A number of individual, ergonomic, and organizational factors of presumed importance for the occurrence of musculoskeletal disorders were investigated in a group of 260 visual display terminal (VDT) workers. The cross-sectional study utilized medical and workplace investigations as well as questionnaires. The results were subjected to a multivariate analysis in order to find the major factors associated with various upper-body muscular problems. Several such factors were identified for each investigated type of musculoskeletal problem. Some were related to the individual: age, gender, woman with children at home, use of spectacles, smoking, stomach-related stress reactions, and negative affectivity. Organizational variables of importance were opportunities for flexible rest breaks, extreme peer contacts, task flexibility, and overtime. Identified ergonomic variables were static work posture, hand position, use of lower arm support, repeated work movements, and keyboard or VDT vertical position.

Cerebral blood flow (CBF) and cerebral metablic rate for oxygen (CMRO2) have been studied during sustained epileptic seizures induced by bicuculline (1-2 mg/kg, i.v.) in paralysed Wistar rats, artificially ventilated with nitrous oxide/oxygen. CBF was determined by venous outflow collection, and by 133Xe desaturation, using sagittal sinus blood (for cerebral cortical flow) or retroglenoid venous blood (for 'whole brain' flow). The procedure employed ensured that arterial oxygenation remained normal and blood glucose concentration was normal or high throughout the seizure. Arterial hypotension was prevented by the infusion of donor blood. CBF increased concurrently with seizure onset, reaching a maximum nine times higher than control value after 15-60 s. This was due to a marked rise in mean arterial pressure (to greater than 180 torr) and a dramatic fall in cerebrovascular resistance to less than 15 per cent of control). Subsequently, with decreasing blood pressure, CBF slowly diminished, being more than four times higher than control at 20 min, and slightly less than three times higher than control at two hours. The different procedures for measuring CBF gave closely similar results. A threefold increase relative to control CMRO2 (7-6 ml/100 g-1/min-1 for 'whole brain,' and 10-2 ml/100 g-1/min-1 for cerebral cortex) was measured after 1-20 min of seizure activity (utilizing either the venous outflow or the 133Xe desaturation procedure for CBF determination). After two hours of seizure activity CMR02 was still more than twice as high as the control. This high metabolic rate during sustained seizure activity will increase the susceptibility of the brain to 'ischaemic' damage during prolonged seizures in man in which an additional metabolic stress may be imposed by cerebral hypoxia, arterial hypotension, hyperpyrexia or hypoglycaemia.

Relationships between visual display terminal (VDT) use and musculoskeletal problems were examined in a group of 353 office workers, using data from medical and workplace investigations as well as questionnaires. There were no general differences between VDT and non-VDT users as to the occurrence of muscle problems. Combinations of specific VDT work situations such as data entry work or work with a VDT for more than 20 h/week and the presence of some other factors were, however, associated with excess risks of certain muscle problems. The extraneous factors involved in the definitions of such risk groups were: use of bifocal or progressive glasses at a VDT; stomach-related stress reactions; limited rest break opportunity; repetitive movements; non-use of lower arm support; and possibly the vertical position of the keyboard; and presence of specular glare.

RETINAL VASCULAR AUTOREGULATION/7ac/i/6aHa et al. CAROTID OCCLUSION is the single most common arterial lesion considered for extra-intracranial bypass operation. 1 Although this procedure is performed in numerous patients, its definitive therapeutic value remains unproven. In most centers, bypass surgery is confined to patients with TIA or only mild stroke at the time of the occlusion, and is attempted to reduce the incidence of future stroke.Recent studies suggest that the long term prognosis in carotid occlusion is favorable, with a stroke rate on the occluded side of only 1-2% per year. 2 ' 3 This would limit the value of bypass surgery as a general prophylactic measure in carotid occlusion. Because a bypass operation is a hemodynamically directed procedure, the identification of a subset of patients with impaired capacity of the collateral circulation would be of importance.In this report we examine the usefulness of rCBF (regional cerebral blood flow) studies in evaluating hemodynamic features in carotid occlusion. Patients and Methods Thirty-nine patients with unilateral carotid occlusion were examined with rCBF by 133 Xenon inhalation. The patients were collected in the following manner. Twenty-six patients were evaluated for bypass operation after angiographic identification of the occlusion at this or at an admitting hospital. The interval between the onset of the symptoms and the rCBF study was one to six months in these patients. From a recent study on the long-term prognosis in carotid occlusion, 3 a further 13 patients with previous TIA or minor stroke were randomly selected for rCBF examination, performed one to nine years after the diagnosis of occlusion was established. The ratio male/female was 31/8 and the mean age of the patients was 60 years (range 34-77 years). An almost constant finding was interhemispheric asymmetry, the degree of which was correlated with the severity of the initial symptoms. An ischemic focus was an insignificant finding. The C0 2 response was normal in patients with angiographic signs of circle of Willis collateral flow and without significant contralateral carotid stenosis, whereas it was impaired in patients with a retrograde ophthalmic flow or collateral flow via the circle of Willis and contralateral carotid stenosis ^ 50%. It is concluded that the CO* response is a useful rCBF variable and may be applied for analysis of collateral flow capacity in patients with carotid artery occlusion considered for bypass surgery.

Several previous studies have demonstrated that severe hypoglycemia is accompanied by consumption of endogenous brain substrates (glycolytic and citric acid cycle metabolites and free amino acids) and some have shown a loss of structural components as well, notably phospholipids. In the present study, on paralysed and artificially ventilated rats, we measured cerebral oxygen and glucose consumption during 30 min of hypoglycemic coma (defined as hypoglycemia of sufficient severity to cause cessation of spontaneous EEG activity) and calculated the non‐glucose oxygen consumption. In an attempt to estimate the missing substrate we measured tissue concentrations of phospholipids and RNA. After 5 min of hypoglycemic coma, tissue phospholipid content decreased by about 8% with no further change during the subsequent 55 min. A similar reduction remained after 90 min of recovery, induced by glucose administration following 30 min of coma. Since no preferential loss of polyenoic fatty acids or of ethanolamine phosphoglycerides occurred, it is concluded that loss of phospholipids was due to phospholipase activity rather than to peroxidative degradation. The free fatty acid concentration increased sixfold after 5 min of coma and remained elevated during the course of hypoglycemia. A 9% reduction in tissue RNA content was observed after 30 min of hypoglycemia. Calculations indicated that available endogenous carbohydrate and amino acid substrates were essentially consumed after 5 min of coma, and that other non‐glucose substrates must have accounted for approximately 50μmol·g−1 of oxygen (8.3 μmol·g−1 in terms of glucose equivalents) within the 5–30 min period. The 10% reduction in phospholipid‐bound fatty acids was more than sufficient (in four‐ to fivefold excess) to account for this oxygen consumption. However, since no further degradation occurred in the 5–30 min period, there is no simple, direct, quantitative relationship between oxygen consumption and cortical fatty acid oxidation during this interval. The possibility thus remains that unmeasured exogenous or endogenous substrates were utilized.