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Biomedical subjects

S Jakobsson

Publications and source records attributed to S Jakobsson.

At least 19 recordsLinked to original sources
PubMed2001

Magnetic cues trigger extensive refuelling.

Long stretches of sea and desert often interrupt the migration routes of small songbirds, whose fat reserves must be restored before these can be crossed as they provide no opportunity for refuelling. To investigate whether magnetic cues might enable inexperienced migratory birds to recognize a region where they need to replenish their body fat, we caught and held thrush nightingales (Luscinia luscinia) in Sweden just before their first migration and exposed them to a magnetic field simulating that at a migratory stopover in northern Egypt, before the Sahara Desert. We found that this magnetic field stimulated the birds to extend their fat-deposition period, indicating that magnetic cues may help small migratory birds to confront large ecological barriers.

Adipose Tissue↗
PubMed2001

Body building and concurrent mass loss: flight adaptations in tree sparrows.

Environmental changes are responsible for the evolution of flexible physiology and the extent of phenotypic plasticity in the regulation of birds' organ size has not been appreciated until recently. Rapid reversible physiological changes during different life-history stages are virtually only known from long-distance migrants, and few studies have focused on less extreme aspects of organ flexibility. During moult, birds suffer from increased wing loading due to wing-area reductions, which may impair flight ability. A previous study found that tree sparrows' escape flight (Passer montanus) is unaffected during moult, suggesting compensatory aptness. We used non-invasive techniques to study physiological adaptations to increased wing loading in tree sparrows. As wing area was reduced during natural moult the ratio of pectoral-muscle size to body mass increased. When moult was completed this ratio decreased. We show experimentally a novel, strategic, organ-flexibility pattern. Unlike the general pattern, where body mass is positively coupled to pectoral-muscle size, tree sparrows responded within 7 days to reductions in wing area by reducing body mass concurrently with an increase in pectoral-muscle size. This rapid flexibility in a non-migratory species probably reflects the paramount importance and long history of flight in birds.

Adaptation, Physiological↗
PubMed2001

Molecular cloning and characterization of spiggin. An androgen-regulated extraorganismal adhesive with structural similarities to von Willebrand Factor-related proteins.

One of the most definitive examples of a vertebrate extraorganismal structural protein can be found in three-spined sticklebacks (Gasterosteus aculeatus). In the breeding male the kidney hypertrophies and synthesizes an adhesive protein called "spiggin," which is secreted into the urinary bladder from where it is employed as a structural thread for nest building. This paper describes the first molecular characterization of spiggin and demonstrates that this adhesive is a protein complex assembled from a potential of three distinct subunits (alpha, beta, and gamma). These subunits arise by alternative splicing, and 11-ketoandrogens induce their expression in stickleback kidneys. Analysis of the predicted amino acid sequence of each subunit reveals a modular organization whose structural elements display a similarity to the multimerization domains found within von Willebrand Factor-related proteins. These results implicate that spiggin utilizes a conserved multimerization mechanism for the formation of a viscous agglutinate from its constituent subunits in the urinary bladders of male sticklebacks. This novel extraorganismal structural protein is therefore ideally suited to its function as an adhesive thread.

Adhesives↗
PubMed2001

Increased cardiovascular mortality and normalized serum calcium in patients with mild hypercalcemia followed up for 25 years.

BACKGROUND: The natural history of mild hyperparathyroidism is incompletely clarified. METHODS: Consistent hypercalcemia was found in 172 patients (aged 28-86 years) participating in population-based screenings in both 1969 and 1971. Mortality until 1994 was compared with 344 matched, normocalcemic controls from the study population. Altogether, 55 case-control pairs underwent biochemical analysis in 1992, whereas 86 patients had died, 8 were lost to follow-up, and 23 had undergone parathyroid operation. RESULTS: Mortality was higher (P = .015) in patients younger than 70 years. Cardiovascular diseases were over-represented causes of death. The hazard ratio for hypercalcemia as an independent cause of cardiovascular mortality was 1.72 (95% CI, 1.24-2.37; P < .001). The initially mild hypercalcemia in patients (2.67 +/- 0.07 mmol/L) decreased over time (P = .0001), whereas the serum calcium value remained constant in the controls. Serum calcium and serum parathyroid hormone values in patients were higher than controls at the follow-up (P < .0001, .01, respectively). All but 17 patients were normocalcemic in 1992, and only 2 (1.4%) developed a serum calcium value higher than 3 mmol/L. CONCLUSIONS: Mild hypercalcemia in patients followed up for more than 2 decades is accompanied by premature cardiovascular death despite trends to spontaneous resolution. The principal cause of hypercalcemia probably is primary hyperparathyroidism, but mechanisms contributing to its regression over time are speculative.

Aged↗
PubMed1996

Incidence of neoplasms in ages 0-19 y in parts of Sweden with high 137Cs fallout after the Chernobyl accident.

The incidence of neoplasms in childhood and adolescence in northern and central Sweden before and after the radioactive fallout from the Chernobyl accident was investigated in an ecologic study, 1978 to 1992. The study included all parishes in the six most contaminated counties classified after aerial mapping of ground radiation from 137Cs and investigated 746 cases of neoplasms in ages 0-19 y, diagnosed in the six counties. Incidence and relative risks of neoplasms were compared in areas with high, intermediate, and low contamination after versus before the Chernobyl accident in 1986. A continuous increase of brain tumor incidence in the ages 0-19 y during the period 1978-92 without clear relationship to the Chernobyl fallout was discovered. No clear relationship between the incidence of brain tumor and the exposure to varying levels of radiation from 137Cs was apparent. A somewhat decreased relative risk of acute lymphatic leukemia appeared in areas with increased exposure. Other neoplasms showed no changes in incidence over time or with regard to exposure. Until now, there is no indication that the Chernobyl accident has affected the incidence of childhood and adolescence neoplasms in Sweden, but it is still too early for any final conclusion about the effect of this event.

Adolescent↗
PubMed1991

Longitudinal studies of mild primary hyperparathyroidism.

In 1969, a health survey was offered to all inhabitants of a town district in Sweden. A clinical examination was carried out, and among other variables, a measurement was made of serum calcium. The same procedure was repeated in 1971. From these two investigations a cohort of 176 individuals (1.1%) with sustained hypercalcemia was identified who could be followed during the subsequent 15 years. Comparisons were made with an age- and sex-matched control group from the same health survey. Survival was significantly lower in the hypercalcemic cohort than in the control group. This reduction was related to the degree of hypercalcemia and apparently mainly due to diseases of the circulatory organs. There was no marked deterioration of renal function, and although there was in some patients a moderate progression of the hypercalcemia, none developed a hypercalcemic crisis during 15 years of follow-up. In consecutively referred patients with primary hyperparathyroidism, psychiatric disturbances of mainly a depressive character were found upon detailed analysis within a majority of the patients, and parathyroid surgery resulted in a clear improvement in mental health.

Adult↗
PubMed1990

No evidence for illegitimate young in monogamous and polygynous warblers.

In animals with internal fertilization, paternity is uncertain. In birds, the occurrence of copulations outside the pair-bond has been documented in a number of species, but the extent to which these result in illegitimate young is largely unknown, and constitutes a major deficiency in our understanding of avian mating systems. The analysis of tandemly repeated sequences (minisatellites), has enhanced our ability to make individual identifications and paternity determinations. Here we describe the use of a bird minisatellite DNA probe in assigning paternity in natural populations of the monogamous willow warbler Phylloscopus trochilus and of the polygynous wood warbler Phylloscopus sibilatrix. In both species this probe detects a multiple locus pattern and a single locus that exhibits a variable number of tandem repeats. Although we observed intrusions by non-resident males into the territories of paired males and extra-pair copulations, no illegitimate offspring were detected among 176 young from 32 families of both species, implying that extra-pair copulations have little or no genetic impact.

Alleles↗
PubMed1990

Observations on intracranial dynamics during respiratory physiotherapy in unconscious neurosurgical patients.

The effects of airway care procedures on intracranial dynamics were studied in 12 patients with intracranial lesions. The patients had controlled ventilation and were treated according to a standardized protocol with endotracheal suction and bag squeezing. Intracranial, arterial blood and airway pressures were recorded and cerebral perfusion pressure was calculated. Both methods used for airway care elicited marked changes in intracranial, arterial blood and cerebral perfusion pressures during the treatment session. However, within 1 min after termination of the procedure the different pressure levels returned to pretreatment values except for the intracranial and arterial blood pressure in endotracheal suction. Cerebral perfusion pressure, calculated at different time intervals: 1, 5 and 15 min after the treatment, showed only minor deviations from values before treatment. The mean values varied from 70 to 90 mmHg (9.3 to 12.0 kPa) and the lower limit of the 99% confidence interval of the means was never below 55 mmHg (7.3 kPa). At times complementary administration of sedatives during endotracheal suction was found to induce a drop in arterial blood pressure and cerebral perfusion pressure. In conclusion, patients with severe brain injuries treated on mechanical ventilation are exposed to equal risks when using bag squeezing for airway care as when using traditional endotracheal suction. Regardless of the method used, patients should be adequately sedated before starting the procedure in order to reduce the risk of adverse effects.

Adolescent↗
PubMed1989

Nucleotide sequence and genomic organization of bird minisatellites.

Two minisatellite loci from a Eurasian songbird, the willow warbler (Phylloscopus trochilus) were isolated, sequenced and used as probes to detect more than 20 related hypervariable loci. In addition, a sequence flanking one of the minisatellite loci was isolated, and used to study a VNTR locus. The bird minisatellites have a repeat unit of either 12 (AGGGAAGGGCTC) or 17 bp (GGGGACAGGGGACACCC), repeated in tandem 40-100 times per locus, and shows partial similarity to the sequence motifs of human minisatellites. These sequences are among the most variable minisatellites known, with the incidence per gamete of new length alleles estimated from family studies of warblers to about 5.6% per locus. The bird minisatellite alleles show mendelian inheritance and segregation analysis indicates that they are derived from families of sequences with members on several autosomal linkage groups. Some of the warbler core sequences cross-hybridize to hypervariable loci in other species of birds, mammals and fishes.

Alleles↗
PubMed1988

Relation of serum calcium concentration to metabolic risk factors for cardiovascular disease.

Data from a health screening survey with over 18,000 adult participants were used to determine the relations between serum calcium concentration and the cardiovascular risk factors hypertension, hyperglycaemia, and hyperlipidaemia. Blood pressure and serum glucose and cholesterol concentrations were all positively related to each other independent of age, sex, kidney function, and obesity. Similar relations between the risk factors were found in subjects with hypertension or hyperglycaemia independent of the degree of overweight. These results suggested that there might be a metabolic syndrome of cardiovascular risk factors. Serum calcium concentration was positively related to systolic and diastolic blood pressures and serum glucose and cholesterol concentrations. Thus a common feature in the syndrome is an increased serum calcium concentration. The relations between serum calcium concentrations and the cardiovascular risk factors were not limited to the upper parts of the distribution, being seen over a wide range. Changes in calcium metabolism seem to be related to a metabolic syndrome of hypertension, impaired glucose tolerance, and hyperlipidaemia.

Aged↗
PubMed1988

Prevalence of hypercalcaemia in a health survey: a 14-year follow-up study of serum calcium values.

Among 16,401 subjects attending two health screenings, in 1969 and 1971, 176 showed hypercalcaemia on both occasions, i.e. serum calcium values above 2.60 mmol l-1. The prevalence of hypercalcaemia increased in women with advancing age and occurred in close to 3% of those above the age of 60, whilst in men it was found in less than 0.7% in all age groups. The mean serum calcium concentration in women above the age of 50 was significantly higher than in men. This observation could at least partly explain why hyperparathyroidism (HPT) is more often diagnosed in females. Only nine persons were initially referred for neck exploration. Most of the others were not even notified of the biochemical disturbance and thus it was possible to study the serum calcium values in an unattended cohort until follow-up after 14 years. In the hypercalcaemic patients there was little or no increase in serum calcium during these years. In no patient did the serum calcium level rise above 3.0 mmol l-1. Altogether, 24 patients from the initial cohort were subsequently operated on for primary HPT but there were only two further cases of verified HPT, which developed during the follow-up period, in those who had been clearly normocalcaemic at the health surveys. In conclusion, hypercalcaemia, presumably caused by primary HPT, is common but apparently develops slowly and with little risk of a progressive rise of serum calcium concentrations.

Adult↗
PubMed1988

A validation of cause of death certification for ischaemic heart disease in two Swedish municipalities.

The aim of this study was to examine whether observed high mortality from ischaemic heart disease (IHD) among males in the municipality of Hofors, Sweden, is accurate, or the result of some artefact. The validity of death certificates from Hofors municipality and from a control area (Gävle) were ascertained by comparing them with medical records from hospitals and district physician offices, and reports from clinical or medicolegal autopsies. The results indicate that the observed high mortality from IHD among Hofors males cannot be explained by deficiencies in establishing the cause of death. Results from other validity studies indicate, however, that there is a risk of local variation when reporting causes of death. In many instances this motivates checking the validity of data before they are incorporated into official statistics and used as a basis for planning.

Adolescent↗
PubMed1987

Survival and renal function in untreated hypercalcaemia. Population-based cohort study with 14 years of follow-up.

172 persons with mild to moderate hypercalcaemia were followed up for 14 years. Life-table analyses showed that, among persons aged 70 years or less at the time of detection of the hypercalcaemia, survival was lower in the hypercalcaemic group than in a normocalcaemic age and sex matched control group. No such difference was found among older persons. The lower survival was related to degree of hypercalcaemia, and this held true when systolic and diastolic blood pressure, serum glucose, serum uric acid, and serum cholesterol were taken into account in a multivariate analysis. The lower survival seemed to be due mainly to deaths from diseases of the circulatory organs. No person with normal renal function at the beginning of the study period had a more than marginally raised serum creatinine at follow-up.

Actuarial Analysis↗
PubMed1979

Single-view mammography screening. Three-year follow-up of interval cancer cases.

In 1974, screening trials indicated that both the sensitivity and specificity of single-view mammography are high. During the subsequent three years, 11 cases of breast carcinoma have been detected in the study population of 6,845 women aged 40 or older. The average incidence was three cases per year, compared to the expected rate of 8.9. The age-adjusted incidence rate in 1975, the year after screening, was 55.4 per 100,000, which is 40% of the expected rate of 140. In 1976 it was 75.9, or 54% of the expected rate of 141. These results support the view that single-view mammography is an efficient screening method, at least in the subject population described.

Adult↗
PubMed1976

Single view mammography: a simple and efficent approach to breast cancer screening.

In 1974 a new approach to breast cancer screening was introduced--the single view mammography method. An urban nonselected population of 6845 women of more than 34 years of age were screened with one roentgenogram of each breast. By this method it has been possible to reduce the radiation dose, while the patient flow is increased and the costs are decreased to an acceptable level. Forty cases of breast carcinoma were detected (6.7/1000). Twenty cases were preclinical.

Adult↗