Central CO2 chemoreception in developing bullfrogs: anomalous response to acetazolamide

2003 ◽  
Vol 94 (3) ◽  
pp. 1204-1212 ◽  
Author(s):  
Barbara E. Taylor ◽  
Michael B. Harris ◽  
E. Lee Coates ◽  
Matthew J. Gdovin ◽  
J. C. Leiter
Keyword(s):  
Carbonic Anhydrase ◽  
Late Stage ◽  
Rana Catesbeiana ◽  
Early Stage ◽  
Lung Ventilation ◽  
Carbonic Anhydrase Activity ◽  
Spinal Nerve ◽  
Before And After ◽  
Hypercapnic Response

Central CO2 chemoreception and the role of carbonic anhydrase were assessed in brain stems from Rana catesbeiana tadpoles and frogs. Buccal and lung rhythms were recorded from cranial nerve VII and spinal nerve II during normocapnia and hypercapnia before and after treatment with 25 μM acetazolamide. The lung response to acetazolamide mimicked the hypercapnic response in early-stage and midstage metamorphic tadpoles and frogs. In late-stage tadpoles, acetazolamide actually inhibited hypercapnic responses. Acetazolamide and hypercapnia decreased the buccal frequency but had no effect on the buccal duty cycle. Carbonic anhydrase activity was present in the brain stem in every developmental stage. Thus more frequent lung ventilation and concomitantly less frequent buccal ventilation comprised the hypercapnic response, but the response to acetazolamide was not consistent during metamorphosis. Therefore, acetazolamide is not a useful tool for central CO2 chemoreceptor studies in this species. The reversal of the effect of acetazolamide in late-stage metamorphosis may reflect reorganization of central chemosensory processes during the final transition from aquatic to aerial respiration.

Ontogeny of central CO2 chemoreception: chemosensitivity in the ventral medulla of developing bullfrogs

2003 ◽  
Vol 285 (6) ◽  
pp. R1461-R1472 ◽  
Author(s):  
Barbara E. Taylor ◽  
Michael B. Harris ◽  
J. C. Leiter ◽  
Matthew J. Gdovin
Keyword(s):  
Cerebrospinal Fluid ◽  
Kainic Acid ◽  
Rana Catesbeiana ◽  
Lung Ventilation ◽  
Ventral Surface ◽  
Spinal Nerve ◽  
Ventral Medulla ◽  
Unilateral Stimulation ◽  
Artificial Cerebrospinal Fluid ◽  
Hypercapnic Response

Sites of central CO2 chemosensitivity were investigated in isolated brain stems from Rana catesbeiana tadpoles and frogs. Respiratory neurograms were made from cranial nerve (CN) 7 and spinal nerve 2. Superfusion of the brain stem with hypercapnic artificial cerebrospinal fluid elicited increased fictive lung ventilation. The effect of focal perfusion of hypercapnic artificial cerebrospinal fluid on discrete areas of the ventral medulla was assessed. Sites of chemosensitivity, which are active continuously throughout development, were identified adjacent to CN 5 and CN 10 on the ventral surface of the medulla. In early- and middle-stage tadpoles and frogs, unilateral stimulation within either site was sufficient to elicit the hypercapnic response, but simultaneous stimulation within both sites was required in late-stage tadpoles. The chemosensitive sites were individually disrupted by unilateral application of 1 mg/ml protease, and the sensitivity to bath application or focal perfusion of hypercapnia was reassessed. Protease lesions at CN 10 abolished the entire hypercapnic response, but lesions at CN 5 affected only the hypercapnic response originating from the CN 5 site. Neurons within the chemosensitive sites were also destroyed by unilateral application of 1 mM kainic acid, and the sensitivity to bath or focal application of hypercapnia was reassessed. Kainic acid lesions within either site abolished the hypercapnic response. Using a vital dye, we determined that kainic acid destroyed neurons by only within 100 μm of the ventral medullary surface. Thus, regardless of developmental stage, neurons necessary for CO2 sensitivity are located in the ventral medulla adjacent to CN 5 and 10.

Carbonic Anhydrase Activity During Embryonic Development

1951 ◽  
Vol 28 (3) ◽  
pp. 332-343
Author(s):  
A. M. CLARK
Keyword(s):  
Bone Marrow ◽  
Carbonic Anhydrase ◽  
Embryonic Development ◽  
Late Stage ◽  
Early Stage ◽  
Carbonic Anhydrase Activity ◽  
Red Cells ◽  
Adult Type

1. Tissue carbonic anhydrase is usually formed at an early stage in the embryonic development of the chick and mouse. The enzyme does not appear in the blood until a relatively late stage has been reached. 2. In the erythrocytes, it is probable that the enzyme is confined to those cells produced in bone marrow. 3. Evidence is presented to support the theory that towards the end of development, there is a replacement of red cells which contain an embryonic type of haemoglobin but no carbonic anhydrase, by corpuscles in which the enzyme is present together with the adult type of haemoglobin.

3-methyadenine inhibits lipopolysaccharides-induced pulmonary inflammation at the early stage of silicosis via blocking NF-κB signaling pathway

2021 ◽  
pp. 074823372110394
Author(s):  
Yujing Zhang ◽  
Shuai Huang ◽  
Shiyi Tan ◽  
Mingke Chen ◽  
Shang Yang ◽  
...  
Keyword(s):  
Lung Injury ◽  
Late Stage ◽  
Caspase 3 ◽  
Inflammatory Responses ◽  
Early Stage ◽  
Pulmonary Inflammation ◽  
Mechanism Study ◽  
Silica Dust ◽  
Tnf Α

Occupational exposure to silica dust is related to pulmonary inflammation and silicosis. Lipopolysaccharides (LPSs) could aggravate apoptosis in alveolar macrophages (AMs) of human silicosis through autophagy, yet how the reduction of autophagy attenuated LPS-induced lung injury and the related mechanisms need to be investigated. In the study, we aim to understand the role of 3-methyladenine (3-MA), an inhibitor of autophagy, in LPS-mediated inflammatory responses and fibrosis. We collected AMs from observers/silicosis patients. The results showed that LPS induced NF-κB-related pulmonary inflammation in observers and silicosis patients, as confirmed by an increase in the expression of IL-1β, IL-6, TNF-α, and p65, which could be inhibited by 3-MA treatment. In mice models, at the early stage (7d) of silicosis, but not the late (28d) stage, blocking autophagy reversed the increased levels of IL-1β, IL-6, TNF-α, and p65 caused by LPS. Mechanism study revealed that LPS triggered the expression of LC3 II, p62, and cleaved caspase-3 at the early stage exposed to silica, which could be restored by 3-MA, while there was no difference in the expression of LAMP1 either at the early or late stage of silicosis in different groups. Similarly, 3-MA treatment did not prevent fibrosis characterized by destroyed alveoli, collagen deposition, and increased expression of α-SMA and Col-1 induced by LPS at the late stage of silicosis. The results suggested that 3-MA has a role in the protection of lung injury at the early stage of silicosis and provided an experimental basis for preventive strategies of pulmonary inflammation and silicosis.

scholarly journals The Periplasmic α-Carbonic Anhydrase Activity of Helicobacter pylori Is Essential for Acid Acclimation

2005 ◽  
Vol 187 (2) ◽  
pp. 729-738 ◽  
Author(s):  
Elizabeth A. Marcus ◽  
Amiel P. Moshfegh ◽  
George Sachs ◽  
David R. Scott
Keyword(s):  
Helicobacter Pylori ◽  
Membrane Potential ◽  
Carbonic Anhydrase ◽  
Membrane Integrity ◽  
Carbonic Anhydrase Activity ◽  
Knockout Mutant ◽  
Inner Membrane ◽  
Acid Acclimation

ABSTRACT The role of the periplasmic α-carbonic anhydrase (α-CA) (HP1186) in acid acclimation of Helicobacter pylori was investigated. Urease and urea influx through UreI have been shown to be essential for gastric colonization and for acid survival in vitro. Intrabacterial urease generation of NH3 has a major role in regulation of periplasmic pH and inner membrane potential under acidic conditions, allowing adequate bioenergetics for survival and growth. Since α-CA catalyzes the conversion of CO2 to HCO3 −, the role of CO2 in periplasmic buffering was studied using an α-CA deletion mutant and the CA inhibitor acetazolamide. Western analysis confirmed that α-CA was bound to the inner membrane. Immunoblots and PCR confirmed the absence of the enzyme and the gene in the α-CA knockout. In the mutant or in the presence of acetazolamide, there was an ∼3 log10 decrease in acid survival. In acid, absence of α-CA activity decreased membrane integrity, as observed using membrane-permeant and -impermeant fluorescent DNA dyes. The increase in membrane potential and cytoplasmic buffering following urea addition to wild-type organisms in acid was absent in the α-CA knockout mutant and in the presence of acetazolamide, although UreI and urease remained fully functional. At low pH, the elevation of cytoplasmic and periplasmic pH with urea was abolished in the absence of α-CA activity. Hence, buffering of the periplasm to a pH consistent with viability depends not only on NH3 efflux from the cytoplasm but also on the conversion of CO2, produced by urease, to HCO3 − by the periplasmic α-CA.

Role of enzymes in the mechanism of shell penetration by the muricid gastropod, Thais lapillus (L.)

1977 ◽  
Vol 55 (11) ◽  
pp. 1846-1857 ◽  
Author(s):  
Roy S. Webb ◽  
A. S. M. Saleuddin
Keyword(s):  
Acid Phosphatase ◽  
Carbonic Anhydrase ◽  
Phosphatase Activity ◽  
Acid Phosphatase Activity ◽  
Carbonic Anhydrase Activity ◽  
Marker Enzyme ◽  
Biochemical Activity ◽  
Significant Difference ◽  
Muricid Gastropods

The role of the boring organ in the mechanism of shell penetration by Thais lapillus (L.), a muricid gastropod, has been investigated by cytochemistry and biochemistry. Sites of acid phosphatase and carbonic anhydrase activity were localized and the biochemical activities of these enzymes were measured in the boring organ of both nonboring and actively boring animals. The lysosomal marker enzyme, acid phosphatase, was investigated to assess the role of lysosomes in the boring mechanism. Acid phosphatase activity was localized on the microvillar membranes of the epithelial cells of the boring organ. There was no significant difference in the biochemical activity of acid phosphatase between actively boring and nonboring specimens. Carbonic anhydrase was localized prominently in the epithelium of the boring organ. The microvilli showed no localization but all other regions of the epithelium were dominated by reaction product. The boring organ demonstrated high levels of carbonic anhydrase activity but no significant difference could be detected between actively boring and nonboring specimens. The possible involvement of these enzymes and their role in the mechanism of shell penetration by muricid gastropods has been discussed.

scholarly journals THE ROLE OF PLASMA CO2 TENSION AND CARBONIC ANHYDRASE ACTIVITY IN THE RENAL REABSORPTION OF BICARBONATE*

1960 ◽  
Vol 39 (11) ◽  
pp. 1706-1721 ◽  
Author(s):  
Floyd C. Rector ◽  
Donald W. Seldin ◽  
Albert D. Roberts ◽  
Jerry S. Smith
Keyword(s):  
Carbonic Anhydrase ◽  
Carbonic Anhydrase Activity ◽  
Renal Reabsorption

Functional role of carbonic anhydrase in intestinal electrolyte transport

1986 ◽  
Vol 251 (5) ◽  
pp. G682-G687 ◽  
Author(s):  
A. N. Charney ◽  
J. D. Wagner ◽  
G. J. Birnbaum ◽  
J. N. Johnstone
Keyword(s):  
Carbonic Anhydrase ◽  
Functional Role ◽  
Carbonic Anhydrase Activity ◽  
Electrolyte Transport ◽  
Sodium Absorption ◽  
Ascending Colon ◽  
Sprague Dawley ◽  
Acid Base Balance ◽  
Descending Colon

We examined the role of carbonic anhydrase activity in intestinal transport by measuring the effect of systemic pH and PCO2 on electrolyte transport in the presence and absence of luminal acetazolamide. Adult Sprague-Dawley rats were anesthetized, and ileal and colonic segments were perfused with Ringer solution that was acetazolamide-free or that contained 0.1 mM sodium acetazolamide. Consecutive states of acute respiratory alkalosis and acidosis were created by changing the inspired CO2 from 0% (room air) to 8% CO2. In the ileum, acetazolamide perfusion did not affect the increment in net sodium and chloride absorption caused by a reduction in systemic pH. Mucosal carbonic anhydrase activity in this segment was measurable, although very low. In both the ascending and descending colon, acetazolamide perfusion reduced the increment in net sodium absorption caused by an increase in systemic PCO2. In addition, acetazolamide increased the chloride absorptive response to PCO2 in the ascending colon but did not affect the chloride response at all in the descending colon. Colonic mucosal carbonic anhydrase exhibited a proximal-to-distal gradient of activity: levels in the ascending colon were severalfold greater than in the descending colon. These findings suggest a functional role for carbonic anhydrase in mediating the colonic but not the ileal absorptive response to changes in systemic acid-base balance.

scholarly journals THE UPTAKE OF INORGANIC ELECTROLYTES BY THE CRAYFISH

1940 ◽  
Vol 24 (2) ◽  
pp. 151-167 ◽  
Author(s):  
N. S. Rustum Maluf
Keyword(s):  
Carbonic Anhydrase ◽  
Fresh Water ◽  
Organic Material ◽  
Carbonic Anhydrase Activity ◽  
The Body ◽  
Equivalent Concentration ◽  
Co2 Output ◽  
Before And After

1. Reasons are given for believing that the uptake of Na+, Cl-, and NaCl by the crayfish occurs through the gills. 2. A crayfish in fresh water, with a Cl concentration of about 0.2 mEq./l., can) by active Cl absorption, compensate entirely for Cl lost in the urine. 3. The carbonic anhydrase activity of the gills is markedly higher than that of other tissues of the crayfish, but the equivalent CO2 output of the crayfish is far in excess of the equivalent Cl absorption per unit time and weight and thus fails to warrant the supposition that Cl absorption is of respiratory importance. 4. The carbonic anhydrase activity of the soft integument of the lobster, before and after molting, and of the hypodermis of the hard-cuticled animal is almost identical and of the same order as that of other tissues of the lobster. 5. The concentration of the electrolytes was about 7.5 mEq./l.; i.e., considerably lower than in the blood of the crayfish. Cl- can be taken up independently of the complementary cation. Na+ can be taken up independently of the complementary anion. K+ and SO4= are not taken up at all. In pure NaCl, the Na+ and Cl- are absorbed evidently largely together. Ca++ is absorbed only in newly molted animals and in animals preparing to molt but is not absorbed by hard-cuticled animals not preparing to molt. Ca++ is taken up independently of Cl- in pure CaCl2. 6. Newly molted animals absorb Ca++ at a rate exceeding that of the absorption of other absorbable ions (Na+ and Cl-) in the same equivalent concentration. 7. A crayfish utilizes the Ca++ in fresh water in the calcification of its cuticle. Since the animal does not swallow water, the Ca++ must enter through the exterior. Reasons are given for believing that, unlike Na+ and Cl-, Ca++ is absorbed directly from the exterior by the integument and does not enter the body through the gills. 8. During molting, only about 4 per cent of the raw ash and 2.3 per cent of the organic material of the old cuticle is resorbed.

Antipyretic role of the NO-cGMP pathway in the anteroventral preoptic region of the rat brain

2002 ◽  
Vol 282 (2) ◽  
pp. R584-R593 ◽  
Author(s):  
Alexandre A. Steiner ◽  
Jose Antunes-Rodrigues ◽  
Samuel M. McCann ◽  
Luiz G. S. Branco
Keyword(s):  
Soluble Guanylate Cyclase ◽  
Early Stage ◽  
Body Core Temperature ◽  
Preoptic Region ◽  
No Donor ◽  
Cgmp Pathway ◽  
Before And After ◽  
Body Core ◽  
Nitrite Nitrate

We tested the hypothesis that nitric oxide (NO) acts in the anteroventral preoptic region (AVPO) modulating fever. To this end, body core temperature (Tc) of rats was monitored by biotelemetry before and after pharmacological modulation of the NO pathway. Nitrite/nitrate and cGMP in the anteroventral third ventricular region (AV3V), where the AVPO is located, were also determined. Intra-AVPO microinjection of the NO synthase (NOS) inhibitor N G-monomethyl-l-arginine (l-NMMA, 12.5 μg) did not affect basal Tc, but it enhanced the early stage of lipopolysaccharide (LPS) fever, indicating that NO plays an antipyretic role in the AVPO. In agreement, intra-AVPO microinjection of the NO donor sodium nitroprusside (5 μg) reduced Tc. The antipyretic effect of NO seems to be mediated by cGMP because 1) NO has been shown to activate soluble guanylate cyclase, 2) intra-AVPO microinjection of 8-bromo-cGMP (8-BrcGMP) reduced Tc, and 3) the changes in AV3V levels of nitrite/nitrate and cGMP were similar in the course of fever. Additionally, we observed that nitrite/nitrate and cGMP levels decreased in the AV3V after, but not before, the onset of LPS fever, showing that the activity of the NO-cGMP pathway is reduced in the AV3V after intraperitoneal LPS, a mechanism that could contribute to the genesis and maintenance of fever. It was also observed that the efficacy of 8-BrcGMP in reducing Tc in the AVPO is increased after LPS, emphasizing that the NO-cGMP pathway is antipyretic. This response could explain why intra-AVPOl-NMMA enhanced the early stage of LPS fever, even though the activity of the NO pathway before the onset of fever was unchanged. In summary, these data support an antipyretic role of the NO-cGMP pathway in the AVPO.

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