Structures of human nucleosomes containing major histone H3 variants

The nucleosome is the fundamental repeating unit of chromatin, via which genomic DNA is packaged into the nucleus in eukaryotes. In the nucleosome, two copies of each core histone, H2A, H2B, H3 and H4, form a histone octamer which wraps 146 base pairs of DNA around itself. All of the core histones except for histone H4 have nonallelic isoforms called histone variants. In humans, eight histone H3 variants, H3.1, H3.2, H3.3, H3T, H3.5, H3.X, H3.Y and CENP-A, have been reported to date. Previous studies have suggested that histone H3 variants possess distinct functions in the formation of specific chromosome regions and/or in the regulation of transcription and replication. H3.1, H3.2 and H3.3 are the most abundant H3 variants. Here, crystal structures of human nucleosomes containing either H3.2 or H3.3 have been solved. The structures were essentially the same as that of the H3.1 nucleosome. Since the amino-acid residues specific for H3.2 and H3.3 are located on the accessible surface of the H3/H4 tetramer, they may be potential interaction sites for H3.2- and H3.3-specific chaperones.

Structural design of a newly developed pediatric circulatory assist device for Fontan circulation by using shape memory alloy fiber

Total cavopulmonary connection (TCPC) is commonly applied for the surgical treatment of congenital heart disease such as single ventricle in pediatric patients. Patients with no ventricle in pulmonary circulation are treated along with Fontan algorithm, in which the systemic venous return is diverted directly to the pulmonary artery without passing through subpulmonary ventricle. In order to promote the pulmonary circulation after Fontan procedure, we developed a newly designed pulmonary circulatory assist device by using shape memory alloy fibers. We developed a pulmonary circulatory assist device as a non-blood contacting mechanical support system in pediatric patients with TCPC. The device has been designed to be installed like a cuff around the ePTFE TCPC conduit, which can contract from outside. We employed a covalent type functional anisotropic shape memory alloy fiber (Biometal, Toki Corporation, Tokyo Japan) as a servo actuator of the pulmonary circulatory assist device. The diameter of this fiber was 100 microns, and its contractile frequency was 2-3 Hz. Heat generation with electric current contracts these fibers and the conduit. The maximum contraction ratio of this fiber is about 7% in length. In order to extend its contractile ratio, we fabricated and installed mechanical structural units to control the length of fibers. In this study, we examined basic contractile functions of the device in the mock system. As a result, the internal pressure of the conduit increased to 63 mmHg by the mechanical contraction under the condition of 400 msec-current supply in the mock examination with the overflow tank of 10 mmHg loading.

Nucleosome formation activity of human somatic nuclear autoantigenic sperm protein (sNASP)

NASP (nuclear autoantigenic sperm protein) is a member of the N1/N2 family, which is widely conserved among eukaryotes. Human NASP reportedly prefers to bind to histones H3.H4 and the linker histone H1, as compared with H2A.H2B, and is anticipated to function as an H3.H4 chaperone for nucleosome assembly. However, the direct nucleosome assembly activity of human NASP has not been reported so far. In humans, two spliced isoforms, somatic and testicular NASPs (sNASP and tNASP, respectively) were identified. In the present study we purified human sNASP and found that sNASP efficiently promoted the assembly of nucleosomes containing the conventional H3.1, H3.2, H3.3, or centromere-specific CENP-A. On the other hand, sNASP inefficiently promoted nucleosome assembly with H3T, a testis-specific H3 variant. Mutational analyses revealed that the Met-71 residue of H3T is responsible for this inefficient nucleosome formation by sNASP. Tetrasomes, composed of the H3.H4 tetramer and DNA without H2A.H2B, were efficiently formed by the sNASP-mediated nucleosome-assembly reaction. A deletion analysis of sNASP revealed that the central region, amino acid residues 26-325, of sNASP is responsible for nucleosome assembly in vitro. These experiments are the first demonstration that human NASP directly promotes nucleosome assembly and provide compelling evidence that sNASP is a bona fide histone chaperone for H3.H4.

Assessment of muscle blood flow volume in elderly poststroke hemiplegic patients using near-infrared spectroscopy

This study assessed the changes in blood flow volume in elderly hemiplegic patients before and after rehabilitation training. Total hemoglobin accumulation (blood flow volume) was measured using near-infrared spectroscopy (NIRS) in both the affected and unaffected gastrocnemius muscles before and after walking. In the gastrocnemius on the affected side, the blood flow volume was larger during the recovery period than during the rest period, and the blood flow volume did not decrease during the recovery period after the subjects walked a corridor. By contrast, the blood flow volume recovered faster on the unaffected side than on the affected side. After the subjects walked the stairs, the blood flow volume increased in the gastrocnemius muscles on both sides. These results suggested that the level of training involved in walking a corridor was too light for the unaffected side, although it was effective for the affected side. In our subjects, walking the stairs was effective rehabilitation training for both the unaffected and affected sides. Our results suggested that NIRS was an objective tool useful for planning rehabilitation training.

Effect of prophylactic bronchodilator treatment with i.v. carperitide on airway resistance and lung compliance after tracheal intubation

BACKGROUND

Lung resistance increases after induction of anaesthesia. We hypothesized that prophylactic bronchodilation with i.v. carperitide before tracheal intubation would decrease airway resistance and increase lung compliance after placement of the tracheal tube in both smokers and nonsmokers.

METHODS

Ninety-seven adults aged between 24 and 59 yr were randomized to receive i.v. normal saline (0.9% saline) (control) or carperitide, 0.2 microg kg(-1) min(-1) throughout the study. The 97 patients included smokers and nonsmokers. Thus the patients were allocated to one of the four groups: smokers who received normal saline (n=21), nonsmokers who received normal saline (n=27), smokers who received carperitide (n=19) or nonsmokers who received carperitide (n=30). Thirty minutes after starting normal saline or carperitide infusion, we administered thiamylal 5 mg kg(-1) and fentanyl 5 microg kg(-1) to induce general anaesthesia and vecuronium 0.3 mg kg(-1) for muscle relaxation. Continuous infusion of thiamylal 15 mg kg(-1) h(-1) followed anaesthetic induction. Mean airway resistance (R(awm)), expiratory airway resistance (R(awe)) and dynamic lung compliance (C(dyn)) were determined 4, 8, 12 and 16 min after tracheal intubation and compared between the four groups.

RESULTS

At 4 min after intubation, R(awm) and R(awe) were higher and C(dyn) lower in smokers than in nonsmokers in the control group. R(awm) and R(awe) were lower and C(dyn) higher in smokers in the carperitide group than in smokers in the control group. R(awm) and R(awe) were lower in nonsmokers in the carperitide group than in nonsmokers in the control group.

CONCLUSIONS

Marked bronchoconstriction occurred in the control groups (smokers and nonsmokers) 4 min after tracheal intubation. Prophylactic treatment with carperitide before induction of anaesthesia and tracheal intubation was advantageous, particularly in smokers.

Within-day variability of whole-body and segmental bioelectrical impedance in a standing position

OBJECTIVE

To assess the variation in whole-body and segmental bioelectrical impedance measured in the standing position over the course of a day.

SUBJECTS

Sixteen healthy men aged 29.6 +/- 3.1 years participated in this study.

MEASUREMENT

Impedance between the hands (Z H-H), the feet (Z F-F), and the both hands and feet (Z H-F) was measured using a bioelectrical impedance analysis (BIA) data acquisition system at 500 microA and 50 kHz. Body weight, Z H-H, Z F-F and Z H-F were measured every 3 h from 0900 to 1800.

RESULTS

Body weight was slightly, but significantly, changed at 1200 (-0.4 +/- 0.4 kg, P < 0.05), 1500 (+0.4 +/- 0.3 kg, P < 0.05) and 1800 (-0.2 +/- 0.2 kg, P < 0.05) compared to their respective previous measurement values. Z H-H significantly increased (P < 0.05) and Z F-F significantly decreased (P < 0.05) over the course of a day. The mean changes in impedance from 0900 to 1800 were +27.2 Omega (Z H-H) and -31.8 Omega (Z F-F), respectively. There were no changes in Z H-H at 1500 and in Z F-F at 1800 compared to their respective previous measurement values. The Z H-F value did not change significantly between 0900 and 1800.

CONCLUSION

Although changes in standing whole-body impedance during the day are small, arm and leg segmental impedance measurements change significantly. Therefore, it is necessary to measure the impedance at regularly scheduled times when evaluating whole-body %fat or body water content using the segmental BIA method.

Selective serotonin reuptake inhibitor treatment of early postnatal mice reverses their prenatal stress-induced brain dysfunction

Prenatal stress has long-lasting effects on cognitive function and on the hypothalamic-pituitary-adrenal response to stress. We previously reported that the serotonin concentration and synaptic density in the hippocampus were reduced following prenatal stress [Int J Dev Neurosci 16 (1998) 209]. Since serotonin plays a role in the formation and maintenance of synapses, we hypothesized that a neonatal reduction in hippocampal serotonin levels may lead to learning disabilities in prenatally stressed mice. To test this hypothesis, we treated prenatally stressed mice with a selective serotonin reuptake inhibitor in order to normalize their postnatal serotonin turnover levels. What we found was that the oral administration of a selective serotonin reuptake inhibitor to prenatally stressed mice during postnatal weeks 1-3 but not 6-8 normalized their corticosterone response to stress, serotonin turnover in the hippocampus, and density of dendritic spines and synapses in the hippocampal CA3 region. Concomitantly, such treatment partially restored their ability to learn spatial information.

Multidetector-row CT analysis of time-dependent changes in lung fields after chest irradiation: usefulness of precision scans

Time-dependent changes in lung fields after chest irradiation were analyzed using multidetector-row CT. Routine scans at 3-mm raw thickness and 8-mm recon thickness and precision scans at 0.5-mm raw thickness and 0.5-mm recon thickness were compared with respect to the number of each finding and the time-dependent changes in the rate of each finding. Among the findings visualized by these scans, ground-glass opacity (GGO) showed the highest overall appearance rate. Precision scans exceeded routine scans in the rates of all findings except GGO and confluent shadows, and the two types of scans showed the greatest difference in the rate of GGO. Since we found that GGO tended to be overestimated on routine scans, we confirmed it by a phantom experiment. Precision scans were similar or superior to routine scans in the rates of findings except 3 months after irradiation. We consider that the concomitant use of precision scans is useful in that it allows more accurate evaluation of various post-irradiation changes in lung fields including GGO, in which the lesion is in a reversible stage.

Propofol alone, sevoflurane alone, and combined propofol-sevoflurane anaesthesia in electroconvulsive therapy

Electroconvulsive therapy is an effective treatment for severe and medication-resistant depression. There have been no reports describing how a volatile anaesthetic affects haemodynamic responses, seizure duration, and recovery characteristics during electroconvulsive therapy. We carried out a repeated-measure crossover study to compare the effects on haemodynamic responses, seizure duration, and recovery characteristics of the following types of anaesthesia in electroconvulsive therapy: propofol alone, sevoflurane alone, and propofol combined with sevoflurane. We recruited 50 patients requiring electroconvulsive therapy for depression. For anaesthesia induction, 1.5 mg/kg propofol (condition P), 5% sevoflurane in oxygen following a vital capacity rapid inhalation induction (condition S), or 1.5 mg/kg propofol followed by 5% sevoflurane in oxygen (condition PS) was administered. Succinylcholine 1.5 mg/kg was then given. Electrical stimulation was administered after fasciculation. Measurements were obtained before anaesthesia induction (baseline), prior to succinylcholine administration, prior to electroconvulsive therapy, and at the peak after electroconvulsive therapy. After electroconvulsive therapy, peak heart rate and peak mean arterial pressure were highest in condition S. Whereas recovery time was longest in condition PS, motor seizure duration was significantly shorter than in either condition P or S. Electroencephalographic seizure duration was significantly shorter in condition PS than in condition P and significantly shorter in condition S than in condition P. Sevoflurane anaesthesia alone is most disadvantageous in terms of haemodynamics. Propofol-sevoflurane anaesthesia is advantageous in terms of haemodynamics, but disadvantageous in terms of seizure duration and recovery time. Propofol alone is most advantageous in terms of seizure duration.

The effects of intravenous lignocaine on haemodynamics and seizure duration during electroconvulsive therapy

Electroconvulsive therapy (ECT) is commonly associated with acute hyperdynamic cardiovascular responses, and we hypothesize that intravenous lignocaine can blunt this response. We have measured the effect of lignocaine 1.5 mg/kg i.v. on heart rate and mean arterial pressure during electroconvulsive therapy. Furthermore, we also assessed seizure duration using both the cuff method and two-lead electroencephalography. We studied 25 patients using a randomized, double-blind, placebo-controlled crossover study design. Patients in the control group were given intravenous saline 0.075 ml/kg, and those in the lignocaine group were given intravenous lignocaine 2% 1.5 mg/kg, and this treatment was conducted one minute before intravenous propofol 1.5 mg/kg to induce unconsciousness. Succinylcholine 1.5 mg/kg was then administered intravenously and electrical stimulation was administered after fasciculation. Measurements were taken at the baseline, prior to succinycholine, prior to electroconvulsive therapy and at the peak response after electroconvulsive therapy. Intravenous lignocaine significantly reduced the increases in heart rate after electroconvulsive therapy, as compared with the placebo. The use of intravenous lignocaine was, however, associated with a remarkably shortened seizure duration. Due to the reduction in seizure duration, routine administration of intravenous lignocaine may not be advisable since it may interfere with the psychotherapeutic efficacy of electroconvulsive therapy. However, intravenous lignocaine medication for electroconvulsive therapy is potentially useful for reducing tachycardia in high-risk patients and reducing the severity of propofol injection pain in comparison with a placebo.

Amiodarone-Induced thyroid dysfunction and ventricular tachyarrhythmias during long-term therapy in Japan

In 232 Japanese patients receiving long-term amiodarone therapy for life-threatening ventricular tachyarrhythmias, hyperthyroidism and hypothyroidism developed in 29 patients (12.5%) and 25 patients (10.8%), respectively. In patients with hyperthyroidism, the recurrence of sustained ventricular tachycardia was significantly higher with thyrotoxicosis than in the euthyroid period (31% vs 3%, p<0.01). Holter monitoring showed that the average heart rate and ventricular premature complexes significantly increased with hyperthyroidism. On the other hand, there was no increase in the recurrence of ventricular tachyarrhythmia with hypothyroidism. There was no change in the dose or the plasma concentration of amiodarone or desethylamiodarone in the euthyroid period or when hyperthyroidism or hypothyroidism manifested. It is important to monitor for arrhythmia when hyperthyroidism develops during amiodarone therapy.

Role of desethylamiodarone in the anticoagulant effect of concurrent amiodarone and warfarin therapy

BACKGROUND

The concurrent use of amiodarone and warfarin inhibits metabolism of S-warfarinby cytochrome P450 (CYP) 2C9, thereby increasing the anticoagulant effect of warfarin. Amiodarone primarily inhibits CYP1A2 and CYP3A4, and desethylamiodarone primarily inhibits CYP2C9. We investigate whether a relationship exists between the plasma concentration of desethylamiodarone and anticoagulation when amiodarone is administered to patients receiving warfarin therapy.

METHODS AND RESULTS

The correlation between the plasma concentration of either amiodarone or desethylamiodarone, and prolongation of prothrombin time-international normalized ratio/dose of warfarin (Delta INR/Dose) on day 7 of amiodarone administration was studied in 25 patients (22-74 years old) with structural heart disease and refractory arrhythmias receiving stable warfarin therapy.

RESULTS

No correlation was found between the plasma concentration of amiodarone and Delta INR/Dose, but a correlation was found between the plasma concentration of desethylamiodarone and Delta INR/Dose.

CONCLUSIONS

It was suggested that inhibition of CYP2C9 by desethylamiodarone, the active metabolite of amiodarone, plays an important role in the interaction of warfarin and amiodarone.

Time-sequential changes in biomechanical and morphological properties of articular cartilage in cryopreserved osteochondral allografting

This study examined time-sequential changes in the biomechanical and morphological properties of articular cartilage that had received cryopreserved osteochondral allografting. Osteochondral blocks obtained from the femurs of 18 rabbits were cryopreserved with dimethylsulfoxide (DMSO), using a two-step freezing method, and allografted to the femurs of another 18 rabbits. Specimens for biomechanical and morphological examinations were prepared at the second, fourth, and twelfth weeks after allografting (n = 18). In 12 allografted rabbits, biomechanical features were examined with an indentation test apparatus, and histological changes were studied with a light microscope (second week, n = 4; fourth week, n = 4; twelfth week, n = 4). In the other 6 allografted rabbits, cartilage surfaces were studied with a scanning electron microscope (second week, n = 2; fourth week, n = 2; twelfth week, n = 2). For controls, fresh, DMSO-treated, or DMSO-treated + cryopreserved specimens were examined biomechanically and morphologically. In the time-sequential examination of biomechanical features, both the parameter for elasticity (i.e., ratio of instant elastic strain to maximum strain) and the parameter for viscosity (i.e., average retardation time) significantly changed. Light microscopy showed chronological decreases in safranin-O staining intensity in the matrix, and progression of degeneration. On scanning electron microscopy, disruption of the cartilage surface was also recognized. Therefore, changes in biomechanical properties due to cryopreservation could cause irreversible changes in the cartilage in cryopreserved osteochondral allografting.

Interaction of Myc-associated zinc finger protein with DCC, the product of a tumor-suppressor gene, during the neural differentiation of P19 EC cells

Expression of the DCC (deleted in colorectal cancer) protein is strongly induced during the neural differentiation of mouse P19 embryonal carcinoma (EC) cells that occurs when these cells are treated with retinoic acid (RA). Myc-associated zinc finger protein (MAZ) is a DNA-binding protein that is widely expressed and functions in human, mouse and hamster cells as an activator, an initiator or a terminator of transcription. However, the biological functions of MAZ remain elusive. We report here that MAZ associates with the cytoplasmic domain of the DCC protein in vivo and in vitro. Yeast two-hybrid assays confirmed this association. An immunofluorescence study demonstrated that DCC protein is expressed at elevated levels in neuron-like P19 EC cells, in particular in axons, in which the MAZ protein is also expressed. We found that MAZ was translocated from the nucleus to the cytoplasm during the RA-induced terminal differentiation of P19 EC cells with resultant loss of the ability of MAZ to bind to the ME1a1 site of the c-myc promoter. Taken together, our observations imply that the DCC protein might play a critical role as a signaling molecule in the regulation of the transcriptional activity of MAZ during the neural differentiation of P19 EC cells.

Electrophysiological characteristic of a patient exhibiting the short-coupled variant of torsade de pointes

A 41-year-old man was admitted because of syncope. The electrocardiogram showed torsade de pointes (Tdp) with no long QT interval and the coupling interval of the initial beat of Tdp was 240 ms. Heterogeneity of ventricular refractoriness was observed together with shortness of the effective refractory period measured at the right ventricular inflow site where the paced QRS morphology was the same as that of the initial beat of Tdp. Verapamil could suppress frequent ventricular premature complexes with a short coupling interval, which lead to Tdp. Polymorphic ventricular tachycardia was induced by triple ventricular extrastimuli. A pure potassium channel blocker was successful in inhibiting polymorphic ventricular tachycardia inducibility by prolongation of refractoriness. These results suggested that triggered ventricular premature complexes may be represent the initiating mechanism, whereas the shortness of local refractory period and heterogeneity of ventricular refractoriness may play a role in the development and the maintenance of the Tdp.

Abnormal neuronal network in anorexia nervosa studied with I-123-IMP SPECT

Single photon emission computed tomography was used to study 14 female patients with anorexia nervosa and 8 female normal comparison subjects. Automatic voxel-based analysis of the images was carried out using statistical parametric mapping (SPM) software. Statistics across the entire brain were displayed as Z scores (threshold: P<0.05). Compared with the normal comparison subjects, the anorectic patients were characterized by hypoperfusion in the medial prefrontal cortex and the anterior cingulate gyrus, and hyperperfusion in the thalamus and the amygdala-hippocampus complex. These results suggest that a dysfunction in neuronal circuitry may be related to anorexia nervosa.