RESUMEN
Tissue levels of adonosine triphosphate (ATP) have been measured in rat kidneys following periods of warm ischaemia: (1) immediately after the ischaemic period and (2) after the kidney had been reperfused with blood for 10 min. ATP levels at the end of the period of ischaemia are similar for ischaemic periods of 10 to 60 min and give no indication of the kidneys subsequent functional ability. The amount of ATP regenerated in 10 min of reperfusion correlates both with the duration of the period of ischaemia and with the subsequent functional ability of the kidney.
Asunto(s)
Adenosina Trifosfato/biosíntesis , Isquemia/fisiopatología , Riñón/metabolismo , Adenosina Trifosfato/fisiología , Animales , Calor , Riñón/irrigación sanguínea , Riñón/fisiopatología , Masculino , Perfusión , RatasRESUMEN
Bacterial contamination of a renal allograft may cause infection of the transplant with eventual loss of the graft and possibly death of the patient. We report two cases that illustrate these complications and that support the suggestion that culture of the transport medium is a valuable investigation prior to transplantation.
Asunto(s)
Infecciones por Bacteroides , Trasplante de Riñón , Complicaciones Posoperatorias/etiología , Humanos , Masculino , Persona de Mediana Edad , Preservación de Órganos , Trasplante HomólogoRESUMEN
Studies on a 27-year-old man with a 3-year history of exercise-induced muscle pain, passage of red urine and elevated serum creatine kinase are described. Histological examination of a biopsy from quadriceps revealed non-specific myopathic changes with occasional clusters of subsarcolemmal mitochondria. The phosphorylase stain was normal. Phosphorous nuclear magnetic resonance (NMR) spectroscopy studies of gastrocnemius and flexor digitorum superficialis muscles showed no abnormalities at rest. During aerobic exercise there was an abnormally rapid decrease in phosphocreatine concentration but the pH remained within the normal range. There was a build-up of phosphomonoester (probably glucose 6-phosphate), usually indicative of a block in glycolysis. However, a primary defect in the glycolytic pathway seemed unlikely because muscle acidified normally during ischaemic exercise. Recovery from exercise was unusual in that phosphocreatine resynthesis and inorganic phosphate disappearance followed similar prolonged time courses (in control subjects the rate of inorganic phosphate disappearance was about twice as fast as the rate of phosphocreatine resynthesis). The transport of inorganic phosphate into the mitochondria appeared to be delayed. These slow recovery data suggested that oxidative metabolism was impaired. However, with all substrates tested, isolated muscle mitochondria had rates of oxygen uptake that were similar to control values, thereby ruling out a primary defect in mitochondrial respiration. A system involving several mitochondrial transport systems, the malate-aspartate shuttle, was measured. The activity in the patient's isolated mitochondria was less than 20% of the activity present in samples from control subjects. This patient is the only one so far reported with a defect involving the malate-aspartate shuttle system.
Asunto(s)
Ácido Aspártico/metabolismo , Malatos/metabolismo , Enfermedades Musculares/metabolismo , Adulto , Humanos , Espectroscopía de Resonancia Magnética , Masculino , Mitocondrias Musculares/metabolismo , Mitocondrias Musculares/patología , Enfermedades Musculares/patologíaRESUMEN
This article presents a view which emphasises the particular perspective of a clinician who has close involvement in magnetic resonance spectroscopy (MRS) and is directed towards readers who wish to understand the likely role of MRS in clinical medicine. Many more complete reviews already exist, including two review articles from our group. Another review would hardly be justifiable and those readers seeking such an article should consult Refs. 1-5. This will be more in the nature of a personal overview of the topic and one which will touch upon some of the problems which accrue from the interactions of scientists with little appreciation of clinical medicine with clinicians who have little understanding of the complexities of the NMR experiment. Moreover, the discussion will be confined to situations where MRS is likely to impinge directly on problems of day-to-day clinical management, as opposed to situations where the results of MRS research lead to an improved understanding of particular disease states, but where there is no need for each and every patient who is a potential benificiary of the technique to undergo an MRS examination.
Asunto(s)
Espectroscopía de Resonancia Magnética , Glucólisis , Humanos , Hipotiroidismo/diagnóstico , Claudicación Intermitente/diagnóstico , Enfermedades Metabólicas/diagnóstico , Enfermedades Musculares/diagnóstico , Análisis EspectralRESUMEN
Phosphorus 31 magnetic resonance (MR) spectroscopy was used for the study of liver metabolism in vivo in seven healthy subjects. Subjects were examined in a 1.6 T whole-body magnet using surface coils for data acquisition. The region of the liver from which MR signals were collected was selected by magnetic-field profiling. The concentration ratios of adenosine triphosphate (ATP), inorganic phosphate (Pi) and sugar phosphates contained in liver cells could be reproducibly assessed. Cytosolic pH and the free magnesium concentration were determined to be 7.18 and 300 microM, respectively. During intravenous fructose tolerance tests the hepatic concentrations of sugar phosphates, ATP and Pi altered markedly. During the first 5 min following bolus injection of 250 mg fructose/kg body weight the concentration of sugar phosphates increased sevenfold whereas Pi and ATP decreased by three- to fourfold. Metabolism of sugar phosphates was complete within 20 min and could be followed by 31P MR with a time resolution of 5 min. Thus, 31P MR spectroscopy yields insight into liver metabolism which has not been accessible so far using conventional non-invasive methods. In conjunction with intravenous fructose loading, 31P MR spectroscopy may provide a means for the functional assessment of the liver.
Asunto(s)
Hígado/metabolismo , Adenosina Trifosfato/metabolismo , Adulto , Femenino , Fructosa/sangre , Fructosa/metabolismo , Humanos , Espectroscopía de Resonancia Magnética , Masculino , Fósforo/sangre , Fosfatos de Azúcar/metabolismoRESUMEN
The potential clinical use of topical magnetic resonance spectroscopy (volume selection by static magnetic field gradients) was tested in 50 studies in volunteers. Topical magnetic resonance spectroscopy (MRS) was shown to be a straightforward method for localising 31P spectra of brain and liver. However, the spherical shape and fixed position of the selected volume posed serious limitations to the study of heart and transplanted kidney by topical MRS. Phosphorus-31 spectra of approximately 30 cm-3 of brain or liver could be obtained in 8 min. Ratios of metabolite concentrations could be determined with a coefficient of variation ranging from 10% to 30%. The ratios of phosphocreatine/ATP and inorganic phosphate/ATP in brain were 1.8 and 0.3, respectively. The ratio of inorganic phosphate/ATP in liver was 0.9. Intracellular pH was 7.03 in brain and 7.24 in liver. The T1 relaxation times of phosphocreatine, inorganic phosphate and gamma-ATP in brain were 4.8 s, 2.5 s and 1.0 s, respectively.
Asunto(s)
Espectroscopía de Resonancia Magnética , Encéfalo/anatomía & histología , Campos Electromagnéticos , Corazón/anatomía & histología , Humanos , Riñón/anatomía & histología , Hígado/anatomía & histología , FósforoAsunto(s)
Riñón/fisiología , Supervivencia Tisular , Animales , Humanos , Trasplante de Riñón , Masculino , Potasio/fisiología , Ratas , Sodio/fisiología , Equilibrio HidroelectrolíticoRESUMEN
Installing high-field magnets in hospital environments has implications for safety, for the performance of the equipment and for the well-being of the subjects who will be examined. This paper outlines the relevant properties of magnets and identifies the requirements necessary for a safe and usable installation. One approach to the meeting of these requirements is described.
Asunto(s)
Seguridad de Equipos , Arquitectura y Construcción de Hospitales/normas , Espectroscopía de Resonancia Magnética/instrumentación , Inglaterra , Ambiente Controlado , Calor , Ruido en el Ambiente de TrabajoRESUMEN
Phosphorus nuclear magnetic resonance (31P NMR) can be used as a non-destructive method for the simultaneous observation of the major phosphate-containing metabolites (ATP, ADP, nucleotide monophosphate, Pi, sugar phosphate) and intracellular pH in isolated rat kidney. The time course of changes in these metabolites and in cellular pH in the ischaemic kidney are examined at two temperatures and in the presence of different flushing media. ATP is rapidly depleted while the pH change is slower and shows biphasic behaviour. Pi production and total nucleotide (ATP and ADP) depletion also occur on the same time-scale as the tissue acidification. The relation of these observations to tissue viability is discussed and the possibility of extending the measurements to human organs is considered.
Asunto(s)
Riñón/metabolismo , Adenosina Difosfato/metabolismo , Adenosina Trifosfato/metabolismo , Animales , Concentración de Iones de Hidrógeno , Técnicas In Vitro , Isquemia/metabolismo , Riñón/irrigación sanguínea , Espectroscopía de Resonancia Magnética , Masculino , Perfusión , Fósforo/metabolismo , RatasRESUMEN
High-resolution 31P nuclear magnetic resonance spectra at 73.83 MHz are reported for rat heart in vivo. In live rats, it was possible to observe the cardiac content of ATP, phosphocreatine, and Pi. Only a small amount of whole-blood 2,3-diphosphoglycerate was observed in the spectra, precluding the possibility that blood phosphate compounds were masking the spectra of cardiac phosphate compounds. The 31P nuclear magnetic resonance spectra of in vivo and perfused rat hearts were similar and support the utilization of the perfused rat heart as a model system for studying high-energy phosphate metabolism of the heart in vivo. The dynamic flux of high-energy phosphate compounds was investigated by subjecting the rat to respiratory arrest. In this experiment, the heart followed the classic metabolic pattern known to occur during cardiac arrest; phosphocreatine and then ATP decreased in concentration while Pi increased in concentration. The 31P nuclear magnetic resonance analysis of rat heart in vivo is demonstrated to be a practical and feasible method for studying cardiac high-energy phosphate metabolism.
Asunto(s)
Adenosina Trifosfato/metabolismo , Espectroscopía de Resonancia Magnética/métodos , Miocardio/metabolismo , Fosfocreatina/metabolismo , Animales , Masculino , Miocardio/análisis , Fósforo , RatasRESUMEN
Eleven men with claudication and ten control subjects had calf muscle metabolism studied at rest and during exercise and the subsequent recovery period by 31P nuclear magnetic resonance (n.m.r.) spectroscopy. The muscle of patients with severe claudication had a significantly greater depletion of phosphocreatine and fall in pH during exercise and a slower recovery of phosphocreatine and pH after exercise. The muscle of patients with both mild and severe disease had slower rates of ADP recovery after exercise than that of control subjects. Surgical correction of the associated arterial stenosis abolished claudication and led to correction of the metabolic abnormalities in two patients. Claudication pain was not related to intracellular pH or concentration of phosphorus-containing metabolites. Energy production via oxidative metabolism is impaired but glycolysis may be increased in the calf muscle of patients with intermittent claudication.
Asunto(s)
Claudicación Intermitente/metabolismo , Músculos/metabolismo , Adenosina Difosfato/metabolismo , Adenosina Trifosfato/metabolismo , Adulto , Anciano , Humanos , Concentración de Iones de Hidrógeno , Espectroscopía de Resonancia Magnética , Masculino , Persona de Mediana Edad , Fosfocreatina/metabolismoRESUMEN
The metabolic state of human muscle in various functional states has been investigated by the non-invasive technique of 31P nuclear magnetic resonance. The concentrations of phosphocreatine, ATP and inorganic phosphate as well as intracellular pH in the flexor digitorum superficialis have been measured during rest, dynamic exercise and recovery from exercise. The observed relationship between phosphocreatine utilization and decrease in intracellular pH during aerobic exercise indicates that lactate production only becomes significant after more than 60% of the phosphocreatine is used up. Surprisingly intracellular pH may reach as low a value as 5.9 to 6.1, indicating that phosphofructokinase is still partially active at pH 6.0. There is no metabolic recovery if the muscle is made ischaemic following exercise, implying that glycolysis is switched off as soon as exercise is stopped. Lactic acidosis is not the cause of this and presumably Ca2+ is needed to maintain the activation of phosphorylase kinase. The time-course of phosphocreatine recovery after exercise reflects the rate of oxidative metabolism, while pH recovery probably represents H+ ion export from the muscle cell. The dynamics of metabolic changes can now be observed with a time resolution of 10 to 60 seconds and thus disturbances in energy metabolism can be readily detected in several pathological states.
Asunto(s)
Músculos/metabolismo , Adenosina Difosfato/metabolismo , Adenosina Monofosfato/metabolismo , Adenosina Trifosfato/metabolismo , Adulto , Metabolismo Energético , Femenino , Humanos , Concentración de Iones de Hidrógeno , Espectroscopía de Resonancia Magnética , Masculino , Persona de Mediana Edad , Fosfatos/metabolismo , Fosfocreatina/metabolismo , Esfuerzo FísicoRESUMEN
A patient with prolonged post-viral exhaustion and excessive fatigue was examined by 31P nuclear magnetic resonance. During exercise, muscles of the forearm demonstrated abnormally early intracellular acidosis for the exercise performed. This was out of proportion to the associated changes in high-energy phosphates. This may represent excessive lactic acid formation resulting from a disorder of metabolic regulation. The metabolic abnormality in this patient could not have been demonstrated by traditional diagnostic techniques.
Asunto(s)
Líquidos Corporales/metabolismo , Fatiga/metabolismo , Líquido Intracelular/metabolismo , Músculos/metabolismo , Esfuerzo Físico , Virosis/complicaciones , Adenosina Difosfato/metabolismo , Adulto , Fatiga/etiología , Humanos , Concentración de Iones de Hidrógeno , Espectroscopía de Resonancia Magnética , Masculino , Fosfocreatina/metabolismo , Síndrome , Virosis/metabolismoRESUMEN
Several metabolites and intracellular pH in intact organs can be studied in a non-destructive manner by phorphorus nuclear magnetic resonance (31P n.m.r.). This possibility was demonstrated by us nearly five years ago. Since then we have developed the appropriate physiological techniques and improved the n.m.r. method for the study of animal hearts and kidneys. Here we described measurements aimed at clarifying three problesm. (1) Having measured the enzyme-catalysed fluxes between phosphocreatine and ATP by the method of saturation transfer n.m.r., we examine the relations between energy supply and heart rate in the isolated perfused rat heart. (2) We describe experiments to establish the validity of the perfusion model. For the first time, we report 31P n.m.r. measurements of an in vivo rat heart and compare the results with those obtained for the perfused rat heart. (3) Ischaemia and metabolism in rabbit kidneys is investigated to establish the relation between functional and metabolic recovery after a renal transplant operation.
Asunto(s)
Adenosina Trifosfato/metabolismo , Riñón/metabolismo , Espectroscopía de Resonancia Magnética/métodos , Miocardio/metabolismo , Fosfocreatina/metabolismo , Nucleótidos de Adenina/metabolismo , Animales , Ácidos Difosfoglicéricos/metabolismo , Frecuencia Cardíaca , Isquemia/metabolismo , Trasplante de Riñón , Perfusión , RatasRESUMEN
The bioenergetic state of 15 human tumours was examined with phosphorus-31 magnetic resonance spectroscopy. A striking diversity in metabolic patterns was observed, and significant differences from normal tissue were seen in all cases. A common feature was an elevation of intracellular pH, which may be related to an increase in Na+/H+ exchange during cell activation. It is unlikely that the patterns observed directly correlate with malignancy, but characterisation of the energetic state of a given tumour in a given physiological environment may help in the design and evaluation of interventions for that specific case.
Asunto(s)
Espectroscopía de Resonancia Magnética , Neoplasias/metabolismo , Radioisótopos de Fósforo , Análisis Espectral/métodos , Adulto , Anciano , Neoplasias Encefálicas/diagnóstico , Neoplasias Encefálicas/metabolismo , Neoplasias de la Mama/diagnóstico , Neoplasias de la Mama/metabolismo , Femenino , Humanos , Concentración de Iones de Hidrógeno , Cinética , Neoplasias Hepáticas/diagnóstico , Neoplasias Hepáticas/metabolismo , Masculino , Persona de Mediana Edad , Neoplasias/diagnósticoRESUMEN
There exists some uncertainty about the hazards which the quenching of a superconducting magnet would present to a subject undergoing an NMR examination. To investigate this problem, a 1.6-T whole-body magnet was quenched with an anesthetized pig lying in the bore. This paper reports our findings which, in the circumstances of this experiment, suggest that the risks are small.
Asunto(s)
Espectroscopía de Resonancia Magnética/instrumentación , Animales , Electrocardiografía , Electroencefalografía , Seguridad de Equipos , Femenino , Humanos , Riesgo , PorcinosRESUMEN
The forearms of six patients with Duchenne dystrophy were examined by the painless and non-invasive technique of high-resolution nuclear magnetic resonance spectroscopy. The phosphorus spectrum was abnormal in that the ratios of phosphocreatine to adenosine triphosphate and to inorganic phosphate were reduced. Absolute quantification under the conditions of this experiment was not possible but it was probable that in dystrophy the concentration of phosphocreatine in muscle was appreciably reduced. A signal in the phosphodiester region of the spectrum was recorded consistently in patients with dystrophy but not in controls. The intracellular pH of the muscle in the dystrophic patients was abnormally alkaline. The clinical application of nuclear magnetic resonance spectroscopy remains to be proved, but it appears to be a promising non-invasive technique for investigating biochemical abnormalities of muscle disease.
Asunto(s)
Músculos/metabolismo , Distrofias Musculares/metabolismo , Adenosina Trifosfato/metabolismo , Adolescente , Adulto , Niño , Antebrazo/metabolismo , Humanos , Espectroscopía de Resonancia Magnética , Masculino , Fosfocreatina/metabolismo , Fósforo/metabolismoRESUMEN
Human skeletal muscle has been studied in vivo by 31P nuclear magnetic resonance. Young adult subjects were compared with healthy elderly subjects aged 70-80 years. Intracellular pH and concentrations of adenosine triphosphate (ATP), phosphocreatine and inorganic phosphate were measured. At rest, no differences were found between the two age groups. Aerobic dynamic exercise resulted in a similar reduction of phosphocreatine in both groups while the ATP concentration did not change. The pH fall in exercise was not significantly different in the elderly and younger subjects. The time to resynthesize ATP in the recovery period as measured by the time to replete phosphocreatine was also not different in the two groups. The results suggest that the aging process does not affect the metabolic ability of human skeletal muscle to respond to exercise and that changes found in muscle of the elderly are not due to alterations in energy production.