Search PubMed⌕ Search

Biomedical subjects

B Larsson

Publications and source records attributed to B Larsson.

At least 127 records · Page 7Linked to original sources
PubMed1996

Photon beams for radiosurgery produced by laser Compton backscattering from relativistic electrons.

The frontal collisions of a laser beam with relativistic electrons result in Compton-backscattered photons. The energy of these photons is dependent on the laser and electron energy in the range from kilo-electron-volts to tens of mega-electron-volts. In a sufficiently narrow backscattering angle the photons are nearly monochromatic. Over the past 30 years there have been several attempts to produce photon beams by laser backscattering from relativistic electrons stored in magnetic ring structures. One aim is to produce photons in the high mega-electron-volt energy range with fluxes useful for nuclear physics research; another is to produce photons in the high kilo-electron-volt energy range, which would be useful for medical applications, such as coronary angiography or treatment of tumour. Our present interest is to investigate the possibility of using 34 keV to 10 MeV photon beams for applications in stereotactic functional radiosurgery. We foresee the possibility of neurosurgical operations through the intact skull with precise and effective destruction of deeply lying millimetre-sized targets with minimal effects on intervening structures, high reproducibility and good prediction of the results. Our paper presents: a Monte Carlo study of radiosurgery based on cross firing with 34 keV to 100 MeV photon beams and 200 and 580 MeV proton beams, a theoretical description of the kinematics of Compton backscattering and estimates of the backscattered photon flux from several combinations of laser cavities at Nd:YAG (1.17 eV) and CO2 (0.117 eV) laser energies and electron storage rings energies in the range 0.1-1.3 GeV. As examples, existing magnetic structures, such as the DA phi NE Accumulator in the lower energy range and the Trieste Synchrotron Light Source ELETTRA in the higher energy range have been utilized in the calculations. The Monte Carlo study has shown that radiosurgery with photon beams of energies in mega-electron-volt energy range enables precise destruction of deeply lying millimetre-sized targets with minimal effects on intervening structures. Its precision is comparable to that of radiosurgery with 200-580 MeV proton beam, but our hope is that radiosurgery with lower energy photon beams could be more precise and less expensive. An average dose of 200 Gy can be delivered to a target of diameter 2 mm at the centre of an 18 cm diameter phantom in 1 h using photon beams of fluences 7.3 x 10(10), 1.8 x 10(10), 6.5 x 10(8), 2.2 x 10(8), 8.6 x 10(7) and 7.8 x 10(6) photons per second at 34 keV, 100 keV, 1 MeV, 3 MeV, 10 MeV and 100 MeV per cross section of beam of 2 mm diameter, respectively. 34-100 keV photon beams were studied in the hope of finding a strong enhancement of their efficiency if a stable high-Z element were to be introduced into the target's DNA. It is shown that, with a low-energy ring running at about 0.4 GeV and a Nd:YAG laser, it would be possible to obtain the required 3 MeV photon beam flux to deliver the average dose within 1 h, assuming an average distance between the source and the target of about 5 m. With a similar machine used at about 1.3 GeV and a CO2 laser, a 3 MeV photon beam is obtained and the exposure time can be reduced to less than 1 min, assuming a roughly 10 m distance between source and target (here a beam angle of 0.1 mrad only had to be considered due to the larger angular energy and yield spread). With a lower electron energy of 138 MeV and a CO2 laser, a 34 keV photon beam can be produced. More than 45 h would be needed to deliver the same dose. We hope that this time could be shortened considerably if stable iodine were introduced into the target with the help of a DNA-seeking molecular carrier. In this case the geometrical precision would be further improved.

Electrons↗
PubMed1996

Interferon-gamma and tumor necrosis factor-alpha treatment of ex vivo human carcinoma cells potentiates their interaction with allogeneic lymphocytes.

Short-term exposure of ex vivo carcinoma and sarcoma cells to IFN-gamma and TNF-alpha induced or elevated to detectable levels the surface expression of MHC class I, class II, and ICAM-1 (CD54), but only rarely the B7 (CD80) molecules. The cytokine-treated tumor cells interacted more efficiently with allogeneic blood lymphocytes collected from healthy donors compared with untreated cells. This was demonstrated (1) by the induction of DNA synthesis and generation of cytotoxic activity in mixed cultures and (2) by the elevated susceptibility to the cytotoxic effectors. Although the cytokine-induced increase in MHC and ICAM-1 on the low-expressor tumors were probably important to the interaction with lymphocytes, it is likely that other properties were also induced that contributed to the phenomenon. This was indicated by the results obtained with several tumors that expressed indigenously high levels of these molecules but reacted with the allogeneic lymphocytes only or more efficiently after treatment with IFN-gamma and TNF-alpha. In these experiments B7 expression did not influence the efficiency of interactions between lymphocyte and tumor cells. The results also showed that, under the conditions used, the untreated tumor cells that did not activate allogeneic lymphocytes were sensitive to appropriately activated effectors. Thus the afferent and efferent arms of lymphocyte-tumor cell interactions appeared to have different requirements.

Antigens, Neoplasm↗
PubMed1996

A school-based, nurse-administered relaxation training for children with chronic tension-type headache.

Compared the efficacy of a school-based, nurse-administered relaxation training intervention to a no-treatment control condition for children (10-15 years old) with chronic tension-type headache and the outcome at posttreatment and a 6-month follow-up. The study was conducted in a controlled between-group design including 26 schoolchildren who were randomly assigned to the two treatment conditions. Results showed that headache activity in the children treated with relaxation training was significantly more reduced than among those in the no-treatment control group at posttreatment as well as the 6-month follow-up. At these evaluations, 69% and 73% of the pupils, respectively, treated with relaxation had achieved a clinically significant headache improvement (at least a 50% improvement) as compared to 8% and 27% of the pupils, respectively, in the no-treatment control group. Thus, a school-based, nurse-administered relaxation training program seems to be a viable treatment approach for children with chronic tension-type headaches.

Adolescent↗
PubMed1996

Measuring depression for Swedish nonclinical adolescents: factorial validity and equivalence of the Beck Depression Inventory across gender.

Building upon earlier confirmatory factor analytic research that validated a 2nd-order 4-factor structure of the Beck Depression Inventory for Canadian and Swedish nonclinical adolescents, the purposes of the present study were twofold: (a) to test the factorial structure of the Swedish version of the instrument separately for males (n = 559) and females (n = 537), and (b) to test for its measurement and structural equivalence across gender. Except for three minor discrepancies involving correlated errors, the hypothesized model best described the data for both males and females. Nonetheless, the imposition of equality constraints across sex revealed differences bearing on the measurement of six items, and latent construct relations involving the Somatic Elements factors. Four gender differences in factorial structure replicated findings for Canadian adolescents. Results have important implications for researchers, clinicians, and others whose interests focus on nonclinical adolescent depression.

Adolescent↗
PubMed1996

Localization and activity of haem oxygenase and functional effects of carbon monoxide in the feline lower oesophageal sphincter.

1. In the feline lower oesophageal sphincter (LOS), the distribution of the carbon monoxide (CO) producing enzymes haem oxygenase (HO)-1 and -2 was studied by immunohistochemistry and confocal microscopy, the HO activity was measured and the possible role for CO as a mediator of relaxation was investigated. 2. HO-2 immunoreactivity was abundant in nerve cell bodies of the submucosal and myenteric plexus. Approximately 50% of the HO-2-containing myenteric cell bodies were also nitric oxide synthase- and vasoactive intestinal peptide (VIP)-immunoreactive. In addition, HO-2 immunoreactivity was seen in nerve fibres, in non-neuronal cells dispersed in the smooth muscle and in arterial endothelium. HO-1 immunoreactivity was confined to non-neuronal cells in the smooth muscle, similar to those positive for HO-2. 3. Activity of HO, measured as CO production, was observed in LOS homogenates at a rate of 1.00 +/- 0.05 nmol mg-1 protein h-1. This production was inhibited by the HO inhibitor, zinc protoporphyrin-IX (ZnPP). 4. In isolated circular smooth muscle strips of LOS, developing spontaneous tone, exogenously administered CO evoked a concentration-dependent relaxation reaching a maximum of 93 +/- 3%. This relaxation was accompanied by an increase in cyclic GMP, but not cyclic AMP levels. The relaxant response was attenuated by methylene blue, but unaffected by tetrodotoxin. Repeated exposure to CO resulted in a progressive reduction of the relaxant response. 5. ZnPP caused a rightward-shift of the concentration-response curves for the relaxant responses to VIP, peptide histidine isoleucine, and pituitary adenylate cyclase activating peptide 27. 6. ZnPP and tin protoporphyrin-IX (another inhibitor of HO) did not affect nonadrenergic, noncholinergic relaxations induced by electrical field stimulation. Nor did ZnPP affect relaxations induced by 3-morpholino-sydnonimine or forskolin. 7. The present findings, showing localization of HO immunoreactivity to both neuronal and nonneuronal cells of the feline LOS, ability of LOS to produce CO and a relaxant effect of CO in circular LOS muscle, suggest a role for CO as a peripheral messenger.

Animals↗
PubMed1996

Auger-electron spectra of radionuclides for therapy and diagnostics.

The present paper documents the calculation of radiation spectra and of radial dose distribution around a point source for 24 selected radionuclides. The radionuclides were ordered into three groups: Nuclides potentially useful for therapy by emission of Auger electrons: 51Cr, 64Cu, 67Ga, 73Se, 75Se, 77Br, 80mBr, 94Tc, 99mTc, 114mIn, 115mIn, 123I, 124I, 125I, 167Tm, 193mPt, and 195mPt, nuclides potentially useful for therapy by alpha-particles with additional emission of Auger electrons: 212Bi, 211At and 255Fm, and nuclides potentially useful for electron Auger-therapy with simultaneous PET diagnosis: 73Se, 94Tc and 124I. The calculations imply strongly the development of labelled DNA-seeking compounds useful as carrier for the Auger- and Coster-Kronig electron-emitting radionuclides.

Half-Life↗
PubMed1996

Nitric oxide inhibits contraction of isolated pig ureteral smooth muscle.

PURPOSE: To investigate the L-arginine/nitric oxide (NO) pathway in the pig isolated ureter. MATERIALS AND METHODS: Functional inhibitory effects mediated by NO were assessed and correlated with cyclic nucleotide levels. Nitric oxide synthase (NOS) activity was measured by monitoring the conversion of [3H]-arginine to [3H]-citrulline. Immunohistochemical studies were performed. RESULTS: The NO-donor SIN-1 reduced in a concentration-dependent manner the frequency of contractions, whereas NO completely interrupted the contractile activity. In precontracted strips exposed to SIN-1 or NO, there were 6- and 12-fold increases of the cyclic GMP levels in comparison with control preparations. Activity of NOS was moderate. Overall innervation of the ureter was sparse, and there were few NOS-immunoreactive nerves. CONCLUSION: Although few NOS-containing nerves were found, pathways regulating the cyclic GMP levels of pig ureteral smooth muscle were demonstrated. Such pathways may be important targets for drugs producing relaxation of the mammalian ureter.

Animals↗
PubMed1996

Efficacy of Interceed in adhesion prevention in gynecologic surgery: a review of 13 clinical studies.

OBJECTIVE: To evaluate the efficacy of Interceed, alone or in combination with other treatments, for adhesion prevention after adhesiolysis. STUDY DESIGN: Review of 13 clinical studies. RESULTS AND CONCLUSION: While Interceed has been shown to be safe and effective in all controlled human clinical trials, its use did not eliminate adhesions in all patients, and in some there was no benefit from the use of Interceed not provided by surgery alone. The efficacy of this absorbable barrier is limited to surgical situations where the area in question can be completely covered. Effective application is limited by technical difficulties, including the need for hemostasis and removal of excess peritoneal fluid.

Cellulose, Oxidized↗
PubMed1996

Economic consequences of sick-leave and early retirement in obese Swedish women.

OBJECTIVES: To describe the pattern of sick-leave and disability pension in an obese sample and to estimate the Incremental, indirect cost due to sick-leave and early retirement for the obese fraction of the Swedish female population. DESIGN: A retrospective study of sick-leave and disability pension in health examined obese subjects was performed. The indirect cost of obesity in Sweden was estimated from reported and recorded sick-leave and disability pension in the sample and from the estimated prevalence of obesity in the country. SUBJECTS: 1298 obese persons aged 30-59 y. The mean age was 46 years. The mean body mass Index was 39 kg/m2 (range 28-68). SETTING: The obese subjects were recruited from eight counties in Sweden. RESULTS: As compared to the general Swedish population the obese subjects had 1.5-1.9 times higher sick-leave during one year. Twelve percent of the obese women had disability pension while the corresponding figure in the general population was 5%. The incremental cost of sick-leave and disability pensions attributable to obesity was 3.6 billion SEK during one year, which is equivalent to about 300 million USD per million female adult population. The total cost for sick-leave and disability pension due to absence from work for the obese fraction of the Swedish female population was 10.5 billion SEK during one year. CONCLUSION: Obesity represents a major health problem with significant economic implications for the society. Approximately 10 percent of the total cost of loss of productivity due to sick-leave and disability pensions in women may be related to obesity and obesity-related diseases.

Adult↗
PubMed1995

Nitric oxide synthase-immunoreactive, adrenergic, cholinergic, and peptidergic nerves of the female rat urinary tract: a comparative study.

The distribution and frequency of NO synthase (NOS)-immunoreactive (IR) nerves in relation to the general autonomic innervation, adrenergic, cholinergic and some peptidergic nerves, were investigated in the female rat urinary tract. NOS nerves were very frequent in the smooth musculature of the urethra together with cholinergic, adrenergic and neuropeptide Y (NPY)-IR nerves, whereas vasoactive intestinal peptide (VIP)-IR and calcitonin-gene-related peptide (CGRP)-IR nerves were much less abundant. NOS-IR, CGRP-IR and cholinergic nerves were also frequent in the longitudinal smooth musculature of the distal ureters and the ureteral orifices into the bladder, where no adrenergic, NPY-IR and VIP-IR nerves were found. In contrast, in the detrusor NOS-IR nerves were scarce. Bilateral pelvic ganglionectomy very pronouncedly decreased the number of any of the populations of nerves studied, whereas bilateral pelvic decentralization selectively reduced the number of CGRP-IR nerves in all structures and locations. Outflow obstruction very overtly reduced the number of NOS-IR nerves in parallel with the general autonomic innervation. Thus, in the rat female urinary tract, NOS-containing nerves particularly occur in regions with sphincteric functions such as urethra and ureteric orifices. In these regions NO may exert a transmitter role, both directly or by interaction with other transmitters/modulators.

Adrenergic Fibers↗
PubMed1995

Carbon monoxide as a putative messenger molecule in the feline lower oesophageal sphincter of the cat.

The distribution of the carbon monoxide (CO) producing enzymes haem oxygenase (HO) type 1 and 2 were studied in the feline lower oesophageal sphincter (LOS), as were HO activity and functional effects of CO. HO-2 immunoreactivity was observed in nerve cell bodies in the submucosal and myenteric plexus, nerve fibres, non-neuronal cells surrounding smooth muscle bundles, and in arterial endothelium, HO-1 immunoreactivity was confined to non-neuronal cells in the smooth muscle layer. CO production, indicating HO activity, was demonstrated in tissue homogenates. CO relaxed the LOS, and activated the cyclic GMP system. These results show that HO is present in the LOS, and suggest that CO can be generated by neuronal and non-neuronal structures and may have a role as a peripheral messenger.

Animals↗
PubMed1995

Co-existence of nitrergic, peptidergic and acetylcholine esterase-positive nerves in the pig lower urinary tract.

The distribution of NO synthase (NOS) immunoreactive nerves and the possible co-existence with other neurotransmitters were investigated in the pig lower urinary tract. NOS immunoreactive nerves were found in the muscle layer, in the lamina propria and around blood vessels. The density of NOS immunoreactive nerves was more prominent in the trigone and urethra than in the detrusor. All parts of the lower urinary tract were supplied by numerous acetylcholine esterase (AChE) positive nerves. The number of adrenergic nerves in the trigone and urethra was moderate to rich, whereas only very few adrenergic nerves were demonstrated in the detrusor. A low to moderate number of nerve fibres containing neuropeptide Y (NPY) and vasoactive intestinal polypeptide (VIP) were observed in the trigone and urethra, while very few were found in the detrusor. A small number of nerves, confined to the trigone and urethra, were stained for calcitonin-gene-related peptide, somatostatin and leu-enkephalin. Nerve fibres exhibiting immunoreactivity to bombesin/gastrin releasing peptide, gastrin/cholecystokinin, substance P or neurokinin A were virtually absent. Co-localization studies revealed that some NOS-immunoreactive nerves also stained for NPY, VIP or AChE. The present study shows that nitrergic nerves are present in the pig lower urinary tract in a density lower than the cholinergic, but higher than any of the studied peptidergic nerves. Coinciding localization of NOS-positive nerves with nerves expressing AChE, VIP and NPY suggests that NO may have a role as a messenger in the lower urinary tract directly and by interaction with other transmitters.

Acetylcholinesterase↗
PubMed1995

New and simplified vaginal approach for correction of urinary stress incontinence in women.

Twenty-four patients with urodynamically confirmed urinary stress incontinence were operated upon with a new and simplified vaginal approach. This new technique is a simplification of a previously described transabdominal surgical method, in which a two-component fibrin sealant (Tisseel) was used. The sealant resulted in an excess of fibrin, which induced fibrosis, securing the urethrovesical junction in an elevated position to the retropubic periosteum. In the present study, the sealant was deposited retropubically with a specially designed needle through the anterior vaginal wall. A great advantage with this procedure is that only local anesthesia is used and the patient can leave the outpatient clinic 1 hour after the operation. The minimum duration of the follow-up period was 18 months. The success rate was as high as 63%, and no side effects were observed.

Adult↗
PubMed1995

Localisation of neuronal nitric oxide synthase-immunoreactivity in rat and rabbit retinas.

The distribution of neuronal nitric oxide synthase (NOS) immunoreactivity was examined in rat and rabbit retinas and was compared with the distribution of nicotinamide adenine dinucleotide phosphate (NADPH)-diaphorase reactivity and vasoactive intestinal peptide (VIP) immunoreactivity. An antibody raised against a C-terminal fragment of a cloned rat cerebellar NOS was used to localise NOS immunoreactivity. NOS immunoreactive cells were not detected in rat retinas at postnatal day 1 or 4, but were seen from postnatal day 7 onwards. NOS immunolabelling was seen in a small population of cells in the proximal inner nuclear layer. Most of the labelled cells had the position of amacrine cells and were seen to send processes into the inner plexiform layer. A few labelled cells were at times also seen in the ganglion cell layer, which are likely to correspond to displaced amacrine cells. The same NOS-labelling pattern was seen in rat and rabbit retinas. NADPH-diaphorase staining was observed in both species, in photoreceptor inner segments, in cells with the position of horizontal cells, in a subset of amacrine and displaced amacrine cells, in large cell bodies in the ganglion cell layer, in both plexiform layers, and in endothelium. Colocalisation of NOS immunoreactivity and NADPH-diaphorase staining was only observed among amacrine cells. However, not all NADPH-diaphorase-reactive amacrine cells were found to be NOS immunoreactive. VIP immunoreactivity was also localised in rat retinas in a subpopulation of amacrine cells, but no colocalisation of NOS and VIP immunoreactivity was observed. Our observations indicate that only amacrine cells contain the NOS form recognisable by the antibody used, and suggest that different isoforms of neuronal NOS may be present in retinal cells. Further, the onset of NOS expression in rat amacrine cells appears to occur independently of neuronal activity.

Amino Acid Oxidoreductases↗
PubMed1995

Immunogenicity and immunosensitivity of ex vivo human carcinomas: interferon gamma and tumour necrosis factor alpha treatment of tumour cells potentiates their interaction with autologous blood lymphocytes.

Human carcinoma cells vary appreciably in the expression of MHC class I, class II, ICAM-1 (CD54) and B7 (CD80) molecules. Short-term in vitro exposure of ex vivo carcinoma cells to interferon gamma and tumour necrosis factor alpha elevated/induced the surface expression of MHC class I, class II and ICAM-1, but only rarely of B7. We found that cytokine treatment elevated the cytotoxic susceptibility and the stimulatory potential of ex vivo tumour cells. This was demonstrated (a) by the increased frequency and elevated level of auto-tumour lysis and (b) by induction of DNA synthesis and generation of cytotoxic lymphocytes in autologous mixed lymphocyte/tumour cell culture (MLTC). The MHC class I and ICAM-1 molecules on the tumour cells were required for interaction with the lymphocytes as indicated by the inhibitory effect of specific mAb both in the stimulation and in the cytotoxic tests. While the cytokine-induced increases in MHC and ICAM-1 on the low-expression tumours were probably important for the modification of functional interaction with the autologous lymphocytes, it is likely that alterations in other properties of tumour cells were also induced which contributed to the phenomenon. This was indicated by the results obtained with several tumours, which expressed indigenously high levels of these molecules but activated the autologous lymphocytes only after cytokine treatment. In several experiments the untreated targets that did not activate the lymphocytes were sensitive to the cytotoxicity of the effectors activated in MLTC. The results show that the afferent and efferent arms of the immune response have different requirements for functional interactions between lymphocytes and tumour cells.

Antibodies, Neoplasm↗