Spatially localized magnetic resonance spectroscopy of the brains of normal and asphyxiated newborns

Phase-modulated rotating frame imaging is a modification of magnetic resonance spectroscopy, which uses a linear radiofrequency field gradient to obtain spatially localized biochemical information. Phase-modulated rotating frame imaging was used to study regional cerebral energy metabolism in the brains of 9 normal newborns and 25 newborns after birth asphyxia. Relative concentrations of phosphorus-containing metabolites and intracellular pH were determined for brain tissue at three specified depths below the brain surface for all neonates. Wide variations in metabolite ratios were seen among normal neonates, and considerable metabolic heterogeneity was demonstrated in individual neonates by depth-resolved spectroscopy. Asphyxiated neonates with severe hypoxic-ischemic encephalopathy and a poor neurodevelopmental outcome showed the expected rise in inorganic orthophosphate and fall in phosphocreatine concentrations in both global and spatially localized spectra. Phase-modulated rotating frame imaging showed that metabolic derangement was less in superficial than in deeper brain tissue. The inorganic orthophosphate-adenosine triphosphate ratio from 1 to 2 cm below the brain surface was more accurate than any global metabolite ratio for the identification of neonates with a poor short-term outcome. These data are consistent with the known vulnerability of subcortical brain tissue to hypoxic-ischemic injury in the full-term neonate.

Interplay between adrenaline and interbeat interval on ventricular repolarisation in intact heart in vivo

STUDY OBJECTIVE

The aim was to examine the hypothesis that an interaction between adrenaline and change in heart rate may alter the normal time sequence of ventricular repolarisation (and hence refractoriness) in a manner that (1) may favour arrhythmia formation, (2) may partly explain conflicting reports of the effect of adrenaline, ie, there are two opposing effects on action potential duration, and (3) be relevant to T wave abnormalities that sometimes occur in normal people.

DESIGN

As a measure of the time course of repolarisation, monophasic action potentials were recorded simultaneously from three epicardial sites in the porcine heart (left ventricular apex, left ventricular base, and mid right ventricle). During steady state pacing, test pulse intervals were interposed at progressively shorter intervals in order to construct restitution curves.

MEASUREMENTS AND MAIN RESULTS

Adrenaline infusion (0.4-1.5 micrograms.kg-1.min-1) resulted in earlier repolarisation in the beats after shorter interbeat intervals, and delayed repolarisation after longer interbeat intervals, tending to turn the restitution curve anticlockwise (ie, there were two opposing effects on action potential duration). The effects were not homogeneous between regions. To show this inhomogeneity, pairs of monophasic action potentials from different regions were subtracted using a differential input amplifier to produce an ECG like waveform at the amplifier output. The resulting T wave was thereby a measure of the time difference in repolarisation between the monophasic action potentials from which it was derived. The inhomogeneity of repolarisation induced by adrenaline and rate change was reflected in the morphology of this derived T wave, particularly at early (premature) beats. These T wave changes correlated closely with the true T wave changes in bipolar electrograms recorded between the same recording sites (R = 0.89; p less than 0.0001).

CONCLUSIONS

These results show that adrenaline altered the normal relationship between interbeat interval and the timing of repolarisation. The effect was not homogeneous and when regional differences were observed they were reflected in changes in T wave morphology. These were marked at short intervals. It is possible that in addition to increased excitability observed with adrenaline, a combination of raised sympathetic activity and early beats predisposes to arrhythmias by exaggerating dispersion of repolarisation.

Elevated blood lead in California adults, 1987: results of a statewide surveillance program based on laboratory reports

California medical laboratories that test for blood lead are required to report results exceeding 1.21 mumols/L (25 micrograms/dl). Between April and December 1987, the California Department of Health Services received 3,077 blood lead reports from 34 laboratories for 1,293 civilian, non-institutionalized adults. Approximately 1 percent of all reports exceeded 3.87 mumols/L (80 micrograms/dl), 7 percent exceeded 2.42 mumols/L (50 micrograms/dl), and 21 percent exceeded 1.93 mumols/L (40 micrograms/dl). Individuals tested were overwhelmingly male (94 percent), disproportionately Hispanic surnamed (44 percent), and most often residents of Los Angeles County (81 percent). Workers in lead smelting, battery manufacturing, and brass foundries accounted for nearly 80 percent of reports. Construction, radiator repair, pottery and ceramics manufacturing, and gun firing ranges accounted for the remainder. All adults with reports of greater than or equal to 2.90 mumols/L who were contacted reported on occupational exposure. Approximately half were not in routine medical monitoring programs. Despite OSHA standards, elevated blood lead with the potential for serious acute and chronic lead poisoning in California adults remains a significant public health and major occupational health concern.

Changes in plasma progesterone concentrations from days 17 to 42 of gestation in mares maintaining or losing pregnancy

Plasma progesterone concentrations were measured in 179 mares bled on alternate days commencing with a positive pregnancy diagnosis on Days 17 to 18 after ovulation and concluding on Days 42 to 45. During this period 17 mares (10 per cent) lost their pregnancies, 11 before Day 25. In 15 mares the timing of the pregnancy loss could be determined with adequate accuracy; in only one did a decline in progesterone precede the loss. Thus pregnancy loss between Days 17 and 42 was rarely caused by a fall in plasma progesterone.

The epicardial electrogram: a quantitative assessment during balloon angioplasty incorporating monophasic action potential recordings

An electrogram was recorded from the angioplasty catheter guide wire when coronary blood flow was interrupted in 20 patients undergoing percutaneous transluminal coronary angioplasty. Monophasic action potentials were recorded from the right ventricular septum together with the routine electrocardiogram. The patients were studied during angioplasty for lesions in the left anterior descending (12), circumflex (3), and right coronary arteries (6). ST elevation in the electrogram recorded in the left anterior descending and circumflex systems was usually more obvious than that in the electrocardiogram. Signals obtained from the right coronary artery were of very low amplitude and registered only minimal ST changes. The ST elevation developed in the electrogram during insertion of the catheter before inflation of the balloon in 11 of the 15 patients undergoing angioplasty of the left system. In eight of the patients showing pre-inflation ST elevation the ST shift lessened after successive inflations. Monophasic action potential recordings were obtained during 45 balloon inflations in 19 patients. In those patients undergoing angioplasty for lesions of the circumflex coronary artery the monophasic action potential showed no change during balloon inflation. In patients undergoing angioplasty for the right coronary artery the mean normalised duration at 60 seconds' occlusion was 99.6 (1.5)% of control. Of a total of 25 occlusions in the patients undergoing angioplasty for the left anterior descending coronary artery 19 showed shortening of less than 5%, five showed shortening between 5 and 10%, and one showed a shortening of 16.4% in the monophasic action potential. The QT interval was satisfactorily measured in the electrogram during 36 balloon inflations, and in 24 of these it was also measured in the electrocardiogram. QT changes in the electrogram tended to be the opposite of those in the electrocardiogram. When changes in RR interval were minimal (less than 20 ms) during the balloon inflation 14 of 17 electrograms showed QT prolongation but only one of 12 electrocardiograms showed prolongation. Conversely one of 17 electrograms showed shortening compared with eight of 12 electrocardiograms. There was angiographic evidence of the development of collaterals in six of 15 patients undergoing angioplasty of the left system. ST segment elevation in both the electrogram and electrocardiogram was less pronounced in these patients than in those without evidence of the development of collaterals. ST segment changes recorded from the angioplasty guide wire provide a more sensitive index of ischaemia than the surface 12 lead electrocardiogram, and fall in ST segments on balloon deflation is a prognostic index of a good angiographic result in the left anterior descending and circumflex arteries, but not in the right coronary artery.

Intraoperative assessment of myocardial revascularisation for the relief of ischaemia using monophasic action potential recordings

We have been concerned with developing a method of assessing regional myocardial perfusion which is simple, quick and without hazard to the patient. Monophasic action potential (MAP) recordings provide a highly sensitive measure of localised myocardial ischaemia. We have developed a hand-held pressure contact silver/silver chloride electrode for recording MAP signals from the left ventricular epicardium. The design enables it to slide within the pericardium on the left ventricle/epicardium with minimal displacement of the heart. Three protocols were adopted providing different permutations of atrial pacing and graft occlusion. Protocol 1: after discontinuing bypass, atrial pacing was established. After 90 s, all grafts were occluded for a period of 90 s. Protocol 2: after discontinuing bypass, all grafts were occluded for 90 s in the absence of pacing. Protocol 3: atrial pacing was established for 60 s before grafting and bypass and repeated subsequent to grafting and discontinuing bypass. Our results show that the most promising method is protocol 3. The most important results were that when heart rate is taken into account, the ischaemic changes in the MAP were significantly less impressive (P less than 0.05) following grafting. With further refinement, this technique may be applicable to the assessment of individual grafts.

Prognostic features and treatment of endocervical adenocarcinoma of the cervix

Adenocarcinoma of the cervix represents an increasing percentage of cervical cancers as well as a controversial clinical problem. One hundred seventy-two cases of adenocarcinoma were treated at The University of Michigan Medical Center from 1970 to 1984, representing 16.8% of cervical cancers. Of this group 84 patients were diagnosed with endocervical columnar cell type and form the study population for this report. Survival was influenced by stage, grade, and nodal metastases. Age did not influence survival. Survival in stage I disease was not influenced by treatment modality. Radical surgery or radiation therapy provided equal survival and ovarian conservation did not adversely influence survival. Radical surgery can be considered a primary means of therapy in young women and offers the same advantages over radiation therapy as those offered for squamous cell disease.

Evidence of inadequate humidification of inspired gas during artificial ventilation of newborn babies in the British Isles

Data on routine humidifier settings used in respiratory support for newborn babies were obtained from 242 neonatal units in the British Isles. For each of the most commonly used humidifiers inspired gas humidity was measured under routine clinical conditions with an electronic hygrometer. Most endotracheally intubated babies breathe inspired gas of well below physiological humidity (44 mg H2O/l) and many below the minimum recommended for adults by the British Standards Institution (33 mg H2O/l). Inadequate humidification could contribute to several complications of artificial ventilation in newborn babies by inhibiting mucociliary clearance.

Inadequate humidification of respiratory gases during mechanical ventilation of the newborn

Proximal airway humidity was measured during mechanical ventilation in 14 infants using an electronic hygrometer. Values below recommended minimum humidity of adult inspired gas were recorded on 251 of 396 occasions. Inadequate humidification, largely due to inadequate proximal airway temperature, is commoner than recognised in infants receiving mechanical ventilation.

Use of monophasic action potential recordings during routine coronary-artery bypass surgery as an index of localised myocardial ischaemia

In 8 patients undergoing routine coronary-artery bypass surgery, monophasic action potentials (MAPs) were measured by means of a hand-held pressure contact electrode to provide an index of local ischaemic changes. 4 patients received left internal mammary anastomoses (LIMA), and there were a total of 27 saphenous vein grafts (SVG). After completion of all grafts blood-flow to the myocardium was reduced for 90 s by means of different permutations of SVG and LIMA occlusion, either on or off bypass. In all patients MAPs indicated typical ischaemic changes. The high sensitivity of the method enables the study to be completed quickly and without hazard to the patient. The technique provides a new means to assess local ischaemia, the viability of specific areas of myocardium, and the efficiency of individual grafts during surgery.

d-Sotalol: a new potent class III anti-arrhythmic agent

We have compared the effect of a new drug d-sotalol which has minimal beta-blocking action with the parent (beta-blocking) compound dl-sotalol on monophasic action potential (MAP) duration in open-chested dogs. In seven experiments d-sotalol was administered in intravenous bolus doses of 1.5, 3 and 6 mg/kg given at 10 min intervals. In a further seven experiments dl-sotalol was administered using the same dosage regimen. The animals were anaesthetized with chloralose and urethane. Atrioventricular block was created by injection of the bundle of His with 0.1 ml of 40% formalin in order to ensure capture by ventricular pacing. After prior beta-blockade with propranolol (0.25 mg/kg), simultaneous epicardial and endocardial MAP were recorded at paced heart rates of 100 and 150 beats/min after each bolus injection. d-Sotalol and dl-sotalol showed similar prolongation of MAP duration (measured at 90% repolarization) in both endocardial and epicardial recording at both paced heart rates. These results show that the dextro-isomer of sotalol possesses similar class III action to the parent compound and that this action is homogeneous with respect to left ventricular endocardium and epicardium at heart rates of 100 beats/min and 150 beats/min over a wide dose range. d-Sotalol may be a useful anti-arrhythmic agent in man.

Inspiratory: expiratory ratio and pulmonary interstitial emphysema

Images

The perceived spatial frequency shift: evidence for frequency-selective neurones in the human brain

1. Prolonged observation of a high-contrast grating pattern causes an apparent shift in the spatial frequency of gratings subsequently viewed with the same retinal region. Gratings of higher and lower frequency than the adapting pattern seem, respectively, higher and lower than in fact they are.2. There is no significant after-effect at the adapting frequency itself nor at frequencies more than two octaves away.3. For very low adapting frequencies, the after-effect remains centred at about 3.0 c/deg and declines in strength as the adapting frequency is successively lowered.4. The magnitude of the after-effect increases with the contrast of the adapting grating and the length of time spent in adaptation. It takes several hours to recover completely from 30 min adaptation.5. The phenomenon is orientation-specific: a horizontal adapting grating has no effect on vertical test gratings. There is partial interocular transfer of the after-effect.6. These findings provide further evidence that the visual system of man, like those of the cat and the monkey, contains neurones selectively sensitive to the orientation and dimensions of retinal images, and that these adaptable cells are actually involved in the encoding and perception of the size of simple patterns.

Size adaptation: a new aftereffect

If, after prolonged observation of a striped pattern, one views a grating of the same orientation with somewhat narrower bars, then the bars seem even thinner than in fact they are. Broader bars seem broader still. This finding implies a system of size-detecting channels in humnan vision. The phenomenon may underlie many of the classical figural aftereffects.