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Biomedical subjects

O Henriksen

Publications and source records attributed to O Henriksen.

At least 163 records · Page 9Linked to original sources
PubMed1989

Effects of angiotensin blockade on the splanchnic circulation in normotensive humans.

The effects of angiotensin-converting enzyme inhibition (ACE-I) by enalapril on splanchnic (n = 10) and central hemodynamics (n = 9) were examined in moderately salt-depleted healthy volunteers, at rest and during 15-20 min of lower body negative pressure (LBNP), reducing mean arterial pressure by 10 mmHg. During LBNP before ACE-I, both splanchnic and total peripheral vascular resistances increased. During ACE-I, splanchnic and total peripheral vascular resistances decreased. After enalapril administration, splanchnic vascular resistance did not increase during LBNP. Total peripheral vascular resistance still increased but not to the same extent as during LBNP before ACE-I. The increases in heart rate and plasma norepinephrine during LBNP were attenuated after ACE-I compared with LBNP before ACE-I. The effectiveness of the ACE-I was clearly demonstrated by unchanged and low plasma angiotensin II levels during ACE-I. We conclude that, in normal sodium-depleted humans, acute ACE-I decreases splanchnic vascular resistance at rest and abolishes splanchnic vasoconstriction during LBNP. Furthermore, it may interfere with autonomic nervous system control of the circulation.

Adult↗
PubMed1988

In vivo determination of T1 and T2 in the brain of patients with severe but stable multiple sclerosis.

In vivo measurements of relaxation processes in multiple sclerosis (MS) lesions by magnetic resonance imaging (MRI) may be important for evaluation of the disease activity in individual MS plaques. To obtain information of presumably chronic plaques, 10 patients with severe, but stable MS were investigated, using a whole-body superconductive MR scanner, operating at 1.5 T. By employing 12-point (or 6-point) partial saturation inversion recovery (PSIR) and 32-echo multiple spin-echo sequences we measured T1 and T2 in MS plaques, white matter, and cortical gray matter. We also focused on the issue, whether T1 and T2 relaxation processes in fact were monoexponential. T1 and T2 in plaques were found to cover a wide range, which could be explained only by inherent biophysical dissimilarity of the plaques, possibly due to differences in disease activity, edema and gliosis. T1 appeared monoexponential in all the plaques, but in seven cases T2 showed biexponential behavior. This was found to be most pronounced near the cerebrospinal fluid of the ventricles, probably caused by partial volume effects or increased free water content. The T2 of apparently normal white matter was significantly longer in MS patients than in healthy subjects.

Adult↗
PubMed1988

Evaluation of right ventricular volumes measured by magnetic resonance imaging.

Right ventricular volumes were determined in 12 patients with different levels of right and left ventricular function by magnetic resonance imaging (MRI) using an ECG gated multisection technique in planes perpendicular to the diastolic position of the interventricular septum. Right ventricular stroke volume was calculated as the difference between end-diastolic and end-systolic volume and compared to left ventricular stroke volume and to stroke volume determined simultaneously by a classical indicator dilution technique. There was good agreement between right ventricular stroke volume determined by MRI and by the indicator dilution method and between right and left ventricular stroke volume determined by MRI. Thus, MRI gives reliable values not only for left ventricular volumes, but also for right ventricular volumes. By MRI it is possible to obtain volumes from both ventricles simultaneously in a noninvasive way and without exposing the patient to radiation.

Adult↗
PubMed1988

Specific problems of children with epilepsy.

In both adults and children, the seizure type and frequency of occurrence largely determine the burden of epilepsy, for the patient and his family. Epilepsy in children can range from the severe to the relatively benign, and it is important to make the correct diagnosis as early as possible. In those under 5 years of age, epilepsy often presents as an age-related syndrome, e.g., West and Lennox-Gastaut syndromes. Later, typical absences and generalized tonic-clonic convulsions are more usual. Drug therapy should take account of the different pharmacodynamics of antiepileptic drugs in children, and phenobarbital should be avoided. Rectal diazepam has an important role in the emergency management of childhood seizures. Psychological difficulties may be manifested by both the child and the parents. They should be prevented if possible by active intervention at an early stage after diagnosis, or managed on a continuing basis by expert medical and paramedical advice. The aim of such counseling is to ensure, so far as is possible, that the epileptic child develops normally in a normal family environment.

Child↗
PubMed1988

Muscle capillary permeability for [14C]inulin and [51Cr]EDTA in human forearm.

Capillary permeability of [14C]inulin and [51Cr]EDTA was examined in human forearm in five healthy, subjects by indicator diffusion technique. Injections of, initially [125I]albumin and [14C]inulin, and after 30 min resting, of [125I]albumin and [51Cr]EDTA, were given in a brachial artery. During light exercise of the forearm, blood was sampled in 2-s periods from a deep cubital vein primarily draining muscles. The plasma flow rate, calculated as the dose of [125I]albumin in the injectate divided by the area under the curve for the venous concentration of 125I, was, on average, 8.5 ml min-1 100 g-1 forearm. Assuming [125I]albumin is a partially permeable tracer, a correction for extraction of albumin was performed. This gave extraction fractions of 0.107 +/- 0.015 (mean +/- SEM) for [14C]inulin and 0.377 +/- 0.033 for [51Cr]EDTA, respectively. The capillary permeability surface area product per 100 g tissue (CDC) was for [14C]inulin 0.90 +/- 0.19, and for [51Cr]EDTA 3.31 +/- 0.38 ml min-1 100 g-1 forearm. The average of the ratios of the CDC values of [51Cr]EDTA to those of [14C]inulin, 4.0 +/- 0.5, is significantly higher than the corresponding ratio between the measured free diffusion coefficients in water at 37 degrees C, 3.07 +/- 0.002 (N = 36 and 17, respectively). This indicates that there is some degree of restriction for [14C]inulin (MW 5200) relative to [51Cr]EDTA (MW 340.2) and it points to an 'equivalent pore radius estimate' of about 160 A in human muscle capillaries.

Adult↗
PubMed1988

In vivo measurement of intracellular pH in human brain during different tensions of carbon dioxide in arterial blood. A 31P-NMR study.

The effect of changes in carbon dioxide tension in arterial blood upon intracellular pH in brain tissue was studied in seven healthy volunteers, aged 22-45 years. The pH changes were monitored by use of 31P nuclear magnetic resonance spectroscopy, performed on a whole-body 1.5 Tesla Siemens imaging system. The measurements were carried out during hyperventilation and with the subject breathing atmospheric air containing 5 vol. % and 7 vol. % carbon dioxide. Intracellular pH increased significantly during 15 min of hyper-ventilation and decreased significantly during 18 min respiration of air containing 7 vol. % carbon dioxide. The intracellular buffer capacity was estimated. These results suggest that the ventilation response to carbon dioxide is correlated to changes in intracellular fluid pH.

Adult↗
PubMed1988

Maintenance of high-energy brain phosphorous compounds during insulin-induced hypoglycemia in men. 31P nuclear magnetic resonance spectroscopy study.

31P nuclear magnetic resonance (NMR) spectroscopy allows noninvasive studies of cerebral energy-rich phosphorous compounds in humans. In an attempt to characterize the relationship between peripheral blood glucose concentrations and whole-brain phosphate metabolism during insulin-induced hypoglycemia, 31P NMR spectra were obtained before and after intravenous injection of insulin (0.15 IU/kg body wt) in six men. Compared with prehypoglycemic measurements, no significant changes were found in brain content of Pi, sugar phosphates, phosphocreatine, phosphodiesters, and ATP, and brain pH remained constant during the experiment. These results show that the integrated brain profile of energy-rich phosphorous compounds is unaffected by experimental insulin-induced hypoglycemia in humans.

Adenosine Triphosphate↗
PubMed1988

Magnetic resonance imaging of the prostate.

Magnetic resonance imaging offers new possibilities in investigation of the prostate gland. Current results of imaging and tissue discrimination in the evaluation of prostatic disease are reviewed. Magnetic resonance imaging may be useful in the staging of carcinoma of the prostate.

Humans↗
PubMed1988

Surgical treatment of epilepsy. Clinical aspects in children.

Neurosurgery, mainly temporal lobectomy, has given substantial relief of serious seizure problems in two-thirds of children with intractable epilepsy. Since the prognoses of children with an intractable epilepsy is poor, surgery should be considered. To prevent sequela of a long standing seizure disorder and side effects of antiepileptic medication as well as the development of mirror foci, surgery should be considered at an early age. The age at which surgery should be undertaken depends upon several factors, for instance: the seizure problem, the EEG findings--are they persistently focal and do they fit with the seizures? Is there a malignant development of the epilepsy and little or no chance of remission? And especially, if there is brain pathology in concordance with the clinical findings and EEG signs, neurosurgery should not be postponed. It is of great advantage for children with an intractable epilepsy to be evaluated at an epilepsy center. Both the children and their parents will profit from the evaluation and information gained as well as education by a multiprofessional team. This will optimise the difficult decision process which may lead to neurosurgery.

Adolescent↗
PubMed1987

Studies on diphosphonate kinetics. Part I: Evaluation of plasma elimination curves during 24 h.

To improve the understanding of diphosphonate affinity to metabolically active bone, the underlying diphosphonate kinetics have been evaluated and compared to Cr-EDTA kinetics. MDP binds to plasma proteins, varying from 25% initially to approximately 70% after 24 h. The renal clearance of diphosphonate is found to be equal to Cr-EDTA clearance. Using simultaneous bolus injection of 99Tc-MDP and 51Cr-EDTA, it has been possible to obtain a coarse estimate of bone uptake of MDP. This uptake is found to correlate well with s-alkaline phosphatase, but since MDP binding to bone is reversible, the plasma elimination curve is not monoexponential. Therefore it has not been possible to describe the uptake of MDP in bone mathematically.

Bone and Bones↗
PubMed1987

Studies on diphosphonate kinetics. Part II: Whole body bone uptake rate during constant infusion--a refined index of bone metabolism.

To elaborate the understanding of diphosphonate kinetics, a non compartmental analysis is introduced. Using continuous infusion of 99mTc-methylene diphosphonate (Tc-MDP) and 51Cr-EDTA, as a cotracer, the diphosphonate clearance to bone (BDC) can be calculated. BDC is found to correlate well with the 24 h whole body retention of diphosphonate (WBR) (r = 0.89, P less than 0.01) when renal function is normal, but not in cases of reduced 51Cr-EDTA clearance. These findings indicate that BDC measurements are superior to the WBR technique in the estimation of bone turnover, especially when renal function is reduced. The BDC measurements may also constitute a useful tool for studies of diphosphonate uptake in bone, the foundation of bone scintigraphy.

Bone and Bones↗
PubMed1987

Prolonged bone marrow T1-relaxation in acute leukaemia. In vivo tissue characterization by magnetic resonance imaging.

In vivo tissue characterization by measurement of T1- and T2-relaxation processes is one of the greatest potentials of magnetic resonance imaging (MRI). This may be especially useful in the evaluation of bone marrow disorders as the MRI-signal from bone marrow is not influenced by the overlying osseous tissue. Nine patients with acute leukaemia, one patient with myelodysplastic syndrome, and ten normal volunteers were included in the study. The T1- and T2-relaxation processes were measured in the lumbar spine bone marrow using a wholebody superconductive MR-scanner operating at 1.5 Tesla. In the patients MRI was done at the time of diagnosis and during follow-up of chemotherapy and related to bone marrow biopsies taken within three days of the MRI. At the time of diagnosis T1-relaxation time was increased two to three times in the patients (range 0.7-3.0 sec.) compared to the controls (range 0.38-0.60 sec.). No significant difference was seen in the T2-relaxation process. In relation to chemotherapy T1 decreased towards the normal range in the patients who obtained complete remission, whereas T1 remained prolonged in the patients who did not respond successfully to the treatment. The results indicate that MRI may be a non-invasive clinically useful tool in the evaluation of acute leukaemia especially as a follow-up control of chemotherapy.

Adolescent↗
PubMed1987

In vivo estimation of relaxation processes in benign hyperplasia and carcinoma of the prostate gland by magnetic resonance imaging.

Tissue characterization for separating malignant from benign tissue is a clinically very important potential of magnetic resonance imaging (MRI). In this study quantitative determination of T1- and T2-relaxation processes was accomplished in five healthy volunteers, 10 patients with benign hyperplasia of the prostate gland and eight patients with prostatic carcinoma. Histological verification was obtained in all the patients. The measurements were performed on a wholebody MR-scanner operating at 1.5 T using six inversion recovery sequences (TR = 4000 msec) for T1-determination and a 32 spin-echo sequence (TR = 3000 or 2000 msec) for T2-estimation. The T1-relaxation curves all appeared monoexponential, whereas the T2-curves in most cases showed a multiexponential behaviour. A considerable overlap of the relaxation curves was seen. Consequently, we found no statistically significant differences between the T1- or the T2-relaxation times of the three groups investigated. It is concluded that tissue characterization based on relaxation time measurements with MRI does not seem to have a clinically useful role in prostatic disease.

Adult↗
PubMed1987

Magnetic resonance: in vivo tissue characterization of the testes in patients with carcinoma-in-situ of the testis and healthy subjects.

Six patients with carcinoma-in-situ (CIS) of the testis and five healthy volunteers were examined with magnetic resonance imaging (MRI), relaxation time measurements (T1 and T2) and magnetic resonance spectroscopy. The study was carried out on a Siemens Magnetom (1.5 Tesla) whole body MR scanner. All patients with CIS had a biopsy taken before MR examination and histology was compared with the MR results. Significant difference between T1 relaxation processes for normals and patients with CIS was shown. It remains to be seen whether these findings are related to the neoplasia or the reduced spermatogenesis.

Adult↗
PubMed1987

Renal vascular adjustments to partial renal venous obstruction in dog kidney.

Blood flow studies were conducted in neurolept anesthetized dogs to characterize the involvement of renal nerves in ipsilateral renal vasoconstriction seen during acute elevation of renal venous pressure above 30 mm Hg. Renal blood flow was measured electromagnetically. The vasoconstrictor response was almost abolished by acute surgical denervation of the kidney, since renal vascular conductance remained unchanged during renal venous pressure elevation from 30-60 mm Hg. However, following additional alpha-adrenoceptor blockade or chronic renal denervation, renal vascular conductance increased progressively during renal venous pressure elevation to 60 mm Hg. The effect of acute decapsulation of kidney was studied in another group of dogs. Decapsulation induced a vasoconstriction. The decrease in renal vascular conductance observed during renal venous pressure elevation was unaffected by acute surgical denervation of decapsulated kidney, but was almost abolished following additional alpha-adrenoceptor blockade or chronic denervation. In decapsulated chronically denervated kidney, the increase in renal vascular conductance during renal venous pressure elevation to 60 mm Hg was still present but considerably attenuated as compared with the chronically denervated kidney with intact capsule. The renin-angiotensin system did not participate in acute vascular adjustments to renal venous stasis in intact kidney or in decapsulated acutely surgically denervated kidney. The data favor the view that neurogenic and myogenic mechanisms significantly influence the vasoconstrictor response to renal venous pressure elevation in dog kidney. The neurogenic contribution to the vasoconstrictor response comprises intrarenal and extrarenal vasoconstrictor mechanisms evoked reflexively by renal venous pressure elevation, and the myogenic contribution to the vasoconstrictor response comprises opposing vasodilator mechanisms due to increase in renal interstitial tissue pressure during renal venous pressure elevation.

Angiotensin II↗