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G J Leppink

Publications and source records attributed to G J Leppink.

7 recordsLinked to original sources
PubMed1990

Morphological changes in the human end plate with age.

We carried out a light and electron microscopic study on end plates and related structures in external intercostal muscles from subjects aged between 4 and 77 years. Light microscopically end plates maintained the same size, did not increase in number and showed no sprouting of terminal axons, all indicating that major compensatory histological changes to maintain adequate neuromuscular transmission with age were not required. At the ultrastructural level end plates became more complex mainly at the postsynaptic side. The latter included increased length and branching of the postsynaptic membrane with enlargement of the postsynaptic area, and degeneration of junctional folds. However, some neuromuscular junctions (NMJs) showed little branching of the postsynaptic membrane, even in old age. At the presynaptic side nerve terminals with an irregular shape were noted in the aged. Schwann cell processes were seen to intrude into the primary synaptic cleft. From these data we suggest that degeneration of the postsynaptic membrane with consequent focal denervation of NMJs is a primary event in the age-related changes of end plates. The muscle fibres showed a minor degree of type grouping in old age doubtless due to loss of motor neurons with age.

Adult↗
PubMed1990

Lip-length and snout indices: methods for quantitative assessment of peri-oral facial muscle strength.

Two simple bedside methods for the assessment of perioral muscle function are described. Using a marking gauge, the width of the mouth can be measured easily and accurately. Lip-length (LL) and snout (S) indices are expressions of the degree to which the width of the mouth can be lengthened or shortened. Facial muscle weakness as present in patients with various neuromuscular diseases results in low values for both indices. LL- and S-indices are measured by 3 observers in 19 healthy volunteers. Interobserver variation is negligible for the LL-index and large for the S-index. Intraobserver variation is moderate for both indices but slightly smaller for the LL- than for the S-index. The LL-index is suited for the assessment of changes in peri-oral musculature in longitudinal investigations.

Adult↗
PubMed1989

Perisynaptic satellite cells in human external intercostal muscle: a quantitative and qualitative study.

It is not known whether or not satellite cell nuclei are more common in the vicinity of motor endplates than in extrasynaptic regions of human muscle, as in animals. If so, perisynaptic satellite cells may have a role in preserving neuromuscular function. We compared the frequencies of satellite cell nuclei and of myonuclei in perisynaptic and extrasynaptic regions of human external intercostal muscle, and found an absolute as well as a relative increase of perisynaptic satellite cells. The mean frequency of satellite cell nuclei per sarcomere was 0.016 in perisynaptic and 0.00003 in extrasynaptic regions. The mean frequency of myonuclei per sarcomere was 0.098 in perisynaptic and 0.014 in extrasynaptic regions. We could not demonstrate any influence of aging on satellite cell distribution. Perisynaptic satellite cells had many processes, and some features suggested a more active state. These cells might add to the pool of junctional myonuclei for synthesis of acetylcholine-receptor molecules or help in the repair of the postsynaptic membrane. Alternatively, they may synthesize basal lamina substances that are specific for the endplate.

Adult↗
PubMed1989

[Spontaneous correction of the rotation of the permanent central lower incisors].

On the basis of a series of dental models from children between five and nine years (twice-yearly examination) with final models being made of 319 of these children at the age of 16, determinations were made of the rotation of the permanent central lower incisors 'shortly after complete eruption of the cutting edge' at the age of 16. The study showed that spontaneous correction amounts to 53% and 60% respectively for an original mesio-lingual rotation (type less than 90 degrees) and for an original disto-lingual rotation (type greater than 90 degrees).

Child↗
PubMed1987

Assessment of the usefulness of weekly knemometric measurements in growth studies.

In 31 healthy children the variability of lower leg length growth over 12 weekly measuring sessions, each consisting of 6 measurements, was assessed with a knemometer. The average SD of 6 measurements was 0.12 mm. In many cases not only a rising trend, but also a zig-zag pattern was observed. The linear regression was not significant (p greater than 0.05) in 1 child. The average (+/- SD) lower leg length velocity (LV) was 0.36 +/- 0.14 mm/week, and the average statural growth velocity 1.27 +/- 0.54 mm/week. The median ratio was 3.3. The range of both velocities was greater than the range of annual height velocities. When LV over the first 6 weeks was compared with LV over the next 6 weeks, a significant difference was found in 5 children. If the effect of growth-promoting or -inhibiting drugs were to be analyzed over such periods, a difference of 0.37 mm/week over two 6-week-periods would be necessary for significance at a 5% level. This would be equivalent with a statural growth response of at least 6.3 cm/year. In conclusion, short-term knemometric growth response cannot be used as a reliable predictor of long-term statural growth response.

Anthropometry↗