Polymer hollow fiber-encapsulated peripheral nerve extracts change their activity towards injured hippocampal neurites in rats.

The regeneration of the adult mammalian central nervous system (CNS) requires changes of the nonpromising environment. Applying peripheral nerve grafts and their extracts are both the useful method to induce regeneration of injured CNS neurites. Our previous reports showed that degeneration of peripheral nerves enhanced their neurotrophic activity in a time-dependent manner. Electrophoretical analysis of proteins obtained from degenerating sciatic nerves revealed significant changes in fractions of low molecular mass. The aim of the present work was to examine the influence of fractionated extracts from 7-day-predegenerated and non-predegenerated peripheral nerves upon injured hippocampal neurites in adult rats. The extracts were closed in fibrin-filled connective tissue chambers (CTC) or within CTC-wrapped polymer hollow fibers (PHF) of 30 kDa cut-off. The cell bodies of regrowing fibers were labeled with FITC-HRP. The CTCs appeared to be useful tool for implantation of artificial grafts into mammalian CNS. Full-spectrum nerve extracts induced strong regeneration of injured hippocampal neurites. The number of labeled cells within hippocampus was significantly lower in PHF groups than in CTC ones, indicating that low-mass proteins present in peripheral nerve extracts are not sufficient to induce successful regeneration.

Dead-ended autologous connective tissue chambers in peripheral nerve repair--early observations.

The effects of the repair of nerve gap injuries are still unsatisfactory, despite the great progress in microsurgery. Until now, there is no effective method to induce the regeneration of the transected peripheral nerve when its distal stump is missing. The aim of this work was to examine whether the implantation of dead-ended connective tissue chambers can promote the outgrowth of injured peripheral neurites. This method differs from all previous nerve guides because it totally eliminates the distal part of the nerve and restricts the influence of surrounding tissues. We have also tried to establish whether some neurotrophic factors can be applied by means of these chambers. The results of this work show that dead-ended autologous connective tissue chambers can be a useful tool in peripheral nerve injuries treatment, even when the distal part of the nerve is missing.

Predegenerated peripheral nerve grafts rescue retinal ganglion cells from axotomy-induced death.

The inability of axons to grow across damaged central nervous system tissue is a well-known consequence of injury to the brain and spinal cord of adult mammals. Our previous studies showed that predegenerated peripheral nerve grafts facilitate neurite outgrowth from the injured hippocampus and that this effect was particularly distinct when 7-, 28-, and 35-day-predegenerated nerve grafts were used. The purpose of the present study was to use the above method to induce and support the regrowth of injured nerve fibers as well as the survival of retinal ganglion cells (RGCs). Adult Sprague-Dawley rats were assigned to three groups. In the experimental groups transected optic nerve was grafted with peripheral nerve (predegenerated for 7 days (PD) or nonpredegenerated). In the control group, the optic nerve was totally transected. RGCs and growing fibers labeled with fluorescent tracers were examined. They were counted and the results were subjected to statistical analysis. Retinal ganglion cells survived in the groups treated with predegenerated as well as nonpredegenerated grafts; however, the number of surviving retinal ganglion cells was significantly higher in the first one. In both groups the regrowth of the transected optic nerve was observed but the distance covered by regenerating fibers was longer in the PD group. No fibers inside grafts and no labeled cells in retinas were present in the control animals. On the basis of the obtained results we can state that the predegeneration of grafts enhance their neurotrophic influence upon the injured retinal ganglion cells.

Postmicrosomal protein fractions from short-time-predegenerated rat sciatic nerve.

The postmicrosomal protein fraction obtained from distal stumps of rat sciatic nerves at 0-6 days following transection were investigated by means of one- and two-dimensional electrophoresis. In all experimental groups, total amount of protein was significantly higher than in the control group. Proteins were resolved into 27 bands after SDS-PAGE. Their molecular weights ranged between 16.2 and 335.4 kDa. Eleven fractions displayed significant quantitative differences. After 2-D-electrophoresis, the pI of the proteins ranged from 4.2 to 7.4. They were resolved to 28 molecular masses from 13.5 kDa to 335.4 kDa. The greatest numbers of fractions (90-109) were observed on the 3rd, 4th, 5th and 6th day after nerve transection. Thus, during first 6 days after transection intensive changes in protein fraction content and composition take place in the distal stump of peripheral nerve. These processes seem to be most prominent on the 4th day after lesion. Results confirm our earlier in vivo findings.

Autologous connective tissue bars as vehicles for the administration of growth-influencing substances to the brain.

One of the main problems in the introduction of growth factors or other substances into the CNS is that most of these do not pass the blood-brain barrier, and so they have to be delivered directly to the target cells. Recently, different methods of intracerebral administration have been introduced such as release of drugs from polymer matrix or hollow polymer fibres, implantation of solution-soaked gel foam pieces or genetically modified cells secreting growth factors. In our studies on regeneration in CNS, the problem of introducing active substances into the brain arose. For this reason we elaborated a new method for the administration of soluble factor by means of autologous connective tissue chambers filled with fibrin. This method is particularly suitable in studies in which the visualization of the regrowth of nerve fibres is one of the main purposes. Presence of an active substance inside the chamber fibres to grow in the direction of the chamber and such fibres can be visualized here. Such visualization is impossible while using other methods of trophic substance delivery into the CNS, e.g. intraventricular steel cannula connected to an osmotic minipump, because there is neither space nor appropriate milieu to allow the fibres' ingrowth. Retrograde tracing methods allow to establish the cells of origin of these fibres. This method is inexpensive, simple and adaptable to histological procedures.

Purified extracts from short-time-predegenerated rats' sciatic nerves promote the regrowth of injured hippocampal neurites.

Our previous studies revealed that purified extracts (submicrosomal fractions) obtained from peripheral nerves predegenerated for 7-, 28-, and 35-days facilitated neurite outgrowth from the injured hippocampus. It is recently known that totally transected peripheral nerve exhibits biphasic neurite-promoting activity. The early phase lasts 7 days. The aim of the present study was to find whether extracts obtained from short-time predegenerated (1-6 days) peripheral nerves exert any neurotrophic effect and when this influence is maximal. Experiments were carried out on adult male Wistar rats. Sciatic nerves were totally transected and following 1, 2, 3, 4, 5 and 6 days their distal stumps were homogenized and centrifuged. Extracts were implanted into the hippocampus by means of autologous connective tissue chambers. Reference groups were treated with extracts from non-predegenerated nerves, NGF solution or fibrin (groups C, NGF and B + F, respectively). In all groups FITC-HRP was injected into the extracranial end of chamber six weeks following surgery. Histochemic technique showed AChE-positive fibres inside the chambers of all examined groups. Fluorescence microscopic examination revealed the labeled cells in all examined groups, however their number was different in each group. They were most numerous at the fourth day of predegeneration.

Autologous connective tissue chamber as a tool for introducing active substances into the CNS.

A new method of introducing active substances into the CNS is described. The autologous connective tissue chambers were obtained by implantation of a silicone tube under the back skin of rats. Subsequently they were filled with fibrine and additionally with NGF or submicrosomal fractions from nonpredegenerated and predegenerated peripheral nerves. Filled chambers were implanted stereotaxically into the injured hippocampus. The neurite outgrowth was examined by means of FITC-HRP and acetylcholinesterase-method. Implanted connective tissue chambers are very useful in getting active substances into the CNS. This method allows to avoid inflammatory processes and does not hinder the histological procedures.

[Occupational exposure of workers in chemical factors and selected parameters of the respiratory system]. / Narazenie zawodowe pracowników zakladów chemicznych a wybrane parametry ukladu oddechowego.

Workers employed in chemical factories are chronically exposed to harmful substances present in the air of the occupational environment. The aim of this paper was to find out whether this situation produces adverse effects on the respiratory system despite the observance of admissible concentrations of toxic substances in the air. Spirometric values such as FVC1 and FEV1%FVC were measured in 647 workers. It was found that workers in some departments (power station and polystyrene) showed restrictive and obturative disturbances of ventilation. In other departments workers exhibited less expressed respiratory disorders. Adverse effect of smoking and long period of employment on the respiratory system of workers was also revealed. These results indicate that apart from substances present in the occupational environment there are other factors which affect as well the respiratory system of persons employed in the chemical industry.

Neurotrophic effect of submicrosomal fractions obtained from pre-degenerated peripheral nerves.

Submicrosomal fractions obtained from pre-degenerated distal stumps of sciatic nerves were implanted by means of connective tissue chambers into the injured hippocampus for 8 and 18 weeks. The nerve stumps were allowed to pre-degenerate for 7, 28 and 35 days. The neuronal outgrowth was examined by means of FITC-HRP injected into the chamber. Eight weeks postoperatively the greatest number of traced cells was present in brains treated with the fraction obtained from nerves pre-degenerated for 7 days. Eighteen weeks following implantation the greatest number of FITC-HRP positive cells was found in brains grafted with the fraction from nerves pre-degenerated for 35 days.

Experimental hyperthyroidism enhances the regeneration of central neurites promoted by peripheral nerve grafts in the hippocampus.

The aim of the present paper was to ascertain whether experimental hyperthyroidism promotes the regenerative action of predegenerated peripheral nerve grafts implanted into the transected hippocampus. Hyperthyroidism was induced by subcutaneous injections of T4. Autologous peripheral nerve grafts were implanted immediately, 7 and 35 days following transection of the sciatic nerve. Cells extending their neurites into the grafts were traced by means of horseradish peroxidase conjugated with fluoresceine isothiocyanate (FITC-HRP). Fluorescence microscope examination revealed that experimentally induced hyperthyroidism considerably enhanced the regenerative influence of peripheral nerve grafts. This effect was particularly pronounced in hyperthyrotic animals treated with either nonpredegenerated or 35 day predegenerated nerve grafts.