Effect of N-methyl-D-aspartate receptor blockade on the control of cerebral O2 supply/consumption balance during hypoxia in newborn pigs

Using dizocilpine (MK-801), we tested the hypothesis that N-methyl-D-aspartate (NMDA) receptors are important controllers of cerebral O2 supply/consumption balance in newborn piglets both during normoxia and hypoxia. Twenty-five 2 to 7-day-old piglets were anesthetized and divided into four groups: (1) Normoxia (n = 6), (2) Normoxia + MK-801 (n = 6), (3) Hypoxia (n = 6), and (4) Hypoxia + MK-801 (n = 7). Regional cerebral blood flow (rCBF) in ml/min/100 g was measured using 14C-iodoantipyrine, and we determined arterial and venous O2 saturations by microspectrophotometry, calculating cerebral O2 consumption (VO2) in ml O2/min/100 g in the cortex, hypothalamus and pons. MK-801 did not significantly affect regional VO2 or rCBF in normoxic piglets. Hypoxia resulted in an increase in local rCBF compared to controls: from 41 +/- 6 to 103 +/- 18 in the cortex; 34 +/- 7 to 101 +/- 20 in the hypothalamus; and 45 +/- 10 to 95 +/- 11 in the pons. Pretreatment with MK-801 abolished this hypoxic flow effect in the cortex (51 +/- 2) and hypothalamus (49 +/- 5), but not in the pons (91 +/- 17). Similar results were observed for VO2 with control values of 1.9 +/- 0.3, 1.6 +/- 0.2 and 2.1 +/- 0.3 for the cortex, hypothalamus and pons respectively. Hypoxia resulted in an increase in the VO2 to 3.9 +/- 0.4 (cortex), 3.8 +/- 0.6 (hypothalamus) and 3.9 +/- 0.8 (pons). Pretreatment with MK-801 prior to hypoxia abolished these effects in the cortex (2.1 +/- 0.2) and hypothalamus (2.1 +/- 0.2), but not in the pons (2.9 +/- 0.2). These findings suggest that NMDA receptors may play a role in the control of cerebral metabolism during hypoxia in this immature porcine model.     

Oxygen consumption for constant work is minimal at lowest working contractility in normal dog hearts

We tested whether minimal myocardial oxygen consumption (MVO2) for a given external work would exist in the middle of a normal contractility range as previously predicted theoretically. The left ventricle of the excised cross-circulated dog heart preparation was connected to a volume servo pump. Myocardial contractility in terms of ventricular end-systolic elastance (Emax) was gradually increased from control 8.9 +/- 3.4 (mean +/- SD) to 30.0 mmHg/(ml/100 g) by epinephrine and decreased to 1.8 mmHg/(ml/100 g) by propranolol while heart rate, end-systolic pressure and stroke work were kept constant. MVO2 was determined as the product of total coronary flow and coronary arteriovenous oxygen content difference in each contractile state. We plotted MVO2 values against E(max) values in each heart. The MVO2-E(max) relation for a constant cardiac work showed that MVO2 was minimal at the low end of the covered E(max) range. We conclude that minimal MVO2 for a given cardiac work is generally obtained at the lowest working contractility in normal dog hearts. This conclusion might pose some problems in the previous theoretical prediction as to the contractility that achieves the minimal MVO2 in a given external work.     

安钢90m2烧结机降低工序能耗的实践

从生产工艺和设备改造等方面阐述了降低工序能耗的途径和措施。     

Botulinum toxin in upper limb spasticity: study of reciprocal inhibition between forearm muscles

To establish whether botulinum A toxin (BTX-A) acts on modifying reciprocal inhibition between forearm muscles in spasticity, 20 patients with post-stroke upper limb spasticity lasting for more than 1 year were studied. Clinical examination, physiotherapeutic evaluation, standardized video-tape assessment and electrophysiological testing (flexor carpi radialis muscle M and H responses with study of reciprocal inhibition) were performed at baseline and 2 weeks, 1, 2, 3, 4 months after BTX-A treatment. BTX-A induced a significant decrease of tone and an improvement of motility and functional status, with a significant decrease of the M wave and the H reflex. The reduction in both inhibitory phases of reciprocal inhibition did not change after BTX-A treatment differently from that reported in upper limb dystonia. These findings indicate that the efficacy of BTX-A in upper limb spasticity is mainly due to peripheral effects.     

Effect of NaHCO3 on lactate kinetics in forearm muscles during leg exercise in man

We investigated NaHCO3 infusion effects on plasma lactate removal by forearm muscles and performance during intensive leg exercise. Seven subjects performed the force-velocity (FV) test with placebo and NaHCO3 (2 mEq.min-1) with a double-blind crossover protocol. Blood samples for arterial ([LA]A) and venous ([LA]V) lactate determinations were taken 1) at rest before infusion, and 2, 6, 10, 14, 18, and 22 min following its start; and 2) at the end of each exercise bout. The arteriovenous difference ([LA]A-V) was determined for each sampling. NaHCO3 significantly increased arterial bicarbonate concentration and pH during rest (P < 0.001; P < 0.001) and the FV test (P < 0.001; P < 0.05). During the test, [LA]A and [LA]V were significantly higher with NaHCO3 (P < 0.05, P < 0.001). At test onset, [LA]A-V became positive and increased until the braking force of 6 kg, with NaHCO3 and placebo, with values significantly lower for NaHCO3 (P < 0.001). Peak anaerobic power (Wanae, peak) and the corresponding braking force (Fmax) were also determined. Fmax was significantly increased with NaHCO3 (P < 0.001). In conclusion, the increasing rise in [LA]A and [LA]V induced by NaHCO3 may be partly explained by a decreased rate of lactate uptake by forearm skeletal muscles. NaHCO3 did not improve Wanae, peak, but improved Fmax, thus increasing FV duration.     

铝冶炼供电系统节能降耗的措施

湖北丹江哆嗦业公司三期技改工程供电整流系统采用了较多的新技术，新设备，新工艺，在该前提下，对运行参数进行详细研究，达到合理利用电能的目的，同时采用全面质量管理工作的方法，成功地改善了电流的稳定性，减少了设备停运率，为安全生产提供了有力的保障，达到了节能降耗的目的，取得了一定的经济效益。     

Activity of spinal interneurons and their effects on forearm muscles during voluntary wrist movements in the monkey

We studied the activity of 577 neurons in the C6-T1 spinal cord of three awake macaque monkeys while they generated visually guided, isometric flexion/extension torques about the wrist. Spike-triggered averaging of electromyographic activity (EMG) identified the units' correlational linkages with 相似文献   

Dependence of muscle VO2 on blood flow dynamics at onset of forearm exercise

The hypothesis that the rate of increase in muscle O2 uptake (VO2mus) at the onset of exercise is influenced by muscle blood flow was tested during forearm exercise with the arm either above or below heart level to modify perfusion pressure. Ten young men exercised at a power of approximately 2.2 W, and five of these subjects also worked at 1.4 W. Blood flow to the forearm was calculated from the product of blood velocity and cross-sectional area obtained with Doppler techniques. Venous blood was sampled from a deep forearm vein to determine O2 extraction. The rate of increase in VO2mus and blood flow was assessed from the mean response time (MRT), which is the time to achieve approximately 63% increase from baseline to steady state. In the arm below heart position during the 2.2-W exercise, blood flow and VO2mus both increased, with a MRT of approximately 30 s. With the arm above the heart at this power, the MRTs for blood flow [79.8 +/- 15.7 (SE)s] and VO2mus (50.2 +/- 4.0 s) were both significantly slower. Consistent with these findings were the greater increases in venous plasma lactate concentration over resting valued in the above heart position (2.8 +/- 0.4 mmol/l) than in the below heart position (0.9 +/- mmol/l). At the lower power, both blood flow and VO2mus also increased more rapidly with the arm below compared with above the heart. These data support the hypothesis that changes in blood flow at the onset of exercise have a direct effect on oxidative metabolism through alterations in O2 transport.     

Spinel-corundum equilibria and activities in the system MgO-Al2O3-Cr2O3 at 1473 K

The tie-lines delineating intercrystalline ion-exchange equilibria between MgAl₂O₄-MgCr₂O₄ spinel solid solution and Al₂O₃-Cr₂O₃ solid solution with corundum structure have been determined at 1473 K by electron microprobe and X-ray diffraction (XRD) analysis of equilibrated phases. The tie-lines are skewed to the solid solution 0.7MgAl₂O₄-0.3MgCr₂O₄. The lattice parameters and molar volumes of both the solid solution series exhibit positive deviations from Vegard’s and Retger’s laws, respectively. Activities in the spinel solid solution are derived from the tie-line information and thermodynamic data on Al₂O₃-Cr₂O₃ solid solution available in the literature. Activities of Mg_0.5CrO₂ and Mg_0.5AlO₂ in the spinel solid solution exhibit strong positive deviations from Raoult’s law over most of the composition range. However, activity of Mg_0.5CrO₂ exhibits mild negative deviation for compositions rich in Mg_0.5CrO₂. The activity-composition relationship in the spinel solid solution is analyzed in terms of the intracrystalline exchange of cations between the tetrahedral and octahedral sites of the spinel structure. The intracrystalline ion exchange is governed by site preference energies of the cations. The difference between the Gibbs energy of mixing calculated using the cation mixing model and the experimental data is taken as a measure of the strain contribution arising from the difference in the radii of Al³⁺ and Cr³⁺ ions. The large positive strain enthalpy suggests the onset of immiscibility in the spinel solid solution at low temperatures. The computed critical temperature and composition for phase separation are 802 (±20) K and =0.46 (±0.02), respectively.     

Controlled undercooling of liquid iron in contact with Al2O3 substrates under varying oxygen partial pressures

The objective of this study was to determine the conditions under which alumina can act as a heterogeneous nucleant to initiate the solidification of undercooled liquid iron. The undercooling of a pure iron sessile droplet in contact with Al₂O₃ substrates was measured under controlled oxygen partial pressures by observing droplet recalescence. The experimental results indicated that the undercooling of liquid iron, in contact with an Al₂O₃ substrate, did not have a unique value, varied from 0 °C to 290 °C, and was significantly affected by the oxygen content of the gas phase and the degree of interaction between the oxide and the metal. Deep undercoolings are possible at low oxygen potentials, provided the oxygen potential is such that substantial substrate decomposition does not occur. The measured undercooling was a strong function of gas phase oxygen content and a maximum in undercooling of 290 °C was measured at PO₂=10⁻¹⁹ atm. The variation in undercooling was related to the wetting of the substrate by the liquid metal, where the deepest undercoolings occurred when the highest contact angle between the substrate and the liquid droplet was achieved.     

Absence of supply dependence of oxygen consumption in patients with septic shock

We tested whether oxygen consumption (VO2) was dependent on oxygen delivery (QO2) in 10 patients with septic shock when QO2 was changed by the use of the inotropic agent, dobutamine. The mean acute physiology and chronic health evaluation (APACHE) II score of the patients was 27.3 +/- 8.1 with a mean blood pressure on entry of 66.8 +/- 12.4 mm Hg, and all had been volume resuscitated to a pulmonary artery occlusion pressure of greater than 10 mm Hg. We measured VO2 by analysis of respiratory gases (VO2G) while calculating VO2 by the Fick equation (VO2F) at three different O2 deliveries. When the dobutamine infusion rate was increased from 2.5 +/- 4.0 to 12.3 +/- 6.0 micrograms/kg/min, thermodilution cardiac output increased from 7.7 +/- 2.6 to 10.1 +/- 2.7 L/min (P < .01). Accordingly, dobutamine increased QO2 from 13.5 +/- 3.8 to 18.2 +/- 4.3 mL/min per kg (increase of 36.4% +/- 19.7%; P < .01), but VO2G did not increase (3.2 +/- 0.5 to 3.2 +/- 0.6 mL/min per kg). During these same interventions, the VO2F tended to increase (2.9 +/- 0.7 to 3.4 +/- 0.8 mL/min per kg, P < .06), presumably a spurious correlation because of measurement errors shared by the calculation of VO2F and QO2. Neither lactic acidosis nor acute respiratory distress syndrome (ARDS) conferred supply dependence of VO2G, but the presence of ARDS was predictive of death in this cohort. It is concluded that VO2 is independent of QO2 in patients with septic shock and lactic acidosis. These data confirm that maximizing QO2 beyond values achieved by initial fluid and vasoactive drug resuscitation of septic shock does not improve tissue oxygenation as determined by respiratory gas measurement of VO2.     

Fluorescent estimation of H2O2-induced changes in cell viability and cellular nonprotein thiol level of dissociated rat thymocytes

Vector control and the detection (followed by treatment) of infected individual are the two methods currently available for the control of sleeping sickness. The basic reproduction rate of a compartmental model (Kermack and McKendrick) is used to analyze and compare the two strategies. The model shows that when there is a long first stage characteristic of an endemic situation, the detection of sick individuals is more efficient than vector control. This higher efficiency of detection decreases in a epidemic situation. In this case vector control in the form of a decrease in vector density and/or an increase in vector mortality is relatively more efficient than detection. Because it is squared in the basic reproduction rate, the probability of a tsetse blood meal on humans is an important and sensitive parameter in the study of control strategies. This sensitivity has been observed previously and empirically by field workers. When the probability of a tsetse blood meal on humans is above a certain value, vector control becomes warranted or even necessary.     

Magnitude estimation of perceived odor intensity: Empirical and theoretical properties.

Four subjects judged the odor intensities of 7 pyridine concentrations and a blank. Computer simulations of a judgment model were compared with the empirical data. The model generates data patterns that closely mimic empirical findings. The following patterns were confirmed: (a) A power function relates magnitude estimates and concentration with an exponent in the range of 0.7 to 1.0. (b) The exponent fluctuates so that the level constant is negatively correlated with the exponent. (c) The standard deviation of the responses is a negatively accelerated function of the mean. (d) The skewness of the responses is relatively high for low concentrations and declines toward zero with increasing concentration. (e) The correlation between responses to successive stimuli is highest when successive concentrations are similar. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Changes in spleen lymphoid tissue and mass under conditions of water consumption with varying microorganism count]

Centimeter microwave therapy (CMWT) was employed in the multimodality treatment of 50 patients with destructive pulmonary tuberculosis. Its results were compared with a matched control group comprising 43 patients. CMWT increased the rate of decay cavity closure, improved bronchial patency and prevented its deterioration. This was followed by improved lipid peroxidation, antioxidative activity, and an immunological responsiveness of the body.     

Relationship between decreased function and O2 consumption caused by cyclic GMP in cardiac myocytes and L-type calcium channels

We tested the hypothesis that part of the decreased function and metabolism caused by cyclic guanosine monophosphate (GMP) in beating cardiac myocytes is related to inhibition of L-type calcium channels. The steady state oxygen consumption (VO2) of a suspension of ventricular myocytes isolated from hearts of New Zealand white rabbits was measured using oxygen electrodes. Cellular cyclic GMP levels were determined by radioimmunoassay. Cell shortening was measured with a video edge detector. The VO2 was obtained after: (1) adding sodium nitroprusside (NP 10(-8),(-6),(-4) M), (2) pretreatment by BAY K8644 10(-5) M (BAY, L-type calcium channel activator), nifedipine 10(-4) M (NF, L-type calcium channel blocker) or forskolin 10(-7) M (FK, adenylate cyclase activator), then adding NP 10(-8),(-6),(-4) M, (3) pretreatment with both FK 10(-7) M and NF 10(-4) M and subsequently adding NP 10(-8),(-6),(-4) M. NP 10(-4) M decreased VO2 from 707 +/- 34 to 410 +/- 13 (nl O2/min per 10(5) myocytes), decreased the percentage of shortening (Pcs) from 5.7 +/- 0.6 to 3.7 +/- 0.5 and the rate of shortening (Rs) from 65.5 +/- 4.5 (microns/s) to 46.2 +/- 5.5. NP 10(-4) M also increased cyclic GMP from 264 +/- 70 (fmol/10(5) myocytes) to 760 +/- 283. Both BAY and FK increased VO2, Pcs and Rs without changing cyclic GMP. NF decreased Pcs, Rs and VO2. Similar metabolic and functional effects of NP were observed with pretreatment with these agents separately, compared to NP alone, and the elevation of cyclic GMP level was not different from the control group. With FK alone, NP 10(-4) M decreased VO2 by 51%, Pcs by 44% and Rs by 39%. In the presence of both FK and NF, the negative effects of NP were diminished significantly. NP 10(-4) M decreased VO2 by 37%, Pcs by 25% and Rs 20%. Thus, in beating cardiac myocytes, the negative metabolic and functional effects of cyclic GMP were related to inhibition on L-type calcium channels only when adenylate cyclase was stimulated.     

Thermodynamic analysis of aluminate formation at Fe/Al2O3 and Cu/Al2O3 interfaces

Subsolidus ternary phase relationships in the systems FeAlO and CuAlO are reviewed in order to provide a basis for thermodynamic analysis of aluminate formation at Fe/α-Al₂O₃ and Cu/α-Al₂O₃ interfaces. Expressions for the critical oxygen activity in the Fe-rich and Cu-rich solid solutions necessary to stabilize the equilibrium aluminate phases (FeAl₂O₄ and CuAlO₂, respectively) in the presence of α-Al₂O₃ are derived using data available in the literature. As in previous work in the NiαAl₂O₃ system, aluminate formation by solid state reaction of Fe and Cu with α-Al₂O₃ was calculated to require a threshold concentration of oxygen in the metal, which is of the order of 1/5 the solubility limit. The sults are presented in stability diagrams and compared with previous results on the Ni/α-Al₂O₃ system in terms of the free energies of formation of the aluminates and the relative free energes of solution of oxygen in the metals. The results are also compared with available experimental observations on Fe/α-Al₂O₃ and Cu/α-Al₂O₃ interfaces.