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Biomedical subjects

S Brody

Publications and source records attributed to S Brody.

At least 19 recordsLinked to original sources
PubMed1998

Cardiovascular autonomic dysregulation in users of MDMA ("Ecstasy").

The present study examined resting heart rate variability (HRV; an index of parasympathetic tone) and heart rate response to the Valsalva maneuver (Valsalva ratio; an index of overall autonomic responsiveness) in 12 repeat users of 3.4-methylenedioxymethamphetamine (MDMA, "Ecstasy"), and a matched comparison group of presumed nonusers. HRV and Valsalva ratio were smaller in users than in controls. Three out of 12 MDMA users but no controls had Valsalva ratios below 1.50, the cut-off for autonomic dysfunction. In several users, there was a total absence of post-Valsalva release bradycardia. All MDMA users were polydrug users. Parasympathetic cardiovascular tone appears impaired in repeat MDMA users, although the ubiquitous problems in such epidemiologic designs (including lack of testing before the first use of the drug and confounding with use of other drugs) preclude definitive causal interpretations.

Adolescent↗
PubMed1998

[Effect of mental and physical stress on intraocular pressure--a pilot study].

BACKGROUND: The aim of the present study was to examine the influence of phasic stressors on intraocular pressure (IOP). SUBJECTS AND METHODS: We exposed 15 ophthalmologically and systemically healthy non-smoking subjects (m:f = 8:7; mean age 25.4 years) to both bicycle ergometry physical stress and a computer-game psychological stress. IOP, blood pressure, and subjective stress were measured. To adjust for between-subject variance, we calculated intra-subject z-scores based on IOP values. Because of the habituation occurring during repeated tonometric measurements, we tested the significance of the difference between the observed and expected IOP z-values for each of the stressors. The expected IOP value was the mean of the pre- and post-stress relaxation-period values. Student's t-tests were used to assess the impact of the stressors on blood pressure. RESULTS: Both stressors increased the systolic blood pressure, but only under mental stress was the intraocular-pressure increase statistically significant (p = 0.048). DISCUSSION: The selective increase in intraocular pressure during mental stress by similar reaction of blood pressure to both stressors is a hint for possible different regulation circuits in the autonomic nerve system for intraocular- and blood pressure, respectively. Additionally, it was possible to demonstrate that mental stress could lead to a rise in intraocular pressure.

Adult↗
PubMed1997

Mitochondrial acyl carrier protein is involved in lipoic acid synthesis in Saccharomyces cerevisiae.

The yeast gene, ACP1, encoding the mitochondrial acyl carrier protein, was deleted by gene replacement. The resulting acp1-deficient mutants had only 5-10% of the wild-type lipoic acid content remaining, and exhibited a respiratory-deficient phenotype. Upon meiosis, the lipoate deficiency co-segregated with the acp1 deletion. The role of ACP1 in long-chain fatty acid synthesis was studied in fast and fas2 null mutants completely lacking cytoplasmic fatty acid synthase. When grown on odd-chain (13:0 and 15:0) fatty acids, these cells showed less than 1% of C-16 and C-18 acids in their total lipids. Mitochondrial ACP is therefore suggested to be involved with the biosynthesis of octanoate, a precursor to lipoic acid.

Acyl Carrier Protein↗
PubMed1997

Differential beta- and alpha-adrenergic activation during psychological stress.

The responsivity of several cardiovascular indices to a computerized mental arithmetic stress and a cold pressor stress were investigated in 22 healthy adult subjects. The major findings were that the largely beta-adrenergically driven T-wave amplitude, pre-ejection period, R-wave to pulse interval, and left ventricular ejection time values responded only to mental arithmetic; a significant decrease in cardiac output and increase in peripheral resistance were elicited during the cold pressor test; inter-beat-interval and subjective stress ratings responded significantly to both stresses compared to baseline levels, but more intensely to mental arithmetic than the cold pressor test; blood pressure, stroke volume and the maximum of the first derivative of the raw impedance signal responded unspecifically to both stresses. These findings support the idea that cardiovascular responses to psychological challenge depend on the level of cognitive processing required for the task. In addition, the superfluity of multiple variable measurements to study cardiovascular reactivity in such situations is discussed.

Adult↗
PubMed1997

Somatotosensory evoked potentials during baroreceptor stimulation in chronic low back pain patients and normal controls.

Nineteen chronic low back pain patients (aged 19-63) and 17 controls (aged 20-41) received electrical pain stimuli during manipulation of their carotid baroreceptors. The non-invasive mechanical manipulation of baroreceptors, using the PRES technique (Phase Related External Suction), simulates the end-effects of phasic blood pressure changes. This technique was developed to assess pain responses induced by changes in blood pressure without the typical shortcomings of pharmacological manipulation or lack of a control condition. During maximum baroreceptor activity, there was an unexpected increase in the amplitude of the somatosensory evoked potentials (SEPs) elicited by the electrical pain stimuli condition (N150-P260 peak-to-peak). In most other studies the opposite effect was found, with decreased pain responses during maximum baroreceptor activity. The chronic pain group reported greater pain during highest baroreceptor activation than did the controls. In addition, the chronic pain group showed lower diastolic blood pressure. To determine whether pain and baroreceptor responses observed in the chronic pain group depended on lower blood pressure levels, a second experiment with a non-clinical sample was performed. Results showed that lower tonic blood pressures are associated with greater baroreceptor activity amplifying pain, while higher blood pressure is associated with pain dampening during high baroreceptor activity. Data suggested that the differences in pain responses found in low back pain patients were associated with their lower tonic blood pressure levels. It is proposed that in general, lower blood pressures may be associated with greater pain during baroreceptor activation.

Adolescent↗
PubMed1997

Four-year stability of cardiovascular reactivity to psychological stress.

The 4-year stability of cardiovascular responses to laboratory psychological stress (mental arithmetic) was examined in 75 adults. The stability coefficients were .76 for heart rate (HR) change and .81 for absolute HR, .66 for systolic blood pressure (SBP) change and .52 for absolute SBP, .16 for diastolic blood pressure (DBP) change and .27 for absolute DBP. Males had greater SBP and DBP reactivity than females in the first session, but this reactivity decreased by the 4-year follow-up session (which was not the case for women).

Adult↗
PubMed1997

Temperature compensation and membrane composition in Neurospora crassa.

The link between temperature compensation of the circadian rhythm and temperature-induced adjustment of membrane composition in Neurospora crassa is briefly reviewed. In common with most organisms, Neurospora responds to changes in growth temperature by adjusting its lipid composition, primarily by increasing the degree of unsaturation of its fatty acids at low temperature. This may result in maintenance of either membrane fluidity or phase transition behavior over a range of temperatures. In Neurospora, there are three mutations (frq, cel, and chol-1) that affect temperature compensation of the circadian rhythm; cel and chol-1 are defective in lipid synthesis, and frq interacts with the other two in double-mutant strains. This suggests that lipid metabolism may play a role in temperature compensation of the rhythm, and that the FRQ gene product may also be involved in membrane function, either in regulating lipid composition or as a sensor responding to changes in lipid composition.

Cell Membrane↗
PubMed1996

Waveform reliability of the phase related external suction baroreceptor manipulation method.

The phase related external suction (PRES) method of controlled carotid baroreceptor manipulation (a neck cuff with cardiac cycle timed pressure variations) has been used to investigate not only the human baroreflex, but extrahomeostatic effects of baroreceptor activity (such as the modulation of cortical activity, peripheral reflexes, and pain) as well. The present study provides quantitative within subject test-retest reliability estimates of PRES effects on 6-s trial-length heart rate waveforms. Mean within subject test-retest reliability for each averaged heart rate response waveform was 0.77 for the baroreceptor stimulation (systolic negative/diastolic positive cuff pressure) condition, 0.56 for the control condition (diastolic negative/systolic positive cuff pressure), and 0.69 for the difference between conditions. The importance of analyzing time-intensity dynamics, rather than merely the mean or maximum effect of any treatment variable is emphasized, and recommended for investigations of a wide variety of short duration, induced physiological time series processes.

Adult↗
PubMed1996

Placenta increta occurring in a blighted ovum.

We present a rare case of placenta increta, confirmed postoperatively by pathologic analysis, occurring before 20 weeks' gestation in a blighted ovum. Hysterectomy was necessary for control of hemorrhage.

Adult↗
PubMed1995

Characterization of the different spectral forms of glutamate 1-semialdehyde aminotransferase by mass spectrometry.

Glutamate 1-semialdehyde aminotransferase produces delta-aminolevulinate for the synthesis of chlorophyll, heme, and other tetrapyrrole pigments. The native enzyme from Synechococcus is pale yellow and has absorption maxima at 338 and 418 nm from vitamin B6. Yellow, colorless, and pink forms of the protein are obtained by treatment with 4,5-dioxovalerate, 4,5-diaminovalerate, and acetylenic GABA, respectively. Compared to the native enzyme, the 418 nm absorption maximum in the yellow enzyme is enhanced and the 338 nm maximum reduced while the colorless enzyme has a heightened maximum at 338 nm and a barely detectable peak at 418 nm. The pink enzyme has an absorption maximum at 560 nm. When the native and colorless enzymes are repeatedly diluted in 0.5 M Na2HPO4, pH 7.0, and reconcentrated, pyridoxamine 5'-phosphate is released and the 338 nm maximum lost. Thus the 338 nm absorption maximum is associated with noncovalently bound pyridoxamine 5'-phosphate. NaBH4 reduction proved that the absorbance at 418 nm is from pyridoxal 5'-phosphate cofactor bound by a Schiff base to the protein. When the native, colorless, and yellow enzymes were subjected to electrospray ionization mass spectrometry, the B6 cofactor dissociated from the protein and gave a molecular weight of 46,401-46,418. Acetylenic GABA and NaBH4 were used for protein modification, and they reacted with the native and yellow enzymes but had no effect on the colorless enzyme. Pyridoxal 5'-phosphate bound covalently to the protein after NaBH4 reduction. Acetylenic GABA attached covalently to the enzyme produced an additional mass peak, 123-126 mass units higher, in the electrospray ionization spectrum.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗