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Biomedical subjects

S Iwase

Publications and source records attributed to S Iwase.

At least 55 records · Page 3Linked to original sources
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

Postural modulation of soleus H-reflex under simulated hypogravity by head-out water immersion in humans.

To test our hypothesis that somatosensory inputs would influence postural modulation of soleus H-reflex, eleven subjects were investigated under the head-out water immersion (HOWI) conditions. Subjects were supine or standing on a tilting bed in each condition. They were instructed to maintain an upright posture with both legs. The water was filled to the subject's neck level in a test tank to reduce 95% of the gravitational effect by buoyancy. Surface electromyography of the soleus and tibialis anterior was measured. The soleus H-reflex was elicited at a stimulation intensity of 1.05 times the motor threshold. The recruitment profile of the motor response was unchanged between the conditions. The background activities of the soleus and tibialis anterior were not detected in any condition. The peak-to-peak amplitude of the H-reflex was significantly different between the conditions while the stimulation intensity (small M size) was not different. The soleus H-reflex during standing was significantly decreased compared with being supine in the control condition, whereas it did not in the HOWI condition. It was concluded that somatosensory inputs due to gravity exert an influence on postural modulation of the soleus H-reflex to maintain static posture in humans.

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↗
PubMed2000

Responses of muscle sympathetic nerve activity to static handgrip exercise after 14 days of exposure to simulated microgravity.

Decrease in muscle perfusion affects on cardiovascular response to exercise. Muscle hypoperfusion enhances the increase in blood pressure responses to exercise. Muscle perfusion depends not only on central blood pressure but also how fit the active muscle is above or below the heart level; muscle perfusion decreases as arm is elevated. Static exercise increases muscle sympathetic nerve activity (MSNA) innervating vessels in non-active muscles. The exercise-induced increase in MSNA is mainly mediated by stimulating chemosensitive muscle afferents in active muscles. However, the effect of arm elevation on MSNA during forearm exercise is not examined. On the other hand, space flight and simulated microgravity exposure causes reduction in muscle blood flow, suggesting chronic muscle hypoperfused condition during simulated microgravity. Therefore, there is a possibility that arm elevation after microgravity exposure alters MSNA responsiveness during exercise. However, arm elevation effect after exposure to simulated microgravity is not examined.

Arm↗
PubMed2000

Effects of leg venous hemodynamics on cardiovascular responses to lower body negative pressure and aging.

In aged people, decreases in stroke volume and cardiac output during orthostatic challenge are less. It is suggested that the stiffness of blood vessels is greater in the elderly, blunting leg venous pooling and drop in central blood volume in an upright position. Leg venous hemodynamics plays an important role in human cardiovascular homeostasis against gravitational stress. This study aimed to clarify how aging influences the leg venous hemodynamics and its contribution to cardiovascular homeostasis during lower body negative pressure (LBNP) in humans.

Adult↗
PubMed2000

Regulation of the venous capacitance during microgravity.

The purpose of this paper is to report our recent investigations on the relationship between sympathetic tone and leg venous compliance, as well as on the baroreflex control of leg venous compliance after simulated microgravity exposure in healthy humans.

Baroreflex↗
PubMed1999

Interferon-alpha repressed telomerase along with G1-accumulation of Daudi cells.

The implications of telomerase on senescence and human carcinogenesis are widely accepted, but the changes of telomerase activity along with cell cycle modulation by anticancer treatment still remain obscure. In this paper, we issued whether the telomerase activity fluctuated along with cell cycle of cultured cancer cells using the antiproliferative effect of interferon-alpha (IFN-alpha). Daudi Burkitt lymphoma cells, treated with IFN-alpha, showed proliferation inhibition and cell cycle arrest at G1. The telomerase activity at 72 h was repressed to about 20% of control cells. Furthermore, after 72 h IFN-alpha treatment, the cells in G1 phase showed the marked decrease of telomerase activity, while cells in S and G2/M still possessed it. Among expressions of telomerase-related genes, only the catalytic subunit of telomerase (hTERT) decreased from 48 h, while the template RNA component (hTERC) and telomerase-associated protein 1 (TEP-1) were not affected. The downregulation of c-Myc preceded the change of hTERT. Moreover, the analysis of cells treated with IFN-alpha for 24 h revealed that cells in G1-to-S transition mainly expressed high hTERT, while S and G2/M cells had higher level of telomerase activity than that of G1 cells. These results indicate that (i) the expression of hTERT precedes the telomerase activity which is higher in S and G2/M phases than G1 phase, (ii) IFN-alpha repressed the telomerase activity in a cell cycle-dependent manner with the downregulation of hTERT.

Antineoplastic Agents↗
PubMed1999

Muscle sympathetic nerve response to vestibular stimulation by sinusoidal linear acceleration in humans.

To clarify the effects of natural otolith stimulation on muscle sympathetic nerve activity (MSNA) in humans, eight male volunteers were seated in a linear accelerator (sled) during the recording of MSNA from the tibial nerve with microneurography, and also the recording of electrocardiogram, blood pressure measured with a Finapres device and thoracic impedance during movement. Sinusoidal linear acceleration with peak values of +/-0.10, 0.15 and 0.20 Gx were applied to the sitting subjects in the anteroposterior direction. Both the total activity and the burst rate of MSNA decreased during the sinusoidal linear acceleration, whereas the average heart rate, thoracic impedance and mean arterial pressure did not change significantly. These results suggest that moderate sinusoidal linear acceleration in the anteroposterior direction may suppress MSNA in humans.

Acceleration↗
PubMed1999

Defective binding of IRFs to the initiator element of interleukin-1beta-converting enzyme (ICE) promoter in an interferon-resistant Daudi subline.

To investigate mechanisms of interferon (IFN) resistance, we have established an IFN-resistant Daudi subline (Daudi(res)), which is 1 X 10(4) times more resistant to IFN-alpha than parental cells. Among the IFN-inducible genes examined, only ICE mRNA expression was deficient in Daudi(res) cells. We then analyzed the regulatory mechanisms of ICE transcription, and found that IFN-induced activation of the ICE promoter was dependent on the binding of IRFs to its initiator (Inr) element. Inr binding of IRFs was markedly diminished in Daudi(res) cells, and forced expression of IRF-1 was able to activate the ICE promoter to the level of parental cells. These results suggest that IRFs and their target genes, as represented by ICE in this study, are involved in IFN resistance.

Binding Sites↗
PubMed1999

Transcriptional repression of the E2F-1 gene by interferon-alpha is mediated through induction of E2F-4/pRB and E2F-4/p130 complexes.

E2F is a heterodimeric transcription factor composed of one of five E2F subunits (E2F-1 to E2F-5) and a DP subunit. E2F regulates the expression of several growth-promoting genes, and thus, can be a target of antiproliferative action of interferons (IFNs). In this study, we investigated the mechanisms whereby IFN-alpha suppresses transcription of the E2F-1 gene. Transfection studies revealed that E2F-1 promoter was functionally divided into two parts: upstream activation sequences (UAS) and a downstream negative-regulatory element (E2F-binding sites). When cells were proliferating, transcription of the E2F-1 gene was primarily driven by the UAS, while E2F sites were not involved in activation. IFN-alpha markedly reduced E2F-1 promoter activity, but introduction of non-binding mutation at the E2F sites completely abrogated the inhibition. Free E2F4 was found to be the predominant species bound to the E2F sites in proliferating cells. IFN-alpha induced upregulation of E2F-4 along with dephosphorylation of pRB and p130, which resulted in the formation of E2F-4/pRB and E2F-4/p130 complexes on the E2F-1 promoter. These complexes function as transcriptional repressors to inhibit E2F-1 mRNA expression. Our findings indicate that E2F-4 is a critical regulator of E2F-1, which offer an excellent paradigm for understanding functional diversity within the E2F family.

Binding Sites↗
PubMed1999

UDP-GlcNAc:Galbeta1-->3GalNAc (GlcNAc to GalNAc) beta1-->6N-acetylglucosaminyltransferase holds a key role on the control of CD15s expression in human pre-B lymphoid cell lines.

Expression mechanism of CD15s (sialyl-Lex, sLex) antigen has been investigated using human B lymphoid cell lines. sLexstructures were not expressed in mature B lymphoids but highly expressed in pre-B leukemia and pre-B lymphoma cell lines. The expression site was mainly on the O -linked oligosaccharide chains and E-selectin mediated-cell adhesion capability of sLex-positive cells were significantly suppressed by benzyl-alpha-GalNAc treatment. Subsequently, the bases of the sLexexpression control mechanism were examined at the levels of enzymatic activities and transcripts of glycosyltransferases. (1) The activities of alpha1-->3fucosyltransferase, alpha2-->3sialyltransferase, beta1-->4Gal-transferase, and elongation beta1-->3GlcNAc-transferase, did not correlate with sLexexpression levels. (2) The transcripts of Fuc-TVII were not parallel with sLexexpression, and those of ST3Gal IV and beta1-->4Gal-transferase were constitutively detected in all cell lines tested. (3) There was no detectable enzyme activity for core 3 and 4 backbone structure synthesis in human B cell lines. (4) By contrast, the enzyme activities and transcripts of UDP-GlcNAc:Galbeta1-->3GalNAc (GlcNAc to GalNAc) beta1-->6 N -acetylglucosaminyltransferase (Core2GnT) had significant correlation with the cell surface expression of sLexantigen. (5) Moreover, Western blot analysis revealed the presence of a major approximately 150 kDa glycoprotein that carries O -linked oligosaccharides recognized by anti-sLexmonoclonal antibody in sLex-positive pre-B leukemia cell lines. This correlation of Core2GnT with CD15s expression suggests that Core2GnT is a regulator of the cell surface expression of sLexin human pre-B lymphoid cells.

Antigens, CD↗
PubMed1999

Responses of sympathetic outflow to skin during caloric stimulation in humans.

We previously showed that caloric vestibular stimulation elicits increases in sympathetic outflow to muscle (MSNA) in humans. The present study was conducted to determine the effect of this stimulation on sympathetic outflow to skin (SSNA). The SSNA in the tibial and peroneal nerves and nystagmus was recorded in nine subjects when the external meatus was irrigated with 50 ml of cold (10 degrees C) or warm (44 degrees C) water. During nystagmus, the SSNA in tibial and peroneal nerves decreased to 50 +/- 4% (with baseline value set as 100%) and 61 +/- 4%, respectively. The degree of SSNA suppression in both nerves was proportional to the maximum slow-phase velocity of nystagmus. After nystagmus, the SSNA increased to 166 +/- 7 and 168 +/- 6%, respectively, and the degree of motion sickness symptoms was correlated with this SSNA increase. These results suggest that the SSNA response differs from the MSNA response during caloric vestibular stimulation and that the SSNA response elicited in the initial period of caloric vestibular stimulation is different from that observed during the period of motion sickness symptoms.

Adult↗
PubMed1999

Sympathetic outflow to muscle in humans during short periods of microgravity produced by parabolic flight.

We have investigated the changes in muscle sympathetic nerve activity (MSNA) from the tibial nerve during brief periods of microgravity (microG) for approximately 20 s produced by parabolic flight. MSNA was recorded microneurographically from 13 quietly seated human subjects with their knee joints extended in a jet aircraft simultaneously with the electrocardiogram, the blood pressure wave (measured with a Finapres), the respiration curve, and the thoracic fluid volume (measured by impedance plethysmography). During quiet and seated parabolic flight, MSNA was activated in hypergravity and was suppressed in microG phasically. At the entry to hypergravity at 2 G just before microG, the thoracic fluid volume was reduced by 3.2 +/- 3%, and the arterial blood pressure was lowered transiently and then gradually elevated from 89.5 +/- 1.7 to 100.2 +/- 1.7 mmHg, which caused the enhancement of MSNA by 91.4 +/- 14.2%. At the entry to microG, the thoracic fluid volume was increased by 3.4%, which lowered the mean blood pressure to 77.9 +/- 2.3 mmHg and suppressed the MSNA by 17.2%. However, this suppression lasted only approximately 10 s, followed by an enhancement of MSNA that continued for several seconds. We conclude that MSNA is suppressed and then enhanced during microG produced by parabolic flight. These changes in MSNA are in response not only to intrathoracic fluid volume changes but also to arterial blood pressure changes, both of which are caused by body fluid shifts induced by parabolic flight, and these changes are quite phasic and transient.

Adult↗
PubMed1999

[A case of aggressive myeloma with abnormal plasmocytes in pleural effusion and cerebrospinal fluid].

Extramedullary involvement of myelomas is common but invasion of myeloma cells into the pleural cavity and cerebrospinal fluid (CSF) is rare. We report an aggressive case of multiple myelomas (Bence Jones lambda type) with pleural and meningeal infiltration. A 66-year-old man was referred to our hospital because of anemia, thrombocytopenia, and dyspnea. His peripheral blood contained 2% bizarre plasma cells. Bone marrow biopsy specimens and immunoelectrophoresis confirmed the diagnosis. A chest radiograph disclosed pleural effusion in both lungs containing M-protein and numerous abnormal cells. The patient also suffered from disorientation, speech disorder, and muscle weakness. A lumbar puncture revealed atypical plasma cells in CSF. Four courses of chemotherapy (cyclophosphamide, doxorubicin, and prednisolone) and the intrathecal administration of methotrexate and cytarabine at 3-week intervals were effective in decreasing the pleural effusions and eliminating plasma cells from CSF. Nonetheless a chest wall tumor, pelvic mass, and pneumonia developed, and the patient died 5 months after initial presentation. Pleural infiltration of myeloma cells and multiple lesions with plasma cell involvement were discovered at autopsy.

Aged↗
PubMed1999

Sympathetic vasoconstriction and orthostatic intolerance after simulated microgravity.

Upon a return to the earth from spaceflight, astronauts often become presyncope during standing. This orthostatic intolerance is provoked by the exposure to the stimulation model of microgravitational environment in humans, 6 degrees head-down bed rest (HDBR). The mechanism for the orthostatic hypotension after microgravity remains unclear. It has been reported that a microgravity-induced loss of circulatory blood volume, a withdrawal of vagal tone, or a reduction of carotid-cardiac baroreflex function may relate to this phenomenon. A recent article has reported that astronauts who showed presyncopal events after spaceflight had subnormal increases in plasma norepinephrine under the standing tests, suggesting that a hypoadrenergic responsiveness to orthostatic stress may partly contribute to postflight orthostatic hypotension. However, it is unclear how and whether or not the sympathetic outflow to peripheral vessels and the release of norepinephrine from sympathetic nerve terminals were altered after microgravity. The vasomotor sympathetic outflow to the skeletal muscle can be directly recorded as muscle sympathetic nerve activity (MSNA) using a microneurographic technique. In addition, the rate of an increase in plasma norepinephrine per that in MSNA in response to applied orthostatic stress can partly indicate the norepinephrine release to sympathetic stimuli as a trial assessment. Therefore, we performed 60 degrees head-up tilt (HUT) tests before and after 14 days of HDBR, and examined the differences in the MSNA response and the indicated norepinephrine release during HUT tests 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↗