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Biomedical subjects

V Vuorinen

Publications and source records attributed to V Vuorinen.

12 recordsLinked to original sources
PubMed1996

Outcome of 31 intracranial haemangiopericytomas: poor predictive value of cell proliferation indices.

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 < or = 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.

Adult↗
PubMed1996

Interstitial radiotherapy of 25 parasellar/clival meningiomas and 19 meningiomas in the elderly. Analysis of short-term tolerance and responses.

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.

Adult↗
PubMed1995

Axonal regeneration into chronically denervated distal stump. 1. Electron microscope studies.

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 diminished 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 denervation, although the progressive atrophy of Schwann cell columns impairs the likelihood 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.

Anastomosis, Surgical↗
PubMed1995

Axonal regeneration into chronically denervated distal stump. 2. Active expression of type I collagen mRNA in epineurium.

During the first 2 weeks after an injury to peripheral nerve, endoneurial cells proliferate and express integrin beta 1 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 beta 1 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 beta 1 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.(ABSTRACT TRUNCATED AT 250 WORDS)

Anastomosis, Surgical↗
PubMed1992

Laminin B1 and collagen type IV gene expression in transected peripheral nerve: reinnervation compared to denervation.

The expression of B1 laminin and type IV collagen was followed in the microsurgically isolated endoneurium of transected rat sciatic nerves from 3 days until 8 weeks. Northern hybridizations revealed that after nerve transection the proximal stumps of denervated, as well as freely regenerating, nerves showed a markedly increased expression of laminin and type IV collagen which lasted from 3 days up to 8 weeks. In the distal stumps, close to the site of transection (2-7 mm), the expression of laminin, and to a certain extent that of type IV collagen, seemed to be enhanced if free axonal reinnervation was allowed. Further distally (10-15 mm), the patterns of B1 laminin and type IV collagen expression were similar in both experimental groups, so that an increased expression was noticed during the first 2 weeks. The present results suggest that laminin and type IV collagen gene expression is markedly different in different parts of transected rat sciatic nerve. During peripheral nerve regeneration, there is a long-lasting basement membrane gene expression in the proximal stump. In the distal part of the transected nerve, the axonal reinnervation possibly up-regulates, but is not essential for, the expression of B1 laminin and type IV collagen.

Animals↗
PubMed1992

Expression of type I and III collagens and fibronectin after transection of rat sciatic nerve. Reinnervation compared with denervation.

BACKGROUND: The regeneration of transected peripheral nerve is thought to happen with the help of cell-cell and cell-extracellular matrix interactions. We studied the role of axon in controlling the expression of extracellular matrix genes in transected peripheral nerve. EXPERIMENTAL DESIGN: Left sciatic nerves were transected in a total of 132 rats. In half of the animals, regeneration was allowed to occur, while in the other half regeneration was prevented. The expression of type I and III collagen and fibronectin genes was studied proximally and distally to the site of transection up to 8 weeks after the injury both with and without axonal reinnervation. For Northern blotting, the endoneuriums of 10 animals from both groups were used at each time point. For in situ hybridization, transverse sections of the nerves were used to observe cellular source of the mRNA. In addition, immunohistochemistry was performed in sequential sections in order to identify the cells expressing the studied extracellular matrix genes. RESULTS: Northern hybridization showed the highest expression of type I and III collagens in the distal stumps of transected nerves 7 to 14 days after nerve transection both with and without axonal reinnervation. The proximal site of the injury showed strong expression of the extracellular matrix genes which lasted markedly longer than in the distal site. In situ hybridizations showed that epi-, peri-, and endoneurium are active for producing type I collagen. S-100 immunohistochemistry suggested that the cell type responsible for the production of type I collagen in the endoneurium during the peripheral nerve regeneration is endoneurial fibroblast. CONCLUSIONS: During peripheral nerve regeneration the expression of the extracellular matrix genes does not seem to be simply related to the presence of axons. Endoneurial fibroblasts contribute to the production of collagen type I and apparently to that of fibronectin, which thus is not totally derived from plasma.

Animals↗
PubMed1989

The long-term effects of a single injection of taxol upon peripheral nerve axons.

To study the long-term effects of a single injection of the microtubule stabilizing drug taxol in vivo, the compound was injected into rat sciatic nerve and the ensuing morphological changes followed for 8-25 weeks after injection. In accord with previously published works, taxol-induced giant axonal bulbs were common and were most marked at 8-10 weeks. From 12 weeks onwards these giant axons decreased in diameter with concomitant remyelination. By 20 weeks axonal bulbs could not be seen. The recovery of axons from taxol intoxication began 8-12 weeks after injection with the growth of axonal sprouts, longitudinally and laterally, from the distal aspect of the proximal stump. During recovery, from 12 weeks onwards, axons showed apparent reorganization of the axoplasmic cytoskeleton where microtubules diminished and neurofilaments became more numerous. By 16 weeks only small groups of microtubules remained, often encircling a mitochondrion. By 25 weeks taxol-treated nerves showed no apparent taxol-induced changes. A common ultrastructural finding up to 16 weeks was the appearance within axons of tubular profiles covered by a double membrane. These structures were sometimes arranged as crystalloid aggregates. The diameter of these profiles was 85 nm, they were most common at 12 weeks and it is proposed that they may be derived from mitochondria. The present results show taxol to have a long-lasting and local effect upon axoplasmic organization in vivo. The cytoskeletal reorganization described supports the concept of the differential movement of axoplasmic neurofilaments and that neurofilaments stabilize axonal structures.

Alkaloids↗
PubMed1989

The long-term cellular response to taxol in peripheral nerve: Schwann cell and endoneurial cell changes.

Taxol, an agent known to stabilize and increase the assembly of microtubules, causes long-lasting nerve damage when injected into peripheral nerve. In the present study, the cellular response to taxol in rat sciatic nerve was studied for up to 6 months after a single injection. The initial response of Schwann cells to taxol at the lesion site involved the accumulation of cytoplasmic microtubules which persisted up to 4 months after injection. Some novel microtubule-related cytoplasmic structures were also noted; these included microtubule-lined cytoplasmic crypts and channels. Despite these structural abnormalities, Schwann cells were able to produce myelin sheaths around taxol-induced axonal bulbs. This myelination showed some anomalies up to 4 months consisting of the widening of myelin lamellae, variability in sheath thickness, paranodal myelin infoldings and myelin protrusions. With time the diameter of the axonal bulbs decreased and, concomitant with this, more normal-appearing remyelination occurred. By 5 months, the previously noted myelin abnormalities were rare. By 6 months only a few naked axonal segments occurred at the lesion site. In endoneurial fibroblasts and macrophages cytoplasmic lamellar microtubule formations were frequent at 10 weeks. Needle-like cytoplasmic structures appeared within endoneurial cells at the site of the lesion after 10 weeks. By 3 months these inclusions were numerous and were often surrounded by extended cytoplasmic processes. The needles were up to 50 microns long and 3 microns wide and probably represented cholesterol. By 4 months the number of cytoplasmic needles decreased and at 5 months onwards none was observed. The present findings confirm and extend previous findings that taxol has a long-lasting effect upon both Schwann cells and endoneurial cells and that this is related to abnormal tubulin synthesis.

Alkaloids↗
PubMed1988

The acute response of Schwann cells to taxol after nerve crush.

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.(ABSTRACT TRUNCATED AT 250 WORDS)

Alkaloids↗
PubMed1988

The acute effects of taxol upon regenerating axons after nerve crush.

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 occurred 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 channels 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.

Alkaloids↗
PubMed1988

Schwann cells and collagen synthesis in taxol-treated nerve crush. An electron microscopic study.

The effect of nerve crush on collagen synthesis in rat sciatic nerve was studied by electron microscope. The crushed nerves were treated with taxol which is known to increase the amount of cytoplasmic microtubules at the expense of other cell organelles such as rough endoplasmic reticulum and Golgi complexes. The results were compared to those seen in crushed nerves without taxol treatment. After the injury the amount of collagen fibrils increased at the site of the trauma in both groups when compared to intact controls. Thin (30 mn in diameter) collagen fibrils were often arranged closely to the Schwann cell surface and were connected to deep invaginations in areas where the basal lamina had lost its typical integrity. This was concluded to indicate a probable site of collagen secretion and it provides further evidence that an adult injured nerve Schwann cell is capable of synthesizing fibrous collagen. In taxol-treated nerves additional, abnormally close connection between thin microfibrils of about 10 nm and thin 20-30 nm collagen fibrils appeared in an end-to-end fashion. The microfibrils showed occasional collagenous transverse band like structures. The rough endoplasmic reticulum and Golgi complex play an important role in the posttranslational modifications of the procollagen molecule. Taxol-induced degeneration of cell organelles such as the Golgi complex, which is also essential in the secretion of proteins may thus lead to defective maturation of collagen and may explain partly the altered collagen fibril formation.

Alkaloids↗