Sensitivity of Campylobacter spp. to irradiation in poultry meat

The sensitivity of Campylobacter jejuni (three strains), Camp. coli (three strains), Camp. fetus (one strain) and Camp. lari (one strain) to irradiation in poultry meat was investigated. There was no significant difference in the counts obtained on Blood or Skirrows agar. Preston agar gave a significantly lower recovery of the pathogens after irradiation so these results were not included in calculations of D ₁₀ values. The D ₁₀ values ranged from 0.12 to 0.25 kGy and there was a significant difference in the radiation sensitivity between different Campylobacter spp. and within strains of the same species. These values indicate that Campylobacter spp. are more radiation-sensitive than Salmonella and Listeria monocytogenes irradiated under similar conditions. Therefore irradiation treatments suggested to eliminate the latter from poultry carcasses would also be sufficient to remove Campylobacter.     

Effect of rising temperature on the heat resistance of Listeria monocytogenes in meat emulsion

The heat resistance of a strain of L. monocytogenes was determined both in broth and in meat emulsion. The D -values for meat emulsion were approximately two to three times higher than those for broth and also the z -value increased significantly. The micro-organism proved to be more resistant when the cells were heated up slowly (0·5°C/min) to constant temperatures of 60, 63 and 66°C in meat emulsion. The D ₆₀, D ₆₃ and D ₆₆ were, respectively 12·95, 5·4 and 2·3 min. Results may have implications in the survival of Listeria monocytogenes in particular food preparations.     

Sensitivity of Listeria monocytogenes to irradiation on poultry meat and in phosphate-buffered saline

The sensitivity of four strains of Listeria monocytogenes to irradiation on poultry meat and in phosphate-buffered saline was investigated. The D₁₀ values on poultry meat were 0.417–0.553 kGy depending on strain and plating medium used. Lower values were obtained in phosphate-buffered saline. Generally tryptone soya yeast extract and McBride agars gave a better recovery (higher D₁₀ value) than listeria selective agar. The D₁₀ values for L. monocytogenes were similar to those reported for Salmonella spp. irradiated under similar conditions. Therefore irradiation doses suggested to eliminate salmonellas from poultry carcasses would also be sufficient to remove L. monocytogenes.     

Sensitivity of some common grain fungi to irradiation on grain and in phosphate-buffered saline

The sensitivity of nine cereal fungi to irradiation on grain and in phosphate-buffered saline (PBS) was investigated. Species of Fusarium and Alternaria were more resistant to irradiation (higher D ₁₀ value) than Aspergillus spp. and Penicillium spp. Generally D ₁₀ values determined on grain were lower than the corresponding values measured in PBS. The plating medium did not significantly affect the D ₁₀ values.     

Human Lymphocyte Proliferation: Dna Synthesis Time

Abstract. The DNA synthesis time ( T _s) of lymphocytes from spleens and lymph nodes of patients with Hodgkin's disease was determined by the double labeling method. ³H-TdR was administered in vivo and removed tissues minced in ¹⁴C-TdR in vitro. Lymphocytes from patients with lymphosarcoma and reticulum cell sarcoma were studied in a similar manner. Lymphocytes were divided into A cells, small with non-basophilic cytoplasm, B cells, small with basophilic cytoplasm, C cells, large with non-basophilic cytoplasm, and D cells, large with basophilic cytoplasm.
The T _s of splenic lymphocytes, in four samples not containing Reed-Sternberg cells, in hours, was: B 11.3; C , 7.9; D , 8.4; combined, 8.8. the T _s of B lymphocytes was significantly longer than that of C and D lymphocytes. A lymphocytes did not label sufficiently to measure T _s. C and D lymph node lymphocytes and lymphocytes in tissues containing Reed-Sternberg cells had a longer T _s than splenic C and D cells. the former was: B , 12.7; C , 11.7; D , 11.0; combined, 11.8. the latter was: B , 12.2; C , 11.3; D , 11.2; combined, 11.6. the T _s of Reed-Sternberg cells in one specimen of a splenic Hodgkin's tumor was 13.1 hr. Macrophage T _s was 10.7 and 15.1 hr. Lymphosarcoma cell T _s was 14.2 and 14.6 hr. Reticulum cell sarcoma cell T _s was 7.5 and 7.7 hr.
The following minimum times were calculated from observation of ³H-TdR only labeled mitotic figures: S to prophase, 71 min; S to metaphase, 75 min; S to telophase, 100 min.     

Biochemical studies on the cell wall degradation of Fusarium oxysporum f. sp. lycopersici race 2 by its own lytic enzymes for its biocontrol

An exhaustive cell wall fractionation of Fusarium oxysporum f. sp. lycopersici race 2 ( Fol 2) with alkali in a sequential procedure yields only three polysaccharide fractions: F1_s (alkali and water soluble), F1₁ (alkali soluble and water insoluble) and F4 (alkali-insoluble residue). These fractions amounted respectively to 15, 1.3 and 52% of the cell wall and have been characterized by infra-red spectroscopy and gas liquid chromatography-mass spectrometry (GLC-MS). F1_s is a β-gluco-galacto-mannan, F1₁ is mainly composed of a β-1, 3-glucan and F4 is a β-1,3-glucan-chitin complex. The F1_s is a very complex polysaccharide and its hydrolysis requires the action of different enzymes. The lysis of the cell wall and its three fractions with lytic enzymes from Fol 2 has been studied and a correlation between the lysis of the cell wall and the lysis of these fractions was found. The amount of glucose, galactose and mannose in F1_s and cell wall hydrolysates were quantified by GLC and they indicated the hydrolysis of the gluco-galacto-mannan polysaccharide. In the hydrolysis of F4 and cell walls N -acetylglucosamine was also found and quantified. When chlamydospores of this fungus were treated with Fol 2 lytic enzymes, the sugars liberated were principally mannose and N -acetylglucosamine. These results indicate that Fol 2 produces during its autolysis the necessary enzymes to hydrolyse its own cell walls. This fact suggests that a biological control of Fol 2 with its own lytic enzymes, conveniently immobilized, could be developed.     

CELL PROLIFERATION IN THE CASTRATE MOUSE SEMINAL VESICLE IN RESPONSE TO TESTOSTERONE PROPIONATE

The cell proliferation kinetics following induced DNA synthesis in the mouse seminal vesicle were measured after treatment with testosterone propionate. Fraction labelled mitosis curves at 24, 48 and 72 hr after injection gave t ₂ values of 1·5, 2·0 and 1·8 hr respectively, and t _s values of 10·5, 8·0 and 8·0 hr. T _c measured 48 hr after stimulation was 17·5 hr. Growth fraction rose from 0·14 at 24 hr to 0·64 at 48 hr, and fell to 0·32 by 72 hr. A simple model is proposed in which the rise and fall of mitotic index and labelled index is determined by the 'cell distribution ratio'.     

Stomata of trees growing in CO2-enriched air show reduced sensitivity to vapour pressure deficit and drought

Stomatal conductance ( g _s) and photosynthetic rate ( A ) were measured in young beech ( Fagus sylvatica ), chestnut ( Castanea sativa ) and oak ( Quercus robur ) growing in ambient or CO₂-enriched air. In oak, g _s was consistently reduced in elevated CO₂. However, in beech and chestnut, the stomata of trees growing in elevated CO₂ failed to close normally in response to increased leaf-to-air vapour pressure deficit (LAVPD). Consequently, while g _s was reduced in elevated CO₂ on days with low LAVPD, on warm sunny days (with correspondingly high LAVPD) g _s was unchanged or even slightly higher in elevated CO₂. Furthermore, during drought, g _s of beech and chestnut was unresponsive to [CO₂], over a wide range of ambient LAVPD, whereas in oak g _s was reduced by an average of 50% in elevated CO₂. Stimulation of A by elevated CO₂ in beech and chestnut was restricted to days with high irradiance, and was greatest in beech during drought. Hence, most of the additional carbon gain in elevated CO₂ was made at the expense of water economy, at precisely those times (drought, high evaporative demand) when water conservation was most important. Such effects could have serious consequences for drought tolerance, growth and, ultimately, survival as atmospheric [CO₂] increases.     

Decoupling the influence of leaf and root hydraulic conductances on stomatal conductance and its sensitivity to vapour pressure deficit as soil dries in a drained loblolly pine plantation

The study examined the relationships between whole tree hydraulic conductance ( K _tree) and the conductance in roots ( K _root) and leaves ( K _leaf) in loblolly pine trees. In addition, the role of seasonal variations in K _root and K _leaf in mediating stomatal control of transpiration and its response to vapour pressure deficit ( D ) as soil-dried was studied. Compared to trunk and branches, roots and leaves had the highest loss of conductivity and contributed to more than 75% of the total tree hydraulic resistance. Drought altered the partitioning of the resistance between roots and leaves. As soil moisture dropped below 50%, relative extractable water (REW), K _root declined faster than K _leaf. Although K _tree depended on soil moisture, its dynamics was tempered by the elongation of current-year needles that significantly increased K _leaf when REW was below 50%. After accounting for the effect of D on g _s, the seasonal decline in K _tree caused a 35% decrease in g _s and in its sensitivity to D , responses that were mainly driven by K _leaf under high REW and by K _root under low REW. We conclude that not only water stress but also leaf phenology affects the coordination between K _tree and g _s and the acclimation of trees to changing environmental conditions.     

Radiation inactivation of some food-borne pathogens in fish as influenced by fat levels

The influence of low (0·39–1·1%), medium (4·25%) and high (7·1–32·5%) fat levels in fish on radiation inactivation of four food-borne pathogens was investigated. Cells of Listeria monocytogenes 036, Yersinia enterocolitica F5692, Bacillus cereus and Salmonella typhimurium at logarithmic phase were inoculated in 10% fish homogenates and subjected to gamma irradiation at ice temperature (0–1 °C) with doses ranging from 0·05 to 0·8 kGy. The radiation survival curves of L. monocytogenes and B. cereus were characterized by shoulders, while a tailing effect was depicted by cells of Y. enterocolitica and B. cereus . The D₁₀ values in kGy calculated on the exponential part of the curve ranged from 0·2 to 0·3, 0·15 to 0·25, 0·1 to 0·15 and 0·09 to 0·1 for L. monocytogenes 036, B. cereus, Salm. typhimurium and Y. enterocolitica F5692, respectively. This order (D₁₀) of radiation resistance of each organism was not affected by the fat content of the fish. Inoculated pack studies carried out separately with each pathogen in fatty (Indian sardine, 7·1%) and lean (Golden anchovy, 0·39%) fish showed no difference in their survival after exposure to 1 kGy and 3 kGy doses, which corroborated the above observation. The practical significance of these results in the application of the technology is discussed.     

Responses of apple leaf stomata to environmental factors

Abstract. Stomatal conductances ( g _s) were measured on the leaves of 3–4 year old Golden Delicious trees and of seedlings of two other cultivars. Measurements were made on container grown trees in the field with a diffusion porometer in 1975 and 1976, and in controlled conditions in a leaf chamber in the laboratory in 1976. Stomatal densities in the Golden Delicious leaves were assessed from scanning electron micrographs. Stomatal density on extension shoot leaves was higher than on other leaf types after June.
The response to irradiance shown by both the porometer and the leaf chamber results could be described by a rectangular hyperbola: where g _max is maximum conductance and β indicates the sensitivity of g_s to photon influx density ( Q _p). The values of β were in the range 60–90 μmol m⁻² s⁻¹.
There was no evidence that apple stomata are sensitive to temperature per se, but g _s was reduced by increasing leaf to air vapour pressure deficits ( D ). There was a linear relationship between g _s and D which was not attributable to feed-back to leaf water potential (ψ_L) as the latter did not affect g _s until a threshold of about −2.0 to −2.5 MPa was reached. Conductance generally declined with increasing ambient CO₂ concentration.     

Effect of selected antimicrobial compounds on the radiosensitization of Salmonella Typhi in ground beef

Aims:  In this study, we extended our previous work to determine the efficiency of antimicrobial compounds in increase of relative radiosensitivity of Salmonella Typhi in medium fat ground beef (23% fat) by testing 41 different essential oils (EOs), oleoresins and food sauces.
Methods and Results:  Ground beef samples inoculated with Salmonella Typhi (10⁶ CFU g⁻¹ ) were treated with each antimicrobial compound at a concentration of 0·5% (w/w). Then, the samples (25 g each) were packaged under air and irradiated in a ⁶⁰Co irradiator at doses from 0 to 1·75 kGy. Radiosensitivity was evaluated by calculating relative radiation sensitivity, defined as the ratio of radiation D ₁₀ value in the absence/presence of antimicrobial compound.
Conclusions:  Depending on the compound tested, the addition of antimicrobial compound decreased the D ₁₀ value of Salmonella Typhi, resulting in an increase of the radiation sensitivity up to more than four times. Among these antimicrobial compounds, Chinese cinnamon EO, clove EO and trans -cinnamaldehyde were most effective to increase the radiosensitivity of Salmonella Typhi in ground beef.
Significance and Impact of the Study:  These observations demonstrate that some active compounds can function as radiosensitizers of Salmonella Typhi.     

The use of a surface adhesion immunofluorescent (SAIF) method for the rapid detection of Yersinia enterocolitica serotype O:3 in meat

This study examined the attachment kinetics of Yersinia enterocolitica serotype O:3 to determine the optimum conditions for its isolation from meat enrichment systems using a novel surface adhesion technique. Minced beef was inoculated with Y. enterocolitica at an initial level of 10 cfu g⁻¹ and incubated at 25 °C in an enrichment broth. Yersinia was recovered from enriched samples on polycarbonate membranes by surface adhesion and enumerated using immunofluorescence microscopy. The surface adhesion immunofluorescence technique (SAIF) had a minimum detection limit of approximately 4·0–4·5 log₁₀ cfu ml⁻¹ and provided good correlation between the estimation of the numbers of Yersinia in the enrichment broth derived from plate counts on Yersinia Selective agar (CIN) and those determined by SAIF ( r ² ₌ 0·94; rsd ₌ ± 0·21). A derived regression equation of the SAIF count vs plate counts was used to predict Y. enterocolitica numbers in spiked meat samples stored at 0 °C for up to 20 d. The numbers as predicted by the SAIF method showed good correlation with counts derived by plating techniques ( r ² ₌ 0·78; rsd ₌ ± 0·42). The application of the SAIF technique for the rapid detection of Y. enterocolitica serotype O:3 from meat is discussed.     

Carotenoids' influence on radiotolerance of Pantoea agglomerans, a plant pathogen

Aim:  The aim of this study was to evaluate the effect of γ radiation on the carotenoid content of two strains of the Enterobacteriaceae : Pantoea agglomerans .
Methods and Results:  Pantoea agglomerans strains ATCC 49174 and RL1 were used for this study. Successive radiation treatments were performed to study the radiotolerance. Total carotenoids were obtained by multiple extraction using chloroform/methanol (2 : 1), quantified by measuring the optical density at 453 nm and their antioxidant activity measured by a colorimetric method. The D ₁₀ studies were conducted using a UC-15A irradiator loaded with ⁶⁰Co. Bacterial counts from various dilutions were carried out after irradiation. Strain ATCC 49174 irradiated at 1 kGy produced 4·3 times more carotenoids than the control, whereas carotenoid synthesis increased by 2·9-fold in the strain RL1. However, there was no significant difference in the D ₁₀ values.
Conclusion:  Carotenoid increased production is influenced by γ radiation but does not modify the tolerance to radiations.
Significance and Impact of the Study:  To our knowledge, this is the first study to demonstrate the effects of γ radiation on carotenoid production levels.     

Molecular Cloning and Characterization of a Lobster Gαs Protein Expressed in Neurons of Olfactory Organ and Brain

Abstract: We have isolated from an American lobster ( Homarus americanus ) olfactory organ cDNA library a clone, lobGα_s, with >70% identity to mammalian and arthropod Gα_s sequences. In genomic Southern blots, a fragment of lobGα_s detected only one band, suggesting the lobsters have a single Gα_s gene. In brain and olfactory organ, lobGα_s mRNA was expressed predominantly in neurons, including many of the neuronal cell body clusters of the brain. Gα_s protein was also expressed broadly, appearing on western blots as a band of 51.8 kDa in brain, eyestalk, pereiopod, dactyl, tail muscle, olfactory organ, and aesthetasc hairs. These results suggest that lobGα_s plays a role in a wide variety of signal transduction events. Its presence in the olfactory aesthetasc hairs, which are almost pure preparations of the outer dendrites of the olfactory receptor neurons, and the expression of lobGα_s mRNA in the olfactory receptor neurons of the olfactory organ indicate that lobGα_s may mediate olfactory transduction. That virtually all ORNs express lobGα_s mRNA equally predicts that hyperpolarizing odor responses mediated by cyclic AMP are a property of all lobster olfactory receptor neurons.     

Oxygen consumption of East Siberian cod: no support for the metabolic cold adaptation theory

Standard metabolic rate ( R _s) at 2°C of eight East Siberian cod Arctogadus borisovi , caught in West Greenland, body mass of 601.5 ± 147.6 g (mean ± s.D.), was 40.9 ± 5.9 mg O₂ kg^-1 h^-1 and 59.0 ± 6.6mg O₂ kg^-1 h^-1 when extrapolated to a standardized 100 g fish. R _s was compared with three other Gadidae, to test the theory of metabolic cold adaptation (MCA). There was no evidence of MCA in the family.     

Formation of aminopropylhomospermidine from homospermidine in yeasts and thermophilic bacilli

Abstract When the yeasts Saccharomyces cerevisiae, Candida albicans and Schizosaccharomyces pombe and the thermophilic bacteria Bacillus stearothermophilus and Bacillus acidocaldarius were cultured in the presence of homospermidine, a new compound accumulated in the cells within a few days. This compound was identified as aminopropylhomospermidine [NH₂(CH₂)₃NH (CH₂)₄NH(CH₂)₄NH₂] by gas chromatographymass spectrometry (GC-MS) and by the enzymatic cleavage method developed in our laboratories. This polyamine was not produced from homospermidine in Escherichia coli, Bacillus subtilis, Bacillus alkalophilus , or a eukaryotic protozoon, Tetrahymena pyriformis , none of which usually contains appreciable amounts of spermine. These findings suggest that the synthesis of aminopropylhomospermidine from homospermidine is mediated by spermine synthase.     

Surface free energies of oral streptococci and their adhesion to solids

Abstract The adhesion of 3 strains of oral streptococci from a buffered suspension onto 3 different solid substrata was studied. Representative strains of streptococci were selected on the basis of their surface free energy ( γ _b), namely Streptococcus mitis L1 ( γ _b= 37 mJ·m⁻²), Streptococcus sanguis CH3 (95 mJ·m⁻²) and Streptococcus mutans NS (117 mJ·m⁻²). Solid substrata were also selected on basis of their surface free energy ( γ _s), and included polytetrafluorethylene ( γ _s= 20 mJ·m⁻²), polymethylmethacrylate (53 mJ·m⁻²) and glass (109 mJ·m⁻²). Bacterial adhesion was measured as the number of bacteria adhering per cm² at equilibrium. Equilibrium was usually obtained within 20 min. S. sanguis CH3, having an intermediate surface free energy did not show a clear preference for any of the 3 solids. S. mitis L1, however, the lowest surface free energy strain, adhered in highest numbers to the low energy solid PTFE, whereas the highest γ _b strain, S. mutans NS, adhered in highest numbers to the highest γ _s solid, glass. Calculation of the interfacial free energy of adhesion ( ΔF _adh) for each bacterial strain showed that this parameter was predictive of bacterial adhesion to solid substrata.     

Anaerobic degradation of 3,4,5-trimethoxybenzoate by a defined mixed culture of Acetobacterium woodii, Pelobacter acidigallici, and Desulfobacter postgatei

Abstract Acetobacterium woodii was continuously grown on 3,4,5-trimethoxybenzoate as pure culture or in commensalistic combination with Pelobacter acidigallici and Desulfobacter postgatei . Under pure culture conditions the following growth parameters were determined: μ _max= 0.112 h⁻¹, K _s= 1.07 mM, Y _max= 35 g/mol, and m = 0.22 mmol·g⁻¹·h⁻¹. In coculture with P. acidigallici the affinity for the substrate increased and the K _s value was found to be 135 μM. Under batch culture conditions mixed populations of A. woodii, P. acidigallici , and D. postgatei completely mineralized 3,4,5-trimethoxybenzoate to CO₂, whereas under continuous culture conditions more than 3 mM acetate remained unused.