J. Flament-Durand

Tanycytes: morphology and functions. A review

Publisher Summary The chapter presents a review of the morphology and functions of tanycytes. The name “tanycyte,” derived from the Greek word “tanus,” which means “elongated,” was chosen to stress the shape of these bipolar cells, in relation at their apical pole with the infundibular recess of the third ventricle and, at their distal pole, with the portal vessels of the median eminence and the floor of the brain. The morphology of tanycytes has been thoroughly explored by means of photonic observations as well as by transmission (TEM) and scanning (SEM) electron microscopy. The review of the chapter will be restricted to the tanycytes lining the ventral region of the third ventricle in mammals, thus, excluding the study of similar cells lining the circumventricular organs (subfornical organ, subcommissural organ, organum vasculosum of the lamina terminalis), the aqueduct, and the floor of the fourth ventricle. The possible functions of the tanycytes will also be reviewed. The Golgi impregnation has been used by several authors to study the morphology of the tanycytes in mammals. Because of the thickness of the sections impregnated by this method, it is possible in favorable incidences to follow the entire length of these elongated cells, allowing a dissection in situ. This method demonstrates two main types of tanycytes according to their location and their morphology. The ventral tanycytes are located on the floor and lower third of the infundibular recess. Dorsal tanycytes have a longer tail process, starting from the base of the tanycyte and arching ventrolaterally in the neuropil of the arcuate nucleus. Glycerophosphate dehydrogenase (GPDH), lactic dehydrogenase (LDH), and glucosed-phosphate dehydrogenase (G6PD) are more active in the perikaryons of β tanycytes as compared to α.

Alzheimer's paired helical filaments share epitopes with neurofilament side arms.

A panel of monoclonal antibodies to neurofilaments have been investigated with regard to the location of their respective epitopes on neurofilament polypeptides and their ability to label the neurofibrillary tangles and paired helical filaments (PHF) which are characteristic of Alzheimers disease. All of the neurofilament monoclonal antibodies that label tangles and PHF are directed against epitopes in the side arm domains of the two larger neurofilament polypeptides, NF‐H and NF‐M, and do not recognise the alpha‐helical rod domains of these proteins. Immuno‐electron microscopy demonstrates that the neurofilament antibodies label the constituent PHF per se and do not simply stain neurofilaments that might be admixed with PHF. These neurofilament epitopes are differentially retained by PHF, following isolation. Thus, antibody labelling of PHF is not simply due to the presence of normal neurofilament polypeptides. We propose that in tangle‐bearing neurons, neurofilaments are degraded by proteases and that it is fragments of the side arms which contribute to the composition of PHF.

Intracerebral calcifications appearing during the course of acute lymphocytic leukemia treated with methotrexate and X-rays.

The authors present the case of a child aged 7 years who suffered from relapsing acute lymphocytic leukemia. Treatment consisting mainly of oral and intrathecal methotrexate and x‐ray therapy produced remission of the hematologic symptoms. Three years after the onset of the leukemia, mental deterioration gradually appeared. Radiography of the skull revealed diffuse bilateral calcium deposits in both cerebral and cerebellar hemispheres. Four years after the onset of the disease, a hematologic relapse occurred. Behavioral disorders became more severe and the child died after a period of seizures and unconsciousness. The main pathologic data obtained by the study of a brain biopsy and after a complete postmortem examination consisted of calcifications located bilaterally in the cerebral and cerebellar cortex. No signs of leukemia were present. Cerebral calcification is an extremely rare complication in the course of the therapy of lymphocytic leukemia. Its possible causes are discussed.

Quantitative assessment of the density of neurofibrillary tangles and senile plaques in senile dementia of the Alzheimer type. Comparison of immunocytochemistry with a specific antibody and Bodian's protargol method.

SummaryCounts of neurofibrillary tangles and senile plaques were performed in two adjacent sections from the temporal lobe in 14 women aged over 75 years at death. The mental status of these cases had been prospectively assessed by the test score of Blessed, Tomlinson and Roth. They were either intellectually normal or had senile dementia of the Alzheimer type of various degrees of severity. The first section was silver-impregnated according to Bodians method; the second one was immunolabeled with an antiserum raised against neurofibrillary tangles. Densities of neurofibrillary tangles and senile plaques evaluated by the two techniques were highly correlated but their means of differences and limits of agreement were large. The correlation with the clinical data was similar for the two methods. Both techniques can thus be used with the same accuracy in correlative studies but their results are not interchangeable without caution.

Studies on the transport of secretory granules in the magnocellular hypothalamic neurons - I. Action of colchicine on axonal flow and neurotubules in the paraventricular nuclei

SummaryThe axonal flow of neurosecretory elementary granules has been studied in the paraventricular neurons of the rat (PVN), with the help of three techniques: light microscopy, radioautography after labelling with 35S-L-cysteine, and electron microscopy.Colchicine treatment does not alter the uptake of 35S cysteine in the PVN but the flow of labelled neurosecretory material towards the neurohypophysis is interrupted. Interruption of the axonal flow is also evidenced by the stagnation of neurosecretory granules at the periphery of the neuronal cytoplasm and by the presence of numerous axonal swellings, heavily loaded with neurosecretory granules and often containing abnormal elongated granules, surrounded by a single membrane, oriented more or less parallely to the long axis of the axons. Other cell organelles and neurotubules are not altered. The present experiments bring further evidence of the arrest by colchicine of the axonal flow of secretory granules without apparent changes of the neurotubules.

Spongiform alterations in brain biopsies of presenile dementia.

SummarySpongiform lesions were observed in close association with typical presenile alterations in three of six frontal lobe biopsies taken in presenile demented patients without any familial relationship. These findings are discussed in relation with recent investigations indicating the production of spongiform lesions after inoculation of nervous tissue from an Alzheimer patient to animals and the effects of saline extract of such material on cultured nerve cells.

Pineal cyst: normal or pathological?

Review of 500 consecutive MRI studies was undertaken to assess the frequency and the appearances of cystic pineal glands. Cysts were encountered in 2.4% of cases. Follow-up examination demonstrated no change in these cysts and they were considered to be a normal variant. Size, MRI appearances and signs associated with this condition are reported in order to establish criteria of normality.

Synaptophysin and chromogranin A immunoreactivities in senile plaques of Alzheimer's disease

Immunolabelling for synaptophysin and chromogranin A, two polypeptides associated with small clear and large dense core synaptic vesicles respectively, has been performed on tissue sections of the temporal cortex in Alzheimers disease in combination with anti-A4 amyloid labelling. The dystrophic neurites in many senile plaques were observed to be labelled by the anti-synaptophysin or anti-chromogranin A antibodies. Some diffuse amyloid deposits, demonstrated by antibodies against synthetic amyloid A4 peptides, were associated with a punctuate increase in synaptophysin or chromogranin A immunoreactivity. The labelling of dystrophic plaque neurites may reflect the accumulation in these processes of synaptic vesicles or material derived from them. We suggest also that the punctuate increase in synaptophysin and chromogranin A immunoreactivities associated with some A4 amyloid deposits may be an early event reflecting neuronal dysfunction.

Sarcoidosis presenting as an isolated intramedullary tumor

We report a case of isolated intramedullary sarcoidosis. The patient developed progressive signs that indicated a spinal tumor, which were investigated with contrast-enhanced magnetic resonance imaging scans. Magnetic resonance imaging clearly revealed an intramedullary lesion, but the diagnosis of sarcoidosis was made on the pathological analysis of the surgical specimen. Magnetic resonance imaging with contrast enhancement is reported in a histologically proven case of intramedullary sarcoidosis. Only 12 other cases of isolated intramedullary sarcoidosis have been reported. We review and discuss these cases according to their clinical presentation, the segmental location of the granulomas in the spinal cord, preoperative and operative diagnoses, and signs for systemic sarcoidosis. In none of the cases was the diagnosis of intramedullary sarcoidosis made before surgery. We think that surgical therapy for intramedullary lesions is the best way to diagnose rare instances of benign lesions like sarcoidosis and to treat them in an appropriate manner.

Characterization of nuclear DNA content, proliferation index, and nuclear size in a series of 181 meningiomas, including benign primary, recurrent, and malignant tumors

The characterization of nuclear area, the proliferation index, and nuclear DNA content was carried out by means of digital cell image analysis, which makes it possible to compute morphometric and densitometric features on Feulgen-stained nuclei from archival, that is, formalinfixed, paraffin-embedded materials. The 181 meningiomas studied included 173 classic (41 meningotheliomatous, 27 fibroblastic, 82 transitional, nine psammomatous, eight angiomatous and six hemangioblastic tumors) and eight malignant meningiomas (three hemangiopericytomas and five tumors that we labeled HFM, that is, tumors exhibiting evidence of histological features of malignancy). The results reveal a strong relationship between incomplete surgical resection and recurrence on the one hand and between the probability of recurrence and histopathological type on the other. Whereas neither nuclear area nor nuclear DNA content assessments were helpful in distinguishing the six classic and the two malignant meningioma subgroups, a statistically significant increase in proliferative activity was observed in the malignant meningiomas as compared with classic ones, excepting hemangioblastomas that proliferate at the same rate as the malignant meningiomas. Furthermore, the multiple meningiomas definitely proliferated more actively than the single ones, but a similar proliferative activity was observed in the nonrecurrent and recurrent meningiomas. Proliferation analyses might be therefore helpful for determining aggressive meningiomas and for planning adjuvant therapy in these cases