Motor cortex stimulation for Parkinson's disease: a modelling study.

Chronic motor cortex stimulation (MCS) is currently being investigated as a treatment method for Parkinson's disease (PD). Unfortunately, the underlying mechanisms of this treatment are unclear and there are many uncertainties regarding the most effective stimulation parameters and electrode configuration. In this paper, we present a MCS model with a 3D representation of several axonal populations.

Type grouping in rat skeletal muscle after crush injury.

Object: Accuracy of reinnervation is an important factor that determines outcome after nerve injury and repair. Type grouping--the clustering of muscle fibers of the same type after reinnervation--can be used to investigate the accuracy of reinnervation. In this study, the degree of type grouping after crush injury in rats was compared with the clustering of muscle fibers after autografting or single-lumen nerve grafting.

Antigenic compartmentation of the cerebellar cortex in the chicken (Gallus domesticus).

The chick is a well-understood developmental model of cerebellar pattern formation,but we know much less about the patterning of the adult chicken cerebellum. Therefore an expression study of two Purkinje cell stripe antigens-zebrin II/aldolase C and phospholipase Cbeta4 (PLCbeta4)-has been carried out in the adult chicken (Gallus domesticus). The mammalian cerebellar cortex is built around transverse expression domains ("transverse zones"), each of which is further subdivided into parasagittally oriented stripes.

Automated characterization of nerve fibers labeled fluorescently: determination of size, class and spatial distribution.

Morphological classification of nerve fibers could help interpret the assessment of neural regeneration and the understanding of selectivity of nerve stimulation. Specific populations of myelinated nerve fibers can be investigated by retrograde tracing from a muscle followed by microscopic measurements of the labeled fibers at different anatomical levels. Gastrocnemius muscles of adult rats were injected with the retrograde tracer Fluoro-Gold.

Effect of nerve graft porosity on the refractory period of regenerating nerve fibers.

Object: In the present study the authors consider the influence of the porosity of synthetic nerve grafts on peripheral nerve regeneration.

Methods: Microporous (1-13 microm) and nonporous nerve grafts made of a copolymer of trimethylene carbonate and epsilon-caprolactone were tested in an animal model. Twelve weeks after surgery, nerve and muscle morphological and electrophysiological results of regenerated nerves that had grown through the synthetic nerve grafts were compared with autografted and untreated (control) sciatic nerves.

Morphometric analysis of the fiber populations of the rat sciatic nerve, its spinal roots, and its major branches.

Correspondence between the nerve composition and the functional characteristics of its fiber populations is not always evident. To investigate such correspondence and to give a systematic picture of the morphology of the rat hind limb nerves, extensive morphometric study was performed on the sciatic nerve, its founding dorsal and ventral spinal roots, and its major branches. Nerve histology was examined in semithin sections via microscopic image analysis.

Pores in synthetic nerve conduits are beneficial to regeneration.

Current opinion holds that pores in synthetic nerve guides facilitate nerve regeneration. Solid factual support for this opinion, however, is absent; most of the relevant studies assessed only morphological parameters and results have been contradictory. To evaluate the effect of pores, the rat sciatic nerve was either autografted or grafted with nonporous, macroporous (10-230 mum), and microporous (1-10 microm) biodegradable epsilon-caprolactone grafts.

Type grouping in skeletal muscles after experimental reinnervation: another explanation.

Type grouping signifies clustering of muscle fibres of the same metabolic type, and is a frequent finding in reinnervated muscles. To elucidate the mechanism behind it, the rat sciatic nerve was either autografted or grafted with hollow synthetic nerve grafts. Twelve weeks later the number and fibre area of the type I and type II muscle fibres in the gastrocnemic and anterior tibial muscles were determined after ATP-ase staining.

Electrophysiology and morphometry of the Aalpha- and Abeta-fiber populations in the normal and regenerating rat sciatic nerve.

We studied electrophysiological and morphological properties of the Aalpha- and Abeta-fibers in the regenerating sciatic nerve to establish whether these fiber types regenerate in numerical proportion and whether and how the electrophysiological properties of these fiber types are adjusted during regeneration. Compound action potentials were evoked from isolated sciatic nerves 12 weeks after autografting. Nerve fibers were gradually recruited either by increasing the stimulus voltage from subthreshold to supramaximal levels or by increasing the interval between two supramaximal stimuli to obtain the cumulative distribution of the extracellular firing thresholds and refractory periods, respectively.

Morphometry of human superficial dorsal and dorsolateral column fibres: significance to spinal cord stimulation.

In spinal cord stimulation (SCS) large diameter cutaneous (Abeta) fibres in the dorsal columns (DCs) are activated and have an inhibiting effect on the transmission of pain signals by Adelta and C fibres from the corresponding dermatome(s). The largest Abeta fibres can be activated up to a maximum depth of about 0.25 mm in the DCs.

Ultrastructural and quantitative motoneuronal changes after ventral root avulsion favor early surgical repair.

This study assesses qualitative and quantitative morphological changes that occur in motoneurons after ventral root avulsion. The motoneuronal perikaryal changes in the ventral horn of the cat's C7 cord segment were studied after survival times of 2, 8, 14, 30, 60 and 90 days. Generally, large motoneurons showed a light type of reaction, and the small ones either light or dark.

Correlation between histopathological findings in C-5 and C-6 nerve stumps and motor recovery following nerve grafting for repair of brachial plexus injury.

Object: Proximal spinal nerve stumps were used as donor sites for grafts to repair brachial plexus traction lesions. The quality of the stumps was assessed histologically, and its correlation with the strength attained in the target muscle was studied.

Methods: Four histopathological parameters in frozen tissue sections of 31 C-5 or C-6 nerve stumps were examined by a neuropathologist.

Preservation and staining of myelinated nerve fibers.

Six procedures are given for preservation of myelinated nerve fibers for light or electron microscopic studies. These procedures fall into two main categories: those with and those without aldehyde fixation. Essentially different effects are attained by application of tannic acid, saline, microwave or conventional heating, or a decreased temperature.

White matter of the cerebellum of the chicken (Gallus domesticus): a quantitative light and electron microscopic analysis of myelinated fibers and fiber compartments.

Low magnification light microscopic examination of the white matter in appropriately stained avian and mammalian cerebellum reveals a mediolateral succession in which areas of large, heavily myelinated fibers alternate with areas containing nearly exclusively small fibers. A large fiber accumulation (LFA) and its medially adjoining small fiber area (SFA) form a fiber compartment, which, with related parts of cortex and central nuclei, constitutes a so-called cerebellar module. The composition and the apparent mediolateral heterogeneity of cerebellar fiber compartments was quantified in the chicken by morphometrical analysis of myelinated fiber profiles in light (LM) and electron (EM) microscopic micrographs.

Preservation of myelinated fibers for electron microscopy: a qualitative comparison of aldehyde fixation, microwave stabilisation and other procedures all completed by osmication.

A qualitative comparison was made of a variety of electron microscopic preservation methods for nervous tissue, especially with respect to myelinated fiber areas. The methods studied were aldehyde perfusion/immersion fixation, aldehyde-tannic acid immersion fixation (stimulated by either microwave or conventional heating), microwave stabilisation, saline treatment with conventional heating (all with secondary osmication), and primary osmication. For all methods three morphological aspects, the ultrastructural quality of myelin sheath and axon and the coherence between the two were judged separately.

The rostrocaudal organization in the dorsal root ganglia of the rat: a consequence of plexus formation?

The dorsal root ganglia (DRGs) of the rat have a rostrocaudal organization. This organization can most easily be demonstrated in fetal and neonatal rats because the spatial relationships of their DRGs are maintained better in tissue sections than those of mature rats. This review is concerned with the way in which the rostrocaudal organization of the DRGs is generated.

Does microwave irradiation have other than thermal effects on glutaraldehyde crosslinking of collagen?

The effects of microwave irradiation (MWI) can theoretically be divided in thermal and non-thermal effects. Because there is still much debate on the contribution of non-thermal microwave effects, experiments were carried out in which the effects of isothermal microwave irradiation on glutaraldehyde (GA) crosslinking of native collagen membranes (NCM) is studied. A total of 20 strips of collagen membrane of porcine origin were isothermally irradiated in 300 ml of a 0.

Does microwave irradiation have other than thermal effects on histological staining of the mammalian CNS? A light microscopical study of microwave stimulated staining under isothermal conditions in man and rat.

The question whether or not microwave irradiation exerts other than thermal effects on histological staining is still a matter of controversy. The present study was undertaken to reveal or reject such a so far hypothetical non-thermal irradiation effect. A device was developed, which enables exposure of histological sections or tissue pieces to microwave irradiation under isothermal conditions, i.

Development of projections of primary afferent fibers from the hindlimb to the gracile nucleus: a WGA-HRP study in the rat.

The projection of primary afferent fibers to the gracile nucleus was studied during development. Injections of wheat germ agglutinin-horseradish peroxidase were made into the hindlimb of fetal, postnatal and adult rats. In most cases the sections were alternately stained for wheat germ agglutinin-horseradish peroxidase including counter stain with Neutral red and for acetylcholinesterase.

Microwave applications in classical staining methods in formalin-fixed human brain tissue: a comparison between heating with microwave and conventional ovens.

The quality of microwave adaptations of three classical neuroanatomical staining methods (the Nissl, Klüver-Barrera and Häggqvist stains) was tested on frozen serial sections from human brain specimens which has been stored for up to 10 years in 10% formalin. The conclusion was that the use of microwave irradiation reduces processing time and/or concentrations of the chemicals used, whereas the light microscopical quality of the stains considered is equal or improved as compared to their original counterparts. Next, a comparison was made between microwave adapted stains and classical procedures, which, except for the use of a conventional oven as heat source together with pre-heated solutions, were entirely identical.

Evidence for a rostrocaudal organization in dorsal root ganglia during development as demonstrated by intra-uterine WGA-HRP injections into the hindlimb of rat fetuses.

The development of the sensory innervation of the rat hindlimb was studied with special attention to the dorsal root ganglia and the lumbar plexus. Injections of wheat germ agglutinin-horseradish peroxidase were made into the hindlimb of 30 rat fetuses of gestational ages ranging from embryonic day 15-18. Additionally wheat germ agglutinin-horseradish peroxidase was applied to the sciatic nerves of 8 neonatal rats and 3 adults.