Pituicytoma, spindle cell oncocytoma, and granular cell tumor: clarification and meta-analysis of the world literature since 1893

BACKGROUND AND PURPOSE

Pituicytoma, SCO, and GCT are poorly understood entities with confusing nomenclature and undetermined imaging characteristics. Our purpose was to confirm published cases of pituicytoma, SCO, and GCT with the newest 2007 World Health Organization criteria and elucidate imaging findings that distinguish these tumors from common entities such as pituitary adenoma.

MATERIALS AND METHODS

A literature search identified 145 published cases (81 GCTs, 48 pituicytomas, and 16 SCOs). Case diagnoses were blindly reviewed by a neuropathologist according to the latest WHO criteria, resulting in 112 pathologically documented cases (64 GCTs, 35 pituicytomas, and 13 SCOs). Imaging illustrations from proved cases were reviewed to determine location, configuration, attenuation and signal intensity, and enhancement characteristics.

RESULTS

Only pituicytomas presented as purely intrasellar lesions (7/33). Most GCTs were purely suprasellar (28/45). All SCOs were both intra- and suprasellar (13/13). Twenty-five percent of pituicytomas (6/22) and GCTs (7/30) appeared separate from the pituitary gland. All SCOs were infiltrating. Seventy-nine percent of entities appeared isointense to brain on T1-weighted image (34/43). Seventy-four percent of pituicytomas enhanced homogeneously (14/19). Twelve of 23 GCTs and 5/7 SCOs enhanced heterogeneously. Most GCTs were hyperattenuated to brain on CT (18/20). Eleven of 13 cases enhanced homogeneously. Visual disturbances were common symptoms for all entities (67/112). Diabetes insipidus was rare (4/112).

CONCLUSIONS

Pituicytoma may be considered for purely intrasellar masses that are clearly separate from the pituitary gland. GCT should receive consideration for purely suprasellar lesions that are hyperattenuated to brain on CT. SCO should be considered for infiltrating pituitary masses with a mixed intra- and suprasellar location. A history of diabetes insipidus helps to exclude these tumors.

Binocular correlation of ocular aberration dynamics

Fluctuations in accommodation have been shown to be correlated in the two eyes of the same subject. However, the dynamic correlation of higher-order aberrations in the frequency domain has not been studied previously. A binocular Shack-Hartmann wavefront sensor is used to measure the ocular wavefront aberrations concurrently in both eyes of six subjects at a sampling rate of 20.5 Hz. Coherence function analysis shows that the inter-ocular correlation between aberrations depends on subject, Zernike mode and frequency. For each subject, the coherence values are generally low across the resolvable frequency range (mean 0.11), indicating poor dynamic correlation between the aberrations of the two eyes. Further analysis showed that phase consistency dominates the coherence values. Monocular and binocular viewing conditions showed similar power spectral density functions.

Pilomyxoid astrocytoma: expanding the imaging spectrum

BACKGROUND AND PURPOSE

Pilomyxoid astrocytoma (PMA) is a recently described variant of pilocytic astrocytoma (PA) with unique clinical and histopathologic characteristics. Because the histopathology of PMA is distinct from that of PA, we hypothesized that PMAs would display distinctive imaging characteristics. We retrospectively reviewed the imaging findings in a large number of patients with PMA to identify these characteristics.

MATERIALS AND METHODS

CT and MR images, pathology reports, and clinical information from 21 patients with pathology-confirmed PMA from 7 institutions were retrospectively reviewed. CT and MR imaging findings, including location, size, signal intensity, hemorrhage, and enhancement pattern, were tabulated.

RESULTS

Patients ranged in age from 9 months to 46 years at initial diagnosis. Sex ratio was 12:9 (M/F). Twelve of 21 (57%) tumors were located in the hypothalamic/chiasmatic/third ventricular region. Nine (43%) occurred in other locations, including the parietal lobe (2/21), temporal lobe (2/21), cerebellum (2/21), basal ganglia (2/21), and fourth ventricle (1/21). Ten (48%) tumors showed heterogeneous rim enhancement, 9 (43%) showed uniform enhancement, and 2 (9%) showed no enhancement. Five (24%) masses demonstrated intratumoral hemorrhage.

CONCLUSION

This series expands the clinical and imaging spectrum of PMA and identifies characteristics that should suggest consideration of this uncommon diagnosis. One third of patients were older children and adults. Almost half of all tumors were located outside the typical hypothalamic/chiasmatic region. Intratumoral hemorrhage occurred in one quarter of patients. PMA remains a histologic diagnosis without definitive imaging findings that distinguish it from PA.

Intracranial neurenteric cysts: imaging and pathology spectrum

BACKGROUND AND PURPOSE

Intracranial neurenteric (NE) cysts are rare congenital lesions that may be mistaken for other, more common non-neoplastic cysts as well as cystic neoplasms. We delineate the imaging spectrum, pathologic findings, and differential diagnosis of NE cysts.

METHODS

History, imaging, surgical and pathologic findings were analyzed retrospectively in 18 patients with intracranial NE cysts. Fifteen were surgically proved cases; 3 exhibited classic imaging findings and are being followed clinically.

RESULTS

Thirteen cysts were located in the posterior fossa; 12 of 13 were extra-axial. Size varied from 1.2 x 0.8 x 0.6 cm to 3.4 x 3 x 2.5 cm. Five were supratentorial, measuring from 7 x 5 x 3 to 9 x 6 x 7 cm. All were frontal and off the midline. Seven of 18 patients had CT scans. Cysts varied widely in attenuation. None enhanced. Eighteen of 18 had MR images. Sixteen of 18 were hyperintense, and 2 were isointense to CSF on T1-weighted imaging. Sixteen of 18 were hyperintense on T2-weighted imaging. All cysts were hyperintense to CSF on fluid-attenuated inversion recovery (FLAIR) sequences. Diffusion imaging was performed on 2 patients. One case showed mild restriction. Mild posterior rim enhancement was seen in 5 cases at the site where the cyst adhered to brain parenchyma.

CONCLUSION

The imaging spectrum for NE cysts is broader than previously reported. Intracranial NE cysts should be considered in the differential diagnosis for intracranial extra axial cystic lesions both above and below the tentorium.

Reversible leukoencephalopathy associated with cerebral amyloid angiopathy

The authors describe three patients with reversible leukoencephalopathy associated with cerebral amyloid angiopathy (CAA). Rapid progression of neurologic symptoms was followed by dramatic clinical and radiographic improvement. Pathologically, CAA was associated with varying degrees of inflammation ranging from none to transmural granulomatous infiltration. In the appropriate clinical context, the MRI finding of lobar white matter edema with evidence of prior hemosiderin deposition may indicate the presence of a reversible CAA leukoencephalopathy.

Office of Rare Diseases neuropathologic criteria for corticobasal degeneration

A working group supported by the Office of Rare Diseases of the National Institutes of Health formulated neuropathologic criteria for corticobasal degeneration (CBD) that were subsequently validated by an independent group of neuropathologists. The criteria do not require a specific clinical phenotype, since CBD can have diverse clinical presentations, such as progressive asymmetrical rigidity and apraxia, progressive aphasia, or frontal lobe dementia. Cortical atrophy, ballooned neurons, and degeneration of the substantia nigra have been emphasized in previous descriptions and are present in CBD, but the present criteria emphasize tau-immunoreactive lesions in neurons, glia, and cell processes in the neuropathologic diagnosis of CBD. The minimal pathologic features for CBD are cortical and striatal tau-positive neuronal and glial lesions, especially astrocytic plaques and thread-like lesions in both white matter and gray matter, along with neuronal loss in focal cortical regions and in the substantia nigra. The methods required to make this diagnosis include histologic stains to assess neuronal loss, spongiosis and ballooned neurons, and a method to detect tau-positive neuronal and glial lesions. Use of either the Gallyas silver staining method or immunostains with sensitive tau antibodies is acceptable. In cases where ballooned neurons are sparse or difficult to detect, immunostaining for phospho-neurofilament or alpha-B-crystallin may prove helpful. Methods to assess Alzheimer-type pathology and Lewy body pathology are necessary to rule out other causes of dementia and Parkinsonism. Using these criteria provides good differentiation of CBD from other tauopathies, except frontotemporal dementia and Parkinsonism linked to chromosome 17, where additional clinical or molecular genetic information is required to make an accurate diagnosis.

Alzheimer's disease

In this case study, we describe the symptoms, neuropsychological testing, and brain pathology of a man with Alzheimer's disease (AD). AD commonly presents with impairment of memory and language function. In this case, language difficulties were noted more prominently than was memory impairment. Throughout the limbic system and neocortex of the patient were large numbers of senile plaques and neurofibrillary tangles, the pathological hallmarks of AD.

Cortical basal ganglionic degeneration

In this case study, we describe the symptoms, neuropsychological testing, and brain pathology of a retired mason's assistant with cortical basal ganglionic degeneration (CBGD). CBGD is an extremely rare neurodegenerative disease that is categorized under both Parkinsonian syndromes and frontal lobe dementias. It affects men and women nearly equally, and the age of onset is usually in the sixth decade of life. CBGD is characterized by Parkinson's-like motor symptoms and by deficits of movement and cognition, indicating focal brain pathology. Neuronal cell loss is ultimately responsible for the neurological symptoms.

Amyotrophy in prion diseases

Amyotrophic lateral sclerosis was once thought to be caused by persistent viral infection, partly because some patients with transmissible Creutzfeldt-Jakob disease showed prominent amyotrophy. However, in the past 15 years there has been little interest in the amyotrophy in prion diseases, and the possible link to amyotrophic lateral sclerosis has been eschewed. We analyzed case reports of prion disease published after 1968 for evidence of amyotrophy. We defined amyotrophy as clinically evident fasciculation buttressed by electromyographic results in some cases. We sought evidence of motor neuron degeneration at autopsy. Prion disease was proved by transmissibility, immunohistochemistry demonstration of protease-resistant prion protein, or finding a mutation in the prion protein gene. Amyotrophy was noted in 27 patients: 13 with sporadic Creutzfeldt-Jakob disease, 2 with familial Creutzfeldt-Jakob disease, and 12 with Gerstmann-Sträussler-Scheinker disease. Of the 27, 23 showed clinical fasciculation and 10 had electromyographic evidence of denervation. The spinal cord was examined in 8 patients: 6 showed loss of motor neurons, 1 showed vacuolation of motor neurons, and 1 reported no abnormalities. Another 23 patients had typical histopathological characteristics but lacked molecular or biochemical proof of prion disease. The total number of patients with amyotrophy and proven prion disease that we identified was 50. This case review supports the belief that amyotrophy is occasionally a prominent feature of Creutzfeldt-Jakob disease and underscores the importance of documenting lower motor neuron function and the crucial role of examining the spinal cord at autopsy in cases of prion disease.

Mother with amyotrophic lateral sclerosis and daughter with Creutzfeldt-Jakob disease

OBJECTIVE

To describe a mother who had autopsy-proved amyotrophic lateral sclerosis and her daughter who had clinically diagnosed Creutzfeldt-Jakob disease.

DESIGN

Case reports with molecular genetic analyses.

SETTING

A tertiary care center.

PATIENTS

The mother had progressive upper and lower motor neuron symptoms and signs starting at the age of 54 years. Electrophysiological testing supported the diagnosis of amyotrophic lateral sclerosis. Autopsy results confirmed the diagnosis. Her daughter had received injections of human growth hormone prepared from pooled human pituitary glands as a child. At the age of 31 years, she experienced the onset of gait ataxia and dysarthria. Cerebrospinal fluid showed the 14-3-3 protein. Cognitive difficulties ensued. She progressed to a nearly akinetic and mute state. She had overt visible fasciculations and muscle atrophy in the legs.

MAIN OUTCOME MEASURES AND RESULTS

Neither patient carried a mutation in the prion protein gene. Both were homozygous for methionine at the polymorphic codon 129. Neither patient carried a deletion of the 5 exons of the superoxide dismutase 1 gene.

CONCLUSIONS

It is uncertain whether the 2 cases occurred in the same family by chance or whether the patients shared genetic risk factors for the 2 diseases. The possibility that homozygosity at codon 129 is a risk factor for amyotrophic lateral sclerosis is being tested in a case-control study.

A clinicopathological comparison of community-based and clinic-based cohorts of patients with dementia

OBJECTIVES

To compare the sensitivity and specificity of the clinical diagnosis of Alzheimer disease, the distribution of pathological causes, and the demographic and clinical characteristics of 2 different groups of patients with dementia.

DESIGN

Retrospective clinicopathological study.

SETTING

A memory disorder clinic in a university hospital and a multiethnic community.

PATIENTS

Sixty-three patients from a memory disorder clinic and 26 patients from a large community-based study who underwent autopsy after clinical evaluation.

MAIN OUTCOME MEASURES

Differential distribution of clinical and pathological findings, with clinicopathological correlations.

RESULTS

Clinic patients were younger at diagnosis, more educated, and more likely to be white. Of the 63 clinic patients we evaluated, 29 (46%) had a pathological diagnosis of definite AD, 15 (24%) had a diagnosis of mixed AD, and 19 (30%) had a diagnosis of another type of dementia. The pathological diagnoses in the community patients were distributed as follows: 6 (23%) had definite AD, 6 (23%) had mixed AD, 6 (23%) had cerebrovascular disease, and 8 (31%) had another type of dementia. The difference in distribution of pathological diagnoses between these 2 groups was only significant for cerebrovascular diseases. For patients seen at the clinic, the sensitivity of the clinical diagnosis of AD was 98% and the specificity was 84%; for the community group, the sensitivity was 92% and the specificity was 79%.

CONCLUSIONS

The difference in sensitivity and specificity of clinical diagnosis was not statistically significant between the groups of clinic patients and community patients. Dementia associated with cerebrovascular disease was more prevalent in the community sample. This difference may be attributable to clinical and demographic differences between the 2 groups.

Characterization of NF-L and betaIISigma1-spectrin interaction in live cells

Neurofilaments (NFs) are neuron-specific intermediate filaments (IFs) composed of three different subunits, NF-L, NF-M, and NF-H. NFs move down the axon with the slow component of axonal transport, together with microtubules, microfilaments, and alphaII/betaII-spectrin (nonerythroid spectrin or fodrin). It has been shown that alphaII/betaII-spectrin is closely associated with NFs in vivo and that betaII-spectrin subunit binds to NF-L filaments in vitro. In the present study we seek to elucidate the relationship between NF-L and betaII-spectrin in vivo. We transiently transfected full-length NF-L and carboxyl-terminal deleted NF-L mutants in SW13 Cl.2 Vim- cells, which lack an endogenous IF network and express alphaII/betaIISigma1-spectrin. Double-immunofluorescence and electron microscopy studies showed that a large portion of betaIISigma1-spectrin colocalizes with the structures formed by NF-L proteins. We found a similar association between NF-L proteins and actin. However, coimmunoprecipitation experiments in transfected cells and the yeast two-hybrid system results failed to demonstrate a direct interaction of NF-L with betaIISigma1-spectrin in vivo. The presence of another protein that acts as a bridge between the membrane skeleton and neurofilaments or modulating their association may therefore be required.

The natural history of CADASIL: a pooled analysis of previously published cases

BACKGROUND AND PURPOSE

Although numerous families with cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) have been reported, our understanding of the disease remains incomplete. Thus, we performed this study to investigate the phenotypic range and natural history of CADASIL.

METHODS

We performed a pooled analysis of previously published cases.

RESULTS

We identified 105 symptomatic patients in 33 families. Vascular risk factors were uncommon, with hypertension reported in only 8 patients. The mean age of symptom onset was 36. 7+/-12.9 years. Stroke or transient ischemic attack was an initial symptom in 45 patients, with a mean age of onset of 41.2+/-9.2 years. Migraine was also a common initial symptom, reported by 42 patients at a younger mean age of 28.3+/-11.7 years. Other initial symptoms included depression in 9 patients, cognitive impairment in 6 patients, and seizures in 3 patients. Regarding clinical course, 71 patients experienced a stroke or transient ischemic attack, and 52 of those patients had 1 or more recurrent ischemic events. Dementia was reported in 44 patients. Only 3 additional patients experienced migraine at a later time, while 13 additional patients developed depression. Six patients had seizures. Twenty-two of the 105 patients had died, with a mean age of death of 54.8+/-10.6 years. Nineteen of those 22 patients had experienced a stroke or transient ischemic attack and 19 patients were demented.

CONCLUSIONS

CADASIL typically becomes evident in early or middle adulthood with migraine or an ischemic event, later manifests itself through recurrent subcortical ischemic strokes leading to a stepwise decline and dementia, and results in reduced survival.

Prospective magnetic resonance imaging identification of focal cortical dysplasia, including the non-balloon cell subtype

The purpose of this study was to determine the role of high-resolution T2-weighted fast multiplanar inversion-recovery (FMPIR) magnetic resonance (MR) imaging in detecting and delineating microscopic focal cortical dysplasia (FCD). We performed MR scans with FMPIR on 42 patients with suspected neocortical epilepsy. Ten MR studies were read prospectively as showing FCD; these case histories, electroencephalographic studies, and neuroimaging data were reviewed. Eight of these patients subsequently underwent focal cortical resection guided by intraoperative electrocorticography. The MR findings were correlated with pathological findings in these 8 patients. For purposes of radiological-pathological correlation, the FCD lesions were divided into two classes. Radiological classification was based on the absence (type A) or presence (type B) of T2 prolongation of the subcortical white matter. Pathological grading as type I or type II was based on a previously described pathological grading system. Specific MR findings associated with FCD included focal blurring of the gray-white matter interface (n = 9), thickening of the cortical ribbon (n = 7), and T2 prolongation of the subcortical white matter (n = 4). In 3 patients, the only MR finding that suggested FCD was localized blurring of the gray-white matter junction. In 2 of these 3 patients, the MR diagnosis of FCD could be made only by FMPIR. FCD was confirmed histologically in 7 of 8 patients, with insufficient tissue for complete histopathological evaluation in 1 case. Radiological classification of FCD agreed with pathological classification in 5 of 7 cases. Correlation of MR findings with intraoperative electrocorticography results indicated that the MR study localized the epileptogenic lesion correctly in 8 of 8 cases. Scalp ictal electroencephalographic studies localized the epileptogenic lesion in 5 of 8 cases; positron emission tomographic scans were focally abnormal in 3 of 3 cases. FMPIR MR imaging permitted accurate diagnosis and localization of FCD in all patients with pathologically proved FCD. MR identification of FCD aided presurgical planning and intraoperative management of these patients.

CADASIL in a North American family: clinical, pathologic, and radiologic findings

OBJECTIVE

To expand the reported phenotypic range of cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL).

BACKGROUND

Despite numerous patient reports, our knowledge of the phenotypic range of CADASIL remains incomplete.

METHOD

We performed clinical, pathologic, and radiologic examinations on members of a family with CADASIL.

RESULTS

The proband is a 61-year-old man with a history of migraine and depression who has experienced multiple subcortical infarctions resulting in a stepwise decline. Neuropsychological testing documented a dementia syndrome with frontal lobe features and neurologic examination noted a left hemiparesis and a right-sided palmomental reflex. Brain biopsy with light microscopy revealed a nonatherosclerotic small-vessel angiopathy with periodic acid-Schiff positive granular changes in the media and white matter gliosis, with unremarkable cortex. Genetic testing confirmed a Notch3 mutation. The proband's first cousin has a history of depression, one seizure possibly resulting from an acute stroke, and a learning disorder. Neuropsychological testing demonstrated deficits in executive function and neurologic examination noted persistent extraneous adventitial movements, poor coordination, and primitive reflexes. Skin biopsy with electron microscopy demonstrated granular osmiophilic material within the basement membrane of vascular smooth muscle cells, which is considered to be pathognomonic of CADASIL. The proband's older son and younger son have histories of migraine and depression, respectively, and both also had learning disorders. MRI revealed diffuse white matter disease extending into the temporal lobes, and lacunar infarctions in these four nonhypertensive patients. Other family members have experienced migraine, recurrent stroke, dementia, and depression.

CONCLUSIONS

CADASIL is a genetic basis for vascular dementia that may be manifest earlier in life than previously reported.

Assembly properties of amino- and carboxyl-terminally truncated neurofilament NF-H proteins with NF-L and NF-M in the presence and absence of vimentin

To understand the assembly characteristics of the high-molecular-weight neurofilament protein (NF-H), carboxyl- and amino-terminally deleted NF-H proteins were examined by transiently cotransfecting mutant NF-H constructs with the other neurofilament triplet proteins, low- and middle-molecular-weight neurofilament protein (NF-L and NF-M, respectively), in the presence or absence of cytoplasmic vimentin. The results confirm that NF-H can coassemble with vimentin and NF-L but not with NF-M into filamentous networks. Deletions from the amino-terminus show that the N-terminal head is necessary for the coassembly of NF-H with vimentin, NF-L, or NF-M/vimentin. However, headless NF-H or NF-H from which the head and a part of the rod is removed can still incorporate into an NF-L/vimentin network. Deletion of the carboxyl-terminal tail of NF-H shows that this region is not essential for coassembly with vimentin but is important for coassembly with NF-L into an extensive filamentous network. Carboxyl-terminal deletion into the alpha-helical rod results in a dominant-negative mutant, which disrupts all the intermediate filament networks. These results indicate that NF-L is the preferred partner of NF-H over vimentin and NF-M, the head region of NF-H is important for the formation of NF-L/NF-H filaments, and the tail region of NF-H is important to form an extensive network of NF-L/NF-H filaments.

Reversible signal abnormalities in the hippocampus and neocortex after prolonged seizures

PURPOSE

To investigate the phenomenon of reversible increased signal intensity of medial temporal lobe structures and cerebral neocortex seen on MR images of six patients with recent prolonged seizure activity.

METHODS

After excluding patients with known causes of reversible signal abnormalities (such as hypertensive encephalopathy), we retrospectively reviewed the clinical findings and MR studies of six patients whose MR studies showed reversible signal abnormalities. MR pulse sequences included T2-weighted spin-echo coronal views or conventional short-tau inversion-recovery coronal images of the temporal lobes.

RESULTS

All six MR studies showed increased signal intensity within the medial temporal lobe, including the hippocampus in five studies. All follow-up MR examinations showed partial or complete resolution of the hyperintensity within the medial temporal lobe and the neocortex. In one patient, results of a brain biopsy revealed severe cerebral cortical gliosis. Temporal lobectomy performed 4 years later showed moderate cortical gliosis and nonspecific hippocampal cell loss and gliosis.

CONCLUSION

Significant hyperintensity within the temporal lobe is demonstrable on MR images after prolonged seizure activity, suggestive of seizure-induced edema or gliosis. Damage to medial temporal lobe structures by prolonged seizure activity indicates a possible mechanism of epileptogenic disorders.

Translation initiation and assembly of peripherin in cultured cells

The peripherin gene has three potential ATG translation initiation sites at positions 38, 56, and 290. The second ATG has been proposed to be the initiation codon used for translation of the protein, but there is no experimental evidence for this conjecture. We have isolated a full-length peripherin cDNA (designated as p61-11) from a rat brain cDNA library. Upon sequencing, we found that this cDNA contains a point mutation at the second potential translation initiation codon, which changes this ATG to ACG. When expressed in SW13 cl.2 vim- cells, a cell line without any detectable cytoplasmic intermediate filaments, the protein product of p61-11 cannot form a filamentous network and the major product is 45 kDa in size, which is most likely initiated from the third ATG. The protein product from the first ATG (57 kDa in size) of p61-11 is also detected albeit in smaller amounts. We introduced a frame-shift mutation upstream of the third ATG in p61-11 to create p61-11FS and showed that the third ATG is able to initiate translation efficiently even in the presence of the first ATG, and the 45 kDa protein leads to a diffuse nonfilamentous staining pattern in vim- cells confirming that the first ATG may not be the preferred translation initiation codon, since it cannot suppress a downstream ATG. We increased the translation efficiency from the first ATG of p61-11 by mutating the three nucleotides preceding this first ATG and thereby placing it in a better Kozak consensus sequence for translation initiation. The resulting 57 kDa protein is able to form a filamentous network in vim- cells. We corrected the mutation in the original p61-11 by polymerase chain reaction and generated two peripherin constructs: perM1M2 (which contains all three translation initiation codons) and per delta 1M2 (the first ATG is deleted, but the other two are present). When transfected, their protein products, about 57 kDa in size, form filamentous networks in the absence of other cytoplasmic intermediate filaments. Since there is no 45 kDa protein detected for these latter two constructs, it is reasonable to conclude that in the presence of the second ATG, little or no translation is initiated from the third ATG. Taken together, these results strongly suggest that the second ATG is the preferred translation initiation codon for the peripherin gene.

Migration of newly generated neurons upon ependymally derived radial guide cells in explant cultures of the adult songbird forebrain

The adult songbird forebrain undergoes neuronal production throughout adulthood, with the production of new neurons in discrete regions of the neostriatal ventricular zone. Upon mitogenesis, these new neurons migrate into the subjacent brain parenchyma along radially directed guide fibers. In long-term ventricular zone explant cultures, derived from the higher vocal center of the adult canary, newly migratory neurons were found to associate preferentially with a characteristic substrate cell type. These small, parvonuclear substrate cells formed tightly packed epithelioid sheets, in which ciliated ependymal cells were common, as recognized by both live observation and electron microscopy. A subpopulation of these cells was immunostained by monoclonal antibody 3A7, which preferentially stains the guide fiber network of the adult avian brain. These 3A7+ cells included ependymal cells and bipolar radial cells, as well as morphologically defined astrocytes. As they matured in vitro, the 3A7+ bipolar radial cells extended long, unbranching fibers, which ultimately traversed the culture substrate. Like ependymal cells, they supported neuronal migration. These cells were likely homologous to radial guide cells in vivo. Thus, neuronal migration in adult avian forebrain culture occurred upon guide cells of ependymal derivation.

Characterization of a panel of neurofilament antibodies recognizing N-terminal epitopes

Peptides corresponding to sequences from the amino-terminal "head" regions of the low, middle, and high molecular weight neurofilament proteins (NF-L, NF-M, and NF-H) were synthesized by a modification of the Merrifield solid-phase method, and a panel of polyclonal antibodies to these epitopes were prepared in rabbits by the injection of synthetic peptides conjugated to the carrier protein keyhole limpet hemocyanin (KLH). An additional, monoclonal antibody recognizing both glial fibrillary acidic protein (GFAP) and vimentin was also produced, by fusion of cells of the mouse myeloma line NS-1 with spleen cells from a mouse immunized with cytoskeletal extracts. Antibody specificities were confirmed by a combination of Western blotting against cytoskeletal extracts and immunofluorescence using both rat brain sections and fibroblasts transfected with fully encoding cDNAs for each neurofilament protein, driven by viral promoters.

Molecular diversity of marine glues: polyphenolic proteins from five mussel species

Adhesive polyphenolic proteins have been purified and characterized from the feet of five marine mussels (Brachidontes exustus, Modiolus modiolus squamosus, Mytella guyanensis, Septifer bifurcatus, and Trichomya hirsuta). All five proteins contain high levels of 3,4-dihydroxyphenylalanine (DOPA), lysine, glycine, and serine or threonine. All but B. exustus also contain high levels (> or = 10%) of proline or 4-hydroxyproline. The polyphenolic proteins of all the mussels have repeated sequences of the motif X1-Y*-X2-Y*-X3-K, where Y* denotes tyrosine or DOPA. In two species (S. bifurcatus and B. exustus), X2 represents 3 amino acids (frequently glycine) and X3 is absent. M. guyanensis is similar except that X2 is reduced to 2 amino acids. In T. hirsuta and M. m. squamosus, however, X2 is absent and X3 occurs as alanine or hydroxyproline. All proteins share approximately equimolar proportions of tyrosyl- and lysyl-derived residues. Although all of the mussels examined thus far are adhesively opportunistic with respect to substratum type, a rigidly invariant sequence does not appear to be necessary for achieving this.

Effects of truncated neurofilament proteins on the endogenous intermediate filaments in transfected fibroblasts

The expression and assembly characteristics of carboxyl- and amino-terminal deletion mutants of rat neurofilament low Mr (NF-L) and neurofilament middle Mr (NF-M) proteins were examined by transient transfection of cultured fibroblasts. Deletion of the carboxyl-terminal tail domain of either protein indicated that this region was not absolutely essential for co-assembly into the endogenous vimentin cytoskeleton. However, deletion into the alpha-helical rod domain resulted in an inability of the mutant proteins to co-assemble with vimentin into filamentous structures. Instead, the mutant proteins appeared to be assembled into unusual tubular-vesicular structures. Additionally, these latter deletions appeared to act as dominant negative mutants which induced the collapse of the endogenous vimentin cytoskeleton as well as the constitutively expressed NF-H and NF-M cytoskeletons in stably transfected cell lines. Thus, an intact alpha-helical rod domain was essential for normal IF co-assembly whereas carboxyl-terminal deletions into this region resulted in dramatic alterations of the existing type III and IV intermediate filament cytoskeletons in vivo. Deletions from the amino-terminal end into the alpha-helical rod region gave different results. With these deletions, the transfected protein was not co-assembled into filaments and the endogenous vimentin IF network was not disrupted, indicating that these deletion mutants are recessive. The dominant negative mutants may provide a novel approach to studying intermediate filament function within living cells.

Transfected rat high-molecular-weight neurofilament (NF-H) coassembles with vimentin in a predominantly nonphosphorylated form

A fully encoding cDNA for the high-molecular-weight rat neurofilament protein (NF-H) has been isolated from a lambda gt11 library, sequenced and subcloned into eukaryotic expression vectors. Sequence analysis shows that rat NF-H has an overall homology of 72 and 88% with human and mouse NF-H, respectively. The head and rod domains are almost entirely identical, and the divergences are due to differences in the long C-terminal extensions of the molecule. The consensus phosphorylation sequence for neurofilaments Lys-Ser-Pro (KSP) is present 52 times. The predicted molecular mass of the protein is 115 kDa, 42% lower than that observed by SDS-PAGE. Upon transfection into vimentin-containing fibroblasts, such as L tk-, L929, and 3T6 cells, NF-H is seen distributed with vimentin by light and electron microscopic examinations indicating that copolymers of NF-H and vimentin are formed in these cells. Only a negligible proportion of the cells is positive when stained with a number of antibodies directed against phosphorylated NF-H epitopes. This is in contrast with the middle molecular weight NF protein (NF-M) transfected into L tk- and L929 cells, which can readily be detected by antibodies against phosphorylated neurofilament epitopes. The mobilities of the transfected protein on 1- and 2-dimensional gels confirm that NF-H is predominantly in a nonphosphorylated form. These results indicate that phosphorylation of NF-H, but not NF-M, on the KSP sequence is due to protein kinases, which are not present in fibroblasts and are presumably NF-H specific. The stable NF-H-expressing cell lines can therefore be used to study these putative neurofilament kinases in vitro and in vivo.

Alpha-internexin, a novel neuronal intermediate filament protein, precedes the low molecular weight neurofilament protein (NF-L) in the developing rat brain

alpha-Internexin is a 66 kDa protein that copurifies with intermediate filaments (IF) from rat spinal cord and optic nerve. This protein is axonally transported in rat optic nerve along with the neurofilament triplet proteins in slow component a. Polymerization in vitro and distribution in vivo confirm that alpha-internexin is a neuronal IF. We raised 2 highly specific monoclonal antibodies to alpha-internexin which were applied to frozen rat brain sections and Western blots of cytoskeletal extracts. These results indicate that alpha-internexin is primarily an axonal protein found in most, if not all, neurons of the CNS. Immunoreactive proteins of similar molecular weight were found in cytoskeletal extracts of CNS tissue from several additional species, including mouse and cow. While the distribution of alpha-internexin as given by immunocytochemical methods is similar to that of low molecular weight neurofilament protein (NF-L) in the adult, its distribution in the embryo is far more extensive. At embryonic day 16, when the expression of NF-L is still limited to a relatively small number of cells and levels of expression are low, alpha-internexin is already found at much higher levels and in cells not yet expressing NF-L in detectable quantities. Similar results are found at embryonic day 12. These data suggest that neuronal IF in the developing nervous system contain a higher proportion of alpha-internexin than their adult counterparts, and that expression of alpha-internexin precedes that of NF-L in many or most neurons of the developing brain.

Expression of rat neurofilament proteins NF-L and NF-M in transfected non-neuronal cells

Two cDNA clones fully encoding the rat neurofilament proteins NF-L and NF-M were subcloned into eukaryotic expression vectors behind the strong constitutive viral promoters from SV40 and Rous sarcoma viruses. Transient transfection of L tk- and Cos cell lines with these expression constructs resulted in cells expressing the neurofilament proteins in an intermediate filament-type pattern. Additionally, a putative juxtanuclear organizing center or region was observed in the transfected cells, most noticeable shortly after the transfection procedure. Stable transfections were performed on mouse L tk- and Swiss 3T6 cells using NF-L and NF-M constructs bearing an SV40 early promoter driven neomycin selectable marker. Although G418-resistant clones were recovered with both the NF-L and the NF-M constructs, only clones expressing immunofluorescently stainable amounts of NF-M were detected and established. Immunoelectron microscopic analysis revealed NF-M and vimentin proteins to be colocalized on the same intermediate filaments.

Complete amino acid sequence and in vitro expression of rat NF-M, the middle molecular weight neurofilament protein

A lambda gtII expression library was prepared from rat brain and screened with a polyclonal antiserum, which recognizes both NF-H and NF-M. An NF-M cDNA clone (pNF-M3C = 1.6 kb) was isolated and characterized. The fusion protein of NF-M3C, when used as an affinity matrix for the anti-neurofilament serum, isolated a subpopulation of antibodies specific for NF-M. Northern analysis demonstrates a single band of approximately 3000 nt and a constant message level for NF-M during postnatal development from postnatal day 0 (PO) to adulthood. Using pNF-M3C as a probe, a second cDNA clone was isolated from a lambda gtII rat brain expression library (pNF-M2D = 2.7 kb). The 2 clones were sequenced and pNF-M2D was found to encode the entire rat NF-M protein. The calculated molecular weight is 95,600, which is only 65% of the molecular weight determined by SDS-PAGE. The amino acid sequence of rat NF-M shows the conserved rod segment present in all intermediate filament proteins. The molecule also contains an unusual C-terminal extension with stretches of glutamic acid, which could contribute to the anomalous migration of this protein on SDS-PAGE and the fact that NF-M does not readily assemble into filaments. The pNF-M2D clone was transcribed and translated in vitro utilizing a rabbit reticulocyte lysate system. The resulting radiolabeled translation products were unexpectedly shown to comigrate with purified rat NF-M on 1- and 2-dimensional gels, even though the translated protein is not phosphorylated.

beta-Internexin, a ubiquitous intermediate filament-associated protein

In this article we show a Triton-insoluble, intermediate filament-associated protein of approximately 70 kD to be expressed ubiquitously in diverse mammalian cell types. This protein, assigned the name beta-internexin, exhibits extreme homology in each of the various cell lines as demonstrated by identical limited peptide maps, similar mobilities on two-dimensional gels, and detection in Triton-soluble and -insoluble extracts. beta-Internexin also shares some degree of homology with alpha-internexin, an intermediate filament-associated protein isolated and purified from rat spinal cord, which accounts for the immunologic cross-reactivity displayed by these polypeptides. Light microscopic immunolocalization of beta-internexin with a monoclonal antibody (mAb-IN30) reveals it to be closely associated with the vimentin network in fibroblasts. The antigen is also observed to collapse with the vimentin reticulum during the formation of a juxtanuclear cap induced by colchicine treatment. Ultrastructural localization, using colloidal gold, substantiates the affinity of beta-internexin for cytoplasmic filaments and, in addition, demonstrates its apparent exclusion from the intranuclear filament network. We examine also the resemblance of beta-internexin to a microtubule-associated polypeptide and the constitutively synthesized mammalian heat shock protein (HSP 68/70).

Monoclonal antibodies to epitopes on different regions of the 200 000 dalton neurofilament protein. Probes for the geometry of the filament

Neurofilaments in mammalian nervous tissues have three subunit proteins. These subunit proteins have apparent molecular masses of 200 (NF200), 150 (NF150) and 68 (NF68) kD. Biochemical assembly studies have indicated that the NF68 protein forms the core of the filament and that the other two proteins are associated proteins. Electron microscopy immunolocalization studies have been performed previously on isolated filaments and on filaments from neurons in culture, and have confirmed the localization of NF68 as a core filament protein and NF200 as a peripheral protein. We have raised two monoclonal antibodies to the NF200 components. Using immunogold labelled protein A, we have been able to localize these antibodies to tissue sections of adult cerebellum at the EM level. With this method, we have found that one of the monoclonal antibodies (NF2) shows a linear arrangement of gold particles directly on the filament, whereas the second monoclonal antibody (NF111) reacts with the filaments to give a periodic arrangement of gold particles. By immunoblotting against chymotryptic fragments of the NF200 protein, we have found that the mAB-NF111 reacts solely with a 160 kD piece, whereas the other monoclonal antibody reacts with both the 160 kD piece and the 40 kD piece. The latter piece was shown to be associated to the filament by binding studies with iodinated NF68. Thus the EM localization studies and the biochemical studies indicate that the two monoclonal antibodies react with different parts of the NF200 molecule, one binding to a part of the molecule which is located closer to the filament, and one to a more peripheral part of the molecule.

Size-variant pp60src proteins of recovered avian sarcoma viruses interact with adhesion plaques as peripheral membrane proteins: effects on cell transformation

We have shown previously that the membrane association of the src proteins of recovered avian sarcoma viruses (rASVs) 1702 (56 kilodaltons) and 157 (62.5 kilodaltons), whose size variations occur within 8 kilodaltons of the amino terminus, is salt sensitive and that, in isotonic salt, these src proteins fractionate as soluble cytoplasmic proteins. In contrast, wild-type Rous sarcoma virus pp60src behaves as an integral plasma membrane protein in cellular fractionation studies and shows prominent membrane interaction by immunofluorescence microscopy. In this study we have examined the distribution of these size-variant src proteins between free and complexed forms, their subcellular localization by immunofluorescence microscopy, and their ability to effect several transformation-related cell properties. Glycerol gradient sedimentation of extracts from cells infected either with rASV 1702 or rASV 157 showed that soluble src proteins of these viruses were distributed between free and complexed forms as has been demonstrated for wild-type Rous sarcoma virus pp60src. Pulse-chase studies with rASV pp60src showed that, like wild-type Rous sarcoma virus pp60src, it was transiently found in a complexed form. Indirect immunofluorescence showed that size-variant pp60src proteins are localized in adhesion plaques and regions of cell-to-cell contact in rASV 1702- or 157-infected cells. This result is in contrast with the generalized localization of pp60src in plasma membranes of control rASV-infected cells which produce pp60src. Chicken embryo fibroblasts infected by rASVs 1702 and 157 display a partial-transformation phenotype with respect to (i) transformation-related morphology, (ii) cell surface membrane changes, and (iii) retained extracellular fibronectin. It is possible that the induction of a partial-transformation phenotype may be the result of the unique interaction of the src proteins encoded by these viruses with restricted areas of the plasma membrane.

Independent hospital dialysis in Brunei

In establishing a chronic haemodialysis unit in Brunei the difficulties encountered were less insuperable than had been expected. Quite unsophisticated patients successfully dialysed unattended in some cases, or with minimal supervision in others.