摘要:

AbstractMetabolic rates of 10 species of invertebrates were determined as they depleted the dissolved oxygen in a small volume of water, and entered anoxic states. The animals included eight marine forms (four mollusks, two brachiopods, a crustacean, and a polychaete), a brackish‐water crab, and a freshwater oligochaete. Rates of heat production (QH) were calculated from measurements of temperature change in a heat‐retention calorimeter. Rates of oxygen consumption (QO) were calculated from concurrent decreases in oxygen concentration (CO) determined by polarographic oxygen sensor.When the water was fully saturated with oxygen, QHand QOof all species were equal, and most rates were 1–7 J/hr‐gm wet weight. A swimming crustacean and the oligochaete had rates five times higher, possibly due to high activity. QOdecreased with COin all species. However, the relation was species specific, most animals showing overreaction to declining CO. InCallinectesonly partial regulation of QOwas observed at COabove 55% saturation. In all species, QHdecreased more slowly than QOover most of the COrange, and decreased rapidly at some critically low CO.The relation between metabolic rate and oxygen saturation was summarized in the fraction (KO) of the fully aerobic rate found when COwas at exactly onehalf saturation, analogous to a Michaelis constant, but not implying a particular mechanism. The KOfor QOaveraged 0.70, and the KOfor QHin 8 species averaged 0.22. In two bivalves QHwas often above the initial fully aerobic level at intermed

ISSN:0022-104X    

DOI:10.1002/jez.1402280302

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY

摘要:

AbstractSome species of invertebrates, particularly benthic infauna, show extreme metabolic fluctuations, from a truly basal metabolic rate while quiescent in anaerobic mode to higher rates as a result of physical activity whether they are anaerobic or aerobic. The fluctuations may be random or cyclic, endogenous, induced by experimental conditions, or by natural changes in environmental conditions; they are readily seen and quantified by direct calorimetry.Biochemists studying anaerobic metabolism sometimes find large quantitative variations in metabolite concentration between individual test organisms. One source of variability may be the variability in the metabolic activity of the control and experimental animals. Information contained in heat flow recordings could be useful in normalizing data and making more precise correlations between actual metabolic rates and chemical measures of metabolism.Theoretical enthalpy changes from known anaerobic end products and results of direct calorimetry do not agree at present. Continual comparisons, leading to consistent agreement or satisfactory explanation of their discrepancy, are necessary to demonstrate full understanding of anaerobic metabolism.

ISSN:0022-104X    

DOI:10.1002/jez.1402280303

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY

摘要:

AbstractDuring environmental anaerobiosis, when the whole organism is exposed to anoxic conditions caused by external, physical factors in the microhabitat, arginine phosphate, glycogen, and aspartate (only mollusks) are the substrates for the metabolism. Main end products formed are lactate (Crustacea, Xiphosura, some Gastropoda and Bivalvia), alanine, succinate, and the volatile fatty acids, propionate and acetate (most Gastropoda and most Bivalvia). Because of reduction of the overall metabolism in bivalves, utilization and production rates of substrates and end products, respectively, are low. They are generally faster in Crustacea, which do not reduce their metabolism.During functional anaerobiosis, when the muscle tissue becomes anoxic because of increased work done by the animal, energy is derived from arginine phosphate and glycogen. The main end products formed are lactate (Crustacea), octopine (active Gastropoda and Bivalvia), and strombine/alanopine (some gastropod species). Utilization rates of the phosphagen and production rate of lactate and opines are sometimes more than 500‐fold higher than during environmental anaerobiosis. These strong variations in the glycolytic flux are probably regulated by the influence of the phosphagen and adenylates on regulatory enzymes and by the NADH/NAD rati

ISSN:0022-104X    

DOI:10.1002/jez.1402280304

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY

摘要:

AbstractThe duration and completeness of recovery from anaerobic metabolism is of important functional consequence in invertebrates. Two basic processes occur during recovery: (1) recharging of the phosphagen and ATP pools and (2) disposal of end products by excretion, oxidation, or conversion back to anaerobic substrates. The recovery process in invertebrates is largely aerobic, as is evidenced by the near universality of the oxygen debt phenomenon. However, there is often a lack of correlation between end product accumulation and the magnitude of the oxygen debt. Typically, ATP and phosphagen levels are recharged very rapidly during recovery–ATP (0.25 to 1.0 hr) and phosphagens (0.5 to 4 hr). Excretion of propionate, acetate, and, occasionally succinate, is relatively common in annelids and has also been observed in a number of bivalve molluscs. Nitrogen‐containing end products do not appear to be excreted. Cephalopods and large arthropods show elevated hemolymph end product levels following anoxia/hypoxia. In arthropods, these end products display a protracted return to control levels during recovery. In cephalopods, some octopine may be rapidly taken up and metabolized by the heart, brain, and gill. The sites of lactate metabolism in arthropods are unclear. In contrast to the situation in cephalopods and arthropods, most end products in the adductor muscles of bivalve molluscs do not appear to be exported, but are metabolized within the tissue itself. End ducts such as octopine, succinate, and alanine thus appear to be metabolized at the site of their production. Octopine and lactate appear to be gluconeogenic substrates in cephalopods and arthropods, respectively. Although many of the enzymes involved in gluconeogenesis are present in bivalve molluscs, this process has not been demonstrated in this group. Recovery from anaerobic metabolism remains a fruitful area for future research. Of special interest is the identification of sites of gluconeogenesis in the larger, more active spec

ISSN:0022-104X    

DOI:10.1002/jez.1402280305

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY

摘要:

AbstractMany groups of invertebrates use metabolic strategies that do not lead to the accumulation of lactate during periods of hypoxia or anoxia. These animals may accumulate some combination of the following: alanine, octopine, alanopine, strombine, acetate, propionate, 2‐methylbutyrate, 2‐meth‐ylvalerate, and succinate. An organism may derive a benefit from production of an alternative end product when the yield of ATP per mole of glucose 6‐phosphate is greater than that found in lactate production. Formations of succinate, propionate, 2‐methylbutyrate, and 2‐methylvalerate have been shown to yield more ATP in a few species. This analysis can be extended to the formation of alanine, as this is accompanied by the conversion of aspartate to succinate.Formations of octopine, alanopine, or strombine apparently do not increase the yield of ATP per mole of glucose 6‐phosphate, because the enzymes forming these compounds are functionally analogous to lactate dehydrogenase. A potential advantage of producing these compounds might be maintenance of a constant intracellular osmotic pressure during periods of anoxia. The significance of this is uncertain, because if lactate were to accumulate, the expected change in osmotic pressure appears to be trivial. Another possible advantage of accumulating octopine, alanopine, or strombine, would be the ability to maintain a lower NADH/NAD+ratio as compared with the accumulation of lactate. This might assist the organism in maintaining a high rate of glycolysis by reducing the inhibition of glyceraldehyde 3‐phosphate dehydrogenase by NADH. Other possibilities are smaller perturbations of the acid–base balance of the cell, or producing a compound that has less effect on the catalytic and regulatory properties of en

ISSN:0022-104X    

DOI:10.1002/jez.1402280306

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY

摘要:

AbstractWhen cells are subjected to stress, an early result is a shift in type and rate of metabolism to reflect their new conditions. The availability of metabolites, their endogenous vs exogenous origins, and the rates at which they can be used, besides availability of oxygen, dictate cell and tissue response. Measurement of heat output in such a response is a means for monitoring cells and tissues. Differential heat conduction calorimeters are reviewed to provide a listing of instrument parameters important in optimum practical use. Data obtained with one cell system, mammalian sperm, are presented to provide an example of how the combination of calorimetry and carbon balance, plus calculation from thermodynamic constants, permit an assessment of the importance of endogenous metabolism to total cellular metabolism.

ISSN:0022-104X    

DOI:10.1002/jez.1402280307

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY

摘要:

AbstractThis survey on calorimetry and thermodynamics of anoxibiosis applies classical and irreversible thermodynamics to interpret experimental, direct calorimetric results in order to elucidate the sequential activation of various biochemical pathways. First, the concept of direct and indirect calorimetry is expanded to incorporate the thermochemistry of aerobic and anoxic metabolism in living cells and organisms. Calorimetric studies done under normoxia as well as under physiological and environmental anoxia are presented and assessed in terms of ATP turnover rate. Present evidence suggests that unknown sources of energy in freshwater and marine invertebrates under long‐term anoxia may be important.During physiological hypoxia, thermodynamically grossly inefficient pathways sustain high metabolic rates for brief periods. On the contrary, under long‐term environmental anoxia, low steady‐state heat dissipation is linked to the more efficient succinate, propionate, and acetate pathways. In the second part of this paper these relationships are discussed in the context of linear, irreversible thermodynamics. The calorimetric and biochemical trends during aerobic‐anoxic transitions are consistent with thermodynamic optimum functions of catabolic pathways. The theory predicts a decrease of rate with an increase of thermodynamic efficiency; therefore maximum rate and maximum efficiency are mutually exclusive. Cellular changes of pH and adenylate phosphorylation potential are recognized as regulatory mechanisms in the energetic switching to propionate production. While enzyme kinetics provides one key for understanding metabolic regulation, our insight remains incomplete without a complementary thermodynamic analysis of kinetic control in energetically coupled p

ISSN:0022-104X    

DOI:10.1002/jez.1402280308

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY

摘要:

AbstractFor more than a week prior to the emergence of a hind limb, a steady electric current is driven out of the ventrolateral flank in the immature axolotl, returning through the integument in adjacent regions of the body. A marked peak in the density of this outcurrent could be observed over the exact area of hind limb formation 4 to 6 days prior to its appearance. After a bud projected from the flank, current densities were observed to decrease in magnitude yet localize about the early limb. In about one‐half of the animals observed, current reversed its polarity and entered the apex of large buds, 0.4 to 0.5 mm in length. We discuss the possible role such endogenous currents and their associated fields may play in limb development and compare it to similar current flow associated with the regeneration of amphibian limb

ISSN:0022-104X    

DOI:10.1002/jez.1402280309

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY

摘要:

AbstractThe relationship between the number of cells and blastoderm development to the formation of the egg envelopes is established for the uterine period of quail embryogenesis. On the basis of this relationship, the developmental stage of the embryo can be estimated without destroying the egg or dissecting the embryo. Data are also presented on the number of cells in the quail embryo at the time of egg laying and during the first hours of incubation. These data are critically compared to those in other reports dealing with quail and chick embryos.

ISSN:0022-104X    

DOI:10.1002/jez.1402280310

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY

摘要:

AbstractThe kinetics, specificity, time dependency, Na+dependency, and exchange behavior of the uptake of methionine, as a model for the uptake of the neutral amino acids, was investigated in rabbit eggs, morulae, and 6‐day blastocysts. Uptake by the blastocyst was physically resolved into components representing uptake into the cellular and cavity compartments. The kinetic data for all material, except the cellular compartment of the blastocyst, could be described mathematically by the parallel activity of a saturable and a linear transport system. The Kmdecreased from 91 μM in the unfertilized egg to 38 μM in the fertilized egg to 13 μM in the 69‐hr morula. The Kmof uptake into blastocysts was 131 μM. The Vmaxof uptake into the whole blastocyst was calculated to be about 5000 times that of uptake into the egg. Competition of methionine uptake by other amino acids indicated that the egg had somewhat more “L‐like” transport specificity than subsequent developmental stages, while the system(s) in the blastocyst were reactive with most neutral amino acids. Uptake into the egg, 69‐hr morula, and the cellular compartment of the blastocyst reached a steady state with time, in contrast to uptake into the 76‐hr morula and the cavity compartment of the blastocyst. Compatible with this, was the observation that eggs and 69‐hr morula, but not blastocysts, exhibited considerable efflux into amino acid‐containing media. The cavity compartment of the blastocyst may, however, act as a reservoir of amino acids for the cellular compartment. The Na+dependency of transport was unchanged throughout the developmental period studied

ISSN:0022-104X    

DOI:10.1002/jez.1402280311

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY