White spot syndrome virus epizootic in cultured Pacific white shrimp Litopenaeus vannamei (Boone) in Taiwan.

White spot syndrome virus (WSSV) has caused significant losses in shrimp farms worldwide. Between 2004 and 2006, Pacific white shrimp Litopenaeus vannamei (Boone) were collected from 220 farms in Taiwan to determine the prevalence and impact of WSSV infection on the shrimp farm industry. Polymerase chain reaction (PCR) analysis detected WSSV in shrimp from 26% of farms. Juvenile shrimp farms had the highest infection levels (38%; 19/50 farms) and brooder shrimp farms had the lowest (5%; one of 20 farms). The average extent of infection at each farm was as follows for WSSV-positive farms: post-larvae farms, 71%; juvenile farms, 61%; subadult farms, 62%; adult farms, 49%; and brooder farms, 40%. Characteristic white spots, hypertrophied nuclei and basophilic viral inclusion bodies were found in the epithelia of gills and tail fans, appendages, cephalothorax and hepatopancreas, and virions of WSSV were observed. Of shrimp that had WSSV lesions, 100% had lesions on the cephalothorax, 96% in gills and tail fans, 91% on appendages and 17% in the hepatopancreas. WSSV was also detected in copepoda and crustaceans from the shrimp farms. Sequence comparison using the pms146 gene fragment of WSSV showed that isolates from the farms had 99.7-100% nucleotide sequence identity with four strains in the GenBank database--China (AF332093), Taiwan (AF440570 and U50923) and Thailand (AF369029). This is the first broad study of WSSV infection in L. vannamei in Taiwan.

Koi herpesvirus epizootic in cultured carp and koi, Cyprinus carpio L., in Taiwan.

Koi herpesvirus (KHV) poses a significant threat to cultured koi and common carp, both Cyprinus carpio L. Since the first reported case in Israel in 1998, KHV has rapidly spread worldwide. This study investigates the spread of KHV to Taiwan by collecting 49 cases of suspected common carp and koi infections from 2003 to 2005 for analysis. Clinical signs included lethargy, anorexia, increased respiratory movements and uncoordinated swimming. Hyperaemia, haemorrhage on body surface and necrotic gill filaments were recorded. Gill epithelial hyperplasia, necrosis and eosinophilic intranuclear inclusion bodies were observed by histological examination, while virions were detected using transmission electron microscopy. By detecting the presence of the KHV thymidine kinase (TK) gene and the KHV 9/5 gene using polymerase chain reaction (PCR), 37 cases were identified as KHV-positive, and the cumulative mortality of infected fish was 70-100%. Positive cases showed identical sequences for the genes analysed, implying that they were of the same origin. For the KHV 9/5 gene sequence, these cases exhibited 100% identity with the Japanese strain (TUMST1, accession number AP008984) and 99% identity with the Israeli (KHV-I, DQ177346) and US (KHV-U, DQ657948) strains. Additionally, a loop-mediated isothermal amplification (LAMP) assay was performed and found to be more sensitive than PCR tests, suggesting its potential use as a rapid diagnostic method for KHV. This is the first epidemiological study of KHV infection in cultured common carp and koi in Taiwan.

Micromechanics of wastewater sludge floc: force-deformation relationship at cyclic freezing and thawing.

This study examined shape changes in two typical wastewater flocs subjected to cyclic freezing and thawing and the associated force exerted by the ice front. While freezing, the engulfing ice front gradually pulled the floc apart. Subsequent thawing only partially restored the floc's shape. By the Maxwell model, used to interpret gross shape deformations, both flocs were visco-elastic objects exhibiting time-varying rheological characteristics which were more viscous than elastic. Detailed observations of floc 1 deformation demonstrated a two-stage force-displacement relationship. Following 1 cycle of freezing and thawing, the interior structure of the floc deteriorated and the force required to elongating a unit length of floc decreased by 60%. The original floc 2 had a dense "core" and loose "tail"; the core was more resistant to deformation under normal stress than the loose tail. Although both flocs had similar shapes and sizes and were acquired from the same activated sludge stream at a wastewater treatment plant, their rheological behaviors differed substantially. A comprehensive theoretical model for freezing and thawing processes should incorporate these rheological characteristics as they corresponded to observed structural changes and reduction in bound water content in sludge following a cyclic treatment of freezing and thawing.

A kinetic analysis of the repair of radiation-induced DNA double-strand breaks.

The repair of radiation-induced DNA double-strand breaks (DSBs) is analyzed kinetically. It is assumed that a fraction of the damaged sites in the DNA duplex are irreparable. The kinetic model takes the effect of radiation dose into account. The analysis of the available experimental data reveals that, although the number of irreparable DSBs is a quadratic function of radiation dose, the normalized number of irreparable DSBs correlates linearly with this variable.

A theoretical analysis of a new drug delivery system: a cylindrical device with a vertical opening on its surface.

A theoretical analysis of a proposed drug delivery device is presented. The device is of cylindrical shape with an opening on its side surface. Analytical expressions for the temporal variations in the amount of drug released and the size of the unreleased portion of the device are derived. The result of numerical simulation reveals that an approximately zero-order mechanism can be obtained, provided that the device is designed appropriately. The applicability of the analytical expressions derived is justified by examining the release of sodium salicylate embedded in polyethylene. The present work is a generalization of analyses suggested previously for some similar devices.

The impact of the addition of naloxone on the use and abuse of pentazocine.

An epidemic of abuse with "T's and blues" began in the late 1970's in which pentazocine-Talwin tablets ("T")--and the antihistamine tripelennamine (known as blues) were crushed, dissolved together, filtered, and injected intravenously. The resulting high was reported to be similar to that of heroin. In 1981, the manufacturer and the Food and Drug Administration met to discuss a possible solution. As a result, 0.5 mg of naloxone hydrochloride, a narcotic antagonist that is pharmacologically inactive at that dose orally but active if administered parenterally, was added to the tablet formulation. The reformulated product, Talwin Nx, was approved for marketing in late 1982 and introduced in the second quarter of 1983. Distribution of Talwin tablets in the United States was discontinued. The Drug Abuse Warning Network (DAWN) of the National Institute of Drug Abuse and IMS America's National Prescription Audit were used to review the use and abuse patterns of pentazocine before and after the naloxone intervention. The number of prescriptions dispensed quarterly for pentazocine products remained fairly stable from 1981 through the first quarter of 1983 and increased after the introduction of Talwin Nx. In contrast, DAWN emergency room and medical examiner mentions decreased after the product reformulation. The rates of both emergency room and medical examiner mentions per million prescriptions were substantially lower in the 2 years following the introduction of Talwin Nx (decreases of 70 percent by emergency rooms and 71 percent by medical examiners), indicating that the product reformulation successfully reduced pentazocine abuse.

A stochastic analysis of the repair of radiation-induced DNA double-strand breaks.

A three-state stochastic model is described for the repair of radiation-induced double-strand breaks (DSBs) in DNA. If irradiated, a site or region in DNA is assumed to be in a potentially damaged state; this site may either become permanently damaged or be repaired after a certain period of time. The result of the analysis of the available experimental data reveals that the present two-parameter model is capable of interpreting the rapid decrease in the number of DSBs in the initial period, which cannot be predicted by previously proposed models. The stochastic analysis yields not only the temporal variation of the mean of the number of DSBs but also its variance, and therefore is a generalization of the conventional deterministic models.

Effect of household preparation on levels of pesticide residues in produce.

In 1993, the National Academy of Sciences released a report on the effects of pesticides in the diets of infants and children, indicating that current tolerances do not take into account the eating habits and metabolism of young children. In response to that report, a study was undertaken to determine pesticide residues in raw agricultural commodities at levels below the tolerances established by the Environmental Protection Agency. The objective of the study was to determine whether normal household washing, peeling, and cooking procedures had any effect on pesticide residue levels. Low levels of pesticide residues were detected in 97 (40%) of the 243 samples analyzed. The number of samples containing detectable residues dropped to 47 (19%) after household preparation. Results indicate that residue levels in most commodities are substantially reduced after household preparation.

Analytical methods for detection of nonoccupational exposure to pesticides.

An analytical protocol is developed to analyze for 33 compounds in ambient air around the household, drinking water, and from dermal contact while applying pesticides. Soxhlet extraction is used on both the polyurethane foam plugs, which were used as air sample trapping media, and the gloves reflecting dermal contact. The extraction procedure of U.S. Environmental Protection Agency (EPA) Method 608 is used for water samples. A stringent gas chromatography/electron capture detection (GC/ECD) and gas chromatography/mass spectroscopy/multiple ion detection (GC/MS/MID) analytical approach parallel to the procedures of the current EPA contract laboratory program is used for analysis.

A parallel fuzzy inference model with distributed prediction scheme for reinforcement learning.

This paper proposes a three-layered parallel fuzzy inference model called reinforcement fuzzy neural network with distributed prediction scheme (RFNN-DPS), which performs reinforcement learning with a novel distributed prediction scheme. In RFNN-DPS, an additional predictor for predicting the external reinforcement signal is not necessary, and the internal reinforcement information is distributed into fuzzy rules (rule nodes). Therefore, using RFNN-DPS, only one network is needed to construct a fuzzy logic system with the abilities of parallel inference and reinforcement learning. Basically, the information for prediction in RFNN-DPS is composed of credit values stored in fuzzy rule nodes, where each node holds a credit vector to represent the reliability of the corresponding fuzzy rule. The credit values are not only accessed for predicting external reinforcement signals, but also provide a more profitable internal reinforcement signal to each fuzzy rule itself. RFNN-DPS performs a credit-based exploratory algorithm to adjust its internal status according to the internal reinforcement signal. During learning, the RFNN-DPS network is constructed by a single-step or multistep reinforcement learning algorithm based on the ART concept. According to our experimental results, RFNN-DPS shows the advantages of simple network structure, fast learning speed, and explicit representation of rule reliability.

Comparison of neutralizing antibody and cell-mediated immune responses to pandemic H1N1 2009 influenza virus before and after H1N1 2009 influenza vaccination of elderly subjects and healthcare workers.

BACKGROUND: The recent H1N1 pandemic virus that emerged in 2009 resulted in high morbidity rates mainly in younger individuals, albeit with relatively low mortality. We investigated both humoral and cellular immune responses against the pandemic H1N1 2009 virus before and after immunization with inactivated H1N1 2009 vaccine. METHODS: We obtained paired blood specimens from a cohort of participants from nursing homes (n=108) and a public hospital (n=60) in Singapore. Serum samples were tested for neutralizing antibodies against H1N1 2009 using microneutralization assays, while peripheral blood mononuclear cells were subjected to interferon-γ enzyme-linked immunosorbent spot (ELISPOT) assays for whole virus-specific T-cell responses. RESULTS: We observed significant increases in geometric mean titers of neutralizing antibodies after H1N1 2009 vaccination (from 23.6 pre-vaccination to 94.7 post-vaccination). Approximately 77% and 54% of the cohort exhibited ≥2-fold and ≥4-fold increases in neutralizing antibody titers following vaccination; 89.9% of the cohort had a post-vaccination antibody titer of ≥32. Adjusted for gender, participants aged ≥60 years were less likely to have a ≥4-fold increase in antibody titers after vaccination than those aged <60 years (0.48; 95% confidence interval (95% CI) 0.32-0.71, p=0.007). There was a 1.4-fold elevation in H1N1 2009-specific T-cell responses after vaccination (p<0.05). Adjusted for gender, age ≥60 years was positively associated with a greater increase in T-cell response (ß=4.9, 95% CI 1.58-8.29, p=0.018). No significant correlation was observed between humoral and cellular immune responses. CONCLUSIONS: Influenza vaccination elicits significant neutralizing antibody and T-cell responses to pandemic H1N1 2009 influenza virus. However, in response to vaccination, increases in neutralizing antibody titers were comparatively lower but T-cell responses were higher in older participants. Therefore, our study suggests that memory T-cells may play a crucial role in protecting older individuals against pandemic H1N1 2009 infection.

Boundary effect on electrophoresis in a Carreau fluid: simulated biocolloids at an arbitrary position in a charged spherical cavity.

The electrophoresis of a charge-regulated spherical particle, which mimics biocolloids and particles covered by an artificial membrane, at an arbitrary position in a spherical cavity filled with a shear-thinning Carreau fluid is modeled under the conditions of low surface potential and weak applied electric field. We examine simultaneously the influences of the presence of a boundary, the nature of the fluid, and the charged conditions on the boundary and the particle surface on the electrophoretic behavior of the particle. The mobility of the particle in a shear-thinning Carreau fluid is larger than that in the corresponding Newtonian fluid, and the difference between the two increases with increasing mobility. For the present case, the particle is negatively charged, and due to the presence of an electroosmotic flow, the electrophoretic behavior of the particle for the case where the boundary is positively charged is more complicated than that when it is uncharged or negatively charged. The factors key to the mobility of the particle include the position and the relative size of the particle, the thickness of double layer, the nature of the fluid, the density of the dissociable functional groups on the particle surface and the associated equilibrium constant, and the pH of the bulk phase.

Electrophoresis of a charge-regulated sphere at an arbitrary position in a charged spherical cavity.

The electrophoresis of a charge-regulated spherical particle at an arbitrary position in a charged spherical cavity is modeled under conditions of low surface potential (<25 mV) and weak applied electric field (<25 kV/m). The charged cavity allows us to simulate the effect of electroosmotic flow, and the charge-regulated nature of the particle permits us to model various types of surface. The problem studied previously is reanalyzed based on a more rigorous electric force formula. In particular, the influences of various types of charged conditions on the electrophoretic behavior of a particle and the roles of all the relevant forces acting on the particle are examined in detail. Several new results are found. For instance, the mobility of a particle has a local minimum as the thickness of a double layer varies, which is not seen in the cases where the surface of a particle is maintained at a constant potential and at a constant charge density.

Engulfed pathogen-induced apoptosis in haemocytes of giant freshwater prawn, Macrobrachium rosenbergii.

Haemocytes of the giant freshwater prawn, Macrobrachium rosenbergii, were investigated for the induction of apoptosis after phagocytosis of pathogenic yeasts, bacteria and non-pathogenic latex beads in vitro. Isolated haemocytes of M. rosenbergii were cultured at a ratio of 1:50 haemocytes to pathogen with the yeast Debaryomyces hansenii, the bacteria Aeromonas hydrophila or Enterococcus faecium, or with latex beads at 25 degrees C for 2 h, followed by washing to remove free particles. At least 200 haemocytes were counted to determine the phagocytosis rate, and the results showed that haemocytes engulfed latex beads at a higher rate than the aquatic pathogens. By transmission electron microscopy, the yeast- or bacterium-engulfing haemocytes displayed morphological changes characteristic of apoptosis, including formation of cytoplasmic vacuoles, chromatin condensation and fragmentation of nuclei. This pathogen-induced apoptosis was further confirmed by DNA laddering and TUNEL (terminal deoxynucleotidyl transferase-mediated deoxy-UTP nick-end-labelling) assays. Neither haemocytes treated with latex beads nor uninfected haemocytes (control group) showed signs of apoptosis after 48 h in culture.

Stochastic modeling of bacterial adhesion: a two-step mechanism with linear adhesion rate.

Stochastic analysis of bacterial adhesion onto the surface of solid substrate is presented. Bacterial adhesion is assumed to occur in two steps: (i) a reversible adhesion between bacteria and solid surface; bacteria on the surface are weakly bound during this period, followed by (ii) an irreversible surface reaction which results in a strong binding force between bacteria and the surface; bacteria are considered to be in adhered form at this stage. The stochastic representation provides both the macroscopic and fluctuating information about the transient behavior of the phenomenon under consideration.

Estimation and hypothesis testing of treatment effects in animal reproductive toxicology studies.

Healy (1) and Dempster et al. (8) proposed statistical methods to evaluate the treatment effects in animal reproductive toxicology research. Both methods assume homogeneous variance for the dams and the pups, respectively, in all the treatment groups. In this paper, via mixed effect modeling, we propose a method to estimate the treatment effects allowing heterogeneous variances for the dams and the pups, respectively, in different treatment groups. Covariates will also be included in the model. A procedure to test the fixed effects is also discussed. An example from an animal reproductive toxicological study is used to illustrate the procedures.

Removal of cadmium ions in wastewater through biosorption.

Cadmium ions in wastewater can be removed by biosorption on to Acinetobacter calca var. antratus, isolated from a wastewater sample from a copper refinery. There are two equillibrium states: the first, which is reached quickly, is probably direct adsorption, and the second may be due to the release of ion adsorption materials by lysed cells.

Modeling the repair of radiation-induced DNA double-strand breaks.

A problem often overlooked in the study of the repair of radiation-induced DNA double-strand breads (DSBs) is the question of what the status of a regular site is in the DNA duplex immediately after a radiation treatment. Here, we suggest a mixed repair mechanism which consists of a gradual process and an instantaneous process. A comparison of the present kinetic model with those which have appeared in the literature shows that the former is a generalization of the latter. We have shown that different repair mechanisms may lead to equivalent mathematical representations. Therefore, care must be taken in interpreting the repair mechanism on the basis of the experimentally observed transient number of DSBs.

Kinetics of bacterial adhesion--a stochastic analysis.

In a previous work (Hsu & Wang, 1986), a birth-death type of stochastic model was proposed to analyze bacterial adhesion onto the substrate surface. The model is based upon the assumption that the number of available active sites on the substrate surface is relatively large compared to that of the cells in the system. This assumption is relaxed in the present study, and thus, the problem is considered in a more rigorous manner. The transient behavior of bacterial adhesion is examined through simulation studies. It is found that the present stochastic model should be employed when the number of available active sites is less than or on the same order of magnitude as that of the cells.