Biomedical subjects

P Laake

Publications and source records attributed to P Laake.

At least 19 recordsLinked to original sources

PubMed2001

Presynaptic Ca2+-activated K+ channels in glutamatergic hippocampal terminals and their role in spike repolarization and regulation of transmitter release.

Large-conductance Ca(2+)-activated K(+) channels (BK, also called Maxi-K or Slo channels) are widespread in the vertebrate nervous system, but their functional roles in synaptic transmission in the mammalian brain are largely unknown. By combining electrophysiology and immunogold cytochemistry, we demonstrate the existence of functional BK channels in presynaptic terminals in the hippocampus and compare their functional roles in somata and terminals of CA3 pyramidal cells. Double-labeling immunogold analysis with BK channel and glutamate receptor antibodies indicated that BK channels are targeted to the presynaptic membrane facing the synaptic cleft in terminals of Schaffer collaterals in stratum radiatum. Whole-cell, intracellular, and field-potential recordings from CA1 pyramidal cells showed that the presynaptic BK channels are activated by calcium influx and can contribute to repolarization of the presynaptic action potential (AP) and negative feedback control of Ca(2+) influx and transmitter release. This was observed in the presence of 4-aminopyridine (4-AP, 40-100 microm), which broadened the presynaptic compound action potential. In contrast, the presynaptic BK channels did not contribute significantly to regulation of action potentials or transmitter release under basal experimental conditions, i.e., without 4-AP, even at high stimulation frequencies. This is unlike the situation in the parent cell bodies (CA3 pyramidal cells), where BK channels contribute strongly to action potential repolarization. These results indicate that the functional role of BK channels depends on their subcellular localization.

4-Aminopyridine↗

PubMed2001

Exposure misclassification: bias in category specific Poisson regression coefficients.

In epidemiologic studies of the association between exposure and disease, misclassification of exposure is common and known to induce bias in the effect estimates. The nature of the bias is difficult to foretell. For this purpose, we present a simple method to assess the bias in Poisson regression coefficients for a categorical exposure variable subject to misclassification. We derive expressions for the category specific coefficients from the regression on the error-prone exposure (naive coefficients) in terms of the coefficients from the regression on the true exposure (true coefficients). These expressions are similar for crude and adjusted models, if we assume that the covariates are measured without error and that it is independence between the misclassification probabilities and covariate values. We find that the bias in the naive coefficient for one category of the exposure variable depends on all true category specific coefficients weighted by misclassification probabilities. On the other hand, misclassification of an exposure variable does not induce bias in the estimates of the coefficients of the (perfectly measured) covariates. Similarities with linear regression models are pointed out. For selected scenarios of true exposure-disease associations and selected patterns of misclassification, we illustrate the inconsistency in naive Poisson regression coefficients and show that it can be difficult to intuitively characterize the nature of the bias. Both the magnitude and the direction of the bias may vary between categories of an exposure variable.

Adolescent↗

PubMed2001

Childhood and adult milk consumption and risk of premenopausal breast cancer in a cohort of 48,844 women - the Norwegian women and cancer study.

Analyses of dairy consumption and breast cancer incidence have yielded conflicting results. In this prospective cohort study of 48,844 premenopausal Norwegian women, we examined the relationship between childhood and adult milk consumption and breast cancer incidence. During a mean follow-up time of 6.2 years, 317 incident cases of breast cancer were diagnosed. Information on childhood and adult milk consumption was obtained from frequency questions mailed to the participants in 1991-92. Milk consumption as a child was negatively associated with subsequent breast cancer among the youngest women (34-39 years) (p for trend = 0.001), but not among older ones (40-49 years). Adult milk consumption tended to be negatively related to breast cancer incidence (p for trend = 0.12) after adjustment for age, reproductive and hormonal factors, body mass index, education, physical activity, and alcohol consumption. Women drinking more than 3 glasses of milk per day had an incidence rate ratio of breast cancer of 0.56 (95% confidence interval 0.31-1.01) compared with women not drinking milk. Analyses according to type of milk consumed and milk fat consumption did not reveal any clear associations. A combination of childhood and adult milk consumption produced a clear negative trend in breast cancer incidence rate ratios with increasing milk consumption (p = 0.03).

Adult↗

PubMed2001

A novel postsynaptic density protein: the monocarboxylate transporter MCT2 is co-localized with delta-glutamate receptors in postsynaptic densities of parallel fiber-Purkinje cell synapses.

Confocal immunofluorescence microscopy showed strong monocarboxylate transporter 2 (MCT2) labeling of Purkinje cell bodies and punctate labeling in the molecular layer. By immunogold cytochemistry, it could be demonstrated that the MCT2 immunosignal was concentrated at postsynaptic densities of parallel fiber-Purkinje cell synapses. The distribution of MCT2 transporters within the individual postsynaptic densities mimicked that of the delta2 glutamate receptor, as shown by use of two different gold-particle sizes. The MCT2 distribution was also compared with the distributions of other monocarboxylate transporters (MCT1 and MCT4). The MCT1 immunolabeling was localized in the endothelial cells, while MCT4 immunogold particles were associated with glial profiles, including those abutting the synaptic cleft of the parallel fiber-spine synapses. The postsynaptic density (PSD) molecules identified so far can be divided into five classes: receptors, their anchoring molecules, molecules involved in signal transduction, ion channels, and attachment proteins. Here, we provide evidence that this list of molecules must now be extended to comprise an organic molecule transporter: the monocarboxylate transporter MCT2. The present data suggest that MCT2 has specific transport functions related to the synaptic cleft and that this transporter may allow an influx of lactate derived from perisynaptic glial processes. The expression of MCT2 in synaptic membranes may allow energy supply to be tuned to the excitatory drive.

Animals↗

PubMed2001

Reporting data following major trauma and analysing factors associated with outcome using the new Utstein style recommendations.

STUDY OBJECTIVE: To collect and present retrospectively the recommended core data from the Utstein style, analyse factors associated with outcome in major trauma, and discuss the value of the Utstein style definition of major trauma. DESIGN: A retrospective trauma cohort study. SETTING: A Norwegian trauma system with a 1200 bed combined local and referral trauma hospital without a formal trauma registry, covering a population of approximately 2.0 million. PARTICIPANTS: 3391 injured patients admitted 12 months from January 15, 1996. MAIN OUTCOME MEASURES: Recommended core data from the Utstein style, and factors associated with outcome defined as in-hospital death within 30 days. RESULTS: 225 patients had an injury severity score (ISS)>15. In each of the 225 patients, we were able to obtain at least 47% of the recommended core data. Age >70 years, fall as a mechanism of injury, and a Trauma Score (TS)< or =14 were significantly associated with poor outcome. Of 22 with no major trauma (ISS<16), two died in hospital and 20 had an intensive care unit stay of more than 2 days. CONCLUSION: We found it difficult to collect retrospectively the recommended core data of the Utstein style. Age and physiological alterations (TS) were significantly related to outcome. The recommended definition of major trauma (ISS>15) did not cover all life-threatening injuries. The implementation of trauma registries based on the Utstein style recommendations could facilitate system evaluation and comparison, but definitions and categorizations should be further developed. Efforts should be made to reduce the number of core data.

Adolescent↗

PubMed2001

Body mass index and weight change attempts among adult women. The Norwegian Women and Cancer Study.

BACKGROUND: Based on concern about the widespread increase in being overweight and obesity along with a substantial demand for leanness, we wanted to estimate body mass index (BMI) and the prevalence of weight change attempts in a population-based sample of Norwegian women. Furthermore, we wanted to examine how weight loss attempts are related to BMI and to age, socioeconomic status, reproductive factors, lifestyle and diet. METHODS: A nationwide, cross-sectional study applying a mailed questionnaire was used. Out of a random sample of 20,000 women aged 45-69 years 10,249 women participated. RESULTS: Based on self-reported data, the mean BMI was 24.6 kg m-2 and 40% of the women had a BMI of > or = 25 kg m-2. More than 50% of the women were trying to lose weight and weight loss attempts were very strongly associated with BMI. Age, education, income, smoking status and perception of diet's importance to health were also significant predictors of weight loss attempts. The effect of age, education and income on weight loss attempts was modified by the level of BMI. Women trying to lose weight reported a different diet than those not trying to lose weight, irrespective of BMI. CONCLUSION: A large proportion of middle-aged women are trying to lose weight. BMI is predominant in explaining weight loss attempts. After adjusting for BMI, age, lifestyle and socioeconomic status also contribute to explaining weight loss attempts.

Age Factors↗

PubMed2000

Efficiency of activation of the trauma team in a Norwegian trauma referral centre.

OBJECTIVE: To evaluate the efficiency (sensitivity, specificity, positive predictive value, overtriage, and undertriage) of activation of the trauma team in a Norwegian trauma referral centre. DESIGN: A cohort study with univariate and multivariate analysis. SETTING: A primary trauma hospital and trauma referral centre, Norway. SUBJECTS: 3391 injured patients admitted during a 12 months period, starting January 15th, 1996. MAIN OUTCOME MEASURES: Activation of the trauma team for severely injured patients and factors associated with correct activation. RESULTS: Of the 3383 injured patients admitted, 283 (8%) were classified as severely injured. Of 507 activations of the trauma team, 240 (47%) were for severely injured patients (sensitivity 85%, undertriage 15%, specificity 91%, overtriage 9%, positive predictive value 0.47). The system of activation was significantly more efficient for patients admitted by anaesthetist-manned ambulances than by ordinary ground ambulances (sensitivity 94% compared with 83%, corresponding positive predictive value 0.55 and 0.33, p < 0.05). Female sex and age over 70 years were independent factors associated with significantly less use of the trauma team in severely injured patients (p < 0.05). CONCLUSION: The undertriage rate of 15% and a positive predictive value of only 0.47 indicates a need for improvement of our activation system. Female sex and age over 70 years were significantly associated with undertriage in severely injured patients. Our protocol for triage and the initial treatment of severely injured patients has been revised in the light of these findings, and we have established a trauma registry.

Adolescent↗

PubMed2000

A simulation study of measurement error correction methods in logistic regression.

Measurement error models in logistic regression have received considerable theoretical interest over the past 10-15 years. In this paper, we present the results of a simulation study that compares four estimation methods: the so-called regression calibration method, probit maximum likelihood as an approximation to the logistic maximum likelihood, the exact maximum likelihood method based on a logistic model, and the naive estimator, which is the result of simply ignoring the fact that some of the explanatory variables are measured with error. We have compared the behavior of these methods in a simple, additive measurement error model. We show that, in this situation, the regression calibration method is a very good alternative to more mathematically sophisticated methods.

Calibration↗

PubMed1999

Different modes of expression of AMPA and NMDA receptors in hippocampal synapses.

Postembedding immunogold labeling was used to determine the relationship between AMPA and NMDA receptor density and size of Schaffer collateral-commissural (SCC) synapses of the adult rat. All SCC synapses expressed NMDA receptors. AMPA and NMDA receptors were colocalized in at least 75% of SCC synapses; the ratio of AMPA to NMDA receptors was a linear function of postsynaptic density (PSD) diameter, with AMPA receptor number dropping to zero at a PSD diameter of approximately 180 nm. These findings indicate that 'silent' SCC synapses are smaller than the majority of SCC synapses at which AMPA and NMDA receptors are colocalized. Thus synapse size may determine important properties of SCC synapses.

Animals↗

PubMed1998

Correlates of subjective well-being in stroke patients.

BACKGROUND AND PURPOSE: Data on survival and functioning after stroke needs to be supplemented by measures emphasizing the patients' subjective perception. We studied (1) subjective well-being (SWB) as a latent variable in a common-factor model with four items, (2) the reliability of these four items, and (3) variables related to SWB in stroke patients. METHODS: Data on all stroke patients (n=1417) and a random subsample of stroke-free individuals of similar age (n=1439) were collected from the Nord-Trøndelag Health Survey, a cross-sectional study of 74977 persons. Based on a two-sample factor analysis model, scores of SWB were calculated, and variables explaining SWB were studied in a regression model. RESULTS: Four items were a priori believed to measure SWB as a latent variable ("satisfaction," "strength," "calmness," and "cheerfulness"). This was confirmed by factor analysis. The reliability of these items (the proportion of the variance of the items that can be explained by the common factor) was between .42 and .53. Regression analyses showed a significant effect of having had a stroke, gender (lower SWB in men), age (increasing SWB with increasing age), perceived general health, nervousness, loneliness, sleep problems, social support, and use of analgesics. There was no statistical interaction between these variables and having had a stroke. CONCLUSIONS: Higher SWB after stroke relates to female gender, older age, good general and mental health, and a firm social network.

Adult↗

PubMed1997

Dietary fat intake and risk of prostate cancer: a prospective study of 25,708 Norwegian men.

The relationship between incidence of prostate cancer and intake of dietary fat and foods rich in fat was studied in 25,708 men aged 16-56 years attending a Norwegian health screening in 1977-1983. Linkage to the Cancer Registry of Norway and the Central Bureau of Statistics of Norway ensured a complete follow-up until December 31, 1992. Diet was recorded on a semi-quantitative food-frequency questionnaire at the time of screening, and 72 cases of prostate cancer were identified during follow-up. At the end of follow-up, mean age of the total study sample was 56 years (range 19-68), while mean age at diagnosis of prostate cancer was 60 years (range 47-67). No association was found between energy-adjusted intake of total fat, saturated fat, mono-unsaturated fat or poly-unsaturated fat and the incidence of prostate cancer. Significant positive associations were found for body mass index (BMI) and consumption of hamburgers/meatballs, while no association was found with consumption of frankfurters/sausages and a significant negative association with the weekly number of main meals with meat. A significantly increased risk of prostate cancer was associated with skim milk as compared to whole milk. Milk preference (skim vs. whole) was associated significantly positively with BMI. Our study of a relatively young cohort does not confirm previous case-control and cohort studies suggesting that dietary fat, especially from animal sources, is associated positively with risk of prostate cancer.

Adenocarcinoma↗

PubMed1997

Diet and risk of cutaneous malignant melanoma: a prospective study of 50,757 Norwegian men and women.

The relationship between dietary habits and subsequent risk of cutaneous malignant melanoma (CMM) was studied in 25,708 men and 25,049 women aged 16-56 years attending a Norwegian health screening in 1977-1983. Linkage to the Cancer Registry of Norway and the Central Bureau of Statistics of Norway ensured a complete follow-up until December 31, 1992. Diet was recorded through a semi-quantitative food-frequency questionnaire at the time of screening, and 108 cases of CMM were identified during follow-up. Use of cod liver oil supplementation and intake of polyunsaturated fat were associated with significant increased risk and drinking coffee with significant decreased risk of CMM in women. Adjusting for height, body mass index, body surface area, education, smoking or occupational or recreational physical activity did not change the results. No significant association was found between the incidence of CMM and any of the dietary factors in men. Important aspects are residual confounding by sun exposure and social class, as well as concern with multiple comparisons.

Adult↗

PubMed1997

Dietary fat intake and risk of lung cancer: a prospective study of 51,452 Norwegian men and women.

The relationship between incidence of lung cancer and intake of dietary fats, high-fat foods, fish, and fish products was studied in 25,956 men and 25,496 women aged 16-56 years attending Norwegian health screening between 1977 and 1983. Linkage to the Cancer Registry of Norway and the Central Bureau of Statistics of Norway ensured a complete follow-up until 31 December 1991. Diet was recorded on a semiquantitative food-frequency questionnaire, and 153 cases of lung cancer were identified during follow-up. Mean age at diagnosis was 56 years. After adjusting for smoking status, gender, age at screening, and attained age, significant lower risks were found for cod liver oil supplement (incidence rate ratio (IRR) = 0.5, 95% CI = 0.3-1.0) and for skim milk compared to whole milk (IRR = 0.5, 95% CI = 0.3-0.9)). No association was found with dietary cholesterol and saturated fat. A threshold of increased risk starting at the second quartile was seen for mono- and polyunsaturated fat. The potential protective effect of cod liver oil, a supplement rich in preformed vitamin A, omega-3 fatty acids, and monounsaturated fat, has to our knowledge, not been reported before. Confounding from lifestyle is possible, but the result deserves further investigation.

Adolescent↗

PubMed1996

Trends in diagnosis-specific mortality for the aging population in Norway, 1966-1986.

For the older segment of the Norwegian population, sex, age at time of death, and time-period of death are important factors to consider when describing cause-specific mortality trends. Correspondence analysis was applied to mortality and provided plots which in a conceptually simple way demonstrated the complex relations between sex, age, time-periods and causes of death. Log-linear modelling was used to confirm the findings of the correspondence analyses. During the period of observation, the elderly, regardless of sex, have experienced greater changes in the most important causes of death, than the younger segments of the population. The main intention of this article is to improve the conceptual understanding of how important parameters are associated with trends in mortality rates for the major causes of death in Norway.

Aged↗

PubMed1996

Incidence and risk factors of cancer among men and women in Norwegian agriculture.

OBJECTIVES: The objective of the study was to examine cancer incidence and identify risk factors among subjects born in 1925-1971 and engaged in agricultural activities in Norway. METHODS: A cohort was established through linkage between agricultural censuses in 1969-1989 and the Central Population Register, which identifies farm holders and their spouses. Available census information on the activity of the farm provided the exposure indicators. Incident cancer in 1969-1991 was identified in the Cancer Register. In an analysis for standardized incidence ratios (SIR), the cohort was compared with the total rural population of Norway. Associations with exposure indicators were investigated in a Poisson regression analysis. RESULTS: In the follow-up of 136,463 men for 1.5 million person-years and 109,641 women for 0.6 million person-years, 3333 and 2145 cancer cases were identified, respectively. The subset defined as farmers had an SIR of 77 [95% confidence interval (95% CI) 73-81] for the men and 92 (95% CI 85-99) for the women, with particularly low SIR values for lung cancer and other sites linked to life-style. The several positive associations found confirmed the a priori hypothesis of an association between dairy farming and acute leukemia among men [rate ratio 1.76, 95% CI 1.02-3.05]. Multiple myeloma was associated with pesticide indicators for both genders, mainly for subjects cultivating potatoes. CONCLUSIONS: The results support the hypothesis of a relationship between acute leukemia and animal contact and between multiple myeloma and pesticides in potato cultivation. Other exposure associations, especially for cancer among women, warrant further investigation.

Adult↗

PubMed1995

The Barthel ADL index: factor structure depends upon the category of patient.

The validity and reliability of the Barthel index were studied in 60 geriatric patients, 87 stroke patients, and 102 patients with hip fracture, using a factor analysis methodology which explicitly accounts for the ordinal nature of the scoring on each item. The findings substantiate that the Barthel index is unidimensional among stroke patients, but not among geriatric patients or patients with hip fracture. In the latter two groups, one factor related to mobility, the other to bodily functions. A sum-score to characterize geriatric and hip fracture patients does not take into account the complex structure of the Barthel index.

Activities of Daily Living↗

PubMed1993

Accessibility of dental services according to family income in a non-insured population.

The aim of this study was to examine the effect of family income on accessibility to dental services among adults in Norway. The analysis was performed on a set of national data collected in 1989, which was representative of the non-institutionalized Norwegian population aged 20 years and above. The sample size was 1200 individuals. The data were analyzed according to a two-part model. The first part determined the probability of whether the consumer had demanded the services or not during the last year according to family income. The second part estimated how the amount of services utilized depended on family income, for those with demand. The elasticity of the odds of having demanded the services with respect to family income was 0.48. Family income had no effect on the amount of services utilized. Additional analyses also showed that there was no effect of family income on the probability of having received a filling or a crown when visiting the dentist. In Norway, almost all costs for dental services are paid by the consumer. It is not possible from the data alone to say whether subsidized dental care is an effective way of reducing the inequalities in demand.

Adult↗

PubMed1992

Hemodynamic evaluation of the CarboMedics prosthetic heart valve in the aortic position: comparison of noninvasive and invasive techniques.

Seventy-three patients with a CarboMedics aortic bileaflet valve prosthesis were examined by Doppler ultrasonography, and 27 of them were also assessed by transseptal catheterization. The ultrasonic mean systolic gradient was 17.1 +/- 5.6 mm Hg for valve size 19 mm, falling gradually with increasing valve size to 6.8 +/- 2.5 mm Hg for size 27 mm. The catheter mean systolic gradient was consistently smaller than the ultrasonic gradient (4.3 +/- 4.8 mm Hg), but Tobit regression analysis showed a significant association between the two methods. In all patients both methods revealed negligible to small amounts of retrograde leakage, which is assumed to be a normal finding for this valve. The effective flow areas of the valves calculated from the ultrasonic data were similar to the in vitro calculated flow areas. The hemodynamic potential of this valve is therefore completely utilized in vivo. The effective orifice area corrected for body surface area increased with increasing valve size, which demonstrates a moderate valve-patient mismatch.

Adult↗