Millimeter-sized belt-like pattern formation of actin filaments in solution by interacting with surface myosin in vitro.

The movements of single actin filaments along a myosin-fixed glass surface were observed under a conventional fluorescence microscope. Although random at a low concentration, moving directions of filaments were aligned by the presence of over 1.0 mg/mL of unlabeled filaments. We found that actin filaments when at the intermediate concentrations ranging from 0.1 to 1.0 mg/mL, formed winding belt-like patterns and moved in a two-directional manner along the belts. These patterns were spread over a millimeter range and found to have bulged on the glass in a three-dimensional manner. Filaments did not get closer than about 37.5 nm to each other within each belt-pattern. The average width and the curvature radius of the pattern did not apparently change even when the range of actin concentrations was between 0.05 and 1.0 mg/mL or the sliding velocity between 1.2 and 3.2 µm/sec. However, when the length of filaments was shortened by ultrasonic treatments or the addition of gelsolin molecules, the curvature radius became small from 100 to 60 µm. These results indicate that this belt-forming nature of actin filaments may be due to some inter-filament interactions.

Polymerization and depolymerization of actin with nucleotide states at filament ends.

Polymerization induces hydrolysis of ATP bound to actin, followed by γ-phosphate release, which helps advance the disassembly of actin filaments into ADP-G-actin. Mechanical understanding of this correlation between actin assembly and ATP hydrolysis has been an object of intensive studies in biochemistry and structural biology for many decades. Although actin polymerization and depolymerization occur only at either the barbed or pointed ends and the kinetic and equilibrium properties are substantially different from each other, characterizing their properties is difficult to do by bulk assays, as these assays report the average of all actin filaments in solution and are therefore not able to discern the properties of individual actin filaments. Biochemical studies of actin polymerization and hydrolysis were hampered by these inherent properties of actin filaments. Total internal reflection fluorescence (TIRF) microscopy overcame this problem by observing single actin filaments. With TIRF, we now know not only that each end has distinct properties, but also that the rate of γ-phosphate release is much faster from the terminals than from the interior of actin filaments. The rate of γ-phosphate release from actin filament ends is even more accelerated when latrunculin A is bound. These findings highlight the importance of resolving structural differences between actin molecules in the interior of the filament and those at either filament end. This review provides a history of observing actin filaments under light microscopy, an overview of dynamic properties of ATP hydrolysis at the end of actin filament, and structural views of γ-phosphate release.

Acceleration of the sliding movement of actin filaments with the use of a non-motile mutant myosin in in vitro motility assays driven by skeletal muscle heavy meromyosin.

We examined the movement of an actin filament sliding on a mixture of normal and genetically modified myosin molecules that were attached to a glass surface. For this purpose, we used a Dictyostelium G680V mutant myosin II whose release rates of Pi and ADP were highly suppressed relative to normal myosin, leading to a significantly extended life-time of the strongly bound state with actin and virtually no motility. When the mixing ratio of G680V mutant myosin II to skeletal muscle HMM (heavy myosin) was 0.01%, the actin filaments moved intermittently. When they moved, their sliding velocities were about two-fold faster than the velocity of skeletal HMM alone. Furthermore, sliding movements were also faster when the actin filaments were allowed to slide on skeletal muscle HMM-coated glass surfaces in the motility buffer solution containing G680V HMM. In this case no intermittent movement was observed. When the actin filaments used were copolymerized with a fusion protein consisting of Dictyostelium actin and Dictyostelium G680V myosin II motor domain, similar faster sliding movements were observed on skeletal muscle HMM-coated surfaces. The filament sliding velocities were about two-fold greater than the velocities of normal actin filaments. We found that the velocity of actin filaments sliding on skeletal muscle myosin molecules increased in the presence of a non-motile G680V mutant myosin motor.

Heterogeneity of patients receiving artificial nutrition in Japanese psychiatric hospitals: a cross-sectional study.

AIM: Artificial nutrition, including tube feeding, continues to be given to dementia patients in numerous geriatric facilities in Japan. However, the clinical characteristics of patients receiving artificial nutrition have not been fully investigated. Therefore, we tried to evaluate the clinical features of those patients in this study. METHODS: Various clinical characteristics of all inpatients at 18 of 20 psychiatric hospitals in Okayama Prefecture, Japan, with a percutaneous endoscopic gastrostomy tube, nasogastric tube, or total parenteral nutrition were evaluated. RESULTS: Two hundred twenty-one patients (5.4% of all inpatients) had been receiving artificial nutrition for more than 1 month, and 187 (130 women, 57 men; 84.6% of 221 patients) were fully investigated. The mean age was 78.3 years old, and the mean duration of artificial nutrition was 29.8 months. Eighty-four patients (44.7% of 187 patients) were receiving artificial nutrition for more than 2 years. Patients with Alzheimer's disease (n = 78) formed the biggest group, schizophrenia (n = 37) the second, and vascular dementia (n = 26) the third. CONCLUSION: About one-fifth of the subjects receiving artificial nutrition were in a vegetative state. More than a few patients with mental disorders, including schizophrenia, also received long-term artificial nutrition. We should pay more attention to chronic dysphasia syndrome in mental disorders.

Effect and tolerability of blonanserin in severe delusion with various types of dementia.

Low-dose blonanserin was effective for treating severe delusions in six patients with various types of dementia, and it was also well tolerated. Delusion and hallucination scores, as measured by the Neuropsychiatric Inventory, improved, and extrapyramidal symptom scores, as measured by the Drug-Induced Extrapyramidal Symptoms Scale, were unchanged. Blonanserin has strong dopamine D2 receptor-, 5-hydroxytryptamine 2A receptor-, and dopamine D3 receptor-blocking activities and weak 5-hydroxytryptamine-2C, α1 -, histamine H1 -, and muscarinic M1 -blocking activities. Its unique characteristics may make it suitable for treating severe delusions and hallucination in patients with dementia.

Subjective depressive mood and regional cerebral blood flow in mild Alzheimer's disease.

BACKGROUND: Depressive symptoms are common in patients with Alzheimer's disease (AD) and increase the caregiver burden, although the etiology and pathologic mechanism of depressive symptoms in AD patients remain unclear. In this study, we tried to clarify the cerebral blood flow (CBF) correlates of subjective depressive symptoms in AD. METHODS: Seventy-six consecutive patients with AD were recruited from outpatient units of the Memory Clinic of Okayama University Hospital. Subjective depressive symptoms were evaluated using the short version of the Geriatric Depression Scale (GDS). All patients underwent brain SPECT with 99mTc-ethylcysteinate dimer, and the SPECT images were analyzed by the Statistical Parametric Mapping 8 program. RESULTS: No significant differences between groups with high and low GDS scores were found with respect to age, sex, years of education, and revised Addenbrooke's Cognitive Examination scores. Compared to patients with low scores on GDS, patients with high scores showed significant hypoperfusion in the left inferior frontal region. CONCLUSIONS: The left inferior frontal region may be significantly involved in the pathogenesis of subjective depressive symptoms in AD. Subjective and objective depressive symptoms may have somewhat different neural substrates in AD.

Abuse of people with cognitive impairment by family caregivers in Japan (a cross-sectional study).

Caregiving is often stressful in an aging society. Our research questions were two. First, In Japan, how often does abusive behavior by the caregivers of elders with clinically mild cognitive dysfunction (mild cognitive impairment and clinically mild dementia) occur? Second, what risk factors affect the abusive behavior? We studied 123 Japanese caregivers and care recipients who had been referred to the Memory Clinic at Okayama University Hospital. We used the Japanese version of the modified Conflict Tactics Scale (m-CTS) to measure abusive behaviors. We estimate the prevalence of abusive behavior meeting threshold (m-CTS score of 2 or higher) for abuse case on the modified m-CTS. The prevalence of abusive behavior was 15.4%. Stepwise multiple regression analysis revealed that the sex of caregivers and scores on the Neuropsychiatric Inventory (NPI), Zarit Caregiver Burden scale, and Addenbrooke's Cognitive Examination had significant effects on the m-CTS scores. We demonstrated that in Japan, caregivers of the elderly with even clinically mild cognitive dysfunction exhibit abusive behavior toward them. The severity of the disease might reflect the prevalence of and factors that affect the abusive conflict score.

Frontal assessment battery and brain perfusion imaging in Alzheimer's disease.

BACKGROUND: The frontal assessment battery (FAB) is reported to be a useful tool for assessing frontal dysfunction. However, the neural substrates involved in patients with Alzheimer's disease (AD) remain to be elucidated. The aim of the present study was to identify the regional perfusion patterns of the brain associated with performance scores on the FAB of patients with AD using brain perfusion assessed by single photon emission computed tomography (SPECT). METHODS: Twenty-four AD patients with high scores and 24 age- and sex-matched AD patients with low scores on the FAB were selected from 470 consecutive Japanese patients of the Memory Clinic of Okayama University Hospital. All 48 participants underwent brain SPECT with 99mTc-ethylcysteinate dimer, and the SPECT images were analyzed by statistical parametric mapping. RESULTS: No significant differences were found between high and low FAB scoring groups with respect to Addenbrooke's Cognitive Examination scores, Mini-Mental State Examination scores, or the depression score of the Neuropsychiatric Inventory subscale. Compared with patients with high scores on the FAB, AD patients with low scores showed significant hypoperfusion in the left middle frontal gyrus (MFG) and the right superior frontal gyrus (SFG) extending to the left SFG. CONCLUSION: Our results suggest that functional activity of the SFG and MFG is closely related to the FAB score. The FAB might be a promising strategy to detect early stages of AD with low SFG and MFG function.

Validation of the revised Addenbrooke's Cognitive Examination (ACE-R) for detecting mild cognitive impairment and dementia in a Japanese population.

BACKGROUND: Early detection of dementia will be important for implementation of disease-modifying treatments in the near future. We aimed to investigate the diagnostic validity and reliability of the Japanese version of the revised Addenbrooke's Cognitive Examination (ACE-R J) for identifying mild cognitive impairment (MCI) and dementia. METHODS: We translated and adapted the original ACE-R for use with a Japanese population. Standard tests for evaluating cognitive decline and dementing disorders were applied. A total of 242 subjects (controls = 73, MCI = 39, dementia = 130) participated in this study. RESULTS: The optimal cut-off scores of ACE-R J for detecting MCI and dementia were 88/89 (sensitivity 0.87, specificity 0.92) and 82/83 (sensitivity 0.99, specificity 0.99) respectively. ACE-R J was superior to the Mini-Mental State Examination in the detection of MCI (area under the curve (AUC): 0.952 vs. 0.868), while the accuracy of the two instruments did not differ significantly in identifying dementia (AUC: 0.999 vs. 0.993). The inter-rater reliability (ICC = 0.999), test-retest reliability (ICC = 0.883), and internal consistency (Cronbach's α = 0.903) of ACE-R J were excellent. CONCLUSION: ACE-R J proved to be an accurate cognitive instrument for detecting MCI and mild dementia. Further neuropsychological evaluation is required for the differential diagnosis of dementia subtypes.

Creutzfeldt-Jakob disease with the M232R mutation in the prion protein gene in two cases showing different disease courses: a clinicopathological study.

We report two autopsy cases of Creutzfeldt-Jakob disease (CJD) with the M232R mutation of the prion protein (PrP) gene that exhibited different clinicopathological features (age at death, 64/54 years; disease duration, 13/26 months). Both cases showed myoclonus, hyperintensity on diffusion-weighted MRI, and increased 14-3-3 protein in the cerebrospinal fluid. The initial sign in each case was memory disturbance and abnormal pharyngeal sensation, respectively. In the first case, the disease progressed rapidly with akinetic mutism developing 6 months after onset, while it occurred 23 months after onset in the second case. Pathologically, both cases had severe neuronal loss with gliosis and spongiform change in the cerebral cortex, basal ganglia, and cerebellum. PrP deposition was the diffuse synaptic type in the first case, but the second case had both diffuse synaptic and perivacuolar types. PrP(sc) immunoblotting revealed a type 1 band pattern in the first case, but both types 1 and 2 in the second case. Based on these findings, together with the results in previous CJD cases with M232R, we noted the possibility that the presence of type 2 PrP(sc) may be associated with both morphological features of PrP deposition and slow disease progression in this genetic prion disease.

Perseverative errors on the Wisconsin Card Sorting Test and brain perfusion imaging in mild Alzheimer's disease.

BACKGROUND: The Wisconsin Card Sorting Test (WCST) has long been used to investigate deficits in executive function in humans. The majority of studies investigating deficient WCST performance focused on the number of categories achieved (CA) and the number of perseverative errors of the Nelson type (PEN). However, there is insufficient evidence that these two measures reflect the same neural deficits. METHODS: Twenty AD patients with high PEN scores, and 20 age- and sex-matched AD patients with low PEN scores were selected. All 40 subjects underwent brain SPECT, and the SPECT images were analyzed by Statistical Parametric Mapping. RESULTS: No significant differences were found between high and low PEN score groups with respect to years of education, Addenbrooke's Cognitive Examination scores, and Mini-Mental State Examination scores. However, higher z scores for hypoperfusion in the bilateral rectal and orbital gyri were observed in the high PEN score group compared with the low PEN score group. CONCLUSIONS: Our results suggest that functional activity of the bilateral rectal and orbital gyri is closely related to PEN scores on a modified WCST (mWCST). The PEN score on a mWCST might be a promising index of dysfunction of the orbitofrontal area among patients with mild AD.

Kana Pick-out Test and brain perfusion imaging in Alzheimer's disease.

BACKGROUND: The Kana Pick-out Test (KPT), which was developed in Japan, is suitable for evaluating frontal lobe function and screening for mild dementia. However, the neural substrates involved remain to be elucidated. The aim of the present study was to identify the regional perfusion patterns in the brain associated with performance scores on the KPT in patients with mild Alzheimer's disease (AD), using brain perfusion assessed by single photon emission computed tomography (SPECT). METHODS: Twenty AD patients with high scores on the KPT and 20 age- and sex-matched AD patients with low scores were selected from 227 consecutive Japanese patients of the Memory Clinic of Okayama University Hospital. All 40 subjects underwent brain SPECT with 99mTc-ethylcysteinate dimer, and the SPECT images were analyzed by Statistical Parametric Mapping. RESULTS: With the exception of KPT scores, no significant differences were found between high and low scoring groups with respect to Addenbrooke's Cognitive Examination scores, Mini-mental State Examination scores, or the depression score of the Neuropsychiatric Inventory subscale. Compared to patients with high scores on the KPT, AD patients with low scores on the KPT showed significant hypoperfusion in the left subgenual cingulate gyrus (SGC) extending to the right SGC. CONCLUSIONS: Our results suggest that functional activity of the SGC is closely related to scores on the KPT. KPT might be a promising strategy to use in detecting early stages of AD with low SGC function.

Up-and-down movement of a sliding actin filament in the in vitro motility assay.

We observed a three-dimensional up-and-down movement of an actin filament sliding on heavy mero-myosin (HMM) molecules in an in vitro motility assay. The up-and-down movement occurred along the direction perpendicular to the planar glass plane on which the filament demonstrated a sliding movement. The height length of the up-and-down movement was measured by monitoring the extent of diminishing fluorescent emission from the marker attached to the filament in the evanescent field of attenuation. The height lengths whose distribution exhibits a local maximum were found around the two values, 150 nm and 90 nm, separately. This undulating three-dimensional movement of an actin filament suggests that the interactions between myosin (HMM) molecules and the actin filament may temporally be modulated during its sliding movement.

Validation of Addenbrooke's cognitive examination for detecting early dementia in a Japanese population.

There is a clear need for brief, but sensitive and specific, cognitive screening instruments for dementia. We assessed the diagnostic accuracy of the Japanese version of Addenbrooke's Cognitive Examination (ACE) in identifying early dementia in comparison with the conventional Mini-Mental State Examination (MMSE). Standard tests for evaluating dementia screening tests were applied. A total of 201 subjects (Alzheimer's disease (AD)=65, frontotemporal dementia (FTD)=24, vascular dementia=26, dementia with Lewy bodies=11, mild cognitive impairment (MCI)=13, and controls=62) participated in this study. The reliability of the ACE was very good (alpha coefficient=0.82). In our patient series, the sensitivity for diagnosing dementia with an ACE score of ≤74 was 0.889 with a specificity of 0.987, and the sensitivity of an ACE score of ≤80 was 0.984 with a specificity of 0.867. The Japanese version of the ACE is a very accurate instrument for the detection of early dementia, and should be widely used in clinical practice.

Two-dimensional periodic texture of actin filaments formed upon drying.

We found that a solution of actin filaments can form a periodic texture in the process of drying on a flat glass surface in the air; the periodic texture was composed of smooth meandering bundles of actin filaments. We also found that a branched salt crystal grows in the space between the meandering bundles of actin filaments. The distance between the adjacent striae (striation period) in the resulting dried two-dimensional pattern of striation decreased from about 50 to 2 µm, as the ambient temperature was increased from 4 to 40°C at 1 mg/ml actin, and showed an increasing tendency from a few to several tens µm with the increase in the initial concentration of actin filaments from 0.6 to 2.0mg/ml at room temperature. As the speed of drying is increased at a certain temperature, the striation period was also found to decrease. We propose that the formation of the two-dimensional striation pattern of bundles of actin filaments is the result of condensation of proteins due to dehydration, and suggest that the solvent flow from the center to the periphery of the sample causes the meandering of actin filaments.

Repetitive questioning behavior in Alzheimer's disease: relationship to regional cerebral blood flow.

Repetitive questioning is among the most common and burdensome of the behavioral and psychological symptoms of Alzheimer's disease (AD). Regardless of the clinical significance of the repetitive questioning, the neural substrates involved remain unclear. Fifty-eight consecutive patients with AD participated in this study. The score of repetitive questioning behavior was evaluated by multiplying the severity by the frequency of the behavior. They underwent brain SPECT with (99m)Tc-ethylcysteinate dimer. Scores of repetitive questioning behavior had a significant positive correlation with regional cerebral blood flow (rCBF) in the bilateral pericallosal regions. After removing the effect of memory test scores, we found a significant positive correlation of scores of repetitive questioning behavior to rCBF in the left pericallosal region. The pericallosal region includes the upper precuneus, cingulate, and posterior cingulate cortices on 3DSRT. Repetitive questioning behavior among AD patients might be a manifestation of mental state associated with a relative increase or preservation of rCBF in the left pericallosal region.

Wisconsin card sorting test and brain perfusion imaging in early dementia.

BACKGROUND/AIMS: The presence of frontal or executive deficits in patients even at early stages of dementia is now widely recognized. We investigated the relationship between the scores of the Wisconsin card sorting test (WCST) and brain perfusion in patients with early dementia. METHODS: A total of 77 subjects participated in this study. They underwent the WCST and brain single photon emission computed tomography with 99mTc-ethylcisteinate dimer. We analyzed the data using a regional cerebral blood flow (rCBF) quantification software program, 3DSRT. RESULTS: The number of categories achieved (CA) scores of the WCST had a weakly positive correlation with regional cerebral blood flow in the bilateral precentral, bilateral callosomarginal, bilateral pericallosal, right thalamus, left central and left parietal segments. The number of perseverative errors of the Nelson type (PEN) scores had a weakly negative correlation with rCBF in the right thalamus. CONCLUSION: The results in this study suggest that CA scores mainly reflect the function of the precentral segments, especially the left side, and that PEN scores correlate with rCBF in the right thalamus. The results suggest that CA scores and PEN scores should be differentially estimated in the WCST.

Frontal assessment battery and brain perfusion imaging in early dementia.

BACKGROUND/AIMS: The frontal assessment battery (FAB) is reported to be a useful tool for screening frontal function. However, the neural substrates involved remain to be elucidated. The aim of the present study was to identify the brain regions responsible for FAB performance in patients with early dementia. We sought a correlation between FAB scores and brain perfusion. METHODS: A total of 117 subjects participated in this study (Alzheimer's disease = 51, frontotemporal dementia = 14, vascular dementia = 13, dementia with Lewy bodies = 7, psychiatric disease = 7, mild cognitive impairment = 11, controls = 14). They underwent brain single photon emission computed tomography with (99m)Tc-ethylcisteinate dimer, and we analyzed the data, using a regional cerebral blood flow (rCBF) quantification software program, 3DSRT (3-dimensional stereotaxic region of interest template). RESULTS: FAB scores had a moderately positive correlation with left callosomarginal and precentral rCBF. Comparison of rCBF between high- and low-scoring FAB groups revealed that the latter showed significantly lower rCBF in the bilateral callosomarginal and left precentral regions. CONCLUSION: The results in this study suggest that the FAB mainly reflects the function of the callosomarginal and precentral segments, especially the left side, and that it might be a valid frontal lobe function test.

Unidirectional movement of an actin filament taking advantage of temperature gradients.

An actin filament with heat acceptors attached to its Cys374 residue in each actin monomer could move unidirectionally even under heat pulsation alone, while in the total absence of both ATP and myosin. The prime driver for the movement was temperature gradients operating between locally heated portions on an actin filament and its cooler surroundings. In this report, we investigated how the mitigation of the temperature gradients induces a unidirectional movement of an actin filament. We then observed the transversal fluctuations of the filament in response to heat pulsation and their transition into longitudinally unidirectional movement. The transition was significantly accelerated when Cys374 and Lys336 were simultaneously excited within an actin monomer. These results suggest that the mitigation of the temperature gradients within each actin monomer first went through the energy transformation to transversal fluctuations of the filament, and then followed by the transformation further down to longitudinal movements of the filament. The faster mitigation of temperature gradients within actin monomer helps build up the transition from the transversal to longitudinal movements of the filament by coordinating the interaction between the neighboring monomers.

Tropomyosin as a regulator of the sliding movement of actin filaments.

We examined the capacity of tropomyosin molecules regulating the sliding movement of actin filaments on myosin molecules in the presence of ATP molecules to be hydrolyzed. For this objective, we prepared tropomyosin molecules modified to be a little bit stiffer compared to the intact ones by applying a fixed cross-linker between a pair of twisted tropomyosin monomers. The cross-linked tropomyosin molecules, when complexed with actin filaments, were found to inhibit the sliding movement of the filaments on myosin molecules even in the absence of calcium-regulated troponin molecules. It is then suggested that the mechanical flexibility of tropomyosin molecules may be instrumental to actualizing the proper functional regulation of the sliding movement of actin filaments.