Heikki Teräväinen

Development of the myoneural junction in the rat

SummaryThe structure of the myoneural junction in the striated muscle of rat embryos and postnatal rats was studied by electron microscopy in order to assess at ultrastructural level the roles of neuronal and muscular elements and the sequence of events resulting in the formation of a functionally mature synaptic organization.From the observations it is concluded that the axon terminals enveloped by Schwann cells contain vesicles prior to apposition of the prospective synaptic membranes. Subsequently, subsarcolemmal thickening of the postsynaptic membrane takes place after the synaptic gap has been formed by disappearance of the teloglial cell from between the synaptic membranes but before the primary synaptic cleft in the strict sense is formed. Secondary synaptic clefts are formed later, when the primary synaptic cleft is regular in width, by local finger-like invaginations of the postsynaptic membrane, which thereafter expand basally, in a plane transverse to the axis of the axon terminal, to resemble flattened flasks. The junction is formed between multinucleated muscle cells and multiple axons, which at first lie side by side and later, when formation of adult-type secondary synaptic clefts is in progress, become separated by folds of the sarcoplasm and the teloglia. In extraocular muscles of adult rats the sarcoplasmic reticulum is closely associated with the postjunctional sarcoplasm.In the light of earlier observations on the development of contractibility after nerve stimulation, cholinesterase histochemistry and muscle fibre physiology, these observations are interpreted to indicate that functional differentiation of the myoneural synapse results from induction by the motor axon and that the association of the sarcoplasmic reticulum with the postjunctional sarcoplasm in adult extraocular muscles is related to modified fibre physiology.

Effect of entacapone, a COMT inhibitor, on clinical disability and levodopa metabolism in parkinsonian patients

We studied the effect of entacapone, a selective catechol-O-methyltransferase inhibitor, on the bioavailability and clinical effect of levodopa in Parkinsons disease (PD). On day 1 (control day), nine patients received their own levodopa (plus benserazide) medication only; for the next 7 days they received 200 mg of entacapone with each dose of levodopa (tid or qid). We evaluated disability in the morning (8 AM) before drug administration and then at 1-hour intervals until 6 PM on days 1, 2, and 8, using a modified motor part of the Unified Parkinsons Disease Rating Scale. Repeated blood samples were taken before and during the 4 hours after the morning drugs for pharmacokinetic evaluation of entacapone and of levodopa and its metabolites. Added to the levodopa treatment, entacapone decreased clinical disability by about 16% (p < 0.05) from day 1 to day 8. The area under the curve (AUC) of levodopa increased by 38% (p < 0.01) after administration of a single dose of entacapone and by 40% (p < 0.05) after 7 days of multiple dosing with entacapone. Entacapone did not change the Tmax and Cmax values of levodopa. After 7 days of treatment with entacapone, the AUC of 3-O-methyldopa had decreased by 44% (p < 0.01) and of homovanillic acid by 26% (p < 0.05) as compared with treatment with levodopa alone. Four patients became slightly more dyskinetic during entacapone treatment than before it. The combination of entacapone and levodopa was well tolerated, judged by the lack of significant changes in hemodynamic and safety variables. We conclude that entacapone may be a helpful adjunct to levodopa in the treatment of PD.

Cognitive performance in early Parkinson's disease

The cognitive, memory and psychomotor performance of 67 patients with Parkinsons disease who had not received any antiparkinson medication was compared with the performance of 43 healthy subjects matched by age and education. The principal impairments in the patients were motor ones, evident in various tests such as general motor slowness and delayed initiation of movement, and they correlated with clinical rigidity and hypokinesia but not with tremor. The performance of the patients was inferior to that of the controls in memory tests involving the processing of information and learning (logical memory, associative learning) but not in less demanding tasks such as the retrieval of numbers. The total disability was due to a combined effect of aging and disease. A decrease of about 15% in the psychomotor and cognitive performance, related to aging alone, can be expected to occur between the ages of 50 and 70. The performance of the patients in memory tests and other tests evaluating cognitive capacity did not correlate either with their motor disability or with their mood. A possibility therefore exists that biological processes behind the cognitive decline and the motor disability are separate, even if they may occur simultaneously.

Satellite cells of striated muscle after compression injury so slight as not to cause degeneration of the muscle fibres

SummaryElectron microscopy of musculus bulbi rectus superior in the rat reveales increase in the number of. muscle satellite cells during the first 10–12 hours following compression injury so slight as not to cause degeneration of the muscle fibre. These satellite cells are situated close to the muscle nuclei and, in contrast to those in the intact rectus superior, they have a pale nucleus with a conspicuous nucleolus, sparse, pale cytoplasm containing a few small mitochondria, a mainly agranular endoplasmic reticulum and numbers of pinocytotic vesicles along their cell membrane. Later on, between 24 and 48 hours, the cytoplasm increases greatly in amount and extendes in long processess over a considerable length of the muscle fibre. An increase in the number of mitochondria and free ribosomes, the appearance of polysomes and great numbers of Golgi complexes and a decrease in the number of pinocytotic vesicles is noted. On the 4th day, some of the satellite cells have still further extended their cytoplasm beneath the muscle basement membrane, while others are apposed to the muscle fibre only with a minor part of their membrane. On the 9th day, only satellite cells comparable in number and structure with those in intact muscles are found.The possibility is discussed that the increase and subsequent decrease in the number of these satellite cells as well as the changes in their morphology at different periods after the injury reflect morphogenesis of satellite cells originating from the nuclei of the muscle fibre by mitotic division even after a trauma, too slight to cause any visible muscle injury. The observations are interpreted as giving new support to the hypothesis that muscle satellite cells may be of importance in posttraumatic muscle regeneration.

Electron microscopy of the paracervical (Frankenhäuser) ganglion of the adult rat.

SummaryThe ultrastructure of the paracervical (Frankenhäuser) ganglion in the rat was studied after immersion or perfusion fixation with glutaraldehyde followed by post-osmification. This ganglion is located at the uterovaginal junction in the vicinity of arteria uterina and contains three neuronal cell types. (1) Principal neurons have a fine structure mainly similar to the ganglion cells of other autonomic ganglia. (2) Small granule-containing cells occur in clusters often close to fenestrated capillaries. They are divided into two subgroups according to the size of their cytoplasmic granules; those containing only “small” granulated vesicles of 800 to 1400 Å in diameter and those having also “large” granulated vesicles of 2000 to 3000 Å in diameter. (3) Vacuolated nerve cells are large cells that resemble the principal neurons in their cytoplasmic components, except that they contain one to ten vacuoles with corpuscles of different size and shape. The possible physiological significance of the small, granule-containing cells in the uterine function is discussed.

Ultrastructure of striated muscle of the rat after temporary ischemia.

SummaryTwenty-six anterior tibial muscle specimens were analyzed with the electron microscope 2h, 1, 4, 18, 45, 90 and 226 days after temporary ischaemia of the rat hind leg produced by pneumatic tourniquet for 1, 2, 3, 4 and 6 h.No ultrastructural alterations were seen after 1 h ischaemia, but reversible disappearance of muscle glycogen and swelling of muscle and nerve mitochondria occurred after 2 h ischaemia.Irreversible alterations such as disappearance of the Z-line, disruption of cell membrane and vacuolation of muscle mitochondria were observed after ischaemia of 3 h and longer in a part of the muscle fibres. Ischaemia for 6 h was followed by autolysis of all the muscle fibres within the specimens. Autolysis and phagocytosis of the remnants of the affected fibres was present on the 4th day. On that day regenerative phenomena were also observed, such as satellite cells and yound myotubes. The fine structure of the muscle fibres was normal on the 18th day after the temporary ischaemia, although some size variation of the muscle fibres was still observed.Degeneration of a part of the presynaptic nerve endings of motor end-plates with or without simultaneous degeneration of the postsynaptic muscle fibre was seen after ischaemia lasting 3 h or longer. Motor end-plates were first seen on the 45th day in the muscle subjected to 6 h ischaemia and were most likely regenerated ones.

Peripheral nerve injury and recovery after temporary ischemia

SummaryNerve (NCV) and motor (MNCV) conduction velocities of the rat sciatic nerve were examined between 1 and 90 days after ischemia for 1, 2, 3, 4 or 6 h. The results were compared to light and electron microscopy of the nerve.Slight diminution in the MNCV was observed 1 day after 1–2 h ischemia, whereas 3–6 h ischemia resulted in a complete conduction block. Diminution in the NCV occurred first after ischemia for 2 h and a complete block was seen after 4 and 6 h ischemia. Reduced NCV and MNCV were seen between 4 and 18 days only in the animals subjected to ischemia of longer duration of 3–6 h. Both the NCV and MNCV were nearly normalized at the 90th day. Ischemia of 4 and 6 h resulted in denervation of some of the muscle fibers, seen as spontaneous fibrillation at the 4th and 18th day.Electron microscopy and histometric studies showed degeneration of myelinated fibers increasingly after longer durations of ischemia; ischemia for 2 h caused a degeneration of about 5%, 3 h of about 35%, 4 h about 45%, and 6 h about 75% of the fibers. Myelinated fibers of different sizes were equally damaged. In the teased fiber preparations normal and myelin sheaths undergoing Wallerian-like degeneration was seen. Regeneration occurred, but even at the 90th day there was a tendency of the myelin/axon ratio towards values less than control values.

Experimental alcoholic neuropathy in the rat: histological and electrophysiological study on the myoneural junctions and the peripheral nerves.

SummaryPeripheral nerves and myoneural junctions of the tibialis anterior muscle of the rat were studied histologically and electrophysiologically after various periods of peroral ethanol treatment. Histochemical distributions of non-specific cholinesterase (ns. ChE; E.C. 3.1.1.8) and acetylcholinesterase (AChE; E.C. 3.1.1.7) activity of the muscle were normal during the first 3 months of daily ethanol drinking. After 5 months of exposure to 10–25% (v/v) ethanol as the sole drinking fluid, pathological ns. ChE activity was seen sporadically along the intramuscular nerves with slight ultrastructural changes in the Schwann cells. After 7 months of ethanol treatment there was further increased pathological ns. ChE activity in the intramuscular nerves while the AChE activity remained normal in the muscle. More prominent ultrastructural changes were seen in the Schwann cells namely swelling and vacuolization of the cytoplasm and dilatation of the rough endoplasmic reticulum. Increased numbers of small axons were also seen. After 9.5 months on alcohol marked increase in the ns. ChE activity was observed along most of the intramuscular nerves. AChE activity of the myoneural junctions was only sporadically weakened.A slight slow-down in the conduction velocity of the large myelinated size A fibers was observed in the animals on alcohol from 7–9.5 months, whereas the conduction velocity of the smaller myelinated B fibers was not appreciably changed. The present experiment indicates that progressive neuropathy can be induced in rats by oral alcohol feeding along with the normal laboratory diet. The first pathological changes were seen in the Schwann cells and could well be followed by the methods employed. The present experimental model can possibly be used in future studies concerning the development of toxic polyneuropathy.

Histochemical studies of striated muscle after temporary ischemia in the rat

SummaryTemporary ischaemia of the hind limb of the rat was produced using a tourniquet with controlled pressure. Changes in the muscle seen after Gomori trichrome staining and after histochemical reactions for NADHdiaphorase, ATPases and phosphorylase were correlated with the duration of the ischaemia and the time of recovery.Histopathological changes were seen first after 2 h of ischaemia and increased thereafter; necrosis of most of the muscles occurred between 4 and 6 h of ischaemia.Necrosis and phagocytosis of muscle fibres and later the amount of regenerating fibres with characteristic histochemical staining properties increased linearly with increasing duration of ischaemia. Even after the most severe lesions of seemingly total necrosis of the muscle after 6 h of ischaemia most of the muscle regenerated within 18 days. Morphological alterations such as variation in fibre size, split fibres and central nuclei were still observed 226 days after ischaemia at which time the follow-up was terminated. Fibre type grouping was seen first after 45–90 days subsequent to 4 and 6 h ischaemia after incubation for ATPase, indicating concomitant neurogenic lesion in addition to the direct ischaemia of the muscle fibres.

Clofibrate-induced myopathy in the rat.

SummaryRats were given daily injections of 0.2 or 0.5 g/kg chlorophenoxyisobutyrate (clofibrate) for 9 to 46 days. Lower leg muscles were studied with light and electron microscopy.Daily treatment with 0.5 g/kg of the drug for 26–46 days caused myopathic changes.