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1.
The flexibility and self-healing properties of animal cell surface membranes are well known. These properties have been best exploited in various micrurgical studies on living cells (2, 3), especially in amoebae (7, 20). During nuclear transplantation in amoebae, the hole in the membrane through which a nucleus passes can have a diameter of 20-30 μm, and yet such holes are quickly sealed, although some cytoplasm usually escapes during the transfer. While enucleating amoebae in previous studies, we found that if a very small portion of a nucleus was pushed through the membrane and exposed to the external medium, the amoeba expelled such a nucleus on its own accord. When this happened, a new membrane appeared to form around the embedded portion of the nucleus and no visible loss of cytoplasm occurred during nuclear extrusion. In the present study, we examined amoebae that were at different stages of expelling partially exposed nuclei, to follow the sequence of events during the apparent new membrane formation. Unexpectedly, we found that a new membrane is not formed around the nucleus from inside but a hole is sealed primarily by a constriction of the existing membrane, and that cytoplasmic filaments are responsible for the prevention of the loss of cytoplasm. 相似文献
2.
V KW Wong T Li B YK Law E DL Ma N C Yip F Michelangeli C KM Law M M Zhang K YC Lam P L Chan L Liu 《Cell death & disease》2013,4(7):e720
Autophagy is an important cellular process that controls cells in a normal homeostatic state by recycling nutrients to maintain cellular energy levels for cell survival via the turnover of proteins and damaged organelles. However, persistent activation of autophagy can lead to excessive depletion of cellular organelles and essential proteins, leading to caspase-independent autophagic cell death. As such, inducing cell death through this autophagic mechanism could be an alternative approach to the treatment of cancers. Recently, we have identified a novel autophagic inducer, saikosaponin-d (Ssd), from a medicinal plant that induces autophagy in various types of cancer cells through the formation of autophagosomes as measured by GFP-LC3 puncta formation. By computational virtual docking analysis, biochemical assays and advanced live-cell imaging techniques, Ssd was shown to increase cytosolic calcium level via direct inhibition of sarcoplasmic/endoplasmic reticulum Ca2+ ATPase pump, leading to autophagy induction through the activation of the Ca2+/calmodulin-dependent kinase kinase–AMP-activated protein kinase–mammalian target of rapamycin pathway. In addition, Ssd treatment causes the disruption of calcium homeostasis, which induces endoplasmic reticulum stress as well as the unfolded protein responses pathway. Ssd also proved to be a potent cytotoxic agent in apoptosis-defective or apoptosis-resistant mouse embryonic fibroblast cells, which either lack caspases 3, 7 or 8 or had the Bax-Bak double knockout. These results provide a detailed understanding of the mechanism of action of Ssd, as a novel autophagic inducer, which has the potential of being developed into an anti-cancer agent for targeting apoptosis-resistant cancer cells. 相似文献
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4.
M Innes Asher Alistair W Stewart Javier Mallol Stephen Montefort Christopher KW Lai Nadia A?t-Khaled Joseph Odhiambo The ISAAC Phase One Study Group 《Respiratory research》2010,11(1):8
The International Study of Asthma and Allergies in Childhood (ISAAC) Phase One showed large worldwide variations in the prevalence of symptoms of asthma, rhinoconjunctivitis and eczema, up to 10 to 20 fold between countries. Ecological analyses were undertaken with ISAAC Phase One data to explore factors that may have contributed to these variations, and are summarised and reviewed here.In ISAAC Phase One the prevalence of symptoms in the past 12 months of asthma, rhinoconjunctivitis and eczema were estimated from studies in 463,801 children aged 13 - 14 years in 155 centres in 56 countries, and in 257,800 children aged 6-7 years in 91 centres in 38 countries. Ecological analyses were undertaken between symptom prevalence and the following: Gross National Product per capita (GNP), food intake, immunisation rates, tuberculosis notifications, climatic factors, tobacco consumption, pollen, antibiotic sales, paracetamol sales, and outdoor air pollution.Symptom prevalence of all three conditions was positively associated with GNP, trans fatty acids, paracetamol, and women smoking, and inversely associated with food of plant origin, pollen, immunisations, tuberculosis notifications, air pollution, and men smoking. The magnitude of these associations was small, but consistent in direction between conditions. There were mixed associations of climate and antibiotic sales with symptom prevalence.The potential causality of these associations warrant further investigation. Factors which prevent the development of these conditions, or where there is an absence of a positive correlation at a population level may be as important from the policy viewpoint as a focus on the positive risk factors. Interventions based on small associations may have the potential for a large public health benefit. 相似文献
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6.
Lovercamp KW Safranski TJ Fischer KA Manandhar G Sutovsky M Herring W Sutovsky P 《Theriogenology》2007,67(4):704-718
Accurate semen analysis is an important issue in the swine industry. We evaluated two candidate fertility marker proteins associated with sperm cytoplasmic droplet (CD), including 15-lipoxygenase (15-LOX) and ubiquitin (UBI) in a controlled single-sire artificial insemination (AI) trial. Ejaculates (n=116) were collected from 18 fertile Large White boars monthly for 8 mo, and analyzed by semi-quantitative, densitometry-based Western blotting and flow cytometry with antibodies against 15-LOX and UBI. Data were correlated with farrowing rates (FR) and total numbers of piglets born (TNB) from 1754 AI services by 13 of 18 boars, and compared with a conventional microscopic semen analysis. In semi-quantitative Western blotting, both 15-LOX and UBI were correlated with seasonal changes in the percentage of normal (r=-0.38, P<0.01; r=-0.27, P<0.05, respectively) and CD-bearing spermatozoa (r=0.35, P<0.01; r=0.27, P<0.05, respectively). In flow cytometry, UBI and 15-LOX levels showed seasonal changes coinciding with seasonal changes of FR and TNB, representing 13 boars, 88 ejaculates and 1,232 AI services. There were correlations between flow cytometric values of UBI and FR (r=0.31; P<0.05), adjusted FR (r=0.30; P<0.05), TNB (r=-0.38; P<0.01) and adjusted TNB (r=-0.37; P<0.01). Flow cytometric measurements of 15-LOX correlated negatively with TNB (r=-0.33; P<0.05) and adjusted TNB (r=-0.34; P<0.05). These data suggested that boar fertility estimation could be achieved within a group of fertile boars by the use of objectively measurable fertility markers. Flow cytometry appeared more informative and more practical than semi-quantitative Western blotting. This technology could be further optimized for the selection of the most fertile sires in an artificial insemination program. 相似文献
7.
Altered epididymal sperm maturation and cytoplasmic droplet migration in subfertile male Alox15 mice
Kelly Moore Kyle Lovercamp Dongyan Feng Jennifer Antelman Miriam Sutovsky Gaurishankar Manandhar Klaus van Leyen Timothy Safranski Peter Sutovsky 《Cell and tissue research》2010,340(3):569-581
Mammalian spermatozoa complete their morphogenesis and acquire their fertilizing potential in the epididymis. Prominent among
the hallmarks of epididymal sperm maturation is the proximal-distal migration of the cytoplasmic droplet (CD), the last remnant
of the spermatogenic cell cytoplasm, down the sperm flagellum. Failure to shed the CD has been associated with male infertility.
Because of the presence of the organelle degradation enzyme 15-lipoxygenase (15LOX) in sperm CD, we hypothesize that subfertile
male Alox15 mice lacking the 15Lox gene display sperm CD anomalies. Caput and cauda epididymal sperm samples from seven adult Alox15 and seven wild-type (wt) males of equal age were examined by differential interference contrast microscopy (DIC) and transmission
electron microscopy (TEM). Compared with wt males, Alox15 males had significantly more spermatozoa with a retained CD in both caput (P = 0.004) and cauda (P = 0.005) epididymidis. TEM and DIC analyses revealed intact mitochondria present in the CDs of epididymal Alox15 spermatozoa. The CDs of wt spermatozoa, however, had a smooth appearance and contained only hollow membrane vesicles, with
no intact mitochondria embedded in their CD matrix. Epithelial lesions, phagocytosis-like figures, and missing or aberrant
apical blebs were observed in the caput epididymidis of Alox15 males. Thus, the process of epididymal sperm maturation and CD migration is altered in Alox15 males. Aberrant sperm maturation might contribute to the reduced fertility and smaller litter size of Alox15 mice, a rare example of subfertile mutants displaying normal spermatogenesis but altered epididymal sperm maturation. 相似文献
8.
Winnie CW Chu Wynnie MW Lam Bobby KW Ng Lam Tze-ping Kwong-man Lee Xia Guo Jack CY Cheng R Geoffrey Burwell Peter H Dangerfield Tim Jaspan 《Scoliosis》2008,3(1):1-24
There is no generally accepted scientific theory for the causes of adolescent idiopathic scoliosis (AIS). As part of its mission to widen understanding of scoliosis etiology, the International Federated Body on Scoliosis Etiology (IBSE) introduced the electronic focus group (EFG) as a means of increasing debate on knowledge of important topics. This has been designated as an on-line Delphi discussion. The Statement for this debate was written by Dr WCW Chu and colleagues who examine the spinal cord to vertebral growth interaction during adolescence in scoliosis. Using the multi-planar reconstruction technique of magnetic resonance imaging they investigated the relative length of spinal cord to vertebral column including ratios in 28 girls with AIS (mainly thoracic or double major curves) and 14 age-matched normal girls. Also evaluated were cerebellar tonsillar position, somatosensory evoked potentials (SSEPs), and clinical neurological examination. In severe AIS compared with normal controls, the vertebral column is significantly longer without detectable spinal cord lengthening. They speculate that anterior spinal column overgrowth relative to a normal length spinal cord exerts a stretching tethering force between the two ends, cranially and caudally leading to the initiation and progression of thoracic AIS. They support and develop the Roth-Porter concept of uncoupled neuro-osseous growth in the pathogenesis of AIS which now they prefer to term ' asynchronous neuro-osseous growth'. Morphological evidence about the curve apex suggests that the spinal cord is also affected, and a 'double pathology' is suggested. AIS is viewed as a disorder with a wide spectrum and a common neuroanatomical abnormality namely, a spinal cord of normal length but short relative to an abnormally lengthened anterior vertebral column. Neuroanatomical changes and/or abnormal neural function may be expressed only in severe cases. This asynchronous neuro-osseous growth concept is regarded as one component of a larger concept. The other component relates to the brain and cranium of AIS subjects because abnormalities have been found in brain (infratentorial and supratentorial) and skull (vault and base). The possible relevance of systemic melatonin-signaling pathway dysfunction, platelet calmodulin levels and putative vertebral vascular biology to the asynchronous neuro-osseous growth concept is discussed. A biomechanical model to test the spinal component of the concept is in hand. There is no published research on the biomechanical properties of the spinal cord for scoliosis specimens. Such research on normal spinal cords includes movements (kinematics), stress-strain responses to uniaxial loading, and anterior forces created by the stretched cord in forward flexion that may alter sagittal spinal shape during adolescent growth. The asynchronous neuro-osseous growth concept for the spine evokes controversy. Dr Chu and colleagues respond to five other concepts of pathogenesis for AIS and suggest that relative anterior spinal overgrowth and biomechanical growth modulation may also contribute to AIS pathogenesis. 相似文献
9.
The catalytic domains of murine Golgi alpha1,2-mannosidases IA and IB that
are involved in N-glycan processing were expressed as secreted proteins in
P.pastoris . Recombinant mannosidases IA and IB both required divalent
cations for activity, were inhibited by deoxymannojirimycin and
kifunensine, and exhibited similar catalytic constants using
Manalpha1,2Manalpha-O-CH3as substrate. Mannosidase IA was purified as a 50
kDa catalytically active soluble fragment and shown to be an inverting
glycosidase. Recombinant mannosidases IA and IB were used to cleave
Man9GlcNAc and the isomers produced were identified by high performance
liquid chromatography and proton-nuclear magnetic resonance spectroscopy.
Man9GlcNAc was rapidly cleaved by both enzymes to Man6GlcNAc, followed by a
much slower conversion to Man5GlcNAc. The same isomers of Man7GlcNAc and
Man6GlcNAc were produced by both enzymes but different isomers of
Man8GlcNAc were formed. When Man8GlcNAc (Man8B isomer) was used as
substrate, rapid conversion to Man5GlcNAc was observed, and the same
oligosaccharide isomer intermediates were formed by both enzymes. These
results combined with proton-nuclear magnetic resonance spectroscopy data
demonstrate that it is the terminal alpha1, 2-mannose residue missing in
the Man8B isomer that is cleaved from Man9GlcNAc at a much slower rate.
When rat liver endoplasmic reticulum membrane extracts were incubated with
Man9GlcNAc2, Man8GlcNAc2was the major product and Man8B was the major
isomer. In contrast, rat liver Golgi membranes rapidly cleaved
Man9GlcNAc2to Man6GlcNAc2and more slowly to Man5GlcNAc2. In this case all
three isomers of Man8GlcNAc2were formed as intermediates, but a distinctive
isomer, Man8A, was predominant. Antiserum to recombinant mannosidase IA
immunoprecipitated an enzyme from Golgi extracts with the same specificity
as recombinant mannosidase IA. These immunodepleted membranes were enriched
in a Man9GlcNAc2to Man8GlcNAc2- cleaving activity forming predominantly the
Man8B isomer. These results suggest that mannosidases IA and IB in Golgi
membranes prefer the Man8B isomer generated by a complementary mannosidase
that removes a single mannose from Man9GlcNAc2.
相似文献
10.
Ying J Nie Mo Y Mok Godfrey CF Chan Albert W Chan Ou Jin Sushma Kavikondala Albert KW Lie Chak S Lau 《Arthritis research & therapy》2010,12(3):R91