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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]

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 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]

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]

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]

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]