Bibliothek

Notizen: Summary The postnatal development of ipsilateral retinofugal projections to the lateral geniculate body in normal albino rats, and in rats unilaterally enucleated at birth has been examined. At postnatal ages ranging from 1 day to 6 months, horseradish peroxidase was injected into one eye of normal rats and into the remaining eye of neonatally enucleated animals. After approximately 20 hours, the animals were perfused, the brains sectioned and reaction product visualised using tetramethylbenzidine. Ipsilateral retinal projections to the lateral geniculate body in normal animals were extensive on postnatal day 1 and became reduced over the next few days, the adult pattern being established between days 9 and 12. In the enucleated group, the terminal fields of the ipsilateral projections to the lateral geniculate body from the remaining eye remained larger and displayed a greater density of terminal labelling than in age-matched controls. In addition, the ipsilateral terminal field in the dorsal lateral geniculate nucleus occupied a more lateral position than in control animals. These findings support previous suggestions that the abnormally large ipsilateral retino-fugal projections observed in adult rats following removal of one eye, at or close to, birth, result from a failure of the ipsilateral projection to become restricted and that terminal or preterminal sprouting of retinal axons may also make a small contribution to the formation of the exuberant ipsilateral projection.

Notizen: Abstract A 22-month-old girl with the syndrome of hypoventilation, pulmonary hypertension, cor pulmonale and pulmonary edema due to adenoidal hypertrophy is described. Adenoidectomy resulted in relief of all symptoms and signs within 24 h. Hemodynamic study using pulmonary artery catheter showed that the pulmonary artery pressure returned to normal 48 h after relief of the obstruction. The normal left ventricular end-diastolic pressure, measured throughout the period of obstruction, in the presence of severe pulmonary edema, could suggest a non-cardiogenic “low pressure” pulmonary edema. However, the highly negative pleural pressure which existed during upper airway obstruction indicated an elevation of transmural left ventricular end diastolic pressure (compared to pulmonary wedge pressure) and thus, suggested that the pulmonary edema in this syndrome is secondary to both — right and left heart failure.

Notizen: Summary Although mature mammalian CNS neurons do not normally regenerate axons after injury, it is well established that they will regrow axons over long distances into peripheral nerve implants. We have autografted segments of sciatic nerve into the brains of adult albino rats and have used light and electron microscopic immunocytochemistry to examine the distribution of the growth associated protein GAP-43 in and around the graft in the first two weeks following implantation. GAP-43 was present, 3–14 days after grafting, in small non-myelinated axonal sprouts in the brain parenchyma around the proximal tip of the graft. At 11–14 days after implantation similar sprouts within the graft itself were GAP-43 immunoreactive. The sprouts were either naked or associated with other cell processes (chiefly of Schwann cells; to a lesser extent of astrocytes). We also show that small numbers of neuronal perikarya around the tip of the graft become GAP-43 immunoreactive 11–14 days after implantation. Thus mature mammalian CNS neurons regenerating axons into a PNS graft display a marked increase in their content of GAP-43. In addition, we report that small plaques of GAP-43 reaction product are sometimes present on the plasma membranes of Schwann cells or astrocytes adjacent to immunoreactive axons, and that narrow sheet-like or filopodial processes of astrocytes, Schwann cells and possibly other non-neuronal cell types, may contain small amounts of GAP-43.

Notizen: Summary The dopamine levels were found to be low in the putamen and relatively high in the nucleus accumbens in two Parkinson disease patients treated with levodopa up to the time of their deaths. Tyrosine hydroxylase immunocytochemistry revealed a severe degeneration of the nigro-striatal dopamine neuronal system in both postmortem brains. The relatively high dopamine levels in the nucleus accumbens may be responsible for the occurrence of dyskinesias.

Notizen: Summary If one end of a segment of peripheral nerve is inserted into the brain or spinal cord, neuronal perikarya in the vicinity of the graft tip can be labelled with retrogradely transported tracers applied to the distal end of the graft several weeks later, showing that CNS axons can regenerate into and along such grafts. We have used transmission EM to examine some of the cellular responses that underlie this regenerative phenomenon, particularly its early stages. Segments of autologous peroneal or tibial nerve were inserted vertically into the thalamus of anaesthetized adult albino rats. The distal end of the graft was left beneath the scalp. Between five days and two months later the animals were killed and the brains prepared for ultrastructural study. Semi-thin and thin sections through the graft and surrounding brain were examined at two levels 6–7 mm apart in all animals: close to the tip of the graft in the thalamus (proximal graft) and at the top of the cerebral cortex (distal graft). In another series of animals with similar grafts, horseradish peroxidase was applied to the distal end of the graft 24–48 h before death. Examination by LM of appropriately processed serial coronal sections of the brains from these animals confirmed that up to several hundred neurons were retrogradely labelled in the thalamus, particularly in the thalamic reticular nucleus. Between five and 14 days after grafting, large numbers of tiny (0.05–0.20 μm diameter) nonmyelinated axonal profiles, considered to be axonal sprouts, were observed by EM within the narrow zone of abnormal thalamic parenchyma bordering the graft. The sprouts were much more numerous (commonly in large fascicles), smoother surfaced, and more rounded than nonmyelinated axons further from the graft or in corresponding areas on the contralateral side of animals with implants or in normal animals. At longer post-graft survival times, the number of such axons in the parenchyma around the graft declined. At five days, some axonal sprouts had entered the junctional zone between the brain and the graft. By eight days there were many sprouts in the junctional zone and some had penetrated the proximal graft to lie between its basal lamina-enclosed columns of Schwann cells, macrophages and myelin debris. Within the brain, sprouts were in contact predominantly with other sprouts but also with all types of glial cell. Within the junctional zone and graft many sprouts showed no consistent, close associations with other cell processes, although some were in contact or adjacent to processes of astrocytes, Schwann cells or macrophages. There was no evidence to suggest that axonal sprouts grew along astrocytic extensions to reach the junctional zone and graft. At eight days many axons in the junctional zone and graft were in contact with Schwann cell processes. Such axons, particularly those in intimate contact with the Schwann cell, were larger than those which had not established contact. By 14 days, most axons in the proximal graft were surrounded by Schwann cell processes, predominantly in basal lamina-enclosed columns. Some axons were associated with astrocyte processes, either in basal lamina-enclosed columns containing only astrocyte processes and axons or in columns containing a mixture of astrocyte and Schwann cell processes. The astrocyte processes involved in such bundles were concentrated at the periphery of the proximal graft, were not seen in the distal graft and probably represent long finger-like extensions of the astrocytes which rapidly form a glia limitans at the interface between brain and graft. This glia limitans was partially constructed at five days, almost complete at 14 days and subsequently became progressively thicker and more complex. At one month the proximal graft had acquired many of the features of a regenerating peripheral nerve and axons were present in large numbers in the distal graft. However the axon-Schwann cell relationships were immature in many of the Schwann cell columns both proximally and distally at one month, and virtually no myelination was apparent. At two months there were numerous myelinated fibres both proximally and distally although there were larger numbers of nonmyelinated axons, many in immature relationship with associated Schwann cells. Thus the graft appears to offer not only support for axonal elongation but also for a substantial degree of maturation of at least some of the regenerating axons, although (as will be reported elsewhere), the regenerated nerve fibres began to regress after two months.