PubMed Health⌕ Search

Biomedical subjects

M Erb

Publications and source records attributed to M Erb.

44 records · Page 3Linked to original sources
PubMed1997

Sequential activation of supplementary motor area and primary motor cortex during self-paced finger movement in human evaluated by functional MRI.

The 'Bereitschaftspotential' attributed to activation of the supplementary motor area (SMA) precedes the 'motor potential' of the primary motor cortex (Ml) about 500-1000 ms during self-initiated movements. A measurement procedure is reported to evaluate the sequence of hemodynamic activation within both motor areas by functional magnetic resonance imaging (fMRI). The fMRI-data were averaged across multiple trials of single voluntary finger movements and analyzed with respect to the onset-time of signal increase. All participants showed a sequential hemodynamic response with SMA preceding M1 activation. The mean latency between hemodynamic activation of SMA and M1 amounted to 0.8 s. These findings suggest that the vascular response parallels the electrical events and that a sufficient temporal resolution can be achieved by fMRI to detect sequential hemodynamic activation of functionally connected cortical areas.

Adult↗
PubMed1996

Heart rate variability and the outcome of head-up tilt in syncopal children.

Neurocardiogenic syncope may be caused by enhanced sympathetic activity evoking a vasodepressor-cardioinhibitory reflex. Heart rate variability (HRV) methods can be used to assess the modulation of sympathetic and parasympathetic activity. To determine whether HRV measurements are related to the outcome of head-up tilt testing (HUT), we studied 29 syncopal patients aged 7-19 y. After 30 min supine, patients were tilted to 80 degrees for 30 min or until syncope occurred. Sequential beats free from ectopy were analyzed. Time domain indices included SD (SDNN), root mean square successive differences (RMSSD), percent exceeding 50 ms (pNN50). An autoregressive model was used to calculate power spectra. Low frequency power (LFP, 0.05-0.15 Hz), high frequency power (HFP, 0.15-0.40 Hz), and total power (TP, 0.01-0.40 Hz) were compared before and after tilt. Data were obtained supine before tilt (baseline), within 5 min after HUT (early), 5-10 min after HUT (mid), and 15 min after HUT or presyncope (late). Seventeen patients fainted (HUT+), and 12 patients did not (HUT-). Variability indices were different for HUT- and HUT+ at baseline: SDNN was 123 +/- 17 versus 78 +/- 6, RMSSD was 127 +/- 23 versus 64 +/- 6 ms, pNN50 was 51 +/- 6 versus 31 +/- 4, respectively. Spectral data demonstrated decreased HFP and TP in HUT+ (834 +/- 133 and 2855 +/- 420 ms2) versus HUT- (3433 +/- 840 and 7062 +/- 1500). With tilt, SDNN, RMSSD, and pNN50 decreased proportionately in HUT- and HUT+. However, sympathovagal balance, measured by the ratio LFP/HFP and by normalized LFP, was markedly increased in HUT+ (2.2 +/- 0.7 and 0.43 +/- 0.03) compared with HUT- (0.8 +/- 0.2 and 0.31 +/- 0.02) at baseline and differences increased with tilt. With syncope, sympathetic activity decreased, and parasympathetic activity increased. Decreased RR variability with decreased parasympathetic activity and increased indices of sympathovagal balance before HUT predict a positive tilt test in children referred for evaluation of neurocardiogenic syncope.

Adolescent↗
PubMed1990

Trophic regulation of nodose ganglion cell development: evidence for an expanded role of nerve growth factor during embryogenesis in the rat.

Peripheral sensory neurons are derived from two distinct embryonic tissues, the neural crest and epibranchial placodes. Studies in the chick suggest that embryonic lineage and trophic dependence are interrelated, such that many crest-derived cells depend on NGF for survival during development, whereas placodal derivates, including nodose ganglion neurons, do not (30). It remains controversial, however, whether or not a similar dichotomy exists in mammalian species, in which trophic requirements during early development of placodal ganglia have not been defined. To approach this issue, the present study examined the effects of nerve growth factor (NGF) on neuronal survival in embryonic rat nodose ganglion cultures. Treatment of E13.5-14.5 nodose explants with 20 ng/ml NGF resulted in a four-fold increase in neuronal survival that was blocked by anti-NGF antiserum. Increased neuronal survival and neurite outgrowth were also observed in neuron-enriched dissociated cell cultures; these effects were seen within 12 h of plating, indicating that NGF-responsive neurons or neuroblasts were already present in the ganglion at the time of explantation. This was further supported by immunocytochemical staining of nodose cell bodies in situ with the monoclonal antibody 192-IgG against the NGF receptor (12). These findings indicate that NGF may be important in regulating nodose development during early gangliogenesis in mammals and suggest that NGF plays a more widespread role in peripheral nervous system ontogeny than previously recognized.

Animals↗
PubMed1987

Presenting stereoscopic stimuli with one monitor.

Two different stimuli can be presented to both eyes on the same monitor in rapid alternation (100 Hz), each stimulus being displayed for 4 msec-periods. Sector discs in front of both eyes, phase-locked to the alternations of the displays, assure that each stimulus is seen by only one eye.

Data Display↗
PubMed1984

6-[(4-bromo-2,3-dioxobutyl)thio]-6-deaminoadenosine 5'-monophosphate and 5'-diphosphate: new affinity labels for purine nucleotide sites in proteins.

Two new adenine nucleotide analogues have been synthesized and characterized: 6-[(4-bromo-2,3-dioxobutyl)thio]-6-deaminoadenosine 5'-monophosphate and 5'-diphosphate. The bromoketo and dioxobutyl moieties have the ability to react with the nucleophilic side chains of several amino acids, as well as with arginine. 6-[(4-Bromo-2,3-dioxobutyl)thio]-6-deaminoadenosine 5'-monophosphate reacts irreversibly with rabbit muscle pyruvate kinase, causing inactivation. Addition of ADP to the reaction mixture (in the presence of Mg2+) markedly decreases the rate of inactivation. Pig heart NAD-dependent isocitrate dehydrogenase is allosterically activated by ADP, which reduces the Km for isocitrate. 6-[(4-Bromo-2,3-dioxobutyl)thio]-6-deaminoadenosine 5'-diphosphate reacts irreversibly with isocitrate dehydrogenase, causing, rapidly, a loss of the ability of ADP to increase the initial velocity of assays conducted at low isocitrate concentrations and, more slowly, inactivation. Addition of ADP to the reaction mixture (in the presence of Mn2+) protects this enzyme against the loss of allosteric activation. It is proposed that the 6-[(4-bromo-2,3-dioxobutyl)thio]-6-deaminoadenine nucleotides react at the active site of pyruvate kinase and at the ADP activating site of isocitrate dehydrogenase and that these compounds may have general applicability as affinity labels of catalytic and regulatory adenine nucleotide sites in proteins.

Adenosine Diphosphate↗
PubMedDate not supplied

A comparative pilot-scale study of the performance of conventional activated sludge and membrane bioreactors under limiting operating conditions.

The behavior of the conventional activated-sludge (CAS) process was compared to that of the membrane bioreactor (MBR) process under limiting operating conditions; that is, at a low solids retention time (SRT) and hydraulic residence time (HRT). The SRT was varied from 2 to 7 days, and the HRT ranged from 5 to 18 hours. The comparison was carried out in terms of nitrification and denitrification kinetics and in terms of the carbon and nitrogen removal performance of these processes. The study involved two pilot-scale units: a CAS unit with a 9-m3 aeration tank and a 225-L MBR. Both of these units were installed and run under real process conditions at a wastewater treatment plant in Evry, France. In the case of the MBR process, the specific nitrification rates, rN, and the specific denitrification rates, rDN, increased as SRT was reduced from 6.5 days to 2 days. This trend was reversed and the rN and rDN decreased only when the HRT was reduced to 5 hours. A similar behavior was observed in the case of the CAS process, although rN and rDN increased only when the SRT was reduced to as low as 4 days; below this value, the rates dropped considerably. It seems that the presence of the membrane renders the MBR more robust by preventing the washout of nitrifiers at low SRT and HRT. Besides the structure and size distribution of the MBR, flocs are more favorable to intraparticle mass transfer than those of the CAS process and could explain the higher nitrification kinetics observed with the MBR process. In all cases, the carbon and nitrogen removal performance of the MBR process was better than that of the CAS system.

Biomass↗