Gerhard F. Walter

Immunohistochemical detection of female sex hormone receptors in meningiomas: correlation with clinical and histological features.

Sixty-one meningiomas from 60 patients were screened for estrogen receptors and progesterone receptors (PgR) with monoclonal antibodies in an immunohistochemical assay. In addition, 43 of the cases were evaluated for tumor size and peritumoral edema, as seen on computed tomographic scans and magnetic resonance images. Sixty-one percent of the tumors contained significant amounts of PgR, whereas no estrogen receptor-positive tumor was observed. Thirteen percent of all tumors were classified as nonbenign variants (atypical and anaplastic meningiomas) and were more frequently found in male patients (P < 0.05). Nonbenign tumors more frequently showed an absence of PgR (P < 0.05), and there was a tendency for PgR-negative tumors to be larger than PgR-positive ones. No correlation was found between PgR status and edema. It is concluded that PgR status in meningiomas is related to tumor differentiation and may be of prognostic value with regard to biological behavior and clinical outcome.

Comparison of unilateral and bilateral intrastriatal 6-hydroxydopamine-induced axon terminal lesions: Evidence for interhemispheric functional coupling of the two nigrostriatal pathways

Partial lesions of the nigrostriatal dopamine system can be induced reliably by the intrastriatal injection of 6‐hydroxydopamine (6‐OHDA) and are considered to be analogous to the early stages of human Parkinsons disease. Previous studies have established a clear correlation between different doses and placements of the 6‐OHDA toxin and the degree of neurodegenerative changes and behavioral impairments. In the present study, the influence of the interdependence between the two nigrostriatal systems in both hemispheres on the effects on sensorimotor behavioral performances after terminal 6‐OHDA lesions was investigated. The behavioral effects were correlated to the extent of nigral dopamine neuron cell and striatal tyrosine‐hydroxylase (TH)‐positive fiber loss. Sprague‐Dawley rats receiving unilateral intrastriatal 6‐OHDA injections (4 × 5 μg) exhibited a 30–70% reduction in striatal TH‐positive fiber density along an anterior‐posterior gradient, an 80% loss of nigral dopamine neurons and a mild degree of behavioral impairments as revealed by amphetamine‐induced rotational asymmetry, and a reduced performance in the stepping and postural balance tests. When the same amount of toxin was injected twice into both hemispheres (2 × 4 × 5 μg), additional behavioral deficits were observed, consisting of a significant, but temporary, weight loss, a stable reduction in general locomotor activity and explorational behavior, and a long‐term deficit in skilled forelimb use. This is interesting in light of the morphological findings, in which uni‐ and bilaterally lesioned animals did not differ significantly in the extent of TH‐immunoreactive fiber and dopamine neuron loss within the nigrostriatal system in each lesioned hemisphere. These results indicate that the interdependent regulation of the two nigrostriatal systems may provide some compensatory support for the function and behavioral performance of the lesioned side via the normal unlesioned side, which is lost in animals with bilateral lesions of the nigrostriatal system. Therefore, this model of uni‐ and bilateral partial lesions of the nigrostriatal system, as characterized in the present study, may foster further exploration of compensatory functional mechanisms active in the early stages of Parkinsons disease and promote development of novel neuroprotective and restorative strategies. J. Comp. Neurol. 432:217–229, 2001.

Cerebral Hypoperfusion and Delayed Hippocampal Response After Induction of Adult Kaolin Hydrocephalus

Background and Purpose— In chronic hydrocephalus, a role for tissue hypoxia resulting from cerebrovascular compression is suggested. The purpose of this study was to evaluate whether changes in cerebral blood flow (CBF) in the time course of adult kaolin-induced hydrocephalus correlated with immunohistochemical neuronal responses. Methods— In 46 adult Sprague-Dawley rats, kaolin hydrocephalus was induced and immunostaining of neurofilament protein (NF68), synaptophysin (SYN38), and neuronal nitric oxide synthase (NOS) was performed at 2 (short term), 4 (intermediate term), and 6 and 8 (long term) weeks. Local CBF was measured quantitatively by [14C]iodoantipyrine ([14C]IAP) autoradiography in the short-term stage and in both long-term stages. Results— At 2 weeks, neuronal NOS immunoreactivity was globally increased in cortical areas and within the hippocampus. Four weeks after hydrocephalus induction, a reactive increase of SYN38 and NF68 immunoreactivity in the periventricular cortex was seen. At 6 and 8 weeks, when the ventricular size was decreasing, immunohistochemical changes in the hippocampus became most evident. A maintained toxic NOS reactivity in the CA1 subfield was accompanied by a loss of NF68 staining. In the CA3 subfield, however, focal increases in NF68 and SYN38 immunoreactivity were found. Cortical and hippocampal blood flow showed prolonged decreases of 25% to 55% compared with control animals. At 8 weeks, control levels were reached. Conclusions— The observed temporary CBF decrease appears to correlate with an early global neuronal ischemic response. In addition, it may also account for the delayed selective response of ischemia-vulnerable structures, eg, hippocampus, in chronic adult kaolin-induced hydrocephalus.

Immunohistochemical characterization of axonal sprouting and reactive tissue changes after long-term implantation of a polyimide sieve electrode to the transected adult rat sciatic nerve.

The development of artificial microstructures suited for interfacing of peripheral nerves is not only relevant for basic neurophysiological research but also for future prosthetic approaches. Aim of the present study was to provide a detailed analysis of axonal sprouting and reactive tissue changes after implantation of a flexible sieve electrode to the proximal stump of the adult rat sciatic nerve. We report here that massive neurite growth after implantation, steadily increasing over a period of 11 months, was observed. Parallel to this increase was the expression of myelin markers like Po, whereas non-myelin-forming Schwann cells did not change. Compared to five weeks post-implantation. where both Schwann-cell phenotypes were intermingled with each other, non-myelin-forming Schwann cells occupied a peripheral position in each microfascicle after 11 months. After an initial increase, hematogenous macrophages were down-regulated in number but maintained close contact with the implant. However, at no time were signs of its degradation observed. It is concluded that the introduced flexible polyimide electrode is suitable for contacting peripheral nerves since it permits substantial neurite growth and offers excellent long-term stability.

Viability of cultured nerve grafts: An assessment of proliferation of Schwann cells and fibroblasts

Previous studies demonstrated that the viability of nerve grafts had a positive effect on nerve regeneration, while the cold storage of nerve grafts obtained few viable cells at the later stage. The purpose of this study was to examine the cellular activities of Schwann cells and fibroblasts in cultured nerve grafts prior to transplantation. 2.5‐cm long sciatic nerve grafts were harvested from 75 male Lewis rats. Two different media were utilized to culture the nerve grafts up to 3 weeks: Dulbeccos modified eagle medium (DMEM) only or DMEM supplemented with 2 μM forskolin and 10 μg/ml pituitary exact (mitogen medium for Schwann cells). In vivo predegenerated and normal nerve grafts were used as positive and negative controls, respectively. We employed a 5‐bromo‐2′‐deoxyuridine (BrdU) incorporation method to evaluate the proliferating cells in the cultured nerve grafts. S‐100 and vimentin immunostaining were used to estimate the presence of Schwann cells and fibroblasts in all nerve grafts at different intervals. The results showed that the proliferating cells increased progressively under culture conditions. The proliferating cells distributed evenly in small fascicles (average diameter 251 ± 71.5 μm), whereas they appeared mainly in the margin of large fascicles (average diameter 624 ± 87.3 μm). The mitogen medium stimulated Schwann cell multiplication more significantly in comparison with DMEM after 3 days of culture (P < 0.01), however, there were fewer fibroblasts present in the mitogen medium than in DMEM after 2 days of culture (P < 0.01). It is suggested that the viability of nerve grafts can be preserved under culture conditions. Furthermore, the cellular activity of the Schwann cells and fibroblasts in nerve grafts can be manipulated in in vitro Wallerian degeneration.

A Schwann cell‐seeded intrinsic framework and its satisfactory biocompatibility for a bioartificial nerve graft

To optimize the internal environment of a collagen nerve tube, we designed a Schwann cell‐seeded intrinsic framework and its biocompatibility was investigated. We fixed 6‐0 polyglactin woven filaments (Vicryl) or polydioxanone monofilaments (PDS) on a silicone ring in a net fashion. It was coated with matrigel and then incubated with cultured newborn or adult Schwann cells. Furthermore, we implanted 1.5‐cm‐long filament‐filled collagen tubes in a rat model. Using a live/dead fluorescent assay and electron microscopy, we found that adherent Schwann cells onto filaments remained viable and oriented longitudinally along filaments. The preliminary in vivo study indicated that a mild inflammatory reaction was present around the tube wall. However, nerve regeneration occurred around and between filaments. We concluded that the arrangement of Schwann cell columns onto filaments was achieved, mimicking Bünger bands. It was shown that the biomaterials did not impede nerve regeneration.

Effects of IL6 and IL1β on aFGF expression and excitotoxicity in NT2N cells

The interleukin-1beta (IL1beta) and interleukin-6 (IL6) have pro-inflammatory and neuroprotective functions and are elevated in many diseases of the brain. Here, mechanisms and effects of IL1beta and IL6 on neuronal survival after excitatory stimulation were investigated in vitro. IL6 upregulated the expression of the neuroprotective acidic fibroblast growth factor (aFGF) and reduced the glutamate-induced cytotoxicity. IL1beta treatment amplified the excitotoxic effects after 24 h, but longer treatment with IL1beta stimulated the neuronal release of IL6 resulting in increased levels of aFGF and a decreased excitotoxicity. These data suggest that (1) IL6 exerts protective functions by upregulating the expression of aFGF and (2) the IL6/IL1beta balance in the brain may regulate neuronal survival during neuropathological processes.

Evidence of recurrent atypical meningioma with rhabdoid transformation and expression of pyrogenic cytokines in a child presenting with a marked acute-phase response: case report and review of the literature

Children presenting with acute systemic illnesses that lack specific clinical or serological defining features may be diagnosed as having a chronic infection, an atypical systemic vasculitis or a connective tissue disease, but often turn out to have occult neoplasias. Cytokines have been implicated in causing many of the systemic effects in such cases. In this study, we describe the case of a 9-year-old boy presenting at an interval of 18 months with a marked acute-phase response due to a recurrent atypical meningioma with rhabdoid transformation of the tentorium cerebelli. Resection of the recurrent tumor was curative. We evaluated in detail the local and systemic production of cytokines released by the primary and the recurrent tumor. Blood and CSF samples were taken pre-, intra-, and postoperatively, and the production of IL-6, IL-1beta, and TNF-alpha was measured by enzyme-linked immunosorbent assays (ELISA). The level of IL-6 in CSF was about 150-fold increased before tumor resection, normalizing postoperatively. On the contrary, the levels of IL-1beta and TNF-alpha in CSF and of IL-6, IL-1beta, and TNF-alpha in serum were pre-, intra-, and postoperatively within normal limits. Cytokine production was also evaluated immunohistochemically, and confirmed strong IL-6 and TNF-alpha expression in the primary and the recurrent tumor, while expression of IL-1beta was lacking. The scattered MHC class II- and leukocyte common antigen (LCA)-expressing inflammatory cells, which were infiltrating exclusively the tumoral stroma, had no detectable cytokine immunoreactivity. We conclude that chronic IL-6 and TNF-alpha production by the tumor cells in this patient was responsible for the severe systemic illness with which he presented.

Cellular activity of resident macrophages during Wallerian degeneration

The resident macrophages have been accepted as an important component of the peripheral nervous system as Schwann cells. To elucidate their role during Wallerian degeneration without interference from extrinsic hematogenous macrophages, we designed a culture system to investigate the behavior of resident macrophages in vitro. A total of 75 adult male Lewis rats were used; 2.5‐cm‐length sciatic nerve explants were harvested. There were three groups. In the culture groups, the nerve explants were incubated in Dulbeccos modified Eagles medium (DMEM) only or in DMEM supplemented with 2 μm forskolin and 10 μg/ml pituitary extract (mitogenic medium for Schwann cells). In vivo predegenerated nerves and normal nerves were used as the positive and negative controls, respectively. The observation periods extended to 3 weeks. Hematoxylin and eosin (H&E) stain was employed to estimate overall cell number in nerve explants. Macrophages were labeled with ED1; S‐100 immunostaining was used to evaluate the presence of Schwann cells during Wallerian degeneration. Trichrome stain and toluidine blue stain were used to visualize the fate of myelin. In the culture groups, the number of resident macrophages increased continuously, although there were significantly fewer resident macrophages than hematogenous macrophages after 3 days of Wallerian degeneration (P < 0.01). Morphologically, resident macrophages contained densely small ED1‐positive granules within their cytoplasm, even at later stages of observation, whereas hematogenous macrophages contained typical large ED1‐positive foam vacuoles characteristic of their mature phagocytic ability. The cellular activity of Schwann cells was well preserved in the mitogenic medium; however, myelin removal was not significantly enhanced as compared with the DMEM groups (P > 0.05). The clearance of myelin debris was shown to be incomplete in culture groups as compared with the complete removal of myelin debris in the in vivo groups. Resident macrophages were actively involved in Wallerian degeneration, but their phagocytic and proliferation ability was limited. Schwann cells played an adjunctive role during the removal of myelin debris.

C-Fos immunoreactivity mapping of the auditory system after electrical stimulation of the cochlear nerve in rats.

The aim of this study was to establish the use of c-Fos immunoreactivity as a marker for functional mapping in the auditory system in response to direct electrical stimulation of the cochlear nerve in the cerebellopontine angle. In rats the cochlear nerve was electrically stimulated with a biphasic current (120-250 microA, 5 Hz) for 30 min using a bipolar concentric Tungsten electrode. Bilateral cochlectomy was performed in a control group in order to investigate basal expression of c-Fos in the auditory brainstem nuclei. The response of auditory brainstem nuclei to electrical stimulation and the completeness of cochlear ablations were electrophysiologically verified. After the experiments, the animals were prepared for cryotomy and c-Fos immunohistochemistry. The results were morphologically analyzed and statistically compared among groups. In anesthetized animals with unilateral electrical stimulation of the cochlear nerve increased expression of c-Fos was detected in the ipsilateral ventral (VCN) and bilateral dorsal cochlear nucleus (DCN), whereas the VCN of the contralateral side revealed only few immunoreactive cells. In animals with bilateral cochlear ablation the number of c-Fos reactive cell nuclei representing basal expression was generally low in the VCN and DCN of both sides. Our data show that electrical stimulation of the cochlear nerve leads to increased expression of c-Fos in the cochlear nucleus. It also confirms bilateral connections between the cochlear nuclei. These experimental results suggest that c-Fos immunoreactivity mapping provides a powerful tool for functional investigations on the cellular level after direct electrical stimulation of the cochlear nerve. Future functional studies analyzing the effect of electrical stimulation of the central auditory system as performed by auditory brainstem implants could be investigated in detail by mapping c-Fos expression on cellular level.