An active 2-d silicon cochlea

In this paper, we present an analog integrated circuit design for an active 2-D cochlea and measurement results from a fabricated chip. The design includes a quality factor control loop that incorporates some of the nonlinear behavior exhibited in the real cochlea. This control loop varies the gain and the frequency selectivity of each cochlear resonator based on the amplitude of the input signal.

The mitotic checkpoint kinase NEK2A regulates kinetochore microtubule attachment stability

Loss or gain of whole chromosome, the form of chromosome instability commonly associated with cancers is thought to arise from aberrant chromosome segregation during cell division. Chromosome segregation in mitosis is orchestrated by the interaction of kinetochores with spindle microtubules. Our studies show that NEK2A is a kinetochore-associated protein kinase essential for faithful chromosome segregation. However, it was unclear how NEK2A ensures accurate chromosome segregation in mitosis. Here we show that NEK2A-mediated Hec1 (highly expressed in cancer) phosphorylation is essential for faithful kinetochore microtubule attachments in mitosis. Using phospho-specific antibody, our studies show that NEK2A phosphorylates Hec1 at Ser165 during mitosis. Although such phosphorylation is not required for assembly of Hec1 to the kinetochore, expression of non-phosphorylatable mutant Hec1(S165) perturbed chromosome congression and resulted in a dramatic increase in microtubule attachment errors, including syntelic and monotelic attachments. Our in vitro reconstitution experiment demonstrated that Hec1 binds to microtubule in low affinity and phosphorylation by NEK2A, which prevents aberrant kinetochore-microtubule connections in vivo, increases the affinity of the Ndc80 complex for microtubules in vitro. Thus, our studies illustrate a novel regulatory mechanism in which NEK2A kinase operates a faithful chromosome attachment to spindle microtubule, which prevents chromosome instability during cell division.

Universal learning network and its application to robust control

Universal learning networks (ULNs) and robust control system design are discussed, ULNs provide a generalized framework to model and control complex systems. They consist of a number of interconnected nodes where the nodes may have any continuously differentiable nonlinear functions in them and each pair of nodes can be connected by multiple branches with arbitrary time delays. Therefore, physical systems which can be described by differential or difference equations and also their controllers can be modeled in a unified way. So, ULNs constitute a superset of neural networks or fuzzy neural networks. In order to optimize the systems, a generalized learning algorithm is derived for the ULNs, in which both the first order derivatives (gradients) and the higher order derivatives are incorporated. The derivatives are calculated by using forward or backward propagation schemes. These algorithms for calculating the derivatives are extended versions of back propagation through time (BPTT) and real time recurrent learning (RTRL) by Williams in the sense that generalized nonlinear functions and higher order derivatives are dealt with. As an application of ULNs, the higher order derivative, one of the distinguished features of ULNs, is applied to realizing a robust control system in this paper. In addition, it is shown that the higher order derivatives are effective tools to realize sophisticated control of nonlinear systems. Other features of ULNs such as multiple branches with arbitrary time delays and using a priori information will be discussed in other papers.

A new control method of nonlinear systems based on impulse responses of universal learning networks

A new control method of nonlinear dynamic systems is proposed based on the impulse responses of universal learning networks (ULNs), ULNs form a superset of neural networks. They consist of a number of interconnected nodes where the nodes may have any continuously differentiable nonlinear functions in them and each pair of nodes can be connected by multiple branches with arbitrary time delays. A generalized learning algorithm is derived for the ULNs, in which both the first order derivatives (gradients) and the higher order derivatives are incorporated. One of the distinguished features of the proposed control method is that the impulse response of the systems is considered as an extended part of the criterion function and it can be calculated by using the higher order derivatives of ULNs. By using the impulse response as the criterion function, nonlinear dynamics with not only quick response but also quick damping and small steady state error can be more easily obtained than the conventional nonlinear control systems with quadratic form criterion functions of state and control variables.

An address-event vision sensor for multiple transient object detection

We present a vision sensor chip designed to detect multiple transient objects - objects that either move or change in light intensity - and output their locations using address-event representation. The sensor uses a novel onset detector to detect transient objects and a dynamically-wired winner-takes-all circuit to group pixels and select the brightest pixel in each object. This paper describes the circuits and also presents measurements that characterize the performance of the sensor chip.

The effect of saliva or serum on bacterial and Candida albicans colonization on type I collagen

Colonization of Candida albicans on oral surfaces can serve as a reservoir for disseminated infections, such as aspiration pneumonia and gastrointestinal infection, particularly in the immunocompromised host. Therefore, the aim of this study was to investigate the effects of salivary and serum pellicles on C. albicans, Streptococcus mutans, S. sanguis, Lactobacillus and Actinomyces colonization on type I collagen, a major organic component of periodontal ligaments. The colonization potential of two isolates each of C. albicans, S. mutans and S. sanguis, and a single isolate each of Lactobacillus and Actinomyces to uncoated (control), saliva-coated or serum-coated type I collagen plates (surface area 143 mm(2), Cell Disk; Sumitomo, Tokyo, Japan) was examined using a bioluminescent adenosine triphosphate assay based on firefly luciferase-luciferin system. The results revealed that with mutans streptococci, a saliva pellicle was significantly more effective in promoting bacterial colonization compared with the pellicle-free collagen disc, and the serum-coated sample significantly inhibited the colonization of streptococci (anova; P < 0b01). In contrast, in the case of C. albicans, Lactobacillus and Actinomyces isolates, a serum pellicle was significantly more effective in promoting the colonization, followed by saliva pellicle and uncoated specimen (anova; P < 0b01). These results suggested that crevicular fluid rich in seruminous components would promote the colonization of Candida, Lactobacillus and Actinomyces on type I collagen as opposed to streptococci which showed greater avidity to saliva-coated collagen.

Functional characterization of TIP60 sumoylation in UV-irradiated DNA damage response

The histone acetyltransferase TIP60 regulates the DNA damage response following genotoxic stress by acetylating histone and remodeling chromatin. However, the molecular mechanisms underlying the TIP60-dependent response to UV-induced DNA damage remain poorly understood. To systematically analyse proteins that regulate TIP60 activity in response to UV irradiation, we performed a proteomic analysis of proteins selectively bound to TIP60 in response to UV irradiation using mass spectrometry and identified a novel regulatory mechanism by which TIP60 orchestrates transcriptional activation of p53-dependent checkpoint response in UV-irradiated cells. The initial step of this pathway involves UV-induced association of TIP60 with SUMO-conjugation enzymes and site-specific sumoylation of TIP60 at lysines 430 and 451 via Ubc9. This sumoylation initiates the relocation of TIP60 from nucleoplasm to the promyelocytic leukemia body, which is essential for the UV-irradiated DNA damage repair response via a p53-dependent pathway. Significantly, inhibition of TIP60 sumoylation by overexpression of non-sumoylatable mutant abrogates the p53-dependent DNA damage response, demonstrating the importance of TIP60 sumoylation in response to UV irradiation. Our biochemical characterization demonstrated that the sumoylation of TIP60 augments its acetyltransferase activity in vitro and in vivo. Thus, this study shed new light on the function and regulation of TIP60 activity in UV-irradiated DNA damage response.

Biological properties of carbon nanotubes

Carbon nanotubes are novel materials with unique physical and chemical properties, and have been considered for use in numerous technological applications. More recently, attention has turned to the unique biological and medical properties of these materials. In this review, the processing, chemical properties, physical properties, nucleic acid interaction, cell interaction, and toxicologic properties of nanotubes are described. Finally, future directions in this area are discussed.

The effect of paclitaxel-loaded nanoparticles with radiation on hypoxic MCF-7 cells

BACKGROUND AND OBJECTIVE

The inability of radiotherapy to eradicate completely certain human tumours may be due to the presence of resistant hypoxic cells. Several studies have confirmed the radiosensitizing effect of paclitaxel, a microtubular inhibitor. The object of this study was to evaluate the physicochemical characteristics of paclitaxel-loaded nanoparticles, and determine the ability of the released paclitaxel to radiosensitize hypoxic human breast carcinoma cells (MCF-7) with respect to radiation dose.

METHODS

The poly(d,l-lactide-co-glycolide) (PLGA) nanoparticles containing paclitaxel were prepared by o/w emulsification-solvent evaporation method. The morphology of the paclitaxel-loaded nanoparticles was investigated by scanning electron microscopy. The drug encapsulation efficiency (EE) and in vitro release profile were measured by high-performance liquid chromatography. Cell cycle was evaluated by flow cytometry. Cell viability was measured by the ability of single cells to form colonies in vitro.

RESULTS

The prepared nanoparticles were spherical with diameter between 200 and 800 nm. The EE was 85.5%. The drug release pattern was biphasic with a fast release rate followed by a slow one. Co-culture of human breast carcinoma cells (MCF-7) with paclitaxel-loaded nanoparticles demonstrated that released paclitaxel retained its bioactivity to block cells in the G2/M phase of the cell cycle and effectively sensitized hypoxic MCF-7 cells to radiation with radiosensitivity shown to be dependent of radiation dose at levels of dosages studied. The sensitizer enhancement ratio for paclitaxe-loaded nanoparticles at 10% survival is approximately 1.4.

CONCLUSION

This work has demonstrated that paclitaxel can be effectively released from a biodegradable PLGA nanoparticle delivery system while maintaining potent combined cytotoxic and radiosensitizing abilities for hypoxic tumour cells.

Biological activities of a novel selective oestrogen receptor modulator derived from raloxifene (Y134)

BACKGROUND AND PURPOSE

Selective oestrogen receptor (ER) modulators (SERMs) are of great value in the treatment of breast cancer and osteoporosis. The aim of this study was to characterize pharmacologically a new class of SERMs synthesized based on the core structure of raloxifene.

EXPERIMENTAL APPROACH

Competitive receptor binding and luciferase-based reporter methods were used to study the bioactivities of raloxifene analogues, followed by efficacy determination in breast cancer cell proliferation assay. ER antagonist effects were investigated in female rats by measuring uterine and mammary gland growth, using wet weight, BrdU incorporation and terminal end bud (TEB) as indicators.

KEY RESULTS

Five analogues, belonging to two different structural series and display higher binding affinities for ERalpha than ERbeta were functionally evaluated. One such analogue, Y134, exhibited potent antagonist activity at ERs in CV-1 cells cotransfected with plasmids containing ERalpha or ERbeta and oestrogen-response element-driven luciferase. The estimated IC(50) value was 0.52 nM for ERalpha and 2.94 nM for ERbeta, comparable to that of raloxifene. Little cytotoxicity was observed at Y134 concentrations below 10 microM. Y134 suppressed oestrogen-stimulated proliferation of ER-positive human breast cancer MCF-7 and T47D cells. At an identical dose, administered to ovariectomized rats, Y134 was more effective than raloxifene at arresting oestrogen-induced outgrowth of TEB and mammary gland DNA synthesis, but their inhibitory effects on the uterus were comparable.

CONCLUSIONS AND IMPLICATIONS

Y134 is a potent ER antagonist with better mammary gland selectivity than raloxifene and shows potential for development as a new SERM for therapeutic use.

Molecular cytogenetic characterization of the 11q13 amplicon in head and neck squamous cell carcinoma

Amplification of 11q13 DNA sequences and overexpression of CCND1 are common findings in head and neck squamous cell carcinoma (HNSCC), identified in about 30% of the cases. However, little is known about initiation of the amplification and the organization of the amplicon. In order to study the structure of the amplicon in more detail and to learn more about the mechanisms involved in its initiation, prometaphase, metaphase, and anaphase fluorescence in situ hybridization (FISH) with 40 BAC clones spanning a 16-Mb region in chromosome bands 11q12.2 to 11q13.5 was performed in nine HNSCC cell lines with homogeneously staining regions. FISH analysis showed that the size of the amplicon varied among the nine cell lines, the smallest being 2.12 Mb and the largest 8.97 Mb. The smallest overlapping region of amplification was approximately 1.61 Mb, covering the region from BAC 729E14 to BAC 102B19. This region contained several genes previously shown to be amplified and overexpressed in HNSCC, including CCDN1, CTTN, SHANK2, and ORAOV1. The cell lines were also used to study the internal structure of the amplicon. Various patterns of amplified DNA sequences within the amplicon were found among the nine cell lines. Even within the same cell line, different amplicon structures could be found in different cell populations, indicating that the mechanisms involved in the development of the amplicons in HNSCC were more complex than previously assumed. The frequent finding of inverted repeats within the amplicons, however, suggests that breakage-fusion-bridge cycles are important in the initiation, but the fact that such repeats constituted only small parts of the amplicons indicate that they are further rearranged during tumor progression.

Hypoxia-inducible factor 1α cDNA cloning and its mRNA and protein tissue specific expression in domestic yak (Bos grunniens) from Qinghai-Tibetan plateau

Adaptation to hypoxia is regulated by hypoxia-inducible factor 1 (HIF-1), a heterodimeric transcription factor consisting of an oxygen-regulated alpha-subunit and a constitutively expressed beta-subunit. How animals living on Qinghai-Tibetan plateau adapt to the extreme hypoxia environment is known indistinctly. In this study, the Qinghai yak, which has been living at 3000-5000 m altitude for at least two millions of years, was selected as the model of high hypoxia-tolerant adaptation species. The HIF-1alpha ORFs (open reading frames) encoding for two isoforms of HIF-1alpha have been cloned from the brain of the domestic yak. Its expression of HIF-1alpha was analyzed at both mRNA and protein levels in various tissues. Both its HIF-1alpha mRNA and protein are tissue specific expression. Its HIF-1alpha protein's high expression in the brain, lung, and kidney showed us that HIF-1alpha protein may play an important role in the adaptation to hypoxia environment.

Two photon induced polymerization of organic-inorganic hybrid biomaterials for microstructured medical devices

Three-dimensional microstructured medical devices, including microneedles and tissue engineering scaffolds, were fabricated by two photon induced polymerization of Ormocer organic-inorganic hybrid materials. Femtosecond laser pulses from a titanium:sapphire laser were used to break chemical bonds on Irgacure 369 photoinitiator within a small focal volume. The radicalized starter molecules reacted with Ormocer US-S4 monomers to create radicalized polymolecules. The desired structures are fabricated by moving the laser focus in three dimensions using a galvano-scanner and a micropositioning system. Ormocer surfaces fabricated using two photon induced polymerization demonstrated acceptable cell viability and cell growth profiles against B35 neuroblast-like cells and HT1080 epithelial-like cells. Lego-like interlocking tissue engineering scaffolds and microneedle arrays with unique geometries were created using two photon induced polymerization. These results suggest that two photon induced polymerization is able to create medical microdevices with a larger range of sizes, shapes, and materials than chemical isotropic etching, injection molding, reactive ion etching, surface micromachining, bulk micromachining, polysilicon micromolding, lithography-electroforming-replication, or other conventional microfabrication techniques.

The glutamate release inhibitor riluzole attenuates the formation of conditioned place aversion induced by naloxone in rats undergoing a single morphine exposure

Acute morphine exposure has been hypothesized to produce long-lasting central changes that contribute to the withdrawal aversion. We have most recently demonstrated that those changes may involve the glutamatergic system, including multiple classes of receptors. The present study was undertaken to further determine the involvement of the glutamatergic system by examining the effect of riluzole, a glutamate release inhibitor, on the motivational component of withdrawal from acute morphine dependence. The role of the amygdala in the action of riluzole was also assessed. We investigated the effects of riluzole on the conditioned place aversion (CPA) induced by naloxone-precipitated withdrawal from a single morphine exposure 24 h before, and on c-Fos expression within the amygdala during the withdrawal period in rats. Riluzole (2, 4, 8 mg/kg) dose-dependently attenuated the CPA without producing place conditioning itself. This result provided further evidence that glutamatergic mechanisms may be recruited in adaptational changes following acute morphine exposure and play a role in withdrawal aversion. In addition, riluzole appeared to produce nonspecific effects on c-Fos expression by itself, without specifically modifying c-Fos expression following naloxone-precipitated withdrawal in any region of the amygdala examined, suggesting that the amygdala may not serve as a specific site of action for riluzole.

Effect of glutamate receptor antagonists on place aversion induced by naloxone in single-dose morphine-treated rats

The neurobiological mechanism underlying the negative motivational component of withdrawal from acute opiate dependence is far from understood. Our objectives were to determine whether the glutamatergic system is involved in the motivational component of morphine withdrawal in acutely dependent rats and such an involvement is associated with dopaminergic neurotransmission. We examined the effects of various kinds of glutamate receptor antagonists on conditioned place aversion (CPA) induced by naloxone-precipitated withdrawal from a single morphine exposure 24 h before. Furthermore, the influence of pretreatment with the dopamine receptor antagonist haloperidol on those effects of glutamate receptor antagonists was also investigated. CPA was attenuated in a dose-dependent manner by all glutamate receptor antagonists examined including the NMDA receptor antagonists (+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclo-hepten-5,10-imine maleate (MK-801) and phencyclidine hydrochloride (PCP), AMPA receptor antagonist 1-(4-aminophenyl)4-methyl-7,8-methylenedioxy-5H-2,3-benzodiazepine hydrochloride (GYKI 52466), and metabotropic receptor antagonists (+/-)-2-amino-3-phosphonopropionic acid (AP-3) and (+/-)-alpha-methyl-4-carboxyphenylglycine (MCPG). The effects of MK-801, GYKI 52466 and MCPG were blocked by haloperidol. These results suggest that the glutamatergic system involving multiple classes of receptors plays a role in the motivational component of withdrawal from acute morphine dependence, and the function of the glutamatergic system would be closely associated with dopaminergic neurotransmission.

Effects of α4β2 and α7 nicotinic acetylcholine receptor antagonists on place aversion induced by naloxone in single-dose morphine-treated rats

Acute dependence can be observed when naloxone is administered 24 h after even a single dose of morphine, and nicotine attenuates this naloxone-precipitated withdrawal syndrome. This acute dependence has been hypothesized to be associated with a dopaminergic mechanism. In the present study, the role of nicotinic acetylcholine receptor subtypes in the place aversion induced by naloxone in single-dose morphine-treated rats was investigated. Methyllycaconitine (1, 2 and 5 mg/kg), an alpha7 nicotinic acetylcholine receptor subtype inhibitor, significantly and dose dependently inhibited the attenuating effect of nicotine on naloxone-induced place aversion. In contrast, dihydroxy-beta-erithroidine (1, 2 and 5 mg/kg), an alpha4beta2 nicotinic acetylcholine receptor subtype inhibitor, did not have any effect on the attenuating effect of nicotine on naloxone-induced place aversion. These findings suggested that the alpha7 nicotinic acetylcholine receptor subtype is associated with the place aversion induced by naloxone in single-dose morphine-treated rats. Nicotinic acetylcholine receptor subtype inhibitors warrant further study as possible treatment for acute dependence.

Amplification and overexpression of aurora kinase A (AURKA) in immortalized human ovarian epithelial (HOSE) cells

Immortalization is an early and essential step of human carcinogenesis. Amplification of chromosome 20q has been shown to be a common event in immortalized cells and cancers. We have previously reported that gain and amplification of chromosome 20q is a non-random and common event in immortalized human ovarian surface epithelial (HOSE) cells. The chromosome 20q harbors genes including TGIF2 (20q11.2-q12), AIB1 (20q12), PTPN1 (20q13.1), ZNF217 (20q13.2), and AURKA (20q13.2-q13.3), which were previously reported to be amplified and overexpressed in ovarian cancers. Some of these genes may be involved in immortalization of HOSE cells and represent crucial premalignant changes in ovarian surface epithelium. Investigation of the involvement of these genes was examined in four pairs of pre-crisis (preimmortalized) and post-crisis (immortalized) HOSE cells. Overexpression of AURKA (Aurora kinase A), also known as BTAK and STK15, by both real time-quantitative polymerase chain reaction (RT-QPCR) and Western blotting was detected in all the four immortalized HOSE cells examined while overexpression of AIB1 and ZNF217 was observed in two of four immortalized HOSE cells examined. Overexpression of TGIF2 and PTPN1 was not significant in our immortalized HOSE cell systems. The degree of overexpression of AURKA was shown to be closely associated with the amplification of chromosome 20q in immortalized HOSE cells. Fluorescence in situ hybridization (FISH) with labeled P1 artificial clone (PAC) confirmed the amplification of the chromosomal region (20q13.2-13.3) where AURKA resides. DNA amplification of AURKA was also confirmed using semi-quantitative PCR. Our study showed that amplification and overexpression of AURKA is a common and significant event during immortalization of HOSE cells and may represent an important premalignant change in ovarian carcinogenesis.

Expression of c-Fos in the rat central amygdala accompanies the acquisition but not expression of conditioned place aversion induced by withdrawal from acute morphine dependence

Conditioned reinforcement is hypothesized to be critically involved in drug addiction as a factor contributing to compulsive drug use and relapse. The present study focused on the neurobiology involved in the acquisition and expression of conditioned reinforcing effects of morphine withdrawal employing a conditioned place aversion (CPA) paradigm in acute-dependent rats. Expression of c-Fos in the amygdala (the central nucleus, CeA; the medial nucleus, MeA; the basolateral nucleus, BLA) following naloxone-precipitated withdrawal and the CPA test was examined using a range of naloxone doses (0.02, 0.05, 0.1, 0.2, 0.5 and 1.0 mg/kg). Naloxone dose-dependently produced CPA in rats given a single morphine exposure. In CeA, but not MeA with high-level constitutive neuronal activity, the naloxone-induced modification in c-Fos immunoreactivity following morphine pretreatment exhibited a dose-dependent pattern similar to that seen in the behavioral study. On the other hand, none of the three amygdaloid nuclei examined including CeA, MeA and BLA showed notable sensitivity of c-Fos to the conditioned withdrawal stimulus. These results suggest that CeA may play a role in the negative affective aspect of withdrawal from acute dependence, and in part suggest that the acquisition and expression of CPA may involve different neurobiological mechanisms.

Withdrawal-induced c-Fos expression in the rat centromedial amygdala 24 h following a single morphine exposure

RATIONALE

An opiate antagonist was found to induce motivational withdrawal signs 24 h or even up to 48 h after a single dose of morphine in rats.

OBJECTIVE

The present study was undertaken to determine whether such a withdrawal state would modify the neuronal activity in the brain.

METHODS

A conditioned place aversion was established following a one-trial paradigm in rats undergoing a single exposure to morphine (10 mg/kg) 24 h prior to naloxone administration (0.5 mg/kg). Subsequently, the expression of the protein product of c-fos gene (c-Fos) following naloxone administration was measured within the extended amygdala.

RESULTS

A significant increase in c-Fos immunoreactivity was seen in the centromedial amygdala (CMA), but not in the bed nucleus of the stria terminalis (BST) and the shell (AcbSh) of the nucleus accumbens (Acb) in rats treated with both morphine and naloxone. Further examination of the distribution of c-Fos-positive neurons along the rostrocaudal axis within CMA showed that the positive neurons distributed throughout this brain area and the caudal level of its central division (the central nucleus of the amygdala, CeA) exhibited the most robust labeling.

CONCLUSIONS

Neuronal activity can be increased by naloxone at a dose that produces conditioned place aversion 24 h after a single morphine exposure. CMA, particularly the caudal level of its central division, was of high sensitivity. The current data also suggest a possible involvement of CMA in negative motivational component of precipitated withdrawal from acute morphine dependence.

Proximal versus distal hyperplastic polyps of the colorectum: different lesions or a biological spectrum?

BACKGROUND

Because of their suggested link with microsatellite instability high colorectal cancers, right sided hyperplastic polyps (HPs) may differ from their distally located counterparts. This is highlighted by the recognition of a variant HP, termed sessile serrated adenoma (SSA), which predominates in the proximal colon. HPs displaying the morphological features now associated with SSAs have been shown to have altered expression of "cancer associated" markers, but no studies have investigated whether this is dependent on anatomical location of the polyps.

AIMS

To evaluate morphological and functional features in right versus left sided HPs from patients without colorectal cancer with the aim of identifying distinguishing characteristics.

METHODS

HPs originating in the proximal and distal colorectum were histochemically and immunohistochemically stained to evaluate a panel of markers related to proliferation and differentiation. In addition, a series of morphological features was evaluated for each polyp.

RESULTS

Crypt serration, crypt dilatation, and horizontal crypt growth were more common among HPs from the right side, whereas histochemical factors including mucin changes, global methylation status, and expression of carcinoembryonic antigen were not significantly different. An age disparity was also seen between patients with right versus left sided lesions, with patients with right sided lesions being an average of more than 10 years younger than those with left sided lesions.

CONCLUSIONS

These findings suggest that right and left sided HPs differ mainly in terms of growth regulation rather than cellular differentiation, implying that these lesions belong to a continuous spectrum of serrated polyps that differ quantitatively rather than qualitatively.