Biomedical subjects
M Peters
Publications and source records attributed to M Peters.
[Administration of vitamin K to newborn infants and infants].
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Unbinding of charge-anticharge pairs in two-dimensional arrays of small tunnel junctions.
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Pocket programmable computers in clinical practice.
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Immunological aspects of antiviral therapy.
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Yeast-derived recombinant human insulin-like growth factor I: production, purification, and structural characterization.
Recombinant human insulin-like growth factor I (IGF-I) is efficiently expressed and secreted from Saccharomyces cerevisiae using a yeast alpha-factor leader to direct secretion. However, approximately 10-20% of the IGF-I was in a monomeric form, the remaining materials being disulfide-linked aggregates. When the purified material was subjected to reverse-phase high-performance liquid chromatography (rp-HPLC), it gave two doublet peaks, I and II. Upon reduction, doublet peaks I and II converged to one doublet peak. This suggests that peaks I and II result from different disulfide structures, and the doublet feature of each peak results from other causes. Different disulfide structures between peaks I and II were also suggested from the near UV circular dichroism of these proteins. Only the peak II was biologically active, indicating that peak II has the correct disulfide structure. Concanavalin A affinity chromatography of the purified peak II doublet showed binding of the subpeak with an earlier rp-HPLC retention time, indicating that it was glycosylated. Sequence analysis of tryptic peptides suggested that Thr29 was the site of glycosylation. Site-directed mutagenesis was used to convert Thr29 to Asn29. This substitution reduced, but did not eliminate IGF-I glycosylation, suggesting additional glycosylation sites. The site of carbohydrate addition was consistent with the model that O-glycosylations occur on hydroxyl amino acids near proline residues in beta-turns.
Neuropsychological identification of motor problems: can we learn something from the feet and legs that hands and arms will not tell us?
The degree of structural and functional specialization that differentiates between upper and lower limb use in humans is quite unparalleled among primates. It is argued that less neural resources are devoted to leg and foot control than to arm and hand control, and that this aspect of lower limb innervation, together with the uniquely restricted use of the lower limb, renders lower limb function more sensitive to general neural insult. In addition, the status of leg and foot control differs from that of arm and hand control both early in life and during the later years of decline.
Protein C activity and antigen levels in childhood.
Hereditary protein C deficiency is an important risk factor for thrombosis. To enable its diagnosis shortly after birth, we determined reference values of protein C antigen and activity levels for the first 3 months of life. To establish an age-related range of protein C levels we also determined median values for individuals up to 18 years of age. A good correlation between the two levels was seen from the 3rd/4th month of life onwards, whereas in the first 2 months the activity levels were significantly lower than the antigen levels. This was not due to interference by the increased plasma citrate concentration at high haematocrit values, and may suggest a dysfunctional protein C molecule in the neonatal period. We found a rapid rise in protein C activity and antigen levels until the age of 7-9 months, followed by a slower progression toward adolescence. In contrast to previous reports, our results indicate that adult values are probably not achieved until sometime during the 2nd decade of life.
Subclassification of non-pathological left-handers poses problems for theories of handedness.
The throwing performance of 104 right-handers, and 96 left-handers with inconsistent and consistent hand preferences, as classified by the procedure used by Ponton (Neuropsychologia 25, 305-311, 1987), was examined. Left-handers with inconsistent hand preference write with the left, tap faster with the left, and perform better with the left on the Purdue Pegboard task (Peters and Servos, 1989), but are stronger in the right hand and throw better with the right hand. In the other two groups, strength and skill activities are laterally congruent. This poses difficulties for theories of handedness.
A clear left hemisphere advantage for visuo-spatially based verbal categorization.
For a range of tachistoscopically presented stimuli that varied from modified complex Shepard and Metzler figures to simple lines, subjects had to judge whether or not the top or bottom of the stimuli contained the target feature. A marked and consistent right visual field (left hemisphere) advantage was observed for all such tasks. In addition, a task that required subjects to judge whether a solid black rectangle was in front of or behind a white rectangle also yielded a clear left hemisphere advantage. The results are explained in terms of a left hemisphere specialization for spatially based verbal categorizations in general support of Kosslyn's (Psychol. Rev. 94, 148-175, 1984) model.
Marked sex differences on a fine motor skill task disappear when finger size is used as covariate.
Purdue Pegboard performance of 16 male and 25 female right-handed college students were compared, and results were replicated with 25 male and 28 female subjects. In agreement with the literature, women performed significantly better than men. When measures of index finger and thumb thickness were used as covariate, all significant sex differences in performance disappeared. Negative correlations between performance and finger size were observed in both sexes. Sex differences in fine manual dexterity tasks may therefore be confounded by sex differences in finger size.
Regulation of heartbeat in Lymnaea by motoneurons containing FMRFamide-like peptides.
1. Intracellular stimulation of single neurons in the Lymnaea CNS was carried out to identify heart motoneurons. 2. Two of the identified motoneurons, the E heart excitor (Ehe) cells, were shown to contain Phe-Met-Arg-Phe-NH2 (FMRFamide)-like peptides by immunocytochemical staining of dye-marked neurons and by radioimmunoassay (RIA) applied to extracts of single dissected cells. 3. Bursts of spikes in the Ehe cells increased heart rate, beat amplitude and muscle tonus. This response was mimicked by perfusion of exogenous FMRFamide at low concentration (10(-6) to 5 x 10(-8) M) through the interior of the intact heart. 4. Application of selective antagonists to 5-hydroxytryptamine (5-HT) and dopamine failed to block Ehe cardiac effects. 5. Detailed evidence that the Ehe cells were heart motoneurons was obtained. 1) Anatomic mapping using the dye Lucifer yellow showed Ehe cells had peripheral projections restricted mainly to the intestinal nerve, the only nerve known to innervate the heart. 2) Perfusion of the CNS with a saline containing Co2+ blocked central chemical synapses but did not affect activity of Ehe cells on the heart. 3) Simultaneous intracellular recordings from Ehe cells and auricle muscle fibers showed unitary excitatory junction potentials following with constant latency from spikes in Ehe cells. 6. The present study elucidates the role of FMRFamide in cardioregulation and provides the first evidence that it acts as an excitatory neurotransmitter on the snail heart.
Excitation and inhibition of the heart of the snail, Lymnaea, by non-FMRFamidergic motoneurons.
1. The present paper extends the model of neuronal control of the Lymnaea heart by the use of intracellular recording techniques to identify further types of cardioactive neurons in the CNS that, like the previously described E heart excitor (Ehe) cells, influence the myogenic heartbeat. 2. Four new types of neuron that act on the heart are described. These are excitatory Hhe and She cells (H and S heart excitors) and the inhibitory Khi cell (K heart inhibitor). The fourth class, tonus pericardium excitor (Tpe), modulates the heart by action on pericardial tissue. 3. Pharmacologic, electrophysiological, and anatomic evidence is presented that shows that these cells are motoneurons, innervating heart muscle fibers directly: blocking central chemical synapses failed to prevent the actions of the neurons on the heart; simultaneous intracellular recordings showed unitary EJPs in heart muscle after 1:1 and with constant delay from evoked neuronal action potentials; intracellular injection of the dye Lucifer yellow showed all cells had axonal branches entering the intestinal nerve (which innervates the heart). 4. The use of selective antagonists to 5-hydroxytryptamine (5-HT) (cinanserin), dopamine (ergonovine), and acetylcholine (alpha-bungarotoxin) provided evidence that the actions of She and Hhe cells are mediated by 5-HT, whereas those of the Khi cell are mediated by acetylcholine. 5. A cyclically active network of three interneuronal inputs acting on the heart motoneurons is described. 6. One of these, input 3, is responsible for periodic excitation of the heart via its effects on the Hhe cells.
[Development and results of autologous blood transfusion in Magdeburg].
The autologous blood transfusion is an important part of the modern hemotherapy. Especially in orthopedics presurgical blood donation of the patients is possible since the operations are exactly planable close. Cooperation between the clinic and the transfusion service is necessary. The results of autologous transfusions in 1,086 patients (1,428 donations) of an orthopedic clinic over a period of six years were critically analyzed.
[Drug-assisted rehabilitation of HIV-infected drug-dependent prostitutes].
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Quantitative assessment of blood flow in pediatric recipients of renal transplants.
We applied a renal blood flow (RBF) quantification technique to pediatric data, which depends minimally on bolus shape, uses a conventional radiopharmaceutical 99mTc-DTPA, and generates a value for RBF as a percentage of cardiac output (RBF/CO). Mean RBF was 16.9% (+/- 4.8) for normal transplants, 13.1% (+/- 2.9) for transplants undergoing mild-to-moderate chronic rejection, 7.9% (+/- 1.3) for those with mild acute rejection and 3.3% (+/- 1.4) for those with moderate-to-severe acute rejection. Very low blood flow values within 24 hr following transplantation may have prognostic significance. Patients who required transplant-nephrectomy had significantly lower RBF/CO values than children who retained their allograft.
Mycobacterium avium-intracellulare serovars in German AIDS patients.
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Geerligs, Peters, and Mooij reply:
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