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J Horiuchi

Publications and source records attributed to J Horiuchi.

At least 19 recordsLinked to original sources
PubMed2006

Differential control of cardiac and sympathetic vasomotor activity from the dorsomedial hypothalamus.

1. The dorsomedial hypothalamus (DMH) plays a crucial role in mediating the cardiovascular responses to different stressors, including acute psychological stress and cold stress. Activation of neurons in the DMH evokes increases in arterial pressure and in the activity of sympathetic nerves innervating the heart, blood vessels and brown adipose tissue. The descending pathways from the DMH to the spinal sympathetic outflow include synapses with neurons in medullary nuclei and possibly other brain stem regions. 2. Recent studies from our and other laboratories have indicated that neurons in the rostral ventrolateral medulla (RVLM) and in the region of the raphe pallidus (RP) in the medulla are important components of the descending pathways that mediate the cardiovascular response to activation of the DMH. Neurons in the RP primarily mediate the sympathetic cardiac components of the DMH-evoked response, whereas the RVLM neurons primarily mediate the sympathetic vasomotor component. 3. Activation of DMH neurons not only increases heart rate and sympathetic vasomotor activity, but also resets the baroreceptor reflex such that it remains effective, without any decrease in sensitivity, over a higher operating range of arterial pressure. 4. Activation of 5-hydroxytryptamine 5-HT(1A) receptors in the medulla oblongata leads to a selective suppression of cardiac and sympathetic vasomotor components of the DMH-evoked response, but does not affect sympathetic reflex responses evoked from baroreceptors or chemoreceptors. Thus, central 5-HT(1A) receptors modulate cardiovascular responses evoked from the DMH in a highly potent but selective fashion.

Animals↗
PubMed2004

Descending vasomotor pathways from the dorsomedial hypothalamic nucleus: role of medullary raphe and RVLM.

The dorsomedial hypothalamic nucleus (DMH) is believed to play a key role in mediating vasomotor and cardiac responses evoked by an acute stress. Inhibition of neurons in the rostral ventrolateral medulla (RVLM) greatly reduces the increase in renal sympathetic nerve activity (RSNA) evoked by activation of the DMH, indicating that RVLM neurons mediate, at least in part, the vasomotor component of the DMH-evoked response. In this study, the first aim was to determine whether neurons in the medullary raphe pallidus (RP) region also contribute to the DMH-evoked vasomotor response, because it has been shown that the DMH-evoked tachycardia is mediated by the RP region. The second aim was to directly assess the effect of DMH activation on the firing rate of RVLM sympathetic premotor neurons. In urethane-anesthetized rats, injection of the GABA(A) receptor agonist muscimol (but not vehicle solution) in the RP region caused a modest ( approximately 25%) but significant reduction in the increase in RSNA evoked by DMH disinhibition (by microinjection of bicuculline). In other experiments, disinhibition of the DMH resulted in a powerful excitation (increase in firing rate of approximately 400%) of 5 out of 6 spinally projecting barosensitive neurons in the RVLM. The results indicate that neurons in the RP region make a modest contribution to the renal sympathoexcitatory response evoked from the DMH and also that sympathetic premotor neurons in the RVLM receive strong excitatory inputs from DMH neurons, consistent with the view that the RVLM plays a key role in mediating sympathetic vasomotor responses arising from the DMH.

Animals↗
PubMed2004

Renal sympathetic and cardiac changes associated with anaphylactic hypotension.

Severe anaphylactic reactions can result in life-threatening hypotension, but little is known about the autonomic changes that accompany the hypotensive response. The aim of this study was to determine the renal sympathetic and cardiac responses to anaphylactic hypotension, and to evaluate the contribution of sinoaortic and vagal afferent inputs in producing these responses. Rats were sensitized with bovine serum albumin (BSA) and, after 10-14 days, were anaesthesized with sodium pentobarbitone and arterial pressure, heart rate (HR), and renal sympathetic nerve activity (RSNA) were recorded. In about two thirds of the rats, injection of BSA evoked a severe and sustained hypotension, while in the remainder, there was either a more transient hypotension or else no significant change in arterial pressure. In control unsensitized rats, BSA injection had no significant effect on arterial pressure, heart rate, or RSNA. The BSA-induced hypotension in sensitized rats was associated with increases in HR and RSNA, the magnitudes of which were correlated with the magnitude of the hypotension. There were two components to the cardiac and renal sympathoexcitatory response: (1) an initial increase in HR and RSNA, which immediately followed the onset of hypotension and which was abolished by sinoaortic denervation and vagotomy, and (2) a delayed and gradual increase in HR and RSNA, which continued even while the arterial pressure was recovering and was reduced but not abolished by sinoaortic denervation and vagotomy. Thus, BSA-induced anaphylactic hypotension causes prolonged tachycardia and renal sympathoexcitation, which is only partly due to reflex effects arising from sinoaortic baroreceptors and cardiopulmonary receptors.

Anaphylaxis↗
PubMed2003

Functional organisation of central cardiovascular pathways: studies using c-fos gene expression.

Until about 10 years ago, knowledge of the functional organisation of the central pathways that subserve cardiovascular responses to homeostatic challenges and other stressors was based almost entirely on studies in anaesthetised animals. More recently, however, many studies have used the method of the expression of immediate early genes, particularly the c-fos gene, to identify populations of central neurons that are activated by such challenges in conscious animals. In this review we first consider the advantages and limitations of this method. Then, we discuss how the application of the method of immediate early gene expression, when used alone or in combination with other methods, has contributed to our understanding of the central mechanisms that regulate the autonomic and neuroendocrine response to various cardiovascular challenges (e.g., hypotension, hypoxia, hypovolemia, and other stressors) as they operate in the conscious state. In general, the results of studies of central cardiovascular pathways using immediate early gene expression are consistent with previous studies in anaesthetised animals, but in addition have revealed other previously unrecognised pathways that also contribute to cardiovascular regulation. Finally, we briefly consider recent evidence indicating that immediate early gene expression can modify the functional properties of central cardiovascular neurons, and the possible significance of this in producing long-term changes in the regulation of the cardiovascular system both in normal and pathological conditions.

Animals↗
PubMed2003

Medullary and supramedullary mechanisms regulating sympathetic vasomotor tone.

AIM: Neurons in the rostral ventrolateral medulla (RVLM) that project directly to sympathetic preganglionic neurons in the spinal cord play a critical role in maintaining tonic activity in sympathetic vasomotor nerves. Intracellular recordings in vivo from putative RVLM presympathetic neurons have demonstrated that under resting conditions these neurons display an irregular tonic firing rate, and also receive both excitatory and inhibitory synaptic inputs. This paper will briefly review some recent findings on the role of glutamate, GABA and angiotensin II (Ang II) receptors in maintaining the tonic activity of RVLM presympathetic neurons. RESULTS: Based on these findings, the following hypotheses will be discussed: (1) RVLM neurons receive tonic glutamatergic excitatory inputs, which originate from both medullary and supramedullary sources; (2) at least some neurons that project to and tonically inhibit RVLM presympathetic neurons are themselves tonically inhibited by GABAergic inputs originating from neurons in the caudalmost part of the ventrolateral medulla (caudal pressor area); (3) under normal conditions, Ang II receptors in the RVLM do not contribute significantly to the tonic activity of RVLM presympathetic neurons, but may do so in abnormal conditions such as heart failure or neurogenic hypertension; (4) RVLM presympathetic neurons maintain a significant level of tonic resting activity even when glutamate, GABA and Ang II receptors on the neurons are completely blocked. Under these conditions, the tonic activity is a consequence either of the intrinsic membrane properties of the neurons (autoactivity) or of synaptic inputs mediated by receptors other than glutamate, GABA or Ang II receptors. CONCLUSION: The current evidence indicates that the resting activity of RVLM presympathetic neurons is determined by the balance of powerful tonic excitatory and inhibitory synaptic inputs. Ang II receptors also contribute to the raised resting activity of these neurons in some pathological conditions.

Angiotensin II↗
PubMed2002

Evidence for tonic disinhibition of RVLM sympathoexcitatory neurons from the caudal pressor area.

Previous studies in the rat have shown that a significant proportion of the tonic activity of presympathetic neurons in the rostral ventrolateral medulla (RVLM) is dependent on the tonic activity of neurons within the caudal pressor area (CPA), located in the most caudal part of the caudal ventrolateral medulla (CVLM). In this study, we determined the extent to which tonically active neurons in the CPA contribute to sympathetic vasomotor tone, and we also investigated the pharmacological mechanisms by which these neurons affect the tonic activity of RVLM presympathetic neurons. In anaesthetised rabbits, bilateral injections of the neuroinhibitory compound muscimol into the CVLM at the level of the most caudal part of the lateral reticular nucleus, which corresponds to the anatomical location of the CPA as mapped in the rat, resulted in an immediate profound hypotension and almost complete abolition of renal sympathetic nerve activity (rSNA). In contrast, microinjections into surrounding regions had little or no effect or else evoked a delayed hypotensive response. The hypotensive and sympathoinhibitory response evoked by inhibition of the CPA was greatly delayed by prior injections of the GABA receptor antagonist bicuculline into the RVLM. In contrast, injections of the glutamate receptor antagonist kynurenic acid into the RVLM did not alter the hypotensive and sympathoinhibitory response. The results indicate that neurons within the CPA tonically inhibit other neurons, which, in turn, inhibit RVLM sympathoexcitatory neurons, via a GABAergic synapse. This disinhibition of RVLM neurons by CPA neurons is essential for maintaining resting sympathetic vasomotor tone.

Animals↗
PubMed2002

Central mechanisms underlying short- and long-term regulation of the cardiovascular system.

1. Sympathetic vasomotor nerves play a major role in determining the level of arterial blood pressure and the distribution of cardiac output. The present review will discuss briefly the central regulatory mechanisms that control the sympathetic outflow to the cardiovascular system in the short and long term. 2. In the short term, the sympathetic vasomotor outflow is regulated by: (i) homeostatic feedback mechanisms, such as the baroreceptor or chemoreceptor reflexes; or (ii) feed-forward mechanisms that evoke cardiovascular changes as part of more complex behavioural responses. 3. The essential central pathways that subserve the baroreceptor reflex and, to a lesser extent, other cardiovascular reflexes, have been identified by studies in both anaesthetized and conscious animals. A critical component of these pathways is a group of neurons in the rostral ventrolateral medulla that project directly to the spinal sympathetic outflow and that receive inputs from both peripheral receptors and higher centres in the brain. 4. Much less is known about the central pathways subserving feed-forward or 'central command' responses, such as the cardiovascular changes that occur during exercise or that are evoked by a threatening or alerting stimulus. However, recent evidence indicates that the dorsomedial hypothalamic nucleus is a critical component of the pathways mediating the cardiovascular response to an acute alerting stimulus. 5. Long-term sustained changes in sympathetic vasomotor activity occur under both physiological conditions (e.g. a change in salt intake) and pathophysiological conditions (e.g. heart failure). There is evidence that the paraventricular nucleus in the hypothalamus is a critical component of the pathways mediating these changes. 6. Understanding the central mechanisms involved in the long-term regulation of sympathetic activity and blood pressure is a major challenge for the future. As a working hypothesis, a model is presented of the postulated central mechanisms that result in sustained changes in sympathetic vasomotor activity that are evoked by different types of chronic stimulation.

Animals↗
PubMed2001

Exogenous ACC enhances volatiles production mediated by jasmonic acid in lima bean leaves.

We report the synergistic effects of exogenous 1-aminocyclopropane-1-carboxylic acid (ACC) and jasmonic acid (JA) on production of induced volatiles by excised lima bean leaves. Application of ACC alone to leaves induced trace amounts of volatiles. ACC positively affected three JA-induced volatiles, (E)- and (Z)-beta-ocimene, and (Z)-3-hexenyl acetate. The ethylene inhibitor, silver thiosulfate, inhibited the production of these compounds. The results suggest synergistic effects of JA and ACC on inducible volatile production by lima bean leaves. Furthermore, lima bean leaves treated with JA plus ACC became more attractive to predatory mites, Phytoseiulus persimilis, than those treated with JA alone.

Acari↗
PubMed2001

Short-time ultrasound of head and neck squamous cell carcinoma under radiotherapy.

To evaluate the efficacy of ultrasonography for patients with head and neck squamous cell carcinoma before and during radiotherapy (RT), consecutive patients with macroscopic lesions were examined before and during RT. Each scan was performed percutaneously in a short time (less than 5 min). The demonstration rate of primary tumors and the largest node of previously known metastatic cervical nodes were measured. Of all 190 patients, 91 primary tumors were detected (47.9%). Primary tumors in oral cavity, oropharynx, hypopharynx and cervical esophagus were determined in over 70% and, for those of nasopharynx and larynx, the demonstration rates were 30% or less. Nodal metastases were visualized in 78 of 80 patients with regional metastases (97.5%). Using the above information, 73 patients (38.4%) received the benefit of radiation therapy. Short-time sonography is a valuable modality for patients with selected sites of head and neck cancers.

Adolescent↗
PubMed2001

Neuronal nitric oxide strongly suppresses sympathetic outflow in high-salt Dahl rats.

OBJECTIVE: To investigate the effects of a selective inhibitor of neuronal nitric oxide synthase (nNOS), 7-nitroindazole, on peripheral sympathetic outflow in Dahl rats. DESIGN AND METHODS: Dahl salt-sensitive and salt-resistant rats were fed either a regular-salt (0.4% NaCl) or a high-salt (8% NaCl) diet for 4 weeks. In chronically instrumented conscious rats, renal sympathetic nerve activity (RSNA) was measured in both baroreceptor-loaded and baroreceptor-unloaded states. The baroreceptor unload was performed by decreasing arterial pressure with occlusion of the inferior vena cava. RESULTS: 7-Nitroindazole (307 micromol/kg intraperitoneally) increased resting RSNA from 24 +/- 3% to 38 +/- 6% with an increase in mean arterial pressure of 15 +/- 3 mmHg, and increased baroreceptor-unloaded RSNA from 100% to 278 +/- 16% in salt-sensitive Dahl rats receiving a high-salt diet However, 7-nitroindazole did not increase resting RSNA, but did increase baroreceptor-unloaded RSNA from 100% to 179 +/- 15%, 177 +/- 15%, and 133 +/- 4% in salt-sensitive Dahl rats receiving a regular-salt diet, salt-resistant Dahl rats receiving a high-salt diet, and salt-resistant Dahl rats receiving a regular-salt diet, respectively. The high-salt diet significantly increased the baroreceptor-unloaded RSNA more than the regular-salt diet did, in both salt-sensitive and salt-resistant rats. After administration of the vehicle for 7-nitroindazole (peanut oil), L-arginine (100 micromol/kg per min for 10 min) decreased both resting and baroreceptor-unloaded RSNA, whereas after pretreatment with 7-nitroindazole, the L-arginine-induced suppression was reversed, in Dahl salt-sensitive rats receiving a high-salt diet. CONCLUSIONS: Neuronal nitric oxide may suppress the sympathetic discharge generated before baroreflex-mediated inhibition in all rats. This neuronal nitric oxide-mediated suppression was enhanced by the salt load in both salt-resistant and salt-sensitive Dahl rats. Finally, the neuronal nitric oxide-mediated suppression in tonic peripheral sympathetic outflow may be greatly enhanced in salt-sensitive hypertension.

Animals↗
PubMed2001

Performance of a partially packed charcoal pellet bioreactor for acetic acid fermentation.

The performance of a partially packed charcoal pellet bioreactor was compared to that of a fully packed bioreactor for aerobic acetic acid production. In the fully packed charcoal pellet bioreactor, it was considered that the shortening of an actual retention time of the culture broth limited the bioreactor performance under high dilution rate and high aeration conditions. By reducing the filling ratio of charcoal pellets to 44%, which increased the actual retention time of the culture broth, the maximum productivity increased from 3.9 g/l/h in the fully packed bed bioreactor to 5.7 g/l/h in the partially packed bioreactor without affecting the operational stability.

Journal Article↗
PubMed2000

The cardiovascular effects of angiotensin-(1-7) in the rostral and caudal ventrolateral medulla of the rabbit.

Previous studies in the rat have indicated that the heptapeptide angiotensin-(1-7) has an excitatory action on pressor neurons in the rostral ventrolateral medulla that is equipotent to that evoked by angiotensin II, but which is mediated by separate receptors. In this study we have compared the cardiovascular effects and mechanisms of action of angiotensin-(1-7) with angiotensin II in the rostral and caudal ventrolateral medulla of the rabbit, a species which, unlike the rat, contains a high density of angiotensin receptors, similar to that observed in humans. Microinjections of angiotensin-(1-7) into the rostral and caudal ventrolateral medulla evoked dose-dependent increases and decreases, respectively, in arterial pressure and renal sympathetic nerve activity, but in comparison to angiotensin II much higher doses (approximately 50-fold higher) were required to produce cardiovascular response of similar magnitude. The cardiovascular effects of angiotensin-(1-7) were blocked by prior injection of the selective antagonist [D-Ala(7)]-Ang-(1-7) but were also blocked by the selective AT(1) receptor antagonist losartan. The results demonstrate that in the rabbit angiotensin-(1-7) can excite pressor and depressor neurons in the ventrolateral medulla, but indicate that these effects are mediated by AT(1) receptors. The much lower potency of angiotensin-(1-7) as compared to angiotensin II may be explained as a consequence of it having a much lower affinity to AT(1) receptors. Thus, in contrast to the rat, the results do not indicate that angiotensin-(1-7) has a biologically significant action in the ventrolateral medulla of the rabbit.

Adrenergic Fibers↗
PubMed2000

Development of a physiologically based pharmacokinetic model of organic solvent in rats.

A physiologically based pharmacokinetic model of the transfer of organic solvents in rat bodies was developed. The model has six compartments, i.e. lungs, vessel-rich tissue, muscles, fat tissue, tail, and liver, each being interconnected by the blood flow system. The transfer of organic solvents was expressed by simultaneous differential equations, which were then solved numerically by a personal computer using a simple spreadsheet program. m -xylene was used to represent organic solvents. The physiological parameters for rats (alveolar ventilation, cardiac output, tissue volume, tissue blood flow, etc.) and physicochemical or biochemical properties (blood/air partition coefficient, tissue/blood partition coefficients, metabolic constants, etc.) of m -xylene were based on the data obtained from the literature and our experiments. The partition coefficient of m -xylene for the tail and the blood flow and the volume of the rat tail were experimentally determined with adult rats. The results of simulation of rat exposure to m -xylene (50 and 500 ppm for 6 h) were essentially in good agreement with the experimental data on rats, i.e. the parent compound (m -xylene) concentration in the tail blood and the cumulative excretion of the metabolites in the urine were consistent.

Administration, Inhalation↗
PubMed2000

Activation of brain neurons following central hypervolaemia and hypovolaemia: contribution of baroreceptor and non-baroreceptor inputs.

In the present study we have used the detection of Fos, the protein product of c-fos, to determine the distribution of neurons in the medulla and hypothalamus that are activated by changes in central blood volume. Experiments were conducted in both barointact and barodenervated conscious rabbits, to determine the contribution of arterial baroreceptors to the pattern of Fos expression evoked by changes in central blood volume, induced either by intravenous infusion of an isotonic modified gelatin solution, or by partial occlusion of the vena cava. These procedures resulted in a significant increase and decrease, respectively, in right atrial pressure over a 60 min period. In control experiments, barointact and barodenervated rabbits were subjected to the identical procedures except that no changes in central blood volume were induced. In comparison with the control observations, central hypervolaemia produced a significant increase in the number of Fos-immunoreactive neurons in the nucleus tractus solitarius, area postrema, the caudal, intermediate and rostral parts of the ventrolateral medulla, supraoptic nucleus, paraventricular nucleus, arcuate nucleus, suprachiasmatic nucleus and median preoptic nucleus. The overall pattern of Fos expression induced by central hypervolaemia did not differ significantly between barointact and barodenervated animals. Similarly, the overall pattern of Fos expression induced by central hypovolaemia did not differ significantly between barointact and barodenervated animals, but did differ significantly from that produced by hypervolaemia. In particular, central hypovolaemia produced a significant increase in Fos expression in the same regions as above, but also in the subfornical organ and organum vasculosum lamina terminalis. In addition, compared with central hypervolaemia, hypovolaemia produced a significantly greater degree of Fos expression in the rostral ventrolateral medulla and supraoptic nucleus. Furthermore, double-labelling for tyrosine hydroxylase immunoreactivity demonstrated that neurons in the ventrolateral medulla that expressed Fos following hypovolaemia were predominantly catecholamine cells, whereas following hypervolaemia they were predominantly non-catecholamine cells. Finally, double-labelling for vasopressin immunoreactivity demonstrated that the number of Fos/vasopressin immunoreactive cells in the supraoptic nucleus was approximately 10 times greater following hypovolaemia compared with hypervolaemia, but there were very few such double-labelled neurons in the paraventricular nucleus in response to either stimulus. The results demonstrate that central hypervolaemia and hypovolaemia each induces reproducible and specific patterns of Fos expression in the medulla and hypothalamus. The degree and pattern of Fos expression was unaffected by arterial baroreceptor denervation, indicating that it is primarily a consequence of inputs from cardiac receptors, together with an increase in the level of circulating hormones such as atrial natriuretic peptide, angiotensin II or vasopressin. Furthermore, the pattern of Fos expression produced by central hypervolaemia and hypovolaemia is distinctly different from that evoked by hypertension and hypotension, respectively [Li and Dampney (1994) Neuroscience 61, 613-634], particularly in hypothalamic regions. These findings therefore indicate that the central pathways activated by changes in blood volume are, at least in part, separate from those activated by changes in arterial pressure.

Animals↗
PubMed2000

Effective onion vinegar production by a two-step fermentation system.

A two-step fermentation system combining a repeated batch process using a flocculating yeast with a charcoal pellet bioreactor was developed for onion vinegar production. Juice from the red onion R-3, which contained 67.3 g/l total sugar, was smoothly converted to onion alcohol containing 30.6 g/l ethanol by repeated batch operation using the flocculating yeast Saccharomyces cerevisiae strain IR-2. Stable operation was possible and the maximum productivity was about 8.0 g/l/h. A packed bed bioreactor containing charcoal pellets produced from waste mushroom medium was then applied to continuous onion vinegar production from the onion alcohol. Onion vinegar was successfully produced, with a maximum productivity and acetic acid concentration of about 3.3 g/l/h and 37.9 g/l, respectively. The total acetic acid yield calculated from the amount of sugar consumed was 0.86. The two-step system was operated for 50 d and proved to be competitive with other systems in terms of its high productivity, high acetic acid yield, operational stability and low production costs.

Journal Article↗
PubMed2000

Continuous acetic acid production by a packed bed bioreactor employing charcoal pellets derived from waste mushroom medium.

A packed bed bioreactor using charcoal pellets produced from waste mushroom medium by thermal carbonization was developed and applied to continuous acetic acid production. The pellets were characterized by their high specific surface area (200 m2/g) with numerous micropores (2-10 microm). The continuous acetic acid fermentation started up smoothly after seeding and was successfully operated for about 180 d under various retention times. The maximum acetic acid productivity was about 3.9 g/l/h using normal aeration and 6.5 g/l/h using air enriched with 40% O2. The pellets are expected to prove useful as a new packing material for bioreactor in terms of their bacterial affinity, high specific surface area with appropriate pore sizes for bacteria, as well as the operational stability of the system and the low production cost.

Journal Article↗
PubMed2000

What drives the tonic activity of presympathetic neurons in the rostral ventrolateral medulla?

1. The present review discusses the mechanisms that maintain the tonic activity of presympathetic cardiovascular neurons in the rostral part of the ventrolateral medulla. 2. Experimental evidence is reviewed that indicates that these neurons receive both tonic excitatory and tonic inhibitory synaptic inputs. The former appear to be mediated, at least in part, by glutamate receptors and the latter appear to be mediated by GABA receptors. 3. There is also evidence that these neurons have the capacity to generate action potentials in the absence of synaptic inputs. However, at present, there is not clear evidence that such an intrinsic pacemaker-like mechanism contributes to the tonic activity of these neurons under normal resting conditions. 4. These neurons are also chemosensitive and this may contribute to their tonic activation under conditions of hypoxia or hypercapnia.

Action Potentials↗