Use of gas chromatography and mass spectroscopy to identify and determine 1,3-pentadiene in cheese or mold cultures

Zusammenfassung Kopfraum-Gasproben, Capillarsäulen-Gaschromatographie und Massenspektrometrie wurden benutzt, um Pentadien-(1,3) in Käse oder Schimmelkulturen zu identifizieren und zu bestimmen. Pentadien-(1,3) wurde in sorbatbehandeltem schimmeligen Käse und in ein sorbat-behandeltes Kulturmedium, das mit einem pentadien-produzierenden Stamm vonPenicillium roqueforti geimpft war, gefunden. Sorbat-behandelter Käse oder Kulturmedien, die schimmelfrei waren, enthielten kein Pentadien-(1,3).

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Use of gas chromatography and mass spectroscopy to identify and determine 1,3-pentadiene in cheese or mold cultures

Summary A headspace gas-sampling technique and capillary-column gas chromatography in conjunction with mass spectroscopy were used to identify and determine 1,3-pentadiene in cheese and mold cultures. Mold-contaminated sorbate-treated cheeses and a sorbate-fortified culture medium inoculated with a sorbate-resistant pentadiene-producing strain ofPenicillium roqueforti were examined and contained 1,3-pentadiene. The compound was not detected in uninoculated sorbate-fortified media or in sorbatetreated cheeses without mold growth.

     

Growth and production of enterotoxin A by Staphylococcus aureus in cream

Behavior of Staphylococcus aureus strains 100-A, 196-E, 254, 473, 505, and 521 in sweet (18 to 80% milk fat) and neutralized sour cream was studied. Cream was inoculated to contain approximately 10(3) to 10(4) S. aureus/ml, depending on milk fat content, and was incubated at 4, 22, or 37 degrees C. Determinations were made of aerobic plate count, S. aureus count, and pH. When growth in cream exceeded 10(7) S. aureus/ml, enterotoxin analysis was done. Sweet and neutralized sour cream supported growth of all strains of S. aureus tested. Strains 100-A, 196-E, 473, 505, and 521 grew sufficiently to produce enterotoxin in sweet cream of 18 or 32% milk fat held at 37 degrees C for 18 h or at 22 degrees C for 52 h. Populations of strains 100-A, 196-E, 505, and 521 exceeded 10(6) cells/ml in sweet cream of 36% milk fat held for 18 h at 37 degrees C. Strains 100-A and 521 grew to more than 10(6) cells/ml in sweet cream of 40% milk fat held for 18 h at 37 degrees C. No strain of S. aureus grew to levels associated with detectable enterotoxin production at 4 degrees C within 14 d in any cream. Incubation temperature, milk fat content of cream, and variation among strains influenced the ability of S. aureus to grow and produce enterotoxin.     

Fate of Staphylococcus aureus in whey, whey cream, and whey cream butter

Fresh Cheddar cheese whey was inoculated with ca. 10(6) Staphylococcus aureus/ml and held at 4, 25, and 37 degrees C for 48 h. Numbers of staphylococci decreased in whey at 25 and 37 degrees C and decreased or remained constant in whey at 4 degrees C. When Cheddar cheese whey was neutralized with sodium hydroxide before inoculation with ca. 10(2) or 10(6) S. aureus/ml, numbers of the bacterium increased at all incubation temperatures. Viability of S. aureus strains in whey butter made from inoculated whey cream (from Cheddar cheese whey) was determined. Whey cream was either neutralized to a titratable acidity of .15% or untreated before inoculation with ca. 10(4) S. aureus/ml. Butter churned from the whey cream was held at 4, 25, and 30 degrees C for up to 4 wk. Viability of S. aureus was enhanced in lightly salted (1%) whey cream butter and in butter made from neutralized whey cream. Strains of S. aureus did not survive in unsalted or in salted (1.5%) butter made from untreated whey cream.     

Sites of action by propionate on Listeria monocytogenes.

Exposure of Listeria monocytogenes to a solution of sodium propionate (8% w/v) for 60 min caused 87% of the population to be injured. Injury was evidenced by inability of the bacterium to tolerate 6% sodium chloride in tryptose agar as compared to ability to grow on tryptose agar with no added salt. Injured cells were allowed to repair in tryptose broth and the repair process was studied by addition to tryptose broth of sublethal amounts of metabolic or synthetic inhibitors. Repair of injured cells did not require electron transport or synthesis of cell wall components, mRNA or protein. No changes which may have occurred in the cell membrane of injured cells, allowed leakage of proteins or nucleotides into the medium. Exogenous cation salts enhanced the rate of recovery of injured cells. The specific activity of lactic dehydrogenase was reduced in propionate-injured L. monocytogenes.     

High serum levels of soluble CD44 variant isoform v5 are associated with favourable clinical outcome in ovarian cancer

In 96 ovarian cancer patients, the present study investigates the clinical significance of pretreatment concentrations of soluble CD44 standard (CD44s) and its isoforms v5 and v6 determined in the serum and the ascitic fluid by means of recently developed enzyme-linked immunosorbent assays (ELISAs). Furthermore, CD44 serum concentrations in the ovarian cancer patients were compared with circulating CD44 levels in 50 healthy age-matched female blood donors. Whereas CD44s was found to be higher and CD44v5 to be lower in ovarian cancer patients than healthy control subjects, no statistical difference between the two cohorts was revealed for CD44 isoform v6. In the ascitic fluid samples, variant isoform v5 and v6 were demonstrated at lower concentrations than serum. Multivariate analysis of overall survival demonstrated that a high pretreatment serum level of soluble CD44 isoform v5 is independently associated with favourable clinical outcome in ovarian cancer. When circulating CD44 isoforms were compared with a panel of serum parameters known to be involved in the immunological network, an inverse correlation between serum CD44v5 levels and indicators of cellular immune system activation, such as soluble interleukin 2 receptor, immunostimulatory protein 90K and neopterin, became apparent.     

Quantitative detection of hepatitis B virus DNA with a new PCR assay

This supplement reports the characterization of 15 new Salmonella serovars recognized in 1997 by the WHO Collaborating Centre for Reference and Research on Salmonella: 8 were assigned to S. enterica subsp. enterica, 4 to subspecies salamae, 2 to subspecies diarizonae, and 1 to subsp. houtenae. In addition, the antigenic factors H:z85 and H:z87 are described and one modification to the Kauffmann-White scheme is reported.     

Release of aflatoxin from the mycelium of aspergillus parasiticus into liquid media

Summary Spores of an aflatoxinogenie strain ofAspergillus parasiticus were inoculated into a glucose-salts medium and incubated at 28° C for 5 days when both mold growth and aflatoxin production were nearly maximal. The mold mycelium thus produced was recovered by filtration, washed three times with distilled water, placed in a nitrogen-free liquid medium (so growth was not possible), and held for 45 h. Samples of medium were tested periodically for aflatoxin content to determine release of toxin by the mycelium. When the mycelium was in a medium with 5% glucose and was held at 7° C; 17, 33, 39, and 56% of the aflatoxin from the mycelium appeared in the liquid after 1, 9, 21, and 45 h, respectively. Aflatoxin B₁ was lost by the mycelium more slowly than were B₂, G₁, and G₂. At 28° C, values for the same time intervals were 27, 60, 70, and 76%, respectively, and at 45° C they were 32, 71, 71, and 79%. At 28 and 45° C, aflatoxins G₁ and G₂ were lost by the mycelium more rapidly than were aflatoxins B₁ and B₂. Elimination of glucose from the medium at 28° C hastened, and use of 50% instead of 5% glucose markedly reduced release of aflatoxin by the mycelium during early stages of the incubation period.

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Zusammenfassung Ein Medium mit Glucose und Salzen wurde mit Sporen eines Aflatoxin bildenden StammesAspergillus paraciticus geimpft und bei 28° C für 5 Tage im Inkubator gehalten, bis sowohl das Wachstum des Schimmelpilzes als auch die Produktion von Aflatoxine den Höhepunkt erreichten. Das Pilzmycel wurde abfiltriert, 3 mal mit destilliertem Wasser gewaschen und in ein Stickstoff-freies, flüssiges Medium gebracht, um ein weiteres Wachsen unmöglich zu machen. Stichproben wurden von dem Medium periodisch gezogen und der Gehalt an Aflatoxine bestimmt, um den Verlust an Toxin aus dem Mycel zu erhalten. Wenn das Mycel in einem Medium mit 5% Glucose bei 7° C gehalten wurde, dann erschien in der Flüssigkeit 17, 33, 39 und 56% des Aflatoxins aus dem Mycelium nach 1, 9, 21 und 45 Std. Aflatoxin Bi ging aus dem Mycelium langsamer verloren als B₂, G₁ und G₂. Bei 28° C waren die Werte für dieselben Zeiträume 27, 60, 70 und 76% und bei 40° C 32, 71, 71 und 79%. Bei 28° C und bei 45° C verlor das Mycelium die Aflatoxine G₁ und G₂ schneller als B₁ und B₂. Das Mycelium gab die Aflatoxine schneller bei 28° C ab, wenn das Medium frei von Glucose war. Wenn das Medium 50% Glucose anstatt 5% enthielt, wurde der Verlust an Aflatoxine vom Mycelium im Anfangsstadium der Inkubationsperiode wesentlich verringert.

     

Strains and suspending menstrua as factors affecting death and injury of Listeria monocytogenes during freezing and frozen storage

Cell suspensions of Listeria monocytogenes strains V7, California, and Ohio in phosphate buffer solution, tryptose broth, or milk were frozen and stored at -18 degrees C. At appropriate intervals during storage, a sample was thawed at 35 degrees C and surface-plated on suitable media to allow colony formation by noninjured or noninjured plus injured cells. Degrees of death and injury were calculated from the data. Cells of L. monocytogenes were more resistant to death and injury when they were suspended in milk or tryptose broth rather than phosphate buffer solution. There was a significant (two-way ANOVA) difference in resistance to death and injury during frozen storage among strains of L. monocytogenes suspended in tryptose broth. The difference was nonsignificant when the cells were suspended in phosphate buffer solution or milk. Listeria monocytogenes strain Ohio was more resistant to death and injury during frozen storage when cells were suspended in tryptose broth rather than milk. The opposite was true for strains V7 and California. Death and injury of L. monocytogenes strains V7, California, and Ohio suspended in phosphate buffer solution were 98.7, 97.9, and 91.2% and 77.5, 51.6, and 70.2%, respectively, after 4 wk of frozen storage. The values were 67.3, 91.6, and 42.3% and 44.4, 65.6, and 32.6%, respectively, when cells were suspended in tryptose broth, and they were 37.8, 40, and 60.7% and 10.8, 66.8, and 46%, respectively, when cells were suspended in milk.     

Influence of crystallography on aspects of solid-solid nucleation theory

Expressions for the major variables in the general rate equation for solid-solid nucleation were developed on the basis of various models of the critical nucleus shape during homogeneous and heterogeneous nucleation. These models are based upon spheres, but in some a facet was incorporated at one boundary orientation to represent the presence of a partially or fully coherent structure. Gibbs’ relationship for the critical radius is applicable to all of the models. The other variables in the nucleation rate equation are affected by the model and by faceting. Reduction of AG* by faceting is concluded to be the primary cause for the presence of reproducible lattice orientation relationships and for the existence of transition phases during precipitation from solid solutions.