PubMed Health⌕ Search

Biomedical subjects

B Hansson

Publications and source records attributed to B Hansson.

At least 19 recordsLinked to original sources
PubMed2005

Surgical smoke and infection control.

Gaseous byproducts produced during electrocautery, laser surgery or the use of ultrasonic scalpels are usually referred to as 'surgical smoke'. This smoke, produced with or without a heating process, contains bio-aerosols with viable and non-viable cellular material that subsequently poses a risk of infection (human immunodeficiency virus, hepatitis B virus, human papillomavirus) and causes irritation to the lungs leading to acute and chronic inflammatory changes. Furthermore, cytotoxic, genotoxic and mutagenic effects have been demonstrated. The American Occupational Safety and Health Administration have estimated that 500000 workers are exposed to laser and electrosurgical smoke each year. The use of standard surgical masks alone does not provide adequate protection from surgical smoke. While higher quality filter masks and/or double masking may increase the filtration capability, a smoke evacuation device or filter placed near (2-5 cm) the electrocautery blade or on endoscope valves offers additional (and necessary) safety for operating personnel and patients.

Air Pollutants, Occupational↗
PubMed2004

Observation of a ZZW female in a natural population: implications for avian sex determination.

Avian sex determination is chromosomal; however, the underlying mechanisms are not yet understood. There is no conclusive evidence for either of two proposed mechanisms: a dominant genetic switch or a dosage mechanism. No dominant sex-determining gene on the female-specific W chromosome has been found. Birds lack inactivation of one of the Z chromosomes in males, but seem to compensate for a double dose of Z-linked genes by other mechanisms. Recent studies showing female-specific expression of two genes may support an active role of the W chromosome. To resolve the question of avian sex determination the investigation of birds with a 2A: ZZW or 2A: ZO genotype would be decisive. Here, we report the case of an apparent 2A: ZZW great reed warbler (Acrocephalus arundinaceus) female breeding in a natural population, which was detected using Z-linked microsatellites. Our data strongly suggest a role of W-linked genes in avian sex determination.

Animals↗
PubMed2004

Between-year variation of MHC allele frequencies in great reed warblers: selection or drift?

The major histocompatibility complex (MHC) genes are extremely polymorphic and this variation is assumed to be maintained by balancing selection. Cyclic interactions between pathogens and their hosts could generate such selection, and specific MHC alleles or heterozygosity at certain MHC loci have been shown to confer resistance against particular pathogens. Here we compare the temporal variation in allele frequencies of 23 MHC class I alleles with that of 23 neutral microsatellite markers in adult great reed warblers (a passerine bird) in nine successive cohorts. Overall, the MHC alleles showed a significantly higher variation in allele frequencies between cohorts than the microsatellite alleles, using a multi-variate genetic analysis (amova). The frequency of two specific MHC alleles, A3e (P = 0.046) and B4b (P = 0.0018), varied more between cohorts than expected from random, whereas none of the microsatellite alleles showed fluctuations exceeding the expectation from stochastic variation. These results imply that the variation in MHC allele frequencies between cohorts is not a result of demographic events, but rather an effect of selection favouring different MHC alleles in different years.

Analysis of Variance↗
PubMed2001

Microsatellite diversity predicts recruitment of sibling great reed warblers.

Inbreeding increases the level of homozygosity, which in turn might depress fitness. In addition, individuals having the same inbreeding coefficient (e.g. siblings) vary in homozygosity. The potential fitness effects of variation in homozygosity that is unrelated to the inbreeding coefficient have seldom been examined. Here, we present evidence from wild birds that genetic variation at five microsatellite loci predicts the recruitment success of siblings. Dyads of full-sibling great reed warblers (Acrocephalus arundinaceus), one individual of which became a recruit to the natal population while the other did not return, were selected for the analysis. Each dyad was matched for sex and size. Local recruitment is strongly tied to fitness in great reed warblers as the majority of offspring die before adulthood, philopatry predominates among surviving individuals and emigrants have lower lifetime fitness. Paired tests showed that recruited individuals had higher individual heterozygosity and higher genetic diversity, which was measured as the mean squared distance between microsatellite alleles (mean d(2)), than their non-recruited siblings. These relationships suggest that the microsatellite markers, which are generally assumed to be neutral, cosegregated with genes exhibiting genetic variation for fitness.

Animals↗
PubMed2000

Host specificity in avian blood parasites: a study of Plasmodium and Haemoproteus mitochondrial DNA amplified from birds.

A fragment of the mitochondrial cytochrome b gene of avian malaria (genera Haemoproteus and Plasmodium) was amplified from blood samples of 12 species of passerine birds from the genera Acrocephalus, Phylloscopus and Parus. By sequencing 478 nucleotides of the obtained fragments, we found 17 different mitochondrial haplotypes of Haemoproteus or Plasmodium among the 12 bird species investigated. Only one out of the 17 haplotypes was found in more than one host species, this exception being a haplotype detected in both blue tits (Parus caeruleus) and great tits (Parus major). The phylogenetic tree which was constructed grouped the sequences into two clades, most probably representing Haemoproteus and Plasmodium, respectively. We found two to four different parasite mitochondrial DNA (mtDNA) haplotypes in four bird species. The phylogenetic tree obtained from the mtDNA of the parasites matched the phylogenetic tree of the bird hosts poorly. For example, the two tit species and the willow warbler (Phylloscopus trochilus) carried parasites differing by only 0.6% sequence divergence, suggesting that Haemoproteus shift both between species within the same genus and also between species in different families. Hence, host shifts seem to have occurred repeatedly in this parasite host system. We discuss this in terms of the possible evolutionary consequences for these bird species.

Animals↗
PubMed2000

Increase of genetic variation over time in a recently founded population of great reed warblers (Acrocephalus arundinaceus) revealed by microsatellites and DNA fingerprinting.

Genetic similarity within pairs of individuals was examined using both 10 polymorphic microsatellite loci and multi-locus DNA fingerprinting profiles in a semi-isolated population of great reed warblers at Lake Kvismaren, south Central Sweden, in 1987-1993. The population was founded by a few individuals in 1978, followed by a gradual increase in numbers until 1988, since when the population has remained relatively stable with about 60 breeding birds. We have previously found that high genetic similarity between pair-mates in the population during the early part of the study period reduced egg hatching success, and hence reproductive success. The measures of pairwise genetic similarity, microsatellite allele sharing and DNA fingerprinting band sharing, were highly correlated with pedigree-based relatedness. Both microsatellite and DNA fingerprinting similarities between pair-mates declined significantly over the study period, and the pattern was most pronounced in the DNA fingerprinting data. Analyses restricted to the microsatellite data showed that the average annual microsatellite similarity between pairwise combinations of individuals, as well as individual homozygosity in males, declined significantly over the study period, and that several immigrants carrying novel alleles entered the population during the study. Hence, the temporal decline in genetic similarity of mates in the population is probably a consequence of increased immigration, facilitated by the recent expansion of the species in the region. These results suggest that the population has now recovered genetically, or is in the process of recovering, from a recent founder event.

Animals↗
PubMed2000

Leiomyoma of the right common iliac vein presenting as a duodenal tumour.

A case of vascular leiomyoma originating from the wall of the right common iliac vein is presented. Clinical and radiological features suggested a well circumscribed tumour arising from the duodenal wall. Laparotomy revealed a tumour without connection to the duodenum, but attached to the right iliac vein. The tumour was totally resected, including partial resection of the common iliac vein. Pathology showed a smooth muscle tumour with histological features of benignity. Six months after surgery the patient is asymptomatic.

Diagnosis, Differential↗
PubMed2000

Evolution of reproductive strategies in the sexually deceptive orchid Ophrys sphegodes: how does flower-specific variation of odor signals influence reproductive success?

The orchid Ophrys sphegodes Miller is pollinated by sexually excited males of the solitary bee Andrena nigroaenea, which are lured to the flowers by visual cues and volatile semiochemicals. In O. sphegodes, visits by pollinators are rare. Because of this low frequency of pollination, one would expect the evolution of strategies that increase the chance that males will visit more than one flower on the same plant; this would increase the number of pollination events on a plant and therefore the number of seeds produced. Using gas chromatography-mass spectrometry (GC-MS) analyses, we identified more than 100 compounds in the odor bouquets of labellum extracts from O. sphegodes; 24 compounds were found to be biologically active in male olfactory receptors based on gas chromatography with electroantennographic detection (GC-EAD). Gas chromatography (GC) analyses of odors from individual flowers showed less intraspecific variation in the odor bouquets of the biologically active compounds as compared to nonactive compounds. This can be explained by a higher selective pressure on the pollinator-attracting communication signal. Furthermore, we found a characteristic variation in the GC-EAD active esters and aldehydes among flowers of different stem positions within an inflorescence and in the n-alkanes and n-alkenes among plants from different populations. In our behavioral field tests, we showed that male bees learn the odor bouquets of individual flowers during mating attempts and recognize them in later encounters. Bees thereby avoid trying to mate with flowers they have visited previously, but do not avoid other flowers either of a different or the same plant. By varying the relative proportions of saturated esters and aldehydes between flowers of different stem positions, we demonstrated that a plant may take advantage of the learning abilities of the pollinators and influence flower visitation behavior. Sixty-seven percent of the males that visited one flower in an inflorescence returned to visit a second flower of the same inflorescence. However, geitonogamy is prevented and the likelihood of cross-fertilization is enhanced by the time required for the pollinium deposited on the pollinator to complete its bending movement, which is necessary for pollination to occur. Cross-fertilization is furthermore enhanced by the high degree of odor variation between plants. This variation minimizes learned avoidance of the flowers and increases the likelihood that a given pollinator would visit several to many different plants within a population.

Animals↗
PubMed2000

Partial albinism in a semi-isolated population of great reed warblers.

Albinism in birds is thought to result from the expression of recessive alleles that disrupt melanin pigmentation at feather development. We have studied great reed warblers Acrocephalus arundinaceus in a recently founded and increasing population in Sweden during 15 years for the presence of birds with albinistic feathers. The study population was founded in 1978 and the few cases of albinism was exclusively recorded during the first five years of our study (1985-1989). This fits to the expected pattern if albinism is governed by recessive alleles; we have previously demonstrated that the population suffered from inbreeding during the first years of our study. The albinistic birds experienced a similar lifetime reproductive success as normally coloured birds.

Animals↗
PubMed1999

Functional attributes discriminating mechano-insensitive and mechano-responsive C nociceptors in human skin.

Microneurography was used in healthy human subjects to record action potentials from unmyelinated nerve fibers (C units) in cutaneous fascicles of the peroneal nerve. Activity-dependent slowing (n = 96) and transcutaneous electrical thresholds (n = 67) were determined. Eight units were sympathetic efferents according to their responses to sympathetic reflex provocations. Mechano-heat-responsive C units (CMH) (n = 56) had thresholds to von Frey hair stimulation </=90 mN (6.5 bar). Mechano-insensitive C units (n = 32) were unresponsive to 750 mN (18 bar). Twenty-six mechano-insensitive units responded to heat (CH), and the remaining six units did not respond to physical stimuli but were proven to be afferent by their response to intracutaneous capsaicin (CM(i)H(i)). Mechano-insensitive units had significantly slower conduction velocity (0.81 +/- 0.03 m/sec), and CH units had higher heat thresholds (48.0 +/- 0.6 degrees C) compared with CMH units (1.01 +/- 0.01 m/sec; 40.7 +/- 0.4 degrees C). Transcutaneous electrical thresholds were <9 mA for CMH units and >35 mA for CH and CM(i)H(i) units. Activity-dependent slowing was much more pronounced in mechano-insensitive than in mechano-responsive units, without overlap. Sympathetic efferent C units showed intermediate slowing, significantly different from CMH, and completely separate from CH and CM(i)H(i) units. The activity-dependent slowing of conduction provides evidence for different membrane attributes of different classes of C fibers in humans.

Adult↗
PubMed1999

Coping with chronic illness: a qualitative study of coping with postpolio syndrome.

The study describes how 24 people with postpolio syndrome (PPS) cope with their problems. Two qualitative interviews were conducted, 6 weeks apart. The interviews were analysed inductively. It was found that the participants experienced many types of illness-related problems in their everyday lives. Furthermore, they describe the progressive deterioration in terms of a general weakness, fatigue and pain--these adding to the emotional stress. A variety of coping strategies are employed and the result of the analysis shows it to be impossible to carry out a clearly differentiated grouping into problem-focused and emotion-focused. By and large the participants have learnt to live with the changes and feel that they have 'a good life in spite of everything'.

Adaptation, Psychological↗
PubMed1999

Comparison between concentric needle EMG and macro EMG in patients with a history of polio.

OBJECTIVES: Acute poliomyelitis causes degeneration of anterior horn cells, followed by denervation. Reinnervation and muscle fibre hypertrophy are mechanisms that compensate this loss of neurones. Concentric needle EMG (CNEMG) and macro EMG are two methods to assess the magnitude of initial involvement and the compensatory reinnervation. The aim of this study is to explore the difference between CNEMG and macro EMG describing the status of the motor unit in patients previously affected by polio. METHODS: Macro and concentric needle EMG investigations were performed in 261 muscles in 121 patients with a remote history of polio. RESULTS: CNEMG was abnormal in 211 muscles, macro EMG was abnormal in 246 muscles. The macro amplitude was 3-4 times 'more abnormal' than CNEMG amplitude relative to the reference values. CNEMG duration was less abnormal and showed only weak correlation with macro amplitudes. The most likely explanation for the difference in magnitude of deviation from reference values for CNEMG and macro EMG, is a more pronounced 'phase cancellation' between single fibre action potentials in CNEMG. This is supported by simulation studies reported here. CONCLUSIONS: In conclusion macro EMG better reflects the size of the motor unit than the CNEMG. For detection of concomitant disorders, CNEMG is the method of choice.

Action Potentials↗
PubMed1999

Frantz's tumour of the pancreas presenting as a post-traumatic pancreatic pseudocyst.

A case of a solid, pseudopapillary and cystic tumour of the pancreas in a 13-year-old girl was presented. Shortly after a blunt abdominal trauma, an abdominal mass became manifest. Clinical features and radiological findings suggested a traumatic pseudocyst of the pancreas. Laparotomy and pathology revealed a Frantz's tumour, which was totally resected. Twelve months after surgery the patient is asymptomatic and CT-scan shows no signs of recurrence or metastasis. To our knowledge, no such acute presentation has ever been described in the literature since the first clinical report of this tumour in 1959.

Abdominal Injuries↗
PubMed1997

Infanticide in great reed warblers: secondary females destroy eggs of primary females

In 1994-1995 artificial nests with attached model eggs were put into territories that were known to have been occupied by male great reed warblers, Acrocephalus arundinaceusin previous years. Because the eggs were made of soft plasticine, predators left peckmarks in them and this enabled us to identify predators by comparing peckmarks with reference marks made by various species. Previous field data had suggested that infanticidal behaviour existed in our study population, as nests of primary females suffered a three times higher rate of nest loss during the egg-laying period than nests of secondary and monogamous females. The presence of infanticide was supported by the experiment. Small peckmarks resembling those of a great reed warbler occurred almost exclusively in territories occupied by great reed warblers, in particular when a new female settled in the territory. The newly settled females built nests closer to depredated than non-depredated nests. That small peckmarks occurred when new females settled strongly suggests that it is secondary female great reed warblers that commit infanticide on eggs of primary females. Females of low harem rank are expected to gain from infanticidal behaviour because a low ranked female gets a higher proportion of male parental investment when the nest of the primary female fails.

Journal Article↗
PubMed1997

Added copper filtration in digital paediatric double-contrast colon examinations: effects on radiation dose and image quality.

Paediatric double-contrast barium enema examinations are usually performed at high tube voltage, 102-105 kV. The aim of this study was to investigate how much the effective dose to the child could be reduced by increasing the X-ray energy further by adding copper filter in the beam, and if this dose reduction could be achieved without endangering image quality. Organ doses to an anthropomorphic phantom simulating a 1-year-old child was measured using thermoluminescence dosimetry for assessment of the effective dose and this value was compared with the energy imparted which was obtained from kerma-area product measurements. To verify that the image quality achieved with this added filtration was still diagnostically acceptable, the study included 15 patient examinations. Since the increased X-ray energy will most probably affect low-contrast objects, image quality was also evaluated with two different phantoms containing low-contrast objects. Effective dose for a complete examination can be decreased 44 % and energy imparted 77 % when a 0.3-mm copper filter is inserted in the beam at tube voltage 102 kV. The patient study did not show any significant deterioration of image quality, whereas phantom measurements of contrast-detail resolution and signal-to-noise ratio was marginally impaired by the added copper filtration. This technique is now in clinical practice for paediatric colon examinations.

Barium Sulfate↗