In vivo study on medullary H(+)-sensitive neurons

1990 ◽  
Vol 69 (4) ◽  
pp. 1408-1412 ◽  
Author(s):  
N. Kogo ◽  
H. Arita
Keyword(s):  
Time Course ◽  
Direct Application ◽  
Ventrolateral Medulla ◽  
Similar Time ◽  
Central Chemoreceptors ◽  
Ph Dependent ◽  
Spontaneously Breathing ◽  
Medullary Neurons ◽  
Stimulation Of

Using the micro pressure ejection technique, we examined responses of medullary neurons with nonphasic discharges (164 units) to direct application of acidified mock cerebrospinal fluid (CSF, pH 6.85-7.05) in decerebrated spontaneously breathing cats. We found 16 H(+)-sensitive cells; they were excited promptly on application of approximately 500 pl of acidified mock CSF in the vicinity of the neuron under investigation, whereas they were unaffected by microejection of the control mock CSF (pH 7.25-7.60). Of the 16 H(+)-sensitive cells, 10 units were further found to be excited by transcapillary stimulation of the central chemoreceptors by using a method of intravertebral arterial injection of CO2-saturated saline. The discharges increased in a similar time course to that of ventilatory augmentation. Distributions of these 10 specific H(+)-sensitive cells were found in the vicinity of nucleus tractus solitarii as well as deep in the ventrolateral medulla. The present results suggest a possibility that pH-dependent central chemoreceptors, if any, would be located in two distinct medullary regions described in this study.

ECF pH dynamics within the ventrolateral medulla: a microelectrode study

1989 ◽  
Vol 67 (1) ◽  
pp. 193-198 ◽  
Author(s):  
K. Ichikawa ◽  
S. Kuwana ◽  
H. Arita
Keyword(s):  
Blood Flow ◽  
Cerebrospinal Fluid ◽  
Time Course ◽  
Extracellular Fluid ◽  
Ph Sensitive ◽  
Ventrolateral Medulla ◽  
Collateral Blood Flow ◽  
Central Chemoreceptors ◽  
Ph Dependent ◽  
Spontaneously Breathing

Using pH-sensitive microelectrodes, we evaluated pH dynamics of extracellular fluid (ECF) within the ventrolateral medulla (VLM) beneath the central chemoceptive areas in anesthetized, spontaneously breathing cats. Static ECF pH was acid in the superficial layers (less than 1 mm), compared with the overlying cerebrospinal fluid pH that became alkaline gradually during the experiments. In the deeper VLM areas (1–3 mm), no systematic gradients of ECF pH were observed. We found various, isolated regions where intravertebral artery injections of CO2-saturated saline evoked acidic shift of ECF pH in the time course analogous to ventilatory augmentation. Those responsive regions were found to be scattered not only in the superficial layers but also in the deeper VLM areas, although many nonresponsive regions were also intermingled among them. Occlusions of the principal vessels supplying the tested VLM regions diminished but failed to abolish the ECF pH responses to the CO2 loadings, suggesting a collateral blood flow by fine pial vessels. The present study suggests a possibility that the pH-dependent central chemoreceptors, if any, would be scattered in the deeper VLM areas as well as the superficial layers.

Regulation of apoptosis in the endocardial cushions of the developing chick heart

2002 ◽  
Vol 282 (6) ◽  
pp. C1348-C1360 ◽  
Author(s):  
William M. Keyes ◽  
Esmond J. Sanders
Keyword(s):  
Heart Development ◽  
Time Course ◽  
Nuclear Staining ◽  
Caspase 9 ◽  
Endocardial Cushions ◽  
Similar Time ◽  
Cleavage Fragment ◽  
Protein Levels ◽  
Developing Heart

During the early stages of heart development, there are two main foci of cell death: outflow tract (OT) and atrioventricular (AV) endocardial cushions. These tissues contribute to the septa and valves of the mature heart and receive cell populations from neural crest (NC) cell migration and epicardial cell invasion. We examined embryonic chick hearts for expression, in the cushions, of bcl-2 family members, caspase-9, and the caspase substrate poly(ADP-ribose) polymerase. Antiapoptotic bcl-2 is expressed heavily in the OT and AV regions throughout embryonic days (ED) 4–7, with a decrease in levels at ED 4 and 5 in OT and AV cushions, respectively. Proapoptotic bax predominantly associated with the prongs of the NC-derived aorticopulmonary (AP) septum but was expressed throughout the AV cushions. Proapoptotic bak also associated with the prongs of the AP septum in the OT, while protein levels were upregulated at ED 4–5 and 4–6 in OT and AV cushions, respectively. Bid expression showed a similar time course. We found the 10-kDa cleavage fragment of active caspase-9 at ED 4–8 and 5–8 in OT and AV cushions, respectively, and the 24-kDa cleavage fragment of poly(ADP-ribose) polymerase throughout ED 3–8 and 7–8 in OT and AV cushions, respectively. Caspase-3 cleavage occurred throughout the time period examined. Using cushion cell cultures, we found that inhibitors of caspases-3 and -9 and a universal caspase inhibitor significantly reduced apoptosis, as did retroviral overexpression of bcl-2 using an RCAS expression vector. Premigratory NC cells were fluorescently labeled in vivo with 1,1-didodecyl-3,3,3′,3′-tetramethylindocarbocyanine. Subsequent nuclear staining of cushion cells with 4,6-diamidino-2-phenylindole revealed the presence of apoptotic nuclei in the NC cells in the OT cushions and in the prongs of the AP septum. These results demonstrate a developmentally regulated role for the bcl-2 and the caspase families of molecules in the endocardial cushions of the developing heart and lend support to the possibility that some of the dying cells in the cushions are derived from the NC.

Cis- andtrans-acting factors regulating transcription of the BGT1 gene in response to hypertonicity

1998 ◽  
Vol 274 (4) ◽  
pp. F753-F761 ◽  
Author(s):  
Hiroshi Miyakawa ◽  
Seung Kyoon Woo ◽  
Ching-Pu Chen ◽  
Stephen C. Dahl ◽  
Joseph S. Handler ◽  
...  
Keyword(s):  
Dna Binding ◽  
Time Course ◽  
Mutational Analysis ◽  
Consensus Sequence ◽  
Dimethyl Sulfate ◽  
Base Pairs ◽  
Biochemical Basis ◽  
Activation Of Transcription ◽  
Stimulation Of

We have previously identified a tonicity-responsive enhancer (TonE) in the promoter region of the canine BGT1 gene. TonE mediates hypertonicity-induced stimulation of transcription. Here, we characterize TonE and TonE binding proteins (TonEBPs) to provide a biochemical basis for cloning of the TonEBPs. Mutational analysis applied to both hypertonicity-induced stimulation of transcription and TonEBP binding reveals that TonE is 11 base pairs in length, with the consensus sequence of (C/T)GGAAnnn(C/T)n(C/T). Activity of the TonEBPs increases in response to hypertonicity with a time course similar to that of transcription of the BGT1 gene. Studies with inhibitors indicate that translation, but not transcription, is required for activation of the TonEBPs. Phosphorylation is required for the stimulation of transcription but not for activation of DNA binding by the TonEBPs. In vivo methylation by dimethyl sulfate reveals that the TonE site of the BGT1 gene is protected with a time course like that of activity of the TonEBPs and activation of transcription. Ultraviolet cross-linking indicates that the TonEBPs share a DNA binding subunit of 200 kDa.

Rapid and transient excitation of respiration mediated by central chemoreceptor

1988 ◽  
Vol 64 (4) ◽  
pp. 1369-1375 ◽  
Author(s):  
H. Arita ◽  
N. Kogo ◽  
K. Ichikawa
Keyword(s):  
Control System ◽  
Dynamic Properties ◽  
Respiratory Rhythm ◽  
Respiratory Control ◽  
Facilitatory Effect ◽  
Onset Latency ◽  
Central Chemoreceptors ◽  
Spontaneously Breathing ◽  
Respiratory Phases ◽  
Stimulation Of

We evaluated rapid and transient changes in phrenic nerve (PN) and internal intercostal (IIC) activities when 0.2-0.5 ml of saline saturated with 100% CO2 was injected into the vertebral artery during various respiratory phases in decerebrated spontaneously breathing cats. The injections evoked an initial transient inhibition of ongoing PN or IIC activity with a mean onset latency of 0.17 s, followed by excitation of subsequent respiratory activities with an onset latency ranging from 0.4 to 2.7 s; the average onset latency of expiratory excitation (1.49 s) was significantly longer than that of inspiratory facilitation (0.89 s). The initial inhibitory responses were analogous to reflex effects of injections of phenyl biguanide, indicating that the initial inhibition was due to activation of vascular nociceptors and the subsequent excitation was due to stimulation of the central chemoreceptors. In addition, CO2-saline injections during hypocapnic apnea developed a quick reappearance of respiratory rhythm, and the first facilitatory effect appeared in tonic IIC activity, which became more active before rhythm started. In summary, the present study, by use of a technique of vertebral arterial injections of 100% CO2-saline, revealed dynamic properties of respiratory control system mediated by central chemoreceptors and vascular nociceptors.

scholarly journals Transforming ras proteins accelerate hormone-induced maturation and stimulate cyclic AMP phosphodiesterase in Xenopus oocytes.

1990 ◽  
Vol 10 (4) ◽  
pp. 1689-1696 ◽  
Author(s):  
S E Sadler ◽  
J L Maller ◽  
J B Gibbs
Keyword(s):  
Enzyme Activity ◽  
Time Course ◽  
Xenopus Oocytes ◽  
Insulin Treatment ◽  
Ras Oncogene ◽  
Ras Proteins ◽  
Phosphodiesterase Activity ◽  
Oncogene Products ◽  
Stimulation Of

Transforming Harvey (Ha) ras oncogene products accelerated the time course of Xenopus oocyte maturation induced by insulin, insulinlike growth factor 1, or progesterone. The transforming constructs, [Val-12]Ha p21 and [Val-12, Thr-59]Ha p21, displayed equal potency and efficacy in their abilities to accelerate the growth peptide-induced response. Normal Ha p21 was only 60% as powerful and one-fifth as potent as the mutants containing valine in the 12 position. In contrast, two nontransforming constructs, [Val-12, Ala-35, Leu-36, Thr-59]Ha p21 and [Val-12, Thr-59]Ha(term-174) p21, had no effect on the time course of hormone-induced maturation. Effects of the transforming ras proteins on hormone-induced maturation correlated with their abilities to stimulate in vivo phosphodiesterase activity measured after microinjection of 200 microM cyclic [3H] AMP. When p21 injection followed 90 min of insulin treatment, there was no increase in phosphodiesterase activity over that measured after hormone treatment or p21 injection alone, but additive effects of p21 and insulin on enzyme activity were observed during the first 90 min of insulin treatment. Even though normal Ha p21 and transforming [Val-12, Thr-59]Ha p21 stimulated oocyte phosphodiesterase to equal levels when coinjected with substrate at the initiation of the in vivo assay, the transforming protein elicited a more sustained stimulation of enzyme activity. These results suggest that stimulation of a cyclic AMP phosphodiesterase activity associated with insulin-induced maturation is involved in the growth-promoting actions of ras oncogene products in Xenopus oocytes.

Lower brain stem controls cardiac ANF secretion

1992 ◽  
Vol 263 (1) ◽  
pp. H198-H207 ◽  
Author(s):  
J. H. Jiao ◽  
P. G. Guyenet ◽  
A. J. Baertschi
Keyword(s):  
Electrical Stimulation ◽  
Vehicle Control ◽  
Nucleus Ambiguus ◽  
Ventrolateral Medulla ◽  
Ventrolateral Nucleus ◽  
The Central Nervous System ◽  
Lower Brain Stem ◽  
Medullary Nuclei ◽  
Spontaneously Breathing ◽  
Stimulation Of

The purpose of these studies was to investigate whether the central nervous system (CNS) can modulate the plasma level of atrial natriuretic factor (ANF). In anesthetized, spontaneously breathing rats, electrical stimulation was stereotaxically applied bilaterally to four medullary nuclei: 1) the rostral nucleus of the solitary tract (rNTS), 2) the intermediate portion of the NTS (iNTS), 3) the ventrolateral nucleus ambiguus (NA) 0.3 mm rostral to obex, and 4) the rostral ventrolateral medulla (RVL). Electrical stimulation of the rNTS and RVL caused a 55 +/- 18% (P less than 0.025, n = 6) and 187 +/- 80% (P less than 0.001, n = 5) increase in plasma ANF, respectively, compared with baseline (56-88 pg/ml), whereas sham stimulations had no effect on plasma ANF release. In contrast, electrical stimulation of the iNTS and the NA elicited a 35 +/- 6 (P less than 0.01, n = 7) and 31 +/- 6% (P less than 0.05, n = 5) decrease in plasma ANF, respectively. In artificially ventilated rats, unilateral electrical stimulation of the RVL induced a 94 +/- 39 (left RVL, n = 6, P less than 0.01) and 186 +/- 68% (right RVL, P less than 0.01, n = 5) increase in plasma ANF over baseline. Unilateral microinjection of L-glutamate into RVL also resulted in a 81 +/- 23% (n = 9, P less than 0.01) increase in plasma ANF compared with baseline and vehicle control injections. These results suggest that activation of the central sympathetic system potently stimulates the secretion of cardiac ANF.

Hydrocortisone restoration of the pH-dependent metabolic responses to catecholamines

1975 ◽  
Vol 228 (4) ◽  
pp. 1053-1059 ◽  
Author(s):  
M Uajima ◽  
M Ui
Keyword(s):  
Respiratory Alkalosis ◽  
Blood Levels ◽  
Beta Receptor ◽  
Ph Dependent ◽  
Metabolic Indices ◽  
Direction Opposite ◽  
Fasted Rats ◽  
Stimulation Of ◽  
Hexose Phosphates

Feeding NH4CL to fasted rats caused changes of blood levels of lactate, glycerol, and insulin, hepatic levels of glycogen and phosphorylase, and muscle levels of glycogen and glucose 6-P in the direction opposite to the changes induced by respiratory alkalosis. The effects of epinephrine and isoproterenol in vivo on these metabolic indices, which are classified as their function mediated via the adrenegic beta receptor, were potentiated by NH4CL feeding in contrast to their attenuation in alkalosis. The prior treatment of the rat with hydrocortisone was very effective in overcoming the alkalosis-induced inhibition of the beta-receptor-mediated metabolic actions of epinephrine and isoproterenol, such as the activation of liver phosphorylase, accumulation of muscle hexose phosphates, and stimulation of pancreatic secretion of insulin. Epinephrine sensitivity of the liver and muscle levels of cyclic AMP was not altered by the hydrocortisone therapy or inductions of alkalosis and acidosis. The mechanism for the hydrocortisone restoration of the adrenergic beta functions in alkalosis is discussed as related to its permissive effect.

scholarly journals Adrenergic control of induction of type II iodothyronine 5′-deiodinase activity in cultured mouse brown adipocytes

1993 ◽  
Vol 292 (1) ◽  
pp. 303-308 ◽  
Author(s):  
S Pavelka ◽  
J Hermanská ◽  
M Baudysová ◽  
J Houstĕk
Keyword(s):  
Cyclic Amp ◽  
Time Course ◽  
Brown Fat ◽  
Fat Cells ◽  
Type Ii ◽  
Brown Adipocytes ◽  
Adrenergic Agents ◽  
Adrenergic Control ◽  
Stimulation Of

Iodothyronine 5′-deiodinase (5′D) of mouse brown adipocytes differentiated in cell culture was characterized in detail with respect to the adrenergic control of its biosynthesis. The stimulation of 5′D required mRNA and protein synthesis and was dependent on the stage of differentiation of the cells. The maximum induction was observed around confluence (7-day-old cells), in pre- and post-confluent cells the 5′D activity was significantly less induced. The transient responsiveness of brown fat-cells to the stimulatory effect of adrenergic agents was reflected also in the time course of the induction of 5′D by different concentrations of agonists. The maximum response occurred regularly after an 8 h incubation and implicated a rather fast turnover of the induced enzyme. On the basis of the inhibitory effects of cycloheximide and actinomycin D, the half-life of the induced 5′D and its mRNA were estimated to be 1.5 and 3.3 h respectively. The noradrenaline-induced 5′D activity was shown to be that of the type II enzyme, insensitive to propylthiouracil (PTU). The estimated values of its apparent Km for thyroxine, Km for the co-substrate dithiothreitol, and Vmax. in the presence of 1 mM PTU were 2 nM, 2.6 mM, and 0.1 pmol of I-/h per mg of protein respectively. The 5′D activity was effectively induced by forskolin and dibutyryl cyclic AMP, as well as by isoprenaline, noradrenaline and CGP-12177, but not by phenylephrine, cirazoline or oxymetazoline. This indicates that, contrary to previous observations in vivo, stimulation of 5′D in cultured brown fat-cells involves elevated cyclic AMP levels and is mediated predominantly via beta-receptors, particularly via the so-called beta 3-adrenoceptors.

scholarly journals Glycolysis in Neurons, Not Astrocytes, Delays Oxidative Metabolism of Human Visual Cortex during Sustained Checkerboard Stimulation in vivo

2001 ◽  
Vol 21 (12) ◽  
pp. 1384-1392 ◽  
Author(s):  
Albert Gjedde ◽  
Sean Marrett
Keyword(s):  
Oxygen Consumption ◽  
Visual Cortex ◽  
Glucose Metabolism ◽  
Oxidative Metabolism ◽  
Time Course ◽  
Complex Stimulus ◽  
Neuronal Activation ◽  
Positron Emission ◽  
Stimulation Of

The regulation of brain energy metabolism during neuronal activation is poorly understood. Specifically, the extent to which oxidative metabolism rather than glycolysis supplies the additional ATP necessary to sustain neuronal activation is in doubt. A recent hypothesis claims that astrocytes generate lactate with the muscle-type lactate dehydrogenase (LDH) isozyme LD5. Lactate from astrocytes then undergoes oxidation in neurons after reconversion to pyruvate by the LDH subtype LD1. On the basis of this hypothesis, the authors predicted that the time course of an excitatory increase of the oxidative metabolism of brain tissue must depend on the degree to which astrocytes provide neurons with pyruvate in the form of lactate. From the known properties of the LDH subtypes, the authors predicted two time courses for the changes of oxygen consumption in response to neuronal stimulation: one reflecting the properties of the neuronal LDH subtype LD1, and the other reflecting the astrocytic LDH subtype LD5. Measuring oxygen consumption (CMR o2) with positron emission tomography, the authors demonstrated increased CMR o2 during sustained stimulation of visual cortex with a complex stimulus. The CMR o2 increased 20.5% after 3 minutes and 27.5% after 8 minutes of stimulation, consistent with a steady-state oxygen–glucose metabolism ratio of 5.3, which is closest to the index predicted for the LD1 subtype. The index is equal to the oxygen–glucose metabolism ratio of 5.5 calculated at baseline, indicating that pyruvate is converted to lactate in a cellular compartment with an LDH reaction closest to that of LD1, whether at rest or during stimulation of the visual cortex with the current stimulus. The findings are consistent with a claim that neurons increase their oxidative metabolism in parallel with an increase of pyruvate, the latter generated by neuronal rather than astrocytic glycolysis.

Sodium-dependent receptor current in a new mechanoreceptor preparation

1994 ◽  
Vol 72 (6) ◽  
pp. 3026-3028 ◽  
Author(s):  
M. Juusola ◽  
E. A. Seyfarth ◽  
A. S. French
Keyword(s):  
Mechanical Stimulation ◽  
Action Potentials ◽  
Time Course ◽  
Receptor Potential ◽  
Sodium Ions ◽  
Similar Time ◽  
Sodium Dependent ◽  
Restricted Environment ◽  
Intracellular Microelectrodes ◽  
Stimulation Of

1. Intracellular microelectrodes recorded the receptor potential and receptor current in the neurons of spider slit sense organs during mechanical stimulation of the slits. 2. Mechanical stimulation produced two patterns of action potential discharge, corresponding to the two groups of neurons described previously by electrical stimulation. 3. Tetrodotoxin eliminated the action potentials and revealed a receptor potential with both static and adapting components. Voltage clamp gave an inward receptor current with a similar time course. 4. Replacement of sodium ions in the bath reversibly eliminated the receptor current, indicating that it is carried by sodium ions. However, this effect was comparatively slow, suggesting that the tips of the sensory dendrites lie in a chemically restricted environment.

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