Biomedical subjects

T Kunitake

Publications and source records attributed to T Kunitake.

At least 37 records · Page 2Linked to original sources

PubMed1998

Differential effects of anesthetics on sympathetic nerve activity and arterial baroreceptor reflex in chronically instrumented rats.

The effects of pentobarbital sodium, chloralose, and urethane on sympathetic nerve activity and arterial baroreceptor reflex were examined using rats chronically instrumented for recordings of blood pressure (BP), electrocardiogram and renal sympathetic nerve activity (RSNA). Pentobarbital sodium (30 mg/kg, i.v.) produced a decrease in BP with a transient decrease in heart rate (HR) and no change in RSNA. Chloralose (50 mg/kg, i.v.) also caused a decrease in BP and no change in HR and RSNA until a later increase in HR and RSNA, while urethane (800 mg/kg, i.v.) increased BP, HR, and RSNA. Baroreceptor reflex function was assessed by constructing a logistic function curve compiled from data obtained by intravenous infusion in increasing doses of phenylephrine and sodium nitroprusside. Both pentobarbital sodium and chloralose administration decreased the gain of baroreceptor reflex control of both HR and RSNA. Urethane also decreased the gain of baroreceptor reflex control of HR but elicited no change in that of RSNA. These results suggest that different intravenously administered anesthetics affect the peripheral sympathetic outflows in qualitatively and quantitatively different manners.

Anesthetics↗

PubMed1998

Abdominal vagotomy attenuates interleukin-1 beta-induced nitric oxide release in the paraventricular nucleus region in conscious rats.

Nitric oxide (NO) has recently been shown to modulate the hypothalamic-pituitary-adrenal axis response to interleukin-1 beta (IL-1 beta). We measured levels of nitrite (NO2-) and nitrate (NO3-) in the hypothalamic paraventricular nucleus (PVN) region using an in vivo brain microdialysis technique in conscious rats. Intraperitoneally administered IL-1 beta produced a significant increase in both NO2- and NO3- levels in the PVN region. We also examined the possible involvement of the abdominal vagal afferent nerves in this effect. In abdominal-vagotomized rats, the increase was significantly attenuated compared to that in sham-operated rats. Our results suggest that the abdominal vagal afferent nerves are involved in intraperitoneally administered IL-1 beta-induced NO release in the PVN region.

Abdomen↗

PubMed1998

Effects of anesthetics on norepinephrine release in the hypothalamic paraventricular nucleus region of awake rats.

The effects of pentobarbital sodium, chloralose and urethane on norepinephrine (NE) release in the hypothalamic paraventricular nucleus (PVN) region were examined in awake rats. An in vivo microdialysis method was used. Extracellular NE concentrations in the PVN region were measured by high performance liquid chromatography with electrochemical detection. Pentobarbital sodium (30 mg/kg, intravenously [i.v.]) and chloralose (50 mg/kg, i.v.) caused a 30-40% decrease in NE release while urethane (800 mg/kg, i.v.) caused a 50% increase. Plasma NE concentration was not altered after pentobarbital sodium and chloralose administrations, except for its increase in chloralose at 5 h, while the concentration increased significantly (P < 0.01) after urethane. These results suggest that, in the rat, these anesthetic agents have different effects on noradrenergic activity in the PVN region as well as on plasma NE.

Anesthetics↗

PubMed1998

Neurons in the posterior insular cortex are responsive to gustatory stimulation of the pharyngolarynx, baroreceptor and chemoreceptor stimulation, and tail pinch in rats.

Extracellular unit responses to gustatory stimulation of the pharyngolaryngeal region, baroreceptor and chemoreceptor stimulation, and tail pinch were recorded from the insular cortex of anesthetized and paralyzed rats. Of the 32 neurons identified, 28 responded to at least one of the nine stimuli used in the present study. Of the 32 neurons, 11 showed an excitatory response to tail pinch, 13 showed an inhibitory response, and the remaining eight had no response. Of the 32 neurons, eight responded to baroreceptor stimulation by an intravenous (i.v.) injection of methoxamine hydrochloride (Mex), four were excitatory and four were inhibitory. Thirteen neurons were excited and six neurons were inhibited by an arterial chemoreceptor stimulation by an i.v. injection of sodium cyanide (NaCN). Twenty-two neurons were responsive to at least one of the gustatory stimuli (deionized water, 1.0 M NaCl, 30 mM HCl, 30 mM quinine HCl, and 1.0 M sucrose); five to 11 excitatory neurons and three to seven inhibitory neurons for each stimulus. A large number of the neurons (25/32) received converging inputs from more than one stimulus among the nine stimuli used in the present study. Most neurons (23/32) received converging inputs from different modalities (gustatory, visceral, and tail pinch). The neurons responded were located in the insular cortex between 2.0 mm anterior and 0.2 mm posterior to the anterior edge of the joining of the anterior commissure (AC); the mean location was 1.2 mm (n=28) anterior to the AC. This indicates that most of the neurons identified in the present study seem to be located in the region posterior to the taste area and anterior to the visceral area in the insular cortex. These results indicate that the insular cortex neurons distributing between the taste area and the visceral area receive convergent inputs from gustatory, baroreceptor, chemoreceptor, and nociceptive organs.

Animals↗

PubMed1998

Difference in water intake but not in renal sympathetic nerve activity in response to central salt-loading or angiotensin II in awake Dahl salt-sensitive and -resistant rats.

Experiments were conducted to examine whether renal sympathetic nerve activity (RSNA) and water intake in response to central salt-loading or angiotensin II (A II) differ between freely-moving Dahl salt-sensitive (DS) and -resistant (DR) rats maintained on a low-salt diet. Intracerebroventricular (i.c.v.) administration of hypertonic saline (0.3 M, 1 microl/min, 20 min) or A II (100 ng/1 microl) evoked water intake, pressor response and suppression of RSNA in both strains. The cumulative water intake in DS rats over a 60-min period after i.c.v. infusion of hypertonic saline or A II was significantly attenuated compared with that in DR rats. The RSNA response did not show a significant difference between the strains. These results demonstrate that water intake, but not RSNA response to acute central salt-loading or A II differ between awake DR and DS rats.

Angiotensin II↗

PubMed1998

Ultrathin films of charged polysaccharides assembled alternately with linear polyions.

As a means of preparation of biocompatible molecular surfaces, an alternate assembly of charged polysaccharides and oppositely-charged synthetic polymers was conducted. Cationic chitosan was assembled alternately with anionic poly(sodium styrenesulfonate) (PSS) at pH 4. Regular film growth and its dependence on ionic strength were detected by the quartz crystal microbalance (QCM) method. Averaged film thicknesses for the chitosan + PSS layer were 15, 31, 46, and 69 A, respectively, when 0, 0.25, 0.5, and 1 M of NaCl was contained in aqueous chitosan. Adsorption of chitosan did not reach saturation in 20 min at 0 M NaCl, while the adsorption became saturated within 6 min with 0.25 M NaCl. Anionic sodium chondroitin sulfate was also assembled in alternation with cationic poly(dimethyldiallylammonium chloride) (PDDA) at pH 6.5. The adsorption of chondroitin sulfate was less sensitive to ionic strength. Surface morphology of chitosan-PSS films was investigated by non-contact atomic force microscopy (AFM) observation. Maximum height difference and Ra value for a 1000 x 1000 nm area were 11 and 0.69 nm, respectively, indicating the formation of a molecularly flat surface by alternate layer-by-layer adsorption.

Adsorption↗

PubMed1998

Central actions of adrenomedullin on cardiovascular parameters and sympathetic outflow in conscious rats.

Adrenomedullin (ADM) is reported to be a peripherally acting hypotensive peptide, but its central actions are unclear. We investigated the effects of centrally administered ADM on blood pressure (BP), heart rate (HR), and renal sympathetic nerve activity (RSNA) in conscious rats and sinoaortic-denervated (SAD) rats. We also investigated the receptors interacting with ADM using two putative antagonists. Intracerebroventricular administration of ADM in doses of 0.1 and 0.5 nmol/kg caused tachycardia and early inhibition of RSNA. Central ADM (1.0 nmol/kg) induced hypertension, tachycardia, and a decrease followed by an increase in RSNA. In SAD rats, increases in BP, HR, and RSNA at the late phase were enhanced by central ADM (1.0 nmol/kg), whereas the early decrease in RSNA remained. Thus the inhibition of RSNA via central ADM may be unrelated to the arterial baroreceptor reflex. Pretreatment with antagonists human calcitonin gene-related peptide-(8-37) and human ADM-(22-52) significantly suppressed the central actions of ADM. The findings suggest that ADM is involved as a neuropeptide in the receptor-mediated central regulation of the cardiovascular system and RSNA.

Adrenomedullin↗

PubMed1998

Responses of neurons in the insular cortex to gustatory, visceral, and nociceptive stimuli in rats.

Extracellular unit responses to baroreceptor and chemoreceptor stimulation, gustatory stimulation of the posterior tongue, electrical stimulation of the superior laryngeal (SL) nerve, and tail pinch were recorded from the insular cortex of anesthetized and paralyzed rats. Forty-three neurons identified responded to stimulation by at least one of the stimuli used in the present study. Of the 43 neurons, 33 responded to tail pinch, and the remaining 10 had no response; 18 showed an excitatory response, and 15 showed an inhibitory response. Of the 43 neurons, 35 responded to electrical stimulation of the SL nerve; 27 showed an excitatory response, and 8 showed an inhibitory response. Of the 20 neurons that responded to baroreceptor stimulation by an intravenous injection of methoxamine hydrochloride (Mex), 11 were excitatory and 9 were inhibitory. Twenty-seven neurons were responsive to an intravenous injection of sodium nitroprusside (SNP); 10 were excitatory and 17 were inhibitory. Ten neurons were excited and 16 neurons were inhibited by arterial chemoreceptor stimulation by an intravenous injection of sodium cyanide (NaCN). Twenty-six neurons were responsive to at least one of the gustatory stimuli (1.0 M NaCl, 30 mM HCl, 30 mM quinine HCl, and 1.0 M sucrose): four to six excitatory neurons and three to nine inhibitory neurons for each stimulus. A large number of the neurons (42/43) received convergent inputs from more than one stimulus among the nine stimuli used in the present study. Most neurons (38/43) were responsive to two or more stimulus groups when the natural stimuli used in the present study are grouped into three, gustatory, visceral, and nociceptive stimuli. The neurons recorded were located in the insular cortex between 2.8 mm anterior and 1.1 mm posterior to the anterior edge of the joining of the anterior commissure (AC); the mean location was 1.0 mm (n = 43) anterior to the AC. This indicates that most of the neurons identified in the present study were located in the region posterior to the taste area and anterior to the visceral area in the insular cortex. These results indicate that the insular cortex neurons distributing between the taste area and the visceral area receive convergent inputs from baroreceptor, chemoreceptor, gustatory, and nociceptive organs and may have roles in taste aversion or in regulation of visceral responses.

Afferent Pathways↗

PubMed1997

Convergence of afferent inputs from the chorda tympani, lingual-tonsillar and pharyngeal branches of the glossopharyngeal nerve, and superior laryngeal nerve on the neurons in the insular cortex in rats.

The responses of single neurons in the insular cortex to electrical stimulation of the chorda tympani (CT), lingual-tonsillar branch of the glossopharyngeal (LT-IXth) nerve, pharyngeal branch of the glossopharyngeal (PH-IXth) nerve, and superior laryngeal (SL) nerve were recorded in anaesthetized and paralyzed rats. Ninety-four neurons responding to stimulation of at least one of the four nerves were identified from the insular cortex. Most of the neurons were located in the posterior portion of the insular cortex; the mean location was 0.8 mm anterior to the anterior edge of the joining of the anterior commissure (AC) and was 1.4 mm dorsal to the rhinal fissure (RF). Of the 94 neurons, 84 (89%) received convergent inputs from two or more nerves, and the remaining 10 (11%) received inputs from one nerve. The neurons responding to the CT stimulation were distributed more anteriorly than those responding to other three nerves in the anterior-posterior dimension. Our results indicate that the neurons recorded mainly from the posterior portion of the insular cortex receive convergent inputs from the oropharyngolaryngeal regions.

Animals↗

PubMed1997

De novo design, synthesis, and characterization of a pore-forming small globular protein and its insertion into lipid bilayers.

The question of how to design a water-soluble globular protein remains. We report here the synthesis of a native-like and pore-forming small globular protein (SGP, 69 amino acid residues). The protein was designed to have four helices: a Trp-containing short hydrophobic helix in the middle surrounded by three Tyr-containing long basic amphiphilic helices. Size-exclusion chromatography and CD measurements indicated that in buffer solution SGP is monomeric with a 50% helical structure. SGP did not completely denature even at high temperature (90 degrees C) and at relatively high Gu x HCl concentration so that the denaturant concentration at the midpoint of the transition is 5 M. Dye binding studies and fluorescence energy transfer experiments showed that SGP possesses a hydrophobic binding site and its Trp of the central helix is present at a relatively hydrophobic region and accepts the energy from Tyr(s) in other amphiphilic helices, indicating that SGP takes a stable globular-like structure in aqueous solution. From the depth-dependent fluorescent studies using egg PC liposomes containing n-doxyl fatty acids and brominated phospholipid as quenchers, it was found that the hydrophobic central alpha-helix is able to enter spontaneously into the lipid bilayers and the Trp in the central alpha-helix is located at about the middle of the alkyl chain in the outer layer of the phospholipid bilayer. The peptide is also able to increase the membrane permeability with two modes of current (basal current and single ion channel) in planar phospholipid bilayers, indicating the spontaneous insertion of the protein into the lipid bilayer (basal current) and then the formation of a uniform size of channel pore (14 pS). SGP is useful as a basic and starting model to find good amino acid sequences that fold to a desired protein structure and to search translocation mechanisms from aqueous solution into lipid bilayers.

Amino Acid Sequence↗

PubMed1997

Micelle Formation of Dodecylammonium Surfactant with Mixed Counterions: Perfluorocarboxylate and Alkanesulfonate Ions

Micelle formation was studied for four mixing combinations of dodecylammonium (DA) salts having perfluorocarboxylate ions (trifluoroacetate (PA) and pentafluoropropionate (PP) and alkane sulfonate ions (methane sulfonate (MS) and ethane sulfonate (ES)) as their counterions, i.e., DAPA/DAMS, DAPA/DAES, DAPP/DAMS, and DAPP/DAES. The fluorocarbon anions as counterions exhibited that the degree of counterion binding to micelle (beta) as well as the extent of stabilizing micelles and lowering ability of critical micellization concentration (CMC) are greater than hydrocarbon anions. The "mixed micelle formation" was examined in terms of CMC as a function of mole fraction (Xi) in each surfactant mixture. The CMCs of the mixed surfactant systems studied here, correspond to those of "surfactant with mixed counterions". However, by regarding tentatively those combinations as binary mixed surfactant systems, the CMC vs Xi curves (singly dispersed phase curves) as well as CMC vs micellar composition (Yi) curves (micellar phase curves) were simulated by applying the present authors' and Rubingh's equations which have been derived respectively with and without taking into account mutual added-salt effect (or the beta value for each pure system). A negative deviation from ideal mixing was observed for each combination, indicating that mixing of fluorocarbon anion with hydrocarbon anion as counterion of DA salts results in more stabilized micelle formation. Plotting the derivative of specific conductance (kappa) by total concentration of surfactant (Ct), dkappa/dCt against Ct, the curves showed a constant value at the sufficiently higher concentration range than CMC, and the constant values were found able to be related to the degree of dissociation of micelles (alpha). Even for the mixed systems, the alpha or beta values were estimated from the conductivity data. The greater power to stabilize micelle formation by fluorocarbon ions was interpreted on the basis of concept of "contact hydrophobic interaction" proposed by Mukerjee (Mukerjee, P., Colloids Surf. A: Physicochem. Eng. Aspects 84, 49 (1994)).

Journal Article↗

PubMed1997

Effects of area postrema lesion and abdominal vagotomy on interleukin-1 beta-induced norepinephrine release in the hypothalamic paraventricular nucleus region in the rat.

Peripherally administered interleukin-1 beta (IL-1 beta) has been shown to increase extracellular norepinephrine (NE) concentration in the paraventricular nucleus (PVN) of the hypothalamus. The present study was carried out using an in vivo microdialysis technique in conscious rats in order to examine the possible involvement of the area postrema (AP) and the abdominal vagal afferent nerves in this effect. Extracellular NE concentrations in the PVN region were measured by high performance liquid chromatography with electrochemical detection. In AP-lesioned or abdominal-vagotomized rats, the NE increase was significantly attenuated compared to that in sham-operated rats; this reduction was greater in abdominal-vagotomized rats than in AP-lesioned rats. The results suggest that the AP as well as the abdominal vagal afferent nerves is involved in intraperitoneal (i.p.) administered IL-1 beta-induced NE release in the PVN region.

Abdomen↗

PubMed1997

Effects of systemic interleukin-1beta administration on daily drinking and renal excretory function in conscious rats.

To elucidate the roles of interleukin-1beta (IL-1beta), a cytokine with several diverse actions, in the control of body fluid balance, its effects on daily drinking behavior and renal excretory function were examined in conscious rats. Administration of IL-1beta (4 microg/kg, I.P.) resulted in the suppression of both daily drinking and food intake and a decrease in daily urinary sodium and potassium excretion, but had no effect on urine volume. The IL-1beta-induced decrease in sodium excretion was abolished in renal-denervated rats. Kainic acid was then injected into the anteroventral third ventricle region, including the organum vasculosum of the lamina terminalis, to examine whether neurons in this region are involved in the IL-1beta-induced responses; the effects on daily drinking and urinary sodium and potassium excretion were abolished, whereas the effects on food intake, although attenuated, were still present. In contrast, electrical lesion of the subfomical organ did not affect the IL-1beta-induced responses. Thus, IL-1beta seems exert its effects on body fluid balance at several distinct sites in the central nervous system.

Animals↗

PubMed1997

Convergence of oropharyngolaryngeal, baroreceptor and chemoreceptor afferents onto insular cortex neurons in rats.

Forty-two neurons that responded to electrical stimulation of at least one of four nerves, the chorda tympani (CT), the lingual-tonsillar branch of the glossopharyngeal (LT-IXth) nerve, the pharyngeal branch of the glossopharyngeal (PH-IXth) nerve and the superior laryngeal (SL) nerve, were identified from the insular cortex by using glass microelectrodes in paralysed and anesthetized rats. Four, 42, 41 and 40 neurons responded to the CT, LT-IXth, PH-IXth and SL nerve stimulation respectively. Of these 42 neurons, most (37/42, 88.1%) responded to three nerves (the LT-IXth, PH-IXth and SL), two (4.8%) responded to two nerves and the remaining three (7.1%) responded to all four nerves. No neurons responded to one specific stimulus. The responsiveness of these 42 neurons to baroreceptor and chemoreceptor stimulation by an i.v. injection of three drugs was investigated. For baroreceptor stimulation, methoxamine hydrochloride (Mex) and sodium nitroprusside (SNP) were used; for chemoreceptor stimulation, sodium cyanide (NaCN) was used. Of the 42 neurons, 31 (73.8%) showed an excitatory or inhibitory response to baroreceptor and chemoreceptor stimulation with at least one of the three drugs, and the remaining 11 (26.2%) showed no response. Of these 31 baroreceptor and chemoreceptor-sensitive neurons, 19 (61.3%) responded to two or all three drugs, and the rest (12; 38.7%) responded to one. Most neurons recorded were distributed in the posterior insular cortex. These results indicate that the neurons in the posterior insular cortex receive convergent inputs from the oropharyngolaryngeal region, the baroreceptors and the chemoreceptors, suggesting that the posterior insular cortex may integrate various sensory information.

Animals↗

PubMed1996

Fiber types of the lingual branch of the trigeminal nerve, chorda tympani, lingual-tonsillar and pharyngeal branches of the glossopharyngeal nerve, and superior laryngeal nerve and their relation to the cardiovascular responses in rats.

The effect of repetitive electrical stimulation at 50 Hz for 20 s of the lingual branch of the trigeminal nerve (LN), chorda tympani (CT), lingual-tonsillar (LT-IXth) and pharyngeal (PH-IXth) branches of the glossopharyngeal nerve, and superior laryngeal nerve (SLN) on the changes in arterial blood pressure (BP) and heart rate (HR) were investigated in anesthetized and paralyzed rats. The compound action potentials in these nerves were simultaneously recorded to know the relationships between the fiber types and the cardiovascular responses. In all nerves except the CT, repetitive electrical stimulation of the nerve elicited a tachycardia and an increase in BP. These cardiovascular responses were mainly related to the component-2 in the compound action potentials in respective nerves. The conduction velocities of the component-2 in the five nerves examined in the present experiment were between 9.5 and 17.0 m/s (mean, n = 4-7). Other components which have faster (component-1) or slower conduction velocities (component-3 and -4) than the component-2 were not likely to elicit the cardiovascular responses. These results suggest that nociceptive and taste fibers of A-delta fibers innervating the oral cavity and pharyngolaryngeal region largely contribute to the cardiovascular responses.

Animals↗

PubMed1996

Influence of cluster formation of acidic phospholipids on decrease in the affinity for ATP of DnaA protein.

DnaA protein is the initiator of chromosomal DNA replication in Escherichia coli. We examined the influence of artificial mixed membrane composed of synthetic acidic (phosphate) lipid and basic (ammonium) lipid on the affinity of DnaA protein for ATP. Two sets of acidic and basic lipids with distinguishable numbers of hydrophobic alkyl chains were devised. Synthetic membranes made of the sole acidic lipid but not the basic bilayers inhibited the ATP binding to DnaA protein and stimulated the release of ATP from the ATP-DnaA complex. The basic bilayer-forming compounds served as the matrix for the guest acidic lipids. Acidic lipids dispersed in the basic matrix membrane had little effect on ATP binding and on ATP release. Conversely, acidic lipids forming cluster structures in the mixed artificial membranes inhibited the ATP binding and stimulated the release of ATP. These observations suggest that in mixed lipid bilayers, a cluster structure of acidic lipids seems to be an important parameter to decrease the affinity of DnaA protein for ATP.

Adenosine Triphosphate↗

PubMed1996

Geographical distribution of the human polyomavirus JC virus type A and B and isolation of a new type from Ghana.

The JC polyomavirus (JCV) is ubiquitous in humans infecting children asymptomatically, then persisting in renal tissue. Since JCV DNA can be readily isolated from urine, it should be a useful tool with which to study the evolution of DNA viruses in humans. We showed that JCV DNA from the urine of Japanese, Taiwanese, Dutch and German patients can be classified into A and B types, based upon restriction fragment length polymorphisms (RFLPs). This work was extended in the present study. We established multiple JCV DNA clones from the UK, Spain, Italy, Sweden, South Korea, People's Republic of China, Malaysia, Indonesia, Mongolia, India, Sri Lanka, Saudi Arabia, Ethiopia, Kenya, Zambia, South Africa and Ghana. Using type-specific RFLPs, most clones except the four clones from Ghana were classified as either type A or B. We constructed a molecular phylogenetic tree for the Ghanaian clones and several representative type A and B clones. According to the phylogenetic tree, the Ghanaian clones constituted a major new group, tentatively named type C. From the findings presented here and elsewhere, the following conclusions were drawn: (i) type A is prevalent only in Europe; (ii) type B is found mainly in Asia and Africa; and (iii) type C is localized to part of Africa. Our findings should help to clarify how JCV evolved in humans.

Base Sequence↗

PubMed1996

Activation of sympathetic outflow by recombinant human interleukin-1 beta in conscious rats.

The present study was undertaken to determine the effects of interleukin-1 beta (IL-1 beta) on renal sympathetic nerve activity (RSNA), arterial blood pressure (AP), heart rate (HR), and body temperature in conscious rats. Either intravenous or intracerebroventricular administration of IL-1 beta elicited increases in AP, HR, and RSNA accompanied by a rise in body temperature. The maximum changes in AP, HR, and RSNA occurred 10-15 min after intravenous injection of IL-1 beta (100 ng) and 20-25 min after intracerebroventricular injection (5 ng). The responses induced by the intravenous and intracerebroventricular injections lasted for approximately 15-30 min and did not appear when the animals were pretreated with the cyclooxygenase inhibitor indomethacin (10 mg/kg iv). Moreover, intracerebroventricular injection of prostaglandin E2 (1 microgram) produced responses similar to those induced by IL-1 but with shorter latency. Plasma norepinephrine and adrenocorticotropic hormone concentrations were increased after IL-1 beta injection. The results suggested that IL-1 beta augments cardiovascular and sympathetic outflow through the central action of prostaglandin E2 in conscious rats.

Adrenocorticotropic Hormone↗