A multiple-threshold AR(1) model

We consider the model Zt = φ (0, k)+ φ(1, k)Zt–1 + at (k) whenever rk−1<Zt−1≦rk, 1≦k≦l, with r0 = –∞ and rl =∞. Here {φ (i, k); i = 0, 1; 1≦k≦l} is a sequence of real constants, not necessarily equal, and, for 1≦k≦l, {at(k), t≧1} is a sequence of i.i.d. random variables with mean 0 and with {at(k), t≧1} independent of {at(j), t≧1} for j ≠ k. Necessary and sufficient conditions on the constants {φ (i, k)} are given for the stationarity of the process. Least squares estimators of the model parameters are derived and, under mild regularity conditions, are shown to be strongly consistent and asymptotically normal.

Some comments on spectral representations of non-stationary stochastic processes

The first part of the paper gives a multitude of essentially different representations of a stationary stochastic process. The second part gives a sufficient condition for the sum of two oscillatory processes to be again oscillatory.

Determination of the order of a Markov chain by Akaike's information criterion

Using Akaike's information criterion, we have presented an objective procedure for the determination of the order of an ergodic Markov chain with a finite number of states. The procedure exploits the asymptotic properties of the maximum likelihood ratio statistics and Kullback and Leibler's mean information for the discrimination between two distributions. Numerical illustrations are given, using data from Bartlett (1966), Good and Gover (1967) and some weather records.

MUC13 protects colorectal cancer cells from death by activating the NF-κB pathway and is a potential therapeutic target

MUC13 is a transmembrane mucin glycoprotein that is over produced by many cancers, although its functions are not fully understood. Nuclear factor-κB (NF-κB) is a key transcription factor promoting cancer cell survival, but therapeutically targeting this pathway has proved difficult because NF-κB has pleiotropic functions. Here, we report that MUC13 prevents colorectal cancer cell death by promoting two distinct pathways of NF-kB activation, consequently upregulating BCL-X_L. MUC13 promoted tumor necrosis factor (TNF)-induced NF-κB activation by interacting with TNFR1 and the E3 ligase, cIAP1, to increase ubiquitination of RIPK1. MUC13 also promoted genotoxin-induced NF-κB activation by increasing phosphorylation of ATM and SUMOylation of NF-κB essential modulator. Moreover, elevated expression of cytoplasmic MUC13 and NF-κB correlated with colorectal cancer progression and metastases. Our demonstration that MUC13 enhances NF-κB signaling in response to both TNF and DNA-damaging agents provides a new molecular target for specific inhibition of NF-κB activation. As proof of principle, silencing MUC13 sensitized colorectal cancer cells to killing by cytotoxic drugs and inflammatory signals and abolished chemotherapy-induced enrichment of CD133⁺ CD44⁺ cancer stem cells, slowed xenograft growth in mice, and synergized with 5-fluourouracil to induce tumor regression. Therefore, these data indicate that combining chemotherapy and MUC13 antagonism could improve the treatment of metastatic cancers.

A note on one-dimensional chaotic maps under time reversal

We have furnished further examples on the connection between some standard one-dimensional chaotic deterministic models and stochastic time series models via time reversal.

On the use of the deterministic Lyapunov function for the ergodicity of stochastic difference equations

We have shown that within the setting of a difference equation it is possible to link ergodicity with stability via the physical notion of energy in the form of a Lyapunov function.

Prenatal diagnosis of trisomy 21, 18 and 13 by quantitative pyrosequencing of segmental duplications

Chromosomal aberration mostly occurs in chromosomes 21, 18 and 13, with an incidence approximately 1 out of 160 live births in humans, therefore making prenatal diagnosis necessary in clinics. Current methods have drawbacks such as time consuming, high cost, complicated operations and low sensitivity. In this paper, a novel method for rapid and accurate prenatal diagnosis of aneuploidy is proposed based on pyrosequencing, which quantitatively detects the peak height ratio (PHR) of different bases of segmental duplication. A direct polymerase chain reaction (PCR) approach was undertaken, where a small volume of amniotic fluid was used as the starting material without DNA extraction. Single-stranded DNA was prepared from PCR products and subsequently analyzed using pyrosequencing. The PHR between target and reference chromosome of 2.2 for euploid and 3:2 for a trisomy fetus were used as reference. The reference intervals and z scores were calculated for discrimination of aneuploidy. A total of 132 samples were collected, within trisomy 21 (n = 11), trisomy 18 (n = 3), trisomy 13 (n = 2), and unaffected controls (n = 116). A set of six segmental duplications were chosen for analysis. This method had consistent results with karyotyping analysis, a correct diagnosis with 100% sensitivity and 99.9% specificity.

Indirect Revascularization for Non-Moyamoya Disease Anterior Circulation Arterial Steno-occlusion: Clinical Features, Surgical Treatment, and Medium-Term Outcomes in Adults

BACKGROUND

Symptomatic anterior arterial steno-occlusion is often associated with neurofunctional deficits or a high risk of recurrent stroke or both. Although both medical and endovascular treatments are useful and suitable, few studies have investigated the continued use of indirect encephaloduroarteriosynangiosis (EDAS) bypass in patients with non-moyamoya disease ischemia. We retrospectively investigated clinical features, surgical treatments, and medium-term outcomes of indirect revascularization for patients with non-moyamoya disease anterior circulation arterial steno-occlusion in China.

METHODS

EDAS without burr holes was performed in 51 adult patients with cerebral ischemic events and diagnosed nonmoyamoya anterior circulation arterial steno-occlusion. Preoperative, postoperative, and follow-up neurologic status was evaluated using the National Institutes of Health Stroke Scale; changes on angiography and perfusion-weighted magnetic resonance imaging were evaluated.

RESULTS

Unilateral EDAS was performed in 48 patients, and bilateral EDAS was performed in 3 patients. Four patients experienced complications before hospital discharge; only 23 patients underwent follow-up angiograms. Of the 51 patients, 44 (86.3%) exhibited improved muscle strength; 21 of 23 patients (91.3%) with follow-up angiography data exhibited evidence of new visible branches from the superficial temporal artery or middle meningeal artery or both. Preoperative and postoperative perfusion-weighted magnetic resonance imaging was performed for 5 patients. Despite clinical improvement in all patients, only 2 exhibited hemodynamic improvement.

CONCLUSIONS

Indirect revascularization may be safe and effective for improving blood flow to the ischemic region following nonmoyamoya anterior circulation arterial steno-occlusion, especially in patients with residual postinfarction neurologic deficits. Our study demonstrates that improvements in ischemic symptoms after EDAS correspond to neovascularization from the superficial temporal artery or middle meningeal artery in ischemic brain areas.

Fluorescence lifetime imaging of optically levitated aerosol: a technique to quantitatively map the viscosity of suspended aerosol particles

A technique to measure the viscosity of stably levitated single micron-sized aerosol particles.

On the preparation of transferrin modified artesunate nanoliposomes and their glioma-targeting treatment in-vitro and in-vivo

OBJECTIVE

To prepare transferrin modified artesunate nanoliposomes (Tf-ART-LPs) and study their glioma U87 cells-targeting treatment in-vitro and in-vivo.

METHODS

Ammonium sulfate transmembrane gradient method was used to prepare Tf-ART-LPs, whose size and stability was detected by a Nanosizer. Besides, the encapsulation efficiency and release rate of artesunate (ART) were tested by a ultraviolet spectrophotometer. Further, isothiocyanate (FITC) was used to label nanoliposomes and the cell-targeting property of Tf-ART-LP in-vitro was observed under a fluorescence microscope. In addition, CCK-8 method was used to detect the effect of single nanoliposomes and Tf-ART-LPs on the viability of glioma U87 cells. At last, a subcutaneously implanted tumor model in nude mouse was established for studying the in-vivo anti-tumor effect of Tf-ART-LPs by caudal vein injection. The tumor volume and mice weight were monitored and pathological sections of their major organs were analyzed.

RESULTS

Tf-ART-LPs were spherical with an average diameter of 94.2 nm. They showed no aggregation after being stored in a refrigerator for 14 days at 4°C. The encapsulation efficiency and highest releasing rate (48 hours after being placed in normal saline under 37°C) of ART was 85.9% and 58.7±2.9%, respectively. The uptake rate of U87 cells was 59.8±3.8% for Tf-ART-LPs and only 18.7±4.5% for ART-LPs. While single liposomes almost showed no toxicity, Tf-ART-LP had a concentration-dependent killing effect on U87 cells. Within 32 days of treatment, the growth of U87 cells was well inhibited by Tf-ART-LPs without significant toxicity.

CONCLUSION

In this study, transferrin modified artesunate liposomes we prepared have a good targeting property to glioma U87 cells and good effect on glioma both in-vitro and in-vivo.

[Exploratory study of 3D printing technique in the treatment of basilar invagination and atlantoaxial dislocation]

OBJECTIVE

To investigate the clinical application value of the 3D printing technique in the treatment of basilar invagination and atlantoaxial dislocation.

METHODS

From January 2013 to September 2013, 10 patients with basilar invagination and atlantoaxial dislocation needing posterior fixation undertook 3D printing modes at the Department of Neurosurgery in PLA General Hospital. The 1:1 size models were established from skull base to C4 level with different colors between bone structures and vertebral arteries. The simulation of screw insertion was made to investigate the fixation plan and ideal entry point to avoid vertebral artery injury. After obtaining the individual screw insertion data in 3D printing modes, the according surgical operations were performed. The actual clinical results and virtual screw data in 3D printing mode were compared with each other.

RESULTS

The 3D printing modes revealed that all the 10 patients had the dysplasia or occipitalized C1 posterior arch indicating C1 posterior arch screw implantation was not suitable. C1 lateral masses were chosen as the screws entry points. C2 screws were designed individually based on the 3D printing modes as follows: 3 patients with aberrant vertebral artery or narrow C2 pedicle less than 3.5 mm were not suitable for pedicle screw implantation. Among the 3 patients, 1 was fixed with C2 laminar screw, and 1 with C2-3 transarticular screw and 1 with C3 pedicle screw (also combined with congenital C2-3 vertebral fusion). Two patients with narrow C2 pedicle between 3.5 and 4mm were designed to choose pedicle screw fixation after 3D printing mode evaluation. One patient with C1 lateral mass vertically dislocated axis was planned with C1-2 transarticular screw fixation. All the other patients were planned with C2 pedicle screws. All the 10 patients had operation designed as the 3D printing modes schemes. The follow-up ranged from 12 to 18 months and all the patients recovered from the clinical symptoms and the bony fusion attained to 100%.

CONCLUSIONS

3D printing mode could provide thorough information of the bony structure abnormalities and route of vertebral artery. It is helpful for setting operation strategy and designing screw entry point and trajectory and avoiding vertebral artery and spinal cord injury and thus deserves generalization.

[Analysis of 160 cases of C1 lateral mass screw fixation in patients with atlas occipitalization and occipito-cervical instability]

OBJECTIVE

To summarize the clinical effect of C1 lateral mass screw fixation in patients with atlas occipitalization and occipito-cervical instability (OCI).

METHODS

Patients of atlas occipitalization and OCI from June 2007 to October 2013 which had been treated by C1 lateral mass fixation in our institution were retrospective analyzed. The clinical neurologic function improvement rate and bone fusion rate were investigated at follow-ups. The nuances of the C1 lateral mass insertion were summarized.

RESULTS

Among the 160 patients, 1 patient died, 1 got worse, 1 was stable, 155 got recovery and 2 lost to follow-up. Among the 157 cases within 12-52 months follow-up (mean 34 months), 147 cases got reduction and release from the cervico-medullary junction compression and 10 got no effective reduction which were resumed to anterior decompression at second surgery.At one year follow-up, 155 cases had solid bony fusion and 2 had no evident fusion.The entry point for C1 screw was located at the midpoint of the posterior surface of C1 facet and the screw was directed approximately between 0-40° cephalad and approximately between 0-20° medially.

CONCLUSIONS

C1 lateral mass screw fixation is a safe and feasible method and could provide solid stability in patients with atlas occipitalization and OCI. The risk of placement of C1 screw could be decreased to a low rate after the preoperative evaluation and trajectory design.

Occipital Condyle-C1 Complex Screw for Fixation of Basilar Invagination Patients with Atlas Assimilation

AIM

To investigate whether C1-occipital condyle complex (CC complex) screws can be safely and rapidly placed without guidance in basilar invagination patients with atlas assimilation.

MATERIAL AND METHODS

The occipital-cervical (OC) junction was fixed posteriorly in 8 basilar invagination patients with atlas assimilation using polyaxial titanium screws inserted unicortically into the CC complex and C2 pedicles and subsequent fixation to a 3-mm rod. Anatomic landmarks were used during the drilling. The screw angles and lengths of the CC complex were analyzed.

RESULTS

The width, length, and height values of the left-side CC complex were 7.96±2.23, 16.06±2.73, and 13.76±2.06 mm; those of the right-side CC complex were 7.84±1.38, 16.66±2.58, and 12.81±2.62 mm. The CC complex entry point was at the central point of posterior surface of the CC complex. The angle used for medialization was 10-15°, which was also the maximal superior screw angulation in the sagittal plane. The screw length required for unicortical purchase was 16-22 mm. The screw was not misplaced or poorly positioned, and no neurovascular complications associated with screw insertion were detected.

CONCLUSION

In patients with atlas assimilation, CC complex screws can be placed safely. The CC complex screws can be safely inserted assisted by microscope without image guidance.

Downregulation of solute carriers of glutamate in gliosomes and synaptosomes may explain local brain metastasis in anaplastic glioblastoma

Advanced grades of glioblastoma are highly aggressive, especially in terms of multisite spread within the brain or even to distant sites at the spinal cord. In advanced grades of glioblastoma, glutamate and glutamine are reported to be increased in concentration in the extracellular fluid. It has been reported that glutamate acts as an extracellular signaling molecule for facilitating local spread of advanced grades of glioblastoma. In the present study, we aimed to examine whether glutamate uptake mechanisms is impaired in advanced glioblastoma. The possible downregulated mechanisms of glutamate uptake would facilitate persistence of glutamate in the extracellular environment, rather than intracellular uptake. We obtained biobanked human specimens of glioblastoma and tested expression of proteins belonging to the solute carrier families of proteins that are known to function as membrane-located excitatory amino acid like glutamate transporters. The present study provides preliminary evidence of the downregulation of membrane expression of excitatory amino acid transporters solute carrier family 1 member 3 (SLC1A3) and its palmitoylated form in gliosomes, as well as SLC1A2 in the glio-synaptosomes. Compounds like riluzole used in the treatment of amyotrophic lateral sclerosis and the antibiotic ceftriaxone have the potential to facilitate glutamate uptake. These medications may be examined as adjunct chemotherapy in the massively aggressive tumor glioblastoma multiforme.

[Treatment of fixed atlantoaxial dislocation and basilar invagination with C1-2 screw and rod reduction and fixation technique]

OBJECTIVE

To introduce a novel technique of reducing fixed atlantoaxial dislocation (FAAD) and basilar invagination (BI) with C1-C2 screw and rod system.

METHODS

From January 2009 to December 2011, 26 patients of FAAD and BI were reduced successfully with an insertion of C1 lateral mass and C2 pedicle/pars screw and rod system. The cohort had 17 females and 9 males. And their most common presenting symptoms were extremity muscle weakness, restricted neck movement and paresthesia.

RESULTS

All of them achieved effective reduction. Among them, 18 attained complete reduction and 8 partial reduction (over 60% extent of reduction). The mean atlanto-dental interval (ADI) value was 2.1 mm postoperatively versus 8.8 mm preoperatively (t = 21.1, P < 0.01) . All of them had relieved compression of dura and medulla oblongata and cervical cord. All clinical symptoms improved. One case had pulmonary infection while another case delayed healing of incision. Both recovered well after symptomatic treatments. Bony fusion reached 100% during a mean follow-up period of 22 months.

CONCLUSION

The C1-C2 screw and rod system may achieve effective reduction and fixation for FAAD and BI. Capable of preserving atlanto-occipital joints in patients without atlas assimilation, this procedure provide more solid immobilization than occipitocervical fusion in those with atlas assimilation.

Association of serum homocysteine levels with the severity and calcification of coronary atherosclerotic plaques detected by coronary CT angiography

AIM

In this study, we aim to evaluate the association of risk factors including homocysteine (Hcy) with the severity and burden of coronary atherosclerotic plaques detected by computed tomography angiography (CTA).

METHODS

Six hundred fifty-nine subjects who underwent CTA for the assessment of coronary artery disease (CAD) were studied. All the subjects enrolled had no clinical cardiovascular disease symptoms. Logistic regression showed apart from age, hypertension, smoking, triglyceride, low-density lipoprotein (LDL) cholesterol, and total bilirubin, Hcy was an independently risk factor of the severity of coronary disease. And Hcy was also found an independent predictor for the presence of calcified plaque. When the participants were divided into 4 groups according to serum Hcy quartiles (Q1-Q4 groups), both the percentage of patients with >50% stenosis and the percentage of patients with calcified plaque were higher in Q4 compared to other groups. The OR of Hcy (>15 µmol/L) for >50% stenosis was 2.212 (95% CI=1.119 to 4.375, P=0.022) and the OR for Hcy (>15 µmol/L) for calcification was 1.668 (95% CI=1.030 to 2.699, P=0.037) respectively.

CONCLUSION

Our study shows Hcy is independently associated with both the severity and calcified plaque detected by CTA. Hcy may provide additional information about CAD in the subjects without clinical symptoms.

Proton pump inhibitors are associated with hypersensitivity reactions to drugs in hospitalized patients: a nested case-control in a retrospective cohort study

BACKGROUND

Previous research has shown that gastric acid suppression by antacid drugs can promote allergic reactions to acid-labile food proteins. No data are available about whether antacid drugs can promote drug hypersensitivity reactions. The most potent and longer lasting inhibition of gastric secretion is provided by proton pump inhibitors (PPIs). We hypothesized that gastric acid suppression by proton pump inhibitors could be causative of drug hypersensitivity reactions during hospitalization.

OBJECTIVE

To estimate the risk of developing drug hypersensitivity reactions during the hospitalization of patients treated with proton pump inhibitors, and other associated factors.

METHODS

A nested case-control in a retrospective cohort study of hospitalized patients from September 2008 to December 2010 (70 771 admissions) was conducted using the registry of cases of interconsultations to the Allergy Department (161 confirmed cases of drug hypersensitivity reactions). A total of 318 controls were matched by first drug suspected in the hypersensitivity reaction, time of admission, age, gender and hospitalization wards.

RESULTS

The relative risk of drug hypersensitivity reaction occurrence during hospitalization of patients treated with PPIs compared with those not treated in the period of study was significant (RR: 3.97; 95% CI: 1.97-8.29). After controlling for confounders in the nested case-control cohort, the use of PPIs persists as a predisposing factor (OR: 4.35; 95% CI: 2-9.45). Personal history of drug allergy and a long hospitalization time were other predisposing factors of drug hypersensitivity reactions (DHRs). The hazard that a DHR has occurred during PPI treatment was 3.7% per day. The hazard for immediate or accelerated reactions was 1.706 (P = 0.003) times that of delayed reactions.

CONCLUSION AND CLINICAL RELEVANCE

In hospitalized patients, the use of proton pump inhibitors was associated with a significant increase risk of drug hypersensitivity reactions along with a personal history of drug allergies and long hospitalization time.

Construction of a recombinant plasmid harbouring the glyceraldenyde-3-phosphate dehydrogenase gene of periodic Brugia malayi and observation on DNA immunity

PURPOSE

Controlling and eliminating lymphatic filariasis will require further research of preventative measures and implementation. Parasite is dependent on glycolysis for ATP production. The glycolytic enzyme glyceraldenyde-3-phosphate dehydrogenase (GAPDH) plays an important role in glycolysis and therefore is either a potential target for anti-parasite drug development or a vaccine candidate. Therefore, we tried to investigate the DNA vaccine-elicited immune responses in BALB/c mice.

MATERIALS AND METHODS

We cloned a gene encoding the glyceraldehyde-3-phosphate dehydrogenase (GAPDH) from periodic Brugia malayi into vector pcDNA3.1. Mice were injected at a dosage of 100 μg recombinant plasmid DNA with CpG intramuscular injection and immunized three times at 2-week intervals. pcDNA3.1 and normal saline were used as control. The tissue of muscles at the 4 weeks after the third injection was collected and target genes were detected using RT-PCR. The humoral responses elicited in mice by inoculation with the recombinant plasmid pcDNA3.1-BmGAPDH were detected using a standard ELISA. Two weeks after the third immunization, stimulation index (SI) was measured using the MTT method and the level of secreted IL-4 and INF-g were detected using ELISA.

RESULTS

Specific gene fragment coding GAPDH was amplified and the recombinant plasmid pcDNA3.1-BmGAPDH was constructed. Post-challenge sera from the mice immunized with the DNA vaccine had specific antibody titres of 1:1600 to 1:6400, and the highest titre was observed in the mice that were inoculated by pcDNA3.1-BmGAPDH/CpG at 6 weeks. At 4 weeks after immunization, the spleens of the mice were obviously enlarged. The proliferation of spleen T lymphocytes seen on the MTT assay was higher in the pcDNA3.1-BmGAPDH group than in the control group (P value <0.05). The levels of IL-4 and INF-γ in serums from the immunized mice were significantly higher than that of the control (P value <0.05).

CONCLUSIONS

We conclude that the recombinant eukaryotic plasmid pcDNA3.1-BmGAPDH could elicit humoral and cellular immune responses in mice.

Microthrombosis after experimental subarachnoid hemorrhage: time course and effect of red blood cell-bound thrombin-activated pro-urokinase and clazosentan

Delayed cerebral ischemia (DCI) is a significant cause of morbidity and mortality for patients surviving the rupture of an intracranial aneurysm. Despite an association between vasospasm and DCI, thrombosis and thromboembolism may also contribute to DCI. In this study we investigate the time course of intravascular microclot formation after experimental subarachnoid hemorrhage (SAH) and assess the effects of the following two drugs on microclot burden: mutant thrombin-activated urokinase-type plasminogen activator (scFv/uPA-T), which is bound to red blood cells for use as a thromboprophylactic agent, and clazosentan, an endothelin antagonist. In the first study, adult male C57BL/6 mice were sacrificed at 24 (n=5), 48 (n=6), 72 (n=8), and 96 (n=3) hours after SAH induced by filament perforation of the anterior cerebral artery. Sham animals (n=5) underwent filament insertion without puncture. In the second study, animals received scFv/uPA-T (n=5) 3 hours after hemorrhage, clazosentan (n=5) by bolus and subcutaneous pump after SAH just prior to skin closure, or a combination of scFv/uPA-T and clazosentan (n=4). Control (n=6) and sham (n=5) animals received saline alone. All animals were sacrificed at 48 hours and underwent intra-cardiac perfusion with 4% paraformaldehyde. The brains were then extracted and sliced coronally on a cryostat and processed for immunohistochemistry. An antibody recognizing thrombin-anti-thrombin complexes was used to detect microclots on coronal slices. Microclot burden was calculated for each animal and compared among groups. Following SAH, positive anti-thrombin staining was detected bilaterally in the following brain regions, in order of decreasing frequency: cortex; hippocampus; hypothalamus; basal ganglia. Few microclots were found in the shams. Microclot burden peaked at 48 hours and then decreased gradually. Animals receiving scFv/uPA-T and scFv/uPA-T+clazosentan had a lower microclot burden than controls, whereas animals receiving clazosentan alone had a higher microclot burden (p<0.005). The overall mortality rate in the time course study was 40%; mortality was highest among control animals in the second study. Intravascular microclots form in a delayed fashion after experimental SAH. Microclots may be safely reduced using a novel form of thromboprophylaxis provided by RBC-targeted scFv/uPA-T and represent a potential target for therapeutic intervention in the treatment of DCI.