Author Keywords: Neuronal thermosensitivity; hypothalamic thermosensory function; Temperature and synaptic transmission; avian thermoregulation; mammalian thermoregulation 相似文献
1. 1.|In 15 conscious Pekin ducks, 40 “warm sensitive” hypothalamic neurons were identified according to their discharge rates at 40°C Thy (F40), local temperature coefficients (Δ/ΔT) and Q10.
2. 2.|Q10 and either F40 or ΔF/ΔT were little or not related.
3. 3.|A positive correlation between F40 and ΔF/ΔT was observed which was particularly close (r = 0.94 and 0.96) when the neurons were classified according to their Q10 of <2 and >2.
4. 4.|The results suggest that neurons with positive temperature coefficients in the duck's hypothalamus mostly exhibit linear to exponential temperature-discharge relationships.
5. 5.|This is an contrast to observations on mammalian hypothalamic thermosensitive neurons and may relate to the absence of the thermosensory function in the duck's rostral brainstem.
1. 1. By varying the redox potential of a chloroplast suspension, we obtained new evidence for an equilibrium between states S0 and S1 in the model of Kok, B., Forbush, B. and McGloin, N. (1970, Photochem. Photobiol. 11, 457–475). The mid-point potential of the S0 to S1 couple is close to that for the pool of the electron acceptor of System II, A to A−.
2. 2. The limiting steps between two consecutive photoreactions of System II in Chlorella and spinach chloroplasts, have been studied.
2.1. (a) The limiting step from S1 to S2 (noted γ1 (Δt)) is not exponential. Its temperature coefficient becomes greater as the reaction proceeds. The shape of the kinetics is an intrinsic property of each center. Chloroplasts fixed with 2% glutaraldehyde, show simple first order kinetics.
2.2. (b) The limiting step from S0 to S1 (γ0 (Δt)) exhibits the same characteristics as γ1 (Δt)).
2.3. (c) The limiting step from S2 to S3 (γ2 (Δt)) shows sigmoidal kinetics; two reactions are involved. One of the reactions exhibits the same properties as γ0 (Δt) and γ1 (Δt).
2.4. (d) The limiting step from S3 to S0 (γ3 (Δt)) is a first order reaction, two times slower than the other transitions. This reaction is interpretated in terms of oxygen release.
3. 3. We also studied the limiting steps in the presence of low concentrations (50 μM) of hydroxylamine. The results favor the binding of two molecules of hydroxylamine to every photochemical center.
Abbreviations: DCIP, dichlorophenolindophenol 相似文献
1. 1.Hypothalamic temperature (Thy), nonevaporative heat loss (R + C + K), evaporative heat loss (E), thermal conductance (k), metabolic heat production (M) and heat storage (S) of rats were simultaneously measured by direct and indirect calorimetry during internal heat loading (2 W per rat) with an intraperitoneal electric heater.
2. 2.The tests were made twice a day; once during the day (1000–1200 h) and once at night (2200–2400 h) at an ambient temperature of 24°C.
3. 3.The resting values of Thy, colonic temperature, (R + C + K), E, M and heart rate, and the Thy threshold for tail skin vasodilation (Tth) during internal heat load were significantly higher at night than during the day.
4. 4.The slopes showing the relationshiop between (R + C + K), k or M and Thy were significantly steeper during the day than at night after Thy exceeded Tth.
5. 5.The slopes showing the relationship between E or S and Thy were not different during the day and at night.
6. 6.These results indicate that the responses of nonevaporative heat loss and heat production to internal heat load vary with the time of day in rats.
Author Keywords: Circadian rhythm; direct calorimetry; heat loss; heat storage; heat load 相似文献
1. 1. Aerobic oxidation of ubiquinol and b cytochromes is accompanied in EDTA particles, obtained by sonication of beef-heart mitochondria, by synchronous proton uptake.
2. 2. The rapid proton uptake associated to oxidation of ubiquinol and b cytochromes is greatly stimulated by valinomycin plus K+, but is unaffected by carbonyl cyanide p-trifluoromethoxyphenylhydrazone.
3. 3. 4 gion H+ are taken up per mol ubiquinol oxidized by oxygen. This H+/2e− ratio, measured in the rapid anaerobic-aerobic transition of the particles is unaffected by carbonyl cyanide p-trifluoromethoxyphenylhydrazone.
4. 4. In intact mitochondria aerobic oxidation of oxygen-terminal electron carriers is accompanied by antimycin-insensitive synchronous proton release, oxidation of ubiquinol and reduction of b cytochromes. The amount of protons released is in excess with respect to the amount of ubiquinol oxidized.
5. 5. It is concluded that electron flow along complex III, from ubiquinol to cytochrome c, is directly coupled to vectorial proton translocation. The present data suggest that there exist(s) between ubiquinol and cytochrome c one (or two) respiratory carrier(s), whose oxido-reduction is directly linked to effective transmembrane proton translocation.
Abbreviations: FCCP; carbonyl cyanide p-trifluoromethoxyphenylhydrazone 相似文献
1. 1. Three b-type cytochromes (b557.5, b560, and b562.5), plus a chromophore with an absorption peak at 558 nm at 77 °K, have been found to be associated with the electron transport system of bovine heart mitochondria. The reduced minus oxidized spectra of these components at 77 °K, as well as that of cytochrome c1, have been recorded with a wavelength accuracy of ± 0.1 nm and presented to the nearest 0.5 nm. All the major and β absorption peaks of cytochromes b557.5, b560, b562.5, c1 and c have been shown by fourth derivative analysis to be present in the dithionite-reduced minus oxidized spectra of mitochondria and submitochondrial particles.
2. 2. The distribution of the above components has been studied in the four electron transfer complexes of the respiratory chain. Cytochromes b560, b562.5 and c1, as well as chromophore-558, were found to fractionate into Complex III (reduced ubiquinone-cytochrome c reductase), whereas cytochrome b557.5 was found in Complex II (succinate-ubiquinone reductase).
3. 3. Cytochrome b560 was readily reduced by NADH or succinate, but b562.5 was not reduced by substrates unless the preparation was treated with antimycin A. In antimycin-treated preparations pre-reduction of c1 with ascorbate inhibited the subsequent reduction of b562.5 by substrates. These results indicate that b560 and b562.5 correspond, respectively, to bK and bT previously described by Chance et al.14 (1970, Proc. Natl. Acad. Sci. U.S. 66, 1175–1182).
4. 4. Similar to b560, chromophore-558 can be reduced by substrates in the absence or presence of antimycin A. However, in antimycin-treated preparations, pre-reduction of c1 inhibits its subsequent reduction by substrates. This property is similar to that of b562.5.
5. 5. Cytochrome b557.5, which occurs in Complex II, appears to have a low mid-point potential. It can be reduced with dithionite and oxidized by fumarate or ubiquinone. CO treatment of dithionite-reduced b557.5 neither modified the spectrum of this cytochrome nor diminished the extent of b557.5 reoxidation by fumarate.
6. 6. Antimycin A treatment does not appear to alter the spectra of the above cytochromes. However, small amounts (< 4%) of ethanol or methanol, which are usually added to particles as solvent for antimycin A, have a pronounced effect on the peaks of cytochrome c1. The spectrum of cytochrome c1 at 77 °K as modified by 3% (v/v) ethanol is shown.
Abbreviations: ETP, non-phosphorylating electron transport particle preparation; ETPH, phosphorylating electron transport particle preparation; TMPD, tetramethylphenylenediamine; Complexes I, preparations of NADH-ubiquinone reductase; Complexes II, succinate-ubiquinone reductase; Complexes III, reduced ubiquinone-cytochrome c reductase; Complexes I-III, NADH-cytochrome c reductase; Complexes II-III, succinate-cytochrome c reductase 相似文献
1. 1.|The jumping behaviour of the Mexican jumping bean (Laspeyresia solitans) is stereotyped and predictable and has the characteristics of behaviour which is under the control of a central programme.
2. 2.|Temperatures above and below about 25°C decrease the length of time that movements occur. The movements stop relatively abruptly and not gradually. The duration of movements is apparently controlled by an internal timer whose duration of operation is influenced by temperature.
3. 3.|The frequency of movements show instantaneous temperature compensation from about 21 to 45°C (Q10 = 1.23), whereas between 15 and 21°C there is a large temperature dependence (Q10 = 21.9).
Author Keywords: Behaviour; insect; Laspeyresia solitans Q10 相似文献
1. 1. The phosphorylation potential, ΔGP = ΔG0′ + 1.36 log ([ATP]/[ADP][Pi]), where ΔGO′ is the standard free energy of hydrolysis of ATP at a given pH, and [ATP], [ADP] and [Pi] refer to concentrations in the suspending medium, has been determined in rat-liver mitochondria under various conditions.
2. 2. The ATP/ADP ratio is relatively constant, over a 10-fold range of phosphate concentration. Thus, the phosphate potential is higher at low phosphate concentration. State-4 rat-liver mitochondria in the presence of succinate, oxygen and low concentrations of phosphate in State 4 maintain a phosphorylation potential of 16.1 kcal (67.3 kJ) per mole ATP.
3. 3. High concentrations of ATP inhibit ADP uptake, and it is suggested that this is the reason for the independence of the ATP/ADP ratio on the phosphate concentration. A steady-state ratio is set up dependent upon two processes that are relatively slow compared with State-3 respiration, namely ADP transport and ATP hydrolysis.
4. 4. The phosphorylation potential calculated from the concentrations of total ADP, ATP and Pi within State-4 mitochondria is 4.5 kcal/mole less than that in the suspending medium.
5. 5. It was shown experimentally that the phosphorylation potential cannot be calculated from the ΔG of the redox couple, the respiratory-control ratio and the P:O ratio, as has been suggested in the literature.
6. 6. The measured phosphorylation potential is 83% of that calculated from the span succinate to oxygen, assuming thermodynamic equilibrium, and 95% of that calculated from the span NADH to oxygen.
7. 7. Based on the measurements of the phosphorylation potential and of the redox potentials and redox states of redox components in mitochondria, ubiquinone and cytochrome b are found at their expected position at the junction of the phosphorylations at Sites 1 and 2. The iron-sulphur centres 2 and 5 and the iron-sulphur centre of succinate dehydrogenase also probably lie at this junction. Cytochrome a3 lies at its expected junction between phosphorylation Sites 2 and 3. A number of electron carriers (cytochromes c, c1, and a, the iron-sulphur centre of Complex III and the EPR-detectable copper), however, lie in the ‘no-man's land’ within Site 2.
8. 8. A phosphorylation potential of 16.1 kcal/mole corresponds to a membrane potential of 350 mV in State 4, on the basis of the chemiosmotic hypothesis.
Abbreviations: CCCP, carbonyl cyanide m-chlorophenylhydrazone 相似文献
1. 1. The inhibition of the ADP-stimulated respiration of potato mitochondria by carboxyatractyloside is relieved by high concentration of ADP or by the uncoupler carbonyl cyanide p-trifluoromethoxyphenylhydrazone (FCCP). Atractyloside is a much less potent inhibitor than carboxyatractyloside. The inhibition of the ADP-stimulated respiration required about 60-times more atractyloside than carboxyatractyloside.
2. 2. [35S]carboxyatractyloside and [3H]bongkrekic acid bind to potato mitochondria with high affinity (Kd = 10 to 20 nM, n = 0.6–0.7 nmol per mg protein). Added ADP competes with carboxyatractyloside for binding; on the contrary ADP increases the amount of bound bongkrekic acid. [3H]atractyloside binds to potato mitochondria with a much lower affinity (Kd = 0.45 μM) than carboxyatractyloside or bongkrekic acid.
3. 3. Bound [3H]atractyloside is displaced by ADP, carboxyatractyloside and bongkrekic acid. The displacement of bound [35S]carboxyatractyloside by bongkrekic acid and of bound [3H]bongkrekic acid by carboxyatractyloside is markedly increased by ADP.
4. 4. Bongkrekic acid competes with [35S]carboxyatractyloside for binding. Addition of a small concentration of ADP considerably enhances the inhibitory effect of bongkrekic acid on [35S]carboxyactratyloside binding.
5. 5. The adenine nucleotide content of potato mitochondria is of the order of 1 nmol per mg protein. ADP transport in potato mitochondria is inhibited by atractyloside 30- to 40-times less efficiently than by carboxyatractyloside.
Abbreviations: FCCP, carbonyl cyanide p-trifluoromethoxyphenylhydrazone 相似文献
1. 1. Preparations were obtained from Azotobacter chroococcum which reduced acetylene to ethylene using physiological electron donors instead of sodium dithionite. These preparations fell into two categories: those which required catalytic amounts of benzyl viologen for acetylene reduction and those that did not.
2. 2. Acetylene reduction without benzyl viologen or sodium dithionite was observed only with particles that sedimented at 40 000 × g after disrupting bacteria in the French press or with preparations obtained by disrupting bacteria protected by a mixture of defatted bovine serum albumin-Ficoll-MgCl2 with liquid N2; supernatant fractions required benzyl viologen for acetylene reduction.
3. 3. Added ATP inhibited acetylene reduction by large particles; ATP and MgCl2 were necessary for maximum acetylene reduction with bovine serum albumin-protected preparations.
4. 4. NADH and carbon substrates acted as electron donors but H2 did not; NAD+ was necessary for maximum acetylene reduction with carbon substrates.
5. 5. Anaerobic conditions were necessary for maximum acetylene reduction in all cases.
Abbreviations: TES; N-tris-[hydroxymethyl]-methyl-2-aminoethane sulfonic acid 相似文献
1. (1) A P-700-chlorophyll a-protein complex, with a ratio of 1 P-700: 38 chlorophyll a: 4 ta-carotene molecules, had similar absorption and fluorescence characteristics to the chlorophyll-protein complex 1 isolated with Triton X-100 from higher plants, green algae and Ecklonia radiata.
2. (2) An orange-brown complex had a chlorophyll a : c2 : fucoxanthin molar ratio of 2 : 1 : 2. This complex had no chlorophyll c1 and contained most of the fucoxanthin present in the chloroplasts. This pigment complex is postulated to be the main light-harvesting complex of brown seaweeds.
3. (3) A green complex had a chlorophyll a : c1 : c2 : violaxanthin molar ratio of 8 : 1 : 1 : 1. This also is a light-harvesting complex.
The absorption and fluorescence spectral characteristics and other physical properties were consistent with the pigments of these three major complexes being bound to protein. Differential extraction of brown algal thylakoids with Triton X-100 showed that a chlorophyll c2-fucoxanthin-protein complex was a minor pigment complex of these thylakoids. 相似文献
1. 1.Single fusimotor fibres were isolated in the ventral roots of lumbosacral segments of urethane-anaesthetized rats, and effects of electrical stimulation of the nucleus raphe magnus (NRM) on their spontaneous activity were investigated. The experiments were carried out in rats whose bilateral preoptic and anterior hypothalamic regions (PO/AH) were electrolytically destroyed to eliminate the influences of these regions to fusimotor activity.
2. 2.Of 44 fusimotor fibres studied, 38 (86%) were found to be affected by NRM stimulation. The effects of NRM stimulation were classified according to their response pattern: primary depression (D-type, n = 24), facilitation followed by depression (F-D-type, n = 5) and primary facilitation (F-type, n = 8). The most predominant effect of NRM stimulation upon fusimotor activity was characterized by a strong depression followed by a complete cessation of firing lasting either for a short period or for more than 30 min (D- and F-D-type).
3. 3.In three fusimotor fibres studied in the different preparations, it was observed that a NRM-evoked depression response was blocked by an intraperitoneal administration of a serotonin antagonist, p-chlorophenylalamine (p-CPA) (10 mg/kg).
4. 4.The results indicate that the NRM exerts descending inhibitory or facilitatory influences on fusimotor neurones, and suggest that cold shivering is controlled by modulating fusimotor neurone activity via the serotonergic raphe-signal pathways.
Author Keywords: Fusimotor neurones; nuecleus raphe magnus; rats; serotonin; parachlorophenylalanine; cold shivering; heat production response; thermoregulation; rats 相似文献
1. The possibility that peripheral exogenous pyrogens can activate brainstem nuclei by abdominal viscera afferents was studied using the NADPH-diaphorase method in E. coli lipopolysaccharide treated rats with and without ibuprofen pre-treatment.
2. NADPH-d staining revealed: (i) a significant increase in the number of NADPH-d labeled neurons in the subpostremal area of the nucleus tractus solitarius lipopolysaccharide treated rats compared with control animals (p<0.05), and (ii) an almost similar number of NADPH-d positive neurons in both control and ibuprofen pre-treated rats (p=0.091).
3. These data indicate that peripheral administration of an exogenous pyrogen stimulates the synthesis of nitric oxide in the nucleus tractus solitarius, and are consistent with the hypothesis of a direct neural link between the periphery and the hypothalamus.
Author Keywords: Hyperthermia; Neural control; Nitric oxide; Vagus nerve; Visceral afferent; Nucleus tractus solitarius 相似文献
1. 1. Functional properties of the ATPase complex are investigated in megamitochondria isolated from livers of weanling mice fed a diet containing 2% chloramphenicol, as an inhibitor of mitochondrial protein synthesis.
2. 2. Whereas the specific activity of ATPase remains unchanged in chloramphenicol-induced megamitochondria, about 40% of the enzyme activity is resistant to inhibition by oligomycin, triethyltin or venturicidin. It is concluded that the ATPase complex lacks one or more components whose synthesis or accumulation is dependent on mitochondrial translation. The inhibitor-resistant ATPase portion appears tightly bound to the mitochondrial membrane.
3. 3. Respiratory chain phosphorylation is tightly coupled in isolated megamitochondria. ATP synthesis and ATP-Pi exchange are diminished by 40%, as compared to control mitochondria, but both processes are sensitive to oligomycin, triethyltin or venturicidin.
4. 4. The decrease in ATP synthesis and ATP-Pi exchange in megamitochondria correlates quite well with the emergence of inhibitor-resistant ATPase.
5. 5. The following electron transport activities in the megamitochondria are reduced: NADH-cytochrome c reductase, by 60%, cytochrome oxidase, by 80%; the amount of antimycin required to gain complete inhibition of the bc1-segment is diminished by more than 50%. On the other hand succinate dehydrogenase activity is increased by 50%.
6. 6. Chloramphenicol-induced megamitochondria appear to be a useful system for studying the role of mitochondrial translation in the assembly of mammalian mitochondria.
Abbreviations: FCCP, carbonyl cyanide p-trifluoro methoxyphenylhydrazone; duroquinone, 2, 3, 5, 6-tetramethyl-1,4-benzoquinone; HEPES, N-2-hydroxyethylpiperazine-N1-2-ethanesulphonic acid 相似文献
1. 1.|H2O content and local-tissue thermal conductivity were measured in cortex and medulla of 7 freshly-excised rabbit kidneys.
2. 2.|Tissue H2O content and thermal conductivity k (83.4% and 0.516 W m−t K−1, respectively) in the medulla were significantly higher than those (77.7% and 0.475 W m−1 K−1, respectively) measured in the cortex.
3. 3.|Correlations between the measured parameters are made, and the variability of previously-reported measurements of kidney-tissue thermal conductivity is discussed.
Author Keywords: Thermal conductivity; bioheat transfer; kidney, in vitro; tissue H2O content; rabbit 相似文献
1. 1. The histamine H2-antagonist, 4-methyl-histamine causes a fall in body temperature when injected into the third ventricle of the rat.
2. 2. The hypothermia is prevented by prior intraventricular injection of an H2-antagonist, metiamide, but not by an H1-antagonist, pyrilamine.
3. 3. The fall in temperature is accompanied by increased cutaneous heat loss.
4. 4. These data support the concept that there are H2-receptors in the central thermoregulatory pathways of the rat.
Author Keywords: Temperature regulation; metiamide; intraventricular injection; histamine; pyrilamine; neuro-transmission; H2-receptor; 4-methyl-histamine 相似文献
1. 1.|Alterations in the fatty acid composition of microsomes were most marked in the exponential phase of both 39.5- or 15°C- grown Tetrahymena pyriformis NT-1.
2. 2.|Activities of palmitoyl-CoA and stearoyl-CoA desaturases were lower in 15°C cells than in 39.5°C cells, while the activity of oleoyl-CoA desaturase was higher in 15°C cells.
3. 3.|Activities of the terminal component of the desaturation system as well as all three desaturases (palmitoyl-CoA, stearoyl-CoA, oleoyl-CoA) were higher in the exponential phase than in the stationary phase for cells grown at both temperatures.
4. 4.|NAD(P)H-cytochrome c reductase activity and cytochrome b5 content were reduced whereas NADH-ferricyanide reductase activity was increased in the stationary phase at both 39.5 and 15°C.
Author Keywords: Cyanide sensitive factor (CSF); cell growth in different temperatures; Δ9- and Δ12-desaturases; microsomal electron transport; temperature adaptation; Tetrahymena; protozoa 相似文献
1. 1. Seven thermal conditions were imposed on male sitting subjects (slightly clothed: 0.6 clo).
2. 2. A thermal mannikin was also used to determine the exact operative temperature, T0.
3. 3. Conditions were: uniform (UN: all parameters at 24.5°C, air velocity at 0.15 ms−1), heated ceiling (HC at 45°C), heated floor (HF at 34°C), cold floor (CF at 14°C), two conditions of one cold wall at 6°C (CW1 and CW2 respectively with and without air temperature compensation) and increased air velocity (AV at 0.4 ms−1).
4. 4. Local skin temperatures and answers to questionnaires were obtained.
5. 5. Skin temperature variations were affected by conditions and slight T0 changes.
6. 6. Comfort judgments were fairly well related to T0, especially when expressed as differences between actual non-uniform environment and the uniform one.
7. 7. It is concluded that, in case of non-uniform environments close to thermoneutral zone, thermal comfort or discomfort reflects the climate alterations better than the thermal sensation does.
Author Keywords: Skin temperature; thermal sensation; comfort; climate heterogeneity 相似文献
1. 1. Cyanide inhibits the catalytic activity of cytochrome aa3 in both polarographic and spectrophotometric assay systems with an apparent velocity constant of 4·103 M−1·s−1 and a Ki that varies from 0.1 to 1.0 μM at 22 °C, pH 7·3.
2. 2. When cyanide is added to the ascorbate-cytochrome c-cytochromeaa3−O2 system a biphasic reduction of cytochrome c occurs corresponding to an initial Ki of 0.8 μM and a final Ki of about 0.1 μM for the cytochrome aa3−cyanide reaction.
3. 3. The inhibited species (a2+a33+HCN) is formed when a2+a33+ reacts with HCN, when a2+a32+HCN reacts with oxygen, or when a3+a33+HCN (cyano-cytochrome aa3) is reduced. Cyanide dissociates from a2+a33+HCN at a rate of 2·10−3 s−1 at 22 °C, pH 7.3.
4. 4. The results are interpreted in terms of a scheme in which one mole of cyanide binds more tightly and more rapidly to a2+a33+ than to a3+a33+.
Abbreviations: TMPD, N,N,N′,N′-tetramethyl-p-phenylenediamine 相似文献
1. 1. The particulate fraction contained all of the respiratory carriers demonstrable in whole cells in essentially the same ratios although enriched by 3–5-fold over their concentration in whole cells.
2. 2. Succinate, formate, and NADH but not glutamate, malate, or dihydroorotate were actively oxidized by the particulate fraction.
3. 3. With the exception of the formate oxidase system which appeared to utilize a system bypassing flavoprotein and cytochrome b1, the other enzymatic activities appeared to function primarily through normal electron transport routes.
4. 4. The NADH oxidase and succinoxidase systems were sensitive to inhibition by 2-n-heptyl-4-hydroxyquinoline-N-oxide and antimycin A. The results suggest that these inhibitors function at the level of cytochrome b1.
5. 5. All three activities were sensitive to complete inhibition by CN−.
6. 6. The results obtained from inhibitor studies coupled with the results obtained from examination of steady state, anaerobic, and chemical reduction of the respiratory pigments permitted a scheme for electron flow to be proposed.
Abbreviations: HOQNO; 2-n-heptyl-4-hydroxyquinoline-N-oxide 相似文献