Localized phosphorylation of vimentin by rho-kinase in neuroblastoma N2a cells

BACKGROUND

Vimentin, which is one of the intermediate filaments, is the major cytoskeletal component in developing neurones or neuroblastoma cells. Rho-associated kinase (Rho-kinase), is rich in neurones and is found downstream of Rho. It is involved in the agonist-induced neurite retraction of neuronal cells, and phosphorylates vimentin at Ser-38 and Ser-71 resulting in in vitro disassembly of the filaments.

RESULTS

We have investigated the distribution of vimentin phosphorylated by Rho-kinase in N2a neuroblastoma cells using site-specific phosphorylation-dependent antibodies. TM71 immunoreactivity, which specifically indicates Ser-71 phosphorylation on vimentin, was found in some neurites of dibutyryl cAMP-differentiated N2a cells. Transfection of the constitutively active form of Rho-kinase, CAT, significantly elevated TM71 immunoreactivity, and induced neurite retraction or cell rounding. Conversely, transfection of the dominant negative form of Rho-kinase, RB/PH(TT), or treatment of 10 microM Y-27632, a Rho-kinase specific inhibitor, abolished TM71 immuno-reactivity, and induced irregular neurite outgrowth. In contrast, 20 nM okadaic acid (OA) induced neurite retraction and specifically elevated TM71 immunoreactivity. In the OA-induced neurite retraction, tubulin disappeared in retracting neurites, where vimentin and actin remained co-localized. Furthermore, the OA-induced elevation of TM71 immunoreactivity and neurite retraction were completely blocked by pretreatment with 10 microM Y-27632, or by the ectopic expression of RB/PH(TT).

CONCLUSIONS

This study suggests that the localized phosphorylation of vimentin by Rho-kinase in neurites was closely related with the cellular morphology of N2a cells, and that the Rho-kinase activity towards vimentin was balanced with OA-sensitive phosphatases.

Results of patch testing with lavender oil in Japan

We report the annual results of patch testing with lavender oil for a 9-year period from 1990 to 1998 in Japan. Using Finn Chambers and Scanpor tape, we performed 2-day closed patch testing with lavender oil 20% pet. on the upper back of each patient suspected of having cosmetic contact dermatitis. We compared the frequency of positive patch tests to lavender oil each year with those to other fragrances. We diagnosed contact allergy when patch test reactions were + or <+ at 1 day after removal. The positivity rate of lavender oil was 3.7% (0-13.9%) during the 9-year period from 1990 to 1998. The positivity rate of lavender oil increased suddenly in 1997. Recently, in Japan, there has been a trend for aromatherapy using lavender oil. With this trend, placing dried lavender flowers in pillows, drawers, cabinets, or rooms has become a new fashion. We asked patients who showed a positive reaction to lavender oil about their use of dried lavender flowers. We confirmed the use of dried lavender flowers in 5 cases out of 11 positive cases in 1997 and 8 out of 15 positive cases in 1998. We concluded that the increase in patch test positivity rates to lavender oil in 1997 and 1998 was due to the above fashion, rather than due to fragrances in cosmetic products.

Phosphorylation of neurofilament-L during LTD

We recently reported that CaMKII-dependent phosphorylation of the neurofilament-L (NF-L) head domain was induced in the apical dendrites during long-term potentiation. Long-term depression (LTD) is another cellular model for neuronal plasticity. In the present study, we examined the phosphorylation of NF-L during hippocampal LTD using a series of phospho-specific antibodies against the NF-L head domain. During LTD, these antibodies visualized NF-L phosphorylation at Ser57 in the apical dendrites of the hippocampal pyramidal neurons. The assembly and disassembly of NF-L filaments are regulated by phosphorylation of its head domain. Thus, our results indicated that NF-L phosphorylation might be associated with alterations of the neuronal structure during LTD.

Functional differentiation in the human auditory and language areas revealed by a dichotic listening task

The human auditory cortex plays a special role in speech recognition. It is therefore necessary to clarify the functional roles of individual auditory areas. We applied functional magnetic resonance imaging (fMRI) to examine cortical responses to speech sounds, which were presented under the dichotic and diotic (binaural) listening conditions. We found two different response patterns in multiple auditory areas and language-related areas. In the auditory cortex, the medial portion of the secondary auditory area (A2), as well as a part of the planum temporale (PT) and the superior temporal gyrus and sulcus (ST), showed greater responses under the dichotic condition than under the diotic condition. This dichotic selectivity may reflect acoustic differences and attention-related factors such as spatial attention and selective attention to targets. In contrast, other parts of the auditory cortex showed comparable responses to the dichotic and diotic conditions. We found similar functional differentiation in the inferior frontal (IF) cortex. These results suggest that multiple auditory and language areas may play a pivotal role in integrating the functional differentiation for speech recognition.

Site-specific phosphorylation of neurofilament-L is mediated by calcium/calmodulin-dependent protein kinase II in the apical dendrites during long-term potentiation

Neurofilament-L (NF-L), one subunit of the neuronal intermediate filaments, is a major element of neuronal cytoskeletons. The dynamics of NF-L are regulated by phosphorylation of its head domain. The phosphorylation sites of the NF-L head domain by protein kinase A, protein kinase C, and Rho-associated kinase have been previously identified, and those by calcium/calmodulin-dependent protein kinase II (CaMKII) were identified in this study. A series of site- and phosphorylation state-specific antibodies against NF-L was prepared to investigate NF-L phosphorylation in neuronal systems. Long-term potentiation (LTP) is a cellular model of neuronal plasticity that is thought to involve the phosphorylation of various proteins. NF-L is considered a possible substrate for phosphorylation. During LTP stimulation of mouse hippocampal slices, the series of antibodies demonstrated the increase in the phosphorylation level of Ser(57) in NF-L and the visualization of the localized distribution of Ser(57) phosphorylation in a subpopulation of apical dendrites of the pyramidal neurons. Furthermore, Ser(57) phosphorylation during LTP is suggested to be mediated by CaMKII. Here we show that NF-L is phosphorylated by CaMKII in a subpopulation of apical dendrites during LTP, indicating that Ser(57) is a novel phosphorylation site of NF-L in vivo related to the neuronal signal transduction.

Quantitative blood velocity mapping in glomerular capillaries by in vivo observation with an intravital videomicroscope

We have evaluated rat glomerular microcirculation under in-vivo condition with an intravital videomicroscope. To measure erythrocyte velocities, a line segment was set along the glomerular capillaries in time-sequential videotaped images and then a spatiotemporal image was constructed along that segment. The angle of striped pattern in the spatiotemporal image which reflects the erythrocyte velocity, was estimated to compute erythrocyte velocity vector mapping. We found that erythrocyte velocities in rat glomeruli were significantly faster in diabetic rats than in control rats (p < 0.05). In conclusion, we have succeeded in quantitatively evaluating the in-vivo renal microcirculation with our videomicroscope system and by spatiotemporal image analyzing method.

Cardiac fibrosis in mice lacking brain natriuretic peptide

Cardiac fibrosis, defined as a proliferation of interstitial fibroblasts and biosynthesis of extracellular matrix components in the ventricles of the heart, is a consequence of remodeling processes initiated by pathologic events associated with a variety of cardiovascular disorders, which leads to abnormal myocardial stiffness and, ultimately, ventricular dysfunction. Brain natriuretic peptide (BNP) is a cardiac hormone produced primarily by ventricular myocytes, and its plasma concentrations are markedly elevated in patients with congestive heart failure and acute myocardial infarction. However, its precise functional significance has been undefined. In this paper, we report the generation of mice with targeted disruption of BNP (Nppb(-/-) mice). We observed multifocal fibrotic lesions in the ventricles from Nppb(-/-) mice. No signs of systemic hypertension and ventricular hypertrophy are noted in Nppb(-/-) mice. In response to ventricular pressure overload, focal fibrotic lesions are increased in size and number in Nppb(-/-) mice, whereas no focal fibrotic changes are found in wild-type littermates (Nppb(+/+) mice). This study establishes BNP as a cardiomyocyte-derived antifibrotic factor in vivo and provides evidence for its role as a local regulator of ventricular remodeling.

Tau protein is a potential biological marker for normal pressure hydrocephalus

A biological marker for normal pressure hydrocephalus (NPH) is beneficial for evaluation of its severity and of indications for shunt operation. Tau protein was initially considered as a biological marker in cerebrospinal fluid (CSF) from Alzheimer's patients. Recently, it has been demonstrated that degeneration in the brain causes elevation of tau in CSF. Therefore, the tau level in CSF from NPH patients was evaluated. Tau levels in CSF from NPH patients were significantly higher than that in controls. The tau levels were correlated with the severity of dementia, urinary incontinence, and gait disturbance in NPH. These results suggest that CSF tau may be useful as a biological marker for NPH to determine the level of neuronal degeneration.

Major phosphorylation site (Ser55) of neurofilament L by cyclic AMP-dependent protein kinase in rat primary neuronal culture

Ser55 of neurofilament L (NF-L) is reported to be partly phosphorylated in neurons and to be phosphorylated by cyclic AMP-dependent protein kinase (PKA). Bovine NF-L was phosphorylated by PKA in a low concentration of MgCl2 (0.3 mM) and digested by trypsin. Trypsin-digested fragments were assigned by MALDI/ TOF (matrix-assisted laser desorption and ionization/ time-of-flight) mass spectrometry. Phosphorylation sites were found at Ser41, Ser55, and Ser62 in the head region, with Ser55 considered the preferred site. A site-specific phosphorylation-dependent antibody against Ser55 rendered NF-L phosphorylated at Ser55 detectable in primary cultured rat neurons. One-hour treatment with 20 nM okadaic acid increased the phosphorylation level of Ser55, and co-treatment with 10 microM forskolin enhanced it. However, forskolin alone did not elevate the phosphorylation level. As a consequence, NF-L may be phosphorylated at Ser55 by PKA or by a PKA-like kinase in vivo; however, the phosphorylation level of Ser55 may be modulated by certain phosphatases sensitive to okadaic acid.

Amnesic confabulatory syndrome after focal basal forebrain damage

A 73-year-old woman developed amnesic confabulatory syndrome after a right focal basal forebrain hemorrhage. The confabulation, despite persistent antegrade amnesia, gradually subsided with improvement of the frontal executive function. The lesion appeared to disrupt connections of the medial and lateral limbic circuits important for memory. Simultaneous dysfunctioning of the two circuits involving the medial temporal and frontal lobes may be necessary for the development of this syndrome.

Unusually high reactivity of apolipoprotein B-100 among proteins to radical reactions induced in human plasma

Relative reactivities of proteins to radical reactions caused in human plasma were studied for the first time utilizing an immunoblotting assay. When radical reactions were caused by Cu(2+), apolipoprotein B-100 (apoB) underwent extensive fragmentation concurrently with the decrease in alpha-tocopherol, while human serum albumin (HSA) and transferrin (TF) were not decreased at all. When radical reactions were initiated by Cu(2+) with hydrogen peroxide or 2,2'-azobis(2-amidinopropane)dihydrochloride (AAPH), alpha-tocopherol and apoB were also decreased steadily but HSA and TF were not decreased. These observations indicate that apoB is extremely reactive, even comparable to alpha-tocopherol, towards radical reactions. These results also suggest that the radical reaction of apoB is a possible process in vivo and it is involved in atherogenesis along with low density lipoprotein lipid peroxidation, which has been studied extensively.

Quantitative analysis of neurofilament proteins in Alzheimer brain by enzyme linked immunosorbent assay system

The abnormality of cytoskeletal proteins is related to Alzheimer's disease. Because neurofilament proteins (NF) are major cytoskeletal components of neurones, abnormality of NF may be involved in the pathology of disease. In this study, insoluble NF in the grey matter of temporal lobes of Alzheimer and control brains were dissolved in a urea buffer and quantitatively measured by an enzyme linked immunosorbent assay system. No apparent quantitative changes of NF-L and NF-H were found between the Alzheimer and control brains, and there were also no significant differences in the mean molar ratio of NF-L to NF-H between them. However, the relative amount of phosphorylated NF-H in Alzheimer brains was increased in comparison with that in control brains. These results suggest that the increase of phosphorylated NF-H might be accompanied with Alzheimer's disease.

Distribution of Rho-kinase in the bovine brain

Rho-associated kinase (Rho-kinase) is a serine/threonine protein kinase downstream of the small GTPase Rho, which participates in signaling pathways of many cellular functions. Although Rho-kinase is implicated in the regulation of the morphology of neuronal cells, the distribution of Rho-kinase in the brain has not been elucidated yet. In this study, we investigated the distribution of Rho-kinase using three antibodies recognizing the different epitopes of Rho-kinase. Rho-kinase was abundantly expressed in the gray matter in comparison with the white matter. Strong immunoreactivity was observed in the pyramidal neurons of the cerebral cortex and hippocampus and in the Purkinje cells of the cerebellum. These results indicate that Rho-kinase is abundantly distributed in neurons and might play an important role in remodeling of neurites.

Renal expression of insulin-like growth factor-l in acute renal failure: a preliminary report

Renal expression of insulin-like growth factor-I (IGF-I) was examined in the specimens obtained at renal biopsy from five patients with acute renal failure (ARF) at the recovering phase. IGF-I peptide and mRNA were demonstrated in the cytoplasm of the epithelial cells of focal proximal tubules in four patients in whom renal function had been ameliorating. The stainings of IGF-I peptide and mRNA were intense in patients with favorable prognosis. Either IGF-I immunoreactivity or mRNA was not detected in the renal tissues in five cases with chronic renal insufficiency and four patients with renal carcinoma. Our preliminary findings suggest that IGF-I is locally produced in the kidney during the recovery period of ARF and might play roles in the repair processes, and extend the experimental observations in animal models into human pathophysiology.

Postencephalitic focal retrograde amnesia after bilateral anterior temporal lobe damage

BACKGROUND

Marked retrograde amnesia with no or almost no anterograde amnesia is rare. Recently, a combination of ventrolateral prefrontal and temporopolar cortical lesions has been suggested as the cause of such isolated or focal retrograde amnesia. It is also assumed that when the right-sided cortical structures are damaged, autobiographical episodic memories are affected.

OBJECTIVE

To search for new anatomic substrates for focal retrograde amnesia.

METHODS

We performed extensive neuropsychological tests and obtained detailed neuroimages on a 43-year-old woman who showed a severe, persistent retrograde amnesia but only a limited anterograde amnesia after probable herpes simplex encephalitis.

RESULTS

Tests of autobiographical memory revealed that she had a memory loss extending back to her childhood for both semantics and incidents; however, the ability to recall specific episodes appeared much more severely impaired than the ability to recall factual information about her past. The patient also showed profound impairments in recalling public memories; however, her scores improved nearly to a control level on forced-choice recognition memory tasks, although the recall of memories for a decade just before her illness remained mildly impaired. MRI revealed focal pathologies in the temporal poles and the anterior parts of the inferotemporal lobes on both sides, predominantly on the left, with some extension to the anterior parts of the medial temporal lobes. There was additional damage to the left insular cortex and its surrounding structures but no evidence of frontal lobe damage on MRIs or cognitive tests.

CONCLUSIONS

A profound retrograde amnesia may be produced by damage to the bilateral temporal poles and anterior inferotemporal lobes in the absence of frontal lobe pathologies, and a dense and persistent episodic old memory loss can arise even with a relatively small lesion in the right anterior temporal lobe if it is combined with extensive damage to the left.

Casein kinase II is responsible for phosphorylation of NF-L at Ser-473

Ser-473 is solely phosphorylated in vivo in the tail region of neurofilament L (NF-L). With peptides including the native phosphorylation site, it was not possible to locate responsible kinases. We therefore adopted full-length dephosphorylated NF-L as the substrate, and employed MALDI/TOF (matrix-assisted laser desorption and ionization/time of flight) mass spectrometry and a site-specific phosphorylation-dependent antibody recognizing Ser-473 phosphorylation. The antibody showed that casein kinase I (CK I) as well as casein kinase II (CK II) phosphorylated Ser-473 in vitro, while neither GSK-3beta nor calcium/calmodulin-dependent protein kinase II did so. However, the mass spectra of the tail fragments of the phosphorylated NF-L indicated that CK II was the kinase mediating Ser-473 phosphorylation in vitro as opposed to CK I, because CK I phosphorylated another site as well as Ser-473 in vitro. The antibody also demonstrated that NF-L phosphorylated at Ser-473 was abundant in the neuronal perikarya of the rat cortex, indicating that phosphorylation of Ser-473 may take place there. This result may support the suggestion that CK II is the kinase responsible for Ser-473 phosphorylation. Despite many reports showing that CK I mediates phosphorylation of neurofilaments, CK II may phosphorylate NF-L in vivo.

[A case report of dementia with cluttering-like speech disorder and apraxia of gait]

A 57-year-old woman presented with a slowly progressive gait disturbance in 1992 (53 years of age). Over the next year, she gradually began to talk less, but her speech itself became more rapid than before. He speech was frequently too fast even for family members to understand. In 1997, she was admitted to our hospital. On admission, the patient was disoriented but able to follow simple verbal commands, to name things, and to write simple words. Neither apraxia, aphasia, hemispatial neglect, nor a corpus callosum disconnection syndrome was observed. There was no muscle weakness or atrophy. She showed a positive Babinski sign with mild spasticity in the legs and Gegenhalten, but no rigidity. Her speech was monotonous and abnormally fast (cluttering-like speech). Her speech became faster and faster toward the end of sentences, skipping several syllables or even words. She was unable to speak slowly and clearly, even when efforts were made to pace her speech to the speed set by the examiner. She was able to stand only with a wide base of support and body flexion. When standing, she was unable to place one foot directly beside the other; as she tried to have one foot near the other, the former repelled the latter. She had great difficulties in taking her first step forward, and showed rapid freezing of gait even when she managed to succeed in starting. She was able to imitate walking or bicycling with her legs unloaded, indicating that her gait disturbance was a kind of apraxia of gait. Her intelligence was somehow difficult to assess because of her peculiar speech disturbance. However, her family members had noticed her memory disturbance and personality change (offensiveness) since 3 to 4 years before the admission. Moreover, she was defective not only on Hasegawa Damentia Scale-Revised but also on Raven's Colored Progressive Matrices which estimates non-verbal intelligence. It was also noted that she was inattentive and lazy in thinking on questionnaires. Thus we considered that she was at least mildly demented and the type of dementia was of frontal pathology. Laboratory data were all normal except for the head MRI, which demonstrated prominent and thinness of the corpus callosum from the anterior part of the body to splenium without any other brain lesions that could cause the thinness secondarily. Our case resembles two cases reported by Sunohara et al in 1985, together comprising a unique clinical feature. Although Sunohara et al did not refer to the thinness of the corpus callosum in their cases, the clinical profiles in our case and theirs raise the possibility that they form a new disease entity. A further study in a large number of similar cases, including autopsies will provide a conclusion.

Presenilin-2 mutation and polymorphism in Japanese Alzheimer disease patients

The Asn141Ile mutation of the presenilin 2 gene is responsible for familial early-onset Alzheimer disease found in Volga-German kindreds. However, the genetic influence of presenilin 2 gene on sporadic Alzheimer disease remains unknown. In this study, the frequency of the mutation and genetic association with the presenilin 2 locus were investigated in Japanese sporadic cases. The Asn141Ile mutation was not found in 88 cases of sporadic Alzheimer disease or 13 unrelated cases of familial Alzheimer disease. Fifty cases of late onset sporadic Alzheimer disease and 50 age-matched controls indicated no association with an exon 3 polymorphism of the presenilin 2 gene. These results indicate that the presenilin 2 mutation is not a major cause of Alzheimer disease.

Dynamic changes in corticospinal excitability during motor imagery

We investigated temporal changes in the amplitudes of motor-evoked potentials (MEPs) induced by transcranial magnetic stimulation over the left motor cortex during motor imagery. Nine subjects were instructed to imagine repetitive wrist flexion and extension movements at 1 Hz, in which the flexion timing was cued by a tone signal. Electromyographs (EMGs) were recorded from the first dorsal interosseous, flexor carpi radialis and extensor carpi radialis muscles of the right hand, and magnetic stimulation was delivered at 0, 250, 500 and 750 ms after the auditory cue. On average, the evoked EMG responses were larger in the flexor muscle during the phase of imagined flexion than during extension, whilst the opposite was true for the extensor muscle. There were no consistent changes in the amplitudes of MEPs in the intrinsic hand muscle (first dorsal interosseous). The EMG remained relaxed in all muscles and did not show any significant temporal changes during the test. The H-reflex in the flexor muscle was obtained in four subjects. There was no change in its amplitude during motor imagery. These observations lead us to suggest that motor imagery can have dynamic effects on the excitability of motor cortex similar to those seen during actual motor performance.

Acute in vivo effects of ACTH by exo utero microinjection on differentiation, steroidogenesis and proliferation of fetal mouse adrenocytes

Mouse embryos on embryonic day (E)13 or 14 were treated with ACTH1-24 by exo utero microinjection and the adrenal was examined after 16 and 32 h. Light microscopic morphometry showed that the ACTH treatment increased cell size and decreased cell density of the adrenocortical cells. Bromodeoxyuridine-labeling index did not alter significantly after the ACTH treatment. By immunohistochemistry, both number of cells expressing 11beta-hydroxylase and the staining intensity increased in the ACTH-treated glands compared to controls whereas expression of aldosterone synthase was detectable in neither the treated nor control groups. Ultrastructurally, the adrenocytes of the inner cortical zone of the ACTH-treated glands were characterized by strikingly increased content of the smooth endoplasmic reticulum, increased mitochondria with more vesicular cristae, lipid droplets with a much higher electron density along with the distribution altered from that in controls. All of the significant differences between the ACTH-treated and control glands occurred at 16 h but not at the 32 h interval. The present results indicated that the mouse fetal adrenocytes are already sensitive to ACTH during early period (E13 and 14) of their functional differentiation. In vivo acute treatment of ACTH stimulates cell-size, increase of fetal adrenocytes but not proliferation, and may directly or indirectly regulate multiple steps of the steroidogenic process of the fetal mouse adrenal.

Spatio-temporally regulated expression of receptor tyrosine kinases, mRor1, mRor2, during mouse development: implications in development and function of the nervous system

BACKGROUND

Drosophila neurospecific receptor tyrosine kinases (RTKs), Dror and Dnrk, as well as Ror1 and Ror2 RTKs, isolated from human neuroblastoma, have been identified as a structurally related novel family of RTKs (Ror-family RTKs). Thus far, little is known about the expression and function of mammalian Ror-family RTKs.

RESULTS

We have identified murine Ror-family RTKs, mRor1 and mRor2. Both mRor1 and mRor2 genes are induced upon neuronal differentiation of P19EC cells. During neuronal differentiation in vitro, the expression of mRor2 is transiently induced, although that of mRor1 increases continuously. During embryogenesis, the mRor1 gene is expressed in the developing nervous system within restricted regions and in the developing lens epithelium. The expression of mRor1 is sustained in the nervous system and is also detected in non-neuronal tissues after birth. In contrast, the expression of mRor2 is detected mainly in the developing nervous system within broader regions and declines after birth. Possible relationships of mRor1 and mRor2 genes with previously identified mutants have also been examined.

CONCLUSIONS

The developmental expressions of mRor1 and mRor2, in particular in the nervous system, are differentially regulated, reflecting their expression patterns in vitro. mRor1 and mRor2 may thus play differential roles during the development of the nervous system.

Rac1 is required for the formation of three germ layers during gastrulation

The Rac1, a member of the Rho family proteins, regulates actin organization of cytoskeleton and cell adhesion. We used genetic analysis to elucidate the role of Rac1 in mouse embryonic development. The rac1 deficient embryos showed numerous cell deaths in the space between the embryonic ectoderm and endoderm at the primitive streak stage. Investigation of the primary epiblast culture isolated from rac1 deficient embryos indicated that Rac1 is involved in lamellipodia formation, cell adhesion and cell migration in vivo. These results suggest that Rac1-mediated cell adhesion is essential for the formation of three germ layers during gastrulation.