Search

Background Preoperative L-lactatemia and heart rate have been suggested as prognostic indicators of outcome for cows with right dilatation of the abomasum or volvulus ( RDA/ AV). However, postoperative L-lactatemia has not been assessed as a potential prognostic tool. Objectives To determine the prognostic value of postoperative L-lactatemia ( LAC2), duration of treatment (Dt), relative L-lactatemia difference (compared with preoperative L-lactatemia [LAC1]) ([LAC2 − LAC1]/LAC2) and change in L-lactate over time ([LAC2 − LAC1]/Dt) as compared to preoperative findings ( LAC1 and heart rate [ HR]) as prognostic factors in dairy cows with RDA/ AV. Animals A total of 41 dairy cows were included: 19 with AV and 22 with RDA; 11 cows had a negative outcome ( NO) and 30 cows had a positive outcome ( PO) based on telephone follow-up with owners 30 days after surgery. Methods Prospective cohort study. Analysis was performed using logistic regression and comparison of area under the receiver operating characteristics curve ( AUC) using nonparametric tests. Results LAC1 > 1.4 mmol/L or LAC2 > 2.2 mmol/L had the same accuracy with sensitivity of 100% (95% CI, 75.1-100%) and specificity of 80% (95% CI, 61.4-92.3%) for predicting NO. The relative L-lactatemia difference ([LAC2 − LAC1]/LAC1) or lactate kinetics ([LAC2 − LAC1]/Dt) were not associated with prognosis. The AUC of the preoperative model (which included HR and lnLAC1) was 0.92 (95% CI, 0.83-1.0) and that of the postoperative model (including only lnLAC2) was 0.95 (95% CI, 0.88-1.0); these were not significantly different. Conclusions and Clinical Importance Postoperative L-lactatemia is helpful to predict outcome in cows with RDA/ AV. The short-term change in blood L-lactate is not a useful prognostic indicator , at least during the period of time spent on the farm for surgery and treatment. [ABSTRACT FROM AUTHOR]

243 measurements of cerebral blood flow by a noninvasive (133)Xe clearance technique have been made in 45 patients undergoing surgery for a recently ruptured cerebral aneurysm. Two groups of patients have been defined by the presence or absence of a postoperative rise in cerebral blood flow which showed a significant correlation with level of consciousness after operation. [ABSTRACT FROM AUTHOR]

Regional cerebral blood flow was measured by injection of (133)Xenon into the internal carotid artery in 11 patients with cerebrovascular disease. All patients were studied under general anaesthesia, first at normocapnia and then at hypocapnia. The 15 minute isotope clearance curves were analysed by computer by two-compartmental analysis and regional changes in flow and the proportions of fast and slow clearing tissue obtained at two levels of arterial CO(2) tension. Hypocapnia caused a fall in blood flow which was consistently accompanied by a decrease in the proportion of fast clearing tissue. Regional changes were not significantly different from the hemisphere mean changes. There was no correlation between changes in blood flow through grey matter and the proportion of fast clearing tissue on a hemisphere mean basis, but on regional analysis the data from 10 out of the 11 patients showed that in areas where blood flow through grey matter changed most the proportion of fast clearing tissue changed least and vice versa. A hypothesis has been proposed to explain this phenomenon. [ABSTRACT FROM AUTHOR]

Objective: Pertussis toxin uncoupling-based studies have shown that Gαi and Gαo can inhibit insulin secretion in pancreatic β-cells. Yet it is unclear whether Gαi and Gαo operate through identical mechanisms and how these G-protein-mediated signals inhibit insulin secretion in vivo. Our objective is to examine whether/how Gαo regulates islet development and insulin secretion in β-cells.Research Design and Methods: Immunoassays were used to analyze the Gαo expression in mouse pancreatic cells. Gαo was specifically inactivated in pancreatic progenitor cells by pancreatic cell-specific gene deletion. Hormone expression and insulin secretion in response to different stimuli were assayed in vivo and in vitro. Electron microscope and total internal reflection fluorescence-based assays were used to evaluate how Gαo regulates insulin vesicle docking and secretion in response to glucose stimulation.Results: Islet cells differentiate properly in Gαo(-/-) mutant mice. Gαo inactivation significantly enhances insulin secretion both in vivo and in isolation. Gαo nullizygous β-cells contain an increased number of insulin granules docked on the cell plasma membrane, although the total number of vesicles per β-cell remains unchanged.Conclusions: Gαo is not required for endocrine islet cell differentiation, but it regulates the number of insulin vesicles docked on the β-cell membrane. [ABSTRACT FROM AUTHOR]

Some anatomical aspects of the blood supply of the brains of mammals have been examined to illuminate their functions. A fundamental explanation of sudden infant death syndrome (cot death) is suggested following experimental1 observations. Speculative contributions have been made to comparative physiological ideas concerning mammals of pronograde and erect habitus, their vascular pressure adaptations and temperature management. Neuro- and interventional radiologists may make some significant future applications of these ideas. Of immediate practical interest is the possibility of influencing the well-being of human embryos' neural tube development in utero by a comprehensive study of their temperature environment. [ABSTRACT FROM AUTHOR]

The ability to visualise multiple selerosis lesions in vivo with magnetic resonance imaging suggests and important role in monitoring the course of the disease. In order to help the long-term assessment of prospective treatments, a semi-automated technique for measuring lesion volume has been developed to provide a quantitative index of disease progression. Results are presented from a preliminary study with a single patient and compared to measurements taken from lesion outlines traced by a neuroradiologist, two neurologists and a technician. The semi-automated technique achieved a precision of 6% compared to a range of 12-33% for the manual tracing method. It also reduced the human interaction time from at least 60 min to 15 min. [ABSTRACT FROM AUTHOR]

All spinal magnetic resonance imaging examinations carried out during a three month period were analysed retrospectively in order to determine the clinical reasons for the scan requests. Technical details of the examinations they received and the clinical profiles formed a data set which revealed 10 separate 'Clinical groups' for management purposes. Hardware, salary and expendables were costed as though the imaging unit had been sited within a National Health Service radiology department. A spread sheet was designed capable of calculating costs per patient for a variety of types of working week and of different staffing structures, sensitive to the mixture of clinical groups referred for examination. The spreadsheet also accomodated straight line depreciation for hardware value and interest rates for borrowed capital. A second, prospectively observed, sample of spinal MR examinations was used to improve the accuracy of the timing of the length of patient examinations. Costs were compared with those for patients submitted for myelography and radiculography at the adjacent hospital during the same period. The comparison indicated that spinal MR was less costly than myelography and radiculography. The most important element of the extra cost of myelography related to the need to admit patients to hospital for at least one night for this examination because of the likelihood of headache and other common (though usually minor) complications following lumbar puncture and/or the injection of contrast medium. From the limited information that it was possible to obtain in the period of follow up, it appeared that MR had either been superior or equivalent to myelography or radiculography in all the clinical groups of patients where both could be tested. There were a number of groups in which no myelograms had been requested, presumably because clinical suspicions had pointed toward conditions like tumours, developmental abnormalities and demyelinating diseases in which neurologists and neurosurgeons have already made up their minds about the superiority of MR. [ABSTRACT FROM AUTHOR]

This paper describes the evaluation of a computer advisor system (BRAINS), which was constructed to aid in the interpretation of CT images of the head. It was developed at the National Hospital for Nervous Diseases, Queen Square, London. The system was transferred, without difficulty, to an 'external', that is previously unassociated, site (the Department of Diagnostic Radiology, University of Manchester) for an external evaluation. Response of external users to the system was mixed. Many were unfamiliar with the concept of formal description of images and the evaluation demonstrated the need for a person to person training programme. Users who accessed the HELP facilities most frequently were the most successful in obtaining accurate descriptions and hence satisfactory diagnostic advice. An objective appraisal of user's success in describing images to obtain the correct diagnosis as first choice indicated that, in general, the system performed well. [ABSTRACT FROM AUTHOR]

This paper discusses the role of a computer advisor in MR image acquisition, interpretation and the diagnosis of cerebral disease. The development of an image and statistical database for use in providing advice is described. [ABSTRACT FROM AUTHOR]

This paper describes a prototype system to aid in the radiological interpretation of CT scan images of patients with cerebral disease. The system is able to provide guidance, both on diagnosis and the need for enhancement. [ABSTRACT FROM AUTHOR]

Although metrizamide is now being superseded by other contrast media, the mechanisms of its side effects may be of fundamental importance. One hundred and four consecutive patients with suspected cervical cord or root lesion were studied prospectively for factors which might influence the side effects of metrizamide myelography. Elderly patients were more prone to develop mental confusion. An earlier onset of dizziness and/or vertigo was associated with the lumbar route of intrathecal injection. Perhaps surprisingly, phenobarbitone prophylaxis shortened the duration of confusion and delayed the onset of headaches. Other factors, viz. sex, excess intracranial flow of metrizamide and myelographic blockage were not shown to have a significant influence on the adverse reactions. [ABSTRACT FROM AUTHOR]

Sixty-nine patients with cervical spondylotic myelopathy (CSM), radiculopathy (CSR), or both (CSMR) were studied with computed tomography (CT). Computer-assisted myelography (CAM) accurately determines the site and nature of spondylotic protrusions and provides good visualisation of the subarachnoid space and cord deformities even in areas with dilute metrizamide. However, excessive vertebral movement and bulging ligamenta flava with their effects on cord deformity, so easily visualised in myelograms, are completely or partially missed. In the assessment of CSM, metrizamide myelography (MM) followed by CAM should be performed, particularly when the myelographic images are unsatisfactory due to contrast dilution or blockage, when cord compression cannot be ascertained with MM and when cord atrophy is suspected. In CSR, the diagnostic information from MM and CAM is comparable. The diagnostic criteria in CAM are, however, less direct and since MM is adequate in uncomplicated cases, CAM is generally not necessary. The APD, APD/TD ratio, area and circularity are sensitive indices of cord deformity and the first two should be used more often to assist visual assessment of cord deformity. The relation between cord parameters and treatment response is better reflected in CSM cases managed conservatively and the results suggest that the degree of cord deformity is helpful in determining the outcome and hence the choice between surgical and conservative treatment. In plain CT, the osteophytes and calcified discs are adequately visualised and canal dimensions measured with accuracy, but the cervical cord and roots cannot be properly assessed and the diagnosis of CSM or CSR cannot be ascertained. At present, its role in cervical spondylosis is therefore limited. [ABSTRACT FROM AUTHOR]

Thirty-six control subjects had computer assisted myelography (CAM) using the EMI CT 5005 scanner. The normal cervical cord is elliptical, more circular at the upper and lower ends and flatter in the mid-segments. Asymptomatic cord deformities, usually mild, were present in nine subjects (25%). Four measurements, namely, sagittal diameter (APD), transverse diameter (TD), area (a) and circumference (c) were made and two more parameters calcultted i.e. APD/TD ratio and circularity (=4 π a/c). These control values form the basis of qualitative and quantitative assessment of cord deformity. When cord measurements are to be used, control values should be obtained for each scanner and procedures should be standardized [ABSTRACT FROM AUTHOR]

The safety of post-myelogram computed tomography (PMCT) as an additional diagnostic procedure to metrizamide myelography was evaluated. One hundred and four consecutive patients with suspected cervical cord lesions were studied prospectively; 50 had both myelography and PMCT, and the 54 acting as controls had only myelography. PMCT did not increase the incidence, severity or duration of common side effects and the majority of patients accepted this additional procedure. It is concluded that as long as care is taken to avoid the occurrence of excessive contrast in the intracranial subarachnoid space, PMCT is a safe procedure. [ABSTRACT FROM AUTHOR]

Experience with the 'BRW' CT stereotactic biopsy system is described and discussed. Some of the implications of CT-guided stereotactic surgery for a busy CT suite are explained. [ABSTRACT FROM AUTHOR]

Rupture of human cerebral arterial aneurysms is followed by prolonged cerebral arterial constriction; there is evidence that cerebrospinal fluid (CSF) from such patients contains vasoconstrictor substances which may cause the arterial constriction. The aim of this study was to develop a small animal model for investigating the effects of such CSF on the calibre of cerebral vessels in situ. Carotid angiography of the cerebral arteries of the rat visualises the internal carotid, middle cerebral, anterior cerebral and stapedial arteries plus the vertebrobasilar system. Prostacyclin was injected during carotid catheterisation to prevent spontaneous and random occlusion of these cerebral arteries; in the presence of prostacyclin there was no arterial occlusion for up to 5 h. The resolution achieved by the angiographic technique, which magnified the cerebral circulations 2.9 times, was sufficient to measure the diameter of the internal carotid and stapedial arteries of the rat. Intracarotid infusion of 1.0 ml CSF collected from patients with ruptured cerebral arterial aneurysms caused a rapidly developing contraction of cerebral arteries lasting up to 5 h. Thus, we consider that the rat may also be used as a model for investigating the aetiology of human cerebral arterial constriction after aneurysmal rupture. [ABSTRACT FROM AUTHOR]

The appearances on computed tomography (CT) in eight patients with mucopolysaccharidosis Type I [five with classical Type IH (Hurler disease)], two with mucopolysaccharidosis Type II (Hunter disease) and two with mucopolysaccharidosis Type IIIB (Sanfilippo B disease) are presented. Reference is also made to two further cases [mucopolysaccharidosis VI and mucopolysacharidosis IIIB] in which the CT showed special features. Follow-up scans were obtained to assess the evolution of the changes. The interplay of neuronal damage, cerebral atrophy and obstruction to the cerebrospinal fluid (CSF) circulation in the production of the cerebral manifestations, and the extent to which non-genetic factors influence the expression of the underlying biochemical lesion, are discussed. This series of patients illustrates the problem of classifying those with α-iduronidase deficiency, who do not have the classical Hurler disease phenotype (mucopolysaccharidosis IS and IH/S; Scheie disease and Hurler/Scheie disease), on the basis of currently available criteria. The place of CT in the diagnosis of complications due to thecal involvement is examined. The density of grey matter on the CT scans was similar to that of normal brain. Inhaled xenon did not produce any special enhancement which could be helpful in assessing the degree of the mucopolysaccharide deposition within cerebral cells. Symmetrical low attenuation in the white matter was a very common finding. It was not specifically associated with hydrocephalus and its relationship to some of the known neuropathological aspects of mucopolysaccharidoses is discussed. This work has shown that the stage in the evolution of the mucopolysaccharidoses at which hydrocephalus develops as a complication is highly variable and CSF diversion procedures are sometimes indicated to improve the quality of the patients' lives. These indications are briefly discussed. We consider that CT is essential for the adequate appraisal of these patients and to identify some treatable complications. [ABSTRACT FROM AUTHOR]

The entry of I-metrizamide and of I-diatrizoate from blood into brain has been studied in rabbits. The blood-brain barrier is very tight to both molecules, all cerebral regions having spaces between 0.5 and 2% after maintenance of constant blood levels for 4 h. In extraneural tissues both compounds appear to distribute in extracellular fluid except for accumulation of metrizamide by the liver and perhaps the small intestine. Profiles of radioactivity through cerebral gray matter have been obtained following ventriculocisternal perfusion of artificial cerebrospinal fluid containing I-metrizamide. The nature of these profiles and their behavior with time suggest that metrizamide passes through gray matter by simple diffusion, that it is largely distributed in the extracellular fluid and that back movement across the blood-brain barrier is small. [ABSTRACT FROM AUTHOR]

The high resolution CT scanning system introduced by EMI in 1978 has added a new dimension to computerised tomography in otology. The apparatus used for this study was an EMI CT 5005 body scanner adapted for head and neck scanning and incorporating a high resolution facility. The latter has proved most advantageous in areas of relatively high differential absorption, so that its application to the demonstration of abnormalities in the petrous temporal bone, and in particular middle ear disease has been very rewarding. Traumatic ossicular disruptions may now be demonstrated and the high contrast of CT often shows them better than conventional hypocycloidal tomography. The stapes is also better visualised and congenital abnormalities of its superstructure have been recorded. These studies have been achieved with a very acceptable level of radiation to the eye, lens and cornea and the technique is clearly a rival to conventional pluridirectional tomography in the assessment of the petrous temporal bone. With further design improvements high resolution CT could completely replace existing techniques. [ABSTRACT FROM AUTHOR]

The spinal cord is not consistently shown by plain computed tomography or with iodide enhancement. Xenon enhancement increases the attenuation of the spinal cord and visualization is improved considerably; fluid-filled cavities, including syringohydromyelia, do not enhance and are clearly defined. [ABSTRACT FROM AUTHOR]

The site of lesions responsible for horizontal gaze palsy and various types of internuclear ophthalmoplegia (INO) was established by identifying the common areas where the abnormal MRI signals from patients with a given ocular-motor disorder overlapped. Patients with unilateral gaze palsy had lesions in the paramedian area of the pons, including the abducens nucleus, the lateral part of the nucleus reticularis pontis caudalis and the nucleus reticularis pontis oralis. Patients with abducens nucleus lesions showed additional clinical signs of lateral rectus weakness. Lesions responsible for bilateral gaze palsy involved the pontine tegmental raphe. Since this region contains the saccadic omnipause neurons, this finding suggests that damage to omnipause cells produces slowing of saccades rather than opsoclonus, as previously proposed. All INOs, regardless of the presence of impaired abduction or convergence, had similar MRI appearances. Frequently the lesions in patients with INO, were not confined to the medial longitudinal fasciculus (MLF) but also involved neighbouring structures at the pontine and mid-brain levels. There was a statistically significant association between the clinical severity of the INO and the presence of abnormal abduction or convergence. The findings suggest that the lesions outside the MLF, which may affect abducens, gaze or convergence pathways, are responsible for the presence of features additional to INO, depending on the magnitude of functional disruption they produce. [ABSTRACT FROM AUTHOR]

Fifty one patients with abnormalities of horizontal gaze were studied with magnetic imaging of the brain (MRI) and eye movement recordings to identify the loci of lesions responsible for isolated abducens palsy, conjugate gaze palsy and different types of internuclear ophthalmoplegias. The lesions responsible for a particular disorder were identified by overlapping enlarged drawings of the individual scans at comparable brain-stem levels and identifying the areas where the abnormal MRI signals intersected. A statistical procedure was devised to exclude the possibility that the areas of overlap occurred by chance. In this paper, the findings in the group of patients with VI nerve palsy are reported since the location of their lesions could be predicted from known anatomy, so validating the procedure. The results were independently obtained with the overlapping technique and the statistical procedure and showed that the lesions were located in a region corresponding to the posterior part of the abducens fasciculus. This confirms that central lesions producing isolated lateral rectus weakness spare the abducens nuclei. The agreement between the procedures used and earlier clinical and experimental results suggest that the method we describe can be applied to locate the site of lesions on MRI scans in other groups of patients with more complex gaze disorders. [ABSTRACT FROM AUTHOR]

Ten patients with multiple sclerosis (MS) and psychosis were assessed using the Present State Examination, and matched retrospectively with respect to age, disability, duration of symptoms, and disease type with 10 MS patients without psychosis. Both groups underwent MRI of the brain. There was a trend for the psychotic group to have a higher total lesion score, particularly around the periventricular areas. This reached statistical significance in the areas around the temporal horn. In all cases, neurological symptoms preceded the onset of psychosis. The psychotic group also had a later age of onset of psychosis than psychotic patients without brain disease. These results point to an aetiological association between the pathological process of MS and psychosis. [ABSTRACT FROM AUTHOR]

The case notes of 170 consecutive patients with a suggestive clinical history, or a proven final diagnosis of a posterior fossa lesion have been analyzed in order to determine the precise value of each radiological investigation. All had had CT scans. The patients have been grouped clinically according to their presenting signs and symptoms. The analysis suggests some well-defined regimes of investigation and indicates the successes and failures of radiology. [ABSTRACT FROM AUTHOR]

The value of computerized axial tomography (CAT) in the management of intracranial infections is described and the findings compared with those of other conventional neuroradiological investigations. The most important contribution is in the diagnosis and localization of cerebral abscess. CAT provides not only information of the nature of the lesion but also the number of loculi and the presence of multiple lesions; it is the investigation of choice for follow-up of patients with cerebral abscess treated either by operation or conservatively. CAT is invalueither in the investigation of other infectious conditions affecting the intracranial structures, especially when patients present with a focal neurological deficit and it is vital to exclude an abscess. [ABSTRACT FROM AUTHOR]

Copyright of Neuroradiology is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Neuroradiology is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Neuroradiology is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Thirty five adults and two children with clinically isolated optic neuritis were examined by magnetic resonance imaging (MRI) to determine the presence of disseminated lesions within the brain at presentation and to compare these findings with the results of evoked potential studies. Of the adult patients, 61% showed lesions on the scans whereas the evoked potentials suggested the presence of lesions outside the visual system in 30%. MRI is a sensitive method for the demonstration of clinically unsuspected lesions in patients with uncomplicated optic neuritis. [ABSTRACT FROM AUTHOR]

Twenty-four cases have been operated upon using a prototype Brown-Roberts-Wells, CT-guided stereotactic neurosurgical system. This device has proved to be practical and flexible in clinical use. No CT scanner modifications were required, a fact which simplified its use in more than one hospital. Multiple targets can be biopsied with ease and relative safety. Drainage and other therapeutic procedures can be carried out with minimal hazard. Future applications of this system may include its use with NMR and PET images. [ABSTRACT FROM AUTHOR]

The responses of baboon cerebral and extracerebral arteries to prostaglandin endoperoxide (PGH2) and prostacyclin (PGI2) were investigated on isolated arteries and in vivo by serial angiography. Both PGH2 and PGI2 could produce dose-dependent contraction or relaxation of isolated arteries. PGH2 induced relaxation was indicative of prostacyclin synthetase activity, the enzyme which converts PGH2 to PGI2. In isolated arteries tested one to four hours post mortem only the vertebral artery showed prostacyclin synthetase activity. Thus PGH2 induced contraction of cerebral arteries may be indicative of a physiological function. Vasomotor tone may in part be the result of a balance between PGH2 constriction and PGI2 dilatation. In vivo PGI2 infusion caused pronounced and prolonged dilatation of cerebral arteries, which lasted longer than the cardiovascular changes. As PGI2 is the most potent cerebral vasodilator drug tested, it may be of clinical use in the treatment of cerebral vasospasm. [ABSTRACT FROM AUTHOR]

The relationship between clinical condition and vasoconstrictor factors in cerebrospinal fluid was studied in 19 patients for up to six weeks after subarachnoid haemorrhage. Vasoconstrictor activity was assayed biologically. Sixteen of 19 patients improved as vasoconstrictor activity declined; this pattern was not significantly influenced by surgery. Serial angiography was performed on three patients and a qualitative relationship was shown between arterial dilatation, clinical improvement, and reduced pharmacological activity. [ABSTRACT FROM AUTHOR]

The mode of anaesthesia used during pneumoencephalography has a significant effect on the size of the cerebral ventricles 24 hours after the procedure. Post-encephalographic ventricular enlargement is less marked in patients examined under nitrous oxide anaesthesia. This appears to be related to passage of the gas into the ventricles during the encephalogram, and subsequent diffusion outwards. Variations in arterial carbon dioxide tension during the anaesthesia do not contribute significantly to changes in ventricular size. However, both hyperventilation and inhalation of nitrous oxide may cause apparent increase in size of the cerebral sulci. [ABSTRACT FROM AUTHOR]

Patients suffering from severe migraine, usually for many years, have been examined by the EMI scanner between attacks. Judged by criteria validated originally by comparison with pneumoencephalography, about half of the patients showed evidence of cerebral atrophy. Perhaps of more significance than generalised atrophy was the frequency of areas of focal atrophy and of evidence of infarction. [ABSTRACT FROM AUTHOR]

Computerized tomography, using the EMI Scanner, allows the diagnosis of cerebral atrophy or hydrocephalus to be made with the same degree of accuracy as conventional neuroradiological methods. Ventricular measurements made on EMI scans have been compared with those from pneumoencephalograms and ventriculograms. A range of normal ventricular measurements for the EMI scan is suggested. [ABSTRACT FROM AUTHOR]