Solid-state NMR structure determination of melittin in a lipid environment

Solid-state C-13 NMR spectroscopy was used to investigate the three-dimensional structure of melittin as lyophilized powder and in ditetradecylphosphatidylcholine (DTPC) membranes. The distance between specifically labeled carbons in analogs [1-C-13]Gly3-[2-C-13]Ala4, [1-C-13]Gly3-[2-C-13]Leu6, [1-C-13]Leu13-[2-C-13]Ala15, [2-C-13]Leu13-[1-C-13]Ala15, and [1-C-13]Leu13-[2-C-13]Leu16 was measured by rotational resonance. As expected, the internuclear distances measured in [1-C-13]Gly3-[2-C-13]Ala4 and [1-C-13]Gly3-[2-C-13]Leu6 were consistent with alpha -helical structure in the N-terminus irrespective of environment. The Internuclear distances measured in [1-C-13]Leu13-[2-C-13]Ala15, [2-C-13]Leu13-[1-C-13]Ala15, and [1-C-13]Leu13-[2-C-13]Leu16 revealed, via molecular modeling, some dependence upon environment for conformation in the region of the bend in helical structure induced by Pro14. A slightly larger interhelical angle between the N- and C-terminal helices was indicated for peptide in dry or hydrated gel state DTPC (139 degrees -145 degrees) than in lyophilized powder (121 degrees -139 degrees) or crystals (129 degrees). The angle, however, is not as great as deduced for melittin in aligned bilayers of DTPC in the liquid-crystalline state (similar to 160 degrees) (R. Smith, F. Separovic, T. J. Milne, A. Whittaker, F. M. Bennett, B. A. Cornell, and A. Makriyannis, 1994, J. Mol, Biol 241:456-466). The study illustrates the utility of rotational resonance in determining local structure within peptide-lipid complexes.

Energy expenditure and the body cell mass in cystic fibrosis

Poor nutritional status in patients with cystic fibrosis (CF) is associated with severe lung disease, and possible causative factors include inadequate intake, malabsorption, and increased energy requirements. Body cell mass (which can be quantified by measurement of total body potassium) provides an ideal standard for measurements of energy expenditure. The aim of this study was to compare resting energy expenditure (REE) in patients with CF with both predicted values and age-matched healthy children and to determine whether REE was related to either nutritional status or pulmonary function. REE was measured by indirect calorimetry and body cell mass by scanning with total body potassium in 30 patients with CF(12 male, mean age = 13.07 +/- 0.55 y) and 18 healthy children (six male, mean age = 12.56 +/- 1.25 y). Nutritional status was expressed as a percentage of predicted total body potassium; Lung function was measured in the CF group by spirometry and expressed as the percentage of predicted forced expiratory volume in 1 s. Mean REE was significantly increased in the patients with CF compared with healthy children (119.3 +/- 3.1% predicted versus 103.6 +/- 5% predicted, P < 0.001) and, using multiple regression techniques, REE for total body potassium was significantly increased in patients with CF (P = 0.0001). There was no relation between REE and nutritional status or pulmonary disease status in the CF group. In conclusion, REE is increased in children and adolescents with CF but is not directly related to nutritional status or pulmonary disease. Nutrition 2001;17:22-25. (C)Elsevier Science Inc. 2001.

Relating body mass index to figural stimuli: population-based normative data for Caucasians

OBJECTIVE: To establish body mass index (BMI) norms for standard figural stimuli using a large Caucasian population-based sample. In addition, we sought to determine the effectiveness of the figural stimuli to identify individuals as obese or thin. DESIGN: All Caucasian twins born in Virginia between 1915 and 1971 were identified by public birth record. In addition, 3347 individual twins responded to a letter published in the newsletter of the American Association of Retired Persons (AARP). All adult twins (aged 18 and over) from both of these sources and their family members were mailed a 16 page 'Health and Lifestyle' questionnaire. SUBJECTS: BMI and silhouette data were available on 16 728 females and 11 366 males ranging in age from 18- 100. MEASUREMENTS: Self-report information on height-weight, current body size, desired body size and a discrepancy score using standard figural stimuli. RESULTS: Gender- and age-specific norms are presented linking BMI to each of the figural stimuli. Additional norms for desired body size and discrepancy scores are also presented. Receiver operating curves (ROC) indicate that the figural stimuli are effective in classifying individuals as obese or thin. CONCLUSIONS: With the establishment of these norms, the silhouettes used in standard body image assessment can now be linked to BMI. Differences were observed between women and men in terms of desired body size and discrepancy scores, with women preferring smaller sizes. The figural stimuli are a robust technique for classifying individuals as obese or thin.

Genetic and non-genetic factors affecting birth-weight and adult body mass index

Birthweight affects neonatal mortality and morbidity and has been used as a marker of foetal undernutrition in studies of prenatal effects on adult characteristics. It is potentially influenced by genetic and environmental influences on the mother, and effects of foetal genotype, which is partially derived from the maternal genotype. Interpretations of variation in birthweight and associated characteristics as being due to prenatal environment ignore other possible modes of materno-foetal transmission. Subjects were adult twins recruited through the Australian Twin Registry, aged 17 to 87 years, and the sample comprised 1820 men and 4048 women. Twins reported their own birthweight as part of a health questionnaire. Body Mass Index (BMI) was calculated from self-reports of height and weight. Correlations between co-twins' birthweights were high for both monozygotic (r = 0.77) and dizygotic (r = 0.67) pairs, leading to substantial estimates of shared environmental effects (56% of variance) with significant additive genetic (23%) and non-shared environmental (21%) components. Adult BMI was mainly influenced by genetic factors, both additive (36% of variance) and nonadditive (35%). The correlation between birthweight and BMI was positive, in that heavier babies became on average more obese adults. A bivariate model of birthweight and adult BMI showed significant positive genetic (rg = 0.16, p = 0.005) and environmental (re = 0.08, p = 0.000011) correlations. Intra-uterine environmental or perinatal influences shared by cotwins exercise a strong influence on birthweight, but the factors which affect both birthweight and adult BMI are partly genetic and partly non-shared environmental.

The use of F-19 NMR for new structure determination in the radiolysis of FEP

The radiation chemistry of poly(tetrafluoroethylene-co-perfluoropropylene), FEP, with a mole fraction of tetrafluoroethylene, TFE, of 0.90 has been studied under vacuum using Co-60 gamma -radiation over absorbed dose ranges up to 3.0 MGy. The radiolysis temperatures were 300, 363, 423 and 523 K. New structure formation in the copolymers was analyzed by solid-state F-19 NMR. The new structures formed in the copolymers have been identified and the G-values for the formation of new -CF3 groups was 2.2 at the lower temperatures and increased to 2.9 at 523 K. The G-value for the loss of original -CF3 groups was approximate to1.0 at all temperatures. At the lower temperatures there was a net loss of -CF-groups on irradiation, G(CF) of -1.3, -0.9 and -0.5 at 300, 363 and 423 K, respectively, but at 523 K there was a net gain with G(CF) equal to 0.8. (C) 2001 Elsevier Science B.V. All rights reserved.

Solid state F-19 NMR determination of new structure formation in FEP following radiolysis at 300 and 363 K

The radiation chemistry of FEP copolymer with a mole fraction TFE of 0.90 has been studied using Co-60 gamma -radiation at temperatures of 300 and 363 K. New structure formation in the copolymers was analysed by solid state F-19 NMR. New chain scission products were the principal new structures found. The G-value for the formation of new -CF3 groups was 2.2 and 2.1 for the radiolysis of FEP at 300 and 363 K, respectively, and the G-value for the loss of original -CF3 groups was G(-CF3) = 1.0 and 0.9 at these two temperatures, respectively. There was a nett loss of -CF- groups on irradiation, with G(-CF) of 1.3 and 0.9 at 300 and 363 K, respectively. (C) 2001 Elsevier Science Ltd. All rights reserved.

The use of NMR for determination of new structures in irradiated TFE/PMVE fluoropolymers

The radiation chemistry of two TFE/PMVE copolymers with TFE mole fractions of 0.66 and 0.81 has been studied under vacuum using Co-60 gamma -radiation over absorbed dose ranges up to 4.2 MGy. The radiolysis temperature was 313 K for both TFE/PMVE copolymers. New structure formation in the copolymers was identified by solid-state F-19 NMR and the G-values for new chain ends of 2.1 and 0.5 and for branching sites of 0.9 and 0.2 have been obtained for the TFE/PMVE with TFE mole fractions of 0.66 and 0.81, respectively. The relative yields of-O-CF3 and -CF2-CF3 chain ends were found to be proportional to the copolymer composition, but the yields of the -CF2-CF3 chain ends and -CF- branch points mere not linearly related ia the composition. rather they wets correlated with the radical yields measured at 77 K. (C) 2001 Elsevier Science Ltd. All rights reserved.

Model-based procedure for scale-up of wet, overflow ball mills - Part II: Worked example

A new ball mill scale-up procedure is developed which uses laboratory data to predict the performance of MI-scale ball mill circuits. This procedure contains two laboratory tests. These laboratory tests give the data for the determination of the parameters of a ball mill model. A set of scale-up criteria then scales-up these parameters. The procedure uses the scaled-up parameters to simulate the steady state performance of the full-scale mill circuit. At the end of the simulation, the scale-up procedure gives the size distribution, the volumetric flowrate and the mass flowrate of all the streams in the circuit, and the mill power draw. A worked example shows how the new ball mill scale-up procedure is executed. This worked example uses laboratory data to predict the performance of a full-scale re-grind mill circuit. This circuit consists of a ball mill in closed circuit with hydrocyclones. The MI-scale ball mill has a diameter (inside liners) of 1.85m. The scale-up procedure shows that the full-scale circuit produces a product (hydrocyclone overflow) that has an 80% passing size of 80 mum. The circuit has a recirculating load of 173%. The calculated power draw of the full-scale mill is 92kW (C) 2001 Elsevier Science Ltd. All rights reserved.

Model-based procedure for scale-up of wet, overflow ball mills - Part III: Validation and discussion

A new ball mill scale-up procedure is developed. This procedure has been validated using seven sets of Ml-scale ball mil data. The largest ball mills in these data have diameters (inside liners) of 6.58m. The procedure can predict the 80% passing size of the circuit product to within +/-6% of the measured value, with a precision of +/-11% (one standard deviation); the re-circulating load to within +/-33% of the mass-balanced value (this error margin is within the uncertainty associated with the determination of the re-circulating load); and the mill power to within +/-5% of the measured value. This procedure is applicable for the design of ball mills which are preceded by autogenous (AG) mills, semi-autogenous (SAG) mills, crushers and flotation circuits. The new procedure is more precise and more accurate than Bond's method for ball mill scale-up. This procedure contains no efficiency correction which relates to the mill diameter. This suggests that, within the range of mill diameter studied, milling efficiency does not vary with mill diameter. This is in contrast with Bond's equation-Bond claimed that milling efficiency increases with mill diameter. (C) 2001 Elsevier Science Ltd. All rights reserved.

Communication and health beliefs - Mass and interpersonal influences on perceptions of risk to self and others

This study investigated the impact of media coverage of a health issue (skin cancer) on judgements of risk to self and others and the role of related communication processes. Consistent with predictions derived from the impersonal impact hypothesis, the effects of mass communication were more evident in perceptions of risk to others rather than in perceptions of personal risk. Perceptions of personal risk were more strongly correlated with interpersonal communication. However, as suggested by media system dependency theory, the relationship between mass communication and beliefs was complex. The impact of mass communication on both personal and impersonal perceptions was bound to be moderated by self-reported dependence on mass mediated information. The effect of this two-way interaction 071 perceptions of personal risk was partially mediated through interpersonal communication. Results point to the interdependence of mass and interpersonal communication as sources of social influence and the role of media dependency in shaping media impact.

Searching for missing pieces of the sex-determination puzzle

Little is known of the mechanisms whereby the mammalian indifferent gonad develops into a testis or ovary. In XY individuals, Sry, the mammalian testis-determining gene, is expressed in the pre-Sertoli cells, which then differentiate into Sertoli cells. Other cell types, which include the germ cells, the steroidogenic cells and the connective tissue cells, must then be instructed to develop in a male-specific manner. Although some genes involved in sex-determination and differentiation processes have been identified, we know little of how they interact and cooperate to orchestrate the development of a testis or ovary. We have initiated an expression-screening program designed to identify additional genes, known or novel, which play a role in these processes. This approach is based on our belief that many of the genes we seek will be expressed in a sex-specific manner during the period of sex-determination and differentiation. Most of the genes identified previously are transcription factors and so we aim, in particular, to find genes involved in cell-to-cell communication, signal transduction, and transcriptional regulation, downstream of the differentiation of Sertoli cells. We have used a suppression subtractive-hybridization method to generate male- and female-enriched probes and libraries. Clones are validated as being sex-specific in their expression patterns by array screening and in situ hybridization. Here we report on our progress to date and the general applicability of the approach for studies in other systems. J. Exp. Zool. 290:517-522, 2001. (C) 2001 Wiley-Liss, Inc.