Aktuell gibt es für Selen (Se) keine Bedarfsempfehlungen für das Damwild (Dama dama) in Gehegehaltung. Diese Studie soll die typische Se-Aufnahme bei Gehegehaltung von Damwild ermitteln und klären, welche Parameter sich eignen, um die Se-Versorgung des Damwildes zu reflektieren. Dazu wurden 19 Damhirsche in zwei Gruppen unter identischen Bedingungen gehalten. Die Tiere ernährten sich von dem natürlichen Grasaufwuchs und Mischfutter (0,15 mg/kg TS bzw. 1,07 - 1,91 mg/kg TS). In Blut, Plasma und die Organen wurden der Se-Gehalt, die Aktivität der Se-abhängigen Glutathionperoxidase (GPx) sowie teilweise die Gesamt-GPx-Aktivität (gesGPx), die Aktivität der Glutathion-S-Transferase (GST) und die Expression verschiedener GPx analysiert. Durch die Se-Supplementierung wurden ein signifikanter Anstieg des Plasma-Se in der Versuchsgruppe und ein moderater Unterschied der Vollblut-Se-Konzentration sowie der Vollblut-GPx-Aktivität zwischen der Kontroll- und der Versuchsgruppe beobachtet (p = 0,08). Außerdem wurde in allen Organen der Versuchsgruppe ein höherer Se-Gehalt als in der Kontrollgruppe festgestellt. In der Hierarchie der untersuchten Organe ist die Niere am höchsten angeordnet, absteigend folgen der Herz- und Skelettmuskel, die Milz und die Leber. Eine Se-Aufnahme von 0,05 - 0,08 mg/kg TS führt beim Damwild nicht zur Ausprägung von Se-Mangelsymptomen und stellt daher eine ausreichende Se-Versorgung dar. Die Empfehlungen zur Se-Versorgung für Damwild sind somit nicht von Hauswiederkäuern zu übernehmen. Im Plasma und im Vollblut scheinen Se-Konzentrationen von 28 - 64 µg/l und 81 - 200 µg/l für eine ausreichende Se-Versorgung zu sprechen, in der Leber Se-Konzentrationen von 270 - 663 µg/kg TS.:Inhaltsverzeichnis Inhaltsverzeichnis I Abbildungsverzeichnis V Tabellenverzeichnis VI Verzeichnis der Anhangstabellen VIII Abkürzungsverzeichnis IX 1. Einleitung 1 2. Literaturübersicht 2 2.1 Se als chemisches Element 2 2.2 Geschichte des Se und seiner Proteine 3 2.3 Se-Gehalte in Boden, Pflanzen, Nahrungs- und Futtermitteln 4 2.3.1 Se-Gehalte im Boden 4 2.3.2 Se-Gehalte in Pflanzen 5 2.3.3 Se-Gehalte in Nahrungsmitteln 7 2.3.4 Se-Gehalte in Futtermitteln 8 2.4 Se im Stoffwechsel 9 2.4.1 Resorption 9 2.4.2 Transport, Metabolismus und Speicherung 10 2.4.2.1 Transport 10 2.4.2.3 Speicherung 11 2.4.3 Versorgung über Plazenta und Milch 12 2.4.4 Exkretion 14 2.5 Biologische Funktionen des Se 16 2.5.1 SeP 16 2.5.2 Funktionen 18 2.5.2.1 Spezielle Funktionen der GPx 18 2.5.2.2 Weitere Funktionen der Selenoenzyme 20 2.6 Damwild (Dama dama) 21 2.6.1 Systematische und historische Einordnung des Damwildes 21 2.6.2 Physiologie und Ernährung des Damwildes 22 2.6.3 Se-Status bei Cerviden 23 2.7 Se-Bedarf 24 2.8 Se- und Enzymwerte im Organismus 25 2.8.1 Se-Gehalte im Blut 25 2.8.2 Se-Gehalte in verschiedenen Organen 28 2.9 Se und Erkrankungen 30 2.9.1 Se-Mangel assoziierte Erkrankungen 30 2.9.2 Se-Toxizität 31 2.9.2.1 Die akute Se-Intoxikation 32 2.9.2.2 Die subakute Se-Intoxikation 33 2.9.2.3 Die chronische Se-Intoxikation 33 3 Tiere, Material und Methoden 35 3.1 Versuchsziel 35 3.2 Tiere 35 3.3 Haltung 35 3.4 Fütterung und Supplementierung 35 3.5 Versuchsablauf 37 3.6 Probenentnahmen 38 3.6.1 Blutproben 38 3.6.2 Organ- und Gewebeproben 38 3.6.3 Wiegen 40 3.6.4 Futterproben 41 3.7 Versuchsparameter 43 3.8 Analytische Methoden 43 3.8.1 Futteranalyse 43 3.8.1.1 TS 43 3.8.1.2 Rohasche (Ra) 44 3.8.1.3 Organische Substanz (oS) 44 3.8.1.4 Rohprotein (Rp) 44 3.8.1.5 Rohfett (Rfe) 44 3.8.1.6 Rohfaser (Rfa) 44 3.8.1.7 N-freie Extraktstoffe (NfE) 45 3.8.1.8 Spurenelemente: Se, Cu, Zn 45 3.8.2 Vollblut-, Plasma-, Organ- und Gewebeanalyse 45 3.8.2.1 Histologie der Skelettmuskulatur 45 3.8.2.2 Se-Gehalt 46 3.8.2.3 TS-Gehalt 47 3.8.2.4 GPx-Aktivität 47 3.8.2.5 Proteingehalt 48 3.8.2.6 Hämoglobingehalt 49 3.8.2.7 GPx-mRNA-Expression 49 3.8.2.8 α -Glutathion-S-Transferase-Aktivität (GST) 53 3.9 Statistische Auswertung 54 4. Ergebnisse 55 4.1 KM der Tiere und Gewichte der Schlachtkörperhälften 55 4.1.1 KM der Tiere zu Versuchsbeginn 55 4.1.2 Gewichte der Schlachtkörperhälften zu Versuchende 55 4.2 Histologie der Skelettmuskulatur 56 4.3 Se-Gehalte in Plasma, Vollblut und Organen 58 4.3.1 Se-Gehalte in Plasma und Vollblut 58 4.3.2 Se-Gehalte in verschiedenen Organen 59 4.4 Se-abhängige und -unabhängige Enzyme 60 4.4.1 GPx-Aktivitäten in Plasma und Vollblut 60 4.4.2 GPx-Aktivität in verschiedenen Organen 62 4.4.3 GPx-mRNA-Expression 63 4.4.4 α-GST-Aktivität 64 5. Diskussion 67 5.1 Kritik der Methoden 67 5.1.1 Se-Supplementierung der Tiere 67 5.1.1.1 Futteraufnahme 67 5.1.1.2 Höhe der Se-Supplementierung 67 5.1.1.3 Dauer der Se-Supplementierung 68 5.1.1.4 Art der Se-Supplementierung 68 5.1.2 Probengewinnung 69 5.1.3 Untersuchungsparameter 69 5.1.4 Vitamin E 69 5.2 Diskussion der Versuchsergebnisse 70 5.2.1 Einschätzung der Se-Versorgung vor Se-Supplementierung 70 5.2.2 Einschätzung der Se-Versorgung nach unterschiedlicher Se-Supplementierung 72 6. Zusammenfassung 81 7. Summary 83 8. Literaturverzeichnis 85 9. Anhang……………………………………………………………………..110 Danksagung 117

Vitamin D deficiency is common in individuals diagnosed with HIV and is known for its detrimental health effects. Its recognition as a potent immune-modulator with possible immune health implications in HIV disease progression was the main impetus for this study. The association between Vitamin D and CD4 count falls short of being consistent and is too weak to allow conclusions. Similarly, the literature is inconsistent with regard to the impact of Vitamin D supplementation on CD4. This observational, retrospective chart review study aimed to explore the relationship between Vitamin D deficiency and CD4 count/percent, and to evaluate whether changes in Vitamin D levels after supplementation corresponds with significant changes in CD4 count/percent in a cohort of African American, HIV-infected men who attended an HIV clinic in southeast Michigan (N = 70). The conceptual framework was based on the role of Vitamin D in regulating the immune responses through Vitamin D nuclear receptors on the CD4 cells. It postulated that an increase in Vitamin D level might enhance immune function, promote cellular anti-inflammatory state, and decelerate CD4 destruction. Data analysis included descriptive statistics, bivariate correlation, logistic and linear regression, t test, repeated measures ANOVA, and ANCOVA. Findings of the study did not support the hypotheses of significant correlation between Vitamin D and CD4 count (p = 0.458) and percent (p = 0.776), or of any impact of supplementation on CD4 count (p = 0.216) and percent (p = 0.918). Social change implications include providing health professionals, researchers, and policymakers with knowledge to tailor health promotion interventions aiming to reduce Vitamin D deficiency in favor of improving the overall health of HIV patients, especially high-risk groups such as African American HIV-infected patients.

No description available.

Tall fescue (Schedonorus arundinaceus), is a cool season perennial that provides grazing into the early summer months for southern livestock. Grazing the tall fescue variety, Kentucky-31, has negative effects on animal health, particularly after jointing. Two studies were arranged as randomized complete blocks in a split-plot design, with three replicates to compare: the effect of ten herbicides on seedhead suppression, or the effect of inter-seeding legumes [white clover (Trifolium repens) or alfafla (Medicago sativa)] coupled with nitrogen supplementation on fescue yield and forage nutritive value. The herbicides imazethapyr + 2,4-D and without, metsulfuron + chlorsulfuron, reduced seedheads emergence, but not yield compared to the control. Kentucky-31 inter-seeded with white clover and fertilized with 11 kg N ha-1 produced greater biomass than tall fescue fertilized with 11 kg N ha-1. The inter-seeding of white clover produced composite forage samples with greater in vitro dry matter disappearance than nitrogen supplemented alfalfa.

<p>(From abstract) </p> <p>In the first study, the urine collection method was effectively applied for evaluation of intestinal permeability using Cr-EDTA, an indigestible oral marker, demonstrating the applicability of the procedure in 1-week-old and 6-week-old neonatal heifer calves (n=15 calves). Calf health observations were recorded during the entire urinary catheterization process and collection period to evaluate any negative health reactions to the procedure, or localized reactions. Proportion of localized reactions were analyzed, and the proportions did not exceed 20% for the calves catheterized at either 1 week or 6 weeks of age. </p> <p>In the second study, the developed catheterization procedure and urine collection method was applied using Cr-EDTA as an oral marker to investigate if L-GLN supplementation would offer improvement to intestinal permeability. In this larger study, 30 Holstein heifer calves [1.5 ± 0.5 days old; 37.1 ± 0.86 kg body weight (<strong>BW</strong>)] were blocked by serum total protein, BW, and age, and randomly assigned to 1 of 2 treatments: <strong>GLN</strong> [24% crude protein (<strong>CP</strong>)], 17% fat milk replacer (<strong>MR</strong>) +10 g L-GLN/kg MR powder) or <strong>NS</strong> (24% CP, 17% fat MR). MR was reconstituted to 12.5% solids with warm water and fed 3.8 L/calf/d until weaning. Calves were weaned at 56.4 ± 0.5 days of age, and had <em>ad libitum</em> grain (17% CP, 2% fat) and water access throughout the experimental period.</p> <p>During the preweaning period, calves were individually housed in hutches and health observations, which included respiratory and fecal scores, were assessed daily. Body weight was measured weekly, and grain and MR intake was assessed daily to calculate average daily gain (<strong>ADG</strong>), average daily feed intake [<strong>ADFI</strong>; grain intake (dry matter (<strong>DM)</strong> basis) + MR intake (DM basis)], and feed efficiency (<strong>G:F</strong>; ADG:ADFI). At weaning, calves were weighed, moved to pens (n = 3 pens/treatment, 4-5 calves/pen), provided free access to grain and grass hay, and then weighed 2 weeks post-weaning. Additionally, urinary catheters were placed at 1 and 6 weeks of age, and calves were orally dosed with 1 L Cr-EDTA in their MR. Urine samples were then collected over a 24-hr period for Cr output analysis as an <em>in vivo</em>biomarker of intestinal permeability. </p> <p>Blood was collected on study days 1, 2, 5, 7, 14, 21, 42, 56, and 70 to measure haptoglobin, serum amyloid A, leukocyte data, neutrophil: lymphocyte (<strong>N:L</strong>), glucose, non-esterified fatty acids, insulin, and cortisol. Two study periods were identified for data analysis representing greater (<strong>P1</strong>; weeks 1-3) and reduced (<strong>P2</strong>; weeks 4-8) enteric disease susceptibility. Data were analyzed using PROC GLIMMIX or PROC MIXED in SAS 9.4 with calf as the experimental unit. There was a decrease in total preweaning Cr output (<em>P</em> < 0.05) for GLN calves, and Cr output in 1 week old calves was decreased (<em>P</em> = 0.04) in GLN versus NS calves. The N:L was decreased overall (<em>P</em> = 0.03) and during P2 (<em>P</em> = 0.01) and P2 neutrophil count tended to be reduced (<em>P</em> = 0.07) in GLN versus NS calves. There were no MR treatment differences for ADFI, ADG, body measurements, post-absorptive metabolic biomarkers, disease scores, and therapeutic treatments (<em>P</em> > 0.10). In summary, L-GLN supplementation improved intestinal integrity and biomarkers of physiological stress in pre-weaned Holstein heifer calves managed under production-relevant conditions.  </p>

<p><em>Objective: </em>We evaluated the potential effect of oral glucose supplementation on: (1) exercise performance and tolerance, (2) the concentrations of plasma uric acid and ammonia (NH₃) and (3) blood plasma markers of oxidative stress in patients with McArdle’s disease (MCD) after non-ischemic forearm exercise testing (non-ischemic forearm exercise test). <em>Methods:</em> Blood samples and exercise performance measures were performed on from 16 patients with MCD and 17 control subjects (CON) matched for age, sex and physical activity status. Subjects performed 2 exercise bouts 30 minutes apart and received oral glucose or placebo supplementation between tests. Blood samples were analyzed for concentrations of 8-isoprostanes (8-ISO), malondialdehyde (MDA) and total anti-oxidant capacity (TEAC). Exercise performance was assessed using a handgrip dynamometer to measure force of contraction over time. Exercise tolerance was assessed based on subject’s self-reported perception of pain and perception of exertion during exercise. <em>Results:</em> MCD was associated with greater fatigue, perceived pain, perceived exertion, and higher uric acid during non-ischemic forearm exercise test (P < 0.05), and higher concentrations of plasma NH₃post exercise (P < 0.05). Glucose did not influence plasma uric acid or NH₃and had no effect on exercise measures in MCD patients. Baseline plasma markers of oxidative stress were not different between MCD patients and CON; however, MCD patients who ingested glucose between non-ischemic forearm exercise tests had lower plasma 8-ISO concentrations (P < 0.05). CON who ingested glucose between non-ischemic forearm exercise tests had lower plasma 8-ISO concentrations (P < 0.05) at +1 min post exercise compared to initial non-ischemic forearm exercise test. The TEAC of control subjects was lower following non-ischemic forearm exercise test (P < 0.05), with no change in MCD patients. <em>Conclusion: </em>Glucose may have a protective effect on oxidative stress following exercise that may be due to attenuated flux through xanthine oxidase.</p> / Master of Science (MSc)

<p dir="ltr">For this dissertation, two experiments were conducted to evaluate the effects of a multienzyme mix and partially defatted black soldier fly larvae meal on chicken coccidiosis, focusing on growth performance, intestinal health, and microbiota dynamics. Experiment 1 examined the growth performance, nutrient utilization, microbiota modulations, and other gut health-related indicators of broiler chickens under coccidia challenge, with dietary supplementation of multienzyme, including phytase, xylanase, β-glucanase, amylase, hemicellulase, and pectinase. Ross 308 broilers were assigned to 4 treatments in a 2×2 factorial arrangement comprising of 0 or 50 g·kg-1 multienzyme and oral challenge with PBS or mixed Eimeria spp. oocysts (250,000 E. acervulina, 50,000 E. maxima, and 50,000 E. tenella). Multienzyme reduced (P < 0.05) Eimeria-induced loss in feed efficiency and nutrient utilization, partially explained by reduced decrease of b0,+ amino acid transporter in jejunum. Multienzyme suppressed (P < 0.05) the overexpression of interleukin-8 in the duodenum and jejunum and ameliorated (P = 0.05) the decreased expression of antioxidant heme oxygenase 1 in ileum induced by Eimeria infections. Multienzyme facilitated (P < 0.01) the bloom of short-chain fatty acid-producing and fiber-degrading microbes. The study concluded that multienzyme supplementation partially alleviated the adverse effects of Eimeria infections through various mechanisms, including enhanced nutrient utilization, reduced local inflammations, and restoration of microbial homeostasis. Experiment 2 investigated the growth dynamics, nutrient assimilation, and gut health responses of broiler chickens under coccidia challenge, with dietary supplementation of partially defatted black soldier fly larvae meal (pBSFLM) with increasing concentrations of 0, 60, 120 g/kg. During the infection phase (from d 13 to 19), interactions between Eimeria and pBSFLM revealed significant associations with gain to feed ratio (G:F) (P < 0.05) and cecal interferon-γ (IFN-γ, P < 0.05), while showing tendencies for crypt depth (P = 0.088) and cecal acetate concentration (P = 0.06). The incremental inclusion of pBSFLM demonstrated a negative effect on the G:F and the generation of IFN-γ and acetate in the ceca during coccidia challenge. Conversely in the non-challenged birds, the impact of dietary pBSFLM varied from neutral (e.g. G:F) to potentially advantageous (e.g. acetate). Challenged broilers exhibited decreased (P < 0.01) BW, feed intake (FI), G:F, as well as the apparent ileal digestibility (AID) and total tract nutrient utilization (ATTU) of DM, gross energy (GE), and nitrogen (N). Eimeria challenge led to reduced (P < 0.01) serum carotenoid concentrations, increased (P < 0.01) ileal crypt depth (CD), and an increase in the generation of branched-chain fatty acids, specifically isobutyrate (P = 0.059) and isovalerate (P < 0.05) in the ceca. Dietary pBSFLM addition caused a linear reduction (P < 0.05) in BW, FI, G:F, and N utilization. Furthermore, a tendency (P < 0.06) was observed where pBSFLM linearly decreased the villi height: CD ratio and reduced goblet cell density in the villi. Results from this experiment reveal that higher levels of pBSFLM supplementation, especially at 12%, had detrimental effects on growth, ileal morphology, cecal acetate production, and downregulated the expression of key cytokines in response to coccidia infection. In summary, these studies shed light on the multifaceted effects of dietary interventions on Eimeria infections in broiler chickens, with a specific emphasis on growth, nutrient utilization, and indicators of gut health.</p>

Two studies were conducted during the grazing season of 1997. Study 1 consisted of three Experiments, and the objectives were to compare milk production and composition, body weight change and body condition score, and to determine time patterns of grazing between cows supplemented with different forms and amounts of corn. Also rumen fermentation parameters were measured in cows supplemented with two different types of corn. In study 2, milk yield was measured when grazing pasture was supplemented to lactating Holstein cows fed a typical TMR diet. Predominantly orchardgrass pastures with lesser amounts of white clover and Kentucky bluegrass were grazed during both studies. In Experiment 1, 36 Holstein cows were supplemented either with 6, 6, 6, or 4 kg/d DM of high moisture corn, coarsely ground corn, finely ground corn, or high moisture corn in two equal feedings, respectively. Milk yield was similar (30.3 kg/d) among treatments. Milk protein (2.97%) and MUN (14.7 mg/dl) did not differ among treatments. Body weight change and body condition score change were similar among treatments (23.1 kg and -0.24). During Experiment 2, four rumen-cannulated cows in mid-lactation were supplemented 6 kg/d DM of either coarsely ground corn or high moisture corn in two equal feedings. After the p.m. milking, ruminal pH was measured and rumen fluid samples were collected to determine ammonia N and VFA. While grazing, this was repeated at 0.5, 1, 2, 3,...8 h post-corn feeding (0 h). Ruminal pH was similar for both corn supplements and was lowest (5.9 and 5.8) at 5 and 8 h, respectively. Rumen ammonia N concentrations started to increase approximately 2 h after cows began grazing, reaching maximum levels 5 h later. In Experiment 3, the number of cows grazing, lying, or standing were recorded every half hour, for two consecutive days, while grazing. Cows grazed an average of 6.4 h/d, 4.1 h in the afternoon and 2.3 h in the morning. Similarity in milk production, milk composition, BW change, and BCS between treatments indicates that the quality and availability of pasture permitted equal response regardless of the type or amount of corn supplemented. Fifty four Holstein cows in mid lactation were used in Study 2. Cows were fed either a TMR diet only, or were fed TMR during half of the day (after the a.m. or p.m. milking according to the treatment) and supplemented with grazing pasture during the other half of the day. Milk production was slightly but significantly higher for cows on the TMR treatment (29.1 vs. 28.2 and 27.6). No significant difference between treatments was observed in FCM (27.7 kg/d), and milk fat (3.47) and protein percentage (3.23). While BW change did not differ among treatments (25.7 kg), body condition score increased more in cows fed only a TMR diet (0.14 vs. -0.06 and 0.01). The TMR intake was significantly different between treatments, being highest for cows on the TMR treatment and lowest for cows grazing after the p.m. milking (26.6 vs. 20.3 vs. 17.5 kg/d DM). Income over feed cost differed between treatments, and was approximately 15.3% higher for cows supplemented with high quality pasture during the afternoon compared to cows on TMR. Dairy farmers may obtain economical benefits by practicing this type of management during the grazing season with little effect on milk yield. / Master of Science

To determine the relationship between infant-feeding practices and diarrhoeal infections, a descriptive survey was conducted to infants between six to 12 months of age. A guided interview was conducted to 105 mothers of infants who attended the health facilities of Mbabane, Swaziland. The results show that breast-feeding is routinely practiced by the majority of mothers and exclusive breast-feeding is very low, but supplementary feed in the form of formula or solids are introduced by the majority of respondents within the first three months of life. Infants who were given colostrum and breast milk had fewer diarrhoeal attacks. Other factors, for example education and cultural factors influenced the feeding practices and number of diarrhoeal attacks. It is recommended that breast-feeding should be promoted as an important intervention in the control of diarrhoea / Health Studies / M.A. (Nursing Science)

The overall objective of this thesis was to examine mechanisms involved in the acute regulation of sarcoplasmic reticulum (SR) Ca2+-handling properties by second messenger signaling pathways in skeletal and cardiac muscle. The aim of the first study (Chapter Two) was to characterize changes in the kinetic properties of sarco(endo)-plasmic reticulum Ca2+-ATPase (SERCA) proteins in cardiac and skeletal muscles in response to b-adrenergic, Ca2+-dependent calmodulin kinase II (CaMKII) and protein kinase C (PKC) signaling. The aim of the second study (Chapter Three) was to determine if insulin signaling could acutely regulate SERCA kinetic properties in cardiac and skeletal muscle. The aim of the final study (Chapter Four) was to determine if alterations in plasma glucose, epinephrine and insulin concentrations during exercise are able to influence SR Ca2+-handling properties in contracting human skeletal muscle. Data collected in Chapter Two and Chapter Three were obtained using tissue prepared from a group of 28 male Sprague-Dawley rats (9 weeks of age; mass = 280 ?? 4 g: X ?? S.E). Crude muscle homogenates (11:1 dilution) were prepared from selected hind limb muscles (soleus, SOL; extensor digitorum longus, EDL; the red portion of gastrocnemius, RG; and the white portion of gastrocnemius, WG) and the left ventricle (LV). Enriched SR membrane fractions, prepared from WG and LV, were also analyzed. A spectrophotometric assay was used to measure kinetic properties of SERCA, namely, maximal SERCA activity (Vmax), and Ca2+-sensitivity was characterized by both the Ca50, which is defined as the free Ca2+-concentration needed to elicit 50% Vmax, and the Hill coefficient (nH), which is defined as the relationship between SERCA activity and Ca2+f for 10 to 90% Vmax. The observations made in Chapter Two indicated that b-adrenergic signaling, activated by epinephrine, increased (P<0.05) Ca2+-sensitivity, as shown by a left-shift in Ca50 (i.e. reduced Ca50), without altering Vmax in LV and SOL but had no effect (P<0.05) on EDL, RG, or WG. Further analysis using a combination of cAMP, the PKA activator forskolin, and/or the PKA inhibitor KT5270 indicated that the reduced Ca50 in LV was activated by cAMP- and PKA-signaling mechanisms. However, although the reduced Ca50 in SOL was cAMP-dependent, it was not influenced by a PKA-dependent mechanism. In contrast to the effects of b-adrenergic signaling, CaMKII activation increased SERCA Ca2+-sensitivity, as shown by a left-shift in Ca50 and increased nh, without altering SERCA Vmax in LV but was without effect in any of the skeletal muscles examined. The PKC activator PMA significantly reduced SERCA Ca2+-sensitivity, by inducing a right-shift in Ca50 and decreased nH in the LV and all skeletal muscles examined. PKC activation also reduced Vmax in the fast-twitch skeletal muscles (i.e. EDL, RG and WG), but did not alter Vmax in LV or SOL. The results of Chapter Three indicated that insulin signaling increased SERCA Ca2+-sensitivity, as shown by a left-shift in Ca50 (i.e. reduced Ca50) and an increased nH, without altering SERCA Vmax in crude muscle homogenates prepared from LV, SOL, EDL, RG, and WG. An increase in SERCA Ca2+-sensitivity was also observed in enriched SERCA1a and SERCA2a vesicles when an activated form of the insulin receptor (A-INS-R) was included during biochemical analyses. Co-immunoprecipitation experiments were conducted and indicated that IRS-1 and IRS-2 proteins bind SERCA1a and SERCA2a in an insulin-dependent manner. However, the binding of IRS proteins with SERCA does not appear to alter the structural integrity of the SERCA Ca2+-binding site since no changes in NCD-4 fluorescence were observed in response to insulin or A-INS-R. Moreover, the increase in SERCA Ca2+-sensitivity due to insulin signaling was not associated with changes in the phosphorylation status of phospholamban (PLN) since Ser16 or Thr17 phosphorylation was not altered by insulin or A-INS-R in LV tissue. The data described in Chapter Four was collected from 15 untrained human participants (peak O2 consumption, VO2peak= 3.45 ?? 0.17 L/min) who completed a standardized cycle test (~60% VO2peak) on two occasions during which they were provided either an artificially sweetened placebo (PLAC) or a 6% glucose (GLUC) beverage (~1.00 g CHO per kg body mass). Muscle biopsies were collected from the vastus lateralis at rest, after 30 min and 90 min of exercise and at fatigue in both conditions to allow assessment of metabolic and SR data. Glucose supplementation increased exercise ride time by ~19% (137 ?? 7 min) compared to PLAC (115 ?? 6 min). This performance increase was associated with elevated plasma glucose and insulin concentrations and reduced catecholamine concentrations during GLUC compared to PLAC. Prolonged exercise reduced (p<0.05) SR Ca2+-uptake, Vmax, Phase 1 and Phase 2 Ca2+-release rates during both PLAC and GLUC. However, no differences in SR Ca2+-handling properties were observed between conditions when direct comparisons were made at matched time points between PLAC and GLUC. In summary, the results of the first study (Chapter Two) indicate that b-adrenergic and CaMKII signaling increases SERCA Ca2+-sensitivity in the LV and SOL; while PKC signaling reduces SERCA Ca2+-sensitivity in all tissues. PKC activation also reduces Vmax in the fast-twitch skeletal muscles (i.e. EDL, RG, and WG) but has no effect on Vmax in the LV and SOL. The results of the second study (Chapter Three) indicate that insulin signaling acutely increases the Ca2+-sensitivity of SERCA1a and SERCA2a in all tissues examined, without altering the Vmax. Based on our observations, it appears that the increase in SERCA Ca2+-sensitivity may be regulated, in part, through the interaction of IRS proteins with SERCA1a and SERCA2a. The results of the final study (Chapter Four) indicate that alterations in plasma glucose, epinephrine and insulin concentrations associated with glucose supplementation during exercise, do not alter the time course or magnitude of reductions in SERCA or Ca2+-release channel (CRC) function in working human skeletal muscle. Although glucose supplementation did increase exercise ride time to fatigue in this study, our data does not reveal an association with SR Ca2+-cycling measured in vitro. It is possible that the strength of exercise signal overrides the hormonal influences observed in resting muscles. Additionally, these data do not rule out the possibility that glucose supplementation may influence E-C coupling processes or SR Ca2+-cycling properties in vivo.