The Coordination of Centromere Replication, Spindle Formation, and Kinetochore–Microtubule Interaction in Budding Yeast

The kinetochore is a protein complex that assembles on centromeric DNA to mediate chromosome–microtubule interaction. Most eukaryotic cells form the spindle and establish kinetochore–microtubule interaction during mitosis, but budding yeast cells finish these processes in S-phase. It has long been noticed that the S-phase spindle in budding yeast is shorter than that in metaphase, but the biological significance of this short S-phase spindle structure remains unclear. We addressed this issue by using ask1-3, a temperature-sensitive kinetochore mutant that exhibits partially elongated spindles at permissive temperature in the presence of hydroxyurea (HU), a DNA synthesis inhibitor. After exposure to and removal of HU, ask1-3 cells show a delayed anaphase entry. This delay depends on the spindle checkpoint, which monitors kinetochore–microtubule interaction defects. Overproduction of microtubule-associated protein Ase1 or Cin8 also induces spindle elongation in HU-arrested cells. The spindle checkpoint-dependent anaphase entry delay is also observed after ASE1 or CIN8 overexpression in HU-arrested cells. Therefore, the shorter spindle in S-phase cells is likely to facilitate proper chromosome–microtubule interaction

Studies on the formation and forming mechanism of the related substance E in potassium clavulanate production by HPLC-MS/MS

O objetivo deste estudo foi investigar a formação da substância E e o respectivo mecanismo na produção de clavulanato de potássio. Confirmou-se a impureza com tempo de retenção de 11,1 min no produto final, clavulanato de potássio, como substância E, por meio de cromatografia líquida de alta eficiência, em conjunto com detecção por espectrometria de massas (CLAE-MS-MS). A análise da substância relacionada E durante a produção do ácido clavulânico mostrou que essa impureza pode ser formada tanto durante a fermentação quanto durante os processos de purificação, especialmente no estágio final de fermentação, filtração, concentração e procedimento de extração. O ácido clavulãnico foi o precursor da substância E. Estudos no mecanismo de sua formação mostraram que a substância E formou-se pela combinação do grupo imina da molécula do ácido clavulânico com o grupo carboxílico de outra molécula de ácido clavulânico, com a abertura do anel β-lactâmico. Resultados do teste ortogonal multifatorial confirmaram que a concentração do ácido clavulânico foi o fator dominante para acelerar a reação, enquanto a temperatura foi outro fator que contribuiu. O pH de 5,0 a 6,5 teve pouco impacto na geração da substância E.The objective of this study was to investigate the formation and forming mechanism of the related substance E in potassium clavulanate production. The impurity with retention time of 11.1 min in potassium clavulanate final product was confirmed as the related substance E by high performance liquid chromatography with tandem mass spectrometric detection (HPLC-MS/MS).The related substance E analysis during the production of clavulanic acid showed that this impurity could be formed during both the fermentation and purification processes, especially in the later fermentation stage, filtration concentration and back-extraction procedure. Clavulanic acid was the precursor of the related substance E. Studies on its forming mechanism showed that the related substance E was formed by the combination of the imino group of one molecule of clavulanic acid with the carboxyl group of another molecule of clavulanic acid with the opening of β-lactam ring. Results of a multi-factor orthogonal test confirmed that the concentration of clavulanic acid was the dominant factor to accelerate the reaction, while the temperature was another contributing factor. The pH 5.0-6.5 had little impact on the generation of the related substance E

The radiation protection role of heparin-SOD conjugate in irradiated mice

Heparin-SOD conjugate (Hep-SOD) was prepared by modifying Cu,Zn-SOD with heparin. An acute radiation-induced mouse injury model was constructed to study the radiation protection effects of Hep-SOD conjugate. Fifty-six mice were randomly divided into seven groups: (I) normal control group; (II) irradiated control group; (III) positive control group (amifostine group, 300 mg/kg); (IV) SOD group (35000 U/kg); (V) high dosage of Hep-SOD group (70000 U/kg); (VI) medium dosage of Hep-SOD group (35000 U/kg); (VII) low dosage of Hep-SOD group (17500 U/kg). Drugs were intraperitoneally injected into each mouse 1 h before radiation except for the normal control group. All the irradiated groups were irradiated with 6 Gy. Organ indices, haematopoietic function indices, peripheral blood cells, liver function test, oxidative stress state and pathological observation were detected to study the effects of Hep-SOD on irradiated mice. Results showed that bone marrow suppression of irradiated mice could be reduced when treated by Hep-SOD before radiation. Oxidative stress detection and pathological observation of the liver and intestine showed that the damage caused by radiation was relieved when mice were treated with Hep-SOD before radiation. This study shows a new direction to prevent organisms from the damage caused by radiation

Direct imaging of a zero-field target skyrmion and its polarity switch in a chiral magnetic nanodisk

A target skyrmion is a flux-closed spin texture that has two-fold degeneracy and is promising as a binary state in next generation universal memories. Although its formation in nanopatterned chiral magnets has been predicted, its observation has remained challenging. Here, we use off-axis electron holography to record images of target skyrmions in a 160-nm-diameter nanodisk of the chiral magnet FeGe. We compare experimental measurements with numerical simulations, demonstrate switching between two stable degenerate target skyrmion ground states that have opposite polarities and rotation senses and discuss the observed switching mechanism.Comment: 18 pages, 4 figure

Experimental observation of magnetic bobbers for a new concept of magnetic solid-state memory

The use of chiral skyrmions, which are nanoscale vortex-like spin textures, as movable data bit carriers forms the basis of a recently proposed concept for magnetic solid-state memory. In this concept, skyrmions are considered to be unique localized spin textures, which are used to encode data through the quantization of different distances between identical skyrmions on a guiding nanostripe. However, the conservation of distances between highly mobile and interacting skyrmions is difficult to implement in practice. Here, we report the direct observation of another type of theoretically-predicted localized magnetic state, which is referred to as a chiral bobber (ChB), using quantitative off-axis electron holography. We show that ChBs can coexist together with skyrmions. Our results suggest a novel approach for data encoding, whereby a stream of binary data representing a sequence of ones and zeros can be encoded via a sequence of skyrmions and bobbers. The need to maintain defined distances between data bit carriers is then not required. The proposed concept of data encoding promises to expedite the realization of a new generation of magnetic solid-state memory

Case report: Reconstruction of the left renal vein with resected autologous right renal vein interposition after excision of an inferior vena cava leiomyosarcoma

BackgroundLeiomyosarcoma of the inferior vena cava (IVC) was a rather rare disease with the characteristics of invading the adjacent viscera. Surgical resection is the only potential curative treatment, and radiation therapy and chemotherapy for leiomyosarcoma are not definite. There is few literature reporting the leiomyosarcoma of the IVC.Case presentationA previously healthy 64-year-old female was admitted to the First Affiliated Hospital of China Medical University with the complaint of right lower quadrant abdominal pain for almost three years and worsening with a radiating ache in the waist recently. Contrast-enhanced computed tomography(CT) scans revealed a large (7.8 cm*5.5 cm*5.0 cm) irregular hypodense retroperitoneal mass with heterogeneous enhancement and invasion of the IVC, and the right ureter was compressed with proximal ureteral dilatation and hydrops. Three-dimensional CT of the IVC revealed that the IVC was encircled by the tumor with moderate invasion. During the operation, the tumor was resected en bloc with the IVC (from the suprarenal to infrarenal segment), the right kidney with ureter, and the duodenum seromuscular layer. As the left renal vein was involved, it was also partly resected. IVC reconstruction was performed with the interposition of a 20 mm diameter polytetrafluoroethylene (PTFE) prosthesis, and the right renal vein was anastomosed between the left renal vein and the reconstructed IVC to guarantee the left renal vein reflux. The patient had an uneventful recovery process with normal renal function after the operation. However, follow-up CT indicated that the left renal vein was blocked two weeks after the surgery. The patient was discharged two weeks after the operation. She continues well and has no evidence of disease fourteen months after the surgery.ConclusionsWide excision of the tumor en bloc with the IVC is the main treatment for leiomyosarcoma of the IVC. IVC reconstruction with prosthetic PTFE grafts is recommended. When the left renal vein is partly resected due to involvement of the tumor, reconstruction of left renal vein should also be performed to avoid renal impairment. If the right renal vein does not show tumor involvement, the resected right renal vein can be used to reconstruct the left renal vein

The relevance study of effective information between near infrared spectroscopy and chondroitin sulfate in ethanol precipitation process

Near infrared spectroscopy (NIRS) is based on molecular overtone and combination vibrations. It is difficult to assign specific features under complicated system. So it is necessary to find the relevance between NIRS and target compound. For this purpose, the chondroitin sulfate (CS) ethanol precipitation process was selected as the research model, and 90 samples of 5 different batches were collected and the content of CS was determined by modified carbazole method. The relevance between NIRS and CS was studied throughout optical pathlength, pretreatment methods and variables selection methods. In conclusion, the first derivative with Savitzky–Golay (SG) smoothing was selected as the best pretreatment, and the best spectral region was selected using interval partial least squares (iPLS) method under 1 mm optical cell. A multivariate calibration model was established using PLS algorithm for determining the content of CS, and the root mean square error of prediction (RMSEP) is 3.934 g⋅L-1. This method will have great potential in process analytical technology in the future

Synthesis and Biological Activities of a 3′-Azido Analogue of Doxorubicin Against Drug-Resistant Cancer Cells

Doxorubicin (DOX), an anthracycline antibiotic, is one of the most active anticancer chemotherapeutic agents. The clinical use of DOX, however, is limited by the dose-dependant P-glycoprotein (P-gp)-mediated resistance. Herein, a 3′-azido analogue of DOX (ADOX) was prepared from daunorubicin (DNR). ADOX exhibited potent antitumor activities in drug-sensitive (MCF-7 and K562) and drug-resistant cell lines (MCF-7/DNR, K562/DOX), respectively. The drug resistance index (DRI) values of ADOX were much lower than that of DOX. The cytotoxicity experiments of ADOX or DOX against K562/DOX, with or without P-gp inhibitor, indicated that ADOX circumvents resistance by abolishing the P-gp recognition. This conclusion was further supported by drug influx/efflux flow cytometry experiments, as well as by molecular docking of ADOX to P-gp. In vivo animal tests, ADOX exhibited higher activity and less toxicity than DOX. The current data warranted ADOX for additional pre-clinical evaluations for new drug development