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Biomedical subjects

G R Sutherland

Publications and source records attributed to G R Sutherland.

679 records · Page 38Linked to original sources
PubMedDate not supplied

Doppler energy: a new acquisition technique for the transthoracic detection of myocardial perfusion defects with the use of a venous contrast agent.

AIMS: This animal experiment was designed to study whether the new technique of Doppler energy imaging could display myocardial perfusion abnormalities with the use of a combination of transthoracic imaging and right atrial injection of a myocardial contrast agent. METHODS AND RESULTS: A series of 11 pigs were studied during (1) normal perfusion, (2) dipyridamole-induced coronary dilatation, and (3) during and after temporary occlusion of the left anterior descending or circumflex artery after a right atrial injection of 8 ml Levovist, 400 mg/ml. Short-axis views were obtained with the four following imaging modes: gray scale imaging (two-dimensional and M-mode), Doppler energy imaging (two-dimensional and M-mode). Visual inspection and off-line video densitometry (results expressed in arbitrary videointensity units 0 to 255) with digital background subtraction were performed. Doppler energy was significantly more sensitive in detecting the presence of contrast than gray scale imaging (background subtracted peak videointensity 32 +/- 17 versus 17 +/- 12, p < 0.001). Mean background-subtracted videointensity increased during dipyridamole-induced coronary hyperemia (40 +/- 14 versus 31 +/- 9, p < 0.003) using Doppler energy technique. Doppler energy imaging consistently detected absent perfusion (background subtracted videointensity -6 +/- 6) and immediate reperfusion (background subtracted peak videointensity 29 +/- 15, p < 0.001). CONCLUSIONS: With the use of a galactose-based contrast agent, Doppler energy data acquisition was superior to standard gray scale imaging in transthoracic evaluation of regional myocardial perfusion, absence of perfusion, and reperfusion.

Animals↗
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Chromosomal mosaicism in amniotic fluid cell cultures.

Six cases of chromosomal mosaicism detected in amniotic fluid cultures are described. In five of these there was no evidence of fetal mosaicism. In one case fetal mosaicism was demonstrated but only by the study of fibroblasts since blood cultures showed only normal cells. The implications of amniotic fluid mosaicism are discussed and it is concluded that this usually does not indicate fetal mosaicism. The value of repeated amniocentesis in the diagnosis of fetal mosaicism was demonstrated by findings in three of the cases. It is recommended that amniotic fluid cultures be harvested in situ for chromosome studies and that cytogenetic results be expressed as number of colonies karyotyped rather than as number of cells analyzed.

Adult↗
PubMedDate not supplied

Phosphate energy metabolism during domoic acid-induced seizures.

The effect of domoic acid-induced seizure activity on energy metabolism and on brain pH in mice was studied by continuous EEG recording and in vivo 31P nuclear magnetic resonance (NMR) spectroscopy. Mice were divided into ventilated (n = 6) and nonventilated (n = 7) groups. Baseline EEG was 0.1-mV amplitude with frequence of > 30-Hz and of 4-5 Hz. After intraperitoneal (i.p.) administration of domoic acid (6 mg/kg), electrographic spikes appeared at increasing frequency, progressing to high-amplitude (0.1-0.8 mV) continuous seizure activity (status epilepticus). In ventilated mice, the [31P]NMR spectra showed that high-energy phosphate levels and tissue pH did not change after domoic acid administration or during the intervals of spiking or status epilepticus. Nonventilated mice showed periods of EEG suppression accompanied by decreases in the levels of high-energy phosphate metabolites and in pH, corresponding to episodic respiratory suppression during the spiking interval. In all animals, status epilepticus was followed by a marked decrease in EEG amplitude that progressed rapidly to isoelectric silence. [31P]NMR spectra obtained after this were indicative of total energy failure and tissue acidosis. In a separate group of ventilated mice (n = 4), domoic acid-induced status epilepticus was accompanied initially by an increase in mean arterial blood pressure (MAP) that slowly returned to baseline level. Isoelectric silence was accompanied by a decrease in MAP to 75 +/- 8 mm Hg. These experiments suggest that domoic acid-induced seizures are not accompanied by an increase in substrate demand that exceeds supply.

Adenosine Triphosphate↗
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Assessment of skeletal muscle ventricle function using tissue velocity imaging.

BACKGROUND AND AIMS: Skeletal muscle ventricles (SMVs) are a potential power source for circulatory assistance. Noninvasive assessment of SMVs is desirable in long-term studies of SMV function. This study evaluated whether tissue velocity imaging (TVI) indices of function correlate with invasive measurements of output and pressure generation and examined the potential of TVI to provide information about SMV geometry and wall contraction characteristics. METHODS: SMVs were constructed in six sheep. After electrical conditioning, SMVs were connected to a mock circulation and stimulated with supramaximal 30-Hz and 50-Hz bursts to contract 35 times/min. The SMVs were tested over a range of preloads, and afterload was adjusted to simulate systemic (80 mmHg) and right ventricular (30 mmHg) loading conditions. Stroke volume and pressure were measured invasively, and stroke work was calculated. TVI was used to measure velocities in two opposing SMV walls, providing a simple wall motion score (WMS). This was evaluated against stroke volume, stroke work, and pressure development. RESULTS: 50-Hz stimulation frequency and high preload optimized SMV performance. Optimal SMV performance indices (mean at 50 Hz) were as follows: (a) right ventricular loading conditions (preload 30 mmHg), stroke volume 17.6 mL (SEM 3.2), peak pressure over afterload 44.2 mmHg (10.9), stroke work 0.05 J (0.02); (b) systemic loading conditions (preload 60 mmHg), stroke volume 10.1 mL (3.2), peak pressure over afterload 58 mmHg (14.6), stroke work 0.08 J (0.03). With low preloads, geometric anomalies were noted in the SMVs using TVI. Collapse of the SMVs and dyskinesis were observed, which normalized with higher preloads. Persistent dyskinesis was noted in one SMV and was associated with poor performance. Correlations (at optimal loading and stimulation settings) were as follows: systemic loading conditions, stroke volume versus WMS, 0.92 (p = 0.026); peak pressure versus WMS 0.89 (p = 0.045); stroke work versus WMS, r = 0.91 (p = 0.046). Right ventricular loading conditions were as follows: stroke volume versus WMS, 0.63 (p = 0.25); peak pressure versus WMS, 0.66 (p = 0.22); stroke work versus WMS, 0.45 (p = 0.39). CONCLUSION: Under systemic loading conditions, TVI indices of SMV wall motion mirror invasive indices of performance, suggesting that TVI may be a useful tool for long-term noninvasive monitoring of SMV function.

Animals↗
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Transseptal mitral balloon valvotomy in patients with atrial septal aneurysms.

Transthoracic and transoesophageal echocardiography (TTE, TEE) were performed in 130 consecutive patients referred for mitral balloon valvotomy. Atrial septal aneurysms were diagnosed by TTE and TEE in 2 and 3 patients, respectively. All 3 patients underwent mitral balloon valvotomy via the transseptal route. The foramen ovale was found to be patent in 2 of these patients, thus rendering puncture of the interatrial septum unnecessary. In the 3rd patient transseptal catheterisation was performed through the wall of the aneurysm itself. There were no significant complications in any of these patients. No left-to-right interatrial shunting could be demonstrated by oximetry in any of the 3 patients. Transoesophageal colour flow imaging showed trivial shunting in 2 patients and none in the 3rd. Transseptal mitral balloon valvotomy can be performed safely in patients with atrial septal aneurysms, especially in those with co-existent patent foramen ovale.

Adult↗
PubMedDate not supplied

The effect of Fluosol-DA on oxygen availability in focal cerebral ischemia.

The effects of Fluosol-DA 35% (15 ml/Kg, IV) on cortical oxygen availability (O2a), a relative measurement of cortical oxygen tension, were examined in 16 cats subjected to temporary middle cerebral artery (MCA) occlusion. The cats were divided equally into control and treatment groups and half of each group underwent MCA occlusion at room air ventilation and the other half at 100% O2 ventilation. Prior to occlusion, Fluosol had no effect on arterial PO2 or cortical O2a at normoxia, however, there was a significant increase in both arterial PO2 and O2a following 100% O2 ventilation (pre vs post Fluosol). In an additional 5 cats, Fluosol resulted in a transient decrease in blood oxygen content due to hemodilution. Concurrent to this decrease, cerebral blood flow increased substantially resulting in a net increase in oxygen delivery. Within ipsilateral hemispheres, MCA occlusion resulted in decreased O2a to levels below the pre-occlusion normoxic values in all animals except those treated with Fluosol and ventilated with 100% O2. During reperfusion, O2a immediately recovered to hyperoxic levels in the Fluosol 100% O2 animals, whereas in the other three groups, O2a returned more gradually towards the pre-occlusion value. Since neither 100% O2 alone nor Fluosol plus room air ventilation significantly improved O2a in the ischemic cortex, we conclude that increased delivery of plasma plus Fluosol bound oxygen was responsible for the observed improvements in O2a following MCA occlusion.

Animals↗
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Intraoperative magnetic resonance imaging and meningioma surgery.

OBJECTIVE: To determine if intraoperative magnetic resonance imaging improves surgical resection and postoperative outcome of intracranial meningioma. STUDY DESIGN: Prospective, non-randomized, cohort study. METHOD: Intraoperative Magnetic Resonance Imaging (iMRI) was used to evaluate patients with meningioma undergoing surgery. Images were obtained after induction of anaesthesia and at various stages of tumour resection. Extent of surgical resection was graded using Simpson grading system for meningioma. The images were reviewed together with histopathology and early outcome. Primary outcome measure was determined by finding unexpected tumur in interdissection images. Secondary outcome measures were determined by postoperative complications including infections and mortalities. RESULTS: There were 39 procedures in 38 patients from January 1998 to December 2002. Surgical-planning images helped to optimize craniotomy placement. Interdissection images revealed unexpected residual tumour in only 1 patient. Complete resection (Simpson grades 1-3) was achieved in 33 procedures. The average follow up period was 16.4 months. Tumour recurrence has been observed in three patients. Two of these patients had anaplastic meningioma. There was no mortality in the 30-day postoperative period. CONCLUSION: Intraoperative MRI was beneficial in siting the craniotomy in addition to providing anatomical relationships between the tumour and adjacent structures in lesions located at the skull base though the full benefit of these is yet to be determined. The low morbidity and zero mortality recorded in the study may be related to all these factors.

Adult↗
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Just how long can we live?

In June this year, United States President Clinton and British Prime Minister Blair jointly announced that the human genome had been sequenced. In another year or so, this information should be assembled into a much more useful form than that in which it now exists. The advances which will be made possible by the Human Genome Project and new genetic technologies may well extend the human life span still further.

Human Genome Project↗
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Extensive organization in a thrombosed giant intracranial aneurysm: case report.

A 58-year-old man presented with a 4-month history of personality changes and transient episodes of right lower extremity weakness, as well as transient episodes of aphasia. Computerized tomography revealed a large basal frontotemporal mass with extensive surrounding edema which was confirmed on angiography to be a partially thrombosed giant aneurysm. Pathologically, the lesion was extraordinary, demonstrating extensive organization, with the entire cavity of the aneurysm occupied by vascular channels of different sizes, some of which were thrombosed. These findings were substantiated by scanning electron microscopy which also illustrated areas of active platelet-fibrin interaction on the remaining luminal surface.

Humans↗
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Patient administration: how to avoid bottle-necks.

The object of this paper has been to outline and to assist others in eliminating the obstacles of which we are all aware in any busy radiography department. From experience the value of team work from the porters to the radiologists cannot be over-emphasized. Any weak link in the chain can produce a bottle-neck and by tackling the elementary problems which we have discussed, a smooth day to day operation of the department, can generally be achieved, making the launching of the computer a relatively simple task.

Computers↗
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Mobile lipid accumulation in necrotic tissue of high grade astrocytomas.

Multiple samples from 42 astrocytomas were investigated ex vivo by 1H MR spectroscopy followed by histological assessment. MR visible lipids were detected in 27 of 32 grade 4 astrocytomas. These lipids were heterogeneously distributed within the tumours. Their amount correlated positively with the amount of histologically detected necrosis. Mobile lipids were also observed in grade 4 astrocytoma samples without necrosis, as well as in one of three grade 3, two of three grade 2 and two of four grade 1 astrocytomas. The clinical significance of MR visible lipids, their cellular location, and their possible biological bases are discussed.

Astrocytoma↗