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Biomedical subjects

H Sakakibara

Publications and source records attributed to H Sakakibara.

At least 37 records · Page 2Linked to original sources
PubMed2000

Immunological analysis of the phosphorylation state of maize C4-form phosphoenolpyruvate carboxylase with specific antibodies raised against a synthetic phosphorylated peptide.

The phosphoenolpyruvate carboxylase (PEPC) isozyme involved in C4 photosynthesis is known to undergo reversible regulatory phosphorylation under illuminated conditions, thereby decreasing the enzyme's sensitivity to its feedback inhibitor, L-malate. For the direct assay of this phosphorylation in intact maize leaves, phosphorylation state-specific antibodies to the C4-form PEPC were prepared. The antibodies were raised in rabbits against a synthetic phosphorylated 15-mer peptide with a sequence corresponding to that flanking the specific site of regulatory phosphorylation (Ser15) and subsequently purified by affinity-chromatography. Specificity of the resulting antibodies to the C4-form PEPC phosphorylated at Ser15 was established on the basis of several criteria. The antibodies did not react with the recombinant root-form of maize PEPC phosphorylated in vitro. By the use of these antibodies, the changes in PEPC phosphorylation state were semi-quantitatively monitored under several physiological conditions. When the changes in PEPC phosphorylation were monitored during the entire day with mature (13-week-old) maize plants grown in the field, phosphorylation started before dawn, reached a maximum by mid-morning, and then decreased before sunset. At midnight dephosphorylation was almost complete. The results suggest that the regulatory phosphorylation of C4-form PEPC in mature maize plants is controlled not only by a light signal but also by some other metabolic signal(s). Under nitrogen-limited conditions the phosphorylation was enhanced even though the level of PEPC protein was decreased. Thus there seems to be some compensatory regulatory mechanism for the phosphorylation.

Amino Acid Sequence↗
PubMed2000

Differential interaction of maize root ferredoxin:NADP(+) oxidoreductase with photosynthetic and non-photosynthetic ferredoxin isoproteins.

In higher plants ferredoxin (Fd):NADP(+) oxidoreductase (FNR) and Fd are each distributed in photosynthetic and non-photosynthetic organs as distinct isoproteins. We have cloned cDNAs for leaf FNR (L-FNR I and L-FNR II) and root FNR (R-FNR) from maize (Zea mays L.), and produced recombinant L-FNR I and R-FNR to study their enzymatic functions through kinetic and Fd-binding analyses. The K(m) value obtained by assay for a diaphorase activity indicated that R-FNR had a 10-fold higher affinity for NADPH than L-FNR I. When we assayed for NADPH-cytochrome c reductase activity using maize photosynthetic Fd (Fd I) and non-photosynthetic Fd (Fd III), the R-FNR showed a marked difference in affinity between these two Fd isoproteins; the K(m) for Fd III was 3.0 microM and that for Fd I was 29 microM. Consistent with this, the dissociation constant for the R-FNR:Fd III complex was 10-fold smaller than that of the R-FNR:Fd I complex. This differential binding capacity was confirmed by an affinity chromatography of R-FNR on Fd-sepharose with stronger binding to Fd III. L-FNR I showed no such differential interaction with Fd I and Fd III. These data demonstrated that R-FNR has the ability to discriminate between these two types of Fds. We propose that the stronger interaction of R-FNR with Fd III is crucial for an efficient electron flux of NADPH-FNR-Fd cascade, thus supporting Fd-dependent metabolism in non-photosynthetic organs.

Amino Acid Sequence↗
PubMed2000

Cytochrome P4501A1-inhibitory action of antimutagenic anthraquinones in medicinal plants and the structure-activity relationship.

We have earlier found that flavones and flavonols in vegetables specifically inhibited one of the carcinogenesis-related enzymes, cytochrome P450 (CYP) 1A1, and subsequently suppressed the mutagenicity of food-derived carcinogens. In this study, we explored other candidates for the enzyme inhibitor in Chinese medicinal plants. Some of them were antimutagenic toward 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2). For example, Rheum officinale contained large amounts of anthraquinones as the active compounds, 3.4 mg of emodin, 2.1 mg of chrysophanol and 1.8 mg of rhein in 10 g of dry matter. Anthraquinones showed similar IC50 values for antimutagenicity against Trp-P-2 to those for inhibition of the N-hydroxylation activity of CYP1A1 toward Trp-P-2, indicating that the antimutagenicity was attributable to CYP inhibition. The structure-activity relationships were then examined with 14 commercial chemicals, and it was found that the interaction with an enzyme required three rings and an oxygen group in the side ring. This characteristic is similar to that of flavones and flavonols.

Anthraquinones↗
PubMed2000

Dietary antioxidants fail in protection against oxidative genetic damage in in vitro evaluation.

Carcinogenesis is believed to be induced through the oxidative damage of DNA, and antioxidants are expected to suppress it. So, the polyphenolic antioxidants in daily foods were investigated to see whether they protect against genetic damage by active oxygen. In the evaluation, we used a bioassay and a chemical determination, a Salmonella mutagenicity test for mutation by a N-hydroxyl radical from one of the dietary carcinogens 3-amino-1-methyl-5H-pyrido[4,3-b]indole and the formation of 8-hydroxyl (8-OHdG) from 2'-deoxyguanosine (2'-dG) in a Fenton OH-radical generating system. Thirty-one antioxidants including flavonoids were compared in terms of radical-trapping activity with bacterial DNA and 2'-dG. Antioxidants inhibited the mutation but the IC50 values were in the mM order. Against 8-OHdG formation, only alpha-tocopherol had a suppressive effect with an IC50 of 1.5 microM. Thus, except alpha-tocopherol, the dietary antioxidants did not scavenge the biological radicals faster than bacterial DNA and intact 2'-dG, indicating that they failed to prevent oxidative gene damage and probably carcinogenesis.

8-Hydroxy-2'-Deoxyguanosine↗
PubMed2000

Thermal perception threshold testing for the evaluation of small sensory nerve fiber injury in patients with hand-arm vibration syndrome.

The aim of the present study was to investigate whether thermal perception threshold testing is a useful method that could replace pain threshold testing in the evaluation of small sensory nerve fiber injury in vibration-induced neuropathy. Vibration, pain, and thermal (warm and cold) perception thresholds were examined on both middle fingers of 50 patients with hand-arm vibration syndrome and 29 healthy controls of similar age. The patients were divided into three subgroups according to the Stockholm Workshop sensorineural scale. Thermal (warm and cold) thresholds as well as vibration and pain thresholds were significantly more deteriorated among the patients than in the controls. Among the patients, warm thresholds elevated and cold thresholds lowered according to the Stockholm Workshop scale. Thermal thresholds were significantly correlated with pain thresholds, and the sensitivity of the thermal threshold testing tended to be greater than that of the pain threshold testing. The present findings indicate that thermal threshold testing for warm and cold perception can be a useful substitute for pain threshold testing to examine small nerve fiber injury in vibration-induced neuropathy.

Arm↗
PubMed2000

[Epidemiology of sleep apnea syndrome].

Recent epidemiological studies found an extraordinarily high prevalence of sleep-disordered breathing(SDB) in an apparently healthy population in the USA, Australia and Italy. Estimated prevalence for apnea-hypopnea index > or = 5 and > or = 10 were 24-78% and 15-35% for men and 9-55% and 5-20% for women in middle-aged populations. Obesity and craniofacial dysmorphism are two major risk factors to SDB. Apparent racial differences in the prevalence of SDB were found in the USA population and the differences could be explained with racial characteristics in craniofacial features. The lower limit of the prevalence of SDB was estimated with 0.5-2.9% in child populations in North Europe. Clinical significance of SDB in children should be carefully evaluated near future.

Age Factors↗
PubMed2000

[Diabetes mellitus and sleep apnea syndrome].

Epidemiologic evidences suggest that obstructive sleep apnea syndrome(OSAS) itself induces risk factors for cardiovascular diseases(= insulin resistance) independent of obesity. Our data suggest that moderate to severe OSA(AHI = > 20) is a contributing factor to the development of hyperinsulinemia, abnormal glucose metabolism and non-insulin-dependent diabetes mellitus(NIDDM) independent of aging, obesity and hereditary predisposition for DM in patients with OSAS. On the other hand, disagreement exists as to the incidence of OSAS in DM patients. Some authors reported that the incidence of OSAS was high among patients with DM, while others did not find such relationship. In these studies, the number of cases studied was small and, in addition, the selection of patients may have been biased. Future clinical research is needed to answer this issue.

Diabetes Mellitus↗
PubMed1999

Inner-arm dynein c of Chlamydomonas flagella is a single-headed processive motor.

Axonemal dyneins are force-generating ATPases that produce movement of eukaryotic cilia and flagella. Several studies indicate that inner-arm dyneins mainly produce bending moments in flagella and that these motors have inherent oscillations in force and motility. Processive motors such as kinesins have high duty ratios of attached to total ATPase cycle (attached plus detached) times compared to sliding motors such as myosin. Here we provide evidence that subspecies-c, a single-headed axonemal inner-arm dynein, is processive but has a low duty ratio. Ultrastructurally it is similar to other dyneins, with a single globular head, long stem and a slender stalk that attaches to microtubules. In vitro studies of microtubules sliding over surfaces coated with subspecies-c at low densities (measured by single-molecule fluorescence) show that a single molecule is sufficient to move a microtubule more than 1 microm at 0.7 microm s(-1). When many motors interact the velocity is 5.1 microm s(-1), fitting a duty ratio of 0.14. Using optical trap nanometry, we show that beads carrying a single subspecies-c motor move processively along the microtubules in 8-nm steps but slip backwards under high loads. These results indicate that dynein subspecies-c functions in a very different way from conventional motor proteins, and has properties that could produce self-oscillation in vivo.

Animals↗
PubMed1999

Medial plantar nerve conduction velocities among patients with vibration syndrome due to chain-saw work.

OBJECTIVE: The present study examined the effect of the vibration syndrome (VS) on the peripheral nervous system in the lower extremities. METHODS: Thirty-eight patients with VS due to previous exposure to vibration from chain-saw work and 55 age-matched controls were examined for sensory nerve conduction velocities in the medial plantar nerve (SCV-P). The patient group was divided into two subgroups, one with (n=19) and the other without vibration-induced white finger (VWF; n=19). RESULTS: Analysis of variance of SCV-P for the three groups showed significant difference (F(2,89)=10.65, P < 0.0001). A significant difference was found between the controls and the VWF(+) group (P < 0.0001) but not between the controls and the VWF(-) group (P=0.0508) by multiple comparison using Scheffe's method. CONCLUSION: These findings suggest that VS affects the peripheral nervous system function in the lower extremities via mediation of circulatory disturbance manifested as VWF.

Action Potentials↗
PubMed1999

His-Asp phosphotransfer possibly involved in the nitrogen signal transduction mediated by cytokinin in maize: molecular cloning of cDNAs for two-component regulatory factors and demonstration of phosphotransfer activity in vitro.

Implication of His-to-Asp and/or Asp-to-His (His-Asp) phosphorelay has been recently reported in signal transduction pathways initiated by ethylene and cytokinin. These signaling systems are generally composed of sensor His-protein kinases, His-containing phosphotransfer (HPt) domains, and response regulator domains. In this study, we isolated maize cDNAs, designated as ZmRR2 and ZmHP2, which encode a response regulator domain and HPt domain, respectively, and we identified their His-to-Asp phosphotransfer activity in vitro. The putative translated product of ZmRR2 was highly similar to that of ZmRR1 (78% identity), a maize response regulator homologue. The putative translated product of ZmHP2 showed similarity to that of HPt domains from Arabidopsis thaliana (AHP1-AHP3: 44 to 47% identity) and Saccharomyces cerevisiae (Ypdlp: 24% identity). In vitro experiments demonstrated that the putative signaling factors can transfer the phosphoryl group from His-80 of ZmHP2 to Asp-90 of ZmRRs. Treating detached leaves with t-zeatin or supplying inorganic nitrogen to the whole plant induced the accumulation of ZmRR1 and ZmRR2 transcripts. On the other hand, the steady-state transcript level of ZmHP2 was not affected by cytokinin or inorganic nitrogen sources. These results indicate that His-Asp phosphotransfer may be involved in the transduction of nitrogen signals mediated by cytokinin, and that multiple response regulators participate in the signaling pathways.

Amino Acid Sequence↗
PubMed1999

High performance in refolding of Streptomyces griseus trypsin by the aid of a mutant of Streptomyces subtilisin inhibitor designed as trypsin inhibitor.

Refolding of reduced and denatured Streptomyces griseus trypsin (SGT) was investigated. In the standard buffer of 50 mM Tris-HCl, the refolding yield of 1 microg/ml of SGT did not exceed 15%. This low yield was assumed to be due mainly to autoproteolysis and/or aggregation occurring concurrently with refolding. On the basis of this assumption, SGT was immobilized on agarose gel in order to suppress such intermolecular interactions, and various refolding media were examined for their ability to minimize misfolding. As a result, 1 M Tris, 1 M diethanolamine, and 1 M triethanolamine were chosen, and their application to the solution system increased the refolding yield considerably, to ca. 45%. A further dramatic increase in yield, to 85%, was observed when a mutant Streptomyces subtilisin inhibitor (SSI, C71SM73KC101S), engineered as a temporary inhibitor of SGT, was added to the solution system to suppress autoproteolysis during refolding. The application of a temporary inhibitor may be greatly effective in not only improvement of yield but also selection of media for the refolding of protease.

Bacterial Proteins↗
PubMed1999

Complementary DNA cloning and characterization of ferredoxin localized in bundle-sheath cells of maize leaves.

In maize (Zea mays L.) two leaf-specific ferredoxin (Fd) isoproteins, Fd I and Fd II, are distributed differentially in mesophyll and bundle-sheath cells. A novel cDNA encoding the precursor of Fd II (pFD2) was isolated by heterologous hybridization using a cDNA for Fd I (pFD1) as a probe. The assignment of the cDNAs to the Fds was verified by capillary liquid-chromatography/electrospray ionization-mass spectrometry. RNA-blot analysis demonstrated that transcripts for Fd I and Fd II accumulated specifically in mesophyll and bundle-sheath cells, respectively. The mature regions of pFD1 and pFD2 were expressed in Escherichia coli as functional Fds. Fd I and Fd II had similar redox potentials of -423 and -406 mV, respectively, but the Km value of Fd-NADP+ reductase for Fd II was about 3-fold larger than that for Fd I. Asparagine at position 65 of Fd II is a unique residue compared with Fd I and other Fds from various plants, which have aspartic acid or glutamic acid at the corresponding position as an electrostatic interaction site with Fd-NADP+ reductase. Substitution of asparagine-65 with aspartic acid increased the affinity of Fd II with Fd-NADP+ reductase to a level comparable to that of Fd I. These structural and functional differences of Fd I and Fd II may be related to their cell-specific expression in the leaves of a C4 plant.

Amino Acid Sequence↗
PubMed1999

Cephalometric abnormalities in non-obese and obese patients with obstructive sleep apnoea.

The aim of this work was to comprehensively evaluate the cephalometric features in Japanese patients with obstructive sleep apnoea (OSA) and to elucidate the relationship between cephalometric variables and severity of apnoea. Forty-eight cephalometric variables were measured in 37 healthy males and 114 male OSA patients, who were classed into 54 non-obese (body mass index (BMI) <27 kg x m(-2), apnoea-hypopnoea index (AHI)=25.3+/-16.1 events x h(-1)) and 60 obese (BMI > or = 27 kg x m(-2), AHI=45.6+/-28.0 events h(-1)) groups. Diagnostic polysomnography was carried out in all of the OSA patients and in 19 of the normal controls. The non-obese OSA patients showed several cephalometric defects compared with their BMI-matched normal controls: 1) decreased facial A-P distance at cranial base, maxilla and mandible levels and decreased bony pharynx width; 2) enlarged tongue and inferior shift of the tongue volume; 3) enlarged soft palate; 4) inferiorly positioned hyoid bone; and 5) decreased upper airway width at four different levels. More extensive and severe soft tissue abnormalities with a few defects in craniofacial bony structures were found in the obese OSA group. For the non-obese OSA group, the stepwise regression model on AHI was significant with two bony structure variables as determinants: anterior cranial base length (S-N) and mandibular length (Me-Go). Although the regression model retained only linear distance between anterior vertebra and hyoid bone (H-VL) as an explainable determinant for AHI in the obese OSA group, H-VL was significantly correlated with soft tissue measurements such as overall tongue area (Ton), inferior tongue area (Ton2) and pharyngeal airway length (PNS-V). In conclusion, Japanese obstructive sleep apnoea patients have a series of cephalometric abnormalities similar to those described in Caucasian patients, and that the aetiology of obstructive sleep apnoea in obese patients may be different from that in non-obese patients. In obese patients, upper airway soft tissue enlargement may play a more important role in the development of obstructive sleep apnoea, whereas in non-obese patients, bony structure discrepancies may be the dominant contributing factors for obstructive sleep apnoea.

Adult↗
PubMed1999

[Management of mycobacteriosis in general hospital without isolation ward for tuberculosis patients. 4. Actual status of the management of tuberculosis patients in a university hospital without isolation wards for infectious diseases].

We retrospectively evaluated clinical findings and the actual status of management of 69 tuberculosis patients admitted to the Fujita Health University Hospital, a hospital without isolation wards for infectious diseases, between 1991 and 1994. Forty-nine patients were smear-positive and 22 patients were smear-negative and culture-positive. Twenty-five cases (36.2%) were classified as type II (cavitary) and 29 cases (42.0%) as type III (non-cavitary) according to the GAKKAI classification of findings on chest X-ray films for pulmonary tuberculosis. Physicians in charge did not diagnose twenty-four patients (34.8%) as tuberculosis on admission. Physicians in charge tended not to suspect smear-negative patients of tuberculosis. Most of the patients with cavities on their chest X-ray films were strongly suspected of tuberculosis on admission, but in some of them, tuberculosis was not considered at all. Smear-positive patients with strongly suspected tuberculosis were diagnosed with the disease within three hospital days, while it took about three weeks in patients who were not considered as tuberculosis on admission to be diagnosed as tuberculosis. In the case of smear-negative patients, it took about one month and two months respectively to diagnose the case as tuberculosis. About half (51.1%) of the smear-positive patients were admitted and treated in single-bed rooms while 44.7% were attended in multiple-bed rooms for 11 days before they were transferred to single-bed rooms. When acid-fast bacilli were detected, 57.4% of the smear-positive patients were transferred to hospitals with isolation wards for infectious diseases, while the remaining smear-positive patients were treated in single-bed rooms at the university hospital. About one-third (31.7%) of the smear-negative patients had already left the hospital when specimens were found to be culture positive for tubercle bacilli. In conclusion, it is utmost important for physicians to suspect to tuberculosis for the early diagnosis of the disease.

Adult↗
PubMed1999

[A study of the long-term effectiveness of an outpatient pulmonary rehabilitation program].

Pulmonary rehabilitation is one of the most important components of comprehensive care for patients with significant disability due to chronic respiratory failure. Because pulmonary rehabilitation has not been popular in Japan, the long-term effectiveness of pulmonary rehabilitation has rarely been reported. We therefore examined the long-term effectiveness of an outpatient pulmonary rehabilitation program for patients with chronic respiratory failure. Our program was composed of a once-a-week introduction program for 2 months and a support program that was continued every 4 weeks as long as possible. Thirty stable patients with chronic respiratory failure were enrolled in the program; 21 patients (COPD: 15, lung complications of tuberculosis: 6) completed the 9-week introduction program and the ensuing 6-month support program. Good compliance with the home training regimen was maintained during the period. The introduction program significantly alleviated dyspnea (Fletcher's grade: 3.3 to 3.0, p < 0.01) and improved the data for activity (Spector's score: 5.3 to 5.8, p < 0.01) and 6-minute walking distance (319 to 384 m, p < 0.01). These benefits were sustained during the 6-month support program. We concluded that outpatient pulmonary rehabilitation can alleviate dyspnea and improve the activity and exercise tolerance of patients with chronic respiratory failure, and that the effectiveness of training can be well maintained with a minimal support program.

Activities of Daily Living↗