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Biomedical subjects

S Holm

Publications and source records attributed to S Holm.

At least 91 records · Page 5Linked to original sources
PubMed1998

Fluorodeoxyglucose uptake in dysfunctional myocardium subtended by an occluded coronary artery. Relation to dobutamine contractile reserve and Sestamibi uptake.

BACKGROUND: Myocardial segments with impaired function may have the potential for functional recovery. Augmented exogenous glucose uptake in relation to blood flow estimated by [2-18F]2-fluorodeoxyglucose (FDG) and positron emission tomography (PET) frequently indicates functional reversibility. The spectrum of FDG uptake levels in relation to Sestamibi uptake and dobutamine contraction reserve in areas with impaired function subtended by an occluded coronary artery has never been reported. METHODS AND RESULTS: Seventeen patients with stable angina pectoris and dysfunctional myocardium subtended by an occluded coronary artery were studied with FDG-PET, low-dose dobutamine echocardiography and Sestamibi-Single Photon Emission Computerized Tomography. In a 16 segment model dysfunctional myocardial segments showed a normally distributed FDG uptake ranging from 34% to 150% when normalized to peak segmental Sestamibi uptake. Low FDG uptake was associated with both lack of dobutamine induced contractile reserve and low Sestamibi uptake (in 73% of the segments) whereas high FDG uptake displayed both contractile reserve and Sestamibi uptake (57%). Segments with intermediate FDG uptake had either contractile reserve or a preserved Sestamibi uptake (62%). CONCLUSION: Dysfunctional myocardium subtended by an occluded coronary artery represents a continuum of metabolic states with a high degree of heterogeneity with regard to contractile reserve and Sestamibi uptake.

Adult↗
PubMed1998

Calculation of the FDG lumped constant by simultaneous measurements of global glucose and FDG metabolism in humans.

The lumped constant defined as the conversion factor between the net uptake of fluoro-2-deoxy-D-glucose (FDG) and glucose was calculated from global CMRglc and from positron emission tomography (PET) using FDG as tracer (CMRFDG). Fifteen healthy, normal volunteers (mean age 24 +/- 4 years) were studied. Global CBF and CMRglc were measured with the Kety-Schmidt technique using 133Xe as tracer, and values were corrected for errors from incomplete diffusion equilibrium for inert gas tracer between brain tissue and cerebral venous blood. Measurements of CMRFDG were obtained with PET using the dynamic and single-scan methods and the K1-k3 model. Measurements with the Kety-Schmidt technique and PET-FDG were performed simultaneously. Global CBF was 47.1 +/- 8.0 mL.100 g-1.min-1, and CMRglc was 22.8 +/- 4.1 mumol.100 g-1.min-1. No difference in CMRFDG was found with the two methods (17.8 +/- 1.6 and 18.2 +/- 1.3 mumol .100 g-1.min-1, dynamic and single scan methods, respectively). Accordingly, the lumped constant ranged from 0.80 +/- 0.16 to 0.82 +/- 0.15, with a mean value of 0.81 +/- 0.15. The mean ratio between phosphorylation of FDG and glucose (k3*/k3) was 0.39 +/- 0.25. The discrepancy between the lumped constant determined in this study and previously obtained values can be explained partly by methodologic problems, and we conclude that most of the discrepancy results from previous overestimation of global CBF.

Adult↗
PubMed1998

Frequency-dependent fatigue development during electrical stimulation in the masseter muscle of pigtail monkeys.

Low-frequency fatigue was investigated in nine female and one male adult pigtail monkeys (Macaca nemestrina) with a mean weight of 5.3 kg (range 4.3 to 6.5 kg). After sedation and anesthesia, silver electrodes were inserted into the anterior and posterior parts of the right masseter muscle. The contralateral muscle was used as a control. The masseter muscles were stimulated for 3 minutes (4 Hz, 2 ms, 100 V). After a 5-minute rest period, the stimulation was repeated with the same duration and voltage but at a higher frequency of 8 Hz. Bite forces were measured, and muscle biopsies were obtained from the central part of the right masseter and immediately frozen in liquid nitrogen. After freeze-drying, a fluorometric analysis that used enzymatic methods for measuring levels of glycogen, glucose, lactate, pyruvate, creatine phosphate, nicotinamide-adenine dinucleotide (NAD), and reduced NAD (NADH) was performed. The bite force decreased by 12% after the initial 3 minutes of work. After the second contraction the bite force decreased to 56%. Prominent substrate depletion was observed. The precontraction levels of glycogen, glucose, and phosphocreatine were all reduced. The NADH and the NAD concentrations increased. An accumulation of metabolites was evident. The pyruvate increased by 32% and lactate levels increased by a factor of 3. The male measurements were comparable to the nine female measures for each assessment. The substantial substrate depletion in combination with a prominent accumulation of metabolites may contribute to the development of low-frequency fatigue.

Animals↗
PubMed1998

In vivo dynamic stiffness of the porcine lumbar spine exposed to cyclic loading: influence of load and degeneration.

The dynamic axial stiffness of the L2-3 motion segment subjected to vibratory loading under intact and injured states of the intervertebral disc was studied using an in vivo porcine model. Three groups of animals with the following states of the intervertebral discs were studied: intact disc, acutely injured disc, and degenerated disc. A miniaturized servo-hydraulic exciter was used to sinusoidally vibrate the motion segment from 0.05 to 25 Hz under a compressive load with a peak value of either 100 or 200 N. The dynamic axial stiffness of the intervertebral disc was calculated at 1-Hz intervals over the frequency range. The results showed that the dynamic axial stiffness was frequency dependent. A positive relationship was found between an increase in mean dynamic stiffness and load magnitude. An increase in mean stiffness with successive exposures at the same load magnitude was observed, despite the allowance of a recovery period between loading. The greatest difference was noted between the first and second load sets. No significant change in stiffness was found due to an acute disc injury, whereas a significant increase in mean stiffness was found for the degenerated disc group as compared with the intact group. The form of the frequency response curve, however, remained relatively unaltered regardless of the degenerated state of the disc. With heavier loads, repeated loading, and/or disc degeneration, the stiffness of the intervertebral disc increases. An increase in stiffness can mean a reduction in the amount of allowable motion within the motion segment or a potentially harmful increase in force to obtain the desired motion. This may locally result in greater stresses due to an altered ability of the disc to distribute loads.

Animals↗
PubMed1998

Metabolic and hemodynamic evaluation of brain metastases from small cell lung cancer with positron emission tomography.

Brain metastases from small cell lung cancer respond to chemotherapy, but response duration is short and the intracerebral concentration of chemotherapy may be too low because of the characteristics of the blood-brain barrier. Positron emission tomography has been applied in a variety of tumors for studies of metabolic and hemodynamic features. This study was performed to determine regional cerebral metabolic rate of glucose (rCMRglu), regional cerebral blood flow (rCBF), and regional cerebral blood volume (rCBV) in brain metastases from small cell lung cancer and the surrounding brain. Tumor rCMRglu, rCBF, and rCBV exerted a broad variability, but were higher than the corresponding values in white matter and higher than or similar to those of gray matter. Tumor rCMRglu and rCBF were highly correlated (P < 0.01, r = 0.79). No correlation between survival and metabolic or hemodynamic parameters could be demonstrated. After radiotherapy, mean tumor rCMRglu decreased from 0.40 to 0.31 micromol/g/min (not significant), and rCBF and rCBV remained unchanged. However, cortical rCBF demonstrated a trend of increased values after radiotherapy from 0.37 to 0.49 ml/g/min (P = 0.13). No change in rCMRglu was observed in gray or white matter after radiotherapy. Global CBF seems to be reversibly depressed by the metastases, but local hemodynamic changes in the tumor could not be detected with positron emission tomography in this study. An association between high tumor rCMRglu and rCBF as an indicator of hypoxia was not observed. Other methods for noninvasive in vivo analysis of tumor hemodynamics are needed, especially for discrimination between tumor necrosis and hypoxia.

Adolescent↗
PubMed1997

[What do people talk about in Danish hospital elevators?].

Hospital elevators make up a part of the public space of hospitals which is used by both employees, patients, and patients' relatives. We performed an observational study to ascertain the frequency of ethically problematic conversations between employees in the elevators of three Danish hospitals. We defined a conversation as problematic if it breached confidentiality or if it could raise doubts about the professional or ethical standard of the hospital or its employees. Based on this definition we found that problematic conversations occurred in 18 out of 201 elevator-trips where more than one member of the hospital staff was present in the elevator (9%, 95% confidence limits 5-14%). The most common types of problems were breaches of confidentiality (6 cases), complaints about stressful work (4 cases), and complaints about the organisation (3 cases).

Confidentiality↗
PubMed1997

The activation pattern in normal humans during suppression, imagination and performance of saccadic eye movements.

The distribution of activated cerebral regions was examined in nine normal subjects during four different eye movement-related conditions: (1) fixation-fixation on a central light emitting diode; (2) saccadic suppression-fixation on a diode in the presence of flashing lateral targets; (3) reflexive/volitional saccades-performance of overt eye movements to two laterally lit targets and back to the centre; and (4) imagined saccades-imagining, but not performing, the same eye movements. The regional neural activity was measured indirectly using repetitive bolus injections of oxygen-15-labelled water and positron emission tomography (PET) to yield time-integrated images of the normalized count distribution. These were aligned and anatomically normalized to a standard stereotactic space and the averages of each condition were analysed categorically using statistical parametric mapping. Compared to central fixation, reflexive/volitional saccades significantly activated regions in the classically known cortical oculomotor regions. The most notable activation during the saccade suppression task, compared to central fixation alone, was a bilateral activation of the parietal cortex with a right-sided preponderance, activation of the supplementary eye field/caudal cingulate regions, and activation of frontal regions close to the frontal eye fields. Imagined performance of eye movements without overt eye movements activated the supplementary eye field and frontal eye fields identically to regions involved in overt eye movements, thus demonstrating that over eye movements are not a prerequisite of the activation of these regions in normal humans.

Adult↗
PubMed1997

Fibre type grouping in porcine masseter and soleus muscles assessed by the enclosed fibre type concept. A statistical and computational analysis.

Muscle function is determined not only by the frequency of slow (type I) and fast (type II) fibres but also the spatial fibre type organization. During ageing as well as in muscle disorders, divergencies from the normal pattern may occur and are expressed as 'fibre-type grouping'. To elucidate whether intramuscular differences in spatial fibre type arrangements may underlie the functional heterogeneity of the porcine masseter, the arrangements of intrafascicular type I and type II fibres were assessed in terms of the number of enclosed fibres in whole fascicles. The intrafascicular proportions of edge- and centrally located type I and type II fibres were investigated. Two hundred and forty-two porcine masseter fascicles (six masseters) and 63 pig soleus fascicles (five soleus muscles) were investigated by ATP-ase histochemistry. All fascicles were from 11 domestic pigs (1 year, 70-90 kg body weight, all female). Sixty-nine to 90% of the total fibres were type II fibres in the porcine masseter (P < 0.01). In four of five soleus muscles the type II fibre population was dominant. No enclosed type I fibres could be identified in the porcine masseter muscles. This was in contrast to the finding of 1270 enclosed type II fibres. Five enclosed type I fibres (two soleus) and 361 enclosed type II fibres were identified in the pig soleus. The spatial analysis indicated that the fibre type arrangements in the porcine masseter muscles were not homogeneous. No biopsies with random type II fibre organization were identified. Furthermore, half the number of biopsies showed type I fibre segregation. These data suggest that the porcine masseter cannot be considered as having one homogeneous structural identity.

Adenosine Triphosphatases↗
PubMed1997

Out-patient rehabilitation improves activities of daily living, quality of life and exercise tolerance in chronic obstructive pulmonary disease.

The purpose of this study was to investigate the effects on activities of daily living, quality of life, and exercise tolerance of a comprehensive out-patient rehabilitation programme for patients with moderate-to-severe chronic obstructive pulmonary disease. In this randomized and controlled trial, the main outcome measures were Activities of Daily Living (ADL) score, York Quality of Life Questionnaire (YQLQ) score, Chronic Respiratory Disease Questionnaire (CRDQ) score, 6 min walking distance (6MWD), forced expiratory volume in one second (FEV1), and forced vital capacity (FVC). The rehabilitation programme included physical training, occupational therapy, education, and smoking cessation therapy, and lasted for 12 weeks. The patients were evaluated at entry, halfway through, and at the end of the programme. Follow-up was at 24 weeks. Forty seven patients were recruited, and 16 in each group completed the trial. There were significant differences in the improvements in ADL and CRDQ between the control and the treatment groups at 12 and 24 weeks, and at 24 weeks, respectively. At 6, 12 and 24 weeks, improvements in the 6MWD were 21.6 versus 79.8, 36.1 versus 113.1 and 21.4 versus 96.2 for control and treatment groups, respectively (p<0.004). A correlation matrix showed only ADL and 6MWD to be significantly correlated; the matrix was also used to validate the translated questionnaires. The programme required 124 staff-hours in total. An inexpensive, comprehensive out-patient rehabilitation programme can produce long-term improvement in activities of daily living, quality of life, and exercise tolerance in patients with moderate-to-severe chronic obstructive pulmonary disease.

Activities of Daily Living↗
PubMed1997

Invasive evaluation of mitral regurgitation: the importance of hemodynamic measurements during exercise.

BACKGROUND AND AIMS OF THE STUDY: In patients with mitral regurgitation, left ventricular angiography is usually performed to grade the regurgitation. This is a semi-quantitative method which gives some information related to the regurgitant volume at a certain time. The aim of our study was to evaluate the benefits of invasive hemodynamic examinations during stress. Patients with mitral regurgitation according to Doppler color flow mapping, and regurgitation of no more than grade 2+ according to left ventricular angiography, were of special interest. METHODS: One hundred and four consecutive patients were examined with transesophageal echocardiography (TEE), left ventricular angiography and cardiac catheterization during rest and during hemodynamic stress. RESULTS: All patients had mitral regurgitation according to Doppler color flow mapping. Thirty eight patients had a mitral regurgitation of grade 0, 1+ or 2+ according to left ventricular angiography. Of these, seven had a resting v-wave < or = 25 mmHg, and a v wave > or = 50 mmHg during stress. When these seven patients were compared with those with severe grade 3+ and 4+ regurgitation, there was a significant difference between the v-wave at rest (p = 0.02) but no significant difference during stress (p = 0.42). CONCLUSIONS: Mitral regurgitation is a dynamic lesion, the complete assessment of which cannot be obtained from a single measure during one hemodynamic situation. Additional information from v-wave recordings during hemodynamic stress identified a subgroup of patients who had near-normal pressures at rest, but whose v-wave measurements during stress did not differ significantly from those of patients with severe angiographically assessed regurgitation (grades 3+ and 4+). In patients with only minor mitral regurgitation which is suspected to contribute to their clinical symptoms, the monitoring of invasive hemodynamic parameters during stress is important.

Adult↗
PubMed1996

[What does the Danish population know about the scientific ethics committees?].

The Danish system of research ethical committees (RECs) was established in 1978 and formal legislation on RECs was passed in 1992. We have investigated the general knowledge about the RECs through a telephone survey of a random sample of the adult Danish population. Among the 1137 respondents only 342 (30%) were aware of the existence of an official body which controls medical research, and only a small minority was aware of the composition of the RECs and that the laymembers outnumber the professional members. Knowledge about RECs was positively correlated to higher education, young age, and being male. It is argued that there is a need for increased public information about the existence and composition of the Danish RECs.

Adult↗