JoVE Video Dataset

Effects of oxygen diffusion and reaction kinetics in photodynamic therapy are considered in the context of a multicell tumour spheroid model. Steady-state measurements of oxygen made with a Clark-style microelectrode (4 mu m diameter tip) enable the authors to determine the rate of metabolic oxygen consumption and the oxygen diffusion coefficient in 500 mu m diameter EMT6/Ro spheroids. These values are 5.77 mu mol 1-1 s-1 and 1460 mu m2 s-1, respectively. Time-dependent electrode measurements of oxygen concentration during laser irradiation of individual Photofrin-sensitized spheroids are fitted to numerical solutions of a pair of diffusion-with-reaction equations. The analysis yields the rate of photodynamic oxygen consumption and a parameter that governs the oxygen sensitivity of photodynamic therapy. These experimentally derived quantities are used to calculate the temporal and spatial distributions of oxygen and the rate of oxygen consumption in a spheroid during irradiation at several fluence rates. The spatial distribution of photodynamic oxygen consumption is strongly fluence rate dependent. Using the experimental and theoretical results developed in this report, previously published survival data are analysed. The analysis indicates that the threshold dose of reacting singlet oxygen in the EMT6/Ro spheroid is 323+or-38 mu mol 1-1 (mean+or-SEM).

Investigation of optimal conditions for equilibrating ovarian tissue with ethylene glycol prior to vitrification.

Acute injections of melanocortin (MC) agonist and antagonist are highly effective in reducing or increasing food take, respectively. Much less is known about how injection of MC receptor active substances affects metabolism, in particular during long term administration. Here we investigated the effect of 8 days continuous i.c.v. infusion of either MC receptor agonist MTII or the selective MC4 receptor antagonist HS024 on oxygen consumption, food intake and body weight in rats. We observed significant increase in oxygen consumption 2 days after the start of the MTII infusion. However, this increase had disappeared by day 4 of the study. No difference was observed in the oxygen consumption after injection of HS024. MTII substantially decreased the food intake during the first days, but then the feeding recovered and the body weight stabilised at a new level. The immediate effect of the MC receptor agonist on both food intake and metabolism was thus transient, even though the weight loss was maintained. The HS024 treated rats were hyperphagic throughout the test period, continuously gaining weight, resulting in increased fat pads and high leptin levels. This is the first study that describes long term effects of MC receptor agonist and antagonist on metabolism and energy balance.

Functional properties and integrity of skeletal muscle mitochondria during the early postmortem period may influence development of meat quality traits, such as tenderness. Angus typically produce more tender beef than Brahman, a Bos taurus indicus subspecies known for heat tolerance. Thus, our objectives were to assess mitochondrial function in muscle collected early postmortem from Angus and Brahman cattle; and to evaluate the effect of normal and elevated temperature on mitochondria function. Longissimus lumborum was collected at 1h postmortem from Angus and Brahman steers, and high resolution respirometry was used to assess mitochondrial function in permeabilized muscle fibers at two temperatures (38.5 and 40.0°C). The main effects of breed, temperature, and their interaction were tested. On a tissue weight basis, parameters of respiratory function were not influenced by breed or temperature, though Brahman exhibited numerically greater values for respiration supported by complex I, complex I+II, and complex II substrates. Citrate synthase activity, a marker of mitochondria content, was affected by breed (P = 0.049). Consequently, oxygen consumption rate (OCR) data were normalized to citrate synthase activity. After normalization for mitochondrial content, the overall mitochondria OCR pattern changed, revealing differences among breeds for proton leak respiration (P = 0.045), as well as a persistent interaction effect primarily related to reduced OCR in mitochondria from Brahman at 40.0°C. In addition, the ratio of OCR for leak relative to complex I+II phosphorylation was lower in Brahman, evidencing greater coupling. However, mean coupling ratios for both Angus and Brahman support that respiration and phosphorylation were well-coupled for both breeds even at 1h postmortem. Thus, mitochondria retain functional capacity and integrity at 1h postmortem; and mitochondria properties may be related to differences in heat tolerance and meat quality development between cattle subspecies.

BackgroundLeigh syndrome (LS) is a common mitochondrial disease caused by mutations in both mitochondrial and nuclear genes. Isoleucyl-tRNA synthetase 2 (IARS2) encodes mitochondrial isoleucine-tRNA synthetase, and variants in IARS2 have been reported to cause LS. However, the pathogenic mechanism of IARS2 variants is still unclear.MethodsTwo unrelated patients, a 4-year-old boy and a 5-year-old boy diagnosed with LS, were recruited, and detailed clinical data were collected. The DNA of the patients and their parents was isolated from the peripheral blood for the identification of pathogenic variants using next-generation sequencing and Sanger sequencing. The ClustalW program, allele frequency analysis databases (gnomAD and ExAc), and pathogenicity prediction databases (Clinvar, Mutation Taster and PolyPhen2) were used to predict the conservation and pathogenicity of the variants. The gene expression level, oxygen consumption rate (OCR), respiratory chain complex activity, cellular adenosine triphosphate (ATP) production, mitochondrial membrane potential (MMP) and mitochondrial reactive oxygen species (ROS) levels were measured in patient-derived lymphocytes and IARS2-knockdown HEK293T cells to evaluate the pathogenicity of the variants.ResultsWe reported 2 unrelated Chinese patients manifested with LS who carried biallelic IARS2 variants (c.1_390del and c.2450G > A from a 4-year-old boy, and c.2090G > A and c.2122G > A from a 5-year-old boy), of which c.1_390del and c.2090G > A were novel. Functional studies revealed that the patient-derived lymphocytes carrying c.1_390del and c.2450G > A variants exhibited impaired mitochondrial function due to severe mitochondrial complexes I and III deficiencies, which was also found in IARS2-knockdown HEK293T cells. The compensatory experiments in vitro cell models confirmed the pathogenicity of IARS2 variants since re-expression of wild-type IARS2 rather than mutant IARS2 could rescue complexes I and III deficiency, oxygen consumption, and cellular ATP content in IARS2 knockdown cells.ConclusionOur results not only expand the gene mutation spectrum of LS, but also reveal for the first time the pathogenic mechanism of IARS2 variants due to a combined deficiency of mitochondrial complexes I and III, which is helpful for the clinical diagnosis of IARS2 mutation-related diseases.

Sodium transport and oxygen consumption have been simultaneously studied in the short-circuited toad skin. A constant stoichiometric ratio was observed in each skin under control condition (NaCl-Ringer's solution bathing both sides of the skin) and after block of sodium transport by ouabain. During alterations of sodium transport by removal and addition of K to the internal solution the stoichiometric ratio is constant although having a value higher than that observed in other untreated skins. The coupling between active sodium transport and oxygen consumption was studied after a theoretical nonequilibrium thermodynamic model. Studies were made of the influence of Na chemical potential difference across the skin on the rates of Na transport and oxygen consumption. A linear relationship was observed between the rates of Na transport and oxygen consumption and the Na chemical potential difference. Assuming the Onsager relationship to be valid, the three phenomenological coefficients which describe the system were evaluated. Transient increases in the rate of sodium transport and oxygen consumption were observed after a transitory block of sodium transport by removal of Na from the external solution. Cyanide blocks completely the rate of oxygen consumption in less than 2 min and the short-circuit current measured after that time decays exponentially with time, suggesting a depletion of ATP from a single compartment.

Predictions of short and long term changes in Sepia officinalis metabolism are useful, since this species is both economically important for aquaculture and also is an ideal experimental laboratory organism. In this study standard and routine oxygen consumption rates of newly hatched and juvenile laboratory raised cuttlefish S. officinalis ranging between 0.04 and 18.48 g dry body mass (Dm), were measured over a range of temperatures (10, 15, 20 and 25°C). The mass exponent (b) ranged between 0.706 and 0.992 for standard oxygen consumption and between 0.694 and 0.990 for routine oxygen consumption. Oxygen consumption scaled allometrically (b = 0.7) with body mass for cuttlefish 2 g, MO2 = 0.076Dm0.9831.091T for standard oxygen consumption; cuttlefish 2 g, MO2 = 0.225Dm0.9621.081T for routine oxygen consumption. Using these equations it was estimated that a cuttlefish of 1 g Dm held at 20°C, eating 5% Dm day−1 and undergoing standard and routine metabolism consumes 21.3 and 35.4%, respectively of its total daily energy intake. Juvenile cuttlefish (3.32–5.08 g Dm) held at 15°C and deprived of food for 27 days maintained a stable standard oxygen consumption rate for the first 6 days following starvation. By the 18th day without food, oxygen consumption rate had declined by 53% and further declined to 65% below the standard oxygen consumption rate on the 27th day. Upon resumption of feeding, the respiration rate returned immediately to the initial level prior to food deprivation. The present study defines the basic energy requirements and general physiological state of young cuttlefish at temperatures of 10–25°C with and without food.

IFNγ Augments the Oxygen Consumption Rate and Metabolism in Monocytes Partially Through P2X7

The effect of hydrogen peroxide on isolated body wall of the lugworm Arenicola marina (L.) at different extracellular pH levels

We investigated the effects of reduction of renal mass on rates of oxygen consumption, sodium transport, and indexes of oxidant stress in surviving nephrons. Rates of oxygen consumption in surviving nephrons were elevated by more than twofold compared with nephrons in intact kidneys in rats on standard protein intakes. Absolute rates of sodium reabsorption (TNa) in the surviving nephrons were increased with a lower ratio of TNa to oxygen consumption. To determine oxidant stress, we measured malondialdehyde (MDA) in the kidney and urine and the glutathione redox ratio in kidney tissue. MDA per nephron was increased in the subtotally nephrectomized model and was accompanied by increased absolute and fractional urinary excretion of MDA but not by an increase in kidney MDA per milligram protein. The glutathione redox ratios were similar. Since increased dietary protein intake worsens renal injury, we studied the effects of dietary protein manipulation (30 vs. 6%) on oxygen consumption, MDA levels, and the glutathione redox ratio. The kidneys of subtotally nephrectomized animals maintained on 30% protein diets exhibited increased rates of oxygen consumption. Increased dietary protein intake led to increased MDA per nephron, increased urinary excretion of MDA, and increased MDA per milligram protein in subtotally nephrectomized animals, and markedly increased the glutathione redox ratio. We conclude that, despite increased oxygen consumption, surviving nephrons compared with intact nephrons in rats on standard protein intake demonstrate no evidence of oxidant stress. Increased urinary clearance of MDA may provide a mechanism that prevents the buildup of lipid peroxidation. Subjecting the remnant nephron to increased protein increases oxygen consumption and imposes oxidant stress.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of thyroid hormones on the oxygen consumption of the liver tissue in the squamate reptiles

Stimulated ovulation with resultant multiple corpora lutea (CL) can result in lower progesterone levels than expected from the increased luteal tissue mass. Unilateral ovariectomy (ULO) was used to increase CL number in rats and determine whether this would compromise luteal tissue blood flow, oxygen consumption and progestin secretion. All investigations were performed in vivo, using a venous outflow technique on Day 16 of gestation, when progesterone secretion is maximal. ULO, performed before pregnancy, doubled CL number and total CL mass in the remaining ovary of six treated compared to five control rats. Growth of CL was not affected. The rate of ovarian blood flow (microL min(-1) mg CL(-1)) fell to 47% of control levels in ULO animals and progesterone secretion (microg h(-1) mg CL(-1)) to 68%. Secretion of the minor progestin, 20alpha-hydroxypregn-4-en-one was not affected. Tissue oxygen consumption was maintained despite the reduction in blood flow by an increase in oxygen extraction from arterial blood. These results suggest that overcrowding of CL in ULO-stimulated rat ovaries compromises luteal tissue blood flow and subsequently progesterone secretion.

We report an analysis of the effect of two different times of day (noon and dusk), body weight and sex on the oxygen consumption rate (OCR) of the freshwater crabs Trichodactylus kensleyi (Trichodactylidae), Aegla singularis and A. platensis (Aeglidae) in their natural environment. Both families are sympatric in the studied locations, with a co-occurrence found between T. kensleyi and A. singularis or T. kensleyi and A. platensis. The mean OCR was highest in A. singularis and lowest in A. platensis. The OCR was higher in Aegla species at noon, and Trichodactylus consumed more oxygen at dusk. In aeglids, there was no difference in oxygen consumption between noon and dusk. T. kensleyi exhibited statistically significant differences in the OCR between noon and dusk. The oxygen uptake of all three species analysed was not influenced by the sex of the individual but varied according to the animals’ weight. The families evaluated share some biological and ecological characteristics, such as diet and habitats, but the strategies used in the regulation of gas exchange at different times of the day were different. Environmental factors may be influencing the oxygen consumption of each morphotype differently.

The extent of hypoxic regions in a tumor tissue depends on the arrangement, blood flow rate and blood oxygen content of microvessels, and on the tissue's oxygen consumption rate. Here, the effects of blood flow rate, blood oxygen content and oxygen consumption on hypoxic fraction are simulated theoretically, for a region whose microvascular geometry was derived from observations of a transplanted mammary andenocarcinoma (R3230AC) in a rat dorsal skin flap preparation. In the control state, arterial PO2 is 100 mmHg, consumption rate is 2.4 cm3 O2/100 g/min, and hypoxic fraction (tissue with PO2 < 3 mmHg) is 30%. Hypoxia is abolished by a reduction in consumption rate of at least 30%, relative to control, or an increase in flow rate by a factor of 4 or more, or an increase in arterial PO2 by a factor of 11 or more. These results suggest that reducing oxygen consumption rate may be more effective than elevating blood flow or oxygen content as a method to reduce tumor hypoxia.

U tNDER ordinary conditions the oxygen consumption may be taken as a measure of the energy turnover of the embryo. On this basis then two dwarf embryos should show a greater total oxygen consumption than one normal embryo when corresponding stages of development are attained. This increase could result from an increased rate of oxygen consumption while the rate of development remained the same, or it could result from a slower rate of development on the part of the dwarfs while the rate of oxygen consumption remained the same as in the normal embryos. The experiments show that the latter is the case. The dwarfs in these experiments were produced by isolating the blastomeres in the two-cell stage of the sea-urchin egg. By suitable technique sufficient quantities of embryos could be obtained for the respiration measurements. As the datainTable 2 show, the rate of oxygen consumption (per mg. Kjeldahl nitrogen) of the dwarf embryos does not differ significantly from that of the normal embryos. This means that in the same time interval two dwarf embryos consume as much oxygen as one normal embryo. The dwarf embryos develop, however, at a much slower rate than the normal. They begin gastrulation at the normal time (at about 19 hours in Eclinus at room temperature) but complete it and pass through later stages at a much slower rate than the controls. The delay in rate of development amounts to about 30 to 40 per cent. For example, in one experiment it took about five and a half hours for the dwarfs to complete gastulation as compared with four hours in the controls. Since oxygen consumption goes on at the normal rate in the dwarf embryos, and the rate of development is slower, then, to reach the same stage of development, two dwarfs will consume more oxygen than one normal embryo. The increased oxygen consumption would amount to about 35 per cent if we take the beginning of gastrulation as a starting point. The expected value for the increased energy requirement (see above) is 41 per cent on the basis of a linear relation between force and wall thickness. Too much significance need not be attached to the actual figures at present.