Identification of physical parameters controlling the dominance of algal species in a subtropical reservoir

Eutrophication is a serious problem of water resource management in Taiwan. The occurrence of annoying algal species as well as abnormally abundant algal mass threatens the quality of water supply. The growth and decline of a specific phytoplankton species are affected by environmental factors, including light, nutrients, temperature, etc. There have been many investigations on the effects of individual factors on the abundance and composition of algal populations. However, many analyses on the effects of environmental factors, especially the concentration of nutrients, on phytoplankton failed to identify the controlling factors on the dynamic change of the phytoplankton species. This study used statistical methods to isolate the effect of seasons on the phytoplankton growth and searched for the relationships between the nutrient concentrations and the abundance of different algal species in Feitsui Reservoir based on the data obtained from 1995 to 2003. We found that the dynamic change of dominance of some species of phytoplankton was strongly related to the seasonal factors. The controlling factors of the survival of an algal species were the settling and mobility of the phytoplankton, the mixing depth and the vertical mixing strength of the water bodies. According to our preliminary findings, the influence of physical factors, varying seasonally, outweighs the influence of nutrients on the algal species composition in Feitsui Reservoir in Taiwan.

Occurrence of pathogens in raw and ready-to-eat meat and poultry products collected from the retail marketplace in Edmonton, Alberta, Canada

A total of 800 meat and poultry products were purchased from the retail marketplace in Edmonton, Alberta, Canada. The products consisted of raw ground beef, chicken legs, pork chops, and ready-to-eat fermented sausage, roast beef, processed turkey breast, chicken wieners, and beef wieners. The samples were analyzed to determine the prevalence of Shiga toxin-producing Escherichia coli, Salmonella, Campylobacter spp., and Listeria monocytogenes. Shiga toxin-producing E. coli 022: H8 was found in one raw ground beef sample. Salmonella and Campylobacter were found in 30 and 62% of raw chicken legs, respectively. L. monocytogenes was found in 52% of raw ground beef, 34% of raw chicken legs, 24% of raw pork chops, 4% of fermented sausages, 3% of processed turkey breast, 5% of beef wieners, and 3% of chicken wieners. The occurrence of pathogens in this study is similar to that in retail products in many other international locales.

Syngeneic hematopoietic stem cell transplantation for women with metastatic breast cancer

Metastatic breast cancer has been a common indication for autologous hematopoietic stem cell transplantation (HSCT). Previous reports indicate 3-year survival and progression-free survival (PFS) rates after autotransplant to be about 30 and 15%, respectively. Most deaths are from recurrent disease. One potential cause for high relapse rates is graft contamination with tumor. We describe 14 women with metastatic breast cancer transplanted between 1991 and 1998 with hematopoietic cells from identical twins. Median age was 41 y (range 34-50). Most women (12 of 14) were treated with mastectomy, and all received anthracycline-based regimens in their pretransplant course; nine women also received a taxane, seven radiotherapy and three hormonal therapy. Four women were in complete remission (one CR, three CRU) at transplant, five were in partial remission, two had stable disease and two had progressive disease. Eight women have died, one of treatment-related causes and seven of progressive breast cancer. Three-year survival was 48% (21-71%) and 3-year PFS was 21% (5-45%). Although the number of patients is small, outcomes for women transplanted with syngeneic grafts are similar to those of women receiving autologous grafts. This suggests that residual cancer in the patient is the major contributor to relapse after transplantation for breast cancer.

Annual variation in semen characteristics of pigeons (Columba livia)

The purpose of this study was to evaluate annual semen characteristics of pigeons (Columba livia). Ten selected male pigeons, aged 2 to 5 yr were housed under natural environmental conditions, and semen collection was conducted via a digital massage twice weekly throughout the year. The success rate of semen collection in a total of 920 attempts was 40% (371/920) over the whole year. The highest success rate was 69% (55/80) in March followed by 66% (53/80) in November, whereas the lowest rates were in August (13%,10/80) and September (13%, 8/60) (P < 0.01). Volume of the ejaculate averaged 11.0 +/- 0.9 microL (mean +/- SEM). The greatest volume was obtained in November (13.5 +/- 1.0 microL), whereas the least was obtained in August (7.0 +/- 1.0 microL). The average sperm motility was 72 +/- 2% of all ejaculates, of which the highest motility (82 +/- 2%) was observed in March, whereas the least motility (48 +/- 3%) was in August. Sperm viability and sperm motility were positively correlated (r = 0.91; P < 0.01). Maximum sperm concentration was 4.9 +/- 0.4 x 10(9) sperm/mL noted in March, whereas the minimum was 3.8 +/- 0.2 x 10(9) sperm/mL observed in October. Donors generally exhibited susceptible (54%) or dull submission (43%), whereas resistance to handling was rarely observed (3%). During collections, a red (47%) or pink (44%) cloacal membrane was often observed, whereas during only 9% of the collections, the cloacal membrane was pale. When the ambient temperature decreased below 15 C, semen could not be obtained (0/80). A high amount of semen (>10 microL) was obtained when the temperature ranged between 19 and 24 C. Optimal sperm motility (approximately 80%) and viability (>85%) was observed when the temperature was between 18 and 24 C. At temperatures greater than 28 C, sperm motility and viability decreased. Sperm concentration was not significantly influenced by temperature fluctuations. In summary, annual variation in semen characteristics exhibited two peaks per year with mean motility and viability reaching peak annual values in March and November. Both of these months had mean ambient temperatures between 19 and 24 C, a range associated with maximal ejaculatory volumes.

Tissue remodeling of rat pulmonary artery in hypoxic breathing. I. Changes of morphology, zero-stress state, and gene expression

The remodeling of the pulmonary arterial tissue in response to a step change of the oxygen concentration in the gas in which a rat lives was recorded as function of time and function of O2 concentration. Three steps of changing from 20.9% to 17.2%, 13.6%, and 10% O2 were imposed. Earlier work in our laboratory has shown that pulmonary arterial tissue remodeling is significant in the first 24 h after a step change of oxygen tension. Hence we made measurements in this period. Furthermore, data were obtained for tissue remodeling of circumferential and axial lengths of the pulmonary arteries. We recorded the activities of gene expressions in the lung tissues by microarray, determined the dose response curves of gene expression in the homogenized whole lungs with respect to four levels of O2 concentration, and obtained the time courses of gene expression in the lung parenchyma in 30 days after a step decrease of O2 concentration from 20.9% to 10%. We would like to suggest that the correlation of gene expression with physiological function parameters, i.e., time, O2 tension, blood pressure, opening angle, wall thicknesses, etc., is the way to narrow down the search for specific genes for specific physiological functions.

Tissue remodeling of rat pulmonary artery in hypoxic breathing. II. Course of change of mechanical properties

When cells and the matrix of a tissue remodel, the mechanical properties of the tissue do change. The mechanical properties are expressed by constitutive equations. In this article the remodeling of the constitutive equation of the pulmonary artery is studied. The remodeling was induced in a rat breathing a gas whose oxygen concentration was suddenly decreased as a step function of time and maintained constant (17.2%, 13.6%, or 10%) afterwards. Since the mathematical form of the constitutive equation has been identified in earlier papers, we need to determine only the elastic constants that change in the process of tissue remodeling. We consider arteries subjected to blood pressure and longitudinal stretch, and limit ourselves to two-dimensional problems involving only circumferential and longitudinal stress and strain. In the neighborhood of an in vivo state, the perturbations of stresses and strains are related by linear, anisotropic, tensor equations involving three elastic constants: the incremental Young's modulus in the circumferential direction Ythetaz, that in the longitudinal direction Yzz, and the cross modulus Ythetaz. Over a 24 h period, changes of Ythetatheta between 164 and 187 kN/m2, Yzz between 64 and 92 kN/m2, and Ythetaz between 61 and 88 kN/m2 are statistically insignificant.

Development of an ELISA for the detection of serum chromogranin A (CgA) in prostate and non-neuroendocrine carcinomas

INTRODUCTION

Chromogranin A (CgA) is a glycoprotein found in neuroendocrine cells and may be useful as a tumor marker for neuroendocrine tumors.

METHODS

We developed an enzyme-linked immunosorbent assay (ELISA) for serum CgA on a microtiter plate.

RESULTS

We established a reference range for both women and men of different age groups ranging from 20 to 80 years. Men appeared to have a slightly higher serum CgA concentration than women. This slight increase in serum CgA concentration was also found in both gender groups with advancing age. We also detected increased serum CgA in a variety of cancers and non-endocrine carcinomas: the majority of the increased serum CgA was associated with specimens containing highly increased concentration of tumor markers. In other words, increased serum CgA was found at later, more advanced stages of the disease in these patients. For patients with prostate cancer, serum CgA was increased much earlier than serum PSA in approximately one-third of prostate cancer patients developing resistance to hormonal therapy.

CONCLUSIONS

The early rise of serum CgA provides an early signal for prostate cancer patients who developed resistance to hormonal therapy: this advance signal could create a critical window for therapy changes to be made before diseases progress to a fatal stage.

Modeling and analysis of a virus that replicates selectively in tumor cells

Replication-competent viruses have shown considerable promise in overcoming the inefficient gene transduction experienced by traditional gene therapy approaches to cancer treatment. The viruses infect tumor cells and replicate inside them, eventually causing lysis. Virus particles released during lysis are then able to infect other tumor cells, and, in this way, continuous rounds of infection and lysis allow the virus to spread throughout the tumor. Motivated by this novel cancer treatment, we formulate and analyse a system of partial differential equations that is essentially a radially-symmetric epidemic model embedded in a Stefan problem. We compare three, alternative virus-injection strategies: a fixed fraction of cells pre-infected with the virus are introduced throughout the entire tumor volume, within the tumor core, or within the tumor rim. For all three injection methods, simple and accurate conditions that predict whether the virus will control the tumor are derived.

Reproductive performance of a cow-calf herd following a Neospora caninum-associated abortion epidemic

This study examines the long-term impact of a Neospora caninum-associated abortion outbreak in a large cow-calf herd in northern Alberta. Blood samples were collected 4 times from all bred females and heifer calves born during the spring before the outbreak: (1) at the time of the outbreak, (2) the following spring, (3) the subsequent fall, and, finally, (4) the second spring after the outbreak. The samples were analyzed using a commercially available enzyme-linked immunosorbent assay for N. caninum. Calves born immediately following the outbreak were also monitored. Individual calving or abortion records were available from all cows for 2 calving seasons. All cows and heifers were pregnancy tested after the 2 subsequent breeding seasons. At the time of the abortion outbreak in 1997, 81% of all bred females and 87% of the heifer calves were serologically positive. In spring 1998, 49% of the cows and 47% of the heifer calves remained positive. In fall 1998, 48% of the remaining cows and heifers were serologically positive. After the first breeding season following the outbreak (1998), 13.5% of the heifers and 22.2% of the cows were open (not pregnant). Animals that were serologically positive in the spring were more likely to be open in the fall (odds ratio, 2.0; 95% confidence interval, 1.1 to 3.7). No subsequent associations with increased risk of abortion, stillbirth, or nonpregnancy were identified.

Transient vs. prolonged histone hyperacetylation: effects on colon cancer cell growth, differentiation, and apoptosis

The role of histone hyperacetylation in regard to growth, differentiation, and apoptosis in colon cancer cells was assessed in an in vitro model system. HT-29 cells were grown in +/-10% fetal bovine serum with either 5 mM sodium butyrate or 0.3 microM trichostatin A [single dose (T) or 3 doses 8 h apart (TR)] for 24 h. Serum-starved HT-29 cells were further treated with epidermal growth factor or insulin-like growth factor I for an additional 24 h. Apoptosis was quantified with propidium iodide and characterized by electron microscopy. Northern blot analyses were performed with cDNA probes specific for intestinal alkaline phosphatase, Na-K-2Cl cotransporter, the cell cycle inhibitor p21, and the actin control. Flow cytometric analysis revealed a time-dependent growth suppression along with early induction of p21 mRNA in the butyrate, T, and TR groups. Histone hyperacetylation, assessed by acid-urea-triton gel electrophoresis, was transient in the T group but persisted for up to 24 h in the butyrate and TR groups. Induction of apoptosis, growth factor unresponsiveness, and differentiation occurred in the butyrate- and TR-treated cells but not those treated with a single dose of trichostatin A. Thus transient hyperacetylation of histones is sufficient to induce p21 expression and produce cellular growth arrest, but prolonged histone hyperacetylation is required for induction of the programs of differentiation, apoptosis, and growth factor unresponsiveness.

Seroprevalence of Neospora caninum in beef cattle in northern Alberta

Blood samples were collected from 1806 pregnancy-tested cows from 174 herds at a northern Alberta auction mart in the fall of 1998. One hundred sixty-two (9.0%) of these samples were positive for antibodies to N. caninum. Thirty-five of 260 samples (13.5%) collected from the same region in the 1980s were also serologically positive for N. caninum.

The development of a staggered parallel separation liquid chromatography/tandem mass spectrometry system with on-line extraction for high-throughout screening of drug candidates in biological fluids

A new parallel liquid chromatography/tandem mass spectrometry (LC/MS/MS) system has been developed, in which the mass detector was shared between two staggered parallel chromatographic runs. Since the chromatography for biofluids assay generally requires good analyte retention and thus tends to leave large blank chromatographic windows, this parallel system allowed the efficient use of the mass detector during these blank windows, resulting in significantly improved sample throughput. Also, in order to remove the bottleneck in sample extraction for this parallel separation system, a high-flow extraction device was used to perform on-line extraction. This allowed for the direct injection of biofluids onto the system. The performance and capability of this system was evaluated in tests that contained a single analyte (oxazepam) and multiple analytes (12-in-1). The results indicated that the data generated from this system were comparable to those obtained on a conventional single-column system. An application of the system for high-throughput pharmacokinetic screening of drug candidates was also demonstrated.

High-speed liquid chromatography/tandem mass spectrometry using a monolithic column for high-throughput bioanalysis

With the ever-increasing workload from a variety of in vitro and in vivo screening procedures, new analytical methodologies to perform bioanalysis in an accurate and high-throughput manner are in great demand. In this work, monolithic columns were used instead of conventional particulate HPLC columns to perform chromatographic separations. Because the pressure drop on a monolithic column was considerably lower than that on a particulate column, a high flow rate (6 mL/min) was used for a 4.6 x 50 mm monolithic column with a total backpressure of about 61 bar measured using acetonitrile/water (50:50). The capability of using a regular column length at high flow rates, combined with the extremely small dependency of separation efficiency on linear flow velocity, allowed for the generation of sufficient chromatographic resolving power in a significantly reduced runtime. As demonstrated in this work, a plasma extract of a mixture of tempazepam, tamoxifen, fenfluramine, and alprozolam were baseline separated within a total analysis time of one minute. An average peak width at half maximum of approximately one second was noted using a generic broad gradient. It was also found that the separation efficiency and signal/noise (S/N) ratios for this separation remained almost constant at flow rates of 1, 3, and 6 mL/min, respectively. The ruggedness of the separation was evaluated by injecting 600 plasma extracts containing the replicates of a standard curve of the above mixture during an overnight run. The chromatographic retention time, separation quality, peak response and sensitivity were highly reproducible throughout the run. This high-speed liquid chromatography/tandem mass spectrometry (LC/MS/MS) system has been used routinely in the authors' laboratory to support drug discovery programs.

Multiple-sprayer tandem mass spectrometry with parallel high flow extraction and parallel separation for high-throughput quantitation in biological fluids

In this work, an on-line four-column high-flow parallel extraction device was set up and interfaced to a four-column parallel separation system with a four-sprayer tandem mass spectrometric detector. This system allowed for the direct and simultaneous sampling, extraction, separation, and detection of four samples in biological fluids, resulting in significantly increased throughput. The performance of this system was evaluated using rat plasma samples spiked with methotrexate as a test compound. The results showed that the relative standard deviation for responses across the four parallel channels was less than 10% for a concentration range from 10 to 2500 nM, resulting in comparable sensitivity (slope of curve) for the analyte on all channels. A ruggedness test was performed using a mixed set of new and used extraction columns and the relative standard deviation in analyte response was found to be below 15%. The inter-channel crosstalk was measured to be about 0.1%. A comparison between the data generated on this system and on a conventional system for a rat pharmacokinetic study showed no more than 20% difference in measured concentrations. This parallel system is a viable tool for high-throughput bioanalysis in a drug discovery environment.

The processing of coreference for reduced expressions in discourse integration

Three reading-time experiments in Chinese are reported that test contrasting views of how pronominal coreference is achieved. On the one hand, studies of reading time and eye tracking suggest that reduced expressions, such as the pronoun he, serve as critical links to integrate separate utterances into a coherent model of discourse. On the other hand, probe-word recognition studies indicate that full anaphoric expressions, such as a repeated name, are more readily interpreted than reduced expressions due to their rich lexical information, which provides effective cues to match the representation of the appropriate referent in memory. The results indicate that the ease of integrating the critical referent into a model of discourse is a function of the congruence of lexical, semantic, and discourse features conveyed by a syntactically prominent reduced expression within linguistic input. This pattern supports the view that a reduced expression is interpreted on-line and indeed plays a critical role in promoting discourse coherence by facilitating the semantic integration of separate utterances.

Estimation of replicative senescence via a population dynamics model of cells in culture

A simple mathematical model is developed for determining the time-varying fraction of senescent cells in culture in terms of the underlying probability distribution of the number of population doublings until senescence. This functional relationship is inverted, which allows for the estimation of the probability distribution of the number of population doublings until senescence given experimental data on the time-varying fraction of senescent cells. The relationship - in particular, the lag - between these two quantities is analyzed under the assumption that the number of population doublings until senescence follows the Weibull distribution. If the number of population doublings until senescence is geometrically distributed (i.e. the Weibull with shape parameter equal to one) then the cell culture appears immortal.

Dynamic optimization of a linear-quadratic model with incomplete repair and volume-dependent sensitivity and repopulation

PURPOSE

The linear-quadratic model typically assumes that tumor sensitivity and repopulation are constant over the time course of radiotherapy. However, evidence suggests that the growth fraction increases and the cell-loss factor decreases as the tumor shrinks. We investigate whether this evolution in tumor geometry, as well as the irregular time intervals between fractions in conventional hyperfractionation schemes, can be exploited by fractionation schedules that employ time-varying fraction sizes.

METHODS

We construct a mathematical model of a spherical tumor with a hypoxic core and a viable rim, which is most appropriate for a prevascular tumor, and is only a caricature of a vascularized tumor. This model is embedded into the traditional linear-quadratic model by assuming instantaneous reoxygenation. Dynamic programming is used to numerically compute the fractionation regimen that maximizes the tumor-control probability (TCP) subject to constraints on the biologically effective dose of the early and late tissues.

RESULTS

In several numerical examples that employ five or 10 fractions per week on a 1-cm or 5-cm diameter tumor, optimally varying the fraction sizes increases the TCP significantly. The optimal regimen incorporates large Friday (afternoon, if 10 fractions per week) fractions that are escalated throughout the course of treatment, and larger afternoon fractions than morning fractions.

CONCLUSION

Numerical results suggest that a significant increase in tumor cure can be achieved by allowing the fraction sizes to vary throughout the course of treatment. Several strategies deserve further investigation: using larger fractions before overnight and weekend breaks, and escalating the dose (particularly on Friday afternoons) throughout the course of treatment.