Temperature mediated processes in teleost immunity: differential abilities of channel catfish T and B lymphocytes to cap membrane antigen

1. The effect of both in vivo acclimation temperature and in vitro assay temperatures on channel catfish T and B lymphocyte membrane antigen (mAg) capping were investigated to determine if capping might be the temperature sensitive step involved in the low temperature immunosuppression of channel catfish T cell responses. 2. Flow cytometry was used to monitor the kinetics of capping induced by a mouse monoclonal antibody (mAb 11G3) specific for a common antigenic determinant present on channel catfish T and B cells. Results indicated that the kinetics of mAg capping were dependent on in vitro assay and in vivo acclimation temperatures and the length of time of in vivo acclimation. 3. T cells from fish appropriately acclimated to 27 degrees C cap mAg more efficiently at low assay temperatures than do B cells. 4. Activation energies were 32 and 47 kcal/mol for B and T cells, respectively, from fish acclimated to 17 degrees C for 3 weeks, but were significantly lower (14 and 22 kcal/mol, respectively) after acclimation for 5 weeks. 5. In summary, it appears that after appropriate in vivo acclimation, channel catfish T cells are better able to cap mAg at low assay temperatures than are B cells. These results suggest that mAg capping is not the low temperature sensitive step involved in T cell immunosuppression in channel catfish.     

Temperature-mediated processes in teleost immunity: the effects of temperature on membrane immunoglobulin capping on channel catfish B lymphocytes

1. In order to better understand ligand-induced redistribution of membrane receptors and lymphocyte activation in ectothermic vertebrates, flow cytometry was used to monitor the effects of both in vivo acclimation temperature and in vitro assay temperatures on the kinetics of monoclonal antibody-induced membrane immunoglobulin (mIg) capping on channel catfish lymphocytes. 2. It was observed that the kinetics of mIg capping were dependent on in vitro assay temperatures, in vivo acclimation temperatures, and the length of time of in vivo acclimation. In the latter situation in vivo acclimation of fish to 27, 22 and 17 degrees C was considered complete after 3 weeks, while acclimation to 12 degrees C required a minimum of 5 weeks. 3. The energies of activation required for mIg capping ranged from 33 to 24 kcal/mol; lower energies of activation were observed with lower temperature acclimation. 4. It was also noted that the lower energies of activation were associated with concomitant decreases in cellular phospholipid saturated/unsaturated fatty acid ratios. 5. It appears that channel catfish B cell mIg capping, presumably a requisite for immune function, can be significantly affected by environmental temperatures; most likely such effects are attributable to changes in plasma membrane viscosities.     

Effect of temperature on the immune system of channel catfish (Ictalurus punctatus)--II. Adaptation of anterior kidney phagocytes to 10 degrees C.

1. Anterior kidney phagocytes from channel catfish (Ictalurus punctatus) exposed to 10 and 24 degrees C from 1 day to 5 weeks were assayed for phagocytic ability and respiratory burst activity to Aeromonas hydrophila and Edwardsiella ictaluri. 2. The results of this study indicated that phagocytosis in channel catfish remained partially functional at low temperature without adaptation, although partial suppression was observed. 3. Adaptation to low temperature did lead to an improvement in the respiratory burst which would imply improved bacterial killing ability. 4. Our study suggests that phagocytosis may play a significant role in preventing disease at low environmental temperature.     

In vitro effect of temperature on phagocytic and cytotoxic activities of splenic phagocytes of the wall lizard, Hemidactylus flaviviridis.

The in vitro effect of temperature on phagocytosis, nitric oxide production and interleukin-1 (IL-1) secretion by splenic phagocytes isolated from the wall lizard (Hemidactylus flaviviridis) demonstrated that changes in temperature altered non-specific defenses. The LPS-induced percentage phagocytosis and phagocytic index were recorded maximum at 25 degrees C. The phagocytic activity declined considerably when the phagocytes were incubated at low (7 and 15 degrees C) or high (37 degrees C) temperatures. The presence of bacterial lipopolysaccharide (LPS) in the incubation medium could considerably enhance the phagocytic activity of splenic phagocytes. A similar temperature-related effect was also observed on LPS-induced cytotoxic activity of phagocytes. LPS could stimulate the nitrite release indicating nitric oxide production only at 25 degrees C. Likewise, the proliferative responses of immature rat's thymocytes to LPS-induced phagocyte-conditioned medium suggest that IL-1 secretion was enhanced when phagocytes were cultured at 25 degrees C. This suggests that 25 degrees C is the optimal temperature for phagocyte functions in H. flaviviridis. The decrease or increase in temperature other than at 25 degrees C dramatically suppressed the phagocyte activities.     

The effects of in vivo acclimation temperature on the fatty acid composition of channel catfish (Ictalurus punctatus) peripheral blood cells

Channel catfish were acclimated in vivo to 12, 17, 22 or 27 degrees C and their peripheral blood erythrocytes, thrombocytes, T lymphocytes and B lymphocytes assayed for cellular fatty acid composition. Excepting cells from 12 degrees C acclimated fish, all cells responded to acclimation to lower temperatures by exhibiting increased levels of phospholipid unsaturated fatty acids. Although temperature independent differences were observed between erythrocytes, thrombocytes and lymphocytes, no differences between T lymphocytes and B lymphocytes were seen.     

Rhodamine 123 permeability through the catfish intestinal wall: Relationship to thermal acclimation and acute temperature change

Temperature is known to influence xenobiotic retention in fish. The effect of acute and acclimatory temperature change upon Rhodamine 123 (Rho123) permeability through an in vitro catfish multi-segment (3) everted sac intestinal wall model was examined in a 9 cell matrix of acclimation and assay temperatures (10, 20 and 30 degrees C). Changes in Rho123 permeability were examined in context with membrane fluidity, xenobiotic solubility and intestinal morphology. When assayed at the acclimation temperature greater Rho123 permeability was noted at warmer acclimation temperatures for the proximal and middle intestinal segments, while the distal segment exhibited little change and apparent compensation across temperatures. Rho123 permeability was increased as assay temperatures were elevated above the acclimation temperature for most comparisons. Cold acclimation significantly increased total intestinal length (43.2%) and proximal intestine weights while total body weights did not differ. Brush border membranes (BBM) increased fluidity with increased assay temperatures, however, composite anisotropy lines were not significantly different between acclimation treatments. In an additive manner, the membrane probe DPH exhibited increased solubility in BBM with increases in acclimation and assay temperatures. Compositely, these results suggest that acclimation and acute temperature change may differentially influence xenobiotic permeability among intestinal segments with interacting mechanisms.     

Critical thermal minima and maxima of three freshwater game-fish species acclimated to constant temperatures

A total of 120 critical thermal maxima (CT maxima) and 120 critical thermal minima (CT minima) were determined for channel catfish, largemouth bass and rainbow trout acclimated to three constant temperatures: 20, 25 and 30 °C in catfish and bass, and 10, 15 and 20 °C in trout. Highest mean CT maximum and lowest mean CT minimum measured over these acclimation temperatures were 40.3 and 2.7 °C (catfish), 38.5 and 3.2 °C (bass) and 29.8 and ∼ 0.0 °C (trout). Temperature tolerance data were precise with standard deviations generally less than 0.5 °C. Channel catfish had the largest thermal tolerance scope of the three species while rainbow trout had the lowest tolerance of high temperatures and the highest tolerance of low temperatures. In all species CT minima and CT maxima were highly significantly linearly related to acclimation temperature. Within each species, slopes relating CT maxima to acclimation temperature were approximately half as large as those relating CT minima to acclimation temperature, suggesting that acclimation temperature has a greater influence on tolerance to low rather than high temperatures. Slopes relating both CT minima and CT maxima to acclimation temperature for the two warm-water species were similar and approximately twice those for the rainbow trout. This revised version was published online in July 2006 with corrections to the Cover Date.     

The effect of temperature acclimation on myocardial beta-adrenoceptor density and ligand binding affinity in African catfish (Claris gariepinus)

This study assessed the effects of temperature acclimation on myocardial beta-adrenoceptor density (B(max)) and binding affinity (K(d)) in African catfish (Claris gariepinus) acclimated to 15, 22 and 32 degrees C. B(max) values were not significantly different (P > 0.05) among the three acclimation groups. Conversely, the K(d) value of the 32 degrees C acclimation group (K(d) = 0.88) was significantly higher (P = 0.002) than both the 15 degrees C (K(d) = 0.48) and 22 degrees C (K(d) = 0.46) acclimation groups. In addition, K(d) of rainbow trout (Oncorhynchus mykiss) was significantly lower (P < 0.001) and B(max) significantly higher (P < 0.05) than that of African catfish at all three acclimation temperatures. These results contrast with those reported previously for temperate species, in which B(max) is inversely related to acclimation temperature, and counter a previous suggestion that B(max) is higher in tropical versus temperate species.     

Kinetics of granulocyte phagocytosis: rate limited by cytoplasmic viscosity and constrained by cell size

Micromanipulation of yeast particles and blood granulocytes has been used to study the kinetics of single phagocytosis events. The ingestion process was quantitated by observation of sequential adhesion and encapsulation times. Both adherence and encapsulation times were found to increase greatly as the temperature was reduced below 37 degrees C; calcium in solution facilitated adhesion of the particle to the phagocyte but not encapsulation; both adhesion and encapsulation processes required a minimum level of plasma components (presumably complement). The general nature of these observations were confirmatory of previous studies, but this study is unique in that the specific time course of single particle ingestion was quantitated. It was immediately apparent that the phagocytosis process was 100% efficient above the threshold concentrations required for plasma and temperature, but variations in times from cell to cell indicated heterogeneity in the population. The total time for ingestion varied from as low as 2 sec/particle at 37 degrees C to above several min/particle below 15 degrees C. Encapsulation times for particles were normalized by estimates of particle surface areas to establish a specific time/unit area of particle surface: from 0.5 sec/10(-8) cm2 at 37 degrees C to greater than 8 sec/10(-8) cm2 at 15 degrees C. The temperature dependence of the encapsulation time correlated well with the temperature dependence of the "apparent" viscosity for granulocytes measured by micropipet aspiration. As such, the kinetic properties observed in these phagocytosis tests are consistent with a model that both assembly of the contractile system and the displacement of the surface by active contraction in phagocytosis are limited by viscous dissipation in the cell.(ABSTRACT TRUNCATED AT 250 WORDS)     

The effect of progressive hypoxia on respiration in the dogfish (scyliorhinus canicula) at different seasonal temperatures.

1. Dogfish were acclimated to 7, 12 or 17 degrees C and exposed to progressive hypoxia at the temperature to which they had been acclimated. During normoxia, the Q10 values for oxygen uptake, heart rate, cardiac output and respiratory frequency over the full 10 degrees C range were: 2.1, 2.1, 2.1 and 2.5 respectively. Increased acclimation temperature had no effect on cardiac stroke volume or systemic vascular resistance, although there was a decrease in branchial vascular resistance, pHa and pHv. 2. Progressive hypoxia had no effect on heart rate or oxygen uptake at 7 degrees C, whereas at 12 degrees C and 17 degrees C there was bradycardia, and a reduction in O2 uptake, with the critical oxygen tension for both variables being higher at the higher temperature. Cardiac stroke volume increased during hypoxia at each temperature, such that cardiac output did not change significantly at 12 and 17 degrees C. Neither pHa nor pHv changed significantly during hypoxia at any of the three temperatures. 3. The influence of acclimation temperatures on experimental results from poikilotherms is pointed out. Previously-published results show quantitative differences. 4. The significance of the present results with respect to the functioning and location of oxygen receptors is discussed. It is argued that as the metabolic demand and critical oxygen tension of the whole animal are increased at high acclimation temperatures the same must be the case with the oxygen receptor. This would raise the stimulation threshold and could account for the bradycardia seen during hypoxia becoming manifest at higher values of PI,O2, Pa,O2 and Pv,O2 as the acclimation temperature is raised.     

The response of the high altitude C(4) grass Muhlenbergia montana (Nutt.) A.S. Hitchc. to long- and short-term chilling.

The acclimation of C(4) photosynthesis to low temperature was studied in the montane grass Muhlenbergia montana in order to evaluate inherent limitations in the C(4) photosynthetic pathway following chilling. Plants were grown in growth cabinets at 26 degrees C days, but at night temperatures of either 16 degrees C (the control treatment), 4 degrees C for at least 28 nights (the cold-acclimated treatment), or 1 night (the cold-stress treatment). Below a measurement temperature of 25 degrees C, little difference in the thermal response of the net CO(2) assimilation rate (A) was observed between the control and cold-acclimated treatment. By contrast, above 30 degrees C, A in the cold-acclimated treatment was 10% greater than in the control treatment. The temperature responses of Rubisco activity and net CO(2) assimilation rate were similar below 22 degrees C, indicating high metabolic control of Rubisco over the rate of photosynthesis at cool temperatures. Analysis of the response of A to intercellular CO(2) level further supported a major limiting role for Rubisco below 20 degrees C. As temperature declined, the CO(2) saturated plateau of A exhibited large reductions, while the initial slope of the CO(2) response was little affected. This type of response is consistent with a Rubisco limitation, rather than limitations in PEP carboxylase capacity. Stomatal limitations at low temperature were not apparent because photosynthesis was CO(2) saturated below 23 degrees C at air levels of CO(2). In contrast to the response of photosynthesis to temperature and CO(2) in plants acclimated for 4 weeks to low night temperature, plants exposed to 4 degrees C for one night showed substantial reduction in photosynthetic capacity at temperatures above 20 degrees C. Because these reductions were at both high and low CO(2), enzymes associated with the C(4) carbon cycle were implicated as the major mechanisms for the chilling inhibition. These results demonstrate that C(4) plants from climates with low temperature during the growing season can fully acclimate to cold stress given sufficient time. This acclimation appears to involve reversal of injury to the C(4) cycle following initial exposure to low temperature. By contrast, carbon gain at low temperatures generally appears to be constrained by the carboxylation capacity of Rubisco, regardless of acclimation time. The inability to overcome the Rubisco limitation at low temperature may be an inherent limitation restricting C(4) photosynthetic performance in cooler climates.     

Effects of cold acclimation on adipose tissue lipolysis and cellularity in the hypophysectomized rat

The study investigated the effects of hypophysectomy and cold acclimation on cellularity and lipolytic capacity of adipose tissue. Hypophysectomized rats (H) were compared to age matched or weight matched controls. Rats were exposed to either 28 degrees C or 15 degrees C ambient temperature for five weeks. In H, despite the inhibition of body growth, it was observed that the growth of epididymal adipose tissue is not entirely inhibited. In comparison with weight matched controls, increase in tissue weight is found to be due to an adipocyte hypertrophy without changes in cell number. No effect of cold acclimation on adipose tissue weight, cellularity and insulinemia were observed in the H group. The in vitro lipolysis effect of norepinephrine was suppressed in 28 degrees C H; a partial recovery of this effect was observed after cold acclimation. This fact is not dependent on adipocyte size, but possibly on structural or metabolic modifications.     

Isolation and characterization of Edwardsiella tarda from fall chinook salmon (Oncorhynchus tshawytscha).

A new bacterial pathogen of chinook salmon (oncorhynchus tshawytscha) was isolated from fish in Oregon's Rogue River. The bacteria are biochemically and serologically related to strains of Edwardsiella tarda. Initially isolated from chinook salmon, the bacteria were also pathogenic for steelhead and rainbow trout (Salmo gairdneri), and channel catfish (Ictalurus punctatus). The 50% lethal doses for chinook salmon, steelhead trout, and channel catfish injected intraperitoneally and maintained in 18 degrees C water were 4.1 x 10(6), 5.6 x 10(6), and 4.0 x 10(5) respectively. When chinook salmon and rainbow trout were injected intraperitoneally and held in 12 degrees C water, the mean lethal doses were 6.4 x 10(7) and 1.7 x 10(6), respectively. The invasiveness of the organism was low in steelhead trout exposed to the bacteria by the waterborne route. The optimum growth temperature of the bacteria in brain heart infusion broth was approximately 35 degrees C. The guanine plus cytosine content of DNA obtained from E. tarda isolated from salmon was 59 mol%.     

An in vitro assay to measure phagocytosis in striped bass hybrids (Morone saxatilis x Morone chrysops)

An in vitro phagocytosis assay was developed for hybrid striped bass (Morone saxatilis x Morone chrysops), using cells collected from the peritoneal cavity of this fish. The findings indicated that: (1) 10 days following a single intraperitoneal injection (1 ml) of Freund's incomplete adjuvant (FIA) was an appropriate time for collecting suitable working concentrations (5.3+/-4.0 x 10(7) cells ml(-1)) of peritoneal phagocytes (83.7+/-1.5% macrophages) from these hybrids held at 23 degrees C; (2) these cells phagocytosed latex beads (polystyrene microspheres 3.12 microm in diameter) after 30 min of in vitro incubation at room temperature (25+/-1 degrees C). The phagocytic ability and phagocytic capacity in a washed adherent layer exposure system were 67.2+/-2.76% and 4.14+/-0.35 beads phagocyte(-1), respectively. These results strongly suggest that a simple methodology, including baseline data serving as guidelines, is now available for conducting in vitro phagocytosis assays in this hybrid.     

Cross Tolerance to Environmental Stressors: Effects of Hypoxic Acclimation on Cardiovascular Responses of Channel Catfish (Ictalurus punctatus) to a Thermal Challenge

Hypoxia and temperature are two major, interactive environmental variables that affect cardiovascular function in fishes. The purpose of this study was to determine if acclimation to hypoxia increases thermal tolerance by measuring cardiovascular responses to increasing temperature in two groups of channel catfish. The hypoxic group was acclimatized to moderate hypoxia (50% air saturation, a P_O2 of approximately 75 Torr) at a temperature of 22 °C for 7 days. The normoxic (i.e. control) group was maintained the same, but under normoxic conditions (a P_O2 of approximately 150 Torr). After acclimation, fish were decerebrated, fitted with dorsal aorta cannulae, and then exposed to increasing temperature while cardiovascular variables were recorded. The endpoint (critical thermal maximum, CTMax) was defined as a temperature at which heart rate and blood pressure sharply decreased, indicating cardiovascular collapse. Fish acclimatized to moderate hypoxia had higher resting heart rate than controls. Hypoxic acclimatized fish had a significantly higher CTMax. Acclimation to hypoxia increases the cardiovascular ability of channel catfish to withstand an acute temperature increase.     

Extended alternating-temperature cold acclimation and culture duration improve pear shoot cryopreservation

Meristems of many pear genotypes can be successfully cryopreserved following 1 week of cold acclimation, but an equal number do not survive the process or have very little regrowth. This study compared commonly used cold acclimation protocols to determine whether the cold acclimation technique used affected the cold hardiness of shoots or the regrowth of cryopreserved meristems. In vitro-grown pear (Pyrus L.) shoots were cold acclimated for up to 16 weeks, then either the shoot tips were tested for cold hardiness or the meristems were cryopreserved by controlled freezing. Cold acclimation consisted of alternating temperatures (22 degrees C with light/-1 degrees C darkness with various photo- and thermoperiods) or a constant temperature (4 degrees C with an 8-h photoperiod or darkness). Compared with nonacclimated controls, both alternating- and constant-temperature acclimation significantly improved postcryopreservation regrowth of P. cordata Desv. and P. pashia Buch. -Ham. ex D. Don meristems. Alternating-temperature acclimation combined with either an 8-h photoperiod or darkness was significantly better than constant-temperature acclimation. Alternating-temperature shoot acclimation for 2 to 5 weeks significantly increased postcryopreservation meristem regrowth, and recovery remained high for up to 15 weeks acclimation. Postcryopreservation meristem regrowth increased with 1 to 5 weeks of constant-temperature acclimation and then declined with longer acclimation. Shoot cold hardiness varied with the acclimation procedure. The LT(50) of shoots acclimated for 10 weeks with alternating temperatures was -25 degrees C; that with constant temperature was -14.7 degrees C; and that of the nonacclimated control was -10 degrees C. Less frequent transfer of cultures also improved acclimation of shoots. Shoots grown without transfer to fresh medium for 6-12 weeks had higher postcryopreservation recovery with shorter periods of acclimation than shoots with a 3-week transfer cycle.     

Rabbit's ear in cold acclimation studied on the change in ear temperature.

The role of the rabbit's ear in cold acclimation was studied by varying the temperature of a climatic room in the range from -10 to +30 degrees C; The skin temperature in a nonanesthetized rabbit's ear showed a characteristic response to changes in ambient temperatures; plotting the ear temperature against the ambient temperature yielded an S-shaped curve. The mean ambient temperature corresponding to the inflection point on the S-shaped curve shifted significantly from about 13 degrees C to about 8 degrees C after cold acclimated of a group fed for 7 wk at -10 degrees C. The shift of the S-shaped curve after cold acclimation may not be due to the change in the norepinephrine sensitivity of the vascular beds of the ear: the effect of norepinephrine on the pressure-flow curve in the isolated rabbit's ear was almost unchanged between the control and the cold-acclimated groups. It is proposed that the shift of the inflection point gives a qualitative index of the acclimated state of the rabbit at a particular temperature.     

Cold-induced ependymin expression in zebrafish and carp brain: implications for cold acclimation.

Cold acclimation has been suggested to be mediated by alternations in the gene expression pattern in the cold-adapted fish. To investigate the mechanism of cold acclimation in fish brain at the molecular level, relevant subsets of differentially expressed genes of interest were identified and cloned by the PCR-based subtraction suppression hybridization. Characterization of the selected cold-induced cDNA clones revealed one encoding ependymin. This gene was shown to be brain-specific. The expression of ependymin was induced by a temperature shift from 25 degrees C to 6 degrees C in Cyprinus carpio or 12 degrees C in Danio rerio. Activation of ependymin was detected 2 h after cold exposure and peaked at more than 10-fold at 12 h. This peak level remains unchanged until the temperature returns to 25 degrees C. Although the amount of soluble ependymin protein in brain was not changed by cold treatment, its level in the fibrous insoluble polymers increased 2-fold after exposure to low temperature. These findings indicate that the increase in ependymin expression is an early event that may play an important role in the cold acclimation of fish.