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J Lindström

Publications and source records attributed to J Lindström.

At least 37 records · Page 2Linked to original sources
PubMed2001

From arctic lemmings to adaptive dynamics: Charles Elton's legacy in population ecology.

We shall examine the impact of Charles S. Elton's 1924 article on periodic fluctuations in animal populations on the development of modern population ecology. We argue that his impact has been substantial and that during the past 75 years of research on multi-annual periodic fluctuations in numbers of voles, lemmings, hares, lynx and game animals he has contributed much to the contemporary understanding of the causes and consequences of population regulation. Elton was convinced that the cause of the regular fluctuations was climatic variation. To support this conclusion, he examined long-term population data then available. Despite his firm belief in a climatic cause of the self-repeating periodic dynamics which many species display, Elton was insightful and far-sighted enough to outline many of the other hypotheses since put forward as an explanation for the enigmatic long-term dynamics of some animal populations. An interesting, but largely neglected aspect in Elton's paper is that it ends with speculation regarding the evolutionary consequences of periodic population fluctuations. The modern understanding of these issues will also be scrutinised here. In population ecology, Elton's 1924 paper has spawned a whole industry of research on populations displaying multi-annual periodicity. Despite the efforts of numerous research teams and individuals focusing on the origins of multi-annual population cycles, and despite the early availability of different explanatory hypotheses, we are still lacking rigorous tests of some of these hypotheses and, consequently, a consensus of the causes of periodic fluctuations in animal populations. Although Elton would have been happy to see so much effort spent on cyclic populations, we also argue that it is unfortunate if this focus on a special case of population dynamics should distract our attention from more general problems in population and community dynamics.

Adaptation, Physiological↗
PubMed2001

Maladaptive mate choice maintained by heterozygote advantage.

Common buzzards (Buteo buteo) show a plumage polymorphism that appears to be maintained by heterozygote advantage and allows a maladaptive form of mate choice to persist. The light and dark morphs have a much lower fitness than the presumed heterozygous intermediate morph, but are replenished through Mendelian segregation in intermediate-intermediate pairs. Light and dark morphs could maximize their fitness by mating light with dark to produce all intermediate offspring, but instead choose partners of their own color, thereby producing broods of minimally fit homozygotes. Such maladaptive behavior argues forcefully against mate choice based on "good genes," and its persistence is best explained by heterozygote advantage maintaining the polymorphism coupled with nongenetic mate choice based on sexual imprinting. Modeling different patterns of mate choice shows that random mating and preference for own morph fit our data poorly, whereas preference for mother's morph yields a good fit.

Animals↗
PubMed2000

The Finnish Diabetes Prevention Study.

The aim of the Finnish Diabetes Prevention Study is to assess the efficacy of an intensive diet-exercise programme in preventing or delaying type 2 diabetes in individuals with impaired glucose tolerance (IGT) and to evaluate the effect of the programme on the risk factors of atherosclerotic vascular diseases and the incidence of cardiovascular events. In this ongoing study, a total of 523 overweight subjects with IGT based on two oral glucose tolerance tests were randomized to either an intervention group or a control group. The main measure in the intervention group is individual dietary advice aimed at reducing weight and intake of saturated fat and increasing intake of dietary fibre. The intervention subjects are individually guided to increase their level of physical activity. The control group receives general information about the benefits of weight reduction, physical activity and healthy diet in the prevention of diabetes. A pilot study began in 1993, and recruitment ended in 1998. By the end of April 1999 there were 65 new cases of diabetes, 34 drop-outs and one death. The weight reduction was greater (-4.6 kg) at 1 year in the intervention group (n = 152) than in the control group (n = 143, -0.9 kg, P < 0.0001), and this difference was sustained in the second year of follow-up. At 1 year 43.4% and at 2 years 41.8% of the intervention subjects had achieved a weight reduction of at least 5 kg, while the corresponding figures for the control subjects were 14.0 and 12.0% (P < 0.001 between the groups). At 1 year the intervention group showed significantly greater reductions in 2 h glucose, fasting and 2 h insulin, systolic and diastolic blood pressure, and serum triglycerides. Most of the beneficial changes in cardiovascular risk factors were sustained for 2 years. These interim results of the ongoing Finnish Diabetes Prevention Study demonstrate the efficacy and feasibility of the lifestyle intervention programme.

Adult↗
PubMed2000

Acarbose treatment does not change the habitual diet of patients with Type 2 diabetes mellitus. The Finnish Acargbos Study Group.

AIMS: It has been speculated that acarbose treatment in patients with Type 2 diabetes mellitus might induce changes in diet as a result of its adverse gastrointestinal effects. The aim of this study was to determine whether poor metabolic control can be improved by acarbose, and whether this might be because the acarbose supplementation provokes changes in diet. METHODS: Poorly controlled Type 2 diabetic patients treated with oral hypoglycaemic agents (OHA) were randomized into either acarbose (100 mg t.d.s.) or placebo treatment. The double-blind treatment lasted for 24 weeks. Four-day food diaries and blood samples for efficacy analysis were collected at 0, 4, 12, and 24 weeks. Thirty-six acarbose and 39 placebo-treated patients completed the trial and were included in the final analyses. RESULTS: At 24 weeks the baseline adjusted means of fasting, 1 and 2-h postprandial blood glucose values were 9.3 vs. 10.5 (P=0.02), 11.6 vs. 14.5 (P<0.001) and 11.0 vs. 13.7 mmol/l (P<0.001) and HbA1 9.3% vs. 10.2% (P=0.002) in the acarbose and placebo groups, respectively. No significant differences in nutrient intakes between groups were observed. The energy intake and energy proportion of fat and carbohydrates remained unchanged in both groups. CONCLUSIONS: Acarbose significantly improves metabolic control in Type 2 diabetic patients poorly controlled with oral hypoglycaemic agents. This effect seems not to be a result of concomitant involuntary dietary changes, since acarbose did not induce modifications in diet during the study.

Acarbose↗
PubMed1999

Acoustic and perceptual evaluation of voice and speech quality: a study of patients with laryngeal cancer treated with laryngectomy vs irradiation.

OBJECTIVE: To compare voice and speech function in patients who underwent laryngectomy with that of 2 control groups. DESIGN: A cross-sectional study comparing acoustic and temporal variables with perceptual evaluations in 3 subject groups. SETTING: University hospital in Göteborg, Sweden. SUBJECTS: Two groups of patients with laryngeal carcinoma were examined: 12 male patients who had laryngectomy and were using a tracheoesophageal prosthesis and 12 male patients treated with radical radiotherapy who had a preserved larynx. The third group consisted of 10 normal controls without laryngeal disease. MAIN OUTCOME MEASURES: Acoustic variables were fundamental frequency, absolute fundamental frequency perturbation, speech rate, and maximum phonation time. Perceptual evaluation included 15 listeners' perceptual evaluation and the patients' self-assessment of speech intelligibility, voice quality, and speech acceptability. RESULTS: No significant acoustic or temporal differences were found between the laryngectomy and radical radiotherapy groups. There was a significant difference between the patient groups in perceptual evaluation. Both groups of patients differed from normal controls in acoustic and temporal measures, where the laryngectomy group generally deviated more from the normal controls than the patient group treated with radiotherapy. There was a weak, but significant, correlation between absolute fundamental frequency perturbation and perceived voice quality. CONCLUSIONS: Perceptual evaluations could indicate significant differences between the patients who underwent laryngectomy and irradiated patients, where the acoustic analysis failed to reflect these differences. Both patient groups could be distinguished according to acoustic and temporal measures when compared with normal controls. The acoustic analyses were more sufficient in voices without severe dysfunction.

Aged↗
PubMed1999

Prevention of Type II diabetes in subjects with impaired glucose tolerance: the Diabetes Prevention Study (DPS) in Finland. Study design and 1-year interim report on the feasibility of the lifestyle intervention programme.

UNLABELLED: AIMS/HYPOTHESIS; The aim of the Diabetes Prevention Study is to assess the efficacy of an intensive diet-exercise programme in preventing or delaying Type II (non-insulin-dependent) diabetes mellitus in subjects with impaired glucose tolerance, to evaluate the effects of the intervention programme on cardiovascular risk factors and to assess the determinants for the progression to diabetes in persons with impaired glucose tolerance. METHODS: A total of 523 overweight subjects with impaired glucose tolerance ascertained by two oral glucose tolerance tests were randomised to either a control or intervention group. The control subjects received general information at the start of the trial about the lifestyle changes necessary to prevent diabetes and about annual follow-up visits. The intervention subjects had seven sessions with a nutritionist during the first year and a visit every 3 months thereafter aimed at reducing weight, the intake of saturated fat and increasing the intake of dietary fibre. Intervention subjects were also guided individually to increase their physical activity. RESULTS: During the first year, weight loss in the first 212 study subjects was 4.7 +/- 5.5 vs 0.9 +/- 4.1 kg in the intervention and control group, respectively (p < 0.001). The plasma glucose concentrations (fasting: 5.9 +/- 0.7 vs 6.4 +/- 0.8 mmol/l, p < 0.001; and 2-h 7.8 +/- 1.8 vs 8.5 +/- 2.3 mmol/l, p < 0.05) were significantly lower in the intervention group after the first year of intervention. Favourable changes were also found in blood pressure, serum lipids and anthropometric indices in the intervention group. CONCLUSION/INTERPRETATION: The interim results show the efficacy and feasibility of the lifestyle intervention programme.

Blood Glucose↗
PubMed1999

Early development and fitness in birds and mammals.

Conditions experienced during early development affect survival and reproductive performance in many bird and mammal species. Factors affecting early development can therefore have an important influence both on the optimization of life histories and on population dynamics. The understanding of these evolutionary and dynamic consequences is just starting to emerge.

Journal Article↗
PubMed1999

Leptin concentrations and their relation to body fat distribution and weight loss--a prospective study in individuals with impaired glucose tolerance. DPS-study group.

Leptin is proposed to be involved in regulation of body weight. Only little information is available on leptin concentrations in individuals with impaired glucose tolerance (IGT). The aim of the present study was to assess the effect of body fat distribution and weight reduction on serum leptin levels in a prospective setting in IGT subjects. Sixty-nine individuals with impaired glucose tolerance aged 45-64 years participated in this prospective study. Serum leptin levels were about 300% higher among females than among males, despite an only 30% higher fat percentage in females. A close association between degree of obesity and leptin concentrations was observed in both sexes. The correlation coefficient between fat mass and leptin concentration ranged between r = 0.467- 0.817 (p< 0.001 - 0.01). A close correlation between degree of weight loss and decrease in leptin concentrations was observed in both sexes. A 10.1 kg (9.6%) decrease in body weight among females was associated with a 32% decrease in leptin concentrations. The corresponding value among males for an 8.0 kg (8.6%) decrease was 29%. Changes in leptin concentrations were best explained by changes in fat mass among both males and females. Body fat distribution was also of importance, especially among females. Gender associated differences in leptin concentrations appear to be largely influenced by gender differences in body fat distribution.

Adipose Tissue↗
PubMed1999

A cross-sectional validation study of Self-Evaluation of Communication Experiences after Laryngeal Cancer--a questionnaire for use in the voice rehabilitation of laryngeal cancer patients.

A psychometric evaluation of the questionnaire 'Self-Evaluation of Communication Experiences after Laryngeal Cancer' (S-SECEL) addressing communication dysfunction in patients with laryngeal cancer was carried out. Ninety-three patients with laryngeal cancer were studied. For comparison of response patterns and external validation, 21 patients with non-small cell lung cancer (NSCLC) and 26 patients with hoarseness, caused by benign laryngeal disease, were included in the analysis. The patients completed three questionnaires; the S-SECEL, the Sickness Impact Profile (SIP) and the Hospital Anxiety and Depression scale (HAD). The S-SECEL questionnaire was well-accepted by the patients, compliance was satisfactory, and missing value rates were low. The reliability of the S-SECEL was satisfactory for the Environment and Attitude subscales, whereas the General subscale did not reach the reliability levels recommended for group comparisons. In general, the response pattern in the three diagnostic groups and the pattern of correlations between the S-SECEL scores and the SIP- and HAD-subscales and dimensions lent support to the construct validity of the S-SECEL.

Aged↗
PubMed1999

A simple model for estimating the particle size dependence of absolute efficiency of fluorescent screens.

The absolute efficiency of a phosphor screen is the ratio of the light energy per unit area at the screen surface to the incident x-ray energy fluence. Particle size is a critical factor in determining the absolute efficiency, but in most models its influence is not accounted for. To allow derivation of the particle size dependence, a model is proposed that describes the optical properties of the screen by means of a single parameter, the light extinction factor, xi, and assumes that the intrinsic efficiency (light energy/energy imparted to the phosphor material) is independent of particle size. The value of xi depends on the type of screen (phosphor, reflective backing, coating and binder) and has to be determined from measurements on at least two screens with known particle size and thickness. The absolute efficiency can then be calculated for an extended range of particle sizes and/or screen thicknesses. To test the model, experimental data from the literature were used to derive values of xi for screens of La2O2S:Tb, LaOBr:Tm and ZnCdS:Ag. The extinction factor was found to vary between -6 and +20%. The non-physical negative value for xi, found from one set of experiments on La2O2S:Tb screens, may be explained as resulting from a lack of accurate knowledge of the actual tube potential, influencing calculated values of the energy imparted to the screen. The results are promising but further well-controlled experiments (including improved dosimetric calculations to account forescape of K-radiation from the screen) are needed to confirm the model.

Biophysical Phenomena↗
PubMed1998

Sexual reproduction and population dynamics: the role of polygyny and demographic sex differences.

Most models of population dynamics do not take sexual reproduction into account (i.e., they do not consider the role of males). However, assumptions behind this practice--that no demographic sex differences exist and males are always abundant enough to fertilize all the females--are usually not justified in natural populations. On the contrary, demographic sex differences are common, especially in polygynous species. Previous models that consider sexual reproduction report a stabilizing effect through mixing of different genotypes, thus suggesting a decrease in the propensity for complex of dynamics in sexually reproducing populations. Here we show that considering the direct role of males in reproduction and density dependence leads to the conclusion that a two-sex model is not necessarily more stable compared with the corresponding one-sex model. Although solutions exist where sexual reproduction has a stabilizing effect even when no genotypic variability is included (primarily when associated with monogamy), factors like polygyny, sex differences in survival or density dependence, and possible alterations of the primary sex ratio (the Trivers-Willard mechanism), may enlarge the parametric region of complex dynamics. Sexual reproduction therefore does not necessarily increase the stability of population dynamics and can have destabilizing effects, at least in species with complicated mating systems and sexual dimorphism.

Animals↗
PubMed1998

Intelligibility and perceptual ratings after treatment for laryngeal cancer: laryngectomy versus radiotherapy.

In Sweden the most common treatment for T3-T4 laryngeal carcinoma is radical radiotherapy (with surgery for salvage), because the voice is thus preserved. A Swedish study showed that surgery yielded a significantly better 5-year survival and locoregional control at 3 years in T4 laryngeal carcinoma than radical radiotherapy. With these results in mind, we wanted to compare the different modes of treatment (surgery with a tracheoesophageal [TE] fistula and radical radiotherapy) with respect to the patients' speech proficiency. Twenty-eight subjects (with 14 patients in each treatment group) were judged by inexperienced and experienced listeners according to intelligibility by transcription and three perceptual ratings. From the perceptual ratings of speech intelligibility, voice quality, and speech acceptability we conclude that there is a significant difference, the irradiated speakers being rated higher than the tracheoesophageal speakers. It is also clear that most of the TE and irradiated laryngeal speaking patients are comparable to normal laryngeal speakers in intelligibility by transcription. Experienced and inexperienced listeners are able to rate TE and irradiated laryngeal speech reliably and similarly according to intelligibility by transcription. The inexperienced listeners rated the TE speakers significantly higher than did the experienced listeners.

Aged↗
PubMed1998

Quality of life and voice in patients with laryngeal carcinoma: a posttreatment comparison of laryngectomy (salvage surgery) versus radiotherapy.

OBJECTIVES: This study was designed to compare the voice and the quality of life (QOL) of laryngeal cancer patients receiving treatment with radical radiotherapy with or without laryngectomy as salvage surgery. We also compared the patients' own perceptual ratings of their voice to the perceptual ratings of a group of listeners. STUDY DESIGN: Two groups of laryngeal cancer patients were studied. METHODS: Fourteen irradiated laryngeal speakers with preserved larynx were matched with 14 salvage surgery laryngectomized patients speaking with tracheoesophageal prosthesis (TEP). To measure patients' QOL, we used the European Organisation for Research and Treatment of Cancer Quality of Life Core Questionnaire (EORTC QLQ-C30), the EORTC Head and Neck module (EORTC QLQ-H&N35), the Hospital Anxiety and Depression scale (HAD) and a study-specific questionnaire. For the perceptual speech evaluation we used visual analog scales. RESULTS: The perceptual ratings of speech intelligibility, voice quality, and speech acceptability showed a significant difference between the treatment groups. Both the patients who received treatment with radiotherapy and the listeners rated the irradiated laryngeal voices higher than the tracheoesophageal speech. The laryngectomized patients scored significantly better than the patients treated with radical radiotherapy on the question about hoarseness. No other significant difference was found for the QOL functions and symptoms. CONCLUSION: When patients treated with radiotherapy were compared with patients treated with laryngectomy as salvage surgery, QOL was similar, only small differences being found in the perceptual speech evaluation.

Aged↗
PubMed1997

Association between salt intake, heart rate and blood pressure.

The present study investigated the association between 24-h urinary sodium excretion and heart rate in the determination of blood pressure (BP) levels in a large random population sample from eastern Finland. Three independent risk factor surveys were performed in 1979, 1982 and 1987 using the same methodology. Data from each survey was pooled for subjects aged 25-64 years who reported a complete 24-h urine collection and were not on the current antihypertensive treatment (1640 men and 1686 women). The effect of urinary sodium excretion and heart rate was examined by regressing BP on urinary sodium excretion and pulse rate, together with age and body mass index (BMI). Analyses stratified by quintiles of heart rate were also performed. There was no association between urinary sodium and BP either in men or in women. There was a significant correlation between heart rate and both systolic and diastolic BP in both men and women. A significant interaction between age and BMI with heart rate was also found in both sexes. Interaction between urinary sodium and heart rate was found neither in men nor in women. Among men, after adjustment for age and BMI, there was a curvilinear relation between 24-h urinary excretion of sodium and diastolic BP (P = 0.054) in the lowest quintile of heart rate (<60 beats/min). No correlations were observed among women in any of the quintiles of heart rate.

Adult↗
PubMed1996

Advanced laryngeal cancer T3-T4 in Sweden: a retrospective study 1986-1990. Survival and locoregional control related to treatment.

Different treatment modalities for advanced laryngeal cancer are much discussed in the literature. One-hundred-and-sixty patients with T3-4, N0-3, M0-1 laryngeal cancer diagnosed in Sweden between 1986 and 1990 were retrospectively analysed. One hundred (65 T3: 35 T4) received radical radiotherapy with salvage surgery (RRSS) in case of residual or recurrent disease. Thirty-eight (11T3: 27 T4) patients received surgery with or without radiotherapy (S +/- RT). Twenty-two patients received no treatment. After a median follow up of 4.4 years, the estimated 5-year actuarial corrected survival and 3-year locoregional control were 59% and 44% for T3 RRSS and 47% and 54% for T3 S +/- RT. No significant difference between the different treatment modalities was found. The 5-year corrected survival rate and the locoregional control at 3 years between T4-RRSS (32%; 26%) and T4-S + RT (58%; 68%) groups were significantly different (p < 0.05 and p < 0.01). This might suggest that surgery with or without radiotherapy still has its place as a treatment modality for patients with advanced T4 laryngeal carcinoma.

Adult↗
PubMed1995

Evaluation of TMJ surgery in cases not responding to conservative treatment.

The aim of the study was to evaluate the treatment outcome after temporomandibular joint (TMJ) surgery, which was performed in 33 patients (27 women and six men) between 1970 and 1986. Before surgery, the patients received different types of conservative treatment for an average time of 29 months. The most common diagnosis was anterior disk displacement (ADD) with or without reduction (n = 10), followed by unspecified arthralgia (n = 8), osteoarthrosis (n = 7) and ankylosis (n = 4). Standardized clinical records served as the basis for comparison of symptomatology at comparable time points. Furthermore, 31 of the 33 patients were subjected to a clinical follow-up, including anamnestic, clinical, radiological and cast analysis, 2-17 years after operation. Pain, sleeping problems and consumption of analgesics were significantly reduced after surgery. The anamnestic, as well as the clinical dysfunction indices, according to Helkimo, were also significantly reduced. TMJ clicking was reduced, but crepitations increased in number. The best improvements were seen in patients with ADD without reduction and in patients with ankylosis.

Ankylosis↗