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Biomedical subjects

A Lund

Publications and source records attributed to A Lund.

At least 19 recordsLinked to original sources
PubMed2006

An ESR and ENDOR study of irradiated 6Li-formate.

Lithium formate ((6)LiOOCH.H(2)O), 95% (6)Li enrichment, combined with an exchange of crystallization water with D(2)O was investigated. The ESR spectrum of the radiation induced free radicals stable at room temperature consists of a singlet with a narrow line width, 0.92mT. (6)Li has smaller magnetic moment and nuclear spin, which resulted in the narrower line width accompanied with an increase in peak amplitude. In comparison with lithium formate with natural isotopic composition, (6)Li (7.5%, I=1) and (7)Li (92.5%, I=3/2), the sensitivity was increased by a factor of two. With optimised spectrometer settings (6)Li formate had seven times higher sensitivity compared to alanine. Therefore this material is proposed as a dosimeter material in a dose range down to 0.1Gy. The g and the (13)C-hyperfine (hf) tensors of the CO(2)(-) radical anion, major paramagnetic products, were evaluated to be g=(2.0037, 1.9975, 2.0017), and A((13)C)=(465.5, 447.5, 581.3) MHz for polycrystalline samples at room temperature. Furthermore, the (1)H-hf and (6)Li-hf tensors observed for the surroundings of CO(2)(-) by ENDOR technique were in fairly good agreement with DFT calculations. The CO(2)(-) radicals are found to be so stable that the formate is applicable to the ESR dosimetry, because of fully relaxing in a fully relaxed geometrical structure of the CO(2)(-) component and remaining tight binding with the surroundings after the H atom detachment from HCO(2)(-).

Dose-Response Relationship, Radiation↗
PubMed2006

Neuropsychological test profiles in schizophrenia and non-psychotic depression.

OBJECTIVE: The study examined to what degree schizophrenia is characterized by a neuropsychological (NP) test profile specific in shape and level compared with depression and normal functioning. METHOD: Fifty-three patients with schizophrenia, 45 with non-psychotic depression, and 50 normals were assessed with a comprehensive NP test battery and clinical instruments. NP test scores were factor analyzed into seven composite scores. RESULTS: Schizophrenia patients performed significantly below normals across all seven composite scores, whereas depression patients were impaired in two. Verbal memory was most impaired. Sixty-two percent of schizophrenia patients were moderately or severely impaired, the corresponding figure for depression was 28%. Impairment was moderately associated with IQ level and clinical symptom load in schizophrenia, but not in depression. CONCLUSION: Schizophrenia is characterized by deficits across a wide range of NP functions. Thirty-eight percent of the patients are within normal limits. A mild and limited NP disturbance is apparent in depression.

Adult↗
PubMed2006

Positive symptoms and duration of illness predict functional laterality and attention modulation in schizophrenia.

OBJECTIVE: Dichotic listening (DL) performance in schizophrenia, reflecting hemispheric asymmetry and the functional integrity of the left temporal lobe, can vary with clinical characteristics. Previous studies have not taken the co-linearity of clinical variables into account. The aim of the present study was to evaluate the roles of positive symptoms and duration of illness in DL through Structural Equation Modeling (SEM), thus allowing for complex relationships between the variables. METHOD: We pooled patients from four previous DL studies to create a heterogeneous group of 129 schizophrenic patients, all tested with a consonant-vowel syllables DL procedure that included attentional instructions. RESULTS: A model where positive symptoms predicted a laterality component and duration of illness predicted an attention component in DL was confirmed. CONCLUSION: Positive symptoms predicted reduced functional laterality, suggesting involvement of left temporal lobe language processing. Duration of illness predicted impaired attention modulation, possibly reflecting the involvement of frontotemporal networks.

Adolescent↗
PubMed2005

Conduction electron spin resonance of small silver particles.

Electron spin resonance (ESR) spectroscopy has been used to study the conduction electron spin resonance (CESR) of small silver particles stabilized in dehydrated Ag-rho zeolite. Silver particles were produced by hydrogen reduction at elevated temperatures and diameter of the stabilized particles was calculated based on the linewidth of CESR signal using Kawabata theory.

Electron Spin Resonance Spectroscopy↗
PubMed2005

Formates and dithionates: sensitive EPR-dosimeter materials for radiation therapy.

Polycrystalline formates and dithionates are promising materials for EPR dosimetry, as large yields of radiation induced stable radicals are formed with a linear dose response. Rapid spin relaxation rates were detected in many of the substances, indicating that a high microwave power can be applied during EPR acquisition in order to improve sensitivity. Different techniques used to further improve the sensitivity, such as the replacement of 7Li with 6Li or exchange of protons with deuterons in the corresponding crystalline matrices and metal ion doping are discussed. It is concluded that formates and dithionates may be up to 10 times as sensitive as L-alpha-alanine.

Dose-Response Relationship, Radiation↗
PubMed2005

Enhanced sensitivity of lithium dithionates doped with rhodium and nickel for EPR dosimetry.

Electron paramagnetic resonance (EPR) studies of X-irradiated lithium dithionate, Li(2)S(2)O(6) x 2H(2)O, doped with Ni and Rh have shown that these impurities enhance the yield of radicals formed by X-irradiation at room temperature. The signal in the doped samples, measured peak-to-peak of the single EPR derivative line attributed to the SO(3)(-) anion was about 3-4 times that of the pure lithium dithionate and more than 10 times stronger than the alanine signal. These impurities also shortened the spin-lattice relaxation time, T(1), which gives the possibility to measure the doped samples at a higher microwave power. This implies that sensitivity could be further enhanced in the already sensitive EPR dosimeter material lithium dithionate.

Dosage Forms↗
PubMed2005

General psychopathology is more important for executive functioning than diagnosis.

OBJECTIVE: Impaired executive functioning (EF) has often been reported in patients with major depression or schizophrenia. We hypothesize that the variance in EF is more affected by level of general psychopathology than by diagnosis. METHOD: Forty-three patients with major depression and 47 with schizophrenia were included. EF was measured with Wisconsin Card Sorting Test, Stroop Colour Word Test, Paced Auditory Serial Addition Test, Digits Backwards and Controlled Oral Word Association Test. The level of general psychopathology was measured with Brief Psychiatric Rating Scale - Expanded and Positive and Negative Syndrome Scale, the General psychopathology subscale. RESULTS: The level of general psychopathology predicted more of the variance in EF than diagnosis. In multivariate analyses, the effect of general psychopathology on EF was more robust for adjustment for diagnosis than vice versa. CONCLUSION: Future research on cognitive functioning in psychiatric patients should include level of general psychopathology to avoid overemphasising effects of diagnoses.

Adult↗
PubMed2005

Cortisol level predicts executive and memory function in depression, symptom level predicts psychomotor speed.

OBJECTIVE: On a group level depression is related to hypercortisolism and to psychomotor retardation, executive dysfunction and memory impairment. However, intra-group heterogeneity is substantial. Why some are impaired while others remain in the normal range, is not clear. The present study aims at discerning the relative contribution of present symptom severity and hypercortisolism to impairment in the three domains of cognition. METHOD: Morning saliva cortisol was measured in 26 subjects with recurrent major depression prior to a neuropsychological examination with tests known to be sensitive to cognitive impairment in depression. RESULTS: Cortisol level correlated with executive dysfunction and post-encoding memory deficits, but not with processing speed. Depression level correlated with processing speed. These patterns remained significant after controlling for confounders through partial correlations. CONCLUSION: The association between cortisol and cognition is not an artifact of psychiatric symptom load. High level of saliva cortisol is associated with aspects of cognition that can be dissociated from psychomotor retardation, which is dependent on symptom load.

Adult↗
PubMed2004

Compounds of 6Li and natural Li for EPR dosimetry in photon/neutron mixed radiation fields.

Formates and dithionates of 6Li, enriched and 7Li in natural composition of Li offer a possibility to measure the absorbed dose from photons and thermal neutrons in a mixed radiation field for instance at a boron neutron capture therapy (BNCT) facility. Tests with formates and dithionates of enriched 6Li and lithium compounds with natural composition have been performed at the BNCT facility at Studsvik, Sweden. Irradiations have been performed at 3 cm depth in a Perspex phantom in a fluence rate of thermal neutrons 1.8 x 10(9) n cm(-2) s(-1). The compounds were also irradiated in a pure X-ray field from a 4MV linear accelerator at 5 cm depth in a phantom with accurately determined absorbed doses. The signal intensity and shape was investigated within 3 h after the irradiation. A single line spectrum attributed to the CO2- radical was observed after irradiation of lithium formate. An increase in line width occurring after neutron irradiation in comparison with photon irradiation of the 6Li sample was attributed to dipolar broadening between CO2- radicals trapped in the tracks of the alpha particles. A spectrum due to the SO3- radical anion was observed after irradiation of lithium dithionate. The signal amplitude increased using the 6Li in place of the Li with natural composition of isotopes, in studies with low energy X-ray irradiation. Due to the decreased line width, caused by the difference in g(N) and I between the isotopes, the sensitivity with 6Li dithionate may be enhanced by an order of magnitude compared to alanine dosimetry. After comprehensive examination of the different combinations of compounds with different amounts of 6Li and 7Li regarding dosimetry, radiation chemistry and EPR properties these dosimeter material might be used for dose determinations at BNCT treatments and for biomedical experiments. Interesting properties of the radical formation might be visible due to the large difference in ionization density of neutrons compared to photons.

Alanine↗
PubMed2004

51V(n, beta)52Cr reaction for neutron dosimetry: development and assessment of a spectrophotometric method for determination of Cr in vanadium at sub ppm level.

With a view to monitoring the changes in coloration caused by the nuclear reaction 51V(n, beta)52Cr in solution of vanadyl sulphate and using it for neutron dosimetry, electronic absorption spectra of vanadyl sulphate solutions were investigated at different concentrations of chromate impurity in micromolar range. It was observed that the presence of chromate enhances the absorptivity over a wide wavelength range serving essentially as a colouring agent for vanadium matrix, presumably due to charge transfer process. The absorbance at 380 nm varied linearly over a wide concentration range. The limit of detection of chromate obtained is shown to be adequate for detecting neutron-induced chemical transmutation of vanadium to chromium under standard reactor conditions, when used with long path length cells. It was observed that the absorbance does not change on electron irradiation, suggesting that radiolytic effects due to beta decay, if any, do not interfere in the measurement of neutron-induced changes. In addition to its potential for neutron dosimetry, this is the first report of a simple and direct method of estimation of Cr in vanadium matrix at sub ppm level.

Chemistry Techniques, Analytical↗
PubMed2004

Release of TNF-alpha from in vitro-stimulated monocytes is negatively associated with serum levels of apolipoprotein B in patients with type 2 diabetes.

Impaired course of inflammation is a likely mechanism behind a number of diabetic complications. The present study was undertaken to investigate lipopolysaccharide-induced production of tumour necrosis factor (TNF)-alpha in monocytes from patients with type 2 diabetes and to assess its relationship with diabetes-associated metabolic abnormalities. Monocytic TNF-alpha mRNA production was lower in the diabetic participants compared to their corresponding controls. Diabetic subjects who had been receiving simvastatin treatment had TNF-alpha mRNA production similar to that of the healthy participants. The release of TNF-alpha from diabetic cells correlated negatively with serum levels of apolipoprotein B (apoB) (R = -0.755, P = 0.001), total plasma cholesterol (R = - 0.702, P = 0.002) and the presence of retinopathy (R = -0.572, P = 0.021). No such associations were found in the control subjects. In a multiple linear regression model, only the level of apoB and diabetes duration demonstrated significant effects on the release of TNF-alpha, with apoB alone accounting for 57% of the variation. We conclude that production of TNF-alpha mRNA in response to the bacterial stimulant is compromised in poorly controlled type 2 diabetes. Lipid abnormalities are associated with the observed defect. Impaired cytokine production represents a significant defect in the functioning of the immune system and may contribute to aberrations in the course of inflammation in the diabetic state.

Apolipoproteins B↗
PubMed2004

Ammonium formate, a compound for sensitive EPR dosimetry.

Alanine EPR dosimetry has been applied successfully when measuring intermediate and high radiation doses. Although the performance of alanine dosimetry is being improved, the sensitivity of the material is too low for a fast and simple low- dose determination. Here we present the results using ammonium formate as an EPR dosimeter material. Ammonium formate is seven times more sensitive than alanine, using spectrometer settings optimized for the latter. Deuterated ammonium formate is found to be more than eight times more sensitive than alanine. Analysis of signal stability with time shows that the ammonium formate signal is stable by 5 min after irradiation and that no change in signal intensity is found during 8 days. The atomic composition of ammonium formate is closer to that of tissue than alanine, and thus the energy dependence is smaller than that of alanine at photon energies below 200 keV. Power saturation studies indicate that the energy transfer between the spins and the lattice is fast in ammonium formate, which gives the possibility of using high microwave power without saturation to further increase the sensitivity. These results suggest that ammonium formate has some important properties required of an EPR dosimeter for applications in dosimetry in the dose range typical for radiation therapy.

Alanine↗
PubMed2003

Attention profile in schizophrenia compared with depression: differential effects of processing speed, selective attention and vigilance.

OBJECTIVE: The aim of the study is to investigate whether subjects with schizophrenia and major depression display attention deficits for different reasons. METHOD: Subjects with schizophrenia (n = 53), recurrent major depression (n = 50) and normal controls (n = 50) were administered with 11 measures of processing speed, selective attention and vigilance. Indices of basal speed, speeded attention, non-speeded attention and vigilance were computed. RESULTS: Both clinical groups were impaired on all chronometric tests. The schizophrenic subjects were also more impaired on speeded attention compared with basal processing speed. Only the schizophrenics were impaired on the non-speeded measures of selective attention. Compared with the schizophrenics, the depressives showed a decrement in vigilance. CONCLUSION: Reduced performance on attention tests in major depression is because of a non-specific speed reduction and loss of vigilance consistent with lack of effort. In addition to generally impaired processing speed, the schizophrenic subjects exposed a deficit in selective attention, indicating executive dysfunction.

Adult↗
PubMed2002

New materials for ESR dosimetry.

New materials for electron spin resonance (ESR) dosimetry have been investigated with the aim to find systems more sensitive than L-alanine accepted as a standard for high dose determinations. Among the investigated systems ammonium tartrate, 2-methylalanine, salts of formic acids and dithionates have been found to be more sensitive than alanine by a factor 2-10. The lower limit applies to tissue equivalent materials, while much higher sensitivities were obtained with formates and dithionates containing heavier atoms. The increased sensitivity was mainly attributed to suitable ESR properties of the room temperature stable radicals as regards spectral shape (narrow lines, little or no hyperfine structure) and microwave saturation properties (short relaxation times). The radical structures have when necessary been clarified by ENDOR spectroscopy, while the saturation properties have been screened by pulsed ESR measurements.

Alanine↗
PubMed2002

Antibody responses in sheep vaccinated against Staphylococcus aureus mastitis: a comparison of two experimental vaccines containing different adjuvants.

A double-blind, placebo-controlled study was conducted to compare two vaccines using different adjuvants with regard to their ability to stimulate antibody production against the alpha- and beta-toxins and the exopolysaccharide of Staphylococcus aureus. The vaccines contained identical antigens, consisting of inactivated whole bacteria of two strains of S. aureus in addition to alpha- and beta-toxoid. One vaccine contained mineral oil, while the other used a water-soluble acrylic acid polymer resin (Carbopol) as adjuvant. Saline served as the placebo. One hundred and forty ewes were vaccinated twice before lambing, by subcutaneous injection with vaccine or placebo in the region of the supramammary lymph node, and were observed and sampled over a period of 6 months. The vaccine containing mineral oil as adjuvant induced significantly greater immune responses to the alpha- and beta-toxins than did the vaccine containing Carbopol. The latter vaccine induced higher levels of antibodies to exopolysaccharide. The degree of local adverse reactions did not differ between the two groups. The results indicate differences between the oil-adjuvanted and Carbopol-adjuvanted vaccines with regard to their ability to stimulate antibody production against S. aureus protein antigens in sheep.

Acrylic Resins↗
PubMed2002

Spleen size: how well do linear ultrasound measurements correlate with three-dimensional CT volume assessments?

Ultrasound measurement of splenic length is standard practice, but it is not known how well this represents the true size of the spleen. Previous studies, using a combination of measurements from in vivo and resected spleens, were subject to error because of changes in splenic size. The aim of this study was to correlate the dimensions of the spleen measured by ultrasound with the splenic volume measured by helical CT. Ultrasound examination was performed on 50 adult patients at the time of their attendance for abdominal CT. Linear dimensions of the spleen were measured with the patient first in the supine and then in the right lateral decubitus (RLD) position. The splenic volume was calculated from a three-dimensional reconstruction of the CT images. There was good correlation, using Spearman's rank correlation, between ultrasound measurements and CT volumes with correlation coefficients exceeding 0.7 for all parameters except one. The linear measurement that correlated most closely with CT volume was the spleen width measured on a longitudinal section with the patient in the RLD position (correlation coefficient (r)=0.89, p<0.001). There was also good correlation between splenic length measured in the RLD position and CT volume (r=0.86, p<0.001). We conclude that a good correlation exists between in vivo ultrasound assessment of splenic size and true splenic volume. The most accurate single measurement is spleen width measured on a longitudinal section with the patient in the RLD position. However, measurement of splenic length, which is the most commonly used in clinical practice, also correlates well with splenic volume, particularly when performed with the patient in the RLD position.

Adult↗
PubMed2001

Conformational preference and remote (1,10) stereocontrol in biphenyl-2,2'-dicarboxamides.

The double ortholithiation and electrophilic quench of N,N,N'N'-tetraisopropylbiphenyl-2,2'-dicarboxamide 1 is diastereoselective, giving the chiral, C(2)-symmetric atropisomers of the 3,3'-disubstituted products 3. These chiral atropisomers can be converted with moderate to good stereoselectivity to their achiral, centrosymmetric epimers by heating. The stereoselectivity of the double lithiation-quench reaction is determined by the stereochemistry of the intermediate doubly lithiated species 2, either diastereoisomer of which may be formed stereospecfically from the corresponding atropisomeric dibromo compounds.[reaction: see text]

Journal Article↗