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Browsing by Author "Johnson, Jay S."

Now showing 1 - 5 of 5
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    Effects of heat stress on carbohydrate and lipid metabolism in growing pigs
    Sanz Fernandez, M. Victoria; Johnson, Jay S.; Abuajamieh, Mohannad; Stoakes, Sara K.; Seibert, Jacob T.; Cox, Lindsay; Kahl, Stanislaw; Elsasser, Theodore H.; Ross, Jason W.; Isom, S. Clay; Rhoads, Robert P.; Baumgard, Lance H. (2015-02-01)
    Heat stress (HS) jeopardizes human and animal health and reduces animal agriculture productivity; however, its pathophysiology is not well understood. Study objectives were to evaluate the direct effects of HS on carbohydrate and lipid metabolism. Female pigs (57 ± 5 kg body weight) were subjected to two experimental periods. During period 1, all pigs remained in thermoneutral conditions (TN; 20°C) and were ad libitum fed. During period 2, pigs were exposed to: (1) constant HS conditions (32°C) and fed ad libitum (n = 7), or (2) TN conditions and pair-fed (PFTN; n = 10) to minimize the confounding effects of dissimilar feed intake. All pigs received an intravenous glucose tolerance test (GTT) and an epinephrine challenge (EC) in period 1, and during the early and late phases of period 2. After 8 days of environmental exposure, all pigs were killed and tissue samples were collected. Despite a similar reduction in feed intake (39%), HS pigs tended to have decreased circulating nonesterified fatty acids (NEFA; 20%) and a blunted NEFA response (71%) to the EC compared to PFTN pigs. During early exposure, HS increased basal circulating C-peptide (55%) and decreased the insulinogenic index (45%) in response to the GTT. Heat-stressed pigs had a reduced T3 to T4 ratio (56%) and hepatic 5'-deiodinase activity (58%). After 8 days, HS decreased or tended to decrease the expression of genes involved in oxidative phosphorylation in liver and skeletal muscle, and ATGL in adipose tissue. In summary, HS markedly alters both lipid and carbohydrate metabolism independently of nutrient intake.
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    Gestational Heat Stress Alters Postnatal Offspring Body Composition Indices and Metabolic Parameters in Pigs
    Boddicker, Rebecca L.; Seibert, Jacob T.; Johnson, Jay S.; Pearce, Sarah C.; Selsby, Joshua T.; Gabler, Nicholas K.; Lucy, Matthew C.; Safranski, Timothy J.; Rhoads, Robert P.; Baumgard, Lance H.; Ross, Jason W. (PLOS, 2014-11-10)
    The study objectives were to test the hypothesis that heat stress (HS) during gestational development alters postnatal growth, body composition, and biological response to HS conditions in pigs. To investigate this, 14 first parity crossbred gilts were exposed to one of four environmental treatments (TNTN, TNHS, HSTN, or HSHS) during gestation. TNTN and HSHS dams were exposed to thermal neutral (TN, cyclical 18–22ºC) or HS conditions (cyclical 28–34ºC) during the entire gestation, respectively. Dams assigned to HSTN and TNHS treatments were heat-stressed for the first or second half of gestation, respectively. Postnatal offspring were exposed to one of two thermal environments for an acute (24 h) or chronic (five weeks) duration in either constant TN (21ºC) or HS (35ºC) environment. Exposure to chronic HS during their growth phase resulted in decreased longissimus dorsi cross-sectional area (LDA) in offspring from HSHS and HSTN treated dams whereas LDA was larger in offspring from dams in TNTN and TNHS conditions. Irrespective of HS during prepubertal postnatal growth, pigs from dams that experienced HS during the first half of gestation (HSHS and HSTN) had increased (13.9%) subcutaneous fat thickness compared to pigs from dams exposed to TN conditions during the first half of gestation. This metabolic repartitioning towards increased fat deposition in pigs from dams heat-stressed during the first half of gestation was accompanied by elevated blood insulin concentrations (33%; P = 0.01). Together, these results demonstrate HS during the first half of gestation altered metabolic and body composition parameters during future development and in biological responses to a subsequent HS challenge.
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    Heat stress increases insulin sensitivity in pigs
    Sanz Fernandez, M. Victoria; Stoakes, Sara K.; Abuajamieh, Mohannad; Seibert, Jacob T.; Johnson, Jay S.; Horst, E. A.; Rhoads, Robert P.; Baumgard, Lance H. (2015-08)
    Proper insulin homeostasis appears critical for adapting to and surviving a heat load. Further, heat stress (HS) induces phenotypic changes in livestock that suggest an increase in insulin action. The current study objective was to evaluate the effects of HS on whole-body insulin sensitivity. Female pigs (57 ± 4 kg body weight) were subjected to two experimental periods. During period 1, all pigs remained in thermoneutral conditions (TN; 21°C) and were fed ad libitum. During period 2, pigs were exposed to: (i) constant HS conditions (32°C) and fed ad libitum (n = 6), or (ii) TN conditions and pair-fed (PFTN; n = 6) to eliminate the confounding effects of dissimilar feed intake. A hyperinsulinemic euglycemic clamp (HEC) was conducted on d3 of both periods; and skeletal muscle and adipose tissue biopsies were collected prior to and after an insulin tolerance test (ITT) on d5 of period 2. During the HEC, insulin infusion increased circulating insulin and decreased plasma C-peptide and nonesterified fatty acids, similarly between treatments. From period 1 to 2, the rate of glucose infusion in response to the HEC remained similar in HS pigs while it decreased (36%) in PFTN controls. Prior to the ITT, HS increased (41%) skeletal muscle insulin receptor substrate-1 protein abundance, but did not affect protein kinase B or their phosphorylated forms. In adipose tissue, HS did not alter any of the basal or stimulated measured insulin signaling markers. In summary, HS increases whole-body insulin-stimulated glucose uptake.
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    Heat Stress Reduces Intestinal Barrier Integrity and Favors Intestinal Glucose Transport in Growing Pigs
    Pearce, Sarah C.; Mani, Venkatesh; Boddicker, Rebecca L.; Johnson, Jay S.; Weber, Thomas E.; Ross, Jason W.; Rhoads, Robert P.; Baumgard, Lance H.; Gabler, Nicholas K. (PLOS, 2013-08-01)
    Excessive heat exposure reduces intestinal integrity and post-absorptive energetics that can inhibit wellbeing and be fatal. Therefore, our objectives were to examine how acute heat stress (HS) alters intestinal integrity and metabolism in growing pigs. Animals were exposed to either thermal neutral (TN, 21°C; 35–50% humidity; n = 8) or HS conditions (35°C; 24–43% humidity; n = 8) for 24 h. Compared to TN, rectal temperatures in HS pigs increased by 1.6°C and respiration rates by 2-fold (P,0.05). As expected, HS decreased feed intake by 53% (P<0.05) and body weight (P<0.05) compared to TN pigs. Ileum heat shock protein 70 expression increased (P<0.05), while intestinal integrity was compromised in the HS pigs (ileum and colon TER decreased; P<0.05). Furthermore, HS increased serum endotoxin concentrations (P<0.05). Intestinal permeability was accompanied by an increase in protein expression of myosin light chain kinase (P<0.05) and casein kinase II-a (P = 0.06). Protein expression of tight junction (TJ) proteins in the ileum revealed claudin 3 and occludin expression to be increased overall due to HS (P,0.05), while there were no differences in claudin 1 expression. Intestinal glucose transport and blood glucose were elevated due to HS (P<0.05). This was supported by increased ileum Na+/K+ ATPase activity in HS pigs. SGLT-1 protein expression was unaltered; however, HS increased ileal GLUT-2 protein expression (P=0.06). Altogether, these data indicate that HS reduce intestinal integrity and increase intestinal stress and glucose transport.
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    The Use of a Tuning Fork and Stethoscope Versus Clinical Fracture Testing in Assessing Possible Fractures
    Moore, Michael Bryan (Virginia Tech, 2005-03-31)
    Traditional fracture testing in the field of athletic training relies heavily on subjective responses of the athlete. Percussion and compression type tests rely on the athlete stating an increase in pain which represents a positive symptom of a possible fracture. The tuning fork and stethoscope method relied purely on a subjective assessment from the examiner. The purpose of the study was to determine if the use of a 128Hz tuning fork and stethoscope were effective evaluation tools in the assessment of possible fractures as compared to the traditional fracture tests that are used in the athletic training field. A vibrating 128 Hz tuning fork was placed on the bone/area where swelling was minor to facilitate good cortical bone contact. Then the conical bell of a stethoscope was placed on the opposite end on the bone or bones. A diminished sound arising from the injured bone as compared to the uninjured represented a positive sign for a possible fracture. Traditional fracture testing was performed and noted. An x-ray, diagnosed by an orthopedic physician, supported the validity of the tuning fork and traditional fracture testing methods. The attempt was to see what testing method, the tuning fork and stethoscope or traditional fracture testing, was a more valid evaluation tool when it comes to fractures. This study was performed at a university's athletic training room and a local orthopedic center. The study consisted of any subject between the ages of 18-85 that presented with a suspected fracture at either testing facilities. The current study examined 37 male and female subjects whose age ranged from 18-85 years old. The long bones that were tested in this research were as follows: the phalanges of the hand and foot, metacarpals, metatarsals, humerus, radius, ulna, fibula (including the lateral malleolus), and tibia (including the medial malleolus). The tuning fork and stethoscope was shown to be an effective and valid tool for evaluating possible fractures by yielding a success rate of 89.2% when compared to an x-ray. The percussion and compression fracture testing methods yielded only a success rate of 67.6% and 64.9% respectively.