Infrared Reflection-Absorption Spectroscopy of α-Keto Acids at the Air-Water Interface: Effects of Chain Length and Headgroup on Environmentally Relevant Surfactant Films.

A variety of organic surfactants are found at air-water interfaces in natural environments, including on the surfaces of aqueous aerosols. The structure and morphology of these organic films can have profound impacts on material transfer between the gas and condensed phases, the optical properties of atmospheric aerosol, and chemical processing at air-water interfaces. Combined, these effects can have significant impacts on climate via radiative forcing, but our understanding of organic films at air-water interfaces is incomplete. Here, we examine the impact of the polar headgroup and alkyl tail length on the structure and morphology of organic monolayers at the air-water interfaces. First, we focus on the substituted carboxylic acids, α-keto acids, using Langmuir isotherms and infrared reflection absorption spectroscopy (IR-RAS) to elucidate key structures and phase behaviors of α-keto acids with a range of surface activities. We show that the structure of α-keto acids, both soluble and insoluble, at water surfaces is a compromise between van der Waals interactions of the hydrocarbon tail and hydrogen bonding interactions involving the polar headgroup. Then, we use this new data set regarding α-keto acid films at water surfaces to examine the role of the polar headgroup on organic films using a similar substituted carboxylic acid (α-hydroxystearic acid), an unsubstituted carboxylic acid (stearic acid), and an alcohol (stearyl alcohol). We show that the polar headgroup and its hydrogen bonding interactions can significantly affect the orientation of amphiphiles at air-water interfaces. Here, we provide side-by-side comparisons of Langmuir isotherms and IR-RA spectra for a set of environmentally relevant organic amphiphiles with a range of alkyl tail lengths and polar headgroup structures.

Early detection of necrotizing enterocolitis by gastrointestinal tonometry.

The diagnosis of necrotizing enterocolitis (NEC) in neonates has traditionally depended on a combination of clinical signs, biochemical parameters and radiological changes. The measurement of intramucosal pH by gastrointestinal tonometry provides a simple means of long-term monitoring which may detect the development of NEC before conventional techniques. We present our experience of tonometry in two 'at risk' term neonates with Hypoplastic Left Heart Syndrome.

Immunoregulatory effects of a suppressor factor from healthy pregnant women's lymphocytes after progesterone induction.

Progesterone-treated pregnancy lymphocytes release an immunologic blocking factor. The mode of action of this substance was investigated. The supernatant of progesterone-treated pregnancy lymphocytes was highly suppressive of natural cytotoxicity toward human embryonic fibroblast target cells as well as of natural killer cell activity. The effect was not observed when progesterone induction was performed in the presence of RU 486, a progesterone receptor blocking agent. The factor was able to inhibit mixed lymphocyte reactions (MLRs), and transfer coculture experiments revealed that this effect was dependent on major histocompatibility complex nonspecific, nonrestricted suppressor T cells. The activation/expansion of suppressor inducer and suppressor effector T cells was further proved by fluorescence-activated cell sorter analysis of the populations from MLRs cultured in the presence of the inhibitory factor. These changes were not observed with MLRs performed in the presence of supernatants from progesterone + RU 486-treated peripheral blood lymphocytes. The inhibitory material, on the other hand, did not affect either production or function of IL-2. We conclude that in the presence of high local concentrations of progesterone, a suppressive pathway dependent on specific progesterone-CD8+ lymphocyte interaction might be established. This mechanism might play an important role in the maintenance of pregnancy.

Immunoactive products of human placenta. I. An immunoregulatory factor obtained from explant cultures of human placenta inhibits CTL generation and cytotoxic effector activity.

Supernatants were prepared from short-duration explant cultures of term human placentas obtained after cesarean delivery. These supernatants inhibited murine and human mixed lymphocyte reactions, as well as CTL generation. The effects were reversed by an excess of IL-2-containing medium. Similarly, the material inhibited human natural killer cytotoxicity against K 562 targets. The material was subjected to gel-filtration chromatography on an ACA 44 or Bio-Gel A15m column. The apparent MW of the MLR-CML material was about 60-70 kDa, whereas the NK inhibiting activity was eluted in high-MW components (greater than 200 kDa) as well as in the 50-kDa range. The relevance of this material in local immunoregulation during human pregnancy is discussed.

Lack of correlation of immunosuppressive activity secreted by human in vitro fertilized (IVF) ova with successful pregnancy.

The high rate of implantation failure in humans following in vitro fertilization (IVF) has been attributed to a lack of production of immunosuppressive factors by cleaved embryos, rendering them vulnerable to maternal immune attack just before or around implantation. Systemic as well as blastocyst-secreted suppressor factors have been described and claimed to be responsible for successful pregnancy. Experimentally, we have screened in a double-blind fashion the suppressive activity of human embryo culture media (B2 Menezo system, France) in which zygotes after decoronization were individually cultured during 24 hr on lymphocyte proliferation as well as natural killer (NK) activity. Suppressive activity in media from cleaved and uncleaved ova did not differ significantly, and activity in media from transferred embryos was not correlated significantly with successful pregnancy. The implications of these data are discussed.