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At least 1,423 records · Page 79Linked to original sources
PubMed1990

Liquid chromatographic and spectral analysis of the 17-hydroxy anabolic steroids.

The liquid chromatographic properties of various 17-hydroxy anabolic steroids are examined under reversed-phase conditions. These anabolic steroids are now listed as controlled drugs in many states due to their abuse potential in athletics, body building, and other areas. These nonesterified steroids are separated on a C18 stationary phase with a 70% methanol in water mobile phase. In a few cases, two compounds display very similar retention properties. However, dual-wavelength detection at 254 and 280 nm allows for their differentiation. Reversed-phase retention parallels steroid lipophilicity based on hydroxyl and methyl group substituents. Also, those steroids containing a dienone substructure are more polar than steroids containing an enone moiety.

Anabolic Agents↗
PubMed1990

Liquid chromatographic and mass spectral analysis of the anabolic 17-hydroxy steroid esters.

The liquid chromatographic separation of the common anabolic steroid esters is accomplished in an isocratic reversed-phase system. These anabolic steroids are now controlled substances in many states in the U.S. due to their potential for abuse and misuse. The esters are designed to be very lipophilic materials for slow release from intramuscular injection sites. With a C18 stationary phase material and a mobile phase of methanol-water (85:15), the more lipophilic esters such as testosterone decanoate show a retention time of about 50 min. These esters of varying lipophilicity are well resolved by reversed-phase liquid chromatography, and this technique is very useful for the identification of these compounds in forensic samples.

Anabolic Agents↗
PubMed1986

Optical transmission of normal and atheromatous arterial wall: a spectral analysis.

In laser angioplasty one of the factors influencing the immediate damage (and therefore the risk of acute arterial perforation) is the optical absorption characteristics of the target tissue. In an attempt to evaluate the differences in optical absorptive properties, the transmission spectrograms of samples of normal and atheromatous human postmortem aortic wall were measured over the visible spectrum. Optical transmission varied inversely with sample thickness and directly with wavelength through both normal and atheromatous samples. Over the whole visible spectrum atheromatous tissue transmitted less per unit thickness than normal tissue. This differential effect was, however, most pronounced at 500 nm, where atheromatous tissue transmitted light 5-10 times less strongly than normal aortic wall. Such wavelength dependent differential optical absorption could provide a means for the selective photovaporisation of atheroma in laser angioplasty.

Angioplasty, Balloon↗
PubMed1991

Heart rate variability in left ventricular hypertrophy and heart failure, and the effects of beta-blockade. A non-spectral analysis of heart rate variability in the frequency domain and in the time domain.

An analysis of heart rate (HR) variability (HRV) was based on quantifying the number and amplitude of HR fluctuations over long (8-30 cycles) and short (2-4 cycles) sequences of acceleration and deceleration-forming oscillations. The 'product' (number times amplitude) is an equivalent of the power spectrum in the frequency domain. In the time domain, positive correlations with HR were found for the number of long (L) sympathetic-mediated oscillations, whereas they were negative for short (S) vagally-mediated oscillations. The L/S ratio, an index of the autonomic nervous system (ANS) balance, closely paralleled the circadian HR values. HRV was studied in the ambulatory ECG of three groups of 15 normal adults (group I), 13 patients with left ventricular hypertrophy (LVH, group II) and 13 patients with heart failure (HF, group III). In basic conditions the mean HR was 77.1 +/- 1.9 beats min-1 (mean +/- SEM) in group I, 76.8 +/- 3.3 in II, 79.5 +/- 3.5 in III (P = NS). The different types of oscillations had smaller 24-h average values of the product in groups II and III than in group I, but the trends did not reach significance. However, the pooled 24 hourly values of the L/S ratio in group I (1.17 +/- 0.09) were lower than in group II (1.33 +/- 0.06, P less than 0.05 at Ancova) and higher than in group III (1.06 +/- 0.09, P less than 0.001). A 3-day treatment with acebutolol non-uniformly slowed the mean HR:--9.5% in group I, --18.1% in II and -19.1% in III (P less than 0.001), and uniformly diminished the L/S ratio by 17% to 20% (P less than 0.01). In conclusion, the sympathetic predominance of the ANS balance in LVH and HF is reflected by the beta-blockade induced HR decrease that is twice as marked in patients as in controls. In basic conditions HRV tends to be depressed in LVH and even more in HF. The ANS imbalance, however, has different modalities depending on the presence of HF, probably because of the different status of beta-adrenergic receptors in this condition.

Acebutolol↗
PubMedDate not supplied

Spectral analysis of Lapine EEG: neurotoxicologic evaluation of new nonionic contrast media.

Effects of the injection of 0.25 ml of nonionic radiocontrast media (280 mg I/ml) and/or istonic and/or hypertonic mannitol into the subarachnoid space on the low frequencies (2--5 Hz) of the EEG were studied in nonanesthetized, curarized rabbits. Compared to the noninjected controls, mannitol did not cause any significant EEG spectrum shifts. P-297 and iopamidol caused a slight decrease in the energy content of the 2--5-Hz band, while DS-1-132 and the nonionic dimer ZK 32347 caused a moderate increase. Since an increase in the slow-wave component of the EEG indicates a pacemaking activity, while a decrease indicates stimulation or irritation, none of the tested nonionic media appear to be biological inert. In this test P-297, iopamidol, and DS-1-132 caused fewer disturbances than metrizamide.

Animals↗
PubMed1989

Spectral analysis of heart rate variability under mental stress.

It has been claimed that an increase in the 0.1-Hz component in power spectra of heart rate variability indicates an increased sympathetic tone. We tested 135 middle-aged unmedicated men (mean age 44 +/- 7 years) with two types of mental tasks, a reaction-time test and a mental arithmetic test, to determine whether the results were comparable with those from tilt tests. Although both tasks significantly increased the heart rate and blood pressure, to the same extent as the tilt tests, energy in the 0.1-Hz band decreased during the reaction-time test (from 899 +/- 641 to 482 +/- 430; P less than 0.01) yet was unchanged during the mental arithmetic test. We conclude that the response of the 0.1-Hz component is a task-specific phenomenon.

Blood Pressure↗
PubMed1992

Effects of yohimbine on heart rate variability in panic disorder patients and normal controls: a study of power spectral analysis of heart rate.

We studied the effects of yohimbine on heart rate (HR) variability in 13 normal controls and 13 patients with panic disorder. Yohimbine produced a significant increase in SD of HR in standing posture in both patients (p = 0.01) and normal controls (p = 0.025). Panic disorder patients had a significant increase in standing absolute midfrequency (MF) power (0.07-0.15 Hz) after administration of yohimbine (p = 0.002). The ratio of post- to preyohimbine standing MF power (0.07-0.15 Hz) during standing was significantly higher in patients as compared with controls (2.3 +/- 1.08 vs. 1.33 +/- 0.38; p = 0.01), which suggests an increased responsivity of panic disorder patients to the adrenergic effects of yohimbine.

Adult↗
PubMed1998

Spectral analysis of photoplethysmograms from radial forearm free flaps.

OBJECTIVE: Photoplethysmography utilizes a green-light-emitting diode to transmit light into a tissue. Reflected light from hemoglobin in dermal capillary red blood cells is received by a photo detector and is analyzed as light intensity along a frequency spectrum. This method of analysis allows for the removal of "noise" above (stray light and alternating current [AC]) and below (room vibrations and respiratory motion) the peak signal (1 to 2 Hz) and results in a means to distinguish between perfused and nonperfused tissues. METHODS: Twenty-two of 30 consecutive radial forearm free flap (RFFF) patients were enrolled in an approved human studies protocol to collect descriptive data for RFFFs that were perfused, arterial occluded, and venous occluded. The protocol was performed following completion of flap elevation and prior to pedicle ligation, flap inset, and microvascular anastomoses. Six 90-second measurements per flap were obtained (n = 132), processed by fast Fourier transform (FFT), and analyzed by blinded reviewers to determine their state of perfusion. Signal was collected 5 minutes after the onset or release of individual vessel occlusion. RESULTS: The reviewers' interpretations were compared with the status of the pedicle and analyzed for sensitivity (0.96), specificity (0.95), and positive predictive value (0.98). CONCLUSIONS: FFT analysis of photoplethysmograms from RFFF patients provides an accurate and rapid means for determining RFFF pedicle vessel patency. Photoplethysmography may provide a clinically useful tool for postoperative perfusion monitoring of free flaps in the future.

Equipment Design↗
PubMed1996

Acoustic reflectometry: spectral analysis and the conductive hearing loss of otitis media.

OBJECTIVE: To test the hypothesis that the quality of sound reflected from the tympanic membrane with acoustic reflectometry is predictive of hearing loss caused by otitis media. METHODS: A pediatrician in solo primary care practice examined 257 patients for middle ear disease using clinical criteria, tympanometry and an acoustic reflectometer with a recording device. Each ear was diagnosed as normal, acute otitis media or otitis media with effusion. Hearing testing with a select picture audiometer was performed by a technician who was blinded to the diagnosis. Paired data were obtained on some ears. RESULTS: A spectrum of < 95 degrees identified 100% of the ears hearing at 30 dB or more because of otitis media. Paired data were obtained on 99 ears with otitis media that failed audiometry on the initial visit. On return 96 of the 99 showed a broader spectrum of reflected sound with improved hearing and clinical improvement of otitis media. CONCLUSIONS: Measurement of the width of the spectrum of reflected sound is the basis for a new technology that shows initial promise for being able to provide objective information about the probability of conductive hearing loss caused by otitis media.

Acoustic Impedance Tests↗
PubMed1979

Unusual amniotic fluid spectral analysis in Rh sensitization.

In our experience delta 450 millimicron OD measurements have shown a progressive decline during the latter half of gestation in pregnancies unaffected by fetal hemolytic disease. However, we have seen two Rh-negative patients in whom there was a rise in delta 450 millimicron OD between 24 and 27 weeks' gestation and who subsequently bore Rh-negative infants. In these two cases the increase between 24 and 27 weeks was from approximately 0.140 to about 0.200. Both infants were unaffected with fetal hemolytic disease. Therefore, we recommend caution in interpreting modest increases in delta 450 millimicron OD during this period of gestation.

Amniotic Fluid↗
PubMed1989

Lumbar myoelectric spectral analysis for endurance assessment. A comparison of normals with deconditioned patients.

A myoelectric protocol to objectively discriminate between test subjects based on trunk muscular performance differences (endurance) was investigated in a group of 11 healthy volunteers and ten industrial patients undergoing functional restoration for chronic disabling spinal disorders. The subjects performed a standardized exercise protocol, holding their upper torso unsupported for successive fixed-time trials while electromyographic (EMG) signals were recorded from erector spinae. A Fast Fourier Transform allowed calculation of the initial mean power frequency (MPF) for each trial. Isokinetic extensor trunk strength was independently measured at each session for comparison with myoelectric signal analysis. The investigation revealed significant differences in group statistics between patients in early rehabilitation and their subsequent tests, as well as between their initial test and the normal subject scores. However, test sensitivity for identifying patients with "low endurance" is questionable. There was no significant correlation between EMG initial MPF measures and isokinetic extensor trunk strength measures, even though all patients showed isokinetic improvement. Data suggest that the protocol used and myoelectric power spectrum temporal shifts may have some value for identification of individual subjects with endurance limitations (or fatigue resistance) in patients of this type. However, lack of a "gold standard" for comparison presents difficulties in documenting the value and validity with respect to endurance. The test may be of value to measure relative loads.

Adult↗