Electron-Transparent Thermoelectric Coolers Demonstrated with Nanoparticle and Condensation Thermometry.

More efficient thermoelectric devices would revolutionize refrigeration and energy production, and low-dimensional thermoelectric materials are predicted to be more efficient than their bulk counterparts. But nanoscale thermoelectric devices generate thermal gradients on length scales that are too small to resolve with traditional thermometry methods. Here we fabricate, using single-crystal bismuth telluride (Bi2Te3) and antimony/bismuth telluride (Sb2-xBixTe3) flakes exfoliated from commercially available bulk materials, functional thermoelectric coolers (TECs) that are only 100 nm thick. These devices are the smallest TECs ever demonstrated by a factor of 104. After depositing indium nanoparticles to serve as nanothermometers, we measure the heating and cooling produced by the devices with plasmon energy expansion thermometry (PEET), a high-spatial-resolution, transmission electron microscopy (TEM)-based thermometry technique, demonstrating a ΔT = -21 ± 4 K from room temperature. We also establish proof-of-concept for condensation thermometry, a quantitative temperature-change mapping technique with a spatial precision of ≲300 nm.

Pediatric research in office settings (PROS): a national practice-based research network to improve children's health care.

OBJECTIVES: To describe the establishment of a national pediatric primary care research network to improve children's health care-Pediatric Research in Office Settings (PROS), and to evaluate the network's progress toward achieving its objectives. SETTING: Pediatric practices in all 50 states and Puerto Rico. PARTICIPANTS: Approximately 1400 pediatric practitioners from more than 470 practices. RESULTS: Beginning in 1986, a core of volunteer pediatrician coordinators from participating American Academy of Pediatrics chapters were identified to oversee local PROS efforts, represent practitioners, and inform the development of proposed research studies. PROS subsequently recruited practitioners from around the country, building a research infrastructure and a system of collaboration between the practitioners, research staff at the AAP, and investigative teams at academic institutions. This PROS collaboration has developed and conducted 10 primary care research studies that have added to the knowledge base of pediatric primary care. CONCLUSIONS: PROS has accomplished two of its initial objectives-development of a structure and process for pediatric practice-based research and provision of research experience to practitioners. Successful and consistent achievement of a third objective-meaningful dissemination of study results to relevant audiences-will depend on meeting several challenges.

Early discharge. Risks, benefits, and who decides.

Over the last several decades, there has been a significant decrease in the length of hospital stays for mothers and their newborns, ranging from the average of 7 to 10 days before World War II to approximately 2 days in recent years. Many women saw the benefit of early discharge as a means to demedicalize the birth process, to be home with their families sooner, and to have their deliveries be a more positive experience. Although the trend toward shorter hospital stays was originally initiated by consumer interest, the recent further shortening of maternity stays has escalated as a result of insurance and managed care plans attempting to contain health care costs. With this trend toward earlier discharge, a litany of problems have been reported, including missed newborn screening, jaundice, feeding problems, missed congenital anomalies, and readmissions. Although cost-efficient use of health care is vital, the ultimate goal should not only be the prevention of unnecessary morbidity and mortality, but the promotion of health and well being for the child and family.

Collaborative office rounds: continuing education in the psychosocial/developmental aspects of child health.

OBJECTIVES: In recent years there has been increasing emphasis on the mental health aspects of primary health care for children and adolescents. The Health Resources and Services Administration's Maternal and Child Health Bureau has contributed to efforts aimed at strengthening primary care not only in early identification and beginning intervention with mental disorders, but also in prevention of emotional and behavioral problems and in promotion of positive psychosocial development. The Collaborative Office Rounds (COR) Program is a noteworthy part of these efforts. METHODS: The COR program supports small discussion groups that meet at regular intervals over sustained periods of time to address the mental health aspects of pediatric care. The groups are jointly led by pediatricians and child psychiatrists. Although they vary in a number of ways, all are concerned with the day-to-day psychosocial issues that confront primary care providers serving children, adolescents, and their families. RESULTS: COR groups have addressed a wide range of areas including numerous problems and disorders, health supervision issues, family and community topics, personal challenges and practical complexities, and clinical management issues. Evaluation information indicates a positive response on the part of participants and moderators. This is reflected in group stability, high attendance rates, universal readiness to recommend the COR experience, and a variety of collateral accomplishments. CONCLUSIONS: Experience to date points to the COR group as a useful tool for addressing psychosocial issues in primary care. Its potential may be more fully realized by applying this approach more widely, even as further assessment is pursued.

Preconceptional and prenatal multivitamin-mineral supplement use in the 1988 National Maternal and Infant Health Survey.

This paper examines the prevalence of multivitamin-mineral supplement use before and during pregnancy, as well as predictors of nonuse, in 9953 women who delivered live infants in the 1988 National Maternal and Infant Health Survey. Ninety-seven percent of the women were advised to take multivitamin-mineral supplements in prenatal care. Sixty-seven percent of Black mothers took supplements during pregnancy, as compared with 84% of White mothers. Multivariate analysis revealed that Black mothers; mothers who are less educated, younger, unmarried, and non-smokers; and mothers who participate in Women, Infants, and Children programs are at elevated risk for nonuse. These data help identify groups in need of supplementation guidance.

Long-chain fatty alcohol quantitation in subfemtomole amounts by gas chromatography-negative ion chemical ionization mass spectrometry. Application to long-chain acyl coenzyme A measurement.

We describe a simple and sensitive method to identify and quantitate long-chain fatty alcohols. Long-chain fatty alcohols were converted to their pentafluorobenzoyl derivative and analyzed by gas chromatography (GC)-mass spectrometry in the negative ion chemical ionization (NICI) mode with selected ion monitoring. GC resolution was obtained for myristyl, palmityl, heptadecyl, stearyl, oleyl, linoleyl and arachidonyl alcohols. As little as 0.4 fmol of fatty alcohol can be detected, which represents a six order-of-magnitude increase in sensitivity over previously described methods. This assay can be used to measure femtomolar amounts of long-chain acyl coenzyme A thioesters after reduction to the corresponding fatty alcohols with sodium borohydride. Other potential applications of this assay include identification and quantitation of long-chain fatty alcohol production by microorganisms.

Testing environmental pollutants on soil organisms: a simple assay to investigate the toxicity of environmental pollutants on soil organisms, using CdCl2 and nematodes.

Juvenile stages of Caenorhabditis elegans (nematoda) were isolated and grown in an axenic medium containing various concentrations of CdCl2. Growth of the organisms was significantly reduced from a level of 1 microM CdCl2. Reproduction of the nematodes was also reduced from that 1 microM exposure level. At levels of 160 and 320 microM, growth was retarded at the early juvenile stages and the organisms did not reach the adult stage and could therefore not reproduce. The test system turned out to be simple and reproducible and is therefore suitable for the investigation of the toxicity of compounds to soil nematodes.

Federal programs affecting rural perinatal health care.

Access to perinatal health care in rural communities often depends on such factors as the availability, cost, and acceptability of services. The federal government has been providing rural perinatal health care both directly and indirectly, through grants for service delivery or research and through direct payment for service. The various federal programs supporting perinatal health care in rural communities are described, and what may need to be done in the future is discussed.

Stimulation of glucose transport in cultured uterine cells by rat and rabbit uterine extracts.

Estradiol-17 beta was previously shown to stimulate glucose transport (as measured by phosphorylation of 2-deoxyglucose) in rat uterine tissue in vivo (Meier, D.A. and Garner, C.W. (1987) Endocrinology 121, 1366-1374) but attempts to demonstrate this in uterine organ strips in vitro, in uterine tumor cell lines or in uterine cells in primary culture have been unsuccessful. However, aqueous uterine extracts and uterine luminal fluid did stimulate glucose transport in uterine tumor cells and uterine cells in primary culture. Estradiol in vivo and uterine extracts in vitro each increased the initial rate of glucose transport 1.5- to 3-fold. In each case, 2-3 h were required for the stimulation to be fully expressed. The stimulation was not inhibited by cycloheximide suggesting that protein synthesis was not required. Uteri from ovariectomized rats injected daily for 4 days with 10 micrograms estradiol contained 4-fold more activity than uteri from saline-injected control animals. The activity was acid- and heat-stable, inactivated by trypsin treatment but not removed by dextran-coated charcoal treatment, suggesting that the activity is (or is associated with) a protein. The activity eluted in the 6-12 kDa range upon chromatography on Sephadex G-50. Insulin (1-1000 ng/ml) and epidermal growth factor (1-100 ng/ml) stimulated glucose transport, but only less than 50% of the stimulation by extracts. The substance(s) present in the extracts, possibly a known growth factor, may be involved in the estradiol stimulation of glucose transport and other estradiol actions in vivo.

Influence of glycophorin incorporation on Ca2+-induced fusion of phosphatidylserine vesicles.

The effect of incorporation of glycophorin, the major integral sialoglycoprotein of the erythrocyte membrane, into bovine brain phosphatidylserine (PS) vesicles on the Ca2+-induced fusion of these vesicles has been investigated. Fusion was monitored by the terbium-dipicolinic acid fluorescence assay for the mixing of aqueous contents of the vesicles and by a resonance energy transfer assay that follows the intermixing of membrane lipids. The Ca2+-induced fusion of PS vesicles is completely prevented by incorporation of glycophorin (molar ratio of PS/glycophorin = 400-500:1) for Ca2+ concentrations up to 50 mM. The ability to fuse is partially restored after treating the glycophorin-containing vesicles with neuraminidase, which removes the negatively charged sialic acid residues of glycophorin. Fusion is further facilitated by trypsin treatment, removing the entire extravesicular glycosylated head group of glycophorin. However, Ca2+-induced fusion of enzyme-treated glycophorin-PS vesicles proceeds at a slower rate and to a smaller extent than fusion of protein-free PS vesicles. The influence of the aggregation state of the glycophorin molecules on fusion has been investigated in experiments using wheat germ agglutinin (WGA). Addition of WGA to the glycophorin-PS vesicles does not induce fusion. However, upon subsequent addition of Ca2+, distinct fusion occurs concomitantly with release of vesicle contents. The inhibition of Ca2+-induced fusion of PS vesicles by incorporation of glycophorin is explained by a combination of steric hindrance and electrostatic repulsion between the vesicles by the glycosylated head group of glycophorin and a direct bilayer stabilization by the intramembranous hydrophobic part of the glycophorin molecule.

Isolation and purification of cardiolipin from beef heart.

A simple and efficient procedure is described for the preparation of cardiolipin sodium salt from beef heart. A crude phospholipid fraction is isolated by chloroform-methanol extraction of the homogenized tissue, followed by acetone precipitation and reprecipitation in 4% aqueous CaCl2-methanol. Cardiolipin is separated from the calcium salts of the acidic phospholipids by partition column chromatography on silica gel (Polygosil 60-63100) using 2-propanol-cyclohexane-water 50:43:7 (v/v/v) as eluent. Further purification of the cardiolipin is achieved by high performance liquid chromatography of the calcium salt on silica gel (Lichrosorb Si 60-5) with a neutral eluent (2-propanol-cyclohexane-water 45:50:5 (v/v/v], followed by quantitative conversion to the sodium salt. The yield of this procedure is 1.5-2.1 g of pure 99% sodium salt of cardiolipin per kg of moist ventricular tissue.

Synthesis and polymorphic phase behaviour of polyunsaturated phosphatidylcholines and phosphatidylethanolamines.

A series of phosphatidylcholines and phosphatidylethanolamines was synthesized containing two acyl chains of the following polyunsaturated fatty acids: linoleic acid (18:2), linolenic acid (18:3), arachidonic acid (20:4) and docosahexaenoic acid (22:6). In addition two phospholipids with mixed acid composition were synthesized: 16:0/18:1c phosphatidylcholine and 16:0/18:1c phosphatidylethanolamine. The structural properties of these lipids in aqueous dispersions in the absence and in the presence of equimolar cholesterol were studied using 31P-NMR, freeze fracturing and differential scanning calorimetry (DSC). The phosphatidylcholines adopt a bilayer configuration above 0 degrees C. Incorporation of 50 mol% of cholesterol in polyunsaturated species induces a transition at elevated temperatures into structures with 31P-NMR characteristics typical of non-bilayer organizations. When the acyl chains contain three or more double bonds, this non-bilayer organization is most likely the hexagonal HII phase. 16:0/18:1c phosphatidylethanolamine shows a bilayer to hexagonal transition temperature of 75 degrees C. The polyunsaturated phosphatidylethanolamines exhibit a bilayer to hexagonal transition temperature below 0 degrees C which decreases with increasing unsaturation and which is lowered by approximately 10 degrees C upon incorporation of 50 mol% of cholesterol. Finally, it was found that small amounts of polyunsaturated fatty acyl chains in a phosphatidylethanolamine disproportionally lower its bilayer to hexagonal transition temperature.

Purification of phospholipids by preparative high pressure liquid chromatography.

A method is described for the purification of a number of phospholipids by preparative high performance liquid chromatography (HPLC). Purification of digalactosyl-diglyceride from spinach and egg phosphatidylcholine, 1,2-dioleoyl-sn-glycero-3-phosphocholine and 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine from its reaction mixture have been resolved. The lipid separation is performed on a polygosil column and the individual compounds are monitored directly by refractive index detection. Chloroform/methanol mixtures are used as eluent systems, providing a wide polarity range to separate the classes of lipids. The developed equipment can be used for columns between 10 and 50 cm long and 4 and 50 mm inner diameter. The flow rate could be varied between 1 and 100 ml/min and applied pressures between 10 and 450 bars.

High-performance liquid chromatographic separation and photometric detection of phospholipids.

A rapid and efficient method for the separation of (phospho)lipids by high-performance liquid chromatography using n-hexane-2-propanol-water mixtures as the solvent system is described. The lipid separation occurs on silica gel columns and the individual components are monitored directly by UV absorption at 206 nm. Of a total lipid extract from erythrocytes as well as suboesophageal ganglia of the snail Helix pomatia, a complete separation is achieved of cholesterol, phosphatidic acid, phosphatidylethanolamine, phosphatidylinositol, phosphatidylserine, lysophosphatidylcholine and lysophosphatidylethanolamine, whereas phosphatidylcholine and sphingomyelin are partly separated under these circumstances. In addition to separation of phospholipids in different classes, separation of molecular species can also be achieved in some instances, as is shown for phosphatidylcholines and sphingomyelins.

High performance liquid chromatographic separation and direct ultraviolet detection of phospholipids.

A fast and efficient method for the separation of (phospho)lipids by high performance liquid chromatography using n-hexane, 2-propanol, water mixtures as the solvent system is described. The lipid separation occurs on a LiChrosorb Si-60 (10 micron) column and the individual components are monitored directly by ultraviolet absorption at 206 nm. Of a total lipid extract from erythrocytes a complete separation is achieved of cholesterol, phosphatidic acid, phosphatidylethanolamine, phosphatidylinositol, phosphatidylserine, lysophosphatidylcholine and lysophosphatidylethanolamine, whereas phosphatidylcholine and sphingomyelin are only partly separated under these circumstances. Furthermore, a mixture of synthetic phospholipids, i.e. 1,2-dilauroyl-sn-glycero-3-phosphatidic acid, 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine, 1,2-dioleoyl-sn-glycero-3-phospho-1'-sn-glycerol and 1,2-dioleoyl-sn-glycero-3-phosphocholine has been completely resolved. In addition to separation of phospholipids in different classes, separation of molecular species can also be achieved in some cases, as is shown for 1,2-dipalmitoleoyl-sn-glycero-3-phosphocholine and 1,2-didocos-13'-cis-enoyl-sn-glycero-3-phosphocholine.

The protein-mediated transfer of phosphatidylcholine between membranes. The effect of membrane lipid composition and ionic composition of the medium.

The phosphatidylcholine exchange protein from bovine liver catalyzes the transfer of phosphatidylcholine between rat liver mitochondria and sonicated liposomes. The effect of changes in the liposomal lipid composition and ionic composition of the medium on the transfer have been determined. In addition, it has been determined how these changes affected the electrophoretic mobility i.e. the surface charge of the membrane particles involved. Transfer was inhibited by the incorporation of negatively charged phosphatidic acid, phosphatidylserine, phosphatidylglycerol and phosphatidylinositol into the phosphatidylcholine-containing vesicles; zwitterionic phosphatidyl-ethanolamine had much less of an inhibitory effect while positively charged stearylamine stimulated. The cation Mg2+ and, to a lesser extent, K+ overcame the inhibitory effect exerted by phosphatidic acid, in that concentration range where these ions neutralized the negative surface charge most effectively. Under conditions where Mg2+ and K+ affected the membrane surface charge relatively little inhibition was observed. In measuring the protein-mediated transfer between a monolayer and vesicles consisting of only phosphatidylcholine, cations inhibited the transfer in the order La3+ greater than Mg2+ larger than or equal to Ca2+ greater than K+ = Na+. Inhibition was not related to the ionic strength, and very likely reflects an interference of these cations with an electrostatic interaction between the exchange protein and the polar head group of phosphatidylcholine.

Relation between various phospholipase actions on human red cell membranes and the interfacial phospholipid pressure in monolayers.

The action of purified phospholipases on monomolecular films of various interfacial pressures is compared with the action on erythrocyte membranes. The phospholipases which cannot hyorolyse phospholipids of the intact erythrocyte membrane, phospholipase C from Bacillus cereus, phospholipase A2 from pig pancreas and Crotalus adamanteus and phospholipase D from cabbage, can hydrolyse phospholipid monolayers at pressure below 31 dynes/cm only. The phospholipases which can hydrolyse phospholipids of the intact erythrocyte membrane, phospholipase C from Clostridium welchii phospholipase A2 from Naja naja and bee venom and sphingomyelinase from Staphylococcus aureus, can hydrolyse phospholipid monolayers at pressure above 31 dynes/cm. It is concluded that the lipid packing in the outer monolayer of the erythrocyte membrane is comparable with a lateral surface pressure between 31 and 34.8 dynes/cm.