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Biomedical subjects

S Holm

Publications and source records attributed to S Holm.

At least 181 records · Page 10Linked to original sources
PubMed1991

Altered modulation of prefrontal and subcortical brain activity in newly diagnosed schizophrenia and schizophreniform disorder. A regional cerebral blood flow study.

To measure prefrontal and subcortical activity during a cognitive task, we examined 19 newly diagnosed schizophrenics and patients with schizophreniform psychosis. Seven healthy volunteers served as controls. The patients were drug naive or had received neuroleptics for a few days only. Cerebral blood flow distribution was depicted by single photon emission computed tomography at rest and during activation with the Wisconsin Card Sorting Test. A significant relative activation deficit in the left inferior-prefrontal region was revealed during the Wisconsin Card Sorting Test in the patient group. Furthermore, the patients had impaired striatal suppression on the left side during the cognitive task. The test performance was significantly impaired in the patients. The inability to reduce striatal activity may be due to a lack of corticostriatal feedback during prefrontal activation.

Adult↗
PubMed1991

Human regional cerebral blood flow during rapid-eye-movement sleep.

Owing to the coupling between CBF and neuronal activity, regional CBF is a reflection of neural activity in different brain regions. In this study we measured regional CBF during polysomnographically well-defined rapid-eye-movement (REM) sleep by the use of single photon emission computerized tomography and the new tracer 99mTc-dl-hexamethylpropyleneamine. Eleven healthy volunteers aged between 22 and 27 years were studied. CBF was measured on separate nights during REM sleep and during EEG-verified wakefulness. On awakening from REM sleep, all subjects reported visual dreams. During REM sleep CBF increased by 4% (p less than 0.01) in the associative visual area, while it decreased by 9% (p less than 0.01) in the inferior frontal cortex. The CBF increase in the associative visual area suggests that activation of cerebral structures processing complex visual material is correlated to visual dream experiences. On the other hand, the reduced involvement of the inferior frontal cortex observed during REM sleep might explain the poor temporal organization and bizarreness often experienced in dreams.

Adult↗
PubMed1991

Factors influencing oxygen concentration gradients in the intervertebral disc. A theoretical analysis.

Oxygen concentration gradients in the intervertebral disc were calculated to examine the effects of exchange area and disc thickness on oxygen concentrations and oxygen flux into the disc. The concentration gradients were determined using the two-dimensional Poisson equation with experimental values for oxygen consumption rate and oxygen diffusion. The calculated gradients were steep, and the oxygen concentrations in the center of thick discs were low, in agreement with experimental gradients. The results support the hypothesis that maximum cell density in the disc is determined by nutrient supply and that exchange area and disc thickness are critical parameters.

Biological Transport↗
PubMed1991

Estimation of Doppler gradients at rest and during exercise in patients with recoarctation of the aorta.

In patients with suspected recoarctation of the aorta the estimation of the pressure difference between the arms and legs is an important part of the examination. Because this difference is often augmented when the circulation is stressed by exercise, exercise tests are a useful part of the evaluation. Doppler echocardiography was used to estimate this pressure difference in 16 adult patients in whom simultaneous pressure and Doppler recordings were made both at rest and during exercise. There was a close correlation between the invasive peak instantaneous gradient and the Doppler gradient both at rest and during exercise. There was only a moderate correlation between the invasive peak to peak gradient and the Doppler gradient at rest and during exercise. Doppler echocardiography is recommended as an easy and accurate method of estimating the peak instantaneous gradient both at rest and during exercise in patients with suspected recoarctation.

Adult↗
PubMed1991

Cerebral O2 metabolism and cerebral blood flow in humans during deep and rapid-eye-movement sleep.

It could be expected that the various stages of sleep were reflected in variation of the overall level of cerebral activity and thereby in the magnitude of cerebral metabolic rate of oxygen (CMRO2) and cerebral blood flow (CBF). The elusive nature of sleep imposes major methodological restrictions on examination of this question. We have now measured CBF and CMRO2 in young healthy volunteers using the Kety-Schmidt technique with 133Xe as the inert gas. Measurements were performed during wakefulness, deep sleep (stage 3/4), and rapid-eye-movement (REM) sleep as verified by standard polysomnography. Contrary to the only previous study in humans, which reported an insignificant 3% reduction in CMRO2 during sleep, we found a deep-sleep-associated statistically highly significant 25% decrease in CMRO2, a magnitude of depression according with studies of glucose uptake and reaching levels otherwise associated with light anesthesia. During REM sleep (dream sleep) CMRO2 was practically the same as in the awake state. Changes in CBF paralleled changes in CMRO2 during both deep and REM sleep.

Adult↗
PubMed1991

Antibacterial effects of zinc oxide, rosin, and resin acids with special reference to their interactions.

The growth inhibiting capacity of zinc oxide combined with ordinary rosin (Portuguese rosin), abietic acid or dehydroabietic acid was studied using two different methods. To mimic the actual treatment of wounds, circular tapes or sensitivity discs were placed on Müller-Hinton-agar plates that had been seeded with various facultative aerobic bacteria, and the zones of inhibition were measured. The agar dilution method was used to measure the minimum inhibitory concentration (MIC). Inhibition of growth was restricted to Gram-positive facultative aerobic bacteria for the individual substances zinc oxide, Portuguese rosin, or resin acids, as well as for combinations of these. In general the combination of zinc oxide and dehydroabietic acid was a more potent antibacterial substance than the corresponding combination of zinc with rosin or abietic acid. These combinations commonly had synergistic antibacterial effects.

Abietanes↗
PubMed1991

Clinical implications of vibration-induced changes in the lumbar spine.

There are strong indications that whole body vibrations are involved in the pathophysiology of different spinal aberrations known or assumed to generate back pain and sciatica. There also are several possible pathogeneses for these pathologic changes, although the proofs still are inconclusive or lacking. A better understanding of the relationships between vibration and spinal disorders in the near future will help us to prevent the occurrence of some of the problems causing pain and disability.

Back Pain↗
PubMed1991

Experimental nerve root compression. A model of acute, graded compression of the porcine cauda equina and an analysis of neural and vascular anatomy.

Nerve root compression has been suggested as one important pathogenetic factor in low-back pain syndromes and sciatica. The underlying pathophysiologic mechanisms are, however, incompletely known, partly because of the lack of experimental data on this topic. In the present study, a model for experimental compression of the porcine sacrococcygeal cauda equina is presented. The model consists of surgical exposure of the cauda equina and compression of the cauda equina toward the ventral aspect of the spinal canal by an inflatable balloon fixed to the spine. This compression system was shown to have a high accuracy in pressure transmission from the balloon to the cauda equina. The gross and microscopic neural anatomy and the vascular anatomy of the porcine cauda equina were analyzed with light microscopic and ink-perfusion techniques. The porcine cauda equina showed a close anatomic resemblance to the human lumbosacral cauda equina. The presented model offers unique possibilities for experimental studies on nerve root compression injury because of the easy surgical exposure and the sufficient length of the nerve roots. In separate studies, this model, along with investigations of solute transport to the nerve tissue and of impulse propagation, has been used to analyze the effects of acute, graded compression on blood flow and edema formation in the cauda equina. The porcine cauda equina would also be particularly suitable for chronic compression studies because any neurologic deficit acquired would be restricted to the tail.

Animals↗
PubMed1990

Cardiac output determinations in the pig--thoracic electrical bioimpedance versus thermodilution.

The accuracy of transthoracic electrical bioimpedance (TEB) for continuous, noninvasive measurement of cardiac output (Qt) in pigs was assessed in comparison with the thermodilution (TD) technique. Using the TEB technique, the different thoracic habitus of the pig had to be corrected for A good correlation with the TD technique was obtained (r = .87; p less than .001; n = 86) using thoracic length value (the measured value plus 25%) in an NCCOM3-R6 cardiodynamic computer for Qt values ranging from 2.9 to 9.8 L/min in pigs weighing from 40 to 75 kg. However, the Qt values given by the NCCOM3 were systematically 11% to 15% higher over the full range of values than the average of NCCOM-3 and TD Qt values. On the basis of the good agreement in the present study between the TEB and TD techniques over a broad range of Qt values, we conclude that TEB offers a valuable continuous, noninvasive alternative to TD for Qt determinations in experimental porcine models.

Animals↗
PubMed1990

Importance of compression onset rate for the degree of impairment of impulse propagation in experimental compression injury of the porcine cauda equina.

The effects of a rapid (0.05-0.1 seconds) and a slow (20 seconds) onset rate of cauda equina compression on impulse propagation, in terms of tail muscle electromyogram (EMG) amplitude, were analyzed in an experimental model of the pig cauda equina. Sham compression and compression at 50 mm Hg at either rapid or slow onset induced no or only minor functional impairment. Compression at 100 or 200 mm Hg induced impairment of the impulse propagation that was proportional to the applied pressure. The effects were more pronounced (P less than 0.01) for the rapid than for the slow onset of compression at both these pressure levels. An important factor for this observed difference in effects between the two employed onset rates seems to be the magnitude of intraneural edema formed outside the compression zone.

Animals↗
PubMed1990

Interactions between antibiotics and antineoplastic drugs on antibacterial activity in vitro.

The effects of various combinations of antibacterial (ampicillin, cephadroxil, doxycycline, imipenem, trimethoprimsulfadiazine) and antineoplastic (cisplatin, epirubicin, mitoxantrone) drugs were evaluated in vitro with regard to antibacterial activity on five clinical isolates from cancer patients of respectively Escherichia coli, Staphylococcus aureus and Streptococcus faecalis. With one exception no significant effects on the bacterial growth were observed in the presence of the antitumor drug alone. In contrast, all five strains of Strept. faecalis grew better when mitoxantrone was included in a concentration of 0.1 mg/l. A synergistic action between imipenem and mitoxantrone was seen for single strains of Staph. aureus and E. coli. Furthermore, a dose-effect related inhibition by cisplatin on the growth of Strept. faecalis in the presence of sub MIC levels of trimethoprimsulfadiazine was observed. The study indicates that interaction between antibacterial and antineoplastic drugs is an erratic phenomenon, which has to be dealt with separately for each combination of drugs as well as for each bacterial strain.

Anti-Bacterial Agents↗
PubMed1990

The effect of zinc oxide on Staphylococcus aureus and polymorphonuclear cells in a tissue cage model.

The effect of zinc oxide on S. aureus (209 P) was studied in steel net tissue cages implanted subcutaneously in guinea pigs and rabbits. Zinc oxide installed in the tissue cages created high, sustained concentrations of zinc in the cage fluid throughout the study. In a concentration of 22 mmol/l zinc oxide reduced viable counts in tissue cage fluid inoculated with S. aureus. No deleterious effect was observed on polymorphonuclear cell function.

Animals↗
PubMed1990

Antibacterial effect of zinc oxide in vitro.

Antibacterial activity, zinc concentrations and pH were measured in Müller-Hinton broth containing different amounts of zinc oxide and inoculated with Staphylococcus aureus (10(6) colony forming units/ml). The minimum inhibitory concentrations (MIC) of zinc oxide to different clinical isolates were determined using the Müller-Hinton agar dilution tests. Gram-positive bacteria were most susceptible. Gram-negative aerobic bacteria and streptococci were usually not inhibited even at the highest concentrations used (1024 micrograms/ml), but staphylococci--particularly some isolates of Staphylococcus epidermidis--were sensitive enough to allow determination of their MIC.

Bacteria↗
PubMed1990

Antibacterial activity of rosin and resin acids in vitro.

The antibacterial effects of rosins and resin acids were studied in vitro using three methods, disc diffusion on agar, agar dilution, and broth dilution. Rosin and some resin acids had antibacterial effects that were restricted to Gram-positive bacteria. The abietic type of acids had a more pronounced antibacterial activity than the pimaric and labdane acids when the disc diffusion method was used but there was no inhibition of growth of Gram-negative bacteria. Among the individual resin acids, dehydroabietic acid was generally the most potent, when disc diffusion on agar was used, and prediffusion increased the inhibitory effect. The composition of the pure resin acids dehydroabietic, neoabietic, and isopimaric acid did not change during the experiment, but abietic and levopimaric acid were converted into dehydroabietic acid by the addition of Müller-Hinton agar. In conclusion the old tradition of treating wounds with pitch, sap, rosin, or rosin containing tapes might therefore have some antibacterial relevance.

Bacteria↗
PubMed1990

Compression-induced changes of the nutritional supply to the porcine cauda equina.

The effects of compression on the transport of 3H-labeled methyl glucose to spinal nerve roots were analyzed in an experimental model of the pig cauda equina. A rapid onset of compression (0.05-0.1 s) induced more pronounced effects than a slow onset (20 s) at corresponding pressure levels. There was evidence that this observed difference may be related to the magnitude of intraneural edema formed outside the compression zone. The results also indicate that the nutritional transport might be impaired at very low pressure levels and that diffusion from adjacent tissues with a better nutritional supply, including the cerebrospinal fluid, may not fully compensate for any compression-induced impairment of the intraneural blood flow.

3-O-Methylglucose↗
PubMed1990

A porcine model for acute distal aortic occlusion.

Periarterial and intramural nerves and lymphatics as well as the vascular endothelium may influence pathophysiologic responses to acute arterial occlusion. For study of such pathophysiologic patterns, experimental models resembling the clinical situation are therefore preferable. In this porcine study acute distal aortic occlusion was mimicked by use of a balloon catheter introduced via a vascular graft anastomosed to the lateral aortic wall. Peripheral circulatory disturbance was assessed by measurements of femoral vein blood flow, skin blood flow in the hind foot and oxygen tension in the calf muscle, which verified the degree of ischemia. During the 4-hour ischemic period, repeated arterial and venous blood gas analyses showed increasing acidosis in effluent venous blood from the hind limbs, which after reperfusion slowly normalized. As highly reproducible conditions are achievable with the present experimental model, it can be used for studies of pathophysiologic responses to acute distal aortic occlusion.

Animals↗