Peroxiredoxins are involved in the pathogenesis of multiple sclerosis and neuromyelitis optica spectrum disorder.

Peroxiredoxins (PRXs) are intracellular anti-oxidative enzymes but work as inflammatory amplifiers under the extracellular condition. To date, the function of PRXs in the pathogenesis of multiple sclerosis (MS) and neuromyelitis optica spectrum disorder (NMOSD) is not fully understood. The aim of this study was to investigate whether PRXs play a role in the pathogenesis of MS and NMOSD. We analyzed levels of PRXs (PRX1, PRX5 and PRX6) in the cerebrospinal fluid (CSF) and serum of 16 patients with MS, 16 patients with NMOSD and 15 patients with other neurological disorders (ONDs). We identified potential correlations between significantly elevated PRXs levels and the clinical variables in patients with MS and NMOSD. Additionally, pathological analyses of PRXs (PRX1-6) in the central nervous system (CNS) were performed using the experimental autoimmune encephalomyelitis (EAE), animal model of MS. We found that serum levels of PRX5 and PRX6 in patients with MS and NMOSD were higher compared with those in patients with ONDs (P < 0·05). Furthermore, high levels of PRX5 and PRX6 were partly associated with blood-brain barrier dysfunction and disease duration in NMOSD patients. No significant elevation was found in CSF PRXs levels of MS and NMOSD. Spinal cords from EAE mice showed remarkable PRX5 staining, especially in CD45+ infiltrating cells. In conclusion, PRX5 and PRX6 may play a role in the pathogeneses of MS and NMOSD.

Comparison of brain atrophy in patients with multiple sclerosis treated with first- versus second-generation disease modifying therapy without clinical relapse.

BACKGROUND AND PURPOSE: The silent progression of patients with multiple sclerosis (MS) has been reported. The aim of this study was to investigate the association between brain atrophy rates and disease-modifying drugs (DMDs) in patients with MS during their relapse-free period. METHODS: Patients with relapsing-remitting MS were classified into two groups on the basis of clinical records, i.e. a first-generation DMD group treated with interferon-beta-1a, interferon-beta-1b or glatiramer acetate and a second-generation DMD group treated with dimethyl fumarate, fingolimod or natalizumab. Brain volume was calculated with SPM12. RESULTS: A total of 45 patients with relapsing-remitting MS were enrolled in the first-generation (n = 22) or second-generation (n = 23) DMD group. The annualized relapse rate was lower in the first-generation than in the second-generation DMD group (median 0.26 vs. 0.59; P < 0.001). The annualized atrophy rate of the normalized brain volume was not different between the first- and second-generation DMD groups after analysis of covariance (median 0.13% vs. 0.59%; P = 0.17). CONCLUSIONS: The median annualized atrophy rate of normalized brain volume in the first-generation DMD group was similar to the previously reported annual brain atrophy rate of healthy controls, which may suggest that treatment with a first-generation DMD need not be changed when patients with MS are clinically inactive.

Observation of a Magnetopiezoelectric Effect in the Antiferromagnetic Metal EuMnBi_{2}.

We have experimentally studied a magnetopiezoelectric effect predicted recently for magnetic metals with low crystal symmetries. In EuMnBi_{2} with antiferromagnetic Mn moments at 77 K, dynamic displacements emerge along the a direction upon application of ac electric fields in the c direction and increase in proportion to the applied electric fields. Such displacements are not observed along the c direction of EuMnBi_{2} or EuZnBi_{2} with nonmagnetic Zn ions. As temperature increases from 77 K, the displacement signals decrease and disappear at about 200 K, above which electric conduction changes from coherent to incoherent. These results demonstrate the emergence of the magnetopiezoelectric effect in a magnetic metal lacking inversion and time-reversal symmetries.

Recombinant thrombomodulin ameliorates experimental autoimmune encephalomyelitis by suppressing high mobility group box 1 and inflammatory cytokines.

Recombinant thrombomodulin (rTM) has pleiotrophic properties, including anti-coagulation and anti-inflammation; however, its effectiveness as a treatment for multiple sclerosis (MS) has not been evaluated fully. High mobility group box 1 (HMGB1) and proinflammatory cytokines, working as inflammatory mediators, are reportedly involved in the inflammatory pathogenesis of MS. The aim of this study was to determine whether rTM can be a potential therapeutic agent for experimental autoimmune encephalomyelitis (EAE). EAE mice received rTM treatment (1 mg or 0·1 mg/kg/day) from days 11 to 15 after immunization. The clinical variables, plasma levels of inflammatory cytokines and HMGB1 and pathological findings in EAE were evaluated. rTM administration ameliorated the clinical and pathological severity of EAE. An immunohistochemical study of the spinal cord showed weaker cytoplasmic HMGB1 staining in the rTM-treated EAE mice than in the untreated EAE mice. Plasma levels of inflammatory cytokines and HMGB1 were suppressed by rTM treatment. In conclusion, rTM down-regulated inflammatory mediators in the peripheral circulation and prevented HMGB1 release from nuclei in the central nervous system, suppressing EAE-related inflammation. rTM could have a novel therapeutic potential for patients with MS.

Serum antinuclear antibody may be associated with less severe disease activity in neuromyelitis optica.

BACKGROUND AND PURPOSE: Antinuclear antibody-positive multiple sclerosis (MS) patients have shorter disease duration and lower Expanded Disability Status Scale (EDSS) scores. The aim of this study was to compare clinical and laboratory features between MS and neuromyelitis optica (NMO) patients with and without autoantibodies and to investigate the prognosis of NMO in patients with and without autoantibodies. METHODS: The frequencies of antinuclear, anti-Sjögren's syndrome A (SSA)/Ro, anti-Sjögren's syndrome B (SSB)/La and anti-thyroid peroxidase (TPO) antibodies in the sera of 75 NMO patients and 131 MS patients were compared. Clinical and laboratory profiles were also compared between NMO patients with and without autoantibodies, including annual relapse rate and time from onset of NMO to EDSS scores of 4.0 (limited walking but without aid) and 6.0 (walking with unilateral aid). RESULTS: More NMO than MS patients had antinuclear and anti-SSA/Ro antibodies (31% vs. 10%, P < 0.001, and 21% vs. 3%, P < 0.001, respectively). Antinuclear antibody-positive NMO patients had a lower annual relapse rate from disease onset to serum sampling compared with antinuclear antibody-negative NMO patients, independent of treatment regimen. Antinuclear antibody-negative NMO patients reached an EDSS score of 6.0 earlier than antinuclear antibody-positive NMO patients (P = 0.026). Cerebrospinal fluid cell counts were higher in anti-SSA/Ro-positive than in anti-SSA/Ro-negative NMO patients. More anti-TPO antibody-positive than anti-TPO antibody-negative NMO patients had oligoclonal immunoglobulin G bands (60% vs. 11%, P = 0.048). CONCLUSIONS: Autoantibodies possibly modulate the pathophysiology of NMO. Antinuclear antibody may be associated with less severe disease activity or less disability in NMO.

Long-term treatment efficacy in primary inflammatory breast cancer by hormonal receptor- and HER2-defined subtypes.

BACKGROUND: Subtypes defined by hormonal receptor (HR) and HER2 status have not been well studied in inflammatory breast cancer (IBC). We characterized clinical parameters and long-term outcomes, and compared pathological complete response (pCR) rates by HR/HER2 subtype in a large IBC patient population. We also compared disease-free survival (DFS) and overall survival (OS) between IBC patients who received targeted therapies (anti-hormonal, anti-HER2) and those who did not. PATIENTS AND METHODS: We retrospectively reviewed the records of patients diagnosed with IBC and treated at MD Anderson Cancer Center from January 1989 to January 2011. Of those, 527 patients had received neoadjuvant chemotherapy and had available information on estrogen receptor (ER), progesterone receptor (PR), and HER2 status. HR status was considered positive if either ER or PR status was positive. Using the Kaplan-Meier method, we estimated median DFS and OS durations from the time of definitive surgery. Using the Cox proportional hazards regression model, we determined the effect of prognostic factors on DFS and OS. Results were compared by subtype. RESULTS: The overall pCR rate in stage III IBC was 15.2%, with the HR-positive/HER2-negative subtype showing the lowest rate (7.5%) and the HR-negative/HER2-positive subtype, the highest (30.6%). The HR-negative, HER2-negative subtype (triple-negative breast cancer, TNBC) had the worst survival rate. HR-positive disease, irrespective of HER2 status, had poor prognosis that did not differ from that of the HR-negative/HER2-positive subtype with regard to OS or DFS. Achieving pCR, no evidence of vascular invasion, non-TNBC, adjuvant hormonal therapy, and radiotherapy were associated with longer DFS and OS. CONCLUSIONS: Hormone receptor and HER2 molecular subtypes had limited predictive and prognostic power in our IBC population. All molecular subtypes of IBC had a poor prognosis. HR-positive status did not necessarily confer a good prognosis. For all IBC subtypes, novel, specific treatment strategies are needed in the neoadjuvant and adjuvant settings.

Gene expression profiles of inflammatory breast cancer: correlation with response to neoadjuvant chemotherapy and metastasis-free survival.

BACKGROUND: Inflammatory breast cancer (IBC) is an aggressive disease. To date, no molecular feature reliably predicts either the response to chemotherapy (CT) or the survival. Using DNA microarrays, we searched for multigene predictors. PATIENTS AND METHODS: The World IBC Consortium generated whole-genome expression profiles of 137 IBC and 252 non-IBC (nIBC) samples. We searched for transcriptional profiles associated with pathological complete response (pCR) to neoadjuvant anthracycline-based CT and distant metastasis-free survival (DMFS) in respective subsets of 87 and 106 informative IBC samples. Correlations were investigated with predictive and prognostic gene expression signatures published in nIBC (nIBC-GES). Supervised analyses tested genes and activation signatures of 19 biological pathways and 234 transcription factors. RESULTS: Three of five tested prognostic nIBC-GES and the two tested predictive nIBC-GES discriminated between IBC with and without pCR, as well as two interferon activation signatures. We identified a 107-gene signature enriched for immunity-related genes that distinguished between responders and nonresponders in IBC. Its robustness was demonstrated by external validation in three independent sets including two IBC sets and one nIBC set, with independent significant predictive value in IBC and nIBC validation sets in multivariate analysis. We found no robust signature associated with DMFS in patients with IBC, and neither of the tested prognostic GES, nor the molecular subtypes were informative, whereas they were in our nIBC series (220 stage I-III informative samples). CONCLUSION: Despite the relatively small sample size, we show that response to neoadjuvant CT in IBC is, as in nIBC, associated with immunity-related processes, suggesting that similar mechanisms responsible for pCR exist. Analysis of a larger IBC series is warranted regarding the correlation of gene expression profiles and DMFS.

Natural and anthropogenic controls on sediment composition of an arid coastal environment: Sharm Obhur, Red Sea, Saudi Arabia.

The present study investigated the natural and anthropogenic processes that control the composition of the bottom sediments of Sharm Obhur, Red Sea. Mineralogical analysis using XRD indicated that the sediments consist of carbonate and non-carbonate minerals. Elemental interrelationships allowed differentiating two groups of elements of different sources and origin. Elements that are in the same group are positively correlated, while they correlate negatively with elements of the other group. The first group includes silicon, Al, Fe, Mn, Mg, vanadium (V), chromium (Cr), Co, Ni, Cu, and Zn, whereas the other group includes Ca, Sr, and CaCO3. The highest concentration levels of the first group and the highest content of non-carbonate minerals were obtained from the sediments near the head of the sharm (zone A), whereas the sediments near the mouth of the sharm (zone B) yielded high concentrations of second group and carbonate minerals. Metal enrichment and contamination factors and pollution load index were calculated. The values of these indices differentiate two groups of metals: lithogenic and non-lithogenic. Except for lead (Pb) at one sampling site, metals in zone A sediments are of lithogenic source, supplied to the sharm either naturally by aeolian transportation and through Wadi Al-Kuraa'a during rare but major floods or by human activities such as dumping and shore protection. Non-lithogenic Cr, Pb, V, and Mn were documented from some sampling sites in zone B, and their occurrences are related to waste disposal and fossil fuel combustion.

Statin use in primary inflammatory breast cancer: a cohort study.

BACKGROUND: Some studies have suggested that statins, which have cholesterol-lowering and anti-inflammatory properties, may have antitumor effects. Effects of statins on inflammatory breast cancer (IBC) have never been studied. METHODS: We reviewed 723 patients diagnosed with primary IBC in 1995-2011 and treated at The University of Texas MD Anderson Cancer Center. Statin users were defined as being on statins at the initial evaluation. Based on Ahern et al's statin classification (JNCI, 2011), clinical outcomes were compared by statin use and type (weakly lipophilic to hydrophilic (H-statin) vs lipophilic statins (L-statin)). We used the Kaplan-Meier method to estimate the median progression-free survival (PFS), overall survival (OS) and disease-specific survival (DSS), and a Cox proportional hazards regression model to test the statistical significance of potential prognostic factors. RESULTS: In the multivariable Cox model, H-statins were associated with significantly improved PFS compared with no statin (hazard ratio=0.49; 95% confidence interval=0.28-0.84; P<0.01); OS and DSS P-values were 0.80 and 0.85, respectively. For L-statins vs no statin, P-values for PFS, DSS, and OS were 0.81, 0.4, and 0.74, respectively. CONCLUSION: H-statins were associated with significantly improved PFS. A prospective randomised study evaluating the survival benefits of statins in primary IBC is warranted.

Silencing of P-glycoprotein increases mortality in temephos-treated Aedes aegypti larvae.

Re-emergence of vector-borne diseases such as dengue and yellow fever, which are both transmitted by the Aedes aegypti mosquito, has been correlated with insecticide resistance. P-glycoproteins (P-gps) are ATP-dependent efflux pumps that are involved in the transport of substrates across membranes. Some of these proteins have been implicated in multidrug resistance (MDR). In this study, we identified a putative P-glycoprotein in the Ae. aegypti database based on its significantly high identity with Anopheles gambiae, Culex quinquefasciatus, Drosophila melanogaster and human P-gps. The basal ATPase activity of ATP-binding cassette transporters in larvae was significantly increased in the presence of MDR modulators (verapamil and quinidine). An eightfold increase in Ae. aegypti P-gp (AaegP-gp) gene expression was detected in temephos-treated larvae as determined by quantitative PCR. To analyse the potential role of AaegP-gp in insecticide efflux, a temephos larvicide assay was performed in the presence of verapamil. The results showed an increase of 24% in temephos toxicity, which is in agreement with the efflux reversing effect. RNA interference (RNAi)-mediated silencing of the AaegP-gp gene caused a significant increase in temephos toxicity (57%). In conclusion, we have demonstrated for the first time in insects that insecticide-induced P-gp expression can be involved in the modulation of insecticide efflux.

Development of a nomogram incorporating serum C-reactive protein level to predict overall survival of patients with advanced urothelial carcinoma and its evaluation by decision curve analysis.

BACKGROUND: The purpose of this study is to investigate the prognostic impact of C-reactive protein (CRP) on patients with advanced urothelial carcinoma and to develop a novel nomogram predicting survival. METHODS: A total of 223 consecutive patients were treated at Tokyo Medical and Dental Hospital. A nomogram incorporating V was developed based on the result of a Cox proportional hazards model. Its efficacy and clinical usefulness was evaluated by concordance index (c-index) and decision curve analysis. RESULTS: Of the 223 patients, 184 (83%) died of cancer. Median follow-up periods of patients who died and those who remained alive were 5 and 11 months, respectively. We developed a novel nomogram incorporating Eastern Cooperative Oncology Group Performance Status, presence of visceral metastasis, haemoglobin and age. The c-index of the nomogram predicting survival probability 6 and 12 months after diagnosis was 0.788 and 0.765, respectively. Decision curve analyses revealed that the novel nomogram incorporating CRP had a superior net benefit than that without CRP for most of the examined probabilities. CONCLUSION: We demonstrated the prognostic impact of CRP that improved the predictive accuracy of a nomogram for survival probability in patients with advanced urothelial carcinoma.

Characterization of three propane-inducible oxygenases in Mycobacterium sp. strain ENV421.

AIMS: Mycobacterium sp. strain ENV421 has the ability to cometabolize a variety of chemicals following growth on propane as a sole source of carbon and energy. In this study, we used genetic and biochemical approaches to identify and characterize multiple propane-inducible oxygenase genes in ENV421. METHODS AND RESULTS: Gene clusters encoding a CYP153-type cytochrome P450 oxygenase (P450), an AlkB-type alkane monooxygenase (AlkB) and a soluble diiron monooxygenase were identified and cloned using degenerate PCR primers. Reverse transcriptase PCR showed that all three gene clusters were induced by propane. Substrate specificity studies revealed that despite the fact that ENV421 does not grow on medium length alkanes, cloned versions of both the AlkB and P450 were capable of octane oxidation, forming n-octanol. Additionally, the P450 oxygenase had the ability to oxidize indole, medium-to-long-chain alkylbenzenes and a variety of para-substituted methylalkylbenzenes. Successful cloning and expression of the diiron monooxygenase was not achieved, so its substrate specificity could not be determined. CONCLUSIONS: Three types of short-to-medium-chain alkane oxygenases were induced by propane in ENV421, even though the cloned AlkB and P450 oxygenases did not oxidize propane. Curiously, they both oxidized octane, which is not a growth substrate for ENV421. Furthermore, the P450, typically operating as terminal alkane hydroxylase, exhibited interesting regio- and stereoselectivity, catalysing linear alkanes, alkylbenzenes and indole. SIGNIFICANCE AND IMPACT OF THE STUDY: This study describes the first example of a propane-inducible P450 with a broad substrate specificity, including linear alkanes, alkylbenzenes and a multiring compound. The induction of three distinct oxygenase classes by propane is also an interesting finding because it might explain why propane serves as an effective stimulant that promotes the biodegradation of a various environmental contaminants.

Ischemia- and cytokine-induced mobilization of bone marrow-derived endothelial progenitor cells for neovascularization.

Endothelial progenitor cells (EPCs) have been isolated from circulating mononuclear cells in human peripheral blood and shown to be incorporated into foci of neovascularization, consistent with postnatal vasculogenesis. We determined whether endogenous stimuli (tissue ischemia) and exogenous cytokine therapy (granulocyte macrophage-colony stimulating factor, GM-CSF) mobilize EPCs and thereby contribute to neovascularization of ischemic tissues. The development of regional ischemia in both mice and rabbits increased the frequency of circulating EPCs. In mice, the effect of ischemia-induced EPC mobilization was demonstrated by enhanced ocular neovascularization after cornea micropocket surgery in mice with hindlimb ischemia compared with that in non-ischemic control mice. In rabbits with hindlimb ischemia, circulating EPCs were further augmented after pretreatment with GM-CSF, with a corresponding improvement in hindlimb neovascularization. There was direct evidence that EPCs that contributed to enhanced corneal neovascularization were specifically mobilized from the bone marrow in response to ischemia and GM-CSF in mice transplanted with bone marrow from transgenic donors expressing beta-galactosidase transcriptionally regulated by the endothelial cell-specific Tie-2 promoter. These findings indicate that circulating EPCs are mobilized endogenously in response to tissue ischemia or exogenously by cytokine therapy and thereby augment neovascularization of ischemic tissues.

OCT4 expression in human uterine myometrial stem/progenitor cells.

BACKGROUND: The transcription factor, octamer-binding transcription factor 4 (OCT4)/POU5F1, is expressed in embryonic stem cells, germ cells and some types of adult stem cells. Human OCT4 encodes two isoforms, OCT4A and OCT4B. While OCT4A plays a crucial role in the maintenance of stem cell properties, including pluripotency, whereas OCT4B does not. We previously reported that human myometrium contains side population cells (myoSP) with a Hoechst 33 342 low-fluorescent profile. These cells exhibit phenotypic and functional characteristics of myometrial stem cells. The objective of this study was to investigate the comparative expression of OCT4 in the stem/progenitor cell population of the human myometrium. METHODS: Human myometrial tissue samples were collected from 18 consenting patients who underwent hysterectomy because of benign gynecological diseases. The resultant isolated or cultured myometrial cells and isolated myoSP were subjected to semi-quantitative and real-time RT-PCR analyses, immunoblot analyses and immunohistochemistry. RESULTS: RT-PCR and immunoblot analyses revealed that OCT4 mRNA and OCT4 protein were detectable in some (but not all) myometrial samples. Immunohistochemistry showed that OCT4 protein was confined to the nuclei of relatively few cells in myometrial tissues expressing OCT4 mRNA. OCT4 and OCT4A transcripts, but not those of OCT4B, were more abundant in myoSP than in non-myoSP, as determined by real-time and semi-quantitative RT-PCR analyses. CONCLUSIONS: Relatively few myometrial cells express OCT4 protein. OCT4 mRNA, in particular OCT4A mRNA, is up-regulated in myoSP that have been reported to exhibit stem cell-like properties. Taken together, the present results indicate that the myoSP population is enriched in OCT4 mRNA.

Prophylactic pancreatic stent placement and post-ERCP pancreatitis: a systematic review and meta-analysis.

BACKGROUND AND STUDY AIMS: Pancreatitis is one of the most frequent complications of endoscopic retrograde cholangiopancreatography (ERCP). The placement of a prophylactic pancreatic stent after ERCP can help prevent post-ERCP pancreatitis (PEP). We aimed to provide an up-to-date meta-analysis regarding pancreatic stent placement for prevention of PEP and review the immediate adverse events associated with pancreatic stent placement. METHODS: We conducted a systematic review and meta-analysis of randomized controlled trials (RCTs) considering pancreatic stent placement and the subsequent incidence of PEP. The primary outcome measure was the incidence of PEP. We also did a meta-analysis of RCTs and observational studies that reported on immediate adverse events, in order to estimate their incidence. RESULTS: Eight studies, involving 680 patients, were included in the meta-analysis; 336 patients had pancreatic stent placement, and 344 patients formed the control group. Pancreatic stent placement was associated with a statistically significant reduction in PEP (relative risk [RR] 0.32, 95 % confidence interval [CI] 0.19 - 0.52; P<0.001). Subgroup analysis with stratification according to PEP severity showed that pancreatic stenting was beneficial in patients with mild to moderate PEP (RR 0.36, 95 %CI 0.22 -0.60; P<0.001) and in patients with severe PEP (RR 0.23, 95 %CI 0.06 - 0.91; P=0.04). Subgroup analysis according to patient selection demonstrated that pancreatic stenting was effective for both high risk and mixed-case groups. Weighted pooled estimates from between one and 17 studies for incidences of immediate adverse events were: overall complications 4.4 %; any infection 3.0 %; bleeding 2.5 %; cholangitis or cholecystitis 3.1 %; necrosis 0.4 %; pancreatic stent migration 4.9 % and occlusion 7.9 %; perforation 0.8 %; pseudocysts 3.0 %; and retroperitoneal perforation 1.2 %. CONCLUSIONS: The meta-analysis shows that pancreatic stent placement after ERCP reduces the risk of PEP.

In vivo imaging in humanized mice.

The radiological modalities that are currently utilized as critical components in clinical medicine have also been adapted to small-animal imaging, among which are ultrasound imaging, X-ray computerized tomography (CT), magnetic resonance imaging (MRI), positron emission tomography (PET), and single-photon emission computed tomography (SPECT). Optical imaging techniques such as bioluminescence imaging (BLI) and fluorescence imaging (FLI) are approaches that are commonly used in small animals. Longitudinal surveys of living (i.e., nonsacrificed) animal models with these modalities provide some clues for the development of clinical applications. The techniques are absolutely essential for translational research. However, there are currently few tools available with sufficient spatial or temporal resolution ideal for all experimental studies. In this chapter, we provide a rationale and techniques for visualizing target cells in living small animals and an overview of the advantages and limitations of current imaging technology. Finally, we introduce a humanized mouse and a novel in vivo imaging system that we have developed. We also discuss real-time observations of reconstructs and clinical manifestations.

Isolation and characterization of circumferential microfilament bundles from retinal pigmented epithelial cells.

Chicken retinal pigmented epithelial cells have circumferential microfilament bundles (CMBs) at the zonula adherens region. We have isolated these CMBs in intact form and characterized them structurally and biochemically. Pigmented epithelia obtained from 11-d-old chick embryos were treated with glycerol and Triton. Then, the epithelia were homogenized by passing them through syringe needles. Many isolated CMBs were found in the homogenate by phase-contrast microscopy. They formed polygons, mostly pentagons and hexagons, or fragments of polygons. Polygons were filled with meshwork structures, i.e. they were polygonal plates. Upon exposure to Mg-ATP, isolated CMBs showed clear and large contraction. The contraction was inhibited by treatment with N-ethylmaleimide-modified myosin subfragment-1. After purification by centrifugation with the density gradient of Percoll, CMBs were analyzed by SDS PAGE. The electrophoretic pattern gave three major components of 200, 55, and 42 kdaltons and several minor components. Electron microscopy showed that the polygons were composed of thick bundles of actin-containing microfilaments, and the meshworks were composed primarily of intermediate filaments.

In vitro microtubule-nucleating activity of spindle pole bodies in fission yeast Schizosaccharomyces pombe: cell cycle-dependent activation in xenopus cell-free extracts.

The spindle pole body (SPB) is the equivalent of the centrosome in fission yeast. In vivo it nucleates microtubules (MTs) during mitosis, but, unlike animal centrosomes, does not act as a microtubule organizing center (MTOC) during interphase. We have studied the MT-nucleating activity of SPBs in vitro and have found that SPBs in permeabilized cells retain in vivo characteristics. SPBs in cells permeabilized during mitosis can nucleate MTs, and are recognized by two antibodies: anti-gamma-tubulin and MPM-2 which recognizes phosphoepitopes. SPBs in cells permeabilized during interphase cannot nucleate MTs and are only recognized by anti-gamma-tubulin. Interphase SPBs which cannot nucleate can be converted to a nucleation competent state by incubation in cytostatic factor (CSF)-arrested Xenopus egg extracts. After incubation, they are recognized by MPM-2, and can nucleate MTs. The conversion does not occur in Xenopus interphase extract, but occurs in Xenopus interphase extract driven into mitosis by preincubation with exogenous cyclin B. The conversion is ATP dependent and inhibited by protein kinase inhibitors and alkaline phosphatase. Purified, active, cdc2 kinase/cyclin B complex in itself is not effective for activation of MT nucleation, although some interphase SPBs are now stained with MPM-2. These results suggest that the ability of SPBs in vitro to nucleate MTs after exposure to CSF-arrested extracts is activated through a downstream pathway which is regulated by cdc2 kinase.

The mechanism of anaphase spindle elongation: uncoupling of tubulin incorporation and microtubule sliding during in vitro spindle reactivation.

To study tubulin polymerization and microtubule sliding during spindle elongation in vitro, we developed a method of uncoupling the two processes. When isolated diatom spindles were incubated with biotinylated tubulin (biot-tb) without ATP, biot-tb was incorporated into two regions flanking the zone of microtubule overlap, but the spindles did not elongate. After biot-tb was removed, spindle elongation was initiated by addition of ATP. The incorporated biot-tb was found in the midzone between the original half-spindles. The extent and rate of elongation were increased by preincubation in biot-tb. Serial section reconstruction of spindles elongating in tubulin and ATP showed that the average length of half-spindle microtubules increased due to growth of microtubules from the ends of native microtubules. The characteristic packing pattern between antiparallel microtubules was retained even in the "new" overlap region. Our results suggest that the forces required for spindle elongation are generated by enzymes in the overlap zone that mediate the sliding apart of antiparallel microtubules, and that tubulin polymerization does not contribute to force generation. Changes in the extent of microtubule overlap during spindle elongation were affected by tubulin and ATP concentration in the incubation medium. Spindles continued to elongate even after the overlap zone was composed entirely of newly polymerized microtubules, suggesting that the enzyme responsible for microtubule translocation either is bound to a matrix in the spindle midzone, or else can move on one microtubule toward the spindle midzone and push another microtubule of opposite polarity toward the pole.

In vitro reactivation of spindle elongation in fission yeast nuc2 mutant cells.

To investigate the mechanisms of spindle elongation and chromosome separation in the fission yeast Schizosaccharomyces pombe, we have developed an in vitro assay using a temperature-sensitive mutant strain, nuc2. At the restrictive temperature, nuc2 cells are arrested at a metaphase-like stage with short spindles and condensed chromosomes. After permeabilization of spheroplasts of the arrested cells, spindle elongation was reactivated by addition of ATP and neurotubulin both at the restrictive and the permissive temperatures, but chromosome separation was not. This suggests that the nuc2 cells are impaired in function at a stage before sister chromatid disjunction. Spindle elongation required both ATP and exogenous tubulin and was inhibited by adenylyl imidodiphosphate (AMPPNP) or vanadate. The ends of yeast half-spindle microtubules pulse-labeled with biotinylated tubulin moved past each other during spindle elongation and a gap formed between the original half-spindles. These results suggest that the primary mechanochemical event responsible for spindle elongation is the sliding apart of antiparallel microtubules of the two half-spindles.