scholarly journals Low oxygen consumption in the inner retina of the visual streak of the rabbit

2004 ◽  
Vol 286 (1) ◽  
pp. H419-H423 ◽  
Author(s):  
Dao-Yi Yu ◽  
Stephen J. Cringle
Keyword(s):  
Oxygen Consumption ◽  
Large Degree ◽  
Rabbit Retina ◽  
Low Oxygen ◽  
Inner Retina ◽  
Visual Streak ◽  
Rate Of Oxygen Consumption ◽  
Oxygen Sensitive ◽  
Oxygen Requirements ◽  
Specialized Region

The oxygen requirements of different retinal layers are of interest in understanding the vulnerability of the retina to hypoxic damage in retinal diseases with an ischemic component. Here, we report the first measurements of retinal oxygen consumption in the visual streak of the rabbit retina, the region with the highest density of retinal neurons, and compare it with that in the less-specialized region of the retina underlying the vascularized portion of the rabbit retina. Oxygen-sensitive microelectrodes were used to measure oxygen tension as a function of retinal depth in anesthetized animals. Measurements were performed in the region of the retina containing overlying retinal vessels and in the center of the visual streak. Established mathematical analyses of the intraretinal oxygen distribution were used to quantify the rate of oxygen consumption in the inner and outer retina and the relative oxygen contributions from the choroidal and vitreal sides. Outer retinal oxygen consumption was higher in the visual streak than in the vascularized area (means ± SE, 284 ± 20 vs. 210 ± 23 nl O2·min–1·cm–2, P = 0.026, n = 10). However, inner retinal oxygen consumption in the visual streak was significantly lower than in the vascular area (57 ± 4.3 vs. 146 ± 12 nl O2·min–1·cm–2, P < 0.001). We conclude that despite the higher processing requirements of the inner retina in the visual streak, it has a significantly lower oxygen consumption rate than the inner retina underlying the retinal vasculature. This suggests that the oxygen uptake of the inner retina is regulated to a large degree by the available oxygen supply rather than the processing requirements of the inner retina alone.

Oxygen consumption in the avascular guinea pig retina

1996 ◽  
Vol 271 (3) ◽  
pp. H1162-H1165 ◽  
Author(s):  
S. Cringle ◽  
D. Y. Yu ◽  
V. Alder ◽  
E. N. Su ◽  
P. Yu
Keyword(s):  
Oxygen Consumption ◽  
Guinea Pig ◽  
Oxygen Tension ◽  
Physiological State ◽  
High Oxygen ◽  
Excess Oxygen ◽  
Low Oxygen ◽  
Inner Retina ◽  
Oxygen Sensitive

Oxygen consumption across the retina of a mammal with a naturally avascular retina has not previously been investigated. The oxygen consumption across the avascular retina of the guinea pig was measured in vivo by spatial analysis of the intraretinal oxygen profile. The avascular nature of the guinea pig retina allows the inner retina to be included in the analysis without disrupting the normal physiological state of the retina. Oxygen-sensitive microelectrodes (1-micron tip) were used to make high-resolution measurements of oxygen tension through the retina of anesthetized, mechanically ventilated guinea pigs (n = 10). Oxygen profiles were then analyzed in terms of oxygen tension as a function of distance from the choriocapillaris/Bruch's membrane, and the data were fitted to an established mathematical model of retinal oxygen consumption. The average oxygen consumption of the full thickness of the guinea pig retina was 1.1 +/- 0.09 ml O2.min-1 x 100 g-1 (n = 10). The average oxygen consumption of the outer half of the retina was 2.07 +/- 0.17 ml O2.min-1 x 100 g-1, while that of the inner half was only 0.12 +/- 0.04 ml O2.min-1 x 100 g-1. A localized region of high oxygen consumption was identified in the outer retina in every case, and this region accounted for an average of 93.9 +/- 2.0% of the total retinal oxygen consumption. Only 5.2 +/- 1.4% of the total oxygen consumption was attributable to the inner half of the retina. When choroidal oxygen tension was increased via a combination of systemic hyperoxia and hypercapnia, high oxygen levels could be sustained in all retinal layers. Under these conditions of an excess oxygen supply, the inner retina still consumed only 0.45 +/- 0.11 ml O2.min-1 x 100 g-1, which was 13.8 +/- 2.5% of the total retinal oxygen consumed. The relatively low oxygen consumption in the inner retina of the guinea pig may reflect an interesting adaptation to the constraints imposed by the absence of a retinal circulation in this species.

RESPIRATION OF FISHES WITH SPECIAL EMPHASIS ON STANDARD OXYGEN CONSUMPTION: III. INFLUENCE OF OXYGEN

1964 ◽  
Vol 42 (3) ◽  
pp. 355-366 ◽  
Author(s):  
F. W. H. Beamish
Keyword(s):  
Oxygen Consumption ◽  
Oxygen Uptake ◽  
Partial Pressure ◽  
Brook Trout ◽  
Low Oxygen ◽  
Low Level ◽  
Standard Metabolism ◽  
Partial Pressures ◽  
Rate Of Oxygen Consumption ◽  
Standard Rate

Standard oxygen consumption was determined in relation to various partial pressures of oxygen for eastern brook trout at 10° and 15 °C, and for carp and goldfish at 10° and 20 °C. Two conditions of oxygen acclimation were compared. In one case acclimation was to air saturation while in the other acclimation was to each of the partial pressures of oxygen applied.Down to a partial pressure of oxygen of approximately 80 mm Hg, standard oxygen uptake remained approximately constant, and further, the rates for the two differently acclimated groups were about equal. Below 80 mm Hg the standard rate first increased to a maximum and then, with a further reduction in the partial pressure, decreased. Below 80 mm Hg the standard rate of oxygen consumption was in all cases less for the fish acclimated to the low level of oxygen than for those acclimated to air saturation.Comparison of standard and active values suggests that the increase in standard rate of oxygen uptake in response to low oxygen does not reach the active level as suggested earlier by Fry (1947). The suggestion is made that a fraction of standard metabolism is derived anaerobically in low levels of oxygen. Further, it appears that acclimation to a low level of oxygen enhances the anaerobic fraction of standard metabolism.

The Respiratory Physiology of the Marine Nematodes Enoplus Brevis (Bastian) and E. Communis (Bastian)

1973 ◽  
Vol 59 (1) ◽  
pp. 267-274
Author(s):  
H. J. ATKINSON
Keyword(s):  
Oxygen Consumption ◽  
Sea Water ◽  
Atmospheric Oxygen ◽  
Respiratory Physiology ◽  
Marine Nematodes ◽  
Oxygen Regime ◽  
Lower Oxygen ◽  
Rate Of Oxygen Consumption ◽  
Oxygen Tensions ◽  
Oxygen Requirements

1. The rate of oxygen consumption of individual male Enoplus brevis and E. communis was measured at 15 °C, after altering the oxygen regime experienced since the animals were collected. 2. When both E. brevis and E. communis were transferred to 35 Torr from atmospheric oxygen tensions, their oxygen consumption was only two-thirds of that of individuals maintained at this lower oxygen tension. 3. The rate of oxygen consumption of the two species at 135 Torr was unaltered by exposure for 2 h to oxygen-free sea water. 4. The results are discussed in relation to the overall influence of fluctuating oxygen regimes on the oxygen requirements of nematodes.

Respiration of a low oxygen tolerant galatheid crab, Munida quadrispina (Benedict, 1902)

1985 ◽  
Vol 63 (11) ◽  
pp. 2538-2542 ◽  
Author(s):  
Brenda J. Burd
Keyword(s):  
Oxygen Consumption ◽  
Carapace Length ◽  
Low Oxygen ◽  
Oxygen Levels ◽  
Saanich Inlet ◽  
Rate Of Oxygen Consumption ◽  
Wet Weight ◽  
Critical Oxygen Concentration ◽  
Relationship Of ◽  
Size Gradient

A recent study on Munida quadrispina in the cliff community of Saanich Inlet, an intermittently anoxic fjord, showed that these crabs have a size distribution corresponding to the vertical oxygen gradient. This study tested the hypothesis that the size gradient was caused by a size-dependent respiratory tolerance. The factor used for comparison was Pc (critical oxygen concentration below which the rate of oxygen consumption declines). Size specific Pc was compared with habitat oxygen levels at which different sized animals were captured in Saanich Inlet. Regulated oxygen consumption and Pc decreased significantly (p < 0.01) with increasing wet weight of crabs. Pc decreased significantly (p < 0.01) as carapace length increased. The slope and elevation of the latter relationship were not significantly different (p < 0.01, ANCOVA) from the slope and elevation of the relationship of carapace length versus habitat oxygen. This observation is consistent with the hypothesis that the vertical size gradient in Saanich Inlet is related to a size-specific Pc. The minimum Pc observed (0.14 mL oxygen/L) corresponded with the lowest oxygen levels at which crabs were found in Saanich Inlet (0.1–0.15 mL oxygen/L).

Respiratory Quotients in Goldfish and Rainbow Trout

1968 ◽  
Vol 25 (8) ◽  
pp. 1689-1728 ◽  
Author(s):  
Methil Narayan Kutty
Keyword(s):  
Oxygen Consumption ◽  
Steady State ◽  
Rainbow Trout ◽  
Metabolic Rate ◽  
Anaerobic Capacity ◽  
Low Oxygen ◽  
Ambient Oxygen ◽  
Rate Of Oxygen Consumption ◽  
Short Time ◽  
Oxygen Concentrations

The respiratory quotients (R.Q.) of goldfish and rainbow trout were measured at 20 and 15 C respectively under spontaneous and forced activity. In goldfish spontaneously active and acclimated to air saturation the R.Q. was 1.02 in ambient oxygen above 50% air saturation and rose to 1.94 below 25% air saturation. Rainbow trout under similar conditions displayed respective R.Q.'s of 0.96 and 1.4. The latter R.Q. could be sustained only for a short time. In both species the metabolic rate dropped at oxygen concentrations below 50% air saturation but spontaneous activity remained high. Goldfish acclimated to 15% air saturation displayed the same R.Q. as unacclimated fish and thus did not display any increase in anaerobic capacity. When forced to swim steadily in water above 50% air saturation both species showed an initial anaerobic phase. This phase was less marked in the rainbow trout and was followed by an aerobic steady state except that at low swimming speeds the goldfish appeared to continuously derive some energy anaerobically. At oxygen concentrations below 50% air saturation the R.Q. of goldfish increased with decreasing concentration during steady swimming. At the single level of steady swimming effort at which comparisons were made, the R.Q. of goldfish did not change with acclimation to 15% air saturation but the rate of oxygen consumption fell to about 50% of the value before acclimation. The rainbow trout was not acclimated to low oxygen for any test.

scholarly journals Recovery heat in muscular contraction without lactic acid formation

1931 ◽  
Vol 108 (757) ◽  
pp. 279-301 ◽  
Keyword(s):  
Acetic Acid ◽  
Oxygen Consumption ◽  
Lactic Acid ◽  
Muscular Contraction ◽  
Acid Formation ◽  
Anaerobic Conditions ◽  
Spontaneous Breakdown ◽  
Rate Of Oxygen Consumption ◽  
Resting Muscle

In a comparison of muscles poisoned with mono-iodo-acetic acid (IAA) in the presence and in the absence of oxygen respectively, Lundsgaard (1930) found:- (1) That the spontaneous breakdown of phosphagen in poisoned resting muscle is much more rapid under anaerobic conditions. (2) That the onset of the characteristic contracture produced by IAA is accompanied always by an increase in the rate of oxygen consumption.

Proximal tubule dysfunction in cystine-loaded tubules: effect of phosphate and metabolic substrates

1996 ◽  
Vol 271 (3) ◽  
pp. F717-F722
Author(s):  
G. Bajaj ◽  
M. Baum
Keyword(s):  
Oxygen Consumption ◽  
Proximal Tubule ◽  
Tricarboxylic Acid Cycle ◽  
Dimethyl Ester ◽  
Proximal Tubules ◽  
Intracellular Atp ◽  
Metabolic Substrates ◽  
Rate Of Oxygen Consumption ◽  
Intracellular Phosphate

Intracellular cystine loading by use of cystine dimethyl ester (CDME) results in a generalized inhibition in proximal tubule transport due, in part, to a decrease in intracellular ATP. The present study examined the importance of phosphate and metabolic substrates in the proximal tubule dysfunction produced by cystine loading. Proximal tubule intracellular phosphorus was 1.8 +/- 0.1 in control tubules and 1.1 +/- 0.1 nmol/mg protein in proximal tubules incubated in vitro with CDME P < 0.001). Infusion of sodium phosphate in rabbits and subsequent incubation of proximal tubules with a high-phosphate medium attenuated the decrease in proximal tubule respiration and prevented the decrease in intracellular ATP with cystine loading. Tricarboxylic acid cycle intermediates have been shown to preserve oxidative metabolism in phosphate-depleted proximal tubules. In proximal tubules incubated with either 1 mM valerate or butyrate, there was a 42 and 34% reduction (both P < 0.05) in the rate of oxygen consumption with cystine loading. However, tubules incubated with 1 mM succinate or citrate had only a 13 and 14% P = NS) reduction in the rate of oxygen consumption, respectively. These data are consistent with a limitation of intracellular phosphate in the pathogenesis of the proximal tubule dysfunction with cystine loading.

Viability and respiratory activity ofPseudomonas syringaecells starved in buffer

1995 ◽  
Vol 41 (4-5) ◽  
pp. 372-377 ◽  
Author(s):  
João P. S. Cabral
Keyword(s):  
Oxygen Consumption ◽  
Electron Transport ◽  
Pseudomonas Syringae ◽  
Respiratory Activity ◽  
Bacterial Cells ◽  
Intact Cells ◽  
Rate Of Oxygen Consumption ◽  
Metabolic Activities ◽  
Different Levels ◽  
Number Of Cells

Pseudomonas syringae cells starved in buffer released orcinol-reactive molecules and materials that absorbed ultraviolet light. The number of cells culturable in nutrient medium decreased more rapidly than the number of intact particles determined by microscopy. The results suggested that starvation resulted in the lysis of an increasing number of cells, and that a fraction of the intact particles were not culturable. Starvation also resulted in a decrease in the rate of oxygen consumption with acetate, glycerol, and succinate, but at different levels. Whereas the respiration of acetate and glycerol decreased concomitantly with culturability, the respiration of succinate decreased to levels similar to the concentration of intact cells, suggesting that all intact particles respired the succinate, but only the culturable cells respired the acetate and glycerol. The results suggest that measuring the activity of the electron-transport system can overestimate the viability of starved bacterial cells, and that complex metabolic activities such as the respiration of acetate and glycerol are probably better suited for the evaluation of this parameter.Key words: Pseudomonas syringae, starvation, culturability, viability, respiration.

Sign in / Sign up

Export Citation Format

Share Document