Positron annihilation in hydrogen-doped alkali-metal fullerides

Hydrogen-doped alkali-metal fullerides were studied by means of mass-analyzed thermal desorption and positron annihilation. The hydrogen desorption spectra reveal the inclusion of hydrogen in the fullerides as two types of components; one weakly adsorbed and the other strongly bound, probably as hydride ion. The positron lifetime spectra demonstrate that hydrogen-doping to alkali-metal fullerides increases a concentration of higher-order vacancy-type defects, through which more than 50% injected positrons decay with a lifetime of 0.42–0.71 ns.

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.

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.

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.

Suppressive effects of nitric oxide production and inducible nitric oxide synthase (iNOS) gene expression by Calystegia soldanella methanol extract on lipopolysaccharide-activated RAW 264.7 cells

Since nitric oxide (NO) produced by inducible nitric oxide synthase (iNOS) has been found to be involved in various pathophysiological processes, including inflammation and carcinogenesis, the modulators of NO synthesis or expression have been considered as potential anti-inflammatory and cancer chemopreventive agents. In this study, to procure the iNOS inhibitors from natural products, we evaluated 57 methanol extracts of natural products including Korean indigenous plants for the inhibition of NO formation on lipopolysaccharide (LPS)-activated mouse macrophage-like RAW 264.7 cells. As a result, several extracts including those from Actinodaphne lancifolia, Calystegia soldanella, Caryratia japonica, Citrus dachibana, Dystaenia takeshimana, Erysimum aurantiacum, Hovenia undulata, Stewartia koreana and Viburnum awabuki showed potent inhibitory activities of NO production (>70% inhibition at the test concentration of 40 microg/ml). In particular, the extract of Calystegia soldanella showed a potential inhibition of NO production in a dose-dependent manner (IC50=4.3 microg/ml). Subsequent study also exhibited that the extract of Calystegia soldanella significantly suppressed iNOS protein and gene expression in a dose-dependent manner. These results suggest that Calystegia soldanella might be a new potential candidate for developing an iNOS inhibitor from natural products and also could be warranted for further elucidation of active principles for the development of new anti-inflammatory and/or cancer chemopreventive agents.

Role of self-assembled gold nanodots in improving the electrical and optical characteristics of zinc oxide films

We have studied the effect of embedding nanocrystalline Au particles on the electrical and optical characteristics of ZnO films. Au-embedded epitaxial ZnO films were deposited on (0001) sapphire substrates with a pulsed laser deposition technique. The crystalline quality of both the ZnO matrix and Au nanoparticles was investigated by X-ray diffraction and transmission electron microscopy. Composite films were characterized by photoluminescence, optical absorption, and low-temperature electrical resistivity measurements. Photoluminescence spectra of theses films showed a sharp excitonic peak at 3.22 +/- 0.05 eV without any signature of green band emission. Electrical resistivity measurements showed these films to be highly conducting, with a room-temperature resistivity of 3.4 +/- 0.2 m omega-cm.

Transcriptional regulation of interferon gamma gene by p300 co-activator

Interferon gamma (IFN gamma) is an important immunoreguratory protein and is secreted from CD4+, CD8+ T cells and NK cells. Expression of IFN gamma gene is regulated by either DNA-methylation or cis-elements of transcriptional factors such as AP-1, NFAT, AP-4, YY-1, ATF and GATA. At a putative ATF binding site in a promoter region of IFN gamma gene, the position from -59 to -43, is important for the IFN gamma promoter activity. Our gel-shift competition studies demonstrated that addition of antibodies against ATF-2 caused super-shifts of DNA-protein complexes. In addition, it was clarified that p300 was involved in DNA-protein complexes by in vitro "pull-down" experiments. Moreover, a co-expression of p300 and ATF-2 enhanced the promoter activity of IFN gamma gene. Thus, these results indicate that p300 and ATF-2 play critical rules in a basal transcription of IFN gamma gene in Jurkat T cells.

Biofilm formation of Candida albicans on the surfaces of deteriorated soft denture lining materials caused by denture cleansers in vitro

Candidal colonization and subsequent biofilm formation on denture materials are important in the development of pathogenesis, such as denture stomatitis. Routine use of denture cleansers is one of the most effective methods of denture plaque control, although the incompatibility of soft liners and denture cleansers cause damage to the materials. The present study, biofilm formation of Candida albicans on the surfaces of soft denture lining materials, immersed in denture cleansers for 180 days were studied. Seven commercially available soft denture lining materials, were artificially deteriorated by immersion into three commercially available denture cleansers for 180 days, and subsequent fungal growth and biofilm formation were studied by measuring pH of the media and by the use of adenosine triphosphate (ATP) analysis. Fungal biofilm formation on the deteriorated soft liners varied depending upon the combination of the soft liners and denture cleansers. Several combinations of soft liners with denture cleansers exhibited the significantly high colonization capacity as compared with each sample immersed in distilled water, used as individual controls. The relationship between the biofilm formation on the samples of each material and the surface roughness of the soft lining materials was analyzed. However, no significant correlation was observed. The results, taken together, suggested that fungal colonization could be predominantly regulated by the combination of lining material with denture cleansers. In clinical terms, our findings suggests that daily cleansing of soft lining materials with mismatched denture cleansers promoted the subsequent biofilm formation of fungi on the materials.

Changes in surface roughness and colour stability of soft denture lining materials caused by denture cleansers

Soft denture lining materials were immersed into solutions of denture cleansers for 8 h at room temperature, and immersed into distilled water for the remainder of the 24-h period at 37 degrees C. Surface roughness of the soft denture lining materials was measured by contact type surface roughness instrument. For the colour stability test, soft denture lining materials were immersed in the denture cleansers as described above for 180 days. Finally, the colour changes of each material were quantitatively measured by a photometrical instrument to obtain the colour differences between newly processed specimen and immersed specimens (P < 0.01). An autopolymerizing silicone material, Evatouch, exhibited severe changes in surface roughness by all denture cleanser, and the generic material GC Denture Relining showed the minimal changes. Severe colour changes were also observed with some liner and cleanser combinations (P < 0.01). Except for Evatouth, the four silicone soft liners were more stable in surface roughness and in colour change than the two acrylic soft liners. One autopolymerizing silicone (GC denture relining) and one heat curing silicone (Molloplast B) demonstrated the best stability.

Centrosomal abnormalities, multipolar mitoses, and chromosomal instability in head and neck tumours with dysfunctional telomeres

Carcinomas of the head and neck typically exhibit complex chromosome aberrations but the underlying mutational mechanisms remain obscure. Evaluation of cell division dynamics in low-passage cell lines from three benign and five malignant head and neck tumours revealed a strong positive correlation between multipolarity of the mitotic spindle and the formation of bridges at anaphase in both benign and malignant tumours. Cells exhibiting a high rate of mitotic abnormalities also showed several chromosome termini lacking TTAGGG repeats and a high frequency of dicentric chromosomes. Multicolour karyotyping demonstrated a preferential involvement in structural rearrangements of chromosomes with deficient telomeres. The majority of malignant, mitotically unstable tumours expressed the reverse transcriptase subunit of telomerase. These data indicate that some of the genomic instability in head and neck tumours is initiated by telomere dysfunction, leading to the formation of dicentric chromosomes. These form chromosome bridges at mitosis that could prevent the normal anaphase-telophase transition. In turn, this may cause an accumulation of centrosomes and mitotic multipolarity. Telomerase expression does not confer total stability to the tumour genome but could be crucial for moderating the rate of chromosomal evolution.

Synthesis and binding affinities of 2 beta-(3-iodoallyloxycarbonyl)-3 beta-(4-substituted-aryl)tropane analogues as ligands for the dopamine transporter studies

Tropane analogues from cocaine, which is known to be one of the most reinforcing and addictive compounds, were designed, synthesized, and characterized for inhibition of presynaptic uptake of dopamine (DA) in brain. Eight new derivatives of 3 beta-aryl-2 beta-(3-iodoallyloxycarbonyl)tropanes were synthesized and tested for their potential abilities to displace [(3)H]2 beta-carbomethoxy-3 beta-(4-fluorophenyl)tropane (WIN 35,428) binding to the rat striatal membranes.

Nonrandom karyotypic features in basal cell carcinomas of the skin

Cytogenetic analysis of short-term cultured 44 basal cell carcinomas (BCC) revealed clonal karyotypic abnormalities in 38 tumors. Relatively complex karyotypes (at least four structural and/or numerical changes per clone) with unbalanced structural as well as numerical aberrations were found in eight (approximately 21%) of the BCC, while the remaining BCC (79%) had simple karyotypes (1 to 3 aberrations per clone). Numerical changes only were found in 16 tumors, 15 BCC displayed both numerical and structural aberrations, and the remaining 7 BCC showed only structural aberrations. Extensive intratumoral heterogeneity, in the form of cytogenetically unrelated clones, was found in 21 tumors, whereas related subclones were present in 10 tumors. In order to obtain an overall karyotypic picture in BCC, the findings of our previously published 25 BCC have been reviewed. Our combined data indicate that BCC are characterized by nonrandom karyotypic patterns. A large subset of BCC is characterized by nonrandom numerical changes, notably, +18, +X, +7, and +9. Structural rearrangements often affect chromosomes 1, 4, 2, 3, 9, 7, 16, and 17. A number of chromosomal bands are frequently involved, including 9q22, 1p32, 1p22, 1q11, 1q21, 2q11, 4q21, 4q31, 1p36, 2q37, 3q13, 7q11, 11p15, 16p13, 16q24, 17q21, and 20q13. When the genomic imbalance is assessed, it has been shown that several chromosome segments are repeatedly involved in losses, namely loss of the distal part of 6q, 13q, 4q, 1q, 8q, and 9p. A correlation analysis between the karyotypic patterns and the clinico-histopathologic parameters has been undertaken in the 44 BCC of the present series. The cytogenetic patterns show a significant correlation with tumor status (P=.025), that is, that cytogenetically more complex tumors are also those clinically the most aggressive. Also, the frequency of cytogenetically unrelated clones is significantly higher in recurrent BCC than that in primary lesions (P=.05). No clear-cut association has been found between the karyotypic patterns and histologic subtypes or tumor sites.

Improvement of generalization ability for identifying dynamical systems by using universal learning networks

This paper studies how the generalization ability of models of dynamical systems can be improved by taking advantage of the second order derivatives of the outputs with respect to the external inputs. The proposed method can be regarded as a direct implementation of the well-known regularization technique using the higher order derivatives of the Universal Learning Networks (ULNs). ULNs 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 has been derived for the ULNs, in which both the first order derivatives (gradients) and the higher order derivatives are incorporated. First, the method for computing the second order derivatives of ULNs is discussed. Then, a new method for implementing the regularization term is presented. Finally, simulation studies on identification of a nonlinear dynamical system with noises are carried out to demonstrate the effectiveness of the proposed method. Simulation results show that the proposed method can improve the generalization ability of neural networks significantly, especially in terms that (1) the robust network can be obtained even when the branches of trained ULNs are destructed, and (2) the obtained performance does not depend on the initial parameter values.

Cytogenetic and fluorescence in situ hybridization characterization of chromosome 8 rearrangements in head and neck squamous cell carcinomas

Structural rearrangements of chromosome 8 are frequently encountered in squamous cell carcinomas of the head and neck (HNSCC). These aberrations often affect the centromeric region, resulting in the formation of isochromosome i(8q) and whole arm translocations. Some tumors may display structural rearrangements of 8p23. To characterize further the localization of the breakpoints in such rearrangements, 12 HNSCC known to carry pericentromeric rearrangements of chromosome 8 and 8p23 abnormalities were investigated with fluorescence in situ hybridization (FISH) by the use of 15 YAC clones spanning 8p23 and 8p11 to 8q11. FISH confirmed that all, except one, aberrations cytogenetically interpreted to be i(8q) were true, monocentric i(8q). Similarly, all whole-arm translocations appeared as centric fusions. It could thus be concluded that the essential outcome of these rearrangements is genomic imbalances and not rearrangement of genes in the pericentromeric region. By the use of five YAC clones mapping to 8p23, different breakpoints at the molecular level were disclosed in cases with cytogenetically identical 8p23 rearrangements. An evaluation of the genomic imbalances detected in the present series revealed that overrepresentation of 8q material was present in 11 of the 12 tumors. The most commonly gained segment was 8q22 approximately qter, found in all cases with 8q overrepresentation. Loss of parts of or the entire 8p was seen in 10 tumors. The smallest overlapping deleted region was localized to the subtelomeric region of 8p.

Alteration of the coadherence of Candida albicans with oral bacteria by dietary sugars

Interactions between bacterial oral flora and Candida albicans are important in denture plaque formation. This study therefore first aimed to quantify the coadherence of C. albicans and bacteria by the use of a bioluminescent adenosine triphosphate (ATP) assay based on the firefly luciferase-luciferin system. The second aim was to examine the effect of i) dietary sugars (used for preculture) and ii) enzymatic digestion of fungi on the coadherence. When yeast was preincubated in yeast nitrogen base medium (YNB) supplemented with 250 mM glucose, the yeast coadhered with all isolates of Streptoccus mutans and Streptococcus sanguis, and no significant coadhesion was observed with the isolates of Streptococcus sobrinus, Streptococcus salivarius, Lactobacillus and Actinomyces. However, when the yeast was precultured in YNB supplemented with 500 mM galactose, the yeast coadhered with S. salivarius and Actinomyces, which was not observed when the yeast was grown in YNB with glucose. In addition, the coadherence of the yeast with the isolates of S. sanguis was significantly reduced. Enzymatic digestion of yeast and a reverse transcription polymerase chain reaction assay revealed that expression of at least two types of proteinaceous adhesins are involved in these phenomena.

Peroxynitrite leads to arteriolar smooth muscle cell membrane hyperpolarization and low vasoreactivity in severe shock

This paper aimed to study the mechanism of vascular hyporeactivity during severe hemorrhagic shock. Rats were divided into control and shock group. Membrane potential of arteriolar strips was measured with intracellular recording method and membrane potential changes in arteriolar smooth muscle cells (ASMC) were recorded with membrane potential sensitive fluorescent dye (DiBAC4) and confocal microscopy. Hyperpolarization of ASMC membrane appeared at the late stage of shock, which correlated to low vasoreactivity. Glybenclamide, an inhibitor of K(ATP) channel reversed the hyperpolarizing effect. S-nitroso-N-acetylpenicillamine (SNAP), a donor of NO, in a higher concentration (400 mol/l) caused membrane hyperpolarization in control and shock group, which was completely reversed by application of Tiron, a scavenger of O2-. The hyperpolarizing effect of SNAP was decreased by ODQ, glybenclamide and (or) charybdotoxin. It is concluded that hyperpolarization of ASMC leads to vascular hyporeactivity. Peroxynitrite (OONO-) involves in the development of hyperpolarization in severe shock. The production of cGMP and activation of K(ATP) and K(Ca) channel contribute to the hyperpolarizing effect of OONO-*.

Processing procedures of brick tea and their influence on fluorine content

China is the only country that produces brick tea, and more than 90% of the brick tea is consumed in the western minority nationality regions of China. The high fluorine content of brick tea is possibly associated with the special processing procedures, but no investigation has been conducted in this field. To explore the characteristic features of brick tea manufacturing and the alterations in fluorine content during the processing procedures, we performed a field survey involving two brick tea factories and the nearby tea plantations. For the fluorine contents of the initial, intermediate and final processing products, altogether eight types of specimens were collected and determined by using the ion-selective electrode standard curve technique. It was found that the raw material tea leaf for brick tea processing was old, coarse and not the tender delicate tea leaf used for ordinary green or black tea processing. For the fluorine content of the raw material tea leaf, the intermediate and the final products showed that the fresh raw leaf contained a fluorine content as high as 489.31-512.68 mg/kg. During one fermentation-like processing procedure, the fluorine content rose by 4.67% and 1.88% in the specimens from the two factories, respectively, which revealed no statistical significance (P>0.5). These results suggest that the high fluorine content in brick tea might be due to the high content in the raw material and not related with the processing procedures.

[Electric pulse mediated high efficient gene transfer]

OBJECTIVE

To study gene transfer mediated by electric pulse and optimize the parameters of electric pulse in vivo.

METHODS

10 micrograms plasmid pcD2/LacZ was injected into the quadriceps of 220 Kunming mice. One to two minutes after the DNA injection electric pulse with different parameters was given to the injection site. Three days after, activity of beta-galactosidase was measured, and the expression of Laz2 gene in muscle was determined by histochemical staining.

RESULTS

The activity of beta-galactosidase in electric pulse group (131.6 U/mg +/- 86.6 U/mg protein) was 30 fold higher than that in direct injection group (4.9 U/mg +/- 1.0 U/mg protein) (P < 0.05). Histochemical analysis of muscles injected with a LacZ expression plasmid also showed that in vivo electric pulse increased both the number of positively stained muscle fibers and the density of staining. When the electric pulse was with the parameters of 200 V/cm, 40 ms, 6 pulses and 1HZ, maximal gene expression was achieved.

CONCLUSION

Electric pulse, with optimal parameters, increases gene expression. Electric pulse makes much more gene expression than mere intramuscular DNA injection.