominance of smooth endoplasmic reticulum rather than the age-specific rough endoplasmic
reticulum, mitochondria still round to ovoid shaped) and showed nonspecific signs of cells damage (swollen mitochondria and
Golgi complex vesicles, increased number of lysosomes). All these features were also present in embryos grown in uterine flushing-supplemented
media, but were less pronounced. Cell damage and impaired cell proliferation had affected trophoblast cells more than embryoblast
cells. Endoderm could be differentiated only if culture had been started with blastocysts—not with morulae—and seems to require
uterine secretions. No significant ultrastructural differences were observed between embryos cultured in synchronous or in
asynchronous uterine flushings. Present results indicate that cultured preimplantation rabbit embryos deviate clearly from
those grown in vivo and maintain, for some time, a better cellular structure—and probably function —in the presence of uterine
flushings than in conventional culture media. Specific abnormal morphologic features related to a particular medium could
not be identified. 相似文献
7.
The microarchitecture of DNA replication domains 总被引:2,自引:2,他引:0
Most DNA synthesis in HeLa cell nucleus is concentrated in discrete foci. These synthetic sites can be identified by electron
microscopy after allowing permeabilized cells to elongate nascent DNA in the presence of biotin-dUTP. Biotin incorporated
into nascent DNA can be then immunolabeled with gold particles. Two types of DNA synthetic sites/replication factories can
be distinguished at ultrastructural level: (1) electron-dense structures—replication bodies (RB), and (2) focal replication
sites with no distinct underlying structure—replication foci (RF). The protein composition of these synthetic sites was studied
using double immunogold labeling. We have found that both structures contain (a) proteins involved in DNA replication (DNA
polymerase α, PCNA), (b) regulators of the cell cycle (cyclin A, cdk2), and (c) RNA processing components like Sm and SS-B/La
auto antigens, p80-coilin, hnRNPs A1 and C1/C2. However, at least four regulatory and structural proteins (Cdk1, cyclin B1,
PML and lamin B1) differ in their presence in RB and RF. Moreover, in contrast to RF, RB have structural organization. For
example, while DNA polymerase α, PCNA and hnRNP A1 were diffusely spread throughout RB, hnRNP C1/C2 was found only at the
very outside. Surprisingly, RB contained only small amounts of DNA. In conclusion, synthetic sites of both types contain similar
but not the same sets of proteins. RB, however, have more developed microarchitecture, apparently with specific functional
zones. This data suggest possible differences in genome regions replicated by these two types of replication factories. 相似文献
8.
A morphometric analysis of the ultrastructure of columella statocytesin primary roots of Zea mays was performed to determine theprecise location of cellular organelles in graviperceptive cells.Vacuoles occupy the largest volume in the cell (11.4 per centof the protoplasm). The nucleus (9.51 per cent), amyloplasts(7.57 per cent), mitochondria (3.42 per cent), spherosomes (2.13per cent) and dictyosomes (0.55 per cent) occupy progressivelysmaller volumes of the statocytes. All organelles are distributedasymmetrically within the cell. Amyloplasts, spherosomes anddictyosomes are found in greatest numbers (and relative volumes)in the lower (i.e. bottom) third of the cell.The largest numbers and relative volumes of mitochondria arein the lower and middle thirds of the cell. Nuclei tend to befound in the middle third of the statocytes. Only the hyaloplasmis concentrated in the upper (i.e. top) thirdof Z. mays statocytes. When the sedimentation of amyloplasts(and the resulting exclusion of other organelles from the lowerthird of the cell) is corrected for, all cellular constituentsremain asymmetrically distributed within the cell. Therefore,the sedimentation of amyloplasts alone is not responsible forthe differential distribution of other cellular organelles inZ. mays statocytes. The quantitative ultrastructure of Z. maysstatocytes is discussed relative to the graviperceptive functionof these cells. Zea mays, corn, maize, root cap, stereology, columella, statocytes, graviperception, ultrastructure 相似文献
9.
Samir El-Shoura 《Virchows Archiv. B, Cell pathology including molecular pathology》1993,64(1):395-400
The interaction between multinucleate giant cells (MGCs) and the fungusAspergillus flavus as seen by transmission electron microscopy (TEM) is described in paranasal granulomas occurring in a Saudi patient dying
from chronic aspergillosis. Two morphologically different types of MGCs were recognized; these were: a) ‘Unhealthy looking’
type I cells, rich in well organized organelles and containing few, partially degenerated and necrotic fungal elements. b)
‘Healthy looking’ type II cells that contained scanty, randomly dispersed cell organelles and normal, or partially degenerated
fungal hyphae. The fungal elements had very thick and multilayered cell walls, and were found either in close contact to the
host cell cytoplasm, or enclosed within phagosomes. The mechanism of the fungus destruction by the host MGCs is described
and compared with that previous reports of MGCs involved in the elimination of extracellular microorganisms. The morphology
and the various physiological activities of MGCs seemed to depend mainly on whether the pathogen is extra- or intracellular.
However, this study showed that MGCs are the cells best suited for killing pathogenic fungi. 相似文献
10.
M.A. Anjum 《Biologia Plantarum》2003,46(1):1-6
Callus cells of potato (Solanum tuberosum L.) cv. Désirée were exposed to various subzero temperatures and examined for the freezing damage. In the cells subjected to –3 °C, plasma membranes appeared to be intact, while tonoplast seemed to be damaged and organelles to be swollen. After freezing at –6 °C, the damage became severe and plasma membranes were ruptured. After exposure to –10 °C, the damage was so severe that the cell organelles could not be recognised and cytoplasm became fragmented. 相似文献
11.
N. Singh 《Journal of biosciences》1994,19(1):91-102
This contribution deals with the scanning electron microscopic surface structure of olfactory epithelium in four hillstream
teleosts from the glacialfed river Alaknanda in Garhwal Himalaya (UP, India). The closely related species—Schizothorax plagiostomus, Schizothorax richardsonii (both bottom dweller, bottom feeder, herbiomnivorous) andSchizothoraichthys progastus (column dweller, column feeder, carniomnivorous) reveal the predominance of different types of olfactory receptor cell types
separately in their respective olfactory epithelium while the distinctly related speciesCrossocheilus latius latius with similar nature as first two (i.e. bottom dweller, bottom feeder, herbiomnivorous) displays the presence of more microvillous cells in the olfactory epithelium.
Possibly, the occurrence of particular receptor cells in a fish species is related to the ecological and feeding behaviours
with distinct mechanism of olfaction. 相似文献
12.
The cardiovasculature is one of the major body systems and probably the one most exposed to stress. There is clear evidence
that increasing levels of cell stress proteins within the heart is cardioprotective. In addition, there is rapidly emerging
evidence that secreted cell stress proteins play a role in the function of the cardiovascular tissues. Those secreted proteins
have three potential functions: (1) as normal homeostatic cardiovascular signals (e.g. protein disulphide isomerase); (2)
as anti-inflammatory molecules, which are able to inhibit cardiovascular pathology (e.g. Hsp27); and (iii) as pro-inflammatory
signals that can induce and promote cardiovascular pathology (e.g. Hsp60). As all of these various proteins may be released—at
different rates—and in different cardiovascular diseases—we need to consider the cohort of potential secreted cell stress
proteins as a dynamic system (network) that can aid and/or damage the equally dynamic cardiovascular system. 相似文献
13.
RB signaling prevents replication-dependent DNA double-strand breaks following genotoxic insult 总被引:7,自引:0,他引:7
Cell cycle checkpoints induced by DNA damage play an integral role in preservation of genomic stability by allowing cells to limit the propagation of deleterious mutations. The retinoblastoma tumor suppressor (RB) is crucial for the maintenance of the DNA damage checkpoint function because it elicits cell cycle arrest in response to a variety of genotoxic stresses. Although sporadic loss of RB is characteristic of most cancers and results in the bypass of the DNA damage checkpoint, the consequence of RB loss upon chemotherapeutic responsiveness has been largely uninvestigated. Here, we employed a conditional knockout approach to ablate RB in adult fibroblasts. This system enabled us to examine the DNA damage response of adult cells following acute RB deletion. Using this system, we demonstrated that loss of RB disrupted the DNA damage checkpoint elicited by either cisplatin or camptothecin exposure. Strikingly, this bypass was not associated with enhanced repair, but rather the accumulation of phosphorylated H2AX (γH2AX) foci, which indicate DNA double-strand breaks. The formation of γH2AX foci was due to ongoing replication following chemotherapeutic treatment in the RB-deficient cells. Additionally, peak γH2AX accumulation occurred in S-phase cells undergoing DNA replication in the presence of damage, and these γH2AX foci co-localized with replication foci. These results demonstrate that acute RB loss abrogates DNA damage-induced cell cycle arrest to induce γH2AX foci formation. Thus, secondary genetic lesions induced by RB loss have implications for the chemotherapeutic response and the development of genetic instability. 相似文献
14.
We have explored the intracellular cell organelle's structural alterations after photodynamic treatment with chlorin p6-histamine conjugate (Cp6-his) in human oral cancer cells. Herein, the cells were treated with Cp6-his (10 μm) and counterstained with organelle-specific fluorescence probes to find the site of intracellular localization using confocal microscopy. For photodynamic therapy (PDT), the cells were exposed to ~30 kJ/m2 red light (660 ± 20 nm) to induce ~90% cytotoxicity. We used the three-dimensional (3D) image reconstruction approach to analyze the photodynamic damage to cell organelles. The result showed that Cp6-his localized mainly in the endoplasmic reticulum (ER) and lysosomes but not in mitochondria and Golgi apparatus (GA). The 3D model revealed that in necrotic cells, PDT led to extensive fragmentation of ER and fragmentation and swelling of GA as well. Results suggest that the indirect damage to GA occurred due to loss of connection between ER and GA. Moreover, in damaged cells with no sign of necrosis, the perinuclear ER appeared condensed and surrounded by several small clumps at the peripheral region of the cell, and the GA was observed to form a single condensed structure. Since these structural changes were associated with apoptotic cell death, it is suggested that the necrotic and apoptotic death induced by PDT with Cp6-his is determined by the severity of damage to ER and indirect damage to GA. The results suggest that the indirect damage to cell organelle apart from the sites of photosensitizer localization and the severity of damage at the organelle level contribute significantly to the mode of cell death in PDT. 相似文献
15.
The content of spinach-leaf cells was compartmented by differential centrifugation. Three fractions were obtained,i.e. chloroplasts, pellet of remaining organelles sedimenting at 97 000g and cytosol. Enzyme activities of L-tryptophan aminotransferase (TAT) as well as L-tryptophan dehydrogenase (TDH) were demonstrated
in all cell fractions. The highest activities of both enzymes were found in the pellet of organelles followed by the enzyme
activities in the chloroplasts. The cytosol had the lowest enzyme activities. Chloroplasts are characterized by a relatively
higher TDH activity, organelles sedimenting at 97 000g were marked by a relatively higher TAT activity. In all fractions both pyridine nucleotide coenzymes catalyzed the TDH activity.
Ca2+ in a concentration of 0.8 minol l−1 increased markedly the TDH activity in both directions of its activity.
An erratum to this article is available at . 相似文献
16.
Cytoplasmic streaming plays an important role in cell processes since it promotes solute exchange between the cytoplasm and
organelles and enables lateral transport for extensive distances. The role of cyclosis in chloroplast functioning should be
most conspicuous under conditions mimicking natural mosaic illumination and consequent alternation of cell regions with dominant
dark and photosynthetic metabolism. Based on this assumption, we examined the light response curves and the induction kinetics
of fluorescence-based parameters of chloroplast photosynthetic activity on small regions (d ∼ 100 μm) of Chara corallina Klein ex Willd. internodal cells exposed to local and overall illumination under conditions of normal cytoplasmic streaming
and after suppression of cyclosis by cytochalasin B, an inhibitor of actin microfilaments. Under control conditions, the whole
cell illumination caused non-photochemical quenching (NPQ) of chlorophyll fluorescence, which approached the saturation at
a photon flux density of about 40 μmol/(m2 s). By contrast, illumination of a small (2 mm wide) cell part did not cause significant NPQ at light intensities up to 100
μmol/(m2 s), indicating that the chloroplast photosynthetic activity was substantially higher under conditions of localized illumination.
After the inhibition of cyclosis by cytochalasin B, the light response curves were represented by nearly identical sigmoid
curves, irrespective of the illumination pattern. When the cyclosis was restored in the cells washed from the inhibitor, the
light response curves measured under overall and localized illumination returned to their original divergent shapes. These
and other data indicate that different photosynthetic activities of chloroplasts in cells exposed to entire and partial illumination
are directly related to the flow of compositionally nonuniform cytoplasm between the cell parts with prevalent photosynthetic
and respiratory metabolism. 相似文献
17.
The movement of cells in response to a gradient in chemical concentration—known as chemotaxis—is crucial for the proper functioning
of uni-and multicellular organisms. How a cell senses the chemical concentration gradient surrounding it, and what signal
is transmitted to its motion apparatus is known as gradient sensing. The ability of a cell to sense gradients persists even
when the cell is immobilized (i.e., its motion apparatus is deactivated). This suggests that important features of gradient
sensing can be studied in isolation, decoupling this phenomenon from the movement of the cell. A mathematical model for gradient
sensing in Dictyostelium cells and neutrophils was recently proposed. This consists of an adaptation/spatial sensing module. This spatial sensing
module feeds into an amplification module, magnifying the effects of the former. In this paper, we analyze the spatial sensing
module in detail and examine its signal transduction properties. We examine the response of this module to several inputs
of experimental and biological relevance. 相似文献
18.
Matthew W Strobeck David N Reisman Ranjaka W Gunawardena Bryan L Betz Steven P Angus Karen E Knudsen Timothy F Kowalik Bernard E Weissman Erik S Knudsen 《The Journal of biological chemistry》2002,277(7):4782-4789
The BRG-1 subunit of the SWI-SNF complex is involved in chromatin remodeling and has been implicated in the action of the retinoblastoma tumor suppressor (RB). Given the importance of BRG-1 in RB function, germ line BRG-1 mutations in tumorigenesis may be tantamount to RB inactivation. Therefore, in this study we assessed the behavior of cells harboring discrete BRG-1 alleles for the RB-signaling pathway. Using p16ink4a, an upstream activator of endogenous RB, or a constitutively active RB construct (PSM-RB), we determined that the majority of tumor lines with germ line defects in BRG-1 were sensitive to RB-mediated cell cycle arrest. By contrast, A427 (lung carcinoma) cells were resistant to expression of p16ink4a and PSM-RB. Analysis of the SWI-SNF subunits in the different tumor lines revealed that A427 are deficient for BRG-1 and its homologue, Brm, whereas RB-sensitive cell lines retained Brm expression. Similarly, the RB-resistant SW13 and C33A cell lines were also deficient for both BRG-1/Brm. Reintroduction of either BRG-1 or Brm into A427 or C33A cells restored RB-mediated signaling to cyclin A to cause cell cycle arrest. Consistent with this compensatory role, we observed that Brm could also drive expression of CD44. We also determined that loss of these core SWI-SNF subunits renders SW13 cells resistant to activation of the RB pathway by the chemotherapeutic agent cisplatin, since reintroduction of either BRG-1 or Brm into SW13 cells restored the cisplatin DNA-damage checkpoint. Together, these data demonstrate that Brm can compensate for BRG-1 loss as pertains to RB sensitivity. 相似文献
19.
SV40 T antigen (LT) transformation of renal MDCK epithelial cells resulted in massive apoptosis in the presence of serum. Cell death was dependent on the ability of LT to bind RB or a related protein, since MDCK cells expressing LT mutants unable to bind RB did not die. Apoptosis could be rescued by treatment of cells with EGF and TPA, a property linked to their ability to promote cell growth. Our results indicate an inverse correlation between proliferation and apoptosis. Thus LT transformation induced survival-factor dependence in epithelial cells, in contrast to its effect in fibroblasts. RB inactivation also resulted in a strong down-regulation of c-myc and c-fos, which were previously found to be highly and constitutively expressed in epithelial cells. RB gene transfer in MDCK(LT) cells restored cell viability and high c-myc expression. C-myc gene transfer in these cells also resulted in a significant survival effect. These results suggest that RB anti-cell death activity is at least partly mediated by up-regulation of c-myc. Overexpression of Bcl2 also protected cells against apoptosis. The role of RB and c-myc in cell survival is discussed and related to maintenance of the differentiation state rather than to their properties in cell cycle progression. 相似文献
20.
B. W. Verdaasdonk H. F. J. M. Koopman F. C. T. van der Helm 《Biological cybernetics》2009,101(1):49-61
Like human walking, passive dynamic walking—i.e. walking down a slope with no actuation except gravity—is energy efficient
by exploiting the natural dynamics. In the animal world, neural oscillators termed central pattern generators (CPGs) provide
the basic rhythm for muscular activity in locomotion. We present a CPG model, which automatically tunes into the resonance
frequency of the passive dynamics of a bipedal walker, i.e. the CPG model exhibits resonance tuning behavior. Each leg is
coupled to its own CPG, controlling the hip moment of force. Resonance tuning above the endogenous frequency of the CPG—i.e.
the CPG’s eigenfrequency—is achieved by feedback of both limb angles to their corresponding CPG, while integration of the
limb angles provides resonance tuning at and below the endogenous frequency of the CPG. Feedback of the angular velocity of
both limbs to their corresponding CPG compensates for the time delay in the loop coupling each limb to its CPG. The resonance
tuning behavior of the CPG model allows the gait velocity to be controlled by a single parameter, while retaining the energy
efficiency of passive dynamic walking. 相似文献