Phospholipase D

The performance of the Pathogen Modelling Program, the Food MicroModel, the Murphy-model and the Ross-model for growth of L. monocytogenes was evaluated by comparison with data from 100 seafood challenge tests and data from 13 storage trials with naturally contaminated sliced vacuum-packed cold-smoked salmon. Challenge tests with both cured and noncured products were studied, and graphs as well as the bias- and the accuracy factors were used for comparison of the observed and predicted growth. The Pathogen Modelling Program could not be successfully validated in seafood challenge tests. Growth rates were markedly overestimated and the mu(max)-bias factor was as high as 3.9 in challenge tests with cured products. On the basis of the effect of temperature, NaCl/a(w) and pH, the mu(max)-bias factor of the other three models studied, varied between 1.0 and 2.3 in the challenge tests with cured and noncured seafoods. None of the models accurately predicted the growth in both cured and noncured seafoods. However, the results indicated that a new expanded model, including the additional effect of lactate and phenol, may provide accurate predictions of the growth of L. monocytogenes in challenge tests with various types of seafoods. Storage trials clearly showed the growth of L. monocytogenes in naturally contaminated cold-smoked salmon to be markedly slower than growth in inoculated challenge tests. Consequently, all four models substantially overestimated growth in the naturally contaminated products. Temperature, pH, NaCl/a(w) and lactate were measured in the storage trials and on the basis of these parameters, the Food MicroModel mu(max)-bias factor was 5.2. Clearly, the model could not be successfully validated with naturally contaminated cold-smoked salmon. To improve the applicability of predictive models to fish products, it is suggested to include studies with naturally contaminated products in the development and validation of models with seafood pathogens.     

Short-column liquid chromatography with hydride generation atomic fluorescence detection for the speciation of arsenic

Increasing concerns over human exposure to arsenic and more stringent environmental regulations require rapid determination of trace levels of individual arsenic species, which presents an analytical challenge. We describe a method that is capable of speciating nanogram-per-milliliter levels of arsenite (As(III)), arsenate (As(V)), monomethylarsonic acid (MMAA), and dimethylarsinic acid (DMAA) within 3 min. Speciation of two common inorganic species in drinking water, As(III) and As(V), is complete in 1.5 min. The method is based on a combination of fast high-performance liquid chromatography (HPLC) separation of arsenic species on 3-cm HPLC guard columns and the sensitive detection of arsenic hydride by atomic fluorescence spectrometry. Detection limits for the four arsenic species in urine samples are 0.4-0.8 ng/mL. This simple method allows for the direct speciation of arsenic present in natural water samples and in human urine samples from the general population, with no need of any sample pretreatment. Our results from the determination of arsenic species in urine and water standard reference materials are in good agreement with the certified values of total arsenic concentration. The method has been successfully applied to speciation studies of metabolism of arsenosugars following the consumption of arsenosugar-containing mussels by human volunteers. Speciation of arsenic in urine samples collected from four volunteers after the ingestion of musseles reveals significant increases of DMAA concentration, resulting from the metabolism of arsenosugars. These results suggest that the commonly used biomarkers for assessing human exposure to inorganic arsenic, which are based on the determination of urinary arsenite, arsenate, MMAA, and DMAA, are not reliable when arsenosugar-containing seafood is ingested.     

Electron microscopy of surface structures of Blastocystis sp. from different hosts

Samples of Blastocystis sp. obtained from humans, monkeys, pigs and chickens were examined by scanning electron microscopy and transmission electron microscopy to compare surface structures. The surface coat of Blastocystis sp. cells from each host species showed some morphological variations, but these were not sufficiently different to allow judgement to be made on speciation. The surface structure morphology appeared similar for samples of Blastocystis sp. from the same host species. The surface coat of the cultured human isolate of B. hominis was much thinner than that of cells from fresh human faecal material, and the cell surface appeared to be smoother and without the small projections seen in the fresh forms. Bacteria were frequently found in association with the surface coat of Blastocystis sp. from all fresh faecal material. Possible functions of the surface coat, especially in relation to protection against osmotic shock, are discussed.     

Parasites of fish and risks to public health

A multitude of parasites have been reported in fish, but only a few species are capable of infecting humans. The most important of the helminths acquired by humans from fish are the anisakid nematodes (particularly Anisakis simplex and Pseudoterranova decipiens), cestodes of the genus Diphyllobothrium and digenetic trematodes of the families Heterophyidae, Opisthorchiidae and Nanophyetidae. Seafood-associated infections by acanthocephalans are rarely reported in humans. All of the helminths mentioned above are associated with social-cultural and behavioural factors, in particular the consumption of raw or undercooked seafood. Measures can be taken during harvesting, processing or post-processing (e.g., by the consumer) to mitigate the risks of infection. The seafood industry and government authorities can apply various programmes to reduce these risks, including good manufacturing practices (GMPs) and hazard analysis and critical control point (HACCP) systems. Such measures may include avoiding particular harvest areas, sizes of fish, or even particular species of fish. The method of capture, handling and storage of the catch can directly affect the quality of the seafood with regard to the presence and numbers of parasites. The extent of processing--including heading and gutting, candling and trimming--and the type of product derived (fresh, frozen, salted or pickled) can all contribute to the control of the risks posed by helminths. The most effective means of killing the parasites are either freezing or heat inactivation.     

Intercomparison of analytical methods for arsenic speciation in human urine

An intercomparison exercise was conducted for the quantification of arsenic species in spiked human urine. The primary objective of the exercise was to determine the variance among laboratories in the analysis of arsenic species such as inorganic As (As+3 and As+5), monomethylarsonic acid (MMA), and dimethylarsinic acid (DMA). Laboratories that participated had previous experience with arsenic speciation analysis. The results of this interlaboratory comparison are encouraging. There is relatively good agreement on the concentrations of these arsenic species in urine at concentrations that are relevant to research on the metabolism of arsenic in humans and other mammals. Both the accuracy and precision are relatively poor for arsenic concentrations of less than about 5 micrograms/l.     

The role of seafood in foodborne diseases in the United States of America

In the United States of America, seafood ranked third on the list of products which caused foodborne disease between 1983 and 1992. Outbreaks connected with fish vectors were caused by scombroid, ciguatoxin, bacteria and unknown agents; in shellfish, unknown agents, paralytic shellfish poisoning, Vibrio spp. and other bacteria, followed by hepatitis A virus, were responsible for the outbreaks. At least ten genera of bacterial pathogens have been implicated in seafood-borne diseases. Over the past twenty-five years, bacterial pathogens associated with faecal contamination have represented only 4% of the shellfish-associated outbreaks, while naturally-occurring bacteria accounted for 20% of shellfish-related illnesses and 99% of the deaths. Most of these indigenous bacteria fall into the family Vibrionaceae which includes the genera Vibrio, Aeromonas and Plesiomonas. In general, Vibrio spp. are not associated with faecal contamination and therefore faecal indicators do not correlate with the presence of Vibrio. Viruses are the most significant cause of shellfish-associated disease: in New York State, for example, 33% and 62% of 196 outbreaks between 1981 and 1992 were caused by Norwalk virus and gastrointestinal viruses (small round structured viruses), respectively. In addition, several illnesses are a result of toxic algal blooms, the growth of naturally occurring bacteria and diatoms causing neurotoxic shellfish poisoning, paralytic shellfish poisoning, diarrhoetic shellfish poisoning, amnesic shellfish poisoning and ciguatera. Current estimates place the annual number of ciguatera cases at 20,000 world-wide. Scombroid poisoning is the most significant cause of illness associated with seafood. Scombrotoxin is of bacterial origin and halophilic Vibrio spp. causing high histamine levels are implicated as the source. Scombroid poisoning is geographically diverse and many species have been implicated, namely: tuna, mahi-mahi, bluefish, sardines, mackerel, amberjack and abalone. Temperature abuse has been cited as a major cause of scombroid poisoning. For routine work, the use of faecal indicators to predict the relative level of faecal contamination should not be disposed of. However, the main source of seafood illness is due to species which are not predicted by these organisms. In order to protect public health, routine surveillance using new pathogen-specific techniques such as polymerase chain reaction should be used. This, in combination with risk assessment methods and hazard analysis and critical control points, will begin to address the need for improvement in the safety of seafood.     

Never on a Saturday (or a Sunday): the case against using weekend urine specimens to assess arsenic exposure

The Wisconsin Department of Health and Family Services Bureau of Public Health recently investigated two cases of suspected arsenic poisoning. These cases involved four adults whose urinary arsenic levels ranged from 340 to 1485 ug/L (normal 0-30 ug/L). These findings were initially interpreted as evidence of an ongoing exposure to a toxic form of arsenic, however follow-up investigations determined that all of the urine specimens had been collected on a weekend and that each of these individuals had consumed fish within 48-hours of urine collection. Most of the fish was consumed at "Friday night fish fries" which are a popular tradition at many local restaurants. Urine samples collected after these individuals eliminated fish from their diets contained normal arsenic levels. This report suggests the need for laboratories to differentiate non-toxic forms of arsenic that are present in fish and seafood products from other species of this element. Until more specific analytical methods become available, patients should be instructed to omit fish and seafood from their diets for several days prior to collecting urine for arsenic analysis. In addition, elevated urinary arsenic levels should be interpreted cautiously and exposure to toxic forms should be confirmed before a diagnosis of arsenic poisoning is entertained.     

An individual patient-based meta-analysis of tamoxifen versus ovarian ablation as first line endocrine therapy for premenopausal women with metastatic breast cancer

Total mercury concentration in the muscle of 417 fish of 12 common freshwater and four anadromous species from Bangladesh were low, varying from 2 to 430 ng/g fresh wt. Depending on Hg speciation, three types of accumulation mechanisms were defined. Type I covers the majority of species and describes a pattern widely accepted as 'normal', with increasing levels of organic (methyl) mercury with length (age), combined to a low and constant inorganic level. This accumulation pattern leads to a relative increase of the organic mercury fraction with age, eventually reaching 90-100% of organic mercury in full grown specimens. Type II is found in both planktivorous genera only and showed increasing levels of inorganic mercury combined to low and constant organic mercury levels, leading to a relative decrease in organic mercury fraction with age. This unexpected pattern was only reported in cases of some marine species where it seemed to be linked to demethylation mechanisms or regional influences on Hg levels. A third intermediate accumulation pattern with increasing concentrations of both the organic and the inorganic Hg fraction with age was found in one bottom dwelling species only. The implications of these observations for the accumulation mechanisms of mercury in fish are discussed.     

Influence of Hydrology on Rainfall-Runoff Metal Element Speciation

Examination of speciation for metal elements transported in urban rainfall-runoff events is critical when evaluating the potential fate, bioavailability, and effective control of such constituents. In many urban areas anthropogenic activities result in rainfall pH levels that are acidic and low in alkalinity. As a result, finely abraded metallic components and exposed metal infrastructure can be leached into rainfall-runoff. This study examines the influence of hydrology on storm water metal element speciation at the upper end of a Portland cement concrete small urban watershed. This study focused on Pb, Cd, Cu, and Zn; metal elements commonly found in urban and transportation land uses. For this site partitioning results demonstrated that Cd and Cu partitioned nearly equally between particulate and dissolved phases while Zn was generally particulate-bound and Pb was highly particulate-bound. Utilizing water quality analyses, measured ion balances and speciation modeling, results for Cd and Zn indicated that divalent ionic forms of these metals dominated the dissolved species for all events, while Pb was predominately associated with dissolved organic matter (DOM), and Cu was predominately associated with carbonate species or DOM. Of the three events examined, only the mass-limited events demonstrated a change in speciation during the passage of the hydrograph. Results from this study indicate that effective control of storm water metal elements at the upper end of the urban watershed requires unit operations and processes that account for the ionic, complexed and particulate-bound species and account for the hydrology at the upper end of the urban watershed.     

风电球墨铸铁轮毂的研制

文章分析产品结构特性,选用了科学合理的铸造工艺、化学成分设计,控制球化处理和孕育处理,生产出各项性能符合风电标准要求的球墨铸铁轮毂,取得了较明显的技术经济效果。     

Molecular evolution of the internal transcribed spacers (ITS1 and ITS2) and phylogenetic relationships among species of the family Cucurbitaceae

Phylogenetic relationships of different members of the family Cucurbitaceae were estimated from sequences of the internal transcribed spacer (ITS1 and ITS2) regions of the nuclear ribosomal RNA genes. Twenty-six species of different genera belonging to different tribes and several subtribes were analyzed. The whole ITS regions were amplified by PCR technique and cloned, and three to five different clones of each species were sequenced; for some species PCR products were sequenced directly. ITS1 and ITS2 regions are slightly variable in length, with each length appearing genus-specific. A substitution rate of 3.62 x 10(-9) substitutions per site per year was calculated assuming 40 MYA separation time. Phylogenetic relationships inferred from ITS sequences of some species is in agreement with morphological data, but deviations to the taxonomic classification were also observed. A polyphyletic origin of the New World species must be considered. In the genus Cucurbita different "types" of ITS sequences within one species exist, possibly due to the high frequency of introgression during domestication or due to polyploidization events; in contrast, low intraspecific variability was detectable in the genus Cucumis, indicating different stages of speciation.     

钢丝帘线用A70L钢的研制

钢丝帘线是一种当前国际上迅速发展的新型橡胶制品的增强材料，用其制造钢丝子午胎有明显优点，Ａ７０Ｌ钢就是鞍钢研制的我国第一个帘线钢。试制帘线结果表明，Ａ７０Ｌ具有良好的拉拔和合股性能，可以批量生产多种结构帘线，其性能达到国际先进水平。     

Diploid hybrid speciation in Penstemon (Scrophulariaceae)

Hybrid speciation has played a significant role in the evolution of angiosperms at the polyploid level. However, relatively little is known about the importance of hybrid speciation at the diploid level. Two species of Penstemon have been proposed as diploid hybrid derivatives based on morphological data, artificial crossing studies, and pollinator behavior observations: Penstemon spectabilis (derived from hybridization between Penstemon centranthifolius and Penstemon grinnellii) and Penstemon clevelandii (derived from hybridization between P. centranthifolius and P. spectabilis). Previous studies were inconclusive regarding the purported hybrid nature of these species because of a lack of molecular markers sufficient to differentiate the parental taxa in the hybrid complex. We developed hypervariable nuclear markers using inter-simple sequence repeat banding patterns to test these classic hypotheses of diploid hybrid speciation in Penstemon. Each species in the hybrid complex was genetically distinct, separated by 10-42 species-specific inter-simple sequence repeat markers. Our data do not support the hybrid origin of P. spectabilis but clearly support the diploid hybrid origin of P. clevelandii. Our results further suggest that the primary reason diploid hybrid speciation is so difficult to detect is the lack of molecular markers able to differentiate parental taxa from one another, particularly with recently diverged species.     

Spoilage and shelf-life extension of fresh fish and shellfish

Fresh fish and shellfish are highly perishable products due to their biological composition. Under normal refrigerated storage conditions, the shelf life of these products is limited by enzymatic and microbiological spoilage. However, with increasing consumer demands for fresh products with extended shelf life and increasing energy costs associated with freezing and frozen storage, the fish-processing industry is actively seeking alternative methods of shelf life preservation and marketability of fresh, refrigerated fish and at the same time economizing on energy costs. Additional methods that could fulfill these objectives include chemical decontamination, low-dose irradiation, ultra-high pressure, and modified atmosphere packaging (MAP). This review focuses on the biochemical and microbiological composition of fresh fish/shellfish, the spoilage patterns in these products, factors influencing spoilage, and the combination treatments that can be used in conjunction with refrigeration to extend the shelf life and keeping quality of fresh fish/shellfish. The safety concerns of minimally processed/MAP fish, specifically with respect to the growth of Clostridium botulinum type E, is also addressed.     

Speciation and reduction potentials of metal ions in concentrated chloride and sulfate solutions relevant to processing base metal sulfides

The speciation, Eh-pH and Eh-log a_Cl- dependence of Fe(III), Fe(II), Cu(II), Cu(I), Ag(I), Pb(II), Zn(II), Ni(II), As(III), Sb(III), and Bi(III) ions in practical (high ionic strength) sulfate and chloride solutions are discussed. The emphasis is placed on those ions which form strong sulfato-, chloro-, and hydroxo-complex species. Measured potentials are compared with potentials calculated from reported association and stability constants to test the applicability of these constants in nonideal solutions and to characterize predominant species. Formerly Postgraduate Student, Murdoch University, Perth, Western Australia     

Speciation durations and Pleistocene effects on vertebrate phylogeography

An approach applied previously to avian biotas is extended in this paper to other vertebrate classes to evaluate Pleistocene phylogeographic effects and to estimate temporal spans of the speciation process (speciation durations) from mitochondrial (mt) DNA data on extant taxa. Provisional molecular clocks are used to date population separations and to bracket estimates of speciation durations between minimum and maximum values inferred from genetic distances between, respectively, extant pairs of intraspecific phylogroups and sister species. Comparisons of genetic-distance trends across the vertebrate classes reveal the following: (i) speciation durations normally entail at least two million years on average; (ii) for mammals and birds, Pleistocene conditions played an important role in initiating phylogeographic differentiation among now-extant conspecific populations as well as in further sculpting pre-existing phylogeographic variety into many of today's sister species; and (iii) for herpetofauna and fishes, inferred Pleistocene biogeographic influences on present-day taxa differ depending on alternative but currently plausible mtDNA rate calibrations.     

Review of the STM range of pressure distribution products

STM Healthcare is a division of the Recticel Group which has been actively involved in the production and use of polyurethane foams for the past 40 years, and is now one of Europe's leading manufacturers of polyurethane foam for insulation, packaging, filtration, aerospace, the automotive and furniture industries, domestic and specialist bedding and seating products. STM Healthcare is able to draw upon the wealth of experience and expertise of the manufacturing facilities, enabling products to be developed using the latest environmentally friendly specification foams best suited to the requirements of pressure-reduction technology. All STM Healthcare mattresses, cushions and Linknurse mattresses are manufactured with Safeguard combustion modified high resilience foams. (Linknurse is a licensed product name; products are manufactured by Recticel and distributed by STM).     

国内外羰基镍技术进展及市场展望

本文简述了羰基法精炼镍的技术原理、工艺技术及其产品的主要应用 ,同时对国内外羰基镍技术的进展及市场展望进行了探讨和分析。利用羰基镍 ,由于可以制备出性能各异、形状不同的产品 ,并具有优良的物理和化学特性 ,因此它们是许多领域 ,尤其是高技术产业的重要原料 ,其市场前景十分广阔     

Concentrations of selected contaminants in cabin air of airbus aircrafts

The concentrations of selected air quality parameters in aircraft cabins were investigated including particle numbers in cabin air compared to fresh air and recirculation air, the microbiological contamination and the concentration of volatile organic compounds (VOC). The Airbus types A310 of Swissair and A340 of Lufthansa were used for measurements. The particles were found to be mainly emitted by the passengers, especially by smokers. Depending on recirculation filter efficiency the recirculation air contained a lower or equal amount of particles compared to the fresh air, whereas the amount of bacteria exceeded reported concentrations within other indoor spaces. The detected species were mainly non-pathogenic, with droplet infection over short distances identified as the only health risk. The concentration of volatile organic compounds (VOC) were well below threshold values. Ethanol was identified as the compound with the highest amount in cabin air. Further organics were emitted by the passengers--as metabolic products or by smoking--and on ground as engine exhaust (bad airport air quality). Cleaning agents may be the source of further compounds.     

Hair methylmercury levels in U.S. women

The scientific community has recently focused its concerns on possible developmental delays in infants exposed to methylmercury via maternal fish consumption. In this study, the authors reported levels of methylmercury in hair specimens that corresponded to 2820 monthly seafood consumption diaries recorded by U.S. women of childbearing age. In this study, the geometric mean hair methylmercury level for diarists who reported some seafood consumption was 0.36 ppm (one geometric standard deviation [GSD] range = 0.14-0.90 ppm); the corresponding value for diarists who reported no seafood consumption was 0.24 ppm (one GSD range = 0.09-0.62 ppm). Therefore, the mean hair methylmercury level associated with seafood consumption was 0.12 ppm (one GSD range = 0.05-0.32 ppm). The results of this study provide evidence that levels of methylmercury in the U.S. population are quite low. There is a significant contribution to hair methylmercury from sources other than seafood. It is not likely that maternal hair methylmercury levels in the range found in our study would be associated with adverse health effects in children.