Solid phase synthesis and biological activities of [Arg8]-vasopressin methylenedithioether

Solid phase synthesis of [Arg8]-vasopressin methylenedithioether, an analog of vasopressin which contains an extra methylene group between the two sulfur atoms of Cys1 and Cys6, is described. Methylene insertion occurred easily when the thiol free peptide on a solid support was treated with tetrabutylammonium fluoride in dichloromethane at room temperature for 3 h. The uterotonic in vitro, pressor, and antidiuretic activities of the compound were reduced in comparison to [Arg8]-vasopressin by one order of magnitude.

Lipid composition, membrane structure relationships in lens and muscle sarcoplasmic reticulum membranes

Membrane lipid composition varies in different tissues and species. Since a defined lipid composition is essential to the function of many membranes, the relationship between membrane lipid composition and structure was determined using infrared and Raman spectroscopy in four membranes containing a calcium pump: rabbit fast and slow twitch muscle sarcoplasmic reticulum and human and bovine lens fiber cell membranes. We found that membrane sphingolipid and phosphatidylcholine content were correlated to a decrease and increase, respectively, in the infrared lipid CH2 symmetric stretching band frequency. We interpret the change in frequency as a change in lipid hydrocarbon chain structural order. This was confirmed by Raman order parameters. The high degree of hydrocarbon chain saturation found in the variable amide chains of sphingolipids is likely to account for this correlation. Lipid phase transition temperature and cooperativity also correlated to sphingolipid and phosphatidylcholine content, and are the forces defining the order in at physiological temperature in the samples studied. Ca(2+)-ATPase caused an increase in the CH2 symmetric stretching frequency in fast twitch muscle sarcoplasmic reticulum (interpreted as an increase in hydrocarbon chain disorder), but had no effect on slow twitch muscle sarcoplasmic reticulum lipid hydrocarbon chain structure. In the natural systems studied, we find that it is the lipid hydrocarbon chain saturation that defines lipid hydrocarbon chain order.

Preparation and properties of novel gramicidin S analogs possessing a tri-, tetra- or pentamethylene bridge between ornithine side chains

Gramicidin S (GS) analogs in which the Ndelta atoms of the two Orn side chains are linked by an oligomethylene bridge [-(CH2)n-; n=3-5] were prepared via the bis(p-nitrobenzenesulfonyl) derivative [Orn(NBS)2,2']GS. For comparison the nonbridged secondary amino group-containing analog [Orn(Me)2,2']GS was also prepared. 1H NMR and CD spectral analysis indicated that these analogs adopt the same beta-sheet conformation as GS. The antimicrobial activities of these analogs were very similar, but were slightly dependent on the bridge chain length, the trimethylene-bridged analog being the most potent.

Exposure-response of asphalt fumes with changes in pulmonary function and symptoms

OBJECTIVES

This study examines possible associations between asphalt fumes and workshift changes in lung function and symptoms among 170 workers exposed to asphalt fumes.

METHODS

The workers were from 5 segments of the asphalt industry, and most of them participated for 2 consecutive workdays. The primary response variables were changes in lung function (measured at the beginning and end of the shift) and incidence of symptoms (measured before, 3 times during, and at the end of the shift). Exposure was estimated from breathing-zone samples of total particulate (TP), respirable particulate (RP), the benzene-soluble fraction of the TP (BSF), volatile hydrocarbons collected on a charcoal tube (VHC), nitrogen dioxide, sulfur dioxide, formaldehyde, carbon monoxide, and hydrogen sulfide. Ozone and wet bulb/dry bulb temperature, as a measure of heat stress, were measured as area samples. In addition, daily cigarette smoking was determined by questionnaire. The exposure-response associations were assessed by both parametric and nonparametric statistical techniques.

RESULTS

Overall, no consistent association was observed between an acute reduction in lung function or the incidence of symptoms and exposure to asphalt fumes. Concentrations in the neighborhood of the maximum levels constitute no-observed adverse effect levels: TP (<1.5 mg/m3 to maximum 6.2 mg/m3), RP (<0.6 mg/m3 to maximum 1.4 mg/m3), BSF (<0.6 mg/m3 to maximum 1.3 mg/m3), VHC (<8 mg/m3 to maximum 19.8 mg/m3). There were no exposure-response trends with ozone, heat stress, cigarettes smoked, or length of workday.

Enhanced thermogenesis in rats by a composite Indian herbal preparation-I and its mechanism of action

OBJECTIVE

A composite Indian herbal preparation-I (CIHP-I) containing ingredients derived from 7 different plants and asphalt was tested for its adaptogenic activity and its mechanism of action was investigated.

DESIGN

CIHP-I was tested using the cold-hypoxia-restraint (C-H-R) animal model in which the restrained rats were exposed to 5 degrees C at 428 mm Hg atmospheric pressure. Rectal temperature (Trec) of the rats was continuously monitored during the exposure and the recovery periods. The time for fall of Trec to 23 degrees C and its recovery to 37 degrees C were used as indices of endurance and the adaptogenic activity. Carbohydrate and lipid parameters were investigated to find out the nature of fuel being used during thermogenesis.

RESULTS

After 12 weeks of administration of an oral dose of 7.5 mg/kg(-1)/day(-1), CIHP-I was found to possess significant adaptogenic activity. CIHP-I helped improve resistance to C-H-R induced hypothermia (Trec 23 degrees C) in animals by increased mobilization of free fatty acids (FFA) from adipose tissue. Blood glucose and muscle glycogen levels were maintained. CIHP-I treatment restricted the release of creatine phosphokinase (CPK) into the circulation during C-H-R exposure.

CONCLUSIONS

The results suggested that CIHP-I is a strong adaptogen. It improved cold resistance during C-H-R exposure and enhanced recovery from hypothermia. The energy-dependent cell membrane permeability was maintained. Stored lipids were mobilised and possibly used for thermogenesis in preference to carbohydrates.

Measurement of intracellular triglyceride stores by H spectroscopy: validation in vivo

We validate the use of 1H magnetic resonance spectroscopy (MRS) to quantitatively differentiate between adipocyte and intracellular triglyceride (TG) stores by monitoring the TG methylene proton signals at 1.6 and 1.4 ppm, respectively. In two animal models of intracellular TG accumulation, intrahepatic and intramyocellular TG accumulation was confirmed histologically. Consistent with the histological changes, the methylene signal intensity at 1.4 ppm increased in both liver and muscle, whereas the signal at 1.6 ppm was unchanged. In response to induced fat accumulation, the TG concentration in liver derived from 1H MRS increased from 0 to 44.9 +/- 13.2 micromol/g, and this was matched by increases measured biochemically (2.1 +/- 1.1 to 46.1 +/- 10.9 micromol/g). Supportive evidence that the methylene signal at 1.6 ppm in muscle is derived from investing interfascial adipose tissue was the finding that, in four subjects with generalized lipodystrophy, a disease characterized by absence of interfacial fat, no signal was detected at 1.6 ppm; however, a strong signal was seen at 1.4 ppm. An identical methylene chemical shift at 1.4 ppm was obtained in human subjects with fatty liver where the fat is located exclusively within hepatocytes. In experimental animals, there was a close correlation between hepatic TG content measured in vivo by 1H MRS and chemically by liver biopsy [R = 0.934; P <.0001; slope 0.98, confidence interval (CI) 0.70-1.17; y-intercept 0.26, CI -0.28 to 0. 70]. When applied to human calf muscle, the coefficient of variation of the technique in measuring intramyocellular TG content was 11.8% in nonobese subjects and 7.9% in obese subjects and of extramyocellular (adipocyte) fat was 22.6 and 52.5%, respectively. This study demonstrates for the first time that noninvasive in vivo 1H MRS measurement of intracellular TG, including that within myocytes, is feasible at 1.5-T field strengths and is comparable in accuracy to biochemical measurement. In addition, in mixed tissue such as muscle, the method is clearly advantageous in differentiating between TG from contaminating adipose tissue compared with intramyocellular lipids.

Urease and hexadecylamine-urease films at the air-water interface: an x-ray reflection and grazing incidence x-ray diffraction study

We report the results of surface x-ray scattering measurements performed on urease and hexadecylamine-urease films at the air-aqueous solution interface. It is demonstrated that although hexadecylamine does not form a stable monolayer on the pure aqueous surface, it does self-assemble into a stable, well-organized structure when spread on top of a urease film at the air-water interface. It is also likely that protein and hexadecylamine domains coexist at the interface.

Synthesis and antiviral activity of D- and L-isodideoxy nucleosides with exocyclic-methylene

Novel D- and L-isodideoxynucleosides were synthesized starting from D- and L-xylose and evaluated for antiviral activities against HIV-1, HSV-1, HSV-2, HBV and HCMV, respectively.

A laboratory rig for studying aspects of worker exposure to bitumen fumes

This study was performed to establish which factors related to the hot application of bitumen products are relevant to worker exposure to benzene-soluble matter (as part of the total fume emission) and to the polycyclic aromatic compound (PAH) content of bitumen fume. Because personal exposure measurements in field surveys can be influenced by many uncontrollable variables, a simple laboratory rig was developed in which bitumen fumes can be generated reproducibly under well-controlled conditions. Laboratory results were related to personal exposure measurements during asphalt paving and roofing. A quantitative relationship for predicting the laboratory fume emission was derived, with bitumen volatility and temperature the only variables. The variable part of the equation is termed the fuming index (FI). The FI correlates well with measured personal exposures in asphalt paving and in roofing and can be used to predict average personal exposures during these activities if bitumen volatility, application temperature, and for paving, the asphalt type, are known. The laboratory fumes, generated at a standard temperature of 160 degrees C, are representative for fumes emitted in the temperature range relevant for asphalt paving, those generated at 250 degrees C for roofing. The PAH profiles of the fumes collected as personal samples during asphalt paving and roofing operations were similar to those of the fumes generated in the laboratory from the same bitumen and at the same temperature. Because it produces conditions representative of actual bitumen operations, this laboratory set-up is an excellent tool for assessing bitumens in terms of fuming tendency and PAH emissions/exposures.

Control of enantioselectivity in catalytic metal carbene reactions

Chiral dirhodium(II) complexes constructed from 2-oxopyrrolidine, 2-oxazolidinone, N-acyl-2-imidazolidinone, or 2-azetidinone ligands are exceptional catalysts for enantioselective metal carbene transformations which provide lactones and lactams via cyclopropanation, cyclopropenation, C-H insertion, and ylide reactions with enantiomeric excesses greater than 90% and, usually, in very high yields. These chiral catalysts present high diastereo-, regio- and chemoselectivities, turnover numbers up to 1000, as well as recoverability and reuse.

Elimination of difluorocarbene from the molecular ions of alpha, alpha,alpha-trifluorocresols with a fluorine atom migration in an ion trap mass spectrometer

The elimination of difluorocarbene (CF(2)) from the molecular ions of m-alpha,alpha,alpha-trifluorocresol (MW 162, 1) and p-alpha, alpha, alpha-trifluorocresol (MW 162, 2) upon electron impact have been investigated using a quadrupole ion trap mass spectrometer. This reaction involves a fluorine (F) atom migration from the trifluoromethyl group to the benzene ring. In the case of 1, an F atom migrates via a four-membered ring transition state to give rise to the molecular ion of p-fluorophenol (MW 112, 5) and a small amount of o-fluorophenol (MW 112, 3). On the other hand, in the case of 2, an F atom migrates to the ipso position of the benzene ring via a three-membered ring transition state to give rise to 5(+). These conclusions were confirmed by the comparison of the energy-resolved mass spectra (collision-induced dissociation (CID) spectra versus collision energy) of the m/z 112 ions from 1(+) and 2(+) with those of reference compounds, o-, m- and p-fluorophenol (3-5).

In vitro release of cytarabine from swellable matrices of CnEmCn triblock copolymers

Matrices loaded with cytarabine were prepared by compression of the tailor made triblock copolymers C17E227C17 and C17E454C17 (where C=methylene and E=oxyethylene). Observations of the swelling characteristics of copolymer matrices on immersion in distilled water indicated an increase in the thickness of the gel layer around the matrices following ingress of water into the matrices. The in vitro release of cytarabine was characterised from matrices of different molar mass and with different known drug loadings. The release of cytarabine from the copolymer matrices was predominantly by a Fickian diffusion mechanism; the release rate was dependent on drug loading and independent of copolymer molar mass.

New methylene specific experiments for the measurement of scalar spin-spin coupling constants between protons attached to 13C

New two- and three-dimensional NMR methods are proposed for the measurement of 3J(H, H) coupling constants between two adjacent methylene moieties. The new experiment, which is based on a combination of the E.COSY principle and double/zero quantum heteronuclear spectroscopy, has been applied to diaceton-glucose and to the protein rhodniin. The coupling constants of CH-CH2 groups have been compared with those obtained from a HCCH-E.COSY experiment to check the reliability of the results. An analysis of the coupling constants derived by comparison between experimental and simulated spectra is presented. Simulations were done with the program wtest considering fully correlated dipolar relaxation. Side-chain conformations in amino acids with adjacent methylene groups can be determined by the new experiment.

The interaction of polycyclic hydrocarbons and nucleic acids

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