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Biomedical subjects

A Ericsson

Publications and source records attributed to A Ericsson.

At least 37 records · Page 2Linked to original sources
PubMed1998

Activation of vagal afferents after intravenous injection of interleukin-1beta: role of endogenous prostaglandins.

Intravenous administration of interleukin-1 (IL-1) activates central autonomic neuronal circuitries originating in the nucleus of the solitary tract (NTS). The mechanism(s) by which blood-borne IL-1 regulates brain functions, whether by operating across the blood-brain barrier and/or by activating peripheral sensory afferents, remains to be characterized. It has been proposed that vagal afferents originating in the periphery may monitor circulating IL-1 levels, because neurons within the NTS are primary recipients of sensory information from the vagus nerve and also exhibit exquisite sensitivity to blood-borne IL-1. In this study, we present evidence that viscerosensory afferents of the vagus nerve respond to intravenously administered IL-1beta. Specific labeling for mRNAs encoding the type 1 IL-1 receptor and the EP3 subtype of the prostaglandin E2 receptor was detected in situ over neuronal cell bodies in the rat nodose ganglion. Moreover, intravenously applied IL-1 increased the number of sensory neurons in the nodose ganglion that express the cellular activation marker c-Fos, which was matched by an increase in discharge activity of vagal afferents arising from gastric compartments. This response to IL-1 administration was attenuated in animals pretreated with the cyclooxygenase inhibitor indomethacin, suggesting partial mediation by prostaglandins. In conclusion, these results demonstrate that somata and/or fibers of sensory neurons of the vagus nerve express receptors to IL-1 and prostaglandin E2 and that circulating IL-1 stimulates vagal sensory activity via both prostaglandin-dependent and -independent mechanisms.

Acute-Phase Reaction↗
PubMed1998

Chemical shift artifact-free imaging: a new option in MRI?

A high-speed proton spectroscopic imaging method with high spatial resolution was used for obtaining water, fat, and chemical shift artifact-free images on a 1.5 T MR scanner. The technique is based on a fast radiofrequency (RF) spoiled gradient-echo sequence. The chemical shift information is encoded by incrementing the echo time in a series of image records. Suppression of water or fat signals is not used. The technique does not require a highly homogeneous magnetic field. Spectroscopic images of a human volunteer were compared with corresponding conventional images obtained using the short inversion time inversion recovery (STIR) and the selective partial inversion recovery (SPIR) methods. The results demonstrate that it is possible to produce images entirely free from chemical shift artifacts using only a few chemical shift encoding steps. The technique also produces pure water and fat images which are significantly better than those produced by using the conventional methods STIR and selective partial inversion recovery. The described method appears to be promising for routine clinical applications because it can be fully automated.

Adipose Tissue↗
PubMed1998

Magnetic resonance spectroscopic imaging for visualization and correction of distortions in MRI: high precision applications in neurosurgery.

We present a method for the quantification and correction of geometrical/intensity distortions of magnetic resonance images predominantly caused by bulk magnetic susceptibility shifts due to susceptibility heterogeneities of measured biologic tissues and shape of the object under investigation. The method includes precise and fast measurements of the static magnetic-field distribution inside the measured object and automated data processing. Magnetic-field deviations in the range (-2.4; 2.6) ppm were found in the human brain at B0 = 1.5 T. For routinely used imaging parameters, with a read gradient strength of about approximately 1 mT/m, the magnetic-field perturbations in the human brain can cause geometrical distortions up to +/-4 mm and intensity changes up to +/-50%. MR images corrected by the described method are suitable for planning high precision applications in neurosurgery.

Artifacts↗
PubMed1998

Magnetic starch microspheres in the MR imaging of hepatic metastases. A preclinical study in the nude rat.

PURPOSE: To evaluate reticular endothelial system-specific magnetic starch microspheres (MSM) as an i.v. contrast agent for MR imaging in a model of experimental liver metastases. MATERIAL AND METHODS: The study comprised 15 nude rats, 7 of which were carrying hepatic metastases from a human colonic cancer. The 15 rats were examined at 0.5 T using a T1-weighted spin-echo (SE) sequence and a gradient-echo sequence. The examinations were performed before and 15 min after the administration of accumulated doses of MSM at 0.25-2.5 mg Fe/kg b.w. The images were compared with corresponding serial liver specimens. RESULTS: A loss of liver signal intensity was obtained at all MSM dose levels. No metastases were detected in the pre-contrast images. The optimum detection rate of hepatic metastases was reached with the SE sequence at a dose of 1.0 mg Fe/kg b.w. MSM and the diameters of the smallest lesions depicted were 1 mm. However, in the SE sequence, the measured lesion-to-liver contrast and liver signal damping were highest at the largest dose, indicating a possible image degrading effect of MSM at high doses. Administration of MSM as a short bolus over 30 s resulted in congestion of the liver with dilatation of the hepatic veins. When MSM was instead injected slowly over 5 min, this adverse effect was not seen. CONCLUSION: The use of MSM dramatically increased the detection of experimental hepatic metastases.

Animals↗
PubMed1997

Evidence for an intramedullary prostaglandin-dependent mechanism in the activation of stress-related neuroendocrine circuitry by intravenous interleukin-1.

We have provided evidence that the stimulatory effects of intravenous interleukin-1 (IL-1) on neurosecretory neurons in the paraventricular nucleus (PVH) that express corticotropin-releasing factor (CRF) depend specifically on the integrity of catecholaminergic projections originating in caudal medulla. Here we report on experiments designed to test alternative means by which circulating IL-1 might access medullary aminergic neurons, including mechanisms involving sensory components of the vagus, the area postrema, or perivascular cells bearing IL-1 receptors. Neither abdominal vagotomy nor area postrema lesions reliably altered Fos expression induced in the medulla or PVH in response to a moderately suprathreshold dose of IL-1beta. Cytokine-stimulated increases in CRF mRNA in the PVH were also unaffected by either ablation. By contrast, systemic administration of the cyclooxygenase inhibitor indomethacin resulted in parallel dose-related attenuations of IL-1 effects in hypothalamus and medulla. Microinjections of prostaglandin E2 (PGE2; >/=10 ng) in rostral ventrolateral medulla, the principal seat of IL-1-sensitive neurons that project to the PVH, provoked discrete patterns of cellular activation in hypothalamus and medulla that mimicked those seen in response to intravenous IL-1. We interpret these findings as supporting the hypothesis that paracrine effects of PGE2 released from perivascular cells in the medulla as a consequence of IL-1 stimulation and, acting through prostanoid receptors on or near local aminergic neurons that project to the PVH, contribute to the stimulatory effects of increased circulating IL-1 on neurons constituting the central limb of the hypothalamo-pituitary-adrenal axis.

Animals↗
PubMed1997

Magnetic resonance imaging of experimental microinfarctions in the rabbit brain.

Small hyperintense lesions are frequently found with T2-weighted magnetic resonance imaging (MRI) of the human brain. A significant number of these lesions are probably infarctions. Because there is often a long delay between the microischemic impact and the autopsy, if any, and as the specificity of the MRI is low for detecting ischemic lesions, it is difficult to draw conclusions about the clinicotopographic correlations. This work concerns the usefulness of MRI in detecting experimental microischemic lesions in the rabbit brain about 24 h after the impact. It seems that the sensitivity of T2-weighted MRI in detecting foci of damaged areas in the rabbit brain is good enough to make it useful for evaluating tissue damage when screening for potential neuroprotective drugs and that the experimental model should be useful for developing diagnostically valuable MRI techniques.

Animals↗
PubMed1997

1H-spectroscopic imaging with read gradient during acquisition in inhomogeneous fields: analysis, measurement strategy, and data processing.

The proton magnetic resonance spectroscopic imaging techniques that use read gradient during acquisition produce proton spectra with high spatial and moderately high spectroscopic resolution in a reasonable time for in vivo applications. These techniques suffer mainly from the spatial and spectral distortions caused by the convolution of spectral/spatial information (chemical-shift artifacts) and from the spectral shifts caused by static magnetic field inhomogeneities. The investigators analyze the chemical-shift artifacts in the presence of nonnegligible static magnetic field inhomogeneities and propose a postdetection processing scheme to correct for such effects. Spectral artifacts caused by chemical shifts, spectral line overlapping, streak broadening, and magnetic field inhomogeneities are discussed. The postdetection data processing scheme is demonstrated on measurements of a phantom as well as a human leg.

Artifacts↗
PubMed1997

The importance of lifestyle to self-assessed health.

Empirical research has revealed a causality between lifestyle and health, and lifestyle is seen as an important factor in explaining health differences among people. However, it is important to note the difference between the significance and the importance of a factor in explaining health differences, since the two concepts are commonly confused. Some research has suggested that lifestyle is not an important variable in explaining health differences, but just how important it is, is uncertain. This study measures the explanatory power of lifestyle for self-assessed health. It is found that lifestyle has only a limited effect; 3-5% of the differences in self-assessed health are explained by lifestyle variables.

Alcohol Drinking↗
PubMed1997

Human uterine smooth muscle exhibits a very low phosphocreatine/ATP ratio as assessed by in vitro and in vivo measurements.

The purpose of the study was to investigate by in vitro and in vivo methods the phosphocreatine (PCr)/ ATP ratio as an expression of the energy metabolic state of human myometrium in comparison with striated skeletal muscle. The contents of PCr and adenylates in biopsies of uterine smooth muscle and m. rectus abdominis from seven term pregnant women were determined in vitro and compared with results obtained in vivo by phosphorus magnetic resonance spectroscopy (31P-MRS) in the uterus and m. gastrocnemius of eight non-pregnant women. The PCr/ATP ratio in the striated skeletal muscle was about three times higher than that of the myometrium. The results of the in vitro biopsy part of the study and the in vivo 31P-MRS part conformed with each other. In the biopsies both PCr and ATP concentrations were significantly lower in the myometrium than in the rectus muscle, but the difference for PCr was more pronounced, accounting for the significantly lower PCr/ATP ratio in the uterine smooth muscle. The energy metabolic pattern of uterine smooth muscle differs from that of striated skeletal muscle regarding the contents of high-energy phosphocompounds and the PCr/ATP ratio. This in vivo finding is the first report on human smooth muscle using 31P-MRS.

Adenosine Diphosphate↗
PubMed1997

Dysprosium-enhanced MR imaging for tumor tissue characterization. An experimental study in a human xenograft model.

PURPOSE: To evaluate dysprosium-enhanced MR imaging for differentiation between morphologically intact and necrotic tumor tissue in a tumor model. MATERIAL AND METHODS: A human colon carcinoma was transplanted subcutaneously into 9 nude (immunodeprived) rats. MR imaging was performed before and after injection of the dysprosium agent Dy-DTPA-BMA. T1-, T2- and T2*-weighted sequences were acquired. The tumors were dissected, histological sections were prepared, and compared with corresponding MR images. RESULTS: In intact tissue, the MR signal intensity in the T2- and T2*-weighted images decreased after Dy injection and the delineation of the intact regions were sharp and corresponded well to the gross histological sections. CONCLUSION: Dy-enhanced MR imaging facilitated the differentiation between intact and necrotic tumor tissue.

Adenocarcinoma↗
PubMed1996

Distinct mechanisms underlie activation of hypothalamic neurosecretory neurons and their medullary catecholaminergic afferents in categorically different stress paradigms.

Intermittent electrical footshock induces c-fos expression in parvocellular neurosecretory neurons expressing corticotropin-releasing factor and in other visceromotor cell types of the paraventricular hypothalamic nucleus (PVH). Since catecholaminergic neurons of the nucleus of the solitary tract and ventrolateral medulla make up the dominant loci of footshock-responsive cells that project to the PVH, these were evaluated as candidate afferent mediators of hypothalamic neuroendocrine responses. Rats bearing discrete unilateral transections of this projection system were exposed to a single 30-min footshock session and sacrificed 2 hr later. Despite depletion of the aminergic innervation on the ipsilateral side, shock-induced up-regulation of Fos protein and corticotropin-releasing factor mRNA were comparable in strength and distribution in the PVH on both sides of the brain. This lesion did, however, result in a substantial reduction of Fos expression in medullary aminergic neurons on the ipsilateral side. These results contrast diametrically with those obtained in a systemic cytokine (interleukin 1) challenge paradigm, where similar cuts ablated the Fos response in the ipsilateral PVH but left intact the induction seen in the ipsilateral medulla. We conclude that (i) footshock-induced activation of medullary aminergic neurons is a secondary consequence of stress, mediated via a descending projection transected by our ablation, (ii) stress-induced activation of medullary aminergic neurons is not necessarily predictive of an involvement of these cell groups in driving hypothalamic visceromotor responses to a given stressor, and (iii) despite striking similarities in the complement of hypothalamic effector neurons and their afferents that may be activated by stresses of different types, distinct mechanisms may underlie adaptive hypothalamic responses in each.

Afferent Pathways↗
PubMed1996

Myocardial cell death in reperfused and nonreperfused myocardial infarctions. MR imaging with dysprosioum-DTPA-BMA in the pig.

PURPOSE: To investigate whether Dy-DTPA-BMA-enhanced MR imagining would permit identification of myocardial cell death, myocardial infarction was induced in 12 domestic pigs. MATERIAL AND METHODS: In 6 pigs with irreversible cell damage, Dy-DTPA-BMA (1.0 mmol/kg b.w.) was administered i.v. 70 min after coronary occlusion. In 6 other pigs, the infarctions were reperfused 80 min after the occlusion, followed by injection of Dy-DTPA-BMA after 30 min of reperfusion. In 4 additional pigs, the hearts were reperfused after 2 min of occlusion. All 16 pigs were sacrificed 10 min after the injection of Dy-DTPA-BMA. The hearts were excised and imaged with MR. RESULTS: Reversibly injured myocardium could not be distinguished from adjacent nonischaemic myocardium after the administration of Dy-DTPA-BMA. Reperfused, infarcted myocardium demonstrated a high signal intensity in the proton-density- and T2-weighted sequences, despite a 5-fold higher Dy concentration compared with both nonreperfused infarcted and nonischaemic myocardium. CONCLUSION: This lack of susceptibility effect in infarcted myocardium, due to a homogeneous distribution of Dy, indicates the usefulness of Dy as a marker of tissue viability.

Animals↗
PubMed1996

Double-contrast MR imaging of reperfused porcine myocardial infarction. An experimental study using Gd-DTAA and Dy-DTPA-BMA.

PURPOSE: Myocardial infarctions were induced in 12 pigs to investigate whether a double-contrast method, combining a positive and a negative MR contrast agent, could improve the visualization of reperfused myocardial infarctions. MATERIAL AND METHODS: All 12 pigs were subjected to 80 min of occlusion followed by reperfusion. In the double-contrast group (6 pigs), Gd-DTPA-BMA (0.3 mmol/kg b.w.) and Dy-DTPA-BMA (1.0 mmol/kg b.w.) were administered i.v. after 30 min of reperfusion. In the remaining 6 pigs, a single injection of Gd-DTPA-BMA (0.3 mmol/kg b.w.) was given after 30 min of reperfusion. All pigs were sacrificed 10 min post-contrast injection, corresponding to a reperfusion time of 40 min. The hearts were excised and imaged with MR. The concentrations of GD and Dy were measured in infarcted and nonischaemic myocardium using ICP-AES. RESULTS AND CONCLUSION: Contrast media concentrations were more than 4-fold higher in infarcted compared with nonischaemic myocardium. The infarctions were best shown on T1-weighted images, and there were no differences between the double and single contrast groups. In the T2-weighted images, the infarctions were significantly better visualized in the double-contrast group, due to a Dy-induced signal intensity loss in nonischaemic myocardium.

Animals↗
PubMed1995

Type 1 interleukin-1 receptor in the rat brain: distribution, regulation, and relationship to sites of IL-1-induced cellular activation.

Systemic interleukin-1 (IL-1) activates the hypothalamo-pituitary-adrenal (HPA) axis, an effect exerted through increased synthesis and secretion of corticotropin-releasing factor (CRF) by parvicellular neurosecretory neurons. The site(s) and mechanism(s) through which circulating IL-1 may access central systems governing HPA axis output remain obscure. To identify potential cellular targets for blood-borne IL-1, we analyzed the distribution of mRNA encoding the rat type 1 IL-1 receptor (IL-1R1) in rat brain. Regional ribonuclease protection assays detected a single protected fragment corresponding to the membrane-bound form of the IL-1R1 mRNA in all areas analyzed. In situ hybridization revealed labeling predominantly over barrier-related cells, including the leptomeninges, non-tanycytic portions of the ependyma, the choroid plexus, and vascular endothelium. Low to moderate levels of the IL-1R1 mRNA were detected in just a few neuronal cell groups, including the basolateral nucleus of the amygdala, the arcuate nucleus of the hypothalamus, the trigeminal and hypoglossal motor nuclei, and the area postrema. No specific labeling for IL-1R1 mRNA was detected over neurons that respond to intravenous IL-1 beta by induction of transcription factor Fos, including hypophysiotropic CRF cells and brainstem catecholamine neurons. Injection of IL-1 beta did, however, provoke induction of mRNA encoding the immediate-early gene, NGFI-B, but not c-fos, in two major loci of IL-1R1 expression, vascular endothelial cells, and the area postrema. Intravenous injection of IL-1 beta acutely down-regulated IL-1R1 mRNA in perivascular cells, but not in neuronal cell groups. These results suggest the parenchymal sites of IL-1R1 expression in rat to be distinct from those reported previously in mouse. The common expression in both species of an IL-1R in non-neuronal elements highlights the possibility that IL-1-mediated activation of CRF neurons may result from cytokine-receptor interaction at vascular, and/or other barrier-related, sites to trigger release of secondary signalling molecules in a position to interact with components of HPA control circuitry.

Animals↗
PubMed1995

Measurements of magnetic field variations in the human brain using a 3D-FT multiple gradient echo technique.

A magnetic resonance 3DFT multiple gradient-echo technique was used for measurements of the proton spectrum for each voxel in the measured slice. Water, fat, magnetic field and T2 distributions in the head of a normal volunteer and a patient with intracerebral hematoma were computed. Magnetic field variations caused by the head were calculated after correction for the static magnetic field inhomogeneity. Large local magnetic field variations up to 3 ppm were found in the human brain near interfaces between air or bone and brain tissues and 0.5 ppm between hematoma and brain tissue. Information about magnetic field variations could be useful for shimming procedures in vivo and for correcting artifacts in imaging and spectroscopy.

Aged↗