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Biomedical subjects

R Rolf

Publications and source records attributed to R Rolf.

4 recordsLinked to original sources
PubMed1996

HIV colonizing peripheral blood monocytes follows lymphocytic isolates in shifting from NSI to SI genotype.

Non-syncytium inducing (NSI) and syncytium inducing (SI) variants of human immunodeficiency virus (HIV) isolated from peripheral blood mononuclear cells (PBMC) could be definitely typed by sequence analysis of the env-gene V3 region. It was thus possible to compare the genotypes of viral variants isolated from PBMC and accompanying monocyte cultures and those derived directly from the patients' blood cells prior to cultivation. Within the investigated group of patients it was shown that HIV variants colonizing monocytes displayed a similar shift from NSI to SI as observed previously for PBMC, i.e. lymphocyte derived isolates. Lymphocytic SI variants could be isolated from the blood of patients, while simultaneously the predominant provirus in both blood and monocytic isolate was NSI. Consequently, we observed a delayed switch in the predominant provirus genotype found in blood which was associated with a synchronous change in the genotype of the corresponding monocytic isolate. The results show that monocytes/macrophages can be colonized by heterogeneous HIV variants in vivo and can therefore also function as carriers for the spread of highly virulent SI variants into the tissues.

Amino Acid Sequence↗
PubMed1982

Slow changes and Wiener analysis of nonlinear summation in contractions in cat muscles.

With regular trains of stimuli at a high frequency, the contribution of each stimulus to the force generated over time declines from the second to about the tenth stimulus, but then begins to increase again. This late increase is referred to as tetanic potentiation in analogy with the post-tetanic potentiation of the twitch after such a period of stimulation. With regular trains of stimuli at a low frequency, a progressive decrease in the essentially unfused twitches (negative staircase) is observed in the slow soleus muscle of the cat, while a progressive increase (positive staircase) is observed for the fast plantaris muscle. The time constant for the approximately exponential changes observed is on the order of 10 s. Random trains of stimuli were applied at intermediate frequencies and analyzed in terms of general methods of analysis for nonlinear systems. Systematic decreases in the magnitude and increases in the time course of the average tension per stimulus were observed with increasing mean rates of stimulation. Similar changes were observed for short intervals between stimuli within a given random train at a constant mean rate. These changes can be described in terms of an early depression and a later facilitation described in the previous papers in this series.

Animals↗
PubMedDate not supplied

Functional electrical stimulation using microstimulators to correct foot drop: a case study.

This paper presents a case study that tested the feasibility and efficacy of using injectable microstimulators (BIONs) in a functional electrical stimulation (FES) device to correct foot drop. Compared with surface stimulation of the common peroneal nerve, stimulation with BIONs provides more selective activation of specific muscles. For example, stimulation of the tibialis anterior (TA) and extensor digitorum longus (EDL) muscles with BIONs produces ankle flexion without excessive inversion or eversion of the foot (i.e., balanced flexion). Efficacy was assessed using a 3-dimensional motion analysis of the ankle and foot trajectories during walking with and without stimulation. Without stimulation, the toe on the affected leg drags across the ground. BION stimulation of the TA muscle and deep peroneal nerve (which innervates TA and EDL) elevates the foot such that the toe clears the ground by 3 cm, which is equivalent to the toe clearance in the less affected leg. The physiological cost index (PCI) measured effort during walking. The PCI equals the change in heart rate (from rest to activity) divided by the walking speed; units are beats per metre. The PCI is high without stimulation (2.29 +/- 0.37, mean +/- SD) and greatly reduced with surface (1.29 +/- 0.10) and BIONic stimulation (1.46 +/- 0.24). Also, walking speed increased from 9.4 +/- 0.4 m/min without stimulation to 19.6 +/- 2.0 m/min with surface and 17.8 +/- 0.7 m/min with BIONic stimulation. These results suggest that FES delivered by a BION is an alternative to surface stimulation and provides selective control of muscle activation.

Adult↗