Heat-tolerant versus heat-sensitive Bos taurus cattle: influence of air temperature and breed on the metabolic response to a provocative immune challenge.

The response of the immune and stress systems have been assessed in response to a lipopolysaccharide (LPS) challenge, yet the role of metabolism in mediating energy requirements during the acute phase response has not been sufficiently studied. This study tested heat-tolerant (Romosinuano [RO]) and heat-sensitive (Angus [ANG]) Bos taurus breeds at different ambient temperatures (Ta) to determine differential metabolic responses to LPS challenge. Twenty-one heifers (ANG: n = 11, 306 ± 26 kg BW; RO: n = 10, 313 ± 32 kg BW) were housed in stanchions in 4 temperature-controlled chambers. Initially, Ta in all 4 chambers was cycling at thermoneutrality (TN; 18.5°C-23.5°C) for a 1-wk adjustment period, followed by an increase in 2 chambers to cycling heat stress (HS; 24°C-38°C) for 2 wk. Five ANG and 5 RO heifers were housed at TN, whereas 6 ANG and 5 RO heifers were housed at HS. On day 19, heifers were fitted with jugular catheters. On day 20, heifers were challenged with LPS (0.5 µg/kg BW; 0 h), and blood samples were collected from -2 to 8 h and at 24 h relative to LPS challenge. Serum was analyzed for glucose, insulin, and NEFA concentrations. In addition, feed intake was measured 3 d before and on the day of the challenge. Feed intake decreased over time (P < 0.001) and was decreased in heifers housed at HS compared with heifers housed at TN (P = 0.013). Glucose concentrations before LPS challenge were greater in RO (P = 0.01) than in ANG heifers and greater in TN-housed heifers (P = 0.02) than in HS heifers. Glucose after LPS challenge initially increased before decreasing below baseline concentrations (P < 0.01) in all heifers. In addition, there was a breed by Ta interaction (P < 0.004), such that HS decreased glucose concentrations in ANG heifers compared with ANG heifers housed at TN (P < 0.001), whereas HS did not affect glucose concentrations after LPS challenge in RO heifers (P = 0.941). Nonesterified fatty acid concentrations before LPS challenge were not affected by breed (P = 0.37) or Ta (P = 0.60). Although NEFA concentration after LPS challenge was unaffected by Ta (P = 0.78), there tended to be a breed by Ta interaction (P = 0.07) such that, when housed at HS, RO heifers had greater serum NEFA concentrations after LPS challenge than ANG heifers (P = 0.009). Insulin concentration before LPS challenge was greater in RO heifers than in ANG heifers (P < 0.01). Insulin after LPS challenge increased (P < 0.01), with RO heifers producing a greater insulin response than ANG heifers (P < 0.01). These data suggest that HS decreases the metabolic response of heat-sensitive ANG heifers in response to LPS challenge, thus providing physiological evidence that may explain differences observed in the acute phase response between heat-sensitive ANG and heat-tolerant RO cattle breeds.

Heat-tolerant versus heat-sensitive Bos taurus cattle: influence of air temperature and breed on the acute phase response to a provocative immune challenge.

The difference in the acute phase response of a heat-tolerant and a heat-sensitive Bos taurus breed to a lipopolysaccharide (LPS) challenge when housed at different air temperatures (Ta) was studied. Angus (ANG; heat-sensitive; n = 11; 306 ± 26 kg BW) and Romosinuano (RO; heat-tolerant; n = 10; 313 ± 32 kg BW) heifers were transported from the USDA Agricultural Research Service SubTropical Agricultural Research Station in Florida to the Brody Environmental Chambers at the University of Missouri, Columbia. Heifers were housed in stanchions in 4 temperature-controlled environmental chambers. Initially, Ta in the 4 chambers was cycling at thermoneutrality (TN; 18.5°C-23.5°C) for a 1-wk adjustment period, followed by an increase in 2 of the 4 chambers to cycling heat stress (HS; 24°C-38°C) for 2 wk. On day 19, heifers were fitted with jugular catheters and rectal temperature (RT) recording devices. On day 20, heifers were challenged with LPS (0.5 µg/kg BW; 0 h), sickness behavior scores (SBSs) were recorded, and blood samples were collected at 0.5-h intervals from -2 to 8 h and again at 24 h relative to LPS challenge at 0 h. Serum was isolated and stored at -80°C until analyzed for cortisol and cytokine concentrations. A breed by Ta interaction (P < 0.001) was observed for RT such that the post-LPS average RT in RO heifers housed at TN was lower than the RT of all other treatment groups (P < 0.001), whereas ANG heifers housed at HS had greater post-LPS average RT than all other treatment groups (P < 0.001). In response to LPS, HS increased SBS after LPS in RO heifers compared to RO heifers housed at TN (P < 0.001), whereas HS decreased SBS after LPS in ANG heifers compared to ANG heifers housed at TN (P = 0.014). The cortisol response to LPS was greater in TN than in HS heifers (P < 0.01) and was also greater in RO than in ANG heifers (P = 0.03). A breed by Ta interaction (P < 0.01) was observed for tumor necrosis factor-α (TNF-α) concentration such that HS increased post-LPS serum concentrations of TNF-α in ANG heifers compared to ANG heifers housed at TN (P = 0.041), whereas HS decreased post-LPS concentrations of TNF-α in RO heifers compared to RO heifers housed at TN (P = 0.008). A tendency (P < 0.06) was observed for a breed by Ta interaction for IL-6 concentrations such that RO heifers had greater post-LPS concentrations of IL-6 than ANG heifers when housed at HS (P = 0.020). A breed by Ta interaction was observed for interferon-γ (IFN-γ; P < 0.01) concentrations such that HS decreased post-LPS concentrations of IFN-γ in ANG heifers compared to ANG heifers housed at TN (P < 0.001), and HS increased post-LPS concentrations of IFN-γ in RO heifers compared to RO heifers housed at TN (P = 0.017). These data indicate differences in the acute phase response between the heat-tolerant RO and heat-sensitive ANG heifers under different Ta which may aid in elucidating differences in productivity, disease resistance, and longevity among cattle breeds.

Learning new word meanings from context: a study of eye movements.

This study examined how readers establish the meaning of a new word from the sentence context during silent reading. Readers' eye movements were monitored while they read pairs of sentences containing a target word, context, and a word related to the target word. The target word varied in familiarity (high, low, or novel). The context varied in informativeness about the meaning of the target word (informative or neutral). The amount of time readers spent on the context depended on both the familiarity of the target word and the informativeness of the context. Readers spent additional time on the related word only when the context was neutral and the target was novel. These results indicate that readers were able to determine which areas of text were relevant and used the information to infer a meaning for the novel word.

Associations to unfamiliar words: learning the meanings of new words.

Five experiments were designed to examine whether subjects attend to different aspects of meaning for familiar and unfamiliar words. In Experiments 1-3, subjects gave free associations to high- and low-familiarity words from the same taxonomic category (e.g., seltzer: sarsparilla; Experiment 1), from the same noun synonym set (e.g., baby: neonate; Experiment 2), and from the same verb synonym set (e.g., abscond: escape; Experiment 3). In Experiments 4 and 5, subjects first read a context sentence containing the stimulus word and then gave associations; stimuli were novel words or either high- or low-familiarity nouns. Low-familiarity and novel words elicited more nonsemantically based responses (e.g., engram:graham) than did high-familiarity words. Of the responses semantically related to the stimulus, low-familiarity and novel words elicited a higher proportion of definitional responses [category (e.g., sarsparilla:soda), synonym (e.g., neonate:newborn), and coordinate (e.g., armoire: dresser)], whereas high-familiarity stimuli elicited a higher proportion of event-based responses [thematic (e.g., seltzer:glass) and noun:verb (e.g., baby:cry)]. Unfamiliar words appear to elicit a shift of attentional resources from relations useful in understanding the message to relations useful in understanding the meaning of the unfamiliar word.

Sensitivity to the frequency of parts and kinds: two principles of organisation in semantic memory.

Are subjects sensitive to the frequency of parts of the same whole in the same way that they are sensitive to instances of the same category? Subjects read a randomised list of words and then estimated how many words on the list had belonged to particular groups, e.g. parts of a bird, or kinds of bird. Groups of words were either parts of the same whole, e.g. feathers, beak, wing, or members of the same category, e.g. robin, sparrow, eagle. Subjects were asked, either, "How many parts of a (bird) did you see?" or "How many kinds of (bird) did you see?". Half of the subjects expected the frequency estimation task, whereas for the other half, who performed a distractor task during encoding, the task was unexpected. In Experiment 1 subjects saw either parts of kinds. Sensitivity to frequency did not differ for parts and kinds nor as a function of whether the frequency estimation test was expected. In Experiment 2 subjects saw both parts and kinds belonging to the same superordinates, e.g. parts of birds and kinds of birds, and were asked to estimate the frequency of both types of groupings for each superordinate. The results were the same as in Experiment 1. In addition, subjects were able to separate the frequency of parts and kinds of the same superordinate. The results suggest that, in frequency estimation, part-of and kind-of associations can function similarly, and that the mechanism responsible for frequency estimation is sensitive to the type of association.

Retrieval and comparison processes in part--whole decisions.

Undergraduate students were presented with word pairs (e.g., egg-yolk) and were timed as they decided whether one word named part of the thing named by the other word. In Experiment 1, "no" responses to nonpart pairs (e.g., fish-flaps) were slowed by the similarity of the stimulus part (flaps) to a part that the stimulus object did possess (fins). This suggested that decisions were made by retrieving parts of the stimulus object from memory and comparing them to the stimulus part. Whereas the parts used as stimuli in Experiment 1 were nonspecific, belonging to several different types of object (e.g., wheel), those selected for Experiment 2 were specific to a single type of object (e.g., thumb). In Experiment 2, "no" responses to nonpart pairs (e.g., foot-thumb) were slowed by similarity of the stimulus object (foot) to an object that the stimulus part (thumb) belonged to (hand). This suggested that decisions were made by retrieving the object to which the stimulus part belonged and comparing it to the stimulus object. The results support a hybrid model of part-whole decisions that includes directed retrieval of relational knowledge from memory and a comparison process.

Effects of relation similarity on part-whole decisions.

Subjects were presented with word pairs (e.g., bed-mattress) and timed as they decided whether one word named part of the item named by the other word. Yes responses were facilitated, and no responses were impeded, by relation similarity (i.e., the similarity of the relation between the two stimulus items to the part-whole relation). Item similarity, the similarity of the two stimulus items to each other, had no effect. The results support the view that similarity effects in semantic decision tasks are due to the comparison of elements of the relation between the two stimulus words against relation elements that serve as criteria for the target relation that the subject has been asked to identify.