Chemical-exchange and paramagnetic T2 relaxation agents for water suppression in spin-echo proton nuclear magnetic resonance spectroscopy of biological fluids.
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Body Fluids↗
Biomedical subjects
S Connor
Publications and source records attributed to S Connor.
Spin-echo proton NMR spectroscopy of urine samples. Water suppression via a urea-dependent T2 relaxation process.
Spin-echo methods have been used to effect solvent suppression during the collection of 400 and 500 MHz 1H NMR spectra of urine samples containing urea in the concentration range 0.7-1.2 M. There was a marked trough of water Tobs2 values in the pH range 2.6 to 4.1, due to acid-catalyzed proton exchange between urea and the solvent water. Minimum values of Tobs2 (9 ms at 500 MHz) of water were obtained at about pH 3.2 in urine samples containing 1.2 M urea. However, good solvent suppression factors were obtained with endogenous urea concentrations of only 0.7 M. There was a strong field dependence on the water, T2, over the pH range 2 to 4. Attenuation of the water signal was estimated to be at least an order of magnitude greater at 500 MHz rather than at 400 MHz. Using the Carr-Purcell-Meiboom-Gill spin-echo pulse sequence, water signals broader than 13 Hz were attenuated by factors of greater than 10(3), and factors of greater than 10(4) were possible with water linewidths greater than 20 Hz, thus allowing the signals from metabolites in the sample to be efficiently digitized. This approach allowed metabolite signals at or near the water resonance to be observed without serious distortion of their intensities. The utility of this approach to solvent suppression in real systems is illustrated by observation of paracetamol and benzyl penicillin metabolites in human urine samples.
Humans↗
Polychlorinated biphenyl congeners (PCBs), p,p'-DDE and hexachlorobenzene in human milk in three areas of upstate New York.
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Chlorobenzenes↗
Photochemical reactions in interstellar grains photolysis of CO, NH3, and H2O.
A simulation of the organic layer accreted onto interstellar dust particles was prepared by slow deposition of a CO:NH2:H2O gas mixture on an Al block at 10 K, with concomitant irradiation with vacuum UV. The residues were analyzed by GC-MS, HPLC, and near IR; a reaction pathway leading from NH3 to complex alcohol, fatty acid, and amide products in 27 stages is postulated. The astronomical relevance and significance of the observations are discussed.
Ammonia↗
Improvements in glass capillary gas chromatographic polychlorobiphenyl analysis.
Separation of a 1:1:1:1 calibration mixture of Aroclors 1221, 1016, 1254, and 1260 on soda glass capillaries coated with Apolane (C-87) or Apiezon L is described. Polychlorobiphenyl congener structures are assigned to 112 separated and partially separated zones. The quantitative composition of Aroclor 1221 is reported. The performance of the two stationary phases on different lengths of laboratory and commercially prepared capillaries is compared and found to be very similar. Aroclors 1221, 1016, 1254, and 1260 are employed (1:1:1:1) for the primary calibration mixture because they contain all components of the commercial materials which pollute the environment; they are also easily obtained from the U.S. EPA Repository so that the method can be used in any laboratory by employing the calibration data given here.
Chromatography, Gas↗
Suppression by diets rich in fish oil of very low density lipoprotein production in man.
The highly polyunsaturated fatty acids in fish oils lower the plasma triglyceride concentration. We have studied the effect of a diet rich in fish oil on the rate of production of the triglyceride-transporting very low density lipoprotein (VLDL). Seven subjects, five normal and two with hypertriglyceridemia received up to 30% of daily energy needs from a fish oil preparation that was rich in eicosapentaenoic acid and docosahexaenoic acid, omega-3 fatty acids with five and six double bonds, respectively. Compared with a diet similarly enriched with safflower oil (in which the predominant fatty acid is the omega-6 linoleic acid, with two double bonds), the fish oil diet lowered VLDL lipids and B apoprotein concentrations profoundly. High density lipoprotein lipids and A1 apoprotein were also lowered, but the effect on low density lipoprotein (LDL) concentration was inconsistent. The daily production or flux of VLDL apoprotein B, calculated from reinjected autologous 125I-labeled lipoprotein, was substantially less in six subjects studied after 3 wk of fish oil, compared with after safflower oil. This effect on flux was more consistent than that on the irreversible fractional removal rate, which was increased in the four normolipidemic but inconsistent in the hypertriglyceridemic subjects. This suggests that fish oil reduced primarily the production of VLDL. The daily production of VLDL triglyceride, calculated from the kinetics of the triglyceride specific radioactivity-time curves after [3H]glycerol was injected, also showed very substantial reductions in five subjects studied. The marked suppression in VLDL apoprotein B and VLDL triglyceride formation was found not to be due to diminished plasma total free fatty acid or plasma eicosapentaenoic flux, calculated during constant infusions of [14C]eicosapentaenoic acid and [3H]oleic acid in four subjects. In two subjects there was presumptive evidence for substantial independent influx of LDL during the fish oil diet, based on the precursor-product relationship between the intermediate density lipoprotein and LDL apoprotein B specific radioactivity-time curves.
Adult↗
High resolution gas chromatographic analysis of nonpolar chlorinated hydrocarbons in human milk.
A gas chromatographic method is described for the analysis of human milk to determine polychlorinated biphenyls (PCBs) as 72 congeners plus p,p'-DDE, mirex, hexachlorobenzene, and octachlorostyrene. The detection limit for individual compounds is about 0.05 ng/g when 30 g milk is analyzed. Total PCBs can be estimated with a detection limit of 1-5 ng/mL milk. Analytical precision is better than +/- 10% for all compounds at 20-50 ng/mL whole milk.
Chromatography, Gas↗
Partial arthroscopic meniscectomy: a preliminary report.
Short-term follow-up in 45 cases of meniscal derangement treated by partial arthroscopic meniscectomy was encouraging. Horizontal cleavage lesions and complex combination tears gave relatively few satisfactory results and resulted in two patients requiring reoperation. Emphasis must be placed on a careful evaluation of the meniscal remnant with a probe to ascertain the stability of the remainder of the meniscus to avoid this problem. Preexisting ligamentous instability when combined with degenerative change also caused fewer than expected satisfactory results. Careful patient selection and counseling may help to prevent this problem in the future. Age did not seem to affect the short term results. It should be emphasized that arthroscopic surgery requires a surgeon with extensive experience and adequate equipment in order to provide a comprehensive evaluation and treatment of the pathologic condition.
Adolescent↗
Occurrence of cold agglutinins in congenital scoliosis.
Eighty-seven patients undergoing spinal surgery for a variety of conditions were surveyed for the presence of cold agglutinins. Patients with congenital scoliosis or metastatic lesions of the spine were found to have a frequency of cold agglutinins that was 250 to 1000 times greater than that in the general population. This greater frequency was independent of ABO blood group, sex, or age. Pre-admission screening of congenital scoliosis patients is urged.
ABO Blood-Group System↗
Preventing bicycle-related head trauma in children.
Although the majority of bicycle-related injuries and deaths could be prevented by the use of bicycle helmets, rates of helmet use in the United States remain well below Healthy People 2000's goal of 50% usage. Educational efforts to improve usage rates often fail to produce significant changes, in part because a child's understanding of risk plays only a small role in his or her decision to wear a helmet. To address the need for more effective injury prevention techniques, the authors propose a modification of the Health Belief Model, which is used by injury control experts to explain the various cognitive, social, and environmental factors that influence preventative health behavior. By incorporating the behavioral theory of self-efficacy in the structure of the Health Belief Model, trauma care providers and injury prevention specialists will be better able to design successful injury prevention programs that address key variables in health-related decision making.
Bicycling↗
Type A behavior and physiologic coronary risk factors in children of the family heart study: results from a 1-year follow-up.
Although Type A behavior is recognized as an independent risk factor for coronary heart disease, little is known about its antecedents. The present study investigated relationships of Type A behavior as assessed by the Hunter-Wolf rating scale to physiologic coronary risk factors in children ranging from 8 to 15 years of age. In addition, gender differences and the stability of Type A behavior and physiologic risk factors were examined. Consistent with data based on adult samples, Type A behavior was generally unrelated to physiologic coronary risk factors and appears to be as stable as the other risk factors. There were no gender differences in either Type A behavior or other coronary risk factors.
Adolescent↗