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  • 1
    ISSN: 1432-0533
    Keywords: Taxol ; Neuropathy ; Axonal branching ; Microtubules ; Neurofilaments
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Previous studies have shown that newly derived axonal sprouts are sensitive to the effect of taxol. Taxol induced an accumulation of microtubules in axonal sprouts, which resulted in giant axonal bulbs with the subsequent excessive proliferation of distorted axonal twigs from the distal end of swollen axonal bulbs 3 weeks after the nerve crush. The present study was performed to evaluate the chronic effects of taxol upon regenerative axons and the morphological changes have now been followed up to 40 weeks post injection (PI). The results showed that 1 month PI, the giant axonal bulbs with the conglomerations of haphazardly arranged axonal twigs were numerous at the lesion site. Later on, the axonal twigs, filled with axoplasmic microtubules, elongated and showed more longitudinal orientation as they grew distally. After 8 weeks PI the axonal elongation progressed and the majority of the original small axonal twigs disappeared and several larger diameter axonal branches developed. Some of the axonal branches emerging from the giant axonal bulbs became myelinated and survived while others degenerated. Ultrastructurally, the number of microtubules remained high in the surviving axonal branches up to 3 months PI. The degenerating branches showed an unexpected loss of microtubules 2 months onwards with the subsequent accumulation of degenerative axoplasmic material. However, neurofilaments were numerous in the degenerating axonal branches even when degenerative axoplasmic material was present. The present results show that some of the taxol-induced axonal twigs develop into larger diameter axonal branches which persist for upto 10 months. The cytoskeletal differences in the surviving versus the degenerating axonal branches suggests local regulatory mechanisms for regulation of axonal cytoskeleton in axons. The instability of microtubules in the degenerating axonal branches seems to be an early indicator of axonal degeneration.
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  • 2
    ISSN: 1432-0533
    Keywords: Taxol ; Neuropathy ; Schwann cells ; Endoneurial cells ; Microtubules
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The present investigation is a continuation of previous studies showing taxol-induced changes up to 4 weeks after a nerve crush. To evaluate the long-term cellular response to taxol, we have extended our morphological analysis of these changes in the taxoltreated nerve crush for up to 40 weeks after a single injection of taxol (PI). The results showed that Schwann cells exhibited a long-lasting and marked response when taxol was injected into the crushed peripheral nerve. During the first 2 months PI, taxolinduced giant axonal bulbs showed the formation of primitive nodes of Ranvier as a result of Schwann cell invaginations. The Schwann cell invaginations developed into nodes of Ranvier after 3–4 months PI together with the recovery of axonal bulbs. Ultrastructurally, cytoplasmic microtubule-related abnormalities were numerous up to 3 months PI and microtubules were seen to enclose degenerative myelin. Taxol-induced abnormalities in Schwann cells did not prevent their ability to produce myelin sheaths, although the accumulation of microtubules between myelin lamellae caused swellings of Schmidt-Lanterman incisures and paranodal myelin loops. Abnormal, extracellular collagen-like 5-nm-thin fibrils were noted closely associated with Schwann cells up to 10 weeks PI. Endoneurial cells, present as long rows without interconnections were noted in areas devoid of axonal sprouts up to 6–8 weeks PI. These cells showed marked cytoplasmic elongations and were covered by thickened basal lamina and contained several microtubule-related cytoplasmic structures, some of which have not been described previously. Taxol, when injected into crushed sciatic nerve induced a long-lasting response upon the Schwann cells with several ultrastructural abnormalities which correlate with changes in myelination and the development of nodes of Ranvier. These findings suggest that normal microtubule turnover is necessary for Schwann cells during nerve fiber regeneration.
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  • 3
    ISSN: 1432-0533
    Keywords: Key words Nerve repair ; Endoneurial cells ; Collagen ; Axonal sprouts ; Denervation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In this study, we have analyzed the ability of axons to regenerate into chronically denervated peripheral nerve. As an experimental rat model, the proximal end of a newly transected rat tibial nerve was sutured into chronically denervated (3 months up to 16 months) common peroneal nerve. Samples for morphological studies were collected 3 and 6 weeks after anastomosis of the tibial and common peroneal nerves. Our results showing a distinct organization of the endoneurial matrix in the chronically denervated distal stumps conformed with those from previous studies. Long cytoplasmic processes of endoneurial fibroblasts in close contact with collagen fibrils (with a diameter of 50–60 nm) surrounded areas of thin collagen fibrils (with a diameter of 25–30 nm). Remnants of Schwann cell columns (i.e., bands of Büngner) were situated in areas of thin collagen fibrils. After 12 months of denervation the majority of the Schwann cells columns were replaced by thin collagen fibrils. Successful axonal regeneration was noted in distal stumps that had been denervated for 14 and even 16 months. However, axonal regeneration diminshed with prolonged denervation. The regenerating axons grew through the areas of thin collagen fibrils. The maturation and thickening of the regenerated axonal sprouts resulted in a decrease in areas of thin collagen fibrils. These results suggest that a chronically denervated nerve stump has the capacity to meet regenerating axons even after 16 months of deneravation, although the progressive atrophy of Schwann cell columns impairs the liklihood of good axonal regeneration. The areas of thin collagen fibrils may act as a ’plastic' bed for successful axonal regeneration, and a study of these fibrils may provide further insight into the role of the extracellular matrix during peripheral nerve regeneration.
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  • 4
    ISSN: 1432-0533
    Keywords: Taxol ; Neuropathy ; Nerve crush ; Microtubules ; Axons
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The effects of taxol, a compound renowned for its ability to promote microtubule assembly, were studied upon axons after its injection into rat sciatic nerve immediately following a local nerve crush injury. The single injection of taxol was delivered into the lesion site and the animals were sampled up to 4 weeks post-injection (PI) for morphological study. At the lesion site, Wallerian degeneration was encountered and this was followed by axonal sprouting by 5 days PI. In contrast to axonal sprouting seen in uninjected controls (crush-only), sprouts in taxol-injected nerves rapidly became swollen due to an increasing number of axoplasmic microtubules. By 2 weeks PI, this led to the formation of giant axonal bulbs from which by 3 weeks PI, a secondary wave of regenerative growth occured consisting of thin, haphazardly twisted axonal twigs largely lacking Schwann cell investment. These were most numerous after 3 and 4 weeks PI. Within the affected axoplasm, microtubules occasionally formed occasional channles around mitochondria. The present results, characterized by the more rapid appearance of taxol-induced giant axonal bulbs in regenerating sprouts than seen after taxol injection of intact nerve, suggest that regenerating PNS axons are exquisitely sensitive to and dramatically affected by taxol. The conclusions support previous observations on a crucial role for microtubules during early axonal growth.
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  • 5
    ISSN: 1432-0533
    Keywords: Taxol ; Neuropathy ; Nerve crush ; Microtubules ; Schwann cells
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The effect of taxol, an antimitotic drug which stabilizes microtubules and promotes their assembly, was studied with regard to Schwann cells over a 4-week period following a crush injury to rat sciatic nerve. A single intraneural injection of taxol in dimethyl sulfoxide (DMSO) was given immediately after the crush into the site of injury in one sciatic nerve and was compared with the other side which was crushed but injected with DMSO only. Sampled sites were taken proximal and distal to the lesion, as well as from the lesion itself, and studied by light and electron microscopy. The Schwann cell response was most marked during the degenerative phase immediately following the crush. At this time, there was a decrease of all cytoplasmic structures except microtubules and smooth endoplasmic reticulum. At the site of the crush lesion in taxol-treated nerves, Schwann cells possessed accumulations of myelin debris and lipid droplets. Mitotic Schwann cells were also engorged with myelin breakdown products. Multinucleated Schwann cells, believed to be the result of abnormal mitotic activity, were also apparent and were filled with large numbers of cytoplasmic microtubules. The latter were sometimes regularly arranged around phagocytosed or intracytoplasmic debris. Some recovery from the crush injury was noted with time, although the number of Schwann cells was much lower than would have been anticipated in the absence of taxol, in that long stretches of naked axon bundles were common and microtubule-related abnormalities persisted up to 4 weeks. Myelination of regenerating axonal sprouts was delayed and might have been related to axons being swollen due to the build-up of microtubules. However, some myelination was noted sporadically along a few axons in taxol-treated nerves after 4 weeks. The present results suggest that the rapid Schwann cell reaction after nerve crush was impeded by the adverse effect of taxol upon mitosis and cell migration and that Schwann cells play an active role in the degradation of myelin phagocytosis of debris during Wallerian degeneration.
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  • 6
    ISSN: 1432-0533
    Keywords: Key words Delayed regeneration ; Type I collagen ; Type III collagen ; mRNA ; Schwann cell proliferation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract During the first 2 weeks after an injury to peripheral nerve, endoneurial cells proliferate and express integrin β1 and mRNA for collagen types I and III. Clinical results for surgical repair within this time are clearly better than those obtained after delayed (months after original injury) surgery. The question of whether this is due to changes in the proliferative capacity of endoneurial cells or to changes in expression of mRNA for collagen types I and III or integrin β1 was studied using rats. The left common peroneal nerve was transected and allowed to degenerate for 3 and 6 months. After these times, the tibial nerve of the same animals were transected, and the fresh proximal stump of the transected tibial nerve was sutured into the chronically denervated distal stump of the common peroneal nerve. At 3 and 6 weeks after the reoperation, samples were collected from the distal stump for morphometry, immunohistochemistry and in situ hybridization. Proliferating cells and Schwann cells were identified by immunohistochemistry. These cells increased markedly in number during the axonal reinnervation. In situ hybridization revealed that in the epineurium and perineurium, which were fibrotic, especially type I but also type III collagen mRNA were highly expressed. The amount of type I collagen mRNA in the endoneurium seemed to increase with progressing axonal reinnervation. Immunostaining for integrin β1 was negative in these distal stumps. In the present study the proliferation of endoneurial cells and expression of type I collagen mRNA in the endoneurium were similar to those found after immediate regeneration of transected peripheral nerve. However, the failure of endoneurial fibroblasts to express the integrin β1 subunit may indicate an advanced degeneration of the denervated distal stump. Moreover, clear expression of type I and III collagen mRNA in epineurial fibroblasts indicates scarring at the region of the transection and may play a role in prohibitting full structural recovery of the injured peripheral nerve.
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  • 7
    ISSN: 1432-0533
    Keywords: Nerve repair ; Endoneurial cells ; Collagen ; Axonal sprouts ; Denervation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In this study, we have analyzed the ability of axons to regenerate into chronically denervated peripheral nerve. As an experimental rat model, the proximal end of a newly transected rat tibial nerve was sutured into chronically denervated (3 months up to 16 months) common peroneal nerve. Samples for morphological studies were collected 3 and 6 weeks after anastomosis of the tibial and common peroneal nerves. Our results showing a distinct organization of the endoneurial matrix in the chronically denervated distal stumps conformed with those from previous studies. Long cytoplasmic processes of endoneurial fibroblasts in close contact with collagen fibrils (with a diameter of 50–60 nm) surrounded areas of thin collagen fibrils (with a diameter of 25–30 nm). Remnants of Schwann cell columns (i.e., bands of Büngner) were situated in areas of thin collagen fibrils. After 12 months of denervation the majority of the Schwann cells columns were replaced by thin collagen fibrils. Successful axonal regeneration was noted in distal stumps that had been denervated for 14 and even 16 months. However, axonal regeneration diminshed with prolonged denervation. The regenerating axons grew through the areas of thin collagen fibrils. The maturation and thickening of the regenerated axonal sprouts resulted in a decrease in areas of thin collagen fibrils. These results suggest that a chronically denervated nerve stump has the capacity to meet regenerating axons even after 16 months of deneravation, although the progressive atrophy of Schwann cell columns impairs the liklihood of good axonal regeneration. The areas of thin collagen fibrils may act as a ‘plastic’ bed for successful axonal regeneration, and a study of these fibrils may provide further insight into the role of the extracellular matrix during peripheral nerve regeneration.
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  • 8
    ISSN: 0942-0940
    Keywords: Haemangiopericytoma ; intracranial ; outcome ; proliferation indices ; p53
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Cell proliferation indices of 31 primary intracranial haemangiopericytomas (HPC) and their recurrences and metastases were correlated with the long-term recurrence, metastasis and survival rates. Paraffin-embedded specimens were used for K-67, PCNA and p53 immunostainings and for estimation of S-phase fraction (S-PF) in flow cytometry. The median Ki-67 and PCNA indices and S-PFs were 10.4, 3.2, and 4.0 for primary HPCs and 14.1, 14.1, and 5.5 for recurrences, respectively. High indices were associated with higher recurrence, metastasis and death rates, but not at the p ≤ 0.5 level. Consequently, these indices do not seem useful in planning of treatment and follow-up of meningeal HPCs. Meningeal HPCs, in contrast to meningiomas, recur almost always despite seemingly complete removal and often metastasize elsewhere in the body. This difference between two sharply demarcated tumours must reflect particularly adhesive and infiltrative properties of HPC cells and not just higher proliferation potential.
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  • 9
    ISSN: 1432-0533
    Keywords: Delayed regeneration ; Type I collagen ; Type III collagen ; mRNA ; Schwann cell proliferation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract During the first 2 weeks after an injury to peripheral nerve, endoneurial cells proliferate and express integrin β1 and mRNA for collagen types I and III. Clinical results for surgical repair within this time are clearly better than those obtained after delayed (months after original injury) surgery. The question of whether this is due to changes in the proliferative capacity of endoneurial cells or to changes in expression of mRNA for collagen types I and III or integrin β1 was studied using rats. The left common peroneal nerve was transected and allowed to degenerate for 3 and 6 months. After these times, the tibial nerve of the same animals were transected, and the fresh proximal stump of the transected tibial nerve was sutured into the chronically denervated distal stump of the common peroneal nerve. At 3 and 6 weeks after the reoperation, samples were collected from the distal stump for morphometry, immunohistochemistry and in situ hybridization. Proliferating cells and Schwann cells were identified by immunohistochemistry. These cells increased markedly in number during the axonal reinnervation. In situ hybridization revealed that in the epineurium and perineurium, which were fibrotic, especially type I but also type III collagen mRNA were highly expressed. The amount of type I collagen mRNA in the endoneurium seemed to increase with progressing axonal reinnervation. Immunostaining for integrin β1 was negative in these distal stumps. In the present study the proliferation of endoneurial cells and expression of type I collagen mRNA in the endoneurium were similar to those found after immediate regeneration of transected peripheral nerve. However, the failure of endoneurial fibroblasts to express the integrin β1 subunit may indicate an advanced degeneration of the denervated distal stump. Moreover, clear expression of type I and III collagen mRNA in epineurial fibroblasts indicates scarring at the region of the transection and may play a role in prohibitting full structural recovery of the injured peripheral nerve.
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  • 10
    ISSN: 0942-0940
    Keywords: Interstitial radiotherapy ; meningioma ; I-125 seeds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary I-125 seeds were permanently implanted into 25 parasellar-clival meningiomas (median age of patients, 56 y) and 19 globoid meningiomas in the elderly (median age of patients, 77 y) using stereotactic technique and 3-D dose planning. Total dose at the tumour margin was increased during the series from 100 Gy to 150 Gy. The procedure caused no mortality and no serious bleeding, but injury to the III cranial nerve due to puncture occurred in one (4%) of the 25 parasellar-clival meningiomas. In two (4.5%) of the 44 cases the postoperative CT scan showed a misplaced seed, located at the tumour surface. Nonenhancing hypodense rings developed around the seeds (‘hot spots’) with a median diameter of 10.5 mm at 12 months corresponding to a median initial activity of 8.7 mCi. In general, meningiomas responded by slow reduction in volume. The parasellar-clival meningiomas were followed-up for a median of 19 months (6–32), and so far 4 tumours have shrunk moderately, 13 slightly, and 5 not at all. Pre-operative III, V or VI cranial nerve signs were present in 17 patients and subsided in 8 of them. On the other hand, facial numbness developed or increased in 9 of the 25 patients, indicating that the V nerve is rather sensitive to this type of irradiation. In the 19 meningiomas of the elderly, the median follow-up time was 14 months (5–26). The median relative tumour volume was 46% at 12 months. Accounting for tumour-related deaths only, the actuarial survival rate was 78% at 12 months and 62% at 24 months. In general, brain oedema persisted despite reduction in tumour volume. Stereotactic implantation of I-125 seeds into intracranial meningiomas is relatively safe. Interstitial radiotherapy represents a potential tool in the control of medium-sized intracranial meningiomas with minimal brain oedema, but its long-term impact and untoward effects remain to be followed-up.
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