Structural studies of the lipopolysaccharide of Moritella viscosa strain M2-226

The structure of the O-specific side chain of the lipopolysaccharide from the Gram-negative psychrophilic bacterium Moritella viscosa strain M2-226, responsible for the winter ulcer in Atlantic salmon, has been determined. Monosaccharide analysis and (1)H and (13)C NMR spectroscopy were employed to elucidate the structure. It was concluded that the polysaccharide is composed of a trisaccharide repeating unit with the following structure: →3)-β-D-GlcpNAc-(1→4)-[α-D-GlcpA-(1→3)]-α-L-Fucp-(1→ .     

Isolation and properties of a bacteriocin-producing Carnobacterium piscicola isolated from fish.

A facultative psychrotrophic lactic acid bacterium isolated from fresh fish was identified as Carnobacterium piscicola on the basis of carbohydrate utilization, G + C content and 16S RNA analysis. Its bacteriocin, designated carnocin UI49, is produced during the mid-exponential phase of growth at temperatures between 15 degrees C and 34 degrees C. Carnocin UI49 is active against a large number of closely-related lactic acid bacteria including carnobacteria, lactobacilli, pediococci and lactococci. Furthermore, the bacteriocin has a bactericidic mode of action which results in lysis of sensitive cells. Maximum bactericidal activity is observed at 34 degrees C with a decrease in activity down to 15 degrees C where it is completely abolished.     

Heat-induced disturbances of intracellular movement and the consistency of the aqueous cytoplasm in HeLa S-3 cells: a laser-Doppler and proton NMR study.

Intracellular particle movements, of both saltatory and streaming types, in HeLa S-3 cells were simultaneously interrupted after 1 h exposure of cells to 43 degrees C, within 10 min at 44 degrees C and within 5 min at 45 degrees C. Intracellular movement inhibited after 15 min at 44 degrees C and 10 min at 45 degrees C was not reversible in cells rescued at 37 degrees C. Brownian motion was not observed in heat-treated cells while they were maintained at elevated temperatures, but became pronounced in blebbing which occurred shortly after they were returned to 37 degrees C. Returning these cells to 45 degrees C intensified the Brownian activity inside blebs, and rapidly induced cell lysis. The same heat-treated cells were simultaneously studied by laser-Doppler microscopy, which confirmed: a) that flow (cytoplasmic streaming) is completely arrested at 44 degrees C within 10 min, b) flow recovered in 10-15 min in cells rescued after 10-15 min at 44 degrees C, c) submicroscopic particles down to the size of water molecules had faster self-diffusion coefficients at 44 degrees C than at 37 degrees C. Proton nmr studies on cells exposed from 4 to 45 degrees C gave corrected relaxation times T1 and T2 which rose with temperature in a predictable manner. Inhibition of cellular movement at elevated temperatures was not specifically attributable to the depletion of intracellular ATP levels.     

Temperature-dependent biotransformation of 2,4'-dichlorobiphenyl by psychrotolerant Hydrogenophaga strain IA3-A: higher temperatures prevent excess accumulation of problematic meta-cleavage products

AIMS: The present work investigates the possibility that temperature could regulate the pattern of transformation of 2,4'-chlorobiphenyl (2,4'-CB) by psychrotolerant Hydrogenophaga sp. IA3-A. Methods AND RESULTS: Transformation of 2,4'-chlorobiphenyl to 2- and 4-chlorobenzoic acid (2- and 4-CBA), and meta-cleavage products by cells of strain IA3-A incubated at 10 degrees C, 25 degrees C, 37 degrees C or 45 degrees C were monitored by UV spectrometry, HPLC and GC-MS analyses. Cultures incubated at 10 degrees C, 25 degrees C or 37 degrees C produced low amounts of CBAs and excess levels of meta-cleavage products from 2,4'-CB. Cultures incubated at 45 degrees C transformed most of the degraded 2,4'-CB to CBAs and low level of meta-cleavage product. Culture extracts contained unusual varieties of isomeric hydroxylated metabolic products. CONCLUSIONS: Efficient transformation of 2,4'-CB to CBAs was possible in cultures incubated at 45 degrees C. Evidence for the involvement of multiple pathways in the transformation of 2,4'-CB in strain IA3-A suggests that differential regulation of the pathways at different temperatures was likely responsible for the change in the pattern of transformation of 2,4'-CB in cultures incubated at 45 degrees C. Significance AND IMPACT OF THE STUDY: It may be possible to condition cells to transform chlorinated biphenyls more efficiently without accumulating excess level of toxic intermediates.     

Binding kinetics of ecotropic (Moloney) murine leukemia retrovirus with NIH 3T3 cells.

A quantitative analysis of the binding kinetics of intact Moloney murine leukemia retrovirus (MoMuLV) particles with NIH 3T3 cells was performed with an immunofluorescence flow cytometry assay. The virus-cell binding equilibrium dissociation constant (KD), expressed in terms of virus particle concentration, was measured to be 8.5 (+/- 6.4) x 10(-12) M at 4 degrees C and was three- to sixfold lower at temperatures above 15 degrees C. The KD of virus binding is about 1,000-fold lower than the KD of purified MoMuLV envelope. The association rate constant was determined to be 2.5 (+/- 0.9) x 10(9) M-1 min-1 at 4 degrees C and was 5- to 10-fold higher at temperatures above 15 degrees C. The apparent dissociation rate constant at 4 degrees C was 1.1 (+/- 0.4) x 10(-3) min-1 and was doubled for every 10 degrees C increase in temperature over the range tested (15 to 37 degrees C).     

Molecular characterization of XVSAP1, a stress-responsive gene from the resurrection plant Xerophyta viscosa Baker

The strategy of 'complementation by functional sufficiency' was used to isolate a cDNA designated XVSAP1 from a cDNA library constructed from dehydrated Xerophyta viscosa Baker leaves. Analysis of the cDNA sequence indicated a highly hydrophobic protein with six transmembrane regions. Southern blot analysis revealed that there are at least two copies of XVSAP1 in X. viscosa. The deduced amino acid sequence showed 49% identity to WCOR413, a low-temperature-regulated protein from wheat. The protein also showed between 25% to 56% identity to WCOR413-like proteins from Arabidopsis thaliana. Expression of XVSAP1 in Escherichia coli (srl::Tn10) conferred osmotic stress tolerance when the cells were grown in 1 M sorbitol. Analysis of gene expression using semi-quantitative RT-PCR indicated that XVSAP1 is induced by dehydration, salt stress (100 mM), both low (4 degrees C) and high temperature (42 degrees C) and high light treatment (1500 micromol m(-2) s(-1)). These results suggest that XVSAP1 may have a significant role to play in the response of X. viscosa to abiotic stresses.     

The behaviour of log phase Escherichia coli at temperatures that fluctuate about the minimum for growth

AIMS: To investigate the behaviour of cold-adapted, log phase Escherichia coli exposed to temperatures that fluctuate below and above the minimum for growth. METHODS AND RESULTS: Log phase E. coli cultures were incubated at a constant temperature of 2, 4 or 6 degrees C or with temperatures allowed to increase from those temperatures for 35 min, to 10 degrees C, at 6-, 12- or 24-h intervals, as commonly occurs during retail display of chilled foods. At suitable intervals for each culture, the optical absorbance value was determined using a spectrophotometer, the forward angle light scatter was determined using a flow cytometer, and portions were spread on plate count agar for enumeration of colony forming units (CFU). Numbers of CFU decreased by 3 log units or increased by 1 log unit for cultures incubated at 6 degrees C for 17 days without or with temperatures fluctuations at < or =12-h intervals, respectively. Cells elongated when cultures were incubated at 4 or 2 degrees C with temperatures fluctuating at 6-h intervals, and at 6 degrees C at constant or fluctuating temperatures, but cells did not elongate in cultures incubated at a constant temperature of 2 or 4 degrees C. SIGNIFICANCE AND IMPACT OF THE STUDY: The minimum growth temperature of E. coli is assumed to be > or =7 degrees C. Elongated cells were able to divide when temperatures rose from 6 degrees C to above 7 degrees C for <45 min at < or =12-h intervals. Such temperature fluctuations may be experienced by chilled foods during defrosting cycles of retail display cases. The finding that cells behave differently under fluctuating than at constant temperatures may significantly affect understanding of appropriate temperatures for the safe storage of chilled foods and for predictive modelling of bacterial growth in such foods.     

Challenge testing of the lactoperoxidase system in pasteurized milk

AIMS: To determine the role of lactoperoxidase (LP) in inhibiting the growth of micro-organisms in pasteurised milk. METHODS AND RESULTS: Four micro-organisms of importance in the spoilage of pasteurized milk were challenged in lactoperoxidase (LP)-enriched ultra-heat treated (UHT) milk after subsequent pasteurization. Milk samples were stored at the optimum temperatures for growth of the individual bacteria. Pasteurization was carried out at 72 degrees C/15 s and 80 degrees C/15 s to determine the effect of the LP system on the micro-organisms. An active LP system was found to greatly increase the keeping quality (KQ) of milks inoculated with Pseudomonas aeruginosa, Staphylococcus aureus and Streptococcus thermophilus and pasteurized at 72 degrees C, but had little or no effect in milks heated at 80 degrees C, presumably due to virtual inactivation of LP at 80 degrees C. However, pasteurization temperature had no effect on the KQ of milks challenged with Bacillus cereus spores. CONCLUSIONS: This study suggests that the LP system, rather than heat-shocking of spores, is responsible for the greater KQ of milk pasteurized at 72 degrees C/15 s compared with 80 degrees C/15 s. SIGNIFICANCE AND IMPACT OF THE STUDY: The study emphasizes the care required in selecting pasteurization temperatures in commercial practice and to avoid the temptation to compensate for inferior quality of raw milk by increasing pasteurization temperature.     

Characterization of a temperature-sensitive mutant of Saccharomyces cerevisiae that undergoes uncontrolled protein synthesis.

A mutant of Saccharomyces cerevisiae, DW137, isolated after treatment of a wild-type strain with ICR-170. The mutant was respiration-deficient and showed abnormal cell division when grown at 30 degrees C. In addition, the mutant was temperature-sensitive and underwent lysis when grown at 37 degrees C. Random spore analysis, induced reversion profiles, and complementation analysis indicated that the abnormal phenotypes were under the control of a single recessive mutation caused by a base-pair substitution in a nuclear gene. Macromolecular analysis of the mutant at permissive and restrictive temperatures showed that at restrictive temperatures the mutant cannot synthesize DNA. Surprisingly, at restrictive temperatures, protein synthesis in the mutant continued at a rate greater than that observed at permissive temperatures. Cell death and lysis of the mutant could be prevented by treatment of cultures with cycloheximide, an inhibitor of protein synthesis. The data suggest that the abnormally high rate of protein synthesis and the inability to synthesize DNA are jointly responsible for death of the cells, and most probably play and integrating role in the incipient cell lysis.     

Survival of the biocontrol yeast Pichia anomala after long-term storage in liquid formulations at different temperatures, assessed by flow cytometry

AIMS: Investigate the survival of liquid formulations of the biocontrol yeast Pichia anomala J121 at different temperatures, and develop a system for comparative studies of different storage conditions and formulations. METHODS AND RESULTS: The survival of P. anomala in liquid formulations with lactose, starch and trehalose amendments was measured during prolonged storage at temperatures ranging from -20 to +30 degrees C. The relative survival of the stored cells was rapidly estimated by flow cytometry. After 4 weeks incubation at 4 and 10 degrees C, 75-90% of the cells were viable, with no significant differences between the various formulations. Supplementing the storage buffer with lactose or trehalose increased the survival after longer incubations (8 and 12 weeks) at all temperatures (-20 to 30 degrees C). Trehalose was the most effective protectant at 20 and 30 degrees C (>20% viable cells after 12 weeks at 20 degrees C). The biocontrol activity was maintained after formulation and prolonged storage of P. anomala. CONCLUSIONS: The storage potential of liquid formulated P. anomala cells can be increased by supplementation with lactose or trehalose. The combination of a custom made incubation chamber and flow cytometry was suitable to evaluate stability of P. anomala formulations. SIGNIFICANCE AND IMPACT OF THE STUDY: Liquid formulated P. anomala have a long shelf life. The developed test system can be used to study different formulations of other biocontrol agents.     

Early steps in specific tumor cell lysis by sensitized mouse T lymphocytes. I. Resolution and characterization.

Addition of high molecular weight dextran to culture medium prevents the initiation of T lymphocyte-mediated killing by holding the cytolytic T lymphocytes (CTL) and target cells in suspension and preventing intercellular contact. Suspension in 10% dextran was used to interrupt the ongoing formation of adhesions between CTL and target cells already in contact in a centrifuged pellet. The results demonstrate that 1) firm adhesions form between CTL and target cells within 1 min at 37 degrees C; 2) once formed, these adhesions are stable at low temperature and are resistant to mechanical shearing forces; 3) these adhesions can be disrupted by EDTA; 4) immediately after the adhesions form, separation of the CTL from the target cells prevents lysis of the latter; 5) after incubation of targets adhering to CTL for an additional 6 min at 37 degrees C, removal of the CTL no longer prevents target cell lysis. Thus, target cells become "programmed" for subsequent lysis within a few minutes after contact with CTL, after which lysis occurs during the next several hours without further participation of the effector cell. At 15 degrees C, adhesions form 1/17 as fast as at 37 degrees C. Programming of target cells for lysis occurs 1/76 as fast at 15 degrees C as at 37 degrees C. Thus, the programming for lysis step is about 4-fold more temperature dependent than the adhesion step. In addition to being detected by subsequent target cell lysis in 10% dextran, the adhering cell clusters can be counted with low power microscopy. This permitted verification that EDTA separates the clusters after programming for lysis is complete. Moreover, the great majority of the clusters seen at 37 degrees C are antigen-specific. Knowledge of the cluster size distribution and the subsequent level of lysis permits the deduction that not less than 6% of the sensitized peritoneal cell populations used were CTL.     

Inhibition of repair of radiation-induced DNA damage by thermal shock in Chinese hamster ovary cells

The effect of exposure to elevated temperatures (41-45 degrees C) on the repair of radiation-induced DNA strand breaks was measured in monolayer cultured Chinese hamster ovary (CHO) cells. Prior exposure of cells to temperatures between 43 and 45 degrees C resulted in significant decreases in the rate of repair of DNA damage. Exposure to 45 degrees C for 15 min slowed the rate of DNA repair to 0.17 of the control repair rate. The To for inactivation of DNA repair was observed to be 34, 13 and 6 min at 43, 44 and 45 degrees C, respectively. Stepdown-heating (45 degrees C for 15 min followed by repair at 41 degrees C) resulted in greater inhibition of DNA repair (0.11 of the control rate) than was observed after acute heating alone. Repair at 41 degrees C was observed to proceed in unheated cells at a faster rate than at 37 degrees C. An Arrhenius analysis of the inactivation kinetics of DNA repair between 43 and 45 degrees C indicated an activation energy of 140 kcal mol-1 of protein for the inhibition of DNA repair. In general, the results were inconsistent with either a retardation of the DNA repair rate or an increase in unrepaired DNA lesions being responsible for heat-induced radiosensitization.     

Hyperthermia and the generation and activity of murine influenza-immune cytotoxic T cells in vitro.

The rate of generation of murine secondary influenza virus-immune cytotoxic T cells in vitro is enhanced under limiting dilution conditions at hyperthermal temperatures (39 versus 37 degrees C). Increased mean values of cytotoxic activity were observed in the presence as well as absence of exogenous helper factors. Elevated cytotoxic activity at 39 degrees C was observed after day 3 to day 5 of culture. The number of autoreactive cytotoxic cells observed was not greater at 39 degrees C than at 37 degrees C. Elevated temperature did not influence target cell lysis or release of isotopes from killed target cells. The results are discussed with a view to the role of fever in augmenting the cellular immune response responsible for the host defense against primary viral infection.     

The effect of temperature on the photoperiodic 'clock' and 'counter' of a Scottish clone of the vetch aphid, Megoura viciae

Photoperiodic response curves were determined for a Scottish clone of the vetch aphid, Megoura viciae Buckton, at three temperatures: 12.5, 15, and 17.5 degrees C. Critical night lengths (CNLs) for ovipara (sexual female) induction were 6 h, 7 h and 8 h, respectively. High incidences of ovipara production were observed in all night lengths longer than the CNL including continuous darkness (DD), as well as in continuous light (LL) at 12.5 and 15 degrees C. At the same three temperatures, the number of long- or short-night cycles required for half of the experimental aphids to be ovipara producers (i.e. the required day number, RDN) was determined. The RDN for long-night cycles (LD12:12) could not be determined at 12.5 degrees C, but was temperature compensated between 15 and 17.5 degrees C. The RDN for short-night cycles (LD20:4) could not be determined at any temperature. However, as induction of oviparae was always 100% in 12.5 degrees C, 94-100% in 15 degrees C and dropped from 100% to between 47 and 71% in 17.5 degrees C, it seems that short-night accumulation was temperature dependent. When fourth-stadium larvae were transferred from LD20:4 at 20 degrees C to the same light-dark cycle at 15 degrees C, the aphids, when adult, switched to the production of oviparae after about 4 weeks. First-born progeny kept in LD20:4 and 15 degrees C switched to the production of oviparae about 7 days after the moult to adult. Thus, the photoperiodic response can be directly affected by temperature, irrespective of photoperiod. Model-generated response curves using the 'double circadian oscillator model' for photoperiodic time measurement (Vaz Nunes, M., 1998. A double circadian oscillator model for quantitative photoperiodic time measurement in insects and mites. Journal of Theoretical Biology 194, 299-311) closely resembled the observations. Differences between these data and the results of previous experiments with an English clone of M. viciae could be accounted for by differences in the photoperiodic clocks (damping rate and period) as well as the photoperiodic counters.     

Deformability and stability of erythrocytes in high-frequency electric fields down to subzero temperatures.

High-frequency electric fields can be used to induce deformation of red blood cells. In the temperature domain T = 0 degrees to -15 degrees C (supercooled suspension) and for 25 degrees C this paper examines for human erythrocytes (discocytes, young cell population suspended in a low ionic strength solution with conductivity sigma(25 degrees) = 154 microS/cm) in a sinusoidal electric field (nu = 1 MHz, E0 = 0-18 kV/cm) the following properties and effects as a function of field strength and temperature: 1) viscoelastic response, 2) (shear) deformation (steady-state value obtained from the viscoelastic response time), 3) stability (by experimentally observed breakdown of cell polarization and hemolysis), 4) electrical membrane breakdown and field-induced hemolysis (theoretical calculations for ellipsoidal particles), and 5) mechanical hemolysis. The items 2-4 were also examined for the frequency nu = 100 kHz and for a nonionic solution of very low conductivity (sigma(25 degrees) = 10 microS/cm) to support our interpretations of the results for 1 MHz. Below 0 degrees C with decreasing temperature the viscoelastic response time tau(res)(T) for the cells to reach steady-state deformation values d(infinity,E) increases and the deformation d(infinity,E)(T) decreases strongly. Both effects are especially high for low field strengths. The longest response time of approximately 30 s was obtained for -15 degrees C and small deformations. For 1 MHz the cells can be highly elongated up to 2.3 times their initial diameter a0 for 25 degrees and 0 degrees C, 2.1a0 for -10 degrees C and still 1.95a0 for -15 degrees C. For T > or = 0 degrees C the deformation is limited by hemolysis of the cells, which sets in for E0(lysis)(25 degrees) approximately 8 kV/cm and E0(lysis)(0 degrees) approximately 14 kV/cm. These values are approximately three times higher than the corresponding calculated critical field strengths for electrically induced pore formation. Nevertheless, the observed depolarization and hemolysis of the cells is provoked by electrical membrane breakdown rather than by mechanical forces due to the high deformation. For the nonionic solution, where no electrical breakdown is expected in the whole range for E0, the cells can indeed be deformed to even higher values with a low hemolytic rate. Below 0 degrees C we observe no hemolysis at all, not even for the frequency 100 kHz, where the cells hemolyze at 25 degrees C for the much lower field strength E0(lysis) approximately 2.5 kV/cm. Obviously, pore formation and growth are weak for subzero temperatures.     

The glutamate decarboxylase acid resistance mechanism affects survival of Listeria monocytogenes LO28 in modified atmosphere-packaged foods

AIMS: The contribution of the glutamate decarboxylase (GAD) acid resistance system to survival and growth of Listeria monocytogenes LO28 in modified atmosphere-packaged foods was examined. METHODS AND RESULTS: The survival and growth of the wild-type LO28 and four GAD deletion mutants (DeltagadA, DeltagadB, DeltagadC, DeltagadAB) in packaged foods (minced beef, lettuce, dry coleslaw mix) during storage at 4, 8 and 15 degrees C were studied. Survival and growth patterns varied with strain, product type, gas atmosphere and storage temperature. In minced beef, the wild-type LO28 survived better (P < 0.05) than the GAD mutant strains at 8 and 15 degrees C. In both packaged vegetables at all storage temperatures, the wild-type strain survived better (P < 0.05) than the double mutant DeltagadAB. The requirement for the individual gad genes varied depending on the packaged food. In the case of lettuce, gadA played the most important role, while the gadB and gadC genes played the greatest role in packaged coleslaw (at 15 degrees C). CONCLUSIONS: This work demonstrates that elements of the GAD system play significant roles in survival of L. monocytogenes LO28 during storage in modified atmosphere-packaged foods. SIGNIFICANCE AND IMPACT OF THE STUDY: A better understanding of how L. monocytogenes behaves in modified atmosphere-packaged foods, and how it responds to elevated carbon dioxide atmospheres.     

Survival or growth of Escherichia coli O157:H7 in a model system of fresh meat decontamination runoff waste fluids and its resistance to subsequent lactic acid stress

A potential may exist for survival of and resistance development by Escherichia coli O157:H7 in environmental niches of meat plants applying carcass decontamination interventions. This study evaluated (i) survival or growth of acid-adapted and nonadapted E. coli O157:H7 strain ATCC 43895 in acetic acid (pH 3.6 +/- 0.1) or in water (pH 7.2 +/- 0.2) fresh beef decontamination runoff fluids (washings) stored at 4, 10, 15, or 25 degrees C and (ii) resistance of cells recovered from the washings after 2 or 7 days of storage to a subsequent lactic acid (pH 3.5) stress. Corresponding cultures in sterile saline or in heat-sterilized water washings were used as controls. In acetic acid washings, acid-adapted cultures survived better than nonadapted cultures, with survival being greatest at 4 degrees C and lowest at 25 degrees C. The pathogen survived without growth in water washings at 4 and 10 degrees C, while it grew by 0.8 to 2.7 log cycles at 15 and 25 degrees C, and more in the absence of natural flora. E. coli O157:H7 cells habituated without growth in water washings at 4 or 10 degrees C were the most sensitive to pH 3.5, while cells grown in water washings at 15 or 25 degrees C were relatively the most resistant, irrespective of previous acid adaptation. Resistance to pH 3.5 of E. coli O157:H7 cells habituated in acetic acid washings for 7 days increased in the order 15 degrees C > 10 degrees C > 4 degrees C, while at 25 degrees C cells died off. These results indicate that growth inhibition by storage at low temperatures may be more important than competition by natural flora in inducing acid sensitization of E. coli O157:H7 in fresh meat environments. At ambient temperatures in meat plants, E. coli O157:H7 may grow to restore acid resistance, unless acid interventions are applied to inhibit growth and minimize survival of the pathogen. Acid-habituated E. coli O157:H7 at 10 to 15 degrees C may maintain a higher acid resistance than when acid habituated at 4 degrees C. These responses should be evaluated with fresh meat and may be useful for the optimization of decontamination programs and postdecontamination conditions of meat handling.     

Shelf life and safety aspects of chilled cooked and peeled shrimps (Pandalus borealis) in modified atmosphere packaging

AIMS: To evaluate the growth of Listeria monocytogenes and shelf life of cooked and peeled shrimps in modified atmosphere packaging (MAP). METHODS AND RESULTS: Storage trials with naturally contaminated cooked and peeled MAP shrimps (Pandalus borealis) were carried out at 2, 5 and 8 degrees C. Challenge tests at the same conditions were performed after inoculation with Listeria monocytogenes. Both storage trials and challenge tests were repeated after 4 months of frozen storage (-22 degrees C). Brochothrix thermosphacta and Carnobacterium maltaromaticum were responsible for sensory spoilage of cooked and peeled MAP shrimps. In challenge tests, growth of L. monocytogenes was observed at all of the storage temperatures studied. At 5 and 8 degrees C the concentration of L. monocytogenes increased more than a 1000-fold before the product became sensory spoiled whereas this was not observed at 2 degrees C. Frozen storage had only a minor inhibiting effect on growth of L. monocytogenes in the thawed product. CONCLUSIONS: To prevent L. monocytogenes becoming a safety problem, cooked and peeled MAP shrimps should be distributed at 2 degrees C and with a maximum shelf life of 20-21 d. At higher temperatures shelf life is significantly reduced. SIGNIFICANCE AND IMPACT OF THE STUDY: Information is provided to establish shelf life of cooked and peeled MAP shrimps.     

Temperature affects physiological stress responses to acute confinement in sunshine bass (Morone chrysops x Morone saxatilis)

Sunshine bass (Morone chrysopsxMorone saxatilis) were subjected to a 15-min low-water confinement stressor at temperatures ranging from 5 to 30 degrees C. Physiological responses were evaluated by measuring hematocrit, and plasma chloride, glucose and cortisol. Fish acclimated to 30 degrees C had initial glucose concentrations of 3.13 mM (564 mg/L) which were significantly lower than in fish acclimated to 5 and 10 degrees C (4.32 and 4.82 mM or 779 and 868 mg/l, respectively). Fish survived the conditions imposed at every temperature except 30 degrees C, where 15 out of 42 fish died during the stress and recovery protocol. The general pattern was an initial increase in hematocrit, followed by a delayed decrease in hematocrit and chloride, and an increase in plasma glucose and cortisol. In general, fish stressed at temperatures below 20 degrees C had lower and more delayed changes in plasma glucose and cortisol than fish tested at 20, 25 and 30 degrees C. Initial cortisol concentrations were 65 ng/ml and increased to above 200 ng/ml in fish held at 20 degrees C and above. At the higher temperatures, glucose concentrations were twice the initial concentration after stress and cortisol changes were four to five times the initial concentration after the stress. Quantitative responses for glucose and cortisol were moderate and recovery rapid in fish stressed at 10 and 15 degrees C; therefore, this range of water temperature is recommended when handling sunshine bass.