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Biomedical subjects

S Brody

Publications and source records attributed to S Brody.

At least 73 records · Page 4Linked to original sources
PubMed1993

Hypochondriacal attitudes, pain sensitivity, and attentional bias.

The relation between hypochondriacal attitudes, thermal pain threshold, and attentional bias toward pain was examined in a non-clinical population (N = 28). Attentional bias was operationalized with a concentration-performance test, which subjects performed while connected to a pain stimulator. Subjects were informed that they would receive a painful stimulus during the second part of the test, while the first part was introduced as pain-free. The pain stimulus was never applied during the test phase. The expectancy of a forthcoming pain stimulus reduced the performance of high hypochondriacal subjects in both parts of the test. Low hypochondriacal subjects, on the other hand, displayed significantly better performance in the first, pain-free compared to the second, pain-related part of the test. Thermal pain thresholds were assessed at four measuring sites (thenar, neck, collar-bone, abdomen), but no relations with hypochondriasis sum scores and locus of pain stimulation were found. A stepwise multiple regression of pain threshold by individual Illness Attitude Scales (IAS) led to 66% of the variance being explained by the scales 'concern about pain', 'worry about illness', and 'disease phobia'. Results are discussed in terms of amplifying somatic style, preoccupation with or attentional bias toward bodily symptoms, and experimental induction of a hypochondriacal state.

Adult↗
PubMed1993

Activation of carotid baroreceptors inhibits spinal reflexes in man.

The present study was designed to investigate the effect of baroreceptors on a spinal reflex. The Achilles tendon reflex (T reflex), a monosynaptic spinal reflex, was chosen as an indicator of descending influences of central activation. The baroreceptors are stretch receptors which respond to extensions of the arterial wall. Carotid sinus baroreceptors can be manipulated non-invasively by means of a cuff around the neck. In this study, the phase-related external suction (PRES) neck cuff technique was used. PRES applies short changes in cuff pressure as a function of heart cycle phase, controlling for non-specific effects found in other baroreceptor manipulation methods. The T reflex was reduced when elicited during the highest levels of baroreceptor activation. Reflex amplitude was largest when elicited during the lowest levels of baroreceptor activation. These results are consistent with previous findings that baroreceptor activation reduces CNS excitability.

Adult↗
PubMed1993

Baroreceptor stimulation alters cortical activity.

The arterial baroreceptors constitute an essential sensory link for the short-term regulation of blood pressure and may also influence higher cortical function. The present study was undertaken to evaluate previous reports of such a cortical influence under conditions of psychologically controlled, mechanical baroreceptor stimulation. This control was achieved by use of PRES (phase-related external suction), a modified neck suction technique. PRES applies short suction bursts that have a different impact on baroreceptors depending on their timing within the cardiac cycle and has the advantage that subjects cannot easily discriminate between conditions of stimulation and inhibition. Electroencephalograms were recorded from 22 subjects during PRES manipulations. A surface-negative shift of about 10 microV developed during the cuff manipulations. Over frontal-central regions, this shift was smaller during baroreceptor stimulation than during inhibition. These data provide support for the proposal that baroreceptor activation influences cortical activity.

Adult↗
PubMed1992

Circadian rhythms in Neurospora crassa: the role of mitochondria.

Energy metabolism and mitochondria have been discussed with respect to their role in the circadian rhythm mechanism for some time. Numerous examples of inhibitors that affect the mitochondria of plants and animals and microorganisms are known, which cause large phase shifts in the rhythms of these organisms. Analogous studies on the role of mitochondria in the Neurospora circadian rhythm mechanism have also been reported and summarized. This communication differs from previous studies on other organisms in that it will focus on two lines of evidence derived from studies on Neurospora strains carrying mutations affecting the mitochondria. (a) Strains whose growth rate is resistant to oligomycin (oli(r)) owing to an altered protein in the F0 sector of the mitochondrial ATPase, showed no phase shifts when pulsed with oligomycin. Control strains (oli(s)) showed large phase shifts when pulsed with oligomycin. This indicates that the phase-shifting effect of oligomycin is due to the direct inhibition of the mitochondrial ATPase and not some side effect of this inhibitor. (b) In Neurospora, many different strains are known that carry mutations in the nuclear or mitochondrial genome that affect mitochondrially localized proteins. Some of these, such as oli(r), [MI-3], or cya-5, showed shorter (approximately 19-h) periods compared with the normal (21.5-h) period. Others showed little or no change in period. Those mutant strains exhibiting shorter periods also contained approximately 60% more mitochondrial protein per gram total protein in extracts compared with the normal strains. Assays of the level of a mitochondrial-specific protein, acyl carrier protein, showed that the cellular content of this protein was approximately doubled.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphate↗
PubMed1991

Evolutionary conservation of a microbody targeting signal that targets proteins to peroxisomes, glyoxysomes, and glycosomes.

Peroxisomes, glyoxysomes, glycosomes, and hydrogenosomes have each been classified as microbodies, i.e., subcellular organelles with an electron-dense matrix that is bound by a single membrane. We investigated whether these organelles might share a common evolutionary origin by asking if targeting signals used for translocation of proteins into these microbodies are related. A peroxisomal targeting signal (PTS) consisting of the COOH-terminal tripeptide serine-lysine-leucine-COOH has been identified in a number of peroxisomal proteins (Gould, S.J., G.-A. Keller, N. Hosken, J. Wilkinson, and S. Subramani. 1989. J. Cell Biol. 108:1657-1664). Antibodies raised to a peptide ending in this sequence (SKL-COOH) recognize a number of peroxisomal proteins. Immunocryoelectron microscopy experiments using this anti-SKL antibody revealed the presence of proteins containing the PTS within glyoxysomes of cells from Pichia pastoris, germinating castor bean seeds, and Neurospora crassa, as well as within the glycosomes of Trypanosoma brucei. Western blot analysis of purified organelle fractions revealed the presence of many proteins containing this PTS in both glyoxysomes and glycosomes. These results indicate that at least one of the signals, and therefore the mechanism, for protein translocation into peroxisomes, glyoxysomes, and glycosomes has been conserved, lending support to a common evolutionary origin for these microbodies. Hydrogenosomes, the fourth type of microbody, did not contain proteins that cross-reacted with the anti-PTS antibody, suggesting that this organelle is unrelated to microbodies.

Amino Acid Sequence↗
PubMed1991

Amplitude model for the effects of mutations and temperature on period and phase resetting of the Neurospora circadian oscillator.

This paper analyzes published and unpublished data on phase resetting of the circadian oscillator in the fungus Neurospora crassa and demonstrates a correlation between period and resetting behavior in several mutants with altered periods: As the period increases, the apparent sensitivity to resetting by light and by cycloheximide decreases. Sensitivity to resetting by temperature pulses may also decrease. We suggest that these mutations affect the amplitude of the oscillator and that a change in amplitude is responsible for the observed changes in both period and resetting by several stimuli. As a secondary hypothesis, we propose that temperature compensation of period in Neurospora can be explained by changes in amplitude: As temperature increases, the compensation mechanism may increase the amplitude of the oscillator to maintain a constant period. A number of testable predictions arising from these two hypotheses are discussed. To demonstrate these hypotheses, a mathematical model of a time-delay oscillator is presented in which both period and amplitude can be increased by a change in a single parameter. The model exhibits the predicted resetting behavior: With a standard perturbation, a smaller amplitude produces type 0 resetting and a larger amplitude produces type 1 resetting. Correlations between period, amplitude, and resetting can also be demonstrated in other types of oscillators. Examples of correlated changes in period and resetting behavior in Drosophila and hamsters raise the possibility that amplitude changes are a general phenomenon in circadian oscillators.

Activity Cycles↗
PubMed1990

De novo fatty acid synthesis mediated by acyl-carrier protein in Neurospora crassa mitochondria.

The acyl-carrier protein (ACP) in Neurospora crassa mitochondria [Brody, S. & Mikolajczyk, S. (1988) Eur. J. Biochem. 173, 353-359] mediated a cerulenin-sensitive, de novo fatty acid synthesis independent of the fatty acid synthetase complex present in the cytoplasm. Incubation of mitochondria with [2-14C]malonate labeled only the ACP as indicated by autoradiography after SDS/PAGE. Under these in vitro conditions ATP was required for the initial acyl-ACP formation, but further elongation required either magnesium or the direct addition of NADPH. Labeled hexanoic (6:0) and caprylic (8:0) acids were detected as intermediates in the pathway, as well as hydroxymyristic acid. All of the intermediates, and the eventual product of the reaction, myristic acid (14:0), were released from the ACP by alkaline treatment. Pulse-chase experiments demonstrated the incorporation on to, and release of label from, the ACP. In vivo labeling of ACP with [2-14C]malonate was also detected and the label was in the form of hydroxymyristic acid. This newly discovered pathway is discussed from the standpoint of its possible role in providing acyl chains for mitochondrial lipids.

Acetyltransferases↗
PubMed1989

Acyl carrier protein is present in the mitochondria of plants and eucaryotic micro-organisms.

Proteins antigenically similar to the acyl carrier protein (ACP) found in the mitochondria of Neurospora crassa were detected by immunoblotting and radioimmunoassay techniques in mitochondria isolated from yeast, potatoes, and pea leaves. These mitochondrial proteins were similar to Neurospora ACP both in their electrophoretic mobility and in their unusual decrease in mobility upon reduction. Authentic ACP(s) show this type of change upon conversion of the acylated to the unacylated form. Purified ACP from both spinach chloroplasts and Escherichia coli cells cross-reacted with antibodies raised against Neurospora ACP. Purified ACP from Neurospora cross-reacted with antibodies raised against spinach chloroplast ACP and E. coli ACP. Mitochondria isolated from beef heart and rat brain were tested extensively and exhibited no cross-reaction with any of the three anti-ACP preparations. The discovery of ACP in the mitochondria of other organisms raises questions concerning the possible relationship between ACP and beta-oxidation in mitochondria, the involvement of ACP in de novo biosynthesis of some of the acyl chains in mitochondria and the subcellular locations of fatty acid biosynthesis in plants and eucaryotic micro-organisms.

Acyl Carrier Protein↗
PubMed1989

Scheduled intermittent periods of in vitro fertilization treatments.

Organization and results of an in vitro fertilization program at the Huddinge University Hospital are given from its beginning in August 1985: 6 months in advance a scheme is scheduled with 2 weeks open for treatment followed by free intervals of 3-4 weeks. Follicular development is stimulated with clomiphene citrate and hMG, and assessed by analyses of estradiol and LH in serum combined with ultrasound examinations. Following the administration of hCG, eggs are collected by transvesical aspiration guided by ultrasound. The ova are inseminated with about 50,000 motile spermatozoa, and cultured for 48 h. Up to four eggs are transferred transcervically to the uterine cavity. 158 egg pickups have been performed (August 1985 to December 1987) in 106 patients resulting in fourteen intrauterine and two ectopic pregnancies, biochemical pregnancies not counted. This protocol has restricted routine work load allowing these treatments to be part of the clinical routine. It has also allowed the application of research programs and thus optimized limited resources.

Adult↗
PubMed1988

Neurospora mitochondria contain an acyl-carrier protein.

Mitochondria of Neurospora crassa were found to contain a protein which was labelled with [14C]pantothenic acid and which carried an acyl group. This protein, when purified 6000-fold, closely resembled the bacterial and chloroplast acyl-carrier protein(s) [ACP(s)] in its physical and chemical properties. The predominant acyl group esterified to the purified protein was 3-hydroxytetradecanoate, as determined by gas chromatographic mass spectrometry. The amino acid sequence of the tryptic peptide carrying the 4'-phosphophantetheine moiety showed a high degree of sequence similarity to the analogous bacterial and chloroplast ACP peptide sequences. The possible functions of this ACP in lipid metabolism are discussed in view of the fact that Neurospora has a separate cytoplasmic enzyme complex which carries out the de novo biosynthesis of fatty acids.

Acyl Carrier Protein↗
PubMed1988

Dehydroepiandrosterone sulphate and dehydroepiandrosterone in serum: differences related to age and sex.

Serum concentrations of dehydroepiandrosterone sulphate (DHAS) were determined in 590 healthy women aged 20-87 yr. Simultaneous assays of dehydroepiandrosterone (DHA) were performed in 417 of the women. DHA and DHAS levels correlated negatively with age while the DHA/DHAS ratio proved to be unrelated to age. When values for 60 healthy men in the age range 20-84 yr were compared with those obtained in 60 randomly-selected healthy women who were exactly age-matched, the DHAS levels were found to be significantly lower and the DHA/DHAS ratios significantly higher in the women. These results might be of use in establishing normal clinical ranges for serum DHA, DHAS and the DHA/DHAS ratio in women.

Adult↗
PubMed1987

Circadian rhythms in Neurospora crassa: a clock mutant, prd-1, is altered in membrane fatty acid composition.

The fatty acid compositions of the phospholipids of Neurospora crassa mutants with altered periods were determined to test the possibility that some of these mutants might have altered membrane composition. In liquid shaker culture in constant light the bd (band) strain, which has a normal period (21.6 h), exhibited a growth-dependent increase in linoleic acid content and a decrease in linolenic acid content during early log phase growth. By late log phase, fatty acid composition was essentially constant. The phospholipid fatty acid compositions of bd strains containing mutations at the frq (frequency) and chr (chrono) loci were indistinguishable from that of the bd strain under the conditions used. However, a bd strain containing a mutation at the prd-1 (period) locus, as well as prd-1 segregants from a cross of this strain to a bd strain, had altered patterns of growth-dependent fatty acid composition; linoleic and linolenic acid contents changed more slow than in the bd strain and continued to change throughout growth. In addition, the fatty acid composition of a bd prd-1 strain on solid medium differed from that of the bd strain. It is proposed that the prd-1 mutation leads to altered membrane homeostasis, which in turn affects circadian rhythmicity because some or all components of the rhythm-generating system are membrane-localized.

Cell Membrane↗
PubMed1987

Circadian rhythms in Neurospora crassa: membrane composition of a mutant defective in temperature compensation.

The cel mutant of Neurospora, partially blocked in fatty acid synthesis and lacking temperature compensation of its circadian rhythm below 22 degrees C, had a phospholipid fatty acid composition in liquid shaker culture distinctly different from that of a cel+ control strain. During growth, cel+ exhibited a reproducible increase in its linoleic acid level from about 32 to a plateau at 63 mol%, and a corresponding decrease in its linolenic acid level from about 40 to a plateau at 10 mol%. The level of palmitic acid was constant at 19 mol%. In the cel strain, the linoleic acid level was constant at 54 mol% while the palmitic acid level increased from about 12 to about 23 mol%. Supplementation with palmitic or linoleic acids altered the patterns of fatty acid composition of cel, but did not affect the pattern of cel+. Altered fatty acid composition cosegregated with the cel marker. The mitochondrial phospholipids of cel in liquid culture also had abnormal fatty acid composition, as did the whole mycelial phospholipids on solid medium. These results are consistent with the involvement of membrane homeostasis in the temperature compensation of circadian rhythms.

Cell Membrane↗