Biomedical subjects

B Persson

Publications and source records attributed to B Persson.

At least 649 records · Page 36Linked to original sources

PubMedDate not supplied

Relation between protein intake, plasma valine, and insulin secretion during early infancy.

During the first 6 months of life the plasma levels of branch-chained amino acids are related to the amount of protein ingested. Thus, the concentrations are lower in breast-fed infants than in artificially fed infants who are on a formula with a protein content which is about 50 per cent higher than in breast milk. At 3, 4 1/2, and 6 months of age the concentrations of valine in plasma and C-peptide in urine and the ratio between C-peptide and creatinine in urine are 2-3 times higher in artificially fed than in breast-fed infants. Plasma valine values correlate significantly with the urinary C-peptide/creatinine ratio. The enhanced insulin response induced by a cow's milk formula is related to the protein content.

Breast Feeding↗

PubMedDate not supplied

Background radiation, electrical work, and some other exposures associated with acute myeloid leukemia in a case-referent study.

The effect of potential risk factors for acute myeloid leukemia was evaluated in a case-referent study encompassing 59 cases and 354 referents, all of whom were alive. Information on exposure was obtained through a questionnaire mailed to the subjects. The possible effect of background radiation was evaluated by means of a gamma radiation index, which accounted for the differences between cases and referents in this respect, i.e., in time spent in concrete buildings both at home and at work places. In the 20-54 yr old age group, there was an association between leukemia morbidity and index of background radiation. X-ray treatment and electrical work were also associated with increased rate ratios. With regard to solvents, only styrene appeared as a risk factor, but the number of exposed subjects was small. Other exposures were less clearly associated with increased risks.

Adult↗

PubMedDate not supplied

Acute myeloid leukemia and background radiation in an expanded case-referent study.

A case-referent study that investigated possible associations between environmental and occupational exposures and acute myeloid leukemia was performed on 86 cases and 172 referents, all of whom were living. Exposure information was obtained through a questionnaire mailed to each subject. An association was found between time spent in concrete buildings at home and work and leukemia morbidity. In addition, extensive x-ray examinations that occurred more than 5 y prior to diagnosis were more common among cases than referents.

Acute Disease↗

PubMedDate not supplied

Quantitative study of flow dependence in NMR images at low flow velocities.

A basic theoretical model that describes the effects of flow in and out of the imaging plane in nuclear magnetic resonance (NMR) images, obtained with the standard pulse sequences single spin echo, multiple spin echo, and inversion recovery, is presented. Theoretically calculated signal values are compared with experimental results obtained from single-slice images of a flow phantom for variable flow velocity v as well as for variable echo time and inversion time at flow velocities less than 10 mm/s, corresponding to those found in cerebrospinal fluid, in capillary systems, and in smaller veins. The quantitative correspondence between theory and experiment is good in the range of velocities studied and for the imaging parameters used, but discrepancies occur when higher velocities are studied. In addition, flow in a capillary model is demonstrated qualitatively for very low linear flow velocities, less than 1 mm/s. It is concluded that the model describes the essentials of the inflow-outflow effect and that this effect can predict the flow dependence of the NMR signal for low flow velocities. Observed differences between model and experiment may be due to effects of flow-induced phase alterations and due to uncertainty in measurements of the relaxation times T1 and T2. The model described here can be extended to suit other types of pulse sequences and to suit multislice imaging. It can also be extended to incorporate flow-induced phase effects.

Blood Flow Velocity↗

PubMedDate not supplied

Reactivity to norepinephrine and effect of sodium on blood pressure during weight loss.

Eighteen moderately obese middle-aged men with untreated mild hypertension were randomized to two groups and placed on a low energy diet regimen for 9 to 11 weeks. In Group I (n = 10) the amount of sodium chloride in the diet maintained the urinary sodium excretion at the predieting level. Mean body mass was reduced by 9.1 +/- 0.7 (SEM) kg. Mean intra-arterial pressure showed no significant change. There were significant decreases in heart rate (p less than 0.05) and urinary norepinephrine excretion (p less than 0.05) but not in plasma concentration of norepinephrine. In Group II (n = 8) energy as well as sodium intake was restricted, with a 95 +/- 22 mmol/24 hour reduction of urinary sodium excretion. Body mass decreased by 9.3 +/- 1.1 kg, and mean arterial pressure decreased by -18.9 to -4.3 mm Hg (95% confidence interval). There were also significant reductions in heart rate (p less than 0.001) and plasma norepinephrine concentrations (p less than 0.01) but not in urinary norepinephrine excretion. The pressor response (mean arterial pressure) to norepinephrine infusion at different dose rates was significantly elevated (p less than 0.05) in Group I during dieting in comparison with baseline. The blood pressure response to norepinephrine during dieting in patients in Group II was not changed from baseline.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Pressure↗

PubMedDate not supplied

Intestinal amino acid content in critically ill patients.

BACKGROUND: The purpose of the study was to determine the concentrations of free amino acids and the total protein content of the human intestinal mucosa during critical illness. METHODS: The free amino acid and protein concentrations in endoscopically obtained biopsy specimens from the duodenum and the distal colonic segments were determined on 19 critically ill patients. The free amino acids were separated by ion exchange chromatography and detected by fluorescence, and the protein content was quantified by the method of Lowry. RESULTS: In general, the typical amino acid pattern of the intestinal mucosa was seen, with very high levels of taurine, aspartate and glutamic acid. The main difference, as compared to a reference series of healthy subjects, was the elevated glutamine concentration of the duodenal mucosa. This amino acid was unaltered in the descending colon and depressed in the rectum. At the same time, the glutamatic acid concentrations were unaltered, suggesting that the degradation of glutamine was not increased in the septic state of the majority of the patients studied. Phenylalanine and the two branched-chain amino acids, valine and leucine, were elevated in the duodenal mucosa, and in the colonic mucosa, methionine and phenylalanine were elevated; otherwise, all the other individual amino acids were unaltered or depressed. CONCLUSIONS: The alterations seen in mucosal free amino acid and protein concentrations in connection with critical illness are different in many respects and contrast with the findings seen after starvation or moderate surgical trauma.

Adult↗

PubMedDate not supplied

Proton magnetic resonance relaxation times T1 and T2 related to postmortem interval. An investigation on porcine brain tissue.

In order to establish the validity of in vitro determination of the proton magnetic resonance (MR) relaxation times T1 and T2 in brain tissue at increasing time delay after death or operative excision, 81 brain tissue samples from 23 pigs were analyzed repeatedly. These samples, representing cortex, caudate nucleus and white matter, were studied microscopically after MR measurements. The T1 values exhibited no time dependence and the T2 values decreased slightly during the interval 2 to 90 hours after death. The samples were stored at +8 degrees C between the measurements. These results indicate that reliable in vitro measurements can be obtained in autopsy or surgical brain tissue specimens within 90 hours after death or excision, if handled properly.

Animals↗

PubMedDate not supplied

Regional differences in the proton magnetic resonance relaxation times T1 and T2 within the normal human brain.

The proton magnetic resonance (MR) relaxation times T1 and T2 were determined in autopsy specimens from 13 different regions of normal human brains. One hundred and seventy-four tissue samples from 25 brains were examined in a pulsed MR analyzer of 0.25 T and were then also studied histologically. There were regional differences in T1 and T2 within the cerebral gray matter but not within the white matter. These regional differences might reflect the different composition and cytoarchitectonic structure of the cortical regions and should be taken into consideration in the interpretation of cortical lesions on MR images.

Aged↗

PubMedDate not supplied

Tumours of the central nervous system. Proton magnetic resonance relaxation times T1 and T2 and histopathologic correlates.

Proton MR relaxation times T1 and T2 were determined in vitro in 136 small specimens of astrocytomas grades I-IV, of oligodendrogliomas, metastases of adenocarcinomas, meningiomas and acoustic neuromas. In addition, 7 samples of peritumoural white matter were analysed. The analysed specimens were studied microscopically in their entirety regarding tumour type and occurrence of necrosis and non-tumour tissue admixture, such as fibrosis and haemorrhage. Most of the gliomas had longer relaxation times than normal white matter and T2 was significantly longer than in the other three tumour groups. The metastases had longer T1 than normal white matter, while T2 varied. The astrocytomas tended to show shorter relaxation times with increasing degree of malignancy, and shortening of T1 and T2 correlating with the proportion of tissue necrosis. Similarly, the metastases with tissue necrosis had shorter T1 and T2 than non-necrotic samples. The meningiomas had T1 values comparable with normal cortex, while the T2 values varied. Tumours containing a large proportion of fibrous tissue had shorter relaxation times than the others. Acoustic neuromas had only slightly longer T1 than normal white matter, while T2 was not prolonged. Both T1 and T2 were significantly shorter than in all other tumours studied. Peritumoural white matter had prolonged relaxation times compared with normal white matter, correlating to increased water content. These in vitro differences regarding relaxation times in various types of tumours of the central nervous system, dependent on various types of tissue alterations, should be of interest for the interpretation of in vivo images.

Adenocarcinoma↗

PubMedDate not supplied

Metabolic control in 131 juvenile-onset diabetic patients as measured by HbA1c: relation to age, duration, C-peptide, insulin dose, and one or two insulin injections.

Glycosylated hemoglobin A (HbA1c), considered to reflect long-term metabolic control of diabetes, was analyzed in 131 patients, aged 2 5/12-19 6/12 yr, with juvenile-onset diabetes. Using stepwise multiple regression HbA1c, fasting blood glucose and plasma 3-hydroxybutyrate were analyzed as dependent variables versus independent variables such as age of the patients, duration of the disease, level of plasma immunoreactive C-peptide (IRCP), insulin dose, and number of insulin injections (one or two) per day. HbA1c was inversely related only to IRCP concentration. A low but significant, positive correlation was found between HbA1c and the duration of diabetes. Stepwise addition of the other independent variables did not further increase the fraction of explained variance. HbA1c was also correlated with a subjective rating score of the metabolic control performed by the treating physician. Fasting plasma glucose was significantly related to HbA1c but not to any of the independent variables. Fasting 3-hydroxybutyrate showed an inverse correlation to the age of the patient. The present study showed that in juvenile-onset diabetic patients, endogenous insulin secretion as reflected by IRCP was the factor best correlated with a low level of HbA1c. After the cessation of endogenous insulin secretion, there is a progressive deterioration of metabolic control and multiple injections of insulin rather than one or two per day may be needed to reach optimal control in the patients.

Adolescent↗

PubMedDate not supplied

Profiles of intermediary metabolites in insulin-dependent pregnant diabetic women with or without endogenous insulin production.

The levels of glucose, free fatty acids (FFA), glycerol, 3-hydroxybutyrate (3-HB), cyclic AMP, and C-peptide immunoreactivity (CPR) were determined in venous plasma samples taken every half hour during an 8-h period under standardized conditions in 10 insulin-dependent pregnant women. The metabolic profiles were determined in each trimester of pregnancy. The women were divided into two groups, one with (group I: 3B, 1C, and 1D according to White's classification) and one without (group II: 1B, 3C, and 1D) measurable plasma CPR levels. Plasma glucose values were significantly higher (P less than 0.01) with greater variability in group II than in group I in the first and second trimesters, while no such difference was found in the third trimester of pregnancy. FFA, glycerol, 3-HB, and cyclic AMP levels were not different between the groups in any trimester of pregnancy. Amniotic fluid CPR was higher and skinfold thickness of the newborn greater in group II than in group I. Neonatal complications occurred only in infants of group II mothers. It is concluded that determination of plasma CPR in diabetic women in early pregnancy could give additional prognostic information to that obtained by the White classification.

Adult↗

PubMedDate not supplied

Absorbed power distributions from two tilted waveguide applicators.

One major problem in microwave-induced clinical hyperthermia treatment of superficial tumours is to obtain therapeutic temperatures at the tumour periphery and adequate deep heating when using a single applicator. The use of multiple applicators has therefore been investigated in order to improve the power distribution. Anatomical surface topography often permits the application of two tilted applicators, e.g. in the head and neck area, on extremities and on large protruding tumours. Theoretical calculations of the absorbed power distribution from such an applicator configuration were performed in a homogeneous muscle equivalent medium. The power distribution from two conventional radiative apertures (TE10) was studied at different frequencies, aperture sizes, tilting angles and non-coherent or coherent fields in phase, both theoretically and with phantom experiments using a thermographic camera. With controlled phase relations between two tilted applicators excited at the lower microwave or upper radiofrequency band, the absorbed power distribution can be varied in a wide range. The theoretical calculations and thermographic phantom experiments in simple geometries give valuable information on absorbed power distributions and guidance for the location of temperature probes in clinical hyperthermia.

Hyperthermia, Induced↗

PubMedDate not supplied

Quantitative assessment of impedance tomography for temperature measurements in hyperthermia.

The objective of this study is a non-invasive assessment of the thermal dose in hyperthermia. Electrical impedance tomography (EIT) has previously been given a first trial as a temperature monitoring method together with microwave-induced hyperthermia treatment, but it has not been thoroughly investigated. In the present work we have examined this method in order to investigate the correlation in vitro between the true spatial temperature distribution and the corresponding measured relative resistivity changes. Different hyperthermia techniques, such as interstitial water tubings, microwave-induced, laser-induced and ferromagnetic seeds have been used. The results show that it is possible to find a correlation between the measured temperature values and the tomographically measured relative resistivity changes in tissue-equivalent phantoms. But the uncertainty of the temperature coefficients, which has been observed, shows that the method has to be improved before it can be applied to clinical in vivo applications.

Body Temperature↗

PubMedDate not supplied

Thyroid tissue characterization by proton magnetic resonance relaxation time determination.

Measurements were performed at 37 degrees C on 49 fresh samples excised from cancerous (n = 16) or non-malignant (n = 33) thyroid tissues of 23 patients. They were carried out for protons at a frequency of 10.7 MHz with pulse sequences (90 degrees-t-90 degrees) and (90 degrees-t-180 degrees-t) for T1 and T2 respectively. The estimates were correlated to histopathology with quantitative measurements of the proportions of colloid, thyroid epithelium, fibrosis, and haemorrhage tissue. Discriminant analysis of malignant and non-malignant tissues using T1 and T2 values, was not successful. T1 and T2 values were correlated to each other. Both were correlated to the proportions of water, thyroid epithelium and haemorrhage and inversely correlated to the amount of colloid. Multiple regression analysis revealed that T2 values were more tissue-specific than T1 values. The analyses indicate possibilities to identify different thyroid tissues by magnetic resonance imaging, especially by T2 weighted MR images.

Body Water↗

PubMedDate not supplied

Role of glutamate-269 in the lactose permease of Escherichia coli.

Glu-269, which is located on the hydrophilic face of putative helix VIII in the lactose permease of Escherichia coli, has been replaced with Asp, Gln or Cys by oligonucleotide-directed, site specific mutagenesis. Cells expressing Asp-269 permease exhibit no lactose accumulation or lactose-induced H+ translocation, but retain some ability to mediate lactose influx down a concentration gradient at high substrate concentrations. Furthermore, right-side-out membrane vesicles containing Asp-269 permease do not catalyse active lactose transport, facilitated lactose efflux or equilibrium exchange. Remarkably, however, Asp-269 permease accumulates beta, D-galactopyranosyl 1-thio-beta,D-galactopyranoside in a partially uncoupled fashion, whereas no transport of methyl-beta,D-thiogalactopyranoside, sucrose or maltose is detectable. Mutant permeases containing neutral replacements (Gln or Cys) or Glu-269 are completely devoid of activity, although the proteins are present in the membrane at concentrations comparable with wild-type or Asp-269 permease. The observations demonstrate that a carboxylate at position 269 is essential for transport activity, and Glu-269 is important for substrate binding and/or recognition.

Amino Acid Sequence↗

PubMedDate not supplied

Determination of clenbuterol residues in bovine urine by optical immunobiosensor assay.

Clenbuterol (CBL) is an orally active beta2-adrenoceptor agonist which has been used in veterinary medicine as a broncodilator and an agent of uterine relaxation. It has however become better known as a drug used illegally to promote growth in farm animals. A rapid and sensitive biosensor assay was developed to detect CBL residues in bovine urine. The method involved a simple extraction procedure using tert-butyl methyl ether followed by analysis on the biosensor with results obtained against a buffer calibration curve. The assay allowed up to 88 samples to be analyzed per working day, with each cycle on the biosensor taking approximately 7 min to complete. The limit of detection (LOD) was determined as 0.27 ng/mL using 20 EU reference blank urine samples. The intra-assay Sr ranged from 4.7-7.6% for 3 control samples while the interassay Sr ranged from 9.2-12.7%. The recovery was found to be approximately 95%. A series of incurred urine samples were assayed and the results compared by Enzyme immunoassay (EIA), radio-immunoassay (RIA), and gas chromatography/mass spectrometry (GC/MS) analysis. Urine samples taken from local abattoirs were also analyzed by the biosensor method and by EIA analysis. The antibody used in the biosensor test exhibited high cross reactivity with at least 7 other beta-agonists allowing detection of these compounds at less than 1 ng/mL in bovine urine.

Adrenergic beta-Agonists↗

PubMedDate not supplied

In vivo evaluation of femoral blood flow measured with magnetic resonance.

Quantitative measurements of blood flow based on magnetic resonance imaging (MRI) using conventional multiple spin echo sequences were evaluated in vivo in healthy young volunteers. Blood flow was measured using MRI in the femoral vein. The initial slope of the multiple spin echo decay curve, corrected for the T2 decay of non-flowing blood was used to calculate the blood flow. As a reference, the blood flow in the femoral artery was measured simultaneously with an invasive indicator dilution technique. T2 of non-flowing blood was measured in vivo in popliteal veins during regional circulatory arrest. The mean T2 of non-flowing blood was found to be 105 +/- 31 ms. The femoral blood flow ranged between 0 and 643 ml/min measured with MRI and between 280 and 531 ml/min measured by the indicator dilution technique. There was thus poor agreement between the two methods. The results indicate that in vivo blood flow measurements made with MRI based on wash-out effects, commonly used in multiple spin echo imaging, do not give reliable absolute values for blood flow in the femoral artery or vein.

Adipose Tissue↗

PubMedDate not supplied

Determination of flow velocities from magnetic resonance multiple spin-echo images. A phantom study.

The purpose of this study was to evaluate a method for the quantification of through-plane flow velocities by magnetic resonance imaging (MRI) from the flow characteristics of conventional multiple spin-echo (MSE) signals. Simulated inflow-outflow-dependent signals, as well as images of a flow phantom were generated and the logarithm of the flow-dependent signal value was plotted against echo time. The normalized slope of the resulting curve was calculated using a least-square fit to simulated and experimental data and was corrected for T2 relaxation effects by subtraction of a slope obtained at zero flow. After this correction, and with certain restrictions regarding the flow velocity (v), maximum number of echoes in the slope calculation and slice thickness (L), the normalized slope of the MSE signal becomes equal to the quotient v/L, and from this relation the flow velocity can be determined. The validity of the proposed method was examined for different flow velocities and for two opposite flow directions. The influence of the size of the region of interest and the number of spin echoes used in the calculation of the slope on the accuracy of the velocity determination was also studied. The sensitivity of the method to flow-induced phase changes was examined in the phantom by comparing the results obtained with different strengths of the slice-selective gradient as well as by comparing results from even-echo data with those from odd-echo data.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Flow Velocity↗