The effect of experimental spasm on the CO2 response of cerebral bloodflow in primates

1972 ◽  
Vol 3 (3) ◽  
pp. 134-136 ◽  
Author(s):  
A. M. Harper ◽  
V. D. Deshmukh ◽  
D. Sengupta ◽  
J. O. Rowan ◽  
W. B. Jennett
Keyword(s):  
Co2 Response ◽  
Cerebral Bloodflow

scholarly journals Stomatal conductance limited the CO2 response of grassland in the last century

BMC Biology ◽  
2021 ◽  
Vol 19 (1) ◽  
Author(s):  
Juan C. Baca Cabrera ◽  
Regina T. Hirl ◽  
Rudi Schäufele ◽  
Andy Macdonald ◽  
Hans Schnyder
Keyword(s):  
Climate Change ◽  
Stomatal Conductance ◽  
Nitrogen Nutrition ◽  
Physiological Control ◽  
Co2 Response ◽  
Nitrogen Acquisition ◽  
Wide Range ◽  
Park Grass Experiment ◽  
Conductance Changes ◽  
Canopy Stomatal Conductance

Abstract Background The anthropogenic increase of atmospheric CO2 concentration (ca) is impacting carbon (C), water, and nitrogen (N) cycles in grassland and other terrestrial biomes. Plant canopy stomatal conductance is a key player in these coupled cycles: it is a physiological control of vegetation water use efficiency (the ratio of C gain by photosynthesis to water loss by transpiration), and it responds to photosynthetic activity, which is influenced by vegetation N status. It is unknown if the ca-increase and climate change over the last century have already affected canopy stomatal conductance and its links with C and N processes in grassland. Results Here, we assessed two independent proxies of (growing season-integrating canopy-scale) stomatal conductance changes over the last century: trends of δ18O in cellulose (δ18Ocellulose) in archived herbage from a wide range of grassland communities on the Park Grass Experiment at Rothamsted (U.K.) and changes of the ratio of yields to the CO2 concentration gradient between the atmosphere and the leaf internal gas space (ca – ci). The two proxies correlated closely (R2 = 0.70), in agreement with the hypothesis. In addition, the sensitivity of δ18Ocellulose changes to estimated stomatal conductance changes agreed broadly with published sensitivities across a range of contemporary field and controlled environment studies, further supporting the utility of δ18Ocellulose changes for historical reconstruction of stomatal conductance changes at Park Grass. Trends of δ18Ocellulose differed strongly between plots and indicated much greater reductions of stomatal conductance in grass-rich than dicot-rich communities. Reductions of stomatal conductance were connected with reductions of yield trends, nitrogen acquisition, and nitrogen nutrition index. Although all plots were nitrogen-limited or phosphorus- and nitrogen-co-limited to different degrees, long-term reductions of stomatal conductance were largely independent of fertilizer regimes and soil pH, except for nitrogen fertilizer supply which promoted the abundance of grasses. Conclusions Our data indicate that some types of temperate grassland may have attained saturation of C sink activity more than one century ago. Increasing N fertilizer supply may not be an effective climate change mitigation strategy in many grasslands, as it promotes the expansion of grasses at the disadvantage of the more CO2 responsive forbs and N-fixing legumes.

Preparation of hemoglobin (Hb) imprinted polymers with CO2 response and its biosensing application

2021 ◽  
Vol 25 (5) ◽  
pp. 1645-1655
Author(s):  
Shuang Bo ◽  
Yue Sun ◽  
Siyu Li ◽  
Yuxi Zhou ◽  
Xuewei Feng ◽  
...  
Keyword(s):  
Co2 Response ◽  
Imprinted Polymers

scholarly journals A molecular pathway for CO2 response in Arabidopsis guard cells

2015 ◽  
Vol 6 (1) ◽  
Author(s):  
Wang Tian ◽  
Congcong Hou ◽  
Zhijie Ren ◽  
Yajun Pan ◽  
Jinjin Jia ◽  
...  
Keyword(s):  
Guard Cells ◽  
Co2 Response ◽  
Molecular Pathway

Breathing, transcutaneous blood gases, and CO2 response in SIDS siblings and control infants during sleep

1993 ◽  
Vol 74 (1) ◽  
pp. 88-102 ◽  
Author(s):  
T. Schafer ◽  
D. Schafer ◽  
M. E. Schlafke
Keyword(s):  
Blood Gases ◽  
Periodic Breathing ◽  
Sleep Time ◽  
Sudden Infant Death ◽  
Sudden Infant ◽  
Breathing Patterns ◽  
Co2 Response ◽  
Cross Sectional ◽  
Apnea Duration ◽  
Age Related

Age-related changes of 20 variables describing breathing patterns, transcutaneous blood gases, and estimated CO2 response during sleep were examined in a cross-sectional study of 30 healthy control infants and 150 healthy siblings of sudden infant death syndrome victims within the first 18 mo of life. Whole-night measurements were performed using noninvasive respiratory induction plethysmography and transcutaneous blood gas electrodes. Each candidate for the study was extensively screened and found to be healthy. Mean transcutaneous PCO2 (PtcCO2, median 40.3 Torr) and maximum PtcCO2 (median 44.8 Torr), as well as the estimated ventilatory response to inhalation of 2% CO2 in air during regular breathing, causing a 20–36% increase of ventilation per Torr PtcCO2, were not related to postnatal age. In contrast, paradoxical breathing decreased from 49.5 to 0% of total sleep time (TST), periodic breathing from 5.5 to 0% TST, and respiratory rate during regular breathing from 40 to 22 breaths/min; the portion of regular breathing increased from 32 to 55% TST and mean and minimum transcutaneous PO2 from 65.4 and 47 to 69.7 and 52 Torr with increasing stability. The largest changes occurred in the first 6 mo of life. Maximum apnea duration (9.5 s, maximum 16 s), mean apnea duration (3.74 s, breathing pauses > or = 2 s), and time spent apneic per hour of irregular breathing (199 s/h) were not related to age. The comparison of data from siblings and controls showed similarities in the above-mentioned variables. No significant differences were found among the groups. Also a comparison of 30 pairs of siblings and controls, matched for age, gender, birth, and actual body weight, did not show significant differences. The present study extends the knowledge of development of breathing control beyond the first 6 mo of life.

scholarly journals Ice-driven CO<sub>2</sub> feedback on ice volume

2006 ◽  
Vol 2 (1) ◽  
pp. 43-55 ◽  
Author(s):  
W. F. Ruddiman
Keyword(s):  
Geographic Origin ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Early Pleistocene ◽  
Schematic Model ◽  
Co2 Response ◽  
Ice Volume ◽  
Summer Insolation ◽  
Northern Summer ◽  
Insolation Forcing

Abstract. The origin of the major ice-sheet variations during the last 2.7 million years is a long-standing mystery. Neither the dominant 41 000-year cycles in δ18O/ice-volume during the late Pliocene and early Pleistocene nor the late-Pleistocene oscillations near 100 000 years is a linear ("Milankovitch") response to summer insolation forcing. Both responses must result from non-linear behavior within the climate system. Greenhouse gases (primarily CO2) are a plausible source of the required non-linearity, but confusion has persisted over whether the gases force ice volume or are a positive feedback. During the last several hundred thousand years, CO2 and ice volume (marine δ18O) have varied in phase at the 41 000-year obliquity cycle and nearly in phase within the ~100 000-year band. This timing rules out greenhouse-gas forcing of a very slow ice response and instead favors ice control of a fast CO2 response. In the schematic model proposed here, ice sheets responded linearly to insolation forcing at the precession and obliquity cycles prior to 0.9 million years ago, but CO2 feedback amplified the ice response at the 41 000-year period by a factor of approximately two. After 0.9 million years ago, with slow polar cooling, ablation weakened. CO2 feedback continued to amplify ice-sheet growth every 41 000 years, but weaker ablation permitted some ice to survive insolation maxima of low intensity. Step-wise growth of these longer-lived ice sheets continued until peaks in northern summer insolation produced abrupt deglaciations every ~85 000 to ~115 000 years. Most of the deglacial ice melting resulted from the same CO2/temperature feedback that had built the ice sheets. Several processes have the northern geographic origin, as well as the requisite orbital tempo and phasing, to be candidate mechanisms for ice-sheet control of CO2 and their own feedback.

Acclimatization to high altitude in goats with ablated carotid bodies

1983 ◽  
Vol 55 (1) ◽  
pp. 16-21 ◽  
Author(s):  
R. A. Steinbrook ◽  
J. C. Donovan ◽  
R. A. Gabel ◽  
D. E. Leith ◽  
V. Fencl
Keyword(s):  
High Altitude ◽  
Pulmonary Ventilation ◽  
Base Deficit ◽  
Co2 Production ◽  
Regulation Of Respiration ◽  
Response Curves ◽  
Co2 Response ◽  
Arterial Blood ◽  
Carotid Bodies ◽  
Simulated High Altitude

In awake goats with ablated carotid bodies, we studied resting pulmonary ventilation, CO2 production, composition of arterial blood and cerebrospinal fluid (CSF), and ventilatory responsiveness to hyperoxic CO2 rebreathing at sea level (SL) and after 3 days at simulated high altitude (HA) (PB 446 +/- 5 Torr, equivalent to 4,300 m). At HA, resting pulmonary ventilation was increased, resulting in marked hypocapnia with appropriate base deficit in blood plasma; CSF became more alkaline; CO2-response curves were shifted to lower PCO2 levels, and their slopes were steeper than at SL. Although these changes in regulation of respiration were not demonstrably different from those seen after normal acclimatization to HA with carotid bodies intact, the mechanisms of their initiation and development are probably different.

Maturation of steady-state CO2 sensitivity in vagotomized anesthetized lambs

1992 ◽  
Vol 72 (4) ◽  
pp. 1255-1260 ◽  
Author(s):  
A. H. Jansen ◽  
S. Ioffe ◽  
V. Chernick
Keyword(s):  
Steady State ◽  
Test Procedure ◽  
Nerve Section ◽  
Co2 Response ◽  
Arterial Pco2 ◽  
Co2 Sensitivity ◽  
Carotid Bodies ◽  
Before And After ◽  
End Tidal ◽  
Respiratory Sensitivity

The maturation of the respiratory sensitivity to CO2 was studied in three groups of anesthetized (ketamine, acepromazine) lambs 2–3, 14–16, and 21–22 days old. The lambs were tracheostomized, vagotomized, paralyzed, and ventilated with 100% O2. Phrenic nerve activity served as the measure of respiration. The lambs were hyperventilated to apneic threshold, and end-tidal PCO2 was raised in 0.5% steps for 5–7 min each to a maximum 7–8% and then decreased in similar steps to apneic threshold. The sinus nerves were cut, and the CO2 test procedure was repeated. Phrenic activity during the last 2 min of every step change was analyzed. The CO2 sensitivity before and after sinus nerve section was determined as change in percent minute phrenic output per Torr change in arterial PCO2 from apneic threshold. Mean apneic thresholds (arterial PCO2) were not significantly different among the groups: 34.8 +/- 2.08, 32.7 +/- 2.08, and 34.7 +/- 2.25 (SE) Torr for 2- to 3-, 14- to 16-, and 21- to 22-day-old lambs, respectively. After sinus denervation, apneic thresholds were raised in all groups [39.9 +/- 2.08, 40.9 +/- 2.08, and 45.3 +/- 2.25 (SE) Torr, respectively] but were not different from each other. CO2 response slopes did not change with age before or after sinus nerve section. We conclude that carotid bodies contribute to the CO2 response during hyperoxia by affecting the apneic threshold but do not affect the steady-state CO2 sensitivity and the central chemoreceptors are functionally mature shortly after birth.

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