PubMed Health⌕ Search

Biomedical subjects

M Trommald

Publications and source records attributed to M Trommald.

10 recordsLinked to original sources
PubMed2001

[Elective surgery--cancellations, ring fencing and efficiency].

BACKGROUND: We set out to study to what extent emergency admissions disturb elective surgical activities, resulting in decreasing efficiency and fewer elective procedures. We looked at the evidence of whether ring fencing elective surgery is an effective strategy to reduce disturbance from emergency activities, and improve the overall efficiency in hospitals with emergency as well as elective activities. MATERIAL AND METHODS: We systematically searched for published studies that have addressed the above mentioned issues. RESULTS: Approximately 10-17% of elective surgical operations are cancelled. In a Norwegian study, about 14% of cancellations seem to be caused by interference from emergency admissions. We did not find any empirical evidence on the effects of ring fencing elective surgery. INTERPRETATION: The belief that ring fencing is an effective strategy to decrease cancellations and increase hospital efficiency seems to be anchored in a priori reasoning rather than in published evidence.

Appointments and Schedules↗
PubMed2000

[Observational units--same good service to lower costs?].

BACKGROUND: With increased demand for hospital services and limited resources in the health sector, modes of organisation of services which give the same health outcome, but at lower cost, are of interest. Observation units in hospitals imply rapid diagnostic procedures and/or brief, but adequate treatment. We looked at the evidence for whether stays in observational units provide similar health outcome and reduce the admissions costs for hospitals compared to standard inpatient stays. MATERIAL AND METHODS: We systematically evaluated four randomized controlled studies that have compared the outcome for chest pain and asthma patients admitted to either observational units or directly to ordinary hospital units. The outcomes in focus were health effects measured as mortality and/or complications, length of stay and direct hospital costs. RESULTS: The studies indicate that for the conditions included, there are no health outcome differences between patients treated in observational units on one hand or in ordinary hospital units on the other. Stays in observational units do not seem to imply increased risk of complication. Furthermore, the studies show a reduction in length of stay and hospital costs associated with the use of observational units. INTERPRETATION: The main reason for the reduction in length of stay and cost is quicker diagnosis in observational units than in the ordinary hospital units. The preconditions for these results are clear by defined criteria for selection of patients to the different units and well-defined protocols for making diagnoses and treating patients. If many patients after staying in observational units are transferred to ordinary hospital units or are discharged and then readmitted, the economic benefits of observational units could be undermined.

Angina Pectoris↗
PubMed1997

Spatial training in a complex environment and isolation alter the spine distribution differently in rat CA1 pyramidal cells.

The hippocampus is critically involved in spatial learning. Spatial training in adult rats, which improved their spatial learning ability, increased the number of excitatory hippocampal CA1 spine synapses on basal dendrites as compared with either isolated or standardly housed animals (Moser et al. [1994] Proc. Natl. Acad. Sci. USA 91:12673-12675). In this article, we report that spine synapses on oblique apical dendritic branches do not increase in density or number after the same type of training. When examining the variability of the spine density on basal CA1 dendrites by using variance component analysis, the variance associated with the cells was twice as large in all three groups as that coupled to the rats. Analysis of the spine density plots shows that the enhanced spine density after spatial training is found in most cells recorded from the trained group but that a small subset of CA1 neurones are particularly well supplied with spines. The trained group had a significant right-skewed tail of the spine distribution, i.e., training caused high spine density to occur in a small subset of dendritic segments. Conversely, the isolated group had a significant left-skewed spine distribution, indicating that some of the dendritic segments were undersupplied with spines, whereas the paired group displayed no asymmetry.

Animals↗
PubMed1997

Dimensions and density of dendritic spines from rat dentate granule cells based on reconstructions from serial electron micrographs.

In the hippocampus, most excitatory synapses are located on dendritic spines. It has been postulated that the geometry of spines and/or postsynaptic density (PSD) influences synaptic efficiency and may contribute to the expression of plastic processes such as learning or long-term potentiation (LTP). Based on three-dimensional reconstructions of dentate granule cell dendrites from serial electron micrographs, we have measured head dimensions, neck cross-sectional areas, neck length, and PSD area and form of 115 spines of dentate granule cells in the medial perforant path termination zone. All dimensions showed a large variability, with up to 100-fold differences in values. A calculated diffusion index for transport of molecules through the reconstructed neck varied over a 100-fold range. The neck and head dimensions were moderately positively correlated, whereas the PSD area was strongly correlated with head volume. Distribution histograms and scatter plots of various spine dimensions did not reveal any systematic clustering, suggesting that there is a continuum of spine geometries rather than distinct classes for granule cell dendritic spines in the middle molecular layer. Transversely (n = 13) and longitudinally (n = 27) sectioned dendrites had mean spine densities of 2.66 and 1.01 spines/microns, respectively, uncorrected for so-called hidden spines. Bifurcating spines made up 2.1% of the total spine number in transversely and 2.3% in longitudinally sectioned dendrites. The twin spine heads never shared the same presynaptic bouton. Fenestrated or split PSDs shared the same presynaptic element in all but two cases, arguing against PSD division as an intermediate step in synapse formation.

Animals↗
PubMed1996

Cellular correlates to spatial learning in the rat hippocampus.

Learning through exploration gives increased synaptic field potentials in the perforant path/dentate synapses, largely due to an activity-dependent brain temperature increase. After temperature compensation, spatial learning was associated with small, but significant, STP-like changes of the field potential lasting 20-30 min. A group of spatially trained adult rats showed faster spatial learning and about 10% higher basal dendritic spine density (LY-filled) compared to two control groups. With unchanged dendritic length and branching pattern, the results suggest the formation of new synapses.

Animals↗
PubMed1995

Analysis of dendritic spines in rat CA1 pyramidal cells intracellularly filled with a fluorescent dye.

The dendritic branching pattern and the distribution of dendritic spines were studied in hippocampal neurones with an improved technique. In slices taken from adult Wistar rats, CA1 pyramidal cells were filled with Lucifer yellow and examined under a laser-scanning confocal microscope. The basal dendrites were found evenly distributed inside a regular cupola-shaped volume. Their total length was about 4,500 microns. The branches divided between one and three times, with the initial segments comprising less than 2%, and the long terminal segments (mean length, 119 microns) including more than 80% of the total length of the basal dendrites. The apical dendritic branches emerged obliquely from the main shaft, ran for a distance of 50 to 250 microns, and made up a total length of about 5,100 microns in stratum radiatum and between 1,100 and 3,200 microns in stratum lacunosum-moleculare. The mean total length of the dendritic tree was 11,900 microns. All values were corrected for shrinkage. Shrinkage was measured in three dimensions and was 20.2% in the horizontal (x/y) plane and 40.9% in the vertical (z) plane. Both the basal and the apical dendritic branches were covered by regularly spaced spines. When corrected for dehydration-induced shrinkage and for hidden spines, the density was 1.80 and 2.00 spines/microns dendritic length for the basal and apical dendritic branches, respectively. Apart from the initial parts of the branches, which had few or no spines, the spines were remarkably evenly spaced. In particular, the distance between spine heads was significantly different from a random distribution, suggesting a regulatory process for the spacing of spines.

Animals↗
PubMed1995

Possible strategies for finding the substrate for learning-induced changes in the hippocampal cortex.

For long-lasting memory traces, structural synaptic changes remain a probable mechanism. However, in higher animals it has proved difficult to provide positive evidence for this notion. The main reason may be that the changes are subtle and are to be found in a relatively small subset of synapses and in a distributed manner in the cellular network in question. Here, we discuss possible strategies for finding structural changes in the hippocampus associated with spatial learning, an activity for which this structure is important. Spatial learning may induce new excitatory synapses in a small subset of hippocampal CA1 neurons because we observe a higher spine density without alteration in dendritic length or branching. The dendritic synapses are regularly spaced, irrespective of spine density, suggesting the operation of an intersynaptic dispersing force.

Animals↗
PubMed1994

An increase in dendritic spine density on hippocampal CA1 pyramidal cells following spatial learning in adult rats suggests the formation of new synapses.

The search for cellular correlates of learning is a major challenge in neurobiology. The hippocampal formation is important for learning spatial relations. A possible long-lasting consequence of such spatial learning is alteration of the size, shape, or number of excitatory synapses. The dendritic spine density is a good index for the number of hippocampal excitatory synapses. By using laser-scanning confocal microscopy, we observed a significantly increased spine density in CA1 basal dendrites of spatially trained rats when compared to nontrained controls. With unchanged dendritic length, the higher spine density reflects an increased number of excitatory synapses per neuron associated with spatial learning.

Animals↗
PubMedDate not supplied

Long-term potentiation is associated with new excitatory spine synapses on rat dentate granule cells.

To investigate possible morphological correlates to long-term potentiation (LTP), three-dimensional reconstruction of serial electron micrographs was employed. LTP was induced in the perforant path/dentate granule cell synapse in two rats. The surgically isolated contralateral side served as control, along with two untreated animals. Longitudinally sectioned and transversally sectioned dendrites were sampled from the middle fifth of the molecular layer and all visibly connected spines were identified. A mixed, unbalanced, nested variance component model was used to make a valid statistical comparison between the LTP and control groups. The spine density was higher in the experimental than in the control groups. The changes were statistically significant in both the longitudinal and transverse sample. In addition, spines with a divided stem and two heads (bifurcating spines) were seen at a higher frequency in the LTP material compared with the contralateral material. From a subset of dendrites all connected spines were reconstructed and detailed measurements of head, neck, and PSD dimensions were made. We failed to find significant differences following LTP on either of the dimensions measured. The results suggest that new spine synapses are formed following LTP, including some of the bifurcating type.

Animals↗