The mechanical response of the mouse cervix to tensile cyclic loading in term and preterm pregnancy

A well-timed modification of both the collagen and elastic fiber network in the cervix during pregnancy accompanies the evolution of tissue mechanical parameters that are key to a successful pregnancy. Understanding of the cervical mechanical behaviour along normal and abnormal pregnancy is crucial to define the molecular events that regulate remodeling in term and preterm birth (PTB). In this study, we measured the mechanical response of mouse cervical tissue to a history of cyclic loading and quantified the tissue's ability to recover from small and large deformations. Assessments were made in nonpregnant, pregnant (gestation days 6, 12, 15 and 18) and mouse models of infection mediated PTB treated with lipopolysaccharide on gestation d15 (LPS treated) and hormone withdrawal mediated PTB on gestation d15 (RU486 treated). The current study uncovers the contributions of collagen and elastic fiber networks to the progressive change in mechanical function of the cervix through pregnancy. Premature cervical remodeling induced on gestation day 15 in the LPS infection model is characterized by distinct mechanical properties that are similar but not identical to mechanical properties at term ripening on day 18. Remodeling in the LPS infection model results in a weaker cervix, unable to withstand high loads. In contrast, the RU486 preterm model resembles the cyclic mechanical behaviour seen for term d18 cervix, where the extremely compliant tissue is able to withstand multiple cycles under large deformations without breaking. The distinct material responses to load-unload cycles in the two PTB models matches the differing microstructural changes in collagen and elastic fibers in these two models of preterm birth. Improved understanding of the impact of microstructural changes to mechanical performance of the cervix will provide insights to aid in the development of therapies for prevention of preterm birth.

STATEMENT OF SIGNIFICANCE

Preterm Birth (PTB) still represents a serious challenge to be overcome, considering its implications on infant mortality and lifelong health consequences. While the causes and etiologies of PTB are diverse and yet to be fully elucidated, a common pathway leading to a preterm delivery is premature cervical remodeling. Throughout pregnancy, the cervix remodels through changes of its microstructure, thus altering its mechanical properties. An appropriate timing for these transformations is critical for a healthy pregnancy and avoidance of PTB. Hence, this study aims at understanding how the mechanical function of the cervix evolves during a normal and preterm pregnancy. By performing cyclic mechanical testing on cervix samples from animal models, we assess the cervix's ability to recover from moderate and severe loading. The developed methodology links mechanical parameters to specific microstructural components. This work identifies a distinct biomechanical signature associated with inflammation mediated PTB that differs from PTB induced by hormone withdrawal and from normal term remodeling.

Kytococcus sedentarius and Micrococcus luteus: highly prevalent in indoor air and potentially deadly to the immunocompromised - should standards be set?

The multifarious types of infections contracted from indoor environments show that buildings can serve as a reservoir for infectious bacteria. This study is an investigation into the type and concentrations of bacteria in the indoor and outdoor environments of an electronic factory, an office and a winery in Malaysia. Trypticase soy agar (TSA) (with ambient air incubation) and TSA supplemented with haemin and NADH (with CO₂ enhanced incubation) were used for the isolation of bacteria. The plates were incubated at 37ºC for 3 days. A random selection of bacterial isolates were Gram stained and identified using the BD BBL Crystal Identification Systems. Kytococcus sedentarius and Micrococcus luteus were the predominant bacterial species identified from indoor air. These bacteria were present at relatively high concentrations in indoor air, at times, above 800 colony forming units per cubic meter (CFU/m³) of air. This indicates that both K. sedentarius and M. luteus can survive a wide range of adverse conditions, including chemical contamination and ultraviolet exposure. M. luteus is a known cause of pneumonia in immunocompromised individuals and has also been implicated in skin infections. Recent reports suggest species of kytococci as emerging opportunistic pathogens of the immunocompromised, paediatrics and the elderly. We postulate that opportunistic bacteria, such as the kytococci and the micrococci, may also have a potential role in instigating subclinical, more subtle symptoms of disease in inmmunocompetent individuals.

Orphan Spins in the S=5/2 Antiferromagnet CaFe_{2}O_{4}

CaFe_{2}O_{4} is an anisotropic S=5/2 antiferromagnet with two competing A (↑↑↓↓) and B (↑↓↑↓) magnetic order parameters separated by static antiphase boundaries at low temperatures. Neutron diffraction and bulk susceptibility measurements, show that the spins near these boundaries are weakly correlated and a carry an uncompensated ferromagnetic moment that can be tuned with a magnetic field. Spectroscopic measurements find these spins are bound with excitation energies less than the bulk magnetic spin waves and resemble the spectra from isolated spin clusters. Localized bound orphaned spins separate the two competing magnetic order parameters in CaFe_{2}O_{4}.

Giant Anisotropic Magnetocaloric Effect in Double-perovskite Gd2CoMnO6 Single Crystals

The magnetocaloric effect (MCE) is described by the change in temperature of a material by magnetic field variation and is a crucial subject in magnetism; it is motivated by the desire to enhance energy-efficient magnetic refrigeration for clean technology. Despite the recent discovery of the giant cryogenic MCE in double perovskites, the role of magnetic anisotropy has not yet been clearly discussed, because of the averaging effect of polycrystalline samples. Here, we investigated the anisotropic MCE in the single-crystal double perovskite Gd2CoMnO6. In addition to the ferromagnetic order of the Co2+ and Mn4+ moments, the large Gd3+ moments align below T Gd = 21 K, exhibiting an isotropic nature. Because of the intricate temperature development of magnetically hysteretic behaviour and metamagnetism, the change in magnetic entropy along the c-axis appears to be relatively small. On the contrary, the smaller but almost reversible magnetization perpendicular to the c-axis leads to a large MCE with a maximum entropy change of 25.4 J/kg·K. The anisotropic MCE generates a giant rotational MCE, estimated as 16.6 J/kg·K. Our results demonstrate the importance of magnetic anisotropy for understanding the MCE and reveal essential clues for exploring suitable magnetic refrigerant compounds aiming at magnetic functional applications.