Seasonal heat load is more potent than the degree of body weight loss in dysregulating immune function by reducing white blood cell populations and increasing inflammation in Holstein dairy cows.

We investigated the effects of seasonal heat stress and the degree of body weight (BW) loss postpartum (PP) on immune and inflammatory markers in transition dairy cows. Blood sampled twice weekly during the transition period (3 wk prepartum to 3 wk PP) from 12 peripartum Holstein cows in summer and 12 in winter was analyzed for plasma nonesterified fatty acids, the oxidative stress marker malondialdehyde (MDA), haptoglobin, and tumor necrosis factor-α (TNF-α). Complete blood counts and white blood cell (WBC) subpopulations (CD4, CD8, CD25, WC1, and CD335) were examined weekly during the transition period. Adipose tissue biopsies were taken at 7 d PP from summer-calving cows. In cows calving during seasonal heat stress, plasma TNF-α concentrations were 4.9-fold higher prepartum and 5.1-fold higher PP, and MDA concentrations were higher prepartum and PP than in winter. Hematocrit was lower prepartum and tended to be lower PP in summer compared with winter, and after adjusting to hematocrit values fewer WBC prepartum (-17%) and PP (-22%), lower monocytes prepartum (-37%) and PP (-49%), and fewer neutrophils (-25%) PP were found in summer compared with winter-calving cows. The percentages of cytotoxic T cells (CD8) and natural killer cells (CD335) were lower, as well as prepartum gamma delta-T cells (WC1) in summer compared with winter-calving cows. Moreover, lower red blood cell counts prepartum and mean platelet volume and red blood cell distribution width prepartum and PP, as well as higher hemoglobin prepartum and PP, were found in summer than winter-calving cows. In summer, cows that lost more BW PP had higher plasma MDA and TNF-α concentrations, fewer basophil numbers prepartum, a decrease in the percentage of cells expressing the IL-2 receptor (CD25), increased ratio of T helper cells (CD4):CD8, and a tendency for increased WC1 percentages in blood prepartum, as well as a higher percentage of WC1 PP and higher abundance of TNF-α and lower lipopolysaccharide-binding protein in adipose tissue compared with cows that lost less BW PP. In conclusion, seasonal heat stress during the peripartum period was associated with lower WBC counts coupled with increased levels of subacute inflammation, indicating dysregulation of immune function, whereas the degree of BW loss had minor effects. This suggests that heat load is a more potent stressor associated with immune function than the variation in the degree of BW loss PP in high-yielding peripartum dairy cows.

Proteomic analysis reveals greater abundance of complement and inflammatory proteins in subcutaneous adipose tissue from postpartum cows treated with sodium salicylate.

This study aimed to investigate sodium salicylate (SS) treatment effects on the proteome of adipose tissue (AT) in postpartum cows. Twenty Holstein cows were assigned to control (CON, n = 10) or SS (n = 10) provided via drinking water (2.3 g/L) during the first 7 d of lactation. Subcutaneous AT was collected on d 7 of treatment and label-free quantitative shotgun proteomics and immunoblotting were analyzed in a subset of 5 AT per group. Eighty out of 1422 proteins (5.6%) were differentially abundant between CON and SS [fold change ±1.5, P < 0.05]. Top canonical pathways differing between CON and SS (Ingenuity) were complement system, interleukin-10 signaling, and acute phase response signaling. The abundances of complement C1r, C1qC, C1qB and C6 were greater in SS than CON. Regarding IL-10 signaling, the abundances of BLVRB, STAT3, and lipopolysaccharide binding protein (LBP) were greater in SS AT compared to CON. Immunoblots revealed increased abundance of paraoxanase-1 and tumor necrosis factor-alpha, as well as a tendency for greater abundance of cluster differentiation 172a in SS AT, which may indicate of increased macrophage infiltration. SS treatment postpartum likely promotes inflammatory signaling in AT of dairy cows, perhaps due to immune cell recruitment. SIGNIFICANCE: This work demonstrates that treating early lactating cows with sodium salicylate, an anti-inflammatory agent that has been shown to have metabolic effects and increase milk production in dairy cows, affects the proteome of subcutaneous adipose tissue in early lactating dairy cows. Unexpectedly, sodium salicylate treatment enriched inflammatory pathways of the complement system, cytokine signaling, and acute phase response, as revealed by proteomic analysis of subcutaneous adipose tissues from cows at 7 d postpartum. These findings imply that SS treatment during the first 7 d of lactation likely promotes inflammatory signaling in AT of the dairy cow, perhaps due to immune cell recruitment. Tissue-specific impacts of systemic sodium salicylate requires further scrutiny.

Lifetime of the Bose gas with resonant interactions.

We study the lifetime of a Bose gas at and around unitarity using a Feshbach resonance in lithium 7. At unitarity, we measure the temperature dependence of the three-body decay coefficient L(3). Our data follow a L(3)=λ(3)/T(2) law with λ(3)=2.5(3)(stat)(6)(syst)×10(-20) (µK)(2) cm(6) s(-1) and are in good agreement with our analytical result based on zero-range theory. Varying the scattering length a at fixed temperature, we investigate the crossover between the finite-temperature unitary region and the previously studied regime where |a| is smaller than the thermal wavelength. We find that L(3) is continuous across the resonance, and over the whole a<0 range our data quantitatively agree with our calculation.

Fermi-liquid behavior of the normal phase of a strongly interacting gas of cold atoms.

We measure the magnetic susceptibility of a Fermi gas with tunable interactions in the low-temperature limit and compare it to quantum Monte Carlo calculations. Experiment and theory are in excellent agreement and fully compatible with the Landau theory of Fermi liquids. We show that these measurements shed new light on the nature of the excitations of the normal phase of a strongly interacting Fermi gas.

The equation of state of a low-temperature Fermi gas with tunable interactions.

Interacting fermions are ubiquitous in nature, and understanding their thermodynamics is an important problem. We measured the equation of state of a two-component ultracold Fermi gas for a wide range of interaction strengths at low temperature. A detailed comparison with theories including Monte-Carlo calculations and the Lee-Huang-Yang corrections for low-density bosonic and fermionic superfluids is presented. The low-temperature phase diagram of the spin-imbalanced gas reveals Fermi liquid behavior of the partially polarized normal phase for all but the weakest interactions. Our results provide a benchmark for many-body theories and are relevant to other fermionic systems such as the crust of neutron stars.

Exploring the thermodynamics of a universal Fermi gas.

One of the greatest challenges in modern physics is to understand the behaviour of an ensemble of strongly interacting particles. A class of quantum many-body systems (such as neutron star matter and cold Fermi gases) share the same universal thermodynamic properties when interactions reach the maximum effective value allowed by quantum mechanics, the so-called unitary limit. This makes it possible in principle to simulate some astrophysical phenomena inside the highly controlled environment of an atomic physics laboratory. Previous work on the thermodynamics of a two-component Fermi gas led to thermodynamic quantities averaged over the trap, making comparisons with many-body theories developed for uniform gases difficult. Here we develop a general experimental method that yields the equation of state of a uniform gas, as well as enabling a detailed comparison with existing theories. The precision of our equation of state leads to new physical insights into the unitary gas. For the unpolarized gas, we show that the low-temperature thermodynamics of the strongly interacting normal phase is well described by Fermi liquid theory, and we localize the superfluid transition. For a spin-polarized system, our equation of state at zero temperature has a 2 per cent accuracy and extends work on the phase diagram to a new regime of precision. We show in particular that, despite strong interactions, the normal phase behaves as a mixture of two ideal gases: a Fermi gas of bare majority atoms and a non-interacting gas of dressed quasi-particles, the fermionic polarons.

Collective oscillations of an imbalanced Fermi gas: axial compression modes and polaron effective mass.

We investigate the low-lying compression modes of a unitary Fermi gas with imbalanced spin populations. For low polarization, the strong coupling between the two spin components leads to a hydrodynamic behavior of the cloud. For large population imbalance we observe a decoupling of the oscillations of the two spin components, giving access to the effective mass of the Fermi polaron, a quasiparticle composed of an impurity dressed by particle-hole pair excitations in a surrounding Fermi sea. We find m*/m = 1.17(10), in agreement with the most recent theoretical predictions.