Polymorphonuclear leukocyte migration through human amnion membrane

A new in vitro model has been developed for studying migration of human polymorphonuclear leukocytes (PMN) through living native cellular and matrix barriers. Human amnion membrane consists of a single layer of epithelium bound to a continuous basement membrane interfacing an avascular collagenous stroma. Living amnion was placed in plastic chambers with separate compartments on each side of the membrane. PMN were introduced on the epithelial side of the amnion, and a Millipore filter (Millipore Corp., Bedford, Mass.) was placed against the stromal side. In response to N-formylmethionyl-leucyl- phenylanlanine (FMLP) chemoattractant, PMN penetrated the full thickness of the amnion and were collected and counted on the filter. The rate of PMN traversal of the amnion was dependent on the concentration of FMLP (optimal at 10(-8)M) as well as the slope of the FMLP gradient across the amnion. The route of PMN migration was studied by transmission electron microscopy. PMN first attached to the epithelial surface, then infiltrated between intercellular junctions. PMN migrated around or through tight junction and hemidesmosome attachments. The PMN then penetrated the basement membrane and migrated through the dense collagenous stroma. The present amnion migration system has characteristics of the in vivo inflammatory state not described in any previous method for monitoring PMN migration in vitro. Prior methods have not used native epithelium, whole basement membrane, or collagenous stroma. PMN penetration of these barriers occurs in the normal inflammatory response and probably involves biochemical mechanisms not required for simple migration through the pores of an artificial filter. The amnion system can be useful for future biochemical and morphological studies of PMN penetration of these barriers and possible repair processes that may follow.     

Human challenges in polar and space environments

This paper reviews literature on psychosocial adaptation in isolated and confined extreme (ICE) environments, focusing on polar work groups and expedition teams, and simulation and actual space crews. Long-duration missions may involve chronic exposure to many stressors that can negatively impact behavioral health, performance and even safety. In the last decades, anecdotal evidence has been replaced by scientific studies, identifying temporal, social, and individual determinants of psychosocial adaptation, and pointing to countermeasures that may minimize or prevent potential problems. Still, many issues remain that require additional investigation, specifically in relation to the integration of psychosocial and neurobiological adaptation. A recognition of ICE environments as natural laboratories for studies of fundamental questions within psychology may attract more scientists to the field.     

Human sleep-wake cycles in the high Arctic: effects of unusual photoperiodicity in a natural setting.

Studies of human circadian rhythms are typically conducted in artificial environments that are low in ecological validity. In the current study, six subjects and the field director lived in temporal isolation in a completely natural environment with constant daylight (a high Arctic research camp) for six weeks. Detailed daily sleep logs were kept. In keeping with past findings, five of the six subjects developed a free-running sleep-wake cycle longer than 24 hours. Unlike past results, the isolated subjects did not exhibit any synchronicity in their rhythins. There was a high degree of intersubject variability in circadian patterns. The findings have important implications for the comparison of the results of laboratory and field investigations of sleep-wake cycles.     

Molecular characterization of an ancient Hepatozoon species parasitizing the 'living fossil' marsupial 'Monito del Monte' Dromiciops gliroides from Chile

The Microbiotheriid Dromiciops gliroides , also known as 'Monito del Monte', is considered to be a threatened species and the only living representative of this group of South American marsupials. During the last few years, several blood samples from specimens of 'Monito del Monte' captured at Chiloé island in Chile have been investigated for blood parasites. Inspection of blood smears detected a Hepatozoon species infecting red blood cells. The sequences of DNA fragments corresponding to small subunit ribosomal RNA gene revealed two parasitic lineages belonging to Hepatozoon genus. These parasite lineages showed a basal position with respect to Hepatozoon species infecting rodents, reptiles, and amphibians but are phylogenetically distinct from Hepatozoon species infecting the order Carnivora. In addition, the Hepatozoon lineages infecting D. gliroides are also different from those infecting other micro-mammals living in sympatry, as well as from some that have been described to infect an Australian species of bandicoot. The potential vector of this parasite appears to be the host-specific tick Ixodes neuquenensis because the sequencing of a long amplicon determined the presence of one of the two lineages found in the marsupial.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 98 , 568–576.