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51.
Rapid detection of microbial contamination in frozen vegetables by automated impedance measurements. 总被引:7,自引:0,他引:7
Automated impedance measurements can be used to rapidly assess whether a sample of frozen vegetables contains greater or less than 10(5) organisms per g. Microorganisms growing pureed food samples cause a change in the impedance of the medium when the organisms reach a threshold concentration of between 10(6) and 10(7) organisms per ml. Estimates of the concentration of microorganisms initially present in the food sample can be made by recording the time required for the organisms in the sample to replicate to threshold levels. In this study, the detection times for 357 samples of frozen vegetables were compared with standard plate counts for each sample. The agreement between the two methods in distinguishing samples containing more than 10(5) organisms per g was 92.6% for 257 assorted frozen vegetables and somewhat higher (93 to 96%) when separate cutoff times were used for each type of vegetable. The time required for analysis was about 5 h, compared to the 48 to 72 h required for standard plate counts. 相似文献
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Ernest B. Cady 《Neurochemical research》1996,21(9):1043-1052
Regional cerebral metabolite concentrations, principally of choline-containing compounds (Cho), total creatine (Cr), N-acetylaspartate
(Naa), and lactate (Lac), can be quantified by in vivo proton magnetic resonance spectroscopy. In order to estimate a metabolite
concentration, it is often necessary to measure the transverse relaxation time (T2). Metabolite T2s depend on cytosolic viscosity: as [adenosine triphosphate] falls leading to Na+/K+ pump failure, cytosolic water increases and T2s lengthen. In central grey-matter in human infants, Naa may be almost exclusively neuronal: Naa T2 may index neuronal edema and energy generation. In this preliminary report, metabolite concentrations and T2s have been measured in central grey matter in human infants suspected of perinatal hypoxic-ischemic cerebral injury. In infants
who developed serious cerebral injury or died, [Cho] and [Naa] were low (the latter suggesting neuronal loss), [Lac] and all
metabolite T2s were increased: the Naa T2 increase possibly reflected neuronal edema following failure of energy generation in a fraction of remaining neurons.
Special issue dedicated to Dr. Herman Bachelard. 相似文献
55.
Background
In a number of species males damage females during copulation, but the reasons for this remain unclear. It may be that males are trying to manipulate female mating behaviour or their life histories. Alternatively, damage may be a side-effect of male-male competition. In the black scavenger or dung fly Sepsis cynipsea (Diptera: Sepsidae) mating reduces female survival, apparently because males wound females during copulation. However, this damage does not seem to relate to attempted manipulation of female reproduction by males. Here we tested the hypothesis that harming females during mating is an incidental by-product of characters favoured during pre-copulatory male-male competition. We assessed whether males and their sons vary genetically in their ability to obtain matings and harm females, and whether more successful males were also more damaging. We did this by ranking males' mating success in paired competitions across several females whose longevity under starvation was subsequently measured. 相似文献56.
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Treatment of an N-terminal-containing His6-tagged insulysin (His6-IDE) with proteinase K led to the initial cleavage of the His tag and linker region. This was followed by C-terminal cleavages resulting in intermediate fragments of approximately 95 and approximately 76 kDa and finally a relatively stable approximately 56 kDa fragment. The approximately 76 and approximately 56 kDa fragments exhibited a low level of catalytic activity but retained the ability to bind the substrate with a similar affinity as the native enzyme. The kinetics of the reaction of the IDE approximately 76 and approximately 56 kDa proteolytic fragments with a synthetic fluorogenic substrate produced hyperbolic substrate versus velocity curves, rather than the sigmoidal curve obtained with His6-IDE. The approximately 76 and approximately 56 kDa IDE proteolytic fragments were active toward the physiological peptides beta-endorphin, insulin, and amyloid beta peptide 1-40. Although activity was reduced by a factor of approximately 103-104 with these substrates, the relative activity and the cleavage sites were unchanged. Both the approximately 76 and approximately 56 kDa fragments retained the regulatory cationic binding site that binds ATP. Thus, the two proteinase K cleavage fragments of IDE retain the substrate- and ATP-binding sites but have low catalytic activity and lose the allosteric kinetic behavior of IDE. These data suggest a role of the C-terminal region of IDE in allosteric regulation. 相似文献
59.
The new hexadentate, bis-pincer ligand, (dipyCH2)MeNCH2CH2NMe(CH2dipy) (dipy = 2,2′-dipyridyl-6-yl) forms a crystallographically characterized Mn(II) complex in which each half of the ligand binds a separate Mn(OAc)2 unit. The structure consists of a distorted N3Mn(η2-OAc)(η1-OAc) core with six normal coordinate bonds and a long (2.85 Å) secondary bond to a seventh ligand atom, an oxygen of the η1-acetate. In addition to demonstrating an interesting coordination mode, the structure also mimics a predicted transition state in the associative ligand exchange of octahedral Mn(II) complexes. 相似文献
60.
Richard Fike Barbara Dadey Richard Hassett Robert Radominski David Jayme David Cady 《Cytotechnology》2001,36(1-3):33-39
To overcome limitations of conventional milling technology, we investigated the application of fluid bed granulation for the
production of dry-form nutrient media. Serum-free, protein-free and chemically-defined specialty media were produced in granulated
format and compared with identical formulations manufactured by conventional methods. HPLC analysis of multiple lots of granulated
materials demonstrated that biochemical constituents were precisely and homogeneously distributed throughout the granules
and that nutrient levels were comparable to conventional formats. Comparison of medium performance in cell proliferation and
biological production assays demonstrated equivalence with reference media. The fluid bed granulation process meets pharmaceutical
quality requirements and may be applied to a broad range of nutrient formulations required for bioproduction applications.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献