Correlation of rapid changes in the average water diffusion constant and the concentrations of lactate and ATP breakdown products during global ischemia in cat brain

Rapid changes in the average water diffusion constant, Dav = 1/3[Dxx+Dyy+Dzz], and in the concentrations of lactate and purine nucleotides and nucleosides were measured upon global ischemia (cardiac arrest) in cat brain, at a combined time resolution of 36 s (n = 7). At this time resolution, the normalized time curves of 1 - Dav and the increase in ATP breakdown product did not coincide, with the changes in Dav being most rapid. The normalized curves of 1 - Dav and the lactate increase coincided for the first 2-2.5 min after which the change in Dav was more rapid. After this time point, an excellent correlation was found between the drop in Dav and the decrease in energy utilization rate, which was calculated from the measured time curves of lactate formation and ATP breakdown, and from the time curve for phosphocreatine use reported in the literature. These results are in agreement with the expected biphasic changes in ion and water homeostasis during ischemia and with the model of diffusional changes being a consequence of a water shift from interstitial to intracellular space.

Rapid monitoring of changes in water diffusion coefficients during reversible ischemia in cat and rat brain

Changes in the diffusion constant of water during reversible brain ischemia and cardiac arrest were monitored with a 10-s time resolution. Results (five cats, three rats) indicate that these changes are reversible and that the bulk of the changes are not caused by temperature or motion related to brain pulsations and blood flow. The rapid time course of the changes corresponds to the known time course for changes in energy state, signal transduction, and ionic homeostasis.

Effects of intra-arterial epinephrine on energy metabolism in exercising rabbit gastrocnemius muscle, studied by in vivo phosphorus nuclear magnetic resonance

Epinephrine has an inotropic effect on skeletal muscle, especially on glycolytic type 2 fibers. The mechanism of this effect is not completely clear and its association with a change in oxidative metabolism or glycolytic activation was not fully investigated. Epinephrine's effects on muscle bioenergetics were studied by in vivo 31P nuclear magnetic resonance to find if mitochondrial metabolism is changed during the inotropic action and if the known glycolytic activation by epinephrine is operative during muscle twitch. The study was also used as a model for the application of in vivo 31P nuclear magnetic resonance in the evaluation of short-term acting drugs. When injected intra-arterially, epinephrine (1 micrograms/kg) augmented the twitch tension of indirectly stimulated, continuously working rabbit gastrocnemius muscle by 15.4 + 6.5%. This increase in work was associated with reduction of phosphocreatine to inorganic phosphate ratio (PCr/Pi) from 3.4 to 2.1 without change in ATP levels. Intracellular pH was reduced from 6.9 to 6.75, but no accumulation of glycolytic intermediates could be observed. The increase in work was not associated with a rise in ADP. All these changes occurred for a few minutes only. The findings suggest that epinephrine's inotropic action is not mediated by a change in mitochondrial metabolism. Glycolytic activation by epinephrine occurs even during twitch and contributes partly to the energy demands of the augmented force. Epinephrine's inotropic effect is, however, not primarily due to changes in bioenergetic kinetics, but to effects on force generating mechanisms, with secondary reduction in energy state.

The synthesis of pulse sequences yielding arbitrary magnetization vectors

A new procedure and algorithm are presented to allow the synthesis of a pulse sequence which will generate an arbitrary frequency-dependent spin excitation. This procedure is a generalization of our previous paper, where this was done subject to the restriction that the spin excitation was symmetric about zero offset frequency, and pulses were restricted to being about a fixed axis. The required final z-magnetization vector (Mz) is expressed as a function of the off-resonance frequency as an Nth order complex Fourier series. We then form a consistent Fourier series for (Mxy). As many as 2(2)N different pulse sequences may be directly generated all of which produce a different Mxy(f), but the same Mz(f). A pulse sequence is then generated which will yield the desired Mz(f) and Mxy(f). This is done by an analytic inversion of the Bloch equation, not by the classical Fourier approximation. This technique enables us to generate any Mz which is potentially realizable by a pulse sequence.

Immediate Hemodynamic Management Following Subarachnoid Hemorrhage during Embolization of Cerebral Vascular Abnormalities

Three patients are reported who suffered intracranial hemmorrhage during interventionally neuroradiology procedures. All had severe hypertension, cardiac arrhythmias and loss of consciousness. Immediate CT scan showed small amounts of blood in all patients. Arrhythmias were controlled with lidocaine. In two patients, the hypertension was treated only with barbiturates plus fentanyl and in the third with labetol and nitroprusside. In the patient treated with nitroprusside and one patient with barbiturate plus fentanyl a 14-20 min period of hemodynamic stability was followed by vasomotor collapse requiring intravenous vasopressor support. The patient initially treated with nitroprusside suffered irreversibly brain injury whereas the other two improved neurologically following their intracranial bleed. These patients suggest that nitroprusside is detrimental in the acute treatment of malignant hypertension following intracranial hemorrhage.

Treatment of mitochondrial myopathy due to complex III deficiency with vitamins K3 and C: A 31P-NMR follow-up study

A patient with mitochondrial myopathy due to complex III deficiency who was treated with vitamin K3 (menadiol sodium diphosphate, 40 mg daily) and vitamin C showed clinical improvement. A 1-year study with phosphorus 31 nuclear magnetic resonance (31P-NMR) monitoring has shown that clinical and metabolic improvement was maintained by this therapy; increasing the dose of vitamin K3 to 80 mg daily improved the bioenergetic state of the patient's muscles at rest; postexercise recovery was less responsive to the increased dose; and a higher dose of vitamin K3 (80 mg/day) did not produce side effects. The differential therapeutic effects of vitamin K3 at rest and during exercise recovery are probably due to the differential kinetics of each metabolic state. Monitoring muscle bioenergetics with 31P-NMR is valuable in documenting therapeutic improvements in mitochondrial myopathies.

Evaluation of energy metabolism in skeletal muscle of patients with heart failure with gated phosphorus-31 nuclear magnetic resonance

Exertional fatigue is a major limiting symptom in patients with heart failure. To investigate the metabolic basis of this fatigue, we used gated nuclear magnetic resonance spectroscopy to compare inorganic phosphate (Pi), phosphocreatine (PCr) and pH levels, and fatigue (1 to 4+) during mild forearm exercise in eight normal men and nine men with heart failure. Wrist flexion every 5 sec for 7 min was performed at 1, 2, and 3 J (average power output = 0.2, 0.4, and 0.6 W). In both groups linear relationships were noted between power output and Pi/PCr; the slope of this relationship was used to compare PCr depletion patterns. At rest both groups had similar Pi/PCr ratios (normal subjects 0.12 +/- 0.06, those with heart failure 0.15 +/- 0.03) and pH (normal subjects 7.04 +/- 0.13, those with heart failure 7.10 +/- 0.11). In normal subjects exercise resulted in a progressive increase in Pi/PCr (slope = 1.17 +/- 0.20 Pi/PCr units/W), a reduction in pH only at 0.6 W (0.2 W: 7.03 +/- 0.10, 0.4 W: 7.01 +/- 0.10, 0.6 W: 6.88 +/- 16) and moderate fatigue (0.2 W: 0 +/- 0, 0.4 W: 1.3 +/- 0.5, 0.6 W: 1.9 +/- 0.6). In patients with heart failure exercise resulted in significantly greater fatigue at all workloads (0.2 W: 1.0 +/- 0.5, 0.4 W: 1.9 +/- 0.6, 0.6 W: 2.9 +/- 0.5).(ABSTRACT TRUNCATED AT 250 WORDS)

Unique aspects of human newborn cerebral metabolism evaluated with phosphorus nuclear magnetic resonance spectroscopy

In vivo phosphorus nuclear magnetic resonance spectroscopy (31P NMR) was used to evaluate the pattern of phosphate compounds in seven newborn babies (mean gestational age, 32 weeks; birth weight, 1,430 gm; age, 37 days) with a history of perinatal asphyxia. Spectra were collected in a 1.9 Tesla superconductive magnet with surface coil techniques. The spectra had characteristic peaks for phosphorylated monoesters (PME), inorganic phosphate (Pi), phosphodiesters (PD), phosphocreatine (PCr), and ATP. In contrast to cortical spectra from mature animals, these newborn infant 31P NMR spectra were dominated by a large PME peak and had small PCr, Pi, and PD peaks. Intracellular pH, as measured from the chemical shift of the Pi peak relative to the PCr peak, was 7.1 +/- 0.1 (SD). We studied one infant postmortem, and a large PME peak was present in his spectrum. The presence of PME 3 hours after death strongly suggests that it is not a sugar phosphate. In NMR spectroscopy, compounds are identified by their chemical shift relative to a known standard (PCr); the chemical shift of the PME peak was 6.5 ppm, suggesting that it is a mixture of phosphoryl ethanolamine and phosphoryl choline. The PCr/Pi ratio (1.3 +/- 0.7) and the PCr/ATP ratio (0.7 +/- 0.4) were lower in these babies than in mature animals (greater than 2 and greater than 1.4, respectively); the PME/PD ratio (1.2 +/- 0.6), however, was much greater in the infants (mature animals, less than 0.2). These findings suggest that there are unique aspects of human newborn cerebral metabolites and bioenergetic reserve.

31P NMR study of improvement in oxidative phosphorylation by vitamins K3 and C in a patient with a defect in electron transport at complex III in skeletal muscle

The bioenergetic capacity of skeletal muscle in a 17-year-old patient with a severe defect in complex III of the electron transport chain has been examined by 31P NMR measurements of the molar ratio of phosphocreatine to inorganic phosphate (PCr/Pi). Resting ratios were 1.3-2.5, which can be compared with roughly 8.6 for a young, normal female control at rest. Quantitative evaluation of the activity of oxidative metabolism was afforded by the rate of recovery of PCr/Pi from exercise and was found to be 2.5% of normal. After administration of menadione and ascorbate, we found a 21-fold increase of the recovery rate relative to the pretherapy value, to within 56% of the recovery rate of the young female control. Thus, NMR examinations of skeletal muscle at rest and in recovery from activity document marked improvement to specific drug therapy in the electron transport capabilities and the ATP synthesis rate of a patient with a deficiency in a cytochrome b-containing complex III. Improvements in functional ability, although not as dramatic as biochemical changes, are also apparent.

31P NMR studies of control of mitochondrial function in phosphofructokinase-deficient human skeletal muscle

Metabolic control of mitochondrial respiratory activity by Pi and ADP has been evaluated by 31P NMR measurements of the levels of Pi in normal exercising human skeletal tissues in the resting-active-resting transition and, in this contribution, in the phosphofructokinase (PFK)-deficient leg. The latter studies show near constancy of Pi in the recovery from maximal exercise of the leg, with large changes of sugar phosphate (SP) complementary to the changes of phosphocreatine (PCr). The PFK deficiency permits observation of PCr resynthesis in postexercise recovery under conditions of nearly constant Pi and ATP--a phenomenon not evident in normal exercising muscle. The constancy of free Pi is inconsistent with its role in control of mitochondrial activity, leaving ADP as a key metabolic control element. These results help clarify previous controversies on the nature of control of metabolic activity of mitochondria and extend the idea of ADP control of mitochondrial metabolic states in vivo and, in addition, provide an appropriate exercise protocol for the evaluation of a genetic deficiency affecting mitochondrial metabolism.

Mitochondrial regulation of phosphocreatine/inorganic phosphate ratios in exercising human muscle: a gated 31P NMR study

31P NMR is used to determine the relationship between work output in the exercising human forearm and the steady-state capability of oxidative phosphorylation as measured by the phosphocreatine/inorganic phosphate ratio (PCr/Pi). Exercise intensities (one contraction per 5 sec) permitting comfortable continuation of activity for greater than 1 hr produced PCr/Pi of about 1 for a subject of moderate training. Linear relationships between work rate per unit volume of muscle and the 5-min mean PCr/Pi were found for the subject's left and right arms. The protocol affords sensitive criteria of muscle performance in normal subjects and of biochemical or vascular disease in abnormal subjects. The Pi, PCr, and ATP levels found by 31P NMR represent the initial values in the cycle of contraction and relaxation which permit restitution of resting state 4 prior to the next contraction and the continuation of steady-state work performance.

Noninvasive, nondestructive approaches to cell bioenergetics

To demonstrate the feasibility of using NMR spectra of human limbs and larger animals for continuous, noninvasive, nondestructive evaluation of cell bioenergetics, we have constructed a relatively simple and inexpensive 31P NMR apparatus. This apparatus consists of an 18-cm (7-in.) bore superconducting magnet and appropriate transmit-receive components for Fourier transform NMR. The principal signals observed by this instrument in the tissues are due to phosphocreatine and inorganic phosphate. The apparatus can be used to detect tissue normoxia and hypoxia. The large phosphocreatine/phosphate ratio (greater than 10:1), and the low phosphate signal from normoxic tissue (approximately 10% of the phosphocreatine signal from brain and human skeletal tissue) make an increased phosphate peak a very sensitive indicator of tissue hypoxia. Direct experiments on the human forearm and leg and the brains of dog and rabbit suggest the applicability of 31P NMR to humans and animals. This method and optical methods can both be used for quantitative determination of oxygen delivery to tissue, function of mitochondria, and the coupling of bioenergetic processes to functional activity in skeletal tissue and brain.