Biomedical subjects

L Nyberg

Publications and source records attributed to L Nyberg.

At least 73 records · Page 4Linked to original sources

PubMed1997

Fall prediction index for patients in stroke rehabilitation.

BACKGROUND AND PURPOSE: The identification of stroke patients who are prone to falls is essential to the development of prevention strategies. This study aimed at developing an easily administered fall risk index for patients in stroke rehabilitation. METHODS: A consecutive series of 135 patients in geriatric stroke rehabilitation was studied. Patient characteristics viewed as potential fall predictor variables were assessed at admission. Univariate and multiple Cox regression analyses of these variables were used in the development of a fall prediction index. RESULTS: The final index included the following items: male sex, poor performance of activities of daily living, urinary incontinence, impaired postural stability, bilateral motor impairment, presence of bilateral cortical or white matter lesions, visuospatial hemineglect, and use of diuretics, antidepressants, or sedatives. The index score correlated significantly with the fall risk (odds ratio, 1.46; 95% confidence interval, 1.26 to 1.69). The score was also used to classify individuals into low-, intermediate-, and high-risk groups, among which the fall rates differed significantly (log rank statistics, 29.86; P < .001). CONCLUSIONS: An easily administered fall risk index is suggested, which might serve as a basis for prevention strategies among patients in stroke rehabilitation.

Accidental Falls↗

PubMed1997

Incidence of falls in three different types of geriatric care. A Swedish prospective study.

The incidence and consequences of falls were investigated in three different types of Swedish geriatric care clinics: a geriatric rehabilitation clinic, a psychogeriatric clinic and a nursing home. Falls were prospectively registered by the nursing staff. The incidence rate (and 95% confidence interval) of falls per 10,000 patient days of the psychogeriatric clinic was 171 (146-196), compared with 92 (72-112) at the geriatric rehabilitation clinic, and 31 (22-41) at the nursing home. Most falls (62%) did not result in injury, while major injuries occurred in 5%. We conclude that accidental falls are a major problem in geriatric care in Sweden, but there is a considerable difference in incidence rates between different types of institutions.

Accidental Falls↗

PubMed1996

General and specific brain regions involved in encoding and retrieval of events: what, where, and when.

Remembering an event involves not only what happened, but also where and when it occurred. We measured regional cerebral blood flow by positron emission tomography during initial encoding and subsequent retrieval of item, location, and time information. Multivariate image analysis showed that left frontal brain regions were always activated during encoding, and right superior frontal regions were always activated at retrieval. Pairwise image subtraction analyses revealed information-specific activations at (i) encoding, item information in left hippocampal, location information in right parietal, and time information in left fusiform regions; and (ii) retrieval, item in right inferior frontal and temporal, location in left frontal, and time in anterior cingulate cortices. These results point to the existence of general encoding and retrieval networks of episodic memory whose operations are augmented by unique brain areas recruited for processing specific aspects of remembered events.

Adult↗

PubMed1996

Network analysis of positron emission tomography regional cerebral blood flow data: ensemble inhibition during episodic memory retrieval.

Two important objectives in the neuroscience of memory are (1) identification of neural pathways involved in memory processes; and (2) characterization of the pattern of interactions between these pathways. Functional neuroimaging can contribute to both of these goals. Using image subtraction analysis of regional cerebral blood flow data measured with positron emission tomography, we identified brain regions that changed activity during episodic memory retrieval (visual work recognition). Relative to a baseline reading task, decreased activity was observed in bilateral prefrontal, bilateral anterior and posterior temporal, and posterior cingulate cortices. Brain regions showing increased activity were the right prefrontal (different from deactivated regions), left anterior cingulate, and left occipital cortices, and vermis of cerebellum. We then performed a network analysis with structural equation modeling to test the hypothesis that regional decreases came about through active inhibition by regions showing increased activity during retrieval. This analysis demonstrated that the influence of activated regions on deactivated regions was more negative during retrieval than during reading, confirming the inhibition hypothesis. Such confirmation could not have been made from the subtraction analysis alone because decreases can come about, at the very least, through reduction of functional influences as well as by active inhibition. The concepts of ensemble excitation and inhibition, as defined through network analysis, are introduced. We argue that is is critical to examine the combined pattern of excitatory and inhibitory influences to fully appreciate the neural basis of episodic memory.

Analysis of Variance↗

PubMed1996

Activation of medial temporal structures during episodic memory retrieval.

Medial temporal lobe structures have been implicated in human episodic memory. Patients with medial temporal lesions show memory deficits, and functional neuroimaging studies have revealed activation in this region during episodic encoding and retrieval when data are averaged over a sample of subjects. The relevance of such observations for memory performance has remained unclear, however. Here we have used positron emission tomography (PET) to examine cerebral blood flow related to verbal episodic retrieval. We observed strong positive correlations between retrieval and blood flow in left medial temporal structures in individual normal human subjects. In addition, multivariate analysis showed that regions in the left medial temporal lobe were dominant components of a pattern of brain regions that distinguished a high-retrieval condition from conditions of lower retrieval. These results suggest that medial temporal activity is related to retrieval success rather than retrieval attempt, possibly by reflecting reactivation of stored patterns.

Brain Mapping↗

PubMed1996

Identification of an alkaline sphingomyelinase activity in human bile.

The hydrolysis of sphingomyelin has been found to generate important signals regulating cell proliferation, differentiation and apoptosis. However, the enzymes responsible for digestion of dietary sphingomyelin have not been well documented. This study demonstrates the occurrence of a sphingomyelinase (SMase) in both human hepatic bile and gallbladder bile. The enzyme was equally found in both bacteria negative and positive bile samples and in samples obtained from patients with or without gallbladder diseases. A bacteria-free gallbladder bile was used for characterization. It was found that bile SMase hydrolyzed sphingomyelin to phosphorylcholine and ceramide with negligible activity against either phosphatidylcholine or p-nitrophenyl phosphate. The enzyme preferred an alkaline condition and the optimal pH was 9. The activity of this alkaline SMase was bile salt dependent and was fully activated by 4-6 mM bile salts. Triton X-100, the non-ionic detergent did not activate bile SMase. Ca2+ and Mg2+ ions had no significant effect at optimal bile salt concentration. The molecular mass of this enzyme was about 85 kDa as measured by Sephadex G200 gel chromatography. In conclusion, we demonstrated a SMase in bile which differs markedly from the known acid and neutral SMase. Its potential important roles in sphingomyelin digestion and gallbladder diseases require further investigation.

Alkalies↗

PubMed1996

Distribution of alkaline sphingomyelinase activity in human beings and animals. Tissue and species differences.

The alkaline sphingomyelinase (SMase) was first found in rat intestinal brush border. The important roles of this enzyme in digestion of sphingomyelin and in mucosal cell proliferation have been suggested. In the present work, the distribution of the alkaline SMase in the tissues of human beings and animals have been studied. By assaying the enzyme activity in human biopsy samples, we found that the alkaline SMase activity was absent in the stomach, increased in the duodenum, present at high levels in the small intestine, and slightly declined in the colon and rectum. High activities were found similarly in the intestinal contents of the healthy adults and infants. The activities were also found in the intestinal mucosa of rats, normal and germ-free mice, and hamsters with the same distribution pattern as in humans, but not in the intestinal mucosa of guinea pigs. Apart from the intestinal tract, a SMase activity preferring alkaline pH was identified in human and guinea pig bile, but not in the bile of rat, pig, sheep, and cow. No activity was found in either pancreatic tissue or pancreatic juice in all species tested, and none was detected in human urine and milk. In conclusion, alkaline SMase exists predominantly in the digestive system with considerable tissue and species differences.

Adult↗

PubMed1996

Age differences in episodic memory, semantic memory, and priming: relationships to demographic, intellectual, and biological factors.

This study examined age differences in episodic memory, semantic memory, and priming using a random sample of 1,000 men and women from 10 age groups (35, 40, 45, . . . 80 years). The main purpose was to determine whether an age effect existed after differences on various demographic, intellectual, and biological factors had been controlled for. The simple correlations of age with episodic and semantic memory performance were found to be significant, whereas no relationship was found between age and levels of priming. After controlling for differences on the background factors, age predicted episodic but not semantic memory performance. It is proposed that the failure to account for the age effect on episodic memory is because it is caused by age-related neuronal changes.

Adult↗

PubMed1996

Falls leading to femoral neck fractures in lucid older people.

OBJECTIVE: To analyze the mechanisms of falls that result in femoral neck fractures among lucid older people. DESIGN: A cross-sectional study. SETTING: An orthopedic university hospital department. PARTICIPANTS: A consecutive series of 123 lucid patients, 65 years of age or more, who were admitted for femoral neck fractures. MEASUREMENTS: On admission, the subjects were interviewed about fracture accident characteristics, and falling mechanisms were classified. An arterial blood gas sample was taken from each patient soon after admission. Based on data regarding drug consumption and social and medical characteristics, a fall-risk index was calculated for each subject. RESULTS: It was ascertained that 95% of the fractures were caused by falls and < 2% were spontaneous. Most accidents (68%) took place indoors, 47% of the falls were classified as extrinsic, 24% as intrinsic, 7% as nonbipedal, and 22% remained unclassified. Almost all outdoor falls were extrinsic; however, intrinsic falls were as common as extrinsic falls indoors (P < .001). Extrinsic fallers presented a significantly lower fall-risk index score than subjects with fractures caused by intrinsic, nonbipedal, and unclassifiable falls. A large proportion of subjects (24%) wre hypoxemic (pO2 < 8 kPa) on admission, and patients who sustained fractures at night had lower oxygen tension than that of daytime fallers (P = .006). CONCLUSIONS: Accidental falls are the primary cause of femoral neck fractures. Preventive actions should be directed toward intrinsic, as well as extrinsic, risk factors for falls. Hypoxemia might be a risk factor for falls, especially those falls that occur at night.

Accidental Falls↗

PubMed1996

Using the Downton index to predict those prone to falls in stroke rehabilitation.

BACKGROUND AND PURPOSE: Falls are a major complication in inpatient stroke rehabilitation. An important issue in preventive strategies is the early identification of those at risk. This study aimed at assessing the fall-prediction accuracy of an easily administered fall risk index in stroke rehabilitation. METHODS: A consecutive series of 135 patients admitted to a geriatric stroke rehabilitation unit was studied. A score on the Downton fall risk index was obtained from the admission assessment data and used as a predictive indicator of the risk of falls. The patients' falls were prospectively recorded during their rehabilitation stay. The correlation between falls and the predicted risk was assessed by means of survival analysis and a multiple regression analysis, adjusting for the time of observation. RESULTS: The risk of falls as a function of the time observed was significantly greater among those predicted to be at high risk (index score > or = 3) than among the others (P = .009, log-rank test; odds ratio, 2.9). Furthermore, the number of falls during rehabilitation stay was moderately correlated (R = .57) with the fall risk index sum when adjusted as for the time of observation. The sensitivity of the fall prediction as to outcome was 91%, whereas the specificity was limited to 27%. CONCLUSIONS: A moderately high correlation was found between the predicted and the observed risk of falls in stroke rehabilitation when the Downton fall risk index was used. However, a low specificity rate limits the accuracy of the prediction.

Accident Proneness↗

PubMed1995

Functional brain maps of retrieval mode and recovery of episodic information.

Positron emission tomography (PET) was used to identify brain regions associated with two component processes of episodic retrieval; those related to thinking back in subjective time (retrieval mode) and those related to actual recovery of stored information (ecphory). Healthy young subjects recognized words that had been encoded with respect to meaning or the speaker's voice. Regardless of how the information had been encoded, recognition was associated with increased activation in regions in right prefrontal cortex, left anterior cingulate, and cerebellum. These activations reflect retrieval mode. Recognition following meaning encoding was specifically associated with increased activation in left temporal cortex, and recognition following voice encoding involved regions in right orbital frontal and parahippocampal cortex. These activations reflect ecphory of differentially encoded information.

Adult↗

PubMed1995

Alkaline sphingomyelinase activity in rat gastrointestinal tract: distribution and characteristics.

Previous studies indicated that there was an alkaline sphingomyelinase (SMase) activity in small intestine, but its properties have not been studied in detail. In the present work, we studied the distribution of this enzyme activity in rat gastrointestinal tract and characterized it in intestinal mucosal homogenates. Little alkaline SMase activity was detected in the stomach and the duodenum. The activity in both mucosa and intestinal content increased in the small intestine and reached the maximum at the distal jejunum, then declined in the ileum and slightly increased again in the colon. The activity distribution pattern differed markedly from those of acid SMase and alkaline phosphatase. Little alkaline SMase activity could be found in bile, liver and pancreas before or after treatment with trypsin. The optimum pH of the alkaline SMase was 9. It specifically hydrolyzed sphingomyelin (SM), not phosphatidylcholine, to ceramide and phosphocholine. The alkaline SMase was bile salt dependent and was optionally activated by 3 mM bile salts. Triton X-100 could not mimic the effect of bile salt, rather dose-dependently inhibited the enzyme activity. Ca2+, Mg2+ did not change the alkaline SMase activity in the presence of bile salts, and reduced the activity in the absence of bile salt. Trypsin inactivated acid SMase in pancreas, liver and duodenum but had no influence on intestinal alkaline SMase activity. In conclusion, the intestinal alkaline SMase has a specific distribution pattern and the characters of it differ in several respects from the known acid and neutral SMases.

Alkaline Phosphatase↗

PubMed1995

The role of enactment in implicit and explicit memory.

Enactment during the encoding of simple imperatives has been found to improve substantially performance on conceptually driven explicit-memory tests. In two experiments the effect of this manipulation on a conceptually driven implicit test (category association) was studied. A conceptually driven explicit test (free recall) was also included. In Experiment one three different study conditions (enactment with real objects, reading, and generation) were considered. In Experiment two there were two study conditions (enactment with imaginary objects and reading). Compared to reading, generation was found to improve the performance on both free recall and category association, whereas enactment affected free recall only. In a final experiment subjects imagined that they performed the tasks, and this manipulation was found to improve the memory performance on both tests. Taken together, this pattern of results is interpreted as suggesting that free recall and category association have a process in common that is sensitive to semantic processing at study (promoted by generation and imagery, but not by enactment), and that free recall involves a retrieval process in addition that is facilitated by a rich encoding environment (provided by enactment).

Adolescent↗

PubMed1995

Determinants of word fragment completion.

A current debate in the memory literature concerns the validity of word fragment completion (WFC) as a test of implicit memory. It has been claimed that language variables exert a strong influence on the task, and that the task reflects memory only to a small extent (Hintzman & Hartry, 1990). For these reasons, the use of contingency analyses of recognition and WFC performance as a means of studying underlying memory processes has been criticized. The present study addressed this issue by examining the influence of language variables on completion of a set of computer generated single-solution fragments of Swedish words (Olofsson & Nyberg, 1992). It was found that language variables indeed had a large effect on completion performance, and that priming only accounted for a small portion of variance in the task. It is therefore suggested that the method of triangulation should be employed for contingency analyses involving WFC.

Adult↗

PubMed1995

Dissociative effects of elaboration on memory of enacted and non-enacted events: a case of a negative effect.

One experiment compared the effect of elaboration on enacted and non-enacted events. The commands were either presented in a basic form (e.g., "wave your hands") or in an enriched form. The commands were enriched by adding statements to the commands of how to perform the actions (e.g., "wave your hands as a conductor"). Free- and cued-recall data showed elaboration to have a dissociative effect on enacted and non-enacted events. Memory for the non-enacted events benefited from enrichment, whereas simple enacted events were remembered to a higher extent than complex enacted events. Lack of benefit from elaboration on memory of enacted events is suggested to be due to enactment leading to a sufficient degree of item-specific processing, and a negative effect of elaboration is suggested to occur when the way of manipulating item complexity decreases the familiarity of the actions. Familiarity ratings of the items by two independent groups of subjects supported this interpretation.

Adolescent↗

PubMed1995

Patient falls in stroke rehabilitation. A challenge to rehabilitation strategies.

BACKGROUND AND PURPOSE: The risk of falls is very high among stroke patients, and falling is a major complication in stroke rehabilitation. This study aimed to investigate the incidence, characteristics, and consequences of falls in an inpatient stroke rehabilitation setting. METHODS: One hundred sixty-one patients consecutively admitted to a geriatric stroke rehabilitation unit were studied. Falls that occurred during their rehabilitation stay were prospectively registered and analyzed. RESULTS: Sixty-two of the patients (39%) suffered falls. The total number of falls was 153, which corresponds to an incidence rate of 159 falls per 10,000 patient-days. Most falls occurred during transfers or from sitting in a wheelchair or on some other kind of furniture. Seventeen falls (11%) were classified as the result of extrinsic mechanisms, 49 (32%) were intrinsic falls, 39 (25%) occurred in a nonbipedal position (while sitting or lying), and 48 falls (31%) remained unclassified. No injury was observed in 109 of 153 incidents (71%), whereas 6 falls (4%) involved fractures or other serious injury. CONCLUSIONS: Since falls are so frequent, they must be considered a significant problem in stroke rehabilitation. Fall prevention strategies should therefore be developed and included in rehabilitation programs.

Accidental Falls↗

PubMed1994

The effect of retrieval enactment on recall of subject-performed tasks and verbal tasks.

The effect of retrieval enactment on memory for nouns (objects) or verbal phrases describing simple actions (e.g., "lift the box") was addressed in two experiments. In Experiment 1, the type of object involved in the actions was manipulated, with three different types of object being used (body parts, laboratory-related objects, and external objects). In Experiment 2, the integration between the verb-noun pairs was manipulated (well-integrated vs. poorly integrated). Results from both experiments showed that whereas encoding enactment (motor encoding and verbal test) substantially improved the memory performance compared with a verbal condition (verbal encoding and verbal test), retrieval enactment (verbal encoding and motor test) had no major impact on the number of recalled nouns or phrases. Moreover, there was no additional effect of dual enactment (motor encoding and motor test). The overall pattern of the results suggests that there is a fundamental difference between motor processing at encoding and motor processing at retrieval, and the lack of encoding specificity advantage for the motor modality contradicts the view that encoding enactment of verbal commands results in storage of motor representations.

Adolescent↗

PubMed1993

Bambuterol and terbutaline in human cerebrospinal fluid and plasma.

Concentrations in cerebrospinal fluid (CSF) and plasma of bambuterol and its active metabolite, the beta 2-adrenoceptor agonist terbutaline, were measured in man after four once-daily doses of 30 mg bambuterol hydrochloride (Bambec). Nine patients scheduled for orthopaedic surgery under spinal anaesthesia completed the study. The concentrations of both substances were much lower in CSF than in plasma, the ratio CSF/plasma being 0.09 for bambuterol and 0.19 for terbutaline, at apparent steady state. While the rank order of the ratios was expected from the fractions of unbound bambuterol and terbutaline in plasma, their absolute values were only about 1/6 (bambuterol) and 1/4 (terbutaline) of those predicted from diffusion equilibria between plasma and CSF. Thus, the rates of transport of bambuterol and terbutaline from plasma into the central nervous system appear to be slow relative to transport out of the system, e.g. by outflow of CSF. The findings are in agreement with animal experiments and suggest that bambuterol and terbutaline are less likely than lipophilic beta 2-adrenoceptor agonists to interact with central receptors.

Aged↗