Biomedical subjects

Y Niimi

Publications and source records attributed to Y Niimi.

At least 37 records · Page 2Linked to original sources

PubMed2000

Skin sympathetic neuroeffector response is attenuated dose-dependently by systemic prostaglandin E1 injection in humans.

To clarify the effects of prostaglandin E1 (PGE1) on the vasoconstrictive responses, we compared the correlation between the amplitude of integrated skin sympathetic nerve activity (SSNA) and per cent reduction in skin blood flow (SBF) before and after the infusion of lipo PGE1 and placebo (bolus one-shot infusion, single blind study), and constant rate infusion of PGE1 (10 and 50 ng kg(-1) min(-1) by infusion pump, dose-dependency study) in ten healthy men. SSNA was recorded microneurographically from the median nerve simultaneously with SBF by laser Doppler flowmetry at the index fingertip. The measurement was conducted 30 min after injection of lipo PGE1 or placebo, and during the drip infusion of 10 and 50 ng kg(-1) min(-1) of PGE1 with maneuvers to enhance SSNA. The resting and activated skin blood flow were not significantly different between 10 ng lipo PGE1 and placebo administration, and between baseline and 10, 50 ng kg(-1) min(-1) of PGE1 injection. The vascular response, defined as the slope of regression line between logarithm of amplitude of integrated SSNA bursts and the reduction in SBF, was significantly suppressed by injection of lipo PGE1 as compared with that by placebo. It was also decreased dose-dependently by the constant rate infusion of PGE1 (10 and 50 ng kg(-1) min(-1)). We concluded that the intravenous injection of PGE1 attenuates vasoconstrictive responses to SSNA, and analysis of the relations between SSNA and vasoconstrictive response, i.e. the neuroeffector response, is suggested to be an important tool to assess the drug effect.

Action Potentials↗

PubMed2000

Effect of xenon on autonomic cardiovascular control--comparison with isoflurane and nitrous oxide.

STUDY OBJECTIVES: To clarify the effect of xenon on the autonomic nervous system by comparing similar effects of isoflurane and nitrous oxide. DESIGN: Prospective, randomized study. SETTING: Operating room at a university hospital. PATIENTS: 39 ASA physical status I and II patients scheduled for general anesthesia. INTERVENTIONS: Patients were randomly allocated into one of three groups and received one of the following inhalational anesthetics: 56% of xenon (Group X), 0.94% of isoflurane (Group I), or 70% of nitrous oxide and 0.15% of isoflurane (Group N). Phenylephrine (pressor test) and nicardipine (depressor test) were given to assess baroreflex sensitivity. MEASUREMENTS AND MAIN RESULTS: Continuous blood pressure (BP) and electrocardiogram (ECG) were recorded before and during anesthesia to analyze heart rate (HR) variability and baroreflex sensitivity. Power spectrum of HR variability was calculated by fast Fourier transformation and power spectrum densities at low frequency (LF: 0.04-0.15Hz) and high frequency (HF: 0.15-0.40 Hz) were compared. Baroreflex sensitivity was calculated from the slope of regression for BP changes versus associated changes in R-R intervals. For HR variability, Group X showed lower power spectrum densities (ms(2).Hz(-1)) in LF and HF than did Group I (LF: 0.09 +/- 0.06 vs. 0.35 +/- 0.53; p < 0.05; HF: 0.40 +/- 0.34 vs. 0.98 +/- 0.68, p < 0.01). Group X had the lowest baroreflex sensitivity (ms.mmHg(-1)) via pressor test of the three study groups (Group X: 2.00 +/- 0.87, Group I: 3.53 +/- 2.14, Group N: 3.78 +/- 2. 17, p < 0.05). CONCLUSIONS: Xenon depressed both sympathetic and parasympathetic transmission more than isoflurane at 0.8 MAC. Xenon was also suggested to be relatively vagotonic.

Adolescent↗

PubMed2000

Effect of xenon on endotracheal tube cuff.

STUDY DESIGN: To investigate the effect of xenon on the endotracheal tube cuff in comparison to that of nitrous oxide. DESIGN: Prospective, randomized study. SETTING: Laboratory in vitro testing of endotracheal tubes. INTERVENTIONS: Exposure of air-filled endotracheal tube cuffs to xenon or nitrous oxide (79 vol%) mixed with a balance of oxygen (21 vol%) for 3 hours. MEASUREMENTS: The intra-cuff pressure and gas volume in the cuff were measured for 3 hours. MAIN RESULTS AND CONCLUSION: Increase in pressure and gas volume was significantly less and slower with xenon than with nitrous oxide. More nitrous oxide passes into the cuff than xenon.

Air Pressure↗

PubMed2000

Characterization of the 5'-flanking region of the rat TIS11 gene.

To understand the mechanism underlying the transcriptional regulation of the immediate early gene TIS11, we characterized the 5'-flanking region of the rat TIS11 gene. When fused to the luciferase reporter gene, the 5.3-kb 5'-flanking region of the rat TIS11 gene exhibited functional promoter activity in pheochromocytoma PC12 and hepatoma H4IIE cells. 5'-Deletion analyses indicated that multiple negative and positive regulatory regions were present in the 5'-flanking region, and that some of these regions functioned in a cell type-specific manner. Promoter activity of the rat TIS 11 gene was enhanced by phorbol 12-myristate 13-acetate (PMA) in both cell lines, and the PMA-responsiveness resided within the 5'-flanking region. The induction of promoter activity by PMA was completely blocked by GF109203X or PD98059, inhibitors of protein kinase C and mitogen-activated protein (MAP) kinase kinase, respectively. These results suggested that induction of the rat TIS 11 promoter by PMA is mediated by activation of the protein kinase C/MAP kinase cascade.

Animals↗

PubMed2000

Cloning and characterization of the rat TIS11 gene.

The TIS11 gene is an immediate early gene that is induced rapidly and transiently by phorbol 12-myristate 13-acetate and various growth factors. To study transcriptional regulation of the gene, a genomic clone of rat TIS11 was isolated, and the organization of exon-intron structure and transcriptional initiation site were determined. The rat TIS11 gene consisted of 2 exons spanning approximately 2.5 kb. Several canonical sequences for binding of transcriptional factors were found in the 5'-flanking region. The 5.3 kb of the 5'-flanking region fused to a luciferase reporter gene showed promoter activity when introduced into rat pheochromocytoma PC12 cells. Analyses with serial 5'-deletion mutants suggested that the major positive regulatory region is located at the region of -241 to -76, and that the minimum promoter region is within the 76-bp upstream of the transcriptional initiation site. Gel mobility shift assays revealed that PC12 cell nuclear proteins specifically bind to the major positive regulatory region of the TIS11 gene. The identified nuclear protein components may act as the positive trans-acting factors in the basal expression of the TIS11 gene in PC12 cells.

Amino Acid Sequence↗

PubMed2000

Removal of catalytic activity by EDTA from antibody light chain.

Gp41 peptide antigen of the HIV-1 envelope (TP41-1:TPRGPDRPEGIEEEGGERDR, a highly conserved region) was enzymatically degraded by the antibody light chain 41S-2-L after an induction period. The peptide bond between Glu14 and Gly15 was cleaved early in the reaction. When EDTA was added in the induction period, it inhibited the degradation of TP41-1 thus ceasing the catalytic activity of 41S-2-L. In contrast, when EDTA was added after the induction period, only a small reduction in the catalytic activity was observed. These observations suggest that metal ions are important in stimulating catalytic activity early in the reaction.

Amino Acid Sequence↗

PubMed2000

Type XVIII collagen is newly transcribed during bovine adipogenesis.

To isolate candidate genes concerned with bovine adipocyte differentiation, we have constructed a subtraction cDNA library from a clonal bovine intramuscular preadipocyte (BIP) cell line. We have isolated a set of cDNA clones whose respective mRNA levels are upregulated during the differentiation of BIP cells. The sequence of one subtracted cDNA fragment was highly homologous to that of mouse type XVIII collagen. Northern blot analysis and reverse transcriptase polymerase chain reaction (RT-PCR) showed that collagen XVIII gene expression increased during adipocyte differentiation. The collagen XVIII gene was also highly expressed in fat tissue. Although its function is unclear, these expression patterns indicate that type XVIII collagen may be associated with adipocyte differentiation in cattle.

Adipocytes↗

PubMed2000

IgA pemphigus: a case report and its characteristic clinical features compared with subcorneal pustular dermatosis.

We report a case of IgA pemphigus. A 35-year-old woman had vesiculopustular eruptions on her scalp, trunk, and extremities. Histologic examination showed a subcorneal pustule containing numerous neutrophils without acantholysis. Direct immunofluorescence revealed IgA deposits in the intercellular space throughout the epidermis, more intense in superficial layers and less intense in lower layers. The titer of circulating IgA antibodies was 1:160 in normal human skin as a substrate. Skin lesions responded to dapsone. The IgA autoantibody from this patient did not react with desmogleins or desmocollins when immunoblotting, enzyme-linked immunosorbent assay, or complement DNA transfection was used. We consider the characteristic clinical features that favor the diagnosis of IgA pemphigus rather than classic subcorneal pustular dermatosis as follows: (1) the lesions involve the scalp and/or face, and (2) the distribution of the lesions is more widespread.

Adult↗

PubMed2000

Bispectral analysis of the electroencephalogram does not predict responsiveness to verbal command in patients emerging from xenon anaesthesia.

The bispectral index (BIS) is derived empirically from the electroencephalogram database of patients receiving common anaesthetics, but it may not be valid for uncommon agents. Therefore, we investigated how xenon affects the BIS. Nine and 11 patients were anaesthetized with 0.8 of the minimal alveolar concentration (MAC) of isoflurane (0.92%) and xenon (56%), respectively. After the end of operation, these concentrations were decreased in decrements of 0.1 MAC (isoflurane 0.12% or xenon 7%) and each new concentration was maintained for 15 min. This was repeated until the patient first opened her eyes or squeezed the investigator's hand on command. Isoflurane and xenon at 0.8 MAC reduced the BIS to a median of 40 (range 36-53) and 36 (30-61), respectively. With decreasing concentrations of isoflurane, the BIS increased progressively and it reached a median of 96 (90-98) when the patients awoke. In contrast, four patients receiving xenon responded to verbal command while the BIS was below 50 [median 45 (range 41-49)]. The remaining seven patients in the xenon group awoke when their BIS was greater than 80 [median 96 (range 82-98)], but in four of them the BIS was no greater than 50 when the xenon concentration was only 0.1 MAC (7%) higher than that associated with awakening. We conclude that low BIS values (< 50) do not guarantee adequate hypnosis during xenon anaesthesia.

Adult↗

PubMed2000

Plasma concentration of fentanyl with xenon to block somatic and hemodynamic responses to surgical incision.

BACKGROUND: Although anesthesia with xenon has been supplemented with fentanyl, its requirement has not been established. This study was conducted to determine the plasma concentrations of fentanyl necessary to suppress somatic and hemodynamic responses to surgical incision in 50% patients in the presence of 0.7 minimum alveolar concentration (MAC) xenon. METHODS: Twenty-five patients were allocated randomly to predetermined fentanyl concentration between 0.5 and 4.0 ng/ml during 0.7 MAC xenon anesthesia. Fentanyl was administered using a pharmacokinetic model-driven computer-assisted continuous infusion device. At surgical incision each patient was monitored for somatic and hemodynamic responses. A somatic response was defined as any purposeful bodily movement. A positive hemodynamic response was defined as a more than 15% increase in heart rate or mean arterial pressure more than the preincision value. The concentrations of fentanyl to prevent somatic and hemodynamic responses in 50% of patients were calculated using logistic regression. RESULTS: The concentration of fentanyl to prevent a somatic response to skin incision in 50% of patients in the presence of 0.7 MAC xenon was 0.72 +/- 0.07 ng/ml and to prevent a hemodynamic response was 0.94 +/- 0.06 ng/ml. CONCLUSIONS: Comparing these results with previously published results in the presence of 70% nitrous oxide, the fentanyl requirement in xenon anesthesia is smaller than that in the equianesthetic nitrous oxide anesthesia.

Abdomen↗

PubMed2000

Minimum alveolar concentration-awake of Xenon alone and in combination with isoflurane or sevoflurane.

BACKGROUND: The minimum alveolar concentration (MAC)-awake is a traditional index of hypnotic potency of an inhalational anesthetic. The MAC-awake of xenon, an inert gas with anesthetic properties (MAC = 71%), has not been determined. It is also unknown how xenon interacts with isoflurane or sevoflurane on the MAC-awake. METHODS: In the first part of the study, 90 female patients received xenon, nitrous oxide (N2O), isoflurane, or sevoflurane supplemented with epidural anesthesia (n = 36 for xenon and n = 18 per group for other anesthetics). In the second part, 72 additional patients received either xenon or N2O combined with the 0.5 times MAC-awake concentration of isoflurane or sevoflurane (0.2% and 0.3%, respectively, based on the results of the first part; n = 18 per group). During emergence, the concentration of an assigned anesthetic (xenon or N2O only in the second part) was decreased in 0. 1 MAC decrements every 15 min from 0.8 MAC or from 70% in the case of N2O until the patient followed the command to either open her eyes or to squeeze and release the investigator's hand. The concentration midway between the value permitting the first response to command and that just preventing it was defined as the MAC-awake. RESULTS: The MAC-awake were as follows: xenon, 32.6 +/- 6.1% (mean +/- SD) or 0.46 +/- 0.09 MAC; N2O, 63.3 +/- 7.1% (0.61 +/- 0.07 MAC); isoflurane, 0.40 +/- 0.07% (0.35 +/- 0.06 MAC); and sevoflurane, 0.59 +/- 0.10% (0.35 +/- 0.06 MAC). Addition of the 0.5 MAC-awake concentrations of isoflurane and sevoflurane reduced the MAC-awake of xenon to 0.50 +/- 0.15 and 0.51 +/- 0.16 times its MAC-awake as a sole agent, but that of N2O to the values significantly greater than 0.5 times its MAC-awake as a sole agent (0.68 +/- 0.12 and 0.66 +/- 0.14 times MAC-awake; P < 0.01, analysis of variance and Dunnett's test). CONCLUSIONS: The MAC-awake of xenon is 33% or 0.46 times its MAC. In terms of the MAC-fraction, this is smaller than that for N2O but greater than those for isoflurane and sevoflurane. Unlike N2O, xenon interacts additively with isoflurane and sevoflurane on MAC-awake.

Adult↗

PubMed2000

[Power spectrum analysis of heart rate variability to orthostatic challenge in cases of Binswanger's encephalopathy].

The autonomic nerve activity was evaluated in cases of Binswanger's encephalopathy by power spectrum analysis of heart rate variability during supine rest and standing upright, in order to elucidate the role of autonomic nervous system function in the pathophysiology of Binswanger's encephalopathy. There was no difference in the ratio of low frequency (LF) power to high frequency (HF) power (L/H ratio), which reflects cardiac sympathetic nerve activity in each position among Binswanger's encephalopathy, control and lacunar stroke. Binswanger's encephalopathy had significantly lower HF power, which reflects cardiac parasympathetic nerve activity, than control and lacunar stroke in a supine rest, and HF power did not respond to standing. Moreover, there was no difference in HF power between mild cases and severe cases of Binswanger's encephalopathy, and L/H ratio decreased in severe cases during standing. These results suggest that cardiac parasympathetic nervous system function is impaired in the early stage of Binswanger's encephalopathy, then cardiac sympathetic nervous system dysfunction occurs with advancing the disease stage.

Aged↗

PubMed2000

Leg venous compliance in orthostatic intolerance before and after 14-day head-down bed rest.

To test the hypothesis that increased leg venous compliance (LVC) is one of the contributory factors to orthostatic intolerance (OI) after simulated microgravity, 28 healthy young males were exposed to a 14-day head-down bed rest, and LVC was measured by venous occlusion plethysmography. Orthostatic tolerance was evaluated by a 60 degree head-up tilt (HUT) for 15 min. Sixteen subjects suffered from OI after the bed rest. They were then divided into orthostatic tolerance (non-fainters, n=12) and intolerance (fainters, n=16) groups. We found that fainters had significantly larger LVC before bed rest (0.055 +/- 0.003 vs. 0.065 +/- 0.002 ml 100 ml-1 mm Hg-1, non-fainter vs. fainter; P < 0.05). After bed rest, LVC markedly increased in both groups. In all the subjects calf circumference was reduced on average by 4.7% and the percent change in LVC was negatively correlated with the percent change in calf circumference when all subjects' data were combined after bed rest (r = -0.42, P < 0.05). Our results did not support the hypothesis that increased LVC is the contributory factor to OI after a 14-day bed rest; however, the mechanisms behind the large LVC in the fainters before bed rest are unclear, and the initial LVC might be a predictive indicator for OI after microgravity exposure.

Adult↗

PubMed2000

Arm elevation enhances muscle sympathetic nerve activity during static exercise.

The purpose of the present study was to evaluate the effect of hypoperfusion to the static-exercised-muscle induced by arm elevation on muscle sympathetic nerve activity (MSNA) recorded from the right tibial nerve (n= 10) by microneurography. Subjects performed static handgrip exercises (SHG) at 30% of maximal voluntary contraction (MVC) for 2 min, followed by 2 min of posthandgrip muscle ischemia (PHGMI) at the heart level (control) and with the arm elevated (50 cm above heart level). Basal heart rate, mean blood pressure and MSNA responses expressed as burst rate (bursts/min) and total MSNA (%) were unaffected by the arm-position. Heart rate response during SHG was not influenced by the arm elevation, while mean blood pressure and MSNA responses were increased by it (P<0.05). MSNA responses were increased during the second minute of the SHG period (P<0.05) and the PHGMI period (P<0.05) in the elevated arm position. In conclusion, arm elevation increased MSNA responses to SHG and PHGMI, suggesting an increased magnitude of muscle metaboreflex.

Adrenergic Fibers↗

PubMed2000

Muscle sympathetic nerve activity (MSNA) during high-intensity, isometric leg exercise in humans.

Muscle sympathetic nerve activity (MSNA) is activated during mild-intensity isometric handgrip exercise, but not during isometric leg exercise at a similarly relative intensity. It is unclear whether MSNA is increased by leg exercise at heavy intensity in humans. We aimed to examine how MSNA responds to high-intensity, isometric leg exercise in humans. Eight young healthy male volunteers performed isometric plantar flexions of high intensity (70% of MVC) for 2 min, followed by 2 min of post-exercise muscle ischemia (PEMI; isolated muscle metaboreflex stimulation), with monitoring of muscle sympathetic nerve activity (MSNA), heart rate and arterial blood pressure. MSNA was increased at the onset of exercise (p<0.05), and further increased to 512 +/- 111% of baseline at the second min of exercise (p<0.05). Furthermore, MSNA remained elevated above baseline during PEMI (259 +/- 41 % of baseline, p<0.05). Heart rate also rose at the onset of the test (P<0.05) and gradually increased all through the test (p<0.05), but decreased to baseline level during PEMI. Mean blood pressure was progressively increased from the onset to the end of test (p<0.05), and remained elevated above baseline during PEMI (p<0.05). In summary, MSNA was increased progressively throughout high-intensity, isometric plantar flexion in humans, primarily due to muscle metaboreflex.

Adult↗

PubMed2000

Effect of aging on muscle sympathetic nerve activity and peripheral venous pressure in humans.

To elucidate the effect of aging on blood pressure regulation, especially cardiopulmonary baroreflex in humans, we measured the resting value of muscle sympathetic nerve activity (MSNA), heart rate (HR), blood pressure (BP), peripheral venous pressure (PVP), and calf blood flow (CBF) in eight healthy young male subjects and eight healthy aged subjects, and compared the responses to the low level of lower body negative pressure (LBNP) between the two groups. The resting MSNA was higher, and the response of MSNA to LBNP was lower in the aged group than in the young group; the response of PVP to LBNP was also lower in the aged than in the young group. Delta MSNA/delta PVP showed no significant differences between the two groups. The present findings indicate that the effect of LBNP on cardiopulmonary baroreflex is greater in young people than in aged people, but that cardiopulmonary baroreflex may be preserved with advancing age.

Adult↗

PubMed2000

Body temperature and skin blood flow during a 14-day bed-rest in a head-down tilt position in humans.

Exposure to microgravity or simulated microgravity is known to affect regulatory function in autonomic nervous system. With regard to thermoregulation, simulated microgravity impairs sweating and induces lower skin and higher internal temperatures during physical work. During supine rest after HDT bed rest, the internal temperatures were reported to be higher than those of pre-HDT bed rest in some studies but not in others. There is no report about the dynamic changes of skin blood flow during 14-day HDT bed rest. The process of HDT bed-rest deconditioning on the function of the thermoregulatory system is virtually unknown. The HDT induces an immediate cephalad fluid shift which would inhibit the sympathetic outflow through the arterial and cardiopulmonary baroreflexes, which may increase the skin blood flow. On the other hand, prolonged HDT bed rest induces dehydration, which will increase sympathetic outflow through cardiopulmonary baroreceptor modulation. Both sympathetic activation and dehydration itself will decrease skin blood flow. It seems probable that the general effect on skin blood flow may reverse along the HDT bed rest. However, the dynamic characters of skin blood flow and body temperature during the HDT bed rest have not been studied thoroughly. Therefore, the purpose of present study was to investigate the changes of skin blood flow and body temperature during 14 days HDT bed rest.

Adult↗

PubMed2000

Arterial baroreflex control of sympathetic vasoconstrictor traffic and orthostatic intolerance after head-down bed rest.

The purpose of the present study is to examine the changes in the arterial baroreflex control of muscle sympathetic nerve activity (MSNA) after head-down bed rest (HDBR), in relation to orthostatic hypotension after HDBR. Therefore, we performed 60 degrees head-up tilt (HUT) tests before and after 14 days of HDBR, with monitoring MSNA, heart rate and blood pressure. We calculated the gain of the arterial baroreflex control of MSNA, and compared the gains between the subjects who did (defined as the fainters) and those who did not (defined as the nonfainters) become presyncopal in HUT tests after HDBR.

Adult↗