Task demand modulations of visuospatial processing measured with functional magnetic resonance imaging

Brain imaging based on functional magnetic resonance imaging (fMRI) provides a useful tool to examine neural networks and cerebral structures subserving visuospatial function. It allows not only the qualitative determination of which areas are active during task processing, but also estimates the quantitative contribution of involved brain regions to different aspects of spatial processing. In this study, we investigated in 10 healthy subjects how the amount of task (computational) demand in an angle discrimination task was related to neural activity as measured with event-related fMRI. Task demand, indicated by behavioral performance, was modulated by presenting clocks with different angular disparity and length of hands. Significant activations were found in the cortical network subserving the visual and visuospatial processing, including the right and left superior parietal lobules (SPL), striate visual areas, and sensorimotor areas. Both blood oxygenation level-dependent (BOLD) signal strength and spatial extent of activation in right as well as left SPL increased with task demand. By contrast, no significant correlation or a very weak correlation was found between the task demand and the BOLD signal as well as between task demand and spatial extent of activations in the striate visual areas and in the sensorimotor areas. These results support the hypothesis that increased computational demand requires more brain resources. The brain regions that are most specialized for the execution of the visuospatial task can be assessed by relating the imposed task demand to the functional activation measured.     

Rapid activation of haemostasis after hormonal emergency contraception

Hormonal emergency contraception (EC) is a well established contraceptive method, recommended to all women, although the effects on haemostais are not fully evaluated. The aim of this study was to evaluate whether exposure to EC has effects on well established cardiovascular risk factors, and also to examine whether differences exist between two EC treatments. In a prospective randomized cross over design 11 women used two different EC methods, one with estrogen and levonorgestrel (EE-EC) and one with levonorgestrel only (LNG-EC). Plasma concentrations of haemostatic factors (APC resistance, antithrombin, fibrinogen, prothrombin fragment 1 + 2, free protein S, factorVII and PAI-1), sex-hormone-binding globulin (SHBG), the apolipoprotein (apo)B/apoA1 ratio and C-reactive protein (CRP) were followed frequently during the following 48 hours. A rapid haemostatic activation was induced with both treatments, although more pronounced with EE-EC. Already two hours after EC, the plasma concentrations of haemostatic parameters and SHBG were significantly different from baseline concentrations. An ETP-based APC-resistance method showed increased APC resistance with EE-EC and decreased APC resistance with LNG-EC. The ApoB/ApoA1 ratio was affected in a favourable direction with EE-EC.CRP increased slightly regardless of treatment. Even a very short exposure to exogenous sex hormones causes prompt effects on hepatic protein synthesis and the coagulation system. This must be taken into consideration whenever exogenous steroid hormones are administered, especially to individuals with a genetic predisposition to thrombosis or transiently disturbed haemostasis.     

Patient selection has a strong impact on cystatin C and Modification of Diet in Renal Disease (MDRD) estimated glomerular filtration rate

ObjectiveEstimation of the glomerular filtration rate (GFR) is essential for the evaluation of patients with kidney disease, and for correct dosage of drugs that are eliminated from the circulation by the kidneys. In most cases GFR is estimated based on serum creatinine and the Modification of Diet in Renal Disease (MDRD) formula. As both cystatin C and creatinine are used for the determination of GFR it is important to investigate if estimated GFR by the two methods differ in various patient groups.Design and methodsWe have compared cystatin C and MDRD estimated GFR calculated from the same request from primary care units (n = 488), a cardiology ward (n = 826), the cardiointensive care unit (n = 1026), two oncology wards (n = 919 and 1021), and the neurosurgical intensive care unit (n = 1515) in an observational cross-sectional study.ResultsWe found better agreement between the two GFR estimates in samples from primary care patients and patients in the cardiology wards, than in samples from oncology wards or the neurosurgical intensive care unit. In the latter settings there was a pronounced difference between the two GFR estimates.ConclusionThe comparisons show that differences in patient selections have a strong impact on the agreement between cystatin C and MDRD estimated glomerular filtration rate.     

Zygoma fixture in the management of advanced atrophy of the maxilla: technique and long-term results.

Despite refinements in surgical technique, including bone grafting and sophisticated prosthetic reconstructions, there are limitations to what can be achieved with bone-anchored fixed prostheses in patients with advanced atrophy of the maxillae. A new approach was suggested by a long-term study on onlay bone grafting and simultaneous placement of a fixture based on a new design: the zygoma fixture, and the aim of this study was to assess its potential. Twenty-eight consecutive patients with severely resorbed edentulous maxillae were included, 13 of whom had previously had multiple fixture surgery in the jawbone that had failed. A total of 52 zygoma fixtures and 106 conventional fixtures were installed. Bone grafting was deemed necessary in 17 patients. All patients have been followed for at least five years, and nine for up to 10 years. All patients were followed up with clinical and radiographic examinations, and in some cases rhinoscopy and sinoscopy as well. Three zygoma fixtures failed; two at the time of connection of the abutment and the third after six years. Of the conventional fixtures placed at the time of the zygoma fixture, 29 (27%) were lost. The overall prosthetic rehabilitation rate was 96% after at least five years of function. There were no signs of inflammatory reaction in the surrounding antral mucosa. Four patients with recurrent sinusitis recovered after inferior meatal antrostomy. To conclude, the zygoma fixture seems to be a valuable addition to our repertoire in the management of the compromised maxilla.     

Mild cognitive impairment--beyond controversies, towards a consensus: report of the International Working Group on Mild Cognitive Impairment

The First Key Symposium was held in Stockholm, Sweden, 2-5 September 2003. The aim of the symposium was to integrate clinical and epidemiological perspectives on the topic of Mild Cognitive Impairment (MCI). A multidisciplinary, international group of experts discussed the current status and future directions of MCI, with regard to clinical presentation, cognitive and functional assessment, and the role of neuroimaging, biomarkers and genetics. Agreement on new perspectives, as well as recommendations for management and future research were discussed by the international working group. The specific recommendations for the general MCI criteria include the following: (i) the person is neither normal nor demented; (ii) there is evidence of cognitive deterioration shown by either objectively measured decline over time and/or subjective report of decline by self and/or informant in conjunction with objective cognitive deficits; and (iii) activities of daily living are preserved and complex instrumental functions are either intact or minimally impaired.     

Urinary excretion and blood concentrations of trace elements and electrolytes during total parenteral nutrition in crohn's disease

Urinary excretion of trace elements (Cr, Co, Cu, Fe, Mn, Se, Zn, Sb, Cs, Rb), electrolytes (Na, K, Ca, Mg, phosphate), and nitrogen were determined during days 1–5 and 54–79 of total parenteral nutrition (TPN, nil per os) given to six patients with Crohn's disease. Whole-blood concentrations of Cr, Fe, Zn, Cs, and Rb and serum concentrations of electrolytes were determined before the TPN and on days 54–79 of TPN. The 24-hr urinary excretion of zinc was lower on days 54–79 than on days 1–5, but the rates of excretion of the other essential trace elements during TPN displayed no significant change. The urinary excretion of Cu, Fe, and Mn was numerically lower than the intravenous administration of these elements during days 1–5 and 54–79 of TPN, whereas the urinary excretion of zinc was lower than the supply only during days 54–79. The whole-blood concentration of zinc was low but constant during TPN, whereas the initially low levels of Cr and Fe were normalized on days 54–79. The results suggest that the supply of the essential trace elements Cr, Co, Cu, Fe, Mn, and Zn was largely adequate during two to three months of TPN and that the human body may adapt to a somewhat low supply of zinc, 20–30 mol/24 hr.     

Melagatran attenuates fibrin and platelet deposition in a porcine coronary artery over-stretch injury model.

Melagatran is the active form of the oral direct thrombin inhibitor, ximelagatran. The purpose of this study was to compare the effects of different doses of melagatran with heparin or placebo on platelet deposition and relative fibrin content after coronary angioplasty in pigs. After 125I-labelled fibrinogen and autologous 111Indium-labelled platelets had been infused a balloon injury was performed in the left anterior descending and the right coronary arteries. Pigs were randomized to receive either heparin 200 IU/kg bolus plus 20 IU/kg per h infusion (n = 7); melagatran 1 mg/kg bolus plus 0.33 mg/kg per h infusion (n = 7); melagatran bolus 0.5 mg/kg plus 0.17 mg/kg per h infusion (n = 7); melagatran 0.15 mg/kg bolus plus 0.05 mg/kg per h infusion (n = 6) or saline (n = 4). Seventy-five minutes after the angioplasty, the pigs were euthanized and the injured vessel segments were measured in a gamma counter. Compared with placebo, platelet deposition and relative fibrin content were reduced after both heparin and melagatran, in the latter case with a dose-response relationship. Melagatran reduced platelet deposition and relative thrombus size in a dose-dependent manner when compared with placebo after coronary angioplasty in pigs. No statistically significant difference between melagatran and heparin was found.