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At least 181 records · Page 10Linked to original sources
PubMed1991

Reaction of formate with the fast form of cytochrome oxidase: a model for the fast to slow conversion.

The ability to isolate preparations of cytochrome oxidase which are highly homogeneous has facilitated a study of the effects of various reagents on the purified enzyme. The addition of either sodium formate, formamide, formaldehyde, or sodium nitrite to enzyme which reacts in a single rapid kinetic phase with cyanide causes a blue-shift of 4-6 nm of the net (cytochrome a + cytochrome a3) Soret maximum. Only the derivative prepared by adding sodium formate demonstrates measurable intensity in the g' = 12 region of the low-temperature electron paramagnetic resonance (EPR) spectrum. This g' = 12 resonance is characteristic of cytochrome oxidase which has undergone a modification at the binuclear center and thereby reacts sluggishly with cyanide. As the site of cyanide binding in resting enzyme as been demonstrated to be CuB [Yoshikawa, S., & Caughey, W.S. (1990) J. Biol. Chem. 265, 7945-7958], it is proposed that formate can bind to CuB and the fast to slow transition is rationalized by using this proposal. The g' = 12 signal is also produced upon the addition of sodium formate to mitochondrial preparations, suggesting that the species responsible for this behavior may have possible physiological relevance. Physical properties of the formate derivative and data for other reagents reacted with the fast-reacting enzyme preparation are presented.

Animals↗
PubMed2006

Quantitative assessment of patellar cartilage volume and thickness at 3.0 tesla comparing a 3D-fast low angle shot versus a 3D-true fast imaging with steady-state precession sequence for reproducibility.

OBJECTIVES: We sought to compare patellar cartilage volume and thickness measurement between 3D-FLASH and 3D-True fast imaging with steady-state precession (FISP) image data at 3.0 T. MATERIALS AND METHODS: One knee each of 6 healthy adults was examined by axial magnetic resonance imaging (MRI) performed with a 3D-fast flow angle shot (FLASH) water-excitation sequence and a 3D-TrueFISP water-excitation sequence (spatial resolution 0.31 x 0.31 x 1.5 mm3). Patellar cartilage volume and mean/maximum thickness were calculated. Intraindividual/average reproducibility and interindividual variability were determined from 3 consecutive data sets acquired for each volunteer and sequence. RESULTS: Patellar cartilage volume and thickness as well as reproducibility was slightly but not significantly lower for the 3D-TrueFISP data than for the 3D-FLASH data (volume: 3.4-6.3 mL (3D-FLASH)/3.1-6.0 mL (3D-TrueFISP), average reproducibility 1.8% (3D-FLASH)/4.4% (3D-TrueFISP); mean thickness: 2.1-2.8 mm (3D-FLASH)/1.9-2.6 mm (3D-TrueFISP), average reproducibility 2.8% (3D-FLASH)/3.8% (3D-TrueFISP); maximum thickness: 4.7-6.6 mm (3D-FLASH)/4.5-6.2 mm (3D-TrueFISP), average reproducibility 2.6% (3D-FLASH)/4.1% (3D-TrueFISP)). Interindividual variability was comparable for both sequence techniques. CONCLUSION: At 3.0 T, the 3D-FLASH sequence showed tendency to be slightly superior to the 3D-TrueFISP sequence considering robust and valid assessment of quantitative cartilage parameters in young healthy adults, although there was found no significant statistical difference between both imaging techniques. However, in patients suffering from osteoarthritis (OA), the 3D-TrueFISP sequence might prove advantageous for monitoring of disease progression and evaluation of therapy success, particularly because the substantially higher signal to noise ratio/contrast to noise ratio values might allow for higher spatial resolution and hence for improvement of the accuracy of segmentation process especially at the articular surface.

Adult↗
PubMed2000

Experimental evidence of electric inhibition in fast electron penetration and of electric-field-limited fast electron transport in dense matter

Fast electron generation and propagation were studied in the interaction of a green laser with solids. The experiment, carried out with the LULI TW laser (350 fs, 15 J), used K(alpha) emission from buried fluorescent layers to measure electron transport. Results for conductors (Al) and insulators (plastic) are compared with simulations: in plastic, inhibition in the propagation of fast electrons is observed, due to electric fields which become the dominant factor in electron transport.

Journal Article↗
PubMed1983

Sustained "slow-fast" and "fast-slow" AV nodal re-entrant tachycardia in a patient with recurrent supraventricular tachycardia.

A case is presented of a 21-year-old woman with recurrent paroxysmal supraventricular tachycardia. Electrophysiologic study demonstrated the presence of both antegrade and retrograde dual AV nodal conduction pathways and both conventional slow-fast and atypical fast-slow forms of the AV nodal re-entrant tachycardia could be induced. Both tachycardias were successfully suppressed with a combination of digoxin and verapamil.

Adult↗
PubMed2001

MR evaluation of ventricular function: true fast imaging with steady-state precession versus fast low-angle shot cine MR imaging: feasibility study.

Short- and long-axis cine magnetic resonance (MR) images were obtained with a standard fast low-angle shot, or FLASH, sequence and a first-generation true fast imaging with steady-state precession (FISP) sequence on a 1.5-T MR imager. Contrast-to-noise ratios and volumetric left ventricular measurements were compared for manual and automatic segmentation. True FISP images were associated with significantly (P<.01) higher contrast-to-noise ratios and allowed better detection of the endocardial border. True FISP images were provided with short acquisition times and excellent contrast between the myocardium and the ventricular lumen.

Adult↗
PubMed1994

Radiofrequency ablation for the fast pathway of atrioventricular node reentry. Evidence for partial damage to the fast and lower common pathways.

Radiofrequency ablation was attempted in a 30-year-old woman with atrioventricular (AV) node reentry of the common variety. Energy was delivered to ablate a fast pathway. After energy delivery, the atrio-His interval prolonged following transient AV node block. Retrograde conduction was no longer present. However, dual AV nodal physiology and AV node reentry with similar retrograde atrial activation sequence could be shown post-ablation. These observations suggest that both fast and lower common pathways were partially damaged by ablation.

Adult↗
PubMed2001

Fast three-point Dixon MR imaging of the retrobulbar space with low-resolution images for phase correction: comparison with fast spin-echo inversion recovery imaging.

A new phase-correction algorithm for three-point Dixon (3PD) MR imaging allows on-line image reconstruction of three images per section: pure water, pure fat, and water plus fat. When combined with fast spin-echo acquisition, the sequence is suitable for routine MR imaging of the retrobulbar space. The 3PD pure water images have double the image signal-to-noise ratio of fast spin-echo inversion recovery images. The dramatic contrast-to-noise ratio of the 3PD pure fat images may offer improved lesion detection.

Adolescent↗
PubMed1997

[Dynamic MR hepatocholangiography with the SIP Fast GRE (saturation inversion projection fast gradient echo) method].

The purpose of this study was to assess the utility of dynamic MR hepatocholangiography with the Gd-EOB-DTPA enhanced SIP Fast GRE sequence in the hepatobiliary system. The SIP Fast GRE sequence was used for sequential imaging of the hepatobiliary system with a frame rate of 3 sec in a 256 x 192 matrix. Dynamic sequential acquisition was performed for 51 min before and after the injection of 30 mu mol/kg of Gd-EOB-DTPA in a rabbit. Dynamic images of the hepatobiliary system were obtained in the rabbit study. Dynamic MR hepatocholangiography provides better functional information than conventional MR cholangiography.

Animals↗
PubMed1991

Coaxial continuous flow fast atom bombardment for higher-molecular-weight peptides: comparison with static fast atom bombardment and electrospray ionization.

A comparison of coaxial continuous flow fast atom bombardment (FAB) with static FAB and with electrospray ionization (ESI) for the analysis of 'high'-mass peptides (Mr = 3000-4000) is presented. Sensitivities of the peptides by coaxial continuous flow FAB is nearly an order of magnitude better than by static FAB. Single-scan spectra with good signal-to-noise can be obtained from as little as 200 fmol (by flow injection analysis). Detection limits by ESI mass spectrometry were found to be equivalent to 20 times higher than by coaxial continuous flow FAB on a per mole basis, but 4-20 times lower on a concentration basis, owing to the greater flow per unit time employed in the ESI mass spectrometric experiments.

Mass Spectrometry↗
PubMed1987

Organ and tumor distribution of (18F)-2-fluoro-2-deoxy-D-glucose in fasting and non-fasting rats.

Differences in the uptake of (18F)-2-fluoro-2-deoxy-D-glucose ((18F)FDG) in various normal organs and the Rous sarcoma of fasted and unfasted rats were studied at 5, 15, 30, 60, and 120 minutes after i.v. injection. The uptake of (18F)FDG in the tumor, spleen, and testis increased for 120 minutes, while uptake in the other organs was either level (brain, heart, white fat) or cleared off. The uptake was higher in the tumor than in the normal organs. The fraction of viable tumor tissue as measured morphometrically correlated intraindividually with the uptake of (18F)FDG--an increase of 1% of vital tumor corresponded to a 1.01-fold increase in tumor uptake of (18F)FDG. The nutritional state was of importance for the uptake of (18F)FDG into the heart, testis and brown fat. (18F)FDG is taken quantitatively up by the viable parts of the Rous tumor; this may make it possible to follow the response of treatment in individual tumors also in man with (18F)FDG and positron emission tomography (PET).

Animals↗
PubMed1995

Stimulation of gluconeogenesis leads to an increased rate of beta-oxidation in hepatocytes from fasted diabetic but not from fasted normal rats.

We have investigated the effects of imposing an ATP demand, generated by the addition of lactate, on hepatocytes isolated from fasted normal and streptozocin-induced diabetic rats. The stimulation of O2 consumption upon lactate addition was much greater in hepatocytes from diabetic rats, as a result of a lactate-induced stimulation of beta-oxidation that was not observed in control cells. This lactate-induced increment in beta-oxidation was extremely sensitive to inhibition by low levels of a number of inhibitors of energy transduction, implying that the increment was tightly coupled to ATP synthesis. Such sensitivity of the beta-oxidative pathway to the addition of similar low concentrations of these inhibitors was not seen in control cells. Inhibitors of the gluconeogenic pathway were also more effective in decreasing beta-oxidation in cells from diabetic animals than in cells from normal rats. The increment in beta-oxidation was not accompanied by increased rates of glucose synthesis, fatty acid esterification or ureogenesis. We propose that it may be associated with higher rates of glucose cycling in cells from diabetic rats.

Adenosine Triphosphate↗
PubMed2004

Effect of glucosamine supplementation on fasting and non-fasting plasma glucose and serum insulin concentrations in healthy individuals.

OBJECTIVE: To test the hypothesis that glucose intolerance does not occur when healthy adults consume normal, recommended dosages of glucosamine sulfate. METHODS: Healthy adults (N=19) ingested 1500 mg of glucosamine sulfate or placebo (double blind) each day for 12 weeks. Three-hour oral glucose tolerance tests (OGTT) were performed using 75 g of dextrose. These occurred before the start of supplementation, at 6 weeks, and at the completion of supplementation (12 weeks). RESULTS: There were no significant differences between fasted levels of serum insulin or blood glucose. Glucosamine sulfate supplementation did not alter serum insulin or plasma glucose during the OGTT. There were no significant differences within or between treatments, ages or gender. Glycated hemoglobin measurements at the three time points showed no significant change over time, within or between treatments, ages or gender. The lack of significant changes may have been due to large standard deviations in the data. CONCLUSION: The data suggests that glucosamine supplementation, with normal recommended dosages, does not cause glucose intolerance in healthy adults. This cannot be determined conclusively, however, until further studies are conducted using alternative types of testing.

Adult↗
PubMed1997

The Fasting Hyperglycaemia Study: II. Randomized controlled trial of reinforced healthy-living advice in subjects with increased but not diabetic fasting plasma glucose.

Self-referred subjects (N = 227) thought to be at risk of developing non-insulin-dependent diabetes mellitus (NIDDM) and with fasting plasma glucose (FPG) in the range of 5.5 to 7.7 mmol.L-1 on two consecutive tests 2 weeks apart were randomized to reinforced or basic healthy-living advice. They were simultaneously allocated either to a sulfonylurea group or a control group in a two-by-two factorial design. A total of 201 subjects in three English and two French centers completed 1 year's follow-up study. Reinforced advice recommending dietary modification and increased exercise was given every 3 months, and basic advice was given once at the initial visit. Glycemia was monitored by FPG, dietary compliance by body weight and food diaries, and fitness compliance by bicycle ergometer assessment and exercise diaries. Both reinforced and basic advice groups had a significant mean reduction in body weight (1.5 kg) at 3 months, although the weight subsequently returned to baseline. After 1 year, subjects allocated to reinforced advice versus basic advice (1) reported a lower fat intake (34.1% v 35.8%, P = .04) with no difference in lipid profiles, (2) had improved fitness as shown by increased calculated maximal oxygen uptake ([Vo2max] 2.39 v 2.18 L.min-1, P = .007) with no change in insulin sensitivity, (3) showed no change in FPG, glucose tolerance, or hemoglobin A1c (HbA1c), and (4) showed a greater tendency to withdraw from the study (16% v 7%, P = .03). In conclusion, reinforced healthy-living advice given to self-referred subjects with increased FPG did not encourage sufficiently pronounced life-style changes for significantly greater effects on body weight and glycemia in a 1-year study than basic healthy-living advice.

Adult↗
PubMed1997

The Fasting Hyperglycaemia Study: III. Randomized controlled trial of sulfonylurea therapy in subjects with increased but not diabetic fasting plasma glucose.

Self-referred subjects (N = 227) thought to be at increased risk of developing diabetes who had fasting plasma glucose (FPG) values in the range of 5.5 to 7.7 mmol.L-1 on two consecutive occasions 2 weeks apart were randomized to sulfonylurea therapy (gliclazide, < or = 160 mg.d-1) or to a control group allocated either to double-blind placebo or to no tablets. Subjects were randomly allocated also to reinforced or basic healthy-living advice in a factorial design. A total of 201 subjects have been evaluated for 1 year in three English and two French hospital outpatient centers. Those allocated to sulfonylurea had a significant (P < .001) reduction in median FPG compared with the control group (6.0 mmol.L-1 to 5.6 mmol.L-1, P < .001, v 6.0 mmol.L-1 to 6.0 mmol.L-1, NS). Median hemoglobin A1c (HbA1c) also improved (P < .0002; 5.8% to 5.6%, P < .001, v 5.7% to 5.6%, NS), as did mean beta-cell function (62% to 70%, P < .01, v 62% to 61%, NS). Mean body weight was unchanged in subjects allocated to sulfonylurea (81.7 kg to 82.4 kg, NS), but decreased in the control group (81.6 kg to 80.4 kg, P < .01). More subjects in the sulfonylurea group versus the control group reported one or more minor symptoms of hypoglycemia over 1 year (50% v 24%, P < .0001). Only two subjects reported major hypoglycemic episodes requiring assistance, both of whom were taking sulfonylurea. Insulin sensitivity did not change between groups. Sulfonylurea therapy with gliclazide improved glycemic control and beta-cell function significantly in subjects with increased but not diabetic FPG levels. The study is being extended to determine whether sulfonylurea therapy prevents progression to non-insulin-dependent diabetes mellitus (NIDDM).

Adult↗
PubMed1981

Microdosimetric investigations on collimated fast-neutron beams for radiation therapy: I. Measurements of microdosimetric spectra and particle dose fractions in a water phantom for fast neutrons from 14 MeV deuterons on beryllium.

Lineal energy spectra of fast neutrons, produced by bombarding a thick beryllium target with 14 MeV deuterons, were measured with a proportional counter simulating a sensitive diamter of 2 micrometers. The mean neutron energy of the collimated beam was 6 MeV. The total lineal energy spectra, measured at different positions within a water phantom were separated into three different components: the gamma component, the recoil-proton component, and the component of heavier recoil ions. It is shown mathematically that the components of a linear energy spectrum thus derived allow the calculation of their fractional dose contributions. These dose fractions i.e. the gamma dose, the recoil-proton dose, and the dose fraction of heavier recoil ions, are shown as a function of the spatial position in the phantom.

Beryllium↗
PubMed1998

Baseline ventilatory function predicts the development of higher levels of fasting insulin and fasting insulin resistance index: the Normative Aging Study.

A consistent but as yet unexplained association between baseline ventilatory function and risk of coronary heart disease (CHD) has been reported from many prospective studies. Insulin-resistant states are associated with increased risk of CHD. Forced vital capacity (FVC), forced expiratory volume in one second (FEV1) and maximal mid-expiratory flow rate (MMEF) at study entry were examined as predictors for indirect measures of insulin resistance after a mean follow-up interval of 20.9 yrs in 1050 nondiabetic male subjects in the Normative Aging Study. Males in the top quintile of insulin or fasting insulin resistance index (FIRI) levels at follow-up were defined as being relatively insulin resistant. FVC was negatively associated with risk of being relatively insulin resistant using the insulin (p=0.002) or FIRI (p=0.0001) criteria at follow-up in logistic regression models adjusting for baseline age, body mass index, fat distribution pattern and cigarette smoking. Similar associations were found for FEV1 and MMEF. Additional adjustment for baseline postcarbohydrate challenge glucose levels made little difference to the results, suggesting that baseline glucose intolerance was not a significant source of bias. These findings are consistent with the possibility that insulin resistance may be one of the factors mediating the previously unexplained prospective association between impairment of ventilatory function and risk of mortality from coronary heart disease.

Adult↗
PubMed1980

Fasting or feeding? a survey of fast-jet aircrew nutrition in the Royal Air Force Strike Command, 1979.

The dietary patterns of 266 fast-jet aircrew serving nine operational bases in the RAF Strike Command were studied by questionnaires and statistical analysis, including interrogation of a computer package. There were 113 aircrew (42.5%) who admitted to specific symptoms which, in 59 cases (22%), could have been due to inadequate feeding, apart from or in addition to other stresses associated with the high workload and nature of the operational task. Surprisingly, missing breakfast or eating a light breakfast did not appear to be significant, but diet-related symptoms were associated with missing a meal, during the flying programme, which the individual would normally expect to eat. Because of the pressures and tempo of the flying task, many aircrew said they could often not spare the time to leave the squadron for a meal. Provision of decentralised catering facilities at these units was recommended.

Adult↗
PubMed1977

Study on the biological effect of fast neutrons 1. Effect of fast neutrons on germinability of barley seeds and on the chlorophyll content of the seedlings according to the dose used.

Barley seeds were irradiated in the active zone of the reactor at 500 watt, at favourable flux of fast neutrons in the dose interval of 823--2144 rad. Seeds after irradiation were "cooled" for 48 hours, then germinated, and the length of shoots of the seven days old seedings was measured. The value of the half lethal dose is 1130 rad, estimated from the growth curve. There is a well-defined relation of chlorophyll content (calculated for fresh weight unit) to the dose used. It was concluded from the phenotype of the leaves that the decrease of chlorophyll content was due first of all to the presence of chlorophyll-less cells and cell lines and not to the decrease of chlorophyll content of the individual cells. Irradiation yielded genetically defected cells.

Chlorophyll↗